texts: What are the indicators of insufficient decoupling

texts:
(This question occurred to me as a result of a different question here.)

I am usually fastidious about using decoupling capacitors near all power pins on ICs, large and small, analog or digital. I also use power and ground planes in PCB designs when possible. Generally, I try to use "good practice" in order to obtain reliable robust design. And, as far as I can tell, I've been successful.

The question is, what are the indicators of inadequate decoupling. Suppose I decided to not include the bypass caps at the power pins of a microcontroller or CAN transceiver, or something else.

There are some obvious indicators like the microcontroller spontaneously resetting, but there must be more subtle problems that I might not even see, or might not attribute to inadequate decoupling.


texts:
There are a total of three postulates of lumped matter discipline.

Rate of change of magnetic flux outside the conductor is zero.
The change of chrage inside a conductor is zero.
Signal timescales must be larger than the delay of propagation of the electromagnetic wave.

The magnetic flux is changing will induce a current in a opposite direction inside the conductor.(Faraday's and Lenz's Law.)
No net charge can exist inside the conductor. (Kirchhoff's Current Law)
???

Am I right? Can someone explain to me the third postulate. I am not sure what it means. Here is the similar answer that I found here. 3rd lumped circuit abstraction postulate


texts: Can a DPDT switch be used in reverse so that it selects 2 of 4 inputs to go to the 2 outputs?

texts: I mean title, but I’m trying to have it so that it will select 2 of the 4 inputs to connect to the 2 outputs.


texts:
I want to ask how to correctly connect an ADC pin to an MCU.

I've found this two practice in some datasheets:

simulate this circuit – Schematic created using CircuitLab

Which one is correct? Or how I should connect ADC pin?


texts: Can you have a pin floating on a microcontroller

texts:
Possible Duplicate:
  Is it really a bad idea to leave an MCU input pin floating?

I am using a pic microcontroller that has about 36 GPIO pins, I am only using 31 of them, is it ok to have the ones that I don't use just floating or do I have to connect them to Vdd or Vcc


texts:
I'm currently trying to reverse engineer a remote in my headphones (one of these three button things). The remote seems to work fine, but the mic is intermittent - at times it will work perfectly, at other times it will go completely silent.

In order to proceed further in trying to figure out what the mystery IC is doing, I need to figure out what microphone is being used so that I can identify the connections. All I know is it's an SMD mic with all pads underneath the chip so I can't trace them easily.

Above is a photo of the microphone (apologies for the poor quality, I'll try for a better one later). I'm pretty sure that it must be an electret one as there are no inductors/filters anywhere that could otherwise create a supply for a MEMS microphone given that the whole controller is powered via a bias resistor embedded in the phone. (*)

The markings are as follows:

Top Line: 1005
Bottom Line: 7406 (I think. Might be 74C6)

The overall dimensions are roughly 4mm x 2.4mm x 1.1mm give or take. The black dot is the microphone membrane itself (so entry is on top).

The output of the mic is analogue not digital and seems to be on the order of a few millivolts.

A cursory Google search returned nothing, so I'm opening the floor for suggestions.

Again, the aim of this question is simply to identify the part.

(*) This is for an Android phone typically a 2.2V ish supply with a 2.2k or 5k series resistor (depends on which spec you read).

For those that want some background:

In terms of an overall picture of the circuit, as I say it's a 3-button remote in a set of headphones for controlling a mobile phone. The remote is supposedly both for Android and iPhone, but doesn't behave correctly. Initially on connection the mic works fine, but as soon as any button is pressed the mic will subsequently go silent until the whole thing is disconnected for a while.

My best guess at this is that my phone is an edge case that doesn't work properly with the way they have designed the controls - iPhones and Android use different signalling schemes so they seem to have some extra circuitry involved to switch between them. I am trying to work out the various connections so that I can start modifications to suit the Android spec.

Below is the schematic that I have thus far deduced. Again it is not possible to complete because I cannot physically see or measure what connections are beneath the microphone. In the schematic in the red box I've drawn the routing to match the physical layout as pictured in the photo.

Of interesting note the voltage at the input is never more than 1.4V. When it is working correctly (i.e. mic can be heard) the voltage is about 1.06V. When the mic can't be heard it has jumped to 1.4V.

Pin 3 of the unknown 6-pin IC is sitting at 1.4V when the mic is not working. When it is working this voltage drops to near 0V. Beyond that it is hard to get an idea of what is going on from the voltages as the rest of the pins seem to be roughly the supply voltage with the exception of pin 1 which is sometimes 0 and other times floats up to 0.4V ish.

The voltage at the phone input when buttons are pressed are as expected - roughly 300mV for VOL-, 150mV for VOL+ and 0V for CNTRL. From what I can assume the unknown IC is probably some form of multiplexer, but there is no information marked on the chip.

But to be honest the aim is to simply identify the connections to the microphone after which I am planning to remove the mystery IC entirely and find a way to wire in the mic correctly.


texts:
I needed some basic advice about impedance matching. I have an RF amplifier with 50 ohm output impedance, capable of generating 400W output power at 500kHz. I am trying to deliver this to a 12 ohm load.

I looked online and figured out that I need to match the impedance of the amplifier to the load. What is the best way to achieve this? Would it be possible to simply use a capacitor and inductor and put an L section to the output of the amplifier? I saw that online stores have very cheap capacitor and inductors that are rated for very high voltages.

If that is not going to work, is it possible to buy any transformers that would do that? For instance I saw that there are many cheap 220V-110V voltage converters, which should have 2:1 coil ratio. So in theory that should convert 50 ohm to 12.5 ohm and matches to my load. Will these work at 500 kHz as required for my application? Or are there other type of transformers that I can use for this purpose (there are many many types of transformers and I got confused which ones are suitable for impedance matching)?


texts: Which BJT-parameters need to be derated at raised ambient temperature?

texts:
I am designing a discrete MOSFET-driver stage based on BJTs in simple push-pull configurations and wondering, which of the values under absolute maximum ratings I have to derate at higher ambient temperatures. The device in consideration is the BC807W which only has to conduct during turn-off of the MOSFET.

The datasheet gives me a max value for I_{CM}=-1A. Can I drive this peak current only at 25°C of ambient temperatures or also at higher temperatures as long as the maximum junction temperature is not exceeded?

The background of this question is that I head a similar issue with diodes some time ago. The datasheet would give me a maximum surge-current which has to be linearly derated above 25°C (according to the very competent FAE). This current must not be exceeded, even if a nice margin of the junction temperature remained. The point there was, that not only the heat destroys the diode, but also the current density.

So, to bring this to an end: is it the same with the peak collector current of a BJT?


texts: Frequency plot with a node as reference in Proteus

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I'm trying to make a frequency plot in Proteus of an inverse adder amplifier.
This is the schematic:

The thing is that when I use the frequency plot properties editor to change the property "reference" it don't let me put the node "vin" as a reference, it only lets my put voltage sources as a reference. I want to make a bode plot of the circuit using as reference vin which is the signal I want to amplify.
Does anyone know a solution to this problem? I know how to do it in LTspice or Pspice, but I need to do it in Proteus.


texts: How to find voltage across the 2k ohm resistor in the given circuit?

texts: I have to find Vo in the network given below using Thevenin’s theorem. After removing load resistance i.e. 1k ohm, i know that Ix=V2k/2k but I am stuck on finding voltage across the 2k ohm i.e. V2k. I am familiar with voltage dividers but confused by the current source


texts:
For my boost PFC design that I am currentely working on, I need a current limiting circuit for the capacitor inrush current in start up, the widely used circuit in this type of applications cases is shown in this figure

The relay is turned on after some miliseconds when the capacitor is fully charged and the diode is reversed baised

My question: how can I determine the amount of current drown by the capacitor and more importantly, on what criteria will I choose the diode and the NTC resistor on and based on what?

Thank you very much.


texts: Measuring voltage of a storage system with RPi

texts:
simulate this circuit – Schematic created using CircuitLab

I'm trying to figure out how I can measure a voltage of a storage system (~48 V DC) and construct a safe input into an MCP3008 ADC.

I built a voltage divider and I am not sure if it's possible to connect the RPi ground via the digital_GND of the ADC to the analog-ground of the circuit?

Any suggestions would be appreciated, thanks!


texts: I forgot to plug in my computer's ups(uninterruptible power supply) pin in socket.UPS was turned on.I accidentally touched the neutral pin.I got a electric shock.Why?


texts:
This is probably more of an algebra question.
I do not understand where the "1"s come from in equation 1.10 given the much simpler voltage divider equation in the line just above it. And why do they convert a simple  resistor division problem, into a division over a division problem?
The second part that loses me is the jump from equation 1.11 to 1.12. I have been trying and trying and I just cant get 1.11 to look like 1.12.


texts: Is it possible to simulate hardware of MIPS architecture computer defined using Verilog/VHDL?

texts:
I am reading Digital Design and Computer Architecture book and if I will be persistent then I will have MIPS architecture computer at the end, implemented from scratch by me .

I wonder is it possible to somehow define different components of this computer using Verilog or VHDL or something else maybe and simulate them on a computer? I'd like to build it from most basic blocks like NAND or AND and do one step at a time building each layer of abstraction. Then when I am done with hardware part I'd like to write an operating system for it.

Is it possible to do all of this without buying any real hardware and using only some simulation software?

If so, please, point me to some resources where I can read more about it.
Or explain how this can be done.

Thanks in advance.


texts:
I am trying to answer the question

  If you connect a detector between Va and Vb, knowing that the frequency to which the bridge is balanced is 6820,58Hz, what is the current that passes through the detector if the frequency goes off by 1%?

My attempt:

If I find the thevenin equivalent of the circuit then it should be straightforward. However the expressions that I end up with are:

$$
Z_{eq}=\frac{R_3(1+j\omega R_1C_1)}{j\omega C_1R_3+(1+j\omega R_3C_3)(1+j\omega R1C_1)}+\frac{R_2R_4}{R_2+R_4}
$$

$$
V_{eq}=\bigg(\frac{j\omega R_3C_1}{1+j\omega(R_3C_3+C_1R_1+C1R_3)+(j\omega)^2C_1R_1C_3R_3}-\frac{R_4}{R_4+R_2}\bigg)V_{in}
$$

But dividing these equations so as to get the current seems like going for the hardest and most tiresome way. Surely there has to be a far simpler and straightforward way that I am missing.

simulate this circuit – Schematic created using CircuitLab


texts: Can we capture and reproduce the bluetooth signals

texts: Are there any devices that can capture bluetooth signals and reproduce them? Or is it simply possible to capture bluetooth signals if we have any bluetooth device? Does a bluetooth device have separate components for sending and receive signals?


texts: (Ideal) Amplifier networks/nullors - determining the gain

texts:
I am having trouble understanding how the different amplifier networks actually do "their magic". In these networks a nullor is a unite that has always 0 voltage over the input and no current through it. The output has infinite power to match the requirement set. The "easiest" version -a voltage to voltage amplifier- I can easily understand:

Because the current and voltage over the input of the nullor is 0 the voltage at the output must follow the equation \$V_s  = V_{load} \cdot \frac{R_2}{(R_1 + R_2)}\$

However I do not see how this works in other types of amplifiers; say the following standard "voltage-to-current" amplifier setup:

What is the gain here? And what is the equality equation to solve?


texts:
I would like to do a DIY intrusion detection system.
I think I understand roughly what it's needed (door magnetic switches, windows magnetic switches, IR motion detection, password prompt, webcam), though I'd like to know how you can actually call the police.

