texts: Metal Halide circuit without a capacitor?

texts:
I recently inherited an awesome 4foot 2x250Watt metal halide lighting unit for my marine tank.

The previous owner wanted to dump it because one of the lights was flickering and he could not really figure out why.

So after I got it; I stripped it down and realised the terminals on the coil transformer were overheated and the wires were not in good contact. I replaced the terminals, made sure there is good contact and re-stripped the wires and made sure they were still up to the job.

I figured out that one of the ignitors was faulty and I need to order a new one. When I could not find the same model I ran into a horde of different ratings, models, packages. In the end I found the one I need. Then looking at some circuits - everybody says there should be a capacitor ... I do not have one? But the one working light does ignite and sustain.

From this page I can say my circuit is 1 - but without the capacitor?

Looking at the lookup 250HQI/MBI it says I should have a 35 µF cap before the core transformer?
 I have read various articles and they say that the light won't ignite WITHOUT this capacitor but mine does - Also I have two ballasts and ignitors.

Should I put a cap in there to help the two ballasts?

EDIT:

I just bought two new ignitors.

One is a standard ignitor (<250W) for £5 (no cap shown in schematic)

And a newer electronic ignitor for £20 (<1000W) (shows cap in schematic)

I wired this one in - Nothing happens! :( Going back.


texts: When to use an active filter instead of a passive filter?

texts:
I want to build a low-pass or a band-reject filter to remove 50/60Hz humming noise. I couldn't decide where to start with. I will use this filter to remove 50Hz noise where I make data-acquisition of a signal through a BNC cable.

Active or passive filters both could be used but I don't know the trade-offs.


texts: Replacing fuse in Dewalt battery charger

texts:
This is a photo of a Dewalt DW9104 battery charger (ie for a cordless drill).

It appeared to be dead but I think I've narrowed the problem down to the fuse labelled F1 which is located just to the left of the + in the photo.

But how do I replace this? It looks like it is in a fuse "holder" which is rigidly attached to the board. I hope that detail is clear enough in the photo.

Many thanks!

EDIT:

The accepted answer was correct, it was not an existing fuse holder, just a funny looking (to me) fuse. I clipped the existing fuse out leaving its leads soldered to the board. I then soldered an actual holder to those stub leads (easier for me, than soldering to the board). It now works well!


texts: Should PCBs be rinsed after being cleaned with IPA?

texts:
A lot of people recommend using 99% IPA to clean flux (and other stuff) off PCBs. I haven't been rinsing off boards after cleaning with IPA as to my knowledge it's not corrosive, but I'd like to hear from someone more experienced on the matter.

Should I be rinsing boards with something like distilled water after cleaning them with 99% IPA?


texts: What kind of motor to use in a PCB drill?

texts:
I'm trying to use this super-cheap PCB drill that I bought recently, but it's too weak for human convenience (takes about 10 seconds to get through standard 1.6mm FR4).

The drill uses a small DC motor (40 mm length, runs off12V, RPM unknown, my PSU shows < 100 mA current draw), which is clearly of concern.

Luckily, it's very simple to detach the drillbit collet from the original motor shaft, by simply releasing the black set screw in the photo.

So I wanted to substitute a more powerful motor. I'm supposing I can just use any standard DC motor to replace the original one.

What motor specs should I look for, if I want to achieve more powerful drilling? Also, should I ideally go for non-geared (higher RPM) or geared (higher torque, but at the cost of rotation speed)?


texts: Is an MPU capable of equal quality digital synthesis as a dedicated DSP chip?

texts:
Is there any factor which would cause a modern microprocessor ( such as an ARM Cortex A/M ) to be inferior at performing digital synthesis compared with a dedicated DSP chip of comparable speed?
At a glance, it looks like most digital synthesizers designed prior to the 2010s use dedicated DSP chips for tone generation and filtering. There seems to be more new synthesizers, for example Korg's WaveState or Volca series, built around ARM Cortex A/M chips, without dedicated DSP hardware.
I'm wondering if certain factors like the real-time processing capability of the chip may affect the overall sound quality of the output signal, all other things being equal. Admittedly, I'm not even remotely an expert in this area. I'm mostly curious based on my observations of a trend in this industry.


texts: I'm new to this group and have limited electronics knowledge so I will ask for those that can help me to be gentle.  I'm trying to build a 3 digit display using a ICL7107 A/D and have it mostly figured out.  I'm reading voltage off a sensor that puts out variable voltage between .42V and 4.45V so my total range is a little over 4V.  I am using a voltage divider to drop the 4.45 to 200mV.  I want it to display 0 at .42V and 15 at 4.45.  As its sits now, it displays the actual voltages.  So, should I be using a completely different circuit or is there a way to get the display to read 0 - 15?  Perhaps I could us Dual OP-AMPs to change voltage ranges before dropping to 0-200mV?


texts: using 7.62mm screw terminals on prototype board

texts: What have people done to be able to use 7.62mm screw terminals on prototype boards?  I am trying to prototype something use screw terminals that have 7.62mm posts, but the prototype boards do not have holes that large.


texts: Connecting copper pours in Cadence (OrCAD) PCB Designer

texts:
I'm trying to climb the Cadence learning curve, coming from an Eagle background.

My board is four-layer, with a ground plane underneath the top layer.  I have a surface mount IC that has an exposed pad, which should be soldered to ground.  I want to avoid putting vias in this pad.  Since two edges are free of pins, I am trying to pour a copper region larger then the opening in the solder mask, and then I'll put the vias there, connecting it to the ground plane.

Here is the part:

In Eagle, I would pour the polygon and assign it the same net name as the exposed pad.  The two areas would merge nicely.

I have done this in Cadence, using a dynamic copper fill, on the top layer, and assigning the same net name ("GND_SIGNAL").  The two areas do not connect, and I get a trace between the two "floating" areas, connecting them to the exposed pad:

I suspect that this may be thermal relief between the pad and the pour.  Is there a method to force Cadence to NOT use thermal reliefs, on just this one pad?  I've looked over the docs, and asked google, but I'm not finding an answer.

Of course, it may be something else completely.  Does anybody know how to do this?


texts: Physical significance of positive group delay with negative phase delay

texts:
This question is an addendum to: Is group delay the same as the delay of a certain frequency?

Lately, I've been going back to basics to better understand the concepts of group and phase delay, so I did some simulations with the following simple LPF and HPF:

simulate this circuit – Schematic created using CircuitLab

For the LPF the transfer function is:

$$H(jw)=\frac{\tau}{j\omega + \tau}$$

and for the HPF:

$$H(jw)=\frac{j\omega}{j\omega+\tau}$$

where \$ \tau=\frac{1}{RC}\$

In case of the LPF its group and phase delays are:

$$\tau_g(\omega)=-\frac{d\phi}{d\omega}=\frac{\tau}{\omega^2+\tau^2}$$

and

$$\tau_\phi=-\frac{\phi}{\omega}=\frac{\text{arctan}\left(\frac{\omega}{\tau}\right)}{\omega}$$

To get a better feel, I simulated in Multisim with the resistor and capacitor values of 1K and 1uF respectively, I exported the phase angle VS frequency values to an Excel spreadsheet to numerically check the results, I entered the formula for the phase delay and then I differentiated numerically to get the group delay, these are the graphs:

Both graphs seem consistent with the analytical formulas.

Now for the HPF the group and phase delay are:

$$\tau_g(\omega)=-\frac{d\phi}{d\omega}=\frac{\tau}{\omega^2+\tau^2}$$

and

$$\tau_\phi=-\frac{\phi}{\omega}=\frac{\text{arctan}\left(\frac{\omega}{\tau}\right)-\frac{\pi}{2}}{\omega}$$

As you can see, the group delay for the HPF is the same as the group delay of the LPF, however the phase delay is different. Here are the simulated graphs

So here is the question: What does it mean (in the time domain) to have an increasing negative phase delay while having a decreasing positive group delay?

The way I see it, is that the envelope of the output waveform is still lagging but the phase seems to be leading the input waveform?


texts:
When I am trying to do simulation of the following program on Modelsim Altera  10.0d then gives Error : Code Error 9:
** Fatal: (vsim-4) * Memory allocation failure.

Attempting to allocate 131072 bytes

Please check your system for available memory and swap space.

The following is my code :-

module sipo (gsclk, sclk, rst, sipo_in, sipo_out, sipo_out_i, dcsel, blank, gs_enable);
   input gsclk, sclk, rst;
   input sipo_in;
   input dcsel, blank;
   output reg [47:0] sipo_out;
   output reg [47:0] sipo_out_i;
   output     gs_enable;
   integer i;

   assign  gs_enable = (~dcsel & sclk==1'b1) ? 1'b1 : 1'b0;

   always @(posedge gsclk, posedge rst)
     i=0;
   begin
     if (rst)
       sipo_out_i  <= 47'b0;
     else
       if (gs_enable)
         for (i=1; i<= 48; i=i+1)
           @(posedge sclk)
             while (i < 48)
             begin
               sipo_out_i  <= {sipo_out_i[46:0], sipo_in};
               i = i+1;
             end
           sipo_out <= sipo_out_i;
   end

Please help me if  it requires any change in verilog code?


texts: Anti-static mat connected to earth directly or 1E6 ohm resistor?

texts:
Should an anti-static mat be connected to earth directly or with 1E6 ohm resistance in between?

2 layer mat. Upper side: dissipative (10E7 ~ 10E10 ohm/m²). Bottom: conductive.

To be a little more precise: connection to earth will be thru a CGP (common ground point) which is at earth potential. So, 1E6 ohm resistance or not, between mat and CGP?

In response to Lorenzo Donati: so, the workstation environment explained in Op Amp Applications Handbook, chapter 7, page 95, looks like this:

Why not the following setup? Note the wrist strap grounding, which i edited from the original image.

Now, instead of 2E6 ohm resistance to earth, there is 1E6 ohm between the wrist strap and earth. Is this enough?

Page 96: "Again, a 1E6 ohm, from the wrist strap to ground, is required for safety".


texts: I want to know if it is possible to use this raw e-ink display  with Arduino. Is it possible to directly connect cables from this ribbon cable to Arduino without any driver PCB and control it with 3 or 4 wire SPI? I was looking for some tutorials but I haven't found anything. In the future I would like to use it with nRF52832 BLE chip.  the pinout of the display is on 6th page


texts: voltage traces across pwm driven dc-motor: is that ok?

texts:
I'm driving a dc-motor with a BJT turned on and off with a 555 generated PWM signal. Here's the circuit (V1, Rl and L1 simulate the motor):

There actual circuit - same parts - is on a breadboard and is running a small 7W dc-motor. I'm using an oscilloscope to look at the voltage across the motor leads. Here's what I get when the motor is running fast (CH1 yellow is on 5V, CH2 cyan is on the BJT's collector and in red is the voltage across the motor leads CH1-CH2):

All seem fine:

CH1 is 5V fixed
CH2 shows a small VCE sat. when BJT is on and the EMF of the motor acting as generator when the BJT is off
the red trace is as expected

Here's what I get when the motor runs slowly:

That doesn't look as good:

CH2 shows a much higher VCE sat. when the BJT should be on with pronounced noise/ringin

Is that ok? According to the BD139 datasheet Vce shouldn't be more than 0.5V so something must be wrong here. Maybe the BJT is not fully on? I chose Rb considering the 180mA no-load current listed in the motor datasheet. Should I lower it? Any other hint?

