texts: Altium Trace, Silkscreen not solid ie only showing outline

texts:
Whilst working with Room Copy key command (D-M-C) I have inadvertently changed something which has resulted in my traces and overlays showing as their outline only.

Does anyone know what I've done to change this back? I can't find any information related to this view (likely as I don't know what it is called).


texts: local/bench earth leakage for testing mains electronics

texts: I sometimes find myself testing switch mode power supplies and such that I have repaired, and often some undetected fault causes them to trip the earth leakage breaker on the distribution board when plugged in. Can I setup a second local earth leakage on my bench to prevent tripping the whole building?


texts:
I want to design a circuit that has 3 LEDs connected to it.

When the voltage of the power source connected to the circuit is...
3.6 volts I want only the first LED to light.
7.2 volts I want the second LED to light. The first LED can light also.
14.4 volts I want the third LED to light. The first and second LED can light also.

Is this kind of thing possible? and how do I make a start?

Thanks,
Karl

EDIT: sorry guys, the dashes were confusing. I'm trying to measure positive voltage. What I'm making is an enclosure system that allows you to make battery packs of various voltages, 3.6, 7.2 and 14.4v. I want to make a measurement tool that confirms there is power and indicates what voltage the pack currently has.


texts:
I cannot understand how this IC works from the block diagram given in the datasheet. I understand the concept of an H-bridge, but cannot figure how this one operates.

I drew on the schematic to illustrate my confusion.

To run a motor in the given way (red path) you would need to enable the transistor in the top left and bottom right, while disabling the other two. Do to that, the AND gates at the base of those transistors (conducting) need to have two HIGH terminals in order to provide feeder current for the transistors.

However, in order to turn on only those two transistors, you must enable IN1, IN2, and ENA (ENA is simply a pin you enable to power the left H-Bridge of the L298N - is has two as shown).

Given how the wires are connected, there is no way - that I can see apparently - to turn on two diagonal transistors without enabling the other two ..

I obviously must be missing something ..

According to what I have read, in order to drive the transistors you need to have IN1 HIGH and IN2 LOW for one direction and the opposite for the other. I just do not see, from this schematic, how that even is possible.

Also note: the ENA/ENB pins are used in conjunction with PWN signals to drive the motor are variable speeds.

Here is the original:

Here is the illustration:


texts:
My doubt pertains to the usage of termination resistors. This is a continuation of the discussion I saw in this link - Termination resistor.

I understand that any transmission line can be simulated using a set of LC components (viz a number of tank circuits).

When it says a transmission line, it can also mean a microstrip, right ? Because a microstrip can also send a high speed signal, right ?So, does that mean I will need a termination resistor even in a microstrip ?


texts:
I have a power supply with multiple outputs (5v, 12, 24v)
According to the manufacture (and after testing) there must be a minimum load on the PSU for it to supply the stated voltages. Without a minimum load the voltage can go up to 37V (which is very bad)

As I can't garentee that the system I'm building will use minimum W all the time, I've added 'dumb' resistors to do the job. They get really hot but I used a 20W resistor when I just need to 'consume' 2W.

After this, everything works fine.

But in order for me to sleep well at night I would like to guarantee that if one of these resistors would fail for any reason, the high voltage would not burn the electronics.

I have used a PTC for limiting current in the past but I would like to use a similar device to limit the voltage.

Is there such device? Can you recommend on a different solution? I can't change the PSU now as it was the only one available in a very short notice.


texts:
I have a little question about the TOVn flag located in the TIFRn register.

The datasheet says, if the TCNTn counter overflows, then the TOVn flag located in the register TIFRn will be set to 1. (at the same clock cycle the overflow occoured).

The code to handle such event is the following:

/* Check if TOV1 flag is set */
if (TIFR1 & _BV(TOV1)) {
    /* Since TOV1 is set, we know we missed an overflow interrupt */

    /* Handle the event... */
    // ... timer_ovf_cnt++;

    /* Prevent ISR to be called, because we already handled the overflow */
    TIFR1 = _BV(TOV1); // .. but TOV1 is already set in TIFR1?
}

But what confuses me is: why should I set the TOV1 bit when its already set by hardware?
Does setting the TOV1 flag in TIFR1 to 1 by user hand disable the timer interrupt? (Even, if the TOV1 flag is already set by hardware?)

EDIT: Found the answer: Clearing flag bits by writing 1?


texts:
My motherboard has a WS2812B header for use in addressable RGB LED strips. However I am not using them for those strips, as instead I would like to use the signal to separately control several other RGB LED devices (fans, reservoir, GPU, monoblock, ...). The WS2812B connector itself is rated at 3A (5V) and needs to be split up into 12V RGB signals (I'm sure 500 mA or so will be fine).

I have some experience with Arduino programming and have the equipment to solder, but any solution that makes it work will be fine. However, it is paramount that there is no way that I can damage my motherboard.

To further clarify, this header on the motherboard has the following pins: +5V, Data and Ground. The motherboard is the ASUS ROG Zenith Extreme. You can find the header I'm talking about on page 40 of the manual.

Is this even possible? Is there already some device that makes this work? How would I go about making this work?

Thank you in advance,

CX


texts: Car battery spot welder. How to reduce battery power?

texts:
I built a spot welder that is powered by a car battery. The battery is 12V and 100amps. But unfortunately, it is a little bit too powerful, because it burns through the nickel strips and also through the battery really quickly most of the time.

So I would like to know what is the easiest way to reduce the power/voltage of the battery just a little bit? Will a voltage divider work in that instance?
I added the picture of the spot welder.

It is really simple, no buttons nor switches:


texts: Using LTSPice to make Function Blocks for SIMULINK

texts: I have a PLL that I want to model in Simulink using the control theory toolkit. I have the schematics for the PLL in LTSpice. Does anyone know of a way that I can integrate the spice model with my MATLAB simulation? I'd like to to turn the individual parts of the circuit into Simulink functional blocks (based on the SPICE netlists)


texts: I have MOT transformer, which I want to use for DIY spot welder. I measured 0.85V on one turn of primary open circuit, it means cca 2.55V on three turns etc. This seems ok. What I do not however understand is the short-circuit current measured with my clamp meter. It just doesn't make sense to me. On one turn there is about 100A, on two turns 200A and on three turns of secondary about 300A of current flowing. But current in transformer should be directly opposed with the raising voltage, doesnt it? Can anyone explain to me why with more turns (and higher voltage) of secondary, the short-circuit current is also higher?


texts: The mysterious case of the random leakage current

texts:
Disclaimer: I already know the solution of this circuit debugging conundrum (and it is not trivial), and I'll post it after some time, so that other people could give their contribution to this mystery story! I think it may have some educational value for circuit designers!

Some years ago (~8, IIRC) I stumbled upon a very interesting special offer at a local general store: some very nice (so I thought) Osram DOT-IT LED light appliances at half the price.

As you can see, they were small appliances, powered by three
AAA batteries, encasing three very bright white LEDs. The whole
thing was switched on through a soft switch actuated by
pressing the transparent dome. At 1st press the three LEDs
would turn on, and at every subsequent press one of the LEDs
would turn off. So you could have the possibility to choose
the amount of light the appliance would produce. The outer
case, besides the transparent plastic dome, was very strong
anodized aluminium, with the back cover being plastic with a
strong magnet, which allowed to stick the thing to the
fridge, the car body shop or whatever suitable metallic
surface you might want.

Since at the time LED lighting was very expensive here in Italy, and small gadgets like those were either monstrously expensive or totally crappy, I thought it a very good idea to buy a dozen of them (I first tried with just one unit, and I verified it made very strong light and was of very high quality). I intended to use them as emergency lights in every room of my house and in my car.

All was fine until a brief black out happened after about 6 months. To my great disappointment, about 10 out of 12 of the things had their batteries dead!

Of course my first thought was "crappy leaky soft switch" and I ran for my micro-ammeter! Effectively I found a couple of units that had excessively high leakage currents (~1 mA), but the other ones had a quite honest ~20 μA. I was puzzled.

I replaced all the batteries in the low-leakage ones and decided to give them another try.

After a couple of months, surprise, they failed again! I measured the leakage again and got different results. Some units sported the terrible ~1 mA leakage, whereas the other were "normal". Moreover, I retested the two units which originally showed high leakage and... they didn't leak any longer!!!

I was fed off and since I had got no more time to waste on the issue back then, I scrapped them all, put them in a junk box (after all, they had three nice and expensive white LEDs in them, and I planned to salvage them) and forgot about them.

I found them again a couple of weeks ago and, in a reorganization frenzy, I thought to dismantle the units and salvage the LEDs. So I discovered that the internal circuitry was a tiny PCB holding just a momentary switch, the LEDs, a driver chip and a cap. The PCB is shown in the photos below (for curiosity I tried finding a datasheet for that driver chip, but with no luck).

I tested the PCBs again, just for fun, and I still got the erratic leakage behavior I had observed before, but in the process I finally discovered the culprit.

Guess what was the cause of that random and erratic leakage!


texts: Confused about zero component orientation

texts:
I always thought that component orientation in EDA tools (IPC-7351) is separate from component orientation on tape (EIA-481).

This made total sense to me: first, PCB design defines rotation relative to standard orientation, so pick-and-place file specifies exactly how component is oriented relative to PCB. Second, the orientation of a component on a tape is specified by a manufacturer. The combination of the two gives exact rotation the pick-and-place machine should perform when placing a component.

... and then I stumbled upon a document that implies that library footprints should be oriented exactly as the components on a tape. Which, unfortunately, is often different for different manufacturers. Not only that, but the EIA-481 standard itself changed orientation between -C and -D revisions, prompting some manufacturers (e.g. IDT) to issue bulletins notifying customers that they will stick with older revisions of the standard for the time being.

Now, this does not make sense to me. It basically means that I should know in advance the position of the PCB relative to the tape. Which is far fetching, considering that automatic panelization often rotates PCB to fit more of them.

Finally, what blew my mind completely, is that various sources seem to disagree what quadrants really mean. The EIA defines them like this:
1 | 2
--+--
3 | 4

Some manufacturers, like Analog Devices, define them like this:
1 | 2
--+--
4 | 3

Not to mention that neither corresponds to 300 years old Cartesian system...

When I asked the manufacturing house for the clarification they replied with "use EIA-481 for zero component orientation, and use the IPC-7351C to design the size of the pads." With all the standard changes and discrepancies this basically tells me nothing.

So, should I really redefine packages in KiCad according to each manufacturer, losing an ability to quickly change suppliers of the same part? Or should I just go ahead with built-in packages and hope the house will figure it out somehow?

