texts: Chaining up 5v LED strips using 5v cellphone chargers

texts:
I want to chain up a very long LED strip to a single source of data. I will be using an ESP8266 and about 15 meters of WS2812b LEDs. With about 30 LEDs per meter, I need to power about 450 of these total. I've read multiple places they're about 60 mAh each, so 60 * 450 = 27A required to run all of these, assuming I want full brightness at red or white (not sure which draws most).

I've experienced that I can (but should not) power about 6 meters (180 LEDs) with a single 2.1A supply, which actually ended up drawing 2.3A (Samsung phone charger). I wrapped the 6 meters around a tube, so I could easily solder some wires from the top to the bottom, so the voltage drop was lower. Every color looked great, but white had a yellow look to them. I know that wasn't suitable at all, but I was simply trying it out.

I'm now trying a different approach, which should work much better. If I for every 3 or 4 meters wire up a wall charger to the strip, can I achieve what I want? This is what I had in mind:

Here's another thing I had in mind, which would help a lot, since I don't have wall outlets every x meters in my house. Can I do something like this instead, if I make sure to use good gauge wires, so they don't lose voltage?:

As a third option, I have a couple of 12v 2A supplies (like the ones above). Can I buy some cheap, alternative hardware, such as voltage regulators, and wire it up in an alternative way?

The question here is not powering the strips. The question is really if chaining the supplies as my first image is possible and what might could go wrong, if I do it that way.


texts: TF-Mini S lidar not sending any serial data

texts:
I have a TF-Mini S Lidar. I have hooked it up to my arduino like so:
(Above image from learn.sparkfun.com)

And have uploaded this code to the arduino board:
#include<SoftwareSerial.h>
// soft serial port header file
SoftwareSerial Serial1(2,3); // define the soft serial port as Serial1, pin2 as RX, and pin3 as TX
/*For Arduino board with multiple serial ports such as DUE board, comment out the above two codes, and directly use Serial1 port*/
int dist;// LiDAR actually measured distance value
int strength;// LiDAR signal strength
int check;// check numerical value storage
int i;
int uart[9];// store data measured by LiDAR
const int HEADER=0x59;// data package frame header
void setup()
{
  Serial.begin(9600);//set the Baud rate of Arduino and computer serial port
  Serial1.begin(115200);//set the Baud rate of LiDAR and Arduino serial port
}
void loop()
{
  if (Serial1.available())//check whether the serial port has data input
  {
    if(Serial1.read()==HEADER)// determine data package frame header 0x59
    {
      uart[0]=HEADER;
      if(Serial1.read()==HEADER)//determine data package frame header 0x59
      {
        uart[1]=HEADER;
        for(i=2;i<9;i++)// store data to array
        {
          uart=Serial1.read();
        }
      check=uart[0]+uart[1]+uart[2]+uart[3]+uart[4]+uart[5]+uart[6]+uart[7];
      if(uart[8]==(check&0xff))// check the received data as per protocols
      {
        dist=uart[2]+uart[3]*256;// calculate distance value
        strength=uart[4]+uart[5]*256;// calculate signal strength value
        Serial.print("dist = ");
        Serial.print(dist);// output LiDAR tests distance value
        Serial.print('\t');
        Serial.print("strength = ");
        Serial.print(strength);// output signal strength value
        Serial.print('\n');
       }
     }
   }
 }
}

(from forum.arduino.cc)
An when I run it, the Lidar shows a laser beam, however no serial data is being sent to the arduino board, and if it is, its just random symbols.
Is there anything i can do to fix this?


texts: What is a Data-to-Segment Delay (MAX7219)

texts: My guess is how long the data takes to be shown as a segment/digit. Is that true? In the datasheet is says 2.35ms but I would need 1ms or below. Is there a faster alternative? Datasheet (Page 3 at the bottom)


texts:
I have a trip in near future, I have a hub dynamo fit to my bicycle which has 6.0 V DC output of 3 Watts power. I have read few posts and realized that it is risky to charge my iPhone directly through the Dynamo hub.

I thought of an alternative, charging cheap AAA batteries (I can afford to lose some AAA batteries due to voltage fluctuation while charging than my iPhone itself!) and somehow charge my iPhone with it.

I need to know how to connect the AAA batteries so that I can charge my iPhone.

An iPhone needs one of the 2 configuration to be charged with:

Slow mode: 5 Volts, 0.5 Amps, 2.5 Watts
Fast mode: 5 Volts, 1.0 Amps, 5 Watts
(Reference: https://discussions.apple.com/docs/DOC-3511)

A AAA battery output is something like this:
1.25 Volt, 300-500 mAh.

Now how do I safely connect the batteries so that I get desired output to safely charge my iPhone?

What best do you suggest?


texts: Mounting Hole Connected to Ground Through Capacitor

texts:
I've inherited several board designs where each of the four [plated through] mounting holes are connected to the board's ground plane through a capacitor [1000pf, 1KV]. I can understand why you might want either mounting holes connected directly to signal ground, or why you might want holes that are totally isolated. But I'm confused about the benefit of a connection to ground through the cap.

While metal hardware is used to install the board, there's no guarantee that the material the board is mounted to will actually be in contact with system ground [or will even be electrically conductive].

Background: the boards are part of a piece of commercial food service equipment. All boards have microcontrollers and handle digital I/O, 24V loads. One board has a configuration where it can drive brushed DC motors.


texts: Designing an amplifier circuit with coupling capacitors

texts:
I am attempting to do the following:

  Design an amplifier circuit consisting of input and output coupling capacitors (\$C_1\$ and \$C_2\$), a voltage source (\$V_s\$), a source resistor (\$r_s\$), an output resistor (\$r_0\$), and load resistor (\$R_L\$). Choose the resistances for input and output resistors of the amplifier, and the source resistor by yourself. Suppose the two sub cutoff frequencies (\$f_1\$ and \$f_2\$) are equal to each other (\$f_1 = f_2\$). The lower cutoff frequency (\$f_L\$) of the overall circuit is 50 Hz. The mid-band gain \$|V_L / V_s|\$ in terms of decibels is 100 dB.

  a. Draw the circuit diagram, label input and output terminals, and show the component values of your design.

I have already designed the circuit in PSpice as shown below, but I'm not getting any output. What am I doing wrong?


texts: System verilog on Quartus synthesis issue

texts:
module blockingbad(input logic clk,a,b,c,output logic y);
    logic x;

    always_ff @(posedge clk) begin
    y=x|c;
    x=a&b;
    end
    endmodule

For the above Sysverilog snippet, the quartus 13.1 synthesizes a netlist shown above.

But when I interchange the ordering of calculation of y and x, I get a synthesized netlist shown below.

Why exactly am I getting a different netlist? I know it has got to do with the blocking assignment "=" but I can't understand the change in number of flip flops. Can anybody explain it to me.
Thanks


texts:
1st sense IR - no relay ON
2nd sense IR - 9 VAC relay ON
3rd sense IR - 12 VAC relay ON

Mean while if operate the switch there is a chance shorting the 9V/12 VAC at transformer?
Relay datasheet:https://datasheetspdf.com/pdf-file/657851/TIANBOGANGLIANELECTRONICS/HJR-3FF-S-Z/1


texts: Control LED strip with MOSFET and PWM Arduino

texts:
I want to control the brightness of my LED strip. In this way, I'm thinking about using a MOSFET N-channel. Can you see what I conceive below :

I want to manage the Id current by shifting the Vg voltage thanks to PWM of Arduino. Can you see below my idea :

May I have your opinion about :

Can I control Id current by shifting PWM on the pin D6 of Arduino MEGA (i.e by controlling Vg)?
I have big trouble to understand MOSFET datasheet, could you help me and explain me which one could I use ?

Thank you for your help !

EDIT

I have added an example of the Vg voltage which is a PWM applied on the GATE.
Could someone says me if :

Does voltage on the GATE of the MOFSET (here Vg) control the current flowing between the DRAIN and the SOURCE ?
If yes, can I control the current flowing through the MOSFET by applying a PWM on the GATE of the MOSFET ?


texts: How do I safely discharge this Trinitron CRT when the HV connector seems glued on?

texts:
I'm trying to discharge a Sony PVM-1353MD which suffered shipping damage. Unfortunately, I am unable to get my tool under the HV connector. It seems bonded to the CRT with some kind of white silicone like material. I tried to pry under both the black and white parts of the cap and can't get under it without damaging it. Most HVs are easy to discharge.

EDIT:
Found this label affixed to the inside cabinet:


texts: 2 LED strips in parallel dimmed with PWM

texts:
If i have 2 LED strips of 10 amps @ 12 volt and I connect them in parallel . Can i run them off a 10 amp transformer if I use a 50% PWM duty cycle ?

I assume that if the PWM is not in sync that the total amps used will be 10 as the 1 strip will be ON while the other is OFF.  But if the PWM is in sync will the total amps be 20 because both is ON and OFF the same time, or does it not matter as amps is a measured Coulomb per second so the total charge moved in 1 second is still 10 amps?


texts:
I am trying to create custom board with WM8960 IC with Raspberry Pi. I am able to use Wolfson drivers for pi to detect the IC via I2C but I am not able to play or record any audio. This is the schematics.

I am able to use Seed Studio Respeaker pi Hat with same drivers but not able to use my custom board. I2C device is indeed detected. So it is not problem with detection. Is there something missing or some pre-settings needs to be done?


texts:
I was looking over a datasheet for the NE555 Timer and I was wondering if the max supply current given under the electrical characteristics page is the max current you can supply to the 555 without damaging the chip.

I ask because it seems like the supply current (for 15V input) is relatively low (10mA) compared to the output current (225mA).

Is the supply current the max current you can put on pin 8 without burning out the chip? If so, why is it so low compared to the output current? If not, how does one find the input current?


texts: Arduino Mega 2560 USB died due to short circuit

texts:
I have found some Arduino tutorials where the voltage regulator died on board:

https://www.instructables.com/id/Fix-a-fried-Arduino-Mega/

However this is not the case for my Arduino Mega 2560.

The Arduino was powered through the 5V pin along with bunch of other sensors. In the meantime it was connected via USB to my laptop sending data through the serial.

Stupid mistake having my multimeter in amp measurement mode I shorted out the 5V line not even on the Ardu but on a sensor but that effectively shorted it for all of them.

After this surprisingly the Arduino perfectly worked kept running the code over restart however I can no longer use the USB port anymore, it does not even show up on the computer like it would not be plugged in.

What I tried:

I tried from both 12V adapter and powering the Arduino through USB (this works fine, I can measure 5V on the V+ in both cases).
I tried it on different laptops. No change.

Did anyone run into similar issue? If so is there any way to fix it?