Edit:

I did some more calculation considering conservative values Imax= 180mA, Voh = 3.3V, hFE = 25, Vbe = 1 V) and got around 300 Ohms for Rb. I tried lowering its value and got much better results with 150 Ohms: I can slow the motor down much more before Vce rises to the point the BJT can't be considered in  the saturation area anymore (1 Volt or more).

I gave a look at the current with a 1 Ohm series power resistor and found out that unexpectedly the current is higher when the motor turns slow. That could explain why I get such a bad behavior (BJT not fully on) at lower speeds. Apparently the motor in not running smoothly and current is pulsed with a higher value.

I also tried putting caps to smooth things out with no success. I tried with a 470uF + 100nF across the power supply but the voltage keeps falling when BJT is ON; furthermore putting a small cap across the motor has no effect on the ringing/ripple/noise caused by the motor.

Edit 2:

I tried raising the PWM frequency swapping the 390nF capacitor. With a 3.9nF cap I get a perfectly square signal but even if it seems better I'm not convinced it's a good thing current wise. Reading on textbooks I get something like that with the former cap value:

showing the voltage accross the motor and the current sensed with a shunt resistor. Raising the frequency (2kHz) I get something like that:

where the voltage is apparently better but:

the diode is alway ON when the BJT is OFF (which I think is bad power wise)
the current never reaches its final value (bad for motor performance I guess)

So which one is better?


texts: Placing through hole and SMT on the same side

texts:
I have a design with huge push buttons (with 6 TH holes.)
There's a few of them so they do take up quite a bit of space mechanically from the top.
I was thinking of placing the majority of the SMT part on the other side (same side where the TH would be soldered.) This way I could place the SMT directly underneath the buttons and with some clearance to its pins.
I was told that this is a bad idea from a manufacturing point of view  since there are two processes: one reflow for the SMT and then a solder bath for the pins. The solder bath may cause problems for the SMT.
For this prototype space is not really an issue and so I will take his advice and lay out the SMTs on the same side. But for the next revision, is this something I can consider? I suspect I won't have this much space next time around.


texts:
I am simulating a project on Proteus simulation software using this microcontroller. My issue is, I have made a 2 sec interrupt on timer0. But simulation is showing it as tooo fast (w.r.t simulation clock).

I used the Mikroelectronica Timer calculator using these settings:

The simulation schematic is as follows:

I am using MikroC pro for PIC compiler. And yes, I have double-checked the Clock frequency in the compiler, of the quartz crystal and the MCU in proteus, all are 4 MHz. I have set the crystal as XT in the compiler as well.

What could be the reason behind this inaccurate timer?

The code I'm using is as shown below:

int toggle1 = 0;
int toggle2 = 0;
int toggle3 = 0;
int toggle4 = 0;

void InitTimer0(){
  T0CON  = 0x84;
  TMR0H  = 0x0B;
  TMR0L  = 0xDC;
  TMR0IF_bit = 0;
  TMR0IE_bit     = 1;
}

void Interrupt() {
  if (INT0IF_bit && INT0IE_bit) {
     INT0IF_bit = 0;
     if(toggle1 == 0){
          LATC0_bit = 1;
          LATC2_bit = 0;
          toggle1 = 1;
          INTEDG0_bit = 1;         // Interrupt on rising edge on RB0
     }
     else{
          LATC0_bit = 0;
          toggle1 = 0;
          INTEDG0_bit = 0;         // Interrupt on falling edge on RB0
     }
   }
   if (INT2IF_bit && INT2IE_bit) {
     INT2IF_bit = 0;
     if(toggle2 == 0){
          LATC3_bit = 1;
          LATC2_bit = 0;
          toggle2 = 1;
          INTEDG2_bit = 1;         // Interrupt on rising edge on RB0
     }
     else{
          LATC3_bit = 0;
          toggle2 = 0;
          INTEDG2_bit = 0;         // Interrupt on falling edge on RB0
     }
   }
   if (INT1IF_bit && INT1IE_bit) {
     INT1IF_bit = 0;
     if(toggle3 == 0){
          LATC0_bit = 1;
          LATC2_bit = 0;
          toggle3 = 1;
          INTEDG1_bit = 1;         // Interrupt on rising edge on RB0
     }
     else{
          TMR0IE_bit     = 1;
          toggle3 = 0;
          INTEDG1_bit = 0;         // Interrupt on falling edge on RB0
          delay_ms(500);
          LATC0_bit = 0;
     }
   }
   if (TMR0IF_bit){
    TMR0H    = 0x0B;
    TMR0L    = 0xDC;
    if(toggle1 == 0 && toggle3 == 0)
          LATC2_bit = 0;
    if(toggle4 == 0){
         LATC4_bit = 1;
         toggle4 = 1;
    }
    else{
         LATC4_bit = 0;
         toggle4 = 0;
    }
   }

}

void main() {

  ADCON1 = 0x07;           // All digital I/O
  RBPU_bit = 0;

  TRISB = 0xFF;            // Set PB0 as input
  TRISC = 0x00;            // Set PortD as output
  PORTC = 0x00;            // Starting value for PortD

  INTEDG0_bit = 0;         // Interrupt on falling edge on RB0
  INTEDG1_bit = 0;         // Interrupt on falling edge on RB1
  INTEDG2_bit = 0;         // Interrupt on falling edge on RB2

  INT0IF_bit = 0;          // Clear INT0IF
  INT0IE_bit = 1;          // turn OFF interrupt on INT0

  INT1IF_bit = 0;          // Clear INT1IF
  INT1IE_bit = 1;          // turn OFF interrupt on INT1

  INT2IF_bit = 0;          // Clear INT2IF
  INT2IE_bit = 1;          // turn OFF interrupt on INT2

  InitTimer0();

  GIE_bit = 1;             // enable GIE

  while(1){}
}


texts: Placing electricity, cable, phone and internet transmission lines tight together

texts:
Will this cause noise in the phone and internet signal? also placing them through concrete with absolutely no air space around them.

This is happening in one of my friends house, he has issues with noise on the phone, the phone and internet company are the same, so the same noise also causes issues with the internet, it's just one cable since it's from the same company. I went to check outside and noticed that the guys who built the concrete roof, built it around the cables, also placed them tightly together, 110v and 220v together with the phone/internet one. They didn't even bother to use a pipe, no, they just built the concrete roof around the cables.


texts: Simulating a simple RC circuit using an arduino and the circuit's equivalent discrete-time transfer function

texts:
Suppose we have an RC circuit with the continuous transfer function: \$G(s)=\frac{1}{RCs+1}\$ with R=1.6k, and C=2uF. Using the bilinear transformation(or better known as Tustin method) \$ s=\frac{2}{T_s}\frac{z-1}{z+1}\$ with the sampling period being \$T_s=0.5ms\$, I arrive to the following discrete transfer function:

\$G(z)=\frac{z+1}{13.8z-11.8}=\frac{X(z)}{U(z)}\$

In terms of a difference equation(recurrence relation) the discrete system is thus described as \$u_n+u_{n-1}=13.8x_n-11.8x_{n-1}\$, where \$x_n\$ is the current output variable, \$x_{n-1}\$ is the previous output. Similarly \$u_n\$ is the current input variable, and \$u_{n-1}\$ is the previous input. The output of this system will obviously be discrete, unlike the real response of the RC  circuit.

The code, I've written for the arduino (Uno model) is here:

#include "Wire.h"
#define PCF8591 (0x90 >> 1)

void AnalogOut(uint8_t value)
{
 sei(); //enable interrupts
 Wire.beginTransmission(PCF8591); // turn on the PCF8591
 Wire.write(0x40); // control byte
 Wire.write(value);
 Wire.endTransmission();
}

int preload;
void setup()
{
 pinMode(A0, INPUT);
 Wire.begin();
 // timer2 initialization
 noInterrupts();
 TCCR2A = 0;
 TCCR2B = 0;
 preload = 6;
 TCNT2 = preload;                                   //setting the preload
 TCCR2B = (0<<CS22) | (1<<CS20)| (1<<CS21);        //and the prescaler for a   0.5ms sampling time
 TIMSK2 |= (1 << TOIE2);
 interrupts();
}

 uint8_t x_n_1=0;   //x[n-1]=0; initial  value of the output

 uint8_t u_n;       //u[n]  current value of the input
 uint8_t x_n;       //x[n] current value for the ouptut
 uint8_t u_n_1;     //u[n-1] previous value for the input
 //interrupt routine
 ISR(TIMER2_OVF_vect)
  {
   TCNT2 = preload;
   u_n=analogRead(A0);                   //reading the current input value, a/d conversion takes up about 0.15ms
   x_n=uint8_t(0.07246*u_n+0.07246*u_n_1+0.855*x_n_1);   //x[n]=1/13.8(u[n]+u[n-1]+11.8x[n], also converting it to a 8bite integer
   AnalogOut(x_n);                       //writing to the PC8591 d/a converter
   x_n_1=x_n  ;                         //x[n-1] for the next sampling interval becomes the current x[n]
   u_n_1=u_n;                                  //u[n-1] for the next sampling interval becomes the current u[n]

   }
  void loop()
  {
    TCNT2=preload;
    u_n_1=analogRead(A0);  //getting an initial value for u[n-1]
    while(1);

   }

Note that I have used an interrupt routine for generating a 0.5ms delay. Also, the part of the code in the loop() function is better explained next:

 TCNT2=preload; //the timer starts ticking at its inital value
 u_n_1=analogRead(A0); //we are doing this a/d conversion before even one interrupt has happened.

Here is the circuit I put together in proteus:

In proteus, I am sending \$y=3+\sin(314t) volts\$ to the A0 analog input. Also, I set the refference voltage for the a/d covnerter to 5V (in our actual laboratory we can set Vref using a potentiometer). Here is what I got on the oscilloscope in proteus when running the simulation:
I am not sure whether this would work on the actual device since we'll be doing that in our lab in a couple of days as a part of a Digital control systems  course. Is the crappy signal only a result of poor simulation or is there another error? I have tried generating a (discrete) sawtooth wave using this same circuit(but without no inputs or any transfer function, just plain signal output) and it worked well.


texts:
I'm trying to design a circuit that produces
$$
V_{\mathrm{out}}=\begin{cases}V_{\mathrm{in}}-V_{\mathrm{cc}}/3 & V_{\mathrm{in}}>V_{\mathrm{cc}}/3\\0 & V_{\mathrm{in}}<V_{\mathrm{cc}}/3 \end{cases}
$$

I expected the circuit above to produce the result. However, the SPICE simulation (LTspice) and building the real circuit shows that
$$
V_-\approx1.5\,V\ne V_+
$$
causing high output voltage.

What'd be the problem here?


texts: Can't get simulation of single phase parallel inverter working in LTSpice

texts:
Can someone tell me why my LTSpice circuit can not work properly? As I am pretty new to electronics I might have done a big mistake that's obvious to more experienced people, however I can't find it.

