texts: Confusion on operation of bipolar differential amp (long tailed pair)

texts:
Let's say there's a basic differential amp constructed with two npn BJTs.
And a current source is working as the tail.

The task I have is to amplify a small AC signal of around 1mV p-p, referenced to ground. Can I just connect this signal to one of the inputs, and ground the other input to observe an amplified differential signal at the outputs?
I was taught that when Vin is smaller than the base-emitter saturation voltage (~0.6V) the BJT is not active. Does that means my small AC signal is not going to work? (need a DC bias?)
I also read that the current source is biasing the circuit by drawing Ie (and therefore Ic). Then the Vbe "becomes" 0.6V consequently.
So at the end of the day, what parameters are needed for a BJT to enter active mode? Is the current source alone correctly biasing the transistors so my 1mV signal is getting correctly amplified?
Any help is greatly appreciated!


texts: Inexpensive programmable RGB LED driver/IC/solution?

texts:
My desire is to have a simple setup with a dial device (ideal would be a 3 click dial with 3 distinct settings but an analog dial would also be appropriate) whereby position 1 would display a color (yellow, for example) and position 2 would display red and positoin 3 would display blue.  The only programming involved would need to set the colors to each position.

I have managed to do this with a very, very pooly crafted arduino but it feels like this is overkill for a simple project.  I also think that it can be made fairly inexpensively with a little knowledge.  I have tried to look up RGB drivers and this seems to be the way to go but there are a lot of choices.  I also looked up a 555 IC timer, which looks like it would be fun to play with but probably not the right choice for this.

If anyone has a direction for my reading, experience, or other pearls of information I would very much appreciate any help.


texts: Synthesisable alternative to the wait statement in VHDL

texts: I'm writing VHDL code for a filter which I want to implement on a Spartan 6 FPGA. When I tried running a testbench for my code, one of the processes entered an infinite loop, so I added a wait statement before the "end process;" statement, but after some research I found that the wait statement is not synthesisable so it is good only for simulation purposes using testbenches. Can anyone suggest an alternative to the wait statement so that my code becomes synthesisable on an FPGA? Thanks in advance!


texts: Can I use a LED power supply for a general purpose

texts:
I have one simple question: can I use a LED power supply for a general purpose, e.g., to supply some logical controllers etc. Are there any limitations of a LED power supply that I'm not aware of?

For example, I would like to buy this power supply to supply a PLC.


texts:
I am trying to get a logo into my PCB design.
I am using Circuit Studio, and have a True Type font with the logo I want as the letter 'a'.

When I use this font elsewhere on my system (ie. word) the logo displays as expected.

When I use the font in CS, It for some reason only displays a portion of the logo (only some of the lettering, not graphic)

The top image is in CS, bottom is same portion in word using the font


texts: Discrete transistors current feedback amplifier topologies

texts:
I wand to design a headphone amplifier based on CFA topology (for some very personal aesthetic reason). There are two basic topologies of its input stage which is technically an V-I amplifier (I-V converter providing voltage gain is usually implemented via two current mirrors "fighting" each other). I want to know why one can be preferred to another. In both cases the design procedure is unclear for me. In particular how to choose resistors' values? I have some clues, but I'm not completely sure.

In case a) \$R1\$ and \$R2\$, I guess, provide some additional Vce room for \$Q3\$ and \$Q4\$.

Case b) should work well (and it does on simulation) without resistors at all. So, I guess, \$R3\$ and \$R4\$ may help to minimize some differences in \$Q5\$ and \$Q6\$ characteristics. But I have no clue how exactly. In case of non zero \$R3\$ and \$R4\$, \$R5\$ and \$R6\$ may serve for biasing purposes.

Shortly speaking, what is the purpose of emitter resistors in both these circuits?

Unfortunately I can't find any article which can explain the procedure. Can you point me to some?


texts: Cannot find SPICE models of audio transistors for LTSpice?

texts:
I need to simulate a circuit with the following transistors:

MPS8050 OR MPS6560

AND

MPS8550 OR MPS6562

But I cannot find any for LTSpice.
http://ltwiki.org/ also doesn't have.

TINA has these components but I don't want to pay.

How can I find these or equivalents for LTspice?


texts: How do I find transconductance from a biased circuit?

texts:
I am new to biasing and have trouble finding the transconductance \$ g_{m1}' \$ for this biased differential amplifier below.

I know that \$ V_{BE} = 0.6\$ V and \$ g_{m1}' = \frac{I_c}{V_T} \$ but that is about it. I also see that 2 pnp BJTs are used for the differential amplifier, if that makes any difference.

How do I calculate \$ g_{m1}' \$ ?


texts: How does a microprocessor operate in sequence?

texts:
I am trying to understand how microprocessors work. I am savvy about full adders and boolean arithmetic and buses and the like, and in fact, I have "built" a full adder before (in a computer simulation).

But as I try to learn more, I always get stuck on this: how does a microprocessor do things in sequence? All of the documentation and videos say "The control unit does this, and then it does this, and then it does this..." but how can it do that? In my full adder, you would set your inputs and it would pump out the answer, and there was no way for it to start doing something else. So what allows microprocessors to carry out several steps?

EDIT: For the people who have the same question...
A processor has states that it operates in which control its behaviour, and these states are defined by what data is stored in it. Certain devices (such as latches or flip-flops) allow the processor to change its state with each clock pulse. I don't understand all the details but I hope this helps.


texts:
I'm looking into NAND Flash memory to use with my AVR MCU (Atmel Tiny85). I am particularly looking at the 8Gb Spansion S34ML08G101TFI200.

I would like to sequentially read the entire contents of the chip, from the first address to the end.

My questions are:

1) Sequential read across entire chip?: Can I toggle RE# to sequentially read data across the whole chip's memory, or do I need to issue "read" commands periodically for new pages/blocks/planes.

2) Power-up read state?: in the data sheet under "Page Read", it says that on power up, the chip is in read mode, and no 00h command is necessary, but is the following 30h command required to start reading? Or can I just begin toggling RE# to start reading from the beginning of the chip memory? (In other words, can I jump into reading without any setup instructions?)

3) Speed requirements?: I've read that since these chips are so fast (25us read time), they are too fast for slower MCUs, but I feel this doesn't make sense since I can poll the chip and toggle RE# whenever I want. Does that sound correct?


texts: Should I use a current injection method or voltage injection method?

texts:
I am currently designing an earth fault detection system for 110V DC transmission line. As you can see in the diagram, I have a long line of monitoring equipment powering these monitors (which I will model using resistors, capacitors and inductors). I am currently designing an earth fault tracer (ie. earthing occurs in one of the parallel branches) for this DC transmission line by injecting a square wave pulse into the system. In order to do this should I be using a constant current source or a constant voltage source?

simulate this circuit – Schematic created using CircuitLab


texts: Is a dedicated bandpass filter chip really neccessary for the BLE antenna of STM32WB?

texts:
I am designing a custom STM32WB board.
Checking the reference boards of STM32WB (Nucleo and Feather board) I noticed a dedicated multilayer ceramic bandpass filter in the matching/tuning network path. However, in my previous BLE designs and designs with different controllers this bandpass filter is not present.

In STM32WB Nucleo this part is used: https://eu.mouser.com/ProductDetail/81-LFB182G45CGFD436

In STM32WB Feather board this part is used: https://eu.mouser.com/ProductDetail/810-DEA162450BT1295A

Here is a reference design for NRF52832 without bandpass filter:

ESP32 designs also do not use a bandpass filter. BTW, I would like to use an SMD chip antenna instead of a PCB antenna. Something like this:
https://eu.mouser.com/ProductDetail/810-ANT168LCS2442MA2

Is this bandpass filter really needed for the operation of the STM32WB?
Is this just a fancy thing which increases the number of components and so the cost of the product?

Probably it is good for EMI, but other designs are living well without this component.


texts: How to design a new board comprised of multiple already designed sub-boards separated by breakable tabs?

texts:
I want to take advantage of the entire 5cmx5cm given to me by places like DirtyPCBs and Elecrow so i want to design multiple separate PCBs on kicad and then combine them onto one board (like shown in the "panelizing" section of this FAQ page) with this type of breakable tab (slots or mouse bites) as shown in this image from DirtyPCBs. I just started to learn how to design boards with kicad and so far all i have designed is a 777 timer LED blinker and a bluetooh module breakout. I ordered these designs already from OSHPark for one and Elecrow for the other but I want to try and combine the completely separate PCBs onto a single one and add the breakable slots.

Is there an easy way to do this with KiCAD? Or on another program? Can i design all the circuits schematics separately and make all their board layouts separate and then import the board layouts into another board layout project to combine and add the slots?

Note that these aren't V-Grooves. These are just parts of the PCB that are meant to be broken away.

EDIT: by "or another program" i mean a third party program that takes the output of kicad pcb modules or even just gerbers and does it. That way i dont have to rework my entire design flow


texts: How can output from a single logic gate/DIP switch supply input for multiple gates?

texts:
I have googled this quite profusely, and can't seem to find a straight answer. I am a consummate newb when it comes to electronics, so please forgive my ignorance.

I am wondering how it is possible to send approx. 5V* to more than one logic gate simultaneously from the single output (1-bit) of a previous gate and/or dip-switch, assuming one was to build the system physically on a breadboard.

I have just figured out in my head and on paper how to make a very basic adder work, with the help of this site.

The problem, if I'm remembering my high school science teacher correctly, is:

The only way to "double-up" a voltage to 10V (to supply 2 gates with 5V "1" each) would be to run the original 5V signal in parallel, rather than splicing/forking (which, I believe, would be in series, not parallel), which would halve it to ~2.5V (not sure on that, just my memory of how electronic systems were explained back then).

For the adder, you have to send the "A-bit #1" to two different gates from a single dip-switch. Can someone please explain (physically and in terms of voltage) how this is possible.  This is not for homework, simply for my own edification/hobby. Thanks in advance for your answers.

If necessary, I can upload my diagrams (on paper).

*Assuming 5V is the "standard" HIGH voltage i.e. "1" for this type of system, as per the article, and that ~0V is LOW voltage, i.e. "0".


texts: Can a PIC32MZ SPI Have Multiple Ports Transmitting at the same time?

texts:
Can a PIC32MZ have multiple SPI ports running at the same time?  If so, how?

