texts: How do Resistance temperature detectors (RTD) work?

texts: What is the difference between RTD and Thermocouples ?


texts: How to decide, given Voltage & Current source , absorb or deliver the power?


texts:
Are there any requirements towards user electronics working in europe stating that they need to have on/off switches? I am asking especially regarding networked devices. I have seen a lot of unmanaged ethernet network switches without power buttons (device is powered after dc plug is attached and can be turned off only by disconnecting the cable).
I wod appreciate any references.


texts: ESD from plastic enclosure to PCB in floating systems

texts:
I'm designing a battery powered device. The device will be placed in an environment where the relative humidity is below 20%. So it is essential to protect the electronics from potential ESD events. However, it's hard to identify dangers myself. It would be appreciated if someone could answer the questions below.

Possibility of ESD from enclosure to PCB
I need to use a plastic rectangular enclosure and mount my PCBs in the enclosure using nylon screws. Can ESD events occur between the inner surface of the enclosure and PCB through air? For sure charge will build up in the PCB and enclosure at some point, Then the polarity of the coppers in the PCB and the polarity of plastic enclosure, or parts of it, can be different. I wonder if  ESD can happen between them, when they are charged with different polarity.
Mounting SMD components on bottom layers of the PCBs
It seems very hard for me to place components only on the top layers of the PCBs. Would it be dangerous to place SMD components on the bottom layer? Their pads will be exposed to air, and the distance to the plastic surface will be shorter than 5mm.
Shielding PCB from ESD sources using tape
Is there a general solution to protect PCB pads from ESD? Could one use something like Kapton tape?

It would be very appreciated if one could provide useful references(technical documents addressing the ESD protection for isolated systems)

Note: It's not possible for me to change the environment. So it's not a solution to not work in such dry place, to not use a plastic enclosure, or to not have a floating ground. The problem that I have would be common in some applications, so I think this is a relevant question.


texts: How to build an external lithium battery pack for a laptop with 19V DC input?

texts:
I'm trying to figure out how to build an external battery pack for a laptop, plugging into its 19V DC input. In a previous question I learned that I probably want to go for 5 lithium cells in order to closely match the 19V input expected by my laptop. But even if such a battery pack nominally provides 18.5V, it can peak at 21V and go all the way down to 14V and below. Is it correct to assume this could potentially be problematic?

How can I build a battery pack for this scenario?


texts: A sleeping mcu in a product -sent by air to?

texts:
This might be strange, but i guess you guys electrical engineers are the only one that knows that .

Our MCU is turned on by a push button . That means he sleeps most of the time, and when pushing the button he awakes up with interrupt .

The only concerns are :

sending products that are in sleep mode, means- a little current is flow, is it safe in an airplane ? is it "professional" ? will it makes troubles in shipping? can a battery be connected to a product at all ?

2.If your products (pcb's) are sitting on the shelf for a while, that means your battery is going down, not too much , but it take some current .
Is this, again "professional" to do? are you as hardware engineers design a circuit like this to be sent do another country ?

The mcu on sleep will take about 100uA , and the battery is 500mAH .

thanks .


texts: How do I find the row and collumn sections enabled in an SRAM when the input address is th e binary equivalent of 1770 hex .

texts:
This is the actual quesion:

A 16K x 8 SRAM uses coincident decoding. Determine the row and column selection lines that are enabled when the input address is the binary equivalent of 1770(hex).

This is the answer: ROW : 112(Decimal)
                 COLLUMN: 46(Decimal)

Could someone please help me understand how they have gotten this answer?


texts: Code example for FIR/IIR filters in VHDL?

texts:
I'm trying to get started with DSP in my Spartan-3 board. I made a AC97 board with a chip from an old motherboard, and so far I got it to do ADC, multiply the samples for a number <1 (decrease volume) and then DAC.

Now I'd like to do some basic DSP stuff, like a low-pass filter, high-pass etc. But I'm really confused about numeric representation (integers? fixed point? Q0.15? Overflow or saturation?).

I just want some example code of an actual simple filter to get me started. No high-efficiency, fast, or anything like that. Just the theoretical filter implemented in VHDL.

I've been searching but I just find theoretical formulas - I get that, what I don't understand is how to process the signed 16-bit, 48KHz audio samples I'm getting from the ADC. I've been using these libraries: http://www.vhdl.org/fphdl/. If I multiply my samples by 0.5, 0.25, etc, I can hear the difference. But a larger filter gives me just noise.

Thanks.


texts: Mechanical angle, electrical angle, and Park transformation

texts:
I have a question about the electrical angle and mechanical angle of the BLDC motor.

The motor has 8 poles. We have

Electrical angle = number of pole pair * mechanical angle

This would mean that if the mechanical angle covers 45 deg, the electrical angle has spanned 360 deg. After that, should I reset my electrical angle to 0 and start counting again, or it's acceptable if the electrical angle keeps increasing?

I use the electrical angle in the Park transformation for calculations.


texts:
I'm developing an FPGA design in which a VGA display is driven. Within the top-level entity, an rgb signal contains a 12-bit vector describing the current pixel's colour.
Several shapes need to be drawn to the screen. Each shape has its own entity (circle, rect, etc.).
At the moment, each of these entites emits a mask : std_logic output which is '1' when this entity is providing a colour to the output rgb port, and '0' when the x and y co-ordinates fall outside of the shape's boundaries, and therefore no RGB output is provided.
I'm having difficulty coordinating this to avoid multiple driver issues. For example, I thought I could do the following:

Within each shape entity, use the following:
rgb_write : process(mask)
begin
   if mask = '1' then
      rgb <= some_color;
   end if;
end process;

In this way, the rgb port wouldn't have a driver when the mask is 0, allowing other entities to drive the top-level signal.
I also emit the mask output as previously mentioned, and use this in the top-level entity:
-- mask_vec is a std_logic_vector which contains all masks from all shapes

rgb_cleanup : process(mask_vec, rgb)
begin
    if (or mask_vec = '0') then -- Note that this uses VHDL08 unary or
       rgb <= (others => '0');
    end if;
end process;

The above code (should) provide a black pixel whenever the pixel is not being driven by one of the entities.
However, this doesn't work. GHDL is always reading rgb as invalid when I try to do a to_integer(unsigned(rgb)) (for example).

How do I coordinate these shapes properly? Thanks in advance.


texts:
I've placed the circuit on the breadboard and found an unexpected low-frequency noise appearing again and again. The computer microphone doesn't show this type of distortion. But my circuit is showing. Can anyone explain to me why is this happening?

I played a youtube track to test the microphone performance, but that noise distorted it (photo was taken at 390 Hz).

How do I solve this problem?


texts:
How is the trick in the following video possible?

https://www.youtube.com/watch?v=RkTvDjhImwo


texts: circuit protection during supply plug in

texts:
I am using a DB9 to provide voltage(Vcc and GND) to a board. Now, the supply is given a long cable(the length of which is not known). Now, the power supplied is DC(about 30V or so).

Now, I believ that the longer the wire, the more radiation it will leak due to the antenna like property of the cable. Now, when plugged in there might be spikes that can cause damage to the board. How can I protect my board from such spikes? Would using TVS diode help me ?

The problem is that even though the supply is 30V , it can go as low as approx 18V.
I was thinking of placing capacitors very close to the connector that can filter out any spikes or transients. What are the other precautions or design mechanisms I can take to protect my circuit from damage ?


texts: Has anyone used the IMU-3000 with an attached accelerometer?  I am creating a system which interfaces the IMU-3000 and attached ADXL345 (IMU Fusion board from SparkFun) with an Arduino board to do all the computations about a projectile in motion and output values to an LCD.  I was just looking for how to read the various axis individually since it all comes through the same pin.  Does anyone know the commands for that in Arduino?  I am very new so if I am sounding stupid please just help me understand.


texts: Don't take this the wrong way I am new to electrical stuff, so please help me in understanding my confusion. I have an extension cord with 4 sockets and it's plugged into the house mains 240V at 50/60 Hz and 16 amps. 3 sockets of the extension cord are connected to loads, one is a computer using 240V and 6 amps, the second socket is connected to the TV using 240V and 2 amps, and the third is connected to a phone charger using 240V and 0.35 amps. Now if I connect a load to the 4th socket which requires 3 amps and 240V, will it be able to draw 240 volts from the extension cord, or will it draw less voltage as there are already 3 loads utilizing the 240 v? I know that the amperage will be sufficient for it to work but will the voltage be same as 240v at the 4th socket?


texts: How to use coin cell CR2032 in parallel with a power supply?

texts:
I have a device that is powered by a coin cell battery, but occasionally they fail and I would like to run them in debug mode to find the problem. Debug mode requires more power than the coin cell can produce. Sometime I want to flash new program code on them which also requires too much power for the coin cell to handle. My batteries are soldered on; it is inconvenient to remove the battery.

Is it safe to hook up a power supply in parallel to my coin cell? If the coin cell is at 2.9V, can the power supply be at 3.1V? What are the considerations for this configurations? Does anyone have a application note or paper that covers coin cells?

I don't want to put a diode in front of my battery because that causes a constant 0.7V drop.


texts: How do you read newer HDD motors (DC/Brushless) into arduino? (like stepper motors)

texts:
We had a version of the HDDJ working with an arduino reading an old stepper motor (with 4 wires), then sending serial data to processing, using a midi library, and midiox + midiyoke. Having trouble getting reliable forward/back speed data from the newer HDD's (2 or 3 wires), I think they are brushless DC motors? anyone had any experiance with this?

Cheers,
Al


texts:
I have been doing a bit research on ceramic capacitors, as I need one for the output of my synchronous buck converter. And as its very common that ESR is not straight forwardly given in the data sheets, we have to calculate it ourselves by Dissipation Factor value given at a certain frequency (normally 120 Hz) for a certain capacitance value.

$$ESR = \dfrac{D \cdot F}{2 \pi f C}$$

For e.g if i have this ceramic capacitor I can calculate the ESR as

$$ \dfrac{0.05}{2 \pi \cdot 120 \cdot 470 \mu F} = 141m\Omega$$

(page 1 of data sheet, calculating for 470uF cap).

Now my question is, what if I am using this capacitor in my circuit at 100kHz? Its ESR should decrease right? As I think ESR should decrease with increasing the frequency. But the Dissipation factor increases with the increase in frequency as well. So how can one estimate the capacitor ESR at a high frequency? As there is no Frequency vs ESR   OR Frequency vs D.F graphical relation given in the data sheets (I have gone through almost 100s of data sheets). So is there any way by which I can estimate the ESR of this capacitor at a higher frequency of 100kHz?

Actually I will be charging my battery cell with the help of my buck converter and I need the capacitor ESR to be less than 10mOhms, because that is my Battery cell's ESR (mentioned in the data sheet), so I am trying to look for a ceramic capacitor with a lower ESR than this, for minimizing my voltage ripple at the output.

