texts:
Hi I was building a Voltage divider for supplying a fixed voltage to a load, now if the device is  a motor, which practically has some resistance, then is it true that the voltage it gets will be dependent on its own voltage?
And if i have a relay which requires 12V to run, then building a 12V supply through a divider fine? or do i need to consider the resistance of the realy, to actually get the right voltage it will get?


texts:
I have CNY70 connected this way:
And I need to determine the value of R2 for OUT to be from 0V to 3.3V.
I don't know how to calculate it, please help.
EDIT:  Input is the 5V and output goes to microcontroller similar to Arduino, but its inputs can't take Voltage higher than 3.3V. So I need to get the output to 0V - 3.3V. I am sorry for being misleading.
EDIT 2: It goes into one of the microcontroller's analog inputs. Not the power supply.
Thank You!


texts: energy stored in circuit under steady circuit

texts:
Hello there i want to solve this problem

I solved above problem this way.
In steady state condition, capacitor should be replaced by open circuit.
so 2 ohm, 4 ohm and 2 ohm these three resistors are in series. so total resistor is 8 ohm. and resistor only dissipate energy. so energy stored in this circuit should be zero.

but correct answer is 288 uJ.
can anyone tell me??
why i am wrong??


texts: LC Filter for a Full Wave Bridge Rectifier?

texts:
According to what I've read on a few websites and PDFs (http://www.irjes.com/Papers/vol2-issue6/Version-1/E02064249.pdf is an example) using an inductor-capacitor filter to assist AC to DC rectification in ripple management is much better than using either component by themselves. (In the example PDF capacitor was sized down by 75% & inductor was sized down by 94%)

How can I size the inductor and capacitor such that I can get a certain voltage ripple after being rectified by a full wave bridge rectifier? (Even in the paper they recommended a trial and error method, essentially guessing 25% for the capacitor and manually finding the inductance for the inductor)

I haven't taken differential equations yet, but I'm past Calculus III if you prefer to answer in a non algebraic way. (Although algebra is preferred)

I'm running 1kW (split phase, plans on moving to 3-phase) through this bridge (full wave) for high power electrochemistry: $$972W = 18V * 54A$$


texts: Will adding a DC-DC converter affect how a modern car operates?

texts: I'm thinking of adding a wireless charger to my car, and adding a Buck Converter to step down the 12V source to 5V for efficiency sake. However, I am worried about the emissions from the DC-DC converter effecting the vehicle. Is this something I should be concerned about? If so, what's an easy method to reducing the EMI emmisions from the Buck Converter?


texts: Complex impedances of capacitors/inductors in the phasor domain

texts:
I'm trying to verify the complex impedances of passive components in the phasor domain (not s-domain). Take for example the inductor, whose element law is \$ v = L \frac{di}{dt} \$. Assuming a complex exponential current drive where \$ i = I e^{j \omega t}\$ (where \$I\$ is a phasor) then we get: \$ v = L I (j \omega)e^{j \omega t} \$. From this we see that the voltage will also be a complex exponential with a phasor \$ V = (j \omega) L I \$, and so the complex impedance is \$ j \omega L \$ as expected. This works fine.
I'm trying to do the same thing assuming a complex exponential voltage instead of assuming a complex exponential current, which means I need to do an integral instead: \$ i(t) = \frac{1}{L} \int_{0}^{t} v(\tau)d \tau + i(0)\$. Plugging in \$ v(t)=Ve^{j \omega t} \$ and evaluating the integral, I get: \$ i(t) = \frac{V}{j \omega L} e^{j \omega t} + (i(0) - \frac{V}{j \omega L})\$. If it weren't for the term in parentheses then this would be the expected result. If I assume that \$ i(0) = \frac{V}{j \omega L} \$ then it works out. Is this calculation and assumption about the initial current correct, and if so is it just a mathematical requirement without a conceptual reason? Have I made an error somewhere?
Side comments: my understanding is that typically in the time domain capacitors and inductors need to have zero initial condition or else they are technically not linear components (for example, a zero input can give you a nonzero output, which linear systems by definition can't do; and yes, I know that you could model the initial condition as a separate dependent source). Here it looks like you need to assume the initial condition to be a certain nonzero value in order for the component to be linear in the phasor domain.
It's interesting that in the s-domain, you assume that the initial state is zero in order to get linear s-domain components (or alternatively you model the initial condition as a separate independent source). See here for reference.


texts:
[Original question: CCD output buffer;  seemed best to make the transistor part a separate post]

Taken from Wikipedia, the circuit in Fig. 1 acts as a common collector (high input impedance - low output impedance, voltage buffer).

Fig. 1:

In my application, the devices' datasheet (a CCD chip) suggests buffering the output, like in Fig. 2. That is the same as the "classic" CC above, with the notable exception of the 130 Ohm resistor. What is it used for?
The one thing I can think of is to help with biasing, but how will that affect the equations given in Wikipedia?

Bonus question: How much non-linearity can be expected from a CC, roughly speaking? Let's say the CCD's Vout (before the CC buffer) ranges from 0 - 12V.

Fig. 2:


texts: How to increase max input current of logarithmic amplifier 10x-100x safely?

texts:
Is it possible to increase max allowed current of logarithmic amplifier to say 1A by some workaround without loosing capabilities in lower range: 0..1ma ? For example the TI part LOG112 has few milliampere input current limit.

Obviously, 2 parts can be wired in parallel and ouputs can be summed to nearly double upper limit. But it is not economical for 100x goal.

Other thought is to add diodes in parallel, but then the measurement performance/drift will be completely lost even for pA range.

Autoranging with relays can not help, because current can change fast.

Putting an RC, or just a capacitor across inputs will cause the constant leak, it will even allow to employ a relay. But the pA range will be lost.

The dynamic range is pA to 0.1..0.5A, with accuracy in low range.

Answer suggested in accepted variant below TLDR:
Use unprotected fine sensor in series with crude scaled and protected one. Short fine  sensor inputs with use of autoranger. Do the rest of ranging and math in software.


texts: House 240 backup power to junction box from 120 inverter?

texts:
Main power outage happens frequently at my cabin in the woods.
I want to power LOW WATTAGE to both legs of the panel from a single 1500W inverter.  NO 240 will be attempted, but does anyone see a problem with temporary substitution of input to both legs at the same time?


texts: I'm working on building my own Cloverleaf antennas, to work at 1.2 GHz, for the video system on my Quadcopter. At this frequency, what kind of tolerance am I looking at in terms of the length of the wire and the various geometric angles before I lose the advantage of this type of antenna? The calculator I used to find the length spit out a number in millimeters with, like, 8 decimal points after it, but after converting to inches, using a tape measure to measure it out, and trying to do the whole shebang in my dorm room bathroom (no hate on this please, it's fireproof I swear!), I only have about 1/8" - 1/16" accuracy. Is this enough?


texts: Advice on wiring power supply to digital temperature controller

texts:
I'm trying to wire a power supply to a digital temperature controller. I know squat about electrics, but am following this guide - I bought the same components he used to keep it simple, but it seems that the wiring on the temperature controller is different to his so was hoping I could double check that I was going to wire it correctly before proceeding!

This is how I currently plan on wiring it:


texts: FPGA based VGA controller to drive PC monitor

texts: I have implemented a VGA controller in FPGA, for 800x600 resolution @60Hz. Can I use it to drive a PC monitor ? In the PC's monitor resolution settings, it's seen that it supports multiple resolution at different frame rates, including 800x600. The maximum is 1024x768. Its an LCD monitor. Will the PC's monitor automatically "figure out" the intended resolution and frame rate from the Hsync and Vsync signal of my VGA controller, and display it in full screen?


texts:
Recently I bought an LG External DVD Writer that is TV compatible. But after a couple of times it stopped working on my Sony LED TV. It would start spinning, but stop after two seconds. This would go on and on.

I assumed that it wasn't receiving enough power from the TV USB port (the DVD writer was rated to 1.6A). So I made a simple USB Y-connector where I took two male USB plugs and one female. Connected the red and black of the female to one of the male USB and the green and yellow alone to the second male USB plug.

I connected the data Male USB to my PC and plugged in the power male USB to a USB power adapter rated to 2.1A. Finally I plugged in a USB thumb drive to the female USB plug to test it out.

But there doesn't seem to be any activity.

Is there something wrong with the wiring itself or simply because there is an improper connection made.


texts: Material that Degrade GPS Signal Reception

texts:
Between clear tempered glass (see through,thick & very strong) Vs. coloured plastic material, which would result in more degradation of GPS signals if used to make a box? The box contains a positioning module and a GSM module with an antenna.

The thickness of the plastic i'm thinking is about 5mm. But of course, its just a rough figure.

If I am to involve tempered glass, my intention is to use the same only on top of the area of the antenna, may be for the botton top half of the box.

Is there other known fairly strong material (may be even rubber) that will do a better job?

This is only a prototype design.

Your responses will be so much helpful and appreciated.


texts: How is this motor on a Romotive controlled?

texts:
I have bought a Romo Robot by Romotive. Unfortunately I'm having some technical issues(it does not work, at all) with it so I decided to explore the PCB a bit and see what its made of.

I understand most of the PCB and tracked down the pinouts for most of the Atmel Chip but I never had any experience with motors before. They used this motor.

Click here for a 300mm@8mp 'Hubble telescope' close-up of the PCB exposed at 15seconds, 100ISO 24f (5.5mb)

When I turn the bot on there is 3.2 V on the motors [tested the motor - & + to GND)] but  testing the motor + & -  and vice versa yields 0Volts. So taking the H-Brdige into account now that seems normal.

Issuing any commands the motors don't spin..(when I connect a motor direct to battery pack it spins happily away with nice torque.. )
When I issue commands the voltage is the same across the motors(apparently the signals are not loud enough or possibly the protocol changed) while attached to the PCB.. But I cannot determine if the MCU is responding at all to any commands.

Should I assume its controlled by PWM somehow? Am I correct? Most likely not.  I cannot trace which pins the motors are connected to on the Atmel either.  After taking an hour to get the perfect macro shot i managed to decipher some of the tracks on the names on the IC's.

Right motor is connected to pins 3,4
Left motor not in picture to pins 1,2
A on the picture indicated the tracks are connected
? on the picture indicated i have no idea where this track goes.. the left side does not have this
Black "-" on picture indicated GND

D2 as symbolised should be diodes. (KSU)(Y6)[These values are printed twice, right side up and upside down, indicating a combined diode?] I think is a 0.3W zener 18V±5%
Q4,Q3 Indicates Transistors but research takes me to Dual 1N4148 Diodes?
R6 indicates a resistor with a value of 102, making it 10k
Could this whole config be the equivalent of this tutorial?

 Can anyone explain to me what the red block I marked (exact same for the other side), what those SMD's are likely to be.. I tried searching for the markings on them but nothing comes up for any datasheet.(EDIT, because SMD markings are decoded differntly and many manyfactuers have the same codes for different parts, so its long game of deduction and commons sense here.. with help from awesome guys at StackElectronics!)

