texts: Power supply noise/ringing caused by Jetson Nano booting and data processing

texts:
I have a board where I use the Jetson Nano module as the CPU.
During the power-on sequence and data processing the Jetson introduces about 400mv peak to peak noise/ringing on the 5V (SMPS) rail causing my Hall effect sensors to misbehave.
I have tried additional decoupling capacitance, a ferrite bead + additional capacitor near the Jetson on the 5V line and a uni and bidir TVS on the 5V rail, so far nothing worked.
What is an effective way to combat this besides giving the Jetson its own power supply?


texts: Filter cap between positive rails in multi-rail power supply

texts:
Say I have this very simple power supply:
 Variant 1
A = +12V
B = GND
C = -12V
Disregard any problems with additional filtering, regulation, and the fact that the transformer's primary isn't connected. This is just a simplified example to show what the problem is.
Say I want to change it to this:
A = +24V
B = +12V
C = GND
Ideally I'd move the capacitor AB to AC:
 Variant 2
But for simpler routing it would be nice if I didn't have to to do that. I.e. if I could leave the capacitor AB where it is:
 Variant 3
Ideally I would like to select the voltages simply by soldering the diodes (and jumper) into different positions while keeping the copper traces the same.
But the placement of the capacitor AB feels wrong.
What are negative (or possibly positive) consequences of doing it this way?
If I understand right, the effective capacitance between A and C in variant 3 is half of what the capacitor AC would provide in variant 2 (assuming the same capacitance for each idividual capacitor). I assume that makes it less effective at smoothing out ripples?
Please consider these details about my situation when writing your answer (if they are relevant), but a general answer is always appreciated:
This is part of a switching power supply at 132kHz (driven by a TNY268).
The diodes are MUR420.
The capacitors are 470µF electrolytic capacitors and you can safely assume their voltage rating is sufficient.
To the right of what's shown in the schematics above, there will be a 100µH inductor in all non-ground rails, and after those another set of the same capacitors plus 100nF ceramic capacitors.


texts: RS-485 works when USB powered, not when main powered

texts:
I'm thinkering with a RS-485 connection (modbus) to read out my electrical power meter.

The setup is as follows:

ESP32 --> MAX3485 --> RS-485 to USB

when the ESP32 is powered via USB, on the same computer as the USB host is connected, I can see communication in both ways: The computer can read what the ESP is sending and vice versa.

When I power the ESP32 via mains power (converted to 3.3V offcourse), the computer can still see what the ESP32 is sending but when I return something, the ESP doesn't read anything.

Both ends are terminated with a 120Ohm resistor. Ground connected (I have a 100Ohm resistor in series) or not makes no difference.

I guess it has something to do with common ground but don't know how to solve...

Works:
ESP32, powered through USB port from computer

A, B and GND connected to a generic RS-485 to USB dongle to the same PC.

Doesn't work:
Same ESP, now powered via a Hi-Link mains to 5V converter (0.6A), same schematic. A, B and GND connected to a generic RS-485 to USB dongle.
Mind that data sent from the ESP is still received, but the ESP itself doesn't receive anything.


texts: Reason for certain steps in Circuit Analysis

texts:
The image is from this lecture.The instructor Prof. Shanthi Pavan says that the part encircled in orange can be replaced by a voltage source with current through \$v_1\$ as \$i_1\$ and not \$i_1 + I_1\$ as shown in the next figure:

Then he does this for all the branches as shown here:

Please help me by providing an explanation.I'm not able to figure out why the above mentioned thing could be done.

Thanks for reading.


texts: Which Microcontroller can I use on a Arduino board?

texts:
I own a Arduino UNO with the ATmega328 Microcontroller.
Which other Microcontrollers are compatible to the Arduino system?


texts: Will there still be small voltage in transistor OFF state?

texts:
In Bipolar junction NPN transistor which has three legs as shown below:

Case 1: If this transistor is in OFF state i.e. collector is connected to +Vcc and Base is connected to insufficient voltage which is less than the required amount to turn on the transistor, would it still conduct small amount of current (or low voltage which is not zero)?

Case 2: In other case, if only Base is connected to +Vcc, would there be some current in collector or emitter?

What am I trying to know is that does the OFF state in transistor mean zero voltage at collector and emitter?


texts: Parasitic drain - What type of relay is this?

texts:
I am having issues with my car in that my electric window circuit appears to be taking .2A when the car is off.

I have access to the wiring diagram for this circuit and there is a relay (T13) before the two fuses fuses (F47, F48) that supply the two motors (N060,N061). In the wiring diagram it clearly shows a coil inside the relay, but the actual relay is quite different.

I was under the impression that a relay always had a coil. From what I can see here is just a direct connection between two pins.

I have attached the wiring diagram. You can see the T13 relay I am talking about within B002.

Wiring diagram:

Relay picture:

UPDATE:

I swapped a different relay for this jumper style relay and it did not work.

Unfortunately, this means that culling my parasitic drain will be more difficult than originally thought.

So the situation as it stands right now is that I am getting a .1A current draw from each of the two fuses that directly supply either window motor.

One thing I have noticed is that there is clicking in either door when I put one of the respective fuses back in. This would lead me to believe that there is some sort of relay in the door itself.

On the other hand, is it in the realm of possibility that .2A is not a parasitic drain and this is in fact standard. Should my car battery be able to cope with this? As a reference, the battery is roughly 12.7v when fully charged and if I leave it for 10 hours, it dips to roughly 12.25v. The battery is 60Ah


texts: Temperature control fails. Will a PID solve the problem?

texts:
I made a temperature control system without PID (just on/off with an offset) to control the temperature in a tank.
I can only cool the tank with a cooling coil inside the tank (so there is no heating element.) However, I can never reach the target temperature 20C due to the remaining cold water inside the coil (although the pump which transfer the cooling water inside the coil is turned off,) so the temperature drops after some hour or hours below 20C.
If I buy a commercial PID controller can I solve the problem?
If not, what can I do?


texts:
Eagle 6.5 Schematic

I want to be able to flip a logic or op-amp symbol (that is, mirror it about the X axis), but I can't find any UI button or menu item to do that, and it's not mentioned in the manual.

Examples: 741 op amp. Places with plus input above the minus input. How do I get the minus input above the plus?  I could rotate 180 degrees and mirror, but that move also flips the power and ground pins, which I don't want.

Another example: 74xx125, a buffer with tristate-enable pin. Places with enable on top, and I want it on the bottom. This part does look OK if rotated and mirrored, but that's excessively tedious.

A clue would be very appreciated!


texts:
I have been using this fuse blown indicator circuit for a bit, it basically works perfectly fine with positive voltages no matter if there is or nor a load connected

The problem starts when I feed the circuit with negative voltages, as you can see in the picture my MOSFET never activates, It simply won't work as intended, even if I decide to turn around the LED, it uses ground as reference and it actually turns on the led but stays on permanently (meaning the mosfet doesn't open) since it's using GND as reference and providing 5v to the led and resistor in inverse polarization.

Already tried putting some diodes at the bottom but the MOSFET still doesn't respond. My question here is, how can I activate the MOSFET using negative voltages? Considering I will also use this circuit with -12v in the future, I'm thinking of using an inverter but I would like to hear some feedback before I do this.


texts:
In order to calculate the time it takes to charge a certain capacitor with value C at a given constant current of a value I to a voltage of value U, I can use:
$$ C = \frac{Q}{U} = \frac{I\Delta t}{U}$$
Is there something  equivalent for an Inductor? like:
$$ L = \frac{\Phi}{I} = \frac{U\Delta t}{I}$$
I mean, can I calculate the time it takes for a inductor with value L to reach a current I charged with a constant voltage U?


texts: What regulatory hurdles do I need to conform to to sell my products?

texts:
I have products that involve some simple resistors and diodes etc that plug into the microphone jack of a mobile phone (they are sensors).

What regulatory hurdles must I cross in order to sell on eBay to 'test the market'?

The Low Voltage Directive isn't applicable because its below 50V (the voltages are phone voltages).

Someone suggested I can 'self-certify' BS-EN 60950 - The Information Technology Standard.  But my 'devices' are much simpler than that would normally be applied to.

Any ideas?


texts:
How can I use a model from PSPICE into ISpice?

I've been told that Spice models are roughly cross engine compatible.

Intusoft ISpice has a really easy UI, but doesn't have as many models included as OrCad  PSpice

I wanted to shift a model for a level 2 mosfet accorss from the redistributable eval.lib:

So took the following and put it into a file called: extramod.lib in C:\spice8\pr,
then in ISpice SpiceNet, did the File->Update Part Database, which went through without error.
But now I can't find my new parts.

.MODEL MN4016A NMOS LEVEL=2 VTO=1.45 TOX=1000E-10 NSUB=4.7E16
+XJ=3U LD=2U UO=625 UCRIT=1E5 UEXP=0.45 UTRA=0.25 RSH=15
+NEFF=2.5 VMAX=1E6 CGBO=3E-10 CGDO=10E-10 CGSO=10E-10 CJSW=2F
+NFS=4E12  GAMMA=2.2 LAMBDA=0.02
*
.MODEL MP4016A PMOS LEVEL=2 VTO=-1.5 TOX=1000E-10 NSUB=7.6E15
+XJ=3U LD=1.5U UO=225 UCRIT=3E5 UEXP=.5 UTRA=0.25 RSH=15
+NEFF=2.5 VMAX=1E5 CGBO=3E-10 CGDO=10E-10 CGSO=10E-10 CJSW=1F
+NFS=1E12  GAMMA=1.8 LAMBDA=0.02


texts: Interfacing Wiznet W5300 with a Spartan 3 FPGA?

texts: I have to interface Wiznet W5300 chip with a Spartan 3 FPGA for sending packets over Ethernet using the Hardwired TCP/IP feature of Wiznet. I am planning to interface using the direct/indirect bus of Wiznet W5300. Can anyone point me to some good and helpful sources that can help me in this regard since I am quite new to this. So far I have mostly come across Wiznet interfacing with FPGA using the SPI protocol.


texts: Not able to get graphic LCD to work with Uno

texts:
I have an arduino uno and wanted to use the graphic LCD JHD12864E. My further plan is to port the same code to an ATmega32 or similar, but that is not the issue right now.

I am using the library suggested in the playground page here http://playground.arduino.cc/Code/GLCDks0108. The LCD has s6b0108 controller in it, and its compatible with the KS0108, on a youtube video they suggest that we use panel B for this lcd. I uploaded the sketch to the arduino but cannot for the life of me get anything to print on it. It just remains blank. What may be the problem? Have tried the troubleshooting page to no avail.