Your helpful comments would be appreciated.

Thankyou!


texts:
What is DDR software leveling ?

How it is different from DDR2 and DDR3 ?

Why it is required and important ?

Is there a hardware leveling ?

I have found some explanation here about DDR3 and a general one here but it is not clear for software guys !

There is a seed used for this how this seed is calculated ?

Generally leveling is required to ensure proper timing for read /write operation is that the only purpose??


texts: Can anyone tell me what are the units of area parameter used in ngspice?


texts: 120v variable resistor controlled by 5v?

texts: I want to do some work with automating christmas lights later this year and my friend and I think relays may be the way to go. After a little more thought, I think it would be cooler if the lights could be controlled with some type of variable resistor that is "controlled" through arduino or some other low voltage source. I'm not too familiar with the vast amount of parts out there, does anything like this exist?


texts: Adjusting overload relay for single-phase motor

texts: For an overload relay on a magnetic starter, what should the overload current be set at? I'm not sure whether this should be set to the rated running current of the motor, or an approximation of the inrush current upon starting.


texts: Merging audio lines - one channel is quieter

texts:
I'm still learning digital electronics, and analogue electronics is very much a dark art for me.  I have the circuit as shown below, the audio output stage for an 8-bit programmable sound generator.  Channels A, B and C are merged into a mono output for the LM386 amplifier to play through a small speaker, but I'm finding that Channel B is much quieter than A and C.

Everything sounds fine through the headphone socket, it's just the amp that seems to be losing Channel B.  I'm not sure what's going on, so thought I'd ask for some advice on the circuit - any help would be appreciated!


texts: STM32F103 reading value from lightsensor by I2C

texts:
I'm trying to read value from sensor GY-30 BH1750 by I2C but when I check variables in STM Studio, they don't change.

Sensor address is 0x23 when addr connected to GND

POWER_ON 0x01

RESET 0x07

BH1750_CONTINUOUS_HIGH_RES_MODE  0x10

It's my code which I try to get data :

 buffer[0] = BH1750_POWER_ON;
 buffer[1] = RESET;
 HAL_I2C_Master_Transmit(&hi2c1, SENSOR_ADDRESS << 1, buffer, 2, 100);
 buffer[0] = BH1750_CONTINUOUS_HIGH_RES_MODE;
 HAL_I2C_Master_Transmit(&hi2c1, SENSOR_ADDRESS << 1, buffer, 1, 100);
 HAL_Delay(180);
 HAL_I2C_Master_Receive(&hi2c1, SENSOR_ADDRESS << 1, buffer, 2, 100);

Docs: http://www.elechouse.com/elechouse/images/product/Digital%20light%20Sensor/bh1750fvi-e.pdf

What's wrong with code ?
Thanks for help.


texts: How can we alter a single pin of ATxMEGA128?

texts:
this might be a basic question but I did try searching for the answer before posting the question.

So, I am trying to set one of the ports to output. I used

PORTC.DIRSET = 0xFF; //Set Port C to output

Now, I have connected the enable pin of my sensor to say Pin 1. How do I turn it on? As in how to I access a particular pin of port C to turn it high?

Also How can i make it go low?

(I am using a force sensitive resistor and want the sensor to start working only when an input is received from the force sensitive resistor circuit)


texts:
Would someone knows what is the part showed on the attached picture ?

This comes from the inside of Indominus Rex toy GCT95 manufactured by Mattel. I'd like to replace it and have the beast back to life for my son.


texts:
I was going through data sheets of op amps and saw that bias currents usually add unwanted voltages due to voltages generated from the bias current flowing through the source impedances.

What exactly does the source impedance mean ?
I understand what impedance is, but since there could be a lot of circuitry before the input to the op amp, do we just use  normal laws to calculate the total resistance/impedance before it(input) ?

There also might just be a power supply providing constant DC voltage , how are we supposed to calculate the impedance of that ?


texts: Determining the Transfer Function of a Wheatstone Bridge

texts:
I am designing a Wheatstone Bridge, and would like to calculate the transfer function of the bridge input to the bridge output.

The Wheatstone Bridge is designed as follows:

Three of the resistors are identical, with the fourth being a potentiometer.

In this case the bridge input is 5V, but I'm not sure how to relate this to the bridge output.

UPDATE:  There are two voltage dividers, where:

\$V_- = 5V(potentiometer/ (potentiometer + R1))\$

\$V_+ = 5V(R1/ (R1+ R1)) = 5/2\$


texts: TVS Diodes Causing Board Failures by Failing Short, How Do I Prevent It?

texts:
I have a stepper control board with a 12v TVS diode right at the inputs (D11). I added it to the design to protect against static, and I think it's doing that just fine.

The problem is that the diodes often fail shorted and ruin the boards. This happens more often then static damage ever did, so they're actually making the reliability WORSE.

The TVS diode (D11) is a Littelfuse SMAJ12A. D10 is a S5J-E3/57T, which I added for reverse polarity protection. The input is a 12v 5A power brick with overcurrent protection.

I'm not sure exactly what's causing them to fail, but I think it's due to non-ESD events, for example I know that one of the power supplies I have in the shop will produce a 70v + spike for a microsecond or so if the connection to the load is momentarily disconnected, then reconnected (as with a loose connector).

Another common way for the diodes to fail is for a 24v supply to be connected instead of a 12v. Without the TVS diode, this just causes the regulator to run hot, but WITH the TVS diode, the board is fried instantly due to it going into conduction and subsequently failing shorted.

Are there any solid ways to protect the TVS diode? Or at least prevent it from always failing shorted and ruining the board. I've considered added a chip fuse in series with the TVS diode, but I know that will reduce the protection.

Update: I put a scope on the power line with the motors running, it's very clean with no spikes above 13v, so it's not regeneration from the steppers.

Update 2: I tried scoping the power line while toggling the power per Jon's suggestion. There's definitely some noise over 13v, but I don't know if it's enough to be a problem.

Update 3: Solved (probably). It sounds I had the wrong idea when I picked a zener voltage as close as possible to the 12v working voltage. I'll switch to a 30v TVS diode and see if that reduces the failures.


texts:
I'm developing a simple power meter using the ATM90E32 from Microchip. For now, I can read all values: frequency, power factor, voltages, apparent power, etc.

Now the issue is with the energy, I need to read and maybe store the energy.

I can't understand exactly how the energy registers work. Even the datasheet keeps me confused.  Has someone already worked with the ATM90E32?

Edit:

Datasheet: Link
Aplication Notes: Link

Edit 2:
The DataSheet refers to the Energy accumulation in a unit [ CF ] as I understand (and I'm very confused) CF = 1Kwh so in a certain period of time you read the register (clear at reading) and get the Energy represented in this CF unit the chip uses but is this true? Do I need to accumulate this value somewhere?


texts:
Why does reactive power influence the voltage? Suppose you have a (weak) power system with a large reactive load. If you suddenly disconnect the load, you would experience a peak in the voltage.

Is there a good explanation why this happens?

For those interested in why voltage level and reactive power closely related from a reliable source, here is the original paper describing the Fast Decoupled Load Flow algorithm (you need access to IEEE):

"Stott and O. Alsac, “Fast decoupled load flow” IEEE Trans. on PAS, vol. 93, no. 3, pp. 859-869, May/June 1974"

See also page 79 in this textbook by Wood / Wollenberg on books.google.

A quote from the Roger C Dugan, the author of this textbook on Electrical Power Systems:

  Reactive power (vars) is required to maintain  the voltage to deliver
  active power (watts)  through transmission lines. Motor loads and
  other loads require reactive power to convert  the flow of electrons
  into useful work. When  there is not enough reactive power, the
  voltage  sags down and it is not possible to push the  power demanded
  by loads through the lines.

I believe the edit history might be interesting for anyone wondering what the edit and all the comments are about.


texts: First-order hold interpolation in matlab

texts:
I have a sinusoidal signal x(t) sampled with period 1/fs. The result is the discrete signal x[n], where x[n]=x(t)|t=nT. Then I perform an upsampling of factor, let's say, 8 to increase the sampling frequency by a factor of 8. Here's the code in matlab syntax:

f=10e6; % signal's frequency
fs=1e9; % sampling frequency
t=0:1/fs:20/f1-1/fs; % time vector
x=sin(2*pi*f*t); % sinusoidal signal

% upsampling by a factor of 8
x1=upsample(x,8);
% filtering
filt=[1,2,1,2,1,2,1,2,1]/2; %triangular impulse response
foh=conv(x1,filt,'same');

%scale time axis
nt=0:1/(8*fs):20/f-1/(8*fs); % scaled time vector

%plot reconstructed signal
plot(nt,foh)

Now after running the above code I get the following plot as the output of the reconstructed signal, which doesn't appear to be a sinusoidal anymore,

This more looks like a predictive first-order hold than a basic one. There seems to be something wrong with my filtering scheme but don't know how to fix that to get a basic FOH response.

Thanks..


texts: What is good device for generating vibrations, offset weight motor or solenoid or some other?

texts:
I am building a vibrating device for that I am thinking to use a solenoid for vibration. The solenoid will be used such that device will be mounted in the floor and when a stick is put over solenoid, it will start vibration. That vibration needs to be felt by the person holding the stick so so that say she can count those and recognize patterns of vibration.

I come to know through responses to my another question that solenoid may be not a good choice as it is not a vibrating device. Rather an  offset weight motor may serve the purpose better. I did not know about it. I search for offset weight motor but did not find any link to that.

My question is which equipment should I choose for generating vibrations for my device? Can someone put a link of offset weight motor so that I may read about it. I also learned that  offset weight motor acts like a mobile phone vibrator. That is good for my project as I may extend the output to be read by a mobile later so it will help.


texts: What is the role of the capacitors in this circuit?

texts: What is the role of the 10uF capacitors in this circuit? I know that the 47uF capacitor acts as bypassing capacitor, but what about the 10uF ones.


texts: What happens when the Brush in a DC Motor touches two commutators

texts:
I was watching this video and realized that there is a point in time when the brushes positive and negative can be shorted as shown in the image below. And it made me curious.

For people with experience or understanding of dc motors, what exactly happens at that point in time when this short happens?


texts: SmartFusion 2 Pin Assignments using Libero

texts:
I am currently trying to find the schematic or pinout chart for a MicroSemi's SmartFusion 2. I have read all of their reference documents and release notes, but I can't find which pin is wired into the 50MHz clock.
I did find this chart, however it doesn't contain the pin for the clock.
Does anyone here regularly use the SmartFusion 2 and could attach the pinout diagram with the clock pin specified?


texts: Why does the potential difference in a quartz crystal change?

texts:
Please help me out here... If the potential difference at a mid-point between two opposite charges of the same magnitude "Q" is = 0V.. then how does the potential difference in a quartz crystal change, when it's expanding evenly on either sides of the charges?
Perhaps I may not have understood the whole concept...


texts:
I'm making a simple microcontroller based circuit to turn on a computer when certain events are triggered. I am interfacing it using the PCs soft power switch pins on the front panel header:

There are two relevant pins on this header, I'll call them SW+ and SW-. SW- shares the PCs system ground, though I'm not sure this is always the case. SW+ is, in my test system, 3.3v above ground, although I suspect this could be more or less.

