texts:
I'm working on a project to design and build a 1/10th scaled ultra-capacitor powered electric car. I'm a Mechanical Engineer & I really want to focus on the the building and testing of the vehicle - not the electronics, which is why I need your help!

As I have a limited electronics knowledge I was hoping that I could run my initial control system design past some of you in the hope you'd be able to confirm my ideas and maybe point me in the direction of some suitable hardware. Or help correct my errors.

Here is a basic modular outline of my design:

The plan is to have 3 ultra-capacitors connected in series using the Maxwell Integration Kit. I know I need a Buck-Boost converter with the voltage and current rating of the motor. Ideally I'd like something off the shelf - I was investigating these modules from Linear Technology (http://www.linear.com/solutions/Supercap,_Capacitor_*_Battery_Back-Up_Solutions). Would these do the job? Or is there something better out there without creating one from scratch?

I'd also like some motor controller which integrates some form of speed control and outputs the speed, distance travelled etc. I've not researched this in too much detail yet as it's an added extra and not essential.

The motor can then be decided based on the parameters of the rest of the control system but I require a minimum motor torque of around 0.2Nm. I'll probably go for a DC brushless based on efficiency.

The vehicle is intentionally simple and the target is to drive a 50m straight journey at a constant speed.

Thanks in advance for your time and please let me know what you think.


texts: How does a switching power supply reduce its power output? For example, suppose a CPU ends some task, reducing its power consumption. What happens internal to the computer's power supply to cause it to put out less power?


texts: I found this picture explaining a G5V-2-H1-DC5 relay from Omron. My question is if Pin 5/6 can be a higher voltage than 5V while keeping the voltage at Pin 2 at 5V. Also, is there a limit to how fast the voltage at Pin 5/6 can change?


texts: How to create an on/off indicator for a SPST in a circuit?

texts:
I've recently started to work with electronics and I'm truly a beginner. Our teacher asked us to create an on/off indicator for a SPST button in a circuit. When the button is pressed the green light should glow, and when it is released, the red light should glow.

How would I do that?


texts:
I am designing a PID temperature controler; as far as I managed to write it so far, you find the code below.
Can you please help me check if Integrator wind up and other PID elements are configured please?

When i run the code at some point close to the set point , it starts
behaving like an ON and OFF code

I don't know if this is a valid question but im asking it anyways .
and if you can make any edits . i will be glad to check them out
// programing the pid
const int pin = 3;  // PWM analog output
double cumerror = 0; // Initialising the cumulator of the integrator to 0

double input, setpoint, integral, proportional, piderror, pidvalue;

// Input values
double kp = 25; // seting proportional at 25
double ki = 0;  // seting the integral at 0

void setup() {
  setpoint = 37; // seting the setpoint at 37
  Serial.begin(9600);
}

void loop() {
  double inputvalue = map(analogRead(A0), 0, 1023, 0,
                          100); // reading the values from the analog signals
                                // and mapping it to a 100 deg scale

  piderror = setpoint - inputvalue; // calculating the error

  // calculating the integral ((Naturally ki= cumerror *dt), we do not have to
  // multiply by dt, since dt = 0 because i am using the sample time delay(1000)
  // every time )
  cumerror += piderror;
  integral = ki * cumerror;

  // calculating the proportional error

  proportional = kp * piderror; // calculating the proportional error

  // changing the P and I parameters as the error approaches the set point
  if (3 < piderror < 10) {

    kp = 10;
    ki = 0.5;
    cumerror += (1 * piderror);
    integral = ki * cumerror;
  }
  // Making the parameters =0 as the error approaches more 0

  if (piderror < 3) {
    proportional = 0;
    pidvalue = 0;
    integral = 0;
  }

  pidvalue = proportional + integral;

  if (pidvalue <= 0) {
    pidvalue = 0;
  }

  if (pidvalue > 255) {
    pidvalue = 255;
  }

  analogWrite(pin, pidvalue); // sending the pid value to the heater

  delay(1000);

  cumerror=cumerror;
}


texts: How to calculate remaining battery capacity from charge discharge data?

texts:
If a dataset contains data collected over time from a re-chargeable battery and includes information such as voltage, current, average discharge rate and peak discharge rates.

how can the remaining capacity of the battery be calculated based on this data?

Are there any examples which can explicitly show this calculations as I do not come from an electronics background but i am trying to work on this data to predict battery remaining useful life and do not fully understand how to compute the capacity value out of this raw information?.

Thanks.


texts: What are some smallest, cheapest microcontrollers with USB built in?

texts:
The cheaper, smaller, and fewer external components needed the better.

AVR would be preferred, but anything with free SDKs is good.


texts: Heatsink Crossing Primary and Secondary Sides in Switched-Mode Power Supply

texts:
I've taken apart a non-oem laptop power supply. There is clearance on the board between primary and secondary. However, they've placed a single heatsink across the board for the primary and secondary transistors. There is no insulation apart from some tape and silastic on the bulk capacitor. The heatsink is not grounded, and both trannies have plastic bodies.

Is this a safety issue?
If so, would cutting the heatsink to isolate the sides be the preferable solution (assuming transistors don't overheat)?

Thank you.

edit: So I decided to cut the heatsink in two, thus preventing any potential conductive paths between the two sides. I've also ordered a replacement OEM supply as the Y2 cap looked fake and there was no RF shielding.


texts:
I have a LM471 op-amp and a single DC 5V source. Is it possible to double the source voltage using this op-amp? Can the op-amp be powered by the very signal to be amplified? I tried simulating such situation in Multisim and it seems power/signal have to be from different sources. Why is that?

A segment on my 7 segment display requires voltage higher than 5V. I want to boost my 5V power (double it, for example) and use the boosted voltage to lit the display. I don't want to use a separate power source just to power the op-amp. I understand the out current will be lower, but it doesn't matter in my situation.

Of course different elements might be necessary in this circuit, but I don't want to use things like 555 timers, just analog parts.


texts: Parallel Transistors in Constant Current Load

texts:
I'm designing a constant-current dummy load for testing my power supplies. This load should be able to handle a maximum of \$2\mathrm{A}\$ at \$24\mathrm{V}\$. My current design, so far, is loosely based on the design found at EEVblog #102.

Original design:

simulate this circuit – Schematic created using CircuitLab

A simplified version of the original design from the website is shown above. In the schematic,
\$V_1\$ and \$V_2\$ are, respectively, the control voltage, and the power supply under test. The number of amps that this load draws is equal to the number of volts on the input of the op-amp.

For example, when \$V_1=1\mathrm{V}\$, the op-amp turns on MOSFET \$\mathrm{M}_1\$ until the voltage at its inverting (minus) input is also \$1\mathrm{V}\$. This voltage is applied across \$R_1\$. Since, ideally, no charge flows into or out of the op-amp's inputs, we can use Ohm's law to determine the \$R_1\$'s current, \$1\mathrm{V} / 1\mathrm{\Omega} = 1\mathrm{A}\$. Therefore, \$1\mathrm{A}\$ is drawn from \$V_2\$ (the PSU under test) through \$\mathrm{M}_1\$ and \$R_1\$.

If the control voltage is, for example \$1.5\mathrm{V}\$, then the current draw would be \$1.5\mathrm{V} / 1\mathrm{\Omega} = 1.5\mathrm{A}\$. As you can see, the current is equal to the control voltage because of the \$1\mathrm{\Omega}\$ resistor.

The problem:

As previously stated, I intend to build a power supply what can handle \$2\mathrm{A}\$ at \$24\mathrm{V}\$. Using the previous schematic, I ran some quick estimates at max load. . .

$$ V_1 = 2\mathrm{V} $$
$$ V_2 = 24\mathrm{V} $$
$$ R_1 = 1\mathrm{\Omega} $$

For the resistor \$R_1\$:
$$ P_d = 1\mathrm{V} \cdot 2\mathrm{A} = 2\mathrm{W} $$

For the MOSFET \$\mathrm{M}_1\$:
$$ P_d = 23\mathrm{V} \cdot 2\mathrm{A} = 46\mathrm{W} $$

The major problem with this design is that the MOSFET has to dissipate \$46\mathrm{W}\$! This is probably not very healthy for the TO-220 device. Therefore. . .

Schematic 2:

simulate this circuit

In this schematic, the load is split across 2 sets of MOSFETs/resistors. My hope is that each one of the components would only have to dissipate half of the original heat. This means that \$R_1\$ and \$R_2\$ would have to dissipate \$1 \mathrm{W}\$ each, and \$\mathrm{M}_1\$ and \$\mathrm{M}_2\$ would have to dissipate only \$22 \mathrm{W}\$ each.

I tested this design using CircuitSim, and it works! However, practically, I can see a potential issue with this implementation.

Do \$\mathrm{M}_1\$ and \$\mathrm{M}_2\$ have to be matched?
Do \$R_1\$ and \$R_2\$ have to be matched?
Is thermal runaway an issue?

One of my major concerns is that, outside of the ideal, virtual world of the circuit simulator, the MOSFETs' parameters vary, and one MOSFET would hog all of the current, destroying itself. Then, the other MOSFET would quickly follow suit.

What can I do?

Do nothing.
Connect the MOSFETs' sources.
Add another op-amp for \$\mathrm{M}_2\$.

What if I use bipolar transistors? What kind of op-amp should I use? Should I use an op-amp at all? What are the limitations of using op-amps in this application? Please feel free to explore other options or suggest something else!

Thanks for your time! Hopefully this topic can be expanded upon for the benefit of others in the future.


texts: Is it safe to parallel connect components to a single to a 12v DC PSU?

texts:
Prerequisite:
For a home-decor project, we wish to work with different LED strips and even a larger LED chip as a central lighting source by attaching everything to a powerful, high quality 12v CC/CV DC PSU. (eg., Mean Well HLG series).

Each portion of LED strips, depending on chips / resistors, will draw different currents.
For the central lighting, we wish to use a CC / CV DC booster to drive a high-power LED.

Given that the total power consumption from all components is well below 90% of PSU capacity;

Would it be safe to connect all components in parallel and use the single PSU to power them?

  Edit:
  This question is not a duplicate on this site. It is irrelevant to, for example, the following:
  Can I safely and efficiently connect batteries parallel to a DC source?
  or:
  Choosing power supply, how to get the voltage and current ratings?


texts:
I just started studying electrical engineering this semester, and I'm currently working on following impulse counter:

The circuit is basically a power supply regulated to 5V, a pendulum acting as a switch connected to the clock of a counter, with a bit of noise-reducing circuit to limit the impulses, and some 7-seg displays with drivers to display the value of the counters.

