texts: Construction for a homogeneous field using permanent magnets

texts:
Please let me describe what I am trying to achieve and I will pose my question in the end.
I am trying to design a small chamber which can have a uniform magnetic field inside. I want to see if a design using permanent block magnets is feasible in terms of cost and construction. The volume inside the chamber is approximately 13cm x 13cm x 13cm.
I am thinking of using an iron or steel yoke as shown in the picture below. I got the idea from this article in supermagnete.de.
The picture below shows a top-view of my current design, where the green is a block magnet and the gray is iron or steel:

To reduce construction costs, I am planning to laser-cut many pieces and stack them as shown below:

This is an experimental prototype design, in which I care more about the field homogeneity rather than the field strength itself.
My question is the following: Would such a construction produce a fairly homogeneous field? I am concerned that the size of the magnet and the geometry of certain areas of the sheet matter, but I am not entirely sure how to design for them.
Given the technical details of the magnets, for example this datasheet, how can I estimate the field strength inside the chamber?
With that in mind, is there any free software that can easily simulate the fields in such a geometry? I could use that to see the effect of different geometries and magnets.
Thanks for all the help in advance!


texts: What is torque-ampere ratio at electric machines? How it is related with machine efficiency?

texts: When I am reading a journal about SRM (switched reluctance machines) it said that outer rotor design has better efficiency due to higher torque ampere ratio. How it is related with efficiency?


texts: Detecting lamp failure in electronic ballasts

texts:
What would be a simple solution for detecting lamp failure in fluorescent tube ECG's?
There are 3 control gears running 6 (40w/4pin) lamps that need to have detection of lamp failure. While ECG's have a simple way to detect failure on the control circuit how would you go around the issue to detect lamp failure with available high frequency outputs?
Current measurement on input side seemed like a decent idea, but the L-N polarity may be reversed - as such that becomes problematic (the inrush current is another issue ~31A / ecg). I can only think of using the lamp output HF side, but am unsure of how to approach the matter in a reliable way with minimal work and off the shelf components.
There are ballasts available with contacts for lamp failure but they tend to be around 80$ as opposed to 15$ for regular ones.


texts: Is it possible to implement a 3 Input Encoder?

texts:
I was want to implement a 3 input priority encoder.
Is it possible to implement this by cascading two 2-1 encoders?
If so how does this work?
It also needs two outputs?


texts: Linear current driver with several BJTs in parallel

texts:
With the circuit setup shown below, if I have available a type of Q2 transistor with a certain maximum dissipated power and need that D1 withstands a large current that would lead Q2 in trouble, it is necessary to share the current among several transistors in parallel to Q2. One can think that this upgrade can be achieved by connecting the additional transistors exactly in parallel to Q2 as per definition, that is bases connected together, collectors together, emitters together. But transistors are identical only in theory, in practice hfe values usually span a large interval and it is typical that one of them draws more current than the others and gets hotter (being aware that the sum of the collectors current is limited by VBE@Q1/R2). By having all the VBE tied together they are kept at the same value with no possibility to vary in case collector current increase, therefore it may happen that the hottest transistor gets in thermal runaway. My question is: am I right with this assumption? Can this issue be circumvented by placing a small resistor in series eg, 0.1ohm to each emitter, so that VBE can decrease in case collector current rises? Thanks in advance.

@aconcernedcitizen, @Sparky256 I am aware that the topic resembles the one you cited, but my question focuses on the paralellization. Let's put numbers. Supposing I want 500mA flowing throug D1, trying with Q2 only implies to set R2=0.7V/500mA=1.4ohm. Then I am realizing that VCE(Q2)=VCC-V(D1)-0.7V times 500mA gives me a power number that goes beyond the allowable limit of Q2, therefore I decided to add one more transistor, let's call it Q3, in parallel   with its emitter resistor R3 in parallel to R2, by changing R2=R3=2.8ohm (the double as previous). In theory the 500mA current should split equally among Q2 and Q3, but in truth one of them will be more demanding, let's assume 300mA flows in Q2 and remaining 200mA in Q3. Q2 will get hotter and its temperature surge will make Q2 getting more and more current out of the overall 500mA. In this case a feedback aimed at reducing VBE(Q2) as much as IE(Q2) rises would be useful, to me here it looks like VBE(Q2) and VBE(Q3) are tied together to a fixed value, therefore I mentioned the two additional resistor between each emitter and R2 and R3, respectively. Am I loosing anything?


texts: Can a disconnected pin on DDR3 SDRAM go undetected?

texts:
I was testing some DDR3 SODIMM modules using Memtest86+ on a Lenovo Thinkpad T520. I re-tested a module that I previously marked faulty and it came out fine.

So I wonder if it's possible that the module wasn't properly connected before.

Do these modules have some self-diagnostic facilities that would detect a break in one of the lines or would e.g. a break in a higher address line go undetected until higher memory areas are actually accessed?


texts: Wiring Arduino Mini Pro with CP2102 USB to TTL

texts:
I have an Arduino Mini Pro and a CP2102 USB to TTL module as in the image below:

I couldn't find a suitable guide for the module I have. So, how should I wire them together?


texts: What are some alternative power sources for wireless sensors?

texts:
I'm looking to power several small, Wi-Fi enabled sensors, in a domestic home or office environment. As such I'm interested in keeping them powered as long as possible between charges.

Obviously an expensive Li-xx battery would be simple solution, but I've also been looking for more 'inspired' alternatives, such as Micropelt thermogenerators.

What other alternatives are there that would provide a decent amount of power, in a small size?

Alternative wireless networking ideas are welcome, but I'm keen to use WiFi - most homes have a WiFi network and enabled computer - I'd like to keep the extra equipment needed to an absolute minimum.

[There is a related question, about energy storage. My question is about generation and my needs are fairly specific (size, high power etc.]


texts: Pyrometer device compatible with arduino

texts:
I am an undergraduate Mechanical Engineer and currently I am using a laser which heats and melts a surface of any material (plastic, metal etc) which is formed in powder. Although, I have managed to melt some plastic's powder, I want to put more accuracy in the control system of the laser with the temperature of the surface which is being heated.
To be more specific, I want to measure, relatively accurately, the heated material's temperature and when the temperature reaches the melting point I want the laser to be turned off. I googled about the thermal radiation effect and I found about the pyrometer device. I would like to ask if there is a pyrometer which is compatible with Arduino/Tiva microprocessor with a normal range of temperatures. I found some pyrometers/contactless thermometers that can measure up to 380 degrees Celsius which is not enough since the melting point of aluminum is 660 degrees (I want to use later aluminum).
Any suggestions?

Thank you for your time and for your answer in advance,

Chris

EDIT (after Jonk's suggestion):

Chamber:

The chamber currently is in room conditions (20-25 degrees of Celsius) as I just finished building it but I was thinking of inserting an inert gas later to prevent oxidization of the product (in room temperature).

Laser:

The laser is a YLIA M20 with a wavelength of 1064nm and the diameter of the beam is around 1mm. I use it at the maximum power at 20W. I want to measure the temperature of the area that the beam heats (local measurement). The laser distance between the laser and the surface is not fixed but after some experiments I made I calculated that it would be best around 100mm.

Budget:

The budget is around 500-1000 euros. If my idea for the pyrometer works and is a good solution it could be higher (1500-2000 euros).

Material:

The materials are formed in thin powder and supposed to be of any kind (plastic, metal, ceramic, glass). I cannot tell you with certainty the exact types yet because I don't know in what range I am going to use the machine I am going to build, but for a start I want to be able to measure 700 degrees of Celsius. The minimum emisivity could be at 0.5 since I don't use polished materials.

Microcontroller:

The laser's position is controlled by two motors (X and Y axis) via Arduino boards. The Z-axis of the laser is controlled through the movement of the base that hold the powder (the height of the laser in regard to the ground is fixed). The Z-axis' motor is also controlled with an Arduino board. The Arduino boards are then connected via an electronic system with a pmac board, which I use to write G code to control the movements of the laser. This whole set-up has been implemented and it works. So what I want is a control system that can also get feedback from the heated points (so for example if the melting is correct the laser can move from point to point). The microprocessor board compatibility with a non-contact thermometer is a must so I can use it in the system that I already have created.

In case I missed again something, please tell me to include it in my question.


texts:
I am building a microcontroller based circuit that generates some sound out of a loudspeaker.

Basic problem: Not enough volume out of loudspeaker

Strange stuff: Volume is louder if I use a LM386 amp (with a max output of 1W) instead of the PAM8403 amp module (with a max output of 2.5W), but sound gets distorted with the LM386.

What I did so far:
So, to help debugging, I removed the microcontroller part of it and just fed input from PC or phone via headphone jack, wired it into the amp module and ran it to the loudspeaker. When initially speaker made only noise, I added resistors to reduce signal amplitude, so I could hear  something out of the speaker.

See circuit here:

Circuit components

Speakers:
A. 4 Ohm, 10W  (mostly tested with this)(reasonably known manufacturer)
B. 4 Ohm, 3W  (unknown origin)

Amplifier:
1. PAM8403 module ordered on the net. PAM8403 datasheet
2. LM386N datasheet

Observations:
Observation #1. I get some sound from the speaker at a low volume, and when I increase the input volume from the phone or PC, it gets into clipping/motorcycle noise.
Still, not very acceptable volume before the clipping starts.

Then I went and did some calcs:
PAM Gain: 24dB
=> Ratio of 24db => Vo = 15*Vin
If I want 3W, out of 4Ohms, the Voltage should be: V^2/R = P
=> V^2 = 3*4 = 12 => V = SQRT(12)=3.46
Now, if output (Vo) should be 3.5V, then input should be 3.5/15 = 0.23V.
Suppose 2V (line level??) then, we must see this as approximately 2V/10.

So, I got to fiddling with the resistors to get this kind of 1/10 reduction.
Then I was fiddling with resistors of all values for a while before the input to the PAM, to bring down the input signal voltage.

Observation #2. At one point, I was able to reach all the way to the highest volume on the phone without clipping, but the loudspeaker volume is still not going higher.

Change of amplifier
I then switched out the amplifier and tried out an LM386 datasheet using the circuit below.

Observation #3. Clear difference in sound level output: Speaker has an ability to make decent amount of sound. But, it gets muddier and loses clarity at higher volumes (attributable to LM386??)

So, went and did some reading about gain, and modifying input signal.
But, no clarity, yet.

What help am I expecting:
a. Please suggest potential next steps I could try, including some reading.

b. Is what I am seeing normal or should I just throw out the speakers and try fresh (did this with two units of speaker A already, results not changing, but one unit of B shows substantial improvement in sound even with PAM8403, but for extraneous reasons, would prefer to get speaker A working "louder").

c. I have a gut feel that the thing I am missing is not the ratio of the resistors, but the size of the resistors used. Valid?

