texts: Ultra low current pulse generator (for BLE module interrupt)

texts:
At the moment I'm working on a project with at BLE-module. This module is based on the CC2541 from TI. I want the BLE-module to permanently transmit a signal.

This module has two modes: a level- and pulse-enabled mode.

The level mode is basically using an enable pin (EN-pin). When pulled to GND the module will transmit. The problem is that the EN-pin has an internal 20k pull-up, so this means it leaks about 0.15mA (VCC = 3v) when the EN-pin is pulled to GND.

I want to prevent this current leak and want to use the pulse-enabled mode: the module will transmit for 30sec after the EN-pin is pulled to GND for >200ms, then it goes into stanby-mode. This means there is no current leak outside this 200ms pulse. I was thinking of sending a pulse every 30.2 seconds for 220ms, to "permanently" transmit a signal.

The problem is that I haven't really figured out how to send a 220ms signal every 30.2 sec. I know there are IC's around which are capable of doing it, but these are using relatively a lot of power. I'm looking for a solution in the range of a couple uA. I found the css555c, but this one is not widely available and very expensive (almost $2). I'm hoping someone can help me to find a very costs and power efficient solution.

So is there a way to send a 220ms pulse every 30.2 seconds in cost and power efficient way?

(or is there a way to prevent the current leak from the EN-pin when it's permanently tied to GND, due to the 20k pull-up)

Cheers and thanks,

R.


texts: I need direction with part names and/or a diagram

texts: Im suck!!! I have a project with two separate 12v dc connections. I need one to be always on until the second one is activated. When power is there for second 12dc output I need he first one to shut off until there is no longer power for the second connection. I have figured this out by using a relay but I really need this to be as small as possible. Im sure there is something available for this exact application but I have no clue what to search for. Again he smaller the better!!! Any help would be greatly appreciate it!!!! even if its the proper item to search for... TIA


texts: From Proof of Concept on BeagleBone to Prototype

texts:
I've been developing a project with a BeagleBone Black and some other accessories connected to it as a proof of concept. Now, I wish to create a Prototype on my own leaving the BeagleBone behind, with the intention of eventually transforming the project to a commercial final product manufactured in industrial quantities.

I've been searching the web for a couple days now and have found tons of information on going from Prototype to Final Product, but I have found very little information for the previous step; from proof of concept to prototype. Being more specific, what I would like to do now is replicate what I already have with the BeagleBone on pieces I obtain separately and try it out on a breadboard. After this, I would design a final PCB for mass production.

My question, in short, is how do I know which pieces I will need, and how should I connect them (including resistors, transistors, etc)? If the question is too broad, is there any guidance you can give me for me to learn what I need? This is my first project of this kind, and even though I am a Computer Engineer my knowledge is really limited in electronic matters.

I thank your answers in advance. Please if this is off topic, repeated or anything similar direct me to where I can find the answers. I've been looking a lot and can't find the precise answers.

Best regards,
Diego


texts: How can i create a SWR meter that works for 0dBm sources @ 2.4Ghz?

texts:
I've stumbled upon this, but it only works for outputs between 15db and 20dBm. How can I modify it to work for 0dBm sources?

I'm planning to use this to roughly tune my matching circuit for the interface between a RF transmitter and a chip antenna.


texts: Electronics - ISO 42v DC Brushless Fan to 110AC with Speed Knob MOD HELP

texts:
I'm looking to Mod a 42V DC brushless fan to work on an 110-AC outlet and incorporate a speed knob into the build.

This is the info that I have:

Fan was originally pulled from a Cisco 7600 Series Router Fan module; it's about 6 inches in diameter and has 4 wires coming from it.

Tag on the FAN: |
DC BRUSHLESS |
MODEL EFC1748DG |
DC48V 1.84A -4M41R |
(OPERATE: DC42V) |

Connecting Board Info: |
Yellow Wire = P |
Blue Wire = R |
Black Wire = - |
Red Wire = + |

Here is an Image of the fan:


texts:
First of all, I'm fairly new to electronics. I've been working on my own version of a miniature hovercraft just like this one http://www.thingiverse.com/thing:68639. I'm using an arduino pro mini for the controller, a nrf24l01 transceiver, small brushed motors (hubsan motors) running at 3 volts and a 3.7v 500mah 25c lips. I'm also using MOSFET transistors for the speed control. Here's the problem. I wired everything according to this page http://www.circuitmagic.com/arduino/run-small-brushed-motor-for-mini-quadcopter/, but when I turn the motors on, there's a huge voltage drop. When plugging one motor directly to the battery, it drops about one volt. When attaching two motors, the voltage drops down to 0.86 volts.

I don't know how to provide a steady 3.7 volts to my motors (without it dropping significantly), but I know it's possible since quadcopters like cheerson cx-10 runs four similar motors using a 3.7v 100mah lipo while I'm only using two motors. For that matter, how are micro quadcopters running multiple brushed motors without the motors running slow. I can only get a gentle breeze from mine. Please tell me if there's a way to regulate voltage or any other step or component I'm missing in my setup.


texts: I’m trying to identify these 32.768 crystals from the label but can’t find them. What do these markings such as 32C446 and 32C416 mean? The actual part I want to identify is marked with 32C446.


texts: Why do sampled signals repeat in the frequency domain?

texts: I do understand it mathematically, that multiplying a signal with a Kronecker(T) is the same as convolving it with Kronecker(1/T) in the frequency domain, and that makes sense. But is there an intuitive explanation when it comes to this? If I look at my signal, and I see the frequency domain representation, I can see how a number of sines and cosines shown there makes up the original signal. But why does adding even more of the same sines and cosines, but shifted, result in the same signal but sampled?


texts:
I recently purchased a rather inexpensive LPC1768 development board from dx.com.
The board can supposedly be programmed via USB (in a similar fashion to the mbed).

To open the device as a disk, you hold the KEY button, and plug the board in. Opening the device, there is a firmware.bin file.

I first tried copying an LED blink demo bin file over, but an error appears informing me that there is insufficient space available (keep in mind that the program is tiny, as you would expect). I then tried deleting the firmware.bin file, and copying the demo program over again, this time working fine. However, when the board is reset, or board turned off/on, the demo program disappears from the drive, and firmware.bin returns. So, it seems that on reset, the board reverts to it's initial state.

Does anyone have an explanation for this, and a workaround? Anybody with experience of this particular board? There was no documentation issued with the board, and nothing I can find online.

http://www.dx.com/p/lpc1768-arm-cortex-m3-scm-board-148988#.W2h14thKjBI


texts:
I use STM32F030F4 in TSSOP-20 package and the timer doesn't work.
I try to find an example for STM32F103 and it work very good.

Here is the code sample that I use:

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);

GPIO_InitTypeDef GPIO_Config;
GPIO_Config.GPIO_Pin = GPIO_Pin_6;

GPIO_Config.GPIO_Mode = GPIO_Mode_AF;
GPIO_Config.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Config.GPIO_OType = GPIO_OType_PP;
GPIO_Config.GPIO_PuPd = GPIO_PuPd_NOPULL;

TIM_TimeBaseInitTypeDef timer;
TIM_OCInitTypeDef timerPWM;

TIM_TimeBaseStructInit(&timer);
timer.TIM_Prescaler = 0;
timer.TIM_Period = 100;
timer.TIM_ClockDivision = 0;
timer.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM1, &timer);

TIM_OCStructInit(&timerPWM);
timerPWM.TIM_OCMode = TIM_OCMode_PWM1;
timerPWM.TIM_OutputState = TIM_OutputState_Enable;
timerPWM.TIM_Pulse = 50;
timerPWM.TIM_OCPolarity = TIM_OCPolarity_High;

TIM_OC1Init(TIM3, &timerPWM);
TIM_Cmd(TIM3, ENABLE);

TIM3->CCR1 = 50;


texts: Correct ways for implementing standard inbuilt watch dog timers

texts:
I'm bit new with using applications that use watch dog timers and i'm up to use one for the first time. I'm using pic18f26j50 and it got an internal watch dog timer which got a limit from 2ms and can be expanded up to 2 minutes.

I understand the whole purpose of using internal watch dog timers is to prevent any accidental code lock.So i would like to know what are the ways in which the watch dog timer can be tested and proved that it could be fail safe to kick it properly with out any error.

I trust input from you will help me to write test routines so that i could understand the features of it and also i would like to be informed about any possible pitfalls if any.

  And i trust watch dog is usually cleared inside the main and another
  question that suppose i have is if i have certain modules A,B,C..N
  that gets called in main. What are the requirements for a designer
  such that watch dog timer implemented meets the standard and what are
  the things which the developer must look in to properly in such a
  case.


texts:
I am busy thinking of how to test a power supply i am designing and came across an article which discussed using an electronic load to test the supply. I will not have access to an electronic load and so thought of using a dummy load to mimic the load the supply will see. I'd like to clarify if I have the right idea of how this works?

The primary requirement of this supply will be to provide a steady 5v and 3.3v through the use of two buck converters with a 12v input voltage and to meet the current requirements of circuits connected to the 5v and 3.3v lines. The 12v input voltage is derived from 230v 50Hz AC through means of a step-down transformer and full bridge rectifier. I have a list of components and max currents they draw. Am I correct in saying I will need to calculate the sum of current draw from the individual components and then use Ohms law to pick a dummy resistance to simulate this condition? Similar to the procedure described here:
Determining Power Supply Requirements

For example. If components which draw from the 5v line will draw a peak current of 2.4A I would design the buck converter to output a regulated 5v 3A and then calculate the load resistance as \$R=\frac{V}{I} = \frac{5}{2.4} = 2.083 \Omega\$. I'd then connect this load across the output of the 5v buck converter and check that it is supplying a steady 5v for this load? I assume I would also need to look at the power rating of the resistor so using \$P=VI = 5\times2.4 =12W\$ making sure that the resistor chosen is able to handle this power amount of power dissipation?


texts: Utility floating neutral, isolation transformers and getting a shock

texts:
I'm working with isolation transformers and I need to know the concept of power utility pole mounted isolation transformer because they are related.

If the neutral of North American pole utility is not grounded below the the pole, the neutral is said to be floating (as shown below). But how can you get a shock by touching it by there is no direct path to ground?

