texts: The stopwatch function in MPLABX gives a value that's way off in reality

texts:
I have a PIC16F688 running on 4MHz (intosc) and I need a delay for about 1 second. Using this for-loop:

for (unsigned long n = 0; n < 219300; n++) {}

yields this result in the stopwatch function in the simulator:

Stopwatch cleared. Stopwatch cycle count = 0 (0 ns)
Target halted. Stopwatch cycle count = 4038340 (1.009585 s)

That's perfectly fine for my application.

But when I run the code in an actual chip, the delay takes about 10-12 seconds instead of 1. This made me think that the chip is running on a way lower frequency than 4MHz, but I've double checked and it is in fact running at 4MHz. The simulator is also setup to run at 4MHz, so no mismatch here.

Other than a too low frequency I cannot think of any other error that makes this delay way off. Interrupts are turned off (INTCON = 0).

Any clue as to why this happens? Why doesn't the stopwatch value match reality?


texts:
I'm studying amplitude,frequency and phase modulations for an exam. I just studied amplitude and frequency modulations, however i didn't succeed in understanding how the phase modulation changes the spectrum of a signal. Can you help me ?
Thanks so much


texts: How to control interrupt using timer in microcontroller

texts:
Hi I am using 8051 microcontroller. I do have a digital Water Meter which gives binary 0 1 0 1 type data.
I attached it with 8051 INT1 so that i can get interrupt. Now when ever water flow through meter it will start sending interrupt (pulses of 0101) to 8051 INT1.
Now i want to count total pulses and send it.

For that i am using this program in Kiel in C language : [2nd Updated]

#include<reg51.h> // include at89x51 . h
#include<stdio.h>// include stdio . h
#include<stdlib.h>// include stdlib . h

unsigned long  value,x;
unsigned long check;
unsigned long time_overflow_count=0;
void initialize_GSM_modem(void);
void initialize_serialcommunication(void);
unsigned char Command_CMGF[]="AT+CMGF=1\r";
// AT+CMGF for selecting Text Mode
unsigned char CtrlZ=0x1A;
// CTRL+Z for sedning SMS after the message has been entered
unsigned char Command_CMGS[]="AT+CMGS=\"+9xxxxxxxxx\"\r";
// recepient mobile number
unsigned char Command_AT[]="AT\r";
unsigned char msg02[]="Hello!";

unsigned char buf[10]={0};

void send(void)interrupt 1
{
time_overflow_count=time_overflow_count+1;
if (time_overflow_count==5){
if(value==x){

sprintf((char*)buf, "R %lu", value);

time_overflow_count=0;

initialize_GSM_modem();
value=0;
}
}
TR0=1;
}

void input_counting(void) interrupt 2
{
TR0=0;
TL0=0x00;
TH0=0x00;

value=value+1;
TR0=1;

}

void main (void) {

TMOD = 0x21;
TH1 = 0xFD;
TL0=0x55;
TH0=0x55;
SCON = 0x50;
TR1=1;
EX1=1;///Enable external intrrupt 1
EA=1;
IE1=1;
IT1=1;
PX1=1;
ET0=1;

TI=1;
while(1)
{
x=value;
}
}

void delay(void){
unsigned int i;
for(i=0;i<50;i++);
}

 void delay2(void){
unsigned long i;
for(i=0;i<15000;i++);
}

 void initialize_GSM_modem(void)
 {
 delay2();
puts(Command_CMGS);
delay2();
puts((char *)buf);
delay2();

while(!TI); TI = 0;SBUF = 0x1A;
 }

*Updated :*So using this I'm trying to get a timer interrupt which checks when there is no pulses for some time interval then it assumes that meter flow is complete and send the message.

But there an error : I don't know why but our program keeps on sending continues messages for a number of times even if I don't start water meter. If I start water meter it sends the total value at stop and if I don't, it keeps sending 0 at regular interval

What I want is that it waits for water flow (or interrupt to start) and then checks for last value and send it only one time.

Next time I start the meter, it should wait and send the value again, but it should not keep on sending 0s at regular intervals.

UPDATE : I have updated the code and its working fine but its not working as i wish

Please Suggest

Thanks


texts: If I recall correctly, saturation occurs if \$V_{GS}>V_{TH}\$ and \$V_{DS}>V_{Dsat}\$ for NMOS. But is there an upper limit for the voltage? Like, when does a transistor not saturate after continually increasing \$V_{GS}\$?


texts:
I have a lowpass filter (0 - 2MHz). I wanted to measure the phase response but I am a little bit confused. I have a signal generator and oscilloscope.

Any tips how I could accomplish that?

Edit: Changed from frequency to phase response


texts:
I checked the link to this question, but as I was attending a few lectures I was constantly told (also told by some very experienced designers/enthusiasts) that adding an emitter resistor to an NPN transistor reduces chances of saturation and shorting the emitter to the ground drives the transistor to saturation. Is this true? If this is, why is this the case?

The way I see it,

simulate this circuit – Schematic created using CircuitLab

The base emitter loop gives me the equation -

$$V_{in} = I_bR_b + V_{be} + (hfe + 1) I_bR_e$$

$$\dfrac{V_{in} - V_{be}} {R_b + (hfe + 1) R_e} = I_b $$

and for the transistor to be in saturation I would want \$V_{ce} < 0.4V\$. Hence the equation

$$ hfe \, I_b R_c + (hfe + 1) I_b R_e > V_{cc} - 0.4V$$

$$ I_b (hfe \, R_c + (hfe + 1) R_e) > V_{cc}-0.4V$$

Using the value of \$I_b\$ arrived at from the base equation, we get

$$ (\dfrac{V_{in} - V_{be}} {R_b + (hfe + 1) R_e}) (hfe \, R_c + (hfe + 1) R_e)
   > V_{cc} - 0.4V $$

In all this I can't figure out why having \$R_e\$ shorted or having \$R_e = 0\$ would be beneficial in any way towards getting the transistor saturated.


texts: Concept of 'frequency' in wire vs electromagnetic frequency in fibre optic cable

texts:
I am having trouble understanding the concept of 'frequency' of a signal in an electrical sense in a wire vs the concept of 'frequency' in the electromagnetic sense in a fibre optic cable. Are these the same thing? The electricity travelling through a wire is not the same physical concept as the electromagnetic wave travelling through a fibre optic cable, right?

Do we treat them the same when we calculate the Shannon limit? I.e. can I look at the range of optical frequencies (wavelengths) that can be transmitted through an optic fibre and compare it to the range of electrical frequencies that can be transmitted through a wire, and compare them?

How does generating pulses of light compare to encoding signals with voltage changes?


texts: How to make a full adder using 1/4 DEMUXs and 1 NOR gate?

texts: I was supposed to make a full adder circuit of two 1 bit numbers using any amount of 1/4 demultiplexers and only one NOR gate with arbitrary number of inputs.I have no idea how to do this.Is such thing even possible?With just one NOR gate you can have either a carry bit output or a sum bit output, not both.How does one approach a problem like this one?What's the general procedure?


texts:
I'm using a logic-level N-Channel MOSFET, specifically the FQP30N06L. It doesn't appear to work in my circuit, so I decided to attach a DMM to it for test. My test was as follows:

DMM to ohm / diode test mode
Negative (COM) Lead to the source pin
Positive (INPUT) Lead to the drain pin

The results are showing 570k ohms resistance between the two. Is my test flawed, or is this MOSFET bad?


texts: Does a conductor that is heavily negatively charged affect the number of free electrons or conductivity?

texts:
If a conductor is charged with several megavolts of static electricity, does it have a larger number of free electrons? If so, wouldn't they render the conductor more conductive?

To truly test the conductivity, a generator that was charged to the same potential would need to be employed.


texts: Prototyping a smart boxing glove: Where to find a "wearable" force sensor that can detect up to 2000 psi

texts:
I am working on prototyping a "smart" boxing glove that can track the movement (jabs, uppercuts etc.) and punch force.

I am having a bit of trouble sourcing a pressure (force) sensor that is small and can detect up to 2000 psi of force.

Is this even possible given the format?


texts: Normal ESR Values for Capacitors of Various Types

texts:
I am working on a light detection preamp board that went bad. The circuit uses a chopper stabilized opamp TLC2652. Does it have a reputation for being fragile?

Anyway, as usual, I went around to check the capacitors. I found the 4 orange and 2 white capacitors are reading about 15-18 Ohms, the green Sprague 150D tantalum reading 1.6 Ohm. The image of the board in included below. Are these values about right?


texts: 120v motor with only T1, T4 2 and 8 reversable

texts:
This is on an an antique lathe.  Someone tried to replace the rotten wire and never got it right. There are 4 terminals on the motor
T1, T4, 2 and 8.
I expect T1 and T4 will go to line but how to wire drum switch with 2 and 8?  It seems all new diagrams list all as T1 to T8.  Perhaps 8 is T8?


texts: Voltage induced accross an inductor, conceptual confusions

texts:
simulate this circuit – Schematic created using CircuitLab

OK, I always have a hard time to understand inductors. Now, I do know that inductors will not let current through them to change instantaneously. And the voltage induced across them is given by the formula:
$$
V_{ind} = L \frac{di}{dt}.
$$
Suppose, the circuit was at steady state. So the current through the inductor is 1 A at t = 0-. At t = 0, I move the SW1 to position B. Now, using the above formula, the magnitude of the induced voltage across the inductor should be 1 V. And the polarity is such that
$$
V_{node\, C} = GND - 1 V = 0 - 1 = -1 V.
$$
So, node C is at -1 V now, I know that the inductor will try to keep current flowing from C to GND, but the polarity forces me to think the other way around, that is current should be flowing from GND to C from both sides(also from B to C). Then I become getting confused, node C looks like a new ground, a sink to current.

So, it is clear that I am having some hard time on this concept, any help would be appreciated.

Thanks.


texts: Can a linear regulator be cycled on and off repeatedly without damage?

texts: I am looking at using a linear regulator on a load that will be turned on and off once every 10 seconds(3153600 cycles per year). For context I am currently looking at L7812CV. Will this damage the linear regulator? Will a linear regulator be reliable at this level of on-off cycles? Is there a different component you would recommend?


texts:
I've designed and built a small board for supplying about 2A at 12V (regulated) from a 18V unregulated wall wart for a project of mine. It uses two LM7812 linear regulators to supply 1A each to separate loads. My problem is that it is overheating.

Below is the schematics.

Below is the board design.

And here is one picture of the prototype.

My question is: What's wrong with my board?

Is it overheating because of the undersized heatsink, or is there a problem with the design? Or should I just scrap it and throw away all linear regulators in my bins and design a new one using switching regulators?


texts: CC2541 + ceramic chip antenna PCB design

texts:
This is my first bluetooth project, I have done several PCBs for testing with CC2541 (by TI) and I am using this balun for impedance matching with this ceramic chip antenna . I managed to use it as a BLE broadcoaster and it works fine, but there is a problem with transmission sometimes. For example:

When I rotate the PCB 90 degrees, the reception of signal stops, but when I rotate it back, it starts again.
The reception stops for short periods of time, when I place the device for about 8-10 meter away from the reciever.

