texts: High speed PWM sometimes glitches out my gate driver

texts:
I have a Sparkfun Arduino Pro Micro (an ATMega32u4 breakout board), feeding two PWM signals to a custom board I made based around a mic4606 (dual half-bridge gate driver IC)

The IC is driving 4 MOSFETS in an H-bridge configuration, which drive a Peltier device through a pair of LC filters to smooth out the ripple (which improves the efficiency of the Peltier). The PWM and ground connections are made with a couple inches each of ~22 gauge hookup wire.

If I setup my Arduino to generate a 187.5kHz signal, it occasionally "glitches out"; I'll feed the PWM signal into one side of the bridge, leaving the other one grounded, but both sides will switch (and thus no current flows through the peltier). Maybe 80% of the time it works fine though.

I reduced the PWM frequency to 93.75kHz, and now it seems to work 100% of the time. I would rather use the higher frequency to keep my filters smaller while maintaining efficient operation of the peltier, so I need to figure out what the problem is.

Is a couple inches of hookup wire enough to mess up a ~200kHz signal? Or is it likely to be an issue with my (or the Arduino's) PCB design? If it helps, this is what my PCB looks like:

(I've since redesigned it to shrink some high frequency current loops, particularly the fairly large ones in this design through the "bottom" FETs, and all the high dI/dt current loops described in the datasheet, but I haven't ordered it yet. would this help? I assume those will only help with not-important-for-a-prototype EMI issues)

UPDATE: I just recalled that attaching small (100 ohm) series resistors in the PWM linse reduced reliability even further. So perhaps the issue is my MCU's outputs aren't "strong" enough to drive the gate driver inputs? I hope I don't need a "gate driver driver" 0_o

UPDATE: here we go. I've cleaned up my schematic for display purposes:


texts:
I have a question regarding SSRs. I am working on redesigning a PCB for a medical device that needs to pass class B radiated emissions, therefore radiated EMI must be very low.
We have a CPU fan running off 12 V (~890 mW) and I was going to try using a SSR to control its operation, due to the cost savings of an SSR vs. a standard mechanical relay. Do you think the greater "on" resistance of the SSR (1-2 ohms vs. milliohms) could lead to increased EMI? The fan does have a dedicated hub driver.


texts: What do the shades on the IC's edge mean?

texts:
I am trying to get into a bunch of stuff by taking on a large project. I want to create my own FPGA board, for which I am trying to understand the schematics of an available board (In this case a Cmod A7).

The IC has a shaded band on it's edge next to a group of pins. What does this notation mean? I also think that these schematics may have been created using Altium, to which I don't have access.

Also hopefully, someone can confirm if the bidirectional arrows next to the IC symbol are inout pins.


texts: How might one connect a laptop's aux out to an oscilloscope?

texts:
I am using an online pure tone generator (which generates sinusoidal sound waves) on my laptop to output sound.

The AUX-out jack on laptops outputs sound in analog rather than digital signals. Unless I am mistaken in my thought process, in theory, I should be able to somehow display this signal on an oscilloscope.

The only input the oscilloscope I have has is a CH/BNC input and digging through the lab equipment I have found a device that fits into the CH jack and has two crocodile clips (red/black) coming out of it.

Similarly I have also found another device that connects to the CH/BNC jack with red/black binding posts, shown below.

I have access to a male-to-male aux (3.5mm) cable. Is there anything I can do with this setup to view the audio signal outputting from my laptop on the oscilloscope? Looking around online did not help my particular case. I thought of connecting a microphone to the oscilloscope and placing this mic next to my laptop's speaker, however this is obviously less accurate (variable mic quality, takes in background noise, etc.)


texts: What component/device to use for a front-eye display

texts:
I need to display information in front of my eyes, just like Google Glass, but in this case, it has to fill a bigger field of view (is it the good term?). I have already thought about a couple ways to do it, but I am not sure they be relevant :

1) Using reflection on a piece of glass, with a screen on a side. In this case, how can I make the reflection work, what kind of materials to use, the nature of the side screen ?

2) Some type of micro-projector

If possible I would like to plug it as an external display, to a simple computer, running any OS, and it is a plus if it can be displayed on a pair of glasses.


texts: What is the technology of slicing a chip to debug called?

texts: A couple of times, I have heard that there are situations where a microprocesor or chip has to be sliced to look in to the contents, or for the purpose of debugging it. Layer by layer sectioning is performed is my understanding. I did google search but since this information came to me through friend circles, I couldnt find the exact technology used to do so. Please help me understand better.


texts: Why do cell phones sometimes interfere with amplifiers

texts:
I have an old Sony amplifier (TA-F117R) next to my desk where I keep my cell phone. Sometimes I put it ontop the amplifier, because it is pervecly alighed with the surface.

When I hang some call up and land the phone close to the amplifier the loud beeping noises started to burst from the speakers, something like the "modem calls" in the old ages of dial-up internet connection.

I suspect the phone - transmitter negotiation is responsible for that. The radi waves transmitted from the cell phone are strong enough to induce parasitic currents in the amplifiers circuits leading to the noise.

What makes me wonder is that this noise is generated only when I hang up the call and put the phone close the amp. I can send/recieve SMS, e-mails and browse the internet using the phone. I have bluetooth, NFC, GPS and Wi-Fi on all the time.

I have Sony Xperia L now, but I could observe the interference with all phones I used to have (Philips Fisio, SonyEricsson K770i, Samsung Galaxy-Y,...) and amplifiers (Old stereo, PC speakers).

What exactly causes such interferences and why SMS and others are transmitted without such interference.

The answer here blames the GSM protocol and the fact 800 - 900 MHz signal interfers with the amplifier's structures. However it dosn't address why SMS and data transfer do not cause such interference.


texts: Are silicon microbolometers inherently more expensive than conventional CMOS light sensors?

texts:
We're finally starting to see practical thermal imaging sensors (microbolometers) entering the consumer market.  However, they are still vastly more expensive than comparable visible imaging sensors.  The most basic 384x288 17µm pixel (i.e., 32mm2) thermal imagers run about $500, whereas $500 will get a 6000x4000 2µm pixel (i.e., 96mm2) CMOS sensor ... plus 5-axis sensor stabilization and more.

My question: Assuming the same economies of scale were applied as are already used for conventional CMOS sensors, is the manufacturing process for silicon microbolometers inherently more expensive?  Or in the limit is it still just some (similar) number of photolithographic steps?

To elaborate: Thermal cameras look for radiation with wavelengths between 7-14µm, whereas visible light is in the range 0.4-0.7µm.  Based on the physics alone, at the diffraction limit microbolometer pixels will have an order of magnitude greater surface area.  Apparently commercial sensors are at the diffraction limit for both visible light (at 1 micron pixels) and thermal light (at 17 micron pixels).  So, to make it fair, we might compare a 1" 24Mpx visible sensor with a 1" 300kpx thermal sensor.

Both sensors can be made from silicon using a CMOS process.  The structure of microbolometers looks a little trickier than state-of-the-art visible spectrum CMOS sensors, requiring a thermal bridge for each pixel as well as vacuum encapsulation of the sensor.  But I know little of large-scale manufacturing processes, so are these variables significant in the limit on a per-unit basis?


texts: Effects of out of phase angle ac voltage between two power grids

texts: I am currently learning the basic of pmu and its effect in ensuring the reliability of power transmission. I have seen that to ensure grid reliability, synchronisation of 31.78us is needed to keep tve within 1%. However, I do not understand what is the effect of such synchronisation. What is the effect of out of phase angle power grid? How will it affect the reliability of power transmission system? Thank you.


texts: working voltage and output levels of a logical gate chip

texts:
I would like to apply some digital gates to control 12V signals. Concretely I would like to invert some of them using this inverter chip inverters. But I would like to keep Vout = 12V. Controled device needs Vcontrol = 12V.

I choose gates with Vdd max > 12V in order to keep compliance. But looking at this table on page 3, I can see the Voutput field:

When I see at its description that minimum voltage was 5V and maximum one is 15V I firstly thought that I could use whatever from 5V to 15V. But looking at the picture it seems only 3 possible Vout = Vdd levels.

questions:

does it means that I can't input signals with 12V and get Vout = 12V?


texts: Visible and safe laser beam for lit areas

texts:
In an application, I need a laser beam that is safe for indirect exposure and has visible beam in lit areas. I understand that 5mW is the maximum power commonly used without the need of safety glasses but 5mW lasers don't seem to have strong visible beams. Is there any work around /suggestions?

My application only requires laser beams to be visible from 5cm-200cm.


texts: cable gland for pre terminated ip camera cable

texts:
Preamble: First time posting here. I'm a noob in electronics.

I'm installing an outdoor ip camera. I need to route the cables from the camera into a waterproof project box I got off Amazon. The camera has a 3/16" diameter cable that splits into three cables, each with its own pre-terminated connector (one for power, one for ethernet and one that has a reset button) - see attached image. I need to get those three connectors inside the project box and still be able to seal the hole around the 3/16" cable. The largest connector has a 3/4" diameter, so my plan is to drill a 3/4" hole in the project box to feed all three connectors into the box. Are there any diy "tricks to the trade" solutions out there for sealing around a cable who's diameter is narrower than the pre-terminated connector?


texts: How to change clock frequency of STM32L432KC

texts:
I am not entirely sure whats going on here. I think I'm changing the right registers but when it comes to trying to enable the ADC clock and GPIOA clock and etc there's no write action, I can't write anything into the register. Any Ideas?

When I say can't write anything into the register I mean the RCC->AHB2ENR

Reference Sheet: STM32L432KC

Code:

void initClock(){

    RCC->CR |= (1<<3); // Enable: MSIRANGE in CR
    RCC->CR &= ~(1<<7); //
    RCC->CR |= (1<<6); //
    RCC->CR |= (1<<5); //
    RCC->CR &= ~(1<<4); // MSI Clock = 4MHz

    RCC->PLLCFGR &= ~(1<<12); //
    RCC->PLLCFGR |= ((1<<13) | (1<<11)); // PLLN = 40
    RCC->PLLCFGR |= (1<<0); // PLLSRC = MSI

    RCC->PLLSAI1CFGR |= (1<<25); //PLLSAI1R = 4
    RCC->PLLSAI1CFGR &= ~(1<<12);
    RCC->PLLSAI1CFGR |= ((1<<8) | (1<<9) | (1<<11) | (1<<13)); //PLLSAI1N = 43

    RCC->CR |= (1<<24); // Enable: PLL
    while(((RCC->CR) & (1<<25)) == 0); //Wait till PLL is ready

    RCC->CR |= (1<<26); // Enable: PLLSAI1
    while(((RCC->CR) & (1<<27)) == 0); // Wait till PLLSAI1 is ready

    RCC->PLLCFGR |= (1<<24); // Enable: PLLREN Goes into System Clock
    RCC->PLLSAI1CFGR |= (1<<24);  //Enable: PLLSAI1REN Goes into ADC

    RCC->CFGR |= ((1<<1) | (1<<0)); // use the PLL as system clock
}


texts: Converting this logic condition possible without programming?

texts:
I've been busy trying to make a relay print which has 8 inputs of around 6V-24V that powers the relay. However, I want to add a dipswitch which is able reverse the input-relay relation behavior. Meaning;

(DIPSWITCH = TRUE) The relay gets powered by default and by adding an input of 6-24V disables it.

