texts: How can I create one PCB that I can plug-in to two different places in a mother PCB?

texts:
I believe there are many answers to this question, but I would like to have one that works best in KiCad allowing me to run the rule check for all the involved schematics.
What have I tried:
On top of my main schematic A1, with the file name M1.sch (that will be the mother PCB), I created an hierarchical sheet and I gave it a file name, let's say, P1.sch (that will be the plug-in PCB), and the name B1. I copied that sheet and I kept the file name P1.sch, but I changed the name to B2. Both B1 and B2 are using hierarchical pins to connect to the nets of A1 schematic.
P1.sch contains two matched transistors in the same package. I carefully annotated them as U101A and U101B for either B1 and B2, because I want to produce two equal plug-in PCBs (with the same serigraphy) for P1.sch (and not one for B1 and another different for B2).
After that I annotated only the main schematic A1 and tried to assign the footprints to the parts. I was forced to generate the net list again. I selected "Keep existing annotations". Then I got two error lines:
Error: Multiple item U101 (unit 1)
Error: Multiple item U101 (unit 2)
I know this is because the B1 and B2 have the same U101 IC.
The only way I know to solve this is to have two completely separate schematics, in order to produce two different PCBs: one mother PCB and one plug-in PCB that I will produce twice, so that I can have two plug-in PCBs. However, by doing this I can not run the rule check for both schematics. I will not have KiCad aiding me about something being wrong in the two interfaces between the mother PCB and the two plug-in PCBs, which would be nice.


texts: I bought this odd servo motor called the FR 5311M from FeeTech, which is advertised as a programmable servo motor which can switch from position to continuous rotation by flashing it with FeeTech's FR 5311M programmer device. I'm wondering if there is any way to use something like an Arduino or Rasberry Pie to flash the motor instead of using FeeTech's programmer?


texts:
I wanted to use an accelerometer or IMU to measure speed and displacement over a period of about 1 minute or 400m. From this answer I found at stackoverflow, the error propagates at a rate of \$t^2\$ (without considering the rotation), so \$60^2 = 3600\$.

The noise density of the ADXL335 accelerometer is about \$200 μg / \sqrt{Hz}\$, so @500Hz we get $$\dfrac{200}{\sqrt{500}} = 87.67 μg\ (\mathrm{or}\ \ 87.67 \times 10^{-6} m/s^2)$$

Getting the error over the 60 seconds: \$87.67 \times 10^{-6} \times 3600 = 0.32m\$.

This looks suspiciously optimistic, Am I correct, or am I doing bad calculations?


texts:
Hello, actually I am very new in electronics. Im using this as a reference in connecting lcd and 4x4 keypad in my my controller ( an arduino clone) Gizduino ATMEGA644 but I'm having a problem because of its pin different pin description.

When I tried connecting it the same with my reference (without looking at the pin description)I'm only having black box in the lcd after uploading a sample program. can someone help me?

this is the connection I used:


texts:
I have an RGB LED (common cathode) that I would like to trigger from the GPIO pins of an ESP8266 (3.3v).  The device I am using (Wemos pro mini D1) has a 5V supply which I was planning on controlling via a transistor (I have some 2N3904).

From some reading I understand this can be achieved as follows (and I'm happy with the reasoning why):

Credit: here

However, I wanted to know if this was achievable using just one BJT?  I've seen some people suggests just using one NPN and the load on the emitter and no resistor on the base but when I tried this out I had extremely low Ib which was insufficient to fully "switch" the BJT.


texts: Switching Arduino/ATMega to sleep mode when on battery

texts:
I'm trying to make a small clock but want to ditch the need for a separate RTC chip with battery backup. What I would like to do, instead, is keep track of the time completely on the ATMega using the watchdog timer to generate a roughly 1Hz signal to count the seconds with. Not super accurate, but good enough for what I need.

The key though is that I would like to still have a battery backup. So, what I need it to do is detect that it no longer has 5V power (probably from USB) and switch into low power mode (running off a 3V CR2032 or similar) only waking when the watchdog timer ticks in order to increment the seconds. I'm guessing also dynamically decrease the clock speed (switch to internal or something) to save power.

I'm a bit stumped... How would I actually do the hardware for this? I vaguely remember something about "diode ORing" the backup battery... no idea what that means. And bonus points for the software side of things.


texts:
I have been trying to do a transient simulation of a Power supply independent biasing circuit in Cadance but how much ever I try I do not see the transition of the states. I always get only the steady state even if I put the stop time in nano seconds ! This is the circuit that I am trying to simulate and I have marked the nets(Voltage) that I trying to view in my transient simulation,

The simulation result looks like this(below) and the time axis is in nanoseconds range but still I do not get to see a slope or anything other than the steady state response ]2

Could there be any reason why I am not able to see the transition ??


texts: Confusion with applying KCL to three phase delta connection

texts:
Below is a 3-phase delta connected for balanced loads Z:

Since phase to phase voltages(voltage across loads) have 120 degrees phase differences and since the loads have the same impedance we can conclude that the currents Iux, Izw, Ivy across the loads also must have 120 degrees phase difference with same rms values. So one can draw the phasor for these currents as:

I'm experiencing some confusion for writing the node currents as KCL. For example, take node M above in my first drawing.

Vectorially for the currents at node M which one is correct and why?:

Ir = Iux + Izw ?

Ir = Iux - Izw ?

According to what I read Ir must be sqrt(3) times the load current, but I don't know how they derive this by using KCL considering the phasor diagrams.


texts: Ethernet connectors shielding/ grounding

texts:
I am currently trying to derive the relevance of ethernet connections shielding and grounding. This is regarding the robustness of the design (in terms of communication) and eventual ESD considerations as well. I can find the following scenarios possible (assuming 2 devices connected with an ethernet cable).

Both devices have unshielded ethernet jacks, the cable is unshielded,
Both devices have unshielded ethernet jacks, the cable is shielded,
Only 1 device has shielded jack, the cable is unshielded,
Only 1 device has shielded jack, the cable shielded,
Both devices have shielded jacks, the cable is unshielded,
Both devices have shielded jacks, the cable is shielded.

My assumption is that for the cases where the cable is unshielded (1, 3, 5), the shielding of the connectors is irrelevant. My questions are then regarding the points (2, 4 and 6):

If none of the connectors are shielded, does the shielding on the cable provide any difference in terms of noise insulation or ESD?
If only one of the devices is shielded, I assume this is the best case, since we do not have any ground loops and insulation is good. But how does it correlates with ESD? Also, in case the shielded connector device is not connected to the PE pin of the AC connector (i.e. only L and N connection available)- is this insulation effective? We can see many networked devices with a 2 pin AC adapter and shielded connectors.
If both devices have shielded connectors (both connected to their local GND), what exact effects can it have for the whole system (incl. ground loops)? How should we look at it in terms of ESD?

I would appreciate all feedback to my questions.


texts: PSPICE ERROR(ORPSIM-15143): Voltage source and/or inductor loop involving


texts: Avoiding switching transient in IC switch

texts:
I am switching an op amp input between two sources, one is ground, the other is a piezo material.  I have an issue with switching transients which cause the op amp to saturate since I have a pretty high gain (x50). To keep things short, Here is the switch.  I have a piezo element connected to s2, s1 is grounded.  op amp's +input connected to D.  Is there a way to prevent the transient from reaching the amp's input?

Here is what it looks like.

The hydrophone receives a sinusoid burst while the switch is in a logic 0 state, then once the burst is sent, it is switched to logic 1 and connected to the op amp.  The idea is to read any acoustic reflections seen by the hydrophone.  This has all been successful, but the transient is the one piece I would like to remove from the output signal.  Unfortunately this is as far is my knowledge has gotten me so I have no clue where to go next.

Circuit is actually backwards my apologies.  I just put it together in ppt since I don't have my files available with me.  The hydrophone side should be S2 and op amp should be D.

Update:

I have some of the signals and here is what it looks like:

Noise from the switch, with and without the hydrophone

Here is what the reflected signal looks like.  This is what I'm interested in, but as you can see it is quite low in amplitude, and thats why I need to amplify it.

@sperophany: As for the cable, I'm using Alpha wire 3302 twisted pair with a 50ohm bnc connector.  It's about 6' long, 38pF/ft capacitance.  more detailed specs can be found here http://media.digikey.com/pdf/Data%20Sheets/Alpha%20Wire%20PDFs/3302.pdf

Another thought I have as I was looking at the signals was to filter the switch's transient instead.  It is pretty high frequency and well out of my system's range (<500kHz) so I was wondering if it would be possible to completely remove it with a lp filter.  Any thoughts on this?  Any drawbacks or new problems?

Overall, I just want to send a pulse and then listen for echos with the same transducer.  I'm open to any and all suggestions - even if I have to scrap my current design and start from scratch.

Thanks again for your time, guys.


texts: Problems with interfacing Nucleo-F446RE and ADF4153 via SPI

texts:
I am trying to interface with a ADF4153 device via SPI, the problem is that the ADF4153 is not responding. I expect the problem is with the SPI connection. The pin connections are as follows;

MOSI -> DATA,

SCK -> CLK,

D9 -> LE

Hardware initialization is done by STMCubeMX and the software is programmed in Keil uVision.

Here is my code.

