texts: What can I submerge my keyboard circuit board in that would remove the corrosion from it?

texts:
The contacts are between two thin plastic(?). In order to expose the print, I'd have to peel them apart. That's a lot of work since I'd have to perfectly align them to put them back together.
What can I submerge the circuit board in as-is that would remove the corrosion/rust without having to rub/brush it off?
Here's a picture of the board.


texts: Beagleboard Black all GPIOs are activated by a single GPIO

texts:
Earlier I was having a problem with BeagleBoard Black Rev C , which I discussed in the question below.

GPIO.HIGH,LOW doesn't up LED Beagleboard

I've found the real problem. Whenever I turn any single GPIO pin (say , P8_3) , all the other GPIO pins under P8 also becomes HIGH at the same time, that's why I was having problem lighting up an LED by taking both +ve and -ve from two GPIOs from P8. Same goes for P9. In stead if I take one GPIO from P9 and make it HIGH and another from P8 and make it LOW , the LED is lighting up properly(also I checked using Multimeter and its showing potential differences properly). But the problem arises as all the other GPIOs of P9 are HIGH and all of P8 are LOW.

I want to change individual GPIOs HIGH or LOW whenever I wish. What can be the possible problem? Do I need to update the image? But I don't think that would be the reason of this problem.

EDIT: Posting the python code.

import Adafruit_BBIO.GPIO as GPIO
import time

GPIO.setup("P8_3", GPIO.OUT)
GPIO.setup("P8_5", GPIO.OUT)

while True:
   GPIO.output("P8_3", GPIO.HIGH)
   GPIO.output("P8_5", GPIO.LOW)


texts: Level Shifting 1.8V to 5V with N-channel FET

texts: I am using BeagleBoard-xM GPIO outputs to drive some DC motors with the help of L293D IC. The problem is that there is a difference between voltage levels. The GPIO outputs only supply 1.8V while L293D needs at least 4.5V for logic high. So I need a unidirectional voltage level shifting. I have BS170 N-channel FETs for this purpose. However I am not good at semiconductors. What is the proper configuration for the transistor? Do I have to use any additional components?


texts:
I have a simple ESP8266 circuit that detects as pulse when a reed switch is open or closed - nothing fancy. I have anti-bounce code configured and everything typically works as expected.

Hopefully the picture I have drawn and attached works to explain the full story.

Note: The garden reticulation circuit has nothing to do with the NodeMCU circuit other than using the same mains 240v mains power supply.

The problem I have is that there is a 24v AC (500mw~) cable as shown in red in my attached diagram about 6cm away and then in parallel for approx a 15cm length from the leads that make up the reed switch. This is creating a lot of false readings in the ESP8266 circuit when the 24v AC becomes energised.

I tried a 10 nF Capacitor (103) and it stopped the false readings for a few hours and then didn't, I suspect the capacitor was maybe too small for the job, overloaded or unsure...
Or, maybe there is some weird ground or similar induced loop noise / harmonics in the circuit as they are connected to the same mains supply.

I'm open to figuring out how to calculate what size capacitor I actually need, or maybe another option.

I also considered an optoisolator for the reed switch but that would mean I need to put a battery near the reed switch for that side of the optoisolator to work, but i just want to run this simply of the USB 5 power power adaptor.

Moving the cables away from each other is not really an option as they are penetrations through an existing brick wall and not so easy to move..


texts: Powering multiple devices from a single supply with 48V

texts:
First of all I asked this question in DIY.stackexchange.com, because of the cabling in the house. Here I would like to ask about the electronics (or electrical) part of it.

And there is a very similar question here: Powering multiple devices from a single power supply

Yet there are some differences. First of all I was thinking to use 48V to transfer energy from a single power DC adapter, which I would like to place next to the main ethernet switch. Then I want to make a simple board, where I will split 48V DC output to 4-6 parallel wires. I would like to wrap these wires around Cat6 cables with tape (Cat6, because price it much higher for 50m cable, it is a good investment for the future and I don't want to replace these soon) and pull these combined cables through the walls (by replacing currently existing phone line or cable TV both of which I am not going to need).

My goal is here to provide 3 rooms with a pair of ethernet. One for personal computer or TV and the other one for a Raspberry Pi, which would run either as media center or security camera.

PoE is a more expensive alternative. I would like to use a gigabit switch for the future. Raspberry Pi's only support 100M but next model might be 1000M already. TV and PC's should definetely have 1000M. PoE switch 8 port is +100€s, 4 port is +50€. Then I need splitter for each Raspberry Pi (~4x), which is additional +60€ in total.

Since, I am enthusiastic about electronics, I thought I might try to do something on my own and learn more about it. So a single 48V power supply and wires around Cat6 around the house would solve my problem. Then I can solder my own small voltage regulator board. Which is even better, because I would like to attach infra red LEDs to my security cams, which will draw additional energy. My understanding is to feed them extra, since Raspberry Pi has a limited output energy. I can create the board in a way that the LEDs are controlled with a transistor (MOSFET?) and are fed with an extra voltage regulator (6V or something).

I know there are many aspects in this problem and I could split into different questions, but my original problem is to feed Raspberry Pi's with less adapters/cables as possible and with least costs. Is this possible at all? Do you think, this would be the optimal solution? Are there simpler ways to power my Raspberry Pis?

Here is a schematic:


texts: multiple decoupling capacitor circuits (integrating multiple circuits)

texts:
I'm integrating two circuits into one. One being an Arduino Pro Mini (ATMega328P) and the other being a CAN controller+transceiver.

For the Aduino Pro Mini, I'm using a TLF80511TF50 (5V LDO). I've not yet calculated the values here, but they don't matter for the question, I think. The Pro Mini uses two tantalum 10uF caps here (and a third ceramic 0.1uF behind a jumper), but that's for a MIC52505 regulator.

The CAN board:

Of course, I can just copy the two boards onto a single PCB, but I'm wondering, do I have to duplicate the decoupling circuits?

The TLF80511TFV50 will power both the MCU, and the two CAN chips.
It will also power three I2C I/O extenders (PCF8575), but these barely require any power.

The CAN board uses a 8MHz crystal, the Arduino an 16MHz crystal.. In case that matters (I'm thinking noise...)

Q1: Is it advisable to use a set of decoupling capacitors near the VCC input of each chip/pcb section? Or what are the factors to consider here?

Q2: If this is not required, should the number of logic chips on the board influence the values/number of the decoupling capacitors?

.

UPDATE

Based on reply by @peufeu which I feel makes sense, I removed the basically double decoupling and left with decoupling at the regulator, following recommended setup from the datasheet. See schematic:

What I am left unanswered with is how to deal with decoupling at the various logic chips. I've added a cap at the VDD rail to the three expanders, as peufeu pointed out will have a switching behaviour. I remain unsure if I should add caps to the Arduino chip, and CAN chip(s). -- It will all probably work well without them, on the other hand adding caps is easy and cheap.. What is the rule of the tumb here??


texts:
I am using DAC3484(dac) and xc7k160t-1ffg676(fpga) in my design. DAC is interfaced to FPGA. DAC data rate is 153.6MHZ. DAC data lines should be length matched within some tolerance. How to decide that tolerance value??

I have seen in many sites they say that tolerance is decided based on setup and hold time requirements at receiver. Can someone please clearly explain how to calculate the tolerance with the above said dac data rate and setup and hold time of the dac3484 chip??


texts: Does this schematic represent the fritzing circuit properly and can you explain how pulled low works in this IR sensor?

texts:
I'm attempting to represent the following fritzing diagram* as a schematic (using circuitlab).

*from https://learn.adafruit.com/ir-sensor/testing-an-ir-sensor

Here's my representation of the circuit using a custom part in CircuitLab.

simulate this circuit – Schematic created using CircuitLab

Does that circuit properly represent the fritzing diagram?

Also, since the IR Sensor pin 1 is pulled low when the sensor detects infrared light, does that simply mean that internally it gets "connected" to ground?

Can you explain what "pulled low" means, if it means something else than "connected to ground"?


texts: Need help understanding how to calculate the R value for LD1117

texts:
I am really trying to understand how to use adjustable voltage regulators such as the LD1117 sold by sparkfun. I had a look at the datasheet they provide in the product page but it points me to a Fairchild semi conductor datasheet which has a typical application note that looks like this:

All fair and well so I went over to this online calculator and tried to see how these values work. This is where I suspect I am making a mistake or misunderstand something. See below on how I calculated the values:

That did not make sense. So I realized that Vr is not related to Vin. I redid the calculation and I think I understand it now.

This looked much better and more inline with what I was excepting. My first challenge was to do a simple 5V to 3.3V conversion as I have done this before with a fixed output regulator.

Then I had a look at the IC close up and well confusion struck me. The IC is marked a ST Electronics LD1117 E439. Now this IC has a datasheet here. This datasheet is a lot more detailed and on page 24 there is an application note for the adjustable variant.

Which one should I use? I did a calculation based on the sparkfun datasheet and I got a value for R2 of 0.174KOhm/174Ohm using the ST datasheet I got very close to this 0.168KOhm/168Ohm.

I am pretty sure I am correct at this point but I hate the blue smoke monster and I just needed a sanity check from a copilot.

One other question with the adjustable voltage regulators the input voltage can range from 15V downwards? I know at some point when the Vin drops too low there will be now conversion but using these values above would I be able to convert say 9V,12V or even 15V to 3.3V?

UPDATE:

So last night I built a PCB using the LD1117. Initially I got an output of 2V... I was stumped. Then I realized I had the two resistor swapped around...duh... facepalm...

Long Story short. I can confirm this works. With the experiment I have just done I am pretty sure I understand this now.


texts: I am getting smps output +ve wrt E and -ve wrt E zero and + wrt -ve is 24 volt, how is possible?

texts:
At the time of my plc system inspection i found that my smps input is correctly connected with 230v ac supply but when i check the output + and - voltage with respect to ground i found in both condition the voltage was zero but when i measure in between + and - it was +24 .

And when its output connected to my plc system, it is found that the output voltge + with respect to gound is zero and - with respect to ground is -24 volt, how is this possible amd my system is healthy.

Can you explain it how is this possible??????


texts: Why does wiring to a surge protective device need to avoid sharp bends?

texts:
Here is an excerpt from some Schneider Electric installation instructions for their QO2175SB 240V single phase "SurgeBreaker" SPD:

NOTE: The SPD ... must be
installed as close to neutral assembly and main circuit breaker or
main lugs as possible. Keep wire lengths as short as possible with no
sharp bends.

(source)
What is the reason for avoiding sharp bends? Is this more likely to cause the wire to fail under surge conditions? Or would it somehow hurt the surge protection effectiveness?
And how small of a radius bend would be considered "sharp"?


texts: Circuit guidance to output -14V from 12V supply

texts:
Good day to all potential problem solvers!

