texts: I want to solve this exercise in the figure below.The question is "Recognise as many known Sub-circuits as you can in LM386 circuit".I tried it and found only that the transistor down and in the left hand is a current mirror and active load.Also the output looks like Class A amplifier.Can anyone help me to find other sub-circuits.


texts:
I want to set an alternative editor in ModelSim. I tried How to configure my favorite editor in ModelSim? and after I set the altEditor I get "unknown command external_editor". Unfortunately my reputation is too low to comment on that question.

I also tried setting PrefSource(Editor) and specify the one I am using. This had no effect at all.

I am on Linux btw and want to use kate as an editor.


texts: FPGA maximum frequency : limiting factor

texts:
I would like to know which in general may limit the maximum clock frequency of a circuit implemented in FPGA.
In the specific case I am building some FIR filters using Quartus and simulating them on a FPGA of the Cyclone II family.

From my simulation it results that a II order FIR using a direct adders can be clocked at higher frequency than a II order FIR using transposed adders (420Mhz vs 387Mhz).
I did not expect this given that the critical path of the direct is bigger (2sum+1mult) than the one of the transposed (1s+1m).

Is this due to the fact that the direct has a more parallel architecture than the transposed and so the FPGA 'likes' this?
img1) direct
img2) transposed


texts: What is the easiest way to send data via bluetooth?

texts:
I want to send a serial data which comes as RS232 format from an instrument. Data will be sent by using bluetooth to a mobile phone. So I need to convert this RS232 data to wireless bluetooth in some way. Mobile phone will then receive this data via bluetooth and and send it to internet.

My question is which one is easier and reliable: RS232 to bluetooth converter or TTL to bluetooth converter?


texts:
I try to drive two small pcb coils. The coils have a resistance of around 14 Ohms (i dont know the L value). I have a PIC10F200 controlling the base of a BCV27. However i dont seem to get much more than 0.1V across the coils.
Did i make a mistake, or is there something fundamentally wrong with my approach?
Thanks!!


texts:
Let's say we have 2 grounded parallel plates and we place a charge Q between them.
I'm studying Green's reciprocity theorem and in using it the author states that the  charge induced on the plates is such that $$-Q=q_1+q_2$$
where q1 and q2 are the total charge on each plate. It is stated that this happens because the plates are grounded.
That isn't enough for me, I'm forgetting something important or I haven't understood how the distribution works. I'm thinking if it was one plate the charge on it would be -Q so, since we have two plates, each plate should have charge -Q. So why does the total charge induced have to cancel the point charge Q?


texts: Choosing resistor values for Op-amp and inverting/non-inverting configuration

texts:
A LM358AN op-amp is choosen to amplify a AC input signal by a gain of 2.0. The input signal ranges from -1V to +1V and from 0 mA to 16.7 mA. The amplified signal will be read by an analog pin of Arduino (10-bit ADC)

How should the input resistance values and feedback resistance values be selected? I understand if the resistances are too high, there will be input noise which I do not want. However power consumption should be as low as possible, since it will be running off batteries. So would it make sense to choose R_feedback = 2k and R_input = 1k for the inverting confifguration.

Between inverting and non-inverting, since only the RMS of the signal will be used, inverting the polarity does not matter. So would it be wiser to go with inverting, since it is better at rejecting common-mode noise?


texts: Can I connect the ground pin of multiple switches in serial and then to the arduino ground

texts:
I've got multiple switches (buttons/toggles etc) and have connected the ground pin of each in serial#  and then the last one to the arduino ground.
Seems to work - but sometimes get unreliable behavior when one of the switches is closed.
Can the above be done - or do i have to connect the ground pin of each switch to a common ground bus.
Thanks.


texts: Is there a better way of just using a voltage divider to split a single 5v rail into 2.5v and -2.5v? I'll be using USB for powering the circuit


texts: XMega bootloader - How to make use of the functions in assembly source file

texts:
Its been two days I'm trying to write a Bootloader for ATXMega32E5. The Atmel studio doesn't have boot.h header file supporting XMega.

As a result of searching and googling, I found two ASM header sp_driver.S and sp_driver.h. Even after the two readings and trial, I couldn't find how to use that asm functions in the embedded C code.

If someone came across this way, do help me in creating a bootloader. Or to create a makefile linking the source and header with the C file. That way I can call the functions and I will make my own bootloader


texts: Is it possible to make an LED turn on with an HC-SR04 without using an arduino? Only when an object is near it?

texts: I don't know anything about coding so I wish to achieve this effect without a help of an arduino. I'm trying to minimize as much power as possible and trying to achieve the HC-SR04 sensor to sense anything up to 10-14ft to trigger the LED to turn on.


texts: ADC noise measurements gives bimodal (double hump) distribution in output values

texts:
I have designed a current measurement circuit which measures voltage across a shunt resistor. The voltage is basically measured with an instrumentation amplifier and the ouput its connected to the inputs of an 18-bit analog-to-digital converter.

To get an idea of how much noise is present in the samples, I made the ADC convert a lot of samples (65536 samples to be precise) when no current flows through the resistor. I expected the distribution of the samples to be like a normal distribution. However, the result looked like this (figure 1):

The mean is 131085 (close to 131072 which is half of the full-scale range) so that is OK (the interface amplifiers have offset errors etc). But the standard deviation is 22.05 which is not very good. The worst thing is that the distribution have two humps (I found out that this is called a bimodal distribution). I am by no means an expert in statistics and would like to know from a more "electronic" point of view, what could cause this distribution? Inadequate filtering? Bias currents in the instrumentation amplifier inputs?

The circuit is part of a bigger circuit which also includes a voltage measurement interface. This interface uses the same ADC and the same good PCB-layout and both ADCs have appropriate buffering and filtering of the reference voltage. I did a similar experiment with this, very similar circuit, and the result is more what I expected (figure 2):

In this case, the mean is 131090 and the standard deviation is 2.52837. Much better.

The only real difference in the two circuits would be the instrumentation amplifier in the current measurement circuit which is not present in the voltage measurement circuit. The amplifier is a regular 3-opamp-based instrumentation amplifier set to a voltage gain of 10. Could this be the source of the "weird" distribution? The distribution seems quite symmetrical although it is bimodal. I fear that filtering will only reduce the deviation but will keep the distribution shape.

Is this normal with instrumentation amplifiers or could the problem be somewhere else?

Thanks in advance for any ideas on what could be wrong.

(BTW, I am not going to post any schematics since this is a more like a general question and I expect ideas to where to problem could be, not a complete solution. Thanks :-)


texts: Op-amp circuit to control gain of two analog channels with one single-section potentiometer

texts:
I'm working on designing my own headphone amplifier with extremely high fidelity. One thing I want to incorporate is a circuit to control the gains of the two channel's using one single-channel potentiometer, and I want to use op-amps and discrete components for high precision channel to channel matching. A circuit to do exactly this is described in this article, but the schematic picture has 404ed. I'm trying to recreate the schematic from the body of the article. The key is that the wiper of the potentiometer is grounded, so we have two resistors varying inversely. There are some concepts like positive feedback which are difficult for me to intuitively understand, so I was only able to get partway. I'd really appreciate some help in recreating this circuit.

Definitions, from a lot of rereading the article:

V1, V2: input voltages to the first stages. The signals which should be amplified by the same factor.
R: the total resistance of the potentiometer, as well as a resistance value which is used elsewhere for other resistors
Rg: another common resistor value
K: the position of the wiper, from 0 to 1

Here's what I have so far, and my rationale.

  the signal at A1's noninverting input is ... K x V1. This voltage is boosted by A1's noninverting gain of G = 1 + RG/R to produce overall gain as a function of K given by VOUT/VIN = KG.

A1 is in a non-inverting configuration with the gain network defined by passive resistors with values RG and R, and the voltage on the noninverting input is K*V1.

  Positive feedback from A1's output to P's CCW terminal results in constant current drive to the pot, given by I = V1/R. Therefore, the signal at A1's noninverting input is equal to I x K x R = (V1/R) x K x R = K x V1

One of the potentiometer's end terminals is on the non-inverting input of A1, and is receiving a constant current from a positive feedback network. This current is setting the voltage on the op-amp's input terminal. As to the network that is giving it that constant current, I have no idea.

  Surrounding A2 and P's CW terminal is a topology that produces a signal of V2(1 - K)(1 + R/RG) at A2's output

This sounds like the same topology as U1, since the other potentiometer resistor section would be changing inversely to K.

  After attenuation by A3's feedback network to V2(1 - K), this voltage appears at A3's inverting input. So the differential voltage seen by A3 is V2 - V2(1 - K) = V2 x K. When amplified by A3's gain of (1 + RG/R) = G, this voltage becomes V2 x K x G. A3's gain, accordingly, is equal to KG, just like A1's

This is some form of differential amplifier circuit, with the output of A2 going into the inverting input network and unmodified V2 signal going into the non-inverting input. I'm not sure how the mentioned "attenuation in the feedback network" or the final gain value were attained. Presumably we have a bit more freedom here.


texts: Electrically switching between horizontal and vertical light polarization

texts:
I would like to be able to electrically switch between horizontal and vertical light polarization. This polarization filter is supposed to be portable attachment running on a battery in front of a DSLR camera lens thus the filter should have the size of ~3x3cm minimum to cover the whole view. Light transmission through the filter should be the same in both polarization stages and as high as possible (i.e. ideally close to 50%). I would also prefer not to use any mechanical components, such as rotating the filter with a motor, to enable fast switching.

While I was looking for a solution I realized that LCD screens use two cross polarized filters and liquid crystal layer in between the filters to control what light passes through the display by twist the polarization 90 degrees. So I would basically need something like the LCD screen (without the need for controlling individual pixels) without the other polarizing layer and that's also fully transparent in both stages (twister & untwisted).

Another thing I was thinking is if I could possibly repurpose 3D shutter glasses, but not quite sure if this would work.


texts: Overvolting a DC motor while keeping power constant

texts:
So I have a 36 VDC motor rated 70 A at 2000 W (mechanical output power).
I would like to run the system at 48 V (same power) because I have a lot of accessories for 48 V systems (battery chargers, DC/DC converters, motor controllers). Is it possible to overvolt the motor by 12 V (30%) if the current is decreased by 30%?

I was taught in school that the voltage rating is related to winding insulation, and I think 36 V insulation is capable of carrying 48 V.

