texts: How does the speed of a script influence polling frequency?

texts:
I don't fully understand how the frequency of a script running on a MCU influences measurements of a sensor via polling. For example:

I have an ADXL345 chip, and in my (Arduino) code I've set the datarate of the chip to be 400 Hz. This means it should be producing 400 measurements every second.

Now the Arduino script I am writing runs at a certain speed as well (on the MCU), and therefore the function that 'polls' the ADXL345 is called with the frequency at which the 'main' MCU script runs. If I add a while loop, I can regulate the frequency of the main script and put it at e.g. 400 Hz (or alternatively I can add a timer for the individual function to be called at certain time intervals).

However, what happens if the frequency of the script is lower or higher than the datarate I have selected for the ADXL345 data output rate? If the script frequency is lower, are some ADXL 345 measurements destroyed or is there a delay? And if the script frequency is higher, will some of the measurements be duplicated (to fill in the missing gaps?) And is there a good way to go about this, to regulate the polling frequency in an optimal way?

I guess this question is independent of which protocol I use, but for further clarity it's SPI.

Does anyone know the answer or could point me to some good explanation/literature?


texts: Automatically switch between household power and inverter when power is lost?

texts: I’m setting up a backup system for my home’s sump pump. Rather than deal with the installation/maintenance of a separate backup pump I’ve decided to go with an inverter & 12v battery setup. My sump pump claims 9A draw, so I purchased a 2000W inverter & a battery. What I didn’t realize is that the inverter is only for providing constant power, but does not switch between power sources. The inverter has a standard AC outlet on it for plugging in a load. What I think I’m looking for is a relay that switches between two 120V power sources and sends the power to a single load. I’ve tried searching, but I feel like I might be missing the right terms to narrow down to what I’m looking for. Any tips on finding a relay like this? Does such a thing exist?


texts: We have a BLDC motor of the following specifications , and I wanted to ask that :- If the Peak Torque lasts for about 10 seconds once activated, then after what time interval can it be activated again?


texts: How do I program an atmega8 using Arduino Uno

texts:
Possible Duplicate:
  Arduino as AVR Programmer

I am trying to upload a program to a separate chip Atmage8 on a breadboard. Do I just need to connect some wires from the Uno to the ISP of the breadboard mounted chip? Then I think I need something called AVRDUDE but not sure as I have also found this https://github.com/WestfW/OptiLoader Can some one give me some clear instructions on how to do this properly. Thanks

I need to upload also the timerone script i.e

ifndef TIMERONE_cpp
define TIMERONE_cpp

include "TimerOne.h"


texts: Deriving PI controller transfer function when input is reversed

texts:
I'm developing the compensator for the linear DC Bench Power Supply I'm
designing.

As I've come to deriving the transfer function for the op amp-based
compensator, I realize I've been depending on a short-cut for that and now need
to understand the principles underlying the short-cut. Here's my conundrum:

A typical PI compensator (for a switching power supply at least) looks like this:

The transfer function can be derived by combining s-domain impedances with the
standard gain equation for an inverting op amp:

$$G(s) = - \frac{Z_f}{Z_i}$$

to get:

$$G(s) = - \frac{1+sR_2C_1}{sR_1C_1}$$

A more detailed derivation is shown in this earlier question I asked on this same project, for anyone interested in the step-by-step.

However, my compensator circuit is a bit different:

Note that S+ is ground and S- is the output. Overall, the circuit is an
inverting DC operational(-ish) amplifier, of which the LF411 is only part.

Because the output (S-) is inverted (-180°), the error signal is coupled to the
non-inverting input of the op amp. The local feedback loop still connects to
the inverting input, as it must.

So my question is: "How do I derive the transfer function of this compensator, given its input is split from its local feedback?"

I suppose it's possible the same procedure works, and only involves R1, C1, and
R2. But if that's true, I don't know how to explain why \$R_3\$, \$R_{vref}\$, and
\${VR}_{prog}\$ are not involved.

Can you help me understand the steps of reasoning to get to the transfer
function when the error signal input is split from the "normal" input to the
inverting amplifier?


texts: finding polarization of radiated far-zone electric field

texts:
I am given a question in which I have to find the polarization of the radiated far-zone electric fields when phi is 0 and 90. Why are the following formulas used respectively?
For phi = 0
$$     E_\theta = jn\frac{kI_0le^{-jkr}}{4\pi r} cos\theta               $$

For phi = 90

$$     E_\theta = jn\frac{kI_0le^{-jkr}}{4\pi r} . 1               $$


texts: What does a slash over a line in a circuit diagram mean?

texts: In the following diagram (from William Stallings, Computer Organization and Architecture), what does the slash '/' over the lines mean? E.g. there is a / over the s + w line on the top, why is it there and what does it mean?


texts:
I am making a contact less tachometer based on magnets .I am using msp430g2253 micro controller and HD44780 lcd.
I have done certain calculations for calculating rpm in the main code and now i want the values to be printed on the LCD but here i am not able to understand how to do it.

rpm = cycles*60/1000000; //This is what i want to print on the lcd i.e the value stored
                           in variable rpm

The code of lcd which i have used takes only *char as input , so i am not able to find out a way to convert the integer to char(I know it sounds lame but ...stilll.....) and print it on lcd.

The code below is a part of the whole lcd code, but this is used to print on lcd.

void lcdprint(char *text)
{
char *c;
c = text;
while((c !=0) && (*c!=0))
{
    SendByte(*c , dat);
    c++;
}
}

So how should i modify this code to print the integer value on lcd. Do i need to create a function for this purpose or what??

Some details:
1.Microcontroller used : MSP430G2253
2.Software for coding: Code composer studio (CCS)
3.LCD: HD44780


texts:
I need to output 8-bit integers via parallel (i.e. using 8 pins on the same port) at 1024hz. From what I can see, I have two options:

1) Write to each pin individually using DigitalOut.

2) Avoid the mbed library altogether, and do something like:

void sendByte(char byte)
{
    DataPort|= (((byte >>0x00) & 0x01) << LCD_D0);
    DataPort|= (((byte >>0x01) & 0x01) << LCD_D1);
    DataPort|= (((byte >>0x02) & 0x01) << LCD_D2);
    DataPort|= (((byte >>0x03) & 0x01) << LCD_D3);
    DataPort|= (((byte >>0x04) & 0x01) << LCD_D4);
    DataPort|= (((byte >>0x05) & 0x01) << LCD_D5);
    DataPort|= (((byte >>0x06) & 0x01) << LCD_D6);
    DataPort|= (((byte >>0x07) & 0x01) << LCD_D7);
}

I've heard that DigitalOut is rather slow, although I'm not sure of what frequency it can handle. Is the second option likely to be faster? Can anyone compare the two methods?

SIDE QUESTION:
I'll be using the output with a DAC to produce an analog signal. Will I need to use a buffer in between, or are the pins guaranteed to output simultaneously?


texts: I recently bought This MCU and in another question asked how I could flash it. The response was to use a USB to serial Connector (which I wanted to find on newark.com but could not). I wanted to know if I could solder This microUSB female connector to the io pins of my MCU and be able to flash the MCU to over microUSB from my raspberry pi. Can I?


texts: Wireless signal reflection/absorption on different materials

texts:
I'm trying to understand the characteristics of RF signals/waves in different environments. I am wondering if there is any data out there regarding how much a wireless signal reflect from an object or get absorbed by it.

Would this be tabulated under common items such as metals, wood, and concrete? (I'm less concerned with water) I'm mainly interested in 2.45 Ghz, but it might be interesting to look at other frequencies.

If no one knows of a tabulated form, here is the alternative question:
What causes RF waves to reflect or absorb? Does the reflective/absorptive property of RF waves act similarly to light properties? Are permittivity and permeability in electromagnetism causing the reflection/absorption? If yes to the last question, could you elaborate how it is (since Wikipedia only describes when the object is the medium forming the waves, not as the receiver)?


texts: As Beta changes from BJT to another, Vp and Idss also change from a JFET to another, but how can you assure that when the JFET changes, the Q-point does no change greatly?


texts: I always see the option for E-testing when sending PCB's off to a fab house. I gather it is an electrical test to test all the connections. But how do they do it? They don't have my schematic! Only gerbers? And surely it is done by machine?


texts: Can a faulty TVS diode cause power supply problems?

texts:
<img src="https://i.stack.imgur.com/FlUte.jpg" alt="The mosfet is to
Top left above Q111. The TVS is the big SMD next to D100." />
I have no power feeding the mosfet base with positive signal to switch on the relay that powers the ecu. The mosfet is to the top left above Q111. The TVS is the big SMD next to D100. The fault is intermittent and sometimes permanent. The ecu failed after 2 years and wasn't working until I scraped off the conformal coating and it worked for a month and now it's stopped working again. The ecu wasn't communicating due to the mosfet 2n7002 not getting a positive base voltage to feed negative power to the relay. When I removed the mosfet, I got 4.8v base so I soldered a new mosfet and it worked for 1 session (10 mins) of testing. The next day it didn't work.


texts: Why isn't this LM2917 circuit working to turn off a transistor?

texts:
It was suggested to me that I should post a new question (original question here: Minimal Hall effect sensor circuit to keep something off after certain RPM achieved). The below schematic is for turning off the transistor Q2 once a certain RPM is achieved. I do not have an oscilloscope, only a multimeter to test. The sensor I'm using for U2 in the schematic is one of these: Hall effect sensor Unfortunately there is no datasheet for it, but it is a very common NPN sensor.

I confirmed that sensor works by placing a magnet in front of it and away from it.

I'm using a 200K pot for R1 and R2 to set a low RPM threshold, and placed a magnet on the end of my drill to spin it, and no matter what, the transistor Q2 doesn't turn off like it should.

I'd appreciate any help as to help me get this circuit working.


texts: Hobby oscilloscope based on AVR. How to remove op-amp noise?

texts:
I'm building a hobby oscilloscope on an ATmega16 microcontroller. The main problem is that I receive a large amount of noise while measuring the signal. I used LF353 amplifiers to shift voltage and I suspect that they might be causing the noise.

This is the schematic with an op-amp. The signal goes to 'Input' and the 'Output' goes directly to the microcontroller's ADC pin.

And this is the signal that I'm getting when the leads are not connected:


texts: How to isolate coefficiets from complex fourier series?

texts:
I have to find yn/xn ratio.
From the circuit analysis i found out transfer function Uout//Uin = . I am having hard time trying to isolate two coefficients of two complex fourier Series. Any help is highly appreciated. Thank you.


texts: Retrieving data from Agilent 34401A Digital Multimeter over the RS232 interface

texts:
I want to interface Agilent 34401A Digital Multimeter over the RS232 interface. The settings (baud rate, parity, number of start and stop bits) are set to be same on multimeter, pc (device manager) and on the application that I use for terminal. Programming language is SCPI.

