texts: How to tell the difference between resistors in series and in parallel?

texts: So this is my attempt at part (a) of this question. I honestly just guessed that the resistors I chose were in series since to me it feels like I could have done this problem with the opposing resistors in parallel which yields a different answer. How can I tell which way is proper when finding equivalent resistances?


texts: Control register of magnetometer in MPU-9250 reseting itself

texts:
I want to read magnetometer outputs from the MPU-9250 sensor (Datasheet, Register Map) but the CNTL1 Register (0x0A) of the magnetometer resets for certain values. I configured the sensor properly so that I bypass slave adress to read the magnetometer and I am succesfull in reading the WHO_AM_I register of the Magnetometer.
The problem occurs when I try to configure the magnetometer by writing 0x16 (16-bit outputs, continuous mode 2) or 0x12 (16-bit outputs, continuous mode 1) to the CNTL1 Register (0x0A). When I write 0x12 and read back, I get 0x02 and when I write 0x16 and read back I get 0x00.
data[0] = 0x00;
/* Writing to the CNTL1_AD register (Power-Down Mode)*/
result = HAL_I2C_Mem_Write(&hi2c1, MagnetometerAddress, CNTL1_AD, I2C_MEMADD_SIZE_8BIT, data, 1, HAL_MAX_DELAY);
if ( result != HAL_OK ) {
    strcpy((char*)buf, "Error Writing I2C!\n");
    HAL_UART_Transmit(&huart2, buf, strlen((char*) buf), HAL_MAX_DELAY);
}

HAL_Delay(100);

data[0] = 0x12;
/* Writing to the CNTL1_AD register (Continuous Mode 1 and 16-bit output)*/
result = HAL_I2C_Mem_Write(&hi2c1, MagnetometerAddress, CNTL1_AD, I2C_MEMADD_SIZE_8BIT, data, 1, HAL_MAX_DELAY);
if ( result != HAL_OK ) {
    strcpy((char*)buf, "Error Writing I2C!\n");
    HAL_UART_Transmit(&huart2, buf, strlen((char*) buf), HAL_MAX_DELAY);
}

HAL_Delay(100);

/* Reading from the CNTL1_AD register */
result = HAL_I2C_Mem_Read(&hi2c1, MagnetometerAddress, CNTL1_AD, I2C_MEMADD_SIZE_8BIT, data, 1, HAL_MAX_DELAY);
if ( result != HAL_OK ) {
    strcpy((char*)buf, "Error Writing I2C!\n");
    HAL_UART_Transmit(&huart2, buf, strlen((char*) buf), HAL_MAX_DELAY);
}

Writing 0x12 read back as 0x02 and writing 0x16 reads back 0x00. I don't know why it's reseting the 4th bit or why it's reseting Mode 2 and not Mode 1. Does anyone have an idea why this happens?


texts: I need non reactive resistors for use at LF thru HF (100KHz thru 30MHz) for use with radio receiving antennas as terminations. Carbon comp and carbon film work but have their shortcomings in stability and TCR. Thin film resistors have low or no inductance but they are expensive. Wirewound have poor frequency response. What other type resistors are suitable?


texts:
I design 2 PCB's. They are connected with a connector.

First one is PCB1, has the size of 50cmX10cm , the other one is PCB2 and has the size 2x5 cm.

Through this pcbs and connectors some communication channels are travelling, which operates around 300Mhz.

Therefore, I have selected for the longer one a 6-Layer pcb stack up, in order to keep communication stable enough.
For the 6-Layer PCB1 I have the following stack up:

In PCB2, I have basically only the connector and all the signals are travelling through. I want to still keep same 6-Layer stack up. But within this size+connector I can not take communication channels inside the Layer, so they stay on top. As far as I know, 6 layer brings the advantage , since we encapsulate the signals with ground references from top and bottom.

Therefore, I could basically live even with 2 layers for PCB2.

But, should I now worry about the communication reliability ?


texts: Where does the other end of the secondary in a solid state tesla coil connect?

texts:
Yes, i know it's a very elementary question, it's my first time build. All circuits shows that the not- sparking end of a sstc is connected to ground,  but exactly where? do they mean the LITERALL ground or the ground on the wall outlet or just leave it unconnected?
It's based on Steve Wards mini SSTC


texts: Decoupling data fetching from processing and publishing

texts:
I am a software developer working on a personal project involving Raspberry Pi, Arduino and accelerometer sensors.
I already asked this question in the iot.stackexchange but I haven't had much luck. I was hoping someone here could point me in the right direction.

I am working on a project that involves raspberry pi and the accelerometer sensor ADXL355. The raspberry's responsibility is to fetch the data from the sensor, filter only useful data and publish it to a thingsboard.io instance on the cloud. All the different devices are powered by a battery, charged by a solar panel and monitored by the Raspberry.
As of now this is my setup:

This setup works fine but I would like to add more reliability on fetching data. It is vital to me that every single datapoint is fetched and processed. This set up doesn't allow me to operate safely on the linux os without possibly interfere with the process of fetching data. I would like to be able to restart the raspberry without losing data.
The sensor offers a fifo buffer functionality: it will save in an internal buffer up to 32 (xyz) datapoints, but considering that the sampling rate could go up to 1KHz, that leaves me with a 32 milliseconds buffer, which is nowhere close to enough to sustain a possible deploy of a new firmware or reboot of the OS of the Raspberry.
Sometimes (even though I applied the RT patch) and set the priority of the program that fetches data to the highest possible, I see intervals of up to 18ms before the program gets its context back (from some kernel interrupt routine I assume?), I'm worried that it could happen that the interval gets bigger than the 32 ms buffer that the buffer offers and potentially lose data.
What I wanted to know is what are the best practices regarding decoupling data fetch from the transmission and processing of said data?
What I thought about was to move the sensor in a dedicated Arduino board, which runs a bare metal firmware with as little responsibilities as possible fetching the data, assigning a timestamp, saving the data.

With this approach I wouldn't know to access the buffer without interfering with the program which is fetching the data. Is there any specific component that solves my problem? Like some sort of memory component that can be accessed simultaneously by different "users"?
I would like the buffer to be able to save at least up to 1GB worth of data to make up for a possible downtime window of 24 hours.


texts:
How do I connect the following battery and esc controller? They don't seem to fit as it is. Do I need another connector?
11.1V 2200mAh 3S 30C Smart LiPo Battery IC3

GoolRC 3660 3300KV Brushless Motor 60A ESC 6V/3A BEC for 1/10 RC Car USA P3F9


texts: Can I solder the components together? I just started to learn and I don't have a circuit board.


texts: Opam circuit where Vout =(V11/3 + V25/2)1/3

texts:
Hi i need to design an opam circuit where

But I can't find anywhere where I can get exponential outputs can you please help!


texts:
I am so confused, and the book's explanation confuses me more, can anyone explain how to get and identify the following questions displayed? the Book talks about a 2^2 * 3 bit memory but I cant seem to grasp it, I've search the internet but I cant seem to find the correct phrase that would yield any useful resources. How do I read the schematic that indicates how the address space and addressability?

I want to say that the Address space is 2^2  because there four boxes in each column and the addressability is a 4 bit because there are four D's, but I feel like that is wrong and also confused on how to attempt part c


texts: Two analog power planes for same voltage

texts:
I'm designing a board with LAN8720 and LPC1768.

LPC's ADC and LAN's magnetics connections require analog 3.3V power.

Should I separate these two analog power planes with a ferrite as I separate it from digital 3.3V power plane? Or is it OK to use only one analog 3.3V power plane?

I edited this message and added below picture. Ethernet PHY(LAN8720) to magnetics connection and LPC1768 ADC is using 3.3V analog power. Is it better to keep them separate as I draw in the picture?


texts: Fourier transform of a rectangular pulse

texts:
I'm interested in knowing:
 1. Why the frequency content has a larger magnitude at low frequencies
 2. Why the magnitude is zero at frequencies which are composed of multiples of the rectangular pulse's period

\$x(t)\$:

\$X(j\omega)\$:


texts: Why doesn't the Attiny85 work in this circuit?

texts:
I'm designing a circuit to control the power of a heater using an Attiny85.
This is the circuit:

The Attiny85 is programmed to boot with the heater and mosfet turned off.  When the button is pressed, the heater should turn on and stay on (according to the program).
However, when I turn on the circuit with the switch at the bottom, one battery makes a buzzing sound and the Attiny never seems to start running its program. (The voltage on PB1 doesn't change when the button is pressed.)
If any part of the mosfet is disconnected, suddenly the Attiny85 starts running its program correctly.  But, of course, the circuit doesn't work with mosfet disconnected.
Powering everything with a single battery also fixes the problem, but then the heater doesn't produce enough heat.
Why doesn't the Attiny85 load up properly and start working in this circuit?
Side info:
Attiny85 should get 4.2V
Heater should get 8.4V when on
The mosfet is a SIR404DP
Apologies if my diagram is weird
EDIT:
The mosfet and batteries can handle about 10 amps. I measured the voltage across the Attiny85 to be 4.2V, so it should be operational unless it's getting locked up on startup.
I tried moving the switch (SW) to the VDD pin and got the same result.
EDIT 2:
@Andrew Morton's comment to replace the heater with LEDs worked.  The Attiny85 operates them as expected.  Not sure how to get that to work with the heater though.
EDIT 3:
Attaching a capacitor between PB1 and GND as per @Nedd's comment did the trick!  The batteries are still making a scary buzzing sound corresponding to the PWM frequency, but I guess that's a different problem.


texts: How can pipelining hurt the clock frequency?

texts: As I understand it, pipelining is used to speed up the clock frequency by processing more instructions at once, and longer pipelines should improve the clock frequency. However, my instructor mentioned that in some cases pipelining could actually hurt the clock, particularly when splitting on the memory stage. I'm having trouble envisioning how this is possible-- surely it could hurt the CPI due to hazards, but it seems like the clock frequency should be unaffected. Can somebody point out to me what I'm missing?


texts: What MOSFET parameters should I look into for this experiment?

texts:
I want to generate a low freq movement for this loud speaker coil by using a function generator sine output. With the function generator I can generate a sine wave between 0.2Hz up to 100Hz with amplitude up to 2Vpp which is enough for my purpose. I want the coil move between 0.2Hz up to 100Hz.

But the thing is the loud speaker coils passes high currents. So this could be done by a big  expensive audio amplifier with many stages. In my case I'm not interested in audio quality noise ect. but just the crude movement of the coil.

60 W 8 Ohm are the specs for the speaker.

I think that means at 60W the coil will pass from the formula P = I^2 x R --> I = 2.7 Ampere rms current which for a sinusoidal wave a sine with +/-3.8 Ampere amplitude.

