texts: Is it Electrically Correct to Direct Driving Seven Segment in Multiplexed Manner?

texts:
I want to design a voltmeter with minimum no of components so the pcb becomes as small as possible.For this purpose i wish to direct drive the seven segment display.

  Considering the fact Typically for a standard red coloured 7-segment
  display, each LED segment can draw about 15 mA to illuminated
  correctly, so on a 5 volt digital logic circuit, the value of the
  current limiting resistor would be about 200Ω (5v – 2v)/15mA, or 220Ω
  to the nearest higher preferred value.

  if I am going to use PIC16f676 ,The data sheet says PORTA & PORTC Can Source & Sink 200mA combined
  ,with maximum source /sink per pin 25mA

How will i calculate source/sinking current for a seven segment display working in a multiplexed environment( say 4 seven segments )  ??


texts: Strange characters in two arduinos trying to connect with nRF24L01+

texts:
am trying to connect 2 nRF24L01+ modules that just arrived in my inbox with 2 arduinos.

I am using the RF24 library with client in one and server on the other, pingpair, scanners. On ALL of them I am getting strange characters in Serial terminal display:

Unfortunately, I am unable to proceed any further.


texts: I have a simple circuit consisting of 2 ideal voltages sources (each 5V) parallel to a resistor of 5 ohms. The current along the resistor is 1A, right? But by applying the superposition principle (i.e. considering individual sources), I am not getting this result. Am I doing some blunder?


texts:
I have an audio sine signal -300mv to +300mv (600mv p-p), and I would like to read it using a microcontroller. I want to get rid of the negative half of the sine signal. How can I clip it?

I do not want to use a voltage divider to add DC bias to the signal because it may not be stable due to the power supply noise.

Also, the microcontroller accepts -0.5 to 6v on each pin. But is it OK to apply that signal for a reliable project forever.


texts: Need to step down votage to test a heart rate monitor

texts:
I'd like to create a test bed for heart rate monitor devices. The type of monitors I'd like to test use chest straps to detect the voltage fluctuations caused by the heart.  I'm told this votage fluctuation is on the order of 1 milli volt.
Basically, I need a circuit that can be attached to the device to simulate a heart beat so I can test various heart rate monitors without the need for a human wearing the strap.
Ideally, I'd need a circuit that can create pulses from ~.5Hz—6Hz.  The voltage of these pulses needs to be on the order of ~1mV.
I can create such a circuit with say a 555 timer, but the part I'm unsure about is how to step the voltage down from TTL voltage to mV.  Perhaps a bleeder resistor?
Any advice would be greatly appreciated.


texts: what is the pin connectors called that is used on through hole pcb with space above for swappable microcontrollers (or other devices)?

texts:
I have a medium size through hole PCB for prototyping. I remember a project in school that gave us a female to male connector that allowed us plug in a microcontroller (atmega328p, but could be any length of ucontroller) by hand without soldering or directly wire-wrapping the atmega's pins.

It provides black spacing above the PCB for the microcontroller's pins, but we solder the bottom through hole side (I believe the through hole was the standard 2.54 mm round opening). And the above female accepted the standard 2.54 mm as well.

Not sure of the length of the metal. I just remember the black portion was that standard plastic material that would melt when applying too much time soldering the metal.

I think its through hole DIP socket header but when I google that I can't find it exactly.


texts:
I have a sonic sensor which outputs analog voltage in 0-10V range with some noise on it. The sensor will measure the distance changes so I'm interested in an output signal not more than 40Hz. The analog output will go to a DAQ which has more than 1Mega-Ohm impedance. Here is the data sheet of the sensor: http://files.pepperl-fuchs.com/selector_files/navi/productInfo/edb/104092_eng.pdf

I noticed that the high frequency sonic burst noise is interfering with the analog output. So I can filter it by an RC filter easily.

But my question is if I want to set the cut-off frequency to lets say 40Hz, there are many combinations for R and C. What should I consider when choosing R and C in this case?


texts: determining the time constant for KI from a Graph

texts:
I'm having the following graph, I'm using PI controller, so I used a gain of KP = 2048.

I would like to determine the KI from that graph and the time constant of the integral term.
How would I get it
it


texts:
simulate this circuit – Schematic created using CircuitLab

Hi,

I have started studying diodes and In one of the exercises of my book, I have faced a problem.The exercise wants a i/v characteristic, to be more specific it wants me to plot IR1 with respect to Vx. I plotted it, but the manual is suggesting that after Vx=1.8 or 1.7, IR1 becomes constant and equal to (.8/R1). Why does that happen?

P.S : The diode is ideal.


texts:
There are several isolated solutions on the market such as ISO1176DW. These ICs usually pretty big, expensive and consuming.

However I could use non isolated transceiver with isolated power supply for both microcontroller and transceiver.

In some cases this solution can be much cheaper (especially if power supply isolation is given).

Is there any points I didn't aware of?

noise immunity?
safety issues?
data integrity?...


texts: Is the given voltage Peak Voltage or RMS Voltage

texts:
In circuit diagram problems is the labelled voltage RMS voltage
  or Peak Voltage ?

  For example say in problems like this what is the usual convention?

I recently started learning about circuits and i'm in high school.I don't know if the question is suited for this site or not.But I thought of giving it a try.Do let me know if it's off-topic.


texts:
When I pass a 33MHz 'Square Wave' through 3 ferrite beads connected in series, 742792606 (from Wurth), I see that the output wave turns 'Sine' in form. Also there is a delay as it propagates through the beads (close to 8nS) and it reaches the destination late.

How does the Inductor (ferrite bead) convert square wave to sine wave?
What parameters of the FB contribute to the propagation delay? What is the relation between delay and inductance?

Your response will help me to understand the nature of ferrite beads better, so thanks much!


texts: It's hard to see but on the overhead power lines, houses seem to only be grabbing one phase of the 3-wire transmission line. If each house is using a separate phase, what makes the 3-phase system an advantage if each house still has the 0-voltage point of the sine wave?


texts: Reading ADC using Altera DE2 Board (Beginner)

texts:
Question:
Would it be possible and feasible for a beginner to use Verilog HDL and an Altera DE2 board to read input from a weight sensor's HX711 ADC (see below), and if so:

What kind of data am I reading?
Where/how do I connect it?

(I suppose that "is it possible/feasible for a beginner" could be too vague for this forum, but the two bullet points above are the real question.)

Alternatively, if it's not possible/feasible, what would I need to look for in an Arduino microcontroller to use the HX711, in terms of minimum requirements (for the cheapest possible solution)? I believe I could connect an Arduino board to the DE2 via USB (though I wouldn't know what to do with that either).

Context:
I'm a computer science student, working on a final project for a basic (and very rushed) hardware course.  I have little to no prior experience with electrical engineering.

For my project, I'm required to either use Verilog HDL or MIPS Assembly Language -- and I'm far more familiar with Verilog at this point.

I am using an Altera DE2 educational board (with Cyclone® II 2C35 FPGA):
https://www.altera.com/support/training/university/de2.html

For my project, I'm trying to build a system that can detect the amount of liquid in a container, can be calibrated for any similarly-sized container, and then can (theoretically) fill the cup to the appropriate level, or at least calculate the amount of liquid needed to fill it.

I could only find one load/weight sensor in a local shop and I unfortunately don't have time to wait for online delivery, so it seems to be my only option.  It is "Arduino compatible" and uses an HX711 amplifier/ADC:
http://www.dfrobot.com/image/data/SEN0160/hx711_english.pdf


texts: How to troubleshoot a TI launchpad not running under Linux?

texts:
I have no experience with microcontrollers, except for a project a friend started with me and then abandoned midway. I still have the hardware and the code, want to complete the project, but I have forgotten most of the things we did two years ago, and I have reinstalled my OS, so I no longer have my dev environment set up. I also don't know C, but I can program in other languages.

My code does not do anything when I try to run it. To check if the microcontroller is communicating with the computer properly, I looked around for tutorials. This is what I found:

I should start mspdebug. I don't even know what I should expect to happen, but what I get is an error.

rumtscho@simak:~/Projects/sovfor$ sudo mspdebug -d /dev/ttyACM0 uif
[sudo] password for rumtscho:
MSPDebug version 0.19 - debugging tool for MSP430 MCUs
Copyright (C) 2009-2012 Daniel Beer <dlbeer@gmail.com>
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Trying to open UIF on /dev/ttyACM0...
Initializing FET...
uif: read error: Connection timed out
fet: open failed
Trying again...
Initializing FET...
uif: read error: Connection timed out
fet: open failed

I saw a question about a similar problem here, but as you see, the OP admits that he has no idea why it started working for him.

I should run a minimal program. I got to the make step, included <msp430.h> instead of  because the compiler suggested it. Then I got another error:

  rumtscho@simak:~/Projects/had_launchpad-blink-master$ make msp430-gcc
  -Os -Wall -g -mmcu=msp430g2553 -c main.c In file included from main.c:32:0:
  /usr/lib/gcc/msp430/4.6.3/../../../../msp430/include/signal.h:43:2:
  warning: #warning msp430-libc  deprecated, using
   [-Wcpp] main.c: In function ‘main’: main.c:65:11:
  error: ‘TASSEL__ACLK’ undeclared (first use in this function)
  main.c:65:11: note: each undeclared identifier is reported only once
  for each function it appears in main.c:65:26: error: ‘MC__UP’
  undeclared (first use in this function) main.c: In function
  ‘TIMERA0_ISR’: main.c:79:27: error: interrupt vector offset
  ‘TIMERA0_VECTOR’ is not an integer constant make: *** [main.o] Error 1

If I understand it correctly, the included library is deprecated, and so the variables it should contain are not found and the compiler thinks they are undeclared. But I don't know if this is the correct interpretation, and how to find the correct library to use.

As you can see, I'm quite over my head here. Can you suggest what next steps I could try? How do I start talking to the controller?

I am developing on Debian Wheezy, and installed all the packages suggested in various tutorials (everything with msp430 in the name, and a few others). I took the versions available in the Debian repository, did not compile from source.


texts: Is the skin effect a factor for low-current AC applications?

texts:
Another way to phrase the question might be, "Is the skin effect proportional to current flow?"

I am only vaguely familiar with the skin effect, so I read up on the subject to learn more about it, purely for academic reasons. (I don't currently have any projects where it is a concern.)

I understand that in order to determine conductor size for AC (or multiple conductors or waveguides, etc.), one must consider the frequency, the resistivity of the conductor, and the magnetic permeability. The Wikipedia article mentions:

  "It is also important even at mains frequencies (50 – 60 Hz) in AC electrical power transmission and distribution systems."

This statement seems to imply it applies more to high power distribution rather than household mains.

I understand that the center of a conductor is utilized less as frequency increases, but I am not clear on how it relates to current flow.

