texts:
I am a Newbie and I do not have a lot of expirience. The circuit has been put together from pieces I have found on the internet. My goal is to develop a reliable wireless solenoid circuit to water my tomato plants on my balkony.

The circuit I have developed so far.
https://easyeda.com/editor#id=b929cf452b52475bb0b40aca272a42e8.

In order to make the circuit failsafe, I came up with the following idea:

Circuit turns on, valve is closed, watchdog is disabled
ATTiny85 receives periodic PING from Master station
First PING will enable watchdog
ATTiny85 sends periodic heartbeat to watchdog for each subsequent received PING
Missing heartbeat/PING will reset the microsontroller and close the valve

I would really appreciate if someone from the community could look over the design and let me know how to improve the circuit and if above approach is OK to avoid a permanent open valve.


texts: Does the polarity of my AC adapter match that of the device?

texts:
Looking at the symbols, I think the polarity matches the adapter and device (tip positive), however the design of the symbol is different which is is confusing me, so I want to be 100% certain that they are a match.

Polarity symbol on device:

Polarity symbol on AC adapter:

Is it safe to use the adapter with the device? (volts and amps match)


texts: How to plan my LED circuit, voltage, and resistor

texts:
The LED emitters in my outdoor lamps blew out and I need to replace them but I have to rebuild the emitter from scratch because replacement parts are not available.  The whole lamp was made in China.  They are fed by AC.

I have the following:
  - 1 Luxeon K High Power LED Array.  Forward voltage requirement of 20V with 730 lumens at 350mA. Perfect sized emitter and I have a good heat sink to mount it to.  The Part number is LUXEON-K-COBWW08, an 8 emitter array.

1 AC to DC power converter.  It is a MagTech AC Dimmable - 18-Watt, 700mA Constant Current LED Driver. I don't need it to be dimmable at the switch, but I don't mind adding a dimmer to the inner workings of the lamp.  The Part number is M18-U24-0700
I can buy any resistor needed.  That's not the issue.

Curiously, the DC output from the AC converters I measured to be 30V.  Both of them.  They are rated to be dimmable between 14-24 VDC.  This is at a constant 700mA.

When I bought the drivers, I planned a 24V power to a 20V requirement and got planned for a resistor of 12 ohms.  (24-20)/.35mA = 11.4 ohms.  The lights are rated at 350mA.  Any more current and they'll burn up.

Since the output is 30V, should I swap the 12 ohm resistor for a 30-35 ohm resistor? (30-20)/.35=28.5ohms

Is there a simple way of hardwiring a variable drop in voltage?  I can set the output with my multimeter and leave it in the housing of the light.

I'm worried that, within this outdoor light, wiring a 35 ohm resistor will require me to radiate off too much heat.  I'll need a 20 watt resistor.

This is getting out of my league and I think ledsupply.com sold me incorrect equipment.

Thanks.


texts: MATLAB programming of Particle Filter - what is going wrong?

texts:
I'm working on a particle filter experiment for multi-sensor fusion and I just programmed it in MATLAB. However, I get very low accuracies for my final values. Plus, I read a lot of literature where they talk about pdf of state and observations etc. but my practical knowledge is still extremely shaky, since I've had no formal training in filtering/Bayesian estimates etc.

I have devised my algorithm like this:

Initialize particles = I'm doing it as a Gaussian distribution - 10 particles
Move the 10 particles forward using the state transition equation: X_t+1 = A*X_t + 0.1*rand() (only injecting Gaussian noise so far)
Using the observation, calculate the weights for the particles. I do this like a root mean square of the difference between predicted state and observation. For example, if my azimuth(a) = 40, pitch(p) = 3, roll(r)=4 in my state and in my observation it is a = 39, p = 3, r = 3, then I do rms = sqrt((40-39)^2 + (3-3)^2 + (4-3)^2). Then my weight is assigned as 1/rms in order for it to be inversely proportional to the 'distance' between the prediction and observation
Then I normalize these weights to get norm_weight = weight/norm(weight) so that their sum is equal to one.
Then I continue forward for all the observations. I have not included resampling yet because when I run this experiment, I do not experience any degeneracy, which is also very puzzling.

Where am I going wrong? I realized that I haven't 'computed' a lot of the Bayesian equations given in the literature i.e. p(x/z_t) = p(z_t/x)*p(x)/p(z) etc. and I don't know where it fits in here either. Can somebody please help me?

My Matlab code looks like this:

function resultx = particlefilter(resultx_1, observationx, A, noiseP)

    for j = 1:length(observationx)

    for i = 1:length(resultx_1)

        apriori_state{i} = A*resultx_1{i} + noiseP;

        rms(i) = sqrt((observationx{j}(1) - apriori_state{i}(1))^2 +(observationx{j}(2) - apriori_state{i}(2))^2);

        weight(i) = 1/rms(i);
    end;

    norm_weight = weight/norm(weight);

    for i = 1:length(apriori_state)
        plot(apriori_state{i});
    end

    disp(rms);

    disp(norm_weight);
end


texts: Serial line switching through a transistor

texts:
I want to switch my RS-232 TX pin.For this I am using NPN transistor in between the TX line in such a way that the collector terminal is connected to controller side  and Emitter to  external side. The base is connected to a digital pin.

So, when the digital pin is high, the NPN transistor should close and TX line should send data from controller to external circuitry. But, in this case it was not sending data.

when I connect the serial line directly (without a NPN transistor), it was sending data properly.

I have also make sure that the NPN transistor is not faulty.

So, Why serial line is not switching by a transistor? Or is it not possible to switch a serial line like that?


texts: Is it bad to run a 1000rpm rated 12V DC motor at lower rpm?

texts: I'm trying to make a rock tumbler. The 12V DC motor I have is rated for 1000rpm. Can I run it at lower rpm without harming the motor? I'm planning to use an Arduino and motor controller for the project.


texts: How to read current from a non invasive split core transformer AC current sensors

texts:
I was looking for a simple AC sensor and found this. It would seem to be a good option since it is not invasive. The problem is how do you read data from these type of sensors? Im having a hard time looking for a good guide on these sensors. it would seems that they output current(?) which will make reading them difficult with the basic analog GPIO

Further questions:

How accurate are they?
Can they be place beside one another if you want multiple of them?
Will this still work if it will be placed in the distribution board where there are a lot other wires that produces magnetic fields
I only see a current rating (100A) and not the voltage what does this mean?


texts: Is it possible to have a 2-in-1 USB device that is a Flash Drive and Power Bank?

texts: I spent over an hour with no luck looking for a device that would provide flash storage and provide charging power to another device at the same time.  I would think this would be possible as you can plug a phone into a computer and receive data as well as charging power simultaneously.  If a 2-in-1 device is possible, does it already exist for purchase?  Maybe it has a different name and I am searching with the wrong terminology.


texts: Why is the support circuit for switching regulators more complex and expensive compared to linear regulators?

texts: One disadvantage with switching regulators compared to linear regulators is that the support circuitry is more complex. It involves more components and make material cost more expensive. This also makes the board harder to layout. Why can't those components be squeezed into the IC given today's technology?


texts: How do I select the most suitable voltage regulator?

texts:
I'm working on a  3.3V circuit for my ARM chip, and finding it a bit difficult, determining which voltage regulator to select. Looking at for example Texas Instruments only, here are litterally thousands of  voltage regulators. Being spoilt fot choice, I know I want at least the following:

3.3V output
must have short circuit and over temperature protection
must be affordable
must be efficient

How do I select the right one, without picking that is too prehistoric.


texts: Hum on car stereo when source powered by inverter

texts: I have an auxiliary input on my car stereo, which I plugged my laptop into to play music with.  It worked fine until I plugged my laptop into an inverter so the battery didn't die.  An extremely noticeable hum started coming through the speakers which corresponded to the speed of the engine.  Is there any way to prevent this?


texts: How to fix common error causing multiplexed LED segments to flash and dim

texts:
I bought an electrical engineering book and was surprised to see the following figure showing how to use a microcontroller to multiplex 4 LEDs using only 4 pins:

This seemed right, logically, but wrong electrically, because a multi-segment display using this circuit would appear terribly dim with all 8 (or 9) segments sharing just one resistor like this.
Here is a simulation of the minumum subset of the circuit that would show the problem.  When both LEDs are on, they dim each other because they are sharing current, so they show at half brightness.  You can see the problem below from 100ms to 110ms when both LEDs fall from 2.7mA to 1.35mA.

I have actually seen this with commercial products.  Sports scoreboards in particular, which are both big and highly visible.  When you share only one resistor across all 9 segments (including decimal point), the output is only 11% of the original brightness.
Here are how the power sources are defined for the above simulation:

The V2 trace is slightly offset to make it easier to see.
========
EDIT:
This was a question I thought I knew the answer to, so you will see my answer below.  I thought the book was wrong, and I was wrong.  I think that I was thinking of one whole digit being on at one time.  But I do see this display problem.  So, what causes the kind of display anomaly which I see in the real world, that makes digits dim when all of the segments are on?


texts: Brushless DC Motor relationship with speed and duty cycle

texts: Ideally, the motor speed would vary linearly between a speed of 0 at 0% duty cycle and a speed of at 100% duty cycle. What would the constant for this motor be if this were the case?.


texts: Using transistors to prevent short circuit / current limit

texts:
I am designing a circuit where I want to protect Q1 from current overload and popping in the event that Rl is a short. The length of wire in a short circuit situation is 0.7 ohms. Usually Rl is 10 ohms (when it is not shorted) or so and thus 1.25A flows through it. RL has LED's in it so I need to keep 12VDC. I have looked at an LM513 as a current source but it looks like the voltage drop from Vin to Vout is too great.

A microcontroller is driving the base of Q1

I have designed the circuit below using 3A transistors, but I keep popping Q1. I have verified that the circuit works by changing out the Rs resistor value and verifying that it regulates the current correctly.

I chose the Rs to 0.5 so that I could run a max of 1.5A. With the transistors rated at 3A I thought this should be fine.

My thought is that Q1 is popping too quickly before it even has a chance of turning off with the instantaneous current of approximately 10A flowing through it.

Should I replace Q1 with a mosfet transistor?

Schematic is below.

simulate this circuit – Schematic created using CircuitLab


texts: Spectrum Analyzers and nonbandlimited signals.

texts:
I am reading about how spectrum analyzers function and I am somewhat confused about how the Fourier transform is computed.

It seems to me the argument made in the Wikipedia per signal reconstruction assumes the signal is bandlimited - if the function of the spectrum analyzer assumes bandlimitedness of the input, doesn't its output become circular(IE it only produces a correct approximation when the signals frequency range is already known)?

