texts: Finding Transfer Function, Poles, Zeros of an RC Circuit

texts:
I'm trying to brush up on some electronics theory and am working through this PDF.

At the bottom of page F-6 there is a problem, F.1, that I am currently trying to solve. The circuit is as follows:

simulate this circuit – Schematic created using CircuitLab

In order to find the transfer function, $$T(s) = \frac{Vo(s)}{Vi(s)}$$

I first obtained the following equivalent circuit:

simulate this circuit

where $$V'i = \frac{Vi*C1}{C1+C2}$$

From this I get the transfer function using the Laplace transform: $$T(s) = \frac{s}{s + \frac{1}{R(C1 + C2)}}$$

At this point I'm not entirely sure if I have done everything correctly so I would like some verification. If this is not correct then please let me know so that I can edit the question showing my math. This should help us narrow down to where the mistake is. I just don't want to post all of the math unless I absolutely need to.

The second part of the question asks if this is a single time constant circuit, which I expect it is because the circuit can be reduced to a single capacitor and a single resistor. The type would be high-pass.

The third part of the question says that for the element values shown, find the poles and zeros. It is clear from the transfer function that there is a zero at s = 0 rad/sec and a pole at $$\frac{1}{R(C1+C2)} = \frac{1}{100k*2*(0.5*10^{-6})} = 10$$ rad/sec.

Are these answers all correct, and are they complete? Have I missed something? I have not done this for some time so I am in dire need of a refresher course.

EDIT:

The last part of the problem asks to sketch the magnitude and phase response Bode plots. I am having some trouble with this part. I have the following for the magnitude:

where plot A is the final gain. Did I do this part correctly? As for the phase, I'm not even sure where to begin. I have that $$Φ = -tan^{-1}(\frac{w}{10})$$ and I believe that the s = 0 term starts us off at +90°, so that would give us a straight line on the plot of degrees vs. rad/sec. I don't know where to go from there. Some assistance on this part would be appreciated. What is the next step (to plot the phase of the pole)? I know the phase would drop but where the drop begins/ends I do not know.

I am happy to provide further clarification wherever necessary.


texts: What is the name, if they exist, of PCB mountable 120 AC outlet connectors?

texts:
I am working on a self device which will plug into the wall, similar to this Wifi extender.

I am having trouble finding a way to attach the AC connectors to my design. I am considering mounting a connector directly on the PCB, something like this example. This one is a bit too large through (the black housing).

Do pieces like the one I am looking for exist? Or what is another way I may consider making the AC outlet connection?


texts: Hot Swappable Battery Circuit with Varying Amperage Demands

texts:
I am designing a UAV that requires a hot-swappable battery circuit. The drone has a peak discharge of 50c at a 6s voltage. In order to increase battery capacity, I intend to use higher capacity batteries with a lower discharge current. A smaller battery with an available discharge of over 50c will be used to supply the system at its maximum amperage draw and when the larger battery is being replaced with a recharged one.
Recap of cuircuit Requirements:

Allows a high capacity low amperage battery (6s max current draw of 40 amps 18000mah) to be hot-swapped
When the UAV is at its maximum current draw, that power comes from the low capacity high discharge
battery (6s max draw of 75c, 2000 mah)
When the high capacity battery is being switched, the UAV remains online powered by the onboard low capacity high discharge battery.
During the majority of the flight (except when at maximum power) the drone drains the large battery pack, leaving the smaller one for emergency backup and hot-swap power.

I have seen circuits like this diode-based one, but I'm unsure how my specific amperage requirement will work. Any circuit guidance or points to existing products would be very helpful.


texts:
I am trying to make 10Mohm of input impedance into a ADC (CS5530). I am planing to use differential input buffer to ADC so I am trying to use TI's document as reference. I tried the one differential in differential out single supply and dual supply. But I am not getting decent signal out of buffer (I am using sinus signal).

Basically I am trying them without ADC putting signal in and look them out with scope. I can't see sine signal out.

I am confused about GND levels I mean I should buffer GND level of signal generator and if it is big from other GND then opamp may broken or may stuck on rail limit. Circuit must consider voltage difference between 2 inputs.

Any suggestion is appreciated about getting 10M input impedance.

Schematic is as follows:

ADC: planing to use CS5530
opamp : LT1013
circuit built on breadboard


texts: 555 Astable Multivibrator Voltage Spikes

texts:
I built a 12V LED dimmer based on (modified from) the circuit below.

Essentially I used a TIP31C instead of the Darlington pair, and provide power to 555 with 7805.

An oscilloscope gave me the waveform with some nasty voltage spikes.

I noticed that a newbie forgot to get capacitors before and after the voltage regulator. Is that the cause of the spikes?


texts:
As far as I could understand, TOA systems, abstractly, work by measuring the time it took the wave to transfer from a transmitter to a receiver and multiplying it by the speed of the wave in the medium.

If the the wave travels at the speed of light ~3 x 108 m/s, the smallest distance can be measured is around 0.3 m if the system smallest measured tick is 1 ns.

So, with a system capable of only measuring nanosecond ticks, the best theoretical resolution that can be achieved is ~0.3 m.

Is my previous conclusion correct? If not, why?

Edit:

Synchronization is beyond my question scope. You may consider that everything is perfectly synchronized.


texts:
I've been trying to interface ADC CS5532 to P89V51RD2. I have reset the ADC, written configuration bits to the configuration registers. I am trying to use the single conversion mode.

However, while reading, I either get a sequence of 24 0s or 24 1s. One thing that does happen is that the overflow bit is set whenever the input is above the reference voltage. This has got me confused very much now. If the ADC is reading the data and is acknowledging the overflow, why won't it give the the value? What seems to be the problem?

Thanks in advance.

I also am not understanding the role of the A0 and A1 latch pins. I'll be trying meanwhile.


texts:
Here is the circuit:

All of the diodes are ideal with Vf = 0. Determine Vx and Ix.

My try: We have 2^6 = 64 combinations of assumptions. My problem is D1 and D2. If we assume D1 and D2 are off then D3 should be on but there is no combination of other diodes such that leads to a valid answer. So we conclude that D1 and D2 both are on and this is meaningless. How two wires without resistance can be in parallel? Also how are we going to find the currents of D1 and D2 to check the validity of our assumption? I'm really baffled about this circuit.


texts: Is it possible to hand crimp a 1mm pitch JST SH connector without a machine?

texts:
This is an offshoot of another question of mine on identifying a particular connector.

When I was talking with sales representative from DigiKey they was mentioned that these crimps are done by machine. Can these be hand crimp these or would it be unusual to do so? I see that it's possible to buy wires pre-crimped in quantity. Is this how these kids of crimps are usually obtained?


texts: Capturing pulse periods by sampling accurately

texts:
Regarding the following statement:

  In order to preserve the integrity of the pulse through a system, it
  is mandatory that the group delay of the system be constant up to the
  maximum frequency component of the pulse.

What is meant by "maximum frequency of the pulse"?

If I sample a f Hz D% duty cycle pulse train coming from a rotating device for instance where each incoming individual pulse period is randomly distributed around f and if I also want to capture each pulse's length(period) with a good accuracy what should be the sampling rate fs? I will capture each rising edges and find the period for each individual pulse by an ADC/DAQ.

If I can quantify the rising time of the pulses of the pulse train by a scope. How can I proceed to decide the sampling rate to have an accurate period of each pulse? Let's say we have a roughly 30 Hz 50% duty cycle pulse train(with each pulse period might be 10% different) but if we measure the rising edge rise time as 1ms. What determines the sampling rate here?


texts: How do I correctly apply KVL in this situation, and why?

texts:
I want to find v1. So I use KVL down the path from v1 to -3V.

I assumed the answer was v1+0.7+-3=0, so v1=2.3

But the actual solution was v1–0.7– - 3=0, so v1=-2.3

Why is this? Is it because the current is going into the voltage source opposite to sign convention? If so, does that mean the -3 terminal at the end should also be treated like a voltage source opposite the sign convention for the purposes of solving? e.g.

So v1 + (-) (+0.7 V) + (-) (-3 V)=0, so v1–0.7+3=0 giving v1=-2.3 ?


texts: Voltage on a disconnected part of the circuit?

texts:
Here's an RTL NAND Gate. I am trying to measure collector-emitter voltages of both transistors when both A and B are grounded. Transistor-A's collector voltage is about 3V. My multimeter reads C-E voltages of both transistors 0. So, my question is: If there's 3 volts on Transistor-A's collector and 0 volts on Transistor-B's emmiter, how come the potential difference of both "3V-TA's Emitter" and "TA's Emitter - 0V" is 0? I assumed an unconnected part's voltage would be 0 so i thought CE-A would be 3 Volts and CE-B would be 0 volts but it's obviously not the case. Also i realized that with some integrated circuits, Not applying a voltage to a pin, 0v or 5v, it acts as if i applied 5v to it anyway.
It may be a noob question but it's been bothering me for some time. Thank you.


texts:
I am learning Altium Designer and I've controling the project with Arch Linux Subversion server. I've made some changes in the project's sheets and when I try to Commit Whole Project, I get following situation:

Now, as we can see, there is unversioned 'PCB_Project1.Dat' file. Is this file mandatory for non-error project import from Subversion or it must be added to version control?


texts:
I'm trying to query the current value of the APB1 clock frequency to input into a USART configuration.  Ideally, I could just query whatever the USART2 clock source is on an STM32F302xx, in case I move to another USART instance that is backed by say, the system clock.

I know what the value is from doing the math, but I want it to be parametrized in case I change clock settings.  What is available in the HAL to call to replace my 36MHz value below?

LL_USART_SetBaudRate(USARTx_INSTANCE, 36000000, LL_USART_OVERSAMPLING_16, 115200);

I don't see any way to inspect what has been set by another part of the sytem, only:

HAL_Driver/Inc/stm32f3xx_hal_rcc.h
811:#define __HAL_RCC_USART2_CLK_ENABLE()   do { \
850:#define __HAL_RCC_USART2_CLK_DISABLE() (RCC->APB1ENR &= ~(RCC_APB1ENR_USART2EN))
953:#define __HAL_RCC_USART2_IS_CLK_ENABLED()  ((RCC->APB1ENR & (RCC_APB1ENR_USART2EN)) != RESET)
962:#define __HAL_RCC_USART2_IS_CLK_DISABLED() ((RCC->APB1ENR & (RCC_APB1ENR_USART2EN)) == RESET)
1024:#define __HAL_RCC_USART2_FORCE_RESET()   (RCC->APB1RSTR |= (RCC_APB1RSTR_USART2RST))
1034:#define __HAL_RCC_USART2_RELEASE_RESET() (RCC->APB1RSTR &= ~(RCC_APB1RSTR_USART2RST))
1337:#define __HAL_RCC_USART2_CONFIG(__USART2CLKSOURCE__) \


texts: What is the distance I can put between a 20watt solar panel and a controller and still have enough current to make it work

texts: I purchased a 20 watt solar panel to be mounted to the hardtop of my boat to charge my batteries. The directions say put the controller within five feet of the batteries and the solar panel can be up to 20 feet from the controller. The wires that came with it we're not 20 ft long. I extended them with 12 gauge stranded wire and used the proper waterproof butt connectors. I do not see either of the lights on the controller lighting up if I move the controller back two within five feet of the solar panel the lights light up as they should I have solid continuity through the splices but the controller lights do not come on when I put the controller back by the batteries. My question to you is can I reverse the connection and leave the controller in the overhead box and run the wires back to the batteries and have the solar panels still perform is proper function.


texts: How current and potential propagate through electrical circuits?

texts:
I have something of a theoretical question. In any given electrical/electronic circuit there seems to be an electric field developed inside (and outside the conductors?) to push the electrons in the circuit.