Thanks for your patient reading.


texts: TCA9517DR on I2C for long distance wiring with high capacitance bus

texts:
I have a CAT6 cable that was used for old temperature sensors that works with 5V I2C at 25/30 meters from the main MCU with cable pairs that brings VCC-GND-SCL-SDA.
Here is the schematic:

I've tried using an ESP32 with I2C bus speed of 100kHz with another PCA9306 at the Gateway end of the cable but it works for maximum 5 meters (and with many errors...)
The speed isn't a problem, i can slow down the speed without any problem.
The cable has a capacitance of 56pf/m, so 30 meters are 1680pf in total, higher than the maximum I2C limit of 400pf.
I know that i2c should not be used outside pcb, etc, etc..i can't change/add nothing more than the main gateway that collects those sensors data.
Now i'm looking for a solution for that: maybe i can use a repeater and level translator like the TCA9517DR and lower the pullup resistor on A-Side in order to fight the cable capacitance?
In any case, i wish have some useful advices about which parts i can use and how i can solve this issue.


texts: What's the best way to plot the "taper" of a potentiometer circuit?

texts:
The problem is designing gain/volume/pan/balance/crossfade/mix controls with a smooth "law" or "taper"; the rate at which the audible volume changes as you turn them.  (Described in The Secret Life of Pots and Changing the Law of a Pot, for instance.)

It's easy to make controls in which the gain changes very little in the middle and then swoops up at the top, for instance, but that's no good.

So I'd like to "draw" the circuit and then plot the gain/attenuation as a function of pot position, with either log or linear pots, and be able to vary component values and quickly see the effect on the gain function, in order to speed up finding the optimal layout/resistor values.

Currently I do one of the following:

Simulate the circuit in TINA-TI.  This sucks because:

The pots only come in linear taper
There's no way that I know of to plot something as a function of pot position.  You can set the pot as a control object and vary the position in steps from 0% to 100%, but I don't know of a way to plot the gain.  I just know you can plot the frequency response at each position, read the gains from the frequency response plot, and put them in a spreadsheet, which is very tedious.

Calculate the curve in a mathematics program like wxMaxima or Python and plot it.  This sucks because:

It requires entering the gain equation by hand, which can be tedious and error-prone for certain circuits.  You can't tell by looking at a complex equation whether it's right or not, and modifying it by adding resistors in parallel to existing circuitry is difficult.
Again, plotting for a log taper pot is difficult.  You'd have to enter the taper as a separate function which feeds into the gain function, and it still wouldn't match the real world exactly.

Any other ideas?

For illustration, here's a plot I made comparing linear pot, log taper pots, and linear pot with "pull-down resistor" to approximate a log taper.  I'd like something that will plot the yellow curve, for different values of the pull-down resistor, so I can make it behave as closely as possible to the other curves, without having to enter an equation manually.  Of course, my real applications are more complex, but this is an example of what I want to do.

(Copied from Electronics Exchange)


texts: STM32F412/413 USB changes from STM32F411

texts:
I have a project that was previously using STM32F411, and I am trying to swap over to using a STM32F412 (UQFN48, so pin compatible).
I thought I should be able to use the STM32F411 firmware on the STM32F412 (just not using the extra RAM/flash). I can flash it over USB DFU (so the hardware works) and the firmware itself runs fine (so clock speeds are fine), but USB does not work on it.
Does anyone know what changed on USB between chip versions that would stop the F411's code from working on F412? Is it just a matter of flipping some bits in a register?
Thanks!


texts: Change in frequency in a grid that has lost generation?

texts:
I have an example about droop and it asks to calculate final frequency in a grid after one generator power generation is lost. The answer is given as 59.889 Hz; however, I am calculating as 59.99 Hz. What am I missing?

The question is

Assume a grid has lost one generator (42MW) and the remaining
generation is 1132 MW. All generators have governors set to 5% droop.
What is the final frequency?

This is the given formula

$$
\Delta(f) = \frac{R.\Delta P_{gen,MW}}{\sum S_{online, MVA}}.
$$

$$
\Delta(f) = \frac{0.05 \times 42}{1132}=0.0019.
$$
Final frequency is 60-0.0019=59.9981


texts: Verifying the switched supply design in AN920

texts:
I am following along with AN920/D Theory and Applications of the MC34063 and uA78S40 Switching Regulator Control Circuits, section Step−Down Switching Regulator Design Example.

That is the diagram from the application note but I have changes. I am using the following parameters:

Input (24V) and output (5V) same
MC34063 instead of the μA78S40, connected the same way (Darlington configuration)
\$f_{min}\$ basically the same at 50 kHz
Maximum \$I_{out}\$ larger, at 150 mA
\$V_{in(min)}\$ larger; for the supply of the previous stage I calculated this as

$$
V_{in(min)} = V_{in(nom)} \left( 1 - loadreg - tol \right)
$$
$$
24 \left( 1 - 5 \cdot 10^{-3}  - 1 \cdot 10^{-2} \right) = 23.64V
$$

\$ V_{ripple-pp} \$ same at 25 mV
Due to the different chip, a higher timing conductance of \$ 45 \mu S \$; and a slightly higher \$ V_{sattyp} = 875 mV \$
Different external diode - Schottky, such as the SB140TA, with a much lower \$V_f\$ of at most 0.3 V, probably lower for these currents

For these parameters, I have calculated the following with a little Python:

 Rsc = 980.1 mΩ ~ 1.0 Ω
  R1 < 12.50 kΩ -> 3.4 kΩ
  R2 = 10 kΩ
  Co > 30.00 μF -> 470 μF
  Ct < 206.8 pF ~ 180 pF
   L > 272.1 μH -> 470 μH
 ton < 4.596 μs -> 4.000 μs
toff < 15.40 μs -> 13.41 μs
   f > 50.00 kHz -> 57.45 kHz
Vrip < 25.00 mV -> 1.389 mV
Vout = 5.000 V -> 5.000 V

I have tried to run the calculations backwards based on the approximated component values to verify:

the frequency - above the minimum at 57kHz
the output ripple voltage - below the maximum at 1.4mVpp
the output voltage - exact, assuming centre values for components

Where I'm less certain is the effect of the much bigger L and the slightly bigger Rsc. In particular, for these calculations involving peak switch current:

Would it be meaningful to calculate a new peak current using the above equation based on my actual inductor value instead of the minimum value, and the actual time period instead of \$ t_{onmax} \$ ?  If so, would having a very large inductor harm the upper limit of the output current? Similarly, if I substitute the actual value of Rsc which is slightly higher, would that have the effect of a slightly lower maximum output current?

Also: the inductor I'm looking at has a DCR of 1.3Ω. How will this affect the circuit?

And does anything in this design look wrong?


texts: How do I use a 15vac output supply for 12vac output?

texts:
I have a Christmas tree 12vac 10w light (MR11) and 12vac 2w synchronous motor assembly that I have lost the power supply.

I want to use a power adapter I have that is 15vac 1100mA. The light is too bright and the motor spins too fast.

Can I add a resistor or something? What value(s) would be good to try?


texts: 9V battery positive soldering pad went off from my circuit board

texts:
OK, so I got a little problem. Today I was soldering something on this circuit board and the positive wire tore apart. I had to resolder the wire, but when I was heating up the old solder to remove it, the copper part went off with the solder too, so I couldn't solder anymore to the 9V positive hole.
I thought this would fix the power circulation from positive to negative but apparently it didn't.. (See pic)

If I did something wrong, please don't hate on me. I don't understand so much about these paths.

P.S: Don't mind some of the bad solders, I kind of did some of them in a hurry.


texts:
assume forward biased
replace the diode with iD going down and short circuit it and make VD=0
combine 70Ω and 30Ω resistors that are parallel and it becomes 21Ω
now 21Ω resistance is in parallel with 3V and the (40Ω resistors and 50mA)
ID=50mA meaning the assumption was correct

This is how i attempted the problem and i'm missing something because the final answer i get is odd.
Any help or pointer would be greatly appreciated, Thankyou.
update:

update:


texts: What characteristics should I look for when choosing a Zener Diode as a voltage limiter?

texts:
I am trying to use voltage limiting zener diode for a MOSFET gate in the following oscillator circuit . (related to this question)
What characteristics should I look for when choosing a Zener Diode for gate voltage limiting and how it relates to the operation of this circuit? E.g. series resistance, parasitic capacitance etc.


texts:
I'm trying to configure my ATMEGA328p to measure temperature using the TMP36GZ temperature sensor. However, the 10-bit ADC keeps returning 1023. I've tried disconnecting the temperature sensor (it should return 0 at this point for the ADC reading), but it still returns 1023. I'm not exactly sure what I'm doing wrong in my code:

volatile uint16_t TMP36_VoutADCReading = 0U;

void TMP36_Init( void )
{
   // Set the ADC prescaler to 128 (i.e., 16MHz/128 = 125KHz)
   ADCSRA |= ( 1 << ADPS2 ) | ( 1 << ADPS1 ) | ( 1 << ADPS0 );

   // Set the voltage reference from AVcc (i.e., 5V).
   ADMUX |= ( 1 << REFS0 );

   // Turn on the ADC.
   ADCSRA |= ( 1 << ADEN );

   // Do the initial conversion (i.e., the slowest conversion)
   // to ensure that everything is up and running.
   ADCSRA |= ( 1 << ADSC );
}

void TMP36_ADCRead( uint8_t channel )
{
   // Clear the previously read channel.
   // ADCSRA &= 0xf0;                      <-- This was causing the bug.
   ADMUX &= 0xf0;                          // <-- This is the fix. Thanks IgnacioVazquez-Abrams!

   // Select the ADC channel to be read.
   ADMUX |= channel;

   // Start a new conversion. By default, this conversion will
   // be performed in single conversion mode.
   ADCSRA |= ( 1 << ADSC );

   // Wait until the conversion is complete.
   // while( ADCSRA & ( 1 << ADSC ) );        <-- This is probably also correct.
   while( ADCSRA & ( 1 << ADIF ) );           // <-- Added. Thanks Adithya!

   // Obtain the ADC reading from Vout.
   TMP36_VoutADCReading = ADC;

   // Clear the ADIF flag.
   ADCSRA |= ( 1 << ADIF );                    // <-- Just added. Thanks Adithya!
}

int main( void )
{
   // Disable all interrupts for the time being.
   cli();

   // Initialize the TMP36GZ temperature sensor.
   TMP36_Init();

   // Enable all interrupts.
   sei();

   while( 1 )
   {
      // Compute the distance.
      uint8_t channel = 1;
      TMP36_ADCRead( channel ); // At this point, TMP36_VoutADCReading = 1023
   }
}

In terms of connections, I'm trying to read the output voltage from pin PC1 on the ATMEGA328p and I have AVcc connected to VCC and pin 22 (i.e., GND) connected to
pin 8's GND. I have disabled setting the voltage reference from AREF, so AREF
isn't connected.

Any help would be greatly appreciated.

UPDATE:
IgnacioVazquez-Abrams pointed out that ADCSRA &= 0xf0; should have been ADMUX &= 0xf0;. I've since modified the code above. Also, thanks Adithya for the suggestion you made about checking the ADIF flag! I'll take it into consideration.


texts: Why resistance should be increased for Photoresistor in night for Street Lamps?

texts:
I can't get why the resistance for a Photoresistor should be increased at night time as said in Photoresistors.