Thanks


texts: Step Response of Ideal Inductor with Current Source

texts:
I'm taking an electronics course to get a physics minor (I'm an applied math major) and today, the professor shows a diagram of an ideal current source connected to an ideal inductor. Crazy stuff I know.

The problem I'm having is that the book and his lecture notes do not treat the independent current source as an actual independent current source. That is, the current is a function with respect to time t, rather than some numerical value like 1A. Hence it is a dependent current source. (Obviously this was done to make the problem easy and/or solvable.)

Despite the lack of care given for using the appropriate symbols, it made me wonder what the actual response would be for an ideal independent current source connected to an ideal inductor. I am a math major after all.

It's been a semester or two since I took ODEs and PDEs, so my differential equations are a bit fuzzy. But I have a feeling that a Heaviside step function and Laplace transforms are not going to work here.

I would argue that the voltage across the inductor would be indeterminate at the edge of the current step and zero after that. Essentially a discontinuous function that approaches infinity at t=0 and then 0 for t>0.

Obviously this isn't physically realizable, but I was curious how one would go about solving this even if the solution diverges.

So my question. How would you attempt to solve this problem? Heaviside step function and Laplace transform or some other method? Also, what change is needed to make this problem solvable? For instance, would a parallel resistor of some finite value do the trick (so you could convert to a Thevenin equivalent circuit)?


texts: Can AC floating ground be used as a common ground to a DC circuit?

texts:
I'm designing a system that uses a power supply to convert 120V AC current from the wall socket to 12V DC current. I'm looking at a Jameco SP-240-12.

Originally I thought pins 4 and 5 output negative DC current, meaning I would have to ground my circuit elsewhere. After seeing the datasheet though, I realized that DC- are grounding points.

But that got me thinking, from my understanding no current runs through the floating ground normally and it is just there as a safety feature. Is it possible that I could have used pin 3 and grounded DC current on an AC floating ground?

Edit: Originally I was unclear, I was asking if I can ground my DC devices to pin 3, even though it gets connected to the "frame ground" of an AC plug, like shown in the image below:


texts: Standard form of 2nd order transfer function (Laplace transform)?

texts:
Say I had a 2nd order system such as:
\begin{equation}
A \dfrac{d^2y(t)}{dt^2} + B \dfrac{dy(t)}{dt} + C y(t) = D \ x(t)
\end{equation}
Dividing both sides by A:
\begin{equation}
\dfrac{d^2y(t)}{dt^2} + 2 \zeta \omega_0 \dfrac{dy(t)}{dt} + \omega_0^2 \ y(t) = \dfrac{D}{A} \ x(t)
\end{equation}
Hence, the transfer function is:
\begin{equation}
H(s) = \dfrac{\dfrac{D}{A}}{s^2 + 2 \zeta \omega_0 s + \omega_0^2}
\end{equation}
But I read some texts and they all list the standard form of the transfer function for a second-order system as:
\begin{equation}
H(s) = \dfrac{\omega_0^2}{s^2 + 2 \zeta \omega_0 s + \omega_0^2}
\end{equation}
Why is this? Thank you.


texts:
I currently have a project requiring the use of a battery. My project has to be able to run off the battery power, but when an outside source is connected, the battery should be able to charge off this source, but the source also has to power my project.

I am looking into using an SLA battery such as this one, because in my lack of experience, it seems to be easier to deal with charging than a battery such as a LiPo battery. Since this is the point in which a screw up could result in a destruction of my project, and I am inexperienced in the area of batteries and charging beyond the basics of electronics, I would like an outside opinion from someone knowledgeable in this area, to let me know if it would work or not.

I attached an image of what I think the layout of my charging system would be. The battery would have the ground connection for the project, and the 12V connection. The relay would go on the ground side of the battery, after the connection to the project. This way, the battery can charge/discharge according to the relay. The voltage monitor would determine when the relay needs to be on or off. The relay and voltage monitor would have connections to the Arduino Nano, acting as the controller for the charger. The Nano would supply 5 volts to the voltage monitor. Also, the Arduino Nano is powered from the same charger, via an inline voltage regulator.

Essentially my question is: Will this work before I go and do it and mess something up? Or is there possibly a better way of doing this?

Voltage Monitor

Charger

Regulator to Power Nano


texts: What is the purpose of the capacitor in this circuit?

texts: Is the purpose of the capacitor, C1, to filter out any possible DC component that the input signal has?


texts:
I usually work with breadboards, but I wanted to use the P2110B from Powercast, and since I couldn't find any breakout boards for it and desperately needed some experience with schematics and PCBs, I decided to make my first design in hopes of turning it into a PCB.
The part that scares me about PCBs is that with breadboard if it doesn't work I can just try again, but once you order a PCB that doesn't work that's it. So I wanted to make sure that this KiCad schematic was okay before I did anything else.
(Furthermore, I am sorry if I have not used proper conventions while making this schematic, it is my first time and I tried to the best of my ability).

I made sure that it passed KiCad's electrical tests, so I'll go by and explain what i was attempting:

The goal of this is to catch RF signals using an antenna and convert them to 5V DC which would be sent through a USB A port.
The documentation stated how the output current could be increased from 3.3V to 5.5V by applying a resistor of a calculated amount from VSET to GND. The value I got for a 5V output was 720k. (I added a 5V regulator just in case.)
The documentation also specified a capacitor was required on the VCAP pin to determine the charging and operation cycles of VOUT. I calculated that for an ON period of around ~7 seconds with 5V and 50mA, a 10F supercapacitor was required.
Lastly, there is an SMA connector near RFIN for the RF supply.

I hope that with that you can make sense of what is most likely a very poor schematic, like stated do go easy on me, this is my first ever attempt at a PCB. I thought I'd start off with something I actually wanted and was also a bit easy.


texts: I'm in the process of making a JK arbitrary sequence counter and I'm now making the k maps to get a logic equation. I was just wondering if this is allowed (looping the bits around the middle bit) as I've not seen it in any textbooks or in videos, but I know that you're only meant to highlight 2,4,8 etc bits. Also, if this is allowed, is the logic equation below correct?


texts: Linear useage of excess power generation

texts:
A friend of mine is fortunate to have moved to a very warm and sunny country, and has installed a photovoltaic system on his property. This is grid tied and any excess that he generates flows into the grid. Whilst this is a great system his only choice of electricity suppliers have taken it up on themselves (or between themselves) to now start charging for any excess power that is generated and goes into the grid. They have now changed all the meters and it now seems that the undesired solution to avoid these charges, is to disconnect the photovoltaic system and run it separately. Obviously this would be annoying as he’d like all his excess power to be available to all his appliances in the home, at any time there is any excess power, and for them to use this rather than power from the grid.

In trying to figure a solution we have worked out a way to measure the power flow by monitoring voltage and current at the grid injection point and doing some maths within an mcu (picaxe) to work out if power is being imported or exported using a CT sensor and AC transformer.

The problem lies with how we control the useage of excess power. We have figured out a way of doing it ‘digitally’ where we have excess generation of say 40w we use the mcu to turn on a 40w bulb. If the excess increases we can turn on say more bulbs or a heater etc.  So If we had a range of appliances at various wattages 100w, 200w, 400w , 800w etc  we could utilise the excess energy by turning on the appliances to match the excess, e.g if we had a 600w excess we could turn on the 400w and 200w device.

This seems a bit of a ham fisted way of doing things, meaning we would be turning things on we didn’t necessarily need and also if we were generating an excess of less than 100w it would go back into the grid. (I realise we could go down to 1w using the same idea) but ideally I’m trying to figure out a more elegant solution. We have looked at using a triac to chop the waveform but it looks like this may upset the smart meters that the utility companies have fitted, and possibly alert them and change the charges to suit. I don’t think we are doing anything wrong as it is only the same as someone reading the power reading and responding by turning something on to prevent power flowing into the grid, we just want to be able automate that process. Therefore the question we have is how to ‘linearly’ utilise the excess power to ensure minimal injection back into the grid? Is there an easy way to do this? Do things such as 1kw voltage controlled variable resistors exist? ;) Ultimately we are trying to waste any excess power as closely as possible until the electric companies change their tariffs to be fair and make sense.

Cheers.


texts: Why does my voltage (reduced with a voltage divider) drop to zero when connected to a 6V DC motor?

texts:
I have the following setup with a voltage divider that steps-down a voltage from 7V to around 6V, so I can plug it into a DC motor.

simulate this circuit – Schematic created using CircuitLab
When I measure the voltage across the point A and B with my voltmeter, I get around 5,95V, but as soon as I plug my 6V DC motor across those same points, my previous voltage of 5,95V seemingly disappear and I can't understand why.
PS: I also tried to replace the LiPo and the XL6009E1 voltage regulator with my power supply  at 7V but I get the same result.


texts: Why the MCU gets too hot when I plug it in to the USB?

texts:
EDIT1: There is nothing connected to the board.

EDIT2: The board works but I don't know why it gets too hot.

I'm testing my new board MSP432P401R LaunchPad Rev 1.0 (black) from Texas Instruments. I've read some of its datasheet, I've downloaded Energia IDE (it's a copy of the Arduino IDE) and the Code Composer Studio. It's a great board but I'm very surprised because it gets too hot when I connect it to the USB port.

Viewing its datasheet in the Features section (page 1) in Operating Characteristics, its voltage range goes from 1.62 to 3.7V. So I think that the USB provides it more than 3.7V but I'm disconcerted because the board has some pins to plug in 5V. It's a board designed to consume less power but it produces a lot of heat, is it not contradictory? Why the MCU gets too hot? Is it damaged?

Thanks anyway


texts: Micro-Controller Operating System with GUI

texts:
I'm looking for embedded OS for w micro-controller, it's not clear until now for me what'll be  the controller type, but my first priority is to found an OS with GUI can be written in C# or any .NET family or JAVA. I found some good operating system like:
emWIN, easyGUI, PEG
but all of them could be customized in C++, Any help please about same OSs but not in C++.

and due to I'm new in embedded systems developing and until now not clear with the main structure, is it possible to let developers create applications and install it on my embedded system or the main structure only allow to customize the software and burn it to micro-controller, or in other words.. in advanced mood. Can I create SDKs for my embedded system or the only way to create a software on an embedded system is to customize my OS with my applications and burn it.. Thanks and sorry if am not clear with that field but am trying to collect a lot about it.


texts:
Anyone know what these switches are. More importantly where I can find a replacement. As you can see one is smashed.

They are 4mm wide by 2mm by 2mm.

Thanks.


texts:
I have a project that has 14 DC motors, 8 of them have 6A nominal current the rest requires 5A. I'm thinking of using 12 LiPo batteries each 5000mAh, 30C~40C, connected in parallel so that total I'd have 60A.

