texts:
We have to count how many times a particular chair/seat has been "sat upon" - how would one go about this?

Brute force approach suggests put together a pressure sensor to flip a digital counter.

Is there any elegant approach that can be used in a commercial space inconspicuously?


texts: Why does micro USB 2.0 have 5 pins, when the A-type only has 4?

texts:
What is the extra, 5th, pin on micro usb 2.0 adapters for?

Here is an image with the different connectors.  Most of them have 5 pins, but the A-type host only has four.

(source: wikimedia.org)


texts: Is more fuel consumed immediately when spinning reserve is brought on-line?

texts:
Spinning reserve is additional capacity (reserve) that generators which are on-line (spinning) are able to apply to the grid quickly in response to a failure elsewhere on the grid, or a spike in demand.

It's my understanding that spinning reserve is controlled primarily through passive frequency response - spinning generators seek to maintain 50/60Hz - similar to how I would pedal harder when I start biking up a hill in order to maintain the same speed.

Where my understanding breaks down is, how is this physically accomplished at the energy source (before the generator)? Specifically:

To increase torque/power, does more fuel need to be burned (or steam produced) at the instant when more torque is demanded?
If so, does this mean that such generators spend most of their time in a less efficient operating state than they are capable of?
Or, is the increased torque output simply a transient response?
What is the timescale of this response?
Is there a portion of response (sub-second, I presume) that is simply due to mechanics of the generator, prior to an increase in fuel consumption?
How do coal or nuclear plants supply spinning reserve (as opposed to natural gas or hydropower), since their thermal cycles operate on longer timescales?


texts:
I has readed the short article about relay & inductive load.
It has a case, what i cant understand.
Prereq: Load - motor, around 3kW. No snubber.
When relay switched ON - huge voltage spike has occured.
Im understanding the spike on disabling, but what about enabling? Is it induction spark bust during contacts bounce or what?


texts: PCB design - Ground fill on every layer?

texts:
Im currently working on a PCB design, where I will have 6 layers

The stackup will be:

Top signals
GND layer
Signal 3
Signal 4
Powerlayer
Bottom signal

Right now I have an full Ground plane on layer 2, but should i also use copper fill connected to GND on the other 5 layers to shorten the GND return path as much as possible?

The design is filled with digital sensors sampling at a 1MHz or 2. - Only impedance that is important is my wire to the wifi antenna, which of course will follow the rules to get 50 Ohm impedance.


texts: Laying out power electronics on analog signal board, practical advice

texts:
to keep this brief I am designing some audio circuitry and also need to design the power supply. The barrel jack in the schematic below sees 18VAC and I am converting that to +/-15V DC rails.

So to tackle this I have routed out part of the board in the hopes that I can control the flow of the ground current and voltage currents while isolating any noise that may come from the other circuitry. Also note that the panel the audio jacks connect too will be grounded.

I am concerned I have overlooked something and was wondering if anyone with practical experience could advise on some things I may have overlooked. Or even if any of this is necessary.

How do I use slots in a PCB design such as this?


texts:
I am currently studying an intro course in digital logic and had a small project I needed to create. I had to use a NOT gate(74HC04) to set off a buzzer when a simulated front door of a house opens(so when a switch opens, the buzzer goes off).

It was a really simple circuit and I got full marks but my question is this, the output voltage of my NOT gate(74HC04) is +5V and is enough to make the buzzer sound but not very loud at all. Is there any way to use the NOT gate setup but somehow also have the buzzer connected to a 9V battery to make the sound louder? I read that the maximum voltage for the IC(74HC04) is +7.0V so I'm worried I will break the IC connecting it straight to the 9V battery.

So to sum up my problem, I need the logic function of the NOT gate but need the buzzer to have +9V across it when a switch opens/breaks. If you cannot do this with a logic gate is there any other simple way this circuit can be set up?


texts:
I am currently trying to run a thermistor through 3.3v in my arduino mega(progressing to mini pro 3.3v)

When I connect the 5.5v to a 100k thermistor and voltage divide it (using 100k resistor) to the analogue pin 8. Here is the code

#include <math.h>

double Thermistor(int RawADC) {
    double Temp;
    Temp = log(10000.0*((1024.0/RawADC-1)));
    Temp = 1 / (0.001129148 + (0.000234125 + (0.0000000876741 * Temp * Temp ))* Temp );// stienhartd equation
    Temp = Temp - 273.15;// k to c conversion
    //Temp = (Temp * 9.0)/ 5.0 + 32.0;
    return Temp;
}

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

void loop() {
    int val;
    double temp;
    val=analogRead(8);
    temp=Thermistor(val);
    Serial.print("Temperature = ");
    Serial.print(temp);
    Serial.println(" C");
    delay(100);
}

When I switch from 5v to 3.3 the reading is off by a lot.
I am trying to understand the code and somehow change the code to fit the ADC voltage reference?

Please help.


texts:
I'd like to automate button pressing on Nintendo DSi for a certain purpose.

For this, I think I will use a raspberry pi and a mini servo motor SG-90.

My question is, would the SG-90 would give enough torque to be able to press the button?

The following figures are provided :

Couple: 1,6 kg.cm at 4.8V

Speed: 0,12 s/60° (probably also at 4.8V)

Thank you


texts: This is a frequency doubler from a graphene frequency doubler paper if anyone know the working with substituting a normal transistor instead of a GFET?


texts: How to interpret voltage/current for relay?

texts:
I look at a relay like this one and see the markings on top but am unsure what refers to the rating for the main circuit and what refers to the voltage needed to throw the latch. Can someone explain it to me?

UPDATE: I'm looking at a datasheet here, and I have two specific questions:

There are lots of entries in the 'coil data chart'. What do they
mean, and why isn't there only one?
The 'performance' table indicates a max operation time of 15ms. Does
that mean that the relay will burn out (or reset the latch) if I try
to run an appliance on it for longer than 15ms? (My intention is to
permanently activate an appliance (see below).)
So what voltage is required to make the latch switch?
At what voltage/current is the main rated?
At what voltage/current is the coil rated?

TMI: The reason I ask is that I'd like to put a relay in a cassette player's circuit (which I expect to be between 6 and 12 volts (haven't procured one yet)) and activate it with a contact trigger (which I intend to throw the latch). It's for a treasure hunt.


texts: How to create a multiple active output decoder, not just one active output?

texts:
i have a project to controll lamp in cupboard. there are several button. okay, lets imagine there is 8 button. when i click 1st button its will turn on lamp 1, when i click button 2, lamp 2 is on.
i use arduino and process it with decoder 3 to 8 bit decoder (ic 74138), but its not what i want, when i click button 1, lamp 1 is on, when i clicked button 2, lamp 2 is on but lamp 1 is turned off before i clicked off button?
i study how decoder work, and then decoder just can active one output, while another output is deactive.
the question is, how can i manage decoder, so the active output is can more than one? when i click button 1 lamp 1 is on, when i click button 2, lamp 2 is on, and lamp 1 also still on. and so on. need help :'( thank you

i attach my lamp condition now based on decoder


texts: I want to design a control module. In my circuit I am using relay for switching .now I again came across some information which said switching in a circuit is better dine by transistors because they are faster than relay .relay can do 50 ms while transistor 10 pico .now I want a transistor circuit that can work like a relay ?


texts:
After getting some helpful critiques from my original post;

Critique my SMPS buck design

I worked on my design and made a few major changes.

L1: 3.3uH 2A inductor
C1: 10uF 25V ceramic cap
C2: 0.01uF 16V ceramic cap
C3: 22uF 6.3V ceramic cap
D1: RB160M (input protection)
D2: RB160M (catch diode)
D3: BAV99W (dual diode)
R1: 10k 0.1%
R2: 31.6k 0.1%
R3: 56R
LED1: blue LED, 2.85V, 5mA
U1: LM2734Z (3 MHz variant), SOT-23-6

I have added some copper around the pins in an effort to remove heat from the IC. The only thing I'm presently worried about is if the trace for the feedback voltage is too long.


texts: proteus dc voltmeter and ammeter results are not accurate / non existent!

texts:
I'm a beginner to Proteus and was just exploring simple circuits and trying out different things on the simulator. I built this simple circuit with a potentiometer and an led and measured current and voltage on different points. They just don't add up! (i.e. make sense with theoretical readings)

Firstly, why is there no reading on the ammeter on the bottom-left? The 1K resistance is a load which has a voltage drop of 2.55v and thus there has to be a current through it! (0.00255A according to calculations, which is 2.55mA)

Second, the series resistance of the LED is set to 1 Ohm, so if 2.45v drops across it, the current should be 2.45A which is ridiculous! Anyways the ammeter connected to it shows only 0.25A (255mA when set to mA measurement) which I don't understand... Is there something wrong with my calculations with the Ohm's Law? Thanks in advance for any help :)

EDIT: Please ignore the second part of the question as I forgot at the moment that LEDs where NON-Ohmic conductors....

Please Note: There are no warnings or errors in the message section of the simulation errors tab.


texts:
I am designing a headphone amplifier around the IC TL074. I have this circuit so far.

This circuit is almost good but the sound I see at the output is slightly distorted. I think it has to do with the cross over between the output transistors T1/Q1 and T2/Q2.

Then I tried to make it an AB amplifier by converting the circuit to...

And now I have no sound at the output.

These were my problems:

I was not sure if I could direct couple the op amp and the base of the transistors, so I have added an electrolytic, C2 and C3 (220uF x 16V) there.
I am not sure if I have calculated R27, R28, R29 and R31 correctly.

I have no sound at all.

VCC = 9V
VCC_1 = 4.5V
load = headphone 32 ohms

Any ideas?


texts: What capacitor type is best for low tolerance and thermal stability?

texts:
I am repairing an old tube-powered audio signal generator (HeathKit AG-9) and want to replace the old wax/paper capacitors that control the frequency of the oscillator circuit. The unit uses a bridged T filter to set the oscillation frequency:

simulate this circuit – Schematic created using CircuitLab

And here is a photo of the caps in question:

Looking at mouser, I see Polyester, Polypropylene, and PET caps in suitable capacities (47pF-500nF) and voltage ratings (100V). Which of those would be suitable for this application? I am concerned about temp stability primarily, but also need a relatively low tolerance part because the exact capacitance is critical to the functioning of the circuit.


texts: Which of these is the correct wiring of an RGB light strip with n-channel MOSFET for Arduino

texts:
In these 2 examples, they connect the source to the gate with a 10K resistor, and both source and gate are connected to ground (edit clarification: gate connects to ground via 10K resistor - source connects directly to ground).  The gate is connected directly to the PWM pins.

https://www.makeuseof.com/tag/connect-led-light-strips-arduino/

https://learn.sparkfun.com/tutorials/non-addressable-rgb-led-strip-hookup-guide?_ga=2.101402305.1769861380.1596832867-1916741455.1596832867

In this example, the 100-220 ohm resistor is between the gate and the PWM pins on the Arduino.  The gate is not connected to ground nor to the source.

https://learn.adafruit.com/rgb-led-strips/usage

I'm new to this, but this seems like a pretty big difference.
Which is right or wrong?
Are their advantages or disadvantages?
(edit - now with pictures from each link included in the question)


texts: Meanig of "Dynamics" in terms of control systems?

texts:
What is meant by "dynamics"in context of control systems?
Forexample what is difference between dynamics of an aeroplane and a car
This below question answers to some extent but not in detail especially in regards to my above example
Layman explanation of "dynamics" or "dynamic behaviour"


texts: Identify live or neutral in 2-way switch

texts:
I have a 2-way switch connecting to a light and it works properly. When opening it up, it has 3 inputs with the same wire color. I don't know the setup and I wish to know if there is a neutral in one of them and how were they wired.
I did a simple test for "live" among the 3 wires, these are the result.
by using a simple "testing screw driver" and testing on the switch

When the light is off (case 1), wire 1 tested to have "live" signal, wire 2 and 3 do not have.
When the light is off (case 2), wire 3 tested to have "live" signal, wire 1 and 2 do not have.
When the light is on (both case), 3 of them have "live" signal.

