texts:
I am trying to create an H bridge circuit from scratch to control a 2 wire DC permanent magnet motor. I have done research online, but I haven't had any formal schooling in electronics, so please be patient and kindly bring any noticeable problems with the circuit to my attention. Is there anything that would make this circuit better? Are the diodes set up properly to protect this circuit from motor voltage spikes?

J2 and J3 are screw terminals where I would connect V+, GND, and the two motor wires. J2 is GND and V+ and J3 is motor output. Input A and B would ideally be controlled by a +5v logic level coming from a microcontroller output.

UPDATE:
Thanks everyone for the constructive comments they are really helping.

Can I fix the shoot through problem by making one a depletion and one an enhancement type FET?
Also,

  gate capacitances and 10 k pull-up resistor will cause the collectro
  voltage to take potentially micro seconds to rise back to the positive
  rail

can I fix this by using a smaller resistor such as 2k ohm and a diode such as this?


texts: Trying to comunicate my nucleo-F411 with a NOKIA5110 display using SPI and DMA

texts:
I did successfully sent data to the display in my main function.
Working code.
uint8_t data[6] = {0x21, 0xB8, 0x04, 0x14, 0x20, 0x0C};
int main(void)
{
  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* Configure the system clock */
  SystemClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_DMA_Init();
  MX_SPI2_Init();
  /* USER CODE BEGIN 2 */
  HAL_GPIO_WritePin(RST_GPIO_Port, RST_Pin, GPIO_PIN_RESET);
  HAL_GPIO_WritePin(RST_GPIO_Port, RST_Pin, GPIO_PIN_SET);
  HAL_GPIO_WritePin(DC_GPIO_Port, DC_Pin, GPIO_PIN_RESET);
  HAL_GPIO_WritePin(CE_GPIO_Port, CE_Pin, GPIO_PIN_RESET);
  HAL_SPI_Transmit_DMA(&hspi2, data, sizeof(data));

  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */
}

But when I try to put the initialization code of the display in a diferent file, it won't display anything.The file that contains my initiation function function.
#include "5110.h"

struct LCD_PINS lcd_pins;

void set_RST(GPIO_TypeDef *Port, uint16_t Pin){
    lcd_pins.RSTPort = Port;
    lcd_pins.RSTPin = Pin;
}

void set_CE(GPIO_TypeDef *Port, uint16_t Pin){
    lcd_pins.CEPort = Port;
    lcd_pins.CEPin = Pin;
}

void set_DC(GPIO_TypeDef *Port, uint16_t Pin){
    lcd_pins.DCPort = Port;
    lcd_pins.DCPin = Pin;
}

void set_SPI(SPI_HandleTypeDef *Handle){
    lcd_pins.hspi = Handle;
}

void LCD_init(){
    uint8_t data[6] = {0x21, 0xB8, 0x04, 0x14, 0x20, 0x0C};

    HAL_GPIO_WritePin(lcd_pins.RSTPort, lcd_pins.RSTPin, GPIO_PIN_RESET);
    HAL_GPIO_WritePin(lcd_pins.RSTPort, lcd_pins.RSTPin, GPIO_PIN_SET);
    HAL_GPIO_WritePin(lcd_pins.DCPort, lcd_pins.DCPin, GPIO_PIN_RESET);
    HAL_GPIO_WritePin(lcd_pins.CEPort, lcd_pins.CEPin, GPIO_PIN_RESET);
    HAL_SPI_Transmit_DMA(lcd_pins.hspi, data, sizeof(data));

}

When I call the LCD_init, instead of using what is in my main, the display does not initiate properly. Any sugestion of what I'm doing wrong?


texts: Current transformer not returning expected result in rectifier output

texts:
I have reading about current transformer to measure current of A/C loads and I don't know if I understood it because the simulation that I made didn't worked properly.
So, I read about it here:
https://resources.altium.com/p/current-transformers-how-project
and I used this diagram:

and the replication of it resulted on this:

PS:
1st - I misunderstood how this simulator worked and I wasn't configuring the transformer properly. Now I Am:

2nd - I removed the second diode as suggested.
So:

The green lines are the voltage and the yellow ones are the current.
The TC transformer is with ratio as 1A in load results in 1mA in the burden resistor. (I think this is 1:1000?)
The op-amp are ideal and feed with symmetrical source of 15V.
The diode is ideal.

Link for simulation
Bu I am probably missing something because the article created this circuit in real life and it worked just fine, with 4.76766A in the load they got 4.429V RMS in the rectifier output (7% off).
But I tried to reproduce this using a load of 50ohms with source of 240V resulting in a current of 4.8A, and I was expecting the value of the rectifier output to be 4.8V RMS but I am getting 1.01V RMS. That is not right. What could I have missed recreating this circuit diagram?


texts: Extending UM91214B to support more channels

texts: In this circuit's description, It is given that we can extend the circuit easily to generate up to 12 DTMF signals. How can that be done?


texts: Induction motor starting torque and pull out torque

texts:
Recently I was doing some work on the induction motor where I found some general theory on starting speed torque curve of the induction motor. Where the theory is the starting torque will be 1.5x of rated torque & pull out torque will be 2x. Is this the always a condition or is there a any chance for the  pull out torque can be 4x or 5x of the rated torque.
Speed torque curve of induction motor


texts: In an inverter with RL load, how does an increase in output inductance result in decrease in the magnitude of the current?

texts: In a full bridge inverter with RL load, how does an increase in output inductance result in decrease in the magnitude of the current?


texts: A circuit/component which can reduce own resistance with increase of current

texts:
I'm trying to build following circuit for single-phase 230VAC grid:
0---(LOAD)---(MY_DC_CIRCUIT)---Phase

MY_DC_CIRCUIT doesn't have its own power source. The power is considered to be taken from the AC grid.
Following solution are feasible:

Use inline transformer and rectifier. 1st coil connected in sequence with LOAD, 2nd coil rectified. Isolated, low heat - relatively good solution.
Connect low Ohm resistor in sequence with LOAD. Rectify dropped on the resistor voltage. Non-isolated, heating - bad solution.

For both solutions bad things are:

High load causes high heat.
Low load generates low voltage.

Practical measurements confirm the theory: If LOAD runs 200 mA the MY_DC_CIRCUIT has 0.5V, 600mA --> 1.5V, 2A --> 5V.

I wonder if there is a circuit or electronic component that can be used in sequence with LOAD in AC grid that can adapt its own resistance to current.
In other words: A component that can reduce its resistance with increasing current.

Practical outcome of such component is:

Same voltage can be on MY_DC_CIRCUIT no matter what current of LOAD.

P.S. I clearly understand that requested component for MY_DC_CIRCUIT must pass same current as LOAD.


texts: Verilog - use a clock signal as a value in its own procedural block

texts:
I tried synthesizing the following code and was surprised to see that it doesn't work (at least with Vivado 2017.2).

module top(
   input wire clk,
   output reg dout
);

   always @(posedge clk) begin
      dout <= clk;
   end

endmodule

It complains with the error: use of clock signal in expression not supported.

Why is this? Shouldn't the value of clk be guaranteed to be 1 in its own posedge procedural block? Or, is this a race condition because skew could lead to the clock arriving before the data input?

Edit
On second thought this isn’t all that surprising since this is very likely to violate the register’s setup timing requirement.


texts: VHDL: Demultiplexing a signal to one of many outputs while driving unused outputs to '0'

texts:
I'm attempting to create synthesisable VHDL that will demultiplex a one-bit continuous signal stream to one of many outputs. The outputs that aren't being sent this stream should be set to '0'. See image below for an idea of what I'm trying to achieve.

The code I've written to create this functionality is:

send_s         <= (line_select_s => prbs_i(0), others => '0');

where 'prbs_i(0)' is the signal stream.

Unfortunately this is unsynthesisable in Vivado, giving the error:

[Synth 8-211] could not evaluate expression: aggregate choice expression

Is there a proper way to do this? The VHDL simulates fine but will not synthesise.


texts:
I recently got a 2 page pdf document on double revolving field theory but I cant find the name of the book.
Can anyone identify this book?


texts:
Our PCB designing team is of 5 members and we want to incorporate IPC standards in our designs from now on.

We deal with a single-sided layer to 18 layers of PCB. We are into digital, analog, RF and mixed designs.

We mainly want to use standards for Schematic designing, Footprint creation, and Naming conventions.

What standards do we need to study and follow?


texts: In an equation like i(t) = CdV/dt, is "V" the cause and "i" the effect?

texts:
In mechanics, almost all the time, force is the cause and acceleration the effect. If you apply a net force on an object, an acceleration can be observed. However this seems not that straightforward in electronics in relation to voltage and current.

I used to think that voltage is the cause and current is the effect. But then I came across solarcells, current sources etc and immediately realized my lack of imagination.

For each of the 3 passive components, is there a preference to think one quantity as cause and the other as effect or it is completely arbitrary?

Mechanics:
If force is applied, velocity is changed .
If velocity is changed(accelerating electrons), a force(emi) is produced.

Resistor:
If voltage is applied, current is produced.
If current is applied, voltage is produced.

Capacitor:
If current is applied, voltage is *changed*.
If voltage is changed, a current is produced.

Inductor:
If voltage is applied, current is *changed*.
If current is changed, voltage is produced.


texts: How to analyze a RC circuit with Integrated Chip in Parallel?

texts:
I have a voltage source of 48 V, an IC and an RC Circuit between Vcc pin of IC and voltage source. RC Circuit is there to give a slow rise of 500 ms in the supply voltage of the IC (There is another long story why I am doing this).

I don't know how to analyze such a circuit to set values for resistor and capacitors. Following is a concept circuit.

How can  I  analyze this?


texts: Is it possible to connect the Rx and Tx pins of the same USART or on two different USARTs on an STM32 discovery board to make a loopback and test the USART?


texts: Using a Dipole Antenna on a 50 ohm FM transmitter

texts:
First of all, while I'm not new to electronics, I'm new to the radio world. I am helping a friend overseas set up a community radio, and am getting everything set up over here before I ship it.

I have a CZE-7C FM transmitter, and I have built a simple half wave dipole antenna tuned to the frequency he wishes to use. However, I have noticed in my research that half wave dipoles have a theoretical impedance of about 73 ohms, where as the transmitter wants a 50 ohm antenna. I've read that an ill-matched transmitter and antenna can damage the transmitter, and therefore I would like to know what further preparations are necessary before I hook my simple DIY dipole up to my transmitter.

Perhaps I just don't know what terms to search, but I can't find any advice. I was planning on using 50 ohm coaxial with BNC terminations to connect them, if that helps.


texts: Which step down transformer for my lovely little u.s.a guitar amp?

texts:
I have  new guitar amp from USA which reads '110-120v, 60 cycles, .35amps'

I need to buy a step down transformer but there are various choices of transformers to get to 110v  and i don't want to feed it the wrong power and break it. Its a small amplifier of just 5w.