The other way to compute this is through direct numerical integration of the Fourier transform which will always produce a correct approximation but that doesn't appear to be the system used.


texts: What is the best way to measure how many amp hours a device (in this case a resistive heater) is using? I have a resistive heater that is pulsed on and off periodically depending on ambient temperature. I can capture the waveform of the current over time with a scope. Do I just multiply the amount of current by the time every time it is turned on? Basically the waveform will look like a square wave.


texts: Designing a Chebyshev filter: am I getting the order wrong?

texts:
I'm solving the following problem:

Consider the design of a Chebyshev lowpass filter with 3 dB DC gain, a passband limited to 1 kHz with a
maximum ripple of 3 dB, and a stopband characterized by AS = 60 dB and fS = 4 kHz.
Show that the necessary filter order is n = 4.

Ok so we have
$$f_p= 1 kHz $$
$$ A_p=3 dB $$
with this we can calculate the filter \$ \epsilon\$
$$ \epsilon = \sqrt{10^{0.1A_p}-1} = 0.998$$
which we will round up to one. So \$ \epsilon = 1\$.
Now my professor told me that now we have to consider two different situations for n even and n odd.
For n odd (ripple starts at the DC gain), we have to consider:
$$f_s= 4 kHz $$
$$ A_s=63 dB $$
$$n\geq\frac{cosh^{-1}\sqrt{\frac{10^{0.1A_s}-1}{\epsilon^2}}}{cosh^{-1}\frac{f_s}{f_p}}$$
We obtain
$$n\geq3.85$$
So, we would take n=5 (the next odd value).
For n even (ripple starts at the DC gain + ripple value):
$$f_s= 4 kHz $$
$$ A_s=66 dB $$
We obtain
$$n\geq4.01$$
Now here we have a problem:
Should I round up this to n=4, or should I consider the next n value, n=6?
Because now my professor told us to take the least value of n (the minimum value of n that works): if we consider n=6 for the even case then the order of the filter should be n=5. Otherwise it should be n=4? Or am I rounding up the value wrong: I should round up the value of n odd to n=4 and the value of n even to n=5 and therefore considering n=4?
Can someone help me?
Thank you!


texts: VHDL Multidimensional arrays with different internal size

texts:
I'm wondering if it is possible or not to create bi-dimensional arrays having different inner sizes.
For example I can create

type type1 is array(0 to N-1) of std_logic;
type type2 is array(0 to M-1) of type1;
signal mysig : type2;

with N and M that are generics or constants defined in a package. In this case I would have a vector of M elements, where each one is a vector of N elements.

Now assume that for me N is not fixed but it passed to the entity as an array of integers, so that for each M I have a different vector size. Is there a smart way to code this situation using arrays?

Thanks in advance.


texts:
Can an LED be used in paralell of a free wheel diode?
All circuit is powered by a 12V alternative.

simulate this circuit – Schematic created using CircuitLab

I think it can be used like that; when power (12 V) gets off; then the power kept in the inductor has to get out in C1 and trough D1 is a little part of the power crossing D2?


texts: What determines branchline coupler bandwidth?

texts:
I'm interested in phase shifters and their applications to the antennas. Generally I found a 90 degree branchline coupler to provide necessary shift. But I wonder what determines their bandwidth.
Take an example below, if all dimensions are calculated with theoretically depends on the frequency here, then how to make it broadband (1 octave in VHF band)?


texts: Is there any sense in carrying assembled enclosed electronics in a static-shielding bag?

texts:
Say I have a Raspberry Pi enclosed in a metal case, such as this.

Would it offer any additional level protection if I put it in a static-shielding antistatic bag whenever I carry it around (e.g. before putting it in a bag or cardboard box)?

Does this offer any additional level of protection, for example from ESD damage?
Otherwise, does it, maybe, create some potential risk I may not be aware of?


texts: Replacing half wave tube rectifier with capacitor diodes in series

texts:
I am very inexperienced.

I am a HAM, I just got a HA-10 amplifier that has been modified. The half wave tubes were replaced with a string of Z5U .01 ceramic caps in parallel with 1M ohm resistors and unknown diodes, four sets on each side.
Please see the pictures and schematic.

There is no visible identification on the diodes, the caps are Z5U .01 2K.  The string is off a 3500 volt transformer that powers this string to the transmitter tubes 4 of 811a's.  I want to replace it with new parts because the wires have black dust on them, I am guessing from running to warm.  It is a 1 kW amplifier.
Can anyone PLEASE help me and explain what this genius did maybe 50 years ago?

I want to build a nice little board with the proper diodes/diode and caps to replace this cardboard setup. I have wiring diagrams and some specifications.  I do not have the knowledge at this level.

Any comments or suggestions are appreciated. I have a drawer of 25amp 50 volt full wave rectifiers and would love to use them.  I am not sure how I would without it being partly guessed.

Correct, I looked with magnifying glass and bright light. If it is there it has long burnt out of eyesight range. You should be able to zoom in on the photo, I may have made it too small, but the only thing I could get was numbers on the caps, and a guess on the code of the resistors because the colors are not according to text book. The two tubes that were replaced were 866a half wave. I will send specs in a few minutes. Thanks, I hoped to just buy the same and rebuild the existing setup.

Correct, I looked with magnifying glass and bright light. If it is there it has long burnt out of eyesight range. You should be able to zoom in on the photo, I may have made it too small, but the only thing I could get was numbers on the caps, and a guess on the code of the resistors because the colors are not according to text book. The two tubes that were replaced were 866a half wave. I will send specs in a few minutes. Thanks, I hoped to just buy the same and rebuild the existing setup.


texts: Why do different value capacitors and resistors sound different in same amplifier circuit?

texts:
I have two questions...

I have seen that different value capacitors in an amplifier circuit, sound different... For example, an amplifier circuit with a 470uf capacitor, has more bass, and treble... A 1000uf capacitor, has a uniform distribution of frequencies more or less... A 330uf capacitor sounds like it has more focus on the vocals... mid range...

So, what is the real reason for them to sound the way they do? In physics or mechanics or electronics sense...

In an electric guitar and amplifier setup... Introducing a resistor value, between the amp and the guitar, changes the way the guitar sounds... I have tried lots of values, some of them are, 330k, 470k and others in that range... Why does this setup, act like equalizers? The resistor i connect is in the positive terminals, not ground ones...

This seems to work in a cd player to music system too... The resistors become like presets of music equalizers...

I understand we are changing the impedance, but why do they sound so different at different impedances...?

Example Circuit:


texts: How do I control a resistive touchscreen?

texts:
The gist of my problem is that I have a resistive touchscreen and a Raspberry Pi, and I need to make one talk to the other using a single ADC of some kind.

I have worked with an Arduino and I also know the basic concept behind a resistive touchscreen. However, I'm having some problems planning out how to attach it to the raspberry pi and I don't want to commit too much to parts unless I know how I'm going to do it. Basically, I need to put voltage across the x+ and x- leads, while measuring the y+ lead using the ADC, right? But then I have to switch leads and put voltage across the y+ and y- leads, and measure the x+ lead.

On an Arduino it's obvious how to do that, because the analog input pins can also serve as digital outputs. But I have no such luck with the Pi. I can wire up an ADC to the pi but I'm not really sure what ADC will do the job, since it seems to have to provide digital outputs as well. I'm looking at basic ADCs like the MCP3008 right now. Is it possible to control a resistive touchscreen with such a chip, and if so how? If not, what ICs do I need?

Also if you're going to suggest an IC, please stick to ones that can be found in PDIP packages. I know that's REALLY restrictive (a lot of the "touchscreen digitizer ADCs" I've seen are TSSOP/QFN only) but this is a small hobby for me, I'm working on a breadboard, and I don't really have the tools to use other packages.


texts: Is it practically possible to transfer electrical power around the World by wires?

texts:
Assume that we installed plenty of solar cells in all continents; mainly in Asia, Africa and America. Can we transfer the electrical power harvested from them around the World through wires? So that the continent(s) in daytime will feed the one(s) in nighttime.

Assume that we use a higher technology then we use today in practice. For example, we will use higher insulation technologies to transfer with higher voltages to decrease copper losses.

Do the practical limits make this scheme feasible?


texts: Is there a way to convert HDMI output to Composite AV? Any wire (HDMI to AV)? I want to connect the display to a development board but the display has composite AV ports and the board has HDMI output. I dont want so many wires so I'd like to also cut the cable and manually solder the wires.


texts:
I saw below Bluetooth chip comparison of many module , most of all are having 8dbm max power ,  what  I know FCC has 30dbm and CE has 20dbm Max power limit so why Bluetooth module are limited to only 8dbm Power. Do Bluetooth have different limit for power or else.
Sine Most of Wifi chip comes with max power +20 dbm may be due to CE limit. so why not Bluetooth module comes with 20 dbm so we can get more range?


texts: Drawing current sensing transformers accurately

texts:
This is more of a stylistic question than anything else, but it important that the sketch be accurate to convey what is really going on.  I'm wondering, how does one draw a current loop that is sensing the current flowing through a wire passing through the loop?

I've drawn an example below that covers three different cases that I'm interested in, all on the same current sensing loop:

-The red wire is current passing through the current loop in the normal sense.

-The green wire is current passing through the current loop twice due to the double turn.

-The blue wire is a current passing through the loop, and then turning back around to terminate elsewhere.

Is there a program, or convention for drawing this type of circuit element?


texts: Transistor current limiter, microcontroller controlled?

texts:
I've come across a few transistor current limiter schematics, similar to this one:

However, I am not entirely sure how I could implement microcontroller functionality to control this. I think Rsense would cause Q2 to conduct if at a threshold (0.65V assumably) and Rbias will determine how much it will be limited, however that is unclear to me, especially if Rsense will be somewhere highside and just turning on Q2 with my uC seems to not do anything (in simulation at least)

How would I come up with the formulas for a variable limit that I can control? I would rather not have to use a digital potentiometer in place of R2, if I can somehow have sense voltage compared with a comparator with a voltage my uC defines, that'd be great! But how could I start the limiting? What do I "turn on" when the sense resistor shows enough current? Does Rbias have to be there to limit it to a certain level, and I'll end up having to use a digipot anyway?

Any solutions to a uC controlled current limiter would be great, that can be controlled easily with just a pin or two.


texts: Eagle PCBs not printing to scale and the letter F shows it?

texts:
I read other answers about scaling problems  when printing with Eagle and I don't think my printer is completely at fault.

I ran some tests. I tried printing a PCB (about 8 inches by 4 inches in real size) with the following settings:

Landscape, and letter size paper
Portrait, and A4 size paper
Portrait, and letter size paper

All other printer settings are the same in all tests.

When I printed (I checked the caption option), the sizes are different each time, and I think the sizes are denoted by the letter "f" in the caption.

The caption format printed is as follows:

"XX/XX/XXXX TT:TT:TT f=S.SS /path/to/file.brd"

where XX/XX/XXXX is the current date, TT:TT:TT is the time and f=S.SS which I believe is the scale factor. The S.SS reported 0.83, 0.96 and 0.93 respectively even though I set scale to 1 in software.

