texts:
In the figure shown below, the chopper feeds a resistive load from a battery source. MOSFET Q is switched at 250 kHz, with a duty ratio of 0.4. All elements of the circuit are assumed to be ideal. What is the PEAK-TO-PEAK source current ripple in amperes for the chopper?

My calculations are :

\$\triangle I=\frac{TV_o(1-D)D}{L}\$

\$T=\frac{1}{25*10^{4}}\$

D=0.4

\$V_o=\frac{V_s}{1-D}\$

\$\triangle I=(\frac{1}{25*10^{4}})(\frac{12(0.4)}{L})\$

\$\triangle I=(\frac{1}{25*10^{4}})(\frac{12(0.4)}{100*10^{-6}})\$

\$\triangle I=(\frac{1}{25*10^{4}})(\frac{4.8}{100*10^{-6}})\$

\$\triangle I=\frac{48}{25*10}\$

Are these calculations correct?


texts: How to identify pin 1 on component with ambiguous marking - bar and dot

texts:
I have a component in a VSSOP (TXS0102DCU), which I am uncertain of the orientation. There is both a bar and a dot. The datasheet just specifies pin 1 marking area, but this does not seem clear to me.

Going by the answer to a similar question (How do I identify Pin 1 on a chip with no corner mark), I would have guessed blue is the right marking. This is based on the orientation of the text. Is this correct?


texts: TRIAC Dimming for LED Buck controller circuits

texts: How can you create a solution for a LED constant current driver that can handle TRIAC dimming? Can you convert the waveform into a PWM and is there a simple solution?


texts: How does PWM affect current? Since current is dependent on voltage (higher voltage allows for more current) decreasing analogue voltage reduces current, but what about PWM? If the actual voltage is only full/none, is the current also full/none or what?


texts: Would a 2 amp audio amp get damaged by a 10ah battery? (im new to this kind of stuff)

texts:
Okay so I'm building a portable Bluetooth speaker, and i just blew current amp by running too many volts through (whoops i wasn't paying attention when i grabbed the adapter). I know this is a dumb question but would a 10 amp hour battery damage a 2 amp board? I'm new to this kind of stuff and i just want to make sure...

Also, would running a 100w amp through 2 12w speakers damage them?

I know that not having enough power supplied for a speaker is potentially more damaging than too much with stuff like clipping, but i don't really want to blow my current speakers up because they were a gift to me


texts: Effect of bootstrapping in amplifier circuit

texts:
I am trying to understand this "bootstrap bias" amplifier circuit. The picture below is adapted from the book "Transistor Techniques"  by G. J. Ritchie:

This circuit is a variation of the "voltage divider bias", with the addition of the "bootstrapping components" \$R_3\$ and \$C\$. The author explains that \$R_3\$ and \$C\$ are used in order to achieve higher input resistance. The author explains this as follows:

With the addition of bootstrapping components (\$R_3\$ and \$C\$) and
assuming that \$C\$ is of negligible reactance at signal frequencies,
the AC value of the emitter resistance is given by:
\$R_E' = R_E || R_1 || R_2\$
In practice this represents a small reduction in \$R_E\$.
Now, the voltage gain of an emitter follower with emitter resistance
\$R_E'\$ is \$A=\dfrac{R_E'}{r_e+R_E'}\$, which is very close to
unity. Hence, with an input signal \$v_{in}\$ applied to the base, the
signal with appears at the emitter (\$Av_{in}\$) is applied to the
lower end of \$R_3\$. Therefore, the signal voltage appearing across
\$R_3\$ is \$(1-A)v_{in}\$, very much less than the full input signal,
and \$R_3\$ now appears to have an effective value (for AC signals)
of: \$R_3'=\dfrac{R_3}{1-A}\gg R_3\$.

To try to understand this, I made an AC model of the circuit. Here is the AC model:

From the AC model, I can verify the author's claim that the emitter resistance is \$R_E || R_1 || R_2\$ and that the voltage in the node labeled as V is slightly less than the input voltage. I can also see that the voltage drop across \$R_3\$ (given by \$V_{in} - V\$) will be very small, meaning that \$R_3\$ will draw very little current from the input.
However, there are 2 things that still I don't quite understand from that explanation:

Why can we simply apply the formula for the emitter-follower voltage gain \$A=\dfrac{R_E'}{r_e+R_E'}\$ here, neglecting the effect of \$R_3\$?

What does it mean to say that the \$R_3\$ appears to have a different "effective value" for AC signals? I don't see why \$R_3\$ would change value.

Note that in order to try to understand this circuit's behavior further, I have tried to analyse it by finding its AC input resistance in two ways. I've posted both attempts as an answer to this question, for reference.


texts:
I am looking for a LED that I can use on my first underwater ROV so that I have enough light to record video under water. I am using a 12V battery so I am looking for a bright LED chip around 9-12V / around 400 lumens.
I am trying to figure out whether LEDs need a separate driver or whether they have a built in driver. I have a hard time figuring this out. What are the things to look for?
for example, I've read that there are different technologies like SMB, Cree, COB. Do any of these "by definition" include the LED driver?
Or is it regardless of the LED, and do I always need a separate driver for these small LED chips?


texts:
I am getting confused in selecting TVS diode for Ethernet Interface.

Should I connect one bidirectional TVS diode across a pair (one pin connecting to D+ and other to D-)? I think if transient is coupled to the Ethernet cable, then the two wires of a pair will be having same transient and it doesn't make any sense to connect a bidirectional diode across a pair.

Should I connect one TVS diode for each wire of the pair (other end of the diode connected to Ground)? Should it be bidirectional or unidirectional?


texts: What solution would be a low power option to signal a computer with button presses?

texts:
I want to make a custom input device with six buttons that when pressed signal computer to run a program. I would like to do this with a very low amount of power. What options are available to me to accomplish this task? I am willing to build a custom solution if necessary.

About this project and motivation:

I have a Wacom pen tablet which is useful for input but is lacking in that it is not well suited for multiple monitors. In my case, I have six monitors and mapping the entire screen space to the tablet is unmanageable.

I would like to make a small board with six buttons on it. For each button I press I want a message to be sent to the computer which I will use to run a program that moves the mouse cursor immediately to that monitor. For example, in an arrangement of two-vertical and three-horizontal configuration of six monitors (2x3), moving from edge to edge from the bottom left screen to the top right would require that I traverse a minimum of four screens if diagonals are not considered. Whereas if I could press a button then I could immediately set the cursor position to the desired monitor.

The tablet I'm using only has four buttons, of which I would like to map to other things. Cycling through monitors with a keystroke or single button press for previous/next is confusing as I have both vertical and horizontal axis. I want to mount this device at the top of the tablet so as to keep the movement of my hand to and from the selection process as minimal as possible.

Considerations:

It would be nice to consider the possibility of this being a wireless solution. Either because the device is low powered enough to operate for weeks or months on a charge or the possibility of tapping into the tablet's power source (USB/battery).


texts: Can I detect nuclear explosions with coherer?

texts:
The metal particles would cling together or "cohere", reducing the initial high resistance of the device, thereby allowing an electric current to flow through it. they use it as radio receiver in 1890, What I want to know:

Is it possible to detect electromagnetic field of nuclear explosions with this simple method or I need more advanced technology?!


texts:
A bit of background:
A want to build a motorised board for my son is 3 and has very limited mobility. He can't crawl but can use his hands to press buttons so I want to build something he can lay on and by using 2 switch buttons he can move himself back and forth.

The dimentions of the board I have are 1m by 60cm. I already have an arduino board but started looking at getting motors and motor controllers and got lost. I need a good place to start.

Here are the actual questions:
Do I buy one or 2 motors? What type of motors would you recommend? Any tutorials on how to wire the motors and what motor controller to get will be great.
What wheels should I buy? It will need to move about 20kg max. What other parts would I need?

Thanks


texts: precision voltage reference for multimeter

texts:
First post, be easy on the newbie. I'm trying to throw together a simple precision voltage reference based on the 5v LT1236. Seems to me the chip effectively has 4 pins, input, output, GND, and trim. I assume I don't connect the other pins at all. Can I leave the trim pin disconnected if I want a straight 5v reference? Probably not that simple...do I need filtering capacitors? How to I decide what size? I like to think I'm familiar with a decent portion of electrical theory, but explaining to me like I'm an elementary schooler couldn't hurt..

Sorry for so many questions, I figure all those questions could be answered in a quickie by almost anyone haha.

Should have started with a more common chip. I looked at the LM4040 datasheet, which made me realize I didn't understand the regulator was basically a zener diode. (And I didn't know enough about zener diodes) Previously I had not questioned how the IC actually operates. (Which would have made this whole thing easier)


texts: Providing phone line current for direct modem-modem communication

texts:
In order to directly connect two modems without a real phone line, one option is to put a battery inline (to create the current loop?). Most information I've found about this relates to the SEGA Dreamcast which has a built in modem and people generally suggest creating something like this:

simulate this circuit – Schematic created using CircuitLab
I don't fully understand how phone lines are expected to behave but this seems incredibly sketchy. I think the 'proper' way to handle this situation is to utilize an FXS Analog Telephone Adapter, but those cost money and I can't find any schematics for how they work. Is there a better way to do this? Or is this approach totally fine?


texts: Multiplexer not switching any audio input

texts:
I have designed this audio switch. 1 out of 4 TRRS inputs is selected.

I am testing it but it does nothing.

I press the switch to switch the next channel and nothing works.

The idea here is:

the 555 debounces the key and a pulse is injected on the flipflop when the button is pressed.
the flipflop is a 2 bit counter, producing a sequence from 00 to 11 as the button is pressed repeatedly.
the two bits from the flip flop selects one of the four channels of the MAX359E switch.
The leds display 00, 01, 10, 11, depending on the input selected, obviously...
I am not sure what to do with the mic input in relation to the input/output capacitor. This is because some TRRS inputs, like iPhone's, send a voltage on the mic line, to supply the mic. If I put a capacitor it will remove that voltage...

Any ideas why it is not working? I may have connected something wrong on the test board. I have double checked the connections several times but at this point I may be tired and not seeing the problem or the circuit is bad designed...

Any ideas? Thanks

EDIT: I have modified the circuit according to WhatRoughBeast suggestions.


texts: Find output given state space representation

texts:
This is usually easy but there are things I haven't encountered in this one. This is the problem. $$\dot x=\begin{bmatrix}0&1\\-2&-3\end{bmatrix}x+\begin{bmatrix}0\\2\end{bmatrix}u=Ax+Bu\\y=\begin {bmatrix}0&1\end{bmatrix}x=Cx\\x(0)=\begin{bmatrix}1\\0\end{bmatrix}$$

First I'm asked to calculate $$x(t)=e^{At}x(0)$$

An exponential matrix in a control theory course seems a bit too much but I solved that. $$x(t)=\begin{bmatrix}1&1\\-1&-2\end{bmatrix}\begin{bmatrix}e^{-1t}&0\\0&e^{-2t}\end{bmatrix}\begin{bmatrix}2&1\\-1&-1\end{bmatrix}\begin{bmatrix}1\\0\end{bmatrix}$$
The second and final question asks me to find the expression of the output y(t) for any input u(t).

