texts: I'd like to re-number the components of my LTspice simulation from left to right and top to bottom to make the schematic more presentable. For example, in the circuit below, I'd like R44 to be R1, R50 to be R2, R28 to be R3, and R27 to be R4 (and similarly for the other components). I know the combination Ctrl+Alt+Shift+R re-numbers all the components, but I think it does it in the order in which components were placed, not in the left to right, top to bottom order I'm looking for. Is there a way to do this?


texts: I'm working on a project with a lot of external peripherals, so this means lots of wires. Any recommendations on how to keep them tidy while working on it? I don't want to use cable ties just yet, as I need to keep moving them so would have to keep cutting the cable ties.


texts: Power devices max voltage, current, power, speed, etc. .. ratings

texts:
I want to know how to get the real world or the most recent or the reliable information about power devices max ratings in volt, ampere, power, speed .. etc., parameters.

I found this picture that is seem to be reasonable, but I'm also interested if there's a better source or table for similar comparison of power devices.

Any ideas for better sources about similar comparisons ? to get the real max ratings about power devices?

For example, the power transistors used in mobiles data/calls towers, they are I think working of a very high frequency speed which is in case of 4G is like 4GHz, am I right ? I'm not sure about my assumption. Or the ones used in the microwave oven magnetron frequency which is 2,450 MHz, I just got that from google. So why these max numbers aren't listed in the comparison in the picture?


texts: latitude,longitude extract from GPS data in MPLAB XC8 compiler

texts:
I have interfaced S1315RL GPS into PIC16LF1937 using MPLABXC8 compiler(MPLAB IDEv3.51).

I am trying to extract the latitude,longitude,time from the GPS output.

uint8_t *str = "$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47\n";

I have strtok() for remove the "," from the GPS output.
But In c compiler its working well.I cant remove the "," in MPLAB XC8 compiler.

So,if anybody knows other methods inform to me .


texts: LVDS length pair matching (HSD connectors)

texts:
For a high speed interconnect (3 - 6GBit/sec over a single lvds pair) I attempted to length match the LVDS data pair as accurate as possible. Something I have failed to get information on is the length matching including the connector conductor geometry.   (ignoring the cable for now, as the cable is a shielded twisted pair , non-cross-over type)

Simple questions regarding propagation delay differnce between pins within HSD style connectors I received irrelvant responses from the 'big' connector manufacturers.

How would I realize perfect length matching within a single LVDS pair without getting information from the manufacturer?  (I dont have access to a TDR with ps resolution)

Edit:
The Connector intended for use is a Right-Angle type.  The Right-Angle construction physically has a longer and shorter conductor for a single data pair. Data Pairs are crossed diagonally, causing right-angle connectors always to have a longer path and shorter path within an data pair.

Today I found out by another HSD connector manufacturer that specifies its propagation time for the signals as in skew with a data pair. According to HSD documentation by T.E.: data pair skew may be <25ps for right angle connectors, and <5ps for straight connectors..

No absolutes or window of ranges are given, is the safe assumption of 24ps skew valid?

Reference:  https://www.te.com/usa-en/product-1-2286546-5.html


texts:
This is in a way a follow up to my previous post Advice on ground plane in my first PCB. I wanted to continue my questions there, and I updated my post after receiving feedback from others, but couldn't tell if my post re-appeared as unanswered. So here is a fresh post. The PCB below (prepared using ExpressPCB) is for a flyback converter implementation using the LT3748 boundary mode flyback controller IC. The circuit is taken from the LT3748 datasheet itself (see very last page). This is for a class project.

Two constraints I am working with are:
1. Transformer is designed by us, but is mounted outside PCB and connected thru the 4-pin connector (since there's no time to order bobbin - plus they won't sell a few)
2. 2-layer design only (lab course instructor wanted a simple design)

My questions are:

Datasheet advises to isolate or physically separate the high current ground from small-signal ground. The secondary ground plane is completely separate, so that's done with. As for primary, the only high-current grounds are those of Vin and R8 (the sense resistor). So, is it a good idea to connect the negative terminals of Vin and R8 with a track and then connect that track at one point to a ground plane that will have all the other small-signal grounds. The only penalty then would be that the R8 to Vin track would be quite long (since I'm using 2-layer only and wouldn't like to break my ground plane underneath, unless it is less worse than running this long track).
As you see from the schematic, I'm running two tracks underneath the IC (i.e. on the same top layer). Do you foresee any problems there? My IC shouldn't get hot, as it works with small current only.
Is it bad practice to have the ground plane run under a switch. I don't have any grounds around my MOSFET so I can cut out from the ground plane there, but I thought this would make it less effective (in that some return paths become longer) .
We're going to order the board from ExpressPCB, but to get a good price we need to stick to a standard board size, which is almost 3 times the populated area (so two thirds is empty space). So the question is do I fill ground in that space, or leave it empty? What about the top layer - also ground?
I realize the shape of my ground planes are somewhat funny. I just tried to fill only as much ground as needed to make straight return paths. What other considerations should one make in this regard (e.g. fill as much as one can? but then do I extend both ground planes, or one of them? how to choose?)


texts: How to calculate the voltage gain in this picture?

texts:
simulate this circuit – Schematic created using CircuitLab

I know that by using \$A_v=-G_mR_{out}\$, and \$G_m=\frac{I_{out}}{V_{in}}\$, we can get the voltage gain of this circuit.

After the small signal simplification, I got:

simulate this circuit

So, as node 1 is 0 volt, there is no current goes thru \$M_2\$, then \$I_{out}\approx g_{m1}V_{in}\$ ? So that \$G_m=g_{m1}\$ which is the \$g_m\$ of \$M_1\$? Also, the \$R_{out}\$ is \$R_{02}\$, and is the voltage gain of this circuit \$-g_{m1}R_{02}\$?
Thank you!!!!

-------------------------------------------------------UPDATE

simulate this circuit

What about this circuit?

After the small signal, I got:

simulate this circuit


texts: Connecting mobile battery and LED bulbs to 10.5v Solar cell

texts: I want to connect a 10.5v solar cell to a number (say 10 to 20) of 3v LEDs with an ordinary mobile battery for power backup (charging the battery). Should I use a resistor? What else I can do in an effective way?


texts: Choice of number of chip select pins in a RAM

texts:
I was going through Mano's "Computer architecture " , in chapter memory organization they have used a RAM chip with 2 chip select pins CS1 and CS2' but i can't think of the reason why , all the chip select features can also be implemented by using only one chip select pin and READ/WRITE pins according to . Why do we need two chip select pins (CS1 and CS2')  here ?

Here is the link to the page in the book(pg no 451).

thanks .


texts: Is the 50% loss of energy when charging a cap from a battery a set rule in stone?

texts:
This question is similar to A capacitor stores half the energy when charged from a battery each and every time?
(And no it is not a duplicate it is different in that it has been made more clearer.)

What seemingly was originally thought as an extremely easy question was not well understood. So it has been reworded again to be even more specific. So not a duplicate question.

It is meant to be understood that a capacitor starts with 0J and 0V in it. Next the switch is closed in order to connect the battery to the capacitor in order to charge it up to the exact same voltage level of that of the battery.

There is now 7.2 milliJoules of energy stored in the capacitor.

I am only referring to the schematic presented, which works exactly like what the schematic portrays. This is a real world circuit done on the work bench. It has losses due to resistance in the wires, capacitor, battery, and switch.

It is not lossless and so it is not perfect, there are losses involved as mentioned immediately above.

Half the energy is lost in doing work to transfer the other half into the capacitor. In other words the amount of work it takes to transfer half the energy into the capacitor is exactly equal to the amount of energy stored in the capacitor. This is a well known fact of life and electronics.

In other words, if 2 Joules of energy came out of a battery, then only 1 of those Joules would make it into the capacitor.

What I am asking is: When charging a capacitor from a battery, is this 50% loss of energy and 50% stored energy in the capacitor a set rule in stone?

I am referring to this exact circuit only or any other similar circuit with different capacitance's or different battery voltages with the exact same process of simply closing the switch just one time only.

I am not referring to ramp charging, step charging, or anything other type of charging. No other components are involved or added into the circuit. Just a simple closing of a switch to connect the battery to the capacitor only.

I know that this is another question but it's directly related to the first question, I don't want to ask it in another question and risk having a duplicate question, which it shouldn't anyways.

Other question: If the 50% loss of energy in order to transfer the other 50% energy is a set rule in stone then what voltage would the capacitor have to be in order to double the energy in the capacitor to make it equal to 100%?

In other words, what voltage should the capacitor be when it has 14.4mJ of energy in it, which should be double or twice the amount of the 50%, if I am getting that correct at all.

It should not be inferred that I am implying that the capacitor is capable of receiving 100% of the energy transferred from the battery as this is completely impossible and preposterous with the given circuit, but only asking what voltage would the capacitor have to be in order to double the 50% of the energy transferred into it?


texts: What is the effect of using wrong DC adapter to power on an electrical device?

texts:
Electrical devices powered by a DC adapter have specific in/out voltage/current values, so as an example what will happen if we used an adapter with 9v/1A output for a 5V/0.5A device?
Consider all cases either the output voltage/current of the adapter is lower or higher than the input voltage/current of the device. What will be the effect of each case and why?
As a real example, I have a power bank with Micro-USB input: DC 5V 2A and USB-C-Input (PD): DC 5V 3A, 9V 2A, 12V 2A, 14.5V 2A. I think I charged it with micro-USB from a DVB USB port used for connecting external HDDs, for recording, etc. After this, the power bank can be charged but it can not charge other devices. Is the USB port have any possible effect!!
Thanks


texts: How to determine PWM Frequency of a MOSFET to drive a BLDC motor?

texts:
What are the factors determining the PWM Frequency of the MOSFET driver circuit that drives a BLDC motor.

Is there any equation for PWM calculation?

For eg. I need to control the speed of a BLDC motor- (PMSM ME0201013001) with spec, 48 V, 5 kW (100 A continuous), 5000 rpm, 0.013 mH p-p inductance, 22 mOhm resistance.

I plan to use STH315N10F7-6 as my MOSFET which has Rds(on)max=2.3 mOhm @ Vgs=10 V and is driven by a Pre-driver L9907.

Since my power electronic knowledge is not so strong, I need to ask, how does the MOSFET circuitry (two half bridges in each phases of BLDC) produce a Very High Current of 100 A in Motor Phases?

Circuit reference is from an evaluation board of ST Microelectronics.

I have seen some posts in Stack but that does not work out for me! (Sorry!!)

Thanks in advance


texts: Attaching circuit boards to form 3D Shape

texts:
I'm at the early design stages of a project and I'm trying to determine the feasibility of   constructing a dodecahedron using PCBs for the 12 faces, similar to this, however, with an easier method of readily accessing and enclosing the contents instead of cable ties.