I successfully control the multimeter, that is I execute the commands such as: syst:rem; :meas:volt:dc? 10, 0.003; :conf:volt:dc 10, 0.003; :sens:volt:dc:rang 100; but I get no response over RS232 interface from my multimeter.

For example when I execute the command :meas:volt:dc? 10, 0.003; the measurement is performed and the voltage is displayed on multimeter’s display, but the value is not sent over RS232 to my terminal. No response what so ever.

In the manual for the multimeter there is a statement after each command -- “bus enter statement". Relevant extract provided below.

I could not find any reference or explanation what is meant by this.
Does a special command exist for retrieving data from the multimeter?

:read? makes no effect on the multimeter.

Useful hint for someone who is also trying to set up RS232 communication with this device: Even if in the manual the colon preceding the SCIP command is not given, the multimeter returns “unknows header” error if it is not present.


texts: Please help me identify this odd-looking component

texts:
When opening up a car alarm system I found this strange-looking component. I thought that it could be something which is light dependent, but the entire board is enclosed in a black plastic box and the alarm should trigger before the thief reaches the depths of the electric system and thinks of opening it.

Here are some photos:

What component is this?


texts: Purpose of capacitors in MOSFET driver circuit

texts:
I'm designing a motor driver circuit which can only operate in one direction - thus is fairly simple:

Bottom most line is sourcing 5V to VDD and the one above is the PWM drive signal. This looks way too simple to me and I just know that's not how things work in electronics. I found this example of an H bridge driver where I saw there are 100nF capacitors on both drivers as well as C1 between the motor and its source voltage.

source
What is the purpose of those capacitors and are they mandatory in such application?


texts:
The circuit below is about as simple as it gets, yet it's not behaving like I expect. V3 is a 3.3Vpp square wave going into the base of the transistor, so I would expect to see V_Out be high when V3 is low and vice-versa. Basically an inversion circuit.

More importantly, I would expect this circuit to be fast enough to keep up with the 400 kHz square wave. A 2222 might have 25 pf of capacitance at its input, which gives a 25 ns time constant with R2.

simulate this circuit – Schematic created using CircuitLab

Yet in simulation I see V_Base taking awhile to react on the falling edge of V_In:

Unfortunately this seems to keep V_Out on much longer than I'd like. See V_In graphed against V_out (keep in mind the inversion):

I can improve the "stretching" by lowering R2 or R3 and speeding up the circuit, but from a first-order view I don't see why I should have to. I also don't understand why only one edge is slow. The base-emitter capacitance of Q1 couldn't account for this, could it? Is there a second-order effect I'm missing?

P.S. I know it's weird to have a common-emitter circuit where the base transistor is smaller than the emitter transistor. Let's just call this an academic exercise.


texts: Looking for the manufacturer of this IC (Identification required by logo)

texts:
I have several different ICs laying around with the same manufacturer icon marked on top of the ICs. I searched on several IC-logo web sites, but so far, I couldn't identify the manufacturer.

Do you know who is the manufacturer of this IC?

Thank you
!


texts: Is it necessary to separate DC power cables and data cables?

texts:
I have had this discussion with my colleague earlier. A DC power supply is non-alternating, so the magnetic field a DC power wire generates is constant (is it?). Now, I know the rule is to separate power cables and data cables, but I'm assuming that's when it comes to AC power. Is it the same rule when it comes to a regulated DC power supply?

We are using CAN bus twisted pair wires next to regulated DC power cables (12V and GND). I understand that CAN is immune to noise, but if you had a different data cable (let's say UART aka serial, or Ethernet), would the DC power cables have any impact? If so, why?


texts: Is there such a thing as a circuit that outputs 1 if the input is high-impedance, and 0 otherwise?

texts:
I am trying to design a circuit that outputs a logical 1 if the input is high-impedance, and a 0 otherwise.

Any idea how I might implement this?  I would prefer to use off-the-shelf parts (no programming).

Truth table:

I|O
---
X|1
0|0
1|0

I was thinking something along the lines of a pull up resistor with an NPN transistor.  Thoughts?


texts:
I designed this schematic for a power amplifier project at university.
The problem with it is the Bode plot, because as you can see on the Y-axis, it doesn't even reach 0 dB and frequencies reach up to 1 Terahertz.
I've been at it for 3 days, scouring the internet for information, so this is my last resort.
UPDATE:So i recallculated the resistor values aslo changed some transistors.
And the is the rusulting bode plot.It still does not meet my requerments(fb 25 Hz fh 25kHz).Maybe I am mising some capacitors or the gain is to high?


texts: GPS consideration for PCB with GSM (interference, setup etc)

texts:
I am working on a project which has a GSM and GPS on the same PCB (fairly near each other in an enclosure). Since I am not familiar with GPS I was wondering if any of you could give me some tips on this matter since I am going to create a new PCB design.

In my current prototype, I have a SIMCOM GSM module and the gp-635t gps. They are both in an enclsoure including antennas (gps antenna is integrated). What I experience is sometimes poor GSM and GPS connectivity and sometimes GPS doesn't get any fix (in the 2 minutes of time i allocate for it) and the GSM fails to send data sometimes.

Are the two modules interfering with each other?
How should I approach the new pcb design? Ideally I would like to have both gsm and gps on the same layer, is that a bad idea?
I read it is suggested the GPS to have its own ground plane?
Are GPS integrated antennas worse than external ones?
GSM have 2 types of antenna: internal and external . Is one better than the other? Ideally my application would require both to be hidden (inside the enclosure) but not if the quality will be awful.

I hope some of you guys who have experienced this before me can give me good tips in this regards.


texts: License dilemma Texas Instruments Code Composer v5 for Stellaris vs MSP430

texts:
As I read the screenshot below, I have to pick the license for Texas Instruments' Code Composer Studio v5 as follows:

option 4: to use with a LaunchPad MSP430
option 3: to use with a LaunchPad Stellaris

But I want to use CCSv5 for both Stellaris and MSP430. What license works best or do I have to create two installs, one for each?


texts: Poor load regulation with LT1074 switch mode

texts:
I have a personal project to make an adjustable switch mode lab power supply. I've used the LT1074HV switcher in standard buck regulator configuration. The end result mostly works except that with a 9V output, at 4A draw it drops down to 8.7V.

The inductor L1 is 330uH Bourns 2318-V-RC
http://nz.element14.com/bourns/2318-v-rc/inductor-toroid-v-330uh-15-5-2a/dp/1929761?Ntt=2318-V-rc

The output cap C1 is Rubycon 470uF/63V YXF a low ESR variety.

The switch diode MBR20100CT is a dual centre tapped diode but I'm only using one side (it was the item in stock at the time)

The regulator FB and Gnd pins are connected by separate wires to the output, so there is low current flowing.

It's only assembled on veroboard, not a PCB. I've tried to be tidy but distances are not as short as they could be on a PCB. Having checked all the other things I can, it seems like it must be due to construction issues, but I didn't think load regulation would be related to that, more like stability or transient response...


texts: What can the dsPIC do which the humble PIC microcontroller cannot do?

texts:
I have not used a DSP chip as of yet. All I know is that their architecture is such that they can carry out calculations quite fast, usually within a clock cycle, they have multiply-accumulate instructions in their instruction set and they have DMAs so the CPU does not have to waste precious time moving data around. I think there is more to it, but these are a few basic points.

I can see that Microchip has dsPIC which is their DSP chip line. Can't we just use a PIC18 or PIC32 which also has built in multipliers to do DSP as well? How is the dsPIC different from the normal PIC?

My main question is this, Why do we need to have something seperate and distinct called DSP chip and not integrate high precision floating point unit calculation capability on all the microcontrollers? Surely with the process technologies we have now, this should not take a lot of space.

Also, how do I know that I need to use a DSP chip in my project rather than a normal microcontroller>


texts: What is the difference between Machine and Time Cycle in 8085 microprocessor?

texts: I have search this topic but their I can not find any specific answer to this . So I need some specific answers .


texts: How can I limit the current drawn by a Li-Ion battery pack BMS?

texts:
I have a Li-Ion battery pack made with twelve 18650 in a 3S4P configuration, using an off the self Battery Management System (rated for 25A), that I purchased on aliexpress. I tried to charge it using a 5A, charger, at 12.6V, But the problem is, the BMS seems to max out the current supply and the charger is blown off. I have following questions:

Should I supply more than 12.6V to charge the pack? Will this reduce the current drawn?
Is there a way to limit the current drawn by the BMS circuit
externally?

Thanks!


texts: Inconsistent Output Voltage in DC-DC Buck Converter

texts:
I'm trying to implement the following tps54302 DC-DC buck converter, for a 5V 3A output:

All resistor values 1% tolerance, capacitors 5% tolerance, inductor 20% tolerance.

I'm testing with a bench top power supply at 12V and under a small load (~15 Ohm) output. I cannot figure out why the output voltage repeatedly drops from 5V to ~0.4V for extended periods of time (~40ms).

When testing smaller output currents (larger resistors), the frequency and duration of these voltage drops seemed to decrease.

For reference, the PCB Layout and FB pin. Note that the green traces underneath the regulator are currently not connected to anything.

As a final note, the application I am designing for is back powering a raspberry pi through its GPIO pins. When trying this, the raspberry pi begins to boot, then when the voltage drops (seemingly when current draw increases) it turns off and begins its boot again.

Here are scope shots of input voltage, switch node, and shunt resistor in series with the inductor (~1.5 ohm) respectively.


texts: Flyback transformer for offline switcher ac-dc PSU

texts:
I am designing a 5V 3A SMPS circuit using Viper22a (60 kHz switching frequency) and transformer design is turning out to be the most difficult part of it. Actual load will draw less than 10 watts but I chose to go for 15 W just to be on the safer side. (Let me know if I am making a mistake here)

I referred to AN4140 by Fairchild for quick core selection. In 10-20 watts section, it suggests these cores: EI22, EE19 and EPC19.

Then I talked to my local vendors about availability and I could find EE19, EPC17 and EFD20. I was able to find a Flyback Transformer design tool by ONsemi and I gave it a go for the suggested core and available cores. Tool looks like this:

Core data and calculated data according this sheet for various cores are as follows: (the only change required in excel sheet was core area Ae for different cores)

Yellow ones were suggested in AN4140 and white ones are what I am planning to go with. EE19 is suggested as well as available but I am rejecting it due to height considerations.

I do not have much experience with magnetics design so would like to get my calculations verified by someone who knows this stuff better than me.

I have these questions as well:

1) Which core will be more suited - EPC17 or EFD20?