Actually I tried to re-solder the antenna with a simple wire (about 10 centimeters long) and the performance of transmission became a little better, which is a bit confusing for me. But anyway I need to use the chip antenna in this project.

So if you`re already experienced in RF designs, please help me to verify if my design is good enough (or it is not). There is no any copper planes under antenna's area.

Will appreciate any help, thanks!


texts: Measuring direction of object (or angle of signal origin)

texts:
I am interested in somehow tracking the "compass" direction of a moving object from a reference-station -- in other words, something similar to submarine sonar systems (although I'm unsure how those determine the angle/direction of the target).

Note that I only need the direction/2D-angular-position of the object, and don't care about its actual distance/spatial-position. So, I wish to know, e.g., the object is at South 45° East from the reference-station.

Some notes:

Maximum size of circuitry at moving object: 10 cm X 10 cm
Maximum size of circuitry at reference station: 15 cm X 15 cm
The angular measurement needed is a relative one (i.e., as measured from the reference-station), not an absolute one.
An accuracy of +/- 10 degrees is more than good enough.
Measurement/tracking rate can be once per second, but faster wouldn't hurt!
While this tracking is being done, the moving object might be between 3 meters (min) to 100 meters (max) aerial distance away from the reference-station.
Assume that cost is not critical and that both the object and the reference-station can be electronically equipped (i.e., with sensors/receivers/transmitters/etc.)
The object and the reference-station will be located in an outdoor/urban environment.

What technique could I use to get started on achieving this kind of direction measurement/tracking?

I've considered using standard wireless signal transmission, but with this, I've only been able to measure RSSI (signal strength), and not the actual angle/directionality! I'm guessing I need some sort of directional transmission sent from the object, whether ultrasonic or RF, and correspondingly a 360-degree sensor array on the reference-station to determine direction.


texts: single port 32x32 synchronous ram design using verilog in vivado hls

texts:
in the verilog code below:

module mem_try(
     clk,
     addr,
     data_in,
     rd,
     wr,
     data_out
    );

      parameter addr_length=32,data_width=32,ram_depth= 1 << addr_length;
      input [data_width-1:0]data_in;
      input clk,rd,wr;
      input [addr_length-1:0]addr;
      output reg [data_width-1:0]data_out;
      reg[data_width-1:0]ram[ram_depth-1:0];//ram variable decalaration
      assign write_only =wr&~rd ;
      assign read_only =~wr&rd ;

      always@(posedge clk) begin

      if(write_only) begin
         ram[addr]<=data_in;
      end

      if(read_only) begin
        data_out<=ram[addr];
      end

      end
endmodule

After synthesis I get the following error:

[Synth 8-3331] design mem_try has unconnected port addr[31](30 more like this)

and a distribute ram is formed.

Can anyone point out the mistake and how a bram can be inferred?


texts: What does this ɣ constant relate to in the carrier motion of BJT

texts:
What does the constant  ɣ represent in the following carrier motion of an PNP transistor?

So I see three components for the base current.

1) According to the illustration I can see that some of the majority carriers in the base which are electrons recombine with some of the holes rushing into the base from the emitter. To replenish this loss of electrons due to recombination, an electron current flows into the base from the base terminal.

2) Thermally generated holes in the base and electrons in the collector cross the collector-base junction contributes to the collector current. The flow of these also forms part of the base current. The reverse saturation current is the flow of holes only I guess.

3) There are also electrons flowing from the base into the emitter. I never saw this before.

What does (1-ɣ) indicate? What does this contribute to? Is this a usually neglected component?


texts:
On what does the signal velocity depend for a signal traveling through a PCB trace?

According to Wikipedia, it depends exclusively on the relative permittivity (ε_r) of the medium (well, it also depends on c, but that one is a constant), under the approximation that for PCBs, the relative permeability of the medium is 1.

My question is: Shouldn't the signal velocity be a function of the characteristic impedance of the transmission line?

My thought process is: If I have a trace that has a width change, then there will be a characteristic impedance change, and that would cause partial reflection of the incoming wave. But there is no energy absorption anywhere, so the only cause for a partial reflection can be a change in the wave's propagation speed, right?

According to the equation in Wikipedia's signal velocity page, there would be no change in velocity, since the medium is the same, so the relative permittivity remains the same.

Can someone shed some light on this?


texts:
I have been assigned the task of laying out an A4-sized 10-layer PCB board using Allegro. Someone else is doing the schematics, which I will receive soon (all I know now is that the board contains an FPGA and an ARM, and that there are less than 1000 components). I have never laid out a PCB before.

My boss has given me a couple days to learn the basics of Allegro and PCB layout. Internally, we have a "PCB Design Guidelines and Checklist" I'm going to read, and a book by Kraig Mitzner

  Complete PCB Design Using OrCAD Caputre and PCB Editor

What recommendations do you have for PCB layout beginners? What are major time savers you wished you knew when you started PCB layout? Are there must-read PCB layout resources online or elsewhere?


texts: TVC PID Controller how to adjust angle and thrust?

texts: Hi there I wanted to simulate a rocket landing like for example the falcon 9. I was able to write myself an simulation in which on every loop turn I adjust the angle and thrust. Now this is for school and we are supposed to use a PID-Controller. I think I understood the basic concept of a PID but in all the examples there were only one input and one output. Now I have two inputs do I build two PID-Controllers or is there another way? Also my Input is a speed vector how to I handle that in the PID-Controller. Any help would be cool.


texts: What device can I use to duplicate a MIFARE ISO 14443A (13.54 MHz) card?

texts:
I'm not familiar with how these devices work. I'm looking to duplicate an ID card for ease of use and this is all the information I can find on it:

MIFARE ISO 14443A (13.54 MHz)

So, is there a simple cloner or duplicator that supports this? If not, is there an arduino device or something else that can do it?

Thanks.


texts: Does increasing mAh reduce voltage drop?

texts:
I have some WS2812B LED strips and instead of hooking them up in parallel, I did them in series. The lights just get dimmer and dimmer as they go on. This was my mistake.

I have a 5v 20,000mAh battery. If I were to change the battery, say to 5v and 30,000mAh or higher, would this help with the voltage drop? Would more current mean more LEDs would become brighter?


texts: What's the use of the 4 outputs of a power entry module (Qualtek 864-10/009), and how to interpret it's circuit digram?

texts:
Main question:  What is the purpose of having 4 outputs?

If I only had pins 1 & 4, I would be able to use 115VAC when it's set to 115VAC, and 240 VAC when it's set to 240VAC.
For 240VAC setting:  pins 2 & 3 are connected together.  They seemingly add no functionality.  From the diagram, it appears they would just be floating and isolated.
For 115VAC setting:  pin 1,2 and pins 3,4 are connected together.  So pins 2&3 just give you an additional pair of 115VAC outputs. Is this the only use?

Background:
I'm planning to use the Qualtek 864-10/009 power entry module (http://www.qualtekusa.com/images/EMI_Filters/pdf/86410009.pdf) in a project which will basically just be a fancy box with a 24VDC SMPS and a number of output connectors.

The box may be run on 115VAC or 240VAC, so I chose this power entry module which has a double-fuse with selectable voltage output by changing the orientation of the fuse-holder.

The diagram has some features which I haven't really seen before.  After staring at it enough, I think it's clear that it's just indicating which outputs have which voltages depending on the orientation of the fuse-holder (which seems to be represented by the DPDT diagram inside the dashed box).

This raises the question: Why give access to pins 2 & 3?  Just to have an additional 115VAC output when the fuse-holder is set to 115VAC?  Is it useful for setting up some kind of transformer system (given the similarity of that part of the diagram to a kind of half-transformer)?

Related Post: This other stackexchange post deals with a similar power entry module in the context of transformers, but I couldn't understand their setup or application.
What is the right way to wire a power inlet to a switch to a dual-primary transformer?


texts:
I have an 8 x 8 grid and would like to detect where on the grid I place a metal object. I'm currently working with the TDA0161 metal detection IC, and so far have the following setup with detection range of 5mm:

I don't fancy using 64 of these ICs and am experimenting with multiplexing the coils.

I'm thinking of using 8 ICs each with 8 coils, and then using an analog switch to switch between the coils checking each position.

So far I have tried the to use the the CD4051BC, with the common I/O connected to one end of the coil in above picture, and each 8 to the other end and then to each I/O of the CD4051BC as you can see in the schematics below:

The above schematics however doesn't work.

When I use the first schematics with a single coil, it works perfect, but when using the analog switch nothing. When I measure the inductance across the single coil I get about 300 uH but when I measure the coil after it has passed through the analog switch, I get some random high number over 10 H.

The datasheets for the two ICs:

TDA0161:
http://www.gremlyn.plus.com/ahme/CD00000119.pdf

CD4051BC:
http://pdf.datasheetcatalog.com/datasheet/fairchild/CD4052BC.pdf


texts: Should serial triac dimmers work for resistive load?

texts:
I have a cheap 120V hot plate that I assume regulates its temperature using a triac dimmer (because the heating element vibrates/hums at lower settings).  But at its lowest setting it still gets too hot for my application.

So my first reaction is to put another household dimmer between the device and the power.  But I'm not sure how the second triac in the series will behave if it's seeing chopped AC from the first.

I think the capacitors in the second triac are going to hold their charge between "cuts," and so the cumulative effect of the dimmers will be multiplicative as expected: I.e., if both are set to "half" power the device will see "quarter" power.  Is that correct?  Or is it not that simple?


texts:
I have tasks to do for school and after 'draw' a circuit I need to start to Stimulate, but it won't work.
If anyone knows how to fix this big thanks

How to fix this with OrCAD Pspice AC/DC Demo. I use ubuntu 18.04


texts: What type of solder to use with unregulated 25W soldering iron?

texts:
I have a general purpose unregulated 25W soldering iron (soldering pencil.)

What type of solder is suitable for this (melting point degrees, composition?)

Mainly for simple repair work (solder wires, terminal connector headers, through-hole mounting components.)


texts: Can a similar crystal and not exactly the one on the datasheet be used on RF 433 receiver?

texts:
The datasheet of SYN531R suggests 13.51783 MHz crystal.
I found available available 13.52127 MHz on an online store.
It seems very similar to me, however in reality would it work and if yes, would it make a big difference or not?
Is it of a so big importance the crystal to be exactly the same one as on the datasheet or not?


texts: 1.2V AAA rechargeable batteries, voltage for almost full charged cell

texts:
Some weeks ago, I bought a new pair of AAA rechargeable batteries, Ni-MH. Its package shows "Panasonic eneloop" model with up to 800mAh.
First I connected them in series and connected two resistors of 10 ohms in parallel to the series of batteries, the voltage measured was 2.2V with around 440mA of load connected. Then I left this working for 80 minutes, and the voltage after this period was 1.36V (they did not heat). Then I disconnected the resistor loads, and the open circuit voltage increased to 1.7V and it began to increase from mV to mV and reached 2.24V after some minutes.
I waited more minutes again with no load on the AAA batteries, the voltage of them was at 2.55V after this. Then I used this high-side current source, of around 350mA, to recharge them, in series also (they were with almost the same individual voltages at this point).

