texts: Implementing Logic Using 2x4 Decoder (Confusions with Non/Negated Inputs/Outputs)

texts:
In a question, I'm asked to implement the below using a 2x4 Decoder with Negated Outputs and a Negated Enable

Truth table for the decoder was:

The given answer was the top diagram, mine the bottom:

How could it be the top? S3 = 1 when BC = 10 not 01?

How do you go about deciphering such logic, I find myself very confused when there are negated inputs/outputs


texts: Square wave at line frequency. How does it work?

texts:
I found the following circuit next to a switching power supply in an electrophysiology amplifier (AXOPATCH 200A, an instrument for a technique called "patch clamp").

References to power outlet:

L: line
N: neutral
G: ground

SEAL is then connected to an AND gate input (pin 9 in a 74HC08), the other input (pin 10) of the gate comes from a selector in the front panel: "SEAL TEST (5 mV line frequency)".

I think the purpose of this circuit is to generate a square wave with line frequency (50 or 60 Hz), 5V and 50% duty cycle, but I'm not completely sure. Can any of you analyze the way this circuit works? What should be the ratings on the zener diodes?

Edit: I desoldered D1 and D2 to see the markings and found that it reads 1N914 which is an older version of the general purpose diode 1N4148. I mistakenly thought it was a zener for its transparent appearance. Resistors are just one (not two or three in series), they are 1% precision, 1/4 W as you can see on the following picture (with one of the desoldered diode).


texts: Understanding purpose of a resistor in reference schematic TIDU034

texts:
Gents,

I'm analyzing this schematic, but do not understand couple of things. I would be grateful if someone could explain in detail these questions:

1) R6 - shunt? What's the purpose of it? Under what conditions it is required? I believe value was chosen pretty much random but high enough?

2) R7 and R10 are input bias return paths - why do they have different values (100k vs 22k) for the same opamp part and signal level (U1A & U1B don't do amplification)?

The original article where this was published is TI's Active Volume Control for Professional Audio (TIDU034).


texts: Why is flyback air gap needed for energy storage?

texts:
Why do so many sources say something along the lines "since a flyback transformer stores energy, an air gap is needed"?  I have seen this reasoning in textbooks and app notes.

I thought air gaps cannot store energy and I thought also a flyback transformer stores energy with its inductance, and an air gap reduces inductance so I would think it also reduces an inductor/flyback's ability to store energy.

Where am I confused?


texts:
I want to make a strong electromagnetic crane that would carry weights from one position to another. I am very unsure about the material. Do I use an old transformer? or What type of rods? What type of wire?
Also, how can I make sure there is no short circuit occurring?
Most important, How can I make the current cut off automatically upon reaching the specified position. I will be using LEGO for the motion and the crane and 12 V battery.


texts: Design a circuit to determine NMOS parameters

texts:
I am studying electronics independently, so this question is perhaps obvious for an engineering student.
I know that, for the ALD1106 MOSFET, we can assume a typical \$V_t = 0.7 V\$. How could I design a circuit to calculate the component's \$K\$ and \$\lambda\$ parameters analytically?
To force a saturation behavior, I will assume that \$V_{DD} = 5V\$ and \$I_D = 500 μA\$.


texts: What is the purpose of UVVM's t_void type?

texts:
In the types_pkg package of UVVM's uvvm_util library, the type t_void is defined as an enumeration type with a single literal:
type t_void is (VOID);

This type is used throughout the library to define procedures that don't take a useful parameter:
procedure whatever (constant dummy: in t_void) is
begin
    -- dummy is not used
end;

When invoking such a procedure, one must pass VOID:
whatever (VOID);

The same procedure could also have been written as:
procedure whatever is
begin
    -- No dummy here
end;

So what is the purpose of the t_void type and the dummy parameter?


texts: Using Ethernet Cable in Electronics Projects

texts:
I'm building a cue light system (think traffic lights for theatre, media and entertainment industries) and I need to connect outstations (the traffic lights) to the control station (Arduino).

Each control station consists of one button and two LEDs - so I use 4 wires in total (ground, 2x 5v for LED and a pull up for the button). In selecting a connector I noticed that RJ45 is abundant (especially with EtherCon connectors) and cheap to obtain.

What is the danger, both to my system and to switches and networking gear, of using these cables in my system? With the low voltage DC current within the rating for the cables I'm confident it works great for my system on its own - but what would happen if someone accidentally plugged my base station into a laptop for example, or an outstation into a switch? Can I use certain pins to mitigate this or should I use an entirely different connector all together?


texts: PIC18F25k50 - ICSP programming - do I need to connect MCLR to PICKIT for new device?

texts:
Im new in PIC world. I purchased few PIC devices, PicKit 3 and now im working on first circuit. I accidently ordered SSOP package and I can't just test it on breadboard - I have to make PCB. I stuck on programming interface.

PIC18F25k50 which im using has:

Single-Supply In-Circuit Serial Programming (ICSP™) via Two Pins

Is this turned on by default?

Can I program new virgin device by 2 pins (and GND) connected to PicKit3?

I couldn't find anything about this in datasheet and PICKit manual, however these are big documents, maybe I missed it.

I also tried to ask about this on Microchip forums, but I created 3 diffrent threads and they are waiting for moderator acceptance for 3 days...


texts: Effect of Leakage inductance in flyback converter?

texts: Can somebody explain me what actually causes the presence of leakage inductance in flyback topology and how it affects the efficiency and related stuff.


texts:
I am having a problem with inductor desoldering. (Bourns 2310-V-RC)
I found a lot of desoldering failure after time.
The inductor is used as an LC filter. Maximum 8 Amps.
This is the PCB view

Are the pads of my design too small? Do you think I did some mistake?
If you need more details please just ask me


texts:
I am using an Actel SmartFusion system-on-a-chip, running a bare-board application that uses the MSS with SPI, ACE and GPIO.  (I am developing in Libero IDE 11.1 and SoftConsole.)  My program successfully runs on the A2F200 package, but when I switched to using the A2F500, weird things happen when I send SPI data and trigger the interrupt.

First it was triggering the interrupt but not reading the data I sent it, then it began crashing the program if the interrupt triggered.  The weird part is that even if I stop debug and relaunch, it wouldn't even start - the debugger would freeze on "cont".  Sometimes power-cycling the chip would fix it and bring me back to where I started, but sometimes even that didn't work, and I would have to eliminate the SPI code from my program to get it to run at all.

Has anyone else seen anything like this on the SmartFusion?


texts: What's the effect of shorting the wiper terminal with one of the ends of a trim pot?

texts:
EDIT: I realized I didn't draw the schematic properly. Previously, the 100 Ohm resistor wasn't there.
I thought I'd done the math correctly for this, but clearly something conceptually isn't straight for me. I need a 5K potentiometer, but the sources I've looked through didn't have it in the package I'd like. I did see a 10K pot in the package though. So I thought by shorting the wiper terminal with one of the ends of the trim pot I'd be able to half the maximum possible resistance offerable by the pot.
$$\frac{1}{R_{total}} = \frac{1}{R_{wiper}} + \frac{1}{10000}$$
$$\frac{1}{R_{total}} = \frac{R_{wiper} + 10000}{10000 \cdot R_{wiper}}$$
$$R_{total}=\frac{10000 \cdot R_{wiper}}{R_{wiper} + 10000}$$
Since the highest resistance Rwiper can reach is 10K, the resulting highest value would be
$$R_{total}=\frac{10K \cdot 10K}{10K + 10K} = \frac{10K \cdot 10K}{2 \cdot 10K} = 5K$$
I could also make a graph by plotting the function of Rtotal.
By this point I was convinced. I tried to measure the resistance on a spare 10K pot lying around, but I saw that maximum value remained 10K. Why is this?

simulate this circuit – Schematic created using CircuitLab


texts:
I cannot figure out a puzzle which is to create a 4-bit bit counter using basic logic gates (NOT, OR, AND, NOR, NAND, XOR, XNOR, MUX, FULL ADDER). A bit counter tells how many bits are set in a value. So, for example, the value '1011' would have the result '011' because three bits are set and '011' means 3 in binary.

I bought a book called "Digital Principles" by Schaum's Outlines and nowhere in this book does it tell how to make a bit counter out of logic gates. I also have the book Hill & Horowitz, used to teach digital logic. Nowhere in this book does it tell how to make a bit counter out of logic gates. I find it extremely frustrating that making basic combinatorial logic circuits is some kind of black voodoo that is undocumented.

Is there any book that COMPREHENSIVELY describes the construction of all common combinatorial circuits, such as bit counters, adders, etc, using basic logic gates?

Note: figuring out how to do this is not easy. This is a 16-row truth table with 3 columns of outputs. If you try to write that all out and simplify it, it will be very complex and a lot of opportunity for making errors. The truth table for a 4-bit bit counter looks like this (inputs on left, output on right):

I tried solving this using a Karnaugh map, but it is still resulting in an expression that is way too big for the puzzle solution area. For example, for the second output column, I got the following Karnaugh map:

which has the following expression:

A'B'CD + A'BD + ABC' + AB'D + BCD' + AB'CD'

Representing this in the puzzle would require 6 4-way ANDs, 1 4-way OR, and 3 2-way ORs. All these components would not even fit in the available area for the puzzle solution.


texts:
I host some drone races at times and I make gates with hula-hops. I fit some led stripes in there and they glow nicely.

We ONLY run micro drones, F36, tinny whoop and those. And mostly indoors (although something that works outdoors would be nice)

I use small nodeMCU boards for lots of projects and I was wondering what would be the best approach to detect the drone.
I'd like to get some advice before starting my tests.

Some of my ideas are:

Infrared emitter and receiver at the other side of the circle:
I have the impression that the drone can pass by without being noticed, maybe two pairs of emitter / sensors but.. sounds fiddly. And not sure about its performance outdoors.
Ultrasounds: I think the drone will pass too fast for it to see it
Hall effect: Gluing an small magnet to the drone but ... runners will hate it.

What do you think guys? Are there any better alternatives?


texts: How to wire a 230VAC motor with 4 wires. Model is: YDK139-300-4 300w

texts: I am newbie in electricity but got to wire a 230VAC motor with 4 wires. Model is: YDK139-300-4 300w. Could you check the diagram in the picture and advise please?


texts: Why is stepping up voltage during transmission considers I^2*R but not V^2/R?

texts:
During the transmission, the generated electric power is delivered after stepping up to hundreds of thousands or even more voltages by transformers.

In that case since P = I*V, increasing V reduces I in the secondary of the transformer.

The reason given is to reduce Ploss = I^2*R losses. Here I decreases so the power loss.

Is that the real reason to step up?

I'm asking because we can write the power loss equation as:

Ploss = V^2/R

Or if we use both I and V in the power equation:

Ploss = (V/R)*I

It seems like if we step up the voltage I decreases but V increases. How about the power loss?

Does the power loss decrease?
Or the real reason to step-up the voltage is to reduce the cross section area of the transmission lines significantly?


texts: I have been preparing for a midterm and my professor posted a sample midterm but no answers, i solved the question here and asked him if it made sense, and he said the answer will be fully correct if causality was taken into account, but i do not get what he means by that.


texts: How create a high precision clock in an FPGA?

texts:
FPGAs can easily run at 100 to 500 MHz and create time resolutions of 10 to 2 ns. That frequency can be used to create timestamp counters, which are in turn used to create very fine grained time measurements / timestamps for profiling.