Looking at the solution manual this is all that's written : $$y(t)=\begin{bmatrix}0&1\end{bmatrix}\int_0^t\begin{bmatrix}-1&-1\\-1&-2\end{bmatrix}\begin{bmatrix}e^{-1(t-τ)}&0\\0&e^{-2(t-τ)}\end{bmatrix}\begin{bmatrix}2&1\\-1&-1\end{bmatrix}\begin{bmatrix}0\\2\end{bmatrix}u(τ)dτ$$

That reminds me of convolution but the integral limits are different. Plus the result from the first question is used. Why would we use the exponential? I can't make the connection and understand the second part. Any ideas?


texts: Does nodemcu/arduino require a current limiting resistor when connecting input pin to VCC?

texts:
The question says it all - I want to connect (possibly) VCC (e.g. via a pushbutton) to an NodeMCU input pin, and read the value (to see if the pushbutton is depressed).

If you connect VCC to ground-level (with no resistor), too much current will flow, and you risk (almost certain) damage to your board.

Does this apply to input pins?

If "sometimes", when? Is the answer the same for Arduino/Atmel? For other chips?


texts: For some educational purpose I want to make some noises on breadboard wires but they barely become noisy , I'd transfer my data with 5v electrical potential on 50cm wire length, I tried multiple strategies like adding resistors or passing high amperage wire near breadboard wires but still no noise,is there any other way to generate noise on a wire?


texts:
I've a third order active filter, without zeros. I know that when \$f=0\$ the gain response is \$1\$. So the cutoff-frequency is located at:

$$\left|\text{H}\left(\omega_0\right)\right|=\frac{1}{\sqrt{2}}\space\Longleftrightarrow\space\omega_0=\dots\tag1$$

The roll-of of the filter can be found by using:

$$\text{roll-of}=20\log_{10}\left(\left|\text{H}\left(\omega_2\right)\right|\right)-20\log_{10}\left(\left|\text{H}\left(\omega_1\right)\right|\right)\tag2$$

In order to get dB/decade I need to have:

$$10\omega_2=\omega_1\tag3$$

And in order to get reasonable values we need to have:

$$\omega_2>\omega_1>>\omega_0\tag4$$

And I know that when \$f\to\infty\$ the roll-of tends to \$-60\$ dB/decade

  Let's say I need a accuracy for the roll-of, up to 4 decimal places. What value for \$\omega_1\$ should I pick? And is there a resource that I can check out to read more about this?


texts: Can anyone explain Phantom Power and, specifically, how it's used in satellite television systems?

texts:
Although I spent many years in the electrical field, I specialized in Electrical Metrology (a long time ago). Bearing this in mind, I really know very little about satellite television system theory.

As we recently lost our ability to acquire certain transponders used by our satellite television receiver, I began looking into the basics of this area of RF theory ... and, in short, I'm intrigued by the idea of sending a DC signal over the same transmission line use to transmit RF signals.  I'm certainly not clear about it at this point, but, based on what I've read (thus far), this combination of DC and RF is commonly referred to as "Phantom Power" by the satellite people.

Having used many power splitters and directional couplers in my day -- mainly for calibration testing of Precision Measurement Equipment (PME) -- I'm especially puzzled by a component of this area of electronics known as "DC POWER PASS".  Apparently, the idea is to pass a DC voltage over the same coax used to transmit down-converted RF satellite signals.  As this seems to run contrary to the division of power I was [once] accustomed to, I would really love to read a lucid explanation of this method of controlling satellite television system circuitry.

I hope that I've been clear enough.


texts: Linear thumbwheel potentiometer obsolete?

texts: I am trying to find a possibly obsolete linear thumbwheel potentiometer, like the type used in old radios. There seem to be plenty of logarithmic pots around. I can find linear but they are marked as "end of life". Are these linear pots obsolete?


texts: Is there any other similar file format like BLIF?

texts: I bump into Cingulata project which uses Berkeley Logic Interchange Format (BLIF) to represent circuit. I find BLIF file format is a very human-friendly text file format and easy to understand, and am curious to know whether there are other similar text file formats. But after some googling, I can't find a counterpart like BLIF file. Besides BLIF file, is there any other similar file format? Very sorry for this layman question.


texts: If I get usb to parallel convereter,can I use the same address  (378H) that are used in lpt interface for data port in this converter ? If yes ,what is the dll library should be used?


texts:
A series of current pulses of 10mA amplitude and 2ms duration are applied to an initially-uncharged, 5 uF capacitor. How many pulses are required to charge the capacitor to 20V?

I thought of this formula:

\$V(t) = 1/C \int\limits_0^{t}idt + v_0\$

\$V(t) = \cfrac{1}{5 * 10^{-6}} \int\limits_0^{2 * 10^{-3}} 10 * 10^{-3}dt + 20\$

\$V(t) = 24 V \$

But then what? Note: The answer is 5 pulses.


texts: Looking for informations & datasheet of OSS-4ES

texts:
I have an (old) dip8 component I cannot identify properly.

It is quite unusual & nice so I'm looking for its datasheet or information about it.

The date(s) code(s) I found seems to be 90's for each information & photo I can find over the internet until now.

I thought it was photo resistor array or photodiode array but while testing it this way determinate it is not.

Any idea about what this OSS-4ES device is?
And where to get a datasheet?


texts:
Could I recreate this molex to female USB cable by cutting off the molex connector of a fan and the female end of an USB extension, then solder the red and black wires together?
If it's possible, would it be safe if I heatshrink or electrical tape it?
I was looking to power a $5 RGB LED strip for a PC that's powered via a male USB-A and controlled with a little RF remote. It looks similar to this: https://www.amazon.com/RGBZONE-RGBZONE-1m-USB-DC-5V-24V-LED-Controller-Kit-17-Key-RF-Wireless-Remote-Control-Dimmer-Inline-LED-Controller-for-5050-3528-RGB-LED-Strip-Lights/dp/B07D3KJN4B/


texts:
I'm a noob in electronics. Actually, I'm asking here in Stackoverflow for my physics experiment :)

I need a AC power source that has a range of approx. 20V - 250V.
I'm using this source to power an electromagnet that is constructed by using enamel coated copper wire of 0.3mm

I need to be able to generate sine waves with frequencies of approximately 100 hz - 3000 hz.

I found that normal function generators do not have enough voltage & power to support my experimental setup. Slidac was also something I considered, but since it transforms the voltage from the input source of 220V, the output current becomes too high in cases of low output voltages.

Thanks a lot in advance.


texts: Reasons not to fill unused board area with power planes instead of ground planes?

texts:
On the (two-layer) board I'm designing, I have a relatively large unused area. Instead of just pouring it with ground on both sides, I'm considering filling it with Vcc on one side and ground on the other, to create a small capacitance between the ground and Vcc. (I will still add adequate decoupling capacitance from regular capacitors, of course.)

The board is not exactly high speed (16 MHz microcontroller, doing only digital IO). And I'd be hard pressed to produced even 1 nF of capacitance from the available board area, I think. So you could argue that this extra capacitance is not doing much of a difference. But is there any reason why it might actually be a bad idea and should be avoided?


texts:
I have an old Braun Cosmophon BMF2020 microphone at home, which I have long been wanting to use for good ol' fun.

I have virtually no technical knowledge, so I am completely uncertain how to power the device, and if it would be possible to connect the microphone to my PC.

The mic holds a slot for a gigantic "torch" battery of 4.5V.
There are four additional ports, two on each side of the stand:

The two on the left are marked with "4V"
The two on the right are marked with "V"

I am thinking these two pairs are for a plus and minus pole, but I wouldn't know why the mic features both a 4V and what I assume is a 1V inlet.

Any help would be greatly appreciated

Useful information

https://www.vintagemicworld.com/html/Mic%20of%20the%20month%20December%202016_Braun%20Cosmophon%20BMF%202020.html
https://www.radiomuseum.org/r/braun_cosmophon_export_bmf2020.html
https://www.radiomuseum.org/r/braun_cosmophon_mikrophon_bmf2020.html


texts: How to calculate poles for a high order system?

texts:
I have a fourth order system which is fully controllable and observable, which needs to satisfy certain design criteria.

I am trying to design a full-state feedback controller for the following system:

$$\frac{-0.00198s + 2}{s^4 + 0.1201s^3 + 12.22s^2 + 0.4201s + 2}$$

Design Requirements:

<5% Overshoot
<2s settling time

  The schematic of this type of control system is shown below where
  \$K\$ is a matrix of control gains. Note that here we feedback all of
  the system's states, rather than using the system's outputs for
  feedback.

A related example, State-Space Methods for Controller Design.

While I am aware how to design second order systems using the above design requirements, I am struggling when it comes to higher order systems.

Below I present equations and working for finding poles for a second order system. Apologies if wording is hard to decipher.

Poles for 2nd order @ -2.6 +- i*2.39

One would then proceed to use MATLAB place function as follows:

p2 = [-2.6 + 1i*2.39, -2.6 - 1i*2.39];
K = place(A,B,p2);

Acl = A - B*K;
mysys = ss(Acl,B,C,D);

Since this method only yields two poles, how can I satisfy my design requirements if I have a fourth order system?

This can also be thought of as designing a full state feedback controller to obtain the specific transient one requires. Closed loops dynamics and more specifically eigenvalues of matrix Acl have a lot to do with finding the desired poles. I am yet to fully understand how. Any suggestions would be appreciated.


texts: What is the difference between these DVR8825 circuits? (stepper motor driver)

texts: I use the one that is down and it works fine, but since I don't understand the difference between these circuits I decided to ask. Both circuits I found online, without explaining what is the difference between them.


texts:
i wrote a code in mikroc for pic16f877A in which i have used a timer0 and timer1. i debug my code and found that timer0 is not working but i am not able to understand the reason behind it. I even checked datasheet for the OPTION_REG but couldn't figure out the problem plz help. i am new to pic programming. I just uploaded the function in which timer0 and timer1 is setup. UART is used to check whether each line is getting executed and i found after printing the value of TMR1H it stops.

 int feedback()
 {
 sh = 0;                                 //variable to come out of the while loop after interrupt occured.
 UART1_WRITE_TEXT("inside feedback");
 UART1_Write(13); // newline

 TMR0=193;
 Uart1_Intout_ReturnInt(TMR0);
 UART1_Write(13); // newline

 INTCON=0xA0;
 Uart1_Intout_ReturnInt(INTCON);
 UART1_Write(13); // newline

 TMR1L=0;
 Uart1_Intout_ReturnInt(TMR1L);
 UART1_Write(13); // newline

 TMR1H=0;
 Uart1_Intout_ReturnInt(TMR1H);
 UART1_Write(13); // newline
                                               //here the problem starts
 OPTION_REG.PSA=0;
 OPTION_REG.PS2=0;
 OPTION_REG.PS1=1;
 OPTION_REG.PS0=0;
 OPTION_REG.T0SE=0;
 OPTION_REG.T0CS=0;
 UART1_WRITE_TEXT("timer0 start");     //this msg and following all messages does not show up
 UART1_Write(13); // newline

 T1CON=0x07;
 UART1_WRITE_TEXT("timer1 start");
 UART1_Write(13); // newline

 sh=1;
 Uart1_Intout_ReturnInt(sh);
 UART1_Write(13); // newline

while(sh==1){
Uart1_Intout_ReturnInt(sh);
UART1_Write(13); // newline

UART1_WRITE_TEXT("inside while loop");
}

UART1_WRITE_TEXT("outside while loop");

TMR1H=TMR1H*1000;
sh=TMR1H+TMR1L;
actualOut=(60*2*sh)/8;
Uart1_Intout_ReturnInt(actualOut);
UART1_Write(13); // newline

return actualOut;
}
void interrupt(){

 T1CON=0x00;
 sh=0;

}

///////////main function/////////////

 void main() {

 UART1_Init(9600);

 pro=0.5,i=0,der=0;
 setPoint=80,sel=1;
 actualOut=20;
 pOut=0,iOut=0,dOut=0;
 out=16;
 error=0,lastError=0;

 ADCON0=0;
 ADCON1=0x0f;
 CMCON = 0x07;
 PORTC=0;
 TRISC = 0b00000001;

  while(1){

 out = pid(actualOut);

 duty=(short)out;
 pwm(duty);

 actualOut = feedback();

  }
  }


texts: multiple MCP4131 potentionmeters with common Slave Select line

texts:
I fiddle with a digital potentiometer MCP4131 which communicates via the SPI protocol. I've seen several tutorials in which multiple SPI devices are connected to a common Slave Select line and the bits of information overflow from the first Slave device to the second, etc.