When I connected the charger to the batteries in series, the total voltage on them increased to 2,89V. After 25 minutes of charge the voltage was 2.98V, after 50 minutes of charge they were measuring total of 3.02V, and after 80 minutes measuring 3.04V.
Then I disconnected the batteries from the charger, waited around 10 minutes, and measured them without load again, measured 2.77V.
Have I over-charged them? What series voltage is to be expected to reach when they are almost full of charge? It should be a lower or higher final of charge voltage (<3V or >3V)?
Other: Which voltage should I consider if I want a single value for Ni-MH and Ni-CD chemestries?


texts: How can I cycle through 4 LEDs with Timer Off Function (TOF)?

texts:
I have 4 LEDs that need to be turned on and off sequentially and cyclically. This is my code from code warrior:
  IF TON2.IN == 1 THEN
    TON2.PT = 3000;
    TOF(&TON2);
  END_IF
  IF TON2.Q THEN
    QB_SET (led_linear_sensor_alarm, 1);
    TON3.IN = 1;
  ELSE
    TON2.IN = 0;
    TOF(&TON2);
    QB_SET (led_linear_sensor_alarm, 0);

    TON3.PT = 3000;
    TOF(&TON3);
    IF TON3.Q THEN
      QB_SET (led_oil_level_check_sensor_error, 1);
      TON4.IN = 1;
    ELSE
      TON3.IN = 0;
      TOF(&TON3);
      QB_SET (led_oil_level_check_sensor_error, 0);

      TON4.PT = 3000;
      TOF(&TON4);
      IF TON4.Q THEN
        QB_SET (led_ptc_motor_temperature_sensor_alarm, 1);
        TON5.IN = 1;
      ELSE
        TON4.IN = 0;
        TOF(&TON4);
        QB_SET (led_ptc_motor_temperature_sensor_alarm, 0);

        TON5.PT = 3000;
        TOF(&TON5);
        IF TON5.Q THEN
          QB_SET (led_down_hold_pressure_sensor_alarm, 1);
        ELSE
          TON5.IN = 0;
          TOF(&TON5);
          TON2.IN = 1;
          QB_SET (led_down_hold_pressure_sensor_alarm, 0);
        END_IF
      END_IF
    END_IF
  END_IF

The duty cycle of the PLC is 20ms.
But the code is in error because the first LED lights up and that's it. Where am I going wrong with this logic?


texts: Small battery cut off when fully charged

texts: I am working on a small 1.2 V battery. I want the charging current of 7 mA to stop when the battery voltage reaches 1.5 V. What cut off circuit should I use ?


texts:
What is the best way to connect ground planes together ?

I know that ground planes are connected together at multiple locations in order to keep a low impedance GND across the whole board and provide a return path for the signals.

But, in addition to the via put very close to every decoupling capacitors,

I have seen layouts where a lot of vias are added with a grid pattern, with a spacing of  1/20th of the maximum wavelength on the board.
On other boards the vias are put along the traces (like "Placement of Vias to Connect Ground Planes").
I have seen the vias scattered randomely.
There is also combination : Vias along the lines + scattered randomely on the GND planes.

Is there noticiable differences ?

What I would like to achieve is good signal integrity, low radiation and a good power supply decoupling.


texts: Wiring colour code/law on universal power supply

texts:
Is it legal to use brown and blue for live and neutral wires in equipment sold in the USA, which uses 110v?

I was looking at a teardown of an ATX power supply and one of the photos (see below) showed that the mains inputs were brown and blue, even though the input is universal and could be 110v.


texts: Class B power amplifier using only Nch FETs

texts:
I'm building a combined linear regulator/electronic load. When the output is lower than the supply Q3 acts as a linear regulator and when the load tries to pump power back the other way, Q6 acts like an electronic load. It's basically the output stage of an opamp. I'd like to keep using only Nch mosfets for both Q3 & Q6 rather than the Pch/Nch combinations I see almost everywhere else. The MOSFETs are more or less rigged up in a class-B amplifier arrangement.

The current arrangement works but I'd like to know if there's a better way to take the output from the opamp and drive the fets. Currently I need a large output swing from the opamp to drive Q3, but only a tiny swing to drive Q6 (due to Q7), I'd like to make the drive electronics more symmetrical. (there is an isolated 15V bias supply to drive Q3, along with +15V and +/-5V for the opamps if that helps). Ideally something that doesn't rely on Q7's emitter resistor to ensure that both Mosfets don't come on at the same time (a small positive voltage from the opamp turns off Q3 - via Q7 - before Q6 comes on, well, in theory anyway).

This is for a power supply, I'm using all Nch fets as I haven't found any Pch fets that would be a good match in terms of price and power handling, the A&O AOT430 fets I'm using can handle the full supply voltage and supply current indefinitely (not many affordable mosfets have an SOA at DC of >200W, so it won't explode if someone shorts the output at full voltage). I did once see a full blown amplifier built only from Nch fets, but it was quite a bit more complex than I was hoping for (lots of compensation networks and such).

simulate this circuit – Schematic created using CircuitLab

This is a simulation result showing the output from the opamp vs the output load voltage, the opamp's output is a bit asymmetric, I'd like to fix that, but I can't think of any simple way to do it.


texts: Current Mirror Gain 1.5 with discrete components

texts:
I was trying to simulate the circuit mentioned in https://wiki.analog.com/university/courses/electronics/text/chapter-11 under paragraph 11.4.1.
I need to make a current amplifier with a current gain of 1.5. Thus I made the following circuit:

As you can see the current mirror does not work as supposed to work.
The current gain is not 1.5 times the input current.
Is there any reasoning behind this or it is just a simulation error.
Thank you.


texts: How can I close a remote controller switch with an optocoupler and a Pi?

texts:
I'm trying to close the contacts of a remote controller (wires are soldered to either side). I have an RPi and I'm yet to buy an optocoupler.

What would I need to get this to work? A Pi outputs 3.3v from a GPIO, but can power a circuit independently at 5v.

simulate this circuit – Schematic created using CircuitLab

shorting a remote control pushbutton with GPIO and a transistor

I was referencing this thread, but they've included a 9v battery, and I don't know what purpose that serves.

Alternatively, I could use a relay powered by the 5v Pi output which is triggered by the GPIO, but I worry that the contacts on a relay are too resistive to conduct a small switch short. Please advise!

Thank-you!!

EDIT: Thanks to user Passerby, I now have formula for finding an optocoupler and resistor.

Assuming the Pi outputs 3.3v at 16mA, what's a suitable resistor/optocoupler combination (x & y on schematic)?


texts: Why doesn’t the focusing anode diverge the electron beam again?

texts:
Consider this diagram of a focusing anode in a CRT:

Question: Why does the electron beam not diverge again when it enters the focusing anode (or accelerating anode) while leaving the pre-accelerating anode (or focussing anode)?

I think the answer is that it does diverge but less than it converges at both entrances. And since it converges first, the resultant is relatively convergent. The following is how I show it, is the diagram below correct?


texts: 1M Ohm Thermistor Circuit voltage drops not adding up

texts:
The circuit is wired as follows

vcc --- R1 (1M ohm) ---|Thermistor --- Ground
                       |
                    Voltmeter
                       |
                    Ground

The Thermistor has a resistance of 1M ohm when it is at 25 C. I am around that temperature now and indeed my ohm meter shows it has a resistance around 1M. I am seeing voltage drops of about 1.1V across the resistors but VCC is 3.3V. This blows my mind but I really don't know enough fundamentals to understand how this is the case.

If I switch the voltmeter out for something like an analog pin on an arduino I get very noisy input which does NOT match the voltmeter. On the arduino I am sampling about once a second.

One last point is that the probe I am using is this probe. It seems that grounding the metal sheath might help reduce the noise I am not yet certain.

Improvements to noise. It seems I could benefit from using a capacitor and multisampling to improve the quality of the signal. Information related to my Microcontroller


texts:
I want to measure signal with ADC and send measurements to PC to generate plots.

My code:

ADC_SoftwareStartConv(ADC3);
while(1)
{
    ADC3ConvertedVoltage = ADC3ConvertedValue * 3300/0xFFF;
    ADCresultsTab[i] = ADC3ConvertedVoltage;
    sprintf(str,"%u",ADC3ConvertedVoltage);
    USART2_SendText(str);
    USART2_SendText(";");
}

The problem is that I want to sample signal as fast as it is possible. Here I'm using baud rate  = 256000 (Windows only). What is the possibility to sample signals faster? What is more optimal code for sample and send measurement?

I see that the problem there is UART transmission.

And my additional questions are:
Is it real time measurement with this code? How it should be made if I want real time measurement?


texts: Voltage rating of series connected fuses

texts:
If a number of fuses are series connected, with the intention to achieve a higher voltage rating, what is the overall voltage rating?

For example if we place two identical fuses that are rated for 120V dc in series. I suspect the overall rating will not be 240V dc as one fuse will blow before the other.

Is the actual rating closer to 120V or to 240V? Is there some mathematical rule?

The example given is two fuses in series but what about n fuses connected in series?


texts: Ringing problems on the output of inverter/comparator

texts:
I'm trying to drive some RF switches that need 0 to -5 V control logic with a 0 to 3.3 V signal. I found 2 topologies for this level shifting effect, one using a comparator and one using an inverter.  Both circuits do the job but have a significant amount of overshoot on the outputs especially when driving switches that are further away.  The current solution I'm trying to replace uses BJTs for the switching but they get too slow once more than 4 switches are connected.

Both the comparator and inverter output -5 to 0 volts just fine right at their outputs, but if I attach a 4 inch jumper wire the over and undershoot grows a bit, and if I connect a few feet of wire the signals overshoot to over 2 volts and undershoot below 8 volts.

I have tried smoothing out the ringing with combinations of resistors, caps, and ferrites but I can get a good looking signal in one location but by the time I look at the far end of the cable the signal is horrible again.  Is there a way to prevent this type of ringing no matter how far away my load is from the output of the chip?

Here is the inverter topology I'm using to get the screenshots, it takes the 0 to 3.3 V signal on the left and turns it into -5 to 0 V signals on A and B:

Screenshots:
Taken from the comparator circuit, yellow trace is the input to the 1st comparator after the zener diode, blue is the output of the 2nd comparator and red/green are the outputs measured further down a wire.


texts: How to leverage CAN bus Mailboxes in my embedded systems?

texts:
I don't understand how to leverage CAN bus Mailboxes in my embedded systems.
I think I don't use them properly because I don't understand the problem they are trying to solve.