Remember the secondary of utility transformers are just like the concept of isolation transformers. If you don't ground the secondary, then you can safety work on equipments as there is no direct path to ground so even if you accidentaly touch one wire and ground, you won't get a shock. But how come I read reports of people getting a shock when they touch a neutral that is not grounded at the utility pole? What is the path to ground in the pole utility isolation transformers?


texts: Battery protection/charge board, could use another set of eyes on it?

texts:
Designed and assembled a single cell liion battery charge/pcb that fits a single 18650. I used the recommended circuit diagrams from the chips datasheets and even the recommended NMOS fets for the protection circuit. There's three of them, but two of them are not working properly.

Normally, if you plug in a 5v USB, or just 5v, the batteries should start charging up until BAT hits 4.2v and the charger drops into standby. If the battery voltage exceeds 4.3v and below 2.8v, the protection circuit should shut off the battery output. It is also suppose to include over-current protection, so I used the FET's the datasheet preferred.

-One has problems not resetting the protection circuitry when 5v is applied, regardless of battery voltage.
-On the other, the STC4054 charge IC will drop about a volt between BAT and Vcc and put about +2v on Vcc with nothing else connected.

It may very well be the case that I've got some dead IC's, but I want to make sure it something stupid I did rather than a bad circuit design or missing protections. I can't find any bad solder joints though.


texts: What will happen if I feed a UA741 op-amp lower negative supply voltage than recommended?

texts:
I have a few UA741 op-amps which I need to use in differential op-amp configurations with Vref set so as to bias the input (2.5V AC pk-pk @ 50Hz) to a baseline of 2.5V. The output is to be connected to an ADC.

I have a 12V DC supply available for the supply rails.

I need the output to be able to reach at least 5V, therefore I want the positive rail to be around 7-8V. That leaves me with 4-5V on the negative rail. As stated in the datasheet, the minimum recommended negative supply voltage is 5V.

I have two questions:

How much voltage should be supplied to the positive rail to ensure that the op-amp can output 5V? How can I find this value from the datasheet?
Will there be any significant damage to the op-amp if I input less than the recommended voltage for the negative rail? (I don't need negative output)


texts: What is the name of the translucent substance on the PCB?

texts: PCB on photo is from the Kinesis Advantage keyboard. I need a similar substance to remount the PCB. What substance should I use?


texts: Vending machine motor and switch circuit

texts:
I have a project using vending machine motors, arduino, pi etc. The motors have a NC microswitch that is OFF when motor spinning and ON when returning to the original / start point, to detect 1 full revolution. It is 6 pins, and I wanted to know how to wire this up to send it on a 360 revolution

[![enter image description here][2]][2]

simulate this circuit – Schematic created using CircuitLab


texts:
I'm trying to solder together a small LED array with a dimming knob out of a bunch of old parts I have laying around, but I can't seem to identify how to wire this component:

The two connectors at the top are labeled A and B and it says ALPHA in the middle.
The red plate is labeled 1 3.

Any help would be appreciated. Thanks!


texts: Why not use monochrome LCDs instead of E-ink?

texts:
Recently I've been reading about E-ink displays and the benefit over LCDs, as I understand it, is that there is no backlight in E-ink displays and thus, physical light is reflected, making reading under direct sunlight possible.

However, this got me wondering, is there any difference, apart from power consumption, that would prohibit the use of monochrome, reflective LCDs (like the ones found in calculators, watches etc.) in eReaders, replacing the slow eInk screens?

This would enable us to have a nicer UI with animation.


texts:
Below is the circuit in question:

Below is my attempt, however, I feel there is something wrong because the value of Rd is not fixed.


texts:
I'm reading this datasheet:
http://www.jaycar.co.nz/products_uploaded/ZD0012%20-%20AL-50-30RGBC-C-004.pdf

The Preferred Value Series Resistor on this page recommends 510/470/470 Ohms for 12VDC which to me seems too low because the maximum current is specified as 20mA per channel while Ohms law says

12V / 470 Ohms = 25.53mA

Which is above the recommended 20mA. Why is this?


texts: What are the most common ways to fry an arduino?

texts: I've fried two Arduinos before: one was an Uno, which I killed with too high of an input voltage, and the other was the ADK version of the Mega, which I never was able to conclusively determine what went wrong. This got me thinking: what are some things (perhaps not immediately obvious) that will damage Arduinos?


texts:
The datasheet for the SN64LVDS31 specifies to use 0805 decoupling capacitors (page 8):

This seems awfully large. I typically use 0603 or 0402. Should I interpret this to mean a maximum size of 0805, or is there a valid reason to not go smaller?


texts:
I am curious to know why can not signals of different tv stations mix together while transmitting. I have seen many towers built near each other in mountain areas in my country.

If two different signals reach the towers in the mountain, how cannot one signal interfere the other? I think this applies to mobile transmission as well. May be this is a stupid question, but I couldn't find an answer by googling.


texts: Is there any way to determine power rating of a potentiometer?

texts:
I salvaged a 1kΩ potentiometer from a broken circuit. Is there any way to determine how much power can it take without destroying it?

EDIT Picture of the potentiometer:

The distance between left-most and right-most connector is about 2cm.


texts: Emitter Follower Power Stage of an Amplifier with Switch-off capacitor

texts:
I know exactly how emitter follower (EF) arrangement of transistors works (when used as power current amplifying stage). But according to my book (G. Randy Slone: High Power Audio Amplifier Construction Manual) there is an improvement that can be added to EF. And that would be the Switch-off capacitor (look at the schematic given below - orange box).

I have given the circuit its values as it is shown in my book.

In the book, the author says (referring to class B amplifier): "...the output transistor must be turned off rapidly, when their conduction period ceases, or we wind up with very undesirable condition of both output transistors conducting simultaneously." And later on, he refers to such undesired condition as "switching distortion".

I have few questions to this topic:

Do the transistor Q1 and Q3 discharge more quickly if that switch-off capacitor and resistor are added to such circuit?
Why should you call a crossover conduction (where both output transistors are conducting simultaneously) a distortion; a switching distortion? It is rather disadvantage for power dissipation of transistors (if operating in class AB amplifier). Also, it is desired for an amplifier to work in class AB amplifier, because it prevents the possibility of cross-over distortion


texts:
simulate this circuit – Schematic created using CircuitLab

I have a wire connected to the base of the transistor that goes to the PWM pin 9 on the Arduino Uno.

On the collector of the transistor I have a 7.5v battery and the emmitter is connected to a motor which then connects to ground.

On the emitter of the transistor I am only seeing 2v, why is this? Is there anything I can do to change this?


texts: Solving for v_out in a non-ideal difference op amp

texts:
I'm having trouble figuring out how to set up the KCL equations for this op amp.  Everything I've tried seems to lead to a dead end.  I've tried setting up three KCL equations at nodes v_n(-), v_p(+), and V_out, and using just node -v_d and v_out.  Anyone have any ideas?

This is what I've tried using \$-v_d\$ as a node:  \$\frac{-v_d - v_2}{R} + \frac{-v_d - v_{out}}{R}+\frac{-v_d}{R_i}=0\$ and \$\frac{v_d-v_1}{R}+\frac{v_d}{R}+\frac{v_d}{R_i} = 0\$ and \$\frac{V_{out}+v_d}{R}+\frac{V_{out}-Av_d}{R_o} = 0\$ but this seems to be trivial as the first and second equation reduce to something that doesn't involve other parts of the circuit.


texts: Computer PSU 5v Output direct with Raspberry Pi USB

texts:
I'm using an old power supply unit from an old computer (2011 HIPRO) to power my Raspberry Pi 2 Model B V1.1 (2014).

I have measured the voltage across the terminals of the 5v output (Red and Black) and have proceeded to hook this up to a USB adapter which goes straight to the Pi.

My problem is that using this PSU the red "on" indicator light does not turn on, versus when I use a USB charger it does.

Was there a problem with this red light not turning on? Is this bad for the Pi?

BTW everything works fine using both power supplies, the Pi turns on and the screen is shown, able to login etc.

Please see my photo of my setup below:

Closer View of the PSU pin outs:


texts: Generating FFT on data recived from 20Amp(ACS712) current sensor using arduino & processing IDE

texts:
Currently, for generating FFT on the data received from ACS712,i used the following method:
 first the data is sent to the Processing IDE from the sensor via arduino. the processing code converts the data into a text file, the text file is then loaded into matlab and fft is plotted.
Are there any other ways of plotting FFT? can arduino be used to directly generate FFT from the data received?


texts: how to pcb mount a mil dtl 38999 connector

texts:
Im on this website

http://www.peigenesis.com/en/amphenol-connectors/amphenol-tv-ctv-tri-start-mil-dtl-38999-series-iii.html#create-pn-military

This are military spec connectors. I'm currently using the D38999/20
Wall Mount Receptacle on a metal box, on the other side of the plug within the box all wires are placed in a wire to board connector which is the soldered on a PCB.

I wish to solder the connector directly to the PCB without the need of the second connector, making the PCB parallel to the box wall. Is this possible? with pins?

For example plug all pins in the connector and use them as through hole pins. soldering them to the PCB.

Thanks!


texts: Resistors for xilinx coolrunner ii cpld pcb

texts:
I am making a pcb which contains among others a coolrunner ii cpld .

I will programm the CPLD through jtag from a digilent cpld  development board .

I read in a xilinx application note that pull-up resistors of 4.7k should be placed on each one of the  jtag pins .

Are series current limiting resistors also required on the traces of the pins ?

Thanks in advance


texts: Why connecting oscilloscope reduces noise

texts:
I am doing a speaker driver circuit. When I connect the oscilloscope probe to the output (emitters of npn/pnp complementaries) to where also the speaker is connected; the sound of speaker and the waveforms on the oscilloscope is satisfying. However, when I disconnect the osc probe and leave the speaker alone, than the sound gets much more noisy.

Why does that happen so?


texts: Help identify part or find replacement for component marked PJ6446. ER1J

texts:
I picked up a Behringer Europower Pmp560M.  The power unit is starting primary side then shutting down.  It  has a number of diodes on the back. One has clearly failed and got a little hot and now has some chunky lumps of solder either side.
Anyway it is marked
PJ6446.
ER1J

I have no idea how to look up component numbers besides googling (which got me nowhere.)
I have no idea how you guys manage to take a code like that ^^ and return with a part number, manufacturer, date of creation, designers family pet name etc.

Please give me some tips for future projects.
The board is a power supply and amplifier.
Top of board:

Bottom of board, you can see the 4 diodes to the right of the top separation hole:

The culprit:


texts: How to reduce drill hole clearance for certain components?

texts:
I made a simple LED pipe device for the LPA-C011301S-X which has 2 pins and requires 1mm drill holes on board. As you can see in the image below, drill hole clearance is very big. How can I reduce clearance just for my LED PIPE components?