In a typical computer, a NO momentary switch on the front panel shorts these two pins when the power button is pressed. I want this to instead be controlled based on a logic level signal from a microcontroller.

My first attempt at a test circuit is as follows:

I tested the polarity of my header and made sure SW+ really was the positive pin. My microcontroller was powered from USB, therefore sharing system ground, so connecting SW- and controller ground was not a problem.

The circuit worked as intended, but it's obviously not very great. I want to make this circuit as universal (not system dependent) as possible. This poses the following problems:

The polarity is not indicated - the user can not be relied on to insure a specific polarity.
The voltage is not exactly known - it's better to assume it will be somewhere between 2-12v.
The controller should be isolated - it might share the computer's ground, but this is not guaranteed.

The simplest solution that comes to mind is using a relay. I may end up doing this, but I really would like to avoid it due to reliability, size and price.

Is there any transistor based solution (essentially like a relay) meeting the criteria above?


texts: poles and zeroes, why the magnitude plot contradicts the actual definition

texts: I know that poles are the frequencies at which the response goes to infinity and zeroes are the frequencies at  which the response goes to zero but when we draw the bode plot or magnitude plot the exact opposite happens. At the poles the magnitude decreases and at the zeroes magnitude increases. What is the intuitive way to understand this ?


texts:
I'm currently learning about the operation of 6 transistor static random access memory cells and I've hit a wall in understanding exactly how the read/write
operations work. More specifically I don't get the gate transistors that control whether the cell is connect to the bit lines or not. Firstly, since the "information gates" are just single FETs, there is the problem of there being no voltage drop across them, so ultimately they don't act as gates at all. A simple solution would be to somehow connect the bit lines to ground (which seems like a terribly inefficient way to fix this problem since that would create a constant current).
How do people solve this? How do you read and write data onto SRAM cells efficiently and reliably?

For a visual aid I've created an SRAM cell in a simulator to show the problem. The bit lines are the wires on the very right and left. As you can see, one of the wires has voltage while the other does not. Ideally they would both have no voltage until I activated the word line (the wire on top) which would open up the transistor "gates". Essentially the gate transistors are useless as for the moment. How do I get them to work?

SRAM cell in circuit simulator:


texts: Shortcircuited motorcycle alternator leads to RPM proportional losses?

texts:
I've had this puzzle for a couple of years but never been able to figure it out. Regulator manufacturers for typical 3-phase alternators provide the 14.4V by 'shorting' the phases. Obviously this comes with great losses but I cannot understand why this design is still in use.
My electromagnetic theory is basic but I assume that somehow after a certain angular velocity back emf induces positive torque into the rotor which lessens the braking effect. I did intend to test that on a bench but I assume some of you at least have tried it or know the theory behind it. Is there a graph somewhere that will show braking torque vs RPMs?
This could also apply to wind generators.

Edit:  The stator is on the bike, contains several wound inductors connected into a 3-phase delta configuration. The flywheel connected to the engine/crankshaft has permanent magnets. The configurations I've seen had magnets inside the flywheel, which would then spin outside of the wound stator. Three wires from the stator go into the 'black box', another (usually) two wires come out.

The rectifier part is a standard 6-diode bridge. Regulator part is a zener-like part that triggers the shunt to all three (incoming) phases simultaneously to the ground after the bridge.
Shorting is done via thyristor-like parts, so the zener triggers the gate for the SCRs.
Typical generator power is about 400W@9000rpm, typical regulator/rectifier rating is about 20A. They get really hot, especially when no consumers are turned on. I suspect also consumers (headlights) also play a role in smoothing the resulting waveform.


texts:
After learning some basics of Phase Locked Loop, I came to a conclusion that it may be defined as a circuit, which in its most basic form, tries to lock(equate) both the phase and the  frequency. But after searching online for a definition, I could not find any definition which resembles mine (explicitly saying that a PLL locks frequency and phase). Wikipedia page also just says

"A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is related to the phase of an input signal."

It doesn't directly say anything about frequency and phase of input and the output being equal. Am I suggesting a wrong general definition? Where am I wrong?


texts: What is the current return path in this condition

texts:
When there is a reference plane the return current will be on it and if that plane is continuous then it is perfect.

However i studied board designs like arduino due etc. They dont have any dedicated ground or vcc plane. It is just 2 layer pcb so they just draw traces for every connection. So in this condition the routing is a mess and what is the return currents path? I mean if you say it will follow the lowest impedance. What is it where is it. For example can the lowest impedance road be another signals trace. If so how they manage to make this board work there is tens of traces to worry.


texts: Calculating the dc motor parameters from motor specifications

texts: I am struggling with series dc motor modelling to study the effect of feedback control system on its performance, is there any method to calculate the parameters i.e. terminal inductance and resistance, inertia and damping constants based on this dc motor specs sheet?


texts: 1-10V fluorescent lighting digital control

texts:
I have a number of fluorescent lights installed that use 1-10V dimming. Note that this is not the same as 0-10V dimming as used in older theatre equipment.

The control gear for the lights outputs 10V on the two control wires. When open circuit, the light is at 100%. When shorted, the light is at ~10% (minimum level). Dimmer controls for this kind of lighting are passive devices, only connecting to the two connections from the fixture.

I want to be able to control this lighting digitally. I'm not too fussed with the protocol, as I can always program a µC to do protocol conversion. I have found commercially available devices such as this DMX 1-10V Converter, which will convert DMX/DALI etc to 1-10V, but they are rather expensive, and building my own would be much more fun.

Has anyone any experience with this control protocol? Or can you offer any pointers to where to get started?


texts: How to build an Audio Spectrum Analyzer/Sensor?

texts:
I am designing a smart RGB LED strip driver based on a Raspberry Pi and an Ardunio. The Ardunio would controll the LED strip, and other LEDs connected to a shift register, while the RPi would manage inputs and a display and would be the I2C master of the Ardunio.

One of the planned features is a kind of 'disco light': the RGB strip would change color based on the Spectral/Frequency input (i.e. blue brightness ~ bass, green ~ treble, red ~ high). There are pretty obivious solutions for this using transistors/mosfets, but I want to have software controll over the colors. What I would need is some kind of audio spectrum sensor:

Option 1: a circuit or microchip that somehow analyzes/interacts with the audio input (without distorting it, of course), and outputs some (preferably 3-5) analog voltage signal for different frequency ranges regarding to their loudness

Option 2: An IC designed/usable for this purpose: it analyzes the spektrum of the input audio and sends the bandwidth data to the Ardunio by SPI.

Option 3: A way to use the Atmega328 itself for the analyzation. The process should not be laggy or 'processor-expensive' since I have other things to do with the Ardunio.

The problem is with me; I have no experience with analog circuits, and even less with audio circuits, and honestly I have no idea how to solve this. Good guy Google did not help me out this time either, so I ask for your help.

Do you know any chip or (considering my near-zero analog experience, preferably as simple as possible) circuit that fits to one of these descriptions?

There is an overall plan of the 'disco part':


texts: Circuit Options and Parts for low-cost price display

texts:
I first want to say that this project is for a charity auction that happens a couple times a year and we would like to remove all paper from this process since the paper requires 7 people to handle and deal with and is way to frantic!

There are around 100 electronic displays we need to make for our next auction. We want it to be as low cost as possible. Right now we have settled on a 4-digit 7-segment LED display with an ATTiny chip. This gives us 4 digits and since the auction is by whole dollar amounts we won't reach anything above $9999 though above $999 will happen. This just straight cost (no enclosures, solder, boards and such) puts us around $4. Adding a battery case or even a wireless chip drives the cost up a bunch.

So my question is, what tricks can we do to drive the cost of this project down? So far the best we have come up with is to chain multiple displays together and drive it off one wireless chip. Any other tricks anyone can think of?


texts: Can a small gauge wire be used in a fractal antenna?

texts:
I want to make a fractal antenna to replace an old set of rabbit ears. All the guides I've seen have used a thicker wire (metal coat hangers seem popular). While I don't have any hangers, I do have an absurd amount of cat-5 that I have been harvesting whenever I need wire. If I pull a length of wire out, would the thinness of the wire restrict its ability to pickup a good signal? Thanks and pardon the relative low bar on this question.

Note: I will be untwisting them and stripping them at the appropriate junctions. I also have a 300->75ohm transformer already.


texts:
I am trying to mimick a sensor on a car that supplies 0.7 V to the car’s computer. So what I would like is a circuit diagram to build a unit that would use the 11  to 14 V  input from the car battery and supply a constant  0.7 V output to the cars ECU. I would like to be able to adjust the oUtput between 0.3V and 0.8V.
I do not know what current the ECU would draw at .7V from this unit. The idea is just that it must give a constant voltage signal to the ECU.Any help would be appreciated. Thank you


texts: Are 3 single phases equivalent to a single 3 phase system?

texts:
I am not an electrical engineer (I did work as an automation technologist a long time ago, but please forgive me my electricity is very rusty). I've been given some data that was measured from a 3-phase delta system using current transformers and voltage leads on a pump system.

The person who gave me it claims that the software for the logger was configured incorrectly, and that the power consumed is half of what it's reading. He insists that the correct way to calculate the power in this situation is to use the averages of the 3 phases (\$V_{avg} \times I_{avg} \times pf_{avg} \times \sqrt{3}\$).

The meter however is using the summation of the three individual phase powers (\$V_1 \times I_1 \times pf_1 + ... \$).

My question is: should these values not come out to be the same in the end?
Should we not be able to calculate the power using both methods?

ETA: Here is a sample row of the metering data I have been given, to try and make what I'm working with more clear:

Each of the 3 real channels are measuring a phase voltage, current and power factor - so my approach was to just calculate power using each phase measurement and summing them (much like the meter did). This should remain the same regardless of the way the system is wired right? (same calculation for Wye / Delta?)


texts: Virtual variable pool between microcontroller and PC over serial USB

texts:
I will be starting a project where we use an embedded microcontroller to control a research set-up. We want to control it from a PC, using a USB connection, where we monitor the current state and can tune a wide variety of parameters.
I imagine this as a virtual variable pool: the microcontroller and PC can read from and write to the same variables.
This sounds like a very general situation, so I was wondering, do current solutions exist for such a variable pool? Maybe there already is a library of some kind?
I realise sending bytes back and forward over serial USB is not difficult. But making a flexible protocol to selectively write to variables would already be a lot harder. So anything pre-made would be great.
I'm largely inspired by ADS variables in TwinCAT. The TwinCAT hosts effectively runs a variables server, that other programs can read from/write to.


texts:
Not sure if this is the right place to ask but this is a homework question.

