texts: Standard 12 Volt DC fan for PC: how much AC ripple can support? Does ripple increase noise?

texts:
I want to know which is the mechanical effect to run a DC 12V brushless common fan with a very basic and poor power supply (just a diode plus a low value capacitor, no regulation at all). In principle,  which are the effects of the AC ripple? If I increase capacitance (so decrease AC ripple) should the DC fan run "better", faster and make lower acustical noise?
Can high AC ripple decrease fan life also?


texts: $random in Verilog doesn't seem to be working

texts:
In Verilog, $random generates different random inputs but this doesn't seem to be working when I try. Each time I use $random for a reg or integer, I must be getting different different values but that is not so. I tried it even in Modelsim simulator.

http://www.edaplayground.com/x/Umt

`timescale 1ns/1ns
module tt;
integer kk;

initial
begin
  repeat(5) begin
    kk=$random % 10;
  end
  $monitor("%d",kk);
end
endmodule


texts: How to solve a RLC circuit with a dependent current source

texts:
I am working on the following RLC circuit in the drawing.

I am stuck at the part where the switch goes to 'b'. That's where the dependent source comes to play. Should I use nodal analysis or find the Thevenin equivalent circuit?


texts: Measurement of output current of a photodiode

texts:
I am a German student.  My task is to conduct a characterization of a photodiode (KPEIMC-UDCOM by Kyosemi.)  The photodiode will be illuminated by 850-1550 nm laser diodes. It would be good (but not absolutely necessary) if I could do frequency measurements up to 20 MHz.
I'd like to measure the I-V curve, spectral sensitivity, rise/fall time, signal-to-noise ratio etc.
To get a measurable output, I'd like to use a transimpedance amplifier. But that is not what this question is about. My problem is more about the measurement of the voltage and the processing of the data.
I'm not sure whether to use just an oscilloscope, a microcontroller (Arduino?) or something else to get the data and get them plotted.
As I have not much of a background in this topic, it would be nice if you could share some insight on how you would acquire the data for the characteristics I am supposed to investigate.


texts: Why the arc when bonding-on during high voltage repairs?

texts:
When working on high voltage power-lines via helicopter the technician will "bond-on" with a steel wand called a hot-stick. During this process an arc is conducted from the line to the wand. Now, since the helicopter is floating both literally and electrically, why is there any potential between the line and the wand?

My guess is that because of the alternating electric current in the power-line there is therefore an alternating expanding and collapsing magnetic field present in close proximity to the helicopter. This sets up a charge polarization in the frame of the helicopter 180 degrees out of phase with the current and therefore an electrical attraction occurs which produces an electric potential.

If this is true, even though the electrons are not free to move in a bird (as they are in the metal helicopter frame) they are able to rotate and still set up a charge polarization (much like a charged balloon sticks to a wall) and therefore when a bird "bonds-on" to a wire don't you think they feel a little tingle at first?

One other thing. Is it true that by virtue of the fact the the helicopter circuitry is an isolated one, they can bond-on to either line and that line will be the ground reference for the ground of the helicopter circuitry?


texts: What are the parameters I should consider while selecting a Memory IC?

texts: I have a Microcontroller which needs to be connected to a memory using SPI Interface. What are the major parameters that I have to consider while choosing a Flash IC?


texts:
I purchased a 2.5mm TRS socket to receive LANC signals. I am try to wire it to an Arduino Mega. Am brand new to this.

The connections for LANC are this:

T = LANC protocol
R = 5V DC
S = Ground.

The connector has 3 prongs on it but they don't seem to be labelled and I can't find anything that distinguishes the tip, ring and sleeve. So can anyone help with that?

Bonus points if anyone can tell me where they go on the Arduino.

Thanks a lot


texts:
I am looking for a microcontroller to use in a project which is very space-limited.  What microcontrollers have some of the smallest packages?  This does not need to be high performance, most microcontrollers are more powerful than is necessary in this case, but it does need to be tiny.  Atmel's ATtiny20 comes in a WLCSP-12 package which is 1.55x1.4x0.53mm, this is not bad.  What other options are there along those lines or smaller?  (From any family, doesn't have to be Atmel)

Update: with at least 4 I/O pins.


texts: SMPS power supply shows strange AC voltage output

texts:
Hi I have been using a simple laptop power adapter (15V) for my electronic
lab-works. And today I'm troubleshooting some RF circuits, and I found a little guilt
about ground loops, So I check everything using a analog AC voltmeter, Finally
I realized that I got 35V AC voltage across power supply lines (output from power
adapter).

What on earth this could be happen? Any idea?
Why this happen ? Should I ignore this?


texts:
I have a schottky diode in a sot23 package that is composed by 2 schottky diodes with a common catode connection. I need to use one of them.

Should I let the second floating with unconnected pin or should I connect it to ground?


texts: Is there any reasonable cause for a LED driver to yield more voltage than it is labeled with?

texts:
I'm trying to make a light using an existing COB LED module of unknown health, and a new 300 mA constant current LED driver. I hooked up the LED to the LED driver and got 38V DC on the output instead of the max 20V it has printed on the case.

Is this a definitive sign for a defect or is there a possible explanation for this (e.g. some LED specific "you start with a high voltage and ramp it down once current flows" strategy)?
(Bonus:) If is this indeed an indication for a defect, how is an LED going to react to such a high voltage? I measured no voltage on the LED and it stayed dark. Is that expected or indication of a defect?


texts: Pull signal to GND in 3.3V circuit, best way to do it?

texts:
I want to pull down a signal (5V logic) via my ESP32 (3.3V logic) to logic low. If the GPIO output is set to logic high, the signal should be set to logic low. If the GPIO of my ESP is set to low, the signal should be untouched.
What is the best way to do it?
Is pulling down a signal-line to GND safe, or is there a better way to do it? Because it's a short circuit, isn't it?

simulate this circuit – Schematic created using CircuitLab
Just FYI: I don't know much about the signal. I just know, that its 5 V logic. I don't know the circuit behind the signal.


texts: Why is the WL charged at Vccp for DRAM cell?

texts:
Qouting from Dynamic random-access memory - Wikipedia

  Reading or writing a logic one requires the wordline is driven to a voltage greater than the sum of VCC and the access transistor's threshold voltage (VTH). This voltage is called VCC pumped (VCCP). The time required to discharge a capacitor thus depends on what logic value is stored in the capacitor. A capacitor containing logic one begins to discharge when the voltage at the access transistor's gate terminal is above VCCP. If the capacitor contains a logic zero, it begins to discharge when the gate terminal voltage is above VTH.

My question is, why does the WL need to be charged at VCCP (i.e VCC + Vth) and not at VCC? How does the capacitor discharging depend on WL voltage?


texts:
Im new to electronics and have been trying to devise a cutoff circuit for a 2s 7.4v Lipo Battery. I have found a few places that have the schematics but am unsure as to that parts are needed for a specific layout. see the link bellow.

Adding voltage cutoff to a circuit?

I have read that a good way is to use the op-amp schematic referenced in the first post. now it shows 2 ICs and im unsure as to if each will be the same TLV431 also is there a way to incorporate a speaker that would sound when the cutoff voltage has been achieved (6.2V)?

parts list that I have come up with is:

TLV431 x 1 (IC1),
unknown x 1 (IC2),
STP80PF55 x 1(P-channel mosfet),
15k x 1 (R1),
10k-100k? x 1 (R3) How does one figure out what resistor is needed?,
R2= R3 x [Vmin/1025 -1]This on im confused of

Any Help will be greatly appreciated!


texts: How to modify this circuit for variable clipping without affecting gain?

texts:
Below is a basic implementation of a circuit used to clip an incoming signal using the diodes in the feedback loop of the op-amp. Since the diodes are different they have different characteristics, specifically Vf which causes each one to start conducting at slightly different voltage. The diodes are also placed in opposite to each other so one may conduct on the positive half of the wave and the other on the negative (given the input signal and gain product is high enough).

Each one of the diodes will start conducting when the voltage between the inverting input and output of the op-amp exceeds its Vf.

I would like to modify the circuit so it would behave in the same manner but I will be able to control the DC offset at one end of the diode.

For example, you can see that the input is bias with a 5V DC voltage, so a diode starts conducting when the voltage reaches 5V + Vf. I would like to be able to adjust the bias voltage over a small range so that a smaller signal and gain might cause clipping or the other way around.

I would like to do this without moving the diodes outside the feedback loop. I tried inserting a simple series resistor after the didoes and it seems to me that by altering the value of the resistor I can obtain the effect I want but in practice this does not work well enough and interfere with the gain of the circuit which I don't want to change because of the diode adjustments.

I'll appreciate suggestions if this is possible.

simulate this circuit – Schematic created using CircuitLab

OK so here is the circuit suggested in an run-able and edit-able version :)

simulate this circuit


texts:
I had some question about the bootstrap capacitor on gate driver.
First, the bootstrap capacitor is used because the voltage on the high side drivers gate need to be about 10-15 volts higher than the voltage on its drain. However , if my input supply is about 20 V and the gate voltage is not higher than the source voltage as well. Is it possible to turn on?

Second, to turn on an N-channel FET, we need a gate voltage which is higher than the source voltage. How can this be? the gate voltage cannot supply more than 15 V right? If my input supply also contribute about 20 V, can it be turn on?


texts: Unknown symbol on schematic (Circle with "M" underlined)

texts:
I have a symbol on my schematic but I cannot figure out what is this? I looked through Internet and didn't find anything(

Is this a microphone? If so give me some helpful links to learn something about it. I have to draw this element and make a pattern for it. So links for pattern would be also great.
The whole scheme looks like this:


texts: Oscilloscope trace shows two voltages at the same time

texts: Sorry if I worded the question strangely, I'm just not exactly sure what's going on. I'm analyzing a PCM audio stream coming out of an ESP32. I've got the DOUT pin connected through a 10x probe to channel one of my scope, and CLK connected to channel 2. CLK looks normal to me, but DOUT is just 2 parallel lines. Normally I would assume the signal is just too fast, but even on the shortest time base, the signal looks like 2 continuous lines, and the signal shouldn't be that fast anyway. The pin can't be at zero and five volts at the same time, right? Am I doing something wrong, or interpreting the data wrong?


texts: Is this a safe way to add extra current control for a DIY tDCs device?

texts:
I have put together the well known DIY tDCs-device Inthinkerator MK1, and wanted to add an extra safety feature, but I dont know if this is the correct way to do it. The original design is without the 2N4393, but I've added it.

tDCs stands for transcranial Direct Current stimulation. The concept is nothing new, but has gained alot of attention lately. Alot of research is being done, and there is alot to read about it. https://www.ncbi.nlm.nih.gov/pubmed/?term=tdcs is one source.

(You can also search for snake oil, but it does'nt seem to have the same medical application potential... https://www.ncbi.nlm.nih.gov/pubmed/?term=snake+oil)

My plan is to set a max current on the 2N4393, so if something went wrong with the original setup with 2N3904, it still would'nt go over set current limit. That's my plan at least.

By setting the trimpot at 2N4393 to never let it put thru more then 2,5mA, and then use the 5k pot to 2N3904 to be able to change the output from 0,36 to 2,0mA.

Can someone say if this is a bad idea? The simulation in Qucs "says" it will work as intended.

