texts: How does control theory apply to my real-world processor-controlled boost converter?

texts:
I have a limited understanding of control theory. I dealt with poles and zeroes and transfer functions in school. I've implemented several microprocessor-based control schemes for DC/DC converters. How these two things relate to each other, I've yet to figure out, and I'd like to. Basing designs on trial and error can work, but I prefer to have a deeper understanding of what I'm doing and what the consequences are.

Answers should focus on how to analyze the system, not on how to improve it. That said, if you have suggestions for improving the system, and wish to give an analytical reason why, that would be fantastic! Just as long as improvement is secondary to analysis.

My example system for the purposes of this question:

C1: 1000uF
C2: 500uF
L1: 500 uH
Switching frequency: 4 kHz
R1: Variable
Input voltage: 400 volts
Output voltage target: 500 volts
Output current limit: 20 amps

I'm trying to regulate the output voltage, without exceeding an output current limit. I have voltage and current sensing, which go through various amplification stages I'm not analyzing at this juncture, but which do include some filtering. This is followed by an RC lowpass filter of 100 ohms and 1000 pF directly at the A/D converter. The A/D samples at 12 kHz. This value goes through a single-pole IIR moving-average filter of the last 64 samples.

After that, I have two PI loops. First, the voltage loop. The below is pseudocode, with values scaled to be volts, mA, and nanoseconds. Assume bounds checking is implemented correctly elsewhere. The structure of these loops defines P in terms of the maximum allowable droop if there's no integral term, and then defines the integral term such that a max'd out integrator can exactly compensate for that droop. The INTEGRAL_SPEED constants determine how quickly the integrators spool up. (This seems to me to be a reasonable way to make sure P and I gains always balance properly regardless of how I set my constants, but I'm open to other suggestions.)

#DEFINE VOLTAGE_DROOP 25
#DEFINE VOLTAGE_SETPOINT 500
#DEFINE MAX_CURRENT_SETPOINT 20000

voltage_error = VOLTAGE_SETPOINT - VOLTAGE_FEEDBACK
current_setpoint = MAX_CURRENT_SETPOINT * voltage_error/VOLTAGE_DROOP

#define VOLTAGE_INTEGRAL_SPEED 4
voltage_integral += voltage_error/VOLTAGE_INTEGRAL_SPEED
//insert bounds check here
current_setpoint += VOLTAGE_DROOP * voltage_integral/MAX_VOLTAGE_INTEGRAL

#DEFINE CURRENT_DROOP 1000
#DEFINE MAX_ON_TIME 50000

current_error = current_setpoint - current_feedback
pwm_on_time = MAX_ON_TIME * current_error/CURRENT_DROOP

#define CURRENT_INTEGRAL_SPEED 4
current_integral += current_error/CURRENT_INTEGRAL_SPEED
//insert bounds check here
pwm_on_time += CURRENT_DROOP * current_integral/MAX_CURRENT_INTEGRAL

So I have a boost converter with two capacitors, a choke, a variable load (which could be a step function), feedback with single-pole RC filters, an A/D converter, single-pole IIR digital filters, and two PI loops feeding each other. How does one analyze such a thing from a control theory perspective (poles, zeroes, transfer functions, etc.), particularly to select my control loop parameters properly?


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I have to provide some isolated inputs that accept 12-24V. There should be some protection against reverse polarization, transient over-voltage and permanent over voltage (up to 40V) to some degree.

So far, I came up with the following circuit:

R15+R21 limit the forward current to ~14mA@12V and 30mA@24V
D1 TVS diode (breakdown ~@13V) protects against transients and voltages above ~26V
D1 protects against reverse polarization
R15 limits the current in case of reverse polarization or when D1 is clamping

This design seems suspiciously simple.
Do I miss something or should it work as desired?

EDIT:
R21 was meant to provide some additional transient over-voltage protection (ESD), because the TVS diode won't clamp instantly. This was also the reason for choosing a TVS diode instead of a normal one. Is this overkill?

As pointed out, If was somewhat high. I will consider something more like 580 Ohm for R15 and R21 to limit the current to 10-20mA.

LTV357T


texts: Have separate instructions for each register or pass register as argument?

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I am trying to design a (very) simple processor architecture. I am in the process of creating a basic instruction set for it, however I am not sure of the best ("best" meaning what most people use - to remove subjectiveness) way to implement some instructions.

Take an output instruction for example, and say I want to output register a or register b - there are two ways that I know of to do this: have two different instructions, one for outputting a and one for outputting b, or it could be one instruction and depending on the next byte in memory (argument) it outputs either a or b.

What is the most common, or most efficient way of doing this?

Thanks in advance.

P.S. This is my first question, so if I've done something terribly wrong point it out and I'll try to fix it.


texts:
I am organizing a bunch of components given to me; some of them not put in a labeled bag.

This SMB diode has the marking "1042 MZ" on it and I cannot find any references to this. And I have checked a SMD Code book without finding anything.

I am running out of good ideas :)

Edit:
Applying 1V in forward direction made it hot and conduct 2A.
Slowly increasing the reverse bias voltage with an LED in series confirmed that it is a unidirectional TVS diode starting to conduct at about 70 volts.


texts: Current carrying capabilities of surface mount ICs

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While putting together a PCB project, I have come across the ACS724 current sensor, for measuring AC/DC current in high ranges up to 50 amps. This chip uses hall effect for measurement and is a 'pass-through' type of sensor: No shunt resistor or any other external circuit is used for sensing.

Now here is where it gets amazing: This chip comes in 8-pin SOIC package! For those not familiar, this is very very small. So I started looking for information about the SOIC package standards, but couldn't find anything relating to electrical capabilities, only dimensions. Using the chip involves thermal management but still, I have a hard time believing that a single pin on an SOIC package can handle 25 amps?!?

Does anyone know where to find electrical data on surface mount packages?
Does anyone have advice on using such a chip in a circuit, without causing some havoc?


texts: Clean/repair/replace the carbon pill of a rubber keypad

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I have several devices (calculators, remote controllers, …) with rubber keypads where some keys are dysfunctioning. As I understand it, this is because of the carbon pill since things work fine if I use something in metal to make an electric contact…

Is there any way to repair this at home? In the past, I tried to clean the carbon pill with alcohol, with no significant success. So is there a known-good way to clean, repair or replace the carbon pill?

EDIT: Here is a photo of the rubber keypad:


texts: Operational amplifier used as a current source

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As a laboratory task at my practical engineering school we were asked to make the simple circuit shown below, prove that it acts as a constant current source regardless of its load, and answer some questions.

One of these questions is: what limits the amplifier? Why would its output stay at a maximum value (clamp?) above a certain load resistance?
Another one is: Why is it necessary to supply the amplifier with a dual-supply? Wouldn't single-supply voltage work just as well?

Theoretically it should be able to supply constant current on R, which is the same current on the load, therefore the voltage should not be limited.
I couldn't find an answer other than the fact that the amplifier has a power limit it cannot go beyond, but I am unsure as to whether that is the answer they are looking for.

Vcc=15v, -Vcc=-15v, R1=R1=5KΩ, R=1kΩ, RL=1kΩ
LM324 datasheet: http://www.ti.com/lit/gpn/lm324


texts: I am after a better specification of fuse than is on the board of a daikin split air conditioner

texts:
I picked up a couple of scrap daikin split Ftxs60bvmb
The fuse on the control board is dead but it only says 3.15a 250v
Is this a ceramic slow blow/ anti surge or a fast blow fuse?


texts: Do hardware designer consider software(Firmware or drivers) while designing hardware?

texts:
I like to know what's the procedure of building a new device? Foe example a hardware designer decides to make a new laptop that can run Windows or Linux, or someone wants to build a new Android device, he choose a proper CPU and other parts like RAM, graphic card, sound card, Wi-Fi, Bluetooth, Storage, LCD, etc.

But what about firmware and drivers?

Totally I like to know what software consideration should a hardware designer has to build a new device?

Simply, in Desktop computer, we buy the parts separately(mother board, graphic card, sound card, LCD, CD/DVD ROM, etc) and do not have huge concern and special consideration to choose(maybe only thinking about they communication protocol SATA, IDE, PCI ports, etc).

But what when we like to make a laptop or Android tablet? Should we write any low-level code for these or we only put the parts beside each other and build a new device?

For example, when DELL company wants to build a new laptop, it chooses the intel HQ6700 processor and Geforce m960 for graphic part and etc. so should DELL write any low level code when doing its laptop?

Or when Samsung wants to build a new tablet or smartphone, and wants to use Qualcomm snapdragon chipset, and other parts like bluetooth and wi-fi IC's, should Samsung write any low level code for building its new device? If yes, in which part and for what reason?

I see many Chinese company they build tablets and smartphone and heard they are little groups at their home! Is it true or lie? If true, how they can do this? amd what exactly they do? are they write low level codes? or even do designing hardware?


texts: Building a temperature-controlled water bath

texts:
I want to build an accurate (±2 °C) water heater (sous vide) that heats water somewhere between 30-100 °C according to user input.

Although I have an engineering background I have no experience whatsover with building controllers and have no clue on how to start. I don't want to spend to much money on the project (< 100 €) thus money is an issue. The good thing is that I already have a power thyristor.

What I (probably) need:

Temperature sensor PT100
Input device to define water temperature (digital?)
Controller (PID?)
Resistor to heat the water (can be taken from old water cooker I assume)

My question is how I can best make the link between the sensor and the heating element. I of course need to build/program a circuit that does this but do I make an analog or digital circuit?

I have a thyristor but is this really necessary or should an on/off regulation also work? Don't forget that I also should be able to define the water temperature.

Any help is greatly appreciated (also useful links).


texts:
I read the answer here Difference between latch and flip-flop? which says that the only difference is flip flops need clock and the output of latches don't depend on clock.

I am reading Morris Mano book on digital logic which clearly says that " latches are level sensitive devices or level triggered and flip flops are edge triggered devices" which means latches also depend on clock.

Now which one is correct? Can someone please explain it clearly?


texts: Bireciprocal lattice wave digital filter

texts:
I am trying to model a bireciprocal Cauer filter in LTspice but I don't get the expected results. More precisely, using

\$\gamma = \frac{re(p_i)-1}{re(p_i)+1} \$

where \$re(p_i)\$ is the realpart of the pole, gives this result:

Among the few references, one that gives a numerical example is a thesis, "Design and Realization Methods for IIR Multiple Notch Filters and High Speed Narrow-band and Wide-band Filters, L. Barbara Dai" and, simply by looking at the numbers and comparing them with what I had, it seemd as if the poles need to be "normalized" to the single real pole, \$p_{\frac{N+1}{2}}\$. That's what I did:

\$\gamma = \frac{\frac{re(p_i)}{p_{\frac{N+1}{2}}}-1}{\frac{re(p_i)}{p_{\frac{N+1}{2}}}+1}\$

so, even if the numerical values still differed, but a not as before, I got this result:

The example used here is not the one used in the thesis, but I seem to get good results (I cannot verify them) with either stop-band, or transition-band optimizations and for any (odd) order.