I saw the "ITEAD SIM900 GPRS/GSM minimum system module" in my local retailer's store and I find the price pretty interesting (~ 45$). This would however "only" allow me to send SMS to a mobile phone when there's an emergency, not being able to directly call the police isn't so good. What do they mean by "It can communicate with controllers via AT commands (GSM 07.07 ,07.05 and SIMCOM enhanced AT Commands)."? Do I need an external phone? I though I could directly interface this module to a MCU.

Another possible solution might be to set up a raspberry pi with GNU/Linux + gammu and an attached (compatible) mobile phone and send SMS to a mobile phone. No possibility to contact the police though.

Basically with either solutions IMHO I could send an SMS to myself / my friends when there's an intrusion and relay the message to the police. It's not a so good solution though, because with all delays summed up the thief may already be gone.

Landline phone wouldn't be a good idea either, since with cable TV/Phone/Internet isn't that reliable at my place.
I though I'd pre-register an audio message and play it from one speaker if I can manage to force a phone to call a given number (which could be done with AT commands, theoretically).

What would you reccomend / do?


texts: Floating value when connecting to IC input

texts:
I'm currently having a strange issue with what I think is a 'floating' signal.

The setup:
I have a bank of inputs (which are connected to a resistor and LED acting as a pull-down) connected to inputs and outputs of a D-type flip flop IC (SN74ALS374AN). The fact I'm using all 8 shouldn't matter as the issue occurs on any one in isolation. They are connected to input and output as I will only have enable or clock on at any given time, and never both (for a bidirectional bus). The datasheet of the chip says it is suitable for this.

The problem:
See the image attached. When I disconnect wire A from the flip flop IC (connection B) and read the voltage between A and ground, I get 0v or 5v depending on whether the switch is on. However when I connect A to B (the goal being to feed this logic 1 or 0 signal to the IC), suddenly the voltage reads as 1.5v (which I believe to be a floating value).

Can anyone explain this behavior? Am I doing something wrong?

A few things to note:
- It doesn't matter if I disconnect Q and D on the IC
- If I connect to Q only, then the logic low is retained, so the problem is really just the D (or input) of the flip flop
- The datasheet for the IC doesn't seem to shed any light on this

Any suggestions would be very much appreciated. If I haven't explained anything properly or you need me to test anything else then please let me know.

Many thanks,
Matt


texts: Understanding cable standards for low voltage conductors in high voltage environments

texts:
I am currently getting some custom cables made and having a serious communication issue with several cable manufacturers. I want several low voltage (5V DC) insulated conductors in a jacket that can protect from 600V external contact. And, I want the cable to be UL marked for flammability and voltage compliance.

If I am understanding my communications correctly, the different manufacturers have all indicated that the insulation for the individual wires must also resist 600V on their own for UL marking which makes the cable diameter very large. To me this does not make sense. I have been going through UL documents to try to see where this might be stated. Looking at AWM (appliance wiring) standards, I see detail about the jacket, but not about the individual conductors as in UL 20201 and UL 2057 for example. Given that AWM wires can contain twisted pair (assuming for communications), I would like to understand what I might be missing that would require cable internal wires to have such thick insulation.

I have looked at the "UL Marking and Application Guide Wire and Cable" in their tables and virtually every cable option requires UL marking with the UL symbol and voltage.

Is this possibly a case of the manufacturers trying to comply to a different standard than would apply?
Is this a case of my application not being covered directly in the standards?
Other options?

Any explanations and possible directions would be appreciated.


texts: Impedance of individual component in complex AC circuit

texts:
In a AC circuit with just a capacitor or inductor, reactance is the impedance of the component, and in a non-complex RLC circuit you can just find the total impedance with vector addition (Ztot = sqrt(R^2 + (Xl - Xc)^2), but in a complex ac circuit how do you find the impedance of a single component?

Say i want to find the impedance of components C2, C3, L2 and L3 in the circuit below.

simulate this circuit – Schematic created using CircuitLab


texts: PWM Generator in OrCAD, doesn't simulate what it should

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I have a project, to design a Pulse Width Modulation Generator in OrCAD 17.2. I surfed the whole internet to find a proper circuit to be able to draw it in Orcad, there are no errors, but when i simulate the input and output signals, all i get is a constant DC voltage. I should have a sine, a triangular wave, and for the output the modulated signal. I will attach the circuit, but i think i'd need help to size the components and set the simulation profile.

The circuit didn't fit in one screenshot, so here's the rest.
The simulation in time domain:


texts:
I've been trying to use WS2815 leds in my stairs, but I'm struggling with noises problem.

I'm using stm32f103c8t6 based bluepill board as a controller for 18 1m long led strips. Each strip is controlled separately, using TXS0108E level shifters. Between each pin and led strip there is ~4 meters of 0,35m^2 wire. I've created a board to place all components but there was a a problem with wire capacity, which I solved adding 4k7 pull-ups (green lines) and 100nF capacitors (pink lines).
The last problem I cannot overcome are noises (or some capacity, making line unable to go LOW).
The problem is, that first pin from power source (first from right) works perfectly, second has a little noise and every next one is worse.
Should I use other resistor for pull-up? Or maybe use pull-down instead?
Problem does not occur if I connect led strip straight to the board, without the long wire.


texts: Problem SAMD21 : ASF4 USB CDC Echo example cdcdf_acm_write() doesn't allow to send data to usb port

texts:
I'm using the USB_CDC Echo Example for Atmel start, for ATSAMD21G18A. the code example runs Ok, but when I try to modify the code in order to send data "Hello World" in the infinity while loop
the data doesn't appear

What do I have to configure in order to run the cdcdf_acm_write() function?


texts: TVS diode with 10 - 15 V forward voltage

texts:
I came across this TVS diode: https://m.littelfuse.com/~/media/electronics/datasheets/tvs_diodes/littelfuse_tvs_diode_smf3_3_datasheet.pdf.pdf

It has a forward voltage drop of 10 to 15 V.
Why? How?
That is so unusually high. What kind of diode has that kind of a drop? Isn't it always roughly between 0.2 and 0.7 V?


texts: Why is the grounded capacitor smaller in a transmitter vs a receiver?

texts:
Here's an FM transmitter that I found on the web:

Here's a regenerative receiver that I found:

The capacitor connected to the base of the transistor in each circuit is different. Why isn't the capacitor for the FM transmitter also at 10uF or why isn't the capacitor for the receiver also 1nF?

I'm trying to understand why such values are chosen for grounding capacitors.


texts: Turning a frequency locked loop into a phase locked loop

texts:
I want to use a GPS module (with a PPS output) to ultimately generate a 5kHz timing signal that is phase-aligned with the PPS positive edge.

PPS-------MSP430-----DAC-------10MHz VCO-------Divider--------5kHz
             /\                            |
             |(count pulses in             |
             |between PPS edges            |
             |inside MCU)                  |
             -------------------------------

Thus far, I can generate a stable 10MHz signal (10MHz VCO connected to an MSP430 Launchpad for control), and then I divide this 10MHz signal down to 5kHz using several 74LS90 chips.

This generates a very stable 5kHz timing signal, but the positive edge of the 5kHz signal, in the pulse of the period, is NOT aligned with the positive edge of the PPS.
How can I adjust the phase, so that the 5kHz and PPS edges are aligned?

----EDIT
Thank you for your comments!  Our timing error budget is 1 microsecond, so 100nanosec would be great.

I was under the impression that, IF we use a 10MHz oscillator, and control that to 10MHz with the loop, and THEN divide the result down to 5kHz, then "by default" the 5kHz would be very precise (controlling a 10MHz oscillator to within 1Hz, is 100 nanosec of timing accuracy).  If I controlled the 5kHz output, and I'm off by 1Hz, then I'm off by 200 microsec (much bigger timing error).  Am I correct in my thinking?


texts:
I'm looking into the feasibility of a project to develop a USB-over-RF device for physical penetration testing engagements. The idea is that our tester could connect a device to a USB port on a machine within the test environment, then leave the building and plug in arbitrary USB devices remotely.

The requirements are as follows:

USB 1.1 support at minimum, but USB2.0 support would be greatly beneficial even if speed is heavily degraded.
Ability to plug in arbitrary devices is mandatory. Keyboard, mouse and USB storage are our primary goals.
Cannot load any form of special software or driver onto the target machine. Client transceiver has to work "out of the box" on a system we've got no access to.
Host transceiver would preferably be nothing more than a box full of electronics that we plug a USB hub into.
Enough speed and integrity to run a USB VGA adapter would be amazing, but we're realistic about this being potentially impossible.
Can be powered from a socket if necessary, but running from host power would be better.
Needs a strong enough signal to go through at least one external wall.

I have a few ideas in my head about what kinds of technologies could be used, e.g. Arduino Mega + USB host shield + XBee for the host transceiver, and a similar setup (with USB client rather than host) for the client transceiver. We also considered TCP/IP over 3G as a potential transmission medium, though I fear it may be too latent / slow.

Do you think this could be achieved with the kind of technology I've mentioned? What issues am I likely to run into with sending USB over a latent connection like this? Is there an easier solution that I've missed?

To clarify, consider our task equivalent to sneaking into a building and installing a device into a computer, similar to the scene at the start of Sneakers. The restriction is due to the fact that the machine will likely be locked or shut down, so we cannot expect to have any interaction with the system beyond plugging in a USB device. We'll often have less than 30 seconds alone with the machine, too. This rules out installing drivers / software, bluetooth pairing, etc.


texts:
I am trying to build a heart beat sensor. I implemented the application circuit suggested by the datasheet of the sensor.

But I get a constant reading at the Arduino. I confirmed that the IR emitter works using my phone's camera.

EDIT

I used 1uF in the actual circuit!