My question is, can the batteries handle all of these motors? I'd like them to run at least 1 hour without any problem. Do you have any suggestions?

Thanks!


texts:
I'm currently working for a company where I design and implement an automated test program to test our products. Currently our tests take quite a bit of time (several minutes per unit) and need to optimize it in the future as the volume will increase (1000+). The tests take that long as the product is quite advanced with many feature that needs time to be evaluated properly (GSM/3G/GPS/Battery charging etc).

We use a PC application that loads the a special test firmware into the device and performs various measurements; While the test firmware communicates with and tests all on board chips and their functionary one step at a time as the PC application controls it via a USB terminal interface.

Our current thoughts are to:

Have test pads underneath the boards so that the operator doesn't need to plug in/out any cables during the PCB test. Just place it on a bed of needles
Perhaps parallelize the system to test several objects at a time

Me and the others at our company are not very familiar with how to do things other than low--volume tests.
So I ask for advice from you experience people on what the proper way to do medium/high-volume tests of a fairly complex product?

Thanks for your time,
Kind regards


texts: Are the stock transistor models in LTspice accurate at RF?

texts: Just checking, I'm doing some experimenting of small signal RF design in LTspice.


texts:
As part of a project I'm trying to prevent WiFi transmission of frequency 2.4 GHz from reaching a Raspberry Pi via a Faraday cage.

Would a 20 micron aluminum foil do the job?


texts: MCU powered from the same PSU as a LED strip

texts:
I want to make a simple controller of WS2812B addressable LED strip. I will consist of a MCU (most likely Atmega328P), a couple of buttons (RESET and mode selection) and 7-segment indicator, which will show current illumination mode. Power to the strip will be delivered by a N-channel MOSFET, which gate is also driven by MCU. Max length of the strip is 4 meters, I plan to use 30 leds per meter strip, so maximum current consumption is 6A (1.5A per meter). Since this current is only required if all LEDs are white at full brightness (which I don't plan), i'll use a Mean Well 5V@5A PSU. I think even 5A will never be reached in any application.

Main question is, is it OK? Or do I need to use secondary small PSU for microcontroller? This I'd like to avoid, of course. MCU together with indicator would draw no more than 150 mA.

Another question is, is it OK to use only two large value capacitors (470 uF), one at the input of power, another at strip output? Do I need a separate small ceramic capacitor close to Atmega pins? It's no problem to add, but I'm not sure if it's required: the board is really small, and distance between input 470 uF capacitor and 5V input pin is just 6-8 mm.

Third question is, do I need a fuse on the board? If yes, how to choose it's value properly?
Below is my simplified schematic (7-segment indicator and buttons are omitted):

simulate this circuit – Schematic created using CircuitLab


texts: Trying to design a switchable LED circuit with no experience or skill - please send help - PART 2: I set a transistor on fire, please send more help

texts:
following on from my previous question:
Trying to design a switchable LED circuit with no experience or skill - please send help
I have an update - a mix of good and bad news...
Good news is the LEDs and correct driver arrived. Soldering went pretty well considering I haven't done that since high school, but a you tube tutorial and some trial and error got me there. Further good news, the driver works - I soldered an LED to just the driver with none of the micro-controller stuff and it worked fine. Pleasingly when the driver was plugged into the mains and the LED circuit wasn't closed, nothing happened and the driver didn't catch fire which makes me think a suitable 'on-off' logic switch should deliver the desired circuit I'm trying to build.
I also validated the python code and circuit with some normal LED pins and PNP S85550 transistors and it worked perfectly. I've pasted in a rough schematic of that validation circuit below:

So with all GPIO outputs set to LOW - nothing happened, and then using a python script I could selectively turn on one of the LEDs for a defined period of time and then the program ended, which is exactly what I want for now.
So then I tried to validate whether the external driver would work the same way using this circuit and just one LED to start:

As you can probably guess from the title of this post - this didn't go so well. These were the following issues:

The driver had 3 pins rather than 2 which I wasn't expecting - I just ignored the middle pin and it seemed to work anyway so that was fine.

when I connected everything together, the LED wasn't lit, but it was flickering a lot faintly (this is withthe GPIO set to LOW). I ran the script to see what would happen, and basically nothing it just stayed the same. When I disconnected the GPIO the light turned off so it seems that some current is still flowing through the transistor, regardless of if the GPIO being high or low.

I had read that if the LED was flickering I might have the polarity the wrong way round - so I swapped the positions of the collector and the emitter cables to see what would happen...

The transistor started smoking almost immediately so I pulled out a cable and got it to stop - I can't even remember if the LED lit up or not because I was busy panicking.
Fortunately the RPi is still alive and doesn't seem to have sustained any damage - the transistor is more than likely dead so I've thrown that away.
In summary:

I'm starting to wonder if BJTs are going to work, maybe I need relays or MOSFETs? Relays look ideal for this scenario (I think) but I was getting confused because they seem to be for much higher Watt circuits than what the LED driver is providing?

maybe the problem is also that the current needs somewhere else to go if none of the LEDs are on? it is important that this system has an 'off state' in which none of the LEDs are lit (the application is for a UV-Vis spectrometer + fluorimeter)

Thanks again for any help and happy to provide more info on request!


texts:
There are a number of materials on the market that help with soldering, prevent oxidation. someone says flux, someone says soldering paste also someone says flux and soldering paste are same.

Frankly, I'm confused.

I also bought 4 different products that I saw in the market. Some are creamy, some are completely liquid. I can use the cream ones in some way, when I pour the liquid ones on the circuit, it flows and gone. I do not know exactly where and how these products are used.

Please tell me where to use each product and what is the benefit.

These are fluxes and soldering pastes:

SR 33 No Clean Flux: Liquid

ASR 41 Flux: Resinous and Liquid

AMTECH: Creamy

Purine: creamy

in side photo


texts:
So I'm making a simple circuit using a transistor as a switch, I've made these a bunch of times before without any sort of issue but for some reason this time it just doesn't seem to work at all.

I've never used this FZT651 transistor before, datasheet is here.  In place of R1 I've used both a 3k resistor and a 510R resistor, measuring B-E I get 0.7V. If I measure between 5V and the collector I don't measure any voltage.

Is there something strange about the transistor I'm using? I don't have any other NPN's to hand but I'm planning to get some 2N3904 and see if they work because from what I've got here I can't seem to see what the problem is.

simulate this circuit – Schematic created using CircuitLab


texts:
In my design I am using a USB2517i USB 2.0 Hi-Speed 7-Port Hub Controller and I am following the microchip reference schematic with the default settings.

I am trying to interface the USB hub with imx6q(NXP) processor board that running Yocto 4.15 kernel. The thing is the processor board is not recognizing the USB hub.

The block diagram representation is shown below. also i am enclosing our schematic design.Schematic for USB HUB


texts: Arduino / Love-O-Meter : wrong temperature read when LEDs are on

texts:
I tried the Love-O-Meter example given in the Startup kit of Arduino. The example is available here. The temperature sensor is the TMP36 given with the kit.

If the three LEDs are off (e.g. when writing LOW in the code, comment the corresponding lines or unplug them), there is no problem: the real temperature in the room is given and the sensor gives a value around 150.

However, if one or more LEDs are on, then the temperature increases to around 10°C for each LED (the sensor gives 215 when the three LEDS are on).

The conversion from the sensor value to the temperature works well. Also, I measure a correct voltage by using a multimeter.

Any idea?


texts: Is there a set of standard symbols for connectors / wires / protocols?

texts:
I am attempting to convey via a diagram how a number of devices are to be connected.

In this specific problem:

A cable connects to the Queuing Controller via an RJ11 connector
The other side of the cable connects to WallSocket adapter through an RJ12 connector (it's a custom-built cable)
The Lane Light system connects to WallSocket Adapter via an RJ45 connector, using a CAT-5 cable. Messages are sent along this cable using the RS-485 protocol.

My drawing tool is Visio, and so far I'm just drawing lines and rectangles and labels.

But I'm thinking that there would have to be a standard nomenclature for this information. Basically, a symbol for "connector" that somebody more experienced than me would instantly recognise as a connector.

If there is a standard way of drawing this diagram? Are there websites that show examples I can follow?

Surely any technician who is installing an audio-visual setup would be following some kind of schematic.


texts: Moderately easy computer circuit to build?

texts: I have a project were I need to make a circuit, and I want to make a circuit that I can put into my computer, maybe in the PCI-E slot. I was thinking of maybe building a capture card or sound card, something that wouldn't need an extreme amount of soldering or small parts to be soldered on. Would any of this be possible? Or ideas for any other circuits that are more likely possible to build for my computer? thanks


texts:
I got a question. I'm building a current sink for a project and below you can see what i came up with. I modified the Linear Tech. circuit (LT1492) because i wanted to have lower Vos.
I also added 3 resistors to control Vin from a bit below 1mV to about 120mV and therefor give me 1mA-100mA through RL. The only important thing for me is, that i can set it from 1mA to 100mA.

What do you guys think about this circuit? I'm not a pro on CC and I'm sure this circuit can be improved.

Thanks


texts:
Please note: Although this question involves EEG, I don't expect anyone here to be knowledgeable in this area! This is a simple electronics question!

I'm trying to understand the circuitry devised in this DIY EEG Instructable. The main thing that jumps out to me is that - at no discernable point - do the analog signals (generated by your brain and then subsequently amplified) get transformed into digital signals via some ADC/converter. But obviously, by the time they reach the Processing program, they must be digital.

It appears that the author is recommending feeding the signals into a laptop via RCA jacks. Is this where the analog-to-digital conversion is taking place, or am I missing something?!


texts:
This is a pcb layout where I am converting 220V rms to a DC voltage (for microcontroller). The pcb has severe size constraints. This is one design I could come up with:

Circuit explanation: Consider the encircled portion. Top pad is not connected. Second one will receive a 220V signal (sometimes). This pin is connected to 270K resistor (blue pads). Other end of resistor goes to opto-coupler (K814P). Same circuit is repeated 5 times. These lines will either be open or will receive 220V rms.