Could anyone help me make the right choice? I'm guessing the cycles bit is Hz.
Thanks
Tommy


texts: Assembling my own antenna cable - considerations

texts:
I need to use a 4 m antenna cable on an application. Due to non-standard cable length and some more unrelated reasons, I am considering to assemble my own cable which I have not done such thing before.

I have a SMA-jack on my PCB and SMA-female antenna on the other side.

My application use 2.45 GHz RF signal. I am considering to buy any type of cable below except RG-58 and RG-8X.

and buy gold finish SMA-male connector for a cable assembly (correct type that would fit to the cable). The datasheet of the cable connector (Crimp) shows recommended strip cable length and dimensions.

I will choose a connector that max frequency is higher than 2.5 GHz.

Is there anything else to consider?
Does anyone know a well written application note or tutorial that explains how the cable should be properly assembled to have a better performance?
Any tips or tricks?

I don't have a vector network analyzer or a spectrum analyzer with a track generator, but I believe the performance should be OK, is it so?


texts: Is it a best option to use IRF9540N P Channel Enhancement mode MOSFET for switching 3.3V to my WiFi chip?

texts:
I am using IRF9540N P channel enhancement mode MOSFET for switching 3.3V to the power pin of the WiFi chip. The connection is as follows
Source --------- 3.3V
Drain ---------- WiFi chip power
Gate ---------- Ground

So now the Vgs is -3.3V which is lesser than the Vgs(th). If i connect the drain to WiFi chip power, the voltage is getting switched but my WiFi module is not getting ON.
I tried connecting an 12V motor to just check whether the MOSFET is switching the power or not. Instead of switching 3.3V my MOSFET is switching only 2.7V and my motor is rotating very slowly.
My WiFi chip works fine with 2.5V also. I have no idea what could be the issue? Why is my WiFi chip not powering up?
If i connect directly without MOSFET then my WiFi works fine.
I dont think so the current should be the problem because the WiFi chip consumes only 300mA and the MOSFET can switch upto 30A. Any help would be appreciated


texts:
i have been designing flyback converter of a 5Volt 5 ampere specifications output deriving from 220v ac mains. But i have been stuck at one point and can't seem to get out it. Efficiency is particularly very poor in this case getting around 49% when running at 25W output. Earlier, due to leakage inductance voltages were going around greater than 600v on the drain of the MOSFET(10n60) causing high stress on the FET.

So to clamp the voltage , introduced RCD clamp(50nF, 3-5k). I know its a very low value of resistance used causing excessive losses. But only at this value i was able to clamp the voltage down to 550v running at full load.(For stability purpose this is too high, but can't go down anymore without decreasing resistance). At this, MOSFET temperature does not increase to high levels.

Whether this problem is coming due to the leakage inductance too high for this circuit or some other problem?

Transformer specifications:

30swg, 61 turns primary, 1 strand(1.7mH)

22 swg, 3 turns secondary, 5 strands(4.6uH)

35 swg, 1 strand, auxillary, 10 turns( 100uH)

EE28 core used, interleaved windings.

Since, i am winding transformer by hand not by machine, already it is a problem to wind 22 swg wire that too 5 strands so that is why i am thinking it might be a problem of magnetizing inductance too high in this circuit.

Uc3844 ic with isolated feedback using 817 opto with tl431 reference.

Any help would be greatly appreciated.

Edit 1: Circuit for the following converter(FET used is 10n60 not IRF840)(earlier IRF840 was used)-

Edit 2: The solution I got was to increase the current sense resistor to limit the peak current thereby less energy stored per cycle causing resistance value used to almost negligible(50kohm,considering losses). Efficiency boosted up to 76% at 5A Load. Still trying to increase it up to 85 by optimizing the core and rectifier losses. Will write the results soon.


texts: IC package reliability with physical stress

texts:
One of the ICs for my design comes in LQFP, TSSOP, QFN and even WLCSP packages. I don't care about the footprint, and the only thing that I want to maximize with the package choice is reliability against physical (PCB drops, bending, vibration) and temperature (-40..+85°C) stress to ensure maximum lifetime for a device.

I understand that this probably depends on the PCB quality, solder and manufacturing process (of PCB and the ICs). All I want to know is a kind of rule of thumb for this kind of choice.

I found this slide from here:

Which seems to imply that bigger packages are more reliable (use saturation of DIP/PLCC > PQFP > TSOP) in certain cases. But is it really the general guideline? Does it mean that tiny WL-CSP and BGA packaging should be avoided when possible in devices intended to be resistant to physical stress? To me it seems counter-intuitive.


texts: Waveshare ADC Board changing analog input range

texts:
This question has been redirected from raspberry pi community. Some of the questions have been answered by @Milliways, so those questions have been edited out.

I'm using this Raspberry Pi High-Precision AD/DA Expansion Board from waveshare. I have some questions regarding its ADC (model name: ADS1256) unable to give out negative value. Specifically, only giving out negative values around -0.1V. Here are details of my problem.

Current situation:

Using the user manual provided with the board, I have managed to read analog input data from on-board potentiometer and LDR (converted to digital data) using their sample code. In order to use the on-board potentiometer and LDR, I've connected jumpers to the appropriate positions as metioned in the manual.
Now, I've connected a function generator, sending out +/-2V amplitude of analog sine wave signal, to the waveshare ADC board.
By modifying the sample code provided, I've printed out the converted data and ploted them, which is the figure shown below (y-axis = voltage, x-axis = number of data)

figure 1: sine wave plot

Here are the questions:

1. Is this normal phenomenon for this ADC board?

2. If so, am I correct to assume that this ADC can only receive analog inputs above zero? (I've looked through the ADS1256 datasheet and studied a bit, but had hard time understanding the input range found in the document, shown below.)

3. If above assumption is true, then can the analog input range be changed?

I've been told (As @Milliways had suggested) that there are established techniques to offset input DC. To elaborate, I need to change the input range of the ADC from 0 to 5V to -2.5V to +2.5V.  Can this be done by changing ADC registers or do I need a separate circuit like op amp?

figure 2: datasheet screenshots, page 2 and page 3

Product page: https://www.waveshare.com/wiki/High-Precision_AD/DA_Board

Manual : https://www.waveshare.com/w/upload/b/b7/High-Precision-AD-DA-User-Manual.pdf

Sample code : https://www.waveshare.com/wiki/File:High-Precision-AD-DA-Board-Code.7z

ADC datasheet : https://www.waveshare.com/wiki/File:ADS1256.pdf


texts: Grounded Coplanar - Impedence calculation of microstrip - Advance Design System software (ADS)

texts:
I want to calculate the impedance of the micro-strip using Advance design system (ADS) software. I cannot locate "GROUNDED CO-PLANAR" or anything like that. I am new to this software. Can anybody help?
I want to calculate the GAP/Clearance constraint for the microstrip shown in the picture for 50-OHM .


texts: Drill hole size suggestion for this pass-through socket

texts:
I'm considering using this pass-through socket for a project. Since I'm newer at this, I was wondering what size through-hole would be best? This socket will solder in, so I understand that I can go bigger than the diameter in the spec and not have an issue. The question is, how much bigger? I have read on here that tighter is better.

Here is the part: https://www.mill-max.com/products/socket/834-XX-XXX-10-001000. Looks like the hole should be at least .043" in diameter, if I am reading it correctly. There is a slightly wider part that is .061" in diameter, but I cannot tell if that is meant to be in the hole or just flush with the board.

Thanks in advance!


texts: Suggestions for switching 800VDC converter on/off

texts:
I'm stress testing(turning them on-off with load every 300 seconds for 1-2 weeks) the components that we are willing to use. have tested several battery chargers with AC input with using a timer relay like this:

My question is what would be the best way of stress testing a DC/DC converter which has input of 800V DC? (This one)


texts: Is there any method to verify the fuse ampere rating without destructing it .I know the fuses works on the principle of resistive heating .If there is any method to verify the ampere rating without destroying the fuse please answer


texts:
I have these nice piezo transducers to characterize (of course the datasheet is incomplete) and make a spice model for oscillator design purposes. Now, Rhea and the other people say "hook it up to a VNA and it will give the parameters", but, of course, I'm poor. So I used the bode plot app inside of the scope. Generator and channel 1 to one pin of the transducer, channel 2 to the other pins, grounds all together.
This should me a poor man S21 plot with a drive impedance of 50 ohms (the generator) and a load of 10meg||12pF (the probe load). It does, in fact, work and the result is sensible. Scope does Ch2/Ch1 so load on the source is compensated.

The phase in resonance is suspicious but a scope is not the best thing to measure small phase deviations, I'm ok with that.
Going to model the primary resonance pair: Fs=1.85MHz, Fp=1.93MHz; Q is going to be quite low, but PZT is notorious for that.
First thing strange: from spec it should be Fs=1.7MHz±70kHz.
Measured one is too high. First idea: is the probe loading the transducer and pulling it? I assume that the datasheet is measured on a calibrate 50 ohm resistive system. Fine with that.
As for the model the formulas are quite everywhere, I used these http://www.sark110.com/application-notes/equivalent-circuit-determination-of-quartz-crystals (which match with the Rhea ones).
Co is specced as 1.7nF; Rs is, well, they say 'less than 1.5 ohms'. 1.4 matches well on amplitude and phase for the simulation.
So I did this spice fixture. It should match decently what I did. Generator, two probes, resonator. Checked against the formulas at
https://www.pspice.com/resources/application-notes/modelling-quartz-crystals and both fs and fs match reasonably.

The AC sweep however… well, doesn't match:

The overall shape is fine. Considering the input loading (green trace) the amplitude matches (the plot doesn't have Vout/Vin) and phase drops a little too much but is still plausible. fs and fp are completely wrong (1.925MHz and 1.93MHz).
What is happening here? Is this a probe pull issue? As in:

The original transducer was 1.7MHz and was pulled to 1.85MHz
I designed a model for the 1.85MHz and the simulated probes pulled the simulator resonator to 1.925MHz.

However, if this is the case, how could I calibrate out the probe load? I know from the datasheet that the main fs is 1.7MHz, but, for example, how could I find the real frequency for the radial mode resonance at about 150kHz (the leftmost one)?


texts:
So I am trying to make a temperature controlled DC fan using IC as voltage comparator. The IC I am using is LM741. This is the layout of my circuit:

Now when I use a 9V battery as power supply, the circuit works fine. But I want to run this circuit using wall socket. So I used a step down transformer to get 12V AC and used this to rectify it:

But the circuit does not work properly. The fan is always on and is not switched off by adjusting the trimpot. Can anyone tell me why this is happening?
I checked the output of the rectifier circuit using DMM, I get around 15.6V DC.

Edit: I am sorry I messed up while drawing the circuit... I did not actually connect the ground of the circuit the way I drew it.. This is how I connected the circuit:


texts:
So I've got two MCP23017's on the same I2C bus connected to a RPi. One is addressed 0x20, the other 0x24. The RPi is running my GUI which in turn controls the MCP's which switch 16-way relay boards.