Is my assumption correct?


texts: Can SDA go low by changing SCL from high to low

texts:
Currently I am trying to use a new haven display (product number NHD-C0216CiZ-FN-FBW-3V) with an i2c to usb device. I am using there bit banger code from the documentation, link http://www.newhavendisplay.com/specs/NHD-C0216CiZ-FN-FBW-3V.pdf, but whenever I send a old bit into I2C_Out I get suck into the while loop, because SDA never goes low. And I see that I never get an ack from SDA. If anyone knows how to solve this issue it would be greatly appreciated.

while(SDA==1){
    SCL=0;
    SCL=1;
}

EDIT I thought that the time was two short between setting SCL low then high so I added in a 1 second delay but I am still getting suck into an infinite loop. Also I have already tried to use the given function that the i2c to usb device gives me, but those functions weren't working as well so I decided to just use the bitbanger code. The reason for this is because with the functions given from the device it sends the i2c_start then sends the data then sends the i2c_stop command. But what I need to do is send the start command then a lot of commands then the i2c_stop command. Here is the complete code that I am trying to execute

 void Show(unsigned char *text){
    int n;
    I2C_Start();
    for(n=0;n<1;n++){
        I2C_out(0x7C);
        Delay(.05);
        I2C_out(0x40);
        Delay(.05);
        I2C_out(*text);
        ++text;
    }
    I2C_Stop();
}

void I2C_out(unsigned char j) {
    BYTE value;
    int n, rc;
    unsigned char d;
    d=j;
    for(n=0;n<8;n++){
        if((d&0x80)==0x80)
            rc = HidSmbus_WriteLatch(i2cDevice,0xFF,0x40); //SDA = 1
        else
            rc = HidSmbus_WriteLatch(i2cDevice,0,0x40); //SDA = 0
        d=(d<<1);
        Delay(.001);
        rc = HidSmbus_WriteLatch(i2cDevice,0,0x80); //Clock = 0
        Delay(.001);
        rc = HidSmbus_WriteLatch(i2cDevice,0xFF,0x80); //Clock = 1
        Delay(.001);
        rc = HidSmbus_WriteLatch(i2cDevice,0,0x80); //Clock = 0
        Delay(.001);

    }
    rc = HidSmbus_WriteLatch(i2cDevice,0xFF,0x80); //Clock = 1
    Delay(.001);
    rc = HidSmbus_ReadLatch(i2cDevice, &value);
    n = 116;
    while(((value &0x20)==0x20) && n--){
        rc = HidSmbus_WriteLatch(i2cDevice,0x00,0x80); //Clock = 0
        Delay(.001);
        rc = HidSmbus_WriteLatch(i2cDevice,0xFF,0x80); //Clock = 1
        Delay(.001);
        //rc = HidSmbus_WriteLatch(i2cDevice,0x00,0x80);
        rc = HidSmbus_ReadLatch(i2cDevice, &value);
    }
    rc = HidSmbus_WriteLatch(i2cDevice,0,0x80); //Clock = 0
}

void I2C_Stop(void) {
    int rc;
    rc = HidSmbus_WriteLatch(i2cDevice,0,0x40); //SDA = 0
    rc = HidSmbus_WriteLatch(i2cDevice,0,0x80); //SCL = 0
    rc = HidSmbus_WriteLatch(i2cDevice,0xFF,0x80); //SCL = 1
    rc = HidSmbus_WriteLatch(i2cDevice,0xFF,0x40); //SDA = 1
}

void I2C_Start(void) {
    int rc;
    rc = HidSmbus_WriteLatch(i2cDevice,0xFF,0x80);//pin 7 is clock
    rc = HidSmbus_WriteLatch(i2cDevice,0xFF,0x40);//pin 6 is data
    rc = HidSmbus_WriteLatch(i2cDevice,0x00,0x40); //SDA = 0
    rc = HidSmbus_WriteLatch(i2cDevice,0x00,0x80); //SCL = 0
}

void init_LCD(){
    I2C_Start();
    Delay(.05);
    I2C_out(0x7C);
    Delay(.05);
    I2C_out(0x00);
    Delay(.05);
    I2C_out(0x38);
    Delay(0.10);
    I2C_out(0x39);
    Delay(0.10);
    I2C_out(0x14);
    Delay(.05);
    I2C_out(0x78);
    Delay(.05);
    I2C_out(0x5E);
    Delay(.05);
    I2C_out(0x6D);
    Delay(.05);
    I2C_out(0x0E);
    Delay(.05);
    I2C_out(0x01);
    Delay(.05);
    I2C_out(0x06);
    Delay(0.10);
    I2C_Stop();
}

int BitBanger(){
    unsigned char text[]={"B"};
    int rc;
    BYTE dir, mode, special, clk;
    rc = HidSmbus_GetGpioConfig(i2cDevice, &dir, &mode, &special, &clk);
    rc=HidSmbus_SetGpioConfig(i2cDevice, dir,0, 0, 0);
     init_LCD();
    Show(text);

}


texts: Accurately measuring temperature with Arduino

texts:
I'm trying to build thermostat with Arduino. I want to power it using mobile phone battery/charger which makes system voltage quite variable. Right now I use Arduino Uno, but once it is complete I will port it to Lilypad.

First I tried to use TMP36 temperature sensor. So far it was complete failure. While the sensor itself appears to be very stable, I can't figure a way to accurately measure its voltage.

Using built-in 5v reference for analog sensors isn't working at all -- even powered from USB arduino's +5V are actually +4.8V (which shifts measured temperature by few degrees). When the board is powered from the battery, voltage drops to about 4V and measured temperature sky-rockets. I also tried to use +3.3V from the board as a reference. It seems to be more stable when the board is powered from USB, but its voltage drops when running off the battery.

Is there any other way to reliably measure sensor output voltage?

For the second stage I'm planning to use thermistors. Just ordered a couple of these 20K thermistors.

From what I understand, these should be easier to measure accurately if I build voltage divider and use V_in as reference voltage for ADC.

A couple of questions about them:

Does it make sense to use few voltage dividers with different fixed resistor to increase accuracy?
I can use programmable pin as V_in, and measure temperature using few different voltage levels. Though its not clear to me whether this will actually increase accuracy.


texts: Choke module in the KNX power supply, what is the purpose of the third winding?

texts:
I have a question concerning the physical interface of KNX, twisted pair.
I was wondering how the KNX (twisted pair) transceiver can produce a pulse like the following:

I thought there must be some sort of inductor or choke in the power supply side, so that it presents a higher impedance at higher frequency. The equalization pulse looks just like the back EMF as we turn off a coil.
Luckily, I found a pic in the KNX standard. (Fig. 12 in ch9-2, basic component)

Clearly, W3-4 and W5-6 form a differential (no common) mode choke, which presents a high impedance while current is sunk, also the voltage drop is due to the two 47Ohm resistors.
What I don't understand is the purpose of the third winding, W1-2.
During active pulse duration, point 2 is more positive than point 1 in W1-2, the 220nF capacitor is charged through the diode and 100Ohm resistor.
In the equalization period, the polarity reverses, the PNP BJT turns on and the capacitor 220nF is discharged.
Do I understand this correctly?
What is the purpose of this capacitor charge/discharge action?
How exactly is the waveform related to this choke circuitry?
Can some analog expert shed some light on this?


texts: Using a USB phone charger to power sensor bin (instead of batteries)

texts:
I have one of those sensor bins that opens the lid automatically when you wave your hand near it. It needs 3 AA batteries. As it just sits in the kitchen near a power socket, I figured it would be better if I could just run it off the mains electrical supply instead of having to replace batteries from time to time.

Also, like a lot of people I guess, I have quite a number of old USB phone chargers knocking around. So, my thought process was:

phone chargers supply around 5V.
The AA batteries (x3) supply around 4.5V.

Therefore, it seems feasible that I could solder the 5V supply connectors to the appropriate terminals in battery holder on the unit, and run it off the mains.

I have a basic working knowledge electronics but am not an expert by any means. I would guess that 4.5V is near enough to 5V that it should be OK, but the other thing that concerns me is I don't know what sort of amperage I should ensure the power supply is capable of, and whether this could be an issue with typical phone chargers.

Does this sound like a feasible project for an novice. Any advice or encouragement/discouragement to try this?


texts: How to protect an externally connected PT 1000 sensor

texts:
I have following circuit reading an externally connected PT1000 sensor. The Sensor is on a cord, the side we are looking at in the schematic uses a a female connector. So the pins are not easily accessible. The device will however be used in a bio lab setting. Moisture (up to 100% rel.) and temperature (might go up to 50°C) might be an issue.
Corrosion will probably not be an issue.

I want to foolproof the device for non-technical personel with an academic background.

What are important scenarios I would need to failsafe the circuit against, and - if a suggestion is easy - how would I do it?

I have already checked following conditions:

Short-Circuit

For people wanting to reuse: The circuit specs to 0-50°C with about 0.1°C resolution on a 10bit ADC. Make sure to use the right Opamp, I've been burned by that.

Datasheet for diodes: SMAJ5.0A


texts:
I'm relatively new to electronics and recently decided to design and build a very simple CPU as a personal project. My instruction size is 32 bits and I want to have 32 bit registers so I am going to need several 32 bit wide, 4 way multiplexers.

I know how to construct one using 32 1 bit, 4 way multiplexers but I'm wondering if there is a better way to do this?

EDIT:

Essentially this:

How to create an n-bit multiplexer

but in terms of actual hardware.


texts:
It's crazy idea, but i wondering if it's possible to build some blinking multivibrator circuit without any leds, where transistors emit light themselves, it would be cool :)

I googled and it seems perspective technology for oled displays, but does LETs exist in standalone packages like LEDs?

I found interesting topic here Why do some power transistors emit light?

So if i buy some of GaAs (it has wider bandgap, so could emit visible light, yes? ) fets like these
http://www.ebay.com/itm/MGF0906B-Manu-MITSUBISHI-Encapsulation-RF-TRANSISTOR-L-S-BAND-POWER-GaAs-FET-/121483823465?pt=LH_DefaultDomain_0&hash=item1c49000969
and break their ceramic package without damaging transistor itself, would i see any visible light?


texts: How to see electronically if a cup is empty or not

texts:
My requirement is just to know when a cup/mug is empty. I searched for weight sensors but they are bulky and expensive for this simple task. Is there any cheap solution for this task? Using weight sensor is not necessary as long as requirement is met.  The circuit will be under  base of the cup. The liquid can be anything from water to black coffee.

update:

I asked i wanted to detect whether a cup is empty or not. The bottom surface of cup is flat.
 One cheap idea is to have a little transparent surface at bottom of mug like 1 cm by 1 cm. Put a photo transistor there to see what's in the mug. If the mug is empty, photo transistor will give a unique value as compared to any other liquid present regardless of its amount in mug.
  Any other ideas are welcome.


texts: VGA digitizer with FPGA (input, not output)

texts:
Producing a VGA signal with an FPGA has been done by so many people it is a common starter project. What I cannot find is information on how to decode a VGA signal with a FPGA for example to capture a frame of video in memory. Assume there is nothing but R, G, B, VSYNC, HSYNC to work with, no DDC. Assume converting analog RGB to digital can be done.
VSYNC gives you the refresh rate and the number of HSYNCs between each gives you the number of lines. Let's say it is easy to count 525 lines and the refresh rate is 60Hz. That part is not hard.
How do you decide the number of pixels in each row and therefore the pixel clock? Is it a case of trying to fit various known values (from a table such as VGA Timing or the VESA DMT spec) based on the known information (lines, refresh) and just seeing what cases result in a HSYNC and front/back porch in expected places, giving a known pixel clock to use for sampling pixels?


texts:
How can I calculate V1 and V2 in this circuit?