So, my question is: is this the way to do it, "normalize" poles by dividing each to the single, real pole?

[edit]

Just for the sake of comparison, here is a comparison using the same settings as in the thesis (\$As=68 => Ap, \omega_s=\frac{2}{3} => \omega_p, f0=2\$), between a normal Cauer IIR filter (V(o3)), Barbara Dai's non-quantized coefficients (V(o1)) and the my coefficients used with the "normalizing" described above (V(y1), \$ \gamma_1=-0.0912405, \gamma_2=-0.3412645, \gamma_3=-0.729655 \$):


texts: Complex power calculation across parallel loads

texts:
I have the following problem which require the calculation of Load L3 apparent power, real power and reactive power.

I have done the following as the described in the figure trying to get 2 equations of 2 unknowns but got to a dead end

how can i proceed with such problem with small information the global power factor is also giving but with no details on whether it is lagging or leading. i assumed it is lagging since L1 and L2 are inductive loads based on the description


texts:
I previously asked a question about how KVL is used in node analysis. I'm betting that KCL is also used in mesh analysis.

Could someone explain if and how KCL is used in mesh analysis?


texts: I salvaged this a transformer from a small 12v battery charger, it has 8 pins, four on one side have continuity one with the other, four on the other are two separate circuits, hope someone can help identify it and how to determine input and output, thanks


texts: Latching/Non-Latching Relay Driver Circuit with darlington optocoupler

texts:
I'm designing a circuit where an ESP8266 controls two types of relays, a single coil latching relay and a normal non-latching relay. The relays are power relays use to control low power electrical appliances such as lights and fans. As the relays will be controlling 240V AC lines, I want to design a driver circuit with optocouplers to isolate the ESP8266 from the relays. Based on my research I have come up with a driver design for each type of relay as shown below.

These are the components that I'm planning on using :

Non-Latching Relay (G5SB-14 DC5)
Single Coil Latching Relay (SCHRACK PE014F05)
Darlington Optocoupler (MOCD223R2M)

This is pretty much the common driver circuit for a simple non-latching relay. However, most driver circuits wire the optocoupler to another transistor which then drives the coil. Since I'm trying to save some space I was wondering if its possible to use a darlington optocoupler instead which can handle the high currents from the relay coil?

simulate this circuit – Schematic created using CircuitLab

I'm not very confident with the driver for the single coil latching relay as its not very common. Hence, will this circuit work? Will the lack of diodes cause any long term effect to the circuit?

simulate this circuit

I'm hoping for this circuit to be able to last long and be durable. Any kind of advice and help will be much appreciated. Thank you in advance.


texts:
I have a question regarding the AC circuit shown below. If we ignore the voltage drop caused by the long cable, I think the device will work and the circuit can be considered as a closed circuit.

Now I am wondering about how the electrons can return back to the source to form a closed path and so a closed circuit!?

As it appears, there are 1000 of Kilometers between GND1 and GND2, or we can say that there is infinite value of ohms (resistance) between the two grounds. So, where is the closed path for the electrons flowing?


texts: Why don't I see the esp8266 chip in many commercial products?

texts:
I am a bit of a novice in the field of RF design, and I was looking around for an RF module to use in a project.  I kept on noticing the ESP8266, which is pretty popular with hobbyists, but it's something that doesn't seem to be used in commercial products, and I can't buy the chip by itself from big suppliers like Digikey or Arrow.  Why is this?

Also, I noticed that the assembled esp8266 module has way fewer passives on the antenna output from the chip than other boards.  How can they do that?  I didn't think that on-chip inductors could be large enough to meet the requirements of rf designs.


texts: Meanwell SMPS voltage regulation, changing the Trimmer (LRS series)

texts:
I needed a 19V-20V source so I ordered some 24V LRS series SMPSs but they offer 10% adjustability, the voltage range just below that is 15V, the adjustability is also the same there. So none of them is going to provide me with the desired voltage range.  I am wondering if there is an option to widen that range by changing the Pot or trimmer.
Unfortunately, I have neither the product nor the full datasheet (no circuit diagram there only block diagram) to check the amplification from the voltage divider.
I need a suggestion if changing the pot will affect the controller-IC / O.V.P  or void my warranty. I don't want to use any buck-boost converter as that might introduce more ripples, and yes some diodes could be added to benefit from the forward voltage drop but that's a crude solution I hope there is something better.


texts:
I am an ultra newbie, so please excuse my design/drawing here and I am sure my terms are not correct, but I want to learn. Here is what I am trying to do and a diagram. I think I got it right, but would love some advice.

Object: To turn on a light and have it turn off automatically after a period of time by a time delay relay.

Ground: Power Source Negative (green) to negative on relay. Lights Negative to negative on relay.

Power: Power Source Positive (red) to positive on relay through a button. Jumper from positive on relay to common on relay.

Button: Momentary Push Button making the initial connection.

Lights: Positive on lights (red) connected to first terminal on time delay relay. After an amount of time, this terminal is switched off and it defaults to turning on terminal 2 which will not be used.

Latching: Both connectors on momentary push button (blue) latched to terminal 1. This is to create a by-pass creating a latched connection to allow the lights to remain on even though the momentary push button is released breaking the initial connection.

Relay Reset: Once terminal 1 is turned off, it will sever the latched connection, thus removing all power from the relay resetting it.

My Biggest Questions is, "is the latching going to work when I release the momentary push button and will it shut off power to the relay once connection 1 is terminated once the time has expired??


texts:
Hi new be to this site hope you can help.

I have a 3 phase vacuum pump on the motor plate it says
50 Hz 175-260/300-450. Does this mean if we rewire to star or delta we can use it on 50 Hz 240 volt single phase. I hope you can help, thank you.


texts: What is the value of this 5-band resistor

texts:
The colors are black, light green, green, red and silver (looks more like gray). I am not sure which side to start reading the values from. Both ends seem to be symmetrical.

Moreover, I have never seen light green on any color code charts. i am thinking that the manufacturer might have intended this to be yellow (but I am not sure).

I know the basic color code and have also worked with simple electronic circuits, but, this resistor got me really confused. I looked up various sites to do some research, but ended up with more questions than answers.


texts: Atmega328p resets and crashes when powering up solenoids

texts:
I'm having problems with my PCB board based on atmega328p microcontroller (very similar to an Arduino standalone board).

This is my current PCB schematics and Eagle board.

SCHEMATICS UPDATED!

I use connectors on VSX, VDX, MOT1A, MOT2A, MOT2A, MOT2B to switch ON and OFF solenoid valves (the valves are rated as 12VDC, 2A at max).

The board works randomly fine only for few seconds or minutes until the micontroller crashes or resets and I think this happens due to solenoids noise.

The main power is 12VDC, 35A (used for the valves and the relay) and then I use a 5VDC voltage regulator to power on the atmega328p.

As you can see, I already added flyback diodes across each mosfet, but may be this is not enough to prevent solenoid noise. I also twisted each couple of wires (maximum wire length is 90 cm) which connect the valves pins to VSX, VDX, MOT1A, MOT2A, MOT2A, MOT2B connectors and I added an additional diode in parallel on each valve pins.

How can I solve the problem?
I was thinking to add 100nF ceramic caps between VCC and GND and AREF and GND and AVCC and GND as close as possible to the microcontroller pads and another 100nF cap in parallel on each valve pins.
Do you think it can be enough to solve the problem?

Unfortunately, I think I can't separate the solenoid power source from the atmega328p power source since they are currently sharing the same GROUND.

What can I do to solve the problem by continuing using the same PCB board?


texts: Can flash memory be used in place of RAM in microcontroller applications?

texts:
In my application I'm using a MSP430, however I need to buffer 11kB of data from a UART connection. Obviously the 512B of RAM available is not enough to do this, however the MSP430 has 16kB of flash which would easily do the job.

My basic understanding of flash is that it is used for program code so I am wondering if it is possible to use flash for this purpose?

Thanks


texts:
I've always wanted a network PDU, however they're super expensive. What would be the downside to building one myself with a,

$10.54 SainSmart 16-Channel Relay Module
Arduino with Ethernet, or add on Ethernet shield.

For comparison a network PDU seems to start around $373. Do switched power supplies have more complex hardware that does something special? Or, is that all there really is to it?


texts: Which Type of IC is this one ? what is its function


texts: Measuring average DC of pulsed analog signal

texts:
I'm trying to measure average DC level of pulsed analog signal. The pulses have minimum pulse width of 10 us and amplitude of max 5 V. Pulses are somewhat gaussian shape and have very random height spectrum. See image for sample of pulses:
Less pulses is lower DC level and vice versa. Sample time of around 1s is desired. I was thinking to use some ADC with high enough sample rate so that every pulse gets ~10 samples which equals 1 MS/s. MCP33141D-10 has 1 MS/s sampling and 12 bit resolution with integrated data accumulation. It can only accumulate and integrate 1024 samples so the sample time is quite low but maybe I can live with that.
I was also considering using a RC circuit to smooth the pulsed signal and then using some low frequency ADC to convert the DC to digital. Raspberry Pi is used for data acquisition so a SPI or I2C bus is desired.
Pulses are produced from two stage transimpedance amplifier where the second stage would be driving this ADC. Second stage is OPA847 which can source ~50mA, gain of 15 - 20 V/V is used in there.
I don't have too much experience with ADCs so what would be the best method for this DC measurement and conversion?


texts:
I am designing a PCB for a Numitron clock. It is just my own project, not for a company. The milling machine at school can only deal with 16mil+ sized traces, so I have some troubles routing traces between IC pins, for example. I must also note that I can only have 2 layer PCB's made at school. I have attempted to route the board several times now, but I always hit dead end, because something always crosses another trace. If I were to introduce vias, that would make things a lot easier, although the PCB would not look as nice, because I would have to connect it with wires externally.