UPDATE:

Just received the boards and wanted to give a quick update. It looks like the comments by The Photon and others were right on the mark - the shop did not have any problems with orientations and placed all components exactly right.

I did not adjust anything to manufacturer-specific tape orientation, simply used footprints from KiCad libraries where it was appropriate. For my own footprints I followed IPC-7351C orientation guidelines, pretty much leaving the shop to deal with EIA-481 discrepancies. Of course, it could be I got lucky and the suppliers I've used in BOM simply happen to use compatible orientations.


texts: Does logic shifter works on analog signals?

texts: I am using a 5V sensors (MQX Gas Sensors) that is connected to an RPi. This sensor is then connected to an ADC converter then to a logic level shifter. I just followed the tutorial I saw on the internet. Since the input varies from 0V - 5V, if I connect it to an logic level shifter, will the output vary from 0V - 3.3V as well?


texts: Why do brushless motors have a kv rating?

texts:
I am wondering why brushless motors, such as ones used for quadrotors, have a kv rating, which supposedly means RPM per voltage across the motor. So a 2300 kv motor spins at 2300 rpm if "1 volt is applied" to it.

The part in parenthesis does not make sense to me. An ESC generates 3 phase AC current. And from what I understand the frequency of the AC waveform completely determines motor speed, and the amplitude (peak voltage minus trough voltage) of the waveform is more or less constant. To me this seems like voltage really has nothing to do with determining the speed of a brushless motor.


texts: Pulse generator and source supply connection

texts:
I need a signal that most of the time will work as a power supply for the microcontroller but at some external event a positive pulse will be generated and added to the normal power supply. Power supply is set once and it never changes, however the pulse will be different.

My question is: I have a powerful glitch generator that can provide only a voltage pulse so I need to add a stable power supply. What is the best way of doing it? I want to keep the parameters of the glitch as close as possible to the device characteristics (rising and falling edges are around 200 ps), hence the schematic does not have to introduce a big distortion to it.
Could you give me some tips or descriptions for doing it.

I am not an electrician, I am mathematician doing research in software and I need to disturb this software during the microcontroller run by this exotic way.


texts: What does macromodel mean in this context?

texts:
I was looking for the meaning of IC "macromodel". And I came across the following:

They call the above schematics of the opmap IC as its "macromodel".

But what is modelled here? They show all the components explicitly with all nodes.

I thought I would find something like a simplified diagram. Is the above schematics correctly called as macromodel? If not, what is an IC macromodel?


texts: How to read 115200 Baud digital signal on Arduino UNO?

texts:
I am a beginner to microcontrollers. I am trying to use Arduino UNO to read data at 115200 Bd. I used SoftwareSerial.h as follows. But I do not think I got correct data. Could you help me take a look?

Thank you so much!

#include <SoftwareSerial.h>

SoftwareSerial mySerial(8,9);  //RX,TX

void setup()
{
  mySerial.begin(115200);
  Serial.begin(115200);
  Serial.println("starting...");

}

void loop()
{
  while(mySerial.available())
  {
    Serial.println(mySerial.read());
  }
}


texts: Anomalous capaictor discharge in pSpice with transient analysis

texts: I'm doing a Transient analysis of the given circuit.My question is why didn't my capacitor discharge fully,according to the graph?


texts: Can pins (breadboard friendly) be added to non-drilled pads?

texts:
Some PCBA's have pads along the edge, where I believe some kind of headers could be soldered (or may be not), but don't have the pads drilled. I guess manufacturers save a little cost on drilling, and is not a problem when these are breakout boards used in production settings. To turn them into something that is breadboard friendly, apart from drilling holes, is there any alternative option -- s.a. a novel way of soldering pins ?

PS> Aversion to drilling is that these are FR4 boards, and I do not have drill-press or access to one.


texts: set and reset of D flip-flops : always physically present?

texts: On various technology (discrete, ASIC, FPGA), I'd like to know if the asynchronous signals set and reset are always present on D (edge-triggered)  flip-flops. If not how the reset process can be handled ?


texts: Stepper Motor NEMA23 and driver A4988 matching problem?

texts:
I am experimenting with a stepper motor NEMA23 with the following specifications:
Rated current: 2.8A/phase
Resistance/Phase: 0.9
Step Angle: 1.8
Rated Voltage: 2.5
Inductance/Phase: 2.5 mH
Holding Torque: 12.6 kg/cm
Rotor Inertia: 300 g/cm2
The driver i am using is a a4988 Polulu with 2Amps maximum current. The Vref is set to 0.66 so depending on the Rsense ( 0.05 ) the Imax is set to 1.65.
I have made the wiring, uploaded the code with a delay of 0.1 seconds but the motor won't move. I use a power supply set to 20V.
Since this is very hard to debug. Is this driver compatible with the motor? Or the max current of the driver is too low to move the motor?


texts: Recording of sensory nerve evoked potential generated through skin-receptors

texts:
If we touch / give pressure to a skin, there are many mechano-receptors like meissner/pacinian corpuscles that produce action potential in neurons.

I am in a need to detect those action potentials from the skin surface like I give physical stimulus to tip of the finger, then is it possible to record just the spikes whether fired or not in neurons?

I mean just the non-invasive circuit which can detect nerve firing and display yes or no.

I searched for the last 3-4 months and developed one circuit (instrumentation amplifier + gain stage + filter + surface electrodes), but all efforts in vain.

Please suggest me, how to proceed ahead. Is this kind of circuit possible? Or is it (even) available commercially?


texts: Contact Bounce - Simple Debounce RC Circuit Question

texts:
I got this circuit from an example.

simulate this circuit – Schematic created using CircuitLab

What kind of circuit is this? I know its an RC circuit and I also know that its designed to be a simple switch debounce circuit.
Is it also a kind of filter circuit? (low-pass/high-pass/etc.)

The EXAMPLE stated that this is one simple version of a debounce circuit.
How does this circuit help eliminate contact bounce?

If it does eliminate contact bounce:
How much bounce will this current setup eliminate? What will the voltage and current be at "A"?
If I want to try to eliminate contact bounce within the first 10 ms, how can I design this circuit to do that? 20 ms?

What kinds of potential side effects could I see from this circuit?

Sorry I am noob and not EE.


texts: PWM signal to SIM800 MIC noise reduction

texts:
I have an audio signal made by a PIC microcontroller using 20KHz PWM (it passes through a low-pass filter). It is very clear on an 8ohm speaker, but when I connect the output to the MIC inputs of SIM800 module, it has a very bad quality on a phone call and can not be understood at all. I connected the audio output directly and through a 100nF ceramic capacitor, but in both cases the audio was very bad.
How should I connect audio output to the MIC input of a SIM800?

simulate this circuit – Schematic created using CircuitLab
I already have seen that output of ISDxxxx (audio recorder and playback IC) is connected to MICP pin of a SIM900 just through a capacitor in a firewall system and the audio quality was very good.


texts: Is it possible to revive a dead battery by passing a high voltage through it?

texts:
I have an almost dead laptop battery and read in this forum that

  "The problem with most of the broken
  batterys is that they are exhaustive
  discharged. the trick to solve this is
  to give them a high voltage
  electricity source like a laptop
  charger (20V). I did that to all the 3
  lion batteries I found inside the
  macbook battery but just for a few
  seconds to reactivate them and now
  they are working fine"

I am curious whether this is theoretically possible if nothing else.


texts:
This component was inside an isolation transformer. It's obviously for limiting inrush current, but how does it work and what is inside?

I believe it's a relay of some sort, switching a resistor in series with the input or something like that. When voltage are applied to it's input i can hear the relay inside oscillating, so clearly somethings wrong. Makes me wonder how it triggers on the inrush current and why they didn't go for a NTC current limiter.

Thanks :)


texts: How about soldering microSD card directly to PCB?

texts: I know that microSD cards are typically not designed for this type of use, but has anyone tried this? Would it be possible in production ( >1000 units), that is, would any PCBA service be able to do this for you?


texts: BNC cable's characteristic impedance and voltage drop

texts:
As far as I understand, the characteristic impedance matters when a signal is oscillating since the BNC coaxial cable can be modeled as having inductors and capacitors as in the figure:

I have couple of questions that confused me:

1-)I'm wondering if I measure a low frequency oscillating signal like 100Hz through a BNC cable with a length "X", how can I calculate the voltage drop across the BNC cable. Ok maybe my signal is not an RF signal, but if I'm after accuracy and I guess the signal voltage will attenuate some amount since it is oscillating right? Any ideas how to calculate the voltage drop?

2-)And how come different lengths of BNC cables have 50 or 75ohm fixed characteristic impedances? Isnt the length of BNC effect its characteristic impedance?


texts: How would you apply high voltage on a piece of dielectric making sure breakdown does not occur?

texts:
Say you have a piece of dielectric with a breakdown electric field, BDE. For some experimental requirement you have to apply an electric field, E > BDE, across the piece of dielectric without reaching breakdown. So you place the dielectric between 2 plates/electrodes with appropriate spacing to reach the desired field, E. Now, to prevent breakdown you insulate the electrodes with another dielectric that has a breakdown electric field, BDE2 >> E. Would this technique work to achieve my goal or is there something I am missing?
The above scenario is related to controlling the behavior of a ferroelectric.


texts: How to understand a microcontroller's name?

texts: I want to know how to get the information about a microcontroller from its name, like the  STM32F407VG. I know that the F407VG has got some information about the STM32 discovery board, but not sure what it is.


texts: just met an industrial computer which has the following power adapter jack. how to identify this jack and where to find? (actually there are lots of different jacks here and there, how to identify all!).


texts: Does an antenna work inside a plastic box

texts:
I need to put two antennas for GSM and GPS communication on my PCB. My final product will be embedded in a user-friendly plastic box with buttons, leds and switches.

I have not choosed yet which type of antenna I will put on my design (PCB antenna, ceramic antenna or SMA antenna), so I am wondering if all those types of antennas work if they are completely inside a plastic box or if some parts have to be outside.


texts:
I'm very new to electronics and I wanted to start with something that would hopefully simple, but also useful.

I'd like to make a circuit that can read a DC input voltage (between 9V and 20V) and output to a multicolor LED.  The color would change depending on the sensed voltage.

Can someone please steer me in the correct direction for getting started on this project?  I'm not certain what terms I should be searching or an ICs I can take a look at.

Is this as simple as making a set of voltage dividers and placing my output to the LED's pins in the appropriate location?

EDIT:
OK.  Here's my first attempt/iteration.

simulate this circuit – Schematic created using CircuitLab

If I understand correctly, anything 13VDC or higher should light the LED?  Should I limit current somehow to the IC or will R1 handle it?


texts: Rise and fall times typical values for a switching signal in 90 nm technology

texts:
I have fabricated  NMOS and PMOS devices on simulation using Silvaco software, the fabricated device (CMOS) is shown below.