The clearance between pad and trace inside the yellow circle is 12 mils. Is it safe?


texts: Should I use an external voltage reference with the PIC24F16KL402?

texts:
The internal ADC of the 8-bit PICs I usually use are quite inaccurate. The datasheet for a PIC10F320 for example, states an initial accuracy of -7% to +6%. I usually use a TL431 or a LM336 with those. The only drawback is the current of a couple milliamps for the reference.
I was looking into the PIC24F16KL402 family which states a 1% accuracy (although I couldn't find an initial accuracy) which outperforms and external reference like the TL431. I can even get rid of the extra current for an external reference. So is there even a need for an external voltage reference?


texts: Need help understanding charlieplex circuit

texts: I understand the principle behind charlieplexing, however I don't understand how the circuit below works. Say I wanted to illuminate LED5, wouldn't I set Pin1 to OUTPUT-LOW, Pin2 to INPUT, and Pin3 to OUTPUT-HIGH? Current will then flow through LED5. However, won't current also flow through LED4 and LED2?


texts:
I recently bought an old two-box metal detector that uses radio tubes and runs on the old radio batteries. There are two boxes, One is a transmitter box, the other is the receiver box. one with 6 tubes and one 45V battery (but has a third, center + connection, so is - + + the center plus terminal is 22.5V ) Then, there are two seperate 1.5V batteries also. The other box has two tubes and a 45V battery (no center 22.5V connection) and one seperate 1.5V battery also.

My question is this: I am trying to change the battery system to rechargable batteries. I made a battery pack out of 5 nine volt batteries, but the rechargables charge up to 10 volts 50V total) initially each, then I made a separate battery pack for the 22.5V out of 1.2 AA batteries, which initally charge up to 1.364 volts each (16 come up to about 23.188V 15 to 20.46V) how can I run down the batteries to get to the correct voltage(s)?

Or, does anyone know if these old detectors will take those over voltages? all batteries are connected "in series".

Also, do you think the rechargables probable higher mHa ratings(250 for 9V and 2,000 for 1.2V) could create any problems? This is the first time I have done this, so kind of new at it!

I was going to use alkalines first, because the voltages are closer, but this machine eats batteries, so I am told and rechargable batteries are so much cheaper, in the long run.


texts: How to ADD a delay to coaxial tv signal?

texts: Is there a way to add a delay that can be increased/deceased as required to a coaxial tv signal?


texts: Questions about current flow, power supplies, and floating/grounded loads

texts:
I've recently started reading through Practical Electronics for Inventors (Scherz and Monk 3rd edition), and have a few questions about a specific figure used when talking about grounding a circuit. Please bear with me.

The book notes how in 2.31a, there will be no current flowing from the power supply, as there is no current return path with the load being hooked up to the + and ground terminals of the power supply. In this case, wouldn't there still be some current flowing to ground until the supply runs out of juice, being that there's no return path for the electrons? There's still a very small amount of resistance in the wire correct? (I'm assuming in all these diagrams, the wiring for the ground and - leads are not actually connected, although the wires overlap in the diagram?)

Second, knowing that there has to be a return path for the current back to the supply, how is the current returning for the floating load? Looking at the left diagram, when the current goes through the load and has to go through the - terminal wire, does it go back all the way to the neutral wire, or does it loop through the transformer? What are the actual electrons doing in this situation, as opposed to conventional current flow?

Lastly, how is the jumper wire in the grounded load work exactly? Wouldn't the current seek straight to ground now that the jumper wire is there, like in 2.31a, rather than attempting to move across whatever internal resistance is within the rectifier/transformer?

I appreciate any help. Just trying to visualize these sorts of concepts.


texts: I have a car console that i wanna test on my work bench. It's rated at 10A DC max @ 12v, but I don't plan on driving any speakers, so the draw should remain fairly low. My power supply can only provide 3A DC @ 12 volts. If the console DOES exceed the 3A draw, will it just not function properly, or could i stand a chance of damaging my power supply


texts: LTSpice: active load current generator soft saturation

texts:
I would like to use a current generator to pull down the voltage to zero (there is a voltage generator with a series resistor). The current generator models the output of a specific circuit, so it is a constraint. In order to model the reality, I would like to use the current generator as "active load", because in this case it cannot pull the voltage below 0V. The problem is that I have experienced a soft saturation: as the voltage across the current generator achieves 1V, the current begins to degrade. In my opinion, the current should be the prescribed value as far as the voltage across the current generator is above 0V, so the current generator remains as a load.

A simulation schematic and a simulation result is also attached. In the simulation, the current of the current generator ramps up linearly, and I would expect that the voltage on the current generator also decreases linearly. It is true as far as the voltage decreases to 1V, but after this, the current begins to degrade.

I thing that the background of this soft saturation is that LTSpice and also other simulators don't like hard nonlinearities because of convergence problems, but in the case of current generator I haven't found any such parameters which influence the curvature of saturation.

R1 supply U_c 10k
I1 U_c 0 PWL(0 0 1 1m) load
V1 supply 0 5
.tran 1 uic


texts:
I am sorry if I am asking a basic question here but have no idea what I am talking about  :).

My question is this:

I have a digital camera that requires DC supply.
I have a couple of power supplies but not sure if either are any good.

On the camera it states:
DC12W 5Watt Max

On power supply 1:
INPUT 100-240 VAC 50/60Hz 0.5A
OUTPUT +12V 1A

On power supply 2:
INPUT 100-240 VAC 50/60Hz 0.8A
OUTPUT +5V 4

Are either power supplies powerful enough or are they too much?

Thanks


texts: Relation between VCO's (Voltage Controled Oscillator's) Frequency and Voltage

texts:
I have a question that what is the relationship between the VCO generated frequency and applied volatage. Is there any formula which we can use to find the applied voltage and get the frequency generated against it?
And thanks in advance.


texts: Finding corner frequency of RC bandpass filter

texts:
I'm working with a RC bandpass filter of the following topology:

I am trying to find the corner frequencies. It has been explained to me that this is just a low pass RC filter and high pass RC filter cascaded together. For instance this site suggests that to find the corner frequencies you just need to use \$1/(2\pi RC)\$ to find the upper and lower corners. But this doesn't seem right. To find the corners like that I would expect a circuit like this:

simulate this circuit – Schematic created using CircuitLab

Is there some simplifying trick to get to this from the previous circuit? Right now my solution is to find the transfer function and set it equal to \$1/\sqrt{2}\$ and solve for \$\omega\$. This is a pain to do without MATLAB and I am wondering if there is another, simpler method.


texts: How do you get from experimental measurements to models?

texts:
Many analytical models in the literature are "based on empirical measurements".

For example, for a radio propagation model, one would go out in the field, take his equipment and perform a lot of measurements in different setups. The output of these measurements would be logged somewhere as a set of point cooridinates,

$$ \{(y_1, x_1),(y_2, x_2), ...(y_n, x_n), ...(y_N, x_N)\} \quad \text{for} \quad 1 \le n \le N $$... Then? What is next?

What is the step between the raw measurement (empirical) data to the analytical formula? Statistical and visualization of the data, maybe?

If we assume we have the formula below:

$$ y = f(x) = a b^x + c $$

how do you come up with the \$a\$, the \$b\$, and the \$c\$, and how do you know which component should be additive, which one exponential and and which one multiplied?

NOTE: I am aware that this question might not fit 100% to this SE forum, please suggest another one where I can get a useful answer


texts: Shape specifications axial lead resistor

texts: We are looking for specifications of the shape of an axial lead resistor. In other words what is the radius in the middle of a resistor and at the ends,...


texts: converting inductance to electromagnetic force

texts:
How might one determine the amount of electromagnetic force produced by an unshielded inductor?

E.g. How much holding force does a 600uH unshielded inductor posses?

Or alternatively in reverse: How much inductance does an electromagnet with 1lb of holding force have?


texts:
I'm studying for an exam, and have come across a question I don't. really understand

The question gives us a back-emf constant and asks for a rated back-emf. Now I know that the back-emf constant is k, but the rated back-emf  confused me at first. When the lecture went through the questions, what he said confused me.

The lecturer says that the rated back-emf is E? I don't understand how the back-emf can be both E and k at the same time. What exactly is the difference between E and k? I think the main question I am asking is what exactly is this question asking me to do?

Here is the question:

A DC machine has a back-emf constant of 0.24 V/(rad/s) and a resistance of 0.5 ohms. It is operating from a 12V DC power supply. At its rated speed of 400 rpm, calculate its rated back-emf (that is, the back-emf at rated speed).


texts: Who sends the USB SYNC/EOP fields, host or device?

texts:
I'm currently studying the USB spec and I have a question about who sends the SYNC and EOP fields in a packet. A typical GET_DESCRIPTOR transaction (say) consists of SETUP and DATA0 packets sent from the host and an ACK packet returned from the device. My questions are:

1) am I correct in the understanding that the device sends the SYNC and EOP fields for its own ACK packet (as opposed to them being sent by the host)?

2) if so, does that mean there may also be a delay until the device responds? (I think I remember seeing something along these lines in the spec).

3) does that also mean that the device clock may not necessarily remain synchronized with the host clock during this delay, and that in order to read the response packet I'll need to re-synchronize the host upon receipt of device's SYNC field e.g. by oversampling?


texts:
I have a mechanical switch that I'd like to use as a signal source for a digital input of a microcontroller. The switch is normally closed, and I'd like to detect the switch being opened as quickly as I reasonably can, while also removing the effects of mechanical bouncing as the switch is opened. That is, I'd like the very first edge of the input signal to flip the state of the output signal towards the microcontroller and for that state to be held for a given duration even if the input signal bounces for a while after the initial edge.
Here's an illustration of what I'd like to see on a transition from closed to open. I chose an arbitrary polarity for the signals, but any polarity would do for my application.

I'm not really concerned with accurately detecting when the switch gets closed again, so it'd be fine if the output state changing in that direction had a fair bit of delay to the input signal first changing.
For the steady state it'd be ideal if the output was different depending whether or not the switch is open or closed, but for my application it'd also be OK if the output went back to its idle state after not detecting an edge for a while, just as long as it's easy to make the duration it's held in the activated state as long as I need it to be.
I feel like this should be achievable with at most a schmitt trigger, resistors and capacitors, and maybe a diode, but I haven't quite managed to work out how to achieve what I need with those, so I'd appreciate any thoughts pointing me in the right direction.
Thanks!


texts: In practical BJTs, why can't Vce become 0 when the transistor is saturated?

texts: Practically it is about 0.2 V when saturation starts. Why can't it go to 0?


texts: I am using a redpine rs9113 WiFi module in my device functioning with stm32l476 micro controller. Spi is used for the communication with the modem. While communicating with the modem, it constantly says boot failure. Is it because the WiFi module is not getting enough current to wake up. If yes, what is the minimum requirement?


texts: I have 2N3823 JFETs in TO-72 package, which has 4 leads.  No problems with Gate, Drain, and Source, but there is also a Case pin that I have been ignoring.  Now I am putting together a PCB for a design that includes one of these FETs and I don't know what the Case pin should be connected to.  I'm guessing ground (?) but I'm not sure and I am having difficulty locating any documentation for other devices with Case pins.


texts:
I built a H bridge circuit and I'm struggling with the analysis part. Below is the H bridge circuit I built. A brief description of the circuit: V1 and V2 both send inverse PWM signals and U1 and U2 are both optocoupler where U3, U4, U5, U6 are MOSFET and the circuit is being powered by a 7.2 volt supply.