The problem is I have two ADS1675s that are 24 bits each with an serial clock maximum of 40MHz.  I need to make 1M readings per second from each so using the same port would go over the time required.


texts: What is the input voltage range for this voltage regulator?

texts:
This regulator is used to obtain a 3V3 output voltage. http://datasheet.elcodis.com/pdf2/78/81/788153/ld1117axx.pdf

What is the acceptable input voltage range for this regulator? I cannot get a clear answer from the datasheet. Would using an DC input of 12V,1.5A be safe?


texts: adjacent voltage sources in nodal analysis

texts:
Suppose you have this circuit:

simulate this circuit – Schematic created using CircuitLab

You need to use nodal analysis to find υ1,υ2,υ3. Would you create a supernode that contains both 10v source and 5i source plus the 6Ω resistor?
If so here's what I have so far:
(let's say that current i goes towards U1 through 2Ω, current I2 leaves U2 towards 4Ω and current I3 leaves U3 through 3Ω). Given that the equations for the supernode are:

i=I2+I3 => U1/2 = U2/4+U3/3 => 6U1 = 3U2+2U3 (Equation 1)

Then from the mesh containing 2Ω,10V and 4Ω we have:

-U1+10+U2=0 (Equation 2)

And from the mesh containing 4Ω,5i and 3Ω we have:

-U2-5i+U3=0 but i=U1/2 so => -U2-((U1)*5/2)+U3=0 =>  -2U2-5U1+U3=0 (Equation 3)

however these don't give me the correct results. The results should be U1=3,043v, U2=-6,956v , U3=0,6522v

Any help would be appreciated!


texts:
I know nothing about transistors except they can be used as simple amplifiers. I do not know which one to use for my project.

A port from arduino would give me volts ranging 0V-5V. I have an external circuit, which consists of a 12V battery and a LED array. The LED array is composed of 4 serially-connected blue LEDs and each rated 3V, 0.25W. How to make a highly efficient transistor circuit, such that the maximum current dropping does not exceed by 2V ?


texts: Any script for detecting PCB size or the trace width/spacing

texts: everytime I place an order on PCB manufacturers (such as PCBWay), I need to fill out the related parameters of my boards - the width, the length, the trace , holes and etc. Has anyone tried to work out a script for detecting PCB size or the trace width/spacing ? Any words would be appreciated.


texts: What is the time derivative at t=0 for a second order low-pass step response?

texts:
For a first order system like an RC filter you have something like
$$y(t)=1-e^{-\frac{t}{\tau}}\\
y'(t)=\frac{1}{\tau}e^{-\frac{t}{\tau}}\\
y'(0)=\frac{1}{\tau}$$

But for a second order system there are 4 different cases. What I'm interested in is y'(0) of any second order low-pass filter in terms of its frequency and damping.

Taking any random image from the web, it can be seen that for all different damping modes, it appears to start slow (low derivative) ad then ramp up. Is y'(0)=0, or some fixed relation like in the first order case? You can't really tell from the graphs, and I've been unable to find any confirmation about what it is.

Doing it the time domain way, you get into pesky situations where some things are imaginary or not, leading to those 4 cases. Is there a way to get a general answer?

Using the frequency approach I did some questionable math to arrive at the following. Taking a generic second order low-pass system
$$H(s)=\frac{\omega^2}{s^2+\frac{\omega}{Q}s+\omega^2}$$
The step response is
$$C(s)=\frac{\omega^2}{s(s^2+\frac{\omega}{Q}s+\omega^2)}$$
Derivative in the time domain is multiplication by s in the frequency domain
$$c'(t) \rightarrow sC(s)=\frac{\omega^2}{s^2+\frac{\omega}{Q}s+\omega^2}$$
Now apply initial value theorem
$$c'(0) = s^2C(\infty)=\frac{s\omega^2}{s^2+\frac{\omega}{Q}s+\omega^2}$$
Apply L'Hôpital's rule
$$c'(0) = s^2C(\infty)=0$$
Does that make sense at all? Can this be seen directly in time domain as well?


texts: I'm generating a 15MHz sinusoidal signal from a Colpitt oscillator that i want to multiply to 90MHz. I'm thinking about doing a triple multiplier and a double multiplier to get the right frequency. What is a fast and easy way to do this using discrete components? I don't have time to purchase any IC's. What non-linear circuit should i use? I read somewhere about using a class C amplifier, and then send it through a band-pass filter to get the desired harmonic frequency, but i can't find any schematic for it.


texts: Relationship between input power and output power of a boost converter and transformer circuit

texts:
simulate this circuit – Schematic created using CircuitLab
I have a few questions regarding variable power supply units powering boost converter circuits with transformers and the relationship between input power and output power.
I have a PSU supplying power to a boost converter (circuit and transformer - as the above simplified schematic) which is converting the input voltage to approx. 20kV, and at the open circuit (no load where the variable resistor is) the PSU is supplying 3.21W.
When I attach a 10M\$ \Omega \$ load across the secondary coil of the transformer (the output, where the variable resistor is) the PSU supply increases to 3.29W. If I then attach a 1M\$ \Omega \$ load the PSU supply increases to 3.41W. The PSU input power increases as I decrease the output load all the way down to about 50\$\Omega\$.
Q1. If I measure the power across the variable resistor can this be related to the PSU input supply? (i.e If at 10M\$ \Omega \$ the power dissipated across the resistor is 0.01W and the PSU is supplying 3.29W. Every time thereafter the PSU supply is 3.29W  can I infer that there is 0.01W dissipating across the load attached to the secondary coil, or the transformer is producing 0.01W power when the input is 3.29W, the transformer and circuit are 0.3% efficient at that PSU input power?)
Q2. If I have a resistor that I don’t know what the resistance is and place it across the secondary coil (where the variable resistor is) and the PSU supply reads 3.26W, can I conclude that the value of that resistor is between Open Circuit and 10M\$ \Omega \$? If I was to measure the PSU supply at different resistances between Open Circuit and 10M\$ \Omega \$ (200M, 100M 50M etc) and find where the PSU reading is the same, could I say that is the resistance of that unknown resistor?
Q3. Is the open circuit power demand of the transformer the lowest it could possibly be or is it possible that the PSU can provide a power lower than the open circuit value (i.e lower than 3.21W open circuit value) if a specific load is attached (inductor, capacitor etc)?


texts: Ways to reduce Vgs range of Logic Level MOSFET

texts:
I try to control two MOSFETs from one microcontroller pin, where one MOSFET shall turn on 400 ms after the first one. The second MOSFET is switching on a relay coil.
My idea was just to use a RC circuit on the Gate of the one to turn on secondly but unfortunately the range of Vgs is to huge to exacty determine the turn on point of the MOSFET.
Can the simple RC and MOSFET circuit be altered, so that the turn on Point can be precisely defined? (+- 50ms)
The goal is a small component count and a robustness against temperature and tolerances.


texts: 2 ground planes vs ground and power plane for 4-layer pcb with many power rails

texts:
I'm creating a 4-layer PCB design that takes a \$12\,\text{V}\$ DC input and converts it into 9 different voltages for various components on the PCB. I understand that a common stackup for 4-layer boards is signal, ground, power, signal. But, given the number of different voltages I have I'm not really sure how to break up my power plane. I could create a localized power plane for each component/set of components taking the same voltage, but this will make routing traces on the back side difficult since I will have to ensure the return current has an unimpeded path. I can do this by avoiding splits in the power plane or by placing a capacitor between the planes along the return current path. With the number of power plane splits I have this will be tricky and easy for me to make a mistake somewhere.

Instead, I'm considering allocating the 3rd layer almost entirely to a 2nd ground plane. This would make ensuring return current paths trivial. To satisfy the power rails, I'm planning to create very small, localized planes for each component. Basically just enough so that the IC power pins and bypass caps can connect to the power rails directly with a via. I would then connect this small plane to a power rail on the back side of the PCB with a ferrite bead. The power rails will then be routed as traces on the back side. This also makes it easy to have signals cross between the front and back layers since all the return current needs is a ground via adjacent to the signal via.

Does this seem like a decent solution to my problem? Are there any better ones? I took a look in Electromagnetic Compatibility Engineering by Ott and in section 16.4.2.2 he mentions this as a fairly effective stackup, which gives me some confidence in it.

As far as I can tell, the main downside to this approach is that I don't get distributed power supply bypassing between PCB layers. However, my 2nd and 3rd layers are much closer to the 1st and 4th layers respectively than to one another so the capacitance between layers should be negligible compared to the lumped capacitance from bypass caps. Any other major downsides?


texts: What Electrostatic Discharge (ESD) protections exist in the gas pumps at gas stations?  I believe that here more than ever even one spark is intolerable.  How can a it be assured that there is never any potential difference between a car and the gas pump that would cause voltage to arc from the gas tank to the pump when inserting the hose?


texts:
Not entirely sure which stack site to post this question to, but I'll give this section a whirl.
I have a question on my homework which reads as follows:

Instruction Set Architecture.
You are designing the instruction set for a new type of computer. The
computer has 64 instructions, 16 general-purpose registers. It supports a
byte-addressable memory of up-to 32MB. Answer the following questions.

a. For a 3-operand ADD instruction that only uses register addressing
mode, how long (number of bits) should the instruction be?

b. For a 2-operand ADD instruction, in which one of the operands is a
memory location with direct addressing mode, how long (number of
bits) should the instruction be?

Without completely giving the answer away, can someone help explain just what the question is exactly asking. I can't seem to grasp the concept.

Thanks again.


texts: How critical is PCB layout for USB Full-Speed?

texts:
I have designed a custom USB hub PCB with a TI TUSB2046(USB Full-Spped hub).
Considering 12Mbps data rate, how critical are the layout constraints for the USB data lines?
I did not follow the exact layout guidelines (had a short stub, slight length mismatch etc, did not use a differential impedance calculator).
The hub gets enumerated on the host PC, but the downstream devices don't. Could the PCB layout have anything to do with this?
Please enlighten, thanks.


texts: What are the tradition ways to signify/advertise that a potentially dangerous long-running test is in progress?

texts:
I frequently need to run long-term tests which have some potential for damage or harm if e.g. someone disturbs the test apparatus without being aware that it's running a test.

Say for example testing an actuator to see how many cycles it can do before failure.

There are two risks I want to avoid:
 1) Harming a bystander who is unaware that the apparatus is performing tests.
 2) Accidentally leaving the premises when a long-running test is executing, creating e.g. a fire hazard when the test is left unattended.

What are the traditional ways of indicating that a potentially-dangerous apparatus is running and should be disabled at the end of the day?

A red light next to the apparatus might be sufficient to indicate that it's operating, but I think that would not prevent someone from setting up a long-running test over the weekend and potentially causing some event over the weekend.

I want to acknowledge in advance that this question is subjective, but I believe it meets the criteria for a constructive, subjective question in the sense that it's relevant to this community and likely to generate useful, constructive answers.