I would love some assistance with a particularly tricky circuit. I have an Arduino board and a particularly elusive green/black 128x128 GLCD screen I came upon in our stores. The model, MGLS128128 R3, seems to be another of Varitronix Ltd.'s forgotten love children and, as such, its data seems scarce. After a long time searching, I found that it makes use of a T6963c display controller.

It took quite a while to uncover that the screen makes use of a negative voltage on its contrast pin (Vo) in order to offset temperature fluctuation. It seems silly, but according to articles, the voltage with regards to the screen supply (5V) should be around -17V. Now, being intent on making use of this screen for other projects, and having invested strongly in it already, I am determined to get it working.I used the U8glib library, along with an external power supply in reverse polarity, to get an output as follows:

This means that the circuit works, provided I can supply a constant -13.24V with regards to ground on the Vo pin. I want to make use of only a 12V battery supply, I thought of using something like the b0515 IC's that give an isolated 15V output at 5V input, yet they are out of stock. I then remembered that I have tonnes of 7805 and MAX232 units floating around the office and I figured that if I were to connect a 7805 regulator to a 12V supply, then connect the GLCD and Arduino grounds to the output of that 7805 regulator, then the internal regulator of the Arduino board would output 10V in relation to its 5V ground. That would mean that the GLCD is still at 5V supply to its ground. The MAX232, connected to true ground (its ground connected to the ground pin of the 7805), works by switching the connected capacitors (0.1uF in my case) and making it look as though it is at near-constant -8.9V. The -8.9V should then, in theory, look like -13.9V to the GLCD screen because of the added 5V of the 7805.

Outcome:
It works only at exactly 12V suppl. The screen does output the "Hello World" image, although in a flicker. I've added a 180 Ohm resistor to the regulator output in case the current can't flow backwards through it. The voltages aren't exactly as expected and are out with more than 1V at certain power rails. Whenever the supply of 12VDC falls, even slightly, the circuit fails to output the text.

Question: I would like to know if my configuration of placing a 5V regulator on top of a 5V regulator to achieve the negative voltage output is a technically good configuration. If it isn't, what are the alternatives? If it is, how can it be improved upon? Here is the circuit (with resistor on 5V out removed):

PS: Please note that the Arduino board has its own regulator. Its input is at 12V on pin Vin. It regulates it with reference to its ground which is at 5V relative to real ground. This outputs 10v at its output labeled 5V on both the Arduino board and the schematic above. This output can often be 1 to 2V out. This influences the difference between the -8.9V pin and the VDD of the screen and therefore influences the contrast. What circuit/changes can make that this does not happen?

Thank you all in advance,

Regards,

Jean


texts:
I'm reading a lot of LCD driver data sheets at the moment and they often have multiple interfaces (serial, 8-bit, 16-bit, etc...).

They are also often also split into two sections "80 series CPU" and "68 series CPU" but I can't find any information on what that actually means.

What is the difference and how do I identify which is appropriate for my application (Ateml AVRs).


texts: Problem with accuracy of AD633 multiplier

texts:
I have 3pcs of AD633 chips, and the accuracy should be ±1% (typical), ±2% (max) according to datasheet.

I wired it like this:

I tried several  input voltages, but it seems, that output is still way out of tolerance.
For example:

IN1=7.008V
IN2=2.003V
OUT=1.4537V

Output should be precisely 1.4037V. But it's 3.5% out.
All 3 my chips are out of tolerance (up to 5%).

I don't know if there is problem in my circuit?
Or problem is that all of those chips are out of tolerance? (bought from China)


texts: What happens when P controller's gain equals zero?

texts:
For example, I use Routh-Hurwitz Cirterion to examine the following system with P controller gain \$K\$:

$$\frac{{K\left( {2 - s} \right)}}{{{s^3} + 3{s^2} + 5s + 3}}$$

I closed loop it with \$H=1\$ and found that \$K\$'s BIBO stability range is

$$ - \frac{3}{2} < K < \frac{{12}}{5}$$

I think when \$K=1\$ then controller will be just ignored.

But what happened when \$K=0\$? Does that cause system unlink together?

What does it mean when \$K=0\$?

Why is \$K=0\$ still stable on the Routh-Hurwitz criterion?


texts:
I'm designing a new encoder pulses counter for my project, my encoder HE50B uses a 12-24 VDC Input, and it has 1,000 pulses per each revolution. also the maximum permissible speed is 5,000 RPM.

Now I want to count the output pulses of this encoder by my micro-controller ATMEGA-32 which has 5 VDC input ports, so I have to buck the output voltage of the encoder to reach this value.

My question is: which is better to do that (taking in consideration the output frequency of the encoder)?

using a 2-stage inverting op-amp to buck the voltage from 12VDC to 5VDC or
use a regular voltage regulator such as 7805 and it will work fine with that high frequency switching.


texts: Simple RC Circuit question: how does a precharged capacitor interact with a lower voltage source?

texts:
So, I have this simple question to solve, but I am uncertain about some details. The circuit I have to solve is the one on the image below:

I have a circuit with one capacitor(C = 1/4 Farad), two switches(s1, s2), two resistors(R1 = 4ohm, R2 = 2ohm) and a voltage source(V1 = 10V).
The question asks me to calculate Vc(t) (the capacitor's tension over time). Right before t=0, both switches are opened, and the capacitor's tension is 20V. At t=0, both switches close, and stay closed until t=0.9s . At that moment, s2 opens. The question then asks me to calculate Vc over time, from 0 to 0.9, and then from 0.9 to infinity(until discharged, I think).
What got me confused is that Vc(0)=20V. That means the capacitor was pre-charged by a 20V voltage source, getting a charge of 5 coulombs(q=c*v). But then, it is connected to a circuit with a voltage source that has a voltage lower than of its own (V of the V1 = 10v).
I imagine that, because of this, the capacitor will discharge. Thing is, does the presence of the voltage source interferes with the discharging of the capacitor? Does it at all? Should I use the Vc = Vo * e^(-t/RC)) equation?
Thanks so much in advance, and I am sorry if I was long-winded.


texts: I have a Sony bluetooth earphone. It has a usb terminal, which I thought it was only for the purpose of charging power. But when I connected it to a computer, it seems like it is detected as a usb device, not just taking power from the computer. What is the purpose of it being designed to be detected as a usb device? I am planning to replace the usb terminal (mini B female) to usb A male so that I can charge power to it without cable. If I only connect V+ and V- and ignore Data+ and Data-, would I lose some function?


texts: Why will electrons move from hole to hole in the p type at forward bias, but not from hole to n type at reverse bias?

texts:
This question is about a diode with a p type and an n type. At the forward bias the electrons from the n type to the p type and from hole to hole in the p type. My questions are these:

At the forward bias, why does electrons go from the n type to holes in the p type?
At the forward bias, why does electrons go from hole to hole?
At the reverse bias, why can not electrons go from to holes in the p type over to the n type? I just can't understand this since it was no problem to remove electrons from holes in situation (2)?


texts: Butterworth bandpass - higher roll-off than expected

texts:
I am looking into filters, and i am using FilterLab and MATLAB's Filter designer.

I know that i need to make a bandpass filter, with a roll-off of about 48 dB/octave. This is quite high, and i would belive that i need a 16th order filter, to  achieve this.

I have now read that a 6th order bandpass filter is enough, which diverges from my knowledge. I thought that a butterworth had a roll-off of 6 dB/octave, per order.

Looking a MATLAB's Filter designer:

This pictures shows a 6th order bandpass, butterworth IIR filter. It also shows a  attenuation of ~48 dB, 1 octave above Fc2.

Why does it have such a high attenuation? What have i missed?

-------Edit------

If looking at these two pictures from Filterlab. They are both analog butterworth filters. BP filter is 6th order, and LP is 3rd order. The X axis is logaritmic.

As stated in the answer, the line looks right if measured farther away from Fc on the band pass, and looks just right on the LP filter.

What i do not understand is:

Why does the bandpass filter not have the same slope as the low pass filter at the start?

Is there a way to calculate the bandpass slope at the start?


texts: Weird but consistent noise in LM35 measurement

texts:
I'm developing an incubator which includes a hot air pump.

I'm generating the heat with 2 40W-12V ceramic resistor from 3D printer conected to a transistor (IRF540N) which is controlled by an Arduino (using PID library.)

For safety, I added an LM35 to check whether the temperature rises over the plastic box melting temperature.
The problem I have is that every time I do a measurement (I'm trying to tune the PID parameters) the same strange noise appears almost at the same time (between 200 and 700 seconds.)

Here you can see the schematics for the measurement system:

A0 is the Arduino's analog input. The LM35 and the Arduino are conected with a 1m long mesh cable.

On the other hand, the PID circuit is as follows:

D3 is the Arduino's PWM output.

The error I'm talking about can be seen in the following pictures. It repeats in EVERY measurement but more or less the same shape.

The blue line represents LM35 measurement over time.

If you were wondering what the PWM signal looks like (I suspect it might have something to do with the ascending signal of the PWM) here it is in a percentage representation:

This signal may change with the PID configuration but the noise is almost the same.

Last but not least, it is worth mentioning that the LM35 is mounted on the same small PCB board where the resistors are.

EDIT:
Here you can see other measurements to ilustrate the repetition of the problem (in shape and in time length):


texts: Wye-delta equivalent resistance question

texts:
I understand that the point of the wye-delta transform is to have the equivalent resistance between every pair of nodes be the same in each form of the circuit.

However, when I see the derivation for the concept, they treat the equivalent resistance between two nodes in the circuit's wye form to be as if no current flows into the other node.  My question is, why?  If one looks at the attached picture, for example, the equivalent resistance between nodes 1 and 2 is R1 + R3.  The resistors are treated as if they are in series.  In the real circuit, however, R2 could have drawn current.  My instinct is that that would affect the situation and make it differ from treating the circuit as if R2 didn't exist at all and that all the current from R1 flows to R3.

I think my question might come from a lack of understanding of equivalent resistance, as lame as that may be.  I am used to thinking of Req in terms of maintaining voltage-current character in a circuit (as in, the same current flows into and out of the equivalent resistor as it did the original element, and the same voltage is across the element), so I don't understand the method of finding equivalent resistance between two points while ignoring the current going into the third resistor.  I don't understand how voltage-current character is conserved in that case.

Thanks to anyone who can help me understand this better!

EDIT:  The derivation I'm referring to is as follows:

http://i.imgur.com/gffFTzt.png (the editor is screwing up and not letting me post the image in here).  Note they set the equivalent resistances equal for each configuration.  This is intuitive, except when the calculate the equivalent resistance of each branch they do not consider current flowing through the other branch (as in, Rxy = R1 + R2 as if they were in series, except the two are not in series.  I don't understand equivalent resistance in this context)


texts: Design an SMPS to provide 5V – Transformer

texts:
I'm trying to design an integrated IoT device that will replace standard light switches. Currently I'm using a Switching Power Supply from eBay: HLK-PM01, just to have an working prototype. Now I spend over a week searching for example schematics, IC and others to create my own small switching psu, but really I'm quite unsure how to begin with.