Would appreciate all help!


texts:
4 Pins, 1 row.  ~1.97mm pitch (hard to measure with my calipers), 6.57mmX10.78mmX10.71mm
Says "1c 5102 MK 1 15" on it.


texts: STM32 DMA: continuous peripheral to memory (array) transfer

texts:
I am trying to use a DMA in circular mode to transfer data from an ADC to an array that will hold the data. I need to concurrently use the incoming data (in this case, I am using AT commands to send the data over Wi-Fi with the esp8266 module)

I am wondering what the software flow would look like.

Here are some questions:

How will the DMAC know when to wrap around when it reaches the end of the array? -- i.e. how can I ensure that the DMA won't transfer data past the last array index? (Is this size limit defined by the DMA_BufferSize?)
Because I want to concurrently use the collected data, I am thinking of using 3 arrays to store the data. I would read & erase the data out of one array whilst the others are being filled by the DMA, and it would cycle around. Is it smart and/or possible to change the DMA destination constantly like this?

Thank you.


texts: Every optocoupler has min and max current transfer ratio. I have read articles that said always design the circuit using the minimum current transfer ratio. However, I want to understand which parameter affect the transfer ratio. I did look at a datasheet of an optocoupler but couldn't find any information about it. Could someone please explain them to me?


texts:
I'm trying to simulate a simple pulse generator that gets activated by a voltage source vs.

vs starts at 0V and switches to 5V at 10us where it remains at 5V for the duration of the simulation.

When I run the simulation and plot v(in), the voltage remains at 0 for the duration of the simulation.

Below is the netlist:

* Pulse Generator - I
* Section 2.2.2 C
* Figure 2.11

* DC bias
vcc 4 0 5V

* input
vs in 0 pulse(0 5 10u)

* Q1
R1 in 1 10k
R2 4 2 1k
Q1 2 1 0 myq1

C1 2 3 10n

* Q2
R3 4 3 10k
R4 4 out 1k
Q2 out 3 0 myq2

.model myq1 npn (bf=100)
.model myq2 npn (bf=100)

.tran 1ns 500us
.end

I figured out my issue.
I sourced a circuit file and assumed I didn't need to source it again after I made edits to the file.

Everytime I make changes to the circuit file, I must source it again for the changes to take effect.
There must've been an error when I first sourced it, and I wasn't seeing the changes I made until I resourced the file.

Thanks! :-)


texts: How does a twisted pair cable reduce inductive coupling compared to non twisted pair cable?

texts: Can anyone explain this concept with figures for both non twisted pair cable and twisted pair cable?


texts: How to estimate solar panel output as a function of solar radiation

texts:
Apparently, according to EarthScience.SE, the measurement of how "bright" a given day is, is measured in units of kWh/m^2, known simply as "solar radiation". Apparently, 3 kWh/m^2 is the average brightness of an American summer day (useless fact).

This solar panel claims an output of 6V at 330mA. Obviously, solar panels will not perform the same on cloudy, darker days.

What I'm looking to do is to put together an equation/algorithm that will take solar power (in Watts) and solar radiation ("brightness"; in kWh/m^2) as input, and tell me what the adjusted power output is for that panel, based on the current brightness.

As an example, using that particular solar panel and a given point in time when, say, there is only 2 kWh/m^2 of solar radiation in the given vicinity, then the equation might yield something like this:

// Example only
AdjustedPowerOutput(normalOutput, solarRadiation) = normalOutput * (solarRadition / 3) = 1.98 Watts * (2 kWh/m^2 / 3 kWh/m^2) = 1.98 Watts * .667 = 1.32 Watts

So, if this equation was correct, at that point in time in the given day, the panel will only output 1.32 Watts.

How can this "adjusted power output" actually be calculated?


texts:
It is widely known that resistive termination (e.g. 50 Ohm to ground) is superior when noise is no concern. Specifically in the block diagrams of RFICs I see many 50 Ohm resistors to ground directly driving a CMOS inverter buffer, when used as clock or LO pins.

This works obviously nice in the absence of parasitics but as soon as the bondwire and pad capacitances come into play, the concept of resistive termination fails for me. Consider the following example:

simulate this circuit – Schematic created using CircuitLab

where the source resistance (50 Ohm) is fixed, Cpcb models the PCB pin, L the bondwire, Cpad the bonding pad on the die and Rt denotes a resistor to be chosen freely.

Not only is the optimum value NOT 50 Ohm but around 30 Ohm, also the best possible S11 I can get seems to be around -12 dB. Sounds pretty miserable for resistive termination.

How is this done in practice?

PS: I am not interested in general answers to the reasons of matching and solutions outside IC context. Clearly off-chip matching networks may be a solution but I do not think this is what is used in the context of RFICs.

By purposefully making the bondwire longer (more L) and adding capacitance to Cpcb and Cpad, one could choose L, Cpcb and Ppad such that sqrt(L/C)=50 (e.g., L=3n, Cpcb=Cpad=1.2pF) I can bring S11 down to -20 dB or even more but this does not sounds like a practical option to me. Above all, -20 dB is not a good number in an "ideal" scenario either.


texts: How to "supply the supply" of a low-noise discrete circuit

texts:
I need to test a sensor, and I want to measure its resolution. My main concern regards keeping noise and disturbs (e.g., 50 Hz) as low as possible.

The circuit itself (amplifiers, filters, ...) is fully analog, and is designed to be low-noise. No problem here. The circuit is designed so that all its active components are supplied between ±5 V. The total current consumption is expected to be something around 200 mA.

Now the problem: which is the best way to provide the supply voltage to these active components (op-amps, VGAs, INAs, ...), knowing that I have a bench-top DC Power Supply and some batteries?

OPT#1

±5 V from DC Power Supply. Just 10 uF capacitors close to the connectors, 100 nF close to the devices (or proper value according to datasheets), and that's all. Is this enough to have a good supply voltage?

OPT#2

±10 V from DC Power Supply -> Resistive dividers to get ±5 V -> Passive low-pass filters (e.g., 1 MOhm, 1 uF --> around 150 mHz pole) -> Analog unity-gain buffers supplied between ±10 V from Power Supply. Is it better to use active filters? Or LC passive filters?

OPT#3

±10 V Battery -> Resistive dividers -> Analog unity-gain buffers supplied between ±10 V from DC Power Supply. In this way, the 200 mA will be supplied by the Power Supply, and the battery will last long (I can use high-value resistors for the divider so that its current consumpion is negligible). Is the PSRR of typical op-amps enough to have a good output signal?

OPT#4

±10 V Battery -> regulator. In this way, the 200 mA will be supplied by the regulator, i.e. by the battery, that will be discharged fast! Which regulator should I use? DC-DC switching? Linear? LDOs? LDOs with ±6 V batteries so that the power consumption / heating is minimized?

OPT#5

Say yours!


texts: Trouble Using Optocoupler (AL-ZARD DST-1R4P-N)

texts:
I'm attempting to use an Al-Zard DST-1R4P-N optocoupler (3.3v to 12v) to take the 3.3v signal from a Raspberry Pi and control a 12v solenoid. The image below represents how I'm attempting to wire it up, but it's not working.
Without any wire to terminal O1, the corresponding LEDs turn on and off in sync with the RPi pin going high and low, as expected. However, when connected as shown below, the LED on the output side stays lit all the time while the LED on the input side behaves as expected.

Switching the cathode doesn't work either. In that arrangement, the output LED never turns on (instead of staying on all the time) and the solenoid still doesn't move.

What am I doing wrong?


texts: Closed-loop systems - discrepancy between Simulink and Arduino

texts:
I am trying to figure out how to reproduce closed-loop systems in Arduino that were designed initially designed in Simulink.

Take the following closed-loop system with unity feedback and gain:

Where Gp(z) is a discrete transfer function, taking the form of:

\$Gp(z) = \frac{0.1288z - 0.06234}{z^2 - 0.7813z + 0.1817}\$

The closed-loop system was replicated in Arduino with the following code:

int iteration(0);
double y(0), e(0);
double Gp_y_0(0), Gp_y_1(0), Gp_y_2(0), Gp_x_0(0), Gp_x_1(0), Gp_x_2(0);

void setup() {
  Serial.begin(115200);
}

double Gp_z (double Gp_x_0) {
  Gp_y_0 = (0.128767938742003 * Gp_x_1) + (-0.062336933973903 * Gp_x_2) - (-0.781272292546052 * Gp_y_1) - (0.181746970098960 * Gp_y_2);
  Gp_x_2 = Gp_x_1;
  Gp_x_1 = Gp_x_0;
  Gp_y_2 = Gp_y_1;
  Gp_y_1 = Gp_y_0;
  return Gp_y_0;
}

void loop() {
  delay(500);
  e = 20.0 - y;
  y = Gp_z(e);
  Serial.print(iteration); Serial.print('\t');
  Serial.print(e, 9); Serial.print('\t');
  Serial.print(y, 9);
  Serial.println();
  iteration++;
}

The plant, Gp, is implemented correctly in Arduino. I tested its open-loop response was tested with a step input - the values acquired matched MATLAB with 12 digits of precision.

However, when I close the loop, I notice that after the first iteration the output is different than the output in Simulink. Arduino shows more oscillations in the step response than shown in Simulink. I am convinced that the reasoning for this is order of operations. My goal is to match the output of Arduino with the simulations I am getting from Simulink - I just can't seem to match them.

Here is the first 10 samples (Interation#, Error, Output):

Arduino

0   20.000000000    0.000000000
1   20.000000000    2.575358775
2   17.424641225    3.340676550
3   16.659323450    3.138910827
4   16.861089173    2.904174249
5   17.095825751    2.831139893
6   17.168860107    2.834391925
7   17.165608075    2.844978145
8   17.155021855    2.847686323
9   17.152313677    2.846717691

Simulink

0  20.000000000000000                   0
1  17.424641225159935   2.575358774840067
2  16.990947091447396   3.009052908552605
3  17.015483465319324   2.984516534680677
4  17.083280988271159   2.916719011728840
5  17.124589277883938   2.875410722116062
6  17.143447412039610   2.856552587960392
7  17.150819802325874   2.849180197674125
8  17.153378468604828   2.846621531395171
9  17.154167672101366   2.845832327898634

By looking into the numbers, it may not seem like a big difference but when designing a controller, its VERY significant, almost making Simulink design tools useless when implementing into Arduino.

Thank you,

EDIT: Clarification for Gp_z() function in Arduino. To implement a discrete transfer function, such as Gp(z) into Arduino. I performed an inverse Z-transform on Gp(z):

Multiply Gp(z) by \$\frac{z^{-2}}{z^{-2}}\$:

\$\frac{Y(z)}{X(z)} = \frac{0.1288z^{-1} - 0.06234z^{-2}}{1 - 0.7813z^{-1} + 0.1817z^{-2}}\$

Isolate Y(z):

\$Y(z) = X(z)0.1288z^{-1} - X(z)0.06234z^{-2} + Y(z)0.7813z^{-1} - Y(z)0.1817z^{-2}\$

Inverse Z-transform:

\$y[n] = 0.1288x[n-1] - 0.06234x[n-2] + 0.7813y[n-1] - 0.1817y[n-2]\$

This formula was implemented in Gp_z() function.