This question (IMO) is a better fit for Electronics rather than SQA since SQA is specifically for software, whereas electronics may include electronic testing.


texts: Can we or should we parallel H-bridge module for increse current?

texts:
Can we parallel H-bridge input and output for increse current?
For specific I select 2 case

L298N (BJT based)
TB6612FNG (Mosfet based)

For L298N as shown in datasheet suggested to parallel chanel to increse current.
For TB6612FNG It have designed dead time.
If we can or we already did it.
The question are

How to ensure it will not short-circuit between chanel?
What about load sharing? if to chanel not share load equally, that means maximun current not twice value of 1 chanel.


texts: Raspberry PI Zero, pushbutton and pullup

texts:
I have a very simple schematic:

GPIO12 -> pushbutton -> R(1.5 Kohm) -> ground

The GPIO12 is set to IN mode and internal pullup resistor is enabled.

With gpio tool from wiringpi package I am trying to detect the falling edge when the button is pressed:

gpio wfi 26 falling ( GPIO12 is numbered as 26 in WiringPi )

For whatever reason that doesn't work.

If I change the wiring in the way:

+5V -> pushbutton -> R(1.5Kohm) -> GPIO12

and configure GPIO12 pin to IN mode and pulldown internal resistor is enabled - everything works as expected, I can detect raising edge just fine.

Am I missing something with my schematics for pullup? Or there's something else involved, that I don't know about?


texts: How to determine the value of termination resistor?

texts: How to determine the value of the termination resistor? Is the termination resistor used to reduce the reflection of the signals and also have to match with the transmission impedance? How am I going to determine the transmission impedance in order to put appropriate value of termination resistor in series with the load?


texts: Calculate battery life when LEDs are different voltage to the battery.

texts:
I'm looking to calculate the battery life in hours with the following setup:

AAA Battery: 1.2v 950mAh
PCB to convert AAA 1.2v to 3.7v
Strip of LEDs. Total 16 leds at .24w each. Total 3.84w at 3.7v

What life would i get from the battery in hours roughly?

Thanks!


texts: How to use this touch screen button in a circuit?

texts:
I have a VCC CTH series touch screen push button, model CTHS15CIC05ONOFF, which I'm trying to use in a circuit to no avail.

As far as I can tell from the datasheet, this is how to wire it:

The LED lights up, but no button presses are detected when I touch the button. I've tried the same wiring set up with a plain push button and it works as expected. I've also tried a variety of resistors from 1kΩ to 100kΩ. What am I doing wrong?

Datasheet: http://www.mouser.com/ds/2/423/VCC_11142016_CTHS15CIC05-1062109.pdf
Product page: http://www.mouser.com/ProductDetail/VCC/CTHS15CIC05ONOFF/?qs=sGAEpiMZZMufv8JNQ5fVHWY5rHfF8YY%252brvRHU%252b5jXA4c%252b8xo7kTh0w%3d%3d


texts: half bridge converter weird primary current waveform

texts: I build up a half bridge converter(as illustated in figure), today I measured current of one of the primary switchs(MOSFET), but something seems weird, while I expecting a triangle current shape, the current is measured as illustrated in graph with blue one, by the way yellow shape is belongs to MOSFET gate signal, current suddenşy rises at the end of gate signal, I don't know whether Transformer saturated or not? parameters when I captured the graph is; input voltage 240V (120V for per capacitor) 0.43Ampers, output voltage 130V with 200 ohm resistive load, efficiency is about %80-85, duty is %50, transformer turns ratio: 1:1.4   Any comment will be appreciated.


texts: How to find the right components for the CAN bus signals merging?

texts:
I have 2 CAN connectors from 2 different devices and I want to design something that takes in both the inputs and gives the output on a single connector. In other words, I want to combine 2 different CAN bus lines to a third CAN bus line. I understand that I would need to use CAN transreceivers and CAN controllers with a microcontroller. From my initial research, it seems like there is hardly any microcontrollers available with a in-built CAN transreceiver. Since I want to build this myself, I am lookig for a quick and easy solution. So I am thinking based on Arduino or Adafruit Feather (both of which I have used in the past). These are the few questions from my side on this :

What are the benefits of using or not using 3 different CAN transreceivers and CAN controllers with a standard micro-controller?
Since there is no logging of data I want to implement, would an RTC be required for this design?
Since I want to use 1 DSUB-9 connector (6xCAN, 1 GND, 1 PWR), would there be an issue to use the same power lines for all three CAN lines?
What are the things to consider while choosing the right libraries for the CAN bus? I have used this library in the past in Arduino and I want to know if there are any worthy alternatives.


texts: how to control peltier element with microcontroller

texts:
I need a little help from experienced people.
I want to control a Peltier element with a microcontroller, with PWM. May?
The peltier element has the following parameters: Imax=8.3 A, Vmax=3.8V.Ok...
I have a 12 volt source for example, and the circuit need to be able to support 8 amps? What circuit can i use to reduce te voltage, And that circuit will support 8 amp  ?


texts:
I know this is probably not the right forum but anyway. I have this old mainboard 01AJ155.
In the picture below you can see it has two PCI x16 connections. One connector is used by my graphis card. I want to solder another PCI x16 connector.
I tried to lookup the datasheet but I could only find this user manual from lenovo: ideacentre Y700–900 Hardware Maintenance Manual. Link: https://content.etilize.com/User-Manual/1037506121.pdf
On p.30 you can see it also states two PCI x16 ports. My question is will this new connector work or is it without function (not connected to anyhting)?


texts: Resistance of an LED in a simple battery-resistor-LED circuit?

texts:
I have a simple circuit arrangement of a 9V battery - 1k Ohm resistor - LED. This circuit has a current of 7.5 mA (measured between the LED and the battery). If there's voltage drop of 2V in the LED, does it mean that my LED has a (2 % 7.5)k Ohm resistance?

Thanks!


texts:
I've been trying to develop an electric guitar tuner using a piezo disk to detect vibration.

I have this design but at the moment the design fluctuates randomly from 0 to 5.09V when it should remain at zero until the piezo is pressed.

The voltage source is a regulated 9V battery which is connected to the rails on my breadboard.

simulate this circuit – Schematic created using CircuitLab

Can anyone explain why this is happening?

Cheers


texts:
anyone have reccomendations for an IC that can be used to access a device with an RS-232 interface from an I2C bus?

Id rather have something that doesnt need programming as I already have a uC master onthe bus that is taking up a good percentage of my time as the main development area of the project.
Howevre I need to get from I2C to SSH and lantronix have what is effectively a RS232 to linux webserver component, about one of the only embedded components that will allow SSH that I have been able to find.

Only prblem is its interface is RS232, which I dont have currently available...

http://www.lantronix.com/device-networking/embedded-device-servers/xport-pro.html

Ta


texts:
Why do we use 3.3 V in circuits? Why not 3 V? Is there a specific standard? Or do we use it because it was 3.3 V from the beginning?
I am just curious to know.


texts:
I have a number of RF PCBs. I would like to test these PCBs, so can someone guide me as to how to test these PCBs. The list of the PCBs that I want to test is mentioned below.

4th order Butterworth filter (Simple passive LC filter)
Power Amplifier (ADL5542)
Logarithmic RF detector (AD8318)
High-speed comparator (TLV3501)

Any idea about what tests that I can do to test them would be really great. Also, I have heard that I can use Network Analyzer to test some of these PCBs. Can someone explain me if its true?

Additional Info:

Their end application involves linking them up for developing a communication system.
Frequency is in the range of 1 GHz for the filter and power amplifier.
RF detector and Comparator operate in the frequency range of 5 MHz.


texts: Why does the frequency of power generation change when there is a change of load on the power grid?

texts:
Back ground : Prime Minister Narendra Modi’s appeal to citizens to switch off lights across India on Sunday to mark the coronavirus fight is generating a lot more work and some tough challenges for India’s power sector workers.

Now it causes a lot of debate about power grid failure and complete black out in India.
News here.

From the above link a small part

  After that, machines shall be withdrawn from the grid through under
  frequency relays graded between 49.90 to 49.70 Hz amongst the units at
  each of the pumped hydro stations.

Now the question is why does the frequency of power generation change when there is a change of load on the power grid? Shouldn't the generators be running independent of the load?


texts:
I want to program at89c2051 chip. I am referring circuit diagram where the optocoupler is used to handle the 2 voltage levels (+12V and +5V).
i didn't understand how Pin A0 and A1 will control the voltage level. Here is the optocoupler circuit


texts: 2xAAA battery => 3.3v/250mA step-up converter with logic-driven power control [superseded]

texts:
EDIT: The requirements in the question below appear to be practically unsolvable, but happily after a bit of digging I actually found an alternative equivalent RS232 device which runs off a 3.7V Li-Po instead of 3.0V AAAs.
Moral of this story: hold off purchasing for as long as you can - it can prove extremely beneficial :)
I've asked a new question for my new set of requirements.

I need to connect a Wi-Fi/RS232 module to a low-powered monitoring device which needs to periodically fire up, "ping" a server, then shut down again. For maximum portability, I'd like to power the Wi-Fi module via the pair of AAA batteries built into the device itself.

This decision was considered viable based on the fact that the device in question is very low-powered and takes just over a month to drain its batteries under normal use, and the fact that the Wi-Fi module will only power on for a few moments at a time and will generally use relatively small amounts of power. I'm very confident that I'll be able to get at least a few days' worth of battery life with the Wi-Fi module attached, and it won't be a problem to put new rechargeables in the unit every so often.

Now, the Wi-Fi module I've selected draws 3.3v at a peak of 250mA, so I need a step-up converter to run it off two AAAs. However:

The converter needs to fit inside a compartment 50x54mm in size, approximately 4-5mm thick. For what it's worth, this area is insulated, so insulation thankfully doesn't need to be taken into account.
The unnecessity of insulation aside, the step-up converter needs to produce virtually zero EMI/RFI due to the electromagnetically sensitive medical environment the device will be used in, which won't tolerate even low levels of continuous EMI/RFI radiation particularly well (although short Wi-Fi bursts will be fine).
I've never dealt with step-up converters before, and I'm unsure what effects the converter's electrical behavior/characteristics might have on the other electronics (a CPU, etc) in my RS232 device. What might I need to consider in this regard?
The Wi-Fi module draws 8mA when idle, which would kill a pair of AAAs fairly quickly. I can control the serial device's DTR line like a GPIO, so it should be possible to set DTR high or low to electrically switch the step-up converter on or off. I have absolutely no idea how to go about this electronically however, although I can say that the RS232 device uses TTL signal levelling, instead of standard RS232 voltage levels.