I have a few issues with the circuit, that I would love to get help or inspiration on how to solve:

The counter (U4) always starts at 1 instead of 0, so I have to use the implemented reset button every time I power on the circuit. Not a major issue, but it would be awesome to find a way to solve this. I assume it is because of the small delay whilst the capacitor (C3) is "loading" initially - making the inverted output HIGH, then LOW when powering on the circuit. If that is the case, I don't know how to solve it while retaining the noise-reducing circuit.
I implemented some logic to keep 7-seg 2 (U7) turned off initially (when it should be displaying 0) and turns on only for 1-9. This works as intended when simulating the circuit in MultiSim, but when I realise the circuit on a breadboard it acts a bit unexpected. Initially it works as intended, but after 7-seg 2 (U7) has been turned on once, it never turns off again and instead displays the value '0' when reset.

I appreciate any help on solving the issues!

EDIT: Solution for the problem, by attempting to implement suggestions by Dan:

Added another (slightly slower) low-pass filter connected to the counters ~CLR-pin to reset the counter to 0 initially, and replaced the logic for U5's RBI-pin with a ground connection to solve the display issues.

EDIT2: Final working solution if anyone is interested, thanks to  suggestions:

Fixed the reset switch and improved the reset module with a diode and some amplification to make it more reliable. Works great now!


texts: I don't seem to understand, when a manufacturer states that their microcontroller has 2 PWM modules but 8 channels, does this mean I can drive only 2 motors but I have 8 pins (channels) to choose to output my PWM?


texts: How can I modify the Chipolo circuit to support earlier versions of Android?

texts:
I have been trying to find out more of the circuit design of Chipolo and would like to modify it so that it can support earlier Android versions because it can only support Android running version 4.3 or newer.

May I know where can I find the circuit design and hints on how I can change to the circuit design to support earlier Android versions (Android running version 2 up to 4.2)?


texts: Creating a bus port in custom made part in LogicWorks

texts: I'm creating some parts in LogicWorks and instead of having individual pins for input and output I want to use a bus pin.  I can't seem to figure out how to make the bus pins appear in the part builder.  I created a breakout in the sub-circuit to symbolize a bus, but when I go to create the part and import the sub-circuit the bus port doesnt show up.  Anyone know how to do this?


texts:
I'm designing a simple breakout board based on Atmel SAM4S4A MCU. I've downloaded complete design of ATSAM4S Evaluation board and it says that PLL filter is missing in it and refers to AT03463 Schematic Checklist that shows following schematic of power supplies:

I've got a question in regards to VDD_PLL line, does it matter in what order RLC components are placed or not? Which capacitor should be closest to MCU? 100nF one or 1R+4.7uF one? From my experience I believe that inductor L1 10uH should be connected to resistor and cap and then closest to MCU there should be a 100nF cap? Am I correct? Thanks!
Another example of VDDPLL from SAM4E EVM:

Here's a cut from ATSAM4S EVM schematic revision 5, in revision 4 there's no such note.

And this is from SAME70 EVM design documentation, just a ferrite bead and 100nF cap on VDDPLL. I'm completely confused.


texts: Variable wattage vs temp control in a soldering iron?

texts:
Presently, I am looking into soldering irons because I am considering making a purchase.  I am considering features in order to find something that is usable and versatile for the value.

One factor I am struggling with a bit has to do with temperature vs. wattage. I have already checked out a number of resources:

https://www.circuitspecialists.com/blog/selecting-a-soldering-iron-temperature-wattage-and-tip/

How does power affect soldering irons? Is 30 Watts enough?

As such, I do get the basic idea about wattage being an issue of the tool's capacity to heat the tip and replace heat that has been lost or sunk.  Where it becomes a bit confusing to me, though, is when it comes to varying one or the other.  For example, the Vastar Full Set 60W 110V Soldering Iron Kit features adjustable temperature, whereas the Weller WLC100 has a dial for you to vary the power (5 to 40 watts).

So, I guess I am wondering: Is there a reason to prefer adjustable temperature over adjustable power?  Or vice versa?  Or am I overthinking the matter?

Your input on this is appreciated, so thanks in advance!


texts: PAM2803 led driver, which input voltage?

texts:
I don't understand what's written in the datasheet (see here on page 3):

Input Voltage Range: min 0.9 Max: Vf-0.2 (Note 1)

Note:  1. VF - LED forward voltage.

What does that mean?


texts:
I currently try to understand a new technology: Profibus, until now I worked with HART, with which I also had some struggle in the begging but now it's clear. I try to understand why in a factory is used both PA and DP.
I understand that to convert a PA Profibus to DP a coupler is needed "...The connection of PROFIBUS PA subsegments to the RS-485 PROFIBUS DP segment is carried out using segment couplers or links. Segment couplers are transparent from the standpoint of the bus protocol...", but what I don't understand is why the PA is used? and not directly DP? (only for safety reasons? "... PROFIBUS PA can be deployed in hazardous environments since its physical layer: MBP, is intrinsically safe..." in this case what does it mean intrinsically safe?)
And what is the difference between these terms:

PA (process automation)
DP (decentralized periferics)
MBP and RS485

I understand that MBP and RS485 are the communication protocols, but in this case what are PA and DP? Only a standard (e.g ISO)?


texts: Choosing and biasing a MOSFET controlled by a microcontroller, does current matter?

texts:
I need some help choosing a MOSFET for the circuit that I described here, which I originally designed using a BJT but decided that FETs make more sense in this case.

The FET will be controlled by a PIC24 that sends a logic high or logic low to the FET. I know that FETs are voltage-controlled devices, but I am wondering if there is also a minimum current needed to switch the FET on?

If so, does the FET need to be biased so that the PIC24 can source enough current to turn on the FET?

I'm also not too familiar with biasing FETs, so I'm also curious about pre-internally-biased FETs but they're somewhat hard to find on Google. Could you recommend any other resources?


texts: I recently purchased the photodiode here and I am a bit confused on how to implement it.  The reviews are all mixed on what is what, and the voltage for each is different so I am trying to be rather cautious so as to not burn one out. For some reason, it lists the photodiode as being the clear package and the tinted being the ir led, which seems strange to me. I have seen this post as well, and I am not sure of it as well. The diagram shows the cathode going directly to the 5v+, where I am used to putting a resistor before the diode. All I am trying to do is read whether it detects light or not with a microcontroller. How would I wire these? Oh, and the specifications listed on the website are different from those listed on the package. Any help is appreciated.


texts: Practical LabVIEW-free Keithley 2400 front-end for Linux?

texts: Is there a high quality LabVIEW-free gui/interface/front-end to communicate with Keithley 2400 on Linux? Not just for single measurements, but also for various sweeps for practical daily use?


texts: Arduino - Use arduino as to switch to power up 12v pump

texts:
I want to switch a 12 V pump from the digital output of an arduino. I have tried using 5 V relays by using this schematic:

and put two of these in parallel. The power they are getting is from the arduino itself which is connected by 12 V in V-in. The relays behave abnormally. Can I get an arduino to switch on a 12 V pump and a 24 V pump?


texts: Help deciphering abbreviated terms in technical manual

texts:
I'm having trouble deciphering some abbreviations in a parts list of capacitors from a technical manual for an old (80s-90s) computer.  I've managed to work out that "CPCTR" stands for "Capacitor", however I'm not sure about the abbreviations after that.  I guess they describe the type of capacitor? Here's the different types listed:

CPCTR CPLT
CPCTR CER ("Ceramic" maybe?)
CPCTR TANT
CPCTR DCPLR ("DC Polarized" maybe?)
CPCTR ALEC

The one I really need to translate is CPCTR DCPLR.  The others are provided mainly for context.  Google has been no help I'm afraid.


texts: Looking for a Micro SD card that can start up in 1.8V signalling mode

texts:
With the SD 6.0 specification, SD card manufactures have the option to design cards that can autodetect and start up with 1.8V signal levels.  I believe they still need to be powered from the nominal 3.3V range but the interface to the microcontroller no longer needs to start at 3.3V and then command the card to reduce to 1.8V signal levels.  I don't think this is inclusive of all SD 6.0 compliant cards, just an option is added to the specification.  If it does support startup with 1.8V signal levels, I think it needs to be marked with the "LV" stamp (if there is any room left with all of the other stamps - sarcastic, not really part of the spec).
With most of the microcontrollers manufactured in the past decade supporting 1.8V I/O, where are the SD cards that don't need level translators to start up at 1.8V.
Does anyone know of a MicroSD card that may not advertise its ability to start at 1.8V signaling but has this capability?


texts:
I have recently received my order of 2 2.7V 500F super capacitors from eBay.

After much searching, my yet unanswered question is:
Can I connect both of these capacitors in series and charge with 5V running absolutely no risk of explosion or damaging the caps?


texts: Low ESR capcitors for switching pre-regulator (LM2596)

texts: In LM2596 switching regulator datasheet suggested to use low ESR capacitors. since I'm going to use LM2596 as a pre-regulator for a linear regulator to reduce the voltage drop on linear regulator, is it still necessary to use low ESR capacitor?


texts: Data from BMA180 accelerometer into arduino is sporadic

texts:
I've been trying to get a BMA180 (I'm on my second one already) to send a continuous stream of accel data via a serial port (eventually bluetooth but that's a problem for a different day). I've looked at and tried to emulate numerous examples and consistently come across the problem of data coming in "fits and starts". One packet, wait a second or two, a few more packets, etc etc. Usually this ends in the data stopping all together a
fter 5, 10, 50 chunks.

My wiring is as show here but I have VIO unconnected. When VIO is tied to 3.3V, my output is all 0's. :

This is my code, which is adapted from several other sources:

#include <Wire.h>
#define DEVICE ((byte)0x40)
#define DATA_X0      0x02
#define AXIS_SHIFT   2
#define DELAY_RATE   500

int counter = 0;

static void readFrom(byte address, byte num, byte *buff) {
  Wire.beginTransmission(DEVICE);
  Wire.write(address);
  Wire.endTransmission();

  Wire.requestFrom(DEVICE, num);
  num = Wire.available();

  while(num-- > 0) {
    *(buff++) = Wire.read(); // receive a byte
  }
}

void setup()
{
  Wire.begin();          // join i2c bus (address optional for master)
  Serial.begin(115200);  // start serial for output
  Serial.flush();
  delay(15);
}

void loop()
{
  digitalWrite(13, HIGH);
  int axis[5] = {0x0101, 0, 0, 0, 0};
  readFrom(DATA_X0, 6, (byte*)(axis+1));

  axis[1] = axis[1] ;
  axis[2] = axis[2] ;
  axis[3] = axis[3] ;

  axis[4] = axis[1] + axis[2] + axis[3];
  Serial.println("");
  Serial.println(axis[1]);
  Serial.println(axis[2]);
  Serial.println(axis[3]);
  Serial.println(axis[4]);
  counter++;

  delay(100);
  digitalWrite(13, LOW);
  delay(100);
}

This is what I get coming into the serial monitor, in weird sporadic thrusts:

-879
321
17077
16519

-411
345
16761
16695

249
0
0
249

........etc......
I suspect the 249 /0 /0/ 249 chunk is the temperature because it will go up and down a little although the application of my desk lamp caused all data to cease.
I am baffled. The 'L' LED on the arduino blinks when the packets get pushed out so I think it's not a serial port problem. I would really appreciate any ideas here.


texts: Phase/Gain margin measurements for current mode boost regulator

texts: I'm looking for where to place a sense resistor in the feedback path of a current mode boost regulator with a layout similar to the one in the picture. Should I place in on the FBL or FBH trace?


texts:
The power tree of the design is indicated in the image below. The UPS module has a supercapacitor that is charged when 5v_DCDC is on. If the 240v is off, the 5v_UPS power is switched on to provide 5V to the load which can last for around 10 minutes. This UPS function is good for saving data when 240v is blackout but is a problem when sometimes a quick system reboot is needed for debugging as it takes a long time to wait for the UPS to run out.
To solve this problem, my solution is to add a DPST switch that controls the 12v and 5v rail. Then the 12v and 5v can be cut off by this switch at the same time(positions 1 and 2 in the image). However, I'm not sure if this solution is feasible or may bring in some other issues, so my questions are:

Is there a better way to reboot the UPS-supported system?
Is there any issue with the DPST switch solution I described?