I need to provide around 300 mA 5V from 240V AC in my whole circuit. I've got an ATmega168PA, nRF24L01+ and other less important components, like status diodes and one analog sensor to power. I'm building the psu on my own to have the possibility to arrange those components on the PCB a bit more and to gain more knowledge about those modules.

Found out that an IC from the TNY263-268 family, from Power Integrations should fit my needs, but now my problem is:

  What type (something like EF12.6 or EE13..?) and from where could I purchase a complete transformer that will fit into my circuit?

Often most examples mention discrete component values, but those transformers aren't really described.

Maybe I'm horrible wrong with all this, but I'm open to all suggestions and advices I can possible get.


texts: What is the difference between circuit switching vs virtual circuit switching data communication?

texts:
The circuit switching method of data transmission which was used traditionally is way too similar to the virtual circuit switching (packet switching) communication technique. What is the difference between this subtype of packet switching? What has improved in this packet switching methodology?
All the steps followed are almost the same and I don't see the reason for the introduction of the virtual circuit switching technique.


texts:
I have an embedded system that is not cost effective to roll a custom PCB therefore my access to certain buses are limited. I had the idea of hooking my FPGA up to the unused NAND port of the system for high speed communications. I would need to write a custom driver based off the Linux MTD driver but It would allow mmap access to the FPGA.

The NAND flash peripheral clock on this specific embedded system is set at 33MHz in the Linux kernel and the SPI peripheral is 33MHz with a max clock of 30MHz. While SPI would be slower due to its serial output is their any underling complexities to the NAND bus that would make it slower than SPI?

All of my communications are 8bit commands followed by 16bit data.


texts:
I have an Harmonic drive and would like to design a PLL (phase-locked loop) controller for speed control of it. Here is a block diagram of a motor-speed control system based on PLL techniques:

My Question is about power amplifier (servo amplifier) (see image above).

What is best circuit for servo amplifier of DC motors?

Desired circuit must have poles at much higher frequencies than the poles of the motor. Any ideas would be appreciated.


texts: driving a medium power darlington transistor with the output of a 555 timer

texts:
Question: What is the limitation on the output of the 555 timer with respect to the requirements of the input of the BDW42G? Can the 555  provide enough current at 5 volts to trigger (sufficiently) the input (base) of the BDW42G?

I am using a 555 timer to generate the pwm signal and would like to drive a power Darlington transistor like the BDW42G.

The Hfe of the BDW42G is 250 for 10amp Collector Emitter

Darlington output requirements: 90volts DC at 10Amps (max)


texts: Can I make a dual output USB charger by connecting two USB sockets in parallel?

texts: I bought an old wall plug that outputs 5VDC and maximum 2.5 A and thought I'd make a USB charger. Considering the amperage I figured I might as well put two outputs, but now I'm not sure how to connect them. Will it work if I just wire the + and - connectors of the USB ports in parallel?


texts: Combining 5V power supplies in parallel to obtain more current

texts:
I need to power 20 5V RGB LED strips, each consuming 1A at full white. I'm working with off the shelf 10A supplies, so technically I can power them all by combining two 10A supplies.

I read that by protecting the 5V DC output from each supply with a reverse bias diode, I can connect them on the output side in parallel to achieve 20A. I can calculate the required cable diameters just fine (yes they're big!) so will be feeding power at several points instead of all at one end. But I do need some help figuring out the exact specs of the Schottky diode I should use for this. Can anyone help me calculate this please?


texts: What are the best beginner project using an arduino

texts:
I'm looking for some cheap beginners projects that show the uses of an arduino.

things like turning on and off an LED

getting back sensor data

...

if anyone has come across useful youtube video tutorials that would be perfect!

that sort of thing


texts:
I'm using an esp8266 to read signals from a water meter.  The meter periodically closes a switch between two wires.
My prototype circuit works fine with either an external pull-up resistor, or using the internal resistor in the microcontroller.  Is there any advantage to using one or the other?
Thanks!
details:

Microcontroller: HiLetgo ESP8266 NodeMCU CP2102 ESP-12E
Meter: DAE MJ-75


texts:
I've seen various projects using copper lugs and compressing them with bench vices but what is the actually use? Can't you just use wires without the lugs?

Image Source


texts: Convert Plugin Christmas decoration to a battery operated light

texts:
I have an old ceramic Christmas tree that I would like to convert to a battery powered source in order to get rid of the cord.

Ideally I'd love to add a timer to it as well.

I'm not sure what would be the best light source to add here since the light needs to be pretty bright.

Any ideas would be appreciated!
Thanks in advance


texts: 3 Phase Energy Meter to measure multi channel

texts:
Can I use single 3-phase energy meter to measure multiple 3 phase load using multiplexing relays for the CT outputs?
For example like below picture.

The intention is to log data for multiple 3-phase load such as V, I, PF over the time. In the market, there is multi-channel energy logger but the price is too expensive for me.


texts:
I bought this RS232-TTL converter
https://www.digikey.com/product-detail/en/seeed-technology-co-ltd/101990008/1597-1306-ND/5487765

and I'm using this along with an Arduino Mega 2560

I'm feeding the Arduino using this dc-dc converter directly to a 5[V] pin (i know this is not recommended and using a dc-dc is advised)
https://www.digikey.com/products/en?keywords=pyb10q24s5u

The DC-DC is feeded by a 12[V] - 12[A] DC power supply.

The same DC-DC is used to feed the rs232-ttl module

Testing configuration:

-2400b 8 bits 1 sb np.

-PC > USB cable > Arduino(usb powered) > RS232-TTL module(powered by the
Arduino)>RS232-USB>PC(com8)

->sometimes it works:

Vcc = 5[V]
V+ = 8 [V]
V- = -8 [V]
C1 and C2 oscillate.
communication** works

-> and sometimes it doesn´t.

Vcc= 5[V]
V+= 4[V]
V-=0.6 [V]
C1 and C2 not oscillating.
Communication** not working.

EDIT: if i send a character from the PC, it starts to work, which is not a desired behavior.

EDIT2: same behavior with the Arduino out of the picture)

Now, using the intended connections .

(usb cable not connected)
PowerSource>DC-DC>Arduino(powered by dc-dc)>RS232 module (nothing
connected)

Symptoms:

Vcc= 5 [V]
V+= 4 [V]
V-=0.6 [V]
C1 and C2 not oscillating.
Communication not working
heats

Same connections, using loopback:

Vcc= 5 [V]
V+= 4 [V]
V-=0.6 [V]
C1 and C2 not oscillating.
-Rx at 3 [V]
-Tx at 3 [V]

Same connections, connected to pc

Vcc= 5 [V]
V+= 4 [V]
V-=0.6 [V]
C1 and C2 not oscillating.
Rx out: at 3 [V], when a signal is sent from PC, it goes from 1 [V] to
4[V] then goes back to 3 [V]
Tx out: nothing

i've been trying everything, i bought 6 RS232 modules and tried 3 so far, all of them have the same symptoms

EDIT:
well, the RS232-TTL works IF a signal comes from the RS232 side first (ie:PC or Modem), if the TTL part does Tx first (ie: Arduino), the max3232 will heat and it becomes unusable, it seems to be a problem with the low power mode.
And that is all, no solutions, just a work around.


texts: DC/DC converter in parallel with analog circuit

texts:
I have a DC/DC converter that takes 6.3 V and converts it to 900 V. I am attempting to run it in parallel with an analog circuit that runs at 12 V (see below).

Without the analog circuit in parallel the DC/DC converter works fine. As soon as the extra circuit is added in the voltage drops to some 0.45 Vdc for the input of the converter.

The dcdc converter is a pcb element (EMCO q15-12). At full load it is drawing 7mA.

Is this some type of impedance matching issue? Something else?  My main focus is physics. I am relatively new to advanced circuit design.

simulate this circuit – Schematic created using CircuitLab


texts: How do reflections of a square wave cause ringing in transmission lines?

texts:
When a square wave is applied to a transmission line which is not terminated with its characteristic impedance, reflection and ringing occur.

I don't understand how sinusoidal ringing occurs when I apply a square wave.

I really don't understand the mechanism of reflection in case of square wave.

When a square wave is applied, is the square wave reflected or are its harmonics reflected?

If harmonics are reflected, why?

Edit: The present answer and comments clarifies regarding the above questions. I mainly wanted to know the case why ringing is observed in the open circuit termination at both ends. What is the mechanism behind it?

Please consider answering the questions in edit.


texts: Why does the voltage across a shunt spike then settle?

texts:
I'm using a 50 Ohm shunt to measure a current of about 50mA driven by a voltage of 110v 60Hz AC as a zero-crossing square-wave (with a step at the zero-crossing).

Using my oscilloscope I can see that the voltage from the supply (an inverter designed for the US caravan market) is a pretty good modified square wave but the voltage across the shunt, at the start of each cycle, rises to a sharp peak about twice the stable value to which it then falls for the rest of the positive cycle. The same overshoot happens with the negative cycle, but to a high negative peak which then falls to a stable negative value for the rest of the negative cycle.

There are similar peaks, positive and negative, when the supply returns to zero at the end of each half cycle.

This seems to be an effect of the shunt alone, since it's an extremely simple circuit and the voltage (1) across the supply shows no such peaks, but why does it happen and how can I get rid of it?

If I disconnect the load, and there's therefore no current flowing through the circuit, I still get peaks (though just one +ve and one -ve per cycle) across the shunt (ie V2) (but not across the supply - V1).

I hope that clarifies.

circuit

Voltage waveform 2 - across 50 Ohm shunt

Voltage waveform 1 - across the supply

Voltage waveform 2 - across the shunt with load disconnected


texts:
Having trouble understanding this ladder logic program. I can solve more basic ladder logic programs but I do not know how to account for small voltage adjustments. Here is the problem:

You are designing a PLC program which controls a cooling van on a vehicle engine.  The engine must stay at 205 degrees F.  The PLC should have 2 outputs for fan control: an output which turns the fan on and off, and a second output which is a voltage value which corresponds to the speed of the fan.  The fan speed voltage should be between 0 and 5 volts, where 0 V indicates a slow fan for 1 degree above temperature (206 degrees) and 5 V indicates maximum fan speed for 10 degrees above temperature (215 degrees).  The input to the PLC is a thermopile which is 0 V at 150 degrees F, and increases by 25 mV for every degree F above that.  The system should also have a third output which is an overheat light which flashes if the engine temperature ever reaches 15 degrees above the temperature setpoint (220F).


texts: A material that gets tough when current is passed through it and becomes soft when current is stopped?

texts:
Is there any material that can harden when electricity is passed through it and soften when current is stopped?

I basically want to use this material in a glove. The glove should get tough and difficult to bend when I pass electric or magnetic field through it. And once the field is removed, it should get back to how a normal glove works.

