texts: Finding out the values in a truth table for a SR-Latch

texts:
My task is to fill in this table the output Q by analysing following circuit

My suggestion would be:

Would that idea be right?

in the digital electronics means: S=1 => Q=1 and R=1 => Q=0

Edit: My question is different from the possible duplicate because I should work here with the previous Q (previous stored data).


texts:
I’m currently designing a circuit. It is required to be powered by a 12v dc input (when connected) else a 3.7v battery (the battery should be charged when 12v is active).

The circuit requires 5v which should be achieved using a dc to dc converter in either buck or boost mode.

What would you recommend as the best and most efficient way of automatically switching the power source and charging the battery without interrupting the supply to the device for any more than a few ms?


texts:
I am a very novice chiphacker and am asking for ideas on how I might implement something like this.

I am about to start an RFID project, which is the easy part. RFID readers are cheap, arduinos are cheap, and RFID tags are cheap.

But I want the ability to turn the RFID tag "on" or "off". I want to be able to say "when this happens, then allow yourself to be 'excited'".

The project I'm working on is testing for the presence of a liquid (which has ions in it.) So one high-level solution would be "separate the RFID chip from its antenna. When the liquid is spilled, it 'shorts' that connection and now the tag may be excited."

So my question is this: first, is there any mechanism for turning a tag "on"? There are plenty of ways to turn them "off" (basically destroy the tag) but nothing that works in the opposite direction. And how farfetched is the "liquid" idea?

Might there be some resource that could help me understand what possible workarounds would be, or different attributes of different kinds of RFID tags? Or even something that tells me why this won't work?


texts:
I have a simple question from an electronics textbook (Electronics Fundamentals, Pearson, 8th Ed., p510 Q 37):

10V 10 Hz AC supply, 4.7K resistor and 10uF capacitor in series, with Vout measured over the capacitor.

What is the output voltage and phase angle?

I think:

Xc = 1592 Ohms

Z = 4700 - 1592i

Vout = 10 * -1592i / (4700 - 1592i) = 1.03 - 3.04i = 3.2V @ -71.3 degrees

The answer given is 3.2V @ 18.7 degrees.

How come the answer is off by 90 degrees?


texts: SystemVerilog Assertion consecutive repetition for overlapping sequences

texts:
I have a specification as follows :

"Check that 'valido' is not asserted when 'validi=1' for only two, one or zero consecutive clk cycles."

the following assertion FAILS (n-3 times) on a sequence of 111..1 :

assert property (@(posedge clk) disable iff (rst) validi[*0:2] |=> !valido);

I guess the problem is in my property, as it does not cover the case of overlapping sequences (?). Is there a way to write a property which would behave right?


texts:
I struggled to compare the EMI filter needed for 24V to 5V non-isolated BUCK DC/DC (running 300KHz to 500KHz) to ensure it passes CE conformance. I wish to keep switching noise within the DC/DC area as well as filtering out external noise entering into DC/DC.

I have two choices:
(a) Simple SMD ferrite beads and COG cap as pi filter
(b) SMD X2Y filter (1206J1000103MXTE03). It claims benefits superior to (a).

I have spoken to support and they have very little application note to demonstrate the benefits of the X2Y technology. No PPT presentation.

Has anyone use X2Y and how they compare with C-L-C pi filter.


texts: Slow-start lead-acid charge - good or bad?

texts:
I have a 300Ah battery which is near-dead (Abused in the past, around 5 years old) and want to replace it with 4-6 new 100Ah.
The current method of charging is with a 30A MPPT solar controller.

As the sun starts rising the panels start charging it, but they start with a trickle and work their way up to around 25A.

My question is, is this method of charging OK (start slow and build up)? Or should I disable the charger until there is more likely to be full-sun and charge it harder to start? I don't mind buying more panels and a bigger charger if I need to.

I can control the charger with an Arduino and the home automation system I have, so that is not a problem.

With the next setup I don't discharge it below 12.1V under load, 12.2V at rest, so new batteries will not get abused.

Thanks in advance.


texts:
I am trying to plan a set-up to store/organize DIP ICs as my am starting to build up a small collection.
I would prefer to keep them inserted in a sheet of appropriate foam in a case. I found these conductive shipping cases from IBM:
https://www.ebay.com/itm/322272828083
Can these types of cases be used with the black type foam, or is pink required? I know the black type foams are usually more conductive, so is there danger to using them in a conductive fype case? If the case functions as a Faraday cage, would black foam negate that and require ponk foam?
It appears the cases come with pink foam but as they were used for shipping cards/boards and not component pin insertion, it might not be the best choice?
Thanks in advance!


texts:
I have a feeling my IR sensor does not work. To make the most 'low level'  test possible I want to check if the +5 and GND are working/are on the pins I expect:

On the right pin put +5 (according to pic below)
On the middle pin  GND
On the left pin the data signal

Can I assume if I check with a multimeter the continuity between +5 and GND, that the sensor is OK (except for the data signal maybe), and if there is no continuity, it is broken?

Update:

My circuit:

Arduino 5V - IR Sensor, Right pin
Arduino GND - IR Sensor, Middle pin
IR Sensor, Right pin - Resistor 220 Ohm - LED - Arduino Digital pin 11

No (useful) sketch run

Remote tested with telephone camera (visible light when keys pressed)
Result when pressed towards IR sensor: LED off (both with or without pressed remote buttons)

I used a multimeter to check the voltage between the right pin and middle pin which is 5.06 volts (and when I reverse the wires it shows -5.02 volts) so it seems the right pins are used. The left pin always gives 0.00V when checked against the +5V / right pin.


texts: OpenOCD flash writing failure with STM32L071C8 MCU

texts:
I have designed custom-made PCB with STM32L071C8 MCU.
I'm using OpenOCD 'master' branch and SWD interface via FT2232H to debug the MCU.

I successfully did some RAM reading and Flash writing, erasing on the MCU via the OpenOCD so the OpenOCD ->FT2232H-> SWD on MCU works.

But, I have a weird problem with writing to Flash more than 192 bytes or in other words 128 bytes (page) + 64 (half page). the OpenOCD prints an error message about failing to write the data to the desired flash address

  error writing to flash at address 0x08000000 at offset 0x00000000

I have executed OpenOCD with debug prints and came up with these logs.

Log of successfully writing 100 bytes to flash.

Log of failure to write 192 bytes to flash - the problem described above.

as you can see in the logs I'm using 'fillb' OpenOCD command to write bytes to flash.

Before each 'fillb' command I take care to erase the desired flash page. I didn't mention the erasing in log.

Have you any advice about how can I investigate this problem? or maybe any solution?


texts: I accidentally ripped out an eyelet/pth to my PCB when changing LED lights on a mechanical keyboard. I'm am a beginner to anything like this so please use layman's terms. Please site places I can use to buy materials for the repair and possibly some good sources of information demonstrating how to.


texts: What are the guidelines behind a simple headphone amplifier circuit?

texts:
I am wanting to design, prototype, and build a very simple circuit that will take a 3.5mm headphone jack as an input, amplify the signal (hi gain, very low distortion), and output the signal via another 3.5mm jack where I could connect my headphones or speakers.

Disclaimer: I have dabbled with electronics, circuits, and digital logic for years and I love making things with embedded systems (Arduino, Spark/Particle Core, BeagleBone) and the hardware side is extremely simplistic but I will be the first to say (I can't emphasize this enough), I am not an EE. My saying I'm an engineer is equivalent to a high school student taking an algebra class and telling everyone s/he is a mathematician. I just want everyone to see that and understand in hopes that I might be assisted rather than crucified for asking for help. I'm not asking for anyone to do it for me, but to just point me in the right direction.

Because I build a lot of projects and I prototype quite frequently, I have a good number of common components. From what I gather from research and experience, I would imagine I have all of the necessary parts to accomplish this.

I figured I could use a capacitor and resistor to filter certain frequencies (not extremely specific but mostly unwanted and undesirable frequencies). I would take the base of a transistor and connect it to the input signal and use that to modulate a separate circuit that is connected to power and the collector-emitter of the transistor. From there, it can be filtered again and then goes to the output jack. Is that a correct understanding of how it would be laid out? If not, what am I missing? Is there a better or easier way of doing this?

I have several 2N2222 transistors, countless capacitors, and even more resistors. I also assume a potentiometer will need to be added to the output circuit to control volume.

Some of the schematics I've seen online use what appears to be an op amp (or another IC but I don't know the exact function it performs) and I'm not too knowledgeable with those (I have a few on hand, though).

I would like to know if my idea a valid and plausible solution or if I should make some changes. Also, is there a relatively simple way to determine the correct resistor and capacitor values? Will I need an external power source (I don't think transistor can source but I could be wrong)?

I'm open to all constructive criticisms, opinions, or suggestions. Please, don't say anything if all you can think of is "read a book" or "take a class". There are a myriad of people that have gotten into this as a hobby and don't have expert-level engineering experience or knowledge, so I know others may find the answer provided useful.

Thanks!


texts: Sharing ARM SWD pins with normal pin function (on Atmel SAM D09 D10 D11)

texts:
The Atmel SAM D09 (an ARM Cortex M0+ MCU) can enable normal pin functions on the pins that are normally used for programming (SWD). But in doing so I presume that debugging will become impossible after programming the device.

Is this correct, or may it be possible to share certain functions (like I2C/UART/SPI/digital input) without disturbing debugging?

Second, the D09 datasheet has this curious phrase: "Only the SWCLK pin is mapped to the normal PORT functions. A debugger cold-plugging or hot-plugging detection will automatically switch the SWDIO port to the SWDIO function".

So it seems I can at use at least one pin in a shared mode with SWD. But this phrase is rather ambiguous: which pin would that be, and what functions can be shared on the shareable pin?

What I am asking is specific for the ARM SWD protocol, and the case in point is  cheap Atmel SAM D09/D10/D11 chips.


texts:
I am attempting to create a circuit that activates a DC motor when the photoresistor detects light, and I used tinkercad to simulate it. It worked in tinkercad, but when I tried to create it in person, it didn't seem to work. When I check the photoresistor values, it constantly reads 0 even when the light is on. The transistor is used as an amplifier. I have attached a photo of the tinkercad circuit and the video of my real life circuit.
int analogValue;
int voltage;
int timer = millis();
void setup()
{
  pinMode(A0, INPUT);
  pinMode(7, OUTPUT);
  Serial.begin(9600);
}

void loop()
{
  analogValue = analogRead(A0);
  analogWrite(7, voltage);
  if(analogValue > 200){
    if((millis() - timer) > 5000){
    digitalWrite(7, HIGH);
    }
  }
      else{
        timer = millis();
       digitalWrite(7, LOW);
      }
  Serial.print("Photoresistor Value: ");
  Serial.println(analogValue);
  delay(1000);
}

Below is a video and photo on the circuit I created:
https://youtu.be/6rysF_x5tOM

If anyone could help me figure out why it does not work, I would greatly appreciate it! Thank you.


texts: Hspice does not give correct energy consumption for a RC circuit connected to a DC supply

texts:
Here is the circuit I am trying to simulate - a RC circuit driven by a DC voltage source. I measure the output across the capacitor.

