texts:
So I just found an old netbook which battery has 6x 18650-26F cells and thought of trying to make a powerbank out of them.  This is the specs page:
http://gamma.spb.ru/media/pdf/liion-lipolymer-lifepo4-akkumulyatory/ICR18650-26F.pdf

I just need some ICs and a bit of soldering to make them work but I still have some simple questions.

Which is the best configuration about parallel/series? So I can use a boost converter.
Should I need a battery management system for each pair?

Sorry for the basic questions, not much into electronics yet.


texts:
I have a Raspberry PI board connected to some external circuitry, and am using Microchip MCP23008 I2C GPIO expander chips to control external LEDs and motor circuitry. One important part of this external circuitry is a 12V buck-boost switching power supply which is powered off of a 9V battery. The buck-boost regulator does not have an enable pin, and I am working out a way to cut the power to the regulator.

I already have a working 9V low-battery indicator circuit (shown below), which turns on the green LED if the battery is supplying a voltage greater than 7.0V, and if the voltage dips below 7.0V, the red LED is enabled. The circuit should also cut off the current coming out of the source of Q4.

Circuit - Version 1

I have two questions with respect to this circuit:

First, does the cutoff logic make sense? My assumption is that if the red LED is off, no current is going through D3, R6, and Q2, so the voltage at the node between R6 and the collector of Q2 would be the same as the power rail connected at the top to D1, D2, D3, and Q4's drain. If the red LED is on, there's a 0.7V drop across it, then a moderate drop across R6 (ie: estimated current, (7.0V-0.7V) / 330R = 19mA, so a 6.27V drop across the resistor roughly), and since this will make the Q4 bias less than that connected to Q4's drain, Q4 is turned off, cutting off power to the buck-boost converter. I'm convinced I'm overlooking V_ce on Q2 though.

Second, is it safe to assume the regulator can run from the output of the source of Q4 and D4? My estimates suggest that I will, when drawing current, have a 0.2V drop (V_ds) across Q4, and another 0.3V drop across D4.

Edit: Adding updated circuit as per earlier suggestions.

Circuit - Version 2

Edit 2: Updating as per latest answers.

I updated the circuit to reflect that of the answer provided by @DanLaks. Attaching DC sweep simulation.


texts: Is there such a thing as an MSP432 launchpad guide for absolute beginners?

texts:
I've done so much research both on this site and on Google and Youtube, yet haven't been successful at finding any good resources to learn how to develop for this launchpad with code composer.

Most tutorials either teach you to work with Energia or are aimed towards professional users. I just started working with this launchpad as part of my engineering training and I already feel left behind, so I'd appreciate it if someone points me to some good resources that assume no background.

Thanks in advance.


texts: How does the cortex m0+ processor use the ahb-lite interface to fetch instruction and data? Are instruction fetches done always using NONSEQ? How does it fetch data from memory(using burst or NONSEQ transfers) ?


texts: What kind of serial communication is this?

texts:
I am trying to reverse engineer a serial communication between to microcontrollers (1 device & 1 microcontroller on a board). One MCU validates the other MCU and I want to crack the validation and mimic the validated MCU. I want to find out what protocol is being used to make sense of the data. I have captured the communication with a logic analyzer and here is a screenshot from PulseView:

PulseView has decoding function but I don't know where to begin. The communication happens via 1 wire only. But I am not sure if the protocol is "one-wire". Are there any known standard methods to identify an unknown communication protocol? Or do I have to identify it by simply looking at it?

I wrote a script to convert the data into time required to change from one state to another (high-to-low or low-to-high) to compare repeated measurements and absence of the validated MCU. Each time the patterns look slightly different. It would have been great to know to decode this into byte array or whatever is intended for.

The first long low period of every cycle is sometimes 90μs sometimes 30μs. Every cycle has 14 switches in total. Long high periods between cycles may differ in length (~270-330μs).

PS: smallest time required for a change is 30μs as seen at the 3rd row on the image (120μs = 4 states).

Thanks!

Edit: Here are examples of signals, which doesn't obey the general rule.

Edit2: Distribution of high periods between cycles:

Edit3: In the first phase (zoomed in on the top row), there are 4 frames starting with 90μs low, followed by 23 frames starting with 30μs low and finally a frame starting with 90μs low again.

Edit4: Here is the sigrok session file.


texts: Spectrum intensity varies depending on the frequency span

texts:
I am trying to measure the noise of a photo detector at different frequencies, using an RF spectrum analyzer. The measurement range was spanning from 10 Hz to 20 MHz. To cover not only the higher frequencies with a sufficient amount of points, but also the lower range, I repeated the measurement several times while varying the span (10 Hz to 20 MHz, 1 MHz, 100 kHz and 10 kHz), but keeping the amount of points constant. Initially, the instrument set the sweep time automatically, resulting in the following graph:

Here the transitions are clearly visible at places where the noise level decreases.
To avoid such rapid transitions, I tried to keep the sweep time constant. This resulted in
Here for all measurements (except the one going up to 20 MHz) the sweep time was fixed, but I still see transitions between the measurements.
Where do those transitions come from, and how can I avoid them in future measurements?


texts: How to control 4 motors which are conected to a flight controller using Raspberry Pi?

texts:
I just started a project to make a drone without a radio controller. I want to control 4 brushless motors connected to a flight controller KK 2.1.5 using Rpi 3 B+. Obviously, the motors are first connected to the separate ESCs and then to the flight controller. What I am not getting is how can I control each motor separately?
I would appreciate any help. Thank you.


texts:
I am currently working on a battery powered project (4 x AA rechargeable batteries) with an Attiny (max vin = 5.5V), which works perfectly so far.
But if I would insert normal batteries into the holder instead of the 4 AA rechargeable batteries (the voltage of a normal battery is much higher than that of a full rechargeable battery), the maximum input voltage of the Attiny would be exceeded, which wouldn't be so great.
For this reason I am looking for the most efficient, cheap and above all power-saving method to lower the total voltage of the 4 AA batteries or rechargeable batteries by about 1V, so that it doesn't matter anymore if I use rechargeable or non-rechargeable batteries for the project.
Should I simply use a diode (voltage drop around 0.7V) or resistors? What are your suggestions?


texts:
I am repairing a board, that has an IC labelled K72 J46 P.
I know it is an op amp MSOP8, and that pin 4 is GND, but I cannot find the manufacturer part number so that I can buy a replacement.


texts: Which is the bandwidth of an analog PAM (needed to design an amplifier)?

texts:
in a university test, I've been asked to design an amplifier for the following signal:
$$s(t)=\left[\sum_{i=1}^{\infty}rect\left(\frac{t-t_i}{T}\right)\right]\cdot Acos\left(2\pi f_0t+\varphi\right)$$
with:

t_i+1 - t_i = 100us;
T = 200us;
f0 = 50MHz;

It seems to me something like that:

In such a test it's written that the amplifier bandwidth must be sufficient enough to work with the previous signal. But I don't know how I can evaluate that bandwidth (the frequency range in which the Fourier transform is non-zero).
Here it's stated that the bandwidth of a product of signals is the sum of their bandwidths. So, if it's true, here we'd get the sum of the bandwidth of a sine wave (the single frequency f0) and that of a rectangular pulse train. The last one is a sort of square wave, which has in theory infinite bandwidth unless a finite rising and falling edge times are specified. In this case they are not specified by the text.
Can you help me on evaluating it or telling me how you would do it (for instance, considering only the first 2 harmonics of the rectangular pulse train etc)?


texts: How can I dampen current spikes when using NPNs to drive an LED

texts:
Hi I have the following circuit, its purpose is to flash an LED once per second. I'm using a pair of transistors as a constant current source but I observe current spikes of 20% or so when it is simulated. Can anyone explain why this occurs and how to resolve it.

Thank you very much for your help! As suggested by The Photon and Bimpelrekkie I tried using a small cap on the collector-emitter of Q2 and it completely removes the spikes - perfect


texts: PA84 op amp instability at high(er) +/- V_s supply voltages

texts:
I'm trying to troubleshoot a piezo-driver circuit, which uses a PA84 op amp (10x gain). The schematic I'm working from  indicates the supply voltages should be +200 / -15 V, which are well within spec... however, I'm getting a lot of noise on the output.

For example, looking at just CH2 in the schematic with no input signal, I'm seeing a threshold voltage for the DC bias input, where I move from virtually no noise (~ mV) to a lot of noise (~V) on the output. With the +200/-15 volt supply voltages on my op amp, the threshold is at about -1.5 V after the R45 pot (~30 V at CH2 out). I noticed, though, that reducing the V_s voltages to e.g., +100V / -15 changed this threshold so I could scan the pot R45 across its entire range without moving into a region of instability.

Has anyone encountered a similar issue before, or have any suggestions/pointers? It's not intuitive to me why the supply voltage would have such a noticeable impact on the op amp's stability... although to be fair, i'm very new to all this :P

NOTE: I also have a 4pf bandwidth-limiting capacitor across the op amp, in parallel with R19,R20,R21. This isn't on the JILA circuit posted online, but was necessary to get rid of serious op-amp oscillations. I've also put in a 10nF capacitor in parallel with R9, which was in a different (paper) copy of the same circuit given to me from someone who used to work at JILA (unclear why there is a discrepancy with the public domain circuit posted on their website...). The paper copy also shows a 3pF (not 4pF) bandwidth-limiting capacitor -- I'm using the 4pF one while waiting for the 3pF one to arrive. The circuit is also laid out on a PCB, and so there could be some issues with my design layout there...


texts: Is there an instrument that can measure the capacity of lead acid batteries

texts:
Background

I have an electrical scooter with 6 x 12Volt lead acid batteries (72 Volts total), which are now in such a condition that they can barely get me to my work and back. I got a bunch of used UPS batteries from a friend, and want to check their capacity and compare them with the batteries that are currently in my scooter.

I roughly think I know how to measure their capacity, after loading them I should discharge them at a certain rate and see how long it takes before the voltage drops below a certain threshold. I'm not sure about the exact numbers though, and I'm also not quite sure how I should discharge them at the same rate as my scooter would typically do (power a heater or something like that?).

Question

Is there a device/machine/instrument that can do all of that for me? Load the battery, discharge it at a constant rate and log the results.

If not, I guess a UPS hooked up to a computer could be programmed to do the job? Any ideas?


texts: How can one make an analog voltage memory circuit?

texts:
I am looking for a circuit that can, on input, remember a certain voltage and output that voltage indefinitely even after the input has been taken away. The circuit should not change its output until a new input has been provided.

I understand that such a circuit can be made by digitally sampling the input up to some arbitrary resolution, but I would like to know if a simple analog solution is possible.

I would also like to keep this solution purely electronic, as I can also envisage a mechanical solution in which a feedback circuit mehanically controls a potentiometer.

