texts: Is there a standalone chip/breakout to measure voltage and current to display externally

texts: I am currently looking for a DC voltage and current meter that I can put between my power source and the load. I can find a lot of packaged products that come with a display and everything, however I do not want to have that, I only want the circuitry maybe with 12V input, 12V output and grounds with an I/O interface (UART, SPI, I2C, whatever) to read the parameters from. First I was thinking about buying a already packaged meter, disassembling and then reverse engineer it, however I cant stop thinking that there is a better way and I am just not using the right search terms. Is there such a thing? And if so, what exactly should I be looking for?


texts: Why ARM CPUs are not used in servers and desktops?

texts: I was wondering why ARM CPUs are popular for mobile and other portable devices but not on desktop/server computers? The only thing I know is that ARM CPUs consume much less power than x86 processors. This is a good argument in favor of using it on mobile devices but also on desktop/servers. Yet it is not so widely used. Is it the instruction set or performance or smth. else?


texts: Why are 40 pin and above DIP packages generally wider than 28 pin and below

texts:
Take for example this datasheet for a Microchip PIC, the 40 pin package has a width of between 0.485 - 0.580 inches, while the 28 pin variant is between 0.24 - 0.295 inches. I have noticed this is the case with many parts, and don't remember seeing any 'thin' 40 pin DIP parts.

Is this due to fitting in the lead frame for higher pin counts, or is there another reason?


texts:
If we start from bottom left and rotate clockwise, then first we visit resistor negative terminal so I expect -Ri but the book says the below equation:

So why isn't the Ohm's law for the resistor negative? (I follow this famous convention in KVL, whenever you encounter the positive terminal of an element you mark that expression positive else you mark it negative)


texts: Can really small transistors be modeled as in undergrad textbooks?

texts:
Most undergrad textbooks on microelectronics (those covering semiconductors, diodes, BJT's, FET's, etc.) that I have laid my hands on discuss semiconductor concepts such as charge carries, drift, recombination, among others, to explain why transistors behave the way they do, and then present mathematical models for how different types of transistors work (e.g. IV curves) in order to analyse circuits involving them.

My question is, can state-of-the-art transistors such as those in modern CPU's be modeled by similar formulas? Given that modern transistors based on 7 nm technology can be only a few atoms in size (~30), do the same concepts apply, or do you really need PhD-level knowledge to even begin to understand how they actually work?

I've seen from other sources how ASIC foundries will share pspice models of the transistors that they can handle to customers and that they tend to be extremely complicated with dozens if not hundreds of parameters, so I got curious about this.


texts: Calculating capacitor capacitance between collector and emitter in radio circuits

texts:
In many radio transmitters and receivers there is a capacitor between emitter and collector. As shown in this answer this capacitor gives positive feedback to prevent decay. My question is that, how to know/calculate farads of that capacitor?
For example, there is a 5 pf in 70-150 MHz radios, 27 pf in 27 MHz and etc.


texts: Recursion versus Tail Recursion on an Arduino

texts:
In computer science, recursion chews up a valuable and limited resource – the stack – and can lead to an unrecoverable type of runtime error: the dreaded StackOverflow. Tail Recursion however is a form of recursion that doesn’t use any stack space, and thus is a way to use recursion safely.

freeRam() is the function to test the usage of memory

static int freeRam () {
  extern int __heap_start, *__brkval;
  int v;
  return (int) &v - (__brkval == 0 ? (int) &__heap_start : (int) __brkval);
}

I am testing  on arduino, in order to see the difference of the memory usage between the recursive way and tail recursive way

// recursive way
int recsum(int x){
    if(x==1)
    return x;
    else
    return recsum(x-1) +x;
}

// tail recursive
int tailrecsum(int x, int total){
    if(x==1)
    return total;
    else
    return tailrecsum(x-1,total+x);
}

however

void setup() {
  Serial.begin(9600);
  Serial.println( recsum(1000) );
  Serial.println(freeRam());
}

recursion 1000 times outputs still 1858 bytes available

void setup() {
  Serial.begin(9600);
  Serial.println( tailrecsum(1000, 0) );
  Serial.println(freeRam());
}

tail recrusion 1000 times outputs also 1858 bytes available

The test shows the recursion and tail recursion way in arduino doesn't affect the memory usage, so I am very confused and about it and in doubt of my results.


texts:
I'm learning programming embedded in atmega328p, i'm not understanding timers.
If you can tell me if I have a 4 Mhz oscillator frequency.
How can I know which timer to use, 8 bit or 16 bit timer and which prescaler to use?


texts:
I'm using an STM32F103C8T6 (aka blue pill).

GPIO Init and interrupt handler:

static void MX_GPIO_Init(void)
{

  GPIO_InitTypeDef GPIO_InitStruct;

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOD_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOC, GPIO_PIN_13, GPIO_PIN_SET);

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOC, GPIO_PIN_15, GPIO_PIN_RESET);

  /*Configure GPIO pins : PC13 PC15 */
  GPIO_InitStruct.Pin = GPIO_PIN_13|GPIO_PIN_15;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

  /*Configure GPIO pin : PA0 */
  GPIO_InitStruct.Pin = GPIO_PIN_0;
  GPIO_InitStruct.Mode = GPIO_MODE_IT_RISING;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

  HAL_NVIC_EnableIRQ(EXTI0_IRQn);

  while(1);

}

void EXTI0_IRQHandler(void)
{
    __HAL_GPIO_EXTI_CLEAR_IT(GPIO_PIN_0);
    HAL_GPIO_TogglePin(GPIOC, GPIO_PIN_14);
}

The problem is that the interrupt handler (EXTI0_IRQHandler) is never called. I tried also with other pins (e.g. using EXTI15_10_IRQHandler). I checked the switch and LED separately (in the main function) and those work.
I also tried with PULLUP and PULLDOWN (which makes no difference).

Is there more needed to trigger the interrupt function?


texts: What is 'DOC' in terms for Depth of Discharge for SLA batteries?

texts:
I'm trying to understand the spec of a SLA battery. There's a chart which is titled "Cycle Life in Relation to Depth of Discharge":

Can I ask what 'DOC' stands for and the chart is read? How come that line exceeds 100 on the left axis? I presume the left axis represents the percentage of discharge.


texts: Is it possible to decrease the speed of a standard servo motor?

texts:
I have TowerPro SG-5010 and its speed is 0.17 sec/60° at 4.8V and 0.14 sec/60° at 6V.

Just to be sure, is it possible to further decrease the rotation speed?


texts: How to build a self-made Qi compatible (wireless) charger

texts:
So I recently discovered that my phone, a Nexus 5, has Qi wireless charging capabilities. I was wondering if it is possible to make my own charging coil with 24/26awg wire that would look something like this (but without the driver circuit).

Then, I would use a micro controller/build my own circuit to drive it at the correct frequency with a DC to AC converter. I was wondering if this would work, how precisely I would have to make the coil, and if I am missing something about Qi charging completely. I ask this because there are very few internet resources on homemade Qi coils.


texts: What is miller shoot through voltage (aka cross conduction)?

texts:
Im studying mosfets switching characteristics and one thing I happen to come across is the concept of "cross conduction".I searched around the web and couldnt find answer to my question.Kindly read whole post.

In the image below, mosfet-1 is on, as the voltage is applied to motor M,for a brief period of time mosfet-2 drain-gate voltage suffers from a sudden voltage spike, which maybe high enough for mosfet-2 to turn on, which is not the behaviour we want.

Voltage spike(Drain-Gate)at mosfet-2(when it is supposed to be off)

All of this is understood, but what I dont understand is "why" this happens? Q) Is it because of inductive load(motor), which may oppose current in initial stage thus effecting the drain-gate voltage of mosfet-2 for a short period of time?
Q) what can be done to prevent this ? Q) Also at lower +Vdd voltages(like 12-24-volts) will this be a significant problem,practically ?

Im talking in context to H-bridges only.
Thank you for your time!


texts: Let there be 3-phase rectifier connected to the standard electricity grid with 400V between phases. Measuring voltage between one of the phases (AC) and negative terminal of the rectifier output (DC), what range would we get? Would the voltage stay always positive?


texts:
This is not homework. I have this circuit, and I want to calculate V2. I know it is equal to V1 at t=0, and equal to \$V1 \cdot \frac{R2}{R1+R2}\$ at t=\$\infty\$, but I don't know how to calculate the charging of the capacitor.

All I find on Google is charging of an RC, without the parallel resistor.


texts: RTOS-rtx (CMSIS) - Synchronizing threads

texts:
In the given Image, there is a program I'm having a difficulty to understand.
If we have created two threads count & barrier then why are we defining "counter"(2nd line)

also, inside thred1 function we are creating count as a thread. someone please differentiate between 'count' & 'counter'. what I've understood is count it a global variable and counter is a thread but I'm confused between their usability and how they are used in this given program.


texts: Building a 20x20 matrix with vibrator motor coins

texts:
I am currently doing a project that requires a 20x20 matrix with coin type vibrator motors.

I am not sure how to pull this off. What is the best way of driving all the motors all together? Provided that I will be applying different PWM frequencies to all of them at the same time.

I am going to be using a motor that requires 60 mA at 3 V:

10x Nuevo DC 3 V 60mA 9000 +/-2000 RPM de la Moneda Del Teléfono Plana Motor de Vibración Que Vibra (10x New 60mA DC 3V +/- 2000 RPM 9000 Coin Vibration Motor Phone Plana vibrating).


texts: Understanding constant current LED drivers (ac to DC)

texts:
I am trying to understand the way constant current LED drivers work. Lets say I have a driver with these specs:

Description:

Power: 18W

Output Voltage: DC 36-63V

Output Current; 300mA

Input Voltage: AC 85 - 265V

I can attach one LED light (which accepts 300 mA current) of 18 watts or 3 LED lights (each of which accept 300 mA current) of 6 watts each (in series) to the driver and it should work. In both these cases, the output voltage will be 60 V so that power demands are being met.

Q1 - Am I right up to this point?

Now suppose, I want to use the same driver to power up two 6 watts LED lights. I can still do so by wiring them in series. Output voltage in that case will be 40 V.

Q2 - Am I right?

Now lets say I want to light up a single 6 W bulb which requires 300 mA.

Q3 - What will happen in this case? In order to drive 6 W LED, the output voltage needs to be 20 V but the driver can give output in the range of 36 V to 63 V.


texts: Is there an IC chip to toggle through three outputs?

texts:
I am making a simple circuit (14 LED's that will create a chase effect), however, I wanted to do it without following any tutorials, to test my skills. I ran into a problem. In my circuit, I have all my LED's hooked up so that the first is connected to the fourth, the second to the fifth, the third to the sixth, and so on in a third-connection pattern. I want the LED's to go through a pattern of 1-2-3.