Assume Voltage source is 1 V. Assume capacitor is 1fF.

Case 1: Resistor = 0.001 Ohm.

Case 2 : Resistor = 0.01 Ohm

In case 1, initial current will be high, since R is smaller. And the capacitor will get charged fast.

In case 2, initial current will be lower than case 1. And the capacitor will get charged slower than case 1.

How does the energy consumption (from time 0 to the time the capacitor is fully charged) compare between case 1 and case 2?
If I simulate this circuit, I get more energy for case 1 than case 2.

Theoretically, the capacitor will always store a energy of 0.5 CV^2 and the energy dissipated in resistor will be equal to 0.5 CV^2 as well making the total energy spent by supply as CV^2.
That is, the energy spent in this circuit should not be dependent on the current level or the resistor value. However, the spice simulation does not show that. The energy consumption of the power supply is not always constant irrespective of the value of R.

My question is, if i increase the current and keep the voltage constant (by modifying R), should not the energy consumption remain constant for such a circuit (as shown in the picture above)?

Following is my spice code.

.param VddS=1.0
.param Lcap=1e-15
.param res=0.001

Vsrc   ptA  Gnd  VddS
R1     ptA  out1 res
Cl     out1 Gnd  Lcap

*************************************************************************
* Measurements
*************************************************************************
.PROBE  V(out1) I(Vsrc)
.OPTIONS POST PROBE
.tran 1p 1000n
.IC out1 = 0V

.measure tran tstop WHEN v(out1)='1' td=0ns rise=1 print=1

* Method 1
.measure tran Q INTEG I(Vsrc) from=0ps TO=tstop
.measure tran Eqv Param='-Q*VddS'

* Method 2
.measure tran Iavg avg I(Vsrc) from=0ns TO=tstop
.measure tran Evit Param='VddS*Iavg*(tstop)'

.end

The output from spice for R=0.01 Ohm is below.

 ******  transient analysis tnom=  25.000 temp=  25.000 *****
tstop=   1.3066p
q= -25.0003p  from=   0.          to=   1.3066p
eqv=  25.0003p
iavg= -19.1342   from=   0.          to=   1.3066p
evit= -25.0003p

The output from spice for R=0.001 Ohm is below.

 ******  transient analysis tnom=  25.000 temp=  25.000 *****
 tstop=   2.1676p
 q= -45.4546p  from=   0.          to=   2.1676p
 eqv=  45.4546p
 iavg= -20.9700   from=   0.          to=   2.1676p
 evit= -45.4546p

The output from spice for R=1 Ohm is below.

 ******  transient analysis tnom=  25.000 temp=  25.000 *****
tstop=   1.2913p
q=-495.6683f  from=   0.          to=   1.2913p
eqv= 495.6683f
iavg=-383.8522m  from=   0.          to=   1.2913p
evit=-495.6683f

The output from spice for R=5 Ohm is below.

  ******  transient analysis tnom=  25.000 temp=  25.000 *****
 tstop=   1.2955p
 q=-100.4239f  from=   0.          to=   1.2955p
 eqv= 100.4239f
 iavg= -77.5151m  from=   0.          to=   1.2955p
 evit=-100.4239f


texts: Can the motherboard of a inkjet printer be reprogrammed to do something else?

texts:
The motherboard of an inkjet printer has some useful functions - controlling position of the printhead, it has axis movement etc., which a plotter would need.
Is there any way to reprogram the ICs to use (like how you would use an Arduino), to build a CNC plotter?
I have done a lot of Google searches without finding much information.


texts: How to detect open circuit conductor inside opaque insulating sheath/cable

texts: How to detect open circuit conductor inside opaque (untransparent) insulating sheath/cable in small scale. I meant the cable diameter only 1 - 1.5 mm with suspected spot within 10 - 20 cm length


texts: Why is the diode forward voltage constant?

texts:
When you have a diode with a certain barrier voltage (e.g., 0.7 V for Si) and you apply a voltage higher than this barrier potential, why does the voltage across the diode remain at 0.7V?

I understand that the output voltage across the diode will increase as a sinusoidal input is applied until it reaches the 0.7 mark, I don't seem to understand why it remains constant after that point however.

It makes sense to me that any potential greater than this barrier potential will allow current to pass, and correspondingly, the potential across the diode should be the applied voltage minus the 0.7 V.


texts:
I'm designing a module around the nRF52832 SOC and I need some help regarding the single-ended microstrip antenna. I have three questions, so please bear with me.

The first question is about how wide to make the feed line. I know I need a 50 Ohm trace, and using JLCPCB's calculator gives me a trace width of 11.55 mil. The problem is that when I consult other technical articles and use the KiCAD calculator, they give me a vastly different trace width of roughly twice the dielectric material of my board, which is ~3mm for 1.6mm FR4. However, this trace width is bigger than entire footprint pad and doesn't even fit...Do I just connect the LC filter with the 11.55 mil width from the manufacturer or make them as large as possible? I've checked the layout files from Nordic and they have used traces about the size of the pads, so I will stick to 11.55 mils until a reply to this question convinces me otherwise. I've also linked a picture of my routing below for clarity(The net named Antenna is also part of the feed line FYI).

My second question is regarding the antenna length. At 2.45GHz the wavelength is C/f = .125 meters, and quartering it yields 31.25 millimeters of antenna length. For now the length of the antenna is 31.25mm according to my own calculations, but Nordic's whitepapers throw me off by stating that the length should be 23mm without really clearly showing how they came up with that, and that is an 8.25mm disparity which will definitely affect the design. Which one is correct - 31.25 or 23mm?

The last question is about the antenna shape. I've linked a picture below with a hook-shape design that I replicated from another source. I don't know what shapes are 'better' than others, but I want to know whether or not there are glaring errors in what I have so far so I can fix them. If you read this far, thank you.


texts: So I am having trouble understanding the following schematic. It is supposed to take an input through the capacitor C6 which is an AC sine wave and add a DC bias to it. However I do not understand how this circuit adds the DC bias. Can anyone explain?


texts: Replace ONE 25v 47uf capacitor with FIVE 60v 10uf capacitors parallel?

texts:
MY 1000 Watt True Sine Power Inverter blew a 25V 47uf capacitor.  The shell was rattling around inside, and the ribbons were exposed.  Yay, I found the problem!  Sooooo, how can I tell the mounting polarity in order to replace the blown cap?

ALSO, would it be a silly idea to replace that cap with FIVE 60V 10uf caps in parallel (I have these available) essentially making a single 60V 50uf cap?  ...  or should I just buy a direct replacement?

Wondering what effect the slight variation in capacitance might have.

I'm kind of a novice, but the smoke is already out...what can I lose :P

Thanks in advance :)


texts:
I'm trying to wrap my head around this problem :

I must admit I'm pretty much blocked from the start, at a). I don't understand how I could derive the power of \$s_{AM}\$ given the frequency of the random signal is unknown.

I thought I could use autocorrelation to find the power of m(t) since it seems a random signal. The power of the 'b' component can be easily found as \$P_{b} = b^{2}/2\$.

For the message power, I'm just lost. Could Parseval be used? How can I find it not knowing the period of a 0/1? Help would be greatly appreciated. And if I was to find the average power of m(t), how would I find the average power of \$m(t)cos(\omega_c t)\$ ?

Thanks!


texts: What is details meaning of output and input Impedance?

texts:
I was studying the CC, CB and CE Amplifier. And I have found a sentence somewhere that,

"Maximum power transfer occurs when load impedance is equal to source impedance."

As much as I understand impedance is something that opposes current. But, what are this load impedance, output impedance, input impedance? I mean how are the related to.
In the case of CC, CE, CB amplifiers, how are they related to each other and what are the meaning in this case?

Thanks in Advanced. Hope somebody will help.


texts:
I am developing a system that needs to drive 4 stepper motors through 4 dual H-bridges, for each phase of movement the AVR will receive SPI messages stating how many steps each motor should do and what delay should be between each step for each motor. The delays will all rounded to multiples of 100 micro seconds so I plan on using the interrupt of a timer set to as close to 100 micro seconds as it can get to count the time passing between the stepping of each motor as to determine when a step function should be executed. The thing is, I also need 4 PWM outputs to "chop" the power supply going to these steppers as to not overtax them.

Now my problem is that I am thinking about using the ATmega8535(L) for this task and it seems to indeed have 4 PWM outputs operating from 3 timers (it seems as if one of them has 2 channels). Now my question is, would I still be able to use the interrupt of one of the timers to drive my stepping functions?


texts: What material(s) are used in IC's as insulating layers between metal layers?

texts:
This question and the answers hits close to the topic. One picture shows it as SOD. Silicon-oxide dielectric?

I'm aware that around/within the transistor, silicon oxide is grown for insulation where needed, but I can't seem to find clarity on the insulators surrounding the metal wire layers. Is it the same silicon dioxide?

I ask because I wondered how we can see many of the details of the integrated circuit when there should be something insulating and physically supporting each metal wire layer. This means it's either clear or the layers are so thin that most of the light passes through anyway (likely both). SiO2 would fit the characteristics observed, but is that correct?


texts: Microcontroller driven N-Channel MOSFET voltage behavior

texts:
As seen in this LTSpice model, I am trying to control a white LED (3.6 Vf @ 20 mA) connected to a 7.5 voltage source with a 2N7002 N-channel MOSFET and a 5V control signal from an Arduino.

Given that my gate voltage is 5V from a micro-controller, I was expecting the MOSFET to basically act as a switch. By looking at the graph for the 2N7002, given that the desired current is 20mA and the Vgs is 5V, I was expecting a voltage drop across the transistor of close to zero such the source voltage was ~7.5V.

However, as seen in the simulation graph, the voltage across the transistor is in fact quite large, such that the source voltage is only ~3V (as opposed to the expected ~7.5V).

When I breadboarded this circuit, I got the same result, a source voltage of ~3V.

Can anyone explain why the source voltage of the MOSFET is much lower than expected? And can anyone please recommend a transistor that would effectively allow me in this situation to create a switch to drive the white LED with the use a 5V signal and a 7.5V supply power?


texts: Is there some kind of jumper for banana plugs?

texts:
I have a three-phase cable harness (low voltage) for connecting to a motor. I have it connectorized so I can easily plug/unplug the motor.

I would like to insert a short inline cable so I can measure the current on any of the three phases. Here's what I have so far, to measure 1 phase:

I've added a pair of banana plugs to connect the white phase to my DMM. I would like to do the same for the red and black phases, but I'm only going to be measuring one at a time, and I was wondering if there is any kind of double-ended banana jack so I could just plug the two halves of each unused phase together so that it conducts current and it doesn't have an exposed conductor. I couldn't find any. Any suggestions?