I wonder weather would be possible to connect two MCP4131 potentiometers with a common Slave Select line, due to the fact that they have a common MISO/MOSI pin.

So, shouldn't MISO/MOSI be in different pins, thus connect MISO of the first device to the MOSI of the second one?

I am a bit confused, so any thought would be appreciated. The following articles didn't help me understand much.

MCP4131: How to know what value resistors to use on the multiplexed SPI IO?

MCP4131 resistor on SDI/SDO multiplexed pin?


texts: How does color LCD work on the Pokémon Pikachu 2 GS?

texts:
The Pokémon Pikachu 2 GS is a small electronic toy that has an LCD screen. What's unusual is that the screen is not the typical black-and-white LCD found on almost all handheld devices, but instead it has an LCD that displays shades of color. These colors range from transparent to yellow to red to black.

But this coloring doesn't involve RGB subpixels; it seems to use a special trick not seen elsewhere. How does the colorization work?


texts: How to build my own 8V 6A PSU using laptop charger

texts: I have a 19V 4A laptop charger. I was wondering could I convert this into 8V 6A psu for my LEDs. They're parallel-only colour LEDs hence the high current demand.


texts:
I've simulated the diode in LTspice and the result indicates two current peaks in the diode, the higher one(5.4A) only lasts 60us in the very beginning and the lower one(1.8A) lasts 3ms.

My question is whether should I choose the diode which can withstand the higher current peak(5.4A)? The reason for this question is because the higher one only last 60us and I'm not sure whether the diode can ignore such a short current peak.


texts:
I need to take voltage measurements separated by long delays (couple of hours) and beep a buzzer when voltage level is met.

Power consumption is important.

What I want is a simple timer chip like RTC chips, but dumb, without serial interface, memory, etc. What's nice about these serial RTC chips is power consumption in nA range though.

I'm aware, I could use 555, but the lowest power consumption I've found is about 500uA.

Can anyone recommend a simple timer chip with low power consumption?


texts: Can't understand why oscilloscope requires incomplete circuit in order to measure voltage in secondary winding of very low inductance transformer

texts: If I build (a very poor) transformer (for pedagogic use) using a few windings of wire for the primary and secondary coils, and use a signal generator on the primary side, I can measure the voltage on the secondary side with an oscilloscope probe, but only if I don't ground the other side of the secondary. If I ground the other side of the secondary to the oscilloscope, I only see noise on the scope. If I use a commercial transformer whose secondary coil has a high inductance, then I can measure the voltage across the secondary in the usual way, by connecting one oscilloscope probe to one side of the secondary, and the other (ground) to the other side. This only seems to be a problem with small, make-shift transformers with low inductance. But I can't seem to understand this behavior. Thanks!


texts: Count the number of flashes on a yellow LED with 1-wire

texts:
I would like to count the number of flashes generated by a yellow LED in my Schneider Me4ZR power meter. This power meter produces 100 flashes for every kWh. I would like to use One Wire protocol to count via my PC.
[EDIT] My consumption is in average around 4 pulses per minute. I already have a working 1-wire network in my house that consists of temperature sensors, contact sensors and voltage meters for light level measurements. Then network is connected to my PC via http://www.homechip.com/catalog/product_info.php?products_id=158. It is working well for all other sensors so this is not causing an issue. As mentioned it is also counting light impulses when they are stronger/longer.

I have built a one wire counter from parts that behaves like this counter.

I have then built a separate light detect circuit identical with this one:

but I have replaced the LED with a 5V relay and protected the transistor with a diode connected to relay pins as shown here:
(source: pcbheaven.com)
. I have connected this circuit to the 1 wire counter.

The reason I chose a relay instead of another transistor was that with a transistor I got too many random clicks when the led got on. With a relay I can get a clean contact on/off.

The relay switches correctly when exposed to a bulb and the counter increments as expected. All ok so far.

When I place the photodiode in front of the LED it does not work ok. I can still hear the relay click but the counter is not incremented.

I assume that the pulse length is too short. One solution I guess will be to increase the pulse duration.

How can I check what the cause of the issue is and, if the answer is to extend to pulse duration, how can I do that easily?


texts: Bus admittance matrix after the removal of reactance

texts:
The bus admittance matrix for a power system network is $$
 \begin{bmatrix}-j39.9 & j20 & j20 \\j20 & -j39.9 & j20 \\ j20 &j20 &
 -j39.9 \end{bmatrix} \text{pu}$$ There is a transmission line connected between buses 1 and 3 which is represented by the circuit
  shown in figure

  If the transmission line is removed from service, what is the modified
  bus admittance matrix?

  \$\begin{bmatrix}-j19.9 & j20 & 0 \\ j20 &-j39.9 & j20 \\ 0 & j20 & -j19.9 \end{bmatrix}\text{pu}\$
  \$\begin{bmatrix}-j39.95 & j20 & 0 \\ j20 &-j39.9 & j20 \\ 0 & j20 & -j39.95 \end{bmatrix}\text{pu}\$
  \$\begin{bmatrix}-j19.95 & j20 & 0 \\ j20 &-j39.9 & j20 \\ 0 & j20 & -j19.95 \end{bmatrix}\text{pu}\$
  \$\begin{bmatrix}-j19.95 & j20 & j20 \\ j20 &-j39.9 & j20 \\ j20 & j20 & -j19.95 \end{bmatrix}\text{pu}\$

I'm confused between option (1) and (3). Since the sum of row in option (1) gives us \$-j0.1\$ so after removal of the branch the admittance matrix sum should still be \$-j0.1\$. Am I right ?


texts:
Looking for help answering a few question about choosing parameters for a small voltage doubler circuit.

I'm looking to prototype a USB powered random number generator based on the shot noise of a Zener diode just entering its breakdown region.   I understand the best noise is from Zener's with a breakdown above 5 volts, so I think I need a voltage doubler.   I'm hoping to drive the voltage doubler with the signal from a GPIO port on the PSOC 5LP, and measure the output using a second pin.    I found a nice old article from 1998 a similar approach, but I think it can be done with far fewer components today.

The article said:  "Optimum noise performance is obtained from a 1N753A Zener diode, which has a 6.2-V Zener 'knee.'" It also mentioned that the optimal current for noise output was about 20 uA, generating about 20 mV p-p noise.

Based on this idea I've sketched out this circuit

So my questions are:

Does driving this from a GPIO port make sense?

Any reason I should try to make the drive approximate a sine wave, or can I just hit it with square wave like digital output?

Is there any limit to the frequency I should drive it at?   I understand that higher frequencies will reduce the size capacitors I need.

With a frequency chosen, how do I size the capacitors.

P.S:  Note that part of the design goal here is to have the SoC chip adjust the "doubled" voltage to optimize the noise generated.   It won't need to fully double VCC.


texts: How does a computer (or USB device) detect that there is a new/lost connection?

texts:
I have two computers, a USB keyboard and a USB mouse. I want to build something that lets me switch the USB devices between the two computers. My approach would be to buy a new powered USB hub and plug the keyboard and the mouse into it. Then, I would use a microcontroller to control transistors for the DATA- and DATA+ lines to the two PCs (so four transistors total). I would just short all the GND wires (from the powered hub and the PCs) – that shouldn't do any harm, right? – and leave the +5V wires from the PCs unconnected. As far as I can see, that should work fine for switching.

However, how would the PCs (or the powered hub?) know when to do a new handshake and so on? Is it sufficient to have the +5V wire to the USB hub high by default and pull it to GND while switching? Would the USB hub initiate a handshake or something when its USB +5V wire goes up?

Also, how would the other PC find out that it has just lost the connection? By checking whether there's a voltage between Data+ and Data-?


texts:
How can I transform the variation over temperature: 25 ppm/K to ppm/°C?
I was searching for the formula and all I could find was that 100 ppm/K = 100 ppm/°C.

Is this true?


texts:
I hope this is the right stackexchange site to ask this question. I'd like to now the meaning of these symbols, visible in the front of two different micro sd cards of the same model:

Backgroung (in case anyone wants to know): I have three sd cards, whose model is Kingston SDC10G2/16GB. Two of them work for my particular purpose (using a raspberry pi), the other one doesn't. I've realized that the cards that work and the one that doesn't don't look the same (I was trying to post pictures of them, but I can't attach more than two images until I have a reputation of 10). The first symbol is on the card that doesn't work, the other symbol is on the ones that do.
In a computer, all three cards perform flawlessly. A badblock analysis reveals none of them has bad blocks. I'm asking about those symbols thinking that maybe the have something to do with my problem.


texts: Is it normal that a clock divider made with ring johnson counter has output Undefined if clk starts high?

texts:
I'm making a frequency divider and the easiest way is to use a johnon's counter with D flip flop. The point is that if I make the clk start high, the counter has undefined output, while if I make the clk start low, it all should be ok.