(DIPSWITCH = FALSE) The relay is off by default and by adding an input of 6-24V enables it.

I want to make this without programming for learning purposes since I wanted to see if this is even possible without a microprocessor and programmable logic arrays.

This is the FBD with my intended function.

Which translates to:

If (signal_6V == HIGH && dipswitch == LOW){
  relay = HIGH;
}

If (signal_6V == LOW && dipswitch == LOW){
  relay = LOW;
}

If (signal_6V == HIGH && dipswitch == HIGH){ //Inverted because of the dipswitch
  relay = LOW;
}

If (signal_6V == LOW && dipswitch == HIGH){ //Inverted because of the dipswitch
  relay = HIGH;
}

simulate this circuit – Schematic created using CircuitLab

This is what I have now and it does now the following:

If (signal_6V == HIGH && dipswitch == HIGH){ //Inverted because of the dipswitch
  relay = LOW;
}

If (signal_6V == LOW && dipswitch == HIGH){ //Inverted because of the dipswitch
  relay = HIGH;
}

However, this does only 2 of the 4 conditions and violates the other conditions. I've been thinking for so long and I can't seem to figure it out to make it work without a microprocessor. My questions is if this is possible and what do I minimally need for it? For those who wants to help me out fully, you can always add a schematic, thank you in advance!


texts: Writing to timer counter while timer is running

texts:
I'm using PIC16F1947 for a project. The project requires real time tracking so a stable 32768 Hz crystal is connected with the Timer1 oscillator. The Timer1 oscillator circuit and the crystal will provide stable clock for our project.
Timer1 can only provide interrupt when the timer counter overflows. It is a 16 bit counter so interrupt will be given each time the counter rolls over to 0x0000 from 0xFFFF.
Since the timer will be used for time keeping purpose from the beginning to the end of the product, Timer1 can't be stopped. Also, it has to be run while the processor is sleeping. So we need to use it in asynchronous mode.
In our project we also need interrupts every 0.5 second. So we plan to initialize Timer1 counter to 0xC000 and then start it. Each time an interrupt will be given, we plan to bitwise OR 0xC0 to the high byte of the register.
According to the datasheet:

Reading TMR1H or TMR1L while the timer
is running from an external
asynchronous clock will ensure a valid
read (taken care of in hardware).
However, the user should keep in mind
that reading the 16-bit timer in two
8-bit values itself, poses certain
problems, since the timer may overflow
between the reads.
For writes, it is
recommended that the user simply stop
the timer and write the desired
values. A write contention may occur
by writing to the timer registers,
while the register is incrementing.
This may produce an unpredictable
value in the TMR1H:TMR1L register
pair.

Is it OK to bitwise OR 0xC0 with the high byte while the timer is running? Or should we use another Timer for 0.5 second interrupt?
Thanks.


texts: How can this layout be improved? (Gigabit Ethernet with discrete magnetics and POE)

texts:
Answer:
No there is nothing majorly wrong with the layout, it turns out that the ethernet transformer was out of spec by 0.2dB on Insertion loss, when paired with the PHY IC we are using.
Question
Is there anything noticeably wrong with the PCB routing of the gigabit ethernet?
Gigabit Ethernet has many design constraints, due to the layout of components on the PCB it is at times impossible to follow all the design rules. This design is required to perform Gigabit speeds, and feed a POE supply.
It must also pass FCC EMC/EMI and ESD testing.
I have read through almost all application notes available (TI, Intel..etc). I have, to the best of my knowledge, followed them as best I can. Traces are routed as diff pairs, and with the best possible spacing to prevent cross talk. Minimum use of vias/stubs of 2 per a segment. They are symmetrical as possible, and post magnetics each pair is matched to within 1.25mm, pre magnetics they are matched to within 2mm. Traces are routed on the bottom layer to avoid crossing multiple power planes as a reference.
However this design presents some challenges which I am too inexperienced to assess. Ie When do you choose to violate design rules, and to what extent can you get away with it.
Specifically

The RJ45 and Magnetics have to be positioned as they are. The traces from the RJ45 to the Magnetics are length matched to within 2mm and are all laid as differential pairs. However is is a bit of a muddle - will this cause an issue with the GBE performance?
Due to constraints the magnetics has two center tap traces laid underneath it (For the POE) - would this become an EMI issue? (Application notes suggest avoiding the area below magnetics)
Post magnetics there are two features to be wary of - a crystal oscillator, and a transformer (in a cutout) which may add noise to the signal.How can this be avoided?
Are the VIAs/Stubs at the phy end laid out in an acceptable manner?

Are there and obvious shortcomings of this layout that I am missing?


texts:
Let me start by saying thank you for taking the time to read this - I really appreciate it!

To the point: I am trying to create a 2-digit timer that resets and then starts at the activation of an external AC solenoid, and pauses at the solenoid's deactivation. The circuit I have created (see schematic below) works fine with a neodymium magnet, but not with an AC solenoid (it will only reset the timer, not start it)

Extended explanation: I work as a barista for a company with various coffeeshops, and in order to improve the quality - and especially the consistency of quality - of our coffee, I want to create an automatic shot-timer for our espresso machines. The time it takes for an espresso (or lungo) shot to complete is important information for a barista to ensure quality, and I want to eliminate the necessity to use separate, manually operated timers.

At the start of this project I had no experience with electrical engineering, and no knowledge of electrical components whatsoever. I have been "self"-teaching with the help of online resources. It has been a very educative experience, and a lot of fun to boot. But right now I believe I have reached a point where I need some professional advice to help me finish the project.

We work with Kees van der Westen espresso machines (Mirages, mostly), and the water supply to the groupheads is regulated by solenoid valves. As I mentioned before, my current circuit (which, as you can see, uses two Reed switches) works fine with neodymium magnets, but not with an AC solenoid. It will only reset the timer, and not start it. And when I place the reed sensors inside the espresso machine, near the solenoid valve, the result is a chaotic flickering of the 7 segment display (presumably because of "noise" form all the power cables).

I would really appreciate some advice as to how to modify the circuit to get it to work with an AC solenoid, and to protect it from any unwanted interference from nearby magnetic fields (if this is really an issue).
Also, this is my first time designing a circuit and a schematic, so any general tips and comments will also be very much appreciated.

I have also uploaded a video demonstration of my current breadboard prototype. As you can see in the video, the reed switches are connected with wires, as they will be when I eventually turn this into an end-product, because the display will be on the outside of the espresso machine, with the reed switches inside of it.
Also, on this breadboard I have connected only one display and 4026 ic for the sole reason of keeping it easier to work with. Also I'm using a 9v battery simply because that is one I have a breadboard connector for. On the eventual PCB I intend to use a 3.3V button battery.

Link to the video (be sure to set to HD): https://youtu.be/Iy0TjIrrIA4

Edit: in the video you can see that sometimes (or more accurately: one time in this video) the timer acts erratically. I believe this to be solely due to the position and approach of the magnet; I can get it to work consistently if I place the magnet right and approach it in the same manner and orientation


texts: How does this buzzer volume regulation work?

texts:
I've found a usage of a buzzer with volume regulation that I hadn't seen before.
Here's the schematic:

Timers PWM are activated like this (Atmel MCU) :
//off
PORTC.DIRCLR = 0b11110000;

//4k7 + 1k
//Enable Timer B/C
PORTC.DIRCLR = 0b01100000;
PORTC.DIRSET = 0b10010000;

//4k7
//Enable Timer A/C
PORTC.DIRCLR = 0b10100000;
PORTC.DIRSET = 0b01010000;

//1k
//Enable Timer B/D
PORTC.DIRCLR = 0b01010000;
PORTC.DIRSET = 0b10100000;

//0k
//Enable Timer B/C
PORTC.DIRCLR = 0b10010000;
PORTC.DIRSET = 0b01100000;

I've cut the complete code since I'm interested only on electrical side.
Can you explain to me how current flows through it to allow volume regulation?
What is not clear to me is that any way I enable or disable pins (GND or VCC), the current should always flow through lines without resistors and will not allow to power BUZZ in other configurations than:

PWM3 +
PWM2 +
PWM0 -
PWM1 -

Maybe I didn't understand the purpose C9 or buzzer principles.


texts: Ok, EAGLE eyes... what am I missing here?

texts:
Ok, so most of my schematic is completed, and I've cleared all the ERC checks but this one. I don't seem to see what the problem is.
all the positive powers are connected using the same (copy paste) v+ symbol, but the ones attached to the IC seem to be warning me. something to worry about, or just ignore?


texts:
Working on a school project and I am stuck on my last bit of code. Let’s say S1 is held down and the red LED is on. If, in the meanwhile, S2 is pushed, the green LED remains off and the red LED continues to be on. This state persists until S1 is released. Now, S2 has the chance to turn on the green LED. And, likewise, if S2 is held down with the green LED on, S1 is ignored when pushed, until S2 is released.

I am currently stuck in the forever loop. I cannot get my code to do as what is described in the above paragraph. Once both BUT1 and BUT2 are held down both green and red led lights turn off.