Here's a simple example to illustrate my conundrum:

  Requirements and assumptions

  Transmit 10 different CAN messages with a period of 250ms.
  Receive 10 different CAN messages with a period of 250ms.

  Let's assume we can only use 1 CAN peripheral.
  Let's assume the CAN bus has only those messages on it.
  Let's assume we have more than 20 mailboxes.

  Solution

  To my understanding, to solve this problem, I could do

  1 mailbox for receiving (with a filter accepting all 10 CAN message's ID)
  1 mailbox for transmitting

  I could also do

  10 mailbox for receiving; each mailbox only 1 message ID
  10 mailbox for transmitting; each mailbox only 1 message ID

  or, of course, an in-between solution.

How can I evaluate what is the proper solution for my design?

As CAN bus can only receive 1 message at the time, why use multiple RX mailboxes? Is it to act as buffers you can pole, instead of using interrupts?

Why use multiple mailboxes to receive messages?

Why use multiple mailboxes to send messages?

Do you have examples of the kind of problems CAN mailboxes help to solves?

Thanks


texts: Finding the output time response of a transfer function with a step response

texts:
The question is finding the output time response of the transfer function below. I solved that it is an underdamped response. The step response is 1/s.
$$T(s)=\frac{20}{s^{2}+6s+144}$$
According to the answer key, the answer is
$$A+Be^{-3t}cos(3\sqrt{15}t+\Phi )$$
My goal is to find A and B.
And I do understand that the poles of an underdamped response is two complex numbers: $$-\sigma_{d}\pm j\omega_{d}$$
So I already know what happened in the second term. Now, I tried solving for A and B via partial fractions. I found out that A = 5/36, B = -5/6, and C = -5/36. Is this the right approach to find what are the proper values of A and B in the answer, even more so that doing the partial fraction brought out three variables: $$\frac{20}{s(s^{2}+6s+144)}=\frac{A}{s}+\frac{B+Cs}{s^{2}+6s+144}$$


texts: Why can't I connect a std_logic_vector signal to a port of type signed or unsigned

texts:
The numeric_std.vhdl says this:

  type UNSIGNED is array (NATURAL range <>) of STD_LOGIC;
  type SIGNED is array (NATURAL range <>) of STD_LOGIC;

Does this means that the unsigned and signed have std_logic as their subtypes?

Why then is it that when I have an entity with a port of signed or unsigned type and I connect a std_logic_vector(3 downto 0) to it, I get an error?

e.g

component dummy is
port(
    a: in std_logic_vector(3 downto 0);
    b: in signed(3 downto 0);
    c: in unsigned(3 downto 0);
    d: out std_logic
);
end component;

If I port map a std_logic_vector to b or c I get errors:

Signal "b" is type ieee.std_logic_1164.STD_LOGIC_VECTOR; expecting type ieee.NUMERIC_STD.SIGNED.

Why?


texts: In the op-amp working principle I was told that if I have a certain input voltage at the non inverting pin, then the inverting pin will also be forced to have that voltage and hence if I attach a feedback impedance to the output, then the output voltage will align itself in such a way that KVL and KCL are conserved along with reflection of a followed voltage at the  inverting pin. My question is, why does this reflection of similar voltage at the inverting pin happen depending on the non-inverting pin? Can I also reverse the ideology? That is if I were to have a voltage V0 at the inverting pin and attach a feedback at the non-inverting pin, will it follow the voltage at the inverting pin?


texts: May I replace ICR 18650 22F with 26H in Laptop battery?

texts:
As in the title, I have a worn laptop battery, made out of 6x SAMSUNG ICR 18650 22F. Now I can't find any 22F near me, nor slightly farther for a sane price. But SAMSUNG ICR 18650 26H are practically swamping me from all sides.

I checked the basic specifications and all seems in order apart from one. My main worries are:

Are 26H only far cheaper because 22F are out of production (or low priority production) and hence out of stock price difference. Or is there a reason for the 50-100% price difference?
Will the chargers, controller, and computer register the battery correctly if it now has 2,6Ah per cell instead of 2,2Ah?

I mean, I can get 26H with tabs already on them for still cheaper than ordering 22F (if i don't even count postage to 22F's price)


texts: What does zero crossing period of a Auto correlation signify?

texts:
What does the first and second zero crossing time of the autocorrelation function signify anything for a signal?

How do we get the period of the signal from its autocorrelation? Im trying it for a periodic signal with some low frequency component in it.


texts:
I got a transformer from a CRT tv (it is NOT a flyback transformer). It has four wires, two on each side. One side, theres a Blue and Orange wire, and on the other side theres a White and Yellow. If I plug 9V into the orange one, and touch the negative side to blue, it makes sparks. I have pictures.

If I connected the positive to white and touch the negative to the yellow wire, it does makes sparks but they are less prominent. If I connect + to orange, and - to white and touch white and blue, it measures at 8.42V on my multimeter, but makes some sparks, and shocks me. So I have no idea whats going on, I think it might be a current transformer but then the voltage would be lower.

Pictures:

UPDATE 1:
@mguima @Marcovecchio That comment made my day ;). I do infact own a multimeter, it's not the best, but it works pretty well. I don't own a sinusoidal generator, and I'm guessing it generates a sine wave. Anyways, back to my multimeter. It's lowest setting for resistance is 200. I've discovered this:

Resistance:
Orange/Blue: 1.9
Orange/White: doesn't read
Orange/Yellow: doesn't read

Yellow/White: doesn't read
Yellow/Orange: 148.2
Yellow/Blue: 0.00

Blue/White: doesn't read
Blue/Orange: 3-2
Blue/Yellow: doesn't read

White/Orange: doesn't read
White/Yellow: 148.2
White/Blue: doesn't read

For reference, doesn't read means that nothing changed. By default, the multimeter reads "1", until I hook it up. So when I say doesn't read, it means that the one didn't change. If it "didn't read" I would check all the setting for resistance on the multimeter. I think the one might mean a resistance higher than my multimeter, which is 20M. On one hand, I'm spooked. On the other, I think Blue/Orange are a pair and Yellow and White are aswell. I'm actually happy, because that matched exactly with what Marcovecchio said! One winding should be in a few hundred ohms, and one just a few ohms. In this case, yellow and white are the few hundred ohms, and blue and orange are just a few.

I'm going to test the voltage ratio, then report back. Should I use a 9V, or my 6V 2.9Amp battery?


texts: Slotted Optical Switch (OPB992T51Z) anode and cathode connections?

texts:
I have an optek Photologic® Slotted Optical Switch.  It is meant to turn off when the near infrared emissions (850 - 940nm) are blocked.

It has five wires as follows:

I am unsure about what to do with the anode and cathode, (most likely connect the anode to Vcc).

Firstly, I connected Vcc and GND but the signal voltage did not change when the LED was blocked.

Next I connected the anode to Vcc and the cathode to GND Aas shown below and retried.

Still nothing.

Am I missing something obvious?


texts:
As my server collection is rapidly growing so is its power consumption. I'm looking for a way to pay for the power before hand. I had something like this in mind. Although I'd use a coin acceptor such as this.

I'd like to program the arduino with the price per Kwh and have it measure the wattage and calculate time accordingly. How could I go about doing this? Any code would be much appreciated.


texts: Double isolation with earthing symbol inside on power supply

texts:
I was looking at my laptop's power supply and i noticed this symbol:

To me totally looks like a "double isolation class 2" IEC 61140 combined with the IEC 60417 - 5018 symbol (Functional earthing; functional grounding), but does such thing exists in any standard? I couldn't find it in IEC 60417.

The negative output of the power supply is connected through a 10kohm resistance to the earth pin of the mains plug (or at least this is what i can measure from the ouside).

Isn't this breaing the double isolation condition?
Is the earthing there only for reference?
If that's the case, why bother with the 10k resistor?


texts:
I've been presented with the following circuit and asked to find an expression for Vc in terms of time

My working is this:

$$
V_S = V_R + V_C\\
I_R = I_C\\
$$

$$
\frac{V_R}R = C\frac{dV_C}{dt}\\
\frac{V_S - V_C}R = C\frac{dV_C}{dt}\\
dt = \frac{RC}{V_S - V_C}dV_C\\
$$
integrating
$$
t = -RC\ln(V_S - V_C)\\
\frac{-t}{RC} = \ln(V_S - V_C)\\
$$
taking exponentials
$$
\exp(\frac{-t}{RC}) = V_S - V_C\\
V_C = V_S - \exp(\frac{-t}{RC})
$$

But I know the answer should be
$$
V_C = V_S - V_S\exp(\frac{-t}{RC})
$$

Can anyone see where my missing Vs has gone?


texts: How important is to have some form of electrical isolation in MIDI connectors?

texts: I want to connect two MIDI keyboards by connecting the MIDI OUT of the first keyboard to the MIDI IN of the second keyboard, but I don't have the connector and I'm nowhere near a music store to buy one. And for that, I want to make my own DIN to DIN MIDI connector. I have two male 5 pin DIN connectors, and the question is, do I have to put some kind of isolation (usually an optocoupler) between the connectors? Or is it safe to just solder them directly without some form of isolation? As far as I know, optocoupler isolation usually found in MIDI to USB interface/adapter. I don't know if a MIDI to MIDI connector is supposed to be electrically isolated or not.


texts:
I am making an open source solar battery shield for the Arduino Uno, would this circuit work? It's pretty basic but I think it would do the trick.
Also,the power from the solar cell will come into the AMS1117-5.0 for positive and gnd for negative.
PS: Yes, I know that I'm supposed to connect the EN pin of the 3.3V reg to Vin.


texts: What is the purpose of marking the positive terminal of an 50% duty cycle oscillating source?

texts:
Some circuit diagrams I look at contain a sinusoidal voltage source with a `+' hovering to the side of the wire a little ahead of that component.

____(~)_+___

If the source has a duty cycle of 50% with no DC component, why bother marking it's 'positive' end?


texts: Can I use a Triac dimmer circuit to control the brightness of an AC powered LED light strip?

texts:
I am using this Triac circuit to control the brightness of several incandescent lights.  The circuit monitors the phase of the 120 volt wall current, then signals an Arduino when the phase crossed zero.  Based on this signal input, the Arduino switches the AC current which goes to the lights, limiting the amount of power that is feed to the lights.   More info can be found here

I read that this circuit can not be use to switch LED lights.  Why is this?  I am assuming it's because the switching rate is around 60 herts, which will cause a visual flicker.  If so, can I connect the MoC3052-M input to a PWM output?  This should switch the AC current fast enough to create an effective dimming effect.  Will I need to alter the circuit in order to do this effectively and safely?

Here are my options for powering the LED's:

1) bridge rectifier only, powering the LEDs with 120 volts DC.
2) Wall Plug transformer (wall wart) to power the LEDs with 12 volts DC.

If there is another option to convert 120v to 12v or 9v DC, one that will work well with this circuit, please let me know.