 Now, I want to find the dynamic power dissipation of the CMOS inverter by applying a pulse to the input and I'm getting right behavior as you can see in the figure below

I used the following command in my code:

vin 1 0 0. PULSE 0 1.2 0 1ps 1ps 500ps 10

The input signal is vin, a pulse signal goes from 0 to 3V, the rise and fall times are 1ps and the pulse width is 500ps. I used 0.1pf as the load capacitor. The supply voltage VDD is is 1.2V.

However my advisor asked me to change the rise and fall times to the typical corresponding values in 90 nm technology. Unfortunately, I could not find a clear answer to my question, and I found some researchers are using values according to their applications. Could you please provide me with a good trusted reference?


texts:
I'm having trouble with this exercise which I don't have a solution for, I'm used to dealing with simpler 1st order RL or RC circuits. Mostly I'm a little confused with the sinusoidal generator and the R2 resistance which doesn't allow me to treat it as the simpler RL circuits I've dealt with.

$$R_1=2 \Omega,\: R_2=5 \Omega ,\: R_3=20 \: \Omega,\: L=100 mH \: \; i_G(t)=10·cos (100·t)\: A$$

At t'=0, voltage is max at the current source and the switch is opened .

For t'>0 I have to find:
$$\tau, u(0^+), u_{\infty}(t)$$

I found the current through the inductor branch (which cannot change abruptly) But I'm confused as to how to find tau and continue.


texts: USB communication between Android phone and MCU while continuously charging the phone

texts:
I am working on a project where I have to communicate between an Android phone and a microcontroller through USB and continuously charge the phone. I have very limited experience with USB and would like some advice in my PCB design process.
The Android device has a type USB-C connector and is using USB 2.0 specification. The device will charge passively the vast majority of the time and I have no critical time constraints so the most simple solution that is robust is my goal.
My questions/considerations are the following:
I have been considering using STM32F446xC/E, the datasheet (page 36) says "For OTG/Host modes, a power switch is needed in case bus-powered devices are connected"
Is it possible to use a usb-c to micro usb-b cable and design the pcb/mcu as a host like the application note from the same datasheet?

Alternatively, if there is a problem with the solution that I do not realize, do I have to design it according to the dual mode like this ?

I have not started the design yet so I am flexible in my solution, if you have any other suggestion I would very much like to hear them!


texts: Moving SP and PC using inline assembly in MPS430-GCC

texts:
I am writing a simple task scheduler for my MSP430F5529 USB launchpad. I need to update stack pointer(SP), then enable interrupts and then update program counter (PC). But I am getting an error with my inline assembly code.

void start_scheduler(void)
{
  asm volatile("mov.w task1stack, SP \n"
               "EINT \n"
               "mov.w func1, PC \n"
          );
}

task1stack is the stack area for the task execution. It is an array.
func1 is a function.
instead of uppercase for 'SP' and 'PC', I tried lowercase also. But the error was still present.

But with the above code, compiler is showing the following error

kernel.c:(.text+0x8e): undefined reference to `SP'
kernel.c:(.text+0x96): undefined reference to `PC'

Questions:

How to update SP and PC ?
Can "mov.w task1stack, SP \n" copy array address to SP? Is my syntax correct?
Can "mov.w func1, PC \n" copy the func1 address to PC? Is my syntax correct?


texts: Can DPAK be used in a through hole pcb if desperate?

texts:
I purchased the wrong component, have no time to order another one. Best way to go about doing this on a PCB with the plated holes?

https://www.mouser.com/ProductDetail/vishay/irfr9214pbf/?qs=iXwvDCb7I7hjm2Ycf0pGIQ%3d%3d&countrycode=US&currencycode=USD

I have a very small heat sink that is slightly larger than the size of the chip, it came with my Raspberry Pi as a heat sink for the baby sized chip on it.

The backside of the chip is the drain, left pin front-side is gate, right pin source.

Schematic:

The circuit is a pulse generation controller that drives an ultrasonic transducer with 100ns pulses, at a sending rate of about 200-800Hz. The energy in each pulse is very low. Cadence simulates the circuit as I'd expect, can post waves graphs if requested. The BJTs do a good job of controlling the current flow for the desired amount of time, don't get spooked because of the high voltage going through the transformer :^) The zener diode avalanches at 220V, and the power mosfet is rated for 250V.


texts:
In many (most??, all??) microcontrollers that I have used over the past years, there where sometimes some silicon level bugs, and the manufacturers provide the engineers with the errata sheets, describing what unexpected behaviour they may face.

Why don't they ever fix these "bugs"? Since the product is still produced, and in most cases solving the problem won't affect the previous implementations, why they do not just revise it? In many cases the product may be stabilized, most bugs may have been found, and may have a significant part of its product life-time ahead of it.

Is it so difficult (technically)? Expensive?


texts: How to feed reference voltage for two op amps inputs with different input signal each one

texts:
Im building a Stereo Buffer and a Baxandall circuit together. In powering the circuit with a single supply of 9v, and i need to bias each four inputs with 4.5 volts. The question is: If i feed the four inputs with the same reference voltage line will a have problems with the signals that are different. Into the buffer the signal is the IN signal, but in the Baxandall input the signal is the output buffer. But if i used the same voltage reference i suposed that im going to have a mix of both inputs signals in the baxandall, im right? How i can fixed that thing?
Thank you for your answer!


texts: Confusion with a simple two stage amplifier design example

texts:
I have been following a lecture on net about a two stage amplifier example.
It is basically a BJT amplifier with a PNP emitter follower as shown below. I named some of the nodes for clarity:

The design restrictions in the example of the video lecture are Ie2 = 2mA and Ic = 1mA and the absolute gain is 5 which means |Rc/Re1| = 5.

The lecturer starts designing this amplifier from the very right side setting Ve2 to 5V for max swing.

So for 2mA he sets Re2 to 2.5k.

So far so good, then he tries to set Ve1 for maximum swing as well and he sets Ve1 to 5V as well.

I'm stuck at that point, If Ve1 and Ve2 is both 5V how come the PNP transistor goes to active region?

Basically my question is: Is Ve1 dependent on Ve2? Or is Ve2 dependent to Ve1? Will one of them fix the other one's voltage? Which one controls the other?

Because otherwise setting both to 5V doesn't make sense in design process to me.
I'm very confused about it, would appreciate any clarification.

The video lecture is a bit long but in case here is the link:


texts: I am designing anenergy regeneration system using a pulley attached to the wire rope of a track elevator using a 3:1 sprocket ratio I am getting around 670 RPM`s I am using two 6 volt lead acid batteries in series match to a 12 volt pure sine wave inverter I am trying to figure out what alternator/ generator should I use that will charge my system and knowing the 670 RPM what output can I expect


texts: 3 phase ac induction motor speed control

texts:
I need to speed control small ( 0.25 HP ) 3 phase 2800 rpm motor to achieve speed in the range of 6000-7000 rpm. I know basic stuffs. ( have created soft starter etc ... which is good enough for achieving slower speed than rated speed...) but How would I increase speed ? another problem is, I have 1 phase input.

I can work out the micro controller ( mostly AVR and ARM ) stuff but have no idea about power electronics

I have read to use pwm to create sine wave form which in turn can be smooth out by motor coil itself. I can generate the frequency and wave forms in microcontroller.

1) How do I create DC from 1 phase AC that can be good enough for 0.25 HP 3 phase motor. ( for at least 10 hour continuous running. )
2) What do I need to convert my pwm waveform to actual ac using dc source. I know theory, but I am concerned about chip selection and detail circuitry.


texts:
How do I find the output impedance of the STM32H743 (and potentially other similar devices)? I've looked through the datasheet (DS12110 Rev 5) and the reference manual (RM0433 Rev 5) however haven't found much information.

I'm mostly interested in the SPI lines, and want to match the track impedance to the output impedance using a series resistor. For now I've put in placeholders of 33R, thinking the PCB trace could be around 50R and the output impedance around 20R.


texts: Bypassing Transistors with a Switch, problems?

texts:
While working on a design last night, I had a question pop up.

Is there any risk in bypassing a transistor, with a jumper/switch? Or shorting the Collector and Emitter pins with a wire? Is there a difference if the transistor is on or off?

For example, the transistor will carry a 166 mA load, driven by a 8 mA base current (through Appropriate Base Resistor, omitted in the schematic) to put it into saturation. If I short the collector and emitter pins so the load bypasses the transistor (which means there is no load for the transistor), but still drive the base with that 8mA, Will it overheat or die, or will it simply pass the base current without issue?

simulate this circuit – Schematic created using CircuitLab

The switch might be momentary, or it could be left on for hours, if that makes a difference.

Slightly related, would a Mosfet bypassed the same way also have any issues?


texts: Missing connection in amplifier example?

texts:
I've been staring at the datasheet for NXP's TDA1308 headphone amplifier IC for a while, and I'm just feeling confused.

Their recommended application circuit (Figure 4 in the datasheet) looks like this:

Notice that Vdd, pin 8, isn't connected to anything labelled as a positive power supply. Instead, it's shown connected through what I believe to be a voltage divider, to ground. In fact, I can't see any positive supply anywhere in the figure.

So, the chip looks like it's not being powered, which is very confusing.

Might this be a schematic error? Perhaps the line that has the ⌜ corner in the top left of the figure should continue to a positive supply?


texts: How much current does it take to injure me?

texts:
I'm building a 5 V and 4 A circuit that will be in contact with the body.

How can I know if this amperage, in case something goes wrong, will not be a problem for my health or my life?


texts: Magnetic field in the air gap of a transformer core

texts:
I am trying to calculate the magnetic field, Hg, and have been looking these formulas. I would like to know if I am on the right track, as something is not working out for me.
From these with a uniform area, the area of the core, Ac is equal to the area of the air gap, Ag. The flux density in the core, Bc, is equal to the flux density of the gap, Bc?

And to work out Hg, it is Bg/Uo, Uo the permeability of free space? And similarly for Hc the magnetic field in the core is Bc/u, u the permeability of the core?

I am looking at the last formula for the magnetic motive force, Ni = Hclc + Hglg
But in my workings I do not get it to match and I think I have gone wrong somewhere or interpreted something wrong.