#include <msp430fr6989.h>
#define redLED BIT0 // Red LED at P1.0
#define greenLED BIT7 // Green LED at P9.7
#define BUT1 BIT1 // Button S1 at P1.1
#define BUT2 BIT2 // Button S2 at P1.2

void main(void) {

    WDTCTL = WDTPW | WDTHOLD; // Stop the Watchdog timer
    PM5CTL0 &= ~LOCKLPM5; // Enable the GPIO pins

    // Configure and initialize LEDs
    P1DIR |= redLED; // Direct pin as output
    P9DIR |= greenLED; // Direct pin as output
    P1OUT &= ~redLED; // Turn LED Off
    P9OUT &= ~greenLED; // Turn LED Off

    // Configure buttons1
    P1DIR &= ~(BUT1 | BUT2); // Direct pin as input
    P1REN |=  (BUT1 | BUT2); // Enable built-in resistor
    P1OUT |=  (BUT1 | BUT2); // Set resistor as pull-up

    // Polling the button in an infinite loop
    for(;;) {

        if((P1IN & (BUT1|BUT2))==BUT2){
                 P1OUT |= redLED;   // Turn red LED on
        }

        if((P1IN & (BUT1|BUT2))==BUT1){
                 P9OUT |= greenLED;     // Turn green LED on
        }
       if (P1IN & (BUT1 | BUT2) == (BUT1|BUT2))
                   P1OUT &= ~redLED;
                   P9OUT &= ~greenLED;

    }
}


texts: Is this NPN transistor AND logic gate practical?

texts:
Most places on the internet that I see give a schematic for an AND gate that is something like this:

simulate this circuit – Schematic created using CircuitLab

The only thing about this is that when B is turned on but not A, which should logically output false, it seems to be somewhere between it (this can easily be seen with an LED at the output: it isn't as bright as it is if both A and B are on, logically satisfying AND, but it still lights up).

I was messing around and came up with this idea for an AND logic gate which works a bit more correct and I have been using it recently:

simulate this circuit

Essentially what I came up with when building that is Input A is put through a NOT gate which is put into another NOT gate, but the Collector on the second NOT gate is only powered by Input B. Therefore, if Input B is off, no output to begin with, but if its on but A isn't, then the first NOT gate powers the base to the second, making B ground.

I like building this design better, and it works so far for me, but I was wondering:

How practical is this design (e.g. why haven't I seen it before; are there any flaws)?


texts:
I have  questions with respect to cell balancing please help me
1.when this cell balancing will occur is it when charging the battery or when any cell goes more then rated voltage.
2.can you please explain below scenario
if am following passive cell balancing where a resistor is used to discharge the excess voltage of cell
I have 3 cell of maximum voltage that it can store is 5v nominal voltage is 3.3v
1st cell is at 1v
2nd cell is at 3.3v
3rd cell is at 2v
Here when cell one reach 3.3 v the second cell voltage will 5.6v
Which may leads to exposion
In all the above I have connect the cell in series
3.how charging of cell will be done in series connection BMS.)


texts: Can a Capacitance Multiplier be used with high voltage outputs?

texts:
I am designing an SMPS which two output voltages of 5kV and 2.5kV. My transformer is split into four equal sections, each feeding a FB multiplier, connected in series to form the final voltages. Output powers are 50W and 500W respectively.

The output voltage ripple on output 2 (2.5kV) is not of particular importance, however the ripple on output 1 (5kV) needs to be a maximum of 50mV. I have been looking into passive RC filters (LC filters would be too large) and I don't think I will achieve the attenuation I require with this alone.

I have been looking at regulating stages on the secondary side, such as series and shunt regulators for example.

My question is, could one possibly employ an emitter follower capacitance multiplier to attenuate power supply output ripple, when voltages are this large? I assume the BJT will not see the entire voltage, and it is possible but I am skeptical. Any help appreciated, thanks.


texts: Flyback Transformer -- RC Snubber vs. TVS Diode?

texts:
I've got a flyback transformer circuit, that was designed by a firm and they tended to over-engineer things (this is in a commercial project).

I re-laid out their circuit and on the primary end of the flyback circuit they have both an RC snubber and a TVS Diode protecting a MOSFET from transient voltages and for inductive loads when the MOSFET closes.

I've actually torture-tested this circuit and removed both the snubber and TVS diode at the same time and no magic smoke pours out of the FET as I am applying the maximum current with a PWM pulse to the flyback transformer (ie. it is receiving current, right below the saturation point and the peak duty cycle -- ie. transformer torture test).

Is there a reason you would want both, do they seem superfluous?

I could see a case where perhaps the RC snubber is protecting the MOSFET, and even though the flyback circuit can run for hours you are prematurely damaging the MOSFET by removing the snubber?

I really don't see the case so much for the TVS Diode... I have no idea what a transient voltage would look like in a transformer failure, but if the transformer fails the board is pretty much trashed anyway from a product perspective.


texts: How does a voltmeter measure the voltage of a PWM signal?

texts:
I have a DC / DC converter in the + -12V output connected to the comparator's power pins. A square wave of 1 kHz is applied to one of the inputs of the comparator.

The output of the comparator should be in the form of a square wave, oscillating in the range of + -12V.

When connecting the multimeter to the output of the comparator, I see a value of -12V. When I switch to the frequency measurement mode, I see 999.6Hz, which approximately approaches 1kHz.

It’s not very clear to me how a multimeter can measure the voltage of a PWM signal. Why does he give out exactly negative voltage? Does he make a specific selection?


texts:
I have a schematic attached that appears to show a switch bypassing an LED, or the other way around. In the working device operating the switch lights the LED and engages (as in turns 'on' a 'normally' off) binary state on the controlled device.

Why would the LED not be in series with the switch?

Some context: I purchased an guitar amplifier used. It does not come with the 5-pin "remote foot switch" that allows one to control the amplifier from across a room/stage.

These foot switches are typically passive devices that plug into an amplifier using a 1/4" Phono plug (single function) or TRS (Tip-Ring-Sleve) for two functions. Latching footswitches on the remote unit ground the Tip (and/or ring in the case of 2 function boxes) closing some control circuit on the main unit. This is usually employed for switching "channels" from "rythym" to "lead", disabling reverb, etc.

That was 50 years ago and now guitar amplifiers have more functions. Some use a 5 pin DIN connector/cable to allow 4 latching switches to double the controls that a single TRS arrangement could provide, but essentially using the same open/closed convention. E.g 4 pins conditionally closed to ground based on latching footswitches.

I found the schematic for the footswitch that I need to replace or replicate and it appears to have an LED and SPDT (functioning as a SPST as far as I can tell) in parallel with an LED.

I haven't yet found the schematic for the amplifier, but how could this possibly work?

Could the schematic be drawn incorrectly (not likely), or is there something the amplifier is doing in its active control switching electronics that I'm missing (very likely).

Relevant schematic attached. The two are essentially the same schematic with different labels on the box.

Thanks.


texts:
I have 4 batteries that are capable of providing a continuous 10 amps each. They will be connected in parallel to drive a motor controller with the intent on delivering 30 amps of continuous average power. It is desired to have each battery in a diode OR configuration such to prevent reverse current flow into the battery, damaging them.

Will a 4 battery diode OR circuit automatically handle load balancing between the 4 batteries? Someone briefly described it to me as working like this: The first battery will deliver a burst of 30 amp current, causing its voltage to drop, in which the diodes will change to enable the battery with the highest voltage, and the process repeats. He said this switching happens so quickly that it effectively balances the voltage across the batteries, causing all diodes to effectively be "ON," acting like batteries that are directly connected in parallel (except with a diode voltage drop).

Is this description generally correct? Are there any other concerns for doing this (IE, use schottky diodes for example).

The batteries are BB-2590/U


texts:
A three-prong to two-prong adapter is also known as "AC ground lifter" or "cheater plug". What is a single socket to ground-only plug adapter for electrical outlets called? It's a single socket adapted into a single metal ground prong, accompanied by insulated prongs for hot and neutral only to keep it firmly attached to the outlet. I've seen an example of one here called "Ground Plug Adaptor", whose socket accepts a banana plug, but I don't know whether the name is vendor-specific. That name doesn't indicate what goes into the adapter's socket. Googling "Ground Plug Adaptor" gives some cheater plug results.

I want this for purposes of grounding shielded Ethernet (possibly powered, e.g. PoE, PoE+, or passive PoE) cables' drain wire. In an industrial setting, these are grounded automatically when attaching shielded Ethernet keystones to patch panels, whose equipment rack has a grounding lug. I'm in a house, and my Ethernet keystones are mounted to a plastic multi-slot wall plate. I want to use the empty slot for a single socket keystone (maybe a banana jack) that bridges all the Ethernet cables' drain wires together, then connect that keystone to this ground plug adapter, and connect the latter to a grounded electrical outlet.

I also want this for purposes of grounding a person via anti-static wrist strap when working on electronics to prevent electrostatic discharge from damaging the components.

I'm in the United States.


texts: Direction of current in Phasors Analysis

texts:
I'm learning AC circuit and phasors form. In the exercise below, when using nodal analysis they choose the direction of current flow in the circuit then calculate the result.
But I wonder why that direction choice is the correct direction since in DC we can relate to its sign but in AC it is a complex number. Is there a way to see whether the chosen current direction correct or not? I think of calculate the equivalent impedance but it is too complicated for some short exercises.


texts: Build variable resistor controlled by Arduino

texts: I would like to build a variable resistor that can be controlled by Arduino. My plan is to vary resistance between the two values, i.e., 1 ohm to 10ohm, to continuously change the load for a small wind turbine. The resistances are for dissipating the power from the wind turbine, and the performance of the wind turbine is determined by the magnitude of the resistance. Would you please let me know how to build such system? Especially, I would like to know how to interface between the two power resistors and the Arduino control board.


texts: Voltage comparison circuit (Voltage level operated switch)

texts: I am trying to implement a voltage level detection circuit for e.g. I have 60V power supply and I need to check that if the input voltage is 1.5V or higher to turn on DC/DC or just high signal so I could implement switch but I am struggling to find anything based on transistor because of high voltage power supply and I do not want to run additional vreg for it as it will operate vreg switch.


texts: Using microcontroller as oscillator for high voltage power suppy?

texts:
MightyOhm has designed a geiger counter which is here. I am not very clear but I think he is using the 555 timer as an oscillator in the high voltage power supply section. I've attached his schematic below.

My question is can the design be changed to use an output from the micro-controller to generate an oscillating signal instead of the 555. The first question is that would such a design work? If it works, is there a particular reason why a 555 timer is used in the design?


texts: What wire do I need to carry 30 A for 18"?

texts:
I have an 11.1v lithium polymer battery pack which has 1300 mAh capacity and has a 20 C rating. Therefore I figure the maximum amperage the battery can supply is 26 A. (C * mAh / 10001) To be safe, I figure the wiring I use with it should be able to handle 30 A in case a higher capacity battery is used later. I figure that I can safely use an ~11.1 V, 1500 mAh, 20 C battery at that current.

The circuit this will be used in has a momentary switch (trigger) and a DC motor. (Airsoft gun wiring diagram) There will be about a foot and a half of wire from battery terminal to battery terminal. The circuit under nominal conditions would be under load for no more than half a second every few minutes. However it could potentially be under continuous load for up to 5 seconds with an average of those cases being 3 seconds.