Is there some simple workaround to this? could I somehow force F to be 1?


texts: How The no Contact Voltage Detector circuit work?

texts:
I saw the no Contact AC voltage detector circuit on some video on youtube and tried to make the circuit except that I wanted to replace it's led with an active buzzer with internal oscillator

Problem is the sound is too dim and when I measured the voltage across the buzzer I found it to be less than 3 volts
I used the same circuit in the picture except that I replaced the led and the resistor with my the buzzer which can safely operate with 9v and used an aluminum foil instead of this copper coil, (" as I think it's working on capicitance after all " ) .

I want to know how can I increase the sound and How did I lost so much voltage without connecting any resistors.


texts: Microphone peak detector circuit no signal response

texts:
I have built a peak detector circuit using op-amps/comparators to amplify the signal from an electret microphone, hold the peak signal and create a sharp logic edge when a peak is detected to be sent to a microcontroller.

I have built the circuit as follows setting up OA1 as a non inverting amplifier with a gain of 1000, but the voltage out from the OA1 remains fixed at about 4.5V no matter how much noise I make into the microphone. The comparator part of the circuit is outputting approximately 2V low and 5V high depending on how I set the potentiometer. All the components appear to be working.

simulate this circuit – Schematic created using CircuitLab


texts: What direction to place electrolytic caps for AC coupling?

texts:
If using polarised electrolytic caps in an amplifier circuit as shown below,

Does it matter which way round I place the caps? If so, why?


texts:
Currently I'm dealing with Tiny2313 for my project. Timer runs in CTC (WGM12) mode so OCR1A is used to set TOP of the timer. I want to use OCR1B to generate output signal.

In documentation is mentioned this: "The FOC1A/FOC1B bits are only active when the WGM13:0 bits specifies a non-PWM mode." Is usage of that bits in non-PWM mode mandatory?
What is true purpose of FOC1A/FOC1B bits?


texts: Would a sulfated lead-acid battery charge at 2.1V per cell?

texts:
I'm trying to charge a 6-year-old OEM lead-acid battery in a 2008 Volkswagen Jetta with an external charger, whilst it's still connected within the vehicle.  (The battery was working fine, until it got discharged to perhaps 25% due to a prolonged episode of charging the mobile phone through the car without the engine running, and wasn't recharged fully since then; I've now added distilled water, and am trying to recharge it after a delay of only a couple of weeks since the last proper charge.)

When tested under slight load (key in the ON position without the engine running, and with the lights off), it would appear that the voltage of the circuit being charged is only about 12.6V or so; when testing under no load, it's maybe around 13.5V (with the charger being in maintenance mode).

Is there any point in trying to recharge a sulphated battery with a charger that appears to only be capable of producing merely 13V in its maintenance mode, for a 12V battery?  Would I have a much better luck with 14V for trying to de-sulphate my battery?


texts: Energized circuit in a 3M Static Shielding Bag (silver color)

texts:
I'm wondering if it's safe to put an energized circuit in a static shielding bag...as part of a high altitude balloon project.

I'm not too sure how these work, so I tried seeing if either the outside or inside of the bag was conductive on a regular multimeter, which I found that it was not.


texts: How can I implement a simple, Q only, D-latch using VHDL?

texts:
I just started VHDL today and I'm the type of person that can only learn by doing stuff, so after I made some basic gates in VHDL, I tried making a simple D-latch(so no clock signal), however without success. I get all kinds of errors such as in1 not defined, std_logic not defined, etc.

Here is my code:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity dflip is

end dflip;

architecture structural of dflip is

    component AND2
        port (in1, in2:in std_logic; out1: out std_logic);
    end component;

    component OR2
        port (in1, in2:in std_logic; out1: out std_logic);
    end component;

    component NOT1
        port (in1: in std_logic; out1: out std_logic);
    end component;

    signal D, E, E_NOT, Q, OUT_AND1, OUT_AND2: std_logic;

begin
    U0: NOT1    port map (E, E_NOT);
    U1: AND2    port map (E, D, OUT_AND1);
    U2: AND2    port map (E_NOT, Q, OUT_AND2);
    U3: OR2     port map (OUT_AND1, OUT_AND2, Q);
end structural;

entity NOT1 is
    port (in1: in std_logic; out1: out std_logic);
end NOT1;

architecture behavioral_not of NOT1 is
begin
    out1 <= not in1;
end behavioral_not;

entity AND2 is
    port(in1, in2: in std_logic; out1: out std_logic);
end AND2;

architecture behavioral_and2 of AND2 is
begin

    out1 <= in1 and in2;

end behavioral_and2;

entity OR2 is
    port (in1, in2: in std_logic; out1: out std_logic);
end OR2;

architecture behavioral_or of OR2 is
begin
    out1 <= in1 or in2;
end behavioral_or;

I made it structural, because I could not make it to work behavioral, because it seems I cannot use if statements if I write behavioral(makes sense). The problem is with that Q output which needs to be connected back to the input of an AND gate.

So how do I do this?


texts: Can you help me understand this Node Analyzing Method in Thevenin Norton Circuits

texts:
This is the circuit, and the node method solution is:

Where did 280 come from? why is there two Vt/60 ? Please help me


texts:
Here's the situation:
I have an Arduino mega 2560 and I'm trying to analogRead from 2 different pins.

code:

void setup()
{
  pinMode(A0, INPUT);
  pinMode(A15, INPUT);
  Serial.begin(9600);
}

void loop()
{
  Serial.print("0:");
  Serial.print(analogRead(A0));
  Serial.print(" 15:");
  Serial.println(analogRead(A15));
}

The voltage I'm trying to measure is arduino 3.3V supply connected directly to the ADC input pin and the result I get varies depending on the connection of the inputs:

Both inputs floating:
A0: 376, A15: 376

A0 connected, A15 floating:
A0: 771, A15: 655

A0 floating, A15 connected:
A0: 409, A15: 696

A0 connected, A15 connected:
A0: 782, A15: 780

What is the cause of this fluctuation?


texts: Finding resonant frequency or damping ratio from Bode Plot

texts:
I am working on a question where I have to estimate a transfer function from its bode plot.

I plotted the asymptotes of this bode diagram, and was able to find out that this is 3rd order system with a pole at s = 0 and two complex poles.
$$\dfrac{w_n^2}{s(s^2 + 2\zeta w_n s + w_n^2)}$$
where I found out that $$w_n = 6.7 rad/s$$ from the asymptotic bode plot.
I was also able to find the system gain \$K\$ from the magnitude plot.
I am unable to find \$\zeta\$ here. I tried finding the resonant frequency \$w_r\$ from the bode plot so that I can calculate \$\zeta\$ using: $$w_r = w_n\sqrt{1 - 2\zeta^2}$$ but I was unable to.
I know that the frequency at which the phase plot crosses zero is the resonant frequency but the phase plot here doesn't cross zero.
I tried approximating \$\zeta\$ using the fact that maximally flat response is obtained for \$\zeta = 0.707 \$, so that for the given plot, \$\zeta < 0.707 \$. But I wasn't able to exactly find a value.
Is there any other way to find \$\zeta\$ or will I be just able to approximate it?
The solution says that the value of \$\zeta\$ is \$0.447\$.


texts:
From the background and responses to my other question I gather that 5 NiMH batteries can provide more than 4 A current, and that Alkaline or Manganese batteries cannot.

So, what about LiPO, LiFePO4, Li-Ion?

Also, how can I find this information? Have googled a bit and looked at several tables of battery data but not seen anything remotely resembling this max current.

Edit: am trying to understand the available choices for powering a bunch of servos in a robot.


texts:
I am trying to use FDMQ8403 IC which has 4 nmos. It will be used for an h-bridge, so 2 of these will be for high side and 2 for low side.
I am trying to drive the hide side nmos with MIC5018.
On page 5 of the driver chip it shows the functional diagram shown below. I just started learning about gate drivers. My understanding is we use a gate resistor to prevent the MCU or whatever is driving the gate to have excess current drawn from it, thus saving the driving component.
The question is why don't they include a resistor between the gate of the mosfet and pin G of the driver?
Thanks


texts: Can the resistance between two points in air be calculated? How?

texts:
If I have just a battery, the terminals are separated by air, a very good insulator. We can say, practically, that no current flows.

However, air has a very large, but finite resistivity. Wikipedia gives a range of \$1.3\cdot 10^{16}\$ to \$3.3\cdot 10^{16} \Omega \mathrm m\$, which I'm sure varies by pressure, temperature, humidity, pollutants, and so on.

From that, can we calculate the resistance between the battery terminals, knowing the dimensions of the battery, and assuming that there is an infinite space of air around the battery? What's the math?

Could this be extended for calculating the resistance between two points in an arbitrary material, of infinite volume, with a known resistivity? The practicality of obtaining an infinite volume of a thing aside, I'm wondering how resistivity relates mathematically to idealized volumes of things that aren't extruded blocks of things. (That is, not \$R = \rho L / A\$.)


texts:
I'm having issues trying to decode a XBee API packet. I start decoding it, but I'm not sure what my actual analog data should be. Several of them look like:

7E 00 12 83 56 78 43 00 05 02 00 00 00 03 FF 03 FF 00 00 00 00 60
7E 00 12 83 56 78 43 00 05 02 00 03 E8 03 FF 00 2A 00 00 01 C8 84
7E 00 12 83 56 78 43 00 05 02 00 03 FF 02 DE 00 0D 00 00 03 FF 73
7E 00 12 83 56 78 42 00 05 02 00 03 FF 00 00 00 00 03 DB 03 FF 83

So far I have:

7E - start
00 - length byte 1
12 - length byte 2
83 - API identifier
56 - source address byte 1
78 - source address byte 2
43 - RSSI value bytes
00 - option byte
05 - sample quantity byte
02 00 - channel indicator 0000 0010 0000 0000  (A0 is active) (IO header) (I'm not sure if this is right)
last byte is chechsum

I'm using the XBee series 1 using XB24 firmware. I have a Lilypad temperature sensor based on the MCP9700.

The documentation for the XBee module is:
http://ftp1.digi.com/support/documentation/90000982_G.pdf

Every time I try to get the ADC data I get a huge number like 51228675.

The doc also says if any of the DIO lines are the first two bytes are the DIO sample. Why do I get "03 FF" or "E8 03" and sometimes "00 00" if I don't have any of the DIO lines active?

Schematic: Lilypad Temperature Sensor (pin S) --> Xbee (pin AD0)

Any help is greatly appreciated trying to find the sensor output.


texts:
I am using pic16f1823 and MPLab as IDE. I want to have simple interrupt on RA2 and turn on LED, when it come. I've wrote This code, but it doesn't work!