Code of ring johnson's counter ("divide_by is unusued at the moment"):

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity double_period is
    port(
        clk : in std_logic;
        --i 3 bit seguenti rappresentano 8 stati (stato 0 : divisione frequenza per     2, stato 1: divione per 4, stato 3 : divione per 6, etc...)
        divide_by : in std_logic_vector(2 downto 0);
        out_clk : out std_logic
    );
end double_period;

architecture double_period_behaviour of double_period is
signal filoFlottante : std_logic;
component ffd is
    port(
        clk : in std_logic;
        din : in std_logic;
        dout : out std_logic
    );
end component;
signal dInternal : std_logic_vector(8 downto 0);
signal dFirst : std_logic;
begin
dFirst <= not(dInternal(2));
f0 : ffd port map(clk, dFirst, dInternal(0));
f1 : ffd port map(clk, dInternal(0), dInternal(1));
f2 : ffd port map(clk, dInternal(1), dInternal(2));
--f3 : ffd port map(clk, dInternal(2), dInternal(3));
--f4 : ffd port map(clk, dInternal(3), dInternal(4));
--f5 : ffd port map(clk, dInternal(4), dInternal(5));
--f6 : ffd port map(clk, dInternal(5), dInternal(6));
--f7 : ffd port map(clk, dInternal(6), dInternal(7));
--f8 : ffd port map(clk, dInternal(7), dInternal(8));
out_clk <= dInternal(0);
end double_period_behaviour;

D FLIP FLOP CODE:

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity ffd is
    port(
        clk : in std_logic;
        din : in std_logic;
        dout : out std_logic
    );
end ffd;

architecture ffd_behaviour of ffd is
begin
process(clk)
variable qvar : std_logic := '0';
begin
    if clk'event and clk='1' then
        qvar := din;
    end if;
dout <= qvar;
end process;
end ffd_behaviour;

The following is the TESTBENCH:

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity double_periodTB is

end double_periodTB;

architecture double_periodTB_behaviour of double_periodTB is
component double_period is
    port(
        clk : in std_logic;

        divide_by : in std_logic_vector(2 downto 0);
        out_clk : out std_logic
    );
end component;
signal clk : std_logic;
signal out_clk : std_logic;
signal divide_by : std_logic_vector(2 downto 0);
begin
process
begin
clk <= '1'; wait for 10 ns;
clk <= '0'; wait for 10 ns;
end process;
process
begin
divide_by(0) <= '0'; wait for 10 ns;
divide_by(0) <= '0'; wait for 10 ns;
end process;
process
begin
divide_by(1) <= '0'; wait for 10 ns;
divide_by(1) <= '0'; wait for 10 ns;
end process;
process
begin
divide_by(2) <= '0'; wait for 10 ns;
divide_by(2) <= '0'; wait for 10 ns;
end process;
sg : double_period port map(clk, divide_by, out_clk);
end double_periodTB_behaviour;

"DIVIDE_BY" IS UNUSUED AT THE MOMENT!!!!


texts: How can I improve my 3 decade counter design so that it counts sequentially in Verilog

texts:
How can I improve my 3 decade counter design so that it counts sequentially?
I am attempting to build and simulate a 3 decade BCD counter by cascading 3 decades counters that produce an output to indicate when the count of 9 is reached.
My design works, in that it counts sequentially, apart from the times when any of the decade counters reach 9, as this instantenously triggers the next counter to start and instead of going from 008 to 009 or 018 to 019, my design goes from 008 to 019 or 018 to 029, respectively.
Please see extract of code below:
  module ThreeDec_Synch_BCDCounter(output [11:0] A, output y, input clk, reset);
  wire DQ1, DQ2;

  Synch_BCD_Counter SBC0({A[3:0]}, DQ1, clk, reset);
  Synch_BCD_Counter SBC1({A[7:4]}, DQ2, DQ1, reset);
  Synch_BCD_Counter SBC2({A[11:8]}, y, DQ2, reset);
endmodule

module Synch_BCD_Counter(output [3:0] A, output y, input clk, reset);
  wire w0, w1, TA1, TA2, TA3;
  wire Q0b, Q1b, Q2b, Q3b;
  supply1  PWR;

  and  #(1) g0 (TA1, A[0], Q3b);
  and  #(1) g1 (TA2, A[0], A[1]);
  and  #(1) g2 (w0, A[0], A[3]);
  and  #(1) g3 (w1, A[0], A[1], A[2]);
  or   #(1) g4 (TA3, w0, w1);
  and  #(1) g5 (y, A[0], A[3]);

  TFF2  T0 (A[0], Q0b, PWR, clk, reset);
  TFF2  T1 (A[1], Q1b, TA1, clk, reset);
  TFF2  T2 (A[2], Q2b, TA2, clk, reset);
  TFF2  T3 (A[3], Q3b, TA3, clk, reset);
endmodule

Please also see waveform below:

I have tried about everything that I can think of to try to get it to work, but I am not having much success.
Therefore any asistance/insight that anyone can provide will be very much appreciated.


texts: Maintain multiple connection intervals/slave latencies in Bluetooth Low Energy network

texts:
Is it possible for a Bluetooth Low Energy network to operate with two different connection intervals and slave latencies?

To clarify, assume I have a network with one host and two slaves. These slaves are connected with interval A and slave latency B. A desired event occurs and the pairing between the host and one of the slaves modifies the connection interval to C and slave latency to D, while the other slave keeps operating at interval A and latency B. Is it possible for the host to maintain these two connection settings?


texts: Quick Question - What is the TPM Connector Size?

texts:
Anyone know the connector size for the TPM port? I wanna take the 5vSB power from it.
If it helps its a MSI B450+ Tomohawk.
Thanks!
P.S. I have searched but TPM means too many things!
Edit: WHOOOOOPS! Yes I meant TPM instead of TMP!


texts: Decoupling with multiple caps per pin. Which should be closest?

texts:
I have an Ultra Wide Band transceiver with an internal power amp.  This PA has two input pins for Vdd.

According to the manufacturer, each of these pins should be decoupled with three caps; 10p, 330p, and 0.1u.

I'm using 0402 packages for all of the caps.  In which order should I physically place them, relative to the IC?  In other words, should the placement be

0.1u -> 330p -> 10p -> IC

or should it be

10p -> 330p -> 0.1u -> IC ?

Thanks!


texts:
As always I have a rookie question. In a project, I need to analyze the circuit below in a way that the transistor would be in forward active mode. I need to calculate resistors and voltage sources, any combination would be acceptable as long as the transistor is in forward active. Then I need to apply a sinusoidal voltage to the input (base) and see the waveform of output (Vc). I have trouble using Pspice to do so. What type of analysis should I use? Can you walk me through it?

Also, considering there is no DC source connected to the base, how can it get into forward active, considering Vbe will always be negative?


texts:
I have been working on a project where so called Lundell alternator plays a crucial role. I haven't got any experience with this device sofar so I have decided to study some literature regarding this device at first. In the Power electronics handbook 3rd edition I have found on page 655 following equation describing alternator output power \$P_o = \frac{3\cdot V_o\cdot\sqrt{V_s^2-(4V_o^2/\pi^2)}}{\pi\omega L_s}\$, where \$V_o\$ is the battery voltage, \$V_s=k\omega i_f\$ is the back-emf voltage magnitude, \$\omega\$ is the electrical frequency and \$L_s\$ is the armature leakage inductance.

I have plotted a graph of the function \$P_o=P_o(V_o)\$ with following parameters
\$L_s=135\,\mu H\$, \$k=9\cdot 10^{-3}\, V/(A\cdot rad\cdot s^{-1})\$, \$i_f=3.6\, A\$, \$n_m=3000\,min^{-1}\$ (mechanical speed of the combustion engine), \$p=3\$ (number of alternator pole pairs).

From the graph it seems that the alternator power function has "interesting" behavior only for unrealizable (at least in standard vehicle with 12 V lead-acid battery) voltages. Does anybody have any suggestion what could be the main idea behind this function? Thanks for any suggestions.


texts: What is the amplification when both input terminals of an opamp are at same potential?

texts:
(Ideal opamp discussed here)

I know

  Vd=Vo/(V1-V2) ....eq 1

where Vd is differential gain, V1 and V2 are the voltage at the inverting and non inverting terminals and Vo is the output voltage.

Again

  A=Vo/Vd,(A = amplification)....eq 2

If V1=V2 then V1-V2=0 in equation 1 then Vd becomes infinite as eq1 becomes:

  Vd=Vo/(V1-V2)

  Vd=Vo/0 =>  Vd=infinite

As a result eq 2 becomes

  A = Vo/Vd

  A = Vo/infinity [ As Vd=infinity]

  A = 0

But the book says the amplification is infinite in such a case.What is going on?


texts: Dynamically configure FPGA from the ARM core?

texts:
I'm bootstrapping a new stand-alone, network-attached project based on an FPGA. The target chip is from the Xilinx Zynq UltraScale+ series.

The architecture I'm thinking of is:

All the network stack and latency-critical logic is implemented in
hardware, and attached to a 100GE interface.
The ARM cores would
run Linux, handle all management systems (statistics and management
agent, cluster maintenance server, ...), and be attached to a 1GE interface.
The two would be connected via a PCI-Express bus using Riffa
(for example).

One question I'm asking myself is whether it is possible to program the FPGA right from the linux distribution running on the ARM cores, using command-line tools. Or does it have to be done right from an external device?

Doing so would allow seamless user logic updates without adding yet another chip in the box dedicated to performing remote upgrades.

Thanks.


texts: Using a multimeter, can I tell if a lithium-ion battery pack is brand-new?

texts:
A few years ago, I ordered a replacement cell phone battery from Amazon, and while it worked, it didn't last as long as I expected. I wondered if the seller had scammed me by selling me a battery that had been previously used, so it gone through a few dozen (or hundred) discharge cycles and had a lower capacity than a new battery would have. That phone is long-dead by now, but I still wonder: was there some way I could have tested the battery when I received it, to tell if I had truly gotten a new, never-been-used battery as advertised?

In my attempts to search the previous questions here, I've found several references to internal resistance increasing as a lithium-ion battery pack ages, so that's a partial answer to my question. But I still have two things I haven't been able to find answers to yet:

1) Would all lithium-ion battery packs have the same low internal resistance if they are new? (Or at least, all battery packs intended for use in smartphones, which means their physical size and voltage will be roughly similar to each other even though there will be some variance.) Or  do different lithium-ion batteries vary too widely for this question to be answerable without a model number? (In which case I would have to find the manufacturer's data sheet for that battery to know what its internal resistance should be when new.)

2) Can I measure that internal resistance with a multimeter, and if so, how? Can I simply set the multimeter to resistance mode, then touch the red probe to the battery's positive terminal and the black probe to the negative terminal? And a sub-question: is this safe? As I understand multimeters, when in resistance mode they put a small voltage across the probes, so that a trickle current would pass through the battery. I don't think that this would be dangerous to the battery, but I'm certainly no expert. (I understand enough about electronics to know that V=IR, and to know how to use a multimeter, but that approaches the limit of my knowledge. I'm a software developer, not a electronics engineer.) So if this is dangerous and I shouldn't do it, I'd rather find out now than by having a battery explode in my face. :-)

NOTE: The question I'm asking is close to How to measure capacity of a Lithium-ion battery, but I'm coming at it from a slightly different approach. I want to know whether I can tell if the battery is new if it's been heavily used (where "heavily" is a little vague, but I'd define it as "enough to make a significant, measurable difference when compared to a brand-new battery of the same type"). Maybe measuring the capacity is exactly what I need, but I'm too ignorant to know how to interpret the capacity results to tell if the battery is new. If that's the case, please feel free to close this question as a dupe, but I'd appreciate a brief explanation of how I should interpret the capacity results. :-)


texts: I have a level sensor and transmitter(4-20mA standard) of Qidian Automation for sensing level of liquid in tank having capacity of 1000 litres. On transmitter it is displayed 0.516 when tank is half filled. How to know the unit in which transmitter is displaying this value?


texts: Troubleshooting noisy FET buffer for contact mic

texts:
I'm trying to follow the schematic on this page to create a preamp/impedance matcher for a balanced piezo contact mic. I've reproduced the schematic below.

I've built it on a breadboard and I'm finding that the output is at least 20dB below that of the contact mic on its own, and has considerable noise. I'm finding it difficult diagnosing this, not having very in depth electrical engineering knowledge myself. I wonder if someone could suggest the likeliest causes?

My JFETs are 2N3819, matched by hand using the technique suggested on that page. My R3 is 1K, and my R1,R2,R5,R6 are 3M3 (easier to source). My capacitors are polypropylene, rated for 100V, and all resistors are carbon.

