texts:
I received a job to add distributor part numbers to the existing BOM, which is a bit lacking in detail of description. One of the entries is 1N4148 diode with description: D3515. The other one is diode SS26 with description D5035. I can find some mentions of 3515 being some sort of package size I guess. I can not find any mention of the other one though. Are there any standards that use those codes? Here's how it looks like:

As you can see the numbers are separate from the reference designator, they are under the tab of "Footprint".


texts: drawing bode plot and the meaning of the amplitude and phase

texts:
I'm having trouble understanding how to infer from the transfer function amplitude how to draw the bode plot. i.e given the following transfer function:

Is the amplitude is the slope of the graph? when I'm looking at the analysis of the amplitude I can't relate what's written in the table to what I'm seeing

What are the physical meaning of the amplitude and the phase shift? I understood that the amplitude gives me the intensity of the signal, but that doesn't mean much to me either. can anyone please give me a practical example to how is this information used in planning and designing a system?

Thank you.


texts:
We are currently evaluating a nRF9160 for a consumer/industrial product. It does not have a built in antenna for GPS/LTE. There are detailed specs on designing for an external one from Nordic. Now normally, my understanding is in agreeance of what @tcrosley wrote FCC Certification? in this answer. If the module has a built-in antenna, or a connector for an external antenna (and you use a pre-tested one) you can be exempt from FCC testing as an intentional radiator.
The nRF9160 seems to be different. According to: FCC TCB

This grant is valid only when the module is sold to OEM integrators and must be installed by the OEM or OEM integrators. This module can only be used with a host antenna circuit trace layout design in strict compliance with the OEM instructions provided.

My take on that document is that as long as you follow Nordic's design doc's, and you don't exceed the power listed, you will be exempt from certification as an intentional radiator. That goes against all of my past experience and really doesn't make sense to me, since:

a host antenna circuit trace layout design in strict compliance with the OEM instructions provided.

is very open-ended and could easy be done improperly, causing the module to fail a test, if it was tested.


texts: How to speed up charging of output capacitors of ADXL335?

texts:
Problem statement

I need to obtain as fast as possible after power-up a reading from an accelerometer. The accelerometer is located in a car and is powered by the same rail of the rear braking lights, therefore it is powered only after I press the brake pedal. The idea is to obtain as fast as possible a clean reading of the initial gravity vector, before the car actually starts decelerating. Later I will subtract it to obtain the deceleration vector. If the first reading takes too much time (20 ms is already too late), I would be reading a combination of gravity + deceleration.

My intermediate solution

I used an Arduino Pro Mini (5V, 16 MHz) connected to a GY-61 accelerometer module. The module has a 3.3V low dropout regulator, an ADXL335, low-pass capacitors. The ADXL335 is ratiometric, therefore the Vcc of the ADXL335 is used as Aref for Arduino.

Arduino is set to wait 16k cycles + 0 ms upon power-up, the other options being 16K + 4 ms or 16K cycles + 65 ms. The setup is tested as working: I can obtain the first analog reading about <1.5 ms after application of input voltage.

The low-pass filter of the board was originally set to 50 Hz, but I changed the capacitor to have 200 Hz bandwidth, therefore the analog input (A0) takes about 5.5 ms to provide stable readings. This was also tested.

simulate this circuit – Schematic created using CircuitLab

The stable output voltage of the accelerometer can be (depending on mounting) between 1.43V and 1.77V for -1g to 1g. The ADXL335 does not tolerate more than about 3.5V on any pin (to be on the safe side).

Problem

I would like to stabilise the output of the accelerometer faster, without waiting the full 5.5 ms after power-up: this would allow me to sample more times the initial gravity value, before it changes due to deceleration. I would like to keep 200 Hz as bandwidth to reduce the noise later during the following measurements of braking deceleration.

The ADXL335 has a resonance frequency 5.5 kHz and a bandwidth of >550 Hz when no capacitors are used: before the low-pass capacitor the first reliable value is ready about 2 ms after power-up. That means more than 3 ms saved compared to my current case.

How can I do that?

Can I connect the output of the capacitor also to an additional pin, set as output for about 1 ms and then set as high-impedance input, through a resistor? or would I damage the ADXL335?

Is it maybe better to perform all the filtering in digital to change the bandwidth as needed? Even in this second case, would the setup I described work?

simulate this circuit


texts: Why can we see the current source as a open circuit and voltage source as a close circuit?

texts:
What is the \$R_L\$ value can maximize the power of \$R_L\$?

simulate this circuit – Schematic created using CircuitLab

The solution:

simulate this circuit

\$R_{th}=1+2+1=4\$,so when \$R_{L}=R_{th}=4,\$ it has the maximal power

I want to ask

1.Why can we seem the current source as a open circuit,and voltage source as a close circuit?

2.Why can we know when \$R_{L}=R_{th}=4,\$ it has the maximal power?

3.why is the \$R_{th}=1+2+1\$,not the \$R_{th}=1+2+1+5+3\$ or \$R_{th}=5+3\$ ?


texts: What is difference between I2C and TWI interfaces? Wikipedia says, that TWI is variant of I2C. Some other sources says that only name is differ...


texts:
I recently acquired an STM32F429 Discovery Kit (pictured below). I'm new to the M4 cortex series microcontrollers and ARM in general having only worked with PICs before. I've seen some really nice debugging features of this microcontroller using SWD (serial wire debug) but it seems that this only works if you're using a programmer. Unfortunately I'm not using an SWD/JTAG programmer/debugger like the ST-Link to program the board but rather using the USB cable to do so.

I'd like to find out from users on the forum who have worked with these before what my options for debugging are. I'm going to be working on a Fast Fourier Transform application that uses the LCD screen so more advanced debug techniques like live variable viewing and real time data plotting will be extremely useful. Without the ISP programmer if I want to use printf() statements for debugging purposes in my code will I have to do so by outputting over UART to a terminal application like Putty or using the LCD screen to output test data?


texts: Mounting orientation recommendations for PCB spring antenna?

texts:
I have been looking at 868MHz through-hole spring antennas for an application, but I can't seem to find any sort of information in datasheets regarding layout recommendations.

Here's the most detailed datasheet I can find for the type of antenna I'm talking about.

I was hoping to have this mounted in a corner cutout of a PCB, which means it will have no ground plane directly under it, but it will have ground plan on two sides (feedline side and parallel with the coil direction). Similar to the orientation below, but with the feedline coming in from the right side.

Has anyone used an antenna like this in a similar orientation/setup?
Does anyone know of any doucumentation/guidelines for helical antenna orientation and ground plane keepouts?


texts:
I want to build a small console with the Bourns PSL slide potentiometers (nothing big, it's a just-for-fun project). Unfortunately, I couldn't find the right connector on their website.

The datasheet doesn't seem to have the complete measurements (the bottom opening has no dimensions). I did search on their website but it looks like they only have spring loaded battery connectors.

So my question: Can anyone recommend a connector that fits the Bourns PSL?

Thanks!


texts: Current adjustment circuit seems to skip resistors?

texts:
I have the following current adjustment circuit, VDC is 32V. I want to be able to switch between two COB LEDs and adjust the current however the current should be much lower than it is in practice (it's 800mA on red when it should be a few hundred less) and completely detaching the potentiometer from the base of the transistor changes nothing.
When the Red COB is activated the intent is that there should be 3k ohms more resistance than if the UV were activated because they need different currents to produce similar brightnesses.

My old circuit was the following and worked fine but I hadn't yet tried to add switching between two LEDs:


texts:
I have a PIC32 starter kit and I am making a program such that when I apply input 1, MCU will send this data to my PC using UART and INPUT 1 ON will be displayed on terminal, same goes for input 2 & 3. These inputs are coming from opto couplers and these are basically 3.1v. So whenever I apply these inputs, MCU pin become high, data is send to PC using UART and INPUT 1 ON or INPUT 2 ON is displayed.

But the problem is let say, I have applied input 1 and terminal is displaying INPUT 1 ON and at the same time if I apply input 2, INPUT 1 ON goes off and INPUT 2 ON started displaying. I want that both INPUT 1 ON INPUT 2 ON should be displayed and if I apply input 3 at the same time INPUT 3 ON should also be displayed along with INPUT 1 ON INPUT 2 ON. I dont know how to make logic for this. Can anyone just help me with this. Thanks

CODE:

    if(PORTAbits.RA6 == 0)
    {
        putsUART2(">>Input: 1 ON\r\n");

    }
    if(PORTAbits.RA6 == 1)
    {
        putsUART2(">>Input: 1 OFF\r\n");

    }
    if(PORTAbits.RA7 == 0)
    {
        putsUART2(">>Input: 2 ON\r\n");

    }
    if(PORTAbits.RA7 == 1)
    {
        putsUART2(">>Input: 2 OFF\r\n");

    }
    if(PORTGbits.RG13 == 0)
    {
        putsUART2(">>Input: 3 ON\r\n");

    }
    if(PORTGbits.RG13 == 1)
    {
        putsUART2(">>Input: 3 OFF\r\n");

    }

EDIT

Right now what I am trying to do is if(PORTAbits.RA6 == 0) the it should display Input: 1 ON and if if(PORTAbits.RA6 == 1) then it should display Input: 1 OFF and  same for other inputs. But what's happening is when there is no input Input: 1 OFF Input: 2 OFF Input: 3 OFF is displayed but when  if(PORTAbits.RA6 == 0) comes it shows Input: 1 ON for just one time and then continuously displays  Input: 1 OFF Input: 2 OFF Input: 3 OFF. I dont know why its behaving like this.


texts: Can a MOSFET be used for dimming instead of switching a LED?

texts:
I have a simple circuit that uses a MOSFET to switch on and off a ~100W LED spotlight (30V, 3A). It works for this application.

I have been asked to modify the circuit so that the LED can be dimmed instead, but without using PWM (the reasons are beyond the scope of this question, but I can explain if needed).

So my naive solution was to drive the gate of the MOSFET with the output of a DAC, per the schematic below:

simulate this circuit – Schematic created using CircuitLab

The DAC I am using is the MCP4725 (specifically the breakout board from Sparkfun). The MOSFET is a logic level one, IXFP5N50P3, and it is properly heatsinked.

After some testing with the DAC output at voltages other than 0 or 5V, I notice the MOSFET starting to fail. In some cases they end up letting some current flow even if the gate voltage is zero. In other cases they fails by never letting enough current flow for the LED to reach full brightness.

I suspect I am using the MOSFET in a mode of operation that is not safe, but I am not sure why, or how to tell by looking at the datasheet.