I need a way (I believe that there is an IC chip for it, but I can't find it) to toggle through three outputs when I effect one input. For example, the output pins of the IC chip be connected to the strings of first, second, and third LED. I would have a 555c timer that ticks every so often, and the output signal of the 555c timer would be connected to the input of the IC chip. Each time the IC chip is triggered by the 555c timer, it would switch the signal, from 1, then to 2, then to 3. Is there such an IC chip, and if not, how can I simulate it (I could possibly get by with just alternating one and two LED's instead of three, if there is a circuit or IC chip that would just toggle between two).


texts: How build coil for respiratory magnetometer or find a better option (hall effect)?

texts:
I am trying to build an respiratory magnetometer. This device is no longer widely used even thought it was well liked. The reason it is no longer used is due to the fact that the coils used in it were custom made and the maker stopped making them. Over all with the advances in technology it seems to be much easier to produce. However I am still having problems recreating the coils. I have talked to several engineering students and contacted a few manufacturers that make custom coils and no one can help me (this may be due to my production size). There are 2 transmitter coils and 2 receiver coils. They are tuned to 5900 Hz and 4300 Hz.

The description in the patent (which has long since expired) is "Encased in a round plastic disk, each coil has its winding axis oriented parallel to the skin surface, and is roughly rectangular in shape, being about 3/4 inch (19mm) along the axis, and about 7/16 inch (11.1mm) by 3/8 inch (9.5mm) across the axis. The coils have inductance of 50 mH." There is a Q of 20. I can not figure out how they built the coils at such a small size with the 50 mH inductance, but this is not my area of expertise. Any help on how to build this or where to buy one would be greatly appreciated.

Another option could also be to use a hall effect sensor instead but many of the people I have spoken with did not think that this would be a good option at these distances. Any advice is welcomed.
Thanks!

Here is a link to the patent: http://www.google.com.ar/patents/US4258718


texts: Viewing phase difference between two signals

texts:
I need the SPI clock and the device clock to be synchronized. I am using an Arduino (ATMega 2560) to communicate with the device. The device clock is being generated from using a timer on the Arduino (16-bit Timer).

The SPI clock is also from the SCK pin on the Arduino (pin 52 in this case). From the ATMEGA2560 data sheet I am sure that both these clocks are derived from the onboard crystal oscillator so theoretically they should be in sync. However, I want to visualize this and then make sure they are in sync. I tried using an oscilloscope, but I am unable to trigger both channels at the same time. I am using a Siglent SDS 1052DL+. Can somebody give me guidance on how to use a scope for this purpose?

Edit: removed Arduino code.


texts:
I'm working with ATmega1280 (Datasheet link) Currently I'm using the internal RC-oscillator at 8MHz
I'm also using Telit LE910 for sending data that can take up to 2A (from the Telit hardware user guide).

You can see my voltage drop in the ignition state of the modem:

My supply voltage is 3.3V from a battery and I have a lot of EEPROM writes, so I want to protect my EEPROM.

And flash corruption:

I'm facing EEPROM corruption on low battery conditions, therefore my Brown-out level is at 2.5-2.9 (the line corresponding to 101).
My question is if I'm using the CLKPR – Clock Prescale Register
with a division factor of 2 for receiving a 4MHz clock.
Can I switch to Brown-out level corresponding to 4MHz 1.7-2.0 (line 110)?

The BOD detection takes place in the reset logic?
So even in 8MHz the BODLEVEL will refer to the clock after the Prescaler(4MHz)?

The safe zone is for the Vcc frequency after the Prescaler?


texts: How to power a big high voltage 7-segment array with minimum parts, without frying my wimpy power supply?

texts:
I am trying to design a clock with a big 8-digit 7-segment display formed by about 250 LEDs, but with a power draw limit of 1A from a 5V USB phone charger. Each stroke is four LEDs in series and requires 9V 50mA to drive, and every digit have a maximum of 8 segments (7 segments for the number and one segment for the dots making up the colons.) There is only one boost converter on the board, and I must minimize the amount of constant current sinks I use.

The rest of the system runs on 5V straight off the phone charger, with ATmega328P being the main microcontroller and DS3231 keeping time.

Questions:

Will lighting up all 8 segments in a digit fry my MC34063-based boost converter? If so, how do I prevent it from being fried?
How to control the thing with minimum amount of power transistors, N-channel only?


texts: LTspice subcircuit with behavioral voltage source

texts:
I'd like to use behavioral voltage source in subcircuit block, as showed below:

With block "comp":

But when I try to simulate it doesn't work and gives mi this message:

Someone could explain what's wrong with that?

below the netlist:

V1 Vramp 0 PULSE(0. 5 0 9.9u 0.1u 0 10u)
V2 Eamp 0 3.3
XX1 Vout Eamp Vramp comp
R1 Vout 0 1

* block symbol definitions
.subckt comp out in1 in2
B1 out 0 V{if(V(in1)<V(in2), 5, 0)}
.ends comp

.tran 50m startup
* Parametri da inserire
.backanno
.end

The subcircuit netlist:

.subckt comp out in1 in2
B1 out 0 V{if(V(in1)<V(in2), 5, 0)}
.ends comp

Thanks

below the netlist:

V1 Vramp 0 PULSE(0. 5 0 9.9u 0.1u 0 10u)
V2 Eamp 0 3.3
XX1 Vout Eamp Vramp comp
R1 Vout 0 1

block symbol definitions
.subckt comp out in1 in2
B1 out 0 V{if(V(in1)

.tran 50m startup
* Parametri da inserire
.backanno
.end

The subcircuit netlist:

.subckt comp out in1 in2
B1 out 0 V{if(V(in1)

Thanks


texts:
Could somebody explain to me the principle of this current mirror? I don't understand why I throughout my R2 and R3 is not dependent on R1 (R bias)?

My goal is to have 0,8V voltage drop on R3.

Many thanks in advance.

simulate this circuit – Schematic created using CircuitLab


texts:
I'm trying to understand the following section of the Arduino Uno's schematic:

(Here's a link to Arduino Uno R3 complete schematic)

The Arduino's site recommends that Vin should be between 7 and 12V. However, I was reading the datasheet for the comparator (LM358) and it seems that the voltage range is -0.2 to 5.7V, where 5.7V is absolute maximum for the input pin.

As a result, wouldn't 12V damage the chip since 12V would input 6V into the comparator?

I tried asking this question in another forum. However, no one really knew the answer why, and tech support at SparkFun was also stumped.

Thanks for the help in advance!


texts: I am going to be wiring up a custom circuit.  Audio is output from two LR audio cables.  I am going to wire them up to two mini speakers, one for each LR cord.  But how do I add in a part to detect if headphones are plugged in so instead of playing audio from the speakers it would play to the headphones that were plugged in?


texts:
I am going to install 30kw solar system? Who will have nore efficiency if a use a single 30kw inverter or 3 inverters of 10kW in parallel? And which would be best combination?
Note: three 10kw can be synchronized and every unverter has an efficiency of 90%.


texts: Differential amplifier IC vs op amp with resistors to make it amplify a differential signal

texts:
What is the advantage of using a differential smplifier IC instead of using a normal op-amp and designing the resistor network around it?

The ICs seem to be more expensive and require more power.

The application I am looking at is to amplify the signal from a Wheatstone bridge, and I would like to minimise cost and power if possible.

Would it be advisable to use an instrumentation amplifier?


texts: Need Clarification on Choke Placement (Vintage PS)

texts:
I came into possession of an old Electro D-612T variable DC power supply. Based on what I've read here and other places it was manufactured in the 1950s, and sold for a whopping $39.95 US at Radio Shack, which today would run around $390 US. These were apparently used quite often at car radio repair shops. I wanted to clean it up a bit so that it could be used 'safely' in the garage for odds and ends where I don't need super clean filtered DC, and might need higher currents. This meant removing the selenium rectifiers and cloth insulated wiring.
I started tearing it apart last year, and as these things sometimes go I did not document the original wiring. After sorting out the windings for the variac portion, the rest is fairly simple to put back together. This brings me to my question. There is a reasonably large iron core coil, which I am fairly certain is meant as an AC line choke, but wanted to get some clarification in case someone else on here has come across one of theses supplies or similar. I have seen chokes in configurations both before and after the variac on various power supply circuits, but in this particular case I am leaning towards it being on the input due to the fact that the variac steps down the input mains voltages to a range of 0 to 12VAC. So I am thinking it would be more effective to filter harmonics / noise before the step down occurs. Would love to get feedback on this to make sure I do this correctly.


texts: Simulating a thermopile on the bench -- is this a reasonable/reasonably accurate way to do it?

texts:
Primer

Most people know about 24V HVAC control systems, as that's what's commonly found on furnaces, heat pumps, central air conditioners, and other such systems.  If you have electric unit or radiant heat, you may have seen line-voltage thermostats as well that run directly on mains voltage.

However, there is a third type of control system for gas valves, the so-called "millivolt" system.  This system uses a device called a thermopile made of many thermocouple junctions in series to produce a control voltage on the order of 500 to 750mV when heated by the pilot flame.  This is enough to operate a gas valve through the contacts of a manual switch or mechanical thermostat.  This system has the advantages of being intrinsically safe (the system won't attempt to run at all if the pilot's not lit) and self-powered (it needs no external AC supply to work), so it's most commonly found on gas fireplaces.

An example thermopile is the Honeywell Q313 series; we can assume that its specs are representative.

My problem

However, if you want to test this type of system, a problem arises.  Running a gas valve with all the ports open to outside air won't hurt it, as far as I know.  However, I don't know about your workbench, but mine is not rated for the temperatures needed to get such a thermopile to generate its rated output!

So, in order to mess around with making a timer, fancy-thermostat, etal that works with such a system, or to test theories about suitable switches, you need a thermopile simulator.  In the past, I built one according to the below schematic (with Roffset = 54.9kΩ, a 20kΩ single turn pot for Radj, and Rseries selectable between 1.5Ω and 3.6Ω) and it appeared to produce reasonable results, but I never was able to fully test it with an actual gas valve, and do not have the constructed unit at hand any longer.

simulate this circuit – Schematic created using CircuitLab

The question

Is this a reasonable/reasonably accurate simulation of a gas valve control thermopile under steady-state operating conditions, assuming that my open-circuit voltage and series resistance are chosen to match the specifications of an HVAC thermopile (for the Honeywell linked above, I'd be setting up the LT3080 as before, but with an Rseries of 2.87Ω)?  By "reasonably accurate", I mean that if I took 100 random, known-good millivolt gas valves, and attempted to operate them "on the bench" with this rig, 99 of them would operate normally for say, at least 10 on-off cycles of operation.


texts: What type of pin in this (see picture)? I see them in FSRs but they don't appear to be Dupont connectors

texts:
Here are the images of the pins:

And here is the FSR that it came from:


texts: Proteus Ground Plane with thin trace in Pad

texts:
I am doing a project on Proteus Ares and applying a ground plan.
However, the points of the terminals that are connected to ground to ground-pad connection is by a thin trail.

