texts: Dimmer for Nth-Light Narrow LED Flexible Strip Light

texts: I wish to dim a Nth-Light Narrow LED Flexible Strip Light (https://www.adafruit.com/product/3683), will the LED Strip Lights PWM Dimming Controller For LED Lights or Ribbon, 12 Volt 8/10 Amp, 3301 (https://www.amazon.com/dp/B003L4KKF2) will be suitable?


texts: Is the energy flow due to a an alternating current constant or cyclic

texts: I understand that the Poynting vector shows us that energy flows in the region outside, or between, conductors, but the maths gets too deep for me to discover, when the current is alternating, whether the flow is constant, or varies cyclically with the varying electric and magnetic fields. Can anyone please resolve this for me?


texts: How could I essentially design an if/else statement as a circuit using basic logic gates?

texts: So for my circuit, I have set up a simple game of rock paper scissors. I have the actual gameplay of rock paper scissors working, where it will correctly choose the winner and light up corresponding leds on an icestick. The way the game works is that player one picks one of the top three inputs (Rock, paper, scissors from top to bottom) and player 2 picks at the same time. The resulting circuit will lead to one of the three outputs, with the top output being a player 1 win, the middle output being a draw, and the bottom output being a player 2 win. What I'm trying to add is a win tracking system, which would be done with having 2 leds for each player. When a player wins once the circuit would light the first led and after the second win the circuit would light the 2nd led. I'm currently lost on how to implement a way for the circuit to essentially have an if/else statement to check if the first led is getting input in order to light the second. Can anyone offer any advice for this?


texts: Is the Serial Port pin CTS an inverse logic, meaning if you have a logic high input the PC terminal will register a logic low?

texts: Because as I see my code accessing the serial port I see a boolean 'false' value of the CTS instead of 'true' where as my input is high. Please kindly confirm and give a little explanation. Thanks a lot in advance.


texts:
I'm designing a measurement and control board to interface with an old (70s) PLC. The board consists mainly of I/O ports, both analog and digital in- and outputs. To have my boards not fried by the first thunderstorm, I'm trying to ESD protect these inputs.

A few remarks:

wires of up to 200 m length connect to the ports
these wires are not especially shielded. It's not bell wire, but close enough.
I cannot change the wires.
There's no high speed signals going over these wires. The fastest signal is a (up to) 115 kbaud RS-485 bus, everything else is below 50 Hz.
I have voltage levels of ~1 V (RTD excitation), 10 V (0..10 V analog) and 24 V (digital "power" outputs)
every input consists of a signal- and a ground line

My ideas so far:

directly connect the ground wire to the respective board ground (PWRGND, AGND, DGND)
connect signal to its ground with a 100nF capacitor to short HF
connect signal to PWRGND with a single bidirectional TVS diode to divert high-voltage peaks e.g. induced by lightning close by
maybe connect a SMD ferrite bead (or other small inductance) in series

After looking for parts, however, I'm a bit confused. Mainly, there's lots of high-speed data line ESD protection ICs, but no dedicated (and cheap) low-speed ESD protection ICs. This made me wonder if I'm doing anything wrong.

What's the suitable approach to protect a circuit board in these conditions from overvoltage?


texts:
I'm trying to get a stable 48VDC power source with at least 500mA. I have a power transformer with two secondaries, each with 24V 0,73A. The transformer is rated at 35VA.
What I've tried is connecting the middle lugs of the secondaries together to give me 48VAC, but it's giving me closer to 52VAC. After the rectifier bridge it's giving me around 52VDC, but when it gets to the circuit's power capacitors (680uF across the power rails), it goes up to around 70VDC. It's supposed to power an audio amplifier and some extra LEDs.

Is there a way to get constant 48VDC from this, or am I better off regulating each of the secondaries on their own to 24VDC, and then wiring them in series? If so, what's the best solution to get the 24VDC? I was thinking of using 7824s or something similar.

Thanks in advance


texts: Is it possible to make a Tri-State Bidirectional buffer without any tri-state buffers?

texts:
I'm currently making a computer on an application called Smart Logic Simulator. However, it doesn't have any tri-state buffers and therefor I cannot make a bus (based off the DM74LS245 chip). Is there a way to make a tri-state buffer?

EDIT:
Note - I don't know much about logic, and it's possible that the thing I want to make isn't a tri-state buffer, but that's what I think it is.

Here are the elements in the app I'm using:


texts: Ferrite toroid vs E-core for high frequency transformers

texts:
I found 2 ferrite rings in a power supply I was stripping for its magnetics. I was wondering why is it that I've never seen these employed as transformers.
I've read that for a number of reasons toroidal cores make superior transformers.
Why couldn't I employ these toroids in a half bridge or push-pull topology as opposed to the E-cores in the photo?


texts:
While building an opamp based non-inverting amplifier for my project I noticed that it always has some considerable output voltage despite having the input at zero. To verify that problem I built the following simple test circuit:

I would imagine that the output voltage of this circuit would be very close to zero, however it's about 5 mV. According to the datasheet of OPA189 the input offset is only 3 uV, so not sure why am I getting 5mV output considering so low gain of only 2? In fact based on my tests, the output offset voltage doesn't even depend on the gain value. I tested another op amp ADA4522, and this one has similar problem with more than 7 mV output offset. Could anyone give me pointers on why this could be happening and what can be done to lower the output offset to 1 mV or less? Thanks!


texts: What is the purpose of \$C_E\$ in this circuit?

texts: I understand it acts like a filter for \$R_E\$, but what is the point?


texts: How to designate a specific portion of a design in altium

texts:
I copy and reuse portions of a design, I'll copy and the designation numbers follow the copy (for example: I'll have U1 and R2, then copying you end up having to U1's and two R2's, I don't want that.). There are sections that I'd like to re-designate (or clear designations to U1->U? for example) or have Altium renumber the designators.

1) Is there a way to make a selection and clear the designators?

2) Is there a way to clear designators in a sheet or redesgintate only a sheet?

I think I remember that you can use a 'special paste' and paste a design without designators labeled. I don't want to know about that way, I'm not a fan. I'm running 15 right now but could update.


texts: Can I use a power supply that supply slightly higher current than the rated current from my dc motor?

texts:
I have a 12v, 0.9A dc motor. Currently I have two 12v dc supplies which I borrowed from my friend. The current of the 2 dc supplies is 1.0A and 0.5A respectively.
Is it safe for me to use the higher current  supply from 12v dc supply (1A) or a 0.5A 12 dc supply to my dc motor?


texts:
I have a circuit as follows:

Note that \$V^+\$ is a voltage source that has both an AC and DC component. I want to see how the OpAmp affects both components. My guess is that we can write:

$$V_{out}(AC)=(1 + \frac{R2}{R1} - \frac{X_c}{\sqrt{X_c^2+ R_1^2}})V^+(AC) $$

Where I assumed the role of the RC part as a low pass filter as seen by \$V^+\$. Then, since low pass filters let all DC pass through unaffected, I would say that as long as C1 is not very large, $$V_{out}(DC)=(1 + \frac{R2}{R1})V^+(DC) $$

If I was told C1 is large enough to be considered as a short for AC and an open for DC, I would say $$V_{out}(AC)=(1 + \frac{R2}{R1})V^+(AC)$$ and $$V_{out}(DC)=V^+(DC)$$

Can someone tell me if this is correct or provide alternative explanations?


texts:
I've been introduced to the concept of equivalent isotropically radiated power (EIRP) and so far I've used it to calculate RF power density at distance of 100m radiated by a directional antenna with a gain of 20dBi at 10W output power.
The EIRP is 60dBm (1kW) so using the inverse square law 1kW/4pi100^2 got me ~7.9mW/m^2. I'm not sure I haven't made a mistake so please correct me if I'm wrong but under the assumption that I was in fact correct, a question arose.
If EIRP is supposed to represent a hypothetical isotropic radiator that would result in the same signal strength as produced by the directional antenna (at least in the area covered by the latter) then what happens if we were to measure power density close to the antenna? If we perform the same calculation as above but for 1m we end up with 1kW/4pi1^2 and that gives me ~79W/m^2. Now, ignoring near-field radiation and other circumstantial effects, why is the power density so high?
I feel like this is a good proof that I don't really understand gain but the argumentation that it's just the same power as from the isotropic source, just focused down to a beam doesn't cut it for me. I am assuming that if I input 1W into a 100% efficient isotropic antenna I get a total of 1W output power in all directions, now if I were to focus that to a point/small area I will get closer and closer to 1W but never above it. Where am I wrong?
Edited:
I think it would be wise to clarify my misunderstanding now that I know the answer. The confusion in the above question stems from the fact that you can get a higher power density than input power. Of course, this doesn't violate any laws of physics as it's not the power that's higher but the area that gets smaller than m^2 so the density increases.


texts: Calculating voltage monitor positive and negative threshold?

texts:
Voltage supervisor circuit using TPS3890-Q1:

My Vin (5 V) is connected to Vmon. R1 and R2 are already defined. Intention is to calculate  positive and negative threshold. So I think, this is a kind of reverse engineering.

R1 = 27 K,

R2 = 47 K

From the above read, I calculated as 5 V = Vitp ( 1 + 27/47)

Input Threshold Positive, Vitp = 3.176 V

Questions

1) I was not clear threshold calculation from the datasheet. Above calculation is correct or not?

2) What will be threshold negative value, -3.176 V or How to calculate it?

Please comment. Thanks.


texts: Common mode (CM) and differential mode (DM) filters components reduction

texts:
I have a 24VDC system where I have designed common mode (CM) and differential mode (DM) filters. As system works with lower voltage I use TPS54560 buck regulator. The goal is low conducted emi.

question 1:
Common mode filter is frequently depicted w/o return path capacitors. In my picture red circled C83,C86. Can CM filter work w/o them? In this example chassis is earthed and earth point is accessible. However mentioning the case when earth is not accessible may d be also educative.
my considerations:
When I calculated CM I have set filter cut off two decades back compared to desired attenuation frequency and with simple formula C = (1/2pif)^2 / L_choke I got cap(s) value(s). However omiting the caps I believe it means there is only some stray cap representing return path and cut off freq is then pretty unpredictable. So I tend to believe that common mode choke without return path capacitors wont work well. Correct?

question 2:
Can I somehow "merge" differential mode filter capacitors (blue circled) with switching psu input capacitors (circled as orange)? Or is it better to keep them separate? The goal is to keep emission low but do not overkill design itself.
my considerations:
I understand that layout rule strictly requires to have psu input caps as close as possible to psu pin so its not always possible. And also that parallel combination nicely improves ESR. But anyway I tend to believe that C69 and C70 are little redundant and can be avoided.


texts: ATtiny85, ARduino IDE, TinyDebug: Error sending int values

texts:
The setup:

An ATtiny85 is programmed using the Arduino IDE, it is supposed to read the ambient light from an LDR and turn on/off an LED accordingly. To get a better understanding of what my sensor readings are in different lighting situations I'd like to send the reading to my serial console using TinyDebug, a part of the Arduino-on-ATtiny libraries.

