texts:
For some reason I can't wrap my head around this concept. I find it really hard to find the loops in circuits. This is problem, since I can create all the equations from second Kirchhoff law. Is there any precise algorithm, which I can use to find them. When I'm searching for the loops i'm starting from the top-right element and go to the lowest-left element. But I'm constantly missing loops. I'll give an example of the process which is happening in my head when I'm searching for loops.
Given this circuit:

Start from R1, pass through the whole circuit 1st loop
Start from R1, pass through r2 then v2 and r3, 2nd loop
Start from R2, pass through R4 then V3 and R5, 3rd loop
Start from R3, pass through R6 then R4 4th loop
I don't see any other loops on the circuit


texts: I need to know the area of 2oz copper needed to dissipate 24 W. The max temp is 100 C and the ambient temp is 40 C. Any equations I can use?


texts: Calculate number of ADC clock cycles required for sample time

texts:
I'm working with a micro, which has a 12-bit ADC. I am using this ADC to sample a 125Hz signal, with a duty cycle that ranges from 0-100.
On the rising edge of that PWM signal, the ADC will collect a sample.

The reason for the question is that the 12-bit ADC has a sample time register (INPSAMP), which influences the total sample phase duration. The problem is, I'm not sure what the ideal value for that register is.
To get the total conversion time, the following formula is used:
convTime = PRECHARG(Fixed at 2 per chip vendor) + INPSAMP (min 6, max 255 per chip vendor) + EVAL (fixed at 12 per chip vendor) = X SARADC Clocks (fck)

Where:

ADC_CLK: 16Mhz
PRECHARG: Pre-charging phase duration. Fixed at 2 ADC clock cycles.
INPSAMP: Sampling phase duration
EVAL: ADC evaluation time. Fixed at 12 ADC clock cycles.

To get things running, I arbitrarily chose a value for INPSAMP (127), and with that value, everything seems to work fine. However, I'd like to understand what the ideal value would be. I'm not looking for the answer, as in, "The ideal value is 200"; rather, I am looking for the calculations required to get there.
Using the formula above, with my arbitrary value for the INPSAMP register (127), the total conversion time would be calculated as such, at least I think:
numberOfClkCycles = PRECHARG(2) + INPSAMP (127) + EVAL (12)
totalConvTime = numberOfClkCycles / 16Mhz;

So in the case above, it would take 8.8us (141/16) for that particular ADC channel.
Similarly, if I maxed out INPSAMP (255), it would take 15.9us (255/16) per channel.
The question is, how do you determine the ideal number of ADC clock cycles, or sample time in general, based on your particular application?
For example, do you say, "my signal frequency is X, and its pulse width is Y, so I need a sample time of Z"? And if so, how do you come up with that number(Z)?
Or, is it the sort of relationship where, by lowering the sample time, you increase the speed and which the ADC can read/sample, at the cost of how accurate the resulting sample is?
Meaning, if accuracy is critical, then always go with the highest number of ADC clock cycles allowed if you can afford the time to collect?
Any help or guidance would be greatly appreciated.
Thanks!


texts: What is the purpose of the 10K resistor that is connected across the input and the supply?

texts:
I was checking out some transistor amplifier circuits online when I came across this one.

Now my question is what is the use of 10 kilo-ohm resistor that is connected between the power and the input terminals? What happens is this particular resistor is removed? Please explain.


texts: Boost converter simulation keeps getting fried

texts:
In my project I want to use a couple of old russian VFDs. To drive them, I need 28V from a 12V power supply. The plan is to use a DC-DC boost converter as calculated  here and here.

I've ported the designs to Yenka, a circuit simulator, but for some reason the MOSFET and inductor keep burning up because of sudden peeks of current of hundreds of amperes.

That surely can't be caused by the lack of Schottky diodes in the software, a small difference in frequency of switching the diode and the voltage drop can't cause such immense currents - or can it?


texts: ESP-WROOM-32: Timed out waiting for packet header

texts:
I just got back my custom PCB using the ESP-WROOM32 module. I'm using an FTDI with it. GPIO0 is connected to ground via a jumper.

I made a very stupid mistake and forgot to include a pushbutton and pull-up for the EN pin.

Anyways - the chip boots up (I can see from serial monitor in the Arduino IDE) and I can also almost flash to it but it fails after writing with the error "Timed out waiting for packet header". Is it due to the fact that my EN isn't being pulled down to ground at boot? It's going to be super difficult to get a pull-up in there now.

My Arduino IDE settings are as follows:

What's going wrong?


texts: viability of idea for low voltage signal clipping (distortion) for guitar effect

texts:
I want to create an guitar distortion effect.
What I want is a unity gain buffer op-amp that clips the signal.
In the drawing below there is a circuit found on this forum here
which will clip a very low voltage (~200mV) signal.
However it will only clip at a particular voltage. What if you need (as I do) to clip simply the peaks off every wave?

I could provide some sort of rectified average peak of the input signal int 'mclamp' and 'clamp' such that the clamping voltage roughly followed the input signal as it rises and falls. For this I would presumably use some sort of 'ideal' rectifier (because of the 0.7 breakdown voltage of a diode bridge).

First.. is there an IC that will do this that anyone knows of?
And secondly.. Is what I'm proposing viable?


texts:
I'm trying to design a low-power passive communication system. It receives its power via wireless transmission from a nearby transmitter and to power a sensor which digitally modulated a signal via backscattering. The power calculated to the antenna @ 915 MHz with Tx and Rx gain around 9dBi was to be roughly 1.5 Watts or 1.76 dB. FCC regulations limit the directed power to 4 W maximum in the ISM Band.
I was considering using multiple receive antennas and using a Wilkinson Power splitter as a combiner to increase the power received, however, I know the theoretical power loss is 3 dB, which is more than what I receive.
My question is can I use the Wilkinson Power combiner in low power environments such as my example? Is there an alternate way to increase the power received without altering the antenna design?


texts: I am almost done routing a board.  However, Eagle is telling me that there is still one more  wire.  I have looked but I just can't seem to find it.  Is there a way to make Eagle tell me where it is?


texts: Is it possible to have a device with metal case and wireless charging?

texts:
Recently I encountered the following idea: that a mobile device manufacturer is not interested in including wireless charging in his devices because that prohibits him from using metal cases in the future (without excluding wireless charging from future devices of course). Sounds reasonable but...

Wireless charging uses the same technique as the transformer and the transformer includes a core. Perhaps the metal case could act as such core.

Is wireless charging indeed impossible for a device in a metal case like for example a mobile phone? Would it be possible to perhaps leave a small window permanently covered with plastic and use it for wireless charging?


texts:
Hello I have some problems to understand how to bind a Timer to a Pin and because of that my code isn't running...

#include <avr/io.h>

void init_PWM(void)
{
    TCCR0A|=(1<<WGM00)|(1<<WGM01)|(1<<COM0A1)|(1<<CS00);

    //Set OC0 PIN as output. It is  PB3 on ATmega16 ATmega32

    DDRB|=(1<<PB7);
}

void setPWM(uint8_t duty)
{
   OCR0A = duty;
}

void main (void)
{
   uint8_t brightness = 0;
   init_PWM();

   for (brightness=0; brightness<=255; brightness++)
   {
      setPWM(brightness);
      _delay_ms(100);
   }
}

My problem is how to assign the timer to PB7?

My goal is blinking LED on PB7 with FastPWM Mode.


texts: Why consider Linear Time-Invariant systems?

texts:
Okay this could be a very silly question but I am asking it anyway.

Why do we consider in most cases of signal processing that the system is Time-invariant?

Is it because most signals are linear and time-invariant or is there a more compelling reason to consider a system as LTI while looking at problems in this field?


texts: How to amplify RF signal to high enough level for a CMOS downconverting mixer?

texts:
I've been reading original academic papers on mixers and now a RF textbook and I have been unable to understand a very basic thing, which is how do I get a RF signal, say -65 dBm, at a high enough voltage level for input into a CMOS-based downconverting mixer?  Everything I read shows a LNA blackbox, which is fine and good, but LNAs amplify signals at what, 15-20 dB typically?  How on earth is that even remotely close to activating a CMOS NPN transistor in the mixer with a typical threshold voltage of 700mV?  +15dB gain on -65 dBm doesn't get it to 700mV+.  And chaining multiple LNAs to get it to 700mV+ would destroy the signal with noise, no?

I know I'm missing something extremely obvious here so be kind.  I'm just starting out.  I know there's a lot more to downconversion (filtering, etc).  This question is solely about the initial amplification.


texts:
With the following circuit:

How to calculate Vo using Mesh analyses.

I have already made the following loops:

Loop 1: 1KΩ x l1 - 5V + 4KΩ(l1 + l3) + 4KΩ(l1 + l2) = 0
Loop 2: 3mA + 4KΩ(l2 + l1) + 2KΩ(l2 + l3) + 20V = 0
Loop 3: -20V + 2KΩ(l2 + l3) + 4KΩ(l3 - l1) + 1KΩ X l3 = 0

But that's as far as I got.


texts: How dangerous are portable CRT televisions?

texts:
I want to use an old portable CRT for a project, but I don't know how dangerous the capacitors are, and if they'd be as bad as the ones inside a normal CRT. It takes in 12v dc via adapter, or 8 D cells. It is branded Curtis and has the model Number: NO.RT063

Here is a picture of the TV:


texts: RC Circuit with exponential input - Laplace

texts:
I have a given RC-circuit with

$$RC*\frac{dv(t)}{dt}+v(t) = v_{0}*u(t)$$

and I'm looking for the output waveform and the 50% delay with an exponential input given by

$$v(t) = v_{0}*\left(1-e^{-\frac{t}{T}}\right)$$

where \$T\$ is a time constant, using Laplace.

What I've done so far is finding the output wave form:

$$v(t)=v_{0}\left(1-e^\frac{-t}{RC}+\frac{T}{RC-T}*e^\frac{-t}{T}-\frac{T}{RC-T}*e^\frac{-t}{RC}\right)$$

1.) Is that correct? Is it possible to simplify it even more?

Next I've tried to compute the 50% delay:

$$v(t)=0.5*v_{0}$$

$$0.5=\left(1-e^\frac{-t}{RC}+\frac{T}{RC-T}*e^\frac{-t}{T}-\frac{T}{RC-T}*e^\frac{-t}{RC}\right)$$

leading to

$$\frac{RC}{2T}-0.5 = e^\frac{-t}{T}-\frac{RC}{T}*e^\frac{-t}{RC}$$

2.) Is that correct? How can I solve for t?


texts: Do the temperature coefficients of the resistors in the LM399/LM199 "Portable Calibrator" significantly effect the output stability?

texts:
I'd like to know how voltage reference stability is obtained in products like 6.5 digit multimeters that use LM399 as a voltage reference in spite of using two gain resistors. Let's assume an ideal LM399 and ideal op-amp and ideal current source (so ignore the 200k and 5k resistors.) It would seem to me that even at 5ppm, the output would be very sensitive to temperature (relative to a real LM399.) So then how can this work? Is it the case that the resistor temperatures do not fluctuate much because they are near the temperature controlled heater? Or are they measuring the temperature with something like an LM35 (and matched tempcos on the resistors) and calibrating in software?