The best options to be used seem to be the Electrorheological or the Magnetorheological fluids but there seems to be a problem for both-
1) Which fluid can I use for Electrorheological application. Can it be made at home via some chemical or physical reaction?
2) If I use a mixture of Iron fillings and vegetable oil as a magnetorheological fluid, how do I create a magnetic field using arduino?


texts: Does combinational and sequential logic correspond to some mathematical logic systems?

texts:
Is it correct that the functionalities of digital circuits are divided into combinational logic and sequential  logic?
Is combinational logic the same thing as propositional logic in mathematical logic?

In automata theory, combinational logic (sometimes also referred to as time-independent logic) is a type of digital logic which is implemented by Boolean circuits, where the output is a pure function of the present input only.

What mathematical logic system does sequential logic correspond to, if any? Modal logic, temporal logic, ...?
I have heard of finite state machine/automaton (a topic in formal languages and automata) for sequential logic. Are finite state machine/automaton and temporal/modal/... logic  different (unrelated) approaches to study sequential logic?


texts: How does a non-integrated compact fluorescent lamp work?

texts:
I have some bulbs similar to this one: Osaga UV-C Lamp 36 W PL-L 2G11 (I can't find a manufacturer page for it)

Can anyone explain how does such bulb work and what other components I need to make it work ?

Note: the fact that this is a UV-C lamp should be irrelevant, based on the comments and some answer attempts.


texts: Keil : LPC1768 UART : Error: L6200E: Symbol a multiply defined (by main.o and uart.o)

texts:
I am learning ARM programming. I've configured uart of lpc2148 before. But there I included entire code in single file. Today I separated them in .c and .h file. But When tried to build, I got following error

uart.axf: Error: L6200E: Symbol a multiply defined (by main.o and uart.o).
uart.axf: Error: L6200E: Symbol i multiply defined (by main.o and uart.o).
Target not created

Below is the code
main.c

//main.c

#include "uart.h"

int main(void)  {

    uart_init();
    uart_tx("Hello\r\n");

    while(1)
    {
        uart_rx();
        uart_tx(a);
        uart_tx("\r\n");
    }
    return 0;
}

uart.c

//uart.c
#include "uart.h"

void uart_init()    {
    PINSEL0 |= (5<<0);
    U0LCR = 0X83;
    U0DLL = 97;
    U0LCR = 0X03;

}

void uart_tx(char *data)    {
    while(*data)    {
        U0THR = *data;
        while(!(U0LSR&(1<<5)));
        data++;
    }
}

void uart_rx()  {
    for(i = 0; ; i++)   {
        while(!(U0LSR&(1<<0)));
        a[i] = U0RBR;

        if(a[i] == '\r')    {
            a[i] = '\0';
            break;
        }
    }
}

uart.h

//uart.h

#ifndef UART_H
#define UART_H

#include <LPC214X.H>
#include <stdio.h>
#include <stdint.h>

char a[100];
int i;

void uart_init();
void uart_tx(char *);
void uart_rx();

#endif

I found some links, but none of it seems to give a solution

link1

link2


texts: Can a NMOS transistor be used as a Current Controlled Voltage Source?

texts: Assuming an NMOS transistor is in saturation. Can you apply a current \$I_{DS}\$, resulting in an output gate-source voltage (\$V_{GS}\$)?


texts: Non-inverting unity gain buffer appears to be inverting

texts:
I have constructed a circuit which uses two non-inverting unity gain buffers on one chip as stage seperation. I'm using a TL072CP chip with dual op amps on it and have followed the datasheet design for a non-inverting unity gain buffer. I'm having a problem whereby the output on both op-amps on the chip is giving what looks like an inverted signal of the inputs. The inputs are pulses generated from two seperate 555 timers, an output from one 555 timer feeds into the non-inverting input of one op-amp.

In my circuit I measure the following signals (in red) at each of the pins. I've triple checked the connections and I am fairly certain that I haven't wired something up wrong.

When I measure on the non-inverting input terminal my input signal looks like this. The datasheet which gave the schematic above advised to ensure that the input voltage must be within the recommended common-mode range. The valid common-mode range is 4 V to 12 V and my input signal amplitude is 4.64V so I don't believe this to be an issue.

Measuring on my output terminal shows this and the signal looks to be inverted

Could anyone suggest why this may be happening?


texts: Sleep modes on Raspberry Pi Pico / RM2040

texts:
I am developing a circuit with Raspberry Pi Pico. To power the system from battery, I need to put the Raspberry Pi Pico / RP2040 into sleep mode in order to increase energy efficiency. For this purpose, I used the hello_sleep and hello_dormant examples from the Raspberry Pi Pico examples as a base, added functionality to save and restore clock registers, but encountered two problems:

Whenever I put the MCU into sleep mode, there will be no more output from printf visible on the serial monitor. Output to SSD1306 works as expected.
After a couple of sleep phases, the MCU seems to freeze.

Did anyone else encounter similar problems and could come up with a solution?
Is there any working example for putting the Raspberry Pi Pico or other RP2040-based boards into sleep mode?
All hints are highly appreciated.


texts: Vias or traces through two pins of e.g. resistors on a PCB?

texts:
I made the design below in KiCad. It's for me a test to see if I can solder SOT23, 0604, 0805 and 1205 components.

Someone said it is not a good idea to make traces between two pins of a component (see all blue circles,) however, if I do not do that, I need a lot of vias, since I cannot route them around the component because on both sides traces move away from the component.

Is there a good way to tackle this? Or what should I prefer? The way below or using vias?


texts: How do I use series and parallel combinations of inductors and resistors to achieve a certain resistance+inductance?

texts:
I'm building a current driver for a load of characteristics 20mH and 5ohms.
I don't have the load with me so I'm trying to create it using inductors + resistors so I can test my driver ckt.

I have four 5mH inductors (highest I could find) and each has 10ohm resistance. I propose the following circuit, do you see any issues or have alternative recommendations? Important to note the incoming signal has a max frequency of 100Hz, so the contribution of the reactance to the inductors' impedance (Z = R + jwL = 10 + 2j) at 100Hz is not negligible. I can tolerate that for now. I can always tweak the driver signal later on once I'm testing with the load.

Also other tips like proximity of the inductors to each other (considering magnetic field effects) are fiercely welcomed. I'm not knowledgable in that area.

Thanks in advance :)

simulate this circuit – Schematic created using CircuitLab


texts:
The whole pcb layout is as the picture below(haven't poured polygon to GND).I hava some puzzlements about power wire routing.
My teacher told me if the power wire is placed like a circle or half circle,it will become an inductance which my make the pcb doesn't work.
(1)I don't know if my power routing makes a circle.Could you please help check if my pcb routing have this issue?

(2)The input 3V3 wire of top layer(red) is connected to the bottom(blue) by a via,the angle of red wire and blue wire is below 90 degree.Is this kind of routing right?


texts: How to interpret the static voltage susceptibility table?

texts: What does the range actually indicate? Does it tell the range of operation of these devices or the range in which the devices can perform optimally given an external polarizing field. correct me if i'm wrong.


texts: Measuring output voltage (Single ended probe vs differential ended probe)

texts:
I have a SMPS buck 3.3V output. I am trying to measure the output voltage at the output capcacitor using Oscilloscope.

I am using a single ended probe with spring ground tip to measure the output voltage.

The oscilloscope ground is connected to the module ground. (The module ground is not the same as board ground)

When I measure the output voltage at the output capacitor (with single ended probe with ground tip) , I find the output voltage to be very noisy.

But when I measure the output voltage using differential probe, I am not able to find the noise?

Can someone tell me where the noise is coming from?

Is this due to different grounds or some common mode current?

Can someone explain me a little clearly with basic terms?


texts: Coupled inductor vs an actual transformer?

texts: What is the difference between a coupled inductor and an actual transformer? The LT3757 datasheet mentions that I need a coupled inductor for the SEPIC to work


texts: Charging a smartphone with lead acid battery

texts:
I am trying to do this prototype where I require a smartphone to be charged for a substantial amount of time(probably as long as possible, like months or if possible years). Hence I was thinking of charging it with a deep cycle battery(like a lead acid marine battery) with a USB converter like this :(https://www.amazon.com/Marine-Dual-Charger-Socket-Waterproof/dp/B00H56BIDU)

But I want to calculate how long will one marine battery last me to charge the phone. I am quite a noob in electrical engineering and wonder how can I check the power discharge rate of a smartphone, and what is the battery capacity of a marine battery?


texts: The FCCID website is great to see what frequencies are used by different systems. The FCC is of course limited to the US/North America. Is there a similar site for Europe or other regions?


texts: Why is voltage 0 after the last component in a circuit given electron current flows from negative to positive?

texts:
Perhaps a different way to ask my question is why does voltage drop occur on the negative side of a component and not the positive given what is known about electron current? E.g. in the diagram below voltage would read 9v at node2 and 0v at node1. This would make sense if conventional current were true, but electron current makes me feel like the drop should occur at node 2, not node 1.

simulate this circuit – Schematic created using CircuitLab


texts: Which one is better as voltage divider: resistive, capacitive , low pass filter,...?

texts:
There are different types of voltage attenuators for AC signals ( a short explanation is here). The most well known is a resistive one. Others like capacitive, inductive or low pass filters are available ( Low passes may include many designs including passive or active .Thanks to Andy Aka who provided a very good link to them in another thread). I know asking which one is better (especially for high frequencies) is not a good question and the answer is :"It depends".

What I want to know is their advantages and disadvantages of them that may lead to a conclusion for selecting the best design.


texts: Advice on Electrolytic Capacitor Discharging

texts: An electrolytic capacitor of 47uf/50V is charged through a 2M ohm resistor.When it charges to 13V, the circuit shuts down and the charge remains on the capacitor. To reset the shut-down state the power is switched off and then turned on. As the cap will take too long to discharge on its own or through a bleeding resistor, Ive used a NPN transistor that switches on for 5ms and grounds the cap. Is it safe to discharge the cap this way? The circuit seems to be working fine, no faults yet.


texts: Would this button trigger alarm circuit work?

texts:
This is a dead easy question for most of you! But I'm relatively new to circuit design, so I'd just like to ask whether this circuit might work (at all!)

Here's a picture of the circuit

Basically, what it's trying to do is if the push to make switch is NOT triggered, then it should sound the buzzer, and light the LED. When the push to make switch IS triggered, then it does nothing. The toggle switch on top triggers whether the circuit is running or not, as checked by the AND gate.

It's meant to be an alarm for something of value, ideally, the push to make switch is under a glass cube that encases the item, when the glass cube is moved, the alarm sounds!

Specific components aren't really needed at the moment, in generalized terms, would this circuit do the job it's trying to do? Or would it fail miserably!

Also, if you don't understand my horrible drawing, then:

The two circles with the line on top, is the push to make switch
The triangle is the op amp (comparator)
The bent line connected to 2 circles on the top is the toggle switch
The box with 1 rounded edge is the AND gate
The rounded triangle on the right is a buzzer
The thin rectangle is a resistor
The ugly LED symbol is the LED.

