texts: Can you drive a motor bidirectionaly with just N channel mosfets?

texts:
I bought a bunch of IRFZ44Ns from China in the hopes of driving a motor bidirectionaly controls from and Arduino, but now I realise that a full bridge requires both P and N channel mosfets.. Is it possible to make a half bridge, or even a full bridge from N channel fets only?

Also, is there any reasons I don't see any schematics using IRFZ44Ns? Are they a poor choice for the application? It's only a small 4v motor.


texts: Determining Maximum Amplitute of Sinewave that can be applied to an OpAmp

texts:
A noninverting amplifier with a closed-loop gain of 1000 is designed using an opamp having an input offset voltage of 5 mV and output saturation levels of ±13 V. What is the maximum amplitude of the sine wave that can be applied at the input without the output clipping? If the amplifier is capacitively coupled in the manner indicated below, what would the maximum possible amplitude be?

The first part of the question I've worked out by rearranging:

\$V_{out} = [1 + \frac{R_2}{R_1}]V_{in} + [1 + \frac{R_2}{R_1}]V_{offset}\$

to

\$V_{in} = \dfrac{V_{out} - [1 + \frac{R_2}{R_1}]V_{offset} }{ 1 + \frac{R_2}{R_1} }\$

\$V_{in} = \dfrac{13 - (1001)(5) }{ 1001 }\$

\$V_{in} = 8 mV\$

So 8 mV is the peak voltage (which according to my professor is the right answer). However I am completely lost to what happens once the capacitors are couple


texts: Sending data over network via MicroController (Sparkfun Thing // ESP8266)

texts:
I'm getting frustrated and keep hitting a wall. My basic setup is I have an Apache server running on my Raspberry Pi and I am looking to send sensor data over the wireless network both are connected to in order to post live data on the server.
I've tested the server config and I'm able to stream random data from a WAMP server that is also on the network. So I think the server side is alright.
Microcontroller side I have a Sparkfun Thing, it connects to the network and gets an IP address which I can ping. But I just can't seem to get it to send data properly.
Can anyone give me any advice on my code?

#include <ESP8266WiFi.h>

//Raspberry Pi Login Credentials.
const char WiFiSSID[] = "Alamo";
const char WiFiPSK[] = "12345678";

//Pin Definitions
const int LED_PIN = 5;
const int ANALOG_PIN = A0;

//Variables
const char host[] = "192.168.44.1";

void setup()
{
  pinMode(LED_PIN, OUTPUT);
  pinMode(ANALOG_PIN, INPUT);

  byte ledStatus = LOW;

  WiFi.mode(WIFI_STA);
  WiFi.begin(WiFiSSID, WiFiPSK);

  while (WiFi.status() != WL_CONNECTED)
  {
    // Blink the LED
    digitalWrite(LED_PIN, ledStatus); // Write LED high/low
    ledStatus = (ledStatus == HIGH) ? LOW : HIGH;

    delay(100);
  }
}

void loop()
{
//for testing purposes set temp to a default value.
//int temp = analogRead(ANALOG_PIN);
int temp = 43;

  WiFiClient client;
  const int httpPort = 80;

  if (!client.connect(host, httpPort)) {
    digitalWrite(LED_PIN, HIGH);
    Serial.println("connection failed");
    return;
  }

String data = "temp1=" + (String)temp;
String url = "GET /data.php?" + data + " HTTP/1.1";

client.println(url);
  client.println("Host: 192.168.44.1");
  client.println("Connection: close");
  client.println();
  client.flush();
  delay(500);

  //End of Send.
  digitalWrite(LED_PIN, HIGH);
  delay(100);

    while(client.available()){
    String line = client.readStringUntil('\r');
    Serial.print(line);
  }
  client.stop(); //Stopping client
  //Deep sleep not necessary for testing
  //ESP.deepSleep(60U*60*1000000); //U for unsigned
  delay(100); //for above sleep
}
enter code here

Thanks,
Pete


texts: I have a tablet case with a keyboard in it. It came with a large USB type A plug and a large Y-adapter to USB micro-B. It has always worked. The tablet has a micro-B type connector and it works fine. I wanted to replace the A plug and adapter with a micro B plug, so I bought one on e-Bay. I searched about to find the pinout, and confirmed the A plug is -, data+, data-, + with the data+ wire blue coming out of the keyboard. When I put the new micro-B plug in the tablet I could not measure the 5V. I soldered the wires on and it doesn't work. When I connect the power and gnd (+ & -) I still don't measure the 5V. The tablet USB port still works and I can charge the tablet. Any ideas? In the photo the wires are (left to right) -, n/c, data+, data-, +.


texts: Diodes on SPI bus data lines and pull-up resistors

texts:
Take a look at this schematic provided by Adafruit with a MAX31855 to read a thermocouple.

They use diodes on CLK and CS pins while also pulling them up on VCC.
I would like to ask why the use those diodes?
Maybe as an ESD protection?
And on another note:
Let's say, on the PCB I am currently designing, I have multiple SPI devices on my bus. Should I add those same pull-up resistors on all of the devices or just place them once for the whole bus?
Maybe I should use multiple buses?
Yes, I know about the sink current of my μC and I should adjust the values accordingly if I have to place multiple pull-up resistors. But should I?


texts: What's the small signal model of this CMOS differential pair?

texts:
I cannot derive the small-signal model for this differential pair:

My goal is to observe the effect of transistors M6 and M7 which should create a hysteresis effect in the output equation for Vo1 or Vo2 depending on their size ( W/L ). I would like to use one or multiple instances of this differential stage to create a comparator with hysteresis.


texts: Automotive 20:1 Oscilloscope Passive Attenuator Design

texts:
I'm currently working on designing a switched, passive 20:1 attenuator for use in an automotive educational environment on PicoScope PC based oscilloscopes. In automotive electrical diagnostics, it's common to measure the control side of injectors or ignition coils (primary side) to view the voltage waveform. Due to the large voltage spike at that terminal as the coil is disconnected from the supply or gnd, it's common to use an attenuator before the oscilloscope input to reduce the signal magnitude to a safe range for the oscilloscope.
For my design, I chose a 20:1 passive attenuator which can be enabled or disabled by a switch (similar to a standard scope probe). The attenuation is set by a resistive divider with compensation capacitor. Note: the PicoScope input impedance is 1M || 24pF. Additionally, as this device will be used in an educational environment, I decided to add a 1.5kW bi-directional TVS diode (Vishay TransZorb series) to clamp any unintentional voltage spikes in the 1X mode to below the maximum input voltage of the scope (±100V).
Here is my current schematic:
Note: V_IN_1 is the BNC which the test leads connect to and V_OUT_1+, V_OUT_1- go to the PicoScope input.

My issue is that I'm having trouble selecting an appropriate switch for enabling or disabling the attenuator. The maximum voltage across the switch (worst case) may be around 250-300V. Most of the through hole toggle and slide switches that I can find are rated at around 120-250VAC (much less at DC I assume). Is having a switch for this a bad idea? I've thought about just having two input BNC jacks (1X, 20X) that the user will switch between. Though, I'm worried that students may damage the BNCs will repeated connecting/disconnecting. Are there any other options I should look into?
Thanks in advance!


texts: What's needed to put a PC fan into reverse?

texts:
I've got a PC fan here (I've peeled off a sticker).

And although this one doesn't come with the usual 3 or 4 wire connectors, it has enough electronics in it to only operate when power + is on red, and - is black but/and it won't operate when power is connected the other way round. I don't know anything about how these (brushless?) PC fans are controlled, but I assume one of the basic/first steps in the circuitry is to make sure polarity is right. Right?

So, now, is it possible to reverse the motor with a simple hack, or is is not possible without heavy modification of the controller or stuff...

Ideas how to trick it into spinning the other way round?

(Notes:

Sorry for not providing the exact model of the fan. Let's assume it's pretty generic.
Also, I know the fan blades are designed to spin this way round, and reversing it would mean having a less optimal fan.
I can't just flip the housing. It's a long story why, but that's not an option.
I couldn't get the casing open or the fan blades off, it's all pretty sturdy)

Update:

Taking all the feedback I had so far into account, I first tried to get that darn thing open (no success) and then had a closer look from the outside:

What we see here from the side is (4 legs) a hall sensor, right?

That means/would mean: it's the "sensored type" of fan, meaning that even breaking it open and swapping motor cables would have no effect (no cables btw., the motor seems soldered to the controller board).

As I have a hard time deciding on the accepted answer, I think I have to check Olin's as he was the first to point that out, although pericynthion was first with an answer.


texts: How to calculate overall average propagation delay for digital circuit given

texts:
Using the circuit shown with 3 inputs {A,B,C}, and outputs {F1,F2,F3}, and using the average propagation shown below for each gate:
AND -> tpd = 9ns,
XOR -> tpd = 8ns,
OR -> tpd = 10ns
Calculate the average propagation delay for the below-given circuit.

My approach:
Average propagation delay:
Adding 2 AND gates in series 9+9 = 18ns
Adding 1 AND and 1 XOR in series 9+8 = 17ns
As 18ns is bigger value, we take 18ns and ignore 17ns and add tpd for OR gate
18 + 10 = 28 ns
Is 28 ns the correct answer?


texts: Tips for designing 4 pad feedthrough capacitor in Altium Designer

texts:
I'm doing a PCB design in Altium Designer where I would like to include a feedthrough capacitor from Murata (MPN: NFM18CC101R1C3D). This is a special type of capacitor with 4 physical terminals where two of them are internally connected, i.e. 3 logical pins. I have not been able to find the component anywhere and the "IPC Compliant Footprint Wizard" does not include a such footprint.

My question is: What is the best way of making this type of component in AD

Would you create 4 pads in the PCB editor where two of the pads have the same designator?
Would you include the 3 recommended through-holes as part of the component or would you just include them as free via's in the board file?
I would like to have the board produced at Seeedstudio which accepts a minimum via dimension of 12mil (0.305mm) hole and 25mil (0.635mm) diameter. Based on this I don't think the inner through hole will be possible to make. Can I simply skip this without having to worry too much about lost performance?

I'm looking forward to hear you suggestions.

Best Regards,
Andreas

I'm new to Altium Designer


texts: How is jitter of an oscillator measured and quantified in practice?

texts:
One of the characterisation parameters of oscillator is jitter. But I guess this requires a measurement technique with good timing accuracy.

In practice what sort of lab equipment is used? How is jitter is measured and quantified?(as a big picture)


texts: Charlieplexing: a LED producing light very slightly, although it shoudln't, based on its forward voltage

texts:
I have a display of a few LEDs, using charlieplexing:

The display devices don't have any other parts, and don't have any space to place any parts either. The resistors are on the wires A, B and C between the controller and the display device.