(The red/white/black connectors are Anderson Power Products connectors, by the way.)


texts:
I'm trying to build some low power circuits at the RTL level. How would I go about coding operand isolation so that the synthesis tool (ASIC/FPGA) recognizes it. Assuming the spec requires the output of a module to be either 0 or 1 (don't care) when not on and the product of inputs when on. Assume that once the module goes on, it cannot go off unless reset. The code with operand isolation I think would go something like this...

module some_module(input clk,rst, input on,
input [3:0] in1, in2, output reg [7:0] out);

reg state_ff;
reg [3:0] isol_in1, isol_in2;

// Make inputs change only when on (Isolation)
always @* isol_in1 = !state_ff ? 0 : in1; // When state=0,isolate inputs.
always @* isol_in2 = !state_ff ? 0 : in2;

always @*
 out = isol_in1 * isol_in2;

always @ (posedge clk)
if ( rst )
     state_ff <= 0;
else case ( state_ff )
     1'd0: state_ff <= on;     // After reset, wait for on = 1.
     1'd1: state_ff <= 1'd1;   // Needs reset to turn off.
     endcase

endmodule

I'm assuming AND type isolation in the above code. When the unit is off (on = 0 since reset), transitions on the input will not be seen by the logic so will prevent unnecessary transitions in the multiplier. Does this actually save any power (assuming several other modules are being driven by in1 and in2)?


texts:
I am in the process of rebuilding a commercial mixer (Hobart L800, single phase) and have an issue that wasn't present before a wire got stuck in the brake and shorted out the mixer.

After rebuilding, I turned the mixer on, everything sounded great, a supply wire got stuck in the brake and sparks flew. Immediately after the sparks flew the motor sounded different. You could hear it as it winded itself down, almost as if the bearings (or a ball or two) fused together...

After repairing the wire (and securing it all), the motor has a permanent grind to it that I can only compare to failed bearings. I'm far from an electrical motor expert though.

Could it be possible that a bearing failed or is it more likely to be some kind of winding failure? Or perhaps something different completely? I double checked to make sure it wasn't the (external) brake, but it is completely disengaged...


texts: Power supplied by voltage source at non-inverting op-amp input

texts:
Take this differential amplifier:

Where Vout is proportional to (V2-V1). Both op-amps are ideal with linear output. How to determine the power supplied by input voltage sources? Power should be P = V*I, but in ideal op-amps input current should be zero, and so the power, but it makes no sense to me.


texts:
Let me preface this by saying I'm a total beginner to this. My area is Software, not usually electronics; and I haven't done any since I was in high school.

I've done a lot of reading about Wheatstone bridges in preparation for this, but I'm struggling to apply the diagrams to what I have in front of me.

I'm trying to follow this tutorial. In terms of the code side of it, I'm totally fine with what it does, how it calibrates the readings etc. My main problem is the actual scales part of it.

I have the I/O shield that they use in the example as well.

My main problem is the scales. I have a set of scales with 4 load cells in each corner. I have no idea where to start with wiring this up. I desoldered the cables from the board, which also handled the power supply, as I figured I would need to rewire a lot of it.

The tutorial itself isn't very clear as it refers to a certain scale, which I can't get in the UK.

Each load cell has 3 cables coming from it: a red, black and white.

My basic questions:

How would I go about wiring this into a Wheatstone Bridge?
Where would I then connect the battery back to the cables?
How can I determine what the individual cables actually do?

If I need to provide any more information, I'll do my best to reply with what you need. Thank you in advance


texts: I am looking for some help here. I have a photo eye that controls a 120vac pilot relay which acts as an interposing relay to drive several high voltage lighting contactors throughout a plant.  Problem is: when the sun rises in the morning the photo eye's lack of a large deadband causes on/off chatter which effectively blinks light throughtout the whole plant. I was thinking an rc circuit in series withe the A1 of the pilot relay could help eliminate this chatter.  Any idea or suggestions would be appreciated. Also, is it possible that the coil on the pilot relay could have such a low impedence that it iscausing this hysteresis?


texts: Transmitting digital signal long distances, without complex parts

texts:
I'm controlling several multiplexers from NI DO modules.  The multiplexers channel select inputs, A0-A4, are 5v.  The DO modules output 5v TTL.  On the bench I have everything working exactly the way I want.
Real world application is going to require 500+ feet of transmission distance.  I can't go into specific details, but on the receiving end I can not use 'smart' components due to extreme environment.  The muxes are specially made and only complex part.  The only parts I can use are passive components, RLC, diodes.
Opamps, optocouplers, etc. fail in this environment (Where the muxes are located.  Where the NI equipment is I can use any technology available)
My thoughts are to use FETs, controlled by the DO's, to transmit 48v signals.  Then reduce them with a voltage divider in the harsh environment, to bring it down to 5v to control the muxes.
I'm brainstorming any other ideas, or reasons why this will not work reliably?  Most likely will be switching in the 10-50kHz range.


texts: Correct way to wire an Alpha TX433S/RX433S

texts:
I would like to deploy some wireless, battery powered sensors around my house that will wake up regularly and send readings to an Arduino base station receiver. To keep the cost per sensor low I have been looking at using an ATTiny85 MCU with a simple one way RF link.

For the RF link I was initially looking at units like this which just exposes a single data input wire and would work with the Arduino Virtual Wire library. I ended up buying a TX/RX pair from Maplin.

I have now realized that the units I chose are much more complicated to wire up. The datasheet describes the 14 pins but I am at a loss about how I should be wiring these up. In particular, on the TX module:

There are 3 GND pins. Do I need to wire all of these to GND?
SDI/SCK/nSel - I am guessing that these pins are to do with configuring the module. How would I wire them up and what code would I need to run on my Arduino to configure the module?
FSK - I think this is the single wire to send data on. Can I use the VirtualWire library with this input?
nIRQ - This is the interrupt line. Can I ignore this or must I handle interrupts?

EDIT: The datasheet says "The ALPHA Transmitter is a low cost FSK transmitter. It needs only an MCU, crystal, decoupling capacitor and antenna to build a high reliability FSK transmitter"

Where do I need to wire in a capacitor?


texts:
I have to find the transfer function of the following circuit (AC, sinusoidal), using complex numbers, Kirchoff point rule with potentials or Millman's theorem.

The transfer function is \$\underline{H}=\frac{\underline{i_1}}{\underline{u}}\$ .

Here is what I did for now. Schematic using complex impedances:

simulate this circuit – Schematic created using CircuitLab

Then we have :
\$-(V_B-V_A)\frac{1}{Z_L+Z_C}-(V_B-V_A)\frac{1}{Z_C}+(V_C-V_A)\frac{1}{Z_L}+u(t)\times i_1=0\$
^-- False, check in comments for the right one

But what to do now, how to find i1 and u?
Thank you in advance.


texts: If a device has UR sign on the label, it called it is UL approved or not?

texts:
In the data sheet for a device there is a code to indicate it is UL approved.
on the label this code not there but there is a sign UR.
IS UR also can called it is UL approved?
or
UL approved not just mean that it is UL listed it also can mean it is UR?


texts: Using a transformer to step down 230V to 12V

texts:
My circuit uses main electricity in parts of the circuit. However my AVR and other components only need 5V. So I'm using a step down transformer to generate 12V. It's then regulated to 5V.

The transformer won't convert it to dc for me will it?

It just steps it down then outputs a certain voltage depending on it's coils. So I would need to convert it to dc myself right?


texts: Are TI TMS320C6x and TI TMS320C2x compatible?

texts:
I never learnt assembly language programming. But, I know C and C++.

I need to learn C2000 Piccolo programming. I found no book on C2000, there are only manuals from TI website.

But, suddenly, I found this book.

I only have 02 months in my hand to learn this C2000 thing. Would it be worth reading, if I want to learn C2000 Piccolo programming? Or, would it be a waste of time.


texts:
I need a LED in an application, where the temperature cycles from 0 - 125 degree C.
All I can find is LED´s that goes to 85 degree C, can that be true?


texts: Current running through an instrumentation amplifier

texts:
I am building a heart rate monitor using the INA122. In these cases, my electrodes are attached directly to the skin, meaning that above 1mA of output current, I could feel pain from electrical current.

I know that the INA 122 has an input bias of 10 nA for its inputs, but I would like to calculate the current running into its reference terminal. The reference terminal is a 3rd electrode also attached to the skin that aids in noise reduction -- if you've never done biomedical workbefore, think of it as a floating offset voltage. What is the best way for me to calculate, on paper, the current flowing into the reference terminal? Specifically, the current flowing into my reference electrode? The reference terminal appears as "ground" for the single supply case being considered here.

One of my problems in just doing this by hand is that the positive supply voltage isnt connected to the rest of the circuit? Or rather, it's connected only by a 0.1 uF capacitor. I know this must be a noob question, but how can I calculate the current flowing from the battery to the reference terminal/electrode, since this is likely the bulk of the current entering? Is this even safe to do in the INA's single supply case, where reference and the negative terminal of the battery are shared?


texts:
I'm an electronics newbie. I have a circuit in which I have two input voltages, Vin and Vflag, and one output, Vout. Basically I want the following: If  Vflag =0, Vout =0. If Vflag = 1, Vout = Vin. My friend told me I can do it with a MOSFET, but from what I understood, a mosfet either lets current pass through or acts like an open circuit. Basically, a gate for current, while I want a gate for voltage.

Any help will be greatly appreciated.


texts: Detect fitness machine mechanically folded in a certain position

texts: I am developing a controller for a multi-use fitness machine that can be folded/unfolded, somewhat like a foldable bike. It means that after folded, it will stay in that configuration for a long time. What would be the best way for the MCU to detect folding/unfolding in a certain configuration? I can imagine something like a simple button that is pressed when foldable parts touch each other but that doesn't seem to be mechanically reliable. Is Hall sensor a better way to do this?


texts:
I want to setup two-way digital communication between 2 Arduinos, but I'm only allowed one wire between them. One may be "master". Are there any well known methods for synchronizing communications, etc.? I don't want to reinvent the wheel.

I've been teasing the idea of analog signaling allowing for multiple channels on the same wire, but that seems to involve some more complicated electronics.


texts:
I am trying to interface a 16x4 LCD with an atmega32 chip. I wrote the following code which used to work for 16x2 LCD

#include<avr/io.h>
#include<util/delay.h>

#define dataport PORTC // LCD data port
#define commport PORTD
#define en PD6 // enable signal
#define wr PD5 // read/write signal
#define rs PD4 // register select signal

int wrcomm(unsigned int data)
{
  dataport=data;
  _delay_ms(10);
  commport &= ~(1 << rs);
  commport &= ~(1 << wr);
  commport |= (1 << en);
  commport &= ~(1 << en);
  _delay_ms(10);
  return 1;
}

int wrdata(unsigned int data)
{
  dataport=data;
  _delay_ms(10);
  commport |= (1 << rs);
  commport &= ~(1 << wr);
  commport |= (1 << en);
  commport &= ~(1 << en);
  _delay_ms(10);

  return 1;
}

int lcd_putchar(unsigned char x)
{
  wrdata(x);
  return 1;
}

void lcd_init(void)
{
  DDRC=0xff;
  DDRD=0x70;
  wrcomm(0x38);
  wrcomm(0x01); //turn on display and cursor
  wrcomm(0x0E);//cursor line 1 postn 1
  wrcomm(0x80);
}

int main(void)
{
    lcd_init();
    lcd_putchar('a');
    return 0;
}

I am guessing that it should work for 16x4 LCD too. But it doesn't. The LCD is a JHD539 164b.