Is there any way to adjust to the ground and the point does not have that spacing?

Below a example:


texts: Bode plot graph: Frequency vs. Angular frequency

texts:
I am wondering, why are some Bode plots made with \$f\$ or frequency of signal representing x-axis, and why other Bode plots use \$\omega\$ or angular frequency of signal representing x-axis? Why don't all use same quantity (in my opinion, frequency)? But even if one may be using angular frequency for plot, and other may be using frequency for plot, two plots will look exactly the same...

Do you use angular frequency with imaginary unit \$j\omega\$ when plotting complex poles and zeros onto Bode plot? Or is there any other reason?

Also \$rad/sec\$ doesn't equal to \$Hz\$ so this is another fact that confuses things up.


texts:
The part sn74lvc1t45 we are sing as an SPI translator.

We usually use B -> A which means DIR goes to ground, however in a new design we are reversing this, and as a result, as per the DS it (being the DIR pin) needs to go to VCC 3v3 - that being said, the default layout PCB design guideline shows an R on this pin - but no mention of its requirements elsewhere.

Any thoughts as to what its value should be? And if so, how were they arrived at?

Thanks


texts: Why does Basler GPIO need to have an external powersource + resistor to its GPIO output

texts:
Background
We are usingzBasler camera with an output trigger. The camera output gpio is 3.3VDC and the consumer can handle up to 5V, logical 1 is above than 2.7V. The camera can output up to 50mili amp max. Out consumer will draw from 3.3v no more than 12 miliamp.
Questions
First
According to the attached diagram, Basler writes that an external power source with a resistor is needed. I thought maybe its because the output voltage is typlical? Does it mean that the voltage can vary? so the current consumption can be higher?   Or maybe its
2nd
If I do attach external power source then what is the output voltage? (given power source of V and resistor R )?
Thanks
Oak


texts: How is it possible to use a phase as a return path?

texts:
On the 3 phase system, it is possible to supply a 380V load using 2 phases, say L1 and L2.
I understand that the phases alternate and that one phase acts as a return path for another, but this doesn't seem to always be true when looking at the graph.

Lets say I supply a 380V coil with only the Red and Purple phases, at time 0.1 both will be in the positive half. Now, does this mean that there wont be a return path at time 0.1? What will actually happen to the load at the instant where both phases are either in the positive half or negative half?


texts: drawing current from multiple sources in parallel

texts:
I'm working on a project which consists of repurposed training bike to generate electricity. We have 8 bikes connected in parallel to a battery. The bikes are equiped with AC motors and a diode bridge to convert to DC and produce a tension around 24v.

I would like to measure the current produced by each bike separately. I already did it with one bike, but I wonder if it is posible to do the same with multiple DC sources in parallel. Won't I read basically the same measurement on each source ?


texts: How are a Tesla's batteries charged below 0degC

texts: According to this link, charging a lithium ion battery below freezing temperature can damage it. How does Tesla manage this problem? I assume they have a solution since they sell their cars in countries that experience severe winters.


texts: Reverse polarity protection - PMOS vs Schottkey diode

texts:
I have a circuit running from 2 AA cells in series, meaning I get 3.0V when fresh (or 2.4V if NIMH cells) and it goes down to 2.0V, that's when my circuit cannot function anymore (no DC/DC onboard).
It's a very low current circuit (<30mA 99% of the time).
The circuit is very very cost-aware as it's going to mass production. Every cent counts.

I want to create the an efficient reverse polarity protection. Right now I am using A schottkey diode and getting ~0.24V voltage drop across it. I guess I am wasting some good battery juice this way when my circuit shuts down even before the battery was really exhausted.

What will be the advantages & disadvatages of switching to PMOS style protection?

I am confused on what are the parameters & numbers I need to verify in the PMOS datasheet so it can provide polarity protection for this low voltage/low current input?


texts: Simulate Shift Register on AVR (Configurable Logic/Timers?)

texts:
Recently I set up two MCUs (ATtiny1616) to perform basic serial communication using shift registers I made myself.

simulate this circuit – Schematic created using CircuitLab

Here is the logic diagram for my shift register. I made it out of logic gates I had lying around. All it does is shift whatever is on the data line into the register when the clock (active high) goes from high to low:

simulate this circuit

Ignore my non-standard flip-flops, I wanted to visualize the bits on my LED indicator panel and shift in from the least significant bit (right). I wired the clock line into the receiver so that it would only read PORTA.IN when the transmission is finished. As each byte is transmitted, TIMER A counts clock falling edges in 8-bit mode. When the counter gets to 8, it triggers an interrupt that resets the counter and reads PORTA.IN.

The receiver/slave then pulls the data line low, triggering an interrupt on the sender/master, now waiting idly for a transmission confirmation. I added a timeout detector as well. To signal the end of a transmission, I send a byte with all bits high. The receiver will not expect a response back after receiving the final byte and pulling the data line low, and the transmission is complete.

I tested this out with two 512-byte arrays: an empty byte array on the receiver, and an array with bytes representing an ASCII message and some trailing random junk at the end on the sender. The data was successfully transferred from sender to receiver in a fraction of a second. I am quite impressed with the results.

The downside of this method, apart from only allowing one-way communication at the moment, is that it uses up a whole port to read the data. I would like my 'shift register' to be internal within the MCU, and not outside cluttering up my prototype and wasting lots of I/O pins. Then I could just feed the clock and data into the controller and do it all there. Hardware only until the final read, of course.

Any thoughts on how this might be achieved? The 1616 supports Configurable Custom Logic but I don't think it has the number of inputs required for an 8-flip-flop shift register. I suppose I could resort to sending nibbles at a time... Also thought about using timers to achieve this, but don't know just how that could be done. Perhaps a combination of the two?


texts:
I bought a couple of those 3 digit 0-30 volt dc voltmeters.  Im taking ac 0-24 volts (Lionel train transformer)  through a rectifier and measuring it with the led meter.  My problem is the meter never settles?

I was thinking a cap across the +- on the rectifier but since I dont have any caps in my part bins to experiment with I have to buy one so I need to know the value in advance.


texts:
I have a 6V 3AMP power supply and I wanted to reduce the voltage output to 5V 3AMP.

I saw buck converted on ebay of the following spec. Can i use it to step down 6V to 5V without losing Ampere? or any suggestion, how i can step down 6V to 5V while keeping 3AMP.

DC-DC Buck Step Down Converter Regulator Power Supply Module 9V 12V 24V to 5V 3A.

Mini DC-DC Step Down Converter

Input voltage 7V~28V

Output voltage 5V(Precision 1%）

Output current 3A(max),long time work within 1.5A

Conversion efficiency 96%(max)

Output ripple <30mV

Switching frequency 1.5MHz(max), Typical 1MHz


texts: Why use a custom module instead of a clock divider?

texts:
Background
I have created a VHDL module that continuously generates a one-bit wide pattern of "1010101010..." as long as it's enable bit input is asserted high, as part of a class assignment. In the description of the assignment, the justification given for creating this module is that they are used in many devices, and an example is the Ethernet I1 preamble, which consists of eight repeating octets of "10101010".

Here is my simulation result:

The Question
I understand the usefulness of the preamble for synchronizing packets, but I got the impression from my instructor's description that hardware designers will write modules like this to generate this pattern without referring to it as a "clock divider", even though it essentially is one. Why not just call it a clock divider instead of a "preamble_generator" or other such names?


texts: How could I interpret these-2 YUV modulated picture given in wikipedia? is it correct simulation? or something I'm missing?

texts:
While reading the wikipedia article on YUV color modulation (which is used in PAL color tv receivers); I visited this diagram:

 (Wikimedia);

(and according to the image description there; i.e.

  "An image along with its Y′, U, and V components respectively";

the 3rd one is U-component and 4th one is the V-component of the 1st image. Well.

But there;  the component U has been described as

U = approx  0.492 (B - Y')   ... (where Y is Luma).

So, if the 3rd image show only U; i.e. 0.492 (B - Y') or 0.492 X (Blue-(0.299R+ 0.587G + 0.114B)) ; then in the ultimate result;  there would be equal visual reduction in R and G; and B would be the most prominent.

(As well; they've provided a formula too;
U= -0.147R -0.289G +0.436B ; that shows a positive value for only blue, and a negative values of both R and G)

If someone try to simulate it as visible picture; the picture would contain only-blue (which is non-negative).

But surprisingly, in image 3, there is high portion of green too ; i.e. green is  behaving in similar, positive way) ; though there I could not find any trace of red component with ms-paint Eyedropper tool.

(My eyedropper samples on downloaded original-file ranges from R=0, G=83, B=172 to R=0, G=191, B= 64; and in all samples R=0; on Paint's 255 scale)

So; my question is; is it a wrong picture of U component?

Even if I consider they made a negative copy of U (i.e. gave a -U); still we would obtain Red and Green together as positive; and blue as negative.

U= -0.147R -0.289G +0.436B

= > -U = +0.147R +0.289G -0.436B

But the image shows G and B; not R and G.

In the same way; the 4 th image (V or approx. 0.877(R-Y')) also seems to me showing anomaly from the definitions.

Given equations;

V= +0.615R -0.515G -0.100B

So the positive image would only Red color. But similar to 3rd image; it show proportions of Red and Green; not Red-only.

(ms-paint eyedropper samples from original image shown R=147, G=81, B=0 to R=102, G=153, B=0; and in all sampled dots B=0)

If it was a negative copy of V-component; Then we should get positive values of G and B. Not R and G.

So; if these 2 images are correct examples of U and V; what thing I missing about the concept of U and V? what is the basis behind that "extra green" in both the image 3 and 4?

in simple words;

If from a blue image (Component B) if I snatch away a colorless component (Y') then how I get a blue-green picture and not an only-blue picture? or why not blue red?

And same way, if I snatch away a colorless component (Y') from a Red image (Component R); then how I can obtain a Red-Green image and not a only-Red image? or why not blue-red?


texts: measurement of differential signals using multimeter

texts:
Though differential signals are measured through oscilloscope or differential probe, i tried measuring the signals through a multimeter out of curiosity and my observation was that when a voltage was measured across Rs-485 'A' terminal and Ground, the multimeter gave high reading >100V.

Could not find the reason why the reading showed such a high voltage
. It would be great if anyone could help me with it.


texts: Controlling 1.5A Stepper with Easy Driver

texts:
I have a 1.5Amp stepper motor (nema 17 size) and I want to control it with an easy driver v4.4. The maximum output per phase for this chip is 750 milliamps. My question is: can I use this board to power the motor by using the current limiting pot on it? I currently have this set to about half and the board is getting very hot, and burns to the touch.
Thanks


texts: Why can batteries store much more energy than capacitors even though they are much smaller?

texts: Why are batteries significantly smaller than capacitors yet can store much more energy ?


texts:
I have a UPS that has two 12V batteries wired in series. I'd like to pull 12 volts off of one of the batteries to directly run some 12v DC equipment without going through the built in UPS AC inverter and a 12v transformer due to the extra draw those have.