My best idea at the moment is to use epoxy to create a lower and upper half of 10 faces each - this way the angles between faces can be fixed - alongside some simple plastic clips to join both sections.

I have looked into some conventional forms of mechanically attaching PCBs, such as castellations, headers and hinged-standoffs, but I haven't managed to come across something that allows a fixed angle other than right angles. Is there something I've overlooked? Can anyone suggest other options?


texts:
Talking about diff  signals, we hear that they carry equal & opposite voltage. How will I conclude that referring the figure below :-

What is the significance of common mode voltage in diff signals. Also, what are VoH & voL meant for??


texts: Near-field-communication / NFC at no cost

texts:
My company is developing and producing measurement devices.
To quality check and adjust the full devices automatically, we need to be able to read the display indication and trigger functions like high resolution, zeroing, etc.

We are using usually the built-in communication interface (RS-232, WiFi, Ethernet). However, cheaper variants do not have a communication interface except the buttons and LCD display for the customer.

Reading would be possible with OCR, but pressing the various buttons with a robot hand (morse code or similar) is even more "complicated".

To keep product cost low, we are thinking of having a more or less hidden connector with a MCU UART connected to it directly.

Personally, I'm wondering if it would be even cheaper and more convenient to connect a processor pin to a medium sized tiny PCB antenna. Then try to use an UART or bit-banging to "radio" out signals, basically to intentionally cause low-frequency EMI. Outside of the device under test, there is a very close and big antenna for receiving the signal. I assume trigger functions in the device is the harder part.

Is this a viable idea? Can you point me to a term or solution I can further research?
Thank you very much!


texts: Why use a star or delta connection instead of having a second output

texts:
I am winding my own small three phase ac alternator and have learned about star and delta connections. Should I use 2 three phase rectifiers to turn the current to DC or only one with a star connection on the other end?
EDIT: To be more clear, there are 3 sets of wires which current will be induced to. Most alternators take the first end of each set of wires to make a 3 phase current, but take the other ends of the wires to make either a star or delta connection. Why not just have another three phase output for twice the power output? Note I am also using rectifiers to change the AC current to a DC current (I am using a three phase alternator so the output of the full wave rectifier will be smoother).


texts:
I have a system where a setpoint temperature can be set. A heater and a cooler is connected to the object. Right now both the heater and the cooler regulate on the temperature separately with separate PID controllers. This ofcourse causes them to "battle", and also I imagine they could be stuck in a position where both the heater and cooler is working.

What is the general approach to these types of problems?


texts: which kind of design of level shifter suitable for high frequency data transfeing in range of 1MHz?

texts:
A circuit needed to convert 3.3V and 5V logical voltage. However, the issue was that the circuit was supposed to handle very high data transfer at or above 1 MHz and up to 16MHz.

I thought of

using resister(to lower the voltage)
use op-amp circuit to rise andowering the circuit.
use level shifter. (however they seemed to be working at 400khz, not fast enough)
use TXs0108e, but the "Open Drain" wa only at 1.2 MHz.
using voltage regulator.
Use transistor as gates to operate the circuit.
Which design will work for such high speed data transfer?  and which will fall?  how to construct a shifter circuit that handle 16MHz data transfer?


texts:
I am building a solar charge controller. I have based the design on pwm5 by Julian illet (circuit diagram attached). I am trying to convert this PWM charge controller in to a mppt one.

The buck converter I am using is shown on the second picture. Switching frequency is 31.5 kHz. I have no idea of the inductor I'm using (see the third picture).

My problem was that both IRF3205 are getting very hot. But the IRF3205 I'm using as a diode in the buck converter stopped heating up when I changed the switching frequency to 31.5kHz.

Switching MOSFET is not heating up when it is operating in PWM mode, but the addition of the buck converter circuit makes it toasty. There are no heat sinks on any of the MOSFETs.


texts: Is it possible to connect 3 LM317s in parallel to get upto 4A of current output ? I need 4A but I'm not able to figure out any other possibility. Is there any other possibility to achieve this ?


texts: What the function of bjt and diode in this circuit

texts: I want to know why we need to use bjt and diode in this circuit to activate the dc motor, thanks


texts:
I'm working on project where I have to lift up/down an object about 5-7 kg heavy at speed of about 6.6 mm per second. Does anybody have an idea how to do that?

I was looking at asynchronous motor and reductors for them but reductors at very small speed are very expensive (1000 euros). Any suggestion will be appreciated :)


texts: Direct connection of UART serial port to USB type-C

texts:
in my project I have a USB type-C 3.1 2nd Generation (24 pins), which should provide 5V to a charge battery/battery system. In addition, there is a uC powered at 3,3V where the maximum voltage on GPIO pins is 3,6V.

The question is: can I connect directly the UART pins of the uC to the Rx/Tx pins of the USB port? If I connect the USB to a laptop or wall adapter, what will it be the voltage in Rx/Tx pins? Is there a risk that I overcome the maximum 3,6V of the UART pins of the uC?

Note: I prefer to not use a bridging between a USB port and an enhanced UART serial port.


texts: Maintaining voltage at 5V, but voltage must be able to change

texts:
Okay so I'm a beginner at electronices not sure where to begin looking so I'm just going to ask, is there a way to maintain voltage at 5V but it must be able to change to below 5V.

Basically, I'm hooking up an output from a sensor and going to connect it to an Arduino for data logging. But the problem is the output from the sensor can go up to 7V or more(According to the a program that monitors the sensor, it doesn't do data logging), and i wish to avoid frying the Arduino board so is there a way to fix that?

Will a voltage regulator do it? All I know about voltage regulators is it maintains voltage at a certain point.

So to make it clearer, is there a way to prevent the output voltage of the sensor from shooting above 5V and also be able to change from 0V to 5V.


texts: How to use the dft function in Cadence Virtuoso Calculator?

texts:
I had the following setting for the dft function in Cadence Virtuoso Calculator:

But it gave me some negative values in the spectrum:

So why there are negative values? Is there anything wrong in the dft function setting?
Thanks.
Edit
The time domain signal is as follows


texts: Does cache access time scale down with frequency in modern CPUs?

texts:
I have an application where I suspect the main overhead is accessing L3 cache. It is run on a modern Intel server-grade microprocessor with a huge L3 cache. There are many microprocessors available with various core counts and frequencies, and selecting between these is hard.

So, that led me to wonder whether L3 cache access (hit) time scales down with frequency. So, if 2GHz CPU accesses L3 cache in e.g. 12 ns, does that mean that a 3GHz CPU accesses L3 cache in 8 ns? Of course, this may depend on internal implementation details of the CPU, so let's limit answers to modern i386/AMD64 microprocessors.

I know that at least in the case of DRAM the delays are practically constant, so if you do a random DRAM access, higher frequency means only better sequential data rate after the random access penalty has been paid. But is SRAM fundamentally different? It is based on transistors, so I guess it could be clocked at pretty good frequencies.

Sorry if this is the wrong place to ask, there is no better place to ask detailed computer architecture questions. I have considered CS StackExchange and StackOverflow, but I think Electrical Engineering StackExchange was the best place. There really should be a Computer Architecture StackExchange but there isn't!


texts: Question about a trigger input of a modern ARB/VSG (Vector Signal Generator)

texts:
Given a common setup:

The green box is a PCB mainly consisting of a data acquisition device (ADC+RF frontend) which is controlled by a Spartan-6 FPGA.

The ADC & FPGA use a clock from a Tektronix signal generator which itself is configured to take the 10 MHz reference clock from a R&S SMW200A Vector Signal Generator.

Data acquisition is started from a laptop which sends a trigger event to the FPGA. Internally, the FPGA has multiple clocks but all of them are synchronuous to (and generated from) the 80 MHz clock.

The trigger event is synchronized to the respective FPGA clocks and start ADC capture. Furthermore, the "Trigger Signal" is synchronized to the FPGA slowest clock and stretched.

The SMW200A is configured to start outputting data exactly at this "Trigger Signal". Assuming all clocks are synchronized, all delays should be fixed for each trigger event.

However, this is the captured data for multiple runs:

The data always starts at either 118.5us or 118.75us delay. The difference is exactly one ADC sample (ADC is 4 MSps but uses the 80 MHz clock).

Now I am trying to figure out what could be wrong here.

Does the output of the SMW200A always start exactly after a constant time after the trigger is applied (I don't think so).
Is the trigger on the SMW synchronized to an internal clock? If so, which clock is this?
How can this clock be synchronized with the rest of the system? (I assume the 10 MHz reference clock sharing only makes sure that that all systems share the same frequency uncertainties)


texts:
How to get rid of the following errors:

  planar_marchand_balun (C:/Users/kevin/Documents/Ansoft/)
    EMDesign1

  [error] An error occurred during the mesh generation. Check the message window for additional details. (11:06:56 am  Jul 06, 2019)

  [error] HFSS port 'Port1' does not have a valid reference plane above or below it. (11:06:56 am  Jul 06, 2019)

  [error] HFSS port 'Port2' does not have a valid reference plane above or below it. (11:06:56 am  Jul 06, 2019)

  [error] HFSS port 'Port3' does not have a valid reference plane above or below it. (11:06:56 am  Jul 06, 2019)


texts: Operation of a micro USB phone charger outside its limits

texts:
Many micro USB phone chargers give 5V DC and 1500 mA output at input 100-240 V AC at 50-60 Hz (these values are from a Sony EP 880 charger).
What happens to the output when voltage rises above 240 and when it falls below 100? What happens when the input is not 50-60 Hz? What happens to the battery and it's circuitry ?


texts: Remote control's battery bay issue, no voltage at the end of circuit

texts:
I have a remote which needs 6 AA batteries, I put fresh AA batteries in and I tested via volt meter and at the last battery's negative connection is showing zero reading. The same battery's positive connection is showing 6.7 v something reading.

These are AA rechargeable

I am attaching a pic as well.


texts:
My understanding of an analog comparator is that you have a fixed reference voltage applied to one input and an AC signal to the other input, when the signal's voltage > reference voltage, the output of the comparator will be logic high, else logic low.

I was looking at the input stage of one of the MCU's analog comparators. Signal applied at AIN0, reference is applied at AIN1, pin5 toggles between Vcc and 0 to shift AIN1 by +- ~0.04V.

But what I don't understand is it has a 100k resistor (R2) connecting both inputs. What's the purpose of that? Wouldn't that make the reference vary as well?

Any suggestions are greatly appreciated, thanks.


texts: calculation of total capacity of Bank of 3 single phase transformer?

texts:
Imgur

This is a nameplate of single phase auto-transformer. However in this transformer i'm not sure how do I get the capacity of this transformer. 3 of these transformers are connected in to form delta-star connection and I also would like to calculate the total capacity of the bank.

