texts:
I'm trying to send data by STM32f103 to an Arduino board using UART. Data isn't received properly. The code is generated using STM32CUBEMX and here is the part I added:

STM32 code (Transmit):

uint8_t Test[] = "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 \n"; //Data to send

HAL_UART_Transmit(&huart1,Test,sizeof(Test),10);// Sending in normal mode
HAL_Delay(1000);
HAL_UART_Transmit_DMA(&huart1,Test,sizeof(Test));// Sending in DMA mode
HAL_Delay(1000);

    /* USART1 init function */
static void MX_USART1_UART_Init(void)
{

  huart1.Instance = USART1;
  huart1.Init.BaudRate = 115200;
  huart1.Init.WordLength = UART_WORDLENGTH_8B;
  huart1.Init.StopBits = UART_STOPBITS_1;
  huart1.Init.Parity = UART_PARITY_NONE;
  huart1.Init.Mode = UART_MODE_TX_RX;
  huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart1.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart1) != HAL_OK)
  {
    Error_Handler();
  }

}

the received data is:

  {1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 1}
enter code here

in both DMA and normal modes the received data is pretty similar. The UART baud rate is 115200.

Why is my data being truncated? Is it an array bounds problem? Or am I hitting the limit of my buffer?

Edit:

Arduino Code (Receive):

#include <SoftwareSerial.h>
SoftwareSerial mySerial(10, 9); // RX, TX ports

void setup() {
  // set the data baud rate
  Serial.begin(115200);
  while (!Serial) {
    ; // wait for serial port to connect.
  }
  mySerial.begin(115200);
}

void loop() {
  if (mySerial.available()) {
    Serial.write(mySerial.read());
  }
}

Data transmission works good between two Arduino boards.


texts: I have a 30wp solar panel which charges a 28amp 12 V dc battery. Can I use an ac fan (with less power) on that battery? I am newbie to electronics.


texts:
I was making this automatic street light project with a slight change i.e replacing LDR with vibration sensor on proteus.

While using LDR it worked well as it changed color depending upon light (red for no light and yellow for light.) I want to use vibration ensor instead.

What should I do here?


texts: Driving Constant Current Through 2 LEDs from 2 Batteries

texts:
I'm working on a design where space is limited. I need to drive 2 LEDs from 2 AAAA batteries and using a switching regulator requires too many components and won't fit.
EDIT: The PCB space I'm dealing with is 0.25" x 0.25" (6.35mm x 6.35mm) with an exposed pad in the center which is about 0.1" (2.54mm).
I could use a simple circuit where I just use current limiting resistors for each LED and connect it to the batteries. This is good for the space claim but I want to try to keep a steady brightness with a constant current. There are linear constant current ICs available but I'm having trouble finding one that fits my requirements. Here are the specs I'm working with:

LED Forward Voltage: 2.75V
Desired LED current (for each LED): 50mA
Power Source: 2 AAAA Batteries in series (3V nominal voltage)
EDIT: I want power the LEDs for at least 4 hours.

NXP's PSSI2021SAY is the closest part I've found but I don't think the battery voltage will be able to turn this thing on, http://www.nxp.com/documents/data_sheet/PSSI2021SAY.pdf:

EDIT: I also found this constant current circuit. I'm not sure if I'll need the negative supply though, http://www.linear.com/solutions/1562

(source: linear.com)


texts: If the auxiliary I2C pins are not used are they grounded or pulled up on the MPU9150?

texts: I am working with a MPU9150 and am having difficulty with how to connect the es_da and es_cl pins. I am not using any external sensors so am I suppose to leave the pins floating?


texts: Avoiding DC voltage drop for surveillance cameras over long distances

texts:
Trying to power 2 HD-TVI cameras 800 ft away from my home office.

The wall mounted adapter provides 12v DC at 1 amp. I am looking for a good solution at the lowest possible cost.

There are already some great answers posted for a 5v camera. This, however, involves at least 2 cameras at 12v and the wire will run in the ground.

It seems Ignacio Vazquez-Abrams and others have simple solutions by running 24v or 48v and a regulator module just before it attaches to the camera. The best answer does seem to be: distribute higher voltage and use regulators at the far end. I am not sure how to do that or what to use or if it will work?

10 gauge wire would likely solve the problem, but I would like to use the 20 gauge wire I already have.

There is not power 800 ft away at the location being monitered.


texts: Why does my multimeter's overload indicator come on during normal use?

texts:
I have a new digital multimeter (Kopp GCM-620) that has auto ranging, and an overload indicator on its LCD.

When testing a mains outlet (the voltage where I live is 230V), the LCD shows a reading around 220V-230V, but the overload indicator always comes on as well.

I'm a bit concerned about the fact that the overload indicator is showing up every time. The multimeter is rated up to 600V AC. Is there any good reason for the overload indicator to be appearing when the voltage readout is far below the voltage range that the multimeter is capable of? Is it possible that the multimeter itself is faulty? Or is this normal on an auto ranging, digital multimeter?


texts: Does setting pins as virtual affect timing?

texts:
I have a Verilog submodule which I am testing independently. This module has too many top level pins to fit in my FPGA, so I have set some of the pins as virtual so that it would compile without optimizing away the corresponding signals.

I am however concerned that the timing analysis is affected by setting those pins as virtual. I have a feeling that the pins are effectively false pathed.

Does setting top level pins as virtual in Quartus II affect timing? If so, how can I make sure that the timing analysis is as if the FPGA had enough pins to start with?


texts:
I am using the DW01 in one of those tp4056 & DW01 lithium-ion charging and protection boards. I was trying to figure how much current I can pull until the protection trips/ One small problem the values make no sense.
http://prntscr.com/i3k4ad

the first 4 entries in the table make sense but what does the over current voltage mean. can I calculate the actual current I can pull until it trips?
If not can I increase the current to power bigger things?


texts: Connecting stages of active filters vs stages of passive filters

texts:
Does connecting 2 stages of Sallen Key topology Butterworth characteristic filter only create a 4th order Butterworth filter with same cutoff frequency (-3dB point) but double the roll-off (-40dB per decade instead of -20dB per decade)?

Is the same pattern followed when we connect another identical stage to increase it to 6th order?

Is it true that this does not hold true for passive filters e.g RC filter due to "loading of following stages". Why?

I want to understand that if we can just multiply transfer function of each stage in active filter, why does same not apply to passive filters?


texts: What's the difference between EMSE vs. IMSE when buying components? (Linear Technology parts?)

texts:
For example, see this page for buying a LTC3388 step-down regulator, and note the difference between the LTC3388EMSE-1#PBF and LTC3388IMSE-1#PBF.

What's the difference? Is this notation specific just to components from Linear Technology? Why is one more expensive than the other?

I've tried to Google this a number of times with no luck.

Edit: I've also seen EDD vs. IDD. What does the 'E' and 'I' stand for in all of these acronyms?

(It'd be helpful to know what the rest of the letters stand for too)


texts: CPLD ispmach 4256ze starter pin connention configuration

texts:
I am an undergraduate student that working on a project which need to use an ispMACH 4256ZE CPLD to implement some data transfer function in my circuit.

Need someone whoever have worked with CPLD to answer two very basic question:

For those gnd pins, do I need to connect all of them to ground? Or only some of them if I am using relative pins for in/out?
I want to use external power instead of the usb power. I see three VCCO_3.3 pin so they should be connected to 3.3 v source. But what about three other pins called VCC_EXT, VCCO_EXT_0 AND VCCO_EXT_1. Should I just connect them to groud? And is there any other pin that I need to connect it to something for external power?

Thanks!


texts: What exactly exactly is the difference between rms and average voltage value

texts: I hear that rms is the ac value which would produce the same heat effect as a dc value... but I don't understand why this rms is different from average value. I also read that the average value of an ac value is zero for a full circle. But why is the rms value of an ac half circle not the same value of that ac half circle .


texts: Why do server mainboards use different capacitors for their VRMs?

texts: Recently I noticed that server mainboards use a different type of capacitor as part of their VRMs (after the inductor). I believe they are ceramic capacitors, whereas consumer boards usually use electrolytic capacitors. What is the reason for this? What advantages do each have in the context of Mainboards? As an example, I have included images two Asus mainboards, one being the server part (Z10PA-D8), the other the workstation/consumer counterpart (Z10PE-D8). If you look at the area next to the socket, you can see the different capacitor types being used.


texts: In the given circuit of a regulated power supply, why is error computed twice, i.e., before and after isolation?

texts:
Circuit Operation
\$R_4\$ and \$R_5\$ constitute the potential divider which is fed to the error amplifier \$A_1\$. The reference voltage is generated by the Zener diode \$Z_1\$. The error signal is fed to the controller using an opto-coupler. The + and - in the controller indicates the corresponding terminals of the error amplifier inside the PWM IC.

Question
Why does this circuit compute error twice?


texts: Turnigy Aerodrive SK3 280kv Outrunner Substitute?

texts: I want to build me an electric longboard, and online, everybody has been using the turnigy aerodrive sk3 280kv outrunner brushless motor. They have been out of stock for months now, and I was wondering what specifications made it such a good motor for a longboard, so I could choose a substitute. The original website is here: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=18175 I was planning on running it off of a few (4 or 5) 11.1 volt laptop batteries. I would also need a speed controller recommendation, because I am horrible at searching for them. The one I was planning on using is here:http://www.hobbypartz.com/07e-ezrun-150a-pro-esc.html but it is also out of stock... (I'm hoping to be able to go around 30MPH on flat/slight uphill...)


texts: Can I replace the transistor in this circuit (Esaki oscillator) with a Zener diode?


texts: Please can you assist me in my solution if it correct. I need to know the basics if a negative resistor will change my node two equation? are my natural frequencies correct? Please help. Thanks.


texts: Using a Optocoupler - Determining Parameters

texts:
I'm looking at possibly using an optocoupler to drive a higher powered circuit from a lower powered one.

This is the device I am looking at: http://www.vishay.com/docs/83641/il755.pdf

The circuit I am switching is a 30V @ .5A circuit. Am I reading this correctly?

V_CEO = 60V, meaning the circuit on the output side can handle a voltage of up to 60 volts
V_F   = 1.2, meaning, if I apply 1.2 volts, the output should be fully on.
How much current will it draw? Under the forward voltage condition of 1.2 V it pulls 10mA.
Where in the data sheet does it state the max current the switching side of the coupler can handle?

So then, if I supply 5V to this thing, how much resistance to I need to put in front of it to get the required 1.2 V? (5 - 1.2)/.01 = 380 ohms.