My question is - are vias an acceptable solution, or is it a last resort? I imagine that in real life each via increases production cost, and that is a part of PCB design considerations, but what other pros and cons are there to vias?


texts: What is the purpose of using only the coil of a relay?

texts:
In these two examples:
http://www.electronicecircuits.com/electronic-circuits/cd4060-timer-circuit-1-minute-to-2-hours/comment-page-4#comment-48679
http://www.zen22142.zen.co.uk/ronj/24hs.html
A relay is used to, well ...
...Why are they used?
Exluding the relay doesn't seem to change anything but the nice click sound.


texts: Using rectifier + inverter to get 50Hz AC output

texts:
I am currently in the theoretical (until I am very sure that it is safe) situation that I have an alternator powered by a gasoline engine that provides 220V 1500W AC power with RPM dependent frequency. My goal is to get this into 50/60Hz AC (also 220V). I do have a 24V -> 220V 4kw inverter that would be capable of converting back 24V DC to 220V 50ish HZ AC. I also have 8AWG cables that should be able to handle the roughly 60A that 1500W would be at 24V DC. My problem now is, I am really confused by the rectifiers I find online. I am not really sure how to select the right one. It should be able to rectify high frequency 220V AC to 24V DC (is this even possible? Or will it be 220V DC?) and obviously in theory up to 1500W.
So essentially my target setup would be:
220V AC generator (not 50Hz) -> rectifier 24V DC -> inverter 24V DC to 220V 50Hz AC -> utility
Is this possible and how do I find an appropriate rectifier that can handle this? Simply searching for rectifiers I found for example this: https://www.amazon.com/Aodesy-Bridge-Rectifier-Module-MDQ100A/dp/B07N3Y6LVN which apparently handles up to 100A at 1600V (160kW?) but it seems so small for that task...
edit: If there are easier/better ways to get the generators variable frequency output to fixed 50Hz output I am open to that!


texts: Ignore Pulses Less than a Given Width in a Pulse Train

texts: Let's say I have a 5V pulse train that varies between 0 and 75000 pulses per second. Pulse width, let's say, is 5 microseconds. How could I calculate or determine the best way to filter out all pulses less than 4 microseconds in width?


texts: How to display a double digit decimal value on a seven segment display?

texts:
I recently finished a 4 bit adder project and I wanted to "extend" it.Right now,the output is represented by 4 led's(1 for each bit).I want to display the answer as a decimal in a seven segment display.The biggest value that the adder can output is 15(since it is a 4 bit adder).I have two single digit seven segment displays.I was thinking of using the 74ls47 chip to do the binary to seven seg conversion.Here is the datasheet for BCD TO 7-SEGMENT CODER/DRIVER

How do I check to see if the addition output is a double digit number?Using this information, how do I "tell" the binary to seven seg converter, that it is double digit?Do I need two of these chips?My final question is:the biggest decimal a single digit seven segment display can represent is 9. When the 74ls47 gets an input greater than this it starts display jibberish:( I got that information from Using the 74xx47 BCD to Seven-segment display.

How would I prevent the jibberish from getting displayed(basically I need a way to check if the output of the addition is 10 or greater.)

Sorry about all the questions this is the first digital logic circuit that I have made.


texts: I am trying to use a MOSFET as a switch for my LEDS. I have 6 LEDS in series connected from 9V to gnd and for the gate of the mosfet i will be connecting from a microcontroller. This will be providing 1.5-5.5V. Just asking will this mosfet work well? IRFZ44R Data sheet


texts: Making a clock cp for counter, using a photodiode

texts: I need to make a device that counts light impulses, basicly a light detector counter, i need help with my counter cp, how to implement a photodiode(can't find phototransistors in the stores) to do clocking, do i need a IC 555 timer, or can i just use an common transistor and use photodiode as base current of the transistor? im using a 7493 counter a 7447 decoder and BPW 34 photodiode.


texts:
http://forums.benheck.com/viewtopic.php?f=18&t=38664

In the link, there is a thread discussing replacing gen 1&2 Pokemon cart sram ICs with fram equivalents. The only differences between old and new ICs (besides architecture) is the operating voltage, so they leave Vdd floating. Isn't this a Very Bad Idea?


texts: What is the use of this 2-digit 7 segment display

texts:
I just came across this weird device while searching for a 2-Digit 7 segment display with an inbuilt BCD decoder. This is because I am using an MSP430G2553 with limited number of GPIOs with few ADCs & GPIOs used for other purpose & I want to keep the footprint as minimal as possible by avoiding separate BCD decoder IC.

Following are my questions,

In which scenario will this particular 2-digit 7 segment display be useful? Both digits would be displaying identical numbers!!.
http://www.taydaelectronics.com/datasheets/A-756.pdf
Are there any 2-digit 7 segment displays with inbuilt BCD decoder?


texts:
I'm working on a project about electricity pricing, and need to understand the following: to keep the room at confortable temperature (70 degree, for example), does the amount of energy consumed by the AC grow linearly as the outside air temperature rises over the same length of time (a day, say)?

Thanks!


texts: Why specifically use a MOSFET and Schottky diode on a buck or boost converter and not other transistors or diodes?

texts:
My electronics professor is currently teaching DC-to-DC converters. He decided to drop us some theoretical homework and just postpone the experiment. He gave us some questions. This is one of those that I need more insight on.

Reference: https://www.electrical4u.com/buck-boost-converter/
I don't have quite a good grasp yet on the topic but I do know that buck converter causes a step down in the output voltage while boost converter causes a step up in the output voltage.
I am aware that a MOSFET and Schottky diode is used for the buck or boost converters. I am not sure if they are the only specific transistor and diode used. But if they are or if at least they are the common type, why is it so? Honestly I've already seen some answers in other websites but I would love to ask it here as well since the answers constructed here can be really insightful.
What I've read is that MOSFETs are used because they are switching transistors and Schottky diode is used because it allows higher switching speeds. I just mentioned this because I don't want to sound like I'm literally asking for my homework to be done without any effort. I just put this here so that I have at least some input.
Edit: Here is a more accurate basic buck topology.


texts: Is there an inexpensive way to get started with GAL (Generic Array Logic) chips?

texts:
GAL chips seem expensive to get started with, since programmers cost hundreds of dollars and even ISP cables aren't cheap.

Is there a cheaper way?


texts: Small 'blistering' under surface-mount soldering attempt - is this a problem?

texts:
I am very new to SMT soldering - and have started with a small project.

I used resin flux, followed by a small amount of solder paste and then a hot air gun at around 373 degress celcius to flow the solder onto the pins.

I appreciate the images are not zoomed in enough to let you see if there are any bridges (I can assure you - there are not!).

The top side of the board looks like this (right hand edge of board when oriented the way you read the text is where I began - and where the blistering shown below sits under :

The under side - looks like this - it is this area where it looks like 'blistering' on the purple dye of the board has happened -- see near C78.  Is this normal? Is this due to poor soldering flow? How can I avoid this - other than continually moving the hot air gun and potentially turning the temperature down a bit? :

It turns out - its on this edge where I started so unsurprisingly I had multiple bridges to fix which I think may have caused this. Is the board damaged do you think, or will it likely survive through this early inexperienced attempt?


texts: Fourier series coefficient for sin(wt+theta)

texts:
Am trying to find the Fourier series coefficient ck for the following function
\begin{equation}
x\left(t\right)=\sin\left(wt+\theta \right)
\end{equation}
Here is my work
\begin{equation}
c_k=\frac{1}{T}\int_{-\frac{T}{2}}^{\frac{T}{2}}\:x\left(t\right)e^{-jkwt}dt
\end{equation}
Now x(t) can be written as
\begin{equation}
x\left(t\right)=\frac{\left(e^{j\left(wt+\theta \right)}-e^{-j\left(wt+\theta \:\right)}\right)}{2j}
\end{equation}
However:
\begin{equation}
c_k=\frac{1}{T}\int _{-\frac{T}{2}}^{\frac{T}{2}}\:\frac{\left(e^{j\left(wt+\theta \:\right)}-e^{-j\left(wt+\theta \:\:\right)}\right)}{2j}e^{-jkwt}dt
\end{equation}
would look very messy and am ending up with 2 sinc functions for my answer that I don't even know what do with. I can't put all the steps here but if somebody would steer me in the right direction I would really appreciate it.


texts: AC-coupling capacitor destroys output signal?

texts:
As you can see I have designed a simple buffer circuit with a current source. The output is nice and steady as you can see (\$V = 2.6+1.6\sin(2\cdot\pi\cdot 1000\cdot t)\$ is the input, frequency of 1kHz). The current source provides 1mA.

However, when I add a capacitor between the output node and the 8-ohm resistor to function as a dc offset remover, the output gets defaced. The value of the capacitor I added was 1 microfarad.

At first I thought maybe the capacitor and resistor form a high-pass filter on the output node and that's why my signal got distorted, but changing the value of capacitor absolutely did not help and my output was still distorted. This is the output for a 2microfarad value.

So I wanted to 1) ask about the reason for this, since I've been using coupling capacitors at the output of my circuits and never had this problem before, and 2) is there any fix to it? That 8-ohm resistor is actually a speaker, and thus no dc offset should be applied to it, is there any alternative dc-offset removing methods I can use in my circuit?


texts: Why refresh rate is needed in a passive-matrix LCD

texts:
In a passive-matrix LCD we have horizontal and vertical conductors. The intersection points are pixels which are cells of liquid crystal molecules.
For drawing a frame, we provide the necessary voltages to specific conductors. But once we have provided the voltages and the picture has been drawn on the screen, why do we need to refresh?
As long as the voltage is on the picture is still there; it's not like a CRT where the emission from phosphorus atoms decays. If the reason is video or animation, then we are changing the frame buffer and then drawing the new frame buffer. But do we need to refresh the same frame buffer at some rate? If so, why?


texts: Removing collected charges in a IC CMOS circuit exposed under a 30keV electron beam source

texts:
I would like to know if there is any mechanism (for example UV light exposition) to remove charges collected in an IC CMOS circuit that was exposed under a 30keV electron beam source. Presumably, those charges were collected in the MOS oxides.
The CMOS circuit is a photodiode-based Image Sensor and some pixels appear as always illuminated.
Thanks in advance.


texts: How to realize this transfer function with OP-AMPs?

texts:
This is a homework question.

I know that: Given a transfer function of \$H(s)\$ below, we can realize it with an OP-AMP as follows.

\$H(s)=-\dfrac{2}{s+2}=-\dfrac{\dfrac{1}{2}}{\dfrac{s}{4}+\dfrac{1}{2}}=-\dfrac{Z_f}{Zi}=-\dfrac{\dfrac{R_f}{R_f*s*C_f+1}}{Rin}\$

where \$R_{in}=R_f=\dfrac{1}{2}\Omega\$ and \$C_f=1\text{F}\$

However, now that I have to realize a transfer function with complex numbers, I am puzzled on how to do so. Could you lead me to the correct direction on realizing the following transfer function using OP-AMP(s)?