Can a single push pull stage like shown here with two power MOSFET work for the purpose? If I'm in correct path, what MOSFET parameters should I look into?


texts:
Meanwhile in quarantine I been trying to learn about electronics. I am still not able to understand the voltage drop when it comes to long wires. My goal is to be able to send a 5v signal over a very long wire. I have read a lot about Ohm's law, done a lot of exercises and I am still confused.

Before conducting the real experiment with the long wire I will like to simulate it it. Here is the simulation of what I am doing:

According to google the resistance of the cable I am using is .05 ohms per meter. If the distance is 200 meters that means there will be a resistance of .05 * 200 = 10 ohms.
If I intend to send a 5v signal over a long wire this is my simulation:

(The long 200 meters wires represent the resistors in the diagram)
According to Ohm's law the current of this circuit will be V=I*R  ->  5=I*20  -> I=0.25 amps
Knowing the current I can calculate the voltage drop across each resistor will be V=I*R -> V=0.25*10  -> V=2.5. Therefore the voltages of the circuit will be as:(The first part of the circuit has 5 volts. After the long wire there will be 2.5 volts and at the end 0 volts.)
To prove this is correct this is a circuit in real life:  (The yellow cable comes from the power supply with 5V. Then that is connected to the red cable. The red cable is connected to the 10 Ohms resistor. Then there is a blue cable connected to the other resistor. And finally that is connected to the black cable ground)
If I then use a volt meter I can see the the voltage drop between the red wire and blue wire is 2.5 Volts:
Now here is my question. Why do I still read 5 Volts if I place the proves like this:

On the internet everyone says that running 5V signals over long signals is not a good idea. Maybe it is not a good idea if you are planing to send current. I can understand that the current will drop a lot. But the voltage will not correct? On the other end of the 200 meter wire I just want to read a voltage in order to get a signal. What am I doing wrong? Why I cannot send a PWM signal using this approach?

Questions

A. When reading a PWM signal with arduino does arduino read the voltages or the current? I think it reads the Voltage and does not care about current like just like the volt meter? I just want to send a PWM signal over the long wires to trigger an event at the other end.

B. Why people on the internet say there will be a voltage drop when using long cables. I just simulated a very long cable and I am still able to read 5 Volts.

Solution

I know the solution will be to use an optocoupler with a higher voltage because I been researching on the internet. But I still want to understand why is my approach not correct and will probably not work.

Edit

Sorry I broke the circuit. If I place a 10K resistor in order to complete the circuit I still read 5V.

The circuit is complete and I am still reading 5V over the 200meters wire.


texts: I want to use logic analyzer to learn remote control IR codes

texts:
I've just ordered this generic logic analyzer (didn't get it yet).
Does the specs (channels/speed/accuracy) of such a cheap analyzer can be used to analyze IR remote control code sequences so I'll be able to send them later from a device I'll build?
If such an analyzer it enough to achieve this mission, can one guide me please what a circuit I have to build to be able to catch the signals from the IR RC led?
(I have an TL1838 38Khz IR sensor, but don't really know how to include it in a circuit).
The best way for me, I think, will be to see the signal using the logic analyzer (it it capable of it) from a simple electronics circuit, without the need of Arduino connection and programming.
So (and this is an Edit after reading some of the great and informative answers and comments) - A receiver circuit should be simple to build and connect the analyzer into it? What about software to 'understand' the IR codes?


texts: Translating/reverse engineering firmware commands

texts:
I'm trying to build my own Hi-Fi system. So, I recently ordered this Japanese DSP that's able to process Dolby audio. I was all excited until the part had arrived and I found something in the datasheet later.

https://www.njr.com/semicon/PDF/NJU26206_E.pdf

In particular, I saw that they were kind enough to provide a description of the list of commands they offered, but not so kind enough to describe how to actually instruct the DSP of these commands.

My question is, is there a way to instruct these commands to the DSP chip just based on the information I have, or is it just dead weight for now?

Things I've tried:

Contacting the manufacturer multiple times as they've mentioned in the datasheet with no response from them.
Search online for the Software Application note / Manual that's described in this doc with no luck.

The MPU I'm trying to use to talk to this DSP is an Arduino Uno if that helps.

Any help is much appreciated.


texts:
How can we say a battery,say Li-ion battery, is dead when it is 2.8V itself instead of 0V? How can the 2.8V not give current? What is happening? This question, is applicable to all other batteries also. Why do we say a battery is dead when it is not completely 0V, but when it is hanging some very around 2.8V for Lithium ion and 1.1V for the AA battery whose nominal voltage is 1.5V and others?

I have a Li-ion battery which I tried to charge. The maximum voltage mentioned in the battery is 4.4V max. And its nominal voltage is 3.85V. But, when I connect the battery to the USB Charger to charge the dead battery which was at 2.8V, the voltage line reads 4.6V. How is the 4.6V obtained and won't the battery get damaged as we are feeding 4.6V which is more than its maximum 4.4V voltage which is mentioned?


texts: Parsing results from LTSpice step function

texts:
I have a CLLC circuit in which I am trying to find values of the inductors and capacitors. I know the circuit needs a gain of at least 10 dB at 50kHz and below 1 db at around 30-40KHz. This has to be true while varying the load. I have set up the circuit in ltspice where I am using the .step function to sweep through component values and am looking at the bode plots.

The problem is I have so many graphs on the screen that I cannot keep track of them all. In the 1000s. Is there a way I can only display the simulations which have over 10dB at 50KHz and under 1db below 30Khz? Basically I want to get rid of all the sims that don't meet my criteria. The circuit is way too complex for me to solve mathematical.

It's for a tank in a resonant tank charger. The load will vary from 4ohm to 12homs.  The circuit is bidirectional and it would be helpful if the transfer function is similar in both directions. What other info should I post? I've been trying to make something similar to the circuit in this article. https://www.researchgate.net/profile/Ho_Sung_Kim3/publication/260496284_Design_Methodology_of_Bidirectional_CLLC_Resonant_Converter_for_High-Frequency_Isolation_of_DC_Distribution_Systems/links/00b7d5347ada7c098b000000/Design-Methodology-of-Bidirectional-CLLC-Resonant-Converter-for-High-Frequency-Isolation-of-DC-Distribution-Systems.pdf
 I understand basic laplace transforms but not enough to put this all together yet. I'm not overly interested in high efficiency, I know the load varies by a lot.


texts: 8085 MPU; Stepping through an instruction (Timing diagrams)

texts:
Let me write the steps of ADD B, as I've understood it till now.

T0:

ALE goes high
Memory location(say \$2000_h\$) is taken from Program Counter to Memory Address Register(which points to the passed location), via \$\small{A_{15}}\$-\$\small{A_8}\$ and \$\small{AD_7}\$ - \$\small{AD_0}\,\,\$(which will be latched)
ALE goes low.

T1:

\$\small{\overline{MEMR}}\,\$ is generated, the contents in \$2000_h\$ \$^ \dagger\$  is passed to the Instruction Decoder.

T2 and T3:

I really can't understand these two states, I can see that the \$\small{\overline{MEMR}}\,\$ signal goes low  in T2 and its stated tht the addition is done in T3, but the ALU will have evaluated the sum, once the temporary register is set, is the temporary register set only on the T3?

\$^\dagger\$ I could see that different instructions' OPCODE is divided differently, for example, for ADD B, the first 5 bits correspond to ADD and the next three bits correspond to the desired register, but for an instruction like MOV B,C the first two bits corresponds to the MOV and the next 6 correspond to the registers. How are OPCODES actually read correctly? Because, if it was constant that the first 5 bits always correspond to the instruction, then it can be understood easily, but that's not the case.

Finally, can someone please list out the steps in terms of Time-States for the instruction ADD B.

Program Counter is incremented somewhere along the way, but I don't know where that is happening.

In Ben Eater's 8 bit computer,  there is a separate T-state for PC increment, but 8085 is far more advanced I suppose.


texts: Common drain JFET output resistance "problem"

texts:
The output resistance of small signal model for common drain JFET amplifier equals $$ \frac{1}{g_\text{m}} || R_{\text{ds(on)}} \parallel R_\text{S} $$ and since $$ R_{\text{ds(on)}} =\frac{1}{g_\text{m}} $$ we can also write this formula as \$\frac{1}{g_m} \parallel \frac{1}{g_m} \parallel R_\text{S}\$ right?

Which could be derived to $$R_{\text{OUT}} = \frac{1}{g_\text{m}}/2 \parallel R_\text{S}$$ right?


texts: Voltage Translator (SN74LVC1T45) Locking Up?

texts:
I am building a programmer for Atmel AVR devices that includes dual (5/3.3) voltage selection and an integrated FTDI chip for serial diagnostics. I'm using the TI SN74LVCxT45 series for voltage translation and they work great -- the programmer portion works fine.

But the serial connection is coming back garbled for any baud rate > 300 if I set the target voltage to 3.3v.  At 5v it works fine at any baud rate.  The circuit for this is really simple.  VCCA and VCCB lines leading off the image both are configured to 3.3v:

Here, RXD_TARGET is reading input from TXD of a microcontroller, and RXD is routed to RXD on an FTDI serial to USB converter (FT230X). There is a 270 ohm resister to limit current as some board connectors ground unused pins for the ISP header (technically only necessary for the TXD output; I have tried removing this resistor to no effect).

This is a grab from my scope when sending a serial transfer.  The blue trace is the input at RXD_TARGET and the yellow trace is the output at RXD:

As you can see, the output waveform looks good and matches the input pretty closely until about midway through where it appears that the output latches up for about 600us. If I lower the baud rate to 300 baud, everything looks great.  If I switch the programmer to use 5v logic on the target microcontroller, everything looks great (internal logic to the programmer is always 3.3v, so this is just a level shift).  The data sheet for this series of level shifter shows bandwidth at 3.3v to be about 210Mb/s, and this is nowhere near that.  Also, the programming interface, which is SPI, also level shifts with these chips and is working fine, even at 3.3v (and is moving at about 119Kbaud). I also tried sending serial data onto one of the SPI inputs and it looks correct as well. I suspect either a bad chip or some interaction with the FT230X.  The board is tiny SMD so I'm trying to be somewhat methodical before I make a mess of the board.