I must admit that SMD component-based solutions wouldn't work out for me very well; I have passable non-SMD soldering skills, but I've never worked with SMD components, and if possible I would like to build this device myself, preferably successfully.

If an inexpensive premade power converter module exists that meets the above requirements, that would be a very attractive option.

Alternatively, since the adaptor/converter won't be being moved after it is fitted, directly soldering non-SMD components' legs to each other would also be an acceptable solution.


texts:
I have made a few PCB's over the past few months as I have started to learn about design. All of the circuit boards have been Arduino based, so nothing to powerful. I design them up in Eagle and I know this is bad, but I have just used the Auto-router for everything, including the ground and power lines.

My boards have worked fine with this (maybe except for one thing), but I know this is very bad practice. I have been doing some research on ground planes and from what I have read I have not found a reason not to use them on your 2 layer PCB. Should I always add a ground plane to the bottom of my circuit board? When I look at other example boards in Eagle like the Arudino Mega, I notice it does not have a ground plane and I would like to know why someone would not use one. Also, is it okay to run signal wires through your ground plane?

One other question I have is when is it okay to use the Auto-router. From what I found online it should be fine to auto-route signal wires, and that I should manually route ground and power traces. And that these traces should be much thicker than the signal traces.

My last question is about ground loops. I think I have paranoid myself about ground loops and think that they are always gonna happen. As long as I have everything attached to ground on my board (and I only have one common ground), then there should be no issue in having a ground loop correct?

Thank you for the help, I am still very much a beginner with all of this.


texts: Reverse voltage protection: what is the function of C8 in this schematic?

texts:
I am reading about reverse voltage protection and I have found this circuit with its explanation but I do not understand why the capacitor C8 improves the behavior of the circuit when there is a rapid change in input voltage polarity.In adition, Is it really worth adding R2 and C8?

Thanks.

(image source)


texts: Noises generated by OpAmp driving 50 ohm load

texts:
I am trying to drive a 50 ohm with 300mV, 15khz sine wave using an OpAmp. The chip I am using is ADA4610.

However, I found that there are noises of 15kHz(4mV Vpp) and 30kHz(3mV Vpp) at the power rails of the opamp. The noises even influence our DC power supply.

The spurious signals are caused by the output of the OpAmp. And I guess  it may be related with somehow load current, since when the load is disconnected from output of the OpAmp, the spurious signals disappear.

The maximum current used by OpAmp is only 6mA and it influences our power supply already. How to design to reduce the noises greatly? We are expecting high linearity signals without distortion. The noises at 15khz that can be accepted is 40uV.


texts: From my knowledge,checksum can be done using Xor or adding the bytes of the frame...i have to create a communication between ATmega32 microcontroller and matlab to perform some functions...which is the best  for data integrity..Xor or adding the data frame?


texts: How to indentify which PCB revision at runtime?

texts:
I have a board going out into the wild which we know over time will be revised for various reasons including cost, EOL components, reliability etc.

We will also be providing firmware update on an infrequent basis.

What is a good method to allow the MCU / CPU to indentify which hardware revision the consumers baord is at.


texts:
I've been working on a voltage divider circuit that will hopefully allow me to measure voltages between 0-60 kV DC (80 W) as 0-889 volts DC.

The voltage divider section that is used to measure the voltage is circled in red, the rest of the circuit is included to show the other components in the circuit:

The R2 is rated for 65 kV and  60 W (nominal) while the R1 is rated for 17 W (nominal). The multimeter, of course, is able to handle 1000 V nominal (4 kV peak).

My primary concern is with the power ratings of the resistors. Are the resistor power ratings high enough for the circuit?

Also, how much power would be dissipated by the R1 and R2 resistors?


texts: Instrumentation or Differential amplifiers for milliohm measurement circuit design

texts:
I have got a design for milliohm measurement circuit that I have found on YouTube.

Also avaliable in pdf format.

This design uses the INA106U diff amplifiers and I want to replace it with something else less expensive.

I have found a wide range of diff amps. and also a wide range of instrumentation amps, I want to know which is better for this specific application and why?

Also I want to know what is the most important parameter\s that I should look for when choosing the amplifier, like for example should the Input bias current be as low as possible or should it be the offset voltage or maybe the input/output noise I really not sure about those params.

Edit
I want to be able to measure down to  1 milliohm with 0.5 milliohm max. error margin.  Also, ambient temperature  will be fixed and around room temperature(25C).

For the measurement range from 0 ohm up to 10 ohm, For the resistors that I will be using it will be 0.1% and around 25 ppm, For the stability I will zero the instrument every time I use it so I suppose this a short term stability. And lastly, for the power supply, I will go for whatever the components in my hands will require!


texts: Need Clarification on AC to DC Conversion Calculations

texts:
This question from the mechanics.SE site got a bit of an electrical argument going. Basically, dude was asking if it's cheaper to charge a dead car battery or buy a new one. Of course it's cheaper to charge a dead car battery (as long as it can still hold a charge), but the argument started around the proper math for it.

Question: when considering using AC mains to charge a DC battery, which quantity is conserved? The Coulombs or the Joules?


texts: Where did the value of 0.1uF for bypass capacitors come from?

texts: Nearly everyone recommends 0.1uF for bypass capacitors. Why this value? I assume there is no harm to using larger values so is it merely a "sensible minimum"? And if so why do people go for the minimum rather than using higher values - it seems to me you can get higher values at no extra cost.


texts: Use of frequencies in the WiFi channel apart from center frequency

texts:
I understand that there are 14 channels in WiFi band ,each channel designated by  its center frequency,if a WiFi device is transmitting in one channel does it makes use of all frequencies in the channel?For example in channel 1,starting frequency is 2.401Ghz and end frequency is 2.423(center freq-2.412).if it is transmitting only at center frequency,what is the use of other frequencies in channel 1.

Can anyone help me on this?


texts: Pausing sawtooth generator given an input

texts:
I created the following sawtooth generator to go between 5v and 10v. I need a way to keep the output at 5v given a while a certain input signal is high. I've tried various combinations of MOSFETs and diodes to no avail, so I would appreciate any help.

Edit: The input signal will be a 15v signal that is high for a few milliseconds. During this time the sawtooth should jump down to 5v from where it is and then continue ramping up to 10v when the input signal goes low.


texts: How to change -10;10V sine wave to 0;3.3V dor ADC

texts:
I want to build very easy circuit to change -10;10V sine wave to 0;3.3 for ADC in my MCU. I know that I must  reduce the amplitude and change offset.

This circuit would be perfect (Output: 0-3,33V), but I have only 3,3V source (from MCU) and I made another circuit (in which I have output: 0,04-2,83V):

What should I change in second circuit to have output (0-3,3V) like in first circuit? Maybe voltage stabilizer diode or op-amp?
Thanks

For those who would searching the same info to their project:
I chose first circuit from this post.
I changed R11 to 110K and R12 to 22K,
In place of 2V source I put 2V voltage stabilizer (Sanyo LA5002) (between the 3.3V MCU output and R11). And it work great :)


texts: How to specify iCE40 package when using Arachne-PNR

texts:
I am trying to synthesise the picorv32 picosoc for an IceFun board.
So far, I have cloned the HX8Kdemo files, and modified the Makefile and PCF files accordingly.
When I try to run 'make icefun' I get an error:
icefun.pcf:11 fatal error: unknown pin 'A3' on package 'ct256'

Presumably, the problem is that the HX8K demo is designed for the ct256 package, while the IceFun board used the cb132 package.
Question: What do I need to modify to tell the toolchain that I am using the cb132 package? Is this specified in a file somewhere or as a comand line parameter to Arachne-PNR?


texts: xmega serial communication using MAX3232

texts:
Hi I am trying to talk to send a character to the PC using the xmega128a1 and the MAX3232 USART to Serial converter chip. Here is my setup and "send char" function below:

void USARTSetup(){
PORTC.DIRCLR = PIN2_bm;     //Set RxD pin as input
PORTC.DIRSET = PIN3_bm;     //Set TxD pin as output
PORTC.OUTSET = PIN3_bm;     //Set TxD pin high
//The following setup is for a clock of 32MHz
//and a desired baud rate of 19200
USARTD0_BAUDCTRLB = 0xB0;   //set B(scale) to -5
USARTD0_BAUDCTRLA = 0xE5;   //set BSEL to 3301
USARTD0_BAUDCTRLB |= 0x0C;  //set BSEL to 3301
USARTD0_CTRLA = 0x00;       //disable USART interrupts
USARTD0_CTRLB = 0x18;       //enable receive and transmit
USARTD0_CTRLC = 0x03;       //8 data bits, no parity and 1 stop bit
}

void USARTSendByte(UINT8 data){
while(!(USARTD0_STATUS & USART_DREIF_bm));  //wait until DATA buffer is empty
USARTD0_DATA = data;                        //load data
while(!(USARTD0_STATUS & USART_TXCIF_bm));  //wait until transfer complete
USARTD0_STATUS |= USART_TXCIF_bm;           //write 1 to clear bit
}

Debugging seems to hang as soon as it reaches this part of the code:

while(!(USARTD0_STATUS & USART_TXCIF_bm));

And nothing is sent to hyperterminal.

my wiring is as shown below:

As you can see, ive looped the handshaking pins and the CTS/RTS pins.

Can anyone help point me in the right direction? I have no idea why i cannot send a byte to the hyperterminal.


texts: Counting number of bluetooth 4.0 (BLE) devices near me?

texts: Does bluetooth allow you to discover devices around you that are simply on but aren't in any discovery state? I am not trying to pair with all these devices but merely count the number around me and maybe get signal strength information for very basic distance estimation. Essentially lets say I am in a room full of strangers who have their BLE turned on their phones, can I sense that they are on using my phone without them having to do anything? Essentially just notice them and count them?


texts: How to memorize a diode's polarity in symbol? (self-answered)

texts: How to memorize a diode's polarity, such as anode and cathode in symbol?


texts: Toy with non-waterproof battery box: is this an issue? What will happen?

texts:
There is a toy that is intended to be used in water. However, we found out that the battery box (holds 2 AAA's) is not water tight and water leaks into it. Is this an issue? I know that water is conductive.

So, essentially when water leaks in, the batteries are being shorted right?

How dangerous is this? Will it overheat the batteries? How dangerous is this for the user?

Is it going to shock my child to play with this toy in the bathtub?


texts: Connecting two "USB C" hosts, what happens?

texts:
Up until USB C all the USB connectors were carefully chosen so that two hosts could not be plugged into each other.

With USB C both the host and device have the same connector. With this setup it is now possible to plug two hosts into each other. USB C does use an active cable which I assume arbitrates connections preventing any electrical damage.

I assume one of three things could happens.