#pragma config FOSC = INTOSC    // Oscillator Selection (INTOSC oscillator: I/O function on CLKIN pin)
#pragma config WDTE = OFF       // Watchdog Timer Enable (WDT disabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable (PWRT disabled)
#pragma config MCLRE = ON      // MCLR Pin Function Select (MCLR/VPP pin function is digital input)
#pragma config CP = OFF         // Flash Program Memory Code Protection (Program memory code protection is disabled)
#pragma config CPD = OFF        // Data Memory Code Protection (Data memory code protection is disabled)
#pragma config BOREN = OFF      // Brown-out Reset Enable (Brown-out Reset disabled)
#pragma config CLKOUTEN = OFF   // Clock Out Enable (CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin)
#pragma config IESO = OFF       // Internal/External Switchover (Internal/External Switchover mode is disabled)
#pragma config FCMEN = OFF      // Fail-Safe Clock Monitor Enable (Fail-Safe Clock Monitor is disabled)

// CONFIG2
#pragma config WRT = OFF        // Flash Memory Self-Write Protection (Write protection off)
#pragma config PLLEN = ON       // PLL Enable (4x PLL enabled)
#pragma config STVREN = ON      // Stack Overflow/Underflow Reset Enable (Stack Overflow or Underflow will cause a Reset)
#pragma config BORV = LO        // Brown-out Reset Voltage Selection (Brown-out Reset Voltage (Vbor), low trip point selected.)
#pragma config LVP = ON         // Low-Voltage Programming Enable (Low-voltage programming enabled)

And for main app, we have :

#include <stdio.h>
#include <stdlib.h>
#include "main_10.h"

void interrupt tc_int(void)
{
    //if (INTCONbits.INTF == 1)
    if (INTCONbits.T0IF && INTCONbits.T0IE)
    {
        LATCbits.LATC1 = 1;
        __delay_ms(1000);
        LATCbits.LATC1 = 0;
        __delay_ms(1000);
    }
    INTCONbits.INTF = 0;
}

/*
 *
 */
void main (void)
{
    OSCCON = 0x76;//Very Important,this will command micro to use internal oscillator

    //prepare Interrupt on A2
    TRISAbits.TRISA2 = 1; //make interrupt port as input.
    OPTION_REGbits.INTEDG = 0; //make sense to falling edge.
    INTCONbits.INTE = 1;    //interrupt enable.
    INTCONbits.GIE = 1; //Globally enable interrupts.
    INTCONbits.INTF = 0;    //make interrupt flag clear.

    //prepare output on PORTC.bit1
    LATCbits.LATC1 = 0; //initialization of portc.0
    TRISCbits.TRISC1 = 0; //make portc.0 as output.

    while(1)
    {

    }

}

And we have Proteus simulation like this:

where is the mistake?
Any help would be appreciated!


texts:
There exist many coulomb-counter chips which measure the integrated current going into or out of a battery for purposes of estimating the charge state.  Are there any good chips for easy circuits for the purpose of measuring how much charge is used by a particular operation which may take 1-500ms?  None of the charge-counting chips I've looked at offer good resolution on short time scales.  A typical chip, for example, would output roughly two counts per second at maximum input current; if an operation requires e.g. 100mA for 10ms, and 25mA for 90ms, a coulomb-counter which would output two counts per second at maximum current (100mA) would offer one count per 50mC.  The operation described would consume 3.25mC, so the counter would only yield one count every 15 operations.

One approach I was considering would be to use a discontinuous-mode switching power supply, operating from a regulated input voltage, and count the number of switcher pulses.  That should yield a high-resolution count; if the switching power supply always used the same amount of current in each pulse, and if the current always fell to zero between pulses, the number of pulses should be directly proportional to the total integrated current.  Unfortunately, that's not the most efficient way to operate a switcher, and most switchers attempt to operate more efficiently than that.

Supposing the supply voltage will be either 3 or 6 volts, the maximum current is 250mA, and the goal is to have a minimum of 50% efficiency and 3mW quiescent dissipation, what would be the best approach?

Addendum

Although I'd like to have a general-purpose measurement approach, the particular application I have in mind is determining what factors affect the energy consumption of various "intelligent" RF modules which will be used outdoors.  For example, if the modules normally consume one mAs every 15 seconds to maintain a mesh, but during a rainstorm some of the modules will occasionally start consuming 10maS every second for a couple minutes, that sort of thing would be useful to know.  If for some reason the idle current which normally sits at 25uA sometimes goes up to 40uA, I'd like to know that too.

A lot of charge integrating devices work by measuring instantaneous current and integrating the measured values.  My concern with that is that the instantaneous current will have a rather large dynamic range (I'd like to if possible be accurate to 10uA in low-current situations, but be able to capture events up to 250mA), and taking readings with that level of prevision fast enough to ensure that even short events get integrated accurately would seem a bit tricky.

One solution I'm thinking of would be to use a PIC with a built-in or external analog comparator, running off a regulated 3.30 volts; whenever the output is below 3.10 volts, switch on a PFET with a series resistor adjusted to pass 0.50A with a 0.20 volt drop.  If there is a sufficient cap on the output, the PIC should be able to sleep whenever there is adequate voltage on the output; when the voltage falls below 3.10 volts, the PIC could wake up, feed pulses to the PFET until the voltage gets back above 3.10 volts, and, if charging didn't take too many pulses, "go back to bed".

I would expect that measurement scale accuracy should be affected by the accuracy of the PIC's clock, the effective combined resistance of the PFET and series resistor, and the comparison of the output voltage to 3.10 volts, regulation of the 3.30 volt input.  Measurement offset accuracy would be purely a function of leakage.

If the goal is to have an overall accuracy of 10%, the PIC would generally have to keep its output within 0.02V of the target.  Faced with a 250mA load, a 1000uF cap would drop 0.250V/ms.  Keeping the voltage drop below 0.02 volts would require having the PIC wake up within 80us, which I think is probably doable with the RC-oscillator-based PICs.


texts: How to identify filter behaviour without memorizing different topologies

texts: Is there a way to tell if a circuit is high or low pass without memorizing different topologies?


texts: Direct FM generation using varactor diode

texts:
I am trying to generate a constant 1 MHz FM carrier wave. I have achieved it via LC parallel resonance circuit. Initially I let the switch B open and switch A closed, in order to charge the capacitor. When it is charged, I open the switch A and close switch B, to fulfill the oscillation phenomenon.

I am trying to generate the same carrier wave using varactor diode, but unable to do so.

At 1 V reverse biased voltage, datasheet of varactor diode tells that it has around 440 pF capacitance. Solving two capacitors in series gives 220 pF, which on solving with 0.115 mH inductor, gives 1 MHz frequency theoretically. Why am I unable to get the result on simulation?


texts: How to run a motor with lower input power than it's rated for

texts:
I want to try to run a 48 V, 850 W BLDC motor (located within a vehicle wheel) with a 250 W solar panel.

I want to know how the system will react because, as per the motor characteristics, the required starting current is higher than my input power source (i.e. the 200 - 250 W solar panel) can generate.

In between the motor and the solar panel a motor controller is used.


texts: Bezier curves in hardware? (X-Y-mode on oscilloscope)

texts:
As I am exploring how to use an oscilloscope as a raster display in a question yesterday, and building the circuit, I am finding that with about the same (even less) components I could build a vector display also, where I just draw from point to point with Z-channel (intensity) either on or off, like a plotter, pen down or pen up. And as I designed a character mode for the raster display, I am thinking of a character mode for the vector display. In that design I have two 8-bit DACs for 256 x 256 positions on the scope. I have 5 bits of the DAC fed by the character cell position (32 x 32 characters), reading the character code from memory (1 byte per character) and then finding the character model in the char ROM.
In raster display mode we all know how this works: each byte of the char ROM data is 8 pixels, that we then shift the pixels out to the Z-channel (assuming right now the classical 8x8 character matrix.) And it's just a matter of how to connect the address lines and run the counters to arrange the char ROM in 8 consecutive bytes for the 8 rows of pixels of each character.
But instead of 8x8 pixels, I could have, each byte represent one stroke in a cell of 8x8 points.
+---+---+---+---+---+---+---+---+
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
+---+---+---+---+---+---+---+---+
| Z-ctl | Y-coord . | X-coord.  |
+-------+-----------+-----------+

Where X-coordinate and Y-coordinate are the destination of the stroke and Z-control says if the beam is on 11 or off 00.
And now I have 2 more values of the Z-control parameter. I could use it for 4 intensity values, allowing a "grayscale" effect ("green-scale", haha). But I am thinking: what if I could bend the straight lines?
So, for example, I could say

00 - beam off
01 - beam-on, X straight, Y delayed
10 - beam-on, X delayed, Y straight
11 - beam-on, X straight, Y straight

by straight vs. delayed I mean I use a simple RC delay which will delay the voltage change of one of the channels. Here I show a stroke from 0,0 to 1,1 with first Y-delay (red), the X-delay (blue), and X and Y straight (purple).

This would not be too hard to do. And that way I can draw curvy letters, which is so much better than straight, as it could even reduce the number of strokes. Imagine the D would have 4 strokes instead of 5, or the B would have 6 strokes instead of 10 and would look much better.
But -- now comes the question -- the RC function is not really that pretty and I wonder if circular arcs or, best, Bezier curves could be generated in hardware? Specifically the quadratic Bezier curves. Have people built analog function generators to achieve such an effect?
Note: I only care for analog or hardware digital, not computed methods. I know one can throw a micro-controller or an FPGA at anything and call it "hardware".
I'm also aware for the "oscilloscope music" movement which uses the two stereo channels to draw any curves. What I'm thinking of might even be related to that oscilloscope music movement, except that I would generate these wave form segments with some simple digitally controlled analog circuit, without preparing it on a computer.
Perhaps I should think about the RC curve as a Bezier curve and by selection of the time constant and the onset and end point of the stroke one might emulate it. It's mind-boggling. Someone should have thought about that idea, but I can't seem to find anything on Google.


texts: Solder vs screw connection on a cable connector

texts:
I bougth some 4mm male banana jacks today with the purpose of making myself some more test leads. They have screw connection, similar to the ones in this picture (from the farnell product page):

I wondered if I should stick to the screw connection, or if I should fill the hole with solder and insert the cable into that. The guy in the store said they solder all theirs - just get rid of the screw and fill it up with solder.

My first idea would be that "solder is clearly better, it's a pure metal connection!" but I know that this is likely false - crimp connectors are much more reliable than solder joints. Is this also the case here? I'm worried that since it will be moving a lot, the edge of the screw pin might cause a cutting to occur.