Am I reading this all correctly? Especially with regard to the last point. Is it suffient to place a resistor in front of it to induce a voltage drop of 3.8V (leaving the 1.2 to supply to the transistor)? Or do I need a dedicated supply like a LDO?


texts:
i have an input of
$$v_{in} = \sin{(2\pi\cdot f\cdot t)}$$
$$V_{out}=0.5+10\cdot V_{in} +0.1 \cdot V_{in}^3$$
SNDR is the ration between the power of the signal and the power of the noise .
in the Vout we will have harmonics of f,3f,DC which of them i consider noise?


texts:
I was just playing around with a few Op-Amp circuits, and suddenly got stuck on this simple one.
As the circuit shows, the Op-Amp output is connected to its non-inverting input terminal, so it should NOT act as a voltage buffer. However, as my image shows, its a different story (simulated with NI Multisim 14.0, however I got same results using EveryCircuit) We have virtual short. Output is 5V.
I expected -15V (Inverting input terminal would rise, differential voltage would go -ve, output would rush to -ve rail, and differential voltage still stays -ve).
I also cannot understand the output frequency of 50kHz. Why would it oscillate with such a small peak-to-peak voltage? I can't justify this observation. Is this a problem with the simulation software?


texts: Do I need coupling capacitors with this balun?

texts:
I'm connecting an antenna to Atmel's SAMR21 microcontroller and the datasheet provides this guidance:

I've found 2450BL15B100E, an SMD balun, but I'm not sure if it actually contains a transformer, or if it's in fact a lumped LC balun (in which case I'm guessing I wouldn't need the coupling capacitors?).

So, should I put the coupling capacitors between the processor and the aforementioned part?


texts: Are OLEDs in cell phone applications able to be restored?

texts:
OLED displays on cellphones have a display burn in, which creates colormetric non-uniformity in the display.  Is this degredation recoverable?

There are applications which display bright constant color fields in sequences which claim to restore displays.  However there are also claims that these may not work, and tend to lower the luminence of the display as they reduce visible degradation.


texts: I need a 16MHZ resonator for my MCP2515. Can I run it with a CSTCE16M0V53-R0 or would that not be sufficient?


texts:
I am working on a project that checks a sensor every 12 hours and reports the status via cellular modem to our server ..

Power  consumption is less than 1mA  during sleep mode and spikes to 900mA While transmitting  for 30 or 45 seconds every 12 hours .

My question  is  what battery do i need to use to get the longest run time with the smallest form factor ?

Battery needs to be able to handle the following temperature  range  -20C to 55C


texts: Thoughts & questions on custom CPU architecture

texts:
I'm designing a CPU architecture. I've come up with a preliminary design:

I'd like general thoughts on what I can improve in the design and also I have some specific questions:

Is it overkill to have every register inputting to the ALU, or is it more sensible to have one input hardwired to, say, A?
This design is as you can probably tell influenced by the Z80 (hence the register naming). Is it a good idea to base the CPU design off of such an old CPU or does it not make any difference really?
I've not decided whether to have a simple instruction register or whether to implement a pipeline. What kind of performance gains might I be able to achieve in a simple CPU design like this? i.e. is it worth the extra effort of constructing a pipeline?

ISA

I have created an instruction set for the CPU and I will probably be posting it tomorrow (16/10/19) as there are some changes that will need to be made to it.

Final note

I am not sure whether this is on topic. Please suggest an alternative place if it is not on topic here.


texts: How are potentials developed between secondary windings in this circuit?

texts:
I've always had trouble understanding potentials and current flow between secondary transformer windings and this example is fairly typical.

The schematic shown is a straightforward linear regulated power supply circuit from Heathkit (IP-28) with two secondary windings, one of which creates a reference voltage for the control element (Q5).
Looking at the schematic, I'm struggling to see why current would flow through D6 and into Q5 at all.  What would entice current to flow between two otherwise isolated secondary windings?

Original schematic here.

Assuming the bottom of the secondary winding was ground (it isn't in the schematic as far as I can tell), you could say that the negative rail was 4 (or two) diode drops below the reference voltage.  But, that assumes you know that the negative rail sits below the reference voltage; what establishes these potentials?

It could be diodes D9 and D10, but again how are the potentials established.  I'm guessing no current flows through D9 and D10, so this just adds to the confusion for me.


texts: Does an NPN Capacitive proximity sensor exist?

texts:
With proxy sensors you generally have 2 types, the NPN and PNP type sensor. I also realized that you have inductive and capacitive proxy sensors...

My problem is that I've come to understand PNP to be for the capacitive and NPN for inductive sensors.  Is this true?
Is there an NPN capacitive proxy sensor and how does it work?


texts: How does the force given by bi-polar stepper motor relate to the delay between the steps?

texts:
We are using the following Bi-polar motor.(Haydon Kerk 25343-05).

https://prototypes.haydonkerk.com/ecatalog/can-stack-linear-actuator/en/linear-actuator-25343-05

You will find the specs of the motor in the above link.
There is a micro-controller which drives the motor. The motor is rotating in clockwise and anti-clockwise directions with the below pattern given at the micro-controller GPIOs.

0101->1001->1010->0110->0101... the motor will rotate one direction and for

0101->0110->1010->1001->0101... it will go the other way.

If I add a delay between steps, it rotates slower. But does it increase the force exerted by the motor or decrease the force? How is the force given by the motor relate to the delay between the steps?


texts:
I am trying to design my first "big" project, and I have to choose the OPAMPs to use. The problem is that I am feeling overwhelmed by all the possibilities.

I feel tempted to just stick on the LM741 or LM358, but after reading around (i.e. there http://www.electro-tech-online.com/threads/lM741-versus-lM386.91454/), I see that a lot of people say that there are modern opamps  available at    approximately the same price with simply better specs.

All of this to say: which are the modern jack-of-all-trades cheap opamps that can work in a lot of different applications?

I am asking this here because all I have found is about audio, not about electronics in general. I need these information for a signal conditioning circuit.
I have to work in a bandwidth similar to audio (0-40kHz), and I need low offset (around 5-7 mV) and low noise (around 5mV at 10kHz)(by the way, is this really "low" noise or it is just normal noise?).
I have to pilot an ADC converter (so no need for high currents).

If you need more information please let me know.
Thanks in advance to anyone that will answer!

Edit1: Changed the "low offset" to 5-7 mV and rephrased the "low power" requirement since it was misleading.
Also, after reading all your answers, I am starting to think that the TL054 or maybe the TL052 would work nicely in my project (since i need to use 2 unity-gain buffers and 2 unity-gain inverters).


texts: BJT pre-biased arrays slower than discrete?

texts:
I've got a circuit that works - it's job is to convert a TTL square wave into a +/- 12 volt square wave.

simulate this circuit – Schematic created using CircuitLab

Note that the transistors are actually MMBT3904 and MMBT3906. The three power sources represent power supplies (+5 and +/- 12) and the function generator is a 1 kHz TTL square wave source.

What I'd like to do is replace most of this circuit with two pre-biased dual transistor modules. The best candidate so far is from Rohm - UMD9NTR, but I've tried examples from Diodes, Inc, ON Semi, and Toshiba. But what I'm finding is that on the bench the rise time of the MMBT3904/MMBT3906 based circuit is well inside 2 µs. But with the modules? Not so much. Rise times are close to 3 and fall times close to 4. The worst module (the one from ON Semi) was 4 and 6!

By the way, the square wave generator in this case is a microcontroller. The pull-up is there because during programming that pin is high-impedance, and that winds up turning both transistors on, which is obviously bad.

The replacement circuit is two of the array modules - one set up to be the output pair, the other set up to be the input pair, and the 1k pull-up on the common input base line. It's not really possible to use circuitlab to show that schematic, but I can add a screen grab from Eagle:

The only theoretical difference between the two circuits is that the secondary transistors in the original circuit lack the emitter biasing resistors that are present in the arrays, but I don't believe that's significant (or is it?).


texts: I know this might be far fetched. In normal everyday life, we have huge amounts of data traveling through the air in the form of electromagnetic radiation. But what if instead of transmitter data through this channel we instead transmit low energy power. Where by at the receiver side we use the antenna or a custom built transducer that will be able to convert this transmitted power into a clean 5V DC voltage. Is this even feasible?


texts: Galvanic isolation between AC input and DC output?

texts:
An ATX motherboard is grounded to an ATX PSU thru the ground wires, from the 24-pin power connector to the PSU.

  Is there (inside the ATX PSU) galvanic isolation between the DC output and the AC input?

If so, does this mean that the ground wires (between motherboard and PSU) are not connected directly to the earth prong of the AC inlet?


texts: Tx/Rx UART communication between 2 MCU over 1 line

texts:
I'm trying to establish communication between 2 MCU using TX/RX over 1 line. Please refer to the image.

Questions:

Will this work? There will be an echo for sure.

If MCU 1 sends a "123" signal, MCU 1 and MCU 2 will receive "123" at the same time.

If MCU 2 sends a "678" signal, MCU 2 and MCU 1 will receive "678" at the same time.

Is this assumption correct?
In the long run, will it damage the MCU?

Thank you.


texts: Replace internal PCB antenna with external antenna

texts:
I want to replace these internal antennas with an eternal cable antenna - see pictures.

I'm not an analogue engineer...am I going to run into trouble removing one of these and soldering a cable onto the PCB?

Thank you for your wisdom!


texts: Are copper pours hidden by default in EAGLE?

texts:
I'm looking at the EAGLE board file from the Arduino wiki page, and I feel like I must be missing something - none of the ground pins of U1 appear to be connected to anything:

As you can see, the GND pin on the bottom right is unconnected, as is the GND at pin 5. The GND at pin 3 is connected to a via which goes... nowhere?

Here's the board file with just the top layer showing, for further clarity:

For more weirdness, you can see here that there's a weird trace going off to nowhere from the ground side of the upper decoupling cap.

Admittedly I'm not used to using EAGLE, so I tried the brute-force approach of enabling every single layer in case I was missing an obscurely named inner layer or ground pour, but as far as I can tell there's no connection at all.

What am I missing? Is the board file missing stuff, or have I got something hidden?


texts:
Just took a job doing component level repair on computers, mostly laptops, but we don't use schematics.  The boards have many 8 pin dual MOSFETS, and of course sometime they go bad, shorting from source to drain.  This is verified by taking the component out of circuit to test.

However, some of are hooked up to a short circuit by design as part of a circuit.  They read source to drain short until taken out and found to be good.

Given they are being used as simple switches, I am having trouble understanding where they are used in that configuration, hooked across a short by design.

Any examples of circuits that use this configuration in computers, such as laptops, would be appreciated.


texts: How to find SMD resistor values and size?

texts:
I want to do reverse engineering of a PCB, in which some SMD resistors are used. On top of each resistor it has marked with 1R0, 150 , 0 etc. Is that represents the value of the resistor? If so, how to find the size of the resistor.