Finally, I would ideally not like the circuit to rely on the passive stability of any floating inputs. The circuit should be stable for at least hours.


texts: Difference between ISL83078EIBZ and ADM483-EAR for UART-RS485 Converter

texts:
I want to use UART-RS485 converter circuit as in the attachment. The circuit is working when I use ADM483-EAR Transceiver for U1. ADM483's recommended Vcc value is 5V but it can provide communication with 3.3V. However the circuit is not working when I use ISL83078EIBZ for U1. I observe enable and tx signal is fine and same as in ADM483-EAR. But there is no communication. I mean it transmits but not receives. Why does not the circuit work with ISL83078EIBZ?

http://www.analog.com/media/en/technical-documentation/data-sheets/ADM383.pdf

https://www.intersil.com/content/dam/Intersil/documents/isl8/isl83070e-71e-72e-73e-75e-78e.pdf


texts: High base-emitter voltage NPN transistor

texts:
I just bought some NPN transistors for my project. I didn't notice before buying them, that the specification said the transistor had a emitter base voltage \$V_{be}\$ of 9 volts. Can this be true? This value is normally 0.7 Volts right?

Here are a screenshot of the specifications:


texts:
What application do you use for creating plots?

Years ago, I was using gnuplot and then matplotlib (which is just Python library). But none of those were perfect. For example, I was unable to create Smith chart in gnuplot or two Y axes in one plot. And matplotlib is too unfriendly, everything takes hours of reading documentation (but result is very nice and professional).

So is there any other good application for electronic engineers? GUI or CLI.

Note: I am using Mac/Linux and I do not have Matlab license.


texts: How is voltage induced in Yd transformer without neutral connection sinusoidal?

texts:
Thia is regarding bank of 3 single-phase transformers having star connected primary with isolated neutral and delta connected secondary.

I know that for bank of 3 single phase transformer core flux and hence voltage induced will be sinusoidal only if 3rd harmonic currents (which are cophasal - i.e. 3rd harmonics of all 3 phase will be in phase with each other) can flow, otherwise owing to saturation flux will be flat-topped and induced emf peaky.

But all sources I refer (I'll cite them if necessary) says that Yd transformer without neutral will have sinusoidal emf induced in them. I don't understand how, because third harmonic currents can circulate inside closed delta winding but won't it require balancing amp-turns in primary? If so, then wouldn't those balancing amp-turn require cophasal currents in primary which is not allowed as there's no neutral?

Is my thinking that cophasal currents inside closed detla will require cophasal currents in star right?


texts:
I'm trying to build a RS-485 project using MAX485's. However, I'm having trouble finding out how to correctly use the RE and DE pins. Some PDF's and websites say that RE and DE should be tied together and then connected to a pin on a microcontroller (for example). Other places seem to have various combinations of connecting DE to ground and RE to positive, and other such things.

Additionally, the places that say RE and DE should be tied together and then connected to a microcontroller, also have conflicting information about how these should then be controlled through the software.

So my questions are:

What am I actually supposed to do with RE and DE? Do I need any pull up or pull down resistors also?
How do I control RE and DE assuming they are controlled by my microcontroller? Do I set them high/low then send data then set them low/high again? Do I do the same for receiving data?

Any help on this would be appreciated, and also if there are any links to sites with this specific information about DE/RE would be good.


texts:
I have Lattice ECP3 Versa Evaluation Board.
My objective is to connect Ethernet to the FPGA and be able to receive data (and later to send data) successfully. I don't really care on what protocol I will receive the data at, lets assume I want to receive UDP packets.
The PHY that presented on the board is: Marvell 88E1119R Gigabit Ethernet transceiver.
Lattice has Tri-Speed Ethernet MAC IP core that from my understanding using this IP implements the Data Link layer in the OSI model.

I added this IP core and connected the pins that coming from the PHY to the Ethernet interface using this figure and table:

So all left me to do is to program the 'User Host Logic' and 'User Application Logic' according to this figure from the Tri-Speed Ethernet User Guide from Lattice.
OK so I start to program the host user logic:
programmed some random MAC address: AC-DE-48-00-00-80
and few more other internal register flags.
finally asserted the receive enable signal (rx_en).
I getting some feedback from the Host Interface telling me that I'm receiving broadcast frames and short frames, but when I looking at the signals coming to my FPGA, its all just zeros.
The RJ45 led is blinking with orange led (its mean that the Ethernet interface is alive right?)
What should be my next step? How can I receive data to my FPGA through the Ethernet?
How can I know my MAC address? Or I should to choose the address like I did inside the FPGA.
How can I know what is my FPGA port and/or IP address?
I will be glad for any help and leads for how to make this Ethernet happen.
Thanks.


texts:
Consider the following power supply interface.

I'd like to power a number [1,N] of bitcoin miners, 12V, 5A each one.
question is:

do red wires must be connected with V+ pins ?
do black wires must be connected with GND ?
if I connect red wire with GND, and black one with COM (equals to V-), is electrically the same thing as 1. and 2. ? This in order to connect 3 more loads.


texts: Does a TVS diode provide adequate protection for an LCD screen powered from a car 12V outlet?

texts:
I fitted an LCD screen in my car and I want to power it, along with other devices, directly from the car's battery. The other devices are specifically designed for automotive use, but the screen, a 10.1 inch LCD panel paired to a PCB800099 LCD controller board, isn't.
According to the specs, the PCB800099 can be powered from 12V. The seller said it can be powered anywhere from 5V to 24V, and indeed it actually came with a power cord with a USB on one end and a barrel jack on the other and it worked fine powered from a regular USB 2.0 port. So I connected it to the cigar lighter and ran the LCD screen during a 2 hour trip without any issues.
Even though it ran fine, I would like to prevent any failures in the long run due to voltage surges, load dumps, or other problems associated with its use in a car. Therefore, I'm thinking of adding a TVS diode in parallel with the screen:

simulate this circuit – Schematic created using CircuitLab
The LCD panel, according to its specs, has an input voltage range of 5V-21V for the LED backlight. I don't know if the LCD controller regulates the power for the backlight or if it simply acts as a passthrough. Because of that, I chose a TVS diode with a maximum breakdown voltage of 25.2V, or 1.2 x 21V, to allow for some headroom. More specifically, the 1.5KE18CA-LF.
I've read suggestions for using a dedicated DC-DC regulator (googling for 12V output yields results for the more common 12V input and 5V output converters), simply ignoring this possible problem and hope for the best, just adding a varistor instead of the TVS, or more complicated circuitry which I'm not really keen on implementing.
My question is if this is enough to keep the screen alive and well in a car and is there anything else I should consider?


texts: Where to purchase the iron core for an electromagnet?

texts:
I want to build a strong elctromagnet. The design is very intuitive and simple, shown in the above figure. The metal core is in a cylindrical shape.
The current design is 100 turns and 30 Ampere, with a radius of 7cm.
With the air core (without any metal core inside), the magnetic field is only 20-40 mT.
I want to realize a magnetic field of 0.6T.
I think the only choice I have is too use a metal core, which has a high permeability and saturation.
The problem is where to purchase such material?
The metal core should be large, of radius around 7cm and length around 5cm.
I purchased a 1018 steel rod from McMaster-Carr and it turned out this metal core is awful. The 1018 core has only doubled the magnetic field, far behind my expectation.
I have checked the B-H curve of 1018, and if the curve if correct, with a H field of 20-40mT, the magnetization of the metal should be close to 2T. I'm confused!
Can anyone kindly tell me why the 1018 steel core doesnot work? And where should I purchase the metal core? Which material should I choose, pure iron, special alloy or silicon steel?
Thank you very much!


texts:
I have 32 servos running from a 7.5V battery rated at 2500mAh and I'm sure that it has enough power to handle the servos, but it doesn't look like it can handle all of the servos pushing at once.

I was thinking I could add a capacitor to the circuit to solve this issue, so bearing in mind that I'm very new with electronics and have only just found out that amperes are a direct result to the requirement of the circuit rather than what the battery puts out, please could you answer my questions below?

Could I put a capacitor just before the servo controller to deal with the intermittent load requirements?
Would a large capacitor damage the circuit?
Does a capacitor work just like a battery and only output the required power rather than just discharging everything it has into the circuit?
Does a capacitor have to be mounted across the positive and ground or does the positive have to go through it?


texts: Electret Mic Circuit Using JFET Bootstrap

texts:
I thought this circuit was clever so I'm sharing:

The JFET current source is bootstrapping the electret and thereby providing 20dB of linearized gain. The bootstapping network also provides for some frequency shaping and the output is buffered.

So this isn't really a question but criticism is welcome. How would you improve this circuit?


texts:
What I understood from the definition of current sources is that it is a source which supplies a constant current across a load no matter how the other parameters (like resistances for example) in the circuit are changed. Am I right?

If I'm right, what is an example of a current source used in a practical circuit?

Wikipedia gave the example of a Van de Graaff generator as a constant current source. (I didn't read the article, because there was a note that the section appeared to contradict itself. I didn't want to get confused.)

I can think of voltage sources - for example a battery which has a constant potential difference across its ends irrespective of the changes in the circuit it is connected to, but I cannot think of a current source. Any example I can think of involves change in the current when the resistances are changed.


texts: Constant current circuit load and without load for voltage measurement?

texts:
How can I control the constant current block?
What I need?
I need to calculate voltage with constant current load (I = 100ma and after some time I need to calculate voltage without load (I = 0), for that I using BJT to control the constant current block from the microcontroller to turn off and on.

Can I achieve from this circuit? below attached
Why I am doing?
I need this to calculate the voltage of the battery with cc load and without load


texts:
I have coded for Timer 4 in a STM32f407vg discovery board. But while debugging the control is not entering the ISR. Please find the code below and help:

void InitializeTimer()
{

    TIM_TimeBaseInitTypeDef timerInitStructure;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);

    timerInitStructure.TIM_Prescaler = 0;

    timerInitStructure.TIM_CounterMode = TIM_CounterMode_Up;

    timerInitStructure.TIM_Period = 255;

    timerInitStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    timerInitStructure.TIM_RepetitionCounter = 0;

    /*Initialise timer 4 */
    TIM_TimeBaseInit(TIM4, &timerInitStructure);
    TIM_Cmd(TIM4, ENABLE);

}

void EnableTimerInterrupt()
{

    NVIC_InitTypeDef nvicStructure;
    nvicStructure.NVIC_IRQChannel = TIM4_IRQn;
    nvicStructure.NVIC_IRQChannelPreemptionPriority = 0;
    nvicStructure.NVIC_IRQChannelSubPriority = 1;
    nvicStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&nvicStructure);
}

void TIM4_IRQHandler(void)
{

if (TIM_GetITStatus(TIM4, TIM_IT_Update) != RESET)
    {

        TIM_ClearITPendingBit(TIM4, TIM_IT_Update);

    }

}

With this configuration I am not able to enter an ISR.


texts: Find resonance, bandwidth, etc.. from Bode Plot

texts:
I am analyzing the following circuit simulation in pspice:

I need to find the resonance and cutoff frequencies, bandwidth and the quality factor from the simulation. I know how to do it by hand but is there a way pspice can get it for me?


texts: Why is my milliamp and microamp current reading so different?

texts:
When I check the current in my circuit using milliamp I get around 2.54 milliAmp. When I use the microamp setting, I get 1844 microAmps which translates to around 1.84 milliAmp.