  Consider a base station in a cellular network. The base station has the resources to handle 7 calls at the same time. The call inter-arrival times and the durations of calls are both exponentially distributed. A base station may get calls due to handoffs (with rate \$\lambda_H\$ or from users in its own coverage area (with rate \$\lambda_O\$. Assume a priority based handoff scheme where 2 of the servers are kept aside only for handover calls.

Consider the situation where $$\lambda_H = 0$$ and average call length is 3 minutes.

My solution

Form up the queue system and solving this.

$$\mu = \frac{1}{3}$$

$$P_o = \left[\sum_{i=0}^{n=5} {\left(\frac{\lambda_H + \lambda _O}{\mu}\right)}^i \frac{1}{i!} + \sum_{i=6}^{n=7} {\left(\frac{\lambda_H}{\mu}\right)}^i \frac{1}{5!} \frac{1}{(5^{i-5})}\right]^{-1}$$

$$\sum_{i=0}^{n=7} P_i = 1$$

However, I am stuck since it goes up to a power of 5.


texts:
Would the final boolean expression to the circuit be right? Or do I have to multiply the brackets b(c*d)' out to bc' + bd'

simulate this circuit – Schematic created using CircuitLab

Edit: My new idea would be:

(a'+b)*(bc'+bd') = a'bc'+a'bd'+bbc' + bbd' = a'bc' + a'bd' + bc' + bd'


texts: In a RCL circuit; where V_C > V_L is the phasor angle leading or lagging?

texts: Is this example correct in stating that the phasor angle is leading by 38.323deg?


texts: Need help with Relaxation Oscillator with Parasitic Capacitance

texts:
I am trying to build a capacitance meter using a simple relaxation oscillator with a fixed resistor R in series with a capacitor to be measured C. I am applying the formula where Freq=frequency and K is a constant.:

                             C = K / ( R * Freq )

I have however noticed parasitic capacitance in the circuit that affects the measured capacitance and frequency. I am therefore looking for a correct formula that takes into consideration of 2 extra parasitic phantom capacitors, C1 which is in parallel with R and C2 which is in parallel with C. The resulting formula should be in the form of:

                             C = f( R, C1, C2, K, Freq)

Looking forward to any assistance with this problem.


texts: Eagle's PCB ratsnest command reports 3 airwires, but they are not visible

texts:
I am working on preamp input selector PCB in Eagle and I've run RATSNEST command for displaying airwires:

There are no airwires left as can be seen from screenshot, however, particular command reports to me in status bar: Ratsnest: 3 airwires

Why and if so, where are they so I connect them?


texts: Controlling the digital input of a frequency inverter with an Arduino

texts:
I am starting a project in which I want to control the digital inputs of a frequency inverter with an Arduino.
Here's the data sheet.
The pins take in a maximum voltage of 24V and 100mA. The input pins have a input resistance of 4.7kOhms.
I am not an expert in electronics, but my guess is that since the Arduino has a working voltage of 5V, I'd probably need something in between the Arduino and the frequency inverter.
What is required to interface the two?


texts: How to quickly distinguish DO-35 Switching diodes and Zener diodes

texts:
I do not have a magnifier glass handy. And many a times I saw Diode Numbers get wiped out after reusing the diodes. Is there an easy way to distinguish between DO-35 packaged Switching diodes like the very popular 1N4148 and 0.5Watt Zener diodes using multimeter?

Even a simple circuit would also work for me. It would be awesome to keep the circuit handy as a tester and use it everytime I need.


texts:
I've currently got a STM32F777VI microcontroller working with UART receive working through DMA. The problem starts when I try to receive data from 2 UART peripherals using DMA. According to the datasheet it should be possible to have 2 stream concurrently running on 1 DMA as long as you don't have channel overlap, which I checked and don't have.

When I try this only 1 of the UART peripheral work and the other call doesn't  do anything even though the second call to HAL_UART_Receive_DMA(), with the respective buffer and uart handler, returns HAL_OK

What am I missing here?

edit: Now I'm getting HAL_ERROR on the second call if I let the debugger run instead of going through step by step, which makes it hard to debug.


texts: The reflected impedance from secondary muti-windings

texts:
If a transformer with only one secondary winding, the reflected impedance from the secondary winding is

$$
Z_{p,eff}=(\frac{N_{p}}{N_{s}})^{2} \times Z_{s}
$$

This is a well known equation. But what if there are two secondary windings with turns \$N_{s1}\$ and \$N_{s2}\$ each? The simplified circuit is as below (Note: I put 4 meters in the circuit, and denote the readings beside them):

What's the reflected impedance to the primary?


texts: I have seen examples of repurposing cd-r/w or dvd-r/w lasers to use for laser pointers or even 'burning' lasers. I have a project in mind, and I am hoping to make holes in a pingpong ball that range from .3 mm to 5 mm in size. Could those type of lasers do this kind of task? I reailze that there are many other problems to potentially solve (lens, distance, duration of pulse, etc.). If not, what other kinds of lasers (type, price) would be capable?


texts: AC Power measureless using MCU, calculations problems

texts:
I'm done from the hardware design sensing the current & the voltage levels using my MCU (AVR) & some circuitry

Beside I wrote the firmware to handle the ADC data & so on
But I'm, having some troubles in some points :

I need to calculate instantaneous power

The values I get from ADCs are X & Y as an example,
so multiplying them inst. power = X*Y

is this right ??

The second problem is calculating the average power which is the first part of the above equation \$\frac{1}{2}V_M I_M  cos(\Theta_V - \Theta_I)\$, How to obtain it from this ??

The last question is : how to calculate the power consumption KWH ??
is there also any other calculations I need to handle ?

Note : I'm measuring AC power , 220 ~240 V , 50 or 60 HZ


texts: What is the best connector for this RF 434MHz transmitter module?

texts:
I have a few of these cheap RF 434MHz transmitter modules (see image below, on the left) that I want to use with my PCBs, but I don't want to solder them directly to the boards. I'd like to attach them to the PCBs using a sort of female conector. I've tried to use some female headers (image also below, on the right) but the RF module leads seem to be too thin to make a good connection.

What is the best connector for those RF modules?


texts: Ground cable was ripped from the power cord of most expensive oscilloscope in the lab . Neutral and line cables are stil there . Do you think this is done on purpose ? if so , why ?


texts: Should I attempt to repair this mouse damaged due to power surge?

texts:
I have a mouse that no longer works after I unplugged and replugged in my computer at the mains (something I rarely do).

My only guess is that the mouse is designed badly and experienced some form of power surge. When I plug it in, I get a momentary flash of light from it's LED (which is meant to remain constant), though it is recognized as a mouse via the computer, however no function on the mouse works.

Could this be due to a passive component or voltage regulator being damaged? If so I may be able to repair it, though if it is a programmed chip that's damaged I realize I have no chance of repair.

This is (was) my only working good mouse and I can't get it replaced til next week, hence I'm willing to take a risk here. The mouse is a zowie EC2A.

Any help is appreciated!


texts:
I'm making software UART (TTL levels) on ATtiny85. Need I connect current-limiting resistor to output (TX) port? If "yes", what value should I use?

I plan to connect my device to a UART-USB converter (on PL2303, FT232, etc.).


texts: In an ADC, Does UART baud rate affect signal transmission even if they are stored and retrieved from memory?

texts:
If I'm using a NUCLEO-F401RE with ADC throughput rate greater than 2 MSPS and storing the value in an array/memory, will the UART baud rate affect transmission of the signals from memory? How are they related?
The ADC resolution is 12 bit. The data format is 1 startbit,8 databits & 1 stopbit.
I want a 200 kHz input signal sampled at 2 MSPS & transmitted through UART. Is it possible, if not why?


texts: Design a relay driver from TTL input with common parts

texts:
I would like to drive a pneumatic relay from a TTL GPIO source, the TTL may be 0-3.3v or 0-5v
I would like supply and cut 12v to the relay to control the air.
I have a concept of what i'm trying to do in the circuit but my electronic design skills have not been used i a long time.
I'm happy for other suggestions e.g. MOSFET etc.
I would like use common parts available from Jaycar to solder on to veroboard
The datasheet for the relay says 16W (27VA) but I think its actually much less because I have driven 2 relays with a single 15W power supply with no problems.
Can someone provide me with a layout that can do such a thing and can work even if the load is much smaller e.g. 0.1W for example.


texts: How to write a simple feedback loop in difference equation?

texts:
I know how to write a simple close loop transfer function which is
http://en.wikipedia.org/wiki/Control_theory

Now I need to do it in difference equation form, like the equation in http://en.wikipedia.org/wiki/Infinite_impulse_response

How should I start?


texts: Need to hack joystick so I can simulate its input from raspberry pi

texts: I need to trigger a joystick from a raspberry pi. What I mean is, I want to be able to solder to a gamecube controller's board and trigger the input from a raspberry pi. I have little to no experience with electrical work. From what I understand, joysticks are just 2 potentiometers. Is there any way I can replicate the output of the joystick so I can simulate and trick the gamecube controller into registering joystick movements?


texts: Mesh analysis with common voltage source?

texts: What happens if I have a dependent voltage source common between two meshes? Do I need to form a supermesh or is it okay the way I solved it?


texts: Using a microcomputer in the drive circuit of a piezo buzzer

texts:
I am interested in the use of a microcomputer in a drive circuit for an external drive piezo buzzer.
I was reading the FAQ page on the website of a piezo buzzer manufacturer

http://www.murata.com/products/sound/faq/piezo_sound/index.html#q01

Under the heading "Please give me an example of the drive circuit for a Piezoelectric Sounder or a Piezoelectric Diaphragm (External Drive Type)." they said "Examples of typical drive circuits are broadly divided into case 1 where a transistor circuit is used and case 2 where the product is driven directly from a microcomputer." and gave the following image as an example.

I am a novice with electrical engineering and I am trying to understand exactly what components are needed in this external drive piezo buzzer drive circuit. The supplementary comments for this circuit diagram suggested people "consider connecting a Zener diode in parallel with the piezoelectric sound component and Rp if necessary."
Based on this, my understanding is that the necessary components of this drive circuit are - the microcomputer,
the diode,
the resistor (Rp),
the buzzer, and
a power source.

Is this correct? Is it possible to build a drive circuit for a piezo buzzer with only these components, or do I something else?


texts: Stepping down 48V (from power over Ethernet) to 5V

texts:
I'd like to use power over Ethernet to power an ATMega328 microcontroller at 5V, however PoE operates at around 48V for commercial PoE switches. How can I drop the voltage from 48V to 5V efficiently?