Given the wiring diagram from Electronics Hub - How a 2 Way Switch Wiring Works?, it doesn't make sense to me.

How can it be and what is the setup?
thank you


texts: Driving, feeding and similar terms in electronics

texts:
My technical background isn't very strong, and I often hear about one circuit "driving" another, or "feeding" it. Although, intuitively, I believe I understand the concept, I am not sure I would be able to put it into words with enough rigor, hence, I'd like to understand it better.

Since these terms are used almost everywhere in electronics, be it digital or analog, I am sure this post could prove to be a nice place to learn about these concepts for other beginners, too.

Also, how much are these hardware concepts related to their software counterparts, e.g. device software driver vs its hardware driver?


texts: DC filtering for digital audio amplifiers

texts:
I am working with digital amplifiers and from what I can see there is a DC blocking filter that is placed at the start of the signal chain.

Why is this DC filter placed at the start of the signal chain?
The cutoff frequency of this filter is just 4Hz. Any intuition behind having a cut off as low as 4Hz?
This filter is a double precision filter. Is there any reason why DC blocking should be done with a double precision filter rather than a single precision filter?


texts: What actually flows, current electricity or charge?

texts:
I'm new to electricity and electronics, I started with the essentials on Sparkfun but I'm a little bit confused.
On What is Electricity? under Current Electricity:

Current electricity is the form of electricity which makes all of our electronic gizmos possible. This form of electricity exists when charges are able to constantly flow. As opposed to static electricity where charges gather and remain at rest, current electricity is dynamic, charges are always on the move.

While right next on the same page under Circuits:

In order to flow, current electricity requires a circuit: a closed, never-ending loop of conductive material.

What actually flows? The charge; causing current and the whole thing causes current electricity? Or the current electricity?
What is actually electricity in this context?
Thanks
EDIT:
Thanks, everyone!

Introduction
To begin, my problem was with the usage of the term "flow" with the terms "charge" and "electricity current" (which was neither "electric current" nor "electrical current") at first.
Then @Andyaka pointed out:

The term "current electricity" is not a term I would use (at all ever (apart from now when mentioning it)). Electrical current is the term I'd use and that "Electrons flow and they possess charge and the rate of flow of charge is current." definition is correct.

That got me into another problem, many websites use the term "Current Electricity" to describe the flow of electrons along a conductor[1, 2].
And some websites use "Current Electricity" too but with the definition: flow of charge, instead of electrons[1, 3].

I asked a nanotechnology graduate, he told me that this definition is correct, and flow may be used for terms:

Flow of "electrons" as the current (i.e. current is the flow of electrons...).
Flow of "current electricity" if we are relating generally to the direction or the state of moving in a circuit (e.g. our city's current electricity is flowing from that power plant).

My humble conclusion
I'm still a beginner, but I've done some research and concluded these definitions as the solution to my problem:

Electric Current is the same as Current Electrecity[3, 4].
Charge: Electric charge of particles. It is measurable in Coulombs, comes in two types: positive (+) or negative (-).
Electric Current: the flow of charge carriers (electrons for electronics)[3]. Surrounding electrostatic force pushes or pulls—depending on the charge type of the force—weaker electrons out of the atom causing them to drift carrying their charge and look for other atoms to latch to them. The flow of electrons continues to happen until the electrostatic force disappears.
The electricity we use to power up our stuff is Electric Current or Current Electricity.
Lastly, all of the caused confusion is because some tutorials try to simplify things by removing hard definitions leading to wrong understanding (opinion).

I surely may have missed up the whole thing, feel free to correct me and give me advice.

Sparkfun
Direct Energy Regulated Services
Electric Current, Wikipedia
Static Electricity, Wikipedia


texts: What does the feedback capacitor do in Right-Leg-Driver?

texts:
It so happens I have seen some people mention about connect a feedback capacitor across the opamp for RLD would improve something better.

Can someone capable to explain about the use of the capacitor?


texts:
I am using an NCD relay control with 8 channel ADC. I have thermometer that is reading temp of my room to be 70F but the Thermistor Vishay NTCLE100E3 10k is reading 62.26F. The relay board has a built in temperature that reads 62.507. I have been using the Steinhart and hart equation as provided by vishay. I have seen a tutorial on youtube with someone using the same thermistor i have plugged to an arduino and his thermistor seems to be responding better than mine. I have measured the voltage between both resistors and i get 3.27v. I use Rthermisor = R10k*(5.0/Vo)-1 where Vo is the voltage between thermistor and resistor. These are the values i use for the Steinhart eq. A1= 3.354016E-03 B1=2.569850E-04 C1=2.620131E-06 D1=6.383091E-08 my beta value is 3977.

At this point I am not sure what I am doing wrong or why the readings are so off. Should I change the resistor value? I was reading something about self heating but didnt quite understand.

simulate this circuit – Schematic created using CircuitLab


texts:
I'm trying to repair an electrophysiology amplifier (AXOPATCH 200A). It has this power resistor which I desoldered because I suspected it was broken. The color code (red, green, black, gold) gives 25 Ohms / 5%, but it measures 16.6 Ohms. It is positioned directly between +5V and GND, so at 25 Ohms it is disipating 1W. My questions are:

Is it really a power resistor? Is it in a bad shape or am I confused and it is another type of component?
Which is it approximate power rating? (there are some components on the image that can give an idea of its size)
Which could be the purpose of a resistor not doing anything other than disipating power??


texts: Can envelope decay time be calculated based on this circuit diagram excerpts?

texts:
I hope it is okay for you that I as a person not involved with electric engineering ask a question here.

I do not intend to work on an actual circuit but I try to synthesize a sound sample that is coming from an old analog drum machine in audio software.

It was easy to recreate the basic waveforms of the VCOs but I have difficulties analysing the amplifier envelopes these waveforms run through. I seem to not get it by observing the waveform of my sample.

Can you please tell me from looking at the attached images what decay time each of the envelopes has or show me a formula to calculate it?


texts: Speed control of 3 phase induction motor using thyristor

texts:
I am working on project of controlling speed of 3 phase induction motor. To control the speed of motor I am using thyristor TYN16-600CT. As I am searching for different research papers and study material on speed control of 3 phase induction motor I found this MATLAB simulation...

In this simulation, I found that there is individual pulse required for each thyristor. This firing pusle is generated using this equation,

t = alpha/omega= alpha/2*pi*f

For, simplicity if alpha = 30 degree then  t= 30/50*360

My question is, Is it possible to operate all thyristor by applying same pulse??

Can I use below schematic to control speed of motor??

But as I said I have to use thyristor and in this schematic there is use of triac.

So if this schematic can work fine, what changes I have to do to replace triac with thyristor??


texts:
I have a common emitter amplifier on my breadboard (the same circuit as the image) with the following values: C = .01uF, R1 = R2=15k, RL = 5k, RE = 1k, and Vcc= 10v.

The reason I have R1= R2 is I want VB = 5V. (Base voltage)

The reason I have RL=5k and RE= 1k is i want the gain to be -5.

However, I measured the voltage at the base and got 2.7 ish volts instead.  When I removed the tranaistor, the voltage value quickly went to 5v.

Also, the voltage output showed the gain was less than 1.

I am trying to understand how the transistor can affect the base voltage value so much and why the gain isnt consistent with the formula -RL/RE.


texts:
I need to read a value from a DIP switch. It is connected to ports  P1.16 till P1.21. I use following code:

to initialize:

#define PORT_ADDRESS                    0x003F0000
#define PORT_ADDRESS_OFFSET             16

IODIR1 &= ~(PORT_ADDRESS);

to read:

int value = (IOPIN1 & PORT_ADDRESS) >> PORT_ADDRESS_OFFSET;

The problem is that no matter what the DIP switch settings are, the value read is always zero. The code worked earlier, but it stopped, and I have no idea why.


texts: Confusion with short circuits, and when you can ignore a loop

texts:
For the image above, when t<0, howcome it's safe to ignore the loop with the 50V source, and the 60 and 200 ohm resistors?

How do you know when you can ignore a loop, or when to ignore a part of a circuit due to short/open circuit?


texts: Connecting an ac-dc adapter and a battery in series

texts: Can we connect a 12v adapter and a 12V battery in series to get a 24V output ?


texts: Routing thick high current traces to small SMD pads?

texts:
What is the best practice for routing high current traces through the pads of small 0603 components?

I have a wide high current trace which that passes through a 0603 decoupling capacitor.

Initially I kept the thickness high(like below) but someone suggested that due to lack of thermal reliefs this would make the component difficult to solder or prone to tombstoning.

Do I instead take a thick trace as close to the pad as possible and then jump with a thinner trace like below?

What impact would this have on the current carrying capabilities? What is the best practice in this case?

This is a 2 layer board.


texts: How to protect current sense IC from current transients

texts:
I'm planning to use a ACS712 current sense IC to sense motor-current in a project:

http://www.allegromicro.com/~/Media/Files/Datasheets/ACS712-Datasheet.ashx

The device I'm building uses a relay to control 230V to an electrical motor. I want to be able to deliver 2A to the motor.

I want to sense the current to be able to give a ballpark power value, and also to be able to detect short circuit or open circuit.

I've heard that short-circuiting the 230V mains, even in a residential area, can possibly cause currents up to or above 1000 A. This of course means that a fuse in the building will blow.

However, even at 1000A, it may take some time for the fuse to blow. I'm worried (or convinced) that the ACS712 will be obliterated by a 1000A surge, even faster than the fuse can blow (a couple of milliseconds?).

What could I do to alleviate this? I could put a 10 ohm resistor in series with my motor, but that would still put approximately 20A through the resistor, and I'm worried that the resistor will burn out before a 10A fuse will. Also, the resistor would definitely burn during normal operation.

