texts: instrumentation of V-divider dual-thermistor circuit

texts:
here's the circuit - voltage divider with 2 matched thermistors ("matched" means close enough that the measured temperatures when thermistors are right next to each other comes close enough for my needs)

(edited diagram to show series 1K resistor from V2 to DIO1, and V3 measurement)

3.3V--------+------------+
            |            |
            \            \
            T1           T2
            \            \              __
            T1           T2            /V3\
            \            \       +-----\__/------+
            T1           T2      |               |
            |            |       |               |
Vvd --->    o v1      v2 o-------+---/\/\/\/\/\--+--{XBee DIO1 pin}
            |            |              1k ohm
            \            \
            /            /
            \            \
            / 10K        / 10K
            \            \
            /            /
            |            |
GND---------o------------o

In the above circuit exactly as shown, v1 and v2 both measure at 1.31V at common reference T. So far, so good

However, when I connect the o at v1 to XBee pin A and the o at v1 to XBee pin B (XBee shares common 3.3V and GND, power-supply has enough power to power it all) then v1 and v2 are 1.50V and 1.57V respectively - different enough that measurements of T1 and T2 are useless to me.

(the thermistors are right next to each other so that I can validate the temperatures are the still measuring the same when on XBee)

It seems clear to me that connecting the transmitter to v1 and v2 disturbs the system (1.31V becomes 1.50 V and 1.57 V) What's less clear is why it doesn't affect v1 and v2 the same way.

Biggest question I have: is this one of those cases where an op amp should be used to preserve v1 and v2 at their "real" values and prevent the transmitter/instrument from messing with the values?

Edits:
V4 measures 5.5mV, so current is about 5.5 microamps.

V across T2 is about 1.8 V and T2 has R about 16K ohm at these conditions so current through T2 is about 0.1 milliamps.

current to DIO1 is about 1/20th of what goes through T2 - doesn't explain the 0.2V difference as far as I can see.what am I missing?


texts: ratio of zero-pole in a lead compensator

texts:
I have a transfer function of a lead compensator designed for double integrator in the form
$$G(s)=\frac{2025}{s^2}\frac{s/39+1}{s/139+1}$$
The zero frequency is 39 rad/s and pole is 139 rad/s. I just did few simulation and found that when the pole frequency is around 100 fz, the overshoots are around 26%. Whereas for the above TF, overshoot is around 47%, with no advantages over rise time, settling time or BW. Any apparent advantages of this zero/pole ratio of a lead compensator?


texts: Bandpass filter to isolate musical note "A2"

texts:
I would like to design a bandpass filter to isolate the musical note A2 ( 110Hz  ) from its neighboring notes at a precision of a half-step. This means that G2# = 103.83Hz and A2# = 116.54Hz should be in the stop band.

In the ideal case, 110Hz would be at 0 gain. G2# and A2# would be silent (infinite negative gain?), and there would be a smooth roll-off from the A2 to each neighboring note.

How can I select my window type, determine how many coefficients are necessary, and calculate those coefficients?

I took a few EE courses back in college, but I am far from an electrical engineer, so please ask for clarification where it is necessary.

References:

Note frequencies
Filter types


texts: Using reset controllers with modern microcontrollers

texts: Are reset controllers necessary for modern microcontrollers, such as the LPC2138 or 9S12XD256? Most ARM processors I have seen have their own brown-out detectors and reset properly, and I don't see reset controllers used with them. However, I've needed to use them on a 9S12-series part in the past, so I'm debating whether or not to use them on a 9S12X based descendant.


texts:
I am using a USB D/A converter to drive a high-voltage op-amp with a signal between 0 and 3V at 10 kHz. The D/A I am using is capable of outputting between -10 and +10 and unfortunately seems to always output a 1 ms long glitch of -10.7V around 20-30 ms before the signal generation begins.

Although I am trying to get the vendor to supply a software fix, I want a hardware solution to ensure the output can't drop below 0V even in the event of a software glitch.

I am aware of diode clamping circuits but the lowest voltage Schottky I can find is 220 mV with the exception of a very strange diode that seems to have a built-in FET (SM74611), which I'm guessing is not meant for this application.

I would like to keep the output above -100 mV and preferably above -10 mV. Are there any other "passive" solutions I'm overlooking that could accomplish this or do I have to go with something active like an op-amp?

If active is the only way, can someone suggest a suitable circuit?


texts: Is there an easy way to measure the thickness of the foil on FR-4

texts:
Sometimes I find myself trying to guess or recollect what foil thickness was specified for the given piece of FR-4. Shops do not always readily give it - and it appeared that what they write is not always reliable. And sometimes I, regretfully, simply could not remember what was specified.

I do not care about much precision, but it would be good to be able to roughly distinguish between 70, 35 and 18 um foils (to select more suitable for intended traces width). I have few ideas in mind but none deserves to be called "simple"...


texts: FPGA development kit for beginners , Spartan6 or Spartan3?

texts:
I intend to purchase an FPGA, development kit and I have looked at both the Xilinx and Digilent website. Both seem to have good development kits.

I have never worked with FPGA's before but have some experience working with microcontrollers.

I see that the entry level Spartan 6 boards are on a par in terms of price with the Spartan 3A/AN boards. I've not compared the features.

From your experience what development kit would you suggest Spartan3A/AN or Spartan6?


texts: GDS, OASIS, etc. vs LEF/DEF: which is better?

texts:
I have two questions here. By the way, I have searched about the differences but I wanna know more. So,

Can LEF/DEF format describe everything that GDS, OASIS, etc. formats, can? What can I do with LEF without the DEF, and DEF without LEF? Why would I use one of them instead of both?
I've heard that now LEF/DEF is becoming popular over the above mentioned formats. So what's the main reason for this? I mean, LEF/DEF is in plain, ASCII format, and GDS is binary. Isn't having binary "safer"?


texts: Is it a bad idea to switch from using a quartz oscillator for my timing circuit to using a MEMS oscillator?

texts:
I've read MEMS oscillators offer improved performance including phase jitter less than 500fs and frequency stability down to +-0.1ppm. It's difficult to switch from quartz because it simply works and redesign is a bit of a pain, but wondering if anyone has made the switch and what their experience was.

I have a heart rate monitor application circuit. It's powered with a 2.5V coin cell battery and I need an oscillator as my RTC driving my MCU at a 32kHz frequency. I came across a SiTime product SIT1566 with +-5ppm frequency stability, which is key for me. The power consumption is 4.5uA, which is within my power budget. My other option is to use an AVX quartz oscillator that can achieve similar performance. It would be my first time playing with a MEMS oscillator. Any ideas on what would be the best choice from your experience?

Here's the datasheet for SIT1566: http://www.sitime.com/products/32-khz-temperature-compensated-oscillators-tcxo/sit1566

Here's the AVX quartz product datasheet: http://www.mouser.com/ds/2/40/kt3225t_e-838149.pdf


texts: Accidentally punctured a small li-ion battery, any medical harm from the smell?

texts:
I accidentally made a small puncture in an old li-ion battery while replacing it in my phone (it's stuck on pretty tightly with adhesive).  A couple of sparks, but no flames.  It has been safely disposed of.

The damaged battery emitted a sweet smell after it was punctured, so I immediately went outside to complete the removal.  I feel fine and everything, I just want to be sure; is there any potential harm that could come from briefly inhaling the fumes?


texts: Bandwidth of an oscilloscope with differential probe

texts:
I am planning to buy Rigol MSO5204 scope with a bandwidth of 200 MHz. I need to measure the timing difference between 2 (or more) signals of up to +/- 7 ns. Since this scope has 8 GS/s sampling rate, I figured it will suffice my needs. Also, a cheaper model in the line Rigol MSO5074 offers the same features but, with a bandwidth of 70 MHz only. My signal frequencies are less than 10 MHz. The decrease in the bandwidth will increase the Rise time (from 1.75 ns to 5 ns) of the scope. My questions are:

From experience, can anyone tell if 7 ns timing difference between signals can be captured if the rise time of the scope is 5 ns vs 1.75 ns?
Is it worth spending extra money for a better rise time?
I will be using a differential probe and most of the differential probes that I came across are 25-50 MHz bandwidth range. Could adding a differential probe with BW of 25 MHz affect the above timing measurements given that the signal frequencies are going to be less than 10 MHz?


texts: How do I test board components when check pins are available?

texts:
edit: The expected values and higher resolution images are linked below. Higher Res Board Images Acceptable Values
I am a novice at board repair. I am repairing an instrument in a research lab where I conduct environmental chemistry research. The instrument uses combustion and spectroscopy to analyze dissolved organic carbon in a liquid sample.
Unfortunately, the instrument is experiencing numerous issues. One possible source of these issues is  the board which controls the spectroscopy process. The board is built with board check pins installed, and to confirm the functioning of the board I must use a multi-meter to test the voltage at these pins while powered.
Before I dive in, and likely break something, I am hoping someone with any experience in this could provide pointers and guidance.

For each board check pin I was given an acceptable voltage value and instructions to test the pins while the power in on. I do have a basic multimeter.
What setting do I use on the multimeter? Are boards like this AC or are they converted to DC?

Any advice will be helpful.


texts:
We are unable to generate a sine signal properly using a MC68HC908GP32 microcontroller. PWM description begins in page 349. Clock frequency is 2.4MHz, while we have used 7 kHz PWM by using the prescaler and setting the timer modulo to 350 as follows:

T1SC = 0x60;    // Prescaler: Div entre 64
//Counter modulo = 0x015E = 350
T1MODH = 0x01;   // High
T1MODL = 0x5E;   // Low

The PWM output is filter by the following RLC filter, and then DC is removed using a series 1uF cap. The cutoff frequency is way below PWM's 7kHz.