Even at 5ppm/C and only 0.5C change in temperature (leaving out the trimpot), I'm calculating a range of 10.170 to 10.167 (gain ranging from 1.4634 to 1.4629) which would seem horrible for such an instrument. Do resistors effect gain in the way that I think they do?

I've looked at schematics for a couple such multimeters now and they all use at least two or three discrete resistors and usually aim for an stable output voltage around +/-10V or maybe +/-12V, so is the "Portable Calibrator" a reasonable approximation of a real application?


texts: Battery powered device - How to measure external floating differential voltage

texts:
I have the following task. As depicted in the sketch, I have a battery powered device which needs to measure the differential voltage VIN between two external nodes, EXT_NODE1 and EXT_NODE2. It is not allowed to have a conducting path between the two nodes while measuring (you can see it as a battery that can have inverted polarity in a way).

simulate this circuit – Schematic created using CircuitLab

I am very confused on how I could do this. In the beginnning I thought an instrumentation amplifier would be perfect but soon realized that wouldn't work. It is impossible to know the common mode voltage of VIN against the "-" electrode of the battery.

What do people usually do in these cases? I mean, there are a lot of handheld data loggers. How do they handle differential signals?

One easy way to go I guess would be to connect one of the external nodes to the "-" of the battery, converting in essence the differential measurement to a single-ended measurement.

With this implementation, there is the problem of how to handle the potentially negative voltage against the node connected to my "ground". I suppose I'll have to be able to connect both nodes to "ground" and measure, every time I want to know how much VIN is.

Is there another or better way to do this?


texts: Running two threads at the same time is causing a hardfault

texts:
So i'm learning FreeRTOS on STM32 and currently following a tutorial to get things started. Following are my concerns with the first one being the most:

I have two threads, but upon running a scheduler, I see a hardfault. But when I run a single thread, I see no issues. I initially thought it'd be related to the stack size but each thread is taking up 130 * 4 = 520 bytes.

Does stack size refer to the word size in the context of rtos? (if the stack is 16-bits wide and usStackDepth is 100, then 200 bytes will be allocated for use as the task’s stack)

TaskHandle_t is a pointer to struct tskTaskControlBlock. Then why is the address of the xTaskBlinky passed to the last parameter of xTaskCreate(), which takes TaskHandle_t * const pxCreatedTask )?
 typedef struct tskTaskControlBlock* TaskHandle_t; // in task.h

 // main.c

 TaskHandle_t xTaskBlinky = NULL;
 TaskHandle_t xTaskBlinky1 = NULL;

 void vTask1_Handler(void *params);
 void vTask2_Handler(void *params);

 void SystemClock_Config(void);

 int main(void)
 {
     /* MCU Configuration--------------------------------------------------------*/

     /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
     HAL_Init();

     /* Configure the system clock */
     SystemClock_Config();

     xTaskCreate(vTask1_Handler, "Blinky", configMINIMAL_STACK_SIZE, NULL, 2, &xTaskBlinky);
     xTaskCreate(vTask2_Handler, "Blinky1", configMINIMAL_STACK_SIZE, NULL, 2, &xTaskBlinky1);

     vTaskStartScheduler();
     while (1);
 }

 void vTask1_Handler(void *params)
 {
     while(1);
 }

 void vTask2_Handler(void *params)
 {
     while(1);
 }

And the program goes into the infinite loop upon running a scheduler:
  * @brief  This is the code that gets called when the processor receives an
  *         unexpected interrupt.  This simply enters an infinite loop, preserving
  *         the system state for examination by a debugger.
  * @param  None
  * @retval None
 */
     .section  .text.Default_Handler,"ax",%progbits
 Default_Handler:
 Infinite_Loop:
   b  Infinite_Loop
   .size  Default_Handler, .-Default_Handler


texts:
I have an issue sensing the throttle position sensor voltage if the sensor is already being used by the vehicle's own ECM. Namely, the vehicle ECM stops responding to the throttle input after a period of time from 20 seconds to 5 minutes later.

When I probe with my multimeter (positive lead on the TPS #1 Signal and negative lead on the TPS #1 Return), the voltage at the pedal goes from 0.5V to 4.5V. This doesn't affect the vehicle's ECM at all.

When I use my ATMEGA32u4, connecting the TPS #1 Signal to PF0 and the TPS #1 Return to my AVR's GND network, the vehicle ECM complains about not having a throttle connected.

What should I consider adding between the TPS #1 Signal and the AVR to make it 'disappear' in the circuit and not affect the vehicle ECM? Or is this a function of the internal pull-up resistor?


texts: Non equal phase currents at nominal speed vector control Permanent magnet synchronous motor

texts:
I working on my implementation of vector control for PMSM.
I'm having close loops over speed, current in d axis(flux loop), current in q axis(torque loop). I'm using MATLAB/Simulink for vector control algorithm, X2C makes communication with DSP from Texas Instruments Delphino TMS320F28335. HVPFC KIT is used as a driver or a motor.
I'm trying to improve phase currents wave forms. These are also dq currents with they referencies in stacionary state.

At rated speed machine is turning at 3000 rpm, where current frequencies are 200Hz. I tried to move moment when currents are sampled, changed max voltage duty cycle. Tried to speed up current regulators.
Nothing helps, any suggestions?


texts: Ideal supply voltage for stepper chopper driver

texts:
I am aware that chopper drivers for stepper motors need to be supplied with a voltage much higher than the motor's steady state voltage. For instance most 3D printers use drivers based on chips such as the A4988, which is commonly supplied with 12 V, while the motors are rated for only a few volts. See example motor and driver; the common RepRap 3D printers mostly run on 12 V.

My question is as follows: Why stop at 12 V?

As of my understanding, a higher voltage allows for a faster current rise, and hence better torque at higher speeds. So why not increasing the supply voltage to 18 V, or 24 V, which is still within the specs of the driver?

I can only guess at the possible drawbacks. Efficiency of the driver? Safety? Cost of the peripheral electronics (e.g. caps)? Noise?

Note that my question is not limited to the above mentioned hardware; I am interested in the general limits to driving stepper motors with higher voltages of, say, 24 V.


texts: How to find thevenin resistance of a capacitor in an op amp circuit?

texts: for the following circuit could someone explain how to find the thevenin resistance across the capacitor? Most answers use the 10K resistance in parallel as the thevenin resistance but I don't understand why. Why do they neglect all the other branches, resistors and op amp?


texts: Reduce flickering on cheap 220v AC GU10 LED Lamps

texts:
As I am unable to find exact answer anywhere, I am looking for some help.
First of all, I'll explain the current situation.
I have a freshly built appartment where noone ever lived before. We decided to go for LED lights in all rooms and all lightning zones. The wiring is done for every room and every room has its own fuse. In my country we have 220v 50 Hz.
Time has come and we started looking for GU10 220v LED bulbs. We bought a set of 9 bulbs (4 or 5 W each) for one room and another set of 15 bulbs (3w each) later for second room.
Also, we are using the touch switches from Livolo brand everywhere, so, no mechanical switches.
None of the currently installed bulbs are dimmable, but we plan to add dimmable ones for living room.

So far, so good, everything works, except the strange feeling to my eyes on movements.
I started some small research. I found out what is AC, what is DC, what is 50Hz, and after all, what is flickering and what is a cheap LED Lamp with bad LED driver inside. I also tried capturing some videos using manual shutter and the flickering was visible.
Considering all this, I have some questions, but please answer them as simple as possible.

Is there a technology (some box, converter, rectifier, capacitor, etc.) that can be installed already at the beginning of the circuit (after the fuse box) to drive all the lights in appartment with reduced flickering safely, while keeping in mind we're using touch switches? With technology I mean a ready made product which is safe, rated for the total wattage and is in one piece.
If yes, will it work with the touch switches and the future dimmable touch switches and dimmable leds? Livolo switches are phase-cutting / Leading Edge dimmers.
Will choosing a more expensive LED lamps solve the problem with flickering?
If nothing can be done, except buying better LED lamps, which brands are flicker free?

At the moment we have only bought 9 + 15 leds for 2 rooms, 6 high lumen white light led lamps for bathroom, 1 high lumen led + 2 low lumen spotlights for toilet, none of them dimmable.
Touch switches cost us a lot of money, so, they won't be replaced.
If you require any  morespecific information to answer my question, please ask and I will give everything I can find.

I just can't describe my anger on all this LED situation... if I ever knew anything similar will happen, I would have just chosen another solution, before buying...

P.S. Sorry my primitive english, it's not my native language. And thanks in advance!


texts: Question about mesh analysis in frequency domain

texts:
I've been trying to find the Thevenin impedance for an example in my textbook using mesh analysis, in the book it is solved with a different method but I wanted to see if I could find the same result with a different approach but I kind of failed I guess and I am most of the time failing whenever I try to solve an already solved question with a different method.
This time I wanted to share my attempt so I can get some suggestions and hopefully some help since my university is closed due to the pandemic and I don't have much access to our profs etc.
The book's solution and result is here:

And my desperate attempt is here:
(Hopefully it is clear enough and note that current for mesh-1 is \$I_{a}\$ mesh-2 is \$I_{b}\$

The final results are way off, so I'm sure I've messed up somethings, thanks for any help.


texts: How to fit MAX941 macromodel to LTSpice "opamp2"?

texts:
I am new to adding models to LTSpice. I have successfully added OPA350 from TI, but with MAX941 from Maxim Integrated I get some errors due to the LTSpice "opamp2" model does not have the same amount of pins as the MAX941.

I am not interested in simulation the MAX941 N/C, LATCH and SHUTDOWN pin, which then makes it compatible with the "opamp2" model. My question then is: Is it easy to remove the pins (N/C, LATCH, SHUTDOWN) by editing the .sub file? If so, how?

Here is a link to the MAX941 macro model file:

MAX941 macro model file


texts: NXP LPC-Link 2 hangs when flashing and debug

texts:
im using a JTAG probe NXP LPC link 2 , with IAR Embedded workbench and procesor LPC1766.

for some reason when i compile and try to load either a debug or release firmware onto the LPC1766 , it works the first time ... then if i stop the debuger , recompile and try to load again , the loading process gets stuck at this point.

Then im forced to close the IDE , and unplug the usb cable of the probe , and relaunch the ide in order to work again.

