texts: Three-phase active rectifier - Confusion between rectifier and inverter mode

texts:
I understand how a 3-phase inverter works (with 6 IGBTs or Mosfets). However I'm a bit puzzled when using it as an active rectifier. For reference, here's an example of the circuit I'm talking about. https://plex.infineon.com/plexim/fullbridge_inv_3ph.html

I also know that IGBT can only conduct in one direction as they are like a bipolar transistor. That's why they add a parallel diode. Therefore, for a bidirectional inverter/rectifier using IGBTs :

Am I correct in presuming that in inverter mode, the diodes never conduct (if the load has a PF of 1)?

Am I correct in presuming that in rectifier mode, the diodes will conduct to charge the DC-link capacitor?

Edit : Added clarification that I want to clarify how current is conducted when suing IGBTs


texts: Accounting for temperature changes in circuit design

texts:
In my last post about a simple circuit:

+12V -- R1 -- LED1 -- LED2 -- LED3 -- ground

A user said:

  ...you should account for temperature changes and variation between parts. Not all parts (even of the same part number) will have the same Vf, even at the same temeprature, and your circuit design needs to be robust enough to account for that, not carefully tuned to the exact nominal behavior of a part type.

Practically speaking, using my simple circuit as an example, how does one account for temperature changes and variation between parts? Would simply using a 150Ω resistor in series with the three LEDs not work?

Edit:
The circuit will be operating in temperatures of around -10°C to +150°C


texts: Scope probe having ringing with 10x option

texts:
I did a bit of a search in the forum but despite there being a few related topics related I couldn't find the specific answer for this question.

Using a 50Mz scope I connected the probe to an FPGA output pin where there's an output of a 3.3Vp@25MHz square wave signal. I did make sure to connect the grounds as short as possible and close to that clock signal.

Using 1x and 10x scope probe options I got the following results:

1x probe:

10x probe:

Well, for the 1x I think that I'm getting attenuation given by the low pass filter of the 50MHz scope for a 25MHz signal, and that could explain as well why the signal is not square and the amplitude is lower...

But the part I don't understand is the result of the 10x option:
why is that ringing happening? And why is it so different to the 1x?

Obviously that overshooting is causing that the signal to increase the amplitude to 5.39Vp...


texts: What parts on a printed circuit board can make unintended sound?

texts: To rephrase it: Since vibrations are responsible for soundwaves, what parts are most prone to such vibrations? Root causes are probably electrical oscillations between capacitors and inductors in the kHz region - are there different causes?


texts: How to switch "best" between two voltage sources (5V & 3V3) for a single output ("MUX for VCC")?

texts:
How to switch best between two voltage sources (5V & 3V3) for a "load" (e.g. a sensor in the application field or Arduino/Raspberry Pi/etc.). The basic setup is as follows: there are two voltage sources: 5V and 3V3 and based on a MCU OUTPUT should either be supplied with the 5V supply or 3V3 supply. The MCU is a 3V3 system.
I thought of basically two ways (following). The question is, if they are correct and which one might work better (although hard to answer generally, question is for "rule of thumb"). The requirements are roughly: design as simple as possible, no fast switching required (e.g. max. once per minute or even less).
A) Using transistors

Description: Basically two PNP ("high side switches") are used to switch the 5V/3V3 to the output. In order to keep the PNP off the voltage at the base is going to be nearly at the 5V level and this would "overload" the MCU, so an intermediate NPN stage is driven by the MCU which drives the PNP. In order to protect "reverse voltage" a diode has been added (D1 and D2).
The question is, if this would work (I'm not sure regarding Q1 and Q2) and also the diodes reduce the VCC by ~ 400 mV, so OUTPUT would be 4.6V/2.9V, right? This will cause other "trouble" down the road since the OUTPUT should be proper 5V/3V3. A quick solution could be by increasing the 5V/3V3 accordingly. But the max. system voltage is 5V, therefore a boost converter is also required. Any better ideas here?
B) Using a relay

e.g. G6K-2F-Y-TR-DC3
Description: relay limiting resistor (R5) is calculated by dividing the required voltage drop (0,3V: 3V3 -> 3V of relay) by the current of the relay (33 mA). But this solution has mechanical implications (e.g. lifetime)
Edit: it seems that I left out important details:

Imax (load) V tolerance? up to 75 mA and ± 10% for both rails (5V/3V3).
Use-case: the user can plug in different sensor boards (imagine temp sensor, light sensor etc.), everything digital, the MCU knows which device by user input and based on this switches the defined VCC

Edit 2: based on the extensive answer of AnalogKid I redraw the schematic of A) just in case anyone want to see it (@AnalogKid thanks for giving so much detail):


texts: Remove audible noise generated by buck converter

texts:
I'm dealing with a buck converter using an ISP452, an inductor and a capacitor to act as a buck converter driven by a PWM signal coming from a microcontroller.
Some part of the circuit is producing a hogh-pitch audible noise when powered, which I would like to get rid of.
The circuit is driving some standard 3-pin fans.
The carrier frequency of PWM signal is 3.9 Khz.
I measured the output of the circuit and verified at the oscilloscope that it is a stable linear voltage. Thus the noise it is not likely coming from the fans but from the circuit itself! My first suspect goes to the inductor which is acting as a loudspeaker. Might this be possible?
The question is what to do in order to remove the noise?
I cannot really change the capacitor and inductor but I could try to use some "compound" that could absorbe the noise. Would this be a good choice?
The ISP452 is limiting the driver PWM signal frequency to max 4 kHz.
Any other suggestion?


texts: Suggest printer for printing photomasks for homemade PCBs

texts:
could you please suggest printer for printer photomasks at home?
Target is to have 0.1x0.1 features or better.

My tests shows that inkjet are pretty bad when working under 0.3x0.3.
So obviously, only lasers left.

Is 1200x1200 worth it? Any experience showing one models better than others? Any specific examples?


texts:
I need help in understanding the solution from solution manual. The question is from the exercise 4.22.1 of chapter 4 in the book Computer Organization and Design by Patterson and Hannessey (4th edition). The question is about branching in instruction pipeline.

  The question
    We assume that the following MIPS code is executed on a pipelined processor
  with a 5-stage pipeline, full forwarding, and a predict-taken branch predictor.
    Consider the instruction sequence:
      Label1: LW R2,0(R2)
      BEQ R2,R0,Label ; Taken once, then not taken
      OR R2,R2,R3
      SW R2,0(R5)
    Draw the pipeline execution diagram for this code, assuming
  there are no delay slots and that branches execute in the EX stage.

The solution given is as follows:

  The solution

The doubt
I dont understand why in 4th cycle LW have *** (blue underlined). Cant we execute ID of LW in 4th cycle? Is it unsaid rule that if the branch-decision-making-stage (that is red underlined EX of BEQ) gets delayed (here due to data dependency on first LW for R2), then delay all the corresponding next stages in the following instructions?


texts: Inverter feedback when converting clipped sine oscillator signal to square wave

texts:
I inherited a design that uses the following circuit to generate a 40MHz square wave clock signal:

KT2520K is a TCXO that outputs a clipped sine wave and the inverter has a peak output voltage of 3.3V. Is there any benefit to the inverter feedback configuration used here? In other designs I've seen one large-valued resistor used and without the C16 capacitor. I'm considering simplifying the design to use a single 931k resistor in place of R3, R8 and C16. Are there any drawbacks to this?


texts: How does Xilinx ISE determine compilation order?

texts:
I’m working on a VHDL project which is a small SDRAM test. I have these entities:

top
sdramwrapper
sdram <– generated IP core sdrampkg <– contains a package containing constants used several places and a couple of type's to bundle signals

ISE usually organizes the implementation files in a tree and automatically determines the required compilation order. However, in this project it refuses to include the sdram_pkg package when building and thus I have to use manual compliation order. In itself it is silly but works. When I try to simulate the project it refuses to include the sdram_pkg package at all, even if I’ve specified the compilation order.

I'd like to know both how (figure out how) to solve this problem, but also know the rules ISE uses.

Update: By marking the sdram_pkg.vhd file as "global source" it was included and I can use the automatic compliation order.


texts: Whats the difference between these three breakout boards for the ADXL345 Accelerometer?

texts:
I would like to use the ADXL345 in a schematic im working on right now, but as there is no typical/minimal circuit provided within the datasheet i got stuck.

I did a bit of research and found three different breakout boards, where two of them seem to be quite similar, the third one seems completely different:

1: http://www.watterott.com/de/Breakout-Board-ADXL345

2: http://www.sparkfun.com/products/9885

3: http://www.ebay.de/itm/ADXL345-3-Axis-Digital-Acceleration-Gravity-Tilt-Module-For-AVR-ARM-MCU-Arduino-/171532017402

I do have the third one right here and it works quite well when hooked to an arduino, but as i am looking to combine it on one custom pcb i am wondering if it would work out if i use the ADXL345 like in breakout-board one or two.

I think that the third one differs as it features an 6206A labeled ic. After some research it turns out it might be a voltage regulator, which does make sense cause its the only one board that supports 5V for supply voltage. But it surprises me that i can drive the i2c at 5V without any issues although the adxl does not seem to be 5V tolerant.

So what components would you suggest me to use in my Design (my design runs on 3.3V so no need of a regulator) and how do you think could these differences between the breakout board affect the accuracy of the accelerometer?


texts: Interaction of D-Type flip-flops with SR inputs

texts:
I've recently been testing myself on D-Type FlipFlop interactions for an upcoming test. In the picture below, I've assumed that Clock overrides reset in the resulting output, Q:

Am I correct in this assumption, or does Reset always override?


texts: Low power method to turn Raspberry Pi on or off using an Arduino

texts:
I want to use an Arduino to control power to a Raspberry Pi.

The power supply to this system is a solar panel with rechargeable cells, and the Arduino will turn the Pi off to preserve power in darkness or when the cells are running low.

So, I'd like to be able to switch the power as efficiently as possible.

What are my options? How much power might I lose with a suitable relay? I thought an optocoupler might be one way, but can I use one to switch around 500mA?


texts: What does the electric field for twin capacitors in series look like

texts:
I know what it looks like for a parallel plate capacitor, but not for two in series. I'm not currently sure if the field goes constantly from outer plate to outer plate or somehow "pauses" over the connecting wire. If anyone can describe it or even show a simulation then that'd be great.

Capacitors in series

Electric field for one parallel plate capacitor (middle picture)


texts: How are symmetrical +/- voltage supplies obtained in a final (standalone) design?

texts:
Assume, I need to use an opamp with +9 V and -9 V supplies. While prototyping, etc., I can and probably would use a DC power supply. Since it has multiple channels, it is easy to have +9 and -9 volts.

However, when it comes to finalize the project, making it a standalone box, which will get its power, let's say by batteries, how are +9 and -9 volts obtained?

