texts: How Does A Pull Up Resistor In Parallel Work?

texts:
I've been playing with a Raspberry Pi and working with simple circuits. I thought I had a decent understanding of pull up/pull down resistors, but then I purchased an Infrared Break-Beam sensor (https://www.adafruit.com/product/2167) and the instructions for it confused me in terms of pull up resistors. For a circuit with just a switch, I would use a pull up resistor as described here (Pull-up resistor - why input pin is pulled to ground when the switch is closed?) and am able to understand how it works with the explanation in this answer (https://electronics.stackexchange.com/a/339369/170831), using the resistive divider function (https://en.wikipedia.org/wiki/Voltage_divider#Resistive_divider).
However, the instructions for the break-beam sensor describe it as an "open collector" and specify to incorporate a 10K pull-up resistor across the voltage supply wire and the digital signal wire (as shown below if I'm understanding correctly).

My trouble is, from what I've read about pull-up resistors, I would've thought the pull-up resistor would go only on the voltage supply wire, but perhaps I don't really understand how the IR receiver works. The diagram below is how I would've expected to incorporate a pull-up resistor, as well as a basic idea of how I thought the sensor works as a switch.

Is it possible to have pull-up resistors in parallel with other devices in a circuit? If so, how do you use the resistive divider function when the resistors are in parallel? I can build the circuit as specified in the instructions. I'd just like to have more of an understanding of how it works.


texts: I am expecting the blue wave to move up to vcc/2, but it's not the case here. I tried other opamp model with similar result, so it's most likely the problem of the circuit itself. I can't see the wave move through C1 because it's a high pass filter, what value can I set it to to allow the frequency to pass through?


texts: How do I calculate battery life for my devices?

texts:
I want to power coupe devices via car battery, but before I do that I want to figure out how long battery will last.
Most of the devices work from 5V so I am using 12Vto5V converter (link to item on ebay)
The convert powers RaspberryPi, Arduino Pro Mini, and usb hub&devices for raspberry pi. Total current draw is around 2A @5V.
Second converter is 12Vto9V and current drain is 1A at most.
Lastly I am using one of the cigarette ligher socket 12V to usb devices (link on amazon). I have yet to measure idle current draw but at most this will draw 2A@5V.

Now, how do I go about calculating battery life with those devices? I can measure current between 12V and all the devices&converters, but what then?


texts:
I am building a  lab power supply that is going deliver 0-6 A at 0-35 V, maybe 40 V. The power supply is almost ready to go in use.

On the power supply there are nice big banana connectors that can handle easily 10 A.

To wire circuits and other devices I need a cable with banana connectors. I started thinking if I am able to make it myself.

So here is my idea:

I order nice banana male plugs and a nice thick black and red silicon cable.

My problem is: which size do I need for around 6 A? I have looked at wire current tables, they suggest a cable size of 13AWG for 7.4 amps power transmission, but the same cable can handle 35 A for chassis wiring.

They explain that chassis wiring are lose runs of cables surrounded by air. Another calculator says I only need 18AWG.

Can somebody help me with a suggestion on which cables in need to buy.
To clarify the specs that the cable needs to handle are:

0-40 V
0-6 A
80 cm in length


texts: Is FCC certification required for something that is not sold?

texts: Is FCC certification required for something you put together for personal use or only for something you actually sell to someone else?


texts: Could you explain how this current measurement circuit works?

texts:
I have a schematic for current measurement, but I don't really know how can I calculate the output of it. The op-amps are on +-12V. The output of the circuit is 0.2*I(Rs) [V] (--> this is what I don't know how to calculate), thus in the range of 5V, we can measure 25A with it. The V_PWR is 24V.

How should I set this circuit to measure a maximum current of 10A instead of 25A?
What are the diodes and transistors for?

Circuit measurement schematic http://img5013.photobox.co.uk/151954327f8d9d7d42f253c3a9c42b2e44e8b66e7687b35e9972598d1a88bc7f88b9ef41.jpg

simulate this circuit – Schematic created using CircuitLab

Thanks,
Tamas


texts: What is holding the SS pin high in SPI master mode on AVRs?

texts:
A typical AVR datasheet contains the following example of an SPI Master mode configuration (here from page 164 of the ATmega128/L datasheet):

void SPI_MasterInit(void)
{
    /* Set MOSI and SCK output, all others input */
    DDR_SPI = (1<<DD_MOSI)|(1<<DD_SCK);

    /* Enable SPI, Master, set clock rate fck/16 */
    SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0);
}

void SPI_MasterTransmit(char cData)
{
    /* Start transmission */
    SPDR = cData;

    /* Wait for transmission complete */
    while (!(SPSR & (1<<SPIF)))
        ;
}

Note that the initialization of the data direction register, here given as DDR_SPI, sets the SS pin to input (implied by "all others to input").

However, the section on the SS pin functionality (which follows the code, on page 166) states for Master mode:

  If SS is configured as an output, the pin is a general output pin
  which does not affect the SPI system. Typically, the pin will be
  driving the SS pin of the SPI slave.

  If SS is configured as an input,
  it must be held high to ensure Master SPI operation. If the SS pin is
  driven low by peripheral circuitry when the SPI is configured as a
  master with the SS pin defined as an input, the SPI system interprets
  this as another master selecting the SPI as a slave and starting to
  send data to it. To avoid bus contention, the SPI system takes the following actions:

  The MSTR bit in SPCR is cleared and the SPI system becomes a slave. As a result of the SPI becoming a slave, the MOSI and SCK pins become
  inputs.
  The SPIF flag in SPSR is set, and if the SPI interrupt is enabled, and the I-bit in SREG is set, the interrupt routine will be executed.

  Thus, when interrupt-driven SPI transmission is used in master mode,
  and there exists a possibility that SS is driven low, the interrupt
  should always check that the MSTR bit is still set. If the MSTR bit
  has been cleared by a slave select, it must be set by the user to
  re-enable SPI master mode.

(Emphasis mine).

Now, the code works fine for me, but I don't understand why. The Master's SS pin direction is set to input, but what is holding it high? The code doesn't activate the pull-up. It seems to me that a floating pin could possibly trigger the consequences 1. and 2., resulting in the master becoming a slave. But it seems hard to believe to me that the code examples would employ such an unpredictable scenario.


texts:
I'm investigating a circuit with transistors. Below is part of the circuit where a JFET has been approximated with its g-parameters. The circuit continues to the left and right but that isn't relevant.

The current over I1 is \$g_mu_{gs}\$ where \$u_{gs}\$ is the voltage difference between V1 and V3. From the circuit, it looks like no current would flow through R2, making V3=0. Is this correct? Would this mean that \$I_1 = g_mu_{gs} = g_mV_1\$?


texts: DC fan control using an arduino UNO and a N channel MOSFET

texts:
I am trying to produce a variable speed fan control using an arduino UNO. I tried something using a BJT which didn't work and so it was suggested that I use a MOSFET instead. I am just looking for some feedback about something I have designed before I go and prototype something that is useless or breaks delicate hardware.

Here is the schematic that I have drawn:

Basically the PWM value is set serially via the serial monitor varying the pulse width sent to the gate of the MOSFET and hence the amount of time per wavelength that the DC fan is switched on.

I got the idea from this guy here https://www.youtube.com/watch?v=Pw1kSS_FIKk who did the same thing except with the fan powered by a 12 V battery. The battery seemed like it would provide more than enough current but would I be able to get maximum RPM with just the 12 Volt power supply being fed into the arduino?

My fan is rated at 130 mA but I know that the arduino only gives 40mA at best. Does anyone have anything to suggest?

This is what I mean
Ignore the math below because I am pretty sure its wrong. After revising this component I understand it will have a variable current flowing from the drain to source depending on its operating point (determined by the gate to source voltage and the 12v power supply).

With that said the overall output current due to Vgs will be reduced due to the resistance of the DC fan am I right? What would you suggest I do to find the drain current when the FET is switched on?


texts: Why are laptop computers usually powered around 20V DC?

texts:
Most electronic devices use 3.3V, 5V (all USB devices), 9V or 12V (very often for electronic music gear), and we usually all have dozains of such wall adapters at home. Even desktop computers have usually 5V and 12V power supply (ATX power supply).

Is there a historic reason (or electronic reason) why laptop computers are usually around 20V?

Why don't they use a quite standard 12V?

Linked question: Why is a laptop power supply output voltage different from its battery? but here a bit different, I'm not looking for the reason about the voltage being different from the laptop's battery, but rather why it's different to the standard 5V / 12V  used in desktop computers.


texts: Version control of schematics and source code

texts:
I am developing an electronic device which has two parts: hardware (Eagle schematics) and firmware (C++ source code). I would like to track changes in both source code and schematics, but there are some points where I am not sure how to organize my work:

For the source code I would definitely use Git. But are schematics worth
versioning when they are in fact binary files (new Eagle versions
use some XML format, but it is not so human readable...)?
Is it good idea to put sources and schematics into one Git repository? It
would make sense, but on the other hand my log would contain both software
and hardware changes. Also the software can have several branches, but
hardware probably not...
How to deal with hardware revisions? Tag them or save them in separate
directories?
Also there could be some dependencies between hardware revision and firmware
version. How to deal with them?

Could you please share your best practices with me?


texts: How can a capacitor store charge whilst also passing current?

texts:
It's frequently said that capacitors store charge. Just reading through Wikipedia, I find:

Daniel Gralath was the first to combine several jars in parallel into a "battery" to increase the charge storage capacity. Benjamin Franklin investigated the Leyden jar and came to the conclusion that the charge was stored on the glass, not in the water as others had assumed.
Because the conductors (or plates) are close together, the opposite charges on the conductors attract one another due to their electric fields, allowing the capacitor to store more charge for a given voltage than if the conductors were separated, giving the capacitor a large capacitance.
Here Q is the charge stored in the capacitor

Charge is measured in coulombs, and I know from the definition of capacitance that if a 1F capacitor has a voltage of 1V, then 1C of charge is stored in it. If a coulomb is 6.241×1018 electrons, then there should be 6.241×1018 electrons in this capacitor somewhere.
But now consider this. If I use a capacitor as a load to some AC voltage source, some current will flow (the precise amount depending on the voltage, frequency, and capacitance):

simulate this circuit – Schematic created using CircuitLab
I know that current is flowing all the way around this circuit, because if I put a lightbulb on either side of the capacitor, it will light. But if the current is flowing around this circuit, how does the capacitor "store charge"? In other words, how can I ever put electrons into the capacitor if the current is flowing around the circuit, which means for all the electrons I put in the capacitor, the same number come out the other side? If I can't put electrons in without taking some out, then how can the capacitor be storing them?


texts: Is there a limit to capacitor peak power density?

texts:
If so, what is it?

P=V^2/R, so increase voltage and keep R low. R is the resistance of the load, which is equal to the internal resistance. (With superconducting internal and external load R=0 but we have a current density limit of superconductors and inductance. Power could then be transferred to an antenna or motor. I guess then we'd still have impedance matched load.)