UPDATE: By switching the execution order of e and y in Arduino:

void loop() {
  delay(500);
  y = Gp_z(e);
  e = 20.0 - y;
  Serial.print(iteration); Serial.print('\t');
  Serial.print(e, 9); Serial.print('\t');
  Serial.print(y, 9); Serial.print('\t');
  Serial.println();
  iteration++;
}

Here is the resulting output:

0   20.000000000    0.000000000
1   20.000000000    0.000000000
2   17.424641225    2.575358775
3   16.659323450    3.340676550
4   16.861089173    3.138910827
5   17.095825751    2.904174249
6   17.168860107    2.831139893
7   17.165608075    2.834391925
8   17.155021855    2.844978145
9   17.152313677    2.847686323

There is an extra iteration of initial conditions and the numbers look better but still with significant overshoot in comparison to Simulink. I don't believe this to be the solution to the problem.


texts:
I am looking to build a robot that will zig-zag back and forth down a hallway. I am wanting to build an IR LED beam and detection circuit so that the robot will detect the wall and change its direction. Does anyone know of a good way to implement this design? Or do you know an example which I could follow?

I could use something other than IR circuit if you have an example or recommendation.
No microcontrollers can be used.

Thanks.


texts: Fully diff signal to single ended signal

texts:
I'm designign a circuit using the AMC1200 isolation amplifier from TI.

http://www.ti.com/product/amc1200-q1

As you can see the output is differential, and I'd like too feed it to a schmidt trigger to catch the 2.5V transitions. The problem is that the trigger is single ended, so here is my question:
is there an easy way to transform the fully differential output in a single ended output i.e. having the difference between the outputs? I know I can use just one of the outputs but I basically loose half of the dynamic range, and that might be a problem.


texts: How to reduce measuring angle of JSN SR04T?

texts:
I wanted an waterproof ultrasonic sensor. So I used JSN-SR04T. But the problem is it has huge measuring angle(75%) which results in measuring obstacles which are not required. How can I reduce the measuring angle of the sensor?

JSN SR04T:

Data Sheet:

http://www.ekt2.com/pdf/412_CH_ULTRASONIC_MODULE_4PIN_WATERPROOF.pdf


texts: Compatibility between TTL output and LVTTL input

texts:
I would like to provide an external input digital signal to a Xilinx Basys 3 FPGA PMOD GPIO pin. Since the board is powered with 3,3V, I think I need to supply a LVTTL signal. However, I would like to use the TTL output of a NI-USB-6008 board to drive the input of the FPGA.
From the NI-USB-6008 I read that the TTL output is LVTTL and CMOS compatible. Is it safe to directly interface the NI-USB-6008 output to the FPGA input pin? Or is it better to generate a 0V - 3,3 V analog output from the NI-USB-6008 to couple directly with the FPGA?
Thanks for your replies!

Thanks for the detailed reply. I will implement a buffer as suggested.
However, this triggers another question, mainly for curiosity: why the solution that uses the analog output of the NI-USB set to 0 - 3,3V board to interface with the LVTTL of the FPGA should be avoided? Could that possibly erogate too much current and damage to components of the FPGA inputs, or is more elated to a loss in performances in the digital signal level-transition speed?


texts: In an open-circuited transmission line (microwave circuits) the current in the return path is completely zero?

texts:
Since the current meets the open boundary and gets reflected back does this mean that the return path has zero current always on it? Or there is also a standing wave there as well with a current with an opposite direction of propagation?
The same I would ask about a lambda/2 dipole antenna which is a standing wave line as well.


texts: Help with designing a circuit with logic gates

texts:
I want to build a circuit with the following design:

3 inputs
1 NOT gate
2 AND gates
1 OR gate

This is my truth table:

 I1 | I2 | I3 || output

 0  | 0  |  0 ||   0
 0  | 0  |  1 ||   0
 0  | 1  |  0 ||   1
 0  | 1  |  1 ||   1
 1  | 0  |  0 ||   0
 1  | 0  |  1 ||   1
 1  | 1  |  0 ||   0
 1  | 1  |  1 ||   1

Can someone help me with what components should I buy?

I know there are chips that have AND/OR/NOT gates, but I was wondering if there's a single one that have all of the ones I need - if not, then what should I use specifically?


texts:
How are integrated circuits (e.g. a microprocessor) fabricated from start to finish? For example, there must be some wiring with resistors, capacitors to store energy (bits) in a field, transistors, etc....

How is this done? What machinery and chemical processes are required for building an integrated circuit?


texts:
I wanted to add LED flashers to my motorcycle (I previously used 10W classical bulbs). After I installed both on the right side (front and rear) I noticed that they won't blink. They will turn on, dim for 1 second, and then stay on forever (without ever dimming again). I thought the problem was a relay, but then I hooked up one of the old flashers on the rear, and now the front led one worked fine too...
Why does this happen?
Would attaching an extra load solve the problem? (I was thinking of a resistor in parallel with the led flasher, so that it would mimic the classic bulb, though dimming the led brightness)
Is this a good idea?
Do I have other alternatives?


texts: Electret Condense Microphone, the function purpose of parallel capacitor

texts: I got a schematic diagram of Electret Condense Microphone(ECM), shown as in the below. I would like to know the function purpose of C1 and C2. Each of value is 33PF and 10PF. Thanks.


texts: generating clock signal for testbench in VHDL

texts:
I'm wondering why the first assignment for a clock signal in VHDL does not work like the second. I'd appreciate any explanations about the simulation behavior of assign statement with delay. Thanks.

First version: (just produces spikes 50 ns apart)

clk <= '0', (not clk) after 50 ns;

Second version: (produces a square wave of time period 100 ns as expected)

signal clk : std_logic:='0';
begin
 clk <= not clk after 50 ns;


texts: why should we define "the magnetic flux is the dot product of the magnetic field and the plane area , instead of perimeter of the plane

texts:
When a uniform magnetic field \$\mathbf B\$ passes a plane at any angle, the magnetic flux \$\phi_B\$ is the dot product of the magnetic field \$\mathbf B\$ and the plane area \$\mathbf{a}\$,that is ,\$\phi_B=\mathbf B \cdot \mathbf{a} \$

Honestly,this explanation of magnetic flux is really abstract to me,i can write the formula above,but i don't really understand that,why should we define "the magnetic flux \$\phi_B\$ is the dot product of the magnetic field \$\mathbf B\$ and the plane area \$\mathbf{a}\$" instead of perimeter ,\$p\$ , of the plane ,that is ,\$\phi_B=\mathbf B \cdot p\$ ?

Can anyone explain this in detail?


texts: Transfer variables through SWD with Segger J-Trace without using SWO interface?

texts:
I have a Cortex-M0 NXP LPC1114 custom board connected to the debugger J-Trace for Cortex-M from Segger.

The Cortex-M0 is a very limited MCU (and cheap!) and doesn't have a SWO port so I cannot use the very useful printf SWO redirection.

I need to transfer a global variable value from a debugging/running firmware to the computer and access this value in a software developed in C#, using only J-Trace comunications. I cannot use the Cortex-M0 UART since it's being used with another peripheral.

Is it possible to transfer variables values through J-Trace and capture those values and use them?

  Link to the LPC1114 datasheet.

  Link to the LPC1114 user's manual.


texts: Given that you can set the output of a flip flop the way you want regardless its prior state, why it is considered a sequential device?

texts: The literature states that a SR flip flop is a sequential device and that sequential devices are those whose output depends on its current inputs and prior state. However, that doesn't make sense to me: flip flops are the basic building blocks of some memories and I wonder how useful a memory can be if its next state depends on its prior state. That would be a very bizarre kind of storage! You have to have the ability to write anything you need to and, in fact, that is exactly what a flip flop allows you to do. So, my question is: am I missing something (conceptually speaking) or in fact a flip flop does not comply with the definition of sequential logic? Thank you very much in advance!


texts:
Is there anything that can stop the battery from discharging if it hits a certain voltage?

IE. solar panel > battery > fan. I want only to run when the battery has enough voltage so it doesn't drain below 50% if there is no sun for extended periods of time.


texts: This guitar piezo opamp buffer lacks any sort of bass, why?

texts:
My preamp in my acoustic guitar died after I put the battery in backwards. I need to replace it, and fast. Piezos have incredibly high output impedance (5+ mohm) so a buffer circuit is used to knock the impedance down to a sane level.

I tried building this circuit and while it works, it lacks any sort of bass amplification:

I didnt have a 100k resistor, so r3 is 170k. I also didnt have a .1uf, so c1 is 4.7uf. I tried raising the r2 to 5mohm and it sounded the same. v+ is 9v and vb+ is 4.5v from a voltage divider. OpAmp is tl072

Any help or alteratives much appreciated!

EDIT

All caps are thin film, not electrolytic

The DI Box next in the chain has an input impedance of 1mohm


texts: MOSFET Gate driver - negative voltage with Zener circuit

texts:
I was reading about minimizing MOSFET switching loss when I came across an article by Texas Instrument on how to use negative voltage, instead of ground, to faster discharge MOSFET gate capacitance. To create the split voltage (say, +20 V/-5 V to charge/discharge Cgs), one of the schematics uses Zener circuit like below:

In TI description, "If the isolated power supply, VA, is equal to 25 V, the turn-off voltage will be –5.1 V and turn-on voltage will be 25 V – 5.1 V ≈ 20 V... and there will be steady state power consumption from Rz." Can Rz be removed from the circuit?

Question solved by further reading into "Zener diode voltage stabilizer/regulator". Thank you for reading!


texts:
I would like to see if the project that I am currently working on is something that can be done. Any help I can get would be much appreciated. I hope I am providing enough information.

I am looking for some sort of small IR or ultrasonic motion sensor to capture motion within 15 feet (3 meters) in a 45 degree angle. The moving object (a vehicle or bicycle) will be traveling very fast (20 to 50mph). The sensor will have to capture the motion very rapidly and alert me through a flashing LED light and get ready to capture again. The small motion sensor will be attached to a custom made circuit board that will be powered by a small power source (a battery pack preferably). The custom made circuit board wont be not more than 1.5 inch (2.5cm) in width and 2.5 inches (5cm) long. Like I mentioned, I want the circuit board to have a flashing LED light that works as an indicator for motion detected objects. I am trying to get all of this inside a very small custom made plastic case that I can print with a 3D printing machine.

The sensor that I have in mind is the following:

Ultrasonic Sensor: http://www.parallax.com/product/28015

The final product would look something like this. This will give you a perspective on the limited space and final idea.

http://shop.lego.com/en-US/Ultrasonic-Sensor-9846

My questions are:

Would I be able to power this system with a battery pack? If so what power source would you recommend?

Would you suggest an IR sensor over ultrasonic sensor?

Can the PCB be created given the specifications? (1.5W x 2.5L)


texts:
I failed to replicate a simple sample circuit of a N-Channel MOSFET originated in AllAboutCircuit on LTSpice. The current on the load resistor (to mimic the ammeter to measure current on LTSpice) either is in the pic-Amp range (not conducting current, or completely depleted) or in the hundreds of Amp range (the depletion region is enhanced so much?) depending on the polarity of the DC Voltage source (polarity should not matter for MOSFET on Drain and Source). There should not be any voltage difference between the gate and source as both are common out with zero bias voltage.