Say, a 2512 resistor SMD package has a width of 3.2mm and a length of 6.4mm, will it be available with all resistor values like 1kohm , 2kohm etc.

Thanks in advance.


texts:
Its just a simple Question

Lets Say, I have 4 x Lithium Batteries each 6800mah capacity and Lithium Battery Charger IC BQ24618 from texas instruments.

Will I be able to charge these batteries keeping them in series with this IC?

If not what should I do to charge them? I do not want to buy ready made Battery Charger. Any suggestion would be appreciated.


texts: Designing a mixed signal circuit for the first time

texts:
I am designing my first mixed signal circuit. I will then have a analog and digital ground plane and my question is:

To be able to have separate grounds (analog and digital) on a battery powered device, one would have to have two batteries? One that powers the analog part and one that powers the digital part? Or is it normal to use just one battery and connect the ground planes at the battery GND terminal? And if the analog and digital part needs 3.3V and 5V respectively one would just regulate a common power source of, e.g. 6V and only use the 3.3V for analog components and the 5V for digital components?


texts:
I'm using Interlinks 30-49649 Force sensitive sensor(FSR), the FSR resistance decrease when the force applied increase.

the FSR datasheet has the following graph.

Looking into the graph, a 10K resistor for RM would be the best option, as using other resistors shows that there isn't a big variation in voltage.

Below you can see the FSR resistance variation with the force.

Now my question is this, The output will go into a 10-bit ADC, and i feel that this signal would not give a good result in the ADC as the variation is still small and maybe linearizing the signal will give better resolution and accuracy, but i read also that linearizing the signal is useless when using an adc, so amplification is a must, but how does linearization affect the sensor?


texts: Can AC and DC components both exists across the same point within the filter RC series network in parallel with the diode in the power supply?

texts:
Just an enquiry about measurement and getting both AC and DC values across the same point.
Let me introduce the measurement that How i have done to measure voltages across different components of the below power supply circuit.

Please look into the measurement data also to see what values I got during measurement.

My doubt is when I measured between P211 to P202 I got both AC as well as DC and During measurement between nodes P211 to P202 only AC I got not DC (Why?)

Can AC as well as DC exist between P211 to P202?
If it exists what is the rationale if i could get that would be understandable to me.
Note: DC values I measured with separate DC true RMS multimeter.

Thanks.


texts: Can't decipher battery protection/charging circuit for solar light

texts:
I have an outdoor solar flood light that stopped working recently. I did routine checks, saw that the panel was providing power to the main board but, the battery doesn't seem to be receiving it.I've traced a schematic for most of the board but I'm puzzled by the battery related portion.

The mosfets U3 and U4 are 8205A Dual Mosfet ICs. The other chip is marked I2C8 J60A however I can't find any information on it. I suspect it maybe be similar to or even a clone of the DW01 battery protection chip as it's often paired with the 8205A. What's puzzling especially with the 8205A is that the drain of both chips are connected to anything. I've checked multiple times however, the pins seem to be floating.
Any help is appreciated in understanding what's going on here


texts:
This may be a silly one but I couldn't seem to find an explicit answer: with a 3-pin MOSFET, how do I determine whether it's an NMOS or PMOS?

I'm making some assumptions here:

I've already found the Gate pin, which has no conduction to the other two pins (at the voltage level of a DMM diode test)
I don't know whether or not an internal protection diode is in use
I don't know if the Source is tied to the Bulk (not that it matters, since there is no Bulk/Body pin in a 3-pin MOSFET)

Thanks!


texts: Exactly what is an RTU (Remote Terminal Unit)?

texts:
I find the Wikipedia article and other sources ambiguous and I find that the definitions are so broad that I don't know how and when to use the term "RTU". I would like to figure this out because I have to present a project using Modbus RTU and I would prefer to actually know the definitions of the words I will be using.

What are the defining characteristics of an RTU?
Is every slave that allows remote setting and reading of physical parameters an RTU, no matter the protocol?
One version of the Modbus protocol is called Modbus RTU. Is any slave in a Modbus RTU link by definition an RTU? What if the same device was instead controlled by Modbus ASCII or Modbus TCP, would it still by definition be an RTU?
As an example, what about a variable frequency drive set up as a Modbus RTU and being controlled via some field bus by a PLC; is that VFD an RTU? Why/why not? What if it was set up with Modbus ASCII or Modbus TCP, would it still by definition be an RTU?


texts: Does a general computer port or accessory exist which can capture a custom 100 KHz digital signal?

texts:
A device I need to study transmits a very clear rectangular signal, which doesn't conform to any standard communication protocol (UART, SPI, I2C, etc.) The voltage is not a problem, I can make a converter to 5 Volt or whatever is needed.

The signal has pulse lengths between ca. 10 µs and 200 µs, so an effective resolution of at least 100 KHz is expected.

Without building a custom hardware which captures the times between the pulses and transmits them via USB or whatever to a computer, do PC ports or accessories exist which can help me write a PC program which reads data from the device? I might use a digital oscilloscope and capture its output in my software, but that seems like overkill (and overly complicated).

Another possibility would be a very good sound card, but even in that case, I need pattern recognition especially if the signal is distorted, a sound card scope I tried does not provide an easily evaluable output from a 100 kHz digital signal.


texts:
I've been educated that a coaxial cable has two conductors: inner or the central core and the outer conductor or the sheath. Both these carry currents but in opposite directions. The AC current produces Electromagnetic radiation that propagates in the form of a wave. The energy or the information(intelligence) is carried by the Electric and Magnetic fields.
My query is that whether the EM waves propagate between the inner and the outer conductor or inside the inner copper (clad with steel) conductor? If so, does the EM wave travel along the dielectric insulation between the inner and outer conductor?

Ron Schmitt's "Electromagnetics Explained" tells that EM waves travel between the wires and not inside the wires. Does this also apply to a coax cable?


texts:
I'm working on a DIY solar inverter.
The goal is to make the battery connected to it rechargable by both energy from solar panels and AC mains (if there is power supply.)
My battery is 24V DC, AC main is at 220/240 V AC and I'm using an LM 317T for voltage regulation.
I'm stuck thinking about the right transformer for power rectification from AC source, since the voltage applied to the LM 317T input pin must be greater than the voltage leaving it.
Could you please suggest the right transformer?


texts: Can the STM32G4’s DMA multiplexer (DMAMUX) be synchronized to a timer other than LPTIM?

texts:
I’m working with an STM32G474RE chip, and I’m trying to use the synchronization feature of the DMA multiplexer to time when a DMA transfer to SPITX should occur. I’d like to have this timed synchronously to some other timer events.
Looking at the documentation, it appears like the options for synchronization signals come from EXTI 0-15, signals generated in the DMAMUX itself, or the LPTIM timer’s output.

The LPTIM timer doesn’t have the same connections to the synchronization signals as the other timers (advanced, general, and basic), so I can’t use it to generate the needed signal. I suppose I could generate a waveform on a timer’s channel output, route that with a wire to another GPIO pin, and use that as a synchronization signal, but that is so unnecessarily wasteful and introduces the possibility of capacitance issues, etc.
It seems very odd that the DMAMUX peripheral would include the synchronization function, but use an implementation that excludes timers. Is there something that can be done? I’m writing my code using CMSIS, but if there’s a HAL example somebody can point to, I could analyze that.


texts: Sending multiple electrical signal to PC via Serial port

texts:
I am doing a project in which I want to control small toy car using EMG signals from my forearm. I want to send 4 electrical signals to the computer. I have made a processing circuit which contains an amplifier, filter, and ADC.

My question is,

How can I send 4 signals to the computer using Serial to USB cable?
Is there any alternative with which I can send these signals to the computer more easily?

Edit: I ended up using Arduino Nano and Uno boards (used two of them for wireless communications). The processing circuit was not that good. Whenever I flexed my forearm I would get some distorted signal. After changing the interval at which I was receiving the signal from ADC I was able to get an impulse signal every time I used to contract the muscle. I detected the peak of the signal and performed an action.

I used 4 muslces, which gave me 4 individual motions of the motor. Very basic project not much complications.


texts: Resuability of TVS Diodes which are injected by some surge

texts:
I'm using some TVS diodes for USB protection.
Even if their shields are connected to directly for source GND, I soldered some diodes for electrostatic issues.

I searched this site and Korean wikis, etc... and I heard that "TVS is just for single use". Is it true? In other words, if the electrostatic
(or some surge) is injected at the data pin and then TVS diode will play its own role. Then must I remove the used TVS and solder another one?


texts:
I was reading Ian Fritz overview on chaotic circuits.
As an example of non-linear circuit, he presents the following schematics

This circuit is said to output a signal of the form x.(1-x^2) where x is the input signal.
As I understand the circuit, the face-to-face diodes are supposed to introduce a cubic non-linearity x^3.
Could someone explain how two face-to-face diodes can output a cubic non-linearity ?
Thank you.


texts: Voltage Translator (74HC4050) Voltage Fluctuations

texts:
I have a simple circuit with a simple problem that I just can not fix.

I have a 74HC4050D hooked up to an SD card. I have a 0.1uf on the 5V line and 2.2uf on the 3.3V line. Whenever a signal is sent on the 5V line the Vcc on the 4050 will drop down to 0.8V and then rise back up after the signal stops. The 3.3V out of the regulator is rock steady, only the 4050 and SD card are connected to this supply. This happens when the card is removed as well.

I have tried putting a 100nf cap directly across the 4050 but it still drops to 0.8V.

Any idea how to solve this?


texts: DTMF transceiver MT8889CE - trying to make dtmf dialler

texts:
Hi
I'm trying to interface this transceiver chip with my avr. I understand the databits should be connected to my avr. However am unsure of what to do with the rest of the pins. Also how would you get the chip to dial a number.


texts: Relate Bin file (read from uC) to map file

texts:
We have a AT32UC3C1512 presenting a Failure, part of the analysis that is normally performed to isolate the failure is to perform ABA swap of components, we have performed the swap in several components in the board and the failure follows the microcontroller.

The next step is to perform a verification of the firmware in the uC, we have a "master" bin file that is programmed via avr-gcc (in the production floor) and we use that to perform a verification, the verification was failed by the microcontroller, so we extracted the faulty microcontroller flash memory file and perform a comparation using HxD, there are 2 sections that have corrupted data.

I have the .map file of the compiled project. I was wondering if there is a way to obtain the address of the corrupted data from the BIN file to compare against the map file to see in which function or what variables/sections are being the ones throwing the error.

Any ideas? Thank you :)


texts:
I have a rather simple question I would say.

I know that systems having real poles to the right side of the plane will inevitably be instable (for LTI systems at least).

But I'm confused with systems having poles at origin with poles at the left side of the plane.