Is it ok to do this? It seems to read 12v when I check these points with a volt meter.

Will this work? Am I going to prematurely fry one battery or over tax the charge circuit in the UPS? Should I just do this with a step-down converter?

Thanks

simulate this circuit – Schematic created using CircuitLab


texts: How do I protect power out connector from having power in connected to it?

texts:
I'm building an adapter for rotary encoder that reads input of encoder and sends pulses by RS485. I'm using two RJ-45 connectors to provide power both for adapter and encoder. Both connectors have the same pinout. The right side connector receives 12V, theres linear regulator on board that powers RS485 transmitter/receiver chips and encoder.

I want to make some protection mechanism that would prevent failure when user connects 12V cable to output (left side) connector. Indication LED about wrong connection would be bonus.

All I was able to come up is a mosfet Q1 that has it's gate tied to +12V and 5V zener diode in series with resistor and "wrong connection" led.

Could someone advice me on more elegant/better way to do it?


texts: What will be the output of the following circuit?

texts:
The above signal is fed to the following circuit -

It is given that RC>>T and diode is ideal.

Doubt - As RC>>T, the capacitor will not be able to charge during the positive half and output should be equal to the input. In the negative half cycle, the diode is open circuited and entire input voltage appears across it. Hence in the negative half cycle, output equals the input. So the overall output should be equal to the input signal. However I searched the internet and found this solution in the instructor's manual -

How is this waveform even possible? Surely the capacitor is not getting enough time to charge for the clamping to take place.


texts: What is a good approach to detecting distance and speed in model railroads?

texts:
Up front I must admit to little hands-on knowledge of modern microcontrollers and their software - I know power engineering and big motors much better (45 years of it).

Now, my question:
Trying to get grandchildren enthused about electronics. They love model railroads, so we are building a train monitoring system bit by bit.

Current problem: To detect distance (optionally speed) of a locomotive from a specific track location, without messing with track power.

Control platform: Stellaris Launchpad

Options considered:
* TSOPxxxx with "dumb" fixed frequency oscillator and RF LED on loco - How do I get speed info?
* TSOPxxxx and emitter at trackside, reflection from loco - can get speed by time-of-flight, maybe
* 5 Volt red lasers and break detection by red LED as sensor (the kids love the lasers, so...) - no speed detection without multiple devices per detection location
* RFID tags and a coil at trackside (will identify the specific loco which is a plus) - no speed info
* Ultrasonic distance sensors - Ubiquitous and well supported by netizens, but too broad a coverage angle I suspect
* One of many readymade model railroad products - counter to the purpose of this exercise

So, which of these approaches, or any others, will give me the least grief at the software end, and yet will involve sufficient opportunity to engage 8 to 12 year olds in hands on electronic design with results they can experience? What are the pitfalls to watch out for (besides spilled cola)?

The trains are N-scale (1:160 scale).


texts: Control automotive AC switch via TPS voltage

texts:
The A/C compressor is engaged via a single wire that comes from the 'A/C' button on the dash board. I want the A/C button to disengage when the throttle is at 50%. The throttle position sensor (TPS) works based on voltage. 0.5-4.5V to be exact. 0.5V is idle (0%) and 4.5V is wide open throttle (100%).

What do I need to automatically disengage the A/C switch when the voltage exceeds (for example) 2.5V from the TPS?

The A/C compressor draws a lot of power from the crank and makes acceleration hard in a pinch.

Thank you.

Sorry automotive electronics are mostly very simple systems and this actually exceeds my current understanding of circuits and relays.


texts:
I have a circuit in which I have a Li-Ion 3.6V battery, then a voltage regulator that outputs 3.3V and then the circuit. Also it contains a couple of tiny 1uF decoupling capacitors in front of and in the back of the regulator.

Sometimes the battery due to extremely high vibrations it loses contact with the battery holder and as such the microprocessor of the circuit brownouts. I haven't checked it but I guess that the battery loses contact for something like 10 msec.

I thought of adding a capacitor on the battery side to compensate for such kind of loss and as such I started calculating some things. My circuit is using on average around 20mA. If I want to be able to feed from the capacitor for 50 miliseconds after the battery loses contact, how many Farads should be my capacitor?

Following is my thoughts. Could someone please verify if they are correct?

3.3V at 20mA -> 3.3x0.02=0.066 Watts power consumption and 0.066 Whours per hour. In 50 milliseconds, we have needed power consumption of

(0.066 / 3600 seconds) / 20 = 9.167e-7 Whours (equation 1).

Supposing that my microprocessor will brownout when the battery voltage falls at around 2.7V, I thought of the following:

Energy E (in Joules) of capacitor is E=C*(V^2)/2

as such the energy in Joules that the circuit will consume from the capacitor in order to fall from 3.6V to 2.7V will be:
C*(3.6^2)/2 - C*(2.7^2)/2 (equation 2)

in watt-hours we divide that equation by 3600.

So, we have (C*(3.6^2)/2 - C*(2.7^2)/2)/3600 = 9.167e-7 (from equation 1)

Solving for C we have C = 0.001164 Farads

That means that we need at least 1164 uFarads capacitor in order to be able to cope for 50 milliseconds.

Do I think of it correctly?


texts: How to calculate damping ratio and natural frequency of a high order system?

texts:
To calculate the rate of damping and the natural frequency of second-order systems is easy, third order as well. How do I calculate the damping rate, natural frequency, overshoot for systems of order greater than 3?

In other words, if each pole has a damping rate and a natural frequency, how can the damping rate and natural frequency resulting be found.

For example, the system:
$$
f(s) = s^5 + 13s^4 + 100s^3 + 1300s^2\;?
$$


texts: Can you smooth a stepper motor with diodes?

texts:
I've seen a lot of talk in 3D printing  circles about using "smoothers" to reduce artefacts caused by the vibration of stepper motors. Here, for example, and here's a site claiming they "also protect against induction voltages in the unpowered state of the driver". To my mind that's sounding a lot like the psuedo-scientific nonsense you get on Hi-Fi forums.

Basically the smoothers are two diodes wired anode to cathode in series with each pole of the motor. Apart from a voltage drop I can't see how they would effect the motor at all.

simulate this circuit – Schematic created using CircuitLab

Is this based on physics, or just a way to sell overpriced Schottky diodes?


texts:
I'm interfacing to a microprocessor system, and purposefully not using programmable logic. Feel free to call me a masochist. There's a lot of address decoding etc. happening and I may be able to cut costs and save board space if I use some diode logic. I'd probably also be saving in propagation delay — some of the gates are three levels of cascaded 74HC32s or 74HC08s involving 8 to 16 inputs.

The functions I'm considering replacing sit between HC (possibly some AC) family ICs, all running at 5V. They always sit between an HC IC and another HC IC (usually a '138), so signal restoration shouldn't be an issue. If necessary, I can change those to HCT to give more leeway. They're going to be running at clock periods of 500ns to 250ns at most (that's 2–4 MHz).

Can I use wired gates with relative impunity?

Do you have a suggestion on the type of diode to use (ideally available as through-hole and surface-mount), or shall I go with my all-time favourite, the 1N4148?


texts: GLCD touchscreen interference with metal frame?

texts: I am trying to use a 128x240 GLCD driven by t6963 and a resistive touchscreen. When touchscreen and the frame are far apart, everything goes well but when I put them together it starts sending touch signals. Should I use a spacer between them?


texts: Please check my DC / DC schematic. ST1S40

texts:
I want to make a voltage down converter to power my controller (Atmega328P).

Input = 12V / Output = 5V (3A).
As a converter, I use ST1S40.

My connection diagram

I took the circuit from datasheet, changed the values of resistors R1, R2. The rest is unchanged. I did not find the connection scheme of this converter with an output voltage of + 5V.

Why did I choose him? To connect it does not require a lot of components. Unfortunately, I did not find other options.


texts: Can we use bootstrapping technique for resonant inverter?

texts: I am developing a resonant converter and could not understand which technique is not be used for the H-Bridge inverter so the MOSFETs can switch properly. I am using IRF540n N-channel MOSFETs.


texts: Why are the diodes in this circuit forward biased in spite of no current flowing through them?

texts:
Considering the following circuit, Normally in the +ve half cycle SCR1 is triggered after it takes its triggering gate pulse and then D2 becomes intrinsically forward biased so it's on and conducting the load current along with the SCR1. The question is Why do we consider D2 to be forward biased in the period between zero time to when SCR1 is triggered in the positive half cycle? Isn't it supposed to be "off" since SCR1 is not triggered yet so the there's no current flowing in the path in which it is connected?

The same scenario is of course applicable to the SCR2, D1 in the negative half cycle.

Any answers are appreciated, Thanks in advance.


texts: Transformer core shape for IF application?

texts:
I am looking for transformer to use with MC1350 IF amplifier.

Searching online, reference boards seems to use Canned type transformer as shown below.

The transformer has a center tap on the primary side, and looks similar(but not exactly like parts linked below.

Datasheet

However I could not find the parts with specification which I want, so I would like to DIY transformer.

The only core type I have E core that looks like below image

If I make transformer using different type of core, would performance be compromised?


texts: Are control systems and motors typically driven from the same source in robotics projects?

texts:
My control system is a simple microcontroller between 3.3V and 5V, but the stepper motors I require are 12V. I have ordered a 14.8V battery that I intend on regulating down to 12V to drive the motors, but should I also regulate down to 5V for the control system or use a separate power source?

In short, are the control systems and motor drives typically powered by the same source or are they independent? I know that high series resistance batteries can show significant output voltage drop when high current is drawn, but my question is really regarding common practice in power design.

Assuming the voltage drop from high current is low (not sufficient to affect the 5V regulated bus), would it be reasonable to use the same power source for both systems?

Using something like this, for example:
http://www.hobbyking.com/hobbyking/store/__24579__Turnigy_5V_6V_5A_Heli_UBEC_for_Lipoly_6_16V_.html


texts: When solving for circuit consists of  ideal voltages and conventional resistors I get that one of the resistor's voltage is negative- does it mean the resistor delivers power, or the polarity of the resistor need to be changed?


texts: What is the "loaded resistor" for ultrasonic receivers?

texts:
I have an ultrasonic receiver (datasheet available here). On page 2, there are two graphs plotting sensitivity variation and center frequency shift versus "loaded resistor":

What does "loaded resistor" exactly mean in this context?


texts: Confusion with ADC resolution FFT and programming tools

texts:
I have a signed 16 bit ADC which means it maps -10V to +10V range to 16 bit. So the max voltage +10V is 2^15-1 = 32767; zero is 0; and -10V is -2^15 = -32768.