2) Minimum secondary turns is coming out as 12-15. What turn count should I actually go with? Is double of what I am getting good enough? Ex - 24-30 turns.

Please suggest any other improvements that I can implement.


texts: MQTT subscription issue: The length of my received packet is always 19 characters

texts:
This is my first post here so bear with me if I accidentally didn't follow conventional standards here. Here's the issue:

I am using a teensy 3.2 and WINC1500 wifi breakout to play around with MQTT protocols. I am currently using the AdaFruit MQTT library, found https://github.com/adafruit/Adafruit_MQTT_Library, and I have configured my WIFI chip to successfully send and receive packets which I am able to see through MQTT.FX, a client data broker. The issue I have is regarding the subscribe function. When I receive a packet, I want to parse the information however, I only get back the message up to 19 characters. I assume this is some variable in the library that has been set. I unfortunately have searched and found the variable name, SUBSCRIPTIONDATALEN and increased it to hold more data. However, it doesn't change anything. Is there a hardware limitation to the size of a packet received? Or is the size of the message you send limited to the amount of memory you have available? Is there anyway I can increase it to encapsulate the whole message?

The string I want to parse is : {"target":"Lamp", "code":"lamp", "values": { "lampon":0, "brightness":100,"luminosity": 122}}

What I received back is : {"target":"Lamp", "c

Any suggestions would be very appreciated! Also would this topic matter fit better in the CS site or is it appropriate to be posted in this forum? Thank you very much!


texts:
I'm a novice in hardware design so sorry about my 'newbish' question.
I'm designing my first circuit that includes STM32L071KZU6 (datasheet) and I would like to know the 'worst' or maximum current consumption. I've seen this table in the datasheet:

According to the table, it says that the total current of all VDD power lines (source) is maximum of 105mA. It sounds too much for the microcontroller and also it says that it is for 'source'.

Am I missing something?


texts:
I have tryed look at other topics on here, but i cant understand what all they are talking about need something simple and to the point please.
So i got thease 3 watt LED chips, Forward V 2.2 And Forward Amps (Current) 700MA
I want to hook this up to a car battery. I tryed a resistor of 15ohm 1/2watt and i dint think about the wattage power coming in effect so it got hot in a hurry.
So a calculator reccomends 7.6 watt capable resistors. There expensive and hard to find and big. Is there any other way to get the voltage and current were i need it? Please use simple terms. Country Boy Here.


texts: What are the important design considerations when laying out a PCB?

texts:
After filling a bunch of breadboards with some successful experiments, I'm ready to start making PCBs and I'm wondering if there are any design considerations of which I need to be aware?

Some PCBs I've seen are spacious with long traces. On others, components are packed like sardines. Before I go packing a bunch of stuff into the minimum space possible on a PCB, are there any considerations apart from the ones listed below of which I need to be aware?

DETAIL: Since I'm using toner & cupric acid to etch the boards, I know I can't have crazy thin traces or spaces between them.

HEAT: I need to leave ample space for air circulation so I don't fry my circuit with heat buildup. However, I see this more a factor of enclosure (e.g., big enough to allow circulation or a fan if deemed necessary) and heatsink choices.

What else should I know?


texts: Help to determinate stability of Opamp Circuit

texts:
I have background in software but this time I need to build a circuit for scaling a signal from 15 to -15 VDC. At college I took some subjects on Electrical topics so I have read to remember, after that I finished with the next design:

I selected a Rail to Rail Opamp taking as reference the input voltage, slew rate and GBW = 1.1 MHz, my signals to amplify are square waves of maximum 1 KHz, the design is based on the next assumptions:

1) Voltage follower to match impedance.

2) Amplifier stage with G = 0.5 and I have added a capacitor of 180 pF to act as a low pass filter with cut frequency of around 177 Khz with this I have bandwidth to pass the enough harmonics for square waves and filter high frequencies.

3) Inverter again the signal.

However I am aware that stability is important when we work with Opamps but I don't remember how to interpret a bode plot. For this analysis I cut the amplifier portion of the design and got the bode plot without the capacitor, normal configuration for an inverting amplifier:

I got the next bode plot:

When I plot the response with the capacitor I got something different:

My questions are the next:

Is my procedure of only cutting the middle part of the design to analyze the signal ok? I am assuming that the other 2 circuits are stable due the gain is 1.

Is my circuit stable and suitable for my purposes?

Sorry if these are basic questions but Electrical Engineering is not my best skill, I hope you can help me to solve my doubts.


texts: Top GND flood and Stitching Vias vs. Via in pad to ground plane

texts:
I recently watched an Analog Devices youtube video which advocated for high speed PCB ground connections to be made with a via in pad to the ground plane, as opposed to a signal layer ground flood stitched to the bottom ground plane with vias. Then, I watched another video which advocated for a top ground flood with stitching vias spaced at lamba/20 (wavelength of highest signal frequency). Which approach is more effective? Please note that I am a student and cannot manufacture PCBs with blind and buried vias. I also do not have access to impedance controlled PCBs; the best I can do is FR408.

Here is a screen shot from the video, and a link to the video for those who are interested:

https://www.youtube.com/watch?v=6jrVZu7eqiw


texts: Communicating with I2C devices using an RTL8710

texts:
I've connected an RTL8710 (in "Rtlduino" form) to a MCP23008 (on a breadboard) via I2C as follows:

I'm using rustl8710 to program the RTL8710, which works fine and I've already hooked up a display via SPI without any issues.

I've got this code set up to test the MCP23008:

led1.write(DigitalValue::High);
let mut handle = i2c_t::default();
i2c_init(&mut handle as *mut i2c_t, PinName::PC_4, PinName::PC_5);
i2c_frequency(&mut handle as *mut i2c_t, 1000);
led2.write(DigitalValue::High);
if i2c_write(&mut handle as *mut i2c_t, 0x20, &[ 0x00, 0xff as i8, 0, 0, 0, 0, 0, 0, 0, 0, 0 ][0] as *const i8, 11, 1) != 1
{
    panic!("Byte write failed!");
}

led3.write(DigitalValue::High);
loop { }

Feel free to ignore all lines starting with led*, those simply pull some GPIO pins high to light up the 3 internal LEDs on the device so I can see if it works without using gdb.

Alternatively, this C code demonstrates the same problem:

#include "i2c_api.h"
#include "PinNames.h"

void main(void)
{
    ConfigDebugInfo = 0xffffffff;

    char data[] = { 0x00, 0xff, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
    i2c_t handle;
    i2c_init(&handle, PC_4, PC_5);
    i2c_frequency(&handle, 1000);
    i2c_write(&handle, 0x20, data, 11, 1);

    while(1) { }
}

Paste the code above in place of main in main.c and then flash and run the code using make && make flash && make debug. The code will never reach the while loop, and hang on i2c_write.

The code effectively does the same thing as this code in an Adafruit library for the MCP23008.

I2C set-up (first 5 lines) works, but when calling i2c_write the RTL8710 just hangs infinitely somewhere in a loop in RtkI2CSend_Patch () at component/soc/realtek/8195a/fwlib/src/hal_i2c.c:1324 (according to gdb)

The MCP23008 is working fine, I've successfully used that on an ATTiny85.

Other things that might be relevant:

PC_5 (aka GC5) is also connected to a button on the evaluation board, which pulls the pin high when it's not pressed.
The RTL8710 prints RTL8195A[HAL]: ISR 0 didb't bee register!!!␊ to the UART_LOG ports. This appears to be from a function that isn't available in source form so I'm not quite sure how I should interpret that.

What am I doing wrong?


texts: ATMega328P - How to protect application flash memory from reading by ISP

texts:
I created boot-loader code for reprogramming application section. I use Wiznet W5500 SPI to Ethernet chip, my goal is that only i can reprogram the device using LAN / WAN. The read write command is different from atmel's standard, so i assume that no one will know.
The problem is: How do i set the lock bits to prevent reading the application by ISP?


texts: Using 2 Tank Circuits to Determine the Position/Direction of a Wire

texts:
I am building a robot that uses 2 LC tank circuits with some gain and analog filtering to determine the position of a "Track Wire" that has an AC current of a specific frequency traveling vertically. The idea is to detect the wire and by using the difference in reading strengths between the two circuits, determine if the robot must turn left or right. I am trying to avoid simply having one tank circuit and having the robot "snake" left and right while aiming for the peak reading.
My problem is that even after calibrating the sensors I get a very strange effect as the robot nears the wire.

The issue I'm having is that the difference between the analog readings from the left and right sensors zeros out at 3 different orientations. At first I thought I had switched my right and left inputs but after doing some tests, using the very simplified logic of if(left sensor>right center){print left}else{print right} I found the detection arc to look like this picture below.

Is this because of the shape of the EMF from the track wire? Is there a reliable way to detect the direction of a wire using tank circuits or is there a better method?

edit: Updated the picture to show the direction of the robot and the positioning of the inductors.
edit 2: Also I forgot to mention that there is a peak detector prior to the analog input of the microcontroller. I have uploaded the full schematic (its the same circuit twice)


texts: Mono and Astable multivibrators not working when connected together

texts:
I have made a monostable multivibrator and an astable multivibrator using 555 timers using a popular circuit design found on the web.

The monostable (out via pin 3) is used to control the astable (via its pin 4).
When I push the momentary switch on the monostable the astable should flash two LED’s until the mono times out. And it works well  if I use seperate power supplies to each multivibrator. (The zero volt rails are commoned together).
However, when connected together to a single power supply as in the circuit below, the mono will no longer time. Holding the switch closed will operate the astable ok until the button is released.

They only seem to work together if I use separate power supplies for each multivibrator.

I have changed resister and cap values on the mono to no avail.
Any ideas or suggestions would be much appreciated.


texts: Clamp-biasing at JFET Gate in RF Circuits

texts:
Reading the book Communications Circuits by Clarke and Hess, I came upon a chapter entitled "Clamp-biased Square Law Device" (Chapter 4 - 4.9).

It took me a while to realize that they were referring to circuit examples that rely on an intrinsic diode behaviour at the gate of a JFET (as opposed to a diode added to the circuit - previous question).  Here are some images from the chapter:

Is this behaviour device specific? It is often assumed that this clamping behaviour begins at Vgs>0, is this generally true?

The reason I ask, is that I've worked with JFET oscillators with this exact gate configuration and I didn't see any significant clamping.  One circuit I built that springs to mind is the G3PDM Vackar:

UPDATE:
I wanted to be accurate in my assertion that I hadn't noticed any significant clamping, so I rebuilt the Vackar oscillator and made some measurements.

simulate this circuit – Schematic created using CircuitLab

With the circuit exactly as above the DC bias point at the FET gate was -0.3V and the peak-to-peak sine wave voltage at the gate was 3.6V.  That puts V1 as 1.8V and the tips of the positive half waves at 1.4V.