The one thing I have made progress with is that if I do not send any command the 2nd and 4th line remain all black but if I send any command they are all off. The pot is not helping at all.


texts: Why boost converter efficiency increases at low D and load resistance?

texts:
This slide (page 19) analyzes the efficiency of nonideal boost converter. As you can see from the formula below, the efficiency of boost converter is dependent on duty cycle D and load resistance RL.

The smaller the duty cycle D and load resistance RL, the higher the efficiency.

I would like to understand intuitively how D and RL affect the efficiency.
For duty cycle, the smaller duty cycle, the less time that current flows through inductor resistance. So the efficiency will increase.

Is this right?

However, how to explain the similar for load resistance, why smaller load resistance results in higher efficiency?


texts: Dangerous step potential with low (line) voltage possible?

texts:
I've always read about step potential in terms of substations and high voltage powerlines, where we are talking in the kilovolt+ range.
What if there is a manhole cover and a mains(240V/400V) wire touching it and making it live? Given that the manhole is actually partially in the ground, would there be a danger if you are walking and step with one foot on the ground, other foot on the manhole cover? My assumption is since the manhole is actually lying on the ground, it would lower the potential that would pass through you. Am I thinking in the wrong way?


texts: "error #28: expression must have a constant value" - with nRF51822 app_twi

texts:
I have been attempting to copy the nRF51822 app_twi example for own application in order to get a better understanding of how the HAL works.

However, now I have an error now that I don't understand since my code is basically identical to the example.

The error:

src\main.c(170): error:  #28: expression must have a constant value

That function where the error occurs:

void LSM303_read(uint8_t *m_buffer)
{
    static app_twi_transfer_t const transfers[] =
    {
        LSM303_ACC_XYZ_READ(&m_buffer[0])    /* <<<<<<<<<<<< ERROR OCCURS HERE */
        // Additional transfer go in here
    };
    static app_twi_transaction_t const transaction =
    {
    .callback            = twi_read_callback,
    .p_user_data         = NULL,
    .p_transfers         = transfers,
    .number_of_transfers = sizeof(transfers) / sizeof(transfers[0])
    };
}

That function causing the error, which resides in my LSM303.h header file:

extern uint8_t const lsm303_acc_first_reg;

#define LSM303_ACC_READ(p_reg_addr, p_buffer, byte_cnt) \
            APP_TWI_WRITE(LSM303_ADDRESS_ACCEL, p_reg_addr, 1, APP_TWI_NO_STOP), \
            APP_TWI_READ (LSM303_ADDRESS_ACCEL, p_buffer, byte_cnt, 0)

#define LSM303_ACC_XYZ_READ(p_buffer) \
            LSM303_ACC_READ(&lsm303_acc_first_reg, p_buffer, 6)

Not got a clue what the issue is since this is the exact same function used in the app_twi example.

Can anyone give some advice here? (I'm using Keil uvision 5 with SDK v10.0.0)

Edit:
The m_buffer they used (identical to mine)

// Buffer for data read from sensors.
#define BUFFER_SIZE  11
static uint8_t m_buffer[BUFFER_SIZE];


texts: Can anyone figure out this (David Tudor) circuit?

texts:
Here's a link to the (crummy) schematic:

It's a filter/phase shift designed by the experimental electronic musician David Tudor, for use in destabilizing audio feedback loops.

The circuit seems unclear to me, and I don't understand the signal flow, or the use of capacitors here.

Thanks!


texts: finding output voltage of 2 cascaded sub circuits without KCL

texts: Hi I am trying to cascade sub-circuit 1 and sub-curcuit-2 and find Vout2 with given Vin1. I do not want to just cascade them(connecting Vout1 node to Vin2 node) and write bunch of KCL equations. I want to do something smarter. I searched web and found some examples but in all of them sub-circuit 2 did not have any type of sources(just resistive elements), which was not helpful. I tried a few things which did not work out. I tried to find thevenin equivalent of second circuit, which was a useless attempt. Secondly, I found input resistance of second circuit and connected it to Vout1 and found Vout1, then I put Vout1 in place of Vin2 in the equation which relates Vin2 to Vout2 but did not work as well. I am running out of ideas. Can you show me how to do that?


texts: Custom made PCB problem after lost power supply

texts:
I have 2 custom PCB which need to communicate via Spi. Communication works fine when I flash code and MCUs have stable power supply. After disconnecting from power supply and then reconnecting slave MCU send some garbage and I need to press reset button on PCB to allow normal operation to continue, basically after pressing reset button on slave everything works fine. I read that wrong connection on BOOT0 and RST pins can make such mistakes. On logic analyzer I see that I have some glitch on BOOT0, glitch intervals are not periodic and take a little time. I figure out one more thing, when MCU don't have power supply and I press reset button and hold that button and then connect power supply to MCU and then release button I got fine result, communication works good.

Any idea is welcome.

Here is captured start sequence when PCB is connected to power supply.


texts:
I have this relay circuit that can be turned ON/OFF by NodeMCU ESP32 GPIO18.
This circuit allows current to pass through the RL2 even when NodeMCU is turned off. When GPIO18 is HIGH, it will switch RL2 so that current won't pass.
I'm having problem with my relay because after I set it to LOW and set it to HIGH again, after a few seconds, the relay switches ON/OFF randomly and rapidly.
Question is, how can  I stop relay from switching ON/OFF randomly and rapidly?
Additional Information
*I'm using 5V SPDT relay. (SRD-05VDC-SL-C)
*It's drawing out 60mA.
*I created a 5V voltage regulator circuit from my 12V 2A DC Adaptor
*D2(LED) is connected to relay's normally close pin.
Also, the goal of my circuit is  to automatically allow current to pass through even if NodeMCU is turned off.
Lastly, the relay acts weird when GPIO pin is set to LOW.
Thank you everyone for your help!


texts: Why does pin numbering and placement (in general) appears to be done so haphazardly to the uninformed person (me)?

texts:
Be it an ESP development board, an IC controller, even an LED segment number itself, pin placement never seems to follow a logic when it comes to actual numbering, or function. I can't find a simple general answer to why this is. I suppose there are a few parts to this question:
1.  I assume pin placement has some design factors in it, such as trace length and EMF, am I correct on this?
For instance, I would think it would make more sense to put the VIN next to the 5V, next to the 3.3V, next to the ground on the Arduino, just to keep all the power pins grouped together.  Is there a technical reason they are not, or is it just a design choice?
2. When it comes to ESP development boards, why are the GPIO pins usually all over the place?
They seem mostly out of order, and why is the SPI clock always on the opposite side of the board of the MOSI MISO?
3. When it comes to ICs, why are pins with similar functions not always completely grouped?
A great example of this is the MAX7219, not to list them all but pins 1-5 are DIN, DIG0, DIG4, GND, DIG6.
Why not put the digits in the order of pins? It doesn't make sense to me, can someone explain?


texts:
I have a two layer PCB. The bottom layer is mostly ground tracks and some signal tracks. The top layer is signal tracks and power tracks.

I want to pour copper ground since it helps noise issues and is free as far as I learned and for the sake of learning.

But some questions bother me from what I asked yesterday (Some questions from a first PCB design attempt) and I couldn't find any answer on net.

Here are my questions:

Which layer should I pour copper? And if this "copper pour" is on the other layer it will be connected to ground of the circuit by a via, right? And if copper pour is at the same layer it will be connected by a track? I mean at which particular point and how will the copper pour and the circuit ground will be connected? I'm totally confused.
This is a confusion between the "copper pour ground"  and the "ground plane". I already have many ground tracks on one layer of the PCB. Ground pour has nothing to do with decreasing the ground tracks and making PCB manufacturing faster right? By using copper pour the ground tracks will remain the same? But by using "ground plane" instead we avoid using ground tracks and connect the ground pads directly to the ground plane by vias. Is that true and does that make the manufacturing faster?


texts: FPGA Implementation of Matrix Inverse on Basys 3 Board

texts:
So we are implementing inverse calculation of 8*8 matrices using LU decomposition on a Basys 3 Artix 7 FPGA:

http://store.digilentinc.com/basys-3-artix-7-fpga-trainer-board-recommended-for-introductory-users/

1) Upon synthesis and implementation, we found that the LUT consumption and I/O cons is extremely high and exceeds by a huge margin. The values are tabulated below:

Consumption       Number Available in the Basys3 board
LUT    173897     20800
IO        931     106
DSP        90     90
FlipFlop 3743     41600

How do I go about optimizing the number of LUTs and IO consumed?

MORE INFORMATION:

We use an 8 bit representation for each element of the matrix and the code uses a lot of temporary variables inside for statements to get the intermediate results.

The modules are as follows:
In the top module, we compute the LU decomposition of the input matrix and then pass the L and the U matrices to the module that computes the inverse.
We then pass the resulting values to the output port.

2) We are wondering on how to pass the matrix as an input to the FPGA.

We considered two options:

a)Serializing the input completely (stream the bits via a UART connection from the computer) and developing an appropriate decoding circuitry to assign the inputs accordingly at run time. We are apprehensive about the hardware consumption as we have already exceeded the limits for consumption.

b)Inputting the values in the computer and storing the input in the RAM and reading the values from the RAM and feeding it to our program.
We referred to the following link:
https://stackoverflow.com/questions/27211466/storing-array-in-fpga
, but the answer was not very clear on how to go about each of the method step by step. (Like how to create a GUI (if needed) to pass the input values and then passing it to the board and storing it in a RAM and reading from the RAM) and how to incorporate the code (for reading or writing to RAM) into a source code (if required).  I also referred a bit to this manual: https://www.xilinx.com/support/documentation/sw_manuals/xilinx13_2/data2mem.pdf
, but being a complete novice, I am not sure on how to proceed.

Please provide a step by step procedure on how we pass and store the matrix as an input and read from it and store the results in an output, any links to relevant IPs which can be included in the code and any extra references which we can learn from.

Thanks.


texts: What is this symbol, and it belong to which-system or convensions?

texts:
This is a very common- symbol used in school-textbooks as a symbol for antenna.

This website (http://www.chegg.com/homework-help/questions-and-answers/figure-shows-arrangement-generating-traveling-electromagnetic-wave-shortwave-radio-region--q1017746) mentioned this as the symbol of Transmission line.

 (http://s3.amazonaws.com/answer-board-image/8700a5dc-2c5e-473c-89d3-2a6dde823364.gif).