Why is in the rated power, the values are divided by 3? because they are made to be connected as a bank?


texts: Driving power + USB over cartridge connector

texts:
I hack old hardware (mostly microcomputers) by putting new insides in them, but I still consider myself a newbie when it comes to electrical engineering, so please bear with me, because this question might be painfully obvious.

On my next project, I want to put a Raspberry Pi into a dead TI-99/4a computer. I don't want to modify the case, but I would like to use its features. So I am thinking of 3d printing a "cartridge" that would house the pi and a trackball/touchpad and plugging that into the cartridge slot on the TI.

I want to plug in that 3d printed "cartridge" into a matching socket and run a USB and power (5V 2.5A) on the cartridge traces. My plan is to hijack the cartridge and socket by soldering on wires to translate them back into USB and power plug which will run inside the case.

My question is - is that safe? Can I run whatever over a cartridge connector the same way I could run it over a wire?

Thanks in advance.


texts: I'm wondering if it's possible to charge say a capacitor with a stepper motor (~12V DC after rectifying), which when it reaches its maximum capacity discharges. I'd like the discharged power to activate a solenoid?


texts: How to protect MCU IO and 5V from shorted +12V

texts:
I would like to protect an MCU from 12V being shorted either to IO or it's 5V supply.

This is very similar to the question asked by kamil here: How to protect microcontroller board 1-wire from accidental +12V connection? with the addition of protecting a 5V line as well.

I've come up with the following circuit (starting from Brendon Simpson's fantastic answer) but would like to know if it will work or there are better designs. I suspect that D3 may not be necessary and I don't know whether the placement of the R2 current limiting resistor will interfere with the operation of D2.

From my reading of the PSMF010X data sheet, at 12V R2 will allow 400mA which cause it to trip. And since we should never normally draw anything like 100mA on the 12V line the PSMF010X should reset on it's own after the short condition is removed. This also protects the power supply if 12V is shorted to ground.

Background:
We use 1-wire sensors on fairly long run of up to around 500m. Due to the 5V supply dropping too much over this length to power the pressure sensors connected to the 1-wire boards, we also use a 12V line with an LDO (LP2950) at each sensor to provide them with a solid 5V input.

As we use 4 core cable we also pass 5V out on the remaining core so that we can use it to power less sensitive devices like DS18B20 temperature sensors without the need of an LDO.

As our original 1-wire master devices are no longer available to us I have been experimenting with using an ESP8266 MCU with a 5V level shifter as a master with great success. My only real concern is damage due to the 12V line being shorted to any of the other wires when sensors are being installed or due to some damage to the cables.


texts: How an op-amp determines its output without a reference point?

texts:
I was struggling to understand how an op-amp determines its output without a reference point.

The output of an op-amp is A * (Vni - Vi)

Then let's say we have an inverting op-amp with a gain of 1000, that V+ is 9 V, V- is -9 V and Vni is 5 V.

If Vi is 5.002 V, the output is 1000 * (5 - 5.002)  =  -2 V

If Vi is 4.998 V, the output is 1000 * (5 - 4.998)  =  2 V

The output is -2 V or 2 V but with respect to where? With respect to the halfway between 9 V and -9 V or Vni (5 V)?

So how can I set the reference point of the op-amp?

Thanks in advance.

Note: Vi is the inverting input and Vni is the non-inverting input of the op-amp.

Edit: Thanks everyone for helping.


texts:
I have one machine with transformer
from 208 3 phase to 400 3 phase, what will happen if I connect the transformer to 360 V  3 phase as input is it will be okay or not? Because the machine comes from the USA to Egypt which has a different input voltage.


texts: Isolated CAN transceivers as a CAN bus extender

texts:
I am designing a system to 'hack' into a CAN bus. My first idea was to split the target CAN bus, terminating both ends into isolated CAN transceivers, and use a MCU to pass packets between the buses while altering values inside the packets. Below is a rough picture of the setup:

My problem is that while connected to the target CAN bus, the system fails to transmit on either CAN bus. In the program I can see it is receiving, but the MCU gets stuck in a loop of failed transmissions.

The weird part is that I can prove the code and hardware are all viable in a different environment. When I hook up the hardware to a test rig I made using a couple of development boards and a power supply, it works well! The packets from both devices are seen on both buses. The packet bits look healthy and square. I am at a loss figuring out what specifically is different about the environments on my desktop and on the target CAN bus that make it break.

System details follow:

MCU - STM32F746ZGT6

Isolated CAN transceivers - ADM3054

Bus speed - 125kHz (confirmed with oscilloscope and CAN sniffer tool)

I'd really appreciate help thinking through this system design, and understanding how it might cause CAN transmissions might fail.

Thanks!

EDIT:
Upon farther thought, I think I realize the area to focus on is between the TxR and the MCU. If the MCU is refusing to declare a successful transmission, than it must think something wrong is happening on the bus. It can only interact with the bus via TX and RX. I will scope TX and RX to see if I can see any weird errors, possibly caused by reflections or something interfering with RX during transmission?

EDIT 2: added schematic and layout image


texts:
In the two simulations below, Vout is almost the same (to GND) in both while the OpAmp sees the same differences in potential at its inputs, so actually, the second output should be 1V lower. How is that possible?

simulate this circuit – Schematic created using CircuitLab


texts: VHDL - D flip flop simulation goes wrong

texts:
I am trying to simulate a D flip-flop using VHDL code which I compile and run using GHDL and later I ploting the waveform using GTKwave.

The problem is that my teacher told me that, when using D flip-flops, if the clock and data signal rises at the same time, the flip-flop state does not update till the next rising edge of the clock. But when I simulate that behavioral on a test bench, I get this:

Which seems to work perfect, except for the last D signal rising, where Q should update to HIGH after 10 nanoseconds. I don't know where the problem is, and it may be due to bad coding so I give you my code if it can help solve the problem.

D flip-flop module:

library IEEE;
use IEEE.STD_LOGIC_1164.all;

entity d_flip_flop is
    port (
        clk:    in  STD_LOGIC;
        d:      in  STD_LOGIC;
        reset:  in  STD_LOGIC;
        q:      out STD_LOGIC
    );
end entity;

architecture asynchronous of d_flip_flop is
begin
    process (clk, reset) begin
        if reset = '1' then
            q <= '0';
        elsif clk'event and clk = '1' then
            q <= d;
        end if;
    end process;
end architecture;

D flip-flop test bench:

library IEEE;
use IEEE.STD_LOGIC_1164.all;

entity d_flip_flop_tb is
end entity;

architecture testbench of d_flip_flop_tb is
    component d_flip_flop
        port (
            clk:    in  STD_LOGIC;
            d:      in  STD_LOGIC;
            reset:  in  STD_LOGIC;
            q:      out STD_LOGIC
        );
    end component;

    signal clk, d, reset, q: STD_LOGIC;
begin
    uut: d_flip_flop port map (clk, d, reset, q);

    process begin
        clk <= '0'; wait for 5 ns;
        clk <= '1'; wait for 5 ns;
    end process;

    process begin
        reset <= '1'; d <= '1'; wait for 12500 ps;
        reset <= '0';           wait for 10 ns;
        d <= '0';               wait for 12500 ps;
        d <= '1';               wait for 20 ns;
        assert false report "End of simulation" severity failure;
        wait;
    end process;
end architecture;


texts: How can I test the rotor winding of a single phase brushless alternator on a generator?

texts:
Context Generator runs but no power output from the alternator.
The manual gives Ohm readings for the stator, excitation and rotor windings. The stator and excitation coil are to spec and have no short circuits with respect to the ground. However, there are no wires coming out for the rotor (this I believe is normal for a brushless alternator). So I think I might have to remove the stator to test the winding. It has diodes on it, do I have to un-solder the diodes to make it an open circuit to test the windings? Should I test the diodes too?
If my no power problem is due to a loss of excitation field, I have read that I can flash the excitation winding to create a magnetic field within the metal. However, the guide shows that I have to honor the polarity of the excitation winding and yet the 2 wires are both the same color with no sign of polarity markings. Is polarity important when flashing? I have read that $12 ; V$ for 5 seconds should work. Also, I will order a new multi-meter that is capable of testing the capacitor. If you have any advice on testing I would be grateful to receive it.
It is brushless as stated in the manual and because there are no brushes (unless they are in the prime mover end which would require removal of the stator to access)
Its an AP-85
manufactured by Meccalte
2 black wires that connect to the capacitor match the resistance of the excitation coil specified on page 11 in the manual.
the ground wire goes between the alternator chassis and the receptacle panel
the 4 coloured wires are the 2 stator coils (its a 115/130v alternator so I believe they are connected in series for 230v)
I have tested the stator output directly with the receptacle panel disconnected to rule out faulty breakers and changeover switch.
Manual, it's not great!
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiLzZnwjLrvAhWOQhUIHboRCWMQFjAAegQIBBAD&url=https%3A%2F%2Fwww.meccalte.com%2Fdownloads%2FMan_ap.pdf&usg=AOvVaw17WttuQbIAJRNPeE6w3eU6

[


texts: I want to calculate the consumption of a PV inverter connected to a 50 kW PV plant. In the datasheet of the inverter it is written that the consumption of the inverter is: < 0.24% of Pac,r. I really don't know what is Pac,r. I found Pacr that is 55 kW but I don't think that an inverter has a consumption of 13200 W. Is it possible? I allegate the screenshot of the part of the datasheet where it is written. It is in Italian unfortunately, but probably someone that has a experience with inverters can help me anyway. Do you know what is the consumption of this inverter?


texts: How can a marginal connection become "good" by just applying a little more voltage?

texts:
"On the side" I do a fair amount of repair work to guitar gear -- Amplifiers, pedals, guitars, etc...
I've had a similar symptom occur on different repairs, and found the same root cause for each.   But the physics behind how it's possible is baffling to me.
I hate that.  I hate not understanding why.
Basically it goes like this....
"Customer" complains that amp sounds like cr*p.   I will find that it's outputting a weak-ish signal.   Not dead, but has no kick or punch to it like a proper guitar amp should.  It'll sound muffled, sometimes buzzy, dead or lifeless.
I find it's a marginal connection, sometimes a cold solder joint, sometimes a weak jack, etc... but it's always a metal-to-metal connection in the signal chain.   In other words, there's a series resistance added that shouldn't be there.
Here's what's puzzling.   The cases I'm thinking of, the amp can be made to sound "right" by slamming it with an abnormally strong input signal.   i.e. more voltage than usual.   After that, it'll work for a while.
It's like the higher-than-normal voltage signal somehow punches through whatever is the 'bad' connection and makes it good.   Nothing physically moves.
I know it sounds bizarre, but I've seen it too many times to not accept it as "real".
So what gives???   These are AC signals, so it's not like a thyristor type action.  And we're talking about mV to a few volts amplitudes.   Not the hundreds of volts found in tubes - These problems are in the signal chain.  I've even found this to occur on foot pedals, which are (typically) 9V DC devices.


texts:
I want to measure the frequency of a  signal around 200khz (max) and the voltage may vary from 10v to 200v peak-peak. I will have only a constant voltage at the time of measurement. Not varying.