My question is, how does this electric field has so many different values in different components, I.e different potential values across different components!

How does this electric field propagate and decide which values to take, therefore develop the potential difference?

If there is no potential difference across some elements, perfect conductor, then there's no electric field so what really pushes the electrons? How is process energyless?
I know that J = sigma*E, but my question is how this E gets to be decided?

Is current built up instantaneously in the circuit or it needs time? If it needs time, as I suppose it does, thus means that electrons which are moving will collide with the resting electrons right?

I am an electronic and computer engineering major so these topics are hardly discussed.


texts: Getting error `object has no attribute LAYER_ID_COUNT' in KiCad PCBNEW trying to add track in Python script

texts:
I am trying to programatically add a new track to a KiCad board using the Python API. My code fails when trying to assign the layer to the new track.

My code is modeled off this example...

https://github.com/mmccoo/kicad_mmccoo/blob/master/basics/basics.py#L141

...which builds a dictionary of available layers, and then uses that dictionary to look up the desired layer by name.

Unfortunately the field pcbnew.LAYER_ID_COUNT doe snot seem to exist in the latest version of KiCad (5.1.2). To confirm, I typed the following into the Python command prompt...

import pcbnew
pcbnew.LAYER_ID_COUNT
Traceback (most recent call last):
  File "<input>", line 1, in <module>
AttributeError: 'module' object has no attribute 'LAYER_ID_COUNT'

How can I work around this issue?


texts: My first PCB - How do I run signals off of the board?

texts:
I'm an  amateur 3D printed Robotics maker (youtube.com/PatchBOTS).  I come at this from the 3D printing/engineering side and I'm learning the electronics and coding as I go.  Up till now I've been buying prefab boards and wiring them together or making my own little circuit boards on solderable breadboard/scratch board type pieces.  i'm at a point now where I want to learn how to make my own circuit boards to save space/time/etc.  I have never one this before, but I have a copy of Autodesk Eagle and been following Jeremy Blums tutorials, but I have still run into issues I was hoping you could help with.

I'm making a Star Wars blaster gun.   It has two triggers:
1. Single Shot trigger--> sends ground signal to soundboard pin0, also sends ground signal to base of PNP which activates the LED at the end of the barrel.
2. Multi Shot trigger-->sends ground signal to soundboard pin1,  also sends ground singla to base of PNP which goes to pin8 of a 555 timer which blinks the same LED in sequence with the sound.  This is controlled with a 1k variable resistor.

I want to make a board out of this, but I'm running into some issues.  1.  How do I denote a "pinout"  I basically want through holes at the end of the board  for all the black text in the image.  I'm not sure what to put there for "leaves board here".  2.  How do I add the variable resistor along pins 6,7,8. The 555 timer is out of order and I have no idea how to even add in a variable resistor.
3.  Other than my two problems, can you see anything else wrong with this schematic. I'm very new to this and I'm sure I have something backwards or upside down.   Any help would be appreciated.

EDIT:  I've update the schematic to show the HEADERS recommended by others!  Thank you guys!   What about the variable resistor?  How can I set that up along 3 pins that aren't near each other?

EDIT2:  I think I have the variable resistor figured out.  WI think this is right?  Can anyone see anything jump out at them?


texts: Why do I get a high peak in my FFT plot of a 50 Hz sine wave?

texts:
I am plotting the FFT of my signal that is stored in "Array" format obtained from simulation. The signal is a sine wave of 50 Hz so I get a peak at 50 Hz. The problem is that the value is way too high. What is the problem in my code, can someone see it?

figure
plot(data1(2534947:2898217,1),data1(2534947:2898217,2))

Ydata1 = data1(2534947:2898217,2);
tstart = data1(2534947);
tend = data1(2898217);

t_stop = tend-tstart;

Ts = data1(2534940,1)-data1(2534939,1);
Fs = 1/Ts; % Sampling frequency

t = 0:Ts:t_stop-Ts;

nfft = length(Ydata1); % Length of FFT
nfft2 = 2^nextpow2(nfft); % Make it to the power 2

X = fft(Ydata1,nfft2); % Take FFT
X = X(1:nfft2/2); % FFT is symmetric, throw away second half

mx = abs(X); % Take the magnitude of fft of x
f = (0:nfft2/2-1)*Fs/nfft2;% Frequency vector

figure
plot(f,mx); % Generate plot

The signal:

FFT plot:

EDIT:

I've changed one line of the code, and now it is normalized:

plot(f,mx./(max(abs(X))));


texts: How to recognise electro magnetic mode in patch antenna based on current voltage profile

texts:
In my microstrip antenna of L=lambda/2 shown bellow we have current and voltage profiles based on the fact the edged are open circuit.
What electro magnetic mod is that?
How do i recognise what kind of TM mode is it based on the current voltage profile?
Thanks.


texts: where to connect the GND of my coaxial cable in the PCB

texts:
The following picture explain my problem which is related to how connect point A and B to the GND plane of my PCB. All the components are places in the same PCB

case0

The first option is to connect the shield of the LEMO directly in the connector location and, in the same way, connect the R to GND in the location of its footprint. The distances between this two point is about 15 mm.

In this case the returning current loop of the lemo signal shuld be the shortest; but If i'm not wrong, i cannot compensate the disturbances occuring in the lemo shield.

The next image shows the second option

In this case i think that i can compensate disturbances but the loop is bigger.

Can you help me understanding which one of this solution is the best one? and, even better, if there is another solution which i've not considered?

In addition to this problem there is also the problem that the coaxial cable connect two different PCB each one with its own GND. I gave a reading at the
"Electromagnetic Compatibility Engineering" book which take a look at this problem but i find solution which are difficult to implement in this design (like using choke inductor)

Thanks in advance for you help and your suggestions.

Antonio


texts:
I read some books to understand why we need to memorise bits in electric circuits and found the sequential logic circuits are designed to achieve that goal.

The basic element is the SR Latch which can store one bit of information (0 or 1) and erase it. It is made of two cross-coupled NOR gates, that means many relays.

But we can achieve the same operation of memorising by using one relay: if the switch of the relay is closed the bit (1) is memorised and if it’s opened the bit is erased.

My questions are:

Why we use sequential circuits to memorize bits instead of simple relays?
Can the processor make arithmetic operations without using memory?


texts: Adding Wi-Fi to a TCP/IP application that is already running with Ethernet

texts:
What to do if you have an Ethernet application that is already up and running with TCP/IP functionality and now you want to add Wi-Fi. Most of the Wi-Fi modules available have embedded TCP/IP stacks with some kind of api interface you have to use (i.e. TCP_open(google.com, 80)). This is good if you are starting a fresh application and want to be able to quickly get something simple up and running.

But what if you already have a complex application with TCP/IP stack and you just want it to use Wi-Fi? You want to be able to take the raw Ethernet packets that are coming out of your TCP/IP stack and send them to the Wi-Fi module. I have found a few Wi-Fi modules that allow this "TCP/IP bypass" feature but not many.

To me it doesn't seem like that unique of an application and I wonder why it is not easier to find modules that allow this type of solution.
What are others doing in this situation? i.e. - an existing TCP application where you'd like to "drop in" Wi-Fi


texts: How does a transformer transmit power from the primary to the secondary?

texts:
I'm trying to get my head wrapped around transformer operation and in the process regretting the times I snoozed in my Electromagnetics class as a EE student back when I was a lad :)

I'm looking for an intuitive understanding, but not just an analogous one. I'd like it to be grounded in the actual physics of what's happening. I've found several excellent sources on the web, but they all seem to skirt this question.

I've come across a few interesting hints and am now tantalizingly close,
I think, but still yearning :)

Fact 1: Although varying sinusoidally, the "peak-to-peak" flux, so to speak, in a transformer's core is essentially constant (for a given voltage applied to the primary), regardless of the load.

My intuitive hypothesis was that variation in the "strength" of the flux was what transferred the energy from the primary to the secondary, but this fact would seem to
contradict that theory. I had thought that the primary makes a bunch of flux based on the current flowing through it and the secondary sucks it up to make current of its own. No dice, it seems.

Then of course there's the fact that the formula for flux involves only
voltage, time (frequency), and turns :)

Fact 2: The current in the primary is (approximately) 90 degrees out of
phase with the voltage at no load, and approximately aligned in phase at full
load.

This fact seems very promising and also curiously satisfying. It would imply
that the Volt-Amps (VA) of the primary is constant and only the power factor
changes as the current load on the secondary increases.

But I still don't get how the energy is actually being transferred. It seems
vaguely like the flux is just there as an energy conductor or something and
some other phenomenon is actually doing the energy transfer bit.

Can someone see what I'm missing and explain what's actually happening in
there?


texts: Can I get faster than 33 ksamples/second for A/D on my Netduino Plus 2?

texts:
I have a Netduino Plus 2. It looks like if I write a loop doing nothing but sampling one A/D pin 100,000 times, then reporting to the PC via debug statement, I get one report every three seconds or so. So my sample rate is about 33 ksamples/second. If I sample three channels 100,000 times, it takes about nine seconds. So it looks like my 33 ksamples/second are divided among however many channels are being sampled.

I think the ARM controller should be capable of faster sampling than this. Is there any way I can speed up A/D conversion?


texts: How do you arrange six 6-ohm resistors to have a total resistance of 6-ohm?

texts:
Is there a mathematical way to know the answer? (or you can do it only by trial and error)
Could you prove that it is possible or impossible mathematically?


texts: Arduino Uno - Analogue Signal Conversion Issues

texts:
The output of my Low Noise amplifier is a rough sinewave with a peak-to-peak of 1.7V and is shown in the oscilloscope trace below.

I would like to use one of the analog pins on the Uno to perform the analogue-digital conversion. However when I connect the analog pin to the output of my LNA the output immediately changes from a sinewave to sqaure wave and the peak-to-peak voltage rises  (see trace below).