The reason is that I think that to turn on a light it's better not to have a higher resistance so that the electrons can conduct and electron flow takes place which in turn would produce light.Am I wrong in the concept I have stated?Can anyone help me.


texts: How can I prevent my IR sensor from sensing the sunlight?

texts:
I want to use an IR sensor for object detection. An LED will be turned on if an object is detected. But because of sunlight, it's malfunctioning (i.e. always getting logic 1).
So, how do I omit the interference due to sunlight?


texts: What will be the result of a step input?

texts:
simulate this circuit – Schematic created using CircuitLab

Assuming I'm giving a step input( from 0 to Vs) what could be the response?

I analyzed it thus, but I'm not sure if my approach is correct:

I reduced the above circuit to :

simulate this circuit

Now this is a first order RC circuit with tau as RC, Vout will be :

\$\ V_\text{s} + \text{Vs}\left(1-e^{-\frac{t}{\text{RC}}}\right)\$

(Vin = Vs after t= 0)

Is this analysis correct?


texts: Different frequencies of digital signals over long distance

texts:
I am working on a solution which will need to transport some different frequencies of digital signals over 10-20 meters.

I have worked out a design with the following components:

PCB with

An ESP32
An sx1509 I2C multiplexer
(https://cdn.sparkfun.com/datasheets/BreakoutBoards/sx1509.pdf) to
shift the logic level from 3.3 to 5V (and to get enough digital i/O
pins)
One ISL32272E RS422 driver (https://www.renesas.com/us/en/www/doc/datasheet/isl32172e-272e-174e-179e.pdf)
One ISL32173E RS422 receiver
(https://www.renesas.com/us/en/www/doc/datasheet/isl32173e-273e-175e-275e-177e-277e.pdf)

And ~10m away I have the following

PCB with connectors
One ISL32173E RS422 receiver
(https://www.renesas.com/us/en/www/doc/datasheet/isl32173e-273e-175e-275e-177e-277e.pdf)
One ISL32272E RS422 driver
(https://www.renesas.com/us/en/www/doc/datasheet/isl32172e-272e-174e-179e.pdf)
8x active IR sensors; output is 5V logic signal
3x ultrasonic sensors (JSN-SR04T); sending 40 KHz signal after being triggered
1x addressable led strip; requiring 800KHz signal

I want to use 3 UTP awg22 cables to transort the signals

Feedback, hints or tips to improve the design wrt flaws, cost and reliability are appreciated.

And I have 2 specific question:

Would I still need an additional component after the SX1509 (component
A) to eliminate picking up EMI or any ground loop / potential
mismatch?
Could I use VCC=3.3V at the RS422 driver side and VCC=5V at the
receiver side (I do not have any other need for 5V so it would save
me a 5V pwr supply component at driver side). Consequence is that
the driver will output a Differential VOUT of 2.6V but I am not sure
if this will suffice at receiver side at a guaranteed min speed of
800KHz as it has a Input High Voltage of 2.2V at Vcc=5V.

thx!


texts: Single Phase fan induction motor current flow

texts:
I have dissemble a induction motor in a fan. It look like follows.

I have no expereince in this field. When I tried to understand it's current
flow, I got these questions.

What is the main winding and the auxiliary winding ?

I guessed inner winding is the auxiliary winding and outer winding is main winding.
Is my guesses are correct? Please clarify for me.

And I have marked electrical degrees on the rotor like bellow, Am I correct?
again I need some clarification.


texts:
Very simple question. If (say) a 65m radiotelescope obeserving at 5cm (6GHz) has a resolution of about 1mRad, if it becomes a transmitter at that frequency does it radiate a beam of the same divergence angle?
I think it probably does, but would like a second opinion


texts: ATMEGA32U4-AURCT vs ATMEGA32U4-AUR vs ATMEGA32U4-AU?

texts:
What are the differences between the -AURCT vs -AUR versions of Atmega32u4 MCU?
I can't find any info on AURCT from the datasheet


texts: Perfboard/Stripboard insulation techniques and what material to use

texts:
I most often make circuits on perfboard.
Below is an example of a circuit, both bottom and top sides:

This circuit will be in a case but outdoors for many months.
In case of some rain leakage or humidity or rust ect, I want to protect this circuit by isolating it.

I saw some people use an epoxy like thing in both sides. I couldn't find any detailed information in my search.

I'm totally ignorant about this. What kind of material should I use and should I pour and cover it both sides?


texts:
Let's say I want to put a chip antenna 70 mm away from a 2.4 GHz radio. The radio has a male U.FL connector.

Is there any part that is a chip antenna that presents a male U.FL connector, so I can run a 50 ohm, 70 mm U.FL female-to-female coax cable to it?

Or should I buy a cable that is U.FL female to raw wires, and then have the PCBA house solder those wires to the antenna?

Will 70 mm of separation between the radio and the antenna, at 2.4 GHz and 50 ohm, destroy my signal?


texts: How to develop for .NET Micro Framework on Linux?

texts:
Is there an IDE which will allow me to develop for the .net Micro Framework on Linux?

Maybe MonoDevelop?


texts: Finding state equations for an RL circuit with inductors in T configuration?

texts:
I'm working on an exercise which asks to "Identify state variables and write apropriate state equations" for the following circuit.

simulate this circuit – Schematic created using CircuitLab

Trying to find the answer I get the following system

$$
\begin{cases}
v = v_S-R_1i_1-(L_1-M){i_1}',
\\v=(L_2-M){i_2}' + R_2i_2,
\\v=M{i_3}',
\\i_1=i_2+i_3.
\end{cases}
$$

from which I can't properly derive the requested state equations - I end up with equations like \$0=0\$

The difficulty seems to me to be purely mathematical but as the problem is related to circuit design I guess this forum is better place to ask this question than the mathematical one.

So, I need some help.

Thanks


texts: Can I use the USB 2.0 and 3.x channels simultaneously in a USB 3.x port?

texts:
I am designing an FPGA development board for myself. I want a moderately high speed link (400-500MB/s) to the host PC and I'm considering several options, including an FTDI FT-60x bridge IC. The problem is that this chip has no side channel that would allow me to configure the FPGA, unlike the good old FT-2232H.

This article claims that "USB 2.0 is available on the same connector and can be used as sideband", and suggests using both chips in tandem, with a hub on the USB2 lines for both of them to be available, but routing the USB3 pairs straight to the FT-60x. They are apparently doing this on some of the boards they sell.

So here are my questions:

Does the USB specification guarantee that USB2 is still available while using the USB3 lane of the same connector?
Can I really skip the hub on the USB3 lane if I'm using one on the USB2 lane?
I don't really care if functionality is reduced on a USB2-only port. Can I just skip the hubs altogether and connect one device to each lane?


texts: Measuring resistance from 0.01 to 10k Ohms

texts:
I'm attempting to design an ohmmeter that can measure resistance from 0.01 to 10k Ohms. The circuit is based on the 4 wire Kelvin resistance measurement. So far the low end measurements are fine but I'm having difficulty adapting the circuit to measure from 10 to 10k Ohms.

How can I adjust this circuit to measure resistance from 0.01 to 10k Ohms?
Thanks


texts: Should I refactor my C code to optimise it for an embedded microcontroller?

texts:
Below is some code implemented on an 8 bit microcontroller.

The following comment was posted to another question:

  As your code doesn't use the i variable, why not just while(length--)
  instead of the first for loop?

It suggests changing the for(..) loop for a while(..), will this make any practical difference to how optimised the code is for an embedded microcontroller?

uint32_t MyFunction(uint32_t crc, uint8_t *buffer, uint16_t length) {
    for (uint16_t i=0; i < length; i++) {
        crc = crc ^ *buffer++;

        for (uint16_t j=0; j < 8; j++) {
           if (crc & 1)
              crc = (crc >> 1) ^ 0xEDB88320;
           else
              crc = crc >> 1;
        }
    }

   return crc;
}

Note: I wrote this question and answered it myself after posting a comment earlier this week.  That comment was upvoted but I felt I should back it up with some actual testing.  Other answers would be useful, but this was intended as generic proof of a point rather than a specific question about the algorithm.


texts:
In the following flow diagram:

Is the "phase register" a one-bit register? What does it basically do with that summation mark? What type of register is it? I basically do not know what the phase accumulator do as well but for that I need to understand what phase register is doing first.


texts: I have a 60W, 120 VAC incandecent bulb used as a heater. Today it burned out and resulted in a water system freezing. I would like to be able to hook up a spare bulb that can come on if the first bulb goes out, or some similar system of redundancy. Unfortunately I work with DC more than AC, so I'm not sure how I can do this. Is there some easy way (a relay or something) that I could use to detect when bulb goes out?


texts:
I have a design question.
My design has grown in complexity because of new sensors (requires 5v).
In the old design a 3v3 output from my buck was sufficient, however now I have to create both a 5v and 3v3 rail, one for sensors and one for powering the MCU.
Now my question is how should I go about achieving this? My initial idea is to reconfigure the buck to output 5v and feed that output into an LDO to get 3v3 for my MCU (requires ~3v3).
I have omitted filtering, feedbacks and poweroring to simplify the design idea.
Question
Are there any pitfalls to this approach or perhaps a better way to achieve this?
I haven't frozen the design with these two components, I suspect I will try to find components from the same manufacturer at the very least.
The current requirements are within limits of what these components can handle.

I will update this post with the real schematic once I gather some more information on how to do this.
-Thank you.


texts: Circuit to convert 24VAC digital signal to 5V DC digital signal

texts:
I am designing a circuit to convert 24VAC signal to 5V DC signal.
The 24VAC signal is designed where 24VAC is on and 0VAC is off. The signal needs to be fed to an MCU which is 5V DC.

The circuit designed has to be very cheap so more expensive ICs and full wave rectifiers are not options.

There are two designs that I came up with

The first design outputs a 5V DC signal for high and about 0VDC for LOW.

The second design eliminates the capacitor but outputs a 5VDC for low and 5VDC square wave for high which will be accounted for in code.

I would like to know if there is an advantage for one over the other considering that the circuit needs to be as cheap and safe as possible since it will be used in an industrial environment and will be heavily affected by dust, debris, and humidity.


texts: EAGLE 9.3.0 - No mapping errors - How to solve them?

texts:
I've created a preliminary schematic without any package, because at drawing phase were unknown. So I've used "EXTERNAL" attribute to my devices to allow me to add them to schematics. Now I've added packages to my devices and want to update library to change package of all this devices. But when I'm trying to perform this operation, I get this two errors:

"No mapping between external and non external devices. XXXXX (external) can't be mapped to new version of XXXXX (not external)" where XXXXX is the name of a single device.

I've tried to delete all this devices from schematics and add a copy with a different name. But nothing. Seem that my schematic stuck with old device.