If I understand the Clarke & Hess chapter correctly, current leakage (like grid leakage in valves/tubes) through the gate at Vgs > 0 causes this clamp like behaviour and I was expecting the wave peaks to be closer to 0V (i.e., a lower DC bias).

That's why I asked if the JFET part had some influence over this behaviour or whether it was common to all JFETs.

Could it be that the relatively low value of C4 (a feature of the Vackar) is reducing an otherwise strong clamping effect?


texts: Change the frequency of AC voltage from 60 Hz to 2 Hz

texts:
I have Alternating Current 208 V single phase at 60 Hz and need to change it to Alternating Current 30 V at 2 Hz.

How would I do this?

This is for a plating application.


texts: Graphical equivalent to HD44780 LCD controller

texts:
The Hitachi HD44780 LCD controller is an extremely common character-mode LCD controller. Though I believe it is now discontinued, compatible controllers are used in many hobbyist and commercial grade LCD displays that are very widely and cheaply available. Interfacing instructions are also widely available.

I would like to know what an equivalent controller might be for graphical LCD displays, such as a 128x64 pixel display. Something widely and cheaply available to the hobbyist, that is reasonable to interface with from a MCU, either parallel or serial.

Possibilities include the KS0108 (parallel) and ST7565 (serial), but neither seem to be as popular as the HD44780.


texts:
Most of the interface devices have various flag bits (that can also raise interrupts if that functionality is provided) used to check the status of the device/operation.

Usually they are cleared by writing a '1' to said bit.

Just some questions regarding this ...

Why are they cleared by writing a 1? I mean if the flag is already set to 1 by the device, won't it make sense to clear it by writing a 0 to it?
Lets say i have a 8 bit status register with bits distributed as (picked from datasheet of NRF24L01+)

If bit 5 (TX_DS) gets set (ie. turns to 1) and I want to clear it by writing 1 to it, what value do I write to the register.


texts: Identify polarity of 1970's-era dipped tantalum capacitor

texts: Having found the shorted component, now I need to replace it. I'm familiar with dipped tantalum capacitors with painted stripes along one side but these have a dot or stripe up the middle and my Web search didn't help much. I've identified the part as 10uF 25V but I can't figure out which leg should be positive


texts: Do ALUs perform all/most N operations before running through the multiplexer?

texts:
I'm doing some self-study on hardware and currently implementing an ALU. The way I'm designing it is such that I have an N:1 MUX (N inputs yield a single output (16 bit number) based on selector bits). I feed in 2 16-bit numbers with a series of control bits to get my output.

My question is that I have a bunch of gates that execute before they hit the MUX and then the MUX says "based on these control bits I'll output this calculation". Just wondering if it is inefficient to execute all these operations even if they aren't used/outputted.

For example, if I simply want to negate A, the circuit will still perform other arithmetic operations despite not using them at all in the final result. It seems like it would increase the time to get the desired result since you're running through more gates.


texts: How to measure distance/position accurately?

texts:
I am wondering if there is a way to measure distance between two movable points (e.g., the first point is on the hand and the second point is on the back of the human body).

I was looking at different types of technologies. I found ultrasonic sensors but those need a reflective object and this does not work with my idea. I thought about separating the transmitter and the receiver but there is the human body (hip) between those points and it can not be face to face. I considered technology based on magnetic fields so it can be measured regardless of obstacles or motion but I did not find anything close to what I want. And for infrared it needs to detect some object.

Is there any technology that can help me achieve this type of requirement?


texts: How to generate an interrupt on a MCU when a specific frequency sound is made

texts:
I'd like to use a microphone to generate an interrupt on a MCU when a sound with a given frequency is emitted nearby.

I thought using an LRC pass-band filter, coupled with an Op-Amp whose output voltage would be connected to the interrupt pin of the MCU.

Do you think that would work? Any better/more reliable ideas?

This a recording of the FFT of our signal. The record has been made in some representative noisy environment. Our signal has a frequency of 18.5 kHz. Ideally I'd like the interrupt to be triggered within a few hundreds of ms.


texts: Why is induced EMF of an inductor considered as average voltage and not RMS or maximum?

texts:
So my professor discussed to us about induced EMF of an inductor and mentioned that it is an average value and not maximum or RMS if you were to consider which type of voltage it is from the different types of AC voltages. I want to ask, why is this so? It really gets confusing since usually in textbooks they use the small letter e, and I associate that with the maximum value in time domain equations of instantaneous voltage, \$ e = E_msin(wt + θ) \$.
Another additional question is that, should you never assume the category of a quantity based on associated notations? Like for example, although the small e is commonly used for induced EMF you have to know that it is an average value through studying because most textbooks won't use a notation such as \$ E_{ave} \$ just to point that out.


texts: Is everything on a computer represented simply by just "voltages"?

texts:
I am a developer, yes, but there's still some mystery in the deep, dark depths of hardware engineering, system programming, and many other factors that darken the wood.

I know that from the boot loader the CPU must fetch the instructions, perform some I/O, do some MMIO/port I/O, arithmetic, etc.

The machine code is represented in binary or hexadecimal numbers, but implemented on the circuit as high and low voltages, states, or just "bits". That would entail that everything, from the firmware to shut down on an operating system, is all just flip-flop voltages carrying out electrical circuit operations that, in turn, drive the CPU, data, and other peripherals to perform the operations necessary for the computer to be fully used in all parts.

Is this correct or incorrect(i.e., is any part of the computing, hardware, or otherwise software not implemented in voltages under microcode from machine code?)

Hope the question isn't vague, and please let me know if I'm wrong.


texts:
We have a standard SMD 0603 capacitor kit from that I picked a capacitor for use in a 868MHz Antenna matching circuit. I picked this 3.3pF capacitor from the kit.

The Q is listed a 1MHz, but I read somewhere that this value is not valid at 868MHz nor can the ESR be calculated from it at 868MHz.

But nowhere in the datasheet can I find the expected ESR or Q at 868MHz, so is this a good choice for 868MHz. ?


texts: How to get frequency of Angelcare baby monitor?

texts:
Angelcare baby monitor is a device, which is monitoring if the baby is breathing and whether the noise level is above some level. This information is sent to the wireless device. I want to show this information elsewhere on my web, so I was thinking about extracting it from data emitted by baby monitor.

My question is, is there any possibility how to get the frequency that baby monitor is using?

UPDATE1: It's AC403-D (D stands for german market). I read in manual Transmission from the Nursery Unit to the Parent Unit is made on the 864 MHz frequency in Europe. So if I use Channel 7, I cannot say which frequency is that either way, right?


texts: I got a weird question in a circuits analysis test today that asked for the thevenin equivalent across a current source and not a load. Is it valid to ask for the thevenin equivalent across a current source? If so, do you leave or take out the source when calculating the thevenin voltage?


texts: In SystemVerilog, must nets be declared with the **logic** data type?

texts:
I'm reading Sutherland's "RTL Modeling with SystemVerilog ..." book. On pages 77 and 79 he makes the following claims respectively:

  The data type must be the keyword logic, which can be specified explicitly or implicitly inferred.

And

  Nets are declared by specifying a net type and an optional data type. The data type must be the 4-state logic data type, or a user-defined type derived from 4-state logic data types.

However, neither verilator 3.874 nor Vivado 2018.1 have any issues compiling/linting the following code snippet:

module foo
(input  wire  logic should_be_fine,
 output uwire bit   nets_can_only_be_logic);

  assign nets_can_only_be_logic = should_be_fine;

endmodule: foo

With my current understanding, bit is a 2-state data type different from logic, so the tools should at least warn that a net type cannot be declared with that data type. What gives?


texts: I'm trying to create a square wave form from a single AA battery, say 1v. I came across an IC which is essentially a low voltage 555 timer: Semtech SX8122 however it is marked obsolete. I would like to be able to adjust the frequency from 1-10khz. Crystal oscillators seem to be above this range. Are there any other simple circuits or ICs that can operate at this voltage?


texts: Measuring individual Voltage of the connected solar panel in series using I2C Protocol having GND in common as this get short circuited

texts:
I was stuck in a situation when i was measuring solar panels connected in series using I2C communication protocol. The common ground between the system makes the panel disconnected making a short loop.
As i am new to this community please help in this regard.
image of connection https://imgur.com/a/dazZyga

i used voltage divider circuit with ATTiny85 as slave which measures individual panel voltage and communicates to master unit through I2C Protocol.

The problem is that the Ground of solar panel and the I2C are common which is making other panels out from the system.
I get reading of 12Volts in first panel and 0 Volts in other pannel.

What would be the best way to measure individual voltage and communicate to master unit.

i searched for operational and differential amplifier but not able to get it.
Kindly enlighten me in this aspect as i am new to electronics as my core is software development and product design.


texts:
I came across the following circuit in my text book:

Summary of the explanation given in my text book: When control input Q3 is low, Q1 is on and output is HI. When control input Q3 is high, Q2 is on and the output is forced LO. D1 is necessary to insure that Q1 is off, when Q2 is turned on. R1 is necessary to limit the transient current when changing states (because bipolar transistors turn on more quickly than they turn off).

I can't seem to figure out how the control input being low or high results in the output states it does. Would someone be able to walk me through the logic? Basically what would the voltages be at the intermediate points between input and output?

Thanks.


texts: Why is input resistance parallel with the base of BJT?

texts: I'm solving for the third stage. The resistance looking into the base of Q7 is taken between its base terminal and ground as follows during small signal analysis for single end gain of Second Stage Amplifier. Can some elaborate on why the Input Resistance of Q7 taken like this.


texts: Precision angle (0.5° or better) with a motor

texts:
For a project, I am using a Hall effect absolute rotary encoder (AS5048B from AMS: http://www.ams.com/eng/Products/Position-Sensors/Magnetic-Rotary-Position-Sensors/AS5048B). It claims to have 14-bit resolution, but I need to prove the precision is at least 0.5° (required for my project). In order to prove it, I was thinking of using a motor (I was more specifically thinking about servos or stepper motors) to precisely position the magnet, then read the sensor value and compare it with the angle imposed to the motor.

However I don't know how to achieve such a high precision level with a limited budget. Is it worth it to invest in a $20+ servo (like this one http://www.tohobby.com/high-precision-tr213-servo-180-degree-rotation-13kg-accuracy-of-0-5-degrees.html)? Should I use a stepper motor with a larger step than my resolution and use gearing to obtain such a small angular precision? Is there a way to achieve this with a 'normal' DC motor?


texts: Using LCD and other modules with external regulated source and common ground

texts:
I am designing a circuit where I want to interface various modules with Arduino Mega. The way I want to do it is use an external regulated power source for the individual modules, instead of powering the devices through the microcontroller.
For understanding purposes, I am using a 16x2 HD44780 LCD as an example, as shown in the image below. I am following the method of grounding, as explained in this link, where grounds of different source are connected together.
However, in my case I am powering the Arduino Mega through an LM2596 buck converter, which is connected to a 12 V supply and outputs 7-7.5 V. The output of the LM2596 is further regulated through a 7805 to supply the LCD with 5 V.
Since the power source for the Arduino Mega and LCD are the same, do we have to connect the Arduino pin GND to the 7805's GND, as highlighted in the image?