However, these counters rely on an external oscillator and sometimes also on internal clock modification blocks (CMBs like PLL, MMCM, ...). External oscillators have a precision or jitter of 50 (20) ppm at 100 Mhz reference frequency. This gives a possible time error of 50 us per 1 second.

In a customer's system, multiple FPGA boards are coupled via Ethernet and PTP (Precision Time Protocol). One board acts as a server, the others as slaves. PTP can synchronize 2 stations within 10 ns accuracy, whereas the FPGA based master and slaves can not hold the time precision between PTP updates.

Is there any way to increase the timestamp counter accuracy in an FPGA (Zynq UltraScale+) to below 10 us?

Is it possible to measure time drifts (wander) and adjust the timestamp counter?


texts: what is the input impedance of a transistor (bjt)

texts:
That is the Hybrid-Pi model of the voltage amplifier i have. In our lectures we haven't been taught about anything regarding the Hybrid-Pi or transistors input impedance up till today. I figured out that i need to find (equivalent) resistance, something like (R1 || R2 || Rpi).

But i don't know how to proceed! A little help would be really appreciated!


texts: Indoor positioning system using bluetooth low energy

texts:
Does using wireless MCU is better or using a stand alone MCU connected with BLE module is better in terms of power transmitted by the Bluetooth?

Second question is there a way to make rssi value transmitted by the smartphone to the mcu via Bluetooth more stable to calculate the position of the person more accurately?

Third question is the rssi fingerprinting method is more accurate than rssi trilateration or not and is there any other techniques rather than those?


texts: Can I connect up LED strip lighting at alternate ends?

texts: I want to add some simple LED tape/strip lighting to my van. The 12V supply is close to one end of where I want the strip to start, and I have an earth block to chassis close to the other end. I know this sort of lighting normally has 12V and 0V connection done at the same end of the strip for convenience, but in my case it would be more convenient to connect at opposite ends. Although it will only be a short strip, I suppose it would also be of benefit in having uniform voltage drop at each LED done my way? Is there any reason I shouldn't connect at opposite ends?


texts: What s the name of that 6 pin pwm connector fan?

texts:
I m having a special system fan type in my computer which is very noisy (between 60 to 75 Db with vendor provided fans). But if nothing is plugged on it the computer refuse to run.
Here a what the plug looks like on the fan

From the computer s doc (I wasn t able to find the fan specific model)

Is it Molex miligrid?


texts: Using SysTick_Handler in mbed LPC1768 project

texts:
I'm trying to use SysTick_Handler in a project which uses the mbed libraries and RTOS, however on compilation, the following error is returned: Error: Symbol SysTick_Handler multiply defined (by ../../build/mbed-os/rtos/TARGET_CORTEX/rtx5/RTX/Source/TOOLCHAIN_ARM/TARGET_M3/irq_cm3.LPC1768.o and ../../build/main.LPC1768.o).

This leads me to believe that SysTick_Handler is used somewhere in the mbed library. Does this mean I cannot use it, and I have to resort to using the LPC1768s Timers?

The other definition appears to be in irq_cm3.0

Boiled down version of code:

#include "mbed.h"
#include "EthernetInterface.h"

extern "C" void SysTick_Handler()
{

}

// Socket demo
int main()
{
SysTick_Config(SystemCoreClock / 1000);

}


texts: MOSFET driving MOSFET for reduced reduced Rds

texts:
I am using a PIC to drive the gate of a logic level MOSFET. Although the 5V logic output of the pic is sufficient to exceed the threshold voltage I would like to drive the gate using 12V to reduce the Drain-Source resistance.

In order to achieve this I have drawn up the following circuit using two MOSFETs in series (as highlighted). Will this design work, and is it the best approach (keeping in mind i want to minimize the number of components).


texts: 8051 initializing data in external memory

texts:
I am trying to understand the use of external memory with an 8051. When you are using external memory with something like C8051F962 where you have to configure the ports to access the memory, how do you initialize that memory with data. For example, internal RAM you use DB statement to initialize the memory-
MYVAR:  DB  'SOMETEXT'

But I am assuming that will not work with external memory because from the documentation it sounds like you can only move data into it with MOVX. Also, your DB statement would have to come after the port initialization for the external memory.


texts: Confirmation of connection between TSAL5300 IR sensor and BPW34 photodiode

texts:
I need to check whether my NIR LED sensor and BPW34 photodiode connection are correct or not. Does my IR sensor have to be infront of the photodiode?
I am going to place my finger on the IR sensor to detect my glucose level where photodiode will convert the attenuated light into voltage. But even if I turn  on a flashlight and shine it on the 2 sensors, the reading doesn't change. Anode of photodiode is connected to ground, cathode of photodiode is connected to A0, 1k resistor and VCC(5V). Anode of IR sensor is connected to 1k resistor and VCC(5V) and cathode of IR sensor is connected to ground.


texts: On RS Latches (or Flip-Flops), NOR or NAND, via Duality Principle

texts:
Fig. 1 Duality Principle

simulate this circuit – Schematic created using CircuitLab

                                Fig. 2 Alternate Duality Principle in general

simulate this circuit

                                Fig. 3 Alternate Duality Principle in particular

Questions arise from these three configurations are many, especially for beginners.  I myself was always puzzled by the strong similarities and subtle differences among them.  Some notable examples are:

  Why in NOR gate R is associated with Q and S is associated with P yet in NAND gate R' is associate with Q' and S' is associated with P' in your Fig. 1?
  Why in NOR gate configuration we have an active high circuit yet in NAND gate configuration we have an active low circuit?
  Why in NOR gate R is associated with Q and S is associated with Q' yet in NAND gate S' is associate with Q and R' is associated with Q' in your Fig. 3  (or our textbook)?
  Examining the association in the absence of duality can be very confusing indeed.  Consider
  (4a) In a NOR gate, R is associated with Q and S is associated with Q'. Yet in its NAND gate dual, R' is associate with Q' and S' is associated with Q.
  (4b) In a NOR gate, R is associated with Q and S is associated with Q' yet in another NAND gate dual, S' is associate with Q and R' is associated with Q'.
  Is either (4a) or (4b) true but not both? Can both be true?
  I have heard duality priciple, but I am not sure if you can apply it here.  What is duality principle? How can one apply it to digital circuits shown in Figures 1 to 3.


texts: TrackPoint a.k.a pointing stick 2-axis force sensor

texts:
I have an application that would benefit from a sensitive two-axis force or bending torque measurement very much like what a pointing stick (a.k.a. TrackPoint) used to do in a ThinkPad, apparently using resistive strain gauges.  I have been unable to find any commercial sensor with similar functionality at any price; all online references seem to be to salvaged pointing sticks from old laptops and ThinkPads, and the interface is not ideal on these anyway.

My application is not for human/machine I/O but rather to measure the horizontal force (in two dimensions) acting on an object at the top of a ~30 cm tall vertical rigid rod (the rod would transmit the force as a torque acting on the sensor at the bottom).  I would consider constructing the sensor myself from two pairs of piezoresistive strain gages, but there too I have been unable identify parts with the appropriate size, low cost, and sensitivity.

Since pointing sticks were mass-produced at low cost for many years, I have to imagine that force sensors of comparable size and cost are still being manufactured somewhere.

Any leads or advice would be greatly appreciate


texts:
I would like some assistance designing a MOSFET load switch for use in an 12 volt automotive circuit to run a fuel pump controlled by a raspberry pi.
I would like for it to be able to deliver 25 amps continuously no heat sink if possible. I have a P channel MOSFET in mind the ATP304. Problem is I have no Idea if it’s a good choice also I have no idea where to start designing a switch.
I have the ULN2803A darlington driver with 4 of it’s channels paralleled to drive a solenoid, 2 individual channels of the ULN2803A driving 2 LEDs with the 2 remaining channels of the ULN2803A I was hoping to make use of it by possibly driving the load switch ATP304 MOSFET.
Is it a good idea to use ULN2803A to drive the P channel ATP304 gate?
If it is can someone assist me in designing a load switch with appropriate resistors, filter capacitors etc?
*Expected voltage input: 11 - 16 volts
*there will be electrical noise from alternator
*I expect a 15 amp draw continuous but I would like it to be capable of 25 amps or so just in case later I can reuse the PSU design in a different circuit configuration
*device will be installed in a cooler stop in the engine bay.

Thanks]1


texts: How to design a buffer amplifier for STM32 ADC

texts:
So the purpose of this circuit is to buffer a 0-5V signal coming from a potentiometer sensor. The processor is 3.3V tolerate. the sampling switch resistance as 6K. the processor is a STM32F429

are there any issues with what i've done?


texts:
I 'm new to mikro c and PIC programming and I 'm having troubles shutting down the LED on RB5(green)using interrupt on RA2 and this interrupt is possible only in 5 first seconds.
Any help will be appreciated

Here is the circuit in proteus

Here is the codes in MIKRO C

void interrupt(){
  if(RA2 == 1 ){
    PORTB = 0 ;
  }
}

void main() {
  unsigned char j ;

  TRISC = 0b11111110 ;
  TRISA = 0b000100 ;
  OPTION_REG.INTEDG = 1 ;
  INTCON.INTE = 1 ;
  INTCON.GIE= 1 ;

  for ( j=0 ; j<10 ; j++ ){
    PORTC.RC0 = 1 ;
    delay_ms (500) ;
    PORTC.RC0 = 0 ;
    delay_ms (500) ;
  }

  ANSELH.ANS2 = 0 ;
  ANSELH.ANS10 = 0 ;
  ANSELH.ANS11 = 0 ;
  TRISB = 0b10010000 ;

  while (1){
    if (PORTB.RB4 == 1 )
      PORTB.RB5 = 1 ;
    else
      PORTB.RB5 = 0 ;
  }
}


texts: How to enable PIC16 watchdog timer for software control?

texts:
I am working on a project where I have an I2C slave application running on a PIC16F1829. I am finding that because the ISR must read the slave address, wait for a new byte, then read that byte, that very occasionally the bus will hang due to the micro being stuck in the ISR.

I've tried to enable the watchdog to counter this behavior, but it doesn't seem to have been done correctly. I've tried #pragma config WDTE = ON to enable the watchdog followed by setting up the period and enabling the SWDTEN bit, but this doesn't seem to do the trick. In the documentation, it's mentioned that the WDT fuses have four possible settings, so the presence of just ON and OFF for the fuse setting is making me suspicious.

Does anyone have any additional insights on what I'm doing incorrectly?


texts:
I have an air core inductor, and I need to know the capacitance for a tesla coil design-
"Secondary Coil Capacitance", not the Top Load capacitance, though. I have already figured out the inductance from this question, but I need to know the capacitance also, and because my inductor is not standard (the wire is spaced by fishing line, and not just next to each other), the formulas don't apply from here.