Here's the minimum sketch:

String myString;

void setup() {
  pinMode(0, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int sensorValue = analogRead(2);
  String myString = String(sensorValue);
  Serial.write(sensorValue);
  Serial.write("\n\r");

  if (sensorValue > 500) {
    digitalWrite(0, HIGH);
  }
  else {
    digitalWrite(0, LOW);
  }

  delay(500);
}

On my serial console all I receive is garbage:

l

x

x

l

{

t

n

z

u

l

|

q

m

n

o
(...)

Changing the codes Serial.write(sensorValue); to Serial.write("hello"); nicely prints out

hello
hello
hello
(...)

so I suppose the serial communication itself works.

Trying to convert the int value to a string and sending that string, ie Serial.write(myString); gives a compiler error:

(...)
sketch_may24b.ino: In function 'void loop()':
sketch_may24b:11: error: no matching function for call to 'TinyDebugSerial::write(String&)'
/Users/cts/Documents/Arduino/hardware/tiny/cores/tiny/TinyDebugSerial.h:728: note: candidates are: virtual size_t TinyDebugSerial::write(uint8_t)
/Users/cts/Documents/Arduino/hardware/tiny/cores/tiny/Print.h:75: note:                 virtual void Print::write(const uint8_t*, size_t)
/Users/cts/Documents/Arduino/hardware/tiny/cores/tiny/Print.h:74: note:                 virtual void Print::write(const char*)

Any idea how I can send my sensor values to my serial console instead?


texts:
Beginner question, but at least my Google skills didn't yield any results. Why do some capacitors have 5 terminals? Such as this one

What are they used for?


texts: MCP3221 ADC always returns zero in Proteus

texts:
I am interfacing PIC18F2320 with MCP3221 ADC over I2C. When I try to read the converted value from ADC, only zeros are returned. I'm using MPLAB libraries. ADC is in A5 address mode. The AIN voltage is 2.503 V, what should be around 2048 after conversion.

Schematic looks like this (sorry for the mess, there was other stuff around and I'm debugging it so it isn't clean, just ignore MAX232, as removing it doesn't affect the result):

Captured lines look like this (upper is clock; it's easy to observe the three groups of 9b each):

The code I'm using is following:

// Set the ports to input, as the manual instructs
TRISCbits.TRISC3 = 1;
TRISCbits.TRISC4 = 1;

// Open I2C in master mode, slew off, as I'm aiming for 100kHz
OpenI2C(MASTER, SLEW_OFF);
SSPADD = 10; // A bit under 100kHz, because the MCU is on 4.1925 MHz

StartI2C();
WriteI2C(0x9B);      // Address of the ADC is 0x9A, 0x01 is read mode
voltage = ReadI2C(); // voltage is a global int; read upper byte
AckI2C();
voltage <<= 8;       // Make room for the lower byte
voltage |= ReadI2C();// Read lower byte
NotAckI2C();
StopI2C();

I have tried adding a delay after the address byte, but the result stays the same.

I have tried addressing with 0x9A only, in which case the data line is always high during reading.

Any other ideas?


texts: How do I find out if this mobile tower is bad for my health?

texts:
I don't know if this would be on-topic here, but please feel free to migrate this question if that's not the case. I have this mobile tower very close to my house. This photo was taken from my top-floor. It's 15-20 meters away at most.

I am naturally worried about the electromagnetic radiation I'm exposed to. I was hence wondering whether buying a EMF detector would help me find out whether I am safe or not.

Will an EMF detector help me see the radiation emitted by the tower? Would this do it? What kind of readings would be normal?


texts: Is there any simple way or trick to express given signal using waveforms of sum of simple sinusoidal signals?

texts:
We know that Fourier series for periodic signal \$y(t)\$ is given by
$$ y(t) = \sum\limits_{m=0}^{+\infty} a_m \cos(w_m t) + \sum\limits_{m=0}^{+\infty}b_m \sin(w_m t). \quad$$
y(t) is sinusoidal periodic signal with period T

How would you decompose the given signal into simple sinusoid?

If possible can anybody show me  waveforms of  fundamental and harmonics components for the given signal y(t)?


texts:
I built a field mill based on this video link. This device generates a sine wave, where I am interested in the amplitude.

Once i have the peak, or average value (does not matter, but average would be better), I will send it over to an arduino data logger.

What circuit could I build to accomplish this task. This will be on a high altitude balloon launch in a few weeks, and need to find a circuit quickly for a high school high altitude balloon launch in less than two weeks.

The AC wave peak ranges from a bit less than  one hundred millivolts to a few volts, and the data logger will read values from 0 to 5 volts.


texts: Can I hook up more than one device per terminal on a power supply?

texts:
First post!

My question is straightforward, and NOT a duplicate post. This is meat & potatoes here, less on theory, more on practical application. I know you are all more knowledgeable than I am. Hoping for a quick answer (which doesn't theorize about Johnny or his appetite for apples).

I'm thinking of buying a non-PC power supply to do some stuff with LED light strips. I have read some about series and parallel connection options. I'm good as far as that goes. I can follow pictures/procedures. Here's what I have NOT found an answer to searching all across the web. My project might involve other devices and so my question is:

The power supply is 600W 12V 50A. This will exceed my total need. The question has to do with the number of terminals on the power supply itself. Here's a picture of it:

You'll notice it has 3 terminals +/- on the back.

At long last, my question: WHAT IF I HAVE MORE THAN THREE DEVICES?

As long as each and every device is rated for 12V (USA) and the total will not exceed maybe 400-450 watts tops (honestly, not sure how many amps will flow, but definitely under 50), can I rig up more than one device on each of the 3 terminals?

In my mind, I'm thinking I could strip wires and then just stack them on top of one another, considering and then deliberately choosing which terminal to use to try to "balance the load" <--- used here in a logistical sense, not just in terms of numbers of devices to be connected, but also in terms of "equal" power supply per terminal.

Essentially, I want to eliminate wall warts and power bricks. Simple. One plug in the wall, grounded, for everything. Can I do it?

Assuming ALL the components/devices are 12V, don't add up to 600W and won't push anywhere near 50 amps?

Let's say I have 7 or 8 devices, not necessarily just LED light strips. Can I do it? That's all I want to know. Additionally, does it help to try to evenly distribute the total across just 3 terminals?

If I CAN'T do it, can anyone tell me how to achieve my desired result? I've already considered the potential downsides if the power supply fails/cuts out or alternately decides to fry everything. To me, it's worth the risk.

I want to eliminate wall warts. I may buy a power supply so I can hook all sorts of stuff into it. Gentlemen, how should I proceed? No theory; just practice, please. I'm looking for confirmation, yes or no, that I can do what I want. If not, a pointer in the right direction, and thanks for reading my long-winded question!


texts: ST link not working when PCB is powered with a 3v3 smps

texts:
I am programming a stm32 (2 wire SWD: SWDIO and SWCLK) series MCU with a st-link V2 i cut off a nucleo board.
I usually just connect the 3V3 supply off of my arduino, but atm i am trying to make a box with the j link in it, and the 3V3 supply coming out of a SMPS. to be clear, rathen than powering the PCB up using its power ports, I just connect the Vcc net and Gnd net of the MCU on the pcb to my supply.
The error message mentions that the firmware could not restart the target MCU. However, when I connect my arduino back again, it works fine. This happens as soon as I connect my ST link to my PC, when it usually opens the device as a storage, but only this time with the mentioned error message.
This worked perfect with my arduino, but not with my SMPS. Is there a reason? might it be a current surge damaging the st-link?


texts: Shifting into an EE Career - with or without Master's first?

texts:
I've been working in software for way too long, dislike it for a number of reasons, and would like to shift completely into electronics engineering work.  I'd prefer analog, microwave, optoelectronics or maybe some specialty yet to be invented, but any electronics is better than any software.    I have more talent and interest in electronics, and my love of herding electrons goes back to when I was a kid.  I read IEEE publications and understand them far better than anything coming out of the software development or computer science world.

Unfortunately I have no formal degree in EE, only in Physics, a fine subject but apparently not sufficient to land an EE job, so I've found over the past several years.

The question is whether it's best to somehow get into a full time job first, with my existing experience, enthusiasm and education, and then perhaps earn a Master's to further my career, or to go full blast studying for a Master's in EE while continuing work in software, and only then try to land a job.

I'm currently employed, live next to a reputable tech school, and my employer depends heavily on electronics although there aren't any opening right now.


texts:
I'm looking for one of those small numeric LCDs used on OTP authentication keys (the one your bank gives you to access their website, to be clear).

All LCDs I find on the various manufacturer's sites are those big 20x2 alphanumeric displays... I need something that can be fitted on a USB key. (note: it doesn't strictly have to be numeric-only, it could even be a graphical LCD for all I care...)

Any suggestions?


texts: How to fetch the resistor values of AD8403 (digPot) programmatically?

texts:
I'm using Arduino to control a digital potentiometer via SPI. I can set the resistor values, but I wonder,
 1- Can I read the resistor value also via the same SPI interface?
Here is the data sheet of AD8403. I've looked over it but couldn't find related information. There is also a SDO pin on AD8403 which I think is for daisy-chaining.

2- I'm actually using a Java app to send the resistor values to arduino and then to AD8403. I want to know if the values are set. Therefore, I can either reply to Java that Arduino sent the command to digital pot OR I can fetch the values of digital pot directly and have the arduino reply to java that " Yeah, I've asked AD8403 and it's set to your desired values".  Isn't this second approach more robust? What is the standard in industry here?


texts: How could I measure noise of gyroscope angle readings?

texts:
I have a system that uses gyroscopes to ultimately give me the angles/orientation of an object. So, let's say that the object is sitting at 90 degrees. I might get some readings such as:

87.56632 deg
87.25641 deg
87.69428 deg

Let's say I get roughly 100 values, I know that the in a perfect world the gyroscope would give me 90 degrees. Well, since we are not in a perfect world I get values like those shown above.

Let's say that the values are not perfect due to some noise in the system. Is there some mathematical formulas that I can use to get an idea of relatively "how noisy" my data-set happens to be (purely from a fixed sample size of only the angles)?

In other words, what I am trying to do here is:

Get an idea of how noisy the data is bouncing around, with respect to the value I know it should be (exactly 90 degrees).


texts: Why one of my multimeter shows a small voltage when only one probe is connected to AC and the other dont?

texts:
I've recently acquired a Minipa ET-997 multimeter. I noticed that when I connected one probe to 127V phase and let the other disconnected, it will show around 12V.

But I have an older and cheaper multimeter which shows 0V in this same situation. Why is that?