I've looked at voltage regulators and step down converters but I'm unsure if they are suitable. The microcontroller will be using less than 500mA.


texts: LTSpice calculates 1.#INF for operating point

texts:
I calculated on paper using mesh analysis that I(V1) should be 0.716A
Why does LT-Spice give such a weird result?


texts: Negating a number in VHDL using least logic

texts:
I want to do something like this:

variable a, b (both signed)
variable error (signed also)

if (a is positive)
    b = error
else
    b = -error

So far I have something like this:

if (a(a'high) = '0') then
    b <= error;
else
    b <= -1 * error;
end if;

But this doesn't work because the multiplication makes the RHS a larger width.

What is the best way to attack this? I could write a function to do a 2's complement negation and use this, but I'm also rather worried about the effect on timing requirements.


texts: Understanding STM32 datasheet regarding decoupling capacitors

texts:
I'm trying to understand what ST recommends for decoupling caps for STM32F030CC.

The diagram in the datasheet shows "2x100 nF" caps on the Vdd/Vss pairs. Does this mean 2 parallel 100nF caps per Vdd/Vss pair? Or are they referring to the total number of 100nF caps needed, i.e. if there are 2 Vdd/Vss pairs then it's 1 100nF cap per Vdd/Vss pair, for a total of 2 100nF caps?

STM32F030 datasheet


texts:
I was studying this circuit which is for a ±100V 3A pulse and noticed these 0-ohm resistors. As far as I knew, the use of these resistors was usually to pass over other traces considering a low current.
I am going to attach only a fragment of the schematic, the complete datasheet can be found in this link.


texts: Current-to-voltage opamp in DAC application: snubber network between inputs

texts:
In transimpedance (or current-to-voltage) opamp application for DAC, it is reccomended to put at the opamp inputs a capacitor (together with a snubber RC network through the feedback resistor), in order to shunt high-frequency energy to ground and prevent the opamp from going into slew-limiting.
Check for example AD797 datasheet, fig 54.
Datasheet - https://www.analog.com/media/en/technical-documentation/data-sheets/AD797.pdf

The purpose should be to absorb the HF energy of the DAC's current steps and avoid transient intermodulation (TIM) issues.

What about having, instead, at opamp inputs, a damped RC capacitor in order to prevent the full capacitative load for the DAC, and possible ringing at its output?
(In effect I don't know the DAC output current circuitry and stability, hence I cannot simulate the benefits, if any)

simulate this circuit – Schematic created using CircuitLab

)


texts: Which material is used in flex PCB circuits ?

texts:
We are planning to use flexible PCB circuit in our application. Can anyone please suggest the material used in flexible PCBs ? We are looking for the flex PCB material similar to the one used in Olympus Stylus camera. I am attaching the image for your reference.

we are looking for the material which does not break on bending sharply.

Please help me in this regard.


texts:
I am going to design a high speed digital design including an FPGA and GSPS A/D interfaced with multi-gigabit/s serial ports. But I have found the impedance matching problem a little confusing, My questions are:

1-In a serial port (assume gbps or LVDS), is the impedance matched by using series termination resistors or by tuning the traces themselves to suitable width/distance?

2-I have found tools that calculate the impedance of a trace on a PCB. As I know the impedance of a trace should depend on its length. Why impedance is irrelevant to the length of a trace in these tools?

3-Could you please led light on what situation in general we should use resistors and on what situations the traces make the desired impedance?

Thanks


texts: Logic level converter with voltage selector

texts:
I want to use an ADG3304 logic converter. I know that this chip is bidirectional.

I have designed a schematic of this solution. I want to switch between two voltage levels.

My questions are:

does it matter where I have Master and Slave devices (I know it is bidirectional. Just want to make sure)?
Will it work with equal values of VCCa and VCCb?


texts: Simple USB powered PIR sensor with LED attached to it (no arduino)

texts:
I'm new here and I'm re-new in electronic hence why I'm seeking for some help. Last time I touched a breadboard with a transistor was 10 years ago.

So, here's my problem and the problem to the solution to try to fix the first one. I have purchased a PIR sensor from ebay. On a breadboard, I connected the sensor to a single LED and I saw that the voltage was low (1.75V circa). Note: I'm powering the circuit with a USB cable, so the input is about 5V.

Now, I thought that the PIR was just giving me that kind of output and I thought of a simple solution: I connected the PIR's output to the base of a 2N3906 transistor. The collector is directly connected to the source (5V) and between the emitter and the ground I have the load which it the LED. Nothing, same issue. The output's pretty low as before.

Any suggestion? Is it because, perhaps, the PIR is drawing too much to itself that I haven't got much left for the LED (through the transistor)?

EDIT:
I'm adding the schematic I've followed. Also, the PIR sensor model I'm using is HC-SR501 (Ebay PIR Sensor HC-SR501)

simulate this circuit – Schematic created using CircuitLab

Cheers :)


texts:
I need help in selecting proper Regulator for regulator IC for exiting hall effect sensor.Sensor exitation voltgae is +12 to -12 v . Usually i use 7812 1A for exite +12v , I would like to know is there any IC aailable which produce -12v with DIP package. Input voltage 24v.

I thought of using inverting amplifier circuit to produce -12v,I am not sure how much current can provide after conversion.

And out put of sensor mentioned as 25mA. How i can convert 0~5v range for arduino analog out. Since sensor output is current How could i convert it to 0~5v range.


texts: Deformation of Heated Transmission Cable in a Conduit

texts:
Say I have 2000' feet of single phase XLPE cable with a 4" outer diameter in a 6" conduit, for simplicity, assume the conduit's inner diameter is 6".  Also assume the cable is pinned at both ends and isn't free to expand except into the residual space of the conduit.  Further, assume the conduit is rigid but the cable isn't.  I can figure the expansion and the strain, that's no big deal, my problem is understanding the math of cable deformation inside the conduit.  Since the cable will be pinned, it will deform.  I assume that the deformations will take some sigmoidal shape inside the conduit (this remains to be proven), which we can assume will not deform.  I'd like to know the math of solving a problem like this because I've been tasked with writing a paper in which this situation exists. Also, I apologize if this is in the wrong forum as I'm not sure exactly what forum it should be in from the list I looked at.  Further, my search: "cable thermal expansion in a conduit" "Your search returned no matches."
Edit: the current carrying cross sectional area is about 2.5 square inches, or 1600mm^2, which gives a slenderness ratio just over 9000.
Edit2: Some re-wording of the question to eliminate potentially confusing terms.


texts:
I'm working on a project that involves this LCD  for a PCB.

From the drawing, I can easily tell how to connect the pins.  But I am not sure how to tell from the drawing how the display should be mounted.  I've heard of other displays that will have little arms or bars you can solder down.  Not sure what the appropriate way would be to go for this display.

What would be the best way to attach this LCD to a PCB?


texts: Facing some questions regarding my energy meter project

texts:
I am working on my minor project in college and am facing a dilemma/problem with it.

Project Description:
I am working with an energy meter and am trying to make it smart (in the same way as many exist today). I want to extract data from the meter, collect it through a board such as Raspberry Pi/Intel Edison or using any other microcontroller. There are other things to be done with this data, but I face the problem with extraction of data from the meter.

There are two types of energy meter that I was able to find for this project:

Use the conventional ones with no port connectivity like the one below. These are very cheap, like US$5. Only voltage and energy consumption is displayed.

Then, there are others which have dedicated ports for communication using RS-485/RS-232 or may be SPI. These are expensive, but they give all sorts of data and can easily be communicated with to extract the data.

For example,

Now, I demand in my project that it should be feasible. There is no point in using a US$20-US$25 energy meter. I would love to know in what way we can take the data from the conventional energy meters which are not having any dedicated ports for this purpose. Do we need to make any external hardware to do so or if nothing, then are there any energy meters available which have the connectivity port and are cheap as well?


texts: what does "ports can be registered" mean? For circuit design

texts:
I have a homework. I must design a circuit that makes addition with signed and unsigned numbers. I will use registers. I need two output ports. It says "8-bit output ports (2 ports: one for unsigned output and one for signed output) (Ports can be ' registered‘.)
" I don't understand what he means by saying "ports can be registered". I am using max plus 2 for circuit design.


texts:
i do need to replace a diode that fell off / got lost on a circuit board. I do have an identical element that i used to take pictures.
The diode in question is the one on the right, marked "F4":

The size is about 1mm from left to right.
I measure a voltage drop of 0.26v from right to left, so i figure it's a Schottky Diode. However as the diode is soldered onto the board, i know the measurements need to be taken with a grain of salt.
Looking for identification of the "F4" i find mostly Zener diodes though.
If anyone could point me in the direction, this would be much appreciated. Ideally in a way that helps me a place where i can order replacement.
To summarize my question: I need to understand what diode the "f4" one is, so i can buy a replacement for it.
Thanks so much in advance!


texts: WS2812b LEDs intermittently do not respond to data signal

texts:
I have wired up permanent holiday LEDs on the front of my home, using a 5V 60A power supply and several strips of WS2812b's (generic Neopixels), controlled by a Wemos D1 mini.

The Wemos is powered via the 5V pin, and I'm using a logic level shifter to bring the 3V ESP8266 data output up to 5V for the pixels.  I have a 330 ohm resistor at the end of the data line closest to the pixels and a 1000 uf capacitor across the power leads, per the Adafruit best practices guide for Neopixels (https://learn.adafruit.com/adafruit-neopixel-uberguide/best-practices).

The power supply is switched by a Sonoff Basic, so the Sonoff basically acts as a "main" for both the LEDs and the Wemos.

However, when I turn on the Sonoff and the whole system powers up, I occasionally experience one or a few of these:

Randomly colored LEDs down the strip
Only the first few LEDs in the strip running the sequences I've coded
Nothing but the first LED lit at a random color

Sometimes, it powers up and works great.

However, all works fine every time if I put a manual switch on the 5V line of the Neopixels, power up the system via the Sonoff (thus powering only the Wemos), then flip the manual switch to on shortly after the Wemos is powered up.

I understand that interference due to a floating data line is to be expected...

Any ideas what might be causing this?  I'd love to just be able to power on and off the whole thing with the Sonoff and not have to worry about the manual switch.

Could the data line be floating and the pixels somehow start up in a strange state such that they won't respond after the Wemos runs its setup code and initializes the LEDs?

I'm at a loss as to what to try next.  I built a similar setup for my neighbor, minus the Sonoff (he just manually plugs it in), the data line resistor, and some slightly different code, and his worked consistently throughout the holidays.

Any ideas on what to try next would be welcome!

EDIT: Every single time I power the setup in the evenings, it works great.  But when I try to power it up during the day, it usually (90% of the time) doesn't work.  I wanted to wait a few days to test this to be sure - and it's been perfectly consistent.  I don't change anything with the circuit between the morning and the evening either.  This is what makes it so hard to debug!


texts: What's the purpose of these copper coils with resistors inside them in A Yamaha RX-V396RDS amplifier?

texts:
This is an bit of an overly specific question, but I'm curious about the purpose of these coils inside a Yamaha RX-V396RDS amplifier and wondered if anyone could explain what they're for. They appear on PCB Main 1. Also, would having the resistor inside the coil touching the inside of the coil be likely to cause a channel to not work?