I have attached below the excerpt from the tutorial and the result I got from LTSpice simulation. Hope someone can help explain what I did wrong and why I am seeing these two drastically different V-I plot. Thank you.


texts: Does transconductance (Gm) have 3dB bandwidth

texts:
The voltage gain of an amp is Gm*Zout,
the bandwidth of the voltage gain is limited by the Zout as signal freq increases.
I wonder whether the Gm also has 3dB bandwidth or not.
And If Gm has 3dB bandwidth,what element cause it?


texts:
Some devices like MCU board or sensor module have the SCL, SDA pins internally pulled up. If you find that the pull up resistance has not been selected properly, how can you fix it without breaking the MCU or sensor?

Is it okay to add pull up resistor externally? Assuming the external pull up voltage is same with the internal pull up voltage.
What if the two voltage levels are different? Suppose that SCL pin is pulled up to 1.83V internally, but you pull it up again to 1.90V externally. Could MCU or sensor be broken? When the SCL is released, current would flow from the external resistor, internal resistor and then to the voltage regulator in your device. Could it affect to the power rail in your device?


texts: Placement of sensors, Gyro + accelorometer

texts:
Im looking for some placement help for 2 sensors, A gyro     and an accelerometer
both are going into a helicopter.  my guess is to put the gyro and the accelerometer right below the main rotor, getting it as close to the center as possible, but on the rc receiver (has been removed) the gyro was mounted to the front. The data sheets do not give any placement suggestions either. any help would be appreciated.


texts: LED driver suitability and circuit advice

texts:
I'd like to string together 10 of these Cree LEDs in a series circuit (Vf: 3.0v, Imax: 0.3A):
http://www.cree.com/LED-Components-and-Modules/Products/XLamp/Discrete-Directional/XLamp-XQA

I think this constant current driver should be suitable given it can output up to 35v @ 0.3A:
http://uk.rs-online.com/web/p/led-drivers/7063213/

I've done a fair bit of research but my only electrical knowledge dates back to my school days so I'm hoping someone can advise as to whether this really is a suitable driver?

Also if I were to increase the number of LEDs to 12 (requiring a total of 36v) would the LEDs function as normal but the last one appear dimmer?

Lastly, I'm unsure if I should add a dropping resistor at the start of the circuit, and if so is the following calculation (for 10 LEDs) correct?

R = (Vs - Vf) / I
R = (30 - 3) / 0.3
R = 90 ohms *seems very low!*

Please assume minimal knowledge (but a desire to learn)!

Thanks


texts: 3.6 Vo-p rated buzzer on 5 V Arduino circuit

texts:
As a small buzzer to output simple audio, I am considering the
Jiangsu Huaneng Elec MLT-5020. Other buzzers of that size are also an
option, as long as their footprint isn’t much bigger than 5×5 mm.
From the datasheet:

Recommended driving circuit (I guess, substituting the 2SC3199 with a PN2222A is safe):

Rated voltage: 3.6 Vo-p

Operating voltage: 2.0～5.0 Vo-p

I want to connect the buzzer to an Arduino (ATmega 328p) circuit with
5 V. I don’t have a 3.6 V power source in that circuit, although I
could add one, for example with an LDO.
Some questions that come to mind:

For simplicity, can I drive the buzzer with 5.0 Vo-p?

Instead of the transistor circuit, can I just connect the buzzer
directly to a pin via a resistor? (as done in some examples I found
on the web)

I know the sound quality of these buzzers is awful, but I don’t want
to degrade it further by bad wiring.
Update
I tested the circuit with various resistors in series. Applying a
constant high signal, I measured the current. (Interestingly the
current fluctuated by a few mA, despite a constant voltage.)

15 Ω, around 100 mA (maximum rating)

22 Ω, around 90 mA

47 Ω, around 60 mA
Above 100 mA, the audio starts to clip. I compared various resistances
to the 47 Ω proposed in Chris Stratton’s answer. See my video
MLT-5020 Tests.
I also tried connecting the MLT-5020 directly to Arduino pins 9 and 10
and driving it in push-pull mode via the ToneAC library: It was
less loud than with the transistor ciruit. Apparently the Arduino
cannot provide enough power on these pins, and obviously that's
exceeding its maximum current ratings anyhow.


texts:
I would like to control an RGB LED via a (vendor specific) microcontroller. However its maximum output current is 60mA whereas my LED requires 100mA.
I have seen number of LED driver solutions with PWM support where the modulation is controlled by analogue input 0-VDD. However, I would like to use my already modulated signal from my MCU as I don't have 3 analogue output pins and MCU offers nice PWM tools.

What would be the easiest solution for me to provide the LED with the necessary 100mA while still using MCU modulated voltage signals?


texts: Arduino Serial TX to iPhone RX voltage drop?

texts:
Articles I read about this tell me to hook up a 1KOhm resistor between the Arduino's TX and the iPhone's RX. I understand this is because Arduino's signal is 5V and I want 3.3V going to the iPhone.

My question is, where did they arrive at this value of 1KOhm? Is it documented somewhere that the serial signals are 1.7mA?


texts:
I was reading the Power Integrity article on Altera's website and came across the recommendation for the Bulk Capacitor (47uF to 100uF). I'm supposed to have one 47uF-100uF capacitor for every two VCCIO banks. The chip I'm using only has two banks, so that means just one 47uF capacitor.

My question now is, how to feed power to the decoupling capacitors? As of now, the power is fed directly from the source via a star-network. Each VCCIO/VCCINT pin is connected on its own via a 20mil trace.

If I include the bulk cap, should I feed the power to the decoupling capacitors FROM the 47uF cap? In other words, make a localized star network for the chip rather then connecting them to the board network for power? This is what the schematic on the website seems to suggest.

I obviously don't have a Vcc plane (or an unbroken ground plane). However, the operational frequency isn't very high either: just 62.5kHz.

This is what I was thinking basically:


texts:
I am building a 4S8P battery pack and wonder if battery holders would be useful.
I find the 4S battery holder shown below to be nice, but am concerned about its current carrying capacity as I have a 8P configuration.

Another way to hold the batteries would be to use the battery spacers. However are there similar battery holders as the one in picture that could potentially be more reliable? Hope someone can throw in some suggestions :)


texts: Insulation when connecting a (TO-92) sensor with a cable

texts:
I'm considering using a DS18B20 which comes in a TO-92 package, but I have to place the sensor at a distance from the rest of the electronics so I'll have to use a wire to connect it.

However due to that the DS18B20 will be attached to a stainless steel container the pins would probably need to be insulated. Perhaps it would be a good idea to make sure that the pins are individually insulated in case a pin get bent and gets into contact with another pin.

Is it normal/kosher to use these kind of packages in this way? And what are proper ways to avoid short circuits when connecting the sensor this way?


texts: Why is it so hard to find component footprints?

texts:
When designing PCB's, I find myself very often having to make footprints for a significant portion of the components on my board. This tends to be very time-consuming, as (in Altium at least), dimensioning out land patterns for strange connectors or chips (those that can't be created from a wizard) isn't very easy. It seems like anyone that uses these chips or connectors would need a footprint, so I can't understand why these aren't more commonly provided. For example, right now I'm trying to put a USB 3.0 Micro-B connector on a board, but the top 5 connectors on Digikey don't seem to provide footprints. I have access to the Altium Live design content, but even that seems often pretty out-of-date.

I feel like there's something obvious that I'm missing - or else this system seems very inefficient (which usually isn't the case). Can someone enlighten me?


texts:
I am trying to figure out a way to make a ramp (0A - Amax) with a constant voltage. Basically I have a SPST switch that is connected to a 24VDC battery. I need a ramped current output from 0A to 1.9A. Preferably a roughly linear ramp with a 2 sec ramp time. (I'm not sure about that 2 sec so how to get to that would be helpful) I don't even know if this is possible. Any help or direction would be great.

Thanks in advance.


texts: Fade a LED using fast PWM and interrupts on Arduino

texts:
I have a project to make an LED fade in for 1 sec, stay on for 1 sec, fade out for 1 sec and then stay off for 1 sec, all the project must be done with registers and with the help of the timer0 fast PWM functionality without any functions (e.g. analogWrite).

I already have to logical part of the problem, I know how to generate an interrupt on timer0, but I can't figure out the fading part. How do I give a specific brightness to the LED with registers?

Maybe I am missing the documentation, I don't mind if you suggest something to read first and then came back with questions.


texts: Learning about multipliers, confused about cycles in relation to Wallace tree

texts:
At this link:
http://en.wikibooks.org/wiki/Microprocessor_Design/Multiply_and_Divide_Blocks

It says that a wallace tree can be used to perform multiplication in a single cycle.

I'm assuming then that a technique like Booth's recoding takes multiple cycles for outputting a product?

By why exactly does a wallace tree only take one cycle to output a product?

I've read about the process on wikipedia: http://en.wikipedia.org/wiki/Wallace_tree, but I can't grasp the cycle argument.

Is wallace tree better/faster than other multiplication techniques?


texts:
So, I'm designing a reverse battery protection circuit using a MOSFET, following this TI application note. I tested it, it works great, Rds(on) is low as expected. However, I'm not really comfortable with it, since the drain-source current is reversed. Here's the circuit:

simulate this circuit – Schematic created using CircuitLab

My question: when is it safe to assume that a MOSFET will behave in the same way when passing current in the reverse direction? What can go wrong? Can I be sure power dissipation won't be compromised?


texts: Would I need a star topology with a dedicated ground plane?

texts:
Some background:

I have a PCB with a bunch of relays on it. The purpose of the circuit, is to allow signals to pass through from one connector to another (db37), or to stop it - that's where the relays come in - to break the connection.

I have a 6 layer board with the following layer stack(signal, ground, signal, signal, power, signal).

I have +12V supply, +3.3V supply and +5V supply. The +12V is for a bunch of relays, and the +3.3V and +5V are for some microcontroller + other lower voltage ICs and components.

Some of these signals from the db37 connector MAY be higher current signals (3A) but with a frequency no more than 50khz. For the most part, we are looking at 10s of mA and 10Khz signals.

I'm using my power plane for the +12V.

My question is - can I just ground all my components to the ground plane directly or through a close proximity via or should be considering a star topology ?

Are star topologies only useful for situations where there is no dedicated ground plane ?

I suspect that because I have a dedicated ground, I should be able to simply just connect everything to ground. But PCB grounding is fairly new to me.


texts: I've got a project where I have an intricate structure made of fine wire, through which a comparatively large current will be sent. Unfortunately, the conductor itself respons poorly to heat, and if the high current flows, the system fails. Is there a way to reduce or redirect the heat? I thought about using a high frequency current to use the skin effect. That way, if I coated the structure in a heat resistant material, the current would run through that instead of the structure. Unfortunately, this still doesn't work because mezals are great at conducting heat. So, I was wondering if it was possible to solve this problem at the root, as in not generating heat in the first place. If anyone knows how, please tell me. Thx.


texts: bonding laminated sheets in a transformer core with adhesive

texts:
I am building a transformer core out of laminated steel sheets.
As I stack the sheets on top of each other, I need to use an adhesive to bond the sheets together, and I would like to ask the community for advice on the use of adhesive to bond the stacked sheets.