How can I calculate the capacitance of an air core inductor, here are my parameters:

Height = 46.5 Inches

Diameter= 12 Inches

Turns = 1066 turns

Wire Gauge= 24AWG

Spaced out with = Fishing line the same size as the wire

""


texts: ATmega XTAL input capacitance and crystal load capacitance

texts:
I need precise low-ppm crystal for my circuit with 8-bit ATMEGA (AT90USB1286). Currently 18pF TXC HC-49 (11.5x5mm) is used. I need also minimize size to reduce potential EMC and PCB. TXC - 7M/B (5x3.2/3.2x2.5nn) seems as potential alternative. But they are 10pF crystals.

Atmega datasheets do not mention XTAL pin capacitance, there is general Capacitance for each I/O Pin as high as 10pF (with exclamation that is not accurate and not dependend on socket TQFP/QFN). Does 10pF value relate also for XTAL pins? And does it implies that the low load capacity crystal cannot be used because of formula \$C_x = 2 \times (C_{xtal}-C_{pin})-C_{stray}\$? SMD 18pF alternative e.g. Abracon ABM3B (5x3.2mm).

BTW: Does make difference if the crystal has GND pin (4 pins or metal case) or is in 2 pin ceramic socket e.g. Abracon ABM7 (18pF). AFAIR strong EMC recommendation is to connect metal case with GND.

Related posts: MCU crystal capacitor selection, Choosing a crystal and load capacitors for micro controller


texts:
Hey guys i have done a lot of research and testing on different circuits for 230v(50hz) or 220v light dimming, but i cant get my arduino to dim my light. This is the last thing i tried.

made this circuit : Circuit and Code Link

Code which i tried:

int AC_LOAD = 3;    // Output to Opto Triac pin
int dimming = 128;  // Dimming level (0-128)  0 = ON, 128 = OFF

void setup()
{
  pinMode(AC_LOAD, OUTPUT);       // Set the AC Load as output
  attachInterrupt(0, zero_crosss_int, RISING);  // Choose the zero cross interrupt # from the table above
}

void zero_crosss_int()  // function to be fired at the zero crossing to dim the light
{
  // Firing angle calculation :: 50Hz-> 10ms (1/2 Cycle)
  // (10000us - 10us) / 128 = 75 (Approx)
  int dimtime = (75*dimming);
  delayMicroseconds(dimtime);    // Off cycle
  digitalWrite(AC_LOAD, HIGH);   // triac firing
  delayMicroseconds(10);         // triac On propogation delay
  digitalWrite(AC_LOAD, LOW);    // triac Off
}

void loop()
{
  dimming = 128;
  delay(100);
  dimming = 75;
  delay(100);
  dimming = 25;
  delay(100);

}


texts: Can I use tinkerkit hall sensor as compass

texts:
I'm using Tinkerkit shield in combination with an Arduino standard board. I need a simple compass sensor in order to determine the direction (I don't need a great precision), unluckily similar sensor that works "out of the box" with Tinkerkit does not exist. Can I use the standard Tinkerkit hall sensor (http://www.tinkerkit.com/hall/) as a compass? If not, can you suggest me how to connect a standard Arduino compass in Tinkerkit?

UPDATE

The hall sensor does not work


texts: How to compute Vds for this MOSFET transistor

texts: Hi. I am confused when calculating Vsd in this figure as the resistor Rgd makes it an unconventional circuit to calculate when I apply DC analysis on it. How should I go around doing this question? Is there anyway that I can thevenin's Rg2, Rg2 and Rgd together or something? Thanks!


texts: Getting partial flow; downstream from transistor doesn't seem to be working

texts:
I have a circuit in which I want the operation of one part to trigger operation of another part. I am using some adafruit sound boards, and I want that while the sound is being played, a set of lights comes on. Poking around showed the right thing for this would be transistors, being electrically operated switches essentially. Logically, everything seems to be working fine, but the light (LEDs) are coming on SUPER dim. It is noticeable that they are on, but they are not actually throwing any light out.

simulate this circuit – Schematic created using CircuitLab

This instagram post shows how I am expecting the 3xWhite LEDs to look. Nice and blindingly bright (the bright spot on the left breadboard). This is with them just hooked up directly to the circuit, before I tried introducing the switching transistor.

This one on the other hand (video) shows how it is actually working. They are functioning logically correct, in that they are turning on while the audio plays, and then turning off when it is done, however they are only just barely turning on, not bright at all.

My first thought was either the LED or transistor-base resistors were providing too much resistance, so I've stepped them both down (originally they were both 220Ω), and even tried taking them out completely. That didn't help at all.

I've also tried a number of different transistors, the TIP102, TO-92, MC16-0100, and an NTE-199, all with the same effect.

My current working theory is that the line the sound board uses to drive the amplifier does not provide enough amps to fully switch the transistor, so it is kind of "partially" closing. I think that may be the case based on this datasheet segment from the sound board (if I'm reading it right). I think I had seen in my google travels that most of these small transistors switch at around 100mA.

(source: https://cdn-shop.adafruit.com/datasheets/vs1000.pdf )

I don't even know if that is actually possible though. Can a simple BJT actually be "partially" triggered or is it a strictly binary ON/OFF?

The white LEDs I don't know a whole lot about. They are the original LEDs from the toy I am upgrading. I'm hoping to be able to just use them for the new circuit. Using my multimeter's resistance mode, they come on at 200 and 2000 ohms, but nothing above that.

Any other ideas or feedback? I could ultimately move the 3xWhite LEDs onto the trigger switch circuit without the transistor, but then they are just on/off depending on the trigger. I am really hoping to get them to stay on as long as the sound is playing, even if the trigger is released.


texts: How is the common anode 7-segment display in Ben Eater's setup working?

texts:
First question in this community, and I'm a beginner when it comes to circuits. In Ben Eater's video on using an EEPROM for combinational logic, he uses the output of an EEPROM to drive a common anode seven-segment display. It doesn't really seem like it should work the way it does, however.
Here's the setup in question (at the correct timestamp): https://youtu.be/BA12Z7gQ4P0?t=1309

The way I understand common anode to work is that a given segment of the display will only light up if it has a path to ground. In this setup, it looks like every segment has a path to ground from the white wires, through the LEDs, and to the resistors. But when the EEPROM is outputting high on a given bit, somehow the path to ground for that segment is blocked. Isn't there still a path to ground for that segment, though?
Update
Would this be a correct representation of the circuit? The EEPROM essentially acts like a switch, so if it's open, all current travels through the segment of the LED. If it's closed, then the voltage at both junctions of the segment circuit are at the same voltage, so no current flows through that segment. That would make sense.


texts:
I am currently trying to repair a pen-tablet-monitor, which has what i call a 'blind/dead row'.
Meaning that i can draw everywhere, but there is this one row, where any input is either picked up by a row above, or below.

I visualize what a drawing would look like:
The red strokes symbolize the borders of the 'dead row'.

I stumbled upon this video fixing dead areas on graphics-tablet
and tried cleaning any connections using isopropanol, but it didn't solve the issue.

But i took a closer look and found something, which seems strange to me.
On the PCB that receives input from the sensor-board via a ribbon-cable(34P), there seems to be a solder-bridge between two of the pins.
I tried my best taking a picture of it:

Now to my question (finally):

Might this not be something which is done by accident, but something that is actually fulfilling a purpose?
Are there cases, where something like this is used consciously (i.e. soldering together two pins directly after the interface)?

I really don't want to de-solder this connection until i can be reasonably sure, that it is the unwanted solder-bridge that i think it is.
Thank you!

edit:
I was asked to provide further(better) images, and here they come:
Also this time i took a closer look at the pcb, and well... these two pins don't even have two separate traces, but one connected.. at least this is what my nooby self is seeing.


texts: Battery Backup with Monitoring, Low Voltage Cut Off with Hysteresis and Auto Power Recovery

texts:
As an overview of what I am trying to achieve. I want to create a circuit that will trickle charge 8 x NiCd batteries (2200mAH) so that in the event of an “occasional” power loss my 5v circuit is provided power for around 12 hours (duration tested @ 16 hours on fully charged batteries). If the voltage of the NiCd batteries becomes too low to support the circuit then the power to the ESP32 is cut via the MOSFET. When the AC power is restored the batteries start to recharge and at a suitable voltage the power to the ESP32 is also restored. The ESP32 also monitors the NiCd batteries for Temperature and Voltage only for reporting purposes at the moment.

I testing everything on the breadboard with the exception of the Battery Monitoring (LM35’s and Voltage Divider), everything seemed to work perfectly. Power to the ESP32 was cut when the battery fell to 8.81 volts, then after applying the AC powerpack back to the circuit the battery would recover to 8.95 volts and switch the ESP32 back on which would boot correctly and control my device again. Everything seemed good :) - Refer to Picture 1.

However, adding monitoring to the NiCd batteries (LM35 and Voltage Divider) gave me some strange results when the battery hit the low voltage condition and the Q1 MOSFET turned off. While I did not hang around before removing power I believe D1, R8, and D3 started to get very hot. At this stage I’m not sure if the ESP32 was damaged also.

I think the issue is regarding the grounding of the battery monitoring components?  What I think I need to do is take the grounding from the Drain side of the MOSFET so that when the battery is in a low voltage condition the battery monitoring is also disconnected. – Refer to Picture 2

Does anyone see any issues or could offer me any advice?

Note: I do intend to review the type of charging that I am doing, maybe using one of the dedicated IC’s (i.e. MAX713) but for now I would like to get the basics working. I assume currently this circuit would take several weeks to recharge the batteries…

As an update this has worked perfectly (referencing the MOSFET to drive the GND feed) for a number of weeks now in bench testing with figure 2. When the battery voltage drops the ESP32 (a 32bit micro-controller similar to arduino) switches off and on battery recovery it switches back on. I have played around with the hysteresis values though in figure 2 and the Anode side of D3 now connects to the Anode side of D1 (diagram error).

The next step is to have the ESP32 monitor the level of the batteries and switch on and off the charging current as necessary just to save trickle charging all the time - why not since I have spare GPIO ports and the code is simple.

I need to ask another question though because I really am stuck now trying to use 3.3v logic to break the charge feed into the battery while allowing it still to power the circuit.

I have simplified the circuit below in the hope someone can tell me what I should really be doing with Q1 and Q2 before I subject anymore transistors to the magic smoke.

Thanks in advance

[3


texts: Input bias current existing even when no input is given

texts:
While I was studying the DC characteristics of op-amps I came across input bias current.

I understood the concept that it draws some current when input is applied but in proof they put both the voltages at ground and they were still considering input bias current. I'm a little confused that even when there is no voltage at input from where the op-amp is drawing current?


texts: Why is there no resistor in a christmas LED string light?

texts:
I bought a bunch of different LED string lights for Haloween and Christmas. All of them are arranged as 2 sets in parallel. They are either 50 or 100 LEDs.

I noticed that most of them have a molded resistor built into each parallel circuit (which I believe is to handle any left voltage and limit maximum current).

However a few of them (models) don't seem to have any resistors built anywhere into the circuit. These have 50 LEDs (arranged in 2 parallel circuits). For example this one: https://www.homedepot.com/p/Home-Accents-Holiday-24-ft-100-Light-Cool-White-LED-Dome-Light-String-TY-100LD-W/305026726

There doesn't appear to any resistor anywhere. Just 2 tiny fuses in the power socket and the rest at all LEDs.