ATT: JustJeff

Here is what seems to be a bit more clear layout of the tracks and you can notice the thick tracks used for the motor pins and the thin tracks for signals. So like you suggested, there has to be a power source for this current somewhere.. I am looking at this pic and cannot really figure out where from. Obiosly it has to be switched using the paired transistors that @RussellMcMahon identified(q1,q2) and the zenners/diodes(I assume).

Romotive

Romotive is an open source project.. But...

Uncomfortably there is no Source code available for the Atmel, only SDK's.  My robot is dead. with no response some response from Romo team (I know they must be extremely busy because loads of other peoples also does not work).. So I might as well make my own firmware if I knew how to drive the motors. Or at least test them with my Arduino? Or something..

Romotive Hacked You-Tube Link

Want to Hack your Romo?

--


texts: Is it normal for a transistor running a motor to be very hot?

texts:
I've researched for a few hours but I'm still concerned.

I'm building a very low budget quadcopter (think toothpicks) and as I've seen on this site, a D10N05 mosfet would do the job. I've visited 3 of the largest electronics shops in my area but unfortunately, they don't have this specific part, or any mosfet as a matter of fact.

Then, I saw this post here on se and lucky enough I have some 2222's collecting dust in a container. I tried it, and it works like a charm. But, one thing I noticed was the transistors would run so hot to the point that I couldn't touch them. Is this to be expected? I have some small heatsinks and some thermal adhesive that I can attach once I know it's okay.

Thanks in advance!

EDIT: The transistor does not reach high temps immediately. It heats up over time.

Here are the the parts I'm using:

Small motors, rated at 3.7v 100ma
2n2222 transistors
1n4001 as a flyback diode
5v power supply (but I'll use a 3.7v battery on the final build)
Arduino nano (PWM control)


texts: std_logic_vector to unsigned conversion throwing incompatible error

texts:
Below is a VHDL code of a even/odd parity generator for a bus of given width.

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use ieee.math_real.all;

entity paritygen is
    generic( WIDTH : positive := 8 );                          -- Bus width
    port   ( abus  : in std_logic_vector( WIDTH-1 downto 0 ); -- n-bit Bus
             even  : out std_logic;                           -- Even parity bit
             odd   : out std_logic );                         -- Odd parity bit
end paritygen;

architecture behavioral of paritygen is
begin
    process( abus )
        variable sum  : unsigned( natural( ceil( log2( real( WIDTH + 1 ) ) ) ) - 1 downto 0 );
        variable remdr: unsigned( natural( ceil( log2( real( WIDTH + 1 ) ) ) ) - 1 downto 0 );
    begin
        sum   := (others => '0');
        remdr := (others => '0');

        for i in abus'range loop
           sum := sum + unsigned( abus(i) );
        end loop;

        remdr := sum MOD 2;

        if ( remdr = 0 ) then
            even <= '1';
        else
            even <= '0';
        end if;
        odd  <= not even;
    end process;
end behavioral;

When I compile the code in Synopsys Synplify Pro I get an error on the following line:

sum := sum + unsigned( abus(i) );
error: @CD715: Cast of incompatible types

In this line, I am calculating a running sum (of unsigned type) of all bit-lines of the bus. As bus is of type std_logic_vector, I am casting it to unsigned type before using add operator to calculate sum.

The error vanishes if I remove the explicit casting. I am confused as to why this is incompatible casting because as I know std_logic_vector should be casted explicitly to unsigned type using unsigned keyword. Can anyone tell me what is wrong in my vhdl code ?


texts:
I am new to reading electronic datasheets.

The BMP280 (https://www.amazon.com/Adafruit-BMP280-Barometric-Pressure-Altitude/dp/B013W0RR6Y) has this datasheet:

https://cdn-shop.adafruit.com/datasheets/BST-BMP280-DS001-11.pdf

I'm trying to figure out how responsive it is, i.e., how long between a change from one pressure or temperature to another, and the time the new pressure/temperature is reflected in output from the device. (I see that "responsiveness" isn't a tag word on this stack exchange site, so maybe I'm just having a vocabulary problem?)

For my application, I'm hoping the response time is on the order of 0.1 to 0.25 seconds (or faster). Does that document give this information? If not, do you happen to have a guess?


texts: Generally, how do you describe the functions of the basic parts in a buck or boost converter? The parts are enumerated in the post

texts:
Here is a homework question I am answering.
1. Explain the function of the following parts in the DC-to-DC converter.
a. MOSFET
b. Schottky Diode
c. Inductor
d. Capacitor
Here is an accurate basic buck topology which is a DC-to-DC converter.

I'm not asking for a literal verbatim answer to my homework but rather just a good idea to work with to generally describe how those parts work in the converter. I can construct the answer myself after learning it well enough. I just need an idea, and I believe it isn't against the rules to use the site as an additional reference or verification.
I know what the parts do individually. But I want to know how they function as a part of the DC-to-DC converter and yes I am familiar but I just cannot put into words that well and cannot explain the intuition behind how they work.


texts:
I am having some problems regarding using loops in the control section of ngspice. Specifically in this example:

VD0 d 0 0
VG0 g 0 0
VS0 s 0 0
JDS d g s JM
.MODEL JM NJF (VTO=-1 BETA=1)

.CONTROL
let start_d = 0
let delta_d = 0.5
let stop_d = 1.81
let start_g = -3
let delta_g = 0.5
let stop_g = 0.01
let d_act = start_d
let g_act = start_g
while d_act le stop_d
 alter vd0 dc d_act
 while g_act < stop_g
  alter vg0 dc g_act
  op
  print v(d) v(g) v(s)
  let g_act = g_act + delta_g
 end
 let d_act = d_act + delta_d
end
.ENDC
.END

It should go through all the combinations of vd and vg (0,-3) (0,-2.5)... (0 0) (0.5 -3)...

However it does not step vd at all. It keeps vd=0 and steps only vg.

Anybody can help?


texts:
What is the main difference between half and full bridge topologies?

For instance, let's take the full and half bridge dual active bridge converter. I can understand that in the full bridge topologies, there are more switches. Thus we can use more complex and efficient control methods. Is there any main difference between the two topologies? When do we use the one topology instead of the other?

Full bridge

Half Bridge


texts: YuCo YC-CN402-24V CN-PBC402-24V DEFINITE PURPOSE CONTACTOR with a Packard PF42440 Control Transformer Class II Foot Mount 40VA 24V to activate the 2vac coil.  The circuit is a 220v 20amp motor.  My question is how much current draw does it take to open that 24vac coil on the contactor?  Will it take all the current from the transformer to drive the coil?  If it does not take all the current can you split the current out of the transformer and use it for say driving the controller (Arduino). Thank You for your help.


texts: Read out tachometer from PC fan when manually turning the blades ( driven shaft )

texts:
I have a problem. I can read out the tachometer of a PC fan and convert it to frequency with just using a simple microcontroller and labview.

Does anybody here have an idea how to read out the tachometer, without powering the fan? I want to measure the RPM with manually spinning the fan. I want to use the tachometer to measure the frequency of a shaft of a low rpm mini-engine. When I disconnect the power that makes the fan rotate, i do not get a reading anymore from the tacho, even when the blades are still spinning.


texts: How to determine accuracy of multimeter?

texts:
I have two multimeter of local brand both work good but both have slightly different Reading.
When i check it with 7805 ic voltage one says 4.91V and one says 5.12V. I know its very low differance but if one of this multimeter have error how can i know which one have error?


texts: No connection between host PC and mbed via Ethernet

texts:
#include "mbed.h"
#include "EthernetInterface.h"

// Network interface
EthernetInterface net;

TCPSocket listener;
TCPSocket* client;

DigitalOut led1(LED1);

Serial pc(USBTX, USBRX);

// Socket demo
int main()
{

    int remaining;
    int rcount;
    char *p;
    char *buffer = new char[256];
    nsapi_size_or_error_t result;

    int n = net.set_network("192,168,10,101","255,255,255,0","192,168,10,10");
    pc.printf("\n Success? %d\n", n);
    net.connect();

    listener.open(&net);
    listener.bind(80);

    listener.listen(1);

    client = listener.accept(NULL);
    client->set_timeout(1000);

    led1 = 0;
    while(1) {

        int remaining = 256;
        int rcount = 0;
        p = buffer;

        while (remaining > 0 && 0 < (result = client->recv(buffer, remaining))) {
            p += result;
            rcount += result;
            remaining -= result;
        }

        if (result == 0) { //Peer has shutdown connection
            client->close(); //close socket;

            client = listener.accept(NULL); //block again until new connection comes through
            client->set_timeout(1000);
        }

        if (result == NSAPI_ERROR_TIMEOUT ) { //Assume connection has been lost
            client->close(); //close socket;

            client = listener.accept(NULL); //block again until new connection comes through
            client->set_timeout(1000);

        }

    }

}

I'm trying to establish a connection between my mbed and PC via TCP, using Teraterm.

The host PC has an Ethernet cable connected to the breakout board I've wired to my mbed. I've changed the localhost settings so that only IPv4 is selected, and chosen a random static IP, to disable DHCP. Subnet mask has been set to 255.255.255.0 and random IP (192.168.10.10) for Gateway.

When trying to connect to the mbed with Teraterm (Service: other, Protocol: IPv4, host: 80), an "Invalid host" error appears.

I'm new to networking, so don't really know where the problem lies, although I do have some suspicions.

Are the IP addresses parsed in the correct format? The mbed documentation (https://os.mbed.com/docs/mbed-os/v5.8/reference/ethernet.html) isn't clear at all on this.
Is the gateway something I can choose to set, or is this automatically assigned by the host PC?
Do I need to disable wireless?

I'm using the Sparkfun Ethernet breakout board, if that makes a difference.


texts: Help identifying a connector where wires are directly inserted into "slots"

texts:
My question is fairly simple.
Would you be able to identify this type of connector:

I can't seem to find it anywhere.It's not supposed to need any kind of crimp (wire is inserted inside as shown in the picture).


texts: Current limiting circuit for a brushless motor controller

texts:
I have bought a motor controller for my 250W, 36V brushless dc motor. I think that the maximum current for the motor shoudln't exceed Imax = 250W/36V = 7A?
The controller I have bought has a maximum current output of 15A and probably no current limiting circuit.
How can I set a maximum current limit for my brushless dc motor?


texts:
I wanted to ask, what general layout guidelines and/or routing concerns exist for I2C in a PCB design?

Edit - Consider a 31mil thick, 4Layer PCB with stack up:

L1 = signal - 0.5oz + 1oz plating
L2 = ground - 1oz
L3 = Pwr/ground - 1oz
L4 = pwr/ground - 0.5oz + 1oz plating
FR4 dielectric

Let's say you need to route across a 10 inch PCB (just for example sake) covering 2 inches on Layer1, 6 inches on Layer3, and 2 inches on layer1. What would be the design guidelines for this?

At high frequency, your SCK (clock) can couple easier to adjacent nets than at lower frequency. The same could apply to SDA (data), however this would be in regards to driver strength of the chip and the rise time associated with the signal. Are there any other oddities that exist with I2C in regards to behavior?