Increasing dielectric thickness d allows for higher voltage, but we also need to increase insulation at the fringe to avoid corona discharge, which increases volume/mass by d^3, while power increases with d^2, so power density actually decreases.

Could a capacitor made of two charged hollow spheres in the vacuum of space be scaled to ever increasing power/mass (on even volume) density? Large spheres/distance would limit "corona" discharge.

Do we get peak power density by fully exploiting the highest dielectric strength material (diamond?), regardless of capacitor size?

I'm asking, because

https://de.wikipedia.org/wiki/Energiespeicher#Speichern_elektrischer_Energie

said the maximum power of a normal capacitor is 10 kW (0.01 MW in column "max. Leistung in MW"="max. power in MW"), which seemed wrong.

https://en.wikipedia.org/wiki/Power-to-weight_ratio#Electrostatic,_electrolytic_and_electrochemical_capacitors

mentions a 3300 V, 100 kA capacitor, which works out to 330 MW.


texts:
I am fairly new to electrical engineering, and I am planning to build an electric reverse trike.
I am planning to buy a 3kw hub motor from uumotor.com (Model number UMB3K). It states that it can on 48 to 96v. I need to decide what voltage to use, so that I can start building my battery. Anyways, my question is, if I choose a higher voltage, will it run faster, or maybe have more torque? And would it then draw less amps?
Thanks.


texts:
I am working on a project to model the electrical characteristics of a piezoelectric (PZT) and would like to get a sanity check to make sure I am going about it in a way that makes sense.

So I am using the Van Dyke-Butterworth model for a PZT. I have measured the absolute impedance of the PZT using an impedance analyzer and am now working to fit the impedance function for the Van Dyke-Butterworth model to my data to find the value of the model components.

Where I need a check is for the steps of calculating the magnitude of the impedance.
1 write down Z
[2] multiply the numerator and denominator by the complex conjugate of the denominator
[3] separate into real and imaginary parts and square them
[4] take the square root

I want to make sure I am not adding any terms because the steps seem to make sense but I am ending up with values extremely different for my calculated abs(Z) than from my measured abs(Z).

Am I missing something obvious? Any thoughts would be most appreciated


texts: Disconnecting ATX PSU's ground from mains earth to protect my oscilloscope

texts:
Like many I took an ATX PSU, hooked green to black, and have a nice PSU.

I am experimenting with a HP oscilloscope from 1997 and as you know, those are grounded to main's earth, just like my ATX PSU. This is risky as you probably know.

A simple solution to this would be disconnect the PSU black (v0) from the PSU case and thus disconnecting it from the main's earth. Which, as far as I understand would make the PSU "floating". I did it and it seems to work ok.

My question is why are those black wires connected to main's earth and therefore what are the risk in disconnecting them.


texts: Controlling 10k ohm digital potentiometer IC using NI DAQ USB6001

texts:
I am totally new to the DAQ system; used to work on Arduino.

For the requirement of a project, I have to control a digital potentiometer of 10k ohm (AD5245) using NI DAQ USB 6001.

How do I interface Labview with this chip?
Is there any library that I can use to communicate and control the digital potentiometer using the USB6001?


texts: Based on \$f(f) = \phi_{\beta} \; \land \; f(t) = |\beta_u| \$ determine type of oscillator

texts:
Imagine the below characteristics of feedback circuit in sinewave oscillator are drawn:

$$f(f) = \phi_{\beta}$$

$$f(t) = |\beta_u|$$

Based on the characteristics, how can I tell:

Which type of an amplifier should I use: inverting or non-inverting, to fulfill the phase condition given above?
Which frequency (exactly one) fulfills the phase condition?
What is the value of the gain to fulfill amplitude condition?


texts: Can reverse breakdown voltage be used to simulate lifetime aging of phototransistors?

texts:
As phototransistors age, their responsivity to light decreases (a fixed amount of light generate less photocurrent). To simulate long-term aging of phototransistors in a short period of time, one can conduct accelerated lifetime testing by exposing the phototransistor to electrical stresses.

The most common electrical stress is subjecting the phototransistor to high voltage and current (Vce) so that it is forced to dissipate much more power than its rated power dissipation. It seems that this can change the behavior of the phototransistor in a way similar to long-term aging. (E.g. see Surridge, et al., 2002, "Accelerated Reliability Testing of InGaP/GaAs HBTs" here).

I am wondering whether subjecting an NPN type phototransistor to reverse voltage exceeding its reverse breakdown voltage (that is, high voltage at the emitter, with the collector grounded), can also simulate long-term aging.

I believe that high reverse voltage causes impact ionization, which degrades the junction. (Read this in ONSemiconductors - "Understanding Power Transistors Breakdown Parameters here). Experimentally, a sufficiently high reverse voltage will cause current to flow backwards from emitter to collector, cause the sensor to heat up, and quickly decrease responsivity to incident light (tested in Vishay Electronics' BPW96B and BPV11F NPN phototransistors).

Is this similar to the way a phototransistor's sensitivity to light would decrease over years of aging? What is the physical mechanism behind long-term aging of phototransistors, and how does it compare to that of high reverse voltage?


texts:
I have a SASEBO-W / 3-94336-3 board for testing side-channel attacks. I followed the steps that is mentioned in the manual for setting jumpers and switches. But after connecting USB cable and JTAG config cable, LED1 doesn't turn on on the board. Does anybody have any idea what's wrong?

Moreover when I do a right-click in ISE iMPACT and click on initial chain it pop a windows that indicated  There are many unknown devices being detected and the Identify failed.

How can I debug this board?

LED1 on the board is marked with core in the button.


texts:
I need to use the next Ethernet interface design which it's got a RJ45 10 pin, the schematic looks like this:

(The RJ45 datasheet is: https://katalog.we-online.de/pbs/datasheet/7499111446.pdf)
(PHY transceiver:https://www.marvell.com/transceivers/assets/Alaska_88E1512-001_product_brief.pdf)

Being a first prototype, in my design I only need to work with low speed Ethernet interface (10/100) and I´m planing to connect to my PCB this RJ45 breakout board:

The RJ45 datasheet:
https://www.sparkfun.com/datasheets/Prototyping/MagJack.pdf

would it work if I'm connecting the PHY_ signals to the respective pins (p1-p8) of the RJ45 breakout board?

i.e:

PHY_MDI0_P            -->       P1

PHY_MDI0_N            -->       P2

PHY_MDI1_P            -->       P3

PHY_MDI1_N            -->       P4

PHY_MDI2_P            -->       P5

PHY_MDI2_N            -->       P6

PHY_MDI3_P            -->       P7

PHY_MDI3_N            -->       P8

I noticed that the RJ45 with 10p it's got a power lines for the transformers
and the 8p connector don't, what is the difference in terms of functionality?

Thanks in advance.


texts: Can I double (or increase) the frequency of crystal oscillators by combining them in a circuit?

texts:
I'm thinking of a circuit which combines two waves of equal frequency (from two identical crystals), and outputs a wave with a higher (preferably doubled) frequency.
Can this be done? (Making 100MHz out of two 50MHz crytals.)
If so, is it possible to repeat this process (at least theoretically) to reach much higher frequencies?


texts: In Fowler Nordheim tunneling why can't electrons move from conduction band of poly Si gate to conduction band of Si substrate?

texts: The reason why electrons from Si substrate tunnel through the gate oxide barrier is that the conduction band of gate oxide is much higher. Similarly, electrons can also tunnel through gate oxide from poly-Si gate to Si substrate. Is this possible?


texts:
I need to control an electromagnet via USB with an android phone, to make a small educational project.

I know how to write the software, but how can I control an electromagnet via USB?

Via an USB Relay? Any suggestion?


texts: Start in Eletronics/Hardware with Eletronic or Arduino Book?

texts:
I've already received several suggestions about what some people read to start my development in relation to hardware / electronics. I already have a good knowledge in languages such as C, C + +, Python, and now I want to improve my knowledge.

I received recommendations to start learning with books like Practical Electronics for Inventors or The Art of Electronics, Arduino and some books, but do not know if I start earlier with the theory of electronics or if there is any book that covers these concepts along with Arduino.

Could you help me? I'm 17 and a lot of encouragement in learning


texts:
Can someone explain the purpose of this buffer stage? I understand how it works in the sense that I understand the cause of each reading on the oscilloscope but I don't understand why the buffer stage is designed this way. The circuit is a five band equalizer.

I thought the purpose of putting a buffer at the beginning of an audio circuit was generally to amplify the signal (I don't think my output is load sensitive) as explained here:

What is the reason for adding a buffer stage?

Here is the design of the buffer stage:

The corresponding voltage readings are simulated here (red is audio signal, green is amp input, blue is output of the entire stage):

To be clear, the audio input contributes a negligible amount of current so the 12V supply effectively goes through one giant voltage divider which reduces it to 2.4V which it adds as a DC offset to the audio signal which is needed because this is a single supply op amp.

But why would they design the buffer circuit so that the output is REDUCED?

The original design is taken from here where you can see the entire circuit:

https://electronicsforu.com/electronics-projects/hardware-diy/5-band-graphic-equaliser


texts: Short-range radar and LIDAR, how do they work?

texts: I was wondering how does short-range radar and LIDAR work? Considering the speed of light, the receiver sampling rate would need to be extraordinarily high to detect short-range distances(sub 1-2 feet). How do detectors work that avoid needing this high sampling rate? Is there some other way to measure distance than flight time counted by digital ticks?


texts: How does manufacturer determine initial tolerance for capacitors?

texts:
Short version: I understand resistor initial tolerance is commonly obtained through sorting process where manufacturer only picks resistor that has resistance within the advertised initial tolerance. Does MLCC manufacturer use similar sorting process to determine initial tolerance for capacitors?
Long story: This question is related to reliability calculation I have been recently doing where RSS method is used. When I try to find the worst case capacitance change, I combine all the random terms based on manufacturer spec sheet. Let's say for example this capacitor from muRata: GCM31CL8EL225KE07L. The specsheet can be found in this link. I have made the following assumptions when doing RSS for random terms:

Capacitance change due to a random event such as high temp exposure, moisture resistance, thermal shock, etc. falls within the 3-sigma range, i.e. chance of being within stated change is 99.7% under such event (I could be wrong with this too)
Capacitance change due to initial tolerance is uniformly distributed. For example, if the it is a 10% cap, its one-sigma (std deviation) is 5.77% and its 3-sigma is 17.32%.

I am guessing if manufacturer determines MLCC tolerance like resistor, I should use uniform distribution. But I would like to make things easier and assume this tolerance also follow normal distribution. This means the initial tolerance corresponds to the 3-sigma probability range. In this way I can make the RSS calculation easier without worrying about the square root of 3, simply calculating the squared sum of all random terms including initial tolerance.  I couldn't find related information online and hope someone can help me here. If you can explain how you would use these random terms in RSS that's also much appreciated. Thanks in advance!


texts: Replacing alternator warning lamp with LED

texts:
I have an alternator on an in-board motor in a boat, I have almost completed re-wiring the electrical system and am wondering if it is possible to replace the existing filament lamp.