Is this MOSFET only usable for switching a load, and if so are there any other parts that would be suitable for this application ?


texts:
Google has failed me so I'm asking here.

I am looking for an automatic switch, which will change state depending on the number of Watts/Volts/Amps flowing through the circuit.

As an example: When the amount of Watts flowing through the switch is less than 40, the switch remains in the default position. When the amount of Watts is greater than 40, it changes position and opens a different circuit.

Does this type of device even exist? (Forgive my ignorance, I am a beginner)

EDIT

The problem I have:
I have the following circuit, where the sensor is generating enough Watts in its off state, that the LEDs turn on even then.

I am thinking of a workaround like this:

Where an automatic switch would workaround the issue and only connect the LEDs when the sensor has 'sensed' something.


texts: Programming STM32F3 with Atollic TrueStudio: arm-atollic-eabi-objcopy says No such file

texts:
I am using the newly-made-free Atollic TrueSTUDIO for STM 32 and built a CMSIS-based STM32F3 project from scratch.

When I try to build the project, I get the following Build Console error:

arm-atollic-eabi-objcopy: 'ProjectName': No such file

and

arm-atollic-eabi-size: 'ProjectName': No such file

I'm not even sure if the project built itself correctly, although the CDT Build Console seems to suggest that it was built. For instance, if I try to create a new Debug configuration, there is no .elf file. For reference, here is the entire console output:

Info: Internal Builder is used for build
C:\Program Files (x86)\Atollic\TrueSTUDIO for STM32 9.0.0\ide\jre\bin\java -jar C:\Program Files (x86)\Atollic\TrueSTUDIO for STM32 9.0.0\Tools\arm-atollic-reports.jar convert hex sizeinfo list ProjectName
Generate build reports...
Converting build output to hex
arm-atollic-eabi-objcopy: 'ProjectName': No such file
Output sent to: ProjectName.hex
Converting build output to hex done
Print size information
arm-atollic-eabi-size: 'ProjectName': No such file
Print size information done
Generate listing file
Output sent to: ProjectName.list
Generate listing file done
Generate build reports done

10:47:58 Build Finished (took 353ms)


texts: Health risks of exposed contact to a capacitive sensor

texts:
I want to make a wearable metal trinket with the ATtiny85 chip acting as a capacitive sensor (with the same technique that this Arduino library uses), so it can detect when it's being worn.

Are there any health risks to touching what is effectively a low-voltage live wire for an arbitrarily long amount of time?

Here's the schematic from that link:

Be patient please, I'm a beginner :)


texts: What prevents the construction of a CPU with all necessary memory represented in registers?

texts:
Modern CPUs employ a hierarchy of memory technologies. Registers, built into the chip have the lowest access times, but are expensive and volatile. Cache is a middle-man between RAM and registers to store data structures to reduce latency between RAM and registers. RAM holds, for the scope of this query, active program code and their data structures. Non-volatile storage is used by programs to save their data and hold the OS and its programs.

The latency of accessing data in memory has been a major bottleneck to creating faster CPUs that do not sit idle, awaiting further instruction. As such, various methods have been designed to parallelize workloads, CPUs to predict branching to hide memory access overhead, and more. However, the complexity of this has seemingly ignored another possibility: a whole-memory register file.

Such a CPU is built with 4, 8, 16, 32 GB or more, made of registers. No cache. No RAM. Just the CPU, the registers on the chip, and external non-volatile storage (SSD/Flash, HDD, etc.).

I understand that the demand for such a chip is unlikely to be sufficient to justify the cost, but I remain surprised that no one seems to have designed a simple device, such as a high-performance MCU or SoC with a small amount of register-only memory. Are there other (perhaps, engineering) challenges to the design and construction of such a chip?

EDIT to Clarify. I am not referring to a CPU in which all memory (DRAM technology) is integrated onto the CPU die, nor am I referring to a cache that is expanded to multiple Gigabytes. I am asking about a design in which the registers remain their existing technology... just expanded by a few orders of magnitude to be able to hold multiple gigabytes of data.


texts:
Does anyone have any experience with Analog Devices iCMOS high voltage analog switches or multiplexers like the ADG1434 or ADG1411?

The specs for iCMOS sound very impressive. But they've been available for many years and yet I can find virtually no first-hand accounts of anyone actually using these chips. There are no references to iCMOS-anything in AD's press releases for the last 2 years. The availability of these chips on Mouser and DigiKey is very limited.

I want to route audio using a microcontroller and in practice the signal would have to weave it's way through 8 of these switch elements. Assuming the load is >1000 x Ron and the signal level is within say 10Vpp, am I going to trip over something? I'm not an engineer so I'm thinking I should stick with relays but if these things really worked well, they would make things easier, more robust and slicker.


texts: How to understand signal inversion and current flow through OTA?

texts:
In the following example schematic for an OTA, transistor M4 is said to be non-inverting input while M3 is the inverting input. The given explanations are short and i find them rather unclear.

M4 is said to be non-inverting because: M4 and M8 are in common source, thus 2 inversions produce a non-inverted signal. But aren't M10 and M7 in common source too?
M3 is said to be inverting input because: M3, M6 and M10 are in common source configuration, thus resulting in 3 total inversions. Isn't M5 common source too?
Why do we account for M9 in the case of M3 input but not for M10 in the case of M4 input?
How does the current flow through such a device?
Thanks a lot.


texts:
What is the resistance Rx, in order to have Vo/Vs=1/2

Hi, my teacher asked us to solve this question, keep In mind that i'm not asking for you to do my homework, I think is just a impossible question, i've tried every possible method for solving it with no success, and I really need to solve it for my pontuation.

First i've tried Mesh Analysis with no success.

Second i've tried Node Analysis with no sucess.

Then i've tried Voltage divider with no sucess also.

Mesh, Node and Voltage Divider Analisys

If Rx value is zero, the Voltage Source is short circuited. I don't know what else to do.


texts: Selecting right fuse for the short pulse application

texts:
I am trying to find correct fuse for this application.
The purpose of it is to protect current-limiting resistor in case the relay fails to engage.
Coincidentally, blown fuse will also prevent further system activation by cycling main power switch, until the problem is fixed and fuse replaced.
In this circuit the only time current flows through the fuse is when battery is connected. The maximum current is limited to 7-9A (depending on battery charge) by the resistor. However as power capacitors get charged the current quickly drops, and the relay removes fuse/resistor from circuit completely in about 0.1 sec.
Q: Am I correct that current rating of the fuse is pretty much irrelevant in this case, due to very short pulse?
It seems that I2t is defining characteristic here. Unfortunately it cannot be used directly either, as current is not constant. Complicating the matter is that main switch can be triggered several times in a row. The capacitors take about 5 sec to discharge to under 1V, so repeated switching on/off will produce additional power surges.
Any advice on the correct math to be used? I am planning to use 5STP series from Bell Fuse. The requirements are: a) to survive repeated pulses of up to 0.1 sec @ 10A with about 2 sec cool down in between without degradation, and b) to blow when 7A or more is applied continuously for longer than 0.5-1 sec.


texts:
I am currently building (trying to build) a portable speaker system. With a basic aux cable input and a small amplifier circuit for use outdoors.

With a salvaged TEA2025b IC and an assortment of capacitors lying around I started the build. The build I followed seemed to work as the speakers did produced sound albeit very faint. After further experimentation and a few bad decisions later I blew the IC.

After a while I manage to get my hands on a BT2025BH IC chip from Boomtech, salvaged from a different set of speakers. Now the question I have is that can this chip be used as a direct replacement for the TEA2025 IC or are they completely different and only coincidently have the same number code?

Also are there any standard in naming IC’s of this sort?


texts: Simulating real world transformer with LTSpice

texts:
I'm studying LTSpice, and I'm playing in transformer simulation. I want to modelize a real world power line transformer in a reasonable way: I mean I don't need an exact simulation of some specific model, but something reasonably closed to the reality. Let suppose we want to simulate a 12 - 220 v transormer, with some empyrical attempts I ended with this model:

Thats produce the followint simulation ( note I drive from the 12 v side )

Note the 50 Henry inductance on the 220v side: it seems a monster to me, is this value reasonable? Note also the coupling factor is 1, I really suspect this won't happen in reality, which value should I use?
Even for the 12 v Side: how is the correct way in determining the correct value ?


texts: What is a good technique for a soldering novice to connect IC pins to female pin headers on a protoboard?

texts:
I have protoboard, an 8 pin socket adapter and two sets of female header (4 pins).

I want something a little more permanent than a bread board to use when programming ATTiny85s with my Arduino. I think being able to seat the ATTiny into the socket and then access all the pins directly on the female headers will be convenient.

My issue is that I am a super novice at soldering. I seated the header pins right next to the pins for the socket adapter. Then soldered all the socket pins and the header pins. The issue is connecting the two. I read about people who connect solder directly to bridge the adjacent points. And also people who bend pins to make the connection.

Both sounded like great options to me in theory. The problem was the pins are way too small for me to use the tools I have at my disposal to bend. They wouldn't reach anyways. I thought no problem, I'll just bridge solder from the Female header pin to the appropriate neighboring socket pin. But alas I suck at soldering so I ended up connecting it with the other adjacent solder as well so connecting 3 pins together when I wanted to connect two.

I attempted to cut a little tiny piece of wire and place it in between the two pieces of solder but it wasn't very stable just sitting there so I didn't even try it.

A complete solder fail.

What technique should I be looking at to research to try and solder two adjacent pins together in a crowded area where I don't want to accidentally make a connection to other nearby pins?


texts:
I'm writing code for a PID controller. The system is a "see-saw" with a motor attached to a propeller on one end and nothing on the other - you can call it a 1DOF helicopter. I use an angle sensor positioned on the rotation axis to get the reading and generate the P, I and D values accordingly. The "plant" (what I'm controlling) is the motor's RPM...

After a lot of effort, I'm still unable to stabilize the system. Now I'm thinking... It's the thrust that generates angle change - but the relationship between motor RPM and generated propeller thrust isn't linear - can this be the cause ?


texts: UART devices: Baud rates different by a factor

texts:
I have UART devices where I can chose various non-standard speeds, but none of them are matching. There are however some speeds, that are a multiple of the other device's speeds. For instance, I could have the rates 150'000 on the receiving end and and 3'000'000 on the sending device. Communication is only in one direction.

Do you think it is possible to hack something together to have the sending device send every bit multiple times and therefore emulate a slower baud rate? I think I would have to disable all options like start- and stop-bits and implement them manually in my fake protocol, so I can stretch these out as well.

Does anyone have experience with this? Could it possibly work? Or am I missing something?