#include "main.h"
SPI_HandleTypeDef hspi1;
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_SPI1_Init(void);
uint8_t array0[3];
uint8_t array1[3];
uint8_t array2[3];
uint8_t array3[3];
int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_SPI1_Init();
    array0[0]=0x00;
    array0[1]=0x00;
    array0[2]=0x32;
    array1[0]=0x65;
    array1[1]=0x80;
    array1[2]=0x40;
    array2[0]=0xC2;
    array2[1]=0x17;
    array2[2]=0x00;
    array3[0]=0x00;
    array3[1]=0x00;
    array3[2]=0x03;
HAL_SPI_Transmit(&hspi1, array0, 3,10);
HAL_SPI_Transmit(&hspi1, array1, 3,10);
  while (1)
  {
//HAL_SPI_Transmit(&hspi1, array2, 3,10);
//HAL_SPI_Transmit(&hspi1, array3, 3,10);
  }
}
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
  __HAL_RCC_PWR_CLK_ENABLE();
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE3);
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
  RCC_OscInitStruct.PLL.PLLM = 16;
  RCC_OscInitStruct.PLL.PLLN = 336;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV4;
  RCC_OscInitStruct.PLL.PLLQ = 2;
  RCC_OscInitStruct.PLL.PLLR = 2;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
    Error_Handler();
  }
}

static void MX_SPI1_Init(void)
{
  hspi1.Instance = SPI1;
  hspi1.Init.Mode = SPI_MODE_MASTER;
  hspi1.Init.Direction = SPI_DIRECTION_2LINES;
  hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
  hspi1.Init.CLKPolarity = SPI_POLARITY_HIGH;
  hspi1.Init.CLKPhase = SPI_PHASE_2EDGE;
  hspi1.Init.NSS = SPI_NSS_SOFT;
  hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_32;
  hspi1.Init.FirstBit = SPI_FIRSTBIT_LSB;
  hspi1.Init.TIMode = SPI_TIMODE_DISABLE;
  hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
  hspi1.Init.CRCPolynomial = 10;
  if (HAL_SPI_Init(&hspi1) != HAL_OK)
  {
    Error_Handler();
  }
}
static void MX_GPIO_Init(void)
{
  __HAL_RCC_GPIOA_CLK_ENABLE();
}
void Error_Handler(void)
{
}
#ifdef  USE_FULL_ASSERT
void assert_failed(uint8_t *file, uint32_t line)
{
}
#endif


texts: Voltage Controlled Second Order Low Pass Filter

texts:
First time poster. Please be kind!
I'm working on an analog synthesizer project and recently started looking at Voltage Controlled Filter designs. I've scoured the internet for a low pass configuration that would allow me to control the filter's cutoff frequency with a control voltage (from a low frequency oscillator) without resorting to the complicated mathematics of, say, the Moog ladder filter. So far, the top contenders are the filter for the Gakken SX-150 and the filter for the Korg Monotron series. Unfortunately, the physics of even these relatively simple topologies are a bit above me. I've tried doggedly to try and resolve the components in both circuits to the classic Sallen Key filter but without much luck. To date all I concretely understand is that the BJT transistors must function as resistors whose base junction current determines resistance. This resistance then works in conjunction with the capacitor impedance to selectively allow current flow as in a basic first order topology. That's not so bad. Exactly which components achieve this effect however, is still a mystery to me. I like to believe I have done the requisite amount of googling but even the most accessible webpage (Tim Stinchcombe) wasn't much help. The addition of more than two capacitors in both schematics gives me much pause and I'm still not convinced that the feedback diodes are even strictly necessary. Would someone mind explaining to me which components I should focus on and how they work together?
EDIT (Included Monotron Schematic)

(source: korg.de)


texts: Multiplexing an 8x8 Matrix - Why Transistors?

texts:
I'm trying to understand how to properly multiplex an 8x8 matrix (or any large amount of LEDs)
http://arduino.cc/en/Tutorial/RowColumnScanning

However, I'm getting a bit confused, since I've found others like this: http://garagelab.com/profiles/blogs/arduino-scrolling-text-marquee-to-give-a-happy-christmas

That one says to use transistors for the current switching, but the first link doesn't even use any resistors (which I find suspect), nevermind transistors.

I don't really see why the transistors are needed, can anyone explain why?

Thoughts?


texts: Is it acceptable to replace 2 parallel 100uF capacitors for LM2596 with two 220uF capacitors

texts:
I have a printer motherboard with the LM2596 IC. The older version of the motherboard had one 100uF capacitor at the output pin of LM2596 but LM2596 recommends that 220uF be used. Because a cheap 100uF capacitor was used, there were issues with the printer such as temperature fluctuating.

People that had issues replaced the 100uF with 220uF and the issues were solved. I had the-same issue then opened up the device to replace the capacitor. After making this post, I realized that the motherboard version I have came with a supposed fix for this issue. The new motherboard uses two 100uF  in parallel to fix the issue. Those two 100uF parallel capacitors should only give 200uF not the recommended 220uF. Even with this fix, I still get temperature fluctuating sometimes.

Is there a problem if I replace the two 100uF parallel capacitors with two 220uF? Is this going to cause a problem? I mean, that would be 440uF.

If that's going to be a problem, how about removing the two 100uF parallel capacitors and put just one 220uF?

Most post I found also mentioned that the a poor quality capacitor is used for  LM2596 IC is used and this should be replace so that's why I feel like I have to replace those caps with a high quality one.


texts: Can it be safe to break both power and ground in a switch?

texts:
I have a setup with a bunch of synthesizers and guitar pedals wired together with audio cables. I'm also powering the guitar pedals all with the same multi-plug 9V adapter. Since some of the pedals don't have dedicated power switches I bought some inline DC switches online that you stick between the adapter cable and the pedal so you can switch it on and off.
The weird phenomenon I'm experiencing is that switching one pedal on also switches on the others (whose switches are turned off) because the switch only cuts the power line and due to the audio cable connections there's actually an electrical circuit being formed across the ground connection of the audio cables and power line. Basically a pedal is linked to another via the ground wire, that other pedal is linked to a synthesizer via audio cable, another audio cable is linked from the synth to the first pedal, and now we have a ground circuit. It doesn't seem unsafe right now as far as I can tell, just inconvenient.
What I've realized is that if I had switches that cut both power and ground, they would work correctly in my scenario. My question is, would that be safe? I understand cutting the ground wire is supposed to be bad when power is live, but is this a big deal if both are cut and the voltage/amps are relatively low?


texts: LTSpice: How to offset the start time in a transient simulation?

texts:
I see how to set the total run time for a transient simulation, but what if I didn't want the simulation to start at 0s?

For example, if I have two voltages sources that are stepping at offset times from each other, and one of them doesn't start until time = 1s. How can I shift the simulation to start at 1s instead?


texts:
How do I export/generate an pick & place file for my board in CadSoft Eagle?

Is there a standard (like gerber) for pick & place machine files?


texts: I am trying to figure out how I can find Vout in this diagram I am sharing right now. I tried kirchoff but it does not seem helpful or possible to work with and I am assuming Vin is just an arbitrary AC signal coming in(just for now we can assume it is a sinusodial signal). I am aware that the capacitor blocks DC current and let Vin to be coupled to Vout but what I do not understand is how alike Vin and Vout are. What I mean is if Vout is like Vin in shape but with offset or Vout has totally different shape with respect to Vin. Please help me get through this. Whenever I see a capacitor, I am paralyzed because I cannot guess its effect on output voltage like this scenario.


texts: Is is possible for a microcontroller with a single serial output to interact with two serial peripherals?

texts: I'm looking into using Atmel's 2051 microcontroller with an Xbee and a HC-05 Bluetooth module, the micro however has only one serial connection and no possibility for expandability with memory-accessed peripherals. Is this doable or do I have to choose only one of the two?


texts: What does "V.A." mean in datasheet dimensions?

texts:
I'm looking at a datasheet for an LCD panel (pdf link to datasheet).
I don't understand these two encircled dimensions:

What does the acronym "V.A." mean for these dimensions?
I have referenced a couple of other questions here on EE, but they don't cover this:
Abstract Datasheet Dimension Notation
Reading dimension in datasheet


texts: I found this circuit design for constructing a variable resistor. Its seems that the resistance can be controlled by the duty cycle of PWM on MOSFET. Would you explain what is the purpose of having capacitor connected in parallel with the MOSFET? In addition, how to determine a specific value for the capacitor?


texts: When using nodal analysis of a circuit involving CCCS, how do you know which currents are entering and which are leaving?

texts:
I am trying to solve the following circuit:

I believe the answer I'm getting for \$i_b\$ is wrong because I put it into LTSpice and I'm getting that \$i_b = -3.63636\$

This is my LTSpice diagram:

I found \$i_b = 1\$mA by doing a loop voltage analysis on the left loop; for the voltage drop across the \$200\Omega\$ resistor I assumed that it would be \$i_b + 29i_b\$, which works out to be a nice number and in fact all of the numbers are nice in this case--usually when the numbers are nice, you know you're doing it right.

At this point, I'm not sure if I incorrectly modeled this in LTSpice, or if I incorrectly assumed which way the current was flowing.

Instead of giving me the answer directly, I would just like to know how to determine whether the current at a node is entering or leaving a branch.


texts: Finding I2C Slave Address For MT9P031 image sensor

texts:
Here is the datasheet: https://www.onsemi.com/pub/Collateral/MT9P031-D.PDF
On page 12 of the datasheet, it shows an example of I2C communication. The first byte sent is 0xBA. Is this the slave address of this image sensor?


texts: What is difference in link rate and pixel rate in Display Port

texts:
I was going through the Display port Specification. I came across below para
"1.7.1 Make-up of the Main Link
The Main Link consists of one, two or four AC-coupled, doubly terminated differential pairs (called lanes).
AC-coupling facilitates the silicon process migration since the DisplayPort transmitter and receiver may have
different common mode voltages.
Three link rates are supported, 5.4Gbps, 2.7Gbps and 1.62Gbps per lane. All enabled lanes must be operating
at the same link rate. The link rate is decoupled from the pixel rate. The pixel rate is regenerated from the link
symbol clock using the time stamp values M and N. The capabilities of the DisplayPort transmitter and
receiver, and the quality of the channel (or a cable) will determine whether the link rate is set to 5.4Gbps,
2.7Gbps or 1.62Gbps per lan"
What is difference between pixel rate and link rate?
As per my understanding the display port transfers pixel as  part of the other information like HFP, HBP etc. How then the rate is diff


texts: Emulating a USB Standard Downstream Port Charging application

texts:
I have am using an LM5017 to step down a relatively high voltage solar panel (VOC over 90V) to 5V. I have bench tested my circuit and it is providing good buck regulation with input voltages up to 95V. I connect this to a type A USB port to provide a charging port for USB devices. The LM5017 is only capable of supplying 600mA. I would like to emulate a Standard Downstream Port so that the client will draw up to 500mA from the charger.

I tried tying D+/- to ground via a 15kohm resistor. But the port is not being recognized by some devices as SDP. I assume I am doing something wrong.

does anyone have any advice.

I could try shorting the data pins together to emulate a dedicated charging port, but I do not want the client to attempt to draw greater than 500mA.

In general is there a circuit which will emulate a USB Standard Downstream Port without implementing logic?

Thanks


texts: Is Q-Point in Transistor constant? For different configuration if same transistor is used?

texts: Via IV-Characteristics, for specific Ib, I got the Q-Point and using the same value of the Q-Point, I constructed a common emitter configuration biasing circuit that its V_ce = Q-Point_Voltageafter adjusting the value of the resistance. May I know the Q-Point, i_b(to find r_pi) remain constant?


texts: Why does VHDL function declaration not accept bounds for the return type, e.g. std_logic_vector?

texts:
I know that in VHDL each function call is instantiated as a separate combinational circuit. I am writing a function that takes in a 4 bit value and returns a 7 bit value from a look up table. The declaration in the package head looks like this:

function my_function(lv: std_logic_vector(3 downto 0)) return std_logic_vector(6 downto 0);

The compiler is generating error. It seems to me that the function declaration cannot include the size of the logic vector. Why? Does the same apply to integers where the range of integer value be given?


texts:
Is it possible to use pins of Spartan-6 bidirectional. (switch between input/output)

The following is the situation:
I have a high speed ADC and DAC, but this do not have to opperate at the same time.
The ADC and DAC both have an enable line that make the input (for DAC) and output (for ADC) High Z.

