texts:
I was reading the datasheet of DALC208 which is a low capacitance diode array. It is  designed to protect components which are connected to data and transmission lines from over voltages caused by electrostatic discharge (ESD) or other transients.
It is written in the datasheet that the low capacitance of the DALC208 prevents significant signal distortion.
I don't understand how low capacitance is related to signal distortion.
Datasheet:https://www.st.com/resource/en/datasheet/dalc208.pdf


texts: I have output from ADC as MISO and MOSI, can I use this signals to TX and RX in arduino uno? if not what will the solution for this?

texts: I have output from ADC as MISO and MOSI, can I use this signals to TX and  RX  in arduino uno? If not, what will the solution for this?


texts:
I am currently simulating the a AC/DC/AC motor with the rectifier and the inverter stage. The motor is simulated as a L,R and a back EMF. The problem is that my simulation is too slow (practically more than 30 mins for 1 cycle of trans).

I have already tried and made the rectifier (simple diode) and inverter (ideal PWM switches) stages as simple as possible (they run individually in a mater of seconds).

Is there some way to make the simulation faster?

simulate this circuit – Schematic created using CircuitLab

Vga L1 COM SINE(0 {Vac} {fg} 0 0 0) AC 1 0
Lgra L1 N001 {Lg}
Rgra N001 N002 {Rg}
Rgrb N006 N007 {Rg}
Lgrb L2 N006 {Lg}
Lgrc L3 N010 {Lg}
Rgrc N010 N011 {Rg}
Vgb L2 COM SINE(0 {Vac} {fg} 0 0 120) AC 1 120
Vgc L3 COM SINE(0 {Vac} {fg} 0 0 -120) AC 1 -120
R1 COM 0 10Meg
XX1 N002 N007 N011 Vdc 0 diode_rectifier
XX2 Vdc 0 N003 N008 N012 3_ph_inverter
C1 Vdc 0 {Cdc}
L1 N003 N004 {Lload}
L2 N008 N009 {Lload}
L3 N012 N013 {Lload}
R2 N004 N005 {Rload}
R3 N009 N005 {Rload}
R4 N013 N005 {Rload}
V1 N003 N004 SINE(0 {Vload} {fg})
V2 N012 N004 SINE(0 {Vload} {fg} 0 0 120)
V3 N017 N004 SINE(0 {Vload} {fg} 0 0 -120)

 * block symbol definitions
.subckt diode_rectifier Va Vb Vc V+ V-
D1 Va V+ D
D2 Vb V+ D
D3 Vc V+ D
D4 V- Vc D
D5 V- Va D
D6 V- Vb D
.ends diode_rectifier

.subckt 3_ph_inverter Vdcp Vdcm Va Vb Vc
V7 sine1 0 SINE(0 0.87 {fg} 0)
V8 tri 0 PULSE(-1 1 0 {1/(2*fsw)} {1/(2*fsw)} 0 {1/fsw})
B1 1H 0 V=V(sine1)>V(tri)+0.05
B2 1L 0 V=V(sine1)<V(tri)
V3 sine2 0 SINE(0 0.87 {fg} 0 0 -120)
V5 sine3 0 SINE(0 0.87 {fg} 0 0 120)
B3 2H 0 V=V(sine2)>V(tri)+0.05
B4 2L 0 V=V(sine2)<V(tri)
B5 3H 0 V=V(sine3)>V(tri)+0.05
B6 3L 0 V=V(sine3)<V(tri)
DA+ Va Vdcp mydiode
S§TA+ Vdcp Va 1H 0 MySwitch
DA- Vdcm Va mydiode
S§TA- Va Vdcm 1L 0 MySwitch
DB+ N001 Vdcp mydiode
S§TB+ Vdcp Vb 2H 0 MySwitch
DB- Vdcm N001 mydiode
S§TB- Vb Vdcm 2L 0 MySwitch
DC- Vdcm Vc mydiode
S§TC- Vc Vdcm 3L 0 MySwitch
DC+ Vc Vdcp mydiode
S§TC+ Vdcp Vc 3H 0 MySwitch
.model MySwitch SW (Ron=.001 Roff=10Meg Vt=0.5)
.model mydiode D
.ends 3_ph_inverter

.model D D
.lib C:\Users\NVA\Documents\LTspiceXVII\lib\cmp\standard.dio
.param Vac = 230V
.param fg=50Hz
.param Lg = 0.7mH
.param Rg =0.05
.param Cdc =50u
;ac oct 100 1 100k
;tran 0 {30/fsw} {21/fsw} {0.001/fsw}
.tran 0 {2/fg} {1/fg} {0.001/fg}
.param fsw=10kHz
.param Lload=2.5mH
+ Rload = 3
+Vload=200


texts: Need opinions on servo motor control for heavy applications

texts:
I want to control a servo motor using Arduino and sensors. But all the example schemes or tutorials so far I found are for motors used in toys, low power applications. My task is to control a servo motor which can drive higher torques and lifts up to 100 kg. My concerns:

Is the schematics and circuitry same with the RC motor examples or
one should use extra circuitry such as power amplifiers for big
motors?
How to choose the proper type of motor for my task?
Is there any reference to learn more about Arduino control of motors
used in industry or more powerful applications?


texts: Interfacing 20x4 character LCD with TI TM4C1294 generates some random characters

texts:
I have a 20x4 character LCD connected to my TI TM4C1294 kit as follows:

Data bus to port A.
RS, RW and E pins to port L 0-2

I wrote this code in order to drive it:

#include <stdint.h>
#include <stdbool.h>
#include "inc/tm4c1294ncpdt.h"
#include "driverlib/gpio.h"
#include "driverlib/sysctl.h"

void LCD_SendChar(short c)
{
    GPIO_PORTA_AHB_DATA_R = c;
    GPIO_PORTL_DATA_R |= 0x01;
    GPIO_PORTL_DATA_R |= 0x04;
    asm ("  NOP");
    GPIO_PORTL_DATA_R &= ~(0x04);
    LCD_IsBusy();
}

void LCD_SendCmd(short command)
{
    GPIO_PORTA_AHB_DATA_R = command;
    GPIO_PORTL_DATA_R |= 0x00;
    GPIO_PORTL_DATA_R |= 0x04;
    asm ("  NOP");
    GPIO_PORTL_DATA_R &= ~(0x04);
    LCD_IsBusy();
}

void LCD_SendString(char* value)
{
    while(*value != 0)
    {
        LCD_SendChar(*value++);
    }
}

void LCD_Init()
{
    LCD_SendCmd(0x01);
    LCD_SendCmd(0x38);
    LCD_SendCmd(0x0E);
    LCD_SendCmd(0x06);
    LCD_SendCmd(0x02);
}

int main(void)
{
    // Enable clock gating control for GPIO A and L
    SYSCTL_RCGCGPIO_R |= SYSCTL_RCGCGPIO_R10;
    SYSCTL_RCGCGPIO_R |= SYSCTL_RCGCGPIO_R0;

    // Wait until GPIO blocks are ready.
    while((SYSCTL_PRGPIO_R & SYSCTL_PRGPIO_R10) == 0);
    while((SYSCTL_PRGPIO_R & SYSCTL_PRGPIO_R0 ) == 0){};

    // Configure as Output, digital, no alternate or analog functions.
    GPIO_PORTA_AHB_DIR_R = 0xFF;
    GPIO_PORTA_AHB_DEN_R = 0xFF;
    GPIO_PORTA_AHB_AFSEL_R = 0x0;
    GPIO_PORTA_AHB_AMSEL_R = 0x0;
    GPIO_PORTA_AHB_PCTL_R  = 0x0;

    GPIO_PORTL_DIR_R = 0x7;
    GPIO_PORTL_DEN_R = 0x7;
    GPIO_PORTL_AFSEL_R = 0x0;
    GPIO_PORTL_AMSEL_R = 0x0;
    GPIO_PORTL_PCTL_R  = 0x0;

    LCD_Init();

    LCD_SendCmd(0x94);
    LCD_SendString("Hello World!");
    LCD_SendCmd(0xD4);
    LCD_SendString("Hello World!");

    while (1);

}

The board is running at a 120MHz speed.

The problem is with line addressing. I found out that the line addressing for a 20x4 LCD are 0x80, 0xC0, 0x94, 0xD4 for lines 1 to 3 respectively. When sending a "Hello World" on two lines as shown the two strings are displayed on the same line with a random character between. If I try one "Hello World" for one line while changing line address each time it works fine. What could be the reason for not addressing the lines correctly? and what's the deal with such random characters?

I suspect with:

Values provided for each delay function are not accurate.
I have read that I have to check if the LCD is busy or not but I did not understand the mechanism behind it.

Update: Besides Finbarr's solution, I managed to check the busy flag. Here is my function

void LCD_IsBusy()
{
    GPIO_PORTA_AHB_DIR_R = 0x00;
    GPIO_PORTL_DATA_R  = 0x00;
    GPIO_PORTL_DATA_R |= 0x02;
    while(GPIO_PORTA_AHB_DATA_R & 0x80)
    {
        GPIO_PORTL_DATA_R &= ~(0x04);
        GPIO_PORTL_DATA_R |= 0x04;
    }

    GPIO_PORTA_AHB_DIR_R = 0xFF;
}

Which helped me to eliminate all of the delay calls. The above code is updated.


texts:
Below is the schematics of a circuit so far I finalized and soldered on a perfboard:

(please left-click to enlarge)

Basically the circuit converts 0...10V input voltage to 10mV pk-pk square-wave. The goal is to obtain a linear relation between the output frequency and the input voltage. Since LM331 known as quite linear, I used it as a voltage to freq. converter. But when varying the freq., LM331 also changes the duty cycle a lot. That was a problem in ADC side at the output. So to overcome this and to obtain around 50% duty cycle a 74HC74 follows LM331 by halving the frequency. Halving freq. is no problem because it will not affect the linear relationship between the input voltage and output freq.

The circuit works fine both in simulation and in real. I mean it does the job at first look.

But if you wait enough you see a drift in freq. output(at Q or at Fout).

Here are some observations from yesterday for 2.5V constant input voltage:

At 17:00 o'clock 924Hz

At 18:00 o'clock 918Hz

At 19:00 o'clock 919Hz

At 20:00 o'clock 913Hz

At 21:00 o'clock 917Hz

At 22:00 o'clock 912Hz

And today after powering on the circuit with again 2.5V input I measure the freq. output as: 936Hz which keeps increasing to 945Hz ect.

Here is the circuit soldered on perfboard(I marked some ports and components with red color):

What I have noticed is, when I touch slightly with my finger or a pencil to the capacitor C1 or C3 I see dramatic changes at the output. The other components do not make such difference in response to a physical interaction.

For C1 I'm using a ceramic capacitor as you can see in the photo.

In the data-sheet of LM331 C2 is recommended 1u Mylar capacitor which I use ceramic. But interacting it physically does not make such change as C1.

In another forum I found this comment(in the quote I modified his cap names to be consistent with my schematics):

  Finally I solved it.

  I used C1 = 10nF NPO (very stable with varying temperature) capacitor
  in place of C1 = 10nF X7R (high temperature coefficient). As my
  circuit contains lot of transistors and Transformer, due to increasing
  temperature, the frequency was gradually increasing, which doesn't
  happen now after changing it to NPO.