However, I did-not found any information about this symbol in google and wikipedia. As well, outside school-textbooks I yet not seen this symbol in any professional circuit diagram. What is this symbol? and in which sign-convention it is/was used?


texts: Is this interface just a low pass filter?

texts:
I found the following BNC input output box for two channels(left side inputs, right side outputs):

The grounds of the BNCs are connected via the metallic case. I checked this with multi-meter continuity test.

Then I read the cap and resistor values and drew and simulated this interface for one channel as follows:

Could this be just a low pass filter? Anything related to common-mode? What are these 10nF caps?


texts: MPLABX + PICKit 2 programmer could not be started

texts:
I'm working on getting a basic LED flashing program loaded onto a PIC12F615. I'm getting the following error when attempting to read or write to the device from within MPLABX:

  The programmer could not be started: Could not connect to tool
  hardware: PICkit2PlatformTool,
  com.microchip.mplab.mdbcore.pickit2.PICkit2DbgToolManager

Reading and writing to the device works fine using Microchip's standalone PICkit2 app v2.61.

I'm running Windows 7 and MPLABX v1.95 on my PC. I have tried restarting my computer, disconnecting and reconnecting the PICKit2, flashing the PICKit2 to the latest firmware, running MPLABX as administrator, and uninstalling and re-installing MPLABX. Has anyone else encountered this issue? What else should I try?


texts:
$$ \frac{V^2}{R} =  P  = I^2 \cdot R $$

According to this equation, Power is inversely proportional to resistance on the left side and directly proportional to resistance on the right side.

How can power be both inversely AND directly proportional to resistance?

Looking for more of a conceptual answer than a mathematical one.


texts: How similar are ferrite beads with same dimensions, only differing in material?

texts:
For a particular application I'm making use of the TX22/14/6.4-3C81 ferrite bead. The purpose is to reduce noise of the DC supply voltage, with the supply wire wrapped around the ferrite toroid. These are not available any longer, and a distributor recommended replacing them with the TX22/14/6.4-3C91 ferrite bead, which differs only in material.

How can I determine whether these new beads will work for this application? I've done some research and determined that for other ferrite sizes, the parameter difference between the two materials is negligible (see below), but does this apply to any size ferrite bead?


texts: When abstract logic circuits get translated to the electrical equivilant, how are conversions from 0 to 1 handled?

texts:
I've searched around and there's lots of good information out there, but I'm a bit of a n00b when it comes to the precise meanings of words like current, voltage, amplify, resistor, diode etc. So what at first presents itself as a simple explanation quickly turns into a wikipedia tabfest of ever increasing complexity. With that in mind please forgive my probably inaccurate use of these terms in this post.

The basic problem for me is that gates on a logic circuit appear to be creating power from nothing, which is impossible. For example imagine two NOT gates connected in sequence: To my uninitiated mind what seems to be happening is that the first NOT gate cuts the power to the second NOT gate, which responds by magically conjuring new power out of thin air and sending it on it's way. The only explanation I can come up with feels a bit redundant and absurd (That every single gate on the diagram is implied to be directly connected to a power source)

The closest I've come to an answer is something to do with changing the "signal" from "high" to "low" but again, I'm not familiar enough with the language. It still suffers from the same problem, if you've got a low signal how is it that a NOT gate can turn it into a high one without directly drawing on a power source?

To wrap up and present the question in all it's rookie glory:
How do logic gates physically convert 0 to 1 without violating the law of conservation of energy?


texts: PIC assembly: express integer constant as string at build time

texts:
One of my engineers came to me with a question that I can't answer. This is for a project using a PIC16F controller, all written in assembler.

He is defining a constant that he wants his program to use in two different ways: as an integer for use within the program and the same integer expressed as an ASCII string for use within his serial communication routines.

The standard way that I have done this in the past is to simply have the PIC convert that constant to an ASCII string at run time.  However, since it is a constant, it should be possible to have the compiler do the conversion.

I've thought about it and the answer doesn't immediately come to mind.

He is defining the constant as follows:

  #DEFINE gFORCE_MIN 250

He is defining the ASCII equivalent as follows:

  #DEFINE gFORCE_MIN_STR "250"

The idea is that he modifies only one constant and the assembler automatically converts that constant into the double-quotes delimited ASCII value.

His last attempt returns the following after assembly:

  DT "gFORCE value ","gFORCE_MIN"  returns:  gFORCE value gFORCE_MIN

He is currently using MPLAB 8.92.


texts: Multiple traces for single connection in Eagle

texts:
I'm manually routing a power distribution network in Eagle, and am trying to follow the IC vendor's recommendation to attach vias to the power plane both left and right of the bypass capacitor's connection pad.

As soon as I've made a single connection, Eagle believes that to be sufficient, which means I cannot use the "Route" tool to create the second trace and via. Manually drawing a trace, placing a via and renaming everything to the network name works, but is there a shorter and/or easier way of doing that?


texts:
I'm working on an audio project where I'd like to install common-mode filters consisting of a cm choke and 2 caps to chassis at each of the input connectors in order to shunt common-mode noise picked up by the cables to the earth grounded enclosure. In order to get an idea of the frequency response, I want to simulate the CM-filters with source and load impedances. I have measured values of the common-mode load impedances at the device inputs, and would like to measure the impedance of the cable (acting as the source impedance, most likely twisted pair (unterminated)) across a range of frequencies, from 1MHz to about 30MHz (or more).

I don't have a spectrum analyzer, but I have a 30MHz signal generator and a 100Mhz scope. What's the best way to measure this? I was thinking something similar to the setup below:

I'd measure V across Rmeas to get current, varying Rmeas relative to cable impedance to get enough voltage drop to get an accurate reading, then move Rmeas to the other end of the cable and measure Vin across the cable. Sound reasonable? I assume I'm going to be loading the generator heavily, would it be better to add a buffer at the front end, or is this really necessary?


texts: Why is touching the live wire of a socket dangerous inside an apartment few stories up?

texts:
Let's say I touched the live wire of a power socket in my apartment that is located at the fourth floor of an apartment building. The current needs to flow through my body to ground in order for me to get shocked. According to some sources the human body has a resistance that is quite dependent on several conditions, and can be as low as a couple of thousand ohms, so touching the high voltage with feet grounded definitely is dangerous. But how is my body grounded inside my apartment? There is a thick layer of wood and concrete under my feet, and several other apartments below me. Even if my body resistance would be low, wouldn't there be still very high resistance between my feet and the ground?

I read this question but I don't think it really answered the question:
Why do you get shocked touching a live wire?


texts: How many times can I use the Static-Shielding bags? I usually use this kind of bags to prevent to damage electronics. So when I need to touch some circuits, firstly I touch the bag. The problem here is I have already used the bag. Is it safe to do this or not?


texts: how can synchronize two single phase generators?

texts:
I need to a continues power supply for 3 day without interrupt. I use from 2 single phase generators that a generator work for 10 hour and next another startup. for uninterrupted power supply we need synchronization between to generator. can we connect tow generator?
for big 3 phase generator  (<10kw) synchronization can apply with synchronous board but in single phase phase sequence is not important.


texts:
I am building a humane rodent trap, and require assistance. The trap works using an LED (not shown) and LDR (photoresistor). When the rodent walks over the LED, The LDR increases in resistance and more current flows into the transistor. Then a buzzer, An LED and two motors turn on to alert the consumer. The motor cuts off entries and exits for the rodents. They stop spinning when the door activates a microswitch. The voltage out of the transistor is 3.6V

However, I do not how I would wire it up. I know how to use a DPDT to reverse a motor, but I just made a mess when I tried.

I need the motors to go in reverse using the 4.5V wire when the circuit receives an input.

Switch off: Motors forward If dark using 3.6V supply
Switch on: Motors backwards regardless of light using 4.5V

Motor Circuit:


texts: diode and resistor in parallel with resistor

texts:
how do you calculate V\$_{R3}\$ in the circuit below?

V\$_{in}\$, all the resistor values and the type of the diode are known.

By simulating this circuit one can see that  V\$_{D}\$
 is increasing with higher values for R\$_{3}\$. How is that even possible?


texts:
So we have this machine at work, a strapping machine, and it has a long power lead which is left loose on the ground, and it's getting gradually destroyed - accident waiting to happen.

I know that there are fire hazard risks associated with coiling wire, but I don't know how to work out how much you can coil with virtually no risk.

I would prefer that we don't permanently shorten the cable, because it may come in handy to have it long in the future, and we'd have to raise engineering tickets etc... major hassle for what I suspect is a non-issue under these conditions.

Please help! Let me know what other info might be pertinent.

Rated Power: 5A
Volt/Hz: 230/50
Cable length: Around 3m


texts: Daisy chaining I2C modules using CAT5 and P82B715

texts:
I'm planning to connect several modules over I2C with distances between modules ranging 30-180 cm. I understand that in order to avoid the degradation of the signal due to the capacity of the cable a bus extender (such as P82B715) must be used at each point.

My question is if the placing of the bus extenders is correct in the schematic shown below.

Each slave module has one P82B715 behind two RJ45 females and the bus is daisy chained through them using CAT5 cables (in the middle of the diagram). I believe that in this way the buffered signal is more resilient to degradation, but each node is not acting as a repeater and the total capacitance of the cables must be considered.

Is this correct or maybe there is a better arrangement of the components?


texts:
I want to stop supplying power for a short moment if a watchdog has not received a reset order for a while.

Shutting down power is important as this is the only way for some buggy device to function again.

More details:
Buggy device run on 5V. GPIO voltage can be 5V or 3.3V. In normal operation the whole circuit is consuming about 0.5A sometime peaks overs 2.5A for a really short moment.

We can consider that the GPIO can freeze and therefore stay in +5V position.


texts: Using a 3-phase Transformer After a Variable Frequency Drive for Voltage Reduction

texts:
In the plating industry generally 42V - 3P motors are used to rotate the barrels that hold the products to be plated. This is because the contacts of the barrel cannot be isolated (because barrels are moving from bath to bath) so a reduced voltage is used for safety. Normally, we use a 380V to 42V transformer to drive the barrels at 50Hz and select the gearbox according to the desired rotating speed of the barrel.

But in this case our customer asked about variable rotation speed of the barrels. There are two options for achieving this I can think of.

Use a VFD at the input of the transformer. This will probably work but I'm guessing there will be losses at the transformer since the output of the VFD is essentially chopped DC. Also, the harmonics may cause mechanical stress on the windings.
Use a VFD at the output of the transformer. This would be a valid option, but I couldn't find any VFD that works with 42V input.

Are my concerns valid? Are there any other concerns for these approaches? Is there any other way to achieve this?

Also, any references would be good to know.


texts:
I was recently discussing with my son how it's possible to determine the power requirement of a hoist motor given only two parameters.
These two parameters are the weight to be lifted (150 kilos),and the speed at which they are to be lifted (3 meters per second)
I told him to multiply weight by speed, then, multiply that by 9.81 (gravity), the answer being in Joules.
Please tell me I'm right?


texts:
How do I calculate the required inductor current (RMS, saturation) for a class D amplifier?