Right now I am using this sketch

// include the library header
include <glcd.h>

// include the Fonts
#include <fonts/allFonts.h>

void setup() {
  // Initialize the GLCD
  GLCD.Init();

 // Select the font for the default text area
  GLCD.SelectFont(System5x7);

  GLCD.print("hello, world!");
}

void loop() {

}

Here is a video of me changing contrast and nothing happening. http://youtu.be/UyCOGoCAoGA

Here are some pictures


texts: Powering LED strip and Raspberry Pi from a single 10A 5.5V power supply

texts:
I plan on making an ambilight project for my TV, using a ~4m 5V APA102 60leds/m LED strip, controlled by a Raspberry Pi. In order to power the LED strip, I bought a PSU rated 10A 5V, which in reality actually measures to ~5.54V. I know this shouldn't be a problem for the LED strip, which is supposed to endure a max of 6V.

The problem:
I want to power the Raspberry Pi in parallel with the same PSU that will power the LEDs. However (although I couldn't find any official documentation) 5.5V may be too much for the RPi to handle and I'm afraid not to burn it.

I was thinking of putting a diode just before the RPi, which would drop the voltage to ~4.8V, but then this could be too little.
I actually tried putting an SR1100 diode after the power supply to measure the resulting voltage, but it still is 5.5V. Could it be because there is no load?

Would it really be a problem if I directly supply 5.54V to the Rpi?
Would a diode solve problem and why I can't see a voltage drop when I measure it without a load?
Is there a better solution to reliably power the RPi from the same PSU?


texts:
question :
A two terminal network consists of one of the RLC elements . The element is connected to an a.c. supply .The current through the element is I  A.
When inductor is inserted in series between the source and element,the current through the element becomes 2I A . What is the element ?

(a)resistor

(b)An inductor

(c)A capacitor

(d)can not be a single element

answer : the answer is given (c) A capacitor but no explanation is given .

i'm confused how can inductor amplify current without presence of any active source in the network so,  please provide explanation of answer for understanding concept behind the question . thank you.

EDIT:As per hilmer comment i break problem into three cases below is the pic attached for same

in first two cases (with R and L as elements respectively  ) when inductor is inserted in series current is reducing(because denominator is +ve quantity and increases with increase in frequency ) ,but in 3rd case with capacitor as element there is scope of increase in current because denominator is(1-w^2*LC) which decreases with increase in frequency .

but how the current become 2 times is still my doubt? even if W^2*LC =1/2 then numerator will also change accordingly


texts:
I would like to know if anyone has been able to take control over 'Niko Home Control' with a PC or microcontroller (arduino)?

I Googled, but can't find much on this topic. Is it even possible? I guess it's not really open-source.

Things like:

Control the lights
Monitoring which lights are on/off

I'm planning on using the 'Niko Home Control' in my house, but like to use our own interface (Arduimotic).


texts: How come the decoder gives a question mark?

texts:
I'm using a scope to debug I2C (bit banging) by letting it capture the signal. I think that the output should be good, but the scope's decoder gives the following:

where there is a question mark after the second byte (I'm doing a multiple-byte read here). Does anyone know what that question mark might mean? Is it an error?

Thanks

-- EDIT 1

Add scaled out capture.

-- EDIT 2
 Having taken @Michael Karas's advice, I have now used another probe for Ch1. Indeed, the old probe was bad and under compensated! However, the decoder still gives a question mark.


texts: How do I take input from the joystick on the AVR butterfly development board?

texts:
I am currently programming an AVR butterfly dev board. I want to take input from the joystick and my program to do certain things whenever the joystick is puled down. To do this I have the following pieces of code. (There are more but this is what you need to answer the question.)

#define false 0

#define true 1

DDRB = (0<<DDB7);

PORTB = (1<<PB7);

....

while (PINB==1)

....

while (PINB==0)

....

Right now the program avt as PINB is never 0 neither is it 1. I think my problem is that I never even read if the joystick is moved down or not.


texts: magnetic field using solenoid but multiple layer winding?

texts: how to make a solenoid multiple layers winding to produce a desired magnetic field? In that case, the normal solenoid formula(muni) will be valid or not?


texts: Measuring current, instrumentation or differential amplifier?

texts:
I want to measure current at the high side of circuit with 0.1 mV accuracy using a 16 bit ADC. for sensing the voltage drop over a 100 mΩ 1% resistor I need to use an op amp which is cheap and easy to implant.

I have found two suitable chips, AD620 in-amp or AD8628 zero drift op amp configured as differential amplifier with hand matched 1% resistors, both from analog devices and are reasonably cheap.

The AD8628 is 3 times cheaper than AD620, so I thought I can get two of AD8628 and measure the voltage with the same accuracy as well. but since I have little to no experience I can't really tell which one is going to give me the result that I'm looking for.

When do we need to choose instrumentation amplifier over differential amplifier and for this specific project which one is more suitable?

Side question; if I match the differential amplifier 1% resistors one by one using DMM, can it be as accurate as 0.1% resistors?


texts: Convert complex number to phase shift in simulink

texts:
I am currently modelling some dynamic phenomena, combining pure simulink blocks and simscape blocks.

I have measurements (real-valued) on which I perform computations with complex-valued matrices, which give me a complex-valued output.

However, I use this ouput in a feedback loop so I have to convert it back to some real signal for the simulation to run.

My idea was then to convert this complex value that has a relative phase to my input signal into some real signal with same amplitude, but showing a time shift matching the argument of my complex number, but I can't figure it out.

Any suggestions ?

I know of the transport delay / time delay (though I am not sure how to use them in such a situation), but it feels overkill for something that looks so basic. Moreover, I need to perform some linear analysis for stability on this model, which seems to be incompatible with such delay blocks as proposed in shifting signal in simulink.

What is the right way to do this ?


texts: DIY Inductor: Solve for number of turns without knowing the length?

texts:
I'm trying to wrap my own inductors (air coil) for an RF circuit that I am making and I am having a little trouble solving for the number of turns I need to reach the desired inductance.

\$L=\dfrac{D^2N^2}{18D+40l} \$

L = inductance in uH
D = coil diameter in inches
l = length of the coil
N = number of turns

I'm wondering if there is a way to negate l from the equation using the gauge of the wire. I'm using 32AWG magnet wire and have found that 113 turns is equivalent to 1 inch of l. Can I just replace l with N/113?

My goal is to be able to measure the diameter of the non ferrite core I am going to wrap around and plug in the desired inductance. It shouldn't matter how long the coil is in the end unless I reach the end of the core and wrap another layer on top.

If possible, is there an online calculator that will do this for me?


texts: Digital camera sensors and long exposures

texts: Why do digital cameras need a long exposure time in low light conditions? Sometimes the exposures are 15-30 seconds or longer. Doesn't the electronic sensor achieve a steady state under 1 second or so? I can understand long exposures in film, where the light effects are cumulative. But in an electronic sensor? Do they do digital signal processing behind the scenes to build an image?


texts: is there any high quality PCB software that's free for download? I am trying to design a mother board, and want to be sure of the circuitry. Is there any PCB software that if you order your design it takes your design and manufactures it for you? Thanks.


texts: how to know the voltage i can generate from a 240V AC motor

texts:
I have an AC motor from a toilet fan, and i want to use it as an air turbine to generate electricity.

all i know about the fan/motor is the following:

Input Voltage:220-240V AC
Input Wattage: 15W

how can i know the Output Voltage if rotated at the rated RPM?

i tried rotating it very fast (dont know how much RPM but it was visually as fast as if it was connected to the mains), and i only generated a tiny 0.7V AC. why is it that low?

thank you.


texts:
In implementation section of C-element at Wikipedia website: https://en.wikipedia.org/wiki/C-element there is a diagram that points to a weak transistor.

What is a weak transistor?

Below is the diagram that I am talking about:


texts:
Please see attached image. Can you please help me understand how they went from the first to the second? Not too sure how they got (B+1) in there.

Thanks


texts: How much power does a receiver antenna obtain from a radio station?

texts: I have this problem where a transmitting antenna radiated uniformly in all directions at a radius of r. The station broadcasts at 10 kilowatts. How much power is obtained by a reciever antenna 20km away? The antenna of the reciever is 50cm^2. I am unsure of how to set up an equation for this problem, I know the distance and power, but how would I set this in a equation to find the power obtained by a receiver?


texts: Voltage drop using resistor divider for ADC sensing

texts:
I am using a micro controller (TI CC3220 - http://www.ti.com/lit/ds/symlink/cc3220.pdf) which uses 3.3VDC for its operation and has an ADC input range of 1.4VDC.

Questions

In order to use the ADC input for reading values from a variable resistor, can I just use a simple resistor divider to step down the voltage from 3.3VDC to 1.4VDC?
How do I find the appropriate resistor values R1 and R2 for the divider ? I have tried 47K & 22K and they seems to work fine, but not sure about their long term impact.

Note : I do have constraints on the component size and cost, hence would request the cheapest feasible option here.

Schematic

simulate this circuit – Schematic created using CircuitLab


texts:
Recently I have been trying to learn how to program Arduino in Code::Blocks. I used the AVR project wizard to create my project. The program compiles flawlessly into a .hex file that I want to upload using avrdude. I've already looked for about an hour for a solution, but none of them that I find actually work. I am running on Ubuntu, if that is important. Here is what I get in the command line:

me@mePC:~/Desktop/C++/AVRTest$ sudo avrdude -c avrisp -p m168 -P /dev/ttyUSB0/ -U flash:w:AVRTest.hex
avrdude: ser_open(): can't open device "/dev/ttyUSB0/": Not a directory
ioctl("TIOCMGET"): Invalid argument

avrdude done.  Thank you.

I am running avrdude in the directory that the .hex file is located. I looked in the Arduino IDE and the programmer is AVR ISP, the chip is ATmega168, and the port used is /dev/ttyUSB0/. I've already tried the arduino programmer option in avrdude. This is the Duemilanove board that I am using and it has an FTDI chip on it.

I am quite puzzled by this and any help would be appreciated. Thanks.


texts:
I'm going to measure very short times as accurately as possible. The device will get first one pulse and within 150  microseconds six more, each on their own wires. The time between first signal and each of the six other signals must be measured as accurately as possible. The accuracy should be at least 100 nanoseconds but more is better.

Which microcontroller would be best for this? I've found this. They seem to have a timer with period of 4 nanoseconds. It would be accurate enough for me.

Would some other microcontroller be better to do this? Can this be done with AVR?


texts: Searching for 'ground fault' on DC power supply, 0VDC to ground

texts:
We have 3 chargers for DC power supplies (125VDC battery banks) at our facility and had a contractor come in and test them. They said there is a 'ground fault' on 2 of them in their report.  The only evidence they show in the report is from voltage readings between the (+) terminal to ground, and also the (-) terminal to ground.  Voltages between terminals is fine.
The readings they show are:

battery 1: +/ground= 110Vdc   -/ground= 20Vdc

battery 2: +/ground= 26Vdc    -/ground= 108Vdc

I took readings with a handheld fluke multimeter and for battery 1 I get 0Vdc for both terminals in reference to ground.  So the multimeter has a much lower resistance than exists already on the floating power supply to ground. This makes sense, but I don't see how they are saying there is a ground fault...