When only device 1 is connected, in the configuration A = tristate, B = 0, C = 1, the green LED 3 lights up just as it should. However, the red LED 1 also produces a very faint light. It's barely visible, but it's there. There seems to flow some small current through the LEDs 5 and 1, although the forward voltages of LED 5 + LED 1 are much higher than of the LED 3.

All red and all green LEDs are of the same make, the reds having a forward voltage of approx 2.1 Volt, and the greens 3.9 Volt.

When I also connect the Device 2, the glowing of LED 1 becomes slightly stronger. It's understandable, because we just "doubled" LED 5.

How can I eliminate or at least strongly diminish this effect? I cannot place any new parts inside the devices (although I could flip the LEDs and change the software of the controller accordingly), the only place I could insert new parts are the cables: cut an individual cable and put a serial component there.

I managed to diminish the effect of using both devices together, by putting two parallel, reverse-polarized diodes on one of the wires of device 2.

All LEDs are driven by a PWM of appox 300 Hz, if this is provides any additional useful information.

Are there any other approaches I could consider?


texts: Disadvantages of Buying FT2232H Chips of Uncertain Origin

texts:
I was planning to buy this FT2232HL FTDI board from Aliexpress for basic FIFO applications. It is obviously fake; being cheaper than the entire chip itself and having no "FTDI" marking on top of it.

I was wondering, what should I expect from this product in terms of performance and endurance? Will this device function properly or simply missing a key feature that is not noticeable at first look, such as the 4K buffer or some important protection? No need to mention infamous "FTDIgate", I suppose.

I'm basically an electronics hobbyist, so simple words really appreciated, although not necessary. Thanks...


texts: RTD temperature measurement system resistance question

texts:
I am trying to produce a bridge circuit for the following temperature measurement system:

Designed to measure temperatures between 0 C and 100 C with a high accuracy.
When supplied with a 10 V source voltage, the system produces an output ranging from 0 mV to 100 mV.

I have chosen a PT100 platinum RTD sensor for this circuit (which I am presuming will be a 3 wire Wheatstone bridge).

What would the resistances be of R1, R2, R3 and R4?
What would happen if I varied those resistances? (all of them equal or R3 & R4 being much larger/smaller than R1 & R2)
And then how would I calculate the current through this RTD Sensor?

Thanks!


texts: Help identifying a M12-like 4-pin connector with 6mm diameter

texts:
I am trying to make a custom cable for a project, but I don't know what kind of connector this is?
It looks similar to a 4 pin M12 connector but the diameter of this connector is 6mm. Can somebody please let me know the connector type if they are familiar with this kind of connectors?


texts: What function do the resistors and capacitors serve in this 1:1 audio isolation circuit

texts: I want to better understand this circuit, which essentially just puts a +/- audio channel through a 1:1 audio isolation transformer. I am having trouble understanding what the resistors to ground, as well as the RC between the output +/- do. Any resources on the subject would appreciated.


texts: LM338 based psu with arduino based voltmeter

texts:
I want to make sure I'm doing this correctly before I put everything together.

I'm using fixed resistors just for testing purposes. I do have a digital pot.
The LM338 uses a voltage divider to set the output voltage. I've configured R1 as 240ohms and R2 as 3.3K which gives me 16v. I measured the voltage between adj and output pin which gave me 1.2v. Am guessing that's the voltage coming out of the voltage divider yes? So I just wire this to a ADC pin on my arduino yes?


texts:
Im supposed to calculate the gain and impedance (in & out) of the inverting amplifier below. I also need to simulate the circuit with Ltspice using different \$V_s\$ values.

Im aware that the gain is calculated as \$\cfrac{V_o}{V_s}=-\cfrac{R_2}{R_1}\$. The problem with calculations and simulating is the circuit inside the red ellipse. I suppose the voltages +15, and -15 are for the amp (usage voltages).
But how to take that part into account calculating voltage \$V_s\$. Im not quite sure how the potentiometer in this case (or in overall) works. Also if possible, is there some equivalent circuit for understanding and simulating on Ltspice?

Any help will be appreciated.


texts: Complementary pair - Role of capacitor on emitter

texts:
I bought this little kit for a class AB amplifier.

The second stage is quite clear (and typical), but I am struggling to understand the role of capacitor C2 on the emitter branch in the first stage. In the explanation they say that this is a "complementary pair in common emitter mode". However, I would expect to see the two emitters connected and either no capacitor or a capacitor as a bypass. This looks an open circuit in DC.
I also built an LTSpice model to check the voltages and it looks like it is being used to keep the base of Q1 at Vcc/2 (approximately).
I have looked around and could not find any other similar example.
Am I reading the circuit incorrectly? Just learning about electronics and amplifiers just for my own education, so please bear with me.


texts: Current through Capacitor, how is it possible? How does it relate to displacement current?

texts: What my professor is telling us that there is no conduction current through a parallel plate capacitor but the current that is passing through capacitor is the displacement current and this phenomena can be seen in one of the Maxwell's equation. What I know about displacement current is that there is no charge movement in displacement current but I am so confused with that. Can some one explain me the displacement current and how does it work in parallel plate capacitor?


texts: Can over-excited synchronus motor operate on lagging power factor?

texts:
All of the Electric Machines literature I'm using states that over-excited (back emf E> supply voltage V) synchronus motor will operate on leading power factor (one of them states that it may also operate on unity power factor for some value of back emf E).  But my calculations shows that  it may even operate at lagging power factors if E is not that much greater than V.  Specifically,  motor will operate at lagging pf if cosine of load angle is less than V/E . This will cause resultant emf to lead V by less than 90 and thus,  neglecting armature resistance,  I has to lag V.   However as most of (standard) literature are not verifying this,  I am having quite doubt on myself  if I am doing something wrong.  So please let me know if I'm right..

Bonus question : What may be nature of armature reaction if machine is operating on lagging pf while being over excited.

PS: I know that even if I'm right,  in most of cases,  over exciting will mean increasing E much above V so that we'd have leading pf but still,  I thought atleast books must've included this possibility...


texts: I am working on to build a dimmer for led lamp. Led driver AC input is about 220V and output of the driver is 70V under load. I placed a npn transistor (mje13007) between led ground and led driver output ground. I am driving this transistor with a PWM source.When duty cycle gets bigger, it starts to flicker. What is this problem and how to overcome?


texts: Unable to create proper sine wave with 555 timer

texts:
I was trying to create a sine wave with this circuit but with different values.

When I just measure the 555 timer, I get a more or less proper square wave:

But the moment I add my LC low pass this happens:

Green = 555 Output
Yellow = LC Output

Is the lowpass too much of a load for the 555 timer or what else could cause this?
What can I do to fix this?
When I connected a proper triangular wave from a generator the sine from my LC low pass was fine.
The simulation with my values:

Another thing I am wondering, the yellow line is the output of the LC.
Why does it have a flat maximum? shouldn't it slow down its slope reaching its maximum?

Ok I changed the values to: 2.2mH for the inductor and 2.2muF for the capacitor getting a resonant frequency of 2287Hz. I measured the generator with a frequency of 2300Khz. It's looking still better but still has this weird flat maximum. Interestingly I can actually hear a high-frequency noise from this circuit now:


texts: Wide voltage range input regulation (24V - 3.3V)

texts:
TL; DR: I need a circuit capable of handling input voltages from 24V to 3.3V (with a 10mA/5mA maximum current) and delivering 3.3V to the microcontroller (ESP32) input.

Recently, I've been working with the EPS32 microcontroller. And this project in specific requires signals from different sources, with different maximum output voltages: 5V, 24V and 3.3V. The frequency wouldn't be more than 100KHz.

My signal sources can provide up to 10mA, but a 5mA limit would be more confortable for me to work with. Galvanic isolation isn't a requirement, but it would be interesting!

I searched on the web for circuits to implement in the project, but almost every one that I could find, could only handle a single specific voltage. The majority of the designs I found were based on the classical optocoupler circuit, with a current limiting resistor, calculated for a certain voltage.

In fact, I found an Electronics Stackexchange question that was almost exactly what I needed (How is this 5-24V input circuit working?), but I don't have access to any JFETs in my local store, also, I couldn't find any MOSFET to effectively replace this JFET.

I was thinking if OPAMPs could do this job, but I am not sure if this is a good practice.

Any help will be very appreciated!

PS.: Sorry if my question doesn't express my current effort in the project, as it doesn't contain any circuit/design attempt made by me, but I am really lost with this part of my project! So I couldn't figure out any decent circuit.


texts:
I'm working on a 4-layer PCB with a U-Blox module and I'm trying to calculate the space between the fencing vias next to the Antenna trace and for the stitching vias.

According to the datasheet we have the following possible frequencies:

The case which would cause the closest vias is the last one.

According to the calculations suggested here https://electronics.stackexchange.com/a/42028 I should put them ideally with the following spacing:
$$
\frac{\lambda}{20} = \frac{C/2170Mhz}{20} = \frac{138.25mm}{20} = 6.9mm
$$
but if we look at this image from the datasheet it seems way too much compared to what they did; consider that the side of the module (the white outline) shown in the above figure is 16mm, so according to calculation there should be a dot at the beginning and at the end of the track and that's it.

My best guess is they are basing the fence spacing on the Greatest Common Divisor for the mean value of each frequency reported in the table to cover each operational mode.

Stitching wise I report what found in this page:
https://www.edn.com/electronics-blogs/the-practicing-instrumentation-engineer/4406491/Via-spacing-on-high-performance-PCBs

$$
\lambda = \frac{300}{F\times\sqrt{\varepsilon_{R}}} = \frac{300}{2170Mhz\times2.097} = 60mm
$$
now \$\lambda/8\$ is 7.5mm and that should be the necessary spacing for the ground stitching (Er = 4.4 for typical FR-4 PCB material).

To sum up:

1) How much space there should be between each fencing via in my case?

2) How much space there should be between each stitching via in my case?

3) Does the frequency actually relates to the fencing/stitching space, or placing the vias closer than the smallest \$\lambda/20\$ (for fencing) and \$\lambda/8\$ (for stitching) is all that matters?

4) Is all that stitching shown in figure really necessary from an RF point of view?


texts: Should I use shielded RJ45 plug by the computers?

texts: If I have shielded cables, jacks and plugs and I ground the shielding properly, then should I use shielded plugs at the computer's site too? I mean if I do so, then the shielding will be connected to the motherboard or to the case, which I am not sure I want...


texts: How do I easily power a "mashed-up" project?

texts:
I'm working on a hobby project that involves a Raspberry Pi (with a powered USB hub for reliable wireless), an Arduino (driving a hobby servo, controlling some LEDs, etc.), and an audio amplifier (not rolling my own - using a torn down set of powered computer speakers). So basically, I have five things that normally would each have a separate power supply.