So the approach I am trying to use is to feed the AC signal to a simple ultrafast diode clipper circuit to limit the voltages via a huge current limiting resistor of 100k and then feed it to a F-V convertor ADVFC32.

Will this approach work?


texts:
I have been studying buses used in communication systems. From what I read at Wikipedia,

  "In computer architecture, a bus (from the Latin omnibus, meaning "for
  all") is a communication system that transfers data between components
  inside a computer, or between computers. This expression covers all
  related hardware components (wire, optical fiber, etc.) and software,
  including communication protocol."

Does that mean both a wire and a bus is the same thing? What feature makes the bus totally different from a normal wire in the first place?


texts:
I am looking for a way to sniff the data running between a PC ("A") and a USB device ("B") by using another PC ("C").

To do this, I spliced the cable going from A to B and soldered another USB cable to create a Y splitter and ran it to C, thinking the signals will be duplicated.

What happened was the two PCs A and C fought over the control of B (should have seen that coming...) and all hell broke loose.

I have a couple of assumptions/ideas I would like to run by you:
1. Can I disconnect the VCC and GND wires on the sniffing cable, so that C will not try to control B?
2. Can I place a diode on the D+ or D- wires of the sniffing cable of to make the data flow only one-way?
3. Will I be able to read the data off the USB port in C?

Any comments/suggestions will be greatly appreciated.

(Disclaimer - I am a NOOB to USB so go easy on me)


texts: Troubleshooting I2C issues of ESP32-POE-ISO with LAN

texts:
i'm trying to read a I2C HTU21D from this breakout (schematics below) temperature and humidity sensor and send data to an mqtt broker.

I'm using PCA9306 in order to use 5V and go "far" (30m) from the main MCU PCB using CAT5E cable and RJ45 connectors.
The MCU circuit is very simple, one HTU21D, a PCA9306, 30 meters of cable cat5e and a ESP32-POE-ISO with another PCA9306.
The two PCA are used in order to go with 5V in SCL and SDA bus lines.
The cable has a capacitance of 56pf/m, so five meters are 1680pf in total, higher than the maximum I2C limit of 400pf.
I've used my logic analyzer to investigate and it seems that when i plug LAN to the ESP32-POE-ISO there are some logic spikes on I2C lines that produces those wrong measurements, tomorrow i'll post some screen of my oscilloscope
I'm using Arduino with the latest Espressif 1.0.4 Library.
The I2C bus speed is 10khz and there are external pull-up resistor of 10k on I2C bus (ESP32 side) and 330ohm pull-up resistors on the PCA9306 bus side.
Here is the schematic:

EDIT: 27/07/2020 - changed pull up resistors and added oscilloscope traces
I've replaced the pull-up resistors from 330ohm (as suggested) to 2k2ohm, here is the result:
Scope trace of 330ohm pull up resistors (SCL - CH1):
As you can see, the clock waveform is really sharpen, and has around 340mV of delta from 0V (i think that this could be a problem) - In this scenario, data reading works but it's unstable: like 10 measurements wrong every 100,

Scope trace of 2k2ohm pull up resistors (SCL - CH1):
As you can see, the clock waveform is a nice square looking signal and there isn't any delta from 0V, in this scenario the data reading works very unstable: 40 measurements wrong every 100

Any suggestion to solve that issue?


texts: this is probably dumb question, but I am trying to self-study electronics and cannot figure out, why this circuit has only 161mV on resistor. From what I understand, 1V on base should be enough to make collector-emitter basically a short circuit, so there should be 5V on resistor. What am I doing wrong?


texts: Minimal code required to startup a STM32F4?

texts: Which is the most efficient way/minimal code required to startup a STM32F4? The startup files that come from ST seem to have a lot of unnecessary code.


texts:
How to add two 16bit numbers using a 32bit adder (Its a FA)?
32bit adder takes 1 cycle to add two numbers.
how to add "p+q" and "r+s" (16bit numbers) in 1 cycle?
Note: 32bit adder is black box, cannot modify anything inside. But you can add combo logic outside.


texts: Tripping a circuit breaker when using a half wave rectifier

texts: How does a half wave rectifier or phase control dimmer affect the triggering of a circuit breaker? For example, if a 20A resistive load was on a 15A breaker with a half wave rectifier. Now average RMS current is only 10A even though peak RMS is still 20A.


texts: Purpose of resistor to ground in video-amp circuit

texts:
I was watching how to make a nintoaster, that is, an NES (Nintendo Entertainment System) in the form of a toaster. The video is here. One of the things he does in the video is building a video-amp circuit for the video signals from the NES. The circuit looks like this (13:40 in the video).

I believe I understand somewhat what this circuit does (but feel free to point out if I'm wrong). The "VIDEO IN" signal controls the state of the transistor, that is how much current is flowing through it. The \$33\Omega\$ resistor is there to limit the current, and the "VIDEO OUT" is the output signal.
But I'm not sure why there is a \$220\Omega \$ connected to ground. What is the purpose of that resistor, if it even has any?


texts: Is electricity saved by switching off the lights when leaving a room?

texts:
Incandescents are very energy inefficient for sure so they have to be turned off whenever you leave the room. But I have tried to find the answer for CFL lights, some say that it's more efficient to leave them on if you will need them again in the next 15 minutes (because of the in-rush current), but others say that it's more efficient to turn them off, because the in-rush current happens in a fraction of a second, so it doesn't waste a lot of energy and is equivalent to just a few seconds of LED's work.

And how to calculate the in-rush current? For example, if I have a 75 W CFL, how do I found out its energy consumption after 1 minute being constantly on and being turned on and off in 5-second intervals?

It would be really helpful if you would give links to already published scientific researches that I have somehow missed.

P.S. I need this for a science project and it would help if you could give some advice on how to prove which way is more energy efficient and calculations are very important.


texts: Finding unknown load using a smith chart

texts:
I am asked to find the impedance of an unknown load. The precise formulation is provided below:

  The following two step procedure was used to measure the value of an unknown load \$Z_{L}\$. The characteristic impedance of the feeding line is \$Z_{0}=100\Omega\$.

  First \$Z_{L}\$ was disconnected and an input impedance \$Z_{in}=-j150\Omega\$ was measured.
  Next, \$Z_{L}\$ was connected and an input impedance \$Z_{in}=(100-j50)\Omega\$ was measured.

  Find \$Z_{L}\$ both analytically and graphically using a Smith chart.

My problem is that my analytical solution doesn't match the graphical one using a Smith chart and I cannot figure out the reason for the discrepancy.

Solving it analytically I tried using the formula for \$Z_{in}\$. First, for the open circuit,

$$-j150=\frac{100}{j\times tg(\beta\times l)}=-\frac{j100}{tg(\beta\times l)}$$

which yielded \$tg(\beta\times l)=\frac{2}{3}\$.

I then used the same formula for the second measurement:

$$100-j50=\frac{Z_L+j\times 100\times \frac{2}{3}}{100+j\times Z_L\times \frac{2}{3}}$$

which yielded \$Z_L=2.63+j151.27\$.

Using a Smith chart I applied the following procedure: I first marked on the diagram the point \$-j1.5\$ as the normalized \$Z_{in}\$ and then moved from the left end of the diagram (open circuit) clockwise till I reached that point. This yielded a length of \$0.344\times \lambda\$ for the transmission line. I then marked the second normalized \$Z_{in}\$ (\$=1-j0.5\$) and drew a circle of that radius. From \$1-j0.5\$ I began moving counterclockwise (toward load) a distance of \$0.344\times \lambda\$ to reach my unknown \$Z_L\$. Unfortunately, the result was different than that found analytically.

Does anyone have an idea what I might be doing wrong? I'd appreciate any advice.


texts: Is it possible to specify an equivalent RLC network for a loudspeaker?

texts: Can an RLC network be defined that would behave in the same way as a theoretical loudspeaker? Since their behavior is frequency-dependent, would the values of R, L, and C also be frequency-dependent?


texts:
I'm interested in simulating a circuit using a stepped sine wave input. I want to sample a sine wave at regular intervals and have the output constant during each interval, making an output that looks like:

(pardon my silly Excel plot!)

What's the best way to do this? Is there an easy way to create a source that generates an output like this? Am I better off carefully looking at the frequency response of my circuit and comparing it to the frequency content of this input?

A solution relevant to LTSpice or Orcad would be ideal.


texts: Control old printer motor with position ring

texts:
I purchased two old printers at a garage sale today in hopes of dismantling them and playing around with some stepper motors. After tearing both of them apart I discovered that there are no stepper motors. What all of them are controlled by is a translucent plastic ring with several "Dots/Dashes" around the outside. It also has what appears to be some type of sensor that reads the position of the ring.

I am wondering is there a relatively easy way of controlling these motors as they were intended with the plastic rings and sensors? My goal is to make them controllable like a stepper motor. I would like to know more about this system they use perhaps the proper name for it. Eventually I would like the motors to be controlled from my RaspberryPi.

Update:

After looking at one of the sensors with a high power magnifying glass I was able to obtain a manufacturer and track down exactly what it is. I was unable to locate a model though. Has anyone worked with a system like this? How does it work exactly to control position of a motor?

Here


texts: Can I assume input protection diodes in all modern ICs, even when not mentioned in the datasheet?

texts:
I use the A3906 motor driver on a board supplied by 8V. The µC on the board is supplied by 3.3V and is connected to the A3906 via the logic pins. I realised this is a potential pitfall, when supplying the µC only via the programming adapter for programming, debugging and testing, because in that case the motor driver has no supply voltage but is still connected to the logic pins of the µC. I fear this might result in latchup when accidentally powering up one of those pins.
I checked the datasheet of the A3906 for the maximum allowed input current through the protection diodes but could not find a value or any mention of input protection diodes at all.
Can I just assume that all modern ICs have such input protection and just put 10k in series between µC and motor driver to limit the fault current to something like 0.3mA? Or is it likely that some ICs omit this input protection and will be destroyed anway?


texts: What's the equivalent zener voltage of two parallel zeners?

texts: Assume we have two zeners connected in parallel, one with a zener voltage of x volts, and one with a zener voltage of y volts. What will be the equivalent zener voltage of the circuit?


texts: I'm wondering about the industry conventions for switches. I'm looking for a off-(on) switch that makes a click sound and "locks" the button until you release it. There are a lot of switches out there so I want to get the right one from the beginning.


texts: RS-485 Idle Failsafe Is it really needed?

texts:
I'm planning on setting up a sensor network around my house using a Cat5 Cable as both the power source and the signal line for the sensors, I'm planning on using RS-485 Transceivers and and Arduino's for the sensors.