Thank you.


texts: Can I do this (MOSFET instead of switch)?

texts:
This might be a very trivial question: Can I simple swap a switch that is connected to a RESET pin with internal pull-up with a N-channel MOSFET?

My goal is to pull the RESET to ground using a signal (OUTPUT) instead of a switch, but not sure if it is this simple?

So can I replace this:

with this?:


texts: Different recommendations for ethernet front end terminaton?

texts:
I’ve noticed different MAC/PHY manufacturers have different recommended termination recommendations for their Ethernet front end.

Why does everyone do a variant on the same theme? Does it come down to designer’s preference, or is there a good reason?

I’ve included 3 examples below.

In image 1, the center taps of the transformer are tied to 3.3v and the data lines are terminated to ground through a ~50R resistor and 100nF capacitor.

Image Source: http://www.siongboon.com/projects/2006-03-06_serial_communication/an-139%20(how%20to%20route%20ethernet%20PCB).pdf

Image 2, the center taps are tied to 3.3v along with the ~50R termination resistors. The advantage I can see here is reduced component count (no 100nF caps to block the DC path).

Image Source: http://www.nxp.com/files/microcontrollers/doc/app_note/AN2759.pdf

Image 3, this is a bit of a mix of the above two configurations with another small difference thrown in. Only one of the center taps is tied to 3.3V. The other center tap is tied to ground through a capacitor. TX termination resistors are tied to 3.3V, while RX termination resistors are tied to ground through a capacitor.
Image Source: http://docs.tibbo.com/soism/index.html?em200_pin_ether.htm


texts: Zener diode can vary current flow to maintain voltage drop, how does this magic effect work?

texts:
So it seems that a zener diode is "magically" able to change its resistance to allow more current to pass through it, such that the voltage drop across the diode remains the same. My question is simple: HOW?

I also have a question related to normal diodes (the humble non-zener type). I do know that a zener diode is still similar to "normal" ones but just have a much higher reverse break-down voltage. So here it goes: For resistors, their resistance is always the same thus depending on the circuit topology the voltage drop across them varies, considering that we have voltage source in the circuit, current shall vary and result in different voltage drops across the resistor. For diodes, the voltage drop across them is almost the same about 0.6v, what exactly do they vary within them that we always get no more than about 0.6v drop across them? It just looks like magic doesn't it?

I have asked one question about zener and one about normal diode, the questions are related and thus I put them into the same post.


texts:
I'm using a STM32F746 running at 200MHz. A timer (tim2) is counting up at 100MHz and triggers an update interrupt with the following simplified ISR that writes a pattern to GPIOB
void __attribute__((section(".itcm_text"))) TIM2_IRQHandler(){

    GPIOB->ODR=pattern[index];

    index += 4;

    if (index >= size)
        index = 0;

    htim2.Instance->SR &= ~0x1; //clear interrupt flag
}

To improve speed:

ISR in ITCM
Data in DTCM
Interrupt priority is 0 ( no other interrupts at that level)

When triggering on the rising edge of a GPIO pin, there is visible jitter on the falling edge. The time step is exactly 5ns (one clock cycle) and 25ns total.
Question: Why? Can it be improved without using the timers capture/compare output mode?
Usually the interrupt latency is depending on flash memory timing, but this shouldn't involve the flash memory at all.
Could it be AHB bus connection between CPU and GPIOB(also running at 200MHz)?


texts: NOP instruction after branch on ARMv7 Cortex M3

texts:
I'm interested, why for Cortex M3 microcontroller (stm32f103) compiler sometimes generates a NOP instruction after branch. And why it sometimes doesn't.

For example:

0x08000496 2400      MOVS     r4,#0x00
0x08000498 4625      MOV      r5,r4
0x0800049A E006      B        0x080004AA
    64: res=res+a[i];
    65: }
0x0800049C F85A0034  LDR      r0,[r10,r4,LSL #3] // No NOP after B
0x080004A0 EB100808  ADDS     r8,r0,r8
0x080004A4 1C64      ADDS     r4,r4,#1
0x080004A6 F1450500  ADC      r5,r5,#0x00
0x080004AA 1BA0      SUBS     r0,r4,r6
0x080004AC EB750007  SBCS     r0,r5,r7
0x080004B0 DBF4      BLT      0x0800049C
    66: int64_t avg=res/x;
0x080004B2 BF00      NOP      // <------------------- NOP after BLT
    69: int v=countbits1(5);
0x080004B4 2005      MOVS     r0,#0x05
0x080004B6 F7FFFFA2  BL.W     countbits1 (0x080003FE)
0x080004BA 9001      STR      r0,[sp,#0x04]     // No NOP after BL.W
    72: unsigned int b=countLeadingZeros(5);
    73:
0x080004BC 2005      MOVS     r0,#0x05

My initial guess was that long instruction needs word-alignment but BL.W after NOP actually doesn't have it.
If this NOP is related to pipeline somehow than why there are branches without nop's after them?

I'm confused.

UPDATE:

It turns out that branch may be not relevant at all. I tried to moving declaration of unused local variable int64_t avg - and NOP moved along with it.
So I beleive pjc50 comment is right and this NOP is there just to let debugger put a breakpoint on this line.


texts: I want to design a car audio amplifier. I am going to use 4 x Amplifier ICs like TDA7294(Datasheet) for 4 Channels. The problem here is that with 12v input voltage these ICs output maximum 20W. I am thinking of using step-up converter to boost the voltage to 20-30v to power the amplifiers. Will there be any problems going that way? If yes what are other solutions?


texts: Can I charge this li-ion battery with this solar panel setup?

texts:
Since a couple years I've been messing around with a raspi and some motors. Building random stuff with dc-motors and such. I now want to power a self driving boat-robot with some solar power. For this I imagined using a solar panel, a charge controller and a li-ion battery. I chose li-ion because it's light-weight, but not as explosive and difficult to charge as lipo.

So I was thinking of ordering the following:

A 3S 12V 3000mAh battery pack
2W 6V Solar Panel (3 of these)
An MPPT Solar Panel 3S 5A Charger Controller

So I thought of connecting the 3 solar panels in series so that they make for 18V input to the charge controller (the input voltage is up to 28V). That can then be hooked up to the battery.

I have 2 questions about this:

1) Would this be a reasonable setup?

Furthermore, once I can charge the batteries I want to build this into my robot and simply connect the load (raspberry pi and some very small dc motors) to the battery connectors. That means the battery connectors are connected to both the charge controller and the load.

2) Would this work or am I thinking too simple?

After this I want to add a voltage sensor to the battery and read that out from the raspi, so that I can limit power usage when the battery power is going down too fast, or shut the whole thing down if the battery juice is critically low.


texts: Is there a way to check integrity of earthing provisions?

texts:
We have a complex network of earth wires and earth pits. These earth wires are connected to power panels and CNC machines. However, the earthing system is very old and poorly maintained.

Is there a way to check if the panel/ machine is properly earthed or not?

Obviously, visual inspection and line tracing is an option to trace the connectivity of earth wire, but I am looking for a more efficient solution.

For example - Is there any specific method to test if the body of earthed machine/ panel is at earth potential and will remain as such?


texts: How can I work out which pin is which in SPICE model

texts:
I am attempting to simulate a flyback controller from TI, part number UCC28700-Q1, datasheet here: http://www.ti.com/lit/ds/symlink/ucc28700-q1.pdf

I have downloaded the SPICE model from TI (as can be found here: http://www.ti.com/lit/zip/slum455) and am now attempting to build a SPICE simulation in LTSpice.

If I open the model in LTSpice, I can right click the .SUBCKT line and let LTSpice auto draw the symbol for me. When I do so, I get a 6pin block with the pins labelled as: P1 P2 S1 S2 RS1 RS2. These pin names do not match up with anything I can see in the datasheet, and I don't believe that the order of the pins matters in terms of relationship between SPICE model and real world. If I try and draw the symbol myself, I end up with the same issue, as I still don't know how these pin names relate to the signals.

Is there a simple way to work out which pin is which?


texts: I want to measure current that flows from a several kΩ load with source voltage sweeps from 0-200V. I want to measure possible energy losses, so I need both low and high side sensing. Setup is described in the picture. Do you think this is accurate, would 200V damage the AD623? And also I am not sure that where to connect Vref, so I connected it to ground.


texts: How can I create laser detecting flexible surface

texts:
What I'm trying do is creating a game like laser tag for larger areas, I want to detect laser beams on a flexible/wearable surface like a vest. That surface will be connected to an Arduino board.

So small photodiodes will won't work for me, because they are too small to hit from distance.
I've read these: Using a solar panel for laser light detection, Detecting Multiple Lasers Also creating an array of diodes would not be so flexible.

But what I'm thinking is more like photosensitive mesh, like when hit by a laser creating a small current, so I can tell is it hit by a laser. Next step is detecting laser's color by the current's level. But this is not necessary, rather than that, modulation of the laser can be the better solution.

Simply what I trying to achieve is, a flexible, wearable surface that can tell is it hit by a laser. Source count does not matter.


texts: Loading an AC generator with DC Chopper + resistor

texts:
We're in kind of a bind at work and looking for easiest / cheapest way to load an AC generator (Synchronous permanent magnet machine).

We have access to a big 300A Mosfet module along with it's industrial gate driver.

I was wondering if I could rectify the output 3-phase voltage with big diodes such as these ones and then chop the power with the MOSFET into some power resistors.

The big question being : do I need some inductors (this?) to smooth out the current ?
The motor main field inductance is > to 10µH.

And we're looking to chop around 100A @400VDC. The goal being of course to make the load vary form 0 to xx 40kW.

So to sum up our interrogations :

Does this work? :-)
Do I really need an inductor?