First, we have tried using a LUT, which samples were generated using this site (100 samples, amplitude = 250). This comprises a single period.

 int seno[100]={ 125, 133, 141, 148, 156, 164, 171, 178, 185, 192, 198, 205, 211, 216, 221, 226, 231, 235, 238, 241, 244, 246, 248, 249, 250, 250, 250, 249, 248, 246, 244, 241, 238, 235, 231, 226, 221, 216, 211, 205, 198, 192, 185, 178, 171, 164, 156, 148, 141, 133, 125, 117, 109, 102, 94, 86, 79, 72, 65, 58, 52, 45, 39, 34, 29, 24, 19, 15, 12, 9, 6, 4, 2, 1, 0, 0, 0, 1, 2, 4, 6, 9, 12, 15, 19, 24, 29, 34, 39, 45, 52, 58, 65, 72, 79, 86, 94, 102, 109, 117};

The width of the following pulse is computed every PWM cycle:

interrupt 4 void rsi_t1ch0 (void)
{
    //-- disable interruption flag
    T1SC0&=(~0x80);
    //-- pwm to '0'
    PTB&=0xFD;

    //some sensor measures are done here.... 100 out of the 350 cycles are left for this
}
/************************************************************/
/* TIM1 overflow rutine                                     */
/************************************************************/
interrupt 6 void rsi_ov1 (void)
{

    T1SC&=(~0x80);
    //-- set PWM to 1
    PTB|=0x02;
    T1CH0H = ((seno[fase])>>8);   // high bits
    T1CH0L = (seno[fase])&0xFF;   // low bits
    fase+=1;
    if (fase >= 99)
      fase=0;
}

void main(void)
{
float temp;
    int i;

    CONFIG1|=0x01;
    DDRB=0xFF;      //-- Port B is set as output
    PTB=0x00;
    //Timer setup
    T1SC = 0x60;    // Prescaler: Div by 64
    T1MODH = 0x01;   //Counter modulo
    T1MODL = 0x5E;
    T1SC0 = 0x50;  //Comparator setup
    //-- Initial width
    T1CH0H = 0x00;
    T1CH0L = 0x53;

    EnableInterrupts;
    T1SC&=~(0x20); //Run timer forever
    for(;;);
}

When pluggin it into the scope, we get the following signal. We are unable to avoid that strange peak near the minimum.

When zooming around that peak, we can see how the PWM output (up) is in fact incorrect.

So, after messing around for a while and being unable to get rid of it, we have tried computing the sine signal in the MCU, instead of hard coding the value for each sample. We have added the following code in the main function, just before all the counter setup:

 for(i=0;i<99;i++) {
     temp=100*(sin(2*3.14159*i/100)+1);
     seno[i]=(int)temp;
 }

But results don't even look like a sinusoid:

After hours struggling with it, we haven't been able to find our mistake. We would appreciate a piece of advice.


texts: Need a simple explanation of a left-right shift register

texts: I'm familiar with basic shift registers. I'm having a hard time understanding the one below. I feel like I'm overthinking it due its complicated appearance. Would it be possible to direct me to a way of approaching in a way that makes it easier to understand?


texts: Whats the reason for triangular carrier PWM

texts: I understand that triangular carrier PWM uses a higher frequency triangular carrier wave to compare with the desired output waveform but I would like to know more about the process. I've also learned and seen the Fourier transform that shows that it lowers harmonics. Is there an easy intuitive reason for how this was discovered? I understand that a sawtooth carrier will do the same thing but doesn't do as good of a job. Is the triangle carrier the best that it gets? Is triangular chosen for the reason of its harmonic limiting nature? Could you use either method for an inverter just adjust respective amplitudes of the different types of carrier? Does anyone know of a derivation of how we figured out that triangular PWM works well? I just want to understand the process a little better fundamentally. Is there a geometric relationship between the triangle wave and the sine wave that's relevant and adds some beauty or is it just what it is?


texts: Circuit to test ICs at home? (74hc04, 74hc08, 74hc32)

texts: I have the above IC and I want to check them before using them. I don't have access to a lab currently and I only have access to the usual stuff (LED, resistors) and a simple ammeter/voltmeter. What can I do to test them? Obviously(?) the below circuit doesn't work.


texts: Bi polar pulse magnetizer controlled by arduino

texts:
Hello,
I am trying to make a bipolar pulse magnetiser based on the pulse magnetizer design on instructables. I attached my circuit design as image. g1 and g2 terminals of the thyristors will be controlled with arduino connected to moc3023 optocoupler. LEDs are for safety, if capacitors are left full, it will discharge itself slowly through LEDs. I want to turn on g1 thyristor and let it induce the magnetic field and 4ms later firing up second capacitor with reverse polarity so that I could reach saturation magnetization from each side. Would my circuit work fine? Would there be any safety risk with this circuit? One thing I forgot to add this schematic is there is a switch on the mains that I turn off when capacitors are full.


texts:
Gyros with an analog interface represent rotational velocity by a varying DC voltage. The range of my gyro woks from -10 V DC to +10 V DC. I need a circuit to convert this range into this range: from 0 v DC to 5 V DC.

Example:

Gyro OUTPUT   -9 v DC      Circuit OUTPUT    0.25 v DC.
Gyro OUTPUT   -8 V DC      Circuit OUTPUT    0.50 v DC
Gyro OUTPUT   -+5 v DC     Circuit OUTPUT    3.75 V DC
Gyro OUTPUT   +10 v DC     Circuit OUTPUT    5.00 V DC

How to do it?


texts:
Trying to understand this circuit. Will this produce a representation similar to example in second image (if U_inf is the sine wave "original") ?

Assuming that, I expect U_DM to look like the "modulated" signal. How would the signal look like at point A and B ?

EDIT:

I'll add that the circuit (HPS modulation board) was tested with the following outputs. Increasing the U_s voltage level changed the signal to 2nd image.


texts: Why a resistor is connected in series with output of IC's?

texts: I have seen a PCB schematic. I saw an oscillator and the output clock is connected in series with a resistor. I want to know the use of this resistor.


texts:
How can you represent negative values using the flash ADC method?

In books and online I have only ever seen positive references for the comparators used in the flash ADC architecture.

For a simple sine wave, how can you represent both its negative values and positive values using the flash ADC method? Or with this method is it not possible


texts: Does the body diode in MOSFET conduct current in backward direction when the MOSFET is switched OFF? If yes, can we build rectifier-bridge using 4 non-driven MOSFETs?


texts: Can I connect a 5 V CAN transceiver to a 3.3 V microcontroller?

texts:
I have a CAN circuit from another project, and I want to reuse it and connect to my microcontroller, however it is a 5V transceiver and my microcontroller is 3.3 V, is it OK to connect TX and RX directly to my microcontroller?

Microcontroller: http://www.st.com/content/ccc/resource/technical/document/datasheet/03/b4/b2/36/4c/72/49/29/DM00071990.pdf/files/DM00071990.pdf/jcr:content/translations/en.DM00071990.pdf

Transceiver: http://ww1.microchip.com/downloads/en/DeviceDoc/20001667G.pdf

The pins I want to use are pin 93 and pin 163.

Microcontroller output:


texts: How to Make DB9 F/F serial RS232 mini gender changer?

texts:
I want to connect My "USB to RS232(Male end)" to my NanoVolt Meter having RS232 male port. To make both communicate i need to make DB9 F/F serial RS232 mini gender changer. Any Circuit or suggestion will be very helpful.

Thank you.


texts: How to connect with and use a USART to USB converter (CP2102 by Silabs)?

texts:
I figured since this is a very specific problem with a hardware device that many on SuperUser might not be familiar with, I would try posting here.

I searched around on the net a bit and found a very useful USART to USB converter bridge. The CP2102 is a programmable device with many settings insofar as the data framing is concerned. As such, a driver for the device must be used to interface and modify these parameters.

On the Silabs website I found this driver for linux (kernel 3.14.4-1 on Arch Linux). The problem is that this driver is just a single C program with zero documentation. An include make file is about as useful considering it has a single line in it that fails (for me) at run-time.

obj-m = cp210x.o
KVERSION = $(shell uname -r)
all:
    make -C /lib/modules/$(KVERSION)/build M=$(PWD) modules
clean:
    make -C /lib/modules/$(KVERSION)/build M=$(PWD) clean

The driver source can be found here.

Where my make error is

make -C /lib/modules/3.14.4-1-ARCH/build M=/home/branden/Desktop/Linux_3.x.x_VCP_Driver_Source modules

make[ 1 ]: Entering directory '/usr/lib/modules/3.14.4-1-ARCH/build'

make[ 1 ]: *** No rule to make target 'modules. Stop.

make[ 1 ]: Leaving directory '/usr/lib/modules/3.14.4-1-ARCH/build'

Makefile:4: recipe for target 'all' failed

make: *** [all] Error 2

There is no documentation aside from:

  make ( your cp210x driver )
  cp cp210x.ko to /lib/modules//kernel/drivers/usb/serial
  insmod /lib/modules/
  insmod cp210x.ko

Which is actually directed to Ubuntu. The OS I use is Arch Linux, so I realize there may be some discrepancies, but I am unable to resolve them.

Can anyone provide some guidance on the steps to install this driver (or at least where to look) and why there is such a lack of documentation? Are there assumptions here that I am not aware of? How is anyone suppose to use this? If you look in the source there are structures being used as arguments to functions that are never defined as far as I can tell. Perhaps they are part of the header files included at the top, but I could not find some of those on my machine either.

Has anyone else been able to successfully interface with this device? I am able to successfully read the device's information using libusb, but am having issues with this driver.


texts:
In a typical mutual capacitance touch sensor when finger approaches sensor it draws electrical field in effect decreasing the capacitance of the sensor (which is described here and here, for example).

Now, I came across this sensor design and tried to work out the principle of how it's working.

Here, the receive signal (left) is separated with transmit signal (right) via ground (and is also surrounded by it) and instead of a finger, there is a conductor (insulated from GND using a rubber cup) moving in or out above the sensor.

My understanding is, that this sensor is (with respect to the above "usual" situation) normally closed (i.e. electric field lines flow to the GND strip in-between Rx and Tx pads) and when the object approaches these pads it diverts them and increases the mutual capacitance of the sensor.

Is this reasoning correct?


texts: How do I connect a Digital Potentiometer?

texts:
Okay so I am definitely not knowledgeable in electronics and need some help involving a digital potentiometer.

I would like to know how I would use the AD5121 digital potmeter.

Lets pretend I had a simple circuit that consisted on a regular AA battery as the power supply, then the digital potentiometer, and then a transformer or whatever.

How would I connect the potentiometer into the described circuit and have it controlled by a microcontroller.

Also: I tried looking at the technical document but I had no idea what I was looking at.


texts: issue receiving DMX512 protocol over ATmega88 USART

texts:
I am trying to send DMX512 and RDM protocol to an Atmel ATmega88PA with very little results as of late. The USART will receive the incoming data, but processing is not performed correctly.

The idea behind the below code was to check for data overrun, the break, and then the actual data in the ISR and some sub functions.