I'm mostly a programmer with a little electronics knowledge, mostly digital with just enough knowledge to interface with sensors and things. I'd love for this project to have one wall plug, not be powered by four or five wall warts. I also don't want to have to implement a dedicated power supply. I know the Raspberry Pi is a little picky on its power consumption (I'm using a 1A supply for it currently).

I thought about using an old laptop power supply with 18v and (I think) 2A. Could I just do that and use a few power regulators to provide the necessary voltages to the other pieces? If I do, what should I be aware of and watch out for? I also considered an old PC power supply, but it's much too large for the enclosure that I have in mind.


texts: Integrating simple Bluetooth functionality without microcontrollers

texts: I have recently bought a Bluetooth HC-05 Module, and have followed many tutorials on integrating it with an Arduino, or a microcontroller. However I got interested in whether it is possible without one. And the task I need to achieve is pretty simple, just switching an LED on/off. The official bluetooth documentation is impossible to read, so I'm asking the question here, since I know many of you are experts in the subject.


texts:
I'm writing a report on the PI controller I built for my university project, which is supposed to keep a magnetic ball levitating underneath a controllable electromagnet. The prototype works with a table tennis ball, but the full scale project is supposedly for a levitating light ball, which would be outside, thus in the rainy and windy conditions of Belgium. I've decided to consider that rain doesn't really affect the stability of the ball, given that one raindrop's worth of force (i.e. the effect of one single raindrop hitting the ball at a time) is very very weak, even during cloudbursts. In order to be able to assume only one drop is gonna be affecting the ball at the same time, I also have to assume the controller will be able to correct about 1000 impacts per second, which is the average amount I'll be receiving during such episodes of very intensive rain.

I was wondering if a PI controller can actually react this quickly (about 1000 corrections/s).

Thank you.


texts: (Not) Impossible to separate AGND from DGND

texts:
I'm designing a USB-MIDI board and I decided to go for 4 layers. Since the digital and analog inputs (i.e. potentiometers and momentary push buttons) are distributed throughout the board, it's virtually impossible to separate AGND from VGND. What can I do to minimize noise?

I was thinking about routing the return paths of the digital inputs on one of the signal layers and use the ground plane for analog ground only but I don't know if this is a smart thing to do.

Edit: Thank you for your helpful answers and comments. What I took from that is: It is totally ok to have a single ground plane for analog and digital signals but you should arrange your components wisely and shape that plane in a smart way. Since the layout of the components is mainly determined by the layout of the hardware user interface I cannot do much about that. But of course I can shape that plane.

When I asked that question it was pretty early in the morning and I probably didn't provide enough detail. My PCB has a socket for a Teensy 3.6 which serves as MIDI USB controller and controls a few mosfets as power switches for other attached devices (2x 3 amps). The Teensy has an AGND and a DGND pin. Both grounds are connected inside the Teensy board. I just realized that I indeed could separate AGND from DGND but the shapes of those planes would look a little bit unusual:

It is my first PCB ever (yes I know that's a little bit ambitious for a first project) and I'm not sure if this is a smart approach. Thank you for your help!


texts: Is it possible to display HTML page on a LCD display of a discovery board?

texts:
For a start my intention is to make a simple webpage with a couple of virtual buttons to control PWM signal. My board is STM32F429I-DISCOVERY with STM32F429ZIT6 microcontroller and 320x240 color touchscreen LCD. Currently I'm running on MBED platform.

First what I tried is to find any ready-to-use solution like "mbed web browser" or "stm32 web browser", as I thought that it is the right thing to display a web page. However - nothing useful found. Why am I stuck to web-page as a human-machine interface? I think that web-page is scalable so despite the fact that my project can be solved with a couple of drawn rectangles I'd like to try something beter and flexible.

Questions:

Is it ever possible to display a web-page on a such weak device as my board is?
How about Javascript? I think that it would be the only way to interface between the web-page and the hardware. Or there is another way?
What can you recomend to search or use for my case?

Thank you in advance!


texts: Why not use the same size resistors for each stage in a Kevin-Varley divider?

texts:
I was thinking of building myself a Kevin-Varley divider as described for example in this article about a mini metrology lab in the March 1996 issue of Electronis Now by Conrad R. Hoffman.

The normal layout is well described in the following illustration on Wikipedia. One stage for every decade you want to divide, with decreasing resistor values for every new stage. The total resistance for the new stage must equal to twice the resistance of a single resistor on the previous stage:

However, because you can't easily get for example 400 Ohm resistors, and because of resistor tolerances and the importance of matching the total resistance, it seems customary to select a value that's slightly higher, then connect a shunting resistor and a trim-pot in parallel with the whole stage, to get the resistance down to whatever is necessary for the previous stage.

What would be wrong with simply using the same value of resistors for every stage, and using a shunt with a trim-pot to get the combined resistance down to the required range again:

simulate this circuit – Schematic created using CircuitLab

There are at least three benefits here:

The tedious job of hand-selecting 11 closely matching resistors for each
value is reduced to sorting a lot of the same value into bins.
No need to buy hundreds each of odd value resistors when you only need 11 of each. The parallel and serial shunt is from E24 and does not have to be matched with everything since they are trimmed out.
It's more modular. You can construct any number of these and chain. (Of course, the accuracy is still limited by the first segment.)

Perhaps there is some hidden drawback with this scheme. Will it be more sensitive to temperature? More noise?


texts: Can anyone help identify this connection or a Victron Orion DC-DC Charger?

texts: I need a replacement male connector for the female shown below. Can anyone identify the connector type?


texts:
I have a 5m LED strip (Ultimate Fancy LEDs) that consists has 30 LEDs per meter of WS2812B chips.
Is uses a SP601E Bluetooth controller and was delivered using a 5V/6A power supply.
Out of the box, the strip and controller works fine.
What I want to is the extend the wire (about 3m) from the controller to the actual strip. This is to be able to have the strip in the roof and the controller (with buttons) at the floor (so the kids can use it).
The problem comes when I try to dim the strip. When changing from 100% brightness, the strip starts to flicker. My analysis is that data wire (that runs at 800kHz) is to long for the controller to being able to properly drive those extra meters.
I tested a few different cables but can´t really get it to work properly.

Using a typical 3-wire power cable (1.5mm diameter wires)
SFTP network 4 pair network cable, AWG 26 where 5V supply uses 3 conductors, 4 wires for GND and 1 for DATA. In this case the voltage drop is a bit to much, losing about 0.5V over my 3 meter wire. But still this does not work properly for the DATA.

One weird thing though, is that the flickering is worse further down the strip (regardless of cable choice). I don´t really see this issue at the first meter of strip. If this is a signal integrity issue of the data line, I should see this an the entire strip, right?
If I just get a good waveform to the first chip, the WS2812B should reshape the signal after each chip, right?
So, am I having power issues or signal integrity issues?
I will later next week see if I can get a scope and measure some signals/voltages and get some more info.
In the case of signal integrity, would adding a simply buffer/line driver do the trick?
Update 1:
So it seem to be related to signal of data line and not power.
Tested both supplying the strip at both end and this improves the “yellowness” of the end of the strip but does not change the flickering. Also tested with huge cap at beginning of strip, no change.
Also tested to add 220 ohm resistor before cable, things go much worse. Not only flickering but color change as well.
Can’t really see that the data line degrades much over the cable (just some softer edges).
When it comes to the flickering, what actually happens is that the strip does not turn off but actually turns the leds brighter.
I see a small voltage drop on the power line when it happens.
If I short the data, basically don’t run it through my cable (so only power and ground in cable) things works fine.
So the cable must cause the data line to violate some parameter (rise/fall or high/low time).
I’ve ordered some buffers to see if this improve things...
Update 2:
Added a scope picture with comparison of the controllers 2 channels.
CH1 has my extension cable and a led strip attached.
CH2 is unloaded (so should be close to ideal).
I now realize that the controller high output is somewhere around 3.7-3.8V.
When dimming the strip (and not drawing so much current), the supply voltage is at 5.34V. For the WS2812, high is 0.7xVdd which is 3.71V.
Potentially the insertion of my cable, scales of that tiny margin.
Plan is to test a level translator tomorrow to get the data line up to 5V.


texts: Does anyone know if it is possible to file physical objects under creative commons or something similar?  I don't want to make money off anything I make, I want to show the public how to make it and if someone uses one of my creations for a not for profit cause then all the better. That being said I also don't want someone else profiting off something I have created.  Any suggestions would be great!


texts:
I have to find \$V_o\$ (voltage over \$R_3\$), \$I_o\$ (current through \$R_3\$) and the power absorbed by the 1 Ohm resistor in this circuit:

simulate this circuit – Schematic created using CircuitLab

I used \$V=IR\$ to find the current through \$R_3\$ and \$R_1\$ to be 1A. Then I multiplied it by 3 Ohms to find that the voltage is 3V. After this, I found the voltage over \$R_2\$ to be 1V the same way. Then I subtracted the V over \$R_3\$ from V over \$R_2\$ to get 2V, which I answered for A.

I also said \$I_o = 1A\$. After this, I used \$P=I^2*R\$ to find the power absorbed by \$R_3 = 1W\$.

When I entered the values I got, I got parts B and C wrong, but I'm confused on how I got A right if I used Io to find \$V_o\$.


texts: High pass filter to opamp buffer causing an offset (op-amp specs)

texts:
I'm currently building a filter circuit that is required to remove an DC offset from the raw signal and then amplify the gain. The rest of the circuit (not shown) is a 2-stage LPF with extra gain.

My problem is that when I add a HPF (fc = 0.002Hz) (or any HPF for that matter) at the output after the buffer, I get an offset of -10V. I've tried other op-amp models (LM741, LM324, etc) and the offset occurs but of a much lower value depending on the model. What opamp specification should I look at in the datasheet to determine why this is occurring?

The opamp I'm using is the THS4012.
The input is at 100Hz  and is shown as the yellow signal.

The green and red signal are the respective outputs after the buffer.


texts: What accounts for the current vacillation in this JK latch?

texts:
After trying a few different simulators (many of which didn't work for this) I was finally able to model a JK latch with NOR gates. Here is an example:

A weird thing seems to happen though (at least to me). When changing one of the logic inputs to use it "like an SR" latch, there seems to be current fluctuations between it reaches the steady state. Here is a video showing what I'm talking about:

https://gyazo.com/4a4fa7b61369367d7e6ba6dc032d1eb3

Falstad link

Why does this occur, and what exactly is occurring when it's 'flickering' ?


texts: Why are T-Filters better than L-Filters?

texts:
I was watching a beginners video about electronic filters. In that video, the presenter shows the same filter (same inductance and capacitance values) configured as an "L-Filter" and a "T-Filter" as follows:

During the video, the presenter mentions that the T-Filter provides better overall filtering over the L-Filter.

Could someone please help me understand how splitting the inductors as shown in the T-Filter makes for a better filter? What is occurring on the filter that makes one better than the other?