Battery 2 I do measure +/ground= 26Vdc    -/ground= 108Vdc just like the report.  Now, that shows me there is a very low resistance between the power supply and ground (because the internal resistance of the multimeter is able to read the potential), somewhere in the system, correct?

Or at least lower than 10Mohm. And I should isolate components until the issue is found?

Furthermore, is this an actual issue that could damage the power supply?

I haven't been able to find anything wrong by visual/operational inspection of the components operating on the DC bus.


texts: Question about Shockley's equation for JFETs

texts:
I'm currently studying JFETs (Junction Field Effect Transistors) in Navy school. What I know so far is that in JFETs, \$V_{gs}\$ is reversed biased, creating a depletion zone. What this means in plain English is that the more negative the gate is with respect to the source, the more narrower the channel becomes, leading to more resistance in the drain to the source, so the drain to source acts like a resistor. There is a point when current flows constant and we call this the saturation point and denote this as \$v_{gs(off)}\$

We are introduced to this equation and I have no idea where it comes from:

$$I_d = I_{dss} \left(1 - \frac{V_{gs}}{v_{gs(off)}} \right)^2$$

Here \$I_d\$ is the current of the drain and \$I_{dss}\$ is the drain to source saturation. Can someone shed some light as to how we can get this equation?


texts: What would happen if a charger tried to pull more current than a QC 3.0 source can output?

texts:
I've got this charger:

https://store.dji.com/product/mavic-car-charger

It takes 12.7 - 16V input from a car and outputs  13.05V at 6.1A (~80W)

I want to utilize a USB-PD and / or USB-C QC 3.0 charger.

I can get a USB-C trigger:

https://www.ebay.com/itm/UPD005-PD-to-DC-spoofing-detection-PD2-03-0-fast-charge-trigger-QC4-polling-HID-/273424369188?oid=273518419377

It connects to a USB-C QC or PD power source and allows me to select the output voltage.

What I want to do is connect:

QC 3.0 Power Supply -> USB trigger set to output 12V -> 12V car charger for DJI battery -> DJI battery

The idea is to use a QC 3.0 power supply to recharge a DJI battery (albeit slowly).

QC 3.0 can only output up to 18W of power, so if I used the USB trigger to select 12V as the output voltage, the QC 3.0 source would only output a max of 1.5A, but the DJI battery charger wants to output 80W of power.

Would this destroy the QC 3.0 source? Or would the QC 3.0 source just happily output a continuous 12V @ 1.5A and the DJI charger would simply charge the batteries at a slower rate (18W?) without damaging anything?


texts: Differential Amplifier - Active Load Current MIrror Logic

texts:
I'm trying to wrap my head around the workings of a differential amplifier when a current mirror is used as an 'active load'
With reference to this Youtube video leecture: here

My understanding so far (when using resistors as loads rather than current mirror)

A constant current sourrce is sinking say 10mA in the tail
This means each leg has 5 mA when both inputs are matched
When one input increase, its transistor allows more current, increasing the voltage drop across its load resistor thus lowering the output voltage that side
This also means that less current is 'available' for the opposite transistor so the current through its load resistor decreases, its voltage drop decreases and so the output voltage increases.

If we now replace the load resistors with the current mirror (where I think I'm misunderstanding some steps):

When the input voltage increases (left side) the current through the transistor increases
The voltage on the base of the mirror transistor (left side) changes [how and which way?]
This is mirrored to the base of the other current mirror transistor, causing the same current to flow through it

Now, with resistor loads the current was split such that it would add to the 10mA of the tail, with more on one side and less on the other. With the mirror, if left side goes up to 8mA and it's mirrored across - both sides now have 8ma (where 16mA isn't obtainable because the tail is constant at 10mA)
So what is the behaviour/action happening that allows for the increased gain on the output?
The video talks about 'reversing the polarity' of the current on the right hand side but i'm not sure i understand how that can work - Can current flow both down through the mirror and up through the tail? But then how is this aligned to the constant 10mA?
Many thanks in advance for any pointers you can provide.


texts: What do relay switching characteristics mean?

texts:
I am looking for HV realys (3kV) and found a supplier for that. Now they offer relays with different switching characteristics:
"No Load"
"Make & Break"
"Make only"
"Carry only"

On the web page there is no explanation for that. Can you give me a hint of the meaning of these characteristica?


texts: Ziegler–Nichols method, use time value of 63% of process variable or steady-state level line?

texts:
I am attempting to use the Ziegler-Nichols method to PID tune a system.

However, in calculating the tau/time constant value I have come across two different methods and am unsure which to use?

Method 1

Time difference (tau) between intersection at end of delay/dead time and process variable reaching 63% of it's total change.

Method 2

Time difference (T) between intersection at end of delay/dead time and steady-state level of process variable.


texts: what is meant by low frequency noise in a DC to DC converters that the vendors claim for switching regulators? What is the frequency range?


texts:
What is the fastest oscillator I can build for less than $1 in parts ?

Further specifications:

SMT only
Pricing for Quantity 1000
Stable frequency
Sine wave preferable
I don't care too much what the output voltage range is (0.5v < amp < 10v)
Stable and known frequency (2%)
Target frequency: Multiple 100s MHz


texts: Some one could explain to me please the difference between the LP2992IM5-5.0/NOPB, LP2992IM5X-5.0/NOPB, LP2992AIM5X-5.0, LP2992AIM5-5.0? They all seems to be the same thing.


texts: Clearance of Exposed Nodes on High Voltage Relay

texts:
I'm trying to use this high voltage relay for a machine that will assist in HI-POT tests. The relay can handle about 10kVpeak according to the datasheet and I need it to handle 3.5kVrms maximum. I've run 3.5kV across the high voltage nodes in a HI-POT test on the relay and everything works as intended. While designing the PCB that will mount the relay, I looked online to see what the clearance rules are to prevent arcing elsewhere; but according to the IPC-2221B standard, the the exposed nodes need to be about 25mm apart for 3.5kV, which is already farther than the nodes on the relay are.

Can I ignore this standard or is there a different standard I should be using more suitable for HI-POT tests? How close can I actually make two exposed nodes on the PCB at 3.5kVrms?


texts: Temperature logging setup for refrigerator

texts:
I've been having some issues with my refrigerator lately, and so I've been imagining some kind of temperature logging system.

I want it to log the temperature every 5(?) seconds, door open/close events, and compressor start/stop.

Having little to no electronics experience, my head said the following:

Arduino-ish controller (or .NET CF, since I know C# best)
Amp-clamp thing around the power cable to register the compressor on/off (and some way to connect it to the Arduino
Photoresistor(?) to register the light on/off (for registering door open/close)
Some kind of temperature sensor of course (maybe multiple sensors for several zones in the fridge. Possibly with 2 decimal points of accuracy?)

The best would be to log to a web server using some kind of wireless networking (WiFi-shield?), but logging to an SD card could also be a possibility.

What kind of hardware would you recommend for this? And could it be a good "noob"-project?


texts: What is the difference between SoC FPGA and 'regular' FPGA?

texts:
I've recently developed an interest in implementing projects on top of an FPGA dev board, and wish to purchase one such as the Altera DE1.

Looking in the company's site, I noticed there is another class of FPGAs called "SoC FPGAs" (such as DE1-SoC) which incorporates an ARM core.

How does it differ from a 'regular' FPGA?
Is it less flexible in terms of design?


texts: Recommendations for 3.5 switching audio jack which does NOT short to Ground at plug-in or plug-out?

texts:
I have been using a 3.5 mm switching Audio Jack in order to charge/switch-on and off my RC-Glider model. For this I connected the battery of my RC-glider to the one-part of the audio jack and the electronics to the other side. The audio jack I use seems to be a SJ1-3515 (although, I am not sure as this switch was delivered with the model). Here are the schematics:
However I noticed that whenever I plug-in or plug-out a cable, ground is shortly connected to either of the two other pins, which then of course shorts-out my battery! This led to high-current and some very hot wires which desoldered my connections to the switch. Obviously I do not want to short my battery every time I plug-in or plug-out the charger or the on-off insert.
Therefore my question(s):

Is this a normal behavior for a switching 3.5mm Jack?
Can someone tell me if non-shorting-out 3.5mm Jack connectors exist, and how to find those? Or am I just plainly using the wrong tool for the job?

Thanks in advance!
Edit: Per demand I included a (badly drawn) schematic.
Edit2: Generalized the question such that I ask for the class of non-shorting products instead of a specific product.


texts:
Given this NOT gate schematic using a transistor, and assuming the power supply is a battery, won't flow from Vcc to ground discharge the battery when the transistor is on?
If yes, are there any alternatives with power consumption in mind?


texts:
I can't seem to get it to work
the aim is to input a certain number in a1_add a2, and 3
the steps I followed are
set cs to high the select an address and setting to high  the setting we to high to enable it to write and then input data (d1 d2 d3)
I am not sure what I'm doing wrong
the objective is to store data in different addresses and be able to refer to them back
any suggestions ?
thanks


texts:
I am trying to understand the selection criterion for choosing between a signal types and wire type out of the following:
Signal types:

Gnd reference uni-polar signal
Gnd reference bi-polar signal
Differential signal
Balanced signal
Encoded signal eg., Manchester encoded

Wire types:

Single core wire
Multi-core wire
Braided wire
Flexible wire
Co-axial wire
Shielded wire
Twisted-pair wires

I want to understand when to use which signal type and which wire type when designing any electronic system? Are there any guidelines for these selection?


texts:
I need to built a 3x3x3 LED cube. I need to be able to turn every  LED on (not at the same time) in different patterns. I need to use Charlieplexing (note that any other method is not a viable option), with a Arduino UNO (6 pins). I am allowed to use soldering. I have a limited supply of components:

6 Resistors
1 Arduino Uno
27 LEDS
1 Breadboard
Soldering iron and solder
Few wires (these wires cannot be used to connect the LEDs to each other. I need to solder)

How would I go about doing this? Please refrain from suggesting ideas that require components not listed above and do not use Charlieplexing. I searched online but found very tutorials with the above constraints. One useful tutorial was:

http://tomscircuits.blogspot.ca/2010/10/charlie-cube.html

However the above tutorial uses transistors, something that I do not have. It also doesn't show where the pins need to be placed. I was also hoping for something with a bit more detailed instructions. This is not a homework assignment.

Please do not suggest examples (there are a plethora of videos and images of cubes online) but rather some kind of guide or instructions on how to proceed.

I unfortunately have no ideas. I was able to Charlieplex 27 LEDS successfully - however this was all on one layer as opposed to being a cube. Charlieplexing on one layer was simple - just a matter of connecting wires, however Charlieplexing with a cube seems to be much more complex.


texts: Does the CPU of an ARM Cortex M halt during flash self-programming?

texts:
Most ARM Cortex M MCUs do not feature EEPROM memory. Instead, persistent data can be written to the same flash memory that also holds the program.