Why is this happening?


texts: Controling switching regulator digitally

texts:
I found this -piece- of schematic which is for controlling LM2596 output with a MCU, and I'm a bit confused:

What is the purpose of those two schottky diodes? isn't it causing voltage drop which we have to compensate in software?
How the opamp in voltage section works? and is it comparing OUT+ with OUT- or OUT- as ground because of low-side current measurement?
What's the VCC voltage for the voltage dividers next to the opamps? is it the same as OUT+?

I found this schematic in Google images and it's not complete, please share the full schematic if you have it...


texts:
I purchased a set of 4 NeoPixel ring segments and assembled them into a circle.  I am trying to create a circular lamp that will be fitted inside a camper van in the ceiling and driven from a 12V battery.

I would like to add a dimmer switch to the lamp but my understanding is that I need to match the dimmer switch to the type of LED's that I am using.

How could I add a dimmer switch (and possibly a colour changer too) to a NeoPixel ring light?

(Note: the large neopixel ring that I have looks like this:


texts:
Can someone provide me some explanation or clarity regarding the three internal voltage regulators that this Microcontroller has mentioned in chapter 40, page 1227.

From what I read, I think that we are not providing the core voltage (1.2V) to the micro directly. We are providing 3.3 to 5V and we place an NPN outside to get the 1.2V which is then fed to the Micro pins.

is this correct?
How does this work?
If this is true, then the Micro Vcc is 5V only, right?
And how by placing a NPN transistor and giving 5V to its collector, we get 1.2V at the emitter? How does the transistor do this?


texts: Voltage regulation on the high side of a Darlington array?

texts:
I'm looking to build an 3.3V Arduino Pro Mini based LED driver that drives 3 (possibly 6) super bright 10mm LEDs (R, G and B).

I intend to use this 3.7V LiPo battery and these LEDs.
The LEDs have the following specs (units are V, A and Ohm). I've calculated the required resistor values based on a 3.7V supply.

        Max Fwd Cur     VDC Drop    VDC delta   Req'd Resistor
RED     0.08            2.2         0.1         18.75
GREEN   0.08            3.2         0.2         6.25
BLUE    0.08            3.2         0.2         6.25

I want to drive this with a ULN2803A Darlington Array (DA).

I have a few questions.

Have I calculated the required resistor values correctly above?
Will PWM work for the LEDs when wired into the low EDIT:[I mean't HIGH] sides of the DA?
Do I need to regulate the voltage into the common pin of the DA, or can I wire this into the RAW (VIN) pin of the Arduino or directly into the battery? As the battery's voltage drops, I appreciate that the lights might get dimmer -- this is okay (up to a point) as long as the DA continues to function? As an aside, if I used an unregulated wall wart, rather than a battery, would the ripple cause a problem with the DA's operation? Am I being lazy here and should I regulate the high side voltage as a matter of good practice anyway? If I was running it at 5V, say, rather than 3.7V, would the answer be the same?
Do I risk the Arduino by drawing too much current if I wire the DA common pin directly into the 3.3V VCC pin of the Arduino?
I see everywhere that GNDs should be wired together. Is this true in this case, for both the low and the high sides of the DA? Even if the high side is unregulated?
Will picking a higher voltage battery be a better option in terms of brightness, power dissipation, and battery life? Even if the mAh rating of the battery is comparable?
Is there a better way to do this (e.g. a shift register, MOSFETs, etc)?

I want to have the LEDs be able to be as bright as possible without risking the Arduino, and minimising on power loss wherever possible. Physical space is also at a bit of a premium but SMD chips scare me from a soldering perspective.


texts:
I am brand new to electronics and would like to know if there's any way to reprogram the microcontroller or reuse a used PCB. I extracted this PCB from my old Bluetooth speakers. Here's the image:

Also, I don't recognize which part is used as the Bluetooth or FM module or antenna on the PCB. My question might be really basic or silly but I don't know much and am trying to learn, so please help.


texts: How to construct an audio amplifier by using transistor and voltage differential circuit?

texts:
I am trying to construct an audio amplifier circuit as below(which is not working). Is there any modification can be done in order for it to work?
From my understanding, the signal from the input V1/microphone will be amplified at the collector of Q1 and same signal will be amplified at emitter Q3 as well but in opposite polarity(correct me if I'm wrong). This signal is then sent to differential amplifier circuit to get twice the amplified input signal by using a pair of Darlington construction that can then get further amplify by a gain but it is not working?


texts: Using Inductor and Electronic Load Instead of a Permanent Magnet Synchronous Motor (PMSM)

texts:
I would like to test whether my power board can handle to currents required to drive a 1.5 kW motor. My issue is that the motor testbench is still not here and I have to test it now.
I do not have high power resistors at hand. What I do have, are some 30-40 uH high current inductors and electronic loads. My question is: Do you think it is a good idea if I simulate the motor's phases with an inductor (simulating the winding of the motor) and an electronic load (simulating the EMF)?
Any other ideas are also highly appreciated!


texts:
I am trying to make a voltage regulator using an op-amp and a MOSFET:

schematic http://no4nwo.com/images/724278393.png

I'm really new to electronics. Why is \$V_{DS}\$ always so low ?


texts:
I want to design a passive 4-pole low-pass RLC filter for my subwoofer amplifier. So far I found this page:
http://sim.okawa-denshi.jp/en/RLClowkeisan.htm
But it seems that changing the value of R does nothing to the cutoff frequency. I think this is strange and would like to clarify this.

Also, I'm confused about the impedances to consider when designing low-pass filters. Do I include the source impedance only? PC Sound Card output impedance is 50 Ohms I guess? Or do I also include the load impedance, which in my case is the amplifier input, and is 30k? I'm confused.

I'd like a good (true) online calculator or a design tool for 4-pole RLC filters, or at least an explanation.

I forgot to mention this, but I'm planning to cascade the filters through an amplifier. This is different than using an active filter on opamps, but I work with what I have. Basically I have a stereo amp and one of its channels I'm going to use for amplifying between the two 2-pole filters. Still I dont get how the linked page suggests the cutoff frequency is same for different impedances. Somehow I don't think I can use the same micro filter after the final amp output where the signal is powerful and load impedance is low. Intuitively, I'd need much bigger inductors and capacitors. The page doesn't reflect that


texts: Norton's and Thevenin's theorems importance

texts:
Are Norton's and Thevenin's theorems used in real life? And in which situations?

I'm reading a circuit analysis book and I asked myself: do electrical engineers use these theorems to get current and voltage values, or do everybody use Proteus and similar programs to bypass these calculations?

Why are these theorems good to know?


texts: Light spectra for inspecting soldered PCB with microscope

texts:
I intend to inspect hand soldered PCBs with fine very pitch SMD components to check for dry joints and any other possible defects.

I will use a stereo microscope with total magnifications from 5x to 80x. Fluorescent/LED ring lights and halogen/LED spot lights are available for it. RGB car headlight LED rings could also be easily adapted. Oddly, none have filters available. I would have thought different wavelengths of illumination would be particularly valuable? Perhaps also polarising filters?

Goals would be to, for example: exaggerate differences between: flux, solder, solder mask, PCB tracks, device leads (and more?). To see through flux reflections to what lies underneath. To differentiate solder states. Spot gaps (perhaps with shadows), weakened pins, lifted pads or broken tracks.

Are such techniques used? If so, what specific spectra or other filters etc are useful? Might variable RGB LED lights be helpful, or counterproductive? Do any other non-destructive techniques besides electrical continuity checking help achieve these goals?


texts: TDA7294 100W Audio Amplifier Causing Unexpected Problems

texts:
This is the circuit I will be referring in this question:

TDA7294 is described in this data sheet. Upper IC with added external components is a well-known circuit and can be found on many websites and shops, so I presume someone will be reading this with experiences of building an audio amplifier with this IC.

I have build the upper circuit on PCB and tested it. First thing it happens, when I connect power supply leads to +Vs/0/-Vs is that huge amount of current (just like a short-circuit) starts to flow through -Vs (negative rail). +Vs (positive rail) was supplying about 0.5A, while -Vs was supplying more than few amps, while both output connections and input connections were disconnected to speaker/input source. I replaced several TDAs, where all of them show same results. I verified every connection of the circuit between external components and TDA three times, where all connections on PCB were right were they should be. I even breadboarded this circuit two times, where the results are the same as for the circuit built on PCB.

I connected VM (Mute) and VSTBY (Stand-By) to positive rail, as it should be for normal operation of amplifier, where the result were the same as explained before. I also disconnected MUTE (pin 9) and STBY (pin 10) out of circuit, where the results were the same.

But I noticed that if I disconnect IN+MUTE (pin 4), that all the sudden, current consumption of circuit is almost zero. But the circuit still doesn't work with IN+MUTE pin disconnected. Even if it is connected to ground, the circuit doesn't work. It doesn't work in means of applying source signal to input of TDA and scoping output signal without load. In both cases, scope shows nothing at all - straight line.

Would it help in this case, if I would connect "Boucherot cell" to output of the TDA amplifier? Or can I do anything about it at all? Sincerely, I have no idea what else to do about this circuit...

NOTE: I would have made a LTSpice schematic and tried it there too, but Spice's library doesn't include TDA7294, or any TDA at all.


texts:
However this question may seem naive, it is still something that worries me.

I bought this twilight relay kit (to turn on/off my home entrance light obviously).

Thing is: The guide shows that it can only be used with 24Volt/5A. But I (and maybe others alike) want to use it for the home power line aka 230V (110V).

As seent on the picture, on relay is written 240V/10A. So what's the problem then ?

I can guess this: 1) Manufacturer safeguard themselves. 2) the cobberlines on the print is too small to support the voltage. 3) Some other security thing is missing on this kit (like fuse or...).

Anyaway - I dont like to use this with 230V before I are certain about what could be the risk.

note: I dont have a pic of the underside with the lines, but there is two straight 1.5mm lines from the relay to the connetion socket


texts: Using solar power on a dual inverter setup simultaneously, that share different parts of a series battery bank

texts:
I had an idea and wanted to present it here and ask if anyone foresees any problems with doing this...  I have both a 48VDC input inverter and a 24VDC input inverter that I want to run from a 72V series bank of batteries (six identical 12V 100Ah AGM batteries in series).  So imagine the batteries lettered sequentially A thru F, the 48V inverter would attach to A+ and D-, the 24V inverter would attach to E+ and F-, and the solar charge controller would attach to A+ and F-.