Anyone have experience with a similar problem? Thanks in advance for any ideas.


texts:
I'm a bit confused how to correctly wire JTAG input and output.
I have my ST-Link and my STM32 microcontroller.
Which of the configurations is correct?
Pinout St Link  ||  STM32
TDI----------------->TDI
TDO<---------------TDO
TCK<-------------->TCK
TMS<-------------->TMS
RST---------------->RST
Pinout St Link  ||  STM32
TDI----------------->TDO
TDO<---------------TDI
TCK<-------------->TCK
TMS<-------------->TMS
RST---------------->RST


texts: What is meant by the break frequency of an op-amp?

texts: 1.Can someone explain me the break frequency of an op-amp and can an op amp have two or more break frequencies, if so how?


texts: Why do MOSFETs keep blowing after I replace them in a kickscooter controller?

texts:
I have a few Segway Ninebot ES4 kickscooter controllers that I would like to learn how to fix.
Essentially at some point the motor ceased and seems to be fused, won't accelerate, won't brake, and even if power is off there is resistance in the motor rotation.
I narrowed it down to a blown MOSFET related to one of the motor leads. The MOSFET beeped with the continuity test so I concluded it was blown. I tried replacing the MOSFET, at first with one that had the same model number as the originals and after that blew as well I upgraded to a slightly more powerful MOSFET that blew as well.
The MOSFETs blow pretty much immediately after trying to ride the scooter. At first when I put everything back together, the motor spins freely, then when I try to ride it, immediately the motor starts vibrating and eventually dies in like 3 meters of riding. I can accelerate without load and seems to be fixed, but right after adding load, the motor starts vibrating and the MOSFET blows.
This is where I am stuck now, the same MOSFET keeps blowing. What is causing it to blow? Is it the MOSFET driver?
Has anyone here on this forum repaired Ninebot ES4 (or similar) motor controllers with the same issue? What can I try? I have two boards like this that I would like to learn how to fix this kind of issue with.
Info:
Original MOSFETs on the board: NCEP01T13A (Tried replacing with same model from another dead controller)
Secondly tried replacing with: IRF3808 (It was the closest match I could find that was sold in my country)
Pictures were to large to add directly but I did not want to lose quality so I put them on Google Drive for some time:
https://drive.google.com/drive/folders/1NZizmvtqdIiOTcaqg5oKKYEOSOMuvynv?usp=sharing


texts:
I've been thinking about implementing a very simple ALU, and came across this link Verilog 8 Bit ALU. This seems to be a very naive and abstract but intuitive implementation. I'm thinking about breaching the abstraction layers here, and take the implementation to the gate level. The first step in this IMO would be to use a 3-8 Multiplexer for selecting a particular ALU module instead of the Case statement. However, I'm unable to think of a way to do so in verilog. Can anyone please provide a code snippet that does this may be, or point me to the right direction.

Thanks,


texts:
I'm working with ESC controllers which receive PWM signals that are very similar to those that control a standard Servo motor, i.e. a 50 Hz PWM signal (20 ms period) with duty cycle of 5-10% (1-2 ms on-time).

My question is why do servo motors (and most ESCs) use this particular protocol for setting the position (speed for ESCs)? Why not choose a faster frequency, something like 1kHz? Is there some fundamental reason for all servo motors to have agreed on this slow frequency?

I'm using an STM32 microcontroller to send the control signal to the ESCs so I can send some pretty fast and crazy looking signals, but even something as simple as an ATTiny85 operating at 8MHz can output a 1kHz PWM signal


texts: Improve output quality of FM receiver TEA5767

texts:
I have connected a TEA5767 to my Arduino board using I2C and can tune it fine (see instructable.com). As antenna a ~70cm long simple cable is connected. I've connected a cheap 5V amplifier. Unfortunately, the sound quality is bad - very much static noise (though the sender is only 2km air distance away) - with forced mono it is acceptable but still not good. When scanning for stations (muted) there also is noise. Disconnecting the inputs of the amplifier causes absolutely no noise.

Update according to the comments:
When using the FM application on my Motorola/Android phone and put it near the Arduino, it does not cause noise, so the Arduino seems not to "send" - but maybe it is caused by the connected VCC? I've put a 100nF and a 100uF capacitor near the FM receiver and amplifier - it makes absolutely no difference. For me it looks like the TEA5767 causes the noise.

Does someone has an idea how to improve the sound quality?


texts: is it possible to design high-speed PCBs in a modular way?

texts:
I'm going to design an Arm Cortex-A53 based core-board and this core-board will be used in many different projects with different applications. Sometime it will be used in a generic device to just run simple Android applications, sometime in an embedded system for collecting data from different devices USB, SPI, UART, And etc. So in each application i just need some specific peripherals of the SoC. For example when it is used to just run android and simple apps, i just need the display interface to connect to an LCD and a microSD card (No sound, WiFi, Ethernet, HDMI and ... is needed). in another application i will use the board to just connect to HDMI and connect to internet with Ethernet.

I'm checking for feasibility of designing my core-board in a modular way. My idea is to put the main parts that are fixed and nescessary in every systems(processor,DDR Rams, Flash Memory, main power management, Programming Port) on the core-board and then make a collection of connectors around the board. one connector for every video pins of the processor containing LCD, HDMI and Camera and another one for communication interfaces like SPI, UART, USB, Ethernet and audio and other things like this. after that whenever I need this board to connect different devices with USB and UART, I design a separate board containing USB and Uart circuit and connectors and connect this board to the core-board with a appropriate connector. In this way I every other extra connectors are omitted from my design. My goal is reducing the space and cost and improve security.

My questions are:

If I do my design in this way, is there any consideration that i should take care of with highspeed routes like usb, hdmi and ... . I mean if for example the hdmi pins are connected to a connector then this connector is connected to the same connector on the other board with a cable, is there any Signal Integrity problem that i should take care of?
if designing in this way is feasible, which kind of connector is the best choice for connecting two board to each other? are FFC and FPC connectors good choices?
in general, what is the criterion for choosing a connector specially in high-speed designs?)


texts: Modelling of dynamic behavior of a weak power grid?

texts:
I'm modelling the dynamic behavior of a weak power grid. I know the voltage level and short circuit capacity, and that's about it.

Short circuit max = 400A, 3-P
Voltage level = 66000 V

My problem is as follows:

I want to see the dynamic response if I start large motor, in order to determine if soft start / VSDs. For a normal strong grid, I would use settings such as:

Moment of inertia = High (99 s, which is maximum in my simulation tool)
Damping factor = Low (0, obviously minimum)
Direct-axis transient reactance = High (0.98 pu)
Short circuit capacity = High

The problem is, I can't model a weak grid with dynamic data saying it is strong. Not only does it not make sense physically, it also crashes the simulation tool (Paladin DesignBase 5). It works fine if I increase the SC-capacity, or decrease moment of inertia and reactance, but I don't know if it will make sense from a physical point of view.

Does anyone have any experience in modelling weak grids? Any way I can make this more realistic?


texts: Issues with NPN Transistors and RGB LEDs (Common Anode)

texts:
I have a question regarding the use of NPN transistors in an RGB LED (common anode) circuit connected to an Arduino Uno. I have spent the past several months developing LED color control software that communicates over serial to an Arduino board, which then produces color in LEDs over three PWM pins (a fairly common setup). I am now ready to install 10 LEDs instead of the single LED I was using during the testing process. I came across this Fritzing diagram in a solution, and have built the circuit with my NPN transistors and two LEDs to start.

Here are my issues:

Typically in common anode setups, writing a value of 255 to a PWM pin indicates OFF and writing 0 is full brightness. These controls seem to be inverted now with 0 being OFF. Is this normal behavior?
The brightness steps are out of control. Writing 1 to a RGB pin creates a fairly bright light, and anything above 3 is maximum brightness. For my color reproduction to be effective, I need at least 100 brightness steps as I had in my previous setup where only 1 LED was used and no NPN transistors were in the circuit.

Have I overlooked some aspect of NPN transistor electronics? I definitely am in need of guidance. I have only gotten into LED electronics recently and have a lot of learning to do.

Fundamentally, I need a circuit that will allow 10 common anode RGB LEDs to be controlled as a group by three Arduino PWM pins.


texts: Are there any generally acceptable UART best practices when it comes to hardware design

texts:
Are there any generally acceptable UART best practices when it comes to hardware.
Hi, I am trying to design a PCB that uses UART to communicate between two microcontrollers. Are there any generally agreed upon best practices that can optimize performance further that can be implemented on the hardware level.
Something along the lines of pull up/down resistors, resistors in series, TVS diodes


texts: FPGA Simulation - does it need FPGA hardware?

texts:
Reading through Altera documentation on FPGA programming, I can see that the design flow is made of

Design -> Compilation -> Simulation -> Programmation -> HW Verification

The design consists of writing Acceleration function units and using IP to build a circuit in schematics, e.g. using Quartus. The design is then compiled. Simulation is made of functional and timing simulation. Functional simulation verifies that the design corresponds to the functionality we want, while timing simulation is to verify the impact of the propagation delay. Only on the programming phase, the file generated at compilation is loaded onto the FPGA and run on hardware for HW verification.

I infer from this that the simulation phase does not need Hardware. Is it correct? Also, the doc mentions the waveform simulation platform for timing simulation. Are there other tools for timing simulation and what are tools for functional simulation?


texts: Safety of zener diode based non isolated power supplies

texts:
Are the following zener diode based non isolated power supplies safe to use with a touch based application?

I would assume, the circuits are safe if they completely sealed (including the touchpad). Would the TT6061A circuit be safe, if y-Capacitors would be used for C4 and C5 and the touch pad be exposed?

e.g. SGL8022W

e.g. TT6061A


texts: What is a purpose of BJT in an LED driver circuit with MOSFET?

texts:
I am trying to turn an LED on and off repeatedly with a square wave.

Yesterday, I've checked the following circuit works:

(Please note that, the figure has one voltage source Vdd. But I've connected a square wave source to the resistor Rg)

But, the most of LED driving circuits have a form of the following:

I am curious that what roll a BJT does in this circuit. From this article, it has something to do with a constant current source. Then, what is an advantage if there is a constant current source?


texts: Creating a slotted & plated through-hole in EAGLE: where to draw milling outline

texts:
Problem summary

I want to create a rectangular slot in my PCB for this component. Do I draw the milling outline on the footprint library or on the board after placing the component? Does it matter? I am using EAGLE v 9.2.2

A little more detail

I am using this SPDT switch in my circuit and it is to be PCB mounted. The legs are rectangular lugs which make it better suited for a slotted hole, rather than circular (I’m aware I could use a circular hole and increase diameter to accommodate the lug).

EAGLE does not natively support slotted holes. After doing some research, I have found some threads that say this is perfectly doable, however we have to draw the region that is to be cut out, and alert the PCB fab house of this fact. For instance, see these threads/articles:

https://www.autodesk.com/products/eagle/blog/what-you-didnt-know-about-eagle-slotted-holes/
https://forums.autodesk.com/t5/eagle-forum/slotted-pads/td-p/7487203
https://www.element14.com/community/thread/24623/l/slot-holes-for-dc-jack-connector-in-eagle-cad?displayFullThread=true

I’ve drawn a 1.6mm x 0.55mm rectangular slot around my pad using lines of 0 width on the milling layer (layer 46). See here:

Does it matter if this is done in the footprint library file? Does this have to be done after placing the component on the board? Perhaps I missed it, but I didn’t see this discussed in my research. I have drawn the milling outline in the footprint library, but I don’t see it when I place the part on my board. See here:

As an aside, I contacted the PCB fabricator (PCBway, in this case) and they recommended drawing the outline of the region to be cutout on the mechanical layer, not the milling layer which was recommended in the Autodesk article. To quote a PCBway representative:

  "If you need one 1.6*0.55 slot, you can design it on a mechanical
  layer. Generate gerber from your brd
  file,#https://www.pcbway.com/member/brdtogerber.aspx,then check it in
  a online gerber viewer for double check."