Thanks.


texts: Noise from switching fans nearby disrupting the I2C bus

texts:
I have a RPi controlling a solar system which uses temperature sensors on the I2C bus, the sensors are away from the RPi (20m). The problem is that I have cooling towers and cooling compressors which have high switching currents. In the beginning I tried the I2C and it did not work at default frequency. So I reduced the frequency which got it working for a while. However whenever some of the fans start working I lose some readings for a couple of seconds and sensors start acting weird.

I think it is a noise problem, especially that my 230VAC power supply is coming from the same 3~ph power supply of the fans.

What would be the best way to protect the signals on the I2C bus? I use now CAT5 cable to wire the sensors. I wanted to use CAT7 but then I read that this will actually make it worse since CAT7 has higher capacitance which is worse for the bus at longer distances.

More Info:

I'm using 10kHz currently since the default 100kHz did not work.
On a similar setup however (but without the nearby fans) i got away with 100kHz and more than 20m without extenders or anything. System has been running smoothly for more than 2 years now. That is why i'm thinking it is a noise issue.


texts: Best way to have circuit powered by USB when plugged in and battery when not?

texts:
I am building a circuit that uses a rechargeable battery and also has a USB port so it can be plugged in to charge the battery and power the system.

I am using a buck/boost converter to supply 3.3V for the circuit. I want the input for the converter to be the battery voltage when not connected to USB, but when plugged in, I want the input to be the USB.

One way I thought to do this was with a low forward voltage drop diode in series with each supply. Think it would work, but still some voltage drop, not the most efficient.

Another way I thought would be with a P channel FET that switches the battery voltage off when USB 5V is at the gate. Seems like the better method.

Would either of these solutions work?
Thanks

EDIT

Following the advice given, this solution seems like it should work:
*Note the symbol for P channel Fet was re drawn from original image so that source is on top and drain on bottom


texts:
The accepted answer to the question What's this importance of datasheets says that one should ignore "typical" performance and instead design around the min/max performance parameters. All well and good. The answer then goes on to highlight the utility of the "picture's worth a thousand words" graphs. But aren't these graphs necessarily "typical" performance, contradicting the first piece of advice?

Specifically, the referenced BSS138 datasheet specifies the minimum \$I_{D(on)}\$ to be 0.2 A for the conditions \$V_{GS}\$ = 10 V, \$V_{DS}\$ = 5 V. However, the answer's referenced graph

shows that for the \$V_{GS}\$ = 10 V curve, \$I_D\$ is between one and two orders of magnitude greater than the specified minimum of 0.2 A. How would a designer make use of this "typical" information when it is so far removed from the  guaranteed performance? Or am I misinterpreting something?


texts: Where to start repairing a faulty electronic board?

texts:
I am working on electronic card repair of textile machines. When a faulty electronic card arrives, I visually check it first. Is there a burned or cracked componenet next to it, if any, I am replacing these parts and the fault has been fixed. Sometimes an eye-related error is not seen, the card is short-circuited and I solve it with a thermal camera. however, there are some electronic cards that do not have externally visible burns or short circuits. at this point where should my first step be to find the error of this card type? Where should I start card repair? what should i check? This type of fault usually occurs on cards that produce high voltage errors at the input or output.

In short, if there is a fault in the electronic board, where should we start repairing? Is there a order of methods?


texts: When the AUX pin of a stereo is connected to my mobile phone's audio female port, I just measured the voltage at the end of this AUX pin(No load is connected) approximately 2mV using a DMM . But when I measured the current, it didn't indicate any current in the DMM. According to Ohm's law, voltage is current times the resistance. When relating this basic law to my practical case, it doesn't matching. How can it be realized?


texts: Cannot find GND on 7 Segment Display Datasheet

texts:
I'm trying to use a 7 Segment Knightbright LED Display, however, after careful study of the datasheet, I'm unable to find what I believe should be the GND pin to power a segment!

http://www.circuitspecialists.com/content/52077/SA03-11EWA.pdf

Could anybody please help point this out to me.


texts: Proper implementation of creepage and clearance in high voltage PCB

texts:
I am designing a 3phase voltage detector based on optocouplers as shown below:

simulate this circuit – Schematic created using CircuitLab

For this I need to follow DIN 60664-1 and my biggest problem is to understand how to apply those rules for creepage and clearance. Namely, I figured out that with polution degree 2 I need to stick to the following measures: 3mm minimal clearance and 4mm minimal creepage. Fine, but how is that achieved in practice. From the circuit that I have shown, how do I determine the creepage and distance between L1_1 and L2_1, or between L1_2 and L2_2. Does that mean that for every point in the circuit I must calculate the voltage and then to determine the creepage and clearance in the standard?

If you take a lok at the resistor connected to L1 and L1_1. It is 0805 size but should leg L1_1 also have clearance and creepage of 3mm and 4mm with respect to the L1?

At which point may I bring lines closer to each other - legs of the capacitors connected with the optocoupler - there can never be a breakdown between them because the diode keeps that voltage low.


texts: Can I find out the change in angle between two wooden sticks connected to each other with a stepper motor?

texts:
I have two wooden sticks/rulers (Length: 1 ft; Width: 1 inch; Thickness: 8 mm;)

I have fixed the stepper motor to the end of ruler#1
I have attached one end of ruler#2 to the shaft of the stepper motor.
I have fixed the free end of ruler#1 to the edge of a table; The whole setup is pointing out in the air, perpendicular to the edge of the table.

When I move the second ruler through an arc, I want to detect the angle through which it moved. (How) can I do it, using the stepper motor?

Assumed Restrictions:

Movment will be at such a rate that it covers 90deg in 1 sec
The range of angle between rulers will be from 15deg to 180deg

I am planning to send this data to my software code through a parallel port in my PC. How should I decode the data/pulses provided by the stepper motor so that it can be sent through the port?

Above question is an extension of Best sensor for measuring rotation angle?. but I just want to know how to go ahead and implement it using stepper motor.


texts: Phase difference between electric and magnetic fields of EM wave in a conductor?

texts:
When an EM wave travels inside a conductor , we see that there is a phase difference between the Electric and magnetic fields within the conductor. The magnetic field lags behind the E field and this lag is roughly equal to 45 degrees within a good conductor (all from Griffiths chp 9.4). What is the cause of this phase difference though? If an EM wave is incident on a lossless dielectric, then the transmitted electric and magnetic waves are in phase with each other but the presence of a conductor introduces a phase difference
I know that in a driven LR circuit there is a phase difference between the driving voltage and the current through the inductor. Since the magnetic field produced by an inductor is proportional to the current, we know that there is an equal phase difference between the driving voltage and the magnetic field produced by the circuit. Is this phase difference in any way related to the phase difference we get in when an EM wave travels in a conductor? I can account for the phase difference in a driven LR circuit easily: The non-zero inductance of the inductor creates a back emf which "fights" against a change in current which ultimately leads to the current lagging behind the voltage. For large inductances and/or high frequencies and/or low resistance (ie good conductance), the phase lag approaches 90 degrees though. Not the 45 degrees we get for a good conductor when a EM wave travels within it. I can't seem to account for these seemingly conflicting behaviours. Is the phase delay between the electric and magnetic components of an EM wave even caused by a back emf at all or does it arise because of a different reason entirely?
Any help on this issue would be most appreciated as it has been driving me mad recently.


texts:
What is the technical name of the matte material/film that is put on LCD Displays?

Also what would be the method of applying such film on a blank lcd screen (if possible)?

EDIT: (Not my picture, but it illustrates what I'm talking about, left is film and right is no film)

EDIT 2:

Just in case you were wondering, I'm planning on using this for a few portable tablet-like monitors that i want to also use outside and this seems good for reducing glare and improving overall look of the monitor. The screens i current want to use this on are 16.5 inch and 5.5 1080p lcd displays

Would i be able to achieve that? What are The Downsides?


texts:
A single phase, 2000 V alternator has armature resistance and
  reactance of 0.8 Ω and 4 Ω respectively. The voltage regulation of
  alternator at 100 A load at 0.8 leading power factor is _______?

My approach

$$V_{nl} = 2000 \text{ V}$$
When loaded
$$V_{l} = 2000 - 100 \angle \cos^{-1}0.8 (0.8 +j4) = 2206.9 \text{ V}$$
In alternator \$V_{reg}\$ is defined as
$$ V_{reg} =  \frac{|V_{nl}| - |V_l|}{|V_l|} * 100 = -9.38 \%$$
Am I right ? Because when I saw the answer it was given -6.96%.


texts: Using Fuses to Connect Batteries in Series

texts:
I would like to create this battery pack, consisting of 13 Samsung ICR18650-26F connected in series. There are balancing leads for balanced charging, and resettable polyfuses connecting all of the batteries. My current issue is determining the proper fuse rating.

Fuses are rated in amps, but how does the voltage rating play a factor?
Would I be able to use a resettable polyfuse rated at 16v 4a, or 30v 4a? Overall, how would I calculate the proper fuse necessary for this application?

simulate this circuit – Schematic created using CircuitLab

*This is my first post, so I hope that I was able to be as direct as possible.


texts: Shutdown amplifier when headphones are connected

texts:
I'm designing a board for a diy synth, one of the circuits consists in a audio amplifier that drives a small 1W speaker.

The amplifier takes the signals from a Raspberry hat(a Fe-Pi Audio V2) and I wanted the amplifier to shut down when an headphone is connected using the switch pins and the shutdown pin on the IC, which is an LM4861

Is the pull-up resistor placed correctly for turning off the amp?
Here's the schematics


texts: Generating a low noise, +/- 5V dual rail supply

texts:
I'm planning to use TI's DCV010505DP DC-DC converter to generate a low noise, +/- 5V dual rail supply with a ground node. I plan to use a cheap wall-adapter power supply to power the DC-DC converter. At the outputs of the converter, I want to ensure that the voltage remains fixed and also perform some filtering, so I've added an LM317 and LM337 with input and output filtering capacitors as well as reverse current protection via diodes. I'm going to be sensing sensitive analog signals using an 18-bit ADC, so that will be quite important.

Is this scheme feasible for generating a low noise power supply? Specifically,

Should I add anything to the input side of the DC-DC converter to reduce noise?
Are there any "tricks" to generating low noise supply voltages in terms of convenient chips for wall-plug to board low noise interfaces?
Any tips would be greatly appreciated!

My current schematic is shown below.


texts: LCD SPLC780D Initialization sequence fails

texts:
Microcontroller model : PIC32MX340F512H
LCD controller : SPLC780D
LCD module : MC42005A6W-FPTLW3-V2 (20*4)

I have been struggling for two weeks to get a SPL780D based LCD module to work. I checked the wiring and the code with the timers many times, based on the datasheet and a lot of examples. Alone, and with other people.

