texts:
I have an application where I need a solenoid to control a valve at the bottom of a tank. For unimportant reasons the valve needs to be inside the tank at the bottom.

I was wondering are all solenoids inherently waterproof?

Current will follow the path of least resistance (kirchhoff's current laws prove this).

I did some basic internet searches and turned up that on the lowest end the resistivity of water is 20 Ohms per meter. If my solenoid is 24V and draws .6 amps that means the coil (plus added resistor) is 40 ohms.

Therefore the current would prefer to go through the water. I tested this theory by dropping my solenoid in my tank and running the power. It worked perfectly. But it should be noted my tank is plastic and is not grounded.

If I had grounded the water in the tank would my results have been different? or is there something else making the solenoid's coil have a lower resistance than the water in the tank?


texts: What is this component that is found in lots of phones?

texts:
I was taking apart an old phone (an old LG GM360). It was always a terrible phone. Anyway, I found one of these inside when I was tearing it down:

I have also found some of these in the back of my current phone (Galaxy S4 - i9505), where there are several of them, I do not think they are antennas, as according to the instruction manual the antenna is at the top right of the device (as you look down at it from the back), and yet these things are not really in that position.

They have holes cut out from them in the case, so only the plastic, black part is visible.

What are these things?

EDIT: It turns out they are antenna connectors.

Is it possible to actually connect a commonly available antenna to them?

What connector would I need for this type?


texts:
Probably a simple question;
For this sensor, should I connect the interrupt pin 5 to ground?

The function of the pin is unclear to me. To add to the confusion page 3 says the pin is active low. Does keeping it low enable the chip to work? Or does the pin have another function and will keeping it low prevent the chip from working (like keeping a reset pin low)?


texts: Funtional role of op amps in a ADC filter circuit

texts:
I am a student trying to reverse engineer a rather interesting PCB, trying to learn from it but have come across some circuits that I am struggling to identify the roles of.

This is the first part.

"ref" that I have circled inputs a reference signal, which at first I thought was the GND. The negative input pin is connected to other op amps, serving as a ground, and also to the Ref pin of an instrumentation amplifier. The role is pretty clear that it is providing some kind of a stable reference for all the other amps, but I don't know exactly what it is doing.

2.

This is the second part of the circuit which takes in a signal filter from an instrumentation amp. OA3's positive input is connected to OA4's negative terminal. I am pretty sure that it is a rectifier of some sort, judging by the function of the board, but I have never seen one like this. The simulation results show that OA3 has no effect on the signal, the entire this just inverts the signal.
Maybe I have my schematics wrong..?

Q3.

This is the last part of the question. OA5 takes in the signal from OA2(shown above) but weirdly it halves the signal, then amplifies it by 2. The negative termainal is connected to the negative terminal of OA4 from Q1. Why on earth would this kind of a circuit be here? Impedance matching doesn't seem probable because it is between cascade of op amps.


texts: 15% drop in motor RPM when using PWM controller

texts:
I'm new to the forum and a total noob to electrical engineering.

I have a 120W, 24V DC gear motor.  Runs at ~200 RPM no load connected straight to a 24V power supply.

However, when I connect it to a PWM controller, the RPMs max out at ~170. The PWM controller has an input range from 6V-90V DC, rated for 15A, PWM frequency of 15 kHz, duty cycle is supposed to be adjustable from 0-100%, uses a 10k potentiometer.

After doing a little research, I thought that maybe I needed IR compensation. But, it seems that IR compensation is more for keeping RPM stable with and without load. My drop is happening without load in both cases. So, is there a loss of power associated with using a PWM controller?

From what I've read, PWM should yield pretty close to full power. And, since my controller is adjustable from 0-100% duty cycle, 100% duty would be full power or the whole 24V right?  Any insight as to why the motor is not performing at full potential would be greatly appreciated.

Update: Using a Fluke meter I took the following readings, as requested in this answer below:

With meter set to AC, measuring across the motor and varying the pot. The reading bounced around a lot when I moved the pot.  With that said, once things settled down I got 0 at min, 0 at maximum and 2 at middle.

With meter set to DC.  DC input = 24.5.  Motor voltage = 21.2.  +DC input to Motor+ = 0.6, -DC input to motor- = 2.7.


texts: Can I find the Fourier series expression from given terms?

texts:
I found the fundamental frequency, and all the harmonic components (an, bn), but is it possible to find the fundamental expression of an ,bn or cn?
-The last part of the question-


texts: Maximum length of variable and function names?

texts:
I'm not sure whether this is a property of the compiler or something standard to C.  I've heard of limits on the number of characters long a variable or function can be (e.g. 25characters).

I'm not there yet, but just saw a decently long function and began to think about it.  Is there a limit I should know about?


texts: Micro controller serial communication question

texts: Im relatively new to micros and have a conundrum.  My senior project  involves using a touch screen and xbee modules for wireless communication.  My question is, since both of them require serial communication, should I find a micro that has 2 serial ports, or is it possible to have both of them connected to the same serial port and select which one to communicate with?


texts: Two 4-20 mA masters/readers for one sensor

texts:
I need to read the value of a 4-20 mA sensor, however I need to not interrupt the existing equipment that is already running.

I have a plc that monitors a 4-20 mA pressure sensor.  I need to build a 3rd party device, that can get the reading of the pressure sensor, but not prevent the PLC from working.

Is it possible to have two masters / readers on a 4-20 mA current loop?


texts:
I was pondering this problem:

Given a standard small hobby servo motor, is it feasible to reuse it's internal components to drive a larger DC motor?

I tried disconnecting the motor and reconnecting a larger motor and, as expected, the motor turned but slowly and with little torque.

I'm hoping someone might have done this already and have advice.

-Tom


texts: Getting rid of noises after RC low pass filter stage

texts: I am outputting a 40kHz square wave from arduino and passing it through an RC circuit in order to get a clean 40kHz sinusoid out. However, the output wave I am getting is noisy.(see picture) Any advice on how to get rid of noise?


texts: Can I/Q signals from two perpendicular antennas be simplified to any less than 4 signals?

texts:
Say I have two magnetic loop antennas oriented perpendicularly, such that one antenna has a null facing east/west, while the other has the null facing north/south. Each of these antennas is connected to a receiver with an I/Q mixer, and then I feed these I/Q signals to a software defined radio for demodulation and processing.

The goal here is to implement a goniometer (see fig.2) (another description with Adcock antennas) in software, for direction finding or spatial filtering. By combining the antenna signals in some ratio, it's as if I have a single magnetic loop antenna which I can virtually rotate to any angle. But if I can do this in software, I can have many such spatial filters at one time, or make spatial waterfall displays, or other such cool stuff. Think of it as Ambisonics for RF.

This requires four signals: I and Q for each antenna, times two antennas = four signals.

Here's the question: is it practical, through some electric or mathematical manipulation, to simplify this to three or fewer signals I'd need to process? It seems to me that an incoming wave will have some frequency and amplitude, information already contained in just one I/Q pair. My second antenna adds additional information by capturing the rotation of the plane of the received wave front around the up-down axis. Does this require an additional two signals?


texts:
this is my first time on stackexchange and I have a question.
I have a project and I have to write a vhdl code but when i simulate i get a unknown output.  I don't know why but i dont get a error at compiling. It is just a simple fsm that take a average of 8 bit vector. can someone tell me what is wrong? thx

library IEEE;
use IEEE.std_logic_1164.ALL;

entity delay is
port(mem_in       :in    std_logic_vector(7 downto 0);
    flag_in_mem  :in    std_logic;
    reset        :in    std_logic;
clk      :in       std_logic;
enable       :in    std_logic;
    flag_out_main:out   std_logic;
    data_out     :out   std_logic_vector(7 downto 0));
end delay;

library IEEE;
use IEEE.std_logic_1164.ALL;
use IEEE.numeric_std.all;
use ieee.std_logic_unsigned.all;

architecture behaviour of delay is

type delay_state is (main, regi, calc);
signal state, new_state: delay_state;
signal reg, new_reg,buff, new_buff : std_logic_vector(7 downto 0);
signal test : std_logic;

begin

lbl1 : process(clk,reset)

begin
if(reset='1') then
state <= main;
reg <=(others =>'0');
     data_out<=(others =>'0');
    flag_out_main<='0';
elsif (clk'event and clk='1') then
     state <= new_state;
     reg <= new_reg;
     buff <= new_buff;

 end if;
end process;

lbl2 :  process(mem_in, enable, state, flag_in_mem, reg,buff)

begin
new_state <= state;
new_reg<=reg;
  case state is
      when main =>
        flag_out_main<='0';
        if (flag_in_mem='1' and enable='1') then
         new_state<=calc;
        end if;
    when calc =>
        new_buff <= std_logic_vector((unsigned(mem_in) + unsigned(reg))/2);
        flag_out_main<='1';
        new_state<=regi;
    when regi =>
        if(enable='0') then
        new_reg<=buff;
        new_state<=main;
        end if;
end case;

end process;

   data_out<=reg;

   end behaviour;


texts:
I have a small control board with an STM32 controller on it that handles commands from VCP usb port and controls a large ledpanel of 400 leds.
My PWM circuit looks like this and should be able to handle currents up to 1.9A

My board is powered from a 12v DC adapter, but the touchpanel pc has it's own adapter.
As soon as the USB cable is plugged in, the leds started to turn on way brighter.
So with unplugged usb cable I measure like 5 volt between the usb cable plug and my board ground.
I was expecting a tiny bit of potential difference, because they don't share the same ground.
My board ground is from DC 12V adapter and USB ground is from the Touchpanel PC adapter.
I really don't get it yet what is going on here.
Can it be that the large ledpanel is dragging my board ground to -5V?
I'm PWMing at 32kHz, the load is around 1.5A maximum


texts:
I am starting to learn electronics together with an arduino.
The first project is just to make an red LED light up on a 5V power source.
in that circuit they use a 220 ohm resistor.

My question is what formula do we use to calculate the resistor?

I do know that the recommended amperage for an LED is between the 20-25mA and when I calculate the Amperage (5V/220ohm) I get 23mA.

I then googled and saw an other way to calculate the Resistor and now I am not sure on how to calculate this value.

The other formula is taking the Vf value of the LED into account.
datasheet here: https://www.arduino.cc/documents/datasheets/LED(red).pdf
I see a min of 1.9Vf and max 2.4Vf

If I then calculate R, I would get this formula:
(5V - 1.9V) / 23mA = 3.1V / 23mA = 135 Ohm

Can I safely use a resistor of 135 Ohm for my LED on a 5V power source?
Because now my A over the circuit is 37mA (5/135) and the max A in the datasheet is 30mA.


texts:
I'm trying to understand how comparator (used in 555 timer) able to compare two voltages.

I'm searching for comparator schemantics but all I get is the triangle symbol.

AND gate has a symbol "D", and if I search for "AND gate schemantics" It'll show me two transistors that builds up an AND gate.