  Also, I added 47 Ohm resistor in series with C2 = 100 nF capacitor,
  which increased the stability further.

Does anybody have experience or idea about the issue? The capacitor types and tolerances are critical for LM331 in this circuit, I would be glad to hear your suggestions on these.


texts: Are additional smoothing capacitors required off of a voltage regulator

texts:
This is a subset of a circuit I am building to run motors off a PIC 16F884:

simulate this circuit – Schematic created using CircuitLab

I noticed last night as I was drawing up my schematics that I might have redundancy in the use of the smoothing capacitors off of the VDD/VSS pairs on the PIC.

My question is: Does the 0.1uF cap off the 7805 have the same smoothing effect for both VDD/VSS pairs thus eliminating the need for the two extra caps off of the PIC?

simulate this circuit


texts: STM8s Timer1 repetition counter (RCR) not working

texts:
I'm trying to set up PWM on Timer1 Channel 1(N) on the STM8S105K6 together with a repetition counter.
Here is my simple intitialisation function for TIM1 which I used to test PWM:
void timer1_init () {

    TIM1_CR1 &= ~CEN;  // disable timer

    TIM1_CR1   |= ARPE; // auto reload preload enable

    TIM1_ARRH   = 0x00; // just some testing values
    TIM1_ARRL   = 0xff;

    TIM1_CCR1H  = 0x00;
    TIM1_CCR1L  = 0x80;

    TIM1_CCMR1 |= OCM1_PWM2;     // PWM mode 2 */
    TIM1_CCER1 |= CC1NE | OC1NP; // output enable, inv  polarity */

    TIM1_BKR = AOE;  // automatic output enable (MOE) works too

    TIM1_IER |= UIE; // enable update interrupt

    TIM1_CR1 = CEN;  // enable timer
}

And this is my ISR for TIM1:
void timer_isr(void) __interrupt(IRQ_TIM1) {
    TIM1_CR1 &= ~CEN;
    TIM1_SR1 &= ~UIF;
}

This PWM Output works so far (checked with an oscilloscope) and when the ISR is called the timer is stopped on the first PWM Edge.
My understanding is that when I now write a value N into the RCR register it should only trigger the update interrupt on every N + 1 PWM Edge. However when I add
TIM1_RCR = 15;

to my timer1_init() function it does not change anything. My question is whether I am missing something in my initialisation. I have not found any information about additional things to add and all the online resources I looked up also just set the RCR register like above.


texts:
I recently built a 12 V AC rectifier to DC using a 220 V/12 V transformer. I just connected a diode bridge and a capacitor in parallel to give the DC output. But when I connected a 12 V DC motor(automotive AC blower), in just minutes the diode had heat up and wires were burning.

What was the cause of the heat and how can I get away with it in my circuit?


texts: What is feed coefficient / weight of the array factor in an antenna array ?

texts:
In the image, ri means the location of the element in space(x,y,z). and k is alpha + pidcos(thetha)/Lambda and the R(theta,phi) is the radiation pattern of individual element.

In the array factor,

Please explain as to what is the weight wi, Is it the current that we give to the element? Because, the exp part takes care of the phased angle steering.
So, what is the role of w, and what are its probable values ? Please elaborate.


texts:
I am trying to drive a nema 17 stepper motor with a 12v external power source  between
 the collector and emitter. The base voltage will be 5v supplied by an Arduino Uno. I have read a lot on the net about transistors and stepper motors. However, the diagrams on the net have diodes in different places and some have resistors and some have not.

I have tried my best to draw a diagram to represent how I have it currently connected. I do not have any resistors in the diagram because I do not know why I would need it and where to add them. I added the diode between the 5v signal source and the base thinking it will prevent the external 12v from pushing back into the Arduino. Some positive input to help me understand will be most welcome.


texts: How should I wire up the circuit to connect a TSOP4838 (Radio Shack 276-64) infrared receiver to an Arduino?

texts:
Beginner question on datasheets basically.

I have this part, and am working from a tutorial for the code here, but am unsure exactly how to wire up the circuit and what risk I might be at for destroying it if I make a mistake.  In the tutorial, the author doesn't give a circuit diagram, and merely says "All you need to do is supply a resistor (I used 200 Ohms, with a 3.3V supply) to the power line, GND it, then connect the data line to one of your digital pins (I used pin #2)".

However, the datasheet shows an example circuit with a 100 Ohm resistor connected to Vs along with a 4.7 micro Farad capacitor connected between Vs and GND.  I'm guessing that I should connect Vs to the 3.3V output on the Arduino and use a 200 Ohm resistor, but do I need a capacitor?

If I wanted to connect it to the Arduino 5V output, how would this answer change?

Also, for pedagogical purposes, what information from the data sheet would help me answer these questions?


texts:
I've done a preliminary layout of my crystals.  I've never designed a board with crystals so this is just a rough first pass based on my small set of working knowledge of crystal layout.  How am I looking so far?  Anything I could be doing better?

Details on the board:

4 layer (from the top: signal - ground - split power planes - signal)
Y1 is 32.768KHz
Y2 is 12MHz
load caps are 15pF and 18pF for Y1 and Y2 respectively
for scale, the space between Y2's pads and the MCU keepout is 1.75mm

Note: this picture doesn't show the MCU power/ground pins. I have them all bypassed with a bevy of 0.001uF, 0.01uF and 0.1uF ceramics on the outside perimeter of the MCU with direct connections to the 3V3 power plane and ground plane through short traces to vias under the chip

EDIT: Updated the crystal layout and picture.  I pulled in the crystals towards the MCU and pulled in the load capacitors to the crystals.  Even though I'm told it's not important, traces are nearly equal from crystal to MCU.  The traces for Y2 are only off by 4 mils if my math is correct. :D


texts:
I have a backpack mister (basically a leaf blower with a water tank) that is powered by a small 2 stroke gas engine. Another vendor sells an electrostatic charger which draws its electricity from the magneto of a small engine (one wire connects to the spark plug and the other connects to the engine chassis). However, when the device is connected, the motor on my mister cuts out. I assume that the current draw is too much for the small magneto (I think it was designed for a slightly larger motor).

My question is: is there a way to reduce the current draw from the magneto just enough to where the engine will continue to run? Could I install a resistor between the electrostatic device and the spark plug draw? Or would I want to consider a capacitor? If so, what voltage / uf range / etc would I want to use?

Sorry if the question sounds dumb, but I'd really like to get this thing working :-).


texts: Is it good practice to length match all traces of DDR3, or are only data traces important?

texts:
I am researching single board computers with the hope of designing on at the end of this, I am at the stage of DDR3, but can't find any good info on routing ddr3, regarding what traces need to be matched, and so on. Which traces need to be matched? I am assuming it's the DATA traces, and any traces that take data that needs to be in sync, would I be correct in thinking this? Or would it be better to match them all to avoid the chance of missing something or running into issues.
Datasheet: http://www.alliancememory.com/pdf/ddr3/4GB-AS4C256M16D3L.pdf


texts:
In this question Fan7388MX on StackExchange, someone asked how to choose the resistor values for FAN7388MX MOSFET driver.

Datasheet: https://eu.mouser.com/datasheet/2/308/FAN7388-D-1805672.pdf

The MOSFET I am using is the IRFB3207Z.

This circuit is provided in the datasheet, however the datasheet doesn't provide values or mentions how to calculate them.

My system voltage is 60V, and the MOSFETs have a miller charge of 33nC.

He asked about the value of resistors and capacitors marked in blue and red.
I am asking about them in a bit more detail and also the unmarked passives.
I am unsure of how to select the external passive components.

My questions are:

1) What type of diode should I use and which value to check in a datasheet? Any recommended diodes that are easy to find would be helpful.

2) How to calculate the value of the resistors that are not highlighted in blue, the ones connected to the gates of the MOSFETs?

3) What type and voltage rating of capacitor to choose for the bootstrap capacitors (the ones highlighted in red)?

4) What type, value and voltage rating of capacitor to choose for the bypass capacitor (the one connected from VDD (pin12) to GND (pin11))?


texts: What is the maximum run length in PCIe gen 3 serial stream?

texts:
PCIe gen 2 uses 8b/10b and the run length is 5.  What is it for Gen 3?
Thank you for help.


texts: Hooking up LEDs to a drum set - Fire Hazard to plug into a wall?

texts:
I have a friend that wants to hook my drum set's double-bass pedal so that everytime I press it down, it'll light up these kind of LEDs around the 22" diameter bass drum head.  Each pedal would be hooked up to approximately half the circumfrence worth of LEDs.  His friends in EE suggested that 8 AA batteries for each pedal would be enough, but 16 AAs seems to be a lot.  I play drums and kick the pedals at a very fast rate, and we would like to know if plugging them into an outlet (using a 12 VDC power supply) would be safe, given the speed/frequency that the LEDs will be turning on/off.  Would it be a fire hazard?

I apologize in advanced if any terminology is off.  I myself know little-to-nothing about electrical engineering.  (Also feel free to re-tag/re-subject this question - I wasn't sure what to put).


texts: Is a charged capacitor in a power supply dangerous?

texts:
I'm just beginning in hobby electronics and have made a power supply with a bridge rectifier and a smoothing capacitor (4700uF). I want to put a toggle switch in to turn the supply off and on. Should i put it before the capacitor so the supply stays on for a few (15) seconds after I turn it off? Or should i put it after the capacitor so it turns off straight away but the capacitor stays charged? Is it dangerous if the cap stays charged?

Cheers,
Michael


texts: RFID reader for a keyless residential entry system?

texts: What are some good RFID readers to look at for a keyless residential entry system? Are there any on the market that can read a key fob or similar RFID token from a range of 3 feet or more?  This would be a DIY project for a new home, so price is less of an issue than reliability and ease of integration.


texts: 9M resistance on a mixer / DSP interface board

texts:
I am redesigning an old board we have for supporting a signal processing course. It allows students to connect several signal inputs and route them to a DSP board (through 3.5mm aux cable) an an oscilloscope (through BNC connectors).

The original board design has a switch which allows the user to select 10X impedance on the board itself -- essentially, selecting whether the signal to the BNC first goes through a 9 megaohm resistance. The probes we use are also 10X -- and likely always will be.

I'm trying to figure out if I need the switch on the new board, if I need the resistance, or if I need neither. In theory the oscilloscope is capable of being attached to a circuit at any point, and shouldn't need impedance matching... yes? Does the impedance matching provide any particular benefit in this situation? Could I leave it off the board entirely? If keeping the resistance is recommended, could I remove the switch? Or are there cases where having that option is still necessary?


texts: Question about various power/ground sources in one circuit

texts:
I would like some advice on how to handle different power/ground lines on the same circuit. I am not clear about how to wire-up multiple peripherals etc. with their own power sources in a single circuit. For example, i am breadboarding a MCU (with a external 5v supply) and have a USB-UART (or a RS232-UART) connecting it to a PC. So now i have two power sources, one from the USB/RS232 and the other from the circuit power supply. How should the wiring be done so as not to fry anything? I see two options.

Connect power and ground to the entire circuit from the USB/RS232 source (i.e. USB powered) and turn off the external power supply. Use the power/ground lines exposed from the UART device for this.
Power everything from the external power supply. In this case the power pin from the USB is NOT connected to anywhere in the circuit. However the circuit ground is connected to the USB ground (exposed via a UART pin). This seems wrong to me since they could be at different potentials and hence might lead to problems.