PS. I am powering the Arduino through the DC jack, that's why I have shown a single connection to the microcontroller.


texts:
I'm working through the excellent text on SMPS design "Switching Power Supplies A to Z", by Sanjaya Maniktala.  Right now I'm reading the section on the feedback loop and stabilization.  As a first-order rule of thumb to achieve stability, Mr. Maniktala suggests that the loop gain transfer function of the switcher intersect the 0 dB point at approximately 1/6th the switching frequency, with a slope of -1.  To achieve this, one needs a compensation network transfer function that has a pole at the origin, and at least two zeros to cancel the double pole of the switcher's equivalent LC output network.

A type 2 compensation network consists of a pole at zero, a pole, and a zero.  Supposedly, the zero of the compensation netowrk plus the zero created in the loop transfer function by the output capacitor ESR is used to cancel the double pole created by the equivalent output network.  However, in one of the diagrams the author suggests the Type 2 compensation be set up this way: set the compensation network zero at the LC pole, and set the compensation network pole at the approximate position of the ESR zero.

I'm not sure I understand how this will work.  The pole at zero gives a slope of -1.  Plus the LC double pole, gives a slope of -3.  The compensation zero at the LC pole location then gives a -2...but if the ESR zero is then cancelled with a pole in the compensation network, how does one obtain the required -1 slope?


texts:
I'm having trouble choosing a wire gauge for a project I am working on that uses high amperage (100A) at 14.8V. From what I have read here, I think have to use at least 6 AWG to handle it.

What's confusing is that I also have a hall sensor rated for 200A that only uses 10 Gauge wire. Is it ok to use the higher (ie. thinner wire) gauge when working with shorter distances? Or will the hall sensor wires burn up when they exceed 55 A?

My project may consume up to 1480 W  of power from a battery I have. If I am only running short distances (if this makes any difference at all) of about 20 - 30 cm is is safe to use the thinner 10 AWG wire? If not, which wire should I be using?

I am very new to electronics but I am willing to learn. Please don't hesitate to ask me to elaborate on anything.

[EDIT]
My hall sensor:
http://www.mauch-electronic.com/50a-100a-200a-hall-sensor


texts:
Please excuse me if my question is very naive or broad. I just wanted to get some direction. I didn't know how else to ask for help.

I am working on Analog electronics and MCUs. It seems to be manageable with my knowledge. I am looking for a job change but many companies are asking if I have experience in High Speed domain/FPGA and DDR.
Unfortunately, I do not have experience in any of those domains and my current work doesn't involve me in working at those technologies.

I have tried e-learning websites like Coursera and other sites like codementor, But they also don't seem to have that content. I don't know where to start to learn these things.

Can someone help me with this? Is there any video lectures that I may have missed out to look for. I agree, that we can learn all these while working hands-on, but just asking if there's a possibility to learn the theory of this. Like some PDF material, App note, video lectures or something.
As I said, please excuse me for this very broad question. I had no help elsewhere. I specifically would like to start learning about DDR and FPGAs.

Thanks


texts: ESD protection on a solenoid driver circuit

texts:
I have a breadboard circuit that controls some solenoid valves and am trying to move it to a PCB along with improving it for ESD and EMI.

This is the circuit I have on the breadboard that I want to add ESD protection to:

Should I add the TVS diodes before or after the flyback diode?

So far, my thinking is that I should put them after because I want the coil discharge current to go through the flyback diode (which can sustain that current steady-state) instead of the TVS diodes.

Like this:

Clarifications:

Everything below the blue line is on one board.  Everything above the blue line is off board.  There's a connector and a few feet of wire in between the two.
I'm mainly worried about ESD damaging the FET when people touch the connector to plug or unplug the cable.  The only thing on the +12V net is more copies of this circuit for additional valves, so I don't think there's anything else sensitive there.

Basically my question is whether the left or right layout for the diodes better and why:


texts: How to find the power dissapation of a resistor

texts:
I am attempting to repair a circuit (DC-AC inverter) and have incountered a resistor with discolouration.

The measurements indicte a resistance of 1.5Mohms or usually OL leading me to belive the resistor is dead.

Would i be correct in thinking that from the colour bands, the resistor should be 310ohms?

Also, is its size because of the power dissipation of this particular resistor?

I have checked the componants within the circuit as follows

In order to find the power dissipation of the resistor i have used ohms law as follows;

Does this look correct or am i missing somthing fundamental?

Many thanks
Tony


texts:
I want to work in HMI domain and have started learning it.

In first stage I want to develop QT GUI based touchscreen application for ARM9 board.
Can anyone please suggest how to go for it and any budget ARM9 Dev board with integrated touchscreen lcd for this purpose? I want to use opensource platform as much as possible.

I know I can do it with more ease on an ARM board which support some OS like (say) embedded linux or may be rasberry pi with java or QT based GUI. But I do not want to use OS rather want to develop just a simple touch screen GUI application to (say) turn a LED on the ARM board (without running any OS).

My next step of learning will be using touch screen GUI, Rasberry PI with raspbian, where I have already found numerous resources Online.


texts:
My schematic

The components

BSN20 is a N-channel enhancement mode field-effect transistor (datasheet)
IRF7416 is a HEXFET power MOSFET (datasheet)

This is a part of a project in which the line into R2 comes from the PWM of an ATtiny88 (datasheet).

The R2 is set as an output from the ATtiny88, at first the heater line was High all the time when R2 was toggled (PWM).

When attempting to debug the hardware I found that if I placed flux or isopropyl alcohol across the line to R2 (from the ATtiny88) to ground, the heater line would toggle as expected (it took longer than it sounds to come to this conclusion).

In further research I found this webpage which indicated I may need a resistor to help pull down the gate pin of BSN20.  At the time I only had a diode so I placed it with the "flat" side to the gate and the "triangle" side to ground and it made it work.

Questions

My three questions are:

In an ideal circuit should my design work?
In a real circuit was my mistake that I needed a Mega Ohm plus resistor between the gate and ground to make sure the gate went to ground?
Is the diode working as a hack, such that it provides a few Mega Ohm resistance with the way I placed it in my circuit?

In the long run I'd like to turn my DIY prototype into a produced circuit board.  I have a computer science background not EE and would like to know what's going on and where I made my mistakes so that I can produce a valid design.

One more question

With more time to debug, i found one more variable. the voltage on the ground line in relation to the LDO regulator and at the leg of the source pin of BSN20 is reading 7.3mV. The voltage at several points across the ground trace showed different values. So one finial question. This seems to be either bad board design and/or more-likely a flux and other dirt under some of the chips acting like resistors pulling up the ground line. So...

Why is the diode is working for me?

Mohm resistance
when the MCU sets the pin to ground its pulling the local ground line down to match the MCU in other words causing ~0 volts between the gate and the source.


texts: BJT Voltage Divider Bias Circuit Theoretical/Ideal Model Help ..LTSPICE?

texts:
simulate this circuit – Schematic created using CircuitLab

I've been trying to study BJT Voltage Divider Bias Circuits.  In particular, as they relate to their active region, amplification, and operation in getting a crystal to oscillate.  I've followed a video and saw that the node labelled 2.452 below is really 2.6024 in calcs I match.  LT spice says its 2.4922.  Why all the variation, I am using a beta of 200.  I followed equations in the following video...

https://www.youtube.com/watch?v=zTyuzHokWyA&index=4&list=PL4651816D92AB6B2B

I believe they are correct.  I wish to get at exact currents and voltages but cannot match to ltspice or even the sim below.  I wish to look at things theoritical and ignore any time or heat dependent ramp up time.

The video I watched (and hopefully learned correctly from) would break the circuit below to a thevenin voltage source and resistance on the circuit that biases the 3904 transistor.

It arrives at currents and voltages by the following breakdown...

Where Re is R4

Vth = R2*8/(R1+R2)

Rth = R1 parallel R2

Vth  - IbRth -Vbe -IeRe = 0

Vth - IbRth -Vbe -(B+1)IbRC = 0

Ib = ( Vth - Vbe )  / ( Rth + (B+1)Re )

Vcc - IcRc - Vce -IeRe = 0

Ib = BIb

Ie = (B+1)Ib

He made the approx that Ie is equal to Ic in one of the later lines.

In any case, I've got very comfortable with his explanation, but not been able to duplicate the results in LTSpice or below.

Even something simple like the voltage created from the voltage divider.  I wish to know what get at currents and voltages and why there is no match to LTSPice (or below)?  Thanks,Jeff


texts: Why do some SMPS power supplies require an input voltage select switch?

texts:
I have 2 SMPS power supplies near me. One is an ATX power supply, the other is for a 3d printer. They both are rated for 110-240v in, but the ATX supply can handle the full range automatically, while the other supply has an input voltage select switch

One quirk I noticed with the supply with the switch, if I flip that switch to 230v, with my 115v mains, the output is half the rated voltage. I assume that is not a good idea to do that.

What does that switch do?
What is so different about these power
supplies that one needs a switch and one does not?
What are the risks of having the switch in the wrong position?


texts: LVDS/differential driver source impedance matching

texts:
A very basic/stupid question.. I'm designing some LVDS multipoint pcbs, and I'm a bit confused about the source termination on the driver end. my colleague said that ideally there should be a 100ohm parallel impedance matching resistor at the driver output, to reduce signal reflection. but I did some research and 99% of the time, people don't add this parallel termination resistor at the source, and only at the receiver end or the bus end (as shown above).
I understand the termination at the receiver end and bus end, but for the driver end parallel termination, is it really necessary?? my understanding is that if the differential impedance of the tracks is 100ohm, then the driver sees a 100ohm output impedance so adding another 100ohm in parallel wouldn't make a difference. plus the additional 100ohm would load the driver more which could reduce the magnitude of the diff signal.
Can anyone help me to understand why people don't add the 100ohm parallel source termination?