Another thing, the older multimeter shows -127V when the black probe is on the phase wire and the red probe is on the neutral wire. And it shows +127 when the red probe is on phase and the black probe is on neutral. Therefore, I can easily tell which is phase and which is neutral. Minipa ET-997 always shows 127V, no matter how the probes are connected. Is there a way to "fix" this?


texts:
I have a Raspberry Pi Model B and the display unit from a Dell laptop - functional, but removed from the laptop because of a broken hinge.
Is there any way the Pi's GPIO pins can be used to drive the display unit directly, to function as the Pi's monitor?


texts:
I have a 4-20mA signal and want to feed it to my uC. I found this circuit but dont know how it works.
can any one explain this for me?

or suggest a better solution


texts: Why do we need to use special versions of voltage regulators on negative rails when the input is isolated from the positive rail?

texts:
Take the example of the well-known LM78XX voltage regulators: there is the LM7812, and the LM7912. The latter should be used to generate -12V from, say, -24V whereas the former is used to generate +12V from +24V.
I must be missing something because I do not understand why we should use the 7912 instead of the 7812 on -24V rails generated by tying the positive pin of an isolated power supply to GND and the return pin of the same supply to the -24V net. Since the supplies are isolated, why would the 7912 be "aware" that it is in fact handling negative voltages or very loosely said that it is "upside down" with respect to the positive rail?
In a nutshell, why couldn't we use two 7812 to generate +/-12V from two +24V isolated wall adapters tied back to back?


texts:
I am trying to wrap my head around the circuit mentioned in the accepted answer to this post.

It looks like a fairly simple deal except for the part where I wonder what is keeping the signal to LOW at Vo when Vs is HIGH? In other words when Vs is HIGH +5v thus the BJT is letting the current through it, and Vo would be parallel to that flow (or a "tap" into that flow if you will). Why would the current not flow through the tap while it is allowed through the BJT?

If I tap into the power lines going behind my house, the current in my tap never stops, even when the power lines are in use downstream. So what is keeping the Vo LOW?

If the current won't go to Vo because of higher resistance, does that mean the LED L2 should not glow in the following?


texts:
I am done a google search on this and have come up blank. What I have is a signal/sound being fed through a wire that ranges from (0-9V). When the volume is low, and i need 1 or 2 leds to light up, when it's high, more leds should light up. How would I solve this problem?

Since my signal fluctuates between 0 and 9V, I could use a BJT/Mosfet to set at what voltage my LED will light up yes? Basically, create a whole array of them.

By the way, I can only use discrete components for this project. No special IC's are allowed.


texts:
Conventional connectors, where the plug and socket have metal parts which touch, suffer from the following problems:

Limited mating cycles or expensive plating.
Impedance mismatch (relevant for high speed signals only).
Lack of isolation.

Here's an obvious solution that would make for a useful Ethernet type connector. Instead of making the metal electrical parts mate, why not make the magnetics mate instead?

The plug would contain the primary windings, and C-shaped cores, while the socket would contain the secondary winding and more C-shaped cores. When the plug and socket mate, the C-shaped cores would touch. The advantage would be that this design doesn't wear out, and completely isolates the PCB.

Do any such connectors already exist? If not, is there some reason they are not used? Might they end up being more expensive? Might they be less reliable?


texts: Why do toroid inductors have a square cross-section?

texts:
What is the reason behind the square cross-section of most toroid inductor cores?
Correct me if I am wrong, but would not a circular cross-section give the lowest resistance since it has the smallest circumference compared to it's area? Is it because it is easier to manufacture than a round toroid or is there some other reason?


texts: RC High Pass Filter output drift problem

texts:
I am unable to find a proper explanation for this. When I create the passive RC circuit as shown and feed it 8 us pulses at 25KHz, The output of the RC circuit drifts for some time until it settles as shown in the waveforms below. The top signal is the input and the below signal is the output of the filter.

I assume this is caused by the RC time constant of the filter?

What is the best way to prevent this problem? Is decreasing the capacitor value an only option? Will using an active filter help?

Many thanks in advance.


texts: Is full load current line or phase current?

texts: If a question just asks for full load current, is this considered phase current or line current.  Do I need to consider if it is a wye or delta because of this?  With three phase power being VL*IL*srt(3) or VP*IP*sqrt(3), I am not sure if I need to convert if given for example line voltage on a delta, but need phase current (if thats what i need) for full load rating.


texts: Fourier Transform vs. Laplace Transform?

texts:
The question arose to me earlier, and I never really understood it..

What is the difference between fourier transform and laplace transform in terms of analyzing an overall circuit? I don't quite understand.


texts: Can I use a surge protector with an adapter on travel?

texts:
I don't know if this is a question for this site, but here I go:

You know how the US and Europe have different plug in points for the electrical appliances/chargers etc. So if I want to use a phone charger (bought in the USA) in Europe, I will need a converter/adapter. Can this adapter also be used to support a surge protector with 4-6 outlets in Europe?

I normally use surge protectors for all my devices at home, and if I travel, I want to be able to use it on travel also. Hence, my question is, can I use a surge protector with an adapter? Or should I just buy one in Europe?


texts:
What's the easiest way to connect a ring terminal to the ground terminal of an AC outlet? Are there plugs you can buy that make this easy?

I don't need (or want) the line and neutral wires accessible, just the ground terminal, for safety reasons.


texts: Quartus: Error (12004): Port z does not exist in primitive x of instance y

texts:
I cannot find any source for this error, any help much appreciated!

Error: Error (12004): Port "a" does not exist in primitive "tff" of instance "t1"

module part1(SW);
  input [0:9] SW;
  wire q1;

  tff t1(.t(SW[2]), .clk(KEY[0]), .a(SW[1]), .q(q1));

endmodule

module tff(t, clk, a, q);

  input t;
  input clk;
  input a;

  output reg q;
  always@(posedge clk)
    begin
        if(a)
            q <= 1;
        else
            q <= 0;
    end

endmodule


texts: Typical power reflected off wall/window/wooden shelves etc

texts:
For interference purposes, I would like to quantify how much signal power I would receive back when my transmitted signal is reflected off an object (a wall, glass window, wooden shelf) at a distance of d meters and frequency f=c/lambda. In my case, f=900 MHz, d is a few meters.
Intuitively, I would calculate:
$$
P_{RX} = P_{TX} G_{TX} \underbrace{\left(\frac{\lambda}{4\pi d}\right)^2}_{\text{fwd loss}} \underbrace{|\Gamma|^2 G_{\rm obj}^2}_{\text{object properties}} \underbrace{\left(\frac{\lambda}{4\pi d}\right)^2}_{\text{reverse loss}}  G_{RX}
$$
\$P_{TX}\$ is the transmit power and \$G_{TX}\$, \$G_{RX}\$ are the gains of the transmit/receiver antenna. If the object would be an antenna, \$\Gamma\$ would describe the "reflection coefficient" and \$G_{obj}\$ the antenna gain.
I have seen the concept around the radar cross section \$\sigma_{\rm rcs}\$. After doing some math, I arrive at the following relation:
$$
\sigma_{\rm rcs}  = \frac{\lambda^2}{4\pi} |\Gamma|^2 G_{\rm obj}^2 .
$$
which means when I either know object properties \$\Gamma\$ and \$G_{\rm obj}\$ or \$\sigma_{\rm rcs}\$ I could some estimates of reflected signal.
I have not found "typical" values for either of them. What could be typical properties of a wall, window, wooden surface?
PS: I am aware that reality is much more complicated. I really only want to get a ballpark estimate for a simple scenario. Is \$|\Gamma \,G_{\rm obj}|\$ typically -3dB, -10dB or -40dB?


texts: Measure current with a Branford Multimeter

texts:
I have a cheap multimeter called "Branford" and I would like to measure the current used to charge a phone. As a power supply, I use a DC generator, which I rotate by hand. Then I have a DC/DC Step Down Converter to get constant 5.2V. Then I use the power to charge the phone. It works perfectly fine and the phone is charging as it should.

However, I would like to see how much current goes through, but I get very small values. I think I'm doing something wrong, because I'm a noob in this field, therefore I would like to ask if what I am doing is correct. The multimeter front panel looks like this:

and the connections are like in the picture below. I've been looking around the internet and it looks okay, but considering that the multimeter is not the same, I would expect that there might be some other set-ups.

As you can see, I get that 0.7 (A?) which stays constant and that is where the suspicion starts. I also tried to turn the knob to the "20A" option, but there is no change. The generator has the following specs:

Output voltage: 5V-24V
Max load voltage: 40V
Max output current: 1500mA
Max load power: 20W

So, can anyone help me to figure out if it is the measurements that I'm doing wrong or the generator can't deliver more?


texts:
I am trying to prototype this circuit:

However I do not have a 2K Ohm potentiometer for R2, the closest I have is a 100K. So I have used 100K for R2 and 10K for R1. Using the forumula at the bottom these should be valid values for the resistors, however my output voltage only range between 0.01V and 0.4V. Also the output voltage slowly creeps by 0.01V increments the longer I keep the circuit switched on.

I have checked the wiring many, many times and replaced the LM317T twice and checked every component individually but always get the same problem. Can someone tell me what is wrong please?

I rebuilt the circuit so  it is easier to understand the connections:


texts:
I'm facing some problems understanding how Bluetooth LE works.

First: How is a connection established?

Peripheral (e.g. sensor) sends advertisements
Central (e.g. tablet) has to scan actively (generally it does not scan)
Central discovers advertisement and decides to connect to Peripheral
Central sends connection request to Peripheral
How does the Peripheral receives the request. Is the antenna in receiving mode, while sending advertisements? If so, is this receiving mode always on, reacting to any connection request (even without sending advertisements)?

Second: After connection loss/disconnection, is the above procedure mandatory to reconnect again or are there other ways? What about bonding/pairing? What if I know the MAC address of the peripheral?

Third: How could they reconnect (as fast and energy saving as possible) if the connection is lost.

Fourth: Is it possible to send/receive data from outside a connection (others then advertisements)? Or is a connection mandatory to register for notifications/indications etc?

Fifth: What is the best solution to establish an encrypted communication? Usually pairing/bonding allows for encryption. But how get the passkeys exchanged.

Sixth: While receiving advertisements. How do I know if the device is interesting for me? Does I need to connect and discover services? Is there a mechanism to determine the device class or type?


texts: What are those plugs called, and who is the manufacturer?

texts:
These are called "Zwerg-Stecker" and "Zwerg-Kupplung" respectively in German, but I've never seen them anywhere else. It basically translates to "dwarf plug" and "dwarf socket".