With this in mind, is it best to route SDA and SCK on different layers (assuming high freq) to avoid coupling between them? What is considered high frequency for these signals? Is there a standard routing methodology anyone uses? Typical to put a guard trace in betweeen them to minimize the coupling? What about vias in the middle of the traces to test pads?


texts: Bob Smith termination for Ethernet magnetics

texts:
I know that Bob Smith termination is recommended for Ethernet differential pairs. Please refer the below image for Bob Smith termination resistor placement.

As far as I know, Bob Smith terminations are used for EMI reduction. As it is used to reduce the common mode noise by providing a low impedance path for common mode noise.

But I can't get why some of them are referring to this as termination resistors. If I change the value of termination resistor, will there be any change in effects?


texts:
I have a doubt, if anyone here can help me...
How can I find the minimum value of 'io' that can be achieved by only modifying 'R'?
Thanks in advance


texts: How to make a super capacitor jump starter that doesn't empty into battery?

texts:
I have been watching videos on super capacitor jump starters for cars.
I figured out about 90% of how they work, but there is one last thing I don't understand.
The jump starters use a boost converter to charge up the capacitors from my lower voltage source, possibly even the partially depleted car battery. However in the videos, when they jump start the car, they do not disconnect the battery. Since the super capacitors are in parallel with the battery, shouldn't they push all of their current trying to balance the battery with their voltage?
I have been building my own version, and in order to jump start the vehicle I disconnect the battery from the car at the positive terminal and hook it up to the super capacitor bank. Is there a circuit that I can add that will prevent it from draining into the battery but will still allowed to discharge into the car's electrical system?
To see what I am talking about go to 12:00 in this video...
https://youtu.be/l_xojkGW2hY
My guess is maybe they have a high current MOSFET that can push up to 500A and some sort of circuit that senses when the voltage across the terminals drops suddenly from connection to the starter and triggers the MOSFET. How would you detect this if the battery was completely discharged?


texts: using supermalloy as the core for wifi loop antenna

texts:
this is an extension of this question:

Why aren't ferrite rod antennas used in WiFi?

if you don't want to go through the previous question, then basically i was asking if we can loop wifi antennas around a ferrimagnetic cores, so as to concentrate the fields and get a higher gain.

the same way in AM radios, we loop wires around a soft ferrite to concentrate the fields, to act as the receiving antenna. greatly reducing what would probably be hundreds of meters long to just a few inches.

well, since then, i've been told that ferrite just can't hold magnetic fields quick enough in those frequencies and they act as noise dampeners. "noise" being the high frequencies in GHz... so i turned to supermalloys.

http://en.wikipedia.org/wiki/Supermalloy

i'm not entirely sure if supermalloys are a good way to go, though... i've skimmed through abstracts of articles of it being used in GHz, but not as cores of loop antennas. then there's also the issue of it being a good conductor, which would lead to A LOT of hysteresis loss...

but putting aside hysteresis loss, would it make a good core??

please point out where i'm wrong here...


texts: I have been following the two Great Z80 Project guides and the only thing I don't get is the I/O. He uses a 6522 I/O V.I.A. and I don't quite understand the idea of I/O ports.  So my question is, how do I hook more than one 6522 to the CPU so I can control more peripherals?


texts:
I'm looking for a sensor that can track its own position in 3D with an absolute accuracy of around 0.5inch over a 50-100ft area.  I think this is better than what GPS or inertial tracking can accomplish.  I haven't looked at differential or otherwise enhanced GPS but I think this may be hard to do that way too.

What other ways of doing this exist?

The sensor will move around relatively slowly  (let's say 1-2ft/second).  The area it moves around in can have navigation aids (beacons or whatever).  The area has no RF reflectors (eg metal objects), but it may have RF absorbing objects. In general there is no optical line of sight.


texts: Can I use BC558 PNP transistor with 5V DC supply?

texts: How will I know what is the VCC voltage range required so that transistor can work? I was checking the datasheet and couldn't understand much on it. My requirement is that I have got 5V DC supply. I want to connect 5V DC positive to Collector and Emitter and ground to base. This way, If I pass current from base to emitter then the current should pass from Collector and Emitter. I am planning to connect LED with a resistor between collector and emitter. How should I know what resistance value is required? Like If I want to limit to 5mA current in the LED. I need to know the gain value of the transistor. Also, what is the voltage across the transistor CE and CB? How to see this in the specification?


texts: Some doubts regarding truth table for the function \$(cd+b'c+bd')(b+d)\$?

texts:
$$(cd+b'c+bd')(b+d)$$

Expanding we have $$(cd+b'c+bd')(b+d)=bcd+bd'+cd+b'cd$$

Express each function as sum of Minterm and Product of Maxterm.

If you have n-variables then you will have $$2^n$$ products. Following n=3 we have 8 minterm. But my book suggest that there are 16 terms.

I need some clarification on this. Help please.

Another question is why don't we simplified the terms using Boolean Algebra like we normally do?


texts:
I was salvaging a printer and found like three of these components:

To me they look like a solenoid, but it seems to have a switch-looking lever at the end and a round piece of metal at the end.

My guess is that current magnetizes the metal and that makes the lever snap, but I'm not sure, and even so, I have no idea what use I could make of it.

I couldn't find anything useful on the internet, typing in some numbers that came printed on the side...

So, my question is, what is the name of this component, and what is it used for?


texts: Is it possible to draw a border on row on 20x4 LCD?

texts:
I have 20x4 LCD, and I am using the LiquidCrystal_I2C library to communicate with the screen via Arduino.
I want to build a menu with that screen, and I want to illustrate the "currentHover" option.
For example:

If it is not possible, I would love to get other ideas.


texts: How do I figure out which Schottky diode to use?

texts:
I'm not well-versed in the domain of electrical engineering, so please bear with me if this question is too basic.

I'm putting together an automatic watering system for my greenhouse. Basically, it's a solar panel > voltage regulator > schottky diode > battery > timer > water pump.

The Schottky diodes I've used so far came with the solar panels. However, I need extra ones. This is where the problem arise. What type of Schottky diode do I need?

I'm using two 9V/2W/~200mAh solar panels connected in series (18V) and I've been looking at a 40V 3A (1N5822) Schottky diode. Would this be a reasonable Schottky diode to use? The panels are connected in series in order to trickle charge a 12V lead acid battery at 13.8V.

How do I know which Schottky diode is the right one for my use?
What considerations do I need to take?
How do I see what the voltage drop for this type of diode is?


texts: What will happen if the reset button is not pressed while running a synchronous counter on FPGA (using verilog)?

texts: I was using the following code for a multiplexing circuit to activate 7 seg display on the Basys 3 FPGA. As for multiplexing circuit you don't often need to press a reset, so I was just wondering What happens if we don't press reset for long time here? I believe the value of all 18 bits will be 111......1, and if that is the case, how would fpga reset the counting. Will it just get stuck at 111...1? or will it start replacing bits from LSB/MSB to keep the counter on?


texts:
I need confirmation that the following circuit diagrams are correct for their Boolean expressions. I've been told that each logic circuit must have a MAXIMUM of 4 NAND gates, however, I cannot manage any less than 5.
Thanks in advance.


texts: Which standard must Li-ion battery fulfil for CE marking in late 2020, IEC 62133:2012 or IEC 62133-2:2017?

texts:
I am looking for a slim CE-certified rechargable battery to put in my product. All of the (very few) certified batteries that I have found are compliant with the IEC 62133:2012 (2nd edition). But that standard is withdrawn since, I believe, March 2020, and is replaced by IEC 62133-2:2017 (for lithium cells and batteries).
Does anybody have any experience in bringing a product with Li-ion battery through CE certification after the withdrawal of IEC 62133:2012?
Is it still somehow allowed to use batteries that are certified according to the withdrawn standard, or is it mandatory to have batteries certified to the new one?
During my search for appropriate batteries I realised that the standard procedure is to pay the battery maker to certify a custom pack for you. But that is not a viable option for the low quantities that I need.
I know that the UN38.3 must be fulfilled as well, but that seems to be less of a problem in my situation.


texts: Why do we use a common collector on a linear regulator?

texts:
In my electronics class, we just saw the principles of a linear regulator (like the LM140L or uA78LXX). But I didn't understand why we are controlling a common collector with the differential amplifier.
If we use a common emitter or common base, we will have a really big gain…

Can you help me to understand that little thing?


texts: Why does the reverse saturation current not vary with the reverse voltage?

texts:
I can understand that in the depletion region of a diode more covalent bonds are broken(more electrons goes to conduction band) with more temperature hence we say that the reverse saturation current is dependent upon the temperature i.e. thermal energy added.

But what is the argument which explains why the reverse saturation current is independent from the reverse voltage(at least until the zener breakdown)? (Until zener breakdown why does the increasing reverse voltage have no effect on the reverse current?)

But at some "zener" point something happens and the electrons starts to avalanche and create more electrons. But why doesnt this thing happen gradually? I mean the reverse saturation current is constant untill the avalanche why? Things start to happen at a particular point all of a sudden not gradually.


texts: How to identify of this connector used by TinyCircuits batteries?

texts:
I want to buy some replacement batteries and the best priced ones come with bare wires. I would therefore need to attach my own connector to the end.

What is the name if this type of connector and how can I go about identifying this one specifically (which parts do I measure)? I will also need the metal clips that attach to the wires. What are those called and what kind if tool would I need to attach them?


texts: Low entropy transfer function, output impedance

texts:
I am trying to understand and apply the concept of low entropy transfer functions as outlined by C.Basso and equally stated by a couple of people here.

As an example, I wanted to work through an L-C 2nd order filter feeding a load

simulate this circuit – Schematic created using CircuitLab

Working through the example makes sense as the L and C are shorted or opened to quickly determine the tau of the associated elements to finally combine to produce the overall transfer function \$\frac{V_o}{V_{in}}\$

What I am trying to do is then determine the current transfer function \$\frac{I_o}{I_n}\$ as well as the input and output impedance but it's clear I haven't fully grasped this concept. Likewise, \$R_3\$ is my load and it is a constant power load so the impedance will vary. This was briefly covered in the book but only in passing.

Could someone help guide me in determining the current gain, the \$Z_{in}\$ and \$Z_{out}\$ following the EET method


texts:
I have read wikipedia and other websites regarding the purpose of a diode connected BJT.

But I am not clear on where should we use a diode connected BJT.

My questions :

Where is a diode connected BJT used? Like, in what type of requirements do we need to use a diode connected BJT?

Please explain in simple terms.

Referred this link


texts: What is the harmonic content of a PWM signal?

texts: Suppose I'm using a 3.6 kHz carrier to reproduce a 60 Hz sine wave. To properly design a filter for this application to hit a specific harmonic distortion target, I need to know the harmonic content of the PWM signal. How can I predict what that harmonic content is? Is it going to vary dramatically with the pulse widths? Or will there be certain simplifying assumptions I can make?


texts:
I am using a Light Dependent Resistor (LDR) and a laser to make an burglar alarm system.

My laser continuously projects beam on LDR and when the beam is interrupted the LDR starts to ring the electric bell.

Now I want the bell to ring as soon as laser is interrupted but to stop after some time. I know its possible but how can I do it? Shall I use IC 55 timer to add a delay, if so how?


texts: Release of energy stored in Inductor and Capacitor

texts:
I havent had much experience working with inductors and i am fairly new to them.
The question is how is the energy released from an inductor.