Now i was thinking i could use the datalines D0 - D11 in this case for both ADC and DAC, only i do not know how i can switch a FPGA pin from input to output whitin my VHDL code.
Does somebody know this or has experience with this?

example
FPGA pin 1: high is enable ADC Low en enable DAC

When pin 1 = high
FPGA pin 2 to 14 must be inputs, since ADC is connected

When pin 1 = low
FPGA pin 2 to 14 must be outputs, since DAC is connected

I can set a pin to input or output in the plan ahead from ISE,
but cannot find a bi-di option or such.

Also if this is possible how much time does it take the spartan-6 to switch from input to output and <>?


texts: If the voltage doesn't kill you, does the current capability matter?

texts:
Trade electricians often work on live household circuits carrying 120V AC.  I've gotten shocked by accidentally touching such hot wires often enough to recognize the 60Hz AC buzz.  Fortunately, human skin has pretty high resistance: even when drenched in sweat, mine measures in the hundreds of kΩ.  If we assume a lower-end skin resistance of 120kΩ, then through unbroken skin 120V service will only pass 1mA through my body.

Conventional "wisdom" says that working in a main panel calls for more caution because one might make contact with 400A service, as compared to the 20A one is facing working at the end of a typical circuit.  But this sounds incorrect:

If skin has significant enough resistance that at 120V only milliamps flow through it, then is a 200A service supply any different from a 20A breaker in terms of the experience of touching a hot wire (holding all else equal)?

Does ground contact matter in terms of skin contact with residential electric service? E.g., at 1mA, 120V, and half a 60Hz cycle would an insulated 20-gallon vat of saline take enough charge to slow the current significantly relative to the current it would receive if it were connected to the ground?


texts: Driving LEDs: Brightness, efficiency and heat generation

texts:
I'm planning on building a low-cost LED fixture and I'm a bit confused with how I should drive it. So, if we consider these 2 led cobs:

1W 350mA 3.2-3.4V 100-110LM
3W 700mA 3.2-3.4V 260-280LM

If I drive them both with a 300mA constant current driver, I have the following questions:

Would the 3W led generate less heat?
Would the 3W led generate more light? (lumens)
Would the 3W led be less efficient? (lumens/watt)

For reference: leds, driver


texts: Why is my amplified strain gauge output so unstable?

texts:
I've attached a strain gauge to a bending arm of a robot, and it varies by about 1.5 ohms from 356 to 357.5 ohms. I place this in a Wheatstone bridge.

The strain gauge is R3. R1, R2, and R4 are all 378.6 ohms (measured by ohmeter) and I added a resistance in series with R3 to make it range from 380 ohms to 381.5.
I put Vo+ and Vo- as the inputs to a differential amplifier.

Where R1 ~= R2 ~= 1.2 Kohm and R3 ~= R4 ~= 680 Kohm which gives a gain of 567.  Vo ranges from about .003 to .006 volts and Vout ranges from around 1.7 Volts to 3.6 Volts. I want my reading to be as stable as possible for a fixed position of the strain gauge but it ranges by about 20 mV peak to peak when the strain gauge is fixed in place. And it is not a stable oscillation; it will just slowly move around that range, changing by about 2 mV per second.

I am measuring this with a voltmeter, and I have also hooked it up to an Arduino.  My op amp is an LM741 with +- 8.2 Volts power supply. My voltage source is an Arduino, applying 5 V across the Wheatstone bridge.

I realize that any tiny change in the resistance or voltage source would be amplified and could cause my problem, but I'm not sure how to isolate and fix it.  My ohmmeter is only specific to .1 ohms and my voltmeter is only specific to .001 V, so it's hard to tell what is going wrong.

What I can think to check is: how consistent my voltage source is, how consistent my resistance is, and how consistent my op amp is. What is the best way to do those three things given my testing equipment? Is there something else that might be introducing error that I haven't thought of?


texts: Is there any benefit to using twisted pair for short-distance I2C?

texts: I know twisted pairs are important for differential signals, which I2C is not. I also know I2C is not intended to be used over long wires. However, I made a design where I need to use a cable to connect two devices over I2C. The expected length is 0.2m to 0.5m. I am shopping for wires now and there is a nice 4-wire cable that fits the specs and a very similar cable with wires twisted in 2 pairs. I wonder, does I2C communication benefit from a twisted pair? Or might it hurt it perhaps? Or should I just choose the cable of the better color?


texts:
I wonder if ESP8266 or similiar (ESP32 for example) modules are used often in real  mass production in medical/automotive/military/households industries.

I see many DIY projects with it, but there is a better alternative for mass production?

If yes - i need some examples.


texts: Is connecting the V_REF- pin for a dsPIC mandatory?

texts:
While trying to get the ADC of the dsPICF3013 working (I am getting only zeros back), I have studied the datasheet and the (I will call it) ADC reference for the dsPIC30F family. Previously I only worked with the ADC of the PIC16F, so now I have to face a lot of more options.

The ADC is configured to use \$AV_{DD}\$ as the positive voltage reference and \$AV_{SS}\$ as the negative voltage reference. The ADCON2.VCFG<2:0> configuration bits are set to 000 (see page 18-6 of the ADC reference). As I understand it the \$V_{REF-}\$ and \$V_{REF+}\$ pins are now available for general use (although I did not find it documented explicitly).

But taking a look at Table 16-1 and Figure 16-2 on page 116 in the datasheet, it looks like the \$V_{REF-}\$ and \$V_{REF+}\$ pins always have to be connected. Especially the diagram in Table 16-1 confuses me (I marked it red. Shouldn't I be able to connect it to \$AV_{SS}\$?).

The first part of my question: Do I always have to connect the \$V_{REF-}\$ and/or \$V_{REF+}\$ pins or can they be turned into general purpose pins?

The second part of my question refers to the ADCHS.CH0NA configuration bit on page 18-8 in the ADC reference. Here I can set the negative input (=negative voltage reference?) to the ADC: AN1 or \$V_{REF-}\$. AN1 is obviously a pin. But what about \$V_{REF-}\$? They map both to the same physical pin. Does \$V_{REF-}\$ in this case refer to the settings of the ADCON2.VCFG<2:0> configuration bits or to the actual pin (that wouldn't make sense at all)?

I ask this second question, because in table Table 16-1 I mentioned above they (\$V_{REF-}\$ as negative voltage reference vs actual pin name) are not the same.


texts: Constant V/F ratio control of Induction Machine

texts:
I am trying to simulate the V/F control of open end winding Three Phase Induction Machine, this involves a PI controller to be placed for acting on error(ref speed - actual speed ) of motor. I got stuck at deciding values of gains of PI. What could be the approach to get these values. I can think of going with three phase model of IM but i feel like going in wrong direction. Please let me know your views.
Thanks in Advance!!


texts: replacement capacitors - picture attached this time

texts:
https://photos.app.goo.gl/Auk8US8urgpGgjfK6

Not sure if the picture is visible - if not please ignore posting!
These are the capacitors I want to replace but I don't know what type they are.


texts: What can be said about the nature of the noise by looking at this spectrum?

texts:
I use some industrial amplifier modules where each of them amplifies force transducers. All amplifiers are powered by a single power supply and the output.
Amplifier is set to 6kHz filter. And there is no anti-aliasing filter in the system.

Interest of frequency is max 10Hz and the sampling rate is 500Hz. Sometimes when the noise noise appears at the sampled outputs it has a peak around 3.1Hz. So this corrupts the readings below 10Hz.

I took some offset readings to observe the electrical noise better.

I have the following 12 seconds of noisy signal in time series:

And here 1 second view:

And below is the FFT of the signal:

(left-click to zoom in)

And finally comparison when that 3.1Hz noise, green when it is there and the blue plot when it is not there:

I still could not find the source of this noise.

But just by looking at these plots, what can that 3.1Hz noise be?
Can that be aliasing?  If so, is there a way to estimate the real noise freq. by looking at the peaks at FFT given that we only have 500Hz sampling rate?


texts: controlling vibration frequency and amplitude of a motor

texts:
I want to build a hardware circuit that can control the frequency and amplitude of motors. I have a few questions about this.

1) What kind of actuator do I need to use?
I have used ERM motors and the frequency and the amplitude changes together with different voltages. What kind of actuators and drivers do I need to use to control the frequency and amplitude (varying frequency with the constant amplitude or varying the amplitude with the constant frequency).

2) How can I control the actuator?
I looked into some datasheets about LRA and tactors, but I couldn't find how to control their vibrations. Please leave a link or some comments about how to use the actuator in the question 1. (Using Arduino or other microcontrollers).

3) I have used other ERM motors for other project (e.g. the motor in this link. http://www.adafruit.com/product/1201). Is there any actuator that I can control the frequency and amplitude as described in question 1 with the small size like the motor in the link?


texts:
I am trying to simulate a circuit that involves pickup coils in Spice. How would one simulate the magnetic fields that the pickup coils can sense? Additionally, how would one get a frequency response for such an input? (By frequency response, I mean output voltage vs input flux)

One idea I thought of is using a magnetic coupling (K) between the simulated coil and another "input" coil through which a known current can be passed. The current in the "input" coil would cause a current to flow through the simulated coil due to the coupling, and essentially simulate a field causing a current flow. The issue with this problem is that I am unable to get an output voltage frequency response based on the input current (I'm using MultiSim).

Any ideas?


texts: How to show PIC cycles in MPLAB when using PICKit?

texts: The MPLAB SIM has a nice stopwatch that shows the cycle count. But when using a PICKit 3, the stopwatch is not there. Any suggestions on how to bring this function back?


texts: Why would a 150 MHz probe work fine for a 100 MHz oscilloscope?

texts:
I read in many forums that one can use a probe with a higher bandwidth than oscilloscope's bandwidth.

If it is right why it is not a problem? What is the theoretical explanation?


texts: Programming/debugging connector for MCU - best practices?

texts:
I want to ask how to implement programming or debugging interface for a MCU based device.

For example, I have created an ESP8266 based device using development board, everything is working fine and I have ordered a PCB for it. Then I need to flash the MCU over the wires, but for the first time only - afterwards I can use OTA flashing. However I want to have some interface in case things go south and I will need to re-flash it over the wires again. Or, another example, I want to build a small batch of devices (10-50) and flash all of them.

Placing pin header on the board is not good option - it takes some space and creates unneeded wiring. Soldering wires directly to the ESP module worked fine for me, but it is not good option in case of batch or LGA packages without exposed pins.