I have researched and came across a forum discussion which, from my basic understanding, sounds like it is possible but wanted to check and confirm that it is do-able and was hoping that I could get some advice on the resistors/diodes to use.

In the above forum, the OP attached a schematic which has a bridging 5 ohm resistor, a 270 ohm resistor on the anode and a 5 ohm resistor going to the alternator, in this forum it was suggested to use high watt resistors around the 25W mark due to the heat.

Does all of this sound correct, is there a risk of harming the alternator or battery?

Can I use a 12V LED such as this one?


texts: PWM signal is affected when motor is connected

texts:
I am working on a fun side project where I am creating a PWM waveform using the LM324 and a small solar panel. I am using the LM324 for the astable multivibrator, integrator, and comparator. The comparator inputs are the integrated signal (triangle wave) and the voltage level of the solar panel. The generated PWM waveform is outputted to a motor driver (L9110H) that is built into a little fan and motor set up (link)

My PWM generator works great before I plug the PWM output into the input of the driver/motor/fan set up. Before I plug it in I can see the duty cycle change from about 70% to 30% depending on how much light is incident on the solar panel. However when I connect the PWM output of my circuit to the input PWM, it starts acting a little weird. It appears most of the time the PWM duty cycle will not change depending on the solar panel, and sometimes the duty cycle will jump to like 99%. I tried using a unity gain buffer, thinking the motor load was affecting my signal somehow, but that's not really helping. What I expect to see is the fan slowing down when I shade the solar panel, and speed up when it is lit. Any advice or instruction would be most appreciated!

By the way..all op amps have power rails of +/- 9V


texts: How does this tungsten rod not short circuit the batteries?

texts:
Why is the tungsten rod in the following circuit not a short circuit?

(Source: digikey.com)

I found it via this video:

(Source: youtube.com)

I'm just very confused on how this works. It's a high current power supply, and he's running the positive on one side, and the negative on the other, which causes it to heat up.

What I don't understand is how it doesn't short circuit the batteries. Even if this is short circuiting them, would their be a way not to? We are only going to use a battery that is 9-12V with an amperage of 2-5.


texts:
I have boost converter powered by 2 AA batteries (3v) which increases the voltage to around 40v. I have a 12v zener diode to cap the output to 12v. Regardless of the zener diode when I connect a strip of LED lights (rated for 12v, 33 LEDs @ 20ma each) the voltage drops to 8.1v. The LEDs do light up but not to their fullest potential.

Note that the diagram shows four LEDs, but in real life there are 33 in the form of an LED strip -- they're grouped in sets of 3 (you can cut every 3). So I've got 11 sets of 3 LEDs each, in parallel, for a total of 11 × 20 mA per set = 220 mA @ 12 V.

I have a few questions:

How can I increase the current so the voltage doesn't drop when the lights are connected (I think this is what is happening)?
Am I losing efficiency (battery draining faster) by going to 40v then capping it with zener diode at 12v?
My NPN is really hot to the touch, is this normal? I'm using BC337 which has a max rating of 800ma (and BC327 for my PNP).

Thanks


texts: Dark current in a transimpedance amplifier circuit

texts:
I am building a transimpedance amplifier circuit. Feedback resistor used is 1 mega ohm. A photodiode is connected to the inverting input of the amplifier (LM741C).
Using 23 volt supply, current reading is 32 mA. The current across the resistor, measured with a multimeter shows 23.4 uA. (which makes sense, since V=IR). However, the dark current shows a reading of 4 uA (with all other parameters being the same). Is this a suitable value and if not, what is the mistake I am making?

I have already spent a day searching for any links which could guide me and have not found anything useful. Any help would be appreciated. The link I used for the circuit is Fig.2 of the PDF.

http://www.ti.com/lit/ug/tidu535/tidu535.pdf


texts: What is the ON resistance of a BJT like a 2N3904?

texts: I wanted to use a BJT as a switch.e I want to drive the base from a uC pin at 3.3V. I have been told a FET needs a higher turn on voltage so I thought a BJT would be better. I am switching on a voltage divider and sampling the divider voltage with an ADC. So I wanted to know the ON resistance of the BJT to see how it will affect my calculations. But I don't see the on resistance in any BJT datasheets. Am I looking at this the wrong way?


texts: What is the benefit of wrting OpAmp parameters as function of G and Gfc?

texts:
This is a schematic for an oscillator. I am curious about how parameters are written as in the read box. I think G is the DC gain of the OpAmp. However, I am not sure what \$G_{fc}\$ is meant to be and why go we wrtite G as a function of \$G_{fc}\$ like that. What is the benefit of writing G = 10^(-\$G_{fc}\$ /20) instead of G = 10^(35/20)?

Also, because the OpAmp open-loop gain is not large enough (just 56V/V) can we assume the virtual ground here in calculating the voltage gain of invertering amplifier?


texts: Storage lifetime considerations for electronics

texts:
I am working on a single board computer that I am aiming to last for up to 30 years. It will be based on this design, with a lm7805 voltage regulator circuit and address + data line LEDs. I am concerned about the following:

EEPROM Data degredation: I will be using an AT28C256 EEPROM, a chip I know is susceptible to data degredation over the years. I could use PROM, but that is rare and many chips sold as PROM are simply EPROMs with no erasure window. This computer should last much longer than the website with the HEX files.

Electrolytic capacitor lifetime: the electrolyte in an aluminium capacitor is known to dry up over time. The computer will be in an enclosure and the capacitor will be close to the voltage regulator, which will generate heat. If the capacitor leaks, it will seep into the holes on the breadboard (I have no intention to ever manufacture more than one, so I am using a breadboard to save time and money.) and damage it.

Communication standard obsolescence: Go online and buy a new laptop with a serial port. You can't! 15 years ago, every computer had a serial port, some even two. Will USB 4.0 or whatever we will use in the future be backwards compatible?

How can I minimize or eliminate these problems? Cost or size is not a major concern and again, there is no intention to volume manufacture.


texts: Is there a good book on designing for electrical safety with AC mains power?

texts: Is there a good book on how to design for electrical safety, particularly when using AC/mains power? I have look on Amazon without finding anything that seemed appropriate. This topic is largely ignored or else glossed over in at most a chapter in the books I have. I had expected more coverage, particularly in books on power amplifiers and design of power supplies. The best coverage that I have found is in the ARRL Handbook.


texts:
Every book I read explains the current mirror (two transistors, M1 and M2, of which one, M1, is diode connected) neglecting channel modulation. In this way, we get a current

Iout = a * Iref

where Iout is the output current, Iref is the reference current and "a" is a number defined by geometric properties of the 2 transistors.

Now, I know that, assuming both the transistors perfectly matched and making a = 1, the output current is equal to the reference current. This in the theory... But when I put a load (and the load can be complicated, for example a mosfet, that is an active load) above M2, cadence gives values of the output current which are sometimes very different from what the theory says. I assume that this is due to the fact that we neglect channel modulation (that is the drain to source voltage of M2).

I ask a criterion in order to "understand" how a (generic) load modifies the output current. I mean: after I simulate the circuit with cadende and I notice a value of the output current very different from Iref, I always don't know how to change the load parameters (for example, if the load above M2 is a mosfet, I don't know how to change W and L of the load). I also know that in order to have the same output current the drain to source voltage of M2 must be equal to the drain to source voltage of M1 (the diode connected mosfet) because they share the same gate to source voltage.
I think that, by increasing the output resistance of the current mirror, we get an output current which is more and more independent from the load.

Thanks!


texts: Hand-soldering stripline opposed emitter transistors

texts:
I'm used to soldering through-hole parts, and older stuff than that.

I'm seriously considering embarking on an RF power project, that will require the use of stripline opposed emitter transistors (old Motorola MRF-series parts).  These are the things with a circular ceramic body, four rectangular metal tabs, and (usually) a threaded rod out the bottom that is attached to the heatsink.

I've never soldered anything like them before.  Anyone have any good tips, or pointers to tips?

The old MRF454 is one example.


texts:
I'm writing some evaluation code with a lot of rx/tx operations, using the same two buffers and I started to think about how this could easily go very wrong.

I can argue that it is nice to clear/reinitialize the buffers with 0's or any other val for that matter for safety purpose, and it's not like my MCU can't spare the extra X ms operations.

But at the same time I could also argue that flushing them is just bloat operations as the program behaves as it should.

What is the best practice / industry standard when it comes to handling buffers continuously overwritten? Is flushing the buffers after each operation, like wearing a life jacket on land ?

void IIS328DQ_Read_All(void)
{
  txbuf[0] = IIS328DQ_REG_OUT_X_H;
  txbuf[1] = IIS328DQ_REG_OUT_X_L;
  txbuf[2] = IIS328DQ_REG_OUT_Y_H;
  txbuf[3] = IIS328DQ_REG_OUT_Y_L;
  txbuf[4] = IIS328DQ_REG_OUT_Z_H;
  txbuf[5] = IIS328DQ_REG_OUT_Z_L;

  // Request X axis high and low bytes
  ret = HAL_I2C_Master_Transmit(&hi2c1, IIS328DQSADWR, &txbuf[0], 2,
  HAL_MAX_DELAY);
  ret = HAL_I2C_Master_Receive(&hi2c1, IIS328DQSADRD, &rxbuf[0], 2,
  HAL_MAX_DELAY);
  // Request Y axis high and low bytes
  ret = HAL_I2C_Master_Transmit(&hi2c1, IIS328DQSADWR, &txbuf[2], 2,
  HAL_MAX_DELAY);
  ret = HAL_I2C_Master_Receive(&hi2c1, IIS328DQSADRD, &rxbuf[2], 2,
  HAL_MAX_DELAY);
  // Request Z axis high and low bytes
  ret = HAL_I2C_Master_Transmit(&hi2c1, IIS328DQSADWR, &txbuf[4], 2,
  HAL_MAX_DELAY);
  ret = HAL_I2C_Master_Receive(&hi2c1, IIS328DQSADRD, &rxbuf[4], 2,
  HAL_MAX_DELAY);

 // Combine high and low bytes 0b00001111+00001111 (Endianness) to 16 bit int
 x_raw = ((int16_t)rxbuf[0]<<8) + rxbuf[1];
 // Shift the 16 bits to a 12-bit representation
 x_raw = x_raw >> 4;
 y_raw = ((int16_t)rxbuf[2]<<8) + rxbuf[3];
 y_raw = y_raw >> 4;
 z_raw = ((int16_t)rxbuf[4]<<8) + rxbuf[5];
 z_raw = z_raw >> 4;

 // FS bits set to 00 - min 0.9 | typ 0.98 | max 1.1
 // convert raw data using sensitivity (0.98mg/digit ~ normal mode)
 axisArr[0] = x_raw * Sensitivity;
 axisArr[1] = y_raw * Sensitivity;
 axisArr[2] = z_raw * Sensitivity;
 clearBuf();
 }

clearBuf() simply fills the rx/tx buffers with 0's up to sizeof()


texts: Correct wiring for 3 wire single phase motor

texts:
I have a single phase 3 wires ( + ground ) submersible pump , I need to understand the correct wiring what type of motor is this and is the capacitor important ?  the previous owner was not using this capacitor.

nameplate info :

  MultiMotors System
  Model : 4H07M22/A
  Motor: 1~
  KW 0.75   Hz 50 V 220 A 5.7 cosφ 0.98 min 2825
  C30µF/450V ( I assume this is the value of the capacitor to use )
  CI B IP 58

and the diagram on the side of the pump is :

simulate this circuit – Schematic created using CircuitLab


texts: How to determine no of bytes of an instruction of 8085 microprocessor?

texts:
Is there any logical way to understand no of bytes corresponding to an instruction in 8085 microprocessor? e.g: MOV A,M is a one byte instruction, but how, I don't understand.