Thanks for any and all responses!

Cheers,

Karan


texts:
If someone wants to use solar energy in hot places,
temperature is a problem. So, what's the solution for cooling the solar panel?


texts: Suggestion for an easy-to-use connector+cable for simple hobbyist sensor project

texts:
I'm implementing, as a hobby, a simple data logger. I previously asked a question about running a ~10m cable to the MCU for a Dallas/Maxim 1Wire sensor (and therefore 3 wires, since I'm not going to be using parasitic power), and now I'm considering connector and cable. I'd like to, if possible, use something that is easy and cheap to find and use. In that vein, I've come up with a couple possibilities:

3.5mm stereo audio jack and stereo audio cable
6P4C modular jack (RJ11) and telephone wire

Both these ideas use widely-available connectors and cheap multiconductor cable. I'm wondering if one or both of these is grossly unsuitable for some reason, or whether they would work for my purposes. Perhaps there is something much more suitable that I haven't considered?


texts:
simulate this circuit – Schematic created using CircuitLab

Here is the low pass I have used. I used the 347 op amp just because it was cheap from a local surplus house. I will get discrete values off a board if needed.

I have used this circuit to generate sine waves that are one sixth of the clock frequency. With a low pass filter on output it generates a really clean sine wave.
I am not real familiar with the stack exchange circuit editor, so I was not able to get an HC74 or 4018, so I added an inverter to show the last stage /Q going to the first stage D input.
I no longer remember where I found the original circuit, but I do have some notes that read as follows:

7 stage 14x clock resistors 22.1k 40.2k 49.9k 49.9k 40.2k 22.1k

8 stage 16x clock resistors 22.1k 41.2k 53.6k 57.6k 53.6k 41.2k 22.1k

There are a few specific things I want to be able to understand.

1 How does a circuit designer take an arbitrary n-stage walking ring divider circuit and calculate the weighting resistor values that make the sine approximation to feed the low pass filter?
I tried using an Excel spreadsheet sine function, but I was never able to get close to resistor values that I know work.

2 What is the algorithm to determine the signal strength of the harmonics generated by the circuit? So far, my lo pass filters have been trial and error to get good results.
What I have read so far suggests filters are designed knowing (or at least planning for) the worst case input signal.

3 Will this approach work for TTL as readily as CMOS?

I am certain that there are several other approaches to generating multiple clean sines from digital logic; this particular one also provides useful osc/n signals that make it appealing to me.

If the scope of the question is too large for this forum; I would still be pleased with a pointer to a reference book to purchase and read.

Thanks.


texts: Best way to control 75 LEDs with Arduino

texts:
I need to control 25 groups of 3 LEDs or 25 RGB LEDs. Each group will be dismissed from the uC by up to 20 cm (about 8 inches). 20 cm is very safe assumption but I think it will be 10 cm or less.

However, I think If it be even 5 cm, it will be hard to create in matrix way, so I think using MAX7219 likie IC (http://www.arduino.cc/playground/Main/MAX72XXHardware) is not best idea.

I will probably use shift registers (http://www.arduino.cc/en/Tutorial/ShiftOut). I can connect multiple 74HC595 or use something like STP16C596.

I prefer STP16C596 but they are obsolete. I found SCT2026 (http://zefiryn.tme.pl/dok/a04/sct2026.pdf) but I'm not sure is It right choice.

One more note.
My current project requires only "2 bit control" over each group (3 LEDs off, or selected and turned on only one of them), but I don't think it make my project easier or cheaper, also controlling each LED separately will give much more flexibility in case of changes.

What solution will be fit best for my requirements.

It will be nice if parts will be available in this shop - http://www.tme.eu/en/katalog/?&page=1,20#main or http://eu.mouser.com/ (but i prefer first one).


texts:
I want to adapt a standard connector for all my projects. My projects include microelectronics done with a soldering iron, so 0.1” pitch is small enough for me and very convenient for soldering. I’m also not dealing with resistance/capacitance critical electronics (such as radio).

I’m searching for a connector that is:

Widely used and common
Non-proprietary
Polarized (that’s why i don’t like simple pin headers
Relatively small factor connector (best would be about half of pun headers)
Well defined and non ambiguous design (such as jet and molex)
Easy to solder and optionally pogo-plug support
Both PCB and breadboard friendly versions (SMD and DIP terminals)
4 to 8 wires support


texts: Why couldn't my battery pack start my car?

texts: I want to be able to start my truck with a li-ion pack I made. It is a 4S1P pack made from Headway 38120 cells. They have a max continuous discharge of over 100A. I can't recall the max pulse discharge rating, but the site I bought them from  said they had been able to start a car from the same 4S1P configuration. When my car battery died, I connected the pack via jumper cables (14.4V fully charged), but it didn't quite have enough oomph to get it to start. Was this caused by a voltage sag resulting from a huge current demand? Or is it more likely that the impedance of the jumper cables combined with the cells' internal impedance was too high to deliver enough current? Can I fix this by going from 4S to 5S, or do I need to go from 4S1P to 4S2P?


texts:
Let’s assume

bog standard two layer ESD mat with static dissipative top and
conductive bottom layer, with resistance to ground somewhere between
one mega-ohm to one giga-ohm and with both a mat and an operator
grounded to a common ground point;
bog standard consumer or HEDT motherboard.

A) If I were to put a completely new motherboard straight from its retail package onto the ESD mat, would there be any risk of said mat draining CMOS battery or shorting out RTC circuit powered by CMOS battery? Why? Why not?

B) Does the situation change if the motherboard have been on for some time before turning it off and immediately putting it on ESD mat? Why? Why not?

C) Is it safe to turn the motherboard on while laying on the ESD mat? Why? Why not?


texts: Why exactly is a Hertzian dipole inefficient?

texts:
http://farside.ph.utexas.edu/teaching/em/lectures/node94.html states:

Note that the formula (1100) is only valid for \$l\ll \lambda\$. This suggests that \$R_{\rm rad} \ll R\$ for most Hertzian dipole antennas: i.e., the radiated power is swamped by the ohmic losses. Thus, antennas whose lengths are much less than that of the emitted radiation tend to be extremely inefficient.

Of course, this is a well-known fact. But I don't see the reasoning for that.
Let's plug in some numbers (10 kHz, wavelength 300km; length of dipole \$l=300\mathrm{m}\$ (=100x less than wavelength).
\$
R_{\rm rad} = 789 \left(\frac{l}{\lambda}\right)^2 = 78.9m\Omega .
\$
The text above does not clarify what exactly is meant by the swamp of ohmic losses. But on the back of some envelope, let's assume that the wire can't be longer than \$l\$ (by definition) but that also implies that it can't wider (otherwise it would get longer). So as an upper bound we have a metallic cube of length \$l\$. Resistivity of silver is 1e-8:
\$
R = 1\cdot 10^{-8} \frac{l}{l^2} = 33p\Omega .
\$
Orders of magnitude smaller than the radiation resistance!
Even if I make the cross section 1000x smaller than the length, the ohmic losses are still just \$33\mu\Omega\$ ... orders of magnitude smaller than the radiation resistance.
I also take the Skin effect into account but it does not change the result significantly:
\$
R_{\rm skin} = \frac{\rho}{2\pi r \delta} = \frac{\rho}{2\pi r \sqrt{\frac{2\rho}{\mu 2\pi f}}} \approx 27\mu\Omega .
\$


texts: Direction of current in a wire connecting two conducting loops placed concentrically in a time varying magnetic field which is into the plane of paper

texts:
Figure shown plane figure made of a conductor located in a magnetic field along the inward normal to the plane of the figure. The magnetic field starts increasing. What will be the direction of current at point R ?

I know currents in both the loops will be anticlockwise, but I am not sure about the direction at R.


texts: Unexpected ESC behavior upon propeller contamination

texts:
Background:
I am investigating propeller behavior upon contamination.
For that i built a test rig with one DJI E800 brushless motor, E620s ESC (sensorless) and standard prop. I am giving the ESC a constant input signal pulse width and monitoring rotational speed, consumed power and thrust.
I have a continuous increase of contamination over time.
Issue:
Apart from decreasing thrust I noticed that with heavy propeller contamination the motor rotaional speed is reduced (probably due to larger drag/mass of the propeller) and the consumed power increases (Edit: increased Amperage at same Voltage).
Question:
I cannot wrap my head around this.
Edit: An increase of load (drag increase) should lead to a lagging of the rotor, which again leads to an increase of amperage  and finally to an increase of torque and a syncing of the rotor, thus keeping a steady rotational speed (like mentioned in the comments). An increase of Amperage goes along with the design principles of synchronous machines/motors, but somehow the RPM decreases and that is the point i get confused with.
Edit: I am reading the amperage and voltage of the power generator, which i am using to supply the ESC and motor.
The things i know about the ESC - Motor system are:

it's a synchronous machine
User Manual: https://dl.djicdn.com/downloads/e800/en/E800_User_Manual_v1.0_en.pdf

I am grateful for any hint!
Cheers!


texts: Why is the common emitter input insensitive to base width modulation?

texts: According to Robert F. Pierret (1996) in page 411 of the 2nd edition of the textbook Semiconductor Device Fundamentals, common emitter input of PNP BJTs is insensitive to base width modulation. Isn't the common emitter input simply the base current \$I_B = I_E - I_C\$ and assuming that the BJT is operating under active mode, should be sensitive to base width modulation since \$I_E\$ and \$I_C\$ depend on the quasineutral base width \$I_B\$? Moreover, \$I_B=\frac{I_C-I_{CE0}}{\beta_{dc}}\$ and \${\beta_{dc}}\$ is clearly dependent on the quasinuetral base width W which means \$I_B\$, the common emitter input, should be dependent on \${\beta_{dc}}\$ as well?


texts: Op Amp: Gain Bandwidth Product and LP Filter

texts:
What will happen if I use an op amp as a buffer amplifier for signals with frequency greater than Gain Bandwidth Product. More specifically:

1) Say I have a signal with 2 frequencies: a) 2 MHz and b) 20 MHz. Say the Gain Bandwidth product is 5 MHz. Will the 20 MHz frequency be severely attenuated and 2 MHz signal pass as it is?

2) If that is the case, what can prevent me from using the buffer as a Low pass filter, to pass 2 MHz signal only?


texts:
So the main idea is to take the component video of my consoles and convert them to VGA using the LM1881 IC, to strip the sync signal.
If I was going to plug the green cable from my PS2 component into this chip, for example, and then output to the VGA monitor, will it work or do I still need something else?
Consider the scheme below from this thread here: Convert SOG to VGA using LM1881


texts:
I am using two MOSFETs (IXFB210N30P3) at about 100kHz (with different duty cycles) to split current from a 100-200V rectifier into three separate coils. This is a very rough schematic of (one branch of) the circuit (apologies for the diagram, I'm in no way an electrical engineer), where the box is actually a PWM controller putting 15V across the gate at 100kHz.