Any help and explanation would be appreciated.


texts: Need to build a circuit that changes the output to 0V when signal exceeds range and then switch back to actual signal after a certain time

texts:
I need to build a circuit that changes the output for a certain time when my signal exceeds its range.
I have a kHz-bandwidth signal (incorporating DC) that is part of a control loop and sometimes it goes out of range (+/- 15V). When that happens, I want the output to switch to 0V for a certain amount of time (10 ms to 2 s) and then change back to the actual signal.
What I found so far is a Window Detector circuit that triggers when the signal exceeds the range and a 555 timer circuit which can keep the signal on high for a certain time. I do not, however, know how to switch between the actual signal and 0V when the output from the 555 timer is set to high.
Thanks for everyone's help, I am quite new to designing actual circuits.


texts: Maximum Allowed inrush current in Eurpoe

texts:
Context:

I am designing an device that is placed between the main AC network (230V 50Hz) and some consumer devices (PC, TV, etc..). My device is measuring the current drawn by the consumer device, we have a voltage that is proportional to the current.

The problem comes with inrush current. Typical PC (for instance) have DC/DC converter PSU, which have capacity at first from input. When plugged, this cause inrush current to happens. This inrush current causes an over-voltage at input of my circuit and I have to protect it against that. I know that they are inrush limiting options, but this is out of my hands (I don't know how my device will be used).

Actual Question:

Are they any norms (IEC, EN, etc) that tells what is the maximum allowed inrush current by appliance class ? What value should I take to dimensionnement my circuit's protections ? Or should I rely on circuit-breaker manufacturer specification (or IEC 60898-1)?


texts:
I am confused with the above problem. If I connect all 3 windings additively, I will get 3V1/3V2. But, I don't think there will be any change in kVA rating. It should still remain Q. The answer given in my workbook is option A. Please help me with this problem.
EDIT: It is not a homework problem. I am preparing for an exam called GATE(Graduate Aptitude Test in Engg). It is a previously asked problem in the exam.


texts: Trying to decide how large of a battery I will need to power light bulb.

texts:
I am trying to power a 3 Watt light-bulb.  I would like to calculate how long that light would run on a triple A battery versus a AA battery.

How do I do that?


texts: How should trigger the 5V relay with an ESP8266? Using PC817 or transistor? What are the pros and cons?

texts:
I'm working on a product and need somd suggestions:
Which is the best approach to trigger a 5V relay from ESP8266EX WiFi module?
I attached both schematics.
In schematic 1, the relay is triggered using PC817 optocoupler.
In schematic 2, the relay is triggered using MMBT3906 NPN transistor directly.

Schematic 2

Which is best approach in terms of reliability and safe circuit.
What are the pros and cons of both approaches?


texts:
I'm not sure if this is the right place to ask, but I'm building something and am not sure about how to power it (I have zero electricity knowledge).

I'm building out three individually Gledopto controlled RGB+CCT LED strips for some shelf accent lighting, about 4m each.

The guide I read said that I'd need a 12V 3A transformer, but that's for just one strip+controller under 4m.

I want to run all three off the same power supply, so I don't have 3 bricks lying on the floor to hide.

Is it possible to just buy a larger power supply and add a splitter?

Does anyone have a recommendation on power supply size/type to enable me to split the power between all three controllers?

I just have no idea how to scale up power requirements.

Controller : https://www.aliexpress.com/item/GLEDOPTO-ZIGBEE-Led-Controller-Amazon-Echo-hue-lightify-tradfri-compatible-LED-controller-RGB-CCT-WW-CW/32858603964.html

LED : https://www.aliexpress.com/item/5M-LED-Strip-Light-RGB-CCT-RGBW-5050-SMD-Led-Tape-Non-waterproof-Led-Stripe-Bar/32879936721.html

Recommended Supply : https://www.aliexpress.com/item/1-x-AC-100V-240V-to-DC-12V-1A-2A-3A-5A-6A-8A-lighting-transformers/32672191071.html


texts: Unexpected audio signal interference with camera recording

texts: When watching this video I noticed that low audio frequency creates a visual ripple effect. I'd like to know how this is possible. I guess this can't be due to software smoothing of whole-camera shaking, because video stabilizing algotihms produce different effects.


texts: Does ferric chloride etchant "go bad" after some period of time?

texts:
I have some old circuit board etching solution (ferric chloride) that is unused but a few years old and has not been in a temperature controlled environment.  It has been sitting, all but forgotten, on a shelf in my garage.

I'd like to etch some small boards this weekend, but would rather not ruin them with old chemicals.

Should I just go ahead and use it or buy some new etchant?


texts: Can I measure free chlorine content in treated water using ORP sensor?

texts:
In my project, I need to measure pH, turbidity, and free chlorine content in treated water from wastewater.
I found sensors for pH and turbidity but when I search for chlorine sensor, I found it but its cost is too high.
I searched for an alternative I found that the ORP sensor might br able to measure chlorine content but am not sure about it. If anyone tested this please guide me on how to do it or else suggest an alternative way to measure chlorine content. My budget is 62$ to 70$ for the ORP sensor.


texts:
I want to design a low pass filter with common-mode choke that has a cutoff frequency of 100 Hz. This is going to be used in a bus 24V DC power system that will deliver 10A to the load. I want to use it to clear EMI, RF interference and noises. Since there is no AC line in a bus, 50 or 60 Hz noise will be no problem.

Will Butterworth LC pi filter be a good choice?
If so, I was given 470uH and 1.8mH common-mode chokes. How to calculate capacitor values?
Will ouput impedance of the filter matter?


texts:
How would you determine if a DC motor has failed?
I have a ~9 year old treadmill that suddenly stopped working. As far as I can tell, superficially, all the electronics are good. Nothing's obviously scorched or melted or burning. The motor simply stopped turning the tread, and the control console isn't reporting any problems.
This treadmill is fairly easy to service, and I'm able to remove the cover over the motor, exposing the motor and motor controller board. The motor has a label saying it's 1.5 HP continuous duty rated for 90VDC and 12A.
I disconnected it from the motor controller and attached a multi-meter to the controllers motor outputs, powered on the treadmill, activated the motor, and measured 154V.
I don't have a power supply that can provide 90V, but I was able to hookup the motor to a 30V power supply, but the motor didn't activate. Most DC motors still turn with a lower voltage, but maybe there's just too much load to move at such a relatively low voltage.
How do I determine whether the motor, the motor controller, or both, have failed?
Is the fact that the motor controller is outputting 154V, more than the motor's rated 90V, a possible sign that the controller has failed? Or could that just be an initial high startup voltage to compensate for static friction on the tread?
I've looked up the price of replacement parts, and both the motor and controller cost around $230. Even if I have to replace both, that's cheaper than buying a new treadmill. How do I determine which has failed and should be replaced?
Edit: I figured out how to open up the motor, revealing what I think are the brushes.

As you can see, the brushes are in the form of two spring-loaded metal bars that protrude towards the axle. One of the brushes looks to be worn all the way down, probably to the point where it's no longer touching the rotor. Is this what's causing the motor to fail?
How would I find a replacement brush? It's attached via a couple rivets, but I could easy drill those out and attach a new part with a small bolt and nut, but I have no idea how to identity this brush, much less find a vendor.


texts: How many states are possible for this ripple counter?

texts:
How many states are possible for this ripple counter ?

MY try :

If for an instance, I remove the NAND gate, then it works like a down counter.

Assume Q2Q1Q0 = 000.

Here, Preset is active high. If PR = 1, then we have to check the normal functioning of the FF otherwise output is zero.

000 -> 111 -> 010 -> 011 -> 100 -> 101...

I am not sure about its correctness. I might be wrong in the implementation of how preset works here ?


texts:
I am currently working on a school project which involves building an audio amplifier. Right now I am at the pre-amplifier stage and when i tried simulating it in multisim, the output seems to be attenuated greatly (instead of being amplified). Here is a schematic of what I have currently:

I only have a very rough understanding of how the circuit works after following this video. Basically my NPN transistor is acting as a amplifier when i forward bias the base-emitter junction and reverse bias the base-collector, the capacitors C1 and C3 are blocking capacitors such that it blocks the DC from passing through, only allowing the AC signal to pass.
Now, what I am not certain about is how the NPN transistor is supposed to amplify the signal (I assume that because its in forward active mode, it drives the signal up, but in my simulation it shows otherwise).
Any help will be appreciated greatly and please advise any further improvements to the circuit, thanks!


texts: CD 4504B from 12 V digital to 5 V digital level shifting

texts:
I need to translate 12 V / 1 mA to Arduino UNO digital input.

Is CD4504B a good choice? Because I already have one...


texts: How can I raise the current flow in my 32 Volt LED Solar Panel?

texts:
Here is my attempt at making a LED-based solar panel:

I learned that if an LED is reverse biased, it can yield a considerable voltage up to 2.5 volts. I also did this experiment at home and, using my multimeter, I found that the voltage produced by an illuminated white LED is a maximum of 2.5 volts; yet the current is too small, about 0.7µA. I mounted 25 White LEDs in series on the breadboard, and found that if the array of LEDs is exposed to bright sunshine, the output voltage is 29.7 Volts.

The output current, however, is still too small, about 0.07µA. I connected a 10 Ohm resistor in series to the positive output of the panel, hoping that, based on Ohm's law, a considerable current would be forced to flow across the resistor, if we presume that the voltage is about 20V. This did not work, for when I set up the meter on the Ampere measuring function, and connected it in series with the circuit, I still got a reading of the aforementioned value, even with the resistor in series.

I presumed that the internal resistance of the LEDs in series could account for this failure, for it appears to be infinite.


texts:
Apologies if this question was already asked, but my searches didn't end up very consistent on this matter.

I want to build a curing chamber in an old small fridge and I thought the ESP32 board will be a good choice. However, I'm a bit stuck in the powering the whole thing, since I will need different voltages for the components.

The parts I will use will be:

ESP32 board
DHT22 temperature sensor
5V small humidifier
12V CPU fan that is laying around
1.3" TFT screen

Future implementation:

power meter sensor
load cell sensor

So, my first struggle is with powering all this from mains power, to keep it simple and compact. I was thinking to use the Hi Link power supply module to transform the 220VAC into DC 5V 0.6A for the humidifier and relays, and another Hi Link 3.3V for the ESP32 and screen (since the 5v Hi Link doesn't have enough current to power it all). But then, how I power the 12V fan? Or should I get a 5V fan which are a bit expensive and I already have a 12V one.

Maybe someone has a good scenario for my struggle :) It would give me hope that I can eat some good sausages in the near future :)


texts:
What are effects of interwinding capacitance in smps power transformer? What is the influence? For example, i have 83khz smps transformer with windings made of litz wire. The capacitance between windings is 250pF (i measured it by short-circuiting both windings and using u1732c agilent RLC meter). Is it good or bad?
Is electrostatic shield between primary and secondary helpful to reduce value of inter-winding capacitance?


texts: Is it possible to accept analog input, digital input and provide digital output and analog out on a single MCU Pin?

texts:
This is based on my previous question here:
How to accept switched GND or switched Positive on a 3v3 MCU input

But I want to go further so I think it is best to ask a new question.