Follow up questions

  To make a slot plated, simply put copper right to or over the slot on
  both layers.

Does that mean copper traces? e.g. Layer 1 (Top) and Layer 16 (Bottom). I’ve already got copper traces routed to the pads, see for instance this image:

Is that sufficient? I’ve taken a look at the POWER_JACK_SLOT component like you suggested, I don’t see any extra copper being placed on the pads (unless I’m missing something):

Their part looks similar to mine, except they’ve drawn a type of cross-hair symbol on the Drills layer (layer 44), as well as placing  tStop and bStop layers over the pad itself. Do I need to place tStop and bStop layers? I’ve just googled what those are and apparently they’re manually defining where soldermask is not to go. They’ve placed it over a pad, I wouldn’t have thought that soldermask is going over the pad at all anyway, no?

  The slot is probably not visible on your board since either you didn't
  update the library in the project, or layer Milling (46) is not
  visible.

Yep, Layer 46 was not visible. For anyone reading that’s curious, go View > Layer Settings > Click the eye symbol on layer 46


texts: Buzzing noise from speakers when using USB audio interface

texts:
I hearing a continuous fairly high pitched buzzing noise from my speakers as soon as I plug in my M-audio 2x2m audio interface into my computer.

This is my setup:
Computer -> M-audio 2x2m (interfaces and draws power via USB C) -> Line out (Left & Right) -> SBX 10 Subwoofer (TRS Input, Left & Right) -> TRS output into XLR input of speakers -> Genelec Active monitor speakers.

I've tried switching out my power bar for a surge protector one (grounded of course), tried different high-end cables (thinking it was EMI), etc. Recently I've noticed that the buzzing is more intense when my GPU is working harder, hence I think that it's probably some kind of EMI going on inside of my computer.

Might also be worth pointing out that when disconnecting the audio interface from the usb and powering via a power bar makes the noise go away. Turning the computer off while still using the usb port eliminates the noise as well (the usb ports still supplies power when the computer is turned off).

As a non-electro engineer I've ran out of ideas on how to fix this.

Is there a device out there that can be used as a filter for either my TRS cables or USB-C to eliminate this noise? Or does anyone have any other clue on how to eliminate this?

Thanks!


texts: Confused with turn on time definition of an SCR

texts:
The following question I encountered is asking about the minimum time for applied voltage to the gate of an SCR to turn it ON:

And below is the solution:

I can understand the solution looking for the pulse duration for the SCR current to reach 50mA latching current.

But at the same time the question describes a term called “turn on time” which is 5us. But obviously the SCR does not turn on for 5us but 150us.

What is the “turn on time” then if it doesn’t provide us the information about the time taken for SCR to be turned ON?


texts: Help with burning inductor in an LM2576 regulator

texts:
I was helping a friend to design a constant 3A current source using an LM2576 to drive a load. Problem is that the 100uH inductor keeps burning every time the circuit is switched on. One option is to swap the regular inductor with a coil inductor. However, it is expensive and we cannot afford it yet.

There was this vague idea that struck about using a zener diode. I am not sure how I can implement this and is this actually practically viable?


texts:
I have a phone vibrator motor that I want to check. This is what it looks like:

And here is the schematic from the service manual:

The motor is not connected to the circuit. It is by itself as seen in the first image. Opening and closing the phone is not straightforward so I am hoping to test it without having to reassemble the whole phone.

The motor's part number is EAU62024101. The motor controller's part number is ISA1000A. I could not find datasheets for either.

I am a noob so I am not sure how to go about testing it. I see a 3.3V source... Can I just connect the 3.3V line from my Arduino to one terminal, and ground to the other?

Update:
I managed to test it with the phone's circuit using jumper wires. I would still love to hear from anyone who has insight on how you can read the above schematic and deduce an appropriate standalone circuit to test the motor.


texts: Whistle while charging small cell phone power bank

texts:
I've one of those small batteries used to charge mobile USB devices like cell phones when there's no accessible power outlet around. It's a Cellularline FREEPSLIM3000 model HY-L-3000.

Last time I tried to charge it, I heard an unusual sound, like a tenuous whistle. I've uploaded a recording here, it's a 12-second audio file file called "powerbank whistle.m4a".
The sound can only be heard while charging the battery, not while discharging.

I tried to measure the peak frequency with my phone and if the app I used is accurate (no idea about that) there are two frequency peaks, one at 8k and one at 16k Hz.

Now, my question is obviously not about what should I do with my battery or whether there is a warranty on this specific product, but what electric component of the device could produce this sound?


texts:
I'm implementing a Bluetooth module in my design and the modules datasheet calls for a filtering circuit on the 3.3V rail to get rid of transients when the LDO powers up (using a Torex XC6210 LDO).

The datasheet shows this for the schematic:

Does the following layout match the given requirements? I almost think that it makes more sense to feed 3.3V to the module between R2 and C7, but I'm unfamiliar with filters like this.


texts: What does an MCU need to be capable of USB 3.0 communication?

texts:
USB 3.0 has been around for quite some time, since it was released in 2008.  But you don't see any simple microcontrollers with an internal peripheral that can do USB 3.0.

The Atmega32u4, a simple 8-bit AVR, has an embedded USB2.0 phy inside and only runs at 16MHz, as such it is obviously too slow to do USB3.0.  Although there are Cortex-M controllers running at over 200MHz that don't have a USB3.0 peripheral!  At this point, I feel like the clock for the MCU no longer matters.  The lowest end processor I can find that does USB 3.0 is TIs Keystone MPU with an ARM-A15

Is it just taking a considerable amount of time to create the IP for lower end MCUs or does it require a clock generation (or some other) unit that isn't worth the cost to develop it for cheaper MCUs?


texts: Why does this optoisolator circuit behave like that?

texts:
I use 4n25 optoisolator IC. When the duty cycle of Arduino is close to 100%, I expect the voltage across R2 to be 18 V. This happens when R2 is 47 kΩ.

I work in a group and my team found that they read the number 47k by mistake. R2 should be 4.7 kΩ. When they replaced the resistor, the voltage across it became 16 V. It never reaches 18 V although the duty cycle is 100%.

What is the reason behind this?

simulate this circuit – Schematic created using CircuitLab


texts: Simplest, cheapest, fast and minimum footprint current limiting circuit with low resistance in normal state

texts:
I have a digital output, driven by the high-side driver with nominal voltage of 24V DC. The load current normally is below 100 mA. The output is monitored, so I can switch it off quickly if I detect a short circuit at the load side.
The problem is that the driver itself is not protected and short-circuit makes it generating a lot of smoke. So what I need is a simple circuit at the output of the driver which:

has low resistance of below 10 Ω if output current is under 100 mA
rapidly increases its resistance to limit the driver current at 500 mA level or lower
withstand capability at short-circuit current shall be at least 20 ms for short circuit to be detected and driver switched off
has a working voltage of 50V or higher
has minimum components and cheap (0,20$ per channel max)
is not single-source supplier

I tried PTC resettable polyfuses, but they are too slow. Microchip's FP0100 should be good but it's expensive (I need at least 60 channels on my PCB). Bourns TBU series are also OK, but also expensive.

Any other options?

UPD1. My current output circuit is MIC2981/82 driven by 74HC594 shift register. On each output I have Littelfuse 1206L012 PTC.
On my board I need 64 channels like this, and this is small series board so total price per channel and footprint are important.


texts: Why does this cable have 3 wires to PCB on one side but only 2 wires on the other end?

texts: I am working on a stereo receiver and was going to resolder some wiring. When I went to strip one wire on the 3-wire cable, the whole wire pulled out that was bare except for the half inch I was going to strip off of. There were only 2 wires on other end soldered to the PCB. The 3-sided part I was going to reattach to PCB each had a different pin to solder to.


texts: Formula for heat wire Kanthal or NiCr Watt consume?

texts:
The input voltage is 220v in single phase.
How many watt consumed for Kanthal A1 (heat wire) AWG18 for 30m at 1400 degree Celcius ?
How many If I use NiCr 60 or 80 with AWG18 ?

Does anybody know the formula ? Does your formula apply for NiChrome wire ?

I read the following below and confused :
Formula between wire size and current
1000 watts, 220 volt, 52" length, Coiled Nichrome wire


texts:
I have an RS485 USB converter connected with a temperature controller in the controller's datasheet it says that the 12 is (+) and 11 is (-) and in my USB converter there is A and B

Am not sure the D+ and the D- means , is that means that B supposed to be wired with (-) and A with (+)?
Am asking all of that because am having communication problems with my device and am having timeout error in my Labview software that am using to read my controller's registers .
My email is:
Imene_7@outlook.com
Thank you for your time.


texts: Eagle has different shape for pads for through hole components why?

texts: While I understand that have 2 distinct shapes helps in determining which is pin 1, why does eagle have so many shapes: square, round, octagon, long, offset. Which is recommended under what circumstances?


texts: I think I found an error in an electronics book. Are my equations correct here?

texts:
I'm reading Practical Electronics for Inventors, 4th edition, to freshen up my long forgotten knowledge of electronics. I love the book so far, but I just came across an equation there which seems incorrect. I don't want to immediately assume that the error is there, so I just want to make sure I'm not missing something.
It's about the transfer function of a loaded RC filter (page 213 if you have the book). This is the circuit:

simulate this circuit – Schematic created using CircuitLab
The transfer function, according the book is this:

This jump from the formula with the parallel notation to the one with R' didn't make much sense to me, and it's not explained how we get there. After converting the equation, I think there's a 1/R missing.
Here are the steps:

First I expanded and simplified the parallel CR part.

Then I plugged that back in the original equation.

So the same thing, except with an extra 1/R.
I did an other round using the Thevenin equivalent circuit and got the same result.

simulate this circuit
So if I switch RL and C there and cut the circuit before C as seen above, then the equivalent resistance should be equal to R' and the equivalent voltage should be the voltage across RL.

simulate this circuit
So with that:

And the transfer function is:

Do you all see any errors in this process? It makes sense to me, but I'm a bit rusty regarding all this, so I'm doubting myself a bit.


texts: How do I compute the gain on this differential amplifier (in an open loop)?

texts:
Hello! I've got this project due for a college course, and the teacher has reviewed my work and said that it is within specification, but he asked me to compute the gain the good old fashioned way with pen and paper and to submit this proof together with my simulations. I tried researching around but I fear that I am not quite up to the task.
Edit:

The circuit is a series voltage regulator with temperature(t8, t7) and over-current protection(t9), the amplifier is there to provide negative feedback (through p1, r5, t4)against voltage fluctuations and the like. Input voltage would be 40V, output 20V (DC).
I have also started by computing the bias point on paper so as to make sure that all my components would be within the power dissipation or current specifications. It's just that I don't really understand how I would compute the exact gain for the amplifier.
Here are the simulations for those that are curious:


texts: The schematic attached is from a very old device. It's using the microcontroller SAB 80535. According to the datasheet P5.7-P5.0 is an 8-bit quasi-bidirectional I/O port. There's a keyboard, a LCD and some outputs connected in parallel to this port. I would like to design an external/remote board to control this port so I can use the information coming in/out the port somewhere else. I was looking at this chip PCF8574 which looks like I could connect it to the parallel port and send/receive information via I2C using another microcontroller. Am I using this chip right? Any suggestions?


texts: FETs or NPN transistors open at 0V at base in CircuitLab or is something wrong with my circuit?

texts:
I came across what look like a bug in CircuitLab, but I am not sure. There is a good chance that I am knowledgeable only to be dangerous.