I don't want to recude clearances on entire board. For example board screw holes must be far enough from top layer:


texts:
can you help me on understanding the procedure to design this T - matching network?

My aim is that of transforming a resistive load R to a complex value R'', while R' indicates an intermediate value.

By the classical transformation formulas with Q-factor we get the following transformation ratio:

where:

and

First question: According to the previous picture, Q2 is the Q factor of the network made of B3 and R''. But if we look at the transformation ratio, Q2 seems the quality factor of the network made of the global network made of X2 and B1//R. So I do not understand this step.

Second question: is the fact that we see R' at right and at left imposed by us? Or is it determined by other factors?

Third question: why is Qmax = 2 Q and approximation?

Fourth question: which is the procedure if our load is always resistive (R) but we want to see a complex impedance Z'' at left?


texts:
I've purchased this kit:

https://www.adafruit.com/product/1687

I've been using this as a reference:

http://www.ti.com/lit/ds/symlink/sn754410.pdf

I'm trying to power a DC motor from the kit and am having some issues.

I've connected ~5v input to vcc2 and 5v to vcc1 (as instructed - vcc1 connects to en 1/2 and en 3/4).

When I measure the voltage between either of these two and the ground, I get 4.8v (close enough to 5?)

When I then measure the voltage between 1a/ground or 4a/ground (the input pins) I get a voltage of ~0.66v. If I measure the voltage between 2a/ground or 3a/ground I get ~1v. If I disconnect vcc1 (and as such en 1/2 and 3/4) the voltage drops on these.

My issue is this, since 2a/3a voltage is above the max for low input, the 2y/3y pin is always set to high.

I'm struggling to understand this a little - have I screwed up something, or is this functioning correctly? I had to assemble the kit myself, I've double checked all the soldering, and as far as I can tell nothing is wrong.


texts: How can I tell if a relay coil is rated for 240VAC

texts:
I want to monitor a 240VAC line from an Raspberry Pi, my thought was to hook the 240VAC line to an appropriate relay then just sample the contacts from the Pi.

I have a relay which I think would work but I don't know how to be sure the coil is rated for 240VAC. It's about 1 inch in each dimension, the coil resistance is 670k Ohms.

I've attached a photo, I did google around for specs on this but I can't find any clear info.


texts: Why doesn't my charge pump work with 1.5v supply?

texts:
I have been trying to get the following circuit to work with 1.5V AA battery but it does not work, even though it works fine with a 3.3v supply.

I built the multivibrator circuit by discrete components because I haven't been able to find a suitable op-amp or timer IC that works at 1.5v.

I observed the following in my circuit:

At 3.3v supply, the output voltage on 3.3k Ohm load is 4.5v. I did not expect the voltage doubler to actually double the voltage, and I am not using Schottky diodes so I'm okay with with it.
At 1.5V supply, though, the output voltage on the same 3.3k Ohm load is 1.4V. That is not really what I expected. I was thinking that I should be able to obtain at least 2V with the circuit but it decreased. I am trying to use this setup to power an ATtiny (works on >1.8V).

I am really puzzled by it because even at 1.5V the oscillator works fine. It even dimly blinks a led when I use a larger capacitor. So why should it not be able to charge two small capacitors.

My question is, what is lacking in my logic? Why are the capacitors not pumping charge at a lower voltage?

Also, if you have any suggestions on how I can make my design more power friendly(maybe a different oscillator design or another voltage doubling topology) please mention them too. Also, please don't suggest charge pump ICs because it is almost impossible for me to obtain them.


texts:
I have to implement this case using Fpga.
 a car could park in zone A or zone B. In order to open the gate. There should be a car that want to enter and an avaliable barking either A or B. I did the truth table and wrote the vhdl code. Kindly, can someone check them?
Thanks in advance


texts: How long between Arduino digital pin and IC?

texts: My current project involves using 74HC595 shift registers to control an LED display, however the display could be up to 5 or so metres away from the Arduino board. The plan is to use some DB9/RS232 cables between a box with the Arduino, and an enclosure with the display. Would the length be too long for the digital signal to travel from the digital out pins to the shift register without degradation?


texts: Membrane for sht10 (humidity & temperature) sensor

texts:
I made a uC powered device to control the humidity and temperature of a room. I used sht10 sensor. The room humidity provided with a humidifier. The sensor was working well. When trying to test the device at the target room, I think the mist at the room made the sensor to malfunction. Now the sensor just reads 100% humidity and temperature of ~50 degrees. When I touch the sensor it reads higher temperature (although not true), but the humidity is always 100%, so I think the sensor is not damaged.
May I recalibrate the sensor or not. And do I need a special membrane to avoid such problem? May I make a DIY membrane Or I can expose the sensor directly to the mist?. Thanks


texts: WS2811 flicker to random colors when trying to turn them all off in a 3x3 array

texts:
I am trying to do more, but for starters, I am trying to write code to turn all of my WS2811 off that exist in a 3x3 array. Currently, when I run my Arduino project, they are flickering from red, to green, to blue like crazy. Only one of them, the middle one, is staying blue.

I am wondering if anyone with any experience working with the ws2811 could pinpoint the exact issue with just knowing this information. I know my code is correct to turn off the lights, since it is very simple, but I am not sure how to trouble shoot this issue.

Here is the code I am working with:

/**********************************************************************
 file: main_ws2812_basic.cpp - basic ws2812 test

 Copyright (C) 2018 p. chu

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <https://www.gnu.org/licenses/>.
 **********************************************************************/
/*****************************************************************//**
 * @note neo8 is an 8-led strip
 * @note ws2812 is very bright (25% power is enough)
 * @note ws2812 specifies 5-V control signal
 ********************************************************************/

#include "de10_baseline.h"
#include "ws2812_core.h"
Ws2812Core light_matrix(get_slot_addr(BRIDGE_BASE,14),3,3);
int main() {

   int i = 0;
   int j = 0;

   for(i = 0; i<3; i++){
       for(j=0; j<3; j++){
           light_matrix.wr_pix(i,j,0x000000);
       }
   }
   while (1) {

          light_matrix.wr_pix(0,0,0x000000);
          light_matrix.wr_pix(0,1,0x000000);
          light_matrix.wr_pix(0,2,0x000000);
          light_matrix.wr_pix(1,0,0x000000);
          light_matrix.wr_pix(1,1,0x000000);
          light_matrix.wr_pix(1,2,0x000000);
          light_matrix.wr_pix(2,0,0x000000);
          light_matrix.wr_pix(2,1,0x000000);
          light_matrix.wr_pix(2,2,0x000000);
     // sleep_ms(2000);
   }//while
}//main

And here is my circuitry: The first three wires are my voltage, ground, and data wire. (From right to left)


texts: SIM 7600ei AT command error while sending GET request

texts:
I am using the SIM7600ei module with a 4g LTE Sim. I am successfully able to get the IP address.
AT+COPS?
+COPS: 0,0,"Jio 4G Jio 4G",7

OK

AT+CSQ
+CSQ: 29,99

OK

AT+CGPADDR
+CGPADDR: 1,56.196.171.209
+CGPADDR: 2,0.0.0.0
+CGPADDR: 3,0.0.0.0,0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0

OK

AT+HTTPINIT
OK

But the command AT+HTTPPARA always results in an error.
AT+HTTPPARA="URL","www.google.com"
ERROR
AT+HTTPPARA="URL","https://www.google.com"
ERROR
AT+HTTPPARA="URL","http://www.iforce2d.net/test.php"
ERROR

AT+HTTPPARA="URL", "http://www.iforce2d.net/test.php"

I am not able to proceed after that. I tried replacing the URL with www.google.com but still, it immediately shows an error.


texts: I want to OR the bits of a vector together. So say I have a vector called example(23 downto 0) and I want to OR all the bits into another vector, is there any way to do this that does not involve going example(0) or example(1) or ...example(23)?


texts: Can the USB port's metal enclosure be grounded?

texts:
As shown in the image below, the USB port's metal enclosure is touching the copper clad of the PCB (which is a ground plane).

Can Bad Things Happen™ if the port's enclosure is grounded?

I beep-tested the 4 pins with the enclosure, and none of them are connected to it. However, could some shorts be made when plugging something into the port?


texts: Gain in current but not in voltage -transistor "voltage follower" set up

texts:
Suppose we have the circuit set up as shown in the image. Also suppose that  $$V_s=\overline{V_s}+v_S$$, where the smal v is for the variable component of the signal which varies much faster than the time constant of both capacitors. After some analisys we get that there's no gain in the variable component of the source voltage, that is, there's unitary gain, however from the equation of a bipolar transistor:
$$i_E\approx i_c=\beta i_s$$
thus there's a gain in current, how is it possible to hava a gain in current, and consequently a gain in power, but not in voltage? This seems to contradict Ohm's law, shouldn't a current gain be accompanied by a voltage gain?


texts: Design ethernet switch for multiple devices on pcb?

texts:
I'm working on a pcb design with a Raspberry Pi CM module and a microcontroller with ethernet capacity. The goal is to connect the devices to the internet.

I'm currently using a normal ethernet switch, where I connect the CAT5e cables to the different devices. Using normal RJ45 connectors, magnetics, PHY and MAC. The standard setup.

I'd like to try to integrate the switch in the pcb design, while still maintaining the LAN as it should be normally. I did find a few Switch IC's like the KSZ8794 and I think I can create a working switch with this, but only with a regular setup. That is with magnetics and connectors. The IC has integrated MAC and PHY modules.

When I'm trying to wrap my head around the switch concept and with not using cables I end up with a 'maybe' possibility where I'd use the switch as normal, then link a PHY and MAC IC to one of the ports and connect the MAC with an (R)MII interface to the Pi or microcontroller.

I then have very short 100BASE-T traces between the two PHY IC's instead of a cable and connector. While this does seem like a viable solution, it also feels like jumping through unnecessary hoops.

Is there a possibility of still maintaining a LAN network on my PCB, with 1 connector going to the outside world and with not 'simulating' a mini 100BASE-T network between the switch IC and other devices?

EDIT: Added a diagram to hopefully make it a bit more obvious.


texts:
I have a 1.25 to 28 V variable power supply I'm working on. here's the schematic (from here):

What I'd like to do is put in a fan (12v 0.16A) so it runs when i turn it on, however
i don't know where to insert it so that it doesn't blow. I was also thinking of putting in a small bulb as an indicator light - when i turn it up, the light gets brighter. I have quite a few different rated lights, so I'm good for that, but still- don't know how to set it up.