My device is much like a PLC where each pin can be reconfigured through software.

I am using a STM32F105 which is 3v3

I would like to keep pin count to an absolute minimum so I was wondering if there was a way to have one pin that was reconfigurable to the following:

Accept a input switched to GND
Accept a input switched to 30VDC
Accept a 0-15vdc analog input
Provide a Analog output 0-15vdc
Provide a Digital out of either 5v or 12v selectable through software.
Provide a Ground for external sensors.

The reason I need to have these reconfigurable pin is because I cannot change the hardware I am connecting to, sometimes I may need to connect to a switch switched to ground, another time a sensor that outputs 0-5v.

Sometimes I need to simulate a sensor, switch or other device.

Sometimes a sensor is a variable resistor connected to either ground or positive and I would need a way of simulating this through the MCU.

Is there a way of doing this, if yes what would be the best way?

The only way I can think of is to have a group of SPDT analog switches connected to each input such as MAX14763 or the quad MAX394, would this work?


texts:
I have troubles understanding the way the circuit below is solved. I figured out that the solution is:
$$
V_+=\frac{R_2}{R_1+R_2}V_1 \\
V_a=\frac{R_3+R_4}{R_4}V_+
$$
But what is actually the reason that R2 is not considered when calculating V_a? After all V_a=V_3+V_2 forms a mesh right? So the solution would be:
$$
V_a=\frac{R_3+R_4||R_2}{R_4||R_2}V_+
$$
I know that is wrong, but I can't grasp why. As V+=V- isn't R4 in parallel to R2? Probably I am not understanding something basic. Can someone help me out?

simulate this circuit – Schematic created using CircuitLab


texts: Ways to control multiple linear actuators seperately?

texts:
I intend to control multiple linear actuators at the same time (20+). These actuators need ~9V each to run, and I simply want them to either be on (pulling) or off (relaxed). Each actuator is to be controlled seperately

My current solution to the problem is to use a microcontroller with multiple outputs, and to hook up each output to an N channel mosfet, with each mosfet having its sources connected to a 9V source.

I am curious though, would there be another way to control these actuators without the need of so many mosfets?


texts:
I want to design a simple circuit with a 9V Alkaline Battery (it currently have only 6.80V), a Voltage Regulator (uA7805C), a Blue LED (151051BS04000 from Wurth Electronik) and a current limiting resistor.

The circuit is shown below using the Circuit Simulator

simulate this circuit – Schematic created using CircuitLab

According to the Blue LED's datasheet Vf = 3.2V @ If = 20mA, and this is the I-V graph for it

The uA7805C will output a steady voltage of 4.8V - 5.2V
Assuming the VR Vout = 4.80V, Vf = 3.2V, hence i = 20mA.

i = (Vout - Vled)/R,
Vout - Vled = i*R,
R = (Vout - Vled)/i,
R = (4.80 - 3.20)/(20m) =  0.08 KOhm = 80 Ohm

I have an 82 Ohm resistor (5% tolerance, 0.25W), recalculating i, i = 19.5 mA ~ 20mA, there won't be a change in Vf.
When I built the circuit using a breadboard and measured used the oscilloscope (multimeter wasn't available) to measure voltage drops across the components, I found Vout = 5.0V, Vled = +2.96V, and Vr = +2.04V.
calculating i, i = Vr/R = 2.04/82 = 26.2mA

Here is what I don't understand, Vled = +2.96V, and according to the graph If = 2.5mA at Vf = +2.96V, but I calculated i = 26.2mA, and according to the graph Vf should be 3.2V

Kindly help me with this problem.


texts: ADC sampling frequency - Noise filtering

texts:
I have to take the reading of two analog sensors temperature & Fuel level. Both of them are analog signal & i have to remove noise from this reading. And i want to use the Digital filter for these. My MCU is running at 32 MHZ, also i am taking reading of ADC for both the sensors every 5 msec.

Now i want to reduce Noise from my sample by using external analog filter & software digital fileter (IIR & FIR).

This link says we should follow Nyquist criteria for sampling to avoid alising problem.
https://en.wikipedia.org/wiki/Analog-to-digital_converter

Now to design a Digital IIR filter, this link use to state about using cutoff frequency.
https://stratifylabs.co/embedded%20design%20tips/2013/10/04/Tips-An-Easy-to-Use-Digital-Filter/

Now if i am right then Nyquist criteria & aliasing & setting sampling frequency is important for analog signals recording, where we are aware that human voice is < 20,000 HZ.

But how to set these criteria of (Analog or Digital filter cutoff frequency & sampling rate & nyquist criteria) for sensor signal like temperature & Fuel where we get simply the analog signals & we are not aware what frequency is for these signals.

Please suggest.


texts:
How to make a generator of RF signal which have multiple signal outputs ?
Details:

Fout = [ F0, .., Fn-1, Fn ] , where
    F0-F1 = F1-F0 = .. = Fn - Fn-1 = const 1000 Hz (i.e. constant stepping)
    F0 is ajustable from 0.1MHz to 10MHz
    n is somewhere about 100 steps

I can't use white noise sources over a single wave because signal must have uniform spectre and provide constant output to each step frequency.


texts:
I'm new to VHDL so I just have a question to ask about why this produces an error. I have an ALU defined in VHDL:

c <=        a + b       WHEN opc="0111"
ELSE        a - b       WHEN opc="1000"
ELSE        -a          WHEN opc="1011"
ELSE        -b          WHEN opc="0001"
ELSE        ABS(a)      WHEN opc="1110"
ELSE        ABS (b)     WHEN opc="1010"
ELSE        NOT a       WHEN opc="0010"
ELSE        NOT b       WHEN opc="1100"
ELSE        a AND b     WHEN opc="0100"
ELSE        a OR b      WHEN opc="0110"
ELSE        a XOR b     WHEN opc="0101"

(this is the architecture)

But then I want to make it synchronous,

PROCESS (clock)
BEGIN
    IF(rising_edge(clock)) THEN
        c <=        a + b       WHEN opc="0101"
        ELSE        a - b       WHEN opc="1000"
        ELSE        -a          WHEN opc="1011"
        ELSE        -b          WHEN opc="0001"
        ELSE        ABS(a)      WHEN opc="1110"
        ELSE        ABS (b)     WHEN opc="1010"
        ELSE        NOT a       WHEN opc="0010"
        ELSE        NOT b       WHEN opc="1100"
        ELSE        a AND b     WHEN opc="0100"
        ELSE        a OR b      WHEN opc="0110"
        ELSE        a XOR b     WHEN opc="0111"
    END IF
END PROCESS;

This doesn't work, it comes up with various errors like:

';' expected.
Keyword "end" expected.

So I have now changed my code to:

PROCESS (clock)
BEGIN
    IF(rising_edge(clock)) THEN
        CASE opc IS
            WHEN "0101" => c <= a+b;
            WHEN "1000" => c <= a-b;
            WHEN "1011" => c <= -a;
            WHEN "0001" => c <= -b;
            WHEN "1110" => c <= ABS(a);
            WHEN "1010" => c <= ABS(b);
            WHEN "0010" => c <= NOT a;
            WHEN "1100" => c <= NOT b;
            WHEN "0100" => c <= a AND b;
            WHEN "0110" => c <= a OR b;
            WHEN "0111" => c <= a XOR b;
        END CASE;
    END IF;
END PROCESS;

And this doesn't produce any errors. But why does the original code which worked when put in a process not work unless I use the case statement?

Thanks in advance.


texts: Loudest Piezo with low voltage and current?

texts:
I am making a board which will communicate wirelessly with a smart phone. When I send a specific command, I want it to sound an alarm to the user, making it able to be found when lost. I've got everything working with the device and I got the piezo buzzer to sound.

Problem is the piezo is quiet with it's 3v nominal voltage.. Any solutions towards a louder device that's small enough for one to wear on their keychain?


texts: Designing a lead compensation for a 3rd order system

texts:
Question Title:

Consider the control system shown in Fig.1. Design a compensator such that the
unit-step response curve will exhibit maximum overshoot of 25% or less and settling time of 5 sec or less.

What I tried:

I'm not sure how to approach the solution but what I did was indicating the \$\zeta\$ & \$\omega_n\$ from the equations of Mp & ts as in here & then approached the typical solution which yielded the following results:

Results I could get:

\$\zeta = 0.4\$

\$\omega_n = 2\$

\$G_c =\frac{60.944(s+0.438)}{(s+8.041)}\$

\$G_cGH =\frac{60.944(s+0.438)}{s^2(s+4)(s+8.041)}\$

The question doesn't state any further information; it's a mid-term exam.


texts: Reducing the amount of controller output required - making k of n binary to unary decoder out of 1-of-n decoders

texts:
I am a kind of self-taught electronics dabbler and being a selftaught tinkerer has the unfortunate consequence of reinventing the metaphorical wheel quite often. I'd like to avoid this fate again if it's possible and asking smarter people is one of ways to do it.

My current project requires me to drive, among other things, multiple LEDs (60), in a scheme of 1 diode on - 2 diodes on - 3 diodes on - and so forth up to 60 diodes simultaneously on, as opposed to first diode on - second diode on - and finally 60th diode on - one LED alight at any given time. I obviously can't use one microcontroller digital output per one LED approach due to sheer amount of outputs required. I have my hands on arduino mega2560 with 54 i/o ports and I need most of them for those other things - and obviously one needs 6 bits to encode 60 different signals, not 60 of them.

The solution I thought of, adequate to my knowledge and experience, is combining 8 CD4028 3-to-8 decoders like this

That would provide me with 1 of 64 output and here I run into first snag. I thought of joining the outputs with diodes so I have k outputs in "1" state instead of k-th - but the voltage drop while sending the signal through 60 diodes will be massive. Horrendous. How should I "unsnag" here? Is there some k-of-n integrated circuit decoder I am unaware of and can't google?

Then there's the matter of cost and complexity. I tried to avoid charlieplexing LEDs on 9 bits, because that would be one unholy mess of wires. Too big jumble of semiconductors and ICs would also be more expensive to solder than just buying another mega2560 and using one as 6 bits in - 40something LEDs out "dedicated driver".