From reading through many application notes and whatnot from TI and Maxim they all talk about having a failsafe so an Idle Bus goes to a known state.

If I use a master/slave setup why is this needed?  If the master assumes that no slave will transmit unless requested to, and the slaves are constantly listening for their own address.  It seems like this could be expanded for quite a bit of redundancy, without worrying about the state of the line when it's turned on.

Is there something I'm missing?


texts: How to do a counting of a timer configured in Mplab Harmony framework?

texts:
I'm new to harmony framework, and am trying to find how i can count timer iterations, so i'm doing a simple test.

I configured the timer like this:

Now i want to know if this is the correct way:

    uint32_t teste;
    case APP_STATE_SERVICE_TASKS:
    {
        while(1){
            teste = DRV_TMR0_CounterValueGet;
            printf("tmr val %d \r\n",teste);
            DRV_TMR0_CounterValueSet(0);
        }

        break;
    }

It happens that when i go see the print it's always the number 1660931680 doesn't make much sense to me, the timer is 16-bit so the maximum number should be somewhere near 65500.

What is wrong here?


texts: DotStar Micro LED Strip individual capacitor need and PCB questions

texts:
I was designing a PCB to make a DotStar Micro LED (APA102–2020 datasheet) strip and I saw that none of the products sold in the Adafruit store that uses these same LED's have capacitors in each led as every other LED Strip do.

Now in the product descriptions, it says:

  To keep the board small, we did not put any small surface-mount capacitors on the front. Instead, there's a power/ground pad set on the back and a 220uF capacitor that you can solder onto the back for a compact fit

So I'm trying to understand why having only one capacitor for the circuit is enough, in their Powering Neo Pixels (datasheet) guide it says that:

  adding a large capacitor (1000 µF, 6.3V or higher) across the + and – terminals. This prevents the initial onrush of current from damaging the pixels.
  and all of the Neopixels led strips have individual capacitors as well

I didn't find anything that seems to answer my question in the datasheets, but since I'm making my own strip PCB would you say that it's better to have individual capacitors for each LED as well? and wouldn't voltage drops end up

In my application, I will just use the LED's momentarily in a suit so I would appreciate if I could remove the individual capacitors for a single one since I want the LED's to stay very close and would need to put the capacitor in the back of the PCB.

Also, it seems that the back of the PCB in the photo is the copper pour of the Ground and I imagine the same goes for the Copper pour of the top part for the VCC, I've never seen a VCC copper pour (don't really have a lot of experience with PCB's) so it that what is happening here?

To sum everything up:
I want to make 8 DotStar APA102–2020 LED strips 300mm long with 32 LED's in each of them. They will be placed inside a visor in a way to form a matrix with some horizontal space for visibility.

I will power my 256 LED strip with a 2S (7.4V) Lipo Battery and a buck converter, so if the reliability of the power source could change the answer, I can try to buy a converter with the less ripple possible.


texts: AT89S8253 and Keil ULINK2 debugger connection?

texts:
I'm trying to connect AT89S8253 with Keil ULINK2. But the documentation is nil about 8051 controllers. As per the web, the pin connection is this.
ref: http://www2.keil.com/coresight/coresight-connectors#10pin

ULINK2 supports the ATMEL family of 8051 controllers (reference: http://www.keil.com/dd/). ATMEL uses SPI pins for the ISP programming. What is the correct pin connection?

[Updated - Original question referred to AT89C8253, but OP has confirmed this was a typo and AT89S8253 was intended.]


texts: Switching system is not working as intended, unless I use my meter prob whose Negative is on ba3 negative , how can I fix it?

texts:
simulate this circuit – Schematic created using CircuitLab

I want a circuit that could turn on a system and as well turn of that system, and sometimes work as an automatic switch pls guys take a look at the diagram. I'm using a CD4011 ic which have NAND Gate.
The problem now is that, it does work but not perfectly, because some times when I turn on preset 1 no voltage will come out except if I use my meter prob to torch the switch supply before it will now start to work the way I intended, pls guys help out what can resolve this?


texts: Simple and efficient way to send a 5V square wave to an 8ohm 1W speaker

texts:
I want to use a 5 V square wave generated by an ATTINY85 to drive a 1 W, 8 ohm speaker at 1 W. The project has to be battery powered.
I would like to use a 18650 rechargeable 3.7 V Li-ion battery and a 5 V 600 mA boost converter:

With a simple emitter-follower circuit, it doesn't seem possible to me to achieve the required 2.82 V (RMS) swing.
I considered using an LM386N amplifier, but from the datasheet it seems that the output voltage would not be enough to achieve the required 1 W maximum power.
I am wondering if I have to use more capable boost converter, making the project more complex having other stuff which need to work at 5 V, or if it is possible to do something else.


texts: What is (was) this component at ZD102 (top left, next to powered serial connector)

texts:
Part at ZD102 is overloaded with too much current and blown.

It's three legged, with two legs on the south side and 1 on the top.

The left side (white in the picture) is blown and has since crumbled away. There are now  clearly three metal legs. I cannot identify any markings nor polarity. ZD102 appears to be a unique location.

I would like to identify and then source the part to solder in place. Or something equivalent. Or something I can salvage from other electronics. There doesn't appear to be any other damage to the motherboard.

This is a Wacom digitizer II UX-0608-R from mid 1990s.  DC 9-12v 0.10A.

Appreciate your time.


texts: Confused about IN/OUT architecture of z80 chip

texts:
I am reading the manual, and it's a bit complex. I can't understand the machine code encoding for the life of me, but that's not my main concern ... my main concern is the address/data buses.

I do not understand the difference between the "address out" from the OUT instruction, and the port configuration as well, AND the involvement of the register data operands.

Quoted directly from the z80 manual:

  The contents of register C are placed on the bottom half (A0 through
  A7) of the address bus to select the I/O device at one of 256 possible
  ports.

Question time:

1.What does "the bottom half" mean?

2.Where/what are the 256 possible ports, and how does it select one, and where does it go exactly from there?

Next quote:

  If the contents of register C are 01H, and the contents of register D are 5AH,
  at execution of OUT (C),D byte 5AH is written to the peripheral device
  mapped to I/O port address 01H.

So if I have 1 in register C, and 90 in D, and I write OUT(C), D 90 is written to the something mapped to 1? How do I know what is mapped at 1?

PS: Also, if I have hardware at mapped address 1, where does 90 (the value represented) go to in that hardware?

Do not get me wrong by my confusion here, I am a programmer ... I just have very limited experience coding at this low-level, and just need some clarification.


texts: Whats the differences and options when choosing a cellular module?

texts:
I think in most cases you only need to send data in a low rates from a controller to a remote computer when there is no WiFi.

I can see there are some cheap GSM/GPRS modules  like SIM800L , but lately I see more and more LTE modules of companies such as ublox .

When an industrial controller needs to send sensors data, what would be the difference between LTE and GSM ?

I also know its a real hassle to use a sim card and get a plan etc - is there a solution for this ?

Are there any good cheap modules for mass production that are recommended ?


texts: Second order RLC filter and load resistance choice

texts:
In this 2nd order, low-pass filter circuit

simulate this circuit – Schematic created using CircuitLab

I am interested in the transfer function

$$ H(s) = V_L (s) / V_g (s) $$

which is (hoping that I didn't make mistakes)

$$H(s) = V_g \displaystyle \frac{R_L}{s^2 L C R_L + s(C R_g R_L + L) + R_L + R_g}$$

Which could be the benefits of having

$$ R_L = \sqrt{L/C} $$

?

I have some notes referring to this condition as to a "matching condition" and this recalls some transmission lines concepts, but I don't know how the transfer function could be simplified by applying that condition.

Even with \$ R_g = R_L = \sqrt{L/C} \$ it can be written as

$$H(s) = V_g \displaystyle \frac{1}{s^2 L C R_L + s(C R_L + L / R_L) + 2}$$

$$H(s) = V_g \displaystyle \frac{1}{s^2 LC + 2s\sqrt{LC} + 2}$$

but, again, I don't see anything useful.

Does the complex conjugate poles have a particular position? Or what else?


texts: How to read large number of analog-in fast and effectively with Arduino-Compatible Hardware

texts:
I need to read the analog values of up to 50 analog light reflection sensors which are used to determine distance to a specific object with an Arduino-compatible Microcontroller such as:

Arduino Due with the Atmel SAM3X8E CPU
Arduino Zero with ATSAMD21G18, 32-Bit ARM Cortex M0+ CPU

But when thinking about my idea I come up with quite some questions I can't really answer myself:

My first Idea was to use several ATSAMD21G18 to read a bunch of 6 analog devices. But that would end up in having at least 9 ATSAMD21G18 and in having to connect them with SPI or I2C.

So I thought of using several analog Multiplexer/Demultiplexer like the 4067 instead. Even this would end up in multiple units of the 4067 but I could use a single Arduino Due / Zero.

My concerns however are that the 4067 does not switch the analog inputs fast enough for my needs. I really would like to read all those analog values as fast as possible. How fast would a 4067 be in this application?

And also. Using the 4067 I have to use digital I/Os to set the input channel of the 4067. Can I wire them in parallel so that I would be able to share the digital I/Os with every single 4067?

And also does the length of the circuit affect the readings when having to deal with distances between the 4067 and the Arduino of about 50cm?


texts: Tips to design an analog automatic switch selection circuit for CT (Current Transformer)

texts:
I've been beating my brains out in a circuit I attached a figure below. Well I have 2 current transformers(CT). First from current on secondary 100A:50mA and second from voltage on secondary 100A:1V. In my first CT, I need to add burden resistance to measure current on secondary and add an offset of +2.5V because of my ADS1115 (16 bit ADC) Im going to read on its analog input, however for second CT I just need to add offset. About this circuit its done and you can find more info to get update about my following problem:

https://learn.openenergymonitor.org/electricity-monitoring/ct-sensors/interface-with-arduino

I want to know if is possible to have 1 KRE 2 connector on the board im going to design and when I connect 1º CT (100A:50mA) on my KRE 2 connector I should select its circuit (with burden resistance) and then go to my A0 ADS1115 input while my 2ºCT keep disconnect of course. However, if I wanna plug my 2ºCT on my KRE 2 connector, I need to switch for its circuit and then go to ADS1115. Signal track for ADS gonna have 2.5V because my offset. I just would like to know how to do it automatically if possible just using analog components. Any doubt, let me know

Thanks


texts: Problem with impedance matching on DIY 4 pole 3.5mm audio splitter

texts:
I built an audio 4 connector 3.5mm splitter. The goal is to play a sound clip through a phone's mic input across a call, while recording the same sound clip on the computer. I used the TRRS configuration of: Tip = Left audio, Ring = Right audio, Ring = Ground, Sleeve = Mic. This is apparently the configuration for an Apple headset. The recording part works on most phones, but the playing of a sound clip into the mic input of the phone only works on a select few. By the way, I am connecting speaker output on the one side to the mic input on the other side.