What would be the right way to solve this?


texts: I have 12V, Use these 12V to power a device (that has a 12V output signal) and to power a 7805. After the 7805 there is a pic microcontroller where I would have to connect the output from my device. I was thinking of having 2 resistors in a 3/1 ratio in order to have about 4V at the pin of the pic. Can this be done, given that the ground is common, or will it give some sort of problem with the lm7805?


texts: Data Transfer without Transceiver on FPGA

texts:
While going through the transceiver component on an FPGA, I realized that data transfer can take place without transceivers as well, although the speed would reduce or in other words, as tasks increase a speed cap would be reached.
My question is: how can data transfer take place if we do not have transceivers on an FPGA? What is that mechanism?


texts:
Please check the below waveform of my 5V output ripple of the buck converter.

I am measuring the output ripple across the output capacitor of the converter. Why are these spikes coming while measuring even though I am using the short spring type ground tip

Switching frequency of the converter is 248kHz. And one more thing I am observing is that, while I measure on one channel, the switching frequency at the switching node of the converter and on the other channel the ripple voltage, the ripple voltage amplitude is going high. But If I measure it separately, I am able to get the correct ripple voltage amplitude. What might the reason for this? I am using short ground tip while probing on both the channels

Updated Waveform, along with switching frequency. Please check the below waveform. I am probing across the output cap of buck converter with spring tip and the switching frequency at the cathode of the diode (referring common buck topology) . Can you see, when I measure both waveforms together, I am getting this awful spike which I have marked with cursors?

Why is that and what to do to get proper waveform?


texts: DC Fan using less than half of rated current. Looking to overvolt

texts:
I have a project involving a 200mm 12VDC PC cooling fan (FS-200RB) that will be used for cooling me - not a computer.

The fan is labeled: 12V DC / 0.42A / 5.04W

With a source of 12V, it is not moving enough air for my taste.
I don't need the fan to last a long time, it will only need maybe 20hrs of use for my project, but I'd of course prefer to avoid destroying it.

With 12V applied, I measured the current in-line to only be about 0.13A. And if I hold the blades to stall it, the current only rises to 0.18A.
With 15V applied, and the current was 0.17A full speed, 0.22A stalled.

I want to overvolt this fan even more, but I'm not sure where to draw the line. I could continue raising the voltage past 15V, but I don't know how quickly it can be expected to fail.

I'm also not sure why the current would be so much lower than the 0.42A rating. Is this common for DC motors? Is 0.42A only for the instant it starts up? Stalling it doesn't even reach near that much current. This makes me feel like the fan is not reaching its normal potential, let alone an "unsafe" potential.

Why would the fan be using such little current and how can I theoretically/numerically determine an over-voltage limit?


texts:
Is it possible to simplify the following circuit?

My goal is to preserve as fewer nodes as possible since the number of nodes substantially affects the complexity of my further computations. The major difficulty for me is the crossover section formed by R4–R9. I would appreciate any suggestions.


texts:
I'm working on a device utilizing Atmel's AT32UC3C microcontroller. The datasheet and design checklist documents provided by example schematics utilizing some type of RF/EMI inductor to isolate the digital and analog source circuits. However, they don't provide any indication as to what to use.

Atmel's recommended power supply schematic:

How do I calculate/figure out what inductor to use?

I'm utilizing the ADC on the chip and want to sample at the maximum 2MSPS (ADC clock frequency 2MHz) and want to operate the digital end at the maximum spec frequency of 66MHz. I plan on having the device USB powered and operating at 5V.


texts: The role of humidity is BSOD and other glitches

texts: For some unknown reason to me hearing aids require dehumidifying. The humidity somehow very significantly interferes with the microphones and other electronics. Daily dehumidifying stops the interference. Does humidity play a role in tablet, phone and other small devices glitches? If so how large? Will a dehumidifying fix increase electronic device reliability?


texts:
As far as I know, perpetual motion orbital desktops like below use an electromagnet in the base.

Why aren't permanent magnets used on both ends instead?

Does anyone know where I could find a teardown of the base of a generic one?


texts: I've briefly flirted with FPGA development in Verilog, and its admittedly somewhat slower than writing the same program on an MCU (defining pins, and their behaviour, no modules available, etc). I've therefore been on the lookout for a software that can help me design using block diagrams or something more visual. I've heard of Mathworks Simulink, and the FPGA/ASIC line of tools from Synopsys, Cadence, Mentor Graphics, etc, but since I've never had a chance to get my hands on these I don't really know how intelligent or visual they are. Have you ever heard of such a software with such a feature set? and would block diagrams have any advantages over designing textually in Verilog?


texts: What are the possible reasons this current transformer doesn't work?

texts:
On the assembly shown, I have built a current transformer with a toroid coiled with 30 turns of magnet wire.  The brown wire is the phase going through, blue is neutral.
When I connect a fan onto the phase and the neutral wire, I don't measure anything with my coil. I measured using an oscilloscope on my voltmeter.
Is there a reason why it doesn't work? What am I doing wrong?


texts: How Many LEDs can be driven with one WS2811

texts:
I am starting a project and will be using WS2811 LED drivers to create a large matrix (about 40 to 50 panels) with a micro controller (Arduino compatible). I already purchased and received the RGB LED strips. They are the 5050 Type and have 30 LEDs per meter. I want to use the WS2811 to control each panel using a portion of the LED strip in each panel. The LED strip can be cut and the smallest section contains 3 LEDs.

My question is how many of these 3 LED sections can I control with on WS2811?

Since I ordered the WS2811 chips separately I figured I could use one per panel to light up the entire panel with even light. The panels are about 24x18 inches. I know that the WS2811 will keep current constant for the color so I figured that I could possibly put several 3 LED sections in parallel.

Thanks in advance for your responses and I appreciate any advice you can give me.


texts: Can i tie the enable pins directly to the rails?

texts:
i am having trouble with the spaces on my circuit and removing the two pull-up/down resistor on the enable pins would solve my problem ( if of course it doesnt cause other problems). I was wondering if i could  completely removes the resistor and directly tie them to the rails. They are not connected to a GPIO that toggles them they are meant to be a fixed state.
The first is the pull up from the enable pin of LP5907. There already seems to be a weak 1M ohms pull down built to it internally.

Second is the TMUX1574. This also have a weak 6M ohms pulldown internally.

Would it be safe to skip these resistors?


texts: 8x3 Priority Encoder question about the output functions

texts:
Cheers, I have this 8x3 encoder with inputs of Ai and outputs Yj. I have to find the minimized function of the outputs.
[![8x3 Priority Encoder Truth Table][1]][1]
I understand that for Y2 the output is 1, only when A4-A7 are enabled so, $$Y_2 = A4 + A5 + A6 + A7$$
For Y1 and Y0 our professor gave us these outputs: $$Y_1 = A_6+A_7 + \bar{A_5}\bar{A_4}A_3 + \bar{A_5}\bar{A_4}A_2$$
However, I cannot understand why would not want to for the last two sums, to also have A6 bar and A7 bar inside. Is this because we don't care about these? Or does it have to do with the minimized function that we are looking for?
Also, for Y0 he gave us: $$Y_0 = A_7 + \bar{A_6}A_5 + \bar{A_6}\bar{A_4}A3 + \bar{A_6}\bar{A_4}\bar{A_2}A_1$$
Again, we do not have A7, A5 or A3 in some parts.Why are they excluded again?
If I wrote that $$Y_0 = A_7 + \bar{A_7}\bar{A_6}A_5 + \bar{A_7}\bar{A_6}\bar{A_5}\bar{A_4}A_3 + \bar{A_7}\bar{A_6}\bar{A_5}\bar{A_4}\bar{A_3}\bar{A_2}A_1$$
Would this be wrong? Also could I transform this in a way to reach the desired minimized function?Thanks in advance.
[1]: https://i.stack.imgur.com/UNPpm.png


texts: Power supply Circuit for school and will like to add LEDs

texts:
I am trying to add LEDs to a power supply to light up when it comes on I am wondering how to do this and how it will affect the voltage output for the power supply itself?

simulate this circuit – Schematic created using CircuitLab


texts:
So I thought I had enough knowledge to do a simple LED string, but now I'm wondering.
Basically what I did is got a constant current DC power driver (700mA, 15-42V output) and wired it in series with seven colored LEDs. the forward voltages of the 7 LEDs add up to about 21 volts, which I thought was within range of the driver and so would be okay.
a complicating factor is that we hired someone else to build an enclosure for what we're making, and he decided to wire it up without our permission and wired it up terribly. he put everything in parallel, and wired the 120 volt AC directly into the DC circuit. He then tested it several times putting all that voltage directly through everything.
When I got my hands on it and wired it up the way I had intended the green LED was not working. I assumed that he had burned it out, and ordered a replacement.
Today I went to put the green into the circuit, and everything was going fine, but my first few tests resulted in more problems. Now four of the seven LEDs are burned out, including the new green one I had ordered.
So what I'm wondering is, was my initial plan fatally flawed? Did I fail to account for something? Or is it possible that the incorrect wiring did damage to the other LEDs that is just now showing up?
I'm extremely confused, so TIFA for any advice.


texts: Understanding semiconductor failure mode

texts:
Why after serving well for years, a smps controller ic fails without apparent reason?

My Sharp TV (LC46LE835X) worked well for 37 months but suddenly while being watched in the middle of calm night, it blacked out with small explosion.

I managed to repair it after changed a 7-pin dip ic and a 2.2ohm fusible resistor. No other components (SMTs) appear abnormal. TV works well now.

So I'm really wondering what could have caused this ic to fail. If it had manufacturing defect why it worked well for 37 months?

Since the root cause is not known, the failure will repeat?


texts: Isolated closing contact other than relay?

texts:
I need an isolated closing contact, like a relay, but ideally solid state. Rating 24V 100 mA on the contact side would be plenty. 1 kHz operation would be enough as well. I will drive this from 5V 25 mA gpio pins. Ideally with a <10 mA draw!

I've looked at optocouplers, but the ones I can find put VCC on the transistor/contact side; I'd need one with that side having only contacts.

The application is a remote camera trigger with both pre-trigger and trigger inputs, so two channels needed although two singles is fine.

Is there some kind of component or variant I'm missing?


texts: Is it OK to use RS485 with separate wires for each device?

texts:
I know common use of RS485 is top wiring diagram. But in my project we need to use RS485 for extend range and reliability connection but connection will be bottom wiring diagram.
Can I use a single RS485 transceiver IC? Are there any problems with this approach? I'm not sure.
Assuming every device has the same baudrate.


texts: How to calculate capacitor value to reduce PWM load ripple?

texts:
I have a simple MOSFET PWM circuit switching a 12v/8A load at a rate of 500Hz. This is being powered by a 120w switch mode power supply.

The power supply is buzzing loudly and generally unhappy with this arrangement. From my reading it appears that I need to smooth the load ripple created by the PWM circuit, by strapping a low ESR capacitor across the +/- input to the PWM circuit.

Is this correct, and if so, how do I calculate the correct value for the capacitor given the load characteristics?