\$H(s)=\dfrac{1}{s + 0.383 + j*0.924}\$

Above equation is a part of:

\$H(s)=\dfrac{1}{s^2 + 0.765*s + 1}=\dfrac{1}{s + 0.383 + j*0.924}*\dfrac{1}{s + 0.383 - j*0.924}\$

Note: In the big picture, I have to realize a HPF of 4th order using cascaded(serial) decomposition method. Normalized transfer function of the filter is given as:

\$H(s)=\dfrac{s^4}{s^4 + 2.613*s^3 + 3.414*s^2 + 2.613*s + 1}\$

This can be written as:

\$H(s)=\dfrac{s^2}{s^2 + 0.765*s + 1}*\dfrac{s^2}{s^2 + 1.848*s + 1}\$

\$=\frac{s}{s + 0.383 + j*0.924}*\frac{s}{s + 0.383 - j*0.924}*\frac{s}{s + 0.924 + i*0.383}*\frac{s}{s + 0.924 - i*0.383}\$


texts: Transmission Line: characteristic impedance matching

texts:
The textbook explains a situation in which when you have 2 unmatched transmission lines (different characteristic impedance), you can connect a new line in between such that the input impedance would match.

Say I have a line #1 with characteristic impedance \$Z_1=100 \Omega\$.

Line #1 is connected to Line #3 with \$Z_3=20 \Omega\$. There is mismatch and therefore reflection.

If I connect another transmission in between and its length is the quarter wavelength, then this new transmission line (we call it Line #2) would match the characteristic impedance of Line #1.

\$ Z_2=\sqrt{Z_1\times Z_3}=\sqrt{100 \times 20}=44.7 \Omega \$.

\$Z_{in}=\frac{Z_2^2}{Z_3}=\frac{44.7^2}{20}=100 \Omega\$.

Thus, overall input impedance at the junction of Line #1 and Line #2 \$Z_{in}\$ would be equal to \$Z_1\$. Therefore, no reflection at this junction.

But my question is: what about at the junction of Line #2 and Line #3? Since \$Z_2=44.7 \Omega\$ is not equal to \$Z_3=20\Omega\$, then there will be reflection at their junction? If that is the case, what is the point of using matching?


texts:
I have an STM32 board I am currently designing which is going to use the USB bus for communication and programming. The ground connector on the USB will be tied to the board ground, and the D+ and D- lines will go to the STM32's USB_DP and USB_DM with a pull up on the D+ line to signal full speed.

What I want to know is what to do with the USB VBUS line. I have no need for the board to be running off of the 5v USB power, it will always be connected to an external power supply. However I have read that the VBUS line may be important for communications, so I do not want to leave it floating, as that may make the communications inoperable.

What is the best thing to do with the VBUS line in a situation like this?


texts:
I have been attempting to create a portable arduino gaming system. While I have tried normal 'AA' or 'AAA' batteries, they are too large, so have decided to use a lipo battery. I now have this, but I would prefer to be able to recharge it without removing the battery, so need a charging board.

I have contemplated using the sparkfun single cell charger with a place for system out power (to the actual device), but it costs much more than I want to spend (it can be found here on Amazon: http://www.amazon.co.uk/LiPoly-Charger-Single-Cell-Input/dp/B004X7TZ9I/ref=sr_1_2?s=electronics&ie=UTF8&qid=1404232239&sr=1-2&keywords=sparkfun+battery+charger). I would like to use a very cheap generic board to charge the 3.7v lipo battery, but my question is: Can I embed this in my project and charge the battery without removing it.

My desired charger board can be found on Amazon here: http://www.amazon.co.uk/Generic-Lithium-Battery-Charging-Charger/dp/B00E39RGME/ref=pd_cp_ce_0

Thank you for any help!


texts: Simple logic circuit to filter out the even numbered pulse?

texts:
I need a logic circuit to have a function as shown in the figure:

An input signal applied to the input end, I want it to only output the odd numbered pulse and output 0 for the even numbered pulse. To simplify this question, assume the input signal is periodic.

I have looked up, and found divide-by-N circuit which is relative, however, the pulse width is doubled in this example.

So my question is is there any way we can design a simple logic circuit to fulfill this function with basic logic circuit, or is there a way to just use the divide-by-N counter and keep the pulse width same?


texts: What size wattage resistor do I need for this project? Does resistor wattage matter in this case? (Wiring schematic picture included!)

texts:
What I am doing is I have cut off some bulbs off a string of incandescent Christmas lights. However, now I need a resistor for it so it doesn't blow the bulbs out.

Without a resistor, within a few minutes it blew all the bulbs on that half of the string, and now I understand the reason is because the bulbs I removed caused a greater load to be placed on the remaining bulbs.

I am almost done, and I even soldered the resistor onto the string properly.

However, because of the following two factors, I believe it is the wrong resistor, perhaps because I need a resistor to handle much higher wattage, per my speculations.
* resistor got too hot immediately
* bulbs were too bright like without any resistor, indicating the resistor was not taking the load as expected.

Now, keep in mind that not only am I just trying to have good Christmas lights but also I am doing this as a learning experience. Obviously I could just take it down and use an unmodified string, but I want to learn so that is why I want to use the resistor.

Here is my diagram:

Project details:

I removed 27 bulbs from a 100 bulb set, from one side.

You can see in my diagram how these lights are wired.

The Math (my math is wrong, see below*):
So I did all the math, and I know all the variables I need for the project.

1.2v x 27 bulbs = 32.4 v
.408w x 27 bulbs = 11.016 w
amps = 0.34 a
ohms (Ω) = 95.29412 Ω*

>>>> *NOTE: Math is wrong, see update below. Keeping this here for reference.*

(NOTE: I calculated ohms using online calculators. I used this one: http://www.ohmslawcalculator.com/ohms-law-calculator. I also double-checked using other online calculators, with the same result.)

Ok, so according to the radioshack guy, all I needed was a 100 ohm, 1/8 w resistor, he said there is no need for a bigger wattage.

So I went and soldered on a 100 ohm, 1/8 watt resistor, but I noticed that first the bulbs were too bright like before, so it seemed like the resistor wasn't taking the load as expected. Second, the resistor got immediately so hot it burned a hole through the electrical tape within seconds.

So I unplugged immediately and now I am researching the correct solution.

I am wondering is if he had no idea what he was talking about and if in reality, I needed a 100 ohm, 11+ watt resistor?

Also from searching the web I read that a standard is to get twice the wattage of your needs for the resistor.

I have also already done all the connecting, testing and soldering. I just need to know which is the correct resistor to use for my project. Once I have that I can just attach it in place of the wrong resistor and then everything should work!

Please let me know if I need the 100 ohm, 20 watt resistor, or if not which is the correct resistor.

Thank you in advance!

UPDATE:

Ok, so commentors are saying that due to the KVL law of physics, actually it is not 120v split evenly into both strings.

Instead, it is 120 v into EACH string. This changes things.

Also another answerer said that amps is split among the parallel circuits. So looks like I had it backwards originally.

New formula:

120v / 50 bulbs = 2.4v per bulb
2.4v x 27 bulbs = 64.8v for the 27 bulbs.

2.4v x 27 bulbs = 64.8v v
0.34a/2 parallel circuits = 0.17 a
watts = 11.016 w
ohms (Ω) = 381.17647 Ω

So in this case, does this mean that I actually need:

~381 ohm, ~20 watt resistor?

(~ means here "around" since an exactly 381 ohm resistor doesn't exist.)

(20W because 11W is needed and due to research good rule of thumb is double wattage needed)


texts:
I am designing an inverter for a project. The main focus of the project is to design a standalone inverter that is able to produce variable voltage output.
A secondary aim is to have the system solar powered.

I want to understand how to vary the output voltage of the inverter to match the voltage requirements of the connected load. Some AC loads have different voltage ratings.  e.g in South Africa, voltage rating of AC loads may be 220Vrms, 230Vrms or 240Vrms. I realise that it will usually be possible to set the inverter output to a compromise voltage but in this case, designing a variable output voltage inverter is a specific aim.

So, the main question is, how will I vary the output voltage from the inverter to match the load connected.


texts: KiCAD: Cannot see traces on a PCB side which has been filled with copper

texts:
I made a bottom side copper fill.
Then I drew traces on the back side, coming from the top side copper. (Top side copper trace -> via -> Draw Trace -> via -> Back to top side trace drawing.)
When I hit v in order to see the bottom side traces, I see no traces, just a huge green zone.

However, the amount of unrouted traces goes down.
Why does this happen?
How can I see the bottom side traces?
I thought I should be able to see something like this:

This is coming from the 'Getting to Blinky 5.0' KiCAD tutorial series.
NOTE: I am using JLCPCB design rules, coming from this template:
https://github.com/sethhillbrand/kicad_templates
EDIT: This is my layers manager:


texts: HC-SR04 ping sensor cutting out at ~3 meters

texts:
I have some HC-SR04 ultrasonic sensors that I purchased from eBay not long ago. I hooked one up to an Arduino and wrote a quick sketch to test them, and found that none of them work consistently.

It seems that they all stop working when the distance gets too large. I can turn on the Arduino and I hear the sensor clicking while it is pointed at the ceiling ~1.5 meters away. When I turn it towards the other end of the room ~3 meters away, though, the clicking stops and the pulsein() method times out and the distances read 0 cm. Pointing the sensor back at the ceiling does not solve the problem, power must be cycled. I Actually discovered that flicking the sensor can sometimes get it to work again as well, without cycling the power. I searched for people having trouble with the sensor but no one seems to have the problem I am having.

EDIT: I have done some more experimenting and I now think there must not be an internal timeout when a 'click' is sent and not received. The sensor works when aimed at solid surfaces as far as 3 meters away. It stops working in two cases: aimed out a door or aimed at a soft surface. The documentation on the sensor says that it has a range of 4 meters and doesn't work well on soft (sound absorbing) surfaces. My guess is that in these two cases, an echo is not heard at all. The sensor is then stuck waiting for an echo. Flicking it creates the echo it was waiting for and it resumes until another echo is missed.

There are three ICs on the board: an amplifier, a max3232 level shifter, and an unidentifiable one. My guess would be that the third one is some sort of micro controller, so I may try reprogramming or replacing it. Any input on that would be appreciated, though it looks like I answered my own question to the extent possible.

Here is the code I am using. I have triple checked all of the connections and the fact that it works briefly suggests that they are indeed correct.

const int trig = 3;
const int echo = 4;

float elapsed, distance;

void setup() {

  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);

  Serial.begin(9600);

}

void loop() {

  digitalWrite(trig, HIGH);
  delayMicroseconds(20);
  digitalWrite(trig, LOW);

  elapsed = pulseIn(echo, HIGH, 1000000);
 // timeout in microseconds

  distance = elapsed / 58;

  Serial.println((String)(distance) + " cm");

  delay(500);

}


texts: Power Consumption for BLE advertisements

texts:
I have a set of voltage readings that are read at a high rate and they have produced voltage data for power consumption while: advertising events, for connection events, and for no activity. I've produced graphs that I've attached at the bottom of this post.