Anybody has ideas how should I commence from here? I'll be happy even with just a general direction because another arduino is a plan that will work, I just thought I would like more elegant solution.
OFC, I will not power such an amount of LEDs through microcontroller, the question above is all about driving them, not powering.


texts: How to analyze time-varying current signal?

texts:
I want to understand the power consumption profile of my electric blanket in order to determine (a) if it's working properly and, if so, (b) how much power it's consuming.

I took some readings with my clamp meter using the below setup. The problem is the readings seem to vary over time. How can I record the signals coming out of my clamp meter?

Oscilloscopes are very expensive so I'm looking for a cheaper alternative. Is there a way to sample a signal coming from out of the clamp meter and, say, store it on my computer for later analysis in a spreadsheet, for example?

Fig. 1. Clamp meter measuring current through one of the wires split by an AC line splitter

simulate this circuit – Schematic created using CircuitLab


texts:
Further to this question: 434MHz PCB Trace Antenna Design.

If I select a suitable 434MHz PCB antenna design and make two of them, what is the minimum extra circuitry I would require in order to de able to transmit a simple square wave from one to the other over a short distance (e.g. 30cm) ?

(10Hz Square wave) -> (Circuit A) -> (PCB Antenna 1) -> (PCB Antenna 2) -> (Circuit B) -> (10Hz Square wave out)

What could I use for circuits A and B? In this application, I would value simplicity, size and cost over reliability.

Could I literally use a crystal oscillator with enable input for A, and something like an AM radio for B?


texts: Difficulty with Common Emitter Amplifier

texts:
I'm trying to take the input from a microphone and use it to power an LED, so that it's off at ambient sound, and (the peak brightness) gets brighter with noise level. It's okay if it flickers, I'm just trying to get the peak voltage to be proportional to sound levels.

What I know:
 - The loudest sound I use causes the microphone to emit 80mV
 - The LED faintly lights at 1.8 V
 - The LED maxes out at 2.2 V
 - The transistor I'm using activates when V_be > 0.6 V

What I have:

simulate this circuit – Schematic created using CircuitLab

I tried to make a voltage divider so that the voltage between RC and RE was 1.8 volts, and 0.6 for R1 and R2. However, this doesn't work, simulated or on the breadboard. What am I doing wrong?


texts: How are these Data Buffering Methods same or different from each other?

texts:
I am trying to understand the operation of a Serial Bus protocol converter chip. It connects with the serial bus on one side and on the other side it provides its data on the MCU host interface.

Inside the chip it holds the data in its RAM buffers. There are 4 types of configurable RAM buffers in it. Their brief description is as shown in the following image.

My understanding of a buffer is like its a data array with start, end, and current pointers.
I have read details of the above four data buffer methods many times but so far I could not understand them at the fundamental level of operation.

The fundamental question that I want to understand is that how would I know which method out of these four I should use in a certain scenario? Are their different data scenarios for which one buffer method is more suitable than the other? What can be those data scenarios on the bus?

So far I could think of like periodic data, random or interrupt based data, short data chunks after long intervals, or long data chunks repeating back to back etc.

Can someone clarify when to use these four data buffer methods?


texts:
Can you replace a KA336 with a TL431 directly?
I have a circuit board with a broken KA336 and I can't find it here in my country, not even the LM336. It is a 2.5V shunt regulator.

The adjust pin on the printed board is disconnected, so apparently it is working as a common zener.


texts: How to lay out a schematic for review? Please critique

texts:
So, because I haven't posted a schematic for review before, I have no idea how to do it. Apparently, my previous attempt was poor. I got some actionable feedback, but I'm looking for more!

I would be very happy if you could give me concrete feedback on what I can do with this schematic to make it more easy and straightforward to review.

The main functions are:
- input from wall wart
- LDO regulated to 6V
- provides 5.15V on VCC when connected
- MOSFET switched current to a Li-ion battery
- output of battery (as well as LDO output) stepped-up to 5V to VCC

The charge voltage will be sensed through one line, and PWM controlled through another line.

As a secondary concern, I assert that the dual input to VCC is safe, because if both systems are running at the same time, D2 and the fact that Vsense at R25 is higher than target will essentially just "idle" the switching controller.

https://watte.net/charger-switcher-schematic.png


texts: Could I read USB data from the mini USB port on an Arduino board, or is that only for installing Sketches?


texts:
I need to convert 5V (main power supply) to +/- 30V. I have two +/-15V DCDC converters and was wondering if I can connect them in series to generate the +30V and -30V rail?

My simple schematic

I tried simulating this circuit using Mplab MINDI, but there are only DC power sources and I am not sure it is valid to connect them the way I use them. The result show +/-30V. (When I connect the DC source on both ends the Amplitude is split to +15V and -15V therefore I set the amplitude to 30V).

The datasheet for the converter is here (pdf, 224kB)

UPDATE:
After the discussion in the comments I updated my circuit. This would mean I have the separate the supply GND from my circuit GND and also adding two more converters for -30V


texts: Must IO pins each have their own pull-up/down resistor?

texts:
A very basic question:

Must each IO pin of a microcontroller that is serving as an input from a switch or jumper have its own pull-up/down resistor?

In this example, each pin is pulled down by a resistor, then pulled up by a 1P3T switch to VCC.

It seems straightforward, but as more IO pins are used, are more resistors absolutely required? Is there some clever way to keep the resistor count down?

Related question: Sharing a pull-up resistor


texts: Externally powering a series of LEDs at maximum brightness with 470 ohm resistors and fading capabilities

texts:
I'm trying to power a project where I have 14 red LEDs lighting fiber cables controlled by an Arduino Nano. I want to make them pulse at maximum brightness to resemble veins.
I have the LEDs set up in parallel, each with a resistor. Due to time constraints, I used 470 ohm resistors that came with some other LEDs I bought (to avoid ordering more.) I realize now this was dumb, and I can no longer use the Arduino PWM to fade up to maximum brightness.
I understand that I will probably have to use a transistor to make it fade.
I could really use help with the following:

Math help calculating the voltage and current parameters that would make the LEDs shine bright while also being convenient to power with common battery types.
What kind of battery to use.
What transistor to buy, and the best technique to use to fade the LEDs.

Here is the datasheet for the LEDs.

Current - 20 mA max
Forward voltage = 2.0 to 2.4 Volt


texts: Why is the maximum voltage of a surge, 6kV inside home wiring?

texts:
I was reading about the benefits and cons of series mode surge protectors vs MOV-based surge protectors for home use.

First, why is the probability that a surge will exceed 6kV extremely low due to a flashover?  What is a flashover exactly?  Is a flashover when a surge entering the main panel arcs over to the bus bar, reducing the possible voltage to 6kV or is it something else?  And, does a flashover always occur if the voltage is high enough?

I also read that a 10kV surge might be possible within the house wiring within a reasonable probability.  Is this true?  The source was from a manufacturer and I've found most info published by manufacturers to be somewhat biased.

If a surge, even one caused by a lightning strike, will unlikely exceed 6kV due to a flashover, why is a whole house surge protector necessary?  Wouldn't just a point-of-use surge protector be sufficient since it can withstand a 6kV surge?

Is it true that series mode surge protectors are better than MOV-based surge protectors because they do not have an MOV that eventually fails; instead, they will last indefinitely.  Second, they do not divert any part of the surge to the ground wire like an MOV does, which apparently prevents the surge from affecting nearby plugged-in equipment due to the sharing of the same ground wire.  Third, this surge may expand contamination by spreading into data lines such as telephone, ethernet, and cable lines while a series mode protector will not do this.  Is this all true?

Is a prolonged surge possible?  If so, would that make series mode surge protectors ineffective since their "electrical sink" is only about 600 joules?  In other words, most surges are about 10 joules but if a surge is prolonged enough so that more than 600 joules are absorbed by the series mode surge protector, it will then act as a direct conductor so the surge will travel directly to the protected device.  Is this a likely event (within .01%)?  Is this why series mode surge protector manufacturers do not specify their maximum continuous operating voltage (MCOV).  It seems strange since I've also read that MCOV is an important piece of info when assessing a surge protector.

For an MOV-based surge protector, at what voltage does the shunted remnant surge start to damage nearby equipment and data lines?  In other words, instead of safely dissipating into the ground that is located fairly far away (30+ ft) and that is connected by wires with a lot of bends, at what voltage will the surge start to damage nearby equipment?  Even despite the increased impedance due to the previous reasons, why would a surge do this if all devices have the same ground potential?

Sorry for the original question leading to so many other questions.  I just have so many questions.  I have literally zero electrical experience; I didn't even learn any in high school physics.  So, even though I've spent many days, trying to learn this stuff on my own, the learning curve has been unbearably steep.  I have downloaded and read as many as 50 articles/papers.  It's been like trying to walk through waist-high mud.  I have no one I can ask even the simplest questions!

Edification on any of these subjects would be extremely helpful!  (I boldened the questions to make the entire body easier to read.)


texts:
I know that when charging a lead acid battery, there are 3 stages,

1.Constant Current

2.Topping

3.Float.

Referring to this image, I can see that there is some current, 1A in this case, driving the voltage to some voltage threshold, about 1.85 maybe, and then in stage 2 the current decays exponentially till float level is reached.

My questions are the following:

How is the constant current decided? Why is it 1A in this case? How would I pick a current that will be safe?
How is the decay in the topping current decided? Is current a function of the voltage here, or is there a specific timing for the decay?
For float charge, again, how is the minimum current needed decided? At the end of the chart, is the current rising, or is that my imagination?


texts: Can you get "raw" TFT display panels where you drive the gate and drain lines directly?

texts:
I am learning about different display types and how I might interface them with raw electronic components, e.g., TTL chips, op amps, function generators for scan line sawtooth, etc. CRT raster is obviously a natural sequential process and it has defined such things as Vsync, Hsync, and the way we push the individual pixel color intensity as analogue levels for each pixel through the RGB lines. The enormous success that the raster CRT had for decades leaving the vector CRT far behind, that has obviously defined the way we do video interfaces (especially VGA, component RGB.) Fine. But now CRT is dead. And in its stead came matrix displays.

Matrix displays behave entirely different. There is still some sequential component to them, but really only for the vertical selection of the horizontal line. Each display cell is like a FET where the line powers the gate and then the current through the drain sets the intensity of each pixel on that line. But this can be done in parallel. I am trying to figure out how I can attach a raw TFT panel directly to the video RAM without serializing it. And to do that I would like to find a data sheet about the raw TFT panel, not the entire display module with the interface that really emulates a CRT with the same HSYNC VSYNC, blanking time, etc.

But I can only find data sheets of display modules, not raw TFTs.