Is it okay to have a LED string light running off 110v without any resistors?

A couple of these LEDs have stopped working (they are dead, while the rest connected to the same series circuit are very faintly dim) so I need to buy replacement LEDs, without any resistor would I just assume the each LED would be 110v/25 = 4.4V forward voltage LED? What would happen if I used a 3.2v LED?


texts: Correlation between DC & RF voltage gains

texts: I have the following question: how is the DC voltage gain in transistors (gm/gd ratio) related to RF gain? Can good RF gain be expected from a transistor with good DC voltage gain? Can anyone recommend a good reference?


texts: What's the difference between INPUT and INPUT_PULLUP?

texts:
On newer Arduinos, one can set pinMode to one of three states: OUTPUT,INPUT, and INPUT_PULLUP.

This page says:

  The Atmega chip on the Arduino has internal pull-up resistors (resistors that connect to power internally) that you can access. If you prefer to use these instead of external pull-down resistors, you can use the INPUT_PULLUP argument in pinMode(). This effectively inverts the behavior, where HIGH means the sensor is off, and LOW means the sensor is on.

I'm  rather sure that inverting the behavior isn't the only thing that it does, though.

What does INPUT_PULLUP do? What makes it different from INPUT, and  how does one decide which one to use?


texts: How to reliably sample a sensor during the rotation of a wheel in a car?

texts:
I would like to sample the acceleration of the wheel axis (vertically and left-right) N times per rotation (for example once per spoke, but not necessarily). The data would be processed with Arduino.

I have no ABS system in my car.

I can mount the accelerometer easily, but I don't know how to synchronise the sampling with the rotation of the wheel.

Which sensor could be easily mounted on lightweight wheels (no steel wheels) and work reliably in such dirty and vibrating environment?

My current option is only a Hall sensor on the brake caliper, together with a strong magnet fixed in each spoke of the alu wheel, to get about 6 readings per wheel rotation.

Still, I'm not sure the Hall sensor would be close enough to the magnet, and I'm not sure a rare-earth magnet would survive the vibrations of the wheel.

Any other options? I'm thinking also to place the N magnets in the wheel axis itself, as long as it is feasible. Still, is the Hall the best choice?

Edit

Of course, if you think that the magnets in the rims is a good solution and that it can withstand the stress, you can support that option. Additional solutions are fine, but not necessarily required.


texts: Interpreting rating label of DC power supply - supposed to be a constant voltage source or a constant current source?

texts:
Link to product store page

Hi all, bit of a beginner question here. According to the output section of the label, this is a 12V, 1000mA power supply. This is confusing me a bit. Is this device meant to output a constant voltage or a constant current?

My gut feeling is that it's meant to be a constant voltage source, and that the 1000mA value is some kind of failure threshold.

THEORETICALLY SPEAKING, would there be a danger if the (tampered with and exposed) terminals of the output came into contact with human skin (say, at the hand)? Surely 12V won't be enough to hurt anybody?

Also theoretically speaking, can I use this power supply (after voltage division) to act as a cheap power supply for my ESP8266 circuit? Or will this deliver way too much current and fry my delicate microcontroller chip?

Thanks for taking a look at my extremely beginner questions, I really appreciate it. I'm trying to get into a hobby here ;)


texts: Review inverter design: why are there no short circuits?

texts:
I made my first inverter design and I got a lot of help from this website. But I want to get your suggestions before something goes wrong. Circuit output is 12V AC 72Hz square wave.

I used NE555 as frequency generator to get 12V-0V pulse signal (72Hz). When the pulse signal is high (12V) Q3 opens and output is 12V. When the pulse signal is low (0V) Q4 opens and output is -12V.

Also I don't understand why no shortcuts happen in here?

Q5 transistor converts NE555's 0V signal to 12V signal for Q4.

Also I'm sorry if you had trouble to understand it, my English is little rusty.


texts: Why is this signal considered to be uninitialized?

texts:
In my VHDL design, I have a counter, and a reset mechanism. The counter counts up to 50M, and sets the "ready" signal to '1' and starts over. The reset signal is active high and resets the "ready" signal to '0' on a rising clock edge. Following is the VHDL code,

rst_pr : process(clk)
begin
if(rising_edge(clk)) then
    if(reset = '1') then
        ready <= '0';
    end if;
end if;
end process;

cntr : process(clk)
begin
    if(rising_edge(clk)) then
        if(counter = 50e6) then
            ready <='1';
            counter <= 0;
        else
            counter <= counter + 1;
        end if;
    end if;
end process;

"ready" is a std_logic type signal. "counter" is an integer type signal. I also realize that "ready" signal can be multidriven at some point, i.e. the logic is broken. Following is the simulation code, also very simple (vivado)

rst_pr : process
begin
reset <='1';
wait for 50ns;
reset <='0';
wait;
end process;

clkpr : process
begin
    clk <='1';
    wait for 5ns;
    clk <= '0';
    wait for 5ns;
end process;

Simulation shows "ready" is in the 'U' state all the time. This makes no sense, as at the beginning it is set to '0' by the reset process. I didn't share the entire code(entities,signal, library definitions etc.) to keep the post concise. Let me know if you want to see it.

Why does the simulator show "ready" as uninitialized?


texts: How do you use datasheets and that information to determine how many devices supported on a circuit?

texts:
I'm a grade 10 student in an electrical club. We are studying fire alarm systems and have come to a question.

In an apartment building fire alarm systems, there are isolators (CIMs) and attached to each CIM is a silence module (CSM) for silencing sounders that are installed in each apartment. When the alarm goes off, the silence module has a button that will let the resident silence the sounder for 10 minutes. The building code says that the sound pattern has to be Temporal 3.

Given the datasheets for the isolator/silence modules (CIM/CSM) and using 24 V DC low frequency sounders without strobes, what is the maximum number of sounders  that can be on one CSM? (The datasheet shows two sounders.)
Maybe we don't correctly understand the terms in the datasheets, but if the maximum current draw for the sounder (producing Temporal 3) is 138 mA and the output circuit rating of the CIM/CSM is 150 mA maximum at 24 V, then it would seem that only only sounder would be allowed.

Can someone explain? How many sounders maximum can be put safely on the circuit?


texts:
Hello everyone, In the circuit shown above (solving for the open circuit voltage in a RC circuit after switching), I found that the voltage at the essential node on the top was equal to 15 volts.... and that the dependent source generated 30 volts.

Why is it that the open circuit voltage here is 45 volts? In my mind, I would assume that the 15 volts at the essential node gets subtracted (due to the polarity of the dependent source) by 30 volts and that the open circuit voltage would be -15. I got the right answer of 45 by guessing but I don't think I'll sleep well tonight not knowing why.

Thank you!


texts: How can 22 awg cable over 100cm deliver 3A

texts:
I wonder how 22 AWG cable e.g. USB-A to DC power jack  with 100 cm length can deliver 3A.

Why am I asking -> Using this calculator (I hope its correct) by entering values 2% drop, 1 meter, 5V, 3A gives me output 16 AWG. And I am looking for right cable to get.

What I need is stable output 5V, 1.7A (top) over 1.5m from power bank which is capable of 5V/3A over USB-A in winter condition. I mean like max -10C (most likely about -2C)

What would you suggest? Power bank has two outputs USB-C/USB-A. I can use both connectors at same time. There is absolutely not possible to use AC/DC power source.

End of cable will be most likely soldered on-board to avoid contact disruption.

Device powered via cable is ESP-32 with some LED strips (outdoor usage with movement)


texts: Unknown (Obsolete?) Capacitor Markings Green Caps

texts: I am in the process of replacing cracked and leaking capacitors in an old 1970s Johnson Viking 4740 transceiver. But, what I thought would be a simple swap, wasn't. The modern version of these capacitors have markings that don't relate to the ones I have pulled. I have searched all over the internet and can find nothing resembling my problem. There must be others with this problem, or will be in the future. Can anyone "translate" these for me? Any/all help will be appreciated.


texts:
I have a power supply of 5v DC 5Ah and a 12v 2Ah lead battery. I was thinking to make a circuit to switch battery line when power is off.
I made a little schema, what i'd have to put instead of switch that i draw?

Here's the circuit schematics I made.
Thank you


texts:
Many days ago, I published a question here asking about dimming an AC LED using and Arduino and TRIAC, and I was told that most LEDs that support dimming should work with the circuit I linked to them.

Today, I came across another method to use AC PWM to dim a light bulb. The link can be found here. So my question is, would this circuit work if I use it to dim an LED lamp instead? Also, I was told that AC LED normally don't play well with dimming. If I get a regular LED lamp that has an AC/DC adapter, the I modify use it with the PWM circuit, would it work?

Thanks.


texts:
I'm trying to enable an ADC converter. I'm using STM32F3 Discovery with SPL Library. I measure voltage on PA1 pin. I don't know why it doesn't work. What have I missed? The value of 'value' variable doesn't change and equals 0.

#include "stm32f30x.h"
#include "stm32f30x_rcc.h"
#include "stm32f30x_adc.h"
#include <stm32f30x_gpio.h>

uint16_t Read_ADC()
{
    ADC_RegularChannelConfig(ADC1, ADC_Channel_2, 1, ADC_SampleTime_4Cycles5);
    ADC_StartConversion(ADC1);
    while(ADC_GetFlagStatus(ADC1,ADC_FLAG_EOC)==RESET);
    return ADC_GetConversionValue(ADC1);
}

void delay_ms (int time)
{
    int i;
    for (i = 0; i < time * 4000; i++) {}
}

int main()
{

  uint16_t value = 0;

  GPIO_InitTypeDef GPIO_InitStructure;
  ADC_InitTypeDef ADC_InitStructure;
  ADC_CommonInitTypeDef ADC_CommonInitStructure;

  RCC_ADCCLKConfig(RCC_ADC12PLLCLK_Div2);
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE); //PA1 ADC1_IN2
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOE, ENABLE);

  GPIO_StructInit(&GPIO_InitStructure);
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
  GPIO_InitStructure.GPIO_Pin  = LED;
  GPIO_Init( GPIOE, &GPIO_InitStructure);
  uint32_t led = 0;

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_Init(GPIOA, &GPIO_InitStructure);

  ADC_InitStructure.ADC_Resolution = ADC_Resolution_8b;
  ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
  ADC_Init(ADC1, &ADC_InitStructure);
  ADC_Cmd(ADC1, ENABLE);

  while(1)
      {
          value = Read_ADC();
      }
}


texts: In this regulated cascode current mirror how do we find the minimum voltage across the current mirror? Also, I have read that the current mirror will work even if M1 goes into linear region. But how does it go to the linear region in the first place and how does the current mirror function when M1 is in the linear region?


texts:
From point of view of a synthesiser, is there any difference between:

Signal offset: std_logic_vector ( 3 downto 0) := "0100";

Constant offset: std_logic_vector ( 3 downto 0) := "0100";


texts: Why won't my arduino board read an analog pin correctly?

texts:
I'm working with an Arduino Uno board. I have a series of voltage dividing circuits off to the side of a breadboard to give me four different voltages. I'm connecting to my laptop.