So the idea is to use a higher voltage battery bank since the solar charge controller (scc) I am using is a boost converter that requires the battery bank voltage to be higher than the solar panel input voltage.  To get the maximum power out of the scc, I have to feed it close to 60V input which is the maximum allowed since there are 63V capacitors on the input side, which means my battery bank has to be 72V or higher (output capacitors are rated at 100V).

I will attempt to load the 48V and 24V inverters about equal (in proportion to each other), so that the 6 individual batteries are in a similar state of charge (SoC), and so that the scc should charge them all about equally.

Another advantage of using 72V that I just noticed is I also have an identical pair of 36V "golf cart" type chargers that I could use to top off the batteries on cloudy days.  That is, at the end of the day if the batteries are still not charged from solar, to keep the batteries healthy, I can top them off by using a pair of 36V smart chargers each on a 3 battery subbank (charger 1 on ABC and charger 2 on DEF).  I haven't tested to see if my chargers are compatible with that wiring arrangement but I should be able to test it soon.

So will/should this entire setup work?  Anything to "watch out for"?


texts: Simulation of the Micro-kinetic generator

texts:
I am simulating the block diagram of the Autoquartz system during unwinding in Simulink.

I want to get the current of microgenerator (Ibus),
but I get an oscillating pattern, which you can see here .

 This is the bock diagram I simulated for Tdmax = 8. Please help me how to solve my problem.

Thank you in advance.


texts:
Specifically the MAX 10 FPGAs are being looked at. The IO banks are powered through their own power pins. I've already know that the bank 1 and 8 need to be powered up with the core so that the configuration can be loaded.

The question is, for all the other banks, bank 2 to 7, is it safe to power them up and down separately? By separately it also means at random times that the logic will determine based on its internal design.


texts: Interfacing with MIPI CSI-2 camera sensors like the Omnivision OV2732?

texts:
CSI-2 is used in pretty much every smartphone however I'm struggling to find much information on how most companies receive and control CSI-2 sensors. I understand there are NDAs. This is not for a hobbyist project, however I'm a beginner on this topic and the imaging industry.

Ideally I'm looking for some magical IC or SoC that will talk directly to the sensor, control most functionality automatically but allow some basic setup, and pipe video data out over some easy-to-use interface like LVDS RGB or something.

So far I've found this and FPGA IP like this however I'm unsure if these are unusual ways of doing this - what do most companies do?


texts: How to interpret the S-parameters of this result?

texts:
I'm designing an FSS in CST MWS that should be providing maximum reflection for the band (12 to 15)GHz and hence minimum transmission to this band. I've got the results has shown here. How do I find the return loss and transmission loss? Out of these 8 data legends like SZmax(2),Zmax(2), which are the return loss (S11) and transmission coefficient (S21)? By transmission coefficient, forward transmission coefficient is meant. Floquet port model is used.
Fig.1 S-parameter output
Fig.2 CST port illustration


texts:
I recently picked up a "24V Voltage Level Current Converter Module 80KHz 1-Channel Optocoupler Photoelectric Optoisolator 12V PNP NPN Signal Converter PC817 Optocoupler"
Can I supply this with 12V instead of 24V? If not, is it as simple as changing resistors or do I need a different board?
I'm trying to achieve this:


texts: Where should I put my switch - on the enable of my SMPS or the power input?

texts:
I'm designing a simple board with a FitiPower FP6717 step-up converter chip (Datasheet) and a mechanical switch (SPDT) to enable or disable the output power. My design for the boost will be very close to the typical application circuit in the datasheet. What is the best practice in terms of switch location? Here are the two options I've narrowed it down to:

Enable/disable the input power from a battery with a PFET at the input with the switch (VCC goes to the Vin pin of the FP6717):

Enable/disable the input power by switching the EN pin on the FP6717 between GND and Vin:

Is there a "correct" answer to this? My gut tells me to put it on the EN pin, since there will be some non-zero power dissipated over the PFETs RDS(ON), which would decrease the overall efficiency from the battery to the output.


texts: Ceramic capacitors in parallel. Is this configuration suitable?

texts:
I am building a circuit based on an ATmega328P. In the schematic of the datasheet are 3 capacitors (1uF, 4.7uF polarized, 1uF) in parallel on the power supply Vcc. I assume these are for decoupling purpose.

I currently only have 470nF ceramic film capacitors (805) and tantalum capacitors (805). Is it possible to connect 2x470nF in parallel to achieve the ~1uF on the respective lines? In theory the capacitance is 940nF, but since it is used for decoupling it might be bad for the signal, because I solder two parts instead of one (more solder, cables, cable length, more resistance, ...).

Does this matter in a practical situation?

EDIT: I build the circuit on a hole grid breadboard


texts: What component: a glass tube wrapped with a wire mesh and has a single metal pole inside?

texts:
I found this while trying to fix my noisy hot/cold water dispenser. It has a blueish glow and makes a loud buzzing noise of around 56-58 Hz.

I'm planning to replace it, but there doesn't seem to be writing anywhere on it. Are there ways of testing to identify the specs of this component?

What is this?

My guess is that it's some sort of vacuum tube amp (if those are even used anymore). All of the Google keywords I used to search are within this post, but I couldn't find it.

Please, and thanks!

Update: It was actually this...

... that was causing the lamp to buzz while making some noise itself. I'm not sure what this is either.


texts: What causes random ringing in my inverter?

texts:
I'm currently redesigning the inverter for driving my induction heater.

While I've sorted out most problems I encountered I'm still struggling with the actual inverter.

Picture 1 shows the waveform problems I encountered.

Yellow is the actual inverter output.

Purple is the resonator voltage.

Cyan is the driving signal delivered to the driver.

Everything works fine until I go up in power levels.

Oscillations only occur at peaks of mains voltage, so it has to be some sort of current problem.

Scoping the output of the gate of the IGBT modules reveals that the signal supplied to them represents the output fairly accurately (also ringing.)

The IGBTs used are skm100gb128d which have an integrated gate resistor of 5 ohms.

The driver consists of optocouplers, voltage regulators and gate drive ICs.

What could cause this ringing?
Why is it visible in the cyan signal which is optically isolated?
How to prevent this?
Are 5 ohms of gate resistance enough if the signal at the IGBT gate looks alright (no overshoot?)

The second picture shows the setup of the IGBTs and the drivers associated with it.

UPDATE:
The ringing was caused by the oscilloscope ground loop being located too close to the actual inverter.
The voltage induced in the oscilloscope probe then acted back on the signal generation which was part of the reason the distorted signal was visible even before the Optoisolator.


texts: What information exactly does an instruction cache store?

texts:
Processors use both data and instruction caches in order to reduce the number of slow accesses to main memory. However, while it is clear to me that the data cache's purpose is to store frequently used data items (such as elements in an array or inside a loop), I cannot see what exactly the instruction cache stores that helps alleviate memory access times.

In the image above, we have an example of an "addi" instruction which adds a constant value to the value stored in general purpose register "r2" and writes the result to general purpose register "r1".

After this instruction is executed, what exactly is saved to the cache?

It can't just be the opcode - most CPU instruction sets contain just a few hundred unique opcodes or less, so if the instruction cache was pre-loaded with all possible opcodes, it would always have a 100% hit rate. However, that would defeat the purpose of having a cache, plus I've read that instruction cache misses are very much possible.
It can't be the values from main memory which are loaded into the general purpose registers, since that's exactly what the data cache is for.

Thank you in advance.


texts:
How i can make jdy-16 to arduino rx/tx connection? http://prntscr.com/k4dmqg

01 pin > VCC
24 pin > GND
19 pin > TX
20 pin > RX

But device doesn't answer AT COMMANDS!

When i connect jdy-16 with mobile apps, i can give connection and disconnection message on arduino ide. So it's say, your connection is correct.

But at commands doesn't work.

I tried port 5,21 to GND but didn't work.

JDY-16 Datasheet > http://shop.cpu.com.tw/upload/2017/11/BT-JDY16-2.pdf

Thanks.


texts: Why voltage source is not included while using KVL?

texts:
I would like to know why the voltage source is not used in the equation as given in this image below.

In the image the equation is:

\$-I1∙8Ω+I2∙4Ω=0\$

Why can't the equation be \$10-I1∙8Ω+I2∙4Ω=0\$ using KVL?


texts: How the diode mode of a multimeter works

texts:
First of all, I'm new to board repair, but I would like to learn more so I decided to watch a lot of videos to learn. However, I can't find any answer to the questions below about the diode mode.

how the diode mode of a multimeter calcul the voltage drop between one point of the circuit and the ground?
how the current flow through one point to any ground of the circuit
board?
is every grounded metal point attached to the circuit?
If the  multimeter display "OL" that's because the line has a short to the
ground but what happen when the number is low?


texts: What are the consequences of running a component above the recommended operating conditions but below the absolute maximums?

texts:
I am looking at LM6132 specifically. In the datasheet, the absolute maximum "Current at Output Pin" is +-25mA. Yet Digikey lists it's "Current - Output / Channel" as 4mA...

I assume digikey's value is the "recommended" output current.

The amp will be running off a +-12v power supply and unfortunately, in the section for 24v Vcc, the datasheet has no output current figure...

I am just curious as to what impacts I can expect with regard to life expectancy, if any, running the op amp at 10mA roughly 50% of it's life. That is, the opamp will likely be sourcing 10mA half the time it is powered on and 0mA the rest of the time.


texts:
I have a small project which involves controlling 4 solenoids with one hall effect switch. I want to use the switch to cycle through the solenoids. Each time the hall effect switch is triggered i want to switch on the next solenoid...

A flip flop relay seems to do what I want for a single load... but I can't figure out a solution to drive 4 solenoids...

Any ideas?

Thanks


texts: Fire Resistant Bag/Wrap for Internal Rechargeable Li-ion Batteries

texts:
I am making an internal 4s8p 18650 rechargeable li-ion battery pack for a medical device, and for safety reasons, would like to encapsulate the batteries inside a fire resistant bag or wrap.
I've noticed that there many options out there for fire resistant bags and PVC heat shrink wraps.
The bags are definitely bulkier and I wonder if any device manufacturer actually put such bags around the device's internal batteries.
Are heat shrink wraps enough for safety's sake? And how about kapton tape? If so, would the normal thermo tec heat barriers work? They seem to be stronger than PVCs.
Sorry for the naive questions. Hope someone can pour some knowledge on me!


texts: What is the exact meaning of 0.7V voltage drop in a forward-biased diode?

texts:
this question is partially (but not totally) discussed here:
Why do diodes have a voltage drop?
Does the power drop on a diode become entirely heat?
The conclusion is that, in a forward-biased diode with steady DC current:

the voltage drop represents the necessary energy (per unit charge) to push charge carries (electrons and holes) from one semiconductor to the other.

the power drop on a forward-biased diode is entirely heat.