NEW UPDATE:
Ok I did some more research today.. and got more confused..
First of all, TI has this notes about how to terminate differential signal:
https://www.ti.com/lit/an/snla034b/snla034b.pdf?ts=1617704437563&ref_url=https%253A%252F%252Fwww.google.com%252F
It mentioned series termination on both Out+ and Out- for impedance matching.
Then I found this:
https://www.sitime.com/api/gated/AN10029-Output-Termination-for-Differential-Oscillators.pdf
In the LVDS session, it mentioned double termination, which as my colleague/supervisor said, has parallel termination at both driver output and the receiver.
My only way to make sense of it is that in the TI document, it assumes the driver is a voltage source and in the SiTime document, it assumes the driver a current source..i know this is a stupid explanation..
it looks like most of the time impedance matching at the receiver will do the job, but if the driver has good enough driving power and we want a super clean signal, then we should add impedance matching at the driver too.
I'm not confident about my reasoning, it feels like i'm trying to just fit an explanation to all the things I've read. if anyone can clarify it a bit that'll be great.
So my main questions are:

If we want to do proper impedance matching, should there be source impedance matching as well? and if yes, should it be parallel or series or depends (depends on what?)?
What is the purpose of the source impedance matching (if needed)? is it to stop signal bouncing back to the driver at the entrance of the tracks, or to prevent second round of bouncing?

Thanks everyone!!


texts: 5V to 3.3V for bluetooth module - Is a voltage divider ok?

texts:
So I purchased the JDY-10 BLE 4.0 module and a very small MCU which only is capable of feeding 5v.

Since I'm not an electrical engineer, I've been reading a bit on the internet, and so far, I understand that the Bluetooth module will be fried if I hook it up to a 5v power source. As far I can understand, a voltage divider is not usually the way to go, but would it be okay in this case? - I plan to put this on a PCB that I make on my own, therefore the solution should be fairly lightweight/simple.

Furthermore, would the RX pin require a pulldown resistor? (The datasheet doesn't reveal anything in that regard - and to be honest, I don't think it has one)


texts:
Could anyone please refresh my memory regarding op-amps? I am reading this article about Cascodes op-amps to refresh my memory about them - and I see a single input into each op-amp:

Is it assumed that both the op-amp's inputs are tied together?

Update
Is it like that:


texts: Get line to line values from line to neutral reading

texts:
My device can provide reading of Line to neutral values through Modbus , I'm requested to provide Line to Line readings which is not available in our Modbus table for the device.
Is it possible to get Line to line value (U12, U23, U31) from Line to neutral RMS reading (U1n, U2n, U3n)

Thnx


texts:
I have a digital clock made from an electronic kit - it has 3 buttons (1 to set the time, 1 to set alarm, 1 to cancel the alarm).

I want to be able to set it so every time it is connected to power it sets to 20:00 instead of 12:00 (8 hours ahead). The reason for this is I am actually creating two clocks with 2 time zones and I want to set the time on both from 1 button/switch.

I am new to electronics so forgive me if this is an easy question, but how would I go about achieving this? I assume I would be unable to change the default start time on the clock, so is it possible to send a certain amount of "button pushes" (setting the time) each time it powers up?

E.g.

1 button push = +1 minute
480 button pushes = 480 minutes = 8 hours

Is there any way to achieve this?


texts: What is the current state of independent (of producers) studies about the correlation between EMF (with particular reference to mobile devices) and interruption of human DNA? Are the declared SAR by devices manufacturers reliable?


texts: Determine the value of Vx if the power dissipated by resistor Rx is 450W and Rx=50 Ohms

texts:
I keep getting figures that are out of these ranges. Maybe I am doing it wrong. So far I've been adding the possible voltages with 200V to get a total voltage, then using Ohms's Law to see if any of the voltages squared divided by 50 ohms would equal 450W. I also tried finding the equivalent resistance and working from there, but still no luck.

Any ideas?


texts: Why Relays waste power and how to overcome that?

texts:
Let's say that I am going to:

Use a relay to switch between 2 DC +12V power sources (one may interrupt so the other source is a backup).
I will use a capacitor on the load with minimum leak possible I can find to supply power during the relay switch operation.
The lines thikness is around 8 mm.
The current may go as high as 23A and as low as some mA.

I have been told that relays waste power, but it is not clear to me by how much as I don't know the best kind of relays to use for my application. I also read somewhere that an IC can be used to control relays so they waste less power, but that IC may also use power too which may result in more power loss probably.

Anyway, I want the most efficient solution for my specific applications.


texts: Top258YN Voltage Drop and Thermal Shutdown - SMPS

texts:
We designed 24V 6A SMPS on Pi expert. Design documents are attached. But when we load 5A at the output, it enters thermal protection within 10, 15 seconds and Voltage drops about 1V. What could be the reason for this? In addition, the unloaded D pin is in the 1st picture and the output voltage is on the 2nd picture. D pin in 1.6A output is in the 3rd picture and the output voltage is on the 4th picture. As you can see, there is too much noise at the output. I am waiting for your opinion on this topic.
Input: 230VAC Primary inductance of transformer: 314uH
Documentation: https://we.tl/t-tXRGuitv4S


texts: solution to detect radar wave reflection that usgooe to detect human presence through wall

texts:
in the market there are products that generate RF frequency that can penetrate though wall/ concrete, by measuring the reflection of the RF, human presence behind the concrete / Wall can be detected.

One such example is
https://www.xethru.com/x4m300-presence-sensor.html

I encountered a situation where in my unit (top unit with enclosed area) with walls and concrete, the unit below uses similar device to emit RF and from detect my presence and where about in the unit by interpreting the reflected RF.

I have tried using cheap device ( https://www.youtube.com/watch?v=G4TBkpJi5Sc ) to detect the RF presence, and it does feedback positive of its presence.
And so I tried to shield the invading RF using aluminium foil covering potential areas where the invading RF is.
The problem is there are many other RF signal that the CC308+ detects which is not the invading RF. So my attempt to completely block the invading RF is not effective.

I tried reporting this to the police, however, police will only take up the case when I can show evidence of what my allegation.

So I am searching for a solution to detect the exact frequency of this invading RF, and also be able to pinpoint where it is coming from.

Anguish build up as day in and day out of my whereabout in my unit is monitored and the unit below start making harrassment using different creative subtly means targeting at where I am in the unit.

So a solution is greatly appreciated to put an end to this privacy invasion.

Thank you very much


texts: Potentiometer identificaiton Logitech z623 Speaker

texts:
I've been searching and can't locate a suitable part. Perhaps due to inexperience. This is the volume control for a Logitech Z623. I believe it's 100k Ohms based off the code on the side, but cant be sure as it is broken. I found this post but the one they used is not the actual part and I haven't found a datasheet, I'm trying to get nearest to OE as possible. I've read over numerous data sheets on mouser, but can't seem to find what I'm looking for. Are their any services that will help locate this?
Also if someone could explain the pin config. Given their are 6 pins, does this mean two identical outputs?


texts:
I am trying to create what is to be my first pcb, and also my first arduino shield.
The circuit requires the power connector (power jack) that the arduino has.
I am sure i can find that footprint inside KiCAD.
But what do i select for schematic symbol?


texts: Connecting Led in Series with Parallel Switches

texts: I created a diagram for a circuit that i am trying to implement. I have attached my circuit diagram and have been trying to implement it but still have not got it to work. I've checked all the wiring and they are all connected correctly and I am getting a Voltage source. Does anybody have any ideas? Am I missing something? Because when I press the switch, the LED is supposed to light up, but is not.(Not pictured: But I also tried adding a a connection to ground at the end of the first switch as well but that didn't do anything either.)


texts: How does negative feedback change output impedance?

texts:
Hi,
I'm having some trouble intuitively understanding how negative feedback changes output impedance. I was always taught that negative feedback changes the gain of a circuit - from A_OL to (A_OL)/(1+K*A_OL) but we never really discussed about the impact on the output impedance.
If I look into the output node (Vout) in the above figure (Figure 9.7 right), the unity gain feedback is pointing into the gate of M2 which is high impedance. So the entire output impedance should be (ro4 || ro2) which is the same as what it would be in an open-loop configuration.
So, with that in mind, how does negative feedback change the output impedance?


texts: MMF diagram, of a transformer - why layers are numbered this way?

texts:
i have found very interested concept for calculating losses in winding. The MMF diagram is required.
i have found mmf diagram examples on coursera magnetic course and on a ridley engineering website. It looks like they both consider that the core is EE and the windings are both wound around the central leg of the core, but they use strange numering of numbers for some reason.
Why are they doing this?

I am realy confused. How to build MMF diagram, which has a 3 layers of primary (foil, 0.44mm of thickness, a little larger than the skin depth 0.29mm) and 2 layers of secondary (foil 2, 1.17mm of thickness, 4 times larger than 0.29mm of skin depth)
The primary should be wound around the secondary like this:

Note that secondary winding conducts 2 times current of primary because it is 2:1 transformer.
Is my diagram wight or wrong and what is the principle of building the MMF diagram? Why on the pictures i posted this type of layer numbering is used?

P.S > Windings of this transformer are not wound of foil in reality, the foil conductors are just approximation i made for round conductors.


texts: Controlling a MOSFET with a microcontroller

texts:
I'm trying to use a p-channel MOSFET (FQP27P06) to multiplex four large common-anode seven-segment displays. I'm using a TPIC6B595 high voltage high current shift register to sink the segments for each digit.

I'd like to use the MOSFET to multiplex and control brightness of the four digits by giving the common anode 18 V.

Here is a simple schematic for driving the MOSFET. My concern is when the MOSFET is 'open' I'm seeing the 18 V on the pin which would be hooked up to the microcontroller.

Is the NPN transistor even necessary?

The second schematic has an extra resistor forming a voltage divider to limit the voltage going to the gate of the MOSFET. I don't think it is necessary with this MOSFET.

I have put the circuit together on a breadboard, but I am hesitant to hook it up to the Arduino.


texts:
I have a 5V logic signal coming from a pin on my microcontroller.  I would like to use this to turn on and off another circuit which also runs at 5V.  i. e. the logic level is the same, but I need to switch more current than the microcontroller pin can source.

I started with this circuit by Jon Watte, for using a P-channel MOSFET as a high-side switch for 12V:

I tried using this same circuit, but running it at 5V instead of 12V.  It worked, but when I started to draw more than a few mA of current, the voltage starts to sag towards 4V and even lower.

I thought the problem was that the IRF9530 has a drive voltage of 10V, so at 5V it isn't fully turning on.

So, I tried replacing the IRF9530 with a NDP6020P, which has a drive voltage of 4.5V.  I thought that ought to fix the problem:

However, that did not fix the problem.  The voltage doesn't sag quite as much quite as quickly as with the IRF9530, but it still gets lower than I would like.  (The voltage drops to 4.3V at 150 mA.)

Why didn't this work the way I thought it should?  What are the "engineering calculations" I need to perform to choose a MOSFET that will make this circuit behave properly as a switch?