What builds up a comparator?


texts: Why would a wireless smart card antenna have one larger loop and three smaller loops instead of four similar size loops?

texts:
This image is originally from here. I added some annotations. The picture shows an x-ray shot of a smart card with wireless capability (and also a contact pad for direct connection to a terminal).

The antenna is made of four loops of wire laid out in concentric pattern. It's a single piece of wire connected on ends only. One loop goes through the entire perimeter and three other loops only go through the top and the middle of the card.

Antenna totally avoiding the bottom of the card is not a rare thing. This is a popular design which purpose is to allow embossing the text near the card bottom. Antenna could be damaged by the emsossing process so cards where embossing is necessary often have the antenna going through the upper half of card only. Cards where embossing is not required don't need this so they may use antennas which are located along the whole perimeter.

So the two popular designs either have all loops avoiding the card bottom or all loops located along the whole perimeter.

In this card three loops avoid the card bottom but the fourth one does not.

What could be the purpose of such antenna design?


texts: What would be the best way to electrically insulate the high voltage (60-90V) area on a PCB? I've seen a silicon-like coating on several PCBs, but I am not familiar with the product or its application method.


texts: Rocker style light switch: do I need an isolated power supply

texts:
I'm building a Wi-Fi controllable light switch that will use rocker style (up/down) plastic buttons.  My plan is to have all the electronics enclosed behind a metal gang plate (the part that screws onto the gang box) in it's own plastic enclosure.

I would like to have plastic 'legs' on the back of the rocker switch (for up/down) that protrude into small holes in the single metal gang plate so that the plastic legs push tactile switches on the inside PCB, mounted behind the metal plate in the enclosed area.  The depth of the holes is roughly 1.25 cm.

Some of the sensing electronics I'd like to keep mains referenced, so a non-isolated power supply would be preferable.  I would like to have this UL certified eventually.

My question is simple.  Do I need an isolated power supply in this case? The buttons will only ever be pressed by the plastic 'legs', not touched by a finger and everything else is enclosed.

Don't get me wrong, I have experience designing switching mode isolated power supplies in the past.  But am not too sure of what I'll need in terms of certification for this specific case.

Any help / clarification / expertise is appreciated.  Thanks.


texts: Is there a single IC that can control a 8x8 RGB LED Matrix

texts: I was wondering if there was a single IC like the MAX6960 that could control a whole 8x8 RGB LED Matrix because the MAX6960 can only control a RGY.


texts: How to create high voltage levels for high side input of a driver?

texts:
I need to charge and discharge a capacitor up to supply Voltage and down to GND level. Supply voltage of the system may change between 120V and 60V. Also, to drive capacitor charge/discharge switch, I need to use logic structures.

So, I thought, IGBT may be a good fit for my needs.

Commercial simple logic circuits(SR Latch, NAND, OR vs) mostly use 5V TTL. Low side IGBT can be driven with 5V easily, However, I need to provide VCC and VCC-5V for High side IGBT to drive:

So this is my question: How can I provide that signal level(VCC - 5V Low and VCC High) with simple structures? Please be aware that potential difference between Gate and Source of the transistor should not be above 5V and also please avoid to suggest Schmitt triggers because driver is already kinda slow I don't want it to be any slower. Thanks in advance!


texts:
I had a water issue with a PCB power strip that has a PCB inside. About half the width of the 220Volt traces got connected and burned so "luckyily" nothing else broke as the fault stopped there.

The traces are about 1cm wide each, but half the width about 5mm is burned off. Is it possible to fill the burned off lead of those traces or what is the best way to repair them as its quite high voltage I dont feel comfortable running them half width.


texts: Which current can a multimeter measure for an indefinite duration?

texts:
It might vary, depending on multimeter.

But if on a multimeter, there is printed "10A for 30sec. MAX every 15 min" or "20A for 15 sec (time unspecified)", below which approximate threshold is the safe duration of measurement indefinite?


texts: Why there is no shoot-through in CMOS logic gate?

texts:
This picture is shown on Wikipedia.

From my understanding of shoot-through, I think this circuit will shoot-through every cycle of pulse and destroy itself.

Will it shoot through or are there any hidden elements to prevent it?
Can I make discrete CMOS logic based on this circuit? Or which circuit will work?


texts: Why am I calculating a higher current through this inductor than is being supplied?

texts:
I'm trying the find the current (using phasors) through the inductor shown below.

Using the current divider rule, I got that 840+j480 uA are going through the inductor. Additionall, by Kirchoff's laws and the terminal relationships of the resistor, capacitor, and inductor, I got the same answer.

My issue is that the magnitude of the current entering the circuit is 600 uA, but the magnitude of the current through the inductor is 967.471 uA which exceeds the source current. This is not allowed, correct?

Where did I go wrong?


texts: How to Import a P Spice model into LT Spice?

texts:
I want to import the part LM393 into my LT Spice program library. The file down load doesn't have a .lib or . asy file that my other files have. It's from texas instruments and is supposed to be a P Spice file but only comes with a 5_1 File.
https://www.ti.com/product/LM393A?dcmp=dsproject&hqs=sw&#desKits
If you could go over in depth how I could get it over into my library.


texts: Is it possible to load values to a counter upon startup?

texts:
I'm designing a digital clock for a freshman electrical engineering projects course. I am using SN74HC161 4-bit synchronous counter chips for the counting. My design counts seconds and minutes with correct rollovers, and I am going to design the hour logic next.

I am wondering if it is even possible to load values onto my counters as soon as the clock powers up. My counter begins from zero, but I want the clock to default to midnight, for example, because 0 o'clock does not exist. Though I will be adding a feature to set the clock's time (by manually incrementing hours), I don't want my clock to start off with zeros across all my seven segment displays.

This low-res picture is just for a general idea of my design. I am using NI Multisim (and yes, I understand this is a noob-ish piece of software, but I am a freshman electrical engineering student).

Here is a closeup of my counter / decoder chips so you can makeout the pinout.

Any help would be greatly appreciated.


texts:
I want to install front and rear cameras on my car. However, the head unit only allows one composite in.
The circuit I am thinking of is below. I think the power side of the circuit is OK, but to keep things simple, I thought of just joining the composite signals with a simple rca splitter.
I only need to show one camera output at a time and am not too worried if the changeover is a bit rough.
My main concerns are…
Will it work with just a splitter?
Will I damage the head unit?
Any suggestions on a simple alternative would be welcome.
EDIT. After the feedback (Thanks). I decided to go with a DPST relay on the composite signal wire with common earths. This seems to be the same as manual changeover switches. As this is in a car, I will use standard automotive relays for this Any comments?


texts: What is the input resistance of the following inverting op amp?

texts:
What is the input impedance? I have tried to solve it, let me know whether it is right or not?
Thanks in advance.


texts: Understand the JK Flip Flop Logic Diagram

texts:
I'm actually looking for some explanation for the JK Flip Flop :

On a website : logic.ly I can simulate the behavior of logic gates, or logic circuit.

When I use the JK Flip Flop icon, it works as it must work. And when I look on the internet to get a logic diagram of the JK flip flop (to reproduce it using logic gate) I got undefined state for both output... So is something wrong with my diagram ? Does it come from the website ?

Here is the logic diagram I got from internet for the JK Flip Flop

Here is the diagram I made on logic.ly, and I got multiple undefined states (red wire) whether the input are true or false (for each possible possition, clock down or up is the same)

So if someone could tell me what's wrong and help me to solve that, it'll be really appreciated !

Thanks,


texts: Terminology for BJT “regions of operation”

texts:
How regions (modes) of operation are defined and correctly named?
The most controversial thing is the so named “saturated region/mode”. It is defined differently, sometimes radically different, in various sources. The discrepancy surfaced several times at electronics.SE, e.g. here and here, but wasn’t acted upon by experts. BTW, are “mode” and “region” equivalent in this context?
Definitions of “saturation” that can be found include:

Both junctions are forward-biased. En.Wikipedia, but popular on this site too, and quoted e.g. here.
Variant: both junctions are on – implicated to be the same as the above by ru.Wikipedia, but “forward-biased” and “on” are not synonyms.
“minimum voltage drop between collector and emitter”.
Variant: \$V_{\mathrm{CE}}\$ reaches some [low] value.
\$I_{\mathrm C} ≈ I_{\mathrm E}\$. We can infer that they suppose that \$I_{\mathrm B}\$ is negligible. Spanish Wikipedia isn’t anywhere near a trusted site, but they made changes to en.Wikipedia text they stoletranslated, which indicates some doubt about the original.
\$I_{\mathrm C}\$ is less than \$I_{\mathrm B}\$ times the current gain of the BJT (Ignacio Vazquez-Abrams; see comments below).
Variant: no increase in \$I_{\mathrm C}\$ when \$I_{\mathrm B}\$ increases.

Note that any of 2.–4. fully or partially is a part of the Wikipedia’s “active”. Imagine a common base scheme without a load, but with a slightly reverse biased base–collector junction; say, for 0.1 V. The condition 2. holds manifestly, whereas for \$I_{\mathrm B}\$ sufficiently large we can meet the condition 4. and the transistor will not burst in flames. The base–collector junction is reverse biased by construction. The base–emitter junction is forward biased since we have a significant \$I_{\mathrm B}\$ – it’s definitely not a cut-off, so we are in Wikipedia’s “forward-active”.
Is would be also nice to trace the origin of aforementioned English Wikipedia definition.


texts: Good Batteries for (way) Sub-Zero Temperatures

texts:
I am building a PongSat and I need some batteries that can withstand the temperatures found at very high altitudes. The pongsat is planned to go up to around 100 km altitudes where the temperature is around -90 degrees Celsius.

I was planning to use a lithium thionyl chloride (Li-SOCl2) battery since it supposedly can take a beating in terms of low temperature but it is a bit bulky and still doesn't go low enough.

The battery I need has to be as small as possible since it will be housed in a ping-pong ball with the "flight computer" and sensors. It also has to supply 5 volts with at least 25 mA of current.

If anyone knows of anything that could work, please share since I've been trying to get this done for quite a while. I started the project in August 2014 and haven't made much progress because of the battery. More documentation of my project is here: K-Labs PongSat.


texts: How to find out a register contains inputs or outputs or both?

texts:
I don't have much experience with embedded systems and I am trying to check if is possible to determine if a register is made of inputs or outputs or a mix of inputs and outputs.

Let's say I have a 32 bit register like so: "11111111111000000000000000000000"

Is there a possibility to check if this is made of inputs/outputs/both ?