I use this function to send instructions to the LCD module:

void send(int rs, int rw, unsigned char db)
{
    RS = rs;
    RW = rw;
    wait(1000);//26ms
    E = 1;
    wait_k(1000);
    DB0 = (db & (1 << 0)) ? 1:0;
    DB1 = (db & (1 << 1)) ? 1:0;
    DB2 = (db & (1 << 2)) ? 1:0;
    DB3 = (db & (1 << 3)) ? 1:0;
    DB4 = (db & (1 << 4)) ? 1:0;
    DB5 = (db & (1 << 5)) ? 1:0;
    DB6 = (db & (1 << 6)) ? 1:0;
    DB7 = (db & (1 << 7)) ? 1:0;
    wait_k(1000);
    E = 0;
}

I tried many other delays, and I follow the sequence below:

Can someone please help me? Launching the sequence makes the screen blink once, and then I only have two lines of black boxes.

I am starting to think it is broken.

Adding the complete code below:

#define DB0 LATDbits.LATD4
#define DB1 LATDbits.LATD5
#define DB2 LATDbits.LATD6
#define DB3 LATDbits.LATD7
#define DB4 LATDbits.LATD8
#define DB5 LATDbits.LATD9
#define DB6 LATDbits.LATD10
#define DB7 LATDbits.LATD11

#define E   LATDbits.LATD3
#define RS  LATDbits.LATD0
#define RW  LATDbits.LATD1

void wait_k(int k)
{
    while (k)
    { k -= 1; }
}

void    init(void)
{
    LATDbits.LATD0 = 0;
    LATDbits.LATD1 = 0;
    LATDbits.LATD3 = 0;
    LATDbits.LATD4 = 0;
    LATDbits.LATD5 = 0;
    LATDbits.LATD6 = 0;
    LATDbits.LATD7 = 0;
    LATDbits.LATD8 = 0;
    LATDbits.LATD9 = 0;
    LATDbits.LATD10 = 0;
    LATDbits.LATD11 = 0;

    TRISDbits.TRISD0 = 0;
    TRISDbits.TRISD1 = 0;
    TRISDbits.TRISD3 = 0;
    TRISDbits.TRISD4 = 0;
    TRISDbits.TRISD5 = 0;
    TRISDbits.TRISD6 = 0;
    TRISDbits.TRISD7 = 0;
    TRISDbits.TRISD8 = 0;
    TRISDbits.TRISD9 = 0;
    TRISDbits.TRISD10 = 0;
    TRISDbits.TRISD11 = 0;

}

int main ()
{
    init();
    wait_k(1000);
    send(0, 0, 0b00110000);

    wait_k(1000);
    send(0, 0, 0b00110000);

    wait_k(100);
    send(0, 0, 0b00110000);

    wait_k(1000);
    send(0, 0, 0b00110000);

    wait_k(1000);
    send(0, 0, 0b00001000);

    wait_k(1000);
    send(0, 0, 0b00000001);

    wait_k(1000);
    send(0, 0, 0b00000111);

    //----End Of INIT

    wait_k(1000);
    send(0, 0, 0b00111000);//Function Set

    wait_k(1000);
    send(0, 0, 0b00001110);// Display on

    wait_k(1000);
    send(0, 0, 0b00000110);//Entry mode set

    wait_k(1000);
    send(1, 0, 0b01010111);//Write 'W'

    while(42);
        return 0;
}


texts: 4 Pole Connector and USB cable compatibility

texts:
USB 2.0 Cable to pass through enclosure boxes.

Are such cables able to be cut and connected (soldered) to the connectors pictured, and used without effect on their performance.

Are there specific steps to take with regard to the shielding and the separation of the wires to reduce the effects of impedance?

Thanks


texts: Capacitors to smooth output of cheap variable PSU

texts:
I've got a cheap variable PSU (Eventek 0-10A 0-30V) and I'm curious about building something to smooth the output voltage from it. I don't need to do this, the PSU is working fine for my needs right now, but I think it is an interesting problem to work through.
The specs on the PSU say the regulation is ≤1mV in CV mode ≤3mA in CC mode. But the manual says Ripple voltage: Vpp≤1%. So at worst 0.3V? I'll check that with an oscilloscope before buying anything.
Can I just put a capacitor or two in parallel with the output? I'd just put them in a project box with binding posts on both sides. Do I need to worry about ESR capacitors? Do I need to worry about the capacitors feeding power back into the PSU? If so, why? It feels like any DC load with a capacitor on it's input would have the same problem.
Thanks for any advice and help sizing this.


texts:
I want to implement AES-128 CFB (Chiper Feedback) algorithm using HW Cryptographic processor on STM32F437 microcontroller.

I don't want to use "STM32 crypto library" (DocID028112 Rev 2), but I want to write my custom library from scratch.

The problem is:
On STM32F437 reference manual (DocID018909 Rev 14) at page 721 is written that the only AES algorithms implemented are ECB, CBC, CTR, CCM and GCM:

But on "STM32 crypto library" user manual (DocID028112 Rev 2) is written that CFB algorithm is supported on STM32F437:

In STM32F437 reference manual there is no procedure to implement AES CFB algorithm and inside ST HAL driver there aren't function for AES CFB.

What's wrong? How can I implement AES 128 CFB algorithm on STM32F437?

Many thanks!


texts: What is the function of a diode connected to a GPIO?

texts:
I'm reading a schematic (done by a former employee) with a microcontroller, and I came across this circuit:

What is the function of D1?

Also, I think that R2 isn't necessary, because the control input come from another GPIO that always has 1 or 0 as its output.

Besides this one, there is another block of this same circuit but connected to the RESET pin of the microcontroller. This part of the circuit is used to flash the microcontroller via ISP.

R1 = 47k
R2,R3 = 10k
D1 = 1N4148


texts: Additional requirement for checksum over CAN bus?

texts:
Im working on a safety system project and sending messages over CAN bus among systems. Since the CAN protocol already includes a hardware CRC for messages sent over the bus,I was wondering if additional checksum for the data bytes is required or is the hardware CRC sufficient.
For ex: For 8 data bytes sent in CAN, should 1 byte out of 8 bytes be allocated for checksum of the 7 bytes being sent ,or, can I send 8 data bytes and rely on the hardware CRC to ensure the integrity of message?


texts: How to get AC power supply for projects?

texts:
So im planning to do electrical and electronics projects in my upcoming 2 month summer vacation. I bought some books for this (Example Getting started in electronics by Forrest)
But I soon realised that many projects require AC supply to fully implement it and see it effect(clippers, transistor circuit etc). So how can I get AC supply in my home?


texts:
Many of us have lots of devices that uses AC mains (110V/220V) to DC (typically 12VDC, 9VDC and sometimes 15VDC) adapters. There's my Wi-Fi router, my powered speakers, printer, scanner, etc.

So I would like to combine all these into a single device; do the AC/DC conversion once and have everyone tap the DC line, instead of each doing the conversion themselves.

Regarding to this, I have two questions:

is there any commercial solution out there to do this? (bench power supply for example)?
suppose I have one of these beauties powering my stuff and this power supply can deliver 100W of power. Will the device always be consuming 100W of power or will the consume increase as I hang more devices?

thanks.


texts: Formula for electromagnet strength parallel, outside the coil

texts:
I am working on a electromagnet project to collect metal shavings off the floor after machining.

I have a formula for the magnetic strength at a distance from the ends, but not parallel to the coil. How do I calculate F parallel to the coil?

The formula I have now is: $$F = \dfrac{(NI)^2 μ_0 A}{2 g^2}$$

[ Edit - formula from http://depts.washington.edu/mictech/optics/sensors/week2.pdf ]

Here is a visual example of what I am looking for:


texts: Does a series resistor limit power consumption?

texts:
I have a magnetic reed switch connected between two pins of a Raspberry Pi. As far as I'm aware, the Pi can handle a short circuit between two of it's GPIO pins, so having nothing except the reed switch is completely fine. I've heard something about the maximum current of an input pin being 16 mA. My setup doesn't need that much current to do its thing, so I was wondering how I could save power by limiting the amount of current that comes out of the corresponding output pin. Putting a resistor in series with the reed switch would limit the current, and I first thought that this would save power as well, but someone pointed out to me, that the power saved could just be lost as heat, making no difference at all.
Essentially, what I'm asking is this: Can you save power by putting a resistor in series? If not, how would one go about doing this?
Thanks.


texts: STM32H743 FMC with ST7789 doesn't work without delay

texts:
I have an STM32H743 connected to a screen that uses ST7789 via FMC (i.e. parallel connection) using 8-bit bandwidth and A18 to select between command and data.
The current code has an issue that the screen output is messed up (see pictures below) if I don't add a sleep to my write functions that uses FMC.
The code is working (no need for delay) under STM32CubeIDE but I ported it to work as part of MicroPython.
Things that I already considered:

Python speed - The code in C is a nested for loop and calls writeData so it isn't a python speed thing.
System clock/FMC -  I copied the whole code of FMC initialization (including Msp), GPIO and systemclock to MicroPYthon without any fix.
HAL version - MicroPython uses a different stm32 HAL version but I copied the SRAM/FMC files and it still didn't work

Any pointer on what might be the issue? is it a FMC clock configuration? some configuration on external memory location?
Appendix:
#define COMMAND_LOCATION 0xC0000000
#define DATA_LOCATION 0xC0040000
static uint8_t* fmc_command_pointer = (uint8_t*) COMMAND_LOCATION;
static uint8_t* fmc_data_pointer = (uint8_t*) DATA_LOCATION;

void writeCommand(uint8_t command)
{
    *fmc_command_pointer = command;
    HAL_Delay(100);
}
//*****************************************************************************
void writeData(uint8_t data)
{
    *fmc_data_pointer = data;
    HAL_Delay(1);
}

Filling the screen with the color blue without the delay in writeData produces:

With the delay (after a while since it takes 1ms per pixel) fills it correctly:


texts: GPIO connected as open-drain to opto-isolator's cathode

texts:
When connecting GPIO output pins (RPi, uC, ...) to an opto-isolator, the classical way I know is the following (at least I understand that it can roughly be depicted like that):

simulate this circuit – Schematic created using CircuitLab

This will, obviously, lead to the GPIO pins driving the opto-isolator's internal LED (in this case ~18mA). Depending on the amount of used pins, the total current allowed by the uC may be exceeded.

What if I was connecting the GPIO pin in the following manner:

simulate this circuit

For the sake of the question let's assume that both +3.3V are exactly +3.3V. The idea is to use inverse logic: if the GPIO is HIGH, both ends of the internal LED are on 3.3V, therefore no current is flowing and the opto-isolator is off. With GPIO LOW it connects to GND and therefore current is flowing through the opto-isolator, opening the 24V side as well.
The advantage would be that the external power supply is driving the opto-isolator while the uC only has to sink the current.