So what is the correct way to wire up USB-UART, USB-JTAG etc. from a host to a circuit?


texts: Need help with adding volume control to op amp!

texts:
I am trying to add a volume control to this audio headphone circuit I found online:

As you can see, there are two 470k ohm resistors on the input signal.

Here is my circuit that I created based off this one:

I want to know if this would work or not. I have no way of testing this as its all SMD and going on a PCB. Can anyone let me know if this will work??


texts: How to use PIC A/D converter with ACS712 Hall effect current sensor

texts:
I have built a one amp power supply and want to use a Sparkfun ACS712 Hall effect current sensor with a PIC and 7 segment LED display to show the current in milli-amps. The PIC A/D input has ground as its lower reference, but the ACS712 gives a positive voltage out at zero amps. I want to use the whole ten bit range of the A/D converter, which will pretty well give me the one milli-amp per step, so what can I do to adjust this voltage so that the range at the PIC starts at zero for zero volts?

Incidentally I found the adjustments on the potentiometers on the ADC712 to be impossibly fiddly to adjust, so I have wired 20 turn pots in their place.


texts: Optimise Peltier cooling system: PWM or not?

texts:
SETUP
I have a special test setup for some small circuits that should be cooled down (by air) in a closed box with Peltier elements. It mainly consists of 2 peltier elements (ET-127-20-15 from European thermodynamics), where the hot side is cooled down by two independent water cooling systems. On the cold side I have a huge block of aluminium heat sinks with high performance fans to cool the air. The whole box is insulated with polystyrene and closed. Only the cables and water pipes leave the box, but they are precisely fitted into the polystyrene. To observe the temperatures, I designed a circuit board with 4x MCP9600 I2C thermocouple amplifiers connected to K type thermocouples mounted on each cold and warm side of the Peltiers. I also have solid state relays connected to the circuit board that can switch the Peltiers on and off. The current is generated by at least one 15V DC 351W power supply (I have two of them). Since the Peltiers have only 129W power each, one of them should be ok.
FIRST TEST
I kept pushing the Peltiers without doing anything. I can read with my thermocouple board that the hot side stays around 65°C while the cold side drops to 15°C. That is a delta of 50°C. If you look at the data sheet (https://www.europeanthermodynamics.com/products/datasheets/1-ET-127-20-15.pdf) you can see that the dissipated heat is only about 70 watts.
AIM
The aim here is to bring the ambient temperature to a minimum. While a cold side of 15°C looks good, the overall performance is not as expected: The air inside the box only drops by 7 to 10°C compared to the outside. I know that this also depends very much on the insulation and air volume...
QUESTION
How can the control loop be implemented and optimized? When I read about controlling Peltiers with PWM, I found many people who suggested not using PWM because it reduces efficiency. Some people suggested using a slow PWM (at sub-Hertz speed - e.g. 5 seconds on, 5 seconds off). This seems wrong to me, because the heat can travel back to the cold side if the Peltier is turned off for too long. Please also keep in mind that I already have a static power supply with solid state relays. I can add additional caps and inductors, but I would appreciate feedback on how I can get the most out of my current setup without changing too much.


texts:
I designed a simple 2 stage op amp. Now I am trying to make it work as an integrator as shown in image 1.
The frequency response as shown in image 2 is as expected and I am operating between the cutoff frequency and the 0dB frequency.
When I apply a sine wave of 5kHz as shown in image 3 expecting a cosine wave at the output, it doesn't work for some reason. You can see the output waveform doesn't make sense to me.
Any help is appreciated. Thanks!


texts: How many things can Arduino Uno control?

texts:
This is a newbie question, but how many things an Arduino Uno R3 can control?

My idea is to have Wireless + Ethernet modules and Relays module, be it 8, 16 or 32 relays each.

I saw the Ethernet module goes on top of the Arduino, maybe I'm wrong, but how many pins are left for controlling other things?

Sorry for my newbieness, but I need to buy the items on eBay and I'd like to be sure.


texts:
We know that an almost constant current flows in mosfet when it saturates and the channel is pinched off.If this happens then why doesnt the current flows in a MOSFET even when the gate voltage is below the threshold voltage??
After all both the cases seem to have the same thing i.e. no channel for electrons to flow.
Also,suppose that the threshold voltage is 0.6V and the applied gate voltage is 5V and then we slowly increase the drain voltage to a value such that it saturates.Now if slowly  increasing the drain voltage we suddenly put it to a value much greater than saturation, then will this case be any different from the first case?


texts: Is wireless technology only possible due to inductance?

texts:
I asked a friend how capacitative coupling works in glass-mount antennas.
He said it's like when installing a sound system; where you want to keep the power & audio cables separated, to avoid electrical noise/interference.
I guess he was implying the plastic insulation behaves like a capacitor, effectively coupling two parallel circuits.

I'd originally assumed the noise was caused by the electromagnetic field radiating beyond the borders of the insulation, as opposed to via direct physical contact. But I thought to myself, "The cables aren't coiled. The current's direct. There's no inductance here." † And then I wondered if it even actually works like that. I always thought electricity implies electromagnetism, regardless; that anywhere an electric current or potential occurs, there's an inherent field of electromagnetic radiation, no matter how small.

So which is true? Is an inductor required to induce an electromagnetic field (ie. an electric current oscillating about a coil), or does a limited field already exist simply by virtue of the presence of electricity?

And by extension: Is all electronic/electrical wireless transmission technology (i.e. power and communications) made possible by virtue of induction? ‡

† A few things: a) We were referring to an automotive sound system with a 12V+ DC power supply. b) The speakers have coils. c) The audio signal could be considered AC.

‡ a) Sure; speech, music, sign language, smoke signals, etc. These are all technically wireless communication methods. b) Yes; you could perform photosynthesis or cellular-respiration, rub your hands together, or light a match with a laser-pointer and say it's wireless transmission of energy. c) But it's not a trick question, let's stick to man-made devices, and concepts like electricity and RF.


texts: Power LED's using RF transmitter and receiver with Arduino

texts:
I'm working on a project that I have two sensors, two Arduinos (a YUN and an UNO), two LED's, and an RF transmitter/receiver

It's a pretty simple procedure:  Activate a force sensor, send it via RF to the receiver and light up the corresponding LED.  So my design looks like this -

Sensor 1 and Sensor 2 ---> Arduino YUN ---> RF Transmitter --> Wireless

RF Receiver ---> Arduino UNO ---> LED 1 and LED 2

So if Sensor 1 is activated LED 1 lights up and if Sensor 2 is activated LED 2 lights up.

So far I am able to send the signal and distinguish between each sensor by viewing the serial monitor.  If I hit sensor 1, the Uno receives sensor 1's signal.  Same with sensor 2.  I'm just stuck on how to get the LED's to activate.  I tried Serial.read() code so whenever I send Sensor 1 or Sensor 2, it would read the serial then digitalWrite the led high.  But that didn't work.  Any advice would be much appreciated.  Here's my code if you would like to look at it.

Transmitter:

    // Transmitter Arduino Yun
    #include <VirtualWire.h>
    int pin0 = 0;
    int pin1 = 1;

    void setup()
    {
        vw_set_ptt_inverted(true);  // Required by the RF module
        vw_setup(2000);            // bps connection speed
        Serial.begin (9600);
        vw_set_tx_pin(3);         // Arduino pin to connect the transmitter data pin
    }

    void loop()
    {
       int force = analogRead(pin0); //  analog reading from the Force sense resistor
       int force1 = analogRead(pin1); //  analog reading from the Force1 sense resistor

       const char *msg = "Sensor 1";
       const char *ms = "Sensor 2";

       if (force > 100) {
       vw_send((uint8_t *)msg, strlen(msg));
       digitalWrite(led_pin, HIGH);

       vw_wait_tx();        // We wait to finish sending the message
       delay(200);         // We wait to send the message again
    }

      if (force1 > 100) {
       vw_send((uint8_t *)ms, strlen(ms));
       digitalWrite(led_pin1, HIGH);

       vw_wait_tx();        // We wait to finish sending the message
       delay(200);         // We wait to send the message again
    }

    }

And the Receiver:

    //Reciever

    #include <VirtualWire.h>

    const int led_pin = 3;
    const int led_pin1 = 4;
    char data[20];
    void setup()
    {
        pinMode (3,OUTPUT);
        pinMode (4, OUTPUT);
      Serial.begin(9600);  //Debugging
      vw_set_ptt_inverted(true); //Required
      vw_setup(2000);  //bps
      vw_set_rx_pin(2);
      vw_rx_start();  //Start receiver

    }

    void loop()
    {

      uint8_t buf[VW_MAX_MESSAGE_LEN];
      uint8_t buflen = VW_MAX_MESSAGE_LEN;

      if (vw_get_message(buf, &buflen))
      {
        int i;

         for (i = 0; i < buflen; i++)
        {
          Serial.write(buf[i]);  // The received data is stored in the buffer
                                // and sent through the serial port to the computer
        }

      }

      if (Serial.available()) {
         char ser = Serial.read();

         if(ser == 'Sensor 1') {
             digitalWrite(led_pin, HIGH);
          }
          else if(ser == 'Sensor 2') {
             digitalWrite(led_pin1, HIGH);
          }
       }
    }

Thanks again for any insight.


texts: Triangular waveform shown by DSO for DC output. Is this usual?

texts:
Found this, confusing picture on a popular ecommerce site, shows an extremely economical DC-DC (step-down) adjustable voltage converter (based on LM2596S), which apparently works for upto 2Amps of current, and usable on breadboards.

The part which is confusing is the DSO display, which is giving me the impression that this isn't DC, but dirty (triangular waveform) AC, possibly with the DC component bias. My initial thoughts were that this is a switching regulator (which it might very well be), but should the output stage waveform look like this ?

PS> If someone thinks that this is a shopping question, do advice on how to rephrase, because I am trying to make this a generic electronics fundamentals question.


texts: Matching audio against previous recording in real time

texts:
I'm looking to implement an always-on audio trigger for a consumer product with strict size, cost and power requirements, sort of like the "Ok Google" trigger on the Google Home and android phones.

The big difference is that the trigger is set by the user through prior audio recording. I'm trying to figure out the least power-hungry way of generating an interrupt on detection of the trigger, without introducing additional costly hardware.

Is there a standard way of doing realtime audio matching like this?


texts: Sine wave frequency vs. PWM frequency (AVR)

texts:
I'm using an AVR Mega 168 to generate a sine wave via pulse width modulation. My goal is to generate a sine wave with a frequency of approximately 50 Hz. I understand that the PWM frequency needs to be as fast possible so its easier to attenuate in the filter.

So far, my µC is running at 8 MHz using the internal RC oscillator (I plan on moving to a crystal later on - taking this one step a time). This provides me with a maximum PWM base frequency of 8x106/256 (fast PWM mode) = 31.25 kHz.

My program updates the duty cycle whenever timer0 overflows i.e. every 32 µS (I think... since 1/31250 = 32 µS).

My question now is, how can I 'control' the frequency of the actual sine wave? I can easily slow down by prescaling but that would obviously make the base frequency quite low.