The problem is, the wiring has to fit through small passages. And I need to use the smallest possible wire gauge that will handle the current. I currently have some stranded copper 18 AWG wire for automotive use. I'm pretty sure that this will not handle the current this battery is likely to supply3. From memory, (without measuring the clearance of the passages) 18 gauge wire seems to be an ideal size, though I think I really need 14 gauge wire to handle the current if it's just stranded copper.

I have trouble finding any easily understood documentation on the subject and there are so many variables to consider. Such as the length of the wire, the diameter of the strands (if stranded), the number of strands, the coating (if any), the ambient temperature, etc.

My research leads me to believe that if I were to get some 18 or 16 gauge wire with silver coating and a thin insulator (teflon?) that it would fit the bill. What is the proper gauge (solid or stranded), coating, and/or insulation for this application?

Update: I added "duty cycle" information to paragraph 2.


texts: Automatic overflow killswitch for watering pump

texts:
Project
I'm building a controlled watering system for my plants because I keep killing them by forgetting to water... I'm using an ATMega88PV for the logic and a resistive probe (voltage divider) to get a measurement of the moisture content which is working fine. I'll be using an aquarium pump controlled by a relay from the MCU and a large water reservoir for the watering.
I would now like to implement an emergency overflow protection.
My pot is sitting on a tray that will collect any excess water that drains out of the pot so that it can evaporate. I would like to have an automatic kill switch that kills the pump if any water makes it into the collection tray in order to prevent a mess on my floor.
I'm not very good with analogue electronics and I've never used a relay before so I'm asking for your comments on the design.
Here is the design that I have come up with:

simulate this circuit – Schematic created using CircuitLab
I couldn't find a symbol for a terminal so I used the normally open push button (labeled OVFD for OVerFlowDetector) symbol for my overflow detection switch.
It will basically be two electrodes at the bottom of the tray which are normally open and will close when water collects in the tray. I have a weak pull-up to 5V when OVFD is opened.
I then AND this with the control signal from the MCU GPIO pins (5V, 50mA max) and use this to drive the relay which is a SPST (I think?) with Ucoil = 5v and Pcoil=200mW (40mA).
The relay is normally open (pump disconnected) and will connect the pump to the 230VAC 50Hz from the wall socket when closed. Is this the proper way to use a relay? Now when I look at it, it seems odd... Do I need a SPDT relay?
I'm also a bit worried about driving the relay. The relay needs 40mA to switch and according to the datasheets on the 74LS07 it can only source 40mA. Do I need some kind of current amplification or will it work anyway?


texts: Mosfets vs. Buckpucks in driving high power leds

texts:
I searched for an answer but I'm so unfamiliar with some of the terms used in electrical engineering that if there was an appropriate answer I didn't recognize it.

I am running 4 high powered leds and was getting ready to buy 4 buckpuck, which would cost me about 50 bucks. I get conflicting views from various sources about whether buckpucks are necessary, so I thought I would ask you guys if mosfets are a viable option for obvious monetary reasons.

I need to address the leds individually (in parallel) and they need to be dimmed via a microcontroler using pwm. They run at 1000mah and I was told that that must be a constant current, thus the need for buckpucks.

Can mosfets work? And if so, how do I do it and what should I be aware of?


texts: Need help finding datasheet for Mitsubishi Electric AA11SB6C-ADFD TFT

texts:
Searching datasheet for Mitsubishi Electric AA11SB6C-ADFD LCD display.
This LCD is discontinued product, no information on official site.
Already tried sites like datasheetarchive, alldatasheet. Still no luck.

Even just pinout for TTL connector on this display will be much help.


texts:
I am trying to derive a inductor current equation for \$i(t)\$ in a series RL circuit when the switch is closed at \$t=0\$, as seen below:

I have posted my attempt so far but I'm having trouble getting past a certain point which I have labelled equation (7) on my attached workings page.

I am unsure how to take the integral of the RHS of equation (7). I know the integral is the natural log, but I'm unsure of what happens inside the brackets.

I know what the answer should be and it can be seen circled at the bottom of my attempt page.


texts: What does neutral and live both being at +120VRMS above earth imply?

texts:
I am trying to fix a twenty-year old unsupported piece of scientific equipment that is very expensive, delicate, and needed by my boss/the lab in two weeks' time.

I have identified that the reason it is broken is because a full-height rack of digital electronics won't start due a power failure. The back of the rack has two commercial power supplies that are fed by 230VAC mains: a 120 A, 5VDC rail, and a combination modular supply that provides 12V and 5V rails. There is also a power management board which has an independent switched mode supply and talks to a large solid-state relay that turns on the other stuff. The modular supply had failed, and the 12V rail was at 0V. I confirmed this by pulling it out and bench testing it with a current-limited RCD'd mains supply; it also agrees with a blinking red light on the power management board. We also had a lightning storm last week. I suspect the two things are related.

I found an effectively identical (same current rating, same model number, slightly different geometry, slightly different age) replacement supply, and wired it up. Much to my surprise, I found that this did nothing.

I then went probing with an isolated DMM with the supply on (and someone else in the room...); much to my surprise, I found that the input to both the heavy-duty 5VDC supply and the replaced 12V supply were floating at 115VRMS above ground, and the potential difference (as measured by my Fluke DMM) between live and neutral was between 8 and 17V. I don't have a differential scope probe, and don't know if they're actually almost perfectly out of phase, but the wires follow the IEC colour convention for mains supplies, and the input definitely has neutral around 0V, and live around 240V.

What does this mean? I've never seen this before. Has something died, shorted, and pulled the mains "rails" together? If I unplug both PSUs, the input to both goes back to 240V. Could it be that "something else" has failed, and the non-zero current draw of either PSU is enough to pull the two lines to the same potential?

Here's a rough sketch of the schematic as I understand it -- I don't have a proper one, alas! Any advice would be very helpful. I've tested the caps in isolation on an LCR meter -- they appear to be 200 nF capacitors (though they're encased in a metal shell bolted to the inside of the case that I can't easily disassemble (!), so I don't know if they should be!). Not shown are a series of fuses, keyswitches, etc, which are all still conducting.

When energised, the potential difference between A and B is ~8V, between A or B and earth is ~AC Mains/2, between C and D 240V, between C and earth 0, and +240V between D and earth. I really think the probability that both supplies failed is pretty low, and I don't understand how they'd fail in a way to flatten the rails.

What is going on?

simulate this circuit – Schematic created using CircuitLab


texts: Longer digital trace further from analog vs shorter digital trace closer to analog

texts:
In the 4 layer PCB below (top layer) what is better in terms of interference with the analog circuitry on the lower left (current sense amp and buffer op-amp) trace 1 or 2?

The FPGA does have bypass capacitors on the bottom side.
The stackup that I'm currently planning to use is 0.8 mm/4 layer (0.035-0.2-0.0175-0.265-0.0175-0.2-0.035)

The traces are from an ADC to an FPGA, the clock frequency is 50MHz.
My understanding is that having ground and power planes underneath the traces would make the high frequency component of the signals return under the traces.
So placing the traces further away from the analog seems like it might reduce the interference, on the other hand a longer trace is a bigger loop area.


texts: Context Switch without interrupt disabled?

texts: I developing a program on ARM M4 where I don't actually want to disable interrupt even when doing a context switch. If any interrupt occurs during context switch, is it possible to handle it soon after the context switch? Can I use the Interrupt set and clear pending registers (NVIC_ISPR and NVIC_ICPR)" for this purpose? If not, what is the solution?


texts: Is it acceptable to split one wide wire into two narrower wires in PCB layout?

texts: I have an issue about connecting power wire to the IC. The power wire (50mil) is wide than the pin width of destination IC, so I want to split the wide wire into two narrower ones(20mil) which match the pin width. May it cause a negative effect on signal integrity? Or is there any common solution in this scenario?


texts:
Can i physically remove the pin/wire 23 (DIOW --> Write Strobe) for an "IDE read only cable/effect"?

I heard that some hardware write blockers cutting physically the write line, but i have no information if there is also a software part. My mind tells me that this would be nice if you can only change the hardware, but I am sure there is a software part that makes problems.

Do I have to physically rederict the wire to some sort of electronic board with an self programmed software so there is no problem at communication software level? What are the parts/areas that are important for this project/effect?


texts: Can a non-enumerated device conduct DMA operations?

texts: PCIe devices can read or write to memory, i.e. can do DMA without requiring a device driver. For example: pcileech (The PCIe FPGA device is controlled by another computer). If I remember correctly, if you flash a device's firmware (let's say an FPGA device) and input 0xFFFF as device and vendor ID, the device won't be enumerated by BIOS. I am wondering, if a PCIe device can conduct DMA operations (memory read and write) by bus mastering even when it is not enumerated by BIOS.


texts:
If you would excuse the infiltration by a curious computer scientist with very little knowledge of hardware, I would like to understand better how modern displays are updated.

I don't care about HDMI or VGA or whatever, I'm curious about the LCD or OLED panel itself, the layer below HDMI.

Does it have it's own RAM representing 24 bits of color per pixel? And if this is the case does one just update this RAM and the display (errr) "controller" (correctly term?) scan through the ram updating the display at whatever the refresh rate is?

Or does the panel's controller pull data from some other area?


texts: Unsigned addition overflow and synthesis

texts:
Let's say we have the following code where a, b and c are 3-bit wide representing unsigned numbers:

a <= (b + c);

Overflow is expected by the designer in this case. For example, if b and c are equal to 3'd7 then expected result is 3'd6). The code itself is quite similar to that of a binary counter except that operands widths are greater than 1-bit.

The question is whether it is safe to assume that synthesis tools will create hardware that handles above case as expected by designer or should extra care be taken?


texts: Can't get upload code to Arduino UNO from Ubuntu 12.04

texts:
Just finished installing arduino for the first time. I got a prompt about adding a user to a certain group. I accepted and continued. I tried to get the 'Blink' program to work. But everytime I try to upload, I get the following error;

  avrdude: ser_open(): can't open device "/dev/ttyACM0": Input/output
  error ioctl("TIOCMGET"): Invalid argument

I started arduino as root. I know this isn't suggested. But it was the only way I could get the "SERIAL PORT" to be ungreyed. After trying to upload code and getting that error. The serial port option becomes greyed out again.