Will this work?
Is it even possible to have current flowing into an output pin while this is set to LOW?
Or are there any internal resistors preventing this (specifically with an STM32F207 on a Nucleo-144 board 1)?

Also: will it even make a difference in terms of maximum allowed current? Is current flowing in taken into account just as current flowing out?


texts: Why do the high side MOSFETs get hot in this buck converter?

texts:
Here I am attaching step down buck converter circuit.
While testing, mosfets on high side get hot extremely high even for 100W load.
Low side has no problem.
All mosfets are fixed on very big heat sink.
Anyone please help me to overcome this problem.

Components used are as per given in circuit.
PWM frequency is 50KHz & max duty is 80%.
Gate voltage observed is always >10v.


texts: LTC1966 Sallen-Key post-filtering application question

texts:
Just a quick question about an application circuit in the LTC1966 datasheet.

Figure 13 on page 18 shows a third order (when considering output resistance of the LTC1966) Sallen-Key filter, with a resistor RB between the non-inverting input and the output of the op amp.

What is the purpose of this resistor? It doesn't exist on any Sallen-Key schematics I can find, and the datasheet just gives us two values for their measurements - 294K and 0R, with no other information.

The schematic in question:

Can anyone shed any light on the purpose of this resistor?

Thanks!


texts: Interfacing Raspberry PI to HoneyWell alarm system (3V vs 12V)

texts:
simulate this circuit – Schematic created using CircuitLab

I've been working on a similar project as this but with a HoneyWell  alarm system. I've managed to lower the voltage from the 12V or so down to 3v (approx) using a resistor bridge. I now have the leads from the bridge plugged into the GPIO pins on the raspberry pi. I'm reading the pin input via Pi4J and it seems to give me a HIGH and LOW respectively for the 2 pins. This value does not change even if there is an event that occurs in the alarm panel(opening doors etc). Can anyone tell me how to read the data and  clk inputs correctly?

Notes:In the circuit diagram below the voltage source is pretty much the data and the clock lines coming out from the Alarm Panel. I'm feeding the GPIO pin of the pi with a jumper wire to the end of the R1 resistor. I had to use a bunch of 1k and another 300Ohm resistor because I didn't have a 3300K resistor in my small kit.
The clock and data lines are both being downgraded to a 3v input line by passing through this circuit (2 circuits on a bread board).
The model of the Alarm panel is a Honeywell Vista 20p. Circuit Diagram of the panel attached below.I'm feeding the pi with the wires attached to PIN 6 and 7 as shown in the circuit.

[]

The following image is of the wires connected to the breadboard.The breadboard is then  connected to the pi via a cable ( not sure what the cable is called).


texts: Using ATtiny ADC with a system clock of 32.768 kHz

texts:
I am running my ATtiny85 with an external 32.768 kHz crystal because I need to keep accurate time. I also need to use the ADC in my application. However, the datasheet specifies that the minimum ADC frequency is 50 kHz. Furthermore, the minimum divisor for the ADC prescaler is 2, so the effective clock to the ADC would end up being 16.384 kHz.

Now, I have tested this with the mentioned 32.768 kHz crystal, and the ADC seems to work. I am getting good enough results. However, is what I am doing "allowed" or am I setting myself up for failing big-time? The plan is that if this device is something people want, I would make maybe 100 of them, and it would suck if I assume this would work when in fact there might be a problem later.

Does anyone have any wise words?


texts: what is the load line and operating point used for in practical?

texts:
I have a hard time understanding what an operating point and load line represent and why do we need them at all.

After reading some wikibedia,

What I got is this load line represent response of the linear circuit attached to the diode for changing in voltage across it.

But, this doesn't seem to answer my question about

why do we even need this and what does it represent exactly in a little more simple detail.


texts: STM32 HAL CAN does not update value and crashes when setting ExtId

texts:
I'm running my first CAN test program using STM32CubeMX, STM32F103C8T6 and Eclipse.

I used default CAN settings in STM32CubeMX (also tried loopback but the results are equal).

What I see (see pic below) is two things I do not understand;

In the picture below, you can see I exceeded the line with hcan.pTxMsg->StdId = 0x321 (left red oval), but the current value shows 536891392 (right red oval).
When I execute the next line (green): hcan.pTxMsg->ExtId = 0x01, I end up in a hard fault interrupt:

/**

@brief This function handles Hard fault interrupt.
/
void HardFault_Handler(void)
{
/ USER CODE BEGIN HardFault_IRQn 0 */

/* USER CODE END HardFault_IRQn 0 /
while (1)
{
}
/ USER CODE BEGIN HardFault_IRQn 1 */

/* USER CODE END HardFault_IRQn 1 */
}

Why is the value not updated and why do I get a hardware fault (the pointer hcan.pTxMsg is not NULL since it even displays the field StdId (it even can display ExtId which has value 134222077 (not shown in pic below)?


texts: Connect 8 ohm speaker output to microphone input on another system

texts:
I see the question was answered in 2013, but in addition, Id like to ask the follow question(s);

I have a significantly stronger speaker (output) than a computer speaker discussed in previous post.  I'd like to bring the speaker output into a microphone input of another pa system.

Will the diagram below suffice, if I up the resistor (R1) to 20k?
I will install a 1k pot-resistor (R2) as advised by Oli Claser in the earlier post.

Is it necessary to include a diode on the "Speaker Out" line, and the "Speaker Ground" line to prevent the circuit interfering with the speaker?  (As the speaker will stay connected).


texts: The circuit is used to control the bank of LEDs using PWM, my problem is the value of R3 is wrong, now I used 10M ohm and it started switching on and off bt the LEDs dont shine bright which means the 2n2222A do nt saturates.PLz click the circuit is on the link below.


texts: Reading a 12VDC output with digital inputs on an Arduino Uno

texts:
I want to use four pins on an Arduino Uno as digital inputs pins for four 12V DC outputs. I know I have to use a voltage divider first (with resistor values being 14kOhm and 10kOhm) to get the correct voltage range (0-5V) and also use the internal 20kOhm resistors on the Uno to achieve this.

My first idea was to not use the internal resistors on the Uno, but instead use external ones, to pull the voltage to zero, when nothing is connected to the input (prevent floating values). A colleague suggested the usage of the internal pullups on the Arduino, but I have no idea how to wire this up now.

Can someone explain it to me somehow?


texts:
I'll preface this with a little background.  I'm a software engineer with little experience outside of a couple small arduino projects.  I'm excited about the idea of combining both digital and physical components with frameworks/hardware such as arduino.

My question is:
Are there any small/micro pressure sensors compatible with arduino?  The idea would be to detect balance/distribution abnormalities in packaging.

Example:
A grid comprised of 100x100 (the more the better) sensors used to recognize the weight distribution of a box or container (increased pressure on some sensors vs decreased pressure on others).  Container dimensions are roughly 2' x 2' x 4' [lwh] and must remain upright.  The height of the box is what makes the weight distribution important for stability.

Is this possible with arduino?  If so, what hardware would I need?  If not, is there something else I should be using?

Thanks all!


texts:
Looking to build an Arduino controlled current-loop transmitter for driving 4-20 mA over an ~100 Ohm non-inductive resistance with 24V power supply. Also the Arduino should drive ideally 4 independent channels like this because I have 4 separate receivers.

As far as I could understood from googling, a possible way should be if I use the PWM output from the Arduino, passed through an low-pass filter and then passing the DC through voltage-to-current converter.

Now, the vast majority of choices about "current-loop transmitter" confuses me, because I am not an electrical engineer, just an Arduino hobbyist.

So my questions are:

Is the described route (Arduino / PWM 1-5V / low pass filter / voltage-to-current / 4-20mA) even meaningful?
Is there some integrated IC with less extra parts to achieve the voltage-to-current part? (Read about XTR117 but I suppose I can't control 4 with the same micro-controller)
Is it achievable to supply the whole circuit - i.e. Arduino (maybe through voltage controller), the current loop transmitter or op-amp or whatever circuit and the current loop - with the same 24V power supply?


texts: Component change following design freeze

texts:
Our device has been through DVT and compliance testing.  Both DVT and compliance are expensive and time consuming processes.  The compliance includes a comprehensive set of RF tests.

I want to change the PCB board slightly but do not want to have to repeat the compliance tests.

Are there a set of rules that are followed when doing an ECO to a device that has completed design verification testing and been certified by an external body?

I am most worried about RF emissions following a change as we do not have a spectrum analyzer of sufficient range or an anechoic chamber to do the full set of tests.


texts: Boost converter single cell AA battery not delivering enough voltage when connected to Wemos D1 mini

texts:
I must power a Wemos D1 mini at 5V (more on that below) (along with 4 LEDs and a DC motor) with a single cell AA battery. I have tried 2 boost converters (Vin 0.9V-5V) and none worked.
I need 5V for 2 of the LEDs, which are in series and 5V is perfect for them.
The motor will be driven with the 3.3V pin on Wemos D1 mini.
All the boost converters I tried deliver 5V unconnected. However, the moment I connect them to D1 mini, voltage drops around 1.5V. I tried with a power supply at 1.5V, same result.
I wonder, what I am missing. The specification says 600mA output current. I also tried to put a 100μF capacitor either to input or output side for sudden current draw. Supplying >3V worked fine. Dropping from 3V to 1.5V worked for a short while and then the output voltage dropped to ~1.5V. D1 mini draws ~70mA 5V.
I wonder if I am missing something?
Here are the converters I have tried:
https://www.amazon.de/dp/B07PZ8QLB2/ref=asc_df_B07PZ8QLB21613404800000/?tag=ilovetec-21&creative=22662&creativeASIN=B07PZ8QLB2&linkCode=df0
https://www.amazon.de/gp/product/B07SSXVHP8/ref=ppx_yo_dt_b_asin_title_o00_s01?ie=UTF8&psc=1
EDIT: as a test I tried with MT3608, which requires >2V. I supplied it with 3V and got 5V out. It worked just fine. I guess all these cheap undocumented boost converters are bad.


texts: Is RTS/CTS needed for UART with FT232R USB-UART chip?

texts:
I am trying to use the FT232R chip in order to allow for Serial communication between a board based on the ATMEL SAMD21 chip and a PC. I need this in order to obtain input from the user, and display some sensor output to the terminal to alert the user.

In the FT232R datasheet, it connects RTS and CTS of the FT232R to RTS and CTS of the microcontroller for it's UART example, but there are contradicting opinions about whether RTS and CTS are essential for proper communication. How do I know if RTS and CTS are used in this case, and whether my application would function properly without them?

Thanks


texts: Finding a chip that can record and playback 30 seconds of audio

texts:
I would like to make my own circuit to record a tune and then playback about 30 seconds of audio.  I don't want it to be very complicated.