I'm now tasked with things I have no idea how to accomplish.
1. Graph the power consumption for a connection event with a variable which is the number of advertisements it took before we connected (1 to 1000 advertisements, Y axis in uA/hour). 2. Do the same for a case where the sensor had a “bad” connection and had to reconnect N number of times.  Maybe use N = 1 through 5 and add the plots to the same graph.

I'm not sure how to approach either of these as I barely understand what they mean (as I'm not familiar with bluetooth to begin with). Can someone potentially dumb it down for me (and relate to the graphs I have) so I can get an idea of how I can approach it? Thank you.


texts: How to activate FP6293 converter from EN pin?

texts:
I'm making a portable device which is powered by a lithium battery and boosted with a FP6293 boost converter IC. I want to turn on and off the device from a switch that activates and deactivates the FP6293, I know I can do this from the EN pin, but the documentation is not really clear in that aspect:

Following the application circuit, the EN pin is directly connected to the power input (VIN), so I guess the boost IC activates when Vin enters the circuit. Can I put a switch between the Vcc and EN pin to activate and the activate the IC to I can control the shutdown and power up of the device? I don't know if I should put a resistor, connect it to the ground, the documentation is really poor in that aspect...

Here is the datasheet I'm using: https://datasheet.lcsc.com/szlcsc/Feeling-Tech-FP6293XR-G1_C83576.pdf

Thanks for your attention.


texts: What's wrong with my RC circuit transient simulation in Cadence Virtuoso?

texts:
I am trying to do a simple RC transient simulation in Cadence virtuoso. Please see the circuit below:

I am trying to see the transient current and voltage of the capacitor being charged,however I got the following simulation result:

where /net3 is the capacitor voltage and CO/plus is the capacitor current. This looks totally incorrect, and I have my simulation configuration as:

Could anyone help me figure out the issue? Thanks!


texts: Find the power of the real current source?

texts:
I am asked to find the power of the real current source I1:

For that I would need to know the voltage of I1, and I want to find the  Thevenin equivalent for the rest of the circuit. Now in my textbook it says that I can apply this theorem to replace some part of the circuit between "two points" A and B, however here I'm not sure where to put A and B, my assumption was that since I1-R4 are in parallel the Voltage/Potential between them is the same so I can do something like this:

simulate this circuit – Schematic created using CircuitLab

And now just find the Voltage between A and B using nodal analysis (also Rth), are my assumptions correct?

After which $$P_{Ig}=U_{Ig}Ig-\frac{U_{Ig}^2}{R_4}$$


texts: Using a transistor for interfacing different voltages

texts:
I have some solenoid valves that I want to drive from a little beaglebone gpio. The beaglebone is a little ARM based microcontroller.

The gpio on the beaglebone outputs 3v3, and the beablebone itself runs on 5V. The solenoid valves run on 12V. I have some 2n2222a transistors and I thought there was a way to use these to run the 12V devices from the 3v3 GPIO in open collector mode (http://en.wikipedia.org/wiki/Open_collector). What I'm confused about is what this circuit should look like.

I know I need to hook the positive of the 12V supply up to the positive end of the solenoid valve. Then, I think I should hook the negative side of the solenoid valve up to the collector of the transistor. The gpio connects to the base of the transistor via a resistor, enabling me to use the transistor as a switch on the 12V line.

What I don't understand is:

1) Which ground should the emitter of the transistor go to? The one for the beaglebone (which comes off the 5V supply) or the one on the 12V supply?

2) How can I figure out what ohm value of resistor to put between the gpio and the base?

For reference, a datasheet for the 2n2222a can be found here: http://www.csus.edu/indiv/t/tatror/projects/met%20highway%20safety%20project%202010/npn%20transistor.pdf


texts:
I have this error when trying to compile my VHDL code. The purpose of the code is to multiply a 2 bit constant K by some 4-bit number in memory. There are some similar posts here with the same error, but I have been unable to solve the problem even after using those posts. I thought the problem might be I need to make K unsigned, but converting it still gives the same problem. I am stuck, so any ideas are welcomed

    library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity ROM_ent is
       port (CLK : in std_logic;
             RE : in std_logic;
             K : in std_logic_vector(1 downto 0);
             ADDR : in std_logic_vector(3 downto 0);
             RESULT : out std_logic_vector(3 downto 0));
end ROM_ent;

architecture ROM_arch of ROM_ent is

         type ROM is array (0 to 15) of std_logic_vector(3 downto 0);

         constant Content: ROM := (
                  0=>"0000",
                  1=>"0001",
                  2=>"0010",
                  3=>"0011",
                  4=>"0100",
                  5=>"0101",
                  6=>"0110",
                  7=>"0111",
                  8=>"1000",
                  9=>"1001",
                  10=>"1010",
                  11=>"1011",
                  12=>"1100",
                  13=>"1101",
                  14=>"1110",
                  15=>"1111",
                  others=>"0000");

begin

     process(CLK,RE,K)

     begin

          --if (CLK'event and CLK = '1') then
          if (rising_edge(CLK)) then
             if (RE = '1') then
                RESULT <= Content(to_integer(unsigned(ADDR))) * K;  --Gives error, 0 definitions of "*" operator
                --RESULT <= Content(to_integer(unsigned(ADDR)));  --This works fine (but doesnt do what I want obviously
             else
             RESULT <= "ZZZZ";
             end if;
          end if;

     end process;

end ROM_arch;


texts:
I want to protect a MCU (PIC18F67J60) ADC input (0 to 3.3V) against ESD surges.

I have seen different approaches and have some doubt what would be the preferred method. Or possible just pros and cons of each method.

The methods are:

A TVS diode with correct reverse working voltage connected to ground.
Two schottky diodes: one between V+ and adc input, one between GND and adc input.

What to choose?


texts: I am trying to simulate short circuit protection of mosfet.Idea is when current becomes high,voltage across Rsense increases to 0.7v, Hence transistor conduct. Shorting source and gate.But it does not seem to work .Transistor conduct even when resistance is very low.


texts: Power consumption related to cache hit rate

texts:
Studying computer science engineering, I came across this question:

  We place an L0 cache in front of an L1 cache (so a fraction of the
  cache accesses are serviced by the L0 cache instead of the L1 cache), this creates an opportunity to save power. What should be the minimum hit rate in the L0 cache for this organization to save power? (Assume f is the hit rate in L0, and X and Y is the power consumed per access to the L0 and L1 cache, respectively.)

I think it has something to do with the power formula we saw:

\$P = \frac{1}{2} C V^2 a f + I_{LC} V + I_{SC} V\$

But I have honestly no idea how I can relate the cache hit ratio to this. Thank you!


texts: Limit inrush current after emergency stop relay

texts:
I have a power board with an emergency stop (using a mechanical relay). The input voltage is 24V and on the power board I have multiple DCDC converters, some before the emergency stop and some after. See figure below.

When I disengage the emergency stop, there is a sag in my input voltage causing some of the DCDC converters on the input side of the relay to reset. I believe this is because I am switching in a large capacitive load (the DCDC converters). You can see the scope trace below (Yellow: 24V input, Blue: 24V after relay):

To alleviate this issue I have tried

A thermistor which alleviated the issue but my converters after the relay will draw a total of 15A on the 24V line which is quite large for a thermistor, also the wait time after pressing the emergency stop is something I would like to avoid.
A PMOS circuit outlined below however this made no difference on the voltage sag and in fact I ended up blowing up the bottom resistor on the voltage divider. It may be better to move the emergency stop to control the N-channel MOSFET gate which I will now try.

I think the P-channel will work for the high current I need to work with but I am not sure what I have done wrong or if there is a different solution.
Appreciate any hints. If there are details missing in my description, my apology in advance.


texts:
I'm starting a small project involving 3-pole circuit breakers and 3-ph motors. There's this custom built machine with multiple 3-ph motors, each connected to circuit breakers. The purpose of the circuit breakers is only to prevent damage caused by overload of the motors, which in this case, a motor being stuck. I'm trying to build a supplementary system for this machine.

First off, the machine lacks an emergency stop button(you know, that big red button that stays on when pressed). I want to hook the stop button with the circuit breakers so all the circuit breakers are open(tripped?) when pressed.

I also want to make a controller(probably a Raspberry Pi Compute Module in a shielding running Android) which supervises all the other components of the machine. The most important role of the controller would be stopping the machine when a circuit breaker trip is detected.  Currently, a human intervention is needed when this happens(flipping down the main switch, that is).

Other functions of the controller would be: controlling other components of the machine via an RS-485 bus, displaying information derived from sensor data, telling other out-of-scene info(time, weather, news and so on)... all of which are non-essential and supplementary.

QUESTION

I can get all the parts except for this: a 3-pole circuit breaker with DO for circuit on/off status and DI for circuit closure(trip).

Does this thing exist or should I build one from the scratch?


texts: Requirements for using one power supply for multiple sensors

texts:
I am building a 4 leg robot with a Raspberry Pi and 8 servos (Amazon product page).

Currently I have a a 6 V 3A power supply powering the servos through a 5V 5A buck converter and a 5V 2A power supply for the Raspberry Pi.

This set up works great but I would like to lessen the weight on the robot by using one power supply to power both components. I'm new to electrical things and was wondering how do I determine what the power requirements are to power all the servos and raspberry pi with one battery? Do I just need to increase the amps?


texts: Not enough empty space for isolation gap, can a pcb cut works as substitute?

texts:
I have a pcb that needs an isolation gap where no components, pads, taces, or copper must be placed. But due to board space limitation, a cetain area of the isolation gap must have pads in them. This would compromise the isolation.
To get back the isolation specification, I was thinking of placing a slit in that area as a substitute. Because i would assume that air has better insulation than the PCB FR4 material.
In the image below the hight of the gap is 10mm. So i am thinking of placing an air gap of aroun 1-2mm thickness and make sure that the shortest route between pad-pad around that slit is more than 10mm

Am i doing think correctly?


texts: need help identifing IC's and symbols from a diagram

texts:
I am tring to make a circuit and need to purchase the required components but there are some IC's that I can not identify. I tried to google them up but I haven't found anything helpful yet.I also can't understand a few symbols on the diagram, and I want to know what they represent.
the top 3 images are the components.
the bottom 2 imaged are the symbols. what does the green triangle mean? im guessing that the pentagonal blue block is a direct input but i am not sure, also whats the red circle above it?.
in the bottom most image, are the red and blue boxes (with 1 and 0's in them) input as well? and what are the smaller red and blue boxes under them?
thats it for now. i'm sorry if these questions are very basic, i am new to this so bear with me.


texts: How to find the time constant of a water tank control system?

texts:
I've come across a scenario where I have a vertical cylindrical tank filled with water, that has an inlet flow valve and outlet flow valve.