I'll be using a cheap multimeter as a voltmeter - i don't have a standalone voltmeter on it's own and they are quite expensive actually for something so simple.


texts: Why two separate batteries in a circuit don't work?

texts:
If electrons move from the negative side to the positive side in a battery (thus creating electricity when they flow), why does the same circuit with two separate batteries not create electricity?

As you can see in the diagram, electrons should be moving from A to B because the wire is connected from A - side (high pressure) to B + side (low pressure). Why is there no electron flow?


texts: How does this precision full wave rectifier work?

texts:
I am making a VU meter, and I need to rectify the audio signal for the IC comparator chip. I found this circuit in the datasheet, but I am unsure of how it works.

I understand that the LF351 op amp is needed to overcome the threshold voltage of the diodes, but what is the purpose of the LM307 op amp? Is it just a buffer? Why not just use another LF351?


texts:
I have a robot using the following screw terminal :

On the input side 2x 8 awg wires coming from the battery, on the other side 2 x 3 wires for 2 motor drivers and 1 step-down that power a single board computer.

There should be like 45A as peak here, and I would like to improve safety on that.

So what "professional" solution exists and which one are usually used to achieve the same thing in consumer products ?


texts: Why is there a double inverting buffer instead of a single non-inverting buffer in this "equivalent logic" diagram?

texts:
In the datasheet for the DAC8812, there is this diagram in Figure 33:

What is the point of drawing cascading inverting buffers when, logically, it's the same as a single non-inverting buffer? This isn't the only place I've seen it.

edit: This is different than the question here (Why two inverters cascaded in multiplexer control signal terminals?) because I'm asking about an equivalent logic diagram, not physical logical circuitry. And in the diagram in question, there is no pick-off between the buffers.


texts: EMP strong enough to kill devices in an area >20 meters diameter

texts:
I'm writing a scifi short story and i would like to have the facts right. The question is:

Is it possible to create strong enough EMP to fry devices (cell phones, etc.) in an area of diameter around  15 - 20 meters using only generally available stuff (car battery, purchasable  electronics)? Or it would have to be a real weapon like described here http://science.howstuffworks.com/e-bomb3.htm ?


texts: Is it possible for mains power to drop during peak times?

texts:
Disclaimer: I'm not after repair information or modifying any
  appliances myself. I'm after a reason why this is happening.

I have noticed that during peak times (6pm - 10pm) that power to mains appliances "slows down". By that I mean the exhaust fans (bathroom, kitchen, etc.) run slower, and the ignition for my gas stove discharges at a slower rate than in the morning.

I find this very strange, because the appliances in question don't use much power, and the RCD/Circuitbreakers never trip.

Some additional info:

Two 2kW HVAC's running currently without a problem
230VAC, Single Phase
This isn't a one off event, I have noticed it for about a month.
This is in a country with fairly stable electricity grid.


texts:
First off I'll start by saying that I have almost no experience of single phase induction motors but I do have a reasonable knowledge of electrical & electronic stuff.

My neighbour asked me to have a look at a two post lift he has, which was not running properly/at all. First off, I found a few connections which were loose and once corrected the motor tried to run - so it seems to have cured the intermittent problem. The motor is configured to run in either direction through a couple of contactors.

The real issue is that it does not seem to want to start correctly all of the time. Sometimes you can get it to run well, but most of the time it either does not move at all, or runs very slowly and makes that horrible growling noise of a stalled AC motor.

I have checked both capacitors with a DVM and they both measure within the value marked on the side of them. He tells me the motor was sent for a checkup a while back and came back with a clean bill of health, but annoyingly he couldn't find the paperwork that he got for it and the motor has no identification on the outside. At a guess it's a 3-4kW motor. I'm in the UK so we use 240V 50Hz.

There is a starting relay, Klixon 2CR3-285. The datasheet (https://www.muekra.de/downloadfile/download/aitfile/aitfile_id/671/) for this suggests that it does not pull in the contact until a fairly high current and will drop out at 26A min. I am wondering if it may be that this is rated too high and a lower value or alternative part should be used. I wonder if depending on the rotor position sometimes there is enough current to pull the relay in, but at other times there is not. I guess I could measure the approximate resistance of the winding and use ohms to guess the operating current, but all these calcs go out the window during inrush and I don't have an LCR meter.

I've had a Google and can't seem to easily find these relays in the UK. There is some kind of overload protection relay inside the controller which is set to just above 16A continuous, with about double that peak (I'm guessing).

I think the terminals in the box are just so that you have something to screw down to. I don't think they are connected to the motor as there are 4 other wires coming from the bottom of the terminal box, but I'm not certain of this...

Here are a few pictures, not very good I'm afraid I didnt think at the time..:
https://imgur.com/yavoiYK
https://imgur.com/W2MGeDZ
https://imgur.com/WgcxnaU
https://imgur.com/taTTkfb
https://imgur.com/yOCF6wm

Any help is greatly appreciated.


texts: In an electrical circuit, why does the charge move after it passes through the last resistor, when it's voltage is zero?

texts:
simulate this circuit – Schematic created using CircuitLab

From what I know, current is the flow of charges, and charges move because of the potential difference, i.e. voltage. The thing is, charges in a circuit are affected by voltage drops, and total voltage drop is equal to the initial voltage. So, once the charge passes through the last resistor, it's voltage is 0! There is no potential difference anymore, so why is it moving towards the positive terminal?

I have 2 guesses, one is that those charges are still negatively charged so there is still some potential difference. Voltage from the battery is just some sort of additional energy (is this correct?)
My other guess is that they are being pushed away by incoming charges.

You wanted me to sketch it so here it is, but I think it works for most circuits...


texts:
I tried to detect a blackout on an stm32F405VGT6, which should write a counter inside the virtual EEPROM (Flash). It seems, that the writing process was not fast enough. Now, i cannot initalize the Flash anymore, it always gives me back a HAL_ERROR (FLASH_FLAG_PGPERR and FLASH_FLAG_PGSERR) when I call the HAL_FLASH_Program(uint32_t TypeProgram, uint32_t Address, uint64_t Data) function.

I tried already to completely erease the STM32 with the STUtility tool, but also this did not work. Is it possible, that I broke my Flash? Are there any ways to protect the flash from a blackout while it is writing?


texts:
I have to bias the following circuit:

would the MOSFET need to operate in the linear region or the saturation region?


texts: Do TRS connectors short adjacent contacts during insertion?

texts:
I would imagine with everything wiping past each other during insertion, that the following can happen briefly:

    <== plug
  T   R   S
 / \ / \ /
T   R   S
jack

Is this just something that systems that allow hot-plugging have to accommodate? Is there something in a spec to prevent this? If this scenario isn't possible, but something slightly less bad can happen, please explain?

(That is, I'd accept "Yes." as an answer, but "No." would require justification.)

Can internal switches in jacks help mitigate this? I assume most are normally-closed and break as soon as insertion starts, so that's not very helpful. Are there jacks with internal switches that only change state at full-insertion?


texts: LTspice 101: Strange values with DC operating point

texts:
Just started using LTspice and I'm struggling with what is probably a total newbie mistake on a DC operating point test.

Created a basic circuit, 10V voltage source and 1k resistor in series, and I'm not getting exactly 10mA current.

Voltage source has zero internal resistance.

Resistor has zero tolerance.

When I run I get correct value of 0.01A on the results text, but not on the circuit label.
What am I doing wrong? Thanks


texts: I am using a LM2903N to learn about comparators. I am powering the unit with a 9v battery and connecting to the (+) 5v and the (-) 2.5v. However, when I check the output the resulting voltage is 0v. Why is this happening. My wiring diagram looks similar to this picture I created in LTspice. Can anyone help me come up with ideas to try and get this working? Thanks for reading.


texts: How long can I run an Arudino circuit on a capacitor

texts:
I was just thinking theoretically on how long I would be able to run a circuit on a capacitor.

I'm wondering - is my approach for this approximate calculation correct?

Let's say the circuit consits of one Arudino (5V) and one other sensor (5V). Let's say that the total current draw of the Arduino + Other Sensor is 150mA at 5V (asssume constant draw)

Now, I model this cirucuit as a resistor of resistance R = (5V)/150mA = 33ohms.

Next, I choose a capacitor of capacitance 1F with a rating of 10V. Now, I can model my entire circuit as an RC circuit with a 33ohm resistor and a 1F 10V capacitor. The time constant of this circuit is thus (33)(1) == 33. Thus, in a discharging configuration, the capacitor will deplete by 63% of it's total charge in one time constant (33s).

Next, I consider the fact that my circuit needs 5V to run and thus I cannot utilise the full capacity of my capacitor. I assume that I will be using some sort of LDO that provides stable 5V to my circuit for any voltage of the capacitor above 5.3V (5V + LDO drop out).

By the equation Q = CV - if it takes 33s to deplete charge on the capacitor to (100-63)=36%, then it will also take 33s to reduce the voltage across the capacitor from 10V to 36% of 10V which is 3.6V.

By a rough estimate then, I assume I'll get somewhere between 10-20s of usable time.

Is my thought process correct (I know it's very rough calculations) - particularly about modelling the circuit as a resistor?


texts:
I was thinking that speed of light and speed of microwave should be equal (since I think they are same! I am not expert on physics), but due to my calculations:

speed of microwave in the air coming like 150 thousand km per second,

and I know from school that speed of light in the air is just a little (maybe 130 km) less than c (speed of light in vacuum)

Can you explain it.

Thank you so much!!!


texts: Reset back to factory setting after using EPPROM EPCS16

texts: I am a newbie to FPGA world. I just leared and did the instruction to use the EPPROM EPCS16 to load the a different initial configuration for DE2 board of Altera. Now, I cannot get back to the initial point where I turn up the board and all LEDs, 7 segment LEDs and the rest will run as being checked in the factory. I need to reset it because i will return the board to my university.


texts:
I'm currently trying to automate my intercom system. My overall aim is to have it so that I can both detect when the buzzer has been pressed and then also to have it so I can open the door. I am using a NodeMCU as the main controller. I'm fairly familiar with DC but have had virtually no experience with AC. Therefore, it has been easy for me to simply wire a relay triggered by the NodeMCU to open the door when requested.