I even attempted to place a voltage buffer (follower) with no voltage gain in between the output of the LNA and analog Pin but this didn't solve anything. Again, as soon as I connected the analog pin the sinewave switched to a square wave.

int sensePin = 0;
int val = 0;
void setup() {
// put your setup code here, to run once:
Serial.begin(9600);
//pinMode(analogPin, INPUT);
}

void loop() {
val  = analogRead(sensePin);
Serial.println(val);
delay(200);
}

Any help/suggestions would be appreciated, I'm not sure what is wrong. Thanks


texts: How to select standard resistor values for a voltage divider?

texts:
I wanted to select resistor values for a voltage divider that sets the output voltage of a buck converter. I picked the values recommended in the datasheet, because 3.3V is a standard value there were recommended resistor values. But what if there weren't?
How would I go about optimally determining resistor sizes, that are available in standard packages (100k, 470k etc.), I don't mean ideal values that you could calculate.
Is there a software or a method for me to determine the resistor values optimally, as close to the ideal case, but with readily available standard resistor values?
Edit after Winnys comment:
The particular buck converter that made me ask this was BD9E302EFJ. Its voltage output is determined as given in datasheet. As I said there is already a recommended selection in the datasheet as well.
I usually go about selecting the smaller resistor as 100k then calculate the other. But most often this results in an error that is not to my liking due to rounding. For instance a .2V deviation in the output voltage etc.

Link to datasheet: https://fscdn.rohm.com/en/products/databook/datasheet/ic/power/switching_regulator/bd9e302efj-e.pdf


texts: Is there anyway to get a more solid connection from pads to planes in Eagle pcb layout?

texts:
Below, in blue and white, is the suggested pcb layout from the data sheet: https://www.mouser.com/datasheet/2/468/RPX_1_0-1903909.pdf

and here is my pcb layout from eagle

as you can see in the data sheet example the blue plane fully encompasses the pads. But in my Eagle PCB layout the red plane is connected to the pads by only a few connections.
Is there any way to make more solid connections?


texts: How does one reuse a thick film circuit?

texts: I have a thick film circuit from a calculator that I want to use. How can I attach external connections to the sheet? I tried simply using the circuit as a contact in between a battery positive and an led with the negative attached to see if it would carry signal and it doesn't.


texts:
I am working on a board that can take the output of an SDR (or VCO) and provide high accuracy amplitude control (+- 0.5dB). This is an opensource project that I will hopefully launch on crowdsupply when its done :D. The final project will allow you to take a device like the LimeSDR and turn it into a precision RF generator. This will give you PC based RF signal generator with all kinds of modulation functions.

The device will have a USB interface and a python library to control the device. The MCU on the device will be some generic ARM device with a good enough ADC to meet the requirements for the peak detector.

I am looking at different topologies and methods for doing this that fit some of the requirements below. I am flexible with the requirements because I want to see what people are interested in.

1Mhz to 3Ghz (limited by my test equipment)
15 to -75 dBm (this could be extended but would require very good isolation)
relativity inexpensive

Below is the current design that I am exploring.

Typically peak detectors have a range of about 30dB. The idea is that the generated signals amplitude is unknown. The peak detector is used to sample the amplitude and control the DSAs based on the requested amplitude. The device is USB based which allows simple calibration of the peak detectors (and the DSAs if required).

My concern with this design is the performance of the peak detector against different the different harmonics generate by different SDRs. If a selectable band-pass system is needed it will complicate the design but I feel this may be necessary for the peak detector and the LNA.

Any feedback would be great!


texts:
I have Sqaure Wave coming from raspberry pi. It switches from 3.3V to 0 with 50% duty cycle. I would like to connect 3V from external power supply and clamp this output so that it start switching between 3V and 6.3V. Can this be done?

I would like to use this to drive a MOSFET gate which has a threshold of 5V.

Thanks!


texts: What happens: n Hall effect sensors wired in parallel, < n of them is triggered?

texts:
This is almost certainly a noob-level question. I only have one Hall effect sensor to play around with so I can't test this out for myself.

Say I have multiple Hall effect sensors wired like this, but their output pins all connect to the same pin on an Arduino. Namely:

all left legs tied to 5V
all center legs to ground
output pins to 5V via a pullup resistor and also to the same Arduino pin

(image credit to Wei-Hsiung Huang)

With the pullup, digitalRead()will normally be HIGH, going LOW when a magnet triggers the switch. What I'm unsure of is what happens in the scenario of multiple outputs tied together and one sensor being triggered. Could someone help me understand which of these occurs?

the other pins keep the output HIGH since they are still HIGH
the activated pin is like a connection to ground, so the output goes LOW

Followup: in the dream scenario where all of them go LOW upon one activating, do they need separate physical pullups, or would it work to have them all tied directly to the Arduino using pinMode(pin, INPUT_PULLUP)?

Edit: I'm not familiar with all the different types, but per Michael's comment I should have included a specific example. I was considering this sensor, the AH3390Q-P-B from Diodes Incorporated. That said, for the sake of generality, if there were specific cases where this would/would not work, it might be useful to specify for other readers.

For two other examples, Adafruit supplies the Melexis US5881 and Amazon seems to almost exclusively sell the Allegro A3144.


texts: How do I find an ADC circuit's bandwidth experimentally?

texts:
I'm trying to measure the bandwidth of a circuit that I've built. It's an analogue-to-digital converter (ADC) with some input protection and biasing. The ADC samples at a constant/fixed 50 kSa/s.

My approach is to inject a 2 V sine wave of variable frequency \$f_{in}\$ and take the maximum (\$Vmax\$) and minimum (\$Vmin\$) samples. That gives me \$Vpp = Vmax - Vmin\$, and I sweep \$fin\$ until \$ Vpp = 2 \sqrt{\frac{1}{2}}\ V \approx 1.41\ V \$.

I've read the Wikipedia articles Bandwidth (signal processing) and Half-power point, but I remain confused.

When I find the -3 dB point, what is the corresponding official bandwidth I've found? Is it \$fin\$ or \$ \frac{fin}{2} \$ with consideration of the Nyquist rate?


texts: Run program directly with MPLAB X(PIC16F628A)

texts:
I want to blink LED with PIC16F628A and run it directly with the button make and program device main project of MPLAB X. to programing the PIC I did simple wiring  shown in this tutorial  without using any resistor (just wiring).

To blinking the LED I just wired  RA0 ---> resistor ---> LED ---> ground but nothing works.

Should I remove some wires after programming the PIC or add something?

code :

#include<htc.h>
#include <pic.h>
#include <pic16f628a.h>
// Config word
__CONFIG(FOSC_INTOSCIO & WDTE_OFF & PWRTE_ON & CP_OFF);
#define LED  RA0
#define _XTAL_FREQ   4000000
void main()
{
        TRISA0 = 0;                // Make RA0 pin output
        LED    = 0;
        CMCON = 0x07;
        // Make RA0 low
    while(1)
    {
        __delay_ms(1000);       // Half sec delay
        LED = 0;               // LED off
        __delay_ms(1000);       // Half sec delay
        LED = 1;               // LED on
    }
}

MPLAB X output

BUILD SUCCESSFUL (total time: 5s)
Loading code from C:/Users/makhlouf/MPLABXProjects/blink.X/dist/default/production/blink.X.production.hex...
Loading completed
Connecting to programmer...
Programming target...
Programming completed
Running target...


texts: Need component that switches on a higher voltage and current

texts:
I am developing an ATMEGA382 project meant to automate certain aquarium maintenance functions. I need to apply power to 12volt solenoids and pumps. I thought I would use an NPN transistor like a switch with a 3.3v base and 12v collector. I understand this is incorrect. I do not necessarily need high speed switching. What would be a better option? I looked at an IBGF transistor, but that seems to have the same issue I am already facing.

Should I just dump a bunch of 3.3v into both base and collector with a boost converter on the emitter?

Thanks!


texts: Is there a way to connect a non-Bluetooth receiver/turner (Yamaha) to non- Bluetooth speakers (Klipsch) using a blue-tooth converter in receive mode (speakers) and Bluetooth converter in transmit mode (tuner)?


texts: Calculate LED current when Vf is greater than source voltage

texts:
I'm planning on using an RGB LED in my project. \$V_f\$ is different for each die. My \$V_{cc}\$ is 3V.

For the red diode, \$V_f=2V\$ and \$(I_f=20mA)\$, therefore I've calculated:

$$R = \frac{3 - 2V}{0.02A} = 50 \Omega$$

The problem is that the green and blue diodes have a \$V_f=3.3V\$. From experience I know the LED's will work at 3V with a lower brightness (current), but I can't figure out what is the current under that scenario. If I try to use the same formula above:

$$I_{LED} = \frac{V_s-V_f}{R} = -\frac{0.3}{0} (!?!)$$

Any thoughts?


texts: Help finding PWM IC with marking on device '0L346' not sure whether it starts with 0 or O. package of device is sot23-6

texts:
I was troubleshooting my mobile charger where I found PWM IC faulty.
However I couldn't find it's datasheet for ordering information.

The device marking is 'OL346' not sure if it starts with numeric 0 or alphabet O.

The package of this device is sot23-6.

Please help me finding this device name.


texts: OpAmp: inverting and non-inverting amplifier both amplify the signal, how to know which one to use?

texts:
Both the inverting amplifier and non-inverting amplifier use negative feedback. Both provide gain. But one inverts the signal while the other does not. How to know which one to use? Are there applications where only one of the two can be used (provides both positive and negative supplies exist)?

Is it true that single supply op amp can only create non-inverting amplifier?


texts: Using a USP Window Bug in a Custom Circuit

texts:
I have a United Security Window Bug glass break detector. I would like to interface it in someway to a program I am writing on a laptop computer. The sensor is a dry circuit and has a broken pulse time of 10 milliseconds. I am not that great with electronics but am experienced with arduinos and am willing to bit hack a USB port.

The sensor only has a single red and black wire, should I provide power through these wires, if so how much? How do I detect a break event?

Thank you for any advice or help.


texts: How can I modify a home standing fan to run at low RPM?

texts:
I have a house standing fan 220V AC. I need to do modification to make it run on 15 RPM (revolutions per minute), usually fan runs higher RPM than that.

Is there a way to make my fan run around 15 RPM? I know if I connect it to a dimmer that will create a problem and the motor will become hot! But I heard if I connect it in series a light bulb that may make its RPM lower.

Please, can anyone suggest something?


texts: I am having trouble figuring out how to analyze this circuit and check which ideal diode is in forward bias or not. Why is my analysis wrong?


texts: Do electronic fiber optic selector switches exist?

texts:
From my research, I have been having a tough time finding and specifying a fiber optic selector switch or multiplexer.  Do fiber optic selector switches exist?

Background - Simple

I have an application with a not-cheap sensor that does the following:

Sensor emits light
Light travels and hits an object
The object absorbs some of the light, and also reflects some back
Sensor receives returned light
Sensor processes the change and reports a sensed value

You can have the object be far away from the sensor via the use of a fiber optic cable.  I do so, and it works great.

As a cost savings, I would like to have one sensor be able to senses from multiple different objects. This can be done using a bunch of fiber optic cables and a fiber optic selector switch or a multiplexer.

Background - Detailed

To be more detailed:

Sensor is a pH sensor, EOM-pH-mini.
Object is a small pH sensor spot, SP-HP5
Fiber optic cable is polymer, POF

Conclusion

Does anyone here have experience in this area?  In case you can't tell, I have none.  Can you please provide insight into:

Suggestions of fiber optic selector switches
Important parameters in specifying the switch
If this is even possible?