Does the skin effect become more intense as current increases? A chart on the Wikipedia article shows that at 60Hz, the skin "depth" is 8470μm. If this is constant for that frequency, then am I correct in saying that the diameter of conductor should be based on that depth for the intended current flow? Or, put another way, is the center of the conductor beyond that depth effectively pointless, regardless of current?


texts: How can I find i1 and i2 in function of Vg in this circuit?

texts:
Given the attached schema I'd love to find the analytical temporal and frequency expressions for the current in the 2 branches: i1 and i2.
R0, R1, R2, C1, C2 and Vg(t) are given. In the time domain can you show me how to set the system of differential equations that will bring me to the solution? Once I have the system it shouldn't be a problem to solve it using for instance odeint in Python.
Thank you in advance!


texts:
I am a computer programmer and typically post on Stack Overflow, but the tag I stuck in a recent post recommended I post it here.

Does anyone have experience with Bluetooth devices on engines like motorcycles?

We have an Electronic Control Module, or ECM, for a motorcycle, and we are thinking about integrating a Bluetooth transmitter on it.

I know Bluetooth headsets are currently used in motorcycle helmets, but a helmet can be shielded from electrical interference from the engine (induction coils and such).

Obviously, if the engine is turned OFF and the ECM is turned ON, data transmission via Bluetooth would be just normal operations.

We are more concerned with how effective laptops and PDAs will be at collecting data with applications we would write when the engine is running.

Typically, a mechanical machine like a car or aircraft can be shielded, but people are not going to want to shield their motorcycle engines.

Questions:

Has anyone done any work in this field?
Can you give me any information on what works and what does not?
Will the electrical fields from the motorcycle engine interfere with the Bluetooth data?


texts:
I want to power a three-phase 5hp well pump with a VFD. I want the VFD both to serve as a soft start, and to allow variable speed operation of the motor.
Two different pump salesmen have told me that running a VFD off a generator might hurt the VFD. Is this so? And if so, what is the mechanism by which generator power might hurt a VFD, but grid power does not?
EDIT: If the problem is variation in the generator's frequency or voltage, to what extent can that be mitigated by using an inverter-generator?


texts:
Lest's say that I have the following setup:
a split supply (using two voltage regulators: a positive and a negative one) connected to a center tapped transformer (12-0-12). The output of the transformer is rectified. The center tap is the COMMON of the circuit. Except for the actual values the setup would be exactly the same as this one:

Please ignore the values. It is just to make a better picture about the setup.

I have two questions:

In this setup, in order for everything to work properly, the current consumed by the positive rail should be approximately the same as the current consumed by the negative rail? Or it does not matter if one rail consumes less current than the other one.
For example if the positive rail will consume 3Amps and the negative rail only 20mA will there be any problem? Will there be any noise induced in the circuit? Or any other bad things? :)
How about if the transformer will have this setup: 12-0-5, so that on the negative rail a lower voltage will be used. Will it work properly? Or the two voltages of the transformer should be symmetrical?


texts: Question on the right PWM frequency for Permanent Magnet DC Motors

texts:
I know that there are some posts in this site about this question. I don't know if there's a way to find out the "ideal" PWM frequency for motor control. Usually they recommend to be safe in a range from 2 to 25 kHz. For example, in this post: Is there an ideal PWM frequency for DC brush motors? they recommend to compute the motor time constant in order to find the proper frequency.

Now, the main question is this. I took the following test fragment from a thesis.

Is this approach correct or reliable?

This is the motor I'm controlling:

The board that controls this motor measures speed and current. Does this data help in finding what is best for this motor?


texts: Can HC-06 be used as a Bluetooth server to which multiple devices can connect?

texts: Title sums it up. I want to use my AVR to be a bluetooth server for multiple Android devices. Is it possible? If iy is not what other method can be used to achieve this?


texts: Why do I get these voltage offsets when modeling an RC circuit with an AC voltage source?

texts:
During one of my homeworks recently, I became interested in modeling an editable graph of an RC circuit charge and current with respect to time. I used the formula that was derived step by step in my textbook for charge over time, derived for a DC circuit to graph this.

The function is:
$$
q=CE\left(1-e^{-\frac{t}{RC}}\right)
$$
I'm pretty sure that this function can model AC circuits as well, from my understanding of the integration at least.

Anyway, the calculated charge on the capacitor has a weird behavior when in the AC circuit. There's a voltage offset and undershoot that takes place on the first minimum of the charge \$q\$ in the graph below.

Current is yellow, charge is red, source voltage is blue:

I understand the charge time of the circuit isn't fast enough to match the voltage (when capacitance is 1 F, resistance is 1 Ohm, and voltage peak is 5 V) but why does it not match up with it on the second peak? Why does the function model this weird behavior where it doesn't meet it on the first minimum? Is it because in the first green circle, the charge isn't decreasing fast enough yet to meet the first minimum, so you get this weird shift?

Why does the capacitor charge have this behavior?


texts:
When using a soil moisture sensor in a plant to measure water indoor, how can we avoid dangerous water and electrical interaction.

In general, when there's water in the plant
When watering the plant, and accidentally dropping water on the wire connection

This is the sensor of interest so far (open for other recommendation). It seems kinda odd to be powered on 35mA!

http://www.robotmesh.com/soil-moisture-sensor?gclid=CMvW6bSz9bcCFWJqMgod9hYAfA

What I have in mind is to add a 50mA fuse between the power supply and the power input to the sensor itself

Power Source: Possibly 4 AA batteries


texts: PCB antenna connector and copper signal names

texts:
I am trying to build a PCB antenna similar to what is shown in this video. At the 6:24 mark it shows the circuit layout below:

I am using Eagle to layout the PCB on a two layer board.  Red is copper on the top of the board and blue is copper on bottom of board.
I am using a part from a library for an antenna mount.  This mount is so that this PCB antenna can connect to a separate transceiver Lora board.  The center pin is the signal feed.  The other four pins are (I'm guessing here) the ground.  I have attempted to layout the circuit myself.
Here is the schematic and the board.

The connector is shown on the info layer as being to right angle of board, but the connector fits for a variant which has the connector straight up towards viewer.
The vias were added and a ground plane in blue beneath the lower portion.  The vias connect to the bottom ground plane but not the the top layer Ant signal connected to signal feed center pin. During bring-up these can be used forexperimentation by hand soldering via on top.  These vias were added according to Figure 3 sub figure A in this wikipedia link.
In the video, he is showing the four ground pins with the heavy bold vertical lines by the antenna mount.  Are these "gnd" or "mount" pins connected to the signal pin?  I think not.
So the final question is, is the net/signal name "Ant" which is the entire top pour region and the center pin, also connected to the four pads for the antenna "ground," or should it be implemented as shown in the layout?


texts:
The book Crystal Sets to Sideband has discouraged frequencies above the low VHF band due to all of the problems with wires acting as inductors and difficulty on a stable Variable frequency Oscillator.

My goal is to build a 421 MHz 10 watt CW signal.

Would it be possible to build this out of discrete components like transistors, inductors, etc.?

Or is the frequency too high that it just isn't practical without microchips with tiny little traces to keep the lead inductance down?


texts: Switch DEBUG doesn't seem to be working in my code

texts:
Following code I tried on EDA playground with command appended with +define+DEBUG  but DEBUG switch doesn't seem to be working. Its always block is sensitive to error and this variable is changing four times here but still the block is not being sensitive.

http://www.edaplayground.com/x/7Cg

module test;
  integer error;
  event err;

  initial
  begin
      #10 ->err;
      #10 ->err;
      #3 ->err;
      #1 ->err;
      #10 finish(error);
      $display("%d",error);
  end

  initial error=0;

  always@(err)
  begin
      error=error+1;
  end

  always@(error)
  begin
    `ifdef DEBUG
      $display("Error at %d",$time);
    `endif
  end

  task finish(wrong);
    integer wrong;
  begin
    #10 if(wrong==0) $display("-----------TEST PASSED-----------");
        else $display("---------------TEST FAILED---------------");
  end
  endtask
endmodule


texts:
I recently read an article from https://www.fcc.gov/media/radio/am-stations-at-night

It says:

  During daytime hours when ionospheric reflection does not occur to any great degree, AM signals travel principally by conduction over the surface of the earth. This is known as "groundwave" propagation.

My queries are:

Do the AM signals refer to “shortwaves” or the medium waves? I think it can’t be medium waves as they don’t undergo ionospheric reflection and instead undergo ground wave propagation.
Do the shortwaves do undergo ionospheric reflection at daytime also but cover smaller range when compared to night time and at the same time during daytime, shortwaves undergo ionospheric reflection to cover a range larger than that achieved by medium waves via ground wave propagation?


texts:
I found few ferrite cores recently from my tools box they are T60006-L2063W517 -- Ferrite Toroids / Ferrite Rings Core 63x50x25 58.6uH@10kHz well my question is, how do I check they are in good condition,  as they look pretty old and want to check if I can still use them....
Ok so in datasheet I can find :
Inductance test without DC-magnetisation
Ieff x N = 40 mA
f = 10 kHz
Specified value: 44 µH <= AL <= 85 µH
What does it indicate and how to setup this  ...?  Open to any suggestions/ ideas..
Datasheet of T60006-L2063W517


texts: Non-insulated control of inverse parallel SCRs

texts:
I'm converting an inverse parallel (a.k.a. anti-parallel, back-to-back) SCR load switch from insulated control to non-insulated control.  Here is the original circuit using an optotriac to turn on the SCRs:

From OnSemi's Thyristor Theory and Design Considerations pp. 117-118, I want to replace the optotriac with a small TRIAC with non-insulated control:

My first stab at this conversion was to copy a small(ish) TRIAC circuit from elsewhere in the schematic:

A non-insulated (hot-side) microcontroller that is referenced to L1_SRC and -3V3_HOT will toggle Q34-A.
Am I missing anything?  Simulations in LTspice won't converge, and my lab access has been constricted since spring.  I know that I'll probably have to reconsider the gate resistances of R9, R123, and R311; but the rest just seemed too easy.


texts:
I've been using an ABB IRB 2400 robotic arm to gain experimental data and write a report based on the data.

I found that when I operated it at different speeds for pre-programmed paths, I got a larger variance in time taken over repeated paths at below 30-40% speed, and above 70% speed. Is this due to the AC motors in the arm having a certain operating region at which they work best with the least signal noise etc? Or is there other factors that I am missing?

My plot of the time variance is below:


texts:
I have a GPS Tracker that connects and send data to a defined public server: port through GPRS connection. I am getting the result on the terminal.

I have provided with a manual. I don't understand one part where I need the help of you that's why I came here.