It is a 2.6mm mini banana plug system, I remember seeing them on some lab equipment in Uni, but never seen them anywhere else. We use banana plugs quite often, whether it's 4mm or the smaller 2mm system. Unfortunately, making cables ourselves it sometimes a bit of a hassle, since they're more or less designed to be pre-confectionated wires. Now, I was thinking of introducing this Zwerg system, since it is designed to be not confectionated at all. Instead, you're supposed to cut your own wires and put the plugs on it.
It has a weird size, though. 2.6mm diameter and a very short plug. I haven't seen complete cables made with Zwerg plugs, but I have seen them quite often in lab equipment, where people would make their own cables because of a requirement in non-standard lengths, etc...
I don't know the manufacturer, I've seen them in a couple of electronics stores, but that's pretty much it.


texts: Inverting amplifier, k=-2 - Where did I made a mistake? Help needed

texts:
I am trying to create inverting amplifier circut with R in range 20kOhm-40kOhm.
I should get magnitued/amplify factor of -2, but I simply cant.
Due to the expression:
k=U_Input/U_output=-R_2/R_1 the input value of voltage should be 4 to get -2 value on output, and simply because of that the resistors should have two values where 2R_1=R_2. But nothing seems to work.
The counterparts for R_1 and R_2 in expression are R3 and R2 on image, also the input is V3
But I think that I am making a mistake somewhere, but do not know where.
Below is SS of my model.
Please can you at least make a hint for me or explain where I am making a mistake?
Thank you for your help in advance!


texts: How can a grounded gate MOSFET conduct current?

texts:
I am trying to get into understanding of current mirrors, amplifiers and other basic electronic blocks, and I have come across this a lot, but I couldn't find an explanation how that works anywhere (maybe I was Googling the wrong words).
For example, concerning this basic differential input circuit:

How can there be any current flowing through the MOSFETs, when the Gate is grounded? I was under an impression that MOSFETs (the standard ones) conduct Drain to Source (or vice versa) current only when there is a Gate to Source voltage applied (and an inversion layer forms the channel and so on).

Futhermore I came across that you can bias a MOSFET in pretty much the same way, by placing a current source to the Source terminal. How does that work? I thought you can bias only by setting a Gate-Source voltage. Can a MOSFET be opened by forcing the current between the Drain and Source?

Man, I am confused.


texts: How to find macro "usage position" in microchip MPLab

texts:
I'm having troubles when MPLab shows me error within a macros (with assembly language). It gives the line number of where macros is defined. That's not very helpful if the macros is working fine, but the parameters passed are wrong. Is there a way to trace the macros back? (by "trace" I don't mean "runtime debug trace")

P.S.
Note that this is not a question if macros should or should not be used.

For example let's have this macro (defined in an include file macro.inc):

loadWreg   macro x
  movlw x
endm

Then use in in 3 .asm files more than 10 times. One usage is wrong:

  loadWreg 0xFFFF    ; 16 bit value can't be loaded in WREG

Microchip shows the error in macro.inc on line with movlw x. How do I know where I passed wrong parameter to the macro?


texts: How can a voltage follower op amp amplify?

texts:
I have this circuit as a white noise source (with two outputs):-

So the 24V Zener diode makes noise due to a 60uA current.  This is fed into two TL082 op amps.  At the op amp input, the noise level is ~4Vp-p.  However, at the op amps outputs, the noise level is ~11Vp-p.  Both measured with an oscilloscope.

How can this be?  Clearly something's wrong.  The datasheet has clear examples of this chip being used in exactly this fashion as a simple voltage follower (Figs. 19, 26 & 27).  This thing is, I don't recall seeing this weirdness when I bread boarded the circuit.  It only seems to be happening on the PCB.  When I probe the tip of the Zener, the noise seems to be at least in the order of 20MHz.  I would expect the noise output to be lower than the input due to the op amp's slew rate not coping.  What's going on?

The scope grab below shows the input noise signal:-

And this is the output.  Avalanche noise should be a saw wave (as is the input).  What are the highlighted peaks and where are they coming from? The PCB is a single sided one plus a ground plane.


texts:
I am currently trying to incorporate a Freescale i.mx53 into a design. It has three USB High Speed hosts; one has a built in transceiver, the other two do not (OTG is not part of this discussion).

The other two hosts support the following transceivers (p4478 of the reference manual):

ULPI (HS/FS/LS)
Serial (HS/LS)
IC-USB (FS)

Whilst I would normally use a ULPI, the required pads are being used by other peripherals and therefore I must use of the other PHY options. It connects to a 4-port hub close by one the same PCB.

Problem is, I have no idea who makes them or how to use them. Or if I need special Linux drivers for them. The closest, I've found (I think!) is a TI TUSB1105, but it only supports full-speed, not high speed.

Unfortunately, I know even less about IC-USB and Wikipedia isn't really helpful.  Since only full-speed is supported, I can safely ignore this option for the moment.

So, I guess I'm asking:

Can anyone recommend a serial high-speed USB PHY? If so, why?


texts:
I have an circuit with six high torque servos connected parallel to power brick that provides 5V @5Amps. Everything is running fine. But I wanted to add few LEDs to circuit but I dont know how do I do it ?
Connecting LEDs  parallel to other components will I think burst LEDs as current is too high from source. All servos needs to powered on all the times too. Current drawn by servos are very dynamic.

Any ideas?

Thanks


texts: Regenerative braking using a normal RC ESC?

texts:
I am thinking about building my own electric bike using RC parts.

I will be using a 2.2/2.4 kW motor and I will be using a ESC that is compatible with the motor.

My question is, during coasting or when I'm pedalling without powering the motor, is it possible to make the ESC convert the motors kinetic energy to electric energy to create an induced current to charge the battery?

Also, Is it possible to safely charge my LiPo battery with this voltage or should I use another type of battery?


texts: How to set modulation depth with modulating a signal with an analog multiplier?

texts:
For example, I have an AC signal V1 which I'm modulating with another AC signal V2. When V2=0 the output will be also 0 (since a simplified transfer function of the analog multiplier is V1*V2=W). This corresponds to a modulation depth of 100%. I would like to control the depth so that it could be lower when needed. Simply adjusting the level of V2 will not work off course because that would simply divide the gain I'm applying to the signal. I somehow need to merge a DC voltage with V2 but now sure how... Any suggestions will be appreciated!

simulate this circuit – Schematic created using CircuitLab


texts:
Does anyone know of a product like a heating blanket or similar i can have customized to cover my electronic product to protect it against negative temperatures of -30 to -40 etc.
My LCD and Li Ion batteries are not rated for -40 but I have an inquiry to sell into Russia and would like to know if anyone has used something that can help.
Rgds
Richard


texts: Like the title says I want to use a NRF24l01+ with a STM32F4. So far, I realized the communication with two NRF24l01+ and two Arduino but I would like to exchange on Arduino with the STM32. I looked up the internet an found this site: http://www.wvshare.com/product/Open407Z-Package-B.htm but no library for it. Has someone tried it or has a library?


texts: Amplifiers without vacuum tubes or transistors?

texts: Are there amplifiers that can work without vacuum tubes or transistors? Is it possible to create a working amp with high power without vacuum tubes or transistors?


texts: Why does not current flow in open circuit wire connected to a closed circuit?

texts:
I know that current flows from higher potential towards the lower.
I was wondering why it does not flow towards point "a" and why isn't it divided into "i_y" and "i_x"? And if it happened, it would stuck inside the open wire at point "a", and current "i_y" would head back towards the source. Here, I was thinking, what is the potential of an open circuit in this picture and is it lower enough for the current i to flow in it?

simulate this circuit – Schematic created using CircuitLab


texts: How should I connect this switch securely?

texts:
I have a nifty 22mm pushbutton switch with an RGB LED ring light around it. I would like to securely wire this for an application in an outdoor control panel that may get shaken around a bit, so I'm looking for the "right" way to crimp/solder/weld/or otherwise securely connect those poles to wire.

The four large tabs are what the switch actually controls. In my application I'm just running these to an Arduino-type controller so maybe 3.3V or 5V.
The four little tabs painted different colors are for the RGB LED, also 5V. They appear to be 0.1" apart x 0.3" apart.


texts: What happens in a Geiger-Müller tube when there is no voltage?

texts:
What happens in a Geiger-Müller tube when it is not connected to a circuit?

Ionizing radiation must still be creating ions inside it, but they cannot move to the anode because there is no potential difference. What happens to them?


texts:
I am building a system for ultrasonic distance measurement that implements CDMA coding access. Therefore, I am using DAC with 3 outputs for generation of three different signals and an ADC for reception. My final aim is to measure time of arrival.

DAC has 3 outputs, so for simultaneous transmission of three different signals I first need to load value to three registers and then to transmit them at the same time.

I have been trying to understand DAC80504EVM and ADS8920BEVM requirements and way of functioning. Can you somebody please support me whether or not the following is correct:

The datasheet for DAC specifies SPI clock speed of up to 50MHz. If I update the output values of DAC after 3 SPI transmissions, that would mean that I need at least 24x3 = 72 clock cycles in order to update my output. Therefore the update rate of DAC outputs would be 50MHz/72 = approx. 694 kHz. Or every 1/694 ms.

The datasheet for ADC specifies 1MSps sampling rate with 52MHz SPI clock speed. If I have both converters on the same SPI interface with the same clock of approx. 50MHz, it would mean that I would be getting 3x more data from the ADC. So for one sample value from DAC, I get three samples from the ADC.

Considering I would like to transmit signals with central frequency 300kHz and bandwidth 30kHz, would this actually be useful?

I understand that the DAC update rate is not its sampling rate, but I am still a bit confused with whether or not will the output of DAC be too slow for ADC, or does this make sense in terms of computing time of arrival?

I will appreciate any comment or suggestion.


texts:
The problem

I am trying to estimate the 3D pose of a person who is observed with a single camera and 5 worn IMUs (limb extremities and upper-back). The camera frames are converted to shape-based feature vectors, and the IMUs each provide 4D quaternion representations of their orientation.

I have recovered the 3D pose using each modality by learning a mapping from the input feature space to the output pose space. Now I wish to obtain better results by combining both modalities in some way through sensor fusion.

I have tried appending the feature vectors of each modality and also using a weighted average of their outputs. These are very simple approaches, and only resulted in very small improvements on average.

Question

What other approaches can I try to combine these two incommensurate data sources?

Is there any preprocessing on the features that should be done?

Note: My preference is to continue using a learning-based approach if possible. (i.e. I do not want to explicitly model the physics/kinematics/etc)


texts: Charging li-po battery with phone charger

texts:
I am planning to make automatic rechargable emergency led light (automatically lights up when there is a powercut). I scavenged led's from old emergency light. I planned on using this 3.7V 300 mAh battery
. The circuit automatically goes to charging mode when there is power and switches to battery when power is off. Can anyone please clear these points for me?

Can I use my mobile charger which is rated 5V 1A output for charging it.
If so, the circuit is turned on 24/7, the battery seems to have overcharge and overdrain protection circuit. Will the battery last if the circuit is always on?


texts: Easiest way of creating a constant current source controlled by a micro

texts:
I'm trying to figure out the easiest way of constructing a digitally controllable current source. The operation conditions are: 0 - 12 V (regulated by a voltage regulator) at 0 - 1 A. A microcontroller should be able to set the maximum current which is between 0A and 1A.