Somewhere I read that a TFT or some displays like that are essentially like DRAMs -- and I don't even need to have read it, it becomes immediately obvious if you compare an TFT LCD cell with a DRAM cell. You have the row and column matrix and you select and write into them, setting the bits that light up as pixels, each pixel being anyway a capacitor, just like DRAM uses to store the bit. Now if it actually worked like DRAM, then you could really treat it like RAM just map it into the CPU's address space and write to it, and read from it. Would that be possible with some displays? DRAMs need refreshing, and that refreshing would just automatically also refresh the display, reading from it and writing to it.

If there is some reason why you can't read from a DRAM like display panel, then you would back it with VRAM, so that your writes would go into both the VRAM and the display, and your reads would come only from the display.

After "thinking aloud" writing my question I can see that perhaps the serial V-sync, H-sync, RGB input signal might still be valid for digital matrix displays because it might be simpler. Just scan horizontally and vertically over the matrix as if it was a CRT, trying to get a 1024 * whatever your color depth is fed in parallel to the drain lines is something you'd anyway do with some kind of serial approach. But this similarity between a TFT display and a DRAM is still striking.


texts: Insufficient torque from motor connected to H-bridge

texts:
I'm currently attempting to convert my son's broken 1:14 scale R/C Bugatti Veyron (similar to this) into an app-controlled car using an Onion Omega with a servo/PWM expansion. However, I am having difficulties powering the main drive motor effectively.

Specifically, I have tried 2 different H-bridges connected to the servo expansion - first was an L293D, then an L298N. In both cases, I just can't get anywhere near the torque that I get just by connecting the battery (5 x rechargeable AA cells as per the original vehicle) directly to the motor, and consequently, I can't get the thing moving.

I followed the wiring as described here, with the addition that I have also connected the external battery to the 12V and GND pins of the L298N. With the wheels lifted off the desk and the appropriate PWM inputs at 100% duty cycle (using 50Hz), they spin, but once I put it down, it has about as much push as a fly's fart.

Should I be looking at a MOSFET instead, or should I be able to get this working with the H-bridges I have? I'm a software engineer and have pretty limited electrical engineering knowledge at present.


texts:
I'm looking to drive 10 WS2812 LED's at reduced brightness to limit my max current draw below the maximum 60mA per LED. I'm looking to reduce maximum brightness, even when PWM is set to 100% duty cycle.
What would be the most effective method of doing something like this? I suspect it would just be increasing the resistance of the current limiting resistors on each LED, following the usual
$$ R = \frac{V_s-V_f}{I}$$
formula, but I'm also worried about efficiency in the circuit overall. I'm on a constrained 500mA power budget, so I want to make the most of it.


texts:
Good day Guys,

I am working on an AM Modulator and Demodulator circuit using the diode method. My modulation signal is a 10kHz Square Wave and I have a carrier frequency of 850 kHz. My modulation works just fine, according to my general knowledge, however, my demodulator is currently outputting a very weird looking wave, it resembles a square wave but is not close enough to know it was one, at first sight, my question is how can I improve the demodulation?

I have attached a screen shot of my circuit and the various outputs(Input Signal - Blue, Modulated signal - Red, Demodulated Signal - Green) below,

Note 1: I am using LtSpice.

Note 2: This circuit is just for me to learn how the modulation and demodulation works, and thus it has implemented ideal diodes and none practical component values.


texts: Sensitivity of Schottky Diodes to ESD, effectiveness vs TVS diodes

texts:
I'm trying to protect a component against ESD strikes - this component is particularly sensitive, so I am also trying to protect against sub-ns strikes. Forward voltage (max allowable) is 8V, reverse is 2V. Normally operated at 7V.

The normal approach would be to specify a ESD specific unidirectional TVS connected in parallel as close to this component as possible. One with vary fast transient response.

Another might be to use a high speed varistor (such as TDK Ceradiode, claimed <0.5ns response), however this is bi-directional and the clamping voltage may be a little high.

The addition of a ceramic capacitor in parallel may also help absorb some of the excess energy.

After chatting with someone on this topic, they insisted that schottky diode connected anti parallel is the best solution - their claim 'nothing is faster' might be true but I have three concerns:

Schottky diodes may actually be damaged by these transients themselves.
It will only protect against ESD strikes in the one direction.
The forward voltage of a Schottky may be lower, but will it actually be quicker or perform (responsiveness / clamping below 2V) any better than a TVS diode built for the job such as this? (in the one direction).

The forward voltage of unidirectional TVS's don't seem to be specified either.

I'm interested to hear what people think about each of the points above - especially if there would be any benefit at all to using a Schottky in combination with the above.


texts: I want to be able to simply control the cooling tempreture of a small 40 to 60 millimeter thermoelecrtic cooler

texts:
i want to be able to control the cooling temperature of a small 40 to 60millimter TEC.  I understand voltage level plays a part but do not know what voltage level equtes to what temperature on either side of the TEC. Is there a way to ascertain this? Or is there a standard time frame the for the TEC to get to to a required temp using X amount of voltage?

Or am i better to monitor the temp another way and then turn off or hold voltage when the required temp is reached.  I am looking to  get to temperatures between 6 and 14 degrees centigrade. I need a simple, reproducible and cheap way to do this. Thanks


texts:
I am trying to enabling an embedded system built around Intel D1000 MCU. I am mainly from a software background and just starting to catch up with some hardware knowledge.

I am trying to build connection between an EEPROM and the MCU. My target is to enable this path:

User burns the firmware into the EEPROM,
Then MCU boots and runs some code to load the firmware into the SPI FLASH. .

And I see words like USB, UART, SPI. They all have Serial as part of their names. What's the difference? How to use/connect them?

(Excuse me if this is a naive question.)


texts:
I was planning to use the SN74HC595 shift register in association with the ULN2803A and MIC2981 to switch on and off some loads based on the data of the shift register.

What happens if I disable the output of the shift register (using the OE line) and lines Qa to Qh go into high impedance state ?

Would the ULN or MIC chips read the high impedance input as randomly high/low, ie, switching on and off the loads randomly ?

 ----------     Qa Qh    ----------
|          |  --------  |          |  -------- Load A
|  Shift   |  --------  | ULN2803A |  -------- Load B
| Register |  --------  |    or    |  --------
|          |  --------  | MIC2981  |  --------
|          |  --------  |          |  -------- ...
|          |  --------  |          |  --------
|          |  --------  |          |  -------- Load H
 ----------              ----------
     |OE


texts: Can anyone shed light on why a I2C PCF8574 LCD driver would only be using I2C 'read' operations to 'write' to the device?

texts:
I am trying to understand a simple I2C driver for a HD44780 with soldered PCF8574 daughter board, I'm still relatively new to electronics engineering (read: 20 years out of date), but an old hand with c.
The I2C board eludes me, other than I know it's based on a PCF8574, from the markings on the IC. The supplier did not give me enough information to go on to identify it, but it's a very common board, you can pick up from most electronic hobby shops- shown below.

Anyway, I can successfully drive the device from a Pi, using the following source code, modified from elsewhere:
#include <wiringPi.h>
#include <wiringPiI2C.h>

#define LCD_BACKLIGHT   0x08  // On
// LCD_BACKLIGHT = 0x00  # Off

#define ENABLE  0b00000100 // Enable bit
int fd;

void lcd_toggle_enable(int bits)   {
  // Toggle enable pin on LCD display
  delayMicroseconds(500);
  wiringPiI2CReadReg8(fd, (bits | ENABLE));
  delayMicroseconds(500);
  wiringPiI2CReadReg8(fd, (bits & ~ENABLE));
  delayMicroseconds(500);
}

void lcd_byte(int bits, int mode)   {

  //Send byte to data pins
  // bits = the data
  // mode = 1 for data, 0 for command
  int bits_high;
  int bits_low;
  // uses the two half byte writes to LCD
  bits_high = mode | (bits & 0xF0) | LCD_BACKLIGHT ;
  bits_low = mode | ((bits << 4) & 0xF0) | LCD_BACKLIGHT ;

  // High bits
  wiringPiI2CReadReg8(fd, bits_high);
  lcd_toggle_enable(bits_high);

  // Low bits
  wiringPiI2CReadReg8(fd, bits_low);
  lcd_toggle_enable(bits_low);
}

void message(const char* text) {
  while(*text)
    lcd_byte(*text++, 1);
}

int main() {
  fd = wiringPiI2CSetup(0x27);
  lcd_byte(0x33, 0); // Boring init code.
  lcd_byte(0x32, 0);
  lcd_byte(0x06, 0);
  lcd_byte(0x0C, 0);
  lcd_byte(0x28, 0);
  lcd_byte(0x01, 0);

  delayMicroseconds(500);

  message("Hello world"); // my function, works fine.
}

This actually does sort of make sense- and I have happily driven the display from an MCU using the D0-7 / RST / RW / E pins in both 8 bit and 4 bit mode, so the individual hex instructions are readily understandable, because it seems effectively the lcd_byte function takes the value of D0-7, and the state of the RS flag.
What strikes me as odd, but perhaps it's just a kludge that this device uses, is that EVERY call over I2C is to READ a register, but clearly has the effect of setting the D0-7, RST, RW and EN pins.
Can anyone explain this behaviour, and is there a good reference documentation that would explain the supported I2C commands in relation to driving this board? (e.g. backlight state is being sent in every byte, but again, without documentation all I am doing is reverse engineering the protocol for now).
And secondly- I had some luck briefly with the LCD powered at 5v, but had SDATA and SCLOCK connected to a 3.3v MCU, with a common ground. I was able to at least turn the backlight off but this suddenly isn't happening.  Did I get lucky? Or should I be able to drive the I2C pin logic from a 3.3v MCU provided I have a shared GND and the LCD is 5v? (I'm aware that due to the VO pin, I would need to run the display at 5v to get usable contrast, without soldering extra bits to the HD44780).


texts: Connecting a 230 V power supply to a center tapped transformer

texts:
I just bought a small toroidal power transformer, which has a center tap in the primary. It is intended to be used at either 115 V or 230 V; the leads in the primary are marked 0 V, 115 V, 230 V. I only want to use it with 230 V mains.

What is the right way to connect the primary to the mains? I think I have to connect the 0 V lead to the neutral and the 230 V lead to the phase, but what about the 115 V lead? Should I connect it somewhere or just isolate it and let it float?


texts: Powering Small WSP2811 Strip with 3Volts?

texts:
I am a beginner when it comes to electronics and was wondering if I could get someone's help with this project. I was looking at these led's, and was wondering if I cut them up into pieces of three LED's each, would I be able to power the three LED's to a decent brightness with this 3V battery? I know that the ADAFRUIT website states than their led strips can be powered at lower voltages. Here's the quote:

  "Lower voltages are always acceptable, with the caveat that the LEDs
  will be slightly dimmer." -Reference

I would just like to know if 3V is too low, or would this work?