Its very time consuming.
Any hints on how to improve this ?

note:
-The processor is connected to J7 on the probe
-probe is in swd mode

This is my debug configuration:


texts:
I am building a H-Bridge. This is the schematic of my driver board for 1 of the IGBT's. I do not know how to calculate the R1. The Vge is 15v, The Ic is 41A. What would be the best size of resistor to use?
IRG4PC50SPBF datasheet


texts: Reference Plane In Impedance Calculation

texts:
I'm designing an 8-layer PCB with 10 distinct region of power. To attain 50Ohm trace I used Stripline calculators (like this fancy EEWeb) and they work great If you know that you have a complete solid ground both on top and bottom of your signal.

The problem arises if you have copper pour between your signal and your holy ground which may be use as power signal. I already found in "reference plane doubt" that the power plane Can work as a reference plane in these magic Stripline calculators.

So now I have two question regard that. First, does this power plane need to be in the same circuit as signal? I mean suppose I'm routing a DDR signal. can the reference plane be some non-related power plane like 12V power plane?

Second does this plane should be fully continues under signal or split plane work too?

And third, I can't find any literature in transmission line theory that support the idea of "Any copper can work as reference plane". Does anybody see a formal calculation on this?


texts: Is a rotor of an electrical motor charged with electricity?

texts:
This might seem to be dumb question, but as far as I understand it:

An electrical motor is made of a rotor and a stator.
The stator is electrically powered: it has a solenoid and current passing into it.
This creates both a E and B (electrical and magnetic) fields.

Then those fields triggers a Lorentz force on the rotor, depending of:

E -> OK
B -> OK
current speed v of the rotor -> OK
the electrical charge q

I am wondering:

Is it the electrical charge q of the rotor or the stator?
Is it a charge induced on the rotor by the electrical field created by the stator?
What is the link between the solenoid in the rotor and the solenoid of the stator?

For context:
I am trying to calculate the solenoid caracteristics (L) of the stator, possible resistance and capacity caracteristics (of the circuit on the stator), and the solenoids characteristics of the rotor (do I really need it?). All these characteristics should help me to design the input (current and voltage of the stator) and the ouput (rotationnal torque and speed of the rotor), but it seems I need also to power with electricity the rotor.

EDIT:
To answer the different comments: 1/ I want a rotating motor, powered with DC current. I want to achieve at the output some torque and rotationnal speed 2/ @Transistor If we are interested in the current I, is it the current in the rotor or the stator 3/ If I choose a static magnet for the rotor, and an electomagnet for the stator, I don't need to provide current in the rotor (I mean: no battery in the rotor?) 4/ Is a solenoid a possible solution for electromagnet?


texts: voltage transient protection for MV Motors

texts: What types of transient voltage protection is applied on medium voltage motors and are these types of protection that are applied depended on the type of motor it is e.g Synchronous vs Induction motor?


texts: Seeing sine wave output from external oscillator but expect to seeing square wave output

texts:
Buy some external oscillator from eBay and hook up to 5V DC and RF output to DSO.

Seeing sine wave output from external oscillator but expect square wave output.

I connect lab PSU to breadboard and put DIP14 external oscillator in breadboard and connect 1 feet BNC probe to pin 8 (RF out) and DSO, and see all external oscillators give sine wave but they are all square wave ones.

Also put 10uF and 0.1uF caps between Vcc and GND of osc. just in case but no changing in output waveform.

Is problem with using breadboard that might be introduce stray capacitance that skew square wave output to sine wave?

In that case, how I check what kind of output external oscillator give. I cannot solder them to strip board as it is problem to desolder all pins and take it out after testing.

Sample datasheet:

http://www.vishay.com/docs/35025/xo-52.pdf
http://www.ecliptek.com/SpecSheetGenerator/specific.aspx?PartNumber=EC1100-80.000M


texts: Missed ordering 10uH inductors for ICs, do I need them?

texts: Well dumb me apparently forgot to order these 10μH inductors. I'm assuming the L and the C and the R are used for band-pass-filtering/stabilizing the input voltages. I really don't want to make an order from Digikey just for these inductors. The shipping costs will already be magnitudes more than the prices for these components. I'm thinking of just replacing them with wires. Is this OK?


texts: Voltage across inductor immediately after the switch is closed (again)

texts:
The switch in this circuit has been open for a very long time (such that the circuit is in DC steady state condition).

What is v2?

The correct answer is v2 = 0 V, but how does that make sense? I know that the current through the inductor is 0 A, but why is the voltage 0?


texts: what is the name of this yellow tape around high frequency transformer?

texts:
[

what is the name of that tape? , what it is the purpose of it?, can I buy it?
And if not, what is the alternative?


texts: Beam pattern for a linear array comprised of rectangular transducers

texts:
I am looking for the beam pattern of a linear array with uniform spacing, d, between n elements.
I know for an array comprised of circular pistons it can be derived from

$$\frac{1}{n}\frac{\sin[n\pi\frac{d}{\lambda}(\sin\theta-\sin\theta_s)]}{\sin[\pi\frac{d}{\lambda}(\sin\theta-\sin\theta_s)]}$$

where \$\lambda\$ is the wavelength. And it is a narrowband system.
I appreciate if you can provide a reference book and describe how I can derive the beam pattern for the particular case of rectangular elements.


texts: How to do low pass filtering on a differential signal

texts: If I have a differential signal on a pair of wires then how would I do a simple RC low pass filter on this differential signal?


texts: Finding the amplitude response of an LTI system

texts:
I'm asked to find the amplitude response of an LTI system described by the difference equation:

$$
    y[n] - ay[n-1] = x[n]
$$

After taking the Fourier transform of both sides and some math, I get the frequency response:

$$
    H(e^{jw}) = 1/(1-ae^{-jw})
$$

But how do I get the amplitude response from this? I know the amplitude response is

$$ |H(e^{jw})| $$

but I'm unsure how to "get the length" of my frequency response. I have a feeling this is a simple math problem that I'm misunderstanding.

(Disclaimer: this is a question on a past final that I'm using to study. I have the answer to the question (and will post if proof is needed), but I want to understand the method)


texts: Charging two lithium ion batteries in series connection individually

texts:
Any idea to charge two lithium ion batteries which are connected in series each one gives out 3.7 volts (both to give out 7.4 volts) individually? What's the main idea or circuitry to do the task ?

I will use Microchip MCP73831 chip.


texts: Why are circuits drawn like this(see picture) and not closed?

texts: And how do you analyze them if they have a voltage source in the middle of the circuit? What is the Vin supposed to mean if there is a battery source? Thank you in advance!


texts: You’d think electric blankets would use a 12V DC adapter to step down the 240V AC to 12V DC. It has the potential to be just as effective while also being safer. Do you think it’s because of the additional cost of the wall adapter?


texts:
What will be equation of current for the following circuit. Switch is closed at t=0. All the elements are ideal.

simulate this circuit – Schematic created using CircuitLab

EDIT:
My approach ,
$$ i(t) = \frac{V_s}{L}\int dt = \frac{V_s}{L} t + K$$
Let at t=0, i(t)=0
$$i(t) = \frac{V_s t}{L}$$
But from a RL circuit equation of current is
$$i(t) = \frac{E}{R}(1-e^{-(R/L)t})$$
on putting R=0 I get i(t) =  infinity


texts: What is the source of leakage current thru an isolation transformer?

texts:
I want to use my oscilloscope to check the cleanliness of the output a high-voltage power supply (electrophoresis type, up to 3000 volts DC).

I built a 100:1 voltage divider (out of 2 resistors - roughly 700k and 7k ohms), hooked up the scope to the "1x" output of that (to protect the scope from HV damage), then turned on the power supply (set to only about 200 volts, just in case...).

The power supply immediately complained of "leakage current" and turned off the output. (This is a safety feature of the power supply - I wish I knew how to defeat it, but I don't have schematics.)

So - I bought a used isolation transformer on eBay, checked that it worked (it does seem to), plugged the power supply into the transformer, and tried again.

Same thing - leakage current.

Then I put a 1 megohm resistor in series with the 120 VAC supply, and measured the AC current going thru that into the ground lead of the oscilloscope.

Current when plugged into normal AC outlet: 118 microamps (about as expected)
Current when plugged into isolation transformer: 29 microamps (I expected zero)

What is going on? How can any AC current pass thru the scope ground lead if the current is coming from an isolation transformer?  What is the source of the leakage?

And - how can I do this measurement?


texts: What makes some commercial JFETs asymmetric?

texts:
In a MOSFET, the obvious cause of asymmetry is the fact that the source is tied to the body. But in a JFET, no such obvious answer exists, as the body, gate, and drain are all the same piece of silicon with no material differences between them (as far as I'm aware). And indeed, most JFETs seem to be symmetric.
But there are some JFETs on the market have specifications that would imply asymmetry. See for example the UJ3N120070K3S that I just used in a design; it's rated for a gate-to-source voltage of no more than -20 volts, but a drain-to-source blocking voltage of 1200 volts. But if \$V_{ds} = 1200\ \mathrm V\$, and \$V_{gs} = -20\ \mathrm V\$, that leaves \$V_{gd} = -1220\ \mathrm V\$! Even if \$V_{gs} = 0\ \mathrm V\$, \$V_{gd}\$ is still vastly higher than the rated \$V_{gs}\$.
If the FET were symmetric, that would imply that the gate-source and gate-drain ratings should be the same, but they clearly can't be here, as if they were, the drain-source rating couldn't possibly be higher than the gate-source rating, and applying rated \$V_{ds}\$ would fry the gate junction.
What about its physical construction makes this JFET, and others like it, asymmetric? Why can \$V_{gd}\$ be so much higher than \$V_{gs}\$?


texts: White paste and strong plastic smell on induction stove

texts:
My induction hob, when in use for several minutes on high heat is producing a very heavy plastic smell. The hob is working properly besides this smell.
I opened the back of the hob and noticed this white paste that melted, it seems that this is what is causing the smell - what can it be?


texts:
0 down vote favorite

I needed some basic advice about impedance matching. I have an RF amplifier with 50 ohm output impedance, capable of generating 400W output power at 500kHz. I am trying to deliver this to a 12 ohm load.

I looked online and figured out that I need to match the impedance of the amplifier to the load. My question is what is the best way to achieve this? Would it be possible to simply use a capacitor and inductor and put an L section to the output of the amplifier? I saw that online stores have very cheap capacitor and inductors that is rated for very high voltages.

If that is not going to work is it possible to buy any transformers that would do that? For instance I saw that there are many cheap 220v-110v voltage converters, which should have 2:1 coil ratio. So in theory that should convert 50 ohm to 12.5 ohm and matches to my load. Will these work at 500 kHz as required for my application? Or are there other type of transformers that I can use for this purpose (there are many many types of transformers and I got confused which ones are suitable for impedance matching)?