Did I install arduino incorrectly?
How can I correct the mentioned error?
What can I do to keep the serial port from being greyed out?


texts: Sending data from 4 transmitters to 1 receiver without a microcontroller

texts: I am working on a project to wirelessly check whether any of four switches are pressed and I don't want to use a microcontroller on the transmitter side. I have worked with the cheap 434MHz HT12E/D modules before, but they get jammed when more then one is transmitting at a time. Are there any alternative solutions to this problem?


texts: Return path for current flow in transmission lines?

texts: We know that all current flow in loops, i.e. if they start at a source they must come back to the source. So for transmission lines, does the current that flow through our appliances in our homes go back to the generating station? If yes, how?


texts: If a datasheet specifies load capacitance is this quoted per output pin or a total for all pins

texts:
Im using this SN74LV8154 binary counter, which specifies count frequency in terms of load capacitance (Page 6).  The test circuit in the datasheet (Page 8) shows the load capacitance only on a single pin.

In a datasheet is the load capacitance specified as the sum of each output pin's load capacitance or is it the load capactiance of any single output pin?

In the latter case, does this mean that the maximum count frequency will be determined by the pin with the highest load capacitance?

Eg.  If each 7 of the output pins are connected to an input capacitance of 5pf, and 1 of the output pins is connected to an input capacitance of 10pf does this mean the load capactitance (CL in the datasheet) will be:

7 outputs x 5pf + 1 output x 10pf= 45pf
or just the maximum, 10pf?


texts: Can a Triac be driven using only positive voltage due to the laws of Q1 and Q4 quadrants?

texts:
I have a BTA12-600B Triac and an Arduino.
Is it possible I can trigger both positive and negative amplitudes of an AC cycle by suppling only a positive voltage from the Arduino digital pin to the Triac's gate terminal at the right time and moment?
Basically driving the Triac via the Arduino. The Arduino will supply the proper timing positive voltage to the gate pin with reference to a zero cross detection circuit.
It is possible to drive the Triac properly only using the Q1 and Q4 quadrants? Since Q1 and Q4 quadrants can use a positive voltage on it's gate pin?


texts: Does Reactive Power flow between Energy storage elements in a three phase system?

texts:
I noticed that unlike the single phase ac power sources, the power in three phase is constant which means the instantaneous power is the same as the real power which is $$3V_{rms}I_{rms}\cos{\theta}$$

But there is also a reactive power present.

$$3V_{rms}I_{rms}\sin{\theta}$$

Clearly, the complex power would just be the VI for each of the branches leading to the complex power 3VI but the reactive power is clearly missing in the instantaneous power which for single phase sources would have been $$s(t)=cos(θ)P+sin(θ)Q$$
(as shown in this link S = VI*/2 derivation)

But in this case only the real power is present in the instantaneous power. At first I thought I didn't understand something, but now I'm wondering if the reactive power is present but just flows between each load. Am I correct or is there something I don't understand?


texts: 0-10 second on-time with a potentiometer

texts:
I would like to make a simple circuit, where the a potentiometer controls a 0 - 10 second on-time.

If the potentiometer is set to min, the on time should be 0 seconds. If the potentiometer is maxed out the circuit should be on 10 seconds.

I was thinking of using an Arduino, but that would be overkill for such an application. And too expensive as well. Maybe a 555 timer would be an option?

All help is appreciated!

Notes:

Circuit must be 5V or 12V DC
The object to turn on is a 12V car lightbulb. (some advice about a relay?)
Has to be cheaper than using an Arduino


texts: Using normal diodes to rectify high frequency waveforms

texts:
Recently I was try to rectify the output of an “electronic transformer” using an ordinary rectifier diode 1N4007. The output of this device is bursts of frequency around 50kHz, with an envelope of 100Hz and RMS 15Volt measured by scope.

Under these conditions, why does the diode become extremely hot even with a pure ohmic load that requires just 120mA?

Also, what is the effect is we are use a fast-diode to rectify a low frequency waveform i.e. 50~160Hz.


texts:
I have some LEDs (not the high power type) being driven by a 74HC541, one LED per output, with no other load. I've noticed a tendency for people to use the 74HC540 instead (inverting buffer). I've gone through the datasheets and both ICs can sink or source 25mA per output pin (which is fine).

There are obviously four permutations here: inverting/non-inverting, with LEDs connected to Vcc or Ground. It looks to me like these permutations are pairwise equivalent.

Other than for logic reasons, why would you choose an inverting buffer over a non-inverting one, or vice versa?


texts:
I've hit a stumbling block on a relatively simple project. I have a helmet, a Contour camera on which I have piggybacked a microphone interface to put a mic inside my helmet, to be able to speak and reduce wind noise a bit. However, it is still proving too noisy for my liking.

I have three options, and I was wondering if a fourth existed. They are as follows:

Post-processing. Intensive, difficult and annoying. Would work as a last resort or to fine-tune.
Dual-microphone set-up, one within the helmet, the other one outside it. This requires an active IC, which I'd rather avoid (no easy access to the Contour battery :-( )
High-pass filter. Gets tricky at low speeds, works fine at high speeds.

My question is simple: is there a way to use microphone correlation (or lack of it) using just a passive circuit, effectively substracting one feed from another, without requiring an IC?


texts: What actually Power factor is, in practically?

texts: What actually power factor is? I know its formula, but in practically i don't know, what happen if we increase or decrease the power factor? What is the use of power factor?


texts:
I recently purchased an APA102 LED light stip (60leds/m) and read that it requires 18watt/meter, I am using approximately 4.5 meters so will roughly need to provide 81w. I did, however, struggle to find a dual power supply that could provide this, so I settled on an RD-125A power supply that can provide up to 15A at 5v, and am planning on reducing the brightness of the LEDs to 75%, to account for this.

I was then hoping to have a wire connecting the LED strip to a box containing the rest of the circuitry and the power supply. So I could detach the box, I wanted to have a connector that would allow me to plug the LED light strip into said box, and then from within the box, the connector would connect to the power supply and a raspberry pi.

My first thought was to use a 4 pole DIN connector and socket, but I wasn't sure if it's safe/advisable to use one when using ~15A, and thus I was hoping to find out if

This is safe
If not, is there any other connector that would work


texts: Why doesn't the voltage drop across the resistors of my battery charger follow Ohm's law?

texts:
Here's the setup, the three items below are in series:

Battery at 215V
Power supply at 250V (It is a 5A constant current power supply that will drop voltage down to 200V minimum before failing)
8 ohm resistor

When I flip on the charger, I am pushing 3.5A and reading 35V across the resistor. Shouldn't an 8 ohm resistor put through 4.375A? The voltage across the power supply remains at 250V so I don't think it is limiting the current. Or is it?

I have had this issue before and can't explain it.  How can I use Ohm's law to size my resistors in this situation?


texts: H-bridge low side current sensing: Current signal with oscillation why?

texts:
my problem is the following: I am using two DRV8842 H-bridge ICs to control 2 different brushed DC motors, my intention is to use a PI controller for the current loop. The schematic looks like this:

and the pcb layout:

For the current sensing i am using the INA301 chip from texas instrument for low side sensing and a shunt resistor of 30 mOhm. To measure the current i use an ADC interrupt at the middle of the PWM pulse in order to take a measurement each time the transistors are closed. I noticed that for low duty cycle my current readings were higher than those when i increased the duty cycle (PWM frequency 20 KHz). When i checked the voltage signal in the resistor and after the INA301, i noticed there were oscillations in the signal as shown in the picture:

The blue signal is measured directly at the shunt resistor terminals. And the input signal to the ADC looks like this for the case of 10% and 50% duty cycle:

The blue signals are the resistor voltage amplified by the INA301 and low pass filtered with a RC filter with cutoff frequency of ~1.3 MHz. As i am sampling at the middle of the pulse, for low duty cycles i read this peak value and not the steady state value. For a brushed DC motor i would have expected a current signal with a sawtooth like form, what could be causing this oscillations? Maybe my pcb layout is bad and has parasitic inductance and capacitance or is it due to the PWM modulation and i need to use some snubber circuit? Any ideas on what could be wrong or how to solve it will be appreciated. Thank you all in advance!

Regards,
Emmanuel


texts: How can I extend this circuit to use it in our real life?

texts:
I am planning to design a wireless mobile charger circuit next week. For that purpose, I have selected the circuit which is shown below and is collected from the post: wireless mobile battery charger.

I am also planning to add some extra features to that circuit. So, can anybody give any ideas and suggestions to extend the circuit for real-world applications. Additionally, which values are to be given to those capacitors and resistors to make it function in real life.


texts: Boost Converter IC: Swap Decoupling Caps with Equivalent Parallel Capacitance

texts:
I'm working with a Boost converter IC [MT3608] with the data sheet suggesting 22µF caps on both the input line [decoupling] and output lines [output filtering?]. As part of BOM consolidation though, I'm trying to remove these two caps since I don't use 22µF anywhere else.
Instead, I'm looking to use 2x 10µF caps which should have [reasonably] equivalent parallel capacitance as a 22µF. Theoretically, it should also have reduced equivalent series resistance since I'm using 2 caps instead of 1, making it perform better.
Would there be any downsides to swapping these caps out then? Presumeably, they don't serve some value-critical function and should be safe to swap with something close right?


texts:
I’m working on a little project of building a wireless speaker box, I’m getting some help from my dad as he used to build and sell speakers for DJ’s as a hobby so that side is all sorted but what I’m having a bit of worry with is the correct way to wire the battery.

I would need the battery to charge from an input on the side of the box and provide power to the amplifier, what I was wondering is if it would be as simple as getting a 12/24v input Example and connecting it to the terminals on the battery and if I am able to connect the amplifier to the terminals too or would need anything extra, I was thinking about using this battery or similar: Battery


texts:
I have a 1.5kW 220VAC 1 Phase dust extractor.  It's controlled by what looks like a DOL switch KJD17B/5T (so I assume the 5th terminal is an overload).

KJD17B Datasheet

Wiring diagram on duct collector:
From what I can see it's DP/ST and has L/N In and L/N Out and then a 5th connection form the motor which I can only assume is some sort of overload.

I'd like to add a remote start/stop, but it looks like the KJD17B is an enclosed device so I can't wire my remote start/stop in parallel/series.

I'd welcome advice on how to achieve my remote start solution?  Should I try to re-wire the DC and bypass the KJD in favour of two external DOL start/stop controllers?


texts: How do I determine terminal characteristics of a dc motor with known torque and angular velocity?

texts: How do I determine the terminal voltages and currents that will be produced by turning a dc motor at a known angular velocity and a known torque? I know that for a dc motor, the load torque has a linear relationship with speed (negative slope) and with current (positive slope). But these relationships are for when a voltage and current are being applied. Do the same relationships hold when a torque and angular velocity are being applied?


texts: Can I drive 3.75 V / 370 ohm coil relay from Raspberry PI GPIO output?

texts:
I have discovered that there are relays like these available on the market that trigger at 3.75 V and have coil resistance above 370 ohm. I assume this would mean about 14 mA or about that might be within allowed limits of Raspberry PI.