Edit: PWM and PSU are commercial off the shelf units - I can't modify them. I'm after a relatively simple ad-hoc solution to go between the two units.


texts: what will be the average value of puLse train?

texts:
I calculated it by $$I_{av} =\frac{\int_{T_i}^{T_i+T_h}Idt}{\int _{0}^{T_i+T_h}dt }$$
but the answer is different

the questions
actually I am trying to calculate average current through $C_1$, if there is application at the input of frequency f_i and the time for which one shot is active is Th ,hence we get a pulse train like above from the capacitor

Book text


texts: Time-series Statistical Analysis with FPGA

texts: Suppose I have two time series, such as stock valuations or radioactive diagnosis, for which I need things such as covariances (QP -problem) among other things. Covariance calculations should be easy easy speed up -- the future stages are not depended on latter. Can I do this kind of problems in constant time in FPGA? -If I have understood right, yes. What other statistical analysis -toolbox things you can considerably speed up with FPGA? Everything not on depended on the last stage? Look if my thinking is right, there must be a massive potential here -- could someone help me to find out projects specializing in time-series analysis with FPGAs?


texts:
I was looking into Farnell.com catalog for Zilog Z80 microprocessor and I found only Z84C00.

What is the difference between Z80 and Z84? Is there any? And what is the difference between Z84C00, Z84C20 and Z84C30?


texts: How can I model a double pendulum in op-amps?

texts:
I'm interested in chaotic circuits; and while many circuits that model attractors like Chua's Circuit, Lorenz Attractor, and RC phase shift networks are available, I would really like to model the behaviour of a double pendulum using op-amps.

I've seen a few references to the possibility of computing the differential equations describing the motion of a double pendulum; but no concrete implementations. How could I go about modeling this behaviour using op-amps?


texts: How can I verify my ATtiny25 programming? Seeing nothing on output pins

texts:
I'm a complete beginner in microprocessor programming. I managed to program my ATtiny25-20PU with AtmelStudio 7 and an AVR-ISP-MkII. However, I don't get any output on my output pins!

The ATtiny is new and never used before. I'm pretty sure that the programming worked, since device signature could be read and the programmer could verify the program. So I think the problem is in my simple program or in my even simpler circuit. I've never done this before and maybe missed something obvious?

The entire circuit (when testing, after programming) was:

Connect VCC to 5V.
Connect GND to ground.
Connect RESET to ground for a while, then connect it to VCC. I also tried doing this using a button but observed no difference.

But PB3 and PB4 are low all the time! This is the program:

#define F_CPU 1000000UL
#include <avr/io.h>
#include <util/delay.h>

int main(void) {
    DDRB |= 1<<PB4;
    while (1)
    {
        DDRB |= 1<<PB3;
        _delay_ms(200);
        DDRB &= ~(1<<PB3);
        _delay_ms(200);
    }
}

So I'm expecting PB3 to go high and PB4 to give a square wave. What can I do to keep troubleshooting? Or verify that I actually managed to program the ATtiny? I'm completely stuck.


texts: A high pass circuit is a differentiator when used under the condition that input frequency of signal is much less than \$1/RC\$. But that region corresponds to stop band of the filter, so how do we get a differentiated wave at output?


texts: Why use a double fuse for a relay-controlled heater?

texts:
After this question, another refrigerator "mistery" :-)
This is the schematic of a no-frost refrigerator that I had to fix because the no-frost system failed and a huge quantity of ice clogged the evaporator.

R1 and R2 are two heating elements (the no-frost heaters). Power to heaters is supplied by a relay driven from the CPU board.

Question: why those two fuses?

Why put two fuses, in a single case, in a position that requires disassembly of half the fridge just to test them, and almost impossible to replace?

Note that TF1 and TF2, that are described simply as "fuses" in the service manual, and not as "Thermal Fuses" as the "TF" name suggest, are both in a single un-marked sealed plastic case with just the 4 cables exiting from it, placed inside the refrigerator compartment almost in direct contact with the evaporator (as everything else: just the two cables on top of the schematic enters the compartment)

Note that in the service procedures related to no-frost failures there is an explicit statement that asks to "check continuity of TF1 and TF2". And also note that the failure was indeed one of the two fuses that opened without evident cause.


texts: Need assistance to understand Power and Ohm's Law

texts:
Hello I'm looking at a light bar on a vehicle and the specifications say it draws 7.5A at 9-32V and the light bar says it has 36 x 5 Watt LED lights which would make a total of 180 Watts that this device uses is this correct?. My confusion is how can it draw a constant 7.5A at each voltage between 9-32V? If the voltage increase how does affect energy used over time if the current is still flowing to the device at the same speed? and if is powered by 32V at 7.5A this would be a total of 240A which is too much for the device. Would the internal resistance be changing to keep a constant current of 7.5A?
Thank you


texts:
Working with a micro controller, on which exact conditions should we choose between Hardware timers and Software delays on an Embedded Controller?

I have seen articles which do emphasize on use of timers.

If timers are so good then why is Software delays needed?

This is the link that describes the usage of s/w or hardware timers.

http://betterembsw.blogspot.in/2012/12/software-timing-loops.html

But this does not emphasize on the case when h/w timers are available on the controller that we are using.


texts: Missing information when calculating impedance via Blackman's theorem

texts:
The AC course at my university has an ex-exam question where, in the below circuit, the impedance w.r.t. ground has to be calculated for the rightmost node.

The question asks to do this using a test source (on the small-signal equivalent, which I assume makes the current source up top disconnect as it would be set to 0), and then check work using Blackman's theorem (presumably also on the small-signal equivalent). Applying a test voltage to the node, I find
$$i_\textrm{test} = g_mv_{gs}=g_mv_{drain} \qquad\textrm{and}\qquad \frac{v_\textrm{test}-v_{drain}}{10\,\rm k\Omega} = i_\textrm{test} \qquad\Rightarrow\qquad Z_\textrm{in}=\frac{v_\textrm{test}}{i_\textrm{test}} = 10\,{\rm k\Omega} + 1/g_{m} = 10.1\,{\rm k\Omega}$$
Now, I was "taught" (there was very poor teaching involved) Blackman's impedance formula as
$$Z_\textrm{in} = Z_\textrm{in}^\textrm{no feedback}\frac{1+RR_\textrm{short}}{1+RR_\textrm{open}}.$$
where all quantities are defined w.r.t. a cut we make in the feedback loop: the first factor is the impedance we need but when there is no more feedback, and the return ratios are each a ratio of the voltage that appears on the non-amplifier-side of the cut when we apply an input voltage to the amplifier-side of the cut.
However, I can't seem to figure out how to get to that first factor. When I cut the feedback by separating the gate from the drain, I can get as far as:
$$i_\textrm{test} = g_mv_{gs}=g_mv_{gate} \qquad\textrm{and}\qquad \frac{v_\textrm{test}-v_{drain}}{10\,\rm k\Omega} = i_\textrm{test}$$
... but now my equations stay underdetermined, since I have 4 unknowns (we need the ratio of two, so effectively 3 unknowns) and only 2 equations. It seems to me that the gate or the drain would need to be given a certain voltage to be able to work out the equations, but what voltage? If the gate is 0, clearly, we get $$i_\textrm{test} = g_mv_{gs}=g_mv_{gate} = 0\qquad\Rightarrow\qquad Z_\textrm{in}^\textrm{no feedback} = v_\textrm{test}/i_\textrm{test} = v_\textrm{test}/0 = +\infty$$
The only way that could turn into something approaching a solution is if the denominator is also infinity, which might be the case; for the open circuit, \$Z_{in}\$ is floating, so there is no closed circuit and the current through the transistor would be \$0\$ making \$v_{gs}\$ and hence the gate (weirdly) be forced to \$0\$. That means
$$RR_\textrm{open} = \frac{-v_{drain}}{v_{gate}} = \frac{-v_{drain}}{0} = -\infty.$$
Seeing as to how \$RR_\textrm{short} = g_m\cdot 10\,{\rm k\Omega}\$, that leaves me with
$$Z_\textrm{in} = Z_\textrm{in}^\textrm{no feedback}\frac{1+RR_\textrm{short}}{1+RR_\textrm{open}} = +\infty\cdot\frac{1+g_m\cdot 10\,{\rm k\Omega}}{1-\infty},$$
so it's a dead end for me.


texts: Inductive phone charger mod - doesn't work with battery too close?

texts:
I am experiencing a strange issue, likely because I do not fully understand the technology I am trying to make play nice together, but maybe someone here can shed some light on it.

I have an HTC Evo 4G and a Duracell Powermat inductive charging kit. The kit is designed to charge an included battery to externally connect to USB devices, and also comes with an iPhone 4/4S case which the phone would dock into and allow it to wirelessly charge. I had the idea to remove the inductive coil from the iPhone case and install it in my Evo, and happened accross this tutorial here: http://asmd.wordpress.com/2011/09/26/evo-4g-wireless-induction-charging-modification/

The induction coil from the iPhone 4 case wasn't exactly the same, however I did find the +5V lead, connected it to the phone in the way described in the above tutorial, and everything works great - that is, until I put the case back on the phone. The coil is taped directly to the inside of the back case of the phone, and by itself (connected to the phone or not) it works fine. The problem is that when the case is on the phone, OR the phone's battery (which is located directly behind where the coil would be with the back of the phone attached) is closer than about 1/4" of the coil, or directly against but covering more than about 1/2 of the coil horizontally, the Duracell inductive transmitter makes a 'ticking' sound for a second or so and then nothing happens. Normally, it would make a 'bleep' sound and then begin charging.

After some mild testing, it seems like it's just the proximity of the battery to the coil that is the problem, however in the tutorial I linked to, the setup is nearly identical but apparently that person didn't have this issue. Is there some type of interference or something that could be causing this? Would placing some kind of shielding such as a wire mesh between the coil and the battery help? (Haven't tried this simply because I don't have any handy - though I tried a thin sheet of metal and plastic, and neither worked unless the battery was again at least 1/4" away from the coil).

Perhaps I just don't understand the physics behind it but it seems like it should work and I'm stumped as to why it wouldn't. I don't see anything that could be causing a short or anything, so I'm really at a loss. Thanks in advance for any ideas or explanations as to why this might be happening.


texts: Why this small cut in Ampere meter shunt?

texts:
I have seen lot of ampere meter shunt like this.
What is the reason for this small cut?


texts: ON/OFF push button circuit with battery under voltage protection

texts:
I have put together the push button circuit explained in TI's SCEA048B application report with an under voltage protection using TI's LMS33460 chip. I ended up with the circuit attached.
The idea is to have the LMS33460 under voltage detector monitoring the +PACK line from the battery so it pulls down the regulator enable pin to power down the device in case the battery voltage falls bellow 3v, but I have several doubts:

After doing the schematic I realized that I should use an under voltage detector that triggers at 3.4v instead of 3v. I think this because the 3.3v LDO regulator has a maximum dropout voltage of 250mV and the TM4C123GH6PM has a minimum operating voltage of 3.15v, so 3.15v + 0.25v = 3.4v.. under this battery voltage the microcontroller will not have enough voltage supply. But, since I am using a 3.7v lithium battery, this would only give 3.7-3.4 = 300mV of margin for the battery to discharge.. I don't know much about lithium batteries but that doesn't seem to be a lot... is that a problem?
I haven't found the input resistance of the TLV70033's Enable pin in the datasheet, so how can I know the maximum pull down resistor (R33) to minimize consumption and still pull down the voltage to turn off the regulator. Anyway, this pull down resistor is not needed anymore after connecting the enable line to the flip-flop, since the flip-flop's output is not an open drain and it will command the line high or low without ambiguity, right?.
Do you think this would work?  : )
Is there a better way for protecting the battery?