I only can think of using two 9 V batteries with reverse polarities connected to a common ground. However, my insights tell me that there may be another way of doing that without using two batteries. Because I don't think in every module which consists +/- power rails, there exists two separate power supplies.


texts:
I'm trying to find the transfer function of the circuit below. I am aware there are tutorials available online for similar circuits, and I have tried them. But I cannot confirm whether my answer for this is correct. I am more looking for the answer rather than the process, but the process would also be appreciated to confirm my own.
Thank you.


texts: Erratic behaviour in FPGA based I2s loopback (Verilog + Spartan6)

texts:
I am working on a personal project involving a Xilinx Spartan6 FPGA that I program in Verilog. I am not an advanced user, it's my 3rd reasonably sized project and I don't really rub shoulder with FPGA designers, so I basically learned everything alone with books and internet. This being said, I will request for indulgence if anybody find my design inaproriate.

Alright, so I encounter a problem in my design that I find quite fascinating. Basically, after each reset, my design behave differently. Sometimes it works, sometime it does not and the rest of the time, it almost works.

The project

My goal is to make an FPGA based sound processor. I completed the PCB and most of the software and I am now starting to build the FPGA design. Here's an overview of the final goal :

My FPGA (XC6SLX9-3TQG144C) is connected with a TLV320AIC23 codec. Audio is sent over I2S to my FPGA and sent back to this same chip over the same I2S line (In contradiction with the diagram I provided, ADC and DAC are part of the same IC).

I have written the I2S module and made a simple passthrough between input and output so that Line Out signal is the same as Line In. I get good sound quality at the output when it works. When it doesn't, I get either no sound or distorted signal. When that happen, 2 or 3 reset and sounds come back nice, another reset and it start to be distorted, and so on.

The symptoms

I did a lot of behavioral simulation, everything seemed good. I then proceed to hook a Chipscope core to my design to figure out what was going on, hoping to find something obvious, but found a changing behaviour. What I can see is that some DFF doesn't latch what they are supposed to. For instance :

16 bits shift register works, but occasionnaly lose a bit
5 bits counter works, but every 2 or 3 pulse.

These two symptoms, comes and goes aways as I reset my device and can be seen at different place on the design. Here's some screenshot.

On the first picture, you can see a functionnal run with a counter that increment on each edge of BCLK. On the second picture, 1 pulse is missed out of 2.

See also :

The last images shows a shift register being flled by data at DIN input, sampled on a BCLK rising edge. If you look carrefully the yellow edges, you will see that the shift register failed to move the MSB.

More details

Now that the symptoms have been enumerated, I will try to give as much details as possible on what I did.

The whole design has 1 time domain, clocked with 100 MHZ coming from the FPGA PLL which is driven by a external 32MHz oscillator.
I detect BCLK edges by comparing actual value with previous value to keep a single time domain.
I put a timing constraint on each clock signal, Map gives no timing warning.
I normally configure the FPGA with a onboard STM32 microcontroller. I got the same behaviour with a JTAG.
Reset is synchronous, active low. Uses same pin as INIT_B signal (I have no other line available for now).
Codec is clocked at 12.288 MHz which is also generated by the FPGA PLL
The 12.288 MHz Clock doesn't have a dedicated clock line. It is fed directly to a OBUF.  Unfortunately, I made a hardware design error and will correct in a later version. I drives no DFF with it, straight to an output.

I've shared the Top module and I2S code. You will see a loopback at the top level.

Code for I2S module is here : http://pastebin.com/X9stcBP9
Code for top module is here : http://pastebin.com/fkQKhyTn

That sums up the problem I see. I believe there's a timing issue somewhere. Debugging with Chipscope is the farthest I know how to do to debug this kind of issue.

The question

What can I look at ?
What would be the next debugging step here ?
Does anybody sees something wrong that I don't ?

I can of course provide more details upon request.

Thank you


texts: Simplest way to get a rising edge (0 to 1) for a digital input from a selectable value of an analog signal?

texts:
I'm trying to trigger an interrupt on a digital pin of a Raspberry Pi (although the question is valid for any microcontroller), based on an adjustable threshold value of an input analog signal (say 0 to 5V).
In other words, I have a sensor providing a voltage from 0 to 5V, and I'd like that when this value gets higher than an adjustable threshold within the range (e.g.  above 3V), I get a
proper logical value of 1 (say 5V), and when the value goes down that threshold (e.g. under 3V), I can get a proper logical value of 0.
I'd like also to be as simple as possible (even if the threshold is fixed), as I've seen solutions involving op-amps that seem quite complicated for me. I've also discarded an external ADC because I want to drive the microcontroller on interrupts instead of polling values.
What would you consider to be the simplest way to do this? Thanks in advance.


texts:
I am interfacing IR remote which works on RC5 protocol with STM32F405VG. I have a PCB where I am using TSOP 1738 to receive RC5 packets. I have connected the CRO. Whenever I am pressing any buttons on the remote, I am receiving the full packet.

Now to interface this on the PCB . I using  timer to capture the duration between the rising/ falling edges. But it seems not to be working. I am new to the STM32 environment. Can anyone please check and confirm if the configuration set for the timers are correct or not. Here is the code:

GPIO_InitTypeDef GPIO_InitStructure;   //For GPIO pin where TSOP is connected
NVIC_InitTypeDef NVIC_InitStructure;   //Global interrupts
TIM_ICInitTypeDef TIM_ICInitStructure; //Timers

/*  Clock Configuration for TIMER */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3 , ENABLE);

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
/* Pin configuration: input floating */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;    //Pin2 of Port C
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;   //Input mode
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOC,&GPIO_InitStructure);    //Init GPIO

GPIO_PinAFConfig(GPIOC,GPIO_PinSource2,GPIO_AF_TIM3);
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);

/* Enable the TIM global Interrupt */
NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn ;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);

int PrescalerValue=0;
PrescalerValue = (uint16_t) ((SystemCoreClock / 2) / 6000000) - 1;

/* TIMER frequency input */
TIM_PrescalerConfig(TIM3, PrescalerValue, TIM_PSCReloadMode_Immediate);

/* TIM configuration */
TIM_ICInitStructure.TIM_Channel = TIM_Channel_1;
TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Falling;
TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;
TIM_ICInitStructure.TIM_ICFilter = 0x0;
 TIM_PWMIConfig(TIM3, &TIM_ICInitStructure);

/* Select the TIM3 Input Trigger: TI1FP1 */
TIM_SelectInputTrigger(TIM3, TIM_TS_TI1FP1);

/* Select the slave Mode: Reset Mode */
TIM_SelectSlaveMode(TIM3, TIM_SlaveMode_Reset);

/* Enable the Master/Slave Mode */
TIM_SelectMasterSlaveMode(TIM3, TIM_MasterSlaveMode_Enable);

/* Configures the TIM Update Request Interrupt source: counter overflow */
TIM_UpdateRequestConfig(TIM3,  TIM_UpdateSource_Regular);

/* Set the TIM auto-reload register for each IR protocol */
TIM3->ARR = RC5TimeOut;

/* Clear update flag */
TIM_ClearFlag(TIM3, TIM_FLAG_Update);

/* Enable TIM3 Update Event Interrupt Request */
TIM_ITConfig(TIM3, TIM_IT_Update, ENABLE);

/* Enable the CC2/CC1 Interrupt Request */
TIM_ITConfig(TIM3, TIM_IT_CC2, ENABLE);
TIM_ITConfig(TIM3, TIM_IT_CC1, ENABLE);

/* Enable the timer */
TIM_Cmd(TIM3, ENABLE);

And here is the code of Timer3 interrupt handler

void TIM3_IRQHandler(void)
{
  static uint32_t ICValue1;
  static uint32_t ICValue2;

 /* IC1 Interrupt*/
 if((TIM_GetFlagStatus(TIM3, TIM_FLAG_CC1) != RESET))
 {
    GPIO_SetBits(GPIOD,GPIO_Pin_10);
     TIM_ClearFlag(TIM3, TIM_FLAG_CC1);
    /* Get the Input Capture value */
   ICValue2 = TIM_GetCapture1(TIM3);

}  /* IC2 Interrupt */
 else  if((TIM_GetFlagStatus(TIM3, TIM_FLAG_CC2) != RESET))
 {
    GPIO_SetBits(GPIOD,GPIO_Pin_10);
   TIM_ClearFlag(TIM3, TIM_FLAG_CC2);
   /* Get the Input Capture value */
  ICValue1 = TIM_GetCapture2(TIM3);

 }
/* Checks whether the TIM3 flag is set or not.*/
else if ((TIM_GetFlagStatus(TIM3, TIM_FLAG_Update) != RESET))
{
  /* Clears the TIM3 pending flags*/
  TIM_ClearFlag(TIM3, TIM_FLAG_Update);

 }

}

After initializing, interrupt handler starts working but IC1 or IC2 interrupt event never occurred even though I keep pressing the remote key. Please help thanks.


texts:
i have a project which have 4 18volt DC motors, each motor rotate a screw which is 8mm and pitch 1.25mm and 200mm length vertically, load connected via nut in screw, every motor has 3.5 KG load and total load 14 KG.
in my calculation every motor torque 50 oz-in and im selected a motor kindly guide me this motor is best for this or not, and if any other motor under 10-12$

Model: RS-775WC

Operation Voltage 6-18 V

No load: 21000rpm, 2.80A,

At max Efficiency: 1850rpm, 20.9A, Torque=1560 g.cm, o/p=296W

Stall: Torque=13201 g.cm, 156A

Thank you, sorry for bad english


texts: Driving 8 Leds from 4 pins of microcontroller

texts: Is it possible to drive 8 Leds with 4 pins of microcontroller according this picture? Only one Led has to light at the time. The rest two pins will be always high Z. I tried to simulate it, there is a loop around thru high Z buses but the voltage on glowing diode is split between 3 another, so they should be safety off. I don`t want charlieplexing because the lighting diode voltage is split between two diodes only (unsafety off). Is my consideration right?


texts:
I am seeking a nano version of raspberry pi. For my application, I just need 2 two usb ports, 1 for a wifi module and the second to power the board via a 5v usb. I dont need the hdmi inputs in the pi. I want to be able to ssh into the board and run a python program.

I am considering the ATmega328P board. But I need to be abe to run queries on a mssql database and have python installed.

I may need an extra sd card module.

Any thoughts on the suitability of the nano 3.0 ATmega328P-20AU board ?


texts: Solar Li-Po battery charger with MPPT algorithm

texts:
I'm new here but I have read a lot of topics here about my question. I am designing a solar battery charger with MPPT algorithm but I don't know if I am doing it well.

First of all my specs are here:

Solar Panel:

10 W peak power
Maximum Power Current: IMP = 0.57 A
Maximum Power Voltage: VMP = 17.49 V
Short Circuit Current: ISC = 0.61 A
Open Circuit Voltage: VOC = 21.67 V

Battery:

One cell Lithium-Polymer
Nominal Voltage: 3.7 V
Capacity: 1700 mAh (max 1C)

This is my actual schematic:

The µC is working from 3.3 V.