So, I want to ask - are there best practices for solving this problem?


texts: Review request: DIY DC to 50MHz differential oscilloscope probe

texts:
Given the cost of proper differential probes, i've decided to make my own. The requirements are:

DC to 50 MHz 3db bandwidth
A few selectable input voltage ranges, from 3V pk-pk to 300 V pk-pk
Better than 1/500 common mode rejection ratio
A "good enough" noise figure
Realizable with the limited selection of parts from my local electronics store
Layout feasible for a home-etched 2 sided PCB with hand soldered components.

I have little experience designing high speed analog circuits, so I'd love to receive feedback, including criticism, on the conceptual design. I also have a few questions regarding specific aspects of the implementation:

Could I get away without impedance matching both ends of the coax, given how the carried signal would barely reach 50 MHz and the cable is under 1 m long? I'd prefer only terminating the scope end into 50 ohms (and directly driving the coax at the probe end), as a series resistor of 50 ohms at the probe end would divide the voltage seen by the scope by 2.
Are the BJT current sources fast enough to sink a constant 5 mA given a high amplitude (3 V pk-pk at JFET gate) 50 MHz signal?
Is the addition of an inductor between the source of each JFET and the collector of the corresponding BJT a reasonable way of ensuring a constant JFET drain current at higher frequencies, or does such a circuit inevitably oscillate?
How sane is my PCB layout, are there any glaring shortcomings? What would you do differently?

For supporting various voltage ranges, my preliminary design relies on external passive attenuators which plug into the 3 pin header connector (J1). The attenuators will have trimmer resistors and capacitors for matching the inverting and non-inverting inputs over the entire frequency range. Illustrated below is a 1:10 attenuator (roughly +/- 30 V range).

simulate this circuit – Schematic created using CircuitLab

The amplifier front-end is realized with JFET source followers in order to provide a high impedance to the attenuator stage. This topology was selected in order to circumvent the relatively high input bias current (worst case 2μA) of the available op amp. Bipolar transistor current sources ensure a relatively stable drain current to the JFETs over the whole input voltage range.

The op amp -based differential amplifier is also responsible for driving 1 m of RG-174 50 ohm coax. While the op amp is advertised as being able to drive coax directly, there are footprints for termination resistors.

Power is delivered by a 9 V battery, with the other half of the op amp acting as a virtual ground source. A red LED performs the dual function of indicating that the probe is on, and providing a ~1.8 V bias voltage for the current sources.

Components:

Low leakage (< 5nA), 2pF input protection diodes: BAV199
JFETs: SST310
BJTs: BC847b
70MHz GBW, 1kV/μs dual op amp: LT1364
4x precision resistors (0.1%, 2.2kΩ) for the diff amp section.


texts:
I have an MSP430F169 that I'm trying to program using the BSL protocol. I don't have a JTAG programmer. Unfortunately, the MSP430F169 responds with NAK (A0) even to the unprotected commands (except the sync):

Get version:

(sync)
DATA WRITE: 80
DATA READ: 90 (OK)

(get version)
DATA WRITE: 80 1E 04 04 00 00 00 00 7B E5
DATA READ: A0 (NAK)

Mass erase:

(sync)
DATA WRITE: 80
DATA READ: 90 (OK)

(mass erase)
DATA WRITE: 80 18 04 04 FE FF 06 A5 83 B9
DATA READ: A0 (NAK)

The MSP430F169 is supposed to come with BSL version 1.61 (according to SLAU319N, page 37), so the version command is supposed to work. In the web page https://e2e.ti.com/support/microcontrollers/msp430/f/166/t/468602 the author discusses a different issue but reports that his MSP430F169 responds to the version commands.

Regarding the mass erase, I saw in another page that despite the AL AH bytes being documented as don't care, they actually needed to be a valid flash address in some devices/BSL versions. So I've tried sending all of the 0x10000 AL AH combinations, but to no avail.

As far as I understand, the JTAG fuse doesn't affect the BSL, but I'm not sure about that. In any case, I don't expect that the two MSP430F169 boards I have to both have come with their JTAG fuses blown, as supposedly this isn't second hand equipment. Is there any other protection mechanism that could be affecting the BSL?

Any ideas on how to solve this issue?

Edit:

Here's a 'scope capture of the sync and mass erase command (no delay between bytes, to fit in the 'scope window). Everything looks fine to me and to the UART decoder:


texts: What differences between MAX3232 and MAX3232E?

texts:
I'm wondering if just ESD protection or something differs in MAX3232E vs MAX3232. Did I miss something?

I know for C as consumer and I as industrial that differ in operating temperature intervals.


texts: Can someone help finding V(infinity). Ive gotten V(0+) at 93 V. the second circuit i got is attacked below. Thanks!


texts: Can a power bank power a stepper motor with these specs?

texts:
I'm a noob at EE and I'm doing a school project that I'd like some input on. I'm planning to use an Arduino to control a stepper motor and I want to use a typical power bank that would be used to charge a phone to power the stepper motor. Here are the specs:

power bank outputs 5V (I'm not sure what the current rating for output is)
stepper motor is rated at 2VDC and current rating is 2.8A

Would this above set up work? If so, would I be able to get away with a stepper motor that's 3.3VDC/3A? Thanks in advance!


texts:
I am working on a project that requires me to mount a WiFi antenna underneath a roof made of metal sheet. The antenna is mounted at a 2 m height, and the roof is just a few inches above the antenna.

I am using an omni-directional (dome shaped) antenna at the 5 GHz band. The proposed solution is to have a cut out on this metal sheet such that the antenna would still be able to transmit through it hence I was asked to provide the metal free zone required for my antenna.

Is this metal free zone related to the near field of the antenna? Or am I stupid. Please help


texts: Level system of water tank?feedback of close loop?

texts:
I have attached a photo from animation from following link

https://beta.spiraxsarco.com/learn-about-steam/basic-control-theory/basic-control-theory

this photo shows a float in a water tank, it appears to be close loop  controlsystem but how it is close loop system?where is feedback?


texts: How to calculate the output impedance of a adjustable RF amplifer to match the input of a mixer using SA605 chip

texts: I have a FM receiver design I wish to implement using the SA605 chip. The stage before feeding the signal to the SA605 chip is a RF amplifier. I know I have to impedance match between each stage to obtain maximum power transfer. I am just not sure how one goes about in calculating the output impedance of an adjustable RF amplifier stage that uses LC tanks to tune between 88MHz to 108MHz? My goal is to match the output impedance to the input impedance of the mixer of the chip. Furthermore, I have found online a couple of App notes discussing how to design the impedance network between the output of the RF stage to the input mixer of the SA605 chip but its in respect to a specific frequency( n SA605). How would one select the frequency of the mixer? Note A L.O is also mixed with the R.F signal, which will be adjusted respectively to maintain a constant 10.7MHz Intermediate Frequency.


texts: Capacitance measurement, mpr121 touch sensing keyboard

texts:
I have been assigned a project where I have to use interface an MPR121 capacitive touch sensing controller with a microcontroller. Aside from the touch detection, one of the requests for the project was capacitance measurement from the touch pins, and to display it's change using graphs.

image credit

I know that I can get the capacity of the electrode from 2nd filtered data registers that contains 10 bits of data, 2 msb and 8 lsb.

My question is do all these 10 bits represent the capacity, or are they used for some other info rather then only capacity? Thank you.


texts: How are voltage references established in low-power designs?

texts:
I've learned that most Zener diodes require something on the order to 20mA in reverse bias in order for Zener breakdown to take place. However, devices such as the LM431 "Adjustable Zener" can begin regulating at as little as 0.4mA. I understand that the LM431 is basically a non-inverting op-amp with a reference (nowhere close to a passive Zener diode). How are low-power fixed voltage references established?

Edit 2017-06-23:

To clarify, I would like to know how a reference voltage can be generated inside of an IC such as the LM431. I'm mainly interested in the general design techniques used to generate reference voltages in linear/switching regulators, comparators, op-amps, supply supervisors, etc.

I have seen multiple "textbook" regulator designs, but many of them are designed for discrete implementation, and they generally use a Zener or a forward-biased diode to generate a semi-stable reference voltage connected to the output via negative feedback.


texts:
I'm having that touch sensor ST IC ST1633i.
It's integrated into an LCD. I'm trying to interface with it, but don't know or understand the actual protocol.

Here is the protocol

So I'm trying to write multiple data as shown

as shown in the figure, I have to write a start header 0xaa, then the data register that I plan to read which is 0x12.

status = HAL_I2C_Mem_Write(i2c_handler, 0xaa, 0x12, I2C_MEMADD_SIZE_8BIT, 0x01, 1, 1000);

Then I read

 nbTouch = TS_IO_Read_Multiple(0xab, 0x12, buf[0], 1);
  nbTouch = TS_IO_Read_Multiple(0xab, 0x12, buf[1], 1);
  nbTouch = TS_IO_Read_Multiple(0xab, 0x12, buf[2], 1);

In all cases Read and for Mem_Write it gives me HAL_ERROR with ACKF error
I'm using I2C1.

#define DISCOVERY_I2Cx_TIMING                      ((uint32_t)0x40912732)


texts:
I'm learning about different ways to interface physical switches to microcontrollers and I don't understand how scanning interfaces work.

I am told in the notes that the software from the microcontroller would scan each row at a time, in the following scanning pattern:

I dont really understand how it could work, and how the limitation is that it can only detect a maximum of two simultaneous switch closings.


texts:
I have an equation

  y = ab + cb'

How would I implement this with only NOR Gates?

Thanks


texts: Why does DIV AB converts from hex to decimal 8051

texts:
I was trying to solve a problem and I read that this code converts a number from hex to decimal
I mean why . My idea is that div is just for division
can somebody answer my questions that I left as comments

MOV   A,#0FFH      ;why do we need to do this
 MOV   P1,A         ;P1 as an INPUT
 MOV   A,P1         ;Get data from P1
 MOV   B,#10        ;to convert from hex to decimal
 DIV   AB           ;that the question why does div used to do this conversion
 MOV   R7,B         ;does this put 10 in the register r7
 MOV   B,#10
 DIV   AB
 MOV   R6,B         ;it does also puts 10 in the register r6?
 MOV   R5,A         ;if A <10     (why does this do )


texts: What happens when an LCD screen turns black/shuts off?

texts:
I read about how an LCD screen works here, and it made me wonder what actually happens when the screen shuts off. Based off of this, I can think of several possibilities:

Electricity is supplied to all the pixels/crystals, thus making them all appear dark. While this fits with the on/off explanations given in that article, it seems like a significant waste of energy to use extra energy when not in use.
Electricity is not supplied to all the pixels, which would light them all up, but the backlight shuts off, so the screen appears dark.
Electricity is maintained to the pixels that were receiving electricity when the screen was on, but the backlight shuts off so the screen appears dark.