What is the state of the CPU during this erase/write process?
Does it halt? Does it maintain normal operation?
Does the behavior of the CPU depend on the specific MCU family (e.g. STM32, Kinetis L) used?

(To some people this could look like a stupid question, but Microchip's PIC16 halts the CPU for up to 40ms during flash self-programming.)


texts: Input/output impedance of microcontroller

texts:
how to calculate the input and out put impedance for  a micro controller , for the purpose of modeling in LT spice ,

for example RX610 family from Renesas

For example the lumped characteristics can be modeled for a trace , if i know the o/p impedance of the controller and hence the rigging effect can be simulated and debugged accordingly


texts: Can I regulate the already regulated buck converter output (5V) to 3.3V to power my microcontroller? If yes, how to connect both?

texts:
I would like to power two different components with two different voltages in my circuit.

Component 1 : STM32F401 microcontroller (3.3V and 160 mA)
Component 2: AD8205 current sensing amplifier (5V and 20 mA)

In my circuit I am using a battery pack of 36V nominal and 42V maximum as a source. First I have an LTC3638 buck converter to get 5V and 250 mA as output. From this I can source my current sensing amplifier. I want to power my microcontroller also so for that I am planning to use an ADP151 voltage regulator to get constant 3.3V to power the microcontroller.

Datasheet of LTC3638
Datasheet of ADP151

ADP151 has very low power consumption, so it is safe to use.

I am planning to use the output of the buck converter (5V) as input of the voltage regulator to get 3.3V so that I can use 5V for my current sensing amplifier and 3.3V for my microcontroller.

When I simulate both the components separately using LT spice it is working perfectly and giving the expected output voltages. But when I connect the output of the buck converter to the input of the regulator, I am getting regulator output perfectly as 3.3V but my buck converter output is showing as some micro volts.

I think I am connecting it wrong. Please help me to connect it correctly.

Circuit:

Buck converter output voltage: I need 5V and 250 mA but I am getting some microvolts and microamperes.

Regulator voltage output is 3.3V but the current is reduced to 100 mA. I need at least 160 mA.


texts:
I have recently started medelling in the understanding of circuitry and have started creating this project. As i bought the SSR from eBay i strongly suspect it is a fake and will probably not handle 25A of current nor be as safe as the official data sheet states [Even with an optocoupler]. Now to fully let my heart rest i tried to design this basic protection circuit, but have been hitting a wall with the answer to how to calculate a resistor to limit current and voltage at the base of the transistor. I have googled around for a long time now and still can't seem to figure this out so any help would be appreciated. :)

Here are links to the specific data-sheets :

http://pdf1.alldatasheet.com/datasheet-pdf/view/4856/MOTOROLA/MJE350.html
(MJE350)


texts: Can I use two arduino output pins to simulate a RS422 trigger?

texts:
I have measuring wheel encoder like this one, which outputs its position using two RS422-encoded pin pairs, standard quadrature encoding. Note that these are not using the RS422 communication protocol, just the 2-pin differential encoding that RS422 uses.
This is connected to a bespoke PCB that includes a microcontroller, which was designed and programmed by some company for us, which basically counts pulses (and does a bit more which isn't relevant here)
As the software seems to have some bugs, I'd like to create a reproducible test environment, where I can simulate the wheel encoder turned at a specific rate, translating to a fixed, but configurable, frequency. My idea was an Arduino which I can write a small control program for, use the Arduino's GPIO pins to simulate the encoder's output, and connect that to the encoder input of the bespoke PCB.
As I'm not using RS422 to actually transmit bytes, just differential trigger signals, my idea is to set one GPIO pin to 1, another to 0, wait for half the pulse time, revert those signals, wait another half pulse time, and repeat from start. (Actually, I'll need 4 pins, to simulate A and B, and cycle between "set A to 1/0", "set B to 1/0", "set A to 0/1", "set B to 0/1").
A) Will this work? As far as I know, the only thing that's relevant is the differential between the two pins, and the +/- 5V between those pins should work well with the input chip of the PCB, which is a THVD2450.
B) Do I have to connect the Arduino's GND to the PCB's GND, or shouldn't I, to avoid any current loops?


texts: I recently got a parallax RFID reader. The documentation says that it only works with the EM4100 family of RFID tags. So I tried looking it up and can’t seem to find any sort of resource explaining what different families are and what they are used for. One thing I was hoping was to find what hotel keys use so I could make use of some old ones I have lying around. In any case, I just can’t seem to find any good information online, so I was hoping someone here could help.


texts: Multiple ground planes, single point ground, and a level shifter

texts:
I'm using a level shifter to go from 3.3V to 5V (digital/analog). According to the datasheet, if I put 1 ground on the left side of the IC and the other on the right, it would tie the grounds together inside the IC.

This would be bad since I'm trying to use a single point star ground with separate ground planes and it seems like this ruins it. If I want to keep using the same part, whats the best approach? I'm thinking tie both sides of the level shifter to the input ground and have the output current take a long path through the single point ground? or vice versa?

http://www.ti.com/lit/ds/symlink/sn74lvc8t245.pdf


texts: In rc low or high pass filter how to calculate cut-off frequency when a r is connected in parallel to c in low pass filter

texts:
In rc low pass filter how to calculate cut-off frequency when a r is connected in parallel to c.

here vac=1v(p-p) f=1khz,r1=r2=1Mohm,c=1mf,v=5v


texts: 8-bit synchronous up/down counter [Logisim]

texts:
I am trying to create an 8-bit programmable up/down counter using D Flip flops. So far, this is what I have:

The first 3 flip flops function correctly for both up and down, but the 4th doesn't. I was stuck on this problem for the past week and I couldn't find anything which helps.

Also, is there an easier way to solve this problem, perhaps without muliplexers?


texts: Calculate Collector Voltage In Collector feedback bias Configuration

texts: I've tried using KVL and KCL but I always end up with two or more variables, and I've got another question, how can I know if this transistor is in the saturation region?


texts: Why do we need the Fourier transforms of sin and cos?

texts:
As we know we perform Fourier transform in case of continuous and "non-periodic" functions, while sin and cosine both function is "periodic" function then why we perform Fourier transform of sin and cosine?

Can we perform Fourier transform of periodic function?
If yes then why we perform Fourier transform instead of Fourier series?


texts: FTDI chip returns descriptor of unknown device

texts:
I would like to debug the kernel of my nexus 5 and I sent to a fab the design for the debu cable that uses internally a FTDI chip that creates a USB to serial bridge.

Since the chip is a QFN package is a little bit annoying to solder but after some tries I done it; one of the board is seen correctly, indeed from the syslog

kernel: [12174.440550] usb 3-14: new full-speed USB device number 5 using xhci_hcd
kernel: [12174.585763] usb 3-14: New USB device found, idVendor=0403, idProduct=6001
kernel: [12174.585766] usb 3-14: New USB device strings: Mfr=1, Product=2, SerialNumber=3
kernel: [12174.585767] usb 3-14: Product: DCSD USB UART
kernel: [12174.585768] usb 3-14: Manufacturer: FTDI
kernel: [12174.585768] usb 3-14: SerialNumber: A600ASO8
mtp-probe: checking bus 3, device 5: "/sys/devices/pci0000:00/0000:00:14.0/usb3/3-14"
mtp-probe: bus: 3, device: 5 was not an MTP device
kernel: [12174.606497] usbcore: registered new interface driver usbserial
kernel: [12174.606569] usbcore: registered new interface driver usbserial_generic
kernel: [12174.606633] usbserial: USB Serial support registered for generic
kernel: [12174.608070] usbcore: registered new interface driver ftdi_sio
kernel: [12174.608128] usbserial: USB Serial support registered for FTDI USB Serial Device
kernel: [12174.608173] ftdi_sio 3-14:1.0: FTDI USB Serial Device converter detected
kernel: [12174.608245] usb 3-14: Detected FT232RL
kernel: [12174.608427] usb 3-14: FTDI USB Serial Device converter now attached to ttyUSB0

Other two boards instead are seen as a DCSD Status LED

kernel: [11309.878562] usb 3-14: new full-speed USB device number 4 using xhci_hcd
kernel: [11310.024048] usb 3-14: New USB device found, idVendor=0403, idProduct=8a88
kernel: [11310.024051] usb 3-14: New USB device strings: Mfr=1, Product=2, SerialNumber=3
kernel: [11310.024052] usb 3-14: Product: DCSD Status LED
kernel: [11310.024053] usb 3-14: Manufacturer: FTDI
kernel: [11310.024054] usb 3-14: SerialNumber: A101FPA7

I googled it but I haven't found anything related to it.

Since two devices return the same exact descriptor I don't think it's an error of transmission but something else, anyone has idea of what can cause this behaviour?

P.S: The chip has been bought from aliexpress so I can't say are original.

EDIT

As indicated by the solution, the chip was reprogrammed.

BTW thanks to the comment of @pjc50 I looked for a way of rewriting the EEPROM: on a Debian system you can install ftdi-eeprom and after that you have to write a configuration file with the desired VID and PID

vendor_id=0x0403        # Vendor ID
product_id=0x6001       # Product ID

and then use the program to reflash the chip

$ sudo ftdi_eeprom --device i:0x0403:0x8a88 --flash-eeprom ftdi.conf

(ftdi.conf is the name of the configuration file described above).

Now I have the device correctly indentified by the kernel.


texts: What are the benefits of a high voltage in this LTC6090-based photodiode amplifier?

texts:
In an article in LT Journal of Analog Innovation, Linear Technology brags about their high-voltage operational amplifier, the LTC6090, which can operate on ±70 volts. They present an example circuit, a photodiode amplifier:

This is perhaps impressive; I don't know much about photodiode amplifiers.

What strikes me as odd is that, while the feedback loop operates on voltages up to 120 volts, taking advantage of the increased voltage range, they then place a 1:10 voltage divider on the output, seemingly negating the benefits.

Why not replace the 10 MΩ resistor with 1 MΩ and get rid of the output divider? Then you can use a completely average operational amplifier because the output only needs to swing between 0 and 12 volts.

In my simulations, lowering the feedback voltage gave me a number of benefits:

Higher bandwidth (using the same LTC6090)
0.3 pF capacitor can be increased, loosening the layout requirements
Lower output impedance
A larger selection of operational amplifiers are now available
...and so on

I have searched in the article and the datasheet for reasons behind this, but I could not find any. Perhaps it is obvious to people experienced with photodiode amplifiers, but since the "feedback action" makes sure that the photodiode sees the same potential difference, it should not affect its behaviour - there will be 3 volts across it, and the same current will flow.

Why is this circuit improved by a high feedback voltage?


texts: Calculate the charging time of a battery with a solar cell while the battery is being used.

texts:
I'm working on GPS tracking device and I need to know how to calculate how long it would take for it to run out of power.

The unit is using drawing an average current of 5mA from a Lithium 3.7 V 1200mAh battery. If I'm not wrong, 1200mAh/5mA= 240h

Then if I add a solar cell of 5.5v 120ma 0.66w to charge the battery while the GPS is still drawing 5mA of current. how long would it take to charge the battery and in how long will the unit run out of charge using the battery and the solar cell?