EDIT: To clarify, I am not hiding anything, the numbers are correct: I actually want to talk to ESCs on a drone that expect either 150'000, 300'000 or 600'000 bits/s (DSHOT protocol). The board/micro controller I want to use to control the ESCs does not support these rates, but it would offer a custom baud rate of 3'000'000 bits/s (= 5 x 600'000). It offers others as well, but none match any DSHOT baudrate nor are they a nice multiple. So simply put, the idea is to send every bit 5 times and thus have the faster rate appear 5x slower. Does that make sense? Hence I would have to implement features like start- and stop-bit myself and have them sent 5x instead of once for example.


texts: I am trying to find the following connector. I have searched multiple platforms but cannot find the right wire to board connector. The pitch is 2 mm, and it has 14 pins.


texts: Motor enclosure top lid has electric spring

texts:
I fear this might be a little bit too simple for this Stack but I'll still ask. I dismantled a motor from an electric meat slicer of the very old type:

When I opened the enclosure I found that the top part (the opposite of the wired side) could be taken off and on the inside of that enclosure lid there is some sort of electric wired spring mechanism. The wires of the spring where already loose when I took it off, so I don't even know where those cables went:

My question really is this: Can I safely fire up the motor without wiring back on the spring? What does this spring do? How would I wire it back on?

Follow up

According to the answer of Dave Tweed I took a closer look and there are two almost opposite loose wires on the stator. They do rather look like broken than seperate wiring though (there's a third one which is loose but not open ended). Also I cannot make out any kind of capacitor without further disarming this, which is beyond my skills.


texts: SLEEP_MODE_ADC interfering with USART (and beep)

texts:
On an AVR ATmega328P, once per second I am doing 3 AD conversions immediately following each other with 16x oversampling using SLEEP_MODE_ADC like this:

EMPTY_INTERRUPT(ADC_vect);

uint16_t getVoltage(uint8_t pin) {
    ADMUX = (0b11110000 & ADMUX) | pin;

    uint32_t overValue = 0;
    for (uint8_t i = 0; i < 16; i++) {
        sleep_mode();
        overValue += ADC;
    }
    int16_t mV = (((overValue >> 2) * AREF_MV) >> 12);

    return mV;
}

It works fine.

At the same time, I am generating a 4 kHz beep with a timer toggling an output pin, and I am reading and writing data over USART.

The beep has a short click once per second which looks like this:

And every now and then a character sent over USART gets garbled.

While I'd expect that the beep timer is put to sleep during AD conversion in order reduce internal noise, I didn't quite expect USART tx/rx to be disturbed.

When I don't use sleep mode and do AD conversions like this:

    // sleep_mode();
    ADCSRA |= (1 << ADSC);
    loop_until_bit_is_clear(ADCSRA, ADSC);

the beep is "clean", there are no more USART tx/rx issues, and after some extensive measuring, I am pretty sure the AD conversion results are just as accurate as they are with sleep mode.

So I am wondering about two things:

Is it expected that USART tx/rx gets disturbed by
SLEEP_MODE_ADC?
Does sleep mode actually make sense in combination
with oversampling? Does some noise maybe not even help to increase
accuracy (dithering) or does that apply only to noise coming from
the sensors?


texts: How does the Arduino CapSense library work?

texts:
Can anyone give me some help in understanding how the Arduino CapSense library is able to sense proximity? From reading the source code, it seems that it toggles a sending pin and then waits for the receiving pin to change to the same state. The time taken (if I understand this correctly) depends on the proximty of a finger, for example, to the sensor electrode. However, there are several things I don't understand, such as:

Why does the proximity of e.g. a human hand change the time taken for the receive pin to change state?
Why is a resistor needed? I can understand a small resistor, but the example seems to recommend a very large (10 Mohm or greater) resistor for better sensitivity.
The site recommends capacitors for better performance. How do these enhance performance?
Does the frequency with which the send pin toggles play into the detectors performance at all?
And finally: Why does it use a digital pin as the receiver? Why not just pipe the output of the whole thing into an analog pin and measure the voltage via ADC?


texts: Using a PNP transistor with Arduino to close a circuit

texts:
I have teared down a radio controller of an RC car. I'm trying to control the car with a PC through Arduino Mega 2560 Rev 3.

The controller is very simple. It takes 9 V in. There is six wires to control the car. There is left, right, forward, backward and two ground wires. If you want to drive forward you have to connect ground and the wire that says forward.

I've wired the circuit as the following. Arduino outputs four times 5 V through pins 8-11. Then there are 1.2 kΩ resistors for each output (the resistors are wrong in the image). The resistors are connected to the base of PNP transistors (BC327). The emitter is getting the 4.5 V the radio controller outputs in the wires used to control the car. Finally the collector is connected to the ground of the radio controller.

The image isn't perfect but I think it might help a bit. The four collectors are connected together to the ground of the controller. I left the emitters open because there was so little space in the drawing. They are connected as I described above.

What I've understood PNP transistors let the current flow from emitter to collector when no voltage is applied to the base. When I set the pins on Arduino high (5 V), nothing happens. The car is still going.

How do I fix this?


texts:
What's the proper way to solder with bus wire on perfboard.

I used perfboard for the first time on a project recently. I designed a great layout and started soldering the components to the copper pads; the joints were perfect and beautiful. Then I realized I still needed to add the connections. So I put the bus wire down and was successful in getting the device working, but it was pretty ugly underneath.


texts:
I'm currently working on a project making use of ultrasonic proximity sensors. Unfortunately it seems as though well-documented ones are very few and far between (when compared to PIC or MOSFET datasheets).

As such I'm struggling to determine the bandwidth of these sensors. My understanding of bandwidth is that it is the frequency corresponding to the -3db attentuation point of a signal. How does this relate to a sensor?

(On a side note, can anyone explain the lack of quality in these datasheets? Am I looking in the wrong place? Vishay and Texas Instruments are really comprehensive, and then these datasheets barely have more than the sensor dimensions.)


texts: how to determine the current in this circuit

texts:
After calculating total resistance and total current, I am applying current division and I obtain (6/6+6)*1A = 1/2 A. But in the answer key it is presented as 1/3 A.
What am I doing wrong?


texts: Best way to create a daylight charging station and for a laptop of 135W consumption with solar energy and lower battery capacity posible

texts:
I want to create a charging station and for a laptop of 135W consumption with solar energy, because in my area electricity outages are normal (5 hours per day or more), but I need some help?

I want to buy an mppt charging controller, some solar panels, an inverter, and a lower possible capacity battery.

Storing energy is not my priority I just want to use daylight to charge a laptop when possible from 8 am to 6 pm schedule on daily basis, but only when a power outage occurs, and if possible because wheather conditions.

In my area insolation numbers are: kWh/m²/day    4.43, 4.60, 4.70, 4.49, 4.71, 4.94, 5.10, 5.28, 5.32, 4.77, 4.31, 4.13

Well, I have so many doubts, but this is my plan: install a 300W solar panel, connect it to mppt charger controller (10 Amps is enough?), and the controller to the battery, and the battery to the inverter, a very simple and regular circuit, but my priority is not to store energy, just use to charge laptop it if possible or use power directly from solar panel using inverter, because this I want to use and 20 AH or 30 AH battery, just to stabilize charge of the laptop or power consumption but not to store energy.
I believe that if the battery is fully charged the inverter will start using the current directly from the solar panel using battery charge to stabilize it, that's what my idea is based on, but I don't know if I'm wrong?
Are there errors in my assumptions? or What modifications should I make to achieve what I am aiming for?


texts: Explain the HIP 4082 pwm input from the datasheet

texts:
I'm trying to use an H bridge driver ic, namely the HIP4082 from Intersil.  My question is about the pwm input shown on the "Typical Application" diagram from the datasheet.  From the functional block diagram of the part, it seems as if inputting a common pwm signal into the ALI and BLI pins would cause the h bridge to drive the external load one direction and then the other based on the duty cycle differential.  My question assuming this is correct is why would I want to do that?  Why not just have a seperate pwm signal for each?  Otherwise, it seems like it would be hard on the component to be driving it forward and backwards so rapidly even though the net effect might just be driving the load in one direction at a slow rate.
Thanks for any explanation.  I haven't used h bridges before, maybe I am missing something about them conceptually.


texts: Determining magnitude of damping resistor for CMOS image sensor

texts:
I'm designing a camera module using Sony's IMX224 image sensor. This module would be connected to STM32F4 discovery board. At this moment I want to make a simple camera module so that I can write program for controlling the image sensor through the STM32F4. After that I'd optimise its circuits and then make a new module

But I'm wondering if I really need 'damping resistors' for data output pins of the IMX224.

Do you need damping resistors?
The IMX224 has 12 pins for CMOS parallel data output and they would be directly connected to the I/O pins of STM32F4 board. According to data sheet, people need to put a damping resistor for each data pin. But I'm not sure if you really need them. because some camera modules don't have such resistors, like the following link.
 http://www.elecfreaks.com/store/ov7670-camera-module-p-705.html
It has only 2 resistors. But it seems to work fine.
If you really need such resistors for impedance matching. How large resistance would you need? 10Ω? 33Ω?
The data pins of the sensor have output impedance of 50Ω. I guess the magnitude of the damping resistors should depend on data rate of image sensor. But the problem is...you can change data rate after by program when you actually use the camera and then such fixed value damping resistor would make problem, or?

I'm sorry for the stupid questions. But any help would be appreciated. If I have assumed something wrong, please feel free to let me know.


texts:
I'm really new to any circuitry and electrical stuff... just got started with Arduino this week. I'm reading a datasheet for a temp sensor and can't understand all of the variables.

http://www.analog.com/media/en/technical-documentation/data-sheets/TMP35_36_37.pdf

This sheet on page three in the test conditions/comments section repeatedly refers to \$ T_A \$. What is that, temperature average or something?

I've scoured around but it's a pretty specific thing to search for. Does anyone know the best way to learn about these types of variables/abbreviations, or is it just expected that you're going to figure it out and know what this stuff means? I know datasheets are written for engineers by engineers but that makes a high bar for entry for those of us without the necessary tribal knowledge.

There are other things in there too -- \$ I_l \$, \$ V_s \$, etc. While I understand the primary variable the subset throws me off. I imagine there are a set of basic ones that I just need to learn...


texts: Trying to solve a RL circuit by hand but simulator calculates a value I do not understand

texts:
I have this circuit. V3 is just a trigger to close the switch, just ignore it.

The switch is open for a long time. So, the left part of the circuit is working for a long time and the inductor is fully energized. Current is maximum on that part.

At t=0 the switch is closed.

I want to know the voltage across the inductor 3ms after the switch is closed.

