texts:
I have been designing PIC based systems for several years, but this will be the first time that I am involved in a project based on USB communication. I don't exactly  know where to start but I have been searching around the internet for a few days for "PIC USB tutorials". Unfortunately I could not see any information for my situation.

I need to design a system which will have "only one USB port" to connect to PC (in order to pass some logging information to PC) and also a "USB flash memory" to save some data. Of course, these connections can not be created at the same time since there is only one slot. But my system should sense which is connected and behave in a proper way. Is it possible to create a system like this? What kind of electrical designations should I consider? And some guidance links for a starter will be appreciated.


texts: should I use 1 3cell bms board or 3 one cell bms boards with an 18560 battery

texts:
I have two 18560s in parallel for roughly 7A/h as a 'pack' and three packs in series with a 3 cell bms board

or

I could have a 1 cell bms board for all 6 18650s wiring the outputs from the board in the same configuration above.

I think I have mostly seen the first option and I am aware the batteries in parallel needs to be the same voltage to avoid backflow
With the second option there would be a bms between the connected batteries, would that provide any safety with backflow?


texts: Debugging a SA 90.4 800W class-D audio amplifier

texts:
I am using a Re-audio SA 90.4 800W 4-channel class D audio amplifier (https://www.amazon.com/REAudio-SA90-4-4-Channel-Digital-Amplifier/dp/B00RE9EO7K) for some underwater piezoacoustics experiment. The setup is as follows:

The piezo cylinder is mounted in a watertight shell with +ve and -ve cables connected to one of the amplifier output channels. Impedance varies from 50-500 ohm (depending on frequency as checked with a impedance analyzer)
The amp is powered by a labbench 80W powersupply (yes I know it's not enough but I ensured the gain was limited using gain controls of the amplifier)
The amp is fed by a 96 KHz DAC via RCA cable (left and right cable). It has two sets of RCA ports.

During the experiment, after ~10 minutes, one of the RCA ports gave out. I suspect it's the RCA port because when I connected the inputs to the other RCA port, the setup started working as normal, until that port gave out after 10 minutes. Now the amplifier turns on but there is no output. The piezo cylinder is fine (tested with another smaller pre-amp and impedance analyzer). Note that the amp is rated for 4-8 ohms at the output but no rating is specified for the input RCA channels.
I would appreciate if someone could help me narrow down the problem. I opened the amp and did not seem to find any damaged component inside.


texts: Arduino building a pulse proportional thermostat

texts: I'm not much of an engineer, but I have worked with arduino.  I'm looking to see if it's possible to build a pulse proportional thermostat with a probe and an arduino.  Any recommendations on where to begin would be appreciated.  Note: I couldn't find an arduino shield for something like this, so I thought asking here would be a good start.


texts: Put component designators on the PCB's silkscreen in KiCad

texts:
I'm doing my firs PCB design, and I've choose to use KiCad.

The problem that I'm encountering is that when I look at my board in 3D view, the components' designators does not appear to be on the silkscreen by default (or maybe the 3D view doesn't display them ?)

Is there an easy way to add components designator on silkscreen without adding them manually one by one ?

Here is my PCB layout:

And here it is in the 3D view:

PS: The "Input" designator is added manually by me.


texts: Component Symbol identification; 2-pin rectangle with an N

texts:
I couldn't find anything on the web for it.

On first thought it might be an ESD protection diode because in the schematic, t appears near USB and stuff that might be sensitive.

, here in context :

Thanks in advance


texts: SPI readings always high (1) when connected via bi-directional level shifter

texts:
I am trying to read two gas sensors (MQ4 for methane and MQ7 for carbon monoxide) with my NodeMCU ESP8266. Both sensors require 5v (for the heaters) and have 4 pins (GND, VCC, DO, AO). Digital outputs are HIGH when a threshold is exceeded (adjustable on the breakout board).
In order to read analog outputs, I am using MCP3008 10 bit ADC, which works with higher accuracy at 5V. ESP8266 is however 3.3V.

I am using 8-channel bi-directional level shifter to communicate with MCP3008.
MCP3008 and sensors are connected to Vin and GND on NodeMCU ESP8266 board, which provides 5V.

Level shifter is also connected to 5V on HV side and 3.3V on LV side.
Level shifter works fine for digital outputs of sensors.
But when it comes to SPI between MCP3008 and NodeMCU ESP8266, I always read high values (1023).
When I get rid of the level shifter and power MCP3008 with 3.3V with a potentiometer, I can read values between 0-1023.
Also the sensors output analog values between 0-5V (tested with lighter gas and multimeter). So there must be a problem between level shifter and SPI communication.

On the software side, I tried to do the communication manually, with SPI.h and
Adafruit_MCP3008.h libraries.
They work fine, when I remove level shifter and operate MCP3008 with 3.3V.

I was wondering, what the problem might be? I don't have an oscillator and it is my first "real" electronics project. Excuse my lack of jargon...
Thanks!

EDIT: I use this level shifter: https://www.amazon.de/gp/product/B01FRQUQCS/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1


texts:
I have a project about MSP430, data acquisition then sending through UART to another unit.
I have written and compiled all the codes for ADC and UART in IAR Embedded Workbench. The simulation works fine on Proteus ISIS.
Here is my question:
How can I load these codes into MSP430 to run independently from PC. I mean, two designed boards will be used to communicate with each other.

PS: I have a CP2102 USB-Uart Bridge breakout board. Is it possible to load the codes into MSP430 with this interface? Or should I absolutely use JTAG interface?

Thanks in advance.


texts:
Suppose this is the biasing process of an NPN transistor.

simulate this circuit – Schematic created using CircuitLab

The battery to the left forward biases the emitter diode because its +Ve terminal is connected to the the P-type base and -Ve terminal to the n-type emitter.

But how does the right battery reverse bias the collector diode?

I get the +Ve side of this battery is connected to n-type collector, but its -Ve side is also connected to the N-type emitter.


texts:
To learn verilog, can anyone recommend any web-page or book?

I have never seen such type of a language before, so what you recommend should be for beginner.


texts:
I am trying to configure two XBEE S1 both of them using the 10EC firmware.

I tried to set this settings on the first one and the second one :

ATVR        ATVR
10EC        10EC

ATID        ATID
2001        2001

ATMY        ATMY
1253        1254

ATDH        ATDH
13A200      13A200

ATDL        ATDL
1254        1253

ATA2        ATA2
6           0

ATCE        ATCE
0           1

But I still don't have any connections ?


texts: I have a 5 bit decrementer. Using control i/p R, use the decrementer and 2-i/p XOR gates to obtain incrementer when R=0 and a decrementer when R = 1

texts:
The progress I made is that I used a XOR gate with the complement of R, to be fed as input to each of the first 4 inputs of the decrementer. It doesn't seem to work for all input combinations.
 I would appreciate some suggestions on modification, as this doesn't lead to correct outputs.

I tried to find out the logical expressions of the incrementer and decrementer individually to link them together using the control input R. Please have a look at the attached figure.

Kindly refer to the attached figure. The expressions that the output needs to assume in each case (R=0 and R=1) have been derived already by me. I can't find a way to link them together.


texts:
I've got a 3296 trimpot like this one:

http://pdf1.alldatasheet.com/datasheet-pdf/view/78495/BOURNS/3296.html

I don't know whether clockwise or counter-clockwise increases or decreases the resistance?

Is there anyway I can test?

BTW, it is already soldered to a component.


texts:
Here's a good question for the professional electronic engineers of Chiphacker: What is noise temperature, and how is it used in designing receiving systems as a whole? (I've seen it specified for the Arecibo telescope antenna, for example.)

I've seen this specification used mostly in the UHF and higher bands, but I really don't understand how it's used.


texts: Can we connect both ASIC and an FPGA both to the same physical output Ethernet ports at the same time?

texts:
I am doing simulation of my research design on single FPGA, in which I simulated two switching chips ASIC and an FPGA. I mean, I simulated single FPGA working as two chips, and connected them so that they could transfer traffic to the other side. I also connected their logical ports to an "Arbiter" which will forward the traffic to the physical output Ethernet ports on "First in First out" basis. As i simulate all this on single FPGA, so I have logic to implement the Arbiter, which is the important stage of this design. And in simulation all is going fine.Below is the simulated experiment. I want to do it in real ASIC and FPGA now.

I just want to know that is it possible in real ASIC and FPGA to connect them both to the same physical output ports? If yes, then where can we implement the output queue which will buffer the packets coming from both ASIC and FPGA (after processing) and release in FIFO order towards output eth ports. Because here we  do not have the "Arbiter" to forward the traffic coming from both the switching chips on some basis e.g. FIFO.

Two ways I thought about is, 1) Port Buffered Memory and 2) Shared Memory (SRAM, DRAM) could be the solution. Or any other better idea you can give. Thanks


texts: Variation of generator working frequency with load

texts: I am confused with problem no 68. I have added my attempt. I am getting optionA but the book says it should be optionB. Please guide me where I am doing mistake.


texts: Can I drive and reverse this motor with an ESC?

texts:
I've just ordered this motor, which I want to drive and reverse using my Raspberry Pi.

I've successfully used an H-bridge to drive and reverse a brushed DC motor before, but for this motor I think I will need an ESC. So I ordered this ESC.

I now wonder; did I do the right thing? Can I drive that motor with that ESC? And can I also reverse that motor with that ESC?

All tips are welcome!


texts: Question about how the circuit of TV display works

texts: I have a question about how the circuit of TV display works. Does current flow through the gate lines (horizontal lines)?


texts:
I would like to use the LTC3588-1 component native to LTSpice in SIMetrix, however I am struggling to find a way to handle the export/import.

Is it possible to export a component from LTSpice in a format that can be interpreted by SIMetrix, or other simulation software (i.e. a .MOD file)?


texts:
Why does my power op amp IC (TI OPA549) thermally malfunction? IC works electrically perfectly, no oscillations or anything. By thermal malfunction I mean that Rj-c thermal impedance rises from default value (1.4°C/W) to about 6...7°C/W.

What kind of mechanism can cause such malfunction?

PCB has three identical channels (A, B, C) where two of them work flawlessly (B, C) but one (A) constantly malfunctions after short time of use (I have tried three chips).

Below you can see IC and its three important spots center (red), edge (green) and case (blue). With maximium stress ( ~ 40W), channels heat up as follows (measured with thermal camera):

Working ones:
70°C (red), 55°C (green), 40°C (blue)
Malfunctioning:
+100°C* (red), 59°C (green), 40°C (blue)
*throttling, junction temperature reaches 150°C limit and stops.

Thing I have considered:

soldering: I have always screwed the case to the heatsink and after that carefully soldered the pins.
mechanical stress: Heatsink is heavy, but firmly attached to PCB.
case temperature is always same (40°C), so I can assume that the heatsink is working alright.
B and C channels are working flawlessly as I have designed.