However, I have been stuck trying to work out a method of detecting the buzzer press with the NodeMCU. This is due to the fact that the intercom system runs off 12V AC. After some searching around, my options were narrowed to either a Current Sensor or a Relay. The Current Sensor seems to be too much detail for what my purposes are; leaving me to fall once again on Relays. This time, however, due to the fact that the thing triggering the relay (the buzzer in this case) is using 12V AC rather than DC it has left me in a slightly awkward position as I am unsure exactly what I am looking for.

I have found myself upon this relay which seems to be what I am looking for. I would really appreciate it if someone could:

A) Let me know if this is the right sort of relay for my use case. And if not then what is (and costs little)?

B) Point me in the right direction of exactly how to wire this sort of relay.

This is because, unlike DC relays, I expect that AC relays only take 2 inputs (compared to 3); i.e. the relay gets triggered when electricity flows into the module. Is this correct?

Thank you in advance for any help.


texts: Why are there at least two prongs on every electrical plug? If power is traveling in one direction (from the wall to the appliance), why can't there be just one wire carrying it? Circuits need to be closed, but after all, current can flow through a capacitor, and that's an open circuit.


texts: Simple LP filter - calculate cutoff frequency

texts:
If I am correct to calculate cutoff frequency in this LP filter I have to sum up the impedance of resistor and capacitor, right?

simulate this circuit – Schematic created using CircuitLab

So:
$$
Z_1=R_1\\
Z_2 = \frac{Z_{R2}*Z_{C1}}{Z_{R2}+Z_{C1}}
$$

My result is about 80 kHz but correct answer is 230 kHz. Who is wrong? :)


texts: Using back to back zener diodes to clip voltage spikes in bipolar stepper motor

texts:
I have a stepper motor driven by an Allegro A4983 stepper driver chip and in some cases the motor can be back driven even while being powered up. This leads to blown motor driver chips.

Would I be able to use a pair of zener diodes placed in opposite directions between the A+ and A-, B+ and B- coils to to clip high voltages when the motors are back driven to protect my motor driver from being fried or is there another solution to this?


texts:
If in the saturation region the inversion layer is pinched off then how do electrons flow from source to drain?

Doesn't pinch off of inversion layer mean the loss of channel in the MOSFET for current flow?


texts:
We have four LED spot lights or down lights maybe, at 12V (AC/DC), 10W. (We don't have any more information unfortunately) We have them connected in parallel with a driver that outputs 15-34V at 1500mA. This driver also buzzes slightly in this setup, but we're not sure if that's a separate problem.

When we turn this on, the LEDs give a constant light, but at a very low luminosity. With only three LEDs in parallel on this circuit, the LEDs do a slow flicker (a couple of times a second perhaps).

We've tried with a different driver (22-38V, max 50V, 1050mA) and the 4 LED setup flickered slowly again.

Does anyone know what is going on and what sort of driver is necessary? We're banging our heads against the wall here

Thanks!


texts: BiCMOS Amplifier with feedback for DC bias and AC

texts:
In the following circuit, to considerably reduce the effect of RG on Rin and hence on amplifier performance, another 10MΩ resistor was added in series with the existing one and a large bypass capacitor between their joint node
and ground was placed. What will Rin, AM, and fH become?

Here's my attempt:

\$V_i-V_x+V_o-V_x=10M\cdot V_x/(j\omega C)\$

I know \$V_o/V_i\$ of the original circuit, in midband frequency, which shouldn't change in this case. Let's denote that \$x\$.

I can hence infer that:

\$K_1=V_x/V_{in}=(1+x)/(2+10M/j\omega C)\$

and

\$K_2=V_o/V_x=(2+10M/j\omega C)\cdot x/(1+x)\$

Therefore,

\$M1_{in}=10M/(1-K_1)\$

and

\$M1_{out}=10M \cdot K_1/(K_1-1)\$

Similarly,

\$M2_{in}=10M/(1-K_2)\$

and

\$M2_{out}=10M \cdot K_2/(K_2-1)\$

Is this the right way to solve this? Is there a simpler approach? I figured now I could easily determine \$R_{in},f_H\$, as requested.


texts:
I try to incorporate the constant-gm bias circuit (Figure 6 in Improvements_in_biasing_and_compensation_of_CMOS_opamp) into the PFC (positive feedback frequency compensation) opamp, but it resulted in erroneous bode plot

Which part is wrong in the constant-gm bias circuit ?

Note that the PFC opamp itself does not cause the bode plot to go wrong as you can see below :


texts: Why isn't the Fourier transform of a single sine wave cycle a single bar?

texts:
I have tried different Fourier transform codes out there on single sine waves, and all of them produce a distributed spectrum with a resonance at the signal frequency when they should theoretically display a single bar.

The sampling frequency has little effect (10kHz here), however the number of cycles does:

One cycle:

100 cycles:

100000 cycles:

It looks like the fourier transform converges only for an infinite number of cycles, why is that? Shouldn't a time window of exactly one cycle bring the same results as that of N cycles?

Application: This is both out of curiosity and also because I want to get how much the step response of a first order system will be exciting the resonance of a mechanical assembly. Therefore I need an accurate Fourier transform of the response... Which I don't trust anymore. What could I do to improve the accuracy then, based on the "sine wave" case?

P.S: These particular screenshots are based on the code here.


texts:
I need help identifying this connector. It looks a bit like a Mate-n-Lock but I was not able to find this layout in their list. I also browsed Digi-Key, Mouser and a couple of auto parts sites, to no avail.
This carries 230 VAC, about 30 mA.


texts: Does Vbe remain constant when Vb changes but changes when Ve changes for this BJT biasing circuit?

texts:
I was reading about thermal runaway caused by Icbo in a BJT, and seems I understand how the temperature increases Icbo then in turn Ic and Ie. But I also read that the biasing circuit's emitter resistor Re provides some negative feedback by decreasing the base current Ib and doesn't let Ic to go crazy.

So basically what I read says: when Ic and so Ie increases the voltage at the emitter terminal Ve increases. This leads a decrease in Vbe.

But for Vbe to decrease Vb must be constant.(?)

But if we think of the other way around I mean if we change the value of Rb2 and change the voltage at the base terminal Vb then we take Vbe remains constant. Isn't it? But the change in Ve doesn't keep Vbe constant.

So my question is. Is the change in Vbe possible only in one way? I thought that Vbe always a constant in linear region for DC analysis.

For example when we try to find Ib for no signal (DC) situation, we say:

Ie = (Vb - Vbe)/Re

Here we say Vbe is constant around 0.7V even Vb changes.

But going back to my thermal runaway question in this case change in Ve doesn't keep Vbe constant and increase Vb, instead it decreases Vbe and keeps Vb constant.

Can someone explain this? I hope I could explain where I'm stuck at.

Basically in linear region for this circuit a change in Vb will not change Vbe, but a change in Ve will change Vbe?

Edit:

Can it be explained by using the equivalent circuit for this circuit?


texts: pic18f instruction reference for XC8 Assembler

texts: I found lots of tutorials online on PIC18 assembly programming, but i did not found any official document from microchip on PIC18 architecture and assembly programming. Can anybody share the link ?


texts: Should the magnetic field outside a conductor be considered?

texts:
I've simulated a circular disc where a magnetic field is moving out of the page. The arrows in the picture represents the direction of its current density.
I'm wondering, will the induced current produces another external magnetic field near the edge of the disc? If yes, will that external magnetic field influences each other when the current changes? Should that field be concerned or can be negligible and why? This is because most sources I've read only concerned about the internal field.


texts: How can I calculate time constant and charge time of RRC circuit?

texts:
This circuit is part of my time delay circuit. I want to calculate exact value of delay time. Please help me.

simulate this circuit – Schematic created using CircuitLab


texts:
I am making an autonomous bot where i need to power a few sensors (IR, PIR, sonic,etc) and an arduino. In total the sensors draw about 300 mA current(max).

My power supply is a LIPO of 12 V (11.1 V), 25C, 2200 mAh. I need this supply to control the motors and provide them enough power.

My sensors and microcontroller will essentially work on 5V, so I need to step down the voltage from my supply too.

Using 7805 is inefficient as its causing too much heat and as I need to run the bot continuously for a long time, I don't want to use a linear regulator. Should I use a buck switching regulator with a LM2596S?
If yes, why and what other choices are available that i maybe missing out?
Any help would be greatly appreciated.


texts: C to C++ How do I make h/w initialization look neat?

texts:
Doing an experimental conversion of some firmware from C to C++ to try and get a better structure in it, since the C code "evolved" in line with experiments across a 2 year period.

The question is about how I package/wrap the large number of lines of MCU setup that I have, generally of the form

  GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_9;

Where the struct and definitions above are part of the MCU library (which I don't want to touch)

Or do I just drop then into a "floating" function called init()?


texts: 2 x 74LS181 4 bit ALU's cascaded to form 8 bit ALU, Cin problem?

texts:
When trying to add two numbers on my two cascaded 74LS181's I find that the result seems to be right when I tie the carry (Cn) of the least significant one to Vcc, contra my expectation that Cn should be low.

Trying to add zero and zero yields b'00000001'...

I did tie the Cn+4 of the LSB to the Cn of the MSB.

Any thoughts?

Gerard


texts:
So we have an RL DC circuit. If the inductor L1 has a high core permeability, there will be a high inductance and thus a long L/R time constant. So the circuit takes a long time to charge. Would putting a second inductor L2 in parallel with L1 help reduce this time constant at all, if L2 has a much lower core permeability (but is otherwise the same as L1)? If not, is there another way to reduce it other than decreasing L1 or increasing R?

Schematic below. Dotted lines to indicate L2 being added to the circuit.


texts:
I have a UHF TV antenna for ISDB-T Digital TV reception. The transmitter just one only antenna is 70km away and some channels suffer from some "digital noise". That's it, the image is not perfect and some frames are lost.

The transmission line to the antenna is a standard 75 ohm coaxial cable. However, the antenna has a 300 Ohm impedance and I'm using a 4:1 balun to match the impedances.

Does changing the line to 300 ohm ribbon and putting the 4:1 balun right next to the digital TV receiver will enhance the reception?

In the ARRL Handbook 2010 section 20.4.4 ("Matching the Line to the Transmitter") there is a table showing that the most loss is having the balun right next to the antenna (like my setup).

Why does placing the balun at the receiver and using a balanced line result in better performance that using an unbalanced feed line like coax and placing the balun at the antenna?