How good is the idea to drive these relays directly from GPIO, without the amplifying transistor?

There are few similar questions of the site but I think they do not address this group of relays. If not, I would build a circuit as described here but I need a quick and very reliable solution, so less components may help.


texts:
Two parts:

Is it possible to write an
Arduino Bootloader for a Tiny AVR?
Is it worthwhile to write a
Arduino Bootloader for an Tiny AVR?
(more subjective, contingent on 1)

Regards,
Vic


texts: How do you avoid mixing CHASSIS GND and sensor GND when reading a sensor?

texts:
So I'm aware that in some systems they have different circuits with different grounds. For example, cars have at least a chassis ground and a sensor ground, and there is a measurable difference between the two. In fact, you are not supposed to treat one like the other.
So my question is, if we have a 5v MCU reading a 5V sensor of a car, where do we ground our MCU? Sensor ground or chassis ground?
What if we now need to drive a mosfet, where would the source go? Sensor or chassis?


texts: Could anyone please tell me where I am going wrong with this boost converter?

texts:
I want to implement a boost converter using a MC34063A. I have made the circuit as it is mentioned for step-up operation in the MC34063A datasheet.
The datasheet says it can take up to 40V input. But I can see that the IC is getting burnt as soon as my input voltage exceeds 12V. What could be the reason? Here is a schematic of the circuit I'm using:

A 170uH was not available, that's why I used 100uH instead. Instead of a 0.22 ohm resistor I used 0.5 ohm by paralleling two 1 ohm resistors. Due to the unavailability of a 1500pF capacitor I used 1000pF.

The Schottky diode 1N5819 was not available in Proteus, that's why I have drawn the circuit with a 1N4148, but I am actually using a 1N5819 as suggested in the datasheet. Are these differences affecting the performance of the circuit?

However,after reading a comment,below I have given the circuit using the original model or MC34063 in proteus.


texts:
I believe the number 4 corresponds to the number of individual PCBs and the number 1 is for one panel.

Is this the way panelized PCBs are commonly referenced?  With an asterisk mark?
What does the "-up" mean in Panel-up?
Is there a more common way when to refer to quantities and descriptions of panelized PCBs?

Here is a link to where I saw the term used.

Screenshot below:


texts: Calculate current on tri-phase circuit with parallel resonance

texts:
I'm struggling with the following circuit.

data are:

E1=10V (three phase 120°)
\$\omega\$=20 rad/s
XC=-10
R=10
XL=10

About VGO I calculate the tri-phase voltage as

$$E=\frac{10}{\sqrt{3}}=5,7735V$$

and

$$VGO=5,7735V\cdot3=17,321V$$

My problems comes calculating phasor of current I1 (current of E1), due to the parallel resonance that gave me \$\infty\$ as result...

Correct results are:

\$VGO=17,321\$ V
Phasor of \$I1=1,5+1,866025j\$ A


texts: How to plug 2 5m RGB LED light strips together?

texts:
I got two 5 meters RGB LED light strips and would like to connect them together, controlling them as a single strip.

Each strip power is 72 W, the input voltage is 12V, it has 300 5050 SMD LED emitters and the manual says it needs 6A of current. The controller that came with each fits that same spec.

What should I do to achieve it? Each strip comes with a controller and a remote. Should I get another controller big enough or an amplifier maybe?

This is the product: http://dx.com/p/jr-5050-waterproof-72w-4500lm-300-5050-smd-led-rgb-light-strip-w-remote-controller-12v-175950


texts: Switching regulator efficiency TI LM2678 - measured vs. datasheet

texts:
I'm working with a TI LM2678-ADJ regulator (granted, on a breadboard) to power a 40" led strip. Trying to figure out why the measured efficiency is about ~15% lower than what the charts in the datasheet claim.

Input: Vin = 20V, Iin = 0.925A (18.5W*)

Output: Vout = 12V, Iout = 1.255A (15.06W*)

*Didn't measure power directly, but using V x I to calculate power based on measured V and I.

So given those values it would seem the efficiency (Pout/Pin) is about 81.4%.

But the chart in the datasheet claims it should be about 95% efficient:

For refecence here the schematic from the datasheet:

Could the ~15% discrepancy be attributed to the other components in the circuit? I'm not using exactly the recommended components from the datasheet but at least similar spec'd ones (from what I can tell).

This is the inductor I'm using: http://www.digikey.com/product-detail/en/2107-V-RC/M8852-ND/775391


texts: Should I include over-voltage protection for a 3.63V max device using a Lithium-SOCl2 3.65V battery?

texts:
When designing an ultra-low-power device that is powered by a primary lithium battery, is it necessary to include over-voltage protection?

Specifically, I am using a Microchip (Atmel) SAML21J which specifies a supply voltage of 1.62-3.63V.

I am using Lithium-Thionyl Chloride (Li-SOCl2) batteries with an open circuit voltage of 3.65V.

In practice, I've never worried about the small potential over-voltage in testing on the bench, both because the voltage immediately drops slightly with load, and presumably the microcontroller can tolerate short-duration small over-voltage. However, as I look at other components with a max voltage rating of 3.6, I wonder if there is value in adding, say, a Zener diode to clamp the voltage.

The factors against adding protection in this case are 1) cost, and 2) potential battery life decrease.

I'm mainly concerned that brand-new batteries installed during production could cause damage to some percentage of finished units.


texts: Beginner circuit diagram of superposition


texts: Combined RF and baseband noise simulation in LT Spice?

texts:
I am working on a noise simulation of a circuit with an RF amplifier, demodulator, and a baseband amplifier. I would like to accommodate the demoduluation in the noise simulation such that the noise near the carrier is  shifted to baseband, where the noise models for the audio amplifier components sum with the RF noise to produce a realistic end-to-end result.
In other LTSpice simulations I've simulated the demodulation accurately in the time domain. What are suggestions for a way to perform this frequency shift operation within the noise simulation which is based in in the frequency domain?


texts:
and I apologize if the question is repeated. I tried to search around, but by my keywords main answers are about control of stepper motor with MCU and this is not my problem.

In my design I want to put the stepper motor just over the MCU and ADC chips. The distance will be about 5-10mm. My main question is whether this will affect the chips in terms of EM noise from the motor or something else. I don't think heat will be a problem.

Thank you!

Edit: The motor is 5V unipolar. I will drive it with DRV8833. I can rotate the motor and thus distance between cables and MCU will be 3 to 5 cm. Main issue remains the motor itself.


texts: Measuring Vackar Oscillator Output Amplitude and High Frequency Effects

texts:
This is somewhat related to my previous question regarding why I wasn't seeing a clamp biasing effect with my JFET Vackar oscillator.  I think I figured it out and I'm wondering if you guys agree.  Below is a sketch of what I saw on the scope (it's a bit busy, apologies for that!):

As you can (hopefully) see, the gate voltage peaks at 1.2V before falling to -2V (the subject of my previous question).  But, look at the source current measured across the 1 ohm resistor.  It seems to flow towards the gate!  Not at all what I was expecting.  I believe that what I'm seeing is the effect of parasitic gate-source capacitance and its effect at this frequency (~38MHz).

What's interesting is that this effect seems to negate any clamping effect and with the gate voltage now rising to 1.2V, it might account for the other surprising aspect: the source current peaks at over 120mA.  That's way higher then this JFETs Idss (16mA measured).

I should really put this bit in a separate question, but what the heck.  At the end of the day, I'm trying to estimate the output amplitude of this oscillator and I'm not having much luck.  Clarke & Hess offered a reasonable solution for JFET circuits where the sine wave at the gate was clamped to zero, but this effect I'm seeing makes this route a bit trickier.

Does anyone know of a straightforward way of computing the amplitude of this oscillator that doesn't involve simulation?  I'm not against simulation per say, but you need to set things up right and it tends to obscure the complexities that makes a deeper understanding possible (my opinion).


texts: Does a switch schematic symbol have a conventional "polarity"?

texts:
I'm studying Rudy Severns eBook Snubber Circuits for Power Electronics; great read by the way.

In it he has the following figure, notice the phrase in the caption "including voltage and polarity conventions":

Should I take this to mean that there is a conventional orientation for the "opening" and "hinge", so to speak, of the switch symbol in a schematic? At least in a DC context where current would only be flowing the one direction?

I hadn't encountered that before and kind of have my doubts, but my engineering mind would like a convention that leads to a one-and-only-one right way to orient a symbol that otherwise has a degree of freedom to it.


texts: Do conductors in the reactive near field of an antenna cause loss?

texts:
I was reading about the reactive near field of an antenna here part of the relevant portion of which is quoted below:

  "Because of this energy storage and return effect, if either of the inductive or electrostatic effects in the reactive near field transfer any field energy to electrons in a different (nearby) conductor, then this energy is lost to the primary antenna. When this happens, an extra drain is seen on the transmitter, resulting from the reactive near-field energy that is not returned. This effect shows up as a different impedance in the antenna, as seen by the transmitter."

I am unsure if I understand this correctly, or at least its implication in the real world. Does this mean that putting any sort of metal near a transmitting or receiving antenna will cause some extra loss in the form of inductive and electrostatic coupling? Would these losses come from the Faraday Effect and essentially using energy from the electric field to charge a nearby metal like charging a capacitor respectively? Does this mean that in the real world antenna and RF designers must ensure that there are no metals or any other conductors within the reactive near field of their antennas? Am I wrong in my understanding, or is perhaps the effect just too small to matter practically?


texts: References or guidelines for PCB connectors

texts:
Are there references or guidelines to establishing which pins is recommended to use for the power, which for the ground, which for the analog signals, etc. on the various poles of the PCB connectors?

For example, in a board to board connector where is recommended to place the gnd? on one ends near the pins of Vcc or is better to separate vcc and gnd by placing it each other at the two ends. Or again, where is it better to place a pin for analog signals? Maybe between two pins of gnd?


texts:
I'm stuck on a problem and I don't know how to proceed.

I have a circuit that consists of a 10μF capacitor connected in series with a variable resistor (100kΩ, 200kΩ, 300kΩ). I'm supposed to draw the circuit connected to an oscilloscope that has an internal resistance of 1MΩ and an internal capacity that's negligible. The source is DC of 10V.