This is what I tried so far:

Calculate the voltage of R5 through voltage divider but I didn't  find the way, I was looking about second OA circuit but I don't really know what it does.


texts: A confusion on flash memory map of an AVR micro-controller

texts:
I'm trying to figure out the flash memory map of ATmega328P:

Below is from the datasheet:

Program Memory Map for ATmega328P is given as 32KB:  32Kbytes = 32K * bytes

0x0000 means 16 bit wide (for each line of memory there is 2 bytes)

which is 16K * 16bit

What I understand from this, the flash memory is made up of 16K lines of 16 bit wide registers. So for an instruction on the flash memory the maximum address number is 16K.

Is this 16K 2^16 or 16000?

The last three X Y Z general purpose registers which are used for holding the addresses(pointers) are 16-bit which can store up to 2^16 = 65536 addresses.
So I would guess 16K means 65536 here?

But if it is, in the above figure it shows the last memory line as 0x3FFF which corresponds to 16383.

What am I knowing wrong here?


texts: Measure power of solar cell with an esp8266

texts:
Scenario
I plan to buy some bigger solar cells (together around 500 W) and use them to make my electricity bill cheaper. But in order to find the perfect location on my roof before the purchase, I thought about placing an ESP8266 on my roof with a small 0.21 W solar cell that sends the power data every hour to my phone.
This way, I can leave my ESP on a certain location for a few days and check the data. After, let's say, a week, I will place it on a different location and check the data as well. After a few weeks, I should find the perfect location for the bigger cells. I know that this is just a reference and won't be that accurate.
Material

ESP8266
3 V and 70 mA solar cell (= 0.21 W)
a few resistors

Ideas for implementation
My idea is to short-circuit the solar cell all the time and measure the current with a known resistor from the voltage drop across it. Additionally, I can measure the voltage by simply using one of the analog pins and converting the analog value into a real voltage. After that, I can multiply the current and the voltage and have the power (Watt) sent to my phone every hour.
Questions

Is it accurate enough to use a resistor for measuring current?
Will a permanent short-circuit damage my solar cell?
Is the voltage during a short circuit the same as without a load or will it decrease?

(3) would make this whole project useless because I don't have accurate voltage values and so also a wrong measurement for the power.
Thanks in advance.


texts: Is it possible to remove a line of code from microcontroller program memory?

texts:
int main(void)
{
while (1)
{
   delay(50);
      if (ButtonPress1) {
      ResetOutSwitch();
      }
}

Suppose that button press is detected and output switch is reset.
How to make the microcontroller do not pool the button press anaymore.
How to make above code look like below after button pressed and output switch is reset. It will not see any if check in its code.
int main(void)
{
while (1)
{
   delay(50);
}

I am asking how to remove a line of code from execution from microcontroller program memory.
This question was closed because of its answers might be opinion based. So I must make it more specific.
Is it possible to remove some program data from microcontroller flash memory, so it skips these deleted parts and continues with the rest.
What is the way to do this? I only know C programming. Using Eclipse to program STM32 microcontrollers.


texts: T-type flip flop based on SR without additional gates?

texts: I have a question that keeps bugging me. I know how to make a T-type flipflop from SR flipflop by using 2 additional AND gates, but I was wondering, if it is possible to create T-type from SR without additional gates? If so, how to minimize Karnaugh tables to reach such functions?


texts: Efficiently calculate \$-x-y\$ using a single adder

texts:
I would like to know if there is an efficient way of implementing the operation \$-x-y\$ on an FPGA using only a single chain of adders or subtractors, roughly equal in length to the maximum number of bits in \$x\$ and \$y\$.

The bit twiddling trick of replacing \$-x\$ by \$\overline x + 1\$ (\$\overline x\$ meaning bitwise negation) results in the expressions \$\overline x - y + 1\$ or \$\overline x + \overline y + 2\$. Both expressions I don't know how to calculate. How do you perform a subtraction with a positive carry or an addition with a carry of 2?


texts:
I have a device that pulls about 10 amps and is typically powered with a car battery. It runs fine with less amperage but needs 9 to 14 volts. I want to power my device directly from a solar panel but haven't accomplished anything if the solar charger requires a bulky battery.

It works with a DC DC buck converter but inefficiently, pulling ~70 watts from a 120 watt panel. I want something more efficient.

I found a mppt solar charger that powers my device efficiently when connected to a 5 amp-hour battery, but again I don't want the bulky battery.

Can you suggest a way to power a solar charger with a very small battery and not have it discharge when clouds block the sun?
      or

Is there an MPPT out there that doesn't require a battery?

edit:

Many of you asked "what is the load?"...... I have four titanium electrodes, spaced about 1/4 inch apart, and place them in salt water, to produce bleach. The bleach is used for sanitation or disinfecting water in developing countries.

If I had 12 volts and 10 amps the batch of bleach would be done in an hour. I don't need to run at night and it doesn't bother it to stop when a cloud covers the sun.

As far as the buck converters.....The ones I purchased don't have any adjustment..... Someone asked for the circuit diagram for the buck converter. I just hooked the input to the solar panel and the output to the bleach making unit.

The unit will operate fine with less than 10 amps, it just takes longer to make a optimum strength of bleach. It likes 12 volts but will work fine at 9 to 14 volts.

I have been told that the problem is similar to powering a water pump directly from a solar panel.

I didn't know there was a MPPT "controller" that would not need a battery. That's why i tried the "solar charger". I'll look for one or maybe you could point me in the right direction.


texts: Problem about the price of some SMD components

texts:
I'm finding for some SMD components such as MLCC(Multi-Layer Ceramic Capacitor)s.
I tried to find both inexpensive and regularly-sized(which in my words this mean 'comfortable to solder with my hands', for example 2012 or 3216 size, all mm units) capacitors, but they weren't cheap and the price was so unreasonable.

For example, suppose I buy a 2.2uF MLCC(regardless of the dielectric characteristics). In the size of 1608, I can buy some relatively cheap one, however in the size of 2012, they were too expensive(instead they were supplied with a Reel unit).

This is so frustrating because my country doesn't have MLCC makers, of course, paradoxically, Samsung does(their factory is not in Korea, so shipping fee is very expensive and I'm working for the project in my University).

I feel that this question is more alike to economics, however in my experience price and parts selection is important in engineering so I want to know.. why generally smaller size in MLCC is relatively cheap? Is it hard to make MLCCs relatively bigger than the 1608 one? Or, is the cause 'the buyers want to buy a reel unit rather than a private component'?


texts: How to add 0.2V per Ampère that device draws? (Voltage drop compensation)

texts:
I have noticed that many mobile phone chargers already do this: For each 1 A of current that the mobile phone draws, the charger's output will be increased by 0.05V or 0.1V or something similar, to compensate for the ohmic voltage loss due to the resistance of the wire (USB cable).

Example for 0.1V voltage drop compensation, assuming base voltage 5.1V:

0A → 5.1V
1A → 5.2V
2A → 5.3V
3A → 5.4V

This Powstro HKL-USB32 wall charger does exactly that:

That's because through longer cables, the charging IC of mobile phones sees a voltage drop which makes the charging controller falsely consider the charger exhausted. The charger partially compensates for that, to “fool” the mobile phone into drawing a higher current.

When connecting a female USB port to the terminals of a variable laboratory bench power supply (correct polarity regarded), increasing the voltage manually subsequently only increases the charging speed on powerbanks, which only pay attention to the momentary voltage, not the initial voltage drop.

Mobile phones however choose a current at the moment when connecting it to the charger, and then hang onto it, no matter how much the voltage increases afterwards. (No overvoltage. Many mobile phones, including the one I used to test it, support 9V and 12V for fast charging standards. All tests at my own risk.)

Example: If I select 7 volts on the bench power supply that powers the female USB port, then enable power output while the mobile phone is already connected to the USB port, the mobile phone (which supports all input voltages from 5V to 14V, therefore no overvoltage) does choses 0.83A. When I decrease the voltage to 6 volts, it is still 0.83A. If I increase to 10V afterwards, it is still precisely 0.83A. The current can not increase, only decrease under the following conditions: If source voltage goes too low, near 4.5V, or if the battery is becoming sated (full). It can also happen that the phone chooses e.g. 6V 1.6A. Increasing to 12V would result in overwattage for the battery, therefore the current would also decrease. But the phone tries to maintain it's initially decided Ampèrage.

How do I increase the voltage in conjunction to the current?

The goal is that the mobile phone draws it's full power over any length of wire.
Is there any module for that? (I could not find one by searching for “Voltage Drop Compensation” and “cable drop compensation”.)
I don't have a bench power supply with a “sense voltage” feature yet.

There are already boost voltage modules, but they are just as useful as increasing the source voltage manually.
One thing I could do is placing a boost voltage module near to the tip of the USB cable. But is there a way to increase the source voltage in conjunction?


texts: How to shield a battery powered instrumentation with USB interface?

texts:
I would like to ask for advice on shielding the following setup.

I have a measurement target sitting inside a Faraday cage, connected through a shielded cable to a measurement circuit. The cable shield would be connected to the Faraday cage. The circuit mainly includes a microcontroller, AD converters and a single op-amp inverting transimpedance amplifier. The circuit sits inside a metallic box connected to the cable shield.

As the instrumentation needs to be battery powered (3.3V), the transimpedance amplifier is referred to the mid-level potential of 1.65V (wrt battery negative terminal) to allow measurement of current flow in both directions. This in turn means that at zero current flow, the measurement sample is at 1.65V wrt the negative terminal of the battery powering the measurement circuit.
The analog signal bandwidth to be recorded is on the order of 10Hz-500Hz.