Are there any common and widely available linear ICs which will do the job?

I've some LM317Ts and found this schematic. But there is a potentiometer which needs to be replaced by a digital controllable circuit.


texts:
I'm checking current of kitchen timers to estimate operation time.
The obstacle here is that in a "passive" mode (no blinking/beeping/key pushes, only working counters + LCD) devices consume 8-12 uA but my multimeter breaks line if current out of 20 uA range and this happens during power on & menu navigation by pushing buttons.
So I started with 200mA range, altered device state into desired mode and started to lower range via mechanical switch on the multimeter (VC830L): 200mA => 20mA => 2mA => 200uA => 20uA.
I saw some "blinks" on device LCD, fortunately I am able to lower range for all tested devices without ruining their operation.
I'm an amateur and the question how such kind of measurements are performed "professionally":

is there special auto auto-adjustble measuring devices (that jumps through the ranges)?
is there a special design for current measurement that doesn't break a line when ranges are switched?

I saw:

Current measurement over a fairly large range
Dynamic Range Current Measurement
Wide range and high precision current measurement
How to measure supply currents ranging from 1μA to 10mA?

and they are about schematic design. My question is about "industry practice" to measure in lower current ranges with market available multimenters.


texts: How to wire many bi-color LEDs to a single power supply, and switch them on/off individually

texts:
My goal is to have 13 separate stations, each with a bi-color, common cathode LED (Dialight 606). These LEDs do not require external current limiting resistors. Each LED can be 'On Green', 'On Red', or Off.

I have a 1 AMP, 12VDC power supply and four '8 Channel' relays. I am able to discretely control each channel of the each '8 Channel' relay via a 3rd party control system. I am not sure how to correctly wire the LEDs, relays and power supply in order to accomplish this. Please let me know if any additional info is required to help figure this out.


texts:
Could someone help me understanding the markings of this schematic? What the little numbers I circled in red and yellow are.

Is c59 providing power to that entire circled area or is just two points in between it? What about the other row of caps above it?

What about here with L1217 and XW1220 is that a jumper? And what does the dot on the (1) of L1217 mean?


texts:
I need to extend an existing 5V UART over fibre for isolation reasons. Digital isolators / optos are no good as I need more isolation than that (0.1pF coupling max. from one side to the other). UART content is fixed due to backward compatibility requirements - 57600 baud. Maximum transmission distance is 10m.

My initial thought was to use TOSLINK transmitters and receivers. I bought some (three connections - 5V, GND and IN or OUT respectively) and got to playing. First issue I saw was data inversion when driving with a simple 10ms on, 20ms off test signal. Fine, added an inverter - this got fixed.

I then set it up at 57600 with a continuous data stream - and got horrible garbage (character-wise - waveform is clean but incorrect). Reduced the speed to 9600 and sent individual characters so I could observe the waveform - no problem. Increased speed back to 57600 and sent individual characters. Strange things. Basically, the character waveform starts well, but then half way through inverts. It looks to me like the transmitter is trying to ensure 0 DC bias - this would make sense in a way as I believe that TOSLINK uses Manchester encoding.

So two questions:

Is this behaviour people have seen with other TOSLINK transmitters? Are there "straight passthrough" transmitters out there?
Does anyone have an alternative solution using fibre? The best option I have seen so far is the Avago HFBR series - easy to use (it seems) but relatively high cost. Any better suggestions?


texts: Is Electronic Band Gap ( EBG) and Metamaterial same?

texts:
Electronic Band Gap ( EBG) and Metamaterials are used in antenna and filter design.
I am confused if both are same are the difference in nature? What is a  property of Metamaterial and EBG?


texts: Common Ground across SCR and Diode Bridge

texts:
I am trying to use a common ground to enable a regulated output across the circuit, however as you can see the SCRs and Bridge use the common earth to relay the positive channel in the bus..
Is this the common pattern of connecting this or is there a more stable circuit which could be used?

Thanks.


texts:
I am having a very hard time understanding when exactly a transistor turns on. For example in the following circuit from Everycircuit:

Why does the transistor turn on when the push button is off, but not when it's on? The only way it seems to make sense to me is that the voltage relative to the base is "more positive" when the resistance to from the base to the positive terminal is lower than the resistance from the base to the negative terminal. For example, if I change the resistances:

From this, how would current even have anything to do with 'turning on' the transistor at all? It seems like it's only related to voltage from the below. Could someone please describe why exactly the transistor is being turned on in these conditions? Not just conceptually but with equations as well, if possible to show the current/voltage going in and such.


texts:
I'm new to high frequency testing, but I am redesigning an old circuit which uses a bipolar Motorola 2N5160.  The specification sheet says that at a Power In is  400 MHz, 28 volts, PNP transistor, 0.16 watts in. I should get 1 watt out min. or 1.25 watts typically.

I built the test circuit in the spec sheet that Motorola claims is the 400 MHz Test Circuit and I don't get 1.25 watts out. For my Power Out, I get about 0.15 watts power out at 175 MHz and 0 at 400 MHz. I've rechecked all the components on the test board that Motorola used, and circuit is properly grounded. My Gain Bandwidth Product out is barely 9 dB. Any ideas why output is so low at 175 Mhz?

The transistor I'm testing was made by Motorola and is a know good working device in the current application circuit, in which I desoldered the transistor from.  When I apply 400 MHz, the transistor oscillates wildly and gets very hot. Only after I tune the capacitors do I get 9 dB out at 175 MHz. I'm trying to migrate to a surface mount design. My question is about the 400 MHz test schematic. Could the test schematic be wrong? The 2N5160 was a very popular transistor for decades. Was the 2N5160 transistor ever a 400 MHz transistor?  Am I interpreting test circuit incorrectly?


texts:
I'm finding it very difficult to tackle questions in exams involving calculation of Probability of error and Bit error rate for various digital modulation schemes involving AWGN Channel. Firstly is BER and Pe calculation in exams the same? I clearly understood upto the signal representation of the different Keying Techniques (ASK,FSK,PSK,BPSK) ie S(t). Why did we go for Energy/Energy Difference calculations of these signals? What exactly are constellation diagrams and why do we need them? Even in constellation diagrams we convert the Energy back to amplitude maybe because we need to calculate the magnitude of noise at the boundary of the signals that will cause an error. I understand that the channel here adds White Guassian Noise.Which is the best method to tackle Pe/BER problems, is it by drawing the constellation diagrams and then the boundary or are there other methods or standard formula's to be learned? These are a few questions asked in the exam that I'm preparing. Please help me with them also. I mainly have ASK, FSK, PSK, BPSK in syllabus.

  Let Q(√g ) be the BER of a BPSK system over an AWGN channel with two-sided noise
  power spectral density N0/2. The parameter g is a function of bit energy and noise power
  spectral density.

  A system with two independent and identical AWGN channels with noise power spectral
  density N0/2 are in parallel. The BPSK demodulator receives the sum of outputs of
  both the channels. If the BER of this system is Q(b√g), then the value of b is?(Ans given is 1.414)

  A BPSK scheme operating over an AWGN channel with noise power spectral density of N/2, uses equiprobable signals S1(t)(t) = √(2E/T)sin(t) and S2(t) = -√(2E/T)sin(t) over the symbol interval (0, T). If the local oscillator in a coherent receiver is ahead in phase by 45 degrees with respect to the received signal, the probability of error in the resulting system is (Answer key given is Q(√(E/N))

Also please suggest where I can find good problems of the same cadre for practice.


texts: Building a relay circuit for the Raspberry Pi

texts:
To start

I have only a cursory knowledge of electronics... I "know" what all the basic components do, but I have not figured out how to use that knowledge to design anything (much less evaluate someone else's designs). I will be solely reliant on YOUR upvotes to give me the right answer.

Background

The Raspberry Pi is a tiny/low-power general-purpose computer (ARM) which has a set of "GPIO" pins which allow it to interface with other components. It has a 5v power pin, a ground pin, and several pins which can be set to "high" or "low" (where "high" = 3.3v) that can be used to trigger other events.

I know I saw it, but I can't recall now where (and can't seem to find it), but the max current draw for the 3.3v is fairly low... in the low-hundred mA.

The primary "chip" (processor, GPU, etc) is something from Broadcom.... and they refuse to give specs if you haven't signed an NDA.... so, WHAT may damage the computer is a pretty big question, but people have reported that "a little" current going "back up" the GPIO output pins has been enough to fry the board. I assume (but see the aforementioned "to start"), but don't REALLY know, that this means the resulting circuit may need to be opto-isolated?

Background (part 2)

Everyone in the world seems to want to use these things to control real-world objects since they're general-purpose Linux machines (and can, thus, be programmed in your-favorite-language). The problem is that all of the relay boards in this space are, currently, designed for the Arduino's 5v output.

Question
I have seen a design or two for how to build a circuit that can use the 3.3v to use the 5v to trigger a relay, but there doesn't seem to be any consensus in the community for how to do so SAFELY. Given that I'm not qualified to evaluate the supplied circuits, can someone please explain to me how to use a 3.3v trigger to SAFELY use a 5v line to operate a relay?

Bonus Points: There have been people claiming success at using the various SainSmart 5v relay boards (designed for Arduino) on the 3.3v lines... is this safe? Will it ACTUALLY work?


texts: Cutting and resoldering CPU chassis fan power cables

texts:
I have a number of chassis fans in my computer which have cables that are way too long. I've been wanting to cut them, but wanted to make sure that I knew what I was getting into before proceeding.

I was thinking that I would

Strip back wire where I'd cut.
Cut.
After tinning, etc., solder the wire back together.
Find a way to wrap back up the exposed wire.
Profit.

Is this generally speaking how this is done? I've never soldered before and am looking to get my hands dirty in an easy project.


texts:
I bought a good night chipKIT Uno32 to use for projects. I am using the language of c32 with the MPLABX IDE and a pickit 3 debugger. Everything went well but when I want to debug a project, it says disposito not ready to debug (editor: Disposito likely means device), and I get the following message:

  Programming / Verify complete
  The target device is not ready for debugging . Please check your configuration bit settings and program the device before Proceeding.