I received vehicle status value like this FFF7BBFF.And the manual says about this value is

I do not quite understand how to use it. Do you guys have an idea ?. Please anyone can explain to me and help me to translate this code FFF7BBFF


texts: Is there any flaws with this Attiny 85 schematic?

texts: I was wondering if there is anything I am missing in this Attiny85 schematic. It will be first burned with the Arduino bootloader through the pins. I am making something similar to the DigiSpark attiny85


texts:
I want to create my own potentiometer for a project. Part of the reason is because I believe it'll be more adapted to my needs but I must admit that it seems like something really fun to do.

I've read online that the resistive part of the potentiometer is either made of Graphite or a "resistive cable". I know many good stores selling electronics component but I wasn't able to find graphite stripes to make my own potentiometer.

Another idea I had is to use a cable used for heating since they are pretty resistive by definition. I'm just not sure if it could work correctly.

So what are my options?


texts:
A 10 MHz TXCO is driving a receiver’s front end and has a frequency deviation of 10 ppm.  It drives a direct downconversion RF front-end mixing the L5 frequency.  What is the frequency offset at baseband due to the TXCO?
L5 frequency = 1176.45MHz
I dont quite understand this question, help pls. Thanks in advance.


texts: How can I connect two different DC power sources together?

texts:
How can I connecting two different DC power sources together? for example 15Vdc(5Amp) with 5Vdc(2Amp).
I want to make one DC source (20Vdc,7Amp) by more powerful supplies.


texts:
Transformers have hundreds of turns on both the secondary and primary winding, and as a result use very thin copper wires for each.  But, why do they not just use fewer turns on each winding and get the same voltage ratio?

More importantly, why not use fewer turns of a thicker wire for an increased VA?
(instead of 1000:100 turns of 22 awg wire, why not 100:10 turns of 16 awg wire if this would increase VA)


texts:
Studying for an exam
Looking at Data buses using Wired AND and Wired OR configurations.

Using tristate logic, a device is able to gain control of the bus and transmit anything down it.

I don't understand Wired AND or Wired OR.
The way I understand Wired AND at the moment - no device has control of the Bus and the output stays at a constant voltage (say 5V) if no devices are attempting to use the bus.
However when a device attempts to use the bus the line will be pulled to 0V.
Now if any device attempts to use the bus at the same time, it will never be clear which device is transmitting.

Also Wired AND is supposed to be active high however when a device uses the bus the line goes low. I would have thought this was active low.


texts: Picking a transistor for a circuit I'm building- Raspberry Pi

texts:
I am building a circuit that will connect a raspberry pi to a solenoid. I'm following roughly this schematic: http://playground.arduino.cc/uploads/Learning/solenoid_driver.pdf and modifying it so that it connects to pi GPIO pins instead of an arduino.

I need to pick a transistor, as shown in the schematic. I believe it needs to have at least 2.58 A to match my solenoid, and 5V to match the voltage from the Pi. However, when trying to pick a transistor it gets more complicated because I'm not sure what I need for V-EBO and V-CBO.

Can anyone help me figure out what specifications I should be looking for, or suggest a transistor? This one I found has a VCBO of 80V, but I believe that is too high because my Pi will have a power supply of 5-6V.


texts:
I need your advice regarding the USB 2.0 signals routing. When I reach the USB connectors, the data lines (D+ and D-) have to be swapped. I have two options there: 1) swap the lines using vias and go from top to bottom layer for a short, 2) make a loop around the connector, like in the following picture.

What is your suggestion, what is better option in therms of signal integrity ? I just wonder if this loop emphasizes antenna effect, but maybe the option with vias is worse.

P.S. Just to avoid confusion,bellow the top layer, there is a solid GND plane, so this split plane is power plane (layer 3), not the GND plane.

Thank you for your time,
Igor


texts: Panel mounting an LCD screen in a hobby project

texts:
I am looking into the initial design of a project I am working on as a hobby. I would like to use a development kit with an integrated LCD such as the 32F469I-DISCOVERY. I would like to include this screen flush mounted in a durable (read outdoor, non submersed) and professional looking faceplate.

I have access to a low power laser cutter or CNC machine but am unsure the best method to achieve a good looking product.

My initial thoughts are to use an aluminium face-plate and find thin (1mm?) acrylic stock that can be glued/bolted to the back of the face-plate as a window, with some kind of optical adhesive/fluid between the window and the LCD but this seems an overly fiddly and complicated process.

What suggestions to people have for a good method of taking an arbitrary LCD and panel mounting it in a robust and visually appealing manner.


texts: Damaged solder pads on FX-Audio DAC-X6 Alternate solder locations?

texts: I've tried to remove a faulty 6.5mm headphone jack from a FX-Audio DAC-X6 and ended up removing the solder pads from the board. I'm trying to save this instead of trashing it and buying a new one for $50+. If I order a new headphone socket where can I attach the pins (Right, Left, Ground)? I don't understand what the 4th pin is and where it should be attached.


texts: Unable to resolve ADC conversion error in stm8s105s6

texts:
I'm trying to learn ADC on stm8s105s6. But not getting proper adc result. I shorted VCC to analog pin 3 and expected conversion value near 1023 as stm8 has a  10 bit adc.

#include "stm8s105s6.h"
unsigned int a=0;
main()
{
        CLK_CKDIVR=0x00;

        FLASH_DUKR = 0XAE;
        FLASH_DUKR = 0X56;

     //WAP to read ADC Data.

        ADC_CSR                 =0B00000011;// channel 3, ADC not complete
        ADC_CR1                 =0B00100010;// F/4 , continous converion disable adc
        ADC_CR2                 =0B00000000;// Left Align
        ADC_CR3                 =0B00000000;// Data Buffer Disable
        ADC_TDRH                =0B00000000;// Schmitt Trigger Enabled
        ADC_TDRL                =0B00001000;// Schmitt Trigger Enabled
        ADC_CR1                |=0B00000001;// Enable ADC

        while(1)
        {
            ADC_CR1|=0B00000001;//Enable ADC
            while((ADC_CSR&0x80)==0x00);//Till EOC is reached.
            ADC_CSR&=0B01111111;//Not Completed

            a=ADC_DRH;
            a=a<<2;
            a=a | ADC_DRL;
            delay_s(1);
        }
}


texts:
A nooby question:  I installed new LDO regulators on the power supply section of a PCB, and one of the pins severed when I bent it down to screw on to the board (two of the others did not sever but have exposed copper).

I soldered the broken pin back together and am getting continuity again across all the pins, however the unit is not powering on.

Even though I was very quick with the solder is it possible I fried the IC because I was closer to it with the iron?

It also seems possible that the outer surface of the pin is what is joined, not necessarily the copper core- will this make a difference?  Unfortunately I don't have an independent power supply to test the regulator, so I'm just trying to get a feel for what could have gone wrong or if it's potentially something else.

Thanks for your help.


texts: How do I emit an arbitrary 2.4GHz radio wave

texts:
I'm looking to create a microcontroller that would allow me to drive my ceiling lamp that is controlled by 2.4GHz remote. The end goal is to integrate it with home automation tools, and forget about extra remote.

I used SDR radio (hackrf one) to get a better understanding on the communication. Given that the lamp was pretty cheap I didn't expect it to be a complex protocol. I found following things:

The remote always uses the same frequency for communication (2.449 GHz)
The remote codes doesn't change over time (I can drive the lamp from my SDR using my records with no problem)
The remote codes/waves seems to be fairly simple (see images later).

And now I come to a problem how do I replicate this signal? Something that will work best for me is what type of modules (ideally playing well with esp/arduino) should I be looking for?

Having no experience with wireless communication I wrongly assumed that I'll be able to hook up e.g. nRF24L01+ module to esp32 and just do something like delay(16); rf.high(); delay( 16 ); rf.low();. However, after reading about this particular radio module it turned out it has a fixed communication protocol which won't fit this purpose.

For a reference I'll put sniffed code visualization taken with GNU Radio and imported to Audacity for visualization:

the entire signal sequence:

First batch of codes:

Maximal zoom on "1bit" signal wave:

Maximal zoom on "1bit" with less gain as requested in comments:


texts: Preferred or common connectors for CAN bus on the PCB?

texts: Looking for a decent connector to carry CAN bus signal from/to a PCB. What is the most common type? Ideally something compact. I would like to avoid DB9 since it looks too much like RS232. This isn't going into a hostile environment.


texts: If I run electrical current through the conductors in a magnetic shield, can It be used to shield stronger magnetic fields?

texts:
I'm wondering if running electrical current through a shield amplifies its effect to a significant extent, effectively making it into a shield you can "turn on and off" for stronger magnetic fields than what it would normally be used for,

If so, could I run AC, or pulsed dc current through it to repeatedly block and release the field, simulating a significant oscillating(in this case , turning on and off again) magnetic field at normally unobtainable frequencies(sush as 30 ghz)


texts: Connecting an LCD display to msp430 launchpad?

texts:
So im trying to give my lcd display (Lumex 1602) 5v. Im trying to use the test pins on my msp430 launchpad TP1 and TP3.

On the LCD pin 1 is gnd and pin 2 is power. for the launchpad TP1 is power and TP3 is gnd.

nothing lights up after plugging in the usb cable. Does mine just not have a backlight in it? How can i test to make sure its getting power and that it isnt broken?

*Edit So i got it to light up!
Heres how i wired it:
LCD Pin1 to gnd
LCD Pin2 to pwr
LCD Pin3 to Potentiometer. This is what drives the LCD display.

I used TP1(pwr) and TP2(gnd) which are test pins on the msp430 launchpad and provide me 5v power.


texts: LED as transmitter and photodetector in the same circuit?

texts:
As in this answer I plan to use a 5V neopixel RGB LED as both transmitter and receiver to transmit information between ATMega328 boards via fibre optic cable. (This is the Forrest Mimms strategy, for the curious)

Ignoring the coordination problems inherent in it being a half-duplex system (both sides can talk, but not at the same time), what kind of circuitry would I need to switch the LED's mode?

Based on the title of this paper I assume it's possible: Half‐duplex visible light communication using an LED as both a transmitter and a receiver but the paper is paywalled so I can't look up how they did it.

(I assume someone on here has access to that journal, though?)

Bandwidth can be ridiculously low; I'll only be sending ~32 bits max per message, with messages on the 10 to 30s range.


texts: How to calculate temperature through NTC thermistor without its datasheet?

texts:
Thermistor has "103" written on it, that means its suppose to be 10kΩ at 25°C.

That is all I know. I don't know the B-constant. I don't know the manufacturer to find the datasheet.

I connected my multimeter probes directly to the leads of thermistor. Resistance varies between 11.8 kΩ to 12 kΩ at 26-27°C. Is my thermistor faulty?

My required temperature range is 10°C-35°C.

Also, I found different equations on this site, which one should I be using?


texts: Interrupt on Change in PIC16F18877 Not Triggered

texts:
I'm trying to trigger the interrupt service routine method in PIC16F18877 microcontroller, but the code never gets into the isr() method. Not sure what and where am i going wrong. Here is the code i've wrote.