I'm going to be working with quite thin cables (0.5mmsq) because the other end is going into a micrograbber style connector, that can only accept this thickness. I mention it because I don't know if this changes things.


texts: Automating the switch in any circuit using 8051

texts:
I've got the circuit that record and play back voice ,
here is the circuit,

(source: engineersgarage.com)
Mode of operation

Record Mode

The LED glows when the IC records the voice obtained through the Mic. A single voice message up to 20 seconds can be recorded. The IC remains in the recorded mode as long as the RecL pin 27 is grounded. Recoding will be terminated with the last memory when 20 seconds is over. The Speaker driver will automatically mutes in the recording mode. By changing the value of the OscR resistor R1 it is possible to increase the recording period as follows.

    R1 52K 20 Sec.

    R1 67 K   24 Sec

    R1 89 K   30 Sec.

What i want to do is to use 8051 Microcontroller instead of the playback switch,
this is how the circuit suppose to work,
when the record switch is Closed , the timer starts and stays for 30 seconds and after 30 seconds of recording the playback wire which is suppose to be connect with 8051 muse be closed to play back the recorded voice,
I know how to generate delays of specific time using 8051 , and i know all about 8051 programming, what i need is the idea to connect 8051 at playback switch .
Could somebody help ? i just need an idea as i am still a beginner


texts: EAGLE Names not showing up on board after footprint update

texts:
I added the >NAME attribute to the footprint of a device and now the names are not shown on the board.

I have already tried to update the library (with library --> update all) and also the replace function.

But when I place the same part again the name is shown, only the old ones wont update, even with the replace function the names are still not shown.


texts:
I am using an ATTiny88 MCU as master over an Si4012 slave. The MCU is running code produced by Arduino IDE. Connecting a logic analyzer to the SCL and SDA lines produce an output as below - second scren grab. This logic analyzer may not be the best: if I try connecting its CLK input to SCL line then the I2C interface stops working ( and I do not know where else to get a clock signal for the analyzer from). Thus the analyzer is running its own internal clock while sampling @ 16 MHz. However, I can't see why there is this 1.953 kHz SCL reading coming from. Tried with both 100 and 400 kHz SCL rates - the analyzer shows the same 1.953 kHz clock rate... How come ? Any quick other way to establish the real I2C frequency without a scope ?

#define F_TWI             400000L
//#define F_TWI             100000L

....

  Wire.begin(); // Initiate the Wire library
  Wire.setClock(F_TWI);

As per Olin's comment - new image. Forgot to mention the two pullups are 3k3 and the rail is 3v3. Also I should note that the clocks of I2C and logic analyzer go out of sync quite fast as it can be seen in the first screen grab of the first image. Oh, and the MCU is running on its internal oscillator at 1 MHz.


texts:
I need help choosing a microcontroller for  a project I'm doing.

This microcontroller needs to do the following:

1) Interface with a low resolution camera, obtain video feed from it, compress it and send it a wireless transmitter.

2) Obtain analogue data from 4-5 sensors and use that information to drive motors through PWM.

3) Obtain control data from a wireless receiver and use it to control 1-2 motors.

I am totally new to this stuff and I have no idea where to look. Basically I have no idea how to relate the specifications of a microcontroller to my specific needs. What microcontroller would suit my needs?


texts: I'm very new to this topic Operational Amplifiers. Just started studying for my 4th semester. Can someone please explain to me why there is a virtual ground at  the node after Rin. What is the reason for that?


texts: Will stacked Peltiers produce a greater dT?

texts:
I am using this peltier device to ramp an aluminum plate down to -10C in a vacuum environment. I chose this particular device because it had the largest 'Qout' of any single-stage peltier I could find (400W!!), however I am having a hard time achieving my goal of -10C.

I am generally operating at about 20V and 14A with a large heat sink on the back (3"x3" Al water block feeding to a 10-gal ice water reservoir AKA fishtank). In this configuration, I can usually achieve between -5 and +2C, but never -10C.

Now I wonder if I would have better luck using a multi-stage peltier? Still becoming familiar with the technology, but from what I can tell, you tend to sacrifice Qout in exchange for increasing dT and vise versa.

If so, could I expect to see my cold-side temp drop if I switched to something like this?

Thanks!


texts:
So I know that silicon is the most common semiconductor out there by far. But I also know that there are countless other options; silicon carbide, germanium, SiGe alloy, gallium arsenide, aluminum gallium phosphide, the terrifying-sounding mercury cadmium telluride...

So, what properties would make a device designer choose one over the others? I understand that for LEDs and laser diodes matching the bandgap to give the right photon energy would be one reason, but are there others?

Germanium used to be the semiconductor of choice, but it was booted out by silicon fairly early on, and now it's near impossible to find germanium components. Why is that? Likewise, no one uses selenium rectifiers anymore (though they have more obvious disadvantages, like the ridiculously low reverse breakdown voltage and their physical size).

There's a lot of question marks in this question; I do hope that's not too many. While I am curious about this myself, I'd like to also make it a resource for others to use, so I tried to cover as much ground as possible without straying too far from the topic.


texts: Does my device need reverse polarity protection?

texts:
I'm developing a device with changeable AAA batteries running at 3V. Since the end user can change the batteries there is a chance they may be put in the wrong way around. The circuit basically consists of an ATTiny85 and some LEDs. Do I need to add a reverse polarity protection circuit to my design or should it be fine without?

If it needs one, what is the simplest way to achieve this? Just a single diode between +3V and Vcc on the MCU should do, right?


texts:
Has anyone tried twisting very thin wires(of order 100 microns) and then sandwiching it in between 2 layers of a multilayer PCB?
I have a problem of EMI and looks like twisted pair is the only solution as all means of shielding is ineffective due to DC magnetic field near field constrains.

Can experts in PCB comment on this ?

The real problem : Moving pickup coils on top of strong DC magnetic field. These induce heavy noises in a highly complex geometry problem. Of course a normal twisted pair cable would be a temporary solution but it is not robust. Also the use of Via's as twisted pair PCB was ruled out as the movement produces enough jerk to put high stresses on the via's.


texts: Using a dev board as final commercial solution

texts:
I'm working on a small embedded project which controls electrical usage of a factory/department. My solution is limited regarding the production of the solution: I may sell 50 or 100 per year.

My question is: can I use a development board like Beaglebone or less AVR or Freescale to ship my solution to clients (with little enhancement: box it and label it... etc)?


texts: How to identify or calculate the electromagnetic interference (EMI) contribution of components on PCB

texts:
I am designing a circuit using the Motor Driver IC TB6612FNG. Now I am unaware about how can I calculate the EMI contribution by this IC.
I did add the bypass and decoupling, grounding control, transmission line control, and trace termination matching to achieve the Electromagnetic Compatibility.
My question how do we measure the EMI contributed before and after the addition of the bypass and decoupling, grounding control, transmission line control, and trace termination matching ?
Is there a theoretical way to determine or predict this ?
Does the datasheet provide any related information, if yes where can I find it in the datasheet?


texts: How do I design a RC phase shift oscillator using opamp with the help of cmos (pmos and nmos)?

texts: Designing the opamp using cmos (pmos and nmos) to construct RC phase shift oscillator using opamp with the help of opamp (constructed using cmos.)


texts: Why is the neutral pin hotter than the live pin?

texts: I frequently use an Immersion Rod Water Heater (shown below) and I have noticed that the after unplugging the heater, the neutral pin of the 3 pin plug is quite hot (about 5 degrees more - but not very hot) compared to the live pin. How is this temperature difference possible and why?


texts: Impedance matching a variable transmission line

texts:
I have several transmission lines, each with different impedances. These lines are attached to an ADC receiver with a known impedance of 400ohm.

I would like to have an impedance matching network that matches the impedance for an arbitrary transmission line to my 400ohm receiver.

Is this possible? If not, does this mean I need a new impedance matcher for each transmission line of different impedance? I'm new to this so I just want a general idea of what I'm thinking about is possible. If not what do people typically do?


texts: Does a TIP120 transistor have an internal resistance when switched on?

texts:
I'm having an issue with a TIP120 I'm using limiting current flowing through it.

I'm using the TIP120 to switch on/off a 12 V electromagnet. The circuit is working, but it appears the TIP120 is limiting the amount of current that is able to flow through the electromagnet. If I hook the electromagnet directly up to my bench supply I can get 290 mA of current (it has a 39 ohm internal resistance).

When I use the TIP120 to switch the current on/off the most current I can get through the electromagnet is around 240 mA, a 50 mA drop. I'm pretty sure the transistor is getting switched on all the way as I've experimented with everything from 220 ohm to 22 kilohm resistors on the base to the controlling voltage and the resistance to the base of the transistor isn't having any significant effect on the amount of current flowing through the magnet (collector to emitter).

Is this current drop expected? I don't see anything in the specification sheet of the TIP120 that lists an internal resistance that would be limiting the maximum current.


texts: Using series of LM 78XX for power supply

texts:
I'm new in electronics. I want provide 9V (VVD9) and 5V (VCC) for my electronic board including power mosfets (IRF 3205), high power LED (14V-3.5A), micro-controller (at-mega16), and etc. I use this strategy to provide those voltages for aforementioned elements as depicted below:

For more details I provide the main part of circuit as shown below. The circuit provides strobe (5Hz-2%duty cycle) for LEDs and a Camera:

I have two questions:

Is using that strategy (shown in first image) good?
As depicted in first image, input voltage is 24V. I Also use it for high power LEDs (in second image). Is there any side effect? (for example, voltage drops when LEDs are pulsing).

Any help or suggestion will be appreciated.


texts:
I've been looking for a good display for the handheld device that I'm building and I've liked the various HD44780-based displays that I've tried. (like for example this one: https://www.sparkfun.com/products/9054)
However they don't fit the needs of my device because:

1: They are too thick. All the HD44780 LCDs I've seen are atleast 10mm thick. I need something that is 6mm or thinner.

2: Too wide. The display cannot be larger than 45x45mm while still being able to display around 32 characters. (number of rows doesn't matter)

3: They all need calibration with a trimpot to adjust the backlight strength. This isn't a showstopper for me but it would be nice if I could buy pre-calibrated displays.

Questions:

Is there a reason as to why all HD44780 LCDs are so thick compared to graphical LCDs?

Are there any alternatives that would fit my needs? (I just need to display up to 32 characters sent from an Arduino)

Do I need to worry about the reliability of the LCDs? I tried using a cheap Nokia-LCD from Sparkfun, https://www.sparkfun.com/products/569, and it would fit my needs but I get the feeling that the LCDs are of low quality and would start dying after a while in the hands of the customers, and then there is the whole mess of different controllers. Also I'm worried about messing up the SMD soldering since I'm new to electronics and never manufactured devices before.


texts: Why is the chording angle 30 degrees, in a practical alternator?

texts:
So far what i have understood...

Chording angle in Synchronous Generator/ Alternator is introduced to tackle the problem of harmonics that couldn't be taken care of during the design either in -

Salient Pole Rotor: As the POLE PITCH/POLE ARC percentage is ~70%
Cylindrical Pole Rotor : As we can't achieve a stepped sinusoidal mmf in the air gap, given that the manufacturers are reluctant to cut the slots with different dye's as they are costly. Even if this were to be done then slot harmonics will still enter the air gap.