EDIT

I took the sensors from old disposed off electronics. And I was suggested that such sensors only detect signals that are modulated at ~4oKHz. The easiest solution is to use an IR Photoresistor. But I don't have an IR photoresistor. Will it detect it if I modulate the IR signal I send to that frequency? Will I still be able to work with the level of reflection?


texts:
I'm a student working with the Arduino UNO
There's this question always bugging me for the analog input pins, how many samples does it take per cycle.
I know it has 10 bit resolution meaning 0-5v would be 0-1023.I think since Arduino UNO uses ATMEGA 328(8 bit) then maybe 256 samples per cycle, but people say 128 bits per cycle. I'm confused.


texts:
I'm in the process of designing a LED strip driver using a WS2811 chip and 3 MOSFETs.  I've attached the schematic below.  I based it on the reference circuit in the WS2811 datasheet (link), and this breakout board from Freetronics (link to schematic).  I think I'm on the right track with my design, but I had a few questions before I go ahead and order parts.

I have selected the BSS138 MOSFET to drive the NTD4806NG MOSFET which will drive the LEDs.  Is the BSS138 actually needed for the MOSFETs I have selected?  I read over the datasheet for the NTD4806 and it looks like it might be ok at a 5v logic level, but a lot of the WS2811 MOSFET drivers I've seen included the smaller MOSFETs.
Are N-Channel MOSFETs the right choice to go with the WS2811?  Or should I be using a P-Channel MOSFETs circuit. I've seen a few other people build similar circuits both ways - why might I favour one over the other?
Can anyone spot any other "gotchas" with my design that I might be missing?

Thanks for all the help!


texts:
There are two things that confuses me in the below text:

"The ADC uses the successive-approximation method to perform the
conversion.The HCS12 uses two 8-bit registers to hold a ananlog to digital conversion result. The result can be stored either right- or left-justified. The A/D conversion is performed in a sequence from one to eight samples."

1- I always thought that registers are storage locations in the CPU. So ADCs would have their own registers too?

2- What are the functionality and meaning of the right- or left-justified registers?


texts:
I have designed the circuit below for a isolated digital output from a mcu. The switching speed is slow -- only 100ms or so. I would like to be able to switch between 3 and 24Vdc at about 1mA to 500mA. Is this the correct way to build a circuit like this?

APV2111VY


texts: how does interelectrode capacitance reduces bandwidth?

texts: How does inter-electrode capacitances reduces the bandwidth of operation in electronics devices? I am assuming that if capacitance increases the time constant of charging of that capacitance will also increase and this will the rise time. And as BW is inversely proportional to rise time it would reduce. But I am not sure of this explanation. Please confirm on this.   Moreover I would also like to know the relation of frequency and capacitance. As I understood from an explanation in a book, it seems as if capacitance is always there. Its only that at high frequency its reactance reduces and it acts as a short circuit. But that doesn't seem to be convincing. How does actually a high frequency signal causes capacitance to build up or in other words causes charge storage?


texts: Why does triode voltage drop change as a function of grid voltage?

texts:
Imagine a thermionic diode connected in series with a resistor \$R\$. The circuit is hooked up to a voltage source \$V\$. The diode conducts a certain current \$I\$ and \$\Delta V_\text{diode}\ + \Delta V_\text{resistor} = \Delta V_\text{diode} + IR = V\$. That is: the voltage drops across the diode and the resistor sum to the total applied voltage.
Presumably the voltage drop \$\Delta V_\text{diode}\$ arises from the acceleration of electrons as they travel from cathode to anode. The kinetic energy of the electron velocity is lost as waste heat when the electron slaps against the anode.
Now, imagine replacing the diode with an equivalent triode. Imagine the voltage drop from cathode to the control grid is 0V. The grid is effectively superfluous and nothing about our circuit has really changed yet.
Finally, imagine lowering the grid voltage. This should reduce the current \$I\$ that conducts through the diode. Thus \$\Delta V_\text{resistor} = IR\$ also decreases. Thus the the voltage drop \$\Delta V_\text{diode}\$ should increase, since \$\Delta V_\text{diode} + \Delta V_\text{resistor}\$ must remain equal to the applied voltage \$V\$.
My question is: why/how is energy per coulomb lost as charge travels through the triode?
Because of the grid voltage, only electrons emitted at high-enough velocity can "punch through" the grid field and arrive at the anode. (This is why the current conducted by the tube drops.) My intuition was that these electrons that do succeed at passing from cathode to anode arrive at the anode with greater velocity, and thus more energy is lost as heat.
But then I thought: if one integrates the electric field from cathode to anode (the kinetic energy added due to the potential difference between cathode/anode), doesn't the work being done per electron remain constant (regardless the grid voltage)?
In summary: when the grid voltage is at a lower voltage than the cathode, the triode current drops. But what explains why \$\Delta V_\text{triode}\$ rises?
Examples
Example of voltage drop across resistor with no voltage applied to grid:

Example of voltage drop across resistor with negative voltage applied to grid:

Note that the voltage drop across the resistor has decreased (and the voltage drop across the triode has increased).


texts:
Hope you are doing well and solving all your problems!!!

I am new to hardware programming, facing some difficulties to work with DAC interfacing with Atmega128 board. After searching on internet, could not find any any good tutorial or explanation about ADC interfacing with AVR or Atmega. I have Atmega128 connected to DAC8532 through PD4(ICP1), PD5(XCK1), PD6(T1) and PD7(T2) pins of Atmega. I have no idea how to deal with it.

Please, can anyone help or give some suggestions how to programming it.

Thank you very much.


texts: Variable gain amplifier output appears on circuit positive and negative supplies

texts:
I am trying to use the analog devices AD600 in a simple sonar system. However, the performance of the chip is severely degraded because whenever the chip's output is nonzero, a portion of that output appears on the positive and negative supply rails of my circuit. Here's my circuit.

This comes straight from the datasheet. My control voltage and input signal are coming from an arbitrary waveform generator. The input signal is a 20kHz sine wave and the control voltage is a DC voltage from 0V to .625V. Also note that in my circuit, the input sine wave is preamplifier by an LM318N opamp with a gain of 2x. Here is a picture of my oscilloscope showing my issue.

The yellow signal (CH1) is probing the output of the AD600 (pin 14), and the blue signal (CH2) is probing the positive voltage supply of my circuit (pin 13/Vpos). As you can see, the output waveform appears at the positive supply rail, attenuated by approximately a factor of 50 (~-33 db). This is a problem because the chips's datasheet specifies a PSRR of only around -25 dB below 100kHz, my frequency range. When the output amplitude increases, so too does the amplitude of the signal appearing at the positive rail of the power supply.

This quickly ruins the performance of the chip for large output voltages, as the PSRR is too low to reject this noise. Does anyone have any suggestions on how to minimize this. Please note: The 2nd scope picture has clipping on the negative swing of the signal because of the input offset voltage of my pre amplifying LM318N. The negative DC bias from the pre-amp reaches the input of the AD600 in my current testing setup. I have, however, tested this circuit with an op amp with a much smaller IOV and seen the same results.

I have seen the results described in this post when this circuit was assembled on a breadboard and soldered onto perfboard. I am also using proper decoupling caps on the supply pins (no ferrite beads but my power supply is clean).


texts: wireless power transmitter produces voltage but nothing picked up on receiver

texts:
Here's another attempt I made on wireless power:

I borrowed ideas from http://4hv.org/e107_plugins/forum/forum_viewtopic.php?74096 but due to limited stock on hand, I had to use what I can.

I used 6VDC for power in the form of 4 AA batteries. when testing L3 (transmitter inductor) by connecting voltmeter from one end of the inductor to ground, I get 11.6V output which is about double of the measured battery voltage.

So then I placed my mini receiver circuit made on a pcb that consists of a 100uH inductor connected across the analog inputs of a DF005M rectifier. then its outputs are connected to a capacitor in parallel with a jumper that represents the remote power source.

In my test I literally have the insulating materials of each inductor directly touching each other. when I measured the voltage at the pins, all I get is zero volts. How do I make the number greater than zero? Ideally, I'd like to have at least 3 or 4V so that I'm heading in the right direction.


texts: Is the switch representation for this logic wrong?

texts:
In an old text I came across the following for A’B+AB’ logic:

It seems the bottom logic gates follows the logic but Im bit confused about the switch representation. Isn’t it wrong?


texts: Why does a multimeter put more voltage to measure a smaller resistance?

texts:
I noticed this behaviour on two different multimeters (different models and brands as well).
At first I did not put a multimeter in the way to measure how much voltage changed for the different scales of the meter: I realized that by using my own tongue (hell, yeah).
For both the multimeters I own, I could definitely feel that the tingle was getting stronger when the scale was smaller.

So: I tried to measure voltage applied to the probes of one multimeter at various resistance scale reading levels, by using the second multimeter one to read Volts. I am quite impressed by the results.

Here's what I read. On the left side is the "measured" multimeter scale setting, on the right the voltage I read:

200Ω -> 2,96V
2kΩ -> 2,95V
20kΩ -> 2,93V
200kΩ -> 2,69V
2MΩ  -> 1,48V (what a drop!)

If I switch the meters things are even more confusing to me:

200Ω -> 2,71V
2kΩ -> 2,69V
20kΩ -> 0,35V  (!!)
200kΩ -> 0,32V
2MΩ  -> 0,18V

Can please anybody make clarity about why does this happens? I would expect that a higher voltage should be applied to measure bigger resistance.
Just before hitting "Post" I chose to measure current as well - for different ohmmeter scales level. Guess what: those definitely dropped as well, but not with the same ratio as voltage. I am confused as heck. Thanks!


texts: PIC16: Understanding the bound on the argument to _delay

texts:
My PIC16 compiler, XC8, defines a _delay(n) pseudo-function which inserts a delay of n cycles. There is a restriction however (see here, page 59):

  The delay argument must be a constant and less than
  approximately 179,200 for PIC18 devices and  approximately 50,659,000
  for other devices.

Where do these upper bounds come from? The factorisation of 50,659,000 (2^3 * 5^3 * 7 * 7237) does not seem to shed any insight.


texts: Unused BJT in a dual package - Need to do anything for stability?

texts:
I am using several NPN/PNP pairs in a circuit. One of the NPN is left unused.

Do I need to do anything, or just leave all 3 leads of NPN floating or I need to connect them for improved stability? If so how?

Thank you.


texts: I was working with a three pin mosfet. However, a senior suggested me to go for a four pin MOSFET. Now, I wonder, if there is any difference between a three pin MOSFET and a four pin MOSFET. Is a four pin MOSFET considered better than a three pin MOSFET?


texts: Influence the apparent input resistance of a buck-boost converter

texts:
I want to power a buck-boost regulator (for simplification, preferrably one of the integrated circuits from Linear Technology) with a current-limited or high inner resistance power supply.

The power supply (a bicycle hub dynamo) is designed to deliver 500mA in a 12Ω load and to not deliver significantly more than 500mA current, even if the bicycle drives faster than what's required for the 3W output power. Increasing the load resistance to e.g. 24Ω, the current limitation in the hub dynamo still kicks in somewhere around 500mA, but with the higher load resistance, the available output power doubles to 6W.