I realized that each phone has different impedance requirements. How do I adapt the cable to work on any phone? When I do impedance matching, how do I get to the total value of eg. 23 Ohm specified in the technical specifications of headsets? Is there something I can buy that will do the impedance matching for me or should I build it myself?


texts:
I have Monitor Photodiode specs that claim the following:

MPD Reverse Voltage: -10V Min, -3V Max
MPD Forward Current: 0mA Min,    10 mA Max

What is the convention for measuring this voltage and current? Would I measure the voltage the same as I would a normal diode (positive lead on anode, negative lead on cathode), and this would produce a negative voltage (implying that the photodiode operates normally in a reversed-biased configuration)?
For the forward current, would a positive current be flowing in the direction of the diode "arrow" symbol, or opposite?


texts: Slave timer configuration procudes an interrupt STM32f10x

texts:
I am going to config a master and slave configuration under STM32f10x. I connected them correctly but at the first step it generates an interrupt before enabling the master timer or enable the slave timer.
Here is my code:
int Pulse(void)
{
TIM_TimeBaseInitTypeDef     TimeStruct;

            RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE);

            TIM_SelectInputTrigger(TIM2,TIM_TS_ITR3);//
            TIM_SelectSlaveMode(TIM2,TIM_SlaveMode_External1);

            TimeStruct.TIM_Prescaler=0;
            TimeStruct.TIM_CounterMode=TIM_CounterMode_Up;
            TimeStruct.TIM_Period=29;
            TimeStruct.TIM_ClockDivision=TIM_CKD_DIV1;
            TimeStruct.TIM_RepetitionCounter=0;
            TIM_TimeBaseInit(TIM2, &TimeStruct);
            TIM_ITConfig(TIM2,TIM_IT_Update,ENABLE);

        ///Master Configuration code
...

}

void TIM2_IRQHandler(){

   if (TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)
   {
    x=x+1;
    TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
   }

}

after calling the Pulse function, it generates TIM2 interrupt(x=1), I need to know why it generates an interrupt when its trigger source is not configured/enabled.


texts:
Let R1 be upper resistor and R2 be the lower resistor of a voltage divider bias bjt circuit. Then can I visualize the DC bias of the base emitter junction as follows:
I am trying to look at DC biasing in a different way.
Is it correct that if I consider the input into the base emitter junction as a D.C. resistance that is chosen by my choice of Re (not r'e) and an arbitrary beta. Then can that portion of circuit appear as a simple current divider with R2. If this true, then it would seem R2 has to chosen so that adequate current drive is present for the base emitter junction to conduct property. I.e. R2 is not loading the base emitter junction down.


texts: Is there a circuit that can multiply the voltage of wire A by the voltage of wire B?

texts:
Is there a general 2-input/1-output circuit that multiplies the voltage of one wire by the voltage of the other wire?

For example, Voltage of A = 3, Voltage of B = 5, output voltage is 15.


texts: Arduino: Reliable and practical way to connect an I²C device (1 m away)

texts:
This is a combined mechanical/electrical question. It is mainly about getting the I²C connection reliable; this question does not concern itself with the software side (i.e., how to handle an I²C fault on the microcontroller).

I have an Arduino (Pro Micro) and an I²C slave device (an MPU 6050 sensor). The Arduino is already there (happily doing other stuff, connected to a PC via USB) and around 1 m away from where the slave will be placed. The slave is the usual small board similar to https://www.sparkfun.com/products/11028. It provides some capacitors and 10k I²C pull-up resistors.

So far, so good. In the good old "get'er done" spirit, I have hacked everything together with some RJ45 connectors and a 1 m Cat 5 cable I had lying around (carrying VCC, GND, INT, I²C). It kind of works, until it does not. The I²C communication breaks down regularly (after a few hundred or sometimes thousand transactions).

I admit that I still have to figure out who exactly the culprit is; i.e., I will connect the slave directly to the PCB and see if it still happens (that would rule out the cable connection). The software side is probably fine; said problem happens with several different firmware, even the most trivial ones. I have played around with the pull-up resistors (i.e., with/without the additional Arduino pull-up resistors; and with extra external 4.7 Ω resistors), and that did not change anything. The environment is not particularly noisy, I think. I unfortunately have no equipment to measure what goes on on the lines.

Meanwhile: Can you suggest a practical and reliable way to do such a connection? What I thought about:

The "easiest" one would be to get a second Arduino, place it right next to the slave, connect it with USB directly to the PC; that would eliminate the whole problem, but I would really prefer not to do that if I can avoid it.
Try to split the SCL/SCA lines into differential pairs; I don't see how that would work with the I²C open-drain protocol though. I don't want to stick with I²C necessarily; there is no need to fix that if there is an easier alternative.
P82B715PN line buffers
Something like CAN or RS-485 would likely force me to add at least two more chips, or even more per side (for protocol conversion and drivers).

Is there a practical (for a hobbyist), simple, go-to solution for this kind of problem (which seems to crop up once in a while...)? I'm really open to anything here.

I checked my cables... I previously had (INT+nothing), (SCL+nothing), (SDA+nothing), and (VCC+GND). I have added the GND to all pairs, so it's now (INT+GND), (SCL+GND), (SDA+GND), and (VCC+GND) as per @FiddyOhm 's answer. Unfortunately, no change whatsoever :( That wasn't it.


texts: What does metal to metal bottoming mean?

texts:
Some connectors datasheets specify the following:

  Metal-to-metal bottoming for maximum EMI shielding under extreme vibration

Reference: Dualok Connectors

I have also encountered the following for a similar component:

  Improved shielding resistance due to shell to shell bottoming.

Perhaps the following definition applies:

  to place (something) on or upon a foundation; base

However, this is still unclear to me. What does bottoming mean in this context?


texts: What is the main difference between RTL and HDL? To be honest I searched / googled it yet people are divided in their opinions. I remember one saying that HDL is the computer language used to describe a digital circuit and when it is synthesizable, then it is considered RTL.


texts:
I want to use SN54HC244 chips so I started reading the data-sheet.
It can be found here or directly here (PDF).

On the first page I don't understand the logic diagram:

1A1, 1A2 and 1A3 output labels are all 1Y1. From the table on the second page and the given the pin numbers (18, 16, 14, 12) I think the labels should be as the following image:

Am I mis-understanding something or is the data-sheet wrong?


texts: Transient current capacity of sacrifical Zener diode

texts:
The common wisdom is that Zener diodes are suited for only very low power surge protection because of their low current capacity.

But what about where it was used as a sacrificial device for clamping transient spikes?
Surely there would be a very brief period (ie in the order of microseconds) where it shorts completely across the pn junction and the internals become molten but remain temporarily physically intact.

Other typical surge components seem to rely on a massively larger transient current response - for example, the leads on MOVs and the traces on the PCB would normally be capable only of a few amps yet they're usually rated in thousands of amps.

So what kind of instantaneous current handling could you expect from a Zener diode?

Edit: In this particular application, the zener is already used as a voltage regulator.
TVS diodes don't seem to be used for steady state voltage regulation - are they unsuitable or is because of cost?


texts: Questions about the circuit of the Arduino Micro

texts:
So I'm looking at the schematics of the Arduino Micro and I have a few questions.

On their website, Arduino claims that:

  The Micro can be powered via the micro USB connection or with an external power supply. The power source is selected automatically.

I'm looking at their schematics, and more specifically here:

And can't really understand how T1 works, assuming only USB is connected. If there is no Vin, how is there any Vgs voltage, and how does the transistor T1 open/close?

What is the function of the Diode D2?

Thank you.


texts: How do you differentiate between rms and peak voltage?

texts:
In the circuit above I've been asked to calculate the average power absorbed by the 10 Ω resistor. I managed to calculate a value for \$V_0=40\sqrt2\,\angle{-25}\$.

But I'm not sure if this is peak or rms voltage. I've spoken to some people and they say that the rms value is simply \$40\sqrt2\$, which doesn't really make sense to me, and I've spoken to other people who say to follow the \$\frac{V_p}{\sqrt2}\$ formula, which makes a lot more sense to me.

I'm not really sure who to believe, so I've come here seeking help.


texts: Voltage divider bjt biasing with thevenin theorem

texts:
Say I have this circuit:

I am confused as to how using Thevenin's theorem yields correct results. Say I choose a bias point on an I-V characteristic curve at the IC = 16mA. If this transistor has a beta of 200 then that means a IB = 80uA. Lets also say I want 1 volt across the emitter resistor R2. Now lets take the resitive divider biasing scheme and create its thevenin equivalent:

Step 1:

Step 2:

Step 3:

VTH is going to be V1*(R3/(R4+R3) and RTH = R3*R4/(R3+R4). So here is the problem, I know I want the base current to be 80uA, VBE = 0.7V and VE = 1V. Which means I want VB = 1.7V which is what I would have chose for VTH as well. As we can see though, VTH needs to be greater than 1.7V to give me the desired voltage at VB. Where am I going wrong in my thinking?


texts: Reason for brief spike in op amp output when crossing 0V?

texts:
Does anyone recognize this spike in the output of an op amp when the signal crosses 0V? It spikes up when crossing up and down when crossing down. In one of the EEVBlog videos, Dave pointed to something exactly like this on the oscilloscope and said (as an aside) that it could happen when using a 10k feedback resistor or something like that. But I can't remember which video it was. This is the output of a TL071 (actually 1/4 of a TL074). It's fed from the output of 2 other TL071s through 2.2k resistors, and the feedback has a 10k potentiometer.

simulate this circuit – Schematic created using CircuitLab

Update March 10

As mentioned in the comments below, the circuit consists of ATmega328P processor driving 8 lines into an R2R DAC. The output of the DAC and a DC bias voltage intended to center the DAC output at 0V feed into an inverting TL071 op amp. The output of this op amp is "OA2OUT" in the schematic above.

simulate this circuit

The R2R network output has 10k impedance, represented by R4. R1 and R2 give me an offset voltage and have a parallel impedance of 9.5k, which is pretty close to 10k. The feedback resistor R3 is also 10k. So I think that this circuit will sum and invert the R2R and offset voltages.

When I check the output of the R2R network at point R2ROUT, I don't see the spike.

When I check the output of the op amp at VOUT, I see the spike.

I tried a few other things. I tried replacing the 10k feedback resistor with a 2.2k resistor, just because it was lying around and because I remember Dave mentioning something about a 10k resistor in the EEVBlog video. That made the spike worse.

Then I tried replacing the TL074 op amp with an LM6144 op amp. I've been using this circuit to try out various op amps and try to understand what makes them all different, so I know the circuit works (kind of) with all of them. This time I got spikes on every transition.