When I run AC sweep I get a result which I don’t  understand. Why does the AC sweep only have two lines one at -240 dB and another at -390 dB. What are the meaning of these lines?


texts: If I'm amplifying a triangle or square wave, does the GBWP of my op-amp need to be higher?

texts: I want to amplify a 4 MHz triangle or square wave by 2 using an op-amp. Do I need an ~8 MHz op amp, or a much higher rated (and more expensive) device to handle the harmonics?


texts: Simulation is the same as my thinking,but different from the pape r(charging loop)

texts:
This question has already perplexed me for a long time ,after simulating it, the simulation is the same as my thinking,but different from the paper.So now i am confused who is right.

There is energy in the inductor,and when SW1 is closed,the current will flow through the diode,and charge the battery,then precharge the C1 to -\$V_{PD}\$.And the current source will charge the C1 from -\$V_{PD}\$ to  -\$(V_{PD}+V_{OC})\$.

Here is the waveform of proposed schematic

(SW1=SW3)Here is the waveform i build as a concerned citizen said,but i didn't use the ideal switch,i make a new one.And this schematic is much different from his.So i modify some parameter.

(SW1=SW3) For this schematic,i modify C1 from 15n to 60n,Cbatt from 2V to 1V,and as we can see,it is more similar to his,however,it still didn't precharge,but his did.

Here is the schematic i made

The reason i wonder the whether ideal switch has direction or not is because i don't know what is the loop for precharge the C1 to positive or negative voltage first.

Paper link:http://rincon-mora.gatech.edu/publicat/cnfs/new16_pzdamp.pdf

SW1 and SW2 (in the wave)is corresponding to SW1 and SW4 in the schematic,and SW3 (in the wave) is corresponding to SW2 in the schematic .on for connected,off for disconnected.

About the diode,i use the NMOS (draon connect with gate) to replace it

The reason for ours simulation are no the same maybe because of that switch,my switch is transmission gate switch .The first picture below is the TG switch,and  the second picture just an inverter,which in the TG switch.


texts:
I have an AC-DC adapter with 500mA (it was a mistake when I bought it). It has a switch to reverse the polarity and a potentiometer where voltage can be adjusted from 1.5V (min) to 12V (max). Now what I need is a 2A or 1A current. Now, what modification needs to be done to get the same current at 12V?

When I opened the adapter, I was able to see a pot for changing voltage. Second a small circuit where 4 diodes are connected (which converts AC to DC) with a capacitor, a big square shape resistor (if am not wrong) which is connected to the pot.

How do I hack the circuit so I can achieve the required current with adjustable voltage?


texts: In the reactance diagram, why is j0.20 (as circled in the picture) in series with j0.20 + j0.10 + j0.17. Why isn't j0.20 (circled) in parallel with j0.20 + j0.10 + j0.17 and j0.20 + j0.1333 + j0.24.


texts: MOSFET as a switch: operation region during Rise time

texts:
In the below picture, during the time period Tri the drain current Id starts increasing linearly wrt gate voltage Vgs and the voltage Vds is clamped to Vd since the drain current hasn't yet taken up all the load current. So during this period since Vds>(Vgs-Vth), is the MOSFET operating in saturation region. Does MOSFET has to operate in saturation region for a small time period(Tri) even when the MOSFET acts as a switch.
If the MOSFET operates in Saturation region for this small duration(Tri), then does the current should increase parabolically since in saturation region Id=K(Vgs-Vth)^2 ?


texts:
I had an aquarium air pump which broke down a couple of days back as it got water inside it. I knew the electromagnet inside it has been damaged. Even though I could have bought a new one. I thought of experimenting to fix it.

I had seen online that an electromagnet can be made from a transformer. And decided to give it a shot. I followed this video Electromagnet from a Transformer, and used an E-I Laminated core transformer  .

As shown in the video I disassembled the laminated core, stacked the Es together and placed it in the winding.
On turning it on it did act as expected,as an electromagnet ! I placed it in my air pump, and it even pumped air. It sparked and got damaged shortly after though.

I will be honest I did few changes in the design though, knowing the air pump used to work at 5W,still I went with a step down 12V 1A transformer (For no reason). Later replaced the stacked Es with the previous electromagnet core which used to be in the air pump(It resembled in shape and size, and was easier to fit in the air pump casing).

Can you please help me with knowing where I went wrong with this, I am still new to electronics and really to want to know more about it ?


texts:
Hi,
I am designed a full bridge SMPS, like the above schematic.
But when I measure the switch node voltage (I put voltage probe across Q2), I see when the mosfet is on, the voltage across it is -1 volt!!! As I know, the voltage should be Rds(on)*IQ and it is positive, now how does it possible to be negative???


texts:
I'm looking into making a 7 segment LCD display (runs at 7.4 V) powered by a car battery. In order to do it I'll use a CD4511, since it can handle up to 18V. But upon reading the datasheet, I did not quite understand which is the appropriate input logic voltage to control the IC (if it's 5v or the same as the VCC applied to the IC).
Thus, I made a diagram of what I think that would work, but I wanted some feedback before actually building it.


texts: Custom curcit help that has 3 components (Mic/Transistor/motor)

texts:
I would like to create a circuit that will have a microphone or another sound sensing sensor that will connect to a transistor. When the microphone level goes above a threshold, the transistor lets the current flow to a DC motor. See the attached rough diagram.

How exactly will the diagram look like (connection)?
Do I need any resistors or anything else to insert between the components?
What is an example of exact components needed to build this?

Side question: How do I make that threshold that triggers the transistor be variable or adjustable in some way so I can test the system more easily?

simulate this circuit – Schematic created using CircuitLab


texts: 1000uF capacitor to protect 5v 30amp circuit

texts: I wish to build a LED cube but have no experience in shift registers so I am building one with addressable LEDs that can draw 60mA each. I want to make an 8x8x8 cube so that would be 512 LEDs and 30.72 possible amps of current or above 150 watts of power. These WS2811 "Neopixels" are very sensitive to voltage changes and require a 1000uF capacitor to protect them according to the Neopixel guide. Is it safe to put a regular capacitor across the power to even out voltage spikes on such a high current circuit?.


texts:
What sensors do I require to detect multiple objects on a board?
I need to know exact numbers of objects and their co-ordinates on the board.

The board can be anything from metal to plastic. And the object I suppose needs to be with a magnet inside.

What ideas or maybe solutions do you have?

I'm thinking to build a scrum board that can transfer data to digital format.

Currently, no writing recognition is needed. Just object detection.


texts: Need Help on DC Jack and MOSFET Functionality Circuit

texts:
I'm trying to build a specific DC Jack that is supplying 24V power. The main feature of it is there is no voltage in the VCC pin in the jack until a barrel is connected to it. So the VCC pin only gets 24V when the shunt pin in the jack is disconnected from the ground pin.
My initial idea is to use a P-channel MOSFET and came with this idea in the schematic below. But I realized this circuit will do the opposite of what I want. It will supply 24V when no barrel is connected and stops supplying 24V when a barrel is connected. I can't seem to think of a circuit to make the DC jack behave in the way I want it to. Maybe you guys know a way or suggestions?

EDITS:
Here is a new schematic based on the suggestion of using a N-MOSFET to inverse the signal:

Added the voltage divider back. Vgs2 (Vgs for the N-MOSFEt) can only handle 20V so the a voltage divider is added back.


texts: Connecting the primaries of two 110V transformers in series across 220V

texts:
I have 2 identical 110V primary transformers (plug packs but with a small transformer inside) for charging batteries in a pair of US made walkie talkies. Only issue is where I live now is 220V mains.

If I connect the 2 110V primaries in series, and plug into 220V will there be a drop of 110V across each transformer?

Will small varying loads on the output, alter the primary voltage drop across each transformer?

Any and all suggestions appreciated.


texts:
I am using a PIC32MX795F512L which sends CAN messages to a WiFly module (RN-171) using UART.

I receive messages over WiFi but after a longer time (20-60 minutes), the PIC seems to be stuck and I have to reset it. Below is the code for the UART initialisation, the message queuing and message sending.

TCPSending() is called every 200ms in an interrupt routine and PutInTXBuffer() is called whenever a CAN message is received (and then the ID and data are passed to the PutInTXBuffer function).

void InitUART()
{
    UARTConfigure(UART1, UART_ENABLE_PINS_TX_RX_ONLY);
    UARTSetFifoMode(UART1, UART_INTERRUPT_ON_TX_NOT_FULL | UART_INTERRUPT_ON_RX_NOT_EMPTY);
    UARTSetLineControl(UART1, UART_DATA_SIZE_8_BITS | UART_PARITY_NONE | UART_STOP_BITS_1);
    UARTSetDataRate(UART1, GetPeripheralClock(), 57600);
    UARTEnable(UART1, UART_ENABLE_FLAGS(UART_PERIPHERAL | UART_RX | UART_TX));
}

void TCPSending()
{
    if(UARTTransmitterIsReady(UART1) && U1STAbits.UTXBF == 0)
    {
        int i;
        for (i = 0; i < TXelements; i++)
        {
                putcUART1(WiFiTXBuffer[i].id >> 8);
                putcUART1(WiFiTXBuffer[i].id);
                putcUART1(WiFiTXBuffer[i].data >> 56);
                putcUART1(WiFiTXBuffer[i].data >> 48);
                putcUART1(WiFiTXBuffer[i].data >> 40);
                putcUART1(WiFiTXBuffer[i].data >> 32);
                putcUART1(WiFiTXBuffer[i].data >> 24);
                putcUART1(WiFiTXBuffer[i].data >> 16);
                putcUART1(WiFiTXBuffer[i].data >> 8);
                putcUART1(WiFiTXBuffer[i].data);
        }
        free(WiFiTXBuffer);                 // Deallocate the buffers memory
        WiFiTXBuffer = NULL;                // Re-initialize the buffer
        TXelements = 0;                     // Keeps track of the number of elements used
        TXallocated = 0;                    // This is essentially how large the array is
    }
}

void PutInTXBuffer(WORD id, QWORD data)
{
    int MoreAllocation = 50;

    WiFiTXPacket packet;
    packet.id = id;
    packet.data = data;
    if(TXelements == TXallocated)                               // Are more refs required?
    {
        TXallocated += MoreAllocation;
        // Make the reallocation transactional by using a temporary variable first

        void* temp = realloc(WiFiTXBuffer, (TXallocated * sizeof(WiFiTXPacket)));

        // If the reallocation fails:
        if (!temp)
        {
            TXallocated -= MoreAllocation;
        }

        WiFiTXBuffer = (WiFiTXPacket*)temp;

        free(temp);
        temp = NULL;

    }

    WiFiTXBuffer[TXelements] = packet;
    TXelements++;
}

I think the problem has to do with a memory leak but I can't seem to find it.


texts:
I have a power supply that uses a PWM fan with 4 wires.