In ideal conditions, (3.7v*1200mAh)/0.66W= 4.44Wh/0.66W= 6.72 hours to charge the battery. but this is just in ideal conditions and not taking into account that the battery is still drawing 5mA to the GPS.


texts: Time uncertainty of an ADC sample for a given sampling frequency

texts:
I am working on a project which involves time difference of arrival calculations. I need to calculate the uncertainty of my timing measurements. I am using an ADC to sample the signals who's times of arrival need to be compared.
Right now, I am working under the assumption that sample at fs results in a timing uncertainty of 1/fs. For example, if a signal arrives 1 second after the system starts up, and the sampling frequency is 10Hz, the resulting arrival time would be 1s +- 0.1s. Is this method valid if I am interested in considering sample rate only?


texts: PCB routing around capacitors "snake style" possible electric disadvantages?

texts:
Is there any reason not to route the +12V and GND lines in a snaking pattern as shown with C7 + C11? From instinct I'd always route caps in parallel to power and gnd rails.

Top left near D1 is the power supply.


texts:
So I'm pretty new to electronics and just started playing around with the Arduino to learn the basics. In one of the projects there was just a simple button and 3 LEDs that are controlled by the Arduino. Following is the schematic:

As there is no explanation in the book as to why there's a 10KΩ resistor, I did some Googling as to why it's there. I found out it's a voltage divider and keeps a 5V \$V_{out}\$ into the Arduino 2 pin.

My question is, is this resistor necessary? I know it follows the following equation:

$$
V_{out} = V_{in} \times \dfrac{R_2}{R_1 + R_2}
$$

So if there's no \$R_2\$, I'd be dividing 0 by 0. In which I'm guessing it's a short circuit? But any resistor of like 1Ω would still allow the 5V \$V_{out}\$. Which would mean that any resistor avoids short circuits? What if I don't connect it to ground at all? Can't it flow just directly from 5V to pin 2 through some internal ground?

I'm kind of reluctant to just try it out myself and see what happens out of fear I'm going to fry some components.


texts:
Im trying to repair a diagnostic interface, I've got a burnt chip and cant find any board data.
Multimeter: diode mode in one direction reading : 1380, in other way 820
test in resistance ( 2000 ohm setting) I get 1510; in other 1430 in other direction.

In need of identifying silver/Gray SMD part with writing on it "24"
No luck finding it.


texts:
So I was given the electromagnetic E field equation in phasor form and I converted it to sinusoidal form. Is it correct ?

Also will it be a reflected wave since we have (wt+Bz) and not (wt-Bz) ?

Also will it be circularly polarized since it is constant at all angles ?


texts: Downsides of using an existing length of wire as a shunt

texts:
I have an isolated electrical system composed of a couple of solar panels, 4 x 6V batteries and a 12V -> 120V inverter.

I'd like the measure the current flow in and out of the batteries in order to implement a DIY battery monitoring system. To that end, I've purchased a 200A shunt (75mV full scale, so 0.375 mOhm), which frankly looks pretty junky, and proabably is for the price I paid. When the system is running at 200A, the shunt will be consuming 15W, which also kind of sucks (I guess it will get pretty hot at that load and I'll have to careful how I mount it).

While I was contemplating adding the shunt into my existing system, it occurred to me that perhaps I could just use any existing length of wire as a "shunt". For example, I have a ~2 foot length of 00 gauge wire coming off of the battery terminal, which based on my calculation should be about 0.156 mOhm, fairly similar to my shunt. Rather than complicating my system (and adding resistance) with this shunt, what if I just measured the voltage drop across this length of wire instead?

Of course, I'd have to calibrate the measurement with some external source (e.g., run 100A though it and measure the drop) - but looking at the not-so-high-precision construction of my shunt I suspect I might have been doing that anyways.

What are the downsides of this approach?


texts:
I have built a high side MOSFET driver and hooked it to an atmega328p.
Having an issue with the setup,  the MOSFET is not switching on completely due to the low Vgs. For this circuit the expected Vgs is around 5V,  but it measures only 2.1V across the gate and source.


texts: 26 Led Array Component Identification and Failure Cause

texts:
I have the following LED lights. These lights keep failing on me. I'm suspecting that the DPAK(U1) component is failing but I have no clue what it is. The markings on the DPAK reads 5ZYl8GF6D. I'm assuming it is some sort of voltage/current regulator.

How the device fails

Two devices lights are about half the brightness of a working one with a slight flicker. Also takes about twice as long to turn off fully.
Third device is dead as a stone and the PCB around DPAK is discolored

Mesurments

Rectifier:

AC to V+ and V- is 0.6V drop

V+ to V- is 1.14V drop

Meter does not give me a reading on the LEDs.

The rest of the values correspond to there marked value.

The schematic is as follows

The x10 refers to 10 LEDs in series and x16 to 16 in series.

Assuming a voltage drop of 2.5V for the LEDs (White). The input voltage should be about 286Vdc to the DPAK(U1). The device claims to be 18W but I have no way I consider to be safe to test this.

I'd like to replace the DPAK with a better component or at lease keep a supply of its equivalent.

EDIT

After googling a bit more I found this.

Design LM317 Constant Current Circuits
and this chip.

From what I gather the 10R resistor controls the current with Iout=Vref/R so this gives it a Iout of 120mA witch is beyond the chips ratings.

The stated 18W gives a value of 54mA as the max current witch is slightly over the limit of the chip.


texts: 8 Ohm Speaker Gets Hot - Simple 555 Piano

texts:
I have built this circuit and nearly everything works fine. I replaced the piezo with a small 8 ohm speaker and put a potentiometer in, so I can control the volume. Unfortunately the speaker gets really hot. What am I doing wrong? Can't I just replace the piezo? Do I have to add something else?

Thanks for helping me


texts: Incremental optical encoder output to Matlab Simulink

texts: I'm doing a project based on an incremental encoder based position sensor. In order to validate this, I'm trying to read square wave signals from a function generator (since an optical encoder produces square wave pulses as output). Is there any method to read voltage signals from a signal generator using MATLAB Simulink software?


texts: Am I using this multiplexer (SN74LS153N) correctly?

texts:
I'm trying to make an ATtiny85 control an SN74LS153N dual 4-to-1 multiplexer in order to read state of several switches using a single pin (three pins actually), but am having trouble understanding why my design does not work.

This is what my prototype looks like at the moment. The LEDs are there only to explain my issue.

No matter what state the switches S1 to S4 are in D3 never lights up and U2  never seems to be able to read the digital state of PB4 input. U2 is programmed to iterate through all states of A and B inputs to U1 and that is what it does: D1 and D2 flash accordingly - OFF:OFF, OFF:ON, ON:OFF, ON:ON (D1:D2).

I've read the datasheets over and over and checked and verified that everything is hooked up as required. Am I missing something obvious? Are those switches to blame?

SN74LS153N

ATtiny85


texts: ATxmega: reading a register with TWI/I²C

texts:
I am trying to read a register value from the Bosch BMA280 with the ATxmega. But I cannot make it work. The code I tried looks like this:

TWI.MASTER.ADDR = (BMA280_SLAVE_ADDRESS << 1) | 0;      // writing mode
while(!(TWI.MASTER.STATUS & TWI_MASTER_WIF_bm));

TWI.MASTER.DATA = reg_address;                          // send Register address
while(!(TWI.MASTER.STATUS & TWI_MASTER_WIF_bm));

TWI.MASTER.ADDR = (BMA280_SLAVE_ADDRESS << 1) | 1;      // reading mode
while(!(TWI.MASTER.STATUS & TWI_MASTER_RIF_bm));

data = TWI.MASTER.DATA;                                 // get data
TWI.MASTER.CTRLC = TWI_MASTER_CMD_STOP_gc;              // send stop bit

When changing to reading mode, the RIF flag is never set


texts: When there is a very low voltage (AC), even for a compact fluorescent lamp (CFL), it glows very dim (orangish in color) at the beginning of the glass but when I hold the glass just for a second, it starts glowing as usual (generally white in color, don't know what your's is) though a very little bit dimmer than its original capacity. So, I want to know why it happens, i.e. it starts glowing at the same voltage when we touch it (the one I am trying is rated 220V, AC Current freq here is 50Hz, power required doesn't matter as it happens with all of them, voltage is ~30 in my case but it may differ in yours). If it's related to body-heat (because I think so), why does it just keeps glowing continuously even if we don't touch it after that?


texts: Placement of filter components to reduce EMI

texts:
An electro-magnetic interference (EMI) source is connected to a filter and to a LISN.

The EMI source is a common-mode source: it generates an undesirable signal which flows from the generator \$ V_g \$, equally divides itself and flows through the branches HOT and NEUTRAL and comes back to the generator through ground (notice that LISN too is connected to the same ground).

The filter is placed between the EMI source and the LISN in order to deviate to ground the EMI signal before it reaches the AC mains. Input voltage in the LISN is a measure of the EMI signal which will exit into the AC mains.

There are two available topologies for the filter.

First configuration:

simulate this circuit – Schematic created using CircuitLab

Second configuration:

simulate this circuit

\$ L_1 \$ and \$ L_2 \$ are (in both circuits) mutually-coupled inductors, with \$ L_1 = L_2 = L \simeq M \$, so both have a total inductance of \$ L + M \simeq 2L\$.

Notice that the voltages \$ V_L \$ are the same because the two branches are equal and the current produced by \$ V_g \$ equally splits between the two branches. The first configuration gives a higher \$ V_L \$ than the second, so the first configuration is the worst.

Why?

I drawn the equivalent circuits for the whole signal: the returning path to which I am interested in is through ground. So, in the first configuration the equivalent circuit is

simulate this circuit

and in the second one it is as follows:

simulate this circuit

The left resistance is \$ R_{LISN} / 2 \$ because it is the parallel of the input resistances of the LISN seen from HOT to ground and from NEUTRAL to ground: if they are both \$ R_{LISN} \$, \$ R_{LISN} || R_{LISN} = R_{LISN} / 2 \$.

Then I obtained the \$ V_L \$ voltages: in the first case it is

$$V_L = V_g \displaystyle \frac{(R_{LISN} / 2) || (2C_y)}{R_g + sL + (R_{LISN} / 2) || (2C_y)}$$

and in the second one it is much more complicated. If I did not make mistakes it should be

$$V_L = V_g (R_{LISN} / 2) \displaystyle \frac{sL + (R_{LISN} / 2)}{R_g(2C_y + sL + (R_{LISN} / 2)) + 2C_y(sL + R_{LISN})}$$

I know that \$ R_g \gg R_{LISN} \$; moreover, in such cases the inductors should be placed after a small impedance and the capacitor after a great impedance. This is confirmed by the fact that the second configuration is better than the first. But, again: why?

