texts:
I need to replace the following cap:

It was placed at the input of a device that runs off 24Vdc, like the following schematic.

simulate this circuit – Schematic created using CircuitLab

I'm repairing the unit after an explotion due to a maintenance where the board was fed 220Vac instead of 24Vdc...
Bottom line, while repairing the unit i found this Cap (C1) shorted and i need to replace it, but i've never seen a tantalum cap with this markings.

Of course, it's a 47uF cap, but the rest of the data i ignore.

I assumed that K is for tolerance (10%), and 20 for 20V, but this makes no sense in a circuit that runs on 24Vdc, so i need to find out the voltage rating of this cap (sure, i could simply replace it with a 40V and be safe, but i want to leave things as original as possible, and also want to learn to read this codes, it will become usefull in the future...)

So, could you fill the next list and perhaps explain how this code is selected?

R+: ?

476: 47uF

20K: ?

633: ?


texts: Need help with 2 Transistor Current Limiter Circuit in LTSpice

texts:
I am new to LTSpice. I have attached a picture of my circuit below:

The goal of the circuit is to provide current to the R1 until It is too high. Then the BJT will activate, shutting the FET off.

For some reason, the simulation is not able to finish the entire sweep. Can anyone help me with why?


texts: Nyquist plot disagreeing with the unity step response of the closed loop

texts:
Let us assume that the open loop transfer function of my system is:

\$L(s)=\frac{10(s+1)(s+2)}{(s-3)(s-4)}\$

Also, the system has unity feedback, meaning that the closed loop transfer function is

\$T(s)=\frac{L(s)}{1+L(s)}\$
since \$L(s)=G(s)H(s)\$ and \$H(s)=1\$

Then the Nyquist plot is this:

There are 2 RHP poles present and the plot circles the (-1,0) point 2 times, anti-clockwise. \$Z=N-P\$ where \$N=-2\$ and \$P=2\$ so \$Z=0\$ => Stable System.

And the unity step response  is this (for the closed loop):

It looks stable, but if I press on "more time", it looks pretty unstable:

So the Nyquist plot is disagreeing with the unity step response. What is happening?

The transfer function is theoretical in nature, it does not necessarily represent a real system's response. I have taken care to make sure that the unity step response is that of the closed loop transfer function (and not that of the open loop, which is clearly unstable). I used WolframAlpha for all my plots.


texts: Would there be a significant difference if a metal shield is connected or not to the circuit ground?

texts:
Assuming that we have a sensitive electronics that is battery powered, which consist of a very sensitive 32 bit adc is reading a voltage from a chemical reaction and you place it inside a chunky 1 inch thick metal shielding (I could not think of a better example). The circuit inside is built to the best ideal configuration. Would connecting the metal shield to the circuit's ground inside affect the result or its best to leave the circuit inside floating to best protected from whatever stray interference.
What if this time the the electronics inside is powered from mains voltage via a wall power adaptor. The metal shielding is still there but this time from the wall power adaptor 2 wires is passed through to the thick metal shielding to give power to the circuit inside. Would connecting the metal shielding to ground now a must?


texts: How can I add white noise to a low-noise 2 Mhz sine signal from the signal generator?

texts:
I want to add a defined level of noise to a low-noise/exact signal generator which produces around 2 Mhz.
I heard Zener diodes should be good for that job.
But how can I get a defined level of noise onto my signal?


texts: A friend recently gave me this board that he had never used and didn't know anything about it. It had a USB to serial cable plugged into it with the driver software that I installed and it had a servo motor included. Question 1- is this a micro controller (i know it has something to do with servo motors but is it programmable?)? Question 2- if this is programmable how can i program it (what language, what tools) and if so can i UNPLUG it from the computer and still have it run (flash memory or something like that) And last, does this have inputs (digital, analog) so I can perform actions based on the inputs? i notice some pins in the middle that don't look like they are for servos.


texts: Norton Equivalent Circuit of Ideal Independent Voltage source

texts:
For some purpose I need to derive the equivalent Norton circuit of an ideal independent voltage source. I found that it is impossible to do it. I describe the way I found it below and need comments, verifications, corrections, etc.

The ideal independent voltage source is represented as a Thevenin circuit.

Thevenin open-circuit voltage: For A and B being unconnected, it can easily be seen that the Thevenin open-circuit voltage, i.e. the voltage of A with respect to B, \${^{TH}}V_{OC}\$, is equal to the voltage of the voltage source.\begin{align*}{^{TH}V}_{OC}&=V\end{align*}

Thevenin short-circuit current: For A and B being short-circuited, there is no impedance in the circuit, so the Thevenin short-circuit current, i.e. the current from A to B, \${^{TH}}I_{SC}\$,  is equal to infinity,\begin{align*}{^{TH}}I_{SC}&=\frac{V}{0}\cr&=\infty\end{align*}

Constructing its equivalent Norton circuit. The value of the of the ideal independent current source of a Norton circuit is the short-circuit current of its Thevenin counterpart,\begin{align*}I&={^{TH}}I_{SC}\cr&=\infty\end{align*}
Its impedance is the impedance of its Thevenin counterpart, \$R=0\$.

Norton open-circuit voltage: Even no connection between A and B, the parallel impedance is zero then the voltage of A with respect to B, the Norton open-circuit voltage, \${^{NO}}V_{OC}\$, is a short-circuit voltage then it is zero,\begin{align*}{^{NO}}V_{OC}&=0\end{align*}

Norton short-circuit current: For A and B being short-circuited, the current from A to B, the Norton short-circuit current, \${^{NO}}I_{SC}\$, can easily be seen from the circuit that is equal to the current of the current source,\begin{align*}{^{NO}}I_{SC}&=I\cr&=\infty\end{align*}

The Thevenin open-circuit voltage (which represents the ideal independent voltage source), \${^{TH}}V_{OC}=V\$, is different from the Norton open-circuit voltage, \${^{NO}}V_{OC}=0\$. So an ideal independent voltage source has no equivalent Norton circuit. I can not convert an ideal independent voltage source to a Norton circuit.


texts:
I am making a project where i need to control the speed of a DC 12v motor (10A) and i am confused about which kind of transistor to use in this scenario.
so i need your help to suggest me transistor which can handle 10A without heatsink and support PWM with arduino.


texts: Toggle OC1A, OC1B and OC1C using timer in CTC mode

texts:
Most AVR microcontrollers got three dedicated pins for each timer (for example, OC1A, OC1B, and OC1C) that can be toggled automatically when the counter reaches the so called top value in the corresponding three registers (OCR1A, OCR1B, and OCR1C).

I'm not sure how can those three dedicated pins/registers operate in CTC mode for different independent top values, and this is what I want to accomplish. I want to toggle OC1A, OC1B and OC1C (though "output compare", not through interrupt or something like that) at different intervals (to see the having three dedicated registers and pins).

Let's say I want to program the AVR timer to toggle the pins OC1A, OC1B and OC1C at different intervals (for example 1 second, half second, quarter a second), but it does not work as I expect. I set compare match register A and B and C with the three different value, having the greatest value on A (I also tried having it on C).

Only OC1A is toggled at the needed frequency.

To me it seems that if they made only OC1A top clears the counter then it would be possible to have the three pins work at different three independent values. Is this right?

Here is the segment I put in my Arduino Lenoardo's (based on ATmega32U4) setup. I left loop() empty.

  // Initialize timer1
  noInterrupts();           // Disable all interrupts
  TCCR1A = 0;
  TCCR1B = 0;
  TCCR1C = 0;
  TCNT1  = 0;

  OCR1A = 62500;            // Compare match register 16 MHz/256/1 Hz
  OCR1B = 31250;            // Compare match register 16 MHz/256/2 Hz
  OCR1C = 15625;            // compare match register 16 MHz/256/4 Hz

  // Toggle OC1A, OC1B and OC1C => (on Lenoardo) PB5, PB6 and PB7 => digital 9, 10, 11
  // TCCR1A = 0b01010100;
  TCCR1A |= (1 << COM1C0) | (1 << COM1B0) | (1 << COM1A0);
  // TCCR1B = 0b1100
  TCCR1B |= (1 << WGM12);   // CTC mode
  TCCR1B |= (1 << CS12);    // 256 prescaler

  interrupts();             // Enable all interrupts


texts: How to calculate the power of equipments connected to a voltage regulator?

texts:
I have a voltage regulator just like this, I do not know how to use it, so, I wonder if there is a way to calculate the capacity of equipments which I connect to it so that they don't exceed its capacity?

Also, I wanted to know what would happen if the equipments connected was more than its capacity?

And more important is it possible to connect more than one equipment by using a multi-socket?


texts:
I'm using ICL3232EIV-16Z-T in one of my projects for UART communication. As per the datasheet, the max speed is 500Kbps. But I've tested this IC for baud rate up to 921600 and there is no data loss. Also, I've tested with SN75C3232PWR which offers the max speed 1Mbps. Also, it is tested at 921600 baud rate and there is no data loss observed.

In both cases, the time taken remains the same.

Kindly suggest which is the better IC among these two and What is the advantage over the other?


texts:
I am running a transient model of a Type-E PFN circuit (probably not an important detail) and my processing time jumps from about 1 minute for one DC source voltage to roughly 475 years for another.

My circuit basically charges up a series of capacitors and switches the voltage into a resistive load at 1us.

Here is the jist of the circuit that I am working with:

When I set the voltage to 100k the model runs with no issue as seen here:

However when I set the charge voltage to 80kV the model hangs up at ~2ps and the processing time drops to something like 1 fs/s wich will never finish.

Does anyone have any idea why the charge voltage would effect the model?  It works for 30k, 50k, 100k and scaled values (i.e. 30V, 50V, 100V), but does not work for 70k, 80k, etc.

THANKS!

edit:
Here is another view of my circuit (it is too large to show the whole thing):

It consists of 4 stacked versions of the first picture to multiply the voltage.  I am relying on the DC operating solution to generate a floating voltage on my capacitors in the PFN (so I can't use uic I think). I found that I cannot use .ic for these voltages because they will all be ground referenced and the model wont work.


texts: Best way to locate a 4k stray resistance between 2 bus lines in a PCB?

texts:
I have a faulty PCB which is showing an unexpectedly low resistance between certain pairs of bus address lines.  I'm measuring a little over 4k ohms between these bus lines, but according to the schematic I should be seeing 44k.

I'd like to try to isolate the fault down to a particular IC or area of the PCB.  None of the ICs are socketed, so I'd like to have some idea of where the fault is before I start lifting pins.

I've heard of using a milliohm meter to find shorts in PCBs, measuring resistance between various points and looking for a minimum.  But unfortunately as I mentioned above, this fault is about 4k.  I'd be looking for a tens of milliohms change in R relative to 4k (roughly 1 part in 100000), and I don't have a high-enough resolution meter to detect that (all I have is a 3 1/2 digit meter).