EDIT======================

I plan to use this device for the switching:

The goal for this question is to find a way to use this device to dim an LED rope light (as well as the incandescent lights.)


texts: What is causing the oscillation in the feedback loop of an SMPS?

texts:
I am trying to make a switching constant current regulator for a Ni-MH charger. It accepts a current set input from the microcontroller using a PWM DAC. I basically want to source 2000mA and 200mA for 1C and 0.1C relatively for charging the 2700mAh battery.

The way that I've tried to accomplish this is as follows:

An OP-AMP which is configured in negative feedback, takes Vset (PWM DAC) as non-inverting input and Vsense (the voltage on sense resistor) as inverting input. It drives a small signal MOSFET with its output so that buck converter's voltage output is for desired current at the load.

However, I am getting oscillations on TP1, which affects the whole system.

Here is the schematic, I am sorry that it is 3500 x 2500px :

I have connected a short instead of R6, since Rdson of Q2 is about 50mohms. Also, I have connected a 1R 11W ceramic power resistor instead of a battery. Q3 is set off and Q2 is ON. I have connected an ampere meter and it shows about 1.9A through the resistor.

Here are some scope-shots of various test points which I have used very short ground lead on the probe to capture.

Test Point 5; non-inverting input of the OP-AMP:

Test Point 6; inverting input of the OP-AMP, voltage on the sense resistor:

AC Coupled:

Test Point 1; Vsense pin of the switcher, drain of Q1:

Test Point 2; switch node:

Test Point 4 - Test Point 6; probe on TP4, ground clip on TP6, or in other words, voltage on P3 connector, or output voltage:

AC Coupled:


texts: Designing a variable resistor logic for an input module

texts:
I'm currently trying to design a circuit which controls the input of a receiving module which interprets the current flowing through itself as StateA, StateB or StateC. What the input module does with the states is irrelevant in this matter, since I'm focusing on making these currentStates flexible through a raspberry pi.

Normally this input module is controlled with switches and resistors.

But the control circuit I'm designing needs to be maintained (switched) in software and there can't be any physical switches that need to be pressed.
Also, since I want to control which of the current States occur with a raspberry pi, a portion of the circuit will end up running on 5 volts.
The input module is supplied with 24 Volts. (range goes from 19 to 27 volts)

Originally I planned to get an Arduino Mega (which then gets its input from a raspberry pi) and with it's ~50 Digital Pins I'd be able to control a relay per State per Input.
There are 8 Inputs on the module with 3 States each.
That makes 24 Relays with corresponding resistor values.
But this turns out to be very ineffective compared to just using resistors with switches.

See the schematics below for clarification:

simulate this circuit – Schematic created using CircuitLab

Is there a different way to provide these 3 "States" with the usage of GPIO?
Maybe some sort of switch that is controllable with GPIO?


texts: Final steps in device manufacturing - AVR programming and board assembly

texts: After I have prototyped my circuit and built AVR code for a device I want to sell, how do I go about getting mass production done? Will a PCB manufacturing and assembly shop be able to take the component list and the hex file and program it in or do I have to procure the AVR chips and manually program each one? I am completely new to this and want to learn.


texts: What is the practical difference between using an FTDI breakout board and an FTDI cable?

texts:
I have some 3.3V Arduino Pro Mini boards and they require either an FTDI cable or breakout board to be programmed from a USB port.
So far I've been using a board, but it's annoying to have to either solder headers in place or hold the boards carefully every time I make a modification to the code. Also, switching between 3.3V boards and 5V requires resoldering traces on the FTDI board.

The process goes like this:
- ensure FTDI board is soldered for the correct voltage, resolder if necessary.
- connect FTDI board to arduino pro mini.
- plug mini usb cable into FTDI board.
- carefully hold arduino and FTDI board in place.
- click upload in the Arduino IDE.

Then everything works.

I am aware that FTDI cables don't always support 'auto-reset', but I've never had to manually reset my Arduino in order to load new code.
When does one have to press the reset button if using a cable?
before uploading?
afterwards?
What's the deal here?

Also, can I use a USB FTDI cable to load 3.3V and 5V boards?


texts: What happens when a motor is spun faster than its rated RPM from an external force?

texts: I've seen plenty of questions wondering what happens when voltage is applied that would exceed the RPM rating, but what happens on the voltage/current side when something external - the wind spinning blades attached to the motor - spins the motor faster than its rated RPM?  Does it overheat?  Does the voltage eventually saturate?  I'm planning on using a permanent magnet motor, but this question applies to any motor.


texts: Listen Only Mode in CAN and Message Validity

texts:
Most controllers have a "Listen Only Mode" or "CANalyzer Mode" in which CAN module doesn't acknowledge any message but it will read the message silently.

Assuming there is only two nodes on the bus configured at Same baud rate: Node A is Active and other node, Node B, is in "Listen Only" mode.

When Node A will transmit a message, as there is no other node on bus, it will get ACK_SLOT error and message transmission will fail.
My question is

Should Node B get message correctly OR should it discard as message is not completed.
If a node doesn't get ACK for a message, does it transmit CRC or stops the message transmission there?
If it stops message transmission immediately, in above case, Node B will not have complete message i.e. without CRC and Stop bit. Shouldn't it discard the message then?


texts:
This may be a simple question, but I couldn't find anything exactly for this.

I wish to implement LED blinking if a button is pressed, and it should continue to blink, unless button is pressed again. Any suggestion on how to achieve this without microcontroller.
Can a 555 be used for something like this?


texts:
I am working on my final project for class and am STUCK!
I am to design a 3 stage circuit with stage 1 and 2 using a 2N3904 transistor in a votlage divider config. and stage 3 using a darlington transistor in a voltage divider configuration leading to an 8 ohm speaker. I have stage 3 of the configuration done and I get the correct wattage out of the 8ohm speaker. But for the life of me I cant figure out how to determine the values for the resistors in stage 1 and 2 to give me the correct Vb in stage 3. Where do I start these calculations?


texts: Is this circuit acting as an amplifier and how does it work?

texts:
I simulate a diode connected BJT circuit as follows:

And here are the plot for the currents through Rin I(Rin); the wire then collector-base then to base-emitter junction Ic(Q); and through the base-emitter junction Ib(Q):

Almost 99% of the current is flowing through the wire which shorts the collector and the base.

It seems the like majority of the electrons flowing from the ground into the emitter-base junction are pulled by the collector and then all the way to the source. Is this circuit acting like an amplifier? How is the collector pulling the electrons even though its terminals are shorted i.e zero potential difference across CB junction?


texts: Powering 3 DC motors (with limit switches) with AC-DC adapter

texts:
I have 3 DC motors: each motor is being used to drive an independent system of pulleys. This system of pulleys spins a threaded bar in order to raise/lower a shelf in a linear motion. Thus, I have a motor and pulley system for each shelf.

The motors are rated at 12 volts each, and draw 4-6 amps each depending on the load put on the shelf. I was thinking about using a 36 volt power supply so that the voltage would split in series, but I'm struggling to find one rated at a safe 8 amps. So now I am thinking I should power each motor independently with a 12v power supply, but this seems inefficient. My first question is, is there any better way to do this? (I want all the motors to run at the same time when the power source is switched on.)

I am also using Normally Closed circuit switches so that when a shelf hits the switch, the circuit opens and the power to the motor is cut. (I am using a DPDT switch to swap the polarity so that the shelf can move again - in the opposite direction, until it hits another NC switch.) My problem is, I was thinking of using 2 NC switches for each motor (one on the bottom and one on the top of the shelf system). Although, if I do this, I feel like it could damage the motor: the shelves could stop at slightly different times, so if I was using a 36v power supply and each motor was cut out of the circuit at slightly different times, this means the final motor would be supplied with 36 volts for a brief moment. So, my second question is: is there a better solution to this? (I don't want to use one limit switch on either end for the system as the shelves are running independently and could come out of sync over time - this would be especially bad if one doesn't stop in time.)

To summarise: my main issue is with powering all 3 motors from one source, but being able to keep the limit/NC switches independent such that the motors always receive 12 volt each, even if a limit switch is hit.

I hope this made sense - please comment if I missed out on anything. Many thanks in advance for your help!

Edit: I am currently using one DPDT switch to control the whole system, as I wish for the shelves to move at the same time. That's why connecting three 12 volt power supplies wouldn't seem like the best solution to me.

Another edit: My bad, with all the motors in series, it would only take 1 limit switch to break the circuit. This complicates things further; I'm not sure how I would make all the motors function at the same time but have the motors dependent on their own limit switches? If I were to put the motors in parallel, I'd need a 12 volt supply rated at 20 amps?


texts: How can I Access Tiger Sharc DSP processor through host pc?

texts:
I am working on designing of a test board which involves both FPGA(Xilinx- Kintex 7) and DSP(Tiger Sharc) based signal processing.

Now the end user wants to access the DSP processor programming options/ boot configuration through the host PC itself. As I went through the datasheets of these devices, I got the idea that I'll have to use PPLP for the communication purposes with FPGA. My question is that- Is there any device or connector which supports communication for DSP processor with host PC Such as PPLP to USB(- Is this a good idea to use)?

Would really appreciate if anyone has any good and concise idea about this kind of devices.

Thanks!


texts: Oscillation in Voltage Rectifier / Scaling Circuit

texts:
I am working on creating a circuit that will scale +/- 12v input to a unipolar 3.3v centered around 1.65v, in order to scale the kind of CV used in modular synthesis systems to work with the ADCs on the STM32F4 microcontroller, which want to see a 0-3.3v input.

I am encountering problems with noise, specifically a strange oscillation around 8.6 MHz. I have tried adding filtering capacitors, which helps somewhat, but does not completely eliminate the problem, so I think there is something wrong with my circuit.

To accomplish the scaling of voltage I put the input through a 16k/100k voltage divider to scale the input to +/- 1.65v, which is sent into a buffer. I then add a 1.65v bias and send it through two unity gain inverting amplifiers. I get the 1.65v bias by dividing the power supply and sending it through a buffer in the same manner that I do the input. I am using the LM324 quad op-amp, which I power off a +/- 12v supply.

Is there anything flawed in my methodology here that could be causing this unwanted noise, or a better/cleaner way I could be doing this?

Here is the schematic:

P.S. disregard where it says LT103 on the schematic, I am using the LM324, a quad op-amp


texts: What way can be proposed to eliminate common impedance coupling with conductivity paths? za=zb=0


texts:
A Leyden Jar was one of the first capacitors ever. This guy re-builds one.

He connects the outer connector to ground. That, i can understand.
I can also understand tribocharging by rubbing the (insulative) PVC pipe.

But why is he connecting the PVC to ground?!


texts: Is a Synchronous Step-Down Converter powered from industrial 24v a good choice to power a 3.3 volt MCU and sensor ic?

texts: I am building a sensor that will be powered from a 24v industrial power supply. The board will contain a 3.3 Volt MCU and sensor IC. Is it a good idea to use a synchronous step-down converter and just that? The expected power consumption is less than <50mW. Is a linear regulator a better choice? Any suggestions of a book or other source of information that covers power supply design for MCU's in an industrial environment? Thank you!


texts:
I have a Teensy 3.1 and I am wanting to receive data from a reflectance sensor, specifically this one from pololu: https://www.pololu.com/product/2459

!