I can't immediately see this from the expressions I obtained: both have \$ R_g \$ in the denominator. Even if it is not immediately visible from the maths, which could be the physical reason for this behaviour?


texts:
I am busy with a robotic arduino project. I have a 40kHz ultrasonic transducer and receiver. What would be the best way to generate the 40kHz signal to drive the transducer.
I have found two ways to do this:

555 timer
Arduino PWM

I have the following schematic for the 555 timer:

My concerns are related to which of these two will generate the best waveform. I am also concerned that having to switch the Arduino PWM on and off might impact on timing accuracy. Am I missing something or is there a much simpler way to drive the transducer?


texts: Why do the large transistors on computer components have their middle pin cut?

texts: I have seen transistors with the middle pin cut used in computer equipment. What do they do?


texts: Conversion of a transformer into an electromagnet

texts: Is it possible to convert a voltage transformer into an electromagnet by connecting a small DC voltage source to its primary side?


texts: Power an op amp when having only higher supplies

texts: I have a +-24 V supply and I want to power an op amp. I initially tried an LM324 using a single +24V supply, but I then discovered that I want the op amp to be allowed to output negative voltages too (which the 324 can't). I could not find an op amp that can take e.g. max +-25 V so that I can connect it immediately to my supply. Would just a voltage divider do?


texts: Liquid Metal Thermal "Thermal Grease" on a Peltier Element?

texts:
I was wondering if Liquid Metal Thermal Grease could be placed on a peltier's hot side to better conduct heat from the hot side to the heat sink.

I know that aluminum is "Eaten" away by the thermal grease; however, Peltier's have a ceramic casing that is apparently non-conductive.

Thank you


texts: Some sort of reflector behind a spiral antenna

texts:
I was in an antenna laboratory, and I saw a spiral antenna with a sort ground plane, about 0.5 cm behind the antenna (probably a reflector as the antenna was not connected to it.)
Is that a known technique? Is such a reflector thought to increase the gain of spiral antennas in their view direction?


texts:
I have seen a video on the web where a person is testing the galvanic isolation of several phone chargers. I am talking about this kind of phone charger.

They are plugged into the wall with no connection to earth, and are supposed to deliver 5 V between the VCC and GND pin of the USB port. I have measured the voltage between the GND pin and the earth of some of my own phone chargers. The results are disparate: 1 VAC, 8 VAC, 60 VAC and 80 VAC.
I am a bit confused with the process:

How come the (AC) voltage between earth and GND is a means to qualify the galvanic isolation of a phone charger? Shouldn't it be between GND and neutral? The earth is not connected in the circuit.
When the galvanic isolation is not so great, is it GND or earth that oscillates? If this is GND, does it mean that VCC and GND are oscillating but the difference is always 5 V? If this is earth, what does it have to do with the charger?


texts: Detecting ground on GPIO and protect from positive voltage

texts:
I need to sense a logic low on the GPIO. The input will come from external resources (By end user) so I need to protect the circuit as well from high positive voltage. Generally the circuit will be used in places where I don't expect a voltage of more than 30 Volt. So from external input, it can be a ground (If user does it correct) or a max of 30 volt, in case user does a wrong wiring. Is this circuit going to be good enough?

simulate this circuit – Schematic created using CircuitLab

Please suggest if there is any mistake and if this can be simplified.


texts: What are these two white screws on a ps3 power supply?

texts: In this video a gentlemen turns two white screws to fix a play station 3 not turning on anymore.  Could anyone tell me what these screws are, and what turning them a little bit is supposed to solve?


texts:
I used to check complex commercial PCBs specially those of graphics cards to see how professional PCB designers do their layout and learn from their techniques.

When I checked the card shown below I noticed two things regarding the placement of vias:

(A higher resolution image is shown here).

The PCB is surrounded by stitching vias all around the edges. What's the role of all of these? I think they're connected to ground to act as a shield, if that's true, I can't understand technically how by this placement they achieve this shield?
By looking closer to the mounting holes, I noticed they added vias all around the pad, why?


texts:
I have a +3.5V/-3.5V AC signal (audio frequency range) that I need to convert to 0V/5V range so that I can use it as input for an ADC.

I was trying to use a non-inverting summing opamp, but I can't figure how to calculate the resistors.

I know that I need a gain of 7.14 (5V/7V) + 2.5V offset, but I don't understand how to determine the resistors for the non-inverting topology (assuming 5V as voltage reference for the offset).

can anyone help me understand how to calculate that? thank you


texts: I have to draw the corresponding transistor-level schematic of the CMOS layout below

texts:
I am an electrical engineering student and I have the following assignment:
'Draw the schematic that is correspondent to this whole layout'.
I can understand how to translate the inverters from the A,B,C and D,E parts but I cannot seem to find any solution to the connections of the pins from C to D. Until now I have the solution below, which I know it is not fully correct. Can someone help me with an explanation on it?


texts: Times a DC motor can be driven from pair of AAA 1000mAh

texts: If I have 3V voltage made from two AAA in series, both 1000mAh and driving a 3V 1.5W DC motor with it, being the duration of tON exactly 1 second for each drive attempt. Is it possible to estimate the quantity of times the motor will trigger until the end of the baterry charge/capacity?


texts:
this is my first electronics project. I'm using a microcontroller (Adafruit ESP8266 Huzzah) connected to an IR sensor and two L293D stepper motor drivers which are connected to two Nema 17 stepper motors. I will be sending the data via Wifi to a web page. I asked my university professor about the current throughout the circuit and he said he is not sure what I mean and that major consumption, by far, will be the motors. I'm not convinced so I thought I would double-check and ask here.

The nema 17 stepper motor is rated at 0.4A

The L293d drivers have a max continuous current of 0.6A (datasheet shown below).

Here is some info for the microcontroller

And finally, the IR sensor. I found that the supply current is 1.3mA.

I plan on using a 12V battery with and LDO down to 5V to the microcontroller, driver and IR sensor. I am also using inverters to reduce the number of pins required from the microcontroller.

So my question is how do I ensure the circuit will work from those values of current? I'm rather confused by all of this but I'm guessing that the calculations start from the battery. My professor told me not to worry about the circuit current but I am skeptical. Many thanks.

EDIT:

Here is a schematic of my circuit. Hopefully you can read it. I was recommended 74HCT inverters.


texts: Low Side Overcurrent Detection with Adjustable Maximum - Difference amplifier or non-inverting amplifier?

texts:
Situation:

H-bridge circuit with mosfets.
A low-side shunt resistor is used to measure the overall current.
The selected bridge driver IC is equipped with an overcurrent
protection feature.  This is implemented as an input pin (ITRIP)
connected to an internal comparator. The overcurrent protection is
triggered whenever a voltage of 0.5 V or higher in reference to the
IC ground is applied to the input pin.
The IC ground is slightly decoupled  from the main power
ground with an inductor.
A trimmer potentiometer should be used to adjust the current limit.

The first idea here was to use a single non-inverting op amp circuit (below).

However I am unsure if the two different grounds can cause problems here?

simulate this circuit – Schematic created using CircuitLab

The second idea then was to combine a difference amplifier
with fixed resistors and the non-inverting op amp circuit (to allow for adjustable gain):

simulate this circuit

Is this superior to the first version at all?

What solution would you recommend or consider best suitable for this situation?
(Best in terms of reliability,  low cost and low amount of separate components)

Thank you very much!

Update:
Based on @Daniel s suggestion:

simulate this circuit


texts: Why does LTSpice simulation give me negative value on NPN emitter current?

texts: So I built this circuit and I am trying to measure the emitter current, and the LTSpice simulation is giving me negative value reading... any idea why?


texts: RTC backup by super capacitor estimation issue

texts:
I create a RTC backup circuit for a STM32L412CBT6. Circuit work but not as long as I estimate during design.
Here is the schematic (VBKP go directly to STM32 VBAT pin):

SC1 capacity is 0.33F

Here is my estimation :
CHARGE
Tc = RcxC
Tc = 100 * 0.33
Tc = 33 s
To fully charge the super capacitor at 5xTc I theoretically need 165 s (2 min 45 s)
I do measurement and It's OK, my super capacitor from 0V take about 2 min 30 to go to 3.2V.
DISCHARGE
To get the Rd, the internal resistance of the VBAT circuit of STM32, I see in datasheet RTC theoretically need 300nA at 3V, but when I take voltage across R17 during discharge I got 5mV, so current is 50µA (166 times more but it's an other problem so let's take 50µA)
Rd=3 / 0.00005
Rd = 60000 ohms (60 kohms)
Td = Rd x C
Td = 60000 x 0.33
Td = 19800 s
To fully discharge the super capacitor at 5xTd I theoretically need 99000 s (27 h 30 min)
To discharge super capacitor at 0.7xTd (50% is about VBAT min for RTC) I theoretically need 13860 s (3 h 51 min)
I do measurement and I'm totally out :
HOUR    SC1 Voltage [V]
22:00   3,21
22:12   2,62
22:22   2,44
22:33   2,29
22:49   2,10
22:59   2,00
23:12   1,86
23:24   1,74
23:34   1,64
23:47   1,52
0:15    1,25
0:24    1,16
0:42    0,99
0:55    0,86
1:26    0,58
1:35    0,51
1:53    0,37
2:34    0,18
2:56    0,14
3:03    0,13

I take about 5H to discharge the super capacitor (far away from 27H)
QUESTION

I think my estimation problem is from Rd (internal VBAT circuit resistance of STM32) determination, but why I'm so far of my estimation ? Can you help me to find my error ?
If someone got an idea for why my RTC sink 50µA instead of 300nA, let me known (Voltage measurement device error ?)
If someone got an idea to connect (without regulator) the 3V3 of this circuit to a LiPo (3.7V) battery (charge at 4.2V), let me known.

Thanks in advance
EDIT 1 :

Here is an interesting documentation about "How to design a VBAT system on STM32L01"
Thanks to @Marko Buršič , here is a "Good thread about supercapacitor on VBAT and leakage information"


texts:
I recently bought a 3D printer from the USA and imported it to the UK, it came with a Chinese 12v DC 30 Amp power regulator. The PSU is a metal enclosed box. It can take 220 Volts +/-15% so it should be okay to run on the uk mains. It has three input terminals live, neutral and an earth terminal. There are four DC 12 volt outputs and four zero volt terminals.

The unit is a YGY 123000 12V DC rack mounted power supply. The only place I can find selling these units is a shop in Lebanon.

I did some checks with an ohm meter. These checks revaled that the earth was not connected to the metal chassi. The earth terminal is connected to the 0V DC output terminals.

I don't dare connect this PSU to the mains and I have since ordered a quality PSU a COPEK AK-350-12 at great expense.