I tried to build the circuit shown in this video:
https://www.youtube.com/watch?v=a0gmhxZ_Zf0

or here:
https://3.bp.blogspot.com/-aDaheyhgUeY/V4KEc3jym1I/AAAAAAAADEk/IEFywbTiy_4csigNK5IVBqbn62cvRKH2ACKgB/s1600/Untitled%2Bpicture78.png

I think the circuit itself should be correct, I maybe just built it wrong in spice.
Maybe the position of GND in the secondary Inductor is wrong, I thought technically it should work even without, but Spice wanted me to add GND to prevent floating, so I added where I thought it could make sense. Anyway I also tried the other two possible positions as well without any better results.
The values I used for the components are just random values, I tried changing them a lot but couldn't see much impact on the output. I chose the series resistance to be 100mOhm for capacitor and Inductors, just telling because this can't be seen in the schematic and might be important.

I hope someone can help me.

Edit:


texts: ESP-01 isn't booting in operation mode with 3.3K pull up on GPIO2

texts:
This should be a very simple question for most of you but confusing for a hobbyist.
I looked at the ESP-01 data sheet and the recommendation is to put a 3.3K pull-up resistor on GPIO2 to ensure the ESP-01 boots in operation mode.
The ESP-01 boots up my program fine (I have 2 blinking lights twice to denote that the ESP is running) if the OPTOTRIAC is disconnected.
But with the OPTOTRIAC connected to the GPIO2 line, the ESP won't boot. The R200 ohm is lifted from another tutorial and the 3.3K is from the datasheet. At boot, I suspect that the 200 ohm to ground through LED is stronger than the 3.3K pull up which is why the ESP won't boot to operation mode.
My question is, how do I size the 3.3K so that it pulls GPIO2 up when booting, then to operate normally as output for the OPTOTRIAC (output HIGH to activate OPTOTRIAC and LOW to deactivate it).
It might be worthy to note that I replaced the 3.3K with various resistors down to 670 ohm and that is when it started working as expected, but I don't know if this is the right way or if it is going to be reliable.
Therefore, I am not looking for just the answer, but I am looking also at the "why". How should the resistor(s) size be calculated?
Thanks in advance


texts: Update Altium designer schematics library and keep values unchanged

texts:
Whenever I choose a schematic library like a resistor and use Tools > Update Schematic button, all values of resistors that are set in my schematic document are reset to the library default value e.g. 1k Ohms.

Is there a method to keep the values unchanged upon updating?


texts: Understanding electricity as water, what does it mean to "draw 30 amp"?

texts:
Is this analogy correct?  Think of electricity as water.  The source is a big basket full of water, wires are pipes.  Turning a switch means opening a pipe; as the water flows it makes the engine turn.
Does this analogy hold?
If it does, why would there would be a problem if an engine draws 30 amp but you only have 20 amp?  In the water analogy, the engine simply wouldn't turn.  OR maybe the way I should think about it is that if the engine doesn't turn, somehow the water would back up and make a mess?
I'd like an explanation using terminology that even a child can understand, like water.


texts: Simulating 3 phase mosfet bridge with LEDs

texts:
I have a commercial 3 phase BLDC motor driver board (TI DRV8323 BoostXL) and I want to write a firmware from scratch. For testing, I want to make sure I open/close the mosfets in correct order. I am thinking to use 3 LEDs to simulate motor windings but I am confused as the motor windings are in star arrangement... typically something like the image below:

Is there a way to simply attach LEDs to the outputs of the bridge and simulate this?

Another problem is that the supply voltage will be 24 volts but I want to use normal LED which I believe can be damaged above 5 volts...how to take care of that?


texts: How is phase recovered from wireless signals?

texts:
I've wondered for a long time how phase information is captured for wireless signals. It's used in applications like QAM for decoding symbols and radar beam forming to to locate targets, but I've never been clear on how we can get phase information from voltages measured as a time series of real numbers.

Some signals from medical applications like MEG and EEG do not have phase information. What is the difference between such signals and radio signals? Does it have to do with being able to make certain assumptions about the nature of the signals being sinusoidal?


texts: ADC and DAC center frequency upper limit

texts:
I have some RFSoc Evaluation Kit with 12-bit DACs and ADCs that support nearly 4 GSPS

I found out that sampling rate is related to bandwidth.

From experiment, I found out that this board's DAC and ADC center frequency upper limit is about 1 GHz.

I wonder what factor would affect the upper bound of the DAC and ADC center frequency.

I used to doing research on signal processing and is new to electric.
Can someone please help me or provide some idea. Thanks in advance.


texts: Confusion in magnetic neutral plane of DC machine

texts:
I was reading book Electric Machinery by Chapman and in topic 'Armature reaction ' It is written that
"The magnetic neutral plane is defined as the plane within the machine where the velocity of the rotor wires is exactly parllel to magnetic flux lines ,so that E(induced ) in the conductors in the plane is exactly zero ".
This  definition of MNP is very confusing for me because
1.I always consider that velocity of conductors is always perpendicular to magnetic field of stator because velocity is tangential to cylindrical surface and magnetic field is radial to cylindrical surface but after reading this definition I'm not sure whether I had this misconception or I am right?
2.and if velocity and magnetic field is always perpendicular the  how such a plane (MNP ) is possible where magnetic field and conductors  are parllel?


texts: How can I design a low pass filter using Z transform in Microcontroller?

texts:
I have generated a signal which is a mixture of 50 Hz and 250 Hz sine waves using a microcontroller and DAC. Check the screenshot of the excel file:

The values of row 4 (i.e. f1+f2) are feed to an 8-bit DAC to form the mixed signal. Now, if I read the Analog signal using another microcontroller at a 0.0002-second interval then I'll get back these data again.

So for the receiver, x(n) = {120,132,144,155,163, ... ... , 90th value }.
And the Z transform should be, X(z) = {120 + 132z^(-1) + 144z^(-2) + 155z^(-3) + ... ... }

Again, the transfer function of low pass RC filter is H(s)= (1/(sRC+1)) = a(1/(s+a)); where, a= 1/RC.

And the z transform will be H(z) = a(z/(z- e^(-a)))

So, how can I calculate the output response Y(z) = X(z)H(z), as X(z) is a very long series.
My aim is to use the output response equation in a microcontroller to reproduce the low-frequency signal.

Thanks in advance.

It is solved according to the answer of @Warren Hill


texts: Circuit review: Impedance bridging for microphones

texts:
I have a pair of specialist condenser mics with a nominal output impedance of 3.6k Ohm  that I would like to interface with mic preamps with nominal input impedance of 2.2k Ohm. Does this impedance bridging circuit look ok? I have breadboarded it and it seems to work, but I'm very open to suggestions for improvement.

The op amp I am using at the moment is the AD8646 ...

http://www.analog.com/static/imported-files/data_sheets/AD8646_8647_8648.pdf

Thanks


texts: I want to communicate using a serial cable to a device that uses RTS/CTS flow control and 115200 baud speed. I want to use this Sparkfun TTL to rs232 adapter, but it has no RTS or CTS pins. What can I do to get hardware flow control or is there a software solution?


texts: Switch (Relatively) High Voltage from Logic Level

texts:
The Situation:

Basically, I would like to switch a load that requires 30v using a switch that cannot have more than 5v across it.  More descriptively, I am trying to drive the anode of a VFD segment from the output of a shift register (probably a 74HC595).

What I Have So Far:

Because the segments are essentially common-cathode, the anode has to be switched.  You can't really switch that with an N-Channel FET, as when current is flowing drain to source, the source would instantly be at ~30v, which being higher than the gate voltage (5v), would instantly turn off (I guess maybe it would actually reach equilibrium at some very low conductance?).  If a P-Channel FET were used, the gate can be pulled up to the 30v rail for off, but then you have 30v at the logic output, which is far, far outside of spec.  Short of shifting the logic-level ground up to 25v, which seems like a major pain, the best that I can think of is to add an N-Channel FET to drive the main P-Channel FET, and pull down the gate of that to ground, like this:

(I showed it with just a simple switch and load rather than an IC output and a floating anode so that this will be hopefully more applicable and/or easier to understand for people with other applications...)

The Question:

The problem that I have with this is that it seems like an excessive number of components for such a simple task.  There has to be a simpler way to switch the higher voltage, right?  I feel really stupid having so much trouble with something so simple, but I've spent all day on it, and this (or shifting up the logic ground) is all that I've been able to think of.  I guess in the grand scheme, it's only one extra transistor and one extra resistor, but it kind of adds up when you're driving a large number of lines...


texts: How to prevent an arc when a device is plugged in

texts: I have a device that takes arcs when I connect the power plug. It uses 24V. The 24V source is far awar so a 47uF cap is at the input. Charging this large cap causes a big zap every time. A 10Ω series resistor helps, but the device takes ~200mA at peak load; 0.4W is a lot to burn off at the input.


texts: How can I replacing broken DPDT switch with direct wiring?

texts:
The "gearbox" of my kids car i broken. It's the kind you sit in (at least the kid) and pushes a button with the foot and the car goes forward or backwards, depending of the state of the "gear". From what I know the "gearbox" is a DPDT switch, it has two positions. As the DPDT switch is broken I need to replace it, but can't i just temporally put it in forward mode only by creating the same bridge between the terminals?

Here is the simple setup. There is a battery, 12v in the back, a push button for the foot in the front and this switch terminal in the middle. One is double red (+V?) and one is single red. The same for black (Ground?). There is a a double blue and a single white.

If i use a multimeter and check any red/black combination I get +11V so the battery needs charging. Do I bridge double blue with double red or black? Blue with red will maybe make if move forward, and blue and black will make it move backwards? Is that the logic here maybe? Same with the single white with either single red or black? If the double blue is connected to double red, does the single white need to be connected to single black?

EDIT:

I opened up the foot switch and I got even more confused, I found a brown wire:

I opened up for the two motors and BLUE and BROWN goes to the left motor, BLACK and RED goes to the right motor:

Sorry for the bad image, the car is red :-)


texts:
I have created a pcb with KiCAD.
Unfortunately, there were some errors with the pcb and i have to redraw.
The problems all lie within the pcbNew program...
My schematic, footprints and generally everything else is correct.
So i will have to redesign the pcbNew portion of the pcb.
Since i have already designed pcbNew, is there a way to revert if back to the original state (where all the parts were in the middle and i had first to sort them out)?


texts: How to explain the results from different block sizes?

texts:
I vary the D-cache block size for a program. I test different block sizes for the D-cache, block sizes from 1 to 8. Size = 128 words, and blocks in sets (associativity) = 1.