Due to factors I won’t go into here, I cannot use a mechanical method of keeping the sheets together - clamps or screws etc. Can anyone advise me on the best adhesive to use? What should I try to avoid in order to minimize core loss or any other problems?
Thanks!


texts: Meaning of reflection coefficient in English

texts: So I know a reflection coefficient of 0.5 angle 30 at the load (k=0m) means "At this point, 50% of the incident wave is reflected and has a 30 degree phase shift." But what does it mean in English if you measure the reflection coefficient at k=1m?


texts:
car battery making a noise similar to light buzzing ( shorting?) battery just over a year old. car just back from being driven. earth lead removed .noise still there. best described as 'sizzling'
   alternator was exchanged  2 years  ago . ammeter  shows normal charge/discharging . car. tends to stand in garage for some then between use.  starts /cranks easily. never heard a battery make a nose before .12v well know German  type .wet acid sealed.


texts: Is it wise (safe) to connect a Bench Power Supply to a UPS?

texts:
The power at my place is generally reliable but a few times a year we have an outage or brownout.  With my luck, it will happen just when I am testing something on the bench (microelectronics).  I am not so concerned about losing power completely.  Rather, my concern is if there is an intermittent power hiccup that causes a surge/overshoot when the power comes right back on.

Since my UPS provides power to connected devices with a battery, I'm thinking it should keep the Bench Power Supply going without skipping a beat.  Are there any gotchas?


texts: Solar Cell Performance With Varying Incident Angle

texts:
I am trying to calculate the power generated from solar panels placed on the Moon. I have an equation for power generated at the beginning and end of life and have hit a snag in my brain.
If the solar array is on the 'equator' of the moon (I know that the moon is tilted slightly so lets pretend it isn't for sake of ease in this question), so the incident angle of the solar rays would be 0 and the power generated would be at a maximum.
$$
P_{BOL}=(flux)(solar cell efficiency)I_D\cos\theta
$$
$$
P_{BOL}=1386\times0.2\times0.77\times1=116.43
$$
So this is the best case and as the Moon rotates about its axis, \$\theta\$ increases and hence the power output decreases. Good.

Now my question is, what if the solar array is not placed on the equation, i.e. the best case scenario for it is where there is already an incident angle present (for this example I am saying the solar array is placed much closer to one of the poles).
Obviously you still have the change in \$\theta\$ with the rotation of the Moon, but you also have this offset \$\theta\$ which is there to start with - how do we account for this?

I was initially thinking that we take the original \$\theta\$ and only once the rotational \$\theta\$ becomes greater than it do we use that value, but I don't think that could possibly be right.

So I have come to the conclusion that the equation I started with will need to have two \$\cos\theta\$ values, one for the initial offset and the other for the rotation of the Moon. Am I correct in this thinking?

Apologies for the very long winded question, I am not good at concise writing when I am trying to explain my thought process without the aid of diagrams. The values used in the equations are typical values as well. Any questions, please ask and I will try and clarify it.


texts: How to control 4 relays with a not chip (7404)

texts: I have a atmega8 that is working with 3.6V dc, I need to control some 12V relays with a not chip (7404), what is the simplest way to do this? I have connected a 12V dc to the relays, so when I connect the relays to the chip and then the atmega8, the current returns to the atmega through the not chip. Is this solution correct? There a better way to do this?


texts: Why is receiver RSSI so much lower than the output power of a transmitter?

texts:
When we measure the output power of a small transmitter we might see something around 30 dBm (1W) but a receiver/WLAN card/UE right next to the transmitter will report a RSSI in the range of -40dBm, for example.

Why is this such a large power loss (30dBm - -40dBm = 70 dB ~= output power is 10000000 x greater)?


texts: how do I stabilize opamp amplifier oscillation

texts:
I've designed the following amplifier circuit to amplify a DAC signal (sorry for the non-standard opamp symbol):

It's a power amplifier which amplifies a microcontroller DAC signal 0-5VDC and very low current, to 0-22VDC, with current draw up to 2.5A. That would be a gain of approximately 4.4. The input voltage only changes several dozen times per second. Let's say 100Hz to be safe. But it needs to operate over a wide range of (fluctuating) loads. Load could be from 5 ohms to 5 megaohms for example.

It simulates just fine with the default PMOS component, which I suppose is an ideal FET. But when I add all "real" components in, I get oscillation occuring. How might I stabilize this? How accurate is a simulation in such things compared to a real circuit?

Is there anything else that looks like it could be an issue in this circuit, for example part choice, voltages, etc?

LTspice v4.22s schematic download: enter link description here

EDIT:

I've made some changes based on mostly trial and error, but educated by the replies below. I managed to remove the oscillation fairly quickly, but, I have no idea why adding a capacitor in each of these locations solved the problem. I needed both of them, and I needed to fine tune their values a bit.

This is for a power supply so the new voltage spike at the beginning is rather disastrous. Here is a closeup of it now with a resistor added in series with C1 to stop it oscillating:


texts: How can I use the TDR result to evaluate the effect of impedance discontinuity?

texts:
Only the left half is relevant.
Like mentioned before,I want to check out if reflection is one of the reason that deteriorates the signal integrity of high-speed signal.One way that has been come up is to reexamine the impedance of PCB traces(in this case,differential microstrips),connector and cable by TDR.
As can be seen from the pic,the impedance at the connector(around point1) bounces up and down.But then it turns back to normal(about 100ohm）when depicting pcb traces(between point1&2).
So my question is,now that I've been slightly aware of what the TDR wave means,how can I know if this path is eligible for the signal I've tried to transmit?
Are the bumps and dips all I can get from TDR,so that the only thing I can do is to root the problem and try to improve them(like adjust L&C,really roughly)?Or am I able to put the data into some kind of simulation tool and get something like a transfer function for the cable-connector-trace path?


texts: Solving a simple single-ended differential amplifier

texts:
simulate this circuit – Schematic created using CircuitLab
N.B. I_D=KVov^2 without the 2
I’m really confused with this excercise, my problem is to calculate  the A_v=v_out/vd and the cutting high frequency fH neglecting the parasites capacitors of the transistors (there is only C1) . I am confused because with the small signal circuit I can’t calculate the amplification of the differential amplifier because is asymmetrical and the source in not grounded.
I have Vo=-R1gmV_gs2 and I can’t find V_gs2

Here it is my solution

I have tried to use sovrapposition effect and obtained that Vgs_2= -Vd/2 but with a lot of effort obtaining a so clear result means that i'm not getting something about it.
btw in the end i obtained A_v=-19.8 and fH=2.5MHz but i'm not sure they are correct


texts: Xilinx CORDIC 4.0 Translate parameters question

texts:
I'm developing a SysGen model using a CORDIC 4.0 Translate core to pass from rectangular coordinates to polar coordinates.

I need understand the Coarse rotation and Compensation scaling options.

About Coarse rotation, the user manual says that the input must be located in the first quadrant between pi/4 and -pi/4. What does it mean? First quadrant is from 0 to pi/2 radians, isn't it?

Finally, what is the purpose of Compensation scaling? I just don't understand the user manual about this parameter.

I hope that optimizing these parameter the cordic will be lighter enough to complain the timings of the system.

Thank you for your help!


texts: What type of transformer do I need for a 5Hz AC source?

texts:
On the primary side, I have a low-impedance AC supply that can be adjusted to a minimum of 100V, with a frequency variable from 5 to 800Hz (and I need to operate over this whole range). I need to somehow transform this down to 2.5V or lower, naturally as efficiently as possible, with the secondary side drawing up to 12A.

I considered just buying a transformer of roughly the right ratio and maybe a bit higher power rating than I need, but there's rarely any detailed information with regards to resistance, loop counts, wire gauge and/or inductance that I'd need to properly calculate the losses caused by running a 50Hz transformer at 5Hz. I have no idea if it would just get a little hot, or melt through the casing; and even if the losses were acceptable I wouldn't know if it would even transfer enough power to the secondary.

I have looked at audio transformers, as they are designed to operate at a wide frequency range, but even they seem to only go down to 20Hz.

What would a more experienced engineer than I do in this situation? Are there certain specs I can look for in pre-made components, or will I need to look at having one custom-made?


texts: Correct way to wire USB 2.0 Type C connector?

texts:
I'm playing around with building a simple keyboard, that will have just few buttons, nothing complex.
I have decided to use USB 2.0 Type C connector, like this or this.
Now when following USB 3.0 specs, it says we should use pull down resistors on CC1 and CC2 so that host can tell if device is on or not and also resolve orientation.
But USB 2.0 specs says we should use pull up resistors on D+ or D- lines and that without them host would not recognize device.
I'm confused what to do here since I have both CC1 and CC2 but also D+ and D-.
Should I follow USB 3.0 specs and pull down only CC1 and CC2 lines like this:

Or should I also pull D- up to 5V like this, while pulling CC1 and CC2 to the ground like this:

I would be thankful to someone who could explain how to use these 2.0 Type C connectors and point me to some specification I could read. And explain why use pullup on D- when I already pulled CC1 and CC1 down to ground? Or can I just ignore CC1 and CC2 lines and just use pullup on D- line if it's USB 2.0?
Edit:
MCU I'm using does not have internal pullup or pulldown resistors.
Pull up on D- should go through 1.5k resistor, I missed that one.


texts:
I'm designing my own data protocol for communication between PICs, ICs, etc. and in the specification I'd like to compare it to the existing I2C protocol.

There are two types of operation on the I2C bus:

Write operation: master writes START, address, data (the slave sends ACKs only)
Read operation: master writes START, address. Slave sends data, master sends ACK / NACK.

Just to get this clear for me: is there any way to use these operations, according to the protocol specification, to read and write data within one operation? You would win speed because you don't have to send the address twice. So is this possible?


texts: Altium - short-circuit between pad and poly-region with same net

texts:
I draw a grounded trace BLE Antenna.

One pad has the GND Net and the second pad is ANT Net

Here is the error:

  Class Document    Source  Message Time    Date    No. [Short-Circuit Constraint Violation]    control-board-v8.PcbDoc Advanced PCB    Short-Circuit Constraint: Between Pad E1-GND(1300mil,3326.176mil) on Top And Region (0 hole(s)) Top Location : [X = 1299.983mil][Y = 3332.018mil]   7:32:55 PM  6/13/2019   1

and here are my short-circuit rules :

the proof that my pad and polygon got the right NET (GND) :
PAD:

POLY:

How can I get rid of this error ?

PS: I already ran the t,g,a (Tools -> polygon pour -> Repour All)


texts: Grounding audio circuit for RFI immunity

texts:
I am trying to determine the best way to ground the following audio circuit for best RF immunity. Right now I'm looking at two options, and am not sure if there's even really much of a difference between the two.

Option 1:

Option 2:

First off: I've been studying up on RFI so please correct me if I'm wrong, but as I understand it any RF pickup by the input cables (V1, V2) will most likely be common-mode, and will be shunted to earth ground through the chassis via the capacitor network (obviously assuming the interference is in the correct frequency range). The chassis is earth grounded.

In option 1, I have two chassis ground points. The caps C11 and C12 would ground to an isolated island on the pcb directly connected to the chassis. Then the signal ground would be tied at a separate location to a separate chassis ground point. I envision this as keeping the RF noise currents off of the ground plane entirely, but there is another separate chassis ground connection to the circuit. Could this possibly result in some kind of loop? I would imagine the RF current is destined for earth ground, and the shortest path is through the CGND at the input, but I'm not 100% sure if it could/would loop back.