For example say we have this kind of systems:
$$
H_1(s) = \frac{K}{s(1 + \tau s)}
$$
$$
H_2(s) = \frac{K}{s(1 + \tau_1 s)(1 + \tau_2 s)}
$$
$$
H_3(s) = \frac{K}{s^{2} (1 + \tau s)}
$$
$$ \tau_i > 0$$

Those are only examples among others.
If I analyze the response to an impulse, it would make sense to me that H1 and H2 are stable, and not H3 as the response y3(t) would contain a ramp.

But... if I check the response to a step... H1 and H2 are not stable anymore (time response contains a ramp).

So finally my question boils down to : In reference to what kind of excitation do we call a system stable in the EE jargon?
Because from what I see, H1 and H2 can be considered both stable and instable depending on whether the excitation U(s) is an impulse or a step (for example).

So do we only refer to the transfer function (a.k.a. impule response) "as-is" (for pole analysis) or... sorry I'm confused.

TL;DR Are H1 and H2 considered stable, and H3 is unstable?

EDIT: My question refers to open loop systems.

Thanks


texts: Could you please tell me how do you compute the impedance seen by the inverting input? The result is 100k//1M but according to me the voltage between the 100k and the 1M is not the same. So the resistors are not in parallel. This result is true in small signal analysis. But the input bias current is present at DC. Is there a way to resolve this problem with the thevenin's theorem ?


texts:
I'd like to double the frequency of a triangle wave oscillator. The frequency is variable, and the range is within audio range, so 20Hz to 20KHz.
The oscillator output is about 1.5V peak to peak, 0V centered.

I think I just need to rectify the negative (or positive) side of the triangle, then restore the amplitude using a gain of 2x, then correct the offset to get the same kind of output of the original.

Can anyone show me a simple and elegant way to do that? I tried to do some experiment but failed, since I'm not an engineer but just a beginner hobbyist, so I still cannot use opamps properly.!

This is what I tried so far:

But I get something like this:


texts:
I've soldered a stompbox for guitar and stuck into having no sound on the output. Visually I checked everything about the soldering and it seems good. As I am not so good at electronics I wish getting any help on how to  step-by-step check the place where there could be a trouble using multimeter  or some another methods.

UPD:


texts: Having USB-C as power delivery and data?

texts: so I've looked at many posts on the internet and I cannot find one that answers my question. I want to have a USB-C breakout board (I'm planning to use this) that will power my power supply. However, I also want it to act as data transfer to my Raspberry Pi Zero. My question is, can I have the 5v and the ground connected to the power supply and then the other data lines going into the MicroUSB port of the Pi? Will it work the same as just plugging something into the the MicroUSB slot of the Pi in the first place?


texts: Common ground b/w power supplies and analog pin for microcontroller

texts:
Referring to the schematic below, is it best practice to have the 5 V supply on the right powering the MC (arduino-esque microcontroller) share a common ground with the 24 V supply ? The 24 V supply is powering a current output sensor (4-20 mA loop), and the resistor is allowing for an analogRead() of the signal as the MC has no current input pins.

I have a feeling that both power supplies and MC should share a common ground to reduce noise for the analog signal, is this reasonable?


texts: STM32 timer PWM input capture and reset in slave mode (SPL)

texts:
Could someone explain how PWM capture mode employs the Timer's Master-Slave mechanism?
The example sets up input capture on Channel 2 but does not explain how IC1 is configured implicitly to capture the falling edge.

I am especially interested in these three SPL functions:

 /* Select the TIM3 Input Trigger: TI2FP2 */
  TIM_SelectInputTrigger(TIM3, TIM_TS_TI2FP2);

  /* Select the slave Mode: Reset Mode */
  TIM_SelectSlaveMode(TIM3, TIM_SlaveMode_Reset);

  /* Enable the Master/Slave Mode */
  TIM_SelectMasterSlaveMode(TIM3, TIM_MasterSlaveMode_Enable);

implemented in stm32f10x_tim.c. They all write to TIMx->SMCR.

According the diagram from UM0008 rev 14 (rev 16) ...

... TI2FP2 is not even connected to IC1, that would be TI2FP1.
So I can understand that these commands configure the reset. But what causes IC1 to capture?


texts: Three-phase thyristor rectifier - Minimum firing angle

texts:
Why is a minimum firing angle (>0, usually 5-15°) defined for three-phase thyristor rectifier?

I would like a technical explanation.

Thanks


texts:
I'm working on a primarily optical project, but I need to get a simple circuit working.  I'm working with an npn 3-lead phototransistor (datasheet).

I was trying to get the current from the phototransistor to control a cheep set of headphones (64 ohms). I've tried using a configuration like Figure 26, but simply cannot get the transistor out of cutoff.

I'm having difficulties troubleshooting the circuit myself, as I do not understand how a 3-lead (rather than a two-lead) phototransistor works and have not been able to find resources on the topic. Resources, designs, or explanations would be incredibly helpful.


texts: Is there a connector that breaks the default circuit when a plug is connected? (e.g. cut off speaker when headphones are connected)

texts:
I want the normal path from a sound card to go to a speaker/internal mic, but when a headphones or mic (mic with PTT, hence 4-pole) is connected in a 3.5mm plug then I want to reroute there.
Ideally I want this for 3-pole and 4-pole 3.5mm through-hole PCB mount.
I think what I want is TRS and TRRS switched socket. But they seem to only have one path broken when a plug is inserted. Should I use relays to switch the 2-3 signal paths?


texts: Using analog comparators to get 2 different outputs depending on the input

texts:
I am trying to use analog comparators to get two different output voltages, 6V out when the input voltage is -8.5V <= Vin <= -2V and -3V out when the input voltage is -2V < Vin <= 9.5V. I read online about window comparators, but I'm unsure about how I can use them in a situation like this where you have two windows. I tried using two window comparators for the two different windows of input voltages, but that ends up giving me two outputs. I've also tried connecting the output of the first window comparator to the second window comparator but that doesn't really seem to help since the first window comparator essentially becomes useless. Additionally, I am only allowed to use +15V, 0V, and -15V for my rail voltages and not allowed to add any resistors to the rail voltages to alter them. So, my concern is how can I get the 6V and -3V outputs when I can only have the +15,-15, and 0V rail voltages? My understanding is that the output of the analog comparator swings to either +Vcc or -Vcc depending on how your comparator is configured (inverting or non-inverting). I am also wondering how I could set up my circuit using only analog comparators, voltage followers and resistors (since I have a constraint of dissipated power of less than 1 mW without counting the comparators and voltage followers) to fit the aforementioned constraints?
Thanks a lot.


texts:
In a circuit, I've been asked to calculate a current in a certain branch using the node voltage method. My question pertains to the fact that the circuit I was given contains a current source, and I don't know how to factor that into equations for the branch method or the node method.

Since it is a circuit element is there a node before and after the current source? And does the source have any resistance (my guess is no)? If it doesn't have any resistance that would mean the node voltages before and after it are equal?

And if I'm doing the branch method of solving how do I count it as a branch, if at all?


texts: Issues with 4-bit counter when porting to PCB

texts:
I need help or maybe an explanation on a particular issue I am experiencing when porting a small and relatively simple circuit from a breadboard to a PCB. The circuit is for a school project used to receive infrared pulses coming in at a frequency of 4 Hz. The circuit is composed of about 5 or 6 logic ICs, it works flawlessly on a breadboard. However, as soon as I transpose this circuit to a PCB a problem occurs. I have isolated my problem to a single IC which is a 74LS93 4-bit binary counter.

I decided to try and reproduce the problem with as little components as I could and it turned out to be fairly easy. I simply set up a 555 timer IC in an astable configuration to generate a square wave with a frequency of 4 Hz (to simulate the signal input) and fed the output directly into the counter's input:

simulate this circuit – Schematic created using CircuitLab

Again, this circuit behaves as it should on a breadboard; the counter counts on each falling edge of each pulse it receives from 0000 through 1111 and then resets back to 0000. Now, the problem when I transpose this tiny bit of circuitry to a PCB appears on QA, the least significant bit, or rather, the counter's first Flip-Flop. It seems as if the counter counts both rising and falling edges.

The good news is I can fix this problem by adding a 100nF cap between VCC of my counter and GND. I examined it with an oscilloscope on the picture below. To the left of the middle line, you can see the behavior of the counter without the cap and, to to the right, the 'fixed' counter with a cap between VCC and GND. (Yellow is the input signal, Blue is QA. Please don't mind the input fluctuations as I was powering using my Arduino, the same occurs when I use a steady voltage source.)

The bad news is, when I reassemble the circuit as a whole on a PCB, the problem reappears. I have tried putting decoupling caps on every IC, it seems to help but the output is consistently... well, unpredictable. Sometimes it counts as it should but most of the time it is random. I know breadboards might act like very small capacitors at some points, but I have a hard time understanding and figuring out what is the source of my problem here.

I know it may seem like basics, but please excuse me as I have looked around and am unsure as to what to search for, I am also a rookie about electronics as a whole. Anything would help!


texts: Verilog procedural assignment reg guaranteed to keep value when not assigned?

texts:
I'm using the following logic in a design:

module flipflip (
   input wire d,
   input wire clk,
   input wire en,
   output reg q
);
always @(posedge clk) begin
   if (en) begin
      q <= d;
   end
end
endmodule

However, the behavior I actually want is

module flipflip (
   input wire d,
   input wire clk,
   input wire en,
   output reg q
);
always @(posedge clk) begin
   if (en) begin
      q <= d;
   end else begin
      q <= q;
   end
end
endmodule

That is, if the en flag isn't asserted the flip flop should just keep it's old value. Are these necessarily equivalent? I.e. do I have to code the 2nd, or can I get away with coding the 1st?

I wasn't able to track this down in the Verilog 2005 standard. Where is this covered?


texts: Is it possible to use a 558 quad-timer IC as a polyphonic synthesizer?

texts: As the title suggests, After looking at the pinout of the 558 IC, I've noticed that there are multiple output pins for each oscillator, so I'm wondering if there's an easy way to mix all four signals coming from each pin, and use the chip as a polyphonic synth, with the ability to control PWM, frequency, and volume for each separate oscillator?


texts:
Talking about analog offset compensation and offset temperature drift, which is the max signal frequency acceptable to apply correlated double sampling ?

I know it is for low frequency but I don't know the high limit.
Thank you in advance.


texts: Do E-Stop switches/buttons normally operate relay switches?

texts:
I have a high-power system requiring an e-stop button, but a browse on Farnell suggests that no buttons are really designed to do the job of circuit breaking directly, based on their current/voltage ratings. I would have thought a safety system would want to be a simple as possible and not require a relay to function as well, but the search seems to suggest otherwise.
Is there something I'm missing?


texts: Can I program a platform independent PLL in VHDL?

texts:
Most FPGA developement boards have a 50 MHz clock source onboard. However, the FPGAs are typically able to work faster than this. For multiplying the clock speed it seems to be needed to use a custom vendor specific IP of the FPGA, that must be configured and placed in the design.