Thanks a lot for the help.


texts: Help identifying/using some weird pin headers

texts:
EE student who's a little new to the hardware side of electronics here.

I could use some advice on how to use these things- I assumed they were pin headers, but I might be wrong about that.

They almost look like regular female pin headers (like these, which are what I wish I had), but the pins on the bottom are bent out at right angles. The pitch is 2mm. I'm fairly sure they came as extras with some XBee modules, but I wasn't the person who ordered the parts for this group project so I'm not 100% positive where they came from.

The goal is to be able to solder them onto a prototyping board, but I'm not sure how to do that with the bent legs. I've tried bending the legs to point straight down, but they break extremely easily and the few that didn't break are still too short to go through my prototyping board.

Does anyone know how these are supposed to be used? Are these even usable pin headers or have I misidentified them completely?

Thanks!


texts: Considerations for CAN termination resistor location

texts: I'm looking to incorporate a switchable 120Ω termination resistor (using a photo MOSFET) into a CAN design. Are there any issues with locating the 120Ω resistor at the CAN transceiver versus at the CAN_H/CAN_L connector? The CAN_H/CAN_L traces are approximately 100mm long (i.e. the CAN transceiver is located approximately 100mm from the physical CAN connector).


texts:
Reading a presentation on an MPU evaluation board I found this particular circuit:

Can someone please explain me the logic behind this and what is this "back powering" scenario that the presentations talks about?


texts:
Please read the text first in image 2. My question is based on that.

Can somebody explain me how there is a small bump in "b" in the graph figure shown. I dont get it why the bump occurs. Initially b is at 5 V and a at 0 V. If a starts increasing why does b also starts increasing? Is there some intuitive capacitative coupling going on here? how do you explain that phenomenon?


texts: What is the Correct Term for a Touch Screen Type Touch Sensor

texts:
This may seem like a silly question, but while we've all heard of touch-screens, I'm looking to build/prototype a device with a touch-surface (no screen) that can register up to four distinct points of contact (finger presses), but I have no idea what I should be searching for!

I realise a big part of touch sensing and gestures is implemented by software, but presumably there is some hardware first of all. But so far I've only found plain touch sensors, which register only that they were touched, and possibly a measure of force, rather than the kind of locational information I'm hoping for.

If what I'm looking for is a single piece of hardware (the sensor itself) then I'd love to know what the most correct term would be. Otherwise, if what I'm looking for actually needs to be constructed from several parts, then I'd love to know that too.

In addition to the general answer, I'd also appreciate any specific recommendations. My particular requirements are at least 3 finger tips registered, ideally with enough detail that I can ignore things like resting fingers. I probably need to be able to put it beneath 2-3mm of glass or perspex, and ideally I need to be able to make it curved, though if I can just make the surface on top curved then that's fine too, but likely requires a higher tolerance for surface thickness.

Lastly; if anyone reading this has a high enough reputation, then we could probably do with a touch-sensor tag, as both touchscreen and touch-panel seem more specific to a display surface.


texts: How to check the Vendor ID for your company?

texts:
Someone filled out this form a while ago:
http://www.usb.org/developers/vendor/VID_Only_Form_withCCAuth_010113.pdf

I'm looking for a way to lookup vendor ID from company name

f(key=company_name) => VID

My situation is the final paragraph of the copy on this page (only VID, no membership or logo rights):
http://www.usb.org/developers/vendor/


texts: the inverting amplifier get wrong voltage in output

texts: as I know I should get -5 mV in this circuit. (OPAMp is ideal), but in this simulation with an ideal op amp in PSpice, my output voltage is -15 volt, can any one help me?


texts: What is the correct name of a job involving mainly programming measurement instruments and making measurements on electronic components?

texts:
While revisioning my resume I found out that I do not know what is the industry standard name of one of my previous job. I simply called it "Software developer" but I don't think it fits properly.

The job involved the following:

Programming instruments (such as Keithley's voltage/current sources for example) to perform a certain sweep/measurement according to required specs.
Testing and implementing features on programs developed at point 1.
Perform measurements on electronic components and compare with datasheet specs.

I don't think "Laboratory technician" is a good fit either.


texts: My LED circuit stops working after a bit

texts:
So I built a rectifier circuit for my bike to use with the dynamo and placed an LED at the end of it.

The LED has these ratings:
- Power: 2W
- Rated voltage: DC 3.0V~3.2V
- Rated current: 600~650mA
- Brightness: 160~180LM
- Color temperature: 2850~3050K

The bottle dynamo is an AXA HR Traction with these specs
- Power: 3W
- Rated voltage: AC 6.0V
- Rated current: 500mA

I built the rectifier circuit with 4x1N4004 schotty diodes.

Now my problem is that it works perfectly fine for the first few minutes but after a bit, the light goes out and simultaneously drains all power from the rear light as well.
So does anyone know why it does this? I know I might have fouled something up, but I am fairly new to all of this, so bear with me. :P


texts:
I am currently redesigning a PCB utilizing the Xbee 868 Mhz module with external antenna connection on the pad ( https://www.digi.com/products/embedded-systems/digi-xbee/rf-modules/sub-1-ghz-modules/digi-xbee-sx-868 ). I have followed the rules from the datasheet and calculated the proper antenna trace width and distances for 50 ohm impedance. From Xbee SX 868 User guide:

In my application the question is, either it is OK to place the SMA antenna connector not in the exact corner of the PCB:

As you can see from the screenshots, the connector is on the edge of the PCB, but only horizontal. Vertical wise it is closer to the middle. The bigger issue is that in close proximity to the connector (counter side of the PCB to the antenna trace) there are traces and components placed. Even though there is going to be solid ground and shielding between the connector (GND polygon not poured on the screenshot) and the rest of the traces, I fear that the signal quality might get altered by the digital circuitry in the close proximity.

Are there any rules I can follow and a way I could check what is the desired minimum distance of other circuitry to the antenna trace?

EDIT:
A screenshot of the top layer with GND polygon poured:


texts: How to simulate digital logic using CMOS technology (MOSFET) in Proteus?

texts: Hello I'm having trouble with Proteus to do this CMOS logic simulation, I used transistors, I can do the logic perfectly, but when I use CMOS for some reason the logic doesn't work. I used the methods of feeding voltage or applying a digital signal and it still doesn't work. Is there any modification that I must do on top of the component?


texts: What is the shield pin on a potentiometer?

texts:
I am looking at the symbol for a potentiometer and I see the normal 3 pins,  however there is an additional pin called shield.
What does shield mean? Is it ground?
Here is the symbol I'm looking at:

The component.


texts: Trouble to understand Johnson Nyquist noise: why I don't find the "4" in the voltage fluctuation

texts:
I am a little bit confused to precisely understand the meaning of the formula: \$\langle \overline{V}^2 \rangle=4 k_b T R \Delta f\$
Imagine a resistor \$R\$  in \$x=0\$ thermalized at temperature \$T \$ connected to a waveguide on \$]0,+\infty[ \$ of impedance \$Z_0=R\$. This resistor can be seen as a blackbody radiating an average power:
\$\langle P_{\rightarrow} \rangle= k_b T \Delta f\$
It represents the power in the bandwith \$\Delta f\$ that this resistor "injects" in the waveguide.
Now, we know that in the waveguide verifies: \$P_{\rightarrow}=V_{\rightarrow}^2/Z_0\$ (relationship betweeen power and voltage).
In the end, it means that: \$ \langle V_{\rightarrow}^2 \rangle =Z_0 k_b T \Delta f=R k_b T \Delta f\$
My questions:

Do you agree with what I just wrote ? Specifically the expression of \$\langle V_{\rightarrow}^2 \rangle\$
Why I don't find the coefficient \$4\$ of \$\langle \overline{V}^2 \rangle=4 k_b T R \Delta f\$

About (2) it might be because I am not talking about the same voltage. But it is also the source of my confusion. What does this "4" means physically ?


texts: Is this a reasonable way to get >50 capacitive touch sensors?

texts:
I'm looking to include 50-100 capacitive-touch sensors in a project. I've found these SPI 12-key capacitive touch sensors. Would it be reasonable to use several of these for such a project, or is there a more natural solution?

I'm building a chessboard-like "grid" with 7x7-10x10 touchable squares, ca 3x3cm.


texts:
If you must mix synchronous reset and non reset flops in a single always block, would this be the correct way...

always @ (posedge clk)
if ( reset )
begin
    resettable_flops    <= 0;   // Resettable to 0.
    nonresettable_flops <= 'dx; // No reset function. Is this OK?
end
else
begin
     // Functionality goes here.
end

EDIT: If I do not write the x assignment, ISE infers logic to not change the flop when reset is asserted i.e., !reset ends up driving the clock enable which I want to avoid since reset is high fanout and may affect timing. However, assigning 1'dx works and ISE does not use the reset in the timing path of nonresettable_flops.


texts: Is there an easy way to protect a PCB from leaked electrolyte?

texts:
I've come across a LED flashlight that has rather curious design. The flashlight is rather powerful - it can notably heat up in "turbo" mode and so the driver definitely deals with some serious amounts of heat.

It runs on one AA battery and so has usual cylinder battery compartment with a screwed-on cap on one end and the LED, reflector and driver on the other one - this part is usual. However if I remove the cap and look into the compartment I see the "plus" terminal in the compartment bottom center and immediately beneath is the PCB all stuffed with PCB-mount resistors - yes, I look into the cylinder and the seemingly uncovered PCB is at the bottom. Maybe the "plus" terminal is on the PCB itself - I'm not sure.

I can't see more details because the compartment is rather deep and narrow.

Unless there's some clever protection of the PCB I expect it to die of corrosion quickly if there's a minor leak of electrolyte from the battery. In all other flashlights I've seen the compartment bottom has a plastic or metal piece that completely separates it from the driver. This is not the case here - the PCB is clearly visible at the compartment bottom.

Is there any easy way for protecting a PCB in such design like perhaps some varnish-like coating that would cover everything and protect it from electrolyte?


texts: Practicality of using different types of battery cells to avoid DC-to-DC conversion

texts:
One problem with solar systems is the need for high-efficiency DC-DC converters. For example, if lead-acid 12V storage batteries are used, then the user is faced with the problem of down converting that 12V source to many devices that use 3V, 5V, 9V, etc.

One way I thought of to side step this problem would be to use battery cells aggregations, instead of single large batteries.

For example, lead-acid cells provide 2V and Ni-Cad cells provide 1.2V. Therefore, you could combine 2 lead acid cells with 1 Ni-Cad cell to generate 3.2V electricity. By using this strategy, you could make a single large battery that would output the array of DC voltages needed. With this scheme the user would only need very simple regulators on the outputs.

The disadvantage would be the need for a more complicated charger.