Or do I have to remember it?


texts: This is the design for a 5 x 5 keyboard SIMULATION that i have created but it is not working. The encoder doesn't get a low signal when i press a button. Can anyone tell me what is wrong with the circuit?


texts:
I am failing to understand the purpose of the MOSFET in this circuit from Adafruit Feather board.

The FET is connected with source and drain reversed comparing to typical high-side pMOS switch, so this is not a power switch.

The combination of body diode with schottky should work like usual battery switch-over circuit, in which case what is FET doing there other than providing body diode?

My only guess is that it is there to avoid voltage drop on the diode when battery supplies power. If source is at drain voltage (via body diode) and gate is pulled to ground (via R12) then MOSFET should be fully open.


texts: How can I get rid of the noise from this audio amplifier (using a Kemo M031N)?

texts:
I am trying to wire up an audio amplifier circuit using the Kemo M031N 3.5W amplifier:

I have connected the wires from the amplifier to a terminal block. With a suitable 10V power supply and a 2W 8Ohm speaker but no input signal (ie nohing connected to the input wires at all), there is no or very low noise (which is a good start). I have connected one of the input wires to the PSU ground, which is also connected to the speaker.
The problem I have is that whatever I attach as an input signal (even when there is no actual signal), I get a lot of noise from the speaker. The noise is a mixture of bursty static noise (every 2-3 seconds) and a louder fast clicking. This noise appears at a low level even if I just touch the input wire at the terminal block with a screwdriver.
I have tried using a 10V regulated (home brew) PSU, the 5V from a Raspberry Pi and a PP9 battery. All have the same noise effect, to varying degrees (the battery was best but the noise still audible).
If I connect good quality (unscreened) speaker cable to the inputs on the terminal block, the noise is slightly louder. When I touch the other ends of the speaker cable together, the noise is very loud.
I have tried adding a 10k and a 2k2 resistor across the inputs with no change. I have also tried a 330uF capacitor across the supply at the terminal block.
Does anyone have any ideas on what I could try next?


texts: I have YUY2 video data that I want to be sent over USB to a computer. I want the computer to recognize the device as a video device so it can be displayed with software like a webcam viewer. I have tried searching multiple times on different sites, but I can't find out how to send a packet or when to send what packets. Most things I have found about USB don't tell me how to do these things on a smaller level. I am going to be using a microcontroller and a USB-C port.


texts: 10/100Mbps Magnetics with 10/100/1000 PHY

texts:
I have a SOC that has a KSZ9031RN PHY, that is a Gigabit PHY. But I'm going to use only in 10/100 Mode with 4 wires.

Gigabit PHY datasheet recommends a magnetic for Gigabit Ethernet, that are different from Fast Ethernet magnetics.

Can I use 4 Wire Fast Ethernet magnetic with that Gigabit PHY if I'm going to use it only in 10/100 Mode?

Thanks!


texts:
This scheme represents an DAC and an op amp.I need to find R1 and R2 so I came up with this resolve.

 (Vout has to be between [-10,10) V and Vr=10V,Rr=5k)

 I1=current through R1,I2 current through R2.

 Vout = R2*I2;(Kirchoff Vout,through R2 to the negative ground)
 I1+I2-I=0 ==>I2=I+I1;(Kirchoff in node A)
 I=Vr/Rr ==>I= 10V/5k==>I=2 mA;
 I-I1=0=>I=I1=>I1=2mA;(not sure about this,node B)
 10V(the superior limit)=R2*I2=>R2=10V/4mA=>R2=2.5k ,so R2 has to   be
 below 2.5 kohms

 thus R1=Vr/I1 =>R1=5 kohms
[![enter image description here][1]][1] Do you think I have mistaken in my thinking here?


texts: How generator becomes under excited/ over excited?

texts:
I keep reading in power system notes that a generator when under excited/ over excited either absorb/ release reactive power. Question is, what determines these under excitation and over excitation? Rotating rotor produces EMF on stator coils which is injected to grid. I sometimes see that in under excited condition E(terminal voltage) < V(Back EMF) and vis-versa in over excited condition.
What makes E(terminal voltage) constant irrespective of rotor excitation? Should there be some influence of rotor excitation on E?
What happens in case of a Diesel Genset, since there is no concept of constant terminal voltage E?
How to make a Diesel Genset produce active/reactive power, since I don't see the over excitation/ under excitation logic valid here since it is the only power source?
Also, Let us consider that the Diesel Genset is driving a single induction motor. What makes sure that the genset can produce required reactive power?


texts: Using Raspberry Pi GPIO for matrix switching

texts:
I'm working with a Raspberry Pi. I want to be able to connect any two of 7 pins together in a matrix fashion to control a device with a keypad input. This means I need to be able to short any of the 3 horizontal pins to the other 4 vertical pins. I'm not sure if this can easily accomplished with the GPIO pins. Are there any IC's I can do this with or would I need to accomplish this with some kind of transistor?

If at all possible I would like it to be jellybean parts and as few parts as possible. If I can get away with 7 transistors or even just using the GPIO pins somehow that would be fine.


texts: Trying to read serial communication from smart meter with Arduino

texts:
First my compliments for this wonderful site. I'm hoping to find an answer to my problem. I've checked to find answers, however was not able to find it.
My background is somewhat technical, only with minor electrical knowledge.
My project goal is to read the serial signal which is supplied by the P1 port of a Smart Meter (ISKRA type MT382-D2A52-M2K0agnZ) with an Arduino MEGA 2560 @ 9600 Baud rate.
Many before me have succeeded, however I don't seem to manage.
Before the Arduino can 'read' the signal from the P1 port, the signal requires to be inverted.
(General advice on the internet on this topic: Use 7404 hex inverters and transistors to invert the P1 signal)
I'm currently using the following components and schematic:

Arduino Mega 2560
NPN transistor 2N2369A
2x 1k resistor

The 2N2369A is doing something, because the serial output of the Arduino with the schematic of above is as follows:
0-0:96.then rubbish
0-0:96.then rubbish
0-0:96.then rubbish
The 0-0:96. part it spits out every 10 seconds looks somewhat like what it should read:
/ISk52ME382-1003
0-0:96.1.1(4B414C37303035313039)
1-0:1.8.1(00180.912*kWh)
1-0:1.8.2(00001.416*kWh)
1-0:2.8.1(00000.000*kWh)
1-0:2.8.2(00000.000*kWh)
0-0:96.14.0(0001)

etc..
When I connect the TX from the P1 (smart meter) directly onto the RX0 port of the Arduino, the following is produced:
(V
eÔR]d�“ZòövRÖå½Vû‹�“£�´ò«}—“IYÙ–ö–ö–V–Ö’’Ö™Ÿ™�™�™—f'ff+9½Rû‹�´dë^Ÿ“••“£(V
eÔR]d�“ZòövRÖå½Vû‹�“£�´ò«}—“IYÙ–ö–ö–V–Ö’’Ö™Ÿ™�™�™—f'ff+9½Rû‹�´dë^Ÿ“••“£(V
eÔR]d�“ZòövRÖå½Vû‹�“£�´ò«}—“IYÙ–ö–ö–V–Ö’’Ö™Ÿ™�™�™—f'ff+9½Rû‹�´dë^Ÿ“••“£¯ÉSë5\²MÔ3¸²-±00´�

which is absolute rubbish. Therefore I think I'm close with the NPN, however I can't make it to the last step.
Is someone willing to advise me what I'm doing wrong?

wrong choice NPN? wrong resistors?

In advance my gratitude to anyone willing to help.
Kind regards,
Vernon
!! FOLLOW UP UPDATE!!!
Following up on my question above, I have done a bit more testing.
I have tested a Sketch from internet using AltSoftSerial with Digital pin 48 on the Mega as a software RX solution, however with perfect results:
Result:
*0-0:96.1.1(5A424556303035313739303939343133)
1-0:1.8.1(06558.109*kWh)
1-0:1.8.2(05439.071*kWh)
1-0:2.8.1(00000.002*kWh)
1-0:2.8.2(00000.000*kWh)
0-0:96.14.0(0002)
1-0:1.7.0(0000.80*kW)
1-0:2.7.0(0000.00*kW)
0-0:17.0.0(0999.00*kW)
0-0:96.3.10(1)
0-0:96.13.1()
0-0:96.13.0()
!*
Arduino Sketch used:
http://domoticx.com/p1-poort-slimme-meter-uitlezen-hardware/
Connecting the Smart Meter TX to pin D48 without NPN the output is rubish again:
*+9=V{$46{/#++9=V{
vkZJV%V{
4r+}IYYvvVVV
f'ff+9=R{4dk^4rV+*
I'm very close, however I feel like an idiot not being able to get the normal RX0 serial port to spit out the same data as the AltSoftSerial option.
Anybody ideas?
Many thanks in advance!
Vernon


texts:
EDIT: there should be arg[I2] instead of arg[I3]

I've tried to replace V1, C1, R1 with Thevenin equivalent, but I've lost in my calculations. Is there any better approach?


texts: connect series of batteries in parallel?

texts:
I have eight sealed lead–acid batteries connected to my photovoltaic array in the way you can see in the image below.

A friend told me, that it was a bad idea to put those light-green cables in the middle. I put those, because I thought that this would equalize voltages when one of the batteries is loaded faster or unloaded faster due to wearing. Because I’m afraid, that if one battery’s voltage is very low (kind of short circuit in the battery), the one connected in series would be damaged due to overloading.

My question: Is it a bad idea to have those light-green cables connected in the middle in parallel?

(The input is a MPPT/battery charger and the output is an 230 V inverter.)


texts: JST Connector Female to Male Jumper, is this how it works?

texts:
At home I have a small laptop fan with a 1.0mm pitch JST Female connector, and I was looking for a Male JST Connector to hook on to the Female one I have at home.

I found this item on amazon, and apparently you are suppose to attach the loose male head onto the female head of the wired connector, as shown in the picture.

So my question is, once I put the loose male head in the picture into the wired female head to the left, I can then attach the male wired connector we just created into my female JST laptop fan connector at home?.


texts: Measuring change in magnitude of electric current due to change in conducting material characteristics

texts:
I posted this in the physics section. I now think this might be more appropriate section for these questions.

I am looking for answers to the following:

What is the order of magnitude of change in electric current when the diameter of the conducting material (that is tens of nano meters) changes by a few (say 1 to 5) nano meters, like in a chip? I am thinking of constant voltage source as that is more commonly used in circuits involving ICs. Is that correct? I am thinking that the change in current would be of the order of tens of nano amperes. Is that correct?