What should I do? Here follows my bit configurations:

/ / # pragma config UPLLEN = ON / / USB PLL Enabled
    # pragma config = FPLLMUL MUL_20 / / PLL Multiplier
/ / # pragma config = FPLLMUL MUL_24 / / PLL Multiplier
/ / # pragma config = UPLLIDIV DIV_2 / / USB PLL Input Divider
    # pragma config = FPLLIDIV DIV_2 / / PLL Input Divcaider
/ / # pragma config = FPLLIDIV DIV_12 / / PLL Input Divcaider
    # pragma config = FPLLODIV DIV_1 / / PLL Output Divider
/ / # pragma config = FPLLODIV DIV_8 / / PLL Output Divider
    # pragma config = FPBDIV DIV_1 / / Peripheral Clock divisor
    # pragma config FWDTEN = OFF / / Watchdog Timer
    # pragma config WDTPS = PS1 / / Watchdog Timer Postscale
/ / # pragma config = FCKSM CSDCMD / / Clock Switching & Fail Safe Clock Monitor
    # pragma config OSCIOFNC = OFF / / Enable CLKO
/ / # pragma config POSCMOD = XT / / Primary Oscillator
    # pragma config POSCMOD = HS / / Primary Oscillator
    # pragma config IESO = OFF / / Internal / External Switch -over
    # pragma config FSOSCEN = OFF / / Secondary Oscillator Enable
    # pragma config = FNOSC PRIPLL / / Oscillator Selection
/ / # Pragma config CP = ON / / Code Protect
    # pragma config CP = OFF / / Code Protect
    # pragma config BWP = OFF / / Boot Flash Write Protect
    # pragma config PWP = OFF / / Program Flash Write Protect
    # pragma config = ICESEL ICS_PGx1 / / ICE / ICD Comm Channel Select
    # pragma config DEBUG = ON / / Debugger Disabled for Starter Kit


texts: Check my math: Calculating the size of extension cord needed

texts:
I think I've done this right, but I don't trust myself. Will you check my math and see if I'm right about this, or correct my error if I'm wrong?

The facts

I have a device (A Yamaha Stagepas 400i sound system) that consumes 70w at 1/8 power (100v-240v 50hz/60hz)
The device needs to be used 200 feet from the nearest outlet, an outdoor GFCI 120v outlet.

Assumptions

At full power the device consumes ~800w
The outlet is delivering at least 10a

Math

800w at 120v = 6.67 amps
A 16ga copper extension cord carrying 3.4a for 200 feet will lose 10.5 volts (from http://yeroc.us/calculators/wire-resistance)
120-10.5 = 109.5v
To get 800w at 109.5v, we need 7.4a

Conclusion

Since the device will run at a minimum of 100v, and the outlet will deliver up to 10a, using 200ft of 16ga copper extension cord should be acceptable in this scenario (and a higher gauge will also work well).


texts:
I have an ABC watch from Casio that is also an altimeter, barometer, and compass. I'm fascinated that all these features are powered by solar, which makes me curious:

How much power is generated from a typical solar-powered watch?


texts:
I am attempting to design an RFID system. But before I do I need to simulate this system. I know I need to use the link budget equation to see whether or not the RFID tag will receive enough power to activate it and then backscatter the signal to the UHF RFID reader. Unfortunately, there are alot of equations online. How do I choose which one to use? I want to be able to predict the power to within 10-5%.
An example from the equation below there are a few derivations from this equation, in addition, they also use the Friis equation. Which one is more suitable for an RFID system.


texts: Can a constant-current stepper driver be coerced to act like a constant-voltage driver?

texts:
I have a strict requirement1 to drive a stepper motor with an L/R (Constant Voltage) driver but the problem is, nobody seems to commercially make these anymore due to their inefficiencies compared to the chopper-type drivers.

Reading up on how the chopper drivers work, it seems like you give it a current limit and the board uses feedback via a sense resistor to "chop" the voltage on/off to maintain a constant current at the specified limit, independent of motor speed.

This current limiting mechanism got me thinking: If I were to make the current limit high enough such that this limit could never be met, even at max output voltage (supply rail minus some small drop), would I have effectively turned the chopper driver into an L/R constant voltage driver?

For clarity, here are the specs for the stepper motor I need to drive:

2-phase, Bi-polar
1,600 steps/revolution
Winding Inductance: 80mH - 150mH
Winding Resistance: 160 - 220 ohm
Operating Voltage: 15V - 35V

By the way, if somebody knows of a true L/R constant-voltage driver that meets the above specs, that would be ideal!

1The reason it's a strict requirement is that the flight hardware uses an L/R drive and we must Test Like You Fly, a NASA guideline which states that you should test equipment on the ground in the same form, fit and function as flight hardware.


texts:
I'm trying to connect ZTE MG2639 to 5V AVR (or USB<->RS232). This module is using 2.8V at IO. How can I do that? Normal voltage divider?

And how to check if communication is OK in Putty? Just type "AT"? Or "AT" and press something? It's my first time playing with AT Commands.


texts:
I am a beginner in assembler language I was reading some stuff online(belongs to a university) and I saw that
the P bit in psw after executing this instruction mov a,#03h  A=0000 0011B so P=0
first it was difficult to know what is p bit after some research I thought it is parity bit and then you have to count the number of one bits in the result so the number of 1 bit in the result is 2 so it is an even number so P must be equal to one so why is P equal to zero here ?


texts: In my book I often see the N-type semiconductor both drain and source being shown as n+ whereas the p-type semiconductor or the substrate is shown/represented as p only. Why is N-type semiconductors represented as n+ in a N-channel MOSFET?


texts:
I want to design a circuit that can protect GPIO of the microcontroller from high voltages.the GPIO connects externally to mechanical switch.

So my approach was to use zener diode to clamp the high voltages to the low acceptable voltage.My microcontroller can accept maximum of 3.7V on the GPIO.

So the GPIO that i want to protect, has a function of detecting falling edge interrupt. below is my circuit that i have implemented.

In the above circuit D1 is the zener diode with R10 is being its current limiting series resistance. R45 and C36 are part of the denouncing circuit.

So the idea is when someone gives higher voltage like 12V at TP12 and TP13 by mistake, it should clamp it down to 3.0V safely.

here is the datasheet of this zener diode Link

NOTE: R44 was to limit the current flowing through the external switch connected to TP12 and TP13 whenever the zener circuit is not mounted (i.e. R10 0 ohm and D1 not populated).

questions i have is...
   Is this the correct way of protecting the GPIO? Have i implemented it
   correctly?
   what should i do to fix following problem?

problems i am facing...

The zener has leakage current and that's why when zener is in the circuit it
draws 0.141mA through 10K and drops 1.4 V across 10k resulting in 1.9v on the
GPIO, i want 3.3V ( VCC of the microcontroller) to appear on the GPIO. what
should i do to fix this?
Also i selected 1K for zener so that it doesn't affect de-bouncing circuit
much and also limits current through zener enough so doesn't exceeds its
wattage limit.

but if you look at the above image 5mA is what i should i allow through zener
in order to get 3.0V. will i damage zener if i pass more current?


texts:
Series LED:

How do you make a LED circuit in series where the next LED will turn on, with equal brightness after a certain time delay?

For example, when I turn on the power, the red lights will turn on and after 10 seconds, the orange ones will light and 10 seconds after the orange LED lights up, the yellow ones will light up.

We have tried using this circuit for 1 LED but the LED did not have a delay before turning on. The following is the LED Delay circuit??

Where we computed the time delay as resistor value from +9V multiplied by the capacitance.
(Source: http://www.ehow.com/how_7700687_add-delay-led.html)


texts: Shared or separate SPI buses for peripherals in a PCB?

texts:
I have four SPI-controlled chips which I want to control from Zynq-7020 via an FMC LPC connector. Each chip/device requires an SCLK, MISO, MOSI and CS line.

I'd like to give each device their own separate SPI bus, but for my given application, I don't have enough clock capable (CC) pins on the FMC LPC connector to give each device their own SPI SCLK. I do have enough pins to give each device separate MISO, MOSI and CS lines. There are a few options on what I could do, and I am wondering what the advantages/disadvantages of each would be:

1) Every device shares a single SPI bus (Separate CS lines, but shared SCLK, MISO, MOSI)

2) Shared SCLK, but separate MISO, MOSI, and CS lines for each device

3) Separate SPI buses, driving SCLKs through LA pins instead of CC pins on the FMC LPC interface. (I am not sure if my FPGA would like that I am driving a clock from a non-CC pin)

My target device is a PCB, what implications would each of the three options have on my design, and what would be the best option?


texts:
I'm trying to set up a PIC18F67K22 to log data to an SD card, but I am having some trouble getting FatFs working properly. I implemented some low level code following the diskio.c API that is provided, and I am able to monitor the SPI data stream using a Saleae Logic Analyzer. Everything that I see going back and forth is sensible, but I cannot write data to the file.

I am able to create a file, but the file is always empty. After creating the file, my code no longer even attempts to communicate with the SD card (the SD chip select line never goes low during a recording).

Am I using FatFs' f_write and f_sync functions correctly here? What are some reasons as to why the functions would return FR_OK, even though they never write to the disk?

FIL file;
char text[64];

void update_record() {

static unsigned long timer;

if (record == 0 || ms - timer < 1000)
    return;

timer = ms;

UINT bw, i;
FRESULT fr;
f_write(&file, "test", 4, &bw);

text[9] = ',';
text[10] = '\n';

for(i = 0; i < 8; i++) text[i] = 0x20;
floatToString(Values[0].d_double, "");
fr = f_write(&file, &text, 8, &bw);
fr = f_write(&file, &text[9], 1, &bw);

for(i = 0; i < 8; i++) text[i] = 0x20;
floatToString(Values[1].d_double, "");
fr = f_write(&file, &text, 8, &bw);
fr = f_write(&file, &text[9], 1, &bw);

fr = f_write(&file, &text[10], 1, &bw);

fr = f_sync(&file);

}


texts: Equivalent voltage source for this charge pump

texts:
Suppose the charge pump for doubling voltage:

Here diodes are Schottky (voltage dropout is \$V_d\$), the battery has internal resistance \$r\$ and voltage \$V\$, the switch generate square wave with frequenct \$F\$ on bottom pin of the capacitor \$C_1\$.

Question. How to calculate equivalent voltage source (voltage \$V_o\$ with serial resistor \$r_o\$) for this circuit? It's obviously that \$V_o=2V-2V_d\$, but what is \$r_o\$?


texts: Connect LM311 pin 7 to input pin Arduino

texts:
I'm brand new to the world of electronics and not very talented, so have mercy.

This circuit lights up a LED when an IR beam is broken:

I was wondering if I could connect the input pin of an Arduino (or Adruino programmed AVR microcontroller) instead, to count +1 if the beam is broken by a person passing. Possibly with a delay() function of sorts, to keep it from counting up more than once.

EDIT: Apologies for not being accurate on power supply. Unlike this scheme indicates, I used a 9V battery and a 7805 voltage regulator to get 5V on this circuit. Meaning, I believe it would pair well with an ATtiny, programmed via Arduino, that can take 5v as well.

The end goal, to complete the story, is to do this with two IR beams, physically a bit apart, their receivers connected to two pins of an AVR microcontroller. The pins register the time stamp of breaking the beam. By comparing the two, we can determine the direction. Going into the room counts +1, going out - 1. Finally the AVR checks if the sum is larger than 0. If yes, someone is in the room and it lights a red LED.

I understand there are many issues that need to be resolved in the software to make the counting accurate. That's for a later day or, preferably, someone else.:)


texts:
I have a ESP8266-01 and I want to use it to check if my door is open or not using GPIO0 or GPIO2 as input.