Now, my question is: Using one of the mentioned buck-boost regulators, other ICs or in worst case even a proprietary design, is it possible to influence the apparent input resistance of the regulator, so that the regulator prefers to draw a low current at the highest possible voltage instead of a high current at a low voltage, even if both combinations of U/I on the input would suffice for the output power requirement?


texts: I was wondering if anyone had any site or diagram for a cheap (and preferably small) for a circuit for a 60 to 80khz frequency generator.


texts: LED randomizer microcontroller SFF (Small Form Factor) circuit

texts:
I want 12 leds in the circuit programmed to go around at a certain speed. 17 smd leds in total. What I need to do is for the chase to randomly chose to slow down for 1 second or speed up for 1 second with a respective led come on each time it is chosen. It is using a ATMEL AT89C2051-24PU (DIP-20) microcontroller, 3v battery, 17 leds(12 for chase,3 for rotation, 2 for speed up/down notifier) , 1 switch, 1 piezo. Leds go around at the programmed speeds and clocks 1 rotation notified by an individual led 3 rotations in total. Start of rotation notified by piezo and at the end. How can I do this, can I program into the microcontroller or will I need a different one or two?

Im a novice.

Thanks


texts: Voltage and current rating of electrical systems

texts:
Why voltage and current ratings of almost all electrical systems are RMS value of voltage and current not peak value of voltage and current?
First I thought maybe because mostly ac input is sinusoidal and for sinusoids rms and peak values are directly related so it doesn't matter whether rating is in rms or peak
But sometimes even a sinusoidal  input voltage can cause a non sinusoidal current or even if we take worst case scenario where both input and output are non sinusoidal where no direct relationship exist between peak and RMS values and hence RMS value cannot determine peak value in these cases
So ,why RMS rating is considered ?
isn't insulation failure (and many other failure) occur  at peak of current and voltages rather than RMS of these quantities? For example even  a low RMS currents and voltages can have very  high value of peak which might damage the device.


texts: Attaching Arduino TFT LCD screen to Pi 4 without soldering it on?

texts:
Note: Already asked on raspberry stack-exchange. I was directed to this community instead.
So I have this product: https://learn.adafruit.com/2-8-tft-touch-shield/lcd-test
My goal is to connect it to the pi 4, without soldering it on. I plan to use it as a small screen to run raspberry or twister os. I found an article on how to attach the Arduino screen to a pi zero, though, that requires it to be soldered on. The last option I found was to buy an Arduino adapter to add on top of the pi (https://www.seeedstudio.com/Arduino-Adapter-For-Raspberry-Pi-p-2443.html) My only problem is that I don’t know if it will work. For example, lets say I do buy that adapter, will it display the operating system as soon as I turn it on?
Also I had an idea on connecting the Arduino wires ( https://www.amazon.com/Elegoo-EL-CP-004-Multicolored-Breadboard-arduino/dp/B01EV70C78/ref=sr_1_4?dchild=1&keywords=arduino+cable&qid=1619709817&sr=8-4 ) to the pi board and the Arduino screen. Though, I wouldn’t know which pins connect to which.
Am a new learner, so please forgive me for ignorance. I also don’t know which pins belong to which, and what to connect to what?


texts: How do I measure the current flow to a component?

texts: I'm building a hexapod robot using simple servos and I was wondering how feasible it was to measure the current flow to each servo (5-6V DC to a maximum of 0.25-1A (I haven't found the spec for the servo's stall current yet)) using, say, an ATMega168. What kind of circuit would I need to build in series with each of the servo's power lines to give me a useful readout? I assume I'd get a voltage drop across this circuit, what's it likely to be? etc.


texts: Alternatives to USB connector to supply 5V for charging battery on small circuit

texts:
I am looking for a way to get power in my recharging circuit, since my device uses a battery.

The problem is the USB cable: the connector is soldered on the PCB, but with the stress of plug and unplug, the connection is really prone to breakage, and my PCB is quite small.

Is there an equally flexible way to transfer power from a computer to a device, without use the standard USB connector? I do recall that some devices used induction coils to recharge a device (Samsung phones?) although I am not sure how reliable they are.

My ultimate goal is to get 5V to my PCB to recharge the internal LiPo battery, but without the hassle to have a USB connector.


texts: I would like to design a system that works with my ESC/POS thermal printer that activates a siren when a receipt is printed. My thermal printer has an RJ12 port which is intended to connect to a cash register. I can send an ESC/POS command that kicks open the cash register by sending it a pulse through this port (I believe it is ~24V at very low current). My only requirement is that the siren be very loud (for use in a warehouse setting). I am not sure if the pulse itself can drive a siren, or if I am going to have to construct a circuit that is activated by the pulse. I would like to build the simplest and cheapest circuit that I can, but I don't really know how where to start, any guidance would be greatly appreciated!


texts: Can Nios II read addresses in increments of 1 or only increments of 4?

texts:
There is some confusion here. I think that the Nios II having 32 bit data bus. Therefore, it is not capable of individual byte addressing. Therefore, the address bus increases as 0, 4, 8 e.t.c and not 0, 1, 2 e.t.c. The byte enable signal can be used to select individual byte for writing but does not have any affect on reading.

That being said, when I look at the .v files of synthesized modules after Qsys system generation, it seems that they expect the address input to increment by 1 for offset to access the different memory mapped registers, and not by 4. Here is some code from the timer core.

  assign irq = timeout_occurred && control_interrupt_enable;
  //s1, which is an e_avalon_slave
  assign read_mux_out = ({16 {(address == 2)}} & period_l_register) |
    ({16 {(address == 3)}} & period_h_register) |
    ({16 {(address == 4)}} & snap_read_value[15 : 0]) |
    ({16 {(address == 5)}} & snap_read_value[31 : 16]) |
    ({16 {(address == 1)}} & control_register) |
    ({16 {(address == 0)}} & {counter_is_running,
    timeout_occurred});

This code creates a multiplexer so we are able to read the different registers in the memory. The address offset to access the different registers is 1 and not 4. The same information is contained in the Qsys Embedded Peripherals IP User Guide. It presents a table describing the memory map, the offset values are consecutive integers.

Edit:

The document "Making Qsys Components" found via google search is dated "October 2015" in the footer. On page 8 it says:

  "Addresses used by master devices are aligned to 32-bit word
  boundaries. For example,  Figure 8 illustrates four 32-bit addresses
  that could be used to select four registers in a slave device. The
  address of the first register is 0x10000000, the address of the second
  register is 0x10000004, and so on."

What is the truth?


texts: Total response of a first order RC circuit

texts:
I need to find the step response (steady-state + natural response) of the given RC circuit. The step is at t = 0 secs, that is,

where Vp is a constant.

I found the time constant to be

I am stuck at finding at final voltages across the capacitors. I open-circuited both the capacitors but then realized that middle voltage can be arbitrary.


texts: Increasing system clock frequency on STM32F303 drops I2C clock proportionately - why?

texts:
I'm trying to figure out a weird little issue I've discovered while debugging another element of my code.

I've got a STM32F303K8 reading and writing to an I2C peripheral.

The I2C clock speed is configured to be 400 kHz in CubeMX, but that's not the actual clock speed when I look at it via a logic analyzer.

To make things more interesting/confusing, there seems to be an inverse relationship between the system clock speed and the actual I2C speed.

When I'm running at 8 MHz system clock (CubeMX config below):

My I2C clock looks like this on a logic analyzer:

Showing 333.33 kHz.

When I change the system clock up to 72 MHz (CubeMX below):

Logic analyzer trace of the I2C clock looks like this:

Giving me only 46.79 kHz. No other settings were changed.

My I2C settings are below (configured in 72 MHz mode - the 8 MHz mode is the same, except for the timing register).

I've been trying to root out the source of this all day, with not much luck. Does anybody know what's going on here, and what I can do to prevent this causing problems?

Thank you all so much for your help!


texts:
I am using a cable of approx 1600ft to enable communication between two computers using RS-232(pins 2,3 and 5). On checking the transmitted signal on the oscilloscope, i get the output as below (hex code:41H):

However, on oscilloscope at the receiver end, following is displayed:

The connection does not involve any terminal resistances and when I checked the output by connecting the oscilloscope probe directly to the rs-232 pins, the output was as seen in the first image, however, on connecting it to the computer and then checking it on an oscilloscope, a noisy output as seen in second image was displayed.

Can someone please suggest on what should be the correct approach to enable communication using RS-232 for such long distance.

Also, the receiver computer does not show any output on transmitting any of the hex codes. The baud rate used was 300.

Thank you.


texts:
I am trying to identify a thermistor that was used in a "smart thermostat". It is a surface mounted small part  (0603 form factor), bears no markings.
I measured the resistance across at a few temperatures, and got (approximately, perhaps 5% error):

49°F: 16.05kΩ
79°F: 11.1kΩ
81°F: 10.94kΩ
97°F: 10.14 - 10.2kΩ

I also tested the board with a standard 10KΩ thermistor (Type 2, though at room temperature that does not matter) and, predictably, it was showing about 10-15°F too high of a temperature.

Any suggestions would be appreciated.


texts:
I want to add an intermittent function to the wipers on my 40-year-old car without any additional switches.  The details of the wipers can be found here [http://www.globalsoftware-inc.com/coolerman/fj40/5G.htm].  The wiper knob closes the path to ground allowing the motor to begin sweeping the wipers.  (There is another ground at the motor that mechanically closes when the wipers are not parked.  This allows the wipers to park regardless of when the wipers are switched off.)  It seems that all I need to do is complete the path to ground whenever I want to sweep the wipers, but it seems too easy so I’m second guessing myself.  I’ve drawn out a small circuit using a ATtiny85 to detect if the wiper circuit is closed (not shown on the diagram).  If the circuit is closed (knob pulled out) for longer than one second, the wipers operate as long as the knob is out.  If the knob is pulled out and returned in less than one second, the uC activates the relay long enough to start a sweep and repeats this at a predetermined interval.

Am I missing something?  Is this a reasonable approach?  I chose an automotive relay I’ve used before, datasheet here [http://www.farnell.com/datasheets/1809465.pdf] with a diode and RC snubber across the contacts.

[Edited from original to reflect accurate wiring.]

simulate this circuit – Schematic created using CircuitLab

To be completed by OP.

                                 |   A   |   B   |   C   |
                                 +-------+-------+-------+
Everything off                   |12.9 V |12.9 V |12.9 V |
Bulb in, WIPER_LO closed         |   0 V |   0 V | 4.9 V |
Relay energised, WIPER_LO closed |   0 V |12.9 V | 4.9 V |

simulate this circuit

[Second schematic illustrates switch and two ground paths.]


texts: emitter follower oscillation cured by adding base input resistor?

texts:
I made a simple emitter follower headphone amp using fairly high speed BJT- 2SC5994.