Secondly:

I've designed a buck converter with the following values:

simulate this circuit – Schematic created using CircuitLab

The problem is controlling the MOSFET with PWM in full-closed and full-opened states. Should I use a gate driver IC or another method?

Thereafter:

When the night comes, or the PV doesn't generate enough power, I have to stop the charging and MPPT. How do I know that the sun gives enough power to start MPPT, without starting it? (I was thinking about measuring the ISC to know the possible IMPP).

Finally:

Do I have to use a charger IC to protect the battery form bad charging behavior?
What do you think about the MP2615 charger? Is it good in this case?

I hope you can help.


texts:
I am on a hunt for a depth sensor for my septic tank.
The task: to measure the current depth of a septic tank, where I would submerge the device where the sensor would send a ping to detect the distance to the bottom.
I was looking at different types of sensors, for example with infrared using ToF. The issue is the substance has different densities.
How should I approach this problem?
Would a ultrasound sensor be the direction? What kind of wave length should be so it overcomes the density of the fluid and pings back from the actual plastic and or concrete floor?
Constraints: Nothing can be attached to the lid, the device will be looking from the surface level down


texts: Lossless compression technique for digital signals in an embedded system

texts:
Here's the scenario:
I have an embedded system where an ADC logs a 16-bit potentiostat sample every 2 seconds. The system continues to record data for weeks, making memory usage a concern.
Instead of using up 16-bits of storage for each of the millions of samples, how can I losslessly compress the signal as it is logged? Ideally I'd like to break up the signal into 15 minute compressed segments. I'm sure there's a standard out there for this, but I can't find it.
If it helps, the signal will most often have very low deltas between samples (low frequency).


texts: How can I be sure I blew up my WS2812B strip?

texts:
I have a WS2812B strip which, I guess, I ruined it. I connected a 12V adaptor (by  mistake) to the strip.

I have a multimeter and when I check the +5v/GND end terminals of the strip, the meter lights up. But when I check the DIN end terminals, the meter doesn't light up. Can someone please help me understand my questions below ?

Does this mean the DIN strip blew off ?
I connected a high voltage to the +5V/GND which works fine. How did I end up blowing the DIN strip ?
Will any part of the wire still work or should I buy a new one ?

So, I cut up a part of the strip and tried checking. Only a part of the lights glow good while others are glowing low or not at all.


texts:
I want to set up an EtherCAT Network, First I have installed IgH EtherCAT Master in my PC (Ubuntu 14.04) and RTAI 4.1 as RTOS

Can I use microcontroller as a slave without any additional devices provided by Backoff or other suppliers like (FPGA, ASIC)


texts: I am trying to etch my circuit on a double sided copper clad at home. After designing my circuit I took a print on tracing paper and used iron to get the trace on copper clad. When I used iron paper got shrunk and ink spread all over and some connections didn't even go to the clad. Is there any good and easy way to get the circuit on double sided copper clad before etching. As its a double sided pcb I also faced problems matching the pins on both sides. I constantly tried to make sure that the holes on both side are aligned but failed everytime.


texts: Why am I getting an odd pattern from my image sensor?

texts:
I am using an Omnivision OV7251 image sensor with 640x480 greyscale pixels. Currently, it's not properly attached to its lens, so I'm seeing mostly grey. This is the image I'm getting back from it:

Not hugely surprising on first glance, but when we look closer, we can see that the top 50 rows look fine, a little noisy. Here is a zoomed in portion of the image from near the top. I've brightened it up so you can see the details.

But further down the image, a pattern begins to emerge (again I have brightened it to bring out the details):

The bottom right pixel from every 2x2 group is a little darker.
What is going on here? What can be causing this pattern? My only thought is that it might be an electrical issue. Perhaps there isn't enough capacitance for the analog power pin on the sensor, and as it samples the pixels, it's starting to suffer some voltage droop. And perhaps the pattern comes from the way the pixels are sampled according to the Bayer pattern.
Has anyone experienced this before, and knows what to do to solve it?

Update:
I have tried increasing the capacitance on the analog input pin, and it made no difference to the pattern.


texts: how to measure the current from AC-DC supplier?

texts:
I started to learn the AC/DC circuit some times ago. I don't have much experience. But from this semester on, I have some chances to practice it in lab by working on some project. I got a AC/DC power supplier with 12VDC/1.5A output. I want to verify the current is really 1.5A with a meter by connecting a big resistor in series with the meter and the cable, but it gives 3A output instead of 1.5A. I don't understand what cause that, is any wrong I did to measure the output current?

By the way, I check the DC voltage output with the meter too and it gives 12V. I wonder what will show if I use VAC function to measure the DC output? Should I get zero? But very strange it reads 3 to 5V instead.


texts: Why doesn't a commutator cause the rotation to reverse periodically or stop?

texts:
I understand the field magnets attracting/repelling the armature/coil so that it turns one half-turn and then, because the commutator is turned, its contact with the brushes has switched sides, and the current goes in the opposite direction, reversing the electromagnetic polarity. Then, because the polarity is swapped, it attracts/repels to complete the second half-turn. The thing is, isn't it a bit of a gamble that it will turn in the same direction? Couldn't the it just be pulled/pushed back, more or less undoing the half-turn?

I'm also a bit confused how the rotation doesn't just stop once the commutator is oriented so that the brushes are contacting both sides of the commutator. In other words, there's a brief period just as the commutator switches the current directions where each both the brushes are in contact with both sides of the commutator where the current is neutralized. Shouldn't this stop the motor?

For reference, I'm just talking about a simple DC motor.


texts:
How can I use one power cable to connect to 4 relays in parallel?

So for example, I have one power cable and I want to turn on 3 radiators out for 4.

This is my screenshot of the circuit.

Terminal 4 and 3 for each would be connected AC and 2 and 1 would be the radiator.


texts: Problem with Ethernet controller ENC424J600

texts:
I have recently produced a number of prototypes using the Microchip ENC424J600 Ethernet IC.

I can't a full circuit diagram as this is a commercial product but I have reproduced the relevant part of the circuit below.  What I am seeing is that as soon as I apply power the green LED lights, indicating a good link, even without an Ethernet cable plugged in.

If I am to believe the data sheet this LED should not require me to have good communications with the micro that is driving it and this LED should work provided it is powered, the oscillator is running and the Ethernet cable is plugged in and connected to a suitable device such as a hub.

Does anyone have experience with this IC and can suggest what I may be doing wrong.

If I have understood the data sheet correctly this is a typical application circuit

As as been pointed out in comments the data sheet does not show the TPIN transformer with the centre tap pulled up to 3V3.  My original circuit does not have this connection. I added this because it is shown on the circuit diagram of Microchips demo board for this IC. The LED performs in the same way in either case.

I have also scoped the OSC1 pin to confirm it has a clean signal.


texts:
What is the significance of the highly doped n region near drain and source end in mosfet?
What would happen if it was not present there?


texts: I am not able to solve this question , I initially thought that in order to find the current of this series circuit it would be Vtotal / RTotal , however I am not getting the correct answer with this method. There must be another factor I'm not aware of when it comes to dealing with 2 voltage sources. Can anyone shed any light on why I'm not getting the correct answer ?


texts: Apply Thevenin Theorem to a circuit with 2 sources?

texts:
simulate this circuit – Schematic created using CircuitLab

I have this circuit:

Sorry the current source got cut off when loading. It is 3 Amps. I was trying to apply thevenin's theorem to this circuit but I am confused on how to. Usually to apply Thevenin's you have a Vtest and two nodes that are open.

Can someone help me solve this?


texts: Sampling AC Line voltage from isolated DC domain

texts:
I have an application where I want a microcontroller to be able to sample the AC line voltage (scaled down through a voltage divider). The AC power comes into the system, and then an off-the-shelf board-mounted isolating converter is used to generate my DC system voltage. I'm questioning my proposed implementation because it seems that if the DC domain is isolated, it could theoretically be at any potential above or below (within reason) any of the three AC lines.

simulate this circuit – Schematic created using CircuitLab

My analysis says that yes, I do need to connect AC ground and/or neutral to my DC ground. In my actual design I have added clamping diodes near R1 and R2, but I left them out here for simplicity.

Am I correct in that I need to connect the AC Ground or Neutral to the DC ground?


texts: Exceeding maximum current on VRM if well cooled?

texts: VRM spec sheets usually mention the maximum current, but don't seem to say anything about cooling, other then maximum temperature. Do they expect it to be cooled sufficiently, or will they not meet the maximum operating temperature under maximal load? If, for example, I had an LM2596 step down converter, could I use more then the specified 3A maximum by putting a heatsink and fan on the IC?


texts: power on power off pulses to two seperate controllers

texts:
I would like to request a circuit where a 500 ms pulse is sent to one rail when 12 volt power is supplied and another 500 ms pulse is sent to a different rail when power is turned off.  555 is the way to go but struggling with sending pulses to two different controllers.

So for power on pulse, I guess I do not need a 555.  Here is what I have for this:

Also, i intend to use a transistor at output so the memory recall will have a short during the pulse, just like button press. Should give me a half second pulse.

Searching for power-off pulse now.  I guess a cap that holds some charge, enough to generate a pulse after power is cut down.


texts:
It may sound like the "easy way" to ask it here, but this question (along with a couple others I've posted which were more specific) is the result of years of research on the topic - on and off as it's my least used (and weakest) area of expertise, but still, to say that I have seen many videos PDF and posts. Most of them are too specific in their examples, or it's all too vague.

Context

I have tuned a couple of PI controllers until now using on line manual methods, but now that I'm struggling with a PID one it is clear that I need to dive back in proper analysis. After all, if I need to design another type of compensator (say phase lead or whatever, even a multivariable controller), there will be no "magic method" to save the day.

Question

I would like to know what the different methods are to tune a controller assuming the transfer function of the plant is known, and in details how they deal with the following requirements:

Settling time
Phase and gain margins
Overshoot (if not dependent on phase margin)
Steady state error
Max controller effort
Ideally, max ripple due to disturbances but this one is particularly difficult it seems

Research

The tools I've seen around are:

Root locus. I understand the effect of each root depending on its location (complex exponentials being oscillatory etc.), but I don't get how zeros and poles interact to generate the response. The fact that people ignore zeros for stability confuses me even more.
Nyquist. The stability criterions are very obscure in their relationship with the real world, and I haven't seen it being used for anything else.
Bode. Quite familiar with it due to electronics, although the concept of phase margin is still a bit vague compared to the gain margin (can't "feel" it).
Step response. The easiest to understand, although not sufficient.

I really like this Youtube channel, but it is still a bit vague after watching all the videos. And I never saw all the coefficients of a PID be tuned analytically - I really hoped this thread had the answer but it didn't.