Would this idea be a superior to using a 12V charging system?


texts: I am using MSP430F2619 for data acquisition. Channel 10 of ADC12 was shown in Data sheet as temperature sensor. But also on Block diagram a Vref_x is also assigned to channel 10. How did we know if I am measuring Vref or temperature diode ?


texts: How should I modify this back to back MOSFET AC mains circuit?

texts:
I have a WiFi enabled AC mains light dimmer/switch that uses a back to back MOSFET design. The device sits in series with the load (lightbulb) and therefore does not have its own return/neutral connection.

I'd like some help to understand how its MOSFET / transistor arrangement works as I'm not fully confident I do understand how the control circuitry might be managing the MOSFETs and transistors so that:

it always has power for itself (a tiny amount of current flows
through the lightbulb at all times, but not enough to light it); and
so that a controlled amount of current is allowed to flow through
it when any level of light brightness is requested.

Ultimately, what I'd like to do is convert the device to be a user input device only (with minimal modifications to the circuit), connecting directly to the supply and neutral - by somehow disconnecting the path between the two side to prevent dead shorts when any level of light brightness is requested.

For example, could I do this simply by disconnecting the base of each transistor so that they're never open and therefore there is never a direct path between the two sides (i.e. pin 3).

This may seem like a pointless exercise/idea, but actually it would then give me a dimmer that I can use in software (over WiFi) as a user input to control other "smart" things such as mood scene selection.


texts:
On the backside of my Sondpex RUSX903 car radio I found two RCA jacks: a red and a white one. With an adapter cable I connected these to my cellphone headphone jack. So far so good, I noticed two odd things though:

The volume control of the car radio does not affect the volume of the music coming from my cellphone. I gets pretty loud though when I increase the volume on the cellphone.

The music from the cellphone plays independently of the selected input. If the selected input has some audio as well (e. g. the radio,) I can hear them both mixed together.

Recently a car electrician saw my setup and told me the RCA jacks I'm using for input are in fact output jacks.
Questions:

Why is this even working? Why is it even possible to use the output jacks for input?

Is it safe,or should I expect to run into problems or even damage something?

EDIT:
The Aux Input Jack on the Front Panel of the Car Radio is broken.


texts: DC/DC split rail converter with coupled inductor

texts:
I'm trying to build a DC-DC split-rail converter using circuit from this article. My goal is to split 12..14V input voltage into +2.4V and -2.4V. To do that, I choosed LM1501AGR-ADJ IC, calculated the needed inductance value (15 uH) and made the coupled inductor, then built the following circuit:

It works OK, but only when I apply a certain load. When the load is 1K or more, Vout- is about -11V, and Vout+ is -0.2V (input voltage is 12V). Load resistance of 220R or less makes Vout- equal to -2.39V, and Vout+ to 2.36V, which is just fine for my purposes.

I don't like the fact that circuit needs some "dummy" load to work correctly, because it means aditional power consumption. I'm gonna use battery as the power supply, so I whant it to consume as less power as possible. Besides, it looks like a very quick'n'dirty solution. Are there better ways to solve this problem?

To provide some additional information about the circuit, I tried to obtain the inductor's currents waveforms. To do that, I removed C2 and C3 and applied the load resistors 10R, than measured the voltage waveform on them. Here is what I got:

Primary coil

Primary coil - large scale

Secondary coil

By primary coil I mean the coil which is connected directly to IC.


texts: Protecting Microcontroller Input Pins from Soft Power Switch

texts:
I'm working on a soft power switch for a microcontroller where a momentary switch can turn the circuit on (including microcontroller), and then when the switch is pushed a second time, the microcontroller can shut itself off after performing some clean up.

I have the above circuit so far, but I'm not sure if it'll be reliable. I'm using a lithium-ion battery (3.7-4.2V) and the TC1015 regulator (3.0V output). The idea is that when the switch is pressed, the regulator turns on, then the microcontroller sets uC Power high, keeping itself on. When the switch is pressed a second time, an interrupt on uC Switch will allow the microcontroller to set uC Power low, turning itself off.

What I'm not sure about, is if I need to protect the microcontroller from battery voltage. The microcontroller I'm using has an absolute maximum voltage on the I/O pins of Vdd+0.4V, so I'm not sure how to handle that best.

Second, will this circuit actually keep the regulator from turning on when it's in the "off" state? I had thought about using a pulldown resistor on the enable line, but am worried about the current draw while the chip is powered on.

Edit: The microcontroller is the primary load that will be switched, so putting it into a low power mode unfortunately won't work here.

Edit #2 (After answers were posted):

I ended up using the circuit below:

The previously posted circuit didn't work very well, and had issues with a floating enable line when the microcontroller wasn't powering it.

The new circuit uses a flip flop, with the data line normally pulled low. Pressing the switch hits the clock, turning the system on. Subsequent presses of the switch drive the CLOCK line high (allowing the microcontroller to sense the press), but don't affect the output of the regulator. Once the microcontroller is ready to power off, it sets the DATA line high and then sets the CLOCK line high, which will cause the regulator to shut down.

One of the really nice things about this setup, is that the first button press turns the regulator on, and keeps it on until the microcontroller is ready to shut down. Bounce isn't an issue, because no matter how many times the clock line goes high, the data line is still held low by the pull down. In addition, the current draw should be very minimal (just the flip flop and the TC1015 while off), and there is minimal current draw through resistors while on.

The microcontroller does need to be protected from the battery voltage on the clock line, but as @Andy aka suggested, that can be done with a resistor on CLOCK.


texts: pwm or gpio for pled display on beagle bone?

texts: Wondering which adafruit bbio library i should use. I know nothing. My sense is that GPIO will be simpler to  communicate the display info to the screen. The screen is a 128x32 adafruit pled


texts: The level read from a microcontroller Pin

texts:
I want to verify the level read by uC1 in the following config:
uC1|---------|uC2
The pin is shared directly between two uCs 1 and 2 without any external circuit. Each pin has a particular configuration:
uc1: Input with no pull
uC2: Output with Pull-up.
Theoretically, we will read the following values:
From uC1:

HIGH when uC2 doesn't set the level or when it set the level to HIGH
LOW only if uC2 set the level to LOW.

Is this analysis correct?


texts:
SAMD21J18 in a custom made circuit behaves abnormally as following:

Delayed boot time between 2 to 5 seconds randomly
Boots on touching the MCU crystal's metal top with a metal pin
Boots on touching (not pressed) an onboard ESP32 MCU RESET button's plastic bud with a metal pin

Initially chip was not detected by Atmel Studio & Arduino IDEs. After resoldering it behaves as such during boot. Otherwise its works well. Crystal load capacitors were tried from 6pF to 15pF. The specified 12.5pF load caps for the crystal is onboard now.

Never came across such an error before. Anyone can shed some insight on this?

Edited after @voltage spike's reply:
The same mcu when replaced in a different custom board boots normally.
The metal pin used to touch the body of crystal was a thin screwdriver held at the plastic handle.

Crystal https://www.mouser.in/datasheet/2/741/LFXTAL009678Reel-940279.pdf


texts:
I tried two circuits below, none of them seems to be working (I used 74LS04 and 74LS00), the output doesn't change when I press the switch.

I found that the voltage at point "A" doesn't drop below 0.8V (stays around 2V) when the switch is pressed. My guess the reason is that: when the switch is pressed, the capacitor starts to discharge, but there is a also a current flow out of the logic gate to ground thru R2, caused a voltage drop across R2, so that the voltage at A can not reach logic "0".

Any other ways to make it work? Thanks much!


texts: Buck-boost INPUT voltage regulation stability (MPPT)

texts:
I am designing buck-boost converter with Maximum Power Point Tracker. The idea is to build feedback loop that regulates input voltage by changing output current. Output will be connected to Li-Ion battery. Constant voltage output and MCU driven MPPT algorithm will be implemented in the future, the main objective now is to build constant INPUT voltage converter.

I am doing simulations in LTspice but all designs that I try are unstable. I attach one of the designs which after some fluctuations starts to regulate input voltage but there are only few degrees of phase margin.

Could someone suggest the right feedback loop design that would be more stable than that? Would it be enough just to add Type III compensation network instead of Type I or maybe there is completely smarter way to do the feedback loop?

In the end, after designing stable input voltage regulation loop, the idea is to multiply input voltage and current with MCU and with perturb and observe method find the MPP. MCU will regulate input voltage by changing resistance in digital potentiometer which will be connected instead of bottom resistor in voltage divider of the feedback loop.


texts: How to deal with a negative resistor in Z parameters of a passive network?

texts:
This question is so basic but for some reason I am not seeing it: Assume an arbitrary passive 2-port network having only isotropic materials. This implies S21=S21 and Z12=Z21 (see https://www.microwaves101.com/encyclopedias/basic-network-theory and https://www.rfcafe.com/references/electrical/s-h-y-z.htm).
From https://en.wikipedia.org/wiki/Impedance_parameters#Two-port_networks:

This could be a classical passive T network, for example. Fully passive means it should (at least at one frequency) be possible to describe it with real components (nonnegative resistors, capacitors, inductors).
Consider the following circuit:

simulate this circuit – Schematic created using CircuitLab
At 915 MHz, it is easy to verify that that Z12=Z21=-3.75-j112 Ohm. Why is Z12 negative and how to build the proper passive two-port network that's actually reliazable?


texts: MAC data width for 100/40 Gigabit Ethernet system on Xilinx Ultrascale core

texts:
If I remember correctly, Xilinx's 10 Gigabit Ethernet Mac core has 32 bits data bus connected at the mac side at 156 Mhz....

What about the 100 Gigabit and 40 Gigabit Ethernet Subsystem in the Ultrascale+ FPGA's from Xilinx?

How wide is the data bus going into Mac core and 40GbE Mac core?  and what's clock rate on the mac side?

Also, if using backplane KR4 standard to transport 100GbE... how many GTH transceivers on the phy side?


texts: Mystery Component - 3 pin device with printed circuit pattern

texts:
This was salvaged from a dead "Bush" branded "walkman" style product a few years ago and has been rattling around in my parts bin ever since.  The marking on the back simply says "M7." with no other markings at all.  The white material seems to be plastic.  The blue area looks very similar to the surface of a PCB and the "traces" are raised from the surface and can be detected by a fingernail scratching the surface.

My meter tells me there is less than 1 ohm between the middle and left pins but does not measure anything on the other pin combinations.

I wondered if it might be a fancy resistor or some sort or perhaps an exotic inductor.  The part was upright and freestanding when installed in the product, but was near to the AM/FM radio receiver circuits.  Could it be an antenna even?


texts:
I built a simple motor driver circuit using Texas Instrument's DRV8835 motor driver IC.