Possible problems:

My JFET matching went wrong. I gather that unmatched JFETs would result in noise, but would they also result in a signal drop where there should be gain?
The assumptions the circuit design makes about the internal architecture of my audio interface are wrong, ie. "It takes advantage of the fact that phantom power is fed to the balanced XLR inputs via pair of closely matched 6.81k resistors. These resistors are used directly as the drain resitors in the differential amplifier rather than the more usual method of connecting an additional pair of matched resistors to each line to create a +48V supply rail and then feeding the signal back through DC blocking capacitors. Since the mixing desk already blocks DC at it’s inputs it’s not a problem that the signal is floating at +45V or so."
Some of my component selections were wrong: an exact 3M value is critical, or the resistors should be metal film.

Many thanks for all help and suggestions.

EDIT: Here's a photo of my current breadboard setup in case there are any glaring mistakes.


texts:
I have an enclosure and want to add some protoboards inside it. I can place two next to each other, but since I'm a bit out of space I think it's best to stack 3 of them with PCB spacers.

However, I will have some (not many) connections from one board to another (and second to third board).

I can use either pin headers without soldering, with soldering or using terminal blocks. Terminal blocks cost some more space, but when soldering pin headers, I can never replace anything without desoldering, even when I use for the necessary ICs DIP8 sockets. And I wonder if using nonsoldered pin headers would be rigid enough for a device that will be moved around all the time and not handled always softly (except while in use).

What would be best:

Soldering pin headers and when something is broken to desolder the pin headers?
Not soldering the pin headers at all?
Using terminal blocks?

In my case I will use only a few terminal blocks from one board to another, but it's more a generic question for in future use.


texts: Probe testing LFCSP components with a multimeter

texts: If I reflow a LFCSP IC such as an ADV7180 I probably won't be able to see any solder bridges or unsoldered pads because the pads are under the chip. Can I safely test for bridges by using a multimeter to test for continuity between adjacent traces?


texts: N channel mosfet gate-source pin distance

texts: I bought a mosfet said to be rated 600V/5A, yet the gate and source pin are very close together (4,5 mm or something close to that). I've been told 230V traces on a PCB should be at the very least 6 to 8mm apart to prevent sparking. My conclusion was pins with different potential should naturally have that same distance. Is this MOSFET rating faulty or am I missing something out here?


texts: Designing a diode waveform shaping circuit resulting in specific transfer function

texts: Below is the circuit I built, yet the solution has the resistor as a load resistor instead of as a current limiting resistor. I am wondering if this circuit will output this transfer function.


texts:
I recently bought this MX1508 module from AliExpress.

I'm very impressed by its working given the low product cost. I would like to implement this in my next design, but I'm unable to find any schematics of the module online, neither is there any data sheet with an application circuit. Can anyone please share the schematic diagram of this module?


texts: Altera III Cyclone FPGA input synchronization problem

texts:
I have a problem with the  asynchronous input signal synchronization. I am trying to make  the IIC_Slave based on Cyclone III FPGA Starter Kit.

I saw 3 cases:

If I do not use synchronization triggers, I can enjoy a metastable clock control that affects as a number of positive- and negative- edges in each clock front. It is shown at pic 1.
If I use the synchronization triggers, this number of fronts disappears (as expected) but a new bug is appeared (it look’s like a reset signal on some negative edges of the clock signal). At the same time the reset signal are not detected by oscilloscope.
If I use the case 2 conditions with the SignalTap generated module all works correct! But it is not a valid possibility to solve problems. (738 logic elements and 41000 memory bits are wasted)

Here are explanations for the oscillograms.
The digital signal D7 – reset for the counter. The digital signals D6-D1 – bits of the shift counter. The yellow analog signal – data line from IIC. The green analog signal – clock line from IIC.

Please tell me if you have any idea about this situation. I am trying to make it works about a week and have a strong headache. I can’t even formulate a appropriate question for google.


texts: Where do AC/DC power adapter manufacturers get their high amperage (>12.3A) barrel plugs?

texts:
I was looking to swap out a barrel plug on a spare Dell 240 watt AC/DC power adapter to avoid having to purchase a ~$80 replacement with the correct plug.  I went off to Digikey and Mouser in search of a suitable plug (5.5mm OD x 2.5mm ID) and found plenty of options.  To my surprise, none of the options were rated at the 12.3A / 19.5V required for this adapter.
I delved further and visited connector manufacturers' websites and found that even for products advertised as "capable of withstanding much higher temperarure and current than standard power jacks," the maximum amperage rating was still only 10A.
Given the ubiquity of >200 watt @ ~19V AC/DC adapters with barrel plugs, I would never have thought it would be so difficult to find a suitably rated replacement.


texts: 555 timer circuit causes spikes on power supply line - how to decouple?

texts:
I'm using a 555 timer circuit similar to this one to blink a couple of LEDs at around 1 to 30 Hz:

The oscillations are causing huge spikes on the 5V supply line. There is an audio circuit running off the same 5V and the op-amps are picking up those spikes, rendering them audible.
I've tried a few things to decouple the 555 circuit:

insert a 220 Ω resistor between 5V and the supply pin on the 555 to limit the current draw
add 0.1 µF and 47 µF caps between the supply pin on the 555 and GND
add a 220 µF cap between 5V and GND

All of those seem to mitigate the spikes somewhat, but they're still clearly audible. What else could I do? Is the 555 just so greedy on current that I'd be better off with a different kind of timer?


texts: about power supply of opertional amplifier

texts:
I am constructing an operational amplifier as shown in the following figure. I use a batter as supplier for the OP Amp and set it up as a non-inverting amp circuit. I saw that the output was clipped while I feed it with a sine at about 1kHz. I wonder if there is any thing to do with the power supplier, what supplier should I use if so.

p.s. the intpu signal is of sine form, the peak-to-peak voltage is about 650mV, the frequency is about 1KHz or less


texts:
Consider this schematic:

Light 1 has 1.5V across it while Light 2 has 3V across it.

I was explaining to a friend how the points (indicated by Loop 1 and Loop 2) could both be used as a reference point. For example from the "point of view" of Light 1, "Loop 1" could be called ground.

What confused me was when he asked whether electrons (current) can travel both directions at the same time through Light 1.

Normally current flows through Light 1 in a clockwise direction, from V1, returning to V1.

The question he posed is, would any current flow (opposite the current from V1) from V2 through Light 1 and Light 2, back to V2?

I admit, I am stumped.

Edit:

I realize this is a totally basic DC question. If V1 were to become an open, then V2 would have to supply power to both Light 1 and Light 2 in series. (Pretending for the moment that these lights would simply be more dim.)

Given that current from V2 travels through both lights in this series circuit (with V1 open), how is it that the presence of V1 causes current flow from V2 through Light 1 to cease?

If I tried to answer this myself:

Adding the potential difference of V1 makes the node of Light 1 furthest from V2 more positive than the near node, so current will only flow past the point marked "Loop 1" in a clockwise direction. Without V1, the far node has less potential than the near node, so current flows in series.


texts:
I've got bend sensors which I want to connect to analog inputs of an Arduino-board.

Does it matter which of the headers I connect to the GND and which one to the analog inputs?

The bend Sensors are from Flexpoint. This is The electrical specification
http://23.235.218.36/~flexpoint/wp-content/uploads/2015/05/electronicDesignGuide.pdf


texts: Parallel RLC bandpass filter Bandwidth incorrect

texts:
I have been trying to create a bandpass filter with the cut-off frequency at \$\mathrm{200Hz}\$ and \$\mathrm{4800Hz}\$ I have managed to get the centre frequency to \$\mathrm{2500Hz}\$. The bandwidth on the to be non-existent and I have somehow created a really bad high-pass filter.

Below is the circuit I have created:

I am using a \$\mathrm{40nF}\$ capacitor, \$\mathrm{0.1H}\$ and a \$\mathrm{1718}\Omega\$ resistor in parallel which is all in series with another \$\mathrm{1718\Omega}\$ resistor.

This then creates the AC sweep:

In order to get the values I have I did the following:

I knew that resonant frequency is
$$
f_o= \frac{1}{2\pi\sqrt{LC}}
$$

I assigned a value to \$L\$ of \$\mathrm{0.1H}\$ and rearranged to get the capacitance

Then for bandwidth:
$$
B = R\sqrt{\frac{C}{L}}
$$
I knew the values of \$C\$, \$L\$ and the bandwidth (\$\mathrm{2600Hz}\$)

*I realise now that the values of the resistors are incorrect but I have also tried \$\mathrm{1450}\Omega\$ resistors and the same issue

Can anyone please explain to me why this has happened and how to fix it?


texts:
I have designed an assembler program for PIC 12F675, but it gives wrong timing. Datasheet says that internal oscillator is 4 MHz, and its instruction cycle is 4 clocks. Thus single instruction executes 1 us. Thus for timer 0, looping from 0 to FF with prescaler 1:256 I expect to get 131 ms per period (2 times with output value inverted), and for timer 1 and loaded counter value of B8FB I expect time of 18.18 ms.

I get:

  TMR0 -> 108 ms (instead of 131 ms)

  TMR1 -> 30 ms (instead of 18 ms).

What do I do wrong?

Code is below. It does simple things: for TMR0 it just checks for overflow bit and toggles LED state, for TMR1 it checks for overflow, and if it did, it toggles LED and resets counter back to B8FB.

CONF1   equ _INTRC_OSC_NOCLKOUT & _WDT_OFF & _PWRTE_OFF
CONF2   equ _MCLRE_OFF & _BODEN_OFF & _CP_OFF & _CPD_OFF
__CONFIG    CONF1 & CONF2

START
    ; in bank 0
    bcf     STATUS,RP0  ; bank 0
    movlw   02h
    movwf   GPIO        ; init GPIO
    movlw   07h         ; comparator off: set GP<2:0> to
    movwf   CMCON       ; digital IO
    clrwdt              ; clear watchdog
    clrf    TMR0        ; clear timer 0 value (mut be performed before
                        ; writing option register
    ; in bank 1
    bsf     STATUS,RP0  ; bank 1
    clrf    PIE1        ; disable peripheral interrupts
    movlw   07h         ; pull-ups enabled,
                        ; GP2/INT pin interrupt on falling edge,
                        ; TMR0 is clocked by internal oscillator,
                        ; prescaler for TMR0 is 1:256
    movwf   OPTION_REG
    clrf    ANSEL       ; all pins are digital I/O
    movlw   02ch        ; (1=input, 0=output)
    movwf   TRISIO      ; and set GP0/GP1/GP4 as outputs,
                        ; GP2/GP3/GP5 as input
;    movlw   034h       ; (1=enabled, 0=disabled)
    movwf   WPU         ; set weak pull-ups on all input pins

    ; initialize TMR1FLG value
    bcf     STATUS,RP0  ; change back to bank 0
    movlw   01h
    movwf   TMR1FLG     ; starting as NTSC mode until first interrupt

    ; finished configuring, now enabling interrupts
;    movlw   090h       ; interrupts enabled from INT pin,
;               ; TMR0 interrupts are disabled
;    movwf   INTCON     ; set interrupts reg

; test code

    ; start the timer, 18181 = 04705h, and -04705h=0b8fbh (timer counts up)
    clrf    T1CON       ; stop timer to prevent contention
    movlw   0b8h
    movwf   TMR1H
    movlw   0fbh
    movwf   TMR1L       ; set up TMR1 counter to 0b8fbh
    bcf     PIR1,TMR1IF ; clear timer 1 interrupt flag
    incf    T1CON,F     ; start timer with 4MHz/4 (T1CON is 01h now)

    ; clearing interrupt
    bcf     INTCON,INTF

test_loop
    btfss   INTCON,T0IF ; Timer 0 overflew?
    goto    no_tmr0     ; no, continue to main loop

    bcf     INTCON,T0IF ; reset timer 0 flag
    movf    W_TEMP,W
    xorlw   02h
    movwf   W_TEMP
    movwf   GPIO        ; alternate green LED

no_tmr0
    btfss   PIR1,TMR1IF
    goto    test_loop

    ; TMR1 overflew
    clrf    T1CON       ; stop timer to prevent contention
    movlw   0b8h
    movwf   TMR1H
    movlw   0fbh
    movwf   TMR1L       ; set up TMR1 counter to 0b8fbh
    bcf     PIR1,TMR1IF ; clear timer 1 interrupt flag
    incf    T1CON,F     ; start timer with 4MHz/4 (T1CON is 01h now)

    ; clearing interrupt
    bcf     INTCON,INTF

    movf    W_TEMP,W
    xorlw   010h
    movwf   W_TEMP
    movwf   GPIO        ; alternate red LED
    goto    test_loop


texts: Does ferrous/non-ferrous matter for ground planes?

texts:
I'm wondering about the best materials for making a ground plane. I've found some websites that claim that non-ferrous materials (i.e. aluminum) are generally poor ground planes (or at least not as good as the same size of a ferrous ground plane). Other sources claim this is a myth.