    // PIC16F18877 Configuration Bit Settings

// 'C' source line config statements

// CONFIG1
#pragma config FEXTOSC = HS     // External Oscillator mode selection bits (HS (crystal oscillator) above 4MHz; PFM set to high power)
#pragma config RSTOSC = EXT1X   // Power-up default value for COSC bits (EXTOSC operating per FEXTOSC bits)
#pragma config CLKOUTEN = OFF   // Clock Out Enable bit (CLKOUT function is disabled; i/o or oscillator function on OSC2)
#pragma config CSWEN = ON       // Clock Switch Enable bit (Writing to NOSC and NDIV is allowed)
#pragma config FCMEN = ON       // Fail-Safe Clock Monitor Enable bit (FSCM timer enabled)

// CONFIG2
#pragma config MCLRE = ON       // Master Clear Enable bit (MCLR pin is Master Clear function)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config LPBOREN = OFF    // Low-Power BOR enable bit (ULPBOR disabled)
#pragma config BOREN = ON       // Brown-out reset enable bits (Brown-out Reset Enabled, SBOREN bit is ignored)
#pragma config BORV = LO        // Brown-out Reset Voltage Selection (Brown-out Reset Voltage (VBOR) set to 1.9V on LF, and 2.45V on F Devices)
#pragma config ZCD = OFF        // Zero-cross detect disable (Zero-cross detect circuit is disabled at POR.)
#pragma config PPS1WAY = ON     // Peripheral Pin Select one-way control (The PPSLOCK bit can be cleared and set only once in software)
#pragma config STVREN = ON      // Stack Overflow/Underflow Reset Enable bit (Stack Overflow or Underflow will cause a reset)

// CONFIG3
#pragma config WDTCPS = WDTCPS_31// WDT Period Select bits (Divider ratio 1:65536; software control of WDTPS)
#pragma config WDTE = OFF       // WDT operating mode (WDT Disabled, SWDTEN is ignored)
#pragma config WDTCWS = WDTCWS_7// WDT Window Select bits (window always open (100%); software control; keyed access not required)
#pragma config WDTCCS = SC      // WDT input clock selector (Software Control)

// CONFIG4
#pragma config WRT = OFF        // UserNVM self-write protection bits (Write protection off)
#pragma config SCANE = available// Scanner Enable bit (Scanner module is available for use)
#pragma config LVP = OFF        // Low Voltage Programming Enable bit (High Voltage on MCLR/Vpp must be used for programming)

// CONFIG5
#pragma config CP = OFF         // UserNVM Program memory code protection bit (Program Memory code protection disabled)
#pragma config CPD = OFF        // DataNVM code protection bit (Data EEPROM code protection disabled)

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

#define _XTAL_FREQ 4000000
#include <xc.h>

void interrupt isr(void)
{
    if(IOCIE == 1 && IOCIF == 1) //if interrupt on change is enabled, and IOC flag is set,
    {
        if(IOCBF1 == 1) //if interrupt occured on port bit RB1 and the RB1 interrupt flag is set,
        {
            for(int i = 0; i < 5; i++) //blink LED on RC1 five times
            {
                RC1 = 1;
            }
            IOCBF1 = 0; //clear RB1 interrupt flag
            IOCIF = 0; //clear interrupt on change flag
        }
    }
}

void main(void)
{

    ANSELBbits.ANSB1 = 0; //disable analog input on RB1
    WPUB = 0xFF; //enable weak pull up resistors on all port B pins
    TRISB1 = 1; //RB1 is input pin
    IOCBP1 = 1; //interrupt on change positive trigger enabled on RB1;
    IOCBN1 = 1; //interrupt on change negative trigger enabled on RB1;
    IOCBF1 = 0; //clear RB1 interrupt flag
    IOCIE = 1; //enable INTERRUPT ON CHANGE
    GIE = 1; //enable GLOBAL INTERRUPT

    TRISC1 = 0; //RC1 as output
    RC1 = 0; //set RC1 output to low

    while(1)
    {

    }
}

The above code never enters the isr() method. Any guidance is much appreciated. Thanks.


texts: Speaker and player on same 5V charger crackles but not with two separate chargers

texts:
I am using a Samsung mobile phone connected to an external speaker (connected via a standard audio cable with jack connectors).

Audio is playing fine when I use two Samsung-branded 5V-DC chargers, where each device is powered by its own separate charger.

The problem is when I connect both the phone and the speaker to the same shared charger. I do not use any kind of USB hub — I've soldered the wires together without any inserted components.

Specifically, when audio is playing I can hear (not very loud) random "electronic" crackles. They are not any kind of periodic hiss, noise or hum but really like "random singing". Both chargers are always connected to the same wall socket.

My question is: is there any kind of component or action I can add/take to get rid of the audio crackles?

I've tried different brands of charger (Samsung, Google) but the problem was the same.


texts: Good explanations of audio piezo element behavior

texts:
Is there any description anywhere of how voltage, current, mass, momentum, and air interact in a typical audio piezo, and what sort of signal should be expected on the third pin of a three-terminal device (phase relationship with regard to drive, etc.)  I'd like to drive a piezo as loudly and as efficiently as possible from a small battery; presumably that would imply trying to maximally exploit its resonant behavior.  The normal circuit given for driving 3-wire piezos looks inefficient to my eye (similar to a class A amplifier), though perhaps there's something about the way piezos behave electrically which would cause the resistors to spend most of their time sitting with very low voltage across them.

I've google searched for audio piezo electrical behavior, and didn't find anything useful; I did find some explanation of how crystals work, but I would think the diaphragm coupling piezo-element vibrations to the air would substantially affect the behavior.

Addendum

I understand pretty well how motors work: an ideal motor can be modeled as a black box such that the voltage across the motor leads at any given time will be some constant number of volts per (revolution per second), and the current through the motor will be some constant number of amps per ounce inch of applied torque, and most practical motors can be modeled as an ideal motor in series with a resistor and inductor.  What I'd like would be a similar understanding for piezos.

The voltage across a piezo doesn't seem to represent its absolute position, nor its velocity, nor acceleration.  What would the voltage on an "ideal" piezo represent, and what must be added to the model of an ideal piezo to make it reasonably match real-world behavior?


texts:
SCR is good for latching DC source, one trigger will turn on the source indefinitely. But how about AC source?

Latching mechanical relays is good but it is too big for me. Triac is designed for AC but not good for me as the triac must be triggered every time. Is there an electronic component or circuit design that can latch AC source with one trigger (SCR but designed for AC source)?

For example, I made a project before, just a simple motion sensor powered by 5V battery. If the module sense something, it will interrupt MCU which will then trigger the latching relay once to open the light bulb connected to main AC line, but the latching relay made it look big and I don't like it. I want it similar to latching DC in which just a single SCR will latch the source with one trigger and so saves battery power and is smaller compared to relay.


texts: How to use one 12V power supply to supply two Op/amp with 5V and 12V voltage supply?

texts: I am trying to design a circuit and i have two Op-Amp with different supply voltage with -+12V for LT1220 and +-5V for LT1193. i want to use just one power supply with +-12V. in that case for Lt1193 i would like to make a local power supply for that. using Zener diode with zener voltage regulator is good approach or is there any high efficient way in practice for this purpose?


texts: Problems with low-side MOSFET in 12V LED dimming switch

texts:
I'm pretty new to electrics/electronics. I'm sorry if I make dumb questions, and thank you for your time.
I wanted to control my LED strip shipped from Ebay, which works well with 12V 2A DC adapter. To control this, I've made a dimming switch which is designed to work exactly same as the one on Aliexpress. The schematic is like below:

I designed and ordered a PCB based on the schematic above, and it worked pretty well. However, I found two problems:

The load and the circuit are exposed. When I touch a tab(tied to drain) of a MOSFET or SMD resistors on a GND line over the LED strip, the LED slightly turns on.

The MOSFET has no gate pull down resistor.

The latter is not so critical to me because it gives me an expected behavior: being turned on while the ESP-01 is booting. What makes me sad is the former one.
After a few hours of searching, I found that this style of placing MOSFET after load is called "Low-side" switching, and it is not suitable for applications where the circuit or the load can be grounded.
They are in fact physically isolated from the ground by mat wooden surface(my desk), so I expect that they would work without any problems. However the LED sometimes randomly flickers at a very low brightness in the dark even if it has no contacts to any conductive objects. The brightness increases when I touch the tab of the MOSFET or the GND line of the LED, making me think that this is the matter of grounding, which can be a problem with the low-sided MOSFET design.
So my question here,
Q1. Did I catch the right problem?
I don't know if my diagnosis is correct. There might be a number of things that I missed out.

I'm going to redesign the circuit with high-side p-channel MOSFET. I'm currently reading this article and trying to understand why p-channel MOSFET works that way.
My second question is:
Q2. Would it be a good choice to refactor the circuit to use a high-side MOSFET?
Thank you for your time.


texts: Are datasheets translated into other languages (e.g., Japanese, Chinese)?

texts:
A recent video I saw surveyed Japanese folk on the street and their knowledge of English. The majority of those surveyed had little to zero working knowledge of the language. So that got me thinking - how do engineers/designers in non-English speaking countries design electronics? From my basic research, I can't seem to find translated versions of datasheets for very common components (LM7805, LM340, etc.).

For example, on the Ti's Japanese site for the LM340 (http://www.tij.co.jp/product/jp/LM340/samplebuy), even the datasheet is in English.

Do companies provide datasheet translations for their parts? Or do engineers in non-English speaking countries time translating the information for themselves?

Would love to get some insight on this. Help satisfy my curiosity!


texts: In wireless communication, I am confused about what people are referring to when they use the term 'channel tap.'  Can someone explain the term or provide me a definition? Any help will be appreciated!


texts: Can I use a car battery to power my robot?

texts:
I'm building a machine which can fly a kite. It uses a camera to follow the kite in the air, and based on that it pulls the wires using an electro motor which hangs in the air under the kite.

So far I just have a test setup in my house, but I now want to take it outside. At some point I need to strap a battery to the electro motor in the air, but that means I need to buy a pretty large (and expensive) LiPO battery pack while I don't even know if my machine is going to work.

So for now I just want to have a power source at the ground and a wire that goes up to my kite to power the motor. So I thought of simply wiring it up to a car battery. Since the electro motor below the kite is 24V (8A) I need a converter to convert my car battery power from 12V to 24V (such as this one).

The electro motor in the air will be turning right and left interchangably and it will run about half of the time.

My question is; can a regular car battery even handle that kind of load (if needed I can of course keep the car motor running)?