My confusion is that when I perform data-acquisition with such 16 bit hardware and do the FFT with MATLAB or Python tool I dont know how the program know the resolution of the data(like 16-bit). And if I create my own array in MATLAB by coding what would be the bit resolution when it does the FFT.

I don't know if I could articulate where I am stuck at. Basically as I have written before imagine you have a have a signed 16 bit ADC which means it maps -10V to +10V range to 16 bit. So the max voltage +10V is 2^15-1 = 32767; zero is 0; and -10V is -2^15 = -32768. And imagine you have a binary file file full of 16-bit samples recorded by this ADC hardware. Now if you perform FFT in MATLAB or Python these tools will read 16 bit file and convert these unsigned bits to voltage and perform FFT.

But imagine you want to do/mimic the same thing with coding not by using FFT. How would you make such array in MATLAB or Python?

Here is an example: Let's say I want to create/plot a sinusoid in MATLAB or Python where I can mimic exactly that 16 bit ADC which samples a 1V 100Hz sinusoid input for 1 seconds which is sampled with 512Hz sampling rate. At the end I want to obtain the same FFT plot where I would obtain after a real ADC sampling. How can that sort of array be obtained? How does the FFT function know the resolution of the ADC when it calculates the FFT?


texts:
I recently received a Li-ion BMS which has a checkbox called:

Balance function:      with / without

Apparently the BMS does NOT have a balance function. I want to use it with 18650 cells, the specifications are here: https://www.aliexpress.com/item/14S-Lithium-Battery-BMS-for-58-8V-18650-Battery-or-Lipo-Battery-PCB-with-Max-40A/32806164694.html?spm=a2g0s.9042311.0.0.jfSUrh

What does a BMS do when it does not have a balance function? is it ok for 18650s ?


texts: small inexpensive battery powerable component for daily timer circuit with LED and button

texts:
I want to make a small "visual alarm" device that turns on a LED every day at a time (e.g. 17:00) and turns the LED off on button press or (if no button was pressed) at a later time (e.g. 22:00).

I have made something like that on a Raspberry Pi 2. But I now want it much smaller and powered by a small battery (one AAA or one CR2032). Even the Pi Zero is too large for the use case.

What component is a good fit for this task? (Microcontroller? RTC? I do not know what the correct category term is.)

My longer term goal is to make several of these small devices and place at different locations as visual cue reminders to perform a daily task. Like a spatially distributed daily checkbox list.

Required:
As already noted, must be able to turn on/off LED based on time and button press. Time variation +/- 15 minutes accumulated over a week is ok, if I can fairly quickly reset back to the correct time manually once per week.

Also relevant:
- low cost (at most half the price of a raspberry pi zero)
- at least 1 week battery with one AAA battery

Not needed:
wireless connection, quick way to change on/off times, bells and whistles.

Also relevant: I'm not experienced with microelectronics beyond some pretty basic Raspberry Pi use, so components that require advanced skills to program and/or advanced tools to work with are not a good fit.

Note: I have tried to research this but got overwhelmed by a lot of component terms (like RTC ICs) and possible dependencies on other components.

Edit: The use case is at evening in not very brightly lit rooms so even the kind of tiny power notification LEDs some laptops/smartphones have would probably be enough.


texts: Confused what computer architecture is in real

texts:
I am quite sure that this is a question which will be marked as "primarily opinion-based" but I would still like to ask it here only as you do not get so many intellectual, experienced and skilled people at same place.
I have acquired a keen interest in the field of Computer Architecture (CA) and when I say keen I mean I would like to pursue it no matter what (even though I am not from computer background).I read a few books on this and almost every one of them said that it is a study of Hardware/Software Interface.

Now my first question is "when we talk about this interface is it something like we can study both hardware and software in this field and their interdependencies"?

My primary interest is towards the hardware part of CA. I love playing with muxes, decoders and all. We are still using the old x86 architecture (primarily!) in the modern world.

So second question " Are the researchers in this field not able to come up with anything new in terms of the architecture"?

All the simulations which researchers have to carry out today are based on software which by their own admission gives inaccurate results but since we do not have other alternatives we have to stick with it.

Third question "Where are we in terms of adaptive/reconfigurable architectures which researchers can modify according to their own design to get the results instead of playing around with software scripts and altering them"?

My concerns or a sense of jealousy lies in the fact that in CA software and hardware both plays an equal role. So why can't we limit the software research to compiler optimizations etc. and try and revitalised the research in terms of Hardware/FPGA based simulations.Software people have thousands of things to do but for the hardware guys the opportunities are limited. So why can't we try and be competitive enough to go for this sort of research. I went through the profile of professors in many of the top universities, was not able to find many who may be working on something like this.

P.S: I am not suggesting that software in hardware are bad or something. I am informed enough to realise the fact that software makes our task easier but is it the only way of doing things?

I am writing this after feeling disappointed so have not cared much about the flow. Everyone is welcomed to make suggestion whether it be in Hardware part or the software one.


texts: No germanium diode available for small crystal radio -- can active components handle the task?

texts:
I know that germanium diodes are trivial to find online, but as this is for a demonstration  I'd rather not spend $6-7+ on shipping for a single 5 cent part for a project that's academic in exercise anyway.  RadioShack has proven stereotypically useless in stocking germaniums.

I do have available to me jellybean components like the 741 and 324.  I also have several varieties of N & P-channel FETs as well as BJTs.  Is there some small and straightforward circuit I can use to emulate the low-voltage drop behavior of a germanium diode in a low (microwatts?) power application?


texts: Battery Balancing Board Equilibrium Current?

texts:
I just bought some balancing boards for a Bluetooth speaker project and realized after the fact there are two different equilibrium current options. I bought both the 2S and 3S versions as I haven't settled on how much voltage I want to supply to the speaker amp yet.

Needless to say I bought the 300mA version and my pack is only around 3000mA. Two questions, first is "what is equilibrium current"? Second, can I use this board with my project or do I need to get the 100mA version?

  Equilibrium current: 100mA, suitable for 2000-4000mAh battery pack

  Equilibrium current: 300mA, suitable for 8000-12000mAh battery pack

2S 3S 4S Li-ion Lithium Battery 2 3 4 Cell Charger Balance Circuit Board 100mA 300mA 4.2v Battery BMS Charging Balanced balncing

Thank you,
Martin


texts: Connecting 2 external PCBs with a 1m cable

texts:
I would like to connect 2 PCBs. On each PCB there is a MCU and each MCU is able to send and receive commands from the other one.
Also, PCB1 should supply power to PCB2.

The 2 PCBs are separated by ~100cm and I'm wondering what kind of hardware connection/protocol I should use, knowing that I would like to limit the number of wires between the 2 PCBs.

My first guess was to use UART / RS232, so it can be full duplex, and probably fast enough:

1 TX
1 RX
1 Vcc
1 GND

I tested it, and it works (115200 baud rate), there's just a small ~20ms latency getting a reply when sending a request from PCB1 to PCB2. I limited the baudrate to 115200 because I don't want the connection to radiate.

So I was told I could use 2 additional wires and communicate using SPI (which sounded a bit unusual to me when connecting to external PCBs together), so I'm wondering if it's a good idea, what would be the drawbacks?


texts: One MOSFET appears to get hotter than the other

texts:
I am trying to figure out some sources of error in this circuit.
Firstly, the lower FET (in the schematic) seems to dissipate more power and heat up faster than the top FET.

The shcematic above shows my layout, though i cant simulate in LTspice due to numerous issues.
One being the issue of getting my gate drive opto modeled, the other is a minimum timebase error.

If anyone has any clue as to what is causing the lower FET to heat up more than the upper one, i would be grateful to hear it.

Also, i am a little confused with the waveform across my halogen bulb(the load in the diagram, R = 0.5 Ohms when cool).
The picture below shows what i am observing:

This is with my PWM duty around 50-70%.
The load waveform can been seen swinging around 32V peak.
I expected to see a straight light form across the x-asis that is representing the time spent not conducting.
However it seems to be an inverted sinusoid of a much lower magnitude.
Any explanation of the waveform is certainly helpful to my inquisitive nature.

However, I would like to try figure out why my FETS are heating unevenly.

Any assistance is greatly appreciated.
Thanks!

EDIT to explain operation: This circuit is not able to be simulated, i created the symbol for the gate drive opto so i could show the schematic.
I will explain the operation:
A 25V RMS AC source is used to power a Halogen Bulb. Two MOSFETS are connected with their sources and gates connected together - This allows the same gate drive as VGS for both is always the same.

C2 maintains a 35V DC level, with a diode (D1) to stop it discharging to to the supply when its potential drops below +35V.

The schottky, zener and 680Ohm resistor allow me to derrive 12V dc to Supply my gate drive optocoupler.The capacitor C3 is charged to the 12V zener voltage and supplies the gate drive optocoupler with the current it needs in a rapid fashion.

The gate drive opto coupler is powered by this 12V capacitor, Its input is a PWM signal and its output is a push pull configuration for fast gate switching.
The 0.1Uf bypass capacitor (c1) is placed per the datasheet of the opto.
Two resistors on the gate, a low value in series and a high value resistor to the source.

When the PWM duty is raised, current flows from +ve terminal of the supply and through the upper FET (M3) which is open, the body diode of the lower FET (M4)is biased so as to allow current to continue to flow back to the supply.
The same happens when the supply polarity inverses, but this time M4 conducts fully open and M3 conducts via the body diode.


texts: Control block diagram with sampling output

texts:
I'm learning control theory and in my book it shows an example of this block diagram, the output

I'm quite confused  because the last step I got is

 , I can't get the same answer after transfer this answer to Z domain.

Please help me


texts: Should I get rid of my bias towards active high?

texts:
I realise that in all my circuits I consider active-high the "natural" default and active-low a goofy situation that needs to be inverted. I pull down all data and control lines (resets, output enable, input enable, inputs for an ALU or adder...), put inverters all over the place, and generally experience a lot of annoyance over every active-low pin.

Can you enlighten my what the advantages of an active-low architecture might be, or why I shouldn't care? It seems that wildly mixing avtive-high and active-low, based on the ICs demands, can be a nightmare to interpret, document and debug.


texts:
The above graph is pulled from the book "Automatic Control Systems" by Kuo.

The subject loop transfer function is $$L(s)=\frac{K}{s(1+T_1s)}$$
or $$L(j\omega)=\frac{-jK(1-jT_1\omega)}{\omega(1+T_1^2\omega^2)}$$
or $$L(j\omega)=\frac{K(-j-T_1\omega)}{\omega(1+T_1^2\omega^2)}$$

Hence the phase equation should be $$tan(\theta)=\frac{1}{T_1\omega}$$

Now at frequency infinity, which corresponds to origin in the above plot, the value of the phase function is $$tan(\theta)= \lim_{\omega \to \infty} \frac{1}{T_1\omega}=0$$ Also $$tan(\theta)= \lim_{\omega \to 0} \frac{1}{T_1\omega}=\infty$$ At infinite frequency the phase angle can assume value of either zero degree or  180 degree. In this plot it is taken as 180 degree, I can't understand why, when zero degree is also a perfect candidate.