A temporary solution was to create another device with another name. But this create me a redundancy inside my library and also another error:

How I can solve this problem if someone already encounter it?

p.s. I've already tried to contact Autodesk but without answer.


texts:
I saw some other questions here about DC Block capacitors in LTspice and none of them helped me with my problem.

The question is very simple, why we have a DC offset when using capacitors as DC block in LTspice (even with a parallel resistor)?

The facts:

With Stop time = 10 m (very large!), Maximum Timestep = 0.01 n (very small!):

SPICE log (no floating nodes):

Simulation command:

Is there anything I should fix?

Thanks a lot!


texts: What's the meaning of the "key" symbols in Altium?

texts: I'm routing a PCB board with Altium. Today I find when my mouse hover on the pads, it shows some shadowed "key" symbols. What's the meaning of them?


texts: what i have to use to only allow voltages above certin value to pass?

texts:
I have a school project which it requires me to design a logical circuit that tests a 12v battery if it is full or not or half-full and light the corresponding LED, but, I am having a trouble because I want a component that only allow a voltage to pass if it is above 12v in first branch and 6v in second branch and 0.5v in third branch, but, I don't know what to component to use to achieve my goal.
I am thinking to use resistors but I do not know what are the values to assign to it to achieve my goal.
NOTE: I am using Proutuse isis


texts: Calculating gain of multiple antenna system

texts:
Some radars have thousands of antennas, there are also some routers that have multiple antenna systems.

But I want to know how to calculate total gain of multiple antennas in a system? Is it simply equal to the number of antennas times gain of one antenna?

What about beamwidth of the resulting system? If for example I use 64 antennas in a system, all are omni directional, is the total system still omni?


texts:
I need to drive a 3 W LED (Forward voltage 12 V, Forward current 0.2 to 0.3 A) using NiMH Batteries( 1.2 V, 2700 mAh ). As the supply voltage should exceed the forward voltage of the LED, I am thinking of using LT1618 IC, http://cds.linear.com/docs/en/datasheet/1618fas.pdf for boosting the voltage.

I would like to know first if its actually possible to do this, and if so, How many such nimh batteries would I be requiring for this arrangement?


texts: PCB trace width can't meet the rated current

texts:
The rated current for VCC5_AC from AC adaptor is 2A. According to the calculation on http://circuitcalculator.com, the trace width for 2A should be 30.3mil.
However, as indicated above, the width of AC input pin of the BQ24030 is only around 12mil and I think it's useless to connect a wider trace to this pin, so the actual trace width of VCC5_AC connected to the pin is just 12mil.
My question is:
1. Does this mean the regulator cannot drain the rated current 2A?
2. If this is the case, is there any solution to solve this problem?

Edit:
Thanks to everyone's suggestion. I realize my mistakes are

The uncertainty about changing the trace length in the middle, even a short part, which is not very significant in this case;

The misconfiguration of trace width calculation tools;
I've changed my layout as below which widen the power line


texts: Does a mobile phone app have the ability to control the output current?

texts:
After some brief research online, I found that the USB port is capable of starting a simple fan. Meaning the USB charging port can output current into an external device.
Which leads to my question, is it possible for a mobile phone app to alter or control the output current? Has anybody seen or done any sort of experiment on it?


texts: I am trying to instantiate few modules to work in top level design, but even though there is no error but I am not getting proper output

texts:
This is my verilog code. Though I am not getting any output, if any two of the instantiated modules are commented then I am getting proper partial output(For full output I need all of them to work). But all three as simulated together then the variables are as if they haven't been instantiated. All of the calculations are for Posit Numbers. I will send the link for understanding this number format.
I have to perform:x1=xin2 and then x2=1-x1tmp(this is where I am using x1tmp=-x1) and finally err=xx2. Over all I have to perform err=x(1-x*in2).

    module check(x, in2, err, start);//x and in2 are inputs for this module and //err is the output.Start is the signal given from testbench for starting this module
    parameter N = 32;// This is the bus width for all the variables.
    parameter es = 3;// This is the parameter required for calculating
    input       [N-1:0]x;
    input   [N-1:0]in2;
    output  [N-1:0] err;
    wire        [N-1:0] x1;//These are nets declared for intermediate calculation
    wire        [N-1:0] x2;//Same as that of x1
    wire        [N-1:0] oru = {{(3){1'b0}},1'b1,{(N-4){1'b0}}};// This is "1" in //posit number format
    posit_mult #(.N(N),.es(es)) m1(x, in2, start, x1, inf, zero, done);//x1=x*in2, where the rest of them are status signals(1-bit)
    wire        [N-1:0] x1tmp = -x1;//To get 2's complement of x1
    posit_adder #(.N(N),.es(es)) a1(x1tmp, oru, start, x2, inf, zero, done);//x2=x1tmp+oru
    posit_mult #(.N(N),.es(es)) m2(x, x2, start, err, inf, zero, done);//err=x*x2
endmodule


texts: Safely tripping a newly bought circuit breaker to make sure it works

texts:
As the title suggests. I recently bought two circuit breakers as a means of protection for a little project of mine. One's a 60A, and the other's an 80A. I've already tested it to make sure that power does flow through when it's "on" and that it breaks the circuit when manually shut off via a button on the breaker. What I haven't done yet is stress tested it to make sure the breaker will trip when overloaded, and I was curious if anyone had some safe suggestions for how to go about it.
What would be an ideal method?
what would be an ideal power source?
What would be an ideal location to perform the test?
What would be recommended to have on hand should things go south?


texts: Regulating voltage to compensate for random motor load

texts:
I'm currently using an L298N with PWM to control the speed of 2 scalextric cars. I need the cars to move round at a consistent speed, while I understand no 2 motors are the same and simply providing the same voltage won't guarantee that, and as such I have slight variations in the PWM values for each lane depending on the car and my own "by eye" calibration.

However some days one of the cars will have a high amount of internal resistance in that it crawls along while being provided with the same voltage as the other car.

Here is a video demonstrating this:

https://www.youtube.com/watch?v=WpusScFLhj4

As you can see about 6V is going through both lanes.

Could I add a linear voltage regulator between the L298N and the lane to make sure it maintains the desired voltage no matter the random load the car's motor seem to be under at that point in time?


texts:
The problem involves finding the time constant for the circuit that arises when the switch is flipped to the U position. What excactly is happening here? I am having trouble visualizing what is going on with the capacitors once the flip happens.

(And what about flipping it to the D position? Will the time constant change?)
Thank you


texts:
I recently bought a E-board (electric skateboard) which would not charge. I opened up the battery compartment to check the voltage of the batteries. In case of an undervoltage which led to them not charging back up.

I am not great with electronics, but I think I understand the basics.

I measured the voltage of the charger (Plugged in to a EU [Swedish] socket) and the battery with this tool set to VDC 200.

The charger showed 42.2 volt plugged in to a socket

And the battery showed 5.0 volts.

Is the battery "dead" and not possible to be recharged and used again, or is there some way that I can make it functional again?

Battery Info: AHCOF Intelligent Commuting.

Voltage: 36 V

Model: HB-10S1P

Capacity: 2.6 Ah 93.6 Wh

If there is any additional information required, please inform me and I will do my best to describe or give further information.


texts:
I've searched through a lot of threads regarding this and found some answers, however, the data sheet I am provided has some information which is causing some confusion.

I have a switch with the following rating:

Operation - AC15: 250VAC/6A, DC13: 250VDC/0.6A
Electrical Capacitor - Max insulation voltage 600VAC, max thermal
current 10A
Contact resistance - Max 50mohms

I am trying to determine the maximum current rating at 12VDC and 24VDC. Based off of some posts, most say to contact the manufacturer (which has gone unanswered). Others say that the max current will be 0.6A at any DC voltage. However, I have not seen anyone comment on the "max thermal current 10A" and I am wondering if this is the current which should not be exceeded any any voltage.

Thank you!


texts:
I'm using a 3.3 MCU and a 5v logic RS-485 IC. I'm trying to send out some data to another controller. I don't have a logic level shifter as of now. So I decided to use resistor divider, to get it to a safe limit of 3V.

simulate this circuit – Schematic created using CircuitLab
The output I'm getting is confusing. When I don't connect the 3V RX data out to the MCU RX Pin, the logic levels are working fine.

But when I connect this RX out pin to the RX pin of the MCU then the voltage level seems to float.

I checked the ground levels and it was just the same. Then I thought it could be some impedance issue, but nowhere it explicitly states the impedance of the UART input pin.
What's wrong here?
If it helps, I'm using TI's C2000 series controller.


texts: Do i need a resistor between my mcu and a mosfet?

texts:
This post here: 2N7000 connection diagram

  the gate is (very) high impedance, so no resistor is required to limit the current, as a resistor would be needed in series with the base of a BJT

But i also heard on many other place that we should put a resistor between mcu and gate, to limit the current. What is the recommended thing to do, does mcu can directly drive mosfet?

If i need a resistor to limit the current, from which capacitance shall i calculate it?

For example, if i look at a 2n7000 datasheet: http://www.fairchildsemi.com/ds/2N/2N7000.pdf
There is 3 different capacitance, input, output and reverse capacitance, no gate capacitance.

Also, when i look on digikey, i can either sort result by gate charge or by input capacitance, both given in coulomb for a given Vgs, what is the difference between input capacitance and gate charge? Which one shall i use to calculate the resistor? If like the 2n7000, there is no gate capacitance...


texts: I was reflowing and a 2K 603 resistor partially tombstoned. There was solder connecting the lead to the pad, yet my DMM showed an open. When I heated both ends and the resistor came down and contacted the pad, the DMM read 2k ohms like it should. Why didn't the solder conduct between the pad and lead? Also, sometimes when I touch a probe to a solder blob on top of pin, it shows an open. Yet when I touch the pin above the solder joint, it shows conductivity. Is this the same case when there is a cold solder joint? The solder is touching the pin and pad, yet there is no conductivity. Isn't solder a metal and therefore should conduct? How come it doesn't?


texts:
I'm reading about Semiconductor Physics (Semiconductor - Physics and Technology), and I'm confused on one part of MOSFETs.

I understand the PN junction (FINALLY!) and all the basic level stuff. But I'm not sure I understand how a channel is formed between the two n+ regions. This image is pulled directly from the book.

I have drawn what I would consider to be "depletion" regions at thermal equilibrium (I'm guessing they'd look something like that).

With a positive voltage (forward bias) this region would shrink obviously....but the two n+ are still not connected. What exactly forms a channel between them?

edit: Also Side question.....in a MOSFET such as the one below....does where you connect the circuit (source or drain) actually matter. IE Could you put the drain on ground or source on ground and vice versa and it'd still work the same? (Since from the picture I don't see any differences?)


texts:
I want to study the stability of my opamp circuit with LTSpice, I found this video as tutorial: tutorial on phase margin

So, I did the simulation with closed and open loop as suggested and got the following plots:

Closed loop:

And in open-loop as used in the video tutorial:

How to read those plots and conclude if my circuit is stable or not?