I have included my code below:

uint8_t i=0;

int main(void)
{
     int ipwm;

     DDRD = 0xFF;

     TCCR0A = 0b10000011;
     TCCR0B = (1 << WGM12);

     TIMSK0 |= (1 << TOIE0);
     TIFR1 |= (1 << OCF0A);
     TCCR0B = (1 << CS10);
     TCNT0 = 0;

     OCR0A = 128;

     sei();

     for(;;)
     {

     }

     return 1;
}

 ISR(TIMER0_OVF_vect)
 {
    OCR0A=pgm_read_byte(&sinewave[i]); // update duty cycle
    i++;
 }


texts: I was looking for a high-level explanation about the current mirror but couldn't find it. Can someone explain what is current mirror using simple words? What does it do? and what is the real application that uses the current mirror?


texts: What are the correct zener diode and PTC fuse size?

texts:
Noob here.
I need to add overvoltage protection to a small, portable solar power system I'm putting together. The solar PV array has a loaded voltage in the 23-26v range and an open circuit voltage that can be as high as 45v. The PV array is connected to a solar charge controller to charge a couple of deep cycle batteries. The "load" output of the charge controller is connected to a voltage regular that has a maximum input voltage of 30v.

The load is a 10A max circuit. I need to limit the voltage to 28-29v to prevent damaging the voltage regulator.

I started my research to solve the problem and have read about crowbar circuits, zener overvoltage protection circuits and TVS diodes, etc. I think that a basic zener+PTC is a good fit for my needs, but I'm absolutely stumped on the values. The problem I'm finding is that my circuit needs to operate at 10A so I need at least a 10A PTC fuse. When I check digikey for 10A PTC fuses they are all VERY slow which from my initial understanding means I will fry my zener before the fuse has time to blow.

I'm stuck. The 10A PTC fuse (or any fuse) will current protect my voltage regulator and downstream parts but the 10A fuse won't blow fast enough to save the Zener and if the zener fails I lose my voltage protection. - Ahh!

How do I overvoltage protect a 10A, 30v DC signal?

Edit: I just realized that I think this is fundamentally flawed: If the batteries are low or disconnected the solar PV can't produce enough current to blow the PTC. I'd have a maybe 1-2A of 50v shunting through the zener and it would fail.


texts: Spice simulation of a motor switching power supply

texts:
I'm designing a switching regulator for motor controlling, I have tried this circuit with spice but it does not work:

The problem is that the voltage on the load of the regulator never goes down, as is depicted in the picture:

Is there anyone to explain me why?


texts: How to block DC of triangle waveform from 555 powered by single supply?

texts:
I'm using a 555 timer to generate a triangle waveform with a DC offset. I would like to feed the waveform into a comparator along with an AC signal with zero offset to get a PWM signal, so I need the average voltage of both waveforms to be equal. I'm trying to do this with an DC coupling capacitor to make the triangle waveform centered around 0V, but I'm only getting negative voltage after the capacitor. Why is this happening? How can I get a triangle waveform from the 555 with zero DC offset?

Here is the schematic:

Here is the voltage after C7. It has a ~-3.7v DC offset for some reason:


texts: Slowly turn a planisphere at the sidereal rate

texts:
My  problem is to rotate a planisphere (a star chart) at the sidereal rate.

I will set the planisphere to its initial position manually, then turn on some device which rotates the planisphere on its central axis, to keep it in sync with the current sky at my location. That is, the problem is to rotate a circular, laminated bristol-board (heavy paper) disc once every 23 hours, 56 minutes. The laminated disc may be from 10 cm across to 60cm across, and is fairly lightweight. The disc may be horizontal, or vertical (hung on a wall).

Constraints:

A small, lightweight mechanism is preferred.
Battery power is preferred.
High accuracy isn't needed.
The disc would be rotated\updated once every 10 minutes or so.
I'm thinking that the mechanism would likely be placed at the edge of the disc, not the centre, and a little wheel would be firmly pressed against one face of the disc. When the little wheel spins a full rotation, it turns the disc by perhaps a few degrees.
I prefer simpler mechanisms over complex ones.

Can you provide suggestions for implementing this?

Here is a photo:


texts:
In one of my classes we are learning about circuits. For homework, we have to create a finite state machine for a vending machine using an SR flip-flop. The machine can either take a nickel, dime, or nothing until it gets to at least 15 cents, so it has 4 states (0, 5, 10, and 15 cents). Once the machine receives 15 cents, it dispenses its product. Once in this state, if nothing is deposited it goes to the 0 state; if a nickel is deposited it goes to the 5 cent state; if a dime is deposited, it does to the 10 cent state.

The truth table that I came up with is:

Present|Inputs| Next  |        | SR Flip Flop
       |      |       | Output |
Q1  Q0 |D   N |P1   P0|        | S1 R1 S0 R0
_______|______|_______|________|_____________
0   0  | 0  0 | 0   0 |   0    | 0  X 0 X
0   0  | 0  1 | 0   1 |   0    | 0  X 1 0
0   0  | 1  0 | 1   0 |   0    | 1  0 0 X
0   0  | 1  1 | X   X |   X    | X  X X X
_______|______|_______|________|_____________
0   1  | 0  0 | 0   1 |   0    | 0  X X 0
0   1  | 0  1 | 1   0 |   0    | 1  0 0 1
0   1  | 1  0 | 1   1 |   0    | 1  0 X 0
0   1  | 1  1 | X   X |   X    | X  X X X
_______|______|_______|________|_____________
1   0  | 0  0 | 1   0 |   0    | X  0 0 X
1   0  | 0  1 | 1   1 |   0    | X  0 1 0
1   0  | 1  0 | 1   1 |   0    | X  0 1 0
1   0  | 1  1 | X   X |   X    | X  X X X
_______|______|_______|________|_____________
1   1  | 0  0 | 0   0 |   1    | 0  1 0 1
1   1  | 0  1 | 0   1 |   1    | 0  1 X 0
1   1  | 1  0 | 1   0 |   1    | X  0 0 1
1   1  | 1  1 | X   X |   X    | X  X X X

Based on this truth table [and the k-maps I made from it], I created the following logic gates:

My question is, where exactly does the "reset" happen? For example, if I am in the 15 cent state and deposit a nickel, how does it go to the 5 cent stage? Do I have to make the output from "open" loop around? Sorry for such a novice question, I hope that made sense!

Edit: The first two columns are for the present state of the machine, i.e., how much you have deposited so far. So Q0 Q1 = 00 represents the first state (0 cents), Q0 Q1 = 01 represents the second state (5 cents), etc. The next two columns represent adding a nickel or dime. If you are in the state 00 and and 01, you should move to state 01. Since you cannot deposit a nickel and dime simultaneously, we don't care about the the input 11. If you are in state 10 and add 10, you go to state 11 (and don't get any change back!).


texts: Can I get all the energy from a PV system if it is only hooked up to a CC and batteries?

texts:
What I mean is that I know a charge controller regulates the voltage and current into your batteries to protect them (and CC's can incorporate MPPT's to extract more from your solar panels), but do the MPPT CC's take ALL the energy you could generate from the PV panels and put all of that energy in the batteries (neglecting efficiency here because that is irrelevant for the purpose of this question)? Or do they also tone down the rate at which the batteries get charged as they get close to maximum capacity (I know the CC will stop charging the battery once it reaches full capacity).

For example, would the below be something that could happen?

A theoretical PV system could generate 12 watts with an MPPT CC at a given moment in time. If the batteries were at 5% charge, they could accept a charging rate of 12 watts, BUT since the batteries are at 75% charge, they can only be charged at a rate of 7 watts, so the MPPT CC sets the PV panels at 7 watts, thus losing you 5 watts from your PV panels.


texts:
I'm using an 8 output DAC (LTC2666) to control synthesizers via mono 3.5mm jack connections. It works fine most of the time but every once in a while, plugging in a jack into the synthesizer will break the DAC in all sorts of random ways, often requiring a power down.

Is there a proper way to protect my circuitry against whatever glitches are induced by the mechanical nature of plugging in a jack?


texts: Maximum current on gpio header pins (not on device)

texts:
I have a lot of low current devices in need of 5V or 12V power. So far I have been using cable connectors like this:

The problem is that by "a lot" I am talking about 15-20 devices consuming only a few milliamperes. As you can imagine this is starting to take a lot (too much) space when using those cable connectors.
I am now planning to use an empty PCB breakout like this:

and solder a GPIO header onto it. Then I am going to solder all the pins of the GPIO header together using a thick naked copper strand thus providing me a lot of connection points to take power from.
Now my question is, what are those GPIO headers normally rated for? The pin pair that I will be using to supply the power/ground will ultimately have to handle the sum of all devices. The power source is not intended to supply much more than 3A and has built-in overcurrent protection that should trigger at around 3.3A. Since the raspberry pi can also be powered from the GPIO 5V pin which is using the same type of connector I am assuming 3A should probably not exceed the rating, however "assuming" is never good. I was not really successful in finding anything official for those headers since whatever I am searching just shows information about either arduino or r-pi ratings.
Maybe important: I am not using the typical GPIO 26 AWG cables to supply the power, its 18 AWG cables.
Just for completeness what I mean by GPIO header:


texts: Since, resistance is a passive element, so why its value comes out to be negative?

texts:
In thevenin's theorm,

In a circuit with current dependent current source (value=2i, pointing downwards), in parallel with 2 resistors in parallel i.e 2ohm and 4ohm. And current "i" in 2ohm resistor arm( pointing upwards)

By calculating Thenvin resistance, it comes out to be -4 ohm. But as resistance is a passive element and absorb power. But as per negative value of R, it says it is supplying power, which is practically impossible. Why it is so?


texts: LiPo charging in consumer electronics (less than 1C?)

texts: At what (max) rate LiPo batteries in consumer electronics are charged (for example in cell phones). I mean that LiPo-s are dangerous when overcharged, so what is the best charge rate to be absolutely sure that battery will not set on fire. I presume this will be much less than 1C, because my phone has 1750mAh battery and its wall wart is rated only 1000mA (though I doubt a cell phone draws max. current, this would be bad design I think).


texts:
In a superheterodyne receiver, let us assume, I have a signal in the RF range of 88MHz to 108MHz.

From what I have read, my understanding is that by tuning the local oscillator frequency, we can make the incoming RF signal to fall within the IF frequency range which we have designed.

My questions :

Suppose I have a frequency of 95MHz, and my IF filter is designed at 98MHz (Am I correct in assuming this value for the IF filter?) The signal, after going through the filter, will come as a signal having 98MHz, right?
But my actual signal is 95MHz, and all my modulation is done at 95MHz. Not after the filter, the signal is converted to 98MHz. Won't my actual signal present in the 95MHz, be lost or tampered with filter?

In other words, how is the modulation retained even after passing through the IF filter?

Does high carrier frequency imply that more information can be carried and low carrier frequency imply that less information can be carried per unit time? Can someone explain.


texts:
What would be the voltage V1?
I tried voltage divider :

V1 = (R1+R2/(R1+R2)+(4 R0+ R3 +RT) )


texts: Signal Attenuation TVS and series resistor

texts:
This question is in regards to signal attenuation on high speed data lines like RS-485 (and any others as well). I'm new to the signal world, so please bear with me here.