Wires: 12V (red), GND (black), PWM Control (brown), TACH Sig (white)

The fan speed is controlled by the PWM control wire (brown). Fan speed is duty cycle, so 50% means 50% fan speed. Max speed is 22,000 RPM.

Tach signal (white wire) is an open collector with two pulses per revolution.

At full speed we should have 44,000 pulses on the Tach signal, or 733 Hz.

The power supply checks if the fan works, so using another fan or removing the fan altogether is not working. It also seems to check if the fan speed is anywhere near the commanded fan speed.

Here is the datasheet of the fan:
http://www.nmbtc.com/pdf/dcfans/1611ft.pdf

How would one build a very simple circuit that simulates the fan?

I imagine a small circuit that gets the PWM signal, and depending an duty cycle outputs the open collector pulses. ie. 0% duty cycle 0Hz, 100% duty cycle 733 Hz.

I have seen this question asked again and again, so coming up with a small circuitry would be very beneficial not only to my own small project.

Edit: I'd like to add that the fan needs to go because a far superior way of cooling will be employed for this power supply. I am not trying to find a cheap solution not to replace a fan or save some dollars. Power supply and its components are sufficiently cooled. I just need the fan on the PSU itself to be gone.


texts: High voltage (220V) constant current LED driver using transistors

texts:
This electronic circuit is a constant current LED driver using two transistors.

It is designed to work with low DC voltage like 5V or 12V.

But I'm wondering if it is possible to connect it to 220V mains voltage (311V DC after using bridge rectifier) if I used a proper high voltage transistors such as A42 or 13001 instead of low voltage BJT.

If yes, why have I never seen a commercial LED driver that used this simple method?

(My desired load is 100 3V LED in series with 100mA of current.)


texts: 240v AC Voltage measurement using Voltage divider

texts: I'm doing my project on energy based auditing, it's an industrial project... I need to measure the high voltage of around 240v, can I step down to 5v using voltage divider?


texts: Lab power supply CC with comparator: principle

texts:
I'm building a lab bench supply, and it uses a current sensing resistor and a comparator for shunting out the input of the drive circuit when switching to CC mode.

I'm having trouble understanding what exactly happens, when the supply swiches to CC mode.The basic principle is ok, the current and the load is constant, so the voltage must be dropped for maintain Ohms law (I think). But what happens in the circuit? The comparator is a binary device, how does the supply reach the analog characteristic? There are two things I can think of: The comparator goes bananas and switches between high and low rapidly OR the main transistors not closing all the way and there goes some leakage. So, what is happening exactly?


texts: Charging NiMHs: about current fluctuation tolerance

texts:
While trying to make a DIY charging system on my bicycle -based on the hub dynamo- I have seen in action that Li-Ion batteries (typical 18650 ones) do not like charging current fluctuation at all. They hate it and you will soon end with a useless power bank in the middle of nowhere - alas.

I then thought of a hand crank system, to turn the wheel constantly with the bicycle upside down. It works, but time is the problem: I have to spend half an hour of my every bicycle touring day for this. Instead if I could have the charging module connected on the hub all the day long - with the bike stopping and starting all the time - that would be cool and perfect. It is simply a matter of practicality.

I am wondering what if I use NiMHs in the power bank batteries module instead of Li-ions.

So the question comes: do NiMH batteries withstand current fluctuation acceptably well for this case?


texts: Cache access time for write back and write through caches

texts:
I was solving exercise questions on caching from the book Computer Organization and Architecture by William Stallings. The exercise has following question:

  The performance of a single-level cache system for a read operation can be characterized by the following equation:

  $$T_a = T_c + (1-H)T_m$$

  where Ta is the average access time, Tc is the cache access time, Tm is the memory access time (memory to processor register), and H is the hit ratio. For simplicity, we assume that the word in question is loaded into the cache in parallel with the load to processor register.

  a. Define Tb= time to transfer a line between cache and main memory, and W=
  fraction of write references. Revise the preceding equation to account for writes as well as reads, using a write-through policy.
  b. Define Wb as the probability that a line in the cache has been altered. Provide an equation for Ta for the write-back policy.

The solution given was:

  a. $$T_a = T_c + (1 – H)T_b + W(T_m – T_c)$$
  b. $$T_a = T_c + (1 – H)T_b + W_b(1 – H)T_b = T_c + (1 – H)(1 + W_b)T_b$$

Doubts

Shouldnt it be: $$T_a = T_c \color{red}{\times H}+ (1-H)(T_m\color{red}{+T_c})$$? I felt "× H" is required because its during cache hit, when we do only cache access. Also we need "+ Tc" represents cache access time during cache miss.
I know what is write through and write back caches. In write through cache, both main memory and cache are simultaneously updated and in write back cache only modified cache word is copied to main memory when that word is to be replaced with other one from main memory. I also understand why we replaced Tm with Tb. However I am not able to understand how above equations have be arrived. Can someone explain how those formulae were come up? How those two terms involving W make sense.


texts: If you wanted to double ac voltage, you could use one of those capacitor diode voltage multipliers. The thing I'm wondering is can you use it on mains? I've only seen people use them with transformers. For example, if you have a european light bulb and wanted to use it, could you use the voltage multiplier? You wouldn't need a massive transformer, so would it work?


texts: Regarding connecting MOV and SMPS in parallel for electrical meter

texts:
We are working on development of a 3 phase electrical metering circuitry. All the 3 phases are connected to metering IC using resistor divider circuitry for voltage measurement (between phase and neutral).
The rms voltages range from 200V to 260V  for all the three phases (between phase and neutral). However, the power supply for on-board components (3.3V and 5V) is drawn using an SMPS connected between phase 1 supply and neutral of the meter (no separate auxiliary supply is used).
All the three phases are equipped with 3 MOVs (275V rating) and each MOV is connected between one phase and neutral.
We installed these devices in 30 locations, out of which 5 stopped working after a few days. When analyzed, it is observed that the MOV connected along with the PCB track on phase 1 supply is blown in all the 5 devices. The MOVs of the other phases are just fine. We are unable to figure out what the mistake is.
Is there any chance that SMPS is resulting in the damage of the MOV? We are providing the schematic below for your reference. Any help or alternative design strategy is appreciated. Thanks in advance.


texts: Driving an electromagnet through a shift register?

texts:
I want to know if it is reasonable to use a shift register to control electromagnets. We want to drive electromagnets with about 400-500mA.  The TPIC6B595 data sheet claims "Each output provides a 500-mA typical current limit at TC = 25°C."  Is it reasonable to run 2 or 3 outputs at 500mA at once?  Is it poor to chain one electromagnet to two outputs such that we can achieve more than 500mA through one magnet?

Also, is there a way to search for shift registers based on continuous current capability?  Digikey does not have this option, and I am not sure how one would go about this without scanning through every individual data sheet.


texts: Which traits should I look for when purcashing plugs for self-assembled power cables?

texts:
For example, here is a picture of two schuko female plugs I got (I marked the types with numbers), the materials at the connections are different too:

So which one is better and why if that matters? Is there any specific trait that I should look for in the future if I want to get high quality plugs and start assembling power cables with them?


texts: Not understanding why my resistor R4 for the circuit schematic is reading 35k ohms on a multimeter when its meant to be 47k ohms?

texts:
For the following circuit i am confused to as why Resistor R4 when measured on the breadboard is 35k ohms, when it is meant to be 47k Ohms (as it is a 47 k ohm resistor. Also when it is taken out of the circuit and measured it is fine and gives the 47k ohm as expected) . The other resistors when measured match up to what they are meant to be.  I assume the reason it is giving this reading is due to the configuration it is in? Such as something to do with the voltage divider, maybe something else?

Note for the circuit schematics i have just put 35k ohms just to see
if my simulated results would match up to what the breadboard circuit
outputted on an oscilloscope. It is actually meant to be 47k ohms

In short

Not understanding why the 47k ohm resistor (R4) reads 35k ohm on the multimeter
How do i calculate what this resistor value will be due to the difference? As in i find what value i want, in this case i needed 47k ohm for the specified application but due to this resistor value difference, how am i meant to see what 47k will actually be. As in will i need to use a 56k or something to get the 47k due to the difference? Hence what formula am i meant to use to find what value this resistor will actually be when in theory its meant to be 47k ohms?

Circuit Schematics

Circuit implemented on the breadboard


texts:
I would need some directions on how to build a simple circuit with a temperature sensor.

OBJECTIVE: The device measures the time between two temperature values. The values are read from a sensor on the circuit every minute. The device starts measuring the time interval at 10C (or lower) and stops measuring at 20C (or higher). If the temperature has not reached 20C in 5min the LED starts blinking. When the LED starts/stops blinking a notification is sent over bluetooth4 to a remote device (if any).

NOTES: The device should use a coin battery which should last for >=1 year (as little processing as possible).

QUESTIONS:
- Doable?
- What components are you proposing?


texts: unstable systems with positive phase/gain margin

texts:
Open loop Phase/Gain margins provide information on how much margin the closed loop system have until it becomes unstable. In other words, how much you can increase the effective loop gain and or effective phase lag until system becomes unstable.
Is it possible that a system shows positive phase/gain margins (at a range of frequency) but the overall system being unstable (potentially due to system behavior at other frequencies)?


texts:
The figure below is about energy density comparison between inductors and capacitors. This thesis concludes that capacitors possess greater energy density than inductors, as seen in the figure.

Source: Analysis of soft charging switched capacitor power converters by May, Ryan.

I would like to know how to get the data as in the figure. For example, say for one cubic millimeter what formula, which value of L, C, current, voltage do you use to get that data?


texts:
What is the purpose of using these mode conversions?

SCD
Input: Differential
Output: Common

SDC
Input: Common
Output: Differential


texts: Calculating power consumption of optocoupler

texts:
I am having trouble calculating the power consumption of this optocoupler (4n25). In the datasheet the input power dissipation stated as \$ P_{diss} = 100mW \$ and forward current of \$I_F = 60mA\$. In the figure below are two setups with different resistor values.

changing the resistor value of R3 results in:

\$R3 = 100\Omega\$: \$U_{in} = 1.24V, I_{in}=37.22mA \$ => \$ P_{R3} \approx 47mW\$

\$R3 = 10k\Omega\$: \$U_{in} = 1.01V, I_{in}=0.398uA \$ => \$ P_{R3} \approx 0.402\mu W\$

Looking at Fig3 and inserting the \$U_{in}@25°C\$ results in

\$R3 = 100\Omega\$: \$I_F\approx 50mA \rightarrow P_{opto} = 62mW\$

\$R3 = 10k\Omega\$: \$I_F\approx 1mA \rightarrow P_{opto} = 1.01mW\$

(The graph only goes to 1.2V but for my thought experiment I extrapolated the values).