I am using the example given on the Arduino website just to test to make sure the pin is reading properly and that the chip is making the decisions necessary from there. But looking at the serial monitor, I got gibberish. So I switched to an if/then statement, saying if the voltage went high (and put the threshold as low as it can go - 1) to turn on a LED on pin 13.

I even added on my own LED and resistance, since the one on the board didn't seem to be working. But this one isn't turning on unless the voltage is 2.5 V or greater. I've switched out the extra LED and resistance to try to create the most ideal situation to turn on the LED, but still nothing until the voltage going into the input pin is over 2.5V. But on the site and in the datasheet, it says that it SHOULD read anything from 0 to 5. I'm trying to read voltages ranging from 13 mV to 780 mV. Small, but according to the datasheet, not too small.

Does anyone have suggestions? Should I just throw an op amp or something on the end to bump up the voltage?


texts: Why is my Verilog code for 4x4 button matrix not scanning?

texts:
I have a problem with a module in Verilog where I need to scan a 4x4 button matrix. I don't get to scan each row 1 by one but the thing stick with the first row. Can you help me debug it? To me it looks logically correct.

The code is :

module keyboardScanner(input clk,input  [3:0] col, output reg [3:0] row,output reg [7:0] keyCode);
always @(posedge clk)begin
                row = 4'b1000;
                if(col != 4'b0000)begin
                        keyCode[0] = row[0];
                        keyCode[1] = row[1];
                        keyCode[2] = row[2];
                        keyCode[3] = row[3];
                        keyCode[4] = col[0];
                        keyCode[5] = col[1];
                        keyCode[6] = col[2];
                        keyCode[7] = col[3];
                end
                row = 4'b0100;
                if(col != 4'b0000)begin
                        keyCode[0] = row[0];
                        keyCode[1] = row[1];
                        keyCode[2] = row[2];
                        keyCode[3] = row[3];
                        keyCode[4] = col[0];
                        keyCode[5] = col[1];
                        keyCode[6] = col[2];
                        keyCode[7] = col[3];
                end
                row = 4'b0010;
                if(col != 4'b0000)begin
                        keyCode[0] = row[0];
                        keyCode[1] = row[1];
                        keyCode[2] = row[2];
                        keyCode[3] = row[3];
                        keyCode[4] = col[0];
                        keyCode[5] = col[1];
                        keyCode[6] = col[2];
                        keyCode[7] = col[3];
                end
                row = 4'b0001;
                if(col != 4'b0000)begin
                        keyCode[0] = row[0];
                        keyCode[1] = row[1];
                        keyCode[2] = row[2];
                        keyCode[3] = row[3];
                        keyCode[4] = col[0];
                        keyCode[5] = col[1];
                        keyCode[6] = col[2];
                        keyCode[7] = col[3];
                end
    end
endmodule // keyboardScanner


texts:
Given the following:

x, y, z of omnidirectional source source
x, y, z of center of listener's head
pitch, roll, yaw of head

What is a simple fuction that will return the decibel attenuation and the delay of the left and right ears' perception of this source?


texts:
I am trying to determine what value capacitor I need to put after the full wave rectifier to get a smooth voltage for charging my battery. However, I don't understand which current and voltage do the variables I and V mean in the equation for determining the capacitance of the capacitor.
$$C = It / V $$
Thanks in advance for any help.


texts: Determining End-Of-Life for electronic components

texts: What is the best way to determine the end-of-life time-line for ICs other than contacting the manufacturer directly? Is there a central registry or service where I can subscribe and get EOL notifications for the parts used in my designs? How does everybody else handle EOL problems?


texts: Need help with fundamental understanding of voltages in this circuit

texts:
Looking at the below schematic, with LED1 being a red LED (1.7V forward voltage) and LED2 being a green LED (3.2V forward voltage), I have a few questions that probably reflect lack of some fundamental principles of circuits, and I hope someone can get me into the clear :) [EDIT: When I say "Q1 is ON", I mean that I am supplying a 5V "high" signal to input IN1]

if Q1 is ON, LED1 will shine and LED2 will be off. What are the voltages at V1 and V2? [My assumption is that they are both 1.7V as there is just one resistor (R2) in the path]
if Q1 is OFF, LED1 will be off and LED2 is ON. The voltage at V2 is now 3.2V (the forward voltage of LED2). Correct?

Now imagine a scenario where LED1 is green and LED2 is red.

if Q1 is ON, both LED1 and LED2 will shine (though LED1 only shines very faintly). Why is this? What is the voltage at V1 and V2? [From the observation that both LEDs are on I think V1=V2=3.2V, but I fail to see why since my first observation in question 1. above seems to say that V1=V2=1.7V - so I would have expected 1.7V here too and hence LED1 would not be lit].
if Q1 is OFF, LED1 will be off and LED2 is ON. Voltage at V2 is now 1.7V (the foward voltage of LED2). Is this also correct?

simulate this circuit – Schematic created using CircuitLab


texts:
How does one select the values of components used in Amplitude Modulation Circuit (using a Transistor common emitter amplifier circuit)?

The circuit that I designed ends up giving a weird waveform but I am pretty sure my professor gave us the same circuit. Please point me to resources that can help me decide what values of components to use.

NB: I tried Google, but it gives me only theory and no guidance regarding the components in question. Also please note that I am new to electronics. Here is the circuit:

Edited to show better circuit diagram: -


texts:
This is the question given in one of my papers.

Input is a square wave, if phase shift was zero it would be just flat positive line, if phase is pi it would be flat negative line.

Here the phase change is pi/2 but it is not specified whether it is leading or lagging.
I am guessing the output is either a a rising or falling triangle wave, but I do not know how to prove it by calculation or drawing it out.


texts: What is the voltage and amperage rating for "Q" labeled SMD fuse?

texts: I am looking for the specification for the "Q" rated SMD fuse. Since this was found on a 12V rail on a 150W graphics card I can deduce a 12A fuse should work but I wanted to be sure that is good "fusing theory" and if possible grab the exact match from a  major vendor.


texts: Why do DC motors cost more than AC motors of same capacity?

texts: For large capacity motor nearly of 1000Kw, the price of a an DC motor is much higher than that of AC motor of same capacity. I know there is requirement of commutator and brushes but I don't think that that is the only reason behind the much increase in cost.


texts:
I'm building a bookcase, to which I'd like to add lighting controlled by an Arduino or Raspberry Pi. I've gotten most of the software bits figured out, but I'm not sure I've gotten the power part figured out as well as I need to. I'm using Adafruit's NeoPixel LED strip for the lighting.

Each shelf is be 31 inches wide, there will be 8 shelves total in the bookshelf. I can't connect all the shelves in series, because the product documentation tells me each "strip" of LEDs can be no more than 5m long, so I'm planning on having each pair of shelves as one "strip", for a total of four strips in parallel. By my rough calculations, I'll end up with ~ 96 LEDs per series (48 per shelf times two shelves per series), requiring almost 6A of maximum current draw per series.

First, am I at least in the right ballpark with these power requirements, or am I so far off as to need professional electrical help?

Second, if these numbers are correct, should I try to find a single 24A 20VDC power supply, or should I instead use four (4) 6A 5VDC supplies? What are the main drivers for choosing one over another?


texts: Voltage/Current rating of Relay for Inductive load

texts:
I selected a relay for my application by seeing the maximum and current rating of Relays but I am confused if the relays works fine with the given rating for all kind of loads.
In my circuit the relay is being used in the primary side of the LLC resonant converter which is working under 40A rms and 400VAC(Load is primary side of transformer,inductive)
The relay which I selected has rating of max 50A and 480VAC. I could not really understand the contacts rating for different loads. Im really confused it I can use this relay for my application. Please let me know if u have any leads to this. I attach the relay datasheet for your reference.
Thanks in advance  enter link description here
PS: I dont do live switching


texts:
I am unable to obtain the value of  z component,
Here is my attempt at the solution:

I am going wrong somewhere. Can anyone help with this?


texts: Why does the voltage of my Buck converting SMPS drop when a load is added at the output?

texts: I am building a DC-DC buck converting circuit from first principle with no on chip solution. Output Voltage must be 5vdc with a max current @500mA. input is 20+-4vDc. The problem that I am having is that my output voltage is 7.5vdc once bread boarded, but a 5vdc is required. I can solve this by increasing pull up resistance to the TIP122G but there is still a problem of the 5vdc output not being constant and dropping when a load is added. I think this my be due to my feedback circuit but I'm not sure as to what the problem may be and what I should change in it. Saw tooth generator has a frequency of 50kHz.


texts:
I'm trying to make a compass using an LSM303DLHC embedded in STM32F3Discovery. I have prepared such a code.

void LSM303DLHCMag_Config(void)
{
    LSM303DLHCMag_InitStructure.Temperature_Sensor = LSM303DLHC_TEMPSENSOR_DISABLE;
    LSM303DLHCMag_InitStructure.MagFull_Scale = LSM303DLHC_FS_1_9_GA;
    LSM303DLHCMag_InitStructure.MagOutput_DataRate = LSM303DLHC_ODR_200_HZ;
    LSM303DLHCMag_InitStructure.Working_Mode = LSM303DLHC_CONTINUOS_CONVERSION;
    LSM303DLHC_MagInit(&LSM303DLHCMag_InitStructure);
}

void LSM303DLHCMag_Read(float *convertedData)
{
    static uint8_t XYZ[6] = {0};
    LSM303DLHC_Read(MAG_I2C_ADDRESS,LSM303DLHC_OUT_X_H_M, XYZ, 6);

    convertedData[0] = (float) ((XYZ[1] << 8) | (XYZ[0]))/LSM303DLHC_M_SENSITIVITY_XY_1_9Ga;
    convertedData[1] = (float) ((XYZ[3] << 8) | (XYZ[2]))/LSM303DLHC_M_SENSITIVITY_Z_1_9Ga ;
    convertedData[2] = (float) ((XYZ[5] << 8) | (XYZ[4]))/LSM303DLHC_M_SENSITIVITY_XY_1_9Ga;
}

uint32_t LSM303DLHC_TIMEOUT_UserCallback(void)
{
  /* Block communication and all processes */
  while (1)
  {
  }
}

int main()
{
    LSM303DLHCMag_Config();
    float azimuth = 0;
    float convertedData[3] = {0};

    while(1)
    {
        LSM303DLHCMag_Read(*convertedData);
        azimuth = atan2(convertedData[2],convertedData[0])*180.0/M_PI;
    }
}

My problem is that the code executes once only. What should I add to the UserCallback function, if I should at all?


texts: Measuring PSR of a current reference chip

texts:
Some Background:

I'm designing a test board to characterize noise and PSR of a multiple voltages(1V) and currents(1uA) reference IC. The chip has a single voltage source.  I use ultra low noise MUX and deMUX to switch between various voltage/current signals As, I plan to have one Spectrum Analyzer SA44B and one VNA Bode100 only. I also have ultra low noise buffers (MAX4238) before the inputs to the SA and VNA. I'm interested in measuring in the 10Hz to 100KHz range only.
The simulated  specs for the voltage reference: PSR 100dB and Noise: 10 uVrms.
The simulated  specs for the current reference: PSR 65dB and Noise: 85 uVrms.