The IC is driven in IN/IN mode, (the mode pin is left unconnected, pulled down by the internal resistor). VM is 8-9V, filtered with 10uF + 100nF capacitors. VCC is 3.3V regulated, filtered with 10uF + 100nF capacitors. The inputs are driven with a microcontroller through 10K resistors. The outputs connect to the motor directly without any further components. The 100nF capacitors are mounted close to the IC. PWM is applied by pulling down the IC's input through a pair of diodes using a single PWM line.

DVM / oscilloscope measurements on the inputs showed no anomalies.

I'm using the circuit drive LEGO Power Functions motors with it.

I noticed a strange and annoying problem with the circuit: while the servo motor and the two largest motors (XL and L) work fine, the medium motor doesn't work.

I built several circuits and tried several M motors, all of the combination produced the following behaviour:

I switch one of the bridges continuously on using IN/IN mode, but the motor don't start (it was connected before switching the bridge on). An approximately 1KHz noise is audible. The frequency was later confirmed with measurements with an oscilloscope. The problem can also reproduced by switching the bridge on and connecting the motor later.

It seems that the over current protection of the IC engages, despite the fact that the problem only occurs with the smallest motors.

The oscilloscope showed that the IC is trying to drive the motor once in every 1ms, but it quickly turns off. This looks like OCP is engaging, the 1ms time interval fits the behaviour described in the datasheet.

The following changes "fix" the issue:

Connecting a 1 Ohm or 0.5 Ohm resistor series with one of the motor leads (too much EMF, and the de-Q-ing helps?)
Driving the motor with 125KHz PWM, asynchronous current recycling (I did not try synchronous modes)

My question is:

How on earth the smallest motor seem to trip the OCP even when the chip is simply turned on?

Thank you all in advance.


texts: isolated input circuit to check regular switch or photo-transistor

texts:
I am trying to develop a circuit that is compatible with a regular switch (push, reed, other) and also a phototransistor.  The application is pinball, where there are any number of switches and IR emitter/receiver pairs.  I want to be able to connect either (maybe an eddy current switch too, but I know this would need an extra board) right into the same input lines.  I ALSO want to keep it optically isolated.

The receiver is a phototransistors, so I can drive to ground similar to the IC opto-isolator.  The problem I have is trying to bias the optoisolator at 1.2V and 20mA when off, and the switch-phototransistor at .4V and 2mA when on.

Schematic with photo-transistor and normal switch options:

Is there something special I am missing in order to bias the phototransistor AND drive the opto-isolator LED from the same pull-up?

UPDATE:

I don't think using the same pullup is possible.  I'm just not that lucky.  So I've come up with a way to do this with the addition of an FET to sink the LED when the switch circuit is closed.  Resistors should have things biased/current limited correctly.  I think I could swing this with a BJT as well.  Does anyone have any thoughts on this?


texts:
A SPST switch connects HB1 and HB2, to control a lamp connected to HB OUT. I am looking into modifying this circuit to make the slew rate adjustable when switching the output to VCC (around 12V). I would like to be able to control the slew rate with a controller such as Arduino or Rasperry Pi.

The slew rate seems to be affected largely by C1. I found some digitally controlled pots like this one: https://www.sparkfun.com/products/10613 , but there don't seem to be digitally controlled capacitors.

I have also been looking into adding circuitry such as this op amp design from TI to control the slew rate: http://www.ti.com/tool/TIPD140#0

I am a beginner when it comes to electronics so any suggestions/insight would be greatly apprecitated.


texts: How to figure out what resistors are in the E12 and E24 series?

texts: Is there a way, other then remembering, to figure out what resistors are in both of these series?


texts:
My wife has a tabletop light she uses for quilting work. She wants to take it with her to a class that has no access to AC. Output from AC plug to lamp is 12V, 3A.

I have searched for power formulas and I think this means it uses 36 Watts per hour or 3000 mAh. I would like to know what size portable power supply I would need to keep her lamp working for an 8 hour class.

Am I correct in just taking 8 hours times 3000 mAh = 24,000 mAh capacity would work? Or 8 hours times 36 Wh = 288 Wh capacity would work?

Thank you for your input to this question!!


texts:
I use the following function to send data from STM32f1 to a DAC7760:

static HAL_StatusTypeDef WriteSingle_DAC7760(uint8_t ch_Addr, uint16_t ch_Data){
  uint8_t liv_Data[3]; // 0: ch_Addr  1:ch_Datadata?8? 2:ch_Datadata?8?
  uint8_t liv_RXData[3] = {0};
  liv_Data[0] = ch_Addr;
  liv_Data[1] = (ch_Data & 0xff00) >> 8;
  liv_Data[2] = ch_Data & 0x00ff;
  status = HAL_SPI_TransmitReceive(&hspi2, liv_Data, liv_RXData, 3, 500);
  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_3, GPIO_PIN_SET);
  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_3, GPIO_PIN_RESET);
  HAL_Delay(1);
  return status;
}

According to these tables from datasheet
https://i.stack.imgur.com/q4xCj.jpg
https://i.stack.imgur.com/W23P8.jpg
https://i.stack.imgur.com/aIrBi.jpg

I use this initial settings for DAC7760

//Write reset register
WriteSingle_DAC7760(0x56, 0x0001);

//Write control register 1001 0000 0000 0001
WriteSingle_DAC7760(0x55, 0x9001);

//configuration register 0000 0011 0000 0000
WriteSingle_DAC7760(0x57,0x0300);

and this is the last line for taking voltage and current output from DAC

WriteSingle_DAC7760(0x01,32000);

But there is no output on 4-20 mA current output and voltage output. Am I missing a part or did I do something wrong?

here spi configurations

hspi2.Instance = SPI2;
  hspi2.Init.Mode = SPI_MODE_MASTER;
  hspi2.Init.Direction = SPI_DIRECTION_2LINES;
  hspi2.Init.DataSize = SPI_DATASIZE_8BIT;
  hspi2.Init.CLKPolarity = SPI_POLARITY_LOW;
  hspi2.Init.CLKPhase = SPI_PHASE_1EDGE;
  hspi2.Init.NSS = SPI_NSS_SOFT;
  hspi2.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_32;
  hspi2.Init.FirstBit = SPI_FIRSTBIT_MSB;
  hspi2.Init.TIMode = SPI_TIMODE_DISABLE;
  hspi2.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
  hspi2.Init.CRCPolynomial = 10;


texts:
So, I have this circuit which needs <50mA and can be supplied with a voltage between 2V and 3.3V.

I want to supply it with a Li-Ion cell, which has 2.7-4.2V. I don't really want/need the complexity of a buck/boost converter. I know I could just regulate it down to anything below 2.5V, but it still would be great if my circuit would get 3.3V for Input-Voltages above 3.3V and the input voltage for anything <=3.3V.

So basically I want a voltage regulator that only regulates for voltages >3.3V and which doesn't (and ideally doesn't use any power) for voltages below.

What is this thing/circuit called?


texts:
I am attaching a motor to a atmega32 chip. I want to build an H-birdge but before doing that, I want to control the motor using the chip. I bought few NPN Transistors from RadioShack.
I have 5V running though the breadboard. I attached Vcc to the Collector, Base to the Pin, and Emitter to the motor. And other wire of motor is hooked up to Ground. Unfortunately,  the power coming out of the transistor is too low, the motor is barely moving (As oppose when I hook up my motor straight to 5V). What is wrong? Do I need a different transistor or is my setup wrong? If it is the transistor, can you please recommend me the right one, I am not too good at those.

Thanks in advance!


texts: I want to learn how to make a CPU from scratch

texts: I am new to electronics, I program from time to time and i know the basics of the logic gates. I have used logisim in the past and I was just wondering if someone could tell me about a good online class i can take or a good site to learn more. Thank you in advance


texts:
I am building an 8 bit VGA circuit and have 3 choices. One is to use a simple resistor network to convert digital to analog. The second is to use an op-amp. The third way to do this is to use a device like this CS4344. (This isn't suitable because of the frequency, but I am still looking for a low cost DAC.) I am looking for a cost effective but accurate way to do this. I know the pure resistor solution is probably the cheapest but the issue is it requires a lot of digital pins. However with a serial DAC I can use fewer pins. The data rate will be about 24Mhz at 30fps (it will be 640x480 resolution.) What is a good way to do this?

If I just use resistors in parallel, how do I impedance match for 75 ohm? Is this necessary or is it not needed?


texts: How is an accelerometer initially calibrated?

texts:
Referring to a MEMS accelerometer, how is the laboratory, initial calibration being carried out?

Is the gravitational acceleration involved as a reference, or is the actual analog data being interpreted independently of the supposition that the gravitational acceleraion is approximately 9.81m/s^2? In all, it should be able to measure gravity, but I am not sure whether gravity itself plays a part in the calibration process (i.e. couldn't one calibrate that sensor in outer space, in zero gravity conditions?).


texts: Determining Existence of Transfer Function H(s) and Fourier Transform H(w) for Non-LTI Systems?

texts:
Given that $$y(t) = \cos(2\pi t)x(t)$$ where \$x(t)\$ is a system input and \$y(t)\$ is the system's output, I need to determine whether an \$H(s)/H(w)\$ relation exists. Since this system is not LTI, I really don't know how to approach it. I'm not able to apply a Laplace Transform even when converted to polar form, and I'm at a loss.

In another case of a non-LTI system causing headaches, I've succeeded in determining that $$h(t) = \frac{\sin(10\pi t)}{\pi t}$$ (or \$10\operatorname{sinc}(10\pi t)\$ if you prefer), and thus I believe its Fourier Transform \$H(w)\$ should be a unit step centered about \$10\pi\$, but I don't know how to determine whether or not this form has a Laplace Transform (i.e. \$H(s)\$). I certainly don't see it as a standard form on any Laplace Transform  tables I've come across.

Any pointers in the right direction would be greatly appreciated.


texts: on-going quest to understand p-channel MOSFETs

texts:
(Disclaimer in case it isn't painfully obvious - I'm very much a n00b, especially when it comes to understanding transistors).

I thought I had it all figured out - a p-channel MOSFET is (or can be used as) a high-side switch for a different voltage source than what my MCU is running on. To test my understanding, I put together the following on a breadboard:

simulate this circuit – Schematic created using CircuitLab

The code on U1 (a 5V arduino) let me drive the line high or low, or put it in a high-z state to simulate all 3 scenarios. I expected that driving the line low would light the LED at 9V, and driving it high would turn the LED off (0V on the mosfet drain). What actually happened was - no light at all, and the drain having a voltage of 6V (5.9V). I'm quite confused - what's going on here?