Thanks


texts: Interrupt Vector calculation in PowerPC based controllers

texts:
I am working with Freescale MPC5534 based on PowerPC arch. I am not able to understand how the address of a particular ISR is calculated during runtime. There are three registers involved, INTC_IACKR, INTC_IVPR, INTC_IVOR, and the final value of the interrupt vector corresponding to a particular ISR is based on the values loaded to these registers at runtime i.e, some base_address + prefix + offset from the three registers, respectively.

I am just not able to understand the connection these three values and how the vector is calculated from collective value of all these registers.

People who have worked on any PowerPC based controllers might be able to help.


texts: How to trigger a transistor from iphone's audio output jack?

texts:
I want to trigger a transistor using iPhone's audio output jack. My goal is to turn off an LED(which is fed by an external +5V battery) by sending an audio signal from iphone's output jack. At the beginning i thought it is easy but i encounter many problems. I tried to do it with a transistor but it seems the iphone audio output is too weak even for a transistor.

I am confused every time i find different ideas. Let me be more precise, here are the fatcs:

1-) The output voltage of iphone is very low, something like 300 mV

2-) The output is an audio signal

And here are the problems:

1-) How to amplify this voltage? I found some different ideas after some googling such as:

a-Using transformers. This guys says one needs micro-transformer

http://web.eecs.umich.edu/~prabal/pubs/papers/kuo10hijack-islped.pdf

b- Using capacitor. Here one guy is suggesting using a very simple circuit. I tried it didn't work:

Power LED from headphone jack

c- Using op-amp

Can you assist me a little bit about this?

2-) Do we need to rectify the audio signal?

Here is the circuit i was trying at the beginning. I thought it is simple. But the transistor is not triggering with the audio signal:


texts: Need an optocoupler for getting directly proportional output galvanically isolated from the DC input

texts:
I want to use an optocoupler to linearly step down a DC voltage which willy vary from 0V to 400V. That is, I want the output to be directly proportional to the input and I want it to be galvanically isolated from the input

Now, for this purpose I used IL300 and MCT2E earlier.  The problem with IL300 was that the slope (linearity factor) varied across different samples of the IC. I can not allow that to happen. And the problem with MCT2E was that the linearity lived only up to a particular value of input ad the output tended to get saturated after that. I realize that changing Rs might have solved this problem, but the saturation couldn't be eliminated quite very properly. Now, I'm looking for some other optocoupler for this purpose.
I have shortlisted LTV 817 for this purpose but I'm not sure how it is going to perform. So, I want to select atleast two more ICs for this purpose and then test all of them to select the best one.

What I require from the IC:

Directly proportional output for a DC input varying from 0-400V.
Galvanic Isolation between input and output.
Output to vary linearly with the input, between 0 to 12V.

Can you guys please suggest me some optocouplers that will help me solve this purpose?
Note: There might be devices other than optocouplers, available for this purpose, and I welcome suggestions regarding them as well, but I prefer optocouplers.


texts: Necessary parts to build a DIY smartwatch

texts: I want to create a simple smartwatch that can receive text messages via Bluetooth/wifi from a computer. However I start doing research on necessary components and either get completely professional chips that do much more than needed (also extremely expensive) or simple plug ins for arduino. Where can I start searching for this parts? which companies should I look? Also important information on other parts that could help me with this project will be greatly appreciated.


texts: Calculating parasitic capacitance of serial zener diodes

texts:
simulate this circuit – Schematic created using CircuitLab

I have 2 series zener diodes like these in the schematic.

Their capacitance is C=225pF

How do I calculate their equivalent capacitance so I can calculate my time constant?

Is it 225pF || 225pF or just C1+C2?


texts:
I'm attempting to create a very basic pully system.
I am using a DC plug (12V - 2A - 24W), into a DPDT 3 position rotary switch (240V - 20A) running 2 motors from either on position (12V 25GA-370). From what I interpret the values are MAX input, can I run the current straight through or do I need to consider resistors? Therefor, I am looking for advice on resistors; where do they need to go in this circuit, what type should they be? That is if this circuit can even exist with or without these components. Any guidance helpful!


texts: On which side of creepage gap should I put my optocoupler?

texts:
I'm designing a flyback power supply and I need to use an optocoupler for zero-crossing detection. The reference design I was given put the optocoupler on the MCU/low voltage side and I find that to be problematic.

I believe you should group them together with high voltage components on one side of creepage gap? I could be wrong, and I hope to get some input from experts and experienced engineers, thanks.

I have already searched and no one had asked this specific question or anything close.

Edit: by "creepage gap" I actually was referring loosely to creepage clearance and air gap, the deliberate blank area on PCB boards to separate high and low voltage components.


texts: Does this current buffer analysis make sense?

texts:
I've transformed this circuit:

simulate this circuit – Schematic created using CircuitLab

In this one:

I am aware that the input is V_in and the output is the current which enters in drain. I am aware also that here I have considered the V_out as the output of my analysis.

Now let assume that I've found the literal equations of the V_out/V_in, neglecting Cgd and Cds.

Does it make any sense doing such analysis in frequency for stability purposes?
Or should be done on the output current over the input voltage?
While I can estimate the output resistance of the circuit (saw from drain), the one related to the opamp really matters for stability analysis?

Just to address better who want to help, I want to know only how usually is made such analysis. For brevity, I'm not asking for the analysis itself.

My goal is to achieve these informations by calculus and verify them on the field later. I've already made a SPICE simulation and Matlab plot for the transfer function of V_out/V_in. That can be put and commented, if needed.


texts: Noisy non-inverting op amp with gain selection

texts:
I need to measure input voltage by 16bit ADC with 2.5 V reference. There are two different input voltage levels: 0 - 100 mV and 0 - 30 V. I designed the circuit below which should work in the following way:

Range 0 - 100 mV: Optocoupler OK1 is off and OK2 is on, so that input voltage flows via resistor R1 to op amp which works as non-inverting amplifier with gain 25.
Range 0 - 30 V: Optocoupler OK1 is on, so that resistors R1 and R2 form a voltage divider. The optocoupler OK2 is off, so that op amp has only 24k resistor in the feedback and works as voltage follower.

My problem: When I select the range 0 - 30 V, the output is very noisy. When I sample it by 16bit ADC, the noise is several hundreds of ADC divisions. Also I noticed the bigger is the input voltage, the bigger is the output noise. When I replace R3 by 0R, the noise is gone, but the circuit is not able to measure the second voltage range :(

EDIT: I switch the circuits by optocouplers, but I could not find them in the schematic editor, so I drew MOSFETs instead.

Thank you for suggestions.
Klasyc

simulate this circuit – Schematic created using CircuitLab


texts:
I am currently looking for a uC for a project of mine which needs a CAN interface. This would be my first project using CAN. Since I want to send and receive messages between the master and at least 8 slaves I was wondering about the amount of CAN ports I need.

According to this post I can send and receive messages on the same uC using only one port.

Looking at the Part selector of Microchip one of the fields says 'CAN Receivers buffer' and 'CAN transmitters buffer', which suggests otherwise.

Can I use them on the same bus or do I need a busline for sending and a separate one for transmitting?


texts:
I recently purchased LEDs on ebay that were supposed to come attached to star PCB (as a heat sink). The items I received are just the LEDs (no PCB). They are listed as 3W LEDs, with a forward voltage of 3.0-3.4V, and current at 700mA.

I received a partial refund. Will I damage / destroy the LEDs if I use them without a heat sink? If not, what is the best way to mount these to preserve their life during operation?


texts: How to read USB mouse data using STM32f103C OTG USB functionality?

texts:
I wanted to build a project where is a screen displaying a pointer, and I wanted this pointer location to be determined by a USB mouse, so I used the ARM 32bit based STM32f103C microcontroller which feature a USB OTG_FS, I usually use stm32duino core in the ArduinoIDE to program my board, I searched all examples and they were all about emulating a HID device with the STM32f103C but I want the reverse, I want to receive mouse data not to emulate a mouse then send data via USB,So i think this is probably possible but I searched the internet and couldn't find anything to help.

Edit:
So, to be following the curriculum of stack exchange site, my question is converted into which is the best software needed for the STM32 I have that contains USB examples and can be run in my 64 bit Linux computer.

So in a nutshell I want to receive USB data in my board the STM32f103c.


texts:
I'm knew to this site spice so please be gentle :)

I've installed LTSpice (LTspice XVII for OS X, Build Oct 25 2018, 14:56:22 US Pacific) on a MacBook Pro running macOS High Sierra 10.13.6.

When I try to add anything to the schematic the display does not refresh and I get the remnants of moving the component across my schematic.  See the image for what I mean.

Hopefully someone can help me on this as I prefer to run a native tool rather than something in a vm.

Thanks!


texts: Why can't passive components transform energy from one form to another

texts: In parts of electrical components active components can control the flow of current in a circuit but passive components cannot. What is the factor that gives active components the ability to control the direction of flow of current in a circuit.


texts: Flyback converter with dual outputs (12V / 5V)

texts:
I came across the following flyback converter circuit, which has a dual output (12V and 5V), but I am unable to figure out why the secondary windings are connected in series.

Based on the datasheet of the transformer (750343773 - Würth), the secondary windings should produce (considering Vin ~ 85VDC) 13.52V (12V + V(D21)) and 5.79V (5V + V(D22)) respectively, which would make sense if they were sharing the same ground instead of being connected in series. Furthemore, the feedback network formed by the TL431, R26, R25 and R25A apparently is set to an output voltage of 18.56V and 8.72V respectively. Can anyone explain how the 12V and 5V can be achieved with this configuration?


texts:
I am prototyping a few things and wanted to make my own breakout for something that  I haven't done before: GPS. (link to page)
I know that high-freq. PCB are usually different compared to regular PCB.
My question to you guys are as follows:
Is the ground plane nessecary?

Should I put decoupling caps on the PCB or leave them to the prototype?

What should I change to acomodate to the 5GHz frequency /antenna?

How can I put power protection on this aside from a fuse?

Is this a viable setup for prototyping?

Schematic:

refrence:
red: fill
black:nofill
small white text: solder pad
large white text: silk layer


texts:
Why do I get analog reading to the non connected ports, by taping the piezo in channel 1 ?

The piezo element is only connected to Channel 1 (Arduino A[0] port).
The channels Ch 1 – Ch 6 are connected to female mono jacks and the ground(GND)      wiring is in series from jack 1, 2 and 3 so on... till the Ch 6 end to the Arduino GND port.

The channels Ch2 – Ch6 have no piezo connected, but still connected to the arduino board. A1-A[5]

This is the serial read... first column is Ch1 … Ch 6.