Are there some useful concepts and general formulas, to help me get an idea of the degree of signal attenuation which may result from adding series resistances and parallel capacitances (like from a TVS) to a data line. When I model the situation as an RC low pass filter, the usable frequencies I get are way too high (in the Terahertz range). I know from my reading that typical cutoffs are in the 1-100 MHz range so THz is definitely insane.

It would be nice to not only have some useful intro theory, but also some realistic values that engineers typically use and design with.

Thank you.


texts: Is my circuit hitting a limitation of the AND gate on IC 74HC08N?-- How does PWM frequency affect performance?

texts:
How does PWM frequency affect the AND gate performance?  And, is this a limitation of this chip or technology?

Using a PWM signal set to 20 KHz on the input, along with +5V on the AND gate the output was zero volts when the PWM was set to less than 50% on.  However, the results were much improved when frequency was reduced to 5 KHz--and 5 KHz is an acceptable max frequency, but still having problems at the low end.

I sent this part out, so we are using a multimeter, rather than a scope, to measure.  For 5 KHz frequency the PWM in and out are different--of course the absolute voltage values will be different, but the trend or slope should be the same. In other words, if graphed, the voltage reduction from 100% to 0 should be roughly the same for the input and output PWMs. We do not see this at 10%, rather it drops to zero.

Power %,Pin 1 vdc, Pin 3 vdc

10                .29            0

20                .68           .34

30               1.20          .72

40               1.75         1.62

50               2.34         2.42

60               2.96         3.15

70               3.60         4.10

80               4.18         4.78

90               4.65         5.42

100             4.99         5.44

So, as you can see, it is pretty much the same as in the white box. At low power (below 20%), I basically get nothing at pin 3.

The pinouts on the breadboard are:
pin 1 is PWM
Pin 2 is +5V DC

pin 7 is 5V DC ground and PWM ground
pin 14 is +5V dc

In an effort to debug my problem, I removed this chip from its socket and put it on a breadboard.  However, I got the exact same results on the breadboard.  To keep this question simple, it will be stated using the breadboard (not shown).


texts:
I find some random issues that is still unknown. I'm using mean well SMPS 12v, 3A for supply and charging 2 cell battery 7.4v with a charging current 1.2A. The supplies are parallel which is switched by LTC4412 power path controller.

The issue I'm getting in my product:
When turning on the AC supply device stops working and runs only when the battery supply is present.

This issue doesn't happen in all the devices.  In some similar devices it rarely occurs and in some devices it is frequent.
The AC voltage observed is 230v (L & N)   30v in (G & N).  What might be the issue in the input side?


texts: .c to .hex file conversion without using any IDE

texts:
I am new to microcontroller programming.
I have a program written in C or assembly language which I need to convert into a .HEX file to flash into the 8051 microcontroller. I do not want to use an IDE (Keil for example) and want to perform this conversion only using terminal commands incorporating some kind of compiler or executing any other program through terminal. I have read some other answers that address similar issues but they make use of IDE. Please help me with this issue and let me know if there is anything else I should know.


texts: How do I organize robust communication between a PC and a microcontroller?

texts:
I have a Raspberry Pi and STM32F072. What I want to do is very simple: Generate lots of data on the Raspberry Pi and transfer it to the STM32.

There are several things that are important:

The STM32 needs time to process data, so the Raspberry Pi should send data only when the STM32 is ready to process it.
The communication needs to be robust. By that I mean guaranteed delivery and no errors (some kind of error correction must be present). Also I want to be confident that connection can stay alive indefinitely.
Preferable at least 1 Mbit/s speed.

I considered using SPI, I²C, UART and USB, but they all share a common problem: They are all too low-level (level 1-2 of the OSI model) and lack any flow control (therefore aren't robust).

Are there any implementations of some preferably lightweight transport protocol on top these which can be is used?
If I have to implement such a transport protocol myself, which underlying protocol will be the simplest to use? Here are my thoughts; please correct me if I am wrong on any of these:

UART is simple, but slow on Raspberry Pi. I think can use a USB-to-UART converter (e.g. ch340) to make it faster, but is it a good idea?
SPI is fast and simple. There is a snag though: Raspberry Pi supports SPI only in master mode, which makes protocol slightly more complicated.
I²C is probably fine, but it's not clear why it could be better than SPI in my case.
USB is fast, has error correction and guaranteed delivery built-in, but it is very complex.


texts: Calculating what frequencies a dielectric can be considered perfect

texts:
I have a problem that is likely going to be on my E&M final this semester that my classmates and I can not figure out how to solve.  The question is

  At what frequencies can Earth be considered a perfect dielectric if \$\sigma = 5 \cdot 10^-3 S/m\$, \$\mu_r = 1\$, and \$\epsilon_r = 8\$. Can \$\alpha\$ be neglected at these frequencies?

Our professor isn't of much use, and we can't find any information in our book or lecture slides (that our professor has stolen from another university) that can help us.

Note: \$\alpha\$ is this case is in reference to propagation constant \$\gamma = \alpha + j\beta\$.


texts:
One of the basic circuit to step down input voltage is to use a buck converter topology. Some power supplies reduce input voltage using non isolated type while others use isolated type (example use toroidal, EI transformer).

If I am designing a bench supply, which should I prefer?


texts: Constructing an MCU controllable resistor

texts:
I need a resistor that I can control with an MCU like an arduino/raspberry pi. Ideally with 1M max resistance. The resistor will handle an analog signal range of \$\pm\ 9v\$. I've considered using a digital potentiometer with a high range, like an AD5290, but zippering would be a concern in my application. I'd like a  range from <1K \$\Omega\$ to \$1M\Omega\$ , continuously adjustable.

To my knowledge, the most common implementations of what I want would be to either use an LM13700 as a voltage controlled resistor, create one with an LED and an LDR, or to use FETs.

My question is: What would be the best solution here? I'd prefer the most linear response possible so the LED and LDR is a poor solution.


texts: Calculating Mutual Inductance in Parallel Wires

texts: How would I calculate the mutual inductance (Lm) between parallel wires if I know the inductance per length of the wires and the separation between the wires?


texts: How critical is the magnetics circuit diagram in a magjack RJ45?

texts:
I'm looking at an example circuit diagram from ST, and it use sa 48F-01GYDXNL part that I can't find anywhere. It's a gigabit ethernet jack with magnetics, and the datasheet shows a circuit looking like:

Link to the datasheet. I'd like to use a different part, but what I want to know is do I have to have the exact same circuit inside the magnetics ? Is any old RJ45 magjack going to work ? Or is it somewhere between the two ?

The one I'd like to use is   (datasheet here) which appears sufficiently different to cause me to worry they're not functionally the same.


texts: How to cure SMPS output to get upset by a switching device

texts:
I have been having ringing spike issues at the output of SMPS power supplies. I don't know what is this phenomenon is about but it is definitely related to switching devices on the same electrical network. When a switch or switching device is on the same electrical network. The switching device upsets the SMPS output. This is directly related to my previous question. Bu that time I didn't figure out the issue starts with SMPS output getting upset.

To demonstrate that I used a grinder as shown below:

And next to the grinder from the same power strip a 5V SMPS is powered.

Here is the output of the 5V power supply and the spikes "during" the short time the grinder is swithcing ON:

And here looks like high frequency ringing when AC coupled:

The problem is this power supply noise propagates through all sensitive devices it powers.

Does anybody have experience with such phenomenon? I even tried with EMI power line filter and isolation transformer but it didn't help. I guess SMPS already have filters at their input. Is there a way to filter out this at the power supply output? Would that issue happen with a linear supply?


texts: How to tell solid vs. non-solid electrolytic capacitor?

texts:
Datasheet of these capacitors (Panasonic FK series -- surface mount) does not say anything about it (https://industrial.panasonic.com/cdbs/www-data/pdf/RDE0000/ABA0000C1181.pdf).  For reliability assessment, I need to know whether they are solid or non-solid electrolyte.

Is there some way to tell, either from the parameters, shape/look, etc.?

I know I can ask Panasonic, but my experience (with manufacturers in general, not necessarily Panasonic specifically) is that in the best case, it will take ages to get an answer from them.


texts: Controlling an electric motor through labview without knowing its speed

texts:
I'm having a little trouble running my final bachelor experiment. My group and I are to find out what exactly causes extreme high frictional forces when pulling a steel cable through wet sand by varying the height of the sand above the cable.

We are, unfortunately, having problems with our motor. In labview we are using a ramp function to increase the voltage on the power supply over time. Usually from 0.4V to 4V in 400s where the sample rate of the entire system is 10ms. However we have noticed that when the frictional forces get too high, the motor starts acting up as shown in the graph below.

What you can see here is that as the voltage increases linearly (not shown) the current follows as well. We are measuring the force by placing a loadcell between the cable and the motor. As soon as the motor starts moving, the current drops and the motor starts pulling on the cable. The force starts increasing. But at some point the motor stops moving and the current shoots up. The decreasing force could be the tension being released from the pulley, the rope attached to the cable etc.

The stopping of the motor, however, could be caused by the fact that the frictional forces of the steel cable are too high (stick-slip). This is our problem. We don't want the motor to stop moving.

I was thinking of using a control loop to increase the speed at which the voltage increases, but I have no way of telling what the speed of the motor is. The tachometers we have won't work because the motor turns too slow. We only measure force, current and voltage.

EDIT:
These are the motor specs:
http://www.compucanjes.com/manuales/rs-555sh20.pdf

And this is how our (crappy) test setup looks


texts:
I'm trying to recover a signal that is encoded and then modulated as 1mA current load pulses on the supply line. What's the best way to do this?

250us long 1mA current increase on each edge of (followed by 250us normal current state)
Original signal is 2kHz (cannot be changed)
Supply current is 0~30mA (so for 5mA sys current the modulation would be 6mA for 250us)
Need to filter out false pulses less than ~200us wide


texts:
Why is the operating speed of a BJT more when compared to MOSFET?

What makes it faster?


texts: what's the purpose of multiple channels on Bluetooth Low Energy

texts:
a question I'm asking (perhaps its stupid) is that, on BLE (Bluetooth Low Energy) why do we need 40 channels?.

  37 of these channels are used for connection data and the last three
  channels (37, 38, and 39) are used as advertising channels to set up
  connections and send broadcast data.

nrf51 device of Nordic for example has only one receiver available in the chip, so it can listen only to one frequency at a time? so why 37??.

what's the purpose of multiple frequencies while we can do communication with one channel (frequency)


texts: How to use the feedback function in Matlab when we have nothing in the feedback loop?

texts:
Matlab's feedback function is used to obtain the closed loop transfer function of a system. Example:

sys = feedback(sys1,sys2) returns a model object sys for the negative feedback interconnection of model objects sys1,sys2.  To compute the closed-loop system with positive feedback, use sign = +1, for negative feedback we use -1.

My question arises when we have a system of the following type:

According to these docs, we can use feedback to create the negative feedback loop with G and C.

sys = feedback(G*C,-1)

This is a source of confusion, shouldn't the above be:  sys = feedback(G*C,1,-1)? These are not the same.