In the context of How to make a 7 to 3 priority encoder? I built the beginning of my circuit with transistors and funky-diode-OR logic. And I wanted to see it simulated. But it returns wrong results. I traced it to a weird oddity on the input.

Here is my original with NPN transistors:

simulate this circuit – Schematic created using CircuitLab

Then I created a rendition with FETs and also one that is ready to be simulated. My transistor simulations were lost because CircuitLab is upselling hard if you want to work with it anywhere outside the editing of a post here.

simulate this circuit

I just tried to simulate this circuit, and found it doesn't work because the output at the emitter of the initial transistors is > 3 V even if their base is on GND. There's something wrong here either with something I'm doing with those transistors or with the simulator. I then replaced the classical NPN transistors and with FETs. The FETs switch much cleaner and don't require current at the base / gate but only potential. Yet, still J2 is having 4.5V at the drain, whereas the J1 and J3 have 4.999V. But this makes no sense. I think it is a bug in this CircuitLab site.

So, now what I'm going to do is simplify it massively to only the bug:

simulate this circuit

And here too I get > 3 V on H1, H2, and H3. Notice that the switches are inverted, tied to high and shunted to GND, don't get confused by that.

Now I will simplify it even more, to see one FET only.

simulate this circuit

I reduced it all to one single FET with gate shorted to ground, like the transistor here, and with that remaining FET I still had 4.5 V on H1. Now that I replaced the FET with the transistor, I finally get a negligible near 0 V on H1.

Now I will replace that transistor with a FET again:

simulate this circuit

So, with a FET p-channel it didn't work, but with an n-channel it worked. So if that is so, now I go back to the next bigger circuit and change the FETs.

simulate this circuit

So now that part is working and I go back to the original design only with the p-channel FETs.

simulate this circuit

And it is still not working. I suppose I am just doing that all way too naive. I guess what is happening here is that current is flowing out reversely through the gate. I don't understand FETs enough.

But I understand transistors better, and there too I find that it doesn't work in the same way.

simulate this circuit

And it is so strange V(T2.nE) is still > 3V! Even if I disconnect the emitter entirely it is > 2V! So while I could verify that the single transistor worked as I expect, now again it is behaving weird!

I'm trying it one more time to rip out all that might confuse the situation to see if T2 will finally behave!

simulate this circuit

OK, finally I traced the initial problem to the cause: somehow the diode logic is not working or is behaving erratic. I put that little momentary contact button SW4 in for testing. It should be closed to drive my logic. But once it's closed the V(T2.nE) is > 3 V but when I open it is's at near-zero. And also, if I close SW1 (short T1's base to ground), then V(T2.nE) is also OK.

It seems as if potential is leaking/breaking through the diode? How can that be?

I'm not asking you to fix my entire experiment, but perhaps telling me my main mistake?


texts: Current loop protection from wrong connection of the wires

texts:
I have built a current loop protection circuit based on the topic Using a microcontroller ADC to measure a 4-20mA sensor

It works good. The next step is I want to protect the input of the circuit from the incorrect hookup. Can I use two Schottky diodes? Would this work correct? I want this circuit to be compatible with 0-10V sensors as well. In that case should I consider the voltage drop by the software when using an ADC? Or maybe there is an other solution?


texts:
I need to send all port info from one pic to another using serial port..

currently using 9600bps baud rate. on pic18f4550 running at 20mhz clock.

i have used this code to send and receive data of a single port.

send:

while(1)
{
    TXREG=PORTB;
    while(PIR1.TXIF==0);
    delay_ms(100);
}

and receive:

while(1)
{
       while(PIR1.RCIF==0);
       PORTB=RCREG;
}

on tx part PORTB is set as input and at RX PORTB is set as output.

I need to send/receive all ports info.. How can it be done?


texts: Will a buck converter allow current to pass through if Vin is less than the configured output voltage?

texts:
In general, will a buck converter allow current to pass through if Vin is less than the configured output voltage?

Specifically, I'm reading the TPS54308 datasheet and I'm not seeing an answer to my question.


texts:
I'm designing a peripheral circuit between a sensor (U1) and a MCU (U2).
U1 has an open-drain output pin to indicate its status. This pin will be staying at either HIGH or LOW constantly (not frequently toggling). U2 requires 3.3V as input.

I only have 5V supply and therefore a voltage divider is used to produce 3.3V. Since the voltage divider already has high enough resistors (100k and 200k), the current flows through R1 will be really low.

In this case, do I still need a pull up (R3) for the 3.3V? In other word, can I replace R3 with a wire/jumper?

simulate this circuit – Schematic created using CircuitLab


texts:
I am currently working on a circuit but I can't figure out the non-polarized capacitor values, since some of them are not clearly specified as unit magnitude.
Some of them are: 100, 500, 180, 5.6, 56, 220.
What should I use; pF, nF, uF, mF, F?


texts: GPRS data call using GSM/GPRS modem (Siemens TC35 and/or MC35)

texts:
I'm developing a data aquisition module, that amongst other things, it have to comunicate through GSM/GPRS module, since it will be a mobile application.

I can connect to the module and send sms's with not much effort. Since I have to comunicate frequently and with amounts of data "difficult" to manage through sms, what I'm trying to figure out is, can I establish a data call using gprs? In this case I got two modules interfaced to a microcontroller and I want to "call" to the other device, pass the data and hang up.

I'm not sure if this notion of data call between two gprs devices is meant to happen as I expect, but that's why I would grealty appreciate your help!

Thanks!


texts: Best design practice for relying on IC input diode current clamping?

texts:
I have a question about what the "best design practice is" for using ICs with current clamping diodes. Take for example the following IC: CD74AC251M (datasheet : https://www.digikey.com/product-detail/en/texas-instruments/CD74AC251M/296-32961-5-ND/1691823)
On page 3 of the datasheet it lists a current specification of +/- 20ma for the DC inputs, rather than a voltage specification. My understanding is that this means you can exceed the supply voltage (3.3V in my case) as long as you don’t exceed the input current. Texas Instruments has an “Understanding and Interpreting Standard-Logic Data Sheets” document that was helpful with this as well (https://www.mouser.com/datasheet/2/405/szza036b-89603.pdf). Figure 10 indicates a clamping diode is placed on the inputs in this logic family series, as does the IC datasheet.
So, with this in mind, I want to hook up the inputs of this CD74AC251M decoder to a signal that can be from GND to 12V through a 10kOhm series resistor. If my understanding is correct, that will mean that I’m only roughly sinking 0.82mA through the input diode when the input is 12V. (12V-3.3V-0.5V = 8.2V. 8.2V/10kOhm = 0.82mA). Which is well within the input current specifications.
My question is if this is considered a "good/best" design practice. Or is it considered better practice to place an additional diode, like a 3.3V Zener, after the 10kOhm resistor as well? If so, why is that a better design?
Thanks


texts:
The Xiling Zynq 7020 has a dual-core ARM Cortex-A9 and an Artix-7 FPGA in it.

What is the equivalent part number of these chips independently? (i.e. what individual part numbers have the same fabrication method / process size so it has the same electrical properties as these two subcomponents?) Unfortunately, their documentation does not specify this information, nor was I able to procure this information from calls to them.

My company has a database of extensive testing done on many chips. I'm currently evaluating the 7020 and would like to know "if I look at the ARM part ABC123 and the Artix-7 model DEF456, the test results of those should be analogous to the sub-components of the Zynq chip."


texts:
I am really confused why D1 (Dual Switching Diode) is used in the amplifier circuit. I used NEGATIVE impulse signal generator to trace signal at C6 and was almost 10x smaller (OpAmp ckt. was isolated) .....Is it impedance mismatched between signal generator and Diode Configuration itself?

Also, I let impedance of signal generator determine gain of an OpAmp (U3). So, usual Rg is missing. Then, I used dual power supply Vs = +/- 5V as suggested in datasheet. OpAmp BLEW UP twice. I verified circuit connection as well. No short circuit anywhere when circuit is power off. As soon as, power is ON the OpAmp gets hot, smokes and  :(

Update:
I use linear voltage regulator to supply +9V (TPS71501)  and -3 V (TPS72301) to power up an OpAmp and it works fine. Circuit exactly as data. Note that: TPS72301 has internal Thermal/Current protection.

But, when I try to use dual power supply the OpAmp gets very hot.

Why am I doing this???
I want to figure out accurate rail voltage so that when i use an impulse signal above -1.5V to -4V, I do not have signal clipping problem due to +/- Vs.

Any thoughts or suggestions!!! Much appreciated


texts:
This is an example from Feedback chapter in Fundamentals of Microelectronics by Razavi.

As you can see from the picture, the author gives two questions (why?). Could you check if my answers are correct.

If Iin goes up, VX tends to rise (why?), thus raising ID1. As a result, Vout falls and ID2 decreases, allowing VX to rise (why?)

First question: if Iin goes up, VX tends to rise(why?):

Because there is a capacitance between node X and ground, when Iin increases the voltage at node X will be equal to Iin multiplied by input impedance and therefore Vx will increase.

First question: Vout falls and ID2 decreases, allowing VX to rise (why?):

Vout decreases, the current through M2 decreases so the current through input capacitance increases and thus Vx increases.


texts: wheatstone bridge drive by small current, issues?

texts:
I've got question about Wheatstone bridge. I've designed device which contain NCP1210 pressure sensor and works with 3.0V power supply. I've did calculations and now I've got some questions.

My device based on this eval board:

http://www.cdiweb.com/datasheets/ge_novasensor/CDI_Universal_Evaluation_Board.pdf

I read NCP1210 (I've got sensor with 0.025mbar resolution) values for 1.5mA current source. Typical output voltage value is 50mV (for 0.025mbar). Typical NCP1210 input impedance is ~4k.

So... with Ohm law:

U=RI

U=4000 Ohm * 0.0015 A=6V

I need ~6V to properly drive sensor wit 1.5mA. Furthermore voltage on resistor in current sink system has value of non-inverting input. So with this eval board I need at least 6V + 1.2V =7.2V to properly work with 1.5mA current source.