The GUI is written in python and using the Adafruit_GPIO MCP230XX library
The 0x20 MCP is located next to the RPi, and powered by the same power supply and works like a charm. (a 5V 5A power supply)

But, the 0x24 MCP is located about 2 meters (~ 6.5') away, with the 5v, GND, SCL and SDA lines taken in CAT5 from the RPi. The relay board is powered separately, with the GND's connected. But, this little arse doesn't want to work at all. The RPi can see the MCP (i2cdetect), but it doesn't seem to respond. Very occasionally it will start working, but when I unplugged a load from the same socket that is powering everything it cut out and stopped working again?!? I've even rebuilt the board with a new MCP chip and it's changed nothing. Is this me being dumb somewhere?

Any and all help appreciated! Thanks


texts: How might a comparator with only logic gates look like? Isit like:


texts: Why can't the atmega328p accept 5 and 3.3v signals at the same time?

texts: The same chip can be run at 5v or 3.3v so it's tolerant to 5v so why when I run it at 3.3v can't I send in a 5v signal on an input pin? Curious on what's in the chip that makes this a bad idea.


texts:
Consider the step-by-step asymptotic approach for drawing Bode plots given on the last page here. I had two questions about using this approach by hand (instead of adding individual graphs to find the composite graph):

What exactly does the highlighted part below mean? Does "it" (for the limit direction) refer to the network function \$H\$, \$jw\$ (= \$s\$), or something else? If it's \$s\$, isn't \$s\$ always an imaginary number with a positive imaginary part (since \$\omega > 0\$)?
How would you draw the Bode (magnitude and phase) plot if there were multiple different (not repeated) factors in the network function having the same break frequency—e.g. \$G_v = \frac{s^2 + 1}{s^2 + 0.5s + 1}\$, which has a quadratic zero and a quadratic pole with the same break frequency, 1 rad/s? Going left to right, I thought the slope (in the magnitude plot) would change by +40 dB/decade (due to the quadratic zero) and −40 dB/decade (due to the quadratic pole) at \$\omega\$ = 1 rad/s, effectively "cancelling" each other out and producing no change. However, WolframAlpha suggests otherwise. Why isn't the magnitude plot at \$\omega\$ = 1 rad/s just a straight line (continued from the left) with zero change? (Compare the lower right figure mentioned here.)


texts: Is it possible to power an LCD by radio wave?

texts:
We've all heard of crystal radios that essentially draw their power from the radio waves which induces a tiny current in order to generate the sound we hear from them.

There are companies that are working on device chargers that magically pull power from the radio waves and promise to charge our devices wirelessly, 24 hours a day so we might never need to plug them in again... I find that unlikely, but I live in hope.

What I'm trying to figure out is this:

Is it possible to harness enough power from radio waves to drive a simple LCD such as to display the current time and date... and perhaps the weather? These are all signals broadcast over the air almost continuously. It could be an e-ink device for all I care to save more power.

Is there a device out there that already does this that I'm not aware of?


texts: Arduino UNO-CH341 keeps resetting randomly

texts:
A brief summary: I work at a small workshop/factory, and we've got a single three-phase compressor for the whole factory, a week ago the compressor controller flat-out died and that left the entire place without air, which is critical for production.
The compressor has to keep air pressure at a set interval (6 - 8) Bar If it goes to low the machines stop, and if it goes to high the tank safety valve activates and all air goes out. The compressor is relatively simple at an electrical level, just a three-phase motor, a valve to let the compressed air into the tank, and 3 contactors to do a star-delta startup.
Some usefull info: Importing replacement parts/servicing the compressor is a no-go, it is chinesse in origin, with no representative here in my country, and our trade laws make importing a new controller more expensive than just buying a new compressor, (Wich is something we are really trying to avoid as doing so would be seriously expensive, and the mechanical part of the compressor works, it's just the pressure control that's busted)
So to solve this problem I grabbed an arduino UNO and a relay pcb and coded a simple program which manages the star-delta operation, and controls the air pressure valve.
The pressure sensor requires at least 10V to work properly and for that reason there's a 12V switching power supply coneccted to it.
The project works, but it resets randomly, there's no pattern one day it might reset every 15 minutes and another every 3 hours, the conecctions between the arduino and everything else are all done using cables with pins, and the whole thing shakes a fair bit becouse it's mounted on the compressor.
Things i've tryed so far:
-Removed both the reset button and the capacitor that allows the Ch340 to reset the arduino.
-Soldered a 4700uF capacitor directly to the arduino board, thinking that maybe the connectors where shaking loose and the arduino getting powered down for just a second.
-Added an external 5V 5A switching power supply to the arduino, and powered it directly through the 5V pin (not the usb B port)
Finally my question is, does anyone know of any other reason why the arduino could be resetting itself? The only other thing i can think of is something on the ac lines.
I'll show the code if need be, but I'm not using pointers, or dinamic memory or anything that could cause a software reset.

I can't show you a photo of the inside of the box becouse we can't stop the compressor, sorry i forgot.


texts: RFM69 hat for RPI get stuck because of noise caused by missing ground

texts:
I built a RFM69 hat for a Raspberry Pi 3 B+. It works perfectly as long as I do not use the GPIO to switch on the relay that drives a solenoid valve. Unfortunatelly a lot of times the switching cause the radio module to get stuck and I have to reset it, destroying the Radio object, to make it work again.

This is the global schematic:

Looking at the schematic of the relay module it seems that the GPIO should not be disturbed by the relay switching.
I tried to power the radio module with a battery, but the problem remains. The RPI seems to be unaffected by the switching: nothing is reported in the logs. Maybe something gets wrong on the SPI bus or a sudden spike in the relay can disturbe the radio module?
From the schematic of breakout board I see two bypass capacitors that should protect the module from noise.

I tried to detect the change of the pins 11 and 12 from the process controlling the radio module (which is different from the one that controls the relay) in order to reset the radio. It is not very realiable though, because sometimes the event is not fired (?). Maybe there is a more clever solution?
It seems to me that the python library for the RFM69 does not expose a method to poll if the radio is working.

Edit1: if the valve is disconnected the radio module works properly.

Edit2: from the tests that I made it seems that the transformer is not doing a fair job with the noise coming in the RPI and the RF module. I am thinking to build a small board with a pair of big capacitors, say 470uF, in parallel with the supply of each device. I believe that the noise frequency should be low so the big capacity needed. I could leave space for a few smaller capacitors to put in parallel for the higher frequencies. Could it be a good idea?

Edit3: I’ve built this board  but it is still not working!

Edit4: I've just bought an oscilloscope and this is what I see when the solenoid valve opens:

With my brand new oscilloscope I discovered that there is a lot of noise in the line. I bought a new Mean Well power supply (RS-25-5) and it does a great job reducing the noise but unfortunatelly is not enought! I'll try with an EMI filter (CW1B-10A-L). Let's see what happens.

Update: I’ve discovered that when the radio module gets stuck, the register RegRssiThresh changes to 0xFF. Now I check every second if the register has this value and in this case a reset of the radio module solves the problem.

Main components:
Connections to RPI:
Hat:
Power and relays connections (note the lack of the ground connection on the power supply. Could it be the cause of high interferences?):


texts: Signal rate, data rate and bandwidth in digital signals

texts:
I'm trying to understand the concept of signal rate and the relation between signal (baud) rate and bandwidth of digital signals from a book about data communication.

First, the book distinguishes between data element and signal element: a data element is the smallest entity that can represent a piece of information (the bit), and a signal element is the shortest unit (timewise) of a digital signal.

Then, it says that the relationship between data rate and signal rate depends on the number of data elements carried by each signal element, and on the data pattern, stating that, if we have a data pattern of all 1s or all 0s, the signal rate may be different from a data pattern of alternating 1s and 0s. It then formulates the relationship between data rate and signal rate as:

$$ S=\frac{cN} {r}\ baud $$

where N is the data rate (bps); c is the case factor, which varies for each case; S is the number of signal elements; and r is the number of data elements carried by each signal element.

Then it states that the minimum bandwidth (range of frequencies) required for a digital signal can be given by:

$$ B_{min}=\frac{cN} {r} $$

My questions are:

1) Could anyone explain in more detail the meaning of the case factor c? In practice, what does it mean to say that the signal rate depends on the data pattern?

2) Why does the minimum bandwidth for a digital signal equal the signal rate?

3) If we set c to 1/2 in the formula for the minimum bandwidth to find Nmax (the maximum data rate for a channel with bandwidth B), and consider r to be log2(L) (where L is the number of signal levels), we get Nyquist formula. Why? What is the meaning of setting c to 1/2?

Here is a link to the portion of the book where the term c is defined.


texts:
I am designing a product that uses a thermocouple to monitor temperature.

I am trying to decide what is the best way for users to attach the thermocouple to the PCB. I have found the connectors that Omega Engineering offers. The only problem is that they are a little pricey and hard to find through any of the typical component distributors (except Newark).

Does anyone know of any other standard thermocouple connectors? Do you think it would be bad to use a different style connector like an audio connector for example?


texts: Toshiba T1200XE PSU repair. Identifying some SMD component 222/22Y

texts:
Need help. I'm trying to recover an old Toshiba T1200XE laptop and it seems the onboard PSU has a problem. One SMD looks damaged and I think it's better to replace it. I'm pretty sure this happened because old capacitors have leaked and electrolyte leaked to the board which provoked a short circuit. Sign on SMD looks like 222 where first digit underlined and second overlined. PSU board ID: 36M743776G. Size of this SMD 3 x 1.6 mm. Picture of it on board:
p.s. similar topic here

In the Google I've found another picture of this SMD and there different sign 22Y

Please help to identify this SMD and find some analogue of that SMD to replace it. Thank you!


texts:
I'm looking to use a solar + lithium ion battery combination in order to be able to continuously power a Raspberry Pi.

I have found an MPPT solar battery charger, which will output a fixed voltage. From my understanding, however, a fixed voltage output isn't the best way to charge l-ion batteries. So my thought is to feed this fixed voltage into a l-ion battery charger like this one, which will then charge the battery.

Once the battery is charged, it should provide current to the RPi and some other motors via a step-down regulator or two.

The thing I can't wrap my head around is how to make a circuit that will always give the RPi/load the power it needs, but charge the battery if there is any juice left over. If the panels are only getting a little bit of power, the battery should also augment them in order to power the load.

What is the most energy-efficient and reliable way to do this?


texts: How to test if zero crossing is working?

texts:
I used circuit like this:

On led I get: 3.3 mA and 1.3V

What is the best way to test if zero crossing works with arduino or multimetar?


texts:
The is the simulated version of the schematic.

I have designed a protection circuit for my pcb and I would appreciate having some feedback before starting the PCB design.