Background to the question: the front right output of the amp has been behaving a littler weirdly for a while, mostly being slightly quieter and less clear than the left, but I've lived with it. This evening I noticed that it had completely cut out, so went delving inside the amp to see if I could spot any loose connections or burnt out components. Nothing looked obviously out of place or broken, but I noticed that on one of the large boards connected to the output board the resistor in one of the copper coils was touching the inside of the coil.

I'm no expert, but I assumed that having two components directly touching like that probably wasn't ideal, so I carefully moved it to be more central. Having done that I thought I'd test it out and was surprised to find that the front right speaker was back. I tried to google to find an answer and looked at the schematics, but have no idea of what I did actually fixed things, or if unplugging the amp for the first time in a while may have reset something that had tripped or otherwise gone wonky.


texts: How do coaxial cables carry information that a TV can intercept and display?

texts:
Is there a specification for this? Like, say, at the backside of a cable box there exists a singular coaxial cable that is meant to be plugged directly in the back of the TV.

The TV must be set to a certain "mode" somehow ... I want to know the basic understanding of how the cable box sends video/audio signals through the wire, under what terms/specifications it does so, and how the TV "knows" what to do from there on.

This is a little vague, I know, but any basic answer regarding this will be appreciated.

I basically want to know how "picture data" and "sound data" get carried through that wire, and under what basic conditions this works(hobbyist engineer who is avid on learning all of this stuff, and implementing it).

I surmised that maybe the cable's video/audio circuit connects or transfers video/audio data to a specific form for the coaxial wire, and the TV can intercept and render that somehow? I don't know, this is why I ask, and this is an engineering site!

Thanks in advance for any help!


texts:
I'm repairing some instrumentation equipment and I've come across a filter I do not fully understand. It seems to be a band pass filter and the only documentation that came with this device was an old handwritten note on the filter break frequencies and gain. I have copied this as neatly as I can and attached it below.

As you can see, there is no transfer function derivation, and only a graph showing which components set gains and break frequencies. I have simulated this in Spice and it seems to really obey those equations.

As I have not come across this type of filter before I set out to understand it better by deriving the transfer function and those equations as shown on the graph above myself.

I (believe) I have managed to derive the TF (attached below) but now I'm stuck on how to proceed and derive the equations as shown on the graph above.

My question is how to proceed with deriving the filter gains and break frequencies? Any tool I can use to help me? Does anyone know what topology/kind of filter this would be classified as? I have not found anything on the Internet of this topology but maybe my search terms are wrong.


texts:
I have created a simple circuit consisting of a 4017 ic, a tact switch, and arduino. The arduino is just for debouncing purposes. For some reason i have to double press the switch for the input to go through.

int button = 2;
int CLK = 3;

volatile boolean lastbutton = LOW;
volatile boolean currentbutton = LOW;
volatile boolean CLKlvl = LOW;

void setup() {
  pinMode(button, INPUT);
  pinMode(CLK, OUTPUT);

}

void loop() {
  currentbutton = debounce(lastbutton);
  if (lastbutton == LOW && currentbutton == HIGH){
    CLKlvl = !CLKlvl;
  }
  lastbutton = currentbutton;

  digitalWrite(CLK, CLKlvl);

}

 boolean debounce(boolean last){
 boolean current = digitalRead(button);
 if (last != current){
   delay(5);
   current = digitalRead(button);
 }
 return current ;
}


texts:
I'm trying to run my first circuit with a stm32 microcontroller. For debug reasons I soldered a minimum setup.
-No external crystal
-Only capacitors
I connect SWD Debug:
-NRST
-SWDIO
-SWCLK
-Power 3.3V
-GND
However I'm still cannot connect to the board... Is the crystal mandatory to run a program?
STM32F446RETx Datasheet

UPDATE, simplified version of PCB


texts:
I am using an STM32F103C8T6, STM32CubeIDE with HAL.

During accessing an LCD (1602), with I2C, I get a hard fault.

I try to debug it, but somehow I don't see the stack. See the following screenshot:

The breakpoint happens inside the stm32f1xx_hal_i2c, in this code (==> is break point):

static HAL_StatusTypeDef I2C_WaitOnFlagUntilTimeout(I2C_HandleTypeDef *hi2c, uint32_t Flag, FlagStatus Status, uint32_t Timeout, uint32_t Tickstart)
{
  /* Wait until flag is set */
  ==> while (__HAL_I2C_GET_FLAG(hi2c, Flag) == Status)
  {
    /* Check for the Timeout */
    if (Timeout != HAL_MAX_DELAY)
    {
      if (((HAL_GetTick() - Tickstart) > Timeout) || (Timeout == 0U))
      {
        hi2c->PreviousState     = I2C_STATE_NONE;
        hi2c->State             = HAL_I2C_STATE_READY;
        hi2c->Mode              = HAL_I2C_MODE_NONE;
        hi2c->ErrorCode         |= HAL_I2C_ERROR_TIMEOUT;

        /* Process Unlocked */
        __HAL_UNLOCK(hi2c);

        ==> return HAL_ERROR;
      }
    }
  }
  return HAL_OK;
}

This function is called from within many functions inside the same file.

The hard fault occurs after return HAL_ERROR in the same function, than the next function in the 'while' loop, and when I jump INTO the while (so calling __HAL_I2C_GET_FLAG). During the call to that last function, the following stack is shown:

How can I debug what's happening exactly in between the call and the hard fault? Or even better, does anybody have a reason how such hard fault can happen in an STM library inside HAL?


texts:
I need to tether a TO-92 package IC to a PCB - as shown in figure below. The cable length would be less than 50mm.

Questions:

How can I achieve CONN1 - i.e, attaching a cable (comprising of at
least 3 wires, for the 3 pins of the TO-92 IC) to the PCB.
How can I achieve CONN2 - i.e., attaching the cable to the TO-92 IC when the IC is not on any firm surface.


texts: Need circuit to permit the lowest frequency of two input signals and stop the other one (audio)

texts:
I am working on a paraphonic signal processor which shifts the pitch of an incoming note down by a full octave. It's a relatively simple principle which I know well (Flip Flop divide down frequency) but the input of this is going to be presented with two discrete input sources - i.e. two different notes. I need to allow the lowest note to pass, and the higher one to be gated/not permitted to pass into the circuit.
So basically, if two notes are played - an E at 83Hz and an A at 110Hz, I need to allow the 83Hz signal to pass, and the 110Hz to not. Conversely, if only the 110Hz is present, this signal needs to pass (and the other one to be muted to prevent interruption - though this is optional, and not quite so important).
I'm hoping to keep the component count low for this so I would appreciate the simplest principle application here, but any pointers would be appreciated.


texts: Running high current load with 2 5-cell LiPo batteries in parallel

texts:
From various other questions on this site, I have read that running 2 LiPo batteries in parallel is a bad idea, and the best way to fix this is to add diodes in front of them.

I am looking at an application where 2 batteries will be used in parallel and the current draw can be up to 50A.  With a 1 volt diode drop (most higher current diodes are higher voltage drops) this would be dissipating 50W of power.  This would take a sizable heat sink on the diode.

Are there any other ways to run batteries in parallel?  I am looking for extended runtime by placing them in parallel, not more current.


texts: Keystone coil vs leaf spring SMT AA battery holders

texts:
We have been using Keystone 1024 SMT leaf-spring AA battery holders for a particular product:

We are thinking of changing to the newly released coil-spring version:

The leaf-spring are initially very secure, holding the batteries in tightly, however after a while they lose their spring. Hopefully, the coil springs will have a better hold.

Has anyone had experience with the coil spring version and can comment on whether they hold the battery more securely?


texts:
I have a basic question about down-conversion of RF-signals.

The ideal scenario is described as follows.

Given a RF-signal (coming from an antenna), i.e., a real-valued function x(t), and given a  frequency f (say f=100Mhz), one wants to down-convert the band [f-B,f+B] to [-B,+B], say for B=100Khz.

The basic idea is:

to consider x(t) as a complex signal
multiply x(t) by the complex sinusoidal with negative frequency -f, i.e., by \$\cos(-ft) + j \sin(-ft) \$.
This is done in practice by creating two signals \$I(t) = x(t)\cdot cos(ft)\$   and \$Q(t)= x(t)\cdot cos(ft + \dfrac{\pi}{2}) \$
Low-pass-filter I(t) and Q(t) with cutoff frequency B.

The resulting complex signal (i.e., the two signals I(t) and Q(t) ) can then be sampled (by Nyquist, at least at 2*(B+B)=400k samples/sec) with some ADC to do some DSP.

The hardware necessary for doing this appears to be:

Oscillator with frequency f, producing the function cos(f t).
Something to change the phase of the oscillator, to produce \$\cos(f t + \frac{pi}{2}) \$
Two Analog Multiplication units,
One Low-Pass filter with cutoff frequency B.

Question 1: Assuming that the oscillator (perhaps programmable) is given, what kind of hardware would you suggest for (2) and (3) ?

Question 2: Does this setup have significant shortcomings (beside cost of components?)

Since precise multipliers working with high frequencies are expensive, I've read around that one often prefers to multiply x(t) with a complex square wave with frequency f

More precisely,

\$ I(t) = x(t) \cdot Square( f t) \$
\$ Q(t) = x(t) \cdot Square (f t + pi/2)\$

The point is that multiplication by a square wave is just switching, which is probably less expensive to implement!

However the square wave has infinitely many odd harmonics!
And therefore it seems to me that the band [-B,+B] of the resulting complex signal:

I(t) + j Q(t)

really is a superposition of the original bands [nf-B, nf+B] of x(t), for all positive odd numbers n, while we wish it to be equal to [f-B,f+B] only!

Question 3: is this observation correct?

To solve the problem, it appears to me that one would have, at the very beginning, to LOW-PASS the signal x(t) with cutoff frequency f+B.

Question 4: Having an oscillator with programmable frequency f is realistic. But how do we implement a LOW-PASS filter with variable (f+B) cut-off frequency [the variable is f]?

In the schematics I've found online (e.g. Wikipedia) there is not mention of this variable LOW-PASS filter.


texts: Amplifier damage caused by failed power supply capacitors

texts:
MY QUESTION IS THIS:
Would failed power supply caps cause peripheral damage to the amp, preamp or control circuits ? Supposedly there is "protection" for "DC offset, over current and over heat"

I have a Proton AM-656 amplifier with "Dynamic Power on Demand" which is a second higher voltage supply rail (switched to when needed) that creates 6db of headroom and 2 ohm stable. I did not think there was fault protection, turns out the schematic block diagram states there is.