The project that I work on, already does this somehow when run on hardware, but I need to simulate a method that given a register determines what is made of.


texts: Assigning a value to a tri data type variable in Verilog

texts: Suppose there is a 'tri' data type variable A declared in a module m in verilog. A is connected to the output of another module n which is instantiated twice inside m, in both the instances. In one instance the value of A will be 1'bz and in another instance it will be 1'b1. What value will A take? Could you provide reference from any textbook like Samir Palnitkar or any other?


texts: Reason for failed MOSFET and Power Resistor

texts:
I am trying to repair the Power Supply for a Phillips TV (the power board is named DPS-130QP). I quite quickly found a burnt out resistor (R611). And after removing a heatsink on a nearby MOSFET (Q601), I found the MOSFET to be split in half as well.

This is all nice and well, and it's quite easy to replace. However, my problem is that I cannot really understand why these components failed. My understanding and experience with switched mains power supplies are however
very limited.

I've checked all components involved in the driver circuit (driven by IC601), and I've not found any component which seems to be faulty. There are at least no shorts and resistances seems to be reasonable according to their markings (sadly the schematic does not list component values).

My current two theories are:
- R611 failed (it does not conduct any more), causing IC601 to overdrive the MOSFET, which in turn overheated and split open.
- IC601 failed, causing the MOSFET to overheat bringing R611 with it.

I have no way of testing the function of IC601, so this is currently guessing. I'm hoping someone with some experience with Mains power switching supplies can help out with some input. Are any of my theories reasonable? Are there anything specific I should be looking for?

The MOSFET (Q601) is a STP5NK80Z, and the driver IC (IC601) is a ICE2QS02G. The Resistor (R611) is 0.47 Ohm 2W.

The schematic of the relevant part of the supply is here.


texts: What's the purpose of a ferrite bead inductor on this circuit?

texts:
I'm studying the analog voltage reference circuit described in the AVR450 Application Note - Battery Charger for SLA, NiCd, NiMH and Li-Ion Batteries, which schematic is below (copied from page 38).

On page 40, there's a schematic showing the MCU connections for the charger where the analog reference circuit is used (picture below). Marked in red there's a component (a BLM-21) whose symbol looks like an inductor, but I'm not sure what exactly it is.

I found online that it seems to be a ferrite bead inductor.

My questions are:

What is the purpose of that component in the aforementioned circuit? It looks to me that it may be part of a LC filter with C9. Is that it?
What happens if I omit it?


texts: Where to connect tristate pin of oscillator?

texts:
I'm trying to use this oscillator in a project but am unsure of how to connect the tristate pin.
I believe I should NC it but don't want to mess up my design if that is not the case.
https://ecsxtal.com/store/pdf/ECS-5032MV.pdf
Tri State Function

Pin 1                    Output

0.7 * Vdd Min or NC      Active
0.3 * Vdd Max.           High Impedance

Thanks!


texts: What is the purpose of a battery on a GPS receiver?

texts:
My GPS receiver has a small MS621FE battery:

Any ideas what might be the purpose of a battery on a GPS receiver?


texts:
I am trying to use PN532 for Mifare card reading on STM32F4.
Before even trying to go forward I have tried to read firmware version to verify that all works ok and cannot do it.

I am trying to base off NFC READER V3 and ELEC code.

My code looks like:

  uint32_t versiondata;
  uint32_t chip_version;
  uint32_t fw_version_maj;
  uint32_t fw_version_min;

  PN532_SPI__wakeup(&dd_PN532__reader);

  versiondata = PN532__getFirmwareVersion(&dd_PN532__reader);

  chip_version = (versiondata>>24) & 0xFF;
  fw_version_maj = (versiondata>>16) & 0xFF;
  fw_version_min = (versiondata>>8) & 0xFF;

I have ported it to be C not C++ as in original.

Code fails at:

uint32_t PN532__getFirmwareVersion(devicedriver_PN532 *dd)
{
    uint32_t response;

    dd->pn532_packetbuffer[0] = PN532_COMMAND_GETFIRMWAREVERSION;

    if (PN532_SPI__writeCommand(dd,dd->pn532_packetbuffer, 1, 0, 0)) {
 ------- FAILS ------> return 0;
    }

    // read data packet
    int16_t status = PN532_SPI__readResponse(dd,dd->pn532_packetbuffer, sizeof(dd->pn532_packetbuffer),1000);
    if (0 > status) {
        return 0;
    }

    response = dd->pn532_packetbuffer[0];
    response <<= 8;
    response |= dd->pn532_packetbuffer[1];
    response <<= 8;
    response |= dd->pn532_packetbuffer[2];
    response <<= 8;
    response |= dd->pn532_packetbuffer[3];

    return response;
}

Callstack for reference:

int8_t PN532_SPI__writeCommand(devicedriver_PN532 *dd, const uint8_t *header, uint8_t hlen, const uint8_t *body, uint8_t blen)
{
    dd->command = header[0];
    PN532_SPI__writeFrame(dd,header, hlen, body, blen);

    uint8_t timeout = PN532_ACK_WAIT_TIME;
    while (!PN532_SPI__isReady(dd)) {
        dd->delay(1);
        timeout--;
        if (0 == timeout) {
            //DMSG("Time out when waiting for ACK\n");
            return -2;
        }
    }
    if (PN532_SPI__readAckFrame(dd)) {
        //DMSG("Invalid ACK\n");
        return PN532_INVALID_ACK;
    }
    return 0;
}

Which seems to fails at comparing:

int8_t PN532_SPI__readAckFrame(devicedriver_PN532 *dd)
{
    const uint8_t PN532_ACK[] = {0, 0, 0xFF, 0, 0xFF, 0};

    uint8_t ackBuf[sizeof(PN532_ACK)];

    dd->spi_cs_low();
    dd->delay(10);
    dd->spi_write(DATA_READ);

    for (uint8_t i = 0; i < sizeof(PN532_ACK); i++) {
        ackBuf[i] = dd->spi_read();
    }

    dd->spi_cs_high();

    return memcmp(ackBuf, PN532_ACK, sizeof(PN532_ACK));
}

Output from logic analyzer gives:

Time [s],Packet ID,MOSI,MISO
0.001900600000000,0,0x02,0x01
0.001916100000000,0,0x00,0x01
0.012942050000000,1,0x01,0x01
0.012957400000000,1,0x00,0xFF
0.012972500000000,1,0x00,0xFF
0.012987550000000,1,0xFF,0xFF
0.013002650000000,1,0x02,0xFF
0.013017750000000,1,0xFE,0xFF
0.013032800000000,1,0xD4,0xFF
0.013048050000000,1,0x02,0xFF
0.013063450000000,1,0x2A,0xFF
0.013078500000000,1,0x00,0xFF
0.013094650000000,2,0x02,0xFF
0.013109750000000,2,0x00,0x01
0.014950450000000,3,0x02,0x01
0.014965800000000,3,0x00,0x00
0.025992800000000,,0x03,0x00
0.026008250000000,,0x00,0x00
0.026023400000000,,0x00,0x6E
0.026038600000000,,0x00,0xCB
0.026053800000000,,0x00,0xBB
0.026068950000000,,0x00,0x6F
0.026084150000000,,0x00,0x4F

Any hints? Is hardware failing...

If possible could anyone share their logic analyzer output for getting firmware version so I can compare it?

TNX.


texts:
I have a problem with my system and I can't handle the problem.
The problem is that when I power the system with DC volt (3.3V) without debugging then I can't see anything on the receiver side (Arduino Uno as receiver.) However if I use the debugger [FET430 - UIF ] then I can see all of the characters on the receiver side.
This is my code:
#include <msp430.h>
#include "cc430x613x.h"
#include <msp430.h>
#include <string.h>
void terminal_write();
void UART_open();
void UART_close();
void main(void) {

WDTCTL = WDTPW | WDTHOLD; // Stop watchdog timer
//__delay_cycles( 2 * 1e7);
while(1)

{
    UART_open();
    printf("system working\r\n");
terminal_write("AT\r\n");

__delay_cycles(5000000);

//_bis_SR_register(LPM3_bits + GIE);
    UART_close();

}

}

void terminal_write(char *info)
{
unsigned int i;

unsigned int len = strlen(info) ;
for(i=0;i<len;i++)
{

UCA0TXBUF=info[i];
__delay_cycles(10000);

}
}

void UART_open(){
        P1SEL |= BIT5 + BIT6;
        //UART Settings
        UCA0CTL1 |= UCSWRST;
        UCA0CTL1 |= UCSSEL0 ; // ACLK
        UCA0BR0=3;   //UCA0BR0 = 3 ; //32Khz / 9600 –>> 3
        UCA0BR1=0;   //UCA0BR1=0; // BAUD 9600;     ( UCABR1 * 256 ) + UCABR0  = UCABRx    see "slau259e.pdf"

        UCA0MCTL=6 ; //  see "slau259e.pdf" page 602 //
        //UCA0MCTL =| BIT7 |  BIT6  | BIT5 | BIT4 | BIT3 | BIT2 | BIT1 | BIT0 |
        //          |------- UCBRFx --------------|----UCBRSx----------|UCOS16|
        // for 9600 baudrate at 32kHz UCBRFx = 0 , UCBRSx = 3 , UCOS16 = 0
        //          |  0   | 0      | 0    | 0    | 0    | 1    | 1    | 0    |
        //          0b00000110 = 0x06 = 6
        UCA0CTL1  &=~  UCSWRST;//
        UCA0CTL1  |=   UCDORM;
}
void UART_close(){

    P1SEL &= ~(BIT5 + BIT6);
    UCA0CTL1  |=  UCSWRST;
    UCA0CTL1  &=~  UCDORM;

}

If I use DC power then the system consumption is about 450-550 uA. If I use the debugger then the DC power consumption is rises to about 4.8 mA. If I use only the debugger [powered with the debugger voltage without using any external DC supply] then the system can't handle the communication properly.


texts: 2 adapter plugs melting, fire hazard, clueless to why

texts:
Any forensic skills here? Trying to figure out if this fire hazard is due to crappy adapter plugs or difference in voltage/hertz in Japan.

Got this plug in China (cheaply...) where they use 230V/50hz, and have been using it in Japan where they run 100V/60hz to connect a (sturdy Chinese) extention cord, but yesterday when using an electrical kettle (Japanese so made for 100V/60hz, but pretty high W), then this happened.

I didn't see it so I tried with an identical plug and saw electrical arcs from inside the plug, seemingly between the two connection points of the prong and connecting plate.
Does anyone know what happened?

Update: The kettle is 1250W, and the adapter plug lists 10A

...so with the help of the forum the problem was seemingly P/V=I , 1250/100=12.5A, which was just too much for my crappy adapter plug. Thanks!


texts: Programming FabISP Attiny44 with Arduino

texts:
Is there a way to program the Attiny44 on a FabISP board using an Arduino board? I read through a few online tutorials, and the ones that even mention using the Arduino as an ISP for an Attiny44 don't mention the issue of programming a chip that's meant to be clocked at a different speed (12 MHz)than the Arduino itself.

I would like to do this with the components I have if at all possible; I'm a poor student with no job, and I've unfortunately spent a lot of money on parts already. I also don't know anyone who has an AVR programmer, so that's out of the question.