All tips are welcome!


texts: How can I test a USB switch and hub for compliance with USB power standards (e.g. no backfeed)?

texts: I would like to buy a USB switch and hub, or a combination hub/switch to connect several USB peripherals to two computers. According to this answer on a related question, many USB devices like this are cheaply designed and can feed power from host to host or from device to host. I would like to use a multimeter or similar device to ensure that my hubs and switches will not damage my devices. What is the best way to do this?


texts:
I'm trying to create a power supply protection (overvoltage, undervoltage, reverse polarity) for a ±33 V, 7 mA power supply for an op-amp.
The opamp would be powered by a lab supply in theory. So the idea is to protect it in case the operator hasn't set the voltage right, the protection will correct it so it's never above +33V (and -33V for the other rail).
Second point, it would be nice to have: if the current is rising above the set limit, the protection would cap it at chosen value.
Third protection needed: if the operator plugs the cable the wrong way, the opamp is ok.
Do you have any suggestions? My system must withstand ±50 V, about 10 mA, reverse polarity (and no shut down, caused by a fuse for example, would be a massive plus).


texts:
I have a legacy board in my product that has 1 temperature input with 2 rtd temperature probes.

Until the new boards are ready the manufacturer has used a relay already mounted on the board to switch between the 2 RTD's. The relays are not reliable enough and keep failing.

The board has some spare Open Drain outputs that I want to use to switch a 4052 Multiplexer between the 2 rtd probes, replacing the relay function.

The 4052 multiplexer needs +5V at VSS and at "A" the logic pin. I can get +5V from the board, but how do I use Open Drain to switch +5V at "A" the logic pin?

I'm guessing pulling A high with a 4k7 to +5V and then somehow pulling it low with a transistor connected to the open drain pin? But I'm not too sure.


texts: Converting an NO reed switch to a NC with lowest leakage current

texts:
When the switch is closed I need the pin on the microcontroller to be high impedance, when the switch is open I need it connected to the ground. I need the leakage current to be minimal.
What should I use? An inverter, an open drain transistor, or are there any other options, like an inverting relay package?


texts: Can someone explain this gain & offset op-amp circuit?

texts:
I'm having trouble understanding the circuit in the photo below.  I know that it's a gain and offset amp designed to convert 0-2.5 V range to +/-10 V range (hence it has a gain of 8 and an offset of -10 V).

But what I don't understand is how it works.  It doesn't look like any of the 'basic' gain and offset circuits I've seen.

Ultimately I'd like to be able to modify the component values and Vref (currently 5 V) to take a 0-3.3 V input instead.

If anyone can shed any light I'd be most grateful!


texts: How do I find the input impedance of a common emitter amplifier?

texts:
How do I find the input impedance of this common emitter amplifier?

\$V_{CC}\$ is supposed to be at the top of \$R_5\$. I forgot how to do the analysis to find the input impedance. The input goes in through the blocking capacitor, \$C_8\$, the output comes out from the collector of the NPN.


texts: How to connect Electret Microphone module and OPAMP?

texts:
I am trying to build a circuit that gets electret microphone input and maps into 0-1V for utilizing in ADC.

The microphone module suggests using such circuitry
When I tried that circuit and talked to the microphone and used frequency generator app, I observed -200mV - 200mV output which is perfectly fine for my amplifier circuit.

Moreover, when I try connecting 200mV voltage supply to the amplifier circuit

I still get perfect 0-1V output in both LTSpice and from hardware. However, when I connect the microphone circuit instead of voltage supply, the system blows up and doesn't give me any input voltage (right before below 220k) or output voltage.
What do you think that could be the reason for that? Is there anything that I might be missing in the microphone circuit?

EDIT: I changed non-inverting amplifier to such circuit

Would it be better for DC biasing to the microphone?


texts:
What does it mean in itself and in context?. Bolded phrase in section 10.5.2 IEEE Std 519.

  Methods for compensating for existing or potential flicker are much
  the same as those used to compensate for subtransient disturbances,
  such as those evidenced by notching or harmonic currents. The simplest
  and generally most effective technique is to provide a sufficiently
  stiff source of power so that the effect is negligible at the point
  where the flicker source is tapped off from the rest of the power
  distribution system. Compensatory methods are used to emulate the
  stiff source. Series capacitors, thyristor switching of inductors with
  shunt capacitors (static var control), saturating shunt inductors, and
  thyristor switched shunt capacitors may be used to maintain a
  relatively steady voltage at the tie point. As in cases in which such
  schemes are used to provide subtransient compensation, the possibility
  of overall distribution system instability must be thoroughly
  investigated before one can confidently apply the technique.

Thanks!


texts:
Given the following circuit, I would like to calculate the Thevenin equivalent of the voltage in RMS.

I know that R = 400 [Ω]; e(t) = 40 cos(10^4 t) [V].

However, I can't understand why there is a factor of 1/2:


texts: Making a simple solar-powered lighting system, a few concerns

texts:
I'm building a fairly simple solar-powered lighting system to use at home, which charges up a battery by day and then the battery powers a few bulbs at night, switching automatically. So far, I got that switching mechanism working with an LDR and a relay.
Now I am planning my circuit to look like this (a few things omitted for simplicity):

I have a few questions:

1)Does the circuit make sense and do you see it working?

2)I know I need a 'common ground' between all voltage sources, so I simply connect all the grounds (negative battery terminals) to a single node?

3)Each of my bulbs draw 333 mA (4W / 12V). If I put many of them in parallel my total current draw will be very high. Are transistors the best option here, or am I better off with relays?

Thank you


texts: Will this N-Channel Mosfet work as high-current motor controller?

texts:
We are building a mobile robot which will use two motors in a differential drive configuration to maneuver and move around, and we want to choose the right driver IC or transistor circuit for the job of controlling these motors and providing enough current.  Our motors are rated at a power of 14W (link at bottom) and we will be using an 11.1V lipo battery to power them.  We might be changing our battery setup once we get this thing built and tested.

So I am looking for a motor driver IC or transistor configuration which can provide enough power / current for our motors.  The way I understand it, the L298 provides 2 amps max per channel, which I guess would work for us since the 14 watts / 11.1 volts = about 1.3 amps max current draw, is that correct?

We are also curious, the stall current of these motors is rated at 11.5 amps.  I'm assuming that this means that, should the motor stall, it will then draw 11.5 amps of current until it begins moving again as it should.  Should we use a transistor configuration / driver which allows for higher current draw than 2 amps then?  There is a chance that, while operating this robot, it might bump a wall or something which would result in a temporary stall in the motors being able to freely spin.  Forgive my questions please, I am still fairly new to this stuff.

If the L298 wouldn't work for us, I was looking at something like this: https://www.sparkfun.com/products/10213 .  We would need four of these since we need each of the two wheels to go forward or backward.  So two wheels x two directions = four semiconductors.  Again if this isn't right, please feel free to suggest something better.

Thank you so much!

Chris

This is the motor we are planning on using (two of them.)
https://www.andymark.com/NeveRest-p/am-neverest.htm


texts: no-load DC output voltage of DC wall-wart circuit

texts:
I have this question and I believe the answer is 12.73 from the equation

V(N) = V(Rated) * sqrt(2).

Is this the correct formula and can someone show me how we arrive at it if it is. I am unsure about the derivation so I am unsure about whether the a change in the voltage across the diode will affect the no load voltage output. For example say if the forward voltage of the diodes was 0.9V or 1.1V?


texts: What concerns are there with running high frequency traces?

texts:
I am working on a project where i will be laying out some traces that will be handling Gigabit Ethernet traffic. I know that putting these traces on the outside layers (Top or Bottom) is a bad idea, with noise and other EMI issues, but what other issues should i be concerned with?

I'm assuming that the trace width will be a factor, the board in question is currently 4 layers, standard 1.6mm thick FR4 with 1oz copper thickness on top/bottom with 0.5oz copper thickness for the internal traces.

There are two pairs of TX+ TX- and RX+ RX- for gigabit, should all four of these pairs be routed on the same internal layer, or should i route them on separate layers, for example TX1+ TX1- and RX1+ RX1- on layer 2 and TX2+ TX2- and RX2+ RX2- on layer 3?

How should i run grounds around these signals, between each signal, around the block of signals, and should i put ground planes above and below these traces?

Also, i probably shouldn't run the traces directly from the MCU to the connector, but I'm not really sure about what sort of inductors or coils i should use. By the way, the connector is about 10cm away from the MCU.


texts:
I've got a problem understanding formal writing down of complements on inputs.

During my laboratory exercise I was working with a device that had D flip flop embedded in it. The goal was to investigate the working way of asynchronous inputs s and r. Hence, it was not mandatory to plug in the D input or clock input.

Pressed s button and released r button gave Q = 0 result.

Released s button and pressed r button gave Q = 1 result.

So we were dealing with complemented (active-low) async inputs s and r.

Released both s and r inputs gave Q = 0 output (so Reset was dominating over Set).

Pressed both s and r inputs gave Q = previous output value.

That being said, I am having trouble organizing the truth table for it.

Which truth table (characteristic table) presents the above described situation?

The left table is a 1:1 translation of what has been above said, and I would be willing to use that table. But what about right table? In my opinion, the right table is exactly the same as left table, but it just explicity says that the inputs are complemented.

In the case of the left table, it is implicitly said that the inputs are complemented.

Regardless: I believe both truth tables are correct, aren't they? The only difference is that the left table implicitly says that inputs are complemented, and the right table says its explicitly.

Essentially: are those truth tables equivalent, or not? If not, then which truth-table is coresponding to my situation?

Also, adding timing chart. Not sure if it's correct as it is, or perhaps it will be correct only if I change the notation from s and r to ~s and ~r.


texts: Subtract Diff-Signal (Millivolts range) on top of common mode voltage (volts) with opamp - very inaccurate

texts:
I built a  subtractor circuit as shown here with 10k each resistor. Now I want to measure current by using a shunt between the two inputs and letting a current flow through it, see here, figure 4, the only difference is that my reference voltage is not GND but 8V.

The voltage on the shunt is in the 10mV region, the common mode voltage swings from GND to about 20V.

Ideally this should happen: e.g. (10mA current, shunt resistor 1 Ohm) 10mA x 1 Ohm = 10mV at shunt. Let R_Load be 100 Ohm-> 100 Ohm x 10mA = 1V. So we would have on the lower end of the shunt 1V and on the upper end 1.01V, difference is 10mV. Since all Resistors in the difference amplifier (DA) are equal and reference is 8V we should get at the output 8V+10mV, right?
If we changed the load to say 1k, we would have a common mode voltage of 10V at 10mA and still the output of the DA should still be the same, 8.01V, right?
But this is not the case, but different CommonModeVoltages (CMVs) result in drastically different output voltages (means, the difference at the shunt is not multiplied by one for all CMVs but alters heavily).

Why is that?

I suspected, that the common Mode Rejection of the Opamp was not good, but:
Using a TL082 we have 80dB CMRR, means 10^4 = 10000, which should mean, that a common mode voltage added to the difference signal should have an effect of 2mV for a CMV-Swing of 20V, right?

However the difference at the output is way larger (uselessly large).
Does anyone have an explaination for that?