I put this circuit on a simulator and it gives me the voltage across the inductor at 3ms as -11.3022 V. Strangely, the simulator shows a peak of -12V when the switch is closed and 3ms later the voltage is -11.3022 V. -12V? Where is this number coming from???

I am trying to calculate that voltage by myself, but the result I get is completely different.

This is my solution.

Before the switch is closed the voltage across the inductor is zero.
The switch closes. Now, a -15V (V2 is reversed) is connected with R2 in parallel with the inductor.

What I thought was this. Voltage across the inductor was zero before, now it is -15V. So it will discharge from -15 to zero. I was expecting to see a -15V peak when the switch is closed but simulator says the peak is at -12V.

I would use the inductor formula having -15V as a start but simulator apparently uses -12V.

How do I solve this?


texts:
Now, I've been learning Verilog but I got stuck with some easy problems.

always@(posedge clock)
if(reset == 1’b1) leds_r <=0;
else leds_r <= leds_r + 1;

I can understand if(reset==1'b1)leds_r<=0;
but the matter is else leds_r <= leds_r+1; what is that means?

I activated that with only always@(posedge clock) leds_r <=leds_r+1; code
using Spartan-3A/AN Starter Kit Board then, after I pushed reset button, all the leds were cleared.


texts:
I was making a non inverting amplifier,in the first iteration a provided a gain 1000 and at that time I can see the line voltage frequency 50Hz is coming at the output.
I reduced the gain and made it 51 and I can see that there is no 50Hz signal at the output.
May I know how the high gain circuit is capturing the 5Ohz line frequency.What is the mechanism behind it
Is it a radiated noise or conducted noise


texts: why the quantised of DAC will affect the amplitude of the output waveform of AD 9850?

texts:
By referring to the http://www.analog.com/static/imported-files/data_sheets/AD9850.pdf,
for page 9 and figure 5,
why the quantized D/A converter affect the amplitude of the output waveform?


texts: hFE value (a.k.a β or gain factor) for transistor, at different voltage

texts: I've been looking into the BC337 NPN transistor, and I saw in the hFE graph on page 3 of the datasheet, that the graph was at 1V from the collector to emitter. Is there any way to find out the hFE value for a different voltage like 5 or 10V? I've looked for a datasheet with a different voltage but have been unsuccessful.


texts: How can I set the maximum current in my CircuitLab circuit?

texts:
I have designed a circuit for two electromagnets to be turned on and off by a Raspberry Pi, but the total current draw by the circuit is 10.99A and my power pack has a limit of 2A. How can I simulate this current limit so I can calculate the required resistance of Resistor R2 to achieve a voltage of 6V across Electromagnet 1?
Here's the circuit:

simulate this circuit – Schematic created using CircuitLab
Thanks!


texts: Matching impedance of the load after inverting

texts:
I have a very basic inverter circuit with a 2n3053. I basically need around 5V at the collector terminal when the base is at 0V. I am able to achieve this provided the load is not connected. When the load is connected at the collector, the 5V drops to around 0.6 V or so (depending on the pull up resistor). After going through the load's data sheet I realized that there is an input impedance of 1.5K ohm. I could reduce the pull up resistor value to 100 ohms, but don't want to do so because of the high current that will flow through it.

I don't know much about impedance matching but I think that's the way to sort this problem out. Could someone help me? Can I make an emitter follower to match the impedance?

simulate this circuit – Schematic created using CircuitLab


texts: How to monitor the voltage of a bunch of batteries using Arduino?

texts: Ive got about 36 batteries that all stay between 2.8v and 3.6v, and I want to be able to accurately monitor the voltage(and therefor the state of charge) of all of them using an Arduino Nano, the two ways I can think of is use some analog multiplexers to get the 36 different batteries down to the 6 analog pins on the Arduino, or to use an analog to digital converter and then multiplex the digital signal. would either of these ideas work or is there a better solution than what I can think of?


texts: Why do consumer ovens use thermostats instead of PID + PWM?

texts: I measured the temp stability of my oven, and it's a really big swing of 10-15c in a saw tooth pattern.   Aren't PI(D) controllers with variable output meant to dampen this type of oscillation?  I imagine it would even make thermal recovery faster when the door is open and closed.


texts:
I have fifteen 12V 150Ah flooded batteries in series as part of a 10kVA off-grid system. Every once in a while, I test individual battery voltages. I've noticed that a few of them are, regularly, lower than the rest. For example, here's a reading I took today (#1 thru #15):

12.18   12.23   12.29   12.17   12.07   12.17   12.15   12.27   12.24   12.21   12.08   12.17   12.03   12.23   12.15

As you can see, batteries #5, #11 and #13 are "behind" the rest. And, here's the average of about two dozen readings taken over a period of 18 months:

12.19   12.28   12.29   12.12   12.08   12.15   12.02   12.25   12.21   12.16   12.07   12.12   12.03   12.23   12.13

So, this is a chronic problem.

Btw, here's the battery voltage history.

I've tried "equalization" a number of times, but given the nature of off-grid systems and the lack of a suitable generator, equalization hasn't followed the typical protocol (raise individual battery voltage to 16.5, continue charging at 3-6 amps for 12 hrs) ... and it hasn't achieved much.

So, here's what I'd like to do: Using a 12V battery charger, charge each of #5, #11 and #13, in turn, while they are in use. The plan would be to run the charge between sun down and sun up, doing one battery each night.

Can someone point out the holes in this plan?

Also, can somebody answer the key question: is it technically sensible to charge a single battery within a bank of 15 while the bank is connected to the load? [My worry is the fact that the charger will be connected to 2 circuits; one, the battery being charged; the other, the rest of the batteries and the load ... in the reverse direction]. Some explanation of why or why not would be appreciated.


texts:
I want to connect multiple devices which are communicating through UART to Rapsberry Pi3b+. Given that Raspberry has only 1 set of Tx-Rx pins, I am unable to do so. I am designing a PCB so I have the scope to add additional components. One way to do so would have been a UART to I2C bridge but most solutions are expensive and the choice of ICs is very limited (NXP was one).

Edit : They need to communicate every 500 milliseconds and in parallel.


texts: Transfer Function of Inverting Ideal OP AMP with Parallel Combination T feedback network

texts:
I've been staring at this problem for two days now and can't get the correct transfer function. I've modeled it in Simulink (Matlab) and find the magnitude of the transfer function to be ~ $$H(s) = \frac{s+20}{s+0.028}$$

I'm getting huge numbers when trying to solve it so I must be doing something wrong. I've applied KCL to solve for the currents going into the parallel combo. Can anyone offer guidance? My work is shown below.

simulate this circuit – Schematic created using CircuitLab


texts: Can I simulate any component with LTSpice?

texts:
I'm trying to build a very basic 3.3V supply, but would like to simulate the circuit in LTSPice if possible, before I physically build the circuit. I'm using a couple of components not found in LTSpice, for example a AP5100 buck converter.

Is it at all possible to create these custom devices/symbols and simulate their behaviour, or better, do the suppliers typically supply a SPICE model for their components?


texts: How to calculate secondary winding max current output?

texts:
I have removed a UPS transformer. It is a Class B Viking transformer. Its primary side has 4 wires coloured black, green, blue and yellow.
I found resistance as follows-
1. Black to Green - 17 ohm
2. Black to blue - 14 ohm
3. Black to yellow - 15 ohm
The secondary side have 2 thick wires and it's resistance is 0.5 ohm

Now my question is if I hook up 230 V between black and green will it draw 13.5 Amperes? I don't think that much current will be drawn. Where I am wrong?
Actually, I want to calculate the secondary winding's max current output but my multimeter doesn't read Amperes. But by transformer formula, I can find secondary current if the primary current is known.
As Vp/Vs = Is/Ip = Np/Ns

My calculation -
V=IR
I = 230/17
  = 13.5 A
Seeking help, Thanks.

Edit - For 230V input Secondary gives 6 Volts.


texts: why does my voltage regulator produce 5.11 volts instead of 5?

texts:
I'm not sure if my multimeter is at fault here, but I made a partial circuit in which I soldered in a voltage regulator (7805CT) and hooked a 22uF capacitor at the input and output (I connected the other leg of each capacitor to ground). I also added another 0.1uF capacitor at the output as well.

I measured the voltage at the output leg of the regulator using the 20 DCV setting on my multimeter (model DT-830B) and it displayed 5.11 instead of 5.

Is my voltmeter being stupid or do voltage regulators have tolerances? I don't understand why the value should be 5.11 and not 5.

I don't think my tracks have much to do with it because I have everything connected within 3mm of each other and the track width is at least 0.5mm.

Also, my input is a DC wall adapter that outputs 6 VDC and 900mA.

Any ideas?


texts: Power Consumpion on i2c on esp32 on arduino framework

texts:
I am relatively inexperienced with electronics so be gentle please.

I am trying to interface a VEML7700 photodiode sensor with a Firebeetle ESP32 using platform.io and arduino framework.

The connection and library usage was very straightforward so I got it up and running almost immediately.

The schematic is in the image

The problem is when I tried to measure the power consumption. According to the datasheet, the VEML7700 should consume around 40-60 µA.
When I measure the power consumption with it connected on the esp32 I get 540 µA. If I disable the sensor I get a 480 µA consumption, which means that it turns off, and there is a 480 µA draw somewhere.

The strangest thing happens when you disconnect the Vcc. The sensor still works and outputs data.

If I do the same thing with another sensor (BME280 barometric sensor) connected on its own, I get an equivalent consumption (around 500 µA)

If I connect both of them in series, I get double the power consumption (around 1 mA).

The same consumption happens even if I dont initialize the i2c bus. Or even if I  have the SDA & SDL completely disconnected.

If you connect the sensors to a power supply directly with 3.3V and Vin, you get the consumption that they say on the datasheet (around 50 µA each), so I am off by an order of magnitude, even if I have the sensors disabled on the code.

I tried the same thing on an arduino NANO with a single sensor and I get 80 µA with the sensor enabled and 20 µA with the sensor disabled, so this appears to be working correctly.

Does anyone have any idea what the reason may be?

Thank you.

Edit: the same thing happens with the esp32 dev kit 4 which is the official dev kit


texts: 2 sources one speaker - for old rotary phone

texts:
I have built a "mobile" phone using an old GPO 746, a Raspberry Pi and an old Nokia 6301, amazingly I have managed to get the audio to/from the phone's 2.5mm jack plug to through the GPO handset, audio in both directions is not great, but quite authentic!

To finish it off I would like to play a dial tone through the phone's earpiece when the handset is lifted off the hook. As the Nokia can't do this I thought that I would use the Raspberry Pi audio output through the earpiece.