Vcc 16V

R1- 10K

R2- 40k

RE- 100

load - 300 ohm

After powering up there it was clear there was serious issue, the amp would pop in and out oscillation randomly. This manifested as buzzing sounds through headphones and after checking with cheap 2mHz oscilloscope there were HF oscillations clearly visible.

They are high speed transistors so this was anticipated, Firstly I added some resistance at the output to isolate from headphone's capacitive load. This seemed to make it less prone to popping into oscillation but it would push up the output impedance too much so wasnt a suitable solution.

Surprisingly adding resistance to the base input ('base stopper') also fixed the problem. With 40 Ohm there hasnt been any oscillation when loaded with HPs and playing test tones of various frequency.

So if it wasnt capactive load on the output causing the issue what else could it be?


texts: How to hide selected rats nest lines in Altium?

texts:
When you first start to place your components on the PCB all of the rat nest lines are total chaos.

When I use Eagle I like to hide selected rat nest lines (namely VCC and GND) as these will generally connect to an internal power plane or polygon pour. This de-clutters the rat nest lines and allows me to then focus on the general inter-component connections.

How do I hide selected rat nest lines in Altium PCB?

Note: This question is similar to this one but I only want to hide selected rat nest lines, not all of them.


texts:
As the title says, I just can't figure this one out.

I started with the initial function: f(x,y,z) = (x'yz) + (xy'z') + (xyz') + (xyz) and I have simplified it all the way down to this:

f=(xy)+(xz')+(yz).

I found out that the solution was: f=(xz')+(yz)  but I can't see how the (xy) just disappears.


texts:
In LTSpice, measuring a current through passive elements (components) is very straightforward. Now I'd like to measure a current through a neutral wire where no element is connected to it. So can someone tell me how to measure the current through a wire with no element is connected in LTSpice?
Best regards!


texts:
I have a driveway which sometimes gets blocked by cars / people who don’t care or can’t read the sign on the driveway doors saying don’t park here driveway in use.
I am trying to see if there are any distance / range / proximity sensors out there that can detect when an item moves into their field of view and stays there for more than say 10 seconds. (I was thinking distance as if distance is reduced from 10ft to say 5ft something would trigger?)
Like a car parking in front of the driveway. Then from there run some IOT IFTT stuff to run alarms or lights flashing on and off etc. I understand PIR movement sensors but obviously these don’t compensate for when an object moves into the field of view but then doesn’t move after. I have a RPi but don’t want to go to that extent. I am wondering if  anyone has any sensor ideas that could do this without significant outlay! Thanks


texts: Driving a LED in the most energy efficient possible way

texts:
I got into a bit of a challenge with myself, just for the sake of learning something about low power stuff.

I want to build a device that has basically two requirements:

blink an LED every 5-10 seconds with a microcontroller
last the longest time possible on a lithium button cell (something like a CR2032 or smaller)

The input voltage to the system will be ranging from 3 to 1.8 volts, so probably i want to pick a red LED so that the power is above it's Vf until the end. My microcontroller will consume around 10uA when active and 1uA when sleeping. So the LED will probably be the most power hungry component.

Now it comes the question: what's the most energy efficient way to drive it, to get the shortest visible pulse? Putting a resistor in series with the led would mean wasting a lot of power, even half of the power that goes into the LED. A constant current driver would waste as much power as the resistor plus some power to stay on itself.

The only solution that came to my mind until now is to connect the LED directly to the microcontroller and adjust the pulse duration until I can see it blinking. But will this be the most efficient way?

I don't care about simplicity or bom cost, it's a 1-off thing. Even an overkill circuit if it's more energy efficient than the resistor is better for me


texts:
I've been taught that a transformer only works with AC, however I see that in power converters, it is rectified to a DC voltage before going to the transformer. How does that work?

If the rectified AC waveform is now DC, how does it pass through the transformer? Is the rectified signal still good enough for the transformer, because it still has a fluctuating component in it, just not negative anymore?

So for example, if I have a 230V mains (with 10% fluctuation) going into my rectifier, the output DC level will range from 293V to 358V. Is this fluctuation/AC component good enough to pass through the transformer?


texts:
I am new to electrical engineering still so forgive me if I am making a stupid mistake. So I have wired up my 74LS08 AND gate according to this datasheet.

My wiring:

As you can see the LED is on by default despite neither button being pressed. Pressing the buttons does nothing.
It is currently powered by a 5v 1.25amp phone charger plugged into the wall. I have tried switching to a 9v battery and nothing changes.
And after a google search I havnt come up with anything, usually the videos are terrible quality or they are using a different AND gate


texts:
I have made a simulation of voltage divider, and that give me the same value like on this calculator: http://www.ohmslawcalculator.com/voltage-divider-calculator

But when I soldered my board I have measured voltage and It was around 4.5 V, but with that calculator should be around 12 V.

My two resistors have value 2000 Ohm (2 kOhm).

I was want to make 24 V to around 12 V with voltage divider, and then 12 V pass to LM7805 so my Atmega328 will work on 5 V.

Here is my PCB how works, really I'm not sure how is it possible to voltage to be 4.5 V but should be 12 V.


texts:
A firmware style question concerning C.

I have some legacy code I am tidying up. One of the nasty features is global variables being scattered through the source files. I can make a few of them locals, which is fine. However, how to deal with the rest. I favour creating a struct and putting them inside it.

I know that there is theoretically another level of indirection when accessing them, but from a style POV is this better or worse than putting them in files globals.c and/or globals.h?


texts:
I have situation where i need to capture wiegand26 signal. I use it on single twisted pair. But i get a lot of AC noise in UTP cable Cat 6. Shield is not connected anywhere.
The VCC for is from wall AC/DC adapter 12V/1000mA. My tester battery is low so it shows 20V with no load... I guess batteries, but i will check again and change it ASAP :)

I added also 10k ohm resistor to pull signal to ground, but it doesn't. The lines in idle is (or should be) +5V. On data transmit it should be 0V.

This is the setup

Edited: Added supply.

at the Arduino side i get this

I need to lower the trigger level and i would like to ask if this setup would work.
As i understand it should trigger at about ~2.5V?


texts: Atmega168 USART RX Interrupt does not trigger

texts:
I have been trying to get the USART RX interrupt trigger working on my ATmega168A using the tutorial here (updating my registers as per the datasheet): Tutorials

I have setup the system to use a baud of 4800 at a freq of 1MHz (8Mhz internal oscillator div/8), prescale value of 12 came from the microchip datasheet.

Using the normal serial communications (inside my main loop), the system works as expected and echos the transmitted char back to the pc console. I then added the 2 lines at the end of the function USART_Init() which should enable the RX interrupt and the global interrpt but when typing over the same serial connection which worked, noting happens which suggests to me that either its not triggering or theres an error.

I have searched google and the stack overflow for other instances and I havent been able to find anything which matches my issue or the many links i have found suggest doing things which I already have in my code/tried before.

Have I missed something or have I got a fault in something?

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>

#define F_CPU 1000000UL
#define BAUD 4800
#define BAUD_PRESCALE 12

void USART_Transmit( unsigned char data )
{
/* Wait for empty transmit buffer */
while ( !( UCSR0A & (1<<UDRE0)) )
;
/* Put data into buffer, sends the data */
UDR0 = data;
}

unsigned char USART_Receive( void )
{
/* Wait for data to be received */
while ( !(UCSR0A & (1<<RXC0)) )
;
/* Get and return received data from buffer */
return UDR0;
}

void USART_Init( unsigned int ubrr)
{
/*Set baud rate */
UBRR0H = (unsigned char)(ubrr>>8);
UBRR0L = (unsigned char)ubrr;
/* Enable receiver and transmitter */
UCSR0B = (1<<RXEN0)|(1<<TXEN0);
/* Set frame format: 8data, 1stop bit */
UCSR0C = (0<<USBS0)|(1<<UCSZ00)|(1<<UCSZ01);
/*enable RX interrupt */
UCSR0B |= (1 << RXCIE0);
sei();
}

int main(void)
{
USART_Init(BAUD_PRESCALE);
while (1)
{
    //a = USART_Receive();
    //USART_Transmit(a);
    _delay_ms(100);
}
}

ISR(USART_RX_vect, ISR_BLOCK){
char ReceivedByte ;
ReceivedByte = UDR0 ; // Fetch the received byte value into the variable " ByteReceived "
UDR0 = ReceivedByte ; // Echo back the received byte back to the computer

}

I am using ATmel Studio 7 with WinAvr to code, compile and program the chip.


texts: solar PV bypass diode v buck boost v SSR

texts:
I have 20 185W panels in two strings each to a ginlong GCI-2k inverter. The panels are W facing 45deg, between two pitches with some chimneys. The prediction for latitude and moderate shading is 2000kWh but over 9 years I have generated 1450kWh fairly steadily.

From time to time I have thought about solar edge type DC/DC optimizers but the cost (£5,000) isn't justified for payback (£350p.a) as the panels are already 10yo.

Each panel has a bypass diode and the inverters are supposedly intelligently adjusting current draw to maximize power. Will this have the effect of 'automatically' bypassing panels that are shaded (so contributing zero) in order to get full current from the fully lit panels? Or will the shaded panels continue to reduce the current from all the other panels, in which case is it a good idea to make a simple monitoring and switching system to bypass panels?

EDIT - following comments below (thanks). Here are pics of sketches of switching system  and how I thought the issue with the inverter controller might look as a IV graphs  I_had seen the answer to the other question about shunt diodes but the load in that case is a battery with no current control on the solar side (presumably there would be something on the battery). I know the inverters tweak the DC_V/I but I'm not entirely sure how (there is a Voltage/Power curve set up in the inverter but I've not found any info on how it's used)

On my circuit sketches: the idea is to have a box at each panel to allow it to be bypassed (and shorted, does that matter?) using a solid state relay. There is a 3 core control cable to each box with 5V, return to switchable transistors and voltage measuring wire. For every 5 boxes there is a controller box with Raspberry Pi (because I've already done projects networking these with wifi so don't have to learn anything new) Also an A/D converter and power supply running from one of the voltage measuring wires. The relays would all open every now and then to check the voltage.

However there doesn't seem any advantage doing the complicated process if this is effectively already happening. On re-reading the answer in your link I think that is the case but I'm not completely certain.


texts:
I have this below circuit op-amp summing amplifier with its below result:

But in my actual circuit all components are the same except the op-amp.
I am using this op-amp part in my practical circuit :
V1 - 22V
V2 - 1V pk-pk Sine Wave
Output Voltage - 20V
Output Current - 50mA.
Actual Circuit Output Waveform :

Why am I not getting the summed output as in the case of simulation result?


texts: How to identify source and load in AC network?

texts:
If I have a AC network with two black box components connected with each other and I can tap into all voltage and current measurements, how do I determine which component is the source and which is the load.?