When I used a INA122 instrumentational amplifier, the problem was totally solved. Still I don't understand the problem.


texts:
I'm trying to build a MON08 interface to program a 68HC908QB8, as per page 13 of this PDF:

Low-Cost Programming and Debugging Options for M68HC08 MCUs

Below is my schematic, from which I have created a PCB:

I cannot get the Freescale Bootload software to connect, irrespective of any combination of the two switches. It attempts to look for a reset ACK signal, but times out:

Granted this is ageing technology now, but do USB to RS-232 converters run on a different voltage to regular RS-232 interfaces? I believe RS-232 signals are +/-12V? This would determine some of the resistor values in the circuit. If this is the case, would it be worth trying a PCIe-based RS-232 interface?

Am I missing anything in my schematic, compared to the schematic in the PDF?


texts:
With the following circuit:

There is a resistor (R2) in front of RL. So how would you find Vout?

I already know the formula for finding Vout (Vout = -(RF/R1) X Vin), but what do you do with R2 in the way?


texts:
We have some sinus signal at the input and at the output we have offset equal to \$5V\$ and sin wave with \$A=0.5V\$. Calculate \$R_C\$. What will happen with the output voltage (DC and AC), if \$C_E\$ is short-circuited?

Calculating \$R_C\$ is simple:

\$E_C-I_CR_C=5V\\
15-2mA\cdot R_C=5V\rightarrow R_C=5k\Omega\$

But I have no idea what will happen if we replace \$C_E\$ with \$0\Omega\$ resistance


texts: Grabbing EMF meter magnifies signal 10fold

texts:
I have a Tenmars tm‑195.  Holding it in my hand arm's length, still, I read \$2 \mu W / cm^2\$.  In exactly the same spot, without me holding it, I read 10 times lower, \$0.2 \mu W / cm^2\$.  I can reproduce this consistently.  As far as I can tell, the main source of EMF should come from standard city electricity wires from the streets, but I am not sure.

Is this strange behavior normal?  What does it mean?


texts:
How does the current through capacitor and resistor network be decreasing from maximum, when the voltage across them is increasing from minimum?

And also to my knowledge the charge that's get reside the right plate of capacitor repels the electron on left part,for the flow of current. If the resided electrons on the right plate determines increasing voltage from minimum, how can the current be in decreasing from maximum?

Correct me please, if I am  wrong


texts:
I'm working on a solar project that involves using 4 100AH LFE (LiFePo4) cells to supply 12 volts.  The LFE cells indicate the charge rate should be between 0.3C and 2C, which is a lot of current.

The average 300 Watt solar cell only provides 8 Amps, which is less than 0.1C.  Will it do any harm to the LFE cells to just use 8 amps to charge them or is it important to give it at least 30 amps?

The other problems is that I can't find a CC/CV board that does more than 16 amps, but that a question for tomorrow.

Thanks in advance,


texts:
I have a device and the datasheet says the power supply must be a 1.5V AC(Max sine) with an operating frequency of 500Hz-2kHz. Does the 1.5V AC(Max sine) mean that supply is a sine wave with peaks of -1.5V to +1.5V? or is the 1.5V value an RMS value?
I Have attached an image of the specifications below, as well as a link to the datasheet.
https://www.elecrow.com/download/HR202%20Humidity%20Sensor.pdf

I want to simulate it and i cuurently have it as 1.5 peak to peak at a frequency of 1000Hz


texts: How to Solder a Screw Terminal to Square Pad Proto Board

texts:
I want to figure out the best way to solder each terminal of a screw terminal block to a row of this proto board that has square pads. None of the squares are electrically connected. I assume just a wire on the bottom side for each terminal could work but maybe there is a more elegant solution:

UPDATE
I ended up using some of the suggested ideas and a few of my own. This was my first time using a square pad proto board and it was relatively easy to use. I routed the wires on the top side and was able to bend the leads over to the locations of the screw terminals on the bottom side. I am still a beginner so it is not perfect but it works:
Top:

Bottom:

In Enclosure:

Final:

This image helped my thinking of how to do this (not sure the source):

I thought that this track soldering instructables was helpful:
https://www.instructables.com/Track-Soldering/
I also liked some of the boards I found here:
How to solder PCB?


texts: Can a VHDL concurrent assertion reference the LAST_EVENT attribute?

texts:
I'm trying to use a concurrent assertion in an entity declaration to enforce a minimum pulse-width constraint. Everything works as expected if I use a sequential assertion wrapped inside a passive process:

testcase.vhdl

entity testcase is
    port(clk: in bit);
begin
    check: process is
    begin
        -- Require at least 10ns between clock edges
        assert clk'delayed'last_event >= 10 ns;
        wait on clk;
    end process check;
end entity testcase;

-- Keep the compiler happy
architecture empty of testcase is
begin
end architecture empty;

testcase_testbench.vhdl

entity testcase_testbench is
end entity testcase_testbench;

architecture bench of testcase_testbench is
    signal clk: bit;
begin
    dut: entity work.testcase(empty) port map(clk => clk);

    stimulus: process is
    begin
        -- Valid low and high pulses
        clk <= '0';
        wait for 10 ns;
        clk <= '1';
        wait for 10 ns;
        -- Confirm that we're timing events, not transactions
        clk <= '1';
        wait for 5 ns;
        -- Now send a short pulse to make the assertion fire
        clk <= '0';
        wait for 5 ns;
        -- Assertion should fire here, at 30ns
        clk <= '1';
        wait;
    end process stimulus;
end architecture bench;

Build and test:

$ ghdl -a testcase.vhdl
$ ghdl -a testcase_testbench.vhdl
$ ghdl -e testcase_testbench
$ ghdl -r testcase_testbench
testcase.vhdl:6:16:@30ns:(assertion error): Assertion violation

However, if I try to use a concurrent assertion I get a compiler error from ghdl:

testcase2.vhdl

entity testcase2 is
    port(clk: in bit);
begin
    check: assert clk'delayed'last_event >= 10 ns;
end entity testcase2;

Attempt to analyse:

$ ghdl -a testcase2.vhdl
canon_extract_sensitivity: cannot handle IIR_KIND_LAST_EVENT_ATTRIBUTE (testcase2.vhdl:4:34)

******************** GHDL Bug occured ****************************
Please report this bug on http://gna.org/projects/ghdl
GHDL release: GHDL 0.33 (20150921) [Dunoon edition]
Compiled with GNAT Version: 4.8
In directory: /home/simon/vhdl/
Command line:
/usr/bin/ghdl1-llvm -P/usr/lib/ghdl/v93/std/ -P/usr/lib/ghdl/v93/ieee/ -c -o testcase2.o testcase2.vhdl
Exception TYPES.INTERNAL_ERROR raised
Exception information:
Exception name: TYPES.INTERNAL_ERROR
Message: errorout.adb:63
Call stack traceback locations:
0x4978f2 0x4f055b 0x4f0350 0x4f2513 0x4f4806 0x5597df 0x5afbba 0x46eef6 0x433013 0x7f64f836082e 0x432450 0xfffffffffffffffe
******************************************************************
ghdl: compilation error

I get the same error if I move the concurrent assertion into the architecture body, or if I shorten the expression to clk'last_event >= 10 ns. Other expressions like clk'event or clk'delayed = '1' compile fine, even if they are somewhat pointless.

I'm fairly new to VHDL but my understanding is that my two testcases should be equivalent. If they aren't, why not? And if they are, why does ghdl complain about the second one?


texts: Disadvantage of using a Schottky diode across the LDO input/output for reverse voltage protection

texts:
I'm studying a linear power supply circuit design for my future project and I started off disassemblying a good(expensive) LPS out in the market.

While I was studying it, there was a part that I wasn't sure if my understanding is correct.

Near the output circuit, there was a diode across the input and output of the LDO Like the picture below.
From https://e2e.ti.com/blogs_/b/powerhouse/archive/2018/07/25/ldo-basics-preventing-reverse-current-in-ldos

I understand that for this topology, Diode needs to be Schottky Diode. Which costs higher than the normal Diode, but lower forward voltage drop is required for this circuit.

Another simple choice would be to place the diode before the LDO, like the picture below.

To summarize

Diode Across the LDO

PRO : No input voltage drop

CON : Requires Schottky Diode $$

Diode Before the LDO

PRO : Normal Diode is enough $

CON : Input Voltage drop 1V for normal Diode

.

Is this really it or is there a performance difference that I'm unaware of?

Help will be much appreciated.


texts: What is a reasonable sustained current load for a typical AA Li-Po battery?

texts:
I would like to build a cutdown mechanism for a balloon's nylon rope using NiChrome wire.

To make the cut-down mechanism as simple and cheap as possible, I want to stick to using AA batteries.

To heat the 25AWG wire sufficiently to cut the rope work I need about 4.5 Amps at about 2.5 Volts.

I see plenty of 4000-5000mah Li-Po batteries on ebay, but I am concerned drawing at 1C+ will be too much for the battery - and none of the ebay batteries seem to have datasheets.

What is the best approach here? Skip the AA and use a more expensive RC battery? I'm okay with a single use battery, I just don't want it to explode.


texts:
My guitar rig consists of

Guitar -> Audio Interface (Steinberg UR22) -> Laptop (via USB).

I listen to the (processed) audio using headphones connected to the audio interface.

ISSUE:

When the power supply of my laptop is connected to an unearthed outlet, I pick up a loud 50Hz hum, which almost disappears when I touch any metal part of the rig.

The noise also disappears if the power supply is connected to an earthed outlet or disconnected altogether (so the laptop runs on battery power).

Disclaimer: I understand that very similar (if not identical) issues have been discussed in many places, including here, but after a week of hunting for info I am still quite confused.

CONJECTURES:

After some reading and experimentation, I concluded that this hum is mains hum coming from the SMPS secondary being capacitively coupled to the primary. Indeed I can measure a 50Hz AC voltage (~53 volts) between the "-" pin of the power supply (or other conducting surfaces of the rig) and earth.

This AC voltage is in turn sent to the guitar via the audio cable, where it interacts with the pickups and results in the hum (I am saying this because the noise completely disappears if I turn the volume to zero using the guitar potenziometer, but I am not sure what is going on exactly).

I would like to solve the issue without having to use an earthed outlet, as they are only available in the kitchen and bathroom in my apartment (furthermore, no exposed pipes are available outside of these two rooms). I believe this to be safe since I am using a class II power supply. However, my understanding of electronics is very limited, so I would like to ask your opinion before I waste any money in trial and error.

ALTERNATIVE SOLUTIONS?