Here's the mosfet I'm using:
https://www.sparkfun.com/datasheets/Components/General/FQP27P06.pdf

It's meant to be controlled by even a 3.3V logic level, so 5V should be just fine.


texts: Why is shielding effectiveness different for various hole geometries?

texts: I have run into the equation below in various literature/app notes. (example). I have never seen the derivation for such an equation and don't understand why round apertures are more effective at shielding than slot apertures. Could someone clarify or point me to some more study material?


texts: Touch switch for hanging lamp (touching metal bar): Ideas?

texts:
A few years ago, we have bought an IKEA Glimt hanging lamp that operates with halogen lamps. It has a "touch dim" functionality, so when a person touches the metal bar of the lamp, it dims (or when touching for a short time, it switches on/off).
After having replaced the halogen lamps with LEDs and replacing the AC/DC converter, I have noticed that my new LED dimmer has an input that when connected to an external button, it does the same.
My goal now is to build a circuit and connect it to the metal bar such that when touched, it closes the input of the dimmer (pulls down one input to ground).
I have tried a plain darlington pair (with no further components) - indeed on a test board, it is able to close the input as expected similar to what can be seen in tutorial videos on youtube (switching an LED via touch). But the problem is that the LED dimmer emits some electric signal during operation such that it triggers the base of the darlington pair itself via cross-talk, so it keeps being "touched". I have also tried a capacitance sensor (using the touch pins of an ESP32), but due to the large metal parts, there is no numeric change while touching it, it cannot be detected.
So I am a bit lost... what I do remember is that the old halogen AC/DC converter (that supported touch via a single "sense" line) only worked reliably when connecting all three lines (phase and neutral as well as ground).
Any advise/hints? Do I need to equip the darlington pair with more components? The aim again is to pull the switch input of the LED dimmer to ground when touching the lamp's metal components.


texts:
I'm designing a PCB (a shield for Spark Core - microcontroller + wifi board). It is connected to 5 analog sensors (not on board, using 3pin header) and 4 relays (on board).

Output(RJ45) and vias on right is for debug and extension purpose.

(images deleted for copyright purposes)

Bottom Layer: Blue, Yellow
Top Layer: Red, White
Pad, Via: Green
Software used: Eagle

Please tell me anything you think. Any suggestion is appreciated.


texts: Practical method to measure a data acquisition board's noise floor

texts:
Noise floor of a 16 bit system is usually within a few dB of 96 dB. And this is because

20*log10(2^16) = 96dB

But I guess this is the theoretical quantization noise floor. So if this was the only thing I would say for a 16-bit +/-10V DAQ the minimum voltage we can detect would be 20/2^16 = 305uV.

But in practice how can we measure the total noise floor? If I short the analog inputs of a 16-bit DAQ and sample it at a certain frequency and plot the data, would the rms of this data be the real noise floor?

(By noise floor I mean the DAQ's inherent noise which sets the minimum amount of voltage variation we can resolve)


texts: Charge car battery with lab bench power supply

texts:
Is it possible to charge a lead acid car battery with a lab bench power supply?

I am thinking of hooking it up to 13.8 Volts and 1 Amps. Will this work?


texts: Output signal is being attenuated after the Biquad filter direct Form 1, why?

texts:
Thought this would deserve a separate post on its own.
What's going on is that I finally got my low pass digital filter working on the STM32H753ZI using the PMODI2S2 peripheral and I noticed the output signal is extremely low ~340mVpp this is after the biquad filtering. If I take out the low pass filtering the output signal then raises to around ~600mVpp.
What's causing this phenomenon? The digital filter bode plot says the gain from very low frequencies up to the cut off is 0dB so I dont understand whats going on. The only thing I can think of is the biquad filter is causing an attenuation perhaps?
Analog Filter: \$ LPF_{Analog}=\frac{3.94e07}{s^2+8889s+3.94e07}\$
]3
Digital Filter: \$ LPF_{Digital}=\frac{0.00102z^2 +0.002041z+0.00102}{z^2-1.908z+0.9116}\$, using tustin

Pictures:
Input signal(yellow) from wave gen and output signal(green) after the Biquad filter

Input signal(yellow) from wave gen and output signal(green) passthrough with the peripheral no digital processing

Bode plot from Oscilloscope with the biquad filter:

CODE:
#define ARM_MATH_CM7

#include "main.h"

#include "arm_math.h"

void init_Clock(void);
void init_I2S(void);
void init_Debugging(void);
void init_Interrupt(void);
void init_SpeedTest(void);

int32_t RxBuff[4];
int32_t TxBuff[4];
uint8_t TC_Callback = 0;
uint8_t HC_Callback = 0;

char uartBuff[8];
 float32_t iir_coeffs[5] = {0.00102f, 0.002041f, 0.00102f, 1.908f, -0.9116f}; //B0, B1, B2, A1, A2
float32_t iir_mono_state[4];

float32_t Rx_Buff_f[4];
float32_t Rx_Buff_f_out[4];

arm_biquad_casd_df1_inst_f32 monoChannel;

void DMA1_Stream0_IRQHandler(void) {

    if (((DMA1 -> LISR) & (DMA_LISR_TCIF0)) != 0){
        DMA1 -> LIFCR |= DMA_LIFCR_CTCIF0;
        TC_Callback = 1;
    }

    else if (((DMA1 -> LISR) & (DMA_LISR_HTIF0)) != 0){
         DMA1 -> LIFCR |= DMA_LIFCR_CHTIF0;
         HC_Callback = 1;

    }
}

int main(void) {

    init_Clock();
    init_I2S();
    //init_Debugging();
    init_Interrupt();
    //init_SpeedTest();
    arm_biquad_cascade_df1_init_f32(&monoChannel, 1, iir_coeffs, iir_mono_state);

  while (1)
  {

      if (HC_Callback == 1){

         // GPIOA->BSRR |= GPIO_BSRR_BS3_HIGH;

          for (int i = 0; i < 2; i++){
              Rx_Buff_f[i] = (float32_t)RxBuff[i];
          }

          arm_biquad_cascade_df1_f32(&monoChannel, Rx_Buff_f, Rx_Buff_f_out, 2);

          for (int i = 0; i < 2; i++){
                TxBuff[i] = Rx_Buff_f_out[i];
            }

          HC_Callback = 0;

      } else  if (TC_Callback == 1){

        //  GPIOA->BSRR |= GPIO_BSRR_BR3_LOW;

          for (int i = 2; i < 4; i++){
               Rx_Buff_f[i] = (float32_t)RxBuff[i];
            }

                  arm_biquad_cascade_df1_f32(&monoChannel, &Rx_Buff_f[2], &Rx_Buff_f_out[2], 2);

                  for (int i = 2; i < 4; i++){
                        TxBuff[i] = Rx_Buff_f_out[i];
                    }

          TC_Callback = 0;

      }

  }

}

UPDATE 1:
As requested doing a spreadsheet of different frequencies and a block diagram and a physical setup to show you guys.


texts:
I have a PIC18F2550 that I'm trying to get a simple hello world type program to run on.  The code is configured to flash an LED on and off with 250ms delays in between the cycles.  I have a 4Mhz crystal attached to pins 9 and 10 with 2 18pF capacitors.  When I attach my oscilloscope to the output pin and power on the chip, I can see the high low signals go from 0V-5V for about 3-5 seconds then it just flat lines.

If I power the chip off for a while and plug it back in, it starts to work again, but after 3-5 seconds it will go to 0 again.

What can I do to troubleshoot this problem?

Update

I should also add that after repeating the whole process several times (i.e. powering on and off the device), it eventually won't turn on the output at all.

I've tried multiple PIC18F2550 chips with the same software and get the same effect, so it's not the PIC processor.

I'm thinking this must be a hardware issue since the software was copied from a working sample.  In case someone thinks it is a software issues, here's the MikroC code (although I don't think this is the right Stack Exchange site for source code):

void main() {
    TRISB = 0; //Make all PortB pins output

    while(1)
    {
        PORTB = 0; //Turn off the port
        Delay_ms(250);
        PORTB = 255; //Turn on the port
        Delay_ms(250);
    }
}

Here a (very) rough schematic of the circuit.  I have the scope hooked to pin 24.

Here are the parts that I'm using

Crystal
Crystal Capacitors


texts: Is an in-vehicle, "smart" automobile-battery maintainer powered by a "smaller" rechargeable battery feasible?

texts:
Another naive question from a lay-person.
      A standard AC utility-powered Tender or Genius type unit is impossible to use with on-street parking. I am doubtful that "solar-powered" units sold would be sufficient on northern streets which are low-light in winter and tree-covered in summer.
      To put it bluntly, would common rechargeable batteries have enough "juice" to power such an application?
      Say, something like a 7-9Ah 12V (UPS-sized) SLA Battery, or maybe a more expensive (and bit more worrisome to leave unattended) lithium jump-start type battery pack.
      Is this feasible or economical?
      Would being DC- rather than AC- powered be a problem? (As a non-EE, my lay-person take on consumer electronics has been that a switched-mode power supply is so ubiquitous (because of usefulness and low-cost) that utility AC is preferred to power DC electronic devices - including battery-maintainers/chargers.) So would components and circuitry to up the 12.x V DC from an SLA battery, and to usefully modulate the A through the smart charging steps, perhaps be too pricey? (Never noticed anything like this on the market.)
    And apologies if my search terms missed a related post.


texts: Simple Capacitor charging and discharging question

texts:
Below is a circuit consisting of a capacitor, voltage supply and resistors.
There is a switch that lets the capacitor charge and discharge.
I have also uploaded the given answers below;

I understand that for:

(i) Tc:     you find the thevenin resistance and multiply it by the capacitor value.

(ii) Vc Max: the voltage across the parralel (Rz) resistor.

(iii): I am not sure that he has done there. Has he used the capacitor charge or discharge formula and rearranged it of some sort?

(iv): Not sure what hes done here?

.


texts: Where does the term "lumped" come from anyway?

texts: I think I understand the idea of dealing with lumped circuit elements in electrical engineering, but how did they come up with the name "lumped"?


texts: Can you simulate a GPIO input on STM32F0?

texts:
I'm trying a variety of things out with input pins and customized timers on the STM32F0. All timer functions are alternate functions on the pins and therefore you cannot use the user button (PC13 on the NUCLEO) as it doesn't have any timer in its alternate functions.

So, the question is:
Can you (in the software) "simulate" a GPIO pin input going high? This would make writing code easier as you won't have to hook up the NUCLEO test board, header wires, etc. I was thinking of manually toggling bits in GPIO's IDR register but it's read-only. And the BSRR register only affects outputs. Is there a way to achieve this?

ST should have put the User Button on a different pin with more functions...

Thanks!


texts:
In the Digital to analog converter HP16BME, I keep stumbling into " +FS - 1LSB " and I'm not sure what it means.

I mean, I still don't know the exact scale value because I don't know what FS stands for and what they mean by 1LSB in this example


texts: control dc dc converter board with the microcontroller

texts:
I want to control a bidirectional buck boost dc dc converter evaluation board evaluation boardusing STM32 Nucleoboard MCU. The evaluation board is having only I2C interface. I am connecting a 12V lead acid battery at the output terminals of a converter board. I want to control the output of a converter board such that it delivers same voltage of the battery to charge.