ISR(USART_RX_vect){
//hw_wdt_enable();
long data;
int temp;
while ( ! ( UCSR0A & ( 1 << RXC0 ) ) )
    ;

if ( UCSR0A & (1 << DOR0 ) )
{   // check for data over run
    data = UDR0;
    temp = UCSR0A;
}
else if( UCSR0A & ( 1 << FE0 ) )
{   //some form of break detection
    data = UDR0;
    temp = UCSR0A;
    rs485_break_received( data );
}
else if( g_break_received )
{   //if we have a break msg is next
    g_break_received = 0;
    data = UDR0;
    temp = UCSR0A;
    g_checksum = rs485_data_received ( data );
}
if ( g_checksum != 0 )
{
    g_error_count++;
}  }

void rs485_break_received ( uint8_t data ){
if ( 0 != s_slotNext )
{   // 2nd break, it's a DMX message
    // the whole message was received
    s_pBuffer[s_slotNext] = data;
    uint8_t* pLast = s_pBuffer + s_slotNext;
    processing_queue_message ( s_pBuffer, pLast );
}
g_break_received = 1;
rs485_prepare_next_buffer ();  }

rs485_data_received checks the checksum on the message and will either move to processing_queue_message or return an error.
processing_queue_message goes into looking at the start codes to determine if its a RDM or DMX message.

I am using a DMXter 4 RDM module to test this code, trying to transmit a level change to a single channel, but I am getting information that is way off base.

If I actually send data the program just keeps running.
If I do not click send the program is constantly jumping into the Framing Error part.
If I go above 128/255 for the level to be transmitted the program will go into the g_break_received part

2 & 3 happen before I even click transmit.

I think there is a problem clearing the Framing Error bit in USCR0A, but I am unsure how to correct it as the data sheet just says read the register.  Is there some part of the DMX standard that I am missing? or maybe another way to clear the Framing Error?


texts:
while looking for a PT100 transducer from weidmueller, I faced two types of output current: 4...20 mA and 20...4 mA . Why is it like this? what's the  difference between 4...20 mA output and 20...4 mA ?
this is the link to the catalogue: http://catalog.weidmueller.com/catalog/Start.do?localeId=hk&ObjectID=1435590000


texts: Verilog conditional assignments without using procedural blocks like VHDL with/select

texts:
I am trying to find a way to conditionally assign values to a signal in verilog similar to the with/select in VHDL. So far I found two ways https://www.chipverify.com/verilog/verilog-4to1-mux.
This is the first one:
module mux_4to1_assign ( input [3:0] a,                 // 4-bit input called a
                         input [3:0] b,                 // 4-bit input called b
                         input [3:0] c,                 // 4-bit input called c
                         input [3:0] d,                 // 4-bit input called d
                         input [1:0] sel,               // input sel used to select between a,b,c,d
                         output [3:0] out);             // 4-bit output based on input sel

   // When sel[1] is 0, (sel[0]? b:a) is selected and when sel[1] is 1, (sel[0] ? d:c) is taken
   // When sel[0] is 0, a is sent to output, else b and when sel[0] is 0, c is sent to output, else d
   assign out = sel[1] ? (sel[0] ? d : c) : (sel[0] ? b : a);

endmodule

Second one:
module mux_4to1_case ( input [3:0] a,                 // 4-bit input called a
                       input [3:0] b,                 // 4-bit input called b
                       input [3:0] c,                 // 4-bit input called c
                       input [3:0] d,                 // 4-bit input called d
                       input [1:0] sel,               // input sel used to select between a,b,c,d
                       output reg [3:0] out);         // 4-bit output based on input sel

   // This always block gets executed whenever a/b/c/d/sel changes value
   // When that happens, based on value in sel, output is assigned to either a/b/c/d
   always @ (a or b or c or d or sel) begin
      case (sel)
         2'b00 : out <= a;
         2'b01 : out <= b;
         2'b10 : out <= c;
         2'b11 : out <= d;
      endcase
   end
endmodule

Both examples were taken from the link I shared before, my QUESTION IS if there is something in Verilog, similar to VHDL using the with/select, that is easy to understand without using procedural blocks?.
The first verilog example does the job but it takes a bit to understand the logic. Please keep in mind I am not complaining about or criticizing any language, I just want to know how to improve code readability for this particular case.


texts: questions about up-sampling and moving from slow to fast clock domain in FPGA

texts:
I encountered some questions and problems I asked myself lately and hoped I can get a nice lead here before I start reading long articles without even be sure if it's the right way.
Let's assume I have an FPGA design, where I get ADC data with a sampling rate of 40MHz, so I latching the data from the ADC interface in 40MHz.
but I want to make the DSP inside the FPGA in 100MHz clock speed (for example because I have DDR3 memory interface in the DSP block diagram which working in 400MHz in 4:1 clock rate that means the UI clock of the DDR3 is 100MHz).
The data from the ADC interface which coming in 40MHz rate is 90% of the time valid, which means I need most of it.
So the first question I want to ask, How would you move the data stream from the slow to fast clock domain?
I already made a working mechanism for this, I filled up a FIFO (with 1024 depth) and right after that start to fill the next FIFO ( I used 2 FIFOs),
while the Reading process from the first FIFO starting at the moment the first FIFO is filled, and from this time on, I just read the 1st and then 2nd and 1st and 2nd and so on...
while keep to writing to the 2 FIFOs each at a time.
After I finished to write this block, I asked myself if there is a better way,
I encountered the Interpolation filter using FIR, does Interpolation make this job of moving from slow to fast clock domain for a stream of data?
I also saw the Polyphase filter which seems like also a way to move to a faster sampling rate.
Does its filter which easy to instantiate in FPGA is the right way to move the stream of data to a faster clock domain, or my way with FIFOs is the way to go?
thanks.


texts: I'm completely new to electronics, can I make a wireless keyboard wired?

texts: I lost the dongle to an old wireless keyboard, can I make it wired?


texts: Is rheostat the same thing as variable resistor?

texts:
In class notes, it is written that variable resistor is the same thing as a rheostat. I googled it to find that some people on different question/answer forums have different "perspectives" about this. Some say that they are the same thing and some others say that they are not quite the same but they have the same effect which is varying the intensity of the current in a circuit.

I am kind of confused there and would appreciate your input on this.


texts: Why are Edison screws allowed to be used?

texts:
Why are the Edison screws allowed to be used? They seem unsafe. Why are they designed that way?

They require a complete grounding system to ground devices for the rare situation where the hot wires somehow touches the metal case of the device

While they let you use a lamp fixture which has an exposed hot contact when you remove the lamp, and nothing is there to protect your finger from touching it.

I would expect this socket to have a different design which will cover the contact from accidental touch.


texts: Radio Transmitter using Crystal Oscilliator

texts:
I am on the mission to control my RC car using arduino. The simplest way I thought of doing this is to add arduino outputs into the transmitter. Long story short I wanted to learn more about how these transmitters worked.

I have done some research and managed to find a schematic that is similar to the transmitter circuit that I currently have posted below.  My transmitter is using a 27Mhz crystal oscillator to create a carrier wave.

Bigger picture click here

But I do not understand how the crystal oscillator  is biased and how also the carrier wave is  mixed with the transmission signal (message Left, Right , Forward, Reverse)from the IC.

Sorry if I have not used the terms correctly I am new to RF and want to learn :)


texts: Please identify this 6-pin SMD marked AI531

texts:
It is a 6-pin SMD from 1.6W blue laser driver
The code on the case is AI531
Please help to identify this SMD.

https://tr.aliexpress.com/item/33045090236.html?spm=a2g0n.shopcart-amp.item.33045090236

can I use this?                               .


texts:
I'm playing around with a very simple setup:

9V battery
light diode
voltage divider (R1 - three 1 kOhm resistors, R2 - one 1 kOhm resistor), which should give me roughly 3V for the diode

The first time I assembled it, everything was fine, but after a while diode got much dimmer and then stopped emitting light. The battery is ok, as is diode, the problem is in one of the resistors, R2. With power plugged in it shows crazy 10-12 Mega Ohm. When I disconnect the battery it returns to its normal resistance at around 970 Ohm. No wonder diode isn't working given that resistance.
Why is the resistance so high?
I had another, more complex setup and there was the same problem, I decided to assemble something simpler, but there is this problem with very high resistance again.


texts: SYSTEMConfigPerformance not executing in PIC32

texts:
I have PIC32MX795F512L MCU and I am working on its UART communication. I have made the program and its working fine. I was curious about the frequency my PIC is running so I searched a little bit and found this online document which says that :

  SYSTEMConfigPerformance() is a very helpful library function used to easily optimize the performance of the PIC32. You provide the system (instruction) clock frequency and this function will do the rest. It will perform the following tasks for you:

Enable instruction and data caching
Enable instruction prefetch
Configure the Flash and SRAM for minimum wait states
Maximize the peripheral bus clock frequency

So when I included the SYSTEMConfigPerformance(FCY) in my code, my UART communication stops and I was receiving some random chars. When I excluded the SYSTEMConfigPerformance(FCY) it wwas working fine. I don't know the reason behind this strange behavior. I am using 8MHZ crystal with PLL and finally running my PIC at 72MHZ frequency. Following is the code I am using:

#define FCY 72000000UL
#define FPB (FCY/2)
#define BAUDRATE    9600
#pragma config POSCMOD=HS,FNOSC=PRIPLL
#pragma config FPLLIDIV=DIV_2, FPLLMUL=MUL_18, FPLLODIV=DIV_1
#pragma config FPBDIV=DIV_2, FWDTEN=OFF, CP=OFF, BWP=OFF

int main()
{
  SYSTEMConfigPerformance(FCY); //<-- Problem is at this line.
  OpenUART1( UART_EN | UART_NO_PAR_8BIT | UART_1STOPBIT, UART_RX_ENABLE | UART_TX_ENABLE, (FPB/16/BAUDRATE)-1 );
  while(1)
  {
     putsUART1("Hello\n");
  }
}

void DelayMs( unsigned t)
{
T1CON = 0x8000;
while (t--)
{
    TMR1 = 0;
    while (TMR1 < FPB/1000);
}
}


texts:
I'm new to electronics so i came here to ask some questions :

1) i have 4 motors JGA25-370 (6v, 58rpm) and 2 driver motors L298N ; If i put one drive to control 2 motors i will have max torque from my motors?

2) 1 battery per driver of 9v will be enough ? should i put 2*9V per driver motor ( each drive will control 2 motors )?

3) I saw that my motors need  900 mA in full load and, 380 mA in load and 80 mA in idle. Also my driver gave 36mA ; This is less than the needs of my motors. It will be a problem to achieve max potential from my motors ?