I would be curious to know if different phases of the off screen are different (such as a off-screen-like screen saver versus a sleep mode or being shut off, etc.).


texts: Need Help dropping voltage on a signal wire

texts: I am working with a Hall eletric throttle switch 0-5v operation. It is powered by 5v dc. The signal wire reads .86v when in the neutral position and 4.8v fully pressed. I need the starting point to be .5v or lower. Now the voltage of the signal wire needs to run between .5-4.5v as the switch is pressed. There is no load on the wire as it simply sends the voltage to the ecm to increase or decrease the throttle. What do I need to drop the voltage roughly .5 across the scale?


texts:
I have two motors:

24V Mabuchi RS-385PH (liftgate latch)
12V Mabuchi FC-280PT (door lock actuator)

How to know if they are working properly (clockwise and counterclockwise)?
*I have a multimeter.


texts: Can PNP BJT have its collector grounded?

texts:
I am designing a piezoelectric motor driver

To save me inverting the H-bridge driving signal to provide a differential signal (as would be needed in the H-bridge shown) can I flip one side of the bridge so that the PNP is at the 'bottom' and therefore has it's collector directly connected to ground? Therefore I could driver both sides of the bridge from the same signal


texts:
I would like to know how to build a power limiting circuit.

The goal is to be able to combine two PSU's with the same voltage in parallel in order to increase the Power output.

From what I've tested, when I connect two 9V PSU with a Y cable (in parallel), one of PSU's take most of the load and the other is outputing less than half the total Power.

What I would like to assemble is a circuit that would either limit each PSU's power draw to 9W (1A @ 9V or 0,75 @ 12V) or, at least, balance the load on each one (to draw 15W, one gives 7,5W and the other 7,5W as well).

Do you have any idea on how I could acomplish that?

Thank you


texts:
I'm trying to write some code that waits for a pin to change before continuing but it doesn't work. The code that I already have is:

do{
    LATBbits.LATB6=1;

}while(PORTBbits.RB14== 0);

LATBbits.LATB6=0; ... d something else

The RB14 pin is already configured as an input.
I want it to wait until RB14 is high before continuing the code execution. I'm using a pic24f16ka102 microcontroller.


texts:
Oki, so I'm building a 16 bit CPU in logisim and I finished the adder and the subtracter and the NAND gate functions. Then I was like hmmm, right or left carry?
Left is used for multiplication, right for division but since im not good at RISC coding (cause yah, its gonna have RISC ISA) I might not implement it also it will take many more cycles. While I can make multiplication and not division I think I should go with the left carry but im not sure? Which one shall I use, or shall I use both? Thx


texts: What is the difference between TO-3 and TO-204AA packaging?

texts:
I am trying to build a circuit for a power amplifier and TO-204AA is the packaging used in the circuit diagram.
KiCad does not have TO-204AA but it has TO-3.
Looking at the image below you will see that there is a difference of approximately +- 0.45 millimeters between the two packages.
Is this a lot?
Will it matter if I exchange the two?


texts: How can I use multiple Arduino-read photo resistors without interference between them?

texts:
I'm working on a prototype that utilizes a combination of photo resistors and LEDs to simulate a "tripwire" to detect when a coin falls through a clear tube. When using one tube, one photo resistor, and one LED, the analog readings from the photo resistor are pretty reliable; however, when using this combination for a pennies, nickels, dimes, and quarters, the readings from each photo resistor are all over the place. Some suggested that this might be noise interference between the arduino and the circuit.

Could someone give me an idea of what my problem might be and a possible means of alleviating said problem?


texts:
For the complex power equation S=1/2VI, are the V and I the real and imaginary parts or is it just the magnitude?

For example, if I have V as 3+4i and I as 2+6i, is my complex power just 1/2*(3+4i)(2+6i)?

Thanks!


texts: Li-Ion battery charging as simple as possible

texts:
I have read articles here and there about charging Li-Ion batteries. Most of them try to solve the problem of maximizing capacity and also maximizing cycles. The most recommended method is charging with around .5C current until the battery reaches 4.2v and then switching to the constant voltage until the current gets less than a threshold and then stopping it.

I don't need the battery to be fully charged, even half the capacity of 250mAh battery can run my circuit for days, and the circuit is almost always using external power source. I want to see if using no control circuit, but offering a lower voltage, for example 3.7v and limiting the current to for example 50mAh will hurt the battery in long run. Minimum parts in my circuit is essential for me, so I would be glad if I could remove as much as possible! Thanks in advance.


texts:
I'm designing a device with 3.6V Vcc and RGB LED. Blue part of an LED has the voltage drop in the range of 3.2..3.6V and i have to drive it with current limited to 30..50mA. This gives a restriction to the current limiters choice.
I fear that a simple resistor or BJT current source will have a significant voltage drop that will disable my blue LED.
I'm looking at the low Vce(sat) transistors for BJT current source but haven't got them yet (and it seems difficult to me), so i maybe need a MOSFET+inductor current source schematic. Is this possible?


texts:
I have a DAC (datasheet available here) that has a SLEEP mode (see page 14). When SLEEP mode is activated, my oscilloscope reads an output voltage of about 1.65V on each output, which is about half of the supply voltage if 3.3V.

I want to check that this output voltage makes sense, but the datasheet doesn't seem to provide the information. (It specifies that the output current is turned-off, but that's it.)


texts: In an AC coupled Op-Amp circuit where do input bias currents flow from?

texts:
If we have an AC coupled amplifier like the one below, i've read and been told it needs a DC path to ground to allow input bias currents to flow, though I just can't get my head around this, I bias is drawn from ground? physically how does this work?

With reference to the circuit below the bias current seems to be drawn up from ground, fi no input is provided where is the driving source? is this related to internal biasing and therefore the power rail is the source?


texts: Transfer function of RLC circuit without input source?

texts:
Let's say you have an RLC series circuit with an initial voltage across the capacitor and no initial current, and no input voltage driving the RLC circuit, that is: $$v_\text{input}(t)=0$$

The output of the RLC circuit $$V_\text{output}(s)$$ is the voltage across the capacitor.

How would you find the transfer function H(s) of this circuit, since its doesn't have an input?

$$H(s) = V_\text{output}(s) / V_\text{input}(s)$$

The textbook says the transfer function is just:

$$H(s) = V_\text{output}(s)$$

Isn't the Laplace transform of a zero volt input voltage source equal to zero?

$$V_\text{input}(s) = \mathscr{L}[0~~volts] = 0$$

Therefore:

$$H(s) = V_\text{output}(s)/0 = \infty$$

Just curious how they get the result:

$$H(s) = V_\text{output}(s)$$


texts: Why we need start/stop bit for asynchronous transmission

texts:
I was reading a book which says

  Asynchronous transmission is so named because the timing of a signal is unimportant. Instead, information is received and translated by agreed upon patterns.  To alert the receiver to the arrival of a new group, therefore, an extra bit is added to the beginning of each byte. This bit, usually a 0, is called the start bit. To let the receiver know that the byte is finished, 1 or more additional bits are appended to the end of the byte. These bits, usually 1s, are called stop bits.

As the picture below shows:

I don't quite get the idea, why do we need a start/stop bit? Isn't that a byte consists of 8 bits, so the receiver just needs to count how many bits it has received so far, if the number is 8, it has one byte and repeats the process. So why do we need start/stop bit?


texts:
I have a very simple power supply circuit, consisting of a 220V:22V transformer, full bridge rectifier (1n4007 diodes) and a smoothing capacitor (electrolytic, 4700uF). The output voltage should sit around 28V. For some reason, the output voltage is often around 0.5V. This is the case even when there is no load attached. I’ve checked all my connections, checked that my diodes are working with a multimeter, checked that the peak forward current doesn’t go over the maximum using LTspice, replaced the capacitor (I replaced the 4700u with two 10000u in series to five around 4700u but this made no difference).
The circuit I’m ultimately trying to build is quite complex but I can’t even get the power supply to give a 28V output. Any ideas why this is the case?


texts: Constant current LED driver using transistors

texts:
I have this circuit:

I understood the operation:

On power-up Q1 and Q2 are off. There is no collector current so L1 is off.
If the digital control input on the left is brought high (5 V) Q1 will turn on. Current will flow through L1, Q1 and R2.
As the voltage drop across R2 increases to about 0.6 V Q2 will start to turn on and shunt some of the base current away from Q1.
The result is that the circuit will settle at whatever Q1 emitter current will drop 0.6 V across R2.

Questions:

Are both the transistors (Q1 & Q2) in the active region at all times during operation?
Will the load current through the load resistor and the LED will always remain constant and not exceed the limit regardless of the situation?
Is there any scenario when either of the transistors will go into saturation or cut-off during powered condition?


texts: Get an output (like a voltage or dry contact closure) from any/most typical digital alarm clocks?

texts:
New to the community and less than a hobbyist so please advise if this question should go elsewhere.

I am not noting a particular alarm clock or model because I would like this to be repeatable across any/most generic store-bought types of digital alarm clock.

What I'd like is to have the user set the alarm clock as they normally would and when it 'rings' I need some form of an output.  This should be either some sort of voltage (nothing high or high amp, 5 or 12v and 100 or 200ma should be plenty) or perhaps just a contact closure.

This would then be taken to a home control system to perform whatever tasks are wanted for wake up and so that is why the question is in generic terms.

Can this be achieved in a way that can be generically applied to most alarm clocks and if so how? (in somewhat noobish terms if possible)


texts: Need to convert a 12V/300ma alarm output to a dry signal that will interface with my security DVR

texts: Is there a relay that will work with 12V / 300ma input to close a Normally Open output? I've been trying to make it work with Ardouino board and a HiLetgo 12V 1 Channel Relay Module With Optocoupler Isolation Support High or Low Level Trigger, but have not been able to get it to work.  Seems like there should be a simpler solution that doesn't involve a controller board.


texts: How to make the hottest CPU temperature?

texts:
Besides just running an infinite loop, are there any tricks (like maybe cache misses?) to making a CPU as hot as possible?

This could be architecture specific or not.


texts: How does an inverting op-amp feeds back 0 volts when the Vout is not 0

texts: So, I'm a Computer Science major, and have this class, Analogic and Digital Circuits. I'm learning the op-amp now. The inverting op-amp has something that I just can't comprehend . I understood the algebra that lead to Vout = (-R2/R1)*Vin. But, the feedback, Vout is going into V-. V- and V+ are aprox 0. How can Vout be 0V, and another bigger value at the same time?


texts:
I am considering taking a commercial available, FCC certified tablet (with 802.11 b/g/n) and packaging it in a plastic "clamshell" with an additional battery to prolong run time for a specialized application.