The device would occasionally have to be connected to a desktop computer through a USB interface. Then, the USB ground has to be connected to the negative terminal of the battery, 0V for the microcontroller and ADCs, -1.65V regarding zero transimpedance output.

I have received conflicting advice on how best to shield this circuit, one idea being to connect the shield to 1.65V, coupling the shield to the zero level of the transimpedance amplifier or alternatively, connecting the shield to the battery negative terminal, zero for the digital components.

In either case, a further question is whether the USB cable shield can or should be connected to the metal enclosure of the measurement circuit.

I have read a number of other posts on shielding, mainly as this, this and this, however I have not been able to piece these together for my case. Any help pointing me in the right direction would be much appreciated.


texts: Motor Driver Deadtime, on-switching-time and off-switching-time

texts:
I have the following motor driver (DRV8320):
https://www.ti.com/lit/ds/symlink/drv8320.pdf?ts=1616576087660&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FDRV8320
Since I want to implement the deadtime compensation, I need to know what the deadtime, the on-switching time and the off switching time are, according to:
https://www.nxp.com/docs/en/application-note/AN4863.pdf
Since I use the hardware variant, the deadtime is constant at 100ns, but what are the on-switching time and off-switching time? I use the Idrive in the 60/120mA mode (60mA drive, 120mA sink) and the MOSFET types are BSC0702LSATMA1 (https://www.mouser.ch/datasheet/2/196/Infineon_BSC0702LS_DataSheet-1770891.pdf) with a gate charge of maximum 11nC.
Can I say, that t_on = 11nC/60mA=180ns and t_off = 11nC/120mA = 90ns?
If so, the deadtime seems pretty neglictable, right?


texts: When designing an arbitrary count sequence synchronous counter using kanuagh maps and either JK or D flip flops, does it matter whether the flip flops are rising-edge or falling-edge triggered?


texts: Does a splitter still reduce signal if only 1 of its ports is used?

texts:
I'm using a Wilson Electronics signal amplification system to try to get phone signal in my house. I'm going to attempt using a coaxial splitter like this one to split the amplified signal to multiple indoor antennas for broadcasting to multiple parts of the house, since the house is large and has thick stone walls that block signal very effectively.

However, I haven't ordered the second indoor antenna yet. I only have one right now.

What I'm wondering is, once the splitter arrives and I've added it into the system, will I be able to tell immediately if there's a significant signal drop across the splitter, or will it not be apparent until I've bought the second antenna and attached it as well?

To rephrase, if only one port on the splitter is used, is the signal drop to that one port the same as when all four ports are used? Is it the splitter itself which diminishes the signal, or is it the extra devices attached to it drawing part of the voltage away?


texts:
I am studying VLSI Coursers and I came up to a question. what happens if we don't use output load in CMOS circuits? what happens to overshoot/undershoot and circuit delay?
thanks


texts: Can a secondary or additional core be loaded and made active (powered on) without via user application or a boot loader

texts:
Using any multi core IC such as the Qualcomm Snapdragon SoC as the platform.

Can a secondary or an additional core (such as core1 or core2 etc..) be powered on and made active without via some user mode application or by way of a secondary or intermediate boot loader ? Can core0 (the default or primary or main core) have integrated circuit code within which simply powers on the secondary or additional core and then loads a specific OS (which will run on this core) all from within core0 integrated code essentially by-passing the involvement and use of any user application or intermediate boot loader ?


texts: Input resistance of small signal equivalent

texts:
I'm trying to calculate the input resistance of the depicted small signal equivalent circuit.

I was just wondering why I can't see the current source as an interrupt and then the input resistance will be: r_pi+R.

I recall that replacing current sources with interrupts and voltage sources with short circuits is done when calculating the resistance between two nodes in a circuit. Why isn't that allowed in the small signal equivalent?

simulate this circuit – Schematic created using CircuitLab


texts: How the feedback circuitry of a Tesla Coil works?

texts:
I have a project to do in school which is a DIY musical Telsa Coil and I need to build the hardware. I searched on the Internet and found these 2 schematics:

My schematic is completely different from these two because it fulfils a different purpose, but the feedback circuitry is more or less the same. So my questions are:

How do these feedback circuits actually works?
How to choose which one to implement and what are the advantages and disadvantages of both?


texts:
In RISC vs CISC, the load/store architecture:

Load memory data into CPU register
Compute
Store result in memory

In CISC, 1,2,3 is wrapped in a single instruction.
In RISC 1,2,3 are separate instructions.

I'm reading from Naimi - AVR's and he says:

  The problem is there might be a delay in accessing the data from external memory. Then the whole process would be stalled, preventing other instructions from proceeding in the pipeline. In RISC, designers did away with these kinds of instructions.

So if there's bus contention, there's a delay and the process will stall.

But surely it'll stall in RISC as well? So what's the significance of wrapping 1,2,3 in a single instruction (CISC) vs keeping 1,2,3 as independent instructions (RISC-ARM)?


texts:
I am using a SIM5360 and works very well for GPS and GSM communications. Now I am using the SPI too: I have the SPI activated (AT+CGFUNC) and configured (I following the SPI application note). But, when I send a command (only been tested with write commands) I have always 3bytes with 0x00 after addres and before the data that I want transmit.

Someone have the SPI communication working fine in a SIM5360 module?

Thank you.


texts: What exactly does a resistor's tolerance rating mean?

texts:
I thought that I had this pretty much figured out over 30 years ago during my initial schooling, but various answers posted to a support forum of a major semiconductor manufacturer(name withheld to protect the possibly innocent) by staff support engineers (and no countering posts) have caused me to second guess myself.  There are other questions concerning resistor tolerance, but none even mention the problem I talk about below.

EDIT: This is concerning the statements that the chip makers support engineers make concerning why there are differences between measurement runs.  The phrasing used makes it sound like resistors change randomly within their tolerance rating.  When nobody called them on this explanation(which was given over a year ago, which is why I did not post in the thread.), given by two different people, is when I came asking.  The chip in question is a type of ADC. The excitement signal is give or take a 125Khz, 2Vpp sine wave with a max current around 30mA.

I always thought a resistor's tolerance rating was the permissible difference between its actual value and its posted value.
Meaning if we took a group of 100 ohm resistors they could vary as follows:
A 5% resistor could have any value that was -5 or +5 ohms from 100.
A 1% resistor could have any value that was -1 or +1 ohms from 100
And a .1% resistor could have any value that was -.1 or +.1 ohms from 100
But once it was manufactured, and discounting abuse its value would not change, due to the tolerance rating.  I'm not talking about changes due to temperature, that is based on its TCR.  E Nor am I talking about aging, these are measurements taken within an hour(or less) of each other.

What caused this question is that more than once in answering a question they stated that the various different values between measurement runs could be due to a resistors "tolerance".  As if a resistor's value changes randomly within its tolerance rating, something I have never heard before.  If they had stated it might be due to resistance changes due to temperature, I would have thought nothing of it.  Or if the poster had been someone other than a tagged support engineer.  And there were no posts questioning these conclusions, which messed with my head even more.

Maybe I slept through that part of class and it's such a common thing no one bothers to talk about it, but I'm pretty sure that a resistor's value does not change if there are no outside forces(e.g. temp) influencing it.  Am I correct, or have I some how managed to misunderstand how a resistor works for a LONG time?  Or does tolerance have a meaning I somehow just have not encountered before?
I do have medical problems, but I'm fairly sure that they have not degraded my thought processes that much(if they have, I need to stop talking).


texts: I am building a simple reverse-polarity circuit using two relays. Will it create an endless loop?

texts:
I am planning on using the following circuit for my motorized value.

But I'm bit skeptical about how this might continue to work. Although I'll be using two identical relays, my fear is that at one point in time down the line, one of the relays may start switching earlier than the other (wear and tear may be) and it'll short circuit the battery.

And that'll obviously will lead to shut down the relay and again it will turn back on and so on creating an endless loop.

Firstly, is that possible? Or am I thinking too much?
And if my struggle is real, how could I possibly solve this?


texts:
Background:
I just picked up an ASY2400 Xenon Flasher unit from a local electronics store. I found this hookup diagram for it:

I connected a potential difference of 12V to the board. +12V to pin J4 and 0V to pin J1. When I press the power button it makes a humming sound; however, the U shape Xenon tube is not flashing.

Question:

Pin J1 and J2 are labeled -12V and J4 is labeled 12V does this mean that I should connected a potential difference of 24V (0V to J1 and 24V to J4)?

I was not able to find a more detailed spec sheet. Does anyone have any idea what pins J5, J3, and J6 are used for?

Update: Thanks for your continued help, but several months ago I got rid of this board.


texts: Amplifier power problems, power supply limitations, or end stage base current draw

texts:
So I am experimenting with various signal generating, op-amp and power amplifier circuits. And I have limited access to technology. Where I am at, everything you buy is twice the price because of tariffs, so I try to make my own stuff with what I already have. I got a scope but no bench power supply.
I use TTL levels for my signal generation with a simple cell phone charger 5V rated 2.1A nominally. I use a second such charger at 5V rated at 1A for my negative supply to the op amp and the power amp stage. And that is where I think my troubles come from.
I get a nice sine wave with about 6.5V peak to peak (not entirely sure why I can't get the full 10V even if I crank the feed-back up to maximum distortion level, but let that be a different question.)
I have a power output stage constructed with a pair of BC547 npn and BC557 pnp transistors. It gives me a beautiful clean undistorted wave on the output. However, when I actually plug the little speaker in, that's rated at 8Ω 5W, the output waves are suddenly clipped hard at about 2V peak to peak, and all the waves are starting to look ugly.
I think that is because of the power supplies reaching their limits, so they cut off intermittently.

simulate this circuit – Schematic created using CircuitLab
Quick walk-through: I don't show the details of the sine wave generator, it's essentially a 555 astable multivibrator circuit, spitting out its 4V peak to peak, with a 3 stage low pass filters RC network to get a nice sine wave with minimal signal loss, around 2V peak to peak. Then that goes into OA1 as a simple high impedance input voltage follower to shield the finicky RC network from any further load. Then I have a "volume" potentiometer R1 which goes to a decoupling capacitor C1 of 100 nF, because then I bias that signal down with the potentiometer R2 nicely into the middle of the range, then OA2 is the pre-amp bringing the level to 6.5V peak to peak, and finally the end-stage with the pair of BC547 and 557, and the OA3 acting in this genial way to bring a totally clean undistorted wave into the output handling that "dead-zone" of the transistors.
Here I'm going to show you a few pictures of this weird clipping. The wave comes out of the end stage beautifully undistorted:

but as soon as I hook up the speaker, it gets terribly clipped

Since my suspicion is that the power supply just cannot deliver the power required here (I think it's around 1A which would bring it to its limits) I want to hook up a 12V and 10A rated DC power supply that I have spare. Here I am trying to think how I would do the 12V hookup and it should almost work like this:

simulate this circuit
I really am puzzled about the GND. Nothing seems right, even in the first schematics (my current design that breaks down under load).

no obvious relationship between signal ground of the generator and OA1 input
pointless connection of potentiometer R3 to this GND, why not connect it directly to V-?
the speaker's GND goes to nowhere -- how does the power actually flow?