Here is what I got so far (circuit to the left and oscilloscope to the right):

Now I am asked to convert the circuit to it's Thevenin Equivalent, but what confuses me is that there is only 1 resistor which is unusual, and I also don't know what to do with the capacitor C1. I've looked online for well over an hour now, but I cannot find an answer.

I'd be very greatful for a push in the right direction. Cheers!

EDIT: I made an error in the picture; R1 should be 100 kΩ, not 100 Ω.


texts: How to add memory to an ARM Cortex Microcontroller

texts: I am looking into a design that would use the ARM Cortex M4F core but am just the software engineer for the project. The EE tells me that there will be an 64 MByte sdram memory module connected to the chip. After looking at the datasheets I don't understand how I am suppose to access that memory space. Does the EMC make that space globally available to the firmware without any modification? I'm not even really sure I'm asking the question correctly. Any help would be greatly appreciated.


texts:
there is a book that shows common circuits

The text says that C1 helps preventing any DC from reaching the transistor (I understand that) But it also says that C1 helps preventing any DC from Q1 getting back into the previous stage.

What does it mean? How?


texts: How is high impedance state physically different from a logic low state?

texts:
I have read this question and the answers that follow on the electrical stack exchange but I still face a difficulty in understanding the practical difference between high-Z state and 0 state. It is commonly used in hardware description languages. I know that the high-Z state is when the connection is removed. But I want to understand the physical difference.
My question is best understood with the help of this thought experiment:
Consider only the output terminal of a tri-state buffer is visible and available to me, and a demon (like the one in Maxwell's thought experiment) is applying 0 or 1 to the 2 inputs of the tri-state buffer. I have to detect when the terminal is tri-stated. I have only an LED and a NOT gate with me and both are of the same logic family as the tri-state buffer. I can ground my  circuit.
First, I connect the LED to the output terminal of the buffer. I know that the LED will remain off when the output of the buffer is 0 and when the output of the buffer is tri-stated.
So instead, I'll place a NOT gate between the output of the tri-state buffer and the LED. So will the LED will be off only when a logic 1 is on the output of the tri-state buffer?
If so, is it possible to identify whether a terminal is tri-stated or 0 without measuring the resistance of the terminal?


texts:
I'm currently trying to get the hang of using a MOSFET as a switch.

My schematic looks something like this (it's the first schematic I've ever drawn, so please don't be too hard on me).

simulate this circuit – Schematic created using CircuitLab

The problem is that the MOSFET is always-on, no matter the gate voltage (or even any gate voltage present at all).

I'm using a 12V DC LED without fixed polarity (so no real flow direction, which is why I drew it as a lamp) which I don't know the resistance of, which is why I put 100 Ohm. I'm almost certain that it does not matter.

Anyhow, the 12V are coming out of a laboratory power supply and I'm only using the positive and negative terminals there. It does not matter if the gate voltage is connected or left out at all, the LED just lights up no matter what.

I've been told (when first trying on a Raspberry Pi, see my last questions if interested) that it could be "stray voltage" and the GPIO pin being floating turning the FET on. I was told to put a pull-down resistor to prevent this.

I've since changed from using the RPI to using the second supply available to me to just provide +3.3v as a replacement for a GPIO Output to make building the circuit easier and more fool-proof (I think I'm one of the bigger fools in electronics for not getting this to run)

From what I have understood I'm supposed to use source as a voltage input, gate as a switch (on/off signal coming in there with a logic level MOSFET like the IRLZ34N) and Drain to connect to the circuit. So that the MOSFET switches (lowers the resistance, becomes conductive, closes the connection) between Drain and Source. Am I wrong in this most basic understanding?


texts:
I have developed a simulation of the space vector modulation (svm) for standard two level three phase voltage source inverter.

The simulation is created in the Scilab/Xcos with usage of C block (i.e. generic block which can be "filled" with code in C language)

The first results seems to be correct. Please see the below given outcomes of the simulation. The simulation suppose the carrier frequency \$f_c = 1000\,\mathrm{Hz}\$ and modulation
frequency \$f_m = 60\,\mathrm{Hz}\$.

Components of the reference space vector at the input to the SVM block (normalized by the dc link voltage \$V_{dc}=564\,\mathrm{V}\$)

Duty cycles for the upper transistors (S11, S21, S31) in the inverter along with the carrier signal

Firing signals for the upper transistors (S11, S21, S31) in the inverter

Nevertheless I would like to be hundred percent sure that the svm algorithm works correctly. I would like to ask you for assesment of the above given waveforms. Do you think that my implementation works correctly? Thank you for your help.


texts: Can a 220V relay be used to switch 110V appliances?

texts:
Can a 220V relay be used to switch 110V power? If yes, then additionally to this question, does the amperage (A) rating on the relay change when the voltage (V) is 110V instead of 220V?

To the risk of answering my own question, I think any voltage lower or equal to 220V could be switched with a 220V rated relay.  Hope to be right on this, but I'm not sure about the amperage rating.  My guess is that instead of 220V/5A that relay could also be suited for 110V/10A but I'm not sure.


texts:
While I read my college book in signals, I got stuck with some basics:

DC component is component of zero frequency. With no DC component,
a signal has an average amplitude of zero, with a DC component it has frequency term at f = 0 and a nonzero average amplitude.

What is the benefit of average amplitude equal to zero?

What are the pros and cons when a signal has a DC component so the amplitude get zero or has not so get non zero?


texts: What happens to excess electricity generated going in to a grid?

texts: How is excess electricity generated dissipated?  I know that the grid is balanced, etc.  But given that there will be momentary over-generation at some point over the whole grid where does any excess electricity go?  For example, in the event of a significant sudden power outage across the Northeastern US (or any other large geographical section of the grid), how does the grid shed the sudden excess electric flow?  Or is there a gigantic copper wire running into the ground somewhere?  I am not an engineer, but I am a very curious person and would appreciate a focused answer.  Thank you.


texts: Which type of transistor for pulsing LED strip?

texts:
Preface

Hello! I'm trying to determine what type of transistor I need in order to pulse an LED strip I have. I have attached a simplified schematic (omitting resistors) as a visual aid to show basic intended operation. (I have very little knowledge about schematic creation, so I apologize—especially for the LED strip and USB power parts. I hope it is helpful.)

simulate this circuit – Schematic created using CircuitLab

Components

Here is some information about my components:

LED Strip

I did not receive a datasheet with the LED strip or identifying part information to locate one. I know the following:

It contains two different colored LEDs, alternating down the strip.
It has one positive terminal and two negative terminals (one for each color LED).
It requires 24 VDC.
Multimeter tests show that each negative terminal reads 0.5 A, for a total draw of 1.0 A.

Additionally, here is a photograph of one section of the strip (it can be cut across each section of terminals—the intensity of the flash in the photo appears to shift the colors). Also the back has a prepared adhesive applied.

Power supply

Output: 24 VDC, 5 A (Product page)

MCU

Particle Photon microcontroller (Datasheet)

Transistors

BC517 Darlington NPN 30 V, 1 A (Datasheet)

Question

My goal is to dim each of the two colored LED arrays using PWM from two of the µcontroller's +3.3 V I/O ports. The µcontroller hardware/software is not an issue for me—however, I am having this issue: the LED is always on in a less-than-full-brightness state when this circuit is closed. Even if I disconnect the MCU from the transistor base, and connect a floating wire in its place, the result is the same—but if I disconnect the base completely, the LEDs turn off.

Is this an issue with the transistors I have—and if so, which transistors should I use instead? Whichever transistors I use must be able to switch states faster than 200 µs and ideally faster than 150 µs.

Thanks for the taking the time to read!


texts:
I'm trying to make a simple low-battery indicator(3.6V 18650 LiIon) that will turn on red LED. I already tried something(schematic is below) but it doesn't work.
I already have zener diodes(1/2W, 2.7V), and op. amps(UA741CN DIP-8 UA741 LM741 ST), and of course resistors. Threshold voltage is 3.6V(+/- 0.1V).


texts: Current Source version of TLC5940 (current sink LED PWM driver)?

texts:
Is there a current-source equivalent of a TLC5940 (current-sink) PWM LED driver?

I'm working with a large number of linear resonant actuators (LRAs), each of which only uses ~50mA, but must be driven by AC (frequency is constant, amplitude determines power). Each has an independent amplitude from the others.

Currently I'm using PWM output from my MCU to drive the AC voltage in both frequency and amplitude using a PWM to voltage circuit. The involved PWM generation takes up a lot of MCU resources, both computational and pins.

I considered using a number of DACs, but the number I'd need is outside my budget.

I had hoped to use a TLC5940 to move the PWM generation outside the MCU, but as mentioned, it does PWM via current-sink which afaik won't work with the PWM-voltage conversion circuit I'm using.

Are there any other IC options that might work?
I've considered using a TLC5940 to switch the ground on a bunch of MOSFETs, but I don't think that would work right (at least I can't find any references to using a MOSFET that way).


texts: What is the place of 8- and 16-bit microcontrollers? Why hasn't 32-bit taken over?

texts:
What is the real cutoff point in terms of the trade-off between cost and performance for selecting 32-bit microcontrollers?

In other words, with the rise and domination of ARM architectures, why are we still using 8-bit and 16-bit microcontrollers? Are they still much cheaper?

I understand that very low-end devices do not need the resources offered by bigger and more complex architectures. However, what is the real motivation to still use them if costs seem to be converging towards the same range?


texts: Is there any method to communicate with a car ECU?

texts:
I want to build a device with AVR to read the car RPM from its ECU. I don't know how to receive data from ECU at all. The thing is important for me is Reading car RPM. any suggestion?

EDIT:

The car is

Peugeot 405


texts: Microcontrollers - are the output states constant or multiplexed?

texts:
PWM obviously require computing resources (and thus cannot be done simultaneously with other processes), but if I were to set a pin as output 5V or 0V, do these states remain constant or are they repeatedly "refreshed" as the microcontroller works on other processes?

This is hard to explain in text so I thought of an analogy to my question. Imagine I have a glass in my hand and am instructed to put it on the table. Then I am instructed to sit down in a chair.

The glass on the table is a state. Do I leave the glass on the table, or do I pick it back up and sit down and the repeat very quickly so you do not realize the glass was ever removed from the table?

Or perhaps more simply, does the microcontroller "forget," if you will, about the states of its pins unless you explicitly program a state change?

Hopefully I made that as confusing as possible.


texts:
First post here.

I'm making a DC/DC converter which will generate an output of 19.5V 18A.
Its a synchronous buck converter with the LM5145 TI chip.

When I have light load on the converter the output is within +-20mV of the 19.5V which is perfectly well.

When the load is increased enough the immediate outputvoltage falls quite a bit, which makes the output sink below acceptable values. This in turn makes the converter not usable under higher load.