Taped 3 times

787 0 0 0 0 0
191 0 0 0 0 0
19 0 0 0 0 0
937 123 63 5 0 0 < ch2, ch3 ch4 ERROR !>
86 0 0 0 0 0
13 0 0 0 0 0
507 83 126 16 8 0 < ch2, ch3, ch4 ch5 ERROR !>
21 1 1 0 0 0  < ch2, ch3 ERROR !>
0 0 18 0 0 0 < ch3 ERROR !>

This is the arduino code:

const int singnalLevel = 10;
boolean treshold = false;

int sensorReading[6];

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

void loop() {
   int sensorReading[6] = {0, 0, 0, 0, 0, 0};
   boolean treshold = false;
   sensorReading[0] = analogRead(A0);
   sensorReading[1] = analogRead(A1);
   sensorReading[2] = analogRead(A2);
   sensorReading[3] = analogRead(A3);
   sensorReading[4] = analogRead(A4);
   sensorReading[5] = analogRead(A5);

  for (int index = 0; index <= 5 ; index++) {
    if(sensorReading[index] > singnalLevel){
      treshold = true;
    }
  }
    if(treshold){
        for (int index = 0; index <= 5 ; index++) {
          Serial.print(sensorReading[index]);
          Serial.print(" ");
        }
    Serial.println();
  }
  delay(1);
}

This is the circuit schematic.


texts: How to properly set up a multimeter to measure the power consumption of a computer?

texts:
From what I understand, a multimeter can be used to measure the resistance in in a circuit. Multiplied by the voltage, measured in the same circuit, I would get the total power consumption. Is this correct?

I want to use an inexpensive multimeter to measure the average power consumption in an appliance (computer). I was thinking that it should be possible to achieve this by connecting the "measuring hands" of the meter to the connectors in the power socket, and then over a couple of minutes measure first the average voltage and then the average resistance. Then, multiplying these values would give me an approximation of how many Watts a device is using in a given time period.


texts: How to wire a dual output power converter

texts: I am trying to wire a XP Power IZ series dual output power converter. What are the meaning of the pins? Is -V Input the ground from the power source? what about common?


texts: Connecting microcontroller 3.3V output to relay using ULN2803A

texts:
I have a need to connect an ARM micro-controller with 3.3V digital output pins to a few 12V solenoid water valves. I figured that I can use a ULN2803A for this task.

The internal circuit for each input/output is depicted below:

Couple of questions:

Is the attached schematic correct?
Do I need anything else in the circuit to protect the micro-controller?
Anything else needed to protect the ULN2803A?
And do I tie the +12V and +5V grounds together?

EDIT: The load I'm driving is rated at about 400mA, 100mA shy of what this part is rated for ( each output ). The datasheet says the ULN2803A can be put in parallel to handle more current. I'm mot sure how that circuit would look.

Would I just logically connect them as if they are stacked one atop the other?


texts: Precision reference voltage: buffering with OpAmp and BJT

texts:
I'm designing a reference voltage generator for the analog section of a circuit. Two voltages as needed:

Vref = 3 V for ADC
Vref/2 = 1.5 V for signal conditioning circuits (with a load of about 40mA)

simulate this circuit – Schematic created using CircuitLab
The 3 V precision reference is already available, and I need an hint to generate a precision 1.5 V reference with a load of about 40 mA. In the schematic above, were are possible error sources?
I can identify:

divider resistors tolerances
input current of OpAmp "+" pin
OpAmp offset
what else?
I guess that BJT is in the high-gain loop of the OpAmp, so its finite gain and drifts should be automatically compensed. What do you think about?


texts:
I've been trying to setup this op amp for the past couple of hours, and I can't seem to do it successfully. I have a single supply, so I created a voltage divider with resistors to get +ve and -ve. I made the connections based on the data sheet by Texas Instruments. After that, I tried adjusting the offset null, but no luck.

Then I said okay, I'll try my circuit in LTSpice. The LTSpice model perfectly matches the inverting amplifier circuit. I re-checked my circuit and matched the model. Still the output voltage is off (~0.15V). I also tried other op amps and they give me approximately the same results. What am I doing wrong?

AFTER TWO DAYS I FINALLY GOT IT TO WORK

So I believe my issue was that the voltage divider wasn't a true voltage divider because whenever I hooked up my circuit the divider was not splitting the voltage evenly. So I decided to use a voltage follower and use its high impedance to my advantage. Needless to say, it worked! I think I also had grounding issues with my signal. Oh, and I also switched my opamps to the TL051IP since the previous didn't seem to provide accurate results. Anyway, this is the schematic for a Inverting Amplifier with a Single Power Supply! I labeled the V+, V-, and VG for convenience since this tripped me up the most for some reason.


texts:
So, I've cracked open my Roland Micro Cube which is a portable 2W guitar amplifier with digital modelling. The issue I've had with it since recently is the tone control potentiometer. Here's a picture of the front panel:

As you can see, the tone control goes from LO to HI (whatever that means, a shelving filter perhaps?). However, recently the control started behaving strangely - it's pretty much either just bass to the left and overdone highs to the right. I suppose the potentiometer is dead, since it feels looser than other potentiometers next to it. So I opened the chasis and had a look at the control board:

I've desoldered the potentiometer in question. It had the same markings as the other ones next to it, and they're all Alps-branded. Here's a close-up of the markings:

This is after I have lifted the metal support housing off. The unit has been launched in 2004, so I tried to find an Alps catalog from back then, couldn't find one so I went with the current one. From here I think it's safe to guess 3B is their marking for a linear taper:

The tricky part is 10, 80 and 4C. I opened up current Alps catalog for 9mm potentiometers and narrowed it down to the horizontal single-shaft one, which would be the one on the far left (RK09L horizontal):

As the available values are 10k, 20k, 50k and 100k I guess it's safe to assume the pot is a 10k linear. Well, easy, just replace it, right? I've measured the pot just to be sure. Which... threw me off guard. I got 2M when turned all the way to the right and what's more it was drifting all over the place (in the 1.9M-2.1M) without me touching it. Turning the pot to the left I got a reading of 6R. I also found the pot also drifts somewhere in the middle, in the 400k-800k range, without touching it at all. Here's a video to help you visualize the issue.

Is this behavior expected for a faulty potentiometer? Could it in fact be a 10k linear or are my assumptions wrong?


texts: Battery Wattage hour requirement for 12v, 3.75 amp device?

texts:
My cpap machine resmed airsense 10 states the following numbers:
DC 24v,
3.75 A
As per my understanding the wattage required is 24 x 3.75 = 90
I am assuming WattHour is 90x1 = 90.
If I need to use it for 8 hrs, the battery backup should be 90 x 8 = 720wh
But most of the products have around 100wh claiming to last 8 hrs or more . What am I missing?
This example has 97wh only an promises 13 hrs.
https://document.resmed.com/documents/products/accessory/power-station-ii/user-guide/power-station-ii_user-guide_row_mul.pdf


texts: Simple current regulator transfer function

texts:
I did simple op amp MOSFET current source. It was not working correctly, it had oscillations as per picture, so RC circuit was was added and problem was resolved. What I am wondering is transfer function of it and how to treat it. Conroller works as an error amplifier, but is this the simplest form of proportional controller. And after addidtion of the capacitor, does it make this circuit simple PI controller? And if we can treat it as PI controller how to check KP. Do we treat it as unity gain or open loop gain.

Could someone please give me some clues for this?


texts:
I was trying to make a device which can vibrate - so I took inductor, some 220uH 22uH, put 12V pulsed current through it (~10Hz), and put neodymium magnet - I was expecting to feel 10Hz vibration of a magnet in my hands when holding it 1mm from the inductor - but I haven't feel anything.

I tried 2 different magnets, result is the same.

What I did wrong? Is that due to the fact that my inductor is 'cored'?


texts:
I want to set the lower and upper cutoff frequencies of a single supply inverting op amp. Is my understanding of the frequency response correct? I also have some questions mixed in:

simulate this circuit – Schematic created using CircuitLab

The low frequency cut off is \$ \frac{1}{2 \cdot \pi \cdot C_2 \cdot R_3} \$. To be more accurate, I could find the output impedance of the Vin source, and add this to R3 in the calculation.
For the R1/R2 voltage divider, I would find the equivalent resistance (5k) of these resistors in parallel. Then the cutoff frequency would be \$ \frac{1}{2 \cdot \pi \cdot 5k \Omega \cdot C_1} \$. Does this cutoff frequency apply to the Vin signal? If so is this the lower or upper cutoff frequency and why? I read in a TI document that R1 and R2 are in parallel from a "noise perspective", and then it referred to the calculation result as the cutoff frequency, so I'm not sure how this cutoff frequency factors in, or if it only applies to noise...
C3 and R4 create the high frequency cutoff with \$ \frac{1}{2 \cdot \pi \cdot R_4 \cdot C_3} \$.
For C_OUT and R_LOAD, where R_LOAD is headphone impedance, is this forming a passive high pass filter, with \$ \frac{1}{2 \cdot \pi \cdot R_{Load} \cdot C_{out}} \$ ? I have seen a comment before that this would be the low cutoff...but it's in the configuration of a passive high pass filter, so I'm confused.


texts: Why are LCD panels polarized at 45 degrees?

texts: I understand the principle of operation of LCD panels, but I am wondering why the specific output angle of polarization was chosen over, say, horizontal or vertical.


texts:
While going through this youtube video from TI about the RS232, RS422, RS485 differences. One thing that don't understand clearly is following slide from this video.

The blue resistors that I marked on it are the termination resistors of the buses. For the case of point-to-point connection it is clear that there is only 1 receiver so we put the resistor near that point on the bus.

But the other two cases, multi-drop and multi-point, I could not understand why do we put only 1 or 2 termination resistors on the bus instead of putting 1 at every branch-off point?

So in the above picture there should be 3 resistors for the multi-drop case and 4 resistors for the multi-point case.


texts: ATmega2560 assembly pin read and compare logic problem

texts:
I apologize if my question was vague.

Program: Atmel Studio 6

I am trying to make a program that enters an loop which it will only break out of when a pin goes low.

;Set PA0 high before entering loop checking for low
CBI DDRA,DDA0       ;PA0 to input
SBI PINA0,0         ;PA0 pull-up enable
;PA0 is now input & high

chklow: inc r16     ; Increase r16
in r18,PORTA0       ; Copies PINA0 to r18
cpi r18,0           ; Compares r18 to 0
brne chklow         ; Branch if PA0 is not low
nop             ; Loop exit (do nothing)

What happens is that when I set PINA0, PORTA0 goes high. I guess this is good, it's like I pressed a button attached to PINA0.

Now I enter the loop, and I have my I/O view box up, so I see that PORTA0 is set. This is the rightmost box in PORTA.

But "in r18,PORTA" doesn't make r18 become '1'... it remains 0.

And so the Z-bit is set to 1 because the compare succeeded, and the branch doesn't occur.

What's wrong? I want the loop to continue indefinitely until I make PORTA0 low.