In option 2, I've eliminated the second chassis ground connection point and tied the signal ground to the C11/C12 chassis ground point. The signal ground is still only connected to chassis ground in one place, but now there is only one connection to chassis, and the noise currents can flow through the signal ground plane to chassis ground. I would probably make a little half island or lay this out somehow to keep RF noise currents isolated to a small area while still keeping a connection between signal/chassis ground. But there would still be noise currents flowing through this interconnection.

Is either one of these options better than the other?

Update I've added the last half of the schematic as per Dan's response, it was left off initially only because I thought it would make the image too large for some browsers

Update In regard to the comments in the discussion after DanMills's post, I am including a drawing of how I am visualizing the possible flow of shield currents and why I am having a hard time convincing myself that "option 1" is the better solution.

Update Here is an example of how I was thinking to lay out the board to facilitate only one chassis connection for RF noise currents, but keep them off the main ground plane.


texts: Calculating the transfer function and bode plot

texts: What is the transfer function and bode graph when k=0 and k=1?


texts: LM2596, Voltage divider causes delay in voltage changes

texts:
simulate this circuit – Schematic created using CircuitLab

In above diagram feeding 0-5V on inverting input of opamp will vary the output of LM2596, The problem is R1 is getting really hot at 20V.

Yes of course I can increase the R1 and R2 values to 10K and 3.3K but in that case if we close the SW1 it will take several seconds until LM2596 output become ~0V.

Why increasing the R1 and R2 values causes slow voltage drop when SW1 is closed and how to achieve instant 0V when SW1 is closed.

*I don't want to use ON/OFF pin to hit 0V.


texts:
I have a 750 watt ATX power supply that I will be testing with a multimeter to make sure the right voltages are present. How can I make sure that I do this safely? Is there anything that's threatening my safety that I should be aware of before I go prodding away at the leads?

Is the power that the PSU provides through its connectors enough to cause injury?


texts: SPI Read returns only 0 in slave when I hook up SS to INT

texts:
I am coding a SPI slave using a PIC16F877A in CCS C and need to be aware when the SS line (pin 7) goes from high (idle) to low (active) as information from the master is framed as a stream of bytes with the leading byte (first byte after SS goes active) telling me what the remaining bytes are for.

I have shorted SS (from master) to INT(pin 33) and written this:

#include <16F877A.h>
#device adc=16

#device *=16

#FUSES NOWDT                    //No Watch Dog Timer
#FUSES HS                       //High speed Osc (> 4mhz for PCM/PCH) (>10mhz for PCD)
#FUSES NOBROWNOUT               //No brownout reset
#FUSES NOLVP                    //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O

#use delay(clock=20000000)
#use rs232(baud=57600,parity=N,xmit=PIN_C6,rcv=PIN_C7, ERRORS)

// TODO: add a 100ohm resistor between the SS pin and the chip select output of the master microcontroller                                                     // Clock base   Sample on
#define SPI_MODE_3  (SPI_H_TO_L | SPI_XMIT_L_TO_H)   //    high      trailing edge

volatile int1 slave_cs_enabled = false; //has the slave STB been enabled?

//#PRIORITY EXT, SSP
#PRIORITY INT_EXT, INT_SSP

#INT_EXT
void slave_cs_isr()
{
   slave_cs_enabled = true;
}

//#INT_SSP

void main()
{
   unsigned int8 data = 0;

   enable_interrupts(INT_EXT);
   ext_int_edge( H_TO_L );
   clear_interrupt(INT_EXT); //if you read the data sheet, you will
   enable_interrupts(GLOBAL);
   //Now the code will call the interrupt in the rising edge.

   setup_spi(SPI_SLAVE | SPI_MODE_3);

   while(1) {
      if(slave_cs_enabled)
      {
         slave_cs_enabled = false;
         printf("STB\n\r");
      }

      if(spi_data_is_in())
      {
         data = spi_read();
         printf("%X\n\r", data);
      }
   }
}

All I get after STB are "00". Literally zeros.

This behavior remains unchanged even if I physically disconnect pin 33 from pin 7, pointing to an issue in my code.

When I take out the STB logic (including disabling the interrupt code), then I get stream of bytes but that is not useful to me as I now don't know where a stream starts and ends.

Help!


texts: PCB clearance on eagle to make coplanar lines

texts:
I need to define a clearance between my signal path and souronding ground of 0.16mm in Eagle PCB layout.
I tried to setup the "isolate" at 0.16 and do "ratsnets" but it keeps the same distance as before = 0.2mm. How can I change from 0.2 to 0.16?


texts: What is the best way to implement a microseconds precise delay/measurement

texts:
I recently saw some people saying that configuring a timer so that it triggers an interrupt each 1us is not a good way of doing that.

Also, I assume that;

Start = TIMx.CNT;
Bla;
Bla;
Bla;
End = TIMx.CNT;

An algorithm like that will have problems in case of overflow/underflow of the counter during process.

So what is the most proper method to do so?

If needed, I am using 168MHz stm32f4 discovery board.

Thanks.

P.s : I mixed delay and time measurement because I guess they depend on the same logic so it should not be a confusion.


texts: What are the resistor values that I should use in order to get 38dB gain?

texts:
I have build a common emitter-common collector multistage BJT amplifier.
I want to get an output gain of 38 dB under the conditions of 8 ohms load resistance, 6 volts, 25 mVpp input voltage signal. What are the resistor values I should choose to get 38 dB?


texts: AC single phase motor control with a TRIAC - failure to trigger

texts:
I am trying to build speed control for 500W synchronous, single-phase AC induction motor. It is for a fan in my greenhouse.
Here is current design:

I am trying to verify it on breadboard with resistive load (100W lightbulb). The zero crossing detection circuit works well, but TRIAC trigerring does not work.
Notes:

R5 is set such that there is ~12mA current going through the LED in the optotriac. It is above maximum triggering threshold for MOC3052 and well below its current rating (60mA)

R8 is set such that the maximum current through the optotriac is always  below 1A limit (on 230VAC mains)

I have tried with BT139-800E TRIAC (on schematic, with sensitive gate) as well as with BTA140-800

Where have I gone wrong? Could you recommend robust/reliable triggerring circuit?
Thank you,


texts: How can 8-bit processor support more than 256 bytes of RAM?

texts:
If a 32-bit processor can handle approximately 4 GiB of RAM (i.e. \$2^{32} = 4 294 967 296\$) bytes, why does my Arduino Mega 2560 have 8 KiB of SRAM, if being a 8-bit processor allows it to handle just 256 bytes (\$2^8\$)? Or am I reading the following page wrong?

http://www.atmel.com/devices/atmega2560.aspx?tab=parameters


texts: Writing to a Register happens one or two clock cycles after asserting write enable?

texts:
I am using the code shown here Verilog: Writing to a Register Happens A Clock Cycle Late and that user posted a picture where output would change 2 cycles after asserting write enable. That post got an answer which seemed reasonably good to me. However, I decided to simulate the exact same code and create a testbench for it and in mine, output appears only 1 clock cycle after asserting write enable. Could somebody explain to me why is different if I'm doing the exact same thing?

The only difference I can spot is we're not using the same simulator but how could that be the reason?
This is testbench:
`timescale 1ns / 1ps
module test_regblock_tb;

parameter tclk = 10;

reg clk = 1'b1;
reg rst = 1'b1;

always
    #(tclk/2) clk =~clk;

initial begin
    #(tclk*10);
    rst = 1'b0;
end

reg [4:0] RegA_Name = 4'd5;
reg [4:0] RegB_Name = 4'd6;
reg [4:0] RegC_Name = 4'd7;
reg [31:0] RegA_In = 32'd0;
reg [31:0] RegC_In = 32'd0;
reg RegA_WrtEn = 1'b0;
reg RegC_WrtEn = 1'b0;

wire [31:0] RegA_Out;
wire [31:0] RegB_Out;

RegisterFile regblock(
.CLK(clk),
.RegA_Name(RegA_Name),
.RegB_Name(RegB_Name),
.RegC_Name(RegC_Name),
.RegA_In(RegA_In),
.RegC_In(RegC_In),
.RegA_WrtEn(RegA_WrtEn),
.RegC_WrtEn(RegC_WrtEn),
.RegA_Out(RegA_Out),
.RegB_Out(RegB_Out)
);

initial
begin
#(11*tclk);
RegA_In = 32'd126;
RegA_WrtEn = 1'b1;
#(tclk);
RegA_WrtEn = 1'b0;
#(50*tclk);
$stop;

end

endmodule


texts:
so I am taking a summer course and the teacher is not so helpful at the moment so I was thrown the following question to do:

Derive a truth table for the following function: \$f(x,y,z)=\sum m(1,3,5,7)\$

I dont know how to interpret the equation to make the truth table which is why I am stuck. The next two questions are to derive the sum of products & products of sum of the expression \$f\$ but I think I can find that out when I get the truth table (just by learning on my own)

Also some good keywords to google about this would help.

Thank you!


texts:
The Micro (STM23F4xx) I'm using happens to include a SDIO peripheral that is supposed to support the 4-bit parallel bus SD Card protocol. I'm aware that the SD Association holds patents on the protocol and requires a fee for using it. I'm wondering whether this also applies to me when I'm just using the peripheral, or whether ST Micro has payed for it in order to implement it.

Also: supposed I route all signals required for 4-bit mode (for testing, experimenting, ect.), but then happen to only use SPI mode, does the fee still apply?


texts: Is it okay to keep a mobile phone connected to its charger, 24 hours a day, 7 days a week?

texts:
I want to ensure that a mobile phone is always charged, without requiring manual intervention: e.g. disconnecting/reconnecting the charger, switching the charger on/off, et cetera). One idea would be to leave the phone always connected to its charger, which in turn would always be connected to the AC mains. How feasible / practical is this? And are there better approaches?

Note that I am unable to make changes to the phone, because it is an off-the-shelf, commercial phone. But I can make changes to the circuit of the charger.

Edit: This is not a specific phone model I am talking about, but potentially a phone I'd buy, for a very specific purpose. This might be lower-end Android smartphone. The phone would be left in an unattended remote property, and serve as a landline replacement (since the area isn't served by fixed-line phones). A caretaker would use it periodically to report well-being, and share some video / pictures of the place by sending MMS multimedia messages. The place has bad power supply, and thus the I want to keep the phone always charged. I do not want to hand over the phone to the caretaker, since he doesn't live on the property.


texts: How to calculate the conduction angle of a CVD diode?

texts:
This is not a homework question, it's a textbook exercise for which the answer's already provided, I'm just not sure how to do it.