So basically harmonics in the air gap of an alternator are going to be there, no matter what, can't be avoided...

To deal with this chording factor was introduced.

Kc  = cos(a/2)   --> For Fundamental

Kcn = cos(n*a/2) --> For Nth Harmonic

My question is :

In practical data of alternators most of the time the chording angle is kept 30 degrees, to reduce the belt harmonics component i.e 5th and 7th, but wouldn't 3rd harmonic have more effect on the fundamental than the 5th and 7th, why did we not keep the chording angle to 60 degrees, which would had eliminated the 3rd harmonics, something that we usually do?


texts: Can I use a BC547 NPN transistor as a thermometer?

texts:
In the article Electronic Thermometers for Brewers Ken Schwartz talks about how to use a 2N4401 to create a diode thermometer:

I attempted a similar setup with a BC547 transistor ( BC547 Transistor NPN 45V 0.1A ) but I'm not having any luck with it. According to the BC547 datasheet the emitter and collector are opposite from the drawing above, but I tried both ways and neither one seems to work. They both seem to be the exact same. is there actually a 'correct' way in this setup or will either one work if the transistor is not bipolar?

After connecting the B&C I measured resistance with my Fluke and got roughly 55M ohms. I thought that I understood the theory of what was going on, but now I'm not so sure. I was thinking that the transistor was acting as a variable resistor that if it was connected between a fixed resistor then the setup could act as a variable voltage divider, which could provide a voltage that could be measured and the temperature calculated.

I tested this theory but got the same readings for voltage with both a 47K and 47M resistor and so I figured this was perhaps not how this configuration works. The voltage was around 0.6V when using a 3V3 power supply.

When connected to the Fluke meter the resistance does appear to vary with temperature  (holding the transistor for instance) it changes between 55M Ohms at room temperature to 45M Ohms.

Will the BC547 work for this setup?
How does this setup work (if it is not as a variable voltage divider)?

Possible datasheet links:

https://www.fairchildsemi.com/datasheets/2N/2N4401.pdf
http://arduino.cc/documents/datasheets/BC547.pdf


texts: Noise reduction in physiological measurements (EEG/ECG)

texts:
I am building a hobby EEG and I am interested in quantifying how effective are the various noise reduction techniques.

The basic circuit would be two electrodes going to an instrumentation amplifier. Then the signal goes to various filtering stages and then to a final "mundane" amplifier. I am interested in noise reduction before the filtering. Here are the steps that I am considering (hopefully this can evolve into a community wiki).

Adding a right leg electrode directly linked to the ground of the circuit. (against 60Hz hum)
Adding a driven right leg electrode for common mode rejection. (against 60Hz hum)
Adding passive low pass filters in front of the inputs of the instrumentation amplifier (see here). (against DC difference between the electrodes and bias current from the inputs)
Faraday cage (against 60Hz hum)
Shielded cables for the electrodes (against 60Hz hum)

Are there any technical manuals discussing these approaches? Could you share your knowledge about the effectiveness of each approach? Could you suggest other approaches?


texts: Simulating LPM_counter on Modelsim gives 'z' (high impedance) output

texts:
I'm trying to implement a simple 9-bit frequency divider using the LPM_counter Module.
Hardware and Software being used:

ALtera Max V-CPLD
Quartus II 64 bit Web Edition 15.0
ModelSim Altera Starter Edition 10.3d

I wrote a program in Block schematic format (BDF) adn downloaded it into the cpld and it works fine, giving the desired output. However when I try to simulate it in ModelSim it gives 'z' (high impedance) on all outputs.

For the simulation I created a Verilog file from the BDF file using the 'Create HDL design file fron current file' option in Quartus. Then I wrote A testbench to simulate a clock input for the LPM_counter module.

I've tried a lot of different things that I've read from different forums such as trying to run it without a testbench by giving a Clock input directly in ModelSim, trying reg outputs instead of wires and vice versa, amongst other things.

I've been stuck on this for a while now and really need it to work because I'll be needing ModelSim to make programs for some upcoming projects. I'm doing this to get used to the whole process before I actually work on it.

Btw I made a frequency divider using JK flipflops and that worked fine on both, the cpld and ModelSim simulation. Its just this black box module that I'm having problems with.

Source File (Converted to Verilog from .bdf)

module ninebitlpm(  myclk,  q );

input wire  myclk;
output wire [8:7] q; // only using the two most significant bits
wire    [8:0] q_ALTERA_SYNTHESIZED;

lpm_counter b2v_inst(   .clock(myclk),  .q(q_ALTERA_SYNTHESIZED));

assign  q[8:7] = q_ALTERA_SYNTHESIZED[8:7];

endmodule

module lpm_counter(clock,q);

/*synthesis black_box */
input clock; output [8:0] q;

endmodule

Testbench

`timescale 1us/1ns

module test_lpm();

reg myclk;
wire [1:0]q;

ninebitlpm mycounter(myclk, q);

initial begin myclk = 1; forever #1 myclk = ~myclk; end

endmodule


texts: Power management controller with multiple inputs

texts:
I have planned a (quite complex) controller for a project based on a Raspberry Pi (web UI, logging, camera framegrabbing/video processing, LTE uplink), i2c sensors (assortment of environment sensors), an Arduino (for the i2c stuff that I am too lazy to write Pi-compatible code for) and a couple USB modules, and to add to the mix some components controlled using 12V relays - leading to three power levels: 3V3 (for some of the i2c stuff), 5V (Arduino, Pi, USB modules) and 12V (the stuff behind the relays). As power inputs I have the availability of 3x 5V via the microcontroller inputs and 12V, while 3V3 at the moment is coming off the RPi board and I'm not sure if I don't want to go above the 50mA limit there in the future.

Now, before I design a carrier PCB for the stuff that's basically one of a hellfire of breadboards and cables I'd also like to make the project portable and (at least for 10-20 min) uninterrupted from power failure, so I need a power management solution (preferrably already as an integrated IC?) that provides:

the ability to accept voltage from any of the inputs including all inputs be powered at the same time, including especially that there is no "reverse powering" - meaning that, if the microcontrollers are attached as slaves to an USB hub, that supplying power on the Arduino USB should not put power on the 5V rail of the USB input of the Raspberry Pi, thus providing power to the other devices attached to the hub of the Pi
a battery management solution (I'm open for anything battery-related that's not lead-acid batteries and takes care that the battery doesn't go above limits in charge/discharge currents or temperature)
safe handling of 12V in cars which can be anything from 6V or lower during engine start or way above 100V shortly after load shedding - I don't want to fry the project like I once did with a wifi router
stable high quality power (=neither the Pi nor its SD card should corrupt)
at least outputs of 12V@2A cont./6A peak (=motor startup) and 5V@5A cont.
if possible, short-circuit resistant to prevent my own clumsiness from blowing up the battery.

Naive me would solve this by putting a diode on each 5V input to prevent reverse powering, put a 12V-5V DC/DC step-down regulator to the 12V input, then join all the 5V rails together, use this as supply for a 20.000 mAh power bank capable of pass-through powering, and from its output power the 5V rails of the microcontrollers, a 5V-3V3 DC/DC step-down regulator for the I2C sensors and a 5V-12V DC/DC boost converter for the motors. That would however prevent me from catching the "no supply voltage, operating on battery" mode in one of the microcontrollers.

Is this enough or can I do better by doing all the power management by myself? If yes, how? Unfortunately I'm better at programming than at designing circuits.


texts: Changing "Latching Normally Closed" switch behaviour to "Momentary Normally Open"

texts:
I am trying to connect a normally closed gate sensor to a cheap 433 MHz remote so I can monitor the status of the gate at the front of our property remotely.

The remote has a normally open button that I plan to solder onto and connect to my sensor.

When the gate is shut the sensors circuit is closed. When the gate opens the sensors circuit opens until the gate is shut again.

The behaviour I am trying to achieve is... when the gate is opened, the remote button circuit should be closed for a short burst (about a second) to simulate the remote button being pressed, then released, regardless of whether the gate is left open or shut.

Once the gate closes and opens again, the behaviour repeats.

Any ideas how I could approach this problem?

I have done some research and found different methods of converting NC to NO behaviour and latching to momentary but I can't work out how to do both together!

Thanks in advance!


texts: What is the easiest way to get a 50x DC-DC voltage increase?

texts:
I want to have a 3-4 kV DC output to feed a marx generator in which I am planning to use 4kV ceramic capacitors. I have 2 DC power supplies @ 30V 6A rates, so I can have at most 60V DC input by using them in series. What is the best or easiest way to have that approximately 50-60x voltage gain?

I don't think the output current will be important because I will only need fast charge and discharge of capacitors to 3-4kV / from 3-4kV.


texts: Are there any certificates for embedded system developers?

texts:
For example in the field of networks there are CISCO, JUNIPER, CCNA, etc., and in the field of databases there are oracle certificates and so on.

What about the developers of Embedded systems (Hardware & software): are there any certificates for them?


texts:
I am asked to find the schematic diagram of the following breadboard configuration:

What I understand is that the current flows from R1 to R4, as supplied by the voltage. Since the current seems to split into the two resistors after R1, I assumed that there should be a node. After that, I placed R4 as connected in series with the exit node of the parallel circuits.
Is the following schematic correct?


texts: Help me understand the pinout of this 21" LED display driver

texts:
I am trying to connect a 21" LED Display driver's input pins to my power board. There is a datasheet also but it doesn't have the input pin diagram. Therefore, I have got the below attached input pin diagram from the Chinese manufacturer.

The things that I have understood by looking at pinout and datasheet of LED Display driver's is that on/off control takes 5V and that brightness takes the PWM input.

The questions I have in mind is:

Which ground is for which voltage. Does both 12V have common ground and the ground for on/off is separate.
Will the system still work if I don't give the adj brightness (PWM input) input? I just quickly want to test it, so will the brightness default to a certain value or is it necessary to connect the adj.
Will the on/off take 5V momentarily like a switch or do I need to supply constant 5V to keep the display on.

Datasheet

Input pin specs:


texts:
I'd appreciate some help with the following section in this question:

Here's an attempt:

Since it's shunt-shunt feedback I figured I could write:

\$V_o/V_s=-10=A(R_1+R_2+R_L)/(1+AB)\$, where \$A\$ is the open-loop gain. But I am having difficulties assessing \$A=V_o/i_s\$. Could its value simply be \$R_L\$?


texts: Are the same type of antennas used for receiving and transmitting?

texts:
Short version:
Is the same antenna type used for transmitting as is used for receiving if the frequency is the same?