Does having a ferrous material for a ground plane matter? If so, why does it matter?


texts:
I have a problem with low power mode on STM32F030F4 (header board stm32f030f4p6 ).
When I try to put them in Stop mode they still consume about 5.6mA which is too much ( it should be about 500uA).
I put it to Stop mode through:

PWR_EnterSTOPMode(PWR_Regulator_LowPower, PWR_STOPEntry_WFI);

I don't do any RCC on GPIO configuration. Also I don't have any external devices connected to STM, any pullup resistors etc.

What am I doing wrong ?

My code :

    SystemClock_Config();

    GPIO_InitTypeDef GPIO_InitStruct;

      /* GPIO Ports Clock Enable */
      __HAL_RCC_GPIOF_CLK_ENABLE();
      __HAL_RCC_GPIOA_CLK_ENABLE();
      __HAL_RCC_GPIOB_CLK_ENABLE();

      /*Configure GPIO pins : PF0 PF1 */
      GPIO_InitStruct.Pin = GPIO_PIN_0|GPIO_PIN_1;
      GPIO_InitStruct.Mode =  GPIO_MODE_ANALOG;
      GPIO_InitStruct.Pull = GPIO_NOPULL;
             GPIO_InitStruct.Speed =GPIO_SPEED_LOW;
      HAL_GPIO_Init(GPIOF, &GPIO_InitStruct);

      GPIO_InitStruct.Pin = GPIO_PIN_0|GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3
                              |GPIO_PIN_4|GPIO_PIN_5|GPIO_PIN_6|GPIO_PIN_7
                              |GPIO_PIN_9|GPIO_PIN_10|GPIO_PIN_13|GPIO_PIN_14;
      GPIO_InitStruct.Mode = GPIO_MODE_ANALOG;
      GPIO_InitStruct.Pull = GPIO_NOPULL;
         GPIO_InitStruct.Speed =GPIO_SPEED_LOW;
      HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

      GPIO_InitStruct.Pin = GPIO_PIN_1;
      GPIO_InitStruct.Mode = GPIO_MODE_ANALOG;
      GPIO_InitStruct.Pull = GPIO_NOPULL;
        GPIO_InitStruct.Speed =GPIO_SPEED_LOW;
      HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

      HAL_GPIO_WritePin(GPIOA,GPIO_PIN_All,GPIO_PIN_RESET);

         __HAL_RCC_GPIOF_CLK_DISABLE();
      __HAL_RCC_GPIOA_CLK_DISABLE();
      __HAL_RCC_GPIOB_CLK_DISABLE();

while (1)
{

    HAL_Delay(1000);
  HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON,PWR_STOPENTRY_WFI);

}


texts: ABCD to scattering parameters derivation

texts:
I'm currently studying microwave engineering as a subject.

Everywhere on the internet and the books, they've only shown the derivation of S11 and S22 from ABCD parameters of a network. Yes, that's intuitive, since S11 is tau(in) and S22 is tau(out), and I have impedance formulas for both, making their calculation easy.

However, how do I derive S12 and S21 from ABCD parameters of a network? I've tried searching a lot, but I'm not getting the derivation, only the result.

I tried solving this on my own, but I'm not getting a hang of it, primarily because scattering parameters need transmitted and reflected wave while other parameters work on voltages/currents.

Any resources you can point me to? Thanks!


texts:
Please excuse what may be a simple question, I am very rusty when it comes to electronics having not looked at them at all for about 25 years! I hope someone can resolve my query.

I have a circuit design that takes a switch connected to ground. When closed the LED is on, when open the LED is off.

In this diagram the shaded switch and LED are part of a larger existing circuit which cannot be changed. The LED is just an example of my load.

What I want to achieve is to swap the action of the switch around. I want the LED on when the switch is open.

I could do this easily with a relay but I haven't got the physical space for a relay, I'm sure it can be achieved with transistors but I'm not sure how!


texts: Is it OK if a newly purchased electrolytic capacitor is supplying higher capacitance?

texts: I purchased new electrolytic capacitors in order to restore an old tube radio, and when I tested them with my capacitance meter I noticed that one them is having higher capacitance than it should. It's labeled as 22 mf / 450 V. but it's actual capacitance is 27.5 mf, would it cause any problem if the needed capacitance is only 20 mf ?


texts: For a laboratory / field test, I'm looking for an easy solution to measure the soil surface elevation. The test runs a flow on a bed. When the erosion takes place the sediment concentration goes high in the water and makes the water unclear. Therefore, the usual laser, infrared, or ultrasonic depth measurement does not doe to high sediment contents. The range of distance between where a device could be mounted and the bed is 15-30 cm. What kind of device can measure a short distance through sedimented water?


texts: How can I drive a 12V automotive relay with a uC running on 5V

texts:
I have a project where I need to engergize a 40A relay in a car. My uC based circuit is running at 5V via a 7805 and is mainly doing its own thing, but I need a digital out to energise the 12V relay, which in turn is driving an air conditioner clutch (as it happens).

My thoughts were (discounted in turn, possbly incorrectly)
1) a transistor (worried about 5V on base, 12V across CE, and if there's sufficient current)
2) an opto-isolator / opto-darlington (worried if it can drive the current, and at 12V if the power dissipation will be too high)
3) a relay (feels a bit silly using a relay to energise a relay, but otherwise seems sensible) but even so I'm likely to need more coil current than the uC can drive (or do I?)
4) an opto-isolator driving a relay (handles the 5V/12V disconnect nicely and the currents should be high enough) but now I feel like I'm badly overengineering.

I should mention that while I (and everyone) says 12V, in a running car it's usually >14V.

What would be my best and easiest approach, bearing in mind I'll be building a fair number, so cost is also a consideration...?


texts:
I am using LT1084 as a current control Regulator. Circuit shown below

Since the transistor Q2 is controlled by a PWM pulse so output voltage of LT1084 is varying as shown below

Since it is used as current controlled so there is a impact on the input voltage too as shown below

The supply voltage to LT1084 is 5V and 5V is generated by a switching regulator from 12V input.

Even-though in-between 12V and 5V a switching regulator is placed but the same impact(As on 5V supply shown in fig-3) can be seen on the 12V supply too.

Since the variation is very low around 0.0016V so it is manageable. But i am worried about the EMC and EMI. Is this variation will cause an impact on EMC/EMI?


texts: Driving a COB LED, Max Current that can be Applied

texts:
I am using Luminus COB with the rating given as Maximum power 65W and typical power 29W.
At 800mA the power I would get is 29W while at 1600mA it is 65W.

When I connect it to a power supply of 1400mA, the COB worked for 6-7 hours and later it started flickering and was burned out for some reason. The heat sink was for 100W.

However I connected an aluminium plate over the heat sink to fit the COB holder and made sure of the plate and heat sink making proper connection without leaving voids.

What can be the reason behind the COB burning out quickly?

The Current or the aluminum plate?

Link for data sheet of LED
http://www.luminus.com/products/Luminus_XnovaCXM18-GEN1_Datasheet.pdf

http://www.mouser.com/ds/2/260/LPC-60-SPEC-806139.pdf


texts:
In my basic electronics books, like Mileaf, they show an NPN FET as getting depleted if you apply a negative voltage, and the opposite for positive voltage.  And yet, for FETs like the IRF620, if I put 0V to the gate, that is good enough to shut it off -- it's not negative with respect to the Source or drain, is it?

Is it simply that the channel starts out very depleted, and it takes positive charge to populate it?  Just looking for a rough lay explanation, but a reference to more in-depth material wouldn't hurt either.


texts: I want to estimate power consumption of a battery powered digital circuit that has a CPLD (Lattice LCMXO2-256HC). It receives 64 MHz signal into LVDS input and 10 MHz, 2.5V into a schmitt trigger input. Its output is ~50 kHz so I'm not concerned about the output capacitance. So the question is, how does the input capacitance depend on the input settings, supply voltage, packaging etc or its just the process variation? The datasheet specifies 3-9 pF at 1 MHz, 25°C but that's too broad for me, maybe I can narrow it down somehow?


texts:
I develop commercially embedded hardware, using Microchip dsPIC or similar processors.

The firmware I have is sometimes very complex and costly, and needs to be hacker and tamper proof in hardware. All basic software protections are there, but for $500 - $1,000 the hex code can be retrieved via several foreign website services, even if there are security fuses (preventing only not-determined tampering).
After that, it is just a few months and the code can be reverse-engineered using disassembler, like IDA Pro.

How can I protect the hardware design a bit better (no need for military protection)?

Can you recommend another non-readable processors, or perhaps an addition to my existing design?

All I need is to hide few functions, I do not need the whole product. Also, it is not enough just to hide data in secure external memory, I need to hide a piece of program.

Update (based on many comments):
I have dsPIC and 4 full-time years of development on firmware (would take quite an effort to do it from scratch another way):

1) This product already sells and hackers have access if they want to

2) The NEW FIRMWARE is not released yet. Contains 5kB code which no-one from all competition has yet. I need to prevent anyone easily getting it for about 12 months after the release

3) There is no budget to go very exotic or complicated, maybe additional $10 per product, plus or minus

4) A solution like added SIM card might do the trick?

5) The function to hide does very tricky calculation, non-standard, to decrypt/encrypt 16 bytes. Known processes cannot hack it in 1 year, the function is needed, which is why I want to hide it.

6) I do not mind if it is publicly visible, when the request is sent to 'hidden' hardware, or if the response is publicly visible. Only need to hide the process calculating it, and cannot be inside the dsPIC processor.


texts: FatFs f_write not working in LPC1788 Timer ISR

texts:
I’m using LPC1788 MCU with KeilV5 compiler.

I Have a Timer ISR in which I read a value form specific ADC channel and write it into a SD-Card using FATFS library.