The circuit is broken down as follow;

-ESD protection provided by a one channel IC

-low pass filter to suppress noise above 4.5Khz

-pmos to protect against reverse polarity

-crowbar for overvoltage protection

-current sensor which is connected to a uC ( ideally I would like the op amp to work with the PSU IN in the range 3.3v to 16v)

The maximum voltage is 16V and the minimum votlage is 3.3V.

The is the final version of the schematic

Edit:

I have modified the current sensing part, fixed the short circuit issue with R(sense). PSU out is from node R (Load). I am using the PSU IN to power the OP AMP and added a decoupling capacitor.

Edit 2:

The current monitored is in the range of 0 - 1A . ADC is from 0 - 3.3V

The actual models used have been implemented in the schematic for clarity.

The supply voltage range is from 3.3V to 16V

The low pass filter has been replaced by a ferrite bead

Differential Op amp is used for current monitoring with 165K for R load to provide the adequate gain (0 to 3.3V input to the ADC).


texts: Zero sequence component in unbalanced faults rotation

texts:
I am trying to understand the physical/practical meaning of the zero sequence component, I referred to some books. however, I am not sure is me or are there different interpretation of the zero sequence phasor regarding whether they are rotational or not?
I know that positive sequence rotates as the original equipment rotation, whereas, negative sequence rotates in the opposite direction and thus it tends to reduce the positive sequence torque.
But, I don't know how the zero sequence contribute if it does to the rotation, does it have a torque?
I highlighted the confusing information.
The first book:

The second book:

Sources:
The first book:
TRANSIENT ANALYSIS OF ELECTRIC POWER CIRCUITS HANDBOOK
Published by Springer 2005
by
ARIEH L. SHENKMAN
ISBN-10 0-387-28797-3
The second book:
Protective Relaying Handbook, Volume 2
2009 Published by Inter National Electrical Testing Association


texts:
I need to determine the current across the 4 ohm resistor (name it I1).

What I calculated, thought out so far :

Current of 2 ohm resistor : I=5V/2ohm=2,5A. I Think this current is flow towards the A point (because the current and voltage direction is always the same on passive components, is it true?)
The currents on the A point is : 5A+2,5A=7,5 A comes in , and 3.5 flows out. 7,5A-3,5A=4A
This means 4A needs to flow out from the A point , i think it's flow toward the one ohm resistor.
Voltage on 1 ohm resistor is U=4A*1ohm=4V

I cannot calculate from there the current through the 4 ohm resistor.


texts:
Possible Duplicate:
  Power LED from headphone jack

New to electronics (I am a software guy) so pardon me if it's a very noob question.
Can an iPhone headphone jack power a small LED? The LED hopefully can also change it's colours based on the signal so I am guessing there's some going to be some sort of logic component to it.

Also, where can I get started with the hardware side of things?

Thanks


texts: PIC I2C communication problem with I2C multiplexer

texts:
I need to read data from 3 of the same kind of batteries with SMBus so I decided to use an I2C multiplexer for this purpose. I can communicate with 1 battery without any error. But I cannot communicate with the mux. I use PIC18F26K83 and the mux I am using is TCA9546A.

Datasheet of the mux: TCA9546A

This is the SDA line that goes to mux from my PIC: (I am trying to send 0x01 to the address 0xE0)

Does this data that I send to mux looks okay?

And the code hangs in mux1() function  while(!I2C1CON0.B3){ }   //Master Data request loop

And this is the schematic of the mux SCL and SDA lines are connected to PIC. RESET line is also connected to PIC. I make it high in the program.

Edit: This is the last image from the scope. (Blue traces are SCL and yellow traces are SDA from PIC to mux.)

Last Edit: So for MUX to select channel it needs to be reseted all the time...
And for the rest of the problem was occured because I did not correctly do the hardware part. If anyone wonders or needs the code I can send.


texts: What is reference impedance in microwave?

texts: What is reference impedance in microwave circuit design and applications? What should be value of reference impedance in antenna design?


texts: Problem with Arduino and 2 Sharp IR sensors

texts:
I have 1 Arduino and 2 IR Sharp GP2Y0A02YK0F proximity sensors, I connected 1 sensor, with mounted capacitors between GND and VCC (100nF, 10000nF)

Everything is fine, I have good values, but when I connect the second sensor, both get electrically disturbed.

I get strange values from both sensors.  What can I do that I get good Values of both sensors with 1 Arduino board?


texts:
I have tried to mount a Colpitts oscillator twice and its oscillation is not the expected. I get like 13 MHz oscillation when expected 50MHz using the following schematic:

When I change the Inductor value it doesn't appear to change. That's why I thought it could be an effect of the parasitic capacitances, as I'm using the following board to mount it: ´

Any thoughts?


texts: How would I power and wire a raspbbery pi 4 and 20 servos?

texts:
I am trying to control two robotic arms with a raspberry pi 4. I will need to power the pi and 20 SG90 servos. I am pretty new to electronics, so I am not very sure on how I am going to do this.
I am currently thinking of using 3 power supplys. I am thinking of using a power bank which outputs 5v through USB to USB-C to power the raspberry pi, and then one power supply for each of the arms. Each arm will have 10 servos.
I would like to know two things:

What power supply should I buy to power each arm? I would prefer an AA cell pack if that is possible but any rechargeable battery under $40 is fine.
How would I connect all the servos to the power supply? Do I need to use a breadboard?


texts: How is spectral purity measured? or evaluated? I have this signal coming from a 10 MHz crystal oscillator. I know how to calculate the SNR, but how do I calculate the spectral purity? Is it also a ratio involving signal strength?


texts: Need a solenoid to pull a Nerf Gun trigger

texts:
I'm looking for a solenoid  that be used to pull the trigger of a Nerf gun.  Using a strain gauge I determined that you need about 1 kg of force to pull the trigger, and the travel of the trigger is about 17 mm.  I have a solid understanding of general voltage and current basics, but never worked with solenoids or magnetism in general.

I've been looking at solenoids on Digi-Key.  They seem to be rated by voltage, stroke length and power (in watts).  They also rate it by DC Resistance (in ohms) and lots of other things.  Here's an example.

From these numbers, how do I determine if a particular solenoid will be able to generate the force I need?

I've also considered purchasing some enameled magnet wire and making my own.  But I have no idea what gauge wire I would need and how much I would need.  If someone coud help me with the math, that'd be great.


texts:
I am using a microcontroller to drive a flyback transformer. The driving circuit contain speedup capacitor as shown in the figure, as to protect the microcontroller from relatively high currents generated by the speedup capacitor I have added a 74LVC1G14 inverter in between to be used as a buffer.
The problem is the inverter draws more current than expected. It draws about 2.5mA though the load draws 0.5mA only. I know that when the CMOS change its state there is a short circuit between Vcc and GND for short time when the two MOSFETs are On, but with my 100KHz frequency I think this 2.5mA is too much.

Any one know what is the problem with this inverter circuit?
Did I make something wrong?


texts:
I need to create a clock divider which has 2 inputs: n(12 bit) , clock.
For every even N it needs to divide the clock frequency by that number. (2,4,6,8 etc). However I have run into some problems. First of all I created the following divider.

However if I need to do this for 12 bits its going to be too much work. It feels like so much work that there has to be a better way. Also this doesn't cover a lot of values. I do have a question about this design which is: Are you supposed to connect ~Q to the clock input of the next flip flop or should I have connected Q to the clock input?

I thought about a better design and came up with the following.

I will give some explanation: I used a counter which counts untill it equals a number X in the comparator. Then the Comparator sends a 1 to the flip flop and the flip flop outputs this. But here I have the following problems:
- Doesn't auto reset.
- It turns on the flipflop after lets say 4 ticks, but it doesn't switch it off.

The auto reset should be easy to fix. But the fact that my flipflop does not turn off after x ticks is less great. My question is am I on the right course or do I need a new approach? If my second design has the right idea please give me some advice on how to get it working.


texts: How does the second order time constant affect circuit behavior?

texts:
I learned that the transfer function of a second order circuit can be expressed in the following standard way:
$$
\frac{K}{\tau_s^2 s^2 + 2 \zeta \tau_s s + 1}
$$
Where:

\$K\$ is the gain
\$\zeta\$ is the damping factor
\$\tau_s\$ is the second order time constant

In trying to understand the meaning of \$\tau_s\$, I found this link that states:

  The second order process time constant is the speed that the output response reaches a new steady state condition.

This statement made me have some doubts about how to interpret of this constant.

My questions:

Considering, for example, the two transfer functions below:

$$
\begin{array}{c|c}
H_1(s)=\dfrac{5}{2s^2+3s+1} \qquad & \qquad  H_2(s)=\dfrac{5}{8s^2+6s+1}
\end{array}
$$

Both have \$0\$ as the steady state condition. Since \$\tau_2 >\tau_1\$, can we conclude that the output of the circuit represented by \$H_2(s)\$ will reach \$0\$ faster than the one represented by \$H_1(s)\$? Can we conclude that the transient response vanishes faster in \$H_2(s)\$, because it has a bigger time constant?

If we are dealing with an overdamped second order circuit that is a combination of two first order circuits, such as the following

$$
\left(\frac{K}{\tau_{p1}\,s + 1}\right) \left(\frac{1}{\tau_{p2}\,s + 1}\right) = \frac{K}{\tau_{p1}\tau_{p2}\,s^2 + \left(\tau_{p1}+\tau_{p2}\right)s + 1}
$$
         we can say that \$\tau_{p1}\cdot\tau_{p2} = \tau_s^2 \implies \tau_s=\sqrt{\tau_{p1}\cdot\tau_{p2}}\$

If \$T_1\$ is the time constant of one of the cascaded first order circuit \$\left(T_1=-\dfrac{1}{\tau_{p1}}\right)\$ and \$T_2\$ of the other \$\left(T_2=-\dfrac{1}{\tau_{p2}}\right)\$, we have:

$$
\tau_s=\sqrt{\frac{T_1+T_2}{T_1\cdot T_2}}
$$
So, if one defines \$T_s\triangleq \dfrac{1}{\tau_s}\$, will this value have any meaning, like \$T_1\$ and \$T_2\$ have for a first order circuit (for example, the time to decrease/reach certain value)?

A correction about the expressions in the second question (thanks to @TimWescott):

The poles are \$p_1=-\dfrac{1}{\tau_{p1}}\$ and \$p_2=-\dfrac{1}{\tau_{p2}}\$. Thus, we have:
$$
\begin{array}{c|c|c}
   T_1=-\dfrac{1}{p_1}=\tau_{p1} \qquad
 & \qquad T_2=-\dfrac{1}{p_2}=\tau_{p2} \qquad
 &  \qquad \tau_s=\displaystyle\sqrt{T_1\cdot T_2}
\end{array}
$$

Therefore, what I meant was \$T_s\triangleq \tau_s\$. (So, I could have used \$\tau_{p1}\$, \$\tau_{p2}\$ and \$\tau_s\$ directly)


texts:
Just trying to find a suitable buck converter for my application, which is running off ~10-50V (12/24/48V battery banks) and supplying normally a very low load microcontroller (~1mA) but occasionally doing some higher current SD writes (~150mA) and for some reason am unable to find something to meet these requirements.
Are these requirements too tight? Or is an output current range that wide and close to zero feasible?


texts: Can the same capacitor be used to support multiple LP2950s in the same circuit (as Cin)

texts:
I am using multiple LP2950s in the same circuit.  Can the Cin capacitor be the same for all of them (the same physical device)?  I wanted to reduce parts count by using the same physical capacitor for all three LP2950s for Cin.  Is that ok to do?