I've decided to use eval board ideas in my project.
I use:

-> 1.6V Reference voltage

-> 3.0V power supply

With these values I calculate that I must use 8k resistor in current sink. With this resistor I should achieve current with value: 0.2mA.

And now my question:
With this current (0.2mA) proportionally I can achieve ~6.6mV on NCP1210 output.I want to connect NCP1210 output to MCP6N11-100 instrumentation amplifier and I'm afraid that these values will be too small to reach good measurement.

Additionally I thought about build voltage doubler, but It will small battery-powered RF device and voltage doubler may take up too much space.

thank you in advance for your advices!


texts: Determining speed of turbocharger via sound?

texts:
There are inductive sensors which can be retrofitted to turbochargers to measure their speed, like this:

Examples can be seen here.

Installation requires some careful and precise drilling and threading in addition to removing and re-installing the turbo itself, which is something I don't want to do for my personal experimenting.

Now I am wondering if the speed of the turbine/compressor can be determined acoustically. I mean, you can easily hear the distinctive sound of the turbo when it revs up/down.

The question to me is, what kind of sensor could be used to pick up the turbo's sound?

I'm not sure what frequency you hear from the turbo, but it must be either its rotational frequency (up to about 200000rpm/60s~3.3kHz), or the same multiplied by the number of blades (~13 -> 40kHz).

Installation of the pickup inside the engine bay will require, among other things, mechanical ruggedness and temperature resistance to at least 100°C.

Can a cheap piezo ceramic plate do the trick?

Are there special microphones for this kind of environment?

Knock sensors come to mind, but I'd prefer something contactless, especially not needing to be bolted to the turbo, see above :)


texts: Why do different resistor values dissipate power at different rates in RL and RC circuits?

texts:
Physically what is happening here?

RL
My thoughts on this are that the inductor supplies a certain current, and current through a larger resistor dissipates more power.

RC
This one I'm not so sure about. I would say the same about voltage, but I think the current caused by this voltage will be proportional to the resistance values and so will the power dissipated by this. Somet

simulate this circuit – Schematic created using CircuitLab
The switch opens after being closed for a very long time.
hing isn't right conceptually, can someone help me clear this up?


texts: Accidentally connected a GPS antenna to a cellular connector and a cellular antenna to a GPS port. What can go wrong?

texts:
I have two ultra small/sub-miniature coaxial connectors on my circuit board - one for a cellular (4G) antenna and one for a GPS antenna. I accidentally connected the cellular antenna to the GPS connector and the GPS antenna to the cellular connector.

With the wrong setup, I powered the device and started seeing errors when trying to get the GPS signal through AT (modem) commands. However, when I connected the antennas properly the errors went away and I was able to get GPS and cellular signals. The board seemingly functions fine now.

What can go wrong in this case? Is there a chance I could have damaged my circuit board or the antennas with a setup like that? If so, then why?

Board schematic: https://www.waveshare.com/w/upload/c/c8/SIM7600E-H-4G-HAT-Schematic.pdf

The entire circuit board with antennas is shown on the photo below.

Schematic for the antenna connectors:


texts: Circuit that adds offset if input voltage is negative and subtracts offset if input is positive

texts: I'm trying to build a circuit that will have an input DC signal. I know there is a stead DC offset in the signal, and want to subtract it. I do not know if the input signal is positive or negative. If it is positive, I need to subtract the DC offset, and if the input is negative then I need to add the AD offset. Is there any circuit or way to do this? The only way I can think of is using a switch that would go between a summing op-amp or differential op-amp that needs to manually be switched after someone manually checks if the input is positive or negative.


texts: A question about reading and calculating thermal resistance of a voltage regulator from its datasheet

texts:
I have this voltage regulator  from this supplier and the exact model name is given as: "LM317T/NOPB".

I plan to use this circuit to power a windwane's potentiometer which is around 10k:

As you see I want to set the excitation voltage for the vane pot to around 9 or 10V where the opamp will be supplied directly from a 12V switch mode power supply. For this purpose I will use an LM317 to obtain 9 or 10V for the vane excitation. So I will set LM317 for 9 or 10V DC. I will mount the vane in a box around 50m height which will stay there at least 3 months.

Since I will use a linear voltage regulator I decided to find out whether I need a heatsink.

I have encountered two challenges which I put here as questions:

1-) In the datasheet when I check the thermal resistances I cannot figure out which model I should use:

Mine is T0-220, but in the datasheet there is two types namely as KCT and KCS. But my model is "LM317T/NOPB". And on it it is written "LM317T +P". So should I use the thermal resistance for KCT or KCS?

2-) Here is how I calculate the ΔT:

ΔT = θJA * P

In my case:

P = V^2 / R = 10^2 / 10000 = 0.01W

But for junction to ambient temperature I used to use the following:

Junction to ambient = Junction to case + Case to Ambient

But in the datasheet there is no Case to Ambient but there is Junction to ambient. Does "junction to ambient" already include "case to ambient"? Should I in my case only use Junction to ambient? If so in my case ΔT becomes like 4°C, and I conclude I don't need heatsink. Do I calculate correct and does it matter the duration like three months when it comes to using heatsink?


texts: Open/close low voltage AC circuit with 3.3 VDC signal

texts:
I have a small circuit, containing 16 VAC (50 Hz) source, AC device and button  which closes the circuit (pressed - device is working, released - device stops). I would like to replace the button with something that can be controlled with 3.3 V (planning to connect it to Raspberry Pi). Button is pressed around 10 times per day, for a few seconds.

Can I use circuit with triac and optocoupler that controls 230 VAC shown below? If I can, can you suggest how to adjust values for transistors, capacitors and so on, to work with 16 VAC?

Also, if there is a better/simpler solution, please include it in answer.

I suppose I can use relay for this but I would like to use something that doesn't create clicking sound.


texts: Questions about coil voltage and phase shift in the WPT system

texts:
I performed simulations of wireless power transfer in matlab simulink. It was powered with DC voltage which was then converted into a rectangular voltage with a frequency of several dozen kHz. The figures show a schematic diagram and a graph of the voltage obtained at the inverter output (red) and the voltage obtained at the L1 coil (black).

Why are there voltage surges in the voltage obtained on the coil? I
noticed that these jumps occur when switching pairs of transistors
in the inverter and that, the difference between the two sinusoids
forming the voltage on the coil is the value of the set voltage.
Why is there a phase shift between primary and secondary voltages in
this system?

I apologize in advance if this question has already been asked on the website or it is common knowledge that I did not assimilate. Please help.

*edit

V3-measuring voltage at the inverter output (yellow)
V1-capacitor voltage measurement (red)
V2-measuring coil voltage (blue)


texts: How would I calculate the voltage drop across the 60 ohm resistor without knowing the voltage? also, would the total circuit resistance be 7.74 ohms?


texts: Can someone help me ID this components labelling for Li Ion charger

texts: I am trying to fix a charger for a Dewalt 20v Li-Ion power tool set.  I have inspected the board and this little guy seems charred/burnt around the PCB.  I know its a Schottky Diode,  but I don't know what the GK080, VW, or CHN 514 stands for.  I am just a tinkerer trying to learn electronics and want to make sure I know exactly what value I need or don't need.  Digi-Key Part Number 497-2730-5-ND looks similar but the leg on the one in my picture has extra insulation.  Thanks for the help


texts: How to obtain both values from a voltage attenuator?

texts:
Design a resistive voltage attenuator whose input resistance be 1 MΩ (R1,R2) and able to divide by 5 the amplitude of a DC voltage when the output of the attenuator is connected to a circuit with 1 MΩ input resistance (\$R_i\$.)
The result is:

R1=800kΩ
R2=250kΩ

My question is how do I get those resistor values out a voltage attenuation equation?


texts: Reverse Diode and Resistor in parallel for battery connection. What do they do?

texts: Can you please help me understand what the diode and resistor connected to the battery input line of this circuit are doing? Thank you!


texts:
I have an SG electret microphone (see figure below) connected to my phone, and it produces pretty bad signals (keeps mostly the low frequencies while killing the high frequencies). I suspect it is the microphone (although it might be something else in the circuit). The microphone has a static resistance (without any voltage applied) not lower than 1.5KOhm (I can't measure it exactly since I can't take it out of the circuit, and there are additional things connected in parallel to it). I can't find datasheet on it, so maybe someone had a deal with them before.
When I apply voltage to it (1 Volt), the current through it is 0.2mA.
The question is: are these parameters OK for this microphone? Or it is damaged?


texts: Output voltage of MOSFET differential pair with current mirror load

texts:
I've seen this circuit from https://www.allaboutcircuits.com/technical-articles/advantages-of-the-actively-loaded-mosfet-differential-pair/

How are the drain voltages equal?? I can't seem to figure it out, it's not even symmetric?
Vd3 = Vsply+ - Vsg = Vsply+ + VGS
I can see that but what about Vd4??It can't be due to symmetry. Q3 forces its drain and gate to be equal with a short, but Q4 doesn't have that.


texts:
I have a circuit like one on scheme. I would like to drive 12V/3A DC motor with PWM from ESP8266 pin output. Circuit works just fine (FET is only little bit heating), but on ESP startup, engine turns on (for less then a second), probably until the pin is initialized with full value (1023 = 3.3 V - this makes engine off). I am looking for a circuit modification which would keep motor off during ESP startup.

simulate this circuit – Schematic created using CircuitLab


texts: How to calculate heatsink requirements? Explanation of the K/W unit

texts:
I'm planning to make a power supply with the LM2596 (adjustable voltage variant). In the datasheet I read that efficiency for VIN=12V, VOUT=3V, ILOAD=3A is 73%. That means, if I'm not mistaken, that 3 × 3 / 73 × 27 ≈ 3.33W will be wasted as heat.

When a heatsink is rated as 20K/W, does that mean that for every watt that is dissipated as heat, the temperature of the heatsink rises with 20K? When the heatsink is connected properly, is this the value that I should calculate with, or is the temperature of the component always higher than that of the heatsink, s.t. I should actually calculate with for example 22K/W?

In this example then, the temperature rise with a 20K/W would be 3.33 * 20 = 66.7K, which is still OK because the chip can handle up to 125°C according to the datasheet.