EDIT: I'm also looking for some theory and some comments on a balun. Is there any 4:1 balun I can build that has a wide bandwidth on the 473-800 Mhz range?


texts: Why would a tube radio leave the 6.3V heater tap on the transformer disconnected?

texts:
I'm attempting to repair a Clarion C104 tube radio. I started the repair years ago, put it away, and now I'm giving it another attempt. When I started the repair, the transformer (Clarion part no. C80-223) was damaged, so I replaced it with an equivalent transformer (Hammond Manufacturing part no. 270DX).

Unfortunately, several of the transformer wires have become disconnected between then and now, and I'm attempting to reconnect them correctly.

I understand that many tubes use a heater voltage of 6.3V--thus the 6.3V output on the Filament #2 winding. However, the Sam's PhotoFacts schematic for this radio seems to show the Filament #2 winding disconnected:

I'm assuming that the lower winding in the schematic is Filament #1 since the 5Y3GT rectifier tube has a filament voltage of 5.0V:

Why does this radio leave the 6.3V tap disconnected?

In asking that question, I'm making assumptions. Perhaps these questions need to be answered first:

Am I correct in interpreting the stub on the upper tap of the transformer in the PhotoFacts schematic as indicating that it's disconnected?
Why did they ground the other leg of the upper tap if the entire tap is unused?
Why are there two loops on the 5.0 V tap in the PhotoFacts schematic and one loop on the 6.3 V tap? Shouldn't it be the other way around? Did I misinterpret which tap is which?


texts:
I have  an    ardunio setup which is giving me output of 5V and 1A at 50Hz with pulse width modulation. I want to use this as input to the step up transformer and generate output of 60V. considering transformer formula Vp/Vs=Np/Ns I will need to have Ns=12*Np.

My questions:

1.Will the       transformer will work on PWM at 50Hz?(if yes,will there be power loss?)

2.Can I use 60V as input to other step up transformer and generate output of 120V?Or would it be better to add just one another transformer?


texts: Is there any added advantage on applying more ground stiching vias?

texts: I am new to pcb design and i am hearing more about ground via stiching. My questain is there any extra benefit placing more stiching ground vias in PCB.


texts:
As part of our lab' design project, we have to calculate suitable resistance values for this circuit below and for others like it with different sensor resistances. However, in lectures we have never seen an op-amp being used as it is here, presumably as some sort of switch.
I have no idea how to start tackling this circuit as all the information we've been given is the typical resistances for the sensors. In this case, the thermistor will be 1 kOhms at 80 C and 4 kOhms at 20 C. This circuit must turn on the LED on the right when the temperature is high.
Another question, rather than asking how the circuit is works, is: how should I connect components for simulation in LTspice? Should the trailing end of the LED be connected to ground? And, since LTspice doesn't allow voltage rails, should the voltage source's negative terminal be connected to the ground at the bottom?

Thanks for any help and sorry for any dumb questions, I'm just first year. The online pre-recorded lectures aren't the ideal learning environment and our tutors won't respond to any emails.


texts: Black Diamond Spot 3 - LED Identification

texts:
I'm trying to replace LED on my Black Diamond SPOT 3 headlamp since it degraded over lifetime.
The headlamp is rated for 130 lumens.
Can someone recognize the LED or perhaps knows what manufacturer the Black Diamond is using for its headLamps?


texts:
I want to set up an LED display, and I'm looking at using a bunch of 16-bit LED driver chips (like TI TLC5927) to run a 16x16 LED matrix. Then I'd like to maybe put a few of these 16x16 displays together to make a bigger display. Since they are chainable, that should work in principle.

The problem as I see it is distributing the CLK, LATCH, and OE signals, as they aren't redriven by the chips. And I'm thinking the wimpy little Arduino output isn't going to drive much more than 20 or 30 chips before the signals become too blurry to be considered digital anymore.

So... is the solution to just put a 74HCT125 buffer every so many chips to re-drive the CLK, LATCH, and OE signals? Any pitfalls with that approach? Maybe I'm just overthinking it.


texts:
So i have a circuit where R1 = 5 W, R2 = 2 Ω, L = 1 H, C = 1/6 F ja E = 2 V.          And i need to figure out what is iL when t=0.5s with  laplace transform.
Switch opens when t=0
When t<0 i got iL(0)=1A and Uc(0)=0 for initial values.
When t>0 circuit will look like

And now i got for KVL i got

$$  E-U_L-U_R-U_C=0 $$
$$  E-Li_L'-\frac{i_L}{P}-\int\frac{i_L}{C}=0 $$
And now in need to do laplace transform.
$$  E-L(sI_L-i_L(0))-\frac{I_L}{P}- \frac{1}{C}*(\frac{1}{s}*I_L)=0$$
But now i got stuck here. Thanks in advance.


texts:
I have been eyeing USB communication in microcontrollers especially the dspic33 series. Now, when I looking over the physical connector of the USB, I came to know that there are 5 pins used.
VBUS,D+,D-,GND,USB ID pins. In these 5, I got little confusion about the VBUS pin. As per the datasheet of the MCU I am using, it is not self-powered for the VBUS pin. We have to supply externally 5V to the VBUS pin.
On seeing the architecture of the USB engine, the supply given through the VBUS pin is passed to the analog comparator. This is because the VBUS pin in the MCU is to monitor the state of USB communication, stated in the datasheet. No more info.
So, what are the roles played by the VBUS pin in the USB communication? The microcontroller  I am using is capable of playing OTG role.
From the above info I gathered, I need clarifications on these three points.

What is the use of VBUS pin in the microcontroller if it is used as a host? What are the operations are done by USB engine when MCU acts as host?

What is the use of VBUS pin in the microcontroller if it is used as a device? What are the operations are done by USB engine when MCU acts as device?

How the Vbus pin is used in OTG mode?

The answer need not to be MCU oriented. The relevant and general answers are also welcome.
Thanks for the help!!!


texts: How does this under voltage lockout (UVLO) work?

texts:
In my project, I need an under voltage lockout (UVLO) to  connect the load electronics to the energy-storage element via a power-gating transistor when the voltage across the supercapacitor exceeds the threshold voltage set by the potential divider circuit connected to the 1.8-V voltage detector and disconnected when the capacitor voltage drops below the minimum voltage threshold signaled by the 1.5-V voltage detector.
How do these three MOSFETs work to connect and disconnect the load,
knowing that SI-2377 is a P-channel and PMF280UN is an N-channel?


texts: Bulk Rectification Capacitor Exploded on Tesla Coil Halfbridge

texts:
I have been troubleshooting a clicking noise on my Tesla coil driver that causes the system to stop working if my AC line voltage got to high (80V when system is designed for 120V). Suddenly one of the main rectification capacitors (1000uF 250V) puffed smoke violently... I'm guessing the clicking sound was the capacitor breaking down and arcing internally... I have multiple small ceramic capacitors also on the circuit to bypass any RF from the main supply line.

1000uF 250V mfg p/n:381LR102M250K052
2.2uF 630V are generic film caps
4.7nF (Schematic 0.1uF) 1kV mfg p/n:S472M39Z5UN63J5R

I'm trying to figure out if it is my design that caused the failure, or just an unlucky capacitor being ran near its rating.

Does anyone see any issue, such as an RF path through the bulk capacitance (the 1000uF caps)?


texts:
I'm pretty new to CAN bus stuff and I'm a bit confused about how should I start the development.

There are a lot of different USB-CAN interfaces, but are there "easy" ways to generate test traffic etc without actually building your own devices and connecting them to the bus? I'd just like to read some CAN messages on a Linux host PC.

I can buy a USB-CAN interface, but what then? :) In Ebay there's nothing, Farnell sells some Microchip CAN demonstration boards for their chips, but I guess they use a proprietary USB interface and Windows software etc.


texts:
We have circuit like this:

There's no internal resisters in batteries.

Is \$\frac{I}{J}\$ equal to zero? If it is nonzero what is the voltage between the ends of the lamp (assuming the lamp has almost infinite resistance)


texts: How to set the Tektronix oscilloscope for pre-triggering?

texts:
I am a student and I am facing a problem with an oscilloscope configuration.

I have two digital outputs coming from two different switches. I want to find the time delay between the operation of these switches. When one switch operates, time starts and then time stops when the 2nd switch operates. For this I am using two channels of a Tektronix oscilloscope.

After studying on net, I came to know that this can be performed by pre-triggering of oscilloscope saying "The oscilloscope is acquiring pretrigger data. All triggers are ignored in this state" what this mean? I don't know how to set the pretrigger for two channels. The time between these two switches is hardly 200 usec.

Can anyone please explain to me, how to do this with an oscilloscope, or any other method, or explain to me the setting of the quoted sentence?


texts: What does "frequency test" mean with regards to inductors?

texts:
I am shopping on Digikey for an inductor for use in a radio application. The frequency range I am working in will be 200kHz - 900kHz. I noticed that there is a "frequency test" column where most of the inductors have 1kHz written in (a few have 250kHz written there). The datasheet provides no information about this and I'm not sure how to interpret it.

Do all inductors behave the same over a range of frequencies? If not, can I assume that they will at least behave with consistent inductance up to 1Mhz (a reasonably low frequency)?

What does this mean?


texts:
Well I think the prof has made a mistake in one of his exercises, though asking here to be sure, The question is to calculate the supply voltage in the system below.

simulate this circuit – Schematic created using CircuitLab

Now my solution goes as following:
$$\mathbf{Z_1} = R_1 // \mathbf{j}\omega L$$
$$\mathbf{Z_2} = R_2 // \left (-\mathbf{j}\frac{1}{\omega C} \right )$$
$$\mathbf{Z} = \mathbf{Z_1} + \mathbf{Z_2}$$
$$U = I\cdot \mathbf{Z}$$

However the prof used only \$\mathbf{Z_2}\$
$$\mathbf{Z} = \mathbf{Z_2}$$

This is wrong, right?


texts: I need to understand the meaning of this word "2 1/2 turn ferrite bead" ?? What exactly this 1/2 means ? Does this means that the wire is turned twice inside the bead?


texts:
I am currently working on a project that involves charging 18650 Li-Ion battery through USB-C using TP4056. Nothing really fancy (or at least have I thought!).
The circuit is pretty simple - Battery connected permanently to the TP4056; the rest of the circuit (two boost converters, ESP32 etc.) is separated by toggle switch (SW3).