Now, my question:

When measuring noise for current reference signal, can the spectrum analyzer directly take a current signal? (or) Should I convert to voltage with a shunt resistor? I don't like the latter because, the resistor would introduce noise of around 20mVrms in the system. (Voltage noise calculated for room temperature and 100KHz BW and 1Mohm)
Similar case for VNA receiver, can it take a current signal? As I dont want to introduce any noise in such a critical measurement.

Thank you :)
--San


texts: Why does the MC34063 application note show different Vf and Vsat?

texts:
On Semiconductor application note AN920/D, on page 6 in the Step−Down Switching Regulator Design Example, uses a Vf=0.8V for the external diode:

$$
\frac {t_{on}} {t_{off}} =
\frac {5.0 + 0.8}{21.6 - 0.8 - 5.0}
$$

But in Figure 9 they show the diode to be a 1N5819:

This diode - for a forward current of 100mA - has a forward voltage of about 340mV. Why do they use 800mV? Their cited forward current for the example configuration is only 50mA, so it would be even lower than 340mV.

Similarly, the second 0.8V term in the equation above is for the saturation voltage of the output switch. Their example uses the μA78S40 but I would be using the MC34063 which they claim is inter-changeable. The MC34063 datasheet's information on Vsat is difficult to interpret. I think I would be using Darlington mode if I were to translate from the example configuration as closely as possible. However, the data sheet only has data for Isw=1A (Vcesat ~ 450mV) and I would be well below that; also that figure assumes Rsc between the drive collector and Vcc to be 82 ohms but the example configuration uses only 2.7 ohms.

What would be a practical Vcesat to use in this case? Or am I forced to characterize on my own?


texts:
I created a simple design, based on the fundamentals of a parallel plate capacitor. Making a co-axial/tubular design:

Front view:

The "Air gap" is there to allow current flow in one-direction, from connector to end adjacent to the air gap.

I'm curious of the following:

Does the connectors(to the exterior circuit) effect's the capacitance(\$C\$) of the design?

I only see the area between the plates being reduces based on the "width" of the connectors.

As the capacitor charges/discharges (interacting with the exterior circuit) would the flow of current out/in via the connectors cause any effect to the plates and the electrostatic field(\$E_s\$) between them?

As for calculating the capacitance I believe this equation is still valid:

\$C= \frac{2\pi k\varepsilon_0}{ln(\frac{b}{a})} \$


texts: One battery slot kills its sitting battery

texts:
My kid has a battery-operated toy, it runs on three AAA batteries, connected in serial. Once, the toy suddenly stopped working, but all batteries were good. I decided to disassemble the toy and look for internal damage or some loose wire. Found nothing and reassembled it. The next day, on a last attempt before dumping it, I placed the batteries back on, just to confirm, and it just started working again. Have no idea what changed. Humidity maybe?
Now the issue. Since then, the toy is killing one of the batteries in the pack, in a week or so. It stops working, I check the batteries, the one on the left is completely dead with 0 volts, the other ones are ok. I replace the dead battery, it gets back working ok. Another week or so, the toy stops working again, and the newly replaced battery is dead. It's always on the same deck position.
Seems a short, like @Frog stated, but the plates and springs seem to be far apart.
Could be damage to the wires, a pinch, or something like @Kyle B stated. But by looking inside I can't spot anything suspicious. Can't be faulty battery, because replacing just the damaged one by a new one, and the new one gets dead as well, proves the issue cannot be on this battery, I think.
Every time this happens, I now remove the dead battery, place one of the others on this place, and place the new one elsewhere.
I have now placed photos.
Can anyone help?
(this is a re-post as the other one got closed. This time I tried to be more clear, and added photos)


texts:
I wanted to control a 84V LED strip using a ATtiny13a microcontroller with minimal power wasted. I just want to turn it on and off, don't need any PWM dimming. The strip uses 270mA current and is about 22W power. MCU will be getting around 5V and 10-15mA supply and MCU uses only about 3-4mA max.

I have 3 components for this but I don't know which will waste least power as heat.I have IRL540N Logic level Mosfet , TIP122 Darlington power transistor and  BT169D Thryistor/SCR. I'm avoiding sugar cube relays because I only have minimal space in the case/box for this project, which is also why I need the component which wastes the least power since I couldn't fit a heat sink.

I have programmed the MCUs eeprom to turn the circuit on and off alternatively each time the setup is powered on and off so the latching feature of the thyristor/SCR is not a problem here. I also have opto-isolators to protect the MCU from high voltage.

So which one of those components is ideal for my project? Also if there are any other components which will do the job better please let me know.

Thanks in advance.


texts: Simple 24VAC solenoid controller for Arduino

texts:
I am a bit new in making circuits, but I am truly stuck.

I need to control a 24VAC irrigation valve from an Arduino type environment. I have seen several post but I just don't get it. The only power supply I have is the 24VAC so it would have to power the 5V DC Arduino too (that I have been able to manage).
Any ideas of links? With a simple diagram and a good explanation?


texts: Biasing circuit - Voltage follower circuit

texts:
I am using MABC-001000-DP000L, which is and Bias controller/sequencer. I am using this for Providing gate voltage and drain voltage to the power amplifier.
In the datasheet, it is mentioned that the module with combination of EVM can be used in two applications.
Application Option 1: Fixed negative gate biasing with pulsed drain biasing.
Application Option 2: Pulsed negative gate biasing with pulsed drain biasing.
I am trying to design both applications on a single board. The second option for future use.
For the 1st application option, he has mentioned a few pins as No connection and he has used those NC pins on the 2nd application.

The issue I am facing:-
They have used voltage followers for providing a low impedance output path for pin number 3(GCO).
I have reverse-engineered the Ckt from the below-attached image, but I am unable to identify the voltage follower they have used.
Pin number 2 of the voltage follower has been connected to pin number 2 (NC/GCP) of the Module. There has been no description of this pin number.
I am guessing these:-

Pin numbers 1 and 4 are connected together and output is provided through them.
Pin number 5 is +Ve supply hence connected to GND(Highest +Ve supply)?
Pin number 3 is connected to -8V
Pin number 2 is connected to pin number 2 of MABC-001000-DP000L, which I am unable to understand.

I have mailed component manufacturer regarding full schematic, till now I haven't heard from them.
Can anybody help me with this?
Thanks in Advance.
Low-resolution pic of EVM. I don't think it helps in any way.

Layout Image


texts:
Recently I discovered, that some IGBT transistors in IGBT modules have the second pin for an emitter, called auxiliary emitter.

In the picture above 2nd and 4th pins are auxiliary emitters. This is from the datasheet to FS100R17N3E4 module.

However, I did not find any information about what are these pins used for, except that IGBT gate driver is connected to both 1-2 and 3-4 pins, but I do not understand why.

Could someone please recommend any literature on this problem? I would like to have a  strong understanding of IGBT transistors and their drivers.
Is there any difference between 2nd and 27, 28, 29 pins, since they are at the same potential?


texts:
small signal analysis of bjt
in small signal analysis why only ac currents and voltages are used for calculation of resistance and why bias voltage along with ac signal is not taken into account?


texts: Will a I2C switch boost the overall bitrate?

texts:
I am currently working with a wired I2C bus system consisting of 6 individual bus lines with  4 slaves on each. They are currently all connected to one I2C bus and for each slave i add the bus becomes significantly slow.

I lately got the idea of adding a 8 channel I2C switch with the objective of boosting the bitrate in my system. Unfortunately i am not quite sure if this will solve my problem. The idea was to connect the 6 individual bus lines to one channel on the I2C switch and have the I2C master switch between each individual line in order to reduce the amount of slaves connected simultaneously. So instead of calling out to all 24 slaves i will instead take them in chunks of 4 at a time.

The question is, will this give me a higher bitrate or will it slow it further down due to the extra data that has to be passed to the I2C switch?

The master is a RPi2 and the slaves are ATmega32.

Datasheet: http://www.nxp.com/documents/data_sheet/PCA9548A.pdf


texts:
I'm naive in this field, but I will need to use optic fibers for optogenetics application. I already know that my question will sound stupid for the most of you, please forgive me for that.

My problem is the following: we are going to buy a laser for our optogenetic application and we decided to buy a pigtailed laser diode. At this point I was wondering which could be the best fiber to couple to the laser. The company suggested us to couple a single mode fiber (0.07 NA, 35 microns core) but, since we will use multimode fiber (50 microns core, 0.22 NA and 200 microns core, 0.22 NA) in our experiment, I'm scared that this actually will not work. The distance the light has to travel is very short, so the actual problem would be the data loss at the interface.

What would you suggest?


texts: What kind of testing equipment is used for UPS (>15 kVA)?

texts: I work at IT division of a bank. Currently we need to order some Double Conversion True Online UPS ( Uninterruptible Power Supply) systems for our our new data center. The required ratings for UPS are 15kVA & 30kVA. I need to to know what kind of procedures are followed and equipments used during factory test/ witness test of UPS system. I want to know specifically which equipment is used for power measurement of ups. From web, I across of few names -Power Analyzer, Spectrum Analyzer . But I need an exact answer. and what parameters are tested with this equipment.


texts: How do I extend my 4 input NAND to get a 5 input NAND

texts: This is my NAND with 4 inputs. Only using NAND's how do I extend this to create a 5 input NAND


texts: The use of redundant I2C in spacecraft avionics

texts:
I recently read this report about the JPL x2000 avionics development project, which developed more modular avionics platform using commercial silicon, to cut cost and power. They opted for an architecture of two redundant protocols linking all electronics in the spacecraft. A high speed 1394 bus is used for large data, while an I2C bus (at 100khz) is used for low bandwidth controls. This is configured as a multi-master bus, where every node can communicate with every other.

I've not used I2C for more than single sensors, but from what I understand there are serious distance limitations. I within a spacecraft, there could be wiring harnesses of significant length.

In addition to having two redundant I2C busses, each device has a custom ASIC that provides isolation between the bus and the main chip pictured here  and here . Is this chip perhaps providing some kind of conditioning as well?

Can anyone explain why they might have chosen to use a protocol designed for communication within one PCB for communication within a large vehicle?

I know there probably isn't a single definite answer, but id be interested in hearing about what factors into that kind of choice.


texts: Why a low-pass filter applied to a square wave gives a weird wave?

texts:
When a low-pass filter acts on a square wave, the output is something similar to this:

My question is simple. If the filter is a low-pass filter, it should filter all frequencies that are above some constant frequency (the value will depend on the circuit), and let only lower frequencies pass, right?

If this was true, the output should be something like this:

In the image, the square wave is truncated by considering terms only up to the fifth harmonic, which is exactly the kind of behavior I would expect to be the output signal of a system that attenuates higher frequencies.