Application example

I propose to design step by step a PID controller (all 3 coeffs) for a very simple plant, say:
$$G(s)=\frac{1}{1+\tau_1 s}\frac{1}{1+\tau_2 s}$$
Where $$\tau_1=650s$$
$$\tau_2=4500s$$
So that settling time < 5h, margins > 14dB and > 30°, s-s error (and ripple if studied) < 0.01%, controller effort < 1.
This is a system which is inspired by what I need to control (very simplified), I have taken the numerical values from there.

As far as I know, this would be the first time one gets through an entire PID design online, which is highly beneficial to anyone with the same doubts as me. The question probably can be answered without this step by step, but it would be much much clearer with the example.


texts: How does this current limiter work? - and why doesn't it?

texts:
I have a generic Ebay DC-DC buck converter, and the current limiting circuit is not working. I find that such devices often suffer from this issue, so I figured I'd reverse-engineer it in hopes of figuring out the problem.

Below is the schematic I came up with by following traces on the board; and by measuring continuity. I believe it to be accurate.

Unfortunately, the current-limiting (upper) part of the schematic makes no sense to me. Could someone explain what is going on, please?

I see no reason to use a TS431 in full saturation; neither is it clear why the op-amp ground reference isn't connected to ground.

I assume the current-limiter achieves its objective via pin 2 of the XL4015. Perhaps the LED, in addition to indicating, serves to prevent lower voltages from the op-amp reaching the XL4015?

In addition, could anyone offer a possible explanation for the failure of the unit to operate correctly? Where should I begin troubleshooting?

Photos of the board:

EDIT: Fixed schematic and added the 0.05Ω resistor


texts:
The L and C have the same impedance at 14.529kHz. The series LC is at resonant frequency and should act as a short. Therefore R2 should have the same current as R1. However it is nowhere close. When I build this same circuit in Eagle I get the correct results. Why am I not getting the correct results in LTspice?
Note: V1, C2 and L5 are ideal (no internal resistance).
EDIT! L5 was NOT IDEAL (Rpar=65k), when ideal AND timestep=1n, this circuit works as expected.

The LTspice file:
https://www.dropbox.com/s/anci5907ybx8c4v/Tank_serial_v01_v05.asc?dl=0


texts: Why does the LM1117 data sheet specifically specify tantalum capacitors?

texts:
I'm planning on using an LM1117 to regulate 5 V to 3.3 V. Looking at (any of the several) data sheets for the LM1117, they recommend 10 µF tantalum capacitors between input and ground and between output and ground.

I understand the need for the capacitors, but it's not clear to me why these should specifically be tantalum. I have a bunch of electrolytic 10 µF capacitors sitting around here, whereas if it does for some reason need to be tantalum, I'll have to order those.

Why are they so specific about using tantalum capacitors?


texts:
I have worked on a project using high precision clocks for some time now. I have yet to find a clear description on how manufacturers and scientist confirm and verify the precision of clocks like OCXOs.

My approach have been to use time and test two clocks relatively to each other. As time goes, the error between each clock will sum and create a bigger uncertainty.

But how is this done with cutting edge Atomic clocks within NIST standards ?


texts: How does a smart phone measure the battery power?

texts:
A smartphone (assume Android) usually displays the battery percentage from 0 to 100%. I am assuming this is the usable power capacity of the battery. I have several questions:

1) How exactly does it measure the remaining power? Assuming a battery is rated to be 3.2V, it might be providing 3.3 V when fully charged and the minimum required voltage of the phone might be 3V. Does the 0-100% refer to 3V to 3.3V? Is this calibration made only once during the time of manufacture?

2) How is the remaining power % measured so accurately? Are the measurements averaged over a period? If so, what is the sampling frequency and how many reading are averaged to get the final?

3) How is the remaining power % measured when the phone is charging? I guess the output voltage might be different when it is charging.

4) How is calibration of battery power affected by ambient temperature? I am aware that batteries nowadays have temperature sensors. Is the temperature used to calculate the battery power remaining or the optimum charging rate?

5) Assuming battery consumption is not linear as the battery discharge... (intensive games, etc). How does the smartphone handle variable discharge rates? There are apps to re-calibrate batteries. How do they work?

6) How does the OS determine battery usage of each app? Is it just based on CPU cycles and screen time or is there some actual measurement of power dissipation?

My apologies if these are too many questions. I but I believe they are all related.


texts: Can anyone identify this type of communication protocol?

texts:
First off I'd like to say that once I figure out what kind of communication I am dealing with here, I'd like to change the title of this question to something more appropriate (or if someone else understands what I am asking). Anyway, let me get through the details and then to the question...

I am currently talking to a device over RS-232. For a lot of instrumentation you would typically send SCPI commands, say if you have a meter you'd send something like MEAS:VOLT:DC which would measure the DC voltage. Then you might send a command like FETC? to actually retrieve whatever was measured.

In my situation it's quite different, I'd send it an address such as 0x892A4F2C (except in the form of a string) followed by an end-of-line character. The response would then be whatever data is at that address. Although these are not SCPI commands, the functionality is fairly similar. I've heard that this is sometimes done because it's more efficient for an embedded device to think about things in hexadecimal (as opposed to ASCII).

Does anyone know what this protocol/command-set is called? Is there any industry standard associated with this?


texts: How to check voltage and wattage of an unmarked incandescent bulb?

texts:
I've salvaged 160 incandescent bulbs from fairy lights. They were connected in 80 bulbs in series then connected in parallel. They were plugged into 220V.
How do I measure the voltage and wattage of an individual bulb? I have a multimeter and ammeter available if that helps.


texts:
As a beginner in electronics, I would appreciate very much to get some input from you folks for my project, so I can decide in what direction to point my nose :)

What would I like to do?

I would like to superimpose a 1PPS signal coming from a GPS disciplined oscillator over the ADC, Q signal of an RTL2832U software defined radio chip.

This way I can very accurately timestamp received signals, for use in a TDOA application.

Of course, this 1pps signal, would "corrupt" my sampled radio waves, and hence I would like to keep this signal as short as possible.

Because most receiver dongles on the market (like: http://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/ ) all have very small surface mounted designs, a modification must also remain "practical" to do.

Fortunately, most receivers have breakout pins for the Q- and Q+ inputs of the RTL2832U IC.

I was hoping to come up with a modification that uses a RFSwitch IC to short these Q- and Q+ pins using a 50ohms resistor, and hopefully that creates a periodic recognizable pattern on these 8-bit Q samples.

Assuming that this works ( please, let me know what you think ) I would really like to hear what kind of methods and/or components, you would advice me to use to come up with a circuit that could limit the 1pps signal ( which length differs on the many different GPSDO devices ) to 10us.

I hope it can be done using a combination of passive components and 1 or 2 transistors. Having said that, there is also a 28.8mhz clock signal available.

Looking forward to hear your input.

-- René


texts: connector for male usb A plug not on PCB

texts:
I have a PCB that needs 5V input and I want to plug my contraption(PCB + battery in a housing) into a USB power receptacle. The housing has a male USB A plug popping out perpendicular to the PCB and I am trying to look for a connector to connect the male USB A connections to my PCB. I am not entirely sure what such a connector is called. Do you have any suggestions on how to get power to my PCB from the USB?
EDIT: This  illustrates it better I guess


texts: Obtaining Bode plots by using Laplace transform and time domain data from SPICE

texts:
An active filter is given as(for this question the filter can be any other filter):

In LTspice in time domain, I apply a step function V(in) and obtain V(out) plots as below(I skip initial op. point solution):

I know that in AC analysis one can plot the transfer function for the gain and the phase much easier.

But my question is different. I want to export the points for V(in) and V(out). And then I want to obtain the transfer function myself with these data.

Since X(s)*H(s)=Y(s) where H(s) being the transfer function, X(s) is the Laplace transform of input and Y(s) is the Laplace transform of output. So I plan to do the following:

L{V(in)}*H(s) = L{V(out)}

And then I plan to find H(s) by using MATLAB or any other tool. One of the reason trying to do is to check if my results for H(s) will be similar to the one in LTspice. I also plan to use this method for a real life situation.

My question is:

If my way of doing is makes sense, to obtain the Laplace transforms of V(in) and V(out) which interval should I use? As you see the plots start from 0sec to 1sec. And the step ipout starts at 0.1sec. Can I just take the Laplace transform's of Vin and Vout for the entire 1 seconds and do the math? Is there any restriction here?


texts: Scheduling the transmision of CAN frames in an RTOS

texts:
I'm planning to use my STM32 board to send CAN frames. I implemented a simple scheduler that contains 10 tasks; one task will be responsible for sending frames. To do the job I declared a structure for the CAN frame:

typedef struct
{
    unsigned int id;
    unsigned char data[];
    unsigned char dlc;
    unsigned int timeOfSend  //This is the time in ms in which a frame should be sent
} tFrame;

And then I declared a table of the frames to be sent:

aubFrames[MAX_FRAMES] = {
    {0x12, 0xAABBCC, 4, 100},
    {0x12, 0xAABBCC, 4, 1000},
    {0x12, 0xAABBCC, 4, 2000},
    {0x12, 0xAABBCC, 4, 2010}
};

This tells the board to send the first frame after 100 ms, the second after 1000 ms, etc.

What I actually do:

I added a new task in the scheduler with a period of 10 ms. This task will check the aubFrames table, and if it's time to send a frame, it sends the concerned frame. Else nothing is to be done. The probem with this solution is that there is a big loss of time. For example, to send the first frame, the scheduler accesses this task nine times, but with nothing to do.

Is there another solution so that the scheduling will be more effective?

I thought to use a timer interrupt, but I don't think that's the good solution since there are only four timers on the board and the number of frames is more than four, so in my opinion configuring the timers to generate interrupts for different periods of time won't work.


texts: Help Me to Identify Relay Pins of this Circuit Diagram

texts:
This is the circuit diagram that have a Relay Which I need to identify terminals.

By searching on Internet I guess this is how it connected.

My question is, The Way I found match the circuit Diagram?

Regards


texts: What order of magnitude should I expect the parasitic capacitance to be for a solderless breadboard?

texts: I'm trying to account for some error in measurements for a circuit I have produced physically and simulated in spice. The only suspect seems to be the solderless breadboard as the error seems to increase with frequency.


texts: How to build an FM transmitter and how does it work?

texts:
I have become interested in radio transmission and would like to know how to build an FM radio transmitter. When I search for information I either get a block diagram or a video of someone putting it together with no explanation. I have basic electronics knowledge but I don't understand whats going on, for example, here:

How am I supposed to learn this stuff? Can someone give an explanation or a link to where I can learn?

Thanks


texts: transient protection for 0.5W laser diode switching driver

texts:
I'm some way into a project which involves switching 0.5W laser diodes at 100kHz, with a pulse of around 1us in width. I'm having issues with the diodes (which I don't have a datasheet for) failing after about a billion switching cycles.