What would be the most promising direction to take for isolating a fault such as this?  I'm thinking something along the lines of a wheatstone bridge + instrumentation amp, but maybe there's a better technique?


texts: How to drive a HFBR-1541 optical transmitter?

texts:
I want to drive a HFBR-1541 optical transmitter (see page 7; 60mA output current), and I want the driver to have extended operating temperature range (at least starting from -20 degrees Celsius).

The driver recommended in the datasheet, SN75451, does not meet the extended operating temperature range requirement and its corresponding version, SN55451, is not produced any more.

Can somebody suggest a circuit or schematic to drive this transmitter and meet the operating temperature range requirement.


texts: Is my zener diode labeled wrong, or am i seeing a strange failure mode?

texts:
I'm experimenting with a power supply circuit to bring 24VAC down to 5VDC. I have an L7805CV, but rectified (a bridge) and smoothed (a 33μF electrolytic), the input is still \$40V_{peak}\$, which is more than the max input voltage the regulator can take. Looking at the regulator's datasheet, it suggests the following "High Input Voltage Circuit", which notes "\$V_{in} = V_i - (V_Z + V_{BE})\$", but doesn't offer any guidance on Q1 or R1:

simulate this circuit – Schematic created using CircuitLab

I have a 27V (½W) zener (NTE 1N5033A), but either

i'm misunderstanding something,
my diode is mislabeled, or
i've damaged it,

because when i orient it as indicated, with the striped cathode end toward \$V_i\$, the voltage at \$V_{in}\$ is the full 40V minus approx. 2 diode-drops and the voltage across the zener is only about 0.7V. (Note that at this point, i have a 33k resistor to ground in place of the 7805 so i don't damage it until i get the limiter right.)

My multimeter's diode setting seems to indicate that the markings on the diode are backward. That is, it behaves opposite the way my other diodes do.

If i install it the other way around, the voltage at \$V_{in}\$ is only about 12V, which is approximately 40V - 27V - a reasonable \$V_{BE}\$.

It is possible that it's really just marked wrong? I made some mistakes wiring it up the first time and something let out a wisp of smoke before i cut the power, but i wasn't able to figure out which component, and everything i've been able to test measures okay. Could overcurrent have somehow magically reversed this diode?

I added some bits to make it simulate better: https://www.circuitlab.com/circuit/9b6y3x/weird-zener-limited-7805/

Here's a picture of the diode in situ, along with its packaging:

Here's a picture of a 7.5V zener from the same manufacturer with the same diagram on the back of the package:

The second Zener's polarity is what you'd expect; only the 27V zener is weird.


texts: Why does FPGA PCI Express Tx output have on-chip termination of 100 Ohm?

texts:
The Intel Cyclone IV FPGA supports PCI Express (PCIe) generation 1, and the IO standard for the Tx output is PCML at 1.5 V.
The Cyclone IV Device Handbook volume 2 page 1-13 describes that the Tx output supports 100 Ohm termination.  The related figure is this:

I understand that termination is often used at the receiver end to avoid reflections.
Why is there termination at the transmitter end for the PCIe PCML IO standard?


texts: Primary voltage drop in current transformer

texts:
Following on from this question, Current transformer energy harvesting from a mid-voltage line, I've never seen any mention of primary voltage drop in a current transformer circuit.

simulate this circuit – Schematic created using CircuitLab
Figure 1. A typical CT application using a 5 A meter to measure the current through a load.
Since the burden resistance of the ammeter is reflected back onto the primary side by the inverse turns ratio squared there has to be a voltage drop on the primary side.
This raises a few questions.

Where does the voltage drop occur? Does it fade in and out with a peak right inside the CT?
Would we see a larger reading on VM2 compared with VM1 (10 mm and 5 mm from the plane of the CT, for example)?
What is the relationship with the dimensions of the CT?
What is the effect of the angle between the axis of the CT and that of the cable. (CT


texts: How do I make a good electrical connection with wire I can't solder?

texts:
A few days ago my DSL connection kept tripping. After abusing the service provider for a few days, I looked at the stats and noticed signal attenuation was sky high and attainable rate was very low(<1000 Kbps). I checked the wires and found that one of the wires going into the ADSL splitter was hanging on by a few strands and was about to break.

The problem

The main source wire has solid cores, and is joined(twisted together) to a thin stranded wire which has a RJ11 jack to the splitter. I wanted to improve upon this by soldering but later found out that the soldering iron's heat burns off the strands in the thin wire. How do I connect it reliably to the solid cored wire?

I'd prefer if I get to connect the two wires together directly rather than by a jack or something similar(since introducing jacks could cause signal loss).

Edit: My source wire(untwisted) looks similar to this:

The RJ11 cable is something similar to headphone wire - it has 4 non-enameled ultra-thin wires in each colored insulation. It has a red and a green insulation in there(so 4 strands for red, 4 for green). The thin wires also make it a nightmare to strip the insulation off - the wires break too easily.

Here's an actual image of the source cable:

The top and bottom wires are just copper solid-core wires and the printed part is sheath. An electrician came yesterday and 'fixed' the thing. It stopped the tripping problem but I want something more elegant than this.

The other end of the red 'fixer' goes to the splitter. I don't think it'd do much good by opening it up - unless I'd just solder the source wire under the ADSL jack on the splitter's PCB.


texts:
In a cmos driver what controls the amount of current it can source or sink?  Is it the combined RDS on of the internal FETs?   When you try to pull a line low I guess there's voltage stored in the capacitance of the trace and the current from that flows through the bottom FET and it's on resistance to gnd?

Second question how do they do slew rate control in a cmos I/O buffer is there a short burst of current from a one shot or something like that?

I have a clock coming out of an FPGA at 50Mhz, and for some reason it doesn't get to GND, maybe a few hundred mV above it.  It does flatten out though.   So I was thinking maybe it doesn't have enough pull to get it down to GND before the start of the next cycle.  That made me wonder how a real CMOS I/O pad actually works.

I should add the trace is very long maybe about a foot, but impedance controlled to 50Ohm.


texts:
I have a task to solve in electrodynamics, I have really no clue how to solve. Would be very thankful if someone could help!
There is a live conductor loop L, which is situated in a magnetic field B.
Force of the conductor loop:

Magnetic field is homogeneous and shows in z-direction, B = B*e_z
Now I want to show that x-component of force is given as

and show value of F_y and  F_z.
How could force be calculated with Stokes´formula ?
Tanks in advance!


texts: How to interface the HX711 Weight Scale ADC with a microcontroller?

texts:
In my project I need to interface HX711 24 bit External ADC to STM32L100RC6 MCU
How can I do this ?


texts: switch small DC voltage with 90v. 30hz AC signal

texts:
I need to momentarily activate an approx. 50mA @ 24V DC load, using a 90V, 30hz AC signal line. Whatever method is used, it needs to have the smallest current draw from the signal line possible.

I am not sure if it is possible to turn on a transistor or solid state relay with AC, and I cannot seem to find much on the web.


texts: Trouble changing an optocoupler without changing circuit functionality.

texts:
As a part of a circuit an optocoupler was driving the gate of a MOSFET as follows:

Now I need to change the above opto with a 4N46 darlington one.

I'm not familiar with these much and having difficulty to replace it.
Here is the functional diagram of the opto-darlington I need to use:

How should this be connected as an interface so that it would have the same functionality with previous one?


texts: Power demand beyond maximum deliverable power

texts:
simulate this circuit – Schematic created using CircuitLab

We got an elementary dc power system as shown in the figure. The maximum transferable power P_max is 0.5W. Is it possible to vary the load R2 to achieve an assumed maximum power demand of 0.55W. If possible, how? If not why do we get voltage instability in power system?


texts: Linux/open-source program to open (OrCAD) schematics for BeagleBone?

texts:
I'm trying to open BeagleBone's schematics for an OrCAD file in Linux, but EAGLE seems unable to do the job. What are some options?

Original Orcad ZIP file: http://beagleboard.org/static/beaglebone/a3/Docs/Hardware/BONE_SCH.zip

Which extracts to:

BEAGLEBONE_REV A3A.DSN


texts:
So, I'd got a pair of cheap earphones that broken after a while (Left ear is no more receiving sound). I defined the problem: it's some broken wires after the button. The thing is that I cannot figure out what goes where.

As you can see in the picture, there are red, blue, two copper (my first guess is that they're ground) wires. Short notice: the whole picture is of the wire that goes to the left ear.

I have connected blue with blue. When I touch the microphone with one of the copper wires, my smartphone switches to the previous song (or lets music go to the left ear as well). I have tried connecting the three copper wires (one from one end, two from another) together. Music seems to be playing fine. So, my questions to those who already did it at some point: which wires to connect and where to do it right?


texts: Using FPGA specific hardware components when writing RTL

texts:
I have heard at times that someone writing a digital circuit design may want to use actual primitives present on the FPGA directly in the design. This means including the library which contains those primitive definitions into our design and then instantiating them in it. Examples could be a memory block, DSP block, logic array block e.t.c. directly instantiated and connected into our design.

I have not done this yet and don't see when doing so is important. Why would someone want to do so? Does it effect the way we do simulation of the design?

We always like to write our circuit from higher level of abstraction, therefore, instantiating such blocks does not make much sense to me.


texts: Why is earth pin absent in phone chargers plugs but present in laptop ac plugs?

texts:
Both mobile phones and laptop get dc voltage from  ac source for charging.These chargers have transformer for isolation and rectifier + filter if i am not wrong.I guess the amount of output dc and charging current may vary.

Why do modern mobile chargers use only 2pin plug or 3pin with dummy earth pin? But
Laptop chargers use 3pin plugs with earth pin?

1.

2.


texts: C0G vs polypropylene capacitors in signal filtering

texts:
Can anybody give me a comprehensive pros and cons list or explanation about the differences between C0G (NP0) ceramic and polypropylene capacitors?

I would like to use them in signal filtering and amplification (biomedical measurements.)


texts: Stm32L4 microcontroller doesn't wakeup from shutdown

texts:
I'm using Mbed coding on STM32L432KC nucleo board. I'm copying the code from the STM32 cube code examples to put my MCU in shutdown. See here.

The code compiles fine. I just added an LED blink inside the while (1) loop after the shutdown command to see if the MCU has wakeup up but it never blinks.

Any idea what I'm doing wrong?


texts:
I have a vintage megawattmeter. It is able to indicate values from -1 to 7 MW. I wish to be able to provoke it to display any value I want, preferably without actually generating megawatts of power.

If I understand this correctly, it means that both power and voltage are transformed down, from max. 1000A to max. 5A, and max. 6000V to max. 110V. The first symbol seems to indicated that two phases out of three are used for the measurement?

There are 7 Connections on the meter, numbered from 1 to 7. If I understand the diagram correctly, this means that connection should be like this:

phase 1 current in (k) - low voltage
phase 1 voltage - low current
phase 1 current out (l) - low voltage
neutral
phase 2 current in (k) - low voltage
phase 2 voltage - low current
phase 2 current out (l) - low voltage

What would be a good way to control this meter to display my desired values?