Finally I tried a TLV2374, which is fantastic, but I still see the spike. It's smaller but still there.

Still trying to figure this one out. Thanks everyone for your help so far!

Update March 13

Tried measuring the R2R output with an R/10 (1k) load as per @WhatRoughBeast comment below. Now I see the spike! Also seems a lot noisier... which is something I noticed before and attempted to fix with 10uF capacitors across the power rails and the virtual ground. It "worked" in the sense that it reduced the noise, but it also introduced the oscillation/ringing that I mentioned when I tried to install a small cap to smooth the DAC output. All these things are obviously related, just not sure how.

By the way I did try the 100 ohm resistor suggested by @Brian Drummond earlier, but the resulting signal was so smeared out and noisy that I couldn't tell what was going on.

So what's the takeaway here? The problem is obviously the MSB behavior that @WhatRoughBeast identified. It, and the noise, seem to get worse with more current through the R2R network. I thought, okay, buffer the R2R signal through a non-inverting op amp before doing anything else with it, but when I do that, I also see the spike. Is the only solution to filter it out and not worry about it?


texts: Help powering an old heater control board im trying to reprogram

texts:
Not photo of my specific board.

I got 3 old universal controller board's , I'm attempting to reprogram them to learn hardware hacking. But i not quiet sure what would be the best method of powering it.

It says on the board that it uses a 24VAC transformer.  But the minimum is a "12VA class 2 only".  I'm wondering if it would be a safer to wire batteries together to power it, and if i can go under 12 volts. I'm not going to be using the massive relays so i shouldn't need the full amount of power?

Board name: Amana rskp0009


texts:
I don't know if this is the correct forum to ask this, but I have a problem with my audio set up.

The setup goes as follows: PC -> external audio card (via usb from pc) -> stereo equalizer mixer (via headphone output from audio card) -> speakers (via rca audio outputs from equalizer).

I want to add my guitar amp as a speaker and the only available output in the equalizerbis the one for headphones (the equalizer allows to play the sound from rca output and headphones at the same time).

But my problem is that when I connect the amp, the speakers start a high frequency humming sound (which is also heard from the amp).

Details

To be clear, the setup works with no problems when the amp isn't connected.

I tried to put actual headphones in the equlaizer and there was no humming.

When the humming is heard and I move the cursor around, the humming sounds a bit louder.

The amp that I am trying to connect uses a 6.5mm jack

The humming is heard whether the amp is on or off.


texts:
I'm designing a keyboard with the Proton-C and I'm not sure about using decoupling capacitors - how to connect them.
It has 3 GND pins, 1 VCC/3.3V pin and 1 VBUS (5V_RAW) pin (if I'm looking at it correctly.) Do I use 2 decoupling capacitors, one connecting VBUS to GND and the other VCC to GND and then if something needs to be connected to GND/VCC/VBUS I connect it through those capacitors? I'm pretty confused to be honest.


texts: Tutorial for USB communication with a PIC18F4550 using CDC framework

texts:
I am trying to perform USB communication from the PC to a PIC18F4550 microcontroller using the Microchip PIC18 USB CDC(Communication Device Class) Framework which essentially makes the PIC18, connected to the pc through the usb cord to the usb port of the pc, appear as a vritual COM port on the PC. This gives me the ease of sending the data as if I was sending it to a serial port on the pc side and removes the hassle of using a usb to serial converter.

Now the problem is that the demo project provided by Microchip is written so that it can be burned on different devices, with different circuits, or with different conditions - that makes it large, and for me at least, harder to understand. If someone could hopefully just provide a working code with minimal comments for this microcontroller or something similar OR link me to a good tutorial, it would make my life MUCH MUCH easier

Thanks.


texts: Methods or any innovative ways to check the correct layer order independent of the customer given layer stack data

texts:
As a PCB manufacturer do we have any fool proof method to check correct layer order?
I tried to check the impedance with standard Er, H. It works, but I'm not satisfied with the methodology I followed.

I want to ask the community if you have any measures! I want the methodology check to be independent of the customer provided stack up drawing or information.


texts:
(source: desmith.net)
I've built the HV supply shown above (from here http://desmith.net/NMdS/Electronics/NixiePSU.html). And it works great. I would now like to be able to digitally control the output voltage. This is currently controlled by VR1.
I've tried replacing VR1 with a BJT or a MOSFET. However I couldn't get this to work. Should this approach work or is there something I'm missing?
If this doesn't work I was considering putting a high voltage opamp on the output (400V). Are such Opamps available?


texts: LC Parallel Circuit with current source in steady state

texts: I understand that ideal inductor behaves as a short circuit at steady state and the ideal capacitor keeps on filling infinitely. I read that the inductor will be short circuit and capacitor will be open circuit at stead state. But the capacitor never blocks the current, it keeps on charging. So why is it an open circuit?


texts:
I understand that the diode will conduct only for it's positive half cycle, but my question is tank circuit's sine wave half cycle is 180 deg, right? But solution assumes diode will conduct for 90 degree.

What is the conduction angle of the diode in this question?


texts:
I want to build a USB device that can draw 1A.

Some of the PCs at my office can supply 1A, some only 800mA. The USB 2.0 specification says a device can only draw up to 500mA.

I cannot build a software/hardware infrastructure to check if the device is a PC and, if so, to limit the current to 500mA.

What would happen if I try to draw 1A without checking if the host is capable of supplying this current? Does this risk ruining the host?


texts:
I have a piece of code here that was generated by Atmel START Wizard.
It setups a UART and it also creates a ring buffer for reading data.

This is the code that reads data from the buffer:

uint8_t USART_2_read(void)
{
    uint8_t tmptail;

    /* Wait for incoming data */
    while (USART_2_rx_elements == 0)
        ;
    /* Calculate buffer index */
    tmptail = (USART_2_rx_tail + 1) & USART_2_RX_BUFFER_MASK;
    /* Store new index */
    USART_2_rx_tail = tmptail;
    ENTER_CRITICAL(R);
    USART_2_rx_elements--;
    EXIT_CRITICAL(R);

    /* Return data */
    return USART_2_rxbuf[tmptail];
}

When the main program access the buffer it calls an ENTER_CRITICAL(R) macro before decreases the elements counter by one.

Here is the ENTER_CRITICAL macro:

#define ENTER_CRITICAL(UNUSED) __asm__ __volatile__ (   \
   "in __tmp_reg__, __SREG__"                    "\n\t" \
   "cli"                                         "\n\t" \
   "push __tmp_reg__"                            "\n\t" \
   ::: "memory"                                         \
   )

and the EXIT_CRITICAL macro:

#define EXIT_CRITICAL(UNUSED)  __asm__ __volatile__ (   \
   "pop __tmp_reg__"                             "\n\t" \
   "out __SREG__, __tmp_reg__"                   "\n\t" \
   ::: "memory"                                         \
   )

I noticed that it disables the global interrupt, not only the Receive Complete Interrupt of the UART.
Usually what I'd do is to disable only the "Receive Complete Interrupt" letting any other interrupt enabled. This all make me wonder if there's any particular reason that Atmel or Microchip developers make it that way.

Does Global Interrupt need to be disabled? Would the other interrupt affect this operation if they were enabled? Is there any difference by disabling only peripheral's respective interrupt?

This code is running on an AVR8


texts: Why are resistors classed as 'conflict' goods?

texts:
Further to a linked answer for Why recommend tantalum over ceramic capacitor for voltage regulator?
, we have this:-

Why is the resistor in the middle a conflict resistor?  Should I stop buying un-ethical resistors?

I appreciate that it might just be artistic licence.


texts: Limits of dead reckoning using MEMS sensors

texts:
I'm trying to track body parts relative to a person's torso. I see quite a few questions about using MEMS accelerometers and gyros for dead reckoning, and they confirm my suspicions that various factors greatly limit their usefulness for these sorts of applications, but I'm seeking clarification of these limits:

What exactly are these limits?

Other answers have addressed why these limits exist. Naturally the specifications the parts in the system in question and what is considered "acceptable error" for the system will both change the exact limits, but is there a single order of magnitude in time, or distance that I can expect dead reckoning to work? I'm well aware that over long distances (a few yards or so) the error becomes too large for most practical purposes, but what about within a few feet?
What can I do to improve these limits?

I'm currently looking at using an accelerometer and a gyro. What other sensors can I add to the system to improve the error rate? I know over longer distances a GPS can be used, but I doubt any consumer electronics grade GPS has fine enough resolution to help in my case.

Additionally, a general consensus seems to the only way to improve these limits past the point of improved sensors is to provide a reference not subject to error. Some systems solve this using cameras and markers.  What kind of reference points can a portable/wearable device provide?

I've seen the usage of radio waves to measure long distances accurately, but I can't tell if such a system could be accurate on such small scale (in terms of distance measured) using "off-the-shelf" components.


texts: Which Battery pack use for Arduino TimeLapse dolly

texts:
I'm trying to create a small TimeLapse Dolly during my spare time.  I'm planning to take away the dolly to film nature outside but I'm not sure which battery pack should I use.

I would like to maintain the complete system moving for about 2-3 hours, so I presume that using a 9V battery is not enough.

I have the following components:

Arduino Duemilanove
Stepper motor Driver (EasyDriver)
Mercury Stepper Motor SM-42BYG011-25 (12V/0.33A)

I need assistance selecting a battery that will last for at least 2-3 hours, compatible with the component list above.


texts: How to make LM39302R (voltage regulator) work?

texts:
I've bought an LM39302R for my GSM module (SIM808):

The datasheet of the module recommends a Microchip regulator which is not available in my location so I've searched and found  next best option, LM39302R, although I would be happy to find a cheaper replacement with acceptable voltage dropout.
Anyway, the LM39302R datasheet said it follows the famous rule of adjustable LDO regulator:

I built the PCB, and I've put 1K resistor on the top and 2.2K for R2 (I know VOUT trace of the regulator is too thin!)

According to the formulation which you can see in this online calculator it should be 4V on the white arrow on the PCB picture, but I read only 2 volts.
Why does this happen?
Almost all implementations use 100K resistor for R1 and 47K for R2. I don't see how it could output 4 volts, it should be 1.8375 volts.
The formulation has made me think, what is the difference if someone puts 1Kohm for R1 and 2Kohm for R2 or 1-ohm for R1 and 2-ohm for R2 or 1-Mega-ohm for R1 and 2-Mohm? Does it make any difference?
Any help would be appreciated!
Update 1:
lm39302 datasheet.
Sim808 datasheet
Update 2:
It is a shame but the low voltage that I've read was because of a damage capacitor in the circuit! the value in the PCB picture which is recommended (100k and 47k) works fine and lm317 calculator values is almost the same for this chip.


texts:
A balanced AC bridge has the following constants:

Branch AB, R = 2000(ohm) in parallel with C = 0,047uf (microfarad);
Branch BC, R = 1000(ohm) in serie with C = 0.47uf(microfarad);
Branch CD is unknown;
Branch DA, C = 0.5(ohm*farad).
The oscillator frequency is 1000 Hz;

I need to find the constants of branch CD.