Update 1:

removed (not relevant)

Update 2: 0.3v pulse response

Update 3:
Open loop chart with view of 0db point.


texts: What really limits off-chip I/O? Capacitance or Inductance?

texts:
To my understanding, the crucial limiting factor for off-chip I/O is bondwire inductance, something that seeks to be minimized with BGA, flip-chip bonding etc.
The rationale is that an RC wire model is only valid for low frequencies where \$ f < \frac{R}{2\pi L}\$. References:

https://people.engr.tamu.edu/spalermo/ecen689/lecture1_ee720_intro.pdf , slide 10
https://people.engr.tamu.edu/spalermo/ecen689/lecture2_ee720_channels.pdf , slides 7, 8, 20

On-chip, we get away with simple RC-models because L is negligible compared to R if we consider frequencies up to a few GHz. But this is not the case for bondwires or PCB traces.
Now there is an interesting review paper Attojoule Optoelectronics for Low-Energy Information Processing and Communications - a Tutorial Review from David Miller (Stanford) which explains the limits of electrical communication and that the answer to this is optical communication (even for low distance links -- for large distance links this is obvious due to large losses in electrical lines).
In his whole 54-page paper, the word inductance does not appear a single time. His argument is based solely on the energy to charge a wire capacitance to a certain voltage (\$E=CV^2\$). This requires assuming an RC wire model and not an LC or RLGC model.

Why is that?
Why does Miller completely ignore inductance for his general (not only IC) discussion when the RC model is only valid for low frequencies?
What is now actually limiting the limiting factor for off-chip I/O: capacitance or inductance?


texts: How to obtain R1 from MAX31740ATA+T equation?

texts:
How to obtain R1 from MAX31740ATA+T equation ?

The equation:


texts: Avr-gcc does not compile correctly without optimizations, but works (badly) with -Os

texts:
I am developing software for attiny88 with avr-gcc toolchain. This is a cheap microcontroller with 8kB program memory, 512B SRAM and 64B non-volatile EEPROM data memory. This is all sufficient for the task it is supposed to handle. I do not have a debugger for this chip.

The device acts as SPI slave and allows the master to read/program the EEPROM and to read the device state (state of some analog inputs and digital outputs). The protocol is simple - first databyte carries the instruction where highest two bits encode required action (00-nothing, 01-write eeprom, 10-read eeprom, 11-read state) and the rest is address. Second byte is always zero, third byte is the value to read or write, fourth byte is always zero.

Problem is that I am getting weird behavior from the compiler. It is difficult to put a finger on what is going on, so I will just give a few examples. Most striking is that without -Os optimization the device does not respond over SPI. This is not for any of the obvious reasons - the program fits the memory and the stack should not run into .bss/.data sections (the program has ~700B, SRAM is mapped between 0x100 and 0x2ff, where .bss_end is at 0x109; the heap is empty; there are no nested function calls, neither nested interrupts).

If I turn on the -Os optimization, then the program responds as intended. Here is the working code to handle the ISR:

unsigned char state[8];
volatile unsigned char data;

ISR(SPI_STC_vect)
{
  switch(data>>6) {
  case 0:
    data = SPDR;
    break;
  case 1:           /* write eeprom */
    while(EECR & (1<<EEPE));
    EECR = (0<<EEPM1)|(0<<EEPM0);
    EEARL = 0;
    EEDR = SPDR;
    EECR |= (1<<EEMPE);
    EECR |= (1<<EEPE);
    data = 0;
    break;
  case 2:               /* read eeprom */
    EEARL = data & 0x1f;    /* with 0x3f stops working (???) */
    EECR |= (1<<EERE);
    SPDR = EEDR;
    data = 0;
    break;
  case 3:           /* read state */
    SPDR = state[data&7];
    data = 0;
    break;
  }
}

However, the program gets broken when written in semantically different way:

If I change the line "EEARL = data & 0x1f;" to "EEARL = data & 0x3f;", which is desirable as it would allow to address whole EEPROM address space, the ERPROM writing/reading stops working (I do not need full 64B, so I left it as is)
State reading (case 3) gets broken if I replace the line "SPDR = state[data&7];" with switch-case construct that returns value of PORTD/PORTB register when address is 0 and 1 respectively (the current workaround is to keep state[0] and state[1] synchronized with PORTB/PORTD in the main loop).

Am I missing something important? It seems to me that the compiler messes up, but I haven't found any bug reports for avr-gcc or avr-libc (newlib?) that would fit the bill.

The toolchain was installed from current gcc-avr package in aptitude repositories. The makefile is pretty basic:

all: main.hex main.s

main.elf: main.o
    avr-gcc -g -mmcu=attiny88 -o main.elf main.o

main.s: main.elf
    avr-objdump -d main.elf > main.s

main.hex: main.elf
    avr-objcopy -O ihex  main.elf main.hex

main.o: main.c
    avr-gcc -mmcu=attiny88 -Os -c main.c -Wall

UPDATE: Still the same result with latest binutils, gcc and avr-libc (recompiled from sources)


texts: One-time fuse for disconnecting/breaking signal path

texts:
I am looking for an IC solution, ideally, but alternatively also could use a tiny circuit that would allow to accomplish the following feature:

Trigger an event by MCU that will fuse-out/disconnect data lines (D+ and D- in particular). This has to be permanent, irreversible and also data lines must be physically disconnected.

I am not sure if circuits like this exist as off-the-shelf IC solution. What I've found by searching different terms is mostly conventional circuit protection fuses which is _not_ what I'm looking for.

Use case for circuit like this would be when you have to use USB for programming, debugging, data/log transfer and etc. but you don't want to ship your device to end users with USB D+/D- lines connected to anything. This allows to have USB charging and data for debugging/development, but end user doesn't have to worry about "Do I trust this device and is it going to do any harm to my USB host".

I would use this in my future open-source, open-hardware project(s) so there will be a lot of people cracking open this thing and confirming that it's safe for use when you get it "sealed".


texts: What size bridge rectifier do I need to convert 12V AC to 12V DC with 200watt load?

texts:
I have a 12V AC power supply that I want to convert to 12V DC using a bridge rectifier. I have LED lights that will draw up to 200 watts.

By my calculations, that should be about 17 amps (200W/12V = 16.667A). So would any bridge rectifier rated over 12V and over 17A work?

I bought the following thinking it would be more than enough but it started smoking when I connected it. I did check that it was connected to the proper terminals per specs, and verified that I was getting 12VAC from the power supply.
http://www.amazon.com/KBPC50-10-1000V-Housing-Bridge-Rectifier/dp/B00GYTWCP2


texts: How to design for a spectrum analyzer analysis?

texts:
I am designing a board that I will eventually  have to hook up to a tracking spectrum analyzer to tune the PI circuit on.

I have 2 different circuits. The first goes RF-OUT -> PI circuit -> U.FL connector -> external antenna, and the second goes RF-OUT -> PI circuit -> U.FL connector -> On board antenna

In the board design, I assume because I am going to use a tracking generator on a spectrum analyzer that I need 2 U.FL connectors per line, so that I can hook up the analzyer.

Where would I put them? My instinct is to go RF-OUT -> U.FL connector (for testing) -> PI circuit -> U.FL connector


texts: what does "desying" mean in polarimetric radar studies?

texts:
Do you see these two papers? paper1and paper2
It seems that desying has a special professional meaning in polarimetric radar studies.
I'm reading this paper and somewhere it says"

"we present in this paper an improvement to a decomposition scheme using an idea of desying first conceived by Huynen"

I don't want to go through all the details and understand what does desying exactly mean. So I don't read those two papers suggested in the beginning of this question. I just want to have an idea about desying so I decided to ask it from people who are mastered in radar studies.


texts:
Wikipedia gives this example of an I-V curve of a tunnel diode. What is the "noise" in the negative resistance region? Is it a characteristic of the diode or of the measuring circuit? The caption says "taken on a Tektronix model 571 curve tracer."

Source.


texts: Were to find device information about their rated processing use limitations

texts:
I'm an engineer working with device drivers+firmware. Have no much knowledge about the mobile device processing walls and hardware and limitations.

I have to do some engineering testing with commercial devices like google pixel, which tests would last for days continuously and may use the devices processing power completely ( huge image processing task). What I want to know is an information source where I can predict their processing power rated limitations, and I need a formal method derive it from processor specification when manufacture does not share such information. Yes we are pushing the device processing power to it's limits.

What information/specs should I collect?
Any formal method to decide their processing limits so less number of devices will be bricked during the engineering testing.
Any information on benchmarking/monitoring tools that I could use. For a example when I hitting the device limits that wold automatically abort the test or shutdown the device.


texts: Maximum power for Arduino Monster Moto Shield

texts:
I'm reading the specs for the SparkFun Monster Moto shield which specifies that

Max Voltage is 16V
Maximum Current 30A

Given Ohm's law, does that mean that the maximum power is 480 watts? That seems like a lot!!!

Am I missing something? Please do excuse my ignorance, I'm only starting out with robots and electronics and still at the beginning of the All About Circuits book.


texts: The Relationship of Power and Heat to Length of a Resistor

texts:
I have two sections of nichrome wire. They are identical in every way (gauge, etc.) except one is twice as long as the other. If I made it so the short nichrome wire received about 8.485 V and the long nichrome wire received 12 V, they would have equal power (both would release 3.6 W).

I know that the heat that both of these wires release would be the same. Does this mean that the heat released over the entire length of the wires are the same, or does it mean that the heat released at a given point along the length of one of the wires is the same as the heat released at a given point along the length of the other wire?

I use nichrome wires as heaters, and I want the heat at points along both of these wires to be the same; I don't care if the total amount of heats they release are the same.

Thank you!


texts:
What are these circuit symbols (circled in red) in these diagrams?

I am studying high school introductory physics, and this image is from a problem on circuitry in my online course. The problem is unrelated to the meaning of these particular symbols, but I am curious and would like to know.


texts:
So I've been looking at options to create a way of controlling whether a flash will fire based on the amount of light in the surrounding environment.

Early note: Everything has to be surface mount and tiny

One of the companies I contacted about an ambient light sensor says an ALS would work to turn the circuit on\off only if I used a comparator.

I threw together a quick circuit, except with a phototransistor, and this is what I have, but the problem is I feel the amperage really sucks. I can't pull more than 14mA for a single LED (I need closer to 50mA), and about 8mA for two in parallel. So I must have something wrong, or maybe a comparator just can't source more than that?

Option 2 is using Transistors, which this circuit shows to source more, but still a bit under what I'd like.

So I'd like to know what you guys think. Do you think either of these will work with something like this? Is there a better way to do this? As always, thank you guys a ton!


texts: A confusion in an ARM assembly instruction

texts:
My question about a simple instruction code of an ARM micro-controller.