Thanks!


texts: PWM as a voltage regulator for 12V wiper motors and 14.8V LiPo

texts:
I'm using 12V (~40W) car wipers motors for small robotic project. Motors are driven over MOSFET H-bridge (IRF1405/IRF4905) with PWM speed/power regulation. Currently a voltage source for motors is a 3S 11.1V LiPo battery (full charge 12.6V and 9V discharged). So most of the time battery voltage is below 12V (nominal motor voltage).

Now I'm thinking about switching to a 4S 14.8V LiPo (full charge 16.8V and 12.8V discharged) and regulating a voltage on motor with duty cycle of PWM and targeting 13-14V as a 100% power of motors so I could get a little more power and speed in "short and rare" moments when I need it. For the most of the time of robot operation, motors are on 30% duty cycle because robot is typically moving slowly. I'm doubted is this type of voltage regulation safe for motors?
Without load, motors can run on 18V without any problems and heating (tested with lab power supply).
P.S: I'm not concerned with long-term effects like wearing of bearings because I'm planning to change motors with stronger in month or two.

EDIT: Also, what will be "safe" frequency for PWM in this case?


texts:
I am not expert in electronics so there must be many errors that I am not considering. I designed a simple half wave rectifier that gives signal to a LDO voltage regulator of 3V3. In the input I have a sine wave that should have a frequency of 13.56 MHz and an amplitude of 10 V. However, when I choose a 500Hz wave the LED at the output of the LDO is working but at 1KHz, the LED is off. the voltage drops to a few mV.

I am using the following schematic that is extremely simple (the purpose is to design a bioimplantable device for the brain, so that's why it must be simple)

simulate this circuit – Schematic created using CircuitLab

The datasheets of the LDO that I used is:

https://www.sparkfun.com/datasheets/Components/LD1117V33.pdf

Just for leting you know, I am basing my circuit in the design of John Rogers :

https://www.nature.com/articles/s41928-018-0175-0?WT.feed_name=subjects_engineering

What is the problem and how could I solve it. I attach some pictures.


texts: Make a real world example with a NPN Transistor

texts:
I have read a lot about transistors and I still cannot make my last example work. On the internet I see that transistors are primarily used as switches and as amplifiers.

A) Use transistor as a switch

I want to open and close a circuit. For this example it is a 12 V lamp that I have:

The lamp is on all the time. In order to insert the transistor as a switch I do the following:

Now whenever my digital pin on Arduino is set to HIGH the light turns on.

B) Use transistor as a amplifier

Here is where I am getting stuck.

I want to amplify the signal coming from my aduio cable that is connected to my phone. I connect my audio cable to my phone like this:

I soldered the tip of the audio cable to one cable and the middle part to another cable. I soldered it like that because when I connect those two cables to a speaker I could hear sound. Anyways when I connect those 2 cables to an oscilloscope this is what I get:

As you can see the voltage varies from about -0.2 volts to 0.1 volts. This is what I have tried to amplify the wave:

The voltage varies between negative and positive therefore I do not know what cable to connect to emitter or collector. I have bough a simple 12V speaker. How can I amplify that wave to make the speaker that I bought play louder? In short I just want to amplify the waves that I read on the oscilloscope. WHen I lower the volume on the phone the waves get smaller in amplitude. How can I increase the size of those waves even more?


texts: I am trying to build a capacitor bank for a project in order to feed an inductor with "high" voltage(500V) however I only have a dc generator rated at 100V at my disposal. Charging 5 identical capacitors in series all equipped with bleed resistors would not cut it as I would get 100/5=20V on each cap. My question is whether charging each capacitor separately with 100V and then connecting them in series would get the voltage at the two ends of the circuit at 500 Volts? I understand that the capacitance would be divided by 5. So far charging each capacitor separately while they are already connected in series gives me a total voltage of 270 volts.Any idea why that happens? Any answer will be appreciated !


texts: How to select proper capacitors and capacitance for LM78xx voltage regulators?

texts:
I want to use LM78xx voltage regulators for various projects. I want to know in general, how should I choose a correct value for input and output capacitors of LM78xx family when I want to change DC to DC (without a need to think about the reservoir cap in AC to DC applications)?

I have done a quick research and I found that various vendors and people recommend different values:

       C1(uF) C2(uF)

Fairchild  0.33    0.1

KEC        0.33    0.1

National   0.22    0.1

Texas      0.33    0.1

ST         0.33    0.1

MCC        0.33    0.1

Web1       10.0    1.0

Web2       100     10.0

Web3       100     0.1

Web4       10.0    10

What are the consequences of choosing large input and output capacitors?
I have seen some people say too big a capacitor on output has detrimental effect on transient response. But how and when?
I have also seen that people say too big an input is not able to damp oscillation if high frequency impedance of cap being too high. But What if I use a big (3300uf) low or ultra low ESR electrolyte parallel to a metalized film capacitor like 473j100? Isn't the metalized film capacitor with ultra low ESR taking care of high frequency oscillation? While the big 3300uf cap providing a reservoir?
If it is ok to use more than 100nf for output caps, and 330nf for input caps do you you think adding several low ESR metalized disk caps in parallel which lowers the ESR value further is going to make it more robust against high frequency oscillation? Assuming I don't mind wasting several bucks for caps!
I have heard that Low Dropout regulators are sensitive to too low or too high ESR. Is LM78xx considered an LDO? I think it is not. But I have seen some websites are listing them as LDOs.

Please bear in mind that I don't mind about the high losses, heat problems and other sort of problems. I only want to know about the caps value.

I'd be thankful if you could elaborate on these questions as much as you could.

Thank you in advance.


texts:
I am thinking about adding USB support to a device of mine using V-USB. From what I read there and on other sites USB seems to have only 3.3V as a high level on the data pins, whereas the voltage supplied by USB is 5V.

What is the reason behind that? To me it seems to only make things more complicated since that way I need to work with multiple voltages on the board or completely step down the Vcc to 3.3V.


texts: D flip-flop sequencer to light three LEDs up sequentially together and then turn them all off

texts:
This circuit should turn on three lights sequentially whenever there is a high logic level until all are lit and then turn them all off, restarting the cycle.

It seems the following sequencing circuit has a design flaw or I am missing any important concept here (I know D latches change their levels whenever if the D level changes and there is a low-to-high transition at their input)

But... if letter R is lit (Q1 is high), then the output of the NOR gate (logic level for B) would be always zero, thus, making impossible of both B and R be lite together.

This was the official answer to the problem:

many thanks for any advice!


texts: How does iPhone detect when dock connector is connected to an audio input?

texts:
I'm trying to solve a seemingly simple problem with (hopefully) an equally simple solution.  I'm strictly an amateur when it comes to electronics, so I'm hoping someone here can guide me in the right direction so I don't do something stupid and fry my iPhone...

I have an iPhone dock in my car, and the dock routes the audio output from the iPhone's dock connector to the line-in jack on my car's receiver.  Over time, the line-in jack on the car's receiver has become worn and loose, and as a result it seems to disconnect for just a tiny fraction of a second whenever I go over a bump in the road.  The disconnect/reconnect cycle is quick enough to be inaudible, but the iPhone detects it and pauses audio playback because it thinks I've unplugged it from the dock.  This is annoying, because I have to keep hitting the play button on my phone every time I go over a bump.

Based on my (admittedly limited) knowledge of electronics, I'm guessing that the iPhone detects the disconnect by measuring the impedance on the audio output and pausing playback when the output impedance goes above some threshold.  Based on that assumption, my theory is that I should be able to build a cable that will fool the iPhone by providing a small load on the audio output circuit even when the other end of the cable is completely disconnected.  That way, when I go over a bump and the line-in jack does its microsecond-disconnect-thing, the iPhone will still see a load and think everything is still connected.

In its simplest form, this could just be a resistor strung across the two wires of the audio cable, but I have no idea what value to use for the resistor.  I also don't want to fry my iPhone, so I thought I'd ask around first to make sure I'm not doing something totally stupid.

Will this work?  Is it as simple as the resistor idea, or do I need something more complex?


texts: Is it possible to take array inputs in module terminal list?

texts:
I want to create a 16X1 mux with 4X1 mux.So can I create a module for 16x1 mux in this form?
module 16X1 (OUT,I0[0:3],I1[0:3],I2[0:3],I3[0:3],S4,S3,S2,S1)


texts: Two different circuits not working on same power supply.?

texts:
I have designed a SIM900 circuit on a zero pcb board for testing purpose. It is working fine. In my application I need to make a call and then talk to the other person on call. So I have used PIC MCU to  initiate a call whenever a person press the switch. The circuit is working as expected. SIM900 requires voltage between 3.3v-4.8v and PIC MCU works on 5V and my input voltage to the pcb is 12v so I have used a LM317 for SIM900 to give it 4v and have used LM7805 for PIC MCU to give 5v.

When on a call I need to listen to the other person so I have used this speaker but the output audio was very low so I though of designing audio amplifier circuit using LM386. The circuit is also working fine and giving loud audio. As the input requirement of the LM386 is 5v and because I have designed it on another pcb so I have used the 5v from the LM7805. I connected everything and pressed the switch. Speakers were making call connecting sound and as soon as the call is connected, there was no sound. I tried again and again and checked the circuit but nothing was wrong. Then  I used external 5v power supply and gave it to the LM386 circuit and now everything started working. There was clear and loud audio. But as I cannot use two different power supplies( 12v, 5v) I need the complete circuit on same 12v supply.

I don't know why its not working on 5v from LM7805 but its working on external power supply. Does anyone have any idea about it. Please help.

Here is the schematic of power circuit:

Below is the schematic of LM386:


texts:
I am not able to understand how diode clamp protection works.

Considering the diode clamp protection as shown in Figure 1: When the input voltage (Vin) becomes more than power supply voltage (Vss = 5V), say Vin = 12V, then the equivalent circuit becomes as shown in Figure 2. But what I did not understand is that the potential difference between the terminal Vout and the ground is still Vin=12V, isn't it? Could someone please explain this to me?

Same question is asked here How does a diode clamping circuit protect against overvoltage and ESD? but I could not understand it and I do not have enough points to ask for clarification comment there.

Thanks.


texts: Will battery last longer with larger capacity but lower efficiency (high V through LDO) or vice versa?

texts:
Given a simple circuit of a draw around 28mA (when supplied 3.3v).  I'm trying to maximize run time on a battery, but working with what I've got on hand...  I have the following batteries:

5000mAh 3S LiPO (12.6V fully charged)
1700mAh 2S LiFE (7.2V)
600mAh 1S LiPO (4.2V)

I have the following regulators:

MCP1700 3.3V LDO
LM2931 5.0V LDO

The MCP1700 Can't handle the larger batteries.  So I see my options are:

Use the tiny 1S and the MCP1700
Use the 3S and the LM2931 output into the MCP1700
As above but with the 2S

Which should last longer?