Also at zero frequency, the phase angle should be 90 degree but here it is taken as -90 degree. I can't understand this phase thing.


texts: Outcome when logic output of IC shorts to VCC

texts:
I wish to know how to determine what happens when the logic output of an IC becomes shorted to VCC (preferably without actually having to short it). I realize that there are a plethora of ICs out there, all with different properties. I have chosen to use the 74HC74PW so that I have an example datasheet to talk about. I also wonder about AND gates, shift registers, etc.

Consider the example circuit below:

simulate this circuit – Schematic created using CircuitLab

SW1 is there to simulate a pin-short or other similar failure.

Hypothetically speaking,

If SW1 closes while Q is HIGH, then I'll assume no issue because VCC and Q are at equal potentials.
If SW1 closes while Q is LOW, then what process should I go through
to determine the outcome?

Brainstormed ideas (while Q is LOW):

Q is low impedance, and V1 essentially shorts to GND. V1 and or the IC will be damaged.
Q is high impedance, the IC is essentially unaffected, and the micro simply sees the wrong value (HIGH).
Q is "medium/high" impedance. V1 is okay because it can supply ample current, but the IC is either damaged or effected in some negative way.
Something else?

The following table is from the flip flop's datasheet:

Am I able to determine the failure outcome from that table?

I have come across many ICs that don't disclose explicit output current or output clamping current though, so I'm wondering if there is a more general rule I could assume true when I the datasheet isn't helpful. (Perhaps I should assume all logic outputs are low impedance?)

What specifically should I be looking for in an IC's datasheet, how should I analyze it, and what other rules can I use when the datasheet doesn't have said info?

I imagine that relying on simulation software is risky for these kinds of conditions. I also don't want to rely on actually shorting the IC myself, because even if there appears to be no issue, it doesn't mean that there isn't one (especially over long periods of time).


texts: Problem understanding impedance measurement device accuracy format

texts:
I am reading the datasheet of an impedance measurement device. Its accuracy is listed as '±0.4% rdg. ±8 dgt.'. What does 'rdg.' and 'dgt.' mean? And how should I interpret the accuracy?
The device is HIOKI BT4560. And I'll attach an image and here's the link to the document


texts:
I was reading the Tivaware datasheet on GPIO:
http://www.ti.com/lit/ug/spmu298a/spmu298a.pdf

When I came across this(page 257):

"where GPIO_DIR_MODE_IN specifies that the pin is programmed as a software controlled
input, GPIO_DIR_MODE_OUT specifies that the pin is programmed as a software controlled
output, and GPIO_DIR_MODE_HW specifies that the pin is placed under hardware control."

What is hardware vs software control in emb. prog?


texts:
simulate this circuit – Schematic created using CircuitLab

I checking the output of the circuit's current by attaching multimeter(ON 10 A) in series with a load of 3 Ohms resistor. But I am getting a 0.22mA current output.

Here's the diagram (LM338K circuit) :

This is the circuit I am trying to build:

http://www.ti.com/lit/ds/symlink/lm338.pdf on page no.12.

I connected my multimeter's red wire to capacitors (almost red color in the picture) and black to 3 Ohms resistor.

Please tell me what I am doing wrong. According to schmetic, I should already get 5V output. But I am not getting that too.

PS: Every 1.5 + 1.5 Ohms resistor I add as a load after taking out from circuit it doesn't show any resistance on multimeter.

Hi, I have not got a solution for this please help me regarding this.

If I use LM2576 12-V version to get 5.1V with 2.2A will this be fine?

Photo :

I am getting 15.68 V without Load resistor and with load resistor same voltage and this burns resistors. Please help.


texts:
As far as i know rs485 specifies a bus common mode
voltage of: -7V to +12V

the terminating resistor is 120ohm , using VxV/R , yields high power rating to the resistor , certainly more than 1w . (12x12/120 =1.2w)

However looking at many products and evaluation boards , i see that they use 0805 resistors which are about 0.25w only. They might be pulse withstanding type though.

What am i missing here ? the only explanation i could come up with is that the continuous power rating of this resistor is much lower (so my calculation is wrong), since there is some break between transmitted bytes.

But in this case what happens if transmission is continuous?


texts:
I am attempting to build a WiFi controlled power outlet. Essentially all it's supposed to be is an ESP-12E that controls a relay. When I had breadboarded the circuit it worked fine, however after getting it manufactured on a PCB a problem occurred and I do not know how to fix it. Here are schematics and images.

The problem I am having is that the current is barely flowing. I get a read of about 0.02 mAH flowing through the circuit. I can see that the LED turns on however it is extremely dim and barely noticable. If put my finger  across some of the connections on the bottom side of the board the LED goes bright and the ESP-12E LED blinks (meaning that it turned on), but this only happens if I do so in the "right" place. I figured this was a problem that had to do with poor connections but I looked over the entire circuit and found nothing of the sort. I would also like to point out that the schematic is slightly  outdated, and I am actually  using a  46µF capacitor instead of a  0.1µF capacitor.


texts: 3 phase motor calculate proper phase voltages

texts:
I'm driving a brushless motor in "star" configuration using 3 sinusoidal waveforms. I'm getting pretty good results mostly by determining correct wiring and phase by trial and error, but I would like to do even better by understanding what is actually going on in the motor and determining the correct wiring and phase of each signal by applying what I learn.

As far as I understand, the maximum efficiency is achieved when back-emf waveform is precisely in phase with supplied waveform. So I want to ensure this is so by measuring the back emf and aligning my inverter sine waves such that they are precisely in phase with all three back-emf signals.

So I have measured the back-emf using scope across two of the windings for each hall sensor signal. I also know that hall sensor signal tells me when the back-emf waveform crosses zero point, so by measuring back emf and looking at hall sensor outputs I was able to pair each hall sensor line with the correct pair of coil wires to make sure that the hall sensor signal changes state precisely when the back-emf crosses zero point.

For example, in my case it looks like this:

Hall_1: +red -black
Hall_2: +yellow -red
Hall_3: +black -yellow

The above is how I connected the probe to the motor wires while spinning the motor to determine two wires and their polarity that corresponds to the hall signal if hall signal were to output a square wave that switches state at each zero crossing of the sine wave.

So the above picture shows signal of hall3 (square) and the corresponding back emf waveform measured with probe ground connected to yellow wire and probe itself connected to black wire. Obviously if I measure it across any other two wires, it would be the same waveform but it would be out of phase with the hall signal.

Now I would like to determine the input waveforms to all three phases such that the signal across these same two wires corresponds to the back-emf waveform above.

The main issue that I can not quite understand is the fact that midpoint between each two windings above also is fed a sine wave through the third winding. How can I calculate the phase of all three input waveforms then so that the resulting voltage across black and yellow wires corresponds to the waveform above?

This is getting really confusing so how should I be thinking about this to understand it better?


texts:
I have two different types of the NRF24L01+ modules and I'm having difficulties with one of the models. See pictures below for how I have them wired. I'm able to send/receive messages using Model B but I'm not able to send/receive any packets using Model A. When I look online they've suggested using a 4.7μf capacitor between power and ground but this did not help. At first I thought it was a power issue but I also tried wiring them to a 3.3v power supply but this did nothing. When I plug in the module i'm only getting question marks or empty lines via serial monitor. I've attached a copy of my code as well. I don't believe its an issue with wiring because it does work with Model B but not Model A. If anyone has worked with this specific model before and has a working example it would be greatly appreciated.

Model A)

Model B)

Wiring Diagram

Sender

#include <SPI.h>
#include "RF24.h"

RF24 myRadio (7, 8);
byte addresses[][6] = {"0"};

struct package
{
  int id=1;
  float temperature = 18.3;
  char  text[100] = "Text to be transmitted";
};

typedef struct package Package;
Package data;

void setup()
{
  Serial.begin(115200);
  delay(1000);
  myRadio.begin();
  myRadio.setChannel(115);
  myRadio.setPALevel(RF24_PA_MAX);
  myRadio.setDataRate( RF24_250KBPS ) ;
  myRadio.openWritingPipe( addresses[0]);
  delay(1000);
}

void loop()
{
  myRadio.write(&data, sizeof(data));

  Serial.print("\nPackage:");
  Serial.print(data.id);
  Serial.print("\n");
  Serial.println(data.temperature);
  Serial.println(data.text);
  data.id = data.id + 1;
  data.temperature = data.temperature+0.1;
  delay(1000);

}

Receiver

#include <SPI.h>
#include "RF24.h"

RF24 myRadio (7, 8);
struct package
{
  int id=0;
  float temperature = 0.0;
  char  text[100] ="empty";
};

byte addresses[][6] = {"0"};

typedef struct package Package;
Package data;

void setup()
{
  Serial.begin(115200);
  delay(1000);
  pinMode(3, OUTPUT);

  myRadio.begin();
  myRadio.setChannel(115);
  myRadio.setPALevel(RF24_PA_MAX);
  myRadio.setDataRate( RF24_250KBPS ) ;
  myRadio.openReadingPipe(1, addresses[0]);
  myRadio.startListening();

}

void loop()
{

  if ( myRadio.available())
  {
    Serial.print("working");
    while (myRadio.available())
    {
      myRadio.read( &data, sizeof(data) );
    }
    Serial.print("\nPackage:");
    Serial.print(data.id);
    Serial.print("\n");
    Serial.println(data.temperature);
    Serial.println(data.text);
    makeBlink();
  }

}

void makeBlink(){
  digitalWrite(3, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(3, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);
}


texts:
We are building a rocket flight computer with Arduino MEGA which will be powered by a 9V Duracell battery. In other forums we asked what to watch out for while building this computer and one of the answers were:

  Watch out for power failures, batteries might not work properly under high g's
  .
  They suggested that we use Capacitors to prevent any power failures.

How should we connect this capacitor to the circuit?
What kind of a capacitor should we use?

The 9V battery will be connected to Arduino MEGA via the VIN and GND pins.


texts: uncertainty estimation for a DMM voltage measurement

texts: My DMM has a accuracy of 0.0030% of reading + 0.0030% of range, when the voltage range is set to 100mV. If a measurement with this DMM gives 0.1mV, then is the true input voltage between 0.1mV - 3.003uV and 0.1mV + 3.003uV? Or is there a different factor than the uncertainty that I have to account for?


texts: Vector table relocation in bootloader application

texts:
I've written a bootloader application for NXP Kinetis microcontroller.
Following are the things I did to do the same:
1. Created a bootloader application in CFlash addresses 0x0000 to 0x8000
2. Created my main application code from addresses 0x8000 to 0x1FFFF

This code is working fine.
Now my doubt is, I have ISRs placed in both bootloader as well as main application code and didn't use any ISR vector relocation.
Is it necessary to relocate the vector tables in main application?