My question is what is the best way to do this? i.e. connect 2 audio sources to one speaker. I haven't tried anything yet but doubt I can simply connect the 2 outputs to the same speaker without some sort of mixer/splitter which needs to be controlled by the start of the dial sequence.

Sequence is something like: Phone off hook -> play dial tone -> start to dial -> stop dial tone -> switch to audio from Nokia when call connected.

Any ideas would be greatly appreciated.


texts: How is the bootloader and firmware uploaded during production?

texts:
If there was a product with 5 MCUs (STM32303) and a main CPU being a AM5718, how would the bootloader be uploaded to each chip?

The same question about the firmware how would the firmware be uploaded to each.

Would it be done before the chips are soldered, would there be pads on the PCB for probes or something else?

Im only interested in what would happen in production. Any upgrading and uploading in the future would happen via the main CPU through UART


texts:
I have been experimenting with op-amp audio amplifiers powered from a 9V battery. I am just wondering how I should go about splitting the voltage from the battery, as I have found 2 ways of doing this . . .

CIRCUIT 1:

One method is to make the ground rail the -ve terminal of the battery and then DC offset the input signal . . .

CIRCUIT 2:

Or a virtual ground can be created like in the following . . .

They both seem to do pretty much the same thing. Should I prefer one method over the other?

EDIT

Based on Mark's answer, you can also have a rail splitter circuit like the one shown below. The purpose of the (optional) resistor in the feedback loop in the supply is to keep the op-amp stable in the face of heavy capacitive loads. The ground on the non-inverting input is only there to keep the CircuitLab simulator happy.


texts: RV Off-Grid Electrical System Wire Gauge Sizing

texts:
I'm working on building a Tesla battery powered off-grid system in our Airstream 22FB Sport. The idea is to be able to run the 120V AC system from the 5.2KV Tesla battery which is with the existing 12V Battery system not possible.

Here the current schematic:

I'm now very confused about the correct wire sizing for the 24V side of the system. With this calculator and the following settings:

24V, 125A, 6 Feet, 1% allowed Voltage Drop, 90°C Wire Temp

It calculated me that a 4 AWG Wire is good enough. So I went with a 4 AWG Wire from Home Depot and their Datasheet

After I installed everything I went through the spec sheet again and realized that the spec sheet says max 100A at 90°C on the 4 AWG Wire.

Therefore my questions:

I assumed that we have a max amperage draw of 125A (3000W / 24V = 125A), is that assumption correct? Or should I work with higher numbers?
Is the 4 AWG too thin for the application? Should I use 2 AWG?
If too thin, can I just double each of the lines (as I already bought and soldered the connectors it would be much cheaper to just double them)
Is maybe the Circuit Breaker Rating too high?


texts: Autobias Vbe with output current sensing

texts:
this is a question about analog audio amplifiers and automatic regulation of the output stage bias circuitry.

I basically need to implement an autobias circuit on this output stage topology:

As you can see, it's a very simple and classic output stage, the entire amplifier is a classical three-stage: input, VAS and output.

The target, is to use one o more transistor to sense the current flowing in the output transistor and regulating the bias accordingly. Obviously, without using thermal compensation and putting the Vbe transistor on the heatsink.

I found on Douglas Self's book "Audio Amplifier Design Handbook (6th ed)" a circuit capable of doing it:

He use a differential to regulate the current of Tr13, but I can't understand what is V_Ref.

Can you help me to understand how this circuit works? And how to implement this on a common amplifier output stage?


texts: Why does my resistor consume so much power?

texts:
I've created a low battery indicator circuit which lights an LED when the voltage drops below 3.75V. in this circuit, the 62ohm resistor is consuming about 240mW of power. why is this? is there any way to reduce it?

Here is the circuit when the battery voltage is below 3.75V:


texts: Why does a capacitor act like a short-circuit during a current impulse?

texts: While trying to solve questions involving impulses and step functions, we are supposed to assume that an uncharged capacitor or an uncharged inductor acts as a short circuit and open-circuit respectively. But, I don't see the theoretical reasoning behind it. Furthermore, can an impulse show up against a capacitor or inductor with only a step source?


texts:
What is the most optimum way of making a mod-counter that is not a power of 2? The counter increment is a variable

My approach on a mod-13 counter for example:

wire [3:0] counter_d ;
reg  [3:0] counter_q ;
wire [4:0] counter_plus_increment ;
wire overflow ;

assign counter_plus_increment = counter_q + increment ; //small increments
assign overflow = counter_plus_increment[4] ;
assign counter_d = overflow ? 4'd3 : counter_plus_increment ;

always @ (posedge clk or negedge resetn) begin
  if (!resetn)
     counter_q <= 4'd3 ;
  else
     counter_q <= counter_d ;
end

do you think this is correct? Any better, more efficient suggestions?


texts: Can an I2C switch control multiple I2C switches?

texts: I was wondering if I am able to treat an I2C switch simply as another I2C device and use 1 switch to control more switches downstream. This picture below shows what I am trying to do.


texts: Need suggestion in choosing an effective wireless Transmitter and Receiver

texts:
My requirement is to transmit a binary form of data from one Road Junction to another road junction which is around 4 to 5 km away.

I am going to get the traffic information from each road in the form of binary (4 bits) and transmit this data to the connected junctions of my current traffic measured junction.

So I want to transmit a binary form (For ex: 1010) to that junction.

In the other junctions I have a Receiver which receives this binary form of data and manipulates this. So for this requirement which Transmitter and Receiver is good?
I have an option to use FM transmitter and FM receiver based on my past experience. But I want to explore things and find Transmitter and Receiver other than FM transmitter and Receiver.

I hope you got it right. I don't know If I am overlooking anything here.


texts: How to measure the bonding wire inductance in lab by myself?

texts:
Very curious about the IC design. Everytime when we get our chips , we always need to bond wire the chip to connect the PCB. Even though the factory always claims that the bonding wire is 0.8nH/mm for inductance model, then I am still very curious, how to measure the bonding wire inductance value by myself in lab for practical situation?

Does any expert know how to do it ? Thanks so much.


texts: Why datecode is SO IMPORTANT to chip manufacturers?

texts:
With the miniaturization of the devices, chip marking has shrunk, not only in size, but also in content.

And while the part number got compressed to as little as two letters (or in some cases disappeared completely?), the datecode/lot number looks to be there to stay.

But how this information can be useful to the manufacturers? Let's imagine that a defective lot gets to the market, and the buyer reports to the manufacturer the lot number/datecode of that chip. What happens next? Is the manufacturer going to retire from market all the pieces from that lot? Is it just for an internal investigation?


texts: What is the recommended fully-charged voltage for NiMH AA batteries?

texts:
I have done research on different batteries and cannot find a maximum OR minimum voltage to keep NiMH AA batteries within.  It seems that typically battery chargers will measure the negative voltage CHANGE or the temperature, but are not designed to hit a certain voltage limit.

I have seen some claim that 1.5V is a good upper limit and 0.9V a good lower limit, but my question essentially boils down to:

What do most electronics want and expect from the AA batteries they run on?

For reference, here is the datasheet I found for Eneloop AAs


texts: What happens if both sides are forced as inputs on the TXS0108E level shifter?

texts:
Consider the case where A is an input and B an output and, by an error, another voltage is applied to B (5V instead of the output 0V with A=0V). B will now be considered as an input because of the transition detected, and A will become an output of 5V, which will create another short circuit.
Is this a bug in the chip? A vicious cycle?


texts: Capacitor size across power source selector relay

texts:
Two sources of power:

12V switched power supply (primary)
12V deep cycle lead acid battery (secondary)

Note: In practice the switched power supply voltage will be adjusted to match the actual voltage across the battery when it is connected to the load.

12V Relay:

NO connected to secondary power supply
NC connected to primary power supply
Relay coil connected to primary power supply

Load (12V):

Surveillance cameras
Network attached storage
Router
Assume Total 10A

Simplifications:

safety precautions such as fuses ignored for now,
battery Ah, run time etc. ignored for now,
why am I doing this ignored for now.

Question:

When the relay switches from one power supply to the other there will be a temporary open circuit.
How do I calculate capacitor size to use?
The open circuit time is unknown but can I assume it is say 10ms?

Solution? Charge:

$$Q = 10\text{ms} \cdot 10\text{A} = 0.1\text{C}$$

$$Q = C \cdot V$$

Capacitor size:

$$C = \frac{Q}{V} = \frac{0.1}{12} = 8,333 \mu \text{F}$$

Now I realize that this means that at the end of 10ms the Voltage is zero. So I figured I'd ask for some advice:)


texts:
all I'm pretty new to electronics so my question may be a little ambiguous.

I have designed a two-stage amplifier using 2N3904's. the total ac gain should be over 5000. would this circuit do it? according to my calculations, it should work.

as far as the bypass caps, I have no idea on how to calculate them.
any help will be appreciated.


texts: Three phase is 5 core (l1,l2,l3, N,G) yet my driver only has l1, l2, l3, G. What do I do with Neutral?

texts:
It's a motor driver and has connections for L1, L2, L3, and Ground -- by ground it's the universal ground symbol.
My three phase cable has five connectors. I'm not happy with leaving one out, so is this a convention for devices where N is wired in ground (as it connects to ground at some point!) or am I really connecting three live phases to ground? Surely this would trip any RCD?
Link to servo drive: https://www.se.com/ww/en/product/LXM52DU60C41000/lxm52-single-drive-1%2C5a-6a/


texts: LTSpice Has bizzare results for high input impedance devices

texts:
While simulating with LTSpice I discovered the simulator gives milliamps of inverting and non-inverting terminal current in op amps and also the same thing for MOSFETs, milliamps into gates. Here is a simple circuit demonstrating the current into a non-inverting terminal with an op amp. I will also put down that I measured only nanoamps of current into op amp inverting and non inverting terminals and also MOSFET gates in Multisim to verify that LTspice is incorrectly giving results, which leads me to believe LTSpice is seriously flawed and this should be reported to developers. Is this normal or is it a bug which should be reported to developers?

Another circuit


texts: How can I choose the resistors for a push-pull class AB amplifier (diode biasing) to get a certain bias current?

texts:
Hello guys, this is my very first question.

This is a part from a BJt audio amplifier volume control with 3 stages (Pre-amplifier,Buffer, & Power amplifier). This is the power amplifier stage.

I am asked to design the resistors RB3b & RB3a to provide a bias current of Ic=(375/20) mA when the input and output terminals are open circuits and to get Rin.

I proceeded in the problem,The voltage drop between the two diodes is 1.4V so I found that the voltage drop between each resistor is 3.8V and Vce for each transistor is 4.5V.