However, looking at these docs, for a unit loop gain k, you can compute the closed-loop transfer function T using:

G = tf([.5 1.3],[1 1.2  1.6 0]);
T = feedback(G,1);

Why are we using  1 and not -1? This is still negative feedback and not positive feedback.


texts: How is (non-interfering) data communication possible over the tv spectrum? What is the technology used?

texts:
I've heard that FCC-US (Federal Communication Commission - United States) has approved the free usage of TV spectrum for wireless communication. How is it possible to enable such data communication over TV bands without interfering the TV channels? What is the technology used? Is it available for unlicensed public use?

A news link is given below

http://gigaom.com/2012/09/06/need-spectrum-fcc-plans-tv-incentive-auction-for-2014/


texts: Can ribbon cable be reconect to its IDC after it's been pulled out from the IDC? Also can a IDC be disconnected from its connection point on the mother board, then reconected after its ribbon cable has been reconected to the IDC?


texts: Difference between a magnetic field sensor and a hall effect sensor

texts:
I can't understand the difference between a magnetic field sensor and a hall effect sensor, to me are both the same.

I have a voltage detector pen that I can use when I troubleshoot my house I believe it detects the electric field (magnetic), but that's it.

If I wanted to make a circuit with a sensor that knows when any kind of metallic object is nearby, which kind of sensor would I have to use?
What kind of sensor do supermarkets use?
How can I increase the detection distance of such sensors?
How could I detect (for example) a car passing by the street with my sensor?


texts: Isolating main power traces on backside of the PCB

texts:
I am currently making a build-in PSU for my own audio-effect-rack-thing.

The internal PSU consists of two print-transformers(THT), one for 6VAC and the second one for 9VAC. These are also pretty low power ones (max 1A on the output).

I want to put the PSU circuit on a perfboard, since this is a simple design. I am already familiar, that there needs to be a decent airgap between main-rails on the PCB. Therefore, I can remove all the unconnected dots, so there can't be a spark.

Now my concern is, when I put the psu circuit in the case, that the backside of the PCB (and therefore the mains(230V) power traces) are touching the case internally.

How can I safely prevent this from happening and is there a better way around ?

My thoughts:

painting the backside with something
putting a plastic sheet beneath it


texts: SCR "current gain" - calculating gate resistance

texts:
Trying to understand the SCR. Have made this outlay which I shall find the right resistors for.

edit

or

The SCR is a TYN1225

But since I have found it difficult to understand \$I_{GT}\$ and \$V_{GT}\$ I have begun with this outlay. That is, after I had understood \$V_{GT}\$ I began with this setup and realize now that there was a relationship between the load consumption and \$I_{GT}\$

edit

Discovered that at the voltages/current I attempted with that there was a gain on around 480, which I only became more confused about.

If I have to make the first layout to be ha max 10A out, then \$I_{GT}\$ should be about 21mA. From this calculation

$$ {10\text{A}\over480\text{ "hFE"}} = 0.02083\text{mA}$$

Do not assume that this "gain" is the same at the different currents (not examined) and do not seem to see anything in the datasheet which gives me an explanation of the relationship between the load and \$I_{GT}\$

Is there such a relationship I can relate to?

Why do I think of limiting the \$I_{GT}\$ opposed to choosing the resistance to max \$I_{GT}\$ As a extra security if it can be done. For example, if I do not want the output to exceeded, lets say 2A, if I then restricts the \$I_{GT}\$, will this not cause the gate not to open if the current exceeds 2A?

The second I'm confused about is the calculation of the resistance.

If I relate to \$I_{GT}\$ = 20mA and \$V_{GT}\$ = 2V

$$ {240\text{AC}\over2\text{periods}} = 120\text{V}$$

$$ 120\text{AC} \times 1.41\text{ } = 169.2\text{peak}$$

$$ 169.2\text{V} - 2\text{V} = 167.2\text{V}$$

$$ {167.2\text{V}\over2*20\text{mA}} = 4.18\text{KΩ}$$

but

$$ 167.2\text{V} \times 2*20\text{mA} = 6.688\text{W}$$

seems to be to much.

What am I doing wrong?


texts: What is the closed-loop bandwidth of the INA143 at gain 0.1?

texts:
The INA143 difference amplifier datasheet states that the device supports G=10 and G=0.1 when connected in difference amplifier configuration. However, the datasheet only gives specifications for the G=10 case.

The bandwidth there is given as 0.15MHz for the G=10 case (where the internal op amp will see a gain of 11), but I'm interested in the bandwith at G=0.1 (where the op amp's gain is 1.1). Given that op amps typically have a 20db/decade gain/frequency relation, can I extrapolate that the bandwidth in the G=0.1 configuration will likely be around 1MHz or above?

I plan to use the amplifier inside a feedback loop, so good bandwidth will be essential for stability.


texts: LED diodes as both diode and load for boost converter

texts:
I'm doing an LED project with a Cree CXB3590 LED that I intend to underpower to experiment with efficiency and learn about boost converter design.  I've made a 5uH inductor with 14 gauge magnet wire wound onto a T50 toroidal yellow/white(iron powder) core.  I plan to use a 555 clock circuit and a 555 pulse generator with a horrible oscilloscope to determine the maximum pulse length for the inductor core and then experiment with frequency to compare total light output from the CXB3590 at different power levels to the output from single LEDs such as an XP-G or XR-E at the same power level.  I'll be using PWM with a frequency limit ~1Mhz due to the iron powder core inductor.  The large wire on the inductor and a decent MOSFET are intended to keep resistive losses as low as possible, hopefully negligible.

Because the CXB3590 is capable of using much more power than the boost converter circuit is likely to provide, I'm hoping to use it as both output diode and load, making the assumption that with each pulse the inductor will drive voltage up to the on voltage of the LED (~33-34V) and when that voltage is reached because the LED's effective resistance will become extremely low, it will not rise significantly higher as the inductor dumps its stored energy.

I'm hoping that this will result in the LED operating in a favorable efficiency band, operating in discontinuous mode and at close to the lowest voltage that will allow it to dissipate the power being pumped into it.

simulate this circuit – Schematic created using CircuitLab

So my question is this:  For what reason(s) I would benefit from using the topology shown on the right, such as the inclusion of a capacitor helping clamp down the voltage the LED sees? the CXB3590 is rated at 86.4W, so at the ~3-10W I intend to operate it at, as I mention above it will likely operate discontinuously.


texts: Setup and Hold Time: A general method to find whether a block satisfies the constraints

texts: How to determine whether setup and hold time constrains are satisfied in a digital block? I encountered a question on the same, and it would be really helpful to know a general way to determine the same.


texts: Altium compiler gives error on old designator

texts:
Whenever I change a designator in the schematics, the old designator will be placed in grey between parenthesis behind the new one.
For some sort of reason Altium decided to give errors on the old designators in combination with the new ones. See pictures below for clarity:

I've tried resetting all designators and annotating them again. Closing the application. Thus far only replacing the part with a new one seems to work. But that isn't doable for a full project.

The when I try to reset duplicate designators I get the following message:

Has anyone had this problem before or does anyone know what might cause (and solve) this problem?


texts:
After plugging the device to the wrong power supply, it doesn't work anymore. When I plug the good power supply, the alimentation voltage drop to 0V and the component LE3CA is really hot (shortcut maybe?).

Because this component is close to the power supply, I'd like to replace it, just in case it repairs my device. My problem is I didn't find the reference of the component (maybe a zener diode) and the product company doesn't want to tell me :(

You can see the component in the middle of the picture.


texts: Which way are heat sinks supposed to be mounted? With the fins around the component, or facing outside?


texts: VHDL process, nested if statement execution

texts:
I am relearning VHDL and have a question about the code below. This is from a tutorial I have been following. When a button is pressed, an LED gets turned on after the person releases their finger from the button. I am confused about the order of execution in the process.
Specifically this line:
if i_Switch_1 = '0' and r_Switch_1 = '1' then
I have been reading that inside processes the code is executed sequentially, so I do not understand how this gets executed, since they are assigned to the same value right before.
Thanks
library ieee;
use ieee.std_logic_1164.all;

entity Clocked_Logic is
    port(
        i_Clk : in std_logic;
        i_Switch_1 : in std_logic;
        o_LED_1 : out std_logic);

end entity Clocked_Logic;

architecture RTL of Clocked_Logic is

signal r_LED_1 : std_logic := '0';
signal r_Switch_1 : std_logic := '0';

begin
    p_Register : process (i_Clk) is
    begin
    if rising_edge(i_Clk) then
        r_Switch_1 <= i_Switch_1;

        if i_Switch_1 = '0' and r_Switch_1 = '1' then
            r_LED_1 <= not r_LED_1;
        end if;
    end if;
end process p_Register;

o_LED_1 <= r_LED_1;

end architecture RTL;


texts: Sallen-Key filter using LM358 doesn't act as supposed to when fed a 31.25 kHz PWM

texts:
I want to create an Analog Voltage by filtering a PWM signal. After some googling, I found an active low pass filter topology with -40db/decade called the Sallen-Key topology. I tried implementing a circuit which would take a PWM with 31.25 kHz frequency and filter out anything but the DC component. When simulating with LTSpice this seems to work (if I use a dual supply), however when implementing on a breadboard using the LM358 dual Op-amp, the circuit behaves weird...

This is the circuit (OP27 is in my case the LM358):

It works at high duty cycles, but at low duty cycles really large voltage spikes appear.

This is how it behaves, as seen from my oscilloscope, at over 70% duty cycle (NOTE: RED is PWM input and blue is filter output):

And this is how it behaves at about 50% duty cycle:

Notice the large, over 1V voltage spikes.

I did an FFT on both signals with following results:

High duty cycle:

Mid-Low duty cycle:

As you can see, no extra harmonics appear, their amplitude just changes with varying duty cycle, however the filter seems to respond really weird.

Does anybody have an idea why this problem appears and how to fix it?


texts:
I'm (still!) studying Solid State Electronics on Müller, Kamins and Chan's textbook "Device Electronics for Integrated Circuits" and in chap.4's summary about Metal-semiconductor contacts I've come across this statement:

  [The Schottky theory] predicts blocking contacts and rectifying
  behavior for n-type semiconductors if the metal work function \$\Phi_M\$
  exceeds the semiconductor work function \$\Phi_S\$ and ohmic behaviour if
  \$\Phi_S\$ is greater than \$\Phi_M\$. The inverse is true for metal contacts
  to p-type semiconductors

What's the difference between rectifying behavior and ohmic behaviour? I just need to get a gist of it, no need of big and complicated formulæ...


texts: An 8 bit value can range anything from 0 to 255 in decimal, or 00 to FF in hexadecimal. But why did they choose 8 bits for the byte, out of all of the powers of 2 they could have chosen? Even still, a nybble seems like a more suitable value for the smallest addressable memory unit, because it takes only one hexadecimal digit to write down. The main downside with nybbles though, is that they will require double the fetch cycles to execute properly. But in that case, why not just make the byte length equal to the word length, requiring only one fetch cycle per instruction? And if its so useful for a byte to be 8 bits, what is its use in microprocessors that aren't 8-bit? This could really help me out in designing my first Logisim CPU, so why are bytes 8 bits, and what is the use of an 8-bit value in non-8-bit computers?


texts: 4 Layer PCB Altium - 2nd Layer Ground, others Thermal

texts:
I read since a long time but never had an account, now its my turn to ask a question on here:

I have an idea but currently unsure if that works technically or if it is good design:

1st (Top Layer) : SMD Devices + Routing

2nd Layer       : Ground Plane (only Ground)

3rd Layer       : Thermal Plane

4rd Layer       : Thermal Plane + THD Connections.