Assuming the following configuration:

Speaker impedance (Z) = 4 ohms
Power output (P) = 400W

(calculations are rounded and assume no switching losses at the output)

\$V_{pp} = 113V\$
\$V_{rms} = 113V \times 0.3535 = 40V\$
\$P = \dfrac{V_{rms}^2}{Z} = \dfrac{1600V}{4R} = 400W\$

Is the current calculated as follows?

\$I_{pp} = \dfrac{V_{pp}}{Z} = \dfrac{113V}{4R} = 28A\$
\$I_{rms} = \dfrac{V_{rms}}{Z} = \dfrac{40V}{4R} = 10A\$

Does this mean that I need an inductor that is rated for at least 10A RMS and exceeds 28A saturation current?

The Class-D amplifier I'm using is a "H-bridge" output configuration, meaning it generates the required 40Vpp from a single 20V supply. So I need two inductors per speaker output. Does this mean that my required inductor should be rated for 14A saturation/5A current?

Are my calculations correct? I know the ones I posted are valid for a linear amplifier (Class-AB for example) but I don't know if they are the same for class-D, considering a Class-D amp is always switching max V, and thus, I is always at the max during a short period all the time.

In other posts I've seen mention of "core loss" and "V/us". What does this mean?

(The amplifier in question is a TI TAS5630B. The datasheet doesn't specify a suggested inductor, and the EVM was made with custom ones).


texts:
I have reverse engineered a sounder circuit which appears to be using a center tapped inductor. Since then, I have tried to find center tapped / 3-pin inductors and cannot find them from a reliable source, the only place I manage to find was from Huizhou Haicheng Electronics Factory on Alibaba, see below.

After some research, I have found that things such as auto-transformers or coupled inductors can also be used in sounder resonating circuits.
As I understand it, the difference between a center tapped inductor and a coupled inductor is that the CT is a single coil around a core with a wire 'tapped' at some point in the middle of the coil, and a coupled inductor is two separate coils sharing a common core, if the end of one of the coils is connected to the beginning of the next, this essentially, at least in my mind, makes a tapped inductor.
Now, it is very easy for me to source coupled inductors from reliable suppliers such as Mouser, Farnell, and RS, etc, so it is much more preferable if I would be able to use these as a replacement.

So the question is: Can coupled inductors be used in place of a tapped inductor?

If yes, what would the advantage be of using one over the other, other than the fact one is much easier to find?

Or am I way off the bat and they are two completely different things?

Thanks in advance.

Side Question:
Would two inductors in series act similarly, or not due to the fact they do not have a common core like the above two components?


texts: Generation of non overlapping clocks on FPGA using VHDL

texts:
I am trying to implement switched capacitor circuits and I hence need to generate a two-phase non-overlapping clock. I have been trying to use an FPGA for the same. Unfortunately, my synthesis tool- Quartus II is throwing timing warnings. Further, when I dump the code onto the FPGA (Altera MAX7000S series FPGA), I clearly observe metastable levels and unpredictable outputs.

The code that I've written to implement this is given below:

architecture clock_gen_integrator_arch of clock_gen_integrator is
    signal counter_15        : STD_LOGIC_VECTOR(3 downto 0);
    signal phi1_sig, phi2_sig: STD_LOGIC;
    signal counter           : STD_LOGIC_VECTOR(14 downto 0);

begin
phi1     <= phi1_sig;
phi2     <= phi2_sig;

signal_gen: process (reset, clock25M) begin
    if(reset = '0') then
        counter_15    <= (others => '0');
        counter       <= (others => '0');
        phi1_sig      <= '1';
        phi2_sig      <= '0';
        reset_int     <= '1';
    elsif(clock25M = '1' and clock25M'EVENT) then
              if(counter < "000010000000000" and counter_15 < "1111") then
              phi1_sig      <= '0';
              phi2_sig      <= '0';
              counter       <= counter + 1;
              reset_int     <= '0';
          elsif (counter < "011100000000000" and counter_15 < "1111") then
              phi1_sig      <= '1';
              phi2_sig      <= '0';
              counter       <= counter + 1;
              reset_int     <= '0';
          elsif (counter < "100010000000000" and counter_15 < "1111") then
              phi1_sig      <= '0';
              phi2_sig      <= '0';
              counter       <= counter + 1;
              reset_int     <= '0';
          elsif (counter < "111100000000000" and counter_15 < "1111") then
              phi1_sig      <= '0';
              phi2_sig      <= '1';
              counter       <= counter + 1;
              reset_int     <= '0';
          elsif (counter < "111111111111111" and counter_15 < "1111") then
              phi1_sig      <= '0';
              phi2_sig      <= '0';
              counter       <= counter + 1;
              reset_int     <= '0';
          elsif (counter = "111111111111111" and counter_15 < "1111") then
              counter_15    <= counter_15 + 1;
              counter       <= counter + 1;
              reset_int     <= '0';
          else
              phi1_sig      <= phi1_sig;
              phi2_sig      <= phi2_sig;
              reset_int     <= '0';
          end if;

        end if;
    end process;
end architecture;

Unforunately, I'm not able to include the entire code here, I'm having formatting issues. However, since it's just the entity decleration, I have left it out. phi1(out), phi2(out), reset(in), reset_int(out), clock25M(in) are present in the port list.

In this code, I'm arbitrarily choosing the frequency and duty cycles of the required clocks. I specifically want 15 pulses of phi1 and 15 pulses of phi2 and counter_15 helps me achieve this.

I am being told by QuartusII that I have setup time violations.

Sorry for the greyscale image, I had to reduce the size of the image somehow in order to upload it. The first channel is the phi1 output and the second channel is the phi2 output.
Being new to the tool as well as timing analysis, I'd be grateful if someone could point out what I am doing wrong and how I can fix the timing violation. Also, any tips on how to avoid these issues in general are welcome.


texts: Could a USB wifi dongle be used as an Arduino Wifi module?

texts:
I have seen many arduino compatible wifi modules that are rather expensive compared to some other types of modules. I am wondering what is the feasibility of using a consumer grade wifi usb dongle as a wifi module for an Arduino?

Take for instance this module. Is far cheaper than any of the arduino wifi modules. If it were possible to use one of these in my projects it would greatly reduce the cost of a wifi enabled projecct.

If something like that is possible what would be required to the two communicating?


texts: Simple Circuit Giving Weird V=IR Calculation

texts:
I'm new to electronics and learning as I go along.

This is my "baby" circuit: a 1.5V AA battery (at 1.61V) whose terminals are connected to a 10K ohm resistor on a breadboard.

When I take a current measurement across the terminals of the resistor, I get 210-230ma on my multimeter.

As an experiment to determine voltage from the equation, when I plug the current and resistance values into the V=I*R equation:

V = .22 * 10,000

V = 2,200

This doesn't make sense, since my battery is 1.61V.

I have verified my resistor to be 10.3K ohms.

Can someone please help and explain what the problem seems to be?


texts:
I was trying to automate the button on my coffee machine via this tutorial:
www.instructables.com/Smart-Nespresso-Machine-Using-HomeAssistant-Alexa-/
The schematic uses a BUZ11 MOSFET. I only had a TIP120 at homes I replaced the BUZ11 with the TIP120. I connected the base with a 1K resistor to a digital Arduino port. The collector is connected to the nespresso + and the emitter is connected to the nespresso -. See: ibb.co/GCc8dGf.
In the tutorial it is saying that it is switching circuit of ~ 14 Volts
I was thinking that this circuit also should work. Put the digital port to high will close the TIP120. But it is not working. What am I doing wrong?


texts: How to sense current AC of a sinusoide -100mA to 100mA with 70kHz

texts:
Any suggestions about a chip or PCB component that could work?

I tried to use the the current sense transformer PA1005.050NLT https://www.digikey.com/product-detail/en/pulse-electronics-power/PA1005.050NLT/553-1527-1-ND/2362933 to sense a small sinusoidal current (from +100 to -100mA), but it does not seem to produce the expected result for such a small currents:

For 100mA I want to get a 4.4V output, so I set the output resistor to 2k2:
VADC=R*Ipeak/50=2k2*100mA/50=4.4V

In the datasheet it says that the expected current for the component is 1/50 the sensed current, but I much smaller current (something like 1/1000) and the signal is very noisy. If I increase the output resistor the signal is amplified but it is too ugly and noisy. Any ideas?


texts: Running long underground line without neutral or safety ground using transformer, is it to code?

texts:
My prior question asked about a single wire earth return [SWER] system. Both questions are aimed at meeting the same end requirement but this is a sufficiently different method that many of the issues are different.  Please review:

I now plan on running both hots out of a spare 20A 2 pole breaker of house panel, and will terminate 775 ft later into a 5KVA isolation transformer [Hevi-Duty HS5F5AS] to step down to 120V.  Seems like this would negate the requirement to run a neutral or a safety ground,  as I will create these at the secondary of the transformer.

Does this sound legal to code ?  Location is Atlanta,GA
Looks like a 2 cond 6awg aluminum cable will provide a 6% volt drop @ 15 amp load on the primary/240V side.

Thanks for article @JONK March 8th, on grounding between buildings. I think where the danger still exists with the isolation transformer is that on the primary side with only the 2 hot conductors; if one of the those conductors shorts to the transformer case, there is no path to the source ground to trip a circuit breaker on the primary side of the transformer. Also the local ground rod at the transformer secondary is not a good enough path to the source voltage to trip the primary breaker. So I need to also run a bare copper ground wire with my 2 conductor 6 awg direct bury cable. Another thought; even if the hot primary does short to the transformer case, one would not feel it for the same reason, there is no path back to the source ground with low enough resistance to flow any current. i.e. the case would float at 120V with no path to flow any current/shock anyone. Not safe per code, but just thinking of what would happen.


texts: I'd like to know if this MOSFET switches design is okay

texts:
I have a design where the power of my circuit comes from a 12V battery and I use the energy from the battery to turn on/off a solenoid valve using an ESP32 (which outputs 3.3V from it's GPIO).

In general the circuit will have some other elements that require power from the battery.

The logic of my circuit is as follows: If the battery voltage drops below a certain threshold, disconnect the power of the battery from every other component in the circuit BUT the ESP32 (which has a buck converter that converts 12V -> 3.3V)

Now, to do this, I'm considering using a MOSFET for switching on/off the current flow from the 12V from the battery to the rest of the circuit when this condition is met, I'm adding a flyback schottky diode for safety (because I'll have some inductive loads).

Now, I'm not entirely sure if I should connect the drain of my first MOSFET to the source of the second MOSFET. The second MOSFET will be used to turn on/off the solenoid valve using another GPIO of the ESP32.

I'm sorry if I'm not making myself clear, I'm struggling with my english over here. I'm attaching a schematic that I've been simulating on multisim.

The circuit on the left is the switch that cuts off the power from the circuit of the right.
The circuit on the right is the one that turns on/off the solenoid valve (modeled as an array of inductances and resistors that I found on research gate)


texts: in SPI, can MOSI and MISO be connected together?

texts:
I'm using an 8051 series microcontroller, and documentation states that if I use serial mode 0, then its RXD pin can function as a bi-directional pin (both input and output) while TXD is strictly a clock.