Let's focus more in detail on both statements. Let's consider the following band diagram in case of forward biasing:

I'd say that:

when the diode is forward biased, holes are pushed from P to N and electrons from N to P, correct?

both electrons and holes' levels change along the junction, since they correspond respectively to the conduction and valence bands. Their jump is the same since both levels are represented by parallel curves. Is the voltage drop of the diode equal to this jump, to twice this jump or other?

what do the charge carriers injected in each semiconductor do after they have passed the discontinuity? Do they recombine and produce heat? Do they pass undisturbed and continue flowing as electric current? In the first stack question it's written that there is a loss of carriers. How can the KCL law be true if some carriers disappear at the discontinuity?


texts: Thevenin Equivalent of Common-Gate Amplifier

texts:
I'm having some difficulty understanding how Razavi determined \$V_{\text{in, eq}}\$. My understanding was that the small-signal model allows us to model the PMOS device as a constant current source (\$g_mv_{gs}\$) with a resistor in parallel (\$r_o\$) and then he transformed that from a Norton Equivalent to Thevenin Equivalent?
Can someone clarify how the \$V_{\text{in, eq}}\$ is derived?


texts:
Take a look at this diagram (left side) showing a MOSFET channel:
The dotted line shows the Fermi level. On average, all states below this line are filled with electrons, and all states above this line are empty. So in the top-left, there are no electrons in the conduction band (above the green line) and no holes in the valence band (below the red line) (all the valence states are filled with electrons).
I'm not entirely sure how to read these diagrams, but I guess that the gate voltage is positive, since electrons want to move close to the gate (they have lower energy there) and holes want to move away from it. That must mean this shows an N-channel MOSFET.
In the bottom-left image, the gate voltage is stronger, and the conduction band reaches the Fermi level. This means there are now some free electrons on the left side of the channel which can be used to conduct electricity.
My question: If we apply an opposite-polarity voltage to the gate, will the bands bend up? If the voltage is strong enough until the valence band reaches the Fermi level? And then, can the channel conduct using holes? If not, why not? We know that MOSFETs don't work that way, so I suspect there will be a problem at the drain and source which prevents the MOSFET from conducting.


texts: high side MOSFET switch and BJT interface with MCU GPIO

texts:
im operating a 28V contactor using a GPIO from my MCU, i have a 28V supply readily available.

im looking to surpass the gate threshold of the MOSFET by introducing a NPN BJT with a 10V supply, with the base connected to the GPIO,

The MOSFET turns on, however, VGS = V_GPIO - V_BE

and not VGS = 10v - ICRC - V_BE

There is something clear and obvious that im missing?

when the BJT is switched on the voltage should be seen at the gate of the MOSFET??

How can i increase the MOSFET gate voltage without inverting the input?

Thanks in advance.


texts: Power problems related to copper wires and pigtails

texts:
I am using a battery to power a odroid which requires 5V/4A. The battery voltage when measured using a multimeter was around 26.7.

I had two setups:

I used a 1 sq mm copper current carrying wire to connect between the battery and dc converter (24V-5V) and a pigtail to power the odroid and it worked.
In this one I had replaced the 1 mm sq copper wire with a 2.5 mm sq copper wire but the board doesn't seem to get started.

Is their anything I had missed out regarding the copper wires in the 2nd setup?


texts: Need help building circuit for 5V-12V Voltage regulation of external 12V power-source via PWM-GPIO of Raspberry Pi

texts:
I have a project, where a raspberry-pi shall measure temperature, and regulate a 12V non-pwm fan by modifying voltage throughput to the fan between 5V and 12V. The fan has a separate power-supply. Temp-measurement works fine already, but I need help building the circuit (being a beginner, I read tons of howtos and I think I got the idea, but I want to be a bit more safe, to not damage components)

As far as I understood, I have to achieve the following:
Switch a Transistor (which is capable of handling the fan voltage & current) with a specific pulse, generated by a Raspberry GPIO-Pin configured as PWM-Pin and driven e.g. by python-scripts.
=> Smoothen the pwm-generated voltage output.
The consumer in the circuit shall be a 12V Fan that uses only 0.125A peak.

Could anybody be so kind to explain how the circuit has to look like exactly and help me out calculating the correct values for those components ? Of course any ideas are welcome. I just need to achieve analog voltage regulation for that dc fan somehow. If I could read the fan speed in addition (from 3rd-pin, no pwm-fan), this would be additional benefit...
Thanks a lot in advance, Oliver

PS : What software do you use to design circuit-graphics ? Are there any recommendations for open-source electronics-layouting ?!


texts: Science behind mutual inductance dot convention

texts: I have gone through several links about the dot convention of mutual inductance, but nowhere could I find the reason why a dot is placed where it's placed. Is it to do with any direction of current and field or some other reason I cannot understand? Can anyone elaborate on the physics behind the dot position?


texts: HX711 and 50kg load cell - possible update speed / dynamic load

texts:
I bought this 50kg load cell and an hx711 which I want to connect to my raspberry pi zero.
I'm wondering how accurate they are if I load them with a dynamic weight.
To take a simple analogy: could I measure say the force/torque on a bicycle pedal, rotating around 60 rpm with dynamic force, with 10 Hz and an accuracy of <5% (for the bicycle say 4 pounds or 2 kg) ?


texts: Does a wider magnet mean less flux density?

texts: I was using an online magnet strength calculator when I halved the diameter of the theoretical N52 magnet. The dimensions went from 32mm in diameter and 3mm thick, to 16mm in diameter and 3mm thick. The surface field heightened from 1,364 Gauss to 2,598 Gauss instead of lowering (which is what I would expect). Why is this?


texts: Why there is a factor 2/3 added to Clarke Transform matrix?

texts:
Apparently, the matrix to transform the 3 vectors \$ U_a  , U_b, U_c \$ into \$ U_\alpha, U_\beta \$ is:
$$
\begin{bmatrix} U_{\alpha} \\ U_{\beta} \\ U_{0} \\ \end{bmatrix} =
\begin{bmatrix} 1 & -\frac{1}{2} & -\frac{1}{2} \\
0 & \frac{\sqrt{3}}{2} & -\frac{\sqrt{3}}{2} \\
\frac{1}{2} & \frac{1}{2} & \frac{1}{2} \\
\end{bmatrix}
\begin{bmatrix} U_{a} \\ U_{b} \\ U_{c} \\ \end{bmatrix}
$$

Why in Clarke Transform, matrix is multiply by \$\frac{2}{3} \$

$$ T_{\alpha \beta 0} = \frac{2}{3}
\begin{bmatrix} 1 & -\frac{1}{2} & -\frac{1}{2} \\
0 & \frac{\sqrt{3}}{2} & -\frac{\sqrt{3}}{2} \\
\frac{1}{2} & \frac{1}{2} & \frac{1}{2} \\
\end{bmatrix} $$


texts: Why does LTspice XOR gate have more than two inputs?

texts:
LTspice has the following symbol for XOR gate:

But as far as I can see the XOR gate has two inputs.


texts: What is the difference between SIM300, SIM900 and SIM900A

texts: I have came across these SIM modules on an online electronic shop. My primary target is just to receive short text messages from other subscribers. But then this question about these three (if there is anything apart from these, those too) modules. What are the primary differences between these GSM modules?


texts: Does a thicker wire mean more charge carriers in I = n A q V?

texts:
If you have two wires A & B made of same material with A being twice as thick as B, when using the formula I = n A q V will the value of n and Q remain the same for both wires or will they change?

I think because the A wire is more thick it therefore has more valence electrons that can carry charge and therefore the number of charge carriers should increase compared to wire B. But i think i heard someone say that n & q remains constant and only A & V value changes.


texts:
I am trying to identify this part (on left) which I found while cleaning my room. I have placed a micro SD card next to it to give an idea of its size.

Update: This is what the rear looks like:


texts:
I'm designing a keyboard. I found some information online about how to make the keyboard be able to detect multiple key presses at the same time (N-key-rollover).

I found this schematic, from this website.

The website says that A and B are the two inputs, and 1 and 2 are the two outputs. I'd select A, then read the values at 1 and 2, and hence know which keys are currently pressed, then do the same with B.

The diodes are to prevent false-positive keypresses. The website explains this in more detail.

What I don't understand, is how 1 or 2 would ever be high? Let's assume A is high, and the bottom left switch is closed, surely its diode is still opposing the current flow, right? How would any current flow to 2?

Is this a matter of conventional vs. electron current flow? Because that always confuses me, but I just can't figure this out.

EDIT, this is active low.


texts:
Hey everyone I am looking into VGA protocol. I have researched a lot but only thing I could not figure out is this:

Does VGA vertical sync and horizontal sync needs to be sent over and over to keep the image on the display?

Or do you need to send these signals to just change the image on the screen?

So if i send my image to screen once do I need to clock the same image to the screen to keep the image?

Thanks.


texts: Turning a circuit off using a 240v signal

texts:
I have a home-built controller for a HERMS brewing system (Heat Exchanging Recirculating Mash System). The purpose of this controller is to drive liquid (wort) from a large mashing vessel (a cooler box), through a heat-exchanging coil that is submerged in a reservoir of heated water, in order to maintain the temperature of the wort in the mash vessel. This temperature control is achieved through the use of a PID, which takes a temperature reading from the liquid wort as it flows out of the heat exchanging vessel, and drives a 10A kettle element (through an SSR) to maintain the desired temperature. This setup works extremely well, but there is a problem that sometimes occurs that could, potentially, be dangerous: the wort is pumped around the system by a 12V pump. If, for some reason, the recirculation stops (e.g. the pump gets blocked with debris/airlock, or simply breaks), then the measured temperature (just outside the HERMS vessel) does not rise with the temperature of the water within the vessel. This causes the PID to keep driving the 10A kettle element, up until the point that the water inside the vessel boils, and steam starts venting through some pressure release holes in the lid.
This exact situation has now occurred twice. The first time, I was lucky enough to spot it early and switch the system off. After this, I added a new PID to the system that measures temperature within the HERMS vessel. This PID (from Auber) has an alarm feature that can be triggered when a certain temperature is hit. The alarm feature triggers a small, internal, SSR (240v, 3A), which is connected to an alarm unit that flashes and sounds a loud siren. This works, and saved me on the second occasion.
What I want to do now is go further than simply sounding an alarm, and have the kettle element circuit shut off completely if this alarm condition is met (I can't always be within earshot to turn the system off). I am not well versed in electronics, although I do try my best to wire everything I have up as safely as possible. The only thing I can think of is a normally closed relay, that is driven by 240v to open it when the alarm condition is met. This would work, but would only open the circuit for as long as the alarm sounds. I also have some concerns that running this normally closed relay at 10a for, potentially, many hundreds of hours at a time (between alarm events) could see it fuse shut? Is this a reasonable concern? What I would really like is a way of switching a circuit off, in much the same way as a circuit breaker - i.e. the circuit switches off, a physcial switch is thrown and I have to manually intervene to enable it again. Ideally this would happen whilst the alarm siren continued to sound.
Can anyone recommend a solution please? As mentioned, the easiest option for me is to use the already existing 240v alarm signal, but if another way makes more sense I am willing to consider it. Bonus points if the solution can be DIN mounted, as that is the way this thing is currently built.


texts: What parameters of a real op amp determine the lowest voltage it can amplify?

texts:
I am trying to amplify a 0.5mV AC signal (from around 4kHz-8kHz, generated by an electret microphone) to about 50mV. I am thinking of using an inverting amplifier using LM358 op-amp.