Block size     1     2     4     8
Access time   30    20    15    12
Hit rate      1%    50%   75%   87%
Cycle count 34921 24241 18901 15769

Please help me explain the measurement values for hit rate and cycle count. Why does the hit rate suddently improve so much as a increase the block sizes?


texts: Filter ripples and their effect on signal quality

texts:
Ripples cause an amplitude distortion in addition to a phase distortion expressed in terms of RMS phase deviation (from linear) or group delay variation over a certain signal bandwidth.
The question is are they related? , i.e. can one calculate the RMS phase deviation (or group delay variation) knowing the ripple amplitude variation (expressed say in terms of peak to peak)


texts:
Many circuits have two possible states: one state is that in which every current and voltage is zero, the other state is the "correct" state. In order to avoid the trivial state and force the circuit in the correct state, a start-up circuit is required. This circuit injects a current in a transistor in order to force a current to flow. Let's consider the following dynamic start-up circuit:

M4 is the diode-connected transistor of a current mirror belonging to the circuit that we want to "activate" (i.e. avoid the trivial state). When the circuit is turned on, Vdd goes from zero to its value ideally like a step. Assuming Cs initially discharged, node B will remain at zero for a while (and thus transistor MS1 is on, producing a glitch of current which "activates" M4) and then will raise to Vdd exponentially (causing MS1 to gradually turn off, which is correct since M4 has already been activated).

The author of my book says:

"The dynamic start-up circuit doesn’t monitor the reference current but simply
produces a glitch current in M4 that, hopefully, will bring the circuit in the
desired operative point. Therefore, the circuit works properly only if the off-to-on time of the supply voltage is pretty fast, compared to the time constant Rs*Cs. In addition to this, the parasitic capacitance from node B and Vdd should be small compared to the capacitor Cs. If not the coupling of node B with the Vdd line attenuates the glitch at the gate to source of MS1 eventually preventing
it to exceed the threshold."

What does it mean? The author says that if some conditions (which I don't understand) are not satisfied, then the start-up circuit will not work. But actually it seems to me that the circuit should always work: indeed, if the capacitor is initially discharged, node B must go from zero to Vdd exponentially, thus necessarily turning on (and then, as node B raises, turning off) MS1, which "activates" M4.

Thank you


texts: Launchpad MSP430 incremental blink with button

texts: I'm new with this. I'm trying to make an incremental blinking LED with every time that I push the button, I'm using Energia and Launchpad MSP430, I don't know if somebody can give a example code to do this?


texts: Why do common-mode EMI filters lack damping networks?

texts:
I've been going through the design of a few different EMI filters, mainly for buck converter inputs.
In many cases the leakage inductance of the CM choke can provide enough inductance for the differential part of the filter.  Although it's not shown in this picture, it's also extremely common to damp the differential filter via a resistor and damping capacitor (5-10 the capacitance of Cx2) in parallel with Cx2.  This is natural given the peaking in the bode plot of a LC second order filter.
What I have not seen anywhere online, is a design that dampens the common mode filter with a similar network to the chassis.  Why is peaking not a concern for the common mode portion of the filter like it is for the differential?  Maybe the shallow impedance slope of a CM choke is a hint?
Usually the CM chokes are in the milli henries, and they have decent attentuation at >1Mhz, Cy1/2 fall around 1uF.
I'm trying to see if I can save space by picking a small CM choke in the micro-henries, and then having a series inductor, so that I can reduce Cdamp.  This makes Cy1/2 have much larger capacitance values, and I'm not sure how this will interplay.


texts: Can adding inductive load really reduce mains power consumption?

texts:
I have recently bought one of the cheap mains power meters (EL85-2042A to be precise) to monitor power consumption. It's really helpful when I need to know where my electricity bill comes from, or when I want to make sure I switched everything off before going out:

There's one thing I have noticed which I'm not sure how to explain. I have a few 12V LED spots powered via a transformer, and whenever I switch those on, the current on the meter goes down by 40 mA or so. A similar effect happens when I connect an old tranformer-based adapter powering an old clock radio.

As I understand this, most of my appliances ought to have capacitive kind of load, resulting in a leading power factor, so adding an inductive load with a lagging power factor compensates for that. What I would like to know is whether I will be really billed less when adding inductive load and consuming less reactive power, or do power companies take these effects into account and only bill for real power consumed?


texts: Is using vias for split data buses a bad idea?

texts:
I've tried searching for this but can't seem to find the answer I'm looking for.  I'm designing my first PCB and I'm having trouble routing data lines without making the board large.

For example, I have two ICs that need to have 8-12 data lines between them. 7 of the lines line up perfectly and I can rotate the two ICs to support that.  But the other lines are becoming difficult to route without enlarging the board.

I can post pictures if needed by my question is more generic.

Based on tutorials I've found, I try to keep my ground traces on the bottom layer and data traces on the top (only a two-layer board, all through-hole).

So I was wondering, if I have a trace that needs to run over another trace on the same layer, is it advisable to put a via in just before it, run it "under" the trace, and then another via back up?  Basically a data trace on the top would temporarily go to the bottom layer, cross under the top trace and then back up.

I hope that makes sense.

It is my understanding that this is exactly what vias are for.  But I didn't want to use them all over the place if it's bad practice.

Keep in mind that I've rotated the ICs every which way I can.

Oh, for what it's worth, this is an audio board and the two ICs are a 74x595 shift register and a AY-3-8912 audio IC with a max clock speed of 2-4MHz.

Thanks for any suggestions.


texts: Convert a toggle switch into a momentary response

texts:
I'm working on a project and I need to use a toggle switch to control a device that expects a momentary signal.

What I want is send a momentary pulse when turning it on and off. Ie: swith off to on: positive pulse, switch on to off: positive pulse again.

I've got do this with a small arduino-like board but I'm looking for a pure hardware alternative.

My knowledge of electronics are quite small. I thought about using an inverter (NOT gate) to detect both latches (low and high) in the toggle switch plus a few more components, but I'm not sure how to design it.

Any ideas?

Thank you!


texts: How do you calculate a DC offset from RMS and peak to peak voltage

texts:
I am working on a lab for school and did forgot to measure min and max of waveform to obtain the offset, but I do have the RMS and peak to peak values.

I tried using the following to calculate DC offset, but this does not agree at all with simulated results or waveform displayed in the screenshot using the divisions.

DC offset=Vpp/(2*sqrt(2))-Vrms

Is my logic off? Can this not be computed properly from a scope measured Vrms value?

Props to anyone that can deduce the circuit haha!


texts:
A real inductor, because of parasitic contributions, behaves differently with respect to an ideal inductor. In the following slide of a course I am studying the equivalent model of a real inductor is provided:

Assuming negligibile some elements (as explained in the slide), we get the following simplified series configuration:

Now I have problems: in the following slide, an alternative parallel configuration is given:

Question: how does my professor find the values of this alternative parallel configuration? My idea is the following: I impose that the series impedance is equal to the parallel impedance, but as you can see from my computations, I still do not arrive to those formulas.

Thank you


texts: Will I run into a problem if I use an 18AWG extension cable for 240V device?

texts:
I currently have a length of SOOW 18AWG with ground connected to my breaker box.
One lead is connected to phase 1 on a 15A breaker.  One lead is connected to phase 2 on a 15A breaker.  ...3 is ground/common.  The breakers are tied together so they both trip if one trips.
With this, I now have a standard 110V style extension cord that is delivering 240V.
This cord's purpose is to fire up two Martin MAC 500 stage lights in a temporary setting.  The lights are rated at 3.4A each at 240V.  18AWG SOOW is rated at 600V & 10A.
The distance from the breaker box for these lights will be approximately 100'.
Is 18AWG sufficient, or do I need to increase to 14AWG?


texts:
I've got a small LED garden lamp, battery operated, that turns on with a switch.

I am currently trying to use a photoresistor that I have to make it turn on when it gets dark (so I don't have to switch it on manually)

My first thought was to use a microcontroller like an attiny to do it but then I realized I might be able to achieve this with just a transistor (which I already have too)

The problem is that the transistor makes the light fade in and out as I'm using the photoresistor in a current divider configuration attached to the base of the transistor. When it gets dark, the photoresistor gets high impedance and current flows to the base of the NPN.

I would like to know if there's a way of making the transistor turn off and on "fully" without going through the active region.

I tried using a diode at the base of the NPN, hoping it would block everything until the voltage was high enough to go through and fully turn on the transistor but with no success... it still fades in and out.

Any ideas of something I can do with just these simple components?

Thanks in advance.

EDIT:

simulate this circuit – Schematic created using CircuitLab

Added the schematic of what I did initially.

I also tried a darlington pair but the results were similar.


texts:
I have a PCA9685 IC connected to i2c of cubieboard like board. Also OE pin is connected to one GPIO pin. I'm using ic2tools to communicate with PCA9685, I can read/write to registers without any problems, but changes I do to registers does not take effect, LEDs don't change them state.

There are 4 RGB leds connected through a resistor to PCA9685 (as Fig 15 of PCA9685 datasheet), this is, 12 channels are being used. Doesn't matter which value I write to PWM registers, LEDs state are always the same, oddly, colors are not equal to each LED. 1 LED has red, 1 LED has blue, 1 magenta and 1 white. However, colors are not random, always I turn off/on PCA9685 the same colors are assumed by the same LEDs.

I can switch all LEDs on/off by changing OE pin state.

Here is the code I'm using to test.

#!/bin/bash

set -e

PCA9685_BUS=1
PCA9685_ADDR=0x41
PCA9685_OE="pi15"

# config GPIO as output and set initial state
${PWD}/gpio_config.sh "$PCA9685_OE" "out" "1"

# set output logic as inverted
i2cset -y $PCA9685_BUS $PCA9685_ADDR 0x01 0x10

# restart
i2cset -y $PCA9685_BUS $PCA9685_ADDR 0x00 0x91
sleep 1

# change to normal mode
i2cset -y $PCA9685_BUS $PCA9685_ADDR 0x00 0x01
sleep 1

for (( i = 0x06; i <= 0x45; i++ )); do
    i2cset -y $PCA9685_BUS $PCA9685_ADDR $i 0x0F
done

Running i2cdump I can see registers were changed.

[root@board test]# i2cdump 1 0x41
No size specified (using byte-data access)
WARNING! This program can confuse your I2C bus, cause data loss and worse!
I will probe file /dev/i2c-1, address 0x41, mode byte
Continue? [Y/n]
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f    0123456789abcdef
00: 01 10 e2 e4 e8 e0 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f    ????????????????
10: 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f    ????????????????
20: 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f    ????????????????
30: 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f 0f    ????????????????
40: 0f 0f 0f 0f 0f 0f XX XX XX XX XX XX XX XX XX XX    ??????XXXXXXXXXX
50: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX    XXXXXXXXXXXXXXXX
60: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX    XXXXXXXXXXXXXXXX
70: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX    XXXXXXXXXXXXXXXX
80: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX    XXXXXXXXXXXXXXXX
90: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX    XXXXXXXXXXXXXXXX
a0: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX    XXXXXXXXXXXXXXXX
b0: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX    XXXXXXXXXXXXXXXX
c0: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX    XXXXXXXXXXXXXXXX
d0: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX    XXXXXXXXXXXXXXXX
e0: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX    XXXXXXXXXXXXXXXX
f0: XX XX XX XX XX XX XX XX XX XX 00 00 00 00 1e 00    XXXXXXXXXX....?.

I've tried others values than 0x0F, same issue.