The technotes show this as a basic design pattern:


texts: Having some questions about converting a PWM signal to analogue signal

texts:
Hello i am using a Lowpass filter to effectively "create in a sense" a analogue signal. The problem im having is the example that i was shown fourth diagram has a smooth wave essentially. However for mine it has to have an input frequency of 62.5Khz and i have used a lowpass to cutoff half of this (we were told to do this). The problem i have is that i dont understand why for the same circuit with a frequency of 1kHz looks much cleaner than mine of 62.5kHz. Why is this? Is it essentially the same just since the larger frequency makes it look more compact? Essentially im asking is for the input of frequency 62.5kHz will this give me an audio signal? I believe i have done what is correct besides from the output going through an amp (just focusing on the filter stage at the moment). I dont have the equipment to physically test it at the moment either. My main worry is that this (62.5kHz input frequency) output signal doesnt look like a typical analogue, sine shaped signal essentially but however just looks like a lot of noise (diagram 2 red signal). As in also for the enlarged image (diagram 3) from 0 to 1ms, there is no sine shape to it, like the example that was given (diagram4 or like diagram 1?

Shortform: Dont understand why for diagram 2, the output doesnt look like a audio signal such as for example the shape of diagram 1 or 4? Diagram 3 is an enlarged version of diagram 2. Did i do something wrong? I have my high pass filter at cutoff 20Hz and this removes the dc bias and my lowpass at cutoff 62.5/2kHz (as the pwm outputs 62.5kHz, i know a lowpass isnt needed since 62kHz is much larger than the audio heard to humans (i.e. 20-20kHz) but it was stated that it should still be done. Th voltage divider is used due to the output voltage needing to be under a certain voltage due to the amp needing 0.4 to -0.4V. Hence why does my signal change with larger input frequencies and lower frequencies?

I am probing all graphs at the TOP node for C2

Note: Vout is not where i have probed and i know that it is not the actual output voltage for these circuits


texts: how can accsess gnd in full wave rectifier?

texts:
in full wave rectifier without transformer how can access to gnd for regulator or gnd of microcontroller? (assume we dont have trouble with amplitude of voltage)
I think in full wave rectifier in negative part of input voltage cycle, the negative rail in rectifier have voltage that could be dangerous!


texts: Camera circuit with different voltage requirements on arduino

texts:
First off - i'm an EE noob, but i've muddled my way through a number of arduino projects, so have some experience there.

I'm building a breakout board for a CMOS camera sensor for use with an arduino mega (ATmega2560 mcu). The mega has a +3.3v and a +5v rail. The camera has two different VINs, one for the analog circuitry one for the digital. both are listed for a max of +3v, and one is recommended at 1.8, the other at 2.8.

My question is how do i get those voltages from the 3.3 rail - just make a voltage divider? Also, won't this also affect the logic levels dealing with the circuit? if i build a divider, do all lines have to run through one? do i need a level shifter?

a little lost here..


texts: AC current gain of an emitter follower configuration with a Darlington transistor and a source resistance

texts:
We're using the book Electronic Devices and Circuit Theory by Boylestad for our circuits class and are currently on Darlington transistors.
I'm trying to solve the current gain of a circuit with an internal resistance at the source and thought about using the two-port systems approach.
Specifically, this formula.

However, the book derives an equation for the current gain without load and internal resistance which is this:

I got confused because we were taught that the voltage and current gains have opposite signs. Since the voltage gain is approximately equal to 1, I don't understand if I can really use this equation.
The current gain in the Darlington section is positive but for a normal emitter follower, it is negative. I really need help to confirm what equation to use for this scenario.
This is the circuit that I want to solve:


texts: Avoiding electrolytic capacitors in high-pass filters with sub-Hz cut-off

texts:
We need to design a HPF filter to AC couple  a bipolar signal to a high gain amplifier. Any substantial DC left would saturate the amplifier, and thus it must be removed with the high-pass filter(HPF).

But the bandwidth of interest extends down to 0.1Hz and therefore the cut-off for the HPF should be way below 1Hz.

A simple first order solution would use a capacitor in series with a resistor.

Then C needs to be large to achieve a very low cut-off freq., but electrolytic capacitors can not be used as the signal is bipolar. Further, tolerances are poor for electrolytic caps, which would not be acceptable for our precision amp.

What are the best designs for this HPF which avoid electrolytic capacitors?

A possible solution seems to be to implement a second order Butterworth with a Sallen-Key architecture. The (two) Capacitors needed in this design (according to TI's Webench filter design tool) are smaller than the C called for for a first order HPF.

Is this a good way forward (increase order and use multiple stages to avoid large capacitors)?

Which are the established approaches to this problem?


texts: Infrared device responds to multiple remotes/"wrong" codes

texts:
I have multiple IR devices controlled by my Raspberry Pi:

LED strip
HDMI input switcher

I used irrecord/mode2 to build a config file and both devices respond properly to the raw codes I found. However, the LED strip also responds to the codes related to the HDMI switcher. Like, the strip will turn off if I send the code corresponding to the "1" button for the HDMI switch, it will turn red for the "2" button and blue for "3". It even responds to the original switcher's remote control, so I don't think there's a problem with the codes I'm sending from the Pi. I also tried messing with the sending frequency for the switch on the Pi by changing it to 36, 38, 40 and 42 KHz. In all cases both the LED strip and HDMI switch will respond. Use anything outside that range and the switch won't respond anymore.

The other way around (using the LED remote on the HDMI switcher) doesn't trigger anything though.

My questions:

I always thought IR codes were unique to a particular (type of) receiver, so how come the strip responds to codes it shouldn't really respond to? There doesn't seem to be an overlap in the IR codes either. I'll add an example at the end but I'm not sure if that's actually within the scope of this subsite.
Shouldn't every device be sort of "locked" to a certain frequency too? I can understand if something responds to signals sent at 35.9 KHz while it's using 36 KHz itself due to tolerance, but 36k vs 42k seems like a pretty big jump.
Is there any way to make the LED receiver ignore things meant for the HDMI switcher?

If it matters in any way: the IR LED I'm using to send signals from the Pi is a 5mm Vishay TSAL7400 940nm, combined with a transistor.

Raw codes:

HDMI button 1

9339     4509      631      547      633      548
 632      544      649      537      633      542
 632      548      633      548      632     1634
 637     1638      634     1652      628     1638
 625     1633      636     1637      640     1647
 619     1638      632      549      633      548
 635     1635      631      548      633      549
 641      536      636      544      637      545
 639      540      636     1635      636      545
 636     1633      649     1628      636     1639
 627     1633      638     1636      635     1650
 622

LED strip poweroff button

9032    4435     617     511     613     515
 612     515     613     519     609     511
 614     514     613     515     615     513
 614    1616     614    1622     603    1613
 618    1608     618     510     617    1614
 617    1609     617    1615     618     504
 619    1611     618     511     616     507
 618     510     620     522     603     511
 618     510     630    1596     617     511
 617    1609     620    1611     617    1609
 616    1614     617    1609     618    1608
 623


texts: Why disable interrupt is time-consuming in multi-processor computer?

texts:
I have a book statement:

  Disabling interrupt is time-consuming in multi-processor system.

I suspect that this is related to the hardware implementation of how interrupt is enabled/disabled. So what's the mechanism behind it?


texts: Precise timing with a PIC18 microcontroller?

texts:
I'm trying to write a software serial implementation and am having trouble with timing. I'm using Timer0 on a PIC18F242 and for some reason it does not seem to be very accurate.

I've been trying to debug the problem by toggling a pin on the microcontroller and watching the frequency on my oscilloscope. The oscilloscope shows that the period is greater than it should be, and I don't know why.

With my full code the period was something like 10us too long, if I remember correctly, but even with a very simple example, such as the one below, the timing is off.

Here is an example:

#include <p18f242.h>

// fuse configurations
#pragma config OSC = HSPLL
#pragma config OSCS = OFF
#pragma config PWRT = OFF
#pragma config BOR = OFF
#pragma config WDT = OFF
#pragma config LVP = OFF
#pragma config CP0 = OFF

// CALCULATIONS:
// 8Mhz crystal with PLL enabled
// FOSC = 4*8Mhz = 32MHz
// TOSC = 1/FOSC = 31.25ns
// TCY = 4*TOSC = 125 ns
// timer has 1:8 prescaler, therefore timer increments every 8*TOSC = 1us.

main(void)
{
    // port configuration
    TRISBbits.RB1 = 0; // make RB1 an output

    // configure Timer0
    T0CONbits.TMR0ON = 0; // disable (stop) the timer
    T0CONbits.T08BIT = 0; // 16-bit timer
    T0CONbits.T0CS   = 0; // use internal instruction clock
    T0CONbits.PSA    = 0; // use prescaler (prescaler assigned below)
    T0CONbits.T0PS0  = 0; // 010 = 1:8 prescaler
    T0CONbits.T0PS1  = 1;
    T0CONbits.T0PS2  = 0;
    T0CONbits.TMR0ON = 1; // enable (start) the timer

    while(1)
    {
        if(TMR0L >= 100)
        {
            PORTBbits.RB1 ^= 1;

            // reset the timer
            TMR0H = 0; // MUST SET TMR0H FIRST
            TMR0L = 0;
        }
    }
}

My oscilloscope says the period of this signal is 204.0us, which means that the pin is toggling every 102.0us. If my oscilloscope is correct, then the pin is toggling 2us too late every time.

Interestingly, changing if(TMR0L >= 100) to if(TMR0L >= 102) results in the same period, but going below 100 or above 102 results in the period decreasing and increasing, respectively.

Why is this happening?

Also, as I mentioned, having additional code in the main loop seems to exacerbate the problem. Why would that be?


texts: I got 500 78L05's. Does anybody have a suggestion for an interesting circuit which uses a lot of 78L05's? Or is it not really possible to do anything more interesting than simple voltage and current regulating circuits with them?


texts: Indicating the charge level on a capacitor with an LED

texts: I have a capacitor which can charge up to 1500 V that is connected to another circuit. During maintenance, I have to go and work on the circuit and before doing so, I need to make sure that the capacitor is completely deenergized. I would like to have an LED installed which goes ON for voltages higher than 100 V and goes off when it is below 100 V. I thought of connecting an LED in parallel with a series resistor, however doing so will probably damage the LED as it would be designed for voltages greater than 100 V and not as close to 1500 V.


texts:
Is it necessary to declare reg before assignment in Verilog? Or does Verilog-2001 allow to declare reg after assignment?