Update: added some additional pictures and descriptions

I was able to open up the instrument. As far as I can judge, connections 1 and 3 go to one big coil, 5 and 7 go to the other big coil. Connection 4 goes to the chassis of the big coil that has the needle. Connections 2 and 6 go to each of the two smaller coils, and from each of the other ends of those coils, there are wires to the needle mount and the moving element in the other big coil. See pictures below. I'm still not sure how I Shield proceeed to get it to actually show the values I want.

I tried to measure L and R. Wasn't able to find C.

Across 1-3 R 0.3 ohm L 0.5 H
Across 5-7 R 0.3 ohm L 0.4 H
Across 2-6 R 1878 ohm L -4 H
Across 2-4 R 225 ohm


texts:
I have multiple buck converters, model XL4005 (datasheet  ), fed from a 12V battery source to several devices i.e. My motors (require 12V), Arduino (requires 5V) and Transmitter module (require 3.3V).

Do I connect the buck converters in parallel and distribute the voltages to respective devices? Is it safe to do so? I saw some uses diode to even out the supply current but I'm not quite sure how, link: Is it ok to connect the output of buck regulator in parallel?

My specs:

Battery 3S LiPo datasheet  = https://www.robotedu.my/index.php?route=product/product&product_id=448&search=battery+5200
motor BMA2826-4 1100 175g Ф35mm*54mm Ф5.0mm 3-5LiPo 25-37Apk 2.9A max

datasheet  =    qty = 2pc
max load = 25-37 Amp-seconds surge , 2.9 peak amp

means 25A *2 for my 3S pack with 2 motors

transmitter: 15mA  @ 3.3V, 3.8V max.


texts: calculate force on object between capacitor plates without knowledge of area

texts:
I am given an exercise with a very simple circuit

simulate this circuit – Schematic created using CircuitLab
I am asked to find the voltage of the voltage-source V1 such that an object with a given charge \$Q_{obj}\$ and mass \$m\$ of negligible volume lying between the plates of the capacitor C1 is hovering.
Equating a force with the gravitational acceleration and the mass of said object is no problem, I can figure that out, this is not what this question is about.
To find what force is acting on the object, I figured I want to find the electric field \$E\$ between the plates of the capacitor.
Now in all resources I could find, the area of the capacitor-plates is relevant for finding the electric field. However I am not given any area, just the distance between the plates \$d\$ is given. I think one usually assumes an infinite area in such case, but:
$$ \sigma = \frac{Q_{cap}}{A} $$
and
$$ E = \frac{\sigma}{\varepsilon} $$
thus in this case there should be no electric field, and hence no force acting on my object?!
How can I find the electric field between the plates of a parallel-plate-capacitor from just the voltage \$V\$ and the distance between the plates \$d\$, without the area \$A\$?


texts:
For a project, I need a 500mV reference.

Some requirements:

Relatively low cost.
Small size. Preferably surface mount.
Supply from 4.8V to 25V.
Accuracy ±5% or better
Stable over voltage (that is, it doesn't change that much with a different supply.)

I could use a diode drop but it does not satisfy condition 5, being stable over voltage.

Any suggestions appreciated!


texts: Current, Voltage, and Power Sensing for 115 V AC Circuits

texts:
I am trying to sense voltage, current, and power with an Arduino (Due) for monitoring and diagnostic applications. To get reasonably good input (better than Kill-A-Watt), I have designed an AC sensing front-end for the Arduino. As this is my first design, I ask the community to have a look and to tell me if the whole thing makes any sense and if it would work. If the whole thing makes sense and works, I will put it on my blog so other people can use the idea.

So here is how the attached schematic works:

For voltage. TR1 isolates the device from AC and decreases voltage to 6.3 V RMS. This is divided by R7 and R8 and the signal is buffered by IC2A, shifted by R2 and R1 and fed to the Sample and Hold amplifier SMP04, and then to the ADC.
For current, I use the LEM LTSR15-NP Hall effect transducer. Signal is again divided (maybe there is no need), buffered, and shifted and send to the S&H IC.
For power I use the analog multiplier AD835 whose output goes to the S&H IC.

The S&H signal is going to be generated by the Arduino.

Version 2: Thanks for solving my bugs. Here is my second attempt:

Version 3: In version 2 I fixed the current handling as taught and then did something stupid with the voltage signal processing circuit. This is now version 3 where I have followed the advice of Techdude:


texts: I'm building a load bank for testing high power lead acid batteries, and expect to pass up to 800 amps at 12 VDC. I could do it with contactors but would like to use an SCR with a pot and allow the current to be ramped up with the pot. Any thoughts?


texts: How to Improve my Computer Architecutre and Design skills?

texts:
Though my undergraduation was in Computer Science but I like to believe that I am more of an embedded systems enthusiast and I am comfortable in reading datasheets and timing diagrams. But this was before my Master’s course- computer architecture and design midterm, it was quite evident from my attempts that I was not clear with the basics.
In hindsight, my attempts in the midterm was basically laughable. E.g. I was trying to design a 4 bit counter without actually creating a truth table. I also sent a 8 bit data to a 4X16 bit SRAM using SPI.
Since then,  I am doubting my concepts in this subject and want to improve.

So basically, my question to the community is- how can I better myself in the design and computer architecture(low level) skills.

I really want to improve but I dont know where to start.


texts: How to crimp a ferrules(end sleeve)without a crimper?

texts:
Hi.

I know that the best way and the safe method to crimp those uninsulated ferrules is to use the appropriate crimper.
But,since i need to crimp only 3-4 wires,buying a special crimper only for that is not economic.
Which other method can i use in order that the crimp of those uninsulated end sleeve will be good enough?

Thanks.


texts: Mica Insulator for TO-220 Grounded Heat Sink

texts: If I have a three terminal TO-220 voltage regulator where the center terminal and heat sink are connected ground terminals, is there any reason not to mount the heat sink directly to an aluminum chassis (with a bit of thermal grease)? I have a device that has an L78S12CV 12 volt regulator mounted to a finned heatsink, which itself is mounted to the chassis. Between the device and the heatsink there is a mica insulator, but the bolt holding the regulator to the heatsink/chassis is not insulated with a nylon washer. Is there any benefit to using the insulator in this situation?


texts: Question about ADC prescaler register in ATMEGA32A

texts: As you see in datasheet of Atmega32A, it says that the bits ADPS of register ADCSRA are controlling the Prescaler of the ADC clock by dividing the frequency of external crystal on some division factor, what if I am depending on the internal oscillator and don't have an external crystal, do these bits still work?!


texts: How to use Arduino board to automate testing

texts:
ok here goes,
Iam trying to build a device to test nurse call room controllers, these are basically 8 port boards with rs485 linking (have software for this,
what i need to do is test these, to do this i need to close a contact (call) for 1 second then 5 seconds later i can cancel that call by closing another contact to do this i need to automate 16 switchable outputs,
1 to activate it and another to cancel it

i was hoping an Arduino USB Board might be able to handle this?

i used to judt play with 555ic and 4017 ICs untill i got what i needed but i thought i would move into this century and make myself learn something new. .


texts: Can't I make 12V source to feed 12V motor?

texts:
I have a system which includes a Raspberry Pi, 2 a L298N module, 12V Battery source(8x1.5V AA) and a motor (a "PMDC Spur Gear Motor/KGA25RP")

When I connect everything right and run a simple program, only thing I see is a very low buzzing sound from motor while program running. Is my battery too low to move motor?

The code :

import RPi.GPIO as GPIO
from time import sleep

GPIO.setmode(GPIO.BOARD)

Motor1A = 38
Motor1B = 40
Motor1E = 7

GPIO.setup(Motor1A,GPIO.OUT)
GPIO.setup(Motor1B,GPIO.OUT)
GPIO.setup(Motor1E,GPIO.OUT)

print "Going forwards"
GPIO.output(Motor1A,GPIO.HIGH)
GPIO.output(Motor1B,GPIO.LOW)
GPIO.output(Motor1E,GPIO.HIGH)

sleep(2)

print "Going backwards"
GPIO.output(Motor1A,GPIO.LOW)
GPIO.output(Motor1B,GPIO.HIGH)
GPIO.output(Motor1E,GPIO.HIGH)

sleep(2)

print "Now stop"
GPIO.output(Motor1E,GPIO.LOW)

GPIO.cleanup()

Photos :
imgur.com/ujjtbIH,Db3ingN,gXR3vjL

I used Raspberry pi's 7(motor 2 enable),38(IN4),40(IN3)pins.

keytosmart.com/wp-content/uploads/2014/07/B_Diagram_large.png (Can't link more than 2 links.)


texts: How should entites and architectures in VHDL be commented?

texts:
How should an entity and an architecture be commented in VHDL to best be used with Doxygen?

Im trying to use Doxygen to generate useful documentation for my VHDL, but im not sure of the best way to comment what where.

Should entity be commented to describe every signal, their size, their function, their type? Or as a black box?
Should architecture be commented as a black box? Something going in, something coming out? Or should each (mentionable) line be summed up?
Should the architecture and entity have the same description?
How about 3. if I have several architectures using the same entity?

For all I can see doxygen ignores comments inside architectures so for 2. this should possibly be taken into account?


texts: Emitter Follower LED Circuit - LED in Collector, Resistor in Emitter

texts:
I have seen some examples of using an emitter follower circuit with an NPN transistor to light an LED.  In those examples, it's mentioned the collector voltage must be equal-to or higher than the base voltage.  What happens when the voltage feeding the collector side is the same as the base voltage, but the collector has the led on it?

In the circuit below, the INPUT would be driven by the same +5vdc used at the collector.  The resistor would be a low value (110-180ohm).  Forward voltage drop of the LED 2.8v.  No resistor on the NPN base.  Seems in doing this the voltage at the collector of the NPN would be 5v-2.8v = 2.2v due to voltage dropped across the LED.  So the collector voltage would be less than the base voltage?

Can this type of circuit work reliably?  What are the consequences of the voltage at the collector being less than the voltage at the base of the NPN?

I have a project that involves modification of an existing circuit board.  The led is fixed on the collector side.  The original circuit had the NPN in an emitter-follower setup -- with a driver/decoder directly driving the base of the NPN (ie. no resistor).  I am trying to preserver the emitter-follower setup to avoid having to hack the board to add a resistor on the base (if I changed to a common emitter configuration).  With making modifications as in the drawing, the circuit works on the modified PCB.  The LED lights fine.  Yet when I simulate on a breadboard I'm unable to light an led by driving the base directly with +5v.  I have to add a 10k resistor on the INPUT at the breadboard to light the LED.  Just trying to understand why this is and whether what is WORKING (for the modified PCB) is a reliable-enough circuit or a fluke?


texts:
I'm working with an embedded cell modem that will be living on a battery, hopefully for a long period.  It only wakes up and sends data occasionally.  To that end, my plan is to cut power to it when it's not needed to conserve power.  However, I've noticed that if I put a MOSFET-based switch on the power supply to the modem, that seems to successfully shut it down, but there ends up being significant current leakage on the DIN and DOUT pins of the modem (which are connected to pins on the processor, of course).