The audio interface can be powered by an external 5V power supply. The noise is quite a bit lower with a phone charger supply, but it does not disappear entirely so it would not be a "complete" solution in any case. Unfortunately, when the laptop is connected to its own power supply, its floating ground is transmitted to the audio interface via USB even when the latter is powered externally. I am thinking that a USB isolator would do the trick, but such devices (especially those supporting 480Mbps) seem to be quite expensive.
I am also wondering whether an isolation transformer between the guitar and the audio interface, such as the Behringer HD400, could possibly help. I do not see how it can block the AC noise from reaching the guitar though.
Are there other ways to isolate the ground of the guitar pickups from the floating ground of the audio interface?

BONUS QUESTION:

Out of curiosity, I would like to understand why touching metal parts of the rig (such as the guitar strings or the audio interface itself) eliminates the noise, even when my body is not connected to earth. Would it be possible to build a circuit that mimics this effect?

In any case, any thoughts on the matter would be greatly appreciated.


texts: SMD Schottky diode part number from marking code

texts:
I can't find the part number from marking code. I think it's a schottky diode.
Marking is:
94B
1L2
D1 & D2 have the same marking code.


texts: How a multiplier will be implemented with LUT?

texts: How a multiplier will be implemented with LUT(LookUp Table) or with optical LUT?.... I know how the full-adder implemented with LUT and OLUT.


texts: Getting two (or, one and a half) outputs from a single pin

texts:
I am doing a project with an ATtiny85 and of course I'm short on I/O pins.  One idea I had was to use a single pin for two outputs (let's call them EN and DATA).

simulate this circuit – Schematic created using CircuitLab

I know that DATA doesn't matter when EN=0. In other words, these two outputs can only assume the values EN=0/DATA=x, EN=1/DATA=0, EN=1/DATA=1. Is there an easy way to map for example 0 to EN=0/DATA=x, 1 to EN=1/DATA=1, Z (input pin) to EN=1/DATA=0?  Power consumption only matters when EN=0.


texts:
simulate this circuit – Schematic created using CircuitLab

Electronical novice (but Advanced Idiot) here. Trying to interface a phototransistor to a Microchip PIC I/O pin. Per the phototransistor's datasheet, I'm feeding +5V into the collector and have a resistor between the emitter and GND. When the emitter isn't connected to the PIC, a voltmeter on the emitter reads nicely between near-0V to +5V with varying light exposure. But when I tie the emitter to the PIC, that range drops to a maximum of less than +0.5V. Changing the resistor value or swapping the resistor to the collector side (emitter then is to GND) and measuring there doesn't seem to make a difference. Setting the pin up for ADC or not doesn't either. TRIS definitely has it set as input though. Looking online, seems like lots of circuits showing the hardware as I have it. Is it something about the PIC? I'm sure it's something dead simple. Suggestions? Rebukes?


texts: Basic voltage divider issue in my amateur circuit XBee

texts:
Once again I need your help in my project. I have a 4,5v powered circuit. I put a voltage divider with 2 resistors in series to reduce my initial voltage of 4.5 V to 3.4 V (to feed an XBee module).

The issue is that if I do not connect the xbee, the voltage divider reduces the input voltage to the desired voltage(3.4 V), but when I connect the XBee module, the resulting voltage divider voltage drops to a value very low (0.85 V), making the XBee malfunction. Surely it is a basic mistake, I am asking something that is very clear, but I'm newbies.

Basic Circuit:

Vin(4.5 V)-----R2(10 kΩ)---------R1(33 kΩ)--------GROUND
                       |
                       |
                 Vout desired (3.4 V)
                       |
                       |
                      XBee


texts:
Say I have a logic-level square wave, where 0V is "low" and 5V is "high". I'm pulsing this at a constant 60Hz, 50% duty cycle. My intuition says that since the voltage never goes negative, it's a DC signal, regardless of how fast I'm pulsing it. Is that correct?

Furthermore, when considering op-amps to amplify signals from sensors that again produce 60 Hz square waves between 0 and 100mV, can I also consider this a DC signal, and not worry too much about my gain-bandwidth product?


texts: What happens to parts of induction cooker magnetic field not covered with the pan?

texts:
An induction cooker works like this. There's a flat coil of wire under the cooker surface which is connected to a source of high frequency AC and it produces an oscillating magnetic field with field lines oriented vertically. A suitable pan (with thick steel bottom) is put on top of cooker surface and that magnetic field induces eddy currents in the pan bottom and those heat the pan bottom.

So it's a kind of an air core transformer. The coil under the cooker surface is the primary winding and the pan bottom is a shorted secondary winding. And there's no steel core so the energy magnetic flux "extends" from the cooker surface and "sticks into" the pan bottom and the pan bottom presumably absorbs all of that flux. It sound good so far. However modern induction cookers allow use of pans which are smaller then the coil diameter so that for example a cooker will have a coil 18 centimeters in diameter and pans with 10 centimeters diameter or larger are allowed and those are heated just fine.

A 18 centimeters coil forms a circle with square of 254 square centimeters and a pan bottom with 10 centimeters diameter forms a circle with square of 78 square centimeters. This way only about 30 percent of the coil surface is "covered". It looks like two thirds of magnetic flux "leaves" the coil and doesn't quite "stick into" the pan bottom.

What happens to that "uncovered" magnetic flux? Does it affect surrounding electronic devices or humans?


texts: How to update a packaging made in an original design to the one previously used in another design Proteus

texts:
I'm working in a design in Proteus where I'm making a multi-board design. I've made a previous design where I've made a PCB model of an ESP8266-ESP01 but initially I was mistaken with the pin numbering of the model.

I realized that and after updating the packaging and the model itself in the original design, then the next step was to update that model in the final multi-board design. However what I did didn't work at all and the first wrong model is still appearing in the design.

Labcenter clearly says this in the help about editing the packages:

  Remember that all design files carry with them their own copies of the library parts that they use. Consequently, changing a part in a library will not directly change any designs that make use of it. To effect such a change, you must load the drawing into ISIS and use the Pick command from the Library menu to effect a replace operation.

What I couldn't do was the part of "you must load the drawing into ISIS and use the Pick command from the library menu to effect a replace operation" because I don't know how to do it.

The device appears updated in my new design, as you can see in the following image:

But when I place the device and go to place the footprint in Ares, then the pin numbering is shown with the old footprint like is seen in the following image:

How can I solve this?

NOTE: I know that I can simply create a new project and insert the new instance, but I'd like to know how to insert the model in the right way.

Thanks in advance for the help.


texts: Is is possible to communicate over 1 XBee to multiple microcontrollers?

texts:
MC1>XB1 ==> XB2>MC2,MC3,MCn

What I am looking to do is control large LED panels, wirelessly, with control of each LED pixel. My concern is the processing limitations of a single controller and/or the cost of adding many XBee units. Controlling a single LED panel would be done via a PWM enabled LED driver/shift register. I could multiplex or charlieplex the panels but I'm afraid that will take even more processing power than writing out to a set of shift registers.

Does anyone have ideas how something like this might work?


texts: Need help to find the ground loop path in this diagram

texts:
I have been told that there is a ground loop in this diagram especially via USB_GND, Power-, GND. But I don't understand what that means. All the power supplies are SMPS. Can someone draw the loop on my diagram below:

Arduino's digital output above is connected to the digital input of the DAQ board.

I have been told there is ground loop from several forums but I'm not able to verify the loop. Im stuck at that point, I would be glad if someone can draw such ground loop so I can proceed.


texts:
I'm building a 20cm x 20cm table that is divided into cells, it has 4 rows and 4 columns.
There will be different external blocks that have numbers, each block can stand on a single cell, each block has different number.

each cell on the table should be able to detect and recognize different blocks, so that i could know which block on which cell ...

The problem is, what technique can I ably inside the table/matrix to detect and identify these blocks so that, for instance, i know that the block with the number 5 is on the 3rd cell.

I'm thinking of NFC technology where each cell will has NFC reader and inside each block will be NFC tag but it's not practical due to the size and cost of the reader. any suggestions (it could be wired or wireless technique )?

Thank you in advance,


texts:
I have read the other question on this topic, but having gone through the answer I'm still unsure about the answer to my own, so I hope this is helpful.
If a generator generated 20MWh of electricity in a day (24 hours), then how would I express that in MW?
I want to say the generator was running at XX MW on that particular day. But how would I work out XX if I only had MWhs for the day?
Would I simply divide by 24 (hours in day)?


texts: What is the interface that connects the TV LED screen to the PCB

texts:
WHile this may be a rather open question, I see that most TV's expose a HDMI port. The HDMI port connects to something that runs linux which in turn connects to the LED screen. What is the interface between the LED screen and the PCB called? How is it generally done?

This picture may help:(I coudnt not find an exact one, but basically what is that flat cable interface? IS it different from on TV to another?)


texts:
I have a 24 VDC PLC. It is powered by a power supply that takes in 12 V and turns it into 24 V. This 12 V is coming from a car battery. The inputs for this PLC is 12 V.

Here is the smart relay:
It is a phoenix Contact PLC model PLC-V8C/PT-24DC/SAM.

Here is the power supply: MINI-PS-12-24DC/24DC/1 also from Phoenix Contact

I have a separate 12 V system (which is also run by the same 12 V car battery) which has a switch in it. The positive side of this switch I have going to an input on the PLC. This does not produce 12 V on the PLC input. The only reason I know of is that the grounds are not connected.

I have tried connecting both grounds, one from the 12 V side and then the one coming out of the 24 V power supply. This is pulling my 12 V input down to 1.75 V for some reason.

How should this be wired to the PLC can read the 12 V input?


texts: 3-Electrode sensor potentiostatic circuitry

texts:
I'm designing a circuit to read out the C2H4-CA10 sensor.
Following the typical applications document, I designed the following:

To verify the schematic, I created a new TINA simulation:

When probing VM1, I get a output value of 999,952953mV with IG1 @ 350nA (which equals the starting current for the sensor.)
When the sensor is at 10ppm, the current value should be 1550nA, and the voltage over VM1 rises to 1,000000V.
I've got a few questions.

Do both OP1 and OP2 need to have a power supply connected? It's not part of the schematic in the MEM1 document.
If yes, how do I need to connect them? I've searched around on Google and didn't find a single potentiostatic circuit with an external power supply connected.
If I remove the power supply from OP2, the output value drops to 20uV, so I suppose OP2 does need it.
Why is the output voltage limited to 1V@1550nA? I connected it to a 5V supply.