Long version:
My garage door opener uses 433 MHz to receive signals from the remote control. The antenna it a wire, about 30 cm (one foot) long. The door opener transmits its status to a control device we have in the house. When transmitting it uses 868 Mhz. The antenna for transmitting is a wire about 8 cm (3 in) long. The control device we have in the house contains two antennas, both wires about 8 cm long. One I assume for receiving and one for transmitting.

I assume I can replace the 30 cm wire in the door opener with a 433 MHz antenna like this (http://www.ebay.co.uk/itm/New-SMA-Male-Crimp-RG174-GSM-GPRS-433MHz-Antenna-Sucker-Cable-3dbi-Magnetic-Base-/161525785843?hash=item259bafe4f3:g:fcoAAOSwuMFUkqWO) and the receiver antenna in the indoor control device (which I'm anyway going to put in a custom case) with this (http://www.ebay.co.uk/itm/868MHZ-915MHZ-GSM-3G-Sucker-Omnidirectional-High-gain-Antenna-7DBI-super-/201249960496?hash=item2edb6eb230:g:J3IAAOSwuMFUj-2c).

But what about the transmitter antennas? Are there custom transmitter antennas or can I buy a 433 MHz antenna and use that for transmitting at 433 MHz?


texts: Checking and reading bits using while loops

texts:
Note: I am a beginner :) MCU: Atmega328p
I am  struggling to understand how reading registers using while loops work in Embed C:
For example AVR-C USART Protocol:
while (!(UCSRnA & (1<<UDREn)))
;
/* Put data into buffer, sends the data */
UDRn = data;`

Equally:
while (( UCSR0A & (1<<UDRE0))  == 0){}
UDR0 = data;

In this case as when UDREO bit is equal to 1 the data should be loaded into the buffer and sent. The logic seems to say the opposite, it seems to say that when UDRO is full load the data which contradicts the datasheets explanation.


texts:
I'm trying to simulate the MBRB20H100CTT4G for a flyback converter (it's going to be the rectifier).
However, only ".model" files are supplied (no .subckt), so I'm confused as to how exactly I should model the dual diode.

Here is the model i'm using :

.MODEL MBRB20H100CTG d
+IS=2.42014e-05 RS=0.01 N=1.78382 EG=0.753678
+XTI=4 BV=100 IBV=1e-05 CJO=3.72271e-10
+VJ=1.04295 M=0.478361 FC=0.5 TT=0
+KF=0 AF=1

Should I put 2 generic diodes using this model in parallel, or only one ?


texts: Using transistors to minimize the number of Arduino pins used for this stepper motor driver

texts:
Alright, I know very little about what I am currently asking about, but here is the gist of it:

I want to build a cnc machine out of some old floppy drives. I purchased a couple L293D dual H-bridge ICs to drive the stepper motors, and I want to interface with grbl. The problem I seem to be having in designing a proper circuit for this is the circuits for driving stepper motors with the L293D all involve two inputs, one for each direction, and grbl seems to only use one Arduino pin for direction for each axis.

So what I've thought up is using a pnp and an npn transistor to act as a kind of two way switch, when I apply voltage one goes on, other goes off, and vice versa, so that basically 1's and 0's are controlling which way the motor will spin, and the "step pulse" will provide the actual motor power to move it in that direction.

My question is: will this work, or is what I said complete non-sense? I only understand pnp and npn transistors to be something like a "usually on" or "usually off" logic switch, basically, so that's where I've come up with that... Kinda like how an H-bridge works in the first place.

Thanks for taking the time, the diagrams I'm looking at are:

grbl to Arduino pins:
http://www.electrodragon.com/w/images/e/e7/Grbl_Pin_Layout.png

L293D driving a stepper motor:
http://arduino.cc/en/uploads/Reference/bipolar_stepper_two_pins2.png


texts: sim 800c doesn't get registered in network

texts:
I am using sim800c gsm module.

It is showing some weird problems that am not able to figure out.

The at commands are working fine.

The problem is that, the module stops working after inserting the sim card. After the power button is pressed, it gives the following messages:

RDY, +CFUN: 1, +CPIN: READY, Call Ready.
After this, the module stops working, the led stops blinking. If i don't insert sim card this won't happen.

The power supply is proper 4.1 v 3A, even i tested with 4V battery there also it shows the same problem. So I don't think this is power supply problem.

I tried with different sim cards and got the same result.
this is the circuit diagram


texts:
I want to make my homemade LED flashlight into an old utility light body. My plan is to use XHP70 LED from CREE (12V, 2,8A) and power it using 2S Li-Ion cells (6-8,4 V).
My idea is to use boost converter IC to step up voltage and use shunt in series to sense current through the LED and connect it to feedback pin of the converter (and most likely use OP-AMP to amplify shunt drop voltage). At first I thought that I would use LM2577T-ADJ, but it can handle switching current only up to 3A and after some calculations it would be more to 5 amps. Is it possible to use external transistor instead of the inbuilt one? Or do you know about other IC that would do the job? MC34063 with external transistor maybe?
Another problem is with charging. I can't seem to find any CC/CV charger IC that would be suitable for 2S cells and THT soldering. I found this circuit that could be possibility, but I would prefer to use something in small package. The charging voltage would be 12V. Thanks for any help.


texts: Pspice: parametric gain of dependant source

texts:
I am trying to create my first circuits in Pspice and I want to implement this command:

E1 node1 node2 VALUE={I(E1)*V(2,0)}

From my understanding, it represents a voltage-dependant voltage source which multiplies the voltage V(2,0) with the current flowing through the E source itself.

However, I can't find a way to achieve this functionality in Pspice using the Property Editor and when I use {I(E1)} as the gain of the E source I get an error. What am I missing?


texts: If the capacitor plates are not ideal conductors (and have relative dietetic constant > 1), how does that change the capacitance calculations? It is my understanding that capacitance is purely related to geometry and the material BETWEEN the plates and not the plates themselves, is that correct? (The specific material I have in mind is biological tissue such as bone, muscle...)


texts: What are some LED technology for one dimensional coherent light emission?

texts:
I need to emit a unidirectional infrared pattern, i.e. the emission cone should have small angle on one dimension and large angle on the other one (basically laser-like in one dimension and normal light on the other). I tried to illustrate this in the image below (alpha should be much bigger than beta, e.g. alpha = 90 degrees and beta = 4 degrees)

I looked into laser diode arrays, but majority of them are high power, which makes them hazardous and thus not suitable for my application.

Covering a normal LED with a mask is something I though about, but it is rather difficult to realize it with the tools that I have. It also reduces the intensity of the infrared, which I wish to avoid. Another approach is to mechanically sweep a low intensity laser diode, using an dc motor, but doesn't fit into my list of requirements (wrt size and cost)

So mainly, I need to find an LED which optically focuses the emitter light in one direction and not the other.

Do you know of such LED (manufacturer, part number, ...), or any other solutions that can fulfill the following requirements: low cost, easy to reproduce in large quantities (i.e. 100s), and safe for usage without any protection glass and alike.


texts: Which digitally-controlled chip to replace eight transistors (GE D44C7)?

texts:
I would like to programmatically toggle off/on (independently) eight 5 V small light bulbs. It seems that I could use eight transistors controlled by eight independent digital control pins.

(See the attached schema below.)

But I'm sure there is a simpler way using a single chip ... with only one or two digital control pins (my digital control out(s) are 5 V max with a 255 steps resolution, so it could be OK to store all the different combinations within only one byte!).

I'm actually using an Arduino, so some of the digital outputs are PWM (at first, I simply tried to directly use the digital output to light the bulb on/off... But not enough current was available on the Arduino :(
The lights will be triggered on with a 200 mA current, but for a small amount of time (less than 50 ms)
I'm OK if I need to use three digital pins!
I'm aware the magical chip should have at least eight pins (one per bulb)
I'm super newbie, so not too much programming please :)


texts: Constant current, constant power and constant impedance loads

texts:
Ive been looking for information on constant power, constant current and constant impedance/resistance loads, there's some information about the constant current loads, but very little that really explain constant power and constant impedance.

So please correct me if im wrong as ill try to define what I understand about this subject:

A constant current load is the one which varies its internal resistance to achieve a constant current regardless of the voltage which is being fed to it (within certain extent) and therefore the power will vary.
Im assuming a constant power load, also varies its resistance so the power (or voltage and current product) is always the same, regardless of the voltage or current that is being drawn.

And what about constant impedance/resistance loads? does it mean that both voltage, current will vary and therefore power will vary too? yet impedance or resistance will remain the same?

And if we are talking AC, im also assumming this valid for all frequencies in a certain range.

Now, on a more conventional scenario, when we are talking about regular every day loads, say a power supply inside a computer feeding the motherboard and peripherals, or a linear power supply inside a stereo feeding the inside components. Are we talking about a varying current, power and impedance loads?

How can it be determined if a load is constant current, power or impedance?

Thank you very much!


texts: Cause of Relay Coil to stop working ( No resistance) can it be fixed?

texts: Reason for my strand relays HLR6100-1ATJCB 240VAC to break and stop working? The Coil resistance before using was 9.0M ohms. It doesn't last long. Can the coil be fixed? The relay is connected to Strand C16 RCBO. Is the RCBO suppose to protect the relay? Thank you!


texts: How can I make a phase shift in an audio signal without changing the frequency response too much?

texts:
I have the following problem: I have two amplifiers, one is a mono amp for a subwoofer and the other is a stereo amp for two two-way speaker enclosures.

The subwoofer and two-way enclosures have a good overlap in the bass frequencies, however, due to the low-pass filter in the subwoofer amp, there's a phase shift ranging from 60º to 50º in the 0-50 Hz range, the subwoofer being the one "lagging".

And as all speakers are almost the same distance to me (and I can't change their positions), this causes the interference to be not completely constructive at the spot where I listen to them.

But all leading current circuits I see are also high-pass filters, which would be a problem for my sub.

So, how can I shift the phase without causing an dramatic change in frequency response?

Thanks!


texts: Is there a way to change only one of the outputs of a D flip-flop?

texts:
I designed a schematic for a ring counter, but the last two flip-flops' simulation signals didn't shift.

My D-flip flop is designed as set=1,then Q=0; reset=1,then Q=1;

set=1=reset,then Q=1,when D=1 occur at positive edge clk.

set=0=reset,then Q=1=Q_bar

Here is my thinking, if it is wrong, or you have other ways to let my simulation become correct, please tell me.

At first,the output should be 1 0 0, but mine is 1 1 1; I think it is because my flip flop's output,Q and Q_bar,are 1 when set=reset=0. To modify the circuit of my d-flip flop, is there a way that only change (set=reset=0,then Q=Q_bar=1) to (set=reset=0,then Q=Q_bar=0)?


texts: Impedance Matching Network with tracks+connectors in between (practice)

texts:
I've been struggling on how to design (and develop in practice) an impedance matching network with some traces/tracks/paths (whatever you wanna call it) and some connectors in between. So here is the architecture:

Antenna (50 Ohm) + path (50 Ohm) + Matching network + path & SMA connector (?) + SMA connector & path (?) + Rectifier & load (Z_L known)

simulate this circuit – Schematic created using CircuitLab

The perfect matching would be if right after the last component of the matching network comes the first component of the rectifier, but it is not the case by far, since there are paths and connectors in between.