The datasheet says that it has an input offset voltage of 2mV. Does it mean that it is not possible to amplify signals on the order of 2mV?

More generally what are the parameters that I should look for when trying to design amplifier for this kind of application?


texts:
I need help creating an LM3914 voltage meter (in bar mode). I looked at the datasheet and understand how to create a standard voltmeter (0-5V for example). However, what I need is an expanded range meter, and the datasheet seems a bit confusing about that.
To be precise, I need the circuit to meter a 4S lithium polymer battery. The voltage range has to be 12 - 16,8V.

I would appreciate any help,
thanks.


texts: Manual Probe method of finding JTAG pinout

texts:
There is manual Probe method of finding JTAG pinout on RIFF Box JTAG programmer, by measurement of voltage on JTAG pins while alternately setting on JTAG pins the logical level 1 and 0.
Is it possible use this method without the JTAG programmator hardware? (like RIFF, etc). If that's possible, how to set logic level 1 and 0 on JTAG pins? Is this possible via custom generator, and how to implement this? Can anyone show such generator diagram and manual?


texts: Nodal analysis -> transfer function -> step response

texts:
I've been trying to get the transfer function for the circuit in the image below, but I seem to be doing something wrong, since the simulation on Circuitlab gives me a different Bode plot and I can't find the error on my own.

Here, the equations from the nodal analysis (belong to nodes A, B, C, respectively). Va=Vb=Vc=0 due to virtual ground.

The result I'm getting for the transfer function is:

which looks a little weird to me because of the large numbers, and which translates to this Bode plot:

Simulation on Circuitlab, on the other hand, outputs the following:

From this transfer funtion I should get and plot the step response, which I get calculating the inverse Laplace from H(s)/s, but since the transfer function doesn't seem to be ok I'm not getting these right either.

I'd be very thankful if anyone could point me in the right direction.


texts:
I have many problems with TDA 2050.

Why TDA2050 use high-pass filters?
What is the bandwidth of it? Does the range of bandwidth is from the range of frequencies below the human hearing?(20-20KHz)
I used Pspice to simulate this circuit [replaced TDA2050 by uA741(no TDA 2050 in Pspice)], and 8ohm resistor instead of the speaker. The bandwidth is 23Hz to 4.5KHz. If I increase the resistor of load, the graph of frequency response become strange with a jump value in 12.9KHz, how it occurs? Is there something wrong?
If I remove the R6C6, the jump value disappeared, why? In addition, the bandwidth between R7=8ohm and R7=1K is difference, why?

R7=8 -->bandwidth<24-4.5KHz>

R7=1K-->bandwidth<11.5-20KHz>


texts: Is the 4066 appropriate for power switching?

texts:
I am building a serial interface for a GPS module.  This interface will have a "traditional" DB-9 connection, a USB-to-serial connection and a 5.5V power input.  The GPS module will be in a separate enclosure some distance away.

I had considered designing this totally for USB, but it is for my server at home that has more unused COM ports than USB ports so I will design the serial interface around the MAX232.

Now my question about power:  I could power the GPS module from USB with an FTDI Friend, and I have.  But I'm more comfortable running it from a wall-wart, and if I connect it by DB-9 serial, I have to power it that way.  I want to incorporate both the USB module and the DB-9, leaving it up to circumstance depending on where I use this.

I'd thought of using a 4066 switch to some LED's to indicate the state of the interface for troubleshooting (TxD, RxD and PPS) and I'm wondering if the 4066 is feasible for switching power inputs.

The USB module (an EM-406A) draws about 50 mA (rounded up from the datasheet value 44 mA.)

I would have the 4066 control pin connected to my 5.5V power inlet (where the wall-wart is connected) and controlling the +5V from the USB module.  It would (or rather, I intend it to) shut off the +5V from the USB.

Is this feasible?


texts: Creating a calibration table for a power sensor

texts:
I have been tasked with creating a calibration equation for a power sensor. I have taken data with a calibrated signal generator and have plotted the various frequencies. Now I need to understand the noise that is the data. I have the R2 plotted in each set. The R2 look pretty good like 0.997-0.982 depending on the frequency, but when I back-calculate for the points my numbers can be off sometimes by 3% (not acceptable).  I plotted the residuals for the frequency, and its shape is parabolic.

How do I create find the E for the for the
Y = a + bX + e.  Pics are included.

:


texts: How to automatically show component values in Altium (Manufacturer Part Search)?

texts:
I just noticed that Altium 20 is free for students (yay). I'm trying to get used to it again, i was using Altium 17 during an internship for quite some time - with an already very big and well maintained library.
Now, I discovered that there is the "manufacturer part search", but I have a very stupid issue with it:
When I place a component discovered in this part search, it does not show the component value (e.g. resistance or capacity). I know how to turn it on part by part, but is it possible to enable it globally?
Thank your very much!
All the best


texts:
How does a G/H amplifier work?

What does it do to help with power dissipation?

I am trying to figure out how a G/H amplifier works but so far the documentation and videos on the internet I found  are too complex when explaining how it works. I only understand that a G amplifier has multiple power rails but I don't understand how that helps with power dissipation. I also have a hard time understanding this diagram which I found, especially finding out what parts do what.


texts: leakage current of a 10uF MLCC compared with an aluminium decoupling capacitor

texts:
I am trying to track down a ~10uA current leak in my circuit.
My PCB has this 10uF ceramic decoupling capacitor between 1.8V and GND.
I cannot see it's ESR value in the datasheet so I do not know what leakage current I should expect. I also cannot see a minimum voltage listed to check if it is suitable for 1.8V.
I am using a CurrentRanger, a multimeter and an oscilloscope to measure current. When I physically removed the capacitor, the current dropped 10uA.
The datasheet for the LIS3DH sensor that it is attached to, says it should be an aluminium capacitor.
What leakage current should I expect from this capacitor?
Any help is greatly appreciated.


texts: Zener diode as a Voltage regulator, where do the formulas come from?

texts:
I'm currently studying the above circuit and trying gain a better understanding of it, I found the following forumlas to calculate Rs Max and Rs Min:

$$R_Smax = R_L(\frac{V_{in}}{V_z}-1)$$

Which I think comes from:

$$V_{in} = IR_{total}$$
$$V_{in} = I(R_S+R_L)$$
$$\frac{V_{in}}{(R_S+R_L)} = I$$
$$\frac{V_{in}}{(R_S+R_L)} = \frac{V_z}{R_L}$$
$$V_z = \frac{V_{in}R_L}{(R_S+R_L)}$$

Hence:

$$R_Smax = R_L(\frac{V_{in}}{V_z}-1)$$

If this is where it came from it doesn't seem right to me, Isn't the Zener Diode and Resistor L in a paralell circuit? because if the formula came from there it's like saying the zener diode is in series with Rs, but from what I see in the circuit drawing is that Resistor L is in paralell with the zener diode, so why not use the loaded potential divider formula? as opposed to the potential divider? plus it's like saying that the current Is is gonna be the same as the current in IL....

$$I_S = I_Z + I_L$$

The above is true right?

if someone can explain this to me I'd be grateful, it's been bothering me for days.


texts: Digispark: Driving high Zener-connected pin on ATtiny85

texts:
In my project I need all available pins on my Digispark.
Pin PB4 is connected to a 68 Ω resistor and a 3.6 Zener diode.

This pin is used for USB protocol. This means that at some point in time the ATtiny is "writing" to this pin (meaning it is pulling it high). As a consequence the current drawn will be (5 - 3.6) / 68 = 20.5 mA. This is very close to the maximum allowed although it seems it is supported by the chip.

I want to drive this pin (with digitalWrite) high for an unspecified period of time(could be 5 minutes or 1 h). Would this damage my board?


texts: Design of programmable scaling amplifier as a project for undergrad

texts:
I am building a custom microscope, PhD in biomedical engineering. I would like to have a scaling amplifier, with programmable offset and gain, that takes 0..10V signal X (from piezo element) and turns it into output -1..1V Y signal (into galvo mirror) such that Y=A*(X-B) where A~0.1-0.5 and B~-1..+1V are adjustable within 2-3 digits. In fact, currently we use A=0.18, offset B=+0.119

The frequency bandwidth should be around 1kHz or higher. The input signal is usually a sawtooth with 1Hz repetition rate. Input impedance should be > 10kOhm, devices outputs into 20kOhm impedance. The delay between input and output should be as short as possible, but 1ms is OK. I think we can tolerate output noise of 0.5-1mV.

Currently we are using rather expensive 1MHz scaling amp, so I want a copy of that with lower quality and much lower price tag. The problem is that we'll need roughly 4-5 of these, at around $1000 a piece. I feel like there is a way to make these devices 10x cheaper.

Is that a feasible project for an EE undergrad? I have access professor with much more EE experience than I, for double-checking the final design.

I am considering custom PCB as a solution, or something arduino-based for programmable part.


texts: What the relationship between permittivity and resistance?

texts:
Is there any relationship between permittivity and resistance for a material like fertilizer in water solution? In other words, if I know the capacitance using that liquid as dielectric, can I get its resistance (and EC also)?

[I guess there is none, for economical reasons: there is no product AFAIK that exploit this relationship.]

Note: assume we know all about the capacitor (dimensions, materials, construction ...)


texts: Noise level detector circuit design (AC to DC to PWM)

texts:
So I'm building a sound level detector. Design requirements are:

Only basic circuit elements
No IC's, except for op-amps
Sound level will be displayed with a blinking LED
Blinking LED will be controlled with Pulse Width Modulation (PWM)
Sound level, and therefore the PWM, will have several distinct levels, let's say, 0%, 50% and 90%

Here is my general design schema:

AC from microphone will be converted to DC through a full-wave rectifier. The obtained input DC will be passed through 3 parallel op-amp comparators (one for each sound level).