Although I see a pretty well behaved waveform with my 60MHz scope, I'm thinking that the issue might be transients, possibly too fast to be seen on it.

The circuit I use is as follows (a bit simplified):

simulate this circuit – Schematic created using CircuitLab

To switch the diode on, the FET is switched off, obviously. The 10R resistor keeps about 2V across the laser in the off state - that may be superfluous, haven't tried without it. The voltage across the laser in the on state is about 5.5V.The current source is an LM317 with a 6R2 resistor.

Now I am remiss that there is no transient protection, but I am wondering how to do it. A diode to protect against negative voltage is a no-brainer. But what about a clamping diode against overvoltage? Zeners are not fast enough I think. But what about a something like this?

simulate this circuit

D3 and D4 would be Schottky I suppose. The idea is that the clamping voltage is always present, so the speed of clamping is only dependent on the diode, which should be very fast. It's a little bit wasteful of power and parts, but that is not really an issue here.

The leads from the driver PCB to the diode are a bit long (about 15cm), that might also be improved on a driver PCB redesign.

Thoughts? if anyone has direct experience of these circuits and real-world experience to offer, that would be much appreciated.


texts:
I'm not sure how the addition of the intrinsic region affects the built in potential of the diode. I also can't seem to find any information about it online. Thanks for the help.

How does the built in potential of a pin diode compare to a pn diode?


texts: Mosfet thermal problems in linear applications

texts: Modern power FET's can be unreliable in some linear applications due to thermal instability causing die hotspots and premature failure. This is called the Spirito effect. How do Silicon Carbide devices compare ?


texts: modify 30W LED driver for variable current output

texts:
I have a typical flyback converter for an LED chip rated at 30W output.

My goal is to change the brightness of the LEDs using a microcontroller.

If I am not mistaken (please correct me if I am wrong):

The white SMD part on the right side on the picture is also a resistor.
I have measured the resistance to GND and measured 0.4 Ohm in total (13 Ohm || to the white resistor).  The measurement was taken using a battery and another transistor.  The current was 83mA and the voltage drop 32mV.  The 13 Ohm -- through hole -- resistor is behind the capacitor in the image.  Is the 13 Ohm resistor really for fine tuning the resistance?
There is no voltage sense like in the FL7732 circuit.  The transformer loop is only used to power the chip.  (Why is the RS1M diode so big?  It should only power the IC.)
Using PWM on the output will not work, as the driver will try to output ~1A.  The LEDs would get a much higher current when the PWM turns them on, and the current would on average be the same.

Assuming that the switching frequency is high enough I could simply PWM the signal to the FET.

If this is not possible my idea would be to replace the sense resistor with an analog switch, but this other question was unsuccessful in this regard.

Is there an easy way to achieve what I want?  How is this usually implemented?

Here is my reverse engineered circuit (the capacitor with the question mark in || to the 13 Ohm resistor is probably also a resistor):

Here is a very similar circuit from an FL7732 application note, which is probably much easier to read:

Here is a picture of the LED driver:

EDIT:  I would like to point out, that the IC used in the driver is not an FL7732.  The FL7732 circuit is simply very similar.  (Not that I think that the used IC behaves differently.)

Apparently changing the current isn't as simple as I thought.  I guess it's easier to switch between different drivers with different output ratings than to modify an existing driver.


texts: Worthwhile to create some 'building block' PCB instead of handsoldering?

texts:
I am still busy with my DMX splitter. The circuit is (at least for me as beginner) quite exhausting to hand-solder. See circuit below (sorry for my 'artwork' as some used to call it, it benefits me a lot to locate exactly the positions to wire).

I spend several hours to one DMX output PCB. As you can see 4 of them are quite similar.

I was wonder, how worthwhile it can be to make some 'default' building block DMX and/or MIDI circuits and order them.

Let's assume I want to put both a DMX in and DMX out on one PCB, but I want to hand wire the connections between them, to be able to use them

as DMX input only (and not using the DMX output part)
as DMX output only (and not using the DMX input part)
as DMX input and output (possibly by handwiring or use some jumpers to be able to connect the input and output

The PCB I need to order would be a combination of what is shown in the left/right PCBs marked with BOTTOM (which is a DMX input (left) and DMX output (right).

The reason is that ordered PCB normally have to be ordered by 10 so I benefit from equal designs.

The same later for when I'm going to incorporate MIDI (like making a MIDI in + out + thru on one PCB, but being able to use them in any combination.

Would this be useful (with the use of jumpers) or is it better to make the PCB's minimalistic?

(btw, for now I'm continuing handwiring, because I want to have this project finished, getting some more experience with soldering, and also because I never ordered a premade PCB, no knowledge about Kicad or other application that can generate Gerber or alike files needed to order a PCB).


texts: Some LDO's specify noise in nV/Hz, others specify it in μV(rms). How do they equate?

texts:
The "low noise" LDO TI TPS7A20 specifies output noise as 7μV(rms) at 100kHz, whereas the Diodes AP2210 specifies output noise as 260nV/√Hz.
This SE answer compares the two mathematically as:

(nV/√Hz) ⋅ √(bandwidth) = μVrms

If I plug the numbers in then I get each LDO uV(rms)  and nV/√Hz as:

TPS7A20: 7μV(rms) at 100kHz == 0.022 nV/√Hz
AP2210: 82,215 uV(rms) at 100kHz == 260 nV/√Hz

The nV/√Hz and the uV(rms) values are widely different between the two considering both are boasting "low noise".

Did I not understand something, or is the TI component really that much better than the Diodes component?
Did the referenced answer waive over the uV to nV conversion in their math, thus being off by a 1000 from uV to nV, such that the AP2210 is really 82.2uV(rms)—which is still dismal compared to the TI?


texts:
I would like to meaure g-force (100 - 4000 g) within a centrifuge (I know it sounds silly because it can be calculated but it is more of a learning thing). I thought of a 3d printed enclosure housing the necessary components (battery, microcontroller, cables, sensor) and some sort of epoxy resin as filler to avoid any parts moving around.
Is it feasible to use standard consumer electronics for this purpose ?
Do I have to e.g. cover the microcontroller in epoxy to avoid solder joints braking apart ? I found this resource http://www.dtic.mil/dtic/tr/fulltext/u2/a402987.pdf describing consumer electronics surviving much harder accelerations (10k - 20k g).


texts: How to read data from a 3.5mm headphone jack?

texts:
I was searching for a way to read data from a 3.5mm hack using an Arduino, but I couldn't find a well-detailed, beginner-friendly, tutorial on how to make this, at least how to wire everything and create a simple I/O code. Anyone know a good, beginner-friendly, tutorial about this topic?

PS: I don't want to use a modem like this, I to learn and make it not communicate only with iOS/Android devices.


texts: Linear voltage regulator for LiPo and 3.3V@200ma ESP8266 - most juice

texts:
I am looking for a linear regulator that would follow these rules:

input voltage from 3.3 - 4.2. (18650 battery or x3 AAA batteries)
output voltage 3.3V @ 200 mA max. (for ESP8266).
small footprint - ideally would not require extra components except capacitors

Main concern is that in most cases Vout = Vin + 1V which would not work at all.
(What is the name of this characteristic, what should I be looking for ?)
I'm looking for a linear regulator that would allow to get as much juice from battery, idealy Vout=~Vin or some small value that is would not increase price.
P.S. I'm aware of switching / DC-DC / buck regulators, but schematic would contain as few components as possible and would not require all the benefits from them.
P.P.S regarding load and discharge rate. According to picture below, discharge rate would be something like 0.15C, so 80% of battery could be used before dropping voltage to 3.6 Volts.


texts: Voltage of Voltage Regulator changes when a Potential Divider is added

texts:
A Keithley 2400 Source meter is used to provide +7V. Using Fluke 179 Multimeter, the potential across the source meter leads is 7.00V.

The source meter is then connected to a LM317T voltage regular as shown. According to the datasheet, Using R1=150ohm and R2=240ohm should get me a voltage of 2.03V. Why does the voltage regulator output measure 2.308V?

Next I connected the voltage regulator output to a potential divider as shown below. When I measured the regulator output again, it now reads 3.034V!

Why did the voltage regulator output change from 2.308V to 3.034V?

The intention of using the voltage regulator is to create a 2V rail so it can be divided at the 1V point using 2 identical resistors. Something like the following below. (its most likely incorrect, but i'm not sure of another way to represent what I need)

The +2V will go into AREF pin of arduino, and the 1V will be used to bias a signal that swings between -1V and +1V. Any suggestion what would be a better circuit?


texts: KiCad Footprints : What does the P stand for in footprint naming?

texts:
Newbie with KiCad. What does the P stand for in Diodes_THT:D_A-405_P2.54mm_Vertical_KathodeUp?

I am assuming it to be PAD Length, but need to be sure.


texts:
I want to implement typical guitar preamp scheme, like following:

I see, that it will have input impendance =2.2M1.1M and Gain = 1 + R4/R3 = 3.136. So its easy to find R4, knowing R3, and vice versa. But selecting both actual values R3 and R4 is the impossible task.

What is the difference between R4=4.7k; R3=2.2k and R4=47k; R3=22k? AFAIK, no one does ever questioned this topic in details, so I think this is a good question.

How to properly select order of magnitude for those two resistors in feedback circuit?

Upd. I know basic theory how OA works.

OA is a comparator, sticking its output to V+ or V-, dependent on "if In+ greater than In- or less", accordingly.
These two R3+R4 makes a voltage divider between output and a ground, for negative input terminal. And output is is working on R3+R4 circuit, establishing some level at negative.
First plus second facts leads to behaviour, that OP amp is trying to euqalize voltage at its inputs: to make" negative terminal's voltage equal to  positive's.
And divider's ratio determines gain (how much more voltage should OA pop out of its output to equalize negative input to positive)
Inputs does not virtually draw any current to OA, any output current goes from power rails.

What i dont understand is reasoning while choosing magnitude of R3+R4 sum. According to ohms law, total divider resistance will determine value of unwanted current(and power draw) that goes to ground. To save battery I better put there higher resistors, like 2M2 and 4M7, is that correct? Or maybe should I set this current exactly to 3.1415 mA? Or 2.71828mA? I know that humbacker coil DC resistance is 2-3 kOhms, and line level input voltage (what i want to get at output) at next stage ranges from 0.3v for consumer to 2v for profesional hardware. But nowhere current is mentioned: at next stage (the mixer) current is also not coming into op amp.


texts:
Do I need a resistor if \$\frac{V}{I}=0\$?

I am working on a simple circuit of an LED and a buzzer in series where the voltage drop would be 2 and 3 volts, so \$R=\frac{V}{I}=\frac{(5 - (3 + 2))}{I}\$, in that case do I need a resistance?

Would a current flow in the previous case? Isn't current flow due to the voltage difference of maybe 5V and 0V on a 5V battery? So when I drop the voltage of 5V, why would current even flow?