I know that the conduction angle is the angle during which the diode is conducting. The full wave is 360 degrees, so I'd be trying to calculate what portion of that 360 degrees is conducting and what isn't. I'm not sure where to start with the trig, if someone could provide some guidance regarding how the formulas in part A are derived, that would be awesome!


texts:
I have seen the expression for the transfer function of an RLC tank given as the following.
$$H(j\omega) = \frac{H_o}{1+j2Q\frac{\omega-\omega_o}{\omega_o}}$$
I am somewhat able to get this result, but I still have some minor confusions and am unsure if my analysis is correct. I believe you can inject a current (Norton model) into the RLC parallel branch. Where $$H(j\omega) = \frac{V_{o}}{I_{\text{in}}}$$
Then finding the admittance.
$$Y(j\omega) = \frac{1}{R}+\frac{1}{jwL}+jwC$$
$$Y(j\omega) = \frac{1}{R}+jwC+\frac{-j}{wL}$$
$$Y(j\omega) = \frac{1}{R}+j\left(wC-\frac{1}{wL}\right)$$
$$Y(j\omega) = \frac{1}{R}+\frac{j}{wL}(w^2CL-1)$$
$$\omega_o^2 = \frac{1}{LC}$$
$$Y(j\omega) = \frac{1}{R}+\frac{j}{wL}\left(\frac{w^2}{w_o^2}-1\right)$$
$$Y(j\omega) = \frac{1}{R}+\frac{j}{wL}\left(\frac{w^2-w_o^2}{w_o^2}\right)$$
Now getting the impedance.
$$Z(j\omega) = \frac{1}{\frac{1}{R}+\frac{j}{wL}\left(\frac{w^2-w_o^2}{w_o^2}\right)}$$
$$Z(j\omega) = \frac{R}{1+\frac{jR}{wL}\left(\frac{w^2-w_o^2}{w_o^2}\right)}$$
Given that
$$Q = \frac{R}{wL}$$
$$Z(j\omega) = \frac{R}{1+jQ\left(\frac{w^2-w_o^2}{w_o^2}\right)}$$
I believe $$\frac{w^2-w_o^2}{w_o^2} \approx 2\frac{w-w_o}{w_o}$$
Therefore,
$$H(j\omega) = \frac{V_o}{I_{in}} = Z(j\omega) = \frac{R}{1+j2Q\left(\frac{w-w_o}{w_o}\right)}$$
Where $$H_o = R$$
Is this correct? And if so I have a question regarding the phase shift. I have seen this result given for the phase shift.
$$\alpha = \frac{\pi}{2} - \tan^{-1}\frac{L\omega\times \omega_o^2}{R\times (\omega^2-\omega_o^2)}$$
I can see how this could be the result but where does the \$\pi/2\$ come from?


texts:
I have 10 yellow-colored LEDs and ten 220 ohm resistors. I don't have any power source except the Arduino's 5 volt itself.

Is it possible to power all the 10 LEDs using the 5 volt equally? Or will the volts slowly diminish as the LEDs are powered along a series circuit? Also, is it possible to use only one resistor in the series or do I need to use a parallel circuit with one resistor after every LED?

Please help, I'm completely new to electronics and building a arduino project for my school expo.


texts: Frequency Response Sketch from zeros (FIR filter)

texts:
The question is

Sketch the frequency response of an FIR filter with zeros at $$z=e^{j2\pi/3} and z=e^{j4\pi/3}$$

Here's my approach

Now when I use these formulas and plug in say omega=0, I'm getting 2 as my answer however the correct answer is 3. I think my formulae for L1 and L2 and incorrect


texts:
The circuit I am currently working on has a common connector for 12V and up to 48V input - this is fixed due to retrofit of POE to a design.

The target board requires a 12V supply rail. With 12V in through a regulator, however, this voltage will drop and this cannot happen so, a solution would just be to put in a jumper across the input to regulator output (with the EN pin set so that Vin > 12V + Vregdrop). This is acceptable but in order to stop someone plugging in a 48V supply to a board with a jumper, an automatic switch would be ideal.

Now, the circuit I have designed here will do most of that for me. Vin is passed to 12V when it is 12V. If the input is above ~15V, the pass transistor M1 is turned off and the regulator is on.
The issue comes with the startup of a power supply - there is a small peak at the start depending upon the input rise time. The power supplies can vary and that the current draw on the 12V rail is ~2A.

How can I delay this until it has reached a steady input voltage of ~12V or >15V?


texts: High Power Permanent Magnet DC Motor Controller

texts:
I am looking for a way to control both the DIRECTION and SPEED (variable speed) of a permanent magnet DC motor, similar to the ones found on mobility scooters. The motor has the following ratings:

24VDC
18A full load current draw.
0.43kW rating.

Initially my idea was to build a basic H-bridge driver using high power MOSFETS and then use PWM to control the switching. However through research I found out that it is actually quite difficult to build as there is a lot to take into account.

What other methods are there for controlling the direction and speed of a DC motor?. Most circuits online seem to be a repeat of one another or are only designed for low power applications.


texts: 24-bit two's complement division in AVR assembly

texts:
How do I perform a division by 2 of the 24-bit two's complement value in registers r6:r5:r4. (r6 is the most significant byte.)

From what I have this is what I tried:
ASR r6;ASR r5;ASR r4;
but I am not sure whether I did it correctly.

My thought process is that by shifting every bit to the right lets say a 4 bit binary 1110, by shifting to the right from MSB will be 0111. and therefore 0111 is half of 1110. But I am not too sure I have done it correctly.


texts: Implementing digital control on analog potentiometer

texts:
I have an analog sound processor unit, which uses either ICs or spare components.

There are four controls, which are simple potentiometers.
I would like to control their levels digitally, storing the settings in an EEPROM.

Which are the architectural most advisable solutions?

The idea is to transform an analog device into a MIDI controlled device, I am available in doing it with more elementary components or, if possibile, implementing ICs which can do the job.


texts: Cannot seem to initiate Inerrupt in STM8S TIM2

texts:
I trying to initiate an interrupt every 1 minute. The Timer itself is working however, the interrupt does not seem to work. I have added my main code + the vector interrupt code. Please let me know what am I doing wrong.
//Required Headers

#include "STM8S.h"
#define test_LED GPIOB, GPIO_PIN_5
void clock_setup(void);
void TIM2_setup(void);

void main(void)

{

GPIO_Init (test_LED, GPIO_MODE_OUT_PP_LOW_SLOW);

  clock_setup();

  TIM2_setup();

   while(1);

}

void clock_setup(void)

{

  CLK_DeInit();
  CLK_HSECmd(DISABLE);
  CLK_LSICmd(DISABLE);
  CLK_HSICmd(ENABLE);

  while(CLK_GetFlagStatus(CLK_FLAG_HSIRDY) == FALSE);

  CLK_ClockSwitchCmd(ENABLE);
  CLK_HSIPrescalerConfig(CLK_PRESCALER_HSIDIV8);
  CLK_SYSCLKConfig(CLK_PRESCALER_CPUDIV1);
  CLK_ClockSwitchConfig(CLK_SWITCHMODE_AUTO, CLK_SOURCE_HSI,

  DISABLE, CLK_CURRENTCLOCKSTATE_ENABLE);
  CLK_PeripheralClockConfig(CLK_PERIPHERAL_TIMER2, ENABLE);}

void TIM2_setup(void)

{

  TIM2_DeInit();
  TIM2_TimeBaseInit(TIM2_PRESCALER_32768, 3662);
  TIM2_ITConfig( TIM2_IT_UPDATE, ENABLE );
  TIM2_PrescalerConfig( TIM2_PRESCALER_32768, TIM2_PSCRELOADMODE_IMMEDIATE );
  TIM2_ClearITPendingBit( TIM2_IT_UPDATE );
  TIM2_Cmd( ENABLE );
}


texts: Why for a dipole antenna half wave length is optimum size?

texts: For a dipole antenna, half wave length is optimum size. Why is this so? What I understand is that radiation resistance of antenna is around 50 ohms at this size, which matches with the characteristic resistance of transmission line and hence less reflection loss. Is this reasoning correct? If yes, then why transmission line cannot have lower resistance? If no, what is the reason?


texts: Why do we need to install a power transformer for each high building?

texts:
I live in area where many high buildings are being built. Each building is more than 10 floors. A special room is made next to the main entrance or the garage. The room is designed for installing a power transformer inside it. The room also provides good ventilation. The primary coil (winding) of The transformer is 11 KV and the secondary coil is 380/220 V.

Why do we need to install a transformer for each building?


texts:
Can I Consider this OP Amp "AD8672" as Dual/Single supply Voltage or it is for dual supply voltage only?
Also IF it can be used with a single supply voltage, What is its allowable range of applied supply voltage?
https://www.analog.com/media/en/technical-documentation/data-sheets/AD8671_8672_8674.pdf
I appreciate your help.


texts: Where better to pull the NTC thermistor? To earth or VCC?

texts: I have a NTC thermistor, resistance 10k. In various examples, thermistors pull either to the ground or to the VCC. The question is, is there a difference and what is safer?


texts: Electric circuit AC plug to DC Design Help

texts:
I'm new to designing electric circuits... but I have a simple project that I really need help on.
All I need is a AC plug source to be connected to a 100 WATT bulb and a 3V motor(motor should only have 3V across it).
Also, Ive read that I need a rectifier to convert AC to DC for the DC 3V motor?
Can anybody point me in the right direction on how to do this...
or how to learn how to do this?

Here's what my schematic so far looks like (it doesnt work)


texts:
I'm trying to power a ESP8266 and ATMega128 from a LiPo battery via the TP4056 charging module. I get 3.8V out of the charging module. According to the ATMega128 Datasheet it is possible to power the IC with

  Operating voltage 2.7 - 5.5V

so my question is which output voltage from the I/O pins will I get.


texts: What type of antenna does the Xbox One controller use and how can you disable it?

texts:
I recently cracked open an Xbox One controller, the impetus for doing so was two-fold:

First and foremost the engineer in me likes to see how things work under the hood as I learn a great deal that way
Secondly, I wanted to mod my existing Xbox 360 fight-stick controller to work with the Xbox One by splicing into the Xbox One's PCB for button presses; this is colloquially called "pad hacking."

I was able to successfully mod my controller to utilize the Xbox One's PCB and now my attention is aimed at electrically disabling the wireless functionality.  The reason this is necessary is that wireless communication is forbidden in fighting game tournaments due to the possibility of your controller affecting the inputs of your opponent (or vice versa.)

It's been a loooong time since I studied RF but I'm fairly certain that the antenna circled in blue in the picture below is an Inverted-F Antenna (IFA), is this correct?

I had thought that physically de-soldering the antenna would prevent the controller from wirelessly connecting, but I was wrong!  It still connected at a distance of about 6-8 ft.

Next I thought that cutting the trace on the bottom side of the board leading to the antenna (shown in red) would surely do the trick but again I was wrong; it would still connect if I was within a foot or two of the Xbox One.  As an aside, what exactly is that trace's functionality? Continuity tests shows to be at ground potential (this board has a common ground).  Originally I thought this was the feed line but now I'm thinking this is the shorting trace which acts like a parallel inductor.  Any ideas?

So what kind of voodoo is going on here, I had thought that to get a device to properly radiate in a functional manner requires all the right parts in all the right places.  This board, however, seems to be built like the terminator; it just keeps working.  Besides putting it into a Faraday cage, can anybody offer up suggestions on how to electrically disable this PCB from radiating?

As a side note, I'm not 100% sure what frequency band the Xbox One controller uses but if I had to guess it would be 2.4Ghz as that is what its 360 predecessor used.