Thanks !


texts: How come the microcontroller of this board is being powered in this configuration?

texts:
I have this development board with the following pinout:

And I am using the following FTDI to USB interface to communicate with a PC:

Here is a photo of the board and the FTDI wired to the board pins:

So above on the left two wires are connecting the pins as:
FTDI +5V ---> Nucleo +5V(CN6 pin5)
FTDI GND ---> Nucleo GND(CN6 pin7)

and on the right two wires are connecting UART pins as:
FTDI RX ---> Nucleo PB10: USART3_TX
FTDI TX ---> Nucleo PB11: USART3_RX

So first of all, I assume +5V of the Nucleo board means that it is a 5V power supply for some electronics interface such as sensors. And I also assume that +5V in the FTDI board means that it needs to be powered by 5V supply so it is not a power supply pin but a pin for receiving power.
I do the wiring as I mentioned above and plug the FTDI board to the PC via its USB.
The thing is even though I do not power the Nucleo through its own USB port, I still can communicate with the Nucleo's uC through PC.
So how does the uC get power in this case? I am super confused.


texts: string efficiency of a string insulator using Guard rings

texts: Does gaurd rings used in power transmissions increases the string efficiency of a string insulator practically?If yes then how.


texts: Transceivers in the field of FPGAs: When and why will we use them?

texts:
I am recently getting myself into the field of FPGA design and development, and lately I've found myself hearing a lot about transceivers. I tried searching the net for some answers about these components and learn their role in the world of FPGAs but could not find much information but a few articles related to serial communications and Ser/Des's...

I wanted to ask, why, when, and most importantly how will I use transceivers on FPGAs? What are their alternatives (if any exist)? Is there some kind of a thumb rule for transceivers usage? And how can I "harness" all of that transceiving good to my advantage?


texts: Digital Low-Pass Filter When Oversampling Audio

texts:
The human ear can hear sounds up to ~ 20KHz. Some ADC's oversample. For example, to capture frequencies up to 20KHz, an ADC converter might sample at 160KHz. The steps are: 1. Filter the audio with an analog low-pass filter. 2. Sample at 160KHz. 3. Digitally filter the audio with a low-pass filter. 4. Downsample to a lower sample rate.

I understand that it's difficult to implement low-pass analog filters with sharp cutoffs: required to maximize the available bandwidth without exceeding the Nyquist limit, which would otherwise result in aliasing from folded frequencies. Therefore, I might choose to oversample at 160KHz, with an low-pass analog filter at 20KHz that can rolloff in 30KHz and still be below the Nyquist limit at 80Khz.

However, once I've sampled at 160KHz, why would I want to apply a digital low-pass filter before decimation? What are the advantages of this?


texts: I have a 3.7V one-cell polymer battery 350mAh 25C. It's linked to a board over a 50mm wire. What would be a good AWG diameter to ensure a maximum voltage drop inferior to 2%?


texts:
I'm trying to understand something very basic about Control Theory. Let's say I have the following loop:

If we'll relate this loop to a cart with a motor going in its single axis from X = 0 to X = 50, the controlled variable will be the engine speed (v), while the monitored variable will be the cart location (x).

In this case:

The measured output should be the cart location, right? But the system output should be the engine speed, shouldn't it? If so, how does this work in the equations? (units-wise)
What will be the Reference, System Input, System Output?


texts:
I am using the BD9C401EFJ chip for stepping 8.5V to 5V. The system is as stated -

1) I am supplying 8.5V from a bench power supply -> (to) BD9C401EFJ -> (output) 5V ->FT440G (another dc dc regulator) -> 3.3V (output).

2) The final output is fed to 2 KL04 freescale chips and a couple of MOSFETs and an ATMEGA32U4.

3) The whole system was working for about 3-4 months. Then suddenly, 2 BD9C401EFJ stopped working. The thing I noticed was that the o/p 5V and the ground pin was shorted. In other words the output of the BD9C401EFJ and the ground was shorted. But surprisingly there was none of the current inrush usually associated with a Vcc and GND short. The bench supply was sending like 100mAmps or so. But in the o/p of the BD9C401EFJ  there was 0V (nothing).

So, I delved into the datasheet. In the logic level diagram(internal) of the chip , shown below, I noticed the low side MOSFET (from the S-R flip flop) between the pins SW and PGND. Maybe, it is busted was my thought. I then depopulated the chip and did a connectivity test between pins 7/8 and 1. As suspected it was showing short.

How can that be so, I have not exceeded its parameters (input was just 8.5V and went a max of 12V). Also, I was supplying mostly in the range of a 100-200 mAmps.
So how is this mosfet damaged. I do not have any diode(schottky) from the supply. But, it is a bench power supply. But, I suspect that this could be one of the causes. Could anyone kindly help me out pls.


texts: SPICE IC model in-circuit power dissipation

texts:
I'm looking into a way to calculate the power dissipation of any arbitrary IC in circuit on SPICE. I eventually hope to create simple scripts that can list power dissipation of the device and potentially raise a flag if the device is over our de-rated maximums. I've been looking online and can't find any concrete methods to do so.

How do I model the power dissipation of an IC in SPICE?


texts: rotary encoder, got a 20ppr but need more like 200 ppr

texts:
I'm a tinkerer who is attempting to turn a guitar pedal into a remote tempo control for a drum machine, which uses a rotary encoder. In place of the potentiometer in the guitar pedal, I have put in a rotary encoder 858-EN11-HSM1BF20. This works, but the guitar pedal's range of travel only gives the encoder about a quarter of a full turn, just a few clicks. I have tried searching on octopart of "200PPR enocder", or other similar values. I'm in need of at least a hundred PPR for the pedal to be useful.

I'm in need of either an encoder that is around 200 PPR and has a standard 6mm diameter shaft, or a guitar pedal that has gearing in it to turn the encoder many times. Or, maybe somebody has an idea I haven't considered?

I have been unable to locate any encoders beyond 30 PPR on Octopart, Digi-Key or Mouser. But then, I'm just a tinkerer and really don't know what's out there. Any suggestions for a high-PPR encoder, or maybe a guitar pedal that uses gearing that will allow me to get many turns on that 20PPR encoder?


texts: We're looking for a decent hot air SMD rework station to help us fix up our prototypes. In the past, I've used one of the low-end Aoyue models, and found it lacking (the interface had problems, and the air pump got gummed up after a while). What should I be looking for in a rework station? Any model recommendations?


texts:
I recently disassembled a broken Motorola G5+ and saved the battery, vibrator motor,  and main circuit board for whatever I wanted to use it for. Now I'm ready to use it, but need to find a connector so I can still use the phone circuit to charge the battery. The battery is an HG40 LiPo battery, and connects to a small 2 pin connector. The connector is also the same as the one used for the small motor.
What connector type is used in the Motorola G5+, and if you can find it, where can I buy one?


texts: How important are BJT characteristic curves when designing amplifiers?

texts:
I was going to make a voltage amplifier for weak signals with 2SD786, but I noticed that the manufacturers haven't included the characteristic curves in the datasheets. How can I optimize the circuit if I don't know this transistor well? For example, according to the datasheet \$h_{FE}\$ value is very different for different conditions. Should I try to generate the curves myself before using this transistor?

UPDATE:

Assume that for a given \$V_{CC}\$, you want to choose a good load line by choosing \$R_L\$. Also you should choose a good operating point on the load line by determining appropriate \$I_B\$. However you don't have the characteristic curves.


texts: What does a TV receiver circuit look like?

texts:
I found a few circuits for TV transmitters, but no receivers.

I've looked at other simpler RF transmitters and receiver, but it's not obvious to me how to reverse the circuit that I have.

I want to send an expendable RC car into a collapsed tunnel, cable wouldn't work it's a labyrinth.

Can you give me an example of a vhf receiver and help me understand how it works?


texts: Noob: 19v power supply without IEC (kettle) lead

texts:
In terms of specs, I was after something like this external power supply

But i'd like to put it inside an enclosure for a DIY project. I'd prefer a smaller cable connector at the male end, something like the barrel connector or smaller IEC type so that it's easier to pull out in case of accidentally pulling the cable and general aesthetics.

My question is, can I safely change the male connector on this type of power supply? Should I be googleing something different ("ineternal power supply")?

Failing that, any chargeable battery recommendations?

Any links / suggestions welcome.

Thnaks


texts: Can I use a buffer on my bias voltage net?

texts:
I'm a french stompbox / bass guitar pedal hobbyist, probably very bad at designing them.
I've been thinking about bias voltage nets for some time, and how inefficient they sometimes are.
I've studied multiple "classic" distortion and boost pedals, and bias voltage seems to be a tricky thing, some designs just put voltage dividers before every FETs or OPamp channels, increasing passive power consumption, and making the math for voltage drops across the whole circuit very confusing. Sometimes it's just one voltage divider located at the power supply that provides the whole thing with an (ideally) +4.5V bias.

simulate this circuit – Schematic created using CircuitLab
I was wondering if it's possible to make a sort of "virtual ground" using a power-supply-specialized OPamp, by buffering the bias voltage and using it as the 0V reference between a +4.5V and -4.5V supply inside the circuit.

simulate this circuit


texts: Is every wire a transmission line or a transmission line has a special manufacturing process? But why during analysis of normal electrical circuits we never consider parameters like characteric impedance, R,G,L,C etc and only considered resistors, inductors etc which are actually connected in circuit? Don't these parameters affect analysis of circuit or they are considered only in some particular cases? If so what conditions are there that need to be satisfied after which I need to consider effect of transmission line parameters?


texts:
I am comparing breakout boards for VL53L0X sensor by different distributors. Below is from Pololu:

What is resistor R7 marked above for? This is not present in Adafruit's schematic.  Also not present in another distributor I bought from. It is present in DFRobot. It is not present in "typical application" diagram from the sensor's datasheet.

I can understand the purpose of R6 pull-up resistor. XSHUT is active low so when nothing is connected, it is pulled up to 2.8V. XSHUT is activated by connecting XSHUT to ground (e.g. via microcontroller output LOW).

Is R7 for limiting current when XSHUT is connected to ground? XSHUT is input for the sensor so I don't think the current is a problem.


texts: Sensing items on a printed page - suggested technologies to look at for on/off, true/false, etc. detection

texts:
We are developing a product where:

a child holds an electronic stylus
she uses it in conjunction with a book that has multiple choice questions
when she touches the right answer, the stylus will give positive feedback
when she touches the wrong answer, the stylus will give appropriate feedback

The way that we currently have implemented this is using conductive ink (black) and a conductivity sensor on the tip of the stylus. We already have a line of products based on this system.

The CORRECT answer has a 1/4" black dot next to it (printed with conductive ink).
The WRONG answer has a 1/4" black dot next to it (printed with normal ink).

THE CHALLENGE:
 - we're making a new system for younger kids
 - questions have PICTURE multiple choice answers (b/c younger kids want to touch the stylus to the PICTURE and not the black dot)
 - we want the printing technology to not obstruct the picture

Any ideas on a system here? We're aware of the Leapfrog stylus that reads a small pattern of dots on a page. This technology is too expensive for us.

I'm looking for a list of technologies to investigate for on/off, true/false detection.


texts: How does a cascode or beta-enhanced voltage amplification stage work?

texts:
I'm studying electrical engineering and we just finished a project where we had to build a power amplifier. But I think I can do better than what we did.