Nothing at all
An error "don't do this" or something like that
A connection is established with one host submitting as a device to the other host. (seems unlikely)

What happens? Is it one of my propositions or something completely different?


texts:
Some background to what I'm actually trying to do:

I'm working on a project where I need a very smooth motion control at variable, and very low, speeds and I thought induction motors would be well suited for this task. However they seam to be rather expensive to buy compared to other motors so I thought I would try to build my own.

After some looking around some I came across double sided linear induction motors and I got curious if a regular rotor motor would see any benefit from being double sided too. Mainly because I don't want to deal with a squirrel cage, from my understanding they can cause the rotor to "lock up" in certain positions making it run less smooth, especially at very low speeds. So I figured if double sided linear induction motors are better than regular linear induction motors this has to be the case for rotary motors too, right? But I cannot even find a single page about double sided rotary motors.
Does anyone know why double sided induction motors is not a thing?

Also, if anyone has a better suggestion for motors with very smooth speed control I would be very interested to hear about it. It needs to basically be able to be variable down to 0, or "infinitely variable", though a very broad range would probably work too.


texts: disturbances vs variations?in control system?

texts:
I am trying to understand feedback control systems from a text
I have attached a snapshot and highlighted the confusing points, what is the difference between them? especially what is difference between variations and disturbances in a control system?


texts: Short Distance sensitive laser range finder

texts:
I am looking for a reference design for a laser range estimator. I actually don't want to measure the absolute distance but the relative position of the object that is interest. i.e. if it is getting closer or not.

The range of the object is between 50 to 20 cm and object has a movement of a few millimeters and i like to measure this movement using laser. Ultrasound is not an option due to the speed of the object.

Any ideas or pointers?

Thx, Frank.


texts: How do i simplify and calculate the resistance this circuit?

texts:
I am studying this circuit

and I tried to simplify it like so,
I'm confused since there is a wire atop A surrounding the "square" wire. I calculated its maximum resistance as 63.77 ohms. Any help especially how to simplify it is greatly appreciated.
Edit: Thank you for all the responses! It's quite clear that  i still am confused about the topologies of series and parallel, can anyone recommend videos for it so i can understand is better? thank you!


texts: AVR Pin change interrupt: Capacitive Touch Sensor

texts:
I'm reading the book: AVR Programming: Learning to Write Software for Hardware by Elliot Williams. In the Interrupt section of the book, there's a small project to make a Capacitive touch sensor.

Schematics:

/*
   Capacitive touch sensor demo
*/

#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include <avr/power.h>
#include "pinDefines.h"
#include "USART.h"

#define SENSE_TIME   50
#define THRESHOLD    12000

// -------  Global Variables ---------- //
volatile uint16_t chargeCycleCount;

// ------- Functions -------- //

void initPinChangeInterrupt(void) {
  PCICR |= (1 << PCIE1);    /* enable Pin-change interrupts 1 (bank C) */
  PCMSK1 |= (1 << PC1);   /* enable specific interrupt for our pin PC1 */
}

ISR(PCINT1_vect) {
  chargeCycleCount++;                             /* count this change */

  CAP_SENSOR_DDR |= (1 << CAP_SENSOR);                  /* output mode */
  _delay_us(1);                                      /* charging delay */

  CAP_SENSOR_DDR &= ~(1 << CAP_SENSOR);                /* set as input */
  PCIFR |= (1 << PCIF1);             /* clear the pin-change interrupt */
}

int main(void) {
  // -------- Inits --------- //
  clock_prescale_set(clock_div_1);                       /* full speed */
  initUSART();
  printString("==[ Cap Sensor ]==\r\n\r\n");

  LED_DDR = 0xff;
  MCUCR |= (1 << PUD);                          /* disable all pullups */
  CAP_SENSOR_PORT |= (1 << CAP_SENSOR);    /* we can leave output high */

  initPinChangeInterrupt();

  // ------ Event loop ------ //
  while (1) {

    chargeCycleCount = 0;                             /* reset counter */
    CAP_SENSOR_DDR |= (1 << CAP_SENSOR);     /* start with cap charged */
    sei();                            /* start up interrupts, counting */
    _delay_ms(SENSE_TIME);
    cli();                                                     /* done */
    if (chargeCycleCount < THRESHOLD) {
      LED_PORT = 0xff;
    }
    else {
      LED_PORT = 0;
    }
    printWord(chargeCycleCount);                    /* for fine tuning */
    printString("\r\n");

  }                                                  /* End event loop */
  return 0;                            /* This line is never reached */
}

Macros

#define CAP_SENSOR              PC1
#define CAP_SENSOR_PORT         PORTC
#define CAP_SENSOR_PIN          PINC
#define CAP_SENSOR_DDR          DDRC

This is the event loop description of the program:

  The event loop then resets the charge cycle counter, initially charges
  up the capacitor, and then enables interrupts. As soon as the voltage
  on the capacitor drops back down, the ISR will be called, which will
  add one to the counter and then charge the capacitor back up. This
  cycle loops around until the delay is up and the code again disables
  interrupts. Now we can test how many cycles happened during the delay
  time and decide whether a press happened or not.

When reading this description, the first question that came to mind was this: By setting

CAP_SENSOR_DDR |= (1 << CAP_SENSOR);

The capacitor starts charging, but as long as this pin (PC1) is HIGH, the capacitor stays charged, right? So how come it discharges and trigger the pin change interrupt?


texts: Use parallel or series circuit for high power LED strip lights?

texts:
I have a complex strip light installation and am working on the wiring plan. 5 watts per foot x 200 feet = 1000 watts at 24 volts DC which would be about 40 amps.

I have read web sites which give contradictory advice about how to wire LED strips. One web site said that they should be wired in series to guarantee that all LEDs are getting the same amperage. Another said that they should be wired in parallel so that they get the same voltage. Which advice is correct?

Note that I think the strips themselves are internally wired in series, so the question would only apply to the LED strips, not individual LEDs.


texts: Evaluating 741 op amp sensitivity to loading in non-inverting and summing op amp circuits

texts:
I am doing lab preparation but I am not sure how to evaluate 741 amplifier sensitivity to loading based on my non-inverting circuit with a gain of 21 and my summing circuit with a gain of 55.
I know that I should use you find gain for R1 and gain for R2, and then find the ratio of the relative changes. But I am not quite sure how to implement this.

(delta G/G ) / (delta A / A)

note: for non-inverting circuit my R1= 22Kohm, R2= 1.2kohm and for summing circuit R1=82kohm, R2=1.5kohm

Any help will be so very much appreciated.

Summing inverting amplifier:

Non-inverting amplifier:


texts: Electrical properties of LEDs when overdriven

texts:
I've found in a batch of LEDs that they are very variable in the current and/or voltage that they can withstand. Over a period of 24 hours, a proportion will become significantly dimmer, and even slightly change colour. I expect this is because of poor manufacturing.

I would like to quantify the results of such tests so I can determine a voltage/current that for example 99% of specimens can be reliably driven at. However, optical measuring equipment is very expensive, and I am wondering:

Would the electrical characteristics for the partially damaged LEDs change after being overdriven? And if so, what would the changes be?
If electrical characteristics could pre-determine if an LED is more susceptible to blowing?

I am considering plotting forward voltage vs forward current to investigate, (either using an oscilloscope and signal generator, or making some hardware that would facilitate collecting the results for analysis) but statistically quantifying the results would be hard if I don't know what I'm looking for.


texts: Digital 5V signal through a long copper cable with EMI noise

texts:
I'm designing a zigbee switch with additional capabilities in order to give it some flexibility. The main idea is to put this design in the interconection boxes that are in my walls.

So, this PCB will be in a constantly noisy environment because the 220V AC cables around the PCB.

I want to reuse my wall switches rewiring the common to the 5V power supply of the board in order to convert these switches in digital inputs for the microcontroller, so if somebody changes the switch, the microcontroller can read the new status and change the output relay that is controlling the lights, wall plugs or whatever.

The problem is that some wall switches could be around 30 meter from the wall interconection boxes and can be near of power cables with 220V AC.

The power supply of the control electronics is an in-board AC/DC converter whose output is 5V and 3.3V DC and this is the reason the digital signal have to be in that values.

I don't want to change the 2.5mm copper cables that connects the lights with the switches.

Can be reliable this circuit with these characteristics or should I change the design in some point?

I have read in other topics that it can be done with an optocoupler, some capacitors and zener/schotkky diodes but them can change the wires for twisted pair or whatever in their design but this is not my case.

Edit:
Simplified Circuit for clearance:

simulate this circuit – Schematic created using CircuitLab


texts: What is this symbol called? A blue rectangle with a red dot

texts: This is a rectifier circuit in RF Energy Harvesting. I have no idea what does the blue rectangle symbol called. (Found in https://pdfs.semanticscholar.org/d6fe/47f5539a231dfeeef67166977893070788f2.pdf)


texts: How to calculate voltage across capacitor C1?

texts:
If the voltage

\$v_I = \frac{jωC1R3}{1 + jωC1R3}*Vs \$

does that mean the voltage across the capacitor would be equal to \$v_S - v_I\$ ?


texts: Difference between pull up, pull down input high and low current

texts:
I want to ask about the difference between the following when I was reading through a datasheet:

Input high current (pull-up) - Min: /; Max: 20uA
Input high current (pull-down) - Min: /; Max: 500uA
Input low current (pull-down) - Min: -20uA; Max: /
Input low current (pull-up) - Min: -500uA; Max:/

Can someone tell explain the difference between all fours above?.

If the target input high voltage is between 1.7-3.2V, and the voltage source is 3.3V, do I calculate the pull-up resistor value base on the Input high current (pull-up)?


texts: This is a rather noob and potentially silly question. I am planning to allow the user to randomly connect the 8 output pins of the 74HC595 to any of the 8 input pins of the 74HC165 shift out and shift in registers. I am trying recreate a digital Enigma machine. I am wondering if #1 and #2 from http://www.rugged-circuits.com/10-ways-to-destroy-an-arduino/ will allow me to add some extra protection to the input and output pins to the shift registers.


texts: What is the best way to get a receiver in sync with clock? Manchester encoding

texts:
This is my first post here, first off let me know how I go.
I am going to be taking on a new project soon, to design a protocol for communication between two microcontrollers (I understand there is stuff out there but I would like to learn how low level stuff works). At the moment, I am doing some research of encodings and came across Manchester encoding, I understand how the data is sent.
But my current question is how would you get the clocks in sync, there would be a preamble in front  of every message, which would give the receiver some time to detect the clock, but how would I calculate the amount of time between each read. For clarification, there would be no set transfer rate. Maybe I would have to sample the preamble every so often and see if there is a change, but maybe that could fail, if I read in the centre of a high or low.
If it is possible, I would like a detailed explanation on how I could do this, no something vague, but any information would help.
Thank you in advance.
If my question is too vague, please let me know.
EDIT: A solution through software, not hardware


texts:
I need to sense light in 50 different points, but i can only arrange them in parallel because i need to use only 2 wires (this is limited by the application constrains).