Now if we had a capacitor circuit:

Assume switch to be always closed.
Here if the source was to supply current to the resistor, now initially capacitor charges, and till then it allows the current to flow through, but as it is fully charged , it does not let any more current to flow, as this point the top plate of capacitor is +ve , and the bottom is -ve.
 Now if we were to remove the 15V source, and replace it by a short(thus having only capacitor and resistor in the circuit), then current will flow anti-clock wise right?

Now if were to replace the capacitor with an inductor, what would that direction of current be after current reaches its maximum value, and the magnetic energy is maximum and source is replaced by a wire(to short the 2 terminals)?


texts: Last days i decided to use stm32 chips.I am reading stm32f401 datasheet to design my hardware but below the schematic there is a statement " The 4.7 µF ceramic capacitor must be connected to one of the VDD pin.",do i need to add a parallel capacitor between VDD and GND.Any help or suggestion will be good for me


texts: nrf24l01 radio chip seems to return incorrect bytes - am I even talking to the device or I'm just getting pre-existing bytes in SPI_DR?

texts:
So I am running into this issue where I try to read something off the radio module but I keep getting the same value, which is 0x1C, and I have no idea why 0x1C in particular.
NRF24L01 is the radio module I'm using. To do initial testing, I sent 0xff which denotes the status register and I should be receiving 0xE which is the reset value of the register.
Following is how I am configuring the SPI peripheral:
// main.c

nrfl2401 nrfRadio;

void nRF24_GPIO_Init(void)
{
    // configure CE and SCN
    GPIO_InitTypeDef gpioPort;
    gpioPort.Pin = rNRF24_CE_PIN;
    gpioPort.Mode = GPIO_MODE_OUTPUT_PP;
    gpioPort.Pull = GPIO_NOPULL;
    gpioPort.Speed = GPIO_SPEED_FREQ_LOW;

    HAL_GPIO_Init(nRF24_GPIO_PORT, &gpioPort);
    RESET_CE();

    gpioPort.Pin = rNRF24_CSN_PIN;
    HAL_GPIO_Init(nRF24_GPIO_PORT, &gpioPort);
    SET_CSN();

    // configure SCK
    gpioPort.Mode = GPIO_MODE_AF_PP;
    gpioPort.Pin = SPI_SCLK_PIN;
    gpioPort.Alternate = GPIO_AF5_SPI2;
    HAL_GPIO_Init(SPI_SCLK_PORT, &gpioPort);

    // configure MOSI
    gpioPort.Pin = SPI_MOSI_PIN;
    HAL_GPIO_Init(SPI_MOSI_PORT, &gpioPort);

    // configure MISO
    gpioPort.Pin = SPI_MISO_PIN;
    HAL_GPIO_Init(SPI_MISO_PORT, &gpioPort);
}

void SPI_Init(SPI_InitTypeDef *SPI_Config, SPI_TypeDef *SPIx)
{
    SPI_handle.Instance = SPIx;
    SPI_handle.Init = *SPI_Config;

    __HAL_RCC_SPI2_CLK_ENABLE();
    HAL_SPI_Init(&SPI_handle);
}

void nRF24_Init(nrfl2401_Config *radioConfig)
{
    nRF24_GPIO_Init();
    nrfRadio.config = *radioConfig;
    nRF24_Initialization(&nrfRadio);
}

int main(void) {
   // ...
   SPI_InitTypeDef spi_config = {
            Mode: SPI_MODE_MASTER,
            Direction: SPI_DIRECTION_2LINES,
            DataSize: SPI_DATASIZE_8BIT,
            CLKPolarity: SPI_POLARITY_LOW,
            CLKPhase: SPI_PHASE_1EDGE,
            NSS: SPI_NSS_SOFT,
            BaudRatePrescaler: SPI_BAUDRATEPRESCALER_8,
            FirstBit: SPI_FIRSTBIT_MSB,
            TIMode: SPI_TIMODE_DISABLE,
            CRCCalculation: SPI_CRCCALCULATION_DISABLE,
            CRCPolynomial: 7
    };
    SPI_Init(&spi_config, SPI2);

    nrfl2401_Config radioConfig = {
            spiHandle: &SPI_handle
    };
    nRF24_Init(&radioConfig);

    while (1);
}

// radio.c
void nRF24_SendCommand(nrfl2401 *nrf, uint8_t *txBuffer, uint8_t *rxBuffer, uint8_t size)
{
    RESET_CSN();  // disable chip select

    HAL_SPI_TransmitReceive_IT(nrf->config.spiHandle, txBuffer, rxBuffer, size);
    while (nrf->config.spiHandle->State != HAL_SPI_STATE_READY);

    ENABLE_CSN(); // enable chip select
}

void nRF24_ReadStatusRegister(nrfl2401 *nrf)
{
    uint8_t txBuffer[1] = {nRF24_CMD_NOP};
    uint8_t rxBuffer[1] = {0};
    nRF24_SendCommand(nrf, txBuffer, rxBuffer, (uint8_t) 1);

    while(1);
}

void nRF24_Initialization(nrfl2401 *nrf)
{
    nRF24_ReadStatusRegister(nrf);
}

Here's the output from LA:
The thing that looks suspicious is the early dip in MOSI and SCK signals.

NOTE:
I tried sending the same byte multiple times and saw the expected byte 0xE in return in all the reads except for the first one (where I receive 0x1C). Why could that be?
Here's 3 transactions with the 0xE bytes except for the first one.

Here's the capture with CSN (CH5).


texts:
I want to create a mounting hole with vias around it. I don't know how to approach it so I've tried to do it on my own. I'm using OrCAD PCB Designer.

I have created a mounting hole padstack with desired diamater, solder mask, antipad and so on. Additionaly, I designed a padstack of via which diameter is 0.4 mm. Now, I want to combine those 2 elements. I mean, I want to place 8 vias around the mounting hole. I deducted that that footprint must be created as a Package symbol. I've added mounting hole as a mechanical element and 8 vias as an electric symbol.

For now, it goes like this.

I got many DRC errors. How can I fix that problem?

EDIT: In 3D, it looks like this

It is like it was meant to be.

Preliminary symbol in the library is like that. I want to add a Pack Short parameter to merge the pins into one.


texts: Does anyone know what these pins are called? This is a pager from paging system used in certain restaurants. I'd like to know what it's called as I want to use it in my device's design. I need to know what socket is used with it, but that would be easier to find if I can find the pin :)


texts: Why does LTSpice sometimes stop printing midway through a simulation?

texts: Sometimes I run a simulation and LTSpice stops plotting way before the end of it. There seems to be no common cause for this behaviour, it just happens every now and then. What could be causing it?


texts: h-bridge voltage readings using bipolar junction transistor

texts:
I am using the following h-bridge setup using optocouplers, a DC motor and bipolar junction transistors (2N3904 for the NPN and 2N3906 for the PNP)

Everything works as expected, but my question has to do with the voltage readings.

S1 is on

9v Battery = 9.5V (it is brand new, measured directly across anode and cathode)

9v Battery when motor is running = 8.8V (measured on the positive and ground rails)

Voltage across motor (disconnected) = 8.8V (measured with motor directly connected to the battery, disconnected from the h-bridge)

Voltage across motor (connected and running) =  6.4V (measured at the connection points between D4-D3 and D5-D6)

Vce Q2 = 0.8V (measured directly on the pins)

Vce Q6 = 0.3V (measured directly on the pins)

Vce Q1 = 0.02V (measured directly on the pins)

Voltage across R3 = 4.45V (measured directly on the leads)

From what I understand, with this setup (using BJTs) there is going to be a voltage drop. But there seems to be a discrepancy from the transistor readings and the motor voltage. Do these readings represent an inefficiency in the circuit or could there be an underlying issue?

If it has to do with the inefficiency of the circuit, are there better options? (I can't use an integrated circuit due to design restrictions)


texts:
It should be -11V, but the oscilloscope shows something like this:

The frequency of this 'signal' is 100 Hz.
And for the +11V it seems to be normal:

If I understand everything correctly, the input is 220V with 50Hz.

This shape can be obtained only when load is present.

What can be the cause of this behavior?

UPDATE

It was the capacitor - it was too old, so, replacing it solve the DC power supply problem.


texts: Use a PC PSU for powering a Raspberry Pi cluster and number of 5V+ cables

texts: I need to power a cluster of 8 Raspberry Pis 4 and I have a 480W PC PSU with a maximum load of 28A on 5V+. My question is really simple and dumb (sorry for that) but I did not found a precise answer, but when I attach them to the 24pin motherboard connector should I use all the five 5V+ cables and 5 ground respectively? PSU cables are 20awg, and I estimated 3A for the Raspberry Pis so a total of 24A.


texts: What is the fastest arduino to PC communication method?

texts:
I am making an application that has multiple i2c sensors controlled by an Arduino Uno. I want to get all of the raw data from the sensors and transfer them to a PC as fast as possible, on which I will perform calculation with the raw data using python.
My plan is to write the arduino data onto a text file and then have python read that data and perform some calculations immediately after.
I want to transfer the data as quickly as possible so it comes as close to Real Time results as possible. Should I use Ethernet, USB, or something else for comms?
Should I use a raspberry Pi3 for this instead?
Am I approaching this problem incorrectly?
Any help would be appreciated! Thank you.


texts: Capacitor size for battery operated device?

texts:
I am planning to make a battery operated device. I am using spring contacts for the battery. Since the device will be dropped, I am planning to put in a capacitor. I just don't know what type (ceramic or electrolytic type) and value.

Can you please let me know how to compute the value? There will be three NIHM batteries (1.2V each). Maximum load is 500mA.


texts: What is the main downfall of using QPSK rather than DQPSK in fiber optics?

texts:
I've read that QPSK works theoretically in order to encode two bits depending on the phase of the signal. However, practically a reference for the carrier signal would be needed due to some ambiguity of the phase.
DQPSK is supposed to solve this by using the previous phase as a reference to the next one.
I'm not understanding how the ambiguity of phase occurs in QPSK. Wikipedia alludes to this:

there is an ambiguity of phase if the constellation is rotated by some effect in the communications channel through which the signal passes.

Can anyone explain what occurs in the communications channel that changes this phase?


texts: What's the best way to measure sound at very lower power?

texts:
I want to implement a sound meter on a very low power wireless system but I've not had to deal with electret microphones before. The system right now draws around 5uA when in sleep mode, and wakes up occasionally to process some data from sensors. My aim is to keep the average current drain below 70uA so that the system can last ~5 years with a 3000mAh battery.

My goal is to be able to determine the sound level after feeding the signal into the microcontroller's (nRF51822) ADC/Low power comparator, which would be set to record the sound if it was above a certain level. I need assistance with finding  a low power microphone/analogue front end solution.

What would be the lowest power way to implement a sound measuring feature into my system? Is what I'm looking for even possible at low power?


texts: Why not use only a MOV as a snubber for relay control of AC motor?

texts:
I'm building a circuit to control an AC motor using a relay.