Any idea over what can be happening?


texts: What information does one need to size inrush current limiting resistors?

texts:
I am trying to find a replacement for resistor Vishay CP00021R000JE14, a 1 Ω, 2 W ceramic wirewound (R_MED in the diagram). On startup, this resistor limits the current dumping into 200 µF of capacitance.

The instantaneous power is far beyond the 2 W part rating, but because this is not sustained, the part isn't destroyed.

The datasheets for many of these parts give things like "short time overload" power limitations, but say nothing of instantaneous power or current maximum values.

That said, what information do I yet need to assess whether another resistor is suitable for this purpose?


texts: FPGA utilization augmentation in a System Generator core when updating from ISE 13.2 to ISE 14.7

texts:
I have a huge system generator core originally developed with 13.2 version.
Actually we are updating some projects to the latest version of ISE, the 14.7.

In the final step we consolidate the project generated by SysGen, avoiding hierarchies and flattening and optimizing the design. This can be achieved with the -read_cores optimize xst option in command line mode, and the result is a unique optimized NGC file.

In 13.2 version this synthesis strategy give a result of 19% of occupancy, but in 14.7 the result is a 36%!!! of occupancy. I'm trying to change synthesis options to improve the result, without positive results...

Any idea about what have been changed between versions?

Best regards


texts:
I'm trying to build this multiplexed LED matrix with 216 LEDs, NPN transistors, a PIC microcontroller and several shift registers (74hc595) , however I don't know how to calculate the value of the resistors that are connected to the anodes, and also would like to know if I should add any additional resistors somewhere else.
I plan to turn on a maximum of 16 LEDs at once, like 3 columns of 6 LEDs.


texts: If AA batteries don't supply sufficient power, will adding more of them in parallel help?

texts:
My device requires ~4.5 V.
I'm using 4 battery packs connected in parallel
Each battery pack contains 3 metal-encased non-rechargeable alkaline AA batteries.
I used voltmeter and verified that each battery pack individually provides ~4.5 V.
I have also used voltmeter to verify that all battery packs are correctly connected in parallel.
All the batteries are of the same nominal voltage, the same brand and product name (Varta Longlife).
(It shouldn't matter here, but for completeness: The batteries are used as a backup to the main power supply, which supplies about 0.5V more than the batteries. Both the power supply and the batteries are connected via a Shottky diode [1N5822 40V/3A DO201] to prevent "charging" each other.)

The device runs fine on the battery packs, but sometimes, obviously when a load spike comes, the device suddenly switches off.
I measured that the device, when connected to the power supply, draws 1.6 A during spikes. Normally it draws about 300-500 mA.
Question 1: Shall I keep adding more battery packs in parallel? Will it help or does it only increase the lifetime, but not max current/power?
Question 2: If I use a battery with higher mAh rating, will it help, or does it only increase the lifetime?
As a side note: I am also going to try top-notch lithium AA battery instead of alkaline to see if it handles the spikes.
Thank you.
EDIT: The backup is not supposed to be used much, just very rarely, during a power outage (which we haven't had in years).
UPDATE: I've tried the best lithium AA batteries on the market, replaced the alkaline batteries, and found out that they didn't handle the spikes, either. Moreover, they supply ~5.5V instead of the ~4.7V that the alkaline batteries do. So that's not nice, either, because that is higher voltage than that of the power supply.
I'm thinking about using the capacitors or the suggested buck converter with 12 batteries in parallel. The thing is, I have no experience with capacitors and I don't even know what the circuit should look like.
As for buck converter I don't know anything about them, either, and am a bit worried that they would introduce more complexity to the system, possibly increasing the chance of failure.
So adding more battery packs in parallel, and changing to D-type batteries as some suggested, still seems to me to be the simplest (least complex) solution, which I feel capable of designing and building myself.
UPDATE 2: 4x3 D-type batteries (instead of the AA-type batteries I original used) did help and the device no longer shuts down during high-drain events.


texts: Is my radio pulling more current than it should?

texts:
I have an FT-747GX radio that I am using as a RF generator for a plasma cleaning machine.

In the operating manual on page 3 it states:

I have a power supply connected to this radio which outputs 12V at 30 amps. Between the power supply and the radio I have a 20 amp fuse, but this fuse keeps dying on me.

What I dont understand is: is the radio pulling more amps than what it says it outputs? If it so, should I increase the fuse to 30 amps?


texts: The following circuit is said to be an AND circuit. Could you explain how?

texts:
simulate this circuit – Schematic created using CircuitLab

What is the need for R3?
How does the following circuit ANDs the 2 signals X1 and X2? The output corresponding to case 2 and 3 in truth table fall under indeterminate LOGIC level of IC

Additional info:

Output is connected to the input pin of an IC(power sequencer) and it is an active high pin. Default state is floating
Truth table is derived based on simple circuit analysis


texts: Why are UK pins sealed in HK travel adapters?

texts:
This Momax USB travel adapter was purchased in HK. I emailed Momax tech support to ask about the UK pins being sealed (as shown in the photo) and received a response saying that it’s in accordance with HK regulations, and if I remove the seal, I’ll void the warranty. I’m wondering what is the logic behind this.

Why is this regulation in place?
Why not just manufacture the adapter without the UK pins, then?
Is this actually unsafe for use in the UK?
And lastly— is it advisable to just try to remove the seal? I’ll probably have to unscrew the cover to do so.


texts: Why are EI-cores (shell-type) most common for power transformers?

texts:
I notice that most small power transformers (single-phase, 100-240V, 50hz/60hz, laminated core) are shell-type, with an EI-shaped core.  But as I understand they have relatively low efficiency due to much of their surface area being exposed; not wound with wire.  There is already much information on the web about the advantages and disadvantages that toroidal cores have over EI; being entirely covered by windings improves efficiency, but they are intolerant to DC offset, harder to wind because they must be wound when the core is fully constructed (as opposed to wrapped around a bobbin before the core is built around it), and mounting is less straight-forward.

But I want to know why EI transformers are often chosen over core-type core constructions such as U-core, C-core, or L-core?  These are presumably more efficient, due to having more surface area covered in winding (even if less than toroidal).  They seem to have the same construction advantages of EI transformers, such as being wound on bobbins before the core is assembled, mounting methods which are almost as convenient as EI, and laminations for some designs can be cut from a rectangular sheet without significant waste (like EI-cores and toroidal cores).  Also, the air gaps reduce the effects of saturation.

So what are the disadvantages of these core-type transformers that leads to them being less common than EI-cores?


texts:
I've got a solar panel (12V, 330mA, 2W) which I will use to charge a (12V 5Ah) lead acid battery. I'll put a voltage regulator and shottky diode in between the two.

However, could overcharging become an issue?  Say I don't discharge the battery in any way,  what happens when the battery is full and the solar panel just keeps delivering power?


texts: I'm trying to repair Black and Decker Thermal Leak Detector. I was testing the 9v input from the battery when I notices the chip was cracked. I'm thinking it is a transistor, but I haven't been able to cross reference it. Any help would be grateful.


texts: Reducing power consumption of an arduino module (mosfet?)

texts:
I'm trying to reduce power consumption on an MP3 module controlled by an Arduino. The MP3 module specs are:

3.2-5V (typical 4.2V)
<1A peak current, 20mA on standby (which is too much on batteries)

In my prototype, I use a simple diode to lower the 5V regulated from Arduino by around 1V. I also have 1k resistors to adapt logic level on serial communication.

Basically my idea is to use a mosfet as a switch, so that the arduino can enable/disable power supply to the MP3 module, either on high:

Or on low side:

My questions are:

Are the circuits above correct?
What are some good options of widely available mosfets? IRL540?
How do I pick the gate and pulldown resistor values?
In low-side configuration, do I still need the TX/RX resistors?
Should I add a ceramic capacitor to eliminate any noise from speakers/sudden change in current, and what sort of value?


texts: Added parameter variant does not take effect

texts:
I want to add a parameter variant to my schematic.  The parameter being varied, called "Load", does not exist in the DbLib from which I'm pulling my schematic symbols.  Instead I've added the load parameter to certain symbols placed in my SchDoc.

I'm able to add a parameter variant changing the Load parameter from empty to "DNI" in the Variant Manager Dialog, but when I switch to the newly added variant in my SchDoc, I see no change to the "Load" parameter of the target symbol.

Any idea what I might be doing wrong from the above description?

thanks


texts: Underwater train project's battery powered DC/BLDC/Stepping motor gear/non gear requirements and water proof sealing problem

texts:
I am a software developer by trade, having put together a few beginner Arduino projects and such.
My next project entails an underwater roller-coaster (without loops, just going over the surface, so maybe more like a train). I don't really know where to start when it comes to selecting the right motor.
I have learned that brushless motors can be used in water, so that is a good start. Now it comes to choosing size, power consumption, RPM and torque. Basically I want the motor to be as small as possible, as I want the carriage on the track to be around 6x6 cm in total.
I will most likely 3d print the track with teeth and somehow attach the carriage to the track and pull it forwards with a gear.
The train will not have to go fast, say.. 1cm-2cm per second?
If I take 2cm per second with a gear of 2cm in diameter we would need 2/(2/2 (=radius) * 2 * pi) = .31 rotations per second, is 20 rotations per minute? Is this calculation correct?
If this is correct, what kind of power should I be looking at? And would it be possible to battery power that?
P.S I also just found stepper motors might be able to withstand water, any experience?


texts:
By virtue of the open-loop gain being infinity for an ideal op-amp, the two input terminals are said to be virtually shorted.

Yet, the virtual short concept is only applied to op-amps in negative feedback configuration, and not in case of positive feedback.

Is there any plausible reason for this?

Some insight in this regard would be really helpful.


texts: Using the same ESP8266's GPIO for 3.3v and 5v

texts:
I am designing a pcb which should receive various types of sensors. The microcontroller is an ESP32 and the external input are RJ11 linked to I2C GPIOs of the uC. I have already planned a LevelShifter (considering that the voltage of ESP32's GPIOs are limited to around 3.3v) so that the ESP32 can receive sensors with 5v outputs.
The problem is that I want to use the same GPIOS connected to the output of the LevelShifter to take into account 3.3v sensors that could be could be connected to the RJ11 port. For this I thought of using jumpers to either connect the output of the RJ11 port (sensor) directly to the I2C GPIOs of the ESP32 if the sensor is a 3.3v type. On the other side the jumpers are to be placed so that the I2C GPIOs of the ESP32 are connected to the output of the Level Shifter.
Here is what I tried below.
I suppose if the sensor is 3.3v type I cannot connect it to the LevelShifter.
Is this right ? Is there any risk that the floating pins will disturb the communication between uC and sensor through the chosen "way"?
Do you have better solution to suggest me for this case?
Sorry for my English.


texts:
I need a transistor lesson that I could not find on the internet:

I have a standard GND-PNP-Load-(-20Vcc) arrange:

(The two resistors attached to the base are to form a divider - ignore the values).

Im struggling because if I leave the base floating (for testing purposes), the transistor conducts.

I tried making every thinkable voltage divider between GND and -20V to feed the base. The voltage on the base never goes above -0.65V, where (I suppose) it would cutoff.

Was it a NPN transistor, leaving a small voltage (<0.6) on the base would cut it off. Not here.