I'm hoping to add something so that I can send a high signal from a third pin of my processor, which would then allow signals to pass between the processor and the DIN and DOUT pins of the modem, but if hold that pin low, it will isolate DIN and DOUT so that no current can flow.  Any suggestions?


texts:
Wanting to know if the contacts in switch sw1 spark (see circuit diagram below), I did a simple test and found that there are no sparks even with high amperage.
I am unable to explain why this is so? Also, would it make a difference if the switch were to toggle at frequency as there will be rapid current reversal in wire w1, notwithstanding that I appreciate the fact that there is not inductive load?
I appreciate that wire w1 sees no potential difference between its ends.  I am intrigued, however, by the fact that as I vary the effective conductor area either side of sw1, (therefore changing the resistance somewhat) there seems to be no current flow in w1. I have difficulty in grasping things in a visual analogue.
Many thanks.


texts: How to distinguish between GPIO interrupts from the same interrupt handler?

texts:
I'm trying to interface a few modules to my STM32L476 board for which
I need to enable two GPIO interrupts from the same port (portA, pin 5 and portA, pin 6), but the interrupt handler for these pins are handled by an external line common for pins 5 to 9 (EXTI9_5_IRQHandler).

I need to do a different task on both these interrupts, but how would I know which interrupt has occurred as both are handled by same handler?
Are there any flags that I could check to know this?


texts: Find the gain \$K\$ at a point of given rootlocus?

texts:
From the given information i can write the transfer function as

$$G(s)=\frac{384}{s(s+4)(s+8)}$$
now get the value of \$K\$ at \$s=-1.5+j1.5\$ which is in root locus the generalised TF can be written as
$$G(s)=\frac{K}{s(s+4)(s+8)}$$
as the point is in the root locus the magnitude condition should satisfy that is

$$|G(S)|=1$$

from this
\$K=|s(s+4)(s+8)|=|(-1.5+j1.5)(2.5+j1.5)(6.5+j1.5)|=41.25\$

that is option \$(C)\$

But the correct answer given as option \$(D)\$.also its a examination question so i am confused.

is there any mistake i am doing?


texts:
Trying to fix a board that had a SMD inductor. it was labeled L1 on the silk and there was no marking on the part, and I have no schematics. ...or there may have been markings, but someone tried to fix the board before me and plastered the thing on solder. no way I can salvage that part... pic included at the for laughs. (the only part I could read the labeling was R3. probably because it is the less dense than solder so it floated :)

[L1 is right next to C6 there on the right. under that unsightly blob of solder.]

It is used on V+ from the broken USB connector, and then goes to those Resistors/Caps on the right side of the picture and then to the ICs.

I'm going to solder wires and trhu holes compoenents to substitute the damaged ones (because I have nothing SMD here)

Can I just bypass that if I use a USB cable with a ferrite core? ... I confess I'm not really sure what a SMD inductor does there. I always assumed USB had a standard frequency on the power line. is that not the case?

Edit: found the schematics for the USB chip this board uses. The inductor is the one marked L1 on the evaluation board. http://www.nxp.com/documents/user_manual/D12PCKitMan.pdf
there is not spec there. BOM just says "ferrite bead"


texts: Why does the original Nintendo take 9V AC instead of 9V DC?

texts: i have found an old Nintendo NES 9V wall adapter which is in fact not an AC DC adapter because it's an AC AC adapter. It's the first time i see an AC adapter that ouputs alternating current, Why did Nintendo run with that?


texts:
Why is there a phase difference between resistor and capacitor? I am looking for the conceptual reason behind this.
What does a phase difference of \$\pi/2\$ show conceptually? According to me, the one with positive phase difference would reach to its peak value earlier than the another, but how do we come to know the time difference between the two quantities to reach at its peak? What's the reason that there is a difference in reaching at its peak value?
Please illustrate in as much detail as possible.


texts: Getting higher accuracy in measuring AC voltage

texts:
I want to measure AC voltage to build an automatic voltage regulator.

First I use a transformer and this circuit to convert it to a DC voltage. Then I use an ADC to measure the DC voltage.

How can I get higher accuracy?

Is this circuit working fine in terms of practical design?


texts: I have a small, dead power supply for a camera battery charger (cheap replacement, no brand name). I opened it up and discovered that one of the MOSFETs is burned out. The datasheet (in chinese) is at http://pdf.peidan.cn/BCB/cs1n60f.pdf . I'd like to try and replace it, perhaps with something with a better heatsink. What are the key specs that I need to look out for, and which specs is it ok to improve?


texts: Understanding op-amp Schmitt trigger circuit

texts:
This is a follow up to the question Replacing a tactile switch with an ultrasonic ranger.

TL;DR the circuit is meant to take a variable analog signal output that varies between 0V and 5V, and make it 0V for values < 100mV and 5V for values >= 100mV

I built (breadboarded) the circuit referenced there, using an LT1637:

I kept the R3, R4 and R5 values as given, and set R1 to 220\$\Omega\$ and R2 to 10k\$\Omega\$. The analog input of my ultrasonic ranger is plugged into the 'input' line, and I've measured that without this in place, the ranger produces the voltage I expect on the analog output - around 68mV when something is 6" or closer, and more as the object moves away. The R1/R2 bridge sets my voltage threshold to 111mV.

What I'm seeing is that the input line goes from varying between 68mV and 5V (depending on distance to object in front of it) to between 2.0V and about 2.5V, depending on distance. This is very unexpected to me. The output of the op-amp stays fixed at VCC (which is 5.22V from a regulated wall-wart).

When I simulate a DC sweep on this circuit, plugging in appropriate values, I get the input behaving as expected, and the output pegged at VCC, regardless of input voltage.

So:

Is there a problem with this circuit?
And why is my ranger output line being biased and constrained to [2V, 2.5]?


texts: Calculate output of Transistor Common Emitter Amplifier

texts:
I have a waveform selector circuit shown above. The input signal is a 1 kHz alternating Square wave with a pk-pk value of 8.5V (above the x-axis).
The output waveforms in order starting from the left is a square wave, sawtooth wave, triangle wave and sine wave.

I want to calculate the theoretical voltage value of the sine wave (fourth switch from the left). I tried writing KVL equations but the circuit has a feedback capacitor on the collector terminal of the transistor. How do I calculate the output voltage?


texts: I already have the main solution and dosing solution tanks hooked up to each other, with solenoid valve S1 controlled by the liquid level switch through the DC power supply and DC/AC SSR (see image), and it works great. However, I would like to add a third tank and a second solenoid valve S2 so that solenoid S2 turns on/off whenever solenoid S1 turns on/off. Is there any reason that installing them in-series like this would be problematic? Would it be better to install them in-parallel? Or should I just install an additional liquid level switch, 24 VDC power supply, and SSR to control the new solenoid S2 separately?


texts:
I'm using ADAU1761 in my project and its I2S output is configured to stereo 48kHz/24bit, 8 bit padding, that gives 32bit per channel, 64 BCLK per frame. However I need 16kHz/16bits. 24b to 16b can be performed by simple bitshift (>> 8). I'm having trouble with 48kHz to 16kHz conversion. I'm beginner in audio processing but as far as I understood I can't just take every 3rd sample from original audio and save because of aliasing. There must be a low pass filter but I don't know what cutoff frequency and order it should have. Target platform is STM32L4 but it's easier to just code on PC and then port the code. Here is a snippet:

fread(&WAVE_header, sizeof(WAVE_header_t), 1, pFile); // read wave header,
uint16_t* ptr = malloc(WAVE_header.SubChunk2Size); // allocate memory for audio data
fread(ptr, WAVE_header.SubChunk2Size, 1, pFile); // read audio data
uint16_t *ptrOut = malloc(WAVE_header.SubChunk2Size/3); // after resampling
for(uint32_t i = 0; i < WAVE_header.SubChunk2Size/3; i+=5){ //
    ptrOut = ptr+i; // channel 1
    ptrOut = ptr + 1+i; // channel 2
    //filter here?
}
fwrite(ptrOut, WAVE_header.SubChunk2Size/3, 1, outFile);


texts: Help finding an appropriate driver for brushless motor

texts:
I have a 28mm wide dc motor in the device pictured here. I have removed the control board of the device and am looking to replace it with an external driver board with RC PWM inputs for control. The motor will remain stationary for the most part and turn forward or reverse at low RPM when it receives signal from the RC channel. The system is powered by a small 7.4V 300mAh lipo.

I am having trouble determining the proper driver board type for it. An ESC won't work because it's not designed for low RPM usage. Through many Google searches I've learned an H Bridge driver won't work.

The three inputs on the motor are labeled U V W on the original controller board (picture attached). I'm assuming this is a brushless motor with hall sensors to assist in the low RPM operation. I can't remove the motor and diassemble to check.

I'm asking for some insight into the proper method to drive this thing both forward and reverse at low RPM. Preferably a ready made board. Any ideas?


texts:
I am in the final stages of building a fully analog synthesizer. Instead of using +10V, GND and -10V, could I switch these voltages to +20V, +10V, and GND to save weight, bulk, and size of a power supply that has to generate -10V? Would a voltage change generally affect audio circuitry or affect output voltage and ruin other audio equipment?

simulate this circuit – Schematic created using CircuitLab

Basically, is it the relationship between voltages or amount of voltage in this case? And what's the best way to create +10V on the board, since the solution in the schematic most likely isn't very efficient?


texts: Can someone explain to me the difference between these two wiring configurations?

texts:
I am trying to connect a combined pressure transducer and temperature indicator to a DAQ system by Dewesoft and this sensor has two available wiring configurations available, 3 wire and 4 wire. I'm unable to understand the difference between these two according to its circuit diagram and what is the significance of each.

Which configuration would be more suitable if I want to reduce the number of output channels from the sensor to the DAQ, or will the number of outputs remain the same despite its configuration.

(Link to the sensor spec sheet: https://www.pmc1.com/Customer-Content/www/Products/Files/ATM.1st.T.705a.pdf)

This is similar to another question that I have previously asked, but in this question, I want to figure out how the wiring actually works. Thanks!


texts: I have a problem in my textbook "How many 256X8 Ram chips are needed to provide a memory capacity of 4096 bytes?".  I know that the answer is supposed to be 16, I'm just not sure why.  It seem like it should be 2 since it's 256X8 as opposed to 256 alone.  Basically, what I'm trying to say is (256x8)*2=4,096 instead of (256x8)*16 which equals 32,768.  Why is it 16?


texts: In integrated circuit manufacturing I came across the term "risk wafer" which seems to be different from a "normal" wafer. But I can't find any information online on what a risk wafer really is.


texts:
I recently did a proper EMC test on a PCB of mine. It failed the test, and seems to be radiating in the 300MHz - 1GHz region, with peaks every 50MHz, and little peaks on the 25MHz.