Obviously the 5000mAh battery is by far the largest, but that's a pretty inefficient setup.  The 2S is somewhat more efficient and still about 3x the size of the 1S.  The 1S should be by far the most efficient, but the battery is tiny.

I can, of course, just try each and measure.  Thought I'd ask here for insights.


texts:
Does anyone know an official name for this type of crimps?

I am seeing them all the time but never know its proper name. The seller calls them "Female Crimp Pins for 0.1" Housings". They are made for this type of housing:


texts:
How can I effectively measure up to 230 v AC using a PIC micro controller?
I just want to measure Line voltage, and as per the measurement I need to apply in the design.


texts: In wikipedia it says what sign extension is but it doesn't say what it's used for or when it is used. I read Hennesy's book "Computer Organization and Design" and it has a sign-extension mechanism mentioned on page 124. As far as I understand the sign entension is used to align numbers that have different length i.e. 16-bit numbers, 24-bits number etc all to same length e.g. 32 bits. But why do these numbers have different length to begin with? Is it because these number can be different data types and therefore have different lengths? For instance, the number can be the 16-bit immediate part of a 32-bit assembly instruction and then the 16-bit number would need sign extension. Is this true?


texts:
I'm trying the sample provided by K66 SDK from NXP and it doesn't work at all. I attached a scope and monitoring the data that is transfered from the uC to the slave but nothing is there. I have another firmware which is the original software we use it writes random SPI bytes. So I decided to test the NXP SDK SPI Sample to investigate further the problems but there are no outputs at all.

What should I do in that case ? Steps ?


texts: How to use the Non Maskable Interrupt on SAM4S?

texts:
I'm trying to use the NMI on a SAM4S (Cortex M4), but I'm finding some hard time to make it work.
The main objective is to jump to the NMI handler whenever the power is about to go down, so that I can perform a clean shutdown, saving data that could be lost otherwise.

At the moment, I'm using a PIO controller to jump to an interrupt when a power fail is detected. The code is something like this:

gpio_configure_pin( POWERFAIL_PORT_IDX,POWERFAIL_PORT_FLAGS);
pio_set_input(PIOA, POWERFAIL_PORT,(PIO_PULLUP|PIO_DEBOUNCE));
pio_set_debounce_filter(PIOA,POWERFAIL_PORT, 100);
pio_handler_set(PIOA, ID_PIOA,POWERFAIL_PORT , PIO_IT_FALL_EDGE, Powerfail_Interrupt_Handle);
pio_enable_interrupt(PIOA, POWERFAIL_PORT);
NVIC_EnableIRQ(PIOA_IRQn);

I'd like to set this interruption with maximum priority using the NMI. That way, this interruption would be active all the time, even after calling __disable_irq() in some parts of the code. Until now, I searched the SAM4S datasheet and ASF sources/examples, but I was unable to find any obvious way to do it, or simply realize if it's possible.


texts:
I need to choose a transistor for my battery supplied application. What does it mean when it says it has a 5V gate drive. Do I need 5V as supply voltage for that transistor?
What do I have to take care of, when choosing a tansistor?

Thanks a lot.


texts: What is a safe and efficient diy or commercial solution to convert 120VAC to 120VDC?

texts: I want to power a series system of ~4 x high power leds, each with a forward voltage of 30-34V.  I understand that I can use a diode bridge rectifier to convert AC to DC, but this will have a frequency component that is undesirable.  There are ways to get rid of this frequency component, but they seem either too advanced or dangerous for my level of expertise.  Since the desired DC voltage is very close to the supplied AC mains voltage, there should be a highly efficient solution available, but in my searches I am getting mostly AC-AC transformers, and AC to variable DC power supplies (usually low voltage DC).  Any suggestions?


texts:
I had two sensor modules connected to my arduino, after some experiments i noticed that when the both modules are powered, i couldn't get correct readings from either one.
The Only case i got correct readings from one module happened when i switched OFF both power and ground for the other one

It worked fine (although i didnt get the maximum readings from the sensor)

Now I am asking if i can substitute the BJTs with Mosfets to solve the problem of high voltage drops on BJTs (without using MOSFET driver)


texts:
When I have gone through some books I have found the expression of the DC Gain of the the boost converter in current mode is given by

H0=(RL/Ri)*1/(2*M+(RL*Tsw)/(L*M^2)*(1/2+Sa/Sn))

But I did not find out what is the expression of the M, please can you give me the expression of this M and from where does it come??

Here is attached the final expression given by OnSemiconductor


texts:
I have a PCB with many chips on it - it's a "hashboard" for an ASIC bitcoin miner. There are 63 chips on every hashboard, and each chip has a small heatsink on it.

I tried heating the heatsinks with a hot air gun to remove them, but most of time the chip comes off along with the heatsink, and the chip is still stuck to the heatsink.

Is there any solvent in which I can soak the boards or chips that are stuck to the heatsinks, in order to separate them?


texts:
My project has two micros.

One is an ESP8266 - WiFi radio and the other a general purpose micro.

The power to the ESP needs to be clean.

I initially looked at a pi filter using a ferrite bead but then found several articles that state the bead should not be used in the power line to a micro. The resistance of the caps at the noise freq does not supplement current enough to compensate what the bead is blocking (from a TI paper and another post in this forum on ferrite beads)

Can someone suggest how to make sure the 3.3v line to the ESP is clean?

The other micro on the board .. sitting about 1.5 inches away, is running off an internal 48 mhz clock and has several SPI lines that are clocking at 1 mhz.

Thanks


texts: How does 3 phase power operate single loads?

texts:
I am wondering how 3 phase power is used to power, say for example, light bulbs? If I have 3 phase power coming into my house, how are the 3 phase combines to enter the one prong of an electrical outlet and then exit the other prong? How is 3 phase power concentrated into 1 line? Or is it?

I am trying to understand what happens, which is why there are a few (maybe overly broad) questions. And then there are electronic devices that contain converters to go from AC to DC (for example our baby monitor).

Any explanation is greatly appreciated!
Thanks.


texts: I am trying to use microcontroller dsPIC33EPXXXGM3XX/6XX/7XX to generate a PWM 12V circuit with 300Hz frequency. I have a question about how to make sure the output is 300Hz? How to design the circuit?


texts: Why does my ungrounded DC power supply work?

texts:
This is a question about electronics theory that I haven't been able to grasp. I was testing a stepper motor wired like the following: https://learn.adafruit.com/adafruit-tb6612-h-bridge-dc-stepper-motor-driver-breakout/using-stepper-motors

The only difference was that instead of wiring my Yaeccc MS-305D DC power supply to the arduino Vin, I wired from the power supply to the motor power on the driver.  The sketch failed to work, and I measured the voltage from the cathode to ground as around -2.7 V and the voltage from the arduino output to ground as the expected 5 V.  Roughly, it looked something like this:

simulate this circuit – Schematic created using CircuitLab

After unplugging and replugging the ground 1 or more times, the circuit began to work. I figured the arduino ground and my power supply ground should have been at the same potential level so it should have worked initially. I don't know why this was the case.

Then, upon unplugging the ground from the power supply, the circuit still worked. I thought that a circuit has to be completed for current to flow (with the exception of discharging) Can anyone explain this?

//Clarity edit
Here is a more detailed schematic initially:

simulate this circuit

But now, the circuit still works as following:
I'm not understanding how current flows from the power supply to power the motor when the circuit is not completed.

simulate this circuit

The circuit works in all of the following configurations:


texts:
I am currently trying to switch on a nichrome wire for about 5s using an Arduino and an external power source. It will be a single use only activation, I have decided to use an N-Channel mosfet for the job since space is limited.

The power source is a Li-ion battery and therefore I need to limit the power going to the nichrome wire to avoid burning it out. Based off some calculations I will need just about 100ma  at nominal battery voltage to reach my desired temperature.

Since my arduino will only deliver 3.3v I need to use a logic level mosfet such as the FDN361BN which has a VGS of 1 V to 3 V. I have attached a draft schematic to illustrate my intentions, however how can I limit the amperage?

Can I just lower the voltage of the gate using a voltage divider in such a way that I only allows a certain amount of current based on the datasheets graphs?

Also what is the purpose of the 10k resistor, is it to assure that the mosfet won't get switched on accidentally?


texts:
I've implemented above circuit and it was successful.
The given circuit needs 12VDC to run properly.

I want to run this circuit on 5-6VDC or 9VDC whichever is possible. I know I have to change resistors but not confirmed which to use.

Also if I use 9V battery only to activate 6V relay for 8hrs daily, for how many days will that battery work?


texts: PCB designing consideration of high speed (0.5 Hz) relay load switching

texts: Can this design cause any problems? I'm planning on switching 75W (220V) loads with this relays. I'm using 10 such relays and terminals (HB9500M). Note that it's highly unlikely all of the relays to be active at the same, even if they do, it won't last more than 2 seconds. I'm also planning on soldering wires with the PCB traces to improve current capabilities. PCB is using 1oz traces. As you can see, small red trace is controlling the relay, which is controlled by ULN2803. Can this switching induce unnecessary noises in the MCU? BTW all relay loads are resistive.


texts: How to know what files to #include in a Nios II application?

texts:
In the hello world application created by the Nios II Eclipse IDE, it put in the #include "sys/alt_stdio.h". I am not sure why it is not just stdio.h and where does sys/ come from.

In any case, as I add PIO and other peripherals to my design, how do I know what files to #include into my design?

For example, I added a PIO and then writing IORD(BTN_BASE,0); did not work. My trial and error I found that I have to #include "system.h". I am surprised that the IDE does not already do that. Then I still had error message saying that the function IORD is not recognzied. Then via internet search I found that I have to #include "io.h".

Where is all this detail documented?


texts: Understanding common collector amplfier for a piezoelectric microphone

texts:
I copied the circuit of a Throat Microphone that uses piezoelectric disk to detect vibrations. I'm trying to adapt to detect vibrations (i.e door knocks, etc) but the signal is weak when I record the audio using Audacity. I'm trying to understand the circuit to be able to adjust the gain according to the type of vibrations to be recorded. Using an oscilloscope, the weakest vibration measured around 100mV and the highest averaged around 600mV with peaks of 1V.

So far, I found that the amplifier is arranged as a Common Collector and \$ R_{1} \$ and \$ R_{2} \$ expecting around 1V (I found in a post that the microphone port supplies 1.5V-2.5V) and lowering \$ R_{3} \$ increases \$ I_{c} \$ and the gain. I'm not sure if I'm going on the right way and I would appreciate some hints.