It's a BC556.
The transistor does work well on the linear region
The datasheet says ICBO is -15nA. Very low value. Does this change anything ?
Those schematics come from a humble simulator that doesn't allow me to tag the components.

I'm clearly missing a polarity rule or something. Who can point it out ?

Edit:

The schematic above was a simplification. After no success following your suggestions, I started to think that a simplification was not a good idea (probably the "load" messes with the system).

The device on the collector is actually the control pin of the LM7905 IC, which sinks a maximum of 3mA.

I'm away from a PC, so I won't represent it. But you can replace the current source below with it.

Just hope this information doesn't add to the confusion...

My final objective is to vary this current, as best as possible, from 0 to 3mA using the transistor.*

Around -10V is the voltage on this pin when the current is 2.7mA. This voltage probably varies with the current

*Must be a transistor. A resistive divider doesn't span the minimum and maximum current. Also, a transistor worked very well on the positive side.


texts:
the hall sensor of the bldc motor will give 6 states (represents the 0 to 360 electrical cycle). But what is the exact angle of the each state (that is for 101= ? degree, 100= ? degree....)

I googled it before posting this comment. But i doesnt get the exact and correct.
Below images show different degrees, which is the correct one.

Example for

011 = 0   degree  [image 1]...............    011 = 288 degree  [image 2]


texts: Flashing firmware onto NXP QN9020 via SEGGER J-Link

texts:
Here I am attempting to flash the firmware using SEGGER J-Flash Lite.

Below is the ouput when attempting to connect via the SEGGER J-Link Commander.

JLinkExe
SEGGER J-Link Commander V6.46j (Compiled Jul 12 2019 17:31:38)
DLL version V6.46j, compiled Jul 12 2019 17:31:27

Connecting to J-Link via USB...O.K.
Firmware: J-Link EDU Mini V1 compiled Jul 10 2019 16:32:48
Hardware version: V1.00
S/N: 801010920
License(s): FlashBP, GDB
VTref=0.000V

Type "connect" to establish a target connection, '?' for help
J-Link>connect
Please specify device / core. <Default>: QN9020
Type '?' for selection dialog
Device>
Please specify target interface:
  J) JTAG (Default)
  S) SWD
  T) cJTAG
TIF>
Device position in JTAG chain (IRPre,DRPre) <Default>: -1,-1 => Auto-detect
JTAGConf>
Specify target interface speed [kHz]. <Default>: 4000 kHz
Speed>
Device "QN9020" selected.

Connecting to target via JTAG
Cannot connect to target.
J-Link>connect
Device "QN9020" selected.

Connecting to target via JTAG
Could not measure total IR len. TDO is constant high.
Could not measure total IR len. TDO is constant high.
Could not measure total IR len. TDO is constant high.
Could not measure total IR len. TDO is constant high.
Cannot connect to target.

Connecting to target via JTAG
TotalIRLen = ?, IRPrint = 0x..000000000000000000000000
TotalIRLen = ?, IRPrint = 0x..000000000000000000000000
TotalIRLen = ?, IRPrint = 0x..000000000000000000000000
TotalIRLen = ?, IRPrint = 0x..000000000000000000000000
Cannot connect to target.

See also:

Freescale Kinetis KE - writing to flash


texts: Finding the component value of PNP transistor

texts:
This is my circuit

simulate this circuit – Schematic created using CircuitLab

This is the way I tackled this problem:

$$ U_{e2} = 12 - I_e \cdot R_e  = 12 - (2.02 \cdot 2) = 7.96 \text{  V} $$

$$ I_e = \left( 1 + \beta \right)  \left( \frac{ I_C }{ \beta } \right) =  \left( 1 + 100 \right)  \left( \frac{ 2 \text{ mA} }{ 100 } \right) = 2.02 \text{ mA} $$

This is where I'm struggling:
$$ I_{be} = I_e - I_c = (2.02-2) \text{ mA} \rightarrow 0.02 \text{ mA} $$

I don't know how to find \$U_{be}\$ so I can find the resistance of \$R_{be}\$

I have been trying to find a tutorial and some help from  several articles.


texts:
I’m currently learning about transformers. I have a quick question regarding the specification of a 2x24/2A transformer.

Here is a picture of the transformer:

Does 2x24V mean that this transformer has dual secondary windings that creates 2x 12V 1A output or does it have two 2x 24V 2A or maybe 2x24V 1A? I’m quite confused about how the secondary output works on this transformer.

Crude information about the transformer:

Transformator 2x15VAC 72VA
Primary: 220VAC
Secondary: 2x15VAC 2.5A = 75VA


texts: Eagle CAD: method of re-linking schematic and board?

texts:
I've accidentally lost the sync between my schematic and board, with Eagle CAD giving me the following error:

  Board and schematic are not consistent!
  No forward-/backannotation will be performed!

Is there a method of re-linking the two?  I had very little work invested in the board layout so a method of linking the schematic to a new board file would also be helpful.


texts: Limiting Current interference in Photomultiplier Amplifier Circuit

texts:
I've been working on a circuit for a while now. It's a circuit consisting of 4 Silicon Photomultipliers, MicroFJ-60035-TSV, in parallel all going into an op amp circuit. I posted questions about it before regarding separate issues about it, and I learned a bit more about about it by studying how the circuit functions.  You can see it in the image below along with one of my simulations. Apologies for the messy part layout.

In the circuit, I've connected the cathode to ground, and I'm reading the current from the anode. I wanted to get the correct pulse shape as shown in documentation, so I'm following the recommendation of reading from the anode. I am planning to read from the cathode once the circuit is finalized and not in simulation. I'm using voltage sources attached to the photomultiplier parts to control when they 'fire'. The 1 microOhm resistors are just there so that I can read the current coming from the sensors. I figured a low resistance wouldn't affect the circuit much, but ideally, there would be no resistance there.

I'm kind of facing two issues right now. The first issue is with the current coming from the photomultipliers. You can see in the simulation results on the left that when one of the photomultipliers fire, some current also flows back into the other photomultipliers. What can I do about it to remove it or control it so that this doesn't happen?

My next issue is with the feedback circuit. Through reading, I found that the op amp circuit converts the current signal into a voltage signal, and the feedback circuit acts as a low pass filter to hopefully filter out high frequency noise. You can see another test below where three photomultipliers fired at once.

I've increased the capacitance to try and reduce the noise from the 4 parallel photomultipliers, but I'm having issues with the rise time and clipping. The time where three were firing had a faster rise time compared to the one which fired only once. However, the voltage seems to have clipped, staying the same after a certain point. Is there anything that can be done about it? There always seems to be a trade off between the cutoff frequency and the rise time.

UPDATE: I changed my schematic so that I'm now reading from the cathode instead of the anode. The current from the sensors looks a little messier, but the output is now positive as I was planning. The circuit does not require biasing. It's already done in the model of the part. My team is now looking for better signal-to-noise ratio for the circuit, so what can I do in my circuit in order to improve the SNR?


texts: DC motor won't run - how to increase strength of coils?

texts:
I'm trying to make a DC motor, but it won't run and I suspect the issue is the windings. When 12v is passed through, they're magnetised but move only a few millimetres, and only if they're in certain positions.  Everything's connected right, the current is definitely passing through, and the stationary magnets are big and beefy. I used 0.4mm copper wire, 350 coils around an iron core, 3 total connected in series to a split commutator. There's no load, so nothing that really could be stopping it.

So far I've tried different strength stationary magnets, different positioning of the stationary magnets, different voltages, different brushes, readjusting the commutator. At this point I'm almost certain that the armature is the problem. This could be very very wrong, but could it be that doing 350 coils means a resistance so high the electromagnet won't work? I really don't want to rewind everything again if there's not something else that might be the issue?

edit/update: First some extra information, yup, they're magnetised in the right direction. The brushes are energising the coil at the top - I thought that was the right one to get the most torque??  I've tried spinning it to get it started but it still peters out millimetres afterwards.

And then the update: The current was passing through the wire into the core. The threads of the screw must have cut into the wire. So I decided to rewind the whole thing anyway. Hopefully attempt 2 works better?

update 2: rewound so current isn't passing through core. It's working slightly better now, maybe a cm of movement? I'm seriously stymied though because I was counting on that being the issue.

update 3: the magnets are as close as possible without hitting the bolts each revolution. They're about 5 cm higher than the hole, so possibly too high? The coils definitely are producing some magnetism, a compass is changing when I hold it next to the energised one, I just don't think it's enough. I'm now playing around with the commutator and brushes to see if I can adjust something.

update 4: changing the order of the commutator seems to have helped some. Though they're not in the picture I do have two field magnets but now I'm pretty sure they're too small (pole is about 1cm x 1.5cm) so I'll try to get bigger ones tomorrow. There's 3 electromagnets spaced 120 degrees, sorry for the poor picture. I'll add a new one with new magnets. The commutator is intermittently sparking if I manually turn the shaft, I'll try to fix up the ends tomorrow too.


texts:
I am trying to identify this electrical component at my work, it acts a leak detection sensor on a pump that when exposed to water will shut down the system.
Thank You !


texts: How to make momentary connection on power on?

texts:
I have a mini-computer Beelink AP34 with momentary power button and I need to simulate short pressing of this button once it is connected to the power (12V DC).

The reason is that it doesn't start automatically after power loss and does not support Wake-on-LAN or anything - I always have to physically press that button after connecting power adapter.


texts:
I am using electronic switches to create non-TTL square wave clocking. The oscilloscope graph demonstrates two measurements:

Yellow signal: 0-8V
Blue signal: 0-5V

As you can see, yellow signal is contaminated with small voltage jerks every time the blue signal goes high or low.
I use microcontroller to drive DG642 switches, which in turn output high/low voltage;
the schematic below represents the connections.