Now, why is the output the first wave, instead of the second wave? Does this happen because the low pass filter just logarithmically attenuates the signal, instead of act like a perfect ideal low-pass filter? (By perfect low pass filter, I mean a filter that would keep exactly the same gain over the signal until a certain frequency, and for higher frequencies would have a zero gain, like in the image below)

Thanks


texts: Question regarding isolation and level shifting

texts:
What are the requirements that make one choose between physical isolation and simple logic level shifter circuits when you have two devices communicating with each other.
For example, a circuit containing an IC that is powered with 5V and outputs 5V signals that is fed into an MCU that is 3.3V powered with input pins rated for 3.3V.
Am I correct in saying if they are both powered with the same supply, no isolation is required. However if they were supplied with two different power supplies, isolation is required?


texts: IC power pin connection for noise immunity and decoupling

texts:
There's been much talk on other Q&A threads on how to connect decoupling capacitors to an IC, resulting in two completely opposite approaches to the problem:

(a) Place decoupling capacitors as close as possible to the IC power pins.
(b) Connect the IC power pins as close as possible to the power planes, then place the decoupling capacitors as close as possible, but respecting the vias.

According to [Kraig Mitzner], option (a) is preferable for analog ICs. I see the logic behind it, as the inductance of the via and the decoupling capacitor form a low pass LC filter that keeps noise away from the IC's pins. But according to [Todd H. Hubbing], option (a):

  [...] sounds like a good idea until you apply some realistic
  numbers and evaluate the tradeoffs. In general, any approach
  that adds more inductance (without adding more loss) is a bad
  idea. Power and ground pins of an active device should
  generally be connected directly to the power planes.

As for option (b), [Kraig Mitzner] (the author of the above figure) says that it is preferable for digital circuits, but he does not explain why. I understand that in option (b) the inductive loops are kept as small as possible; but still, they allow switching noise from the IC to get quite easily into the power planes, which is what I want to avoid.

Are these recommendations correct? What exact reasoning are they based on?

EDIT: consider that the via from the IC leads to the capacitor and vias are kept as short as possible. They are shown in the figure as long traces only for illustration purposes.


texts: Replacing an LED power supply - but originally there were 2 supplies connected parallel

texts:
I have a LED lamp. It went wrong and I found out that it's power supply is the cause.

Originally two of these supplies were connected parallel (their output connected parallel):

Input: AC90-265V 50/60Hz
Output: DC56-82V 300mA +-5%
Load: (40-50)*1W LED

Is it true (roughly - as a rule-of-thumb) that their common output is somewhere around 600mA (what is the sane reason for connecting SMPSs' outputs)?

I want to replace these PSs but I haven't found the same ones. What I found is a bit different but same in current:

Input: AC100-240V 50/60Hz (OK)
Output: DC60-120V 300mA (OK? If the originals were not below 60V)

Can I connect these new ones in parallel and then to the lamp?

What are the pros and cons?

This is how the lamp behaves when I attach two parallel supplies on both of its sides: https://youtu.be/lKY6Hkomf0Q

Thanks!


texts: What's so revolutional in Broadcom BCM20730 Bluetooth chip that's everywhere in the news?

texts:
Trade magazines are full of reports about Broadcom BCM20730 Bluetooth chip that is expected to have power consumption so low that devices will work for years of a single battery set. Here is their press release.

I don't get it. Yes, power efficiency is important, but chip manufacturers have been designing energy efficient chips for decades so far and modern computers and smartphones are full of those chips. Now some company claims they have some extremely efficient chip. How is that possible?

How is any kind of drastic improvement possible in such design?


texts: Can sampling rate be a floating point number?

texts:
Suppose we have a sampling frequency for a signal of 15.5 samples/sec and we take samples for a period of  7 seconds. This means total samples are 108.5, does this make any sense?

Shouldn't the number of samples taken be an integer like 108 or 109? Or can the particular points in time from 0 second to 7 seconds on which to take the samples be determined in this case? How would one do that?


texts: "Register is illegal in left-hand side of continuous assignment" in modelsim but not verilator

texts:
module foo (A, B, C, Y);
   input  A, B, C;
   output Y;

   reg    Y;

   assign Y = (A && B);
endmodule

Produces the error Register is illegal in left-hand side of continuous assignment when I compile with modelsim, but not with Verilator. I'm guessing this is because they are set to different versions of the Verilog standard. Is that why? Or is this just a tool difference? Modelsim is configured to use "default" Verilog but doesn't say what that is, and verilator advertises supporting many versions but I'm not passing any command line arguments to customize it there either.


texts: FT232HL FTDI consecutive SPI bytes delay problem

texts:
I have a problem with the FT232HL FTDI ic.

Windows application send data to the chip via USB and the chip send the data out with one SPI channel.

I did check with a logic analyser, the bytes are correctly sent out and the SPI clock match the settings. However, between each byte, there is a 64uS delay so it means that no matter how high is the SPI clock, the data transfer takes minutes instead of seconds.

I imagined maybe playing with the channelConf.LatencyTimer would help, but it shows no difference no matter the value used (10, 128, 255), delay remain  64uS between consecutive bytes.

There must be something to fix because there are numerous examples of people reaching high transfer rates. Also, delay between bytes should be a setting somewhere.

I've used sample code provided with sample-dynamic.c
The byte stream is sent with a single call to p_SPI_Write() with total length of 2048 bytes. I've tried other length (256, 8192, etc) no change.
Here is the configuration used:

channelConf.ClockRate = 5000*1000;
channelConf.LatencyTimer= 10;
channelConf.configOptions = SPI_CONFIG_OPTION_MODE0| SPI_CONFIG_OPTION_CS_DBUS3/*|*/ ;
channelConf.Pin = 0x00000000; /* FinalVal-FinalDir-InitVal-InitDir (for dir: 0=in, 1=out) */

OS: windows7 X64
Compiler: GCC
Library and code from: http://www.ftdichip.com/Support/SoftwareExamples/MPSSE/LibMPSSE-SPI.htm

FYI: I've contacted FTDI support, they asked me to update the libraries to latest one (which I did), then they would not provide further support.

Any help appreciated.
Thank you.


texts: BASYS2 - Verilog: how to properly edit ucf file?

texts:
I am a newbie at FPGA. I bought BASYS2 digilent board(Spartan3E). I have background on microcontrollers. C/C++ is no problem for me. But I am having some
trouble with FPGA. Actually, not with FPGA but with Compiler and ISE. As
you can see in the screenshot below, I configured the FPGA chip.

This is the implementation code:

module myModule(A, B);
    input wire A;
    output wire B;
    assign B = !A;

endmodule

And this is the ucf code:

# Onboard LEDs
NET "B" LOC = "M11";

NET "A" LOC = "C11";

As boards technical sheet says, M11 is LED 1 and C11 is BTN 2. So I want
LED to flash when I unpress the button. Do you see something wrong with
the code? Because it aint working. If the code should have been working,
what should I do? Am I skipping something?

As you see I aldready generated programming file and run. So what next?

Thanks.


texts:
For our e-Kart project we need to power a raspberry pi 3 (5V 2A) of a battery of 120V.

We are having trouble finding a good solution as these high voltages seem to high for a conventional (self made) SMPS and its not AC voltage that needs conversion.

Someone suggested using a normal USB wall charger directly. Would this be a possibility? And if not, why?

Any suggestions are welcome, as of now it seems that an extra battery might be needed..

Kind regards!

EDIT:

We were able to produce 5V using a Sony wall charger!

However, as Transistor noted below, it seems that this wont work with all charger types, the one that shipped with the Raspberry Pi (notably bigger than the Sony one) did not work.

The Sony one was rated 100-240VAC as was the RPi one.


texts: Need to convert 40 volts to a 24 volt 2000 amp 1 second duration pulse. long duty cycle. Current must be settable from 500 to 2000 amps and time from 0.1 to 1.0 seconds. Ideas please.


texts:
I'm trying to write a code for an up/down binary counter. The task is to light up 8 leds (up counter)and then reverse the lighting order (down counter). I am trying to create an array of leds in my code but I don't know how to do so.Whenever I use PORTB[i] I get and error pointer required and if I use PORTB.i I also get an error how can i access the leds connected to portb ?  It's my first experience with microcontrollers in general and I would really appreciate your help. Here's my code:

char LED_Direction at TRISB;
void main() {
int i;
LED_Direction=0x00;
PORTB=0x00;
//sbit LED_Array [8] = {PORTB.0,PORTB.1,PORTB.2,PORTB.3,PORTB.4,PORTB.5,PORTB.6,PORTB.7};
    while(1)
   {
      for (i=0; i<8; i++)
      {
          //LED_Array [i] = 1;
          PORTB[i]=1;
          Delay_ms(1000);
          //LED_Array [i] = 0;
          PORTB.i=1;
      }
      for (i=7; i>-1; i--)
      {
          //LED_Array [i] = 1;
          PORTB.i=1;
          Delay_ms(1000);
          PORTB.i=0;
          //LED_Array [i] = 0;
      }
    }
}


texts: Doubt with current across several resistors (serie) and Resistor Power Rating

texts:
I have read that the current that flows across a circuit of several elements connected in serie is always the same but, as far as I understand, resistors consume current and disipates it in form of heat, am I right?

If the above is correct, if you have 3 resistors (R1, R2, R3) connected in serie, the current through R3 will be less than the one through R1, right? If so, is the afirmation "the current flowing in a serie circuit is always the same" false?

Is the above applicable for both AC and DC circuits?

Does the same occur for inductances?


texts: Is this PIC micro-controller powerful enough to drive PWM LEDs?

texts:
Short Question

Is a PIC24F16KM202 (Datasheet) powerful enough to vary the brightness of 12 LEDs from 12 PWM outputs without any visible stepping of brightness levels?

-------------------------------------------

Full Question

After using Microchip's PIC search tool to narrow down an MCU based on my project's requirements, it only really leaves me with PIC24F16KM202.

My concern is that some of the specs it has are at the very low end of the scale compared to other PICs, and having no real experience before with micro-controllers (this is my first MCU / electronics project), I'm not sure exactly if / how it will affect the performance of my project.

The project is really based on driving RGB LEDs via PWM, and I want to make sure that the PIC is capable of fading the LEDs smoothly with no visible jumping between brightness levels, and also if the MCU will be powerful enough to store and run the program.

I'd like to get some advice before buying some and finding out they're not going to be good enough and starting over.

Brief Project Outline:

12*PWM to drive 4 sets of RGB LEDs independently (through transistors).
UART to connect to a bluetooth module (RN4020?) to control the colour of the RGB LEDs.
6 input pins to change the state of the RGB LEDs.
EEPROM to store last state between on/off.

RGB LED colour will be changed infrequently by UART / bluetooth. Brightness / on / off will be driven frequently by 6 inputs.

PIC24F16KM202 specs:

Max. PWM Outputs: 16
PWM Time Bases: 5
PWM Resolution (bits): 16
PWM Resolution (ns): 62
CPU Speed (MIPS): 16
Program Memory (KB): 12

I've been reading the PIC24F Datasheet and Googling for ages to try and figure it out, but honestly I'm overwhelmed by the amount of information that I don't yet understand. I'd very much appreciate if someone could help me out by answering my question, and/or point me to some concise and relevant material that will allow me to learn how to answer the question myself.