Looking at the near field, you can clearly see lots of 25MHz harmonics around:

The board contains a 25MHz crystal, which must be the source of the signal, but the question is, what on the board is radiating? What could the antenna be? Candidates I can think of are:

The ground plane acting as a centre-fed patch antenna. The board is 23mm x 47mm, which makes it quarter wavelength for about 1.6GHz!
The inductors in the power supplies. The board contains TPS84250 and EN5312  integrated inductor switching power supply ICs. Perhaps the 25MHz signal is finding its way back to the inductors in these ICs and using them as antennae.
The cable. Although adding ferrites onto the cable during the test didn't seem to make any difference, which leads me to believe it's something on the PCB itself.
Something else? I can't think what else is large enough to radiate at such low frequencies.

The Equipment Under Test consists of a pair of PCBs stacked together. The bottom one contains the 25MHz crystal and the chips that use it. The top one contains the power supply components.

Question for bonus points: How can it be that there are clearly lots of 25MHz harmonics around in the near field, but only 100MHz and 50MHz harmonics are detectable in the far field?


texts: Turning off op amp for low power application high side or low side

texts:
I have a design where I am using a LM324 to act as a buffer (unity gain impedence transformation amplifier) to feed the voltage from several high-impendence voltage dividers into my MCU's ADC pins.

The idea is that I can get away with super high impedences in the resistor dividers and buffer that voltage via transimpedence amplifier to achieve low power consumption.

I want to go a step further and be able to cut off power to the entire analog front end when I am not using it in order to really reduce power consumption.

My idea in this regard is to use a FET to control current flow to the voltage dividers and op amp.  Ideally, I would use a low-side FET (n-channel) so that I can use that FET to control current from both the resistor dividers and the op amps.

simulate this circuit – Schematic created using CircuitLab

I am worried about the ADC input pin of the MCU when M1 is not conducting.  When M1 is not conducting, the voltage on the non-inverting input of the LM324 is going to float up to 12V (because the voltage divider is no longer conducting significant current).  In fact, the whole op amp is floating in this scenario, since it's ground connection is not referenced to the ground connection of the MCU.

In my experimentation on a breadboard, the output pin of the LM324 never rises above 5.1 V when M1 is in cutoff mode.  Is this the expected behaviour?  Should I be worried about the op-amp output floating up to 12V or will it be "clamped" to the 5V rail (if that is indeed what is happening here)?

EDIT

I'm getting a lot of alternative suggestions (which don't get me wrong, I love to consider alternatives!), but not many answers to my question.

To be clear, my question is:

Could the output pin of the LM324 float up to 12V when M1 is in cutoff mode, and if so, how come it is not doing so in my testing?


texts: Supplying power to PCB with USB voltage (2.5V) regulator

texts: I am designing a normal PCB board. I want to put a USB voltage regulator to supply my PCB. I don't need to design the voltage regulator. I just want to add it to supply voltage in my PCB circuit. The output will always be 2.5V (not more than that). Which USB voltage regulator do you think will be good to add and is there any CAD model of that module so that I can add in my PCB design?


texts: Designing a voltage regulated power supply

texts:
I am trying to build up my own regulated power supply, as a way of getting confident with simple electronics and actual hand labour. I am an electrical engineering student, so this is why I am interested in the subject.

I started designing a power supply some weeks ago, following multiple datasheet components and the internet tutorials. This is what I've got for now:

I'd like to know from someone with enough experience, if the schematics are correct? Also, is there a simple way of adding a current regulator branch to the already done circuit, that is rather simple? (I've seen some online, but they use lots of active components and they do not seem to be worth investing time at the moment).

Finally, does anyone who is familiar with Proteus know why, when trying to simulate, it gives timesteps errors? Thanks!

Update:

After reading the suggestions so far, I decided to switch to a simpler 1A output. This is the result:

The input is 28V AC 1A. Are my potentiometers well placed? (I added resistors in parallel to achieve around 4.5k Ohms).


texts:
I understand the benefits of optocouplers. Always when I'm designing a microcontrolled motor control I isolate the mains from the MCU with those devices. On a few designs I did without the optical isolation I've had some malfunctions on MCU, sometimes it crashes or resets.

Now I'm designing a motor control based on MOSFET, specifically the IRF640N. The motor is the F 006 WM0 310 and it operates under normal circumstances and load at 1.5A. When I've first tried to control it, I've used a TBJ, but the motor presented a loud humming at low speeds. The MCU I'm using is a Atmega328p-pu and after did some research I found I can low its humming rising the PWM frequency. The frequency I've used before was near 500Hz and now will be almost 1kHz, then 1us of period. Due to its price and its availableness (most because of it, since in my town is very hard to find components) I've chose the 4N25 as optocoupler. Its datasheet specify 2us of fall/rise time, which is bigger than the period of PWM. Due to this, I suspect the raise of PWM speed will not reduct the noise of motor and maybe I should not use the optocoupler at all.

Is this a real problem? Since the design has to work on all the country and will be exposed to different mains with different noises, should I really use the optocoupler? May a filter correctly designed will prevent some MCU malfunctions in spite off isolate it from the motor voltage?

Finally, is there any guidelines for when or not to use an optocoupler based on the clock frequency of MCU, current drawn by load, PWM frequency or any other aspect?


texts: Why aren't antennas placed at the ceiling of a microwave oven

texts:
From what I have understand, microwave ovens work by emitting microwave electromagnetic waves from some antenna.   Please correct me if I'm wrong.
In my microwave oven I have seen some empty holes at the left side of and I assumed that from there the waves are emitted. That would explain why whenever I heat food inside a bowl and not a plate, the bowl ends up becoming really heated while the inside not so much due to attenuation.
Why aren't the wave emitters placed in the ceiling of the oven?


texts: Controlling capacitive touch panel on a stove

texts:
I own a stove which is controlled over a capacitive control panel. I would like to make a device which controls power output by checking the temperatur inside the pot: a thermostat.

First thing which came to my mind was a complex two axes apperature which points to the control element which should be driven and removes itself afterwards. This should work but then I discovered that you may drive the stove by capacitive load: I placed a coin on the control element to power the stove on, nothing happened. Then I touched it with my finger and it turned on. Then I touched it with a 10cm wire and it turned off. It seems my fingers were influencing the experiment. When holding the wire with a piece of plastic on the coin the stove does not switch!

The stove itself reacts to permanent capacitive load on any of the control elements with a self turn-off (security mechanism) which has to be avoided.

The Problem is that I am not smart enough to control the capacitive load. My last try so far was a small wire which did not switch the control and a capacitor and a transistor to temporarily enable the capacitive load. But whenever I connect a wire to the transistors base the stove already switched. My intention was to control the transistor with an Arduino Uno which finally should also house the thermistor.

simulate this circuit – Schematic created using CircuitLab

This did not do because whenether I connected a wire to the base of the transistor the stove already switched.

I also tried this solution which should relate to this question but it causes the same problem. This is my code:

void setup() {
  digitalWrite(2, LOW);
}

void loop() {
  pinMode(2, OUTPUT); // touch
  delay(100);

  pinMode(2, INPUT);  // no touch
  delay(2000);
}

So how can I control the capacitive load to control the stove with an Arduino board?

Edit: After further experimentation with the above solution altering a GPIO pin of the Arduino Uno to be output or input I could reliably perform 'touches'... on my smartphone. The stove ran into the same problem, after the first performed action the above mentioned security mechanism pops in and powers down the unit, so I don't know how to handle that yet. Maybe there is another sensor?


texts:
I am developing a power supply for a 24V 10A BLDC motor, which has to work with car and truck batteries (12V-24V). The real thing is that those batteries never have 12V nor 24V, instead, they could be above or below their respective value, so I am in the need of a SMPS.

I started looking for Flyback topology but after that I found that they aren't suitable for this amount of power. That's how I arrived to the buck-boost topology.

I found LTC7813 buck-boost IC which I liked pretty much, but reading the datasheet (link here), I cant find a parameter that leads to know how much output power it can handle. I know it is primarily limitated by the MOSFETs, inductances and discrete semiconductors, but I need to ensure that the LTC7813 can handle around 350W (240W + 110W for margin, because there can be load surges, for example in motor startup). Maybe someone with more experience than me can help me.

Thank you.


texts: Charging a 4.4v lithium polymer battery with 5v?

texts: Can anybody tell me how can i charge a 4.4v lithium poly. battery. I have a tp4056 charging circuit, but the problem is that it stops charging at 4.2v. I have searched on Ali but haven't found any 4.4 v charging module.This battery is from a MI power bank but its circuit got faulty so i am thinking of using it with a specialized circuit.


texts:
I'm working on a DC jack powered Ethernet design and I've downloaded many Ethernet Layout guidelines from many semi vendors with varying recommendations.  I've read app notes recommending almost every possible termination resistor position, for example.  Placing termination resistors at the PHY, at the Magnetics, the TX at the PHY and the RX at the magnetics, and visa versa.  The most popular seem to be at the PHY, and this seems to make the most sense.  Ethernet uses balanced differential pairs, which are typically terminated at the extremes to filter any common mode noise injected into the transmission lines, and the RX / TX traces on the board constitute part of the transmission line (these are being run at 100 ohm impedance to match CAT5 cable impedance).

The other controversy here is what to do with the ground plane.  If this wasn't a DC jack powered app my life would be easier.  Many app notes recommend no ground plane under the magnetics (which are built into the RJ45 connector in my case) to avoid coupling into the ground plane.  But... that is exactly what I want.  Better coupling into the ground plane then into the conformity testing antenna!  A ground plane under the jack will help close the metal enclosure around the rest of the connector.  I've read at least one example of anecdotal evidence on the net claiming better radiation performance with a solid ground plane in a DC jack application as opposed to a separate isolated Ethernet plane tied in with caps.  So... I think I'm going to keep a solid plane under the RJ45 jack.

Some papers also recommend no plane under the RX / TX pairs.  I can't make my mind up about this.  I want to avoid coupling any ground noise into the RX and TX pairs but my experience seems to be any ground plane splitting / opening is usually based on hocus pocus type thinking instead of sound physics.

Does anyone here have any experience or suggestions related to Ethernet layout, specifically with regard to the RX / TX termination resistor placement and whether or not to use a ground plane under the RJ45 connector (with magnetics) as well as under the TX / RX pairs?  Any suggestions greatly appreciated.


texts: How to test a half wave bridge with a multimeter

texts:
I found a box of LAS-8500P half wave bridge interface drivers in my attic.  How can I test them with a multimeter to see if they are any good?
Data sheet
https://datasheetspdf.com/pdf-file/531203/Semtech/LAS-8500P/1


texts: Burned out filament but the light bulb has small resistance

texts:
The light bulb shown below is from a Christmas tree light string. The string is made up of series connected light bulbs. However if one burns out, the other bulbs keep working. Taking out the bulb from its socket makes all the others in series with it to stop working.