The consumed power of the input circuit would be
$$ P_{tot} = P_{R3} + P_{opto}$$

Is this approach correct? If this is the case it would be potentially dangerous to remove the resistor.
Also: Is it best practice to choose a the highest resistor which still guarantees that the opto functions as intended?

EDIT: This post is based on this question


texts:
For my home project I need to connect multiple Arduino's to a Raspberry Pi. My raspberry pi controls everything in my house and the arduino's are going to be used to get sensor data.

I want to connect multiple Arduino's (up to maybe 20 or more) and I think it will be best to use a powered usb hub to do that (connected to the raspberry pi and use serial communication to get the data at the Raspberry Pi). To make it as best for my case I would like to build a PCB so I can make it exactly as I want, the only question is... how.

I have made multiple PCB's but I don't have a degree in it, I just want to make it for my hobby, can someone help me to start with it, or is it too difficult or can't it be done?


texts:
I have PCB antenna . which support multiple band antenna.
https://www.johansontechnology.com/datasheets/0830AT54A2200/0830AT54A2200.pdf

we also have tune circuit before antenna as recommended by antenna manufacture.

SO the question is
" through tune circuit we can tune the antenna to a single Band. and to tune other Band we need to tune the antenna again. ' so what is the purpose of antenna having multiple band , since every band different -2 tune circuit , different BOM , high cost.


texts: Why are there no nichrome resistor pastes?

texts:
Nichrome wire is commonly used for wire coil heating elements.

Other heating elements are formed by screen printing a pattern of "resistor paste" onto a dielectric coated substrate. These pastes are a made up of a metal powder inside a flux, however it seems that nichrome powder is not used. The resistor pastes I have found online generally contain silver particles.

Silver is more expensive than nichrome, and silver is a better conductor. I thought that one of the good points about nichrome is that it is NOT a good conductor and therefore produces more heat when a current runs through it.
Why is nichrome powder not mixed with a flux and screen printed onto substrates?

What kind of problems might someone run into if they tried mixing nichrome powder into a rosin flux and screen printed it onto a substrate to form a heat element?

Update in response to comments
Ah! I understand. Thanks!
I have been looking at some information about conductive silver epoxy adhesive. Some of these cure at room temperature.

https://www.atomadhesives.com/AA-DUCT-902LP-Long-Open-Time-Electrically-Conductive-Silver-Filled-Epoxy

https://www.dupont.com/content/dam/dupont/products-and-services/electronic-and-electrical-materials/documents/prodlib/AirDryAgSelectorGuide.pdf

On page 2, paragraph 1 of the second document, the oven temperature recommended for oven curing is 100°C.
It seems that these rely on a mechanical connection between silver particles to form an electrically conductive connection.

These are conductive pastes, rather than restive pastes, and the operating temperature of the first paste is given as –50 to +170°C. If one planned to operate a screen printed heat element at less than 170°C, would a nichrome in flux be feasible?


texts: How to calculate the power dissipation of a receiver and a driver?

texts:
I'm using the AM26LV32E receiver and the AM26LV31E driver and need to calculate how much power is dissipated on them (max).
I've been told I can calculate this using:
(1) For receiver: Pd = Icc(max)*Vcc(max) + #ofCH*[Vol*Io+[(Vcc-Voh)*Ioh]
(2) For driver: Pd = Icc(max)*Vcc(max) + #ofCH*[Io(Vcc-Vod)]
Two questions:

Are these formulas correct?

Is it possible that for the receiver, Vol should be Vil (and Voh = Vih)?


texts:
This is my first "real" design, a (more or less) universal USB serial interface board with two RS-232 ports, one RS-485 and one CAN interface. Hi-res schematics, top and bottom PCB layers with bottom copper pour turned off. Each FT2232 channel has two interface drivers (a RS-232 and either RS-485 or CAN) that can be connected to it with jumpers. Jumper wires can also be used for e.g. SPI or JTAG modes supported by this chip.

I used a FT2232 breakout board from dangerousprototypes.com (can't post a link) as a reference (not for layout though). Layout is what I'm most concerned with here. I tried to implement most of the good advice I found on this site, such as the ground plane (disabled), power trace along the perimeter on the bottom layer, power polygon under the chip, short traces for oscillators and decoupling capacitors etc. The area of the FT2232 seems much more complicated and cramped than on the dangerousprototypes board. I wonder if that's or because their schematics is simpler and crystal / capacitors are placed farther from the chip, or because I suck at this. (In hindsight, placing some components on the bottom layer would probably simplify the layout.)

I tried to comply with requirements of the seeedstudio.com manufacturing service.

(There's a discrepancy between schematics and layout in pin header placement - RS-485 and CAN headers are swapped.)

I'll appreciate any critique or advice.


texts:
I am not much of an electrical person but I'm trying to get an idea about it, so keep in mind I have very little background outside of college level electrical physics with calculus, and a strong basis in mathematical logic. I was learning about things you can make with logic gates and came across an adder. I like to give things a try before I look at the answer, so I came up with my own adder. The only difference between my adder and the one in the book I'm reading is that there's an OR gate at the end of their adder for the carry out wire, whereas I just put two wires together. It seems to me that putting two wires together is identical to an OR gate, as there is no electricity out of the node if there's no electricity in, and there is some electricity out of the node if there is some in from either or both sources.

My question is: What is the difference between putting two wires together and making a proper OR gate?

My guess is that it has something to do with the amount of electricity (current?) on the output wire from the 3-node/OR gate, but my understanding of circuits is a bit rusty. Thanks for your help!

simulate this circuit – Schematic created using CircuitLab


texts: Measuring voltage without a common ground

texts:
When measuring a power source voltage using a differential amplifier, without a common ground with amplifier supply, to which ground should we connect the differential amplifier resistor ground? V1 ground or V2 ground?

simulate this circuit – Schematic created using CircuitLab


texts: Coupling vs Decoupling filter / Filter in-the-signal-path vs filter on-the-signal-path

texts:
I'm looking at designing an active analog filter module to be used/reused in my designs. Correct me if I'm wrong, but you can design a filter that is in the signal path that has the same frequency domain properties as a filter that is simply a bypass to ground. What are the advantages/disadvantages of both types of filters?

This is for non-RF circuits under 30V with low current.


texts: How to obtain Peak and Average Power in Radar Detection?

texts:
I have a problem solving a RADAR exercise.

The specifications of the 2D radar antenna are the following ones:

Dimensions: Horizontal Lh=5m ; Vertical Lv=0.8m
Turn rate: 12 rpm
Max range of operation: 80 NM (1NM=1852m) being able to detect a constant RCS target of 10m^2 in uniform rain conditions with intensity I = 16mm/hour
Pulse Repetition Frequency: PRF=850Hz (Rectangular pulse transmitted)
Radar Blind Distance: Rc=200m
Integration Efficiency in the receiver: Ei=0.9
Internal Radar Losses: L=6dB
Noise factor of the receiver: F=4dB
2 operation frequencies: 2.7GHz (S Band) and 5.4GHz (C Band)
Attenuation caused by rain with intensity I: 1.6dB (@2.7GHz) and 12dB (@5.4GHz)
Minimum SNR required at the detector input : SNRmin=17dB
Probability of detection: Pd=0.85
Probability of false alarm: Pfa=10^(-6)
The beamwidth of a typical electrically large antenna is 1.2*wavelength/dimension (horizontal or vertical) [rad]

I don't know how to compute:
The peak (Pt) and average power (Pm) required to satisfy the detection requirements for the 2 proposed frequencies of operation

Result:

Pt = 129.7 kW = 51.13 dBW / Pm = 146.8 W = 21.67 dBW @2.7 GHz
Pt = 712.8 kW = 58.53 dBW / Pm = 807.2 W = 29.07 dBW @5.4 GHz

I will appreciate all your suggestions. Thank you!


texts:
I know that regarding proportional valves the dither signal is a signal superimposed on PWM command that actually moves the valve.

It improves the response of the valve because the coefficient of static friction is higher than the coefficient of kinetic friction.

What I don't understand is how that could be. How the valve is moving forward per example and at the same time backwards and forward.


texts: How much does the clock drift for the Arduino Pro Mini board?

texts:
How much does the clock drift (at most) for the Arduino Pro Mini board?

I don't need to correct it on the board, just need to know the specifications, such that I can take the necessary precautions in the cloud with data sampled by the board.

The board is based on the ATmega328, but I guess the clock precision depends on the external crystal as well.

To do an estimate, I've counted pulses from a signal generator Rigol DG1022 and used that as a reference. With a frequency of 100Hz (square wave, 0-5V) this should give 6000 pulses/min. I sum up the counts in packages of 5 seconds on the a
Arduino.

This chip is pretty bad (up to 410ppm deviation). Other chips are ranging from -160ppm to 50ppm deviations.

I don't have enough rep to make all the above links links correctly. Can someone edit? Or I will do myself, when I get the rep. for it.


texts: Merging right & left signals to mono with op amp?

texts:
Sorry for my english i'm a young french.

I want to design an audio transmitter to connect my pc to my Hi-Fi without Jack cables.

For now i just want to send a mono signal because sending a stereo seems to be too complicated and i don't need it.

The problem is that my PC's output is a stereo jack. So is it correct to merge the two signals in once, using an operational amplifier in buffer or summing ? Will the sound be ok, just suming two signals ?

Thanks


texts:
The neutral null wire is said to have potential 0 while the phase wire has a varying potential. It seems that the potential 0 for ground or null wire is just a definition. One can define its potential to be 10. Nothing will change. Now can we assign the phase wire a constant potential 0 instead and assume that the null wire has a varying potential. Will anything change? Is there any physical or experimental clue forcing us to assume the null wire has a constant potential?

We can assign any constant velocity to a free floating stone in space (for example outside solar system). But we cannot assign a varying velocity to it because acceleration is inherent and is physically determinable using an accelerometer. Is the same true for potential. Can we assume the null wire has a varying potential and instead assume the phase wire has zero potential?


texts: Three different development boards for STM32F103C8T6

texts:
I ordered one of these which has a single row of pins

Single-row

While there are also these which have double row of pins:

Double-row

I wonder what I miss ... of course a lot of pins difference, but I'm not sure what those pins are, are those pins I cannot use at all, and are some of those pins I will miss having special functions like UART/SPI etc I cannot use?

For me it's a but unclear what pins mean what (used to the Arduino where every pin has it's own meaning).