Thank you in advance for your help!


texts: Why signals occupy small portion after being scaled and how to change it?

texts:
I am a newbie and try to understand why signals watched on logic analyzer shrink on screen when resolution is changed (as on the pics) so that they occupy a small region on the screen? It'a a continuous signal actually. Is it possible to see the signals on the full screen and how it can be achieved? I don't mind them to look smaller (it's alright) but want them to be seen on full screen, not just a small portion of the screen near its centre where they are overcrowded and not really seen anymore.

I use DigiView Dv-100 logic analyzer.


texts:
1)What happen if a PV array of 30 Vmp is connected to a 12 volt battery(lead acid)?
2)Do i need a buck converter to 12 volt  between the pv array and the battery to connect them together?


texts: 12V lead-acid battery charger with LM317 current limiter

texts:
I've got a Vsrc of 14.97 crossing a LM317 current limiter ( 1.25V / 1.25R = 1A), and at the output of the LM317 I have 14.4V/1A. So far so good.

Next I use a BC239 NPN transistor to switch a P-channel IRF9630 MOSFET with a 4K7 pull-up. Source is wired to 14.4V positive terminal, and I plan to put a charging load on Drain.

My battery is a 12V/9Ah, so charging would be done at ~C/10, and elsewhere I use a zener diode to read the battery's voltage, and cut-off charging at 13.6V, also cut-off loads at
10.8V (that's done with a relay, it's not relevant to this question).

My question is probably simple to answer: What gotchas should I be aware of when charging a >100Wh battery?


texts:
I wanted to use NXP KTY82/220(https://www.nxp.com/docs/en/data-sheet/KTY82_SER.pdf) temperature sensor for my circuit. But I could not see which are the terminals for Vdd, GND and Analog Out in datasheet. Can any one suggest.

I have modified the circuit as following.


texts:
My wife has a bottle tree in the front yard. 50 bottles on it. I would like to put lights in all the bottles to be seen at night. I can wire a house up but can't find any individual small lights that are a/c current. Don't understand why (it seems to me) that all small lights are just D/C voltage. I don't want to put a transformer outside. Or do I have to?
Please help me make my wife happy.
Randy


texts: Will an AC series motor work with DC supply?

texts:
I have read that a DC series motor can be operated using AC supply, but there will be excessive heating in the core and yoke and also a low power factor. So, construction is modified to have laminated core and yoke to reduce eddy current losses (heating) and also compensating winding and inter-pole windings to keep the torque same while reducing the turns of the field winding (to improve power factor (but reducing torque)). This is an AC series motor.

My question is, whether this AC series motor will run on DC supply or not?

I am also aware of universal motors, but they seem to be very similar to these AC series motors.


texts:
I have some limited amateur-level electronics experience, but I'd like to try something new to me. I'm trying to design a small PCB that among some other fairly simple components will house a DC-DC step-down converter. I have tried to familiarize myself with the topic, and I understand that there are some precautions to take when designing the PCB. My main issue at the moment is - how do I actually select the chip to use? There are hundreds of different chips out there by various manufacturers, all with nice-looking data sheets, and besides some obvious criteria to rule out certain models (not enough current) - how should I narrow down the selection?

These are my requirements:

convert 12-14 V down to 5 V, no step-up capabilities required
current 1 A or more
as few external components required as possible (PCB space is limited by external requirements)
SOT or other SMD form factor that can be hand-soldered
should be easily obtainable in smaller batches (10-20 units or so) by a hobbyist in central Europe
does not require "exotic" external components
pricing << 1 € per unit

I'm seeing a lot of pre-assembled modules, but I'd rather not use these - a) they are 10x as expensive, b) they take up too much space and c) there's no chance for me to learn anything new when using them...

What other factors do I have to consider when selecting a component? What is the best approach to narrow down the - to me - overwhelming set of components available?


texts: Conditional electric switch based on two power sources

texts:
Is there any available electric switch in the market for which the following condition satisfies?

It has two power sources, src1 and src2. It outputs src1 when both src1 and src2 are available. Otherwise, there's no output.


texts: Why are resistance matrices always symmetric?

texts:
My book says when using nodal analysis to find the voltages and currents in resistive circuits, the resulting matrix (of the system of equations) is always symmetrical. Why?

The exact quote is:

  The node equations for networks containing only resistors and independent current
  sources can always be written in this symmetrical form

Also the diagonal elements are always positive and the off-diagnonal ones are always negative. Why?


texts: How do you calculate the solar load an en electronic enclosure and the subsequent effect on operating temperature or temperature rise?

texts:
If you are designing an electronic device that goes into an outdoor enclosure how do you calculate the rise in temperature from solar loading? Say my safe operating ambient was 45C how do I understand what my safe operating temperature is in direct sunlight? I get that it has to do with surface area and color and I did find some formulas about determining Wattage for picking a cooling system. But nothing yet that helps me understand the temperature rise.
If the answer is test or simulate, is there a way to get an approximation?
Thank you


texts:
simulate this circuit – Schematic created using CircuitLab

LM358

positive rail: 24V

negative rail: -1.250V

Input voltage: -1.250 - ~20V

Is this the right way to switch between gain of 10 and no gain (simple buffer)?
\$G = 20/2.2 + 1 = 10.09\$ still not a 10, is there a better combination of standard resistors values to achieve gain of 10?


texts: Failed to build Instrumentation Amplifier

texts:
I'm trying to build an instrumentation amplifier, following the schematic attached below. I got two LM358P chips, signal generated by a computer sound card and an oscilloscope. The schematic and overall assembly attached below.

I got two types of resistors here. The blue ones are 1KOhm, the orange are 3.3KOhm. So that Rgain and R2 are 1kOhm, R1 and R3 are 3.3kOhm. I was trying to get the connections clear on the photo, and here's the best I could get. According to formulas on Internet, I should get amplification of around 10 times. Or at least any. But what I see on the scope is the same signal with values below zero being cut (ch1 is output, ch2 is input).

What's even more confusing, if I don't use the second stage of the amplifier and monitor the signal before R2 - it goes even more weird.

I assume I'm taking measurements wrong. Or my assembly is wrong. Could someone explain what is going on and why this whole thing does not work?


texts: Create multiple clocks on FPGA or create clock dividers

texts:
I am thinking in a design and I have a doubt about clocking. What is better? Do I create different clocks or create clock enables and only use one? What is the best option in terms of resources? What is more reusable?

Thanks!


texts: Detecting if two objects are close to each other

texts:
I am an electronics beginner but want to make two devices that can detect if they are near each other.

So if the devices enter a radius of less than 2 meters of each other they will both trigger an audible alarm

I need the devices to be as small as possible, i would use the term "micro" even, and be able to be recharged or even that fancy "wireless" recharging. The devices only need to be active for at least 5 days or longer

Thank you


texts:
In the following schematic with a logic-AND gate:

I would expect that since the inputs are logic-high of 5V for both input A and input B, that the output would also be logic high at 5V, yet it looks like the output is about 0.45V (since V=IR, V=0.455*1). Why is the voltage here that number and not 5V or something close to that?


texts: Transistor amplifier keeps flickering between working and off

texts: So long story short, i got some speakers from an old music player and they are huge (around 2.5 inches diameter and 1.5 inches high), i gave them new wires to use with a breadboard so i used a headphone jack to connect it to my computer. But it was too quiet, even with both youtube and my computer at max volume, so i made a simple transistor amplifier, but for some reason the outputed audio is flickering, i can tell that the audio data from the jack is getting through correctly because you can still sortof hear the melody of the test music, 3.3v is going through the transistor to the speaker, with the flow controlled by the current coming from the jack. I have also noticed that the speaker clicks more frequently with chiptune (or similar).


texts: Are RJ45 jack sockets universal regarding CAT-X cables

texts:
I've noticed some trade/wholesale websites list CAT-X jack sockets separately as the individual numerical version, i.e., (CAT-3 jack socket).
I'm aware CAT is a standard, and RJ45 is the socket itself.

So for example, if I were to buy one labelled as a CAT-3 jack socket, and stick a CAT-6 cable in it, does the contact material of the jack really make that much of a difference, that the cable would then only have the throughput of CAT-3?

Or is it just that the materials used for a CAT-6 jack are GUARANTEED to give the full throughput, whereas YMMV with the CAT-3 jack socket.

Thanks!


texts: How to drive 400W of High-Powered LED's in parallel / series?

texts:
I want to create a luminaire (a lighting unit) comprised of the following:

5 Nichia LEDs running @ 70.2W / 39V / 1.8A
6 Cree LEDs running @ 2.2W / 3.2V / 700mA
14 Cree LEDs running @ 1.61W / 2.3V / 700mA

I have included two schematics, the first separating the luminaire into 6 circuits:

The 20 Crees running on 1 circuit
The 5 Nichias running on separate circuits.

The second circuit groups the 20 Crees with 1 Nichia, and then 2 Nichias per circuit.

I want to drive the circuits using a DC to DC 10-32V to 10-46V 150W Boost constant current power supply Regulator like the one found here:

http://bit.ly/KzHhID (eBay Link)

My questions are these:

Does my first schematic work? And does my second schematic work?
What kind of consideration should I take in running the two Nichia LEDs in parallel if any?
Is the DC - DC Driver stable enough since it is constant current?
Any other suggestions to make it more stable? (When using only 3 drivers as opposed to 6)?

Finally, does anyone have any idea how to maybe run this rig more efficient? I mean, how can I create this same light with only 2 circuits?

Circuit A: Run the 20 Cree LEDs @ 700mA - 39W
Circuit B: Run the 5 Nichia LEDs @ 1.8M - 351W

Does anyone know of drivers or chips that can handle that much power? 350 Watts? And is the choice of my PSU ok? It will be either 24V/16.7A/400W or 12V/33.3A/400W.


texts: What does the arrow on VCC in a BJT bias circuit mean?

texts:
At the top, the VCC has arrows on it. What does that mean?

I thought it would be like in other circuits as empty holes that you could attach, but I'm not sure here.


texts: so it was very cold in my country last week and my car alternator died. I took it out and I found that one coil wire, which connects to rectifier is broken and there is no contact (I guess it could break because of -22 Celsius freezing cold). I added picture with alternator wiring diagram ant point where the solder joint is broken. I can't understand how it affects working of alternator? Isn't it just one coil not working or does it affect inductivity of stator since three coils are joined together? Also I tried to read resistance of voltage regulator (two pins where it connects to 12 V) with multimeter and I had no resistance reading (resistance was above "1" on 2 mega ohm position of multimeter). So my question, is it normal to have no resistance reading on voltage regulator while it isn't connected to 12 V or do I have two problems (my voltage regulator died and I need to re-solder that joint)?


texts: Is there a good topology for splitting a DC power supply from a few LM2576 and LM2577?

texts:
So, this isn't the most serious project, more of a toy/hack, but I have a some LM2576 and LM2577 and I wanted to see if I could somehow get an adjustable dual rail (bipolar) supply out of them, for example, from V(in) = 24V DC.