What would be the FCC requirements in such a situation since the "clamshell" will likely obscure the tablet's FCC label. Would it require a re-test and our own FCC id for the product?


texts:
I've connected a scope probe directly to the ground clip of the scope.  I then observe the signal on the scope and it's reading 0, as expected.  I set my trigger to be 1V above the 0V reading it currently has, put it to single, set the timebase to 100ns/div.  At this point, i plug a standalone usb thumb-drive into the scope usb slot.  The scope immediately triggers and I see a huge oscillating waveform (Vp-p about 8V, around 0V) being picked up for the duration of the 1us that is viewable on screen.

My question is, why does this happen, and can I somehow minimize the effect or prevent the scope from picking it up?

I'm using generic passive scope probes, 500MHz, 8pF, 10MOhm.  I was originally trying to find any power rail irregularity, but I noticed my scope keeps on triggering with these kind of spikes.  The USB thumb-stick was the best way that I can reproduce it consistently.


texts: Turning on multiple leds with arduino using transistor

texts:
I want to be able to turn on 50 red LEDs with one pin of an Arduino. I don't want individual control, I just want to be able to turn them all on or all off.

I found this example. It uses a 2N3904 transistor. Is this the approach I want to take? I presume I would need a higher power transistor?

I am using an external power supply that is wired into a custom board with a 5v voltage regulator so I am powering the LEDs directly from this regulator.

The LEDs come in the form of this LED light bar array (or at least very similar)...

I had mentioned in a comment in an answer below that I was using a 330 ohm resistor with each LED. On another part of this project, I use the light bars as level meters, and each separate LED is controlled via a shift register, thus the separate resistor. I realise after thinking about it that I don't need to have a resistor in series with each LED for this now as they are either all on or all off (hmmm.... sorry for my rather haphazard comments!).

I did have a thought that I could have some sort of electronic switch that can disconnect ground or 5V. Is this viable?


texts: My Coilgun Stage Driver Keeps Burning Out Mosfets. Any idea why?

texts:
Here's my stage driver circuit:

The circuit worked as expected at around 100v. But at 330, both mosfets burned out at the first firing, and the entire cap bank discharged through the coil. I thought it might have been an issue with my firing circuit so I replaced the mosfets and tried again. Again, burned out immediately.

I can't figure out why. The mosfets are rated for 650V, and a pulse current of 520A, which I don't think I've exceeded. The gate drivers are very strong, so I don't think switching speed is the issue.

HV is a 330v 5400uF bank of flash capacitors.

The MCU is programmed to turn on both fets for 100uS, and then turn them off. I checked, and it does. I also checked the mosfet gates (without the cap bank connected), and they pulse up to 12v as expected. The rise time is very quick, <100nS.

The coil is approximately 686uH, with a DC resistance of 1.8 ohms.

The mosfets are normally 20 bucks each on digikey, but I was able to find 10 of them on ebay for $8 each. Maybe they're counterfeit.

Update: Here's my layout:

Datasheet Links:

Gate Driver IXDN614PI
Mosfets STY139N65M5
Diodes C3D10065E
Optocoupler 6N136
Isolated DC/DC Converter PDSE1-S5-S12-S


texts:
I am trying to analyze the circuit given below:

The reference node is in the bottom with 0 V.
At nodes A and B writing down Kirchhoff’s first law equation trying to express each current in terms of the voltage across the branch.
My equation for node A looks like this:
$$
 \frac{V_{G_1}-V_A}{R_1} - \frac{V_A-V_{reference}}{R_2} - \frac{V_A-V_{reference}}{R_3} + \frac{V_A-V_B}{R_4} + I_{G_2} = 0
$$
For node B:
$$
-I_{G_3} -  \frac{V_B-V_{reference}}{R_5} - \frac{V_B-V_A}{R_4} + I_{G_2} = 0
$$
As of now I only have two equations and three unknowns. Therefore I am not sure if my solution attempt is correct.


texts:
I'am trying to solve this problem using superposition but can't seem to get the right answer.

The problem is to look for the voltage in R3 in the following circuit:

The V1 graph is green
The R3 voltage graph is red.
(The red graph, R3's voltage, goes up to about 11V and stays there
until the .5ms and then goes down to at about -71V)

I used LTSpice to find the voltage in R3 and it came out to be this:

Could someone tell me what technique to use and how to start please.

Edit 1: It was hard to see the R3 voltage graph colored blue, so changed it to red.


texts:
I want to make a very cheap tester that I could use on cables that are used in the field at my company. We usually use multimeters but not everyone knows how to use one. It would basically be like a power supply tester on a computer.

How could I do this if the voltage is 14 V dc?


texts:
I have to choose a cable that will be bent and may be "stretch" a bit by our users. Which gauge would you advice between 24AWG and 26AWG to resist better ?
I guess it is better also to have more conductors to get a more flexible wire

For the "plastic" around the conductor which type is better (silicon/non silicon)

Thanks


texts: Energy Harvesting Primary VDD and Battery Backup VDD power for MCU

texts:
Currently I am in the design process of circuitry for my energy harvesting circuit. I am using the CC1110F32 MCU from TI. I am using the Development kit boards that they created for this project.

The goal of this design is to have the MCU powered primarily by an energy harvesting unit we created. This module uses an LTC3108 energy harvesting chip coupled with a CP85 peltier module. The peltier module is being used as a Thermo-Electric Generator and we expect to receive .37 mV per 1 delta T (in degrees F).

What I need help figuring out is a way to have the MCU primarily powered by this energy harvesting circuitry, but in the event that the energy harvesting unit cannot support the power/voltage required by this MCU, the batteries (a set of two AAA alkaline) will power the system as a secondary method. Once the TEG's super-cap/direct voltage output has achieved that level again, the batteries will no longer be drained and the energy harvesting unit will once again be powering the MCU.

I am currently considering using some basic hard wired logic with MOSFETS/Diodes, but I don't want to have to use an I/O pin from the MCU to drive a MOSFET to change the location of the power. (If necessary I could, the system is quite low power) Also, I don't want the possibility of a MCU shutdown when the energy harvesting unit cannot supply the correct voltage.

If anyone has any thoughts, I thank you for your time and your collaboration.


texts: A test circuit requires to generate 1V (50Hz, sine) using a voltage divider made of capacitors. Simulation of the circuit using two identical ceramics capacitors (±5%) gives half of the input voltage as output, as expected. But on breadboard using signal generator, two identical capacitors, and picoscope, I get very small (less than 100mV) output. Any idea about this? Here is the test circuit:


texts: Passing inout port through hierarchy in Vivado

texts:
I am trying to build a driver module for the SMI interface on my ethernet PHY.  My top level module contains the following ports with eth_mdio marked as inout.

    module top
    (
        input        clk_100,
        input        cpu_rst_n,

        output       eth_mdc,
        inout        eth_mdio,
        output       eth_rstn,
        inout        eth_crsdv,
        inout        eth_rxerr,
        inout  [1:0] eth_rxd,
        output       eth_txen,
        output [1:0] eth_txd,
        output       eth_clkin,
        inout        eth_intn,
        input  [15:0] sw,
        output [15:0] led,
        input         btnc
    );

    ...

    smi smi_inst
    (
        .clk_50(clk_50),
        .rst_n(rst_n),

        .valid(read_reg),
        .write(0),
        .phyaddr(0),
        .register(sw[4:0]),
        .read_value(led),

        .eth_mdc(eth_mdc),
        .eth_mdio(eth_mdio)
    );

    endmodule

Inside the top module I create an instance of a submodule called smi which has the following ports.

module smi
(
    input         clk_50,
    input         rst_n,

    output        ready,
    input         valid,
    input         write,
    input  [4:0]  phyaddr,
    input  [4:0]  register,
    input  [15:0] write_value,
    output [15:0] read_value,

    output reg    eth_mdc,
    inout         eth_mdio
);

Inside of smi I assign eth_mdio as follows...

assign eth_mdio   = state == STATE_IDLE ? 1'b0 : (state == STATE_READ ? 1'bz : send_buffer[64]);

When I go to synthsize the design I get the following critical warning...

  [Synth 8-5744] Inout buffer is not created at top module top for the pin eth_mdio, other connections may not have buffer connection ["/home/chase/workspace/EthernetTest/src/top.v":3]

What is causing this and how can I fix it?  How can I pass an inout through the hierarchy?


texts:
I am a hobbist in electronics, meaning I don't have any really training on electronics. Anything I know about electronics is read from books, YouTube or this site.

I am trying to design a circuit that activates a relay when a certain temperature is reached. I also want the temperature to show on an LCD. I have chosen a PIC16F877A-I/P. I have never done this before, so I am in the process of learning C machine language.

I have the circuit designed, but my biggest challenge is determining the amps that this circuit (and each component is drawing) so that I can work it out on paper, before I blow a component up. I read in the datasheets what the Max current is, but does this mean that is the current that it will draw? Does the current build up through each load? Is the end current greater then say in the middle, before a couple load (e.g. voltage regulators)?

I have attached a picture of my schematic. I may be way off. If so, please enlighten me. You will also notice that I have not finished wiring to the LCD or MCU. I am not entirely sure how to wire to the LCD I picked (NHD-C0216CZ-NSW-BBW-3V3-23858). If anyone has tips on how to wire this LCD, this would help also. It does not have the typical 7 data pins. Please help!


texts: How can I reuse this set of buttons from an old Sky cable TV box?

texts:
I'm quite inexperienced with electronics in general, so there could be inaccuracies in this.
I have taken the circuit board from an old sky (cable/satellite) box that had some buttons on it. It has a 8 pin ribbon cable attached to it and 9 buttons. The only other components on the board are 3 diodes.
It's a fairly simple layout so I was able to use my multimeter and work out this diagram.