Is this correct? I'm a little bit worried about being OK with my component getting around 90°C, even though the datasheet says it's fine.


texts: Interfacing a RAM chip from a commercial computer with an ARM cpu such as Stm32

texts: I need to interface some sort of RAM with an ARM processor for my embedded project. Around 128 MB to be exact. I found a computer RAM which claims to be DDR and 1 GB. As I only need 128 MB of RAM for my project, can I just get those individual chips from the RAM and use it in my project? Or is some sort of external circuitry a must? I want to access it through the address and the data bus.


texts: Help identifying serial communication wiring

texts:
I am wanting to view serial data output from a device on a O-scope. This is a serial measurement board from an industrial robot.
I have managed this in the past with other devices, but I am having no luck here. I get a high signal from SDO pins 8 and 4, but no data.  Even if I get data, how would I clock this to be able to interpret the data?
Any help would be appreciated!


texts:
Recently I started looking into micro-controllers, I bought a velleman pc serial interface and a serial to usb adapter for programming pics, I have some experience with micro controllers, but some educational micro controller called PICAXE, it is programmed in BASIC and is very user friendly, but I wanted to take the leap and do something larger, that's why I asked a friend if he could get me a pic, I borrowed one he told me he didn't use for a while but should have some program whose code he had lost.

With this, I decided I wanted to recover his code and maybe interpret it and give it back to him as a gift in exchange for the pic and his help. I started digging the web, forums,  blogs, everything PIC related to look for this. With the velleman interface (K8076) I was able to connect to the pic (12F629) and allegedly "scan" the program, the output was a .hex file, but I was wondering if I could translate that to something like an .asm file so the program is readable and I can interpret it. This was done with velleman's software, called PicProg2009. Can the whole job of reading the pic be done by MPLab X? i downloaded the latest version, but i dont know much on how to work around with it, so I don't even know how to recognise the interface in MPLab...

Also, what is the OSCCAL Value? it seems to be different everytime i scan the pic for code...

A Last question: Could this interface be used for the same purpose if it was an ATMEL micro-controller?

Best regards,


texts: How to read LM34 temperature sensor negative voltage with an ATmega32?

texts:
I'm trying to read the temperature with an LM34 but it only reads from 0 to 50 F.  Its range is from -50 to +300 F. I asked a lot and I found that my circuit below can't read a negative voltage:

What should I do to read negative voltages?
I also found that because I use single pin to read the temperature this makes me only measure a couple degrees not all the degrees.  What should I do to read all of the degrees and what would the code be?
My code:
#include <util/delay.h>
#include <stdio.h>
#include <avr/io.h>

// define port C
#define LCD_DDDR   DDRC   /*LCD DATA DDR*/
#define LCD_DPRT   PORTC   /*LCD DATA PORT*/
#define LCD_DPIN   PINC   /*LCD DATA PIN*/
// define port D
#define LCD_CDDR  DDRD   /*LCD COMMAND DDR*/
#define LCD_CPRT  PORTD    /*LCD COMMAND PORT*/
#define LCD_CPIN  PIND    /*LCD COMMAND PIN*/

#define LCD_RS 0      //LCD RS
#define LCD_RW 1      //LCD RW
#define LCD_EN 2      //LCD EN

void delay_us(unsigned int d)
{
    while(d) {
        _delay_us(1);
        d--;
    }
}

void lcdCommand(unsigned char cmnd)
{
    LCD_DPRT = cmnd;                //send cmnd to data port
    LCD_CPRT &= ~(1<<LCD_RS);       //RS = 0 for command
    LCD_CPRT &= ~(1<<LCD_RW);       //RW = 0 for write
    LCD_CPRT |= (1<<LCD_EN);        //EN = 1 for H-to-L pulse
    delay_us(1);                    //wait to make enable wide
    LCD_CPRT &= ~(1<<LCD_EN);       //EN = 0 for H-to-T pulse
    delay_us(100);                  //wait to make enable wide
}

void lcdData(unsigned char data)
{
    LCD_DPRT = data;                //send data to data port
    LCD_CPRT |= (1<<LCD_RS);        //RS = 1 for data
    LCD_CPRT &= ~(1<<LCD_RW);       //RW = 0 for write
    LCD_CPRT |= (1<<LCD_EN);        //EN = 1 for H-to-L pulse
    delay_us(1);                    //wait to make enable wide
    LCD_CPRT &= ~(1<<LCD_EN);       //EN = 0 for H-to-l pulse
    delay_us(100);                  //wait to make enable wide
}

void lcd_init()
{
    LCD_DDDR = 0xff;                //all pins in port C output
    LCD_CDDR = 0xff;                //all pins in port D output

    LCD_CPRT &= ~(1<<LCD_EN);       //LCD_EN = 0
    delay_us(2000);                 //wait for init
    lcdCommand(0x38);               //init. lcd 2 line, 5 x 7 matrix
    lcdCommand(0x0e);               //display on, cursor on
    lcdCommand(0x01);               //clear LCD
    delay_us(2000);                 //wait
    lcdCommand(0x06);               //shift cursor right
}

void lcd_gotoxy(unsigned char x, unsigned char y)
{
    unsigned char firstCharAdr[] = {0x80, 0xc0, 0x94, 0xd4};
    lcdCommand(firstCharAdr[y - 1] + x - 1);
    delay_us(100);
}

void lcd_print(char* str)
{
    while (*str)
    {
        lcdData(*str++);
    }
}

int main(void)
{

    char buffer[3];

    DDRA |= 0b00000111;             //pin 0,1,2 output & pin 3,4,5,6,7 input.
    DDRB |= 0xFF;                   // make port B output.
    ADCSRA |= 0x87;                 //make ADC enable and select ck/128.
    ADMUX |= 0xE6;                  //2.56 v vref, select ADC6 and make left justified.

    lcd_init();
    lcd_gotoxy(1, 1);
    lcd_print("temperature:");

    while(1)
    {
        ADCSRA |= (1 << ADSC);                               //start conversion

        while (ADCSRA & (1 << ADSC));
        PORTB = ADCH;

        if (ADCSRA&0b00000101)
        {
            sprintf(buffer, "%d", PORTB);
            lcd_gotoxy(1, 2);
            lcd_print(buffer);
        }
    }
    return 0;
}


texts: Is three-phase power in a residential building 'good'?

texts:
I live in a three story building.  Last night, the top floor lost power for about 30 minutes while the rest of the building was not affected.

When I asked a local electrician, he said this was due to the three-phase power coming from the local power company.

I am a software engineer, not well-versed in electrical topics, so I would appreciate insight into what's going on.

Is this type of configuration of wiring by the power company something that is good, or should I ask them to change it?

Where I live, the mains voltage is 220 v.


texts: Using a capacitor instead of inductor in a switching regulator, and viceversa

texts:
Contextualizing more:

In a switching topology, and I am butchering it now, the inductor gets "charged", and eventually will keep an amount of energy "just enough" required for the load. This is achieved by the control circuit and the switch (in any general topology) stops to charge the inductor when the output voltage, filtered by the output capacitor, goes higher than a certain predefined value. Then this excess of energy gets transferred to the load, and the cycle begins. In this way, the energy transfer is chopped over time to fullfill the needs of the load, instead of being dissipated away.

When the inductor charges and discharges, this results in linear current variation flowing through the inductor itself, in which the rising ramp current (over time) translates in the energy took from the input rails, while the falling ramp of the inductor current (over time) corresponds to the energy given to the load.

The output capacitor present on most common topologies, is taking this energy to be provided to the load and forms an LC filter to achieve constant voltage.

So in this way, there is this game of energy taking and giving, by exploiting the L and C foundamental properties (given by their characteristic equations). This two components, L and C, are reciprocal, what works with current in one, the same happens in voltage on the other.

So my question is:
Can a switching topology, let's say a buck converter, with the given adjustments, use as input storage element a capacitor instead of the inductor, and an inductor instead of a capacitor? And why are not used?


texts: Vivado libraries not working in simulation

texts:
I am trying to use some of the builtin vivado libraries to generate two clocks.  I have never used any of the builtin functions before.

wire clkfb;
wire clk_324p;
wire clk_324n;
wire clk_200p;
wire clk_200n;
MMCME2_BASE#
(
    .CLKFBOUT_MULT_F(52.0),
    .CLKIN1_PERIOD(10.0),

    .CLKOUT1_DIVIDE(16),
    .CLKOUT2_DIVIDE(26)
)
clkgen
(
    .CLKFBIN(clkfb),
    .CLKFBOUT(clkfb),

    .CLKIN1(clk_100),
    .PWRDWN(1'b0),
    .RST(1'b0),

    .CLK_OUT1(clk_200p),
    .CLK_OUT1B(clk_200n),
    .CLK_OUT2(clk_324p),
    .CLK_OUT2B(clk_324n)
);

wire sys_clk_p;
wire sys_clk_n;
wire clk_ref_p;
wire clk_ref_n;

BUFG sys_clkp_buf(.I(clk_324p), .O(sys_clk_p));
BUFG sys_clkn_buf(.I(clk_324n), .O(sys_clk_n));
BUFG ref_clkp_buf(.I(clk_200p), .O(ref_clk_p));
BUFG ref_clkn_buf(.I(clk_200n), .O(ref_clk_n));

When I try the run the simulation I get the errors...

  ERROR: [VRFC 10-426] cannot find port CLK_OUT2B on this module
  [/home/chase/workspace/SVESample/src/top.v:53] ERROR: [VRFC 10-426]
  cannot find port CLK_OUT2 on this module
  [/home/chase/workspace/SVESample/src/top.v:52] ERROR: [VRFC 10-426]
  cannot find port CLK_OUT1B on this module
  [/home/chase/workspace/SVESample/src/top.v:51] ERROR: [VRFC 10-426]
  cannot find port CLK_OUT1 on this module
  [/home/chase/workspace/SVESample/src/top.v:50] ERROR: [VRFC 10-2063]
  Module  not found while processing module instance

  [/wrk/2018.1/nightly/2018_04_04_2188600/data/verilog/src/unisims/MMCME2_BASE.v:111]
  ERROR: [VRFC 10-2063] Module  not found while processing module
  instance  [/home/chase/workspace/SVESample/src/top.v:61]
  ERROR: [VRFC 10-2063] Module  not found while processing module
  instance  [/home/chase/workspace/SVESample/src/top.v:110]
  ERROR: [XSIM 43-3322] Static elaboration of top level Verilog design
  unit(s) in library work failed.

It seems like the simulator does not know about the builtin libraries.  Do I need to somehow include them in the project or something?  I thought I could just straight up use them.


texts: Going from Breadboard to PERMANENT circuit but have Arduino shields attached?

texts:
I have made an Arduino project that uses a shield. I am now trying to turn it into a permanent circuit.

I have flashed the microcontroller with the program, and I have all the parts I need to solder on the board. The only problem is, where do I get a shield that I can permanently solder on to the project? Are they still called shields once you move out of the breadboard/Arduino stage?

This is really frustrating trying to find something equivalent with everything revolving around prototype boards like Arduino and etc. Please help.

Here is an example: I have an Arduino project that sends a tweet every time I hit the button.

I flash the program onto the microcontroller, remove the Arduino board and solder everything in place (except the spots where the "shield" used to plug in), what do I replace the shield with is there an equivalent or do I build it myself?


texts: Why don't wires have to be "covered" when making an inductor?

texts:
Possible Duplicate:
Why aren't solenoid/electromagnet windings insulated?

