texts: How to efficiently mux many signals to/from a climate chamber?

texts:
I am building a setup to measure various parameters across a temperature range from -55°C to +125°C. The devices under test will be placed in a climate chamber. There are around 10 signals from each DUT to be measured by equipment outside the chamber. The sampling rate is fairly relaxed (many seconds). Measurements are DC (so no high speed signal issues). Switched voltages are below 12V.

I plan to have around 50 DUTs in the chamber. Only one DUT has to be connected to the measurement equipment at a time.

I wonder what is an efficient and reliable way to mux ~500 signal to and from a climate chamber?

Some solutions that I considered:

Switching signals outside the chamber - physically impossible, 500 wires will not fit through the conduit (and it would be a mess of wires...).
Switching inside the chamber using ordinary relays - may not be reliable
Switching inside the chamber using relays rated for such environment - horribly expensive
Switching inside the chamber using solid state devices - may have unpredictable effect on the measured signals


texts: Oscillation frequency / criteria from Bode plot, negative feedback system

texts:
Got a question, which is very integral to a project that I am writing a report for (which I am to hand in soon, so in a hurry).
Question:

What will my oscillation frequency be?
How will it be affected by reductions/increases to my gain (assuming phase unchanged)?

Edit: It is my understanding that the circuit will oscillate at the frequency where the gain reaches zero, assuming the phase margin is below 0. I am not certain this is correct.
Suppose I have a bode diagram as can be seen below. The gain is 0dB at 2.5MHz. The phase margin is -74 degrees.
The first image is the loop gain. The second is the phase in degrees. Note that it starts at -180 degrees.

Context: The system is a self oscillating class D amplifier. The important takeaway here is that I want the amplifier to oscillate. The output will be a square wave, which is clipped by the supply rail voltage. Thus, the system will 'clip' when becoming unstable.
For those interested, the topology is:

And my linearised model:

Thanks!
Edit: Below is a zoomed out bode plot, just for context:


texts: Why is inverting op-amp behaving like a low pass filter?

texts: can anyone explain why this circuit behaves like a low pass filter despite having no capacitor in the feedback loop?


texts:
I have a simple question that I don't seem to find anywhere, do typical GPS watches only use GPS data or do they also use other sensores and fuse the information with a Kalman filter?

What is usually the case?


texts: Clearing USART (UART) interrupt flags in an STM32?

texts:
I am using an STM32F105 to communicate with a Linx GPS chip using a UART.

If I don't use interrupts (if I just poll the RX flag) then it works just fine.  But I'm getting unexpected results when trying to use interrupts.

For example, if I only enable the RXNE ("RX not empty") interrupt using USART_ITConfig(USARTx, USART_IT_RXNE), then the code should only vector to the ISR for this one specific event.  But the interrupt is being triggered for an Overrun condition, too.

As far as clearing the flags, it seems that the method depends on the flag.
To clear the Overrun flag (USART_IT_ORE), the User Manual explains that I should first read the USARTx_SR register, then read the USARTx_DR register.  This does work; the flag is cleared.

There is also a USART_ClearITPendingBit() function, but it only accepts a small subset of flags.

There are eight different interrupt sources that can be selectively enabled, and ten different flags.  Is there a summary somewhere of how to manage all of these flags?


texts: STM32F411 Discovery Has to connect to an external 3.3V to power up?

texts: I have an stm32f411E Discovery board and I'm working with it  well. After I use it to work with an UART module suddenly it can't not power up anymore. I have to connect its 3.3V pin directly to another external 3.3V pin so it can power up. Does anyone know why? Thank you


texts: Is it possible to have "in-out" communication in a single 56k modem?

texts:
I'm trying to implement a call blocker using a Raspberry Pi and a Zoom 3095 USB Mini External Modem using a guide I found on the web.

The modem used has a single RJ11 jack. It's not clear from the guide where it's connected from the phone line, but it seems a splitter was used out of the wall jack, and the phone and the call blocker were connected "in parallel".

Commercial call blockers, on the other hand, seem to usually have a TEL and a LINE jack, so they're presumably made to be connected in series, between the phone and the wall jack.

Is there a way to use the same modem with "input" and "output", so that I can connect my blocker in series? Or would I need two modems? My phone is analog (DTMF if I'm not mistaken).


texts: Will these two transistors (BC558A and BC558B) function in the same way?

texts:
I'm currently following this guide on making an Arduino OpenTherm Controller. After finding almost all of the parts without any issue; my only question remained with the "PNP transistor" named in the hardware list. As someone who is new to electronics, this did not mean much to me, so I sought out an exact name for this transistor. Elsewhere on the webpage I found this image:

As you can see, it names the transistor as a BC558A. However, after searching online for this transistor I either found few or no results. On the other hand, I found many BC558B transistors like this one so I ordered a pack. After initially thinking that because no specific "PNP transistor" was named; any sort would do, I began to reconsider this which is why I am asking for help.

My question is: Will the BC558B transistor I have ordered function in the same way in the circuit? If not, what would a reasonable alternative to the BC558A transistor be, seeing as it is very hard to find online?

Thank you in advance for any help.


texts: What is the main reason for using speed feedback in a motor positioning control system?

texts:
This question is not to solve a particular problem but rather one of principle to understand the main reason a designer would want to include speed feedback in a motor controlled positioning system. And I'm hoping a veteran motor control expert is able to help answer it.

Consider a cascade controller with displacement being the most outer loop (encoser feedback), followed by a velocity controller (encoder or tach feedback) and the most inner loop a current feedback loop (using shunt resistors, hall devices etc.)

It's clear that current is directly related to torque, and so that helps to overcome torque disturbance as well as speeding the effective electrical time constant. It helps to linearize the transductance of current (command) to torque.

But what does the velocity (speed) loop do to improve performance? Does it further provide linearization? As far as I know there isn't a 'velocity' disturbance to be concerned about.

Typically if you pick the P, I and D gains of the displacement controller in the right proportions (tuning) then you can get by without a speed loop between the position and current controllers.

Cascade control promises tighter control, there are more knobs to turn, but what is the real advantage of having speed in the cascade?


texts: If for example you have an inverting circuit(as the one in the image), can you change the opamp from a VFA to CFA and the circuit would work the same?  And the LM741 is a VFA or a CFA?


texts: Preferred balun location? (Are differential microstrips preferrable to single-ended?)

texts:
I'm designing a PCB with a transceiver that has differential signal pins for rf.  These differential signals travel to a balun, which transforms them into a single-ended signal (50-Ohm characteristic).  This output goes to a on-board chip antenna, with a matching network at the interface between the 50-Ohm microstrip and the antenna.

Say that I have an arbitrary distance from the IC to the antenna.  I can:

Put the balun close to the IC, minimizing the length of the differential traces and having a longer single-ended trace, like so:

Place it close to the antenna, running most of the signal path through the differential traces:

(put it somewhere in between)

Which method is preferred?  There are multiple transceivers on this board, and I suspect the differential traces radiate less.  Is this true?  Are there other considerations?


texts: LV cable sizing for short circuit condition (NEC)

texts: Do we need to perform short circuit condition i.e let through energy condition while sizing the LV cables as per NEC (National Electrical Code)?


texts: Can a transistor send negative voltages when used as a switch?

texts:
I have used relays as a switch in order to turn on and off things. This is how I do it:

My IC is my integrated circuit call it arduino. With a small current I am able to turn on and off things and I can now replace mechanical switches such as this one with a transistor.

Anyways now my question is will this also work when sending negative voltages? We have 2 different internet providers meaning we have 2 separate cat6 cables. Each provides internet. If the internet goes down from one cable then we connect the second Ethernet cable. I just learned that cat6 cables send voltages between -2V and +2V. Since the cat6 cable has 8 wires inside I was wondering what will happen if I do the following for each of the 8 cables inside the cat6 cable:

Cut the cable at the middle.
Connect one side to the collector of a transistor
Connect the other side to the emitter of the transistor
Connect the base to my arduino giving it a small current so that the switch is closed.

If I where to do this will there still be an internet connection? If there is an internet connection then I can use this mechanism to switch between providers instead of having to change the cables manually? I will probably not do this. I am asking for purposes of learning. I do not want to use a relay as they are larger and using 8 for each cat6 cable will be a lot.

Edit

The transistors will not be switching on and off at the frequency of Ethernet. They will be either on or off. They will only change states when switching between Ethernet cables. If they are not able to transmit negative voltages can I use 2 transistors in reverse direction like so:

That will represent the connection of 1 of the 8 cables of the cat6 cable. The base pin of the transistor is on the center. That will always have a possitive voltage to leave the switch on. Because there are 2 transistors in reverse direction it will now be possible to send negative voltages no?

Edit 2

This will represent one of the 8 cables illustrated with a better diagram:

Using something like this I should be able to send signals from both directions correct? I plan on leaving the transistors on until I want to change internet service providers They will not be turning on and off rapidly.

There is a problem though. I can connect the base to +5v of arduino but how can I share the same ground so that this diagram works?


texts: Simulation for Wireless Power Transfer works fine, Prototype on breadboard doesn't

texts:
I am working on a Solar Powered Wireless Power Transfer project. The simulation for the circuit I am working off of works really well.

I have built this design and others on a breadboard but I am getting a DC output across the inductors. I am unsure as to why it isn't outputting correctly.

Any help would be appreciated.


texts: What is the reason for adding a buffer stage?

texts:
I was following this microphone and speaker circuit and I could follow mostly but got confused when the author introduces a DAC buffer.

http://www.instructables.com/id/Arduino-Audio-Output/?ALLSTEPS

This isn't the first place I have seen engineers putting a buffer stage in amplifier designs. I want to improve my understanding of how these unity gain buffers are useful in circuits. i.e what goal do they achieve? How important is it to put buffer stages in amplifier circuits and exactly when should we take introducing buffer stage into consideration? Appreciate it!


texts: How does the dq axis of multi pole motor look like? Typically online images search show dq axis for motor with one pole. Consider a 4 pole stator PMSM motor. Will there be multiple dq axis for each pole pair? Will dq axis be orthogonal electrical angle or by mechanical angle?


texts: In digital systems do we discretize both time and magnitude or only time?

texts:
In studies of Digital Circuits or Digital Electronics or Digital Systems, the very first step is to convert an Analog signal / Analog system into a Digital Signal / System.

In this process of converting an Analog function to a Digital Function, do we need to discretize both time (X-axis) and magnitude/functional value (Y-axis) or only time (X-axis)?

Can anyone give me the correct definition of this (Discretization / Analog to Digital Conversion), as I found at some places it says both time and value (both X-axis and Y-axis) i.e take (X,Y) ∈ ℕ,
whereas at other places it says only time/X-axis values i.e only X ∈ ℕ and Y can have any values i.e Y ∈ ℝ.


texts: How to determine maximum PWM frequency for transistor (2SK2554)

texts:
How can I determine (estimate) maximum reasonable PWM frequency for 2SK2554 transistor?