If the diagram isn't clear, here is a hand-drawn version with the details of the FET driver. The capacitor across the FET is supposed to be a snubber circuit, but I'm not sure if I need a smaller capacitor or a resistor in series to actually work. Either way, with even just a few volts across the coil (the 1 ohm, 6 mH component), I start seeing huge voltage spikes at the MOSFET gate

which I haven't been able to remove. I imagine this has something to do with the enormous inductance of the coil, but I've tried a number of filters and diodes with little success. I'm wondering if someone could explain this to me, and potentially recommend a solution. I have ferrite beads on just about every component, and a few low pass RC filters now, but the voltage spikes are still there. What value resistors and capacitors should I have on the snubber circuit across the FET? The diode and FET are quite large, so potentially they're just too slow for the high-frequency switching.

For reference, here is what the signal looks like for very small voltage across the coil, where yellow is voltage at the gate, cyan is the voltage at the drain, and purple is at the source.


texts:
I have been working on a project for the past four months. Most of my development have been on breadboards and prototyping boards. I am now in the stage where I want to get a PCB printed and fabricated so that I can miniaturize my device.

I am new to the process of sending designs and schematics in for fabrication, and wondered if someone knew how I can get started?

I am at a loss as to where I should go and what software to use (preferably something free). I have worked with Eagle to do very basic things before.

Also, what would be the best way to solder the surface mount components after assembly?

The packages for soldering are VQFN for all IC's and regular surface mount resistors  and capacitors for the rest.


texts: OLED Custom Character not being displayed correctly on Arduino Uno? Too Many?


texts: Transmission line voltage measurement(visualizing standing wave)

texts:
I want to measure voltage across a T-line to visualize standing waves on the line.

something like this video min 6:53 and this experiment Measuring Standing Waves on a Microstrip Transmission Line

I have purchased this VCO to generate RF source signal.It's 5mW.

I am using 12V 5A power supply.

This is my circuit (T-line is open as I want to meassure open, short, and, matched)

Then I used a voltage multiplier circuit to detect the RF signal(also tried half wave rectifier) and connected it's output to my analog voltameter with 0.5V, 0.25V, 100uA scale, but I didn't get any reading.

I used 1n34a diodes with ceramic 10nF caps.

Questions:

Why doesn't voltmeter read any value?
What is the dominant factor that would cause that?
How to diagnose the circuit without expensive equipments?
Is there any easy to find device to get high power RF(from cellphone, TV, ...)?

Note:

I used solder on the microstrip, because I am planing to put a stepper and slide the probe through the line(similiar to slotted line device).
I don't use lecher line as it would require more powerful RF source.
I have designed a circuit to generate around 2Ghz, but I delayed the fabrication to verify the concept with the above VCO.
I know that it is more practical to use microstrip wave guide with ground plane, but it would be hard to get these small vias connecting upper plane with the lower one and It would take a long time to arrive.

I want the minimum setup(just working).

Thanks in advance.

UPDATE:

Here is detector circuit:

I have tried it and it's working as expected"I havn't soldered buffer port yet".

My short circuit is not perfect and it is lowering the maximum amplitude.

@The Photon: thanks a bunch.


texts:
I'm new to microcontrollers and I'm a little confused about the P3 pin on the msp430g2553.

In this tutorial it mentions setting P3DIR and P3IN for the push button, but I can't see where P3 meets the microcontroller on the board itself. The button is labelled as P1.3 on the board rather than P3.

Also, when I searched msp430g2553.h I found that P3 was defined.

Is P3 a legacy pin or is it actually used?


texts:
I have recently been trying to build an Arduino based VSWR bridge. The final goal is to make it feature rich but right now im having trouble calculating the forward and reverse voltage from the ADC inputs (or even from the raw voltages measured with my oscilloscope).

From what I've read in similar projects this is usually a simple linear relationship between ADC input and the forward and reverse voltages, from there its just a matter of calculating the power as if the voltage were across a 50 ohm resistor. My conclusion is that the issue is most likely in my electrical design somewhere.

I only made a single Directional Coupler but tried a few variations for the envelope detection circuit. All variants of my circuit seem to have the same problem so right now my suspicion is an issue in my Directional Coupler. But I've seen other people using the same design as me successfully, so it is just a guess. I could really use some help on what I might be doing wrong.

So let me add some technical details. These are the details I'm testing against or want to achieve.

Operational Frequency: 1.5 Mhz - 30 Mhz

Frequency used for testing: 21 Mhz

Operational Power Handling: up to 1500W

Power used during testing: 5W - 200W

Below is the schematic for my design, the image also includes the various voltages (DC) read under various conditions. These voltages seem odd to me as I get a lot of reflected voltage even when the load is a 50 ohm dummy. Each of the transformers in the schematic are 12:1 winding rations. The "1 loop" winding doesnt make a loop at all but simply passes through the middle of the core.

For some additional information here are pictures of the circuits. The first picture is the Arduino with a proto-shield containing the envelope detector (the AD8302 at the top is currently not used in the software and is high-impedance, so it can be ignored). The second picture is the high-power Directional Coupler. Everything was made by me (obviously).

Here are my thoughts so far on possible causes, but most of them I havent confirmed or am not really certain they are the root of the issue (rather than just considerations).

The diode is in its non-linear region. I ruled this out because the issue persists at high power and doesnt explain the high reflected voltage.
The issue is normal and I need to just calibrate for it in software. Though I've been unable to figure out how.
The hot glue I used that fills the center of the coils is lowering the Q of the coils significantly. This however, I don't think, would result in these symptoms.
The two coils are coupling causing the high reflected voltage. However this didnt seem to be as big an issue in other people's circuits.


texts: Help reverse engineering PWM Dimmer Flicker-less mod

texts:
I've been playing with LEDs for video work for a while. I made some LED panels using strips and off the shelve controllers which always worked nicely while on full brightness. Everytime I dim then down, I start to get some weird "scanline" flickering. That happens to all sorts of leds and dimmers (Arduino included) Ive ever played with.

Yesterday a friend told me he got a modded 12-24V 8A Dimmer which extinguish this kind of problem. Once I got it on hands I was surprised it looked just like a 12-24 Dimmer I got from eBay. Googling around I found out it's a very popular circuit, with MANY different PCB layouts and different vendors.

I tried to find Flicker related mods online but couldn't find anything. Obviously I opened his circuit and it's surprisingly similar to mine, apart from 3 differences I spotted:

I tried to transpose this mods to my PCB. I think I got two of them right (Yellow and Green), but I just can't find where to do the mod which I circled in red (the trail that has been interrupted).

I tried to follow the trails but they go underneath the LM358 and the 3 pinned connector. The other IC is a 555.

I have two questions regarding this situation, which my restrict electric engineering knowledge is not helping me out:

Where I should interrupt the board on my PCB Layout?
What exactly this MOD did that eliminated the flickering on video?

Here are a few other pics of the boards:

Any help or tips are extremely appreciated! Docs and Papers regarding LEDs and Flickering are also welcome :D

Thanks in advance!

EDIT: I managed to unsolder the pot conector and the two ICs so I can get a better view of the board. I did destroyed one pad on the U1, which apparently didn't connect anything, just the jumped pins.

There's also a solder blob between U1 and the middle pot pin. It's a jumper to rejoin a track I manually interrupted and repaired afterwards.

[![Another Overview shot][9]][9]

I'll be posting demos of both circuits working so I can show you the visual difference too.


texts: Cannibalizing a printer, how to figure out what some of the parts are/do

texts:
My son an I are attempting to cannibalize a printer a HP LaserJet 1300.  It used to work and print, but it was low on toner and the company we got it from replaced it instead of buying new toner.

So, we have some parts and are trying to build a centrifuge (the low tech version) using the motor inside the printer.  It is a Nidec RK2-0063 45M0600024 24VDC 1.4A.  You can see what it looks like here: http://www.kpsurplus.com/hp-printer-nidec-rk2-0063-main-motor-45m0600024-24v1-4a.html

Anyway, we have been drawing a blank on finding a datasheet for this motor/control assembly.  The 5 pin connector has a pinout of Vcc FG /DEC /ACC GND but we don't know what FG means, and don't know what to feed it on /ACC and /DEC

Vcc -> Gnd is ~24 VDC which is to be expected since it is a 24 volt motor, but what are the other pins for/what voltages should we use to control the motor.

What kind of motor would you call this?


texts: What is the real problem with fixed point bias circuit?

texts:
In the circuit below, the texts mention the problem with this kind of biasing here is if the hfe(β) varies then the Ic will vary in linear reagion. (What varies what here also not clear, I thought all variation source was Vbe). Anyways:

Their argument is the following:

Imagine for this circuit we want to size R4 for a desired Ic, known R3, known supply voltage Vcc and known β.

So we can say the required Ib is:

Ib = Ic/β

and we can write a KVL equation to find R4:

Vcc-Vbe = Ib x R4

R4 = (Vcc -Vbe) / Ib

Then they say this circuit is biased well but if the β varies i.e if you rely on datasheet, or change the transistor ect, the circuit will fail.

I can understand that, but my problem is when they reach sizing R4 in their calculation they take Vbe as a fixed value like 0.7V. But indeed Vbe changes with R4 and we also know that a small change in Vbe has a huge impact on Ic.

I don't know why they don't mention this as a problem. I'm wondering if I misunderstand something here. So my question is, imagine if the β were guaranteed to be fixed as a constant and we don't have a problem with β variation. Don't we still have a problem here not knowing Vbe's exact value when sizing R4 from that KVL equation? I mean Vbe varies with R4 but they still take it as 0.7V.

(Shouldn't they find the real Vbe form Eber Molls equation to find the accurate R4? But for that we need reverse sat current.)


texts: What's wrong with my simulation for Bi-directional logic level converter?

texts:
I am trying to make a simulation by using Multisum 14 for i bi-directional channel for Logic level circuit from SparkFun which use Philips AN97055 IC as a Bi-directional level shifter...

The shcematic for one of it's four channel is shown below

The circuit design in Multisim is shown below

in this design im trying to simulate the situation of using 3.3v sensor with 5v MCU by make the switch on to send the 3.3v from sensor to logic level circuit then the circuit convert 3.3v to 5v and send it to MCU i use Multi meter to read the final Voltage, but as you see the voltage is still 5v either switch in circuit is "ON" or "OFF" why?

Q2/ why use resistor in the design of chanel one and each channel in sparkfun logic level converter what is the purpose of register also when I compare the Bi-Directional logic level converter to the one direciton

So can someone explain the schematic and how to use the bi directional chip and how it's work without forget the purpose of resistor.