Is there a way around this? Can I program/define my own PLL in VHDL, that is preferably synthesized using the internal hard coded PLL blocks of the FPGA and works for Altera and Xilinx without having to manually insert the PLL to a project via MegaWizard & Cons?


texts:
I've been trying to get into using opamps... I have a bit of experience with digital electronics, but this is definitely new ground for me. I tried to set up an inverting amplifier like this:

simulate this circuit – Schematic created using CircuitLab

When I measured the output, it seemed to be "clipping" in that it suddenly levels off at a consistent level: (these two graphs have equal scale)

I expected the output to go very close to 0 and 5V, perhaps with a slight margin, but in the range of millivolts.

To test this I removed the feedback resistor so the opamp would essentially attempt infinite gain, but the same problem occurs:

Notice how the output is still constrained.

Am I doing something wrong? Is there something I don't know about opamps?


texts:
I'm trying to find the best micro controller package for my computer programs to communicate with the real world. I am hoping for a large number of I/O pins (so far 64 digital is all i need, nothing fancy like analog and PWM) which an I can read and write directly by calling functions from my program running on my CPU.

I don't want to download programs onto the micro controller itself to run, rather i would like something that simply plugs into my USB and gives me a bunch of CPU controlled I/O pins that i can control from my C++ programs.

What would be the best micro controller package for me? I hope for something that is fairly inexpensive but future proof, as in it runs off USB and has 64-bit drivers for modern OS like Windows 7. Being able to interface more than one of these micro controllers with the same computer program would be a great bonus as well (future expansion).

Edit: I don't need high sampling rates (maybe 10 Hz for reading inputs, 1 kHz for output signals) and most of the pins are used for output only. I am working with brand new computers (core i7 860) so even if the sampling is a bit inefficient or slow, it should still be ok (just have one thread dedicated to I/O and have the main program communicate with it).

I also don't need all 64 I/O pins on a single micro controller package. If i can interface many micro controller packages at the same time, that would work too (actually it would be ideal to be able to interface many smaller micro controller packages, that means it's easy to expand).

I've looked at this: http://www.schmalzhaus.com/UBW32/index.html

Has anyone had any experience with something like this? Any idea if it will work or not? The main concern is that it is the micro controller that is running the program, not my CPU.


texts:
Hello I need to communicate with some batteries ( BT-70791CK from BrenTronics). They use SMBus ver 1.1 for communication, but in datasheet of the batteries there is no information about the SMBus address they have or the baudrate... I asked them and they told me that this is the only document that they have. So I started to think that maybe I do not need to know SMBus addresses or baudrate for SMBus communication. My questions are

1) Can I still communicate with devices that use SMBus ver 1.1. without knowing their addresses or baudrates?

2) Are there any spesific baudrate or SMBus address for batteries or for SMBus ver1.1?

Thank you beforehand.


texts: old Weller WTCP2 solder station has a max temp of 450°F

texts: We have an old Weller WTCP2 solder station that has a temperature dial that only goes from 200° F to 450° F.  Since rosin core solder is typically used with irons around 700° F, we do not understand the purpose of this solder station and cannot find any information about it on the web.  It does melt solder, but does not have enough heat to create a reliable solder joint when trying to join wire to a contact.


texts: 433MHz sender/receiver modules share antenna

texts:
I am using a sender and a receiver for the 433MHz band, looking like these.

Is it possible to share the send and receive antenna and attach one good instead of two wire antennas?


texts: Constructing a 4-way multiplexer composed of 2-way multiplexers

texts:
I've constructed a schematic of a 2-way multiplexer, and also have made a 4-way one (and have a good idea of how to make 8, 16, etc. ones).

However, my 4-way isn't a composition of 2-way multiplexers, and my goal is to make it as "composed" (for lack of better terminology; I know there's a word, but a brain fart has fogged my memory :)) as possible.

How (if possible) can I build a 4-way (and thus 8, 16, etc.) multiplexer out of 2-way multiplexers?


texts: Is EMC compatibility required for non-consumer devices?

texts:
I'm working for company X on some devices for smart building (lightning, energy management etc).
These devices are owned by a company X and installed in other companies buildings (shops, restaurants etc).
Company X sells "building management services" to company Y. Devices are used "internally" by company X that manufactures them, but in buildings used by many people.
Devices are installed in electrical cabinets (I'm not sure if this is correct name in english) and nobody has access to them except our company X electricans.
We never sell these devices to the "end users", we use them like "industrial equipment".
Questions:
Do we actually need EMC compliance tests/certification in European Union?


texts: Detect Sound From Google Chromecast Audio

texts:
Recently I have brought a Google Chromecast Audio and the audio signal is fed directly to my stereo. I want to detect on the sound level in order to turn the stereo on and off. Then I successfully managed to decode the data signal on the interface which connects B&O audio devices such as CD and Tape-players to their amplifiers.

Below I have used a naive approach to connect an analog input of an Arduino to detect the sound.

Generally the project is working fine. But the problem is that the sound, especially the bass gets distorted/degraded when the Arduino is connected. How can this be avoided?

I have very limited experience in analog electronics and have no oscilloscope or any other equipment. My guess is that some/large amount of current must flow through the Arduino. Secondly, the Chromecast might deliver levels of voltage higher than 5v.


texts: Direction of Current Flow in the circuit?

texts:
I'm a little bit confused with the current flow in the given power supply circuit.

Does D3 conduct when D1 conducts in the positive half cycle?
Could someone explain direction of current flow through the diodes and regulators in each half cycle?


texts:
I need a trigger circuit that gives several high pulses for an "out_0". After 5-6 pulses from out_0, it then gives one high pulse for an "out_1".

I don't need any circuit that's large or has high component count... so 555 ICs in astable mode or microcontrollers are kind of a no, no...

I'm sure there's a special IC out there that only needs a single resistor and/or a capacitor to set the timings AND can do the triggering in a "looped" or "nested" way... and, if it's also very rare I could always order it online.

EDIT:
by a "single resistor/capacitor", i mean just one every nest.


texts: Why is there a minimum Ic for a optocoupler?

texts:
I got confused when I saw this on a HCPL-181 optocoupler datasheet.

You can get the datasheet here: HCPL-181 datasheet.

So what would happen if the collector current goes below 2.5mA? (In fact I am using the optocoupler for a 50uA output current.


texts: Logic gates that does not need to to tie to 1 k resistor and ground open inputs to drive it low

texts: Hi  I am  trying to build a circuit with 2 common cathode 7 segment display  that will count from 0-14 (even numbers only) and we are not allowed to use a decoder ic.  only logic gates. My problem is that  7400  series ic  requires ALL open inputs  to be tied to a 1 k resistor then grounded to drive it at logic low, other wise the outputs are always on.(plus it will get really messy ) Are there  any IC that has inputs that behaves at logic low  when they are open? Preferrably NAND,AND, OR  gates? thanks! I am using a 9 v  battery and  dip switch


texts: Is there any special purpose of sorting input output of a buffer?


texts:
A couple of days ago I had an issue where I was unable to read data from an SPI slave. I finally fixed and I'm now able to read data quite well.

However, I found another interesting issue today. If I connect the slave's output directly to the MCU, the data is corrupted. The following picture shows this:

However, if I put in a series 220 Ohm resistor the data comes in just fine, like so:

The byte transferred was 11001101. You can see the start and end of the transfer from the two small dips in the waveform. The starting dip is seen near the trigger indicator. These are nowhere to be seen in the corrupted waveform.

The rate of data transfer is not very fast. The clock rate is just 62500 Hz.

What could cause this? And how can I make sure that it does not occur when I finally layout the PCB?

The top waveform is the clock (SCK) and the bottom is MISO.

These waveforms show the ringing in more detail. Again, top waveform is the clock and the bottom is MISO. This picture has the CPLD and MCU connected via 220 Ohm resistor:

This shows the ringing when the MCU and CPLD are connected directly (no resistor between them). Note that I cannot get to the source pin (in this case, the CPLD's pin) because the CPLD is on a development board and the chip is on a BGA package. I will try and see if the pin can be probed. Also, I forgot to add, I also have a 100 Ohm resistance in series on the SCK like. I needed this to reduce ringing from the MCU on the clock and because its required for the AVR ISP programmer. Otherwise, AVR Studio simply puts out an error. So, on the final PCB layout they are going to be needed.


texts: atmega32 communicating using rs-485 modbus protocol

texts:
I am trying to read values from a meter (WDM303FDWA1) through ATmega32. The communication to the meter has to be done by RS-485 modbus protocol. I would like to know what IC do I have to use to connect the Atmega32 and meter, sample codes for Modbus RS-485 protocol.
I am trying to communicate only with one meter and its Slave Id is 1, Baud rate could be anything (default is 9600)


texts:
I'm new to home improvement. Here's my question.

I've got several led strips for ~24V each and I've formulated a circuits to make them work from a 48V outlet at a lab psu. Approx. 16 ampere unregulated.

The 48V standard is a little high for safety reasons here, so I've tested for ~24V 3A per line with some success (much 50hz noise, more), but still unsure how to do cabling and terminals.

Any ideas?

Should I use straight outlet terminals at 48V for instance?

The question is.   Should I secure the installation to send straight 48V all across the place, and regulate each terminal individually, or push an already regulated ~24V at source.

What would you recomend?
What precautions should I take? ex: fuses, max current, current spikes crowbar, individual crowbars at each terminal. etc.

What would be the standards being in place for 48V lab standards for illumination and motor drivers/electronic modules?


texts: What is the response current of a photodiode to an LED emitting light at different intensities?

texts: Let's say I have one of those conventional through-hole LEDs and I'm applying a sinusoidal voltage to it. From what I understand, at a given time, the same LED is either on or off, and to virtually get different intensities, the duty-cycle of being turned on and off has to change. So, the response is like ones and zeros. Now, let's excite a photodiode with the LED. Will the photodiode's response be ones and zeros too? like, at one moment in time, it's either a set value of current and at another there's no current. Or maybe, the electrons remain excited for a while after the excitation is cut off, and you'd get different amounts of currents depending on the duty-cycle of the LED?


texts:
I am not much experienced using relays. Earlier I used any relay with any setup just for the purpose of building something. But now I wish to make efficient and safer projects. For that purpose I was studying about the ratings associated with the relays .

This relay from Goodsky was having four AC voltage ratings and two DC voltage ratings. I read that these two set of values may be for different standards in different places. Even if that is the case why there are two AC values given for each standard? And a voltage must be voltage everywhere, why does it differ for different places? Do it have something to do with frequency of the sine wave?