This is the circuit of the reflectance sensor from pololu's website. The Vin is meant to be 5V according to the datasheet.

To operate it, you set the OUT pin to high, and then set it to low and see how long it takes for it to discharge.

I have a 5V input, but my Teensy 3.1 will only output 3.3V. So, this means when I set the OUT pin to high, there will actually be a 1.7V difference between VIN and OUT. Will this cause current to flow into the OUT pin? (1.7V / 220ohms = ~7mA) Will that cause any issues?

I understand the purpose of setting OUT to high is to discharge the capacitor and that will still happen even with 3.3V applied to OUT.


texts: What does apostrophe mean for a register description in a datasheet e.g. 4'd5?

texts:
The datasheet lists something like this:
[0x01f] EPRXREG

    EPRXLock[3:0] = 4'd5;
    EPRXReLock[3:0] = 4'd5

I understand that it is an 8-bit register at address 0x01f, it contains 2 fields and each of them is 4 bits wide ([3:0] and the 4 in 4'd5). But what is 'd5?
Other registers have
4'd12  1'b0  4'h4  4'hF  7'd32


texts:
I am facing a huge task of checking 1000s (1000s per box and I have nothing less than 20 boxes) of wire wound resistors purchased by my company. I have been assigned to check the resistance value of each resistor and pass it if the measured range is with in 587 ohms to 687 ohms. I am supposed to reject it if the resistance is lower or higher than the said limit.

I have been doing the testing using multimeter and my turnabout time is slow due to the numbers.

I wanted to check with the experts if any one can help me and suggest some circuit idea which I can assemble and make it easy to test.

I tried my hands on LM741 operational amplifier based voltage measurement (while keeping the resistor in series. I understood the voltage range being measured was too low and it didnt work.

I just want to trigger a red LED if the resistance is out of range and turn on a green LED if it is within the set range.

Any help and guidance on this would save me from this huge monotonous task..

Thanks in Advance :-)


texts: When to read Battery voltage and battery current during charging

texts:
I am using a micro-controller to drive a buck converter for Li-ion battery charging purpose(Micro-controller providing PWM to the buck converter). During charging the battery's current and voltage have to be constantly monitored in order to supervise charging. I have used external ADCs for monitoring the charging voltage and current.

To learn how to charge Li-Ion cells, i was going through a couple of documents. These documents tell, when to measure the battery voltage and charging current during charging. The problem is that i have read two different kind of methods in two different documents, and i am not sure which one is right and which one to follow.

1) This document by MicroChip says to measure both the voltage and current during the OFF time PWM duty cycle (when PWM is low)

This can be seen (Page. 6 "Voltage Sense" and Page. 7 "Current Sense").

2) However This document by NEC designs a battery charger, which measures the charging voltage during the OFF time PWM duty cycle and measure the charging current during the ON time PWM duty cycle.

This can be seen (page 23, 6.3 Battery Monitor, also figure 6-6: Battery Monitor) and (page 37 where the code is listed, inside the function "void do_adc_conversions (void){" it states "// measure battery current if charger output enabled... // ...otherwise measure battery voltage") .

So can anyone please tell me what is the right way to go ?

Your helpful suggestions and comments would be appreciated.

Thankyou!


texts: What is the reason of undesired peak current in PFC non-isolated boost converter?

texts: I have attached inductor current waveform of PFC boost converter. After the particular current level, an undesired peak is coming. I have done some study and thinking it might be because of inductor saturation but not sure.


texts: How to See the Stackup in Allegro Free Viewer?

texts:
We are copying some part of a PCB reference design. The stackup information is needed to calculate the trace signal transmission line parameters.

The reference is in _PCB.brd files. It can be opened with the Cadence Allegro Free Physical Viewer. In the viewer, how can you see the thickness of each layer, and its dielectric number?

In the same software package it also installs a SIM and MCM Free Viewer. Would that be what should be used?


texts: Why does an induction motor not have the maximum torque when it is locked?

texts:
In theory the maximum current induced at rotor must be when the rotor is locked hence the force is  B.I.L it must produce the max torque.
But why torque is not maximum when it is locked but it is maximum at a point called breakdown torque?


texts: Questions about A Look-Ahead Clock Gating Based on Auto-Gated Flip-Flops

texts:
For A Look-Ahead Clock Gating Based on Auto-Gated Flip-Flops ,

Why Notice that since FF''' is oppositely clocked and its data is sampled at the clock’s falling edge, its clock enabling signal X''' must be negated. ?

Why does the author state that : F''' is an ordinary FF where the internal XOR gate is connected between D''' and Q'''. ?


texts: What is the recommend power scheme for an Arduino, dc and servo motors? The dc motor supply ranges from 3.5 to 7.5 volts. The power for the servo ranges from 5 to 6 volts. I'm using a 9.6 volt NiMH pack for the robot. I'm considering to use a l317 adjustable voltage regulator for the dc motor supply voltage and 9.6 for the Arduino. Could the servo be powered from the regulated 5 volts off of the Arduino ?


texts: Need help on troubleshooting PCB circuit

texts:
I recently got a freelancer to design a push-button latching circuit that powers a 12VDC motor from a 1S1P Li-Po cell.

I have soldered all the components but the board does not seem to work properly. Only the push-button latching system works. When the push button is depressed, the LED lights up very brightly but only for an instant and goes back to a dimly lit state as if there was a surge (There are no burn marks observed). Input is around 3.8V and output junction reads approximately 0.9V.

The components polarity are soldered as per the guidelines on the PCB. I soldered the 2nd board the same way and it has the same issue. I took extra care in soldering the components for the 2nd board and I am quite confident there was no overheating etc.

Can someone advise on how do I troubleshoot the circuit further? Or if the circuit contains some design errors?

I have contacted the freelancer but he's not as responsive hence I am here seeking help. I still have enough components for 3 more boards to try.

P.S. I have no professional knowledge in electrical engineering.


texts: Is a current signal more robust than voltage signal from noise? Why?

texts: I am trying to transmit a 3.3V digital signal over 20 cm distance. The problem is the environment might be noisy because of high current wire near it. I read that current signal is more robust than voltage signal. Does that apply to my case? and why?


texts:
Do batteries last longer with constant current draw or spiky current draw?

Or, as is implied by the accepted answer to
"Making a battery last a long time in a microcontroller circuit",
do some battery chemistries last longer with a constant current draw,
while other battery chemistries last longer with a spiky current draw?
And if so, which battery chemistries are which?

In other words:
Say I have a microcontroller programmed to wake up and do a few things once a minute, and then go back to sleep for the rest of the minute.

Which kind of batteries last longer with minimum capacitance across the capacitor (so the battery sees a big current spike once a minute)?

Which kind of batteries last longer with a big capacitor (or some kind of LC filter)  hooked up to battery (so the MCU pulls a big spike of current from the capacitor once a minute, and then the battery very slowly trickle-charges the capacitor)?


texts: Why do oscilloscopes use SMPSes instead of linear power supplies?

texts:
I'm wondering why digital oscilloscopes are using switching power supplies instead of linear power supplies.

The SMPS has a higher efficiency, but it can produce some noise during high frequency switching (PWM) and also EMI that can affect the signal shown on the display.


texts:
Im trying to use my PT100 with an Arduino-based PLC from Industrial Shields, which is basically an Arduino Mega encased in a plastic container.  Im using a 250Ω resistor, actually 237Ω resistor between Analog and Ground.
The pt100 range is -200 to 600C & the transmitter according to NFC scanner is -200 to 600C as well.

Here is my code:

int sensorValue = 0;
int temperature = 0;
int ReceivedByte = 0;
float f1 = 0;
float t1 = 0;

void setup() {
  Serial.begin(9600);
  Serial.println("hi...");
  //analogReference(INTERNAL2V56);
}

void loop() {
  delay(1000);
  sensorValue = analogRead(A2);
  Serial.println(sensorValue);
  /**
   current voltage(250 Ohm) ADC Temperature
 -----------------------------------------------------
 4 mA 1 V 205 -50 C
 20 mA 5 V 1023 +150 C
   *
   */
  //original 5V adc values from weber 194,971
  //SO-weber new values 10 bit ADC 97,485
  //204-1023 for 10V ADC with 2x237Ω
  // map the signals (using 194-971 for 5V and 97-485 for 10V)
  // to get decimal values, because map() doesn't work with floats)
  // V = 0.004A x 237Ω = 0.948V => 1024 x (0.948/5) = 194.5 lower bound
  // V = 0.020A x 237Ω = 4.74V => 1024 x (4.74/5) = 970.7 upper bound
  temperature=map(sensorValue,194,971,-200,600);
  f1 = temperature; // Float conversion
  Serial.print(f1);
  Serial.print("\n");
}

I was also told to try 500Ω (237x2=474Ω) with the full values of 10V (due to the datasheets from IS) instead of 5V but that doesn't pan out either as can seen in the results table below.  I tried:

A- 5V full value & 237Ω
B- 10V full value& 237Ω
C- 10V full value& 474Ω

I've tried all the wiring options available with my 3 wire pt100.

So Im wondering about 2 possibilities:
1. Which is the correct wiring configuration, because I want to eliminate that variable.

Could it be Industrial Shields datasheets are incorrect? I just checked the actual plc box and it reads "Analog 0-10VDC" so I dont think IS datasheet is incorrect.

UPDATING RESULTS:
What I dont like about room temp measurements is that its obviously off because it is no 10C in my office, its 22C with a thermometer.  But more importantly that it is wildly erratic, ranging from 0C to 12C at times.  An average of 100 measurements yields about 10C.  I just stuck it in a cup of coffee and the digital thermometer reads 61C and the 100-average of the pt100 reads 58C, so thats encouraging.  But individual readings range as low as 47C so its still erratic.

Here are the results:

Thanks


texts:
I'd like to start my own personal project on making a small device using MCU.
I am currently researching the things that I need to know and buy.

I think I am going to use MCU bluenrg by STM.
I was looking at the data sheet. It seems like we need upload instructions to the flash memory within chips in order to have desired actions.

In order to do so, don't I need a USB to I2C module or USB to SPI module, do I?

Thank you.
https://www.st.com/en/wireless-connectivity/bluenrg-2.html


texts:
I was building a receiver circuit (superhet) for shortwave radio, primarily for 20m (14MHz) band. The circuit uses 3N211 or 40673 mosfet for mixer. However I have only these components available at my disposal :

BC547
BC557
2N2222
2N3904

I searched this website for mixer circuits using BJT:

http://www.radio-electronics.com/info/rf-technology-design/mixers/bjt-transistor-mixer-multiplier.php

Now my question is

Will this circuit suffice practically?
Since 40673 mosfet is unavailable, can any of the above mentioned BJT be used in its place? (No other component / IC whatsoever is available at my place.)