I have basic soldering skills but an IC in an easy to solder package (like PDIP or SOIC) would be best.


texts: How can you build a floating two-port VCVS?

texts:
I have a control voltage at one point in a circuit which I need to duplicate at various other points (3 or 4, if I remember correctly). I'd like to use one potentiometer to control these voltages, so I need to "duplicate" the control voltage at the points I need it in. The problem is that I need to raise and lower voltages in the circuit by the control values, so I can't just use a buffer amp--it needs to be a floating source. Essentially I'm looking to build something like:

The output resistance isn't very important, as in all cases the next input stage is an op amp, and \$V_x\$ is no more than 3-5 volts. How would I go about building something like this? I know I could convert the voltage to AC, use two transformers, and then filter the output, but I'd like to keep this DC if possible.


texts:
I am building a laser room and I'm basically trying to calculate the maximum time of laser radiation to they eye before causing any harm. I found that to be 7 seconds but I would very much appreciate if someone familiar with this topic can confirm that my calculations are accurate.

The lasers I use are green ones @352nm 50mW.
Based on the MPE and coefficient tables, the formula for Hmpe = C1 J/m^2  = 5.6 x 10^3 x (t^0.25) J/m^2 = 5.6 x 10^3 x (7^0.25) J/m^2 = 9.1 x 10^ 3 J/m^2

In terms of irradiance obtained after dividing by t = 7s:

Empe = 1.3 W/m^2

Now, from here "considering the limiting aperture of they eye in the visible region, 7mm,  then
the area over which the visible radiation will be viewed is π/4×0.7^2
= 0.385 cm2 = 3.85 * 10^-5 m^2 "

, the maximum power to avoid harm due to eye exposure is:

3.85 * 10^-5 * 1.2 * 10^3 W = 0.05W =50mW which is my lasers's output power.

You think this calculation is accurate?

Thank you in advance,
Dimitris


texts: Can you clarify what an 1NO1NC switch is?

texts:
I've come across multiple mentions of switches described as 1NO1NC.

They often described as having 2 options: ON/(OFF) and (ON)/OFF and from what I gather they have 3 terminals for wires: a NO terminal, a NC terminal and a C (?) terminal.

Can you explain what these mean?

When would you use an NO or an NC switch?


texts: NG-Spice / Macspice - plot source current?

texts:
It seems that you cannot plot current for circuit elements directly and will therefore have to make use of a series 0V source to display a graph of current vs time in that branch.

For voltage at say node 1 I have: plot v(1)
If my source is labelled Vin, then as I have noticed; plot i(Vin) does not work.

What is the command for doing this?


texts: POE external Magnetics Alternative to magnetic RJ45 jack ieee803af

texts:
I can't use a magnetic jack for this POE PD  (ieee803af), because we use another connector (M12).

Looking for components to replace the internal magnetics,
I found that almost all components and schematics use this no nonsense layout:

But the internal magnetics of magjacks look like this:

If looks more fancy:
 - first tap off the DC
 - then a choke
 - then transformer coupling

It is hard to find transformers that are rugged (temperature to -40degC) and implement all these characteristics.

Should I be worried about not using the first coil where the DC is tapped off separately? If not, why is it implemented like that in the internal magnetics jack?

The transformer I've chosen for now is HX2260FNL (datasheet HX2260FNL), so my design looks like this: (with external Schottky bridge rectifiers) (for future reference, so shoot it if it is not good!).

EDIT after post asndre:

this H1102FNLT transformer has the common mode choke on the cable side in the same package as the first chosen transfo.

EDIT 2 after manufacturing:

After assembling the board: H1102FNLT does not work but HX2260FNL does! I am looking into it.


texts: How to halve the pulse coming from a three wire speed sensor (on a remote control car)?

texts:
I have an electric remote control car which has an electronic speed limit of 40km/h. After putting new wheels (which are around half the circumference) onto it, the effective speed limit is now 20km/h.

How can the pulse from the three wire speed sensor be changed so that the real speed limit is 40km/h with the smaller circumference tires?

Update:
From Russell's answer is seems that a 4013 Dual D Flip Flop CMOS IC will be able to do the job?

Would one like this one work: https://www.jaycar.com.au/4013-dual-d-flip-flop-cmos-ic/p/ZC4013?

The sensor connectors look like this:

From looking at the spec sheet for HEF4013B (which I believe is the same product as linked above?), would the following diagram be correct?

Lastly, are the two connectors standard connectors which can be purchased, and if so what terms should I search for?


texts: Medical Ultrasonography Phased Array Beamforming

texts:
Medical ultrasonography equipment images the interior of the body by reflecting ultrasonic sound waves off of discontinuities between internal tissues / organs. I did some reading about this technology and how it is possible to develop a two dimensional image from only the reflected sound. It seems that modern sonograms work by having phased arrays of both elements which transmit the sound waves and which receive the sound waves. The phased arrays of transmitters allow the energy to be focused in a particular direction, and the phased arrays of receivers allow the device to pick out reflections coming from that direction. I have two questions.

Is it necessary to have phased arrays of both transmitters and receivers, or is it simply more efficient that way? Could an instrument be constructed with a single receiver and a phased array of transmitters, or conversely a single transmitter and a phased array of receivers? Would it work, albeit with reduced noise rejection?
The phased arrays explain to me how the beam can be directed in a 2D plane, but how does this extend to three dimensions? How does the device reject reflections outside the plane it is imaging?


texts:
I recently purchased a LED strip off amazon along with an external power supply, hoping to be able to control the LED's with an Arduino. Unfortunately after testing with the external power supply, the LED strip does not seem to light up smoothly like they do in the test with the Arduino(video example). I am not an electrical expert so I don't exactly know how to explain this one and it puzzles me as to why this happens. If any more information is needed let me know.

After adding a capacitor to the circuit The same problem seems to persist.Video example. The program shown in the video example is set to turn all of the LEDs blue. A link to the program can be found in the comments below.

simulate this circuit – Schematic created using CircuitLab

Do note that is not the exact LED stip.

After some further testing, the Led's will stop changing colors and hold their last color if the data pin coming from the Arduino is removed. Is there any chance that the power supply could be affecting the data pin and what is sent to the ic's?

Here is the LED strip

and this is the external power suply


texts:
I am an amateur, but i'd like to know if this circuit would work to double a 0-30 volt DC input to a 2-60 volt DC output. If so, what kind of CAPS and DIODES do i need to support this? I need to Power a motor that draws 5A max, so based on my understanding, the circuit needs to be able to handle 10 Amps.

(source: coolcircuit.com)

Whatever my input voltage is, I want to double it. I am open to other solutions as well.


texts: High voltage amplification of a waveform generator output

texts:
I need to drive an ultrasonic transducer with a high center frequency (25 MHz) using my function generator that outputs a 25 MHz sine wave at only 5 Vpp. The problem is that the transducer needs at least 50 Vpp (preferably over 150 Vpp). I tried to use a few amplifier I had around (designed for piezo driving) but they all stopped "amplifying" after around 1 MHz...
What is the cheapest but cleanest way to amplify a waveform voltage which is at such a high frequency? I am willing to buy or build but I need to complete this for less than $500.


texts: VBE Multiplier with Emitter Resistance Cancellation

texts:
Function of shown circuit is biasing of output power stage complementary audio amplifier. P1 allows precise adjustment of \$ V_{CE} \$ of VBE multiplier and \$C_B\$ improves its rail rejection. \$ r_e' \$ negates unwanted effects of \$ r_e \$, also known as current-dependent emitter resistance.

simulate this circuit – Schematic created using CircuitLab

In book about construction of audio amplifiers, writer G. Randy Slone wrote next about this circuit and \$ r_e \$ effect cancellation:

  "Re prime (that is \$ r_e \$) manifests itself as small Vbias changes brought on by power supply rail variations and small current variations through Qbias relevant to temperature. To negate the effects of re prime, a resistor can be placed in the collector circuit of Qbias to provide slight modification of the voltage drop across P1."

I don't get it why has \$ r_e \$ any influence on \$ V_{CE} \$ of VBE multiplier regarding rail variation and current variation of Qbias due to temperature variations. Or does it represents and error regarding resistive voltage divider with potentiometer connected to base of Qbias?  As far as I know, it is just a series resistance with emitter that changes with quiescent current of Qbias. Why would \$ r_e \$ cause any error in setting of bias voltage for the following output stage anyway? Also, in what manner \$ r_e' \$ opposes/ negates effects of \$ r_e \$?


texts:
Hello I have an AC motor that i want to make a speed controller to, but before i start i want to make sure that it is possible with the type of motor i have. I do not want to waste the motor attempting to speed control it but then it is not possible.

How I plan to implement a speed control is to manipulate the AC waveform just like how you do it in dimming light bulbs. Using a non-zero Crossing SSR, zero crossing detection optocoupler, and a microcontroller.


texts: Dual shaft servo motors? Do they have another name?

texts: I am trying to find a servo motor where the shaft protrudes through the other side however I haven't been able to find much online. I am wondering if I have the term right though. Am i right searching for "dual shaft servo" or would they be under another name?


texts:
I would like to use a transistor in LTSpice and I don't want to choose a specific one but keep the NPN with parameters added to the model. So basically, my command would be : .model Q NPN(..). I would like to set the Vcesat parameter but it doesn't seem to appear as a parameter on LTSpice's model of transistor. Does anybody know how to fix Vcesat ?
Thank you for your answer and time !


texts: Segments not totally off when multiplexing 7 segments display with CD4051BE

texts:
I'm trying to make a display with several 7 segment displays so I decided to use multiplexing to make it work. I use CD4051BE to do that. The circuit is as follow:
Circuit of the multiplexing
The MCP23017 is then hooked up to a raspberry pi 3 where I code using python and CircuitPython.
The segments look like that, you can see the displays that shouldn't turn on circled in blue.
It seems like it is working at slower speed (when I add delay to the multiplexing).
I think the problem comes from the way I did multiplexing but I really don't know...
My code is the following:
import board
import busio
from digitalio import Direction, DigitalInOut
from adafruit_mcp230xx.mcp23017 import MCP23017
import time

i2c = busio.I2C(board.SCL, board.SDA)

mcp = MCP23017(i2c, address=0x21)

pin0 = mcp.get_pin(8)
pin0.direction = Direction.OUTPUT
pin1 = mcp.get_pin(9)
pin1.direction = Direction.OUTPUT

s1 = DigitalInOut(board.D14)
s1.direction = Direction.OUTPUT
s2 = DigitalInOut(board.D15)
s2.direction = Direction.OUTPUT
s3 = DigitalInOut(board.D18)
s3.direction = Direction.OUTPUT

pin0.value = True

while True:
  for i in range(0, 5):
    if (i % 2) == 0:
      pin1.value = False
    else:
      pin1.value = True
    s1.value = bool(i >> 0 & 1)
    s2.value = bool(i >> 1 & 1)
    s3.value = bool(i >> 2 & 1)

Thanks for any help !
Cyprien


texts: Are the standard techniques of DSP still relevant to modern signal processing applications?

texts:
I am unsure if it's OK to ask this here.