Here is my Timer ISR code:

void TIMER1_IRQHandler(void){
 if (TIM_GetIntStatus(LPC_TIM1, TIM_MR1_INT)== SET){
    ADC_Init(LPC_ADC,838);
    ADC_ChannelCmd (LPC_ADC,0,ENABLE);
    while (!(ADC_ChannelGetStatus(LPC_ADC,0, ADC_DATA_DONE)));
    ADCResult = ADC_ChannelGetData(LPC_ADC,0);
    sprintf(OutputSample,"%ld\r\n",ADCResultScaled);
    f_lseek(&File1, f_size(&File1));
    //f_write(&File1,OutputSample,strlen(OutputSample), &FilePointer);
    Counter++;
    TIM_ClearIntPending(LPC_TIM1, TIM_MR1_INT);
  }
}

There is no problem with above code but when I remove the comment sign from the f_write function, program stops and nothing executes exactly after Timer1 is enabled. (referred to debug, after TIM_Cmd(LPC_TIM1, ENABLE) is executed  in main function)

So I can’t write the data into the SD-Card in Timer's ISR.

I should mention that f_write function works fine outside the Timer ISR.

Can you guess where is the problem?

Thanks in advance.


texts: Cheapest way to limit 4xAA to 5v or less

texts:
I need to limit the voltage from AA batteries to 5.25V or less. Essentially, my circuit can operate from (minimum) 3.5V up to 5.25V, and I want to maximize run time by using 4xAA. Should I just run it off 3xAA batteries (giving 4.5V when full) or is there a way this can be done (without the expense of a switching regulator)? I have read that using zener diodes is not great since it wastes power and limits current, which is critical (I need to draw around 1.5A from the batteries).

EDIT:
Sounds like a boost converter with 2S2P batteries will be best. For reverse polarity protection, should I just include a regular diode in series? Wouldn't that lose 0.7v?


texts: Chua's circuit's pattern not fully shown

texts:
I have made a Chua's circuit, and hooked a soundcard oscilloscope to it, to measure the voltage across C1 and C2.

Circuit diagram:
Source:Kennedy 92(pdf).

Software used: soundcard scope.

The soundcard seems to only support mono input, so I have to log data of p.d. across C1 and C2 separately (Using the "log data" option in the software). I then plot them one against another in excel.

Plot:

A small part of data:

As you can see, the "double scroll" pattern is not clear. If you look at the data, you can see the left column (p.d. across C1) jumps between around 0.12 and 0.18 all the way.

Questions: Is the experiment successful? Is the plot above showing a double scroll? How can I make the double scroll more clear?

Also: I recorded data for at least 20 seconds, but only ended up with 100 data points. I am sure that a soundcard can record something like 40000 data points per second. What's wrong? What other software can turn wave files(.wav) into a .csv file so that I can plot using excel?

Note: both columns of data are with the heading "Channel 1 App" in the log file.


texts:
When there is just 2 field poles, the coil dipole moves to align with the external magnetic field. So a torque is produced.
However when there there are 4 field poles, why will the coil dipole move? From the below picture it seems the armature coil will not rotate no matter the starting position...


texts:
I'm trying to alternate between two 3W LEDs (forward current of 750mA, forward voltage of 3.6V). I've got a 555 set up in astable mode, and am driving the LEDs via npn and pnp transistors.  In practice, the LED that's run via the pnp transistor gets more current when it's switched on compared to the LED connected to the npn, and I'm not sure why. I'd just do away with the transistors all together and let the 555 sink/source the current for me, but I believe it can only handle up to 200mA, and the LEDs need more. FWIW, I'm running this circuit off of 2 3V coin cell batteries, and when connected directly to the LEDs they are extremely bright.

So my questions are:
1. Is there a configuration change I can make to get more current through the transistors? (more base current maybe?)

Is there a better or more efficient setup to perform essentially the same function?

Thanks!


texts: What does "preserving the logic expression" mean?

texts:
I already asked a similar question here but didn't get an answer that explained the reasoning. Now the question is I'm asked to find which of the circuits below preserves the logic expression, but I don't know what is meant by "preserves the logic expression". What I know is when we make the truth table just for the bottom NAND Gate for all cases (connecting the unused input to ground/+5V/E), only the case where we connect it to the ground (!(D&E&G) where G=0) we don't get 0 as an output. In the other cases we can get 1, and 0 as an output. Does this make the circuit with the ground connection, not preservative?  I would appreciate it if I could get an explanation (FYI what I mean by "unused input" is the Pin 1 on the bottom NAND Gate).
Thanks in advance.
CIRCUIT WHERE THE UNUSED INPUT IS CONNECTED TO E (TWO INPUTS CONNECTED TOGETHER)

CIRCUIT WHERE THE UNUSED INPUT IS CONNECTED TO THE GROUND

CIRCUIT WHERE THE UNUSED INPUT IS CONNECTED TO THE +5V POWER SUPPLY


texts: What happens if I use a 1A power supply in a router that requires 1.2A?

texts:
I have this d-link router, it's original power supply was 5V and 1.2A, but I found a 5V 1A supply.

It is working, but does it represent a risk to use it? What could happen?


texts:
Good day

I'm busy designing a small DC UPS to run some appliances when the power goes out. I am, however, having trouble with an element in the battery switch-over circuit.

I decided on using a circuit configuration similar to those that were discussed here, here and here.

I learned that replacing a diode with two opposite facing series-connected MOSFETS has the great advantage of a much smaller voltage drop, while still being able to block reverse currents when the devices are in the off state.

My question is: Does it matter which way around the MOSFETS are connected (e.g. source-to-source or drain-to-drain)? I have seen them being used in both configurations. Could somebody please explain the difference to me?

Please refer to the attached images to clarify my answer.

I am aware that the voltage difference between the two sources will allow me to just use or'ing diodes, but I need the voltage drop advantage on the battery side, unless there is a simple way to construct "ideal" diodes that can be used in stead. Unfortunately I am limited to through-hole components.

I am looking forward to any answers and responses.
Reinforcing critics on my circuit design is also most welcome.


texts: Is low pass filter more commonly used than high pass filter?

texts:
I have heard my teacher saying** that low pass filter is more commonly used than high pass filter because in high pass filter, frequency increases with gain and thus noise also increases and thus it distorts the output. In case of low pass filter, frequency decreases with gain and thus noise decreases and thus output is less distorted.

I was skeptical about this explanation as I thought that low pass filter is used as much as high pass filter according to needs and there is no such thing that 'this' filter is more often than used than 'that'. I thought of doing a bit of research and I found that there are two types of noise- whiter noise and pink noise. White noise increases linearly with frequency and pink noise is inversely proportional to frequency. Generally, white noise is more dominant than pink noise and it is said that pink noise is still not exhibited for frequency as low as \$10^{-6}\$ Hz. So, I am assuming that white noise is exhibited and for higher frequency, white noise is dominant and thus distort the output. I found this forum of help and it says how to eliminate noise in low pass filter.  So, my question is - Is low pass filter more often used than high pass filter? Is there any reason for this or is a false claim?

**My teacher said this statement during we were doing circuit analysis using simulink. He said to always use integrator instead of differentiator because in the laplace transform  of differentiation is \$sX(s)-x(0)\$ whereas the laplace transform of integration is \$\frac{X(s)}s - x(0)\$ where \$s=j\omega\$. So, in differentiator, frequency increase and so is noise(act as high pass filter) and in integrator,  frequency decreases and so is noise(act as low pass filter). So, eventually he made the statement of using low pass filter than high pass filter.


texts: Clearing/acknowledging of level triggered interrupts

texts: I am confused with the clearing/acknowledgement of level triggered interrupts in an SoC. When an interrupt is level triggered should the clearing be done in the interrupt controller or the bus controller (spi controller,gpio controller) or in the peripheral device itself. If I have to clear in the peripheral device itself then I should be connecting a line to from my SoC core to the device, correct? Could somebody also give an example say of SPI device using level triggering?


texts:
I have a weird problem on a Xilinx Ultrascale FPGA (although I think the board shouldn't matter). I have an array called logic[2047:0] enabled which is basically a flag specifying whether something on this index should trigger or not, I read a bit from PCIe which sets this flag. I set it to 1, and then later (many seconds later) I read it back when it should have triggered, it is sometimes 0 then. However, if I read it back again after some time becomes 1 (and remains 1). This happens maybe 1% of the time, rest 99% of the time it's okay.

I have verified that no meta-stability conditions are happening, I also initialize the enabled array to 0 with an initial block. Just wondering if anyone has any hints as to how to go about debugging this problem, I have already been stuck with for a week now, have tried many different things but nothing seems to work.

More info:
I used a vendor PCIe core which has 3 signals mem_w_addr, mem_w_data and mem_w_en. I use the mem_w_en to see if something is being written, and use the addr to find the index of that array, so I do enabled[mem_w_addr[15:3]] <= mem_w_data[0]. They also have a BAR0 register interface, I can read back the enabled being correct after writing it. But later (when it matters) it is 0, and even later it is back to 1 again. Could be a problem with reading back from the registers, but I'm not so sure.

the mem interface is clocked at 250Mhz and design works at 322Mhz so there is async fifo (which is battle tested 16 element fifo) that crosses the signals to the 322 clock.
I'm using vivado 2018.1 and xilinx ultrascale xcku035.
Simplied code

module (
   input i_clk_322,
   input wire[31:0] i_mem_w_data_322,
   input wire[18:0] i_mem_w_addr_322,
   input wire[31:0] i_mem_w_en_322,
   input wire[10:0] i_index,
   input wire       i_vld
);

logic i_vld_f;

always_ff @ ( posedge i_clk_322) begin
  if(i_mem_w_en_322[0] == 1)
     enabled[i_mem_addr_322[14:5]] <= i_mem_w_data_322[0];
end

integer i;
logic enabled_bit_vector[7:0]

always_ff @  (posedge i_clk_322) begin
   i_vld_f <= i_vld;
   for(i = 0 ; i < 8; i = i+1)
     enabled_bit_vector[i] <= enabled[(i_index<<3) + i];

   if(i_vld_f && enabled_bit_vector[x]) // x is index 0 to 7 through some computation
      // do something
end

endmodule


texts: Connecting brushed motor drivers in parallel

texts:
What are downsides of wiring 2 brushed DC motor drivers in parallel, so that they share the same control pins?

I have two identical brushed DC motors that each have a stall current of 2.5A. I have two identical brushed DC motor drivers that can drive a continuous 3A.

For my application, the motors have to spin at identical speeds and direction. Since a single driver can't handle the current should both motors stall, I'm going to use two drivers to handle each motor separately, but wire the control pins together.

Is there any reason this wouldn't work?


texts: how to convert/calculate \$\text{kJ}/\text{m}^2\$ to \$\text{W}/\text{m}^2\$

texts:
I have some solar radiation data that comes in \$\text{kJ}/\text{m}^2\$. These data were formerly available for download in \$\text{W}/\text{m}^2\$. I tried to find some ways to do the conversion from \$\text{kJ}/\text{m}^2\$ to \$\text{W}/\text{m}^2\$, but without success.
Is this conversion possible?


texts:
I have problem when I send high signal from arduino it not open source and drain.

Why is it?

Here is datasheet:
http://pdf.datasheetcatalog.com/datasheet/fairchild/IRF630B.pdf

I found Gate-Source Voltage: ± 30 is that mean I must send 30VDC to open conection between source and drain?


texts: current sensor on arduino inaccurate at zero Load

texts:
I am currently making a power meter and used a Current sensor (SCT013 30A/1V) from yhdc.com. Every thing went fine especially the circuitry following the tutorial from ( https://openenergymonitor.org/emon/buildingblocks/ct-sensors-interface ). Am using an Arduino nano. and emon library to calculate for current.

my problem is at no load connected, even when no load wire is passing through the sensor, I get small jumpy values of readings of the manner below.