I know the LM2576 does inverting buck-boost but if you read the fine print the efficiency is horrible, so I'm disgarding that for now.

The naive approach seems wrong: step-down from V(in) to V(out) and use a second one to step-down from V(in) to V(out)/2. The impedances of the rails would be all wrong and I'm sure that there are other issues, as this just isn't how the LM2576 was intended to be used.

The only other thing I can think of is to use an LM2577 in flyback mode as per the data sheet creating a preliminary V(+) and V(-) which can then each be stepped down by their own LM2566. In this case, I can't seem to find an appropriate flyback transformer (the exact parts in the datasheet aren't stocked by Mouser anymore) and I'm not that confident this would even work. It seems like it might be unstable and noisy.

I'm more interested in just using these parts and quantifying the result rather than meeting specific requirements but I would like to get 1-1.5A out and be able to (adjustably) produce symmetric positive and negative rails from a specific V(in) (e.g. 24V.) The original goal was to get an LM317 and LM337 pair to track an LM2577 each but I'm not sure how realistic that is now that I see generating negative rails is a bit of a pain without a center tapped transformer or already having a negative DC rail.


texts:
I measured the parameters of a thermocouple (R1). R1in=5 Ohm, V=1..10 mV (measured by multimetr).

Ipositive = 5v/20000 = 0,25mА, and  Upositive max = 0,25 * 0,001 * 100 = 25mV
I have lm339, lm324. Can this comparator catch 1-2 mv? Is exist any comparator catch 1-2 mv?
How do I choose the right comparator? What parameter should you pay attention to?
UPD: Later... I found a сircuit that suits me more or less, thanks to the answers I understand how it works.


texts: How does a time delay contact remain open

texts: If input voltage energizes a repeat cycle time delay relay coil, and the contact closes thus energizing output to the load for t1, how is the contact is able to open after t1, if it's still energized to a closing position by the coil? I,m a learner, but it seems the coil is energized throughout the cycle and the contact is both closing and, after the specified delay, opening, despite coil energization.


texts: Short circuit - time constant calculation

texts:
In calculating \$\tau\$, why can't you ignore the shorted resistors?

The capacitor goes to natural response when the gate shuts.

\$\ v (t) = Ve^{t/\tau}\$

where \$\ \tau= R_{eq}C \$

Since there is no current flowing at parallel resistor due to short circuit, we can basically delete it or just make it shorted.

And as seen by the capacitor, with parallel resistor shorted too, shouldn't

\$\ R_{eq} = 10\mathrm{k\Omega} ? \$

rather than

\$\ 20\mathrm{k\Omega}||60\mathrm{k\Omega} +10\mathrm{k\Omega} ? \$

Why did they not ignore the non current carrying resistor? Isn't \$20\mathrm{k\Omega}\$ and \$60\mathrm{k\Omega}\$ same as shorted circuit?

Seen below, they incorporated shorted resistor that doesn't affect the discharge rate in the time constant of capacitor. Why?

Original Question:

Answer:


texts: Can PWM affect a brushless DC fan given sufficient time?

texts:
tl;dr - Is driving brushless DC fans using PWM unhealthy for the fan compared to variable but steady DC voltage? If yes, why and how?

The super simple input [PWM] -> MOSFET driver [PWM] -> DC Fan to adjust the speed of DC fans is well known. The DC fan receives a PWM of the same frequency as the input, with sufficient juice from the MOSFET at higher voltage. Ignoring everything else, assume the fan gets a high-current PWM signal swinging between 0-12V at some duty cycle to vary the fan speed, and that the 0-12V levels are clean (no spikes etc).

Say I have a bunch of 0.5A, 12V brushless DC fans. These are not PWM fans (i.e. they only have 2 wires). I now drive them using the above PWM circuit to vary their speed. Assume the PWM frequency is around 25 kHz, and that the MOSFET can easily switch at that frequency.

I've read that adjusting the speed of DC fans using a variable DC level voltage is "more healthy" for the fan than using PWM like above, but didn't give details.

For the experts out there:

Are there dangers to driving DC fans like the above using PWM (pulsed) instead of steady voltage levels? If yes, what are they, exactly, how do they manifest? How important is the PWM frequency for the fan (assuming the MOSFET is fast)?

p.s. I can build a PWM-to-DC circuit (e.g. source follower, etc) but here I'm  interested to understand the dangers of driving DC fans with PWM.

p.p.s. My personal experience (edit: excellent explanation for this by Tony EE below)

I'm pretty sure PWM may affect them (though here I'm asking a general question). I've heard clicks coming from all my DC fans when driving them with PWM, particularly at low-duty cycles. More importantly, after a little less than 1 year under continuous operation at various duty cycles (50% being the most prevalent), some of the fans no longer respond to low duty-cycle PWM. Specifically, they still spin at 100% speed when the duty-cycle is 100% (practically 12V steady) but any lower duty cycle results in the fan spinning at a very slow speed, regardless of the actual duty cycle value -- as if the fan had 2 speeds only: full and very-low. All these fans responded well to PWM before. They still spin freely when pushed by hand, I feel no extra resistance compared to the other fans (so it's not the rotor).


texts:
I'm trying to draw Root Locus by hand from the following block diagram and confirm the result I got from Routh Hurwitz's table:

The table of Routh Hurwitz that I got is the following:

And from the stability conditions I got K> 0.

I calculate the transfer function for the closed loop:

$$
G_0(s)=\cfrac{\cfrac{10}{(s+2)(s+5)}}{1+\cfrac{K}{s+K}\cfrac{10}{(s+2)(s+5)}}=\cfrac{10}{(s+2)(s+5)+\cfrac{K}{s+K}\times 10}\Leftrightarrow G_0(s)=\cfrac{10(s+K)}{(s+2)(s+5)(s+K)+10K}=\cfrac{10(s+K)}{(s^2+7s+10)(s+K)+10K}=\frac{10(s+K)}{s^3+7s^2+10s+Ks^2+7Ks+10K+10K}=\frac{10(s+K)}{s^3+(7+K)s^2+(7K+10)s+20K}
$$

I have one zero in s=-K, but I'm trying to find the value of K. How can I draw Root Locus, if Root Locus will depend on that zero and I can't set that value, because I'm trying to figure out the K value?


texts: Stranded wire was cut... Connecting it back together, with solid wire... Is this safe and possible?

texts:
I have this connector for a monitor and the wires were cut. So now I’m trying to put them back together with electrical tape.

I stripped the stranded wires and connected it to a short solid wire, then connected the other end of the solid wire to the other stranded wire. Is this possible and SAFE? I’m afraid to test it out. I’m only using electrical tape; I have no soldering iron. Should I just connect the two stranded wires as is, without using a short solid wire as a middle man? Any advice would be very much appreciated.


texts:
Will that create a latch?

always @ (posedge clk) begin
 if (enable) begin
   myvar1[63:0] <= some value;
   myvar2[63:0] <=some value2;
   myvar3[63:0] <= value3;
 end else begin
    myvar1[63:0] <=othervalue
 end
end

Should everything that is on the if, be on the else clause as well? I have understood that leaving an if without an else can cause a latch, but does it also mean that every signal on the if should be on the else?
If that's the case, should I write something like this:

myvar2[63:0] <= myvar2[63:0];

or not?


texts: For a multi-kW inductive power transmission application, rather than Litz cabvling I should like to consider Aluminium tubing, to take advantage of the structural possibilities. What would be the relative efficiency?


texts: Vibration Measurement using Accelerometer ADXL335

texts:
I like to know how to measure vibration in Hz using ADXL335/similar sensor in one axis, With that sensor, after converting digital using ADC, now i have some 8-bit binary value(0-256 in decimal)... could you tell me the steps to measure vibration in Hz?

Is there any math equation? or it will too good if you post a tutorial or program to do that.

Thanks in Advance
Dinesh


texts: What is the lifespan of ultrasonic transducers like the ones used in hobby projects?

texts:
I see ultrasonic transducers used in many Arduino and similar applications for proximity sensing.

I wonder what is the lifespan of such devices (Chinese cheap models, not Chinese more expensive ones) when used about once a second.

I don't consider the use outside specifications, only regular use as from the datasheet.

As plus, additional data about more rugged transducers like the ones used in cars for parking would be appreciated.


texts: I need a circuit that would stay on after being triggered

texts:
I am a year one electrical engineering student, and I am currently doing a project about building an electrical robot car. One of the required features of the car is to add a front sensor to the front, and it will continuously reverse backwards when it detects a white wall. (So, in other words, it will continual to move backwards even after it can't detect the wall anymore) But, I am having problems on how to implement this.

The front sensor provided will be on high when it detects nothing in front, and on low when it detects a white wall. I know that I need the signal to stay on low after it detects the wall. So I need a circuit that would stay in the new state after being triggered.

I hope I have my question clear enough... thank you.

P.S. Some of the ideas discussed in class were D flip flops, I'm not sure if that's the idea to be put in here.

P.S. I need to mention that we are only allow to use ICs like D flip flop, JK flip flop, counter. comparators, timers, not gates, or gates, and gates, and other basic gates ICs.


texts:
So I am having trouble with a circuit I am building for a stepper motor controller, I am currently following this schematic

My problem is that I don't really know what the Vref, control, sync and home pins do in this cirucit and what they connect to, and because of this I haven't connected anything to them when testing my circuit.

However my L297 heats up very quickly whenever I test the circuit so I suspect it is because of those pins.

My question is what are those pins in charge of, their job and what should I connect them to?

BTW I also haven't connected anything to pin 17 and 18 because I know they are inputs


texts: Is there any disadvantage to running an op-amp off asymmetrical voltage rails?

texts:
On a PCB I'm working with, I have analog feedbacks running through op-amps into a 3.3V microcontroller. Thus, signals outside 0-3.3V are useless, and potentially dangerous to the microcontroller. The op amps have +-15V rails, because those rails were available and convenient. However, that means it's possible for my op amp to destroy my microcontroller by railing out positive. In perfect operation this should never happen, but I'm considering edge cases. To improve reliability, I'm considering connecting my op amps to +3.3V and -15V.

Is there any reason I should not run an op amp off asymmetrical voltage rails?

Obviously, railing out negative could also destroy the processor. I'm only considering the positive-rail case at the moment.


texts: Transient analysis of parallel RLC circuit

texts:
Here, I am solving this circuit where Capacitor acts as a voltage source of 10 V. Switch is closed at t=0,and Vc(0-)=10V,I2(0-)=0. When t≥0, what will be the time constant and frequency of the circuit?From my calculation,A=10 and A=B*omega. But how to calculate B? Is omega the angular frequency equal to resonant frequency?I have written the kvl equation I1(t)=dI2/dt Or, Ae^(-kt)cos(wt)=Be^(-kt)wcos(wt)+kBe^(-kt)sin(wt)
When t=0, A=Bw and
Vc(0-)=10V, hence Vc(t)=10e^(-kt)cos(wt)=I1(t)
But what is k and w for parallel RLC circuit?  I also got the equation, I1(t)+I2(t)= -dVc(t)/dt
Or,Ae^(-kt)cos(wt)+Be^(-kt)sin(wt)=Ae^(-kt)wsin(wt)-Ake^(-kt)cos(wt)
By solving it, k= (-1)  and B=Aw
Correct me if I am wrong.


texts:
The inductor equation V = L(di/dt) shows that inductors will resist instantaneous changes in current. Thus, they can be used as in-rush current limiters in power supplies, for instance; the in-rush current here is as a result of the filter capacitors in use. Yet, I've read that in-rush currents occurs with motors and transformers, which are primarily inductive, at start-up. So, which is it? Are the inductive parts really the cause of the in-rush or is it as a result of the capacitive elements of the devices?