Thanks for your time :)


texts: There is something I can't grasp regarding capacitors. Say for example I'm using a simple rc circuit that has one 5v dc power source, a resistor, and a capacitor. The  capacitor will charge until it reaches 5v, then cut all current. What I don't understand is how the capacitor can receive the charge in the first place? Isn't a capacitor effectively an open circuit, therefore there shouldn't be any flow and the capacitor shouldn't be able to charge in the first place? Isn't it analogous to a switch that is in the open state in a circuit?


texts:
I have a couple of not-very-critical process control loops where the flow sensors can transmit a 4-20 mA signal & the HART protocol.

I want to control some valves via a simple PID loop. Is it possible to implement the PID logic via a PC? How would I go about it, any thoughts / ideas?

A HART Modem  (I think also known as a FSK Modem or a Bell 202) seems not that expensive. But I'm not sure what software etc. I'd need to use on the PC to set up the PID logic. Is this fairly standardized or I'd have to stick to vendor specific propitiatory applications.

e.g. In  the schematic below what are my options to impliment the PID  / logging logic on the "PC Control Station" part of the schematic. Are there any well known programs that I should be aware of? Would something like MATLAB or Labview be a good fit for this?

Basically, I want to avoid re-inventing the wheel if at all possible. The idea is to avoid the large fixed cost of a full blown DCS or PLC system which seems the norm.

Again, the application isn't very exacting & safety etc. are not a concern.

Additional motivation was this article snippet:

  **Don’t Overlook Control Opportunities **
  While most facilities use HART
  for applications related to device configuration and maintenance,
  users also should look for opportunities to use HART data for process
  monitoring as well. For example, in applications where conditions such
  as temperature, pressure and levels change relatively slowly, users
  can reduce the number of instruments they need in the field by
  acquiring multiple variables from a single device. Hotard points to
  tank farms as being ideal sites in which to make use of HART for
  applications such as inventory monitoring. (see accompanying story).
  In relatively small operations, users can set up modest, but effective
  SCADA systems that utilize HART technology, says Mactek’s Holmes. “You
  could continuously monitor up to eight points using a PC equipped with
  eight USB HART modems. That’s very do-able,” says Holmes. “For
  software, you could use a dedicated data acquisition package such as
  Wonderware’s InTouch software, or something as basic as a Microsoft
  Excel spreadsheet. I think there are plenty of operations such as
  bakeries or small specialty chemical plants that can’t justify
  spending the money for a large control system. But with HART input and
  a PC, you can build yourself a quick and dirty DCS,” he adds.


texts: How can I determine the specifications of this LED (photo included)?

texts: This LED (and 8 others like it) form the lighting component of a ceiling fan assembly. Unfortunately, they put out a very dim and cold light, and I'm interested in replacing them, but I figure I need to determine what I'm starting from before looking for replacements (although any suggestions on what to look/search for are welcome).


texts: Convert 12VDC fan controller output to TTL signal of laser?

texts:
I'm adding a laser cutter to my 3D printer.  I want to repurpose the cooling fan output to control the laser.  My laser has a power supply which accepts a 5V TTL signal to turn the beam on/off.

The fan output is as follows:
Fan OFF - both red and black wires are held at 12VDC.
Fan ON - Red wire 12VDC, Black wire pulled to GND.
(also supports PWM output at various levels, black wire is used for PWM signal while red wire is held at 12VDC.)

I had wrongly assumed the black wire would be held at GND while the 12VDC wire would be used to control the fan. So I assumed I had a GND reference available, so I built this level shifting circuit (which, of course, doesn't work due to black wire being pulled to 12VDC when off). Its purpose was to simply ground the TTL+ pin to the TTL- pin when 12VDC was present on the input, effectively inputting a logic 0 to the laser controller, or allow TTL+ pin to float high when 0VDC was present from the fan controller, inputting a logic 1 to the laser.  I realize this inverts the fan output (fan off = laser on) but that's not a problem.  And it did work when testing with a 12VDC power supply.

simulate this circuit – Schematic created using CircuitLab

However, since the outputs of the fan controller both go to 12VDC when the fan is off, this doesn't work.  How can this circuit be re-designed in the simplest way possible (hopefully without requiring outside power) to shift this strange 12VDC signal to 0/5VDC TTL signal, or effectively short/open the connection between TTL+ and TTL- pins?  I guess a relay would work for simple ON/OFF controls, but that would preclude using PWM to control the laser...

Thanks for any insight.


texts: What will happen if I go higher than common mode range

texts:
I am planning to use MAX9611 as a high-side current sense solution for my circuit. One thing that I do not understand is the common mode range which in the datasheet it says 0 to 60V:

Nowhere in the datasheet has been pointed out what will happen if a voltage higher than 60V be applied to the circuit. I am planning to use two different voltages for my LOAD, first 20V@1A and 120V@2A (I have a variable load). In the second mode (120V) I am not interested in sensing the current but I do not want to make a switch to bypass the MAX9611.

So does passing 120V in the circuit above damages the chip?


texts: Identifying windings of a single phase induction motor

texts: How can I identify the main and auxiliary windings of a single phase induction motor which has only three terminals (1.Red, 2. Yellow & 3. Black) out of the device? How to connect capacitor and power supply to it?


texts: The development board not detect SD card

texts:
I have problem on the SBC EM2440-III. when I insert sd card 4G or 8G into the board, it not detect sd card. I insert sd card 2G and work OK.
please help me to solve the problem.


texts: Trouble with replacing potentials for cc sources

texts:
I'm studying JFET transistors, and I'm having trouble with two things:
the electric potentials on the following circuits.
Writing the voltage Vds in function of Vdd, Id and Rd.

For example, for the N type (the one on the left), if I wanted to replace the +Vdd potential for a cc source, how would it be? I tried skechting it below, but I'm not sure about it.

If someone could explain this to me, or at least point me some references I would be grateful.

Also, for my second doubt, how can I write these equations using  Kirchhoff's voltage law?

Assuming Vds positive, for the N type I got +Vds -RdId + Vdd = 0
Vds = RdId + Id, but the book is telling me that it should be Vds = Vdd - Id*Rd

Thank you very much.


texts: How to collimate ultrasonc beam from proximity sensor HC-SR04 in measurng distances of 3 meters?

texts:
I am currently doing a project for bicycle overtaking safety in which an approaching vehicle or cycle from behind is found through ultrasonic sensor and indication is given to the rider.

I had a problem that the Ultrasonic sensor HC-SR04 is more divergent when the distance to be measured is more. The safe distance as per design is 3 m and using an Arduino microcontroller

The requirement is to obtained a narrow beam but without any reduction of signal intensity and without any reduction in sensing distance

Can anyone please tell me how to collimate the Ultrasonic Beam so that the angle is less but the sensing distance remains the same ?

Appreciate your help in advance.

Anand


texts:
I'm studying an optimal control for the inverted pendulum in the following figure

the state and the output of the system are defined as
$$x=\begin{bmatrix}r & \theta & \dot{r} & \dot{\theta} \end{bmatrix}^T, \quad y=\begin{bmatrix}r & \theta-\alpha & \dot{r} \end{bmatrix}^T$$

so the continuos state space model at the upright equilibrium is
\begin{cases}
\dot{x}(t)&=Ax(t)+B_u u(t)+B_\alpha \alpha(t)+B_\tau \tau(t)+B_{F_s}F_s\text{sign}(\dot{r}(t)) \\
y(t)&=Cx(t)+D_\alpha\alpha(t)
\end{cases}
where the disturbance inclination \$\alpha\$ is suppose costant, \$\tau\$ is a torque disturbance, \$B_{F_s}F_s\text{sign}(\dot{r}(t))\$ is a Coulomb's friction term and \$u\$ is the input force applied to the cart. The numerical values for the transfer matrices are
$$A=\begin{bmatrix}0 & 0 & 1 & 0 \\ 0 & 0 & 0 & 1 \\ 0 & 2.8040 & -5.2658 & 0 \\ 0 & 18.5885 & -19.6959 & 0 \end{bmatrix}, \quad B_u=\begin{bmatrix}0 \\ 0 \\ 3.7629 \\ 5.5257 \end{bmatrix}, \quad B_\alpha=\begin{bmatrix}0 \\ 0 \\ -12.6447 \\ 18.5885 \end{bmatrix}, \quad B_\tau=\begin{bmatrix}0 \\ 0 \\ 0.5650 \\ 3.7629 \end{bmatrix}, \quad B_{F_s}=\begin{bmatrix}0 \\ 0 \\ -1.1187 \\ -0.5650\end{bmatrix}  $$
$$C=\begin{bmatrix} I_3 & 0_{3\times1}\end{bmatrix} ,\qquad D_\alpha=\begin{bmatrix}0 & -1 & 0\end{bmatrix}^T$$
where \$I_n\$ is the identity matrix \$n\times n\$ and \$0_{m\times n}\$ is the null matrix \$m\times n\$.

For a digital implementation is required a suitable sampling of the previus system, so the discrete relative state-space model is in the form
\begin{cases}
x_{k+1}&=\Phi x_k+\Gamma_u u_k+\Gamma_\alpha \alpha_k+\Gamma_\tau \tau_k+N_k(\dot{r}_k) \\
y_k&=Cx_k+D_\alpha\alpha_k
\end{cases}

Now there is my problem. To counteract the effects of constant rail inclinations a discrete-time integrator is appended to the model \$(\Phi,\Gamma_u)\$. Is taked in the simple form
\begin{equation}\tag{1} w_{k+1}=w_k+r_k\end{equation}
so the extended state of the system become
$$x^{\text{e}}=\begin{bmatrix}x & w\end{bmatrix}^T$$
and the state feedback is designed by minimization of the cost function
$$J(u)=\sum_{k=0}^\infty (x_k^\text{e})^TQx_k^\text{e}+Ru_k^2$$
where the cost's matrices \$Q\$ must be semi-defined positive and the scalar cost \$R\$ must be strictly positive.

I can't understand the function of the integrator \$(1)\$. The rail inclination affect both input and output of the system, so the integral action counteracts only the effect on output. Moreover, the state matrix \$A\$ is singular, so the system at least has one integral action by itself, and no more integrators has to appended to the system.

Maybe the integrator \$(1)\$ is considered for drive the position of the cart to the start of the rail, i.e. \$r=0\$.

Thanks in advance for any suggestion.


texts: Precision opto-isolator voltmeter circuit

texts:
I'm trying to use a LOC110P to make an isolated voltmeter.

Here's the schematic of the important bits:

The left-hand side of the circuit is actually AC powered and the intent of the circuit eventually is to measure the actual AC voltage (R13 is 510K and is flame-proof. R11 is 6.8k). But set that aside for the moment. I'm trying to get the basic functionality of the circuit working without any AC connection, and it's not yet.

The DC-DC module is making 5V (it's not marked, but that's what it is) for the MCP6051. I would expect that if I take +5 from that isolated output and apply it to the left side of R6 that I should see 5 volts (ish) on pin 1 of IC1... right?

This is (trying to be) straight from IXYS' application note on the subject: http://www.ixysic.com/home/pdfs.nsf/www/AN-107.pdf

What am I missing?