In case of DC, I can identify this by looking at the direction of current. In AC, current is alternating, so the information I can obtain is if the network is lagging or leading. Not able to say which block is source or load.


texts: I found in some documents that the creepage and the clearance distance for PCB are calculated according to the value of the tensions Unm and Uni. What does this symboles means ?


texts: Variable is not changing when one button is pressed. (String)

texts:
I couldn't decide whether this belongs in C++ or Arduino. But I guess it belongs here since it's Arduino programming.
Anyways, I'm having a hard time solving this issue. I have 4 buttons, 2 for up/down, 1 for select, and 1 for paging (Switch pages). But the down button is having issues. Here the code:
#include <LiquidCrystal.h>

LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

int buttonApin = 6;
int buttonBpin = 5;
int buttonCpin = 4;
int buttonDpin = 3;

int page = 1;

String option1 = "Option A";
String option2 = "Option B";
String option3 = "Option C";
String option4 = "Option D";

String current = "";
String previous = "";

String arrow = "> ";
String selected = arrow + current;

void layoutMenu() {
  lcd.clear();
  String current = option1;
  String selected = arrow + current;
  String previous = option2;

  lcd.print(selected);
  lcd.setCursor(0, 1);
  lcd.print(previous);
  while (page == 1) {
    if (digitalRead(buttonApin) == LOW) {
      String current = option1;
      String selected = arrow + current;
      String previous = option2;
      lcd.clear();
      lcd.setCursor(0, 0);

      lcd.print(selected);
      lcd.setCursor(0, 1);
      lcd.print(previous);
    }
    if (digitalRead(buttonBpin) == LOW) {
      String current = option2;
      String selected = arrow + current;
      String previous = option1;
      lcd.clear();
      lcd.setCursor(0, 1);

      lcd.print(selected);
      lcd.setCursor(0, 0);
      lcd.print(previous);
    }
    if (digitalRead(buttonCpin) == LOW) {
      Serial.print(current); // it was always OptionA when printed to serial.
      if (current == option1) {
        lcd.clear();
        lcd.setCursor(0, 0);
        lcd.print("Selected A");
      }
      if (current == option2) {
        lcd.clear();
        lcd.setCursor(0, 0);
        lcd.print("Selected B.");
      }
    }
  }
}

void setup() {
  lcd.begin(16, 2);
  lcd.print("   Yanny9000   ");
  Serial.begin(9600);
  pinMode(buttonApin, INPUT_PULLUP);
  pinMode(buttonBpin, INPUT_PULLUP);
  pinMode(buttonCpin, INPUT_PULLUP);
  pinMode(buttonDpin, INPUT_PULLUP);
  delay(5000);
  lcd.clear();
  String current = option1;
  String selected = arrow + current;
  String previous = option2;

  lcd.print(selected);
  lcd.setCursor(0, 1);
  lcd.print(previous);
  layoutMenu();
}

void loop() {
  // Redesigned the menu. No need for loop().
}

Here's the code I'm having problems with:
   if (digitalRead(buttonApin) == LOW) {
      String current = option1;
      String selected = arrow + current;
      String previous = option2;
      lcd.clear();
      lcd.setCursor(0, 0);

      lcd.print(selected);
      lcd.setCursor(0, 1);
      lcd.print(previous);
    }
    if (digitalRead(buttonBpin) == LOW) {
      String current = option2;
      String selected = arrow + current;
      String previous = option1;
      lcd.clear();
      lcd.setCursor(0, 1);

      lcd.print(selected);
      lcd.setCursor(0, 0);
      lcd.print(previous);
    }

A is up, B is down. When the up button is pressed, it selects an option named "Option A" and changes the vars: Current (Which contains the current option selected), Selected (Displays option selected), and Previous (Previous Option).
When B is pressed, it selected an option named "Option B" and changes Selected and Previous.
Issue: Current does not change when B is pressed.
Current is used by C button (Select) to select options. For some odd reason it does not change. I been trying to solve this problem for ages. Can anyone help me? I'm using an mega 2560.


texts: NE555 power controller not working with big motors

texts:
simulate this circuit – Schematic created using CircuitLab

Backstory:

Ok, so I thought that a making a PWM controller would be a fun weekend project, it's been a week now and I still can't make it work properly. The circuit I'm using is from this website.

The problem:

The circuit works perfectly with "small" motors e.g. 12V fans, 9V hobby motors and so on. When I connect a "bigger" motor such as the one from an electric drill or even RC car motors it just doesn't work. I can hear some humming and buzzing comming out of them but they won't even turn.

I've tried changing the frequency to no avail.
I know that the pwm signal works by hooking up leds and fans.
I've tried switching the mosfet for other ones laying around and still nothing.


texts: Buffer amplifier, minimizing PCB footprint

texts:
I have a circuit that needs to pass 22 analog signals through a buffer amplifier before feeding them into an ADC (due to the relatively high impedance on the analog signals). I plan to use non-inverting op-amps in unity gain configuration for this. All signals are under 3.3V and low-frequency.
PCB space is at a premium. General-purpose op-amp ICs use 3 pins per op-amp, but since I know I will be in unity-gain configuration, I am hoping there are some specialized ICs that do what I need and need fewer pins per signal.
Q1: Do you know if there are buffer amplifier ICs that use only 2 pins (total — 1 in and 1 out) per amplified signal? For example, maybe there is an op-amp IC that is internally configured for unity-gain?
Q2: Can you suggest search terms I could drop into a parametric search to look for such things? I'd also take suggestions for specific ICs, because I can work my way backwards from that to a parametric search.
For what it's worth, my prototypes will be hand-assembled, and I am comfortable with soldering SMD IC by hand as long as it's a gull-wing package (down to 0.5mm lead pitch), but a no-leads or a BGA package wouldn't be viable at this time.


texts: Testing a current transformer sensor - I had to reduce input voltage to get lower primary currents. Are my results valid?

texts:
I have a CT current sensor which, according to the datasheet, has a 62\$\Omega\$ burden resistor.

I have logged the output voltage for primary currents from 1mA to 10A. However, to obtain the lower currents I had to reduce the input voltage gradually to 0V since my variable load could not go lower than 200W at 230V.

My question is, does the input voltage matter as long as one is testing with the right primary current values? I need to use the sensor with a power strip connected to the mains. Can I use my test results in that scenario even though they have been obtained at different voltages?


texts: Last batch of PBCs I got from a manufacturer had some silk screen splashes (dots) all over the board ruining the design. I don't have and don't want to have any silk screen on the board. The whole board is covered with solder mask. Is there any way to remove the silk screen without damaging the solder mask?


texts: How to keep heat away from an electronics enclosure?

texts:
I’m converting a simple cooking hot plate to have it’s temperature controlled by an arduino, with an lcd.
It’s metallic casing gets really hot when the plate is turned on.
As I’ll remove the original analog temperature control and use an arduino and thermocouples to control the heat, even I I had space under the heat element, I think it would toast the electronics pcbs  and lcd.
So I’m thinking of using an external enclosure to put the arduino, lcd, rotary dial and sensors connections.
But I want to keep this enclosure attached to the metal frame of the cooking hot plate, not hanging around with cables.
Is there a material to isolate the heat from the metal case from the hot plate to an external attached enclosure, so the circuitry will be in an “acceptable” temperature? Something to be put between the metal frame and the enclosure? Silicone rubber?
I don’t have the enclosure yet. A plastic one would be easier to make holes, but it can be an aluminum one also.
Thanks!
The hot plate is this one attached.


texts: What would happen if I send 220V to my ethernet port?

texts:
I found unused cables at home and I connected them:

This is obviously made as a joke, but I keep wondering what would happen if I were to actually plug both ends in my computer. Is there some safety where I would only toast my network port? Would my computer puff out in an expensive pyrotechnical display? Would the cable melt like butter in the sun? For some reason I am not keen to actually trying it out.
This is in Europe as the plug shows, and in my country the wall outlets can draw up to 16A.


texts: Gnucap: using Vsupply command in batch mode

texts:
I am simulating a circuit with Gnucap, and I'm automating several steps in a Makefile:

all:
        gnetlist power_switch_replacement.sch -s -g spice-sdb -o power_switch_replacement.net
        gnucap -i power_switch_replacement.gnucap

I've created power_switch_replacement.sch with Gschem.  The Makefile generates a net from that and opens it interactively in Gnucap, after running the commands in power_switch_replacement.gnucap:

get power_switch_replacement.net
model BC548 NPN
Vsupply +9v 0 9
list

Unfortunately this doesn't work.  The get, model and list commands run correctly but the Vsupply command fails:

Vsupply +9v 0 9
^ ? what's this?

If I run the command manually (admittedly after a build directive) it works:

gnucap> build
>Vsupply +9v 0 9
>
gnucap> list
<snip>
C1 ( 1 2 )  100.u
Q1 ( 1 4 0 )  BC548 NA( 1.)
Q2 ( 3 2 0 )  BC548 NA( 1.)
R1 ( +9v 1 )  1.K
R2 ( +9v 2 )  1.K
R3 ( +9v 3 )  2.2K
R4 ( 4 3 )  2.2K
.model BC548 npn ( <snip> )
Vsupply ( +9v 0 )  DC  9.

Again I suspect I'm missing something fundamental about the way Gnucap works.  Any help would be greatly appreciated.


texts: Voltage across capacitor in a electrical circuit (LCC circuit)

texts:
My networkanalyses book told me that the voltage across the capacitor C2 is given by:

$$\text{U}_{\text{C}_2}\left(t\right)=\text{U}_{\text{in}}\left(t\right)+\text{C}_1\cdot\text{L}\cdot\text{U}_{\text{in}}''\left(t\right)-\text{L}\cdot\text{I}_{\text{in}}'\left(t\right)$$

Where the network looks like:

And I want to know if it is correct and how they got it?!