Irms: 0.04
Irms: 0.04
Irms: 0.04
Irms: 0.06
Irms: 0.03
Irms: 0.06
Irms: 0.03
Irms: 0.07
Irms: 0.04
Irms: 0.03
Irms: 0.03
Irms: 0.06
Irms: 0.04
Irms: 0.04

I have double checked the hardware and there is no problem.

when a load is connected with a current draw of more than 0.07A, the readings are perfect and stable. I was able to get the below reading when I connected a 75W lamp, and the voltage is 240V.

Irms: 0.31
Irms: 0.31
Irms: 0.31
Irms: 0.31
Irms: 0.31
Irms: 0.31
Irms: 0.32
Irms: 0.32
Irms: 0.31
Irms: 0.31
Irms: 0.32
Irms: 0.32
Irms: 0.31
Irms: 0.32
Irms: 0.32
Irms: 0.32
Irms: 0.32
Irms: 0.32

My code is as below.

#include "EmonLib.h"              // Include Emon Library
EnergyMonitor emon1;              // Create an instance

void setup()
{
 Serial.begin(9600);

  emon1.current(0, 29);        // Current: input pin, calibration.
}

void loop()
{

   float r1=emon1.calcIrms(2000);
   Serial.print(" Irms: ");
   Serial.println(r1);

 }

I would like my meter to accurately measure even the smallest consumption of say a phone charging in a domestic setting.\ or the smallest energy saver bulb.

Does anyone have an idea why this I get this kind of noise and how to solve it?


texts: Plate current use of 12Ax7 vacuum tube at low voltage

texts: Does anyone know the current used by at 12Ax7 (or similar) vacuum tube when in normal (triode) operation using a plate voltage no more than 10VDC? I'm not considering the heater current (~300mA at 6.6V), just the grid to plate current or the current drawn from the power supply. I've simulated the tube in MicroCap with little luck and I don't have my equipment to physically test it.


texts: Modular synth clock and sequencer control by relay

texts:
My modular synth master clock and sequencer don't communicate well. The need to have reset trigger for the sequencer has forced me to come up with a module that can send a control voltage to the clock's start/stop CV input as well as a send a trigger on Stop to the sequencer's Reset input.
I came up with the following circuit centered around a latching reed relay, a DPDT momentary switch in 3-way configuration, and a NPN transistor to send a trigger.
Will it work as expected? Am I missing something?


texts: How to calculate C for an AM demodulator?

texts:
I have read this equation from Savant's book that is used to calculate the capacitor for a demodulator:

I've tried to calculate my circuit with this equation, but it didn't work. Then I tried to recalculate this example from the book, but I don't know what is 'w' here in the example:

A 15MHz radio frequency carrier is modulated with a 5kHz signal with a modulation index (m) of 0.5. If the load resistance is 5 kOhms, what capacitor value must be added in parallel to the load to filter the radio frequency signal?
response: 0.013 uF

Can you please teach me how to obtain w so I can calculate C? I tried with 15MHz, and 5kHz, but I don't get the same answer.


texts: PSPICE temperature simulation of a resistor

texts:
I am using OrCAD/Cadence PSPICE Lite 16.6.
I am trying to do a temperature analysis of a circuit. In particular a resistor.

simulate this circuit – Schematic created using CircuitLab

Now, the temperature is from -30 to 60 Celcius.
I understand that knowing the ppm I can do a .model as shown below -

R9 N1 N2 R1  10K
.model Rmod8 TC1 = 1.5E-3

The TC1 - denotes the ppm (1500ppm).
Now, the resistor als has a random tolerance of 1%. How do I give that ? Like a range. And at each temp ( from -30 to 60) the random tolerance of 1% exists. How can I implement that in PSPICE code ?

Also, if I dont need to use the TC1 approach(i.e through a .model), how can I do it through a mathematical formula. In other words -

Ta -room temp,
Tt - temperature under study(from -30 to 60)
TCR - ppm property of resistor
Ra - resistance at room temp
Rt - resistance at Tt.

Now, the formula for Rt = {Ra*(TCR*(Tt - Ta))/10^6}. I tried implementing this using the .param command as shown below -

.param R1 1000
.param R1t_temp  = {R1*(TCR*(Temp - Ta)/1000000)}
R8 3 5 R1t_temp
.Dc lin Temp 28 60 2

So, I am doing a DC sweep analysis of temp - from 28 to 60.
But, there is an error as the R1t_temp  value obtained from the .param is not put in the R8 3 5 R1t_temp.


texts: Design of a simple transimpedance amplifier for large area photodiode

texts:
I'm a mechanical engineer, who has the luck to design an easy transimpedance amplifier circuit to convert the current of a photodiode to a voltage between 0 and 5V (without really knowing anything about it.)
I used this reference design from Texas Instruments and did the calculations.
After some weired results with the voltage divider in place, I changed the design to the one you can see in the next picture.
(The values of the components are different in my design.)

I ended up with some "useful" measurements, which showed more or less the same signal pattern compared to a professionally built transimpedance amplifier. See picture below. Blue line is my DIY-version, orange line is the bought amplifier.
As you can see, there is a lot of noise in my design. I'm not really deep into electronics so I don't know how to improve the performance.
Can somebody give me some advice how I can reduce the noise?
FYI: I used this opamp.

EDIT: I added the pitures of my PCB + the values of the components.
When I read through the comments I realized that there is more to consider than I expected. I dont need a super low noise transimpedance amplifier, but lower noise would be great. Are there any easy fixes which I can use without additonal curcitry?


texts:
In the following circuit, LEDPWR goes the power lines of some digitally addressable LEDs. But the LEDs are not always on, and even when they are not being lit, they are consuming about half a milliamp each, which will drain the battery over a few days even if it's not in use.

I was under the impression that I could use a MOSFET like a switch. So the micro-controller could simply set the gate to LOW and the LEDs would no longer be connected to power and would not drain the battery when not in active use.

This is the circuit I devised.

But it doesn't work like I expected. When I pull the gate LOW, current appears to continue to flow, and the LEDs continue to draw power. Why?

I tested each prong of the transistor with a multimeter in both the on and off states and found that despite the gate being LOW, I'm getting voltage on the drain. Here's what I measured:

ON

Gate: 4.20V
Source: 4.36V
Drain: 3.73V
Current: ~18mA

OFF

Gate: 0V
Source: 4.11V
Drain: 3.51V
Current: ~5mA

If I disconnect the LED power wire in the OFF state, current plummets to less than 0.1mA, so the MOSFET is clearly not doing what I expect.

So first, how do I get my MOSFET to actually turn disconnect the source and drain?

And second, why am I seeing a 0.6V loss at the drain? With a single cell LiPo (3.7-4.2V) as a power source, that's a lot.

My MOSFET's datasheet: MOSFET datasheet: http://www.nxp.com/documents/data_sheet/2N7002P.pdf


texts: Single supply non-inverting amplifier using op amp

texts:
I'm working on building a distortion guitar effect pedal for an analog electronics class I'm taking. I am struggling with building an amplifying circuit using an op amp (we just began learning about them), and I'm hoping I could get some tips. Guitar pedals generally run on a single 9V supply. This is the circuit I attempted to build in lab today, however, it did not give any output.

simulate this circuit – Schematic created using CircuitLab

In particular, I am wondering if it is necessary for me to bias the non-inverting input at 4.5V, and if this circuit would give me the desired gain of +10 if I build it correctly. This is not the specific Op amp I'll be using, I'm not sure which I'll be using yet, I haven't gotten that far.


texts: Reduce impedance for power traces of a decoupling Cap when ground planes are not directly under

texts:
I am using an SHTC3 temp and humid sensor to send readings using I2C lines to the MCU.

Based on the datasheet for SHTC3 to make sure the sensor is reading ambient temp without the interference of the heat coming from traces and planes that connect to the MCU and other heat producing ICs, it is recommended to limit the trace lines to the MCU and not to have copper filling under the SHTC3 chip. As well as adding an enclosure shield to prevent heat radiation.

When adding a decoupling cap on the power lines to the chip, there are the traces that need to connect to the planes and that requires a trace spacing as seen below. Best way is to increase the trace width to the cap to lower impedance to the cap since there is no copper filling under or around the cap. Does this seem accurate?

Here is the schematics:

I would appreciate any feedback you all could provide. Thank you so much!!


texts: Pop and thump sound coming in through speaker when turning the class D amplifier ON

texts:
I am using TPA2005D1 class D amplifier IC, whenever I am turning ON the IC, while the volume is set to high, it is making loud thump and pop sound, then it goes away and works fine. But while the volume is set to low and then I turn ON the device, then is no thump and pop sound.

The line level input that I am giving to TPA2005D1 contains small DC offset, but I am using coupling capacitor to make offset zero. (Please find the schematic attached below)

After getting the response from the users I am finding two approaches to solve this problem.

Method 1:
Can we connect 100K resistor between C15 and ground ; 100K between C16 and ground, so that there is no buildup of charge in the capacitor as to reduce the pop sound in the first place.

Method 2:

We can delay the start of the TPA2005D1 using RC circuit in the shutdown pin, so that pop sound will be eliminated.

Should I do Method 1 or Method 2?


texts: What happens if I supply a higher voltage than the rated voltage of my jack?

texts:
I want to replace the original jack from my notebook with a new one since it is broken (and I would like to avoid to replace it with the same as the original). The original AC adapter supplies 19V and a bit less than 3Amp. However I can't find on Internet a DC jack (for pannel-mounting use) whose rated voltage is 19 V. All I find are 12V DC / 3Amp MAX jacks.

So what would happen if I use my AC Adapter with that new power DC jack (so 12V 3Amp) ? Will it overheat or is it safe?

Thanks (and sorry if that's a duplicate).


texts: Is making LED at 10MHz blinking rate good?

texts:
I am trying to create a project for transmitting visible light over optical fiber.
I am planning for a frequency of 10MHz for data transfer. Is a LED(including infrared) good for this blinking rate? Or what alternative I have if I want to use visible/infrared spectrum?

Also what should be the best receiver for this blinking rate? Photo Diode, TSOP(if infrared)


texts: Cause of systematic offset in operational amplifiers

texts:
I have some doubts about the systematic offset problem of an op amp. Here (slide 15) it is quite well explained:

Briefly, it is due to the fact that Q6 and Q7 may not be crossed by the same current. But there are two things that I do not understand:

1) I have also been told that the offset is due to the mismatch of the main transistors of the differential pair. Is this mismatch linked to the current mismatch of Q6 and Q7 shown by the previous slide?

2) How is it possible that Q6 and Q7 are crossed by different DC currents? The load is assumed to be an infinite impedance and the only path between Q6 and Q7 goes across a capacitor Cc, which is an open circuit at DC.

In my university course I have also used this schematic for an op - amp:

This schematic is similar to that shown in the initial slide, with the difference that now there is a third stage which is a voltage amplifier. Let's zoom on the second stage (which is the cause of the systematic offset):

The current that flows in M7 and M12 is the same: and it is obvious because there are not other paths for DC current! But there is a small DC offset in output (116uV) when DC input values are 0.

This seems to be in contrast with the definition of systematic voltage given in the previous slide.