The problem is I cannot find beta (current gain) from the data sheet to deduce Ib and the current in the resistors.
the date sheet provide beta for maximum of Vce=1V so I am stuck.

plus I read that the current in the resistors should be 10 Ib, is that right?
I would appreciate any help, thank you.


texts:
this is my first post here pardon me if this question is idiotic :)

I made a voltage divider by following the image below

But when I connect 12v supply the resistor getting very hot just in 2seconds
what am I doing wrong ?


texts:
I have a prototype board which I'm currently testing the signals of its zero-cross circuit.
This is the schematic of the PSU, the power supplies of the low voltage part of my circuit (12V, 5V, 3V3) are galvanically isolated from the high voltage part.

This is the schematic of the zero-cross circuit:

The circuit works well, the output signal is not perfect, not a perfect square, but its waveform is very suitable to control a TRIAC (this part is working fine). The output signal waveform I consider as 'ok', even when input supply is 100Vac.

Here are some scope screenshots of some points of the zero-cross circuit.

Note that all the waveforms below are in respect to GNDP, and the negative probe of the scope is connected exactly at the emitter of the transistor.

(1) Here is the cathode of diode D8.

(2) Here is the cathode of diode D8, with zoom next to ground point.

(3) VBE, when it is all working correct.

(4) Some days, at some moments, a glitch occur on the circuit. Today I was able to catch the problem with the scope, and here is the output signal when the glitch occur (the fast falls from 1 to 0):

(5) Of course this problem comes from a glitch on the input, and I was able to catch the glitch on the input also, here is the VBE signal when the glitches were occuring. Check the short pulse from 0 to 1 at almost the mid of the level 0 period. I realized that when the glitch occurs is because the amplitude of this undesired pulse reached a voltage sufficient to VBE to conduce.

I already modified D8 from 1N4007 SMD/SMA to S1M diode, but it makes no difference. I can't short D8, if I do this there will be much power dissipated at de 39K resistors. And I do know that the zero-cross circuit is consuming around 1mA from 6VP, and this do increase a little the temperature of the IC LNK626, but I consider this is not a problem.

What can be done to avoid such undesired pulses? Or maybe, how to reduce these noises? For me, the noise seems to be the switching of the PSU at around 100KHz.
Regards.

EDIT(1): new tests.

I placed a 100nF capacitor across R19 and the VBE signal remains the same, it makes no difference.

Below is shown the waveforms of AC2 vs GNDP. In all these measures, the negative probe of the scope was connected exactly at the emitter pin of the transistor Q5.

(1)

(2) Zoom, closer to the reference

(3) Zoom on X

(4) Zoom, even closer to the reference. Noise observed.

(5) Noise observed at a different moment. Maybe occured when the output of the PSU demanded more power.

Is there any way to correct this?


texts: How to compensate gain and offset errors

texts:
I have an analog circuit which has an offset error as well as an gain error.

I can measure the analog output of the circuit and I am able to manipulate the gain of the circuit by means of a factor k_gain_comp and the offset by an additive value offset_comp.

What is the right approach to compensate those errors? Should first the gain error be compensates or the offset error?
How can k_gain_comp and offset_comp be calculated?

Any answer is highly appreciated.


texts: Does my Wireless Charging PCB need to have FCC, UL, CSA, certified marks?

texts: I have a simple 5W output wireless charging device that uses a tx coil to transfer power to a phone, this is powered from a 1800mAh battery. Do I need any certifications for this?


texts: What is this circular symbol on my SD card?

texts:
I have bought a SD card, same as in the picture below. I have found a completely new logo printed on that. I have searched on the internet for this logo, but didn't find anything.

Can anyone here tell me what's it?

Thank you.


texts: What is the upper frequency of a zener used for transient voltage suppression?

texts:
I have just answered a question here, and it has spurred me to ask a question:

How fast will this type of protection work? Would it work with, say, a 500kHz signal? And is there an easy way to work this out fro the zener datasheet?
(Using zener and resistive divider to protect from overvoltage)

I would expect, at some point, that oscillations would occur where the zener doesn't break down fast enough?

The previous question: 12V input on microcontroller pin

Schematic example given by Michael on that thread:


texts: Why are these measurements misleading and how do I fix them?

texts:
I am trying to measure the voltage between node 2 and 3, which I am guessing should be zero. With a multimeter I read 0V.  With an oscilloscope I am reading about Vb/2 if I remember correctly. Why are these measurements different and is there a way to fix them?

The idea is to feed node 2 and 3 into a difference amplifier, so I want to make sure the Vb/2 factor is either fixed or understood to be zero so that it does not saturate the opamp.


texts:
X1Iz.png

I have the following questions about the above circuit:

-Why are we even using a trica/diac combo above. Why would a circuit consisting of just the fuse, switch and primary not be sufficient for charging the battery?

-If we do go ahead with the above combo, what is the use of the resistor/capacitor combo attached in parallel above the triac?

Thanks
giv


texts:
I am rusty on my circuit knowledge and looking into wiring my own regulated box mod circuit using an LM2596. I found a circuit diagram to use, and while I could just wire it up and hope it works, I'd really like to understand why it works!

S1 represents a switch, right?
What purpose does the MOSFET serve?
I think my coil is 2.5Ohms, not 0.5 like in the circuit. Would this change anything like maybe the strength of the 15k resistor?

Circuit diagram I want to use:


texts: What is the difference between MOSFET transistor and normal transistor?

texts: I know this might be a stupid question, but what is the difference between MOSFET transistor and normal transistor? There must be a difference but no one says it, people always talk about them as they are the same thing, but there shapes is different, even in circuits' schemes they are represented with different symbols, so there must be a difference.


texts: Triggering event from timer compare channel on ATXmega when timer is set to single-slope PWM mode

texts:
I am writing firmware for an ATXmega. I have a timer configured in single-slope mode to output a PWM signal. I need one of the xmega's event channels to trigger in the middle of that signal. I thought I had it configured to do so, but I am suspecting that the event is actually triggering off of the period.

Some representative example C code:

TCF1.PER = 100;
TCF1.CCA = 20;
TCF1.CTRLA = TC_CLKSEL_DIV1_gc;     // timer will not run until this line
TCF1.CCB = 100/2; // middle of the waveform
TCF1.CTRLB = TC_WGMODE_SINGLESLOPE_gc | SWITCHING_SIGNAL_CHANNEL_ENABLE; // enable timer output to pin
// ... and then later ...
EVSYS.CH7MUX = EVSYS_CHMUX_TCF0_CCB_gc;

And then an diagram showing the situation and the desired and undesired behaviour of the event channel:

How do I get the event channel to behave in the desired way, and then verify that it is not behaving in the undesired way?


texts: RFID reader sensitivity/read range - How does a "hard" ground increase sensitivity/read range?

texts:
I'm working with two RFID readers in my circuit and an arduino to control both of them. The whole thing is powered by a very cheap wall-wart Power supply at 12V which is rather noisy to begin with. And a 7805 Voltage regulator to drop the voltage to 5V for the arduino.

All components have proper decoupling capacitors (in my opinion):
470uF+100nF for the two RFID readers, in close proximity.
100nF for the Arduino (not counting the decoupling on the arduino itself)
22uF+100nF on the input for the 7805 and 100uF+100nF on the 5V output.
There is one additional component which is a MAX232 which is set up according to the datasheet.

Therefore I'd say, the decoupling is done porperly. However sensitivity aka read range is 5mm with the wall wart.
Now if I use my bench-top Power supply (Peaktech 6150, not even an expensive one) read range is around 55mm. The same effect can be had when connecting the scope to the circuit and using the wall wart. So I'd conclude it is not a problem with the noisy wall wart but rather a problem with the grounding as the bench top PSU and the Scope are probably connected to earth(?) and thus provide a "harder" ground I guess?

Update:
Using a scope to probe the 0V or +12V (and any other point) with referenece to the scopes GND, revealed that there are two major components of common mode noise:
355V Pk-Pk @ 50Hz from Mains
10V Pk-Pk @ 125kHz from the antenna-drivers (same frequency).

Probing the +12V point with reference to the 0V on the PCB shows
140mV Pk-Pk @ 1kHz which I belive to be the switching frequency of the wall wart.
Superimposed I can still observe some noise from the antenna driver at the same 125kHz but now with the scopes earth/gnd connected it's around 4mV Pk-Pk. Which is sufficently low to bring the read range up to where it should be.

Solution (sorta)
An accepted solution would be the use of a pre-made power supply with DC 0V connected to PE directly or via Capacitor. Or some other means of grounding the 0V line.
However as Andy aka points out, it would be better to take a look at the susceptibility and source of the noise as this is just a fix for a non-ideal circuit.


texts:
This might seem basic to most of you but I'd like some help with a DT FS question if possible.

From what I understand, the period of a DT signal N is defined as the value such that x[n] = x[n + N].

I have the solution to question here that states the period is N. Should the period not be (N + 1)?

Similarly, in my summation to find the FS coefficients, should I not sum from (0 to N), rather than (0 to N-1)?

Thank you.


texts:
Other than operator errors, machine errors, and rounding, what might cause standard circuit simulators to produce bad results? In other words, are there known circuits for which simulation is "risky"?

Thanks much in advance
Joe


texts: Is the FT232H a single channel version of the FT2232H?

texts:
I'm looking at the Opendous JTAG Project, and would like to integrate a this JTAG debugger circuit on my ARM Cortex M3 experiment board I'm designing.

I noticed that Channel B, on the FT2232H chip is used for the JTAG connector, so can I instead use the FT232H, if I only need a single channel?


texts: Issues ascertaining current x time for battery life

texts:
It is simple to calculate a continuously-on device's theoretical battery life based on the battery datasheet capacity (assuming always nominal voltage, etc.)

An LED @ 20mA..

2800mAh / 20mA = 240 hours.

The issue I am having is verifying calculation of intermittent use of such a device.

Lets say it consumes 20mA for ten seconds three times per day. Would a calculation such as this make sense?