When realising the circuit once the design process has been completed, I want to make Rgain disconnectable from C2 to allow for better tweaking, is the circuitry affected if I use two headers with jumpers to connect/disconnect Rgain?
EDIT:
I just noticed that changing the schematic to this one:

The output voltage is generated according to I = Isensor * Rgain.
OP1 and OP2 both receive a supply voltage of -1V at it's negative pin and 1V at it's positive pin


texts:
Is there any difference between :

Type word is STD_logic_vector(15 downto 0)

And

Signal word:STD_logic_vector(15 downto 0)

?


texts: transfer function of a complicated circuit

texts:
How to find the transfer function of this circuit? The addition of C_1 and another input function v_2 makes it more complicated

Is it:
\$Zout=\dfrac{R1}{1+R1C2s}\$
\$Z0 =\dfrac{1}{C0s}\$
\$Z1 =\dfrac{1}{C1s}\$
\$G= \dfrac{R1C0s}{1+R1C2s}vin1+\dfrac{R1C2s}{1+R1C2s}vin2\$


texts: How to supply an op-amp from a 9V Battery?

texts: I was buildiing an amplifier circuit for +ve voltages only. When I used a 9V battery to supply V+ and V- (+ to V+, - to V-), I get a constant 8V at the output of the opamp. The output is not changing with respect to input. The circuit worked fine when I used a +/-12V dual power supply. However the way I understand it, using a single supply is okay as long as I'm not dealing with negative input voltages.


texts: I want to find \$\frac{\hat{\theta}}{\hat{T}}\$

texts:
I have the following block diagram, and I want to find the transfer function \$\frac{\hat{\theta}}{\hat{T}}\$. I am not sure how to do this, I've got the rules of connection in a series or parallel, but I am stuck.

I started with the entrance of \$T\$ but got stuck, can someone please provide me some help?


texts: unloading capacitor while measuring voltage with multimeter

texts: I have load a 10nF capacitor with a bigger capacitor of 100 uF. Both have the same voltage but when I measure the voltage of my small capacitor I unload it to zero... How can I avoid this effect ? Is it common to unload a capacitor when you measure its voltage with a multimeter ?


texts: Am I calculating my shunt FET power dissipation correctly?

texts:
simulate this circuit – Schematic created using CircuitLab

I'm designing an LED driver circuit that requires very fast PWM switching at a high resolution (10bit at 30khz requiring a minimum pulse width ~30ns). In order to achieve the pulse timing required, I'm using a FET to shunt the LED driving current to ground during the "off" periods. I'm trying to determine the worst-case power dissipation for the FET, so I can plan heat mitigation strategies when designing my board.

One of the FETs I am considering is the BUK9M52-40E, because it works on logic-level voltages and on/off times in the single ns range. It is not a power MOSFET, however, and does not appear to have a substantial heat sink build in, so I would presumably need to rely on copper pours and thermal vias for heat management.

I will be driving 8 LEDs in series at 24V at a constant average current of 360mA with a peak current of 540mA.

The FET has a maximum RDSon of 52mO at 5V, though I hope to drive it with a 3.3V signal, which from what I can determine would result in an RDSon of closer to 100mO. So given a constant average current of 360mA, and assuming 100mO of resistance, (0.36A x 0.01O) the voltage across the drain-source will be 0.0036V. So the power dissipation in the FET will be 0.0036V x 0.36A = 0.001296W.

This number seems... really low. And given that the FET is rated to 31W, I assume that this is well within its capabilities, and I could probably get away with very little thermal management, and potentially a much smaller FET. Am I correct in this assumption?


texts: I do know the question in the title is really stupid, but it is the best phrasing I could come up with.  Let's say I am building a circuit and the schematic says to use a BD139 transistor.  Would there be any issue in using any other NPN transistor?  What would I do if I could not find this transistor?  I can't buy any parts online, and I do not have access to a store where they would sell this stuff, so I am limited to what I can salvage from old broken electronics, most of which have older, outdated parts that have limited information online.


texts: ESP8266 noisy input when wires go through power supply

texts:
I had made a circuit for an LED strip using an EDP12e. I had also attached two buttons to change between colors on the strip.
To make it compact I inserted the circuit board inside the casing of the 12V supply. It is a metal box with power circuit and some empty space where my circuit fits exactly. The LEDs work fine except the button inputs are throwing false positive signals when open (floating.)
I had connected a pull down resistor to the input pin. Below is the schematic I used:

This is the actual circuit:

Please help me solve this issue.
Without passing those wires from supply didn't cause such noisy triggers but I kind of wanted to put my circuit inside the casing.


texts:
How do you read the numbers on a rectifier diode? It only says "06" (or "90") on it (twice, once horizontally and once vertically). I figure I'm supposed to assume this is a 1N4006, but I'm a bit of a newb and not really sure.

Can someone confirm this is correct?

Here's some pictures:


texts: Can the frequency of the SPI sck on an mbed be adjusted?

texts: I'm trying to control a serial dataflash memory through the SPI interface of an mbed. SCK from the mbed is connected to CLK of the dataflash memory. I'm not sure, but I'm starting to suspect that this needs to be running at a certain frequency. Can the frequency be adjusted?


texts:
In the photo shown bellow we have a calculation for SAR ADC voltage NODE sighned as Vout.
Without offset we have -Vin voltage from the sampling stage and the Vfs with capactior voltage divider (depending on the switches)
How all thes stage will be affected when we have Vos on the opamp?


texts:
I am using 64 pin stm32f103RE, Keil and STM32Cube for my project, the problem is when I try to read ADC by polling or interrupt modes with HAL_ADC_GetValue(&hadc1), just a fixed number is returned (0xFF0F0000). AS the pin is float so some noise values must be shown instead.

I also tried ADC_GetConversionValue(ADC1) using CMSIS and Keil but the result was the same, for both polling and interrupt mode.
What would be the reason, may it be something with ADC hardware problem?


texts: What is the use of this diode in Kelly controller wiring?

texts:
I need help in this circuit.
I want to know the use of this diode here.
This is a diode for 4000W motor controller.
If I want to calculate the needed one for 1000W, what are the equations?


texts: Screw machine strips and normal square post terminals

texts:
I find in PCB design, besides the normal square post terminals like this:

there are another similar one:

Why the later called "screw machine" strips? And if it is used more in certain fileds, in comparison to square post terminals?


texts: Why did Adafruit pick a 10K resistor for this phototransistor breakout?

texts:
Adafruit has an ALS-PT19 Analog Light Sensor Breakout.  It looks like it has a 10K resistor on it:

The ALS-PT19 datasheet says that resistor is to convert the output current of the transistor to voltage.  Why would Adafruit have selected a 10K resistor?

Given a 5V power supply, I would assume the breakout would max out at about .5mA.  Is that right?

Based on this graph, it looks like it'll max out at about 4K Lux, right?

If an overcast day is 1000 Lux and daylight is 10K Lux, was the decision to maintain precision at lower levels of the scale and let it saturate at anything higher than "almost daylight?"

Let's say I wanted to also have accuracy toward the really bright incandescent range where the output is as high as 5mA.  If I wanted to do that, would I put a 1K resistor there instead?

If I wanted accuracy at both ends is there a way to include both the 10K resistor output and the 1K resistor output from the same phototransistor or would you put 2 phototransistors on the board for that?


texts: Rechargeable LiPo for Raspberry Pi without having to be unplugged to be charged

texts:
I tried researching this online but failed to find exactly what I'm looking for.

I want to have a docking station for my Raspberry pi, where I just connect it to a micro-usb and it'll recharge the LiPo that I have connected to my Pi and when I disconnect, continue to use the LiPo's power.

I am trying to avoid constantly unplugging the LiPo from the Pi and charging it on it's own, then reattaching it to my Pi.

Ideally I'm thinking that maybe there's a circuit that's designed with a micro-usb port on it that when plugged in charges the LiPo and Pi, and when unplugged continues using the LiPo power for the Pi.

My knowledge is slowly growing, so if this isn't possible please teach me as to the problems so I can learn!

Grateful for any tips or guidance


texts: How does this opamp full-wave rectifier work?

texts: I want to understand how the following circuit works. I understand OpAmps, diodes, and voltage dividers pretty well; but put this circuit together, and I don't know how it affects positive or negative voltage input.


texts: Is the MOSFET NTE2390 broken if connecting only source and drain powers a motor?

texts:
I've got a small motor wired to the drain of an NTE2390, with the other end of the motor hooked up to ground.

When I connect to the source of the MOSFET to power, the motor starts turning even though there are no wires connected to the gate.

Does this mean my MOSFET is broken, or is my circuit wrong?


texts:
simulate this circuit – Schematic created using CircuitLab

Its just the basic diagram (the actual circuit is a low noise amplifier at 5.5GHz).It does work very correctly.In this circuit the BJT operates in active region with Ve=1.61V and Vc=-0.3mV but if I detach JFET,the BJT starts operating in saturation.I don't find this very strange but would like to get a good explanation.Secondly my instructor insisted that I use PNP here.I could use NPN.Why would he insist for me to use PNP?


texts: Final RF envelope of FM and AM are the same

texts:
https://masi.vuse.vanderbilt.edu/images/0/0b/EECE_252_Final_Project2.pdf

Page 2 spectrum plots.

Effective RF electromagnetic power profile is effectively the same for baseband audio content modulated by AM or FM.

Question, Is this right?

**UPDATE

Based on this,

"a 1 kHz tone at maximum volume would make that frequency vary by plus or minus 75 kHz.  So 1,000 times per second, the carrier wave would sweep up to 97.175 and down to 97.025"

museumofbroadcasting.org/fm/fmstereo.html

I would conclude that the RF power envelope should show something very different from FM to AM.  In fact, the FM power plot should literally be flat, or spread spectrum power.


texts: Input impedance of a non-inverting op-amp

texts:
From what I've read (and simulated), the feedback loop of an op-amp modifies the input impedance of the non-inverting input.  The value specified in the datasheet is the open-loop input impedance, and the actual closed-loop input impedance will be some much larger number?  Why does this happen, and how do you calculate the new input impedance?  Does this also reduce effective input capacitance?

Radio-Electronics.com "Op Amp Input Impedance" says it's the differential input impedance of the op-amp plus the impedance to ground seen by the inverting input, with no mention of open-loop gain.  So for a voltage follower with no feedback resistor, the impedance seen by the inverting input is zero and the input impedance is unchanged?  That doesn't seem right.

HyperPhysics "Practical Benefits:Negative Feedback" says it's $$(1 + A_0 B)\cdot Z_\mathrm{ino}$$
where

\$A_0\$ is the gain without feedback (the open loop gain)
\$B\$ is the fraction of the output which feeds back as a negative voltage at the input
\$Z_\mathrm{ino}\$ is input impedance without negative feedback

So for a voltage follower, B = 1 and it's \$\approx A_0 Z_\mathrm{ino}\$?


texts:
So I want to build a circuit that can control the intensity of a light bulb (powered by 220V AC, 60 Hz) through the output voltage of Arduino.

I know I must use Triac but the question is, is the output voltage/current of Arduino good enough to control the Triac current such that I can get different levels of light intensity?

The block diagram of the whole system is given below, the whole purpose is to control the intensity of light through the output voltage of Arduino only, I don't need any kind of light sensor or anything else...

[Arduino] --> [Light dimmer circuit] --> [light bulb]

I'm honestly new to this Triac thing and don't want to blow up things, so I need some guidance from experts like you :)