Edit: Here is how I'm performing measurements:

I've connected the output to a SparkFun Variable Load.  The variable load acts as an electronically-controlled variable resistor.  It also measures the current going through the resistor (MES3), and measures the voltage across the terminals (MES2).  I also have a separate voltmeter connected directly across the power supply (MES1).

The 5V supply, depicted as a battery in the schematic, is actually a 5V, 2A USB wall adapter.

As the load increases, the voltage measured at the output (MES2) decreases.  However, the voltage measured at the power supply (MES1) also decreases.  This would seem to suggest the power supply can't handle the current.

However, if I connect the variable load directly to the power supply, I can draw significantly more current without the voltage sagging by any significant amount.

So that would suggest there is not an issue with the power supply.  This seems very weird.

Conclusion: I never did figure out what was wrong.  But I rebuilt the same circuit on a new breadboard, and it seems to work as expected now.  So obviously I messed something up before, but the design itself seems to work.


texts: How to run/simulate sample code after building code with MPLAB on proteus?

texts:
How do i simulate the PIC controller after compiling code in MPLAB?
COde is :-

#include "16F877A.h"

void main()

      {

           output_D(255);

                      }

When i add this file to PIC in proteus i got this as an error:

"EXTERNAL MODEL DLL "PIC16DLL" NOT FOUND
SIMULATION FAILED DUE TO FATAL SIMULATOR ERRORS


texts: IR2110 PSpice simulation - Convergence Problems

texts:
I have a simple simulation circuit for the IR2110 in PSPice. From my understanding, the convergence errors are related to each circuit in particular and that the IR2110 is very prone to convergence problems. I am open to suggestions what I can modify.

Here are the things I have tried:

"increase the
ABSTOL = 1pA to 10pA or larger or increase RELTOL = 0.001 to 0.01 or larger." As the document included with the model suggests.
Increase/Decrease Run to time (default is 100u) to 10u/1000u and Maximum step size to: default, 1n, 10n, 10u.
Check/Uncheck "Use GMIN stepping".

Orcad Capture version is 9.2, so no autoconverge option.

Below is the schematic, and errors:

These voltages failed to converge:

    V(X_U1.MD4_Uvbs_2)        =   -10.00GV  \   -10.00GV
    V(X_U1.MD4_Inv4_1)        =     4.897V  \         0V
    V(X_U1.MD4_Nor2_2)        =   -10.00GV  \   -10.00GV
    V(X_U1.MD4_Inv6_3)        =    10.00GV  \    -9.64GV
    V(X_U1.MD4_Nor2_4)        =  -756.95KV  \     4.897V
    V(X_U1.MD4_Inv6_1)        =    1.546MV  \    4.897uV
    V(X_U1.X_MD4_Uvbs_Comp.5) =     4.897V  \         0V

  These supply currents failed to converge:

    I(X_U1.E_MD4_Uvbs_ABM18)  =    30.72MA  \    86.40MA
    I(X_U1.E_MD4_Uvbs_ABM19)  =   -30.72MA  \   -86.40MA
    I(X_U1.X_MD4_Uvbs_Comp.E1) =   -19.61nA  \         0A
    I(X_U1.V_MD4_Inv4_V)      =    43.87MA  \    94.33MA
    I(X_U1.V_MD4_Nor2_V)      =  -756.96KA  \   -4.897uA
    I(X_U1.V_MD4_Inv6_V)      =    10.00GA  \   -42.53KA


texts: LM317 - bringing down to 0 volts (with a uC)

texts:
I am wanting to build a custom power supply for myself, and am having trouble understanding how to drive the adjust pin with a microcontroller.

The datasheet for it is here: http://www.ti.com/lit/ds/symlink/lm117.pdf

The issue is that I can make a pseudo? DAC with a low pass filter to get 0-5 volts from my PWM output, however Vout is formed by \$1.25+V_{adj} \$ , meaning, I can only get 1.5-6.5 (or 0-5 if negatively offset) with my solution as is.

My questions are: How do I offset -1.25V? A negative regulator (i.e. LM337) seems a little overkill, however I have never seen a solution with my own eyes and it could be very normal. Are there any quick ways you can think of to offset it?

And more importantly, how do I drive the ADJ pin from ~0-12V if my uC can only output 0-5 with PWM? Is there an indirect method of doing this? A simple building block I can place in between to map this range?

I am quite open to alternatives, however fixing this has piqued my interest and there are not many similar adj. regulators available to me (LT3080 with ~0 offset not available on Mouser at the moment)


texts: How to operate Op-Amp[OP07CP] with 0-5v supply?

texts:
I don't know why I cannot operate Op-Amps! this is my second circuit and I'm trying to make a non-inverting amplifier by an OP07CP. This is my circuit + an example of measured values:

simulate this circuit – Schematic created using CircuitLab

And when I applied 0v to the +input, I got -5.47v in the output. and again for 17.9mv, I got 1.78v. when I change the supply to 0-5v, I just get an amount around 4.5v or 1.5v. I'm harassed! I expected to get 3153.969mv in the output when I applied 9.1mv but as you can see, I just got -1.15!(when supply is -12 - +12). Why doesn't it work correctly? Can I operate this Op-Amp with 0-3.3v or 0-5v supply? how?


texts:
I am looking for a 3.7V LiPo battery circuit that will handle  over-voltage protection along with charging and 3.7V to 5V boost. I've found this popular pcb on ebay:

http://www.ebay.com/itm/1-x-PCB-Li-ion-Lipo-Battery-3-7V-step-up-Convert-to-Output-Power-DC-5V-DLX-UPDC-/130725341903?pt=LH_DefaultDomain_0&hash=item1e6fd66acf#

It seems to cover all that I need but I can't tell if it steps down the charging voltage or if I have to provide it with a regulated 3.7V supply to charge the battery with? I can tell that one IC is an 8205A which provides all the over/under protection features but I can't read the numbers on the other ICs to look up data sheets. Is there a sure way to tell if this pcb has this feature or not?


texts: Are mica flakes like ones found in makeup and body lotions completely non conductive and should I be worried if it gets inside the components of my computer? Or should I be more concerned about regular household dust since it can carry static electricity?


texts: Arduino: Did I damage analog joystick clicker by using analog instead of digital input?

texts:
I am using a thumb joystick for Arduino UNO, trying to work with it.

There are x and y values that I get with analog input A0 and A1, and one z value for the click that I should have gotten from the digital input D7, but unfortunately I wired it to another anolog input (A3).

This is the wiring from the specification

So, now that I fixed my mistake, I get the x from A1 and y from A2, but z is always zero. Is there a chance that the joystick part is physically damaged? Or worse, my Arduino UNO? How can I check?

int sensorPin = 5;
int value = 0;
void setup() {
  pinMode(7, OUTPUT);
  Serial.begin(9600);
}
void loop() {
  value = analogRead(0);
  Serial.print("X:");
  Serial.print(value, DEC);
  value = analogRead(1);
  Serial.print(" | Y:");
  Serial.print(value, DEC);
  value = digitalRead(7);
  Serial.print(" | Z: ");
  Serial.println(value, DEC);
  delay(100);
}

Chinese specific specification is here. I wish it was also available in English! :-/


texts: How to calculate the address fields for a cache?

texts:
I've a homework question about 32-bit cache memories:

  For a cache memory that has size 16kB (16384 byte) and blocksize 2
  words, state the names and the sizes of each field of the address that
  comes from the CPU.

My answer is: 3 bits block offset since 2³=8 and 14 bits for the address tag since 2¹⁴=16384. The rest, 15 bits are for the index of the cache. Is my answer correct?


texts: Scam or Legit: High Voltage Capacitor Manufacturing?

texts:
I have been looking for an 0805 10uF ceramic capacitor rated for 100v. Mouser and Digikey have only appalling prices for such specs (50 cents/piece at 5k for example).

I recently made this shocking discovery on Aliexpress from a (somewhat) reputable dealer:
https://www.aliexpress.com/item/33053004449.html

The price per item comes out to a few cents, and when comparing to U.S. prices, I am wondering if it's a scam. I can see one of these sellers selling 50v caps (much cheaper from U.S. distributors) as 100v caps, and my design blowing up with a bang.

Are these legit? I know it couldn't hurt to test them (100 of these is the same price as three from Digikey), but if there's a 0% chance they will work I would rather look elsewhere and not bother waiting for the shipping.

Perhaps this is an opportunity for someone who knows more than I do about ceramic capacitor manufacturing to explain the cost impact of increasing the capacitor's capacitance and voltage rating. Three factors that come to mind are more expensive materials, specialized design process, and lack of demand to produce economically in large batches. Are any of these remotely reasonable?


texts: Shorting the Output of a voltage regulator

texts:
I am using this Buck Converter
Input Voltage Range - 8-16V
Output Voltage - 5V
Load Current - 550mA
This 5V is the power supply (Vcc) to the mentioned IC loads :
Microcontroller , LED Driver , 2x CAN Transceivers & 5V to 3.3V LDO
My questions :

I want to check what would happen if I short the Output of the 5V Buck Regulator for a fraction of second. (a) How to perform and check what would happen if I short circuit the output of the regulator while it is still connected to the Vcc of the above mentioned IC Loads? Won't those ICs get damaged if I short the Output of the 5V?

Objective of the Short Circuit test : Just want to understand what would happen if the buck regulator is shorted for some reason in my board. Is there a recommended time duration for how long the output can be shorted?

Is it recommended to perform the short circuiting of the Buck Regulator output when it is connected to the above IC Loads?

Usually do the buck converters have short circuit protection? By this, do they mean that if the regulator output is shorted, the IC does not provide a lot of output current (so a to protect the underlying loads and the PCB)? Is my understanding correct?


texts: Do the statements "circuits/components will only draw the current they need", and "V = IR" contradict?

texts: What I'd like to know is how we can resolve the two statements, "Circuits/linear components will only draw what they need", and "V = IR". They seem to contradict one another, in my view. With a given voltage and a given resistance, current will be set by these two properties in the circuit, regardless of "the current components need". If this could be at all explained mathematically as well, I also think that'd be better... these analogies seem limited after a certain depth...


texts: 24 VDC source to 0-5 VDC or 4-20 mA manual input

texts:
I have a PLC which offers analog inputs of either 0-5 VDC (6 VDC max) or 4-20 mA (sink). The source will be 24 VDC and I want the input to be manually adjustable (assuming with a potentiometer). The input impedance for the 0-5 VDC input is 150 kohms and the input impedance for the 4-20 mA input is 200 ohms.

I'm not sure what the best way of going about doing this is or which input would suit my needs better. I'm assuming there are certain pros and cons for each one. Possibly one being more steady than the other? If either can be done and results would be fairly similar then I would probably choose which ever is easier/less expensive.