EDIT: After doing more research, those Coin cells can only pull around 4mA or so, so that definitely won't work. Does anyone have a suggestion on how to power the led strip with only 3 LEDs and an ATtiny85 with the smallest possible battery (smallest in dimensions not mAh, as I want to make my project as small as possible)


texts: Am I unwise to power a low-draw cooling fan off my router's USB port?

texts:
tl;dr: I want to run a 120mm case fan (drawing 0.05A) off my router's USB port, and don't know whether to be concerned about running a DC motor off a sensitive box full of radios.

The CPU in my (ASUS RT-AC3200) Wi-Fi router has a tendency to self-report temps of 70°C and higher when working hard.

Because of my (admittedly potentially unfounded) concern about that temp, and because I like to tinker, I tried sitting the router atop a garden-variety 120mm case fan (marked 12V 0.16A), which I fed just 5V to keep it slow and quiet.

The router temp soon dropped to 57°C, which I like much better.

My cheapo meter tells me the fan draws 0.05A when fed 5.33V.

Given the installation of the router, it would be quite handy to power this fan off the router's USB port.

Though I don't know the USB port's specs, a current draw of 0.05A doesn't strike me as troubling--I know it will fundamentally "work."

What does give me pause, though, is putting a motor on the power bus of a box of sensitive radios, for fear of generating problematic electrical noise or causing other woes.

Should I avoid this? Or am I being paranoid?


texts: Why there is a voltage drop while connect multiple 12 V or 24 V solenoid valve with a 24 V DC adapter

texts:
I am doing a water plant project. I need to control multiple solenoid valves with my micro controller circuit using relays. When I connect more than 4 solenoid valves (12 V) with a 15 V adapter it will cause a voltage drop and the solenoid valves are not working.

Questions:

Why does this happen and how can I fix this problem?
How can I connect multiple solenoid valves (ex:64 solenoid valve) with a micro controller using relays?


texts:
I was recently researching about this Telsa electric car inverters where i found one intresting thing.
Usually in the voltage source inverter the DC bus voltage will be around 600 to 650 V considering 3 phase  motor voltage of 400 VAC    line voltage.
But these Telsa SRM motor voltage is given as 350 and the battery voltage given to the motor, DC bus voltage which is 400 VDC and they don't have any boost converter on the input side.
I am curious on how they running the motor with 400 VDC.


texts:
I was looking in to some accelerometer and wondering how I could determine the smallest acceleration change, certain sensors are able to detect. if I wanted to calculated this for example for this accelerometer can I just do it like this:
Sensitivity:5 mV/g    noise floor : 35 µV typical (12 mA)
35 *10^-3 /(5/9.81)=> 0.0392 m/s2
assuming we are in the Dynamic measuring range or am I over simplifying this
this not really my area  of expertise so I appreciate your help
edit1: back ground info
I’m an aerospace student trying to make a first rough estimation if it would make sense to install a basic of the shell accelerometer (low cost) in order to make a rough drag estimation of the drag acting  on a satellite in LEO orbit ( +- 600km) in order to do this I’m interested Measurement level in m/s2 preferably. (the final goal of the mission is to measure temporal gravity changes with a COST GNSS receiver mounted on cube sate the accelerometer will be used to correct for drag)
the accelerometer I have used in my question Is just an example (  the frequency range is way too high) I’m just trying to see how I would get an idea of the acceleration I would be able to measure


texts:
I am having trouble computing the closed loop gain of the circuit below:

It seems clear that this configuration is a Shunt Voltage but I just can't figure a way of computing the feedback factor and the open loop gain.I know the gain has to be a transimpedance and so it can't just be the transistor gain beta.

Given:

A = Open Loop Gain, Acl = Closed Loop Gain, K = feedback constant

\$ I_{in}=I_{fb}+I_b=I_b+kVout \$

\$ A = \frac{V_{out}}{I_b} \$

Can someone please help me prove that:

\$   A = -\beta R_c \$

\$  k = -\frac{1}{R_f} \$

\$  A_{cl} = \frac{\beta R_c R_f}{R_f + \beta R_c} \$


texts: VHDL Code Fragment Explanation/Questions

texts:
signal m: unsigned (7 downto 0);

...

process begin
wait until rising_edge(clk);
m<=to_unsigned(0,8);
wait until rising_edge(clk);
while m<3 loop
m<=m+1;
wait until rising_edge(clk);
end loop;
end process;

I have some questions about this code fragment.

What is the purpose of the wait until rising_edge(clk) at the end of the loop within the loop - what is it doing ?

What is the purpose of the second wait until rising_edge(clk) before the loop begins ?


texts:
I'm doing a small project for my school and the main point of my problem is that I need a simple circuit, that could activate for a fixed time when the mains power goes on.

For example:
I have a TV, and when it is plugged in an on/off switch should be pressed and held down for 5 seconds to turn it on. What I want to do, is to automate the process of creating contact of that on/off switch with some basic electronics and/or maybe with an IC.

Basically:

1)AC power comes to TV and small circuit that converts it to DC.

2)Another circuit simulates the push of power button for 3-5s and after that stays off till AC current appears again.

Maybe anyone knows some schematics or other material, I could read, to solve this problem?


texts: How can I make a simple voltage-controlled attenuator?

texts:
Having discovered just how awful the AC ripple is on some of my 5VDC wall-adaptors, I decided to make an Arduino program to calculate the RMS AC component and DC component of an adaptor under varying current loads.

My current issue is that the Arduino (and it's ADC's and DAC's) run on 5V, so 0-5V is it's analog input and output range. Many "5V" adaptors output a little more than that (and I want to be able to test 9V and 12V adaptors as well). So, I want a way for the Arduino to attenuate the input down to something within the 0-5V range, and the only way I can think of to do this is to use the Arduino's analog voltage output (which, I realize, is just PWM digital). Hence, I need a voltage-controlled attenuator.

The application requirements are:

It must be able to attenuate the input anywhere from a gain of 1
down to a gain of about 0.25 (to get, say, a 15V input well within
the 0-5V ADC range)
The range of controlling voltages must also
be within 0-5V. Furthermore, the range cannot be too small, since
the Arduino can only select 256 values between 0-5V. In other words,
I can't have a controlling voltage of 2.000V give me a gain of 1 and
a controlling voltage of 2.001V give me a gain of 0.25, as the
Arduino doesn't have that kind of control over its analog output.
Any attenuation needs to affect the AC and DC portions equally, or
else my ac_component/dc_component ratios will be erroneous.
I would very much like not having to supply additional voltage rails.
For example, I don't want to have to supply a +12V and -12V for a
certain op-amp. If it can all be done with a 5V rail, that's
optimal. Or, +12V will probably also be fine.
Attenuation does not need to be linear with voltage. All I'm after is being able to calculate (RMS ac_component / dc_component), and those ratios will stay the same without my knowing the exact attentuation.
I understand that JFETs (see the schematics below) aren't all that well-suited to DC operation for thermal issues or something. Gradual drift in the attenuation is okay. My Arduino program only samples the voltages from the wall-adaptor for about 1/10 of a second. As long as the gain doesn't change appreciably over that time span, things are fine.

The first thing I tried was this sample which I found. It kinda did what I wanted, but it's inverting, so the output ends up being negative (and out of the 0-5V range of the Arduino).

simulate this circuit – Schematic created using CircuitLab

Then, I realized that the op-amp was probably just lowering the output impedance of the what's really just a voltage-divider with a JFET in place of one of the resistors, and I didn't need that because the Arduino has a much higher input impedance than the power-supplies I'll be testing, so I tried this ...

simulate this circuit

but I'm getting something strange. It looks like the AC component is getting affected by the gain-control input voltage, but not the DC component (see requirement 3). I clearly don't understand FETs like I should. Can someone either suggest some fixes to this approach, or suggest an alternative?


texts: Analyzing circuit with dependent sources

texts:
What will be voltage Vz in this circuit

simulate this circuit – Schematic created using CircuitLab

I have tried to solve the equation using mesh analysis by taking i1 and i2 anti clockwise in upper and lower mesh respectively.


texts: Difference between capacitors of same value but different sizes

texts: I would like to know why some capacitors have the same value (capacitance) but their sizes are different? What is different between those capacitors?


texts: Understanding a power switch circuit that includes Schottky diodes at its input

texts:
In the following design, I couldn't find the datasheet for the part U25.
All I could find from Orcad that chip part name is: G5027C.
Anyway, I don't have contact with the person who created this circuit, and I'm trying to understand the design in order to learn and try to use a similar design in other project.
This circuit is a part of reference design for a motherboard that includes a CPU that I want to implement in a motherboard of my own. It's my first motherboard project as a board designer, and I'm to understand this reference design in order to see how it makes sense in terms of signals names as described in datasheets.
As a start, I'm going through the power diagram and following the signals and trying to check mark that I understand the purpose of every signal.
Intuitively, I'd think that U25 is a PWR Switch whose purpose is to deliver "+VCCSTG_CPU" voltage once "GPPC_H_18_CPU_C10_GATE_N" signal is low.
When the signal is LOW, that corresponds to the N at the end of "GPPC_H_18_CPU_C10_GATE_N" signal name, that way the diode connected to it will pass current since pin 1 has a lower voltage that pin 2 (CR28).
Regarding the second diode, with the pin 2 name CR30, it will not conduct. Therefore the ON pin of the "PWR switch" will be low.
My question: What is the designer trying to achieve here with this mechanism? And is my initial analysis correct?
Note 1: Since some of the signals in this circuit come from the CPU, I need to take them into account and know what the best configuration is to use them. In this design, there is a suggested method of using diodes in order to control how CPU\PCH signals affect power delivery (in this case VCCSTG_CPU is the CPU Sustain Gated Power Rail). I want to make sure I understand the purpose of using these diodes, since it might be a standard mechanism that is used many times and could be helpful to implement it in my design, but surely after understanding it.
Note 2: In the OrCAD design, it's clear that U25 is a switch, and it logical regarding the pinout of the device.
I added screenshots that include all the details I have for this device.


texts: Finding Z-parameters from a two-port network and using them to find S-parameters

texts:
So I have the two-port network

and I want to find out the Z-parameters of it (and later, use that to find the S-parameters). For the assignment, \$R_x=8Ω\$.

From what I understood, I should null the ports in turn to have no current on left-hand side and no current on right-hand side respectively and calculate the current equations when ignoring the sides on each scenario (\$2Ω\$ and \$10Ω\$), but I'm not exactly sure what I should get from that or how I should proceed on with that.