Down below is a crude schematic.


texts: What is the general criterion for selecting a MOSFET voltage and current rating?

texts:
I've used an N-Channel MOSFET (IRF540) rated at 100V 28A as a switch with a 54V load and current source that maxes out at 20A. The switch worked however, using the load for a while resulted in MOSFET burned out. I have heard that one should not use rating too close to the load but if these ratings mean nothing then what is the point of listing such ratings?
what is the general guideline and in what theoretical principles is it grounded to choose a MOSFET rating for a load?


texts:
Let's say I have a power source of 4.2V/1A. I know how to reduce the voltage using resistors, but if I would like to be able to 'divide' current in half for example, how can I do that using standard components?

My component is a battery, which should not be able to draw more than 150mA from the power source.

I know I can buy already built components for this, but I want to understand how to do this using only the basic components.
I know that charging battery is dangerous, but I do this daily by hand (from bench power supply with current limiter enabled), but battery is just an example. All I'm trying to do is to reduce the 'max current potential' from the power supply.

I'm familiar with 'voltage divider', I want to do exactly that, but only with current. Can I do this purely with basic components, such as diodes? Thanks!


texts: Why does a classic envelope detector produce a negative voltage for some periods, when high frequencies are put in?

texts:
I'm playing around in ngspice & trying to understand envelope detectors for ham radio.

I'm pumping 150Mhz into the circuit described below - I'm expecting it to go positive in proportion to amplitude + frequency. After a bit, it goes negative. Whats happening here?

Consider this circuit:

150Mhz 2V sine wave input, 50ohms impedance
D1N4148 diode
100pF smoother capacitor
500k bleed/load resistance

Spice input I'm using / working on:

Detector CIRCUIT
.model D1N4148 D (IS=0.1pA, RS=16 CJO=2pF TT=12N BV=100 IBV=0.1pA)

v1 1 0 sin(0 2 150MEG)

rSOURCE 2 1 50

d1 2 3 D1N4148

c1 3 0 100p

rLOAD 3 0 500k

.control
tran 5us 50ms
run
write kek.raw v(3)
quit
.endc
.end

Gives me this:

Note the negative sections.

How does a diode detector go negative like this? how do I stop it?


texts: I am working my way through Make: Electronics. For some experiments in this book, you need a 2N6027 programmable unijunction transistor (PUT). The shop I am buying my parts from doesn't have this exact model, but the 2N6028. The combined datasheet for both models shows some differences. I am wondering whether they are similar enough for simple experiments are whether I should try finding another one that matches the 2N6027.


texts: Shoot through problem in 3-phase BLDC controller circuit

texts: I have designed a 3-phase controller for a BLDC motor. I am checking one side of the bridge with a Pico-scope for shoot through. The wave-forms below are indicating that i am getting shoot through, and this waveform is the same for all 3 legs of the 3-phase inverter. The probes of the Pico-scope are connected to the gate of the FET's but I am not sure if this is correct as the high side Probe its not VGS. I think i would need a potential difference probe for the high side FETs. How can I check if this is actually shoot through or not, all three sides of the bridge give me the exact same waveform?  is this waveform showing shoot through or is this not shoot through?


texts:
I require a passband filter with

bandwidth of 500 MHz.
4 GHz central frequency.
minimize the attenuation of the signal (but there is no restriction on this as I am going to use power amplifiers after the filters to increase the signal strength).

Can someone guide me as to how to design such a filter? Are there commercial ICs available at such a high frequency?

Additional info: I plan to use this filter in a high bandwidth communication circuit. The input signal is a pulse of lower frequency 10 MHz and hence the frequency spectrum would be a sinc curve. I plan to use the lobes around 4 GHz for my transmission and hence would be using this filter on the transmission side. The receiver would also have the same filter after the antenna and the LNA. The detection of pulse is using RF energy detector. Note that there is no modulation happening here.

Edit-1: Input power level is around -50 dB, which I will amplify to around -30 dB using ADL5542 (RF amplifier). The output of the amplifier will be fed to the filter. Post-filtering, I require an output power level of around -35 to -40 dB.

Edit-2: I am not sure of the width of the transition band as I am still identifying the components for my communication circuit but I think I can allow a transition band of around 50 MHz. As far as the ripple is concerned, I can allow a ripple of 3 dB. I need an attenuation of about 10 dB in the rejection band. I am ready to compromise on the above parameters for input and output power constraints. Also, ripple and attenuation of rejection band is of higher importance to me than width of the transition band.

Reference for measurements in dB is 20 dBm.


texts: Audio line level conversion from consumer to unbalanced (presumably) pro 1/4" jack of unknown sensitivity and impedance. 400W 1980s PA amp

texts:
I have a lovely pair of speakers that achieve their almost flat response by dampening spikes.
Consequently they eat amp power for breakfast.
I have been given a 400W RMS per channel 19" rack mount MOSFET PA amp from the 1980s.

It definitely takes pro line level input of some type as it's whisper quiet when driven from a normal consumer level line out.

The PA amp's inputs are via 1/4" mono jacks. The case contains two completely separate amps, they even have their own transformers & power supplies.

The amp was made by a small unknown UK company long before pdf datasheets.
This is all I can find. It's exactly the same apart from output power, mine is 400WPC and this one is 200WPC. And  mine is a bare 19" case.

Since definitions of pro line level have morphed over the decades and this case is complicated by not involving 'proper' balanced inputs I'm rather stumped by what to do.

Has anyone out there faced this situation before?

I'm reasonably competent with electronics so my immediate thought was to knock up an opamp circuit like this one:

From here:
https://www.emusician.com/gear/build-the-em-104-level-converter

Although I'm not bad at electronics my main focus is industrial control systems and embedded stuff. Mostly digital; the majority of analogue stuff I have to face is mostly PSUs and pre ADC grooming of unipolar DC signals.

Am I right in thinking that if I use that circuit and only use the non-inverted output + Gnd to drive the amp I'll only get half the signal amplitude?

I'm quite reluctant to just replace the opamp's gain resistor with a trimmer and Rambo it because my speakers have Decca ribbon tweeters and other nice things in them that are not known for dealing well with clipping etc.

There are too many unknowns involved so before I do anything irreversible I thought I'd ask for advice.
Thanks for any that you might have.


texts: Correct way to drive the L6203 Full Bridge driver

texts:
I need to control a brushed DC motor in both directions using the L6203. The block diagram is shown below. Motor voltage will range from 13 to 16.8V, with a maximum RMS current of around 3A.

From the datasheet it is not quite clear to me how this chip should be driven for brushed DC applications. Should I select the direction using the two input pins and then apply a PWM signal to the Enable pin? Or should I PWM one of the input pins for one direction and PWM the other for the other direction, while keeping the other pins high?

The L6203 is rated for a maximum switching frequency of 100kHz. Although I only intend on switching at about 30kHz, I am concerned that I might damage the chip or degrade performance if I don't use it as intended. Please advise.


texts: How to measure relative light intensity (and ideally duration) of a xenon flashes, cheaply

texts:
I want to compare the light intensity (and maybe also duration) of multiple xenon flash designs. It does not have to give me the readings in any real unit, as long as it is linear (or mathematicaly predictable), so I can calibrate it with a "standard candle".

The simplest method would be to stick a few sheets of paper over the flashes to reduce the intensity, and then use an LDR and a oscilloscope in a dark room. I am just worried that the response time of the LDR will be too slow for the very quick flash. I've considered photodiodes or phototransistors instead as they could possibly be faster, but I'm still not sure if they are the best option, or which one to get.

To make it more difficult, I don't want to spend more than £10 (not including any scope or power supply needed) on the circuit. I understand that I won't get great accuracy or precision for this price, but all I want to see is a trend, and I can vary the brightness difference between flashes to suit the precision of the sensor, in order to see the trend.


texts: Interpretation of pc_status bit location from Xilinx AXI Protocol Checker IP

texts: In the pc_status error bit location , is it bit #32 because in the following simulation waveform, BVALID is never asserted high during the time when pc_status error bit #32 is asserted ?


texts: What is the 3D radiation pattern of this chip antenna?

texts:
I know that the 3D radiation pattern of an antenna could be found by knowing the xy, xz and yz plane cuts and vice-versa. This process is pretty straight forward for a dipole antenna which has a 3D radiation pattern in a shape of donut. But I am not able to find the 3D radiation pattern for a chip antenna that has the following cuts.

I am not an antenna guru I just know the basics. So I would appreciate if anybody could help me with the following points.

1. Drawing the 3D radiation pattern for this chip antenna taking into consideration the antenna's physical orientation

2. Finding the point of the maximum gain (should I find this value according to the vertical plane or the horizontal one?)

3. I know that for two dipole antennas to get the maximum energy both of them should be side by side and in parallel to each other. But when using a chip antenna and a dipole one how should be the orientation?

Thank you in advance.


texts:
I am new to the fiber-optic communication systems, and in reading some relevant papers, I faced to the term "span length" (such as long-span link) which I cannot distinguish it from the length of the cable.

For example in one of the figures, it has depicted a quantity for various spaning lengths vs. the length of the cable.

Can anyone explain what is the "span length" of a fiber-optic link? I surfed the internet, but did not get any answer.


texts: H Bridge Voltage Drop w/ Motor Installed

texts:
first post after searching the net/ site for quite some time.

I have this H-Bridge circuit http://www.circuitstoday.com/h-bridge-motor-driver-circuit

I'm using 3 AA batteries to test this BEFORE using with my microcontroller.
Instead of using 2n2907's I'm using 2n3906 PNP BJT's.

Problem:

My DMM reads 4.5 volts (3AA batteries x 1.5V = 4.5V) ... exactly what I expect.
However, as soon as I plug in my DC Motor (some type of Hing Lung DC Motor), the voltage drops to 0.35V, and the motor barely spins.

I've checked the motor plugged straight into the battery pack, it works fine. Circuit appears to work fine without the motor installed...is there a way to get the full 4.5V on the output WITH the motor installed?

Thank you in advance,

-Tofer


texts: Combining the outputs of multiple SPI devices

texts:
I have a project that has an array of digital microphones whose output I would like to perform some fancy signal processing on, using a high-powered ARM micro-processor.

I like the idea of using digital microphones because I don't have to faff around with pre-amps. Anyway, each digital microphone is connected to a dedicated micro-controller that converts the PDM output to PCM.

I need to be able to get each microphone's data onto my ARM micro-processor. Let's assume at this point that everything is synchronized to give the appearance of N-channel concurrent sample and hold ADC. My current thoughts are that each microphone attached micro-controller would buffer its data to some extent and flush it over SPI when its slave select is wiggled by the master. The master would simply talk to each slave in turn.

My question is, is there a more elegant way of implementing this?

This would probably be a perfect job for a FPGA but that's a little beyond my skill level at the moment.


texts:
I am working on Intel Galileo board and using its one ADC pin (A5) and one digital GPIO pin (pin 8).