Known values:

Resistance or gain R = 1.5 m^3/min
Area of tank = 2 m^2
Gravity due to acceleration = 9.81 m/s^2
Density p = 1000 kg/m^3

The transfer function for this open-loop control system (I think):
H(s)/Qi(s) = k/ts+1.

I'm a bit stuck on how to get the time constant, a lot of the examples I've looked at are two tanks or the tank is horizontal?

Can anyone help explain if I've got the transfer function right and how to get the time constant? I think I'm meant to use Laplace transform but don't know what variables to use?


texts: Potentiometer/attenuator between amp and speaker

texts:
I have a setup where an amplifier with 2 channels drives four 8 ohms 80 watts speakers on each channel. The amplifier has a single volume knob which controls volume of both channels at once. What I would like to do is add a volume control for both channels separately between amplifier and speaker. This as I understand is not the right way because the potentiometer required will have to handle 80 watts of power, and thats why a volume knob is used at the input of amplifier instead of output. Unfortunately i have to use the setup i described. I have looked into T-pad and L-pad attenuaters/resistor divider.

I would like to know whether I can get some good ones in Europe? I am presently living in Austria, and I really cannot find anyone who deals with it in Europe. Also does anyone have experience/suggestions with controlling volumes of 2 channels separately?


texts: Implementing powerline communication on a battery-fed 12V line

texts:
I was wondering if anybody had any thoughts on whether it is possible to implement powerline communication on a lead-acid battery fed-12V power network.

Characteristics:

voltage: 12 V
Fed by a battery-bank of 3 X 140 Ah, AGM lead-acid, non-spiral
typical currents: 2-150 A
wires: stranded copper 1.5 mm² to 50 mm², PVC isolation
wires for powerline communication: 30 mm²
typical wire lengths: upto 30 m

My worry is two-fold:

will I be able to drive up the voltage in the system to allow communication - or is the battery going to "absorb" it as "charging" current?
how "noisy" is such a network typically in the frequency range of 133kHz? I.e. how strongly am I likely to have to drive it to enable communication? (The system comprises several 12V DC motors, an alternator, chargers, etc.)

For implementaion I am looking at Cypress CY8CPLC10 and similar.

Note:

Neither the wiring
nor the DC voltage for power transfer can be changed.

A different way to understand this question is: "What are the ac characteristics of lead-acid batteries in the 100kHz range?"

Update 1: answer to Russel's questions

required datarate: 500+ baud (I was looking at HART)
yes, cable length is <30 m. The cabling cannot be touched as all cabling was put in when the structure was built. It is too restricted and convoluted to be able to put in any additional cables. IR is not possible due to no line of sight. RF is an option I am looking at but I was worried about interference with radio equipment on site. Though I realise this is a very real possibility with powerline as well...
re filters: due to the high currents I was hoping to avoid putting anything in series with the the power carrying line and rely on the digital filters of the modem ICs
similarly for coupling: at 150A, transformer coupling does not really seem to be a light-weight option. Do you think capacitive coupling is possible here?
re feasibility of brute force modulation: how do you estimate that a few watts will be sufficient? I am worried about the battery just smoothing any modulation I try to put into the network. In DC conditions a SIGNIFICANT load is required to depress battery voltage by 1V. How easy it is to achieve about 200mV at 130kHz is the big question. I was hoping somebody would tell me: "don't worry about the battery: it's response is much slower than 10µs." :-)


texts: Where to measure ambient temperature limit inside of an enclosre?

texts:
In a project, we are to place several components inside of an enclosure.
Some of these components are to be considered safety critical, and their specified operating conditions must not be exceeded. The problem is that most manufacturers specify the maximum ambient temperature for their product, but since it will be placed inside of an enclosure it is not trivial to me where to measure that ambient temperature.

One of the components used is a contactor, Omron J7KN-22D-4, with a datasheet available at: https://assets.omron.eu/downloads/datasheet/en/v3/j06e_j7kn_motor_contactor_datasheet_en.pdf

It specifies two different operating ambient temperatures:

Maximum ambient temperature, open:     -40°C to +60°C
 Maximum ambient temperature, enclosed: -40°C to +40°C

My interpretation of this is that the specified temperature is the air temperature outside of the enclosure, and that they assume the air temperature inside of that enclosure will rise by 20°C.

The product we are designing will eventually be sent to a test lab, such as Intertek, that will have the last saying in this. But it would be great if we could design according to the correct constraints.

Does anyone has an idea of where to measure, and what temperature that is the limit in this case?

EDIT

I talked to the compliance manager at the clients company, and he tells me that he doesn't know either. He told me to document how I measure and make the decisions.

For now I think I will try to measure the worst case air temperature in the top of the enclosure and declare that to be my ambient temperature.

EDIT

As pointed out, the datasheet says that the data is according to IEC 60947-4-1, EN 60947-4-1 and VDE 0660. I don't have access to any of these standards currently.

I do have access to SS-EN 60947-1, that includes IEC 60947-1:2007, which states the following:

  Ambient air temperature is that existing in the vicinity of the equipment if supplied without enclosure, or in the vicinity of the enclosure if supplied with an enclosure.

Further down it says that for certain types of equipment this is stated in their relevant product standard. Which might be the case for my contactor. So the real answer is probably written in IEC 60947-4-1.


texts:
Let me first apologize as I know this topic appears to have been discussed extensively yet something isn't clicking for me after researching over many days in stack, google, and youtube! I want to clarify a few thoughts in my head on the applicability of anti-static devices (such as wrist straps and mats) and how they work. I'll list my current thoughts/questions as follows...

1.) The purpose of the resistor in the strap/mat grounding cable: As I understand it the purpose of the resistor is that when there is a potential difference between you and the device you are working on the resistor will limit the current fed into the device to reduce damage. Is this true?

2.) How ESD occurs when working on a device: I understand that ESD occurs when there is a voltage difference between you and the device. I also understand that voltage is a relative measurement between two points. Additionally I've been taught that "ground" and "earth ground" are two different things. My big source of confusion is how you prevent an initial static discharge. As I understand when we are connected to "ground" it is not necessarily earth ground. This "ground" potential can vary depending on the electricity provider. As such, wherever your device is developed will have achieved equilibration in charge relative to whatever "ground" it was prepared relative to (assuming manufacturers develop devices by grounding themselves and all components). Where I am getting mixed up is that say when I take out a computer motherboard (which will be at a certain potential) and put it on an anti-static mat and connect the mat to my local ground source, isn't there still a possibility that very act may lead to a voltage difference (due to different relative "grounds" and cause an initial discharge? Or is the variability in what is considered "ground" standard throughout the U.S?

3.) When working with devices is it best to connect everything to ground? Or do you connect everything to the device? As I understand it you either set yourself and your device to ground potential or you set your-self to the same potential as the device. In both cases wouldn't there still be an initial discharge? A scenario in my head is that I touch the bare metal of a grounded outlet to disperse any static on me initially. When I go to handle the device how can I be sure that the device is at the same grounded potential within its anti-static packaging and that I won't discharge current through it?

4.) Assuming that there is a natural inevitable discharge and that my concern about that is correct, is it just a matter of which is safer, the "natural" discharge or the ESD? As I understand ESD can lead to a potential difference of hundreds to thousands of volts. If I use a CPU as an example device I believe anything over 2-volts has the potential to damage/fry the CPU. In this case ESD is definitely bad news. However, due to just transportation across the U.S and the potential of difference of relative grounds is it likely that there is always a few volt difference between me and anything else that I interact with? In this case, wouldn't I potentially always damage the CPU when removing it from its packaging?

5.) Lastly, as I see it now with all my concerns, ESD devices such as wrist straps and mats do not protect you and your device against any initial discharge (since there may always be a difference in your resting potential), they only prevent the future build-up of static as you are working on the device. Is this true?

Thank you very much for your patience in helping me figure this out!


texts: BLDC motor won't start after reversing the stator axial direction

texts:
I'm adapting a 60V BLDC e-scooter hub motor (see image below) to a custom made EV. In this specific motor, as it's designed for scooters, the wiring and the brake disc mounting are in opposite sides, which requires some adaptions to use it in a car.

As a solution, i'll machine the motor wiring side to attach the brake disc, but then the tire valve will let almost no space to attach the brake callipers. So the next solution was challenging: remove the stator altogether using an hydraulic press and then putting it back reversing its direction. Now the motor won't start and a single clicking noise is heard when trying to.
Due to COVID restrictions in my country I'm not able to right now to investigate the root cause nor try new solutions in the lab. Although, two possible causes come to mind: mechanical assembly and some issue related to the hall sensors.
From my researches, when reversing the rotation direction (which I think that is the same as what i did, but instead of switching wires i've switched the stator itself, but I may be missing something here) there is no need for rearranging the hall sensors wires. I also wonder if maybe the problem is related to a misalignment of the hall sensors PCB position after the reassembly.
Anyone has faced this issue before or can help to find the reason why the motor won't start? My first idea is to power the sensors and check if the signals are healthy (no 111 or 000).
I'll post updates as soon as I get to the lab to do more tests.


texts: Auto Switching 12 volt battery under load

texts:
I have a 120 V / 60 Hz 2000 watt inverter which can draw up to 200 amps from a 12 V DC battery source. An AC oil heater drawing 6 amps max 15 amps is running from the inverter constantly. I want to automatically change batteries without interrupting the current to the inverter.

The scenario is: several batteries are supplying the inverter. When a battery becomes depleted it is replaced with a charged battery. The invertor cannot go off line so a battery must be on line at all times. The depleted battery is switched to a charging circuit until it is fully charged then it is available to be switched to the inverter load. The battery being charged must be isolated from the inverter during charging.

Having many batteries is not an issue. Having many battery chargers is not an issue.

Currently this is a manual process and I'd like it to be automatic. I'm looking for: the best way to detect the depleted battery, swap the battery from the inveter to the charge circuit, detect the fully charged state then return the battery to the load circuit.

This application is an off grid. Any advice will be helpful.


texts:
I'm trying to hack my wireless thermostat to control my heating. I disassembled my unit and found the communication chip ( CC110L - SPI 433MHz). I searched for the datasheet and tried to determine which pin is which. I think I found the right pins and connected it to my digital analyzer, but my readings are strange. My clock signal does not look like a clock signal, and the CSn signal looks more like a clock signal but it does not match the datasheet.

Is it really a clock signal? Because my values do not look right. See attachment please.


texts: How electrons inside copper wire behave when source is ac or dc?

texts:
When a simple copper wire is connected to AC or DC, what actually happens to the electrons inside the wire?