Also, AllAboutCircuits has a page on inductor behaviour and a neon bulb, connected across an inductor, was used to illustrate the back-EMF generated by inductors in opposition to changing current. According to the article, the bulb does not turn on when the switch is first closed because the battery's 6 V is too low but when the switch is opened later, a high enough voltage appears across the inductor and the lamp lights up briefly. Since L is constant, this implies that the di/dt is somehow different when the switch was opened from when it was first closed. How is this possible when nothing was changed in the circuit; same switch, same power supply?

I've also seen Adafruit solenoid product descriptions talking about in-rush current needed to "charge up the electromagnet".

What am I missing here?


texts: Bluetooth pairing on Mac and Windows causes one to dismiss the other

texts:
My company is developing a Bluetooth-enabled robotics kit. We have found the following to be true:

Pair device to computer A (a Mac)
Pair device to computer B (a Windows PC)
Computer A is now unable to connect to the device until...

You ask computer A to remove the device from its list of paired devices and re-pair it. But...
Doing so means computer B can no longer connect until it is re-paired.

The same process as outlined above works as expected if computers A and B are the same OS, e.g. both Windows or both OS X. That is, you can pair the Bluetooth device to multiple computers and connect any one of them at any time (provided you aren't currently connected to anything). No need to re-pair. But going between different operating systems causes a problem.

The Bluetooth chip is an off-the-shelf BM77 from Microchip.

We tried dumping the EPROM from the BM77 and diff'd the memory between each successive pairing. We found that after each re-pair (even on the same machine) the same 16 bytes would change starting at memory address 0x84. The documentation we have does not cover this memory range.

This does not seem like the expected behavior. Any insights?


texts: Very low-quiescent (<2mA), 5V, simple "speaker" driver

texts:
How can I drive a 30ohm speaker from a 5V microprocessor in a simple, very low quiescent-current (<2mA) manner?

The "speaker" is actually a coil, not a speaker - and I'm trying to induce a magnetic field, like in an audio hearing loop.
It's driven from a PIC microprocessor, primarily with brief, digital (rail-to-rail) pulses, but occasional DAC/analogue signals.
It also needs to have separate gain control (that I can control from the PIC - there are plenty of spare legs) and (ideally) disable the whole thing entirely.
I have a 5V, 200mA single rail supply. The coil is 30ohms. Ideally I'd like to be able drop up to 150mA through the coil in short bursts.

Most important thing: low quiescent current, even when it's enabled. Preferably <2mA.
Important things: simplicity, compactness, and low-cost
Unimportant things: fidelity/distortion, temperature stability

I've looked at audio amps (which seem over-complicated, and Quiescent too high), standard op-amps (but they seem to have low current source/supply) and various BJT options (some kind of emitter follower?) but this analogue stuff is a little beyond me.


texts: 1-wire : 4.7k resistor not working / how to compute optimal resistor topology for star layout

texts:
I've build a 1-wire network using a star topology (networking done trough my home's ethernet cables).

At the begining I didn't own a 4.7k resistor but some 1.2k resistor so I lined them to achieve 1.2k*3= 3.6k "virtual resistor".

This first version of my bus was working fine.

Today I tried to replace those 3 resistor by a single 4.7k and the bus stopped working.

==> Why ? :)

[EDIT] second question added below

Following maxim's guide I think I understand that, with a star topology, one should rather use a switched network or a Distributed Impedance Matching.

I'm more keen to try this second option but how can I compute the optimal resistor to add to each branch given their length ?

Star topology metrics are : 4 branches diverging at the master

1st branch = 18.5m
2nd branch = 26.5m
3rd branch = 25m
4th branch = "1cm" (direct connection to my 3.6k resistor)

Thus the radius of the longest branch is ~27m and the radius of the shortest is 0cm and the total weigth is 71m


texts:
This is a followup from my previous question.
Here's a summary of how the circuit works:

I'm designing a circuit that can test for short circuits and open circuits in a wiring harness. The wiring harness does not have a CAN bus or anything complicated like that - just simple wires.
I have two CPLDs, one as a designated driving end (all pins are output) and another as an receiving end (all pins are input). The driving end CPLD is programmed to be a Serial In Parallel Out shift register and the receiving end is a Parallel In Serial Out shift register.

I was given an excellent answer by Majenko that I should use pull up/down resistors and tri-state the my inactive output pins to avoid bus contention.
The problem is that, after some discussion with my colleagues, I realize that a single wire may end up driving upto 70 or so wires in the harness. Let me explain more clearly - assume we have a junction in the harness that has about 20 wires going to various places. We also have another junction with a similar no. of wires.
If the junctions get shorted with each other, a single pin from my CPLD will end up driving 40 wires. If each wire, on the receiving end, is connected with a 10k pull down it means that the pin testing the wire must be able to output 3.3/10k * 40 = 13.2mA.
Here's a schematic that illustrates this more clearly:

Please note I drew this only for the purposes of this question. This is NOT a schematic but merely a picture to illustrate what I'm saying. In this circuit, each junction has 5 wires. If one of them gets shorted together, the single pin with 3.3V will need to drive all 10 of these wires. In an extreme case, its possible that larger junctions get shorted and the pin needs to drive upto 100 wires!
Since the CPLD's current rating is just 25mA (Absolute), I guess need some sort of buffer between the harness and the CPLDs. Any suggestions regarding this?
The obvious solution is to just increase the pull down resistor. But I was told that because the length of wires be quite large (around 10 meters), its best to have a stronger pull down.
EDIT: I was playing around in Falstad Circuit Sim. I find it helps me clear things up conceptually. I ended up making this circuit, after someone's suggestion, for my problem:

This would solve the current issue as the current isn't source/sinked from the pin. But is this a good solution to the above described problem? Perhaps I'm overlooking something obvious. One inconvenience would be that each IO trace would need this MOSFET. Since the goal is to have a tester for harnesses containing upto 300 wires, I'm going to need 300 MOSFETs on the board(!)


texts:
I have connected 10 LEDs in series, the LEDs have a current rating: 20 mA which is 0.02 A and forward Voltage: 2V.

My power supply provides me with: 5V DC 2A

By using the formula down below:

$$R = \frac{vs-vf}{i} = 5 - \frac{2}{20} = 150 \Omega$$

I can see that LEDs need 150 ohm.

Which is in total \$10*150 = 1500\Omega\$

I connected:  1 k resistor, 2 x 150 ohm resistor and 2 x 100 ohm resistor which is a total of: 1500 ohm.

But the 10 LEDs dont turn on, what's wrong?

I can still turn 3-4 LEDs with or without the resistors.

Try to explain this down below please:

I tried to connect a single green led by itself without a resistor. It turned orange which is a sign that it needs a resistor.

Then I connected 150 ohm resistor to the led and it became green. I then changed the resistor value from 150 ohm to 1 k ohm, but it did not change the brightness of the led, it still the same green, no fading in brightness.

I tried to change the value to 33k ohm, it faded in brightness, but I can still see some greenish brightness in the LED.

What's wrong? Why is the LED responding like that to the resistor's value? I mean 1k ohm is much more then 150 ohm but it worked the same.

P.S.: I bought the resistors from China via eBay.


texts: What's so great about PPC? There's gotta be something

texts:
With this question in mind (the first one that stackexchange is offering me right now among the "Questions with similar titles"), I'd like to steal the idea of the question and ask it about PPC.

What's so great about it? All other chips I've seen - ARM, MIPS, SuperH, x86 - crunch numbers just fine.

The background of this question - about PPC, that is - is that the PPC architecture is used in many DSP chips, in particular in the automotive industry. Of course, this could simply be a question of momentum, and allow the developers to stay with an architecture they know well, including the toolchain. And the software they've written until now, of course.

But assuming I'm starting a DSP project anew, without any old baggage to lug around - is there any compelling advantage of the PPC architecture that would persuade me to prefer PPC to, say, ARM?

Knowing about the power efficiency of ARM chips, let me mention that my design would run off the grid, not on batteries.


texts:
What is the correct way to use STD_ULOGIC as a range in VHDL without simulation error, if the signal for indexing could be undefined? (Reason: I find it clearer to see a signal as currently ndefined, rather than it being defaulted)

I ran into a simulation error (index out of range) with the following code:

SUBTYPE RANGE_R IS STD_ULOGIC RANGE '0' TO '1';
TYPE ARRAY_T IS ARRAY (RANGE_R) OF INTEGER;
SIGNAL choice : STD_ULOGIC;
SIGNAL mux_in : ARRAY_T;
...
some_integer_signal <= mux_in(choice);

The reason being that choice is (in simulation) undefined 'X' for a delta cycle, thus I am trying to access an index in mux_in which does not exist. While I can work around this using bit, is there a propper way to write this without getting a simulation error that halts the simulation (modelsim 10.4c)?


texts: How to control the output current in when using a transistor as a switch?

texts:
Assuming that I have the following circuit where I use a transistor as a switch:

When the transistor is not active Vout will be equal to the Vcc and the current will become very high right? So if I want to add a combinatorial circuit or any other IC what should I do about that?
edit:
The circuit that lead me to this question:

S1 simulates what happens if the IR gate is blocked, and U1 is a quadruple NAND gate IC wired to form a NOT gate. I posted this question because XMM2 is measuring extremely high currents. Is that because the simulator is ignoring the saturation limit of the phototransistor?


texts: Can I apply Kirchoff's law in the open contour in the picture

texts: So is it right if I apply Kirchoff's law : Vcc=I1R1+I2R2+I3Re if I1 is the current that flows in R1 resistor, I2 in R2 and I3 in Re


texts: Ensuring 'common' ground on my devboard : powering externally, + JTAG + VirtualCom with USB

texts:
Before I ask, I did see other similar posts, but it's not easy for me to apply them (I'm not an experienced EE..).

My question in brief is, how to get common ground, to avoid potential gremlins.
(Or, if it's ensured by board design than it's all good .. )

So I have a devboard. It has 3 options to be powered, one through USB, other is from 3.3V regulated, from batteries, and also 5V from external power supply.
I need to get away from the first option - through the default USB 'debug' plug, but, I do still need it connected - for VirtualCOM.

I'm also in need to connect external JTAG to it, through dedicated JTAG connector. VirtualCOM and JTAG would be connected to same PC.  Mmm, so as I understand, I still have 2 different/uncommon grounds here : my external 3.3V (or 5V) and my PC (VirtualCOM, JTAG).