20 * 10 * 3 = 600mAs? / 60 / 60 = 0.166mAh/day

To be novel, resembles $$0.166 \centerdot 10^{-3}
\ C \centerdot s \centerdot hour \centerdot day^{-1}$$

Now to extract days from that I would possibly do this:

2800mAh / 0.166mAhd? = 16867 days / 365 = 46 years battery life

Does this seem at all coherent? The only proof I can muster:

16867 days * (30 * 10 * 2 / 60 / 60) = ~2800mAh

Had never seen anyone use this before, maybe I have pioneered some new units.


texts: Good design for reading a DIP Switch once

texts:
I want to read an 8bit DIP switch at MCU startup, after that it will be disregarded. I have enough pins on the MCU to read this directly. My question is; is it worth while to stop the power for the switch after it is read? Power is not a huge consideration but as it will be on 24x7, running on large batteries I at least don't want wasteful usage. What would be the best practice? I could sacrifice one more pin on the MCU to do this.
Originally I was thinking of a multiplexor, but the price difference for an MCU with more pins is so small it would be easier to go that way. Thanks!


texts: Help understanding power ratings in optocoupler datasheet

texts:
I want to understand this the datasheet for the Everlight EL817 optocoupler but don't know what is the maximum power can the output hold.

I see an optocoupler as a kind of switch that closes a circuit when a signal is given. But surely is more complex than this because of the emitter, collector, input & output concepts in datasheet.

I need to know how much voltage and intensity can I support with this optocoupler (passing trough the part of the circuit to be closed or opened).

The input is 6V and 60mA (is it right?). And the output is 35V and 50mA, but that is 1.75Watts, so can it hold 194mA if the output voltage is 9V?


texts: The total size of 32-bit memory address, 32-bit data words memory arrays?

texts:
I see that the total size of 32Kb = 32 x 1Kb.

The ARM architecture uses 32-bit memory addresses and 32-bit data words.

This means, the ARM memory array depth-width is 2^32 words and 32-bit, which is 32 x 23Kb = 736Kb in total size?


texts:
Design the following memory with D Flip-Flops. (you can use other gates or decoder if needed)

The following memory has 4 one-bit locations and can access 2 locations in each moment and read from those two locations or write in them. consider that the addresses that are put on the address lines are always different.

Here is my own design and I'm not sure that if it is correct or not, also I do not know that what should be connected to the enable of the decoders:


texts: I have a 24FC01, 1 kbit EEPROM on my board. The SDA and SCL lines are pulled up to 3.3V through two 2k resistors. I'm using a STM32F407 MCU to read and write data to the EEPROM. Using the HAL libraries, I'm trying to check if the device is ready using HAL_I2C_IsDeviceReady(&i2c2, 0x50, 2, 100) function. However, this fails and returns false. The I2C is configured in CubeMX with 100 kHz clock speed and 7-bit addressing. What am I missing?


texts: Can I transmit to several FM radio channels concurrently using one digital transmitter?

texts:
I have an Si4720 that can transmit at one FM radio frequency at a time, and if I use several of them on my board, I would be able to transmit at several FM radio frequencies at the same time. This solution is not feasible for me (due to board size and cost limitations) so I would like to know if the following makes sense, and if it does, which hardware and software (ideally a combination of a micro-controller and an RF unit) I would need to implement it:

Generate the information signal (human voice recording, so limited to about 4kHz)
Generate N carrier signals (ideally, N=101, corresponding to the number of FM radio channels in the USA)
Modulate
Transmit

This is for an extremely low power application (effective service range of less than 200ft) so licensing is not an issue.

Thank you.


texts: Would you ever be advised to solder hookup wire to a terminal pin (and maybe sleeve it with heat shrink) instead of soldering it directly to the PCB?


texts: Synchronous Generator Resistive Load Characteristics?

texts:
I have a permanent magnet synchronous machine (PMSM) that I intend to run as a generator. I'd like to test its load characteristics under resistive load. The PMSM is Y-connected. Assuming Y-connected load, the circuit will look like this.

simulate this circuit – Schematic created using CircuitLab

My objective is to plot the load characteristics of the generator (load voltage vs. load current), for 10-12 different values of load resistance, starting from a maximum resistance to a minimum resistance. I want to be able change the load resistance while keeping the load balanced. However, I only have access to potentiometers and simple resistors. If I manually change the POT resistances by hand at each step, there is bound to be imprecision and thus, load will become unbalanced.

My questions: (1) Is there any way I can achieve this using potentiometers? (2) Is there an alternative way to do it, keeping the load balanced? Thanks a lot!


texts: Why the current in this graph is so strange?

texts:
I have a question about a 3-phase 400V motor used by an hydraulic pump.

I read its currents and their graph is quite strange to me, far from the usual (deformed) wave.

What could be going on here?


texts: Transformer, how the primary current is adjusted to be equal to the secondary load (without considering magnetizing current)?

texts:
I am happy to always not understand how does a transformer works ... One answer give me 10 questions ... (So I suggest you to not answer to this question, if you do not want to have more questions :D)

Here is the circuit :

So I put the "coupling" factor to 1, in order to have no leakage inductance and I set the value of the inductors very high in order to have a very low magnetizing current. So the primary current is approximately equal to the secondary current. My question is the following : How the primary current can reach an equilibrium to be equal to the secondary load current ? I will not accept answer which tells Pout is equal to ... So Pin is equal to Pout... There is something happenning into the transformer ...

Thank you very much and have a nice day !


texts: Combining speaker outputs to one secondary amplifier

texts:
Background
I have a Denon 5.1 av receiver and have bought some new speakers. The only restriction (from my wife) was on size so I have managed to get hold of a set of speakers for the Sony DAV-IS10 (http://www.trustedreviews.com/Sony-DAV-IS10-DVD-Home-Cinema-System-review) which should work. Five 10ohm satellites and a mid/bass dual driving woofer. The dual driving woofer is required as the satellites are very small and don't output a full range. What I planned to do was have the dual driver run off the receivers sub out. I built a lm3886 dual mono amp from chipamp.com driving each woofer as the old amp was fully integrated and needed to work with the original Sony DVD/receiver. I now realise that the Denon receiver sub out is set to low pass at around 100-250hz which is no good for the dual driver.
What I have at the moment is 5 satellites and the sub working with the receiver but the mid-woofer is not really receiving any signal. What I want to do is to use a line level adapter on the speaker outs to draw a 1v line (speakers are around 27v) to the input of the mid-woofer amp similar to http://www.dougcircuits.com/lineout.html. I believe this is simple enough for a single speaker circuit but then I would have to choose which circuit to use. The left and the right channels clearly have different signals at different times. The center speaker is where the bulk of the dialogue sits but I don't know if it contains all the range and effects the left and right get. Ideally pulling one line off the center speaker would be easiest (if that works then great) but I am considering whether I need an output from the left AND right or even all three to get the full range through to the mid-woofer.
Question
What I have not been able to work out is: can I combine these line level signals into one RCA input for the mid-woofer amp? It would be a separate line level adapter at each speaker output but then combined into the mid amp. Is this even necessary... does the center channel put out enough range to cover the mid for the left and the right?
I know that you cannot do this for speaker level outputs as there will be interference and likely shorting of the amp. I believe that the Denon amps use common grounds so that side of things should be okay.


texts:
I'm attempting to build an LED bed lamp that will be powered by 240V mains. The LEDs are these ones which if I use with a 12V supply and have calculated correctly will draw 0.24W each. I plan to use 5 or 6 of them in the lamp so will consume a maximum of 1.5W.

Initially I thought I'd use a transformer and bridge rectifier to get the required 12V DC but the transformer weighs a ton and is too bulky. The next option was to use a plug pack but I'm wondering is there is a better way?

I think it would be possible to power the LEDs directly from mains using only a rectifier without mains and stepping down the voltage but then it's not safe. Are there any smallish components that can both isolate the mains and supply a DC voltage?


texts:
I'm making a part in Eagle (4.15) for a SOIC-8 package.  There is a thermal pad in the center and I'm trying to add vias stitching the top and bottom pads together.  In the Eagle package editor there are no vias, I can add pads or holes.  Is there a standard way to do this?  I've found some related questions,  and this, but no answers that help me.

I'm using an old version of eagle (4.15)


texts: Capacitor Identification for speed board

texts: I've got a Speed Control Board that a Cap fell off of.  It came out of a pair of Andis Clippers my wife uses for Dog Grooming.  It plugs into 120V outlet. I can't find any info on what the specs, besides the 470uF, are on it.  The Cap goes right in the middle of the board where the solder pads are.  It is not through hole soldered.  The board has a power button in the middle and an increase speed button above it and decrease speed button below it.  I have ordered a new board but I need this functional until it comes in if possible.  Any other info just let me know and I'll do what I can.


texts:
I am trying to design and build an antenna + LNA board.

Antenna: http://www.yageo.com/documents/recent/An_FR4_1690_2405_0.pdf

LNA: http://www.avagotech.com/docs/AV02-1237EN

The antenna is specced to run at 168 MHz.  In the LNA documentation it provides a suggested circuit for a 500 MHz signal.  The suggested circuit is below.  My Antenna feeds into the left, and my output is on the right.  In building the board following the suggested circuit, only my trace between my antenna and the start of the LNA circuit and the trace between the end of the LNA circuit and my output SMA are 50 ohm traces.

My Question is basically why isn't this working?  Am I missing some vital piece of information I have no considered?  Given that the circuit is designed for 500 MHz I would expect lesser performance with a 168 MHz signal, however I am unable to pick up any signals.

My test setup consists of an RF generator with an antenna attached, and a network analyzer with this antenna design attached. These two components sit a few feet apart.

I believe all of my soldering connections are correct, and I have confirmed that the board is receiving the appropriate amount of power.

An Image of My board.  Dimensions are roughly 1.5"x1.25"  and all of my components are 0204 size.

So to recap, I receive no signals on this board even when I am blasting on my RF source right next to it.  I have tested other antennas to verify that the broken piece is indeed this new antenna design.  Could the mismatch between the frequency used to build the recommended circuit and the frequency my board is running at really eliminate all signals?  Or is there some aspect of antenna design that this novice is glossing over?

Any thoughts would be appreciated!

EDIT**

Per the suggestions below, I have modified my design to remove the ground pour and add the suggested traces to the Antenna.  My new design is below.  How do we feel about this.  I should also state that I tested my board with the antenna placed vertically to get it away from the ground plane and I added a short wire tail to it to mimic the suggested trace outline and it gave me a signal!


texts:
I have a ZCS buck circuit which I simulated on PSIM first, and wanted to simulate it in Pspice now with the real components. However, I am getting wrong results in Pspice, and I can't figure out why. Here's the Pspice circuit followed by PSIM,

Here are the same quantities (VGS and switch current) plotted in PSIM(correct) & PSpice(Wrong!).