2.What is the easiest way (circuitry) to measure the change in electric current due to change in conducting material? I would like to measure the change NOT necessarily the original current flowing. Is it possible to find a source which has circuit of a pico ammeter that I can use in the circuitry?

Look forward to your thoughts

Thanks in advance

Kind regards


texts: Using 3N128 mosfets as 12V controller with microcontroller

texts:
I recently found a bag of 3N128's at a yard sale, coincidentally, a couple days after I saw this video on YouTube about controlling a 12V motor with a mosfet, car battery, and arduino:

https://www.youtube.com/watch?v=Lzxuro0Z2Ew

Here's the schematic he drew:

What I'm unsure about is if I can use these as a direct substitute for the mosfet he used. It has 4 legs and the symbol that I found on the datasheet looks a little different than what he used:

http://html.alldatasheet.com/html-pdf/108468/ETC/3N128/110/2/3N128.html

I'm tempted to just connect (4) to (2).


texts: On the possibility of lead acid battery recoverability

texts:
I have a 6 V 4.5 Ah lead acid battery which I did not charge for the last 6 months. Now the battery voltage fell to 3 volts and then I charged it for 24 hours at 50 mA. Now when I measure the voltage it is shown as 6.37V which is the nominal voltage which then decreased to 6.1 volts in half an hour. Another thing is that it started gassing above a charging voltage of 6.7 volts.

My question is does these symptoms mean the battery is not recoverable? Or does it take a few more charge discharge cycles to attain normal capacity?


texts:
I am working at oil pump station plant as electrical technician, I have 4 years experience in the field, and I face a problem which you can help me with. I appreciate any kind of information that will help me.

First of all, I was assigned to repair our plant fence lights. We have huge area of fence lights and at the switchgear room, we have 4 circuit breakers 480 VAC from main substation feeding 9 loads. It's our fence light divided in several loops including some area lighting.

My job is to clear a short circuit on isolated fence lighting loop. After finding shorted connection terminal in lighting pole, I clear this issue and return that loop in service, but when I was checking the voltage
Phase to phase I got 460 to 470 VAC, and I got 270 phase to ground which is good, because I don’t have neutral in the circuit. So I started to energize second breaker while I am checking voltage at breaker number 1 I found (unbalanced voltage) phase to ground I got
A-G = 418
B-G = 170
C-G = 200

Then I switch off second breaker, and I got normal voltage, then I start third one, found again unplanned voltage
A-G = 600
B-G = 190
C-G = 70

I started all 4 breaker one by one and I check them. Each one working alone is balanced, but when any 2 of 4 breakers working together, I got unbalanced voltage.

Note : all breaker running together (phase to phase voltage readings are 480 VAC) which is good and our transformer in each lighting pool needed that amount of voltage.

The breakers are not tripped and all lights working fine because it gets 2 phase 480 power. But I still don’t understand if this issue will affect our lighting systems or what?

Also the current reading for each phase is different in all 4 breakers.
I am really thankful if you reach this point in my long explanation.

I hope you can help me.


texts: Compression schemes sending difference between successive samples only, what would happen if error occurs?

texts:
There are multiple inginious data compression methods in which we send the difference between current and next sample rather than the actual value of the sample. This makes it possible to send the data in fraction of the actual bandwidth required to send original samples.

I have following questions:

1) How does data transfer start? i.e if we only send the difference, how do we assign value to the data at the beginning when there is no previous sample to refer to?

2) The difference between previous and current sample will usually be small but sometimes very large e.g when the scene or focus in a video changes to something different. Does this mean that small and large differences between the samples are sent using the same bandwidth? Really??

3) Error in data can occur quite easily. What if error occurs in the current "difference sample" sent across the channel? Won't this cause the error to propagate to all future samples values at the output reciever???


texts: What is the difference between a Controller and Microcontroller?

texts:
I read, that I need to use a controller, if I want to communicate with a device over Input/Output Adressessing. It is sad, that I need 3 steps:

Put the I/O-adress on the motherboard bus
The hardware controllers are listening to that bus
The particular Hardware-Controller (e.g. the keyboard) is answering

So I am currently a bit confused.

Is a Controller the same thing as a Microcontroller ?
Is a Controller hardware or software ? If it is hardware, why do I need drivers in an operating system. The hardware is still able to communicate...


texts:
I'm trying to make a pulse oximeter using IR Light,Red Led and a Light to frequency converter with STM32L4 Controller and Timer Input Capture.
The  wavelength input of both the lights gives a similar graph as given below(when the finger is placed)  .
If the inputs are converted to frequency ,the graph that comes up is just the inverse of it(as f=1/l).
I have referred many papers and once such is given here,which shows a similar graphAnother Note.
I had already tried with the frequency inputs that was giving correct heart rate but SPO2 values were between 82% and 86%.
The formula used is Percentage SPO2 = 110-25R.
where R = (RMS of RED/Average of Red)/(RMS IR/Average Red)

RMS values are calculated by multiplying 0.3535(1/2*sqrt(2)) with peak to peak value.

Am I following the correct method? if not how should I proceed?


texts: "Ground" vs. "Earth" vs. common vs. negative terminal

texts:
This may just be me not having a degree in electrical engineering or electronics, but the whole notion of "ground" and "earth", when used in electrical circuit diagrams (especially integrated circuits), is extremely confusing. I guess the whole notion of current "comming from" the positive terminal (which is often how current seems to be described) seems backwards and misleading to me, given the quantum mechanical description of electrical current as the flow of electrons. So, I'd just like to clear up my understanding of things.

First things first...to make sure my understanding of voltage and current is correct. Assuming a direct current context (I understand things are more complex when using alternating current, and I understand that it is possible to have ground at a positive terminal in some systems and things like that.)

A. The positive terminal in a circuit is what creates voltage. Voltage is a potential, so given that it is the positive ions in, say, a battery, which are generally fixed in place, it makes sense that the + terminal in a circuit would create voltage.

B. The negative terminal in a circuit is what provides current. Current is the flow of electrons, and that flow is towards the terminal that is creating the potential for current.

Assuming these statements are true...then why is the term "ground" (primarily) or sometimes the symbol for "earth" used so extensively in electrical circuit diagrams? Why is it ground or earth, rather than just a negative terminal, or a 0V terminal, or maybe just a "common" terminal? The use of ground or the earth symbol, particularly in IC circuit diagrams (which are not necessarily used in circuitry that is even remotely capable of being "grounded" to the earth...such as in an airplane or a spacecraft, or even any number of isolated, insulated systems that cannot be directly connected to the earth), is extremely confusing to me.

Is this just some old convention that hasn't ever been broken? Is ground (the GND terminal) or the earth symbol in a circuit diagram just a thing that's done, because that is always how it's done? Because that's how it's always been taught? Does it really just mean a negative terminal, or a terminal from which electrons flow? When is the use of a literal ground, a point where a circuit actually connects to the literal earth, actually required? It seems clear that not every circuit, like an IC, does not actually need a literal connection to the earth in order to function.

Well, sorry if this is an odd question, however as I play more and more with electronics, and since I'm powering most of my little projects with batteries, this whole concept seems odd and confusing to me...there is no literal "ground" or "earth" involved in the circuit. Only the battery terminals and electronic parts.


texts: How does a computer know when to "get" the output from the ALU?

texts: Basically what the title says, I guess I've got some sort of misconception or somthing probably. The ALU can have, say, a ripple carry adder which doesn't produce its entire output all at the same time (it ripples). So how does a computer know when the output is ready? Does it have to do with the clockspeed and propagation delay?


texts: Power Failure Detection Circuit via Flip-Flop

texts:
I'm trying to create a circuit that will detect complete power failure. I think I understand what major components I need, but I'm unsure as to how to go about connecting them.

My plan is to take 3.3V line input, and somehow wire it up to a latching switch to preserve state information. Ideally I would also store information on this flip-flop. Output of the flip-flop would go to a microcontroller that could perform some analysis to determine if the latching switch changed states, thus determining that the power went completely off.

I just don't know where to begin in terms of selecting components or wiring them together. If anyone has some tips or suggestions for where to look, I would greatly appreciate it.


texts: I usually forget to turn off the geyser. To solve this problem, I want to create an alarm that will go off, 10 minutes after I have turned on the switch for the geyser. I'm a computer science student. So I'm not sure how do I even start. Any help would be appreciated.


texts:
I'm trying to create an outdoor installation with simple embedded electronics. I was hoping to use conductive paint to connect leds. The leds would be covered (waterproof) but the conductive paint would be exposed. However, I was wondering:

1) if conductive paint being exposed to water is just as a bad as exposing regular electronics being exposed to water, or if it would be ok for outdoor use?

2) if not, what would be a good alternative for waterproofing electronics?

Thanks.


texts:
I need to derive the output expression for this circuit in terms of ui1, ui2 and ui3. I am stuck on this for hours and have an exam next week.

So far,
I was able to get the sum of 3 voltages. I also know the part after R2 is a non-inverting amplifier. I am unable to get the voltage across the R2 which would serve as input to the noninverting amplifier. Any help is appreciated.


texts: I have already attempted this problem and it takes 6 wye-delta transformations to determine the equivalent resistance across the marked points. But I was looking for other possible methods that might simplify this approach. Note that I'm not asking for a solution. I'm asking for reasonable methods to apply to this context.


texts: Vector Network Analyzers: Bode100 vs Keysight P5000A

texts:
I have been using Bode 100 machine earlier to measure Impedance and Phase of my piezoelectric transducer.
The frequency range i work in is from 10kHz to 2.5MHz.
I was just comparing this Bode100 with Keysight P5000A VNA as it is more coapct than Bode100. But was wondering if it is possible to do the same job of Bode100 of measuring Impedance and Phase over certain frequency sweep.
Which would be a overall better choice?
Thanks


texts:
So I'm starting with the Nilsson/Riedel electronics text and got confused early on. They show a simple loop circuit (figure 2.15 for those who have it) with 1 ideal voltage source and 3 resistors and, across one of the resistors, the current flows opposite to the rest of the circuit.

I understand that, in the Passive Sign Convention, positive current flows from + to - across a load; what does this mean physically, though? It was my understanding that electric current only moved in one direction; I've apparently forgotten something from my undergrad electronics class.


texts: What device can measure the amount of water though a line?

texts: My dream device is a way to quickly make tea. I can use most of the parts from a Mr. Coffee tea maker but the last part is a way to start the flow of water, measure say, 1/2 a gallon and then stop the flow. It can't be hard . . . ice makers do it all the time. How does an ice maker do it?


texts:
In the formula shown bellow why the charge between V+ and GND is minus to the charge of Vref and V+ ?
Thanks.


texts:
Given the following circuit diagram

I know that in order to find either values, I can apply...

or ...