Then I came across the following relay which did not have four but two AC voltage ratings but no symbols as previous relay had(why not). But it had an open and a closed circuit symbol shown in front of the values. What do these symbols signify?

I tried to look online for these details but could not find a complete explanation for them. I am not sure if it is appropriate to ask a question in such a way. Correct me if I am wrong somewhere!

Thanks!


texts: Can I use xilinx PLL's locked signal as a reset?

texts:
I'd like to make reset signal.
now I'm using the xilinx pll and I found that LOCKED_OUT signal.
can I use that LOCKED_OUT signal as reset my fpga?
the follow is some example for my idea of question.

 pll100 u_pll100(
        .CLKIN1_IN  (aclk       ),
        .RST_IN     (!rst   ),
                .CLKOUT0_OUT(clk_19 ),
                .CLKOUT1_OUT(clk_24 ),
                .LOCKED_OUT (lock   )
                );

assign areset_n = lock;

always @(posedge wr_clk or negedge areset_n)
begin
        if(!areset_n) begin
                data_d0 <=0;
                end
        else begin
                data_d0 <= data;
                end
end


texts: What is inside the "trigger" of a DC drill switch

texts:
What is (most likely) inside of the switch of a cordless drill?

I'm guessing there is:

A mechanical switch to select direction
A MOSFET
Protection for the MOSFET: diode? Another MOSFET?
A PWM generator (555?)
A potentiometer

Is that correct and complete? Or is something else used?

I've checked 4 very different switches (from 9.6-18V drills) and was surprised to find they all worked on a single 3.7V cell, albeit on/off only, jumping from slight noise but no movement to "full on". Would have to be a logic-level MOSFET for that behavior, I think.


texts: Is it possible to derive complex impedance (magnitude + phase) from VNA 1-port network?

texts:
With the scattering parameters of a 2 port network I can measure reflection and transmission by a network analyzer and calculate complex impedance, via S-parameters.

Now I've heard (no source) that one can also measure amplitude and phase with a 1 port network, where we have a ac voltage source, a complex impedance in series and a load impedance of 50 Ohm at the end to terminate it on the wafer surface correctly (for example microprobes connected to coplanar waveguide terminated on-wafer). Is this possible, does this need a special kind of VNA or measurement procedure. Does this give same accuracy compared to a "normal" 2-port reflection and transmission parameters measurement?


texts: Manufacturable technology for force-sensitive button

texts:
I'm hoping to hear your perspectives on which force-sensing technologies would be most reliably and inexpensively manufactured at volume. The application is a pressure-sensitive button, as are found on video game controllers, musical performance pads, etc.

One option I had considered is self-capacitive. It seems like this has the advantage of potentially being "free", if one already has an MCU with capacitive measurement support built in. The downside is that it would need to be topped with a deformable layer with a known spring constant in order to get an actual force reading.

Another obvious option is FSR (under a force spreader). I'm not sure what pricing is like in volume for these. I understand that hysteresis is a problem, but I don't think some minor hysteresis would be a big issue for my application. My bigger concern is overall reliability and cost—it seems like FSR is no longer widely used in industry, and I'm wondering why.

Finally, I'm wondering whether a single-axis strain gauge could be a good alternative. I don't know much about these. I worry that FSR and cap-touch would both be a pain to take to production, turning into a mess of manufacturing tolerance analysis. If strain gauges or some other technology would be less troublesome in this regard, then it'd great to know.

Many thanks.


texts: Is it suitable to wire 'protected' li-ion cells in series and parallel? 2S6P

texts:
Here is the circuit designed to give about 7V. Each cell would be a protected cell.
Is it safe to connect these cells that way?
Thanks


texts: LM567 understand math to get right frequency

texts:
I am trying to create a little module that can listen to a specific tone, like high peak that are not audible from humans, probably 11+ kHz.

Looking at this project http://www.instructables.com/id/Sonic-Control/ I have bought the same items but apparently when I had the microphone, it is always blinking the LEDs but when I get the a jack wired to my PC, it response to some low frequency.

I am not 100% sure what are the values and formula to work out the right capacitor and resistor values.


texts: What protocol does a TDD/TTY use to communicate with a cell phone's headset jack?

texts: Some cell phones are TTY/TDD (telecommunications device for the deaf) compatible, meaning a terminal can be plugged into the headset jack for text communications. Is it just a hidden RS-232 interface?


texts: Can someone tell me what this machine is?

texts: It has two probes on two cables. I think it might be an xray machine but I can not be sure since there is no readable info on it. Can someone please identify it?


texts:
I am trying to simulate the solution to an old text book example on a simple Shunt-Shunt feedback amplifier.

simulate this circuit – Schematic created using CircuitLab

The book only shows BF = 150, no other parameters for modeling.

1.) Can somebody demonstrate modeling this to get the answer from the book?  Yes, I'm not getting the same answer as the book on the forward gain, but I haven't tried trans resistance or trans conductance before.

2.) How do you simulate loop gain?  That is really what I am after.  I came back to this example after trying a different one further from the book.  The schematic below is what I think it should look like.

simulate this circuit

From the book:

DC conditions found are IB = 25.66uA, IC = 3.849mA, VCE = 0.785 V.

Hfe = 150, Hie is calculated to be 1.020 kohms.

Partitioning the circuit into the proper modules finds f = -1/3300, Ri =400 ohms, Ro = 1.788k, the transresistance is -21.05k.

Desensitivity factor is 7.3782, and so Rif = 54.23, Rof = 242.3, Rmf = -2.8525 k, and Avf = -5.70.  Output resistance is 242 and input resistance becomes 60.8 ohms.

EDIT - I determined the simulator (LTSpice) was causing my simulation issues with item one above, so I can at least simulate closed loop gain (-5.705 V/V).  Below is the LTSpice simulation with the edited source in series with the feedback resistor.  Is this correct?  The simulation shows voltage across the inserted source (node 2 is V2 negative and node 3 is V2 positive in the picture).


texts:
I am trying to build a kind of frame where I have laser diodes on one side and LDRs on the other, and current flows through the LDR circuit if the light from the laser opposite to it is blocked. Basically kind of an IR touchscreen frame, but with lasers. The power supply is just a 5v power supply with a 10k resistor and a 5k-20M LDR. Here is the schematic for the detector circuit.

simulate this circuit – Schematic created using CircuitLab
I have 10 identical circuits corresponding to 10 lasers on the other side, and current will be flowing through only one of them at a time based on which one is blocked. I want to figure out a way to detect which circuit the current is flowing through. Maybe like a number between 1 to 10 sent to a Rpi. My initial thought was that I could make a junction at the same point in each circuit (somewhere on before the collector perhaps) and connect resistors of different values to that, and then the other end of all of those resistors could go into an INA219, which could then go back to the original circuits. So basically a bunch of wires going into and out of the INA219 but the current flowing through only one of them. Then I could read the current value received by the current sensor and based on the value I would know which circuit it was because of the different values of resistances. But this seems very inefficient and doesn't sound like a good idea for more than 10 circuits together (or a good idea at all). I wonder if there is a better way to do this (using ICs or something).
I am very very new to electronics, just trying to pick it up as a hobby, so I apologise if my question is extremely stupid. I have been trying to find resources but considering that this is an entire profession, it is a bit hard to look for information that I can understand easily. I don't even know what tags go best here, so any help is appreciated.


texts: optimal Voltage dividers for measuring ec/thermistor

texts:
I'm trying to find the optimal, or at least a good resistor to put into a voltage divider to measure a thermistor, and an electro-conductivity K10 probe. The range is 10 uS/cm to 1 S/cm, and an operating temperature of 0-70 Celsius.

So equations gave me a working resistance of ~80 ohms to 19M ohms. I'm thinking that given the range of resistance it might be difficult to have a single resistor to compensate.

Also I'm using a 1k thermistor, and was wondering if in that case a 1k would be the optimal resistor to pair with that as well?

____/\/\/\_____thermistor____ |||gnd
|     ?     |    probe
(5v dc)   mcu

I've played around; seems a 10k is more accurate in getting the value of the thermistor.

So if I have known solutions, and a known probe the resistance should be in theory known. A K 10 probe and a .15 S solution should come out w/ 1.5 ohm?, or would it be ohm/cm?


texts:
I want to add a user button to my schematic design, so I first take a look at what I consider it could be a good source: the ST Discovery board schematic.

Their use case is the same as mine: user button, microcontroller configuration unknown, Vdd at 3.3 V.

Their button looks like this:

I think I understand most of it (correct me if I am wrong):

R35 may protect the microcontroller (i.e.: PA0) in case the user configured that pin to be an output (high/low) rather than input (high impedance). Otherwise if PA0 is set to low, pressing the button could be dangerous.
R39 lowers the Vdd-GND current when the button is pressed (no need to waste current).
The capacitor should filter the button bouncing and I guess it should charge/discharge through a resistor as well (R38?).

Now, here is what I do not understand: when the button is not pressed, considering stable conditions, at one side and the other of the button we have Vdd and GND potential, same with the capacitor. So...? (initial thoughts that I know must be wrong, but anyway...)

When we press the button, are not we shorting two cables at different potentials with no resistor in between? (3.3 V from the power source with 0 V from the condenser)
My intuition would have lead me to put the R38 between Vdd and the switch, rather than between Vdd and the capacitor, but it seems my intuition is bad (STM engineers must be right and I must be wrong).

So, maybe what happens is that when the button is pressed, the lower part of the capacitor (as drawn in the schematic) becomes 3.3 V instantly and then the upper part becomes 6.6 V? (and then discharges through R38)

If that is correct then I guess that if at that exact instant we release the button again (imagine the button bouncing), the upper part of the condenser keeps the 6.6 V potential and goes smoothly to 3.3 V back again and the lower keeps the 3.3 V and goes smoothly as well to 0 V? Otherwise the de-bouncing would not work, right?

Could someone clarify how this works?


texts: I tried to wrote verilog code of 4-bit register with parallel load. But i failed. I am pasting code with output.Please identify whats wrong with it

texts:
The circuit is :

The verilog code I wrote :

module four_bit_register(out,in,load,cp,clear);
  output [3:0] out;
  input [3:0] in;
  input load,cp,clear;
  //Instantiate sr_flip flop with other input circuit.

  sr_ff sr0(out[0],in[0],load,cp,clear);
  sr_ff sr1(out[1],in[1],load,cp,clear);
  sr_ff sr2(out[2],in[2],load,cp,clear);
  sr_ff sr3(out[3],in[3],load,cp,clear);
endmodule

module sr_ff(out,in,load,cp,clear);
  //Input output port declaration.
  output out;
  input in,load,cp,clear;
  //internal wire declaration.
  wire s,r,sin,rin;
  wire qbar;

  assign s= load & in,
         r= load & (~in);
  // sr_flip flop.
  assign sin=s&clear&(cp),
         rin=r&clear&(cp);
  assign out=~(rin|qbar),
         qbar=~(sin|out);
endmodule

module stimulus;
  reg [3:0] in;
  reg load,cp,clear;
  wire [3:0] out;

  four_bit_register register (out,in,load,cp,clear);

  initial begin
    #5 in=4'b1101;
    load=1'b1;
    clear=1'b1;
    cp=1'b0;
  end

  initial
    forever begin
      #50 cp=~cp;
    end

  initial
    #700 $finish;

endmodule

The verilog output:

I am getting a high impedance on all input output. I checked it many time but not able to run it correctly . Please help anyone.