For example this code is synthesized by Quartus and simulated by ModelSim without errors

module my_module(output out_my_reg);
 reg my_reg;
 assign out_my_reg = my_reg;
endmodule

And this code is synthesized by Quartus without errors but in ModelSim its simulate leds to an error Undefined variable: 'my_reg'

module my_module(output out_my_reg);
 assign out_my_reg = my_reg;
 reg my_reg;
endmodule


texts: How many resistors do I need for an 8 switch DIP switch block?

texts:
I was thinking of giving each switch it's own pull-up resistor, but this seems like it would be expensive and a little bit of overkill. But using just one pull-up for the entire block seems like it might overload the resistor (unless I just use a big one).

Are there any guidelines in this situation?


texts: How to measure coils without inductance measuring device?

texts:
I have a multimeter that can measure capacitance, resistancr, voltage and current.
If I have a known coil and unknown coil, can I measure the ratio between the inductance of the two coils?
Is it possible to determine the inductance of an unknown coil?


texts: Any suggestions on a small hydroponic system using a NiMH AAA rechargeable battery to run a pump & small PV cell to trickle charge battery?

texts:
Let me start off by saying I am in no way an engineer or electronics pro; merely an amateur/DIY-er and High School Physics & Biology teacher. I enjoy building things in my off time to both bring better scientific inquiry into my classroom and build my overall background knowledge of various subjects.

Currently, I am trying to scale down a hydroponic system to an all-in-one, single plant hydroponic growing system that runs on a AAA NiMH 1.2v*850mAh and is trickle charged by a solar cell. I hope to keep this set-up as SIMPLE as possible for my Freshmen & Sophomores to build w/o much knowledge on electricity/circuits.

BELOW is the current/iteration set-up w/o battery and PV cell

My first iteration of this prototype came from the plans found here and after asking a question on this board about running the PV cell directly to the pump was met with some frustration by both myself and the user who was trying to help (to which, if you are reading this; I apologize for not having the information you needed at the time but after much work, I think I have the required info!).

The voltage put out by the PV cells is fine, but due to the current needed to kick over the pump, I would have needed several PV cells in parallel just to get it started which then would run the pump at an unnecessary current (nominal voltage) and would have issues running on cloudy/low light days. So I ditched possibility of adding a few (3-7) thousand microFarad capacitors in-line; I would try something else...

The current iteration is to have a single, rechargeable AAA (open to ideas) run the 4.8VDC vacuum pump (open to ideas) while being trickle charged by a PV cell (one of the following below):

60mm x 80mm:   SUN - 1.5V @ 0.246A ~ Indoor - 0.9V @ 0.0015A
136mm x 110mm: SUN - 6.8V @ 0.21A ~ Indoor - 4.8V @ 0.0012A
130mm x 150mm: SUN - 5.5V @ 0.375A ~ Indoor - 4.1V @ 0.0025A

I have soldered a 1N914 blocking diode inline with each positive wire from the PV cells above and all work properly. The circuit diagram I was trying to follow can be found here and the schematic is below:

Ultimately I am replacing the 1300mAh battery with a smaller one to keep the project simple enough and keep the pump running at a slower, steady rate. The pump I am using can be found here.

So I soldered two additional leads to a AAA battery clip and put in the rechargeable NiMH AAA 1.2V @ 850mAh (See Below)

This battery runs the pump at right around the speed I want it to, but I have no way of knowing if the solar cell is trickle charging the battery, let alone which of the aforementioned solar cells would be the best to hook up to the extra leads to the battery terminal.

At this point, I am at a stalemate with my electronics & engineering knowledge. I will take suggestions, constructive criticisms, ideas, etc. on how to get this project up and running efficiently. Keep in mind I am hoping for the simplest setup for students with very little electronics knowledge, but I am more than happy and willing to go the extra mile for them in doing any pre-PCB building/soldering if necessary. Your help and guidance is greatly appreciated!


texts:
I am currently getting into the topic of electric vehicles and I often come across the terms link voltage and link capacitor.

simulate this circuit – Schematic created using CircuitLab

As far as I know is that the fully charged battery must not be switched suddendly to the system (AC/DC and Motor) because of the link capacitor. The high inrush current could damage this capacitor and the link voltage should be raised steadily using a pre-charge switch which is in series to a pre-charge resistor.
After pre-charging the intermediate curcuit, the main switch (without the pre-charge resistor) of the battery can be closed. Therfore without power loss.

First of all I don't know to which component this capacitor belongs. Is it built in the AC/DC converter? If so why is it needed?
Or is it just because of the capacitive behavior of the cable?

Where do the terms link voltage/capacitor belong to? To the field of power electronics?
Could someone plase give me more information on the terms link voltage and link capacitor regarding charging and discharging of the battery system?
How long does it usually take to load the capacitor and what are the damages that could happen if no pre-charging happens?
Does the link voltage has to be the same as the current battery voltage?
Where do you measure the link voltage? Across the link capacitor?

Are there any online materials or books available you can recommend?


texts: charging 24v LiFePO4 with DC power supply intended for LED strip lights

texts:
I want to charge my 200Ah, 8 cell GBS LiFePO4 using my Honda 2000 watt generator.  (I live on a boat). I have a BMS, active monitoring and all that.  I just want to make sure the below power supply is capable of  charging my batteries.  FYI. I have 1Kw of solar that does the job most of the time, but sometimes you just need dinosaur bones to get you some amps ;-) I have a small 5 amp charger that I can use from my Honda now, but I would rather get 2 x the 24v 33a units below and get the job done fast with a minimum of generator noise in my life.  It would also serve as an emergency power for my 2000w anchor witch, IE if the battery's reach LVD I NEED to be able to get my anchor up!  Thanks for your help, I mostly ask because I am remote, and the below unit is what is available to me.

https://www.ebay.com/itm/AC-110V-220V-TO-DC-5V-12V-24V-2A-10A-15A-20A-40A-60A-Switch-Power-Supply-Adapter/151928719853?hash=item235fa849ed:m:mGHQzsM2zsbvEUasc4rRv6Q:rk:7:pf:0


texts: How would I measure an Ultracapacitor's Specific Capacitance using a PGSTAT128N?

texts:
I am building a capacitor using nanomaterial grown on a substrate. We are trying to figure out what our test fixture configuration should be when doing Cyclic Voltammetry on the cell. Our group would ideally like to use a two-electrode configuration, but we believe the potentiostat is only capable of doing three electrode measurements. Our goal is to get reliable and comparable results.

An article about standardizing the capacitance measurements called "Best practice methods for determining an electrode material’s performance for
ultracapacitors" says that the three electrode setup is flawed:

  In a symmetrical two-electrode cell, the potential
  differences applied to each electrode are equal to each other and
  are one-half of the values shown on the X-axis of the CV chart.
  Therefore, for a given potential range on the X-axis of the CV,
  the working electrode of a three-electrode cell has twice the
  potential range applied as is applied to the electrodes in a twoelectrode
  cell and this results in a doubling of the calculated
  capacitance...

The article goes on to listing a few other reasons not to use it. Given this limitation, and our desire to use a two electrode set up, is there a way to do a two-electrode setup on our machine? The setup would like the one below:

We have been told that we can create a two-electrode system by attaching both our counter and reference onto one plate, and the working onto the other, that we would essentially have a two electrode setup. Our concern is that this would only apply voltage to one electrode, and not the other.

Is our concern valid? Can someone clarify the mechanics here for us or explain how to achieve our desired setup?


texts: Very long battery life with rechargeable lithium ion batteries

texts:
I'm building a device with a battery life of at least one year. The options are to use alkaline batteries or lithium ion (with appropriate capacity). I suppose the self-discharge of both batteries is small enough for this use. The lithium ion battery lifetime is usually measured in cycles, however I suppose in this case the shelf/calendar life is the limiting factor. I've tried searching some shelf life numbers for lithium ion, but it seems the value is 1-10 years depending on the source, also I haven't found any datasheets stating the shelf life (searched for some Samsung, Panasonic and LG 18650 cell datasheets as a reference).

How/where could one estimate/find performance of the lithium ion battery in this case?

The main reason to use a lithium ion battery in this device is that it can be slim compared to for example AAA batteries. However I cannot even come up with any commercial device (for comparison) that would have such battery life with a lithium ion battery. The batteries and required charging chips are rather unexpensive in my opinion. Now that I think of it, I haven't been able to find reliable source for the self-discharge either, some sources state ~2% and some 10% and the datasheets state nothing.

Why would one not make a device with one year battery life using lithium ion batteries? Is the reason perhaps the combination of vague shelf life, vague self-discharge and slightly higher cost?
Is there any research on how much battery life a device with a non-rechargeable battery should have from the usability point of view? (slightly unrelated)


texts: My first arduino project: what parts do I need to create the simplest vehicle?

texts:
This is my first time in this electronics stackoverflow forum, and I´ve been reading about arduinco since some time now. And I just love the possibility to build a little robot.

I´ve done nothing with robots before, so, this would be my very first time trying something like this.

Is is relatively easy (aka "do-able") to do a robot with Arduino for a completely begginer in electronics?

I want to do something like this as a hobby, and I don´t know what parts would I need to create a little vehicle.

I´ve read that there are several arduino versions out there, and I don´t know what to choose and why.

Any thoughts on this? Any starting point?

Thanks!!


texts: 8th order butterworth frequency response

texts:
Ok I'm sure people are getting tired of seeing my filter questions but here's another one.  With my new understanding of 2nd order Butterworth filter design I set out to try to design an 8th order.   I made a big excel sheet that helped calculate all the values I'd need for each stage and verified that they were all produced the same frequency and the appropriate Q for the stage.   The Q of the last stage is pretty high according to the table at about 2.5.

Anyway I got a high output bump in my filter response after that last stage.  Is that what's expected or have I done something wrong?  If I turn down the Q of the last stage I can dial the bump down.

Here's what it looks like.   I tried searching for pictures but most of what I found looks like the ideal response.

The plot below shows the response for each stage on top of one another.


texts:
Suppose I have an improper transfer function, for example:

\$T(s)=\frac{s^2+1}{s+2}\$

I know that this transfer function is unrealizable. Moreover, I have seen that to make it realizable it is possible to make an approximation by adding a pole at high frequencies, so it becomes realizable.

Why if I add a pole at high frequencies to an improper transfer function it becomes realizable?


texts: Solving a source free series RLC circuit

texts:
How do I proceed to solve this problem. If I write a KVL equation, I get
$$4 (4 Vc)  +1/10^-3  integral i dt - 10=0$$
What to do next?


texts:
i made an water level indicator using IC: ULN2803

  Refer: Easiest water level indicator

It works well when used on glass of water, but when connect to my rooftop tank all the leds slowly diminishes and turns off. I think this has to do with high resistance of the tank water, but i doubt it since it worked well for first few days.

i am not any expert (clearly) so any help is appreciated.


texts: Measuring pulse width with limited components

texts:
I have an impulse train of amplitude 1V with constant pulse width \$\tau\$ and I would like to build a circuit that takes this signal and converts it to a constant DC voltage of value \$\tau\$. I can only use opamps, comparators, resistors, DC power supply, diodes and capacitors. How can I build such a circuit?