But I am having some trouble understanding how I can get rid of the imaginary term j in both cases, even with conjugate root theorem I can't seem to rid of j totally.


texts:
I am new in Cadence and doing a schematic design.
My circuit requires a varactor.
In the varactor specifications there are these parameters:

How should I change the value of the capacitor and what is the connection setting?
I have attached images below.
What should I do if I want capacitance of, for example, 0.1pF?


texts: LM301 comparator and diodes on compensation

texts:
I'm trying to understand what's the purpose of the two diodes connected to the compensation pin (8), and what the output of the comparator is supposed to be.
Also, I'd like to remove the 5V supply and modify it so that the comparator outputs 0V to +15V (or a bit lower), as it should drive a CMOS chip input (powered with 0V/+15V)

datasheet: http://www.ti.com/lit/ds/symlink/lm101a-n.pdf
update:
is this equivalent? it should still provide 0V to +5V more or less, able to drive a MCU or CMOS


texts:
I have an activation system with a unique password per activation operation.
If the system goes down or is not working correctly and I need to reset it to a operational state I could design a hard reset key combination so that the system recovers. Nonetheless I would need the password to be different each time the system recovers (this was the original explanation, and is wrong) process an activation operation.(correct)

I would like to know if, during a hard reset operation, a microcontroller is capable of changing a variable, store it and use it after the hard reset operation.

The thing is that the new password should be also known by another device that is not connected to that microcontroller.

In a normal operation both devices are synced with their passwords so, maybe, if the microcontroller detects a hard reset, can the current activation password be saved in non-volatile memory before resetting and use it after reset?


texts: Do I need a heatsink for my voltage regulator?

texts:
I use L7805CV voltage regulator (TO-220) to get 5 V from a Li-Po 7.4 V 2200 mAh battery. However, after a while, voltage regulator gets really hot.

Current measurement showed 200 mA.

P=I*V=0.2*(7.4-5)=0.428 W.

From datasheet:

Thermal resistance:

junction-case = 5 °C/W, junction-ambient = 50 °C/W, total 55 °C/W.

In this case, temperature rise will be 0.428*55=23.55 C. Seems low to me, but I can't touch voltare regulator for more than one sec. Do I need a heatsink or it isn't necessary. Datasheet refers there is thermal overload protection. In this case, can I calculate how long does it take for voltage regulator to shut off (if this will happen)?


texts: PIC18 Robot - Travelling exact distance straight using two wheel encoders problems

texts:
(EDIT: Added TMR0 & TMR1 set-up code)

I have a small robot vehicle controlled by a PIC18f4585.  It has two wheels (ball bearing on the front) as well as two rotary encoders.  The following function is supposed to travel a specified distance in inches perfectly straight.  It travels straight enough, the problem is the distance. the travelled distance has an error of up to 2cm.  I was just wondering whether anyone else could see an error I have missed.

Additional info:  The PIC is clocked at 40MHz.  I am counting the encoder ticks using TMR0 and TMR1 in 8-bit mode.

Any help/suggestions would be greatly appreciated, thanks.

TMR CONFIG:

TRISAbits.TRISA4 = IO_INPUT;
    OpenTimer0( TIMER_INT_OFF &
            T0_8BIT &
            T0_SOURCE_EXT &
            T0_EDGE_RISE &
            T0_PS_1_1   );

TRISCbits.TRISC0 = IO_INPUT;
OpenTimer1( TIMER_INT_OFF &
        T1_8BIT_RW &
        T1_SOURCE_EXT &
        T1_PS_1_1 &
        T1_OSC1EN_OFF &
        T1_SYNC_EXT_ON  );

MOVE STRAIGHT FUNCTION:

void moveForwardDistance(double distance, int power)
{
int tickGoal = distance * 5.13348;      //This seems to get ~the correct distance

int masterPower = power;
int slavePower = power;
int error = 0;
int kp = 50;            //error factor
int totalTicks = 0;     //used to keep track of total ticks

resetEncoder();

while(totalTicks < tickGoal)
{
    SetRightMotor(masterPower);
    SetLeftMotor(slavePower);

    error = TMR1L - TMR0L;
    slavePower = power + (error / kp);

    resetEncoder();
    DelayMs(100);
    totalTicks += TMR1L;
}
SetRightMotor(0);
SetLeftMotor(0);

DelayS(1);
}


texts:
I'd like to make my own binary watch, and something pretty small. Using surface mount LEDs would work but they use a lot of energy (~30mA a piece for something I'd consider reasonably bright) so there'd have to be a mechanism to "show the time".

Instead of this I'd like to only update my display once per time unit and leave it in a stable state in between - exactly like an e-ink display, thus massively reducing the power requirement.

I only have 6 binary display parts in my design so I really need individual e-ink cells, but I've no idea if this kind of thing even exists!

Does such a component exist? Is this the 'right' line of thinking? Thanks!


texts: Op Amp integrator (square to triangle) not always start working correctly

texts:
I created an Op Amp integrator with LM358 to convert square wave to triangle wave as shown below.

simulate this circuit – Schematic created using CircuitLab

Though the circuit sometimes works as I expected, but sometimes when I restart my signal generator square wave output, the output will be exceed voltage rail.

(The yellow one is the output of signal generator and the blue one is the output pin of the Op Amp, both 1V/div )

I am 90 percent sure that this problem raised because my generator not outputting perfect waveform on the beginning and the waveform take some time to become stable. And this will make the integral result go to voltage rail and cannot be integrated back. However, I am not sure how to solve this and make the circuit more stable and always start working. I hope this can be bettered because latter I want to connect it to a 555 timer and the timer, just like my function generator, not start working perfectly as I observed on the scope days ago.

Thanks for any suggestion.

Thanks to vangelo's suggestion, I changed the cap to a 224 one. And then the circuit works a lot of better that I turned on and off the signal generator ten times and all of them works well. However, I found I can still repeat my problem by screw the R3 to a low resistance. (Originally the connected side measures about 5kOhm and now I turned it to about 2kOhm) And here I finally captured how the circuit go out of control. (Same scope configuration as the above and before this experiment I checked probe again and it's OK)

The screenshot was taken by one shot but what happening, if in Auto mode of scope, I can notice triangle wave after turning signal output on in several seconds or frames maybe. And in that way it is after my generator works stable state that the circuits go wrong... Also, I found another problem is when the signal was turned off, the output of Op Amp is about 3.6V but not 2.5V, I believe this is caused by offset voltage and offset current. Should I compensate it in this application and how?


texts: Adding ethernet jack and transformer to device designed without one

texts:
I'm attempting to add an RJ45 Ethernet jack to a commercial device without one by replacing an embedded WiFi module, which, according to its datasheet, is connected to the rest of the system as follows:

The section labeled "PHY" here is a PHY on the device (on a Micrel Ethernet switch chip elsewhere on the board), while the section labeled "HF-A11-SMT" is the WiFi module I'm attempting to replace with an ethernet jack.

I'd like to be able to connect the jack directly to a regular ethernet port on a computer, so I need some way to add a jack and magnetics, or a MagJack-equivalent, to the board without modifying any of the circuitry supposed to connect "transformerless" to the WiFi module.

There's plenty of examples out there for how to hook up a MagJack if I was able to remove the "transformerless" circuitry in the schematic above and connect directly to the Micrel chip, but since I haven't been able to fully trace this part of the board (it's quite a complicated design, and there's a lot of other unrelated stuff around this module that make trying to trace it difficult) and I'd like to interfere with the rest of the device as little as possible, I'm looking for a way to connect a regular RJ45 jack with magnetics to the pads meant for the WiFi module's RX/TX pins ("transformerless" circuitry intact).

I can't find any information on how adding a jack to a design like this might work. If there's either a circuit that could do this which I could design a simple board for, or some sort of off-the-shelf version of the same for testing devices like these, what are they? If not, what's the minimal amount of modification that would have to be made to the "transformerless" circuitry in order to make this feasible?


texts: How to transfer raw video data from a device to a computer using royalty free wired connection?

texts:
I have RGB video data captured from an LCD and I would like to send it over to a computer for capturing however it seems all video connectors require a significant investment if one intends to use them commercially (5k to 10k sign up + royalties for each product between $0.2 to $1). What connector could be suitable and be royalties free?

The data comes from two 256 × 192 LCDs, 18bit color depth, 60 frames per second.


texts:
I'm trying to make a IR laser diode driver which needs 1.9V and ~80-100 mA constant current. Most of laser driver circuits in web has LM317 as a current source but that design has always voltage drop around 2.5V. Since I have 3V supply, i'm trying to find an alternative way with low drop-out voltage.
I have found LT3085 (Datasheet) which says 275mV dropout voltage.

In datasheet's typical application section there is a circuit for Current Source but Vin=10V. Since LT3085 has "Wide Input Voltage Range 1.2V to 36V". How can I use with 3V supply?


texts: How to determine whether electrial appliance is On or Off using ADC or Optocoupler

texts: I want to sense the On/Off state of an electrical appliance (e.g. light bulb 100W) using a microcontroller ATmega16L. How do i go about doing this? My mains supply specs are 230V, 50Hz


texts:
i am trying to recreate the calculation for INL and DNL
for n=100
$$S_{avg}=0.091$$
$$INL=\frac{(V_{actual}-V_{uniform})}{S_{avg}}=\frac{(0.33-0.35)}{0.091}=-0.21$$
$$DNL=\frac{(V_{actual_{100}}-V_{actual_{011}})}{S_{avg}} -1=\frac{(0.33-0.17)}{0.091} -1=0.75$$
both of them doesnt match the INL and DNL results in the table for 100 .
Where did i go wrong?
Thanks.


texts: Power supply problem, what is the correct solution?

texts:
My result is "No" because the DC voltage is around 14.86 v and the ripple voltage is around 9.9 volts but I'm not convinced about the result especially for the ripple voltage. Does anybody get the same result?
Here are my calculations
$$V_{peak} = 15 * 1.414 - 1.4 = 19.81$$
$$V_{rip} = \frac{1}{f \times R_{load} \times C} \times V_{peak} = \frac{1}{100 \times 20 \times .001 }\times 19.81 = 9.905V$$
$$V_{dc} = 1-1/(2 \times f \times R_{load} \times C) \times V_{peak} = 14.86V $$


texts: How do I determine the Schottky diodes to use with my H-bridge?

texts:
I am trying to build my own H-bridge to drive a DC motor (12 volt, 25 amp stall). This is one of my first attempts ever at making my own circuit.

I want to use the HIP4080A to control four N-channel MOSFETs, and the datasheet for the HIP4080A is clear about the basic setup.

I have read that Schottky diodes should be used to deal with EMF from the motor. I do not know how to determine what kind of Schottky diode to get, or even if it's really necessary.

I will be using PWM to drive the motor at varying speeds.

Is this diode ok? I don't really understand how to know.


texts: I am trying to find a simple hardware solution to implement a 2-bit timer that gives out 2-bits continuously repeating data 00, 01, 10, 11, 00, 01.... whose time period is approx 1ms. The accuracy and jitter in the period is not an important design parameter. The simplicity in design is important. Simplicity means without any programmable logic. The voltage levels can be any.


texts:
I'm making a Sous Vide using Arduino with a DS18B20 temperature sensor. My problem is that the DS18B20 reacts too slowly to temperature changes. For example, if you take it from ice water (1°C) to boiling water (100°C), DS18B20 takes a full minute to reach 95°C. Worse, the temperature show asymptotic convergence; near final temp, DS18B20 approach at like 7sec/°C.