As GPIO0 and GPIO2 both needs to be high or floating at boot, I cannot directly connect my switch to either of it. The solution is that I connect the switch between GPIO0 and GPIO2 so that at boot-up both are high, and once the chip is booted, set GPIO0 as output and low. Now, if the switch is open, GPIO2 will read high and if it is close it'll read low. This is what I understand from the discussions and posts at several places.

But, I'm new and confused! :P

Can I connect GPIO0 and GPIO2 directly without anything else? No pull-ups, no resistors in between?

Is it okay to directly connect GPIO0 and GPIO2 with a wire at boot-up? And also when GPIO0 is output-low and GPIO2 is input?

As I understand, in output mode, GPIO is connected the with VCC or ground with very low resistance. What about input? How is it implemented? If I connect GPIO0's output to GPIO2's input, is there any chance of short-circuit?

When setting that up after boot, is there any specific sequence I should be setting GPIO0 and GPIO2 as output or input respectively? Does it matter?

From what I understand, the chip has internal pull-ups. But discussions around the web gives a very confusing idea about the need of external pull-up resistors. Are pull-up resistors needed to implement this?


texts: I've opened up a Lutron dinner, and I'm trying to understand how the microprocessor gets its DC voltage. With my limited knowledge I'm not seeing an AC/DC converter. I've attached pictures, can someone explain how this works?


texts: How should a SPDT switch be wired for a digital input?

texts:
I want to connect a switch to a digital input on a logic board and make it so that the input goes high when the switch is pressed. I'll be using a SPDT switch:

Should I connect the digital input to COM, GND to NC, and VCC to NO?

Or could I connect VCC to COM and the digital input to NO? (this would leave the digital input "floating" when the switch isn't pressed, but is that necessarily a bad thing?)


texts: hi could you please help me to know how did they find the derivative of V lyapunov function


texts: Would it be possible to design a SoC have to two antenna?

texts: If you use an actual SoC such as the Qualcomm Snapdragon Processor for mobile communications would it be possible to have two cores both sharing a common IO (Cellular/WiFi/GPS/Bluetooth) integrated circuits but its own separate antenna ?


texts: Can the Data wires of a USB cable power a LED?

texts:
I got a USB wire from an old mouse and the wires were soldered to the circuit as: Green - D, Orange - C, Blue - V and White - G.
Assuming orange was red and white was black; they should be VCC and GND respectively. Meaning they transmit power.

However I found that the green and blue writes could power a LED, with blue being positive and green negative. The other two couldn't.
I don't have a voltmeter to check so I was wondering whether the wires were mixed up or if this is normal. If the wires are mixed up, how do I separate D+ from D-?

Thanks.


texts:
Consider this schematic, which is intended to symbolize two nine-volt  batteries connected in series with two lengths of (4-gauge) copper wire and is not to scale:

\$\mathcal{E}_1\$ and \$\mathcal{E}_2\$ are idealized emf sources
\$R_1\$  and \$R_2\$ are internal resistors of very minute, but significant, resistances
The additional “wire” between points \$\mathsf{A}\$ and \$\mathsf{C}\$ has no resistance
The wire between \$\mathsf{A}\$ and \$\mathsf{H}\$ and between \$\mathsf{C}\$ and \$\mathsf{K}\$ has a resistance per length of \$8.47\times 10^{-4} \ \left. \mathrm{\Omega} \middle/ \mathrm{m} \right.\$
The wire between \$\mathsf{A}\$ and \$\mathsf{H}\$ measures \$ 1 \ \mathrm{m} \$ in length
The wire between \$\mathsf{C}\$ and \$\mathsf{K}\$ measures \$ 1 \ \mathrm{m} \$ in length
Points \$\mathsf{H}\$ and \$\mathsf{K}\$ are literally grounded into the earth
Conventional current \$I\$ flows in the direction in which positive charges would drift (in the direction of decreasing potential)

As I understand it, charge will flow between the grounded points and the earth until the electric potential at \$\mathsf{H}\$ and at \$\mathsf{K}\$ can be considered to equal \$0 \ \mathrm{V}\$ (with respect to earth, of course).

My question is this: will current flow around the circuit? That is, will the current labeled \$I\$ in the diagram equal \$0 \ \mathrm{A}\$ or will it not?

I can imagine two things happening: (1) the earth does not as a conductor, so the circuit remains open and no current flows, or (2) the earth does act as a conductor, so current does flow through the circuit. If (2) were true, then the following equations would have to hold:

$$ -I\left( 1 \ \mathrm{m} \right) \left( 8.47\times 10^{-4} \ \left. \mathrm{\Omega} \middle/ \mathrm{m} \right. \right) -IR_1 + \mathcal{E}_1 -IR_2 +\mathcal{E}_2 -I\left( 1 \ \mathrm{m} \right) \left( 8.47\times 10^{-4} \ \left. \mathrm{\Omega} \middle/ \mathrm{m} \right. \right) = 0 $$

$$\mathcal{E}_1 + \mathcal{E}_2 = I\left( 1.69\ \mathrm{m\Omega} \right) + IR_1 + IR_2 $$

$$I = \frac{ \mathcal{E}_1 + \mathcal{E}_2 }{ 1.69\ \mathrm{m\Omega} + R_1 + R_2}$$

Also, these three equations do not factor in the resistance due to the earth, which might need to be considered if (2) were true and which I have no idea how to calculate.

Retrospective note: As pointed out in the comments, my schematic leaves a lot to be desired and does not conform to standard conventions that ease legibility. However, I will leave these errors as they are (at least for now) so that others might be able to learn from them.


texts: How can I reproduce ambient EM fields inside a Faraday enclosure?

texts:
I am part of a research team looking at the possible effects of EM fields on psychological function. The experiment calls for participants to perform a series of tests while inside a Faraday tent that blocks most of the radio spectrum. We'd like to have the participants perform the same tests inside the tent, but now while being exposed to roughly the same EM fields that are present outside of the enclosure. If we open the door or a panel to allow EM fields inside, then the participants will know. Instead we need the participants to not know whether they are being exposed to ambient EM fields.

Our current plan is to link 2 broad spectrum antennas outside the Faraday tent with a matched pair of antennas inside the tent. We'd have a relay switch in the cable to control the on/off function, and a preamp to slightly boost the signal. I'm not convinced this will work though.

What would you guys recommend? It doesn't have to be a perfect replication, just "good enough." We're most interested in reproducing the 25MHz-3GHz range.


texts: Finding impedance Z and \$ \cos (\alpha) \$ in RLC circuit

texts:
I would like to have some help with this problem:

U = 93 [V]

f = 600 [Hz]

L = 0,24 [H]

C = 0,16 [μF]

R = 950 [Ω]

This is the RCL circuit which I need to find the impedance \$Z\$ in and \$\cos(\alpha)\$

The first two questions that I had was to find the inductive reactance, XL, and the capacitive reactance, XC. I figured them out and I got XL = 905 ohm and XC = 1658 ohm.

I thought that I would use this formula:

$$\mathrm{impedance} \, Z = \sqrt{R^2+(X_L-X_C)^2}$$

But I can't get it right.
I would also like to know if \$\cos(\alpha)\$ is solved through \$\cos(\alpha) = \frac{R}{Z}\$


texts: Can we send multiple signals in same core at the same time in the fiber optics? If yes, how?

texts: I am curious to know how exactly does the fiber optics works. I understand the basic concepts of the fiber optics communications but am curious to know if there is a way to send multiple signals in same core at the same time in the fiber optics? How is it possible? Is there a way you can send light of different wavelength and able to detect them at the rx end?


texts: GP4 on a PIC12F683 microcontroller not functioning correctly

texts:
I am attempting to make a project wherein I have some LED's on pins GP2 and GP4 of a Microchip PIC12F683 microcontroller flashing in a simple pattern. The problem is that I cannot write to GP4 correctly, or that it at the very least won't respond to me writing to it. As far as I can tell, there's nothing wrong with my configuration registers, and when I tested the pin with a multimeter, it reads at about 2.5 volts. When I probed the pin with an oscilloscope, it seems to have a sine wave floating on the top. This might be interference of some kind, but to be honest, I have no idea. I'm using MPLAB X and a PICKIT 3 to program the controller.

TL;DR: GP4 doesn't work and I have no idea why.

My code:

/*
     * File:   newmain.c
     * Author: Malachi
     *
     * Created on May 3, 2018, 4:38 PM
     */

#include <stdio.h>
#include <stdlib.h>
#define _XTAL_FREQ 8000000
// PIC12F683 Configuration Bit Settings
// 'C' source line config statements

// CONFIG
#pragma config FOSC = EXTRCCLK  // Oscillator Selection bits (EXTRC oscillator: External RC on RA5/OSC1/CLKIN, CLKOUT function on RA4/OSC2/CLKOUT pin)
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config MCLRE = OFF       // MCLR Pin Function Select bit (MCLR pin function is GP3)
#pragma config CP = OFF         // Code Protection bit (Program memory code protection is disabled)
#pragma config CPD = OFF        // Data Code Protection bit (Data memory code protection is disabled)
#pragma config BOREN = ON       // Brown Out Detect (BOR enabled)
#pragma config IESO = ON        // Internal External Switchover bit (Internal External Switchover mode is enabled)
#pragma config FCMEN = ON       // Fail-Safe Clock Monitor Enabled bit (Fail-Safe Clock Monitor is enabled)

// #pragma config statements should precede project file includes.
// Use project enums instead of #define for ON and OFF.

#include <xc.h>

/*
 *
 */

int main(void) {
    OSCCON = 0b01110001;
    TRISIO = 0b00001000; // all bits are 0, setting them as outputs (except for GP3)
    //NOTE: WHEN YOU CHANGE GP3, BE SURE TO CHECK THE MCLR BIT AT THE TOP IDIOT
    CMCON0 = 0b00000111;
    ADCON0 = 0b00000000;
    ANSEL = 0b00000000;
    GPIO = 0b00000000;

    while(1) {
        GP2 = 1;
        GP5 = 1;
        __delay_ms(500);
        GP2 = 0;
        GP5 = 0;
        __delay_ms(500);
    }
}

For context, while I'm not necessarily new to writing code, I'm by no means experienced.


texts: Transistor Choice for LED Control Circuit

texts:
I just completed an introductory course in digital design.  During the course I designed a circuit for driving multi-color LED's with an automotive application (for a personal project).  The following is what I made:

The circuit basically turns the LEDs amber and makes them blink when the turn signal comes on.  After designing the circuit I decided that I wanted to control enough about 450-500 LEDs with it.  The LED strips I'm using are set up for 12 Volt power sources and 450 of them would require 10 Amps.