LDR R2, [R1]

In the above instruction I interpret it as: R1 a RAM memory register and R2 is a processor register. What I understand from this was R1 represents the memory content in RAM and R2 is a processor register. So it says: Go to the address of R1 in RAM memory and load its contents to the processor's R2 register. Is that right? R1 is in RAM but R2 is in processor?


texts:
I just came across this site looking for answers on some questions I have concerning microwave oven transformers (M.O.T.). I am currently going into my third year as an E.E. student and I am trying to design a DC stick welder using M.O.T. I have been researching this topic for a week or so, but haven't found all of the answers that I need. The question I currently have is, if I separated two M.O.T. cores, removed both of the I portions of the E.I. cores, and stacked the two E parts to make an E.E. core, would I need to rewind the primary coil or will it still be usable?

Because welding machines need low voltage-high current, the secondary is going to be rewound with a 4 AWG wire that has a current rating of 95A. Due to the thickness of the wire, it is impossible to get 20 turns in the M.O.T. core as it currently is. The diameter of the wire is 5/16" and will wrap side-by-side in the core twice. As the transformers currently sit it is possible to approximately get 4 layers of wraps for 8-9 total turns on a single E.I. M.O.T. core. To get an amperage low enough for the cable rating, I think I need approximately 20 turns. (At school I rarely go over 95 A using  1/8" rod and probably won't be using more than a 3/32" on my DIY welder. (welding sounded like a cool thing to do with my summer break)). However, if I combine two practically identical E cores from the M.O.T., I calculated that I can fit 22 turns around their cores with them put together.

From what I have put together, this sounds to me like a good idea to reduce saturation (still trying to figure out the physics behind this because our semester was shortened), copper loss, and to allow for the thicker gauge wire to fit in. I thought about using magnet wire, but to get to a 4 gauge there it appears that I would have to use a Litz wire. This would be my first time using magnet wire, but I did try to salvage some from a core that I cut open and twisted 8 16 gauge wires together to get an overall 7 gauge (it was too stiff to use in one core.) A side note on that, molten NaOH (sodium hydroxide) will do work on the enamel that coats the copper wire.

I have enough M.O.T.'s that I can stack two cores and have two transformers to run in parallel on the mains (120v), and series on the secondaries (unless someone wants to talk me into running the mains in series and plugging them up to a 240v outlet). I intend on using a 300A 1600V bridge rectifier to convert to DC then a choke/inductor and maybe  3 6000uF 50V Electrolytic Capacitors that are available to smooth out the ripple. Once I make it to this point I would like to install a power control circuit to control the power input to the primary coil variably limiting the output on the secondaries. Then I feel like a 555 timer would make a nice duty cycle but I've only watched two videos on that and still don't have anything to use it for yet.

Thanks in advance.


texts: Arduino - Using NPN transistor as a switch to pull-up/down analog pin

texts:
Let me start by saying that I am not an EE, and my knowledge in Electronics is basic, so please bear with me and be patient if, initially I am bending a few rules.

In Epee fencing, a touch is awarded when contact is made at the end of a weapon's tip: when A (Analog Pin A0) and B (Analog Pin A1) are in contact, both A0 and A1 read 2,5V and a touch is awarded.

In Foil fencing, I need to establish that a fencer has been touched on its Lame (a conductive jacket). Therefore, in addition to the Analog functionality, I also need to implement a Capacitive sensor on the A0 pin. The Cap sensor uses a digital Pin (D4 in Diagram) to charge the Capacitor via a large (1M) resistor and reads the Voltage/status of a Receiving Pin (here A0).

The A0 pin is therefore used both for Analog and Digital readings purposes. This is the source of my issue, and why I am here.

I have no choice but to share the analog pin A0 for both analog and digital read purposes (there is only one line A). I have established that I cannot read the Analog levels and the Cap sensor output at the same time, without exposing myself to adverse side effects (wrongfully sending 5V to the Cap during the Cap sensor operation when A&B are in contact being one of them...). I, therefore, perform these tasks simultaneously:

Sampling both Analog A0 and A1 Pins (Analog ON/Digital OFF),
Sampling Analog A0 as a Digital INPUT (Analog OFF/Digital ON),

My primary concern is to achieve some form of isolation of the Cap sensor when in operation: this is to avoid the 1K resistors getting in the way of my capacitive sensor sampling, and CRUCIALLY, the A1 pin (connected to 5V via a 1K resistor) not charging the Cap during a touch sensing operation, thus destroying the significance of the values sampled.

simulate this circuit – Schematic created using CircuitLab

I also critically need to avoid the limits of the Cap Sensing circuit extending beyond its absolute necessary boundaries, which is not the case if the tip is depressed, or if the 1K resistor is pulling the A0 to GND, preventing the Capacitor from being charged properly.

So, I have a few questions:

In the diagram, I show what I THINK the solution to this problem is (but I am not saying it IS the solution).
Do you think I am right?
Am I going in the right direction using NPN Transistors? Are they used correctly?
If you did not use this method, What would the correct circuit be, etc,

Thank you very much in advance to all of you for helping me out. Don't hesitate to ask for more details.

Note: changed the schematics to use Q2 as a PNP following a suggestion from 'Captain Normal' below.


texts: Can hardware damage cause a computer (or a smartphone) to make miscalculations or logical errors?

texts:
I want to put an example.

If I have a motherboard, some elements dropped (such as capacitance or resistance）. When I install it into a computer, it can pass Power on Self Test and successfully launch the OS. Then I can operate it as normal.

In this situation, can I think the device runs normally? Can I believe its operation result (calculate result or logical result )?


texts: How to solve for node voltages using mesh analysis?

texts:
I am given the following circuit to analyze:

The problem asks me to solve for the unknown currents and then find the node voltages at N1 and N2.
Here are the mesh equations I came up with:
$$Mesh1$$
$$24000i_1-20000i_2-4000i_3=20$$
$$Mesh2$$
$$-20000i_1+22200i_2-200i_3=0$$
$$Mesh3$$
$$-4000i_1-200i_2+610i_3=0$$

Solving for the system of equations, I get the following:

The thing I'm stuck with now is calculating the node voltages N1 and N2. Do I calculate the individual voltage drops on the resistors first?


texts: How does concentric antenna wire cross the antenna in a wireless card?

texts:
Here's a typical layout of a wireless smart card. I simplified it as far as I could. The black filled rectangle is the chip. The black lines are wires comprising the typical concentric antenna layout. I only showed two turns because that's enough to show the problem.

The whole assembly is then covered with plastic and turns into a plastic card which has size of a bank card - about one millimeter thick. Obviously with any concentric antenna design fitting the antenna into a thin card requires that the most outer wire crosses the other wires at some point.

As the card is being normally bent antenna wires in this crossing will have to slightly move one over another and cause abrasion of each other unless some measures are taken. So I'd guess that if I just use magnet wire and let it cross itself and put all the assembly into plastic the wire will have its insulation work out in perhaps a year or two of normal card life and the antenna gets shorted.

How is this crossing done such that antenna wires insulation survives years in a card that is being bent often?


texts: What does a transceiver like MAX 483 do, especially when it is connected to RS-485?

texts:
I cannot understand the principle that the transceiver uses. Why do we need to connect it to RS-485, and how is the data transmitted? I mean how does it transmit the data and why? It is like I cannot understand the concept.
These are the datasheets, but I am more interested in what they do rather than the technical characteristics.
https://datasheets.maximintegrated.com/en/ds/MAX1487-MAX491.pdf
https://www.st.com/resource/en/datasheet/st485b.pdf


texts:
Q: Connecting Two Analog Sources to One Analog Sink without the sources effecting one other

What I want to do:

I basically want to add a radio tuner/MP3 player in a car. Now, that car already has a Cassette Player (Kenwood KRC-265 [Link]). This cassette player (aliased CP hence forth) is not to be removed. So the option is to just add one.

Problem

Now the problem is that the CP has no AUX in nor the MP3 Player has an AUX out. So the only option is to share speakers (4) between the two.

Possible Solutions

If I directly join the wires in a Y join directly then the voltage can sink into the circuit of the other and cause damage.
If I add a diode (on + speaker line) to avoid a back flow, then the analog signal may get cut due to the diode's 0.7V drop. The current can exceed an amp or two so I don't know if a germanium diode will do good (having low voltage drop).

I need you guys' advice on what to do.

Regards

EDIT:

Due to the lack of a word in my vocab. I used the word MP3 Player. It's a Car MP3 Player with built-in amp. Something like this: Link to AliExpress

But due to @Marcus Miller's answer providing me a better approach, I am planning to use that. That did come to my mind but failing to see that it is a 13 Pin connector (I assumed it was a CD Changer - a single signal/single wire connection), I did not google.


texts: Use condition from one clock with registers from another, synchronized clock

texts:
Is it permissible to use a condition generated by one clock with another, fully-synchronized clock (generated by a PLL with 0 phase shift) of different frequency?

This works as expected in simulation:

`default_nettype none

`timescale 1ns/1ps
module top;

   reg base_clk = 0;
   reg fst_clk = 0;

   reg cond = 1'b0;
   reg [2:0] ctr = 3'd0;
   reg some_reg = 1'b0;

   always #15 base_clk = !base_clk;
   always #5 fst_clk = !fst_clk;

   initial begin
      $dumpfile("top.vcd");
      $dumpvars(0, top);
      #10000 $finish;
   end

   always @(posedge base_clk) begin
      ctr  <= ctr + 1'b1;
      if (ctr == 3'd5)
        cond <= 1'b1;
      else
        cond <= 1'b0;
   end

   always @(posedge fst_clk) begin
      if (cond)
        some_reg <= 1'b1;
   end

endmodule

Can I assume this will also work when synthesized (in synthesis fst_clk would be generated by a PLL)? In my mind there shouldn't be any issues here since the clocks are synchronized and so I'm not crossing clock domains. Am I correct in thinking this? Or, have I overlooked something and I should only use a condition generated by the same clock.


texts: DSP Cutoff vs Sampling frequency question on low pass filter

texts: Is it unrealistic to have a 125 MHz sampling rate with a cutoff frequency of 5 Hz? I downloaded a few filter programs and used their methods and it seems that even with thousands of taps it still looks pretty bad. Is there a better way to implement this digitally or should I just stick with an analog implementation?


texts:
I have the plan to convert a few old LED backlit monitors into false windows. While I theoretically could buy direct LED drivers to power these panels, I'd prefer to keep the existing circuitry, since I know it works and provides the right voltage and current ratings.

The problem is that by nature, without an actual input, these monitors automatically turn off after just a couple minutes.

The question is - how can I trick a monitor (via VGA or DVI) to think they're attached to something and not automatically shut off after idle time?

PS - The LCD panels have already been removed. It's just the backlight.


texts: Broken Photodiode - how to find a replacement?

texts:
I have nearly no knowledge at all in electronics - but maybe you can help me :)

I got here a vintage moving message LED sign (brand: litek lmr 6002) and it seems that its controller is broken. The sign itself works, I can confirm that the IR leds on the remote are flashing (by pointing a digital camera on it) but the sign itself doesnt react on any command.

So I startet looking for the receiver but all I found was an unexpected solid looking diode - maybe a photoresistor. It seems to be connected to a TDA stereo amplifier chip (huh?).

I unsoldered that mysterious 2-pin diode and there is a high resistance between both legs - and its not changing when I point a flashlight, laser or the IR sender to it. So I think that diode is gone. Maybe - if I am lucky - I can bring life to that controller again by replacing this diode?