Looking at some pictures of inductors, such as this one:

(source: ddmcdn.com)
The wires don't seem to be covered with a layer that prevents current from simply flowing from one wire to the next, all the way down. What keeps the electric current going in loops, rather than just flowing straight down the coil and producing no magnetic field?


texts: Capacitors between multiple positive power rails in cpu power system

texts:
Many years ago, when I was working in samsung aftermarket supply chain with set top box repairs I had  access to basic schematic of one of stb. In a power supply part for powering RAM there were a few rails - 1.0V, 1.5V, 2.2V, 3.3V etc. Normal part of this schematic have decouplig capacitors between power rails and power supply ground.
A bit unusual part was decoupling capacitors between positive supply rail, for example between 1.0V and 1.5V - here were a lot of capacitors with value about 10-1000nF, i suppose NP0 or C0G.
Why? What is the role of these capacitors? Did it idea have own name like as snubber or something?
I tried to google it but I always find basic info about decoupling capacitors or anyway - basics info.


texts:
In Verilog, what techniques can be use for mapping an address bus onto different memory modules. Typical case: a microprocessor core whose address space is mapped to various memory modules:  RAM, ROM, video RAM etc...

I've seen two approaches to this:

mapping the data bus according to the selected address range.
using a chip select on the target memory modules and enabling the the appropriate one according to the address.

Are there other techniques?

My understanding is the for the chip select approach, the memory modules should put their address and data ports into a high impedance state to effectively disconnect themselves from the bus.   Is this correct and is it possible to synthesize this?


texts:
As of now, I have a fairly good understanding about the 4-20mA current loop standard.

It needs, of course, a sensor with either 2-wire or 3-wire output 4-20mA (4mA as zero reading and 20mA full-scale output).

A Power supply that must be sufficient for the input voltage of the sensor input and voltage drop across a 220Ohm Resistor.

Then lastly, since analog current passes through the resistor, the analog voltage drop can be obtained by a microcontroller via ADC.

But I noticed in my research that only one sensor is being used.

I want to use 2 different sensors with 4-20mA output. How do I start with this? Should I use two different loops for each sensor? Can I just use 2 different analog input channels?

Thank you.


texts: Textbook passive high pass filter with problematic fluctuation

texts:
EDIT: I found the problem: with these values cut-off freq is 33MHz and the signal is only 1MHz, duh.

Please have a look at my very simple schematic

And here is the scope dump

BLUE is output from square gen. RED is X3 output, and 0.4V/div 5uS/div

The square is rock steady, but after C1 all the fluctuation begins, but I'm expecting a stable amplitude. I even switched to battery power to eliminate any potential noise from the power supply, but the problem persists. I'm not using a breadboard, and wires and component legs are max 20mm (3/4 inch).

It's probably a normal occurrence with hi-pass, but I have no experience with it, any ideas or suggestions?


texts:
While ordering free samples from Maxim I have often seen components packaged as µMAX.

What is µMAX?  When googling for it all I get are some Maxim components.  If I look at google images I get an assortment of SMD and DIP package pictures that bear no resemblance to one another.

Is there a comprehensive list of component packages (cross-provider) around anywhere?


texts:
I have an RFID tag for access to my apartment building that I would like to clone(buying one through strata would be 100s of dollars).
I have a proxmark 3 easy and have cloned tags in the past with great success. However the proxmark cant even see that its there on either HF or LF. So im assuming its a UHF tag.
Is there a way to tell what type of tag it is without pulling it apart?
Is there another device or attachment I can use to read and clone this tag?
Thanks in advance


texts: What is this transformer-like component, and why is it not really connected?

texts:
Recently, a power surge took out a few components in my PC's ATX power supply. While repairing (I hope), one component in the power drew my attention. I'm an electronics engineer, but I'm confused about it's purpose:

At first sight, it looks like a transformer, but with only one connection (the blue cable). Too intrigued, I cut away the tape, and found that the cable was just hooked to the plastic lip. No winding, no other connections.

To make it even more intriguing, the connector goes to the ATX's supply circuit board, but both contacts are on the same trace (i.e. shorted together), just after the mains fuse.

Does anyone know of a legitimate function for this component? I have not been able to find the part number anywhere.

PS: This is not a delayed April 1 prank.

EDIT: Thanks for all the replies and comments below! Later, I found another picture on the 'web, showing an even more sophisticated plastic form to hook the wire loop onto: it even had an anti-falloff feature to avoid to loop from freeing itself.


texts:
Today I tested a DC driver with a STM32 MCU. The schematic is like this:

I have a problem with the ENABLE Signal between the DRV8840 and the MCU.

When the DC Motor is disconnected, I toggle the EN pin and I can see +12V and -12V alternatively on the out pins of the DRV8840. Everything is OK.

When the DC Motor is connected. The MCU init is OK. When I set the EN Signal, the motor runs. But when I ask to toggle the EN Signal, it keeps 3.3V and the motor can't stop.

I can't toggle the EN Pin when the motor is running. WHY?

I don't understand why. My GPIO Pin is configured as Push Pull Output.


texts: What resisters for inverting op-amp should I use?

texts:
I am not an electrical engineer by any means so go easy on me here. I am simply experimenting with a speaker amplifier.

My situation: I have a Clarion xc1410 4-channel amplifier with a 10k input resistance that is non-bridgeable. They are powering two 4 ohm speakers. The amp is capable up to 2 ohms.

My goal: I want to bridge the amp to create 2 channels producing twice the power. My understanding is if I invert the input signal on 2 channels I can bridge those channels with the non-inverted channels.

My setup: I have a couple TI TL071 op amps for my inverting setup.

My Question: I'm not 100% sure what resistors to use as my input resistor and my feedback resistor to match this ideally with my 10k input resistance on the Clarion amp. If I use 10k resistors for both will that suffice or should I use 5k resistors as they add up to 10k to align with my Clarion input resistance? Am I even on the right track? This is what my test circuit looks like:
http://www.learningaboutelectronics.com/images/Inverting-op-amp-circuit-breadboard-schematic.png

As I said I am just a hobbyist, not an electrical engineer so this might seem like child's play to you but any genuine help will be greatly appreciated!


texts:
I'm using an Avr microcontroller and I've been wanting to build a simple robot, for some time now, from scratch.

In every robotics project I have seen, seem to have a separate board driving the servos and I want to know what that board doEd different and how could I make one from scratch.

I think it might be called a motor driver (I'm a novice); so why can't I just run the servo from the microcontroller - I assume it's something to do with power.

Ask any questions if anything is too ambiguous.

EDIT:
Every reference to servo is to a servo motor.


texts: How does an engineer go about mapping opcodes to machine instructions? For example, say a new architecture has been designed that the engineer wants an ADD instruction to correspond to  3-bit binary code as 011. How would he/she "tell" the computer about this correspondence?


texts:
I did an experiment with an op-amp for measuring slew rate of a 741. After a certain frequency, with the help of an oscilloscope, I measured a slew rate which was approximately 25 V/ms. After that I was expecting that as I increase the frequency, the slew rate will also change, but it didn't changes at all. I varied my frequency up to 100 kHz, and I found the same 25 V/ms. Why is this happening?

Before I did the experiment, I was also wondering what frequency I should use to measure my slew rate. Through my experiment, I found it to be constant over frequency, but I still don't understand why this is happening. Is it due to the maximum rate of change of voltage?


texts:
Some days ago I saw this device called Touch Board. It looks a bit like an Arduino (in fact it's based on Arduino). You can connect conductive materials to it, like aluminium foil. The board is able to detect when you touch this material.

How does this work? How would you make this yourself (with a standard Arduino if possible)?


texts: Motor monitoring over temporary connection

texts:
I have an application where I need to determine whether a DC motor that is used as a vibrator is operating correctly. Normally this would be a straightforward problem that could be solved using an accelerometer. The problem with using an accelerometer for my application is the motor is mounted to a mobile structure that is passed down an assembly line like setup. All connections to the mobile assembly and motor need to be temporary. They also need to be made in an automated fashion (no human in the loop).

The motor power connection is a little simpler, the current setup uses copper plates and the weight of the mobile structure to make the connection. Would it be possible to send dynamic signals over a similar type of connection? On paper it looks like it would work, but it seems like noise might be an issue. There is also the fact that all of the connections are temporary, so there may be inconsistencies that would be hard to resolve.

Can anyone think of a better way to determine the health of the motor that would work in this type of an application?


texts:
Here is the circuit:

I have to find maximum average power. By $$Pmax= |Vth|^2 /8 Rth     $$
 For that I need load impedence Z

I correctly found it as,

$$   Z= (j10- j4 + 8)|| 5 =3.421 + j 0.737$$

But I'm unable figure out How to find Vth?

Is this solution correct: open circuit the capacitor then the left side of circuit  Is at 8*2=16 Volts . We have to find Vth so by voltage division Vth=16 (5/5+j10)


texts: Driving 60 signals one at a time, in constant sequence

texts: I have an application where I need to turn on/off one of 60 signals one after another in a constant order, ever repeating. (1, 2, 3, ... 59, 60, 1, 2, ...) Only one signal is on at any given time. The load sinks up to 500 mA each. I'm looking for ideas on how to achieve this in the simplest (not necessarily cheapest) way. Obviously, a large microcontroller or FPGA could do it, but that would be way overkill as the logic for the circuit is very simple.


texts: MSP430 USB Module and Baud Rate Detection

texts:
I am working on a project which uses the USB module integrated into the MSP430F5529, specifically using the MSP-EXP430F5529LP development board from TI. I am using the USB API provided in MSPWare.

The host talks to my device over MODBUS, and I am saving the current baud rate in NVM. Generally, to change the baud rate, I write a value to a MODBUS register. The device reads this value and configures its UARTs accordingly, so that it can act as a bridge between USB and a TTL device.

The problem is that not all MODBUS implementations will use this MODBUS register as a baud rate config, so writing to that address may not be intended to change the baud rate. Therefore, this method has to go.

I was hoping I might be able to detect the baud rate being used to communicate over the USB signal. The first thought was to use a timer to measure the width of the start bit, and use that to calculate the baud rate. The issue with this is that 1) I need to send an entire dummy byte over USB to my device in order to detect the baud rate, before starting normal communication. The other issue is that the way the MSP430 USB API is built, I do not seem to have access to the individual bits as they come in, but rather the message is stored in a buffer which is then provided after the message is completed. I would not be able to time the start bit in this event.

I don't believe there is a way to just "know" what the baud rate of the host is without sending data, since that information (to my knowledge) is not communicated over the bus. Please correct me if I'm wrong.

How might one go about determining the baud rate of a USB connection, preferably without sending a dummy byte first? I'm not entirely convinced this is even possible, it seems to be asking for the impossible, but I figured someone here would be able to give me a definite answer.

I have been through the TI documents describing the USB module, the API, and their application and have not yet found a solution to this problem.