I thought about using an integrator but this will not really give me the area under the pulse but rather an antiderivative of the signal I believe.

EDIT : In response to a comment of @pipe, here's what I can tell more about the circuit :

The input impulse train can have a pulse width from [~0 to 300us] that is constant.
Let's say that my expected values for the output voltage is in mV such that 300mV correspond to a pulse width of 300us.


texts: Is it possible to use ESP32, BLE4 or BT 2 and WiFi same time?

texts:
I am planning to use ESP32 module to transfer data using wifi (ESP32 web server AP)to remote PC and also the same time I need BLE to communicate with a mobile app and get some data to eps32.

so I will be needing to use both wifi connection and ble same time
is it possible to use or establish wifi and ble same time (in the loop WIFI data transmission 1st and then BLE date receive)?


texts: Power supplies in series, can you ground the middle leg?

texts:
Let's assume I have two 15V DC power supplies. These power supplies are allowed to be connected in series (per the user's manual).

I have a device that requires a signal from +15V to -15V (motor driver circuit).

Typically, I would put both my power supplies in series, I would then provide 15V (relative to ground) to the motor driver circuit to use as ground. So from potential earth perspective, the motor driver circuit has 0V as its -15V, 15V as its ground, and 30V as its 15V.

However, what would happen if I were to put both of my power supplies in series and then ground (potential earth) the middle leg from image below (i.e. ground negative terminal on power supply 1/positive terminal on power supply 2). Would I need to worry about power supply 2 shorting to potential earth?

I would guess that since each power supply can be used in series, that means the + and - terminals are isolated from ground. Thus, it would be possible to connect the middle leg to ground. This would require that power supply 2 be able to maintain a truly negative voltage relative to potential earth.

Am I correct in this assumption?


texts: Using a P-channel MOSFET as an on/off switch

texts:
The project I want to build is shown below.  I want to operate the P-channel mosfet on and off with variable frequency from 20-100Hz and I choose P-channel to do this so that the +350V will not be present on the load when the control circuit is off.

I want also the high power supply to the mosfet and the load to be separated from the control circuit.

My questions are:

Will this circuit works? please give me suggestions or revisions.
What if the load is disconnected or fails and becomes "open circuited" - will be high voltage present on the drain or will the mosfet still switch on and off in that case?

I am new to electronics.


texts: How should I scale intermodulation products?

texts:
I'm trying to automatically measure the amount of intermodulation based on a broadband spectrum capture(which is averaged over time). There is a given set of reasonably narrowband carrier waves, which are always present. If there's a non-linearity in the RF-path, such as a rusty bolt(which is basically a point contact diode) or an amplifier that's over/under driven, these will produce a set of intermodulation products.

So far, I've managed to automatically calculate the composite second order(CSO) and composite trible beat(CTB) frequencies. The thing is: a lot of CSO/CTB frequencies are exactly the same. So there are e.g. 10 CSO products at 622.25 MHz and 2 CTB products at 623 MHz. But that means they scale differently.

My idea to detect intermodulation is to numerically integrate the received power in a very narrow bandwidth around the precalculated CSO/CTB frequencies and try to find some thresholds for the result of that integral.

My question is: how should I scale n CSO/CTB-products that come together in a single point? Should I just subtract 10*log_10(n) dB from that datapoint? Should I also include scaling for the binomial coefficients of the CSO/CTB products?

Side question: are typical nonlinear distortions very frequency dependent? If yes, I would imagine that scaling for the number of products won't be very significant.


texts: Transceiver Supply isolation with Transformer

texts:
I need to supply the Vcc2 for 2 different transceivers, one for the CAN-BUS, like the ISO1042-Q1 that have a Vcc2 of 5V, and another one (not yet defined) with a Vcc2 of 3.3V.

On my PCB I have both the 5Vdc and the 3Vdc (used for supplying other ic) and I can't use other dc/dc isolated converter for the Vcc2. I must, therefore, use and isolate the two existing voltages.
For this purpose I think that I can use, for isolating both the voltages, only one power isolation transformer like this from Coilcraft:

but I'm not sure and I'm a little confused about how I can wiring the transformer for isolating both the voltages.

Referring to the schematic of the transformer, can I wire the 5V at pin 4 and the 3.3V at pin 2 of the transformer with pin 3 and pin 1 connected to their respective digital ground and connect the Vcc2 of the first transceiver at pin 8 and the Vcc2 of the second transceiver at pin 6 (with pin 7 and 5 of the transformer connected to their respective GND)?

Does everything work with the two Vcc2 correctly isolated (even among them) or am I wrong?

The transformer datasheet is here.


texts: Use of free() in PIC Microcontroller Programming

texts:
In my Microcontroller PIC18f4550 code, I am using a function which returns an array, I know, C doesn't allow to return an array so I am just returning the address using pointers. Now after the address is returned and performing some action on them, I am freeing the address value I stored in the pointer variable so that the function can be called again and new array address can be passed.

My code(Just to explain):-

int *a,ans[5];

while(1)
{
a=returnarray();
for(j=1;j<5;j++)
       {
          ans[j]=*(a+j);
       }
free(a);
}

My problem:-

I am using MPLABX with XC8 compiler and I am getting error shown on the free() statement, so is there a substitute for this function that I can use here or is there any other way I can perform this task.

Thank you.


texts: Easier ultrasonic distance measurement technique

texts:
In ultrasonic distance measurement a train of pulses is sent using typically a 40Khz piezo transducer. After some time the same piezo transducer is used to receive the pulses and distance calculated by Time Of Flight.
https://www.jtaibwing.com/index.php?main_page=product_info&products_id=367861
The pulses are generally created by MAX232 to generate a high voltage of 10V needed to generate pulses of sufficient intensity
I was wondering if just 1 pulse could be used. Instead of 10V, we could use say 20V to generate a single pulse. On way back, just detect that 1 pulse.


texts: Arduino board not detected when connected via USB

texts: I have an Arduino clone called the InduinoX. It works with my mother's laptops and I can program it, but in my other laptop it goes undetected. It's last uploaded program works when connected though.Both run Windows 7. Please help since. It worked before but stopped working with it abruptly.( In the IDE it asks me to go to tools and select serial port but it is grayed out)


texts: Why is MOSFET transistor not off when Gate Voltage at 0V

texts:
I am using transistor NXP PSMNOR9
http://www.nxp.com/documents/data_sheet/PSMN0R9-25YLC.pdf

and I have it in an OR power controller circuit using a TI TPS2413
http://www.ti.com/lit/ds/symlink/tps2413.pdf - Page 18

When I apply 5V to the source and have the gate grounded then I am getting 4.5V on the drain.

I also have the transistor by itself simply hooked up to a power supply with 5V on the Source and ground on the Gate and the Drain is at 4.5V.

My prototype PCB works the way that we intended, but we wanted to add a way to drop out one of the multiple power supplies by forcing the gate low. This looks like it will still work by doing this. However, I was under the impression that bringing the gate voltage to 0V would thus bring the drain to 0V.

I understand this is an unconventional use of a MOSFET, and I can not find any information on why it is performing this way in this use.


texts: Range of Holes Flow in pn junction diode

texts:
Lets suppose we have a pn junction diode made of silicon. When it is forward biased we say depletion region shrinks because electrons in the n-region are pushed towards the junction resulting in the decrease of width of positive charges layer also these electrons cross the junction and current starts flowing from n-type to p-type(electron`s flow) and the holes move opposite to the electrons flow, giving the direction of conventional current. There are no holes in the n-type and the electrons are essentially free electrons(in result of pentavent dopping)  that exist in conduction band and go to p-type to fill holes and do not leave any hole behind them because they are not coming from a bond but are free electrons.

Holes move opposite to electrons but upto which point inside the diode? How the holes could go into the n-type material? Would they move opposite to electrons and remain only in the p-type and stops near the junction and new electrons are injected into the p-type and process continues.


texts: Digital Alarm Clock in Multisim. (Home Work/ Final)

texts:
I apologize for the schematic. I know it is not the prettiest to look at. My clock runs slow. I know this is because of my 555 timer. I was off somewhere in my calculations and ended up with a 70hz frequency rather than the 60 target. I will revisit that later. My issue is that I have added in comparators trying to simulate an alarm clock. ( I intend to make better with a rotary BCD setup later but for now I was making sure that it would work.)
The problem:
 I can set any BCD value in to match the clock. Voltage will prove that A0 and B0 are equal, so on and so forth all the way through, however no signal ever makes it through the comparator. Any of them. I am stumped. Is it me or the comparator. Am I not set up correctly? The goal is to light the probe when the BCD switches match the clock. There are no pins to power or ground the comparator in the simmulated version. Any help is greatly appreciated.


texts: Why is it not possible to continuously run a 7W LED bulb alone using a computer UPS? When I tried, the UPS went off after every minute.


texts:
I am wanting to create an amplified speaker system with a subwoofer.

I am fairly new to electronics and this is complicated for me so please be as descriptive as possible and patient with me. The internet has been my guide, so some of my knowledge may be incorrect. Any additional information required I am happy to provide.

I am understanding most of the amplifier circuitry and am following
this tutorial on creating it for the correct components.

Edit: Now using D class thanks to user110971 recommendation

I was wanting to use this subwoofer that takes to a max power input of 100W, as stated on the document.

My issue is finding/building a DC voltage regulator that will suit this speaker using a standard Australian 240V power socket. It would be best if someone could direct me towards a pre-made regulator if possible as I don't want to breach any government regulations.

Part of my problem is that I am unsure of how to obtain the correct voltage/ampage from the watts required. (FYI I know about the W=I*V formula, just cant see a way of solving my issue with it as I only have W)

Any links to tutorials providing an overview of building regulators or constructing an entire amplifier including regulator would be much appreciated. Even giving me directions to general electronics books that I can obtain would be helpful.

Thanks,

BFB

Edit:

Many thanks to user110971, Justme and Swedgin for thier help on my issue.

A quick recap of the solution for anyone wondering the same (I wish more people would do this XD)

As outlined by user110971 I needed to use a D class amp for such high wattage as 'the transistor would melt'.

Again, user110971 provided feedback on using the SMPS (Switching Mode Power Supply) as a voltage regulator.

Justme clarified my misunderstanding of the speakers power draw (Its 50W)

Swedgin provided me with useful links I recommend checking as well as alterations to the circuit to improve its performance.

Thanks all for the quick and helpful support!!!