I am switching a relay from GPIO pin and using ULN2003A for isolation and LM60 temperature sensor attached to ADC.I have given power to ULN2003A IC from board only.

Now the problem is when GPIO pin is logic 0 (relay is open) ADC output at room temperature is 125 but when GPIO is logic 1 (relay is closed) ADC output increases to 127.

To debug it I have done below permutations:

-I disconnected relay from isolation IC (ULN2003A) then there is no change in the ourput of ADC (it remains constant).

-I have used electro-mechanical relay and solid state relay but having the same problem.

-I measured voltage with relay connected when GPIO is logic 0 (relay is open) is 4.95V but it drops down to 4.93 when GPIO is logic 1 (relay is closed).

-When a separate power is given to isolation IC (ULN2003A) (from another power source) it works perfectly (ADC output remains constant).

Schematic is below:

I am unable to understand why ADC output is changing with switching of relay.


texts:
I have a custom four-layer PCB (Signal, Ground, Power, Signal) with an STM32F4 (72 MHz) connected to a Si4684 receiver and a Si4711 FM transmitter through SPI.

It seems that my design has some signal integrity issues. I can communicate with the Si4711, but I can only communicate short commands with the Si4684. Communication with Si4684 fails (some bits are incorrect) when transferring the firmware image from the STM32 to the chip (large data transfer).

When I connect my logic analyzer to the Si4711 MISO pin, this turns around. No communication is possible with the Si4711, but communication with Si4684 works flawlessly. If I connect the logic analyzer to the Si4711 MISO pin and send the POWER_UP command to the Si4711, it seems like there is no reply from the chip. Probing at the Si4711 MOSI pin clearly shows that the command is being received correctly.

The behavior is the same if I run the clock at 300 kHz or 8 MHz. Unfortunately I don't have a oscilloscope available, but I guess this could be a slew-rate-issue since it's independent of the clock.

What could be the reason that I need to connect the logic analyzer to the MISO pin to get the Si4684 working, and why does this make the Si4711 stop working?

What I've tried so far:
- Series termination (50 ohm, 100 ohm) on the CLK line
- Adjusting the GPIO speed of the SPI pins on the STM32 (LOW, MEDIUM, HIGH). I believe this sets the slew rate of the pin.
- Connecting the logic analyzer to the other SPI pins.
- Double checked that I have the correct SPI mode (0,0) set

I understand that I will have to make a new design, but I would very much like some input on why this happens.

Please find layout and partial schematic below. SCK, MOSI and MISO signals are highlighted.

UPDATE: I moved the Si4711 to I²C instead, and now there are no issues.


texts: LTspice on mac, how to specify value for a dependent voltage source?

texts:
I am completely new to LTSpice. I am trying to build this circuit in LTSpice on mac. The first problem I notice is that I can't rotate the components. I googled for a while and only found solutions to rotate components on Windows, so I bent the wires to fix this.
The real problem is that, I'm having trouble to add the dependent voltage source. As shown in the image, I need to have a 3v0 voltage source. So, 1) how to I tell the software which voltage is v0? and 2) how do I set the voltage source as 3v0?
Thank you so much in advance.
This is what I have right now, v0 is the voltage across A & B.


texts: Turn 9V device off using 3.3V logic level signal

texts:
i'm facing the problem to turn a 9V (battery) powered device OFF using the output of a 3.3V based microcontroller. To do this i already threw together the following circuit (which works - assuming i drew it correctly...) EDIT: oops,  the pulldown resistor R5 should of course not be 220ohms but something bigger.

The device I have to switch off is represented by LED1 and the digital Output from the microcontroller by switch S1. The problem this circuit gives me is the high voltage drop of about 1V which would probably toggle the device to battery-low mode. Is there any alternative circuit i can use that has a very low voltage drop? And also, the design should be "fail safe", so the microcontroller could die/become unresponsive/whatever and in most cases the device will still be functioning like in my example above. Thanks


texts:
I'm working on a home project where a microcontroller records time when outdoor lights are switched on/off. Outdoor lights are 220V activated by built in PIR sensor. They're located outdoors 20-30m from the controller board. I was thinking to put a reed switch next to power lines so that when lights are switched on reed switch is shorted and microcontroller is interrupted.

I've checked other topics where people use current transformers but that seems over complicated to me as I don't need exact current value but rather just on/off state. My aim is to keep it simple and robust. Now questions:

What is minimum distance between different reed switch/power line combos?
There are some relays on the same board that control loads. Would relay coil affect reed switch? How should I protect reed from unintentional activation?
What would happen to reed switch if it's activated by AC generated magnetic field?


texts: Connecting audio line to ESP8266 / ESP32

texts: I don't know how to correctly connect audio line to ADC input of ESP32 board. The audio line is common stereo output from phone, PC or audio mixer. I didn't find any schematic or advice how to do that for 3.3V ADC range. Do you have any idea or advice where is possible to find it out?


texts: Determining error in output voltages of a flyback converter

texts:
I'm currently designing a flyback converter and I just want to know how the error tolerances are calculated for a multi output flyback converter.
I calculated the required primary number of turns:

Next I calculated the the secondary turns on the lowest output voltage:

Then I calculated the other additional windings like so:

I know its probably a simple one but can someone explain the process of calculating the output voltage error from the rounding of the turns?


texts: Possible test patterns produced by ATPG Software like Tetramax

texts:
I am developing a pattern generator in VHDL for testing ICs. The problem is I need to make it as universal as possible and need to consider a few factors such as output rate, binary or tristate etc. I found out that the pattern files are generated by an ATPG software called Tetramax, but we don't have access to the software. It would be helpful if I could find out whether there is a norm for the test vectors.

We have one vector file in .wgl at hand, but to draw any conclusion I may need to learn how these ATPG software work. At least take a look at a few other pattern vector files that these software generate.

I appreciate any comments or help.


texts: EMG, Muscle Sensor Arduino - Troubleshooting

texts:
I've been testing the EMG sensor below:

http://www.ebay.com/itm/Muscle-Sensor-EKG-EMG-Developemt-Electronics-Module-Interface-Kit-For-Arduino/351850511727?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

During my tests, I could not get any changes in the signal caused by muscle tensions. When all (3 of 3) of the electrodes where disconnected, my Arduino read 1023, the max analog value. When I had them hooked up, the Arduino read values between 30-40. One problem I encountered, was that it didn't say which of the colors (red, green and yellow) should go where. There were linked a user manual from the ebay link, but they were using different colors. Anyways, I tried all of the possible combinations, but I still got the same result; between 30-40, no remarkable changes in value.

Could it be the adjustable gain? Polarization?

If someone has any experience with EMG, or ideas about what might be the problem, please let me know.

Thanks.


texts: Help needed in understanding MOSFET datasheet

texts:
I am trying to find a logic level MOSFET for 3.3V operation.

In my case, I am trying to compare AOD510 & AO4402.

AOD510: \$\mathrm{R_{DS(on)}}\$ @ 4.5 \$\mathrm{V_{GS}}\$ = 0.004 ohm but has no rating for 2.5 \$\mathrm{V_{GS}}\$
AO4402: \$\mathrm{R_{DS(on)}}\$ @ 4.5 \$\mathrm{V_{GS}}\$ = 0.005 ohm & @ 2.5V = 0.007 ohm.

Will AOD510 have less \$\mathrm{R_{DS(on)}}\$ @ 2.5V then AO4402, since its \$\mathrm{R_{DS(on)}}\$ @ 4.5V is lower ?

I want to control a 12V, 2A load with a 3.3V microcontroller by using PWM &
a MOSFET.


texts: Calculate 3 phases VA apparent power from DC load after bridge rectifier

texts:
In a tomatoes greehouse I try to power some high bay led light with 3 phases (400V between each phase: 230VAC*SQRT(3)).
After 3 phases rectifier bridge i use the average DC line about 540V.
All the connected led light devices consume an amount of 5000W.

How can i calculate the 3 phases apparent power (VA) from those 5000W ?
I tried this but i'm not sure:
Pfactor = 3/pi, so Papp = 5000/(3/pi) = 5236 VA.
Is it right ?


texts:
This is about a very specific RF system on a chip -- NXP's SA636, "Low voltage, high-performance mixer FM/IF system...". Datasheet is here: https://www.nxp.com/docs/en/data-sheet/SA636.pdf. The datasheets and application notes differ in what looks like a critical way to me, and I'm wondering what route to take before I spend cash on PCBs.

I'm trying to build a radio for 162MHz, a frequency that should be well within limits for this IC. I'm injecting my local oscillator (LO) signal, but where, exactly, I do that isn't clear. The chip has four relevant pins, two for the RF input and two for the LO; the RF and LO signals are internally mixed via a Gilbert cell. On the LO side, the two pins look like this, with one pin connected to the base of an internal transistor and the other to its emitter:

The datasheet itself has the LO injected on the OSC_IN (base) pin:

But in the application notes, the LO is injected on the emitter side of that transistor:  (note that the application notes are using the SSOP package, with different pin numbers compared to the HVQFN package. Pin 3 & 4 in SSOP == pin 1 & 2 in HVQFN, respectively)

So, I'm wondering where to connect my 151.3MHz LO -- should I connect to the base or to the emitter? My guess is the emitter, but that's going by feel and I'd like to think things through rather than just go with my gut.

Datasheet: https://www.nxp.com/docs/en/data-sheet/SA636.pdf
AN1996: https://www.nxp.com/docs/en/application-note/AN1996.pdf


texts: Why did my FM transmitter mysteriously die?

texts:
I made a little FM transmitter project a few months ago. I used an Arduino, a litle 4-digit serial LED display, a couple of buttons and an FM transmitter component with breakout board

I had this put together on a breadboard and was lazy so I never turned it into anything more permanent.

I used it in my car as a FM transmitter so I could listen to my phone's music through my car's FM radio.

Anyway, after about 6 months of it being operational, it mysteriously died. Everything seems to work, but no broadcasting. It occured out of the blue one day. I was driving and listening to music and it suddenly stopped broadcasting. When I got to my destination, I checked it and nothing appeared wrong. All the wiring was still in place and such.

The schematic was fairly simple. I used it's i2c mode of communication and had filter capacitors at the power lines. The whole circuit was powered by a 12V car USB adapter. A USB cable was hooked from that to the Arduino which I used for the 3.3v source. I also had some resistors on the i2c lines hooked to 3.3V (pull up resistors?). Also, it was just enclosed in a cardboard box, and the antennae was a simple piece of wire.

Honestly, I'm not for sure if the FM transmitter component died, but I don't really have any way to test if it's working without it broadcasting. There is no way to get the module to "return" data over i2c as far as I can see.

Anyway, what could have killed my FM transmitter and what should I do to keep it from happening when I order a new one? I'm thinking it could have been ESD, but I would've thought that'd happen when inserting or removing my phone from the 3.5mm jack.