Now, as a sound loudness display, I need to use a blinking LED, whose on/off times will be determined by a PWM input — a 25% duty cycle will mean the LED will be on for 25% of the period and 75% off.

In order to obtain a PWM, we need triangular waves, so, to each comparator, a triangular wave generator will be connected, with amplitudes 0%, 50%, and 90% of the max voltage, respectively.

Now, I am uncertain about a couple of things, mainly:

Would a full-wave rectified output work with triangular wave method?
If yes, then I suppose the period of output PWM will be twice as
less? If no, then what other method would I use to convert AC from
the mic to DC?
In the end, now that I have outputs from all comparators, can I just
"combine" them (through comparators again I suppose?) like this?

Equipment:

Passive elements (resistors, capacitors, inductors, diodes)
LEDs
Analog Microphone
Op-Amps
DC Power Supply in the laboratory

Any general commentary/advice on the circuit design would be highly appreciated! Thank you.


texts: Can I use a 220v soldering iron on 110v?

texts: I ordered a 110v soldering iron, but received one marked 220v 60w with a usa-compatible plug. If I plug into 110, will it still heat up?


texts: Generating variable frequency PWM with Attiny85

texts:
Bit of Background: I am currently working with my ATX Power Supply and trying to re-purpose it to use its voltage outputs (3.3V, 5V and 12V). But I would like to have a PWM feature with my power supply when I complete it. For this purpose I am thinking to use Attiny85 and use it's fast PWM mode to generate what I need. I need a PWM signal whose duty cycle and frequency can be varied through the use of potentionmeter.
Problem:Link to datasheet Going through the datasheet, I figured out that it is possible to vary the duty cycle as I want through the manipulation of Output Compare Register (OCR). But I can only vary frequency in pre-determined values. Varying the clock prescale factor does the basic job. But what I want is PWM with frequency I can adjust with a potentiometer as I want (within the supported range of course).
Possible way for solution from my study: I came to the CTC mode in which I can vary the frequency by changing the values in OCR. But this would limit the duty cycle varying feature. So, I wonder if there is any way to combine these two modes.I came to this thread where the question deals with varying frequency only but not the duty cycle.
I can do the  basic operation of generating the PWM with fixed frequency. Although, I went through the registers involved in generating PWM, I can't scrap any idea to generate the PWM I wish for.
This is basically what my primary problem is. I would love some recommendations from this community about what I could add to the features of my power supply. Thanks for the help.


texts: Why are there small coils prior to the brushes in a drill?

texts:
I'm trying to repair a drill where the switch got broken. It's turning into something more difficult than I expected due to several issues. One of them is that the brush wires  got peeled due to some unknown friction or wear somewhere in the path. The brushes themselves don't look worn enough to be replaced, so I simply replaced the wire.

Then I noticed something that puzzled me on the old wire. Instead of being a single, continuous one, directly attached to the switch, there was a split in the middle, covered with heat shrink tubing. Even the wire color was different on each part. By chance, I peeled the tube off as I discovered something "solid" on the inside. At first sight I thought it was some reservoir wire for attaching it to the other half of the wire, but looking carefully, with its ferrite in the axis, I came to the conclussion that it's a coil.

What's the purpose of these coils?
What would happen if I connected the brushes directly to the switch?

Bonus question: As I cut it too tight from the edge of the coil, could it have any harmful side effect if I unwind, lets say, a turn of the coil in order to use the copper wire to attach the coil to the wire?


texts: Return Current of a 200MHz signal sandwiched between GND and split power planes

texts:
Here's my relevant 6-layer stackup:

L2: GND,
L3: Power,
PP: 37mil,
L4: Signal,
core: 4mil,
L5: GND

I have a 200MHz signal on L4 and my assumption is that most return current will go through L5 and some will return through L3.  But on L3, the power planes are split.  Should I put separate caps on these split power planes and place them right next to each other so that the return path can continue through the caps?  My confusion is whether the caps will reduce the impedance and let more return current flow through and make EMI worse.  Or should I not put these caps and somewhat force the return current to flow through L5 GND.  Greatly appreciate your response.  Thanks.


texts:
Y=K'J'Q+K'J+KJQ'

  The output Y should be that of a JK flip-flop. That is:   Y=JQ'+K'Q

I tried to solve the following way:

1. Y=K'J'Q+K'J+KJQ'

2. =K'(J'Q+J)+KJQ'

3. =JK'+K'Q+JKQ'

4. =J(K'+KQ')+K'Q

5. =J(K'+Q')+K'Q

6. =JK'+JQ'+K'Q

It appears as if the term JK' is 0. Please help.


texts: Altium - Variation components wrongly displayed in 3d mode

texts:
I'm currently working on a project in Altium 16.0 with three different variants of assembly. After selecting which components should not appear on each variant o schematic, I updated the PCB. Afterwards, on PCB mode, I went to the variants linstings and everything is according to the list made on schematic side.

My problem is, when I go into 3D mode, some components appear on the wrong variants, despite being correctly set to "not fitted" for that variant.

My question is, did anyone experience the same issue? If yes, how can I solve it?


texts: Current sensing in boost PFC controllers

texts:
I was going through the datasheets of a few active PFC controller ICs (like this: https://www.ti.com/lit/ds/symlink/ucc28019a.pdf?HQS=dis-mous-null-mousermode-dsf-pf-null-wwe&ts=1619350669153&ref_url=https%253A%252F%252Fwww.mouser.in%252F) when I noticed something odd about the way the switch current is sensed.

Because of the location of the current sense resistor, two things happen: the load current gets added on to the switch current and the voltage across the current sense resistor is negative, as seen by the IC.
As I scrolled through the datasheet, I found the functional block diagram of the IC.

You can clearly see that the sensed current is fed to a -1x amplifier!
So my questions are:

If the voltage across the current sense resistor, which is negative, is fed to a -1x amplifier, then why sense it in that manner instead of doing it like this:

And why is the load current added to the switch current?

I would like to build a PFC circuit, but at a low voltage (like 24V AC) for safety reasons (I have zero experience building high-voltage circuits). These ICs are designed and optimized for mains voltage applications, so will it lockout at low AC voltages or will it still function normally?
3)
Could I just use a regular boost converter (without the input filter cap) to perform PFC, or do I really need to use a dedicated PFC chip for this?


texts: What pins on a nRF51822 do I connect to a STM32 programmer?

texts: I want to be able to program a nRF51822 with this programmer but I'm not sure what pins on the actual chip I should use, and all the guides seemed to be using a different chip


texts: Magnet Shake Generator - how to replicate in LTspice?

texts:
I made a generator for my wife's 3rd grade class, since they are learning about magnets, electromagnets and electricity. It's a simple pipe with a stack of magnets inside and you shake it to produce some power. I'm sure you've seen them.

The pipe (which is just a scrap plastic tube taken from one of my kids' "bubble wands") is about 1 inch diameter and the magnets are ceramic 3/4 inch ones from "Hobby Lobby". It's a sloppy fit, but it works. The coil is 26 gauge magnet wire and I made about 1,050 turns. At the ends of the coil, I soldered 2 LEDs with opposite polarity since it's AC and I wanted to show that. It all works, but I eventually want to go further with the project.

This leads me to my actual question. I discovered LTspice and want to replicate this in the simulation, but I have no idea how to setup the voltage source. I have been out of the electronics game for a long time and I think I'm missing something obvious. It requires a ground to simulate the circuit, but I have no idea where to put it. The more I try to do things with it, the more I don't know. Would any of you be able to show a quick way to setup this circuit, with the above information? Maybe even just estimate how much power I'm generating.

Thanks in advance.


texts: Seamlessly powering 12v CPU fan with regulating speeds

texts: I am trying to have an economical and reliable control system to seamlessly power two 12v, 0.3a CPU fans with varying speeds while also charging a 12v 7ah lead acid battery for backup. I could not find a ready-made product to buy, can somebody please suggest me on how I can achieve this in a cost effective way? Thanks.


texts: Can I use arduino USART tx and rx separatly?

texts:
My idea is to receive GPS sentences in the RX pin, parse the data and send the result to my computer via the TX pin. (with same baud rate. 9600 for instance)

Is it possible or may I encounter buffer issue for non-consume bytes ?


texts: IP5306 questions (battery management IP)

texts:
I have some question about this IP
Datasheet link https://github.com/Xinyuan-LilyGO/LilyGo-T-Call-SIM800/blob/master/datasheet/IP5306%20REG%20V1.4.pdf

Is the lithium ion cell is embedded within the chip or external?
How does it charge the cell when needed?
How does it discharge it when needed? (high consumption peek)

Thanks


texts: Can a Verilog code for a component model be used to create a new part in OrCAD Capture CIS?

texts: I have read an instruction manual where some Verilog-a code that contains multiple memristor models is used to create a part in cadence virtuoso, that can be used in cricuit design. Is it possible to do this using OrCAD capture CIS with PSPICE A/D. If this is possible, I have been unable to find a guide showing how to create a part using Verilog code and would be grateful if anyone could point me in the right direction.


texts: Mosfet datasheet reading and power calculation problem

texts:
Mosfet datasheet: http://www.farnell.com/datasheets/2255289.pdf

Hello, i have few questions about datasheet because they are so confusing. I would like to run 1,5 amps under 12 volts from drain to source. To control mosfet im using Atmel processor which is similar to Arduino, it is able to put out 5 volts and like Arduino, up to 40 mA.

1) Power calculation: Rds(on): 88 mOhm if 2.5 volts between gate and source. Since power is current squared times resistance then 1.5*1.5*0.088= 0,2 Watts
In datasheet it says temperature rises 300 degrees Celcius per Watt without any heatsink. 0,2*300 = 60 degrees + ambient temperature. It makes 80 degrees celcius when there is 20 degrees outside. Is this correct? Without considering rds(on) change due to temperature change and power dissipation changes due to temperature.

2) Why they say that steady state power dissipation is 1.25 W? 1.25W*300 = 375 degrees. How it can allow so high power dissipation? Only under heatsink? Whats the point of this number when there is already said how many degrees per Watt its temperature rises?

3) I had several these mosfets. They started smoking instantly as soon as i put there 12 V and load what draws 1,5 Amps.

4)Following graph causes me misunderstanding. What units is rds(on)? If Rds(on) would rise too high then it would be understandable.

5)Following graph causes me misunderstanding as well. If i use let's say only 1,2 Volts to control the gate then i can't draw basically any amps through it?

6) Does the following graph mean if i use too low gate voltage respect to source then rds(on) is huge? Why they say then that threshold voltage is minimum 0.65 volts and maximum 1.2 volts? Its not pretty much possible then to run some bigger load between 0.65 volts and 1.2 volts?


texts:
I'm having major problems making a good layout with a through hole USB-C connector. Have anyone done a good layout for one? The best I have managed now looks pretty terrible and one of the differential traces has 5 vias, which is not recommended.