Also in the following picture:

In this picture, that 98.90A is where current tends to infinity as resistance is too low, but in the first one, how did it calculate that 49.22mA ?

\$R = \frac{(5-2)}{49mA} = 61 ohms\$, how did Circuit Wizard add 61 ohms, isn't that way too high for wire resistance?


texts: When I rework an SMD capacitor or resistor, it will sometimes stick to the soldering tip. Does this high temp then destroy it?

texts: When I rework 0402 capacitors, then often stick to the tip of the soldering iron. My iron is set at 350. I then discard the cap because I am worried the sustained temp for a few seconds has destroyed the cap. But has the cap actually been destroyed, or possibly damaged? I see the temp rating is much lower than 350.


texts: Electric noise filtering seems not to have any effect over voltage input noise

texts:
I have designed two PCBs with slave SPI nodes at both. One of the two PCBs is connected to a Raspberry SPI port, it became the master node. This PCB also has a 74HC51 (suggested for i2c and spi lines multiplexing) multiplexer for multiplexing CS signal.
The second PCB will  be connected to this first PCB through flat cable. I know working with wired SPI adds a complexity and limitations, such as SCLK frequency that should be lower.
But now I will talk about power lines on first PCB design and noise filtering, abput something that I can't understand.
At this point of hardware testing, there is no master node connected. No clock signal, no control signal, no data signal at bus lines. There is no other PCB connected.
The fact is that I have connected the 5V power supply to the first PCB. As any other industrial shed there are at least two devices such as "water dispenser machine" and a "drill machine" connected to the same electric net. And when water machine starts to cool water or the drill machine starts to run, an electric noise about 14Mhz appears at Vin. The noise always has the same pattern and frequency. And it only appears when two of this machines are activated.
Part of the circuit works with 5V, the other part works with 3.3V. I use the regulator MCP1825ST-3302E/DB with the capacitors that manufacturer suggests to use with (4.7uF in, 1uF out). I put the osciloscope probe at regulator Vout (3.3V) pin and the noise is also there. So, I thought that noise was coming from the outside of my PCB, from the electric net.

I also put the probe at SPI connectors lines, and there also are until 1.3 Vpp noise signal, with the same pattern, and 15Mhz freq but amplitude seems smaller than signal noise at Vin. I think this SPI lines noise could increase when bus communications go on and Raspberry starts operations if those machines are activated for a while or whenever someone wants, even other part of the circuit could be affected by the noise. We saw it at other circuit parts. As the 4.7uF needs a Resistor close to 0 Ohms for being RC pass low filter, I thought that this capacitor works iqual as a low pass filter that obviously is not working for 14Mhz signals. Maybe it was not enough and a 2n order filter could help more than RC or RL one does.
So, here, at lab I connected resistor and inductor to the soldered Cin = 4.7uF of regulator and I configured a Butterworth filter for a f = 15000Hz. I also removed the LED resistor before. I used a filter calculator web page and the values were:

R = 3 Ohms
C= 5uF
L = 0.022mH = 22uH

I choose circuit form 1: RLC calculator and configurator web page
So, even if the filter is not well adjusted and cutoff frequency is bigger, 15Mhz is so far from 15, 20 or 50Khz, and some kind of noise attenuation must be seen. But we don't see absolutely any change. It is the same when the filter was not there.
A little sample of noise pattern (14Mhz were measured):

My questions:

What can it mean that a filter does not affect to the noise signal that seems to come from the electric network? Even if it is not well adjusted to the desired cutoff freq of 15 Khz, until 14Mhz there is a stretch of margin to at least tickle it, I think. But it seems not to be any filter connected (any kind of attenuation), although filter is there.

Maybe does it means that noise is not entering through the Vin connector, but, leaving the PCB towards the source? If this could be possible, how can the noise be activated inside the board by any external trigger event (a several meters away machine)? Am I filtering wrong or am I looking at the wrong site?


texts:
Tl;dr tested pot and it doesn't show any variation across center pin. Is it reasonable to conclude it is the broken part?

Hey everybody,
so recently a coworker and I were reassembling an expensive piece of lab equipment that involves a pot for speed control of a stepper motor. Everything was working pretty well, but while replacing the button that sits over the pot, someone decided that brute force was the way to attach it and hit the button. The stepper no longer turns. Looking at the board nothing appears different, but I grabbed a multimeter and stuck it on the pot where the center pin showed no variation no matter how it was turned. Is it reasonable to conclude that just the pot broke? What else would a more experienced trouble shooter check before ordering a replacement that costs $80-$120?


texts: Can I run a stepper motor rated 12V with a 24V or above power supply?

texts:
We are using this stepper motor (https://www.sparkfun.com/products/9238) in our project. In its datasheet, the motor rated voltage is mentioned as 12V.
How is motor rated voltage different from max Voltage?
How can we determine the max voltage of this motor since it is not specified?
Can we use a supply of 24V instead of 12V and make sure that the current remains the same in order to increase the speed of the motor?


texts: How to find phase shift(angle) between two signals in simulink?

texts: So I'm doing a delta wye transformer in simulink and phase shift between these two signals should be 30 degrees, but how to show that, or calculate it? And how to find angle of each signal?


texts: Can I use the same "don't care" condition as high and low while finding SOP or POS on the same K-map?

texts:
The definition says that we can use a don't care as either 1 or 0. It seems that if we consider a don't care as 1, we can't consider it as 0 while computing product of sum from the same k-map. Is it true?
Any explanation on this stating the actual significance of don't care would be highly appreciated.


texts:
I'm looking at a very simple method for overvoltage protection of a load connected to a standard external switching power supply.
The load is powered by a 12V power supply, but this could be mistaken and exchanged with a higher voltage power supply instead, i.e. a 15V power supply.
I was planning to simply connect a diode in parallel with the load. Is this a bad idea? My point is that the diode should have an activation voltage bigger than 12V (we can say 13V for safety reasons) and, since the power supply itself has overcurrent protection, it will automatically shut down once the diode is ON.
Here it comes the circuit:

simulate this circuit – Schematic created using CircuitLab

How should the diode be rated? The load is a 150W resistive/inductive type.
Should I use a zener diode instead? What are the differences between the two types of diodes?


texts: How to implement an interconnection matrix in VHDL?

texts: I was reading through the documentation of the AXI standard when I came across the interconnection matrix shown below. In short, the interconnection matrix provides a path for several masters to connect to several slaves at the same time. If there was only 1 master, then the interconnection matrix is basically a demultiplexer. However, with many masters, it is much more powerful. I was wondering how we can design such a thing in VHDL.


texts:
I have a strange problem with the MOSFET Push-Pull configuration of an output stage of a simple buck converter.

On the falling edge of the Low-Side MOSFET I get an effect like ringing, but it is actually following the rising edge of the other MOSFET. What can it be? Can it be caused by stray inductance and the current of the High-Side MOSFET induces some into the gate of the Low-Side MOSFET?

I will include three pictures. One with the circuit, one with the PCB (Some explanations under the picture) and the last one with the problem.

Schematic:

PCB:

The green trace is carrying the Low-Side MOSFET signal and it goes right under the pin where the High-Side MOSFET signal is outputed from the IR2011 (MOSFET driver). Could this be the problem?

Oscillogram of the MOSFET driving signals (blue - Low-Side, yellow - High-Side):


texts: Aluminum sheet as an underlay for electonic equipment

texts:
I am planning to build a NAS into a (sufficiently ventilated) closet. For flame protection and heat spreading, I mean to put a 2x700x550mm aluminum sheet under the equipment. Is this a good idea?

Specifically:

Should I ground the plate?

If I ground the plate using the earthing conductor of the same power outlet I use for the NAS, will this influence the signal quality of the Power LAN that I mean to use as a network connection for the NAS?

Will an aluminum basis wreak havoc on wifi reception, which I mean to use as a backup connection? 3 sides of the closet are brick wall/plaster, the front is wood. The router is maybe 5m away in the next room.

For wifi connectivity, does it make a difference if I ground the aluminum sheet or not?


texts: Design a circuit from logic gates, flip flops and/or multiplexers

texts:
I would like to create a simple circuit from logic gates, flip-flops (no RLC components) to do the following task:

This circuit has 5 inputs (4 positive real-valued signals \$x_1, x_2, x_3, x_4\$ and a clock signal \$clk\$). The output signals \$y_1, y_2, y_3, y_4\$ are determined as follows:

At the rising edge of \$clk\$, the output signal \$y_i\$ with \$i =1,4\$  correspoing maximum input \$x_i\$ with \$x_i = max(x_1,x_2,x_3,x_4)\$ at this time will have value \$1\$ while other output signals are zero during that period.

For example, \$x_3 = max(x_1,x_2,x_3,x_4)\$ then  \$y_3 =1\$ and \$y_1 = y_2=y_4=0\$.

Because I don't know how to do starting from logic gates, I tried to write verilog code and then synthesized it to get the circuit. However, I think the result is too much complicated than necessary. Components such as logic gates, flip-flops, multiplexers are OK but the comparator block is maybe too complex.  Is there a simple circuit to do this task? It can be obtained from circuit design from logic gates or synthesized from verilog.

Input signals \$x_1, x_2, x_3, x_4\$ are positive real-valued signals but I don't need high precision, only about 3 significant figures are OK.

Below is my code and the circuit obtained from this code.

module example (clk, x1, x2, x3, x4, y1, y2, y3, y4);
input clk, x1, x2, x3, x4;
output reg y1, y2, y3, y4;

always @(posedge clk)
    if((x1>x2) && (x1>x3) && (x1>x4))
        begin
            y1 <= 1'b1;
            y2 <= 1'b0;
            y3 <= 1'b0;
                y4 <= 1'b0;
        end
    else if((x2>x1) && (x2>x3) && (x2>x4))
        begin
            y1 <= 1'b0;
            y2 <= 1'b1;
            y3 <= 1'b0;
            y4 <= 1'b0;
     end
    else if((x3>x1) && (x3>x2) && (x3>x4))
        begin
            y1 <= 1'b0;
            y2 <= 1'b0;
            y3 <= 1'b1;
                            y4 <= 1'b0;
        end
     else if((x4>x1) && (x4>x2) && (x4>x3))

        begin
            y1 <= 1'b0;
            y2 <= 1'b0;
            y3 <= 1'b0;
        y4 <= 1'b1;
        end
   endmodule

Schematic obtained from the code above:


texts:
In theory, What is the resistance of a wire? I have heard that it is 1Ω before, is that correct? in a standard PCB circuit, should I be more worried about the theoretical resistance of a wire, or of the real-world equivalent resistance?
Theory, defined as Circuit Analyzation , primarily, Ohms law.


texts:
I have been working on a project for ACDC Constant LED driver with 1.2A, 36V specifications. While going through the internet, I found one of the circuit and couldn't understand the working the of the same. Few things I understood but I am not sure of those.
Herein, I am attaching the PDF file I found.
Another thing I was not able to understand is the how can change the circuit to work as per my specifications.
Can anyone help me understant the working of the same?


texts:
I tried to identify the component marked with "t 30" the SOT23 package. I looked for the "t" of "7" symbol in this list

and also tried smd marking search engine but couldn't find it.


texts: How do I use an adjustable LDO regulator to power devices with USB that usually use AA/AAA batteries (or should I)?

texts:
I want to use USB to power devices designed to work with one, two, or three AA/AAA batteries. Three seems to be the trickiest, because it involves dropping the voltage only ~0.5 V from 5±0.25 V to 4.5 V.