Although my sawtooth voltage source output is correct (200 kHz, 3V peak) here is the way I defined it in Pspice:-

What's going wrong in my Pspice simulation?
EDIT 1: I did not correctly add the gate drive isolation!! Problem solved.


texts: Term for pcb test fixture that can access both sides of the board

texts:
What is a good term for a pcb test fixture setup having, say, pogo pins that can reach lands on both sides of a device?
Could it be dual-side or double-sided?


texts: Inconsistent values read from PCA9955B error flags

texts:
The PCA9955B is a 16-channel LED driver that features programmable PWM and current and has gradation support. It also features open/short detection for all of the 16 channels, which is reported in the 4 error flag registers EFLAG0 to EFLAG3. However when I read those registers I get inconsistent values. The EFLAGx registers are divided in two-bit quartets, which 2-bits indicate the status of error detection for each channel; zero means no error, 0x1 indicates a short circuit condition and 0x2 an open circuit.

Indeed the status register (MODE2) has bit 6 set, which means an error condition was detected on at least one channel but when I read the four EFLAG registers I get 0x80 four times, regardless of what channel is open or connected to a LED — I didn't try to short any. It occured while all of the 16 channels were connected and functional. But I also read those values on a previous board that had several channels not connected.

As the datasheet reports, error detection will no occur if the LDRx registers are set to 10b or 11b and the PWM value is less than 8 or equal to 255. It's not the case as I set the value for those registers to 0x20, which is between 8 and 255.

I am using an Atmel ATmega64M1 to do the I²C job with a software library of my own but I already ruled out possible errors on the bus. All I²C chips I've used with my library do work as expected and I compared my results with that of an Arduino and its hardware I²C support. I've also compared the signals with an oscilloscope and there's no difference. So I would tend to believe there's something particular with that chip that's not in the datasheet...

I hesitated to ask the first time I used the PCA9955B but now I have two of them fully working but that very feature, I'm posting my question here. Can anybody explain why I would get inconsistent values for the error detection while the chip seems to behave perfectly otherwise?

The chip is a PCA9955BTW I ordered from Digi-Key. Except on that very detail the chip conforms to the datasheet.


texts:
Does someone know a digital gates (inverter, buffer, nand, and, or, nor, etc...) that can go from 0V to 5V in about 1ns?

I have check TTL, but they are not so fast.

Ideally, I should found it in Farnell, Digikey, Mouser, etc...

Alain.


texts: Connecting 5 pin 3.5MM Stereo Jack Socket to TDA2822M

texts: I'm trying to make a portable amplifier based on TDA2822M IC. I've bought several stereo jack sockets but faced the following issue: I don't know the pin-out of these sockets. I'm interested in how i can discover the pin-out using a multimeter or some other way?


texts:
I'm trying to test the magneto from my riding mower.  I followed some YouTube videos and tested it with a multimeter putting one probe where the spark plug would go and touching the other to the metal plates.  I get a resistance of about 5.84 kilo-ohms.  But I don't know what that means.  Is it too high?  Are there any other tests I should do?  (the mower has no spark).
The mower has a Briggs & Stratton 11.5hp engine, model 28D707-0123-01 (1996). I tested for a spark by holding the plug to the engine while turning the key.   (Maybe the "redneck" method but recommended by my service manual too in the absence of a spark tester.) The starter motor appears to work properly and the flywheel turns freely by hand.  I also tried a new spark plug and all the safety interlocks appear good. The replacement part is here https://www.jackssmallengines.com/jacks-parts-lookup/part/briggs-stratton/591459 but I can't find any specifications for the old or new one. I'm not yet 100% sure that the magneto is the problem so I'd rather confirm that it's bad before replacing it.


texts: coocox suspends and hits the break-point

texts:
I am a complete beginner in the ST micro-controller programming.
Intention was to evaluate the software set-up one and board functionality.
So tried to blink an LED using standard code available.

ST evaluation board: STM32F407VGT6 based evaluation board

CooCox CoIDE: Version: 2.0.7, Build id: 20170510-2.0.7

Following is (Also highlighted in the red rectangle) the message shows when tries to flash the code.
Please advice, How I can rectify this issue.

GDB Hardware Debugger (24/11/17 10:14 PM) (Suspended)
    Thread 1 (Suspended: Breakpoint hit.)
        1 main() main.c:15 0x080010de

I have to tired to add enough info here, please let me know any other information required.


texts: Measuring Load Capacitance and resistance of 4~20mA transmitter

texts:
In order to make a spec sheet on a loop powered 4~20mA product, we need to measure the Device Capacitance and Device Resistance.
Is there any standard procedure for measuring such parameters?


texts:
Can someone please help me identify these? I think they are capacitors. I have no background in electrical engineering. Just trying to learn this stuff as a hobby. This came out of an audio amplifier board ICEPOWER 200ASC. I have no schematic and could not find one that tells me what those are.
First Capacitor:

Second Capacitor:


texts: Why are AWG charts rated in amperes and not in watts?

texts:
American wire gauge chart is rated in Ampacity. Isn't it wise to be rated in watts?
Let say a wire is rated to conduct a certain amount of current what's going to happen when the voltage goes higher and higher?
edit:
My question is concerning the AWG chart that I think should be in watt or VA but after saying that who am I to dare.


texts: Confusion about when to use B*Ib = Ic vs the voltage diode equation for transistors to obtain Ic

texts:
When we have an NPN transistor in forward active mode, why do we sometimes use this equation to find the collector current I_c (whereby V_be would be the voltage across the base emitter junction)?

But then other times use I_c = B*I_b (whereby I_b is the current into the base of the NPN transistor)?
Thanks


texts: Relationship between offset in electrical angle and BLDC motor performance

texts:
I am controlling a BLDC motor using Field Oriented Control (FOC). I use a 14-bit absolute encoder to read the rotor's position \$\theta_{m} \$, and use it to reconstruct the electrical angle \$\theta_{e}\$, which is given by:

\$\theta_{e}=\theta_{m}\cdot N_{p} + \theta_{offset}\$

This angle is used in Park's transformations to reconstruct current readings, and to produce, with inverse transform, PWM voltage references.

Given knowledge of the number of pole pairs \$N_{p}\$, and a perfectly homogeneous distribution of the pole pairs, how sensitive is motor's performance to the accuracy with which we experimentally define \$\theta_{offset}\$?

How accurately is it usually defined for high-accuracy torque control application field such as robotics?

Edit: with some more research, I found \$\theta_{offset}\$ accuracy is mostly sought for torque efficiency. What I am surprised not to find yet is people discussing its induced disturbances on the closed-loop current control systems. How does it affect, for instance: bandwidth, vibrations, audible noise, and energy consumption?


texts: Wireless power transfer - Inductive vs. resonant mode

texts:
When talking about how wireless power transfer is done, the standards (e.g Qi) distinguish between inductive and resonant mode. (Link)

They claim that when the units are in very close proximity it is more efficient to oscillate at the inductive side of the resonance frequency, but when further apart it is better to ride on top of the resonance peak.

Im not quite sure as why this is the case.

I know that oscillating on the inductive side have some pros, like ZVS to increase efficiency in the switching, but they also claim higher power output by using this at close proximity. why is this not the case when the units move further away from each other?


texts: Expected E-field results vs simulation results

texts: In the below question I wanted to know how they are getting the expect result of .74u for the e field, e field should be v/m it works out correctly for this simple example but as soon as I change the radius of the second sphere to 9 and its charge to +3 and then first sphere to radius 4 and charge -2 when simulating I get effectively 5v/m. ok I get 5v because the fields will add since both vectors will be in the same direction but how do the meters become apart of the units without actually involving the radius? If I perform the math the same as the first example for the second scenario I get way off answers since using the equations for e field and V  E= V/r  which once the radius is more than 1 will not be able to simply add the voltages so really confused as to why my simulations are seemingly just adding the voltages for the max electric field. Can someone point out the disconnect please.


texts: In the image above, why does current flow backwards toward the left GND but not toward the right ?


texts: Voltage drop in a Permanent Magnet Generator

texts:
A small alternator type 4-pole permanent magnet generator(PMG) outputs AC sinusoidal voltage from 1V to 30V where output voltage amplitude increase with frequency.

I first set the generator to rotate with a constant rpm.
When I hook up the output of the PMG directly to the oscilloscope I can see the true voltage output. So far so good..

My aim is to decrease the voltage output of this PMG by a voltage divider and couple it to a comparator as an input. The reason is, if I don't do that the input to the comparator from the PMG will exceed comparator's rail voltages at high rpm.

So I decided to use a 330k and a 33k resistor to make a voltage divider. I set the generator rpm such that its output was 12V when hooked up to the scope.

Then I coupled the output of the PMG to this voltage divider. I wanted to be sure if I'm doing things in the right way, so I checked the voltage across the voltage divider (across 330+30 = 360k), and what i saw was there was almost no signal in the scope. The voltage output dramatically dropped.

Here is a simple illustration about what I wrote:

Why does it happen? Should I  use a much higher resistors values for the voltage divider?

simulate this circuit – Schematic created using CircuitLab

Figure 1 and 2. 12 V AC on open circuit. 0 V when loaded with 360k.


texts: Are there any reasons I shouldn’t use a nodemcu’s 3.3v pin with this component?

texts:
I have this Hydrogen Sulfide gas sensor and the datasheet says the supply voltage requires a regulated voltage with a min of 2.6v and max of 3.6v

I can’t find any datasheet for the nodemcu v3 (spent hours looking, but none mention anything relevant) that’s says whether or not the power output of the 3.3 pin is regulated (how can I tell?) but others have said an Arduino Uno’s 5v and 3.3v pins are regulated.  Assuming it is regulated (I know what they say about assumptions), are there any reasons why I should be concerned about using the 3.3 pin?

What about using the aforementioned Arduino Uno, whose power pins are regulated?

This sensor is kinda pricey and I don’t want to burn it out due to stupidity.


texts:
I'm working with convolutional neural networks and I have written a code to make the convolution of two 3x3 matrices. This is my code: https://www.edaplayground.com/x/6G7h
Now I want to make the convolution of two matrices: 400x400 and 3x3. That is 160,000 elements x 9 elements, I think that's a lot.

So I would like to ask you guys, what's the most optimized way to do this?

Thanks in advance.


texts: USB connection to BeagleBone Black drops

texts: I figured out that BeagleBone Black acts weird when it doesn't have power supply from 5VDC supply jack, and it is only powered from USB connection's 5V. When it is powered like that it drops USB connection constantly, I thought BBB drivers are the problem, but even after I installed them, connection hangs up every 3-5 minutes. What to check next?


texts: Do I need a 50/60Hz notch filter for battery powered devices?

texts:
Given that battery powered devices are not plugged in the mains power, can I assume that there will be no 50/60 Hz frequency noise?

This question came up while thinking about what the circuit for a portable ECG monitor would look like and it seemed obvious that the 50 Hz notch filter could be eliminated. But is it so?

Thank you