Thanks for everyone shearing his knowledge in this site,


texts: Why 2 equal decoupling capacitors are needed for each STM32 VDD pin?

texts:
I was watching this Kicad tutorial for an SMT32 chip and at 9:15 it says that the recommendation for each ot the VDD pins on the SMT32 chip is to put 2 100nf capacitors.
On this video: https://www.youtube.com/watch?v=BcJ6UdDx1vg I understood what decoupling capacitors are for, and I also understood why they're needed in parallel and why we can't simply substitute all of them for an equivalent one. It has to do with the curve of impedance. Each capacitance is able to reduce the impedance for some frequency. So that's why we use different capacitances.
However, I can't see a reson why 2 equal ones are needed for each VDD pin. Why not one with equivalent capacitance?


texts: Connecting a low-side gate driver to a FET with current sense resistor

texts:
When connecting a low-side FET gate-driver to a FET (N-channel MOSFET) that has a current sense resistor connected between its source and ground, where should I connect the ground of the gate driver?

I am of two minds on this. First, all of the data sheets that I have looked at do not show a current sense resistor on the FET's source. As a result, the gate-driver has its ground connected to the source. Because it is the capacitor between the gate and source that I am charging/discharging with the driver, I am inclined to connect the gate driver's source, as this way the sense resistor will not degrade di/dt into the gate. However, if I connect the gate driver's ground to high side of the sense resistor, that means that the reference for the input to the driver will move with source current. If the sense resistor is small, then I should not expect the driver's ground to move much and as long as I make sure my driving signals take this into account it should not be a problem.

Long story short, should I connect my low-side gate-driver's ground to the high side or low side of the current sense resistor that is between the FET's source and ground?

Edit: I was asked what this circuit does. This is an active dump load for a tether-operated remotely operated vehicle. In order to provide sufficient power to the vehicle, the operator side power supply will need to increase its output voltage at times to compensate for tether losses. This circuit monitors the voltage at the vehicle-end of the load and diverts power to a power resistor when the vehicle-side voltage exceeds a limit in order to keep the input voltage to the vehicle within an acceptable range. The circuit also measures current through the power resistor and communicates this (as well as vehicle input voltage) to the power supply's controller at the top end so that the power supply can be commanded to reduce its output voltage as necessary. Conversely, when vehicle input voltage drops too low, the power supply is commanded to increase output voltage. The FET controls current through the power resistor via PWM.


texts: What do the following terms mean for verification engineers?

texts:
When it comes to verification of digital circuits, what is the difference between the meaning of the following terms:

What is the difference between specification and requirement?

What is the difference between feature and function and how do they relate to specification and requirement?

Finally, what does the term configuration refer to for a design being verified?


texts:
I followed SNOA999 for a zero crossing detector using TLV7011 as a comparator. I am not sure about short-circuiting grounds between AC and DC power sources. My concern is creating negative currents on the DC side and thus damaging some more sensitive components.
I tweaked the circuit from the application note to achieve the following:

simulate this circuit – Schematic created using CircuitLab
Where D1 and D2 are schottky diodes.
Vout works as planned in a SPICE simulation. But, my doubt is if by not short-circuiting V- with the inverting input will affect the stability of Vout as zero-crossing reference.


texts: What factors affect a thyristor's "circuit commutated turn-off time"?

texts:
In datasheets, they give this value at a certain operation point (voltage, current, and di/dt).  My question is... What are the effects of changing these parameters.

For example, if di/dt is increased, will this make the circuit commutated turn-off time less? Or is the circuit commutated turn-off time an inherent property of the thyristor?

Thanks!


texts: How to detect the phase sequence of a 3-phase ac (R-Y-B or R-B-Y) using Atmega32?

texts:
I am using an 8-bit AVR microcontroller in my project to detect the phase sequence of a 3-phase AC supply. Which method shall I use to do the work with the least number of components required along with ATmega32?
I have thought of using zero crossing detectors but that would need a step-down transformer(for reducing 230V ac). Is there any other convenient way?
I have also found some other circuits and attached the images below . )

But my purpose is to detect the sequence using only atmega32(no transformer should be used


texts: How to connect bathroom scale (arduino+hx711+spark load connector)

texts:
Im a new user in the electronic world. I tried to hack my bathroom weight scale but no success. There is a great tutorial which I followed:

https://www.youtube.com/watch?v=iywsJB-T-mU

my parts:

cheap bathroom weight scale (4 load 50 Kg weight sensors)
HX711Dual-Channel Weighing Sensor Module (like here:https://www.itead.cc/hx711-dual-channel-weighing-sensor-module.html)
SparkFun Load Sensor Combinator(https://www.sparkfun.com/products/13878)
Arduino esp-32

Could somebody who has more experience take a look at my solution?

I checked with multimeter and all wires are ok.

to save place I showed only one connected load sensor but 3 next I connected in the same way.

Im getting only:

one reading:    0.0 | average:  0.0
0
one reading:    0.0 | average:  0.0
0

What can be a problem? Im trying to do a whole week with different arduinos and no success :(

code which Im using:

#include "HX711.h"
#include "soc/rtc.h"

HX711 scale;

void setup() {
  Serial.begin(115200);
  rtc_clk_cpu_freq_set(RTC_CPU_FREQ_80M);
  Serial.println("Diska");

  Serial.println("Initializing the scale");
  // parameter "gain" is ommited; the default value 128 is used by the library
  // HX711.DOUT - pin #A1
  // HX711.PD_SCK   - pin #A0
  scale.begin(26, 25);

  Serial.println("Before setting up the scale:");
  Serial.print("read: \t\t");
  Serial.println(scale.read());         // print a raw reading from the ADC

  Serial.print("read average: \t\t");
  Serial.println(scale.read_average(20));   // print the average of 20 readings from the ADC

  Serial.print("get value: \t\t");
  Serial.println(scale.get_value(5));       // print the average of 5 readings from the ADC minus the tare weight (not set yet)

  Serial.print("get units: \t\t");
  Serial.println(scale.get_units(5), 1);    // print the average of 5 readings from the ADC minus tare weight (not set) divided
  // by the SCALE parameter (not set yet)

  scale.set_scale(233.82);    // this value is obtained by calibrating the scale with known weights; see the README for details
  scale.tare();                     // reset the scale to 0

  Serial.println("After setting up the scale:");

  Serial.print("read: \t\t");
  Serial.println(scale.read());                 // print a raw reading from the ADC

  Serial.print("read average: \t\t");
  Serial.println(scale.read_average(20));       // print the average of 20 readings from the ADC

  Serial.print("get value: \t\t");
  Serial.println(scale.get_value(5));       // print the average of 5 readings from the ADC minus the tare weight, set with tare()

  Serial.print("get units: \t\t");
  Serial.println(scale.get_units(5), 1);        // print the average of 5 readings from the ADC minus tare weight, divided
  // by the SCALE parameter set with set_scale

  Serial.println("Readings:");
}

void loop() {
  Serial.print("one reading:\t");
  Serial.print(scale.get_units(), 1);
  Serial.print("\t| average:\t");
  Serial.println(scale.get_units(10), 1);

  int ww = (int)(scale.get_units(10) + 0.5);
  Serial.println(ww);

  scale.power_down();                   // put the ADC in sleep mode
  delay(100);
  scale.power_up();
}


texts:
Can anyone identify this gyro?

It's from the guts of a (deceased) hovering toy and I'd like to find a datasheet.

alt text http://www.hodgepig.org/gyro.png


texts: What is the name of the device that combines and synchronizes two AC sources into one?

texts:
I saw this device on Amazon for $450, I already forgot what it was called and am trying to find it again.
It let you combine two AC sources, and the voltage would only flow one way, and it would create one AC output with the two sources synchronized.


texts:
What is the difference between bitstream and SRAM Object File?

I understand that both are outputs of the FPGA design compilation. It seems to me that the SRAM Object File is what is loaded onto the FPGA for programming.

Then, what is the bitstream for? Or are those different names for the very same thing?


texts: Calculate distance travelled by vehicle using "knots" of NMEA data

texts:
I'm using L80 quectel GPS module. Which sends the NMEA protocol data string which has latitude, longitude, UTC time, knots, etc. We are going to use  this GPS module in a vehicle. We have to calculate the distance travel by the vehicle using GPS. We have to show the total distance travel by the vehicle like an odometer. Is it possible to calculate total distance travelled by vehicles using "knots" value from a GPS? If it is possible, then how to calculate?

Thanks..


texts: BLDC BEMF unequal power-on stage length for different phases

texts:
i'm driving BLDC using sensorless method. The driving algorithm is woking fine, but on the bemf oscilogram i can see, that the power-on stage length is little bit different for each of the 3 phases. I'm just curious why. I think that it could be caused by the motor assymetry or imperfect magnets positioning, but i'm not sure. Could it be caused also by something else? Lets assume the motor is perfectly symetrical. Will i see this effect too? Why?
Thank you for any ideas.


texts: The MOSI pin of SPI1 on STM32L073 is not giving output without pull-up resistor

texts:
I am working on SPI communication with STM32L073.
I download the example program of ST to MCU but SPI1 did not work. So I looked at the SCK pin of MCU with oscilloscope and it works fine. But when I look at the MOSI pin, I did not see anything. After that I pulled-up the MOSI pin with 10k resistor and I saw that it worked but not high enough which is not 3V3.
So what should I do to get enough output value from MOSI pin?
Pinout:
SP1,
MOSI: GPIOA, GPIO_PIN_12.
MISO: GPIOA, GPIO_PIN_11.
SCK:  GPIOA, GPIO_PIN_5.
NSS:  GPIOA, GPIO_PIN_4.
Thanks...
Edit1: I tested SPI with Nucleo-073rz. SPI worked just fine. But when I test it with my pcb, MOSI pin doesn't give output at all but SCK, NSS are fine.
Edit2: We replaced chip to stm32L152, it works!!! But I need to use STM32L073.


texts: Can I slice a flex cable to reduce its width?

texts:
I have a cable for my raspberry Pi camera that is bulky in its current wide state. While tricky, is there any downside to slicing it length wise, and stacking the pieces on top of each other? Would there be too much interference?

I also have a thicker cable that feeds a display that I would like to make narrower (see picture)


texts: How to open/close a high (~110V) voltage circuit from a low voltage (5V) one with a transistor?

texts: I'd like to turn on/off a Nixie tube from a 5V circuit system (Arduino). I've found a solution that uses transistors (1 pnp and 1 npn). Can't we do it with 1 singe transistor? What to consider? What's the best/simplest way? Thank you.


texts: Eagle PCB components do not match pin layout of actual components

texts: I a using an arduino and an ADXL335 accelerometer for a project, and trying to make the PCB for it. Unfortunately, all the eagle lbr files for these two components seem to be wrong. None of the lbr files match the actual pin configuration. Is this an issue during the schematic phase? Can changes to the pin locations be made in the board design phase? Or will the pin layouts have to be corrected in the schematic phase. If so, how can the components be adjusted to match the actual component layout?


texts: Does magnetic flux depend on the orientation of the ferromagnetic rotor?

texts:
I have attached a picture of a reluctance motor setup. When I turn on the AC source, magnetic flux lines will build up.