I found timings in datasheet:

I could estimate frequency from this (and make sure that all these times are 20-50x shorter than my PWM cycle length or something like that. But I have Vgs is between 4-5V, my maximum current is 10A.

Im asking because I have slow PWM now (~1kHz), but want to know how fast my PWM can be without loosing too much power while switching.

My load is big lead-acid battery (charging) or resistive (discharging).

So far - I've done simulation with similar, a bit smaller transistor (2SK2553) because there was no 2SK2554 in my Multisim.

This is graph for Vgs = 4V.

How much time (in percent for example) my switching time can take from PWM cycle time?


texts: Limitations of using minimum no. of MUXes for a given boolean function

texts: Given a specific Boolean function, is there any restriction on the minimum no. of multiplexers required to implement that function? Is there any theory on that?


texts: I found this relay inside an industrial x-ray machine. What does the rectangular box with a horizontal line through it, in the bottom left of the first picture, mean?


texts: Transfer function of a classic controller

texts:
I want to calculate the transfer function and the gain, zeros and poles of the transfer function, considering that: $$R_1=R_2=R_3$$ $$C_1=C$$ I want to know if this circuit is a P, or PI, or PD, or PID controller or a lag/lead compensator.

To get to the transfer function, I think AMPOP entries must be matched. I think that is a lead controller, but I'm not sure. How can I solve?

My work so far:

$$\cfrac{v_0-v_i}{R+\bigg(\cfrac{1}{R}+\cfrac{1}{Z_C}\bigg)^{-1}}=\cfrac{v_i}{R}\Leftrightarrow \cfrac{v_0-v_i}{R+\bigg(\cfrac{1}{R}+sC\bigg)^{-1}}=\cfrac{v_i}{R}\Leftrightarrow \cfrac{v_0-v_i}{R+\bigg(\cfrac{1+sCR}{R}\bigg)^{-1}}=\cfrac{v_i}{R}\Leftrightarrow \cfrac{v_0-v_i}{R+\cfrac{R}{1+sCR}}=\cfrac{v_i}{R}\Leftrightarrow \cfrac{v_0}{R+\cfrac{R}{1+sCR}}=\cfrac{v_i}{R}+\cfrac{v_i}{R+\cfrac{R}{1+sCR}}\Leftrightarrow v_0\Bigg(\cfrac{1}{R+\cfrac{R}{1+sCR}}\Bigg)=v_i\Bigg(\cfrac{1}{R}+\frac{1}{R+\cfrac{R}{1+sCR}}\Bigg)\Leftrightarrow \cfrac{v_0}{v_i}=\cfrac{\cfrac{1}{R}+\cfrac{1}{R+\cfrac{R}{1+sCR}}}{\cfrac{1}{R+\cfrac{R}{1+sCR}}}=\cfrac{\cfrac{1}{R}}{\cfrac{1}{R+\cfrac{R}{1+sCR}}}+1\Leftrightarrow \cfrac{v_0}{v_i}=\cfrac{1}{R}\times \big(R+\cfrac{R}{1+sCR}\big)+1=2+\cfrac{1}{1+sCR}=\cfrac{2+s2CR+1}{1+sCR}=\cfrac{3+s2CR}{1+sCR}$$

poles:

$$1+sCR=0\Leftrightarrow s=-\frac{1}{CR}$$

zeros:

$$3+s2CR=0\Leftrightarrow s=-\frac{3}{2CR}$$


texts: How can I open and run the blink example from the STM32F3 MCU package?

texts:
I have previously written, compiled and flashed applications to an STM32F3 Discovery board succesfully with the STM32CubeIDE.
ST offers an STM32Cube MCU Package for STM32F3 series, which I downloaded to try some of the examples. I have a hard time following the instructions (see screenshot below) to open the example projects given in the file /Documentation/STM32CubeF3GettingStarted.pdf. I try to follow the instructions for TrueSTUDIO, given that it's the predecessor of STM32CubeIDE.
Problems:

I'm supposed to use a TrueSTUDIO directory as workspace, but there's no such directory. Am I supposed to create it?

Later I'm supposed to browse to that directory to open the project:

Browse to the TrueSTUDIO workspace directory, select the project

I cannot find a TrueSTUDIO specific project folder or file (see screenshot at the end of this question), there's only EWARM, MDK-ARM and SW4STM32.

How can I open an example project in STM32CubeIDE?


texts: Using discharge protection, BMS and balance charging?

texts:
I am building a small high quality headphone amp which needs power supply +/-7V up to +/-17V. According to the manual it uses maximum 200mA.
I like to use 2 x 3 16340 rechargeable lithium batteries because they are relative small.
I think it is necessary to make sure the batteries are not discharged too low. This is why I think about using a BMS (battery management system). I plan to use two of these BMS:

To charge the batteries I think about using a RC hobby balance charger for 6S charging which I will connect when needed.
I will never use the amplifier while it is charging. There will be a switch which connects the batteries either to the amp or to the charger.
For the balance charger I need to connect all individual batteries to the charger. And all the individual cells are connected to the BMS.
Now my question is: Is it ok when all cells are at the same time connected to the BMS and connected to the balance charger? Or do I have to disconnect the cells from the BMS when I charge them with the external balance charger?
Or what are the alternatives? Is there another easy way to make sure the cells are not discharged below a certain voltage?
Or should I charge the batteries just by applying 12.6V, 500mA to the BMS and let the BMS handle the charging?
About the BMS in the picture: I think about using that model because I could buy it easily and it's cheap. I looked at big electronic distributors and I didn't find any BMS in their shops.


texts: I am designing a 2 resistor MOSFET amplifier but the output is generating square waves

texts:
I am learning about MOSFETs and I was tasked to design a 2 resistor biased amplifier. This is what I came up with. I am really not sure what a 2 resistor biased amplifier is, could someone please help me out?
Why is the circuit that I have attached giving me square waves as the output? If I reduce the amplitude of V1, the output is a straight line.


texts: Choosing a bypass capacitor for long wire

texts:
I've built an IR remote and for integration purpose, I need to bring the led about 1m (3 feet) from the microcontroler. Led Freq is 455KHz. Temperature considered as room temperature.

I choose to move the mos and the led at the end of the wire. Here's the schematic:

It's not very surprising that supply and signal are "a bit" distored when arriving to the led and the mos (yellow = signal, orange = power) :

I suspect that I need some bypassing. I'm thinking about adding a capacitor beetween gnd and VCC. I plan to choose a capacitor with a good response around 18 MHz (for the ripple in orange after the 7th division on the graph).

My questions are:

is it the good way to go?
If not, what should I do? Starting from the graph, is there a way to calculate the capacitance value?
forums and docs talk about low ESL and low ESR but what is low? 1? 1mR? 1µR? Same question for inductance?
Should I add something on signal too?
Any other advice?

Thanks for your help.


texts: VHDL test bench file not accepting all set of inputs

texts:
My VHDL test bench here is not accepting the third set of inputs and is looping back to the start of the process. Please help me.

Code: (comp4bit.vhd)

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

--4 bit comparator
entity comp4bit is
port ( a, b: in std_logic_vector (3 downto 0);
AgtB, AltB, AeqB: out std_logic);
end comp4bit;

architecture behavior of comp4bit is
begin

process (a,b)
begin

if (a>b) then AgtB <='1'; AltB <='0'; AeqB <='0';   --A is more than B
elsif (a<b) then AgtB <='0'; AltB <='1'; AeqB <='0';    --A is less than B
else AgtB <='0'; AltB <='0'; AeqB <='1';        --A is equal to B
end if;

end process;
end behavior;

Code: (comp8bit.vhd)

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

--8 bit comparator using 4 bit comparator as component
entity comp8bit is
port( a: in std_logic_vector(7 downto 0);
    b: in std_logic_vector(7 downto 0);
    AeqB: out std_logic ;
    AgtB: out std_logic;
    AltB: out std_logic);
end comp8bit;

architecture behavior of comp8bit is
signal AgtB1 , AgtB2 , AltB1 , AltB2 , AeqB1 , AeqB2 , sig1 , sig2: std_logic;

component comp4bit is
port( a: in std_logic_vector(3 downto 0);
    b: in std_logic_vector(3 downto 0);
    AeqB: out std_logic;
    AgtB: out std_logic;
    AltB: out std_logic);
end component ;

begin
u1:comp4bit port map (a=>a(7 downto 4), b=>b(7 downto 4),
AeqB=>AeqB1, AgtB=>AgtB1, AltB=>AltB1); --Port map of first 4 bit comparator

u2:comp4bit port map ( a=>a(3 downto 0), b=>b(3 downto 0),
AeqB=>AeqB2, AgtB=>AgtB2, AltB=>AltB2); --Port map of second 4 bit comparator

AltB<=AltB1 or (AeqB1 and AltB2);
AgtB<=AgtB1 or (AeqB1 and AgtB2);
AeqB<=AeqB1 and AeqB2;

END behavior;

Test bench:

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use ieee.numeric_std ;

--Test bench file for 8 bit comparator
entity tb_comp8bit is
end tb_comp8bit;

architecture structure of tb_comp8bit is
component comp8bit is
port( a:in std_logic_vector(7 downto 0);
    b:in std_logic_vector(7 downto 0);
    AgtB: out std_logic;
    AeqB: out std_logic;
    AltB: out std_logic);
end component;

signal a, b : std_logic_vector( 7 downto 0) ;
signal AeqB, AltB, AgtB: std_logic;

begin
Dut1: comp8bit port map(a=>a, b=>b, AeqB=>AeqB, AgtB=>AgtB, AltB=>AltB);

process
begin
wait for 0 ns; --simulating a<b
a<="11110000"; --a= F0 (Hex) or 240 (Decimal)
b<="01101111"; --b= 6F (Hex) or 111 (Decimal)
wait for 20 ns; --simulating a=b
a<="01110000"; --a= 70 (Hex) or 112 (Decimal)
b<="01110000"; --b= 70 (Hex) or 112 (Decimal)
wait for 30 ns; --simulating a>b
a<="10011111"; --a= 9F (Hex) or 159 (Decimal)
b<="01101010"; --b= 6A (Hex) or 106 (Decimal)
wait; --changed this line
end process;
end structure;

configuration tb_comp8bit_con of tb_comp8bit is
for structure
end for;
end tb_comp8bit_con;

Output: (Simulated for 100ns)

Signal Waveforms

EDIT: Fixed the problem by inserting another wait; after the third set of inputs, before ending the process.


texts: How can I identify the increasing and decreasing side of half cycle of sine wave using MATLAB code (.m file). For example the flag should set 1 if the amplitude of sine wave is increasing from 0 deg to 90 deg and should set 0 when amplitude is decreasing from 90 deg to 180 deg.


texts: How to hook up circuit to drive 5x7 1 Watt White LED

texts: I am not a electronics guy but want to design a display using 5x7 Ultra Bright 1.2 W, 350 mA OSRAM DRAGON-X Plus LED. I want to have a simple circuit so as to be able to control (Switch ON/OFF) individual row and columns using 12 switches (1 each for a row and column). Will be thankful if someone can suggest a appropriate circuitry.


texts:
I would like to design a 3GHz high gain antenna.  S11 has to be below -10dB and the gain to be above 9dBi - and I want to make it smaller than 8cm.

What kind of antenna is better to satisfy the condition?

It doesn't matter about the antenna type, but I hope it will be a patch antenna.

Please recommend an antenna specification.


texts:
My thesis group is building a project involving the Raspberry Pi.

It is known that the RPi runs around an average of 700mA of current and my project would probably need a little over 1A of current due to attached components.

I am looking into cellphone batteries for the supply because they are already compact and lightweight, since our project needs to be portable. So i am asking those who have already tried using cellphone batts for their projects. Will it be able to supply the raspberry pi efficiently if i use a 5v regulating circuit? and will the batteries be able to supply the needed current mentioned above?

Oh and i would also like to know what kind of setup you used and how long your project lasted running. :)

These are the components attached to the RPi that will probably consume relevant power:

GPS shield
Ultrasonic sensors (2 or more)

*The RPi will also be installed with text to speech software, so it will be playing audio every now and then while keeping the ultrasonic and the gps components running the whole time.

I will look into everyone's answers. I will update as soon as something works. :) Thanks!

EDIT:
Finally ended up using a 10k mAh power bank due to the ease of charging and connecting :)


texts: Digital filters work on digital data. When we implement digital filters in hardware, does that data which was stored in the form of bits needs to be converted back to its quantized voltage level? If so, how is this conversion done? If not, and the filters work directly on the bits, how does that work?


texts:
I am using an Arduino uno currently with the Si4735.  I can not currently get the audio from this shield to the Arduino or other sources without using the 1/8 jack.  To fix this I am thinking about adding another shield with the functionality I need that has an audio in and audio out.  I need the ability to play audio from an SD card or some other source.  For example this shield: Audio Shield. I known that a lot of the same pins are used, but do I need to use all of the pins from the Audio Shield?  Thanks for any help.

tl;dr:  Is there any way to stack these two shields?


texts:
From what I understand, both of these things inhibit electronic devices from communicating with each other.
A scrambler does this by altering the signals sent out by the transmitter device in such a way that corrupts the data the signal is trying to relay.

What about a signal jammer? Does it work the same way? Are both of these devices the same thing?

(Note: I have asked a question on here before that was not related to electrical engineering. If this is another such question, please let me know! I will happily remove it.)


texts: Help needed in understanding this LED chaser circuit

texts:
Here is a circuit called LED chaser that I found the other day. I watched some videos on Youtube and saw that its function is to blink the LEDs in some kind of sequence:

https://www.youtube.com/watch?v=W0IfnI_caHU

But I don't fully understand what the circuit does or how it works. In the video the LEDs seem to blink in groups in somewhat random order (this could be cool for a disco light application). Is this the function of the circuit?

I also have a hard time getting my head around how this circuit works. There are the sections that consist of an LED with a series resistor, a transistor, and a capacitor. These sections are connected together with some kind of biasing resistors (?) going into the bases of the transistors. Then finally the collector of the transistor at the final section is connected back to the base of the first transistor as well as to the ground. But how do these sections work? I just see the transistors turning on when the circuit is powered, conducting current, lighting the LEDs.. Then the capacitors do something and I just get confused.

Help will be much appreciated! Googling hasn't produced any explanations.


texts:
I am trying to measure the current draw of a 5V analogue hobby servo. I estimate it to be around 100mA. Is it a good idea to use the ACS712 module? I'm not sure if my math is correct, but each count the sensor outputs seems to represent 26mA which is relatively large given the 100mA current draw.

Are there other cheap current sensors that give a better sensitivity?

Any thought appreciated.


texts: Has anyone built an rs232 to usb converter?

texts: I want to implement serial communication into one of my projects, but I'm hesitant to use a serial cable due them them being exceedingly hard to find nowadays.  I found an old converter and took it apart to see whats inside it, and to my surprise, they were all components I already own (basically). Just a pic microcontroller (a really old one which I don't own), and a level converter (not the max232 which I have).  Are there any tutorials that include code that would explain how to build one of these from scratch?


texts: Are these circuits equivalent? (Arduino on breadboard)

texts:
Small background: I would print a PCB with an ATMEGA. Per Gammon website instruction (http://www.gammon.com.au/breadboard) we need 2 ceramic capacitors, on both "side" of Atmega, connected to the VCCs and GNDs.

I cannot figure if I can "delete" one capacitor and use schema 1 because the circuit 1 will be equivalent to 2 or not.


texts: Altium -- how to link multiple real parts to a library component for supplier live links?

texts:
I have an interesting use case for the Altium Supplier Live Links feature: I have several library components that I've made as one schematic component/footprint, but requires two real parts.

An example, you ask? Let's say I have several different pin headers that are integer multiples of a common part (say 4 pins, 8 pins, 12 pins). To keep the BoM count low, I buy just the 4-pin variety, and populate the 8/12/16 etc. pin headers with multiple 4-pin headers.

Is there a way to tell Altium that a single component actually requires 2 (or more) parts to be ordered?


texts:
I have an electric adjustable bed, but the electric components just stopped working a few years ago.
calling the company to repair it will cost way too much, so I wanted to finally try to fix it.
I believe that the problem is in the "Control Box" and those are the specs of it(can't upload more than 2 picture...), because nothing is turning on. not the LED on the remote, nothing.
Input: 220V-240V~50Hz,4VA
Output1: 22V-...,0.1A
Ouput2: 220V-240V~50Hz
Duty cycle: 10%,max. 2min./18min

When I opened it, A burnt smell came out of it and I noticed that the capacitor has a dried brown liquid on the bottom. I removed it, and this is how it looks:

This is the capacitor specs:
MIRAN 1000uF 50v -40 +105C

My questions are:
Can I fix it by just ordering a new capacitor (with the same specs, of course) and solder it to its place?
Will it be safe to do so?
And with what can I clean this liquid, alcohol?
Thank you!


texts:
I want to build an alarm for my soldering iron that goes off if it is hot for too long. Rather than rely on batteries I am wondering if it is possible to generate enough power from the heat of the soldering iron itself.

The device only needs to function when the iron is hot, and it does not need to start right away. The micro controller I using can operate from 2.8V to 5V. It will use 25µA most of the time in sleep mode, only waking up once a second to use 15mA for about 2ms.

I have already confirmed that I can run the MCU from a capacitor using such a small amount of current.

By my estimate it will use ( .002 seconds * .015A ) + (.998 seconds * .000025A) = an average of about ~ 55µA draw.

If it has been on for too long it will make a quick chirp every second. If the iron gets cold it should run out of power and lose its state thus resetting the timer.

My question is can I create enough current to run the chip in sleep mode and charge a capacitor enough to have to do brief awake times using only the heat from the iron?


texts:
I bought a couple components for a quick project and like to know all of the math behind the voltages / current / resistance before I hook stuff up.
For example, I bought multiple vibration motors off Amazon. They are small and cheap, but I cannot find any IV curves.
https://www.amazon.com/tatoko-Vibration-Button-Type-Vibrating-Appliances/dp/B07Q1ZV4MJ/
I look through this and find only "DC 3V". On other products which look the exact same with DC 3V, I find that it pulls 80mA at 3v.
How is one supposed to find a reliable IV curve before you buy? What if my project requires it to be only 20-40mA? Just like an LED, I may want different intensities (not counting PWM).
Is the IV curve the right thing to be looking for, or is there some underlying database that I am looking for?
Thanks for the input on how you find what to use.


texts:
I am wondering if it possible to create a USB device (in following the device) composed from

a custom circuit (eg arduino) and
a flash storage

in such a manner that the device is recognized as a standard usb flash storage (and as such is operable with standart OS drivers), while said storage holds the utilities to operate with the custom circuit (dispalying the data colled by the circuit); and if so, how?

My first thought was to smack a cheap usb-hub and usb-pen before my circuit but that solution, is not pleasing to me.

My goal is to eliminate the need to carry an extra flash-drive just for the operating software, and use default os drivers, make it plug-and-just-work:

i plug the device in
the os (windows) mounts a new flash-drive without needing a special driver
is start (manually or via autorun) my custom.exe from that flash-drive
i recive data measured by the circuit


texts: I am designing a PCB with many pairs each consisting of an IC and a pin header. The autorouter does a lousy job, but I found good manual routes for one pair. How can I route all the other pairs the same way, without having to re-do the routing over and over again?


texts:
I removed all unnessesary cables from some old 200W PSU and added connectors, so I can use it as Power supply.

But there is problem :D When I turn PSU on (this is one without green start wire) I have only 4v/9v on output.
I know old PSU must have some load to work properly, but is there way how to disable this?
I dont want to drain 2A just to stay on.


texts: Back EMF in a transformer with an external power source to the secondary coil

texts:
When discussing an ideal transformer, Wikipedia says “varying flux at the secondary winding induces a varying electromotive force (EMF, voltage) in the secondary winding due to electromagnetic induction and the secondary current so produced creates a flux equal and opposite to that produced by the primary winding, in accordance with Lenz's law.”
It is my understanding that a real transformer experiences core losses that mean the flux created by the secondary coil is not as great as that produced by the primary. I am wondering what would happen if the flux produced by the secondary coil was actually greater than the flux produced by the primary coil.

Suppose the secondary coil in a transformer was connected to an external power source. As the voltage is induced in the secondary coil, the external power source also supplies power to the secondary coil, flowing in the same direction as the induced current/voltage. Would the flux produced by the secondary coil be stronger than the one produced by the primary, and what would happen as a result?

I am not planning on actually doing this - I just want to know if it is possible, and what would happen.


texts: Using STM32F10x RTC to trigger some function

texts:
I am a new hand to STM32F1x and I am trying to do a project that really needs to use the RTC/TIM function.

What I am trying to do is to display a 20 second count-up timer on the LCD.
Something that looks like:

  TIMER: 12.34 s

So what I want to write in the program is:

var s =0
if "counted 1s "
{
  drawchar (3, 1, s)
  s++
}
if "counted 10s"
{
  drawchar(3, 0, x)
  x++
}

So the problem is what to write in order to get:

if (counted 1s);

Thank you very much and sorry, that I don't really have much knowledge on it.

Let me explain more, base on my little knowledge.
What I know is like, when I press a button, I can do sth/ interrupt.

while(1){

    if(GPIO_ReadInputDataBit(GPIOB,GPIO_Pin_9)==1){

        LCD_DrawString(0, 0, name, 8);

    }
}

Thats basically what I can do.

So, instead of pressing a button to draw sth, I would like to make it draw when the timer/RTC rising edge.


texts: Ericsson NiMh battery - Klintland CF1330B

texts:
An old Ericcson GH388 uses a NiMH battery pack (Type 3008)
On the back of the battery, there are 3 contacts, named (+), (-) and (T).

While trying to change the battery, I noticed that the flexible pcb used to connect the contacts with the battery itself is a "MIDSIZE KLINTLAND CF1330B".

The question is, what is the purpose of the "T" terminal, and what is the blue part (which somewhat looks like a capacitor) bridging the "T" terminal with the "-" side of the battery.


texts: The back of a pot used as a signal ground, in a grounded chassis design; how reliable?

texts:
This question relates to those large pots with solder terminals that are still used in electric guitars; they used to be common in metal-chassis radios, amps, TV, as volume and tone controls.

It was common practice that the metal chassis was a signal ground, and often signal-ground connections would be made to the back of the pot - in the simplest case, one of the pot terminals was bent back and soldered there; but also, caps or resistors were often connected between a terminal on the pot and the back of the pot.

However, in many pots, the back cover is connected to to the front of the pot assembly by crimped tabs. There is often a lockwasher between the front of the pot and the chassis, which provides a good connection there - but it seems to me that the connect made by the crimped tabs could be unreliable in the long term.

So I'm asking if people have seen issues related to this - are there some types of pots which are better than others (in particular, it seems possible that OEMs might have selected pots for this issue back in the day, whereas in newer pots the reliability of the connection may not be a big concern for the component manufacturers).
Would it be reasonable when servicing any such equipment, to add soldered jumpers to ground the backs of any pots which are used as a signal ground?  Or would that depend on the types of pots?

The problem is it can be very tricky to simply check, since these issues can often be intermittent, and the act of placing a probe on the back of the pot can cause a flaky ground to suddenly be OK. I ran into this issue recently with an electric guitar that started acting is if there was an open ground within; when I opened it up, the issue had (of course) gone away, but I found that it had been wired so the ground path actually passed through both pot cases in sequence (via the metal plate in which they both were mounted); I added a connection between the back of them to remedy this, and never had a problem after that (which doesn't prove that that was the problem, of course, but...)

UPDATE

@ThreePhaseEel has suggested a fix which also covers a different issue. I appreciate the remarks; I'm working on this Traynor bass amp, and had not considered isolating the ground, as suggested. It's a lot of extra trouble since there are a number of connection points - including the output tube cathodes, and also the negative ends (and outer shields) of two 'chassis mount' electrolytic caps, and the signal input jacks.
As a nearly continuous metal plane, the chassis should actually be a pretty solid ground, whatever issues are there with power supply current coupling into the signal path, are likely quite minor compared to the ripple on the unregulated supply, (and likewise this is probably not the highest-gain point for RF pickup).
But it may be practical to leave the power stage connections (and associated power caps) on the chassis and just make sure everything else goes to a common point, thanks for that suggestion.

The method of adding reliable grounding wires to the backs of the pots (as rework/maintenance, not in original design) solves the separate issue of  intermittently open signal-ground connections, and is not much trouble to do; I was wondering in particular

If anyone had experience with seeing problems solved by this; and
Is anyone aware if 'old' pots were made in a way which gave them better electrical integrity, to support this construction method.


texts:
I want to use mmbt2222 and/or 2n3904 as switch with in it's maximum safe limits continuously not pulses

I have tried to go through the datasheet but couldn't figure out what is the important params. to use to calculate the surrounded resistors

I have tried some values with the transistor base and when I add load the transistor burn within seconds
the circuit that I use here

My question as described in the title:
How to Calculate transistor params as switch to operate within the maximum limits safely?

EDIT: I mentioned those transistors as an example, they just happened to be in my collection, I am not asking for circuit design for those transistors , I am asking for a generic way to calculate the params based on those trans. as an example only.

thanks


texts: Is there a common way to generate relatively accurate microvolt (like 5uVpp, 0.5uV resolution) waveforms with bandwidth under 4kHz, output impedance around 1k? I can't think of much more than resistors divider on  a bigger signal.


texts:
I need to do similar things to this question on Stack Overflow:
"Using Serial Peripheral Interface (SPI) to talk to several slaves simultaneously
"
I have no confirmation if it works. Has someone succeeded with this method?

I go further with my request...for some reasons:

all the MISO lines have to be connected together
no CS pin is used to select the slaves

If I ensure, during the "broadcast", that MISO of slaves becomes high impedance whatever is CS level (programatically or using an external tri-state buffer). Do you think it will work well?


texts: I have an 8 cell 9.6v 600mah battery. If I take out 2 cell, making it a 7.2v battery 6 cell battery will the mah change? Also can I still use the same charger that came with the battery if I change the battery?


texts: Converting 12V capacitors from parallel to series: do they need to be rated for 250V?

texts:
I have designed a DC-to-DC voltage multiplier. It works by first loading 21 capacitors in parallel with +12VDC and then switching them to series using my homemade 42 pole relay. The output would be about 250 volts.

The question is, should all the capacitors be rated for 250 volts?
Is the voltage through one capacitor 12 or 250V?


texts: Gunn diodes are usually specified to work within a range of frequencies, e.g ~10GHz. I can easily understand why there is an upper bound for the frequency of operation of a Gunn diode, but I can't figure out why there is a lower bound: after all, what is used is the negative resistance of the diode: what prevent us to use this negative resistance at frequencies as low as 100hz, beside the fact that it would be very stupid to use a Gunn diode at such frequencies?


texts: How can I deposit metallic electrodes on a temperature-sensitive wafer?

texts:
How can I deposit metallic contacts on a wafer in a process that won't heat the wafer above 80C? The size of the electrodes should be around 1mm2.

The wafer could be glass or silicon, coated with a sensitive organic/polymeric film, functioning as a dielectric layer.


texts: Does a resolver distinguish between negative and positive angles?

texts: If a motor spins in the reverse direction and completes 1/8 of a revolution what angle will the resolver output? The angle that the resolver measures should be -pi/4 However if it only treats angles as positive then it would measure pi/4. But pi/4 and -pi/4 are completely different motor positions? How does the resolver distinguish between positive and negative angles?


texts: High Voltage & Current Circuit From Small Power Source

texts:
Is there any way that I can create a high voltage and current generator circuit from low power source such as lead acid battery? eg; 12V to 10 kV and 1A

Most high voltage generator such as ZVS or Cockroft-Walton do provide a large amount of voltage but small in current.Do I need to charge a large capacitor to make large peak currents?


texts: What happens if D2 and D4 is shorted in a full wave bridge rectifier?

texts: Hello, What happens to the circuit if D2 and D4 diode is shorted?


texts: Looking to Identify a connector, to engineer a solution using a USB connector

texts:
I have been tasked with installing an NCR 76 (7876) Scanner/Scale in my grandfather's store. The device was purchased over mercadolibre.com and was not sent with documentation, but was supplied with some cables similar to this, without the splitting part:

https://www.ebay.com/itm/NCR-SPLITTER-CABLE-PN-497-0439684-NEW-IN-PACKAGE-FREE-SHIPPING-LOT-OF-10-CABLES/222763414231?epid=3011716892&hash=item33ddbbf2d7:g:wTEAAOSwqbxaOpe2

On that cable, one side has an RJ type modular conector called 10C10P and on the other side is the connector in question. The cabling follows the RS232 Standard.

Once I figure out what connector it is I can see how it reads data, and I can work on a solution where I change de conector to a USB interface, so that I can hook up the Scanner/Scale via USB to a PC.

Here is the User Guide: https://drive.google.com/file/d/1n7yshrSeB5ulE-ajyHoGEf6zJtdGUfYz/view?usp=sharing

Thank you


texts: Can an LED run by harvesting energy from mains hum?

texts:
One morning 2 weeks ago I found a green LED in a carpark attached to a deflated ballon. It had obviously landed overnight. I left it there and when I returned in the evening it was still glowing quite brightly. Impressed by the battery life I took it home, cut it from the balloon and put it in a dark cupboard. Then I checked it every morning to see if it was still glowing.

There's no visible battery, just the LED and I assume a battery inside the tiny plastic surround.

It still is glowing, after 2 weeks. Which surprised me. So...

2 weeks running an LED should run down even a sizeable battery. How little energy does an LED need? If it needs so little energy could it be made to run from energy harvested from mains hum?


texts: I am trying to fix my robotic sweeper, and I saw this highly suspect capacitor on the PCB, I presume it is gone and needs to be replaced. However I dont see any rating over this unit, so I am not clear on  how I can replace it.. Is it something that isnt exposed? Or is it directly tied to the package size?


texts:
I'm trying to understand nmos mosfets. My textbook has plenty of examples dealing with the nmos with resistors. But I'm currently dealing with a problem with a capacitor on the drain. I just haven't seen this type of problem before and would like some guidance, or better yet, examples.

How do you know when the nmos will be saturated or ohmic?

I want to solve for the voltage across the drain and source.

EDIT:
here is my problem:

assumptions: before t=0, there is no voltage across the cap and Vg is turned on at t=0


texts: What's wrong with this simple PCB design? (midi synth)

texts:
I am designing a simple synth with Arduino (just the Atmega IC) and it works fine. The only thing is this annoying clicks I barely hear constantly if I raise the volume somewhat.

I had this problem in the past that's why I was trying to fix it by designing the PCB, separating 3 ground sectors in digital and analogue parts on one side of the PCB. In theory that should stop the digital part contaminating the analogue part.
It seems it didn't quite worked because I can still hear the clicks.

There are two things making clicks at the same time, according to my tests:

1- the Atmega crystal: If I remove the Atmega IC, that click stop.
**UPDATE: **That click was caused by the Atmega program. But I still have this other midi click sounds:

2- the Midi messages: When Midi is not connected, there is no click. After each midi message is sent (a note or clock i.e) I hear a click. For example the clock makes a constant stream of clicks and are sped up if I increase the tempo on the master device sending the BPM. If I take the Atmega IC and send midi messages, I can hear the clicks, so it's independent of it. That's why I'm thinking it's a PCB design issue

To strip down the problem I removed the LM358 part where the "scissors" are in the schematic picture and I just get the output from where it says PWM, that's just the output from the atmega IC.

So, my question is: Do you see any PCB design flaws? What could be causing the click noises?

Thanks!!

PD: I can upload the Eagle file if requested.
][]


texts: Do LEDs require more power to function as they age?

texts:
I have a strange issue with the LED backlights of the LCD monitor i'm using. I have had it for about 5 years and up until this time have run it at only 10% brightness to reduce eye strain. However recently I have had an issue where some of the LEDs that make up the backlight will switch off leading to dark areas of the screen.

The problem is getting progressively worse. I bumped the brightness to 25% when I first had the issue a year ago and that caused the problem to go away, more recently I have bumped it up to 50% when it reoccurred but today it did it again and I now have to run it at 75% brightness which is starting to cause eye strain.

Is this an issue with the LED requiring more power to run as the semiconductors wear? does running LEDs at low power for years on end do extra damage? Or could it be another problem that I could fix?


texts: Is input impedance of an opamp independent from its input's frequency components?

texts: If input impedance of an op-amp is infinite (theoretically), does frequency of an input signal have any effect on input impedance of the op-amp?


texts:
I'm planning a device that can switch a 240VAC 1A current - most likely 0.5A but it's nice to have the head room.

A relay seems the most obvious choice but given the low current it seems over the top and is pricey. Are there alternatives that I've missed?

UPDATE: Load is an IR heating pad so no initial rush current that I am aware of.

UPDATE 2: Load would turn on for an hour and then turn off, 5VDC or 12VDC timing circuit to control the relay to do this. Basically, push a button and the 240VAC load stays on for 1 hour and then turns off. Press again if more time needed.

UPDATE 3: Would this do the trick? https://www.mouser.co.uk/ProductDetail/Sharp-Microelectronics/PR36MF21NSZH?qs=sGAEpiMZZMve4%2fbfQkoj%252bCr9xHrLc8XaMpgkbqJI%2f1s%3d


texts: Breakpoint Alters PIO Interrupt Behavior - ATSAMV71

texts:
So I'm baffled by this...

I'm working with an ARMv7-M microcontroller and GCC compiler, debugging some code where I'm trying to enable an interrupt. I'm trying to do the following: enable an interrupt so that on a value change for pin PA31, pin PA9 gets set to low, using the MCU's PIO controller. The interrupt handler is just called PIOA_Handler, it is declared in one of the device files as:

void PIOA_Handler         ( void ) attribute ((interrupt));

And the guts of the function are in main.cpp:

void PIOA_Handler(void)
{

    if ((*((Pio*)PIOA)).PIO_PDSR < PIO_PDSR_P31_Msk) {
        ((*((Pio*)PIOA)).PIO_CODR |= PIO_CODR_P9_Msk);      // clear output on pin 9 if pin PA31 is logic low
    }

I start by enabling global interrupts and setting PA9 to out, and enabling the change interrupt for pin PA31 on the peripheral side and also enabling the NVIC interrupt vector so the processor accepts and handles the interrupt:

        gpio_set_pin_direction(PIN_PA9, GPIO_DIRECTION_OUT);    // set PA9 to out and PA31 to in
        sys->setPin(PIN_PA9, true);                             // enable PA9

        ((Pio *)PIOA)->PIO_IER |= PIO_IER_P31_Msk;
        NVIC_EnableIRQ(PIOA_IRQn);

The actual problem that I'm having is this: for some reason, when I'm debugging without setting a breakpoint, rather than calling PIOA_Handler when there is a pin change, it just gets called continuously, over and over for the entire length of the debugging session.

If, however, I set a breakpoint on the line of code where I enable the PIO level change interrupt:

((Pio *)PIOA)->PIO_IER |= PIO_IER_P31_Msk;

this somehow doesn't happen and PIOA_Handler gets called as it should, when there really is a level change on PA31.

One more thing I've noticed is that if I set a breakpoint on the next line NVIC_EnableIRQ(PIOA_IRQn);, and look at the NVIC Interrupt Set Pending Register (ISPR) in one of the debugger watch windows, there is a pending interrupt for PIOA_IRQn. But if I set a breakpoint on ((Pio *)PIOA)->PIO_IER |= PIO_IER_P31_Msk; and step over to the NVIC_EnableIRQ line, there is no pending interrupt.

I've tried inserting NVIC_ClearPendingIRQ between the two lines, but it doesn't clear the pending IRQ. For whatever reason somehow the breakpoint clears it, but using an actual Clear Pending function does not do the trick. Why is this and how do I write code that doesn't need a breakpoint for the interrupt handler to be called properly?

Thanks in advance!


texts: 10 Watt LED and LED Driver related question

texts:
I got a 10watt LED from Ebay but never thought that the driver and heat sinks are must-haves for this little master. When googled, I found several circuits of LED driver. But none of them are precisely a 'simple' circuit with takes 12v 0.5mA ~ 1.5A DC input and lit the LED to full brightness. So here are my questions folks:

I got few 220V to 12v transformers (with 500mA, 1A, 2A current ratings). Can you please give me a simple circuit diagram (preferably with a linear regulator or NE555 or any other easy-to-find IC/Transistor) to lit the 10 watt LED?
Just saw a video, where the maker claims, even though the forward voltage rating of the LED is 9-12v, it will burn itself if connected to 12v and furnished a meaningful explanation. Whereas, we has shown that the LED glows ok with a simple 9v NiMH battery. I knew these LEDs need 2-3AMP current at 12 volts. What's the real fact of voltage and current for these LEDs?

Many thanks in advance. Please help.


texts: How are Transistors in the Cut-off Region in Double Reverse Bias?

texts:
To get an npn (say) BJT in the cut-off region, you set the base current to 0 and the voltage less than 0.7V. This means that \$V_c > V_b\$ and \$V_e > V_b\$. However, the emitter voltage is 0 (ground) normally, and the base voltage would be less than 0.7V, which is not less than 0, so \$V_e < V_b\$.

So when people say BJT's in cut-off have both junctions in reverse bias, what do they mean?


texts: Blowing resistors in parallel, in an order-controlled way

texts:
I'm supposed to make some questions, to gain some badges (just the excuse), so I'll throw one I've always been very curious about.

Imagine I want a set of resistors arranged in parallel to blow in a sequential and order-controlled way, just for me to admire the show, or to share it with someone else.

Look at this schematic:

I want to blow as many resistors in the set {R1, R2,... RN} as possible, as I said, in an order-controlled way. First R1, then R2, etc. I don't want to blow Rs. We can choose the values for Vs, Rs, R1, R2,... RN, the power ratings for each resistor (let's call them Psmax, P1max, P2max,... PNmax), and the maximum current Ismax that the source is able to provide. Also, assume that a blown resistor is always an open circuit.

Let's call M to the number of resistors (out of those N) that will eventually be blown.

Question: How would you choose those values, to maximize M?

I see two cases:

1) Mathematical "world", with unbounded parameters, and even making unreal assumptions such that a resistor does not blow for P < Pmax, and blows for P >= Pmax. I'm not interested in this one (because it is clear that there are infinite solutions, and with M=infinity).

2) Real-world case, with feasible values for all those parameters, and with the real thermal behavior for the resistors. This is what I'm interested in.

I know that this is a relatively complex question, and with little practical use, but I'm still curious about it, as a mathematical/engineering challenge. Aren't you? Just take your time.

Edited: Actually, let's bound Vs, so that we don't end up with HV generators. Since Olin already used 12 V in his example, let's fix Vs=12 V for all of us. Also assume a value of Ismax=100 A.


texts:
I am going to design power drivers for a high power LED that is capable of high currents (up to several amps). I am using a power MOSFET for fast switching. I have designed a PCB for this circuit, but I have some problems with it.
I connected a dimmer circuit with the pcb. When I give 5V to the circuit the LED doesn't glow. I can check voltage switching between 5V at the gate of mosfet but there are also little voltages switching at drain and source and mosfet gets hot after some time.
Can anyone tell me the reason why there is no current at load, that is, why the LED doesn't light? Why is there some voltage at the drain and source of the mosfet, and why does it get hot very quickly?

Vcc=5 V, Vs=12 V, LD1=ordinary LED.
Datasheets: MOSFET, MOSFET driver.
Update
I have removed the diode from the circuit but very low voltage is present there on the output that cannot drive my led. I am facing the same problem. the supply voltage is vcc=10V and Vs= 3V. and the resistor r1 is 80 ohm. can anyone tell me what could be the problem...


texts:
There are temperature sensors which are powered the following expensive supply: http://www.prelectronics.com/pdf/2222-2476-US.pdf Here it is mentioned: "The power supply is based on primary switchmode technology to achieve a high efficiency." and "Galvanic isolation between the primary and the secondary
voltage is achieved through the double-isolated safety transformer."

I need to install a new system with new sensors and need a new power supply. I found a cheaper power supply which has the data-sheet: http://docs-europe.electrocomponents.com/webdocs/0802/0900766b808023f1.pdf

Someone used the first power supply model I linked and I don't know if there was a specific reason for that power supply. I'm guessing for transducers like temperature sensors the isolation, ripple voltage ect. might be important.

I have couple of questions:

1-) Is the cheaper power supply I found(second link) an SMPS? Because it is not mentioned.

2-) And again in the second power supply the Isolation resistance > 5MOhm. Does that mean there is good galvanic isolation?

3-) Would it be okay to use the cheaper one instead of the first one?

I'm asking because I'm wondering if there is something special about the first power supply(first link).


texts: Effect of switch rise time on an LR circuit transient response

texts:
Below is an RL circuit and transient response plots of the inductor voltage V(vl) and current I(L1). V1 = V(n001) is the voltage applied to the circuit at time 0.1sec. (I set all series and parallel resistances and capacitors of source and inductor to zero for simulating a pure RL circuit)

What is happening above is that, the moment the switch is ON the inductor immediately opposes the current change and inductor voltage at that moment jumps to the voltage of V1. And current starts from zero so at t=0.1 I = V1 - VL = 0. These can be seen in the above plots.

But now when I change the values of the inductor and the resistor as in the circuit below things do not follow the same logic:

As you see the inductor current again starts from zero at time t=0.1sec; which means the inductor voltage should again be equal to the source voltage V1 at time t=0.1sec. But the inductor voltage is VL 200mV in the above plot which confused me.

When I reduced the rise time of the rising edge of the switch the VL became equal to V1 again which is 1V. I think texts consider duration of the switching action is in infinitesimal amount of time.

Does the transient theory considers rising edges almost 0 seconds?
And what is the relation between the rising edge of the switching and the initial inductor voltage here?

In other words how can the rising edge effect on the inductor voltage can be explained or formulated here?

EDIT:

Solving this with Laplace and plotting in MATLAB gave the same results.

Here is what I did in MATLAB:

(Got help from the math guys here for V(s))

clear all;
clc;
syms s t

R=10;%resistance
L=10*10^-6;%inductance

a=1;%final voltage 1V
t1=0.0005;%rising time for the switch
m=1/t1;%slope of the rising edge

V = (-m*t1*exp(-s.*t1))./s + m*(1-exp(-s.*t1))./s.^2 + a*exp(-s.*t1)./s;%V(s) switch voltage
I = V./(R+s.*L);%current in s domain
VL=V-I.*R;

y= ilaplace(VL,t);%inverse Laplace

ezplot(y,[0,0.0004])
ylabel('Voltage [V]')
xlabel('time [sec]')

grid on;

Both in LTspice and MATLAB I set the rising time as 0.0005 sec.

Here are the plots from both LTspice and then MATLAB:

It seems like results agree. So it seems LTspice does not calculate anything wrong here. Its just if the rising edge is slow thats what expected.

Do you agree?


texts: Internal structure of MOSFET gate driver integrated circuts

texts:
As far as I know, a typical MOSFET is driven by a circuit like below.

I read several MOSFET driver IC datasheets. It looks like they have a more complicated internal structure.

For example, the ZXGD3003 IC has two different inputs and source & sink outputs.

Can you please give me internal structure of an IC like this.
Why do they take two inputs and how do they give separate source and sink outputs?


texts: Producing Voltage Spikes from a bench top power supply

texts: I need to test a tantalum capacitor(check if it gets shorted for a spike higher than the rated voltage) and I'm planning for providing voltage spikes to the input connector from a bench top power supply. Is there any technique apart from switching the supply ON and OFF quickly to provide a voltage spike?


texts: How is the current resulted from the full wave rectefier equal to 10.2?

texts: how is that possible ? shouldn't it be much less


texts: Is hobby relay adequate for air conditioner automation with microprocessor

texts:
I'd like to use a Beaglebone Black(3.3v Logic) plus a 3.3V  to 5V logic level shifter(74HC125) to control an opto-isloated Songle Relay that has the following specs:

Rated Resistive load: 10A 125VAC; Rated Inductive Load: 3A 120VAC

The relay would be switching on/off the mains plug for the following window AC unit:

link to Ac Unit

It's 4.8 Amps, 115 VAC (with a GFCI plug)

Is a compressor a pure inductive load? If so it appears the 4.8 amps is over the rated 3A for inductive load.

If so, what does that mean? What is the failure mode? Will it blow up? will it just  not last as long? Will it maybe be ok? What would be a suitable replacement that works with my controller?

This is a proof of concept, so if it lasts a few months, I'm ok with that.


texts: A basic question about RF multiplexer practical use

texts:
Below shows an RF switch(multiplexer):

So what I understand is that the same RF input is routed to multiple outputs. This can be I guess used to couple the same RF signal to many different equipment such as spectrum analyser, oscilloscope ect.

But lets say the scenario is such that we have many signals from several devices which we can couple these as inputs to a device under test's input. I tried to draw it as follows:

Now as in my above example, we can select which analog input will be coupled to the ADC. I named it as MUX.

So in such a case are RF switches used as well? Or only analog multiplexers are used? If RF multiplexer can also be used, what could be the reason?
(is this called switch matrix?)


texts: Secondary linear lamp circuit interrupter switch

texts:
Following on from this answer to a previous question from a while back, I want to add a new lamp (with its own button/switch).

The new lamp should be controlled separately (i.e. not controlled or affected by the timer).
When activated, the new lamp should emit a single flash.
Triggering the flash should interrupt/reset/disable the timer (if it's active), killing the lights.

The idea is to mimic the behaviour of a (photo) flash with auxiliary lighting that automatically cuts out when the flash fires. In reality flash lamps are usually high voltage xenon tubes. But for now I'm more interested in the switching, and the rest of the circuit so I'll just be using a regular incandescent bulb to demonstrate the concept.

20-Second MOSFET Timer


texts: I can't figure out whether it's a varistor or any other non polar capacitor. Please also suggest how to test it.


texts: Series Termination Resistors Sharing a Common Point

texts:
Suppose I have a high speed digital signal (represented as a square wave) that splits off and is shared between two subsequent inputs stages (represented as MOSFETs).

Is it better to have two series termination resistors for each input stage?

simulate this circuit – Schematic created using CircuitLab

Or better to have a single resistor for both stages?

simulate this circuit

My hunch tells me the former would work best, but the latter could work as long as the post resistor line is routed correctly and kept short.  The Internet doesn't seem to have much to say on the matter.


texts: Why don't we make CPUs with 1000s of layers to make use of space in the third dimension?

texts:
I am wondering why don't we make processors such as CPUs with 1000s of stacked layers to make use of space in the third dimension now that we have three-dimensional transistors. To be clear I'm referencing making something of a rectangular-prism shaped processor.
To be clear there's a vast amount I am not aware of when it comes to processor manufacturing, I am not an electrical or computer engineer, but I am very curious. I am aware of the heating problems this would cause considering an even more dense packing of transistors and the manufacturing problems considering you would have to laser etch through so much silicon, but unlike enlarging the size in width and height there wouldn't be problems with making the most of the circular silicon wafers, and unlike with that you would be keeping the parts very close which means it wouldn't slow down the speed of the electricity getting from one part of the processor to the other because the processor already has 1000s of transistors stacked horizontally and vertically.
I am curious if you could solve the heating problems by laying down thin intermittent heatsinking layers, while keeping the vertical throughput. And fix the manufacturing problems partially by using separately etched wafers every 10 layers or so. Could this be possible or are there lots of problems I'm not thinking of (and I'm sure there are)? Thanks.


texts: Providing power to additional load (PN532 Board)

texts:
SETUP: I've put together a board comprised of:

24 V DC Supply voltage connected to 60 Ohm (10 W) Resistor that is in series with a LM7805C (5V Regulator). The LM7805C has a .33 uF cap on the Vin terminal, GND is connected to GND, and a 0.1 uF cap on the Vout terminal. When I measured my current coming out of this, I saw 400 mA (like I expected).
Out of the LM7805C, I have an ATMega328PA that has a crystal oscillator connected to it and is connected to a Adafruit NFC board via SPI in the same way as this setup.
The NI hex buffer (HEF4050B) you see is also attached to Vout of the LM7805 but using a resistive voltage divider, I "feed it" 3.3 V
The Adafruit PN532 (NFC) board is connected also at Vout of the LM7805 and being supplied 5 V.

ISSUE: I'm currently facing a low current problem --- there's not enough current flowing to the PN532 board --- it requires about 150 mA to function appropriately, but when I put in my ATMega, my current drops to about 20 mA. Should I need to have a separate regulator for the PN532 and the 4050?

Schematic:

(click to view full size)


texts:
Even though the electronic device is powered off, isn't there a risk of doing a continuity test on connections in the middle of the circuitry ?
I mean, you do apply voltage doing so - couldn't that harm the components? Or is the voltage too low?


texts: Async counter that starts counting from 2

texts:
I have to make an async counter that counts from 2 to 8. This is what I've done so far:

It counts from 0 to 8 and I don't know how to make it start counting from 2.


texts: Continuous assignment during SystemVerilog simulation

texts:
I am providing input to an SPI interface. The input signal is a concatenation of several different signals. What I would like to do in simulation is have continuous concatenation of the different signals into one final string that will be sent to the SPI:

logic [7:0] foo;      // Signal 1
logic [7:0] bar;      // Signal 2
logic [15:0] combine; // Final signal
assign combine = {foo, bar};

task SendSPI;
begin
     foo = 8'hFF;
     bar = 8'h00;
     SendToSpi(combine); // Want it to send 16'hFF00;
endtask;

The above code compiles and runs on the simulator (Cadence NC sim), but the value of combine is undefined (xxxx). I know I can get around this by having a concatenation task:

task CombineSignal;
begin
     combine = {foo, bar};
endtask;

and I would call that task everytime I wanted to concatenate, but having continuous assignment work would be really nice! Does anyone know if continuous assignment is possible in a situation like this?


texts:
Given that:

Power=Current*Voltage
&
Current=Voltage/Resistance

And that the total power you get out cannot exceed the total power you put in, Step-up transformers shouldn't exist.

So my powersource releases 9v, in a circuit of 2 Ohms, meaning the current has to then be 4.5A according to the second equation. That gives us a power of 40.5 watts according to the first equation.

I have a transformer that steps a voltage of 9v up to 400,000v next to me. And if I was to feed the same 9v into this transformer, then if we were to negate the loss of energy due to heat loss (etc, etc...) we should still get an output of 40.5 watts. If this were to be true; the power 40.5 watts, the voltage 400,000v then the current would be 40.5/400,000=0.00010125A. But if we then plug this back into the second equation, the resistance would need to now be 400,000/0.00010125= 3950617283.95 Ohms.

So "how does the transformer increase the resistance so dramatically", is my question?


texts: Replacing capacitor across power input to VS1838B infrared sensor

texts:
This is a schematic of VS1838B infrared sensor. The problem is that I don't have a 10 uF capacitor. Can I replace it with a 100 uF / 1 uF electrolytic capacitor?

Kindly also explain its purpose; is it only for decoupling or does it also form a separate filter, like the 100 ohm and 0.1 uF one?

Also, if I have several of these sensors, can I just use these components once, make the VCC and ground common to all the sensors and hook up the output to Vcc individually?


texts:
Concerning the technical documentation of the BC337 BJT NPN Transistor.

https://www.onsemi.com/pub/Collateral/BC337-D.PDF

I'm just learning the jargon. I am under the impression that in the 'on specifications' Vce = 1.0Vdc means the voltage from the collector to emitter pin cannot exceed 1.0V? Is that correct?

Thanks


texts: How to correctly calculate dBv using voltage sample points?

texts:
I'm working on a noise detection application and now I can read the Vout value of the MEMS microphone VM1010.
By searching on the Internet, I find dBv = 20 * log10(V / 1) to calculate the dBv value. However, using this formula with my sampled average 0.8V voltage, I get a -2 dBv value. But the normal range of dBV stated in the datasheet of the microphone is about -17 to -98 dBV for 35dB SPL to 115 dB SPL. Where possiblely am I missing?


texts: IEEE 1588 PTP phase and time synchronization

texts:
Why everywhere is said that PTP synchronize phase and time together?

phase and time are totally separate concepts. does it mean after using PTP rising edge of slave and master clocks happen simultanously?
Actually I think PTP synchronizes just the time(not phase)


texts:
I have a 3 pin 12 V Fan, rated at 2000 RPM max. Its nominal voltage is 12 V which will make it spin at full throttle. That's what is happening when I plug it in the motherboard. However I don't like that, because the fan is making a lot of noise. I would like to lower its speed to about half. I have figured out I should supply it with 7 V instead. There are methods online here, here and even a famous video on YouTube here demonstrating the procedure.

I've read a lot about this and I'm unsure about whether this is safe. I use a modern and pretty good and reliable 80 Plus PSU. So I'm skeptical now and I want to ask here to understand better. What we have to do is pretty much shown on the picture below.

Instead of supplying the fan with 12 V, using the yellow 12 V pin and the black ground pin from the Molex cable, we instead supply it with 12 V for VCC and 5 V for "ground". So the fan sees voltage difference of 12-5=7 V, but shouldn't there be a path to 0 V ground? This is the part where I'm confused.

Is this secure, is this possible?


texts: Different ways or sensors to detect the weight on an object in a system

texts:
I am starting to gather information for a project I am excited about; my project is essentially a barbell that can detect the weight loaded on it. I will quickly summarize the function and restraints. So normally the barbel is made of stainless steel and has two areas where you can load the weight, each side can hold about 7 plates without bending or warping so about 630lbs of safe load.

What I am trying to do is be able to detect the weight placed on both of the loading areas but I'm unsure of an elegant way to do this.

It has been proposed pressure sensors but I don't see this as elegant as it potentially could be. This is where I need your help; My question is - what sensors are able to detect weight in a robust reliable way that would make sense for my project?

Specifications/ info  of embedded system:
A men's Olympic bar is a metal bar that is 2.2 metres (7.2 ft) long and weighs 20 kilograms (44 lb). The outer ends are 50 millimetres (2.0 in) in diameter, while the grip section is 28 millimetres (1.1 in) in diameter, and 1.31 metres (4.3 ft) in length.

Electronics involved: stm32** chip with Bluetooth and accelerometers.

Requirments

able to detect weight from 5 lbs - 315 lbs
robust and easy calibration cycle
will not interfere with the loading of weights and de-loading process ( bar must be able to
fit inside an Olympic barbell)

What we have tried
As mentioned we have brainstormed a few ways to potentially embed this but most of our ideas involve a spring system. Although we have been exploring a fiber optic strain system but are unable to dig up info on this or how we could implement one or even if it would be reliable in our project.


texts: Arduino remote IRsend undefined reference error

texts:
I'm trying to use Arduino to transmit a code. I keep getting an error upon compiling.

After tons of research, i couldn't find a solution. Can someone please see what i'm doing wrong?

My code:

#include "IRremote.h"

IRsend irsend;

void setup() {
Serial.begin(9600);
}

void loop() {
delay(10000);
//Power//
IRsend irsend;
unsigned long int iri = 0x80BF51AE;

irsend.sendNEC(iri, 32); //Power Code
Serial.println("Power");
delay(10000);

}

Here is the error:

Arduino: 1.8.7 (Windows 7), Board: "Arduino/Genuino Uno"

C:\Users\user\AppData\Local\Temp\ccV39V2V.ltrans0.ltrans.o: In function `loop':

C:\Users\user\Desktop\IRecord/IRecord.ino:15: undefined reference to `IRsend::sendNEC(unsigned long, int)'

collect2.exe: error: ld returned 1 exit status

exit status 1
Error compiling for board Arduino/Genuino Uno.

Here is the IRremote.h:

https://github.com/z3t0/Arduino-IRremote/blob/master/IRremote.h


texts: Determine capacitor value gives amplifier characteristic independent of frequency

texts:
I have an amplifier for the needle EMG electrodes signal like image below. The question is : Determine the C2 capacitor value gives electrode–amplifier characteristic independent of frequency. Can you help me how to determine that value?

I very appreciated with your support.


texts:
I have a circuit where I am using a tactile switch to pull 3.3v down to ground and investigating debouncing the button. My relevant part of the circuit is

The 100nF cap does work here my signal has ringing that operates in the undefined region and causes a few false clicks. Increasing the capacitance to 1uf makes it worst. I tried using 10nF which was better. It reduced the ringing time but did not remove it.
Image of scope trace below for 10nF.

This ringing is not really a switch bounce contact problem is it.
What causes this ringing. There is capacitance on the power rail could it be that ?

My best results are with removing the caps entirly.

I know I can use software to solve this issue so it is not a big issue but I am using this as a learning exercise.

My easyeda design:

Top:

Bottom:


texts: Why does gyroscope drifts and is it possible to use position based calibration to calibrate it?

texts:
The MPU 6050 chips has gyroscope and accelermeter, and if you google anywhere they will tell you that the gyroscope drifts, usually at constant rate.

My question was, how does this drift come from? Was it because of the motion of the earth? If so, can we use position based calibration, like GPS coordinates to calibrate such misalignment instead of using a complementary filter?


texts:
I am using a low side driver from Infenion BTS3080EJ. Details here.
The input from the microcontroller will drive the IC BTS3080EJ which will drive a contactor (12V, 1.3A). I want to know whether I should use an optoisolator in between the microcontroller and BTS3080EJ . Is it needed? The circuit provides features like overvoltage prrotection, short circuit detection and current limiting, thermal shutdown. But signal isolation is not provided by BTS3080EJ. If I have to use an isolation, what should I use? Will Digital isolators be good? Please help


texts:
I'm trying to make an FM modulation with a Hartley oscillator that oscillates at 45MHz. The problem is that it's supposed to have an unitary gain. I can't find a good adjustment between a really low gain and maintaining oscillations. Here's a transient plot of my output voltage for an input voltage of 500mV that as 1/10 of the frequencies of my oscillator:

Here's a picture of the circuit I'm trying to realize:

What arrangements can I make to help me adjust for amplitude higher without struggling the shape of my oscillations?


texts:
Hi what’s the best/easiest/cheapest way to test 2 6v Trojan 105 leisure batteries.

If low how could I charge these batteries as all the chargers I can find are for batteries rated to 60ah Max. The Trojan batteries are around 250ah


texts: Voltage Required to Ignite 10ohm resistor

texts:
I just read http://www.bigclive.com/ignite.htm
It shows igniting a 10ohm resistor with 12 volts.
I was wondering, could a 10ohm resistor be ignited with less voltage(say, 9Volts), and if so, what is the minimum voltage?


texts: Can we make a rechargeable zinc air battery at home?

texts: I've read a lot of material about zinc air batteries, many firms successfully made their own prototypes of rechargeable zinc-air batteries. Is it possible to do it at home?


texts:
I have a box full of 1-6amp 12v power supply and 1 short run of 24v led strip, rated about 1.5amp draw at full blast.
Can I take 2x 2A 12v supplies (ungrounded plug) to run in series to easily achieve this?
Not that I can't find a small 24v source, I just want to repurpose some of the 20+ 12v wall warts I've been hoarding all this time.


texts:
I am following this document Loop response consideration in PCM. Here I am implementing fig 5 schematic in page 9. From equation 1 to 22 got me some of the hidden values of the schematic which I have inserted.
Some of them are gm * Rcomp =9.54 Rcomp * Ccomp = 26.5u Rcomp * Co_EA= 1.06u from equation 21 and 22.
Vslope = 0.476V from equation 21 and I am assuming Vslope = T* Ri * V /L From here I got Ri = 1.88
which I inserted it as gain of the sense amplifier. Fsw= 1.1MHz.

I am getting D = 39% for 5V output I am supposed to obtain 41.6%
Is my calculation incorrect? Here am trying to understand the control loop and dependency of signals on each other and its theoretical equations which are necessary for transient modelling of PCM buck.
Is there any better way to understand modeling steps/parameters (equations) to be followed while transient modeling of current mode buck?


texts:
I'm just starting to get my feet wet with electronics so please pardon my ignorance. I bought an LED light-bar to mount to my mountain-bike for some night riding: https://www.korrlighting.com.au/product/xd-series-18w-slimline-led-driving-light/

I've been powering it with an 18V 4Ah Ryobi drill battery and it's done me well, but I would like to extend run-time by dimming it. Given that the light-bar takes a voltage range between 10 and 30 volts, I had assumed that I would not be able to dim it by limiting voltage. I have no idea what the internal driver setup is. I'd hazard a guess that it's a constant-current driver? I've ordered an inline PWM dimmer to try with it but I'm unsure if this will cause it damage. I did email the company though and they responded that they're unsure about PWM dimming but that their lights are designed to work with their own voltage dimmer: https://www.korrlighting.com.au/product/led-light-dimmer-switch/ It seems to be more targeted toward camp strip lighting though?

How would I best proceed with this? Any suggestions?

EDIT:

I realised my warranty period is up so I pulled the cover off to take a look:

Since the driver and LEDS are one unit, I won't be able to replace the existing driver. There doesn't seem to be any information on the manufacturer's page about the light, but I did find some information from a different retailer using that model number: http://swledlight.com/1-1-led-work-light/

Off the bat, almost all the figures are different from the specifications from the company I bought the light from. Turns out it's a 25W light and operates between 9 and 36V. I also noted "PWM thermal management regulation" as a feature, so I'm assuming the light PWM dims if it starts overheating? And I'm guessing inline PWM dimming between the LED/driver unit and the battery is going to cause problems.


texts: What do you call a "de-amplifier" device(is there such a thing)?

texts:
So if an amplifier is an electronic circuit(/device) that boosts the voltage and/or power of an AC electrical signal, what do you call such a device that decrease the voltage without increasing the current or better yet reduces the power of an electrical signal?

What I'm thinking of is essentially an amplifier with a voltage or power gain less than unity(in terms of magnitude).

Such a device might be used at a power substation to reduce both the voltage and current from a HV power source. Or when measuring a very high voltage current or signal(with high wattage) by means of a computer where the signal carries enough power to fry the low-power components. As step-down transformer reduces the voltage but increases the current, so I'm not talking about those.


texts:
I was just watching this video: https://www.youtube.com/watch?v=ti5jD7Q7BSA
At 25:10, he says that if you have an active high SR latch with initial conditions S=R=0, Q=1, and you set S to 1, Q will still remain 1. Can someone explain why this is the case? A NOR gate with input 1 and 0 has output 0, so shouldn't that set Q to 0?


texts: Are Common Mode Choke Coils needed on USB?

texts:
I was looking over the schematic for the GumStix Palo 43 and noticed they used a common mode choke coil on the data lines coming in from USB.
I understand how this design can help remove noise coming in on the USB lines, but I wonder if it is actually something I should start doing on my designs. The datasheet for the FT232R has no mention of adding common mode choke coils, and I have used this chip before with out one.
So, would you recommend I change my USB design or keep it the way it is?


texts: Is this a safe way to create a single OFF switch for multiple loads?

texts: Here is an example of a scenario that describe the question using a car electrical wiring harnest as the complete and complex system unit overall. The tail lights, brake lights and reverse lights are each seperately wired using different fuse ratings individually. To create a "kill switch" that can turn off and disable all three lights simultaneously, i wonder if the following approach would work. First, i would identify and consolidate negative wires of each circuit and terminating it to a common grounding point after connecting a simple SPST switch between the connection. This switch can allow the ground connection to be disconnected off all three circuits and reconnected it back on simultaneously. If the wiring connection are done correctly and soundly, will this method (disconnecting and reconnecting ground connection of multiple circuit from a single point using only a switch) create any potential harm to the components, bettery or the overall system such as the ECU? If it does, i would like to know how and if there is a better way to tackle this.


texts: While working through the question ,I calculated the field copper losses and field armature losses which came to be 1250 watts and 271 watts respectively so total loses should be 1521 watts but they have given it to be 2771 watts.I didn't get why they added the extra 1250 watts that we get from No load condition from the DC motor case.


texts: LM358 Operational amplifier Output voltage rising with stable inputs

texts:
I'm modifying a step-up circuit based on UC3843 SMPS Controller to add a current limiting feedback to it. I'm using a low-side sense resistor (Rsense) amplified by an LM358:

simulate this circuit – Schematic created using CircuitLab

The feedback seems to work but there is a problem with the op amp: its output is slowly rising from the time i turn it on by about 1mV/s making the output current of the step-up module slowly going down.
The LM358 behaves like this even when disconnecting its output. I also tried replacing it to no avail.

Can you help me solve solve this issue?


texts: How to create a zero crossing detector using a full bridge wave rectified circuit

texts:
Currently

1) I have a full bridge wave rectified ac waveform of 10Vmax.

2) I also have a potentiometer adjustable DC waveform.

3) My rail voltages are +12V and -12V.

4) I currently supply my full bridge wave rectified wave in to the non inverting terminal and the DC voltage to the inverting terminal.

5) Using an opamp or a comparator, I want to compare the two signals and produce a square wave which varies from 0 to a positive voltage at the output.

6) At every zero crossing , my square wave should go to zero. In all the other times it must stay positive.

I have created an incomplete schematic below and have also tried many different methods but I am having difficulties in achieving my result.