MY WORK:

$$\text{I}_{\text{C}_2}\left(t\right)=\text{U}_{\text{C}_2}'\left(t\right)\cdot\text{C}_2=\frac{\text{d}}{\text{d}t}\left(\text{U}_{\text{in}}\left(t\right)-\text{U}_{\text{L}}\left(t\right)\right)\cdot\text{C}_2=$$
$$\frac{\text{d}}{\text{d}t}\left(\text{U}_{\text{in}}\left(t\right)-\text{I}_{\text{L}}'\left(t\right)\cdot\text{L}\right)\cdot\text{C}_2=$$
$$\frac{\text{d}}{\text{d}t}\left(\text{U}_{\text{in}}\left(t\right)-\text{I}_{\text{C}_2}'\left(t\right)\cdot\text{L}\right)\cdot\text{C}_2$$

So, we get:

$$\text{I}_{\text{C}_2}\left(t\right)=\text{U}_{\text{C}_2}'\left(t\right)\cdot\text{C}_2=\left(\text{U}_{\text{in}}'\left(t\right)-\text{I}_{\text{C}_2}''\left(t\right)\cdot\text{L}\right)\cdot\text{C}_2\Longleftrightarrow$$
$$\text{U}_{\text{C}_2}'\left(t\right)=\text{U}_{\text{in}}'\left(t\right)-\text{I}_{\text{C}_2}''\left(t\right)\cdot\text{L}\Longleftrightarrow$$
$$\int\text{U}_{\text{C}_2}'\left(t\right)\space\text{d}t=\int\text{U}_{\text{in}}'\left(t\right)\space\text{d}t-\int\text{I}_{\text{C}_2}''\left(t\right)\cdot\text{L}\space\text{d}t\Longleftrightarrow$$
$$\color{red}{\text{U}_{\text{C}_2}\left(t\right)=\text{U}_{\text{in}}\left(t\right)-\text{I}_{\text{C}_2}'\left(t\right)\cdot\text{L}}$$

And knowing that:

$$\text{I}_{\text{C}_2}\left(t\right)=\text{I}_{\text{in}}\left(t\right)-\text{I}_{\text{C}_1}\left(t\right)=\text{I}_{\text{in}}\left(t\right)-\text{U}_{\text{in}}'\left(t\right)\cdot\text{C}_1$$

We can write the red part:

$$\color{red}{\text{U}_{\text{C}_2}\left(t\right)=\text{U}_{\text{in}}\left(t\right)-\frac{\text{d}}{\text{d}t}\left(\text{I}_{\text{in}}\left(t\right)-\text{U}_{\text{in}}'\left(t\right)\cdot\text{C}_1\right)\cdot\text{L}}=$$
$$\color{red}{\text{U}_{\text{C}_2}\left(t\right)=\text{U}_{\text{in}}\left(t\right)-\left(\text{I}_{\text{in}}'\left(t\right)-\text{U}_{\text{in}}''\left(t\right)\cdot\text{C}_1\right)\cdot\text{L}}$$


texts:
I have the same exact problem as in this question, except that I have an ATmega16 microcontroller. But the answer on that question doesn't solve my problem. ie:

The command: avrdude -c avrisp -p m16 results in the following error message:

avrdude: ser_open(): can't set attributes for device "/dev/ttyS0":
    Inappropriate ioctl for device
avrdude done.  Thank you.

I don't whether to ask the question is right but I badly need an answer to this problem.

After connecting the device lsusb, I get the following:

Bus 001 Device 018: ID 16c0:05dc VOTI shared ID for use with libusb


texts:
I am trying to control a lamp powered by AC current from my wall outlet. To control the lamp I am trying to use a 5 V microcontroller, Arduino to be exact.

My two questions are:

Is there a way to use a FET to achieve this? If so, how?
What type of FET would be the best to do this?


texts:
Here is an amp that is going into protection mode:

The two (correct me if i'm wrong) voltage regulators circled in red appear to be burnt.

Up close image of the voltage regulators:

I believe that simply replacing these components may have a chance in fixing the amp. Unfortunately, I am not sure which voltage regulators I need to buy, when I look up "KIA 7815A PI 437" and "KIA 7915PI 449" I find similar components but with a different 3-digit ending. Are these digits important, or should I make sure that I am looking for  "KIA 7815A PI XXX" and "KIA 7915PI XXX"?


texts: Need a solution to sent i2c data long distance (prefereably convert to CAN)

texts: Is there any IC available that can read I2C data from a sensor and convert to CAN. I was looking for a low-cost solution to reading i2c data and putting it on a CAN bus. Reading i2c with a microcontroller and converting to CAN would be an option, but the cost is the primary factor.


texts: Tips and sequence to troubleshooting ICs on PCB

texts:
I have PCB that has a pretty sophisticated IC on it (Ethernet switch). Some of the boards work fine but some do not. The reason is that IC doesn't seem to work. There is even no clock on clocking inputs from the crystal and I think that it means that the IC is damaged. My questions are:

Are there some tips how to debug ICs on the PCB, I mean check if the IC is operational or damaged.
What can cause IC damage on the PCB, can it only be electrostatic discharge or maybe there are some common mistakes in the PCB design.
There matter is that I have a pretty big amount of that PCBs (~20) and half of them are not operational because the IC doesn't seem to work and I want to find the cause but don't no how...


texts: I want to find out how many Nios processors are on the board that I am linked with using JTAG, how to do this?

texts: I just want to test how many Nios II exist inside the Qsys system and if they are in reset or executing code. Can this be done via the Nios II terminal?


texts: Is it possible to make a power auto-selector (ORing) with just a Diode and Mosfet?

texts:
I know there are ways to create a simple auto-selector using a mosfet and op-amp, or even simpler using just Diodes, but is it possible to have this work:

The mosfet is P-Channel so floating gate will flow the battery current while high will (or should) stop it. The Diode should prevent the 3v battery voltage from oscillating the gate open and shut when the USB cable is not plugged in. In other words when the USB cable is plugged in, 5v will suddenly flow to the gate which will stop the battery supply but allow the 5v through the diode to go to the main VCC line.

The battery is 3.7v (LiPo) and USB is 5v as expected. I realize this is a perfect candidate for just using ORing Diodes but I'm trying to understand why this technique would (or would not) work. In that light please be explicit as possible in your explanations (I am not a university educated EE so my theory is not great).

[Edit] Corrected "N-Channel" to "P-Channel" as schematic shows and was intended.
[Edit] Changed image to reflect LiPo voltage (3.7v, not 3.3v).


texts: Dim LED lamp with constant current power supply using resistors

texts:
I own a really bright led lamp that I want to dim. It is powered by a constant current power supply that can supply 37mA between 11V to 17V. If my lamp is connected the voltage settles at 13.58V.

Please note, that there are more than four LEDs in unknown wiring in this lamp. I only drew four of them as illustration.

With a bench powersupply I determined, my desired brightness is reached at 1mA where the voltage drops to approximately 12.7V. To limit the current to 1mA while still using the constant current source I've added a parallel resistor like this:

For some reason this wont work. The voltage drops to 2.7V, the current on the branch with the resistor is 7.28mA, and the current on the branch with the led lamp is immeasurably small.

Is there something I'm missing? Or is there another possibility to dim the LEDs besides PWM? I thought abouth changing the sense resistor of the power supply but I don't really want to mess with the power supply.


texts: Stepper motor holding/cogging torque ratio

texts:
I need a stepper that has the highest possible holding torque (when power is on) and smallest possible cogging/detent torque (when power is off). This goes back to the holding/cogging ratio - is there a general rule on this ratio or does it differ on a product by product basis?

My application is on a vehicle with dual mode Ackermann steering where I need possibly high torque for automated mode (steering by electronics without human intervention) and I need small cogging torque when in manual mode (steering by hand - the stepper should not have much mechanical resistance so that the steering is not made much harder - ideally zero resistance).

Regarding mechanical solution - because of simplicity the plan is to have a something like a "single stage gear reducer" where there is a big gear on the steering column which directly touches a small gear on the stepper thus giving the stepper quite some power to turn the steering.


texts:
I have a question that has really been eating up my mind since High School on Ac current and voltages,
If its really true and i know it is that Ac current terminals keep alternating at a rate of 50 Hz per sec as in the case of my country.
 Why do we have one constant positive terminal that keeps lighting up a tester and can even  shock you?


texts: How to maximize inductance of a homemade coil?

texts: So how can one maximize inductance of a homemade coil made out of copper wire? I assume adding a ferromagnetic core to the coil increases inductance? Also how can we calculate this  inductance roughly?


texts:
I have designed printed circuit board for a project that requires a (logic-level) MOSFet controlled directly by an AVR micro at 5 volts feeding a step-up transformer. The boards have already been completed. I had originally used a MOSFet I stole off a reference board and tried to source it from a Chinese factory. This was my mistake as I can not source this MOSFet any more. I've been trying to find a drop in replacement from Mouser. I think I may have found one but I want to be sure.

Update:
Looking through some stuff, I'm feeling comfortable with the second replacement part I posted (The BUK9880) I also read in the data sheet the minimum and maximum gate voltages were between 1 to 2 volts. So I chose to change the voltage divider values to 10K ohm for R15 and 5.1K ohm for R16. I have yet to do any testing on the board, I just got it soldered up. Can anyone confirm if running this without a Piezo element attached would release the magic smoke from the MOSFET or the coil? and if so, why and also how can I put a dummy load on it to test?

This is the original part PA110BDA Datasheet PDF

This is the new part that I think might work NCV8403BDTRKG Datasheet PDF

EDIT: I've been made aware that the replacement I originally choose may not be able to handle to switching frequency needed. I looked again and this is the closest thing I could find in the required package type.
BUK9880-55A Datasheet

This is the way the board is designed; (NOTE: R17 is actually a 330uH inductor, I used the wrong component in the schematic.)

The circuit uses a PWM signal from the AVR to drive an ultra sonic transducer at around 113khz with a supply voltage of no more then 5 volts. current draw is negligible at less the 600ma but I'm sticking to the reference design used for the driver with similar MOSFet values.


texts: Return Loss \$ (S_{11}) \$ Equation for a nth-order Butterworth Filter

texts:
I need a closed form equation for the return loss \$ ~S_{11}~\$ of an n-th order Butterworth low-pass prototype filter.

I am designing a high power RF (lumped element) n-th order Butterworth bandpass filter for the transmitter side, so will be transforming the return loss equation for the low-pass prototype to a bandpass filter. I have the equations for the transfer function and for the insertion loss, but not the return loss.

Also, if someone can provide me with a reference text or handbook for this type of question, I'd much appreciate it.

I did check the first 7 suggested posts, but this question has not been answered before.

\$ Z_{source} = Z_{load} \$, in this case, 50 Ω


texts:
I have a NRF24L01 model with an included screw-on antenna and apparently also an integrated RF amplifier (something like this, image sourced from eBay seller top_electronic1980). I have a lot of interference where I want to use this chip, and therefore my range with this is not more than a few meters, and even less if there are obstacles such as walls.

How are my chances to modify this device to output drastically more power? It does not need to be portable, so power consumption is not an issue. Also, it can use a highly directional antenna as I want to reach a specific receiver device that I know the approximate location of. I know it operates in the 2.4 GHz frequency band, so maybe something like the WiFi cantenna?

Thank you for your help!


texts: Radio waves reception through USB device

texts:
What do you have to do to receive radio waves, not only radio broadcast, but analyze what radio waves are around me, just using a computer, and some USB devide + antenna?

I suppose getting wifi through an USB adapter is not much different than this scenario. It would be nice to have a USB RF spectrum analyzer. Or a USB cell-phone.


texts:
I am using the tp4056 module with protection to charge NCR18650 li-ion battery.
is it OK to connect to the load to the battery while it is charging?