I only need to know if any of the 50 points detects light, like 50 inputs with an OR gate. I would be using a micro controller with and ADC connected to a resistor and the 50 LDR in parallel in a voltage divider arrangement.

Could this work?

Resistance changes between 10Kohms to 100kohms between presence and absence of light.


texts: Want my PCB design to work right the first time!

texts:
Just finished a design of a 8-Layer PCB, the highest frequency is 125MHz.

I want this design to work right the first time, how should I revise the design and what should I take care of?

Something like a checklist will be much appreciated :)

Edit #1 : 6 Mar 2012 : Board Received & Tested

I Received the PCB and finished testing it. It's working very good, yes it "Electrically"worked right the first time :D .. But, found 2 Mechanical problems that will be solved in Rev 2.0. Thanks all :)


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I'm going to be using 2 sets of three 12v 9W leds, purchased from that well known auction site so that's all the info I have, as daylight running lights.

Obviously I could simply connect them up (in parallel) and hope, but I'd like each of them to both last AND output very similar (preferably adjustable) levels of light. I'm aware that a cars voltage can rise to as much as 16v so somehow I'd like to protect them from that too.

Can someone simply advise me on what I should be looking for pls? Somewhere in my head I've got constant current as a prompt but TBH I've no real idea what that means or how it works.

Any pointers would be really appreciated.


texts: Will swapping the input terminals on my op amp give me a negative reference voltage?

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I am using an AD8031 op amp which outputs a 1.6V reference voltage with the circuit in the picture. I am powering it using 3.3V. I thought the output would be negative since the feedback is negative.

How can I get a negative voltage output? Will swapping the input terminals accomplish this?


texts: Hardware description language describes our circuit but what does Hardware Verification Language do? How does it verify the design?


texts: How firmware [like BIOS] gets added to hardware

texts:
I am reading about BIOS, which is a piece of non-volatile Firmware. Wikipedia says of firmware:

  Common reasons for updating firmware include fixing bugs or adding features to the device. This may require ROM integrated circuits to be physically replaced, or flash memory to be reprogrammed through a special procedure... Firmware such as the program of an embedded system may be the only program that will run on the system and provide all of its functions.... The BIOS may be "manually" updated by a user, using a small utility program.... proprietary firmware as a security risk, saying that "firmware on your device is the NSA's best friend" and calling firmware "a trojan horse of monumental proportions".

Anyways, not much is said about how the firmware actually gets added or updated, and it all seems like a black box.

I am interested to know in more detail how the BIOS system gets installed on the "system board":

  The BIOS firmware comes pre-installed on a personal computer's system board [wondering how], and it is the first software to run when powered on.... Most BIOS implementations are specifically designed to work with a particular computer or motherboard model, by interfacing with various devices that make up the complementary system chipset. Originally, BIOS firmware was stored in a ROM chip on the PC motherboard. In modern computer systems, the BIOS contents are stored on flash memory so it can be rewritten without removing the chip from the motherboard. This allows easy, end-user updates to the BIOS firmware so new features can be added or bugs can be fixed, but it also creates a possibility for the computer to become infected with BIOS rootkits. Furthermore, a BIOS upgrade that fails can brick the motherboard permanently, unless the system includes some form of backup for this case.

Basically this question is, what actually happens to get the software onto the hardware in this case. In my head I am imaging a laser engraver engraving the software into the metal somehow. That is as much as my knowledge goes, which is probably wrong. So I would like to know how to get it on there, how you install something without even the BIOS system being available to help you bootstrap your hardware.


texts: ESP32 - Touch sensitive pins and magnetic fields

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For a project I plan on using an ESP32 board, to make use of the touch sensitive pins.
The final "touch plates" will be near a magnet that is moving. By near, I mean about 7 cm. It is a 12mm diameter x 20mm length neodymium magnet.
The magnet's movement will be slow, about 2 cm per second.
I have no idea on how those touch sensors work inside.
Will/could the sensor detect touches when the magnet is passing, even if nobody is touching the plates, or is the work principle not affected by magnets?


texts: Not visualizing signal in oscilloscope when a speaker is connected

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Hope you can help me with this, because I really don't understand what is happening.
I have the following electronic circuit.
The Arduino is generating a tone and I am changing the volume with a digital potentiometer.

The problem I found is when I connect an oscilloscope to point A and GND I am able to visualize the signal 720mV  with the oscilloscope. However, when I connect an 8 ohm speaker to the output I have 50mV. I can hear it though,  but I would like to know what could be happening and how to solve it. Shouldn't I have the same voltage value at point A?


texts: Phase shift between pole voltage and line-to-line voltage (3 phase)

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I understand that the pole voltage phase shift is 120degrees for 3 phase and the line to line voltage is equal to the difference in 2 pole voltages. However, how do I work out the phase shift between a pole voltage (say phase a) and the line to line voltage (vab)?

Thank you.


texts: How to get the full range of output voltage (0-5V) from a differential pair circuit as a schmitt trigger?

texts: The circuit works in the hysteresis range of 2.5V - 1.5V. The output voltage does not reach the full range because I have a dc offset of 1.8V. What's the easiest way to get the full output range with this kind of circuit? Adding a capacitor removes dc offset, but I need another gain stage to get the 0-5V output... Thanks


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My application requires me to drop voltage from 12v to 6v or any other lower voltage.

I have used resistors but they are not efficient for prolonged use as they tend to heat up and burn my fuse.
I want to know whether there are any other IC or a simple circuit which 'll be small in size, inexpensive, efficient and does not heat up much to cause problem.


texts: Why were hatched polygons pours used instead of solid pours in the past?

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While reading [David L. Jones]'s PCB Design Tutorial, he mentions that hatched polygon pours are a thing of the past.

  Solid fills are preferred, hatched fills are basically a thing of the past. (Page 8)

I clearly see the advantage of solid pours over hatched pours: overall better thermal and electrical properties.

But then, why were they so common in older electronics?

Actually, I still see them on some relatively new products¹, so I don't know if it has something to do with industrial etching procedures back in the days, or if it has something to do with EMI.

¹ For example, on a cheap phone charger I took apart the other day.


texts: Step-Down convertor. Why does the input voltage go to the output

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At the moment when I insert the USB cable, at the output of the converter, 5 volts appears for a short time. Why is this happening?

Circuit:

Voltage Oscillogram:

BUT! When I connect the ground oscillograph to the board, this effect disappears. The ground of the oscillograph and the computer are connected in an electric outlet.

This effect is a measurement error or an error in the circuit?


texts: Identify This Connector (Polar Bear Water Distiller)

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I am building an automatic water drain for our water distiller. The water distiller is a polar bear 26-D8. The company is basically out of business and is no help.

The distiller has two connectors on it, one for a constant 120V to power the automatic drain circuit and another one that is controlled by a float.

I would like to use the connectors that are there but I don't know what they are and I have been unsuccessful at finding them on google, mouser, digi-key, etc. so I was hoping someone here would recognize them.

Above are two photos and dimensions I measured with a caliper. The only markings that I can see is 7A-125. It seems to be polarized by pin size as one is bigger than the other.

Any help would be greatly appreciated.


texts: Limiting current in an ac op-amp circuit

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I have a simple op-amp circuit (picture) designed to drive a capacitive load (~1nF) with a variable ac voltage up to 40Vpp and variable frequency up to 150kHz. The circuit takes signal from a function generator, amplifies it with a gain of 2, and passes it to the load. The op-amp used is an LTC6090, with rails connected to a (9V in) +24V, -24V DC-DC converter than can supply 21mA.

The circuit works well for the above requirements, but I need to limit its maximum output current to 2mA for safety reasons. The danger is that the user could bypass the capacitive load and get a shock.

I have considered a current sense amplifier interfaced to the output disable pin of the op-amp (difficult with bipolar signals), a 10k resistor in series with the load (limits the frequency by forming a low-pass filter with the load capacitance), a 10k resistor in series with each of the supply rails (spoils op-amp performance and adds noise) and I'm running out of ideas. I've also considered constant-current diodes, but I'm pretty unfamiliar with these and I'm unsure of their limitations in ac circuits (any ideas?!). Also, I can't seem to find any DC-DC converters at these voltages that have small enough maximum currents to limit it inherently.

Does anyone have any ideas for how to limit the current in a neat way, without impacting the voltage and frequency performance of the circuit? Thanks in advance!


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For some reason I need a flexible wire whose cross-section is equilateral triangle with the length of one side is 2mm.

I couldn't find any wire or even material in the market in such shape.

So Im planning to find the closest possible round wire option.

If I would use a triangular cross section's area would be:

sqrt(3)/4 * d^2 where d is the edge length

for d = 2mm

Are becomes 1.732mm^2

So I need to find a cable with around this area.

From the tables I could closest find 15AWG which corresponds 1.6502mm^2

Is my way of thinking correct?

In wire sizing AWG is measure for the entire wire together with its coat or for the copper part only?


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Find x[n]
[]1

this is my solution, however the textbook solution is different and I was wondering what did i did wrong.

this is the textbook solution

Thank you


texts: Replace mechanical switch with electrical switch or relay

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I have a remote controller for a portable heater, and I am working on a small project to be able to control the fan on/off from an arduino with Bluetooh HM-10 module. I thought a solenoid might work by mounting on top of the remote but it doesn't have enough force, I want to remove the mechanical button and figure out a way to control it without the switch but I don't really know what circuit I should use.

Also, there is a 2.3V difference between the two left pads and 0.2V when the switch is pressed on.

Any idea how I could wire this up to arduino via some switch/relay circuit? Any circuit design/schematic would be helpful.

Here are the images of remote and button traces.


texts: Error in simulation of a DC/DC buck converter using LTspice

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I am using LTspice to simulate a buck converter, but I am not getting the expected output voltage and I don't understand why.

The specification is simple: I need to get an output voltage which is half of the input one. This is the circuit I am using in the simulation:

I am using a 100kHz PWM, with a duty rate of 50%, and the value of the inductance was chosen using the lower bound to keep the circuit in CCM (using the formula L > D.(Vin-Vout)/(f.0,2.i), where D is the duty ratio, f is the frequency and I am supposing a 20% oscillation in the load current i).