My question is: are the standard DSP methods still important in signal processing areas?(FIR, IIRF, etc) or have new techniques come out which have replaced these LTI(or pseudo LTI) operations? From a practical perspective are they still worth learning?


texts: How uniform fields obtained between a set of electrodes in High Voltage Engineering?

texts: In high voltage engineering, sometimes we need uniform fields between a set of electrodes.  Parallel plate electrodes are not solution for that because they are finite so they will have fringing fields at edges of plates. I am wondering that how effectively engineers obtain uniform fields between a set of electrodes? Please give their real configuration.


texts:
I struggle to understand how can you switch positive or negative supply from a battery.

Firstly, what is a positive voltage and negative voltage?

I read many posts stating it all depends on your point of reference. To my understanding, current flows from negative to positive. Positive and negative current is just a difference in current flow.

The reason I am asking is I am in a process of studying Inverter Field control for Hybrid vehicles.

The booklet states:

  By switching the positive or negative post of the battery to the three MG (Motor Generator) connections a current starts flowing through the MG's coils. The current through the MG coils creates a revolving or still magnetic field, making the rotor magnets in the MG's follow this field.

Please notice the current flow highlighted orange. I don't understand how can you switch positive or negative voltage and how does that affect anything. I also don't understand how can you have a positive voltage flowing in and the other end has negative voltage flowing out.

Moreover, how can 'give' or rectify negative voltage to the negative terminal a positive voltage to the positive terminal depicted below. What does that even mean?

I would appreciate an answer from an engineer explained in non-engineer terms. I know there are a lot of smart folks out there, but please keep it simple.

Thanks.


texts:
Consider this voltage doubler:

.

I simulated the circuit using NON-polarized capacitors and WITHOUT the transformer as in this schematic:

and the output voltage (at C1) was still doubled. I have a couple of questions about this:

Why would people want to use polarized capacitors?
What is the purpose of the transformer?

Finally, after playing around with the circuit,

What happens if I reverse the orientation of both diodes? It seems that it inverts the sign of the output voltage, but this is only possible using non-polarized capacitors, which brings me back to my first question.


texts: How to find and remove the buzzer from a Morphy Richards Breadmaker

texts:
I just bought a Morphy Richards breadmaker that is great in all ways, but it beeps in the middle of the night and wakes me up (both when it begins baking and when it's finished). So I was wondering if you could help me locate the buzzer, and then I will try to remove it, or cover it up in some ways.

In advance, thank you very much!


texts: How to show all the designators in Altium? I've done it by double-clicking a component one by one and uncheck hide column in Designator. Is there another way that possible to unhide all of the components at once?


texts:
I have a 3 phase inverter H bridge which has 6 MOSFETs (IPD90N04S4_05) as shown in the picture.

I have numbered each leg of a MOSFET as 1, 2, 3, 4. The middle leg (number 2) of the MOSFET has been cut and pushed down.

I have found the data sheet:

http://www.mouser.com/ds/2/196/Infineon-IPD90N04S4_05-DS-v01_00-en-1226334.pdf

How can I find out whether MOSFETs are OK or not?

My second question start here.

I use these MOSFETs with an Infineon chip and my programing environment is Keil Microvision 5.

Earlier I was able to operate the MOSFETs using PWM from the Infineon chip for a BLDC motor application. But all of a sudden , one day when I supply PWM pulses to the gates of the MOSFETs, the error I get (from the debug window of Keil, screenshot below) that "external FET source–drain short" for all 6 MOSFETs.

But surprisingly when I check physically with multi-meter the source and drain (leg no 2 and 3) don't show any short.

How is it possible?


texts: Why do switches and relays have lower current ratings at higher voltages?

texts:
I have a switch which reads 6A 125VAC / 3A 250VAC.

I can't figure out why this would be the case. The only reason I can think of the rating is the wires and contacts are only rated to take so much current and so much power dissipation. A higher voltage should not lead to more power dissipation. So why do switches and relays have lower current ratings at higher voltages?


texts: BJT Transistor Open/Low or variable load behavior

texts:
How does a BJT react when saturating the base with a very low collector current? For example, 10 mA into the base of a 2n2222a with a collector current of 20 mA in a common collector setup. Will the base forward drop increase or decrease, or otherwise overheat, or anything else?

What about variable loads, like a led controller that may go from 10% to 100% PWM . Would this cause any unwanted behavior?


texts: What's wrong with giving a really long low pulse to a 555 timer?

texts: A number > 0 of 555 timer tutorials warn against holding the trigger of a 555 timer in monostable configuration low for longer than the duration of the output pulse. Why not?


texts: Any chance to build a dual 2-to-1 line selector/multiplexer from a single chip?

texts:
I a need 2 units of 2-to-1 selector/multiplexer functions on a crammed board, ideally with a single DIP-14 or -16 chip. Looking around for something I found this formula
(S nand A) nand ((not S) nand B)

which is great, as I can build it with a single 74LS00 quad NAND gate chip as:
(S nand A) nand ((S nand S) nand B)

So I know I can do it with two DIP-14 chips. But I want only one!
Truth table:
S A B|Y
-----+-
L L x|L
L H x|H
H x L|L
H x H|H

or fully expanded sorted by binary value of S,A,B:
S A B|Y
-----+-
L L L|L
L L H|L
L H L|H
L H H|H
H L L|L
H L H|H
H H L|L
H H H|H

or fully expanded sorted by Y
S A B|Y
-----+-
L L L|L
L L H|L
H L L|L
H H L|L
L H L|H
L H H|H
H L H|H
H H H|H

I tried a combination of two NAND or two NOR gates also don't work. None gives a L L L -> L or H H H -> H.
A standard AND-OR-invert (AOI) gate also doesn't work as nothing gets any L L L L -> L or H H H H -> H. The 2-2 AOI gate will always output 0 if three or all four inputs are 1, and 1 if three or all four inputs are 0. Same problem with and OAI gate.
For a moment I thought the double XOR combination suggested in Can I simplify this to a 2-to-1 multiplexer? was going to do it, which would have been so nice as I could have built two with one chip, but then it doesn't work. It seems so close though!
Maybe I should say what I am really ultimately trying to do: I use 74LS161 counters (or any TTL counters) as registers, 4 bits (one nybble) each, and I have two such counters chained together where the ripple carry out of the low nybble connects to the clock of the high nybble. I want to be able to synchronously preset either one independently. Easy to do for the low nybble, not so easy for the high nybble as the synchronous load happens on the rising clock edge, and the clock for the high nybble is connected to the ripple carry output.
So I figured a selector should be doing it, but the 74' series only has quad 2-to-1 selector/multiplexer with a single selector, but I need two independent selectors!
Any trick? Perhaps a counter which can be synchronously pre-set but has a different ripple clock input from the clock edge that triggers the pre-loading? That's really all I want. Oh boy, if it could also be three-state it would be perfect. But none such exists. That's why I am so short on space already.
UPDATE: the comments asked if I could show schematics, if you will excuse my hand drawn one, for this circuit drawing tool isn't good with ICs.

Dave Tweed had provided the final clue in the comment, so that answers it. But in correct StackExchange-iquette, I put the answer into a separate ... answer ... [drumroll ...]


texts: Why the place where I clear TMR0IF changes the behavior of the program?

texts:
I'm programming a PIC16F877A microcontroller in C, compiling with Microchip XC8 1.44.

I have set up a TMR0 interrupt for every 800 microseconds that scans through a LED matrix, lighting each 8 LED column at a time using the settings as follows:

    OPTION_REG = 0x04; // TMR0 prescaler (1:32)
    GIE    = 1;
    TMR0IE = 1;

And this is my ISR:

void interrupt isr()
{
    static const uint16_t divs[4] = { 1000, 100, 10, 1 };
    if (TMR0IF)
    {
        PORTB = 0x00; // PORTB is the 8 LED column
        if (i)
        {
            PORTAbits.RA0 = 1; // pin that clocks CD4017 for next column
            __nop(); // give a brief delay just for good measure
            PORTAbits.RA0 = 0;
        }
        else
        {
            PORTAbits.RA1 = 1; // pin that resets CD4017 to first column
            __nop();
            PORTAbits.RA1 = 0;
        }

        // pattern to be displayed
        PORTB = font[i % 8U + 8U * ((c / divs[i / 8U]) % 10U)];
        i = (i + 1U) % 31U; // increment i for next iteration

        TMR0 = TMR0_OFFSET; // 240 for 4MHz crystal for 800us delay according to my calculations (I am bad at calculations)
        TMR0IF = 0;
    }
}

Basically c (for 'counter') will hold a number between 0 and 9999, and the 31 column LED matrix displays it using the data in font to draw the numbers.

Now, this code works just right. But if I move TMR0IF = 0; to the beginning of the block, something strange happens:

The program seems to become slow, as if the clock dropped by a factor of 100 or more, and the main program loop crashes and because of that I stop receiving the external signals that I use to increment or reset the value of c, only the ISR remains being called and keep the LED matrix lit, but flickering due to the clock drop.

If I move TMR0IF = 0; to the end like in the code above though, everything seems to work normally and the world is perfect. But why?

Everywhere I see code reference for Timer 0 interrupt usage people set TMR0IF = 0; right away, why is it causing all that hassle in my code?


texts: Question about the resulting real voltage of pwm (pulse-width modulation)

texts: I understand that pwm simply emits a voltage in either a LOW or HIGH state. But I read that for practical reasons, one can simply take the average voltage. If I would measure the voltage in practice, would that apply?


texts: Energy meter neutral current measurement

texts:
I was reviewing an energy meter specification and I came across neutral current measurement.
What is the importance of neutral current measurement in an energy meter for three phase power supply?
I tried to find the importance, but  all I found was that it enhances tamper-detection techniques but does not say how.
Can someone tell me if it is really necessary to have this feature on an energy meter?


texts:
I was checking out the new features of Android and I stumbled across a bullet point for USB Audio. Additionally, from the Android website:

  USB audio output support allows hardware vendors to build hardware such as audio docks that interface with Android devices. This functionality is also exposed with the Android Open Accessory Development Kit (ADK) to give all developers the chance to create their own hardware.

Is there some standard out there for audio data across USB?  Can anyone point me to some references/specifications?


texts: Multidrop bus protocol on the BeagleBone Black PRU

texts:
I am truying to implement the MDB protocol on the BeagleBone Black, the problem is :
the protocol requires a 9 bit data via UART (9th bit used to differentiate if the sent/received data frame is an adress or data) and the BeagleBopne Black UARTs doesn't support 9 bit characters, I decided to use the PRU_HW_UART but the last doesn't support 9 bit mode also, is there a solution for this problem ?