The NPN transistor is 833-2SC1623-L6-TP.

$$ \begin{align} 470\Omega &= \frac{V_{cc} - 0.5 V_{cc}}{I_{c}} \\
&= \frac{0.5 \cdot V_{cc}}{0.001} = 940 mV \\
Gain &= \frac{R_c}{R_e} \\
&= \frac{470}{26} = 18 \\
&= \frac{470}{100+26} = 3.73 \\
V_{b} &= V_{e} + 0.6V \\
&= .032 + 0.6 = 0.63
\end{align}
 $$


texts: Linux on board without 3rd party modules. Where to start?

texts:
I would like to be able to design my own Linux board the way I design my own micro-controller boards. The complexity is obviously going to be higher from PCB design and assembly point of view, but I can manage that.

What I don't understand is the software part. What all does it take to get a get Linux running on a CPU. Are there some choices that make your life easy?. Such as choosing a processors where manufacturer provides XYZ software components.

Actually, to begin with I don't even wan't to be able to go full-custom with processor choice. I am happy to stick to one processor (or its variants) as long as I can put it on a custom board I design.


texts:
I am building a localization system for a robot. The robot works on two 12V DC motors and is connected to its own circuit and battery. I connected the motor encoders to a pic18f4520 microcontroller. Each time I start the motors the pic halts and stops working.
Things to take into consideration:

The motors and the PIC work on two different circuits and power sources, the only common things are the encoders but the same problem occurs even when they are completely removed (so the problem is not from the encoders)
Grounded everything (EVERYTHING including the reset pin)
Grounded the outer shell of the motors
Put one to three 10nF capacitors between the motor positive and negative pins
Wrapped the motors and PIC in aluminium foil
The microcontroller doesn't halt when the motors are fed with 3V or lower

What's even weirder is that even when nothing is attached to the microcontroller, as soon as we bring a DC motor close to it (closer than 40cm) it halts.
Any ideas how to fix this?


texts:
Updated based on feedback with better screenshots (I hope) - I am also working on getting the files onto a file sharing site so they can be accessed at full resolution

I am really confused about the attached LTSpice circuit behavior

The voltage source V2 is simply a 5V supply and Voltage source V1 is a square wave of 40us period (5 volts)

I run the simulation - with the 5V square wave I would expect the Q1_Collector voltage to drop to 0 within 500ns of Q2 collector voltage going to 5 volts however the Q2_Collector voltage does not drop to 0 for 3us and I am trying to understand why.

On the plot show below - I am plotting collector voltages at net Q2_Collector - in Green and voltages at Q1_Collector in purple - The cursors show how when the Q2_Collector voltage rises to 5Volts the Q1_Collector voltage does not switch off for almost 3us

I see from the data sheet that Q1 has a switch off time of 70ns and a storag time of 70~100ns. I created the circuit to model the switch off times and I noticed that the turn off times I observe in the simulation are of the order of microseconds (2-3) microseconds to be precise.

I also built a circuit to see if what I was observing was a simulation issue but the circuit showed a similar behavior - infact I saw switch off times of almost 6us.

My question - can someone please help me understand why I am seeing such a difference between what I would expect from the Datasheet? Obviously I am doing something wrong and just cannot get what.

I am working on posting links to the files if these are still not very clear.


texts: Arduino: Measuring Current, Voltage + using the 5V and GND pins

texts:
I am new to the Arduino world and I don't wanna destory my brand-new Arduino, so I am asking here first. Basically what I am doing for a school project is creating a circuit that will measure current and voltage of a solar panel while increasing the resistance of the circuit.
I am using a ACS715 for measuring current and a MCP4142 as an digital resistor. I am also using a basic voltage divider for measuring voltage.
Maybe my bad designed paint scheme would help:

Will that work like I painted it here or will I have a short circuit and destory my Arduino? My problem is that I put P0W also on ground by using my voltage divider (the whole line from the 30k resistor to P0W is basically grounded by that). So I think there's a problem if Vss and P0W of the MCP4142 are both on the same ground, or am I wrong?

It might sound dumb, but I am just a dumb student, so please bear with me :D

Edit:

To be more clear about what I want to achieve. I want to increase the overall resistance of my circuit and measure the voltage/current that my solar panel has using that resistance to create like R-U-diagramms.


texts: Measuring Current Consumption of USB Devices

texts:
I was trying to measure the current draw of a USB-powered device (a Raspberry Pi) to determine the suitability of powering from an external battery pack.  So I took a USB cable, split the +5v (red) line, placed a DMM on the line, plugged it in, and got.... nothing.  The pi wouldn't boot.  Replacing the DMM with a jumper worked fine, so the cable was good and I didn't screw it up with splitting the +5v line.  Is it possible the internal resistance of the multimeter caused too much voltage drop on the line for the Pi to boot?  What's the right way to do this?

To clear up other possibilities:

The meter works fine on other applications.
I double checked the setting of the meter, set to mA.


texts:
I am trying to measure a signal with a voltage amplitude between 10-100 microvolts and a frequency between 7-30Hz. The guide I am following suggests filtering out 60Hz noise using a notch filter, as well as additional LPF and HPF to focus only on this range (5 and 40 Hz), then one more notch filter at 60Hz.

Of course noise will need to be filtered out in order to see such a small signal. My  concern is, with today's computing prowess, what's the benefit of doing this through hardware? Couldn't I design a circuit to scale the voltage between two values (say -1 and 1V), such that it can be easily and safely read by a second device, then do the filtering on this second device?

As strange as it sounds, the problem I am trying to solve has bountiful resources for software, but limited ones for hardware.  Imagine an audio recorder sending data to a computer. You want the audio recorder to have a battery that lasts as long as possible, and would like to minimize the power-intensive circuit components involved in filtering. Is it a bad idea to do the filtering on the computer since it's plugged in to a wall outlet & is made to handle much larger computational tasks? I'm not trying to put electrical engineers out of a job; I have a real world use case for this scenario!

In short, is a purely software filtering approach valid for a signal like this? What about other signals? In general, with regard to modern technology, why do we ever filter using hardware?


texts: How to create device variant with different pin count in Eagle?

texts:
I have a part that has 2 variants SOT-23-3 and SOT-23-5. Both have different schematics as one has 3 pins and other 5 pins. Package is also different due to difference in pin count.

The problem is that I can't create a device variant as the pin count is different. I also tried simply creating a second device but then I end up with invalid part name as device names have to be unique and variant name is appended to the device name.

What is the proper way of creating such a part?

Here is a datasheet for the part: https://www.diodes.com/assets/Datasheets/AP2210.pdf


texts: Difference between 1N914 and 1N4148 diodes

texts: I always thought that the 1N4148 was an improved replacement for the obsolete 1N914, but I see that the 1N914 is still produced, and overmore, looking at the parameters for both on digikey they seem to be identical. What was the reason to create the 1N4148 if it's identical to the existing 1N914?


texts:
I'm doing an application using RTC on STM32F091.
I'm using a small rechargable Li-Ion battery (such as MS920SE-FL27E) as the Vbat power source for the RTC.

My concern is, how can I protect the battery from deep discharge?

Battery is small (due to physical restrictions), thus changing it after one 'season' (3-6 months of OFF time) is not a very good option.
hoping to reuse the battery more by cutting off the battery usage when V level is getting dangerously low.

I'm aware I can measure the Vbat voltage level to know when the battery is getting too low. What would be a good way to cut power from the Vbat entirely (and thus 'kill' the system completely) in RTC mode?

My one idea was to abuse the RTC_ALARM output. Set it high (during normal application) to keep a transistor open in-line with VBAT (ALARM should keep the state when VDD cycles on/off...). If VBAT is measured too low, the ALARM would be LOW and killing the connection to VBAT. Haven't been able to think of any other idea though :/.

EDIT 22.06
From 1st Answer I made a PMOS equivalent circuit. Current consumption for such circuits seems to be an issue for me. RTC usually consumes <3uA.

EDIT 28.06
Took some time to look for appropriate MOSFET and I believe I have found it.
NX1029X (using the P-channel one). I set the gate voltage so that the MOSFET should turn itself off around 2.3V-2.4V of RTC Battery voltage. Seems to work.
Only issue is, can I reliably use MOSFET's Vgs, to make the cutoff? Have used it before though but on higher voltages (was easier to set the gate-source voltage).

I'd go for this:
RED (Chl A), BLUE (Chl B), GREEN (Ch C)
(capacitor is for avoiding convergence issues)

ON current is ~470nA extra, so 3.47uA. OFF consumption is ~20nA (around the transition 0.5uA or so). I think I can live with that :P.


texts: Electronitc switch without common contact

texts:
As I understand it, a transistor can be schematically described as a variable resistor controlled by a tension (when it is correctly biased). That is, the resistance between emitter and collector is regulated by the difference of potential between base and emitter. However, the "regulating circuit" and the "controlled circuit" must share a contact (the collector).

Is there a component or a simple circuit with four contacts that implements something similar to a transistor, but without requiring that the two circuits share a contact? So I would like to have something such that the potential difference between contacts A and B controls the resistance between C and D, without requiring that (for instance) A and C have the same potential.

One could probably do something like that with a relay or by optically coupling a LED with a phototransistor; however, I wonder whether this can be done in a purely electronic way.

[I ultimately need this component for coupling two circuits that may have different grounds; probably they actually do not, but I would like to avoid relying on that; and I am also interested in the abstract question]


texts:
I've been working on a project where i'm building a h bridge motor circuit i have easily spent 15 hours on it and have made extremely slow  progress on it in the last 3 days. The project sheet is seen below and i'm still on task 1 heavily struggling on the dc sweep of the inductor.
[
I will attach the circuit i have made on lt spice below

Every time i do a dc sweep these are the errors ( attach below) i keep getting i have no idea how to fix them i have no idea if it is something to do with my circuit.


texts:
I'm designing a board which contains an LTE module on it. I am a little confused about designing the trace between module and antenna.

As far as I know I need to match these:

Impedance of module's antenna output
Characteristic impedance of the transmission line
Impedance of antenna

Impedance of module and antenna are noted as 50 ohms in their documents. In that case I need to design a transmission line which has characteristic impedance of 50 ohms.

I am planning to use coplanar waveguide with bottom ground layer as transmission line. (2 layers board, 1.6mm board height) I tried a couple of online calculators and Appcad to calculate values for trace width and spacing to get 50 ohms impedance. I couldn't find any suitable values for my design because of pad widths of other components and restrictions of manufacturing process.

Is there any way to match this characteristic impedance with external components, like pi matching network? Or is it just related to trace width and spacing (also dielectric thickness copper thickness etc)

I tried to make an adaptable design. I added a pi network to match transmission line impedance (?). I added a high pass filter which is recommended by module manufacturer. I also added an extra uFL connector to connect VNA. Is it a good way to do like that?


texts:
Is there a way to disconnect or bypass a low voltage shutdown operation? I have a factory made electronic shooting gallery (toy) that runs on 4 AA batteries. I want to run it to a steady 6VDC supply from a power converter that plugs into 110VAC so there is no more replacing the batteries. The target (receiver) has an on/off switch on the rear. If it is turned on, you can shoot the target all you want as long as it is consistent.