Update

Well, before I went to order the part, I decided I'd try to get the FM transmitter working one last time. Amazingly, I plugged it in and it worked. I used it for about 15 minutes and it was working flawlessly. Then, I unplugged it and such. After about 6 hours or so, I went to try to get it to work again. This time, once again, the module appeared to just be dead. Everything worked, but no broadcast. I don't believe there was any kind of environment difference between the two times I tested it. Now I'm completely baffled.

Update 2

Ok, the module is definitely still in working condition. I tried changing the filter capacitors and that made it work a bit more often. Anyway, basically, it seems like sometimes the module just will not receive the i2c initialization code. If I continuously reset my Arduino to make it resend it, I will eventually get it to work(I mean sometimes I have to try 8 times).

This sounds like a noise issue. I'm not for sure what else I can do to fix it though. I'm pretty sure you can't put filter capacitors over i2c lines, and there are already filter capacitors on the power and ground lines.


texts: Using one RF transmitter to send an On/Off signal to multiple receivers

texts:
I want to create a system where I can send an On/Off signal to multiple receivers, to say, tell them to turn on an LED. Would I need to have a transmitter/receiver pair for each LED, or can I just send one signal and have all the receivers pick it up?

I don't have much experience with electronics, nor have I ordered anything. Any help would be greatly appreciated.


texts: How is the boolean expression for mux2 and mux4 deduced?

texts:
I've been looking at the following article: https://www.electronics-tutorials.ws/combination/comb_2.html

I am confused as to how the boolean expression Q = a'b'A + ab'B + a'bC + abD is deduced for mux4, and what it would be for mux2. How is it done with kmaps?


texts: 0.9v boost with Tp4056 for 6v Solar Panal?

texts:
Can I use it like this...

If so how can I limit my solar panel to only output 5v cause my booster can only handle up to 5v input.


texts:
I have been learning a bit about electronics. In particular I have been playing with the shift register 74HC595. Here I understand how bits are moved into the register serially, that is one bit at the time. The output can then be read on the output pins (parallel).

My question is: Are there parallel to serial types of shift registers? I guess it wouldn't be called a shift register, but it would be something that takes, say, 8 bit in (in parallel) and then outputs the 8 bits in series.


texts: In the image below, I do understand that a grounded inductor can be simulated using op amps. However, to make a floating simulated inductor, I have read some posts that said two ground simulated inductors must be connected back to back. I am not sure why they should be connected back to back, as shown in the bottom diagram. Why must they be connected back to back?


texts: USB-C Strange voltage bias detected on shield and unconnected pins interfering with signal

texts:
I'm having trouble figuring out why there is a 1.8 V bias on the shield and the unconnected pins of my USB-C connector.

Some background... I am attempting to use USB-C connectors to connect two ICs together across two boards and also pipe the USB data from a PC to the second IC. So the configuration looks like this:

So the regular USB lines (GND,+,-,VUSB) are adapted, so to speak, through the USB-C connectors. I've tried to use the extra pins on the USB-C connectors for the data, clock and reset lines required to connect the two ICs across the two boards.

It seemed like a good idea since I need a user friendly way to connect the two boards and USB-C provides plenty of unused pins that I could repurpose. So far nothing is working as it should. I see a mysterious 1.8V bias on all the unconnected pins of the connector as well as the shield which seems to also be interfering with my signal. It shows up on the data line, but not the clock which is odd. Here is a capture showing the bias:

Is there something fundamentally wrong with using the USB-C connectors in this way? I want to provide a common connector so that the second board can be charged conveniently as it is a battery powered device. The first board is a programmer for the device and it requires 3 pins to do its job. This seemed like an ideal solution until I found out what a challenge USB-C can be.

I would really appreciate any guidance from folks who have experience working with USB-C and who can tell me what I am doing wrong. Is there any way to make this work? Thanks so much!


texts:
Due to some problems in my project, I am curious about the inner resistance of TRIAC when it turns on. I have run some tests. The setup is just like the schematic picture.

Rs is the source resistance with about 160 ohm. Rg is about 50 ohm. The trigger voltage Vtr is about 2.5V. Then with different input voltage Vs, the inner resistance Rt (resistance between MT1 and MT2) of triac when turning on seems to be varied.

Vs = 20Vpp 1kHz Sine wave, then Rt = 13.8 ohm

Vs = 5Vpp 1kHz Sine wave, then Rt = 26.5 ohm

Vs = 0.5Vpp 1kHz Sine wave, then Rt = 56.2 ohm

Vs = 4V DC, then Rt = 31.1 ohm

My question is that are these values of Rt quite normal? I mean is it the normal case that the inner resistance of TRIAC is about tens ohm and it would decrease with the increasing of Vs. Thank you very much.

(The TRIAC I used is Z0107MN)

simulate this circuit – Schematic created using CircuitLab


texts: Is it safe to touch 1000 Volts DC at 1 mA of constant current? 0.1 mA? 0.01 mA?

texts:
I would like to study the phenomenon where thousands of volts are safe to touch. Generators like Tesla coil and static electricity generators generate discontinuous sparks, which is why they are safe to touch. If I were to build a Class-E Tesla coil capable of generating 1000 Volts at 0.01 mA of constant current, will it be safe to touch? will I see an arc at all?

My understanding is that in practice, it is not just current or just volts which are the deciding factor in whether or not it is safe to touch, but instead it is both of them combined: Watts. I expect 1 Watt to be safe to touch no matter if it is 1 Volt at 1 Amp, or 1000 Volts at 0.001 Amps, or 0.001 Volts at 1000 Amps.

If my understanding is wrong, please correct me.

Also, how would I then go about generating 1000 Volts DC at 0.01 mA of constant current or anything close for this study?


texts:
If i have a Buck Regulator switching at 200KHz and i want to sample the Voltage and current using OpAmp in tha path connected to ADC(12 bit).

What would be the sampling frequency to measure the signal by ADC?
what shall be the Bandwidth of the OpAmp for Voltage and for current sense?

If somebody could provide some rule of thumb i could work further

P.S. : In my understanding sampling freq be >2 the switching freq.
      voltage sense  would require lower BW OpAmp as it is slow, i also get confused either to choose the Opamp based on cross over freq or switching freq.


texts:
I am trying to implement a circuit where 2 SPI drives (basically two masters) speak to 1 slave. Both operate on a 3 wire SPI.

Keeping that in mind I was going to have the CLK and MOSI of both as inputs (4 inputs), and would need 2 as output. A 4:2 multiplexer.

Was going to use CS, or some other signal to act the select signal to decide between which spi goes through.

Can't seem to find anything of the sort anywhere. Is there a different type of switch I should use?

I could add two 2:1 mux's together, but I'd much rather have 1 IC - space and cost is a premium for me.

Any thoughts?

edit: To make thing's clearer, the reason i would like to add a way of isolating the two masters is because one MCU turns on before the other by a couple of seconds. I am not entirely sure the default state for the MCU that turns on later. I would like to avoid the possibility where the second MCU tries to communicate whilst the first MCU is speaking to the slave device as they will both be share the same MOSI line.


texts: Long shunt DC motor speed control characteristics?

texts:
So from what I can see based on stuff published online:

Series wound motors:

Are not good for variable speed applications
Can achieve very high starting torque
Speed is almost entirely dependent on load

Shunt motors:

Are great for variable speed applications
Have lower starting torque
Can maintain speeds, to some degree, under varying loads

For a short shunt motor, the series field comes first, then the armature and shunt field come after it. For a long shunt motor, the shunt field is in parallel to the series field and armature.

My question is: How do long-shunt compound wound motors compare to (straight) shunt motors in terms of speed control characteristics? Assuming that the shunt field is larger than the series field, can a long shunt motor work well in a variable speed/torque application?


texts:
A question on stack exchange exists regarding the following circuit:

Brief:
The original question concerns finding component values to amplify a signal ~10 times.  I would like to know how the man who answerred (Olin Lathrop) arrived at certain values.

Question One: How is the output impedance derived?

  With R1 and R2 10 kΩ, the output impedance of the divider is 5 kΩ.

Question Two:
Formula for C2?

  R1 and R2 only need to be equal to make 1/2 the supply voltage. You mention no special requirement, like battery operation where minimizing current is of high importance. Given that, I'd make R1 and R2 10 kΩ each, although there is large leeway here. If this were battery operated, I'd probably make them 100 kΩ each and not feel bad about it. With R1 and R2 10 kΩ, the output impedance of the divider is 5 kΩ. You don't really want any relevant signal on the output of that divider, so let's start by seeing what capacitance is needed to filter down to 20 Hz. That is 40 µF, which is rather large. OK, lets make R1 and R2 higher, like 100 kΩ each. Now C2 only needs to be 4 µF to filter down to 20 Hz. I'd make it 10 µF because that will be readily available, and extra filtering here does little harm.

The following does not agree with the 40 microfarad outcome
$$\frac{1}{2\pi \cdot R \cdot f}=\frac{1}{2\pi \cdot 5\times 10^3 \cdot 20}$$

Question Three: What can be done to reduce the stabilisation time?

  Note one issue with this topology. Frequency-wise, C3 is acting with R5, but the DC level that C3 will eventually stabilize at is filtered by R4+R5 and C3. That is a filter at 1.4 Hz, which means this circuit will take a few seconds to stabilize after power is applied.

Thanks in advance

Daniel


texts:
I've made level shifting circuit to shift pulsed ~10 kHz 5 V signal to 15 V by using gate driver and level shifter IC: TC4427 and CD4504.

There is a condition that the circuit output should be 0 when "enable" bit is zero. I have done that by placing an optocoupler to disconnect main 15 V supply from the ICs, but only after assembling and testing I have found out that ICs have these ESD protection diodes from input to VCC which leads to condition that input has to be always < VCC + 0.3 V.

Now when enable is 0, the +15V VCC floats. Now when I connect input i get some voltage at the VCC rail and outputs of IC:s because the voltage is "leaking" through the esd protection diodes.

Is there any workaround that could be done with minimal changes to the design so that the output will be as close to zero as possible (while there is still pulsed 5V input)?

Of course by still keeping the lifetime expectancy of ICs as high as possible. Condition where enable is 0 while there is some input voltage is quite rare and not normal operating condition.


texts:
I'm currently studying logic circuits for my exams and came across a question "7. An electrical circuit is set up with four switches. A lamp will light only if the following happens:

Switches A and B are both on.
Either Switch C or Switch D is on, but not both.

Draw a logic circuit to represent this. I made a AND gate for A and B, made an XOR gate for C and D but don't know how to close the circuit into one output as I now have two outputs. I hope you guys understand my situation and help with it, Thank you. If this is the wrong site please lead me to the correct site, please.


texts: If flash drives have an address mapping lookup table for wear leveling, how does the memory for the lookup table not wear out?

texts:
First of all, sorry if this is in the wrong SE. Not sure where else this should go.