I guess in my first design the speaker's GND does flow directly into the common lead connecting the two 5V power supplies. So it did make sense that way. But now if I want to use that 12V DC power supply then where can I connect that GND now? I have seen people using another op-amp to simulate a GND, but I don't see how I could put power through this.
What else can I do? When I was young, I built a kit of a guitar amp, which had a husky power supply where two large capacitors connected positive and negative to ground. But the ground was also connected to the transformer from what I remember. It was like this (from memory):

simulate this circuit
I don't remember if there was a center tap from the transformer or if the ground was simply established by the two capacitors. They might have been even bigger that 100 μF, maybe 500 μF, they were about 1 inch in diameter and 2 inch height, all from memory, it's been like 35 years.


texts: How do I produce a 1Hz clock output using a 555 timer IC? Are there better ways other than a 555 timer IC?

texts: I've been messing up with timer ICs, looked up on how they work and now I want to design a simple digital clock using a 1Hz pulse generator. Is a 555 timer IC sufficient enough to make accurate 1Hz pulses or is there any other way to design a pulse gen? Is there a specific resistance/capacitance value for the IC or am I wrong and there's a better oscillator for such purpose?


texts: Why does GET_REPORT on my HID Keyboards sometimes return an empty packet?

texts:
I'm writing boot firmware on a PowerPC board, and I have a problem with spurious USB keyboard repeating. My firmware is based on u-boot: after enumeration it puts the keyboard into boot protocol, then polls it by sending GET_REPORT control packets. From my reading of the HID specification, the keyboard should simply send back the key states and leave my firmware to detect key changes.

This brings back the key states correctly almost all the time, but every keyboard I have tested also sends back occasional empty packets, which the firmware interrupts as a key-up event. In the worst case this happens every 7ms. Here's a trace from the analyzer:

In the image above transfers 76 and 78 show the correct key code (I'm holding down 'a' throughout), but transfer 77 is all zeroes.

Is there some configuration I'm missing here, or is the only workaround to ignore empty reports unless I see two in a row?


texts:
I'm working on an automatic battery charging source switching between solar power and a 24Vdc wall adapter.I'm using a LM741 as voltage comparator and a relay for power switching. Basically, if solar power is not available or solar voltage is below a threshold value then battery charging source should be automatically switched to the DC wall adapter supply. So, for detecting solar voltage threshold, I'm using a LM741 as voltage comparator.

I'm facing issues with the LM741.

Whenever solar power is available whether it is as low as 3.1V or as high as 12V, the relay remains switched to solar power source.

To set the threshold value I'm using a 10K potentiometer.

The relay switches to the DC wall adapter when solar voltage goes below 3.0V.

I have tried changing the potentiometer position, but at every position the threshold value remains 3.0V, and the relay switches back to solar power when the solar voltage gets above 7.7V. I have tried changing the potentiometer position, but at every position this value remains 7.7V.

I have attached my schematic diagram. Can someone please tell me why I'm not able to change the threshold voltage using the potentiometer?


texts: Python to trigger USB square wave pulse for camera

texts:
I'm sorry if this was posted somewhere, but I'm trying to trigger a FLIR camera for acquisition using a USB port.  I already purchased a USB split cable, and have queried the ports, so I know exactly which one I want:

Bus 003 Device 092: ID 1004:633e LG Electronics, Inc. G2 Android Phone

I also checked the FLIR camera and it can be triggered for acquisition in principle with any 3-5V pulse.

I just would like to know how to send out a pulse via Python to one of those channels.

What is the best Python package for doing this?  I saw pyusb.  Is that the best and simplest to use?


texts: I am working at a project which requires an application which has some devices connected through a bus (RS-485 || CAN), I haven't decided yet.The problem is that some of this devices are hot pluggable and I don't know which devices to have the termination resistor.The bus is formed by 2 or 3 devices and I could disconnet almost all of them(only the one end will remain), so I think what happens if I disconnect the device with the termination resistor, I know that a differential bus has two termination resistor, one in each end.Could you give me some ideas how I can fix this issue ?


texts: Can I change a frequency band of an EQ board?

texts:
Is it possible to change one of the frequency bands of this EQ board?
In particular, the low frequency adjuster is 100Hz and I want to make it 60ish Hz.
My understanding is that i need to meddle with the capacitors and resistors around the IC controlling that particular band, but is this the case?
I think the IC is 4558d but I can't really see from the photos.


texts: nRF52 GPIO configuration in sleep mode to prevent peripherals from drawing current

texts:
I have a battery-powered board with an nRF52832 and some peripherals that I am writing a new firmware for. When set to sleep (NRF_POWER->SYSTEMOFF=1;) the board still draws way too much current (around 2mA, the nRF is rated for <1 uA when in sleep). The pcb itself is fine, with the firmware it came with, the power consumption in sleep mode was very low. At first I thought this might be a software or configuration issue, but I guess it is probably the peripherals drawing too much power.

When the board is set to sleep mode, most of the SoC-internal peripherals are turned off, but the GPIO configuration is preserved. I tested the power consumption with minimal code (first statement in main() is sleep) so all GPIOs were set to default confguration (input with disconnected internal switch).

Do I need to set the GPIOs to a certain configuration to prevent them from wasting power?

Some peripherals are connected via SPI or I2C. Should the nRF Pins
used for SPI/I2C be in a specific configuration when SPI/I2C are not
used, or is the default (input with disconnected internal switch)
fine?
One GPIO is driving a n-channel mosfet (with ext. pulldown on gate)
that drives a small motor. I guess since there is an external
pulldown, the default pin config should be fine?
Some LEDs are connected (GPIO -> Resistor -> LED -> GND). Again, I guess default should be fine?
Battery voltage is measured via ADC on voltage divider.
A active-low switch has an external pull-up.

Is it for any of these peripherals critical to configure the GPIOs in a specific way to prevent power loss?

Schematics: https://mbientlab.com/community/uploads/editor/f6/3zbfr2s08vsb.pdf

(I was posting this question on the nordic forums, but I noticed that the issue is probably more general about GPIO configuration. Link to Topic)

Edit: I measured the current with a scope. I could not get to the voltage regulator pin (tiny) but I measured in series with the battery (put a 10 Ohm resistor in series with battery and measured with probes across the resistor). 10mV equals 1mA, so the scope shows around 2.2mA


texts: Altium Designer - Create keepout based on board outline

texts: Is there a method in Altium Designer where I can immediately create keepout lines on each edge of my board? My board shape has a complex design which is why I am looking for this method.


texts:
I recently asked this question over at stackoverflow, but I was told by a user that it was off-topic, so I am posting it here since it's more of a hardware question.

I'm trying to study for an exam and I'm trying to answer the question below.

I'll be honest, I've asked this question on here before, but now that I have a better understanding of it, I felt I should make a new question to fine-tune my understanding, since my question is somewhat different now.

  Consider a virtual memory system with the following properties:

  35-bit virtual address
  16 KB pages
  32-bit physical address

  Assume that this virtual memory system is implemented with an eight-way set associative TLB. The TLB has total of 256 TLB entries, with each TLB entry representing one virtual-to-physical page number translation.

  A 64 KB data cache is a two-way set associative cache. The data cache’s block size is 128 Bytes.

  Show the virtual to physical mapping with a figure drawn in a way similar to the figure below (but with all necessary changes required for the TLB and the data cache specified in this question).

  Specify the width of all fields and signals coming in and out of (as well as the number of comparisons done by) the TLB and the data cache for each memory address.

So far, I've come up with the following:
(Direct link here for larger image)

I've come up with this:

In case you're curious about the font, it's called Waltograph, a TTF I downloaded from the web, it was set as the default in paint, so I decided to enlighten my studying with some Disney magic.

Anyway, since the problem states that we have 16KB pages (\$2^4 \cdot 2^6 = 2^{\textbf{14}}\$ byte pages), we then need an offset of 14 bits as indicated in my schematic.

Then, since I have a total of 256 TLB entries and an 8-way associative TLB, we need an index of 5 bits wide (\$256/8 = 32 = 2^{\textbf{5}}\$). Then whatever is left over is used for the tag as indicated.

Then I have 8 comparators, as shown, which compare each tag at some index to the specified one. The result is put through an and gate with the valid bit to determine if we have a hit or not (I put the outputs of the and gate through an or gate to concatenate it into one signal)

Once we know we have a hit, we need to extract the data (physical address) from the TLB. I used a one-hot mux to select the physical address of the desired TLB entry. Then the output of the physical address is concatenated with the offset from the virtual address.

Now what I'm confused about is the cache part. I understand that the TLB is essentially a cache of most recently used physical addresses. However, I don't understand what's going on in the book's diagram. It suddenly splits up the physical address and uses it to index the cache, I guess. But why is it showing the cache and data separately? and why is the byte offset just left floating? I'm pretty sure the cache is supposed to store data as well. I don't think its sole purpose is to determine whether or not there's a hit or miss inside of it. I apologize for my ignorance in advance, but the book barely covers TLB's (it's like a little more than a page) and it doesn't do a very good job at explaining the relationship between a TLB and cache.

I'd appreciate if somebody could verify what I've done so far and explain what cache has to do with this to me. Thanks.


texts:
If I use a P channel MOSFET as a switch for a battery 9v 0.5Ah controlled by an external power source 12 volt will battery last its shelf time if MOSFET is by off?

Update: I dont mind the leakage of the external power supply.


texts: Is it possible to connect to non-miso device

texts:
Is it possible to setup a connection to my device? Is it SPI ?
The device is x96 android tv box, (manufacturer unknown, may be TT TV Box, listed as both x96 and X96, its casing is lower case). Managed to brick it. On others I’ve used another technique for connecting which o has an available here. For more info it’s a s905x soc board with on board storage and wifi.
What pins need linking? I usually use RX/TX/GND but there isn’t any pins for it on this device.
Or am I barking up the wrong tree?
Thank you.


texts: Tech stereo damaged by dimmer switch outlet, why?

texts:
A low end Tech stereo was plugged into an electronic dimmer switch outlet.  The stereo was only a few years old and was functioning properly prior to plugging into a dimmer controlled outlet.  I plugged the stereo into a normal outlet after the incident, however, there is no indication of life.  If possible I would like to fix the stereo, but before hand I would like to better understand what component might be damaged, and why.  Example, could low voltage require higher current from regulator thus burning out the regulator circuit?