Since the motor is an inductive load, there will be a voltage spike when the relay opens.

It seems that best practice for dealing with this voltage spike is to connect a capacitor across the load (or the relay), with a series resistor to limit inrush current to the capacitor.

why not just put a cheap, beefy MOV in parallell with the relay contacts? One example of such a MOV is the "Panasonic ERZE14A391": https://www1.elfa.se/data1/wwwroot/assets/datasheets/ERZE_series_eng_tds.pdf

What are the pros/cons of this solution?

Is the main problem that the MOV allows the voltage to rise too high, thus putting more wear on the relay than a capacitor-based solution would?


texts: My first STM32 code - please criticize me

texts:
I have just wrote my first code on STM32 - blinking LED. It combines a fragments from different sources; please criticize me so I can learn how to write proper code and don't learn stupid habits.

#include "stm32f30x.h"

void SysTick_Handler(void);
void TimingDelay_Decrement(void);
void Delay(__IO uint32_t nTime);

static __IO uint32_t TimingDelay;

int main(void)
{
  RCC->AHBENR  |=  ((1UL << 21) );                  // Enable GPIOE clock??
  GPIOE->MODER |= (1 << 2*8);                       // PIN 9 as output

//GPIOE->BSRR = 1 << 9;                             // LED ON
//GPIOE->BSRR = 1 << 9 << 16;                       // LED OFF
//GPIOE->BRR = 1 << 9;                              // LED OFF

    if (SysTick_Config(SystemCoreClock / 1000))
    {
    /* Capture error */
    while (1);
  }

    while(1)
    {
        GPIOE->BSRR = 1 << 8;
        Delay(50);
        GPIOE->BRR = 1 << 8;
        Delay(50);
    }
}

void SysTick_Handler(void)
{
  TimingDelay_Decrement();
}

void Delay(__IO uint32_t nTime)
{
  TimingDelay = nTime;

  while(TimingDelay != 0);
}

void TimingDelay_Decrement(void)
{
  if (TimingDelay != 0x00)
  {
    TimingDelay--;
  }

}

Why I have to enable GPIOE clock? And what's the difference between 1UL << 21 and 1 << 21?


texts: Is the direction of an electric field opposite to the direction of a current?

texts:
I consider electricity to be an observation of the property of electron mobility.

If electrons go the opposite way of the electric field, what is the connection between the electric field and an electric current in a simple planar circuit?


texts:
I upgraded to Eagle 7 a couple of days ago the the scroll behaviour seems to have changed.
Using a two finger scroll on a mac trackpad I used to be able to pan around in Eagle 6 but using Eagle 7 this has now become zoom in and out.

Has anyone else experienced a change like this or does anyone know how to revert the behaviour?


texts: Wireless transmission of energy through a layer of non-conductive material

texts:
Is it possible to effectively transmit energy by electromagnetical induction?
I have a plate of nonconductive material (5-10 mm) and I would like to transfer electrical energy from circuit on one side to circuit on the another side without drilling into the material.

I have been thinking about attaching coils (similar as coils in RFID tags) to each side and let the electromagnetical induction do the work. The first circuit has alternating voltage up to 70V and the another circuit should have very similar voltage.

But I have no idea about how big the coils need to be, how big current should pass through the first circuit and whether it is reasonable to use it anyway.


texts: What makes the charge on a capacitor change?

texts:
I have just realized that I actually do not have a through understanding of capacitors and hence, I am asking this basic question.

I was trying to understand how an astable multivibrator works using this source and I have come across the following part (diagram is in the link, and below):

  ...

  The next significant thing which happens is when the voltage on
  the right hand plate of C1, and therefore TR2’s base, approaches
  +0.6V.

  TR2 begins to conduct.

  The collector voltage of TR2, which by  now will have increased in
  value as C2 started to charge through R4, will fall and go down to
  +100mV.

  The voltage across C2 can’t change instantaneously so when the voltage
  at its right hand plate goes down the voltage at its left hand plate
  goes down by the same magnitude.  If TR2’s collector voltage had risen
  to, say, +3V, then when it reduces to +100mV (a negative-going change
  of 2.9V) the left hand plate of C2, and the base of TR1, will also go
  2.9V more negative, but starting from +0.6V.

  They will end up at –2.3V.  This will cut TR1 off.

  ...

So, as far as I understand, the following happens:

\$ C = Q / V \$ equation must hold for capacitors at all times. When we consider a particular capacitor, \$ C \$ is constant. This means that only \$ Q \$ and \$ V \$ may change in order to make the equation hold at all times.

However, there is a quirk with the capacitors. In a capacitor, \$ Q \$ cannot change instantaneously. That is, it takes time to change \$ Q \$.

Hence, when the voltage at one plate of a capacitor undergoes a sudden change (while the voltage on the other plate remains untouched), this event creates a situation where the equation \$ C = Q/V \$ does not hold. The reason is, \$ V \$ has changed, while \$ C \$ and \$ Q \$ are the same. (\$ Q \$ is the same because charge on a capacitor cannot change instantaneously)

However, we know that the equation \$ C = Q / V \$ must hold at all times. Hence, the capacitor responds this change by altering the voltage at its other plate, putting the equation \$ C = Q / V \$ in balance once again.

Here comes my question: Since the capacitor has changed V at its other plate in response to a sudden voltage change on the opposite plate, the equation \$ C = Q / V \$ is once again satisfied. However, we observe that the capacitor starts charging or discharging after this event.

Since the equation \$ C = Q / V \$ has been put in balance by the voltage change at the opposite plate, the reason for (dis)charging cannot be to balance the equation.

So if a capacitor does not (dis)charge in order to satisfy the equation \$ C = Q / V \$, then why does a capacitor (dis)charge?


texts: How to get electronically controlled multiple individual voltage outputs from a single source?

texts:
I am planning to make a digital control board which can draw a DC Voltage of the order of say 12-15 Volt, from a single source and give multiple number ( approximate #100 ) of voltage lines of different values range from 0.1 to say 6/7 Volt with a fine resolution ( it is possible to differentiate between two output lines on the order of say mV).  Voltages appeared to output lines should be controlled  electronically.

So how to design this board ?  What type of programming needs ?


texts: I've purchased a Thlevel Car USB Charger Socket to install in my 12v system campervan and I'm confused regarding the fuse and wire I need to use to wire things together. By my calculations, given that I could be using all the sockets at the same time, I would need around a 30 amp fuse and a 12 gauge wire (4 mm2). But then I wonder, what if I'm using most of the time only the usb chargers (each only 2.1A). Wouldn't it be that the wire and fuse is too big? Could someone point me out in the right direction? Thanks a lot.


texts: How do I sense sinusoidal voltage/current on a resistor?

texts:
I have an experimental circuit like below:

My aim is to measure maximum or effective value the current on the load.
The current sensor is a simple \$ 0.1 \Omega \$, \$5W\$ resistor.

I filtered the voltage on the current sensor with the following cascaded RC filter:

The output of the filter show no signal (\$0V\$). This was an expected result since I was applying a sinusoidal signal to filter like this.

I can't use a diode at the filter stage since the voltage on the current sensor is at the level of millivolts.

Is there any simple trick for reading the voltage on the current sensor? If possible, I don't want to change the main structure of this circuit too much.

EDIT:

How about this alternative circuit?

Assuming that both alternances of the AC signal have the same shape on load, I can calculate the current on the load by only considering the positive alternance.

Notes:

AC frequency is 50Hz.
I'm using the transformer to protect my oscilloscope.
At the filter stage, all resistors and capacitor have the same values (\$R=100k \Omega , C=1 \mu F\$).
The ADC is on a microcontroller (maybe I can add an opamp beforehand for scaling), so I can do any algebraic manipulations on the sensed value.
The load is generic. I want it to be as wide range as possible. I'm using a \$60W\$ lamp for this experiment.


texts: How would I use an arduino to detect the state of a dimmer switch?

texts:
I have an AC Dimmer Switch you'd normally put in a gang box and use to dim lights in your house. If I wanted to hook up this switch to an Arduino (and JUST an Arduino, NOT mains voltage), how would I check the state of the switch?

My understanding is that a dimmer switch trims the AC waveform at the leading or trailing edge using Zero Cross Detection. So would it be possible for me to use a DAC to generate a 60Hz waveform and trick the switch into trimming it @ 5V instead of mains? Is there an easy way to do this? How do LED light fixtures do it?

Thanks.


texts: How do I determine the current load at which my buck regulator will operate in DCM?

texts: I am using an TI TPS56121 buck converter and I have designed it to supply 4.6V at 5A.  However, my load current can vary from 500mA up to 5A (the load normally runs at about 3.6A).  How do I determine the current load value at which my design will no longer operate in CCM, but will begin operating in DCM (which is something that I do not want to happen)?


texts:
I hope my question is in accordance with the rules of the site.

I'm doing a power meter using a voltage transformer, a current transformer and an arduino, besides the components to create the interface for the transformers for the arduino. For this, I am relying on an open-source project called OpenEnergyMonitor.

I do regular sampling of voltage and current, and then I can calculate the RMS voltage and RMS current to thereafter calculate the apparent power as the product of these two quantities.

But I am confused in calculating the real power. My references indicate that this calculation is quite simple: is the average product of voltage and current samples. But in the firmware available on the project, the voltage is considered "altered".

This voltage is calculated as follows:

shiftedV = lastFilteredV + PHASECAL * (filteredV - lastFilteredV);

Where:

ShiftedV is the voltage used to calculate the real power.
lastFilteredV is the instantaneous voltage of the sample immediately preceding it.
filteredV is the instantaneous voltage of the current sample.
PHASECAL is a coefficient calibrated by brute force. I could not find any explanation of its meaning.

After searching the entire site in search of explanations, I have been able to collect the following information:

shiftedV removed the phase offset associate with the different hardware components.

Phase calibration goes here.

I just can not understand the motivation to do something like that. Could anyone help me?

EDIT

Let's see two graphs representing two circuits, the first is completely resistive and the second is reactive. (source of the images)

In the first graph, because it is a resistive load, all the power is used, giving us a PF of 1. Why PF is equals to 1? Because the real power (the average of the product of instantaneous voltage and current) is maximum (and thus equal to apparent power) because the signals are always the same (positive and positive or negative and negative). That way, no energy is removed (negative).

In the second graph, because it is a reactive load, all the power is absorbed and then returned to the circuit, giving us an PF of 0. Because the real power (the average of the products of instantaneous voltage and current) is just zero because the signals are shifted and what is lost now is won just ahead.

You see my point? My "theory" is you do not need do anything too fancy (for example, use shiftedV) to calculate the real power, just pick up a large number of pairs of samples and average their product.

What I want is just a confirmation of what I'm thinking is correct, or because the method used in the project is correct.

After all, what I want to know is: Is there some reason the project that I have used that different voltage (whose understanding completely escapes me) to calculate the real power? And most importantly, should I do the same? Or should I just multiply the instantaneous samples and calculate the average?

Sorry about any english mistake, it is not my primary language.


texts:
I need to create sixteen isolated power supplies on a single PCB.

Input voltage 9v DC.
Output voltage 100v DC.
Output current 10mA each.
No precise regulation needed.
Efficiency not terribly important.