The block diagram of the above mentioned scheme is below:

For additional details see:

http://www.sm0vpo.com/_pdf/miscellaneous_tech_info/Design%20tips%20for%20Simple%20Superhet%20Receivers.pdf

(I have decided to remove BFO since I do not plan to communicate on morse code. Also IF filter will be used)

Another of my concerns is that the circuits given in the above mentioned link are simply too complicated for me to understand. So if I substitute simple textbook circuits (or those found on online tutorials) with required component values (for example as local oscillator, I plan to use a Hartley oscillator with variable capacitor and an active op amp filter) will this suffice or do I need to stick with the same circuits ?


texts: One digit on seven segment display not working

texts:
So I have a circuit using the 4510 and 4511 chips as well as 3 seven segment displays on a PCB (designed and created). What it is meant to do is count up to 9.99 in 1's, 10's and 100's by cascading and manual input. It can also count up and down as well as being able to reset. I have used Push-to-make switches, push-to-break switches and a rocker switch (display ON/OFF). When powering the circuit everything works as expected - when I count 2 out of the 3 seven segment displays can show up to a 9. However, the 10's seven segment display only counts to 8 and then goes straight to 0, thus cancelling the cascading effect onto the 100's seven segment. It displays all digits on the seven segment display except 9! However this only happens when counting up as when counting down it seems to be displaying a 9 on the display.

I have no idea how to troubleshoot this problem - I have replaced the chip and have also checked the continuity of the track and the same thing happens. Any ideas on how to solve this problem (I know I haven't explained this well)?

All help appreciated.


texts: Library for easily interfacing with USB tranciever

texts:
Im very new to the field of anything USB related, sorry in advance!  I hope my question is clear in conveying my level of understanding and of what I wish to learn.

My project involves connecting a digital signal processor to a computer via a USB at as low cost as possible.
Ive found a chip that looks promising to ease in doing so, the USB3310C a "Hi-Speed USB Transceiver with ULPI Interface".  Right now Im thinking of using a DSP (dsPIC33EP32MC202) to interface between the device sensors, logic and the ULPI provided by the USB transceiver.
What I think I need is some kind of library (C/C++) to run on the processor to manage the USB connection to the host, responding to tokens and such (Dont know much about how that works).  What I need in the end is something that can advertise itself as my custom device, that I should then be able to exchange data with on the computer.
From how I see it there are five parts to this

Slave side software that more simply handles the data itself, streaming to and from the computer, processing a stream of ~220MB/s.
Slave side 'driver', controlling and responding to low level requests. (What I need)
Slave side hardware, the physical layer.
Host side drivers, I want to avoid having to create drivers, re-purposing another driver, maybe some kind of general purpose and cross platform driver.
Host side software, some program to stream to and from the device.

I'm sure there is much more to know on this subject, but for now I just want to successfully send data around ~30MB/s from device to host, and a small amount of control data from host to device.
In summary, I need some way to interface with a USB host, having all the low level stuff managed by something other than myself so I can simply focus on the data itself.  Ideally some kind of C/C++ library that can interface with the USB3310C chip, or some alternate low cost chip.


texts: Making a transistor circuit with sharp turn on (Small threshold interval)?

texts: I am measuring an analog voltage which should trigger an MCU by a GPIO when it falls below or goes above certain thresholds. At first I was planning on using comparators in order to get well defined thresholds, but I want to see if it's possible to make it work with only transistors somehow. If I connect BJTs as a Darlington pair I should get a sharper turn on, but is there any other way to get an even sharper turn on?


texts: Verilog - connecting multiple bidirectional buses

texts:
I've been designing a retro computer in verilog as an exercise and so far have a simple 8-bit CPU that communicates directly with a single RAM chip via a bidirectional data port. This works great in my testing, however the need has arisen to include a second RAM on a different bus, as video RAM that both the CPU and a graphics processor can interact with. To achieve this, I implemented a memory controller module. This module connects directly to both RAM chips on separate buses, and reads/writes to/from the CPU now have to go through this module.

Simplified module connections:

module memcontroller(inout[7:0] CPUdataBus, inout[7:0] RAMdataBUS, inout[7:0] VRAMdataBus)

When connecting the CPU directly with the RAM, I would just set the data bus to Hi-Z to use it as an input and read data from RAM. However, now I do this on the "RAMdataBUS" port and need a way to "connect" the input to the CPUdataBus port, which I can't figure out.

Perhaps naively, I thought something like this would work:

assign CPUdataBus = write ? CPUdataBus : RAMdataBUS;
assign RAMdataBUS = write ? CPUdataBus : 8'hZZ;

Which produces during synthesis:

RAMdataBus[7]" has multiple drivers due to the always-enabled I/O buffer "CPUdataBus[7]"

for each bit

There's likely a really obvious reason why this is invalid, but nonetheless I can't find a solution to the problem or fully understand the error.


texts: At what frequency is a transformers rated impedance measured

texts:
Where transformers have a specific impedance rating for the the primary/secondary, what frequency is this measured at?

For example, this transformer is rated at 40MHz - 860MHz with an impedance of 50/50ohm.

https://www.digikey.co.uk/product-detail/en/tdk-corporation/ATB2012-50011-T000/445-6138-1-ND/2465465?utm_adgroup=General&mkwid=sJoLbxdi4&pcrid=153600060853&pkw=&pmt=b&pdv=c&productid=&slid=&gclid=EAIaIQobChMIgaPRubGs4gIVL7ftCh2hCAlBEAAYASAAEgKcD_D_BwE

I assume the impedance cannot be 50ohm at all frequencys within 40MHz - 860MHz?


texts: I have what I've been told is one of these cables, but not sure what it means.


texts:
I need a part similar to a 74HC148 8:3 encoder, but which takes 32 input lines and encodes them to a 5 bit value. I can guarantee that only one of the 32 will be high at a time, so I don't even need the priority feature although it would be a plus. If possible I would like to stay in the 74HC series, or at least compatible chips.

I could implement it with 5 16-input OR gates, but that would require something like 10 chips to implement the entire encoder. It feels like there must be a better way.

Is there a single chip made to do this? Google and digikey searches failed me. Is there a better way to implement it than with a whole bunch of OR gates? I was trying to find a way to combine the 8:3 encoders, but a clever working solution escapes me.


texts: How to switch something else on with an arduino

texts: How would I press the electrical switch on say an electronic paintball or airsoft gun? Let's say it is just a SPST switch.


texts: determine the cutoff frequency of a nMOS in common gate with gate resistance

texts:
I have to determine the upper cutoff frequency of this circuit.
I absolutely mustn't use the laplace domain because it's too time consuming so not compatible with the time I have at the exam.
A rapid calculation shows the capacitances are by no means time separated
They are not mesh separated
They are not feedback capacitors so miller is out of the questions.
I've run out of ideas.


texts: How do I solder this tiny (0.5mm pitch) MSOP10?

texts: I am soldering a 10 lead MSOP (LMH1980) onto a PCB. Or trying to do so. The chip has a pitch of 0.5mm. I find that every time I use the "tack and glob" method I have been taught, I cannot remove the excess solder; it just sticks to the pins. (Tack and glob: pin a few crucial pins down, then glob solder over the pins. Wick away excess solder.) Tack and glob seems to work for a TQFP44 dsPIC and an TSOP16 ADG733 chip, but every time I do tack and glob on the LMH1980 I find that I cannot remove the excess solder, and in the process of trying to do so, I have damaged two PCBs (pulled the pads off) with components already on them. How can I solder this chip? BTW, I have only a basic temperature controlled soldering iron and hot air station (Aoyue 968.) Nothing fancy.


texts: Is it better to connect ESD (TVS) Diodes to chassis ground or signal ground?

texts:
Application: We have a PCBA inside a vehicle's embedded system. The PCBA receives DC voltages from a power input connector. We do have access to signal ground aka 5V_return at the power connector and we have a mounting hole nearby that will be chassis ground. Note chassis ground and signal ground will be isolated on our PCBA, but the may be connected in some manner within the larger system. (Outside the scope of our design)
Plan: Place ESD (Electro-Static Discharge) suppressor (TVS) diodes near the power input connector to protect the voltage rail inputs from sending ESD strikes "downstream" to the various circuits/ICs on-board.

Questions:

Is it better to connect the ESD diodes to chassis ground or signal ground?
Should we use unidirectional or bidirectional diodes?
Should a more complicated array of diodes be used for better protection? i.e. a diode from +5V to chassis and a diode from GND to chassis?


texts: Simulate Piezo "knock" Sensor in CircuitLab

texts:
How can I simulate a Piezo knock sensor in CircuitLab? I would like to ensure that the circuitry that I have set up to protect the Arduino and divide the voltage is going to work as expected.

I would like to use a voltage signal source to approximate the voltage of a Piezo buzzer after a knock. Specifically, what should I enter as a Fequency for my voltage source (I am going to test with multiple Voltages) and what do I enter in the "Run" screen.


texts: What is the best preamplifier circuit for electret condenser microphone?

texts:
I have one old German directional dynamic microphone "SEL BST 205-1" and I remove everything inside it and pack 2 condenser microphones from mobile phones "Nokia 5130".

Like preamp I use this shematic:

My problem is that any voice recorded via those microphones sounds like output from a can. I know that these microphones can record better sound and I think my preamp need some tweaks or some special filters.


texts: Current drop a certain vds in a transistor

texts:
I am measuring the I-V characteristics in a transistor using a 2 channel source measurement unit (SMU) when I change the \$V_{ds}\$ and measure the current while connecting the gate and the source to the SMU and change the \$V_{gs}\$ the current(\$I_{ds}\$) drops at certain \$V_{ds}\$, but when I leave the gate floating the current is normal,

maybe when the Gate and the Source are connected to the SMU there is a connection between them and at a certain point the resistance between the gate and the source drops and the current can pass at a certain \$V_{ds}\$ but when the gate is floating there is no connection and the transistor works properly I don't know if that's correct but has any one faced this problem before or have a better explanation?


texts: Can I wake up a sleeping Li ion battery pack without dismantling it?

texts:
I have three dead lithium-ion battery packs - two of these and one of these.

My multimeter informs me that the voltage of the batteries and they both read 5.6V. I understand that by dropping below the 3V per cell threshold, the protection circuit has kicked in and is stopping me from charging the packs. I have also read that it is possible to revive individual cells, by providing a 'boost' with a small current, when the voltage is below the threshold.

My question is this: is it at all possible to revive the whole pack (protection circuit included) without dismantling it?


texts: Johnson-Nyquist noise for a lossy inductor?

texts:
In searching the internet for thermal noise on an inductor and I'm not finding much on the basics for a real lossy inductor.  I'm interested in thermal noise for a fixed inductor in a surface mount package.  Here is a diagram TDK provides for their surface mount inductors that shows a loss model for the inductor..

At point 2 in the above diagram, is the Johnson-Nyquist noise the following?