I have been put on hold due to asking a repair question.  15 yard penalty still 3rd down...  :)  JK  Andre's below response however was helpful, so glad I posted above question.

I researched my dimmer type "Lutron Maestro" which uses standard phase control, or leading edge.  Basically power is provided at certain time points within the AC +/-  voltage phases.  Different start times control light luminescence by controlling power on time.  A DC voltage can be supplied which does not bode well with magnetic transformers.  My stereo does not have a fuse from plug to transformer therefore the copper wire blew open.  I confirmed transformer input to be open with OHM meter, and I did not observe 120V AC at the input when plugged in.  Thought this might be useful for others who like electronic dimmers.  Bottom line do not connect a dimmer to an outlet as it can damage an electronic device that is plugged into it.  Good news though, transformers are cheap, and it is an easy fix.  My daughters Stereo is up and running.

Go Niners!!!


texts: Can an opamp have its own voltage regulator?

texts:
I'm wondering if we use batteries instead of stable power supply for the opamp power rails what would be the consequences.

If we use an opamp for precision application would using batteries a bad idea since the battery voltage drifts might effect the opamp output directly?


texts: How do I calculate Distance between two sensors?

texts:
How do I calculate the distance between the two light sensors (ie. Infrared LED and PhotoDiode). Actually I am designing a device based on the similar principle of GPS to control the mouse position on my computer system. Here is the schematic diagram of what I am trying to do:

I placed 3 photo diodes receivers (Red,Green,Blue) and one infrared led (Yellow), I have to find the position of infrared led for which I have to calculate the distance between LED and PhotoDiode, through the distance I can easily create imaginary circles around Photo diodes and can easily find out the position of LED (The common points of circles)

  This question might be off-topic for this forum, but I asked it here
  because I think it is right place for it.


texts: Will a large variable power supply burn out a heating element?

texts:
I'm currently learning about electronics so I bought myself a variable power supply - something I think will be useful over the coming years. I would like to know if I use a hot wire cutter (most likely nichrome wire? polystyrene cutting pen from ebay - link at the bottom of this post) then could I use my variable power supply to power it rather then getting a separate transformer?

The power supply I have is around 20v up to 25a and it has a dial to change the voltage. I was wondering if I dialled the voltage to 6v will the heating element just take enough current required to heat up or will it be greedy, shoot up to 20 or so amps then melt? If so then might there be a good option to limit the current?

Just to assure - I looked through many posts on here and couldn't find something specific to this (perhaps I just wasn't sure what to look for and peoples posts on using a variable pot to control power to a heating element says all).

https://www.ebay.co.uk/itm/273337454116


texts: What electric component is this? (its on an old electric organ)

texts: I'm trying to find out what this is and where I can buy one. To me, this looks like a capacitor, but I'm no expert. After using a multimeter, this seems to be the cause for the organ not turning on. (it's an old electric organ that I bought to try to fix) Can someone help me?


texts: Controlling a PSC motor with a triac thermostat

texts:
I have a multizone hydronic heating system that has a pump for each zone.

The Pumps are Taco 0015 three speed pumps like this one that I am to understand are permanent split capacitor motors.

The thermostat I am testing is an Aube TH401 like this one that uses a triac for switching.

(I have been using old style bi-metallic thermostats to hold the temperature in each zone but they are very inaccurate and allow large temperature swings.)

So, the new Aube TH401 is a little more expensive but it holds temperature better. It operates on 5 minute cycles on "Fan" mode for a baseboard heater with an integral fan, and 15 second cycles when it is set for straight resistive heat. I have it set on the "Fan" mode since the resistive mode cycles are too short to actually move any water in the zone.

The thermostat has one to four little heat waves on the display to indicate "heat intensity". That is what the manual says. I am assuming it actually controls the amount of electricity a baseboard heater would receive by controlling the duty cycle of the triac.

And now my question:
If the duty cycle on the triac is being controlled to hold a tight temperature instead of just turning it full on and full off, can operating a PSC motor on a thermostat like this damage the motor?

EDIT: In the last half of this video the gentlemen shows what he believes is a Triac based fan speed controller. If ceiling fans use PSC motors and Triac speed controllers then it would seem that a Triac based thermostat and PSC pump would be able to work together. I have set the three speed selector to the highest setting so the minimum speed from the thermostat is less likely to be below the pumps starting torque/speed. So far, no black smoke from the motor so the experiment continues.


texts: How do I power a device with a 4-directional 4-pin connector? I have an idea and I would like you to point out what's wrong with it

texts:
Let's say I have a matrix of square 12.7 mm cells. Every cell is a connector to which an independent little piece ("little piece" is a building block) may be connected. Actually, it's a little puzzle/sandbox game (a hobby project) where you have to build a circuit out of small building blocks like wires, logic gates, sensors and so on.

Every little piece has 4 contacts connected to it: +5V, CLK, RST, GND. Originally I wanted to make 4 rings: the inner is RST, then CLK, then +5V, then GND.

I'm planning to make the little pieces as PCBs at some cheap prototyping website or just at home. Making a PCB for the connector board is an overkill and will be quite expensive. I could buy some perfboard on Aliexpress and solder everything but this would be too prototypish, IMO. On the other hand, connecting the 4 rings or similarly put pin sockets in some plastic container with holes is very complicated, so I decided to switch things up a bit.

Now I have just 4 pins. Pins A, D are both =RST, and pins B and C always have different values: CLK and ~CLK. Therefore, the little pieces can go either way, and that's important. The little things would identify which two pins are complementary CLKs and which are RST using an XOR gate. The power is collected into a capacitor through a bridge rectifier in case both CLK and ~CLK go low or if the piece needs extra current.

simulate this circuit – Schematic created using CircuitLab

This is the internals of a "little piece":

simulate this circuit

My questions are:

1) Are there easier ways to do this? Are there readily available sockets or designs for my purpose?

2) What obstacles and problems will I encounter actually designing everything (apart from size constraints, although I can make a little piece occupy several cells)?

3) How to choose the right R and C values for a given frequency?


texts: Did anybody ever measure the watt use (startup, idle/low/intense use, stalling) of a 18 V power tool?

texts:
I am curious about the actual power in watt a 18 V power tool like an angle grinder or router actually use over time (Makita, DeWalt, Bosch, etc.).

I have seen people running such tools not with a battery but with a benchtop power supply. So in theory they could measure the watt use for startup and during idle-, low- and high-power use and even stalling.

I would love to see such watt profiles (little charts) for a router.

I googled my little heart out to find this kind of data with no success. Does anybody know if/where I could get this data?


texts: Can this ATMega328-PU ATMEL microchip be used instead of MCP3008

texts:
I wanted to follow this tutorial as a first project.

I've got all the parts I need, but I could not purchase the chip that was linked in the article.

So I found another chip that sound similar (To a complete beginner) .

My question is, will I be able to use the chip I brought, in place of the one suggested in the article or am I trying something thats impossible?


texts: How do you use a current to voltage converter to probe a specific part of a circuit?

texts:
I want to probe a part of this circuit that I have using a current to voltage converter. Problem is, I don't know if I'm doing it properly. Most current to voltage converters I've seen take an input current directly from the source load, but I haven't seen one that takes input current from a junction.

Here's the part which I wanted to probe (Ids) - https://i.imgur.com/9pjdYKI.jpg  And here's the attempt I've made to probe it using a current to voltage converter - https://i.imgur.com/gKrKqoY.jpg

I have a gut feeling that I'm doing it wrong.

P.S. not an engineering student.


texts: What difference does the clock make in synchronous vs asynchronous communication?

texts: I am new to embedded programming and have very little knowledge in how digital/electronic system works, but I have been given a task to bring up  USART communication between two chips. For that, I have started learning from the basics of serial communication etc etc. What I don't understand in serial protocol is that what is the difference between synchronous and asynchronous communication? Let us say I have two devices d1 and d2. They both are aware of their baud rates. d1 sends data at a baudrate of 9600 and d2 receives data at the same rate. Then my question is, how the clock plays role in synchronous communication? Means with baud-rate I think we have all the information of the communication channel. With this confusion I am not able to clearly understand the exact difference between synchronous and a synchronous communication.


texts:
I have decided that I would like to design a DIY DSO Oscilloscope, the idea has been in my mind for a while, I just haven't had the time to look into it, I am surprised as there doesn't seem to be that much projects for digital storage oscilloscopes out there and if they are, they are often not well documented! I know it may take a while to build something accurate but I have the time.

Is the triggering for a DSO to be done in the digital domain or the analog front end?


texts: Best way to flatten PCB again after cutting with utility knife

texts:
I cut my presensitized PCBs down to size with rulers and a utility knife when I need a custom PCB.

I noticed every time I cut one, the cut is always clean, but the copper on the board at the same edge as the cut I made is uneven. In fact it curls up and that makes PCB development difficult because the board isn't 100% flat to the glass when exposing it.

Here's a picture illustrating what I am talking about:

Currently, I use sandpaper to try to sand the excess copper so the board is as flat as possible but it wears the sandpaper fast.

Sometimes I use the utility knife at a 45 degree angle on the edge. While this often removes the curl, it also removes at least a good 30mils from the copper.

What's the best way to remove the curl without wasting a lot of PCB material or wasting any other materials? I don't think sandpaper is up to the task.


texts: Why are capacitors used in battery chargers

texts:
I'm looking at this IC: link here

And noticed under "typical application" a simple circuit diagram. What is the purpose of the capacitor that connects Vin directly to ground?

How does this affect the current/voltage being applied to vdd and the LED?

I have virtually no understanding of how/why capacitors are used in general. My very limited electronics experience has just about covered resistors. Would appreciate small words, and possibly somewhere to get further information (free online courses?)


texts:
I have a Zigbee Pro with Arduino whose range is 2 miles as per specifications. But practically its maximum range is only 200 meters. I am using XCTU software. Is there any setting/configuration in XCTU to increase range?
If not possible to increase range, is there any module which is compatible with Arduino?


texts:
I have a geometry as follows:

This is a hollow metallic cylinder with a small metallic rod inside. The rod is connected to the bottom of the cylinder but is a bit shorter than the outer cylinder. It is some type of coaxial cavity. The larger radius is rc, the length is l, the rod has radius rr and length l-d. What I want to do now is to solve the wave equation in this domain. I don't know whether it is possible to analytically do that, but I read in an IEEE paper that it should work.