So all of my devices are SMD, apart of a few connectors which are THD.

The 3rd and 4rd Layer are only copper planes which are connected to a heat/cold source to regulate temperature of whole PCB. Obviously I will need vias which go only from 1st Layer to 2nd (to ground). Is that maybe too expensive to manufacture?

I am only concerning about my connectors: the pins are soldered on the bottom. Normally THD are like vias, so it also has a connection on the top layer. Which I can connect then to a local ground plane which goes with vias down to the 2nd Layer.

Is that alright?

Maximum Frequency will be about 90 MHz.


texts:
Why is transmission gate connected this way (source of NMOS connected with drain of PMOS, and source of PMOS connected with drain of NMOS)?

Why don't we connect source of NMOS to source of PMOS and drain of NMOS to drain of PMOS?
Is there a difference?


texts:
As generally all node voltages can be found out by node analysis.
But how to find all node voltages if all currents in a circuit are known, otner than node analysis.


texts: Termination method of a connector pins and noise

texts:
In applications like a 24V transducer to be powered and its signal to be delivered to an enclosure ect. I mean low power electronics sometimes cable mount or panel mount connectors needed.

Im wondering whether the termination method of such connector pins matter in terms of noise in a signal chain? Below are examples for screw and solder types:

Is there any disadvantage of using screw type instead of solder type?


texts: Interpreting thermal shutdown threshold values from TPS659037

texts: I'm studying the datasheet of TI TPS659037 PMIC. The MIN / TYP / MAX values are throwing me off here. Are these 3 numbers indicating variations between every IC manufactured?


texts: What is the electron density in a capacitor relative to source/ground?

texts:
I just started studying electrical engineering. So far I'm trying to figure things out by visualizing the electron flow and density in different scenarios. But I'm having a hard time when it comes to this particular case.
For example, in this configuration the capacitor is fully charged, and the voltage difference between ground and the lower pin on the capacitor is essentially 0.

When the switch is opened , the voltage difference between ground and the same pin is suddenly 5 volts.

I understand that ground should be seen as a zero level for the circuit, and following that rule this makes sense. I just can't quite grasp how this works on the electron level. I believe the capacitor pin that's connected to ground has a higher density of electrons than ground itself, but because the other side of the capacitor has a lower density of electrons, it ends up "pulling" the electrons on the other side. And that's why the potential difference between ground and the lower pin ends up as 0.
Is this correct? If we removed the plate on the opposite side of the ground pin, would there be a potential difference between ground and the plate that's left?


texts: Why are power supply decoupling capacitors used on both supply rails in dual supply opamps?

texts:
I have seen circuit diagram in analog devices application note which shows that both supply rails have a 1uF and 0.1uF capacitor for dual supply opamp but only the Vcc has them in a single supply opamp.

Why are decoupling capacitors used on both supply rails in dual supply opamp?


texts: Any information on BLS, BLD, HU, etc connectors

texts:
There are a few similar types of connectors: BLS, BLD, HU, PHU. They are frequently encountered in electronic devices, but I couldn't find any information on them. Google only finds a bunch of places to buy them, sometimes with a picture and a short description. Where can I find more information? What do their names stand for? What company invented them, and when? Where is any documentation, specifications, or other documents? What other similar types of connectors exist? Why does any information on these connector types seem to be completely absent from Wikipedia and other informative websites?

Here are some images:

(source: cablesandconnectors.com)

(source: cablesandconnectors.com)

(source: cablesandconnectors.com)


texts:
I'm trying to imagine a fancy electronic circuit for an electric guitar with lots of customization options. Is it possible to design a guitar pickup analogous to an electro-dynamic speaker? Ie. using electromagnets for the pole pieces instead of fixed magnets? My hope is this would provide an extra dimension of customizability by varying the magnetic strength, but my fear is that the coils of the electromagnets will "short circuit" and induce a current in the outer pickup coils.
If there is induction (transduction?) among the coils, can it be shielded somehow without interfering with the needed magnetic field? Or can it be tuned to a very high frequency and removed later with a low pass filter?

Please ignore the op-amp portion for the purpose of this question, they are intended to compensate for the varying signal strength from the multiple coil taps.


texts: DC Motor + 9 V battery + 270 ohm resistor = Nothing (Motor won't turn)

texts:
I'm trying to wire up a DC motor to a 9-volt battery with a resistor in between, and the motor just won't turn. It works if I connect the motor directly to the battery, but not with the resistor in between. Why is this?

Motor: 1.5-volt DC motor.*
Resistor: 270 ohm. (Red-Violet-Brown-Gold) (Because it's what I had laying around)
Battery: Normal 9-volt battery.

* I'll try to find more specific details, like a datasheet, when I get home. Unfortunately, I don't have the motor with me while I'm typing this question.

More specifically, I am trying to create something like this circuit:

With the intention of, when the switched is flipped, the motor changes direction. However, when I make this circuit, the motor doesn't spin, so in troubleshooting, I reduced it down to a single resistor, the motor, and the battery, with no switch or direction-changing, but the motor still doesn't spin.


texts: Identifying source and drain for a transistor

texts:
My question is related to this post (the comments below).
Basically, how can I identity the source and drain of a transistor ? I thought that drain and source were totally symmetric inside of NMOS or PMOS from the P/N structure behind as also explained here.
But apparently, in the comment below this post, a PMOS source should be the highest voltage of a circuit and the NMOS source is the ground.
I would like to understand why. Also I am not sure to understand this explanation because what happens if actually a NMOS transistor is not plugged to the ground on any of its port (but at some "intermediate" voltage).


texts: What components do I need to wirelessly transmit a small signal via Bluetooth?

texts:
So I'm doing a project trying to create a wireless Electrocardiogram (ECG or EKG) system.  I built the hardware, connected it to a human subject, and it works perfectly - you can see the heartbeat well on an oscilloscope.  Here's a little more information on my signal:

Amplitude: ~800 mVpp
f < 30 Hz (and there are important frequencies that are ~ 1 Hz)

I am having a hard time choosing which IC to buy because there are so many to choose from, and I don't know which ones will satisfy my needs.  Let's assume I have a display that can receive the wireless signal and display it (i.e. a mobile phone with Bluetooth capabilities, and an oscilloscope app).  What specs should I be concerned about when looking at the spec sheets for the ICs?  Is a microcontroller necessary?


texts: Looking for identification of an electrical component

texts:
Kind of an odd source I'm referencing, but I'm looking for the identification of an electrical part in a video game item.  Here are two pictures (screenshots of the 3d model), where I've circled the item in red...

The part actually looks really familiar to me, but I can't place what it is.

Keep in mind this is a virtual item in an artistically created computer game.  But that said, I believe the artists may have referenced a real item, and I'm trying to figure out what it is.

My reason to identify it is because I'm building a prop reproduction of the item - the "Rail Gun" from the Metro 2033 game.  I've got a build thread on the reproduction prop forum at http://www.therpf.com/f9/metro-2033-volt-driver-research-build-journal-167421/ if you're into that kind of thing :)


texts: I2C to 1-Wire@ 3.3v and 5v output transportation

texts:
I am feeding the I2C pins of a micro-controller into the converter shown in the circuit below to convert it to 1-wire protocol: However, the output will be at the level of 3.3 volts.

I was considering the fact that with the voltage drop along the electric cable holding the Data_Sig Bus, we will lose data. Is it a better idea to convert it to 5v using this circuit:

I am confused about the following scenarios:

Converting the two wires SDA and SCL seperately to 5 volts and then feeding them to the Single-Channel 1-Wire Master?
Feedback the Vcc of 5 volts to the "Single-Channel 1-Wire Master" so the output will be one-wire at the level of 5 volts?

Converting the Data_sig from 3,3 to 5 volts at the output?


texts: How to connect breakout boards to bread boards?

texts:
One of my components for a prototype lies on a breakout board. The rest are connected on a breadboard.

How can I neatly connect the leads on the breakout board (seven in the picture) to rails/holes on the breadboard? I'd prefer not to solder, since I'd like to reuse the breakout board.

Would simply putting the breakout board on a 1x7 header work?


texts: I keep getting an odd result from an LSM6DS3 (common IMU device) and I'm not sure where else to turn.  I have it hooked up to an MCU (nordic nrf52840, not that it matters) and I see my clock signals, and the correct input on MOSI, but I get data back in MISO at the wrong times...  I can always get the correct signal back from WHOAMI, but then it goes off the rails.  You can see in the scope captures, first I get a successful WHOAMI (value 0x69), followed by a write to a control register, then on the next write to a control register, you see that the device returns a value while I am still feeding it an address. I also include a screenshot of later on in the logic, the same behavior.  I get this same behavior with three different samples of LSM6DS3, which leads me to believe I'm doing something wrong, but I have the pins hooked up and configured correctly (at the very least shown by the WHOAMI) - so maybe there is something I'm missing about configuring the IMU?  Does anyone have experience with these devices?


texts:
Need help to indentify this IC, i have googled for "CD10347", "B20", "N02". And can't get a match. Need the datasheep and a replacement part.

Thank you


texts: Given thermal capability of a transformer, how to best estimate the voltage regulation?

texts:
I'm working with a system that has 3 2MVA transformers for which there is an existing estimate of the peak load and the power factor. The xfmrs appear to have a greater thermal capability than the rating (up to ~120% per xfrmr), and we're adding a shunt cap-bank ~1MVA to improve the voltage regulation.

I'm trying to nail down what the MVA rating of the cap bank is going to be and whether to increase or lower the rating to decrease the load to the thermal capability of the xfmrs. However, I don't know how to estimate the quantity of voltage regulation given the thermal capability. I'm assuming this is due to I^2 R losses in the transformers.

Much appreciated.


texts: What are the drawbacks of using a ferrite inductor in a boost converter circuit

texts:
I have dissected a boost converter so I can remake it on my own PCB. It works fine but I am now experimenting with using different inductors to reduce the overall footprint. I tried installing a ferrite inductor which I had lying around. I don't even know what value it has but to my surprise it seemed to work and held a relatively stable voltage when I attached a motor to the circuit.

What are the drawbacks of using one of these because they are smaller and easier to solder than coils and so it seems like a no brainer to use them although I’m sure there must be reasons not to...


texts: wrong answer for convolution with \$ e^{-t}\delta (t) \$

texts:
I am trying to do convolution of a function \$ x(t)\$ with \$e^{-t}\delta(t)\$

Here are the steps I followed:

\$ x(t)e^{-t}\delta(t) = \int x(\tau)e^{t+\tau}\delta(t-\tau)d\tau
=e^t\int x(\tau)e^{\tau}\delta(t-\tau)d\tau=e^t x(t)e(t)=e^{2t}x(t)\$

But if I put back \$x(t)=\delta(t)\$, we wont get impulse response.

Can some one tell me where I made a mistake in convolution?


texts: How are processors tested before going to production?

texts:
No matter how much experience an engineer has, or how many engineer works on the design of a processor or a microcontroller, we are human at the end, and it is possible to make mistakes. Before sending a processor design to production, how are they tested so the processor works correctly?