BFB


texts: How does a multimeter convert voltage/current to a numerical value?

texts:
Just wondering... How does a digital multimeter work ? How can it convert a voltage, a current or a resistance to a numerical value ? I guess there is some programmable chip inside, but how does this chip give a specific value to a voltage ?

For example, my arduino is capable of giving a value between 0 and 1023 to a voltage applied to one of its analog inputs. How is this implemented ?


texts: Should I use a buffer or a simple output with a signal?

texts:
When I implement a clock divider, I often wonder whether I shold use a buffer or a regular output with a signal. Consider the following codes :

Option 1 - Output with signal

library ieee;
use ieee.std_logic_1164.all;

entity divider is
port (Clock : in bit;
      OutputFreq : out bit);
end divider;

architecture behave of divider is
signal Counter : integer range 0 to 155;
signal CurrentState : bit;
begin
process(Clock)
begin

if Clock'event and Clock = '1' then
    if Counter < 155 then
        Counter <= Counter + 1;
    else
        Counter <= 0;
        CurrentState <= not CurrentState;
    end if;
end if;

OutputFreq <= CurrentState;
end process;
end behave;

Option 2 - Buffer

library ieee;
use ieee.std_logic_1164.all;

entity divider is
port (Clock : in bit;
      OutputFreq : buffer bit);
end divider;

architecture behave of divider is
signal Counter : integer range 0 to 155;
begin
process(Clock)
begin

if Clock'event and Clock = '1' then
    if Counter < 155 then
        Counter <= Counter + 1;
    else
        Counter <= 0;
        OutputFreq <= not OutputFreq;
    end if;
end if;

end process;
end behave;

Both of these codes produce the exact same output. So, which one I should use and why?


texts: How to power an attiny from a solar panel?

texts: I'm using an attiny microprocessor that uses around 6mA plus another 3mA for the LED. It periodically runs a servo ( Tower 9G ) that according to a few source online draws 120 - 200 mA ( for around 6 seconds ). (200 x 6)/3600 gives me .33 mAh. If I add the two together, I get a draw of 10 mAh a day. Now lets say i had a tiny battery, something like this one. that has 100 mAh. If i then add a solar panel like this that is capable of providing 45 mA in peak sun, It sould ba able to provide more than ample power to keep the battery fully charged indefinely ... are my calculations correct? or am I missing something?


texts: How is it that the induced EMF in an alternator is in quadrature with the main flux?

texts:
Looking at the simplified diagram of an alternator, the flux "linked" with the conductor is maximum at 90, 270 degrees, is also when induced EMF is maximum. So isn't the main flux in phase with the induced EMF, or are my assumptions flawed?
It's important to note that in an alternator, motional EMF is created which depends on the spatial angular displacement between an uniform magnetic field and a conductor perpendicularly placed. A time varying EMF is induced only because the angular displacement is a function of time, not the magnitude of the magnetic field itself.


texts: How do I test a circuit breaker out of the circuit box, and still hooked up to the circuit box?

texts:
I have a digital multimeter, but I'm having the worst of luck testing whether a circuit breaker I have is working properly, or if it is a different issue with the wiring in the circuit box. I first used this video as an instruction, but failed to realize that although the video doesn't say it, it is important to make a distinction between the common lead and positive lead. I almost fried my multimeter. Not wanting to try that again, I figured the best approach would be to turn off the main power, remove the circuit, and test the resistance instead. I can't seem to get a reading at all on the breaker no matter what I do. Can someone provide better instructions?

I know it is a problem with a single circuit (either the breaker or the wiring for that circuit) because all of the other circuits and breakers are functioning properly. This happened after I plugged a light into an outlet, and thought I saw a small spark. Nothing on that circuit is working now.


texts: Is there a simple way to DIY a coaxial male connector?

texts:
I have a 12V power supply that has a female coaxial plug like the one on the right in this image:

I rigged something up with tinfoil just to see if it would work, but it's not ideal at all. Basically, I have two stripped wires that need to connect to the inside and outside of the female plug, respectively. Does anyone know of a trick to do this (DIY) without finding a matching male part?


texts: How charge Ni-Cd battery from cordless drill

texts:
I have a question about charging Ni-Cd battery, if question is stupid or something like that, I'm sorry but I'm only 15 and just starting my adventure with electricity.

I want to build LED flashlight, I found heatsink from old cpu and bought dc-dc boost module to change voltage and now I only need battery, I can't afford to buy 3s lipo battery pack because it also requires special charger which costs much.

So I found old cordless drill, drill is broken so I took battery pack from it and disassemble this battery, inside I found 15x1,2V some ooooold cells but every cell looks fine, I measured voltage on each cell and thats what I got: 1,2V 1,21V 0,4V 0,2V 0,2V 0,2V 1,02V 1,13V 1,11V 0,2V 0,8V 1,02V 1,15V and two 0V cells each cell has 1200mAh

Which one can I use to build working battery pack ? And how can I charge this battery pack ? I found in google how to charge Ni-Cd battery using power adapter and 2x resistor and diode but I can't work out which resistors and diode use to charge it safely.

I want to use this battery to build LED flashlight and LED I want to use is 30W 32-34V 900mAh

Any help will be very important for me because as I said I just started my education in this kind of things :)

Thanks a lot !!


texts: Tips for optimizing through-hole soldering

texts:
I make and sell low voltage, mostly digital, retrocomputing expansion boards as a hobby/hustle.  I use all through-hole components partly because of the retro aesthetic and partly because I find soldering through-hole relaxing and fun to do.
I'm selling enough boards now that I'm feeling like my assembly and soldering process should be optimized.  One of the boards has about 30 components on it and if I'm making 10 of them, it can take up a whole Saturday afternoon.
Currently I place a part, flip the board in my hand while holding the part, tack one of its pins with the iron while making sure the part is fully inserted and aligned if necessary, lay the board down and solder the rest of the pins, then move on to the next part.  I am pretty sure this isn't the best way to do this.
Do you have any tips or tool recommendations to help me optimize my board assembly / through-hole soldering process?
Thanks!


texts:
Please excuse my ignorance. I'm an 'old-fashioned' guy who thinks that there is just 'software' and 'hardware' - and these are two separate things. Along this line of thinking an OS is part of the software, and a microkernel is part of the OS. (I'm aware of the debate about Microkernels - and how Linux didn't really end up using one).

I'm also aware you can do fairly amazing things with FPGAs - but perhaps I assumed this was limited to microcode and DSP.

So when I hear the quote:

  Apple is using the L4 kernel ... It's the microkernel in the Secure Enclave

I'm fascinated.

I'm aware that L4 is the microkernel that has been 'proven correct' against its specification. But to me - that is part of the OS. (ie loaded from disk into memory and then instructions are transferred down to the CPU over the Bus.)

My question is: How does part of a microprocessor (Apple secure enclave) use a microkernel (L4)?
(Is this a kind of FPGA? Do they feed it into the part that lays out the transistors and 'embed' the software in silicon?)


texts: MSGEQ7 producing max output for all frequency bands

texts:
I have been following a MSGEQ7 tutorial by J Skoba (http://nuewire.com/info-archive/msgeq7-by-j-skoba/) and have set up my circuit in the exact way he has:

And I'm using his code:
int analogPin = 0; // read from multiplexer using analog input 0
int strobePin = 2; // strobe is attached to digital pin 2
int resetPin = 4; // reset is attached to digital pin 4
int spectrumValue[7]; // to hold a2d values

void setup()
{
 Serial.begin(9600);
 pinMode(analogPin, INPUT);
 pinMode(strobePin, OUTPUT);
 pinMode(resetPin, OUTPUT);
 analogReference(DEFAULT);

 digitalWrite(resetPin, LOW);
 digitalWrite(strobePin, HIGH);

 Serial.println("MSGEQ7 test by J Skoba");
}

void loop()
{
 digitalWrite(resetPin, HIGH);
 digitalWrite(resetPin, LOW);

 for (int i = 0; i < 7; i++)
 {
 digitalWrite(strobePin, LOW);
 delayMicroseconds(30); // to allow the output to settle
 spectrumValue[i] = analogRead(analogPin);

 // comment out/remove the serial stuff to go faster
 // - its just here for show
 if (spectrumValue[i] < 10)
 {
 Serial.print(" ");
 Serial.print(spectrumValue[i]);
 }
 else if (spectrumValue[i] < 100 )
 {
 Serial.print(" ");
 Serial.print(spectrumValue[i]);
 }
 else
 {
 Serial.print(" ");
 Serial.print(spectrumValue[i]);
 }

 digitalWrite(strobePin, HIGH);
 }
 Serial.println();
}

And yet the output of the serial monitor is the max for all frequencies regardless of the input:

I have two of these chips and I have tried both and they both give the same result. I believe that both of these chips are faulty, or have I made some error?


texts: Connecting 100 DC motors (3V) to a battery or mains

texts:
I'm doing an art project in which I want to connect 100 3V motors together to all spin at the same time. I have used junction boxes before for lights and I'm wondering if these could be connected to the mains or even a car battery if mains is not possible?
If I cannot connect 100 then is there a maximum number that I could connect?
Thanks for your advice
Luke


texts: Selecting proper resistance based on tolerance

texts:
I want to replicate a project.
The specification lists several resistances.
But they only specify the value of the resistance.
I went to buy resistances, but they first had me select a tolerance.
These were 0.1%, 1%, and 5%.
Which one should i pick?
Please keep in mind, these are going to be smd resistances (i don't know if that matters).
EDIT:
Here is the picture of the schematic:

Here is a list of the component's values:

There are two other resistors not listed here. They are the voltage divider that will drop 5V to 2.5V, for the Vbias.
Each of these tw oresistors is 1M Ohm.
Operating voltage of the OpAmps (Vbias) is 2.5V (produced by the voltage divider).
EDIT:
I actualy got these components.
They are all Though-Hole components.
In the first part i will name the component in the schematic, and then i will mention the component i bought for that specific component.
Do you think the components i picked will be good enough for this circuit?
R1 and R3: THT 10kΩ 0.4W ±1% Ø1.9x3.7mm 50ppm/° (M0.4W-10K)
R2: THT, 2kΩ, 0.6W, ±1%, Ø2.5x6.8mm, 50ppm/°C (M0.6W-2K)
R4: THT, 36kΩ, 0.6W, ±1%, Ø2.5x6.8mm, 50ppm/°C (M0.6W-36K)
Rbias: THT 100kΩ 0.4W ±1% Ø1.9x3.7mm 50ppm/&deg (M0.4W-100K)
Rdiv1,2: THT, 1MΩ, 0.6W, ±1%, Ø2.5x6.8mm, 50ppm/°C (M0.6W-1M)
---------------
C: Capacitor ceramic, 100pF, 100V, P350-N1000, ±5%, THT, 5mm, -55÷85°C (CCK-100P)
Decoupling capacitors for the 3 ICs: Ceramic Capacitor, 100nF, 100V, Y5V, -20÷+80%, THT, 5mm, -55÷85°C (CCK-100N)