To solve my problem, I first took the scalar Helmholtz equation
$$
\frac{1}{\varrho} \, \frac{\partial}{\partial \varrho} \left( \varrho \, \frac{\partial \psi}{\partial \varrho} \right)
+ \frac{1}{\varrho^2}\,\frac{\partial^2 \psi}{\partial \varphi^2} + \frac{\partial^2\psi}{\partial z^2} + k^2\,\psi = 0
$$
and tried it to separate as follows:
$$
\psi = R(\varrho) \, \Phi(\varphi) \, Z(z)
$$
I am now interested on the z component of the electric field. The boundary conditions are: the z component must vanish at the outer wall of the cylinder from z = 0 to z = l, and it must also vanish at the inner wall from z = 0 to z = l-d.
Using above separation, one finds the three ODEs
$$
Z'' + k_z^2\,Z = 0
$$
and
$$
\Phi'' + n^2\,\Phi = 0
$$
and
$$
\varrho^2\,R'' + \varrho\,R' + R \left( \varrho^2\,a^2 - n^2 \right) = 0
$$
and I do know that I need the Bessel function of the first kind to solve the last ODE. However, I don't know what to do with the boundary conditions because I have two different ranges for z, where psi must vanish. How can I proceed?


texts: How do I combine multiple common-collector stages without circuit loading or distortion?

texts:
I'm learning about how to combine common-collector stages for an audio amplification project, and clearly there is something I don't understand.  The circuit shown combines 5 stages of emitter followers.  I've designed stage each to have a DC bias point of one diode drop above 0.5Vcc.  Each stage has an output impedance far less than the subsequent stage's input impedance (about 1/20).  Unfortunately, it doesn't work.  The output voltage (before the output capacitor) rises to about 16.7 volts but refuses to go below 9.55 volts, making a horribly distorted output signal.
If the stages were numbered 1-5 from left to right, here are the impedances I calculated:
Stage 1: Rin = 12.5k, Rout = 125
Stage 2: Rin = 2.5k, Rout = 25
Stage 3: Rin = 500, Rout = 5
Stage 4: Rin = 100, Rout = 1
Stage 5: Rin = 20, Rout = 0.2
I used a 10v amplitude (20v p-p) input signal at 1 kHz.
I set the input capacitor to 2 Hz and the output capacitor to 20 Hz to act as a 20Hz. high-pass.
I know there are other solutions better-suited to these needs such as a Darlington, cascode, push-pull, etc.  I'm not interested in other ideas, but merely seeking to understand how CC stages can be coupled together.  Here's the question:
How do I design multiple CC stages to follow one another so that there is no distortion?
As for design specs, Vcc is 24v and I'm hoping to be able to drive an 8ohm speaker at something around 0.5 to 1 watt from 20Hz to 20kHz.


texts:
I have a question about the difference between transceiver modules and transceiver ICs.

I want to integrate a 2.4GHz transceiver IC - nRF24L01+ onto a PCB instead of using the NRF 24l01+ module.

What are the steps I have to take or components I have to add to get it to work?

Do I have to add an antenna like the module version has to the PCB?


texts: Using oscilloscope for measuring AC mains from an inverter?

texts:
I've read the answers from a similar question but didn't find it to answer my question.

I'm trying to make a phase control circuit to control an AC motor, and would like to monitor the output.

The input can sometimes be normal mains AC, but other times from a battery/230VAC inverter. The inverter seems to have two opposing hot lines (e.g. -115VAC + +115VAC = 230VAC) rather than neutral/hot wire.

Can I measure directly?

I've got a DSO1054Z, which has a maximum input voltage of "CAT I 300 Vrms, CAT II 100 Vrms, transient overvoltage 1000 Vpk With RP2200 10:1 probe: CAT II 300 Vrms".

I understand from this article that CAT II would be recommended for a standard wall outlet.

The oscilloscope is only rated at 100 Vrms CAT II.

So I assume the answer is: no

Can I measure through a voltage divider?

I'm considering using this circuit to reduce the voltage (from 230 VAC to 2.27 VAC). Since there are two hot wires, the voltage divider has to go in both directions.
Also, the high resistance should reduce the short-circuit current to about 0.23mA, greatly reducing the outcome of a worst-case scenario.

I'm assuming the answer is: yes, the probe will now be safe.

simulate this circuit – Schematic created using CircuitLab

Notes:

I'm thinking to use the differential measurement on the oscilloscope to add the two signals.


texts: What expression can I use in matlab to remove the negative component of a sine wave so it can look like the picture below?

texts: The image shows a sine wave is obtained using MATLAB. I would like to know what they possibly multiplied or what expression could one use in MATLABto get this wave instead of a complete sine wave.


texts: What is the max current of this contactor? CDC65-24

texts:
I'm attempting to power a 50kW DC Fast Charger with 3 phase 277/480V. It needs ~55kW which is 66A per phase. I'm trying to find a contactor. This one is CDC65-24. It is a 3 pole, 100A continuous. However, when you look at the technical information, it says at 3 phase 400-480V it is rated at 50HP (horsepower). This is much less than 100A per phase.

50HP = 37kW
37kW/277V/3poles = 44.5A

What rating should I go off? Does the HP rating only apply to motors?


texts:
It was one of my first experiments related to embedded systems.I was following this document : http://groups.csail.mit.edu/lbr/stack/pic/pic-prog-assembly.pdf
Problem emerged at Tutorial 6.I was trying to blink the led at different pace when pressed button.First, I took what tutorial give as an example word by word ,however, it didn't work.When not pressing it sometimes blinks slower sometimes faster, when I push button it blinks in an expected frequency.Then I changed the code to the program below for simplification:

LIST p=16F84A
INCLUDE "p16f84a.inc"

RES_VECT  CODE    0x0000
GOTO    START

MAIN_PROG CODE

TIME equ 0x0f
Delay

COUNT1 equ 0x0c
COUNT2 equ 0x0d
COUNT3 equ 0x0e

    movlw   0xFF
    movwf   COUNT1
LOOP1

    movlw   0xFF
    movwf   COUNT2
LOOP2

    movfw   TIME
    movwf   COUNT3
LOOP3
    decfsz   COUNT3,1
    goto LOOP3

    decfsz   COUNT2,1
    goto LOOP2

    decfsz   COUNT1,1
    goto LOOP1

    return

START

    bsf     STATUS,5
    movlw   b'00011111'
    movwf   TRISA
    movlw   0x00
    movwf   TRISB
    bcf     STATUS,5
    movlw   0x00
    movwf   PORTB

MAIN_LOOP

    movlw   0x01
    btfss   PORTA,0
    movlw   0x14
    movwf   TIME

    bsf     PORTB,3
    call    Delay
    bcf     PORTB,3
    call    Delay

    goto MAIN_LOOP

END

Same thing happened. While it flashed irregularly without pressing the button, when I pressed button at RA0 it blinked faster. I want first phase to be always slow. Where is the problem ? Is the problem in circuit, in software, or in PIC itself. Given physical conditions, as if btfss doesn't work properly either because the switch is problematic or because PIC is burnt. It is more likely that I am failure rather than the hardware is. Maybe there is a logical error in software in spite of similar program flow being expressed with different codes.Could oscillator not have been set up properly ? I had difficulty to set up an RC oscillator. When I add its R it works normal(or I think so). But after adding a capacitor and connecting its other terminal to negative voltage the led always shines.Can you say exactly where the issue lies? What's going on the background?

Additional Information :

At first, I used RBO/INT to do bit test with the switch. But the INT part was suspicious to me. Then I changed it to RA0.(which is what is asked in the question) The result didn't change.

Additional Information 2 :
Configuration bits ->
__CONFIG _FOSC_EXTRC & _WDTE_OFF & _PWRTE_OFF & _CP_OFF

Additional Information 3 :
It turns out that there is no any unintentional reset.Problem remains unsolved.


texts: What is the conduction angle on the following?

texts:
i have found the problem and i am confused with the solution provided.
As far as i know conduction angle is given by the equation
ϕ=π−(2θ)
where ϕ is conduction angle, θ is where conduction starts.

The question and circuit diagram is shown in image.
Using the above equation the conduction angle is just 60, but here in the solution it said 120. Is it wrong or am i misunderstood?


texts: In discrete memoryless channels what is meant by output probabilities?

texts:
In my book it is mentioned that P[Y]= P(X)* P(Y/X) Where P[Y] is the output probability matrix, P(X)=input probability matrix, P(Y/X)= channel matrix. I understand the physical significance of input probabilities and channel matrix probabilities because any input X can be generated which inturn determines the probabilities of generation of Y. But what do we mean by output probabilities?
My question: is there any physical significance of output probabilities without defining which input is producing them?


texts: NPN audio amplification, what is the difference between outputing from the collector or emitter

texts:
I am working on a simple NPN transistor audio amplifier.  I have found several diagrams which show how to build a NPN amplifier.  These diagrams differ in that some show the output coming from the collector side of the transistor and some from the emitter.  Here is a good diagram showing both:

In this diagram, there are two stages of amplification, each with a single NPN transistor.  the second stage NPN is connected to the Emitter of the first, however the final output is connected to the Collector of the second stage's NPN transistor.  Does it matter which side the output is acquired from?  What are the differences and different applications?


texts: Link between phase noise and linewidth for a oscillator?

texts:
I was googling for a formula to transform the dbc/Hz value given in data sheets for VNA, spectrum analyzers and VCO is often given in dBc/Hz with offset. Now looking up research papers about future oscillator devices based on new nanophysical effects, the physical oscillator is often measured with a spectrum analyzer and the linewidth (f/delta_f) is given)

Is there any calculable link between both measures to see how well such devices compare to state of the art oscillators? Only very seldom a dBc/Hz value is given in research papers, as the measure makes less sense without a given standard carrier frequency and offset. The linewidth is more a physical than a technical measure and makes different published devices better to compare. Is this reasoning correct or is it also that to define the dBc/Hz measure you need a very accurate spectrum analyzer while the linewidth can be deduced basically from a plotted graph?

Is there a way to transform the dBc/Hz of a standard VNA @ 100 MHz being around 110-120 to a linewidth. I need a value here or order of magnitude. I also read here, the dbc/Hz of a function/waveform generator is often better than that of a spectrum analyzer, so determining it this way is also no option?

Thanks for your advise and time


texts: Hard drive place in Processor Memory map

texts:
As we know that every Processor/Microcontroller has a memory map which is divided into different regions. on each region a peripheral is mapped like RAM etc. following is the memory map of general x86 processor.