Is there anyone who can give me some advice how to identify that diode?

There are no marks or letters on it and it doesnt seem to be very transparent. It has a mark ("cut corner") on top but thats pretty much all.

I can supply some pictures of the small controller board - I marked the diode and its soldering points:

http://www.directupload.net/file/d/4523/iuyyurf5_jpg.htm
http://www.directupload.net/file/d/4523/rqfmcu8d_jpg.htm
http://www.directupload.net/file/d/4523/43n26du8_jpg.htm
http://www.directupload.net/file/d/4523/8333hzop_jpg.htm

Any hints are highly appreciated - and sorry for my lack of electronic knowledge again!


texts: How do you rewrite a transfer function to standard form?

texts:
How can I rewrite a transfer function in terms of resonance frequency \$\omega_0\$ and damping factor Q? Referred to as "standard form" in the university materials.

I'm still at it, trying to understand LCL filters, and found a gap in the university material. They always let us calculate the transfer function, then the standard form was given, so we just had to fill in the blanks and use the given function to draw a Bode plot. Now that I have a real circuit, I'm stuck. The university book only contains this section on the matter

Nilsson & Riedel has a section devoted to Bode diagrams in the appendix. It says all you need to do is divide away the poles and zeros and factor the result. Poles and zeroes seems to refer to the coefficients of the highest exponents in the numerator and denominator.

None of this is very revealing to me. Say I have the following transfer function. This is indeed in the general form, but how on earth do you factorise that? Getting rid of the poles and zeros is not very helpful either.

simulate this circuit – Schematic created using CircuitLab

$$
H(j\omega)=\frac{j\omega C_fR_f+1}{j\omega(L_1+L_2) + (j\omega)^2C_fR_f(L_1+L_2)+ (j\omega)^3 L_1L_2C_f}\\
H(j\omega)=\frac{C_fR_f}{L_1L_2C_4}\frac{j\omega+\frac{1}{C_fR_f}}{j\omega\frac{L_1+L_2}{L_1L_2C_4} + (j\omega)^2\frac{R_f(L_1+L_2)}{L_1L_2}+ (j\omega)^3 }\\
H(j\omega)=\frac{\omega C_fR_f-j}{\omega(L_1+L_2) + j\omega^2C_fR_f(L_1+L_2)+ j^2\omega^3 L_1L_2C_f}\\
$$

I put that in Wolfram Alpha, and it gave the following roots for the denominator. Besides being humongous, I don't feel they bring me much closer to a solution.

[update]

The factorization finally clicked, and I came up with the following for the undamped case:
$$
\begin{align}
H(j\omega)&=\frac{1}{(j\omega-0)((L_1+L_2) + (j\omega)^2L_1L_2C_4)} \\
j\omega&=\frac{\pm j \sqrt{4L_1L_2C_4(L_1+L_2)}}{2L_1L_2C_4} \\
H(j\omega)&=\frac{1}{(j\omega-0)(j\omega-j\frac{ \sqrt{4L_1L_2C_4(L_1+L_2)}}{2L_1L_2C_4})(j\omega+j\frac{ \sqrt{4L_1L_2C_4(L_1+L_2)}}{2L_1L_2C_4})} \\
&=\frac{1}{(j\omega)(\frac{L_1+L_2}{L_1L_2C_4}+(j\omega)^2)} \\
&=\frac{\frac{L_1L_2C_4}{L_1+L_2}}{(j\omega)(1+(j\omega)^2\frac{L_1L_2C_4}{L_1+L_2})}
\end{align}
$$
Putting this in standard form gives
$$
\begin{align}
H(j\omega)&=\frac{1}{(j\frac{\omega}{\omega_0})(1+j\frac{\omega}{\omega_1 Q}+(j\frac{\omega}{\omega_1})^2)} \\
Q&=0 \\
\omega_0&=1 \\
\omega_1&=\frac{L_1+L_2}{L_1L_2C_4}
\end{align}
$$

I hope that's not terribly wrong.


texts: In the below schematic for the Tube Screamer guitar pedal input buffer, there is a 1k resistor (R1) after the coupling capacitor (C1). What is the purpose of this resistor? It has no effect on the DC biasing of the transistor, and only appears to degrade the signal.


texts:
I was trying to repair the main board of a monitor (Samsung S27B750V), and after a few hours I did something I shouldn’t have, and blew this component.
I have tried to search for this but I am unable to find anything about it. Need to have it replaced. It reads “SOZ B21” I believe.

Perhaps there is an alternative to it?
I have a lot of old PCB's laying around, but have never seen this kind on any of them.

EDIT:
After uploading both photos I see they have different text in the middle.

Dimensions are 4.3 x 2.4 mm


texts:
I am using MEMSENSE nIMU for getting only the Euler angles.
However, i have a problem in the following case:

When i try to rotate the IMU randomly and return to the initial position (i.e. lying still on a flat table), my data does not confirm that. (if i start from phi=0;si=0 and theta=0, at the end, my angles are not all zeros)

as you can see except Phi angle, none of the angles returns to the "zero state".

Any suggestions?


texts: I have searched a lot for a content addressable memory chip, but I couldn't find any part numbers. Why aren't there any chips for this kind of memory?!


texts: Is there a full list of the names & abbreviation of electronic components

texts:
I came by a few electronic components that I don't recognize them from their shape nor their letters printed on the PCB. Is there a full list of the names and abbreviation of electronic components?

Some of the letters that I don't know their components' names.

Q (SMD with 2 terminals from one side and 1 terminal from the opposite side)
Q (Not SMD with 3 terminals & has a tower shape, 3/4 circle)
IC (3 terminals from one side and 1 wide terminal from the opposite side)
OJ (It's like SMD resistance with a 0 written on top of it)
X (It might belong to the below component with SC8.000 writing on top of it)
SC8.000 written on the curved metal rectangular in the picture below.


texts: How to use a LM1117T-3.3 voltage regulator to convert voltage

texts: I am doing a project where the components require 3.3v input instead of 5v, but my arduino pro mini can only supply 5v. Thus, I bought a lm1117t-3.3 voltage regulator to regulate the voltage, but the output from the voltage regulator is not 3.3v, but around 1v. This is the way I connected the voltage regulator, please give me some suggestions to overcome this problem, thank you.


texts: Questions about a design for an SMPS post regulator filter circuit?

texts:
For minimizing SMPS ripple and especially noise, I’m trying to make a small interface which is a post regulator cascaded after an LC filter. I have come across some papers related to this topic and the idea is to establish good noise rejection by using a low drop out LDO regulator for frequencies lower than like 100 kHz and for higher frequencies by using an LC filter. At this video it also gives a very nice example at around 2:56.

The topology can be seen in the circuit I have drawn in LTspice. Here is my circuit in question(the one inside the dashed box is the filter):

The circuit is set for 120mA load with 12V regulator output to a 15V input.

Now my biggest problem in simulation was that since I don't know the DC output resistance R3 of an SMPS and it can be different for any different SMPS. So for the worst case I took it as 0.02 Ohm. I say worst case because for the LC filter this doesn’t prevent the resonance problem. So to prevent the LC resonance, I added a parallel 1 Ohm resistor R1 with the inductor L1. In simulation L1 and C2 forms a very nice high freq. filter. Then I use this LT1086 as an LDO. Here is its datasheet and in applications it is mentioned that it is also recommended for SMPS switching noise filtering(it says "Post Regulators for Switching Supplies"). R2 and Rp set the output to around 12V for a 15V input. Rp can be a potentiometer to fine-tune the output voltage. According to the datasheet if I’m not mistaken the C1 is needed to be a tantalum capacitor and C3 is a ceramic capacitor both with low ESR.

Now I have made transient analysis in LTspice for this filter where the input is 15VDC with 1V pulse noise (with 10p rising falling edges) superimposed on it. So I repeated the same procedure for different noise pulse frequencies 50Hz, 100Hz, 1kHz, 100kHz, 1MegHz.

Below are the simulation results for input and output for these frequencies:

At 50Hz:

At 100Hz:

At 1kHz:

At 100kHz:

At 1MegHz:

The results are peak to peak amplitudes at the output for 1V pulse input noise at different frequencies. And here are the results for each:

50Hz ------> 1.6mV

100Hz -----> 3.8mV

1kHz ------> 173uV

100kHz ----> 41uV

1MegHz -----> 1uV

Here is the power dissipation for the regulator which is around 0.5W:

And finally here below is the current drawn from the SMPS and flow through input stage:

My questions are:

How can I reduce this supply current? Apparently it is 6A. Obviously there is something wrong with this even though the filtering looks fine. Never made such filter before for such purpose. I would be glad to hear any other fundamental issues for this circuit. SMSP cannot handle more than 500mA or maybe 1A, so reducing C2 can be an option but that degrades the filtering.


texts: Effects of joining the middle points of N parallel (2-battery serial sets)

texts:
Assume I need about 3V but large current:  First, I will need 2-battery serial set for the 3V.   Then, to meet large current need, I will need to parallel joint multiple those 2-battery serial sets.
What if I joint the middle points of all those 2-battery sets with wire?
Will it has some negative effects?
I asked this question because I have three "2-battery serial sockets" installed on a rotating plate.  If I joint the middle points, I can freely select to install 6 batteries or 4 batteries (the middle four, due to the need to balance the rotation).
See the pictures for detail.

In the normal configuration, installing 4 batteries in the center is not possible (have to install two on the side, which unbalances the rotation.
In the Mid-point jointed configuration, installing 4 batteries is possible.
But I am worried about other side effects...


texts: Why does my Arduino DUE not recognize my external interrupt?

texts:
I'm simply trying to get my Arduino DUE to toggle a pin based on an external clock.

I have a 14.31818 MHz Oscillator that is connected to a 74HC4040 Counter so that I can divide the clock in half (7.16 MHz).  This will have another purpose later on.

Anyway, I will need the DUE to run some code during each pulse of the 7.16 MHz clock so for now I'm just toggling a pin and measuring it with my scope.

Also, since the DUE isn't 5V tolerant on the I/O pins (so I've read) I'm running the Q0 output of the counter through a simple voltage divider using two resistors (1k and 604).  When I measure the output from the counter/divider, I get a 7.149 MHz signal (close enough) with a Vpp of 3.28V.  As you can see from the picture.

But when I put that same output to one of the DUE inputs I get get nothing.

Here is my code:

int pin = 53;
volatile int state = LOW;

void setup() {
    pinMode(pin, OUTPUT);

    attachInterrupt(A0, blink, CHANGE);
}

void blink() {
    state = !state;
}

void loop() {
    digitalWrite(pin, state);
}

Notice that I have the interrupt attached to A0 (also tried pin 52) and the output tied to pin 53.

What am I missing?

Thanks

UPDATE

OK, so I have this development breadboard that has a pulse generator built in.  I changed the input of A0 to the output of that pulse generator (running at 1KHz) and I get a clean signal from the DUE as you can see:

So, obviously it does not like my divided voltage signal.  How can I clean that up and make it more "square" like?  Or is this a separate question?