The power of +5V and +8V comes from independent power supplies. Connecting 10uF bypass caps to pin(1) of each switch does not help. Why does such signal contamination happen and how to fight it?


texts: I am using a 5V relay for switching ON/OFF a starter motor. The motor draws 12V/16A to run. The relay has the specification as shown below. My question is will this relay work or it will burn due to large current drawn by the motor ?


texts: Location of Amplifier for Signal Integrity

texts: Let's say I have a photodiode that outputs a current with respect to incident light on the die. If this photodiode will be located 12 inches or so away from the control board, would it be better for signal integrity to filter and amplify this signal (transimpedance amp) close to the sensor (as in a small PCB with wire harness) or does it not matter? I do know that current is more immune to noise (i.e. 4-20mA systems). To me it might make sense to locate the amp closer, since the long lead could degrade the original signal?


texts: Positive to negative rail if Opamp has Single Supply

texts: Can the output go to -5V to 5V if an opamp has a rail supply voltage VDD = 5V and VSS = 0V


texts:
I designed a circuit to do the switching from a 12v car battery to a 8.4v Li-Po battery with a relay, both batteries go through a LM7805 regulator to supply a constant 5v to a raspberry, however when I connect the output of the circuit to the raspberry and do the switching from main battery to backup battery the raspberry resets because it drops the voltage while switching the relay.
So my question is:
How I managed to do that switching without the raspberry rebooting?
I appreciate the help, I have been trying to solve this problem for two weeks now but I have not been able to yet.
Thank you very much.


texts:
I see some unexpected behaviour from (what I thought) is a relative straight forward RLC oscillator circuit:

The idea is that a coil is charged over a certain period of time (during this pulse the current is rising), and the RLC circuit (R12 L1 and C5) is then isolated quickly by two MOSFETs with large enough break-down voltages to withstand back-emf. The generated large back-emf then drives the oscillator and current is measured over a (22 mOhm) sense resistor. The differential amplifiers are just there to condition the signal to input into a 12 bit, 3.3V ADC. A LTspice simulation agrees with my expectation to see a damped oscillation. However, what I observe experimentally with the circuit with three different pulse lengths (25us black, 50us red and 100us blue) is the following:

While the pulse length and the current peak in the inital oscillation seem to be ok and the oscillation frequency is correct within error of the inductor and capacitor, between about 15-35us current is sunk to the same level in all three cases. This is the zoom-in:

Can someone please explain what could be happening here? Any advice would be much appreciated.


texts:
Let me tell you right off the bat that I am new to electronics, more specifically the creating of electronics. I recently discovered a project that I would like to make, a pocket power supply(link at end of question). I gathered up all the parts for it as it didn't work( I.e. I tried prototyping on breadboard and found no sign that it was working), and after multiple retries, I noticed the Vin and Vout on the project, or rather focused on them more as the possible problem to the circuit. I am not sure if both sets are supposed to be grounded, or rather one is the positive voltage of the battery and another is the negative terminal. I am honestly confused by this and would like another who is well experienced to cover this. Thank you and here is the link to the project.

Link:                          http://m.instructables.com/id/Pocket-Size-Power-Supply/?ALLSTEPS


texts: Soldering iron tip size for through hole components

texts:
I want to solder through hole components on a 2.54mm pitch perforated board. I have a 30W soldering iron with a 2mm wide chisel tip.
Is my tip too big for the job, should i buy a new one?
Best regards,
Explyy


texts: Recommended capacitor rating for this mains zero-crossing detector

texts:
I found this zero-crossing detecting circuit here

I want to recreate it, using the parts that I have on hand (or can get cheapest), but I'm not sure how to choose the correct 0.1uF capacitors.

Firstly, why are there two capacitor/resistor pairs instead of one? Won't the current be the same with 2k and 0.05uF? The additional capacitor only seems to isolate the optocoupler further, but shouldn't that be unnecessary?

Secondly, I am assuming these parts are class X, since they are connected directly between line and neutral. How do I choose the correct ac voltage rating, if I am using 230V mains? How much margin should I include? I want to use a 310VAC capacitor I have found.


texts: KiCad Simulation VSOURCE Triangle waveform

texts:
I want to simulate a second order active low-pass filter in KiCad, using the internal spice-based simulation tool. The input signal must be a triangle waveform of 30kHz and 0,5 V peak to peak, and the problem is I can't find any tutorial, on how to create a triangle waveform using the VSOURCE (Can't find the right settings). I know that I can build a triangle wave generator circuit using an op-amp, but I don't want to do that yet. Any ideas?

Thanks


texts: How short can an RF transmission line be?

texts:
Design for connecting transmitters to antennas often mentions the transmission line, and the standing wave ratio (SWR) for matching.  But what if the transmitter is on the antenna?

Background: I've an old 151 MHz narrow band FM 10mW transmit module TX1 from Radiometrix that I'd like to deploy monitoring a solar powered pump on a stock dam.

I plan to attach the RF out and RF ground pins on the module directly to either the base of a quarter wave with groundplane, or at the feed point of a yagi, or across a "slim jim" or J-pole antenna.

An Arduino Pro Mini will be adjacent to the transmit module, and a multi core cable will head down to the other equipment.

So the transmission line will be only a few millimetres long, and measurement of SWR seems impractical.

(This is a licensed use per schedule 1 item 15, 150.7875 to 152.49375, max EIRP 100mW.  Source code, which details connections, is here)


texts: Digital pin connected to SS relay: voltage is 2V across control inputs when digital pin is supplying 5V

texts: I have a digital pin, from an ED-008, with 0/5V outputs. However, when I connect the pin to the control inputs of a solid state relay, I only see 0/2V at the relay inputs; the relay requires 3.5V to be activated. Why am I only seeing a logic high signal of 2V when I connect to the relay when I see 5V otherwise?


texts:
I've got an inground swimming pool, and was inspired by an ill-formed question that was recently posted. I would like to non-invasively measure the volume of water my pump is circulating through the pool over a given period of time. By non-invasively, I mean I would rather not have to hack into the plumbing and embed a sensor into the stream, but rather I'd like to measure it inferentially somehow (e.g. perhaps the water current actually has an electrical current that can be measured through the PVC pipe with a hall effect sensor an an instrumentation-amp — not to bias the answers or anything).

For the sake of bounding the problem with some requirements, I'd be happy with an accuracy of ±1 gallon/min and a component cost of less than $100. To be clear though, these are artificial requirements, since I just want to build something like this for myself.


texts: accuracy shunt resistor beter than 0.1%?

texts:
I want to make a circuit that can measure a current more accurate then 0.1%. For instance if I measure 7A, I want to be able to read 7.000 A. If I use a 0.1% shunt resistor I do not know if it is 7.007A or 6.993A it can be +/- 7mA. I did take a look at some big stores and the best shunts they sell are 0.1% accurate with a price about 5 or 6Eu a piece. How can I get a better accuracy? Can I even go further like 6 digits? What is possible?

thank you for the help!


texts: PICC18: Certain __CONFIG() -macros cause syntax errors

texts:
__CONFIG(0, 0xFFFF);
  __CONFIG(1, FOSC_HS  );
  __CONFIG(2, BOREN_OFF);
  __CONFIG(3, WDTEN_OFF);
  __CONFIG(4, 0xFFFF);
  __CONFIG(5, 0xFFFF);
> __CONFIG(6, CP0_OFF && CP1_OFF);
> __CONFIG(7, CPB_OFF && CPD_OFF);
> __CONFIG(8, WRT0_OFF && WRT1_OFF);
> __CONFIG(9, WRTC_OFF && WRTB_OFF && WRTD_OFF);
> __CONFIG(10, EBTR0_OFF && EBTR1_OFF);
  __CONFIG(11, EBTRB_OFF);

The rows that I have marked cause a syntax error while building, others are fine.

C:\Users\Oppilas\AppData\Local\Temp\s6bc.:14: error: syntax error

I am using HI-TECH PICC-18 PRO v9.66, lite mode.


texts: Replacing two corresponding switches as one with logic gates, to supply power, around a DPDT relay

texts:
This is one section of a project I'm working on. A user can choose between DPDT functionality (so having "DeviceI" be a motor that goes forward and reverse) or the alternative option to add another sensor (SensorII).

The DPDT requires two +VccRelays. So the relays on the left can be effectively thought of as Vcc. This is my current design. It works. (I implemented and tested it.) It's for powering interchangeable sensors.

Although, I want the user have less switches to screw up. So I figure there's a way to replace the two switches on the right (SW2 & SW4).

So A⊕B = C = D'?

Without the truth table, intuitively, I think this will work:

I tried to make it easier to understand where the switch labels have corresponding letters (where A matches everywhere with A, and B with B). The user has two options: either change all the switches to position "A" or to position "B" (on each of the four switches). If they choose position "A", they get one DPDT powered device, nothing else. If they choose position "B", they get to power two regular devices.

Like that? Did I go wrong somewhere? (I changed "Device" to "Motor" so it's more intuitive to understand; it's just like switching the polarity of a DC motor.)

If it's kosher, I would buy the CD4070B XOR and the CD4081B AND. Before this section of the project, the user has the option to power the device by either 5 or 12V. My second question is if these (3 V ~ 18 V logic high) gates can handle ~13.5V. Vcc could either be 5 or 12V depending on what sensor the user chooses.


texts: Poor man's IR obstacle sensor make sense(improve) from signal under daylight

texts:
I'm talking about this kind of sensor:

Question and then long description: can I do something to improve their blindness in front of window? At least for detection of object in front of the robot, like 10cm for example? not to detect distance but only prevent crash. Is there a sense to equip robot with them at all?

When I've ordered these IR receivers and leds I didn't think they will be so slow and more than that useless during day even in my room. My bad, must have googled more. They are too slow for signal modulation.
I was going to wrap them around my robot, but now I don't know should I even use them or not. Just for obstacle avoidance at least. During night they are great for this..
Here's my configuration with foil shielding.

simulate this circuit – Schematic created using CircuitLab

Green signal is from IR leds ON part and blue when IR leds OFF
Sensor under the table directed horizontal. I wave my hand in front of sensor.

And this directed horizontal to window on level of floor. And today is very cloudy. Wave much closer. Around 4-5cm.

And this same as previous only it directed opposite from the window in front of window.

Also when pointing to the side of window (not on it or the opposite) then signal is a little better. And all this when almost there is no sun..

Here's maximum frequency of modulation. 12mS or 83Hz.. IR led inside that foil tube.


texts: Where to put low-pass filter on the analog signal path?

texts:
I want to test my basic pH sensor circuit to find if there is a need for a low-pass filter. How I can test it?

The signal pathway is:

Sensor probe---> Buffer op-amp circuit ---> ADC ---> MCU

So is this correct way:
Sensor probe ---> LP filter ---> Buffer op-amp circuit ---> ADC ---> MCU

or:

Sensor probe --->  Buffer op-amp circuit ---> LP filter ---> ADC ---> MCU

And a note I should use to active filter according to my old question. So I will use an active LP filter.


texts: Do capacitors automatically release their energy over time?

texts:
Will a capacitor automatically release its energy over time?  Or will it stay in there until manually discharged?

So let's say I've had an old computer sitting around for a year and decide to take every piece apart... am I in danger of being shocked by the capacitors?


texts: How to Choose value of Output Frequency Carrier for PWM

texts:
I want to choose a PWM frequency using the formula from this article: How to use fast PWM (Pulse Width Modulation) Mode of AVR microcontroller Timer.
The formula is \$f_{\small PWM}  = {\Large{f_{crystal}} \over {\large prescaler \times 510}}\$.
What does 510 mean?


texts: Datasheet term for transistor power consumption when OFF?

texts:
I'm trying to find a transistor that can power up to 1A (1000mA) on an animated LED strip lighting circuit.  From this thread I found the BC517 darlington:

Choosing the right transistor for a switching circuit

Since I'm trying to switch off as much passive power consumption in the circuit as possible when sleeping, I need to know how much power the transistor will draw when it is off. Is there a name for this characteristic on the datasheet?

I heard that a typical low power transistor (like 2N3904) might "sleep" around 50 nanoamps, but since I'm using a higher power transistor I thought it might use more than that when off. Even a consumption of 1mA takes the sleep time from months or years to mere days.

Thanks for any suggestions!

Edit: The voltage of the circuit is 3-5v dc.


texts: Do i need to protect a DC adapter from current spikes (produced by buck converter)?

texts:
I wonder if i need to protect my ac adapter, which has over-voltage, over-current and short-circuit protection. The ac adapter feeds a buck-converter which uses a low-side n-mosfet switch configuration.