PS: I may not be facing the issue just because the ISRs in both the apps are same.


texts: IS heat the only thing keeping CPUs from a faster clock rate?

texts: Is heat the only thing that keeps CPUs from having a faster clock cycle or are there other limiting physical factors which keeps CPUs under 3~5GHz?


texts:
Mystery Encoder

I think this is some sort of rotary encoder, but it doesn't seem to act like one (no quadrature output from the pins).

Tests I've run: 5V input in each pin, monitoring the other three on an O-scope. I rotated through until I ran out of pins to put the power into...

Images of the whole assembly are below.

Purpose of This Question

Thank you to user28689 for pointing out that I had not stated the purpose of my question. Here it is:

I am seeking to drive the motor assembly with a micro controller (Arduino to start with). At this point I am seeking to use only the necessary parts from the assembly, in this case I think the sensor and the outrunner motor are the only things that need to be kept which is why I am trying to find out what kind of sensor it is and how to read the data from it. I have four of these motor assemblies that are relatively unmolested and being able to use them in projects would be useful.

Assembly Pictures

Here's a picture of the part in assembly.

Here it is by itself.

A closeup of the sensor 'head' for added clarity.

Assembly Details:
As per request: the assembly is identified by PN: RH7-1495. It was pulled from an HP Color Laserjet 4650. The board logic runs on 5VDC while the outrunner DC motor runs on 24VDC. There are 7 pin outs on the end of the board.

This afternoon I probed the whole assembly and tentatively identified all 7 pins. I say tentatively because I haven't found anyone else who is looking for information on the assembly (RH7-1495) or the specific part. I can post images of each test from my multimeter if there is interest.

As an added bonus I dug out the position sensors that go with these motor assemblies. The top one has its cover, the bottom one I stripped to see what was inside.

Printer Details
So that no one has to go haring around the internet for more information on this printer I've included as much as I have here.

This link says that it is part of the fuser drive assembly (LaserJets have a heater that fuses the ink to the paper, click for more on LaserJet operations theory).

The service manual, on page 219, calls these assemblies (RH7-1495) 'drum drives'. The printer contains five of them. One I've torn down to get a good look at components. The others I've left intact for testing and (hopefully) later use.

The service manual also mentions that the homing sensors are not part of the overall assembly (page 222).

Below is the DC control board (I think) for all of the drum drives (RH7-1495 assembly).

On the rightmost side of the image is the power header, a 5 prong receptacle that is labeled for 5V, 3.3V, and 24V.

[edit]
Here is the inside of the motor housing. The purple ring is non-magnetic, the metal housing is magnetic and the inner ring is the motor's magnet.

[/edit]


texts: Control multiple LEDs with switches on the same circuit

texts:
I've searched and searched for this but I can't find an answer and when I find something that looks like an answer I don't understand it.  I'm very, very new to this, I can basically pick the correct resistor for an LED and wire it all up.  I use electronics in model making.  I'm aiming to control 3 arduinos with switches on the same circuit. I'm fine with the arduino aspect for simplicity I'll just pretend I want to control LEDs.

Currently I have two leds connected to two SPDT toggle switches and I think they are wired correctly however I can't individually control the leds.  I have to have both switches set to on for both LEDs to come on, I can't have one off and one on.  I don't really understand the diagrams I see on this site so I'll draw a very crude diagram of what I have wired up.


texts:
I'm not an electrical engineer so forgive any obvious ignorance that may be unwittingly baked into the question.

Background:

My kids have these Disney Infinity Light FX figures that, now that Infinity is being shut down, I think I'll want to end up displaying in their room.

Since there are 7 of these things, but only two can live on the pad at any given time, I need to find a different solution to allow for "always on" light from all of them - (ie - all 7 lined up on a bookshelf)

The Infinity base uses NFC as far as I can tell.

I've been noodling on this and done some reading on the Qi standard and devices but it looks like most of the new Qi devices are v1.2 which contain foreign object detection - ie - it won't send power to non-phone devices.

Question:

So - I thought, what if I bypass the Qi controller all together and just directly shoot power through the coil - that should work...right?

Can I wire a wireless induction coil to a USB cable and expect it to:

a) receive power

b) not burn through the table

c) deliver inductive power to another NFC type device?

I've taken a quick first stab at this via wire-nuts. A stripped USB cable to a coil and plugging the USB into a small iPhone transformer plugged into the wall. It didn't work like I expected but nothing exploded so that is good :|

Is my expectation here even correct?

Couldn't I just tear apart the figures and hard-wire the LED to a battery? - Sure - but that isn't as fun and I don't want to tear up the figures


texts: Reading BJT Transistor Datasheets. Two different values for collector emitter voltage?

texts:
I've been trying to read up on BJT transistors to figure out how I can use one for a simple switching application. In order to calculate the resistances I need, I need to figure out VCE, the collector emitter saturation voltage and VBE, the base emitter voltages. But I'm noticing some of these data sheets seem to have conflicting data the way I am interpreting them.

For example, in this P2N2222A NPN transistor, I can look in the "ON CHARACTERISTICS" table and see that VCE has a max of .3V for IB=15mA and IC=150mA.

However, in Figure 4 there is a graph of IB vs VCE. If I look at the plot for IC=150mA, and then go to IB=15mA, I see VCE=.1V and not .3V.

Is the datasheet just telling me that at a maximum, the graph will be shifted up so that the value is .3V at IB=15mA? And if so should I expect the general shape of the graph to still hold?


texts: isoPower Input-to-output dipole emissions

texts:
In ADI's Application Note: Recommendations for Control of Radiated Emissions with isopower Devices. Section "Input-to-output dipole emissions", it says:

  Input-to-output dipole radiation is generated by driving a current
  source across a gap between ground planes. This is the predominant
  mechanism for radiation for isoPower applications. Isolated power
  supplies, by their very nature, drive energy across gaps in ground
  planes. The inability of high frequency image charges associated with
  the power signal to cross the boundary causes differential signals
  across the gap driving the dipole.

In its isoPower chips, such as ADuM5000, the main "barrier" is transformers. So ideally, there will no current flow from primary side to secondary. So this don't agree with the first words: "Input-to-output dipole radiation is generated by driving a current source across a gap between ground planes." . But the following words are interesting,  "Isolated power supplies, by their very nature, drive energy across gaps in ground planes". I don't understand it well, does it mean the energy transfer using transformer will generate "dipole emission" if there is no current flowing across the gap?


texts:
Can someone who understands the bad subject in english can fix it
schematic where exactly is the error
ST-Link V2 debug programs error


texts:
I created a simple Verilog module that displays random numbers. This module has a counter that counts up at every clock edge and at the press of a button, whatever the number is in the counter at that time is displayed. Here is my code:

module counter (input wire in, input wire clock, input wire reset, output reg [3:0] number)
reg [3:0] cur_state;
reg [3:0] next_state;

always @ (posedge clock) begin
    if (reset) cur_state <= 4'b0;
    else cur_state <= next_state;
end

// next state function
always @ (*) begin
    next_state = cur_state + 4'b1;
end

// output
always @ (*) begin
    if (in) number = cur_state;
end

number[3:0] is sent to a display module to display the corresponding number. (Inputs are debounced properly.)

Everything works fine on the FPGA, but the program notifies me that I've used a latch in output. Is there any way to prevent this and implement the same behavior using a flip-flop?

Thank you.


texts: PIC16F877A microcontroller security project

texts:
Recently I was working on a security project using PIC16F877A. The program works fine on Proteus, but when I build my circuit on a breadboard, it gives random sentences. It should wait for the input through the keypad, but instead it enters random inputs by itself and displays wrong password.

Here is the code:

char keypadPort at PORTb;
// Lcd pinout settings
sbit LCD_RS at Rd4_bit;
sbit LCD_EN at Rd5_bit;
sbit LCD_D7 at Rd3_bit;
sbit LCD_D6 at Rd2_bit;
sbit LCD_D5 at Rd1_bit;
sbit LCD_D4 at Rd0_bit;

// Pin direction
sbit LCD_RS_Direction at TRISd4_bit;
sbit LCD_EN_Direction at TRISd5_bit;
sbit LCD_D7_Direction at TRISd3_bit;
sbit LCD_D6_Direction at TRISd2_bit;
sbit LCD_D5_Direction at TRISd1_bit;
sbit LCD_D4_Direction at TRISd0_bit;
int kp;
int password[5];
int DefaultPassword[5]={1,2,3,4,5};
int i;
void main() {
     trisc.f0=0;
     portc.f0=0;
    Keypad_Init();
    lcd_init();
    lcd_cmd(_lcd_cursor_off);
    lcd_out(1,1,"Welcome");
    delay_ms(2000);
    lcd_cmd(_lcd_clear);
    Begin:

     lcd_out(1,1,"Enter Password");
     for(i = 0 ; i<= 4 ; i++)
     {
     kp = 0;
     do
      kp = Keypad_Key_Click();
      while (!kp);

     switch(kp)
     {

      case  1: kp = 1; break;
      case  2: kp = 2; break;
      case  3: kp = 3; break;
      case  4: kp = 'A'; break;
      case  5: kp = 4; break;
      case  6: kp = 5; break;
      case  7: kp = 6; break;
      case  8: kp = 'B'; break;
      case  9: kp = 7; break;
      case 10: kp = 8; break;
      case 11: kp = 9; break;
      case 12: kp = 'C'; break;
      case 13: kp = '*'; break;
      case 14: kp = 0; break;
      case 15: kp = '#'; break;
      case 16: kp = 'D'; break;

     }
      password[i]=kp;
      lcd_out(2,i+1,"*");
     }
     if( strcmp(password,DefaultPassword) ==0)
     {
     lcd_cmd(_lcd_clear);
     lcd_out(1,1,"Welcome");
     portc.f0=1;
     }
     else
     {
     lcd_cmd(_lcd_clear);
     lcd_out(1,1,"Wrong Password");
     delay_ms(2000);
     goto Begin;
     }

    }

and this is the output:

Added: This is the schematic:


texts:
There is a 332 1kv ceramic disk capacitor in a battery charger that I use on my desk. The capacitor emits a very high frequency and headache-inducing "singing" noise. I understand that this is normal operation for a ceramic capacitor if the circuit is not designed properly. How can I rid of this noise? Is there an equivalent capacitor that I can solder in that will not vibrate at an audible frequency?

I have read it is common to put 2 capacitors in parallel to reduce noise, if this is an option should i be replacing it with 2 equivalent capacitors or with 2 capacitors of half the rated capacitance value?


texts:
I have a huge number of primitives in my PCB layout. If I try to much as select half of them, it will take Altium several minutes to respond. It also takes Altium several minutes to respond to trying to cut and past them.

My CPU is only at 13% usage when Altium is working on one of these tasks, and there's still lots of RAM available.