Minimal

This one does not have the JTAG (I also ordered a USB TTL converter and JLINK 'stick'. Do I have the same functionality as like 1 or 2 above in this case?


texts: Why is one return conductor for each forward conductor in a ribbon cable better than a shared return conductor?

texts: I don't understand why second way of implementing is better than the first one? I have my own basic logic regarding this topic, but i am not confident if what i think is correct! so i was looking forward to have some general view on this topic!


texts: I have a pcb with two 3mm holes for the positive and negative from a 12V battery. I need some sort of connector to solder in the holes for wires to attach to. The holes are separated so I must have two individual connectors rather than 1 connector with two connection points. I was thinking of pin headers but they seem to be only suitable for smaller holes. The holes are too wide to attach the wires directly. Whatever I use must be narrow as the holes are quite close (either side) to a capacitor.


texts: Unbalanced to balanced variable impedance matching

texts:
I want to design an impedance matching transformer to convert an audio line from unbalanced ( stereo phono jack type) to a balanced type ( XLR jack with 600 ohms). What can be the easiest way around ?

What if I need to handle other audio jack types ( may need variable impedance matching) to XLR, how to design in these circumstances?

EE already answered similar query in the past but not for variable type.


texts: Modelling a Braking DC Motor Speed Controller

texts:
I'm trying to simulate a brushed DC motor. The model comes from the following circuit diagram

KVL yields:
$$v = Ri + L \frac{di}{dt} + K_b \omega_m$$

My rudimentary understanding of speed controllers is basically as a variable voltage source. Therefore I solve for the new current each time step like so:

$$i = \frac{v - L \frac{di}{dt} - K_b \omega_m}{R}$$

where v, i, and omega are modeled/provided by the simulation (other physics concerns are taken into account elsewhere) and everything else is a constant.

The speed controllers I'm using have a "brake" and "coast" mode. In brake mode, a neutral signal will, as the manual puts it, "effectively short the motor terminals." I know from experience that brake mode results in the system slowing much quicker. How is the short in brake mode different from applying 0 volts? What equations model the behavior of shorting the terminal?

My main confusion comes from trying to model the short-circuit as such:

$$\Sigma V = 0 $$
$$0 = Ri + L \frac{di}{dt} + K_b \omega_m$$

but this is the same as applying 0 volts in the original model.


texts: Confusion regarding a 12V DC motor's RPM

texts:
I have a 550 DC motor of 12V, 45W and 10K RPM installed on a wheel, which is not causing the wheel to turn fast enough when the motor is connected to a 12V battery.
I replaced the motor with an older DC motor which I had, having the same specs of the replacement, however with 9K RPM (I thought it would be slower).
Sarcastically it generated more speed to the wheel than the 10K RPM one.
Some electrician told me to ignore the labeling on the DC motors outside since they are not accurate.
I wasted plenty of time trying to fix the issue by following the book higher RPM means higher speed. I first thought that the gear train inside the gearbox was the issue, but I used the same gearbox for the older 9K RPM motor and still it gave higher speed.
I am willing to buy additional DC motor but I need to generate even higher speed, I am confused to whether I should buy a higher or lower RPM DC motor for this purpose.

The following are the full specs of the project:
MOTOR1
Power:20-45W
Voltage:12 V
RPM:10,000

MOTOR2
Power:20-45W
Voltage:12 V
RPM:9,000

each motor was individually attached to gear train having the following teeth:

Motor1 turns a 10 teeth pinion, which turns a 52 teeth cylinder C1, attached to C1 is a little cylinder C1' having 10 teeth again, C1' turns a cylinder, C2, having 48 teeth, attached to C2 is C2' having 9 teeth, C2' turns a the last cylinder C3 having 38 teeth, connected to a wheel. After doing some calculations, the final output for the gear train would be 100RPM

Motor2, before replacement, had the following installations:

Motor2 turns an 11 teeth pinion, which turns a 56 teeth cylinder C1, attached to C1 is an 11 teeth cylinder C1', turning a 45 teeth cylinder C2, C2 is attached to C2' 11 teeth cylinder, C2' is turning a 42 teeth cylinder C3, C3 is finally attached to the wheel. The final output of motor2 in the above gear train would be 112RPM


texts: If I'm wiring a bunch of speakers in parallel, is adding a resistor to the circuit path sufficient to protect the amp?

texts:
My house has quite a few outdoor speakers, 6-8 of them. My amp has a "Zone-2" stereo output that I'm planning to drive them with. Each set of speakers has a rotary volume control on a wall in the house nearby.
It's not practical for me to take down and disassemble the speakers to check their ratings. But if I wire them all in parallel, can I simply add 6-ohm resistors to one pole of the amp's Zone-2 speaker terminals before it feeds all the speakers?
UPDATE: Based on comments, it looks like this is not a viable solution. I did find this speaker selector with "protection"; can anyone weigh in on how effective these are? The Q&A says it applies a fake load to protect the amp. Another source says it uses resistors and not a transformer.
I have hooked one speaker lead up to the wire that runs through the house and the volume control to the outdoor speaker, and with full rotation of the rotary control it sounds about the same volume as a similarly-sized one I have hooked up in parallel inside (if that answers the question about a 100V system).


texts:
I am trying to convert sine wave of 50 Hz and 10 mV to square wave of 10 mV of positive side only.

I used the following circuit. But the square wave has higher voltage compare to my requirement.

What changes are need to make in this circuit?


texts:
TLDR: I'm trying to create a simple 200 feet range "morse code transmitter" (which is legal according to the FCC), which is really just an AM transmitter that can transmit a single frequency tone (lets say, a nice 400 Hz tone).

What I plan to do is have a pushbutton to allow or block the 400 Hz tone (created using 555 IC) from going into the transmitter, which will allow me to send dots and dashes (by quickly pressing the pushbutton for a dot, or holding it down for a little longer for a dash).

My goal is to keep this circuit very basic (not too many components) so that it is easy to understand and learn from. This means that I also don't need any "quality" features (such as cleaning up sound quality, etc). I'm just hoping for a bare-bones transceiver, so I wanted to ask here for suggestions for a circuit that meets the following requirements:

Antenna(s) less than 3 ft (the smaller the better)
Can be powered using a 9V battery (or two)
The receiver can "play" the received Morse code signal using a DC piezo buzzer or an LED
Can transmit to 200 feet (which is legal without a license, according to the FCC)
It can transmit at any frequency.

Other than those, feel free to use your creativity. Also, I'm planning to use this in a university setting, which is for educational purposes, which is also allowed by the FCC. Please let me know if you have any questions; I'd be happy to elaborate.

Also, please note that I don't need a Morse code generating mechanism; I'll simply do that using a 555 timer; I just want to learn how to extend its range. From my research and experimentation, I've only been able to transmit around 5-10 feet, and despite weeks of searching, I wasn't able to get it to transmit further.

Lastly, I know that this question is quite similar to this post, but I found the answers hard to learn from, as not much circuitry is discussed.


texts: Calculations: Antenna specs; SWR, Bandwidth, Rad.Eff, Q-factor

texts:
Is it possible to give approx. answers about what an antenna is capable of? There is a lot of formuals out there, but every single one I found is based on actual measurement; input, output, SWR (Standing Wave Ratio) etc.

eg: I want to build a dipole for 450 MHz, what can I expect in bandwidth, q-factor, impedance matching, SWR ?

Is there some kind of standard chart board for diffrent antennas regarding the specs mentioned above? Like standard values you can expect if the construction is not that bad.

If you have a good website that can help me out please let me know. I want to learn how to do this for diffrent antennas.


texts: Bandwidth required for an arbitrary digital signal

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For a project at work, I need to figure out the bandwidth requirements for a digital signal so I can spec components.
My first thought was to look at the Fourier Series for a pulse wave. I got so far as determining that the Fourier Series for a pulse wave or rectangular wave was something with the sin(x)/x function in it. I didn’t actually compute the Fourier Series myself I just found that information online – before I could attempt anything like that I found this rule that I had forgotten about. That the spectral content of a digital signal is related to the rise time. When I tried to use that "rule of thumb" for this project I found myself with a few questions.
Why is it seemingly universally recommended that you use the rise time to find the spectral content of a digital signal and not the Fourier Series representation? Seems that they would be equivalent, is it just that using the rise time is "easier"?
I can find the rise time for a signal easily with an oscilloscope, however, once I run that signal though anything, a longer cable, a coupler, an amplifier, a power splitter, an IC, won't the component affect the rise time of the signal? How do I know the bandwidth requirements of the signal after its gone through some component or device? How am I supposed to know the bandwidth requirement at any point along the signal’s path without directly measuring it after each component or device?
More Details: I have a 1.28 MHz clock signal, a pulse wave, that is already synthesized. It runs through a ~100' cable to a rack of electronics. I need to design a chassis that takes the signal, buffers it and distributes it, providing a copy of the signal for use at that area, and two more copies of it, to be sent through similar ~100' cables to be used elsewhere.


texts: How to make final good looking prototype of our project?

texts: The handmade projects we make contain a lot of loose wiring and are actually bad looking products. So what should I do to make my product look better and that we can actually sell directly to people? Also, we want them to look attractive when displayed in my school exhibition.


texts: Open circuit volts and short circuit amps

texts:
I am looking to buy a few solar cells to mess around and learn with and I don't understand what exactly this part in the description is telling me:

"...offering 4.5V (open circuit) and 18mA (short circuit)"

Can someone please explain?


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I'm trying to come up with a good circuit from common parts that will allow me to set predefined contrast levels to the LCD from the microcontroller. I've seen an example on the internet but its for the PIC micro and it uses pulse width modulation.

I cannot afford to use pulse width modulation since I need to use my CPU cycles in the micro elsewhere.

So I thought of using a simple switch setup where depending on the value of the port pins, the contrast will be low, medium or high.

The maximum voltage that will enter the LCD as well as the micro is 5VDC. Eventually I will be running this circuit on batteries.

It is important that the display can produce clear text (not faint grey) when the battery level is very low (about 2-3V)

Question is, if this circuit setup is perfect, I would assume I could use 2N3905 for PNP transistors, but what about the resistors? Do I use some inverted voltage divider equation of some sorts?

I remembered in the past when I was playing with LCD's that when I hooked a resistor from the contrast to ground without initializing the LCD I see a bar of black squares (normal), but when I instead connected the resistor from contrast to VCC, I saw nothing. So that's why I asked if I needed some sort of inverted voltage divider equation to calculate the optimal resistor values.

Say the voltage level each battery produces is the following:

4V, 3.5V, 3V.

and in each of those cases, I want the display to be of maximum darkness without melting anything inside the display.

How do I choose the optimal resistor values?

And if my transistor setup is incorrect, how would I be able to improve that?