One day with the amp power on I tightened/snugged up the speaker binding post. There was a single frayed speaker wire (unnoticed) that shorted. The amp proceed to billow smoke. I looked inside to find several power supply caps having oozed their electrolyte onto the circuit board.

I am shopping to recap two of my other amps and was thinking of recapping the Proton, however I do not want to waste my time if there is likely to be damage to the circuits other than electrolytic capacitors.


texts: In order to charge the glass rod, why do we RUB it with a sillk cloth?

texts: Why can't we get the same results if is wrapped with a silk cloth for some time? What actually happens when we rub it?


texts: Switching between battery voltage and solar voltage to control load. in solar charger?

texts:
I designed a solar charge controller using arduino and MOSFET IRF9530. Main purpose was to charge 12V 7aH battery and then control the load. Here load is a solar blinker which needs 12v and around 1Amp. Following is the schematic of the circuit. The circuit is working fine.

In the above circuit, resistor R1 R2 are used as voltage divider to sense the solar voltage by reading the analog values of A0 pin. If the solar voltage is good, then digital pin D1 is turned on, so MOSFET conducts solar volts to battery and battery starts charging. By reading the analog values at A1 pin, we can read the battery voltage and if battery voltage is good then turning on the digital pin D2 will start the load.

Later on I thought of modifying the circuit in such a way that if the sun light is good and we are getting enough voltage from panel, then turn on the load using solar voltage and keep charging the battery. If there is no sunlight & battery has enough voltage, then the load will be using battery voltage. So I made the following changes:

Changes which I have done is that I added another pair of transistor and mosfet and connected them to digital pin3. SO if there is a good solar voltage and I want to turn on the load using solar voltage then I will make the D2 low and D3 high so solar volts will be given to the load via 7812 because I don't want to give higher voltages like 19-20v to the load. If there is no sunlight, then D3 will be low and D2 will be high to give battery voltage to load. I have used the diode D2 D3 to block the voltage.

To control the switching of load between solar and battery voltage, I have written folling code in arduino:

if(solVolt > 14 )
{
 //Its a bright day & we are receiving full sunlight
 //so turn on the load using solar voltage
 digitalWrite(solarLoadPin,HIGH);
 digitalWrite(batteryLoadPin,LOW);
 digitalWrite(solarLed, HIGH);
 digitalWrite(batteryLed, LOW);
}
else if(solVolt < 12 && batVolt > 12.4)
{
 //Its a dark night and we are not receiving sunlight
 //so turn on the load using battery voltage
 digitalWrite(solarLoadPin,LOW);
 digitalWrite(batteryLoadPin,HIGH);
 digitalWrite(solarLed, LOW);
 digitalWrite(batteryLed, HIGH);
}
else if(batVolt <= 10.8)
{
 digitalWrite(batteryLoadPin,LOW);
 digitalWrite(batteryLed, LOW);
}

Now I have few questions regarding this design:

Is this circuit fine? I tested the circuit by first plugging only battery and load. So the load was on and working fine. Battery Led was on showing load is using battery. But as soon as I plug in panel, it didn't switch to the solar voltage. I unplugged everything and then plugged in panel and battery so the load was on and using the solar voltage but the voltage was very low while the voltage from the solar panel was 18-19v.
Battery not charging? I unplugged the load and only allowed battery to charge. Battery volts at that time was 12.44 but instead of charging, voltage reduces to 12.40
Solar voltage vs current? There was very low sunlight and the panel was still showing 18v. I think it should show low voltage, around 12v when there is not a bright sunlight. But its voltage was high. So does that means, its output current will be low in this situation as Power = volts x amps. So if volts is high, amps will be low.

Basically I need to design the circuit which automatically switch between solar voltage and battery voltage depending upon the conditions of the day and night.


texts: Best way to get +5V or +12V or 0V from arduino pin

texts:
I am working on an eeprom programmer as an Arduino shield. There are two pins on my EEPROM that require a 12V signal as part of the programming process. One of them is an address pin that I am also driving by a signal through a 595 shift register, and the other is the output enable pin which is connected to a regular Arduino pin for 5V and 0V operation.

I would like to have a pin on the arduino for each of the 12V pins that will set it to the higher voltage without damaging any other components.

I was thinking I could use a simple transistor setup like Figure 1 on this page, but I'm really not sure how well that would work when connected to both sources at once. I would need diodes to protect my 5V components from getting damaged by the 12V signal, but I suspect that circuit may work out. I will simplify things by ensuring I that Vin is a solid 12V supply.

Here's my initial design:

My main problem is that I don't understand the circuit elements in play here very well. Will this explode? I'm still a bit confused by simple transistor circuits, and not sure what specific parts to use. I feel like what I am trying to do is not that hard, but my circuit skills are not good enough to know the best way to accomplish this. Thanks.


texts:
I'm building a dimmer, and got some questions about the resistor in the zero cross circuit.

My circuit is like the image above, and I'm wondering if in the case of 100V input the current is to small. I'm using smd resistors, with 1/8W and 300V max overload voltage. For the optocoupler I'm using Vishay H11AA1.

At 240 V, \$ I = \frac {V}{R} = \frac {240}{240k} = 1~mA\$.

Calculating the power on each resistor:

\$ P_{120K\Omega} = I^2R = (1mA)^2 120k =  0,12~W \$
(OK... the resistor has power of 0,125W.)

Otherwise, when 100V: \$ I = \frac {V}{R} = \frac {100}{240k} = 0,41~mA\$.

How can I calculate if 0,41 mA is OK for the zero detection?
These resistors affects the 10k pullup resistor?


texts:
I have a very low current PCB which connects to a disposable band aid.
The problem is that I need some sort of way to identify that the band aid has never been used before.
So I though about adding a fuse that I can burn after each use. I am just not sure how to do this, I could not find any fuse that I can burn at such low currents.
There is probably a smarter way to solve this issue, I am just not to familiar.
The band aid is suppose to touch the skin so I cannot raise the current in fear of electrifying.


texts: Switching power supply: why is the primary current rating 1A off when calculating power?

texts:
So I bought a couple of switching power supplies for a project of mine and I am currently recalculating my actual power usage out of my wall socket to figure out how to distribute power. I have made sure that my power supplies will never exceed 90% of its capacity, but the normal operating will be around 40-50%.

I tried to calculate the values and compare them with the ratings of my supplies and they are way more off that I anticipated. Example:

I have a 5V power supply that can deliver 20 amps for DC output. My AC input rating for this supply says: 230V (170-264V) 1.5A. However my calculations for 240V is 0.416A. So the theoretical and stated power usage is 1 amp off. I figured there would be some waste but not that much.

So:

Are my calculations way off?
Are the producer of the power supply
just overly careful?
Or does the power supply really waste the much
energy in the conversion?

Does the power supply have a poor power factor ?
Is the part load efficiency poor ?


texts: What is the difference between IMUs and other devices that have accelerometers and gyroscopes (smartphones, tablets, sensewear etc.)?

texts: The general definition of IMU says that any device that has accelerometer, gyroscope and magnetometer/GPS packed together is an IMU. Then why aren't other devices that have the same sensors called IMUs?


texts: STM8L Timer 1 unexpectedly low overflow frequency

texts:
I'm running the MCU off the high speed (16MHz, confirmed) internal oscillator and I've configured timer 1 to overflow with maximum overflow frequency:

/* No system clock pre-division, overflow upon reaching 0x0001 (starting from 0x0000) */
TIM1_TimeBaseInit(0, TIM1_CounterMode_Up, 0x0001, 0);

Once in the timer 1 overflow handling routine, I toggle a pin. For some reason I'm getting only getting a 32kHz square wave on that pin (hence 64kHz interrupt frequency).

Why is it so slow?

The same problem occurs with other timers as well.

Update: Ok, so I ran the timer with reasonable settings. Below are results for:

500 counts

300 counts

200 counts (unstable as hell)

100 counts

50 counts (frequency is the same down to 0 counts)


texts: Initial Transient Response of Boost Converter

texts:
I have been reading about switched-mode DC-DC converters and I'm having some trouble fully understanding the behaviour.
Take the following circuit for example (no feedback loop):

I understand there are a few things happening here:

The switching frequency of the converter should be much higher than the cut-off frequency of the LC low-pass filter. This is to ensure that we (ideally) do not see the switching frequency or harmonics of the switching frequency at the output. Of course, there will be some attenuated output voltage ripple that does make it through. This is what allows us to use the small-signal approximation.
The LC filter has a 2nd order time domain response which should be a decaying sinusoid, is that what we see in the initial transient of the simulation?

Why do we not see this decaying sinusoid every time the switch switches - that should be like applying a step input to the filter each time, correct? Can someone explain to me where the initial transient response is coming from and when do we consider the time-domain response of the LC filter?


texts:
I've made a VCO and ADSR-generator with two Arduinos.
The VCO uses a DAC made with a resistor ladder, the ADSR-gen uses a 12bit DAC. Everything is 5V powered (USB charger of 1A).

In my search for a VCA with opamps or transistors I only found VCAs with a double powersupply (+ and - 9v or 12v).

I'm trying hard to avoid such a setup because of simplicity.

I've tried this circuit, but gives a fairly distorted sound at lower levels of the envelope. I've tried to attenuate the VCO level and ADSR level overall, but to no avail.

I want to try these 2, but am not sure I can use a LM358 opamp and BC337 transistor for this.

I'm not that great with calculating the correct resistor values with opamps and such.

My questions:

Because it's all low level (between 0-5V) signals, is it possible
to replace the opamps in the designs with LM358 with 5V powersupply?
Is it ok to replace the BC549 with a BC337 (they are both NPN?)


texts: What does an inductor's current stabilize to in DC?

texts:
As you can see from the below graph, after an inductor is turned on, the current is stabilized to approximately 6.5mA. My question is: what does the 6.5mA represent? Where did that number come from?