Update: 29 June 2017

As Chupacabras brought up, I have noticed that problem has something to do with the Vcc line.

I previously had a common heatsink for all channels, but then I installed individual heatsinks for each chip. This had unexpected results:

C channel works flawlessly
B channel malfunctions as badly as before
A channel is something in between.

I also figured out that when I was using linear lab supply, no malfunctions occurred. By default I have been using switching (65kHz) PSUs connected in series, where middle tap is ground.

However, I'm unable to measure any kind of differences in Vcc pins.


texts:
I'm trying to determine whether the absolute maximum rating for Vin on load switch ICs applies for when the switch is both open and closed.

When the switch is closed, it makes absolute sense to me that you should not try to have Vin above this rating. But what about when Vin is open? Isn't the voltage just floating then? Could I theoretically have the voltage above the datasheet's absolute maximum for Vin?

I'm trying to understand whether why or why this isn't possible in a load switch IC. Thanks in advance.


texts: How to compute the sensitivity of this control system?

texts:
I am learning control systems on my own and am having some trouble understanding how Richard C. Dorf and Robert H. Bishop found \$S^{T}_{G}\$ in Modern Control Systems (12th edition):

The problem:

The corresponding answer:

Where does, the very first equation, $$\frac{1}{1+GH(s)}$$ come from? No matter what I try I never find this equation. Could someone please explain and show how he got this equation? It doesn't seem to be the equation of the entire system because - according to what I tried - this equation should be $$T=\frac{RG_CG}{1+HG_CG}$$

I know how he found \$S^G_\tau\$:

$$S^G_\tau = \frac{\tau}{G} \frac{\partial G}{\partial \tau}$$

$$\frac{\tau}{\frac{100}{\tau s+1}} \frac{\partial}{\partial{\tau}}(\frac{100}{\tau s+1})$$

$$S^G_\tau = \frac{-\tau s}{s\tau +1}$$


texts: Why is voltage higher at positive wire instead of negative wire in this example?

texts: If electrons travel from "-" to "+" and voltage decrease going through resistor why is voltage higher at positive wire instead of negative wire?


texts: Can the machine readable files for integrated circuits be verified by the manufacturer design team?

texts: My question is simple if you take the chip design files (blue print files for the fabrication process) which are used by the fabrication process that the design engineer(s) have completed the files which contain GDSII machine readable commands can these files be verified by the design group(s) to be authentic and exactly and identical to one being used by the fabrication or manufacturing facilities ? Is there some computer generated test and verification application that the engineers who designed the blue prints for the fab facilities can use to verify that the machine readable files have not been tampered with or altered at and by the factories ?


texts: Calculating power dissipated at a resistor with Thevenins and Nortons should they give the same answer?

texts:
I have drawn up both Nortons and Thevenins equivalent circuit. Next I am tasked with calculating the power dissipated at a resistor.

I have had a disagreement with a fellow classmate about the answer. I believe that the power dissipated should be the same for both Nortons and Thevenins, he believes that they will be different.

Who is correct?


texts: assembling PCB, Cx is shown within IC outline - does this mean Cx goes on other side?

texts:
Embarrassing question. I am assembling a PCB. Please see attached picture. C9 is within the boundry of IC3. Does this mean that C9 is installed on the other side of the board?

C9 = 100n X7R


texts: How can I transform 12 Volt DC to 17 Volt AC?

texts:
I am new to electronics and me and my friend want to build a big speaker out of some old small ones.

We are going to use a subwoofer from PC speakers as main speaker, but there is a problem. We are going to use a car battery to power this thing, that gives 12V DC. The subwoofer, however, uses 17V AC.

Is there a way to use the power from the car battery to power this subwoofer?

Like transformating the power? Or will it harm the subwoofer?


texts: snubber circuit or opto isolator with relay

texts:
I have a relay module link with a built in opto-isolator circuit.
When there is no load connected to the relays, the relays switch as expected. But when an inductive load (240V 0.5 HP) motor is driven. It causes the Arduino to reset every time the relay is switched.
Please suggest ways to rectify the issue.
I have gone through some of the articles and it suggests to have a snubber circuit at the relays. Would a snubber help in this circuit where the optoisolator is already present. If yes, please suggest the connections as well.
Thanks


texts: Is the ATMEGA328P's serial baud rate quantised?

texts:
I'm using an ATMEGA328p, running from its internal oscillator (divided by 8 = 1MHz).

I've (roughly) measured the oscillator output, using my Salae logic analyser, as ranging from 960KHz to 1000KHz, so it's not awful.  I did this using the "Clock output on PORTB0" fuse.

If I set the baud rate to 9,600, it outputs serial at 10,220 baud.  (Is this because I'm not using a crystal, or because of quantisation?)

If I either increase F_CPU or decrease USART_BAUDRATE, gradually, the output serial baud does not decrease, until it jumps to 8,800 baud.

#define USART_BAUDRATE 9600
#define BAUD_PRESCALE (((F_CPU / (USART_BAUDRATE * 16UL))) - 1)

int main(void) {
        // serial port setup
        UCSR0B |= (1 << RXEN0) | (1 << TXEN0);
        UCSR0C |= (1 << UCSZ00) | (1 << UCSZ01);
        UBRR0H = (BAUD_PRESCALE >> 8);
        UBRR0L = BAUD_PRESCALE;
        ...

Is there some form of quantisation affecting the output baud?

P.S. I'm using GCC on Linux to compile code, and I'm not using Arduino code/IDE.


texts: Do I need to add a current limiter to this battery pack I'm making?

texts:
I have a motor that came with a 9 volt, 1.0 amp AC to DC wall converter to power it and the text next to the power connector on the motor seems to indicate 9 volts @ 1 amp is the preferred input. I wanted to make a battery pack for it so I have 6 1.5v 'D' alkaline batteries in series with a barrel jack to connect to the motor.

As is, the battery pack runs straight to the barrel jack. Should there be a current limiting component on my battery pack such as a resistor or capacitor?


texts: How to isolate two signals from each other if they use the same power source?

texts:
See the very simplified schematic down.
As what you can see: Two inputs are in the form of a DC signal. We operate each input individually. RL represents a motor. The two inputs are initialized by a micro controller. The transistor used is an NPN type (BJT) (or General Purpose one).

The problem is this: When we input one signal, the two motor spin while there should be only one of them spins.They affect each other. We do not want that.

Suggestions made by ourselves:

Note that the signal is amplified by an op amp for each input's path. We used diodes for each input's path but it did not work.
We tried to buffer the the power source rail but it did not work.
We tried to create two separated power sources for each input (but with a one common ground and one micro controller) and it did not work.
We put also diodes with each motor and it did not.

So, how can we isolate these two signals? Note that we are beginners with this.

simulate this circuit – Schematic created using CircuitLab

The physical circuit is this (I am pretty sure it looks messy)


texts:
I would like to get an advice on handling tasks in a firmware.

I have 3 major tasks to do:

Scanning for whether a switch is being pressed or not.
Data transmission via SPI - To EEPROM
Data Transmission via USB - To PC

I have managed to do a timer interrupt each 1 ms to see if whether the switch has been pressed or not. But the SPI transmission occurs  every 6 hours only [takes 50ms to complete] and the USB transmission can occur anytime.

My question is how do I manage the tasks?

  Should I disable the switch check once it enters state2/state3 and enable it after it exits the states?

How am I supposed to handle such situations?


texts:
part of my design, the primary power supply to a chip is converted 3.3V from the main power supply. I also have a backup battery if the main power failed. a relay is being used to switched between them. however, there is a noticeable voltage drop (to~2V for less than 1s). Is there any solution for this problem?
Can I have a maybe 1F capacitor at the output?

Thanks!!


texts: Confused about the shape of 3D s-domain plots

texts:
Why in these type of 3D plots does the gain value (z axis) come back down from infinity for sigma values that are greater than the sigma value of a pole?

I thought that these plots are the value of the a systems impulse response multiplied by a probing waveform (exponentially decaying or growing sine wave for all values of sigma and jw)

A pole is when the probing waveform is one that grows at exactly the same rate as the the impulse response is decaying. And the multiple of the 2 waveforms produces a waveform that is has an infinite area.

Pole

If the sigma value is then increased the area of the resulting waveform will be greater than infinity (undefined, in a region of non convergence). So why does the value go back down to finite values in this graph?

Sigma greater than pole


texts: Self resonant frequency of inductor in VCO

texts: I am designing nmos only LC VCO in cadence TSMC180. I have chosen the self-resonant frequency of the inductor to be twice the working frequency of the LC tank. Is it a proper design for LC tank? Or do I have to increase the SRF?


texts:
currently I'm working on 4S(2P) BMS mainly focused on TI's ICs.
I'm stuck at the start - First, for now I want to use BQ2954 IC for charger, and BQ77915 IC for balancing and protection.
Now, I'm not sure for to connect these two IC's so they work "as one".
Basiclly I don't understand what charger IC for 4S battery pack does when it doesn't balance cells at first place? Is then cell balancing necessary at all? Why there's no IC that does both jobs?
Also, in my case if you look at bBQ2954's datasheet(Figure 3), can I somehow use less components or swap BJTs with MOSFEts to get same result? D4, Q1, R2, D1, Q2 and L1 are used for?
For power supply I'll use 18V 3.5A old laptop "charger"(adapter).
If someone can anwser questions above and/or provide steps, I would be thankful.


texts: Why do single transistor oscillators work to power a transformer, if a transformer needs AC?

texts:
I have been making some high voltage projects lately, such as a spark gap Tesla coil, slayer exciter, and a flyback transformer HV supply.
The flyback transformer uses a single transistor circuit, just like the slayer exciter circuit.
I know that solid state Tesla coils use a pair of transistors in order to create an AC signal to power the primary.
How can only 1 transistor create an AC signal to power the primary of a slayer exciter or flyback transformer?


texts:
I have this projector which takes in 19v and has a power consumption of 65 watts.
I want to buy a 12v 6A car inveter, that plugs in the cigarette lighter, which would give me 72 watts.
The question is if it will drain the car battery if the engine is running or if there is any risk of frying anything up.


texts: Does LVDS always need 100 ohm differential impedance?

texts:
LVDS pairs need 100 ohms differential impedance. However, I am having trouble achieving that in my design.

My design requires that the pairs travel over very thin flexible PCB, about 50mm total transmission length. The substrate is 50um, with a 50um coverlay. Using Saturn's PCB Toolkit, it seems to be extremely difficult to achieve 100R impedance without making the tracks too thin to manufacture, or the S/H ratio going out of spec.

However, I can achieve 80R impedance without too much difficulty.

My question is: Can I just use 80R tracks, and terminate them with a 80R resistor?

As far as I understand it, as long a every part of my transmission line has the same impedance, I shouldn't get any reflections. The only down side will be a reduced voltage at the receiver, but since I should have very few other losses in the system, that should still be plenty of voltage swing for the receiver.


texts: To make input-output pin of sensor high from mcu is it better to give logic high from mcu or making the mcu-pin input with pull-up?

texts:
I drive sht11 temperature-humidity sensor from mcu, the reference design from MikroElektronika uses the following:
To make sda pin high, the pin connected to sda (which is pull-up) is not given to logic 1 instead, it is made input to make sda high.

I used this and it worked, I ask is it better and why?

/***************************************************************
* Generates a transmission start
*       _____         ________
* DATA:      |_______|
*           ___     ___
* SCK : ___|   |___|   |______
***************************************************************/
void Transmission_Start() {
  SDA_Direction = 1;                     // define SDA as input
  SCL = 1;                               // SCL high
  Delay_1us();                           // 1us delay
  SDA_Direction = 0;                     // define SDA as output
  SDA = 0;                               // SDA low
  Delay_1us();                           // 1us delay
  SCL = 0;                               // SCL low
  Delay_1us();                           // 1us delay
  SCL = 1;                               // SCL high
  Delay_1us();                           // 1us delay
  SDA_Direction = 1;                     // define SDA as input
  Delay_1us();                           // 1us delay
  SCL = 0;                               // SCL low
}


texts:
I'm interested in the following IR sensor breakout board with the QRE1113: https://www.sparkfun.com/products/9454

However, I would like to control the LED (on/off, PWM if possible). Should I disregard the breakout and see if I can get the QRE1113 seperately (hopefully nearby), or could I wire the LED to a pin on the Arduino (Nano)?


texts: Configure avrdude for programming with a ft232r cable

texts:
I bought a ftdi cable with the following pins.

Vcc
GND
RX
TX
RTS
CTS

It's possible to use this device to upload code to an ATmega328p using the avrdude utility?

When I run this line on linux terminal:

sudo avrdude -c ft232r -p ATMEGA328P -P "/dev/ttyUSB0" -b 57600 -U flash:w:led.hex

I get this output:

avrdude: invalid portname '/dev/ttyUSB0': use 'ft[0-9]+'

I know that some ft232r boards can be used for this purpose, but all of them that I've seen until now rely on the DTR pin, which I don't have access.


texts: Is there a correct resistance value for I2C pull-up resistors?

texts:
The datasheet of the 24LC256 EEPROM states that:

  The SDA bus requires a pull-up resistor to VCC (typical 10 kΩ for 100 kHz, 2 kΩ for 400 kHz and 1 MHz).

I thought that any resistor with a kΩ value would do the job (and it seems that my EEPROM works fine at different frequencies with a 10 kΩ resistor).

My questions are:

is there a correct value for pull-up resistors ?
is there a law/rule to determine this value ?
how do different resistance values affect the I²C data bus ?


texts: When predicting the junction temperature (Tj) of semiconductor chips (for example IGBTs) by available thermal models such as FEM simulations, how much is the maximum permissible Tj estimation error with reference to the measurements for thermal design processes and reliability applications?


texts: Can you identify this diode? (vintage audio amplifier)

texts:
I am restoring a Japanese Teisco mixing amplifier from the 1970s. It's a solid state 5-channel mixer with 16ohm speaker outs and a line out.
Amongst other problems, I have discovered a couple of the bridge rectifier diodes have shorted out.
Here is a photo of the diode bridge:

Now i am trying to find a suitable replacement for these diodes as they have no markings.
I cannot find any circuit diagrams or info on the unit at all.
The diodes and the PCB both have no markings.
If we can't identify this component ~ Is there a common equivalent used for typical solid state amps from this time? Surely.
The filter capacitor is 2200uf 63V.
Would a 1N4007 do the job?
Thank you in advance, Looking forward to a reply.


texts: Is it safe to use a 19V DC adapter for a 12V input if it can provide enough watts?

texts:
I have a small TV which expects 12V DC at 34W. Can I use an adapter with a higher voltage rating (19V for example) as long as it can provide enough amps to satisfy the amount of watts needed by the TV?

If the adapter says 19V, does that mean that it can provide "up to" 19V safely or will it always provide 19V and damage the TV?


texts: Upgrading Bluetooth earbuds case battery

texts:
Recently I got Chinese true wireless earbuds called Redmi AirDots. It has 3.7V 300mAh Li-Po battery in it's charging/carrier box that I want to replace with the one with higher capacity. I opened the box to get to the board so that I can identify the battery controller chip to check compatibility. The problem is that, it's a Chinese product so the chips has no datasheet or any info available online. There are three chips on the board & one of them must be battery controller but I can not identify which one is it. There are some numbers printed on all these chips that I have mentioned in attached image.
So I need confirm these two points

Can I replace battery with higher capacity one without worrying about the compatibility of the battery controller on the board?
If I must use battery compatible with my board, then how can I get information of that chip?

Thank you.


texts: Can I use one LM386 amplifier to drive 2 speakers(no stereo needed)?

texts: Can I connect 2 speakers to the same output of the LM386 audio amplifier?


texts:
https://electronicsprojectshub.com/how-to-make-an-automatic-night-light-using-ldr/

Can someone explain this project to me? Can you explain the schematic so I understand how it works? A very very simple explanation please. I will be starting my electronics degree soon and I just wanted to get ahead so assume I know nothing except the real bare basics.

Circuit:


texts: Is a current transformer appropriate for a voltage step up flyback converter?

texts:
I am designing a flyback converter, input 170V output 1200V at 2mA.

I am having trouble finding an appropriate transformer, most do not have a high enough N. Current transformers seem to have ranges in 1:500, so I could work with that.

Is it proper to use a current transformer as a conventional step up voltage transformer?


texts:
I have this circuit. I did the truth table but I wasn't able to understand what operations this circuit do on pair of 2-bit binary inputs (A1, A0) and (B1, B0).
I thought it was mod or div but it's not


texts: ATmega - Why is the prescaler factory defaulted to 8?

texts:
Why do ATmega (e.g. 328P or 644P) have CKDIV8 (or CLKPS = 0011) factory programmed along with a default internal 8 MHz oscillator?

From the 644P documentation: 6.12.2 CLKPR - Clock Prescale Register, Page 40:

  The CKDIV8 Fuse determines the initial value of the CLKPS bits. If CKDIV8 is unprogrammed, the CLKPS bits will be reset to “0000”. If CKDIV8 is programmed, CLKPS bits are reset to “0011”, giving a division factor of 8 at start up. This feature should be used if the selected clock source has a higher frequency than the maximum frequency of the device at the present operating conditions. [...] The Application software must ensure that a sufficient division factor is chosen if the selected clock source has a higher frequency than the maximum frequency of the device at the present operating conditions. The device is shipped with the CKDIV8 Fuse programmed.

Is it just a precaution to ensure the CPU clock does not exceed say a 16 MHz limit when configuring the MCU to run with an external oscillator of too high frequency (and forgetting to change CLKPS accordingly). Or are there other reasons?


texts: Is Compare Pulse sooner than OC1REF in STM32 Advanced Timer output trigger

texts:
The options for trigger output signals seem not very well documented. According to the datasheet (P509, here) they include:

Compare Pulse - The trigger output send a positive pulse when the CC1IF flag is to be set (even if it was already high), as soon as a capture or a compare match occurred.

OC1REF signal is used as trigger output (TRGO)
OC2REF signal is used as trigger output (TRGO)
OC3REF signal is used as trigger output (TRGO)
OC4REF signal is used as trigger output (TRGO)

I'm interested in the difference between Compare Pulse and OC1REF.
I understand that either of these should cause a trigger when a capture occurs on CC channel 1, so what is the difference between the two.

The wording suggests that Compare Pulse might occur sooner in time than OC1REF, I would be grateful if someone can confirm whether this is the case or not, thanks.

In the StdPeriph lib, the function is TIM_SelectOutputTrigger and the options in question are TIM_TRGOSource_OC1 vs. TIM_TRGOSource_OC1Ref.


texts:
I am working on a project in which we have an an i.MX53 to driving an LCD through the LVDS connector and we fail the required EMC criteria. There are multiple peaks at 40 MHz intervals (starting at around 500 MHz) which I believe corresponds with the LVDS clock rate of the MX53:

The yellow is with the standard cable and the blue/cyan is the measurements with a twisted pair LVDS cable.
I know we are in the red with that broadband noise between 200-300 MHz but I'm fairly confident we will have it fixed with the new expansion board that's in the works. Also I'm pretty sure it's the LVDS cable causing the trouble because those spikes go away when I unplug the cable.

My question is: how can I reduce the harmonics from the LVDS cable? I've tried ferrites (although I got no specs for the ferrites so it was a toss up) and twisting the pairs with very little effect.

Also is it possible that the i.MX53 sends out way too strong signals? Based on the schematics, they didn't overdo filtering.

I would be happy to hear any suggestions. Here's what we've tried so far:

twisting the differential pairs
ferrites
shielding the cable (although that one is anecdotal, I didn't work at this company than)

And here's what I'm considering:

Spread Spectrum Clocking (not sure if possible on the LVDS)
47 Ohm resistors in series (an act of desperation)
shielding (give it another go)

Thank you,

David


texts:
I want to use this LAN transformer for my design but I'm getting confused by the datasheet. The electrical schematic section on the first page shows two images. One is a simplefied top view and the other is a pure schematic symbol.

It seems to me that these two representations are conflicting. The simplified top view on the left shows via the transformer windings that pin 1 and pin 7 make a pair and that pin 2 and 6 make the other pair. However on the right side this flipped. Is this datasheet conflicting itself or am I just misunderstanding ?


texts: Why AC points on PCB are separated by a hole

texts:
I want to find out why, in professional PCB's, they separate between the AC (220 VAC) points on the PCB with a hole in the PCB:

Is it for more isolation between the AC lines?
Is leaving a distance between the two AC input points on the PCB not sufficient?
I'm making a board that needs to stay connected to AC permanently, and I'm using a Varistor for more protection from AC spikes, is this hole urgently required for me to make?

Here are images for the hole I mean:


texts: I made a custom EAGLE Part and it shows up at the board and schematic alright. But when I try to move the symbol in the schematic I am unable to select it. EAGLE keeps saying ´Group is empty!`. Any ideas?


texts: Hysteresis threshold changed when connecting a transistor to the output of a comparator LM393,

texts:
simulate this circuit – Schematic created using CircuitLab

Hi all, I have built an inverting comparator with hystersis using LM393. First I calculated \$R1,R2,R3\,R4_{pull-up}\$ and got the exact upper and lower hysteresis threshold \$V_{TH}=1.8V\$ and \$V_{TL}=1.39V\$. However, when I connect a transistor \$Q1\$ (I want to use it as a switch, when its ON, let as much as possible current flow through the load \$R6=20\Omega\$), the upper hysteresis threshold has decreased to  \$V_{TH}=1.47V\$ and \$V_{TL}\$ didn't change.

Here are my questions:

I thought I need to take \$R5,R6\$ into hysteresis calculation. But how? The load resistance \$R6=20\Omega\$ cannot change.
How to make \$Q1\$ saturate when it is ON? I have iterated \$R5\$ with many different values from \$100\Omega\$ to \$10k\Omega\$ but cannot make B-C junction forward bias. My goal is to get maximum current flow through the load.


texts:
I am using a 47uF 10V SMD capacitor (GRM31CR61A476KE15L) mainly for DC blocking. But it make a phase shift on the signal, we can deal with this phase as long as it remain constant(hence the capacitance is constant too).

After 60 days the performance of the circuit has degraded, the capacitance has been reduced to 35uF. By accident I have soldered it again and the capacitance return to 44uF (which is in the tolerance range +/- 10%). I read about this and found this page, talking about aging in high dielectric constant capacitors and the curing occur by temperature when soldering.

I really got shocked by this fact.
So the question is how expert designer, design devices that could work for 10-15 years without degrade in performance with such phenomena?


texts: ATmega48PA power consumption during EEPROM write

texts:
PLEASE, PLEASE! My question is about power consumption of the CPU during EEPROM write NOT about the power supply! PLEASE! Thank you!

I have a device (ATmega48PA) powered through a 150k resistor directly from the line (with regulation of course!):

In more details (however this is FAR from the question and I don't know why so many people discussing the power supply schematic and NOT the question I asked):

I've estimated the consumption of the CPU itself about 300-400 uA which looked realistic with 2.5V VCC and 1M frequency.

However after I tried to write some data to CPU's EEPROM VCC goes dramatically down (generating BOD reset).
After some investigation I realized that the current goes to 7 mA (and the current growing dramatically further if VCC higher).

I tried to find any information in the datasheet, but the only thing I found was this chart (on page 538):

Which is not really comply with my experience (and it looks like FLASH programming, not EEPROM).

So what is the reality of the current consumption of CPU during EEPROM write? And is it possible to reduce it?


texts: Cap Value for Full Wave Rectifier Circuit

texts: Why do we use a capacitor of specific value and not an arbitrary value for a full wave rectifier circuit?  For example in this circuit diagram below shows a 470uF capacitor so why can't I use a capacitor of 100uF or 1000uF?  How can I pick the correct value? Also what is the significance of capacitor C4?


texts:
I have been searching for a storage solution that can be written to an infinite amount of times, and RAM comes up every time.
So is it possible to connect RAM to a controller and use it like a pendrive?(I realize that it would be volitle)

I've heard some people say that a necessity for such a project is a CPU is that true?

This has nothing to do with external RAM, I am not planning to use such a device as external RAM.

Any ideas?


texts: Intuition behind ambiguity of direction using linear array

texts: I have recently started studying array signal processing. I am struggling to understand the intuition behind ambiguity of direction using a single linear array and how it is solved using two parallel linear arrays. Can anyone please explain me?


texts: How do I find compatible coax connectors if I don't know the type of coax?

texts:
I have some small diameter coaxial cable, which we use in harsh environments.  I want to buy connectors for it. Most suppliers list thousands of connectors by cable designation, so finding compatible connectors can be a pain if you don't know the number.

The layup of the cable is:

Inner conductor: 0.2mm/0.008" diameter stranded copper
Insulation: PTFE or FEP, 0.4mm/0.016"
Shield: braided copper, 12x100um wires
Jacket: PTFE or FEP, 1mm/0.04"

Anyone know what RG number, or Belden number I should select on my supplier's website?  If anyone can post a link to a huge chart of coax designations and diameters, even better.


texts: What can be the missing values of BOM components acccording to datasheet ? LoRa sx1272

texts:
I have the schematic of LoRa sx1272 but some BOM components have no value. Could anyone help me to determine what are those missing values according to Datasheet?
Datasheet: https://www2.mouser.com/datasheet/2/761/sx1272-1277619.pdf


texts: How long is the wire wrapped around a modern resistor?

texts:
So there is an equation for resistors that says:

Say rho is a small value such as a resistivity of copper which is 1.68 *10^-6. And we want the resistor to have a value of roughly 100kohms(for example). Say the area is small then the L value, the length of wire wrapped around the resistor is HUGE; literally miles of wire wrapped around a tiny resistor.

How is this possible? Inside a modern resistor today, how much wire is wrapped around to output desired resistances?

Edit: Say you are in the 19th century with limited technology and you wanted to create this resistor using this equation (wrapping wires around an object to cause resistance), then the wires would have to be miles long right to achieve this value?


texts: Electrocuting a fruit fly using magnetic induction

texts:
We are electrically inducing heart attacks in fruit flies to test the effects of various treatments on survival. We are shooting for roughly a 50% survival recovery rate in our control group.

I work with a lab that is studying cardiac function in insects. We have been inducing cardiac arrest using electrodes applied to the outside of the fruit fly. This has a lot of problems to it, attachment of the electrodes is labor intensive, the carapace is a pretty good electrical insulator , Etc

I'm new to the lab and was asked to look over the situation to see if I had any ideas on how they could improve fly handling and throughput. I got the idea of maybe putting the Flies inside a solenoid and inducing Eddy currents to shock them.

I have very limited experience in building electronic devices though I have a decent undergraduate level understanding of physics including electromagnetism.

I don't really know where to start here. I thought of just looking for solenoids online or maybe just an automotive coil. Putting the fruit fly inside a little plastic tube. Sticking it in the core of the coil after the coil is already running current from a car battery. And then just suddenly disconnecting the terminals of the battery and letting the magnetic-field collapse to see what happens to the fruit fly.

I would consider it a victory at this point if I could just show that we could get the fruit fly to die without actually cooking it. We can systematically lower the the magnetic field intensity that we collapse using lower voltages through the coil until we get what our Target is, a shock level that creates about a 50% survival rate.

I'd appreciate any advice on how to approach this or even criticism regarding whether or not it would work. I'm in electronics hobbyist but haven't really done that much period just some basic stuff.

This is an example of the physical principle I am talking about, though out problem is simpler since we want a single disruptive shock and have no portability issues.

https://www.google.com/patents/US5170784


texts: Resistance/Voltage relation in Rheostat?

texts:
According to "How Computers Work" (Tenth Edition) by Ron White, he features a graphic of a potentiometer with three terminals on the bottom with the one on the left being for current flowing in and the center terminal connected to a wiper for current flowing out.

In the written explanation, Ron describes that "When the knob is turned clockwise, the electricity has less wire to travel through so that the resulting current is stronger and the volume is louder."

This confuses me as the graphic appears to show more resistance wire being used as the wiper is turned clockwise. Wouldn't the voltage decrease as you increased the amount of resistance? I obviously am a complete novice in terms of electrical engineering or else I would not be reading this book. Please help if you can. Thanks!


texts: Problem with mixed CMOS op-amp supply voltages on a square to saw wave converter

texts:
I am designing a square wave to saw wave converter by first integrating the square wave into a triangle wave, then toggling between the triangle wave and it's inverse, using 2 CMOS 4066 switches triggered by the original square wave.

The output is an incomplete saw wave because of the triangle wave going too negative relative to the 4066 supply voltage.

I know I could fix this by scaling and adding a DC offset to the triangle waves at the input of each 4066 switch. But for a number of reasons I want to keep the waveforms balanced with no DC offset. I also want to keep the circuit as simple as possible because it will be repeated many times in this project.

Can I power the with 4066 and 4069 with -12v to +12v so as not to cause this problem? If so what is a simple way to shift the logic level of the input to the 4069 to the right level?


texts:
I have designed a computer case (enclosure) for mini-itx motherboards.
Its bottom and rear are made out of 2mm thick aluminium and the sides and top out of 4mm plastic (ABS).

I'd like some advice please on EMI/RFI emissions.

I am thinking of making a few for interested people and the end user will be completing the assembly (install their choice of motherboard, hard drive, memory and internal picoPSU), I'll just provide the case.

I have read this question here:

emi standards/best practices for PC cases

and The Photon very kindly answered another user. From what I gather there is no need to FCC computer cases but I'd like to make sure the user can shield the case themselves if they want to.

So is it ok if I provide the case as it is? The aluminium is punched with some air vents on the rear (4mmx12mm holes), some on the base (same hole dimensions) where the motherboard would sit and some where two 2.5" hard drives would sit (again same hole dimensions).

I've heard of nickel based paints that can be sprayed to the plastic parts (on the inside) but is this safe? Does the paint need to be conductive? Is there a risk of short circuiting the components inside, fire or other? If sprayed, would the plastic parts need to be grounded and to what?

What about shielding tape, is that any good? Would I or the user need to cover the plastic parts entirely? What about the bits where aluminium and plastic join? And the vents in the plastic parts?

And finally how do I calculate the exact area required for the air vents so that it doesn't affect RFI/EMI too much?


texts: Designing a CE Fixed Gain Amplifier with a PNP Transistor

texts:
I was given a task to design a fixed-gain CE amplifier using (NB) a PNP transistor. I have a bunch of requirements and set values.

Most of the tutorials online only use NPN transistors, and while I know that they are essentially the same apart from a few current directions and polarities, I have no idea where to start. I know how the diagram is supposed to look, but I'm not sure in how I'm supposed to do the design to get the required values. Also, most of the questions already asked refer to NPN or to variable gain amplifiers.

Features needed:
- Input voltage range input should be 10mV(p-p) - 100mV(p-p)
- for a frequency of 10kHz, the output is expected to be 2V(p-p)
- bandwidth test should be performed with respect to a -3dB cut-off point, altering the frequency when the amplifier is energised.

Requirements:
- Vcc = 19V
- R(LOAD) = 432R
- Av = 8V/V

I just need to know where to start - I don't know what to do with the fixed-gain. I don't want someone to do the design for me - just provide a guideline of the starting steps I should take to do the design


texts: 2004 Chevrolet Avalanche surface mount component identification

texts: My instrument cluster stopped working and when I plug it in, I smell some burning. I found this component smoking and seems to be the source of the trouble. Can anyone please help me identify what it is?


texts:
I want to perform a speed control for a 1500W brushless DC motor.
The documentation and videos I've seen use arduino uno and are for smaller engines.
I would like to carry out this project without using arduino uno.

Could someone recommend me books with examples of controls for brushless DC motors?

On the other hand I have found contradictions between PWM and ESC.
Are the ESCs for brushless DC motors and the PWM for brushed DC motors?
Or is it indistinct?


texts:
Can someone help how to find formula and calculate this task?

How many times per second will be reset if the microcontroller is set to 1:128 preskaler microcontrollers and works on Frequency of 8 Mhz.

Could someone explain me how to solve this kind of task? Please.


texts: How frequently must Microchip's USB HID USBDeviceTask() Task run?

texts:
I'm integrating the example USB module into my existing app and can only get it to work when I disable interrupts.

I'm working off the mla example installed at the path:

C:/microchip/mla/v2013_12_20/apps/usb/device/bootloaders/firmware/pic18fxxjxx

Details

I'm implementing each of USB callback functions exactly as done in the example.
USB clock is 48MHz
CPU (f_osc) clock is 16MHz
pic18f25k50
one high-priority interrupt for Timer1 ticks every 250us, everything else happens about every 1s

never go to sleep, yet this still seems to reset

Is microchip's USB stack not thread-safe?

Am I not running the USB task fast enough?

while (1)
{
  // Clear the watchdog timer
  ClrWdt();

  // Run the USB task faster than xxxHz?
  USBDeviceTasks();

  // Do stuff
}

// high-priority foreground loop takes ~5us
void high_priority interrupt HighPriorityTasks(void)
{
  // Do stuff quickly, clear sources of interrupts
}

// low-priority foreground loop takes ~5us
void low_priority interrupt LowPriorityTasks(void)
{
  // Do stuff quickly, clear sources of interrupts
}

When it fails, I see device manager continue to refresh accompanied by one of these popups about every 5s in Windows 7:


texts:
I'm trying to make a block in VHDL that will send to the output sequece of ones and zeros (signal code) but I can't make any progress. Code is compiled, but in simulation the output doesn't react as I expect, it keeps sending zeros. The following is my code:

--beacon
library ieee;
use ieee.std_logic_1164.all;

entity beacon is
        port
        (       START : in std_logic;
                CLK : in std_logic;
                Q : out bit
        );
end;

architecture dataflow of beacon is
signal code : bit_vector(0 downto 45);
signal index : integer;
begin
        code <= "0111010111000101011100011101110001011101110100";
        index <= 46;
        st : process(START)
        begin
                if rising_edge(START) then
                        index <= 0;
                end if;
        end process;

        b : process(CLK)
        begin
                if rising_edge(CLK) then
                        if(index < 46) then
                                Q <= code(index);
                                index <= index + 1;
                        end if;
                end if;

        end process;
end;

I'm new to VHDL. Could anybody give me some advice on what's wrong in my code?


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

texts:
Soldering Irons seem to come in different Wattages. I imagined that it was just an indicator of how fast they get hot but might there be other considerations?

How do the different power ratings affect the soldering process and are some power levels more suitable to certain tasks?


texts:
I have this question on my exam I couldn't answer:

A diode ROM has been built using a decoder and multiplexers. If A4A3A2A1A0 = 01001, what is D3D2D1D0?

Here is the first schematic:

The answer is supposed to be:

Can anyone explain the solution?


texts:
What is the best way to test the load response of a DC DC buck converter? I thought that a power resistor to fully load the circuit would be the best thing to do. Any thoughts on that?

Specs:

synchronous buck converter
200kHz
VIN: 18-36V
VOUT: 3.3-12V
IOUT: 2A
Pmax: 10W

Hope this is enough information to help me, otherwise give me some time to include more information.

Thanks in advance.


texts: How do I calculate the position of a piston in percentage from the significant bits?

texts: I have a ARINC label with 12 bits. This label is connected to a solenoid valve that is commanded to open partially or completely. If I get a feedback for bits set to 1 (significant bits). How do I calculate the position of the valve in percentage?


texts:
Could Anybody help in getting started on I2C signal Static Timing Analysis.
I just wanted to start with 1 single master slave combination. I have MPC8343EA as Master and TMP100 as slave.
I know the analysis should have two conditions read and write and not sure what parameters to consider.if I get the idea as to how to go about to analyse the write condition I could easily finish the read part.


texts: Why do we need the MOESI/MESIF protocols?

texts:
As I understand, those two protocols add an extra state to identify which cache should respond to a miss request from another cache for a particular cache-line.

But, in the MESI protocol, only one cache can have a cache-line 'A' in the modified state. The other caches can have 'A' in the invalid state or not at all in the cache.

Instead of adding an extra state, can we not just make the cache which has the requested cache-line in the modified state respond to a miss request generated by another cache for said cache-line?

Additionally, is there another motive for introducing the MOESI/MESIF protocols?


texts: Why is the voltage of a capacitor equal to the voltage of a battery connected it?

texts:
I am confused by this question.
If we connect a resistor in series to capacitor then the voltage will drop across the resistor and now voltage across the capacitor is less than the source, then why would capacitor charge till it has volts equal to the source?

and why in the below image when the capacitor is fully charged, its voltage is not same as source?


texts: Why did this triac driver resistor let the magic smoke out?

texts:
I hope the title is acceptable under this website rules but it is exactly what happened. I wired up this circuit that I thought I tested in the past multiple times, but I might have wired up slightly different. However the following schematic is an accurate description on what I had.
The optocoupler triac driver is for the sake of this experiment always kept "on". When this works it will be controlled by a microcontroller, but for now it's tied to Vcc. NOTE: No, I do not want to use a zero-crossing sensing driver. This circuit will be used in a way that will make that inherent, but that part is not the subject of my tests and I want to understand why this circuit blew up.
The load is an oven element that works with the typical 240VAC split phase common in North America. The power triac is a beefy BTA40 mounted on a big heatsink. Datasheet links below.
When I was about to close the breaker to power this circuit, resistor R4 immediately became white incandescent. However, I have tested a variation of this circuit successfully in the past. What is really going on?

R4 at 330R should guarantee that even at peak voltage (240*SQRT(2)) there is never more than one amp through the MOC3053 (Itsm max = 1A according to the datasheet). In reality, as also the datasheet says:

The power dissipation of this current limiting resistor and the triac driver is very small because the power triac carries the load current as soon as the current through driver and current limiting  resistor reaches the trigger current of the power triac. The switching transition times for the driver is only one micro second and for power triacs typical four micro seconds.

However it looks like that in this configuration the poor resistor had to dissipate so much more than that.
Datasheets:
MOC3053, BTA40
EDIT: I was suggested to move the load, so I tried to put it "under" the triac; will this work?


texts: How to check if MEMS microphone is working?

texts: I am using a MEMS microphone that I got from Digi Key ( Part Number: 1428-1021-1-ND). I soldered the mic on a PCB board using hot-air and then add an amplifier to increase the gain (Operational Amplifier Mouser Electronics 595-LPV802DGKR). I made sure to follow the datasheet and check that everything was power correctly by measuring the voltages in different terminals with a multimeter. However, the microphone is not working.  I am measuring the output of the circuit with an oscilloscope and I am not getting anything. I noticed that the output of the microphone is less than what I was expecting. Any idea why the MEMS mic is not working? I have already done 4 of these and none is working.


texts: Why is there a need for level shifter in this circuit (charge pump)?


texts:
I am doing a personal project to learn a bit about electronics but I do not have much prior knowledge about it.

I am using a STM32L476RG microcontroller, a 3 digit seven segment display (common cathode), a 1N4148 diode and a 220Ω resistor.

My initial issue was that when the digit was meant to be off (but the segments should be on to light other digits), there was a dull light on the segments. To get around this, I put a 220Ω resistor in series with the common pins on the seven segment display. This fixed the issue of the digit being dull when it should be off, but it made the digits dull when they were meant to be on.

So to bypass the resistor when the digit is meant to be on, but not when the digit is meant to be off, I added a small signal diode in parallel with the resistor. A diagram of a single segment in this layout looks like the below. This shows the diode and resistor attached to pin 12 (the pin that controls digit 1 being on or off).

simulate this circuit – Schematic created using CircuitLab

The way I thought this would work was when the segment pin is high and the digit pin is low, the segment would be on and be bright (which it is) as it goes through the diode. But when the segment pin is high and the digit pin is also high, the segment would be off as it is going through the resistor. However, this is not the case, when both pins are high, the segment is on and dull as if it were still going through the diode.

What am I doing wrong?

A comparison of the when the diode should be on and off with the resistor and the resistor / diode. The segment pins are all high and it is the common digit pin that is high for off and low for on.

The 3 digit 7 segment display pin layout for reference.

Edit


texts: Can the diode be ignored in this Op amp circuit?

texts:
Consider the circuit below:

The diode is ideal and \$R=1000\Omega\$.
What is \$v_o\$ when \$v_{in}=3V\$?
What is \$v_o\$ when \$v_{in}=-3V\$?

So my idea was just to make node equations to solve these to find \$v_o\$, but when I do that I completely ignore the diode. I do like this.
For this op amp we have: \$v_-=v_+=0V\$
When \$v_{in}=3V\$:
\$\frac{v_--3V}{R}+\frac{v_--v_o}{R}=0\$
Inserting \$v_-=0V\$ and solving this equation we find that: \$v_o=-3V\$
When \$v_{in}=-3V\$:
\$\frac{v_-+3V}{R}+\frac{v_--v_o}{R}=0\$
Inserting \$v_-=0V\$ and solving this equation we find that: \$v_o=3V\$
As you can see, I'm not really thinking about the diode at all. Am I solving the problem correctly?


texts:
I am trying to build a circuit featuring multi-channel digitally-control current source and voltage meter.

Each current source is required to supply up to 5mA of current to a load that could reach a voltage as high as 10V. I chose a NXP constant current source device which can supply maximum 50mA of current and support a max voltage of 50V. The current source can be adjusted using an external resistor. I use a digital potentiometer to act as this external resistor so that I can control the current source digitally. The current source circuit is illustrated as followed.

I have to generate both the 3.3V and -15V power supplies because the Digital Potentiometer requires that the voltage applied to both terminals should not exceed the [0V,3.3V] range in either direction, while my current source load requires a voltage range of 0-10V.

To generate both 3.3V and -15V, I use a power op-amp like TI's LM675 to split a 24V power supply into [0V,+9V] and [-15V,0V] dual ranges. Then I use the +9V to generate two 3.3V supplies for analog and digital circuit respectively. U108 and U109 in the figure below are voltage regulators and generate fixed 3.3V output.

In the last part of my circuit, I use a 24bit ADC to measure the voltage of a signal, which is buffered using an Op-amp that directly connect its output to the negative input (voltage follower). In the figure below, U1 and U3 are two-channel 24-bit ADCs and U2 is a four channel op-amp. The DVDD is only used to communicate with the ADC chip and configure the digital potentiometer.

In total, I have 20 channels of those current source and volt meter all sharing the same AVDD, DVDD, AGND and VGND.

Problem: the output of the power op-amp (U114) is extremely unstable. The power supply path is oscillating.

I have tried to remove both the 3.3V voltage regulator, but the same problem remains and now DGND=2.5V while DVDD=2.1V (with reference to the 24V power ground). Can anyone provide a hint?


texts: I get different results whenever I try to solve this circuit problem with superposition theorem. Can you please help?

texts:
My recent results are like this:
i= 11,174
the current exiting from Vg= 3,304
V=53,1
I am doing something very wrong but I can't see it. My values even don't correct each other. Another thing is if I try to combine the current source with 10-ohm resistor my calculations goes downhill. Why I can't apply this rule to this particular question?


texts:
I do not understand the cause of this spike which can be observed in an RTL inverter (but also in a CMOS inverter). In the following image it is the peak at 10 mS (I have considered as input a signal which starts at 0V and begins VCC at 10mS).

I have been told that it is due to the parasitic capacitance between collector (output) and base (input), since at the high frequency of the vertical transition of the input signal it becomes a short circuit and therefore the output follows the input (which is now high) instead of going down. But, if the reason is this, why the output signal is higher than input (and not simply equal to it)?


texts: Are either a Multiplexer or Decoder going to help me with this circuit design?

texts:
I have 2 2-bit inputs (eventually need to design for k-bit, but let's start here) and there are 2 2-bit outputs that output the max on one side and min on the other.

What I have so far...

{Image attached if helpful}...

...given the two inputs, I have one output that is 1 if X is Max or 0 if X is Min, and another output that is 1 if Y is Max, or 0 is Y is min.

Conceptually, I'm thinking to use these as inputs for a multiplexer, where one takes in both those inputs and uses them against the X and Y bits to determine which ones it's outputting to MAX, and another for MIN. Then I remembered that a Multiplexer gives out one bit.

I thought maybe another circuit we learned, a decoder, might be helpful, but I can't quite see that working either. Having explained my approach so far, can somebody guide me to the next steps? My teacher is very unresponsive, and threads relating to this problem have not been helpful, hopefully somebody can help me specifically with what I have so far!


texts:
I want to make a electric leakage protection circuit for a water heater in case of heater gets corrupted in time. We use rezistance 220V - 1500 watt. We grounded the water (because rezistance have coating outside and doesnt convey electric to water) but when there is electricity in water, RCD at office cuts off electricity for all devices. We only want heater to turn off. So, we bought another RCD and connected it to water heater, then we plug water heater to electiricty. It works but two RCD triggered at the same time. We only want one of the RCDs that connected to the heater to trigger. I can't connect different RCD in fuse board because system must be portable and this safety system must be included to main circuit.

Is it possible to do this with RCDs? Or can we add something after RCD of water heater to delay the current, so RCD of office wont trigger?


texts: Calculate Buffer Op Amp Output Impedance (With Data Sheet)

texts:
For a given op amp, in my case a OPA197 by TI, I'm trying to calculate the output impedance for a near DC signal.

The datasheet gives an "open loop" output impedance of 375 Ohm, to me that seems high, unless I have lulled myself into believing op amps are more ideal then I though. I expected something in the 10s of Ohms. Also Wouldn't an output impedance be gain dependent?

Can anyone give me the proper way to find/calculate output impedance? Note I'm not looking for a method to measure it.

This question may have the answer and I am just not understanding...

Output impedance of Op Amp with Voltage Divider?


texts: LED panel refresh rate and scan rate (multiplexing) relationship

texts:
Considering high-end panel as ROE Ruby 2.3 https://www.roevisual.nl/uploads/bestanden/ruby-r2.3-brochure-lr-v12020.pdf the scan rate (multiplexing) is \$s=1/12\$ and refresh rate is \$f=1920\$ Hz.
What does the refresh rate mean? Does it mean how many times per second are \$1/12\$ od LEDs illuminated, or the whole display? Meaning that scan refresh rate would be \$f_{scan} = \frac{f}{s} = 23.040 \$ KHz?
Or is it that refresh rate means \$f_{scan}\$ and actual whole display refresh rate is \$f = f_{scan} \times s = 160\$Hz?
Thank you for clarifying.


texts:
I want n 12V 1A supply for a project. I want a transformer-less topology.

I was reading and experimenting with readily available traic based dimmers. They use phase control to cut the input voltage to a load. So I thought it might be used to provide a stepped down voltage.

Here's what I have done so far:

Connected a simple dimmer to the phase line, set it to minimum (which is about 20% I guess), rectified it and  connected a filtering capacitor to the positive and negative terminals of the bridge. The output voltage was still 220v.
Next, I connected a 10k resistor to the between the positive and negative terminals. The voltage dropped significantly.

Now, the the output voltage was dependant on two things.

The output voltage increased as I increased the phase from the dimmer which was as expected.
The output voltage also depended in the load resistor. If I increase the load resistor, the output voltage increased. Now, this was something that I think will cause problems depending on the type of load I connect in the future.

The scope of the project is not just limited to the 12W requirement. Ih I can convert 220vac to 30vdc, then I can connect a buck-converter to this and use it as a variable power supply.

Please help me complete this.


texts:
Was just trying to identify the contacts on this jack socket (datasheet: http://www.farnell.com/datasheets/2047485.pdf )
Image of schematic below.
I was thinking that 1 would be ground? Which I guess would then lead 2/3 to be right/left? This may be totally wrong however, and I'd appreciate the help of anyone who can clear this up.
Thanks.


texts: Kids Bluetooth Headphone Volume Limit mod

texts:
I have purchased a set of NIA X2 Bluetooth headphones for my kid which are very convenient.

However, my advice for lowering the volume is constantly bypassed, so I would like to mod them in order to decrease the maximum volume to a safest level.

I have disassembled them as you can see in the attached photo.

I was thinking of adding a suitable resistor in line to each speaker's input. Would that do the job?

I have measured speaker resistance and it is 38 ohm. The signal voltage at the speaker solder tabs is around 6 mV in full volume.

Would a 5 ohm resistor suit for a 15% volume drop, or should i connect a larger (e.g. 200 ohm) resistor in parallel with each speaker?


texts:
How to intuitively guess the output waveform of a rc differentiator to a ramp input? I know it will be a constant value if RC is very small but that's from calculation. How can I intuitively guess it?
And if possible are there any books which help in developing intuition regarding rc circuits? I have an interview coming up with An analog design company .


texts: I've been looking at 3 phase disconnects, and I'm uncertain what the rated amperage means in this context. Since each blade (phase) has its own fuse in a fusable disconnect, does that mean that for a 100A disconnect you would give each phase a 100A fuse? Or, would you use a 30A fuse for each?


texts:
I am attempting to build a C++ program that performs all of the necessary steps generate a bit file using the ISE (14.7) tool chain. I generate the Command line Log File for my project and try to run all of the commands by hand on the command line. When I try to run the XST command I need the GUI generated .xst script, .syr report file and the .prj file.

I believe that in theory I should be able to complete syntheses with these however I get

ERROR:Xst:439 - No write access in xst/projnav.tmp

The GUI creates an xst folder with projnav.tmp when xst is run. It seems that running xst from command line doesn't

Is there a command or xst argument to have this folder made?


texts:
In Matlab/Simulink there is an example of a DC Motor (power_dcmotor)

I can not understand how it converts the speed w (rad/sec) to Torque TL (Nm)

It says:" Torque is proportional to speed; TL=Bl*w ". What B and l stand for?


texts: How many flip-flops are required for the implementation of this Mealy diagram?

texts:
I'm trying to create a circuit diagram that corresponds to the Mealy diagram I created for the following problem, but I'm not sure how many flip-flops I should use.

Problem:

A data stream receives serial data of 1 bit, synchronised by a clock pulse. Create a Mealy State Diagram that:

Starts from an initial state (IS).
Outputs xy = 01 when it recognises the bit-sequence 1001 and returns to IS.
Outputs xy = 10 when it recognises the bit-sequence 011 and returns to IS.
In any other case, the system should return xy = 00.

Mealy Diagram (Corrected):

(This is the diagram I came up with)

Based on the Mealy diagram above, I would say 3 flip-flops are needed, because 100 needs 3 bits to be represented. Is there, however, a way to implement it with less? If so, why?


texts: Buffer management for SD card in SPI mode

texts:
I'm looking into implementing storage of large audio files onto an SD card. I'll be using SPI to access the card to avoid any patents by the SD card mafia. I'll be generating a lot of data, about 150 kbyte/s per second and that needs to be read from an ADC and written to a DAC + stored on the card.

I need to use some buffer in external memory (I don't know if I'll have enough RAM on any small MCU, so I'll use something with an external bus). I have no experience doing this, so I'll appreciate any pointers to what strategy to use here.


texts:
I am writing code for Register file (32 registers, each of 32 bit) for MIPS Single Cycle processor.
I want writing to happen at the negative edge of the clock. As usual, reading can happen any time (as soon as it gets a proper Register No). Given below is the code for this:

module regfile(clk,reset,ReadReg1, ReadReg2, WriteData, WriteReg, RegWrite, ReadData1, ReadData2);
    input clk, reset;
    input [4:0] ReadReg1, ReadReg2, WriteReg;
    input [31:0] WriteData;
    input RegWrite;
    output[31:0] ReadData1, ReadData2;

    //Register File has 32 registers. This module has access to each register through the RegFile array of nets
    wire [32*32-1:0] RegFileAcc;
    wire [0:31] decOut;
    wire [0:31] regClk;
    dec_5to32 dec1(decOut,WriteReg);

    //Creating 32 memory cells, each is a 32 bit register (made up of 32 DFFs)
    genvar j;
    generate for(j=0;j<32;j=j+1)
                begin: regFile
                    assign regClk[j]=(clk & RegWrite & decOut[j]);
                    reg_32bit r1(RegFileAcc[(32*(j+1))-1:32*j],WriteData,regClk[j],reset);
                end
    endgenerate

    //The reading part
    bit32_mux32to1 mux1(ReadData1,RegFileAcc,ReadReg1);
    bit32_mux32to1 mux2(ReadData2,RegFileAcc,ReadReg2);
endmodule

Here is the code for the 32 bit register:

module reg_32bit(q,d,clk,reset);
    input [31:0] d;
    input clk,reset;
    output [31:0] q;
    genvar j;
    generate for(j=0;j<32;j=j+1)
                begin: reg_loop
                dff d1(q[j],d[j],clk,reset);
                end
    endgenerate
endmodule

The code for D F/F is:

module dff(q,d,clk,reset);
    input d,clk,reset;
    output q;
    reg q;
    //active low reset
    //we can read the dff using q

    always @(negedge clk)
    begin
        if(reset)
            q<=d;
        else
            q<=1'b0;
    end
endmodule

I have implemented a testbench to test the Register File. But I am getting some unexpected output:

Testbench code:

module testbench;
    reg [4:0] ReadReg1, ReadReg2, WriteReg;
    reg [31:0] WriteData;
    reg RegWrite,clk,reset;

    wire [31:0] ReadData1, ReadData2;

    regfile rf1(clk,reset,ReadReg1,ReadReg2,WriteData,WriteReg,RegWrite,ReadData1,ReadData2);

    initial
        forever #5 clk=~clk;

    initial
    begin
        $monitor($time," ReadReg1=%2b ReadReg2=%2b WriteReg=%2b WriteData=%8h ReadData1=%8h ReadData2=%8h \n RegFile=%32h\n",ReadReg1,ReadReg2,WriteReg,WriteData,ReadData1,ReadData2,rf1.RegFileAcc);

                clk=1'b0;
                reset=1'b0;
                RegWrite=1'b0;

        #12     reset=1'b1;
        #6      WriteReg=5'b00000;
                WriteData=32'hAFAFAFAF;
                ReadReg1=5'b00000;
                ReadReg2=5'b00010;
                RegWrite=1'b1;

        #10     WriteReg=5'b00001;
                WriteData=32'hBBBBBBBB;

        #10     WriteReg=5'b00010;
                WriteData=32'hCCCCCCCC;

        #100    $finish;
    end
endmodule

dec_5to32 is the decoder 5*32. bit32_mux32to1 is mux 32 to 1 (each input is of 32 bits). I have checked them, they work fine. Also, reg_32bit and dff are also working fine.


texts: Lock-in amplifiers, signal averaging and signal post-processing

texts:
I would like to know about what are the benefits of using a lock-in amplifier. I have read that they basically consist on multiplying a signal by a reference which switches the frequency to DC. Then the signal is integrated to remove the noise thanks to their randomness.

My question is: what is the difference of this with respect to simply averaging the signal in an oscilloscope?

Additionally, reading on DSP Lock-in amplifiers, is it not equivalent to perform some post-processing techniques on a recorded signal?


texts: Differential Equation of a First Order High Pass Filter

texts:
I am just stumped right now b/c I do not know how to write the "differential equation that describes this system. I did learn to write equations with impedances but I believe this is not what this question is asking for.

I tried writing a KVL around the loop and obtained:

note: U stands for voltage(my prof likes this notation as opposed to 'V')

\$ -U_{in} + U_c + U_R  = 0\$

\$ U_{in} = U_R + U_c\$

\$ U_{in} = RC\cdot \frac{dU_o}{dt}\:+\:U_R\$

Let \$U_{in}\$ = \$x\$

and

\$y\$ = \$U_o\$ or \$U_R\$ (same thing)

combining the \$R*C\$ to \$\tau\$ then I would get something like this:

\$x = \tau \cdot \frac{dy}{dt}+y\$

which would be my differential equation???

I feel like this equation is wrong from the start since I derived the same exact equation for low pass filter. How can both low pass and high pass have same exact differential equation? What am I doing wrong? If you do not mind please provide the correct solution with the laplace transformation as well b.c I have no ideas where to begin with that.


texts: Converting 6c (3s2p,4.5v) DC motor to 1s4p 18650 charging/protection

texts:
Having a hard time figuring this one out, I am trying to convert a 4.5v 25w dc fan from an air mattress pump to run off a rechargeable battery pack made with 18650's. This is going to be charged and discharged often and I desire a long run time which makes c cell batteries considerably cost prohibitive long term.

The motor will run off 3.7v just fine and is more than adequate power for my purposes however That being said I have a few questions.

How would I go about discharge protection? Do I need a protection module for each cell or would one suffice for the entire battery circuit?

How would I go about charging them? The bms boards I have been able to find seem to be designed for series applications. Would a bms designed for a 1s cell work for multiple cells in parallel? I am not opposed to using sleds and charging the batteries individually however it would be nice to keep the batteries internal and charge via usb. I know this would take longer however I plan to charge them overnight so time isnt super important.

Lastly this is not necessarily related to charging/protection but when I run the motor off a single 18650 for testing purpose it seems to be drawing more current than with the 6c batteries at 4.2v vs 4.5v with the alkaline batteries. The dc motor no load speed is noticeably faster is this due to bypassing the existing wiring/switch and running straight off the dc motor +/-? I plan on adding a trimmer pot to the circuit anyway to keep the current down and hopefully extend battery life however I am not really sure what resistance value would be appropriate. Short of pulling the motor from the housing and checking the current draw outside the housing using the alkaline batteries is there a way for me to determine a safe operating current for this motor?


texts: how to make a system respond to IR laser?

texts:
Lets say i have 2 separate systems called Box A and Box B. Box A has an IR laser beam attached to it.

What equipment can i use to make Box A make a certain action ONLY when the IR laser attached to is pointed at Box B?


texts:
I am trying to follow the TI document on NFC antenna matching for the TFR7970A chipset.

http://www.ti.com/lit/an/sloa241b/sloa241b.pdf

I am under linux, and while I could try wine to use the smith chart simulation software, I was wondering if I could use qucs or qucs-s for simulating the matching circuit. (or other software available on linux).


texts: Why is the logic probe reducing current from the power supply?

texts:
I am troubleshooting a very basic circuit using an inexpensive logic probe to check values. Typically when I use the probe I see current output go up about 7mA, which I assume is to power the sound and light.

There is one particular pin where I should be getting a signal, and when I use the probe the current actually decreases, significantly. It goes from 43mA down to 26mA.

Why would the current decrease when the logic probe is hitting this pin?

This is pin XTAL1 on 80C31 microprocessor, see diagram. There is a crystal, two capacitors, and the microprocessor itself. I'm not getting signal on XTAL1.


texts: Calculation of cutoff frequency in larger circuit

texts:
I'm having some difficulties choosing appropriate resistors and capacitors to get specific cutoff frequencies. I guess it's because I'm just considering the single pole components rather then the whole circuit when I'm dimensioning my filter. Given this circuit:

What should I consider when choosing values for the resistors and capacitors to get a 2MHz cutoff bandpass filter and at the same time a DC component of 1.65V?


texts:
I have a water level sensor in which by varying the level of the water, an inductance change his value in a mobile coil. The sensor have the internal simple schematic like this (i don't know the value of the components)

The suggested working circuit use a Colpitts oscillator made by some HEX inverters, producing a frequency from 21 kHz to 25 kHz linked to the coil position and at the end to the water level by a provided lookup table.

I should read this frequency (level) by a micro, and I know how to do it, but in my project I used all the internal microcontroller timers. So, what I would ask, is if I can get around, using this variable inductance to produce a variable voltage to be read by the micro (avoiding to measure a frequency). And if it was possible avoiding a cascade of a Colpitts oscillator and a Frequency-Voltage converter (like the LM311).


texts:
I found this circuit in STM32F401VET6 schematic:

As you can see, VBAT line has a lot of 100 nF capacitors. Is it there to mimic a battery? If yes, won't it be better to put a reverse leakage current protection diode in between?

100 nF capacitors add up to 0.8 uF, almost equal to 1 uF. Why not use 1 uF capacitors on either side of R26? Is this bigger network used for better noise filtering?

What's the use for R26? It has a value of 0 ohms.


texts:
Consider the following instruction sequence:
Add R3, R4, R5 (R4+R5->R3)
Or R2, R4, R5 (R4 OR R5->R2)
Add R1, R2, R3 (R2+R3->R1)

Assuming no data forwarding, what are all the data dependencies?

Isn't the only data dependency from the third instruction where R2 and R3 have not been written back yet.  So to correct this dependency a stall of 3 cycles would be needed before the third instruction could decode the registers. If data forwarding was allowed, the register values could be forwarded and no stalls would occur, correct? Am I missing something? Is there a data dependency between the first two instructions since R4 and R5 are used in both?

For the following instructions:
Load R2, 20(R5)
Add R4, R3, R2
Store R4, 20(R5)

Would the data dependencies be that for instruction 2, you would need to stall 3 cycles before R2 would be available, and for instruction 3 you would need to stall 6 cycles before R4 was available? If data forwarding was permitted there would be one stall in instruction 2 for the memory from the first instruction to be forwarded to the execute portion of the 2nd instruction.  This would then lead to one stall for the third instruction during the decode phase.  Is this also correct?

Thanks


texts: solution for driving multiple 7 segment LED display from 3 volt µC

texts:
So I am looking to drive 6 digits worth of 7 segment LED digit display...
I want to use a 3v PIC, the interface IC's that I am finding (ICM7218AIPI+ for instance) list voltages like 2-6V, but upon investigation, the 2V is some low power shutdown mode, and require +4v input for serial communication.
So am i barking up the wrong tree, or do I need some sort of charge pumped serial
IC (or UART) in between?


texts: USB bus powered hub - more than 100 mA per device?

texts:
I'd like to ask a quite specific question regarding the USB power management.

First of all, I will outline the design of my device. It is a symmetric signal line driver with a builtin audio codec for my DIY speaker system. The device is internally split into two mostly independent blocks: the very line driver with a controlling MCU and the audio codec (TI's PCM2706). Both need USB data connectivity (via an FT232R for the driver block) and the whole device should be bus-powered. The two blocks will be linked together by an USB hub chip, yielding a single uplink USB connection to the PC. I expect the consumption of the driver stage to be something between 100 and 200 mA (definitely more than one load unit).

Here comes the problem: According to the USB specification, a bus-powered hub can provide only one unit per downstream port while drawing max 5 units from the upstream. I'd like to know, what would the hub do if I requested two units via the FT232 for the driver stage. The 5-unit upstream limit will not be reached (1 unit for the hub, 1 unit for the codec and two for the driver), so the computer should be physically able to supply that current.

For the hub chip, I've been checking out http://www.ti.com/lit/ds/symlink/tusb2036.pdf. There is an option of "ganged" powering mode, would this be any help? Or would the chip just refuse to grant two units to the driver? And in this case, is there any dirty workaround?

I am aware of the requirement that high power devices are also required to draw max 100 mA during enumeration; this is not a problem as the FT232 is able to turn the driver on just after the enumeration. The hub will turn the stages on independently as well.

Hope I stated my problem clear enough and thanks for your time in advance :)

UPDATE:

I did some more research on the TUSB2036 chip. The overcurrent protection can be turned off by the /OCPROT pin. The hub then reports to the root controller that it is not able to detect overcurrent. There is a warning in the datasheet, that OC protection is required by USB 2.0 specification - this does not matter for me, I only need 1.1 Full-speed. The PC's root hub should then IMO supply 500 mAmps to the whole device. Thus, I could set the driver's FT232 to require 100 mA only and the hub would never know if I would have exceeded the limit (respecting the 500 mA from the PC of course). Can someone tell if this could work?


texts: Does grounding to earth make a circuit (allowing electricity to flow)?

texts:
This question is mostly extending on a question that has been asked here:
Single terminal of voltage source attached to earth ground

I'm learning the basics of electronics and this question has always bothered me. The post above explains that a single terminal of a voltage source, when connected to ground (earth), will have no current flowing, as there is no circuit. It then goes on to talk about how capacitance might play a small factor.
My main question is this: Why then would you get electrocuted if you touched a live wire while grounded, since it is not a proper circuit? Is it different with AC and DC?