To my understanding, flash drives accomplish wear leveling by having a microcontroller remap sections of memory on the fly. These new locations need to be remembered, so it must use some sort of extra memory for a lookup table. My question is, how does this extra memory not fail in exactly the way the microcontroller is trying to prevent?

Or am I completely misunderstanding how flash drives work?


texts:
I grew up as a boy doing soldering kits in the 80s. I wanted to do the same for my daughter so bought a soldering iron online.

It came with a box of orange resin with Chinese writing on it. I'd never seen something like this to do with soldering. Running it through Google translate comes with something like 'solder additive'.

When I google search online for 'solder additive' I get vague descriptions of better joints, or coping better with dusty joints. I don't understand how that would be solved by resin.

My question is: What does solder additive do?

EDIT: Thanks for all those that contributed to this question and the EE SE community. I asked my Dad what we had done for resin when I was growing up. He responded, "We used resin-core solder, that's why you never saw the resin."


texts:
Can anyone help me understand whats wrong in my logic for writing a push button that toggles a LED in this way? I know the XOR way, I just want to figure out why it doesn't work when written in this form.

Here is the code:

#include <avr/io.h>

#define LED 5
#define BUTTON 0

int main(void)
{
    DDRD |= (1<<LED);
    DDRD &= ~(1<<BUTTON);

    unsigned char flag = 0;

    while(1)
    {
        if(PIND & (1<<BUTTON) && flag == 0)
        {
            PORTD |= (1<<LED);
            flag = 1;
        }

        if(PIND & (1<<BUTTON) && flag == 1)
        {
            PORTD &= ~(1<<LED);
            flag = 0;
        }
    }
}

Edit: Now the code works just fine after adding the delay but could you explain why i need it (delay) when toggling led with this way but not when toggling using the XOR method?
Here is the code for the xor method :

#define F_CPU 8000000Ul
#include <avr/io.h>
#define led 5
#define pb 0

int main(void)
{
    DDRD|= 1<<led;
    PORTD &= ~(1<<led);
    unsigned char press=0;

    while(1)
    {
        //TODO:: Please write your application code
        if(PIND&(1<<pb))
        {
            if (press == 0 )
            {
                PORTD ^= (1<<led);        //toggling the led
                press =1;
            }
        }

        else
        {
            press = 0;
        }
    }
}


texts: Most efficient way to generate 3-4 volts from less than 0.5 to 1.5 volts

texts:
I am looking for a way to convert power from a 1 farad supercapacitor charged by a solar cell into enough voltage to power an LED. The supercapacitor will contain up to 2 volts from the solar cell. I have tried using a modified joule thief (schematic below) to do this. It is capable of running the LED for 10 hours on a 1F supercapacitor charged to 1.3 volts. The only issue with this setup other than inefficiency is that it stops working when the input drops below 0.55 volts.

Is there a more efficient way to do this and would it be possible to make it work with lower voltages? It should be able to be made with off-the-shelf discrete components and/or basic ICs (op amps and comparators).

simulate this circuit – Schematic created using CircuitLab


texts: So essentially looking for the most efficient and effective way to take a 3V 50hz AC signal and convert it to an 11-33V DC signal (any voltage between 11 and 33 works for an input to embedded pc) . I have looked into a couple different options such has bridge rectifier with a cap for small ripple then into amplifier or an open loop comparator with the rails set in the 11-33V range (positive and negative) then just do square wave rectification (no cap so no ripple) or even setting the high and low voltages of the comparator to say 15v low and 25v high which both register as high for the embedded pc digital input. (Not sure if this one will work, haven’t messed around with opamp comparators and not sure if the ‘low’ voltage can still be a positive DC value)


texts: Get clean 9VDC power from 9VAC using a LM317T

texts:
I'm having trouble with this design, I have this circuit below, but I already have the 9vAC transformer, so I just need to convert the current to DC, so:

If I remove the Vadj part of the LM317T on the circuit below and keep everything else at it is, would that still keep the current clean or I would be removing something important?

note: I'm not experienced in electronics at all, sorry about it :(

Thanks for your answers :


texts:
I'm having difficulty fully understanding how exactly a zero is created in a circuit. I would like some way of visually recognizing (without computing a transfer function) that a zero will be present, the same way I can see a pole when there is a resistance and capacitance to AC ground associated with a node.

Q1 (a): What exactly is a feedthrough path?
Q1 (b): Why isn't coupling through the gate-drain capacitance considered a feedback path, why is it a feedthrough path? It's connecting input to output, but it is also connecting output to input.
Q1 (c): Would a zero still be created if the gate-drain capacitor was replaced with a simple resistor?
Q2: How can the zero be computed by noting the transfer function must drop to zero for that particular zero frequency? If you look at Fig 6.17 (right bode plot), at the zero frequency the transfer function does not drop to zero, so how does this computation make sense?
These are not homework questions, these are just all the doubts in my head when I read this. I just made this into question format to make it clear what my doubts are.
Thanks very much!


texts: Instrumentation amplifier - schematic review

texts:
I'm trying to make an instrumentation amplifier to measure a sine wave signal of 0 - 1Vpp (max) 50Hz that comes from a non-invasive current sensor (30A SCT-013-030). It gives 1Vpp at 30A current.

This is the circuit I made. The output goes to an MCU.

According to this note, my circuit with the selected values should have GAIN = 3.

I would like to know if this circuit is okay for that kind of application.

Also, I found on the internet that in AC-coupled signals require a common-mode voltage applied to both inputs of the circuit. And that voltage should be the less of the maximum value of the signal which in my case would be 0.5V

Do I need that voltage in my case?
What does it do exactly?

Link to the schematics


texts:
I need to convert a simple program (C or Java) to HDL (especially Verilog). However, I have no idea about this conversion.

Another problem is that the resulting code must be gate level. Now, This idea does not seem possible for me. I have not much expeience so I need some help.

I searched for these problems but I could not find anything helpful. Is there any tutorial about these topic?

Thanks in advance.


texts:
I understand what it means for an LED to be a DIP LED, but what is a 4-DIP LED?

For example, here is a 4DIP cool white LED. Does it just have two leads for the cathode and two for the anode, or do these leads do something else?


texts:
Most circuits that I have designed in the past deal with low voltages...sensors, communicating with other chips, etc. When would I need to consider the addition of fuses into my designs? Sometimes I need to control higher voltage devices like motors that require 24V for example.
Fuses protect against shorts and large spikes in current. When should these be introduced?


texts: Similarity between Atmega162 and Arduino

texts: I am going to be taking an embedded systems course where we will be using the Atmega162 and I want to get started learning the stuff before the course begins.Now my question is, considering that there are many good resources for the Arduino and relatively scarce resources for the Atmega162, and that the Arduino is a lot less intimidating than the Atmega162, would it be beneficially if I just learned the Arduino and then used some of that knowledge on the 162?, or do the two microcontrollers have significant differences that would make using this strategy inefficient? Plus I already have access to an Arduino Uno but I probably won't get access to an actual Atmega162 until I start the course.


texts: PI controller to drive a constant power source

texts:
So I have a load that needs constant power to maintain a specific temperature and this load changes over time. For this, I am using the design outlined in the following article:

https://www.maximintegrated.com/en/app-notes/index.mvp/id/4470

Now to design the error amplifier shown in the article I want to use a difference amplifier with a closed loop gain of 5 V/V along with a 100uF shunt capacitor at the output of the amplifier to create (at least what I think is) a PI controller.

Now my question is, is the capacitor necessary and does adding it actually create the behaviour of a PI controller? I added it because I wanted to prevent crazy oscillation when I turn on the system. I would also like to avoid feeding too much power to the load as well since it could damage the system. However, I am not too sure if adding that helps at all.


texts: Troubleshooting Strange Circuit Behaviour...Missing Diode?

texts:
I've built this circuit to control a submersible pump with a PIR sensor.

The circuit works as expected (the PIR sensor activates the mosfet, turning the pump on) but only after about 30 seconds from when power is initially turned on. Before that the circuit behaves almost randomly - as soon as the power is turned on the pump immediately runs for 10 or so seconds then turns on and off a few times randomly, not in correspondence to what the sensor would be outputting.

My only slightly educated feeling is that this has something to do with transients or the lack of diodes in the circuit so any insight into how to improve this would be appreciated.

Link to PIR sensor here

Edit: I've added a flyback diode in parallel with the pump and whilst this was obviously required, it didn't change the strange start up behaviour.


texts: How To Repair Ripped Off Solder Pad On PCB

texts:
I was trying to flash OpenWrt onto my BT HH5 wireless router and it involves soldering wires to very tiny balls of solder, which in the guides I've been following are referred to as pads. I've tried putting a small amount of solder in the little caveat hole but it doesn't stay in place. I known this would have been produced in a factory by a machine but is there any way I can repair the broken pad?

UPDATE

I've put a 1p coin in the corner for a scale comparison to show how small the pads really are. The blue circles represent the pad I have been referring to.

As there is a hole wear the pad was, is there nothing I can use to refill the hole? I knows this sounds stupid but is there a conductive glue that the solder can stick to?

I've been using a battery powered soldering iron, but should I be using a temperature controlled iron with a low temperature and maybe using a smaller head on the iron?

N.B I only usually solder leads for audio equipment so moving down to micro PCB components isn't too much for my hand in terms of keeping it steady, but the fact that I think I need to invest a decent soldering station possibly?


texts: Common-Drain Amplifer vs OP-Amp for unity gain (voltage Follower)

texts:
What is the difference between using a nFET vs OP-Amp as a unity gain amplifier, i.e. voltage follower.

Application: Provide constant voltage with a variable load, see example below:

Min Current 0.1mA, Max Current 600mA


texts: Relay turn off delay with ability to cancel

texts:
I want make it so when the switch is turned off, the relay would be still on for about 15 to 30 seconds, and if it is switched on again in that time period it would just continue running. I am wondering if it would be enough to just put a capacitor connecting relay's coil, but I don't think I would achieve the desired time period and I don't really know how to calculate that time period. Maybe someone knows a better way to achieve this functionality or guide me in the right direction..

simulate this circuit – Schematic created using CircuitLab


texts: What are the details about link files and startup code one needs to know to write an Operating System for a uC?

texts:
I know some people will say I don't need to write an OS because there are lots of options out there. But I'm not interested in using an OS to solve an specific problem. I want to write one by myself to learn how to do it.

I know a lot of things about the theory of Operating Systems and I also know how to program microcontrollers in bare metal. But I know very little about the configuration details that are not directly related to programming. I'm talking about link command files, startup code, etc.