So, what is the fastest temperature sensor available today (and cheap) ?


texts: Searching for exotic SOT23 P-channel mosfet where source drain swapped

texts:
Due to an error in the layouting process a batch of PCBs has to be scrapped. Instead of the standard pin assignments:

1 - Gate
2 - Source
3 - Drain

we used:

1 - Gate
2 - Drain
3 - Source

As a last resort before ordering new PCBs I would like to ask you if you ever came across a P-Channel Mosfet (SOT23 package) where the source and drain pins were swapped?


texts:
Below schematic is what I have on the breadboard:

simulate this circuit – Schematic created using CircuitLab

R1 is there to sink 10mA of current to bias LM317, but 470 ohm is a value that I achieved by trial and error!

What's the equation for this circuit to calculate how much current is being "sink" by the NPN transistor?


texts: Why putting more logic seems to increase working frequency?

texts:
I'm working on a design in Xilinx Zynq. After synthesis and implementation, the worst negative slack is about 8.9ns which means that the circuit runs at about 112MHz. However after adding ILA cores in order to debug some signals, the worst neg. slack falls to 4.180ns which effectively doubles (nearly) the working frequency.

I believe that this is due to different re-arrangement of the LUTs inside the FPGA, but could someone answer me for sure? Why more logic provides faster circuit?


texts: 12W Antex Iron taking 15+ seconds to melt my lead-free solder, do I need a new Iron?

texts:
I don't recall ever having the problem with the iron before, but it's been a few years since I used it, as I'm just getting back into some projects since my Electronics degree.

I bought some solder for a new project (I need a lot) and it's lead-free:

95% Tin
4% Silver
1% Copper

Now, I'm not sure how tolerant the values are for melting point but I can say that it does appear to act Eutectic, like the known combination 95.5/4/0.5 (Indalloy 246) which has a melting point of 217 degrees Celcius.

According to the manufacturer of my Iron (Antex) it has a tip temperature of 370 celcius.

I sanded down the tip yesterday with a fine grain metal sanding paper to see if the tip just needed cleaning, however it's now gone "black" instead of the shiny silver it was when I first sanded it.

The real question I wonder is where the problem lies, is it that my tip is dead, is my iron too low power or is it just that my iron is dead.

I ask because I need to know whether to replace the iron, the tip or a higher power iron. My preference is to stick with the Antex irons, and I prefer "precision" bits like the on in my current iron, so, what are the recommendations?


texts: Will an opening fuse cause an inductive kick, or not?

texts:
I'm looking at designing a high-current crowbar circuit. We need to blow a 1400A fuse on demand. One question that has arisen is, what about inductive kick? If you short a large capacitor through a fuse, like so:

the current in the fuse path may well reach 50kA before the fuse opens. That's a lot of energy built up in the inductance of the path between the cap and the fuse. So where does that energy go? Does it get burned off in the fuse as it opens? Or do you get an inductive kick on that node, potentially damaging anything else connected to it? Some of each?


texts: I need to simulate the following circuit in LTSpice. I don't know where to ask so you're my only hope.. I made the scheme but I don't know what value to choose for R2 and Cinf in order to have theoretical gain Av=1500. The following constraints are imposed: Vcc=10v; VCM=1.5V; vg it's a sine wave with a frequency of 1Khz and R1=15kOhms. I need to simulate the circuit(transient, AC sweep), choosing an appropriate amplitude for vg in order to minimize output signal distortion(I put 100 uV but idk if it's correct..), and to specify a method for decreasing the voltage gain (without changing R1, R2, VCC or VCM). Implement the change and re-simulate the circuit in order to demonstrate the effect. Here it's the link for the LTSpice .asc scheme: https://drive.google.com/open?id=1qL4ZDORlUAnp7sdpu3l2T4dKp_5WRAlH


texts:
Recently, I have undertaken a Solar sun tracker project with the soul purpose of learning in mind. The basic operation of the project is to implement a dual axis solar sun tracker, this is done by using an Arrduino Uno board to operate a mechanical structure, the movement is based on readings from 4 LDR's. This part of the project has been successful.
The part where I'm a bit lost is at the output of the solar cell. The solar cell is rated at 5.5V, 320mA - I am looking to somehow boost the 5.5v to around 14v. I have looked into DC-DC Boost Converters and I have realised that there are various ways to implement them. I first took the route of using the raw components of the circuit with no IC chip, this ultimately failed and I came to the conclusion that I needed to take a different approach. I started to look into the various other methods and came across using a MC34063 chip, this seems quite appealing as I'd be able to calculate the components using the data sheet. The problem I'm facing is that as the DC input is a solar cell, the voltage input of the DC-DC Boost Converter will vary a fair bit. Could I get away with having a Vin of around 3v (+/- 50%) or is this just plain stupid?
Alternatively, I have been looking into creating a boost converter using a microcontroller, this is something I haven't looked into as much but seems promising. In time, I'd like to also attempt to implement the MPPT algorithm and have an inverter circuit on the output, in order to create a 'smart inverter'. But for now I'd like to take things one step at a time. Can anybody offer some guidance on the matter? which route would be the best to go down considering my goals?
Revised Plan;

MPPT Control Algorithm;
What I can work on from here is to have my readings from the solar panel input into my Arduino UNO - then I can start to have a look at the different readings and how a MPP can be found from these readings. Based on the findings I'll be able to alter the duty cycle of the square wave input and hence, increase Vout of the boost converter. I started to have a look at the various implementation methods of the MPPT algorithm and I've come across the 'Peturb-and-Observe' method. Is this a good place to start?
DC - DC Converter;
I'm still struggling to get my head around the application of the converter types, I understand how both Buck and Boost Converters work but I'm still unsure as to which circuit would be more fitting for my project. Currently, the vision I have is that I would build a Boost Converter circuit with a Vin of approximately 3v and a Vout of 14v. I'm aware that as my application uses a solar panel the input voltage will constantly change, but based on the readings from my solar panel I'll be able to alter the duty cycle so no matter what the input voltage is (within reason) I'll always be able to produce a figure reaching 14v at the output. Is this a viable solution? and how would I begin to calculate my component values, based on the fact that I don't have a definitive Vin.


texts: What causes uneven evaporation of lead acid battery electrolyte?

texts:
I bought a brand new lead acid battery for my motorcycle after the previous one was at the end of its lifecycle. Just to mention the battery is of the brands associated with a good quality. It was a dry model that I needed to fill myself with the electrolyte sold with the battery. It worked well after following instructions carefully. No problem.
However after some 50h of driving and forgotting park lights on the battery was drain out. Voltage was down to some 10.5V or so. No hope for starting. No problem either. Just charge the battery. I took it apart just to check the overall condition and charge overnight.
Now, I understand that such an energy drain to low voltage can damage battery but what surprised me was that 3 cells had lost a lot of electrolyte and the rest 3 cells were at specified level. Anyway I added distilled water to specified level, charged overnight and there was again enough peak amperes to start.
Next I checked the regulator (roughly) after charging by checking the system voltage and it was (at "low rpm" like 1500 - 4500, about the rpm of of the travel speed of my bike) between 13.8 - 14.5V.
Ok, maybe for that specific battery - say 14.5V - is too much. I could understand that it could cause some (or even big) loss of electrolyte. What I can not understand is why some cells - in a brand new battery - were like nothing happened and the rest were like totally dry.
I do not know if it matters but the dry cells were at positive side of battery but not the most positive was the most dry. The amount of electrolyte (6 cells from - to +) was approximately 100%, 95%, 100%, 55%, 20%, 75%. These amounts just roughly describe the amount of electrolyte needed to satisfy the specified level average.
Is this kind of wearing in such a short time usual or should I return this battery to the dealer?


texts:
guys i was going through this diagram in my book when these lines came along(i am a student):
Here RG(usually in M-ohm range) establishes a dc ground at the gate and presents a large resistance to input signal..... I want to ask why resistor is used? can't we directly ground it?


texts: DC motor temporary speed change with simple Boost Converter

texts:
I would like to know is if it is possible to give a slight voltage change to a dc motor with simple electronic items.  Meaning that the voltage would normally be a set amount (10v) but would either drop or increase slightly at set or random intervals to produce variations in motor speed.

I haven't been able to find any references to this type of implementation and am wondering if it's possible.  Currently the idea is based around a simple boost converter diagram, with possibly a 555 timer chip controlling the switch. To my knowledge of how the circuit works, when the switch is very quickly closed it produces a current build up from the inductor which produces a higher voltage at the cap, which can then be used by the motor for the speed increase. Or is the cap unnecessary?

I am not sure if I am on the right track or if there are references that I should be referring too. But any help would be appreciated.  I know there are better ways to control motor speed but this is a low cost application and the random/timed speed burst are more for effect then anything else.
Thanks,

Demsey


texts:
On studying RLC circuits, I have come across two definitions of Q factor. One is obviously the measure of selectivity and goes as this:

The other is this:

Is there any link between these 2 definitions? Can we start from the first one and arrive at the second one or vice-versa?
While I do understand that the first one comes from the half-power points computation and is a measure of selectivity, I don't get the origin of the second definition besides the link between them.
Some insight would be appreciated.


texts:
I'm very new to electrical engineering and I'm trying to read microphone input with arduino nano. I've made a separate microphone module (based on this example) and plugged it into aruino like this:

Unfortunately it was the last time my arduino was working. It's no longer displayed as a connection, and acts "randomly", so I think my microphone toasts controller for some reason. Here are some more pictures and a scheme of my mic module, could someone explain what am I doing wrong?

simulate this circuit – Schematic created using CircuitLab

R1 - CR1/4W 10 (brown,black,black,gold)

R2 - CR1/4W 2KO (red,black,red,gold)

I have no education in electrical engineering, so I'm not sure about the corectness of this schema of units, just pasted what's written on the pack


texts: Use of Dual Schottky diode in voltage supervisor output

texts:
I was exploring one of the popular Tiva C launchpad (http://processors.wiki.ti.com/index.php/Tiva_C_Series_LaunchPads) to create a custom board based on TM4C123GXL evaluation kit.

There is a Schottky diode connected to the RESET output of the voltage supervisor in the schematic as shown below

One of the anodes goes to the RESET pin of the main microcontroller and the other one to the RESET pin of another microcontroller which act as an inbuilt debugger/programmer.

What is the use of a Schottky diode in the output of a voltage supervisor like this?

Note : +VBUS is the +5V coming from USB connector


texts: Is there an oscillation happening when powering a 24 VAC irrigation valve? Since the solenoid is being driven by an alternating current (AC), does that mean it goes "on" and "off" at some points of its AC phase (e.g. at zero volt crossing) at a fast rate that no one really notices it?


texts:
I`m trying to create a basic delay circuit using a capacitor. I am using a momentary switch in series with a 220 Ohm resistor, a H332 100uf 25V rated capacitor and an LED, all connected to a PP3 8.4V 200mAh battery. I've tested all of my components, with the exception of the capacitor, which I tried substituting for another, which also didn't work.