Now, very weird thing happens when the user tries powering on / off the rest of the device by toggling the switch - the TP4056 starts drawing approximately 1A from the battery and instantly overheats, even though it is not plugged into the USB (+5VP rail is disconnected). This does not stop until I take out the battery.
This problem happens only from time to time, so it is pretty random. However one interesting thing is that when I tried to power the device with my lab PSU instead of the battery, it used to happen a lot more.
I managed to capture the moment, when I toggled the switch and the problem occurred. The screenshot shows voltage on pin 5 of the TP4056 when toggling the switch:

but IMHO there is nothing that special, that should "lockout" the IC until it is reset.
The TP4056 that was causing me problems was ordered from LCSC, PN C16581. Then, I swapped it with another TP4056 (again from LCSC, but PN C382139), made by a different manufacturer and now it works flawlessly. But I am still a little bit worried that this problem could come back even with the "good" TP4056, because I highly doubt that same ICs from different manufacturers should behave so differently.
For those thinking that it might have been only one bad TP4056 - it was not. All C16581 that I had at home were having the same problem.
Has anyone ever experienced something like this? Does anybody know what could be causing such problem?


texts: Is the "Volt" a measure of force or energy consumption?

texts:
A little confusion on my part.   I see that a volt  is the SI unit of electromotive force as the Wikipedia may show.

I also see that One Volt is defined as energy consumption of one joule per electric charge of one coulomb. Or. 1 ampere of current against a one ohm resistance.

One joule is equal to the work it takes to make a watt of power for a second, or to move a body one meter with a one-Newton force.

In the first definition there is no time dimension but then in the second definition a time dimension mysteriously shows up.   Does the definition depend on the context perhaps?


texts: Decoupling capacitor across Raspberry Pi GPIO input (+ Arduino + robotics)

texts:
I've been messing around with a robot kit from Parallax (the BOE Shield Kit), which has a 5xAA (7.2 V?) power source. The BOE shield includes its own 5 V regulator, which is used to control servos that in turn spin the wheels of the robot. The regulator is rated for up to 1 A of regulated power.
Now for the fun part: I want to also power a Raspberry Pi from this same circuit. I've been able to successfully power the Raspberry Pi via the Arduino's own 5 V output (not through the BOE regulator) and the GPIO pins. The Raspberry Pi has a single USB peripheral - a Wi-Fi adapter. When the servos are not running, or when they're running steadily, there's no problem, and the whole system, including the Raspberry Pi, chugs along happily. When the Raspberry Pi isn't doing anything over Wi-Fi, turning the servos off and on also has no effect on the Raspberry Pi's operation.
However, when the Raspberry Pi is using Wi-Fi heavily (I ran 'apt-get update' as a proof of concept), and I start turning the servos, the Raspberry Pi resets. I'm assuming it detected an undervolt condition and rebooted to protect itself.
Would a decoupling capacitor across the Raspberry Pi's inputs work to overcome these periods of "startup" servo load? Something like this:

(source: circuitlab.com)
If so, what type and size of capacitor should I use for this? Does it make a difference how far from the Raspberry Pi the capacitor is placed (I don't really want to solder one directly to the Pi)?
(Yes, I know, I used a relay symbol to depict the servo in the CircuitLab diagram, but they didn't have a "servo" block. Just imagine it as "thing that draws a lot of current for a very short time".)


texts: TTL NAND analog amplifier does not work in Multisim - why?

texts:
I have found in Dieter Nuhrmann's book an interesting approach to amplifier circuit and decided to test it.

Unfortunately the Multisim simulation does not work as expected. The signal is not amplified at the output.

What's wrong or what I'm doing wrong?


texts: Attempting to make a NES Zapper Lamp and need wiring help

texts: So I have a Nintendo Zapper gun that broke and I want to turn it into a Desk lamp.  But I want to use the Trigger as the On/Off switch.  Can somebody please help me and point me in the right direction on how I would wire that? Anybody familiar with that?


texts: Minimum current to measure from a 30kW motor?

texts:
We've been troubleshooting a problem here at work and we're kinda stuck so I thought about asking for some opinion from you guys. We have a 30kW 240V 3-phase motor with a rated current of 109A that is driven by a Toshiba VF-A7 inverter. The inverter trips a few seconds after startup with an over-torque error - and current soars above 150A - when with load, though we feel the mechanical parts driven by the motor isn't really that hard to move manually. So we're trying to determine if the problem is the inverter or the motor. If we determine they are both alright then our problem might really be mechanical in nature.

That isn't what I want to ask about though - I just thought I had to say it so you'd understand the situation. Anyway, when we run the motor without load, we get a current of around 38A. The voltage supplied is around 105V at this point. Would this be normal? In any case, what would the minimum current we could measure from such a motor running without load at that voltage? Is there a way to calculate that?

I ended up working as an all-around machine technician but I'm no electrical engineer, so when it comes to formulas and stuff, I'm somewhat clueless. I hope someone can shed some light for me. Thanks!

Edit: Whoops! I originally accidentally wrote 150V for the supplied voltage to the motor. It's actually 105V.

Final Edit: The problem was confirmed to be mechanical and we were finally able to fix it. Though turning the machine manually was easy at first (hence we didn't think it was a mechanical problem), but after several more turns, we found out that it was getting more difficult to turn.


texts:
I am buying a rotary switch, and I have found these terms:

2 x Off/(On)

and

2 x Off/On

Could you please explain me the difference?

edit:
example of a switch with Off/(On) specification

(originally from this page)


texts: Low-pass Filter with zero drift amplifier

texts:
Can an auto-zero or chopper amplifier be used in a low-pass filter to remove a high frequency carrier? I am trying to design an active low-pass filter with a 1kHz cutoff and very low DC drift, offset, 1/f noise. The noise needs to be less than 20μVrms in 1kHz BW and -80dB attenuation is needed at 100kHz. I intend to use a Sallen-key 2nd order Butterworth with a single op-amp.

My concern is whether I need to worry about my 100kHz carrier (that I am trying to extinguish) beating against the chopping amplifier modulator to produce more low-frequency artifacts in my 1kHz pass-band, or that higher frequency intermodulation products could alias when I digitize. Would I be better off using a passive filter and dealing with any residual aliasing of the 100kHz carrier digitally?

My power supply will be ±5V and the output will drive a single ended ƩΔ ADC.


texts: Set STM32 GPIO clock and data pins as fast as possible

texts:
I have an STM32 that toggles nine GPIO pins repeatedly (one clock pin and eight data pins to load an FPGA image using SelectMap). I am doing this using the standard library function GPIO_WriteBit that modifies one GPIO bit, and changing one pin at a time.

Unfortunately, this turns out to be quite slow. Is there a way I can make "raw GPIO toggles" very very fast? Is there a clock parameter I should change? Can I use some sort of FIFO, or interrupt-based method?

I have configured the GPIO pins as follows:

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

(Note: The reference manual (see page 133) states that the GPIO is capable of:

Fast toggle capable of changing every two clock cycles

But I cannot see how to activate this fast toggling.)


texts: Isolated way to detect 240V contact closing

texts:
I want to create a small project with an ESP8266 that makes a server call when a thermostat is open or closed. My main problem is detecting the thermostat status.

The electro-mechanical thermostat has two wires going to it, one 220V line and a return line. When closed, the switch passes 200mA 20mA through it, to keep a relay closed. There is no neutral line available. I don't have access to the relay.

For safety and legal reasons I want to have the ESP8266 battery-powered. I could be smart and "leech off" current but charging a battery once a month is not that bad. I also want the detection to be isolated and non-contact, if possible.

One thing I could do is: add a kind of light indicator and use a light sensor to detect that. Not sure if I could make it light in the on-state, but should be straightforward to do for the off-state, with a resistor, LED and diode.

I don't have enough place inside the thermostat housing for a complicated circuit and I want to keep the ESP8266 module outside the thermostat housing, as a clip-on solution.

TL;DR: an easy non-contact way of detecting whether there is mains voltage without a neutral wire, to read by ADC or digital logic.

Edit:
Inside one of the thermostats there is a neutral wire available. I guess with a little digging the other one has it as well. The available space inside the thermostat is around 20x20x20mm, so a module like TSP-03 would not fit.

I might switch the scope of the project from contactless to low-voltage, since it's a bit more reliable and easier to use. The idea is to provide two pins, that either have a voltage difference or close a contact (optocoupler). Whatever choice, it has to fit inside that enclosure and provide a safe output.

Edit2:
FYI: The relay is in a remote location (fuse box) and triggers a 3-Phase heating element. No use going that route, even if I could.
The uploaded picture shows the insides of the thermostat. The available space is on the left side.

The outside dimensions are 65x65x30mm.
Another solution would be to completely replace the thermostat with another model that provides WiFi or access to the signal.

A very comprehensive discussion about a similar topic can be found here: https://www.raspberrypi.org/forums/viewtopic.php?f=45&t=9617&start=25 as well as throughout StackOverflow. I've read most of those.


texts:
For a project I'm planning, I'd like to be able to plug a USB device into an Arduino and capture the raw usb events (handshake, interrupts, etc) and reply to the device on an equally low level. I've been eyeing the Arduino USB Host Shield (Docs) for this project, but I had some questions / concerns that I hoped to clarify before getting it.

The library is, at least from what I see, designed to make high level interfacing with common types of USB devices very easy. So I'm wondering, what would I have to do if I wanted to deal entirely with raw USB speak? Is it possible with the Arduino and this shield?

Thanks in advance for any help.


texts: Which jumper wire to use to connect MSP430F5529 with a breadboard?

texts: Which type of jumper wires will I need in order to connect this MSP430 to a breadboard to build simple circuits? Are all jumper wires equal or is there special ones to supply power vs. those used for communication back and forth? Lastly, can someone confirm if the 20 pins on each side are male or female?


texts: Switching between outputs using irfz44n mosfet

texts: In the circuit shown, the input voltage to the op-amp ua741 is 1V and the output will be 5.7V, which switches the bottom left irfz44n mosfet on and the off voltage irfz44n mosfet off. So i would expect the voltage from the first voltage divider [0.8*12= 9.6- 0.7= 8.9 Volts] which is 8.9V to appear at the output (at the junction where sources of both mosfets and the 10kohm pull down resistor meet). However i get 2.13 volts with minute fluctuations. Why is this happening? How do i fix this. Threshold voltage of irfz44n is 4V.


texts: Can I debug this simple circuit without VNA and proper RF equipment?

texts:
I am debugging a very simple circuit (existing PCB, not designed by me) that downconverts an AM modulated signal at 900 MHz:

The problem: What I measure at "Vo" does not match my LTspice simulations by quite a bit (I assume a constant unknown attenuation factor) and I do not have proper RF equipment (I have power supplies, multimeters, oscilloscope, an Ettus SDR and a very cheap and unreliable signal analyzer, but no VNA). I can basically only probe "Vo". For example, according to LTspice, the L-match is properly designed for 900 MHz but in measurements, the voltage would drop 10x for these values.
I tried to get creative and remove some unknowns by removing the L-match: I remove C1 and replace L2 with different resistors (0 Ohm... 1k). Here is what I get:

What could explain such profound differences? I tried adding various parasitics at various places but in the simulation, the voltage never decreases so rapidly as a function of resistance. As can be seen, for different input powers, the curves always fall off more gently.
Which kind of parasitics or effects could I have forgotten? What else could I try to model?
Is there any way to infer something about the RF nodes (bypassing the diodes)? I would really like to try something that does not need the diodes.
Could you think of any other clever way to simplify the setup further?


texts: Can anything be done to shield a record turntable from picking up unwanted radio transmissions?

texts:
So, I just bought a new record turntable (Audio-Technica AT-LP60BK) since… Hey! I guess I still like records. This is the base model AT-LP60BK turntable that only has RCA connectors for output; no Bluetooth or USB connection. Put analog connections happening for audio output.