I'm including the datasheet for the strips themselves (even though it isn't all that informative): LED Data Sheet

I did some research and it seemed to me that transistors were the thing to use for switching given the 12V 10A load.  I should note that the control circuit will be run off of a 5V regulator and the LEDs off of a 12V regulator.  At least that's the plan.

So here is the circuit after labeling where the transistors will be (labeled as "Trans.").

Now the task of transistor selection arose and I'm struggling because I am in entirely unfamiliar territory.  I need to measure the output from the turn signal before I can select those transistors, but I can select the transistor coming from that OR gate.  Here is the OR gate I'm planning on using:
OR Gate

I have to say I'm slightly confused that there is a negative value in the "Maximum High Level Current" category.  Other than that I know I need to select an appropriate Hfe and I'm fairly sure, based on my reading, that I want an NPN transistor.

Any selection advice is very much appreciated.  I realize that there are other more common ways to run LEDs like PWMs.  I used combinational logic because it was the only thing I knew and it still is the only area of electronics with which I have any experience.  I am willing to consider other methodology if I really should, but the functionality I'm making is fairly simple and I feel like I'm just a few components away from making it work.  I'm open to all commentary, suggestions, advice, et cetera.  I'm totally new to electronics so I may have to ask for further explanation of some comments, but we all have to start somewhere!


texts: Does CKDIV8 save battery life when programmed?

texts:
On ATmega328P there is a CKDIV8 fuse bit that when programmed divides clock by 8.

I'm wondering if the power consumption is equal on these two setups:

micro with 8MHz external crystal and CKDIV8 fuse bit programmed
micro with 1MHz external crystal and CKDIV8 fuse bit not programmed

In both cases I get 1MHz clock which is sufficient for my application.
The reason is I can't find any cheap 1MHz crystals, for some reason they are incredibly expensive $15+ Digikey Store 1MHz crystals.
Comparing to 8MHz crystals with better ppm (+/- 10ppm) for less than $0.50 Digikey Store 8MHz crystals


texts: I have found this board installed and I am unsure what it is or what its function is.  I have googled it to no avail.


texts: Choosing Collector Current for Transistor Amplifer

texts:
I see in the guides to standard Bipolar Transistor circuits (emitter-follower, common emitter amplifier), they always say: Choose a quiescent current of 1mA.

How is this value chosen?  I look at the specification sheets and I am not sure what I am looking for specifically.  From my understanding it should be based on the output characteristics of the transistor so that clipping does not occur and maximum symmetrical swing is obtained. However, I have to use the 2N3904 transistor, and the spec sheets don't have the output characteristics. I also have to drive a load of 100k ohms. Does choosing a quiescent current depend on the load?


texts: AC vs DC Measurement using an Oscilloscope of a half-wave rectifier

texts:
This question is a follow up to a previous question found here.

As a follow up question: for a half-wave rectifier, what is the "AC" voltage and how do you measure it? Additionally, What is the DC voltage and how do you measure it? From another answer, the DC voltage is the "offset" between the AC and DC signals when viewed in AC and then DC mode. How do I then measure AC signal? Go into AC mode and measure from the peak to GND? If I do it that way, the those values are: VDC= 2.9V and VAC=6.0V (from reference to peak). Does that seem correct? Finally, is it incorrect to talk about the voltage in this way?


texts:
In an extreme low power project (MCU+BLE SIP running on a CR2016 battery for year(s)) I would like to measure the power consumption under different environments/algorithms.
What would be the correct way or setup to measure micro (nano ??) watts? in a short duration and over a long period of time?

The input voltage can be 3.2v - 1.7v (changes over time). I would like to eventually determine (or at least give a good estimation) to the duration a single battery would hold the device.


texts: Real Power or Reactive Power in Superconducting Motors?

texts:
My circuits class is teaching that in AC power, there are two kinds of loads. One is a resistive load, with absorbs power at all times. The other is a reactive load, which absorbs zero average power.

I'm trying to understand this concept in relation to motors, which are inductive.

A superconducting motor has no resistance.   Yet it will have an inductance. If the superconducting motor is turning something, it must be receiving power. Therefore it must be resitive. However, the coils themselves have no resistance. What is going on here?


texts:
Comment from http://electronics.stackexchange.com/questions/356185/nand-flash-retention-using-usb-charger/356190?noredirect=1#comment855287_356190 claims that reading from flash storage is no lossless operation, so they get refreshed by the flash controller on spare time.

  These filesystems do not use journaling, so ejecting the card or
  losing power during a write can corrupt it. Even with journaling,
  power loss during writes on flash is a touchy issue... you might lose
  more than the data that is being written, and it can spread to
  adjacent blocks too. A simple write may cause the controller to decide
  to move data around, etc...
  https://cseweb.ucsd.edu/~swanson/papers/DAC2011PowerCut.pdf

  https://www.embeddedarm.com/about/resource/preventing-filesystem-corruption-in-embedded-linux

Doesn't repeated refreshing wear out these floating-gate transistors?


texts: Reverse function optocoupler in series with physical NC switch?

texts:
I've read this answer

(reverse function optocoupler) but my case is different:

I've got a CNC mini lathe.

I have a limit switch on one of the lathe's axis ends (X+) wired as NC to my Gecko G540 controller and it works normally. When the switch is closed, the Gecko's input is grounded, the lathe works normally. When the switch is open, the input is not grounded, the lathe halts, for protection. And, if the switch eventually fails, or a wire disconnects, the controller's input will see it as OPEN also and will halt the lathe also. So it's for extra protection.

If I add another switch wired in series with the first, (as  in the A picture) for example to limit the movement of the axis to both extremes of movement, it works also normally. If any switch is open, or if any switch malfunctions, the controller halts the movements of the lathe's axis.

But I can't use a switch in one of the lathe's axis extremes. I'll need to use a slot optocoupler.

But I can't figure it out how to do the same thing with the Optocoupler, which will sense the presence or not of the X leadscrew between it's IR LED and it's phototransistor (X+)

If I wire it the way the B picture shows, it's in a normally open configuration. It works normally as the X+ NC Switch. If the led light reaches the transistor it allows the Gecko's input to be grounded. If not, the system halts. If the switch or the Optocoupler fails, the input won't be grounded, and the system will also halt. (Do I need a resistor between the collector and the gecko's input??)

But I want the optocoupler to behave the opposite. When the led light is blocked I want the gecko's input to be grounded, and when the led light reaches the phototransistor, I want to have a high state on the Input. I can't figure how to wire it in series with the physical NC switch (to still use only one input), even with a transistor for inverting the signal, and still mantaining the safety of if any of the switches (opto of physical) fail, the circuit will be open and the controller will halt.

So I'd like the optocoupler to behave exactly as any of the switches on the A picture, but with it's logic inverted. Can it be done in a simple way?

Thanks a lot!


texts: Internal and external storage for a FPGA

texts:
I want to store at least 2Mbits on a FPGA. What is the normal practice for storing data on a FPGA internally?
Also, if I wanted to store 4GBytes externally, how would I go about doing this? Is it possible for a FPGA to read directly from a USB drive?


texts:
I am going to design a stereo audio amplifier with TDA2030A. This is going to be an amplifier that is going to be powered from 27.6V DC and 12W per channel.

Is there any sources that I can learn PCB design guidelines for audio amplifiers from? Or can you give some tips?


texts: Is there an easy way to find out if my 0805 SMD components are ferrite beads?

texts:
I ordered SMD 0805 components among other items and I received a package with the SMD components but there is no description at all.

Also, there is no identification on the components itself.

Is there an easy way to find out if the components I have are ferrite beads? (that's the most logical type I can expect from the post).

When I used a DMM to measure the resistance it is 0 ohm, which seems normal for ferrite beads.

(note I don't have any EMI test, but I have an (old) oscilloscope if needed).


texts: What does the symbol and rating mean on this power plug?

texts:
Why is "no load power input 75mW max @230V AC 50-60Hz", but input is "100-240V ~ 50-60V 0.5A which results in 115W (230V x 0.5A)?

What do the 3 symbols mean?

Thank you for reading and answering. Just want an understanding. It is a vacuum cleaner charger.


texts:
I think I've phrased the title correctly, although happy to be corrected. For some reason I'm having a huge problem wrapping my head around the use of ground in low voltage (e.g. 3.3V / 5V) circuits. I've read this answer a few times and have a better understanding, however still have this unanswered question.

As far as I understand, in the UK, if I were to plug in my DC power adapter into a socket the voltage is 230Vac, referenced, at some point, to the actual earth. Inside the adapter, a SMPS circuit using transformers, regulators and filters outputs a 5V DC voltage, for instance. What is that 5V referenced to? Is the negative line of the DC output tied to the AC earth?

If I were to take two different power adapters, hypothetically, I assume it would be possible for one of the two to have a potential of 100V on the +ve line and 95V on the -ve line? That provides a 5V potential difference, therefore working the same as the other that had a potential of 5V on the +ve line and 0V on the -ve line. What would happen if the -ve lines of these were tied together in a circuit (i.e. a common ground)?

My questions stems from the desire to use an auto switching power mux such as the TPS2113A. The grounds from the two supplies must be tied together, but what if they're at a different potential? An example circuit from Pololu is below.


texts:
I am not an electrical engineer, but I am curious enough and my mind tells me to make a radio circuit.
Now I am into it, so to make one, I need some components, but before that so that I can be a little more into basics of the working of the device, the only device I can't find an explanation for is the LM386 IC.
It is an audio amplifier but its pin-out is not that clear.  It shows a simple triangle but no information.
What is it? A logic gate,  another IC?
Please explain to me how the LM386 works.


texts: Why simple digital multiplexer uses OR gate to combine chip parts outs?

texts:
Why not just wire together outputs of the internal AND gates. For instance, consider the following Mux scheme:

Here outputs of the internal AND gates are combined using out OR gate to produce output, but why not to just wire them together rather than use additional chip? it seems to be a common practice to wire together multiple pins so we get ONE (or True) when at least one of the internal chips produces ONE.


texts: Is it posible that two devices plugged in different PCI slots share single PCI bus

texts:
Let's assume we have two network cards, Foo and Bar plugged in slots 5 and 4 on motherboard, with some BDF id assigned, for example:

Foo => 09:00.0
Bar => 02:00.0

That's the usual scenario. But is it possible, that these two devices will share the 'bus' part, and differ only in 'device' part, like:

Foo => 09:00.0
Bar => 09:01.0

While still being plugged under different slots?

Does x86 architecture allows that, do you know any edge case when this would be true?

Maybe multiple PCI slots stacked on single PCI bus, like a hub, or something, is this even possible? I have a limited knowledge in electronics.


texts: Xbee data messed up with 2 sensors communicating to master

texts:
I have an Xbee Master and slave set up as below (from Arduino website):

This way works great for 1-1 communication. I'm getting my serial data perfectly. However, when I had one more slave, the data is completely messed up. How exactly can I get data from both sensors? (I thought, the master xbee module would separate node data by new line but it seems to be mixing the bits itself.)

Master

Slave