But if you leave the target ON and idle (don't shoot it) for more than a couple of minutes, it turns off. Turn the switch off and then on again and it works/receives the shots again. I have tried this with batteries and a steady 6VDC power supply and it continues to go off after non-use for a couple of minutes. I want it to stay on all the time, unless I flip the switch to the off position.

Could it be something different since it still has the same problem with a steady, unwavering power supply? Is there a way to bypass whatever is causing this?


texts: Without buying an expensive calibration tool, how can I accurately calibrate my multimeters?


texts: Measuring current using low side shunt method (MCLV-2 board)

texts:
I am trying to measure the current through the MOSFET switch M1 using low side shunt resistor method (on MCLV-2 dev. board).  I can read the signal `Vout' on the analog input of a dsPIC33F MCU. I believe that the capacitors are there to filter high frequency switching noise and clean up the measurement. Converting the ADC reading from MCU to a meaningful current reading in amperes requires solving this circuit. So I used a simplified circuit to apply the circuit theory to solve for the voltages. I arrived at the simplified circuit using the fact that in steady state the capacitor will behave as an open circuit. I came up with the following equations:

Vn = Vp                       (negative feedback)
(V1 - Vn)/2K = (Vn - V3)/30K   (KCL at node Vn with shown current direction)
(Vref - Vp)/30K + (V2 - Vp)/2K = 0      (KCL at node Vp with shown current direction)

My questions are: (1) Is the simplified circuit correct? (2) Are these equations correct? (3) Do I need knowledge of V1' andV2' for solving this circuit? Any other help regarding this will also be greatly appreciated!
The schematics of the original and simplified circuit are shown below.

simulate this circuit – Schematic created using CircuitLab

simulate this circuit


texts: Why ngspice doesn't accept UIC for TRAN?

texts:
I'm using ngspice and trying to add UIC at the end of the TRAN statement, but I get an error:

$ ngspice 1 -> tran 10m 5 UIC
Warning:  Error: unknown parameter on .tran - ignored

Why does this happen and how can I make it work?

ngspice compiled from ngspice revision 20

Thank you.


texts: What do you use to connect simple battery holders?

texts:
I'm sorry for this very rudimentary question, I'm completely new to this hobby.

I need to have a ~30V power source and I want to buy 22 AA batteries and connect them in a series. I intend to use several of this holders:  http://www.ebay.com/itm/4-x-AA-2A-Battery-Holder-Box-6V-Case-W-lead-ON-OFF-Switch-Enclosed-Box-Snap-On-/130685755489?pt=AU_Electronics_Batteries_Chargers&hash=item1e6d7a6061

but the problem is I have no idea what to use to make them join together, I don't think glue would work. I suppose I could make a cut in the middle of the wires and solder a wire from one casing to another, however I would rather want something more comfortable.

So how do you guys connect your circuits?
Like I said I'm a total noob, and if I'm posting in the wrong forum (it seems to me like a more professional environment) I apologize in advance.

Also, if you have any suggestion of how I can achieve my goal in an easier or cheaper manner I would appreciate any suggestion.

Thank you.


texts: Project help, need a way to allow voltage flow only if certain limit

texts:
Not sure exactly how to word this but I'll give it a shot. In my project a detector will output anything from 16uV to 750mV. To succusfully trigger a Time-to-Digital converter the voltage around the minimum of 16uV will not suffice to it needs to be amplified. I have an amplifier and comparator circuit that will achieve this, however I do not need/want it to amplify when the voltage is above 100mV. Is there anyway to set it so anything lower than 100mV will go to the amplifier and anything 100mV and above will go straight to the detector. It also needs to be in an analog way.
Basically:
If input<100mV go to amplifier then to detector
If input>100mV go to detector
If clarification is needed I'll be happy to try
Thanks!


texts: Question for using 8051(AT89S52) and CD4094BE

texts:
I want to use  AT89S52 connecting with CD4094BE  to control  8 LED  light bulbs.                                                 The program lanuage is ASM.
                                                                                My aim is  the led lights up are as follow   :     1011 0011    ,1=off,  0= light up

The program are as follow :

       ORG 0000H

       AJMP MAIN

       MAIN:

       SETB P1.4      ;STR

       MOV A, #10110011           ;put the data into acc

       MOV P1.3 , A

       RRC A

       SETB P1.2                  ;CLK

       CLR P1.2                   ;CLK

       AJMP MAIN

what's wrong with my program/the schematic diagram  and how to correct it ?  Thank you.


texts: Orientation of Polarized Capacitor in a High Pass Filter

texts: Recently I have decided to learn Arduino and circuits during my summer break. I have been doing different projects with a book I bought. One of the projects inside has a High Pass Filter. I understand the function of it but I am very confused as to the polarity of the capacitor. I am confused as to why the negative side is facing Vin when usually, for example LEDs and other diodes, the positive terminal would be facing the input. Granted, the input voltage in this case is supplied by a pin set to output as pulse width modulation with square waves. Essentially, why is the polarity going from left to right (negative to positive) when the voltage going in would, from my understanding create a drop of from left to right(positive to negative)? Thank you.


texts: A circuit to find 3D position of an object using changes in magnetic fields

texts:
There is a project at

http://www.instructables.com/id/DIY-3D-Controller/

to make a DIY 3D controller with capacitors to infer the 3D position of the object being tracked (hand) without using any wiring to hand. My question is it possible to build a 3D sensor that uses changes in magnetic files and inductors (instead of the capacitors) to also build a hands free 3D tracker?-probably the hand would need a metal object possibly a finger ring to create a change in the three or more magnetic fields.
So, if possible, whats the circuit for the 3D sensor using changes in magnetic fields instead? Also is there a simple circuit to do it like known capacitor circuit mentioned above?
As a guess it could probably be done with two magnetic fields if it works something like 2d vision tracking where two 2d pictures (in suitable planes and orientations) can be used to determine the 3d position of the object.


texts: dimmer on input of stepdown transformer for amp regulation?

texts: If have a step-down transformer designed for low voltage high amps, and I put a dimmer on the input will that allow me to lower the output amps? I don't care about voltage as it will be negligible, I'm combining two coils in series 110v each stepped down from 100 coils to 2 coils. I'm anticipating over 300 amps, and I want to be able to easily adjust the amps.


texts: Can an open circuit have negative voltage potential? We are performing an accelerated thermal cycling test for PCBs and the "zero time" voltage of components usually read at 1 V. A failed part, that's, a part with open will have more voltage than the "zero time" reading. However, in one of the cases the voltage potential has negative value and this is the reason for confusion. Note: it is connected to a ground terminal and not a battery. Thanks!


texts: Use of different diodes in a bridge rectifier

texts:
I'm repairing the circuit for a motion-activated LED light. The PCB uses a capacitive dropper circuit as the power supply. Photos of the PCB and the corresponding reverse-engineered power schematic are shown below.

In this case, the two glass diodes in the bridge rectifier have failed short (D4, D5). Before I replace them, I'm wondering what's the significance of using two different diodes for the bridge rectifier? I would have thought that for such a simple circuit, any efficiencies saved by a potentially lower diode forward voltage drop wouldn't be worth it.
Edit Here's a closeup of the glass diode markings. The band appears to be green, which, according to some of the links posted in the comments, would imply a Schottky diode. Update after finding some more information online regarding this specific circuit, I can confirm that the glass diodes are indeed zeners.

Update I'm happy to report that after replacing the two glass diodes with 24V 500mW MINIMELF diodes, as well as transistor T2 (BC81-40), the light now works fine.


texts:
I had an homework to do for school. One of the questions of this homework was to find the equivalent of a circuit using Thevenin's theorem. Unfortunately, my teacher told me that I didn't get the right answer for this question. I asked him what I did wrong but he didn't really looked at what I did and said that this isn't the right answer. I would like to know what I did wrong. Here is the circuit and how I tried to find its equivalent circuit using Thevenin's theorem :

Thank you!


texts:
I am designing a battery run device and would like to check with you if my calculations are correct. To make it simple, the battery will be used to charge repeatedly a capacitor:

Capacitor: 40uF @ 300V

Repetition rate: 1Hz

My calculations are:

To charge the cap to 300V, I will need 40uF x 300V = 12m Coulomb.
To charge the cap repeatedly at 1Hz for 1 hour, I will need 12mC x 3600/h = 43.2C/h.
A 1000mAh battery is a 3600 Coulomb energy source.
Using this battery I will be able to run the device for 3600C/43.28C/h = 83.3 hours?

Thank you


texts:
I am looking for a small simple switch. But it has certain restrictions because I want to use it for salt water aquarium and copper exposure is lethal to some fauna, as well as some plastics.

Looking around the internet i found floating switches, optical switches, rod inducting switches, a few diy projects switches i.e. a Sonar switch- very promising just with salt.. well salt accumulates in every place possible under the hood.

I might go with the sonar and a small arduino or attiny...

but I am wondering if it is possible to use a single wire to detect resistance change? or something clever like that. I only want to detect if the aquarium is about to overflow and shutdown pumps in case off emergency- so minimum copper exposure wont kill anything but flooding my wooden floor.. well the wife will kill me..

My aquarium (and most other Marine hobbyists will have these spec ranges)(only advanced people will go over or under these for other specific reasons)

Temp 22~26 Celsius (ME: 24oC)
Salinity 1.022 ~ 1.026 (ME: 1.026) (Specific Gravity)

But I would like to assume this works on Clean water too( as in Reverse Osmosis with no minerals or salt) The distance would be max 1 cm apart- no need to measure the entire tank.


texts: line-level audio into an iPhone headset jack?

texts: What level and/or impedance matching (or pre-amp) circuits should be used to send a line-level audio signal into the mic input ring of an iPhone headset jack with minimal distortion and/or loss?


texts: why it is hard to generate an impulse train ?

texts: I have understood the concept of Ideal impulse sampling ,but i have struck upon the fact that practically generation of impulse train is not possible.


texts:
I just bought a LIDAR with the intention of building an indoors robot that uses it to navigate rooms in my apartment.

The manufacturer website states:

  Low power infrared transmitter conforms to the Class 1 laser safety
  standard and reaches the human eye safety level.

So, I went to the FDA site about laser classes to inform myself about it (https://www.fda.gov/radiation-emitting-products/home-business-and-entertainment-products/laser-products-and-instruments), and in fact they say Class I is considered non-hazardous (with hazard increasing if viewed with any optical aid such as a magnifier).

It seems this is a Chinese product, I don't know if the FDA is actually regulating this product, or the manufacturer is including this just as a reference.

I'm concerned about the safety of pets and people in the household, so I thought it could be a good idea not to trust this Class I rating at face value, but to double-check the emission intensity with some equipment.

Can this measuring be done and if so with what equipment? Does it make sense to do it?

(I tried posting this question in the robotics site, no answer after a week there, so I'm trying here as well).