The picture doesn't show it very clearly, but the filament is broken in two. However, when I used my multimeter to check the resistance across this bulb it showed me about 1.5 ohms which explains the behaviour (all the other series bulbs still lighting).

My question is: what is the working principle of this bulb? I guess is that they use a parallel resistor connected (see the winding wire inside bulb, left to the filament in the picture). But if this resistor is only 1.5 ohms, how does the bulb lights up? Assuming equal resistances, each light bulb gets about 7 V AC. Imagine how much current would draw that 1.5 ohms "resistor" alone...


texts: Multiple 74HC595 chained together won't light all LEDs

texts:
I'm new to Arduino - and electronics in general - and am having a frustrating problem with two serial-to-parallel 74HC595 chips trying to drive two 7-segment LED displays. The LEDs are both common cathode, and each LED input has its own 510 ohm resistor, connected up to an output of a 74HC595. If I unplug the common cathode from A, I see the correct display in B. If I unplug the common cathode from B, I see the correct display in A. But when both common cathodes are plugged in, B starts displaying rubbish (mostly it's just blank though) while A displays correctly. It's like there's not enough power to go around. I'm using the 5V power output, because that's what the 74HC595 chips need (actually it can be between 2V and 6) and I don't want to start frying chips.

If anyone can point out what I'm doing wrong (or what I could potentially try to get it working) that would be great. I am working on a hobby project where I was hoping to have 6 of these LED and 74HC595 chips hooked up.


texts: Why is probability theory that important to communication theory?

texts:
Since Shannon's paper Mathematical theory of communications, probability theory has played an important role on communications (digital and analog).

I've been checking some course descriptions on my college and noted that for almost every course related with communications an important prerequisite is probability.

Why is that? What is the role of probability in communications? Is it a practical approach or just theoretical?


texts: Why is my microcontroller passing a current through it when not connected?

texts:
MCU: ATTiny13

I noticed this after trying to debug why pushing my switch (connected via R2, a 507kOhm pulldown resistor) makes the LED dimmer while depressed. The switch was powered by the same supply line as the Vcc input to the microcontroller.

Upon disconnecting the Vcc input (Pin 8), I noticed that the LED was still lit when the switch was depressed. If I removed a connection from the ground pin 4, the LED still lit up, but less brighter.

The circuit below represents what I observed. The switch is removed to simplify the problem:

Why does this happen, and how can I stop it? It is interfering with the output when the button is depressed.

Here is a picture of the circuit on a breadboard. The supply line (5V is the red wire, Ground is black):


texts: Why do most FPV 5.8 GHz video transmitters use PAL or NTSC?

texts:
I am not much into the details of video transmission in general. However, I wonder since most displays and electronics are digital, why have suppliers for FPV equipment chosen an analog transmission system, which moreover is limited to 30/24 fps and low resolution?

Would it be possible to enhance the resolution by simply choosing a different (digital) protocol without changing the channel number?


texts: Require help designing VFC (voltage to frequency converter) circuit

texts:
I need to use a VFC (voltage to frequency converter) circuit that operates with bipolar voltage (-10 V to +10 V) and with a bias (i.e. when the input is within +/-2.5 mV, the VFC shall not produce any output).
I was looking into commercially-available VFC such as VFC32 and so-on. Can this requirement be met? Alternatively, can anybody suggest if VFC can be designed from first principles? Linearity should be at least 0.1% for 0-100 kHz range.


texts: LM358 (as comparator) output voltage less than supply voltage

texts:
I've setup a simple circuit with an LM358 configured as a comparator (the ground rail and supply connections are off screen).

Schematic:

Breadboard: (in case I wired something wrong)

Measured values:

V+ = 4.97V (expected)
GND = 0V (expected)
In(-) = 2.47V (expected, via voltage divider)
In(+) = 4.97V (expected)
Output = 3.63V (???)

Here's the pin mapping for your convenience:

Since 4.97V is greater than 2.47V I was expecting the output to be 4.97V. Why is it 3.63V? Is this normal for this particular op-amp or am I doing something wrong?

I've tried looking through the datasheet but I'm new to this stuff so I'm not sure what to look for.


texts: What is the best transistor model for bjt transistor ac analysis(middle response)?

texts:
Nowadays I am working on bjt transistor ac analysis. I use r(e) model for bjt transistors ac analysis in my university. I know there are separate methods for low frequency medium frequency high frequency in Bjt Transistors.
I have read in some comments that the re model does not correspond to real physical values.
Transistors - What is re model?
see LvW 's comment.
What is the most realistic model I should use if I want to work on ac analysis of medium frequency bjt transistors (amplifier design etc.)?


texts: what is the differetial logic in steering DAC

texts:
till now i am used to the logic of as we increase the number of currnt sources going thew resistor.
It thermometer or binary weighed.
BUt here we have some sort of subtraction between out put voltages and i cant see how this subtraction could make the starecase form of DAC where as we increase sumthing we get a largers voltage value.
It seems that this subtraction makes one side "fight" with the other
Thanks.


texts: Is it better to use a microcontroller or pushbutton controller for simple on/off delay functions?

texts:
I'm working on a LiPo charging design with the intention of producing several 1000 of them. There needs to be a switch to turn the charging function on and off. To me, it seems to overcomplicate the design and manufacturing process to have to program a microcontroller just to handle the on/off functions. I would like it to have a 3-second delay to turn on and a 3-second delay to turn off, SOME kind of delay. Do pushbutton controllers exist for this purpose?

What is the better option given that I intend to produce 1000s of these?


texts: How does a high voltage condition break down a semiconductor?

texts: I have TVS diode in parallel with circuitry for ESD/lightening/transient voltage protection.  Say I receive an over-voltage condition which is beyond the specifications of the part, what happens internally?  I assume that the part is unable to dissipate the heat generated internally fast enough which causes a break down in the junction doping resulting in an open circuit (like a blown fuse).  Is this an accurate assessment of what happens? Could an out of spec transient condition ever cause a permanent short instead?


texts: Bi-stable switch activated in both directions by a momentary electrical input

texts:
I am trying to find or build an electro-mechanical "switch" for a unique application. It should act a little bit like the snap switch used in thermostats (where a bi-metal disk snaps from concave to convex due to uneven expansion), but I need the switch to have two states that are both stable, i.e. none of them requires additional energy once switched from one state to another and can change back to the other state upon request.

The application needs to be very low power, and result in meaningful mechanical output.

The way an ideal switch for this use case would work, would be as follows:

switch is normally closed
momentary input changes the state of the switch, which now remains open until additional input or use of electrical energy.
another momentary input is sent
the switch is now closed again, without additional input or use of electrical energy

The best solution I have now is 2 snap switches that are mechanically connected to one another and can be actuated separately. When one snaps, it pushes the other one to the unsnapped shape and vice versa. I am hoping to find a better and simpler solution here and would greatly appreciate any ideas thanks!


texts: How do I reduce cost for a circular PCB shape?

texts:
I'm designing an electronic product that has a circular housing. There needs to be a PCB inside this form. In order to reduce costs as much as possible for high volume production (5K-10K), what shape PCB would cost the least?

A circle PCB works, but so does an octagon and hexagon. I'd like to know if any of these shapes lead to a lower cost due to how production is done.


texts: how to calculate Parasitic series resistance in tank circuit

texts: Kindly let me know how to calculate the parasitic wire resistance in the tank circuit.


texts: Eliminating the humming noise from a cheap SMPS

texts:
I am trying to build a power supply unit that powers eight 9V guitar pedals (usually pedals consume 10-100mA). So, I thought I'd buy 8 cheap 9V-1A SMPS adapters and probably fix some bypass capacitors at the output to remove the ripples. This would make a very powerful isolated power supply unit with eight independent 9V-1A ports.

But this didn't work as significant humming noise was heard when connected to pedal and to amp.

I compared the performance by powering the pedal with a linear power supply which consists of a single transformer and eight LM7809 regulators at parallel outputs.

Result: Linear power supply gave very less humming noise than the cheap SMPS.

A probable problem could be that the switching frequency of the cheap SMPS is not high enough, even though I am not sure of it.

What Can I do to remove the humming noise from the cheap SMPS unit?


texts: How can I find out which resistor is short-circuited and can be ignored?

texts: I don't understand how the current flows in the circuit below. How do I deal with the wire between nodes c and a, a and b, g and d. Why is the 5 Ω resistor shorted out? I am having a little trouble understanding what results from short circuiting.


texts: A way to measure unknown high voltages with an oscilloscope

texts:
I have a sort-of black box of a circuit that is used to generate plasmas. I'm sure it outputs on the order of kV but I'm not sure at all about the current. I was wondering if there is a way to measure the voltage waveform in consideration of the fact that the oscilloscopes I have available to me are rated for 300V rms. Measuring the current would be great also but not as much of an issue (I'm aware of this answer Measure current in high voltage (10kV) but I don't have the same materials).

Any help is much appreciated.


texts:
I'm trying to output a slow clock (4kHz) on an I/O from the STM32F0. I'm wondering what the advantage is (if any) of using one of the timer pins to output this clock vs toggling another GPIO on the timer interrupts.

I was thinking I could do PWM mode with 50% duty cycle if I use a timer pin but I could also just as easily toggle any I/O each time the timer interrupt triggers an update.


texts: Roland Microcube modification, need a hand

texts:
My Roland cube has stopped working, the guitar input connector for the main channel has been faulty for a while but now its gone completely. I opened it up and it looks like the connector is badly damaged.

I want to take the connector from the clean/line in channel at the back. Its the same connector as the main channel. I have a soldering iron. I am a noob.

Here is a photo of one of the sockets:

How do I remove these connectors? Can I do it with just a soldering iron?


texts: How many watts to power up my POE camera?

texts:
I have a couple of IP cameras at my home. Brand/Model is EMINENT 6355. They work well with the provided injector.

However, to avoid having a lot of injectors, I bought a switch LINKSYS LGS108P-EU (POE+)

The problem is that when I plug the camera on the PEO port of my switch, the camera doesn't work.

On the data sheet of my camera I can read this:

  LAN/Power – this is a combined connector LAN and power, the camera is
  powered with the supplied PoE injector. The power needed for this
  EM6355 is 12V/1A, please make sure you are using the correct power
  adapter.

On the switch datasheet I only found this:

  PoE+ Total Budget: 50W

  Standards : IEEE 802.3, 802.3 u, 802.3x, 802.3ab,
  802.3az, 802.3af, and 802.3at (PoE+)

I suppose there is not enough power? In this case how many watts are needed to power up my cameras?


texts:
What is the best way to transmit analog signals between 100 Hz and 100 kHz over a distance of up to 6000 m with minimum frequency depending loss, the level is 50 uV to max 1V (always less than 100 mV above 10 kHz).
I consider using a coaxial cable (50 Ohm or 75 Ohms) to route the signal.
Shall the cable be considered a transmission line?
Should I use impedance matching in both ends?


texts:
How to do the sensor fusion using the 4 IMU sensors. Here, 4 IMU sensors are used to know the location of every point where the IMUs are placed?
I need the location of the every point on a 3D graph where you can see the location of each IMU sensor.


texts:
sConfig.SamplingTime = ADC_SAMPLETIME_28CYCLES_5;

This is an expression from ADC init function for stm32f1xx. I would like to know what this expression really does.I used cubeMX to generate code. Also kindly define the difference between sampling time,sampling rate and sampling frequency in ADC.Thanks.


texts: Separating odd and even pulses in a pulse train

texts:
How would one go about separating odd and even pulses in a pulse train and displaying them using LED indicators?
A schematic would be of great help.


texts: Analog video chrominance decoding - PAL/NTSC

texts:
I'm implementing an analog video decoder on FPGA.
I find some difficulties during chrominance decoding. I appreciate if you can help me.
These are the steps as I'm doing:

I generate an NTSC ColorBar signal from a TV pattern Generator. I do acquisition through an RF board with the following parameters:: Local Oscillator=500 MHz, Sampling frequency=54 MHz(4*13.5 MHz), BW=6 MHz, ADC resolution: 12 bits

After inverting the signal, I implement a digital LPF+bandpass FIR to separate luma and chroma.

I'm generating localling, through a DDS, the chroma subcarrier signal (3.579545 MHz (NTSC)). Actually, it's a SIN + COS signals coded on 16 bits.

I multiply, through an IP from Xilinx, the chrominance signal by COSINUS (V), and by another multiplier, the same chrominance by SINUS (U) in order to create a 90° phase between them.

After that, I'm using 2 LPF with a cutoff frequency of 500 kHz and 1.3 MHz for U and V, respectively. Then, I get Red and Blue signals as below:

source
At this stage, it's OK.
PROBLEM:
I'm expecting to have the same output on all video lines! Or it's only the case for 4 or 5 successive lines, then, it changes and it doesn't represent Red and Blue levels. This is an extract from what I get:

Any explanation please?
Thanks in advance.


texts: Should I use an FPGA output for an MCU Clock?

texts:
We are laying out a board that was designed ages ago, the main purpose of the update is for part obsolescence.  The board has several PIC uC's on it as well as an FPGA.  Each of the PIC's needs a clock and the system has a 20MHz CTS oscillator for this purpose.  Is there any reason we shouldn't use the FPGA to generate these clock signals?  The FPGA is replacing other digital logic on the board but I'm not sure if there are issues with clocks in particular.

Besides the fact that the uC's would need to come up after the FPGA was all done coming out of reset are there other reasons not to reduce parts count in this way?  (And no I can't use the FPGA to replace the PIC's).


texts: Driving low voltage P-MOS N-MOS half bridge with dead time control, without bootstrap and one control line

texts:
I should need a driver of a PMOS NMOS bridge with dead control controlled by a one line from the microcontroller (because I have to use several PWM lines) that inserts a dead time control to avoid both mosfets conducts at the same time. The diagram is this:

I wondered to do this because I do not need floating power supply and there are P-MOS 3x3mm that conduct 64A like NVTFS9D6P04M8L


texts: Why is \$r_{o1}\$ connected to the ground in the second diagram which is the small signal equivalent (formal solution, hence most likely correct)?:


texts: How can I Power a 20-50mA LED from the 240V AC Wires of a Motor in a Safe Way?

texts:
I own an ice cream machine which is perfect, except it lacks a light so one can check the state of the process. The motor case would be the perfect place to install a white LED, which will consume just 20-50mA current.

My problem is: the motor is powered by 240V AC, as shown in the following three photos.

The Motor Case (open)

All Connections

The Label on the Motor

The label on the motor contains this text:

6020D 220-240V 50Hz
20W Class B
Zhongshan Donlim weili
Electrical.Ltd

There are four connectors, neutral N and phase L and two unknown 1 and 2 wires.

Question

What would be the safest way to power a 20-50mA white LED from these wires?

There is only enough space for an SMD LED. A regular indicator LED is too bulky.
I can easily create a custom PCB for the solution.
I can also create professional connectors and insulated cables.
The solution can be complicated and expensive, involving special chips and components.


texts: How to choose MOSFETS by using the datasheets infos?

texts:
I know all the theory behind the MOSFETs, how to calculate the Id current based on (W/L) and (Vgs-Vth) and etc. But, now that I need to project a real solution, I feel like all of this is kinda useless. There are so many types of mosfets - power, logic level, small signal - and so many parameters that I'm not sure of what they actually mean, I'm totally lost, I dont know where to start.
This is the circuit that I want to project. Its a very simple and common one:

simulate this circuit – Schematic created using CircuitLab
By my researches, I think the resistors are correct.
The MCU GPIO Voltage is 3.3V. The maximum current that goes to my load is 200mA.
What kind of MOSFET M2 and M1 need to be? I think M2 need to be a singal level or small signal idk, but how I know the right one? The data sheets that I looked describes an "Max and Min VGS Threshold", but what does that means?
M1 can be any P-Channel? There is anything else that I need to worry about besides the source current? Does the VGS Threshold matters in this case?


texts: LTspice sinusoidal voltage source with offset much larger than amplitude broken?

texts:
I've been troubleshooting an analog circuit and have just come to the realization that Sine Voltage sources at mV are broken.

Here is one that is supposed to provide a 1mV 1Hz sine wave on top of a 300mV DC signal. Instead I get complete garbage.

Running LTSpice version 4.22. Anyone else seen this issue or can advise what is the problem?


texts: Driving a GPIO input with a momentary switch

texts:
I'm looking for a momentary switch (like this one) that can be safely driven by the GPIO pins on a Raspberry Pi 1 Model A (hereafter RPi). This model of the RPi can sustain 3.3V and up to 16mA safely on its input pins.

The idea is that the switch will be open by default, but if a person is pushing down the momentary switch, it will send a signal to a GPIO input pin and reacted to at the software layer. The moment the person releases pressure on the switch, it opens again and stops sending the signal. Additionally it would be wonderful if the switch illuminates while it is being pressed.

Can a momentary switch like this be wired to safely work with this particular of RPI? If not, why? If so, what types of support devices (transistors, receivers, capacitors, etc.) would need to be put in place?


texts:
I am controlling a DC fan by an AVR MCU and I am curious about the thermal characteristics of a 2N3904 NPN transistor over which the fan is connected.

Reading the transistor's datasheet, I find the following values:

$$
R_{\theta J-A} = 200\text{ }^{\circ}\text{C/W}
$$

$$
R_{\theta J-C} = 83.3\text{ }^{\circ}\text{C/W}
$$

I would expect the thermal resistance between the ambient and the case to be:

$$
R_{\theta C-A} = R_{\theta J-A} - R_{\theta J-C} = 116.7\text{ }^{\circ}\text{C/W}
$$

That is, I would expect the case to rise \$116.7\text{ }^{\circ}\text{C/W}\$ over ambient temperature for every watt of power that is put through the transistor.

Now, reading the voltage across fan's terminals with my multimeter, as well as the current that the fan is eating up:

$$
V = 11.45\text{ V}
$$

$$
A = 73\text{ mA}
$$

I now calculate the temperature of the case I should expect:

$$
P = V \times A = 0.83\text{ W}
$$

$$
T_C = T_A + P \times R_{\theta C-A} = 18 + 0.83 \times 116.7 = 114.86\text{ }^{\circ}\text{C}
$$

After having the fan run for 5+ minutes, I proceed to touch the transistor and fail miserably in getting my finger burnt. The temperature of the case is perhaps a bit above the ambient, but not warm enough that I would feel any hot sensation in my fingers.

Somewhere along the line, I made a huge mistake in my understanding of thermal design. What am I doing wrong?


texts:
I played with a BLE device recently (VSN V.BTTN) and was able to get interesting functionality with the button and a Raspberry Pi. However, I still have a few questions regarding the device pairing behavior:

1) Once the pairing occurred, am I correct to assume that most BLE device will not even try to ping each other to know if they are still there? The rational behind that would be to save batteries of both devices?

2) In that case, my watch sends a notification that data is available to be fetched. Does it ever know that the notification was received via an knowledge or the only way to know is when the host device sends a data request?

3) Assuming that the watch goes out of the range of the raspberry pi. Will it lose systematically the pairing?

4) In general, do you need to go through pairing each time you shut down one of the device? Is there a way to simply avoid that?


texts: Can a differential ADC's low pass RC filter be simplified to use less components

texts:
I am making a circuit using an ADS1115 analog to digital converter to read an AC signal using the differential mode of the IC, the datasheet recommends that I add a low - pass RC filter:

Can the circuit be simplfied to use lesser amount of components? Like the resistor combined to a single 200 ohm resistor. My rational on why I think it is possible because the formula in the datasheet just adds them.

$$f_C = \frac{1}{2\pi(R5+R6)C_{Diff}}$$


texts: Identifying a multiple secondary unknown transformer

texts:
Background

I have a step-down isolated power transformer (EI-66x36) designed for 60Hz with one primary input Vp=110V and three secondary outputs : Vy=10V, Vb=26V, Vr=30V.

Unfortunately I don't know which wires is what.
I DON'T want to connect the transformer to the main line (not even in-series with a current limiter resistor) in order to figure out which coil is linked to what. I would rather try an invasive method using the theoretical knowledge, if possible.

By using the coils turns ratio equation E: Np/Ns=Vp/Vs=SQRT(Rp/Rs), where Np/Ns is the primary-to-secondary coil turns ratio, Vp/Vs is the primary-to-secondary coil voltage ratio, I deduced that on a step-down transformer the primary coil impedance is greater than any secondary coil impedance, ie. Rp/Rs > 1.

By measuring each coil impedance I found 4 pairs of wires as following:

thick red wires with impedance of Rp=14.9 Ohm
thin red wires with impedance of Rr=10.6 Ohm
thin yellow wires with impedance of Ry=3.95 Ohm
thin blue wires with impedance of Rb=1.67 Ohm

I concluded that the thick red wires must be connected to the primary coil and the others represents the secondary coils.

I've checked that there is no continuity (infinite resistance) between the secondary coils, which means that the secondary coils are completely isolated of each other.

The problem

What bothers me is the fact that the above equation (E) doesn't seem to apply to this transformer and I don't understand why.

For instance the ration between the primary coil and the secondary coil identified by the thin red wires is: Vp/Vr=110/30=3.7 while the SQRT(Rp/Rr)=SQRT(14.9/10.6)=1.19, which is not as expected (ie. 3.7).

The same applies to the other ratios:

Vp/Vb=110/26=4.23 while SQRT(Rp/Rb)=SQRT(14.9/1.67)=3, which is not as expected (ie. 4.23).
Vp/Vy=110/10=11 while SQRT(Rp/Ry)=SQRT(14.9/3.95)=1.9, which is not as expected (ie. 11).

What am I doing wrong?


texts:
I would like to know why in most of Mosfet Datasheets there are parameters like Maximum Vgs or Maximum Vds but never Vdg, the maximum voltage acceptable between Drain and Gate.

Maybe because it's similar to Vgs or Vds?


texts: Balanced Class A Quiescent Current Regulator (OPS of Amplifier)

texts:
In my book there is a circuit like the one shown bellow. The author (G. Randy Slone) explains the operation and performance of it but there is still one thing that left me wondering.

simulate this circuit – Schematic created using CircuitLab

Since the signal from Voltage Amplification (VA) stage is not applied directly to both of bases of Q3 and Q4 but only for Q4, how can whole sine wave be normally buffered through the Output Power Stage (OPS)? Or does the signal from the VA goes to both of the bases via capacitor? Since author wrote: "...CB filters small signal variation applied to bias network...", does that mean that VA signal goes to the base of Q3 via CB?


texts: 12v dc motor speed control using pwm and h bridge

texts:
I was wondering if yous could lend me a hand with my college project.
I have been asked to control the speed of a dc 12v motor.
It must go in forward and reverse.
See i know i need to make an h bridge. And would like to use a 555 timer to create the PWM.
Would someone be able to direct me to which components i will require?
I was thinking of getting a 555 timer, and a h bridge driver but do i need a micro controller to control this. I really need some help lol.
I know you can make an h bridge with transistors but do i need to use mosfets.
 The 12v dc motor rating is 80.16W, 8311 rpm. 92.13mNm.
Any assitance would be greatly apreaciated


texts: Brand new soldering iron tip turns black, solder won't stick

texts:
I have a brand new soldering iron, the tip turned black while heating on my first use, and now solder won't stick to it, it just rolls off.

All the answers in similar questions here tell me to stick solder to the tip but it won't stick because the tip is black. I have never used this iron and have been unable to tin it.

I've tried cleaning with a damped (not wet) sponge as several people suggested, but nothing comes off with several minutes of scrubbing.

How do I solve this chicken / egg situation?


texts: Can someone explain to me how to associate  smaller RAMs and ROMs to make a bigger one? For example: How do I make a 1024x8 RAM with 512x4 RAM?


texts: From C to Silicon: How to implement software/firmware solution as hardware?

texts:
In light of this question, I was wondering if there was a fairly standard process for turning a software solution into a hardware implemention.  Forgive me and my imagination, but would there be a compiler that could take a C program and compile it in terms of a schematic of transistors, resistors, etc. or maybe even well-known PCBs?

I realize that I could be looking at this scenario from the wrong perspective.  Historically from my own experience, typically you have some piece of hardware that somebody has implemented as a software solution (think hardware emulation).  Does this concept in reverse even exist?  How do these bigger companies do it such as software vs hardware IP routing?


texts: I write this module to arithmetic shift to left and right in verilog

texts:
this is my code:

module zero(out,A,B);
   output signed[5:0] out;
   input signed[5:0] A,B;
   assign out = A[5:0]<<<2 + B[5:0]>>>1;
endmodule

but the output is always zero.

is there anything wrong?

(I don't want to use @always)


texts: Buck converter operating frequency range:

texts: I am looking for a buck converter IC for my project. In the data-sheet if the operating(or supporting) frequency range has not been mentioned, then how do we know about the range of frequencies it supports? For eg. in this data-sheet LTC3637 there is no mention of operating frequency range and am not able to figure out the same.


texts: Count RPM on diesel truck using an Arduino

texts:
I'm trying to make an truck RPM reader that will output a signal once the RPM's exceed a set-point. I believe that I can easily code an Arduino to do this, but I'm having trouble with the circuit.

I have 2 approaches into what I'm trying to build, a simple RPM and a complex (not really complex).

Simple: have a potentiometer as a setpoint and simply read the alternator's frequency and when the reading gets over the mapped value on the pot the output LED will light up.

Complex: have a setpoint or maybe more than one setpoint that will light up 1 or more outputs, depending on the quantity of setpoints.

My problem:

I don't know the best way to actually shift down the signal to interface with the Arduino; in the simple approach a voltage divider might do the trick, but I'm not sure if I could trust the not-so-stable voltage output of the alternator. I'm looking for the cheapest way of doing this reliably. I'm researching what opto-coupler I could use since from my understanding the voltage is not always stable.

For the complex one, I'm not sure how to measure RPM since these trucks are diesel fueled and I don't have a spark-plug where I could sense the voltage on it to know revolutions. Does anyone have a suggestion on this approach?


texts: HC-05 Bluetooth AT+INQ command not working

texts:
I have followed the directions from the site below for bluetooth comm between an Arduino board using the HC-05 and an smartphone. It works fine.

The problem is that I need to measure the RSSI from my phone and using the command AT+INQ the response from the HC-05 is "OK" and nothing else.

I paired both devices using my phone as master and the HC-05 as slave, and when I am sending commands to the HC-05 through the Arduino, the pin KEY from the HC-05 is set to high (3.3V).

Do you have any suggestion to solve the problem I am facing?


texts:
I'm trying to figure out a good LED + resitor pairing for my circuit. However, I'm provided with a challenge and limited knowledge.

Here's the situation:
I'm creating a minimized version of THIS sensor board. The board breaks out THIS sensor, which requires a 3.3V supply voltage. To minimize the size, I took out all voltage regulating components. Now I need to power a white LED with 3.3V and add a current limiting resistor. Getting a sufficient voltage drop is the challenge for which I could use some help.

Now, my solution was to increase the supply voltage to 3.6V instead of 3.3V, which shouldn't be a problem for the color sensor according to the datasheet. I found THIS LED with a supposed forward voltage of 2.8V and current of 20mA. With this situation I CALCULATED that I would need a resistor of at least 47 ohm.
Would my suggested solution work or did I miss something??


texts: Computing Power Requirement For Solar Setup

texts:
In relation to this question:
Solar power wattage requirement

I'm trying to get to the math of understanding my wattage for my plan solar-setup. I would like anyone here who knew can correct me on my computation.

My main goal for my solar-setup is not much about concerning the type of devices I can plug, but more on the capacity and efficiency.

My setup:

1 80W solar panel as seen in the specs here

and for storage a 12v 40AH deep cycle battery

I will be using a battery controller for this, but for the sake of this question, let's leave it out of the equation for now (Or not if it's relevant)

From my reading in the internet, a 12V40AH battery will yeild me a wattage of 480Watts. But given the these kinds of batteries to last longer, the consumption should not go below 40%, so my usage capacity should not exceed 240Watts, am I right?

Battery Capacity: (voltage) * (AH) = total capcity * 0.6 = usage capacity

My next math is how long it needs to charge. Let's assume that I get 6 hours of direct sunlight (equator). I get the advertised, 4.44Amp current from the sun. So if I need to fill the battery for the first time, a 4.44Amp * 6 will give me 26.64AH of current on that time. It will take me 12 Hours of direct Sun in order to fully charge my battery.

Charging capacity: Solar Current * Hours of Sunlight = Total Current Produced

Lastly, I also want to compute to the power consumption of a device I would like to connect it to. In this example, I have a router that is drawing 6 watts and it's open for 24 hours a day. If I'm going to plug it on batteries, I would like to know if my current setup can take this.

Total Power Consumed: 6W router * 24 hours = 144W

Since I have an operating capacity of 240 watts, I could power my router in a battery for a shy of 2 days. Am I getting this correct?


texts: How to measure a temperature with a NTC thermistor and an Op Amp?

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I have a NTC thermistor with R0 = 10kΩ at 25° and a Sensitivity index (B) : 4080 +/- 3% (25-85°) and I have an op amp.

I'd want to measure a temperature from 20° to 100° or so. I don't need an extreme precision.

How do I have to proceed ? Should I use a Wheatstone Bridge Circuit ?
Do I have to linearize my curve between resistivity and temperature ?

Thank you for your answer


texts: I need help identifying a vintage battery

texts: I found what looks like an old battery in the middle of nowhere. The plates are thick and soldered by hand. There is a matting between the plates like an AGM or maybe nickel iron battery. It's housed in some kind of clear green plastic that's not sealed and has some holes even. Perhaps it isn't a battery but some kind of sensor? I haven't a clue, honestly.


texts: Are harmonics always the peaks in the frequency response plot?

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I would like to implement a certain type of audio alarm with 1 fundamental frequency and 4 harmonics.
The example frequency response of a qualified alarm on the spectrum analyzer is shown in the picture below:

I note that the fundamental frequency (aka 1st harmonic) and harmonic frequencies are all outstanding peaks in the plot.
Is that always true？Even so, how can we tell that those peaks are for sure harmonic frequencies instead of noise?


texts: Why is my circuit's current far lower than expected with 2.6v / 220Ohm / and LED?

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I have a very simple circuit which I have measured the current to be only 3mA but should be in the range of 18mA.
I have a simple circuit using 2 AA batteries (NiMH) at 1.3V each in series for a total of 2.6V and a 220Ohm resistor along with my basic red LED.

simulate this circuit – Schematic created using CircuitLab

I = E/R

Using Ohm's law I calculate that I should get approx. 11mA of current
.011 = 2.6 / 220

Double-Checked Resistor Value

I double-checked my resistor with meter and they are at 215 Ohms but that would mean I would get slightly more current anyways.

Double-Checked Voltages

I also measured total voltage in circuit and it does measure at 2.6V.
I measured the voltage drop across the LED and it was at approx 1.775 which seems correct also.

Why might I be getting less current than expected (3mA versus 11mA)?  Is there something I'm not calculating properly for?


texts: How to create a plug detect of a 3.5mm audio jack with 2 connection that carry an AC signal

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Hello i am creating a circuit that take in a 3.5mm audio jack from a Non-invasive Split Core Current Transformer AC current sensor and according to its datasheet the:

Sleeve --- OUTPUT 1
Tip    --- OUTPUT 2
ring   --- NC

In the post here we can see that the there will be a time where the voltage on the output goes below zero, this is becomes tricky for me. I was hoping that i can put a low power LED indication that a jack has been connected without altering the signal that will be read.

I am aware that there are female receptacles that have tip switches, but i would like use it as a last resort.


texts: Solid state relay voltage ratings -- how to choose?

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I am trying to control mains power, which around here is 220VAC @50HZ. Should I be using a SSR that's rated for 24-280VAC (Load), or one that is rated for 48-480VAC? The reason I'm asking is because I'm currently using a 24-280VAC SSR ("KD20C25AX"), but I'm getting significant voltage drop at the output. When I read the voltage between live and neutral after the SSR, I'm getting ~55VAC, while at the mains it's the proper 220VAC.

(It's a new SSR so I am assuming it's working properly)