This is what I got so far, in the image is the circuit and the solution I'm giving to it, I suppose that to find z4(CD branch) I have to divide it with z1(AB branch) but my question is, what I have to do with the imaginary (i), how the result will involve that imaginary (i) or what is the purpose of it. How will be the solution?


texts: When a vendor like Analog Devices offers a DAC family with nearly identical parts like the AD5671/AD5721 are both devices the same die but rated into different accuracy classes like CPUs? Is the 12-bit version just the dies where the high precision part of the R/2R ladder failed testing so they disabled the lowest 4 bits with a fuse or something?


texts: How to design a Sallen-key Low pass Oscillator that gives undamped oscillations? I've grounded the input of the Sallen-key low pass filter but still can't get any oscillation at the output. I've searched on the internet for days and I have not made any progress. Please help.


texts:
first I must say, I am new to the HW programming, but I really enjoy it.
My first project is writing a library for MT7623N (BananaPi R2) that handles GPIO pins. I got the GPIO part done and I can set pin HIGH or LOW and now I moved to SPI, which didn't seem as a big problem either, but..
I got stuck on the clock for SPI. I don't know how to properly set clock speed, because there is no mention of clock divider.
I understood, that the clock speed is selected through clock multiplixer.

List of PLL is below
Here starts my first issue. SYSPLL is probably misnamed MAINPLL? And what does SYSPLL_D4 mean? I am guessing, that it means frequency dividing by value 100, which should be /2, so for MAINPLL with frequency 2184MHz, it should be 1092Mhz. Is that correct? I haven't found any mention about this in the datasheet itself.
Then there is UNIVPLL2_D2. Only one UNIVPLL is documented. Does it mean multiplication? So the value is UNIVPLL*2/2
I am trying to calculate values for the SPI0 MUX. Can you please help? I am guessing that the first (default) clock is 26Mhz? I would like to use much lower values.

The datasheet reference https://drive.google.com/file/d/1GwXa5BNJFExP4HFEBcDFKAHYCWC46bdA/view
Thank you very much for any kind of hint! I am stuck on this second day.
Here are the PLL frequencies


texts: Verifying maximum switching frequency calculation of a hard switching IGBT

texts: I have recently been working on a power H-Bridge meant to drive an inductive load in hard switching mode. I calculated the maximum operating frequency limitation due to maximum power dissipation of the IGBT that I have chosen. I am not very experienced in this topic because all my knowledge comes from reading and I would greatly appreciate if someone could verify the accuracy of my calculations and correct me if something is wrong. I would also be happy to hear any general advice regarding this topic if you have some on your mind :) Thank you for your time and have a great day!


texts:
For

For a BJT why is the diode current Ic and not Ie?
Ie = Ic + Ib
The base current also passes through the B-e junction modelled diode


texts:
I am trying to create a circuit but I don't know exactly which switch design or logic chip I would use to accomplish my goal.
Here's the scenario:
I have 6 pins, let's call them A, B and C and 1, 2 and 3.  Each of them are carrying a low voltage (<5V), low current (<20mA), analog signal which pertains to an analog synthesizer patch.  I want to use a pushbutton switch to move through 3 different ways of connecting these pins.
Position 1: Pin A is connected to Pin 1, Pin B is connected to Pin 2, Pin C is connected to Pin 3
Position 2: Pin A is connected to Pin 2, Pin B is connected to Pin 3, Pin C is connected to Pin 1
Position 2: Pin A is connected to Pin 3, Pin B is connected to Pin 1, Pin C is connected to Pin 2
What is the simplest way of accomplishing this circuit using a pushbutton as the control interface?
Attached is a diagram in case that helps.
Thanks so much for any feedback!


texts: How Can the Quantization Noise of an ADC be Measured using the Digital Output?

texts: The ADC quantization noise is the error signal generated by rounding the sampled analog values of  signal. Suppose that we have the digital output of an ADC, how can we measure the quantization noise, only using the digital data, and without converting the digital signal to analog and comparing it against the original analog signal?


texts: Effect of Input Frequency on Output of Class A amplifier

texts:
I've got the following small signal amplifier that I am simulating on multisim. The gain is around 5 and the setup works to amplify the given AC signal.
The problem is that I have played around with the frequency of the AC source from 1kHz to 100MHz and haven't noticed any change in the gain of the amplifier. Is this supposed to happen ?

I would've thought the Gain would have been affected etc or that I would have seen something different ? I'm a bit puzzled and would like to know how the frequency of the input voltage affects the output signal in such an amplifier


texts: Leds in series with buzzer without resistor

texts:
So I'm pretty new at this, so I'm sorry for any dumb questions/statements.

I'm trying to build a puzzle box where you activate a circuit with a reed switch using a hidden magnet. Activating this circuit needs to make a sound and make 2 LED's light up.
I'm using a 9V battery, 2 green LEDs (no datasheet available, no multimeter of potentiometer either. But the operating voltage range is 2.9-3.6 V at 20 mA) and a mechanical buzzer rated at 2-4 V at 20 mA.

So here is my thought process: 2 LEDs with a voltage drop of about 3V, will leave about 3V for my buzzer (well in the operating range if the LEDs happen to drop more/less). Since all of the components are using 20 mA, I can safely put them in series.
The only thing I'm not sure about, is the current that will flow through. I know you normally would place a resistor in front of the LEDs to limit the current, because the LEDs are basically a dead short, but will the buzzer do the same job?

So:

Is this possible: all of them in series without a resistor?  Will this have any effect on the brightness/sound level?
if not, can I just put the 2 LEDs in series with a resistor (needs about 140-150 ohm resistor in front of it) and those LEDs in parallel with the buzzer (with a 300 ohm resistor?
If both of them are wrong, what's the solution?

Thanks!


texts:
I´m playing around with some PIR-Sensors (I don´t know the exact type) and I don´t have any experience in designing circuits for this type of sensor. I have googled some basic circuits and I took a look into the D203B datasheet to get some ideas how I have to design a circuit for this sensor. I want to test this one:

But the transistor doesn´t pull down the signal line. I have measured the output voltage of the sensor and my oscilloscope displays a voltage of 520 mV, but this voltage doesn´t change when I move my finger in front of the sensor. So I´m pretty unsure if this sensor is broken or if my circuit is "too cheap".


texts:
I'm hoping to see if my Bluetooth speaker could pass FCC Part 15. No certification is needed at this point - just to purely see if it'd pass when it becomes ready for certification. I believe this is called a 'walk-in' test - correct?

As I'm not familiar with the testing procedure, are there labs that would be happy to test it without certification? What do these labs need from me in order to test all operating modes, e.g., pairing, transmitting audio, etc.? Do I need to write them a custom program that activates each and every mode?

Thanks


texts:
I'm trying to replace a 2 pin JST connector with a micro usb female connector to supply 5v to my circuit.

Obviously I should connect VBUS to +5v and GND to GND.

Should I connect shield to GND?

Should I do anything with the other pins (D+, D-), or just leave them not connected?


texts: Problem of Convergence in simulating a model using Cadence Orcad 16.6 Pspice software?

texts:
I have a simple problem in simulating my circuit. First I will post all the details, Schismatic and netlist, then I will talk about the error and its options.
I am using Cadence Orcad 16.6 Pspice and simulating a simple circuit the schematic along with simulation setting is given below.

The schamtic is very simple. I am giving input sine wave to my device and it has two output ports. The first is "N". Which I modeled using a voltage controlled voltage source.
Before Going further, I will upload the netlist file I have written and integrated with the circuit.

.SUBCKT mem cap n vg
.PARAM p1=1, p2=-2, p3=3, p4=4,
+ epsilon0=8.85e-12, d_mos=0.65e-9, epsilon_mos={5*epsilon0},
+ d_g=30e-9, epsilon_g={19*epsilon0}, vt=-1, e=1.6e-19,
+ u=30, h=1.05e-34, weight=0.70,c_g={epsilon_g/d_g}, c_mos={epsilon_mos/d_mos},
+ c_t={1/((1/c_g)+(1/c_mos))},

.PARAM n_initial={((c_g*(-vt))/e)*0.0001},

En n 0 VALUE={(n_initial)}
.ENDS memcapacitor

Now the netlist  is really simple...There is the parameter "n_initial" the value of which is calculated on the basis of previous parameters.When I calculated it value, It is equal to  in the order 10^12 . Now I just want to output this n_initial value at the output node "n". This is constant value of the order 10^12 and it is not dependent on any input voltage .Its just a simple constant value calculated based on the previous parameters.

Issue:
When I simulate this code, I get error given in the pic below, i.e Convergence issue in transient analysis.

I used almost all the techniques used in the file attached, i.e GMIN stepping and simulation option setting , change in number of iterations etc. But couldn,t solve the issue.
Option:
Then I changed the value of n_initial and reduced it to by using larger vale of "e" which is in the denominator.  I used e value in the power of 10^-12 instead of 10^-19 and it worked.
Conclusion:
I concluded that problem is in the n_initial parameter value. If I increase this value and assign it to some node, It gives me error . When I reduce its value, It works just fine.
Kindly give me suggestions. Thanks in advance.
Note : if you need any other info, I will provide it happily. I can send all my file to anyone who will help me solving this problem.


texts: Local Interconnect Network(LIN) default status

texts:
How does slave identification takes place in LIN protocol by the master ?

What is the default status of a LIN bus ?

How are collisions avoided in LIN ?

What is the role of Sporadic frame ?


texts: Read data from 134kHz tag from a smartphone

texts: Is there a way to configure the NCF reader from a smartphone to read 134kHz tag or is a smartphone able to power up an external reader so it can read the frequency? I need to read from a passive chip (EM4305) from a distance ~7cm. Another option that I was thinking is if I can convert the 134kHz signal into a NFC signal which mean I no longer need to connect something to the phone.


texts: How critical is winding a solenoid/electromagnet neatly?

texts:
We've all seen the expensive toroidal winding machines on YouTube, and manufactured solenoids are always so neat in construction - as in: Each winding is neatly packed to its previous, without overlapping itself: like "-/////////-"

There's no explicit numerical answer here - I'm just after an indication of significance - if a winding was to be done in a factory - perfectly rolled, no overlaps, each coil immediately next to the previous one vs. one of the same specifications done at home with a few gaps, a few overlaps, and other imperfections here and there - what is the "ballpark" performance hit of that? Are we talking 0.1% or 10%?

If it's actually possible to perform some sort of calculation (with some assumptions put in there) - let’s use the example of: winding a ⌀35 mm annealed soft iron rod with ⌀1.2 mm magnet wire, wound 200 times across a 40 mm length.