*Note .. I am using Xilinx ISE 10.1


texts: I am simulating the double pulse test to test the working of the Overcurrent pin. Although I like that there is no phase lag between the sense voltage and the OC pin voltage, I am getting this peak in the drain current for all values of DC Bus, L1. Is this got to do with the RC filter values? Changing this does not change this peak very much. Why does this show up?


texts: TCA9548A (I2C multiplexer) works for a few minutes and then hangs

texts:
I'm having trouble getting the TCA9548APWR to communicate for longer than a few minutes. I'm only able to get it to "reset" by resoldering it. I have used both an Arduino Mega and a Beaglebone Black to communicate with it (successfully, for a few minutes).

Here's the overall schematic and board design below. Currently I have only installed the +3v / +5v / +12v power converters, the MCP23017T-E/SO (which I will use to drive a relay board), and one I2C sensor I'm using the test read/write capabilities.

This is a tough question to ask since I have little insight into what's causing the issue, so apologies if this is too vague – please ask any clarifying questions you may have. Thank you!

Edit: I clarified the exact chips I'm using with links

The I2C Multiplexer is the chip in question, right in the middle.

This board image may be unreadable. If you'd like to check out the Eagle file, I can add a link.


texts: Will a 30 mA RCCB trip if the differential current is less than 30 mA?

texts:
All available literature states that an RCD trips whenever there is imbalance between the currents flowing through the Live and Neutral wires.
But does it need to be higher than the labelled value?


texts: Programming Amiga Kickstart with TL866CS

texts: I wanted to burn Kickstart 3.1.4 to AM27C400 using TL866CS programmer, in theory it is supported, but when looking into list of ICs in MiniPro software I get AM27C4096 @DIP40, apologies for daft question, you can tell I'm noob to electronics, but I bought this chip (prior to checking). is it the same as on the list in software? will it work or I need any adapter board? Using legit Hyperion A500 3.1.4 rom.


texts:
I'm heavily experimenting with ATtiny AVR's and I can't afford to buy a new AVR for every experiment, so I thought up a backup script. The idea is that I can bring my AVR back to factory defaults after I've used them. Especially fuses and calibration are tricky here I want to be able to recover, as they may change 'boot' parameters, clock speed and power efficiency.

The idea is to backup my AVR with the following script:

#!/bin/bash

baud=115200
avr=attiny45
dst=$avr.`date +"%Y%m%d_%H%M%S"`
port=/dev/ttyUSB0

# calibration  One or more bytes of RC oscillator calibration data.
# eeprom       The EEPROM of the device.
# efuse        The extended fuse byte.
# flash        The flash ROM of the device.
# fuse         The fuse byte in devices that have only a single fuse byte.
# hfuse        The high fuse byte.
# lfuse        The low fuse byte.
# lock         The lock byte.
# signature    The three device signature bytes (device ID).
# fuseN        The fuse bytes of ATxmega devices, N is an integer number for each fuse supported by the device.
# application  The application flash area of ATxmega devices.
# apptable     The application table flash area of ATxmega devices.
# boot         The boot flash area of ATxmega devices.
# prodsig      The production signature (calibration) area of ATxmega devices.
# usersig      The user signature area of ATxmega devices.

for memory in calibration eeprom efuse flash fuse hfuse lfuse lock signature application apptable boot prodsig usersig; do
        avrdude -p $avr -c stk500v1 -P $port -b $baud -U $memory:r:/dev/stdout:i > ./$dst.$memory.hex ||
                rm ./$dst.$memory.hex
done

The only exeption is the fuseN memory, but I don't use ATxmega and I just didn't care about that.

EDIT1: I use an ATmega168 powered Arduino Duemanilove with ArduinoISP sketch, which emulates stk500v1, to program my devices. High voltage programming is not supported.

EDIT2: Managed to succesfully unbrick my ATtiny45 with my Arduino too using the information at http://www.rickety.us/2010/03/arduino-avr-high-voltage-serial-programmer/

Now the question is as follows: The backup script seems to work as designed, but before I 'brick' my AVR, will programming the resulting files bring the AVR back to factory defaults?


texts: Oscillating DC polarity reversal for LED lights

texts:
I have a cheap battery powered LED light strand that had a corroded and non-functional control board. The LEDs looks like they are rated for about 3.3V with up to 20mA per bulb, and the original string controller ran them at about 2.9V and 2mA per bulb.
The LEDs are wired where they are all wired in parallel, with alternating LEDs alternating in polarity. Putting DC power on the light string lights up every other light. Swapping the input polarity lights up the other lights. Apparently, reverse voltage does not hurt these LEDs. The control board must have alternated power at different rates to make the lights appear to flicker, dance, or all appear to be constantly on through persistence of vision.
I can reliably drive these LEDs with a power supply regulating voltage and current with fixed polarity. How would you recommend to automatically oscillate the voltage polarity at a rate to make use of the alternating LEDs, particularly with an adjustment to control the oscillation rate?
Thanks,
H


texts: Over current Protection for Ne555 circuit?

texts:
I made simple frequency generator circuit with Ne555 but almost in every circuit Ne555 IC burns after few use. Ne555 starting to heat up then outputs weird signals , if I don't stop the supply Ne555 literally burns to crisp .
I'm thinking the reason is over current but I always add minimum 1k ohm resistor to output and supply voltage is 12v (with 10A fuse)
My first question is where the over current happens and second question is how can I prevent it ? ( Prevention and fail-safe (fuse or extra resistor))
D1 is schottky diode (1n5819) Speaker is 1W 8ohm , I tried to remove L1 and C3 , change C2 with 100nF capacitor , changed R3 location between L1 and LS1
Last picture is my last circuit before Ne555 start to heat up (C2 is 100nF picture wrong)
I found the problem L1 and C3 caused short circuit with 0.3 ohm resistance but can anyone suggest general over current protection for this circuit ?


texts: D flip flop simulation: which simulation output is right?

texts:
I have always wondered, what is the right solution to the D flip flop when the input changes right at the rising edge of the clock? I have found two solutions of these online but have no clue which is the right one.

or

I think the right answer should be image 1 (on top) where the output q appears at next rising clock edge. This is what flip flop should do, i.e create a delay of one cycle.

But I always get image 2 (bottom image) when I run my Verilog code. My code is:

module beh(q,d,en,clk);
input q,clk,en;
output d;
reg d;
always@(posedge clk)
begin
if(en==1)
d<=q;
end
endmodule

What am I doing wrong?


texts: How is the formula for the base current value derived in a three-phase per-unit system?

texts: When analysing a power system using the per-unit system for a three phase system, why is \$S_b = \sqrt{3}*V_b*I_b\$, where as shown in the link, \$S_b\$ is the base power value, \$V_b\$ is the base voltage value and \$I_b\$ is the base current value?


texts:
I'm using 2 12V motors, an L298n, an Arduino Pro mini and 4 switches to control the motors (forwards/backwards 1 and forwards/backwards 2).
The problem is that when I press one button at a time, the motor spins but very slowly. As soon as I press let's say forwards 1 and forwards 2, they both spin much faster. Any idea why and how to fix?
This is the code:
// Motor A connections
int enA = 9;
int in1 = 8;
int in2 = 7;
// Motor B connections
int enB = 3;
int in3 = 5;
int in4 = 4;

void setup() {
  // Set all the motor control pins to outputs
  pinMode(enA, OUTPUT);
  pinMode(enB, OUTPUT);
  pinMode(in1, OUTPUT);
  pinMode(in2, OUTPUT);
  pinMode(in3, OUTPUT);
  pinMode(in4, OUTPUT);
  pinMode(10, INPUT_PULLUP);
  pinMode(11, INPUT_PULLUP);
  pinMode(12, INPUT_PULLUP);
  pinMode(13, INPUT_PULLUP);

  // Turn off motors - Initial state
  digitalWrite(in1, LOW);
  digitalWrite(in2, LOW);
  digitalWrite(in3, LOW);
  digitalWrite(in4, LOW);
}

void motor1_forward(void) {
  analogWrite(enA, 255);
  digitalWrite(in1, HIGH);
  digitalWrite(in2, LOW);
}

void motor2_forward(void) {
  analogWrite(enB, 255);
  digitalWrite(in3, HIGH);
  digitalWrite(in4, LOW);
}

void motor1_bakcwards(void) {
  analogWrite(enA, 255);
  digitalWrite(in1,LOW);
  digitalWrite(in2, HIGH);
}

void motor2_bakcwards() {
  analogWrite(enB, 255);
  digitalWrite(in3, LOW);
  digitalWrite(in4, HIGH);
}

void stopit(void) {
  analogWrite(enA, 255);
  analogWrite(enB, 255);
  digitalWrite(in1, LOW);
  digitalWrite(in2, LOW);
  digitalWrite(in3, LOW);
  digitalWrite(in4, LOW);
}

void loop() {
  if (digitalRead(10) == HIGH){
    motor1_forward();
  } else
    stopit();

  if (digitalRead(11) == HIGH) {
    motor1_bakcwards();
  } else
    stopit();

  if (digitalRead(12) == HIGH) {
    motor2_forward();
  } else
    stopit();

  if (digitalRead(13) == HIGH) {
    motor2_bakcwards();
  } else
    stopit();
}

The wiring was copied from this tutorial here.


texts: Differentiate between ground wire and neutral wire

texts: Are the ground and neutral wire connected and if so how does the circuit gets completed (shouldn't the current go to the ground) ?


texts: Triangular waveform to square waveform circuit

texts: I am working on a frequency counter project and I am in the midst of thinking about how to go about doing a triangular wave to square wave converter. I have done some research but couldn't find any circuit diagram that could help. It was mostly just triangular wave to sine wave. I would appreciate if anyone could help. Thanks.


texts:
I need a SSR to switch AC less than 5v. It is a very small AC load and according to my multimeter, it varies between .5 and 1 V. I have looked every where but every SSR available the I've found have a minimum load requirement. The OMRON G3MB-202P for example requires a minimum of 75ACV to work. I know I could use an electromagnetic relay but I have found that those don't last to long.