After reading around (my electronics knowledge is extremely rusty), it seems an adjustable low dropout (LDO) regulator is the way to go (but please correct me if I'm wrong). The best option locally available seems to be an NCV59302, and because I'm expecting to draw 1A max @ 4.5 V, its ~175mV dropout voltage @ 1A should mean I can get 4.5 V as long as the USB power is > 4.675 V.

However I'm not exactly sure how to get it working correctly. The data sheet is here, and my interpretation of the instructions is illustrated in the circuit diagram below. The thing I'm most unclear about is the resistors, though I'm aware I could have made other major mistakes. Someone has already asked here about the resistors for an NCP59302, a very similar component (I'm not sure what the difference between the NCV & NCP is), but after reading the answers I'm still not sure which resistors will work. Nor am I 100% sure about any of the components or wiring.

R1 is a 500 Ω potentiometer, unspecified wattage rating (does it matter? I assume this only has to carry the 100-350 nA "Adjust Pin Bias Current")
R2 is a 180 Ω 2 Watt wire wound resistor

The formula given in the data sheet to determine the output voltage is:

$$V_{OUT} = 1.24 V × (1 + R_1/R_2) + I_{ADJ} × R_1$$

IADJ is typically 100 nA and can be up to 350 nA, but this makes a negligible difference to VOUT. From what I can tell, with R2 as a 180 Ω resistor, this would output 1.5 V, 3 V, and 4.5 V when the R1 500 Ω potentiometer was set to ~37.7 Ω, 255.5 Ω, and 473.2 Ω respectively. Or am I missing something?

As for the other components:

CIN is a 1 μF 50V electrolytic capacitor
COUT is a 47 μF ±20% 6.3V X5R dielectric SMD ceramic multilayer capacitor (it would cost me the same to get a 100 μF model with the same specs if there is some advantage)

I guess the most important question is: if I wired all this up as in the circuit diagram above, should it work? Or have I made a mistake?

Thanks a lot in advance.


texts: How long can a brand new PCB last before additional protective coating is required if any?

texts:
I have just made several PCBs for a large project using the photoresist method. (I ran the boards through sodium silicate developer then through ferric choride) I then rinsed off all chemicals and dried the boards.

I believe there is some chemical electronic stores sell (conformal coating? I don't know) that would protect the circuit board from any sort of corrosion (which can include introduction of open circuits).

I know the next steps are to drill holes and solder components in, but after that process is complete, how long can I leave the board like that before it is absolutely necessary to add some sort of protective coating to it?

I want my board to last forever but at the same time, I don't want it to corrode (or have traces break up) as the years go by.


texts:
I'd like to make a 4x4 pressure ( force resistance) sensor grid to use with an arduino. But 16 sensors sure need a lot of pins.
During my research on this topic I stumbled upon a couple of suggestions. An example I've seen at least 100 times is the one which generates a 4x4 LED-grid. But in this example, there is no sensordata to be read.

So, backed up by the factories manual on how to hook the sensor up and on how the 4x4 LED-grid tutorial suggested I created my own idea on how to wire the whole thing with one arduino.

My thoughts on that:
Keep D1 to D4 defined as OUTPUT HIGH.
Set D5 to D8 alternatly as ground.
Gather analog information through A2 to A5 of the current selected row.
Save data and look at next row.

My question now, before ordering all the components: Does that sound realistic from an electrical point of view?

! EDIT:

So the first answer got me thinking, and here is my new circuit plan:

Didn't I break the paralellity of the resistive sensors because I'm not measuring the resistance at the pins 5-8, instead I measure values at the analog pins 2 to 5.
So now, if D5 is set to gound, the upper row of the sensors is powered and sensing data, which is gathered by analog pins 2 to 5. And then grounded in digital pin 5.


texts: Is there a RJ45 with magnetics for PHY less network switch

texts: I have a network switch indoor and camera outdoor. I plan on having a PCB with RJ45 with magnetics. Can any tell me how to choose an RJ45 with transformer for a PHY Less network switch.


texts:
Dear Fellow Engineers,

I have just recieved two RC522 modules from eBay, both of them came with a card and a tag. Both of them read the cards just fine with miguelbalboa's library (https://github.com/miguelbalboa/rfid). But it does nothing when I am trying to use the tags. I have also tryied using the sainsmart library: cards ok, tags no joy.

What could possibly cause this issue?

I am working with an Arduino MEGA.

~Z


texts:
I am using ATmega32A and 24c16A EEPROM for testing an I2C code. For every state transition, controller responds by changing the status register TWSR. After start condition is transmitted, EEPROM responds and then also for Device address and write instruction (SLA+R/W), status register updates fine. But when I transmit next 8 bits, instead of ACK (Data byte sent ACK), status changes to repeated start. The code is given below. I never could find the possible solution to make it work.

int main(void)
{
init();
twi_start();
twi_write_device_address();
twi_write_data(0x08); // Data-write Memory transmission
twi_write_data('U');  // Data transmission
twi_stop();
}
void twi_start(void)
{
// Clear TWI interrupt flag, Put start condition on SDA, Enable TWI
TWCR|= (1<<TWINT)|(1<<TWSTA)|(1<<TWEN);
while(!(TWCR & (1<<TWINT))); // Wait till start condition is transmitted
while((TWSR & 0xF8)!= 0x08); // Check for the acknowledgment (start transmitted)
}

void twi_write_device_address()
{
TWDR=0b10101110; // Device address and write instruction
TWCR|=(1<<TWINT)|(1<<TWEN);    // Clear TWI interrupt flag,Enable TWI
while (!(TWCR & (1<<TWINT))); // Wait till complete TWDR byte transmitted
while((TWSR & 0xF8)!= 0x18);  // Check for the acknowledgment (SLA+W transmitted)
}

void twi_write_data(unsigned char data)
{
TWDR=data; // put data in TWDR
TWCR|=(1<<TWINT)|(1<<TWEN);    // Clear TWI interrupt flag,Enable TWI
while (!(TWCR & (1<<TWINT))); // Wait till complete TWDR byte transmitted
while((TWSR & 0xF8) != 0x28); // Check for the acknowledgment (Data written)
}

void twi_stop()
{
// Clear TWI interrupt flag, Put stop condition on SDA, Enable TWI
TWCR|= (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);
while(!(TWCR & (1<<TWSTO)));  // Wait till stop condition is transmitted
}

Instead of 0x28, 0x10 is updated in the status register while calling twi_write_data(data) function.


texts: What does it mean that an operations amplifier is 'high gain'?

texts: I dont have much of a background in electronics, but need to know about operational amplifiers for my physics course. I keep reading the term 'high  gain'. What does this mean?


texts: Can I generate two PWM with 90°phase shift from stm8 microcontroller?

texts:
I am using stm8 microcontroller(STM8AF288) to generate a PWM of 1KHz frequency with timer-1(16bit) . I am giving this as input to a circuit， which generates two PWMs with 90° phase shift. But unfortunately that circuit got damaged. It's no more working. So I thought to generate  2 PWMs with 90° phase shift.

Is it possible to do so? In stm8 user manual I couldn't find anything like this.


texts: Why would you protect a 120-277 LED driver with a fuse that is 600V rated

texts: Sorry about the silly question but is there a reason why you would want to protect a 120-277V LED driver with a fuse that is 600V rated?  Does that really protect the device/driver?


texts:
I do not understand why no current flows through my circuit.

This question seems closest to my problem, but I am still having issues. I have tried two different transistors to make sure the issue was not a damaged transistor and have triple-checked that the polarity in the circuit matches the polarity in the datasheet. Here is my schematic:

simulate this circuit – Schematic created using CircuitLab

As you can see, I have a voltage divider to bring my 18V power supply down to 12V (this was included in case it is causing problems). The 12V supply then connects to an LED package, then to a 2N3904 NPN transistor.

A 3.3V supply is hooked up to the base of the transistor.

I have checked the voltages at various places around the circuit and they seem correct, but no current seems to be flowing. I will admit, that I don't really understand how to read the 2N3904 datasheet so I can provide the correct energy to the base of the transistor.

I have verified that the simplified circuit below works correctly:

simulate this circuit

Conclusion

My difficulties were created primarily from me assuming I could approximate an LED network as a single LED with similar voltage/current characteristics. Brian Drummond pointed out that I couldn't do this because current draw from the LED network would lower the voltage coming out of my voltage divider, preventing the LED network from lighting.

Jim Fischer then pointed out that a voltage divider was probably not what I want to use in this particular application and provided some really great theoretical info.

Going forward, I'll redesign the circuit using a different power delivery mechanism.


texts: Why this Op Amp LC oscillator doesn't oscillate outside the simulation?

texts:
I want to understand why this circuit I have made works in the simulation (Multisim), but when I tested it in the protoboard it does not oscillate.
If anyone can help me, I will be grateful.

(Sorry for the bad English)


texts: Are Molex PicoBlade connectors compatible with JST GH?

texts:
I've read that Molex PicoBlade is often confused with JST GH as they both have the same 1.25mm pitch and similar connectors.
https://en.m.wikipedia.org/wiki/JST_connector
Will a JST GH female terminal fit in a Molex PicoBlade male terminal?  Although the incompatibility isn't explicitly listed in Wikipedia (and other articles), I suspect it is implied.


texts: Is there another name for "terminal ground bar"?

texts: I am trying to source this part http://www.theelectricbrewery.com/10-terminal-50A-ground-bar, but I can't find it at digikey. Is there another name?


texts: How to validate that a function is executing from RAM?

texts:
I'm trying to execute a control function as quickly as possible from SRAM on an STM32F3xx using GCC (System Workbench toolchain).