Thank You

simulate this circuit – Schematic created using CircuitLab

EDIT

New schematic

Removed the Buffer, Positive Feedback resistor, Ac source floating and load resistor added.

simulate this circuit


texts:
In analog servo, how to set the position with hands then check the position in raspberry pi,yes i know potentiometer can do that but i want with servo motor.

Now, i can increase decrease the speed of servo motor.

If some how it change its rotation how i am gone reset

I am using raspberry pi zero w.
Software language: java (pi4j).
My servo motor's name:sm-s4315r(analog servo).


texts:
I have a question regarding PCB design and rubber keypad contacts. I did this circuit for prototyping a piano keybed but some contacts seem to be unstable: when pressed it switches from 0 to 1 continuously - this isn't a classical debounce issue but some kind of electrical instability. I know that it is best to use carbon ink, but it is way too expensive for a prototype.

My question is then: do you think my design of the pad could be the issue, or is this a pull-up resistor issue, or simply some dirt?

Thanks


texts: S-plane poles,zeros to components without table

texts:
Given N poles and zeroes, how do I find out the circuit element values? And how do I know how they are supposed to sit together (circuit wise)?
For an example, let's say I got a 2nd order analog filter.

Zeros = ±i
Poles = -1±i

H(s) = Output(s)/Input(s)

        (s+i)(s-i)
H(s) = -------------
       (s+1+i)(s+1-i)

Output(s)(s+1+i)(s+1-i)=Input(s)(s+i)(s-i)

I'm not sure what to do with that information, I know that capacitors become 1/CS and inductors become LS. But I just don't know how to continue down this path. I've done digital filters, but analog filters is something I also want to conquer.

I've seen some matrix-calculations showing how to systematicly recieve H(s) seeing each and every capacitor/inductor as a tiny system (2 pins input, 2 pins output).

And yes, the filter in this example is a very shitty and impractical one.

All I want is a push in the right direction, and I would gladly love if you continued from my example, or made another one.

EDIT: I'm talking LC filters, I'm so sorry that I fogot to mention that. The hidden goal is to filter out a huge current (1.6 A) with Cauer filter. Yes it's overkill but at the same time I'm learning.


texts: Battery chargers that can recharge disposable batteries. How do they work and are they safe?

texts:
A few years ago a product called SecondWind appeared, which claimed that it could recharge disposable batteries. To a layman like me that sounded like a great idea, but does such a product really work, and is it actually safe to use?

The labels on the batteries promise nothing but certain death if you try to recharge them, and a charger for disposable batteries seemed like something that might be potentially hazardous.


texts: How to read a multimeter (digital) -- should I get 2A readings from a couple of AA batteries?

texts:
I have been using some old multimeters in a high school science lab. We did a current an voltage reading from a AA supply (two batteries) with a variety of resistors. In some cases a 1M resistor.

I noted that the only way to get current readings was to set it on the 10A circuit. OK, I thought, maybe the batteries put out that much current in toto.

But I saw this happen even when the 1M resistors were hooked up -- we would get readings of 2.7 V or so which makes sense (old batteries and all) and then when we measured current we would have to put it on the 10A and get readings like 2.0 A or 1.8. Ultimately, the digits made some sense in terms of Ohm's law, it was just the powers of 10 seemed off. So I wasn't sure if I was just reading the thing incorrectly. (Like, was it actually showing milliamps?)

To give one example: I put a resistor in line with a 3V supply. It's 46.4 Ohms. (The multimeter is an Extech instruments, found in a drawer). I touch the probes to the resistor and get 2.60 V, which seems reasonable enough. I connect the red probe to the 10A input and check current and I get ~1.9 A. But V = IR says that it should be

(2.6V) = I (46.4) --> I = 2.6 / 46.4 ~ 0.05A

We have gotten similar results with other meters, though my "good" one (a new Mestek DM91A) reads 0.04A when it's hooked up to the mA side (if I try to set it to mA range the alarm goes off, with the message "FUSE") and about 1.8 A on the 10A side.

In at least one multimeter I replaced the battery. I tried similar readings with a 965,000 Ohm resistor. I got 0.03-0.04 A with the newer Mestek, and 1.8 A with the Extech, which wouldn't read it when i used the milliamp connection.

I suspect there is some stupid mistake I am making in reading the things, and yes I checked that the positive was to positive and negative to negative. (I grew up with analog meters, and you could just read the scale :-) )

Anyhow I hope people about can help me figure this out.

Thanks in advance.


texts:
Wikipedia states

  Torque motors are normally induction motors of toroidal construction.
  Their main differences from other similar motors are their wide
  diameters, to allow for high levels of torque, and their thermal
  performance, to allow their continuous operation while drawing high
  current in a stalled state

But I have seen DC torque motors around. Does that mean torque motors are really AC asynchronous machines with short circuited rotor windings or squirrel cages as a rotor, only designed for operation when stalled and driven using an inverter, or are they really something else?


texts: Find the voltage drop across each resistor in the circuit

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I have this question to do.

  The current through LED is \$7.5\ \rm mA\$. Find voltage drop across each resistor in the circuit and value of \$R_3\$.
  Verify KVL in the circuit

I have personally solved the question. Here is my solution:

I have current and current is always same in series circuit. I used that current value to find to find voltage drop across each resistor. When I found that I used Kirchhoff's law $$V_s = V_{R_1} + V_{R_2} + V_{R_3} + V_d$$ to find \$V_{R_3}\$ and then using that I found \$R_3\$.

$$\begin{align}
V_{R_1}&=8.25\ \rm V\\
V_{R_2}&=3.375\ \rm V\\
V_d&=2.1\ \rm V\\
V_s&=V_{R_1}+V_{R_2}+V_d+V_{R_3}\\
&20-8.25-3.375-2.1=V_{R_3}\\
V_{R_3}&=6.275\ \rm V\\
V_{R_3}&=IR_3\\
&\frac{6.275}{7.5\times10^{-3}}=R_3\\
R_3&=836.67\ \rm\Omega
\end{align}$$

Is my solution correct?


texts: Why don't hall effect current sensors exist for low currents?

texts: There do not seem to be hall effect current senors available for small currents, say on the order of 500mA. I'm guessing this is due to some technical or physical limitation. What is it?


texts:
I have a power distribution board for my Quadcopter. It is powered by a 3s Lipo and the following are connected:

12 Volt outlet for ESCs: 4 ESCs 12 Amp
5V Outlet: Connected my 5V Gyroscope and Arduino Nano
12 V outlet: Connected a receiver using 3.3 V regulator.

I don't have any additional outlets.

Question is, how do I add more devices by pulling voltage from existing outlets by connecting in parallel, as the Volts will be the same. I understand Amps will get divided.

Is it ok, to add more devices in parallel to let us say my 12V outlet, where I connect couple of more 3.3 V regulators to run 3.3 V devices and couple of 5V regulators to run 5V devices.

Based on the specification of LIPO and power dist module below, is there a way I can determine the max devices I can connect to both 5V and 12V outlets on my power distribution module?

here is the spec of my power distribution module:
General:

Input voltage range (3S-4S LiPo operation): 9 - 18V DC
Regulated 5V and 12V outputs
6 ESC outputs & 1 pair VCC/GND pads

ESC outputs:

Continuous current: 25A*4 or 15A*6
Peak current (10 seconds/minute): 30A*4 or 20A*6

BEC 5V output:

Designed for RC Receivers, Flight controllers, OSD, and Servos.
DC/DC synchronous buck regulator.
Voltage: 5.0 +/- 0.1VDC
Continuous current: 2 Amps (Max.2.5A 10s/minute)
Output Ripple: 40mV (VIn=16V, VOut=5V@2A load)
Short-circuit tolerant (5 seconds/minute)

BEC 12V output:

Designed for Video TX or FPV camera with linear regulator.
The battery should be 4S LiPo (13~18V DC)
Voltage: 12.0 +/- 0.3VDC
Continuous current: 500mA (Max.0.8A 5s/minute)
Short-circuit tolerant (2 seconds/minute)

BEC 12V @ 3S LiPo

Output voltage= 3S LiPo voltage -1V


texts: How does a forward biased diode conduct electricity?

texts:
I am having a hard time imagining the flow of current through the p-n junction.
When a diode is forward biased, the holes on one side of the barrier and electrons from the other side try to cross the barrier. But as soon as they do, shouldn't the electrons fall into holes and fill them, making a neutral entity just like the barrier in the first place? How does the current flow then? How do the holes and electrons cross over without fusing into each other?


texts: Help! Why don't my connections show up on my pcb gerber files? But they show up on the Eagle layout?

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Below is a screenshot of my Eagle pcb layout. and below that is a screenshot of my gerber file extracted from pcbway.com
As you can see none of the connections show up but they do show up if I take off the red polygon layer. But I need that layer for gnd.
Is there a way to fix this?
Am I exporting my gerber files wrong?


texts: PR-ASK architecture and S2LP Transceiver IC

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I am trying to understand if there is any way by which I can achieve PR-ASK modulation in the Transceiver IC S2LP from STMicroelectronics.
The Transceiver IC supports ASK and OOK modulation. In ASK modulation one can control the ramping up and down of the RF envelope. This will give me DSB-ASK modulation easily. But I am also looking for SSB-ASK and PR-ASK modulations in order to meet GS1 standards for RFID applications.
Any suggestions on how to go about this? Is there any way by which PR-ASK can be achieved in this transceiver IC?


texts: Does creep always occur with load cells, or is there an optimum weight capacity?

texts:
I want to make a scale which I will place under a wood stove (downdraft gasifier) to measure the amount of wood that goes into the wood stove. The amount of wood which is being measured will be displayed using a raspberry pi on a local page. After some research I was about to order four S-type load cells. The problem which I encountered was the permanent load placed on top of the load cells, which will result in 'creep' ([explanation of creep])1. Most important quote from the link:
"The change in load cell output occurring with time while under constant load ( >90% of the load cell capacity ) and with all environmental conditions and other variables remaining constant."
The load cells are designed to measure weight for a short period of time. The load cells under the wood stove will be loaded with permanent weight. Does anyone know which load cells I could use to put permanently under the wood stove without loosing accuracy after long periods of time? Some technical information:
Wood stove itself weighs around 700 kg.
The capacity of wood in the stove is between 20 kg and 50 kg.
The desired accuracy is 0.5 ~ 1.0 kg. (0.1%, better accuracy would be great.)
The load cells won’t be (extremely) heated. The temperature will vary between 10 and 35°C, but that won’t be a problem I assume.
It is a little project on which I intent to spend a maximum amount of 200 euro’s on. Because it is quite some weight it would be the most steady if I use 4 load cells (each corner one load cell). All ideas are very welcome, even if the accuracy and/ or price won’t meet the desired conditions.


texts: How to remove excess top silk in Proteus?

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I have some markings on my plate made in silk and I believe they can hinder the welding, since a line is passing inside my pads, I know that when a silk line passes over the track there are no problems, but if a line passes over a pad and its welding mask? Wouldn't that be problematic?

Below are some attachments and markings where problems occur;