My question is, will the magnetic flux will be a function of the angle turned by the ferromagnetic rotor w.r.t. d-axis?

Magnetic flux undoubtedly varies in the time domain. Is time the only variable the magnetic flux depends on, or is it also a function of θ?


texts: "Rigorous" motivation behind the model of transmission line for microwave engineering

texts:
I am trying to understand under a rigorous enough point of view the model of transmission lines.

More specifically I am interested to this question under the context of microwave engineering.

Important precision: I am not an engineer so I might not understand technical temrs you might use. I thus would like to stick the closer to the vocabulary of physics in the answers.

If we consider a "long" transmission line, that current and voltage won't be uniform in it and we will be able to see propagation phenomenon.

Then, to model it we use the following model as explained here: https://www.microwaves101.com/encyclopedias/telegrapher-s-equations for example.
For an length $dx$ of the line, we say that we have the following electrical circuit.

My general question is the following:

What motivates rigorously this model for microwave engineering ?

This model has wider application than for microwave engineering but I would like to understand why it works in this context.

Thus, we will assume that the "+" line and the "-" line are composed of a single metallic layer. It is thus not a "big" cable in which you may have little ones inside (sorry for my limited vocabulary in electronics). Both + and - are really intrinsically single wires.

More precise questions:

In understand the presence of the capacitor in the following way:

The + and - cable are separated by some insulator, we can model their connection as a capacitance (because metal - insulator - metal = capacitor behavior).

We can also include a resistor in this modelling (the air is a resistive material in a sense), which motivates G

Would you agree with what I say here ?

For the inductance now, I would say that it physically correspond to the magnetic flux between the + and - metallic "wires". Indeed as I said my wire are really single metallic layer so we cannot have some "intrinsic" inductance on those.

Would you agree with what I say here ?

For me the + and - wire should be symmetric with this description, so I don't see why we would'nt add as well a resistor and an inductance on the - wire ?

Why don't we add those extra resistor and inductance on the - wire ?


texts: Problems with DC analysis of a PMOS circuit

texts:
I'm beginning with electronics and I've picked up the book from Donald. A. Neamen - Microelectronics. I'm stuck at a simple example of DC analysis for this PMOS circuit.

simulate this circuit – Schematic created using CircuitLab

I have to find:
$$I_D, V_{SG}, V_{SD}$$

Parameters given are:
$$K_P = 120uA/V^2, V_{TP} = -0.3V$$

Correct results are:

$$V_{SG} = 1.631V, I_D = 0.2126mA, V_{SD} = 3.295V$$

This is how my calculations go:

$$V_G = (R_2/(R_1+R_2))*(V_+ - V_-)+V_- = 0.33V$$

I took the assumption that the transistor is in saturation, therefore:

$$I_D = K_P*(V_{SG}+V_{TP})^2$$

Now I used the upper right loop:

$$V_+ - V_G = R_S*I_D + V_{SG}$$

After these two equations, I used a handheld computer to solve
these two equations for \$V_{SG}\$ and got two results and none of them is right...

$$V_{SG1} = -2.03V, V_{SG2} = 1.24V$$

What am I doing wrong here? The correct \$V_{SG}\$ is ~1.6V.

Thank you!

EDIT:

Here are the results from the book.


texts: Using board-to-board pins and crimp receptacles to attach a non-board receptacle to a board

texts:
I imagine this is a bit of a stretch, but I'm working through some iterations of a cable harness for a 3D printer. I've considered that a custom PCB may be in order (still on the fence there), but the actual connectors I'm using right now really fit the bill (the TE1981921-1 here: https://www.te.com/usa-en/product-1981921-1.html).  I'm really intent on that due to the pin density at the given wire gauge and haven't found anything designed for boards that's close.

All that said, there isn't a wire-to-board option.  I briefly toyed with the idea of crimping the receptacles to board-to-board pins, adding a touch of solder, then soldering THOSE to the board, but I can't tell if this is "Hillbilly electronics" or if it's a feasible idea.  Is there a reason to avoid this method?  Obviously proper spacers would need to be involved, both between the jack case and board and the board and cut-through to prevent the board from cracking when you plug it in.  But are there any other reasons this would be bad?  The actual power draw should be fairly low - though it's rated highly and I considered pushing my hot end power through that connection (up to 24V @ 40W), though would be happy to also run a cable and surface mount some XT30s for power if there's a resistance or possible desolder issue with the power line.

Anyway, I'm new to DIY electronics, so thought it'd be best just to ask.  Thanks!


texts: Schmitt trigger output waveform coming as sinewave

texts:
I am new to Proteus. I tried simulating an easy circuit which was a Schmitt trigger using an op-amp.
After simulation, the output waveform was an sinewave instead of rectangular wave.
Any idea where I made a mistake?
Please let me know as I have to simulate further circuits in Proteus.


texts: What are the options of having multiple I/O pins and a constant duty cycle?

texts:
For some context, I want to create something like this.
For now, until I change my chips (which I know I need to do as a plan to use a lower voltage Vcc2) I'm using the sn754410 h-bridge IC, 74HC595 Shift Register. I find that using two of these ICs (a total of 4 electromagnets) results in almost all of my digital I/O Arduino pins being in use. I'd like to use about 8+ of these h-bridge ICs (that would be 48+ I/O pins for the 8+ h-bridge ICs) but I don't know how I could do so while also maintaining a full duty cycle current (complete on 100%) at times needed.

My question would be what can I use to achieve this and still have the option to have a bunch of inputs on HIGH all at the same time (or really close to each other where they seem to have turned on all at the same time to humans)?

It seems like shift registers may have a PWM effect on the pins (clock?). Do shift registers have a PWM effect on the pins, therefore reducing the current going into the output of the h-bridge ICs?


texts:
I'm just starting out in Electrical Engineering and was wondering if anyone could clarify a question about the following RC circuit regarding the LM386.

My question is about the following circuit:

How has adding such a small value cap (between pins 1 and 5) in parallel to the internal resistor of the op-amp boosted the bass?

I have been reading the data sheet; under gain control it says the following:

  Additional external components can be placed in parallel with the internal feedback resistors to tailor the gain and frequency response for individual applications. For example, we can compensate poor speaker bass response by frequency shaping the feedback path. This is done with a series RC from pin 1 to 5 (paralleling the internal 15 kΩ resistor). For 6 dB effective bass boost: R . 15 kΩ, the lowest value for good stable operation is R = 10 kΩ if pin 8 is open.

But I do not understand how it works, as far as I knew the bigger the cap the less capacitive resistance it has, so wouldn't a small cap (0.033 µf) as in the diagram be more resistive to bass frequencies? I know I have misunderstood something here.

All help appreciated.


texts: Control system -- closed-loop system problem

texts:
Given a closed-loop system as shown below:

Suppose that \$x(t) = u(t)\$ and \$d(t)=0.5u(t)\$. Determine the output response of \$y(t)\$ and it's steady state at \$t\rightarrow \infty\$.
I've tried to solve the problem but I'm not sure about my answer since my professor only gave us a brief introduction to this material. Here's my attempt:
I know that \$Y(s)=\mathcal{L}\{y(t)\}=\frac{1}{s}\$ and \$D(s)=\mathcal{L}\{d(t)\}=\frac{1}{2s}\$, then
\$
\begin{aligned}
Y(s)&= P\cdot C \cdot \left(X(s)-Y(s)\right) + D(s)\\
Y(s)\left(1-\frac{9}{s+1}\right)&=\frac{9}{s(s+1)}+\frac{1}{2s}\\
\frac{s+10}{s+1}Y(s)&=\frac{9}{s(s+1)}+\frac{1}{2s}\\
Y(s)&=\frac{s^2+19s}{2s^2(s+10)}
\end{aligned}
\$
Using inverse Laplace transform
\$
\begin{aligned}
y(t)&=\mathcal{L}^{-1}\{Y(s)\}\\
&=\frac{19u(t)-9e^{-10t}}{20}
\end{aligned}
\$
For the steady-state value, I used the final value theorem
\$
\begin{aligned}
\lim_{t \rightarrow \infty} y(t) &= \lim_{s \rightarrow 0} sY(s)\\
&=\lim_{s \rightarrow 0} s\frac{s^2+19s}{2s^2(s+10)}\\
&=\frac{19}{20}
\end{aligned}
\$
Any mistake?


texts:
I got this error in Altium when I try to compile schematic. i don't understand what is the problem exactly. I have searched online and didn't find any solution so far. does anybody already had this problem ?

Details of the error below

This is the sheet

Here are the parameters of the page


texts: I was wondering how that so-called "coilgun" works, I know what it does but I was wondering how it works under-the-hood and eventually how to make a basic one ? Also, how much energy would be required ?


texts: Circuit analysis (Intro to Parallel Circuits & Series)

texts: We are just in the beginning phases of learning how to simplify circuits by finding equivalent resistance.  I've gotten every problem right except for this one.  The answer says its 2000 ohms, but I keep getting 1200 Ohms. My method was by combining the 480 and 320 Ohm resistors, and then doing the math to combine them with the 1200 ohm resistor.  Then added 720, as it was in series at that point.


texts: How to amplify a signal for piezo transducer from 1 Vpp to 200 Vpp at 400 kHz and 500 pF load

texts:
I'm a researcher working with phased ultrasonic transducer arrays.

I need to amplify a sine wave at 400 kHz and 1 Vpp to 200 Vpp. It has a capacitive load of 500 pF.

I'm little out of my op-amp depth, I researched audio amplifiers but the frequency is too high so any suggestions are greatly received.


texts:
I want to make a MOSFET switch to drive a 12 V 300 W heat bed. Instead of buying one, I decided to make myself one.
I used IRF48N MOSFET and FAN7392 Mosfet driver to make circuit and when tested it, it worked(I tested it by heating a 40 W hotend). I later had to solder few male header pins to provide connections for FAN to cool the MOSFET & Heat sink. Then when I tried to heat the hotend, it's not working(May be I damaged it when soldering).

IRF48N MOSFET data sheet
FAN7392 data sheet

This is my current circuit

I think I damaged the FAN7392. With input from Arduino, LO pin should give 12 V to turn the MOSFET ON, but now its not. I don't know how it damaged, but I'm little skeptical of my circuit.

One guy suggested me to

add capacitor to the supply pins(when checked the datasheet of FAN7391, it says that, my mistake)
Add a Zener voltage protection to MOSFET gate
Don't leave any pins left floating

Based on this I made following modifications

Not tried the circuit yet(need to source components).

Q1. What should be the value of capacitor? 1 micro-farad ? Is it always necessary even if the supply to driver is a regulated one?

Q2. 12 V zener for protection

Q3. Should I use pull-up or pull down for unused pins?

Q4. Do I need to make any additional modifications?

Q5. Which graph or table to give more importance when designing Switch? I mean required gate voltage to create channel for specific current. I came up with 12 V for Gate from Rds ON value and Vds vs ID characteristics