I'm using the spraar7f manual from Texas Instruments for spacings, linewidths etc. I have never done anything USB3 or USB-C, only 2.0 and I'd be really happy with some guidence. Will this implementation be OK? I have tried routing it some different ways, this is at least symetrical. Everything is length-matched according to spec.

Image of USB-C:

Image of trace with 5 vias:

I have chosen a through hole connector to make it easier to solder and for robustness, but I'm currently thinking of replacing it for a completely surface mount one. Currently I'm designing for a Wurth 632723300011 (there are other brands with the same footprint)

It's a 4-layer PCV

Any ideas? :)

EDIT: As noticed out by asdfex, there is an error in the footprint. Do not follow the answer in this thread. It will give an incorrect layout. (Thanks for noticing!)


texts: PoS-SoP convertion of function bellow (NOT using K-map)

texts:
Function F as: $$ F=\overline{C} \space \space \overline{D} +A\overline{D} + A\overline{B}$$
is a SoP (sum of products) which is given by grouping K-map's 1's.

I tried to complement the function \$F\$ to get PoS (product of sums), like: $$ \overline{F}= (C+ D) \cdot (\overline{A}+D) \cdot (\overline{A}+B) $$ but I checked the K-map's 0's to see if it's a correct PoS, but it is not even a PoS because it contains max terms that the correct PoS  shouldn't have.

Does any one know where I'm wrong?


texts:
I want to evaluate the energy flow in a battery powered system. So when the system runs a specific task the energy distribution between the different loads can be obtained ( similar to a Sankey diagram). For this a timescale in the range of [100..10] ms in the processed data would suffice.
Electric energy can be calculated as \$W =  \int_{t_{0}}^{t_{1}}u(t)\cdot i(t) dt\$. Thus measuring voltage and current at a given sample rate will provide the necessary data. For further processing on a PC voltage and current should be logged.

As can be seen in the image the power supply converts the input of the batteries to a steady 24V. The motor drivers use a 40 kHz pulse-width-modulation (PWM) to control the brushless direct current (BLDC) motors. Up to 9 motor/driver combinations can be in such a system. There are more loads supplied by the power supply which show only slow changes in energy "consumption".
The measuring will be controlled by an Arduino Due (84 MHz). The ADCs will likely have multiple channels and will be connected via SPI.

My concern is to measure with good accuracy whithout hitting a bottleneck in the processing:
Speed of the bus (SPI) to the ADCs, data processing ( both limited by microcontroller ), and especially the write speed to SD card ( limited by the Arduino lib <700 kB/s? )

The voltage of the batteries only changes slowly under load and thus the sampling rate can be low. However the motors show multiple harmonics in response to the 40 kHz PWM.
Considering the nyquist criterion measuring frequency would need to be more than twice as large then the fastest signal of interest (here the n-th harmonic with significant magnitude). Other signals need to be low pass filtered to prevent aliasing.

Question 1: Which steps for measurement and processing can be taken to maintain accuracy while reducing demand on the bottlenecks?
My thoughts are:

Using arithmetic averages over a set interval \$\Delta T\$ to reduce data to log: \$\overline{W}=\overline{u}\cdot \overline{i} \cdot \Delta T\$
Writing binary data to the SD card instead of plain text.
Measuring only one phase per motor, assuming phases are driven equal while maintaining constant speed at constand torque. Thus this approach is limited by the conditions.

Question 2:Is it possible to get a good approximation by measuring slower than the PWM frequency?
I get that undersampling is not applicable here, as it uses the alias of a higher frequency band in an empty lower frequency band.


texts:
I am making an infrared break beam to detect insects, using an IR emitter LED and detector. The insects fall into a channel and then eventually cross the beam, which travels the length of the channel.

The insects are quite small, so I want to make the beam as narrow as possible; otherwise an insect could block part of the beam and go undetected. The infrared light from the LED has some spread. I was using a pinhole to screen the light into a beam.

Through trial and error with 3D printing I found a pinhole profile that works: pinholes of diameter 1.3mm and depth of 3mm on both the emitter and detector can detect an insect with a cross section of 3mm by 1mm.

However, I want to make the beam even smaller, to detect an insect with a cross section of 0.5mm by 0.5mm, and I would like to find a more rigorous way to define a pinhole profile. I am not sure what effect the pinhole diameter and depth have on the size or spread of the beam. I have three questions:

1) How do I choose a pinhole diameter? If a laser goes into a slit, there is diffraction, but is this a problem for an extended source like an LED?

2) How do I choose a pinhole depth? A thicker depth could reduce false readings from IR light reflected from the side of the channel.

3) Do I need pinholes on both the emitter and detector? I had some challenges with IR reflections from walls when the emitter did not have a pinhole, but that might be avoided if the pinhole is made sufficiently deep.

Right now the insect trap is being 3D printed, but eventually it will be manufactured (eg injection molded). I would like to avoid lasers or lenses for size and cost restrictions. I am not interested in focusing the LED, and I understand that I will only be accessing a fraction of the LED's output light.

EDIT: The emitter (datasheet) and detector (datasheet) are both lensed to increase their angular spread, so some sort of aperture is necessary to get a narrow beam.


texts: PIC18F67J60 programming errors with PicKit 2

texts:
I'm trying to program a PIC18F67J60 with a PicKit 2 but the device won't program.

The output from MPLABX PicKit 2 log is:

Found PICkit 2 - Operating System Version 2.32.0
Target power not detected - Powering from PICkit 2   3.25
2014-01-03 11:35:52
PIC18F67J60 found (rev = 0x3)
Erasing Target
Programming Program Memory (0x0 - 0x3f)
Programming Program Memory (0x1ff80 - 0x1fff7)
Verifying Program Memory (0x0 - 0x3f)
Verifying Program Memory (0x1ff80 - 0x1fff7)
Programming Configuration Memory
Verifying Configuration Memory
PK2Error0027:  Failed verify (Address = 0x1fff9 - Expected Value 0xf4 - Value Read 0x0)
PK2Error0027:  Failed verify (Address = 0x1fff9 - Expected Value 0xf4 - Value Read 0x0)

The code is basically just blink an LED:

#include <xc.h>
#include <stdio.h>
#include <stdlib.h>

//general defines
#define _XTAL_FREQ 25000000

// CONFIG1L
#pragma config WDT = OFF        // Watchdog Timer Enable bit (WDT disabled (control is placed on SWDTEN bit))
#pragma config STVR = OFF       // Stack Overflow/Underflow Reset Enable bit (Reset on stack overflow/underflow disabled)
#pragma config XINST = OFF      // Extended Instruction Set Enable bit (Instruction set extension and Indexed Addressing mode disabled (Legacy mode))

// CONFIG1H
#pragma config CP0 = OFF        // Code Protection bit (Program memory is not code-protected)

// CONFIG2L
#pragma config FOSC = HS        // Oscillator Selection bits (HS oscillator)
#pragma config FOSC2 = OFF      // Default/Reset System Clock Select bit (INTRC enabled as system clock when OSCCON<1:0> = 00)
#pragma config FCMEN = ON       // Fail-Safe Clock Monitor Enable (Fail-Safe Clock Monitor enabled)
#pragma config IESO = OFF       // Two-Speed Start-up (Internal/External Oscillator Switchover) Control bit (Two-Speed Start-up disabled)

// CONFIG2H
#pragma config WDTPS = 32768    // Watchdog Timer Postscaler Select bits (1:32768)

// CONFIG3L

// CONFIG3H
#pragma config ETHLED = OFF     // Ethernet LED Enable bit (RA0/RA1 function as I/O regardless of Ethernet module status)

/*
 *
 */
int main(int argc, char** argv) {

  //OSCCONbits.SCS = 0b10;

  TRISB = 0x00;

  while(1){

    LATBbits.LATB0 = 1;
    for(unsigned char i = 0; i < 25; i++)
      __delay_ms(10);
    LATBbits.LATB0 = 0;
    for(unsigned char i = 0; i < 25; i++)
      __delay_ms(10);

  }

  return (EXIT_SUCCESS);
}

Using PK2CMD I can see that the device is recognised with the auto detect however when I try to flash the HEX straight into the PIC I get this terminal output:

> pk2cmd -PPIC18F67J60 -M -F main.hex
PICkit 2 Program Report
3-1-2014, 11:34:51
Device Type: PIC18F67J60

Program Memory Errors

Address   Good     Bad
01FFFE    00FFFF   00F000

Which seems a different problem to the MPLABX output. Could this just be a bad chip (unlikely?) - any suggestions would be great.

UPDATE:

Schematic below:

Vcc is 3.3V so ENVREG is ties high to use the built in regulator to reg down to the 2.5V the chip actually uses, as a result the VDDCORE/VCAP is tied to ground with a 10uF electrolytic. X1 is 25MHz and I have tried the Pickit 2 MCLR straight into the pin, as it is here and also without the 0.1uF cap (as the datasheet suggests)

UPDATE 2:

I tried erasing the device with the following using PK2CMD

> ./pk2cmd -PPIC18F67J60 -E
Erasing Device...

Operation Succeeded

but sadly I still get the same error when trying to program - is there an alternative way to erase or is CP being set permanent on these chips?

UPDATE 3:

Interestingly if I unplug the PicKit 2 and run the circuit on external power only the LED is on - not pulsing, just on. Not sure if that is of interest but it's something.

And the device checksum in the project view in MPLAB for the device is Checksum: 0xC0C2


texts:
I'm trying to calculate maximum input voltage that can be applied to a voltage divider based ADC circuit attached in the picture below along with converting the ADC raw value to actual voltage.

In the above attached image, P8 is a terminal screw block connector where the external analog voltage is applied. And as you see, the resistors form the voltage divider circuit. AN0-AN7 go to the ADC pins of a microcontroller. This is a 5 volt system and so I believe the reference voltage should be taken as 5 volts. I am trying to figure out what would be the maximum voltage that I can apply to the pins on P8 connector and also how to convert the raw ADC values to actual analog voltage that was applied. So, based on the circuit,
5 = (V x 10k)/30k  -> V = 15 volts. [Here 5 volts was taken as the reference voltage since it is a 5 volt based system.] So the maximum voltage that can be applied is 15 volts. The resolution of the microcontroller is 12 bits. So, to calculate the actual analog voltage from raw ADC values, Actual Voltage = (Raw ADC value)*15/4095. However with this calculation I'm not getting the right voltage that was applied. Can anyone guide me regarding where I am going wrong in this whole calculation ?

EDIT: Circuit 2

In this above circuit, when the dip switch S2 is turned ON, if I am correct the 1k resistors come in parallel with the 20k resistors. So, the new calculation would be 5=(20k||1k)X V/((20k||1k)+10k), which would turn out to be V being equal to 58 volts approximate. Is this correct ?