The result that I obtain from the simulation is:

I don't get the 6.5V that are expected at the output. Is there any conceptual mistake here?

Thank you


texts: What kind of tape is used to hold together electronics during shipping?

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Not so fast! This isn't that kind of tape (Kapton).
By holding electronics together, I mean to hold mechanical parts together for shipping such as flaps and other parts that can flop such as printers and scanners.
It's a very thick material that holds firm but always comes off easily. I've seen it in a variety of colors such as green, red, but most often in blue.
What kind of tape is this?


texts: When driving a Nixie tube with the HV5622 shift register, how hot will the chip get?

texts: I am a beginner in electronics. I am trying to drive the IN-12A Nixie Tube using the HV5622 Shift register. I am trying to calculate the temperature of the HV5622 during normal operation. For each Nixie tube, one cathode is always on. My approximate circuit schematic is shown below. How hot will the HV5622 get?


texts: Monoshot false triggering and latchup problem

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I use a monoshot to extend the duration of a short duration pulse (few microseonds) to 150 milliseconds. The issue is that the monoshot undergoes false triggering in the absence of valid input:

The output of one such monoshot gets latched (Q = High and /Q = Low) and the latch goes away on cycling the power. The output of another monoshot in the same configuration alternates between High and Low from time to time.

I have probed the input of the monoshot with an oscilloscope in falling-edge trigger mode and found that the input is clean, free from spurious inputs.

Power supply is from a DC-DC converter with 5V output. On probing, the max switching noise is 0.2Vpp @ 12kHz. Fairly clean, I feel.

This is the datasheet of the monoshot, which according to the manufacturer is obsolete. I have a few of these lying around, hence using them for a hobby project.

Any ideas on what I might be doing wrong? Thanks!


texts: What is the purpose of a resistor in parallel with a buffer gate?

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I am trying to build and understand the following circuit, it is an interface to load programs to a Commodore-64 using a mobile or mp3 player:

Can you please tell me what is the role of R5? Any reference to where I can read about it would be nice too.
The circuit works fine. Later, I added another not gate just before the output to READ(4), to inverse the output. And it caused the signal to become so weak. I needed to set the volume on the input device to max, to get a useful output. Why? Is that related to not using another resistor in parallel with my added not gate? The reason for the extra not gate I added is that some mobile phones seem to play the file inverted. So the signal should be inverted again. Some apps can do it optionally (like TapDancer, which is an android app to play C64 tape images). I got the idea of adding a jumpered not gate to be used if needed from this article

Edit: It seems that the second question is not related to the parallel resistor, and I need to ask it separately. I posted a new question here

(Circuit source)


texts: Is there a built-in serial number in PIC chip?

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I have tens of PIC16 chips. I would like to retrieve some kind of unique serial number from the chip for identification purposes. I know it can be done manually. But it's tedious.

Questions:

Does PIC has a built-in serial number?
If the answer is No, is there a easy way to upload a code with unique serial number to each chip when I order the chip from Microchip?


texts: Using STM32F4 Discovery I/O PINS attached to another device on the board

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I am trying to communicate with a device over SPI using an STM32F429 Discovery kit.
I would like to use the SPI5 but according to UM1670, table 7 and STM32F429xx Datasheet, table 12, page 76, there is no "Free I/O" available. Pins PF7, PF8, PF9 have as Alternate Function SPI5, but those pins are connected to L3GD20.
I thought that I could just de-assert (i.e. set to "1") the CS (chip select) of L3GD20 (which I do not want to use) that is connected to pin PC1. But according to L3GD20 Datasheet, table 3, page 8, chip select is used for "I2C/SPI mode selection".
Can I use PF7, PF8, PF9 pins or will I interfere with L3GD20? Should I configure PC1 somehow and why?


texts: Method for assigning unique per-board addresses

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We're designing transmitter/receiver boards for an RF remote-control application. To avoid talk between mismatched pairs, we want unique per-board addresses. The address is specified to encoder/decoder chips through 8 address pins.

We'll probably assemble a small batch (about 25) by hand, but will have the PCBs professionally fabricated.

What's your favorite way to do unique per-board addresses in a situation like this? I've pondered DIP switches, jumpers, and cutting/jumpering traces. I'm leaning toward cutting traces, but I'd like to hear what more experienced people typically do.


texts: PCB trace width / via size calculator for intermittent signals

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Somewhat a duplicate of Can a PCB trace support peak currents?

Are there rules of thumb for a PCB designer to compensate the output of via / trace width calculators to account for cases where the trace / via carries no current at all most of the time?

If it's easier to work from an example, let's assume that the circuit carries 20 amps when on, 0 when off, that the relevant part of the electronics is limited to a high-side driver, that the power line enters and exits the PCB via 18AWG wires soldered into properly sized vias, and that the high-side IC is 1/4" away from both of those vias. Power pulses last at most 5 seconds, and I can disable the high-side driver for as long as I want between pulses if needed - but the goal would be to allow at least 3 pulses anywhere in any 5 minutes timeframe. We can also assume that this is a standard 1oz, two layers PCB, in an airtight box, at room temperature.

I've searched for temperature vs time graphs for PCBs and found very little (there's one in figure 18 of this document, but the context is quite different).


texts:
I am trying to repair a nespresso machine(not a job, just for fun) and the PCB had the following switch:

I tried to google it as "switch", "switch 4 pin", "1552", but nothing returned a switch similar to it, not even a datasheet. am I searching it the wrong way?

Thank you


texts: Can I use a Potentiometer to reduce 18vdc to 14.5vdc for a 36W filament?

texts:
Thanks in advance for anyone who can help me with my specific question!

I have many 18v Li-on battery packs (1.5Ah-4Ah) due to the other tools that use this voltage, and I am making a lamp using a specific 12v 36W filament. The spec sheet for the filament states colour temp up to 14.5v input so I know it can take this voltage no problem.

Using P=VA, I know the filament will draw 2.91A and so the resistance of the filament is 4.12 ohms. Hopefully I am correct so far!

I want to reduce the voltage from the battery to 14.5 volts, and have adjustment due to the slight variation of voltage from the battery as it depletes (20v-16v), to enable the colour temp of the filament to stay constant.

What is the best way to do this? Can I use a simple adjustable voltage divider such as a potentiometer, and if so, what rating do I need, 10k, 50k? It's this part that I cannot work out, confused!! Many thanks.


texts: How much current can a solder joint carry?

texts:
I built a PCB to run some stepper motors. In the past I created some PCBs to turn on/off LED lights but that's the first time I will supply a motor. The current will be higher than my previous experiences and it is the first time I need to really think about the track widths therefore I want to make sure some points before going further. My stepper motor is rated 1.5A per phase but I will limit the current to 1A on the A4988 driver (If required I can lower this limit).

As the worst case I assume the motors will be supplied with 2A (2 phases x 1A per phase)
I tried to make the track width for each motor about 1.5 millimetres. I cannot measure them properly in the final product but when I check with a ruler I see each of them are thicker than 1 millimetre.
My search on the web shows that 1 mm track width must be sufficient (if not I am OK to decrease the limit.

My concerns are mostly on the solder joints.

The drivers have pins and I need to solder it onto the PCB. The gap between the pins and the copper on the PCB needs to be filled with solder.
Also I have some small disconnected paths on the PCB. They are small enough to be filled with solder but as I want to be safe I want to connect this paths with jumper cables. However again I believe there will be some solder between copper tracks and the copper wire at some points.

How can I know that the solder joint will be able to handle about 2A? In my opinion the solder will be much thicker than the tracks, even though the conductivity of the solder is about 10% of copper I believe the thickness of the solder will compensate it. However as I am not experienced I just want to confirm this. Could you please give me some guidance?


texts: Disadvantages of MOSFET over Triac for line voltage control of AC/DC devices

texts:
Background:
(Proper galvanic isolation, e.g. opto-isolation, isolation transformer, etc., is assumed for the question)

When working with 110/220AC, switching elements are typically relays (solid state and electro-mechanical) or triacs/thyristors. Doing AC power control requires phase angle detection and zero crossing switching. Less frequently I've seen rectification+MOSFET as a control strategy. A previous question here links an Instructables tutorial which implements a possible DC switching method.

Both share some disadvantages, like any time an AC supply is switched, power factor is affected. Advances in MOSFET technology mean that prices for high-voltage transistors have evened out.

Question:
For loads that are compatible*, what are some reasons against "rectify AC and use a high voltage MOSFET" and favor "triac phase angle control with zero crossing detection"?

*Some AC loads also function on DC: resistive bulbs or heating elements, universal motors, etc. and therefore maintaining AC is not a requirement. Assume higher non-RMS voltage is not an issue.

Side note: I'm analyzing different strategies for controlling heating elements in a SMD reflow oven-style device.


texts: Vacuum tube voltage regulator - capacitor on the output

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I'm thinking about building a tube-based voltage regulator to provide the power for the screen grids of the output tubes.

I have seen multiple designs of this and am currently thinking of doing it this way:

If I place a capacitor (say, 100uF) on the output to help with the peaks, will something bad happen?


texts: 160 ohm circuit with only 100 ohm resistors

texts:
Can anyone please show, or describe how to get 160 ohm resistance out of a circuit with only 100 ohm resistors, maxium of 5 resistors?

I know it is probably a combination of a series and parallel circuit but can't quite figure it out. Bit of a brain teaser I guess.

Thanks for any help.


texts: Implementing Texas Instruments WEBENCH solution for Buck converter into exsisting PCB design

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I have used TI WEBENCH solution for buck converter design. I entered my requirements: input voltage 12 - 15V, output voltage 5V at 1.5A. I have choose TPS563219 which gives me efficiency of 95% and nice BOM cost.

The reason I am using WEBENCH tool is that I am not familiar with buck converter design and the tool gives me PCB design as an output, which is really great. My question is, how to implement that design into my existing PCB? This is example output:

the PCB is much larger that the design requires. May I reduce it?
I need to implement this design into another, bigger PCB. Should I just copy it and merge the ground polygons?
for VOUT, should I just add traces going out of the VOUT polygon and use that trace for powering the system? Does VOUT in that case really need that big polygon?
The back of the PCB, does it require that big ground polygon or it may be populated with other components/traces?
Does VIN also require polygon or it may be connected more closely to the switcher VIN pin(but using thick enough trace, of course)

Thanks!


texts: AVR [ Why IO Registers have IO addresses and SRAM Adresses ]

texts:
I was checking ATMEGA16 datasheet , and at pg17 I found that there is the IO registers that happen to have " IO addresses and SRAM addresses " ,
I don't know which we use and why there is two kinds of addressing for IOs ?
I need to know if it's part of the SRAM or not , Please enlight me ^^


texts:
As shown the answer is 15 Ohm's . I don't get the trick of the question. can anyone explain to me how we can get the value of R

Thank you all!


texts: Can not fine tune Colpitts oscillator with crystal

texts:
I'm trying to design a cheap Video Synth. In order to do it, I need to provide my Arduino Nano with some  external clock so it can drive the Timer that generates the complex video pulses I need. What I wanted was to have the possibility to "move" the horizontal timing in order to sync it to an external video source or not, and also have the possibility to slightly move the H timing for video feedback purposes. For this, I first tried to make a clock with 4046 IC and some caps at 15.625kHz (scanline rate) but it jitters a lot and it's not as precise as I need. So I have the idea to build a basic oscillator with a 4.43MHz crystal with a variable capacitor and a Varactor Diode for using as a timing source of the Arduino Timer, and modify the timing settings in my arduino code because they are calculated right now for 15.625kHz. I saw similar approach like these on other systems and they work. There are some differences thou and that's why I can't do the same thing with my design.