Have I done the right thing and what should I tell the manufacturer of the 3D printer?


texts:
I just recieved 2 OLED displays SSD1327 128x128 16bits, 1.5", but I can't connect them to my arduino uno R3.
I first tried with the Adafruit library, set the address 0x78 as printed on the display, but it didn't work.
Then I tried with the address 0x3C according to the 7bit-8bit encoding difference, but it didn't work aswell.
So I tried to find the address with a I2C scan sketch, and the things start going weirdly :
When the display is correctly wired up, the sketck blocks at the line Wire.endTransmission();
But when the display GND is not connected to anything and the display VCC is connected to 3v3, the sketch detects an I2C device at the address 0x3C, whis is the good one!
And I get this for the both displays I recieved.
I tried with an other I2C device (SSD1307), to check my wirering or the sketch if anything could be wrong, but no, I got the expected results: the device was detected only when it was well wired.

Any ideas ?
Do you think the displays are dead ?
EDIT : shematics added


texts: What would be the best way to power 10 AAA powered torches with mains power (240v)

texts: We manufacture small AAA powered RGB torches. To test them I'd like to power up 10 at a time with crocodile clips. Ideally, the power source would be a mains powered supply. Would wiring off a multi-battery charger be a viable solution?


texts: VHDL: Kan sequence of if/else be optimized?

texts:
I am new to VHDL and I try to find all places where I can replace if/else statements with cases of inlined OR/AND operations to get more things executed in parallel instead of sequence.

Now I have the following statement:

if (val = 0) then
    returnVal := 0;
end if;

if (val > 0)
then
    returnVal := 1;
end if;

returnVal := 2;
return returnVal;

As I can see, this will be executed sequentially with a depth of 3.

Is this exact statement possible to do in a more efficient manner?

NOTE: The values 0, 1 and 2 are not important - they must just be different, e.g. could be -123, 234 and 432 if that makes it easier for optimizing

Thanks

UPDATE: As pointed out, this logic was broken. The intended logic is:

if (val = 0) then
    return 0;
end if;

if (val > 0)
then
    return 1:
end if;

return 2;

UPDATE 2: I am programming VHDL and deploying to an FPGA which is important as it differs from microcontrollers in the terms of parallelism.

UPDATE 3: I realise, that I may not have been explicit about my exact question, so my apoligies. What I mean is: The three statements are mutually exclusive: Than value is either < 0, = 0 or > 0. And even though a case switch cant be used here, I was wondering if anyone had another input to how to improve performance of this.


texts: Do any rotary encoders allow zero idle current

texts:
Many microcontrollers and logic devices (programmable or otherwise) are capable of drawing very little current when nothing is happening.  If a double-throw switch is wired to such a device, then when the switch is moved to one contact-closure position, it's possible for the controller to sleep, drawing essentially zero current, until the switch is moved to the other position.  Even if the switch were to sit between the two positions for an extended period of time, or repeatedly oscillate between one position and "open", the system wouldn't have to care, and could remain in a near-zero current state.

Monitoring a single switch input, by contrast, requires consuming a certain amount of quiescent current whenever the switch is closed; the amount required is related to the speed with which software must notice if the switch is open.  This is fine for many scenarios involving mechanical switches (in many cases, one can either arrange to have switches be open most of the time, or will be able to get by polling a switch e.g. once every 100ms or so).  Rotary encoders, unfortunately, satisfy neither of those conditions.  They're as likely to be on an active spot as an inactive spot, and in many cases one will need to respond immediately to a change if one is to have any hope of maintaining an accurate position count.

If a rotary encoder has just two contacts, there will necessarily be a position where both are active simultaneously; the only way to determine when the encoder leaves that position would be to feed current through those contacts to test their state, likely increasing quiescent current by an order of magnitude beyond what would otherwise be achievable (depending upon required response time).  If there were three or four contacts wired as:

       **  **  **
Out1: -AAAAAA-----
Out2: -----AAAAAA-
Out3: AAA------AAA

       **  **  **  **
Out1: -AAAAAA---------
Out2: -----AAAAAA-----
Out3: ---------AAAAAA-
Out4: AAA----------AAA

then it would be possible for a processor or other circuit monitoring such an encoder to ignore the state of any closed contact until it saw a different contact close.  In the first case, the processor could resolve 1/6 cycle when awake, and be assured of waking up when the device moves to any position marked with ** after having been on another such position (typically 1/3 cycle; just under 1/2 cycle worst-case).  The second case would allow 1/8-turn resolution when awake, and would wake up when the device moves 1/4-3/8 cycle.  The second design would be somewhat easier to interface with a quadrature decoder, since feeding Out1 and Out3 into one RS latch, and Out2 and Out4 into another, would yield clean debounced signals for the decoder circuit.

I've seen rotary encoders with more than two contacts, but they've all used the extra contacts for purposes of yielding a more detailed binary position.  Do any companies make encoders which use extra contacts to allow near-zero-quiescent power while maintaining an accurate position count?  Alternatively, would there be any other approach which could be used to monitor an encoder (possibly a higher-resolution one) with near-zero quiescent power?


texts: Digital oscilloscope minimal sample rate to capture SPI data going at 500 kHz

texts:
I need to debug an SPI bus coming out from a beagle board XM rev. C. The clock of this bus is 500 kHz.

To do this, I have a SIGLENT SDS1022DL digital scope. Its sample rate is 250 MS/s and the analog bandwidth is 25 MHz.

According to Nyquist, the minimal sample rate to have a reliable digital measurement in my case should be 1 MHz but, in practice, I need at least a 4x faster sample rate, so 2 MHz should be fine. If so, my scope specifications are adequate for my purpose.

Am I right?


texts: Cheap PIC programmer, must be Linux compatible

texts:
I'm comfortable with working on Arduino based projects, but I'm looking to start experimenting with PIC programming.

How would I go about building my own pic programmer? I thought there must be a way to save money compared to something like this one I found online.


texts: Battery temperature charging cutoff protection methods

texts:
We have run into a requirement where we need to terminate the charging of our Lithium Polymer battery when the battery temperature exceeds the manufacturer rated temperature.
My immediate reaction is to wire in a thermocouple to the battery pack and run that into the MCU input which would then might toggle some sort of MOSFET charging cutoff switch. Obviously, this would be pretty disruptive to an already very space constrained design.
Are there any cleaner solutions to meet this requirement?


texts:
Update: I've removed all irrelevant information and simplified the question.

The OPA548 operational amplifier provides adjustable current limit that can be controlled digitally with a current-out DAC. Below is a circuit from the datasheet. I've calculated that Iset current 0~6.7µA will give me desired output range 0~100mA.

However, OPA548 is powered by isolated ±25V DC-DC. So, I would like to isolate current limit control too, using IL300 optocoupler.

Question Can I simply connect photodiode to control pin like this:

Or do I need something more complicated, like current mirror:

As I understand it, the first option corresponds to input range about 0.56 mA at forward gain K2 = 0.012. This is just a fraction of the optocoupler's normal operational range 10 mA.

I think the formula for resistors in second option is Ilim = Id * R1 / R2, which means it can be adjusted to better use operational range.


texts: What happens when a program needs to use more than the allotted 16 registers?

texts: I'm just learning about how programs work under the hood of a computer. We discussed how registers are a limited resource to the CPU. So what happens when a program is massive and needs more than 16 registers? I've tried looking this up and couldn't find any answers regarding it.


texts:
In a Nucleo L476RG  with system/timers/peripherals CLK at 80MHz,
in the main loop I have code to directly access GPIOA register:
GPIOA->ODR = GPIO_ONE;
__NOP();
...
GPIOA->ODR = GPIO_ZERO;

The required pins have been configured for very fast speed:
        GPIO_InitTypeDef GPIO_InitStruct = { 0 };

        /* GPIO Ports Clock Enable */
        __HAL_RCC_GPIOC_CLK_ENABLE();
        __HAL_RCC_GPIOH_CLK_ENABLE();
        __HAL_RCC_GPIOA_CLK_ENABLE();
        __HAL_RCC_GPIOB_CLK_ENABLE();

        /*Configure GPIO pin Output Level */
        HAL_GPIO_WritePin(GPIOA, GPIO_PIN_5, GPIO_PIN_RESET);
        HAL_GPIO_WritePin(GPIOA, GPIO_PIN_6, GPIO_PIN_RESET);
        HAL_GPIO_WritePin(GPIOA, GPIO_PIN_7, GPIO_PIN_RESET);

        //
        GPIO_InitStruct.Pin = GPIO_PIN_5;
        GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
        GPIO_InitStruct.Pull = GPIO_NOPULL;
        GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
        HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
        ...

And the assembly generated looks fine:
 80010f4:       615a            str     r2, [r3, #20]
 80010f6:       bf00            nop
 80010f8:       bf00            nop
 80010fa:       bf00            nop
 80010fc:       bf00            nop
 80010fe:       6159            str     r1, [r3, #20]
 8001100:       bf00            nop
 8001102:       bf00            nop
 8001104:       bf00            nop
 8001106:       bf00            nop
 8001108:       615a            str     r2, [r3, #20]
 800110a:       bf00            nop
 800110c:       bf00            nop
 800110e:       bf00            nop
 8001110:       6159            str     r1, [r3, #20]
 8001112:       bf00            nop
 8001114:       bf00            nop
 8001116:       bf00            nop
 8001118:       615a            str     r2, [r3, #20]
 800111a:       bf00            nop
 800111c:       bf00            nop
 800111e:       6159            str     r1, [r3, #20]
 8001120:       bf00            nop
 8001122:       bf00            nop
 8001124:       e7e6            b.n     80010f4 <main+0x11c>
 8001126:       bf00            nop

However:

If the str fn is followed by none or a single nop, the pin does not toggle.
If the str fn is followed by 2 nop, the pin does toggle regularly, with a period of 40ns.
If the str fn is followed by a number of nop > 0, the pin toggle with a random period. In mean, it is the proper one, but clearly there are differences from one execution to the next one.
In the attached picture, I captured how on an iteration of the loo where 3 and 2 pair of nop operations generate a different periods.
In the next iteration, the pair of 2 nops generate the desired wave.

I am directly loading the pin with the logic analyzer.
Thanks

What could be happening?


texts:
Suppose a pin can be set to three modes, high (5V), low (0V), and high impedance (?V). What is the voltage associated with high impedance? I.e. if I stuck a probe on a pin set to high impedance, what voltage would I read?

Does high impedance mean no current? If so, does that mean voltage measured would be 0 because of V=IR? If so, how would you differentiate high impedance and logic level low?


texts: How to comment at the end of a command in LTspice?

texts:
Commenting in a spice file is quite straightforward. Start a line with an * and the entire line is a comment. The first line is comment by default. An example is as follows:

  * This is how your write a comment in a spice file

That much is clear from the following references:
http://newton.ex.ac.uk/teaching/cdhw/Electronics2/userguide/sec2.html
http://www.ecircuitcenter.com/Basics.htm
http://home.olemiss.edu/~atef/engr360/tutorial/qgspice.html

However, I have been unsuccessful so far in finding a reference, which explains how to add comments at the end of a line. The third link mentions the use of ; but it is unclear about it. For example:

  R1 3  4 1K ; Is this a comment?