I do follow devboard guide on setting jumpers right, to supply board externally. But, not much about ensuring common ground ... ( I guess the basics are obvious, but .. not in my case).

I'm worried for gremlins in my setup, which will cause me weird issues, and potentially cause me hours debugging (for me, that's SW ..).

The board guide/description is here :
SimpleLink Launchpad kit user guide

I follow sec 2.5.4 Power Connections, 3.3V input (for now, but 5V also an option..).  I also do as sec 2.6.2 Battery Power - again more jumper settings.

The design archive with schematics is here :
archive with design files - my board is CC3220SF_Sch

Unfortunately, don't know how 'common ground' works, so for that purpose schematics not for me ;(  ...


texts:
A metal cone is heated at certain temperature  . say 45 -50 deg C. i placed a thermocouple(k type) over the surface of the metal  to measure the heat transferred over the metal surface.  The thermocouple reads about 45 to 50 deg C (which is expected) .
But the issue is when i put a plastic cap over the metal cone ,the temperature drastically decreases . So i think am missing some thermal fundamentals here which i couldnt recognize .

EDIT : The heating setup is used to heat the plastic cap which is put over the metal cone.Without the plastic cap the metal surface heats up fast.When the plastic  cap is placed it struggles to increase and reach atleast 44 deg C.


texts: internal resistance of accumulator (luminous 12V 100Ah)

texts:
I'm making my final project for monitoring the power of wind turbine using arduino. The energy from wind turbine will be stored in accu. I must have a planning calculation of the component that i need to make my final project, one of which is 'internal resistance of accumulator'. I using luminous accu 12V 100Ah. Specification doesn't tell the information about 'internal resistance' of it.
My question is how can i know the internal resistance of luminous accu 12V 100Ah or maybe how can i measure 'it' ? (maybe there is a book or a theory)
Thank you for your help


texts: Opto-isolator to read 30V with ESP8266 3V3 input

texts:
I've an old board with an output of 30-31V or 0. I need to read these high and low values with an ESP8266 that works at 3V3.

Do you think I can use a PC817 opto-isolator or something similar?

Can you point me to some schematics?


texts:
I have always had a huge fascination with electronics, but never the time to devote to learning it beyond a couple of quick tutorials here and there (and the basics you learn in school). So, sorry if this is too dumb a question for this forum, but here goes anyway.

I have a (SATA) harddrive caddy which I use for backups and moving these from one computer to another. It works well but is notorious for using bad (ie, loud and pretty useless) fans. The device is currently connected so I cannot check, but I believe the fan is 5V (I doubt it is 12V, but it is possible). I can disconnect this fan, and the device works fine, but it causes one of the LED indicators at the front to remain on.. which is also pretty annoying (it's the same LED used to signal when the disc is being accessed, so if it is always on, that renders this function useless too).

But this got me thinking, "what if I just connect an equivalent resistor there instead of the fan? This might mean I can remove the fan, and the noise, and not have that LED permanently lit up." So, am I thinking correctly here? I have a multimeter, so I can check the resistance of the fan, and find a resistor of the same resistance. Would this work? And, what should I have in mind when trying to do this? Thanks in advance.

Edit:
A few of the answers have been asking this, so I thought I would just clarify that this is a 2-wire fan. I don't want to replace the fan, I just want to know (also out of curiosity and to learn more about electronics) if this is possible (which, given some of the answers, it looks like it is) and how to go about doing this (safely).

In case anyone is curious, this is the item: KingWin SATA Aluminum Mobile Rack with Single Fan, KF-811-BK


texts: What effect does Gamma radiation sterilisation have on embedded electronics devices

texts:
We just received back 3 pieces of equipment that may have been inadvertently put through a Gamma radiation sterilisation process. The equipment is a low-power embedded device consisting of a 16 bit microcontroller with peripheral FLASH memory and SRAM backed up by a lithium battery. The equipment appears completely dead.

What possible effects would Gamma radiation have on embedded devices? FLASH memory corruption? Circuit degradation? Component failure?

More info:

The equipment is three nephelometer instruments that we make, which use a quite expensive COTS logger as the brains. The instruments were sent back to us from overseas along with some sediment samples. Customs / quarantine decided that they wanted to sterilise the sediment samples, and I think they must have put the instruments through as well.


texts:
So the problem goes as follows:

We have a simple circuit with a voltage source of Vs in series with a LED and a Resistor R_L. We are given that the barrier voltage of the LED is 1.5-2.2V and the the LED works best in the region of 20-30mA. Also the PIV is around -4.5-5V.

The Question is:

What are the upper and lower bounds of the voltage source so that we have a current of 20-30mA and the LED won't burn out if someone connects it to the circuit in the opposite way.

So in the solution Vs_max=4.5 for obvious reasons. But what troubles me is the way the load lines are crossing the graph of the LED.

Why is the 30mA current "matched" with the 1.5V of the LED. I mean why don't we consider it the other way around.
Edit: PIV is the breakdown voltage. The (negative) voltage in which the diode, in this case the LED, will become useless as it will no longer block the currents in one direction.

Why these two points, and not choose to intersect the Vs_max load line in the point of 20mA?


texts: Is it valid to connect a 5V 74LS241 output to a 3.3V Raspberry Pi input?

texts:
I need to communicate with some Dynamixel servos from a Raspberry Pi. There's a commonly published circuit to achieve this using a 74LS241 buffer to manage the half duplex connection. (This page lists several versions, all essentially the same: https://pypi.org/project/pyax12/).
However, it connects a 5V part directly to the Pi inputs, which as I understand it aren't 5V tolerant. Is this circuit valid? It seems to be widespread, so why isn't it breaking things?


texts: How to choose the appropiate analog power supply filter inductor

texts:
I'm currently studying designs for a pulse oximeter for use with Arduino, I have seen two Schematic designs form the same company, https://www.protocentral.com/sensors/1113-protocentral-afe4490-pulse-oximeter-shield-for-arduino-v2-642078949425.html and https://www.protocentral.com/open-source-health/1252-healthypi-v3-basic-hat-kit-for-raspberry-pi.html . Both of them are identical and are base around the AFE4490RHAT IC from Texas Instruments. Both designs have 4 inductors : L1, L2, L3 , L4.

1) What are these inductors used for in the design?

2) In one of the designs they are using 4 CIG22L100MNE and in the other 4 LPS3010 (they don't specify the full part number) but the Samsung one seems to be discontinued and the other one seems to be not recommended for new designs, I'm trying to choose and equivalent I have compared the specifications between the two parts and a part from the inductance they seem to have very different properties regarding current rating, DC resistance and inductance frequency, what specifications are more important when choosing a replacement part?


texts: How to design a unity gain with LM358 op amp?

texts:
I am trying to get a unity gain out of an LM358 to increase the current of an AC sine wave input from 5mA to something slightly higher.  I thought I had it hooked up correctly for unity gain, but most of the negative parts of the sine wave are getting clipped.

Is there something I need to be doing to get the negative parts of my input to pass through correctly?

Below is an image of basically what I have.  I ended up switching to  +12 and -12V references where as previously I was using just a ground at pin 4.  I was getting this clipping even with no voltage supply attached and just the + of the input in Vin and the - into ground (pin 4).


texts: Designing a testbench for a multi-cycle circuit?

texts:
Let's say I have a circuit that performs a function which takes 100 clock cycles to complete. My testbench feeds inputs into the circuit and then checks whether the output is correct.

I'm unsure how to put the 100 cycles delay in the testbench. Could I somehow pipeline it or should I feed input, wait 100 cycles, check output, repeat? I thought about using "wait for ns" statements, but this would stall all activity, which means the circuit will not be clocked the 100 times it needs to be.


texts: Amp circruit from PC speakers, why the connection to cable shielding?

texts:
I've taken apart some Logitech PC speakers in order to use the amp inside an bartop Raspberry Pi arcade game I'm making. There's something I don't understand. The donor speakers work as follows: R speaker has a 2 pin mini IEC mains input and a 9.2V PSU. It connects to the other speaker via a shielded multicore cable carrying the power and return signal. The L speaker contains the amp, has the user controls, jack, etc. audio goes via a heaphone jack then is sent to its own cone, and back to the R speaker via the multicore cable mentioned earlier.
Looking at the connections to the PCB, everything makes sense to me, apart from the fact that the shielding from the multicore is soldered to the PCB. What is the purpose of this? The speakers are obviously ungrounded. In the R speaker the there's notthing connected to the shielding.
When I'm wiring everything up in my bartop arcade, can I just snip that connection? I won't be using the multicore cable at all, as the PSU will be located somewhere totally different to the right cone.
In the picture, you can see the white/blue cables are the 9.2V DC, and the black one above those two is the one that connects to the shielding.


texts: What does this schematic of an Op-Amp and Capacitor mean?

texts:
I'm still learning about electronics and electricity.

But I'm puzzled by this question from a past exam.

I'm not sure if any voltage is getting across the capacitor, since Vin and 3v are seperated by the capacitor. Maybe if it was an AC Voltage, but I'm not sure even if that can pass through a capacitor.

I tried calculating Vout and ended up with a negative saturated Voltage.
I have no idea if this is correct.

Any help would be greatly appreciated.

My calculations


texts: Best way to voltage divider a output from a precision oscillator

texts:
I have a design where I'm using a oxco oscillator with a CMOS 0-4.3V output and the input Xin IC requires a Max of 2.4VPP.
What is the best way to descrease the voltage?
I've experimented a simple resistor or capacitor voltage divider and the chip works but is this the recommended solution? Or there's a better way designed for high precision oscillators?


texts: Stellaris 6/8/9000 part libraries for Eagle?

texts:
Someone pointed me at the freeware version of Eagle as a good starter dev tool. So I start playing around and I can't seem to find a part library for the chips I want to use. I found a library (the works) on the eagle site but it doesn't have the right parts and I found a library on the TI/Luminary Mico site (that I think has the right part) but it wont load (it has .src files and I seem to need .lbr) despite the fact it has files tagged specifically as for eagle.

Does anyone know where I can get files that will work? (Or how to make the files I have work?)


texts: Ideal ripple current on a DC to DC step down switching regulator

texts:
I was studing a linear's datasheet, a step down DC to DC switching regulator.

More specific: the LTC3615.

I am a little bit confused with ripple curent which involved to inductor value calculation. In the datasheet, PAGE 25, "Design Example" a ripple current considered 1A.

And here is my problem.
In my research on google i found plenty information about this and all of them refer the ripple current, for properly application, a value of 10 - 30% of maximum DC Load current on the Output. And in the datasheet, Linear choosing that value 1A, for 3A maximum output. 1/3 of maximum current.

Is there some information that i haven't notice?


texts: Poles, meaning when referring to pins on a switch?

texts:
What are the poles on a 9 pin switch; does this mean a row of pins, if so which direction? And also what do the poles represent, and is there so much different between a 6 pin and 9 pin switch other than the extra 3?

Here is the switch:

Thanks, all advice appreciated :D


texts: STM32 prototype unable to connect to PC using ST-Link/V2 SWD

texts:
Circuit Diagram

Background & What I have tried.