I was thinking that maybe I could just wind my own transformer with one primary coil, and 16 secondary coils. Drive the primary coil with an H-Bridge, then use bridge rectifiers and capacitors to smooth the outputs.

Does this sound sensible, or is there a better way to do it?
Do I need a sinusoidal input waveform, or will a square wave do?
Does it matter how many turns I use? Is more turns better? (As long as the ratio is correct)
Does the frequency matter?

My cost and space budget are small, but negotiable. So I'd rather not just buy a whole load of off-the-shelf supplies.

Added: Schematic


texts: i'm building a white LED strip to mount above my kitchen counter. there is really nothing fancy about it: it's a 1.7m of 5V LED strip that i soldered an USB plug and mounted an on-wire switch to turn it on/off.it will be powered by an old iphone power adapter (hence the USB plug) and it draws a total of 130mA. my only worry is that being mounted in the kitchen opens up the possibility for water to get accidently spilled on it. is there a way i can build a short protection for it?


texts: How to use a Hall effect sensor in a rotary encoder?

texts:
I'm designing my own rotary encoder using magnets and a Hall-effect sensor.
I'm not getting the linear output I was hoping for. I'm using two magnets and putting the sensor in the middle - like this:
n[]s X n[]s

The n[]s is the magnets, and the X is the sensor. I do get the middle value when it's in neutral position, and the minimum/maximum value when it's 90 degrees to each side (trying for a full 180 degree encoder). But the values in between is more logarithmic then linear.
When looking at the data sheet for any Hall-effect sensor it shows a linear output based on gauss. I have no idea how this Hall effect works and if I should expect a linear gauss based on angle and therefore a linear output.
At this point I'm hoping it's my cheap-directly-from-china-components that are bad so if I buy locally I will automagically get the result I'm looking for.
If this is how Hall effect sensors are supposed to behave then it simply cannot be used in a rotary encoder and I have to go for potentiometers.
EDIT: As requested - a photo:
The outer ring with the magnets are rotating while the sensor is stationary. It can rotate indefinitely, but I'm only interested in 180 degrees.


texts: Charging devices with different max voltages

texts:
I have a project that requires me to make a portable power pack that can be charged up and then power different devices. The product needs to have two USB charging ports and hold around 7Ah.

The problem I have is that the devices it will charge vary in minimum/max current and voltage and I would like to not damage the devices it is charging. What is the best way to do this as the only way I would know is to state the rails, yet I cant list all the devices it could charge so should I go for a general voltage and current.

Also what are some of the important circuits I should be looking to make sure the device has to make it more safe. Any answers are appreciated


texts: Ground with one sensor vs multiple sensors

texts:
I'm pretty new to the world of electronics and was working on an Arduino project using load cells and HX711 amplifiers. The project consists of four HX711 connected to the Arduino and Pi, with all sensors sharing the same ground and power.

I have by now gotten everything working, but I did notice something I thought was strange. When running code to only use a single HX711, that sensor worked fine. But when code was run to use all four HX711, that same sensor would not work. The cause I found out was there was what seemed to be too much resistance from the ground connection on that HX711. Doing some resoldering fixed the issue.

So I was wondering what causes this. Why does the ground connection work when it is the only HX711 working, but not when there are more running? It was my impression that if the connection is good enough when running one sensor, it would be enough for it when running them all.

Here's kind of what the circuits look like (minus the CLK and DT connections to the Arduino):


texts: Error with Serial Communication between Processing and Arduino

texts:
I have a sensor which can give information about X and Y position movement, and I want to create a simple interface in which a circle on the screen will move in the same direction as I move the sensor. I use Arduino to send position data (float) through serial communication.

However, the code doesn't seem to work well. The circle I create, sometimes it disappears from the screen, and after a while, it shows up again. Besides, the circle seems to "blink" (I mean it appears/disappears in high frequency) all the time. I'm doubted that the problem is about the buffer, but I'm not so sure. Here is the code I use:

PROCESSING CODE

 // import libraries
import java.awt.Frame;
import java.awt.BorderLayout;
import processing.serial.*;

// Serial port to connect to
String serialPortName = "COM3";

/* SETTINGS END */

Serial serialPort; // Serial port object

void setup() {
  size(900,900);
  noStroke();

    serialPort = new Serial(this, serialPortName, 9600);
}

byte[] inBuffer = new byte[50]; // holds serial message

void draw() {
      background(0);
  if (serialPort.available() > 0) {
    float[] x= new float[2];
    String myString = "";
      try {
        serialPort.readBytesUntil('\r', inBuffer);
      }
      catch (Exception e) {
      }
      myString = new String(inBuffer);
      String[] nums = split(myString, ' ');
        try {
            x[0] = float(nums[0]);    //X
            x[1] = float(nums[1]);    //Y
        }
        catch (Exception e) {
        }
      ellipse(x[0]+500, x[1]+500, 70, 70);      //+500 to make the circle in the middle of interface
  }
  }

Serial communication in Arduino:

Serial.print(xf,DEC);        //méthode 1
Serial.print(" ");
Serial.print(yf,DEC);
Serial.print('\r');

Please help me to find the root cause of this problem. Thank you so much!!


texts: [STM32F103RB][C] - DMA, can't change PWM period

texts:
Hello i woul'd like change PWM period with DMA. I wrote code but i don't know why LED BLINKING with constant time

#include "stm32f10x.h"
#include "stm32f1xx_nucleo.h"
#include "stm32f10x.h"

int i =0;
u16 PWM_Buf[198];

void TIMInit(void);
void GPIOInit(void);
void DMAInit(void);
void PWMInit(void);

int main(void)
{
 GPIOInit();
 TIMInit();
 DMAInit();
 PWMInit();

 for(i = 0;i<198;i++)
 {
  PWM_Buf[i] = i * 10; // <-------- VALUE OF TIM PERIOD
 }

    while(1)
    {
    }
}
void TIMInit(void)
{
 TIM_TimeBaseInitTypeDef TIMInit;

 RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);

    TIMInit.TIM_Period = 1000;
    TIMInit.TIM_Prescaler = 64000;

    TIMInit.TIM_ClockDivision = TIM_CKD_DIV1;
    TIMInit.TIM_CounterMode = TIM_CounterMode_Up;

    TIMInit.TIM_RepetitionCounter = 200;

    TIM_TimeBaseInit(TIM1, &TIMInit);
}

void GPIOInit(void)
{
  GPIO_InitTypeDef GPIOInit;

 RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
 RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);

   GPIOInit.GPIO_Pin = GPIO_Pin_8;
   GPIOInit.GPIO_Mode = GPIO_Mode_AF_PP;
   GPIOInit.GPIO_Speed = GPIO_Speed_50MHz;

   GPIO_Init(GPIOA, &GPIOInit);
}

void DMAInit(void)
{
 #define TIM1_ARR_Address 0X40012C2C

 DMA_InitTypeDef DMAInit;

 RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
 DMA_DeInit(DMA1_Channel5);
 DMAInit.DMA_PeripheralBaseAddr = (u16)TIM1_ARR_Address;
 DMAInit.DMA_MemoryBaseAddr = (u32)PWM_Buf;
 DMAInit.DMA_DIR = DMA_DIR_PeripheralDST;
 DMAInit.DMA_BufferSize = 198;
 DMAInit.DMA_PeripheralInc = DMA_PeripheralInc_Enable;
 DMAInit.DMA_MemoryInc = DMA_MemoryInc_Enable;
 DMAInit.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Word;
 DMAInit.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
 DMAInit.DMA_Mode = DMA_Mode_Circular;
 DMAInit.DMA_Priority = DMA_Priority_High;
 DMAInit.DMA_M2M = DMA_M2M_Disable;

 DMA_Init(DMA1_Channel5, &DMAInit);

    DMA_Cmd(DMA1_Channel5, ENABLE);
}

void PWMInit(void)
{
 TIM_OCInitTypeDef  PWMInit;

    PWMInit.TIM_OCMode = TIM_OCMode_PWM1;
    PWMInit.TIM_OutputState = TIM_OutputState_Enable;
    PWMInit.TIM_Pulse = 500;
    PWMInit.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OC1Init(TIM1, &PWMInit);
    TIM_OC1PreloadConfig(TIM1, TIM_OCPreload_Enable);
    TIM_ARRPreloadConfig(TIM1, ENABLE);
    TIM_DMACmd(TIM1, TIM_DMA_Update, ENABLE);
    TIM_Cmd(TIM1, ENABLE);
    TIM_CtrlPWMOutputs(TIM1, ENABLE);
}


texts:
I am new to electronics, and I'm reading a book on embedded systems and bumped into an "Open Collector". I know that a transistor has a base, which acts like a switch for the current to flow from collector to emitter, but what does open collector mean?

What is it (in simple terms!), what does it do, and where to use it?

The picture below shows the one I got stuck on. For the record, don't ask me about what COM signal means.. The picture is something called a darlington transistor. (From the book "Introduction to ARM cortex M microcontrollers")


texts:
I have interfaced a humidity sensor with MSP430F2274 on pin P2_2 (Kit CC2530 ZNP) and using the following code to read the output voltage from the sensor. But it doesn't seem to be working.
I am getting a different value each time and it's way off the actual output from the sensor. I have a separate module which takes care of the clock and timers. The Kit has on-board Light and temperature sensors which seem to work perfectly fine. Could you please have a look?

getHumidity()
{
  int result, volt;

  ADC10CTL0 &= ~ENC;
  ADC10CTL0 &= ~ADC10ON;

  // P2.2 -> Humidity Sensor - A2

 P2DIR &= ~0x04;
 P2SEL &= ~0x04;

 ADC10AE0 |= 0x04;
 ADC10AE1 = 0x00;

 ADC10CTL0 = SREF_1 + ADC10SHT_3 + REFON + ADC10ON + ADC10IE + REF2_5V;
 ADC10CTL1 = INCH_2 + ADC10DIV_3; // Input Selct and Clock Div

 ADC10CTL0 |= ENC + ADC10SC; // Start to sample

 while(ADC10CTL1 & ADC10BUSY);
 result = ADC10MEM; // Store Result

 volt=(int)((result*2500.00)/1023.00);

 ADC10AE0 = 0; // Reset Selection Bits
 ADC10AE1 = 0;

 ADC10CTL0 &= ~ENC;
 ADC10CTL0 &= ~(REFON + ADC10ON);

 return volt; // Return Result
}


texts: Does the battery have to be rated for the full starting current of a DC motor

texts: Do we have to select a battery capable of delivering the full starting current (which is high as it is the stall current) of the DC motor, or is it enough if the battery is rated for a bit more current than the rating of the motor?


texts:
I am trying to build an ignition cut module with an arduino as part of a DIY quickshifter on a motorcycle. I have build the circuit shown below.

The points A and B on the circuit fit inbetween the circuit on the motorcycle that powers the primary circuit of the ignition coils. The sketch on the arduino is configured in a way that when pin D2 goes low (When the sensor trips) a HIGH signal is sent out of pin D11, this high signal lasts for around 60ms and turns off the p-channel MOSFET that that amopunt of time. The effect of this is that the spark is cut on the motorcycle for around 60ms.