I have an IC which have MOSI, MISO and clock pins. and I also use multiplexer/demultiplexer IC's as well.

I want to take advantage of the microcontroller RXD pin so I don't have to do alot of CPU time-wasting bit-banging routines for each device I want to control.

So is it acceptable to connect MOSI, MISO, and RXD pins together or should there be a resistor somewhere?

And Is it safe to connect an output of a demultiplexer (Example: 74hc151) to the 8051's RXD pin and to an input of a decoder (Example: 74HC138) or should I use resistors?

If resistors are required, what values would you suggest and why?


texts: What are these pull ups for on this SDRAM?

texts:
Apologies for all these questions about SDRAM, but I want to get this next board run right.

I have an LPC1788 processor with an external memory controller I am interfacing with SDRAM. There is no reference design in the user manual of the microcontroller, but I have a development kit I am using as a reference.

For some reason they have pull ups (not termination resistors) on signals such as CLK, CLKE, DQM0-3. Why is this? I was under the impression the microcontroller has internal pull ups for this sort of thing? Are they necessary, or just there out of good practice (is that the same thing)? Should these be places at the source or sink?

Also, what is the capacitor on the CLK line for? Will this not disturb the signal?

I have implemented the termination resistor packs in my own design (currently at 22Ohms although I understand it depends upon the trace impedance).

Many thanks.


texts: STM32 HAL_UART_Receive_IT doesn't get called for size argument of 2 or more

texts:
I am trying to use STM32 HAL function HAL_UART_Receive_IT with more than 1 element but it fails to be called, while it works without any issue with size of 1.

Please correct me if I am wrong, but in the code below there is part for the size:

    huart->pRxBuffPtr = pData;
    huart->RxXferSize = Size;
    huart->RxXferCount = Size;

Isn't it wrong, because if both things are size that means you cannot have 1 byte data and 10 bytes of count (elements)?

Is this bug or something in the HAL ? Or....?

Full code for the function is:

/**
  * @brief  Receives an amount of data in non blocking mode.
  * @note   When UART parity is not enabled (PCE = 0), and Word Length is configured to 9 bits (M1-M0 = 01),
  *         the received data is handled as a set of u16. In this case, Size must indicate the number
  *         of u16 available through pData.
  * @param  huart Pointer to a UART_HandleTypeDef structure that contains
  *               the configuration information for the specified UART module.
  * @param  pData Pointer to data buffer (u8 or u16 data elements).
  * @param  Size  Amount of data elements (u8 or u16) to be received.
  * @retval HAL status
  */
HAL_StatusTypeDef HAL_UART_Receive_IT(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size)
{
  /* Check that a Rx process is not already ongoing */
  if (huart->RxState == HAL_UART_STATE_READY)
  {
    if ((pData == NULL) || (Size == 0U))
    {
      return HAL_ERROR;
    }

    /* Process Locked */
    __HAL_LOCK(huart);

    huart->pRxBuffPtr = pData;
    huart->RxXferSize = Size;
    huart->RxXferCount = Size;

    huart->ErrorCode = HAL_UART_ERROR_NONE;
    huart->RxState = HAL_UART_STATE_BUSY_RX;

    /* Process Unlocked */
    __HAL_UNLOCK(huart);

    /* Enable the UART Parity Error Interrupt */
    __HAL_UART_ENABLE_IT(huart, UART_IT_PE);

    /* Enable the UART Error Interrupt: (Frame error, noise error, overrun error) */
    __HAL_UART_ENABLE_IT(huart, UART_IT_ERR);

    /* Enable the UART Data Register not empty Interrupt */
    __HAL_UART_ENABLE_IT(huart, UART_IT_RXNE);

    return HAL_OK;
  }
  else
  {
    return HAL_BUSY;
  }
}

My code is:

#define GPS_Rx_buffer_size  10
uint8_t GPS_Rx_buffer[GPS_Rx_buffer_size];

HAL_UART_Receive_IT(&huart3,GPS_Rx_buffer,GPS_Rx_buffer_size);


texts: Is this speaker crossover design correct?

texts:
This is the schematic for 2-way crossover, the speakers I want to use are:

Woofer: https://thomann.de/pl/harley_benton_15tb065_b4.htm?o=2&search=1537173360
Tweeter: https://thomann.de/pl/bc_de_108_ohms.htm?o=0&search=1537173394

I wanted to use resistors in high-pass side of crossover to attenuate speaker by the value of 10dB. I chose my crossover frequency on 2.6kHz. With this bunch of information could you tell me if this schematic is correct and I can start to design a board?


texts: Confused about the way this speaker is wired

texts:
From this article:

I don't understand why one end of the speaker is connected to the + of the battery.  If the output of the 555 goes into one end of the speaker, shouldn't the other end of the speaker go to ground?


texts: programming 3.3V PIC32 board with pic32prog and PICkit 2

texts:
I already managed to overwrite the bootloader of my clients's PIC32MX7 board while experimenting with mikroe-uhb. so before I can continue the assignment I need to reprogram it, and all I have on hand is a PICkit 2. I have a PICkit 2 to ICD3 cable on order, but my worry is that the different voltage levels (5VDC on the Pk2, 3.3 on the MMB) could fry the board. googling around, I've seen suggestions for using diodes or resistors, or adding capacitors here and there, but I'm wondering if it really needs to be that complicated. I saw at least one post that indicated if the PICkit2 sees a voltage on the VDD line, it won't put out its own. can anyone here tell me authoritatively what the deal is?

[added later]
just for reference, here is the adapter cable I bought: http://www.ebay.com/itm/251569322951

it turns out that its pin numbering is in reverse to the PICkit 2, i.e., hook the blue wire to pin 1 of the Pk2, rather than the white wire. I powered up the mikroe board, then connected the PICkit2 to the ICD3 port and ran pic32prog:

jcomeau@aspire:~/rentacoder/jm_____$ pic32prog/pic32prog pic32mx795f512l_bootloader_firmware_v130.hex
Programmer for Microchip PIC32 microcontrollers, Version 1.96
    Copyright: (C) 2011-2014 Serge Vakulenko
      Adapter: PICkit2 Version 2.32.0
    Processor: MX795F512L
 Flash memory: 512 kbytes
  Boot memory: 12 kbytes
         Data: 12428 bytes
        Erase: done
Program flash: ########################### done
 Program boot: #### done
 Verify flash: ########################## done
  Verify boot: #### done
Rate: 1517 bytes per second


texts: VHDL interview question - detecting if a number can be divided by 5 without remainder

texts:
I saw a nice interview question for VHDL - build a system that receives a number and detects if it can be divided by 5 without remainder.  I tried to solve that with a state machine (I suppose they don't want you to use mod or rem) and while I did have initial success (numbers like 5, 10, 15, and numbers such as 20, 40, 80 worked), other numbers like 130, 75 and so on failed for me.

I would show my state machine but it's a complete mess (it's not a code, it's a drawing), and like I said, not even working.

Basically what I tried to do is write down in binary numbers that are divisible by 5, and build a state machine that will work for them.

I would be glad if you could show me how to solve this problem, and how to think when facing something like this.

Thank you!


texts: Adjustable voltage source 10 – 50 V and adjustable current limiter 2 – 70 mA

texts:
I would like to build a source that gives on the output an adjustable voltage from 10 V to 50 V and that current be limited from 2 mA to 70 mA
or make some circuit that let me choose 2 mA, 1 0mA, 50 mA and 70 mA for example.

Do someone know how to make a source like this one?

I was thinking to make a DC DC Step Up, and then to put an current limiter on the output of the last one. But how to make an current limiter?


texts:
I want to convert a sine voltage with frequency around 32kHz , what should i keep the amplitude of this signal to get the best conversion.
I looked up the datasheet , but the input range given is around  200mV, isn't this too low?


texts: Converting Acceleration of ADXL335 data into displacement

texts:
I'm currently using a ADXL335 chip two measure acceleration then converting it into a displacement. I'm wanting to measure the vetical (-z direction) displacement range of maximum 10cm, so quite small. I have read the data from the ADXL335 and converted it into "g's". I then numerical integrate (trapezoidal) it twice in order to convert the g's into displacement. I only want to measure the vertical displacement in the -Z direction.

Sample rate == 100Hz; using a 12 bit ADC; Vref == 3.3volts;

here is my CVI/c code:

//every sample (0.01 seconds)

acceleration = (((((adc - 2420)*3.3)/4096)/0.3)*-9.8);//subtracting 2420 to account for the acceleration due to gravity.

acceleration_1 = acceleration;

velocity = velocity_1 + (((acceleration+acceleration_1)/2)*0.01);

velocity_1 = velocity;

displacement = displacement_1 + (((velocity+velocity_1)/2)*0.01);

displacement_1 = displacement;

....//then I output the displacement data and have a condition to reset the values of the velocity and displacement to zero (when the acceleration goes positive as only need the vertically down direction).

My problem is that I'm getting incorrect values of displacement and my observation so far is that the faster the accelerometer moves the higher the displacement will be.

Would appreciate all the help i can get, been stuck on this problem for a while and not able to make sense of it.

I also tried using a High pass filter to remove the dc offset of the acceleration with no luck (The subtract works?). I also tried implementing another button to control when I integrate. For example integrate when the button is push and set the data values to zero when not pressed.

Hope my problem is clear, In essence my displacement output depends on the rate of acceleration and not the total distance.


texts: what is shunt charging in power systems?

texts: I am currently working with Power World Simulator. When inserting transmission lines, there is a parameter called shunt charging. What is this and what effect does it have on power loss in the line?


texts:
I have seen how to do circuit analysis with ideal diodes, that is replace forward-biased diodes with connections and replace reverse-biased diodes with gaps. But the problem is that I want to know how to analize real circuits that contain non-ideal diodes. How do I do so?
I need a few leads.
EDIT
See comments.


texts: I'm building a circuit based on the DRV8840 (datasheet: http://www.ti.com/lit/ds/symlink/drv8840.pdf). Unfortunately, I can't get it to work. I think something might be wrong with my design. When I apply the "ENABLE" pulse at 5V, there is no actuation of the motor. I've checked the motor with a DC signal and its fine. I've also checked the voltage levels around the board and the soldering of the board and it all seems solid. Any ideas???


texts:
I have to design a headphone amplifier circuit. We are told the impedance of the headphones and the minimum voltage they require and also the voltage source. After researching I have found that the LM386N-4 is a popular choice. (According to a datasheet of LM386N-4 - https://www.icrfq.com/part/2377557-LM386N_4.html ). I've seen many circuit diagrams but what I don't understand is how to pick the voltage gain needed for the amplifier?

I originally thought that you would need to know the input audio signal voltage and when you multiplied that by the gain that would need to give the minimum voltage required by the headphones, but it appears that what matters is the current which I don't get.