So, the problem: I tried the schematic posted and get the 4.43MHz sine but I can't fine tune it with the variable capacitor. When you move the variable capacitor, the sine changes his amplitude but the frequency does not change. I didn't try the varactor yet because first I wanted to know if the schematic works... I also tried a Pierce design on a TI paper and it makes the same thing or doesn't make any modifications on frequency or amplitude at all. What am I doing wrong? I made some changes in the original schematic because there are some parts I don't have... Those changes are in red.

Thanks in advance!


texts: How is companding different from pre-emphasis and de-emphasis?

texts:
What I know is that interference increases linearly with frequency and thus noise power is concentrated at higher frequency. So, to reduce noise, pre-emphasis and de-emphasis filters are used which works by boosting the input signal before modulation and at receiver, it is deemphasized to original signal and the noise signal is not boosted and eliminated through deeemphasis filter. In this way, a great deal of noise is reduced. So, why companding is introduced then? What companding achieves more than preemphasis-demphasis?

Both emphasis and companding vary the input signal is some way or the other. Preemphasis-deemphasis vary the frequency and companding vary the amplitude range, to be precise dynamic range. But what advantage companding achieves when compared to emphasis?

In this site, it is written that most of the noise is reduced through companding but that can be also achieved through preemphasis-deemphasis. Also, if we see companding as compressing-expansion of signal, isn't the frequncy of signal gets changed? That is principle the emphasis. So, how companding is different from  preemphasis-deemphasis?


texts: How to select gain for an amplifier before ADC?

texts:
The circuit has been simplified as shown in the picture. Signal source is connected with an analog amplifier, which amplifies the ac signal and also raise it by 1.5V to match with the range of the 0-3V ADC. Some characteristics of the circuit:

Signal of interest: 10kHz sine wave with maximum amplitude 8mV
Signal noise density: \$5 \times 10^{-4} V/ \sqrt{Hz}\$
Signal bandwidth: center at 10kHz, width of 200Hz
ADC effective resolution: 9 bit
ADC sampling rate: 96kHz
Calculated ADC quantization noise: \$ 6.8 \times 10^{-6} V/\sqrt{Hz}\$

I want to measure the amplitude of the signal. The ADC cannot be changed. My question is, how to determine the gain of the amplifier?
Under above conditions, the low-resolution of the ADC does not seem to be a problem any more, since it operates at a high frequency. And the analog noises dominate the ADC quantization noise.

The ADC quantization noises will not worsen the SNR, since the analog noises dominate. And the amplifier will not improve SNR either. Could I make the amplifier gain =1, assuming the noises added by the amplifier is negligible?

However, since the signals are very small, I am not sure if the voltages can be detected by the ADC actually. Under this case, how should the gain of the amplifier be designed? Are there any theories behind this? I dont want to amplify the voltage to the full range, since that will lead to addition of several OpAmps and it does not improve SNR at all.

Thank you very much!


texts: Why is my sound level LEDs bar indicator not working?

texts:
I want to amplify a microphone signal and use the output to drive a speaker and an LEDs bar, all works nicely except for the LEDs bar:

simulate this circuit – Schematic created using CircuitLab

The LEDs bar is supposed to change level (number of illuminated LEDs) in accordance with the sound level, but all it does is either light all LEDs at once or none. How do I make it proper reactive to sound like this one on YouTube?


texts: Mosfet behaving differently with other power supply and same voltage

texts:
I have this very basic circuit featuring:

12V LED strip
N-Channel Mosfet BUZ 11
12V Power supply
NodeMCU (ESP8266 wifi dev. board)

I'm trying to use the NodeMCU for dimming or simply turning off the LED strip.

It works just fine, even with PWM (Video, 1.6MB):

But as soon as I use a different 12V power supply (I have tested 3, from old routers and other devices), it doesn't work anymore. The LED usually stays on but on one other power supply it always flickers.

Even more strange the negative pin of the power supplies sometimes seem to work as the gate pin of the MOSFET as when I touch it without a resistor, the light flickers or turns off.

I have tested:

3 different power supplies, it only works on my lab bench power supply
3 different NodeMCU controllers (just in case)
With or without the 10kΩ resistor between the NodeMCU and the Gate
Changing all cables I used
Using a 12V voltage regulator before the MOSFET
Using different MOSFETs (2N7002, IRFZ24NPBF, BS170, BUZ11)

I'm fairly new to electronics as I've always been a "software guy" so it could be that I'm missing something very basic here.


texts: Monopolar DC transmission line: why is the preferred polarity negative and water used return path?

texts:
How and why energized conductor is of negative polarity for Monopolar link in DC transmission.
And how can water be used as return path?
And why negative polarity cause lesser radio interference?

Refer Image given for clear understanding.


texts: How to model two parallel transmission lines with the same load?

texts:
In the picture provided, the first diagram shows the circuit I need to analyse. There is a transmission line, of characteristic impedance 75 ohms.

This is connected to two transmission lines in parallel, each with a load resistance of 75 ohms.

In the mark scheme provided for this problem, they have modelled the whole circuit as a single Transmission line of 75 ohm characteristic impedance, with a load resistance of 37.5 ohms.

I understand how they calculated the load resistance of 37.5 ohms, but I do not understand how they simply got rid of 1 Transmission line.

I would appreciate it if someone could explain this. Thanks!


texts: What happens to the circuit Voltage, Energy?

texts:
I was recently asked this question to calculate the voltage across a capacitor. The problem is described as follows :-

Consider a capacitor "C" connected across a voltage source "V". Once the capacitor is charged fully, it is disconnected from the source. Now this fully charged capacitor is connected across another uncharged capacitor of capacitance "C". Assuming ideal conditions, what are the various parameters of the new circuit. Like the voltage, Equivalent Capacitance, Energy etc. at the equilibrium point?

Note :- Guys this is not a homework or assignment question. This was one of the question that was asked to test my ability in which I failed.


texts: What kinds of short circuit detection circuits are possible?

texts: I'm trying to make a kid-proof breadboard, and for this I'd like to add some kind of system that would first warn that a short circuit is imminent, and then blow a fuse or similar if the warning is ignored. What would be the best way of doing this?


texts: Correct way to simulate and visualize 230V AC voltage in LTSpice IV

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I want to simulate a 230V ac power supply in LTSpice IV. Apparently LTSpice requires to input the voltage amplitude in some special format - e.g. for 230V you have to input 325 as amplitude (at least that's what some credible posts on forums suggest). However, if I simulate such a power source, I get the voltage wave up to 325V, whereas I want the results to be in 230V format.

So, does LTSpice require the AC voltage amplitude in some special format?
If so, how do I get the correct visual plot results?


texts: 12v to 300v Boost Converter - Ideal Inductor for 9kOhm load

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I'm currently working with a MAX1771 chip, the design can maintain a stable voltage up to around 15kOhm and is as follows: 12V to 300V DC-DC Boost : Disregard NMOS and DIDODE Value

The inductor currently being used is a SRN1060-151M, unfourtanately it has a peak current of 1.25A and a saturation current of 1.8A. My guess is that the low saturation and peak current are causing problems with lower loads. I'm rather inexperienced with actually ordering proper parts and mostly ended up getting parts that fit the initial specs (matched values and picked low DC-resistance).

I take it that for a 9kOhm load I would need an inductor that can handle up to 3A. The NMOS is a STD8NM50N which can handle up to 5A and the DIODE is an EGL34G-E3/98GICT-ND.

Can anyone recommend an affordable inductor on DigiKey that can get the job done? Or changes to the circuit that may assist in making the 300V with 9kOhm load possible?

EDIT: 9kOhm load not 3kOhm, my bad.


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I'm calculating the link budget for a rocket communication that reaches 3km altitude.
I'm using HopeRF RFM98W for both ends of the system.

Max RF output: 20dBm
Antenna Gain: 3dBi
3km FSPL at 433MHz: 94,72dB

After the receiver antenna gain we get: 20+3-94,72+3 = -68,72dBm
The RFM98W has a receiver sensitivity of -148dBm. We calculate the link margin:
-68,72-(-148) = 79,28
The link margin seems a little off. In the examples I saw, they get a link margin of around 8dB, and for another RF module I got a link margin of 29,49 dB which seems normal. This module couldn't sometimes connect in a clear line of sight at 500m so I'm curious how I can get a link margin this big.
I think I'm missing the cable RF loss here. I have used this module with an adapter board now I'm switching to custom PCB. I couldn't find any datasheets for the adapter board itself. I would like to calculate cable rf loss due to a 2mm wide 10mm long 0.5mm thick copper wire on a PCB.

datasheet for the module and antenna: rfm98w
antenna


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I'm a beginner at electronics and I'm trying to construct a battery-powered LED lamp which I could turn on and off using an IR remote control. My question is what parts do I need apart from an IR receiver and how do I connect them? I'd like the construction to be as simple as possible.
Thanks in advance ;)


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tl;dr: how to procure a SMD replacement if all i know is the 3R3 marking and sizes (square 6.5mm sides, 2.9mm tall), with no extra information on thermal, etc.
One component on my motherboard fried to the point i can barely read the top markings. It's a large SMD one with only two large pads, so i believe I can replace it with a hand soldering iron.
I have zero experience with SMD stuff and can't really ID it. Looks like a resistor from the rest of the circuitry. 3R3 = 3.3Ω? That is a stock photo and shows top markings 3R3 348 CXD, On my same revision board, both of those are labeled 3R3 518 R06 so I am guessing the last 6 digits are just factory/serial garbage.
That region of the motherboard is clearly the power regulator from the 12-19V input plug. So i guess don't have to worry too much about anything else other than correct resistence value and Thermal capacity i guess, right?