__attribute__((ramfunc)) f1(void) {
  // Set GPIO pin
  // Do something that is faster from RAM
  // Clear GPIO pin
}

void f2(void) {
  // Set GPIO pin
  // Do something that is faster from RAM
  // Clear GPIO pin
}

How can I check to make sure that it is actually executing from RAM?  Will printing its address tell me the flash location or the RAM location?

printf("f1 address = 0x%p\n", f1);
printf("f2 address = 0x%p\n", f2);

Is there an operation that will have an extremely different timing behavior if I measure it with an oscilloscope that I can compare?

f1();
f2();

From the output.map file:

.text.f1       0x0000000008007470       0x18 src/controller.o
.text.f2       0x0000000008007488       0x18 src/controller.o

From the log:

f1 address = 0x0x8007471
f2 address = 0x0x8007489

Relevant links:

http://www.openstm32.org/forumthread5894

https://www.silabs.com/community/mcu/32-bit/forum.topic.html/how_can_i_executeco-6Zv7

Excerpt from LinkerScript.ld file showing my added ramfunc section that doesn't seem to be enough:

/* Initialized data sections goes into RAM, load LMA copy after code */
  .data :
  {
    . = ALIGN(4);
    _sdata = .;        /* create a global symbol at data start */
    *(.data)           /* .data sections */
    *(.data*)          /* .data* sections */
    *(.ramfunc)        /* .ramfunc sections */
    . = ALIGN(4);
    _edata = .;        /* define a global symbol at data end */
  } >RAM AT> FLASH


texts:
I have a basic question about the utility of a power-flow study versus a phasor simulation of a network.

Here is a description of phasor simulation from the Matlab Simpowersystems manual

"If, in a linear circuit, you are interested only in the changes in magnitude and phase of all voltages and currents when switches are closed or opened, you do not need to solve all differential equations (state-space model) resulting from the interaction of R, L, and C elements. You can instead solve a much simpler set of algebraic equations relating the voltage and current phasors. This is what the phasor solution method does. As its name implies, this method computes voltages and currents as phasors. Phasors are complex numbers representing sinusoidal voltages and currents at a particular frequency. They can be expressed either in Cartesian coordinates (real and imaginary) or in polar coordinates (amplitude and phase). As the electrical states are ignored, the phasor solution method does not require a particular solver to solve the electrical part of your system. The simulation is therefore much faster to execute. You must keep in mind, however, that this faster solution technique gives the solution only at one particular frequency.
"

and the wikipedia definition of a power-flow study

"In power engineering, the power-flow study, or load-flow study, is a numerical analysis of the flow of electric power in an interconnected system. A power-flow study usually uses simplified notation such as a one-line diagram and per-unit system, and focuses on various aspects of AC power parameters, such as voltages, voltage angles, real power and reactive power. It analyzes the power systems in normal steady-state operation.
"

To do a phasor simulation, I imagine that any load injections can be modeled as current injections at constant voltage or voltage sources at constant current. (?)

My confusion is the following. Why would one do a power-flow study if all the information of the voltages, currents and phase angles can be obtained from a phasor simulation (considering that we don't need to assume steady-state)? Wouldn't one get a more realistic description of the dynamics of the system (and all the corresponding information that power-flow study will provide) with a phasor simulation?

I am obviously confused about what each method is supposed to accomplish or may have made incorrect assumptions. I would be grateful if someone pointed out what that may be.


texts: Design of 50 ohms RF trace for 2.4GHz...Double layer FR-4 PCB

texts:
I will use a 2.4GHz transceiver on my new project. The PCB material will be FR-4 with 1.6mm thickness and the connector is a SMA. My doubt is about the RF trace that should have 50 ohms impedance. Using AppCAD 4.0, inputing the parameters shown below I have got a 50 ohms result for Width = 45mils and Gap = 8 mils from RF trace to GND. Also I got almost the same result on the online calculator. Does this combinations (45/8 mils) looks correct for you?

What more can I do to improve my layout?
Regards.

transparent view:

edit: this is my final layout...

edit: newer...


texts:
I just had an application where ground capacitance and stray capacitance of all power supply options (Switch mode wall warts, grounded switch mode supplies) was to large and spoiled measurements by injecting relatively large mains frequency dependent voltages.

I actually helped myself out by building an optical power insulator (a LED driving a small solar panel).

I wonder why I found no low capacitance (stray and to earth) power supplies.

All supplies I checked out either showed symmetric mains capacitance (providing about half the mains voltage at the output GND) or ground connection (output GND tied to mains GND).

Is there any special type of supply that connect mains or earth in the smallest possible way? How would it be named?


texts:
I have been doing some research into the effectiveness of applying the 20H rule to 4 layer PCB designs and have been finding some very conflicting information. Some sources (including a few IEEE research papers and case studies) show experimental results that suggest that applying the 20H rule to a 2-plane stackup will actually increase edge radiation into free space, while other sources show evidence that it will cut emissions significantly.
After doing some thinking about this, the pull-back on a power plane in respect to a ground plane is almost exactly the same as a microstrip.
So my question is this, in a non-impedance controlled design, shouldn't adding a fairly continuous ground plane on the adjacent layer to the power plane make the power plane behave more like a stripline in regards to coupling to the sandwiching ground planes? Does anyone have a preferred method of cutting emissions in 4-layer designs apart from the usual mix of proper partitioning and slew control?

~~~~~~~~~~~~  Signal Layer Top

~~~~~~~~~~~~  Ground plane

~~~~~~~~       Power plane with 20H pullback

~~~~~~~~~~~~  Signal Layer Bottom w/Ground pour


texts: Pointer to a reception buffer seems to have zero in all the other elements differents but the zero index , why with an STM32F401VE

texts:
how are you?. I'm having some trouble analizing streamed data. Recently I made a program that analizes streamed data and works for the first message of the stream as you can see in the following post
Problem with structire packing
when I noticed that program will work only for the first message for the way the buffer is being filler I changed the focus of the processing to move the compare variable to the position of the last byte arrived and then compare backwards since I need to check first the suffix of the message to determine where the prefix is, after that then decide what to do (this last part is not done yet).
The problem that I have here is that as I'm inside the analize_stream function I want to use the pointer to the reception buffer I declared to compare instead the original reception buffer name, so when I try to use the pointer then the first element appears perfectly but the final three appears as zero as you can see in the following image

and the code is this
uint8_t analize_string(uint32_t * incomming)
{
    static uint8_t incCounter = 0;
    static uint8_t arreglo[Long_Rec] = {0};
    arreglo[incCounter] = incomming[incCounter];
    if((incomming[incCounter] == 0xff)
        && (incomming[incCounter  - 1] == 0xff)
        && (incomming[incCounter - 2] == 0xff))
    {
        incCounter = 0;
    }
    if(interface.aHMI)
    {
//////      screen_handler();
        interface.aHMI = false;
    }
    receive_data((char *) &U2rxBuffer[incCounter], (uint16_t) sizeof(uint8_t));
    return incCounter;
}

as you can see in the image the incomming pointer is correctly directed since it has the correct data to analize (0xffffff86) but when I did the comparison with the "if" then it didn't worked so I added the operation to mirror the incomming pointer (U2rxBuffer actually) in the array "arreglo", then arreglo is showing the second, third and fourth element equal to zero but when I do the same operation but mirroring directly U2rxBuffer into arreglo it shows the content of arreglo as should be as you can see in the following image:

the only thing that I changed to the code was "incomming" for "U2rxBuffer", so, why if incomming is correctly directed then it doesn't assign the data for addresses beyond initial address?.
This program righ now what does is to call analize_string every time a new byte arrives and exits until a new one arrives.
NOTE: Seeing again my previous post I noted that yesterday I was this problem too but I didn't noted.
Please help.


texts: Can I connect a button on my motorcycle to the main button on a garage door remote?

texts:
I want to connect one of the existing switches (high-beam flash, or turn signal middle push button, or horn, or pretty much any other switch/button) on my motorcycle to the main switch of a garage door opener, so once I am home and hit that switch on my motorcycle, it should open the garage.

I have seen someone do it using a different logic, by keeping that main switch pressed all the time, and opening the garage by sending power through the switch on the motorcycle. However, my garage door remote has a 3V battery and I don't want to get into using the 12V->3V converters.

How can I use an existing switch/button on the motorcycle to press the main switch on this remote???

Sorry for not using the needed tags for this question, I literally don't know what tags to use in electrical engineering.


texts:
I understand the difference between AC and DC. What I don't understand is how does AC power anything when it's reusing the same electrons over and over as they are moving back and forth?

A visual picture is this link at 0:35.

Wouldn't it require new electrons? Eventually?


texts: I have a 3.3V LDO TLV755 connected to a FTDI chip FT2232HL. But I only get 0.9V at the output terminal. I am not entirely sure what the reasons of this could be. When the FTDI chip connected with a power supply the curernt reading is about 70mA. Is the LDO not suitable for this purpose?


texts:
I've Googled but didn't find an answer. Is it problematic to extend load cell wires? I would like to have the 4 cells under the 4 corners of something (since the object rests on those 4 corners), but we are talking about 2 meters by 2 meters. I can put the electronics in the center but want to put a load cell under each corner.

It's for this load cell:

https://www.sparkfun.com/products/10245

Do I risk getting losses over that distance (approx 1.4 meters) that could render it useless?

Thanks


texts: Make: Electronics (Experiment 11) LED blinks only once

texts:
There is one more question about Experiment 11 from "Make: Electronics" by Charles Platt.
The trouble is that my LED blinks only once, when I connect circuit to power source. (I tried 6V, 9V and finally 12V DC)
As I understand, capacitor should discharge, but it holds the voltage and there is no "charge/discharge" process described in the book that forces LED to blink.

There is the original circuit from the book:

Photo of my circuit is below (yes, it is connected to power source):

Also I created Fritzing breadboard diagram and marked some points:

I checked voltage between points displayed on the fritzing diagram (I use 12V DC power source):

Vab = 0.04V (after multimeter touch voltage reduces to 0.01V)
Vcd = 11.4V (after multimeter touch voltage reduces to 9.47V)
Vef = 4.9V
Vgh = 8.83V
Vij = 0V

Any ideas why LED blinks only once but not constantly?
Finally, one more noob question. As I understand, 'gate voltage' is Vgh. What is then 'anode voltage'? Is it Vcd?


texts: By way of resistors, I was wondering if there is any easy way or product in the market to be able to control the current in a circuit without having to take apart the circuit and put in new resistors.(So something with a dial perhaps so that I can change the current instantly)


texts:
I am designing a device which must power a number of RGB LEDs. I am currently looking at WS2812 "NeoPixel" style LEDs, which have a max current draw of 60mA each. I would like to have a large number of these, but running at lower brightnesses.

The problem is that I want to supply this from a standard USB port, and I have more critical functions that run off of the same USB power, so I want some sort of current limiter/protection to ensure that the LEDs don't consume so much current that the USB controller shuts off the device.

Would a simple PTC/Re-settable fuse work?
Or something like this current limiter from Wikipedia.
Or should the supply be cut completely?

I don't need very high accuracy,but I would like to keep current under ~250mA±30mA.

Also since I need >100mA from the USB VBUS should I include a MOSFET or other way to disable the supply while the microcontroller is starting/restarting.

Finally I have seen some people recommend large(100-1000uF) smoothing capacitors to the LED's VCC. Which side of the protection should this be on?