I am sometimes observing small, short, dim bursts of light from the LED when I`m messing with the power supply, but otherwise the LED remains unlit, even after I have been holding the switch closed for several minutes. My understanding is that the LED should be unlit whilst the capacitor charges, then constantly lit once the capacitor has charged up and then should the power supply be interrupted by the opening of the switch the light should still shine for a short time before the capacitor runs out of charge. I could be completely flawed in my thinking - I'm a self-taught hobbyist and this is my first time using a capacitor to create delays.

Am I wiring the capacitor up wrong? Is that an unsuitable rating of capacitor for a short delay? Am I just expecting the wrong result? If the capacitor rating is the problem can you recommend a more suitable rating for a delay of roughly a second? I`m just using what I have on hand for the while, but I've got an order of assorted capacitors that should be arriving soon.

Thanks.


texts: Oscillating voltage in Wheatstone bridge

texts:
I am using a simple wheatstone configuration to measure resistivity of a material I have.

The problem is that when I am measuring the Voltage (Vg) with a multimetre and it is oscillating(fluctuating). It doesn't let me have an accurate reading since multimetre shows different values change each second.
I checked my circuit by measuring a 10k,12k and 15k ohm resistances without any problem (no fluctuation in the reading), so the circuit is fine.
What do you thing the possible causes of this oscillation on the readings? material structure/composition? the way how I should measure the Vg voltage?
Pd: Vs is DC


texts: Coax cable loss drops by approximately 0.5 dB at a specific frequency

texts:
I am trying to understand why the measured loss of our coaxial cable is decreased exactly at a specific frequency. My understanding is that the loss should be linear with the frequency. However, there is a strange drop which I cannot explain to myself. (The two lines are two different cables, but from exactly the same supplier and type.)

Cable loss vs. frequency:

Does anyone have an explanation?

Thank you in advance.


texts: Do reed relays have shorter opening than closing time?

texts:
I see that 'normal' relays generally have shorter opening than closing times (see for example: http://www.langirele.com/pdf/pcb-relay-T73.pdf). Do reed relays also have shorter opening than closing times? If so, typically by how much?

I am interested in this for the W171DIP-25 (http://www.mouser.com/ds/2/357/105A_117SIP_107DIP_171DIP-6475.pdf) reed relays.


texts: Using a 7 segment display to show numbers 1, 2, 3 and 4 with four inputs

texts:
I have in my car 4 LEDs which illuminate in the instrument cluster depending on the gear the vehicle is in. This is a factory standard setup which I have already run feeds from ready for the next part.

I would like to, using those 4 led inputs, build into my dash board a 7 segment LED display to show which gear the car is in, 1, 2, 3 or 4.  I'm not really sure where to start with this but I'm ready to do some fast learning!


texts: AtTiny85 analog / digital pin configuration order in setup

texts:
Bug in compiler or what ever?

Simplified circuitry there is 2 LEDs and 1 analog input.
LED connected to pin PB1 lights very dim when output is high.
It seems that output has been configured to high impedance mode.
That happens if inside setup() analog input A1 (pin 7, PB2) is configured after digital output PB1.
If order of pin configuration is changed everything is OK.
Is that compiler bug?

/*            ____
    D5 PB5  1|o   |8  Vcc
    D3 PB3  2|    |7  PB2 A1   Voltage measurement, potentiometer
    D4 PB4  3|    |6  PB1 D1   --|>--|
       GND  4|____|5  PB0 D0   --|>--|
*/

byte led0 = PB0;
byte led1 = PB1;
byte potentiometer = A1;
int voltage;

/* It is important in which order pin configuration has been set.
Wrong order causes PB1 to high impedance, low current, output.
This must be compiler bug, I think.
If port BP1 setup has been made using straight to register there is no problem in order.
Any other analog input port and digital port combination works correctly.
*/

void setup()
{
  pinMode(led0, OUTPUT);
  pinMode(led1, OUTPUT);  // Doesn't work if this is before pinMode(potentiometer, INPUT);
  //DDRB &= ~(1 << DDB2); // Alternative working setup for analog input A1
  pinMode(potentiometer, INPUT);
  //pinMode(led1, OUTPUT);  // Works if this led1 setup is after pinMode(potentiometer, INPUT);
}

void analog_input()
{
  voltage = analogRead(potentiometer);
  if (voltage < 500) {
    digitalWrite(led0, HIGH);
    digitalWrite(led1, LOW);
  }
  else
  {
    digitalWrite(led0, LOW);
    digitalWrite(led1, HIGH);
  }
}

void loop()
{
  analog_input();
}


texts: STM32F407VG DISCOVERY BOARD micro controller CAN messages

texts:
I am wondering if anyone is familiar with any STM32f407VG
micro-controllers?

If so, I am having some problems configuring a CAN driver.
I can run the demo code, which is set to a loop-back mode, but I cannot get
normal mode to work.

I think message is not going out of the transmit mailbox. Status is going
to pending all the time.

I read through all the data sheets, and everything is configured
correctly except the INAK in the CAN_MSR register never resets to 0.
I can provide more detail if needed, but first I need to know if
there is someone who has worked with a STM32F4 microcontroller and
CAN messages.

Here is my sample code:

RCC_APB1PeriphClockCmd(CAN_CLK, ENABLE);
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
GPIO_PinAFConfig(CAN_GPIO_PORT, CAN_RX_SOURCE, CAN_AF_PORT);
GPIO_PinAFConfig(CAN_GPIO_PORT, CAN_TX_SOURCE, CAN_AF_PORT);
/* Configure CAN RX and TX pins */
GPIO_InitStructure.GPIO_Pin = CAN_RX_PIN | CAN_TX_PIN;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_UP;
GPIO_Init(CAN_GPIO_PORT, &GPIO_InitStructure);
CAN_DeInit(CANx);
CAN_StructInit(&CAN_InitStructure);
CAN_InitStructure.CAN_TTCM = DISABLE;
CAN_InitStructure.CAN_ABOM = DISABLE;
CAN_InitStructure.CAN_AWUM = DISABLE;
CAN_InitStructure.CAN_NART = DISABLE;
CAN_InitStructure.CAN_RFLM = DISABLE;
CAN_InitStructure.CAN_TXFP = DISABLE;
CAN_InitStructure.CAN_Mode = CAN_Mode_Normal;
CAN_InitStructure.CAN_SJW = CAN_SJW_1tq;
/* CAN Baudrate = 1 MBps (CAN clocked at 30 MHz) */
CAN_InitStructure.CAN_BS1 = CAN_BS1_6tq;
CAN_InitStructure.CAN_BS2 = CAN_BS2_8tq;
CAN_InitStructure.CAN_Prescaler = 2;
CAN_Init(CANx, &CAN_InitStructure);

/************transmit message config***********/

TxMessage.StdId = 0x11;
TxMessage.RTR = CAN_RTR_DATA;
TxMessage.IDE = CAN_ID_STD;
TxMessage.DLC = 2;
TxMessage.Data[0] = 0xCA;
TxMessage.Data[1] = 0xFE;

CAN_Transmit(CANx, &TxMessage);
uwCounter = 0;
while(( CAN_TransmitStatus(CANx, TransmitMailbox)  !=  CANTXOK) && (uwCounter  !=  0xFFFF))
{
    uwCounter++;
}
uwCounter = 0;
while((CAN_MessagePending(CANx, CAN_FIFO0) < 1) && (uwCounter  != 0xFFFF))
{
    uwCounter++;
}
k = CAN_TransmitStatus(CANx, i);


texts: Triggering BT139 Triac from Microcontroller Using 4n35 Optocoupler

texts:
This is my first time posting on a forum so please pardon me if i do anything incorrectly.

I'm kinda new with using TRIACs, i'm using them as a replacement for a Relay and my sole goal is to switch a light bulb on and off from an arduino. I'm having serious trouble with combining the Optocoupler (4n35) with the TRIAC. When I first prototyped the TRIAC on a breadboard without the optocoupler, using wires, it worked totally fine, would switch ON and OFF when I made contact/removed contact of the GND wire at T2.

When I introduced the optocoupler, the Gate on the TRIAC seems to be triggered on all the time and i'm not to switch ON / OFF as expected on a relay.

Can somebody please tell me what i'm doing wrong here and provide me with a more accurate explanation on the triggering of a gate on a triac? All i understand is that you need some current flowing between Gate and MT1 (Some say MT2!), which means that you put the gate on 5V, MT2 on GND (or vice versa) and you'll trigger the TRIAC and short MT1 and MT2 allowing AC conductivity between them

Thanks and sorry for the long post.


texts: Programming an ATtiny13A with Arduino Mega 2560 (blink sketch load wrong, LED stays on)

texts:
I'm trying to program an ATtiny13A with an Arduino Mega 2560. I load the blink sketch, and AVRDUDE says it uploads completely, but the LED on the ATtiny13A doesn't blink; it just stays on (it's specified on pin 4), I've tried other pins, with the same result.

What may be the issue, and why is the loop not looping correctly? I'd love to hear the debugging process of others on issues like this, because I'm out of options.

I've tried different IDE versions (I'm on a Windows 7 64-bit machine), I've downloaded both this: http://sourceforge.net/projects/ard-core13/ and https://github.com/tekstop/attiny/tree/Arduino1 to try and get a more accurate ATtiny13A specification, if it had to do with the specifications in the board, but none of them change the result.


texts: Why ARM cores consumes relatively lower power than x86

texts:
Why ARM cores consume little power compared with x86 CISC implementations?

What are the valid reasons?

because of it's fabrication technology?

Could this be right? ARM cores have been fabricated on various fabrication technologies worldwide even some fabrication technologies are not advanced like Intel's fabs.

Due to the RISC simple instructions and pipelines.

Is that because simple instruction set need very little silicon area and that area could save lots of power.

Due to the load store

Due to the simplicity of the load store architecture , so there are no macrocode to microcode translation required. So again low silicon area as well as branch prediction
algorithm could easily predict memory locations which would be used in future, so
low cache is required due to less cache misses. So again small silicon area which leads to
small power consumption.

Due to AMBA bus and SoC

Since the RAM and ROM and system peripherals were designed closely to the Core very low
cache is required and it would save energy.

Due non backward comparability

Unlike Intel, it does not need to support for backward comparability so when it comes to
ARMv7 almost all energy hungry deprecated instructions were gone and new instructions
are there for their place.

Due to power saving modes.

However these modes are also available in x86 processor too.

Because of historical decisions.

ARM is keep everything new and updated. Unlike x86 there are no historical mistakes affecting continuously. They were reviewed and corrected in next ISA.
And ARM is formed newer than the x86, so historically decisions are made concerning
it's power wall. Unlike Intel.

Due to the operating system and Kernel , firmware power saver support.

Is that due to the support in OS and kernel itself. For a example linux embedded have
patches for advanced power saving mode. To automatically reduce the speed when battery
power detected low. But this fact did not related to the power wall at all.Anyway could we
still consider this as a fact? Up to what extent?Android power management

What are other valid reasons?