I.e. What kind of path do they follow when they reach the end of the wire? If anyone can provide a video demonstration link it would be great.


texts: What is meaning of active low input in combinational logic circuits?

texts:
I am currently doing self study on combinational logic circuits. I encountered few terms like active low output, active low input. I understood what active low output means (putting not gates at output side). I guess active low means putting not gate at input side.

It will be very helpful if some one can explain this using an example (note that I have knowledge of encoders, decoders, Multiplexers so you can use these in your example).


texts: Is it possible to make a ring modulator where we replace the transformers with op-amps?

texts:
I've tried making a ring modulator like the one in following picture but without using transformers (as the right ones are quite a bit harder to get and more expensive compared to op amps).

I assume that both signals (Ux=V1 and Uy=V2) are measured with respect to ground. (I hope that this is a good assumption.)
Then "translating" the left transformer is rather easy, basically we can assume that the center tap must be our V2, and the signal in going to the left (lower left) node of the diode bridge must be proportional to V2-V1, and the one to the right (upper right) node must be proportional to V2+V1.
But now I have a hard time implementing the transformer on the right side in the picture. My first approach was just using a "floating" resistor (R15), but that doesn't seem to work very well (see brown curve).

Is there a way to improve this output signal (within the given constraints of not using transformers, just standard op-amps)?

simulate this circuit – Schematic created using CircuitLab


texts: Hard drive that has the ability to "read" old data while it performs a write?

texts:
Is there a hard drive (protocol command, specific model, etc.) that, while writing new data over old data, it "read"/return the old data back to the controller/OS? (Analogous to a simultaneous read-write).

I've been looking up SATA/hard drisk protocol(s) in search of something that meets the criteria, but it's quite possible that I lack the vocabulary to search properly.

The closest I've found is an ATAPI command for Read-after-write - which resembles the opposite of what I'm looking for.  I want to "read-just-before-write" or "read-as-i-write".


texts: Finding transfer function of an amplifier

texts:
I would like to know if the transfer function i found is correct :
TF = Vs/Vi = -(R-Rg)/(R+Rg)
In my case Rf = R1 = R2 = R ( i just did not find the right schematics )
And V1 connected to V2 and equal to Vi .


texts: Short-circuit capacity at the point of common coupling?

texts:
I'm reading about voltage fluctuations and flicker and I can't relate 'change of power in loads' and 'short-circuit capacity at the PCC'.

  Equipment or devices that exhibit continuous, rapid load current variations (mainly in the reactive component) can cause voltage fluctuations and light flicker. Normally, these loads have a high rate of change of power with respect to the short-circuit capacity at the point of common coupling.


texts: Cannot send two digit number using realterm to xilinx microblaze through serial port

texts:
I am using the default example which can be found here.

The part of the code I am interested is this:

#define TEST_BUFFER_SIZE        16

u8 SendBuffer[TEST_BUFFER_SIZE];
u8 ReceiveBuffer[TEST_BUFFER_SIZE];

for (Index = 0; Index < TEST_BUFFER_SIZE; Index++) {
    SendBuffer[Index] = Index;
    ReceiveBuffer[Index] = 0;
}

XUartLite_Recv(&UartLite, ReceiveBuffer, TEST_BUFFER_SIZE);
XUartLite_Send(&UartLite, SendBuffer, TEST_BUFFER_SIZE);

while ((TotalReceivedCount != TEST_BUFFER_SIZE) ||
    (TotalSentCount != TEST_BUFFER_SIZE)) {
}

for (Index = 0; Index < TEST_BUFFER_SIZE; Index++) {
    if (ReceiveBuffer[Index] != SendBuffer[Index]) {
        return XST_FAILURE;
    }
}

The buffer can hold values of 1 byte long. Using realterm I send a text file which hold values such as:

  0 12 3 4 56 7 8 91

but what I read at the ReceiveBuffer is '0', ' ', '1', '2', ' '... etc
I know that it sends ASCII characters because during debuging I see that the SendBuffer sends characters such as '\r', '\f' which my terminal translates as numbers but how do I send a two digit number????


texts: Make an LED (20 LEDs) circuit battery efficient

texts:
I want to wire up a miniature wargaming figurine to have 20 LEDs. As I've poked around options my concern is the battery life and how often the battery would need to be replaced. Since each gaming session lasts 4-5 hours, it'd be great if I could find a battery that would last multiple gaming sessions (though I think this is impossible...)

I'm VERY NEW to all of this so I would appreciate explanations/solutions that understand I have little knowledge of the terms or techniques (I still don't understand what current is...)

EDIT: Here are more details on what I'm trying to do

I am trying to light up this figure (Knight Castellan).

Locations for the lights would be (and their specs):

8 blue for right arm (3.4V, 20mA)
2 Red-Blue-Green for the eyes (3.4V, 20mA)
10 red/orange lights for left arm and engine (2.2V, 20mA)

So altogether that's 20 LEDs, all at 20mA and none above 3.4V.

The battery would go inside the torso -- I can't find an exact image but the dimensions are roughly 2" wide, 2" tall, 3" deep.

My concern is battery life, as I'd like the batteries to last at least a few game sessions (so let's say 10-15 hours). I don't mind replacing or recharging a battery, but there's no point if I have to do it halfway through a game.

I should add that I don't know how bright these LEDs are (the specs say 8-10,000 mcd for the blue ones), and that I don't know how to dim them, but would prefer them bright since they are usually in a well-lit room.


texts: Need to amplify a square wave, 20 amps or so

texts:
I need to supply 4 MSD ignition coils with a square wave (normally unipolar) sine, triangle wave at 5v and amplify that signal up to say... 20A MAX.

Usually people use one or two darlingtons and the power is not sufficient.

I used 8 MJ11033's in parallel, which was sufficient, but I apparently didn't bias them right and they all burned eventually.

So what I'd like to do is just take advantage of the many amp boards offered on ebay such as http://www.ebay.com/itm/600W-High-power-Class-D-amplifier-switching-power-supply-board-DC-58V-/131947454104?hash=item1eb8ae5e98:g:HEIAAOSwwo1XeTiH.

Is there any reason this wouldn't work?

One problem might be(?) that I want to use a square wave, will the dc filtering remove this?
Does uni vs bipolar square make a difference?

There's too many types of amplifiers out there; here's the basic idea

Thanks for the reply. Yeah that's all there is really to these, usually. If it helps here's a link to the coil specs I'm using- https://www.summitracing.com/int/parts/msd-5527/overview/make/ford/model/mustang , 4 in parallel, and an 8" phanotron plasma tube, I will be using one switchable vintage spark "tube" instead of the spark plugs. I just want to replace the darlington section with something that an engineer actually built. Will use any power supply that's required for the amp stage, not the transformers/rectifiers Again, the 8 MJ11032's in parallel that I tried were fine, they just didn't last.  Hope that helps a little, and thanks again.


texts: Powering a LED off a 1,2 volt rechargeable battery

texts: I would like to power a LED off a 1,2 volt rechargeable battery,850mAh,energizer without any resistors.Since the LED has a forward voltage around 2 volts,working fine when connected to a 1,5 volt alakaline AA battery,it's obvious that the voltage isn't a problem.However,I am not so sure about the current.Would the LED be fried if I connected it to this battery?


texts:
I'm working on a personal project for college right now. I'm working on a circuit that can change the direction of current flow going through a solenoid, depending on an input signal. I'm using an ELVIS Prototyping board to output the 5 V signal through a Virtual Writer on NI LabVIEW, if that matters.

Right now, I'm doing this with an electromechanical relay, and my 5 V output decides if it is open or closed. The COM is connected to the solenoid and into the ground, the NC to a 10 V and the NO to a -10 V. Because of the way it is set up, switching the relay's state changes the direction of current flow depending on the 5 V I/O, hence changing the solenoid's polarity.

Now, I have read on many websites that relays usually take a lot of time to change state, in comparison to transistors. Also, the relay produces a lot of noise when switching, as my montage is switching between the two states a couple of times every seconds (which I read is not that good to do with relays).

I would like to know if there is a way I could do the same type of thing, but using transistors. If not, is there a type of relay that would be best suitable for frequencies of around 5-20 Hz, current of around 1.25 A and voltage of 20-50 V?


texts:
Can anyone tell me what is a Schottky Diode? Scheme? Symbol? Where is it used? I mean in what type of circuits is it used? And for what is used?

I have searched online but not found what I am looking for.


texts: Normally any sort of video signal received by means of RF,contains a Hsync and Vsync component for instructing the electron beam.My question is ,how does the television do this using external sync generators if the received signal has no information of sync signals.


texts: How to use external ST-Link to debug/program STM32F103 MCU?

texts:
I'm using STM32F103 MCU for my own project and want to use the ST-Link of STM32F411 Nucleo board for external debugging / programming purposes.

I've set the CN2 jumpers OFF and my actual question is in the pinouts of SWO (CN2). How I proceed on this is as follows:

PIN 1 (of SWO) is VDD_Target
PIN 2 is SWCLK
PIN 3 is GND
PIN 4 is SWDIO
PIN 5 is NRST
PIN 6 is SWO

To the best of my knowledge, I shouldn't use all these pins above. As in, I've connected

PIN 2 to PIN 37 (or PA14) in MCU
PIN 3 to GND
PIN 4 to PIN 34 (or PA13)
PIN 5 to PIN 7 or (RESET) in target MCU.

Not sure if I should connect SWO pin as it's set as "reserved" (Why?). Also I'm giving 3.3 V to VIN pin of MCU, means that I don't need to connect VDD (PIN 1 of stlink).

Please refer to this table I've taken from the official datasheet:

Here's the general pinout configuration of the MCU here:

I've tested "almost" everything with oscilloscope and tester and everything seems okay. What else I'm missing here? Should I do anything with BOOT0 or BOOT1 pins?


texts: Mystery! LED lights unplugged yet still lights perpetually

texts:
I got a string of LED Xmas lights hung behind my TV connected with an extension cord. I want to buy a power bar with a switch to turn it off but for now, I just unplug the strand from the extension cord and to keep the extension plug from falling I plug the lights using only one prong leaving the other open. At first, I thought it was just a reflection but in complete darkness and with my hand cupped, I can see all the LEDs are lit. Not much but you can easily tell that they are on.

For this to work a 120v to 9v DC plug in block adapter is plugged in to the string at the other end. But that doesn't get power either as it is dependent on the power coming from the string of lights.