I read Distortion In Power Amplifiers where Douglas Self discusses several VAS stages and their benefits over the basic CEC stage.

In his results, circuit C and D perform best, apparently by increasing local negative feedback through Cdom.

As I understand it, Cdom is very small (pF) and serves to make the circuit dominantly first order by filtering very high frequencies. Isn't it essentially an open circuit for audio frequencies? The only advantage of C and D seems to be a possibly improved input impedance.

I tried simulating his circuits in LTspice (though all of the biasing circuitry is not included in his schematics), but both the beta-enhanced and cascode don't work very well.

LTSpice file

Can anyone explain how these circuits work and what I'm doing wrong?


texts:
I'm working with a nano scale motion stage with high precision. To move the stage I supply Sinusoidal wave using (Agilent Keysight) function generator.

This F-gen, goes as low as \$20mV_{pp}\$ in HighZ mode. \$20mV_{pp}\$, corresponds to \$30nm\$ of motion of the stage. For my experiment I need it to move the stage about \$6-7nm\$, so I need to supply small input voltages. My initial attempt was to build a voltage divider circuit (shown below). The output voltage \$V_{out}\$ according to equation (1) should be \$3.7mV\$ when \$V_{in}=20mV\$. Now the problem $is that the circuit produces a huge noise and I cannot read the correct output voltage with oscilloscope. The \$V_{in}\$ (yellow) and \$V_{out}\$ (Red) are shown in the snapshot of the oscilloscope.

\$V_{out}=V_{in}\frac{R_{2}}{R_{1}+R_{2}}\$ ........ (1)

I'm not an expert in field of electronics, I would like to hear your suggestions on how to improve the overall noise issue.

Thank you very much in advance.

simulate this circuit – Schematic created using CircuitLab


texts: Making a logic circuit with only NAND GATES?

texts:
I am trying to create a logic circuit using only NAND Gates for this expression:
(NOT Q AND P) OR R

This question has really gotten me stuck! Can somebody please help?


texts:
How would I go about obtaining the transfer function of the circuit below? I have seen some examples that use a voltage source, but none with a current source. Would I first obtain the impedance of the 3 components in parallel? What would V_in be? V_out is measured across R2.

simulate this circuit – Schematic created using CircuitLab
I believe if I convert the current source to a voltage source the schematic would look like the one below with R1 in series. Could I then obtain the transfer function as $$H(s) = \frac{V_{out}}{V_{in}} = \frac{R_2||Z_{C1}}{Z_{tot}(s)} = \frac{\frac{1}{1/R_2+Cs}}{R_1+\frac{1}{1/R_2+Cs}}$$

simulate this circuit


texts: Influence of the position of the voltage divider resistor

texts:
I've got an input protection circuit (from here) that works for digital inputs, but now I'm looking at expanding it to analog inputs, so I need to add a voltage divider. What is the influence of the position of the extra resistor?
(Connected to EXTERNAL_INPUT, you'll typically have an adjustable resistor)

In the top one, I'm pretty sure the extra resistor that are here for protection will not have any impact. In the 2nd one, I would expect an impact as it's add resistance to the first branch of the voltage divider. Am I right? Is there any other impact? Could I just make up for it by using a higher value for VDAIN49?


texts: I want to drive an EOM crystal at 20 MHz for phase modulation. I recently bought a step up RF transformer (1:4 turns ratio), but it's not working fine above 2 MHz. I tried winding a transformer myself on a toroidal ferrite core, but the cores don't seem to work properly at such high frequencies, they start attenuating once I enter the MHz regime. Are there alternative methods to facilitate stepping up voltage? Power requirement: 1-2 W. I have been thinking of using voltage preamps or power op-amps, but not sure of these yet.


texts:
I'm currently building a jumping RC car. for the jump mechanism i consider using solenoids. they can produce alot of force and would seem to be simple to use on the mechanical side of things.

However im struggling to find anyone else using solenoids for this reason. or seeing them jump off there own stroke. i did find a video of someone using a car door lock solenoid and making it hop lightly on its own stroke and another video of a solenoid push an object very far. which gave me hope i could do that on a smaller scale for my purpose.

i have researched some physics and found that force alone doesn't exactly mean it can propel its self from the ground. but im not exactly sure what i should be looking at.

i apologies that this question is a bit half electrical and have physics. not particularly sure which one i should go to.

thank you for your time and any advice or direction you can give me in my research/project would be helpful.


texts: Initiating DDR Reads From Zynq PL With DMA

texts:
I am trying to initiate reads from the Zynq PL over Xilinx AXI DMA IP, but I haven't been able to find an example to make things fully clear for me.
If I am using the DMA in Direct Register Mode, what's the recommended way to get data from DDR to my IP?
I thought I should attach a state machine to the M_AXI_MM2S port, but (1) after running block automation, that port already is connected; and (2) it looks like there are a lot of signals I'd need to design around.
Is there any easier way to get data from DDR to BRAM in the PL than building a state machine around this port?
I've taken a look at the AXI DMA IP user guide which had some programming tips (p70), but this looks like how I would initiate reads from the PS. Here is a picture of the relevant area of my block design, with the port I am talking about highlighted.


texts:
I have designed a circuit in Cadence Virtuoso. As a first step, I used all the transistors without fingers (i.e. each transistor is a single transistor).
Once the circuit satisfied all the requirements I wanted (dc gain, location of the poles, slew rate and so on) I decided to use fingers for each transistor in order to realize the stick diagram. To my astonishment, after using fingers, the dc analysis was completely different with respect to the original circuit: the dc voltages at each node were considerably different with respect to the original circuit.

Question: I know that fingering is used to reduce parasitic capacitances. Anyway, since a capacitor is an open circuit in dc, theoretically nothing should change as far as regards the dc analysis. Why then did Cadence give completely different results in dc when I converted my original circuit into the "fingered" version?

Here the circuit without fingers:

It is a two stages op-amp in open loop configuration (frequency compensation network has been omitted). If now I put 9 fingers for PM21, I get the following dc result:

As you can see, the output dc voltage has changed!


texts:
I ask this mainly for curiosity and am not trying to make shortcuts for real projects.

I have a couple of devices (mcu development boards) that connect to each other using various communication busses. One of which is UART.

For normal situations, you need a common ground as reference as said here: https://stackoverflow.com/questions/27138706/does-ardunino-serial-need-a-common-ground

However, all my devices in my test setup get power from usb from the same computer. Accidentally, I disconnected one of the ground wires between two devices and everything remained working.

Is this just 'luck' or is it because the voltage source for all devices is the same?


texts: Gibberish output from an ESP8622 WiFi module

texts:
Recently I've got myself a couple of ESP8266 modules. I flashed the latest NodeMCU firmware, and tried to communicate with a PC using UART.

Here's how I wired my circuit:

Using a simple USB to Serial interface or FTDI I tried to communicate with the ESP8266 with ESPlorer v0.2.0. I opened a Port on baud 74880 because It's the only successful one for some reason.. Here's the log.

  ets Jan  8 2013,rst cause:2, boot mode:(3,6)

is the only 'reasonable' output from the ESP8266, sometimes I get

  Fatal exception(0):

from ESP8266 module but It's very rare.

I've been struggling with this for a good week now.
ESP8266 is very unpredictable to work with.. For every command I send I get garbage output or that ets Jan...

Any good ideas? Maybe the FTDI can't draw enough current?


texts: Voltage across capacitor is shifted -20 VDC in PSPICE simulation

texts: I tried to create a simple simulation in Orcad PSPICE. For some reasons, the measured AC voltage across the capacitor C is shifted -20 Vdc. Its value should vary in the range [-20V, +20V] as far as I'm concerned. Very appreciate if anyone can give me an idea of what's going on here. Thank you very much.


texts: Of the two - which is the better archival media - Standard HDD or Flash

texts:
There are two totally different "bit rot" mechanisms in place here in the two technologies, so which would be expected to last longer?  Which is inherently superior for archival purposes.  Will a magnetic domain (GMMR) in a "standard HDD" last longer than the floating gate of Flash cell in a CMOS process.  i.e which physics dictates the decay process that is slower. Assume climate is controlled, and also assume that cost, interface and physical size is not a contraint. This should be judged/argued based upon the relative merits of the bit decay mechanisms/physics ONLY.

Update - 1 day before bounty expires:

Since this site is about design I limited the question very deliberately.  If you're designing a product (with a uController etc.) that will need to be idle for long periods then bit rot does come into play - do you know that the system will light up again when needed? i.e. you probably need archival type storage.  Do you design-in Flash?  or do you then put in a HDD interface?  That is the natural first branch of the decision tree.  Once you put in a IDE/SATA or similar interface for the HDD then all the other technologies could possibly come into play.  But I deliberately limited it to prevent getting off the rails into arguably declining technologies or at least technologies that would limit the scope of applicability.

I also edited the question to limit discussion on interface(s), since I didn't want discussion on relative interface speeds, density  etc.  A menton of these issues is of course welcome, but as an adjunct to the answer to the main question(s).

So far there has been a very high degree of anecdotal personal reflection.  Not at all desired!  I will not award a bounty based upon reminiscing.  I will call out @Danny-kmack for at least researching some 3rd party verifiable sources i.e. University of Twente *.ppt, (the superuser link falls into the anecdotal category) but then he fails to bring the salient info forward into the post.

More math, more reputable sourcing, NO anecdotes.  Bonuses for bringing up Activation energy and how that ties into the Arrhenius equation will earn extra! Details on how magnetic domains fail and what drives them, and the same for how the Fowler-Nordheim (F-N) Tunnelling onto a floating gate leaks back off - is it still F-N?.

Another call out: this time to @kitt-scuzz for the clever idea of building a system that refreshes the flash drive to ensure that the bit rot doesn't eat the data, you're trading off wear-out for longevity.  Unfortunately the wandering/Wondering before hand detracts from the good idea.

Note to Mods:
- Yes, I will come back and clean up this superfluous stuff here - either once I see better answers or it is clear that that will not arise.

Remember the key part of EE is the ability to analysis and do the math, understand the physics involved.

This certainly can help people in the future for the design of embedded systems that could reside in the field or even for long term products.  - that is the hope anyways.


texts: How do I store analog input into the msp430 nonvolatile memory?

texts: I am using Energia to program MSP430G2553 chip in a BristleBot circuit and I would like to store data in the nonvolatile memory, so next time I turn it on it remembers the inputs. How do I define this in Energia? I couldn't find reference on their website. Thank you!


texts:
I'm want to design a RF 433.42MHz transmitter, but I'm not finding good documentation to help me design.

This is a model that I found RO3112E but it's not clear to me how do I calculate the components (resistor, capacitor, etc).

I found this design node , but is intended for 433.92MHz.

How would be the circuit to aply this resonator, and how would be calculated the components?


texts:
I connected a green LED to pin 13 and digital GND on Arduino Uno R3. pinMode was set to OUTPUT and digitalwrite was set toHIGH. The LED glowed normally.

However connecting same LED to the 5V and GND burnt it out. How?

Did not pin 13 on HIGH also have voltage of +5V ?


texts:
Firstly I have V1 and V2 values very close to each other in voltage.
(used symmetric supply of +12 V and -12V, I did not draw it to create complexity)

I subtracted one from the other with opamp U2 then eliminated DC value with capacitor.

Now I have values between -10mv ~ +10 mv and I have to multiply with 11 these values but
last part is not doing his job. The output is the same before and after opamp U3.

What is the reason ot that?


texts: Driver impedance of a microcontroller pin, for series termination?

texts:
Many guides instruct that digital signals should have a series resistor placed by the driver, whose resistance is equal to the line impedance (Z0) minus the driver impedance (Zd). Here is one such guide.

However, I can't find output impedance specs for any microcontrollers. I've looked in the datasheets for the Renesas and PIC MCUs I use, and it's not even mentioned.

The situation I'm currently facing is a Renesas MCU talking to an SD card via 21cm-long traces, at 33MHz I think. (Some of the signals are bidirectional, but that's another story.) In order to avoid ringing and EMI emissions, which seem like they could be a problem with such long traces and high frequency, I want to terminate correctly.

Possible solutions - would it be likely that the driver impedance is really low, like only 1 ohm or so? I can calculate my line impedance, and if the driver impedance is far smaller, perhaps I could just neglect it?

Or, could I possibly attempt to detect the EMI caused by the ringing by (don't laugh) holding an AM radio next to the transmission lines, and try different termination resistor values until the ringing is minimized? Is there any better way to do this at home?


texts: LM741 saturation problem in MultiSim modeling

texts:
Since in my case Vs+ = 12V, Vs- = -12V

I expect that when I do an open loop OpAmp, the output should be limited by +- 12V, which is not the case in my simulation.

What is the problem?

P.S. with a closed loop everything works as expected.


texts:
How will this Verilog line be synthesized?

data = (s == 0) ? bus0 : 16’hz

The problem is that if I use mux/buffer it won't put Z if s!=0 because the output of the mux/buf is x (undefined) if the input is z.


texts: A constant current source simulation using transistor: problem in Proteus

texts:
Here, in the picture attached, I've simulated a constant current source using an NPN transistor, TIP series.
My task is to vary the R2 resistor and measuring the current change. This picture holds the info for a certain value, R2=50k. But the current, Ic is still constant. even at that value. The calculation in Ares is quite wrong as the voltage drop is 500V in this scenario while the supply is only 100V!
 Is there any delicate simulation software that can do the math correctly?
Thanks in advance.


texts:
If there is a phase difference between output and the input of a PLL, an error signal would be generated by phase detector, implying that the loop yet needs to settle to a final state. This may happen even when the frequency of the input and output becomes equal. Hence even if the output frequency is exactly the same as that of input, we may get an error from phase detector and consecutively the VCO will change the output frequency, which further deviates the output from input frequency. This way aren't we going further away from the locked condition because now even the frequency is not same (which was same earlier) for the input and the output.
I tried to think how it can lock even after deviating from the frequency, but it was a bit challenging to imagine all of this stuff.

What am I missing?


texts: House wide automation network: CAN or Ethernet?

texts:
I am half-way through building my home automation system. As an electronic engineer/software developer a lot of this has been rolled myself from scratch and I will hopefully be starting to blog more and build up/publish my story and workings once complete.

I am now at the point of lighting automation. I have approximately 30 wall switches running a prototype touch sensor faceplate and I need to now connect these back to my Win7 Embedded automation computer. I also need to connect about 30-40 dimmers and relays.

As far as I can see I have a couple of options for protocols both at physical/application level and really am looking for any comments or advice on the below options, plus if anyone has any other suggestions.

Right now, all controllers are running off ARM M3 processors and I have both Ethernet and CANopen stacks available. The system needs to be "multi master" and ideally support both event driven (e.g. someone presses a button) and process driven (querying a sensor every 30 seconds, or asking a specific node a question).

CANopen

Multi-master and automatic error correction/collision avoidance
Process, service and event options for messages
Can be complicated to "virtually wire" up device. Lots of configuration potentially required
Cheap to implement in hardware, relatively scalable. Limit of 127 devices on a bus. Daisy-chain network.

Ethernet

Multicast UDP, or broadcast? Not sure which is more appropriate
Probably have to roll my own messaging protocol or API on-top to handle all the types of events I require, not sure about event driven actions
Star network, BUT could support PoE which is nice
More expensive in hardware
Much more expandable in software (potentially infinite number of devices, etc).

Has anyone got any comments or thoughts on which may be the best route to proceed? I have a feeling Ethernet may be the way but worry there is far more implementation required in software.

Thanks


texts: Operating a MOSFET as a switch: A strange dip occurs on the drain voltage

texts:
[POST IS EDITED]

I'm trying to debug a circuit shown in Fig. 1.

The gate of the FET is driven with a square wave 0...3 volts. The voltage source V1 = 3.3V. The circuit is built to control the voltage presented to the non-inverting input of an operational amplifier. R2 and R3 are trimmers, so the two input voltages can be trimmed to different values if needed.

Driving the FET with a square wave I notice a rather odd behaviour. The voltage between R1 and R2 are shown in Fig. 2 as a function of time (green). The voltage of Vgs is drawn blue.

As can be seen, the voltage v+ first dips to a negative value and then rises slowly to the steady state value. When the voltage v+ should drop to the lower value (vgs = 3 V) it first overshoots after going down to the steady state. The simulation and oscilloscope measurements agree together.

What could be causing this, and how can i get the voltage between R1 and R2 (green waveform) to be as closes as a square wave as possible. Fet in use is Si2318CDS. Datasheet provided in the comment. I have tried higher Vgs amplitudes han 3V.


texts: Homebrew Computers - TTL/FPA computer that can run a POSIX OS?

texts:
The internet is filled with inspiring examples of homebrew computers, including ones made from relays and TTL gates.

In the first year of Make Magazine - they describe a person who builds a simple programmable computer using TTL gates. They conclude with the spin "I'm going to extend it until I can play Zork!"

My question is: Is there a Homebrew-style TTL/FPGA computer that can run a POSIX OS?

Edit:

Here they suggest not using TTL but using FPGA with HDHL or Verilog.
This appears to cover similar ground - but doesn't deal with the OS


texts: Does the Y-Δ transform suffice for every resistor network?

texts:
Suppose I have a (finite of course!) network of resistors only. Is it always possible to calculate the equivalent resistance between any two points using only parallel, series, Y-Δ and Δ-Y (wye-delta and delta-wye) transforms?

Conversely, is there a resistor network where the star-mesh transform for n>3 is absolutely necessary to find the equivalent resistance between some two nodes?


texts: What does the bar above a pin name in a datasheet mean?

texts:
This Serial Communications Controller from Zilog lists a few of its pins with a bar above the name. What does this bar mean?

From a schematic I have been looking it seems a few of these are inactive when high and active when low?


texts: How to get ip address Schneider PLC controller TM218LDAE40DRPHN?

texts:
I am new to PLC technology and I am doing the following step, listed below:

Connect from PLC to retrieve data through Ethernet using Modbus TCP/IP.

I found that PLC didn't have its IP address listed on it (do PLCs usually have their IP address on it?) but I do have a MAC address: xxxxxx. Then I read some documentation:

  The default IP address is based on the device’s MAC address. The first two bytes are 10 and 10. The last two bytes are the last two bytes of the device’s MAC
  address.

  The default subnet mask is 255.0.0.0.

  NOTE: A MAC address is always written in hexadecimal format, and an IP address
  in decimal format. You must convert the MAC address to decimal format.

  Example: If the MAC address is xx.xx.xx.xx.xx.xx, the default IP address is
  10.10.128.242,

So I tried to convert the last two MAC address. Here I got 10.10.161.157, and when I try to ping it it doesn't work.

Any suggestion would be nice, thank you.


texts: What's the purpose of an array of same VALUE capacitors?

texts:
I'm looking at the schematic of the AM3354 EVM and I don't know why I see so many of the same value capacitors used in parallel and typically around the processor or memory.

I understand that different capacitors will have different self resonant frequencies and perhaps that is advantageous for noise filtering but why so many of the same value? Isn't one sufficient?

This question is based around the same value of components not simply combining different value capacitors into one larger capacitance part.

TI AM3354 EVM Base board schematic


texts: How to shutdown op-amps for low-power standby

texts: What is the best way to shut down the analog front end of my sensor system for a low-power standby mode. My circuit is battery powered via a 3.3V buck/boost converter I would like my STM32 microcontroller to shutdown the analog circuitry (op-amps) before going into low-power mode. Is this as simple as putting a MOSFET switch on my AVDD rail controlled by a GPIO pin? Should specialty power switching ICs be used? The combined current draw of the analog circuitry is only around 1mA but will deplete the battery for long standby intervals.


texts: Do digital Anti Aliasing filters exist for traditional ADCs?

texts:
I'm currently learning about Analogue to Digital Converters. From what I understand, aliasing occurs if the input signal being sampled has power above the "Nyquist frequency" of the ADC(Sampling frequency of the ADC/2). So, then logically, I assume then that all the anti aliasing filters have to be analogue. Or the same problem of aliasing due to sampling would exist, no? Either that of the digital anti aliasing filter has to sample at very high frequencies? Not to mention, have an DAC in the filter module to put the signal back into the analogue domain. Which would ask the question, why wouldn't we then simply just use a high frequency digital sampler and then have digital filtering done afterwards.

I'm asking because most of the tutorials and lectures I come across seem to miss how the signal is actually filtered before the sampling. Rather they just simply say the type and order, e.g. Butterworth 4th order. But no mention of how this would be implemented.

Where usually do people put these filters?. On the IC for the ADC itself? Or as an external filter before the sampling stage. Are physically big filters (e.g. through hole capacitors, inductors and resistors) the norm? Or rather integrated filters? For example, I'm guessing the ATMEGA328 (used on Arduino UNO) has an integrated anti aliasing filter since we usually don't filter the signal.

Particularly, I am referring to audio band ADCs, especially regarding the types of the filters. But the rest of the question, I am asking in a general sense.


texts:
I'm using TI's 18-bit DAC9881 and need the output to go a little below 0Volts in order to account for offset voltages of following Op-Amp stages.

The DAC allows to provide a "low reference" between -0.2V and 0.2V to offset the output, which is just what I need.

My question is how to generate this reference voltage? It does not need to be  very accurate (I need to calibrate the whole circuit anyway), but should be precise, i.e. stable over time. I have +5V/-5V LDO output power supply rails (TI LM27762).

One option would be to use a voltage divider connected to Op-Amp in voltage follower configuration. However, supply noise and load transients will disturb this poor man's reference.

The other option I see is a shunt regulator. I didn't find any with a fixed reference voltage of 0.1V-0.2V, so the suggestion in this answer https://electronics.stackexchange.com/a/383440/197145 does not work.
I did find a 4.9V reference (Diodes ZRT050) though, which could be used like this:

simulate this circuit – Schematic created using CircuitLab

However, this way (if it works?) the reference voltage is established with respect to the -5V power supply instead of GND, so I fear to get the same problems with noise and transients as with the op-amp solution.

Does anyone have a better option to implement a reference voltage of -0.1V to -0.2V from a 5V/-5V supply? If not, which of the two solutions seems more suitable and why?

Cheers,
Kai

EDIT:

I built the circuit from the accepted answer and it provided the expected bias voltage. However, I read the datasheet of the DAC9881 wrong and found that my goal of shifting the output below GND by providing a negative bias voltage to the REFL input does not work. The amplifier in the output stage of the DAC has some fixed headroom to the negative supply (GND), which cannot be worked around by adding a negative offset. This can only be achieved with external circuity behind the DAC output.


texts: Why won't these two BJTs connected in series work?

texts:
I cannot get the second BJT amplification of Experiment 11 of Charles Platt's Make: Electronics to work, and I'm all out of clues. This question is very similar, but not identical as my circuit works fine up to the first amplification. This question is also about experiment 11, but does not seem related.

The first 2N2222 is fed the output of the 2N6027, which discharges the 0.0047uF cap with a frequency in the kHz range; this amplifies this signal. If I hook up a speaker between the first 2N2222's emitter and ground, I hear a buzzing sound, just as the book says.

Now, if I attempt to amplify this buzzing with the second 2N2222 as shown in the circuit, the speaker just cackles a bit. Initially I thought I might have overloaded the speaker, but no matter how much I experiment with the various resistors, I don't here any buzzing.

I guess this is something that can easily be analyzed with an oscilloscope, but unfortunately I don't have access to one yet.


texts: Confusion between analog & digital signal and modem

texts:
Telephone wire is a lowpass chaneel so the process looks like below. (Maybe right?)

Voice(analog signal) → Sampling(digial data) → Coding(digial signal) → transmit

There's no need to convert digital signal to analog signal because it is not a bandpass channel. Meanwhile, Wikipedia states that the digital signal which is converted from digital data of computer can not be transmitted well if it is sent immediately. And that's what modem does. (Modulates the signal according to the characteristics of the transmission line)

The strange thing is, it also states that the modem converts digital signal to analog signal so that it can be transmitted through telecommunication line. Can't the digital signal be transmitted without converting to analog signal like how our voice is transmitted through the line?


texts: Voltage reference that can drive current in both ways

texts:
I am designing a device that at some point needs an oscillator in order to work. The whole circuit is fed by a 9 V battery. The V20 label corresponds to 20 V coming from a Boost converter whose input is the 9 V from the battery, and its output is 20 V.

The oscillator I'm looking forward to use can be seen in the picture below:

In the terminal with the label V10, I need a good reference of 10 V. I first thought of connecting the battery directly to it (9 V would not be so terrible), but the problem is that I realized that current can't flow both ways through a battery and, in this design, current should be able to do so.

In a nutshell, I need to put a reference of ~10 V in that terminal in such a way that current can flow in both ways in that branch. Also, it would be great if the solution was as simple as it can be (i.e. small amount of components). Is there a way to achieve this?


texts:
How do you make it so that a light goes on after a button has been pressed twice then off when pressed twice more?

I'm pretty stumped on this one and searches don't yield results. Any help is much appreciated, thanks.


texts: Why does a Pull down resistor not affect AC

texts:
I've been reading up and trying to learn about Guitar Pedal circuits.

I have a very basic question about how a Pull Down resistor is used at the beginning and end of a circuit to avoid a popping noise. See Diagram below.

Based on my understanding - A popping noise is usually caused when there is some leakage from the Capacitor. When the circuit is activated - the leftover leakage is sent to the resistor rather than the circuit, therefore avoiding a "pop" coming out of the your pedal. This makes sense to me.

However, my question is more based around when the circuit it is activated. Why does the pull down resistor not affect the guitar signal?

Every description I've read about a pull-down resistor implies it has no affect when the circuit is switched ON. Suggesting it's not drawing current at all? For example "

  And that's where our unicorn pull-down resistor comes in.  It sits
  there biding its time, drinking tea, eating crumpets and politely
  gives the potential bleeding somewhere to go,
  aside from our amplifiers, speakers and ultimately ears.

Can someone help and explain why the resistor only really has an effect on the signal when there is leakage?

OR, is the answer it does affect AC signal, but because its in parallel with the circuit, or because ioff its value, its not an issue?


texts: PSpice Simulation of a 741 Op-Amp BJT configuration not working?

texts:
I'm simulating the following circuit of the 741 operational amplifier with BJTs:

I've configured my circuit to be a non-inverting fashion, so in theory the gain would be -Rf/Ri. However, no matter what I set my values of Rf and Ri to, my output voltage remains constant.
Here is an image of SPICE simulation, with the output voltage boxed in blue, the Rf boxed in green, and the Ri boxed in pink:

Does anybody see what's wrong with my circuit? And why my output voltage is always -4.81 V no matter what the values of Rf and Ri are?


texts: Beginner Question on Whether Running A Fan and Peltier off a Battery Pack Would Work

texts:
If I have a 2.4A 5V Max Output Battery Pack, and I buy a 12V, 60 Watt Peltier Element and a 5V .4A computer fan (leaving room for comfort, item is actually 5v .36A), could I run both off of that one battery pack?

For Further clarification, I will split the USB cable that powers both objects two ways (Y Split connection). As referenced by someone else, using Ohm's law a 12V, 5A 60Watt Peltier would run at 5V 2.1 Amps when plugged into a 5V power supply, and added with a 5V .4A computer fan would run at a total of 5v, 2.5A. The Peltier I am using is the TES1-12706 or TEC1-12706 (12v 60Watt)

Thank you so much, I mainly want to see if you guys think this would work, or I need to get a lower powered Peltier to be on the safe side, also I want you guys to tell me if that Ohm's Law conversion is correct.


texts: Raspberry Pi with 74HC14 connecting to LED strip (WS2812B)

texts:
This might be a stupid question, but I can't seem to figure out how to convert 3.3V to 5V with the 74HC14. I have a power source which can supply 5V (see the power adapter at the left), and use it to power the Raspberry Pi and the converter. The Raspberry Pi has GPIO at 3.3V, while the LED strip (WS2812B) operates at 5V. This means I would like to use a logic-level converter to convert the 3.3V from the RPi to the 5V for the LED strip.

Unfortunately, I do not have a lot of experience in schematics, nor can I find any possible location where they use the 74HC14 the way I need it. I could use any help needed!

Design

74HC14 (from this forum)

EDIT 1:
It appears that the 74HC14 does not support 3.3V input, but as suggested by @Justme, the 74LS14 seems to work well. I also found the TXB0108, should that also be useful, or is it better to use the 74LS14?

EDIT 2:

Thanks to the comments section, I stumbled upon the 74HCT125, which might work I've updated the design based on the suggestions, is there anything wrong with it or that could be improved?


texts: Is it important to have common ground between you microcontoller and high-power devices on the same PCB?

texts:
I noticed that there are more N-channel mostfets than P-channel mosfets on the market.

Then I realised that probably in many applications, the high powered device runs on a higher voltage and therefore a P-channel mosfet cannot be used.

An N-channel mostfet connects the ground lines of the high-power device to ground. However this is not "common" ground. Its ground + the potential of the mosfet.

I actually have a lot of components (all 5V) to be controlled by one MOSFET switch including digital logic. I need this to isolate out that part of the board when my board is only being powered by PC USB. (ie: 500mA limited, and this part of the board draws 1.5A and should only work when on USB charger)

I was thinking of putting in a P-channel mosfet into my design so that my microcontroller is controlling the highrail of my high-powered device (a light, a motor, etc), rather than the ground rail. It feels like that would make sense because then one maintains a solid ground plane on the entire board. Perhaps this is not as important as I was lead to beleive in school?


texts:
I'm looking for some advice on what type of relay I should use for my circuit.

I have a 5v power supply and I want it to act just like a switch.  I will be controlling it with an Arduino like described here: http://tronixstuff.wordpress.com/2010/04/20/getting-started-with-arduino-chapter-three/


texts: How does Apple's ADB's collision resolution work?

texts:
I've read several different documentation sources explaining how Apple's asynchronous ADB protocol works. Although quite convoluted, it makes some sense of several rereads.  I am having difficulty wrapping my head around how ADB's collision resolution works. This protocol is ancient and no longer used, but perhaps someone with a fresh mind can parse the documentation better than me.

https://developer.apple.com/library/archive/technotes/hw/hw_01.html#Section2

First, during the device address resolution (device enumeration) the ADB Manager polls devices and the devices are responsible for detecting collisions. When a device responds, it is supposed to supply a "random" address to the ADB Manager.  It's unclear how this random address factors into the address resolution.  Specifically, here's what it says the ADB Manager does:

  An ADB device's register 3 is 2 bytes long, and includes 4 bits in which the address is stored. When the device receives a listen register 3 command, it should take its address from this 4-bit field. When it receives a talk register 3 command, it would be redundant to put the device's address in that field: the device's address is already uniquely determined by the fact that the device is responding to the talk register 3 command, which was sent to a specific address. Instead, a random 4-bit value should be returned in this field; this makes it easier to detect collisions between two devices responding to a talk register 3.

It only says "it makes it easier to detect collisions."  There's no further discussion about how it uses this address to determine a collision. Microchip's technote AN591, says the device is responsible, but it is still unclear:

  When a device recognizes that the Host issued a “Talk Register 3”
  command, it responds by sending a random address. During the transfer
  of each Bit Cell of the random address the signal line is monitored
  for the expected signal level. If the signal is not what is expected
  there is an address conflict. If the address is sent successfully, the
  host will respond with a Listen Command to that device. The command
  will have a new Device Address to which that device will move. The
  device then only responds to commands at the new address. If there is
  a conflict, where two devices have the same default address, and
  respond at the same time, the device that finds the line low when it
  expects it to be high, immediately stops transmitting because it has
  determined that a collision has occurred.

Given this is an asynchronous operation, it's impossible to read the ADB signal while writing a signal.

Second, ADB is supposed to support up to 16 devices since the device address is 4 bits. During the device resolution, however, addresses $8-$F are used for address resolution.  This means there can be a maximum of 8 devices of a specific device family, not 16?  Am I correct here?


texts: This is a question I found in one of the textbooks I have. The textbook didnt explain thoroughly about the concept or theory of the op-amp, and that left me confused. So please correct me if I'm wrong. I was just wondering if the voltage of the noninverting pin of the op-amp is zero, as shown in the picture. Does that mean the gain is infinity? (Assuming that the op-amp is ideal.) Or how can we find its gain? Any help is greatly appreciated.


texts: Is booth multiplication algorithm for multiplying 2 positive numbers?

texts:
Is the Booth algorithm for multiplication only for multiplying two negative numbers such as \$-3  * -4\$ or can it also multiply one positive and one negative number such as \$-3 * 4\$? I believe that it's not for multiplying two positive numbers, whenever I multiply 2 positive numbers using booth algorithm i get a wrong result.

For example : \$5 * 4\$

 A = 101 000 0   // binary of 5 is 101

 S = 011 000 0   // 2's complement of 5 is 011

 P = 000 100 0   // binary of 4 is 100

 x = 3

 y = 3

 m = 5

 -m = 2's complement of m

 r = 4

After right shift of P by 1 bit 0 000 100
After right shift of P by 1 bit 0 000 010
P+S = 011 001 0

After right shift by 1 bit 0 011 001
Discarding the LSB 001100

But that comes out to be the binary of 12 . It should have been 20(010100)


texts: Signal fidelity from fiber optic crosstalk

texts:
I was watching a video about tapping fiber optic cables when it brought up some points from an early US govt document describing security concerns about fiber optic cables.  The relevant part:

  Tapping attacks are possible at several points within the network due
  to component crosstalk. For example, contemporary demultiplexers
  within network nodes separate each individual signal (or wavelength)
  received from a single fiber on to separate physical paths. These
  demultiplexers may exhibit cross-talk levels between 0.03% and 1.0%.
  These cross-talk levels allow a little of each signal to leak onto the
  wrong path. Yet these signals may have enough fidelity to permit an
  attacker to detect their presence and recover a portion of data.

If I'm understanding this correctly, this means that after some fiber station de-muxes the signals, the signal that gets sent to someone's house has some "noise" that is actually cross-talk from someone else's signal.  I'm unfamiliar with signal processing, but it seems to me that it would be possible to glean some information from that "noise."  That would essentially be like a low-quality copy of someone else's mail getting delivered to my mailbox.

Does modern fiber in homes (or businesses) send enough physical signal from cross-talk to be usable in some way?  That seems...not great.


texts: How good are commercial DDS IC's for low frequency applications?

texts:
I'm making a precise, low-current current source for a bio-impedance meter using a howland current pump.

Currently the current pump is driven by a wien-bridge oscillator to produce a 1V p-p 100hz sine wave, my goal is to make it programmable by swapping this for a DDS (AD9852 tentatively). Most commercial DDS ic's are designed for telecom and other high frequency applications and have performance specs available on the MHz level, however information on performance in the low frequency domain is sparse.

SO my question is, how well do commercial DDS IC's perform at frequencies on the order of 100Hz - 1Khz? I'll be sticking an atmega or similiar MCU and will probably drive both the MCU and DDS with a 10MHz clock


texts: Does a hybrid DC relay suffer from contact erosion (albeit much less than normal), or is it effectively eliminated?

texts:
Given a hybrid DC relay, I've been wondering if contact erosion is occurring (albeit at a slower rate), or if the design eliminates this entirely.

(Assume that there is no snubber or other contact protection)

I'm presuming that there is erosion for the following reasons:

According to my old H W. Ott book ("Noise Reduction Techniques in Electronic Systems" Ch.7), there are minimum voltages (9 to 20 V) and currents (10s to 100s of mA) where contact arcing will occur.  With a hybrid relay, once the the solid-state switch (or relay) turns on, the EMR contacts stay below the voltage minimum due to the low voltage drop of the device.  However, once the EMR is closed (or opened) the contact current minimums (e. g., rated > 1 Amp) will be exceeded.  The reason? The contact's inductance in conjunction with the contact bounce during closure (opening?) will resulting in arcing once the current flow exceeds the minimum rating.

So it suggest to me that there is contact erosion (albeit much less than a standard EMR).

Is this correct, or am I missing something?


texts: What is needed for basic PIC programming?

texts:
I have a bunch of PICs that have been sitting in the basement for a year, and I really want to learn how to program and put them to use.

I have some 16C57's, 16C73, 16C71, 16C54, 16C74, 16C55, and 16C505. Some are write only, but a few from each category are erasable.

I want to do basic I/O with LED output and digital voltage sources.

What are the basic components I need, and where can I find instructions on programming them assuming I am a beginner programmer.

For example, if I acquire a USB programmer, do I also need a crystal, capacitors etc. for a basic setup?


texts: How can I calculate the minimum switch time between main battery and back-up battery for my board?

texts:
I have UpSquared board for an embedded system. I have a main power supply(battery) to feed it and I also have a back-up battery for some situations.

For example, something happened and main battery is not able to feed my board anymore. My question is that how many minimum time is required to switch from main battery to back-up battery because I don't want my board to shut down. Or how can I calculate that time?

Edit:

Here is schematic of my entrance power of my board:
My dV is 5V and I is 4 Amper


texts: Low-power alternative to Arduino, for simple project

texts:
I have a really plain Arduino project: ultra-sonic sensor HC-SR04 returns distance which is then used as sleep time during a LED-wave effect. So it's a simple distance <-> LED-wave velocity relation. The closer you walk towards the device, the faster the LEDs. That's all.

The current being drawn when not running LED-wave and just checking 5 times per second if the distance is lower than 2 meters: 15 mA. This value is in my opinion huge.

I then heard about ESP-8266. It can fully replace Arduino. However the power levels are still not good enough. Browsed more, read about Teensy and others, and they all draw power like a crazy – it appears like this if only a person thinks about using batteries for a moment.

I think that professionals know the solution. Hobbysts are stuck in very fun Arduino world.

Can someone reveal the truth? There must be an answer as e.g. computer mice can run months on two AA. Or, for example, a shopped motion-detection-triggered lamp nicely worked for 7 days before I got bored with it and have put it into drawer. The lamp was giving actual light, not LED blinks, and didn't drain the three AAA batteries it used.

What can I use for my plain project? Need ping functionality for HC-SR04, 8 pins for LEDs and that's all. How to do this correctly and have battery lasting for months?


texts: What metal-printing methods exist to create this style of finish?

texts:
I have an old panel faceplate (circa 2000) that I am trying to create a replacement for. It appears that the two commonly available methods to put graphics on a metal faceplate are UV printing and engraving. My best guess is that this panel started with a plain sheet of aluminum and then had an image UV printed onto it (including the black background).

From the pictures, can anyone determine if this is correct or if another method was used? My goal is for the new faceplate to be as close to the original as possible.

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I'm building a small and simple 4-bit CPU and I'm looking for an IC to store the program opcodes.  I've considered using eeproms although they seem too large for my purpose, being in the kilobyte range.  I was hoping that there was an easy to access memory that stored 8 bit numbers and could be addressed using 4 bit values, or 16 addressable 8 bit values.  I would also prefer not to have to purchase an eeprom programmer so that memory could easily be programmed with a micro-controller.

What type of memory IC would be recommended for this purpose?


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I am building a program for a PIC16F877A. It seems to be running correctly in the simulator MPLABX. I'm using about half the available program and data memory.

During programming I receive the following message:

The following memory area(s) will be programmed:
program memory: start address = 0x0, end address = 0xfff
configuration memory
Debug Executive
Address: 1f00 Expected Value: 1170 Received Value: 3fff
Failed to program device

Under the simulator situation I have looked in the program memory. Address 1F00 is not used and has indeed the value 3FFF. How to proceed in finding the error?

The program is written in XC8.


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I know this is an awkward one, but need some answers. Is it a good practice to fix/lock the shaft of a motor, and consequently the body of motor shall start rotating?

Essentially, there is a shaft which has a hollow diameter. I have to mount the motor inside the shaft (the outer diameter of the motor shall be equal to the hollow diameter of the shaft), and rotate the shaft as my final product?

Any recommendations about suitable motors, or any suggestions are much appreciated.

Thanks.


texts: Do a diode and a resistor in parallel have the same voltage across them?

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Example attached. My intuition is telling me that they're the same because of Kirchhoff's laws.

I know that a constant voltage model exists but I was worried about the nonlinearity of the diode disqualifying basic KVL.

simulate this circuit – Schematic created using CircuitLab


texts: Why do we use dB to represent the difference between two voltages?

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For example, the passband of a LC resonant circuit is the differences of frequency at +3db and -3db.

Why do we prefer dB?


texts: Why is a transistor used in a night sensor circuit?

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The following circuit is often used in introductory (high school level) physics courses to introduce transistors or to give an example of why transistors are useful:

Is it correct that one could achieve the same effect using just an LDR parallel to a resistor (and another resistor in series)? If so, what is the advantage of using the transistor?


texts: Let's suppose there is a battery which powers a DC load. There is a solar panel which gives power from time to time. How do I connect them all together so that the solar panel powers the load and charges the battery when the sun comes out and the load is powered by the battery the rest of the time?


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There is this formulae we use to determine the space charge width of a pn junction forward biased by Veb and phi-oe represents the built in potential.

Now what happens to the space charge width when Veb is greater in magnitude than the built in potential ?


texts: When should I use opto-isolators and isloated DC-DC converters?

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I am using multiple DC-DC converters to obtain 12V and 5V. Shall I use non-isolated or isolated converter for Arduino's? From what I have read so far, isolated are used when you have inductive loads and you need isolation in between your motor and the signals which are used to control the motor.
Also, Shall I use an opto isolator in between the Arduino and the DC motor,as my Arduino is going to control the DC motor like this:

Also do the use of isloated DC-DC converter eliminate the need of opto-isolators , precisely because the ground terminal is separated?

PS: I know my questions previously were vague and I understand the requirements of this forum. I have tried to take care of it this time and I will appreciate if someone can help me with the confusion here. Thanks


texts: Powering multiple devices with different ratings from a single supply

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I'm planning to power devices with different ratings from a single supply. Some of the devices have ratings such as 5V/2A, 5V/4A, 12V/2A etc., Currently they're being powered with seperate adapters. I plan to use a single supply to power all of them, and from other questions/answers, I've gathered that the best way to do it would be to use different DC-DC converters.

My question is, since they have different ratings, would the power supply be chosen such that the max. current rating is the sum of all of the device's current rating? Would it pose a problem then, if I'm connecting the converters to that single power supply since it's likely that the converters would be having different input current limitation.