EDIT

Here is zoomed in picture of the trace that I cut.  I followed the trace with blue dots so you can see how it connects to the antenna on the other side of the board. The trace appears to have an SMA connector as well as AC-coupling cap in series.


texts:
Rorguitars claim to have the best MIDI* guitar system on the market. Their website says:

  Our guitars do not have MIDI pickups. There is NO pitch detection to send the MIDI signals. Our instruments use an electronic system that senses the frets you press on the fretboard and sends the corresponding notes. [Thanks to Steve G for pointing this out.]

It's not possible to get polyphonic guitar to MIDI conversion based on electrical string/fret contact scanning alone (segmented frets pose wear problems, and it doesn't look like they use them in their product),
so some additional sensing must be involved. Multipress keyboards are possible but they can use diodes to prevent crossfeed between rows and columns. This isn't possible on the point of contact between string and fret.

Apparently developed at University of Limerick, Ireland, there is no further info on the web. Probably they don't want to disclose it.

What techniques could be employed to determine the highest fret pressed on each string in such an instrument while handling the short circuits produced by multiple string presses on multiple frets? (Each string press contacts the fret above and below the point of pressure.)

To illustrate:

Frets and strings form a matrix which can be scanned.

Single notes and notes apart more than two frets pose no problem, but ambiguity arises with close spaced chords, here a simple doublestop.

Both the G and D string read frets 2,3 and 4, as the conducting path in blue crosses strings.

Determining the shortest path (in green) provides the additional information required to discern chord shapes.

Out of the possibilities

Capacitance
Resistance
Reflectometry

for string sensing, lets pick the last option - not least for the purposes of being specific.
Also the first two might be influenced by hand contact.

It is not necessary to detect exact lengths, being able to compare whether one fret is closer than the other is sufficient.

So the question is whether it's feasible, given the required rise times, to implement this in a suitable form factor.

Edit:

I found an interesting patent from 1984 (US4630520) by Turtle Beach cofounder Carmine Bonanno.

Wonder why it never took off.

It's the combination approach I had in mind, only with resistance sensing, as suggested by Transistor.

Frets and strings are scanned separately by multiplexers. As reliability issue he stressed the fret/string contact resistance, requiring low current, therefore high input impedance.

I wonder however if an (initial) sufficiently high wetting current (snubber capacitor?) might help alleviate noisy junctions.

MIDI (/ˈmɪdi/; short for Musical Instrument Digital Interface) is a technical standard that describes a protocol, digital interface and connectors and allows a wide variety of electronic musical instruments, computers and other related devices to connect and communicate with one another.

MIDI carries event messages that specify notation, pitch and velocity, control signals for parameters such as volume, vibrato, audio panning, cues, and clock signals that set and synchronize tempo between multiple devices.

Generating MIDI signals from non-keyboard instruments such as, in this case, a guitar poses some interesting electronic design challenges. While keyboard instruments are relatively straight-forward to digitise string and wind instruments have many more nuances that are difficult to detect and measure and, therefore, difficult to convert to MIDI.


texts:
When reading from a GPIO pin, at what frequency do the crests and troughs of a wave begin to blend together to the point that the CPU can no longer distinguish between them?

I assume the answer depends on the CPU and implementation, so to keep this simple, let's assume I'm using a BeagleBone Black (because I am).

If I have a 1Ghz sine wave, ranging from 0V - 3.3V, will be BeagleBone Black still be able to read it as anything other than a blur of ~1.65V?

Edit: Ok, I'm not worried about 1GHz specifically.  I'm just wondering at what frequency the GPIO pin can no longer discern between the crests and troughs of the wave.  The 1GHz example was just meant to be an extreme case.


texts:
There are 2 software tools provided by ST to flash their STM32 MCUs namely STM32CubeProg and STLINK Utility

STM32CubeProg Page says:
STM32CubeProgrammer (STM32CubeProg) is an all-in-one multi-OS software tool for programming STM32 microcontrollers. It provides an easy-to-use and efficient environment for reading, writing and verifying device memory through both the debug interface (JTAG and SWD) and the bootloader interface (UART and USB).

STLINK Page says:
STM32 ST-LINK Utility (STSW-LINK004) is a full-featured software interface for programming STM32 microcontrollers. It provides an easy-to-use and efficient environment for reading, writing and verifying a memory device.

I wonder if both fulfill the same purpose or if they have any specific use-cases also?

Edit: More details and Link included


texts: What is the max current from a 9 V battery?

texts:
Let's take, for example, a 9 V battery. Forgetting about internal resistance or any temperature restrictions, what is the maximum current I can draw from this?

Using Ohm's law with a 1 Ω load, this should give us:

V = I/R
I = 9 V * 1 Ω
Current = 9 A

According to my calculations, this would give us ≈3.5 min of battery life

I also thought of it like this:

9 V battery, 550 mAh battery life
550 mA for 1 hour
550 mA/h * 3600 secs = 1980 A for 1 sec

Drawing this much current at 9 V would require around 5 milliohms according to my calculations. I know this isn't possible in the real world, but theoretically maybe?

Even theoretically ignoring the temperature restrictions and internal resistance, this seems obviously impossible. Where am I going wrong?


texts: Using diy lm386 preamp on standard commercial amp?

texts:
I have a small intercom-like device that has been siting around.
It looks something like this.
I suppose that inside is just a basic elect-mic and a button.
Also i have an power amp which i used to play music at occasions. Amp model.
So now i'm wondering can i make an basic lm386 mic preamp which will operate at 12v and plug it in amps input? or i have to make maybe some sort of passive mic pre-amp if there is such a thing?
I hope i did not confuse you with my explanation since im very good at doing that.
P.S.
I need to have separate preamp for my intercom device since im also making passive audio mixer which will use audio from pc and audio from this mic which will then go into one channel in my power amp.
Also here is my very poor done schematics of my idea:


texts: ESP32 receive BLE data and send via WiFi possible?

texts:
I searched quite a long time now but I'mstill not sure whether it's possible using (just one) ESP32 module.
What I need/want:
I have some sensors sending their data using Bluetooth Low Energy about every 200 ms. But they are too far away to catch them all with just one receiver, and mesh has too high energy consumption. My idea now is to use ESP32 modules as gateways/repeaters (their consumption doesn't matter.)
The ESP32 should connect as a central to like 3 or 4 of the peripherals and receive their data, and then using WiFi push it into a MySQL database on a nearby server/hotspot.
Is this possible? Stay connected to WiFi, receive Bluetooth data, send via WiFi with good timing, or would I need to involve like two modules per gateway one for Bluetooth receiving and one for sending via WiFi and those two connected via SPI/I²C?


texts: How to transmit high current (2.6A) with low voltage (1.2V) for a long distance?

texts:
I want to supply a DSP with 1.2V. This DSP needs 2.6 Amps of current at full load. The minimum supply based on the electrical specs of this DSP is 1.16V, which means that the maximum voltage drop caused by power planes, traces and connectors  should not exceed 40 mV.

In my case, I found it very hard to achieve this since the distance between power source and DSP is about 8000 Mil (~ 20 cm) and this supply passes by two connectors which add 100 mOhms, so the drop is 260 mV (100m x 2.6A) without counting in planes impedance. I drew a simple schematic for my case shown in the next image:

My questions are:

Is the total distance only 20 cm? or should I add the return so that the actual distance is 40 cm ? ( Much worse :( )
How can I solve this issue? knowing that the distance between source and DSP can't be less than 20 cm. Should I add another regulator beside the DSP? or is it better to generate a slightly larger voltage to compensate this drop? (there is other components the need 1.2V supply and are at different distances from the DSP).
How can I calculate the plane impedance, shown in the above image as R(Plane)?

# Edit 1:

Regarding point 1, ok, the total distance now is unfortunately 40 cm.

I thought of a solution to reduce the connectors resistance, which are the main factor of high resistance. According to connectors data sheet, the resistance of the pin is 25 mOhms, I have extra free pins, so I'll use 8 Pins to transmit the 1.2V so that the is now divided by 8, but the question now is, I don't know if this resistance is for the pin only or is it the total after mating? and after mating should they be treated as series or parallel resistors?


texts: The symbol for an inverter (logic gate) is usually the one shown below left.  But I have sometimes seen the symbol shown below right.  (See, for example, the last image in this answer.)  What does this difference in symbols represent?


texts: Why are these switches connected to ground?

texts:
Sorry for the vague title. This is a schematic of a Nerf Rayven foam dart gun:

Why did they make the connections that I circled in red? I'm guessing it has something to do with the inductors on the left side of the motors, but what exactly is it doing?


texts: Using 12v car battery to supply multiple "3.5v" devices

texts:
I'm trying to supply power to strings of LED lights for emergency lighting
purposes with a 12v car battery.  With the 12v supply I figured I could get 3 sets going at the same time.

The power supply that comes with them says:

INPUT: 120V-60HZ,0.06A -  OUTPUT: 3.5 =-=-= 0.45A

For using DC only with a battery, I figured that a simple voltage divider would work.  So in trying to determine the best value for the resistors in the divider I tried taking a resistance reading on the string of LEDs.  I am unable to get a reading and at the 200ohms range setting, the meter is actually lighting the LEDs.

Here's what else I know:

The actual voltage coming out of the power adapter is 4.3v without the LEDs connected and only 3.2v with them connected.  The resistance of the DC side of the adapter is 430 ohms.

So, am I right in assuming the following circuit would work?

simulate this circuit – Schematic created using CircuitLab


texts: Why is the voltage across my nichrome wire so low?

texts:
I have a 37 AWG nichrome wire (0.6 mm diameter) with 5 ohm (about 3 m wire) resistance, 12 V DC supply with max 1 A output.
I only measured 1-3 V across the nichrome wire, the wire does warm up but the V across it is too low, the multimeter didn't read any current through the wire for some reason. I tried it with a short nichrome wire and the voltage went 0 V probably because the resistance was too low.
I want the wire to reach 100°C.  The datasheet (RD 100 / 0,6) says that needs 2.21 A, according to Ohm's law that's 24 W and with 3 V across it that needs 8A (I = P/V).
How I can increase the V across wire so that less current would be required? Why is the voltage so much less than the supply? I obviously need a supply with higher current rating but with an actual 12 V across wire I would only need 2 A and supplies with lower ampere limit tend to be cheaper.


texts: In this example of using a 3Q triac, could the AC voltage flow into the DC terminal?


texts: Why are integrated circuits powered by low voltage and high current?

texts: I've heard that a typical graphics card uses around 100 A of current and only 1 V of voltage. Is there a specific reason why not to use the other way around, so high voltage and low amp? Usually high current leads to high losses, that's why power transmission lines usually prefer high voltage instead of high current. So what am I fundamentally not understanding why that is a bad idea for integrated circuits?


texts: Why are 10-pin DIP integrated circuits so uncommon?

texts:
This is a tangential thought from this answer, specifically the line "There are 10 and 12 pin DIPs".

After some searching around, I finally located only one 10-pin DIP part: NTE1450, 5 Watt audio power amplifier. The part is evidently obsolete, and the one datasheet I found, I cannot locate again.

I found many other components in 10-pin DIP  though: LED displays, DIP switches, resistor packs and of course DIP sockets.

There are many 8 pin PDIPs 14 pin PDIPs flood the logic gate listings, but 10 and 12 are apparently pariahs. I haven't actually searched for a 12-pin DIP IC yet, but I suspect that too will be a rarity.

Why are 10-pin DIPs so uncommon?