Thanks!


texts:
I have put together a 4-axis robot operated by brushed DC motors for a haptic feedback system. Unfortunately I am not well versed in robotic control systems so would really appreciate any advice you guys could offer.

My issue is that robot is meant to operate with positional control at sub <1mm accuracy (this is considerably larger than quantisation error of my encoders ~0.1mm) and I do not know how to sync the robot axes together - some of the 4 axis controllers cost upwards of £1000 so are completely unrealistic. So my current plan is to use two Roboclaw 2x15A  controllers to operate 2 axes each. Then control both of these off of an arduino or something similar.

Will a cheap microcontroller, like an arduino, be able to operate at a high enough frequency to control the two drivers quickly enough for accurate positional control? Also if anyone could guide me to some literature on where to understand the theory behind controlling motor axes quasi-simulataneously that would be greatly appreciated - google has only provided vague solutions.

Thanks for your help in advance


texts:
Suppose I have a system with feedback. Consider the input \$d\$ that represents disturbances to the plant; also, consider the input \$V\$ that represents sensor noise on the feedback loop. I can calculate the closed-loop transfer function \$\dfrac{Y(s)}{d(s)}\$ and \$\dfrac{Y(s)}{V(s)}\$. Then, my question is: does it even make sense to talk about the transfer function \$\dfrac{D(s)}{V(s)}\$, if so, could it be calculated as \$\dfrac{d(s)}{V(s)}=\dfrac{d(s)}{Y(s)}\dfrac{Y(s)}{V(s)}\$?
Thanks!


texts: Can this circuit be called a 12v,5A zener regulator?

texts: If this circuit can be called a 12v,5A zener regulator, then I know that 12v here is the varying input voltage. What is the 5A current here,I mean where can it be represented in the picture?


texts: How to write a voltage in phasor form (using a reference-voltage)

texts:
I have the following problem:
Consider two voltages described by

v1 = 325 sin(wt+10º) V
v2 = 326 sin(wt+130º) V

Write v2 in Phasor Form using v1 as reference...
My Question is:
I understand that the angle will be 120º, but what will the voltage be?
Below is a drawing of how I am imagining it to be from a trigonometric point of view, but maybe this is the wrong way to look at the problem?


texts: How does this Digital-to-Analog converter work?

texts:
This question:

  RoboCup Junior IR Ball detection

has a link that includes the attached circuit for D-A conversion.

I understand that the output of the sensor contains several amplitudes, and that the "summation" of the signals is being stored as a charge in the capacitor.  Is this correct?  Why is the function of the resistor?  Is it the low pass filter, and if so what does that do?


texts:
I have one bridge rectifier operating at the constant junction temperature of ~72°C, (GBPC3510W datasheet), which is rising to ~80°C in some specific cases.

I'm trying to find a kind of "aging curve" which shows the lifetime of the bridge rectifier in function of the junction temperature.
Since there's no such thing specified in the datasheet, I thought it would have been easy to find a "general curve" for PN junctions on the internet. It seems to be a common thing to specify in LEDs but unfortunately the only thing I could find related to "normal" diodes is the 10°C rule of thumb explained here. This rule requires you to know the lifetime of the component, and is not useful in my case.

So my questions is:
does a general curve which specifies aging in function of junction temperature exists? Is its existence feasible, or there are too many variables involved not allowing to define it?
And why is not common to include such information in the datasheet?


texts: How exactly do clock speeds of computers relate to operation speeds?

texts:
I was wondering about this the other day when I was explaining binary and hexadecimal to a friend of mine and this came up.  The question goes something like this:

How exactly do instruction execution speeds relate to clock speeds in modern computers?

For instance, say a clock signal of 1 MHz is used by a computer processor.  The processor will execute operations on the edge of that clock (on the negative edge if I'm not mistaken), but this doesn't mean that a full instruction will be executed for each clock cycle.

To have a more specific example, if an Intel x86 processor has a MOV BX, 45 command, I am assuming that it will take several clock cycles to complete this since the number 45 has to be generated, and the BX register has to be located and so on.  Maybe this one might be a single clock cycle since it is an immediate value being moved into a register, but hopefully this kind of explains my question.  Maybe a JNE command would be a better example.

On top of this, there is the fetch-decode-execute cycle which would reduce the instructions-per-clock ratio to less than 1:1, is that correct?  Please forgive me if I totally misunderstand how this stuff works.  I am very interested in it and know that lots of you know quite a bit about it.  Please feel free to shed some light on my ignorance :D

Thank you so much

Chris


texts: Material Suitable for Self-insulating Solders and Electrical Contacts?

texts:
I have been working on this personal project of water-proofing an electronic alarm clock, when I came across the idea of making electrical contacts non-conductive when produced. Specifically I have been thinking about the unique properties of passivation of aluminium. When exposed to air, solid aluminium reacts with oxygen to produce a thin layer of non-conductive (and quite inert) aluminium oxide on its surface.

So I thought it would be logical that if all exposing contact pins on electronic components are made from aluminium (or other metal/alloy that exhibits passivation), and all components are soldered to a PCB using aluminium, passivation will occur over all exposed metal surfaces of the PCB, so it would be intrinsically water-proof without additional treatment such as lamination (assuming the electronic components themselves are well insulated)(assuming no need for fingers or external connectors).

So my question is whether this is a practical thought, and if so why hasn't it seen much/any application?


texts: Illuminating the wall of a transparent tube

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I have a plastic tube that has a wall thickness of around 3 to 4 mm and it is transparent. I am trying to build a ring for the top of the cylinder that just illuminates the sides of the tube, but nothing inside of the tube.

For more context, I am trying to light up the sides of the tube as shown below. I don't want the rat inside to be illuminated by the light as much as the sides of the tube will be illuminated.

I'm thinking of using LED light pins, but I am unsure of whether that will just illuminate the side of the tube or the whole thing. Any help?


texts: SSR selection - how is on resistance related to output IV curve?

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I am looking at the datasheet at the link below, and I can't for the life of me figure out what I am missing.
http://www.digikey.ca/product-detail/en/TLP3542(F)/TLP3542F-ND/871299

This is a Toshiba SSR whose on resistance is 100mΩ maximum. There is an on-state I-V curve that shows a current of 0.5A at 25V, implying an on resistance of 50Ω! The problem is, I'm looking for at least 2mA output at 12VDC, and based on that IV plot, I won't be getting it.

I am clearly misunderstanding something here. Please help!


texts: Is a 5V DC Voltage @ 30mA applied, applied to water, unsafe?

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As my question states, I have 5V DC, with an input current of 30mA, being applied across two exposed metal electrodes which are inserted into water.  I am trying to measure the conductivity of water for a scientific experiment.

Would there be any concerns about the safety of this system, in case someone touches the water?


texts: How to properly place AC current transducer sensor in the circuit

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Hello i am going to setup current sensor like this  (datasheet)   in my home, and would like to know where is it proper to put these sensors in the circuit.

Consider the two setup below:

rent sensor

So here are my questions. Consder label X,Y,1,2,3,1B,2B,3B as AC current transducer. and the resistor are just placeholders for AC load e.g. lights, aircons,small pumps,computers,tv's, and other home appliances.

In setup A, Is it okay to put the sensor either in the live or neutral part of the circuit? So sensor X and Y should read the same value. The same goes for 1 and 1B,2 and 2B, 3 and 3B
Now setup A would waste a lot of wires if the three devices are close to each other but the distance back to neutral is far. So in setup B i joined the neutral while they were still close to each other and run only 1 wire back to Neutral line. thus saving some wire. Is this setup still okay? X and Y would still read equal, and 1,2,3 should read the current of the individual loads.

If you can provide a much more efficient setup i am all eyes.


texts: Cortex M4 memory management suggestions: best data/code placement

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I'm trying to implement a rather complex (at least for me!) system on a Cortex M4 mcu: LPC4370. This one has HighSpeed ADC (up to 80Msps), DMA and DSP (Single Instruction Multiple Data) instructions.
Here's what I want to do:

Let the ADC sample in a continuous manner (at least at 10 Msps)
Move the data to SRAM
Process them in real-time w/ cortex M4 DSP (pulse shaping filtering)

MCU clock is 204 MHz and for now let's assume ADC fs is not a design spec, but ideally I would like it to be as high as it can. So I need the code to be as fast as I can.
Here's the MCU memory set up.

And here the AHB MULTILAYER MATRIX

As of now I am considering more the general firmware architecture, and specifically memory management.
Some considerations:

I don't want core M4 and DMA to fight for memory: I need the DMA to be able to write data while the M4 is doing the processing
most of the code and all acquired data should be in SRAM for faster execution
Instruction fetch should not interfere with data storing (DMA) and processing (M4)

In the LPC4370 user guide (chap.2):

To optimize the CPU performance, the ARM Cortex-M4 has three buses for Instruction
(code) (I) access, Data (D) access, and System (S) access. The I- and D-bus access
memory space is located below 0x2000 0000, the S-bus accesses the memory space
staring from 0x2000 0000. When instructions and data are kept in separate memories,
then code and data accesses can be done in parallel in one cycle. When code and data
are kept in the same memory, then instructions that load or store data may take two
cycles.

My idea at the moment is to hold the sampled data in two different buffers placed in two different memory areas (like LocRam128 and LocRam72) and "ping pong" DMA and M4 between these two areas.
Only problem is that these are the two areas used for instruction (I). So I guest code should be placed here also, and this is not good to me.
I wonder how could I use RAMAHB32 effectively since it is only connected to M4 system bus (S) and not to data (D) nor instructions (I).
Any hints?


texts: Design a filter that allows frequencies below 5 kHz to pass freely, but all frequencies above 5.2 kHz must be undetectable

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My biggest challenge with this question is its ridiculously steep roll-off rate.

I am assuming that the signal is undetectable if its gain is -20 dB. This means that, within the transition band of 200 Hz, the signal strength needs to drop by 20 dB.

If my calculations are correct, this filter requires a roll-off rate of 1200 dB/dec. That requires 60 poles, which is obviously not feasible.

I would like to use an analog active filter with minimal ripple in the pass band. A large phase shift is not too important.

One potential solution is to use a notch filter at 5.2 kHz. However, frequencies above the bandwidth of the notch filter are still not sufficiently filtered.

Please point out any flaws in my logic and or propose potential solutions. Thank you.


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When the delivery man dropped my capacitors off earlier yesterday he did not ring the doorbell and I had no idea they had arrived on my front step. Then an intense rainstorm showed up and soaked the whole lot of my eight 1500uF, 450V caps. They have a tight plastic coating, and did not seem to consume hardly any water as they dried quick.

Are they okay to use?? How would you recommend to safely test one at a time to see how well they're working?

Maybe it would be best to do a typical charge-up with a rectified variac power source, voltmeter, and discharge into a bleed resistor and ground. I really don't need any extra possible dangers with the high current power supply I'm building, and want to be careful.