So why is the string of lights powered with 1 prong of the plug disconnected?


texts:
I would like to know, how could I draw a component picture like datasheet? I have attached one picture also. I want to draw the same component as the attached picture. Should I use Autocad electrical or Inkspace or any other software?
Thanks


texts: Life of a heated coil using a 9V battery

texts: I've been looking into heating a nickel chromium wire with a 9V battery for one of my projects. Can anyone feed me an equation for calculating the life of the battery? I'm sure it will include gage of wire, length of wire, resistance, etc. I can find out these aspects if I can get the general equation. Thanks in advance.


texts: Charging batteries at different rates and the associated side-effects?

texts:
I am quite new to batteries and charging them. I have a Polymer Lithium Ion battery (7.4V) and am about to attempt to charge it with a battery charger. The charger has a myriad of options from battery type, charge voltage, and current. I do not want to destroy the battery by attempting to over or under charge it. I peeked at a generic datasheet for LiO batteries and found an interesting charging plot.

The datasheet can be found here: DataSheet - see page 19.

What is going on here? The description of this plot writes that the maximum charging voltage is 4.2V (which presumably is for the battery they were using to collect this data).

Is this plot showing that at a charge voltage of 4.2V, the charge increases linearly for the first hour or so and then tapers off and the charge capacity of the battery is reached? Is this type of behavior governed by the controller inside the battery or does the battery suppress input current (like a charging a capacitor in an RC network)?

For a 7.4V battery, do we charge it at 7.4V? What are the differences between slow and fast charging (i.e. high or low input current)?

What are the side effects of charging at high current? Of course the battery would charge much faster, but does that shorten the life of the device?


texts: How can I connect a BeagleBone Black using I2C to my TI host-controlled battery charger?

texts:
I have a battery charger that I want to program /control. http://www.ti.com/tool/BQ24261EVM-079?keyMatch=bq24261evm-079&tisearch=Search-EN-Everything

How can I use a BeagleBone Black (BBB) to connect to this charger using an I2C interface ?


texts: Multiply a frequency by 227.5 times? The quest to get to 3.57954MHz

texts:
I need to somehow multiply a 15734.26Hz signal by 227.5 times. Those with a keen eye (or a calculator) will notice the result is very close to NTSC subcarrier frequencies. 3.579545MHz or close as damn it.
I realise I could just use a crystal that's that exact specification, and I have been, but the problem is, this crystal is not on the same domain as the rest of the video signal as I'm encoding RGB into composite video.
This is where the dreaded dot crawl comes in. If the subcarrier frequency is derived from the same domain, the dot crawl is gone completely.
I've no way to get on this clock domain BUT I know that the HSYNC x the line clock cycles = the subcarrier frequency. I just don't know how to get there.
Most ICs or circuits don't seem to be able to multiply that much and it's likely for a good reason looking at how they do it.
I assume I will need something that can sample the frequency and generate a clock, based on my criteria, from it.
Assumedly, I'm going to be looking at a microcontroller or FPGA which I'd really rather avoid.
Any ideas?


texts:
I was working on a layout for a guitar effect, and noticed on the schematic that 1 opamp has a 1N4148 diode on V+.   IC6 on the schematic below.
Given it has an internal power supply, I'm assuming this is not for polarity protection (guitar effects often run off external power supplies, and diodes are commonly placed on the input of V+)
Q1) What is the purpose of this diode
Q2) Would it matter if it was not there
Thanks for any assistance available.
EDIT:  SCHEM UPDATE, PREVIOUS INCORRECT


texts: How to find output of ideal op-amp system?

texts:
[edited the picture]

I have the op-amp system like this. I've just learnt how to apply the characteristic of each O-A for finding the output (using the given Av formula for inverted amplifier or integrator O-A). But for this we just can assume the O-A is ideal and have to find the output voltage.

Do you guy have any idea how to do this, I had failed to do this in my exam this afternoon and feeling curious about this...


texts: Microstrip Transmission line characteristics impedance

texts:
The question is from GATE 2016-ECE-paper 2.
Here in the question, we need to comment on the characteristics impedance of Microstrip line and we are given 4 options:  The ANSWER GIVEN IS (B),
My Approach for the problem is as follows:

Since the width of the microstrip line is smaller than the grounded plate, there will be some leakage of the Electric field to the air from the microstrip line, i.e. not all the field lines are bounded between the dielectric material and the microstrip line.

Therefore effective permittivity (\$ \epsilon_{eff} \$) of the transmission line will be less than (\$ \epsilon_{r} \$)[ dielectric] but more than \$ \epsilon_0 \$ [air].

The characteristic impedance of the lossless line is given by \$ Z_0 \$ = \$ \sqrt{\frac{L}{C}} \$, where L is the inductance per unit length and C is the capacitance per unit length.

Also, Capacitance= \$ (\frac{\epsilon_{eff}*Area} {length}) \$

Hence the characteristic impedance will be more than the impedance, I.e My Answer is Coming as option (A)

So where I get wrong, Since the answer given is option (B)?


texts: How to sample audio at Nyquist frequency with MSP430F5438?

texts:
I want to:

Input an analog audio track
Using the microcontroller ADC, convert it to a digital output
Then have the microcontollers/boards timer sample the data at selected intervals
Resample the "Sampled audio track" at twice the highest frequency content
Convert it back to analog as a perfect reconstruction of the initial audio track

Using Fourier Analysis I will determine the highest frequency at which I will sample the track at.

It sounds easy enough and straight forward, but what I need is to program this in C and utilize my MSP430 chip/experimenters board to sample the track.
I'm going to be using Texas Instruments CCS and Octave for my programming and debugging. I am using the MSP430F5438 Experimenter Board.

Is C the right language for this? Can I get any examples of how to sample the track at Nyquist frequency using C? What code in C will tell the board to utilize the ADC component? And any recommended information that is similar or that will help me on this project.


texts: Is the buffer in this power supply circuit required?

texts:
In the circuit below, the potentiometer is used to adjust VCOMMON to the specified (usually around -1.25 V) output.

VCOMMON is supplied to an e-ink display, and the datasheet says that the typical current draw is 0.2mA.

My understanding is that the LM358 acts as a non-inverting buffer. Is this really needed? Can't the potentiometer be directly connected VCOMMON?

Or is this a safety feature for impedance matching?


texts: How do you choose components for a gps antenna

texts:
I have to solder an active gps antenna on a pcb. But I don’t know how to choose components.
In my case antenna will be used outdoor on a pet collar.
First of all there are a lot of different ceramic antennas, what are they differences? Mainly they have various sizes but other parameters are the same. I’ve read on one forum that smaller ones are much worse.
And amplifiers, I want to use some  cheap circuit like here - https://www.arrow.com/en/categories/amplifiers/gps/gps-amplifiers
But most of them have very poor datasheets. How to choose such ones? Could They be connected to passive ceramic antenna directly? Are other components needed ? Like filters or so?
What would be main differences between such antenna and for e.g. topgnss active one?


texts:
I've made a huge mistake when trying to create a 400-Pin LGA in EAGLE. I've right clicked when mindlessly placing pads and now they're all rotated by 90 degrees.

My OCD demmands that I set the rotation to 0 so they're easier to read but I cannot work out how to do this. You can see in this image what I'm talking about.

The manual lists how to set the angle of an object absolutely using the ROTATE command:

ROTATE =R0 NAME

But I cant figure out how to rotate a group of parts, without rotating them around a single part.

Also some tips on how to mass rename these pads would help my sanity a lot...


texts:
I want to know how to calculate Vgs , assuming load current Id is constant , Vd = voltage of battery is constant , and fet is operating in thermal stability region , so there is no thermal runnawy , connecting gate to ground leads us having

Vgs = - Vs , so we need to calculate Vs

Vds = Vd - Vs = V battery - Vs = Ids Rds

so how to measure Rds ? i know it is dependent on temperature

but measuring temperature in thermal stability will be difficult , as temp increase Ids decreases so temp decrease until certain point so no change after that , so the temp that it will settle at is what matters

can i assume max Rds to know min Vgs ?
is there anoghter approach to control mosfet ?

update :

after reading :

https://www.infineon.com/dgdl/Infineon-ApplicationNote_Linear_Mode_Operation_Safe_Operation_Diagram_MOSFETs-AN-v01_00-EN.pdf?fileId=db3a30433e30e4bf013e3646e9381200

i know that there is safe operating area,

assuming Ron on limit i did these calculations below

**is it right? or should i assume that Vgs = 10 Volt at max Rds

when to use Rds on limit and Max power line limit ?**

update 2 :


texts: Customizing pin orientation in Altium schematic library

texts:
In Altium, I want to have the Name of the pin in horizontal orientation while the pin is in vertical orientation like

But do not get the option in the pin properties dialog box.

Here, the tutorial shows how to change the orientation. But there is no option for that in my case. Does anyone know how to get that option?


texts:
I'm building a supply for a 90 VDC 1/2hp motor.

So far I am using a garage sale variac (until I can find a regular 120/90VAC step-down transformer) and a bridge rectifier.

It runs the motor just fine, but I'd rather be kind to the motor and take out  as much ripple as reasonable.
The motor may pull as much as 5 amps (max) but the load probably just won't be too much.
I was hoping someone could just say "get this and it will work fine."
The motor will just be turning an observatory dome, so there might be a bit of a pull to start it but then probably not a lot of load.

Mostly it's going to be a full on and off situation. A control board and relays will turn on the power to the motor. Then if it needs to go the other way the other relay will turn on the reverse power. Mostly it's job (after homing) will be to move the dome incrementally to keep the opening in front of the telescope. So on/off 90vdc.


texts: Battery charging over USB-C (using USB-PD?)

texts:
I'm designing my first PCB, a wireless Keypad/Macropad with a battery. I'm probably going to be using a 2Ah Li-Ion battery because there will be a lot of LEDs on it and I just want it to last longer but I'm not sure how exactly would I charge it over a USB-C port on it.

I'll be charging the battery at 1C (2A) and 5V from USB using a Li-Ion charging IC but I'm not sure if I need any special circuitry to enable that, do I need USB-Power Delivery for 10W or not? I'd also want to be able to charge it from a regular PC USB port (so 5V at 500mA or 900mA on USB 3 apparently) so how exactly would that work with USB-PD if I'll need it? Would USB-PD just use max. current it can get from the source even though it's not what it's trying to negotiate?

I've been researching this topic quite a bit in last few days and I've came across the TPS6598x IC series and I'd probably end up using that in case I need USB-PD so that's what this question is based around.


texts: I have wheel that is on an axle running through two supported bearings. In one quadrant of this wheel, there is a (small) mass. As expected, the mass has a bias of being as close to the ground as possible (because of gravity). However, I have noticed that if I connect the axle that the wheel is on to a DC motor, this bias goes away. I was wondering what the source of this frictional force in a DC motor is. Is this force still present when the motor is running (will the wheel not have bias while spinning, resulting in an approximately constant speed as it spins)? Thank you!