So...

Should I count the impedance of the load starting from the connector? --> then... probably there are reflections between the connector&path and the rectifier.
Should I characterize the rectifier with a TRL calibration (having out path and connector) and count it as part of the matching?? --> I don't have a clue how to do the matching like that... with ADS or directly with the Smith Chart I haven't arrived that far.
Looks like it is not possible and what I have to do is include the rectifier in the PCB1 and the rest of the load in the PCB2... But again... even the small path connecting the last component from the matching and the first from the rectifier could have an impact. How could I include this into it? (it would be the same case as the current one though).
Any other solution? :C

If somebody could throw some light there, I'd be eternally grateful.

emece


texts:
I have an 8-bit input and my goal is to increment the input on each clock cycle. The new value will then be saved into a register to be used to search memory.
Say, for example, the input is currently 2. On the first clock cycle, the input will be saved into the register as a 2. On the second clock cycle, it will become a 3, and then a 4, and so on.
What I've tried is using an 8-bit adder that goes into the register. The issue I'm having is that the clock rises at the same time on both the adder and the register, so the value from the adder is incremented after the register can do anything with the new value. Also, it's not really changing the input value, so in this case it would only ever be a 2 or 3.

Adder circuit:

Register:


texts: Can we use ethernet cable instead of coaxial cable without adaptors.?

texts:
I am a mechanical engineer. Trying to build a computer vision system using endoscopic camera. I have a camera with 4 pin input, 2 input pins for power supply of 5 volt and 2 input pins for video signal transmission. I am using a 2+1 coaxial cable for video signal and power supply transmission. My camera is continuously moving at a certain speed, which causes the coaxial cables to break from inside. Since my application needs a robust cable with smaller dimension, around 4mm OD, I want to change the cable to CAT5 OR Unitronic FD Lapp cables (which has high torsional strength).

Can I use a cat 5 or other simple multicore cables instead of coaxial cable.? Why should I use only coaxial cable? I like to simply substitute the coaxial center strand and insulation with normal multicore cable. Will it work efficiently in long run ? I have tried an experiment, video signals where getting transmitted but suddenly the camera does not work. Dont know what has gone wrong with the camera.

Kindly suggest a possible solution. Thank you very much !


texts: bi-directional motor control using two mosfets

texts: I am trying to understand how a dual motor controller works. It drives two DC motors with support for running the motors in the opposite direction, as well as stopping them. Looking at the board I spotted two FDS4953 Dual P-Channel mosfets, presumably one for each motor, as well as a transistor. Their schematic shows that each is comprised of two mosfets. How is the board able to achive this with just two mosfets per motor?


texts: How the relay contact resistance is measured?

texts:
Many OMRON's relay specify the contact resistance with this:

  The contact resistance was measured with 10 mA at 1 VDC with a voltage
  drop method.

Such as http://www.omron.com/ecb/products/pdf/en-g6a.pdf.

Then, how the test circuit are arranged? It's apprently 1VDC/10mA is not equal the contact resistance they stated. If we already know the current flow through the contact, then why they specify the voltage '1VDC'?  Apparently it's not the voltage drop on the contact. Any special reason?


texts:
I am making first steps in VHDL and ISE (from Xilinx).

I've tried to create a simple 16bit -> 32bit converter.
Converter receives a compliment to 2 number (16bit, so it is 1 bit for sign and 15 bits for modulus number) and outputs its 32bit form.

I've written such a piece of code in VHDL:

library IEEE;
--using standard lib
use IEEE.STD_LOGIC_1164.ALL;
--lib provides arithmetic functions for vectors
use IEEE.NUMERIC_STD.ALL;
--using lib for operating on U2-code numbers
use IEEE.STD_LOGIC_SIGNED.ALL;

-- Uncomment the following library declaration if instantiating
-- any Xilinx primitives in this code.
--library UNISIM;
--use UNISIM.VComponents.all;

entity MB_16b_to_32_conv is
    Port ( X_16b : in  STD_LOGIC_VECTOR (16-1 downto 0);
           Y_32b : out  STD_LOGIC_VECTOR (32-1 downto 0));
end MB_16b_to_32_conv;

architecture Behavioral of MB_16b_to_32_conv is

begin

 Y_32b <= std_logic_vector(resize(signed(X_16b), 32-1));

end Behavioral;

running a simulation in Xilinx ISE gives me an error:
input is "0000000000000101"
and output is "0000000000000101U" (orange in iSIM).

When converted to decimal in iSIM i get input = 5 and output = U.
I don't know why there is U and how to get rid of it, so I am looking for help.


texts: Separation of channels in simple audio LED VU meter

texts:
I'm trying to build a very simple VU meter based on LEDs and transistors. I used this tutorial as a base - basically I copied the LED array setup but replaced the input with full bridge rectifier. My signal input circuit looks like this:

simulate this circuit – Schematic created using CircuitLab

Overall I understand how this circuit works. I built one channel and it works as expected. However, my goal is to have a stereo indicator with common power supply. So I built the second channel the same way, with common ground. However, I noticed a weird thing: I tested the circuit with 1Hz sine wave and noticed, that when I turn the balance all the way to the right channel the right channel lights every 0.5s, which is expected. However, the left channel also lights up but every 1s, as if it's receiving half of the cycle as input. Understantably, for higher frequencies just both of the channels light up, regardless of which channel receives the input signal.

My question is: why and how does this happen?

Side note: please bear with me if this question is silly, I just recently picked up electronics as a side hobby and am still struggling a bit. I have tried to find information about this but I don't even know what to look for.


texts: Trying to heat a wire to around 94F for a few seconds using Pi3 and Nichrome

texts:
First off I am trying to figure out if this is possible. Trying to use it to work with thermochromatic pigment that changes at 92F The pigment would be on a fabric with the heated wire on the other side. The fabric is quite thin, similar to a morphsuit. I would like to power it or at least control it with my Pi3 because I want to flip it on just long enough for it to heat up to that ~94F for a moment. My main issue I think I am going to run into is the max current across GPIO pins which seems to be around 16mA per pin or 50mA across all 3.3V pins in the rail. I want to power with a portable batter pack If there is a good way to control it from the Pi and use the power straight from one of the outputs on that battery pack that would work well too.

I will post back here if I find a solution on my own. Thanks for taking the time to read and or respond.

EDIT
I guess I forgot to clearly post what my main question for this community is. Does anyone know if that low current output would even be enough to get something like 32 AWG Nichrome to around 100 degrees.
Looking at the problem I think a good way to go about it would be to use the Pi to control some other circuit powered either straight from the battery pack or using a AA or 9V battery pack. However I have no idea what I need to purchase and how I would make such a circuit. I have an idea of what I want to do but I do not have the know how to accomplish it.
Thank you again for taking the time to help me.


texts: Tertiary control loop in Automatic generation control of Power system

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Here I need help with AGC related research paper. I have certain confusions about tertiary control...
Why do we use tertiary control loop in automatic generation control of Power system? Because primary control of frequency controls the dropping characteristics,Active Power-frequency,and Reactive power-voltage droop characteristics and secondary control loop is used to maintain the reference power order, bringing the frequency back to nomial value and regulation of inter-area power flow. Then why secondary control can't do the economic dispatch process? Why we need the tertiary control loop which  is very slow process in AGC? What is the benefits of tertiary control over secondary control when both processes are almost same? Does tertiary control loop change reference power order or regulate frequency to maintain grid level control manually? Please explain briefly.


texts: Generating Hexadecimal checksum for a NMEA (PMTK) message

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I am trying to use quectel L80 GPS receiver for my project. I am trying to configure the L80 using the PMTK strings. But the problem is the string should also contain a hexadecimal check sum.

eg. $PMTK314,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*29

This is the example string given in the "protocol specification" document.
In this string '29' is the check sum. My question is how do I generate the checksum? I know that for NMEA strings, the check sum is generated by 'XOR' operation of consecutive characters between '$' and '*' . while calculating the check sum do I also need to include 'comma'?

Thanks


texts: P-Channel MOSFET high side switch in an MPPT buck converter gets very hot with no load

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I am a novice working on an MPPT solar charge controller. Q5 mosfet (SUP53P06) gets very hot even when I have no load attached.
The circuit is just like below except I have no current sensors in it yet. So ACS712s are missing. And R5 is actually 47K ohm (i had 10k in there as well, same result).
Solar voltage on Q5's source is 18.85V, but it's only 18.41V on drain. Rds for this fet is 0.02 ohms, so I don't understand why there's such a big drop.
The gate is driven via an NPN transistor with a voltage divider since the solar panel has a max of 22V and i think that would exceed Q5's Vgs(max). The gate voltage is 12.4V. (when i had R5 = 10k ohm the gate voltage was about 9V i believe, so almost -10V to the source).
Sorry for my messy schematic and for possibly too of an open ended question but I've spent a couple of days on this and can't seem to figure it out.
Let me know if you have any ideas about what I am missing here. Thank you!
EDIT: The current is at about 50mA at 0 duty cycle (and that's i believe to power arduino nano, not going through the Q5 fet). However if I allow the duty cycle to rise the current goes up to 140mA. Is it shooting through? IR2104 has plenty of dead time built in. Still though, at such low levels I'd expect the fet to be cool as a cucumber.
EDIT: Q3 needs to be flipped in this schematic. It is the proper way in the actual circuit. I've had this circuit power an LED as a test so far, so it functions. I'm just worried about hooking up a bigger load before figuring out what the issue is with the Q5.


texts: Power Source Symbol -- Which to use (Arrow, Bar, Circle, etc.)?

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I'm wondering if there is anyone out there with a definitive answer to why and/or what standard would call out the usage of the different voltage sources.  There are Bars, Arrows, Dots, Waves, etc. I have in the past defined this, but I'm wondering if there are actual standards that also define it.

What I've used in the past is:

Wave: AC power source
Bar: DC Power Source (regulated)
Circle: DC Power source (unregulated)
Arrow: no idea...

If anyone has any reference to something more concrete, I would love to hear it (and bonus if there's actually reasoning to why we have so many available).

Update: Picture added.


texts: Can I build a laptop like power supply for my PC with a car battery?

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Power outages are quite common here(india) and I want something better than a UPS: I don't wanna shut down the system. I was quiet inspired by Make Your Computer UPS Last for Hours that uses a car battery with a UPS. I was wondering if I could save on the DC to AC conversion and back and make the battery last longer.

I could not find anything on how laptop power supplies work but I am assuming they are more effecient.