So, is there a SSR with DC control and for small AC load?

If there is no SSR, would there be another alternative to control small AC loads with DC?

Also, I am using an arduino to switch the relay ON/OFF so the SSR's control voltage has to be DC.


texts: Protecting MAX485 data or supply from shorting to 24v DC supply

texts:
I have 2000 infrared proximity sensors along 100 meters, divided to 2 meter sections with an arduino reading them sending results by MAX485. For the power, I am supplying same 24v dc from each end of the line to prevent voltage drop, I don't have much space for a big wire, so I had to do that.
In every 2 meter section there is a small switching buck reducing voltage to 5 volts for arduino and other components including MAX485. This is a design for an industrial purpose where emf noise is present and the air is so humid and dusty, increasing the possibility of shorting on the PCB itself! I have already read other questions which were close to mine, but some points still not clear to me:

In case of a short between 24v and 5v to the micro what will happen?! And how to prevent it?
What about a short between 24v dc and rs485 data? How to prevent that?
For the first point, even if it happens, in the worst situation I will lose my components on one section, but for the second one I guess all 50 sections are in danger.

I will use TVS diodes like SM712 which is really designed for transient and rs485 voltage levels, but I guess it can not help me for the short circuit.
The 380v ac to 24v dc power supply has enough protection, and also a circuit breaker will be provided for the whole 24v line.

As I read in the same questions before, I will separate data and power cables, use earth connection, use different connectors for them, so the installation will be fool proof!


texts: How to implement critical sections on ARM Cortex A9 for GCC, no OS?

texts:
I am porting some legacy code from an ARM926 core to CortexA9.  This code is baremetal and does not include an OS or standard libraries, all custom.  I am having a failure that appears to be related to a race condition that should be prevented by critical sectioning of the code.

I want some feedback on my approach to see if my critical sections may not be correctly implemented for this CPU. I am using GCC. I suspect there is some subtle error.

Also, is there an opensource library that has these types of primitives for ARM (or even a good lightweight spinlock/semephore library)?

#define ARM_INT_KEY_TYPE            unsigned int
#define ARM_INT_LOCK(key_)   \
asm volatile(\
    "mrs %[key], cpsr\n\t"\
    "orr r1, %[key], #0xC0\n\t"\
    "msr cpsr_c, r1\n\t" : [key]"=r"(key_) :: "r1", "cc" );

#define ARM_INT_UNLOCK(key_) asm volatile ("MSR cpsr_c,%0" : : "r" (key_))

The code is used as follows:

/* lock interrupts */
ARM_INT_KEY_TYPE key;
ARM_INT_LOCK(key);

<access registers, shared globals, etc...>

ARM_INT_UNLOCK(key);

The idea of the "key" is to allow nested critical sections, and these are used at the beginning and end of functions to create reentrant functions.

Thanks!


texts:
What is the difference between a power meter and a power sensor?

If I got this right a power meter is the instrument that reads and displays the measurements of the power sensor. Also, power meters have some reference RF signal to calibrate power sensors.

Are there power meters with integrated power sensors?
So are these two independent things or each one needs the other?


texts: Clarification on AUTOSAR BswMLinScheduleIndication container

texts:
I didn't manage to understand content of AUTOSAR BswMLinScheduleIndication container. This container should configure mode request ports associated with BswM_LinSM_CurrentSchedule API function. The issue is the meaning of BswMLinScheduleRef parameter.

From AUTOSAR Guide to Mode Management I got the impression, that current schedule table should be the mode value, but then why it is mentioned in BswMLinScheduleIndication container? If both BswMLinScheduleRef and BswMLinSMChannelRef serve as mode request source description, then what is the value of BswMLinScheduleIndication?


texts: Second order all-pass filter input impedance

texts:
I have a question about the second order all-pass filter input impedance when ω = ∞ and ω = 0 and I would appreciate if you could help me to understand the logic.

When ω = 0, all capacitors can be seen as open circuit, because we are at DC level. In this case I expect the Zin to be R3+R4, what would be 3 kOhms, because the voltage at opamp inputs would be 0V. From the simulation I see that the expected input impedance is 1.5 kOhms. Why?
When ω = ∞, capacitors can be seen as short circuits, and therefore the current will travel along C with no electrical impedance and R3, R4 are the only impedances that separates V1 from ground. In this case I do not understand why the input impedance is 3 kOhms.

Thank you in advance!


texts: Can someone please show me how these circuits would look in LTspice? Can you also point out where I need to probe?

texts: Can someone please show me how these would look in Ltspice and what their waveforms should look like? I though I was building them correctly, but they would not work. Could you also point out where to probe the circuits for the requested values? I was not able to probe anywhere for the output voltage on circuit 1. Thank you.


texts: Impossible to find the energy stored in an inductor without resistance and given a constant DC current source?

texts:
Here's my circuit:

simulate this circuit – Schematic created using CircuitLab

After doing some series and parallel inductor combining I get the value $$L_{eq}=20.8 mH$$
My question is, how would you go about getting the energy stored in any one of the inductors, given the information in this post (no initial conditions or functions of t for the source current)

Here are some fundamental equations:
$$W_L(t)={1\over2}Li^2_L(t)\;\;\;\;\;\;\;V_L(t)=L{{di_L(t)\over dt}}\;\;\;\;\;\;I_L(t)={1\over L}{\int^t_{t_0}V_L(t)dt+I_L(t_0)}$$

If I try to find the voltage using my equivalent inductance, then I will get zero since the derivative of a constant is zero, thus my energy anywhere will be zero.

I'm just curious to see if this is possible, thanks!


texts: PIC microcontroller and different EEPROM sizes?

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What is the significance of how big the EEPROM is for a microcontroller. I'm trying to select another PIC (first one I chose - PIC16LF1827 - didn't have enough RAM for the application I needed it for) and am unsure what I gain/lose by having less than 256 EEPROM or greater.

Also, HEF (High Endurance Flash)-- does that really add anything to the functionality or rather to things that may be background to the functionality but still important?

RESOLUTION:

Peep Dan Laks' answer below...


texts: Why is the power consumption of electrical lamps specified in kWh/1000h?

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This is the box of a LED spot I just bought. I'm wondering why the power consumption is measured in kWh/1000h and not simply in Watts.

Edit:

The labeling standard can be found here. (Guide for the application of the commision regulation (EU) No. 874/2012 with regard to energy labelling of electrical lamps and luminaries).


texts:
I have just learned GPIO and I've read a lot of in internet. As I understood GPIO port can be at one of two states: out and in. In any states it can work with 0 and 1. For example, if we need to turn on a LED we change state to out and send 1. But I can't understand what happens when we connect to GPIO temperature sensor. It is clear that we change state to in. But what do we read from GPIO? 0s and 1? How can we get the temperature? Please, explain.

P.S. I use Olinuxino A13 board and currently I don't have any sensors. I just want to understand how it generally works and buy after that.


texts: 2.4GHz Wi-Fi interference between devices in close proximity, even though they're using completely non-overlapping channels?

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Is there any known electromagnetic / interference / [no idea] effect which can cause IEEE 802.11 (Wi-Fi) 2.4GHz devices located in very close proximity (one on top of the other) to severly interfere with each other, even though they are using completely non-overlapping channels of the available ISM 2.4GHz spectrum?

The general knowledge about 2.4GHz Wi-Fi suggests that networks operating on non-overlapping channels should not interfere: answer at Network Engineering explaining 2.4GHz Wi-Fi channels and their interference

2.4GHz Wi-Fi channel structure:

Having a network topology like this (dots mean wireless, dashes are ethernet wire):

laptop . . . router A ----- router B . . . router C ----- ISP's box (FTTH ONT)
(client      (access        (client)       (access
 to A)        point)          to C          point)

Router A's network uses channel 6, router C's network was tested on both channels 1 and 13 (13 gives even more clearance than needed and is legal to use in my country).

If routers A and B are placed physically on each other, the maximum achievable throughput to/from the ISP's speedtest server is about 4Mbps, which would normally resemble an overcrowded channel or channel with many collisions. However, everyone seems to claim that networks in my setup should not interfere as they are assigned non-overlapping channels with enough clearance.

If I move router A a few meters away from B (not sure how much minimum distance would be enough though), the throughput rockets to about 20Mbps, which is around the expected maximum of both wireless networks and means they both perform close to their maximum capacity.

No other changes in either configuration or topology are made on any of the devices, the only change that affects the throughput is physically moving the router A away from B.

Tested multiple times over multiple days to rule out short-term conditions (neighbors), in two different rooms to rule out environment/furniture, no other wireless clients connected in either network during testing, no microwaves in the vicinity, no issues with bandwidth to/from ISP (100/100 Mbps fiber connection achieving full speed to the ISP's speedtest server when on ethernet wire).

Any ideas?

Other notes:

This happens on two different vendors' hardware which should fully conform to Wi-Fi specifications, so it should not be an issue with a single vendor or hardware piece or any non-standard 802.11 protocol modifications.
I'm not using the wider 802.11n 40MHz channels, this happens on pure 802.11g-only (22MHz) settings too.


texts: Christmas lights: 8 groups in the chain, only 6 cables?

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How do you control 8 groups of LEDs independently with only 6 cables?

So, today I've put up my Christmas decoration. It's a long chain with several independent groups and a controller with a couple of programs, you know the deal.

At first I was puzzled, in my case: 8 LEDs and a ground => 9 cables.. but there are only 6 cables. I tried following the cables to draw a diagram, but they are twisted so tight it's impossible.

After a while I realized that the LEDs could be wired in both directions: at first only the odd ones light up, change the direction of the current and only the even ones light up. But this implies that an AC current is present when all LEDs are on.

Is AC and differently positioned LEDs the (most plausible/used) solution to my conundrum? Or is there perhaps a very obvious way of cabling, or another trick that I just haven't thought about?


texts: Telling which way a KY-040 Rotary Encoder has been turned

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I am stripping this problem down to the bare minimum.

I have KY-040 Rotary Encode,
When it is turned clockwise I want a blue LED to blink for every increment it is turned.
When it is turned anti clockwise I want a red LED to blink for every incremented is turned.

I can have anything between them (but not a PI or arduino type barebone computer)

I have looked at flip flop chips but with the wave signal that comes out of the KY-040 Rotary Encoder I got quickly confused.


texts:
When a dc voltage source is connected with an ideal inductor we get a linear change/increase in current in inductor with respect to time.

But when we add resistance in series with inductor and apply dc voltage we get exponential increase in current in the circuit and so the change in current is not linear now.

What is the reason behind that?

I wonder how a resister can modify the rate of change of current in an inductor or circuit? Resistor just decreases the current in the circuit, what it has to do with the shape of the current or current change?