EDIT: I changed it now, using your advice:

CBI DDRA,DDA0           ;PA0 to input
SBI PORTA0,0            ;PA0 pull-up enable

chklow:
in r18,PORTA        ; Copies PINA0 to r18
cpi r18,0x00        ; Compares r18 to 0
brne chklow         ; Branch if PA0 is not low
nop             ; Loop exit (do nothing)

So what I changed was I copied the entire PORTA byte, instead of trying to copy the PORTA0 bit, which isn't possible (at least using my method), and now it works. Thanks ;)

Also, I know this is a dirty solution, because it fails if ANY bit in Pin A is set, but I can refine that later, this is a working prototype :D


texts: Effects of bootlace ferrules to connect load-cell with amplifier

texts:
My colleague and I had an argument about whether or not to use bootlace ferrules for a load-cell (4 stranded wires + 1 shield | 100mg precision | OIML C3 | max. 3kg) going into an amplifier (spring-type terminal | including shield.)
Is there a general or personal recommendation in regard of precision whether or not to use bootlace ferrules on wires of sensors (like load-cells) providing analogue non-amplified signal?


texts: How does measuring amps on a multimeter work?

texts:
When I measure the amperage coming from two AA batteries to an LED, these are my results:

On the 2m setting: .002
On the 20m/10A setting: 0.02
On the 200m setting: 00.2

I have one wire in the COM port, and one in the 10A port. Does this mean that my that my LED is drawing 20mA? Thanks!


texts: Measure distance to object with angular precision - invisible for camera

texts:
I want to build myself an arduino based follow-focus. There is one mode intended for using a joystick for manual control of focus and zoom. This code already works a treat.

Now I want to add a solution, to track the object. Honestly it does not seem like there is a cheap and at the same time good solution to track any object. And the Face-Following autofocus in cameras is pretty... proprietary. No luck on a smart automatic solution.

What I thought of:
 - Ultrasonic measuring (Not precise enough - might reflect of an object that is close in angular distance.
 - Laser pointer based system (Also not good, since a laser is absolutely visible for the camera. And that is a no go for video.

I thought of another way. Is it maybe possible, to use an UV laser (with low power of course!)? I mean, it would not be visible to my camera. But how do I see it? I was thinking, if there is a way with fluorescence glasses?

This is absolutely hypothetical. I mean, I have no idea, if any of these parts exist in a way that I can use it in combination with an arduino.

A quick search on ebay for uv distance sensor is not revealing anything usefull at all.

So is there anyone who can help with that? All that I really need is something, to measure the distance to an object in the range of 5-50 meters (better to 100 or higher). The accuracy is not important. If 5 meters gives 5.3 it is okay. If 20 meters gives me 22m as a result, it is also okay. This would not be a problem at all.

It only needs to be accurate in angular distance. It would not help, if I measure tightly around the edge of a house and it accidentally picks up the house and not the object right next to it (at a different distance).

Any ideas?

Edit: Also a very good solution would be, to give the person to track a tiny device that sends some form of EM and the amplitude to measure at the camera is giving information about the distance. But the problem would be (i think): regardless of the frequency, the object/person to focus on will likely influence the waveform more, than the distance itself would. Or what is about very low frequency stuff like 20-200khz? Are there frequencies, which pass through basically everything and are easy to produce and detect precisely? Of course with permission.


texts:
One of my amplifiers has died so I need to find out if I can hookup a spare I have lying around as per "Section B" of the below block diagram.
I have done the same modification before on simpler circuits but the circuit I have on hand is far more complex in design than those I have worked on, and ideally would not like the smoke to escape from it.
Basically, I want to replace the input transformer of "Section A" with a direct 12V source like a battery. I would solder the transformer secondaris to +12V and the Heatsink to 0V (GND). Would this work?
Please also advise if I want to completely remove high voltage potential from the circuit, would I be correct in assuming I have to remove the DC transformer alltogether to avoid backfeeding it with 12V at the secondary or is there nothing to worry about. I measure 320VDC at its primary when connected to the mains. The ciruit will still be isolated in a project box for asthetics and saftey.


texts: How can I determine if a microcontroller is damaged?

texts:
I have a few microcontrollers sitting in my "junk parts" bin. I think some of them arrived there when, after programming them, they exhibited strange behavior. I've since learned a lot, for example, how having the wrong optimization on the compiler can cause such strange behavior. On the other hand, some of the microcontrollers may have well been damaged due to static, out of tolerance voltages, etc. Thus, I believe some may be in good working order.

Before I throw everything out, I wondered: Is there a relatively straightforward or easy way to test a microcontroller to determine if it is still good?

The micros in particular are the Atmel ATTiny13, ATTiny26, and ATTiny2313, both DIP and SOIC versions.


texts: How to fit this schematic into my circuit

texts:
I am trying to learn how to put schematics onto a breadboard and currently I have this wheatstone bridge used for measuring the voltage change when my R2 resistor is affected by temperature.

Now I want to put this amplifier in my circuit to make the measuring more accurate and transform the output signal. The amplifier is chosen due to high impedance and the output from op-amp should be between 0-0.5V, where 0 is room temperature.

My question is how to actually insert this amplifier circuit into my wheatstone bridge circuit on my breadboard? If Anyone could show that would be greatly appreciated, since I tried following the image but is very unsure how to actually do it in practice. From what I understand it's supposed to be between A and B, where A is going into the op-amp and B is the output signal of it?


texts: Control capacitor charge current with a GPIO?

texts:
I have drawn the following schematic:

Vp/Vm are +/-12V rails.  The capacitor charges through R1.  A 3.3V pulse is produced at regular intervals on an MCU GPIO to turn Q1 "on", short C1 and discharge it.  This arrangment generates a ramp signal. I want to vary the frequency of the signal by issuing pulses more or less frequently.  With pulses every 50uS, the ramp is shaped the way I'm after:

Of course, the RC charging time is fixed so with pulses every 100mS, the ramp looks like:

I have plenty more GPIOs that I can use to generate a continuous control voltage ranging from 0V to 3.3V.  I thought a simple & economical way to unify the ramp shape throughout the frequency range would be to control the the B-E current of Q1 during the charging phase and "sink" some of that charging current directly into the negative power rail.  I'm having a hard time coming up with voltage-controled circuitry that injects the right current levels into Q1's base without side effects on the rest of the circuit.
How can I implement this? (Side question: is this a bad way to go about it, and if yes why?)


texts: Charging LiFePO4 at low voltage - how do you know when to stop?

texts:
I've read that the most typical approach to charging, is to provide as much current as you'd like (lower current causing less loss of capacity over time), and to stop when the cell reaches 3.6V. The cell should then come to a resting voltage around 3.3V.

My problem is that my car alternator may only be able to provide 13.6V, or even less.

If I charge a cell at 3.4V, or 3.3V for that matter, obviously the charge current won't be as high, which is acceptable. But how do I know when to stop charging?

One guy did some tests and charged to different voltages, and stopped only after leaving the current was down to 30mA (C/100), and found that charging at 3.4V was still able to charge until 99% of capacity.

But is C/100 the correct current level to stop at?


texts: finding missing current and voltage in a circuit involving superposition

texts:
We are given a black box that contains only linear circuit elements and a pair of ports. We conduct the following two experiments with this black box.

With the right port open, we applied V1 = 2V to the left port and measured I1 = 4mA and V2 = 8V.
With the left port shorted, we applied  I2 = -10 mA to the right port and measured  I1 = 5mA and V2 = -10V.

Now we connect a current source to the right port and a voltage source to the left port. I1 = 8mA and V2 = 4V now. Find I2 and V1, in mA and V each.

I don't get this. Since we have analyzed the circuit separately for each source, adding them should give me the final values of I1, V2, I2, V1 etc. However, that's not quite true—from cases 1 and 2, I should have I1 = 4 + 5 = 9 mA, but it's 8mA. Hence, I thought that the black box consumes 1mA; hence I2 = 0 + (-10) - 1 = -11 mA. Similarly, V2 = 4V even though adding the V2 from first two cases gives -2; hence, the black box provides an additional 6V, and so V1 = 2 + 0 + 6 = 8V. However, this approach is wrong.

How might I solve this?


texts: Most efficient generator for charging 12 V batteries

texts:
I have a Honda GX25 mini 4-stroke engine that I want to built a battery charging generator for 12 V lead acid batteries.

My first idea was to use an old car alternator as the generator part, but now I am not so sure. How would I go about selecting the most efficient (and hopefully compact) generator for this motor?

Also as a side note, I will need to make an automatic starter for this motor. Would it be possible to combine the starter motor with the generator somehow?


texts: Implementing an Avalanche Photo Diode Circuit

texts:
I am working on a circuit that will make low light measurements in the visible range. The measurements will be of biological samples that are fluorescing. For this application an Avalanche Photo Diode (APD) has been chosen. The intent is to build a circuit that does not necessarily have fast response but can detect very low light levels.

I wish to use the LT3482 (datasheet). This chip has a demo board here (datasheet) that I want to copy. I also wish to use the Hamamatsu S12053 range of ADPs (datasheet).

I have several questions about this setup:

1) Temperature Compensation

In order to ensure a good signal the bias voltage needs to be temperature compensated. The LT3482 datasheet specifies "The LT3482 features high side APD current monitoring with better than 10% relative accuracy over the entire temperature range." Is this 10% error an additional error to the amplification error that results from temperature differences? The gain curve is shown below:

2) Bias Voltage

The gain and dark current curves of the ADP are shown as follows:

The LT3482 is only capable of a 90V output. Is this too low? Judging from the gain curve it seems like I want to be in the 130 -140V range for best performance without risking breakdown.


texts:
I am about to make a revision of a PCB that has 60 mills of Intra-Pair Skew in PCI-E (Gen 2) RX differential pair:

Considering the capacitors the skew is ~50 mills:

this is the relevant part of the stack up for my question:

the traces are on layer 1, and the chip is on bottom layer (overall 6 layers) . the traces have 85 Ohm impedance.
Looking in Wikipedia, I learned that for 5 GT/s (Gen 2) the limit is 8 ns skew.
how can I approximate if the 60 mills skew are critical in my case?
since the layout is so dense, I can barely do anything to minimize the skew. I was wondering if I can leave everything the way it is right now without affecting the performance.
Note: This design is a board that converts from PCIE to USB 3.0 using VIA-LABS VL805-Q6 Host Controller.
Additional Question:

did anyone understand where did the 20 picosecond in the first answer come from? how it was calculated?


texts: How do I cutoff power to ultrasonic HC-SR06 when it is not been used, to save power

texts:
I want to read an ultrasonic sensor data every 10 minutes and expect that the module should be turned off in order to save power.
How do I do this?
I tried with a BC547 and PN2222 transistor but I end up with failure.
Can you please suggest a better method to cutoff power from the module? It has 4 pins (VCC,GND, ECHO,TRIG.)


texts: Why do some electric circuts need 2 or more voltage sources

texts:
Why would we put 2 voltage sources(bateries) into an electric circut  ?
What are some real world examples where they are needed ?


texts: Faster 8051 not taking the slower 8051 pin status correctly

texts:
I'm trying to do a rather simple data transaction between two 8051 microcontrollers using a variant of the SPI protocol. The large one is a slave and the small one is a master.