Also, when the single terminal of a flyback transformer (usually the anode cap on a CRT monitor) is placed near the ground, it creates a bright arc to the ground. How does that happen if it's not a complete circuit? In high voltage projects, most people connect the live wire from the flyback transformer straight to ground to complete the circuit.


texts: Can I use a power supply to power a solenoid electromagnet?

texts:
I've got several unused coils of 14 gauge wire that have ferrite iron cores cut to the length of their spools. They have maximum current power transmission ratings of ~5.9A, and according to a resistance by length calculator on google the overall resistance is less than an ohm for the entire spool. I'm trying to figure out a part that could be used to power the solenoids. I'm hoping to find a simple unit that can plug into a surge protector with 1 cord for each of the three solenoids.

Eventually after the solenoids are each powered correctly, I'll want to be able to control the current going to each with a microcontroller with a reasonable resolution. Is there any simple way to do this without needing to purchase many more components? I've looked into using a voltage-regulator IC + voltage-divider/digital potentiometer setup. The output of the voltage IC would then adjust a power transistor to let current through based on the voltage.

Would a power supply such as this one be able to be controlled by a microcontroller in this way?

https://www.amazon.com/Adjustable-Converter-110V-220V-Switching-Transformer/dp/B0777MH681?ref_=fsclp_pl_dp_3


texts: When I learn the transmitter and receiver architecture? They have each own heterondyne architecture they use intermediate frequency to upconvert to higher frequency or downconvert to lower frequency? I have a question? What is the difference between I up or down a little bit of frequency or up or down a half of RF frequency? For example RF freq = 1GHz, I up or down to 500MHZ or seperate it to many small parts like 100Mhz, 200Mhz.


texts: Is it possible to mix split and single-supply circuit sections

texts:
I'm making an audio synthesizer which works with single supply. Now I'm interested to include a section that uses dual-supply (a filter using LM13600).

I'm thinking that it could be possible to do it, and I will scale and offset the dual supply part output so to add it in my single supply circuit chain. Can dual and single supplies be mixed in the same circuit? How should I connect the grounds together?


texts: Solving circuit design problem with two approaches

texts:
A voltage of 200V is applied to a tapped resistor of 500 ohm. Find the resistance between two tapping points connected to a circuit needing 0.1A at 25V.
I have solved this problem with two approach. But the correct answer is coming only by one approach.

Total resistance is Ra+Rb = 500 ohm.
Va+Vb = 200V ; Vb = 25V ;
Hence Va = 175V.
Applying KCL at the tapping point we get:
-I + 0.1 + 25/Rb = 0 ; I = 0.1 + 25/Rb;
Va = I.Ra;
175 = (0.1 + 25/Rb)(500-Rb)
If we solve we will get Ra = 420.85 ohm and Rb = 79.15 ohm.

So far so good.

Consider second image in which Ra and Rb variable are taken such that Ra + Rb = 500 ohm
Va = 175V
Applying KCL at the tapping point we get:
-I + 0.1 + 25/(500-Ra) = 0 ; I = 0.1 + 25/500-Ra;
Va = I.Ra;
175 = (0.1 + 25/500-Ra)(Ra)
If we solve we will get Ra = 2079.15 ohm.
which is wrong, but I am unable to understand the flaw in the second case. It is perfectly fine. The answer is not correct. Just by changing the way variable are taken the answer is changing.


texts: I'm looking for a chip which can play media files stored in a pen drive connected to it on LCD tv

texts: I am searching for such a chip which has a usb input to connect a pen drive to it. The chip should have a HDMI output (or any other suitable output) to display on a LCD tv. For example, I have a movie stored in a pen drive which is connected to the chip and that chip's output is given to the LCD tv. On start up the chip should start playing the movie automatically on the tv. Please give me solutions for this requirement like name of such a chip, where can i get it, etc.


texts: How to consider lifecycle in PV power smoothing?

texts:
I am planning to size Battery for Solar PV system by smoothing the PV output. Capacity size can be obtained by looking at Max charge/discharge needed to smooth the fluctuation.

This should make able to optimize Battery size thus reducing the capital cost. But in the case of annual cost, Battery life should be taken into consideration.

Can someone give a brief explanation on what to consider?


texts: LF356 integrator simulation using LTspice

texts: I used the LTpsice to simulate the feedback performance of a integrator circuit with op amp LF356 which is a JFET input op amp but I go strange results (see the image below).  The model of the LF356 was the Pspice model downloaded from the TI website (http://www.ti.com/product/LF356/toolssoftware).  For this circuit, if I understand correctly, the gain at the low frequency should be as high as the open loop gain of the op amp which is ~100 dB according to the datasheet while at the high frequency (before the secondary pole frequency) should be 20 dB.  However, from the simulation results, I only got something like 19 dB gain at low frequency and 15 dB at high frequency.  Just to verify that I didn't make any mistake when importing the op amp model, I did the same simulation with another op amp (OPA627) and the simulation results were reasonable (see image below).  All of this makes me wonder if there is anything wrong with the spice model of LF356 downloaded from the TI website (which seems not likely) or if there is something about this JFET input op amp I didn't understand (not suitable to use for integrator circuit).  I would appreciate if anybody could clarify this.


texts:
Currently, I am using a function generator to drive MOSFET with a 5V square wave. Now I need to rise frequency up to 14 MHz for educational purposes. Before I post an order for specific IC, I want to consult with more experienced people. This is my first time using a mos driver.

So, I need to drive only one fet. I found this driver

The datasheet states: Wide Input Supply Voltage Operating Range: -4.5V to 18V.
But later it reads, in Absolute Maximum Ratings: Input Voltage –5V to VDD + 0.3V
So wich is it,? As input, I consider a signal from a function generator, correct?

Also, on pin 1 and 8 is Vdd. I am guessing pin1 is for powering a chip and pin 8 for driving MOSFET. Correct me if I am wrong.

Matched Rise and Fall Times: 25 ns. Does it mean operating frequency of 50ns which is 20MHz?

Last question, if I feed input with 5V does the output equals input 5V or Vdd from pin8?


texts: Why aren't high-current ammeters protected with a fuse

texts:
Why is it that the low-current range on an ammeter (200mA) is fused and not the 20A range?

I recently lost a multimeter because I connected the ammeter in parallel with a power source by mistake.

All the ammeters I have lack a fuse on the 20A line, even the supposedly resilient ones in my university labs.


texts:
I recently purchased the Angry birds spinning toy which works like this. The hand crank basically rotates and from the power generated,Dissecting the product into various parts, I came across certain elements which I have failed to understand and seek to get more clarity into it:

Is there any power generation that is harvested through the turning mechanism that is utilised by this toy? I strongly suspect this because on close inspection, I could find magnet and a copper coil winding as shown below. I fail to understand how there is a relative flux difference which is used for power generation, as the whole top spins on its axis.
What do the recoil springs on the LED Driver circuit do?
There are three wires- yellow, red and green coming out from the battery. How are they used to charge/discharge the battery?


texts: How do I solder to a soldered overlay board?

texts:
I have several rather important circuits on breadboards that I want to move to solder overlay boards. Unfortunately, my project involves a lot of wires that need to plug into this board - and I cannot move the board or get access to the underside with all the wires in place.

Accordingly, I want to be able to solder wires into holes from the top of the solder overlay board. What's the best way to do this?


texts:
I am using an arduino to measure the battery level of a LiPo battery using a simple voltage divider and performing an analogue read of the battery level (against an internal 1.1V reference). My question is if this method of reading battery level will work to indicate the battery level during charging? or will this only work when not charging?

If so how can i also indicate the battery level while charging?


texts: Isolate a digital signal that changes its amplitude

texts:
I have to isolate a digital signal that has the following characteristics:

frequency: between 1 and 1000 Hz
amplitude pk-pk: 12V
offset: 0-6V

With "offset" I mean the actual voltage may change from 0-12V to 6-18V.
It seems, but I cannot know this for 100% sure that the output circuit is something like an npn bjt with a 5k pull-up resistor (and something else, otherwise I cannot explain this offset, measured with an oscilloscope).

The goal is to isolate it with an optocoupler and get a steady 0-12V signal.

Here my attempt:

simulate this circuit – Schematic created using CircuitLab

Because I have to replicate this section x16 times, I wonder if there's a smarter way to do the same using less components.


texts: Send signal from one output connected to multiple modules

texts:
Hi I am learning verilog and I am trying to find an answer if I have an output of type reg in a main module connected to the inputs of multiple modules, how in verilog would I specify which module I want the signal from the reg output to go to based on some condition.

    module one(a,b)

        input a;
        output b;
        wire a,b;

        //do something
        assign b = some value;

    endmodule

    module two (a,b)

        input a;
        output b;
        wire a,b;

        //do something
        assign b = some value;

    endmodule

    module main(c)

        output c;
        input d;

        reg c;
        reg d;

        one mod1 (.a(c), .b(d));
        two mod2 (.a(c), .b(d));

            always(sens list)
            begin

                if(condition)
                    //send reg value to mod1;
                else
                    //send reg value to mod2;

            end

    endmodule

I would think to have the output of the main module AND'ed with a signal specific to that module that I want to send it to based on some condition, but I am unsure of how to translate that into verilog. Thanks!


texts:
How can one control on/off and direction for a single phase reversing AC motor using relays? I have wired an AC motor correctly with 5 wires: green (ground), red (live), black (neutral), blue (coil 1), and yellow (coil 2).
If AC current is passed between [red+blue] and [black+yellow] it spins clockwise.
If AC current is passed between [red+yellow] and [black+blue] it spins counterclockwise.
I understand that speed cannot be controlled with relays and do not need that. For a DC motor, I can use two relays and diodes to achieve this functionality as outlined by this question How to use a flyback diode on a +/-12V motor
If it helps, this is the motor I am using https://www.baldor.com/catalog/L3503#tab=%22drawings%22, but I think the suggestion should be generalizable (please explain if I am wrong and the suggestion is motor specific).


texts: Six wires on one side of a transmission line

texts: I dont know if any of you have observed that a transmission pole carrying high voltage transmission line and big insulators have in a total of 12 conducting wires! 6 wires on one side and other six wires on the other side of the pole. Can anyone tell me why is that so?