Now, I was planning to connect this to a micro controller, a pi pico to be specific. However I can't work out how I can read which button has been pressed. (aside from IO7 & IO8)
I was thinking that I could supply 3.3v on each of the diode inputs, but if I do that then multiple buttons can trigger the same IO output.
My next thought was that I could supply each of the input diodes one at a time, scanning the outputs before moving to the next input. I imagine I can do this on the controller, but wasn't sure if that's the best way to go about this?
Is this a common type of button setup? I'm happy to do a bit more googling if someone can give me the right keywords.


texts: How to calculate the \$\mathcal{H}_2\$ norm of a second order transfer function?

texts:
I'm having trouble to calculate the \$\mathcal{H}_2\$ norm of a second order transfer function
$$H(s) = \frac{\omega_n^2}{s^2+2\xi\omega_ns+\omega_n^2}$$
where \$\xi>0\$ and \$\omega_n>0\$. I know that the \$\mathcal{H}_2\$ norm is given by
$$||H_2|| = \bigg\{\int_{-\infty}^{\infty}|H(j\omega)|^2d\omega\bigg\}^{1/2}$$
and that the magnitude of the frequency response is given by
$$|H(j\omega)| = \frac{1}{\sqrt{\bigg(\dfrac{2\xi\omega}{\omega_n}\bigg)^2+\bigg(1-\dfrac{\omega^2}{\omega_n^2}\bigg)^2}}$$
Can someone help me with this? Is there another away to calculate it?
Thanks a lot.


texts: Upgrade user application using custom bootloader via UART (STM32)

texts:
I'm using an STM32L4 board and my flash memory looks like this:

  |______________
  |
  |  USER application
  |
  |
  |______________
  |Vector table(UA)
  |______________  0x8000 - 8000
  |
  |  Custom Bootloader
  |
  |
  |______________
  |Vector table(BL)
  |______________  0x8000 - 0000

My board is connected to another board using UART (Let's define the other board as Master and my board as Slave).
Master board shall be able to upgrade the user application of Slave board via UART. The idea is to send a binary file via UART and write it in the user application section.

According to ST's application note, there is a command called Write Memory command:

  The Write Memory command is used to write data to any valid memory address (see note below) i.e. RAM, Flash memory, option byte area
  When the bootloader receives the Write Memory command, it transmits
  the ACK byte to the application. After the transmission of the ACK
  byte, the bootloader waits for an address (4 bytes, byte 1 is the
  address MSB and byte 4 is the LSB) and a checksum byte, it then checks
  the received address. For the Option byte area, the start address must
  be the base address of the Option byte area (see note) to avoid
  writing inopportunely in this area.

  if the received address is valid and the checksum is correct, the
  bootloader transmits an ACK byte, otherwise it transmits a NACK byte
  and aborts the command. When the address is valid and the checksum is
  correct, the bootloader:

  • gets a byte, N, which contains the number of data bytes to be
  received

  • receives the user data ((N + 1) bytes) and the checksum (XOR of N
  and of all data bytes)

  • programs the user data to memory starting from the received address

  • at the end of the command, if the write operation was successful,
  the bootloader   transmits the ACK byte; otherwise it transmits a NACK
  byte to the application and aborts the command

  • The maximum length of the block to be written for the STM32 is 256 bytes

This means that I can only upgrade 256 bytes by a packet coming from Master board to Slave board.

Now let's say that Master board has an SD card that contains a binary file and I want to flash this file to the user application section. How can I do this? Should read the binary file, and send a series of 256 bytes, each 256 in a packet?


texts:
I am presently working on an energy harvesting system using RF signals. I have read some of the other posts made on this topic and have learnt quite a few things. However, I have some questions that I would like answered just to clarify some doubts.

The intention is to acquire 2.4 GHz wi-fi signals from an AP (access point) to an antenna.

That antenna that I am planning to use is either a quarter wave whip antenna (with a ground plane) or a half wavelength dipole antenna tuned to 2.4 GHz. Since its omni-directional, I can expect the gain to be around 3 dBi. I am still unsure about which antenna would be most suitable. According to my theoretical study, a half wavelength is more appropriate as I can acquire more energy but then someone suggested a quarter wavelength is more suitable. Also, does it matter what type of end connection I require, e.g. SMA connection or a BNC? So I would like someone to shed some light on this or maybe link me to a web address so I can do my own research.

Next, assuming I have selected my antenna, I can expect it to have 50 ohm impedance (as this is generally the case). Now, I need to design an impedance matching circuit to ensure max power is obtained. In order to do this, I have to know what load impedance I have on my harvesting circuit. But here is the issue. Since I am designing the harvesting circuit, I actually don't know what the load impedance is. I understand how to design the impedance matching circuit mathematically speaking, however, without knowing the load impedance, I don't know how to work on this. A friend suggested I work on the next part of my harvesting circuit (which is the voltage multiplier circuit) and based on this, I will have a load impedance which I can use to calculate the impedance matching circuit. Once again, I need some assistance on this. Another source suggested I connect up a "dummy load", however, I need to do some more research on this and how it works.

So to summarize,

1) Which antenna is more suitable for this project? A half wavelength dipole antenna or a quarter wavelength whip antenna with a ground plane?

2) What kind of end connection is needed? E.G. SMA?

3) How do I calculate the load impedance in order to calculate the inductor/capacitor value required for the impedance matching circuit?

The circuit that I intend to design is given in the diagram.

Any tips or ideas I should think about would help. I am still learning. If there are any questions, please let me know.

Regards


texts: Can a M74HC595 shift register directly drive LEDs?

texts: I'm going to use a shift register to turn off and on some LEDs. However, I just read on the M74HC595 datasheet that it can only output 6mA on each pin. The LEDs I got are rated at 20 mA. Do I need the 20mA to power the LED or is 20mA the limit?


texts: DC Power supply stopped working properly

texts: When I needed to set a maximum current I shorted the outputs and set the desired value with the current knobs. Now it doesn't work for some reason. Here's a short video. Any idea what's going on?


texts: Choosing the correct transformer for the dual rail Welleman regulator kit 8042

texts:
I have this dual power supply 1 A kit by Welleman

with this schematic:

My problem is understanding what transformer I could apply. If you have seen schematic, I must select a transformer with two windings on the secondary but the question is:

How could I evaluate voltage and current which exiting from secondary winding of transformer? In general what calculations which I have to apply to dimension voltage and current coming out from the secondary of a transformer in order to select right transformer for projecting my custom power supply?


texts:
I have a Noctua NF-F12 computer fan (specs: https://noctua.at/en/nf-f12-pwm/specification). I also have a Samsung USB Wall Adapter (Originally for charging my tablet). The USB Wall Adapter says it can output 5V 2.0A.

My computer fan, according to the specs, runs at 12V 0.05A. How do I go about powering this? Some have said to purchase a 5V to 12V step up module with a USB connection, then solder the fan wires onto that, and plug the USB end into the wall adapter or would it work if I plugged it into a computer's USB port?

I've also seen DC wall adapters for sale. I saw a 12V DC Wall Adapter, and it says it can output 12V 100mA. However, most of them supply 500 mA, 1A, or 2A. My fan says it only needs 50 mA (0.05A). What happens if I solder the fan wires to this DC Wall Adapter? It is 12V but isn't it too much current? Will this burn out the fan?

Edit: With all that said, is it best to just purchase a DC power supply and splice the fan wires, or can I go with a 5V to 12V step-up module with a USB connection and use any of my USB wall chargers instead?

Thank you in advance.


texts: How do I create a portable, battery-powered relay that switches in the daytime?

texts:
I have been trying to make a (hopefully very simple) circuit for this that just uses a couple resistors, diodes, and transistors that can fit on a small breadboard and be powered by a 9V battery. Something like this would be perfect, except for the fact that it looks to need +12V and -12V, instead of just positive and ground.
I have done a bunch of experimenting with Tinkercad Circuits, trying to use photoresistors and photodiodes in any way I can to get the desired effect, but I keep running into problems with them. The transistor will either go between active and cutoff modes and I don't have the voltage swing to get it to go all the way to saturation, or it can't be tuned at all with a potentiometer, or it uses too much energy when not switched on.
I've never really done anything with transistors before, but I thought I would start at least trying to use them as switches. I understand Ohm's law, I can read circuit diagrams and I built circuits in labs for school, but it was all simple stuff that didn't require a deep understanding of the physics. I think I need to be pointed in the right direction here. Any help would be appreciated.


texts:
I need a motor that can deliver 500 to 4000 RPM unloaded. I figured I could salvage one from an old HD, and now I have one. It has 4 wires, and I measure 25ohms from any two points I measure.

From that can anybody tell me how it is wound, and how I should drive it from a microcontroller?


texts: Why is the threshold voltage kept large in an LED?

texts:
My book says

  ... But the threshold voltage are much higher and slightly different for each color. The reverse breakdown voltages of LEDs are very low.

While I understand that the reverse breakdown voltage should be low because of the heavy doping, but I do not understand reason for high threshold voltage.

I know that the band gap should be higher because the wavelength of the light emitted needs to be smaller. So does band gap have any relation with the threshold voltage?

Edit: I found out that barrier potential depends on the negative logarithm of \$n_i\$ and so does the band gap


texts:
I am trying to build induction heater with the help of the following schematics(taken from this page):

So I am using 220:10Vrms(15Vpeak) transformer with fullbridge rectifier and a capacitor to get 15V DC. If I disconnect everything from this simple "PSU", I do get 15V DC.

But, when I actually connect the circuit and measure my voltage rails I get this strange behavior on my oscilloscope, as you can see it shows 5V with some ripples.

The circuit draws 0.27 Amps on the primary and 1.84 on secondary of a transformer, which I measure with the voltage clamp.

My coil is 1.2 uH (measured with LCR meter).
I use 0.47 uF 250V Polypropylene capacitor.
This should result in approximately 220 kHz resonant frequency.

I also use the choke of 2.2 mH on center tap.
My MOSFETS are IRFP460A.
So, questions:
1) The circuit doesn't work for me, i.e. if I probe the coil there is nothing on it, zero. If I put metal object inside(screwdriver) nothing changes. Also the overall current consumption is not affected(looking at clamp meter) if metal part is introduced.
I already tried to:
Re-wire everything from scratch, making sure everything is connected properly.
I checked the mosfets with simple testing circuit - they both work fine.
I tried to measure MOSFET output on the Drains without coil or cap in the circuit - it also shows zero on both mosfets.
2) Why if I measure voltage on my 15V rail it shows 5V with ripples? It shows perfect 15V DC if nothing is connected to it. Is this some kind of feedback? I have a choke to eliminate high frequency feedback, but overall it doesn't make sense, since the circuit does nothing to cause feedback as I think. The capacitor after full-bridge rectifier is 1000uF, seems enough too.


texts: Voltage Drop Across Capacitor Driven with Square Wave

texts:
I was having a discussion with a colleague. Imagine a circuit with ideal components. The circuit is a capacitor divider (1uF and 1pF capacitors) with the midpoint being pulled down to GND by a 1Meg resistor. We drive the circuit with an ideal 1kHz 1V square wave. What is the maximum voltage drop across C1?

My colleague argued that at t=0, the capacitor C1 will see the entire 1V drop across it, since the midpoint is weakly biased to GND by the resistor.

I argued that the largest voltage drop the capacitor will ever see will be equal to the divider across Z1/(Z1 + Z2). Where Z1 = C1 and Z2 = C2||R1. The value will be almost 0V since Z1 << Z2. The R1 bias resistor is not able to effectively hold the V_mid node at GND, current will mostly flow through C2 (since its resistance is so low at 1Khz).