The circuit works fine when attached to a 12v bulb, however, when I connect the ignition circuit, wierd things start to happen, the arduino acts like the sensor is being tripped when it remains open. I believe this is down the back EMF from cutting the power to the ignition coils primary circuit. These are cut on a regular basis by the ECU to produce the spark, not only being cut by my circuit.

My question is how can I prevent the back EMF spikes from interfering with my circuit? From my reasearch it seems a flyback diode would be needed accross the inductive load. This isn't really an option as the coils are located elsewhere on the motorcycle and are sealed units, they are only fed by wires.

EDIT: Here is a diagram explaining where the circuit fits in relation to the ignition system.

Unfortunately I cannot add any more links, but I can give you the part number of the MOSFET: Infineon Ipp80P03P4L-04

The MOSFET needs to be constantly open, it makes sure that the engine will run, if the MOSFET is closed the spark plugs wont spark. This is why there is a pull down resistor on the MOSFET gate, so that if there is a problem with my circuit the MOSFET should be off and the coils will still fire. I considered using a depletion mode MOSFET but they seem surprisingly much harder to get hold of.


texts:
I've been thinking about this on and off for a while and I thought I would ask the experts.

The cone and coil of a loudspeaker have mass, so it takes time and energy to move the cone to another position. This led me to think that surely the actual position of the loudspeaker over time does not precisely reflect the amplitude driving it, and that this would presumably be more apparent for higher amplitudes and frequencies.

So i was thinking: why aren't loudspeakers designed to be driven by the derivative of the signal, or some normalised mixture of both? That way, drastic changes in amplitude per sample will result in more power to move the cone to where it needs to be.


texts:
I am not sure which other parts (except PIC KIT 3) do I need for in-circuit debugging of PIC 16F684...

Do I need additional ICD header?

What about RJ-11 adapter/cable to connect PICKIT and header? Do I need one or is it included with header?

Is it possible to use in-circuit debugging functionallity without those two parts (is there any other way)?


texts: How to power CCFLs from backlight using original inverters (from a disasembled LCD screen)

texts:
I've search the net and dealers for specs of these inverters, no chance!

I'd like to make somme discreet lightings with the CCFLs, as the screen was disasembled in a hurry, without noting the connections, I can't figure out the power and the wireing to use.

As there were 18 CCFL and 2 inverters in this screen, it's easy to figure out that each inverter can power 9 tubes, but I'm stuck there.

Must I use all tube or the power will adapt to 3, 4 or 10?

Thanks for your time!


texts: Easiest way to create a constant 1V voltage drop

texts: I need to find a small, cheap, easy way to get a 1V drop in a circuit. It needs to be such that below 1V it acts like an open switch, and above 1V the drop is a constant 1V. Basically an LED without (necessarily) light, except LEDs don't tend to have a forward drop that low - is there any other simple component that will work? I don't really want to have to use a 3-terminal transistor, just to keep it simple.


texts: Placement of OV/UV OC protection circuits

texts: Should the over voltage protection circuit placed after the TVS diode? What is the general way of placing the protection blocks? Am I missing anything apart from these protection blocks?


texts: Use unused SPI MISO pin for I/O on ATTiny

texts:
I want to use an attiny85 for a project that will be controlling some LEDs over a pseudo SPI that only needs to use SCLK and MOSI.  Is there any way to reconfigure pin 6 (MISO) on the 85 to be used as a digital read/write after configuring SPI?  I need 3 digital read pins as well as the 2 for SPI and the only way I can d it is either disable the reset pin, which would than mean I would need a high voltage programmer to program it :(, or use the MISO pin...

Any way to do this?


texts: Difference between op-amp input swing and common mode input voltage range

texts:
What is the difference between:

Input swing
Common mode input voltage range?

I thought they were the same thing.

Yet in this datasheet for example, it says:

  the MCP6231/1R/1U/2/4 family supports rail-to-rail
  input and output swing, with a common mode input
  voltage range of VDD + 300 mV to VSS – 300 mV.


texts: What's the purpose of this resistor into a NOT gate?

texts:
I'm trying to understand part of an envelope generator circuit. Here's the part of the schematic for the GATE IN, marked by the K, which can accepts a signal of between 0V and +5V.

I understand that the 470k resistor is a pullup resistor which will keep the NOT gate (a CD4069 hex inverter with a +5V supply voltage) input pin high if there is no signal from the gate.

What's the purpose of the 330k resistor though? Why shouldn't I just connect K directly to the input pin?

Update: More details on the GATE IN signal.

This circuit is intended to be used in a modular synthesizer. The GATE IN control voltage is expected to trigger the attack stage of the envelope generator at +5V and the release stage at 0V.

There shouldn't be any other values presented to GATE IN. However, other voltages present in modular sythesizers typically range from -15V to +15V, and with some effort (to break things) could be presented to GATE IN.


texts: Is a separate safety earth connection necessary when using an earthed power entry module?

texts:
Testing the Schaffner FN1394-10-05-11 power entry module with a multimeter shows continuity between the ground pin and the body of the module. Consequently, when the module is fitted into an aluminum panel (into a non-anodized, raw metal, opening), the chassis is connected to earth.

In this situation, is a separate safety earth setup necessary, as per this diagram?


texts:
I am working on integrating single 4.2V Lithium battery(400mAh capacity), charger IC, and battery fuel gauge for an embedded project.
I have watched several TI training videos about battery management, and understood the following:

The battery has internal resistance, and what we will measure on the battery terminals should always be below 4.2(Vmax). E.g. if max voltage deliverable by battery is 4.2, we will have 0.1V internal drop, and thus measure 4.1 on battery terminals.
As the battery ages the internal resistance increases, hence, after few years, I should read even less voltage  on battery terminals.
Majority of charger ICs terminate the charging once the battery terminals reach fixed voltage threshold, usually 4.2V. It is the point where charger IC understands that battery is now fully charged.

I have 3 questions:

Are my conclusions above correct?
Let's say we are charging an aged battery. During fully charged state, since it is aged, it should have less than 4.2V on terminals due to high internal resistance . Let's take 4.0V as an example as a fully charged terminal voltage(when it is 4.0, the 0.2V is lost on internal resistance->4.2Vmax). Charger IC will keep charging the battery until the terminal voltage reaches 4.2V, but it had to charge it until 4.0. So it will actually overcharge it. Is my understanding correct?
Many battery fuel gauges have an alarm interrupt for low battery voltage. For the most batteries, the 3.0V is considered as 100% discharged. Let's take 3.1V as an alarm condition. Battery fuel gauge is reading voltage from the battery terminals. Let's say it is reading 3.1V. In my understanding alarm should not be generated, because when terminal voltage is 3.1V, the actual overall voltage would be around 3.2-3.3V for example. I think the correct behavior would be for the fuel gauge to approximate internal voltage based on the externally sensed terminal voltage, and generate alarm based on approximation of internal voltage level. I know it is a general question, but I believe majority of fuel gauges should have common behavior for this. Do they generate alarms according to internal or external voltage?

I would appreciate your help.


texts: Output capacitance in analysis of Buck Converter

texts:
In an analysis of buck converter, we make few assumptions.
Those are:

The circuit is operating in steady state.
The inductor current is continuous.
The capacitor is very large and the output voltage is held constant.
The switching period is \$T\$; the switch is closed for time \$DT\$ and opens for time \$(1-D)T\$
The components are ideal.

Here we say that the capacitor is very large to keep output constant.
How large, in Farads, should the capacitor be?


texts: PDM to PCM conversion workload on 32-bit micro (such as STM32)

texts:
Can anyone provide a rough estimate of the processing power required to do PDM (e.g. audio from MEMS microphone) to PCM conversion on a 32-bit microcontroller ?
Specifically - I see ST provides a PDM to PCM library (with audio rate up to 48KHz) for the STM32F407 which is an ARM Cortex-M4 at up to 168MHz: I wonder how many processor MHz this PDM-PCM conversion may eat up.
And - would PDM-to-PCM be doable on the less powerful STM32L1 (Cortex-M3 at 32MHz) - perhaps at a degraded audio rate as I'm not looking for top quality audio.
Thanks.


texts:
I have 4n35 optocouplers, I am using these to isolate a motor driver circuit and the Arduino controlling it.  I put one on the slave select pin and one on the tx line to the motor controller (there is no rx), however it is not working.  I am using a 220ohm resistor between pin 1 of the 4n35 and the tx line from the Arduino and using no other resistors or capacitors.  I am following this circuit  I have been doing a lot of research on optocouplers and the 4n35.  I have seen blogs and forums where people have achieved 9600 baud with it, but I don't understand how they did it.

What can I add to this circuit to make it work? Do I need to use a higher speed optocoupler such as the 6N137A?


texts:
Problem description

I have a small formicarium for ant keeping, it is basically a tiny glass tank with inside dimensions of 20cm x 10cm x 2cm, filled with sand or soil. Ants I am keeping, like to dwell in the nature under rocks, which are heated by sun rays, and they are using its heat for faster pupae (final stage of ant cocoon) hatching. They are moving pupae to such vicinity of the stone so the correct temperature is achieved. I would like to replicate this in indoor conditions for my ants.

Solution suggestion

I intend to use old laptop power source, characteristics from its sheet:

90W AC Adapter
Output DC 19,5V 4,62A

And basically just put resistor to its output connector big enough to provide power of about 10W. Then either put this resistor to e.g. some concrete mixture to create artificial stone or (if it will be too big) attach it to the outside glass to create one spot temperature increase. Close to this resistor there will be thermostat sensor which will cut of power to the laptop power source as soon as the temperature increase would suffice. It will be operated indoor and desired temperature increase will be 3-5 degrees of Celsius for the 40 cubical centimeters of soil/sand.

My Questions

If I put five 2W 10R resistors just after each other I am effectively creating 10W 50R resistor, correct?
If having 50R resistor, my math is telling me that with the 19,5V of the power source, it will be drawing 0,39A and will provide power of 7,6W. Is my math correct? If not please provide description of how to calculate this.
I totally do not know how would I calculate if this power would suffice to provide desired temperature increase for that amount of soil/sand and artificial concrete stone. I intend to experiment with different resistor size, but if someone would be able to provide me with the info on this or point me to some articles on this topic it could be nice.
Safety - it will be in wet environment most of the time. Do you have any tips on how to  insulate this water proof, electrical proof but with low thermal insulation? It needed to be cheap and possible to apply in the small size since it will be quite small

My level of knowledge

I have high school education in electronics but I am not working in that field for 20 years. So my knowledge is fuzzy at least :)

What I (believe) cannot use and why

Artifical heating stones from pet shops - they are too big for my use case. Maximum dimension 2cm
Heating cables - they are too long and thus most of the heat would dissipate without use and I am not sure what to do with the rest of the heating cable length
Light bulb - its too big and is heating entire formicarium and not only part of it
Heating mats which work by spreading infrared light - they are too big and thus would heat larger area


texts: Are there any disadvantages using magnetic couplers instead of opto-couplers?

texts:
I'm trying to find the disadvantages of using magnetic couplers versus opto couplers (1). I'm deciding which of the two I should use to create a galvanic isolation between two PCB's that are going to communicate via SPI in a normal environment e.g house living room.