Is it possible to place a "big" cap on the output to soften the immediate voltagedrop?

Any other suggestion is happily taken.


texts:
I need to connect an AVRISP MkII microcontroller programmer to my ATTiny2313 microcontroller in order to program it. I've never done this before and don't want to damage the programmer,  so I have a question on the power supply connection. On this page it states that

  The AVRISP mkII does not provide power on the Vcc pin, but uses this pin to sense the voltage on the target circuitry. Your circuit needs to be powered by external means to operate.

Does this indicate that I have to connect the microcontroller's Vcc pin to 5V and then connect the programmer's Vcc pin to the same microcontroller pin? Also, does the power supply have to be exactly 5V?


texts:
I found this formula used in a circuit to calculate the RC delay time. Can someone please explain what it means?

*Delay time = - 14.7K * 4.7uF * ln(1 - (1.2/5))= 18.96ms

Thank you


texts: Insulated TOP3 triac soldered to Aluminum plate -- will it last?

texts:
So I ordered a cheap SSR from Aliexpress and it finally arrived. I immediately disassembled it to look what's inside. It wasn't so bad -- BTA40-800, MOC3063.. assuming the components are not counterfeit of course. Pcb has some flux left and triac terminals were bent at some questionable angles and too close to the package.. but I can live with it. What surprised me though is how the triac was mounted.
SSR has an aluminum plate that you attach to the heatsink. I expected to see a screw, but there was none. The package (TOP3) was just soldered to the plate. Triac is 40A-rated, so maybe it's the way to minimize the thermal resistance. But I have questions.
1 Does the TOP3 package even allow that? I realize it's tab must be manufacturer-soldered for a reason, but the amount of the heat applied must be massive. I wonder if the triac is half-cooked already.
2 Will it last? Soldering aluminum is a tricky business, since the material is quite active chemically. So with the frequent heat-idle cycles, is there a danger it will "unstick"? Not unsolder due to the high temperature but just get off?


texts:
I'm trying to understand few things about triacs etc. and I found datasheet for MOC3041

And there're two resistors which purpose I don't really understand. I'm talking about the 330Ohm and 360Ohm resistors. What they're used to? Is it for some gate protection? And if so, why, when I'm seeing other schematics (not from DS), there's never that gate-load resistor?

Regards


texts: How do dual output in waveform generators make sense

texts:
I'm a noob in electrics and getting very confused with experiments about the electrical instruments' grounding...
I have a dual output waveform generator like this

(ignore the 'sync' as I don't use it here..)
I don't understand how it works when both CH1 and CH2 are used.
Since both CH1 and CH2 are grounded, the schematic should be:

Since the ground is viewed as a single point, the schematic is as:

Then looks like the two outputs cannot ever be separate or parallel.
And, what should I do when I wish to connect the two signals in a series? Connecting CH1+ and CH2+ to the rest of the circuit?
It looks like the ability of the dual output is too restricted, and the schematics looks really weird, all because of the grounding...
Am I somewhere wrong? Or ...Should I float the waveform generator and find another point in the circuit to explicitly ground the entire circuit?


texts: How to calculate the reactance of a capacitor with an input signal that is 2 sin waves of difference frequencies added together?

texts:
I am trying to calculate the reactance of a capacitor with an input signal that is not a single frequency.  For example, x = sin(4t)+sin(5t), or a capacitor that is used in an audio circuit like the following:

I found the following equation to calculate reactance:
$$ X_C = 1/(2*pi*f*c) $$
but I don't know what to use for the frequency.

Is there a better way to calculate this?

PS, what I'm doing in the long run is trying to calculate what the voltage will be at pin 3 if VIN is the output of my Arudino Due DAC that's supposed to have a max voltage around 2.5V


texts: Standard 2.54/1.27mm pinheader impedance

texts:
Note
I turned my answer into something of a collection of free impedance calculators..

I was thinking of using one of the most ubiquitous connectors in the world - 2.54mm pin header. The snag here is that I need to push a relatively high frequency over it 4MHz UART, edge frequency much higher of course.

Update
4Mbit UART is just the tip of the iceberg, if I decide a standard header is fine for RF, there's SPI, SDIO, RGMII, 900MHz RF link antenna connection.. At some point it certainly stops being fine.

Update2
With regards to signal integrity and EMI, fundamental frequency is fairly meaningless, see this EDN article about what's the spread of RF energy on a 1MHz signal with 0.1ns rise time. An extreme example but 1ns rise time is fairly normal.
https://www.edn.com/design/pc-board/4430165/Getting-EMC-design-right---First-time--Part-3--High-speed-signals---Impedance
What is a safe margin for trace length vs rise time depends on who you ask, you get full reflection if round trip delay is equal or higher than the rise time. Some people suggest 1/3rd is a decent margin while others go as far as to 1/10th.
On a standard FR4, 1ns propagation time equals to approximately 160mm, so 80mm trace would be "critical length". With 1/3rd rule, ~25mm would be fine.
Here is an analysis of the 1/3rd rule, which may not be good enough for 15R drive impedance:
https://blogs.mentor.com/hyperblog/blog/tag/critical-length/

You'd think that such a popular connector would have ready reference on the impedance of it. This does not seem to be the case however. 1.27mm ribbon cable has ~100R impedance in GSG configuration but it's not quite the same as 2.54x2.54 2-row connector.
I'd use the connector like this:
GSGSG
SGSGS

So each signal is surrounded by ground pins in three directions, essentially making it a co-planar wave-guide. Now CPW calculators are around, but I'm not quite confident they can handle the case where trace width and thickness are the same. In fact majority of the calculators dismiss the trace thickness out of hand.
Now I used this CPW calculator http://wcalc.sourceforge.net and plugged in these values:

width = 0.6mm
s=1.94mm
length=10mm
Thickness=0.6mm
Surface roughness=1µm
substrate thickness=1.94mm
Dielectric constant=3.4

0.6mm width comes from typical header post size, it varies a bit from manufacturer to manufacturer, 0.64mm is another popular choice. 3.4 is polyamide dielectric constant.
It spits out 119.5 R as a result. Fair enough, but is that realistic? Any thoughts on this? Removing the ground plane REDUCES the impedance to 72R, which would imply the calculation can't handle thick traces + ground planes. In fact it seems to ignore the trace thickness entirely if there's a "ground plane".


texts:
I made the simplest circuit with a 9V battery, a green LED (3.3v and 20ma) and a 550 ohms resistor (green green brown gold)

The LED was brand new and died immediately and the resistor was burning hot.

The same circuit with a red LED worked fine.

Does it matter where the resistor is in the circuit (in this case I put it at the end, between the LED and the - of the battery as I read it doesn't matter)

Does it matter which end of the resistor you connect to the battery? (does it have a + and -?)

According to http://www.hebeiltd.com.cn/?p=zz.led.resistor.calculator a 330 ohm resistor would have been enough for a 3.3v LED in a simple circuit.


texts: Three AA batteries in series, only 1 depleted?

texts:
I am powering an ESP8266 with 3 rechargeable AA batteries. The ESP logs the voltage, so I saw the voltage getting lower over time. Much earlier than expected, the ESP stopped working since the voltage got too low. I measured the batteries afterwards and I noticed one of them had a really low voltage while the other two were fine (1.2v). What would cause only one cell to get depleted faster than the others? And how can that situation be avoided in the future?
Thanks!


texts:
We have a board design with four layers that uses coplanar waveguide with ground plane:

The trace has via fences.  Originally, the design was: W=0.35mm, S=0.2mm, and H approximately 0.2mm (for one of Isola dielectrics, which the manufacturer reports an epsilon of 4.04). The resulting impedance is 50Ω.
The via fence is about 1mm away from the center of the trace.
We are modifying the design to make it a two-layer board.  At 1mm board thickness, we can obtain the same 50Ω with a 0.68mm trace width, and 0.13mm clearance to the ground plane on the sides.  Or, at 1.6mm, 0.75mm width and the same 0.13mm clearance.
My question is:  do I need to adjust the distance from the via fence to the trace to compensate for the increase in the distance to the ground plane underneath?  That is, H (as defined in the above figure) is now approx. five times the H in the original board;  does that affect the required distance to the via fences?
Note:  I already increased the distance to compensate for the wider trace;  that is, I tried to maintain approx. the same distance from the via fence to the edge of the trace.  But that was a small increase;  I wonder whether the increase in H implies a significant adjustment in the via fence distance to the trace.


texts: looking for a sensor that activates when hit by a certain note

texts: The reason may seem a bit silly, but anyway: I am trying to turn a violin steampunk. I have never done this before and I'm not the best at engineering, so could someone help? The circuitry doesn't have to be invisible (cables showing etc. are A-okay), but it would be cool if I could find something to light up LEDs when a certain note is played. Does anyone have any ideas?


texts: Considering Transmission Line Effects for Clock Generator

texts:
I'm trying to design a clock circuit to convert a 50 MHz 5-volt clock signal down to 3.3 volts without inverting it. The concept is relatively simple, but as I never designed anything like this from scratch before, I'm beginning to look into concepts that I never considered in designing circuits. For the scope of this question, lets limit it to the output signal.

Assuming that I manage to generate a 3.3 voltage clock source at 50 MHz, the signal has to travel across a SMB cable, for now at most 6 feet (1.83 meters), to a NIM module, whose connector has a 50 ohm impedance at its inputs. This got me thinking about transmission lines in general. When using other devices that require a coaxial connection, such as an oscilloscope, I've used various lengths of cables to connect from a source to them, and the signal stays relatively intact with minimal voltage drop. At 50 MHz in the very high frequency range, I would assume that there will be some voltage drop from the generator output to the NIM module input, but aside from matching the impedance at the output of the generator, is there anything I can do to mitigate the probable voltage loss across the line?

Sorry if the question is unclear. I was just thinking about this since cables come in various lengths, and signal generators tend to produce waveforms within significant tolerance since there's no guarantee way to match the characteristic impedance for every length. I'm just trying to design it in such a way that I don't have to rely on a certain cable of a certain length, so if the situation arises, my team can use a different length cable.

For a rough reference, here's a quick and dirty schematic of how I roughly imagine this problem to be. The input port of the module may have a 50 ohm impedance, but I'm not sure if you could treat it as a 50 ohm load in a schematic.

simulate this circuit – Schematic created using CircuitLab

If you really want specifics, I'm working under the assumption that the cable is coaxial, with copper for the conductors and teflon for the insulator. The cable itself is 2.489 mm in diameter while the center conductor is 0.508 mm in diameter.