In LTspice (and in spice in general) is it a frowned upon practice to add comments at the end of the line?


texts: Pulse distortion low pass filter and group delay

texts:
What is really meant by pulse distortion? I have come across several paragraphs which mentions the cause of the pulse distortion is group delay. But doesn't a LP filter still distort a pulse even though the filter would have a constant group delay? I mean a LP filter attenuates the amplitude of an input differently at different frequencies. A pulse would be composed of superimposed sinusoids at different frequencies and each sine component of the pulse will be attenuated differently by the filter. Wouldn't that cause a distortion as well?

I ask this because the sources I come across never mentions this and relate the distortion only to the group delay. So I suspect maybe I don't know the true definition of pulse distortion. Would you call a pulse distorted if it is filtered by a LP filter with a constant group delay?


texts: Braking a motor commanded by an IC H-bridge

texts:
Firstly, some premises of the design are related to the high speed needed (maximum as possible) and precise stop point. The motor is feed at a maximum of 40V and consumes at normal operation 1.5A. Due to this I've relied on the L6203, which at begins seemed a good choice.

The machine operates on a cycle that it goes forward and then goes back. It should be done at the minimum time as possible unless the user selected a lower speed. It does also have to stop every time at about the same point (chosen by user). Some tests showed us the great variance at speed given different conditions, like temperature, voltage level on net or mechanical differences. Due to the speed requirement and because there is none acceptable overshot (the machine can't goes back while on a forward command) I've discarded an implement of a PID or another simple control. The machine knows the stop point by an optical encoder and it's behaving well (the problem is really the variations on speed).

Even that it does not stops as desired, the robustness is validated. The machine is being tested at several weeks, sometimes 24h a day and did not shown any worrying issue even without any fan attached on L6203. It has worked on a nonstop routine since Friday until almost now.

I think the easiest way to stop it is by an electronic brake. But the L6203 apparently does not allow this function (I've already searched for Appnotes, reread DS and searched on a tons of sites). Beyond this, I think the L6203 has some issues regarding to dI/dT, because at the begin of the project some bridges were blew, solved by a greater delay between the direction reversion.

So, to brake it, I've made an auxiliary PCB and did minor modifies on the uC code. The PCB consists on a TRIAC which triggers when A and B are 0 (transistorized NOR) closing a loop and braking the motor. To avoid damage on L6203 I've programmed to send 0 to its enable port right before send 0 to both directions (so I'm sure the L6203 is off when the motor is being braked). Also, to avoid turning it on again while the motor is short-circuited, it has a delay between trigger some direction and enable the L6203 (so I'm sure the brake is cut before the L6203 is enabled again).

The snubber, although delays a little the brake, was added to limit the dI/dT (a critical spec on triacs).

My last L6203 has burned on a mistake during the test with the brake board. I believe due to a mistake while connecting the command (A and B). So I can't test it before thursday.

The questions are:

Does the TRIAC (precisely the BT139-800E) provides a reliable operation on this design?
Is there any simpler way (and cheaper) to brake the motor while still using the L6203?
Are there any other issues with all I've described before?

If needed I can also upload the entire schematic or the code.


texts: Seperate protection circuit for charger and system for Li-ion battery

texts:
I'm thinking of using the BQ2971x for battery protection.

http://www.ti.com/lit/ds/symlink/bq2971.pdf

One thing that anoys me is that most batterys (18650 Li-ions) usually have a lot higher discharge than charge current.

So using one like this:
Would imply that it has to be configured for maximum charge due to that the charge current is alot lower than what the discharged is allowed to be.

To go around the problem I've this idea of using two BQ2971x instead, like this:
By that way I can configure the discharge and charge current separetly by selecting different mosfets or variants of the BQ271x.


texts:
I am currently building my own high voltage power supply running off of a 10v input and a 360v output. The circuit will use a 555 timer switching at a frequency f that will drive a MOSFET to power a transformer with a winding ratio of 1:36. The output will then be fed into a full wave rectifier.

I would like to know how exactly the frequency of the 555 timer will affect the output voltage (I am thinking of using 60-120 Hz so the skin effect should be negligible), what effect using a PWM signal on a transformer will have, any changes I should make to the circuit, how I would be able to calculate the impedance of the drain and source of the MOSFET and since I am creating the transformer myself, what effect using a ferrite cage versus an open air transformer would have on the circuit.

The circuit will be used to charge up capacitors that powers a xenon flash lamp (triggered by an external source).


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I am learning to find the voltage drops across the capacitors in a DC circuits.
we all know that capacitor charges till it equals the input voltage (assuming initial charge of capacitor is zero). If a DC voltage is applied

For the above circuit  Vc= Vs(1-exp(-t/rc))

Now I considered little complex circuit something like below.

Here capacitor is not directly connected to a voltage source. After googling I found that the circuit can be solved by considering the capacitor as a load and finding the Voc and Rth  by using Thevenin's theorem( Or its dual Norton's theorem). Now R value in the time constant is replaced with Rth value and Vs voltage with Vth voltage.

Finally the voltage across capacitor, Vc= Vth(1-exp(-t/RthC))

Now I considered more complex circuit. Suppose if the circuit consists of more than one capacitor in the circuit. Something like below.

Now I am stucked here. How do I solve for the voltages across the capacitors C1 and C2.

I am wondering what would be the capacitor voltage equations for both capacitors. If there is a single capacitor, we used Thevinin's theorem but how do I solve if I have more than one capacitor in the DC circuits.

Vc1= Vunknown1(1-exp(-t/Runknown1 C1)
Vc2= Vunknown2(1-exp(-t/Runknown2 C2)

How do i solve for Vunknown1, Vunknown2, Runknown1 and Runknown2. Could anyone kindly explain me. How do I solve if we come across these type of circuits. Kindly help me through this.Thank you.


texts: Are network theorems (KVL, KCL, Thevenin, Norton, Superposition, Max Power Transfer) applicable on both DC and AC networks


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I have a trimpot code(502) that after many searches I cant find the correct way to connect it the way I want and of course if it can be done.

As usual all potentiometers and trimpots as searched around the net are using the classic way of connection from the left leg until the middle rotation is 100 to 0 and from middle leg to right leg 0 to 100 as if we say it was a volume value the 0 and 100

So whatIi would like to know is how to connect my trimpot the way that from the left leg until the right leg rotation it gives me 0 - 100 or the opposite without the middle goes to 0 or even changes the value.
I want my full left rotation to have the 0 or 100 and the full right rotation to have the other full or 0 value (like a volume knob)

Until now nowhere exists an answer or I am not searching enough.

Is there anyone who knows how to make the connections so it will work as I want or is not even possible and it needs something specific ?


texts: Is there a tool to automatically convert Sequential Circuits into Flip Flops

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I am working on a project which requires me to convert Mealy and Moore Machines into Flip Flops. Although the task isn't difficult, but it is exceptionally boring to repeat certain set of instructions, this makes it time consuming as well.

Is there an online/offline tool to automatically generate flip flop diagrams/Input Equations from a Finite State Machine?


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In the newest Make magazine, they show how to connect LEDs in line to speakers to have the LEDs light up when the speaker is playing music (pulse with the music).  They say you may want to hook up the LEDs to a 9 volt battery in order for the LEDs to come on at lower volumes.  They accomplish this via a transistor. I don't get how this works.

The connections are as follows:

NPN transistor:

Base goes to + lead from Amp

Emitter goes to Negative lead of Amp and 9V battery

Collector goes to cathode of LED

Battery:

Positive lead of battery goes to anode of LED (through resistor)

Somehow, when voltage is applied to the + lead of the Amp (music is playing), this turns the LED on?

I would have thought the LEDs would always be on, the connection goes + battery, LED, collector of transistor, emitter of transistor, - of battery.  I thought that if a positive voltage was applied to the collector, with the emitter at ground, this would be a closed circuit?


texts: Electrostatics - Homework: Energy of a parallel plate capacitor

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I need help with the following problem:
Plate capacitor, with area of electrodes S, and distance between them d has perfect dielectric, of relative permitivitty Ɛr. Capacitor is connected to constant voltage. Then, it is disconnected and dielectric is removed. What is the energy of a capacitor after dielectric is removed?

In the first case (with dielectric), energy of a capacitor is $$W_e^{(1)}=\frac{\epsilon_0\epsilon_rSU^2}{2d}$$

In my book's solution, energy in the second case (removed dielectric) is:
$$W_e^{(2)}=\frac{\epsilon_r^2\epsilon_0SU^2}{2d}$$

which doesn't change anything because dielectric is perfect (Ɛr=1).
So, in both cases, energy is the same.

Is this correct?


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I am writing to the flash memory of an STM32G474RE using the HAL libraries.
Here is the section of code I've been using:

   /* Unlock the Flash to enable the flash control register access *************/
   HAL_FLASH_Unlock();

   /* Clear OPTVERR bit set on virgin samples */
   __HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_OPTVERR);

   EraseInitStruct.TypeErase    = FLASH_TYPEERASE_PAGES;
   EraseInitStruct.Page         = ADDR_FLASH_PAGE_255;
   EraseInitStruct.NbPages      = 1;
   EraseInitStruct.Banks        = 2;

   HAL_FLASHEx_Erase(&EraseInitStruct, &PAGEError);

   HAL_FLASH_Program(FLASH_TYPEPROGRAM_DOUBLEWORD, ADDR_FLASH_PAGE_255, 0);

   HAL_FLASHEx_Erase(&EraseInitStruct, &PAGEError);

   HAL_FLASH_Lock();

The first program function works, if I erase all flash on debugging. However the following erase function does not work. I can monitor the values in the flash locations using STM32CubeIDE.
When I change
   EraseInitStruct.TypeErase    = FLASH_TYPEERASE_MASSERASE;
   EraseInitStruct.Page         = ADDR_FLASH_PAGE_255;

The erase function will start to work. But of course the whole bank gets erased. Which is not what I want.
What I don't understand is if I change
   EraseInitStruct.TypeErase    = FLASH_TYPEERASE_PAGES;
   EraseInitStruct.Page         = ADDR_FLASH_PAGE_128;

Only page 128 gets erased?
Can anyone explain why I can page erase page 128 but not 255? They're the same bank, the program memory is in a different bank, I can erase other pages in this bank? The datasheet also specifies that I can do pages erases?
Any insight is appreciated.


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I'm working on a circuit which measures the phase difference between to signals that work in ultrasound range (~20 kHz).

With help I could achieve the circuit that I expected:

But now I need to use only positive DC.

The changes I made in the circuit allow me to detect positive phase difference (when I change the bottom generator) but it gives only ~0v when I put a negative value in the generator.

I want to bias the output so the circuit works as the old one but mounted to a DC. The range will be divided by two but it doesn't matter.

Here are the links to both circuits in LTSpice
https://www.dropbox.com/sh/be6k6jhx6h9ipo5/AACywKL40KTgJz2wyFPXie0sa?dl=1