And are you able to design such a circuit without knowing about the audio input signal? If you do need to know about it what is it you need to know about it and why?

I would greatly appreciate any help as I am very lost.

Thanks.


texts:
I am trying to create a binary adder. I have this truth table:

This is the Karnaugh map that I made for this function (see that there is a mistake: instead of c, it had to be "c-in"):

Now, as the map looks like that, it gives me that s = c + c but that is certainly false. Can anyone help me with this?


texts: (System)Verilog: signal is x or 1 depending on placement of concurrent blocks in the code?

texts:
I'm basically aware that the Verilog scheduler is inherently indeterminate, but I really don't understand why that's the case with the following code (I've simulated both cases with Icarus and Incisive on EDA Playground). The differences between the TB_A and TB_B is in the order of the initial and always blocks.

Case A:

module TB_A ();

reg nrst;
reg signal;

initial
    nrst = 1'b0;

always @(negedge nrst)
    signal = 1'b1;

initial
    #10 $display("value is: %b",signal);

endmodule

Case B:

module TB_B ();

reg nrst;
reg signal;

always @(negedge nrst)
    signal = 1'b1;

initial
    nrst = 1'b0;

initial
    #10 $display("value is: %b",signal);

endmodule

I would expect that at T=0 the transition on nrst occurs and inevitably triggers the always block, putting signal at 1. This happens in Case B but not in Case A, where is displayed the value x for signal. In other words I wouldn't expect indeterminacy in this case, but evidently I'm missing something. Switching to SystemVerilog doesn't change anything.


texts: Static Shift Registers for Serial In / Parellel Out Operation

texts: I'm looking for an 8bit static shift register with serial in-parellel out operation but can't seem to find one . Can anyone help me with this, thank you !


texts: Remotely (long-distance) triggering a 12V solenoid?

texts:
I have purchased a "1CH DC12V 2000M Long Range RF Remote Controller Kit" - this is a remote relay.  With this gear, I have to power both the receiver and the load with 12V sources.

I'm trying to remotely trigger a 12V solenoid, where the solenoid/receiver are both battery-powered.  The total setup must also remain as lightweight as possible.

Is there a way to configure this with a single battery, so that I can minimize the weight of the setup?

Update:

Solenoid current: not specified - Rated Voltage : DC12V; Power : 17W

Receiver current: Standby ≤10mA, Working ≤128mA

On Time: <1s

Standby Time: ~10 minutes minimum, but longer is better to minimize cost of recharges/replacements


texts: How are engineers protected against lightning strikes when testing transmission lines?

texts:
Transmission lines have protection systems to protect themselves from lightning strikes, but in the case of a strike hitting a line under test - how is the user protected?

I'm looking for an answer in the scenarios of a strike hitting the line 20 miles from the engineer, and a strike hitting the line under test directly at the engineers location? - if there is a difference in these scenarios of course.


texts: Different behaviour when using single supercap vs several in series

texts:
I'm designing a circuit where I need a supercapacitor to continue powering the circuit for a few seconds after the main power has been removed. A simplified schematic of the circuit is shown below.

The circuit consumes 200mA and needs to remain on for 3 seconds. I've calculated the required capacitance as follows:

Regulator dropout voltage is 250mV, therefore min input voltage = 3.3V + 0.25 = 3.55V
Diode Vf is 0.4V, therefore max input voltage is 4.6V
Capacitor V = 4.6V-3.55V = 1.05V
Combining the Q=CV and Q=It equations results in C=It/V. Plugging in the numbers results in a required capacitance of 0.2*3/1.05 = 0.57F

I've tested the circuit out with a few supercaps and here are my results (time measured using a stopwatch and stopped when multimeter shows that voltage has reached 3.55V):

1.6F (3x4.7F, 2.3V caps in series). Calculated time = 8.2s, actual time = 8.5s
2.35F (2x4.7F, 2.3V caps in series). Calculated time = 12.3s, actual time = 13.2s
0.5F (2x1F 2.7V caps in series). Calculated time = 2.6s, actual time = 3s
A single 1.5F, 5.5V cap. Calculated time = 7.9s, actual time = "instantaneous".
A single 1F, 5.5V cap. Calculated time = 5.3s, actual time = "instantaneous".
A single 0.33F, 5.5V cap. Calculated time = 1.73s actual time = "instantaneous".

What I'm confused about is why the single 1.5F and 1F capacitors don't seem to behave at all according to my calculations, whereas the capacitors formed for more than one in series work just as calculated.


texts: Are Schottky diodes the best option for this application?

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I want to make bridge rectifiers for some toy field phones so that the wires that connect one phone to the other will work regardless of polarity.

I was wondering if Schottky diodes would be the best option because of there low forward voltage drop?

But I don’t know if the higher reverse leakage of a schottky would be detrimental to proper function.

6v dc (from AA batteries) would be the maximum voltage involved.

If they are what would be a particular diode with the lowest forward voltage drop?

Thanks.


texts: Input Current to Output Current for a step-up voltage regulator?

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I am buying one of the many step-up regulators available on Amazon, the Icstation 2577.

In my project plan, I will be using either a 150mah or 300mah 3.7V 25C lipo battery. I will be stepping that up to ~5V and drawing between 1-1.5A on the 5V output.

What I am trying to figure out, which I can't locate the seemingly simple answer to from searching around, is how the input current will relate to the output current. If I am drawing 1.5A at 5V from the regulator output, what can I expect the input current from the battery to look like?


texts:
I have designed in a FT230X chip to take RS232 Tx,Rx,CTS,RTS and convert to/from USB on a PC. The problem I am having is that I do not trust my terminal emulator RealTerm. I just cannot seem to get anything out of it that is related to the USB port. I can see it as VCP, but setting it up to the same parameters as when I go direct RS232 doesn't produce anything.
Any suggested alternatives or test strategies?


texts: After changing a symbol, how do I update a device with the new symbol?

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I have a device in a custom eagle library, consisting of a symbol and a package.
In the editor, I've swapped two symbol pins.

How can I bring the new symbol into the device?
It does not seem to flow automatically.
I understand of course that at least two pins on the symbol to package mapping will need adjustment as well.

So far I've been able to delete the symbol and bring the new one in, but at the cost of having to reconnect all the pins.  There must be a better way, and hopefully you are about to share the secret.  Thanks.


texts: What does this circuit symbol mean? (Circle with horizontal line through it)

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I came across the following symbol in a datasheet (functional block diagram on page 8).  What does it mean?

For future searchers, the symbol is a circle with a horizontal line (diameter) through it.

Does it just indicate that the current through the branch has a particular value? A current limit? Something else?  Thanks.


texts:
I saw in a code usage of the module IDDRX2D1, this module is inside the FPGA Lattice ECP3, I found from its Libraries Ref Guide this information:

someone can help me about what is it and for what is it used for if someone used it already? why we need it?
is it just a DDR? what the theory behind this module?

thanks!


texts: Need help to determine whether Mosfet is suitable

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I am going to make a regulator circuit with 3.3V 2A output using MAX1655 Step down controller.

I am going to use a solar panel with following specs for input:
Max output voltage: 8.4V

Nominal voltage:6V

Current at MPP: 0.62A

As per the datasheet for MAX1655(at page 11)  i have to use dual N-Channel Mosfet IRF7303 for the circuit diagram(3.3V /2A Output) at page 10 of the datasheet.

Questions:
1)Can i use two units of IRFZ44N instead of  IRF7303 in the circuit(3.3V/2 A Output)? ( IRF7303 is unavailable  at local shops near me and the Mosfet they have with closest specs to IRF7303 is IRFZ44N )

2)Would the MAX1655 Controller be damaged by the use of IRFZ44N? Would i face any other problems?


texts: Someone knows if it's possible to set the internal ground as input in the ATXMega256A3BU? I need it to find the zero offset.


texts:
Hello there I am trying to understand this proof:
foo.
I dont understand why $$\cos{(2 \omega t +\phi)} $$ vanishes when it's integrated between 0 and T.
When I try to do this alone I get: $$V_{rms}=\sqrt{\frac{V_{pk}^2}{2}-\frac{V_{pk}^2}{(2T)(2\omega)}(\sin{(2\omega T+ 2\phi)-\sin{(2\phi))}}}$$ Can I get some help to understand this please?


texts: How reliable are motor power ratings through time (old motors vs new motors)?

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I'm making this question here because I'm a little bit confused with what I've been seeing from some old and new 1/2 hp motors.
I've bought a 1/2 hp induction motor (4-pole, single phase, capacitor start and no run capacitor) and both its standstill and pull up torque seem quite tame. Having a ~ 2 inch diameter pulley on its axis, I can easily stop it whenever I want with one hand. I'm sure that up to 3 times that torque could still be held with one hand only.
This matched well with what I saw in two bench drills, both of which also use 1/2 hp, 4-pole induction motors, the only difference being they use both a start and a run capacitor. In both cases I could stop them by holding the chuck with a single hand, and even in the highest reduction (with reasonable effort but still), which was about 1:3.5 in both cases.
I always thought that to be kinda weak but ok.
Then, last week I saw a 60 year old drill with another motor that should theoretically be similar (1/2 hp, 4-pole). But it was a 3-phase motor, which, as long as I'm concerned, should have a lower standstill torque than a single-phase motor with start capacitor, given their torque vs slip curves.
But I had no luck holding it. Even using adherent gloves and using both hands I couldn't stop it from starting in any way and I couldn't stop it while running either.
It was also in the max torque (~ 1:3.5) relation, so maybe I could stop it in a 1:1 relation, but didn't feel like it. While others could be even stopped with one hand, this one didn't even seem to slow down while using two hands.
Is there something I'm not considering here? Once all of them have the same power rating, nominal speed and reduction, I'd expect them to be at least similar in torque, but the older one seems to be just so much stronger (and the motor itself is also much bigger and heavier).


texts: Can I do KVL around transistors? (MOSFET and BJT)

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I'm having a lot of trouble with more complex transistor DC circuits (can't wait for the AC, heh). Basically, what I want to ask is does KVL holds "around" a transistor as well?

For example, if I have a p-type MOSFET, and I successfully calculate Vsd and Vdg, can I find Vsg like Vsg=Vsd+Vdg? I think I remember seeing that this is true only in saturation mode, but I can't seem to find it again anywhere for the life of me.
Similarly, can I go "through" a wire when doing BJT circuits? What I mean is, if I know that BJT is in saturation (and Vbe=0.7, Vce=0.2), is it allowed to have both of them in the equation while doing KVL (effectively going through the emitter wire).

TL;DR: Is it valid to write Ib*Rb+Vbe-Vce=0 regardless of the mode of operation. Same for the MOSFETs?


texts: Please help to identify SOT23-5 packaged "T1-R17"

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Picture of good component:

Picture of bad component:

These are photos of identical twins. The first is in perfect health, the other burned up and rendered the Sony VAIO PCG-8111L laptop in came from, useless. I would love to ID this 5-pin package, (T1-R17), and replace it. I have searched until I am blue in the face, but not sure if I was searching correctly.