I made 2 LTSpice simulations, as seen in the image attached.

In the simulation on the left hand side I added a 10mF capacitor. This way i could smooth the current originating from the power supply. For comparison, i set the capacitance of the capacitor to 0mF.

In the online stores i know, i couldn't find a 10mF non-polarized capacitor for my application. But i don't know if it is need in the first place.

Kind regards


texts: What is a power factor correction choke (PFC choke) and how does it work?

texts:
They Exist

This Link at Newark displays "Power Factor Correction Chokes", which I did not know existed.  I have a linear motor which I suspect really needs power factor correction.  Please tell me what a PFC correction choke is, how it works, and more importantly, how I can tell which one to specify for my application.

Poor Explanations On-Line

The following links (What is a pfc?) and (Why are PFC chokes needed?) from Wurth were early hopefuls in trying to answer this question, but they were very disappointing, as their english was not very good, and their verbage not terribly elucidating.  Why do the job half-way?  You just make your company look bad, and I otherwise respect Wurth.  Anyway...

Our Motor

Our linear motor directly connects to the line, at either 110v or 220v, I believe.  I am really a software developer teaching myself power electronics, so I have some knowledge, but big gaps, I suspect. I entered pursuing this field through my love of a hobbyist circuit, a self-oscillating boost converter called the Joule Thief, so I am familiar with boost converters, which I recently found out here (EEsx why boost PFC topology is the most used?) are often the topology of a PFC correction circuit.

The motor is performing an actuation, and suspending a small weight, but then applies up to 15 kilograms of force, so varies in its power consumption from about 10 Watts to about 500 Watts. The current power factor seems to be about 30%, and gets much worse as greater force is applied.  Some customers use our device constantly, and other customers use our device somewhat infrequently, so perhaps PFC could be an option?

Related to the Common Mode Choke?

Finally, In telling me what a PFC choke is, please tell me if and how it relates to the common-mode choke (which I believe has a different purpose). Thanks again.

Thanks

If buying one of these PFC chokes will improve efficiency for our customers, and deliver power to our motor more efficiently, I want to know.  Thanks.

Edit #1

Though I may have indicated that this device needs help, it is actually in production, and working fairly well at customer locations. In some testing of the device I uncovered an obscure mode where the motor gets full power and then over temps -- but that's only with an administrative console and creatively power-cycling the controller+motor.

I really just want the questions in the Title answered.

In response to a question, "Must you replace the existing supply or improve it?"
Improve, I think... Here is some more information that might help:

The linear motor controller is a Parker IPA15-HC,
a SINGLE-AXIS SERVO DRIVE/CONTROLLER : 6.3A / 1*100-240VAC (2.5KVA)
Links: 1. Brochure 2. Quick Ref Guide 3. HW install'n Guide

We wrote the firmware for the controller (in AcroBasic, a firmware Domain-Specific-Language specific to motor control). But the resource who wrote it may not be available, and I have only been at the company for 6 weeks.

Here is a first guess at the actual connections in the device, though the motor in the picture is rotary, and ours is linear -- this is a Basic connection diagram pulled from Hardware Installation Guide of IPA15-HC Servomotor Controller at URL 8:


texts: Finding output values in a circuit with a zener diode in parallel with a resistor

texts:
Find Vout for all possible values of Vin. In this problem, Vf is the forward voltage drop across the diode and Vr is the reverse voltage drop across the diode. (You must break the problem into 3 ranges)

simulate this circuit – Schematic created using CircuitLab

I know the ranges are when Vin is positively large enough so that there is a voltage drop across R1=Vf, when Vin is negatively large enough so that there is a voltage drop across R1=Vr, and when Vin is between these two ranges. How would you express Vout in terms of Vin and the resistor values?


texts: Control paintball gun with Arduino/Similar Microcontroller

texts:
In terms of theory, can anyone suggest any hardware or products that would allow me to attach a paintball gun to an arduino or similar microcontroller and then give the arduino coordinates/instructions to move the gun up,down,left and right but also trigger the gun to fire paintballs.

Is this possible or has anyone got any ideas?

Thanks


texts:
I'm trying to implement the PMP7760 reference design by TI
(http://www.ti.com/tool/pmp7760)

It uses a flyback transformer namely, the G094215LF which I cannot seem to find anywhere. I found several other threads about this where nobody seems to know what's going on with it and TI hasn't seem to provide an alternative since the design is quite old. I was wondering if anyone would have any idea of what alternative I could use to it in that PMP7760 design

PMP7760: http://www.ti.com/tool/pmp7760

BOM: http://www.ti.com/lit/pdf/snvr020

Schematic: http://www.ti.com/lit/pdf/snvr019


texts: Driving Inductive Load with MOSFET: N-Channel vs. P-Channel

texts:
Problem

I am driving an inductive load from a microcontroller using a MOSFET. I have a current sense resistor in series with the load. I don't have much experience with transistors (should have paid more attention in school!) so I'm trying to implement the circuit using both an NMOS and PMOS transistor.

The problem is that the PMOS circuit is behaving as expected while the NMOS circuit is behaving erratically. I would like to know what is causing the differences.

P-Channel MOSFET

Here is the circuit with the P-Channel MOSFET. V1 is a 32 kHz PWM signal with 50% duty cycle. Since the current sense resistor is connected to ground, I can easily measure the voltage using a non-inverting amplifier.

As the simulation results, the circuit does exactly what you expect; the voltage across the current-sense resistor tracks perfectly linearly with current in the inductor.

N-Channel MOSFET

Here is the circuit with the N-Channel MOSFET. V1 is a 32 kHz PWM signal with 50% duty cycle. The current sense resistor isn't connected to ground so I use a differential amplifier to measure the voltage across it.

LT1677 data sheet

The behavior of this circuit is not what I expect it to be. The current through the inductor is much lower than the PMOS topology and V_SENSE is a mess.

Here is a zoomed in version with the PWM signal V1 included (shown in RED).

Questions

Why is the current through the inductor in the NMOS circuit half that of the PMOS circuit? EDIT: Fixed schematic, swapped PMOS drain & source
Why is the differential amplifier not working as expected? I am guessing that R2 is somehow coupling the op-amp inputs to ground. Since R_SENSE is "floating", this is causing issues.
You can't tell from my graphs but in the NMOS circuit, the current through the inductor is much noisier than the PMOS circuit. EDIT: Fixed schematic, swapped PMOS drain & source


texts: How to use a sensor in order to detect if a mechanical component has moved?

texts:
Specifically, I am trying to detect whether an umbilical boom from fueling a rocket has retracted, and other miscellaneous tasks (vents raised / retracted).

I have done some research and have found ways to determine the displacement of an object - is that actually to be the best way to do it? For example, say the boom needs to retract 10 ft. In that case, if the sensor finds a displacement of 10 ft +- 10%, then MovementStatus = True.

Or is there some form of light sensor / position sensor that just detects the fact that the object is in the position where it's supposed to be, in an efficient way?


texts:
I'm reading about spectrum analyzers from Keysight's AN 150 and I have two questions regarding phase noise.

The AN states:

  No oscillator is perfectly stable. Even though we may not be able to see the actual frequency jitter of a spectrum analyzer LO system, there is still a manifestation of the LO frequency or phase instability that can be observed. This is known as phase noise (sometimes called sideband noise).

Another paragraph that confuses me is this one:

  If we reduce the resolution bandwidth by a factor of 10, the level of the displayed phase noise decreases by 10 dB.

My two questions are:

Why is it that lack of accuracy in LO system leads to the skirt we see on the display when looking at phase noise? I would expect that, if the frequency of the LO shows some error, then the peak in amplitude on the display should by displaced by that error. Why is it that the peak is on the correct place and those weird skirts are produced? I'm not being able to intuitively understand how the display recieves that shape due to LO unstability.
I think that if the IF filter is wide enough, then the phase noise would be hidden under the skirt of the filter itself, thus the phase noise wouldn't be easy to appreciate. If the IF filter is narrow, the phase noise shows up. Thus, I believe that reducing the RBW increases phase noise. So why does the AN state that reducing the RB decreases the level of phase noise?


texts: Arduino LED brightness switching using pushbutton

texts:
I'm trying to switch between 4 different brightness of an LED using an Arduino Uno. I've used analogWrite and not digitalWrite with PWM. The problem i'm facing is that the brightness does not switch at all when the pushbutton is pressed.
Here's my code:

#define led 11 //assign pin 11 to LED
#define BUTTON 7 //assign pin 7 to pushbutton
int val=0; //val used to check current status of pushbutton later in the program
int old_val=0; //old_val to check previous status
int state=0; //state to check button presses

void setup()
{
  pinMode(led,OUTPUT);
  pinMode(BUTTON,INPUT);
}

void loop()
{
  val=digitalRead(BUTTON); //check status of pushbutton
  if((val==HIGH)&&(old_val==LOW)) //button pressed
  {
    state++; //increment state
    delay(10); //debounce consideration
    if(state>4) //want only 4 brightness options
    {
      state=1;
      delay(10);
    }
  }
  old_val=val;
  if(state==1)
  {
    analogWrite(led,0); //0 brightness
  }
  else if(state==2)
  {
    analogWrite(led,75);
  }
  else if(state==3)
  {
    analogWrite(led,150);
  }
  else if(state==4)
  {
    analogWrite(led,255);
  }
}

How can I resolve this problem?


texts: TMOD value for timer 1 in mode 0 in 8051 microcontroller

texts:
What will be result of this statement:

MOV TMOD,#00H

Will it set it to timer 0 in mode 0 or to timer 1 in mode 0?

Other statements like:

MOV TMOD,#01H ;----- sets timer 0 mode 1
MOV TMOD,#10H ;----- sets timer 1 mode 1

didn't create any ambiguity.


texts:
I want to find the minimum resistance \$R_L\$ so as to maintain \$V_z\$(voltage of the zener corresponding to the minimum current \$I_{z_0}\$) across the same resistor \$R_L\$.

simulate this circuit – Schematic created using CircuitLab
I have two ways of looking at this, one of them is wrong and I need your help to figure it out!
First method:
I take off the diode as the load and find thevenin voltage :
$$V_{th}=\frac{R_L}{R_l+R_s}V_s$$
Since
\$V_{th}=V_{R_L}\$
I'll equate it with \$V_z\$ which gives :
\$\frac{R_L}{R_L+R_S}V_S=V_z\$
thus
\$R_L=\frac{R_S.V_z}{V_S-V_z}\$
Second method:
If \$R_L\$ is minimal then \$I_L\$ passing through it would be maximal and \$I_z\$ minimal (\$= I_{z_0}\$) thus we'd have :
$$I_S = I_L+I_{z_0} \Leftrightarrow \frac{V_S-V_z}{R_S}=\frac{V_z}{R_L}+I_{z_0}\Leftrightarrow R_L=\frac{R_S.V_Z}{V_S-V_Z-R_S.I_{z_0}}$$
(I'm skeptical concerning the implication \$I_L\$ maximal \$\Rightarrow\$ \$I_z\$ minimal, or in other words \$I_z = I_{z_0}\$)