(1) http://www.wisegeek.com/what-is-an-opto-isolator.htm

I have found several websites and documents that show the advantages of magnetic couplers vs opto couplers. Here is one that summarizes most advantages(2)

(2) http://www.nve.com/isopdf/WP1201.pdf (Page 3).

But I'm having a hard time believing that there is not a single disadvantage to using magnetic couplers versus opto couplers for galvanic isolation between two PCB's.

So my question is: Are there any disadvantages using magnetic couplers instead of opto couplers?


texts: Safe solenoid driver: can I use a slow blow fuse?

texts:
I'm building a device that uses a microcontroller to control 15 solenoids via a preexisting multichannel DC solid state relay board. When all is working as intended, at most one solenoid will be actuated at a time, and each actuation consists of a 100 millisecond 24V/3.5A pulse.

I'm looking for a way to insure that a solenoid won't be overheated even if there's a software fault that causes an output pin to remain high, and consequently cause the SSR to remain open, driving the solenoid.

So my question is this: is using a a slow-blow fuse in series with the shared 24V supply a prudent way to protect against burning up solenoids?

If so, what specs should I use for the fuse? Should I just take the the I^2 * T value (1.2) and double it?

If there's a better way to do this, I'd love to hear it.


texts: The concept of virtual ground allows us to approximate both input terminals of an op amp at the same potential. People say that both the terminals are 'shorted'. Do this mean that the current can flow between these terminals like they were really short circuited? Or this concept of 'shorting' is valid just for voltage equivalence at the two terminals?


texts:
simulate this circuit – Schematic created using CircuitLab

See the schematic above. This is a simplified schematic from a more complex circuit divided using nodal analysis, but my question is only directed toward this part.

Could you explain me clearly why the equilibrum equation for node Va (nodal analysis) is (note the "s" is used as Laplace transform, i.e. derivative or integral) :

$$
V_{a} \cdot (\frac{1}{R_{4}} + \frac{1}{R_{8}} + \frac{1}{L_{1}s}) - V_{b} \cdot \frac{1}{L_{1}s} - V_{c} \cdot \frac{1}{R_{4}} = \frac{v_{s}}{R_{8}}
$$

The part confusing me is related to \$ R_{8} \$, I guess because it's placed after the voltage source, between it and the ground. I would guess \$v_{s} = V_{a} \$ right? That would mean technically from the above equation (taken from the solutions book) that \$ R_{8} \$ would not appear in the (simplified) equation as \$ V_{a}/R_{8} \$ and \$ v_{s}/R_{8} \$ would are on both sides of the equation?

What I was doing intuitively is:
$$
\frac{v_{s} - 0}{R_{8}} + \frac{V_{a} - V_{c}}{R_{4}} + \frac{V_{a} - V_{b}}{L_{1}s} = 0
$$

By the way the current directions \$(i_4, i_8, i_1)\$ are given as-is in the book's exercise's schematic. I only tried to follow them in the above equation, seems like I'm all wrong...

How would you approach this using nodal analysis?

Side note, if \$ R_{8} \$ had been between \$V_{a}\$ and \$v_{s}\$ instead, I would have gotten the same answer as the book. Yet, since \$ R_8 \$ is next to the ground, I don't think I could throw \$ \frac{V_{a} - v_{s}}{R_{8}} \$, no?

Thanks


texts:
Is there a place that I can get a hold of a table with common voltages by using standard resistors? (Sorry that this is poorly worded but I cant figure out how to say it better, so I will give an example)

For example, a website that has a table that says for 5 volts on a LM317 you can use the "standard" resistor values of x for R1 and y for R2; with x and y being common resistor values.


texts: Trying to get 2 LEDs blinking of 3v mains supply

texts:
I've installed 2 dummy security cameras, and they use 2xAA to supply 3v to a self-blinking LED.

I would like to wire them so that I don't need to bother with replacing batteries so I have purchased a 3V DC 300mA mains adaptor.

I've struggled by simply wiring them in parallel. First one installed and flashed fine. Second one appeared to have got burnt out. Ordered a replacement, but this won't flash off the 3v mains adaptor (but will off battery), in the process of trying to diagnose it appears I've burnt out the first LED now.

So I'm thinking I need to start again, with a proper flashing LED circuit, but hopefully being driven off the 3v mains supply I've already got.

I've struggled to find clear instructions for something so simple. Can I just grab a couple of flashing 3v LEDs and a suitable resistor? Or do I need to go with static LEDs and a more complex circuit?


texts:
I need to power a coil (electromagnet to be precise) using a PWM singal generated by an arduino or a 555 timer.
I can esily power the coil when the PWM signal is in the HIGH (5v) state using a simple N-CHANNEL MOSFET.
My problem is that I can't find a way to power the coil when the PWM signal is in the LOW state (-5v) in order to reverse the polarity of the magnetic field cerated by the EM.
After some research I assume that I need to use an H bridge Like described here however my electromagnet will probably draw a lot of power, using a driver like DRV8837 won't be sufficient.
Any help would be much appreciated on how to design a proper H bridge circuit.


texts: Cut Off Frequency in three phase LC filter

texts:
Good afternoon all

My question is what will be the formula to calculate cut off frequency of attached LC filter.

Its a three phase LC filter.

\$(L1=L2=L3= 6.1 \mathrm{mH}) \;\mathrm{and} \;(C1=C2=C3=29\mathrm{uF}). \$

I know formula for single phase LC filter is \$\dfrac{1}{2 \pi \sqrt{LC}}\$.

What wondering same will apply to three phase system or its different. Please Help.
Also what is doffrence between cut off frequency and resonance frequency.


texts: Why is there a voltage between the mains ground and my radiator?

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I have an anti-static mat that comes with a plug that only has a ground lead. Out of curiosity, I measured the voltages between the live, neutral, ground, and my radiator.

As expected, there is 240VAC between live and neutral, and in my case there is no AC voltage between neutral and ground. However, I measure 1VAC and 20mV DC between ground and my radiator.

I understand that there might be a difference between neutral and ground due to wire resistance and large return currents on the neutral wire. What I don't understand is where the potential difference between ground and my radiator comes from. It is my understanding that any ground current would trip the RCD.

As a follow-up question: What is the better location to connect my anti-static mat? I would prefer to not expose myself to random voltages, even though I understand it should not matter too much as long as I'm not grounding myself to two different potentials.


texts: Can some clamp meters measure voltage through their clamp?

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A simple question, is it possible any clamp meters to provide voltage readings when a cable is between their clamp?  I see from specifications for meters that they don't seem to do that and instead provide an amp reading.

I assume this is likely because its not possible via this kind of non contact measurement but can someone confirm?


texts: What is this glass bulb with two parallel electrodes on my PCB?

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Might be super obvious, but I've not encountered one of whatever this little dude is before:

I figured some sort of vacuum tube, but no idea beyond that. The two poles aren't linked. Found inside a heating control panel. Help would be greatly appreciated!


texts:
I've got a Blade Nano QX micro drone. It's awesome. It arrives with a USB charger for the 150mAh 1S lipo battery, that has one very annoying feature.
When it's charging a red LED is on, and when it's done charging the LED turns off.
Overcharging the battery will damage it, so when charging I sit by the PC (or a USB wallwart) and wait till it's done.

In the meantime I've hacked a better solution using an Arduino UNO and some passives - I've taped an LDR on the LED, and connected another LED and a small piezzo buzzer to the Arduino.
Now, when the LED is on (charging) my LED is also on (so I know what state the charger is in even though electrical tape is hiding the original LED), and when the LED turns off my LED turns off and a short melody is played on the piezzo.
This was I don't have to sit by the charger.

Before I go on and move the project to an ATTINY and create a custom 3D printed housing for everything, I wanted to ask if there's a way to cut power to the charger, so I can have it connected to USB, but stop drawing current and stop charging the battery, in a way that I can safely leave the battery plugged in but not charging anymore.

I thought about using a transistor to monitor the LED and as soon as the LED is off, connect the transistor's base to ground and have it stop providing current to the charger.

The charger only uses the vcc and gnd wires on the USB.

Several questions that I had, but don't have enough data to answer:

Is a standard p2n2222a bjt OK for this?
Is it OK to leave the battery connected to the charger even if the charger isn't connected to anything?
what sort of protection should I add to the circuit if the solution I thought of is adequate?

Thanks.

EDIT:

A picture of the charger (a simple USB dongle with one LED and the eflite micro connector)

As far as schematics or datasheets go - I couldn't find any. The user manual for the charger has no specs (http://www.horizonhobby.com/pdf/EFLC1008-Manual.pdf).

Only info available is :

Input: DC 5V, 350mA
Output: 4.2V, 300mA

EDIT2:

I've created a (very) crude schematic (Eagle newbie alert).

Power comes in through the male USB connector, and goes  out to the charger through the female USB connector.
The Transistor should stop providing power to the charger as soon as the photocell resistor detects that the charger led is off.

I currently have the circuit working WITHOUT the transistor - meaning the microcontroller and the charger get their power from separate USB ports, and I have to manually disconnect the charger when charging is done.


texts: Distribution of component values with a given tolerance?

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Suppose I have a collection of parts with the same nominal value and some tolerance, say 50 Ohm 1% tolerance resistors.  What distribution of actual component values can I expect?  I can imagine several definitions:

The parts follow a normal distribution with standard deviation 0.5 Ohms
95% of parts will be within 0.5 Ohms of the nominal value
100% of parts will be within 0.5 Ohms of the nominal value
...

What is the actual technical definition of component tolerance?

My reason for asking is that I wish to simulate many instances of a particular circuit, each time selecting 'realistic' component values, to determine what variation in the final circuit performance I can expect, based on the tolerances of the underlying passive components.


texts:
I am using a PM2515-03 Stepper motor and with the following ratings:
Current/phase= 0.5A
rated voltage= 5V
step angle=7.5 degrees
inductance = 2.7 mH
resistance/phase = 10 ohms
Now, in order to start the motor I need to figure out the minimum delay between pulses that will tend to rotate the motor. If anyone knows how to calculate the delay please explain in full details, how can I calculate the delay. Thanks in advance.


texts: Is there a practical method to verify whether the noise have CM component in this setup?

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An SMPS power supply unit namely Vsupply output can be composed of its desired DC output Vdc, differential mode noise Vdm and common-mode noise Vcm.

If we have such a power supply and an earth grounded oscilloscope(with passive probe), is there a practical way to check whether there exists common-mode noise?

I draw the following diagram for ease to depict the power supply, scope and the nodes. Can there be a way to manifest the existence of common mode noise by using a resistor in between some of the nodes or any other way? I have never tried to quantify how much part of the noise is DM and how much is CM and have no practical experience on it.

Edit for an answer:

1) Where is the probe tip connected?

2) Can we measure CM by this way?:

Edit 2 for a comment:

LAST EDIT:

Scope screen shots:
(Ch1 and Ch2 are AC coupled)

Pink is the function waveform:

Ch1-Ch2:

Ch1+Ch2