I have wired wrapped this setup myself using a fresh STM32F411RC MCU from digikey (on a proto-advantage LQFP-64 to DIP-64 breakout board).
I've wired up the SWCLK, SWDIO, NRST, GND, MCU_VDD, as outlined in the ST-LINK/V2 User Manual (UM1075).
I power my prototype using the USB, a multimeter confirms 3.3V is getting to each of the VSS/VDD pairs & VBAT pin.
I've tried the various frequencies for SWD as well as the various Reset Modes and Modes in the windows GUI.
My wiring is as minimal as this guy using the STM32F030, so i'm not sure what the problem is: https://www.newbiehack.com/categories/newbiehack-tutorial-ARM-Video6-GPIOCreatingTheCircuit-nomenu
I am able to connect using UART however it seems like the STM Flash Loader program only provides the capability to load to the 512K version, but I have the 256K version.

Error message

arch:~$ st-util -v99
2016-05-18T12:50:58 DEBUG src/stlink-common.c: stlink current mode: debug (jtag or swd)
2016-05-18T12:50:58 DEBUG src/stlink-common.c: stlink current mode: debug (jtag or swd)
2016-05-18T12:50:58 DEBUG src/stlink-common.c: *** looking up stlink version
2016-05-18T12:50:58 DEBUG src/stlink-common.c: st vid         = 0x0483 (expect 0x0483)
2016-05-18T12:50:58 DEBUG src/stlink-common.c: stlink pid     = 0x3748
2016-05-18T12:50:58 DEBUG src/stlink-common.c: stlink version = 0x2
2016-05-18T12:50:58 DEBUG src/stlink-common.c: jtag version   = 0x19
2016-05-18T12:50:58 DEBUG src/stlink-common.c: swim version   = 0x4
2016-05-18T12:50:58 INFO src/stlink-common.c: Loading device parameters....
2016-05-18T12:50:58 DEBUG src/stlink-common.c: *** stlink_core_id ***
2016-05-18T12:50:58 DEBUG src/stlink-common.c: core_id = 0x00000000
2016-05-18T12:50:58 DEBUG src/stlink-common.c: *** stlink_read_debug32 0 is 0xe0042000
2016-05-18T12:50:58 DEBUG src/stlink-common.c: *** stlink_read_debug32 0 is 0x40015800
2016-05-18T12:50:58 WARN src/stlink-common.c: unknown chip id! 0
2016-05-18T12:50:58 DEBUG src/stlink-common.c: *** stlink_close ***

Under linux ST-LINK/V2 is detected however the MCU is not.

Windows STM ST-LINK Utility trace.log:
Error (0x16) after target cmd F2 36 04 20 04 E0 00 00 00 00
W at 0xe0042004: 0x00000000
Error (0x12) after target cmd F2 35 04 20 04 E0 00 00 00 00
W at 0xe000edf0: 0xa05f0000
Error (0x12) after target cmd F2 35 F0 ED 00 E0 00 00 5F A0
cErrLog::SetLogTraceOn
STLinkUSBDriver.dll loaded
ST-Link/V2 device detected
Target voltage detected: 3.222947
Driving NRST low
Error getting target IDCODE: if SWD, check SWD connection
Error (4) while initializing ST-Link in SWD mode
ST-Link/V2 device detected
Target voltage detected: 3.221382
Driving NRST low
Error getting target IDCODE: if SWD, check SWD connection
Error (4) while initializing ST-Link in SWD mode
ST-Link/V2 device detected
Target voltage detected: 3.221382
Driving NRST low
Error getting target IDCODE: if SWD, check SWD connection
Error (4) while initializing ST-Link in SWD mode

The windows GUI shows "Detection Failed" for "Target" & "Target Voltage", and provides the error message "Can not connect to target.".

Questions

Any ideas on what I should try next, or what might be preventing SWD from operating?
I am able to connect using UART however the STM Flash Loader program detects the chip model however slightly incorrect, I only has the 512K version in the dropdown http://i.imgur.com/Zu2c57K.png yet my chip is the 256K version, so it seems like I can't use the Flash Loader to load on a program. Are there any other tools that know the memory map of the 256K chip and are able to flash a binary?

What I have yet to try

Put a 22ohm resistor on the NRST line between the ST-LINK/V2 and the board. (AN4488 pg42)
Fully wire up and ground all the other ST-LINK/V2 header pins like shown in AN4488 pg42, even though I don't think it's necessary.

Datasheets

Product page with all datasheets: http://www.st.com/content/st_com/en/products/microcontrollers/stm32-32-bit-arm-cortex-mcus/stm32f4-series/stm32f411/stm32f411rc.html


texts: Using 110V-120V appliances in Europe (230V)

texts:
I wish to use American designed 60 Hz  110 V appliances in Europe with a 220 V 50 Hz supply.

I have a transformer that can convert the voltage and supply sufficient power to run the devices. Are there any other problems that I need to consider in powering these appliances? Some of them may include motors.


texts: Integrating momentary switch with a Raspberry Pi

texts:
Please note: Although my question involves a Raspberry Pi, this is a pure electronics question at heart.

I'm trying to figure out how I can wire this illuminated momentary switch to my Raspberry Pi 1 Model A (hereafter RPi) such that:

The switch is normally open
When pushed down: it closes the circuit, lights up and fires a HIGH signal to a GPIO input pin (GPIO 04 in my case)
If needed, I can make the GPIO 07 pin an output pin and make it available to help run the light/LED inside the switch, but not sure if that's needed

I will be setting the RPi's internal resistor on this pin, so I don't think I need a resistor for the switch, but I believe I still need one for the switch's LED/light (please confirm!). I will also be working out a "debouncing algorithm" at the software layer if needed.

But I'm stuck trying to figure out how to wire the dang thing to my RPi:

According to page 15 of that switch's datasheet:

So I'm not sure:

What GPIO 04 on the RPi is supposed to connect to on the switch; and
What I'm supposed to do with Pins 1 and 2 on the switch; and
What I'm supposed to do with Pins X1 and X2 on the switch; and
What I'm supposed to wire GPIO 07 up to (if anything)

Can anyone nudge me in the right direction here?


texts: How does a role swapped USB OTG A-device detect that it has been disconnected from the host?

texts:
Let's say I have a USB OTG A-device that has negotiated a role swap via HNP, i.e. it is providing VBUS while acting in the device (non-host) role for data.
More commonly USB devices do not provide VBUS and therefore can detect that they have been disconnected from the host when VBUS disappears.
This is differentiated from a suspended state, where activity on the bus ceases but VBUS remains.
In the role swapped example, however, since the device is providing power it can't rely on the disappearance of VBUS to detect when the host is disconnected.
The only other option is to detect when activity on the bus ceases, but then how can this be differentiated from a suspended state?
I'm obviously missing something.
TIA


texts: Different level TTL driving each other? A problem?

texts:
I connected a GPIO of a 3.3V level board (schematic, pin is 5V tolerant) as output to a 5V Atmega328p (schematic) pin configured as INPUT_PULLUP.

I perform a low active control function with that.

The 3.3V device is going into a deep sleep mode from time to time. During this time the 3.3V GPIOs are floating, that's why the input pullups are configured on the Atmega328p.

Is there current flowing between the 5 V input pin and the 3.3 V output pin if the output is high? Does that do any harm to the 3.3V IC as the levels are not equal?

Schematics:

OpenMV3 3.3V

Arduino 5V (Atmega328P)


texts: Why does this potentiometer in an op-amp feedback path cause noise when adjusted?

texts:
I have placed a dual-gang 100k potentiometer in the feedback path of two op-amps that work as a Sallen-Key filters. This controls gain but also the Q factor of the filter (somewhat demonstrated on wikipedia. However, when I move the knob, it makes some rubbish noise.

The noise is demonstrated in this youtube video.

The schematic of the filters is shown below. The Q factor pot is RV3A and RV3B. The minimum Q is set by R7 and R10. The power supply for the op-amps is from a boosted 9V battery up to 18 V with an LM27313 regulator.

I'm really not sure what is causing this noise or how I could go about preventing it. My only thought is having the pot in the feedback loop is not a good idea, but there is no other way of controlling the Q factor.

How could I alleviate this noise?

Edit: I accepted @Catalyst's answer since it was the most technically correct. I appreciate all of the suggestions on how to fix it. I simulated some tests on placing capacitors in parallel with the potentiometer but they really messed with the frequency response.

What did fix the circuit was by placing it in an enclosure. Using an aluminium enclosure linked all of the pots strongly to ground which seems to have generally improved noise performance hugely. Here is a link to the a new video demonstrating a lack of noise. The audio is recorded in exactly the same manner as before. I don't fully understand why a better ground fixed the travel noise but I'm certainly glad it did.


texts: What tools can I use for PCB making at home?

texts:
I want to create my own PCBs for prototyping and hobby purposes. I have experimented with buying them in China, which is cheap but not very fast. No idea on the quality either, but for $5 for 5 boards, you can never go wrong.
I have checked local manufacturers, but a prototype board easily goes for €75, which is too much for experimenting.
So I was wondering what would be a solution to make them at home. When researching, I find some CNC machines but I fail to understand how I could make PCB with that.
I thought perhaps some kind of 3D printer could do the trick, but no idea where I could find that or if it even exists.
I am fine with spending money, but the price per board should be low and the process should be easy.


texts:
For a University project I have to build a small box containing ice cubes. The box is a shoe box, isolated with newspaper and aluminium foil, cooled by thermal packs. In this box I want to store ice cubes for about one to three hours.

Now comes the tricky part: The ice cubes should drop out of the box, one after another, about every minute.

I was thinking of a motor with an oval disk which opens a flap gate. The second idea was a small conveyor band which transports the cubes out. Are there better solutions than that? What minimum motor power do I need for this? How do I control the motor?

It's a low-budget project, so the cheapest solution is the best.


texts:
I tried to make a generator for the course assignment.
I am confused in the phase connection in the generator.
what is the difference in one phase, two phase or three phase generator connection??


texts: How to measure available amps? Do i need more load?

texts:
My new 200W 18v 11a(max) solar panel reads about 24v 4a  50% efficiency at midday  on my MTTP Rich solar controller.  I presume this is not great.

I was wondering... I have  a 48v to 12v stepdown converter, will that increase amps at 12v? https://www.amazon.com/gp/product/B00BWKXTUU/ref=ask_ql_qh_dp_hza.  How can I measure available amps off that device? would I need a large load to test that?


texts: What is the recommended battery chemistry for digital multimeters?

texts:
I would like to know if the different internal resistances of different battery chemistry somehow affects the calibration of a digital multi-meter.
If so, then what would the optimal battery chemistry be for commercially available multimeters.

For instance, would low self-discharge Alkaline batteries contribute to a more accurate reading than rechargeable Nickel-Cadmium batteries? Or vice-versa?
Since Capacitors have ESR, I'm assuming so do batteries.
Do certain battery types give a better ERS rating? Does this even matter for digital multimeters?