Anyway, this turntable has a built in phono pre-amp. It amplifies well for true line level output, but there is a catch… Sometimes when the phono pre-amp is switched on I can pick up what sounds like CB (or maybe even HAM?) radio signals from my neighborhood. Possibly from a local car service? Definitely not a baby monitor since it’s clearly the sound of a conversation into a microphone.

No full voices are discernable but that kind of mumbling that sounds like an adult in the Peanuts/Charlie Brown cartoons. It’s incredibly annoying. FWIW, these rogue transmissions are sporadic in nature and there are times of day I (thankfully) hear nothing but the sweet tunes I am playing on my setup.

If I switch it to normal phono level output the levels are obviously lower, but then there are utterly no mumbling radio interference nonsense. Tested with it hooked up to my Sony CMT-SBT100 receiver as well as a stand alone speaker so I am 100% positive the issue is isolated to the turntable and only when the phono pre-amp is hooked up. I can hear this stuff if I simply have the turntable powered, not spinning and plugged into a speaker… All I have to do is switch on the built-in pre-amp.

I went ahead and opened up the bottom of the case to see if I could see anything obviously “off” about things; see picture below. Like most modern electronics, it all seems like a single-board setup and simple enough. But one thing comes to mind: Perhaps the issue is because there is utterly no shielding around the circuit-board?

I’m at a loss at what to do: Maybe get an external phono pre-amp and just use that? Or something else perhaps? Maybe add some simple shielding to the setup?


texts: Why is there a pull-up torque during the starting of an induction asynchronous motor

texts:
taking into account the definition of pull-up torque:

  Pull-up Torque:  The Pull-up Torque is the minimum torque developed by
  the electrical motor when it runs from zero to full-load speed (before
  it reaches the break-down torque point)

  When the motor starts and begins to accelerate the torque in general
  decrease until it reach a low point at a certain speed - the pull-up
  torque - before the torque increases until it reach the highest torque
  at a higher speed - the break-down torque - point.

  The pull-up torque may be critical for applications that needs power
  to go through some temporary barriers achieving the working
  conditions.

I can't find anywhere in this text( and in other articles on the subject) WHY  the torque lowers a bit(inflexion point) and then it raises again. What is the mechanical explanation for this?


texts: Buffering the input to a passive RC integrator used to measure magnetic flux density

texts:
Note: this is part of a larger question which I was asked to separate into subquestions.
Other subquestions: 1 and 2

I'm using the method outlined here to measure the induced magnetic flux density in a toroidal transformer made of Nanoperm (additional datasheets here and here). I am trying to adapt the method to use a passive integrator rather than the op-amp integrator described in the tutorial. (I tried building the active one but it was giving me issues.)

The diagram of my circuit is given below:

simulate this circuit – Schematic created using CircuitLab

where I am varying the input frequency of V1 to be either 50 Hz (as reported in the datasheets to measure hysteresis), 350 Hz, and 380 Hz, and I am varying R2 to be either 5 kOhm, 10 kOhm, 27 kOhm, or 37 kOhm. Note that the signal generator is connected to an audio amplifier capable of driving large currents. A result from one of my experiments is shown here:

For more details about the experiment and results, please see my original larger question.

While the shape of the hysteresis loop looks somewhat similar to that of the loops reported in the data sheet, it is orders of magnitude off in terms of both H and B. I posted a related question about this possibly being attributed to the way I was calculating H and B and/or to the fact that the gain of the RC integrator at the frequencies I'm looking at being much less than 1. I'm also wondering, since I'm using a passive integrator, does the EMF induced in the measurement coil need to be buffered before being fed into the integrator?


texts:
Complete noob here. I don't need a ready to implement solution, pointers on what to read upon and ideas for even simpler projects to gain experience first are perfectly fine.

I'm trying to feed both microphone and the right speaker of a motorcycle helmet intercom (Freedconn TCOM-SC) into the 3.5mm external microphone adapter of an action camera (Ghost Drift X). There's no ready to use solution for output from the intercom (it uses weird plug) so I need to tinker one out.

I got a "Y" headphones splitter that I can use to connect two microphones to the camera and record both simultaneously so I thought I could take that further, cut the splitter's input terminals off and tap into + and - on the intercom's speaker and microphone cables instead. However, after reading on how microphones and speakers work I realised there can be a huge difference in both voltage and current there. How do I match those? What are the terms I'm looking for and how do I Google for this specific subject (all I found in Google and here is how to match speakers to amplifiers)?


texts: What's the difference between the chisel tip and screwdriver tip for soldering irons?

texts:
I've decided to take up learning soldering and I've seen people recommend the chisel tip for the kind of work I want to do. I took a look online and found that screwdriver tips look very similar to the chisel tips mentioned.

However, I see these two tips listed separately on this chart I found:

From the chart and other pictures I found online, I can't see any difference between the screwdriver tip and the chisel tip, other than the "thinning" of the tip starting closer to the bottom on the screwdriver. It's a similar story for the wedge tips.

Does one tip transfer heat more effectively, or is the screwdriver tip better for getting into tight spots? Why would one be preferred over the other?

I've noticed that tips are often sorted by model numbers rather than types; are "chisel" and "screwdriver" just arbitrary names people assign to them rather than official tip types?


texts: Which cut off frequency I should use in order to cancel AC noise with the low pass filter?

texts:
it may sound a bit stupid, but the thing is that I want to cancel the noise caused by AC frequencies in a circuit. I know I have to use a low pass filter, but which cut-off frequency should I use?

I'm confused because the DC current does not suppose to have any frequency right? Then the lower the cut-off value is the better, but until what value?


texts:
The clock of my STM32F303CC (links to datasheet; for reference manual see here) sporadically dies away, resulting in highly decreased code execution speed (see picture below). I already replaced the oscillator and experimented with different capacitor values. I also tested this on different boards, all exhibiting the same error.

The firmware of the STM32 always runs the same lines of code, so transitions in firmware code can't be the reason.

The components used are:

Oscillator: 7A-8.000MAAE-T
Capacitors: 2x 22pF, 6V3, 0603, C0G

Any idea why this happens?

Edit: Replaced layout image as I forgot to render polygons.

Edit: The decoupling capacitors are on the direct opposite of the board, just beneath the STM, and are connected through vias with both top's GND and 3V3 pins (former through PCB wire, latter through the copper plane).


texts: PIC capture interrupt not triggering at 0.65v

texts:
I connected pulse input to CCP1 pin( capture1 pin), maximum and minimum volt of pulse is 2.5v and 0.65v

interrupt setted on falling edge

problem is, interrupt not triggering at 0.65v

but when I connect ground to CCP1 pin its triggering.

so is it normal that CCP1 requires 0v/Vss not 0.6v?

Microcontroller: pic16f876A

void timer1Int(){
T1CKPS1 = 1;    // 11 = 1:8 Prescale value
T1CKPS0 = 1;
T1OSCEN = 0;    // Oscillator is shut off
TMR1CS = 0;     // input clock to the timer is F OSC/4,   T1SYNC has no effect
TMR1ON = 1;     // Enables Timer1
TMR1IE = 1;
TMR1 = 0;

//CCPx Mode Select byte
CCP1CON = 0x04;  //  Capture mode, every falling edge
CCPR1 = 0;
CCP1IE = 1;     //  Enables the CCP1 interrupt
}

CIRICUIT DIAGRAM, this never goes 0v


texts: I/O card couples analogue ground to 0V - how can I work around this?

texts:
I'm building a system that has to measure analogue voltages accurately. This system is being tested using PC-based test equipment that has an expansion card in it generating both digital and analogue signals. The digital signals also route to the system under test.

My problem is that the system under test has a measurement offset error of around 50mV.

The cause of this appears to be that the PC expansion card couples the analogue ground reference AGND to 0V. This is a surprise, because AGND and 0V are clearly distinguished on the labels of the card's output pins, and I expected them to be isolated. The 0V and AGND are intentionally joined in the system under test very close to the ADC.

It looks as though part of the return current that should be flowing in the 0V line is instead flowing down the AGND connection to the expansion card and causing the AGND near to the ADC to be at a slightly higher potential than at the expansion card source. If I temporarily replace the analogue inputs to the system under test using the outputs of a fully isolated power supply, the measurement offset goes away.

I am at a loss as to how to resolve this. I can't modify the system under test. Is it perhaps possible to put a unity-gain isolation amplifier between the expansion card and the system under test? Or replace the expansion card with one that isolates AGND and 0V from each other?


texts:
I'm reading ZipCPU's tutorial and got confused. Specifically, I'm referring to this page.

To transcribe the Verilog code:

input   wire            i_S;
input   wire    [7:0]   i_V;
output  reg     [7:0]   o_R;

always @(*)
if (i_S)
        o_R = i_V;

I can understand that if o_R is declared as a wire, then a latch will be inferred as wires have no memory, and thus some external memory is required to keep the previous value. However, o_R is a register here, and registers can keep their state. For example, we can simply connect i_S to the "write enable" pin of the flip-flop corresponding to o_R, so why do we have a latch now?

As a bonus, why is a latch, rather than a flip-flop, inferred in such a situation? I'm under the impression that they basically serve the same purpose.


texts:
I'm trying to emulate via Arduino the volume down button of the remote mounted on iphone earbuds, and I can't find anywhere how that function is achieved; I imagine that certain passive components housed in the earbuds are shorted to the mic-gnd TRRS pins (upper ring and sleeve), but I can't really figure which ones.

Thanks.