\$\overline{v^2_n} = 4k_BTR1 + 4k_BTR2\$

I'm working on building my first LNA for a hobby project and wanting a basic understanding of noise added by inductors.  I know there are other sources of noise for a LNA.  This question is about the noise contribution by the inductors in particular.


texts: Is there any advantage to have a dedicated hole to measure milliamperes on a multimeter?

texts:
I have noticed that high-end multimeters usually have four holes:

Common (COM)
Volts (V)
Milliamperes (mA)
Amperes (A)

While cheaper ones usually have three holes only:

Common (COM)
Volts (V) / milliamperes (mA) (shared)
Amperes (A)

Is there any clear advantage to have a dedicated hole for mA measurement?


texts: Significant low frequency content from digital oscilloscope measurement

texts:
I have been using a digital oscilloscope to measure a fast transient signal and have then processed the data in MATLAB. Performing an FFT on the data I consistently see a significantly large low frequency component which I believe is not part of the actual signal but rather to do with how the oscilloscope is measuring the signal. I have a few questions and would be very grateful to anyone that can help:

How can I prove the low frequency component isn't actually part of the signal (assuming this is true)?
What techniques can I use to remove this low frequency component from the data?

On question 2, I have tried using a high pass filter in MATLAB however when I then perform and IFFT the time domain signal looks significantly different to what I would expect.

Thanks in advance for any help.


texts:
I am designing a Schmitt trigger with a variable resistor. I used this online calculator to help discover my values.

I have placed it all into a circuit that appears as such and used LTSpice to model it.

My goal is to have it go high at 2.3V and low at 1.97V, but everytime I run it, it does no behave as I would believe.

Any help would be nice, thanks!

EDIT 1: I got rid of the op-amp and the resistor like was suggested. The circuit starts high and goes low when my resistor is at 2.235k and when my voltage is at 2.2V, which is not how I intended it.

[![enter image description here][3]][3]


texts:
I'd like to use TI's DRV8432 motor controller (because it's the only >6A, integrated dual motor controller I can find). The trouble is, it requires a heatsink mounted on top of the IC. See this picture from its datasheet

I've never encountered a package like this before. I'm not sure how to find a mechanically compatible top-mount heatsink, or how it would be secured in place. So I need some design guidance for heatsinks like that.

I've noticed adhesive-backed heatsinks online, but I'm not sure if those are the standard way to solve the problem or if there's something better. (I'm baking the PCBs myself in a toaster oven, so I'm not constrained by manufacturing concerns, though I would like to know the manufacturable way to solve this.) I'd appreciate any help or links.


texts: Oscilloscope 'ground' displaying at +2.4VDC

texts:
When ground-coupled, trace is a dead flat zero volts on the display.  At 5V per division,  DC or AC-coupled, with ground lead clipped to any point on circuit ground, the minimum voltage displayed is +2.4V even when probing the same trace as the ground lead is clipped to.
At smaller values of V/div the voltage of 'ground' is still above zero volts but less so, to a degree which appears to correspond with the resolution.
This happens regardless of probe used. The circuit is powered from a bench power supply, +12VDC, the PSU and oscilloscope are both referenced to the same earth ground.
I'm sure I'm making some dumb error, thoughts?


texts: Arcing contacts corrupt communication. What to do?

texts:
I have a robot with external charging contacts and a docking station with exposed pads this robot has to drive into to start charging.
When trying to dock and charge I seem to get a lot GND bounce, which in turn corrupts the SPI communication. I assume this is due to arcing contacts:

I have already tried using a time-delayed relay to add a second or so of delay between the docking itself and the connection of the V+ and GND to the battery pins and an RC snubber. So far nothing has helped. What is the industry standard for dealing with this?

I do not know the component values by heart, but here's some necessary info:
- 5τ of the RC on the transistor base is about 1 second
- The voltage divider converts the Vsup to 12V for my Digital input.

Here's the schematic, please don't pay attention to the component values, I don't know them by heart:

simulate this circuit – Schematic created using CircuitLab

PS: I assume that the REAL best practice here would be to make the dock intelligent and let it detect when the bot is properly docked, this is something I wish to add in the future, but at this point it is not an option.


texts: Logic circuit for making sure that only one of several signals are logic-high

texts:
simulate this circuit – Schematic created using CircuitLab

I have a circuit as seen in the schematic above. It has 4 different output stages. Each one has an "Enable" pin. The user is able to freely use the mechanical switch to enable any of the output stages. When an output stage is not enabled, its all output pins become Hi-Z. All output stages have a common output connector, and their output pins are shorted together at the output connector side. Therefore, only one of output stages must be enabled at the same time. According to the datasheets of the ICs I used in the output stage circuits, the output pins tolerated short time period of short circuit. So, there is no need to handle the transition between different user choices.

Now, my problem is, I don't trust the mechanical switch. If it fails and enables more than one of the outputs at the same time and it stays like that for a long time, there will be big damage on the circuit.

Can you suggest me a logic circuit which uses least amount of ICs to guarantee that always only one of the enable signals will be logic-1?


texts:
I have designed a board with the ICM-20789, but am having trouble keeping stable voltage values on the I2C bus. Datasheet

I have followed the schematic that was listed inside the datasheet, and that is pictured below. I have a 5V ATMega32u4 that is acting as the master and for this reason, I wanted to run the device at 3.3V logic on I2C.

I have listed my schematic and board layout below as well.

The issue I am having is with the I2C bus and 1.8V line not being the correct voltage. (The lines I am referring to are highlighted in my schematic.)

When using 10K pullup resistors for the I2C line and a 10K resistor for R6 in the datasheet and R15 in my schematic, the voltage regulator runs at a perfect 1.8V, but the I2C lines are running at 2.5V, to low for the ATMega32u4 to read as a logic high. (3.0V when running at 5V).

When I replace the I2C pullup resistors with a 4.7K resistor, then the voltage I2C lines run at above 3V, but the 1.8V is now at 2.1V.

I then trying using 4.7K resistors on the I2C bus, and a 1K resistor for the pull down on the regulator. Again, I have the issue where the regulator gives a perfect 1.8V, but the I2C voltage is to low.

It appears the schematic is saying that it is possible to run the device at 3.3V logic, but I cannot seem to get it working. Any ideas as to why this is happening and how to fix it would be greatly appreciated!


texts: Coil output from variable magnetic field

texts:
If I put a coil with X Henry value and N turns in a variable magnetic field of Y Tesla peak value (coming from another coil excited by A sin(wt) signal), how to calculate the output voltage across the coil and the current running in this coil?
I am designing a coil and a conditioning circuit to measure the value of the magnetic field. The output of the coil will be analyzed by the conditioning circuit in terms of magnitude and phase. I could know the field at a point by using ANSYS Maxwell software but I just used measurement point not real coils and the software gives me the B and H directly. Now from these values, I want to estimate the power level (coil output voltage or current) so I can design the system accordingly, for instance, the AWG of the coil wire and if I will need an amplifier or not, etc.


texts: BLDC Motor Commutation Based Speed Control

texts:
I am working on a project which has a motor to drive a gyroscope (it has quite a bit of mass, and we want it to run at 60k RPM or more).  The motor we built has very low inductance.  We started using a couple of developer kits from major manufacturers, but have found that the PWM frequency that we need to use in order to not have current ripple destroy the waveform (about 100kHz or more) is outside of their normal operating range. Once we get to 100% duty cycle, things tend to behave pretty well (although still not perfectly).

We were thinking that, since we don't need speed or torque control, that the commercial boards are really overkill.  We just need to spin the gyro up to a set RPM, and then apply some energy every now an then to keep it running at that speed.

So we got to thinking, what if we dispensed with the PWM voltage control, and just ran that at 100% duty cycle.  But to control the speed, we would just adjust how often we apply that 100% by not applying it every commutation.  It has enough inertia to run for a long while before losing much noticable energy).  I have been looking around to see if anyone else has described this method, but have come up empty (so I figure there is a fatal flaw in our reasoning).

The motor does have hall sensors.  And we figured we could adjust the PWM at startup for a smoother ramp up, although that is a very insignificant part of the total operating time of the device.

So my question is, before I start programming this, would this be an acceptable method or am I missing something?  And if so what kind of controller would be good to develop it on.  For example, would an Arduino work.

(As background, I am a programmer with a Physics degree from a while ago, and not an engineer with a motor background.  But am really enjoying learning about it)


texts: Highpass and lowpass filter phase-shifted by 90°

texts: If I wanted to build a circuit that consists of an highpass filter and a lowpass filter, what should I consider if I wanted to ensure, that their exits are phase-shifted by 90°?


texts: Generating bit stream in hardware. Glitches with Arduino

texts:
Background

I have a bit sequence that I want to transmit through a digital output. My first attempt was to use direct port assignment on an Arduino. I set the duration of each level with noops. For example, if I wanted to transmit the sequence [1, 0] with 3 clock cycles per bit the code would be

void setup() {
  pinMode(7, OUTPUT);
}

void loop() {
PORTD = B10000000;
__asm__("nop\n\t");
__asm__("nop\n\t");
PORTD = B00000000;
__asm__("nop\n\t");
__asm__("nop\n\t");
delay(1);
}

I am trying to transmit 3 periods of the sequence [1,1,0] with a bit width of 1us. The expected output is shown in the first picture below. The problem is that the Arduino glitches occasionally. The problem can be seen by turning on the scope persistence; see the second scope shot below.

I have scope trigger hold off set to just greater than the duration of the entire sequence (10us).

Questions

Why is the Arduino glitching?
Is there a way to implement this on the Arduino without the glitches?
Is there a preferred way of generating a digital signal in hardware that works better than this?

Thanks!


texts: KiCad: can I give different names to different parts of the same net?

texts:
Is it possible to give different names to different parts of the same net in KiCAD?

I'm setting up to do an autorouted layout (yes, I know, autorouters are evil, but they save a lot of time and should work fine for my large, but simple, design) where there are many sections of the board that need very different trace widths.  For example, a high current line runs through a resistive divider and the current is measured by an ADC.  The high current section of the net needs to be a wide trace, but the ADC measurement section does not.

The way to tell the autorouter about trace widths is through the Net Classes Editor in Design Rules.  I'm looking for a way to break a net into two, but still maintain connectivity.  I guess this would be a 2 terminal device in eeschema schematic that splits the nets, but it has no footprint and doesn't show up at all in pcbnew layout.

Is this possible and does it exist?  Is there a better way to tell an auto-router about nets that will need multiple trace widths?  In know I can do it by hand, but the simple drive circuit is repeated many times and I really don't want to hand route this board.  If it can't be done, then I guess I'll just leave all of the traces on a given net at the large size and deal with the larger board.


texts: Beginner in Arduino, what materials are needed?

texts:
I'm a programmer and i would really like to have with Arduino. I don't know anything in electronics but if there are things to learn, i can do it. I want to know what materials are needed to get started with it.  Just like what type of Arduino board is needed, do i need the segment display so on..

Can you guys help me??