I am using a booster to boost 3.7V to 9V(load voltage 9V) and load current is around 100mA


texts: Does changing the Resistor from button debouncing reference design require a cap change?

texts:
I have a board design using the STM32F411 chip. I have setup the wakeup button circuit as per the Reference Design on the Eval Board.

The value of the Capacitor is 0.1uF.

I need to change the 220K Resistor (R194) to a 5.1K Resistor and am wondering if I need to change the Cap (C92) from 0.1 uF to a higher value as well for debouncing to the same degree.

I have tried to do this by changing to a 4.7uF Capacitor, and simulations before and after the change.

In practice:
220K + 0.1uF : No debouncing issues
5.1K + 0.1uF : No debouncing issues
220K + 4.7uF : Debouncing insufficient
5.1K + 4.7uf : Debouncing insufficient

If anyone has any clues as to why a Cap change is not needed or why my change is not behaving as expected, I would appreciate the help.


texts: I'm currently working on a project of mine and I've hit a roadblock concerning programming the 8051 microcontroller in C. I have never dealt with embedded programming before so some of the syntax is a little confusing to me. Essentially what I'm trying to do is to take the byte of data coming in from the ADC port shown and transmit that serially to a transceiver (not shown or important right now). First I should ask, is this possible? Most explanations I see just deal with the Rx and Tx ports that assume data is already coming in serially, but as you can see, I will not need the Rx port. Where should I start? I'm sorry if this is really simple, I am very new to this side of EE.


texts: Why does STM32 use a two-stage initialization process? What is the primary purpose of each stage?

texts:
I'm learning to use STM32 microcontrollers using CubeMX to generate a project. I've noticed that CubeMX generates two basic stages of initialization for nearly every peripheral:

(A) Within the stm32fxxxx_hap_msp.c file, it defines a number of callbacks of the form HAL_XXX_MspInit().

(B) Within main.c, it defines a number of functions of the form MX_XXX_Init().

Sometimes a given peripheral's HAL_XYZ_Init() function is called from within (A) as it is with the ADC and RTC. Other times a given peripheral's HAL_XYZ_Init() function is called from within (B) as it is done with GPIO.

Both sets of functions call __HAL_RCC_xxxx macros extensively.

I can't make heads or tails of the usage pattern and neither the HAL guide nor reference manual give much direction here.

So, questions:

I suspect that the callback format provided by (A) has something to do with the uC waking from low-power modes, but I am not positive about this. Is this correct, or what is the purpose of the HAL_XXX_MspInit callback format?
I noticed that (A) contains more user-definition block comments indicating room for my code to cohabit the functions generated by CubeMX. But why, for instance, would it be wrong to move code from (B) into the space of (A) in order to keep my initialization sequence clear and easy to read?


texts: In this link it explains how to calculate bootstrap capacitor for IC Mosfet Driver. In the Vboot formula as shown there is Vgsmin (minimum gate source voltage). Is Vgsmin the same as Vgs or not? Before it, i used mosfet IRF3205 and IC Driver Mosfet IR2103 and Diode FR207.


texts: Why are caps configured this way in EMC filters?

texts:
Every EMC filter I've seen has capacitors between the AC lines and earth, configured like this:

simulate this circuit – Schematic created using CircuitLab

Why are the caps not configured like this?

simulate this circuit

What is the advantage of having the extra cap from neutral to ground? It seems like it would reduce the capacitance to ground, and thus the effectiveness of the filter. Is it a safety issue, in case the capacitors fail short? But isn't avoiding that the point of using Y-rated capacitors?


texts: i know how a relay works, my question is this. i have a load that needs to be turned off and on remotely. The piece of equipment is 220volts at 30 amps. is there such a thing as being able to use a small, low voltage  of 12 or 24vac or dc to actuate the relay? It sounds simple, and what relays are for, but i can't find relays on line that can do that. this is in a commercial building application. thank you.


texts:
I'm trying to build a guitar pedal switcher (efectively a box that provides multiple effect loops that can be independently bypassed from a single microprocessor) and while building a working breadboard prototype for a single loop, I've encountered some grounding issues which made me rethink my approach.

Now, I'm not exactly the EE, so grounding is a topic I don't grasp so well. Question is: do I need to route the audio ground as well, or should I just route the audio signal and link all grounds together?


texts: Help with SPICE parameter (in)dependence and real transistors

texts: I am simulating an IC off a manufactures datasheet schematic using suggested integrated BJT Spice parameter values from a textbook. The simulation works well BUT i need to increase storage time and that requires over a magnitude increase in TR from the original value. Even though the simulation seems to work, how physically realistic is this bjt given that all the other spice parameters remain the same. Would other parameters need to be adjusted besides TR so the bjt model would match something in the real world?


texts: What happens in real and how is it modelled when electric and magnetic fields couple to this simplified circuit?

texts:
I’m trying to make the question clear by simplifying a single ended circuit as a constant voltage source is coupled to a measuring device such as a scope or an ADC ac below:

The source V1 above has an output resistance Rs we can vary. And the source is coupled to a measuring unit which has 100Meg input resistance. And as in the drawing the wires form a rectangle  |ABDC|. I also draw x y z coordinates where x is horizontal axis of rectangle y is the vertical axis and z is the axis going out of screen which penetrates the rectangle loop.

Now It I assume there is 60Hz magnetic and electric fields around this circuit.

1- If we only focus on magnetic field’s effect on this can we say the following?

According to Faraday’s law, the varying magnetic field component through |ABDC| (along with z axis) will induce voltage across the loop. Can we say that the more Rs is increased the more the 60Hz noise will be observed at B? How can we model this coupling as a lumped circuit element? A series 60Hz voltage source?

2- If we only focus on electric field’s effect,  regarding Maxwell equations what is the 60Hz electric field’s path which induces 60Hz displacement current through the circuit? Is it the electric field looping through |ABDC|? (x an y axis). And how is this type of coupling modelled? Will increasing Rs increase the 60Hz current?


texts:
We are as a team with four members intending to design an augmented reality oriented smart glass which shall contain a CMOS camera, wireless communication and transparent screen. The algorithm below as flow diagram.

simulate this circuit – Schematic created using CircuitLab

The main problem we are having is to find a transparent display fitted into project (2"-2.5 is reasonable for smart glass.) My question is what else can be done instead of transparent display? Are there really fitted displays that we missed?


texts:
Have a high voltage CAP (C4) that was put into a new design.  Supposedly it was chosen with the old design parameters in mind.  But since its inception it continued burning out.  Should we attempt swapping it out for a higher Voltage rated CAP?  It should be noted that the new CAP (C4) is rated for 4 AMPS where as the old was 24 AMPS.

C4 is on the top rail after the inductor chain.


texts: how to design switching regulator in battery operated device?

texts: My device consists of ATMega, GPRS modem and sensors. Modem occasionally hangs and I need to reset it from mcu. The whole system is powered from li-ion battery. I can't find any switching DC-DC converter that would be controlled from the microcontroller, is capable of delivering 3 A current and eats no battery in on-state.


texts: North American standard symbol for ferrite bead?

texts:
Many of the schematics I've seen in reference schematics use an the symbol of an inductor as the symbol for a ferrite bead (makes sense).

But I've also seen other variants of it as well. I don't have the IEEE 315 document, but I know that there are somethings that we do in North America that isn't exactly IEEE standards.

Bonus question: Is there a document or source that lists North American standard symbols ?


texts:
I m making a small RC car and to control it, I m using a HC05 Bluetooth module. My car is rear wheel drive using two dc motors and the front wheels will just turn left or right for navigation. Can the Bluetooth module take more than one command at a time so that I can turn the car while moving as it happens to be in RC car toys found in market? If not, please suggest me on how do I achieve this objective of turning while moving at the same time.
P.S. I am using arduino nano in this project. For navigation, I m using MG995 servo motor.


texts: Where should I place the capacitor in this TL431 + TRIAC crowbar circuit?

texts:
I'm building a replacement power supply for my C64 and want to add some protection against overvoltage. For that purpose, I tried to find a suitable crowbar circuit that would short-circuit the supply if overvoltage is detected.

There is a pretty thorough discussion of different crowbar circuits on this page, which includes the following:

This circuit is originally from the TL431 datasheet from Texas Instruments. The idea is to use the TL431, which is a shunt voltage regulator, as a kind of comparator. If the voltage on its ref input (left) rises above its internal reference voltage of 2.5V, it will start conducting and thereby pull enough current out of the gate of T1 to trigger it.

I understand that much, but the capacitor seems strange to me. It is probably intended to prevent triggering the TRIAC on short spikes, but shouldn't it be better placed parallel to R2 then (filtering the ref input), or at least parallel to R3? As far as I can tell, where it is now it could actually cause the TRIAC to trigger if the supply voltage rises too steeply on power-on.

The datasheet also says:

  Refer to the stability boundary conditions in Figure 16 to determine
  allowable values for C

This refers to the chart of allowable output capacitance values under different conditions, but I don't quite understand why those limits are relevant here or how they apply - after all, we're not using the TL431 in its normal voltage control configuration. Ref doesn't get any feedback at all until the TRIAC shuts everything down, so where is the feedback loop that could become unstable?

Finally, the On Semiconductor datasheet for their version of the TL431 also shows a crowbar example, but without the capacitor.

I guess my question boils down to this: Where should I actually place the capacitor, if at all, and why? And if it should go in the indicated place, how can I figure out which value to use?


texts:
So I'm trying to make a shift register with the 7475 IC /4-BIT BISTABLE LATCHES/.
The problem is that the single latches doesn't seem to switch their states properly.
I'm using this schematic:

        PART OF A 7475
(Set)-----|D1    Q1|------[LED]--|
(Enable)--|C    !Q1|X            |
      |---|GND  VCC|---|         |
      |                |---------|
      |                |
      |-[5.05V supply]-|

The IC uses positive TTL logic.
I'm expecting that the LED will turn on when the 'Enable' and 'Set' inputs go HIGH(+5V on them).
But nothing happens.Instead when 'Set' is LOW, the LED glows slightly and in any other case it's off.  Is the IC burnt up or I'm wiring it wrong?


texts:
So I am trying to get into higher voltage projects, namely I got a bunch of nixie tubes very cheap. I was thinking of making my supply by connecting a 230v -> 9v transformer back to back with a 230v -> 12v transformer, which by my calculations should give me 171 volts of isolated AC, without counting in voltage losses. Is this correct? Then I would rectify it to give me around 170VDC.

Is that correct?

Also can I rectify the 9V AC in the middle and connect it to a common ground to power the logic?


texts: Why do household appliances use DC motors?

texts: Couldn’t appliances like fans also use AC motors? What is the advantage of converting to DC?