My question is: what do I need to know about these "configuration" related things in order to put the OS running? Please link some external content about those things, if possible.


texts: What is the maximum power for an 8-pin PC PSU cable?

texts: I have a non-modular 600W PC PSU which has one 8-wire (3 yellow, 5 black) cable split and connected to two 6+2 connectors (see the image below). I've read that according to the ATX standard, an 8 pin is restricted to 150W. So what maximum power can the two 6+2 connectors transfer together within the standard? 150W or 300W?


texts: Need specifications to operate this stepper motor with RPi or Arduino

texts:
Here is the disassembled stepper motor that I'm working with:

I need to identify this stepper motor that was retrieved from scrap for a project. Budget constraints force us to use the scrap motor. I tried to drive this using a L298 H Bridge, but I couldn't find the right bit sequences to get this running smoothly. I also tried to search for a specifications sheet in the internet with the label, unsuccessfully.

I'm using either an RPi or Arduino board to run this.

I just need a pin diagram and the specifications of the motor, if you guys have seen this type before.


texts:
I should start off by saying that I'm really new to this electronics engineering thing and I really have no idea what I'm doing.

I am working on building a display stand that turns some LEDs on/off over wifi/alexa. To do this, I am using a NodeMCU since it has an onboard ESP2866.

I am having an issue getting the GPIO pin on the NodeMCU to trip the relay. It's a 3v relay, so it should work. I tested this with an Arduino Nano and everything is working as expected. The only difference is that the NodeMCU outputs 3.3v@12mA on it's GPIO pins and the the Arduino Nano outputs 5v@40mA. I'm guessing my issue is that there is not enough current.

In order to boost the current, I "think" I need to use a transistor. I happen to have a BC547 handy and from what I understand it will boost the current. I'm just not sure how to wire it. Would one of you be willing to e-hold my hand and help me wire this correctly? or tell me this wont work if I'm going about it the wrong way? Here's how I currently have it wired.

simulate this circuit – Schematic created using CircuitLab

The relay datasheet - I have the 3VDC version from Amazon


texts:
It's a simple question. What's the turn-off time of this "diode" and does it have a recovery time when turning off?
Since the transistor does not get into saturation I think it should be the same as turning it off normally, so pretty fast. The transistor is D44H8.


texts: Is there a rule to calculate the correct voltage for a light bulb?

texts:
Say I have an unknown led light, independently several person know it could be 12v or 24v or 110v even 220v

Say It's rated for 9v (and you dont know), let's say you start applying  fewer volts until it start turning on and stronger, but how can you know the PROPER and CORRECT voltage?

Does it apply for a small motor? Rated say at 6v but you think it's rated at 12v or 9v.

What's the rule resistance? watts? amps?

Thanks in advance


texts: Micro controller clock speed requirement for delay measurement

texts:
I am trying to measure the absolute time between two 1Hz clocks (GPS PPS events) to within 50 nanoseconds. I do not necessarily care which clock occurs first, I am only looking for the delta T between each pulse.  The pulse width is on the order of 100s of milliseconds so it is not a constraint for me here.

My plan is to use a microcontroller to read in these two 1Hz clocks as 2 different interrupt events. The rising edge of the leading PPS signal will trigger a counter which will count cycles until the arrival of the second PPS signal. I assume this clock/crystal for the counter will need to be 20MHz or greater due to the 50nS resolution I need.

My questions is, how do I go about determining how fast of a dedicated micro-controller  I need to perform such a task?

I highly doubt an MCU with a core speed of 20Mhz will suffice, since the code to answer interrupts and hold a count will consist of more than one instruction. I understand that if I want to do anything else with this microcontroller such as send this time delay via UART will consume more clock cycles as well. For simplicity, let's assume the controller is just being used to count rising edges from a 20MHz clock between two interrupt events.

I am  looking for a guideline as to how I can calculate/ballpark the bare minimum MCU core speed needed to handle a 20Mhz internal/external timer for the measurement portion of this project? I am asking to get a better idea of how to source appropriate hardware instead of simply throwing a >200MHz ARM at the problem and hope I overshoot my requirements.
Thank you.


texts: What is the name of this wire-piercing probe?

texts: I'm looking to get can bus data without cutting the wires. I would like to know the name of the probe pictured below and where to find it.


texts:
I need to go through the 4 cases where v1 and v2 are either 0V or 5V, and then use that to show the voltage value of the output, Vo is either low or high.

However, I think I'm hitting a contradiction here. So when V1 is 0V and V2 is 5v, my assumption is that D1 would be off (iD1 = 0A and VD1 < VD0), and that D2 would be on (VD2 = VD0 and iD2 >= 0A). This is a silicon diode so VD0 = 0.7V.

But given that Vo = V1 + VD1 = V2 + VD2, this would lead to the conclusion that Vo = V2 + VD2 = 5.7V. And that Vo = 5.7V = 0 + VD1, so VD1 > VD0!!!

And if I go in the opposite direction, setting D1 to be on and D2 to be off (for the sake of argument), then Vo = V1 + VD1 = 0.7V, which is much closer to 0V than to 5V. The main issue, of course, is that it doesn't makes sense for D2 to be off when it is receiving a 5V input and should be forward biased.

Please let me know what I'm doing wrong here.


texts:
I am designing an audio amplifier and I realized that the footprints that came with KiCad are wrong. I connected the transistor Q9 like this:

But in the CvPCB, the transistor appeared like this:

As you can see, the colector is connected to VCC in the PCB, but it was the emitter which was connected to VCC in the schematic.

I'm afraid that this has happened with other footprints, as well. How can I fix this?


texts:
This is a BLDC motor with the magnets on the shaft and the windings near the casing. The casing doesn't get hot only the shaft. Also my ESC shuts the motor down after a few seconds, if I throttle down then throttle up again it will run for a few more seconds. The ESC does not get hot at all but the motor shaft is getting very hot. I will list the components, I'm using a 6s 8p battery, the voltage is 24.4, at full throttle it drops to 23.9. Everything is connected well with 8 gauge wire what could be the problem?
Motor-
SSS 56104/500KV Brushless Motor 6 Poles W/O Water Cooling For RC Boats
Specification:
56104 6 Poles Inner Runner Brushless Motors
Model No.   Tum KV  Max Amps(A) Max Voltage(V)  Max Power(W)    Idle Current(A) Max RPM Shaft(mm)   Motor Dimension(mm) Weight(g)
56104/500kv 8Y  500 116 88  11000   1.4 45K 8   56*104  980
Length of extend shaft:25mm
ESC-
300A BOAT ESC 12S R-SNAKE
300A  Electronic Watercooled Speed Controller
Suitable for catamaran with a motor size of 1.4 meters or more
High continuous amp: 300A
Programmable via USB Link and Programming-Box (available at our Ebay store)
Included 8mm Bullet Connectors
Includes USB LINK* to set it by PC (only windows)
Flier warranty
*Program and manual available at fliermodel website
SPECS
300A BOAT ESC Flier mod. R-Snake
Voltage (LiPo): 3-12S
Voltage: 12V to 50V
Anti-spark cable: yes
Wires: 8AWG
Connectors: 8mm Bullet
BEC: No
Size (mm): 2405735
Weight: 387g
Battery- 6s 8p
?


texts:
I need some help using a mosfets as a switchs. I have both 2N7000 and STD5NE10L N-Ch mosfets. I want to use an Arduino logic signal (5V) to turn on and off a 3.3V regulator. The regulator takes its power in from a 2 cell lipo battery (7.4-8.4V). I tried circuits with both mosfets but the voltage from the mosfets was always below the drop out voltage of the regulator so I never got my 3.3V I usually only got about 2.9V.

I dont think that the mosfet is fully on, how could i fix this?

http://pdf.datasheetcatalog.com/datasheet/SGSThomsonMicroelectronics/mXyzsyxr.pdf
http://www.fairchildsemi.com/ds/2N/2N7000.pdf


texts: Determining Buck Converter's source voltage average value from current waveform

texts:
Dear all,

Given that the above is the instantaneous source current drawn by a buck converter, may I know how I should go about determining the corresponding average value of the source voltage?

Edit:
Here's what I have attempted or understand could lead to a solution.
1) The gradient of the positive slope in the current waveform equals to the source voltage over inductance value. However, the inductance value is not given.
2) I could calculate the duty cycle of the converter using the on and off period. And possibly find source voltage if I have the output voltage but the output voltage is not given either.


texts: How do two UARTS know which baud rate to use?

texts:
I am reading about the standard protocol for UART and I think that if the receiving UART does not have any idea on what baud rate the data was transmitted, there would be lots of problems. If the assumed baud rate is lower than the baud rate in which the data is transmitted, there will be bits that would not be 'seen' by the receiving UART. On the other hand if the baud rate used by the receiver is higher than than the baud rate in which the data is transmitted, there will be bits that will be counted twice and would result the data being 'read' incorrectly.

My knowledge around UART is that when the line is idle, it is kept to a '1', the Start bit is a '0' and the Stop bit is a '1'. Also, the Stop bit being '1' does not have any difference with the '1' when the line is idle or is there a way to differentiate?

Do two communicating UART's first agree on which baud rate they will use? If yes, how do they do it?


texts: PWM Solar Battery Charger for 192V battery

texts:
I bought a solar controller for my 192V solar system that did not work as advertised (instead of MPPT, works with ON-OFF cycles - Chinese ripoff - but that is offtopic).I want to redesign the control and power stage to make it a real PWM controller. I came up with the following schematic:

The PV array has a maximum voltage of 340V and maximum point at 270V. The actual controller connects the PV directly to the battery until the voltage reaches 232V. Then it cuts the connection until the voltage drops to 216V when it connects the PV back. Cycle repeats. That is not fully charging the battery.
By using a variable duty cycle (generated with an Arduino), I want to reproduce the 3 stage battery charging method.

Now be gentle with me, this is my first project and all the help is apreciated.
Let's jump over the "WARNING: High Voltage message". Is taken into account :)

The snubber from the IGBT is made after the ones my controller has. The only difference is the controller has no gate resistors/diodes, no resistors between gate and source and has a big 1uF/450V capacitor between the PV+ and B+.

Regarding IR2110, I know using it as High Side driver requires a bootstrap circuit. Since in the first stage, the IGBTs will be continuously closed (100% Duty Cycle), I want to use an isolated dual power supply (B1 - powered from the 192V battery) to power the Arduino (5V) and IR2110 (5V/12V).

The frequency I tested the circuit with is around 100Khz. It works good until I apply a big load (I applied 24V on the PV side and 2 halogen car light bulbs in series on the output, with a variable duty so the output is around 13V), moment when, randomly, the Arduino controller either resets or locks. I am stumped ! I have no idea why this happens. If the load is smaller (like trying to charge a 12V battery), the circuit works without any issues.

Seems the resets/locks of the uC happened because of high ground bounce. I was getting between PV- and B- a potential of over 1000V (going over the scale on my digital voltmeter). I added C2 and things calmed down.

I have a strange reading on my oscilloscope, between point A and B, that I have no idea what it means. Is this reading OK ? Happens when Duty Cycle is under 20-30%. Frequency 100Khz.

Thank you !