Is anybody able to make suggestions on how I can make this process faster (other than by having fewer primitives in my layout)?

Suggestions on what may be bottle-necking Altium's performance may be helpful for solving this.


texts: Noobie is trying to match a solar power bank and a wireless camera

texts:
my dear friends all around the world!

I'm very interesting about this cool solar power thing, and I really want to start connecting all of my stuff to panels and so.

But for my first and ,hopefully, successful try, I will simply use a simple (apparently not so simple for me, otherwise I wouldn't be here..) solar power bank. No need for charger regulators and other exciting things that might burn down my roof top..

The solar power bank is 20Ah (but I don't know how much watt per hour. The nice seller hasn't replied me yet) -

http://goo.gl/0svXM6

The camera is 12v/2A and 6-7W, and have to work 24*7 -

http://goo.gl/MKM0yR

That is the question.

I really appreciate your kindly help. A lot.

Thanks,

Roni

Note:
I really did tried to understand it by myself, but I still have doubts (and those items aren't cheap at all when buying bulks of them as need to). I'm a programmer, so I did have a few lessons in electronics. 10 years ago..

Few of the posts here that help me the most -

Solar panel & battery math verification

Solar panel and 120mm Computer fan

Why isn't the solar panel charging the battery?

Battery recharging via solar panel


texts: measure temperature in a solenoid without sensot

texts:
is possible to meassure the temperature change in solenoid , without using a sensor?

I know the resistance will change with temperature, but are other parameters affected also ? will my current waveform change ??


texts:
I would like to control the output of two LEDs with a single pushbutton. When the button is open, D2 should be off and D3 should be on; when the button is closed, D2 should be on and D3 should be off. I would like to achieve this effect using only BJTs.

The following circuit worked as intended in an EveryCircuit simulation:

simulate this circuit – Schematic created using CircuitLab

However, I'm almost certain that this is not optimal; for example, I have a feeling that a solution can be achieved without requiring D1.

Can anyone point me to a better solution?


texts:
I am trying to come up with simplest solution to reduce 0~2.5V DAC output to 0.09V swing and shift it into -19.34~-19.25V range for controlling current limit of OPA548 op-amp within 0~100mA. There is an example circuit in OPA548 datasheet but it uses single power source and full current range, so all they had to do is buffer DAC output and keep it above ground.

After researching dozens of examples on the web (like these: voltage shift, another one) I ended up with two options:

basic inverting attenuator with bias
inverting summing amplifier

Technically, I think the latter one is also attenuator, since individual input gains are 0.8 and 0.036.

What bothers me is that about 80% posts on the web claim unequivocally that configurations with gain < 1 are unstable. The rest are equally adamant that this is wrong (see unstable op-amps). It should be possible to "shrink" DAC output with resistor divider enough to use gain > 1, but I always prefer simplest possible solutions.

My question(s): Will these work and if yes than which one is better? Are there other options available?

UPDATE:

Posted alternative idea that addresses the concerns raised in answers and comments.


texts: How to know if a verilog code is sequential or combinational?

texts: How to know if this piece of code is for a sequential or a combinational circuit?


texts: Electricity generation with diamagnetism

texts:
Will a strong diamagnetic material like bismuth allow for electricity generation if the copper coils are on the other side of the bismuth plate from the magnet? Imagine the following three layer system:
Magnet

Bismuth or Equivalent Strong Diamagnetic Material

Stator

Is it at all possible to transfer the flux through bismuth to the stator, assuming a thickness of an inch for instance?


texts: Power adapter giving a specified current

texts:
I often see power adapters indicating 5V 900mA (or) 5V 1000mA or sometimes 5V 3.4 A. Obviously they are converting current coming from 220V/110V source to 5V DC using some step down converter. But how do they know the amount of current that can be given by them ? i.e., 0.9 A or 1 A or 3.4 A etc.. What I mean is, based on Ohms law ( V=IR) the current is dependent on V and R where V is step down voltage given by adapter ( lets say 5 V in this case). However R is dependent on the circuit that is going to be connected to the battery or charger. The circuit may have higher or lower resistance and accordingly the current would vary. So then what is the meaning of the current notation mentioned on the chargers ? Is it the max current ?
If that is the maximum current in Amps that charger/battery can deliver does it mean that the resistance of the charger circuit is lets say 5V / 1 A = 5 Ohms ?

I know this is a very basic question. Appreciate your patience.


texts: Why does high voltage imply a high "pushing force" on electrons?

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Another word for potential difference, is apparently, "voltage drop", although I've heard potential difference be interchangeable with just voltage, as well, a bit confusingly. However, if I understand it properly, the battery has an electric field. Things closest to it are being pushed with the greatest force.
However, my understanding of potential difference needs a bit of refining.

Then the difference in voltage between any two points, connections or junctions (called nodes) in a circuit is known as the Potential Difference, ( p.d. ) commonly called the Voltage Drop.
The Potential difference between two points is measured in Volts with the circuit symbol V, or lowercase “v“, although Energy, E lowercase “e” is sometimes used to indicate a generated emf (electromotive force). Then the greater the voltage, the greater is the pressure (or pushing force) and the greater is the capacity to do work.

The greater the voltage drop, the greater the capacity to do work? Does this have some similarity to closely spaced contour lines? If there's a big voltage drop in a small distance, this implies we are in close proximity to the battery? Because the electrostatic force obeys the inverse square law, so the electrostatic force will be exponential with distance, and thus a high voltage drop implies high force difference in short distance, implying a close spatial proximity to the battery? Is my understanding correct? If not, could someone help refine it?


texts: I got this Chinese single cell power bank that I modded with a higher capacity 18650 cell which works fine. I want to add an another cell in parallel with the other one. Will it still charge? will the two batteries reach the cut-off voltage of the charging module? The IC on the board is MP3401 a pretty common in most of the Chinese power banks.


texts: How should I go about protecting a supercapacitor from reverse polarity?

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I have several supercapacitors in series, and they're quite old and probably drifted from their original spec by quite a bit. Completely draining them in series will draw at least one of them below 0v. How should I protect against this?

I thought to use a schottky diode, but the best one of those would still allow the caps to be drawn to -0.3v. Also, many ideal diode circuits need some power, but the goal here is to protect fully discharged caps.

The ideal behavior I'm looking for is something that acts like an open circuit above 0v, and looks like a dead short below (or just shy of) 0v.


texts: How do you simplify this resistor circuit?

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Is R3 + R4 in series, R1 + R2 in series and R12 + R34 in parallel, giving a total resistance of 8.5ohm correct?
EDIT:
Redrew with all the resistors vertically

So R1 and R2 are parallel, R3 and R4 are parallel R12 and R34 are in series, giving a total resistance of 7.96ohm?


texts: Sourcing low torque/small stepper motors

texts: I am looking for some small and cheap stepper motors with <10oz-in torque. Most of the steppers I can find from my regular sources/ebay are 60-1000oz-in which is far too much for my purposes (and will almost certainly push the cost up). Does anyone know of a good source for these types of motors ? Unfortunately I would like 6 (and potentially more) of them, so scrounging from old floppy drives is not really an option.


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How is the nominal voltage of a battery determined?
A NiMH cell's usable voltage ranges between around 1.4-1.0V and the nominal voltage is quite in the middle of that at 1.2V.
Similarly, the nominal voltage of a LiPo is given most of the time between 3.7V and 3.9V, with the usable voltage being between 3.0V-3.5V and 4.2V-4.6V. So again, the nominal voltage looks to be in the middle of the usable voltage.
But for Alkaline cells the nominal voltage of 1.5V is at the very top end of the usable voltage of 1.6V to 1V.
So how is the nominal voltage determined, and is there a difference between primary and rechargable cells?
To clarify the question because there are a few answers that apparently misunderstood the question.
On some chemistries the nominal voltage is close to the maximum voltage of the cell (e.g Alkaline with 1.5V, where a fully-charged cell has 1.6V), while others have their nominal voltage at the average charge (e.g. NiMH at 1.2V or LiPo at ~3.8V).
Why are some nominal voltages close to fully-charged voltage, while others have are at 50% charge?
Is the difference that primary cells have their nominal voltage at 100% and rechargable cells have it at 50%?
I am NOT looking for answers to those questions:

How can I find out the nominal voltage of a battery?
Why have different chemistries different voltages?
What are primary/rechargable cells?


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i need to find a time between rising edge of input signal and generating new output state. I dont have a scope so i cant measure

Does someone have imagine how fast it is and how the edges looks like?


texts: Finding R for max power deliverable to R and determining the max power

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This relates to max power transfer. Here's my circuit:

simulate this circuit – Schematic created using CircuitLab

My goal is to try and find the value of R for the maximum power that can be delivered to it. Then I'll calculate that power as well. I have tried drawing the circuit with an a port on the left of the R resistor and a b port on the right of the R resistor and then trying to calculate Rth by shorting the independent voltage sources, but each time I do that and apply KCL or KVL I get equations that equal zero or not enough equations to solve for all the unknowns.

That's just Rth, I do not even know where to get started for calculating Vth for this circuit. My best guess is that I will ignore the R or load resistor and then apply nodal analysis or some other techniques but I'm not sure which one to use.

I know these equations:
$$V_{oc}=V_{th}\;\;\;\;\;\;I_N=I_{sc}\;\;\;\;\;\;R_N=R_{th}={V_{oc}\over I_{sc}}\;\;\;\;\;\;R_L=R_{th}\;\;\;\;\;\;p_{max}={V_{th}^2 \over {4R_{th}}}\;\;\;\;\;\;When\;\;\;R_L \ne R_{th}\;\;\;p=i^2R_L=({V_{th}\over{R_{th}+R_L}})^2R_L$$ I know those equations but just do not know how to get them correctly.

Sorry I can't show work or explain it more, this is as far as I can get right now. Any help would be very appreciated. Thank you!

Right now I'm most familiar with superposition, Thevenin, Norton, Nodal, Mesh, and Ohm's law.

EDIT: in case anyone is still reading this, I'm still stuck and every time I try to solve for Voc or Isc I get a system of equations that can't be solved.


texts: Laptop charger voltage decreases gradually when plugged in, laptop won't charge

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Recently, I tried to charge a laptop I had not used in a long time, but it didn't work.

I took out a multimeter and measured the voltage coming out of the laptop charger, a Delta Electronics charger that is meant to output 19V at 3.42A, and noticed that the voltage was gradually decreasing from the moment I plug in the charger to the mains power supply. For instance, when I plug in the charger, the voltage starts off at 19.2 volts, but it goes down to 18V within a few seconds, 10V within 1 minute, and gradually approaches 0V over the next few minutes. This decline occurs even when I switch off and on the mains outlet switch, and the only way to get the charger to produce 19V again is to unplug it and wait for a few minutes - and the cycle repeats.

Is there something wrong with my charger? Greatly appreciate any info that could shed some light on what's going on.