I was originally trying to figure it out using 2 resistors as a voltage divider to get down to 5 VDC and then a potentiometer to vary the voltage on that 5V leg. Or possibly using 1 resistor in series and 1 in parallel with a potentiometer to vary the current? I'm a bit lost on exactly how to do it as well as which way is best. If you need anymore info just let me know.


texts: Add permanent component in LTSpice from asc and asy

texts:
I'm trying to add a new permanent component (ULN2803) to LTSpice, having asc and asy files.
I have read some tutorials in the web but focused on .lib and .sub files.
How can I add the component from these files?
Thank you


texts: What is the best practice to measure 3 phase grid voltage using a dsp chip for synchronization?

texts:
I want to measure the current grid voltage to synchronize a dc power supply with the grid using an inverter. Now I'm particularly interested in finding noise and harmonic information about the grid voltage.

So my plan is to use a transformer to to step the grid voltage down  on two of the phases and use resistor dividers to get the voltage in an appropriate range for the ADCs of my dsp. Is this the best way to measure grid voltage for synchronization purposes(I'm particularly interested in unbalanced conditions).

Further more will i lose harmonic and noise information by using this method(through the inductance of the transformer)?

It's a bit of a repeat of this question though am interested if there are any other factors I need to take into account for voltage measurements for the purpose of grid synchronization. (If not i guess this question is kind of redundant)


texts: Why 2 diodes in parallel buck converter design?

texts:
I  have been looking up dc-dc buck converter designs and have question regarding the diodes.

It says "5A High current Schottky diode" is it common in buck converter design to parallel diodes and I would guess this is two 2.5A diodes?

I understand that connecting them in parallel will share the load and result in a higher forward current but wont one diode try to carry a larger current due a potential for a lower forward voltage. Resulting in one diode overheating?

I know to remedy this is to add a series resistor with the diode to have a equal current drop across each resistor resulting in a almost equal current share between each diode. However this will result in a overall higher power loss due to the parallel branch and due to the large current drop in the resistor. Wouldn't you just be better paying a little more for a single diode that can meet the current requirement for your buck converter?

I would apprecitae your feedback.
Thanks,


texts: I was reading about source transformations and came across an example where there was a change in the order of two series elements, is this always possible? The same for in parallel elements but that makes sens since they have the same voltage.


texts: What kind of serial cable do I need? (TTL vs RS232)

texts:
So I have a headless NAS that I'm trying to connect to via a serial console so I can install a different OS. It has a 3.5mm jack on the back I/O labeled COM1.
I had a USB->TTL cable I had used for a raspberry pi that has 5V for the power, and 3.3V for the RX and TX pins. I cobbled together a USB-> 3.5mm cable by splicing a 3.5mm aux cable to the TX,RX,GND pins and while I get stuff printed to the console, it's all gibberish. I've read that this is usually due to an incorrect baud rate, but after checking the serial port settings on the NAS via an SSH connection, I can confirm that I do have the correct baud rate. I've also messed with all of the other settings like the # of bits, parity, stop, etc and haven't been able to get anything legible.
After posting this question over on the UNIX stackexchange, someone suggested measuring the voltages to make sure it's really TTL vs RS232 levels, and seeking advice over here. The voltage of the 3.5mm port on the NAS gives almost -6V (it usually jumps to -6, then drops to 5.9/5.8), which from reading more about RS232 vs TTL leads me to believe that what I need is RS232 levels since RS232 uses negative voltages and TTL doesn't, am I correct in that assumption?
I came across this question on this site regarding serial cables, and although I'm still fairly confused by all of this, I think I either need a USB->3.5mm RS232 cable (if they exist), or 2 cables: USB->RS232(DB9) and RS232(DB9)->3.5mm.
Am I on the right track with this? I appreciate any help anyone can give. Also, if anyone could recommend a good quality cable too I would be most appreciative, since that's another issue that's come up in my searches.
I can also provide pictures of the board if needed. It's a QNAP TS-963X and unfortunately I haven't been able to find any information or schematics or anything on the motherboard online. Searching what appears to be serial or model numbers don't yield anything relevant.


texts: Microstrip blocking capacitor ground cutout -- large cutout size

texts:
I'm attempting to minimize the \$S_{11}\$ of a \$10\,\text{pF}\$ DC blocking capacitor on a microstrip trace for my signal frequency range, which is \$5.3-5.9\,\text{GHz}\$. My microstrip trace width is \$0.38\,\text{mm}\$.

I started by using a 0402 cap (\$0.5\,\text{mm}\$ width), but the performance was poor (results below). I'm using OpenEMS to simulate the behavior. Using a 0201 cap (\$0.3\,\text{mm}\$ width) improved the performance significantly, but still yielded worse performance than I would like.

To improve the performance further, I used a ground cutout below the capacitor. Since I didn't know the size to use, I let Scipy choose a cutout width that minimized \$S_{11}\$ in my frequency range. I chose the length of the cutout to be the full extent of the capacitor+pads in all simulations. Interestingly, the optimizer came back with a really large cutout: almost \$4.5\,\text{mm}\$. Sure enough, though, this improved the performance dramatically in the signal frequency range at the expense of broadband performance. Here's a bird's eye view diagram showing the cutout, followed by a plot of the results.

The Qucs line is a Qucs simulation that I've used as an ideal baseline to compare against the other simulations.

Does this result seem reasonable? Previously, I'd thought cutouts were only used when the capacitor was wider than the signal trace, and in that case, the cutout would be much smaller than it is here.

EDIT

I'm using Oshpark's 4-layer process, which has a dielectric of 3.64 (substrate is FR408), substrate height of \$0.1702\,\text{mm}\$ (I'm using the 1st and 2nd copper layer) and 1oz copper top layer and 0.5oz copper 2nd layer.


texts:
Currently i am doing a circuit for achieving voltage regulation. Please refer below for the same.

I am looking for a split voltage supply design using a single supply.

On No-Load i am getting the split supply across the zener and the remaining voltage across the resistor.

But upon loading the situation changes,as the load resistor intervenes with the 25 Ohm and the voltage drops. A figure for the same is given below:

The Load will not be present simultaneously as i am using this supply for IGBT ON/OFF. So the voltage split is bizarre when individual loads are removed or connected.

I understand that there are IC's for performing this function of creating a dual voltage from single supply, but i am looking a cost effective one. This is one reason i went with this conventional way .

Please suggest me a way to solve this problem.

Thanks in advance.


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I have designed a dual slope integrating ADC on Multisim, but I am having some practical limitations.

To switch between the input voltage and the reference voltage, I am using the following switching circuit:

IO_1 can be given a digital signal to switch between the two voltages. The first voltage is from IO_2, and the other is the 0.4 V input at the second transistor.

Now, to combine the outputs IO_3 and IO_4, I am using a summing amplifier, but the summing amplifier needs to be powered above the range of the input, otherwise the output from the summer will saturate. This is severely restricting my range.

How can I overcome this problem. Is my switching circuit inefficient?


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I'm new to Kicad and I'm having some problems using Eeschema. Every time I connect a power source to an IC pin, in this case the L293D, I get the following error:

ErrType(3):Pin connected to some other pins but no pin to drive it

I'm just connecting the IC's pin to a +9V power source icon. I'm using an external library that includes this H-Bridge. I can't see what I am missing.

Thanks in advanced.


texts: Differences between OLED, LED, LCD, and TFT Screens

texts: I have heard about these different types of screens on DIY websites and in consumer electronics. What are the differences in these types of screens and what are their advantages and disadvantages?


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I am collecting raw data from a radar sensor using source code from the manufacturing company to allow me to plot data.

I am looking for a repetitive movement that would be considered sinusoidal.

The image above shows a pulse bounced back indicating where the object is located. The pulse after it is the signal being bounced from a ceiling.

Questions:

Can I perform the Fast Fourier Transform or does it have to be plotted in terms of time?
Is there a better way to find repetitive movement over a period of time?


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I recently came across the term "Power Supply Pumping" in an answer provided to me in return to one of my questions. Although I tried googling I didn't have good luck with it.
I would appreciate if someone can explain how I could utilize this concept to drive multiple high impedance amplifier inputs efficiently (about 10, 9 KOhm each) by an MP3  player output.


texts: Find \$H(j\omega)\$ for a function, if I have \$H(s)\$

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Let's suppose I know that $$H(s) = \frac{-2}{2s+3}$$
I know that \$s=j\omega\$. But how do I find \$H(j\omega)\$ based on this?
That would be $$H(j\omega)=\frac{-2}{2j\omega+3}$$ then what?


texts: How to calculate PWM duty cycles for Solenoid current control

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How to calculate the PWM duty cycle for Solenoid current control

I am trying to design a current control driver for Solenoid. I know the peak and the holding current range for solenoid.
How would I find the PWM duty cycle based on the current that I need to control?

Solenoid resistance at different temperature

1.1 Ohm @ 20 C
1.61 Ohm @ 150 C
0.85 Ohm @ -40 C

Voltage Range
9 V min
13 V Normal
16 V Max

Current Range

Disengaging clutch current 7 A min & Max 16 A, but I would like to limit the max current up to 10 A only.

Holding current for clutch is 1.2 A min to 2.2 Max

Frequency Range: 1000 to 50 Hz

Microcontroller is used for PWM output.

I want to design a current control circuitry using N MOSFETS for Solenoid

I am using current sense opamp to monitor the current through solenoid.  I am using 20 m Ohm resistance for the current measurement.

I am trying to figure out how to calculate the PWM duty cycle for the disengaging current & holding current?

Should I go 100% duty cycle and control the current once the clutch is disengaged by the solenoid?


texts: FTDI (FT232RL) powers itself through RX/TX lines

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I have an FT232RL connected to an AVR Atmega2184P (running the Arduino core) UART. The microcontroller has two power supplies - a LiPo battery (VBat), and USB power (Vin). The way I've designed the circuit is that if the USB is plugged in the battery is disconnected from the circuit and Vin powers the entire circuit. When the USB is unplugged, VBat takes over

The VCC and VCCIO on the FT232 is connected to Vin. Therefore the FTDI chip should only be powered on when the USB device is connected.

I'm noticing weird behavior when the battery is plugged in but the USB is not. As soon as I initiate the UART bus on the microcontroller, and current is sent down the RX and TX lines, the FT232 powers itself up. What is strange is the power is then transferred into the Vin power rail.

This is affecting other parts in my circuit that rely on there not being any power in Vin when the USB is unplugged. If my code doesn't initiate the UART bus, everything works as it should.

Has anybody seen this behavior? I can't see any reason why the FTDI chip would be relaying power back into the VCC line.

I've tested this with multiple processors (different Arduino boards), and multiple FTDI breakout boards. Initially thought it might be a chip issue, but the behavior described is consistent across each device.