The documentation for the slave (larger micro) states the clock output speed is 6x slower compared to its external crystal speed. Because of this, the master also runs 6x slower I added a bunch of nops (no-operation) commands in my code for the slave.

Hardware wise, the circuit is on a PCB and the track going to the clock is roughly 40mils wide and the other tracks are 12mils wide. Their lengths are less than one inch and the clearance for all tracks is at least 12mils.

After various tests, the SSEL (aka "slave select") line does go low when the master sets it low, but the slave does not make the SPICLK (aka "SPI clock") line high which is what it should be doing.

What am I doing wrong?

;Big micro (slave) code

SPICLK bit P3.6
DIN bit P2.5
DOUT bit P2.6
SSEL bit P2.7

org 0h
setb DIN
setb SSEL
clr SPICLK
debug:
    acall SPISS ;stall until remote does valid cmd
    jc debug ;carry = remote didn't set low yet
    jz debug ;zero = invalid command
    ;process code based on accumulator value
ret

;SPI slave routine
SPISS:
    setb SSEL ;Set high so master can set it low
    nop     ;wait 6 cycles because master is 6x slower
    nop
    nop
    nop
    nop
    nop
    jnb SSEL,nospiop ;if line isn't taken low
    setb C     ;then set carry
    ret        ;and return. This always happens which is a problem!
    nospiop:
    mov R7,#8h     ;Setup 8 bits
    s:
    setb SPICLK    ;tell other micro we are ready
    nop         ;let it catch up
    nop
    nop
    nop
    nop
    nop
    clr HWLED   ;turn our light on
    jb SPICLK,$ ;wait until master lowers clock line
    clr SPICLK  ;we keep it low to make master wait
    mov C,DIN   ;get bit
    setb HWLED  ;turn off light
    rrc A   ;shift into the byte
    mov DOUT,C  ;and take other bit as output
    djnz R7,s   ;continue for remaining 7 bits
    setb SPICLK ;tell micro we are ready again
    nop
    nop
    nop
    nop
    nop
    nop
    clr HWLED   ;turn on light
    jnb SSEL,$  ;wait until master turns slave select to high
    clr SPICLK  ;tell micro we are always busy
    setb DOUT   ;reset other values
    setb DIN
    setb HWLED
    clr C       ;C=0 for normal completion
ret

;Little master micro code

DOUT bit P1.1
DIN bit P1.2
SSEL bit P1.3
SPICLK bit P3.2

org 0h
mov A,#COMMAND ;Some value irrelevant to the problem
acall docpucmd
sjmp $

docpucmd:
    acall SPISM ;Send command out but we don't care what comes back
    clr A         ;Make command as zero..
    acall SPISM ;because now we want the result to the last command
    clr C
ret

;Master SPI routine
SPISM:
  setb SPICLK   ;Make clock line so slave can pull it low
  setb DIN  ;Make input high so slave can set it
  clr SSEL  ;Lower slave select to start transaction
  mov R7,#8h    ;8 bits to transfer
  m:
      nop       ;wait until remote RAISES clock line to indicate
          ;slave is ready but slave likes to keep line low always
      jnb SPICLK,m
      mov C,DIN     ;Get bit
      rrc A ;Shift it in and shift old bit out
      mov DOUT,C    ;Send out old bit
      clr SPICLK    ;lower clock line to tell slave we have data
      nop       ;add small delay. this is executed on slow micro
      setb SPICLK   ;raise clock line
  djnz R7,m ;repeat for remaining bits
  jnb SPICLK,$  ;wait until remote is ready
  mov C,DIN     ;get official last bit
  rrc A     ;and make byte correct
  setb SSEL ;and reset lines
  setb DOUT
  setb DIN
ret


texts:
If I want to process data in the order it arrives, it seems that a FIFO would be most appropriate; however, I want to look over the data multiple times (at least 20 times), so I am considering either rewriting to the FIFO when I read from it or using RAM, which I can read from many times.

The data are points and I want to compare them with another set of points to identify ones that are within a certain distance.

My question is what are the benefits of each in terms of complexity, time, usage of FPGA resources, etc? I plan on using a Xilinx FPGA (likely kintex 7) if that is relevant.

Thanks


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Can I charge a 15V Cap with a 24V supply, as long as I have the supply disconnect, once the cap reaches 15v ?

I have seen the analogy of comparing the voltage to the max psi of a tank, and if you go over, it will quite literally spill out.  So in this case, it would be like filling a 100 psi tank with a 150 psi source and simply shutting the fill valve when reaching 100 psi.  Should work no?

Thanks for you input in advance!


texts: difference between a DC motor and gear motor

texts: Isnt DC motor the same as gear motor? Because what is the use of dc motor without gears?


texts:
I am currently attempting to construct an high side driver of Mosfet. There is scheme:

When there is no signal on IN pin:
HO = CS = Vs = 8.3 V.
When I send pulsing signal ( pwm like ) with 4 V amplitude I expect to see 11.4 V on HO and LOAD and 22 V on VB but it is not happens. There is still 8.3 V on HO, CS and Vs pins.
It seems like MOSFET can't open because Vgs = HO - CS = 0.
So, after that I connect Vs to ground and get Vs = CS = HO = 0 v while there is no signal on IN. But still nothing happens if send signal on IN.
Finally I get expected 11.0 V on LOAD and 21.0 V on VB using this method: disconnect Vs from GND same time high level signal on IN.
So, what I miss? How can I get Vcc on LOAD by using only IN pin? Is there is wrong scheme? I get it from datasheet. Explain me please.
Edit:
After modification of scheme:

I get expected 22 V on Vb and 11 V on Vs when 4 V on In. Is it correct scheme?


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I try to power a WS8211 based ledstrip. I first achieved to make it work with an Arduino UNO.

The ledstrip needs to be fed with 12V power.

Here is the working schematic :

Once I apply power every 2 or 3 meters, everything works great !

I need to make it work with a Node MCU board with the ESP8266 wifi onboard.
The main issue here is that this board use 3.3V logic. And because the ledstrip only understand 5v logic, I need to shift that. So I'm using a levelshifter I found on amazon here if you need details.

Here is the actual non-working schematic :

The problem is that the ledstrip is flickering and does not light up all the leds. Since it worked perfectly on the Arduino, I am pretty sure the logic level sent to the ledstrip isn't powerful enough (even though I'm using a level shifter).

Since I'm pretty new to electronics, I am not very sure if I did a correct wiring with the level shifter, the common ground and so on...

Here are some notes :
I tried to measure the voltage on the levelshifter with a voltemeter. I put the red cable of the voltmeter on the signal pin and the black cable on the ground pin :
In the code I put the selected pin on OUTPUT mode and HIGH.

In the lower column voltage I barely get 3V.
In the higher column voltage I barely get 4V.

Again, because I'm a newbie I don't if I made correct measurements.

Any suggestion is welcomed ! :-)


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I am trying to run a test that requires a board to have 57 signal layers, however in the layer stack manager, I am unable to get more than 32 layers.  Signal is grayed out when I go to add another layer. Is there a way to add more layers or is 32 the max?

I am using version 20.0.13

EDIT: The test is to see if the Dragonfly (3D PCB printer) can actually do it because 57 is stated as it's max but good to know that 32 is indeed the max.


texts: Help understanding this pulsing LED circuit

texts: I started learning about op amps, and I came by this circuit and thought I should be able to understand it. What is tripping me up is how is it pulsing or varying with time? The source is supposedly a 9v battery, so the time dependence doesn't come from there. I thought maybe it comes from the capacitors, but I can only come up with is that the capacitors act like a short circuit at time zero and act like an open circuit at time infinity. I know they have to do with how long the pulses are but I don't know how in a technical sense. Like how are they charging and discharging? Maybe the capacitors are causing a flip between positive and negative feedback?


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The following code is a hspice code. what are the exact formulas for calculating the matrice elements Lo, Co, Ro, Go, Rs, Gd? In other words, I want Lo, Co, Ro, Go, Rs, and Gd calculation formulas. thank you.
The following input netlist file shows RLGC input for the W Element:
W1 N=3 1 3 5 0 2 4 6 0 RLGCMODEL=example_rlc l=0.97
V1 1 0 AC=1v DC=0v pulse(4.82v 0v 5ns 0.1ns 0.1ns 25ns)
.AC lin 1000 0Hz 1GHz
.DC v1 0v 5v 0.1v
.tran 0.1ns 200ns
* RLGC matrices for a four-conductor lossy
.MODEL example_rlc W MODELTYPE=RLGC N=3
+ Lo=
+ 2.311e-6
+ 4.14e-7 2.988e-6
+ 8.42e-8 5.27e-7 2.813e-6
+ Co=
+ 2.392e-11
+ -5.41e-12 2.123e-11
+ -1.08e-12 -5.72e-12 2.447e-11
+ Ro=
+ 42.5
+ 0 41.0 + 0 0 33.5
+ Go= + 0.000609
+ -0.0001419 0.000599
+ -0.00002323 -0.00009 0.000502
+ Rs=
+ 0.00135
+ 0 0.001303
+ 0 0 0.001064
+ Gd=
+ 5.242e-13
+ -1.221e-13 5.164e-13
+ -1.999e-14 -7.747e-14 4.321e-13
.end```

Lo: DC inductance matrix, per unit length [H/m].
Co: DC capacitance matrix, per unit length [F/m].
Ro: DC resistance matrix, per unit length [Ω/m].
Go: DC shunt conductance matrix, per unit length [S/m].
Rs: Skin effect resistance matrix, per unit length [Ω/m√Hz].
Gd: Dielectric loss conductance matrix, per unit length [S/m.Hz].


texts: My MCU(ATMega328) configured to get clock from ext. oscillator. Can I still program this MCU without external oscillator using ISP, by just connecting 6 pins to MISO/MOSI/SCK/RST/GND/VCC?


texts: Efficient way to get multiple analogue voltages out of an Arduino?

texts:
I've read in my research that most microcontrollers are not built with DAC outputs as they are expensive to include on silicon chips. Also applications that require analogue outputs typically need a higher resolution than is feasible on a microcontroller and would probably use a dedicated IC anyway.

I am planning to build an analogue synthesizer with patch memory (storage and recall of voltage states). Apparently these functioned by reading the voltage of an analogue potentiometer into a microcontroller and applying a control voltage to the synthesizer using a DAC. This state could then be saved and recalled as 'presets'.

I would like to know a suitable way to control multiple analogue outputs to a circuit from an Arduino. The analogue outputs in most (if not all) Arduino boards are actually PWM, and I want to output a true analog signal.


texts: Difference in self discharge rate between Lithium iron phosphate battery vs Lithium Polymer Battery

texts:
What is the difference in self discharge rate between lithium iron phosphate battery and lithium polymer battery?

I have a remote application in which the self discharge rate matters a lot.