I can measure the voltage of the battery using voltage divider or current sensor
I am thinking to use high side current sense amplifier for measuring the current. But my confusion is where and how to measure the current.
Using MCU I can generate PWM using duty cycle. But how to interface board and MCU.
Can someone please help me in this task.

Thanks and Regards


texts:
So for the past couple of days, I was testing out the LTC3112 Buck-Boost IC from Linear Tech. I'm using this for my heated glove project to step up/step down the voltage across the heating element. Using the typical application schematic for my test schematic with a 5V input (while changing the inductor from 4.7uH to 10uH), I tested the output voltage on an LED with a 1K resistor, and it was outputting 5V with appropriate current (of course). But when I switched to a piece of my conductive fabric (at 14 Ohms) as a load, the IC got damaged somehow and now is drawing 300mA - 400mA on the input side of my power supply even when there is no load attached and I am no longer getting a 5V output. Compared to a current draw of 0.027A when the IC was properly working.

I'm just trying to figure out what went wrong and why the IC failed me. The PWM/SYNC, Run, and Vin pin all received 5V. Unless my load somehow shorted itself (which I don't believe to be true), this IC should have been capable of outputting the appropriate current. I honestly don't know what the issue is at this point.

https://www.analog.com/media/en/technical-documentation/data-sheets/3112fd.pdf

The yellow wire I'm point to/touching is Vout with no load connected.


texts: How would you design a variable current divider for non linear loads?

texts:
What part or circuit would you put in the box in the center to be able to variably control the current between the two loads to smoothly dim between the two LED strings?

simulate this circuit – Schematic created using CircuitLab

Can you think of a way to do it without any inductors?

Can you think of a way to do it with high efficiency? (the sum of the load currents is approximately equal to the current supplied by the source)

Can you do it without PWMing between the loads? (Smooth current in, smooth current out)


texts:
I'm looking the mindshare book for TX compliance test.
Somehow I'm confused about the method to enter the Polling.Compliance substate.
In Gen1/2, it seems that of the transmitter detects a 50 Ohm load, it'll enter the compliance substate.
However, in Gen3, I can't find such condition.
Can anyone help me on this?
Thanks.


texts: Negative resistance in a regenerative radio receiver?

texts: Why is an amplifier with a tuned circuit and positive feedback, such as a regenerative radio receiver, said to exhibit or have negative resistance?


texts: how to simulate 4 bit ring counter using max+plus II

texts:
I'm newbie with max+plus II and digital modelling world just want to simulate a simple ring counter https://www.dropbox.com/s/47tlv3g7o9zi8gb/all.jpg the ring counter's initial value must set to 1 (input port A) so I can not delete input A as you see the output of dff #3 is connected to the input of dff #0

I keep getting this error:output Q and input A are tied toghther I'v tried using three state buffer to solve this but no luck so far gdf file: https://www.dropbox.com/s/y4zp8x6q5o9uf1y/ringcounterdff.gdf thanks


texts: Name for PCB isolating tape (usually found in notebooks)

texts:
Looking for the name and, at best, part number for the tape usually used to isolate the PCBs, in particular inside notebooks (black tape on the pic below):

My design is having through-hole capacitors lying on the board, and while they are in the protective insulating sleeve and board is having mask under it, I want to consider putting additional protection between them.
Bigger picture:

I do not have naked NB MB right now to shot, and funny enough it appears uneasy finding good quality picture (without alibaba seller name on it)!
This tape is usually used between CD-ROM assembly and PCB (as protection against physical damage to PCB when CD-ROM is removed and inserted), between boards to ensure no accidental contact between board assemblies, and between other mechanical components (e.g. cooler) and PCB. The tape (film) is having glue at one side. I am sure people familiar with notebook design / repair must know what the tape / film is.


texts:
I have this BCR116 NPN Transistor
In the datasheet, they mention as Input ON Voltage instead of Base Emitter voltage like below :

But my doubt is, when they say Input ON Voltage is 0.5V minimum, since this part has an inbuilt internal resistors, does that 0.5V mean, that is before the series resistor or after the series resistor?

At which point are they mentioning that 0.5V should be? Before or After R1 in the above diagram?


texts:
I have a heat pump with an RS485 interface. Via a simple RS485 chip. No isolated interface, no isolated power supply to it.
I want to add a power meter at 400+ meter to it and want to properly isolate the heat pump from that line. Speed is 9600Baud. Is there an isolator solution that comes to mind? I could not get further than converting RS485 to Tx and Rx, and then take a properly isolated RS485 chip as the interface. I think this is overdoing it (1), but I also hadn’t figured out how to do the Driver Enable of both ICs (2). The latter made me think that I want to understand how to do it as simple as possible.
What would be the simplest way isolating bidirectionally used Half duplex RS485?


texts:
I have used the THS4151 op-amp to create a circuit that takes two inputs and subtract them to give an output. Below is the schematic for the circuit:

R1 is where I will input a 1 MHz, 2V sinusoidal signal, and R6 is where the other input signal should come from. In this case, I grounded that input. Below is a picture of the input signal for R1:

My problem is when I try to power the op-amp, It will oscillate, and the input signal will look like:

And the output signal will look like:

Any suggestions?
Thank you


texts: Do I need individual connections to +5 V for this circuit?

texts:
I have the following circuit:

See that +5V in the top left corner (ignore the bottom one for now)? It is connected to J, S, J, and S. I know that I can simply grab 4 wires and connect each on to my +5V on my protoboard, but I was wondering - instead of using 4 long wires, can I just use 1 long wire, connect it from my voltage source to some spot on my breadboard, and then connect 4 wires in series (same row) to it to grab +5V? Or would this reduce the voltage each port receives?


texts: Serial Communication and Local Clock error calculation

texts:
For a 24MHz system, the local clock error associated with transmitting 10-bit character frames at 38.4 Kbaud using the SCI of a Freescale Micro is 0.16%.

How? I can't figure out the math that actually makes sense to get that number. Any ideas? I'm sure it's easy.


texts: How is electromagnetic interference measured in an environment?

texts:
I see many people are concerned about EMI issues, particularly noise due to this phenomenon. Many SMPSs are enclosed in boxes which looks like Faraday cages:

But how is EMI identified or investigated or measured practically?
What characteristics of the measurements let one to conclude that the measured data belongs to EMI?
Is this a difficult practice only done by RF engineers or are there also easier ways/methods/circuitry?

edit: By the way here:Switching power supply using faraday cage and EMI protection? it is claimed that that the meshed SMPS case in the above picture has nothing to do with the use of Faraday cage and will not block EMI.


texts:
I have one of these HV dc converters and I was wondering if I can use it to supply a small Russian SMB21 Geiger muller tube. What other parts would I need to add not to fry the GM tube? Keep in mind I would also like to add a nice Arduino nano and display and turn it into a simple Geiger counter.

The step up dc dc converter is a EMCO A series A04P


texts: ATEX - Infallible Current limiting resistors

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I'm preparing an intrinsically safe electronic board according to 60079-11.
In this standard film type resistors are accepted as infallible current-limiting resistors, which means that that they fail only to an open circuit.

In my opinion "film type" is quite general. For example, common SMD resistors are thin film type or thick film type.

Because of this, can SMD resistors be considered as infallible current limiting resistors?


texts: I'd like to know how can I calculate TL0 values. For example, when we have assigned hex value 0x05 to TH0 flag, we set our timer reloading time for 250 microseconds. So the question is: how can I discover how many microseconds that for example the value 0x80 equals?


texts: How to determine which diode conducts in diode-OR application

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Say I have two 12V power sources - 12V_A and 12V_B. What happens in the following scenarios:

If 12_A = 12_B = 12V. Do both diodes conduct?
If 12_A is slightly higher than 12V_B. Does the top diode conduct? Or both?
If 12_A = 12V and 12V_B = 0. We know that top diode conducts for sure, but is there also leakage through the bottom diode?


texts: RS232/RS485 Converter Circuit Receiving Problem

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I'm trying to make an RS232/RS485 converter circuit. I used a circuit from http://airborn.com.au/layout/232cnv/232to485.html site and i changed some components on that circuit. Then I established my converter circuit:

I used copper pour as ground and i connected lacking ground connections with additional wires after the board was prepared. To test my circuit, I used another RS232/RS485 converter circuit which I know that is working without a problem. I connected A and B outputs of my circuit's RS485 connector to the A and B outputs of other circuit's connector. Then i connected these two converter circuits to computer with RS232 USB cable. I tested the communication between these circuits using CuteCOM serial communication terminal. I used two terminals for my circuit and other. (Baud Rate:9600)

I observed that data is transmitting from my converter circuit to other but not receiving from other circuit to mine.

I also tested the other converter circuit with another RS232/RS485 converter circuit which I know that is working without a problem, and i realised that there is not any problem during transmitting and recieving process, so data can be sended and recieved.

These are the list of the changes that i made on original scheme in for my converter scheme;

Maxim's MAX232CWE was used instead of ICL232.
Texas Instruments' SN65HVD3082E was used instead of 75176.
As voltage regulator, Exar's SPX3819 was used instead of LM2936Z5.
As transistor, BC256A (pnp) was used instead of BC557 (pnp).
22 uF capacitors were used instead of 2.2 uF, for the ones connected to MAX232CWE.
On original scheme, a 6 pin connector was used as RS485 connector and two pins were used for A,B connections, one pin was connected for ground, one pin was connected to the 9th pin (RI - Ring Indicator) of the RS232 connector with a jumper. Unlike these, in my circuit, 2 pin connector was used as RS485 connector and only A,B connecitons were made. (RI and ground connections were not used.)
On original circuit, A and B pins of SN65HVD3082E RS485 Transreciever were terminated with a 120 Ohm resistor and a jumper. I did not do this on my circuit.

I'm investigating about the problem which can be related with changes that i made on original circuit or another reason. I will be very happy if you share your idea about the problem of just transmitting and not recieving data on my converter circuit.


texts: I have a set of four panasonic 18650 3.7v 3400mAh batteries that I am using for a project. All four are wired so that the voltage is doubled (7.4v) and so that the amps are doubled (6800mAh). I've been checking the voltage with my multimeter frequently over the past couple weeks I've had them, and the voltage has dropped from 7.1v to 5.9v over that time. The thing is, I've hardly ever used the batteries in that time, only a couple times. I wouldn't expect these batteries to drain without hardly any use, especially since its 6.8 amps. I'm just trying to think of reasons it could have done this.. The best one I can think of is the fact that I accidentally shorted ground and voltage when measuring the batteries (the two traces are super close) and it resulted in a spark, though it still supplied voltage fine, even to this day. If anyone could either confirm this theory or give another, that'd be great.