As one can see there is memory range for RAM, DMA,  PCI etc. My question is Where is Hard drive mounted in this memory map??? and how is it accessed?


texts:
I'm stuck on the part b of this tutorial question. I thought I understood the theory, but I can't get the right answer.

For part a I got: Af(jw) = 10^3 * jw / (3jw + 200)

From my understanding, the formula I should use for part b is:

Af = s*Am / (s + wL), where Am is the mid-high frequency gain and wL is the lower 3dB frequency.

However this gives me an Am of 10^3 and a wL of 200, which doesn't match the answers.

If anyone could show me where I've gone wrong I'd be extremely grateful.

Edit: I've realized part of my mistake. I'm looking for the NEW Am and wL, meaning the values for when I include feedback. According to my notes I should find the original values from A(s) using the formula: A(s) = sAm / (s + wL).
So this gives me Am = 10^3 and wL = 200.

Now I need to find the new Am using this formula:
Midband gain = Am / (1 + Am*B).
This gives me 333.3, which is the correct answer.

Next formula I am supposed to use: wfL = wL / (1 + AmB), where wfL is the new value for wL now that feedback is included. I used 200 as my value for wL and 0.002 as my value for B. I tried both 10^3 and 333.3 as values for Am, giving me wfL = 66.7 and wfL = 120. I still cannot get the right answer for wfL; the answer is supposed to be 10.61Hz.


texts: What is the technical term for a hardware message authentication code generator IC?

texts:
I am looking for a way to identify devices I build.
Basically I am looking for a chip to which I can write a non-recoverable secret and that uses this secret to then "sign" messages I send to it and returns the signed message to me.
Cryptographically, I imagine the chip would generate a message authentication code (MAC).
I am not particular regarding the algorithm used. Coming from a programming background, a HMAC implementation or concatenated SHA3 hashing are my naive ideas. That said, I do not need anything bullet proof. Just something to make forging non-trivial.
While we are at it, are there any cheap chinese solutions?


texts: Why do PC bus frequencies often end in multiples of 33MHz?

texts: It seems like there are a lot of frequencies for different system buses that end in 33 or 66MHz. Is there a particular reason for this?


texts: Why should half-bridge driver have resistance in series with VCC?

texts:
I am using the three of the RT9624A half bridge driver as part of a 3-phase motor control circuit. Everything was working well in testing until I got to about 80% duty cycle and one of the drivers started getting hot. Probing it found that the low-side output had gotten internally shorted to VDD.

I looked back at the datasheet of the RT9624A and noticed that all the example schematics include a resistor in series with the VCC, apparently limiting current into the IC. Why is this necessary and is it always necessary? Could this have something to do with my failure? The datasheet does not seem to explain. I also notice that the datasheet warns that too small a bootstrap capacitance can lead to overcharging and damage the chip. They give a minimum of 0.1uF, and recommend 1.0uF. I have 0.47uF, which seems fine to me, but could I need a higher value?

This is my circuit, with GHA and GLA directly wired to 51nC total gate charge N-type mosfets. At 12V, this makes 4.25nF, and with a PWM frequency of 20kHz, switching losses should be less than 100mW. The part handles up to 800mW, so that shouldn't be the issue.

Edit: Although I haven't confirmed anything, I have several action items to prevent similar issues in the future.

Adding gate resistors, and also fattening and shortening the gate traces to limit potential harm from inductance loops.
Similarly reducing inductance of the SW/PHASE trace, and adding a schottky diode on the SW/PHASE node to prevent damage from negative voltage spikes. Currently my mosfet's body diode will be limiting those spikes to at worst -1.1V, but the RT9624A can only handle voltages below -0.3 for at most 100ns, so extra protection will help. If anything, based on my probing my circuit, I think it was low voltage produced by motor back EMF that might have caused the damage.

This different datasheet says "Pulling HO more than –0.3 V below HS can activate parasitic transistors resulting in excessive current flow from the HB supply, possibly resulting in damage to the IC. The same relationship is true with LO and VSS. If necessary, a Schottky diode can be placed externally between HO and HS or LO and GND to protect the IC from this type of transient."

The IR2301 specifically notes it is "Tolerant to negative transient voltage dV/dt immune" and says the VS/SW/PHASE pin can go as low as the bootstrapped voltage -25V, which in my case would be something like -8V. When dealing with a BLDC/3-phase controller, this is probably an additional feature that could be very useful. (and saved me this problem).

This guide gives the motivation behind using a series resistor to not only bypass noise but also decouple the chip from the rest of the circuit. Accordingly, I will also be adding in the 2.2Ohm example resistance from the datasheet in between the battery power and VCC. I do find it interesting, though, that in looking at more than 10 other half bridge datasheets, not a single other included a series resistor on VCC.


texts: Holding Current and Latching Current dilemma

texts:
I have gone through lots of resources looking up for holding current and latching current. All I can get is:

Latching current is the minimum current that is required to maintain the "on" state of the SCR.

Holding current is the minimum current below which the SCR turns off.

Considering the two transistor model of the SCR, if I feed the gate with very little current, this current induces a regeneration of current within SCR. Once the Anode to Cathode current reaches latching current after this regenerative process, the gate current can be cut-off. The SCR maintains it on state.
Now, in order to turn-off the SCR, I have to bring the Anode to Cathode current below holding current.

simulate this circuit – Schematic created using CircuitLab
My questions are:

Why does SCR need such high Latching current to keep it on? My understanding about the regenerative process makes me think even a tiny amount of current would suffice to turn the SCR on.

Why are Latching current and Holding current different? Why can't SCR just switch on once A-C current reaches Latching current and turn off if the A-C current is less than latching current? Or, with respect to holding current, why can't SCR just switch on once A-C current reaches holding current and turn off if the A-C current is less than holding current?


texts:
With a lot of advancement in solid state electronics and signal manipulation, isn't it easier to simply take high amplitude signals with frequencies near 1 MHz and multiply the signals using diodes and frequency filters(LC/RLC) than to use a magnetron?

Since in frequency multiplication the amplitude is halved, we can take much higher amplitudes for the low original frequencies which is easier to do than amplifying a very high frequency signals.


texts: What are some tips to routing a one sided PCB?

texts:
I'm having trouble routing this PCB in Eagle 7.1:

I have tried the following:

Autorouting - it could not complete
Moving components around
Manually routing - I always ended up getting stuck
Adding a ground plane - autorouter still failed.

The restrictions I have placed are 0.2mm wires with 0.45mm gap between pad-to-wire (I don't want wires running inside the SV1, but the other IC's are okay.), and 0.2mm wire-to-wire gap.

I understand the SMD led and resistor are on the bottom of the board, along with the rest of the wires.

What are some things I can do to route this board without having to route wires inside SV1?

Related question: If the autorouter can't get a 100% completion, is the chance of manual routing pretty much zero?


texts:
I am using 100k NTC from Murata (SMD, 0603 package) for temperature Measurement. I will drive NTC (MCU_Output) only when i need to measure the temperature. Which of the following options is better?

simulate this circuit – Schematic created using CircuitLab

Sink and source current is about 10 mA. I am looking at best interface in terms of quiescent current and impedance (I need more help here).

I have added the ADC section impedance details.


texts: Designing a cable for bidirectional communication between 2 iphones via TRRS (headphone jack)

texts:
I'm trying to design a cable that allows bidirectional communication between 2 iPhones,  connecting into their TRRS jacks.

I've made the cable but it is temperamental at best -- can anyone help me understand why it is misbehaving, and help me towards a working design?

Obviously I would have to combine left and right speaker channels.

Main problem is that the lineout level is in the range of volts wheres the microphone level is in the range of millivolts, i.e. much lower.

I used this question:
line-level audio into an iPhone headset jack?
 to get the basic circuit diagram of what is needed.

Here is a picture of my effort:

Here is a link in case I'm not allowed to post pictures, being a new member: http://cl.ly/FU2p

Now this cable is infuriating.

Yesterday I tested it between ( if I remember correctly ) and iPhone 4 and an iPod Touch ( latest generation ),  and could successfully transmit sound from either device and pick it up on the other.

but working on different combinations of devices I get either unidirectional performance or nothing.

frequently the device doesn't even think that an external microphone is present; it continues to receive audio from its inbuilt microphone.   I guess as if a stereo headphone jack was inserted in the TRRS.

I'm wondering whether my resistor values are somehow close to some borderline;  maybe the impedance levels  are different on different Apple devices,  and sometimes it is failing a check of ' is there a microphone present? '

also added to this, typical headset units also have an on / off switch; I don't know how this is implemented -- maybe it shorts the microphone momentarily straight to the ground,  and the iPhone's circuitry catches this.

also not sure whether I should be connecting across the ground lines.   as you can see my breadboard has a white wire that does this ( this is the only difference between the breadboard configuration and the circuit diagram above )

breadboard Electrical layout is:

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by the way.

can anyone shed some light upon the problem or improve upon the design?


texts:
I have to interface a specific motor, it has a  weird driving board, I was in contact with the technical team from the manufacturer, and they told me that I have to send a -24V on a pin to allow it to turn. I have a +24V power supply, several step down modules, on 5V and 3.3V for my microcontrollers and other things.So here is my question:
What is the simple way to produce a -24V voltage source from a  24V or lower one?
I have searched a lot, but found nothing...
My first idea was an inverting opamp, but if I were able to power it down to -24v then I would'nt need it at all :)

Any Ideas are welcome.

My ideas are now oriented to step down ICs able to output negative voltage from a positive one... I guess something around -18V should be enough to be understood by the driver.


texts:
In this answer, there is a schematic showing the internals of a 7805 voltage regulator, reproduced below:

First of all, what is the sense pin in the first place? Every 7805 I've ever seen had three pins, Vin, Vout, and ground. Is it internally connected to Vout?

But the main question I want to ask is this: What's with all the shorted-out resistors on that sense line? Is there a reason they're there? Surely something as common as the 7805 doesn't go through individual laser trimming on each die, does it?


texts: Serial communication protocols used in spacecrafts and airplanes

texts:
I always see that CAN bus is used in automobiles for communication between nodes and for on board diagnostics and basically for the overall functioning of vehicle. What are the similar serial communication protocols used in airplanes and spacecrafts? I googled a lot but could not arrive at an exact answer.
Thank you


texts: I started coding for Arduino very recently. And these bugs in the code are killing me. As there is no hardware debugger in the Arduino, serial.print() is my only resort. What are the methods/practices you implement to debug Arduino code?