Thanks

** SOLVED **

@gbulmer had it spot on.  Makes total sense when I think about it.  7+ million inputs per second is simply way too fast to trigger the external interrupt (especially with the built-in Arduino code).  I'm not sure what the maximum input frequency could possibly be even using bit banging/asm but it's not worth it for my circuit. I'm going to redesign it and try something different.  But on a side note, I used the 74HC4040 and iterated through each output (which halves the signal each time) to see when it broke.  I got down to 57KHz before I saw any kind of signal.  And it was pretty dirty with jitters but it worked.

So 57KHz is WAAAAY off from 7MHz.  LOL

So I'm disappointed that my idea didn't work but it's AWESOME that I now understand why.  :-)  Thanks!


texts:
Requirements:
I need to design a load that will be powered with 1-4 supplies at any given time. The design requirements are merely that if 1 or more supplies are 'on', there needs to be at least 1 Amp draw from EACH supply.

Application:
Each supply will drive it's own LED. These LEDs draw an extremely low amount of amperage compared to standard LEDs that I'm used to.

If I need to choose different parts, for example, a MOSFET with a smaller Vgs... then I can easily do that. But I'm having a hard time figuring out what to do with the load. It needs to handle up to 4 amps and as low as 1 amp while keeping steady voltage applied to the LED rail.

The capacitor is designed to delay voltage to the gate of the MOSFET by at least 2ms.

LM338 dropout voltage ~2V minimum

If the supply is at 12V for all 4, the maximum voltage after the diode is 8.5V. So I design the load to be 2 Ohms to ensure 4 amps of draw total. But with this same load, if there is only 1 supply on at a time and its limited to 1A, the voltage across the load will be only 2V, and this is not enough to power the LEDs. This would also mean a large voltage drop across the current regulator.

What can i do to clean this up/make it work as desired? (This was designed from scratch by me). There may be ICs or components out there that are already made to do what I'm wanting, and I'm not the most experienced with these things yet.

I know I'm going to need forced air, so I wanted to include that in the load.
Any help will be appreciated.


texts: Why are Star-Star transformers not used in the transmission of power at high voltages which would reduce the cost of transformer(as lesser insulation needs to be applied across the phases). And for the circulation of zero sequence components we can provide a tertiary winding ?


texts:
I need to figure out how to physically mount the following AC-DC converter to a PCB to be used as part of a regulated power supply. The pin height is min 3.0 mm.

Should I mount it as a through-hole component, a surface mount component, or have a header that this component is plugged into?


texts: How to represent a microphone using a voltage dependent current source in LTspice?

texts: I am using the following schematic and I'm trying to simulate it in LTspice but I am not sure how to represent the microphone. My instructor said I should use a voltage dependent current source but I don't know how to hook it up or simulate the circuit? If you want more information on the circuit go to https://www.ti.com/lit/an/sboa290/sboa290.pdf?ts=1606276354037.


texts: Calculate current and voltage through resistors

texts:
I'm trying to get a better understanding of the voltage and current dividers.
The question for this circuit is:
What are the voltages and current through all the resistors?
I calculated the total current that flows through the circuit, but now I'm stuck with this question. I'm not asking for the answers but I need a plan to tackle this problem. In the attachment you can find the circuit with all the information.


texts: May I use relay rated for 5A to switch 12A?

texts:
I would like to use an electromechanical relay as an H-bridge, which is capable to drive 12A at 12V.

Relays able to control this current are big and expensive.

Is it ok to use a compact relay with nominal max switching current 5A if I promise to switch it over always at zero current?


texts:
I'm currently designing an esp8266-based board for a project. It has an LM317 for voltage regulation and the esp8266 is used to drive a RFID card reader (those RC522 reader board from china) and some addressable LED (WS2812). I also took an antenna design from Texas Instruments documentation (AN043 antenna) which is used in most of esp8266 designs I've seen so far.

Thus I've made a PCB and ordered it already assembled from jlc pcb a couple of weeks ago. It has a bit of an odd design, but it's on purpose.

When I received the pcb I ordered an FTDI from Amazon (FT232) and tried to program the esp8266. First thing I've learned is that I've had connected the wrong pin to the reset header (facepalm). I Bypassed this problem by unplugging it to reset it. So, I connected the GPIO0 to GND, reset it and try to flash it with Arduino : Trying to connect : Timeout error. I tried different config, different baudrate : same result. Triple checked my wiring and seemed good.

When I reset, my esp8266 sends garbage characters. I read online it was a common thing, so I don't know if I need to worry about it. I also tried sending AT command with Arduino serial monitor, but no response (AT and AT+RST same result).

After this I tried with my terminal and esptool to get more info about my problem. So I ran "python esptool.py -p COM3  --trace -b 115200 read_mac" and got the same error and not very interesting logs.

only this log in loop as I could expected it:

_TRACE +0.051 command op=0x08 data len=36 wait_response=1 timeout=0.100 data=
    0707122055555555 5555555555555555 | ... UUUUUUUUUUUU
    5555555555555555 5555555555555555 | UUUUUUUUUUUUUUUU
    55555555                          | UUUU
TRACE +0.001 Write 46 bytes:
    c000082400000000 0007071220555555 | ...$........ UUU
    5555555555555555 5555555555555555 | UUUUUUUUUUUUUUUU
    5555555555555555 5555555555c0     | UUUUUUUUUUUUU.
TRACE +0.101 Timed out waiting for packet header

Since the esp8266 gives absolutely 0 response except garbage code at startup, it seems that the problem is hardware and comes from the esp board itself (not the ftdi).

I hope someone can help me. Thank you in advance for your ideas.


texts: How to find a amplifier that named "ISP" on a circuit?

texts:
I am analyze the circuit. I can't find any relation about the name ISP of a op-amp. When we look the high pass filter we see there "ISP" name. I search it on google but I can't find nothing related.
I also check other circuits of backyardbrains, than I see there are two "ISP" named components. Example at virtual ground part.
What is that?


texts:
I am currently interfacing with a temperature sensor (MLX90616) which stores data in certain ram addresses which can be accessed.
I am interested in looking at the raw IR data as opposed to the calculated object or ambient temperature. This would involve accessing addresses 0x004 and 0x005 which have not been indicated as readable on the table below from the datasheet.

my question therefore is if RAM always readable? or does it depend on the device.
if so why would a manufacture not indicate that these addresses are readable on the datasheet?


texts: AC phase current sensing using Isolated delta-sigma modulator

texts:
I am trying to design a isolated AC current sensor.

I've chosen the AMC1106 Isolated Delta-Sigma Modulator.
(change my mind if you think there is a better solution for 220V AC; 2A Max; 0.25%)

The output of this chip is digital signal with the frequency of 5-20MHz

Is there a simple way to decode this? I don't really want to overwhelm my MCU with so frequent interrupts. Should I use shift register to divide it? Should I choose different part altogether?
Would it be viable to use I2C ADC and I2C isolator instead?


texts: PIR sensor outputs HIGH for too many seconds

texts:
I've a pretty simple set up which consists of a PIR sensor and ESP8266.
This PIR sensor outputs a HIGH value when presence is detected. This HIGH value lasts for 8 seconds.

I want this trigger to wake up a ESP8266 chip from a deep sleep. To do so, I must send a LOW to the RST Pin.

So with a NPN transistor, I switch it LOW once PIR outputs HIGH.

This works. However, as the HIGH lasts for 8 seconds, the RST remains in LOW and the ESP does not boot until it's back to HIGH.

So question is: Is there any way to convert this long output to become a fast "trigger"?

I attach an screenshot of the schematics in case it helps.

(credit of the picture: https://github.com/rgrokett/ESP8266_PIRv2/blob/master/ESP8266_PIRv2.pdf)


texts: Patient protection resistors in the biopotential amplifiers

texts:
In biopotential amplifiers like ECG amplifier, I often see protection resistors (around 100kohm) between electrode and the input of instrumentation amplifier or ECG amplifiers like ADS1298. I understand that the resistor are supposed to limit the current flowing into the patient. But the input impedance of the amplifiers are already in Gohm range. How does adding the resistors make difference?
Here is an example:


texts: Suitable op-amp and voltage regulator for 16-bit ADC

texts:
I would like to use the AD4008 16-bit ADC from Analog Devices to sample a load cell.  I also need a linear regulator and driver amplifier and instrumentation amplifier.
I am curious to know if these two parts have a low enough noise spec to be suitable for a 16-bit ADC application.
For the linear regulator I have chosen the MIC5205 from Microchip. It has 260nV/√Hz output noise.
For the instrumentation amplifier, I have chosen the INA821, which has 7nV/√Hz noise.
Should these parts both be suitable for a 16-bit ADC (assuming they are implemented correctly), or should I be looking for lower noise parts?


texts: L298N motor driver not working after connecting SPST switch

texts:
So when I had all wired as depicted in the first image, it worked fine, no problems. The red LED on the L298N board was illuminated and the dc motor was following commands from my Raspberry Pi.

Now I tried to add an SPST on/off rocker switch to the circuit, and this is where my L298N stopped working. I connected the SPST switch as depicted. When the switch was set to off nothing happened, as I would expect. When I toggled the switch to on, the red led on my L298N flashed, and that was the last time it did. I can confirm that is not only the LED that ceased to function, due to the fact that the DC motor won't respond when I recreated the circumstances of when it was functioning.
Other variables/variations:
I was using 4x AA batteries in both cases, however, I used a thicker wire to connect the SPST switch to the L298N than I did in the first situation/image, when it was working.
In the second case, I did not have the wire properly connected to the L298N, I just touched the screw of the L298N wire connection.
The Raspberry Pi was not connected to power in the second case, however, if i remember correctly, it was in the first.
How come my L298N stopped working? I am new to electronics and I would like to learn from this experience.


texts: What is this dial with 3-4 outputs that fits on a breadboard called?

texts:
I saw this new 'toy' called the Fidget Cube, but one certain side interests me:

It seems to be a small dial which can spin 360* without much friction  / resistance.
If I wanted to buy one of these types of components, which may be able to fit on a breadboard (It doesn't have to, just somewhat smaller) which has a common anode or cathode, and can have outputs depending on the degree the dial is rotated to, what would I search for/ask for? Thanks!


texts: Can I use a CP2102 USB to TTL IC for programming an ATmega 328p?

texts:
I am going to start working with microcontrollers. I will need to programm it. To programm it, I want to use a USB to serial port shield.
There are several options.  Should I use https://www.electronicscomp.com/cp2102-usb-to-ttl-serial-converter-module?search=usb%20to%20ttl  this one?


texts: How to control the current output from usb slots of computers?

texts:
Is it possible to control output from a computer usb port so, for instance if I have a usb led I can make it blink or do whatever with it. Whenever I send a high signal it would glow and whenever I send a low signal it would turn off. Is it possible?

NOTE: I don't know if it is the appropriate site for this question. So, tell me where to ask if not from here.