Are they designing the whole processor in FPGA? or is the whole design checked and debugged by software? (I am considering the complexity of x86 processors, ARM, PIC etc.). Thinking about 1970s with the design of 8086, they didn't have that much technology.


texts:
I have an application that requires optical transmission of 4x16 Gbps SERDES lanes over fiber. A QSFP28 module for 100G ethernet seems like a great commercial solution--it can take the four lanes and combine them over a single fiber channel. The only hitch is that all of the QSFP28 modules I can find are only characterized over a narrow electrical lane rate, about 25-27 Gbps.
Here's an example from FS, but it's a similar story for all vendors I've checked: https://www.fs.com/products/75309.html

I understand why the datasheet recommended range is so limited, since they are designed for a singular networking application. However, my gut also says that a lower but not-too-low lane rate like 16 Gbps would be okay for the internal SERDES transceivers. It would also enable the modules to be used in 40G/4x10G applications, so I'm wondering if there are any resources that would serve as evidence to this point.

Additional Research
I accepted Joren's answer since it showed quite clearly that the limitations of the CDR/retiming functionality of QSFP28 modules would be the foremost barrier. I also did a little research that I want to share here. There is a workaround provided in the QSFP28 memory map. See the snippet below from SFF-8636: Management Interface for 4-lane Modules and Cables, which shows that it is possible to disable retiming functionality. This presumably comes at the expense of signal integrity at the receiving end and consequent maximum link length.
I'll probably run some tests, and also take advice to look at alternate fiber specifications.


texts: Connecting two op amp circuits each of which use dual supplies, but where the two supply voltages differ

texts: One of the op amps uses +- 12 volts and the other +- 5 volts. With only one circuit, I understand that the common ground for the entire circuit is midway between the two supply voltages, but when the second circuit is present, I do not understand where the common ground is that connects the two circuits.


texts: How to find the load resistor's resistance?

texts:
Use max power transfer theorem to calculate the value of RL for the following circuit.
I've done the Thevenin's equivalent circuit but from there I don't know how to find the \$R_{Load}\$.  I need it to do a table of current and power against \$R_{Load}\$.
Any suggestions or help would be appreciated.


texts: Fast Fourier Transformation of incomplete signals

texts:
I would like to perform a FFT on a signal with equally sampled values of which some are missing.

(Actually, they are not even missing, but simply erroneous, so I can't use them, but I can detect when I have a wrong samplepoint.)

Is there a way to compensate for those missing values and get a good transformation? I suppose this is a frequent problem, but so far I only found this and somebody interpolating the missing values.

As far as I understand it, if my signal is, say, 100 HZ and the frequencies I care about are, say, 5 Hz, following the Nyquist theorem a 10Hz signal should be enough, so I could downsample the signal in a way that removes the missing points.

So my question is, is there a way to use a fourier transformation (preferably FFT) on a signal with missing values and get an (at least almost) correct spectrum for small frequency values while retaining the other information? How about other transformations (orthogonal like wavelets, etc.), is it the same problem or a completly different?

Edit:

Thanks for all the input, I will definitly review the literature, I was just hoping there was a good starting point or standard solution I had missed so far.

One commenter said I didn't provide enough information, so I'll add some. The signal processing should be real time (best case), so more processing time would be a big issue. The data cannot be recorded continuously and then sampled as the recording method per definition uses sampling (like a camera).

I am looking for a recurring signal with a frequency which is between 15 and 100 times smaller than the sampling rate, though most times it's rather 20-40 times smaller. The recurring signal itself however has higher frequency components, so it's not exactly staying below my sampling frequency.

My actual problem, for which I was trying to gather ideas with this question, is that at random points in time I get baseline shifts (inherent, no physical solution possible). They can be detected as they are way greater than the actual signal and others are working on ways to compensate them algorithmically. However, during signal analysis, as of now, I have thos shifts of baseline that may or may not happen fast.

Those shifts can either produce spikes and effectively killing any interesting signal or be more or less filterable, talking for example a ramp signal overimposed on a part of the original signal.

I'd like to retain as much data as possible - and as I'm trying to work real time, just using a transformation on the part before the shift and another one on the part after the shift would be a bad solution.

I do know the base frequency range (in which the signal is repeated) and more or less the signal form (however not exactly amplitude and length, it may be a little shorter or longer losely depending on the reptition frequency) I am looking for.


texts: How does a boost converter allow for a gain in output voltage by just switching the positions of the inductor and switch?

texts:
I get that in a buck converter, a low pass LC circuit was attached and this effectively filters out high frequencies. If the bandwidth is configured so that it is lower than the switching frequency, a pure DC output is produced. But what I don't get is that why in a boost converter, the positions of the switch and inductor are interchanged so that the the output voltage increases. How does this work?

I guess I could also ask for how the buck boost converter works through putting the switch and inductor in series.


texts: What sort of protection does a 2 pole circuit breaker offer?

texts:
I am trying to understand the advantages of using a 2 pole circuit breaker. I mean when the 2nd pole is used in the Neutral line in a single phase 230VAC system. Normally they cost more so they must have some advantages over the single pole circuit breaker. So please explain to me the actual advantages of using 2 pole circuit breakers in a 230VAC L and N lines.

The answers I found are mostly related N.American electrical systems which are 120 or 240VAC, so those are different than European systems. I also know there are regulations to use them depending on the installation area and the type of protection sought but I want to given the option of choosing one, which one should I be using.


texts:
I'm toying with the idea of trying to build an inverter:  12v DC - 240v AC.

I'm thinking that I could use a buck-boost converter to convert 12v DC - 325v DC, then use an H-Bridge to chop the 325v DC up to an AC waveform.  I like the idea of doing it this way a little more than chopping up 12v DC - AC, and then using a transformer.

I'd like to supply around 2amps.

My question is simply whether this is within the realms of possibility?  Could this circuit feasibly work or am I barking up the wrong tree?

Edit:
I should clarify that I am unsure whether I'd be able to deliver the required current at these voltage levels with a buck-boost?


texts: Potentiometer overheating - is it due to current rating?

texts:
I need to get a pump running at different speeds so I ordered an electric motor, a potentiometer and a power supply adapter. I put them all together and they worked, however the potentiometer got burnt out.

These are the items:

Electric motor: RS PRO, 12 V dc, 3000 gcm, Brushed DC Geared Motor, Output Speed 1425 rpm

Potentiometer: RS PRO, DC Motor Controller, 6 → 15 V dc, 3 A, Panel Mount

Power adapter: JnDee™ 12V 6A 6 amp 72W AC/DC POWER Supply ADAPTER Transformer ## Great For CCTV, LCD Monitors, TVs and Powering LED Strip ## (12V 6A)

And this is what happened with the controller:

I am trying to find where the problem is. Is the power supply not giving a non-digital dc input? Is the current rating (3A) of the potentiometer being different to 6A given by the power supply?


texts:
Practicing Mesh Analysis I came across this problem and te answer is really  alluding me and I believe is just one polarity that I'm not understanding, the problem is the following...

  Vs=10V, R1=100Ω, R2=50Ω, R3=25Ω, Is=2A.

  Calculate the current I1 in amps that goes through R3 from left to right. Enter >only the numerical answer for I1 in the text box, omit the units. Note: this >problem can be done different ways, but try using Mesh Analysis.

Now, I'm setting up my equation using the passive sign convention as following.

Vs voltage rise
R2 voltage drop
R3 voltage rise (since current is flowing clockwise entering the "negative" terminal of R3)

so it would look something like this:

  -Vs+R2(I1-I2)-R3(I1)=0

  -10+50(I1-(-2))-25(I1)=0

Now the answer to the question is 1.2 which I could achieve if the voltage across R3 was in fact " 25(I1) " instead of negative as in my equation, the thing is that I don't understand what I'm doing wrong and I don't Understand why it is positive if it is a voltage rise?


texts: How can I know which constellation diagram has a lower symbol error just by looking?

texts:
So for the following example:

How would I know which is less prone to error?

$$C1=[−3−3j,−3+j,1−3j,1+j,−1−j,−1+3j,3−j,3+3j]$$

$$C2=[−3\sqrt2j,−2\sqrt2−\sqrt2j,2\sqrt2−\sqrt2j,\sqrt2j,−\sqrt2j,−2\sqrt2+\sqrt2j,2\sqrt2+\sqrt2j,3\sqrt2j]$$


texts: Are PTC/resettable fuses really moisture senstive?

texts:
I recently bought some 0805 Multicomp PTC/resettable fuses from Farnell. They were MC36213 (500mA) and MC36206 (200mA). I plan to use these in product which may exist in a high humidity (~80-90%) environment, although that is not my main concern: instead, what is written on the package:

CAUTION: MOISTURE SENSITIVE DEVICES!

The product in this package is a moisture sensitive device.

The package in which it is supplied will offer physical and
electrical protection but will not offer sufficient protection
to prevent moisture ingress.

These items should be baked for a minimum of 48 hours at 125C
prior to reflow.

Moisture sensitivity level: 4

Now, I have no idea how I will be able to bake them at 125°C for 48 hours. I do not have the ability to do so. Especially not at a reasonable price.

Do I have to do this, or is it a mistake? How can I prevent damage to these fuses from moisture? What happens if they do get moisture on them? Will they not work properly to protect a power supply against short circuits and over-current? How can I bake them at such a temperature? I plan to reflow them on a hotplate for the initial prototypes, but I'm not sure if that's the "reflow" they talk about.


texts: Capacitor bank design considerations for coil gun?

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I am designing a coil gun using a schematic that specifies a capacitor bank of 10 1500uF capacitors in a 2x5 arrangement to provide an effective 600uF at 1000V.

I am wondering why this configuration is desirable rather than, for example, using all 10 capacitors in parallel. An all-parallel design would reduce the maximum voltage requirement to 200V, avoid problems arising from variances in capacitance for capacitors in series, and would deliver the same energy through the coil.

Are there other advantages, disadvantages, or considerations to be taken into account when designing the capacitor bank?


texts: Issues with driving LEDs with a CC driver

texts:
My circuit consists of 16 MP-3030-1100-40-90 connected in series which I'm driving with this CC driver @ Vs = 48V.

I'm setting the current by changing the voltage on the control pin.

I'm having trouble with the LEDs overheating:

@ If = 50mA (1/3 of Itest), they reach a stable temperature of 85°C.
@ If = 100mA (2/3 of Itest), they go >150°C.

The PCB they're mounted on is 1.6mm FR4 with minimal copper coverage.

Questions:

Is the overheating caused by a lack of cooling? Are manufacturer's specs measured with in some kind of active cooling setup?
It was my understanding that a CC driver keeps the current constant and the dimming happens by changing the voltage supplied to the LEDs. That's not what I'm seeing. Why?
My plan for driving the LEDs was to use an accordingly sized CC driver. Since I can't seem to be able to drive these LEDs safely at If > 50mA, how do I prevent them from going over that number in hardware?

Here's my attempt to calculate a current-limiting resistor based on this tutorial:

If = 50 mA @ Vf = 2.53 V (measured)
R = (Vs - V) / If = (48 V - 2.53 V * 16) / 50 mA = 160 Ohm

However, the maximum current I'm seeing after connecting this resistor in series is 31.3 mA. What gives?