Who is right? I tired simulating the circuit but it was not enough to convince my friend. Can someone provide a more rigorous physics explanation of what happens at t=0?


texts: Adding Profibus capabilities to a product

texts:
We are currently developing a product and now the "idea" has come up to integrate Profibus since it is quite used in that specific area. Now I was wondering if anyone has made such a product. If I understand correctly, Profibus is actually a RS-485 bus with some additions (especially in layer 2).

According to my research, our device would probably be a DPV-0 slave (Slave device, cyclical data exchange). We are intending to only produce low quantities of this product (max. 200 pcs / year). The whole product is a small sized machine, cost will be around 1k-2k €/pc.

Two options exist:

Implement the protocol stack in software and be limited to lower baudrates + the risk of not being fully standard conform.
Buy a specific IC, e.g. the VPC3+S from Profichip and only handle the required part manually

Now for the actual questions:

Will we need to be a Profibus Member to sell our product?
As far as I understand, every manufacturer needs to create a GSD file for his product, are there any tools available for creating this file?
How can I easily set up a test environment?
Are there any other fabricators of Proficbus ICs compared to Profichip (not only RS-485 transceivers)?
Has anyone already implemented the protocol in software? What were the main challenges?


texts: Induction Motor Rotor Position and Speed Control

texts:
I am not an expert in this, but I have built some basic BLDC motors. I was recently reading up on induction motors. While I understand the idea of the AC causing a rotating magnetic field, the part I don't understand is how the speed is controlled precisely in induction motors.
I know BLDC motors are controlled by an Electric Speed Controller (ESC) that changes the magnetic field orientations based on the position of the rotor. The position of the rotor is determined by a hall effect sensor or back EMF through the coils. From my reading, the speed of an induction motor is controlled by a Variable Frequency Drive (VFD). However, when I dig into the details, the result of this is a change in the speed that the field rotates which seems no different from running a BLDC motor without knowing the position of the rotor (i.e. open-loop). The problem being, that without knowing the position of the motor it is easy for the rotation of the field to get our of sync with the position of the rotor. This is easily seen with magnetic coupling as well, where permanent magnets on the rotor are being dragged around my paired rotating magnets. It works up to a point, but once the rotation of the magnets exceeds a certain speed, the system goes out of sync and the rotor stops spinning.
So, my question is - how is the speed of induction motors controlled precisely without knowing the position of the rotor? Or, put another way - why doesn't speed control in induction motors require knowledge of rotor position, but speed control in BLDC motors does?


texts:
I have been studying DMA provided by the Infineon in XMC4100 & XMC4200 microcontroller series. I have questions that are listed below, everyone will be highly appreciated to answer them and help me to understand the working of DMA. If you find any question IP specific then kindly give its general answer.

When DMA is a flow controller, in which condition hardware
handshaking interface will be used or software handshaking interface
will be used for either source or destination peripherals?
Is the hardware handshaking interface also includes single and burst
request signals along with request and acknowledge signals?
When source or destination peripheral is flow controller then why
hardware handshaking interface is not supported?
When DMA is a flow controller (means DMA knows the block size and
DMA should transfer the data using maximum possible bursts and where
possible using single or early-terminated burst), then why do
peripherals request for single or burst transactions?
For peripheral-to-memory, memory-to-peripheral and
peripheral-to-peripheral single or multi-block transfers, if the
peripheral is either source or destination then address to read from
source and address to write on destination should be fixed
throughout the single or multi-block transfer. Is this a correct
statement?
I have confusions in DLR (DMA Line Router) that how it selects a set
of service sources from a set of DMA compatible service sources?
Then how the selected service sources are further used for hardware
handshaking? Kindly refer me to any resource from which I can
understand the working of DLR. And also refer some resources for
priority Mux for handling hardware requests from DLR.


texts: Offset in frequency doubler design problem

texts:
I designed a simple low frequency doubler, but I'm having trouble fixing the offset of my output signal. Below is my LTSpice model:

On the graph you see my green input signal, blue inverted signal, and then red re-combined signal with double frequency. My main issue is that my output is offset by 35mV. I've tried a few things but none of them seem to work. Does anyone know a simple way to bring the offset back to zero?

Frequency range: 50Hz - 1500Hz. Low voltage input. Op amp is receiving +-5V.


texts:
I am building a VU meter. Searching in the Internet and coming up with some things on my own, I ended up with the following circuit

First, there is an amplifier whose role is to give the VU meter the amplitude it needs to work. I put a voltage follower after that stage to isolate the input impedance of the VU meter from the amplifier. The thing I don't understand about the circuit is why the diode circled in red (D1) is there.

I built the circuit on a protoboard and checked what happened if the diode was not there. The result was that, with D1 connected as shown in the picture, some LEDs turned on steadily when the input signal was a sinusoid (i.e. constant amplitude and frequency); as I took D1 out, some of the LEDs that were on turned off. Apparently, the amplitude the VU meter was "recieving" was reduced.

I came to think that perhaps the diode is acting like a clamping diode, due to some research I did on the subject. Nevertheless, I'm not too sure about this and, even if it was correct, I don't know how clamping is related to this specific circuit.

What's D1's function? And how can the behaviour described above been explained (I mean, the fact that less LEDs turn on when D1 is not connected)?


texts:
I am using a MAX9929F Current sensing IC and I have a question to someone to may have used it before, or may have some experience with these types of circuits.
The circuit I built around the IC is the recommended circuit in the Datasheet. (Not much, just a current sense resistor, decoupling capacitors and a filter).
I am converting the output voltage of the sensor to current by proportionality, since it is a linear device. However the weird thing that I can't understand is that the constant of proportionality is not constant.
That is, for example, when you increase current up to 600mAh, and the output voltage is 2.15, then you decrease the current to 0mAh and increase it up again to 600mAh, and then the output voltage of the sensor is 2.2V.
This changes every time. (Hence I can't read the current accurately)
I would appreciate some hint to were the issue might lie, since I don't know where the error might be coming from since there is no other circuit that might be interacting with it.
Could it be that I am not using a purpose made current sense resistor ? (I don't think this is an issue since the input signal is DC)


texts: Electrical Discharge Machining (EDM) an insulated metal

texts:
I am interested in using a Wire EDM process to cut some silicon steel. As defined by Wikipedia - “Electrical discharge machining (EDM), also known as spark machining, is a manufacturing process whereby a desired shape is obtained by using electrical discharges (sparks).Material is removed from the workpiece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage.”

Material suitable for EDM must be electrically conductive of the process to work. The steel I want to cut is laminated in a dielectric coating however. I contacted a few Wire EDM cutting companies and was told by some that it was not possible to Wire EDM cut a dielectrically coated material, and told by others - “maybe, it depends”.

What factors would this depend on? I am thinking that if the voltage used in the EDM process is above the dielectric breakdown point of the coating, then the process would work - is this a correct way to think about it?
For example, this website (http://www.engineersedge.com/edm.shtml) states the peak voltage used ranges from 40 to 400V. This website (http://www.industrialcoatingservicesblog.com/coatings-dielectric-strength) lists the dielectric strength of some coatings as ranging from 800 volts/mil to 6000 volts/mil.

If the Wire EDM uses 400V, but the coating on the material has a dielectric strength of 800 volts/mil, is it a safe bet to say the coating is too strong an insulator, and that the EDM process will not work?


texts:
I have a very simple circuit with two op-amps which is latching up, as described below. I suspect that one of the IC's is simply defective.

Don't worry about the implied circuit continuation to the right; not all the parts are installed so that is not connected. Likewise, no input source is connected.

The power supply is +/- 15V. The op-amps IC's are NE5532. The expected behavior is that a maximum of 1000 nA of input bias current flows from through both + inputs across R1, resulting in a voltage of up to 50 mV across R1. That is tolerable in this application, which is why I don't have any additional resistors to try to to compensate for input bias current.

What actually happens is that somehow enough current flows out of the + inputs to drop -15V across R1, sticking both + inputs to the negative power rail. (This is beyond the common mode voltage range given on the datasheet). The output cannot swing that far; it only goes to -14, so a differential voltage of 1V develops. This is enough to forward-bias the back-to-back protective diodes which connect the inputs, a feature of the NE5532. Both IC's run fairly hot.

Have I done something that these op-amps don't like, or do I have a defective part?


texts: questions on powering a router with 9v alkaline battery

texts:
so I have a Linksys router which I want to power with batteries. so it can be a portable router.

The Original Power supply for the router is rated 12V DC 0.5A MAX.

I've tried powering the router with a 9v alkaline battery and weird things happened. ive expected it to be under powed, by that it won't even turn on or work, but what happened was The * Battery got hot and the* router main chip got really hot.

so my question is why did the Chip and battery get hot, and will it work fine and not get hot if I add two 1.5v batteries and make a total of 12v.

also what are the problems i can face when using batteries, to power an electronic such as this.


texts: virtual terminal in proteus is not showing values?

texts:
int val=0;
void setup()
{
Serial.begin(9600);
}

void loop() {

val = analogRead(A1);
Serial.println("the ldr intensity");
Serial.println(val);
delay(1000);
}


texts: Why doesn't light destroy the PN junction voltage gradient in a solar cell?

texts:
I understand that a solar cell is, essentially, a P-N junction.  A P-N junction, roughly speaking, will do the following:  The free electrons on the N-side will flow over to fill holes on the P-side.  This produces a voltage gradient where the P-side is slightly negative and the N-side is slightly positive.

Now, when light strikes the P-N junction, it excites free electrons all over the place.  These electrons, if they are close to the junction, are drawn towards the positively charged N-side.  This creates current and this is how a solar cell produces power.

The way it has been described to me is that, at first, the N-side is slightly positive and the P-side is slightly negative (it's acting like a normal diode).  But after light hits, this reverses. The N-side becomes very negative and the P-side very positive.  By attaching a conduit between these sides, you can draw power from that current.

Here is my question

After light strikes the P-N junction, and all those electrons are drawn to the positively charged N-side....wouldn't the N-side quickly lose it's positive charge and return to being neutrally charged?  This would destroy the drift voltage... so any free electrons would have no reason to build up on the N side and there wouldn't be any voltage.

What am I missing here?


texts: Complex power reaching and leaving 2 Current Sources

texts:
Given the following circuit, where the voltage of each source is unknown:

I'm trying to find the complex, active and reactive power that reaches and leaves(provided by) each of the two voltage sources. I suppose I have to find the voltage between each element and, by multipling with the current, I could find the power, but I'm having trouble understanding that.
For example, the votage right after the first source should be V1 and right after Z should be V1 - I*Z?
I'd appreciate an input on what I might be doing wrong.