When a capacitor is turned on, the voltage is stabilized to the source's voltage:

I can understand a scenario where the voltage of a capacitor and the voltage source do not match in voltage. But it doesn't make sense for an inductor and the source's current to not match in current. They have to match in current because they are in series.


texts: Will I get electrocuted by touching an exposed wire of a closed circuit?

texts:
Let's say I have some electrical appliance plugged into the wall outlet and turned on. If one of the wires coming from the plug is stripped bare and I touch it, what would happen?
I ask this because I saw on a youtube video about electrical engineering, the ground wire can be connected to the conductive metal casing of an electrical appliance so in the event that the hot wire was somehow making contact with the casing then it would take the low resistance path through the ground wire and save a person from an electrical shock. But if you are touching that metal casing which is connected to both hot and ground, how are you protected? Would you still not be in contact with a closed circuit and potentially get electrocuted?


texts: Optocoupler design - why does this circuit work?

texts:
I am busy with some calculations regarding the components around the optocoupler and I am now finding myself in a bit of a mental struggle. I have done quite a lot of reading (at least here, here, here, this Vishay guide, this Toshiba guide and this Avago guide to name a few) and I still find myself unable to answer a few questions. The more I try to figure out the correct math, I just end up with more questions that need answers.
The application for this circuit is to isolate signals from mechanical switches on one power network (supply voltage of 5 V) to the inputs of a port expander IC on another power network. The optocoupler used in the design is the TLP621-4.
This is the circuit in question:

Firstly, there is the input stage of the optocoupler. Designing for that seems to be rather straight forward – choose a suitable current to drive the LED at in order to switch on the phototransistor so that the correct logic voltage can appear at the pins of the port expander. The port expander runs at a supply voltage of 3.3 V, so the switch signals will also be translated/shifted to 3.3 V signals. Choosing a forward current of 5 mA corresponds to a \$V_f\$ of approx. 1.2 V at 25 °C, according to the datasheet.
For the LED this yields: \$R_{LED} = \frac{V_{supply} – V_f}{I_f} = \frac{5 – 1.2}{0.005} = 760 \Omega\$.
According to the optocoupler datasheet, \$I_f\$ = 5 mA corresponds to a CTR of 120%. Thus, the collector current \$I_C\$ = 5 mA \$\times\$ 120% = 6 mA. Now here comes my question – how do I design for the output stage of the optocoupler? If I want to convert the collector current to a voltage at the emitter so that the port expander can detect a logic HIGH/LOW, for what collector current and pull-down resistor values do I design?
Below follows the circuit as I have built it for testing purposes - it works. However, it is all nice that it works perfectly for this application so far, but it bothers me WHY it works:

The LED current limiting resistor value is 10 kΩ, which yields a forward current of only \$I_f\$ = (5 – 1.2) / 10000 = 380 \$\mu\$A. The CTR curve in the optocoupler datasheet starts at approx. 75% at 1 mA, so the true CTR is probably below 70%. This yields a theoretical collector current of approx. \$I_C\$ = 380 \$\mu\$A x 70% = 266 \$\mu\$A. Furthermore, the pull-down resistor value at the output stage of the optocoupler is also 10 kΩ. Where does the collector-emitter voltage \$V_{CE}\$ come into play? If the output stage supply voltage is 3.3 V and the desired logic HIGH at the emitter is also 3.3 V, then this means that \$V_{CE}\$ must be 0 V - is this possible? If so, what do the various \$V_{CE}\$ - \$I_f\$ and \$I_C\$ - \$V_{CE}\$ curves in the datasheet mean?
I would appreciate it if someone could shed light on why the above circuit works and what the corresponding parameters are. Also, if the above design is not optimal, what would the correct approach be to designing the circuit for the mentioned desired specifications?


texts:
I bought an TSL2591 breakout board and wanted to write driver for my board.

After looking at the documentation, i found that i cannot calculate the illuminance value (in Lux) as their was algorithm not given.

I tried the Adafruit TSL2591 Arduino code but no description.
I tried for App note on how to use the device or some physics description, Nothing.
I also tried Adafruit forum (no acceptable answer  ~2 days) and emailing AMS (no reply   ~ 2 days).

uint32_t Adafruit_TSL2591::calculateLux(uint16_t ch0, uint16_t ch1)
{
  uint16_t atime, again;
  float    cpl, lux1, lux2, lux;
  uint32_t chan0, chan1;

  // Check for overflow conditions first
  if ((ch0 == 0xFFFF) | (ch1 == 0xFFFF))
  {
    // Signal an overflow
    return 0;
  }

  // Note: This algorithm is based on preliminary coefficients
  // provided by AMS and may need to be updated in the future

  switch (_integration)
  {
    case TSL2591_INTEGRATIONTIME_100MS :
      atime = 100.0F;
      break;
    case TSL2591_INTEGRATIONTIME_200MS :
      atime = 200.0F;
      break;
    case TSL2591_INTEGRATIONTIME_300MS :
      atime = 300.0F;
      break;
    case TSL2591_INTEGRATIONTIME_400MS :
      atime = 400.0F;
      break;
    case TSL2591_INTEGRATIONTIME_500MS :
      atime = 500.0F;
      break;
    case TSL2591_INTEGRATIONTIME_600MS :
      atime = 600.0F;
      break;
    default: // 100ms
      atime = 100.0F;
      break;
  }

  switch (_gain)
  {
    case TSL2591_GAIN_LOW :
      again = 1.0F;
      break;
    case TSL2591_GAIN_MED :
      again = 25.0F;
      break;
    case TSL2591_GAIN_HIGH :
      again = 428.0F;
      break;
    case TSL2591_GAIN_MAX :
      again = 9876.0F;
      break;
    default:
      again = 1.0F;
      break;
  }

  // cpl = (ATIME * AGAIN) / DF
  cpl = (atime * again) / TSL2591_LUX_DF;

  lux1 = ( (float)ch0 - (TSL2591_LUX_COEFB * (float)ch1) ) / cpl;
  lux2 = ( ( TSL2591_LUX_COEFC * (float)ch0 ) - ( TSL2591_LUX_COEFD * (float)ch1 ) ) / cpl;

  // The highest value is the approximate lux equivalent
  lux = lux1 > lux2 ? lux1 : lux2;

  // Signal I2C had no errors
  return (uint32_t)lux;
}

query is:

what is "cpl"
why calculating cpl (though, related to above)
what is "TSL2591_LUX_DF"
what is "lux1", "lux2"    (is related to infrared? and visible?).
why the comparision between "lux1", "lux2"

any pointers of algorithm or the actual physics behind the calculation would be helpful (i would love to read/know the physics behind the sensor).


texts: What happens to a DSB signal if I use an envelope detector instead of Low Pass Filter

texts:
What happens to a DSB signal Modulated signal  if I use an envelope detector instead of Low Pass Filter ? I am interested in knowing how the output signals vary in case of a
envelope detector. I know that I get the signal back in case of a low pass filter.
Thanks for your time.

Envelope Detector

Low Pass Filter I used instead of the above envelope detector to retrieve the signal

This was the message signal : 2 volts pk-pk cosine wave 100 Hz
Carrier signal : 20 volts pk-pk 25khz

note that the when the low pass is connected the envelope detector is removed

DSB Modulated signal

OUTPUT From the Envelope Detector

OUTPUT from the low pass


texts: Is it safe to connect the GND of an input to the analog common of a differential ended DAQ?

texts:
When I connect a digital to analog converter(as shown in Figure 1) to a single-ended data-acquisition hardware I noticed that the signals are upside down. It seems like the DAC is providing differential ended output signals. Because when I connect Signal-high to + of DAQ(“a” in the figure) and GND to the – of DAQ channel(“b” in the figure) I got the mirrored(upsidedown) image of in the case of Signal-low to + of DAQ(“a” in the figure) and GND to the – of DAQ channel(“b” in the figure). But when I connect Signal-high to + of DAQ(“a” in the figure) and Signal-low to - of DAQ(“b” in the figure) there is no signal rather than some noise.

Now I’m planning to use the following differential ended DAQ hardware: http://www.mccdaq.com/PDFs/manuals/USB-1616HS-BNC.pdf
Regarding Figure 2 in my drawing I’m going to connect Signal-High to “x”, and Signal-Low to “y” since it is diff-ended DAQ. This DAQ has also an Analog Common pin. Should I connect this pin to the GND of DAC.

I checked with a multimeter’s continuity mode and found out power supply’s GND which goes to DAC and DAC’s output GND are all connected. Would it be safe to connect Analog common to the the GND of DAC.


texts: cause of photoresist removal after etching

texts:
I just tried to do a new PCB today with the photoresist method but what is very strange is that after etching it, I rinsed the board with water and wiped it dry, but as I wiped it dry with toilet paper, the photoresist came off and the underlying copper is exposed.

How is it possible for the photoresist to come off so easily like that?


texts: I am reading this datasheet and there are some graphs that says (Normalized) on one of it's axis...what is this?


texts:
I am designing a new PCB board these days, and I am confused about how to connect interfaces' shields. The interfaces on the board include USB, RJ45 and D-SUB, should them be connected directly to signal GND? I've seen a lot of solutions these days and I don't still konw which one is the easiest and at least effective.
I am only responsible for drawing the schematic diagram. The PCB routing is handed over to other engineers and is almost finished. Currently, there is no dedicated GND layer for shields on the board, I just hope to find a good solution that does not require a lot of changes. Thanks.
PS. The board containes both USB host and USB slave interfaces. RJ45 is used for Gigabit Ethernet port. There are currently 6 D-SUB interfaces, two of which are used to transmit analog signals (generally concerned with frequencies of several hundred hertz), and the rest are used to transmit low-rate digital signals (Mhz).


texts:
I am developing a Kit with GSM module which have to receive and send commands. I have gone through many GSM modules(SIM900). All of them consume around 1.5A at burst time. So I am in trouble to develop a power efficient Kit.

My doubt is normally mobile phone battery has the capability of 1000mAh. According to the calculation it has to work around 1 (busy) hour. But normally they stands for 1 day at-least. Are mobile phones uses any low power GSM modules? Is there any specific sleep-wake up mechanism with them?

Your suggestions and helps around this topic is appreciated.

Thank you


texts:
I tried to write a Verilog code for the finite state machine whose diagram shown below. I see nothing as an output. What is the wrong part of my code? or Is my code completely absurd?

My code:

module FSM(D1,D2, NextState);
input D1,D2;
output [1:0] NextState;
reg [1:0] CurrentState=2'b00;
reg [1:0] NextStateOut;
parameter S0=2'b00, S1=2'b10, S2=2'b11, S3=2'b01;

always @(D1 or D2)
 begin
 case(CurrentState)
 S0:
 begin
    if(D1==1'b0 && D2==1'b0)
        NextStateOut <=S0;
    if(D1==1'b1 && D2==1'b0)
    begin
        NextStateOut <=S1;
    end
end
S1:
begin
    if(D1==1'b0 && D2==1'b0)
    begin
        NextStateOut <=S0;
    end
    if(D1==1'b1 && D2==1'b0)
        NextStateOut <=S1;
    if(D1==1'b1 && D2==1'b1)
    begin
        NextStateOut <=S2;
    end
end
S2:
begin
    if(D1==1'b1 && D2==1'b0)
    begin
        NextStateOut <=S1;
    end
    if(D1==1'b1 && D2==1'b1)
        NextStateOut <=S2;
    if(D1==1'b0 && D2==1'b1)
    begin
        NextStateOut <=S3;
    end
end
S3:
begin
    if(D1==1'b1 && D2==1'b1)
    begin
        NextStateOut <=S2;
                end
    if(D1==1'b0 && D2==1'b1)
        NextStateOut <=S2;
    if(D1==1'b0 && D2==1'b0)
    begin
        NextStateOut <=2'b00;
    end
end
endcase
CurrentState<= NextStateOut;
end
assign  NextState= NextStateOut;
endmodule

State diagram: