texts: Principle for converting dual power supply to single

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I was recently attempting to build a voltage controlled oscillator from this website: http://www.schmitzbits.de/vco4069.html.

I struggled with it, for various reasons, and eventually found this website, which modifies the schematic to run on a single rail power supply (9v). http://hackaday.com/2015/09/11/logic-noise-playing-in-tune-with-an-exponential-vco/

I've found this schematic usefully and it works adequately for what I was trying to build.  I've used 7660s and MAX1044 chips before to create a negative voltage, but for this particular project I'm trying to keep everything running nice and simple on a single +9v supply (never mind that I somehow keep accidentally frying 7660 ICs!) and I have found multiple circuits that I'd like to try that use a dual voltage supply, that I want to run on single.

I'm not particularly fussed on the knock-on effects to the fidelity of the device, this is more an exercise in understanding a principle. For example, I want to build one of these:

(Of course, a VCO needs a VCA) but it uses a dual power supply. I'm not fussed on the fidelity or headroom, I'd just like it to work in principle. Is there a principle I can apply from the modified VCO in the link above, that I can apply generally every time I want to make a dual power supply powered schematic with a single supply?


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I am working on a system which comprises an inverter with output LC filter feeding an induction motor

Its trivial to calculate the resonant frequency of an LC filter, when the filter is loaded with an induction motor the frequency response is altered (no surprise here!)

Looking at this paper

https://pdfs.semanticscholar.org/40b4/76cc10d10cad506870fad6c4baad82a87bd2.pdf

They treat the motor as purely reactive and calculate the Thevenin equivalent which works quite well

I am trying to calculate the effects more accurately, so I use the equivalent circuit for the motor to derive a transfer function which is then put in parallel with the filter components with the clearf goal of reducing it all to one R one L and one C which then allows me to calculate things like the -3db point

I have written a Matlab script which generates a transfer function Z3 but no matter what I try to do I can not reduce the transfer function to R + Xj

In fact I am confused by the fact that if I substitute s = jw I end up with the equivalent resistance depending upon the supply frequency

clc
clear all
close all

syms    C L R Lm Le1 Le2 Rs Rr
s=tf('s');

V = 72;
f = 1200;

 Rs = 1.4;              % Stator resistance (ohms)
 Rr = 0.918;            % Rotor resistance (ohms)
 Rc = 23.87;            % Core loss resistance (ohms)
Le1 = 2.32e-3;          % Stator leakage reactance (H)
Le2 = 2.32e-3;          % Rotor leakage reactance (H)
 Lm = 25.25e-3;         % Magnetising reactance (H)
 Lr = Lm + Le2;
 Ls = Lm + Le1;
 P = 4;                  %Poles
Rn = 100000;

% Filter
R  = 0.05;               %Parasitic resistance
C  = 10e-6;              %Set C
L = 2.94e-3;             %Set L

Z1 = Rs + s*Le1 + s*Lm*(s*Le2 + Rr)/(s*Lm + s*Le2 + Rr);

Z2 = R + s*L;

Z3 = Z1*Z2/(Z1 + Z2);

Zc = 1/(s*C);

Hs = Zc/(Z3 +Zc);

Vos = minreal(Hs)

W=logspace(0,7,40000);
h=bodeplot(Vos,W); grid;
p = getoptions(h);           %Create a plot options handle p.
p.FreqUnits = 'Hz';          %Modify frequency units.
setoptions(h,p);             %Apply plot options to the Bode plot and
                             %render.

And if we type into Matlab

minreal(Z3)

  0.00177 s^3 + 0.9529 s^2 + 34.25 s + 315.6
  ------------------------------------------
             s^2 + 333.9 s + 6538

It gives us the transfer function for everything except the capacitor and my question is how do I convert this transfer function into its equvalent R and L. I tried replacing s with jw but I got no where

Thanks in advance


texts: From a 3.3v Pin do we separate Positive and Negative flow? If so, how?

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If we do not separate Positive and Negative flow, what is the flow from a 3.3V connection?

A Little more background on why I ask this question and my confusion follows

I have been reading simple circuit design tutorials online, most of these include a battery with two terminals, one positive and one negative, which we connect cables to and eventually complete a circuit.

However as I began to progress, I noticed certain circuits began to have a 3.3V connection - One example would be a GPIO pin(Pin #1) on a Raspberry Pi.
If I was to make use of this pin, would this be a Positive or Negative terminal?
Perhaps it doesnt matter? or perhaps it is neither?


texts: Running up to 40M (130Ft) of WS2801 IC LEDS

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After many hours of searching the internet for information and gathering what I could, I have run into my final problem that I am having trouble finding an answer for.

I have 40 Meters (130) Feet of 5V WS2801 RGB IC LEDs. 32 LEDS per meter, individually addressable.

The question

How do I run the clock and data lines through the whole set of LEDs?

What I think I know so far

I will be powering 2M (6.5 foot) sections at a time through 2 separate power supplies to avoid voltage drop though the lines. making sure to ground on each end.  This takes care of the power issue nicely.

If my math is right the whole set up should use 360 Watts - 72 Amps - 5V

I have one 28 Amp - 5V DC power supply and one 60 Amp - 5V power supply

Here is a diagram of what I think (from research) This should look like for the power end of things: (20 x 2M = 40M) * (one power supply is larger than the other.)

it would be great if someone could confirm that for me.

Next is the clock and data from the controller.

The real question is, do I need a repeater / amplifier or something for this because it's so long?  If "yes" could you recommend one to me?

This is the only way I can see it happening right now:

EDIT: For clarification I understand how to daisy chain the clock and data lines through the led strips. What i am more concerned about is signal loss as the length of the entire thing is 40 meters.

From the datasheet i can see on page 13 there is something written about putting in a 50 Ohm resistor at the data input or output.
Would this be suitable in this situation to put a 50 Ohm resistor at the end of each 2 Meter strip? Or do i just daisy chain the entire 40 meters and hope it works?


texts: Combining ground traces and ground planes using the same connection?

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I have a board that will take some 10 MHz clock lines and I was planning on surrounding said clock lines with ground traces to minimize interference with some other traces. I've been told to keep these ground traces about 30 mils from the signal line to reduce the capacitive load.

It is a 4 layer board, with two ground planes in the middle. My question is, should the ground trace connections also be connected to the ground plane? (This will happen through the same via where the connector is mounted to the PCB).

I'm aware that they are already technically shorted, since they are both sharing the same ground, but wanted to check if there was some reason why this is or is not a good idea (beginner at PCB design here).

Thanks


texts: Communication - 2 Battery Powered Circuits, 1 Conductor, no common ground

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TL;DR I need to do is successfully transmit a wave across a single conductor between two battery powered circuits with no common ground.  I already know how to create the wave and detect the wave when there is a common ground, but I don't know how to design a circuit that can detect the wave without the ground.  My scope grounded to the receiver can detect the wave.

My friends and I are are building an open source fencing box to score matches (The kind of fencing with swords).   Competitive fencing is scored electronically by using a sword rigged with a button and jackets made of conductive material.   We want to improve on the existing designs available today which require expensive mechanical reels to maintain tension on the cables.

To make a long story short, we need to be able to communicate over one "wire" (the sword) between two Arduinos.   Our plan was to use the Arduino PWM generators to generate tones that can then be detect by FFT of the analog inputs on the other side.   We're using 7 total tones between the frequencies of 9khz and 18khz.  We got all that working great.   The problem is what happens when we go to batteries and no common ground.   The PWM signal goes from 5V peak to peak to 1.2V peak to peak.  I don't understand why this is happening.   Any enlightenment here would be appreciated.

Can anybody recommend a circuit design for transmitting a wave over 1 conductor between two systems with no common ground? (And amplifying it on the other end if required) I'm thinking it's going to have to be similar to radio technology.  Alternatively I can try to take what I've got and feed it into some sort of amplifier and see if I can run with that, but I hate doing that without understanding the forces at play, and so far none of the circuits I've tried have reacted to the signal.

Some additional Information:

We have a button on the sword.   We can always detect that button press and use it to turn off/on the transmitter, so that if we cannot tell the difference between touch and not touch via attenuation of the wave we can just make it not transmit when there is no touch.


texts: Increase Autopilot drive motor capacity with SSR's and maybe an arduino

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I have a Raymarine X5 wheel pilot on my boat.  It is simple enough, it uses a small motor to drive a belt that turns the wheel. It has a controller called an ACU (in my case an ACU-100) to take course and heading information and out put 12v to the motor-- reversing polarity to reverse the motor and there for the direction the boat steers.  I don't know if it uses PWM to control speed, but for sure it turns the wheel fast and slow depending on what the ACU feels is necessary to steer a smooth course.
The ACU-100 that i have has a maximum continuous output current capability to the motor of 7.5 amps.  I have up graded my drive motor and need a larger current capability-- more like 15 amps.
The manufacture insists I need an ACU-200.... another thousand bucks...
I was thinking there must be similar concepts used in hobby robotics and there might be a solution that uses my existing ACU.  Perhaps to trigger some solid state relays?
What i need help understanding is how to deal with the reversing polarity.
So ideally the output from the ACU could go to 2 SSR's with diodes to trigger only one depending on the polarity from the ACU. But then the source voltage would have to have different polarity, and you would not want a short circuit so maybe you need 4 relays? one on each of the positives and negatives?
This is where i lose the plot.  Or could one get an arduino involved somehow to sort out the polarity somehow???
Is this a road worth going down? or do i need to bight the bullet and spend the $$$ on the ACU-200?


texts: Estimate kanthal's temperature by power dissipation

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I've a bare Kanthal A-1 wire, And I want to Estimate it's temperature, basically to  make a °C vs W plot.

In this post

Thermal resistance is used to do it as:

Thermal_resistance = 200°C/W.
power_dissipation = 400 mW

T = 400 mW*200°C/W
T = 80°C

According to wikipedia

  Thermal resistance = L/(kA), measured in K·W\$^{-1}\$ (equivalent to: °C/W)

But I can't find this parameter in the wire specifications

But they do show a Thermal Conductivity table:

+----------------+-----------+
| Temperature °C | W m-1 K-1 |
+----------------+-----------+
| 50             | 11        |
+----------------+-----------+
| 600            | 20        |
+----------------+-----------+
| 800            | 22        |
+----------------+-----------+
| 1000           | 26        |
+----------------+-----------+

If I've a wire with:

l = 40cm
d = 0.3mm
P = 50W

How can I use the provided data to find the temperature?

Edit:

I made the measurements but the experimental results are quite off from the theoretical values, at least regarding to temperature. I somehow expect it because of the effect of the thermocouple touching the wire during the measurement   is quite evident

Resistance was calculated by measuring current and voltage, and temperature was measured  with a K-type thermocouple.


texts: Routing 5 differential pairs over a short distance with limited space

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I have 5 differential pairs (4-lane MIPI-DSI) going from left (SOM header) to right (FPC connector). As you can see on the right, for each lane, the signals end on opposite ends of the FPC connector. This is -unfortunately- a given, because the panel I want to drive just has this pin assignment.

To make the lengths of each pair match, I have to have the signals leave the SOM header in opposite directions, to make up for the length difference they have on the other end of the signal. As you can see some signals also have pointless vias, just to make sure each signal has exactly the same amount of vias.

Now my question is if in this form, does it still make sense to adhere to the spacing rules of differential pair routing. i.e. I chose 6 mil width, 5 mil spacing for 100 Ohm diff impedance with a specific stackup. But there is no actual location in any of these pairs where the N and P data would actually be the same at any given point in time. Isn't it just better to leave them apart, and what would it do to impedance?

All signals are about 7.7mm long and length matched within 6 mil.

I can't really move the SOM or connector further apart.


texts: Astable timer: Halve frequency while maintaining the same "up" pulse width?

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Disclaimer: I am not an electrical engineer, but an environmental science student. I'm trying my best here.

I have a basic astable 555 timing circuit with the following components:

\$R_1 = 10k\Omega,~~R_2 = 1k\Omega,~~C = 0.1 \mu F\$

\$T = 0.7 \cdot (R_1 + 2R_2) \cdot C = 0.7 \cdot 12k\Omega \cdot 0.1 \mu F = 0.84 ms \\
f = \frac{1}{0.84 ms} = 1.19 kHz \\
t_{up} = 0.7 \cdot (R_1 + R_2) \cdot C = 0.7 \cdot 11k\Omega \cdot 0.1 \mu F = 0.77 ms \\
t_{down} = 0.7 \cdot R_2 \cdot C = 0.7 \cdot 1k\Omega \cdot 0.1 \mu F = 0.07 ms\$

I am being asked to halve its frequency but maintain the same "up" pulse width.

I know that doubling the reactance of the capacitor from \$0.1 \mu F\$ to \$0.2 \mu F\$ will halve the frequency, as it will take roughly twice as long for it to charge. However, my "up" pulse width \$t_{up}\$ is also being doubled.

\$T = 0.7 \cdot 12k\Omega \cdot 0.2 \mu F = 1.68 ms \\
f = \frac{1}{1.68ms} = 595Hz \\
t_{up} = 0.7 \cdot 11k\Omega \cdot 0.2 \mu F = 1.54 ms \\
t_{down} = 0.7 \cdot 1k\Omega \cdot 0.2 \mu F = 0.14 ms\$

The desired output would have a frequency of 595Hz, but an "up" pulse width of 0.77 milliseconds.


texts: How to connect a generator and LED device of different polarities?

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I have a device that generates light impulses when connected to a LED device. The intensity of the light is regulated by a potentiometer, within the generator. There are 2 independent channels. The generator works with "Common Ground" polarity, but my LED device works with "Common Power" polarity and doesn't work at all. To my eyes it seems the LED device is just a bunch of LEDs, with no other electronic parts. I tried to change the connections, with only one channel working at best. I naively imagine the circuits are:

Is it possible to change the polarity to make the CP LEDs work with the CG generator and make it still possible to be able to control the light intensity?


texts:
For the UPS model Niky 900 by Daker, I'd like to replace the original CSB HR1234W F2 battery with something I can buy on amazon.it, e.g. FIAMM models: could you suggest what are the relevant parameters to match, in particular how do I compare the 34W datum for the above model with more common Ah specs?
Is e.g. the model FIAMM FG 20721 (12V - 7,2 AH - 7AH) good enough?
(I've made a 'translation' from W to Ah looking at this post) Should I opt for a 9Ah?


texts: Skin depth at 50 Hz is much longer than the thickness of the shield of a coax cable. Then how does it work?

texts:
The title already narrates the question.

We know that using a coax cable for audio amplifier input remarkably reduces 50 Hz noise. However the skin depth of the EM radiation at 50 Hz for copper is about 10mm (http://chemandy.com/calculators/skin-effect-calculator.htm).

Then how does it prevent 50 Hz EM wave from penetrating to the core?


texts: How to calculate the cost of a BLDC motor? Assume I need 24 stator coils of height 10 mm and width 5 mm. Is there any formula for torque comparison with increasing the number of poles?


texts: when DC supply is given to ATmega16 micro-controller, I want it to continue functioning from the same state, from where it was stopped

texts:
I am writing my code in BASCOM-AVR. It has 2 if loops and 1 for loop inside the 1st if loop. I will give DC supply to ATmega16 controller.
Now, what I want is, if the power is cut off when code is in for loop, the functioning should continue from that very step inside for loop when power is switched on. Is that possible?

If anyone is unable to comprehend my question, please let me know, I'll try to explain it in a different way.

Kindly waiting for help.


texts: Laplace Domain Representation for Phase Detector

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I am trying to model an LTI system and determine the overall transfer function of the system. The setup consists of a laser signal being fed through some filters, amplifiers, etc. represented by transfer function 1 (TF1) which is then mixed with a local oscillator by a phase detector. This mixed signal passes through a few more components represented by transfer function 2 and is then used as an output signal.
The trouble that I am having is with the representation of the local oscillator in the Laplace domain. The mixed signal leaving the phase detector is given by $$U_m = K[\theta_{m}(s)] = K[\theta_{lsr}(s) - \theta_{LO}(s)]$$
Where $\theta_{m}(s)$ is the phase difference between the two signals of the phase detector. How would I represent this phase signal from the local oscillator in the Laplace domain?

simulate this circuit – Schematic created using CircuitLab


texts:
Related:

How in CDMA mobiles receiver gets unique code to decode its respective signal?

This question says that a cdma "channel" has a publicly known code associated with it. Ok. But, how is this code (the pseudorandom number sequence) is synchronized between both receiver and transmitter ?

Having the code is not enough, because a out-of-"phase" code will have the same effect as having other code instead of the correct one.

How both correlators synchronize in order to both codes to match ?


texts: ATX Power supply and its protective features - not happy with motor as load?

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I'm building a chicken coop opener - I've build my circuit (let's say arduino) with a DS3231 clock module and if functions as follows: My DS3231 will pull down its interrupt pin which is connected to my ATX supply (I-ARENA SERIES GPB-500S) enable wire (green). This will turn on my supply and power the arduino. So far so good. The arduino then do some funny stuff and eventually decide to either open or close the chicken coop door. So far this works and i successfully tested it. I want my circuit to be robust - so i chose a windshield motor because of conditions where i want to use it. The problem starts when my motor is running. I've measured that when the motor is spinning, it draws arduino 1 - 1,5 Amps @12V (Not bad, my atx supply should be very in range). I've limited the in-rush current using an 2 Ohm NTC thermistor, which helped start the motor and prevented my supply shutting down. But after few seconds (3 to 20) Of the motor and whole circuit doing just fine, the supply will shut down. I have no idea why because the current is in range... Is there some feature in my ATX that i'm not aware of? Is my supply not happy with inductive loads?

What i know:

The problem is not in my circuit - if i connect a lab bench supply it works fine.


texts:
I'm using CircuitMaker (Altium 'Free') and I get on a lot of components/traces red crosses, but sometimes only part of a trace (see screenshot).

What do these crosses mean?

Note, I haven't connected everything yet, but these are annoying as when I'm zooming out I cannot see what traces are on the front and bottom layer as they all show in red. See screenshot below.

The first picture show the C7 and C9 capacitors.


texts: Not understanding how the gain works in the 1st stage of an instrumentation amplifier

texts:
For the following instrumentation amplifier, I am having some confusion understanding the gain process for the 1st stage. I understand that the 2 input amps are essentially 2 non-inverting amplifiers tied together.

However what causes the gain for V1 and V2 to be the difference between V1 and the common-mode voltage?

**For example if V1 was 2.49V and V2 was 2.51 V, with the common-mode voltage being 2.5 V, if the gain from the 1st stage was 100, output labelled A would be 100*(2.5-2.49)+2.5 and hence it would be 3.5V. At least I believe that is what it is.

Essentially what I do not understand is why the gain of the 1st stage isn't just V1 * 100, but what causes output A. Since output A only multiplies the gain by the difference of the common-mode voltage from V1 or V2. Then the outputs add this value to the common-mode voltage.

Basically what causes the 1st stage (the 2 buffers) to only multiply the difference of the common-mode voltage from V1 by the gain? Then the output (A and B) adds the common-mode signal and this gain calculation. Why isn't it just V1 * Gain of a non-inverting amplifier for output A (like a normal single non inverting amplifier?)

Please include any textbooks or links that might possibly explain this as well as I lack some fundamental understanding for amplifiers.


texts: Detect button/signal on for a certain time period

texts:
I'm trying to design a circuit that can detect if a signal is on for at least 1 second. It's an problem for intro EE class, so I'm restricted to only simple logic gates, DFF's, TFF's, capacitors, resistors, opamps, and we're given a 1Hz clock.

I know I can use a DFF to check the clock edges for when the signal is on, but how would I check if the signal flipped on and off during the 1 second cycle? Also, how would I sync the signal (asynchronous) with the synchronous 1Hz clock?


texts: Clamp TO-262 transistor against heatsink?

texts:
I'm designing an enclosure for a device with mains voltage power mosfet devices.

First I thought about using TO-220 MOSFETs, and mount them up against the aluminium enclosure. However, screwing them to the heat sink using the TO-220 package tab hole  seemed unnecessarily difficult, what with the tab being conductive and all. So instead I opted to clamp them to the enclosure.

However, now that I'm thinking about it, if I'm not going to use the hole, why can't I just use a TO-262 package instead?

I googled a bit, but couldn't (in a few minutes) find an example of anyone using a TO-262 clamped to a heatsink.

Is there any reason not use a TO-262 vertically mounted, clamped to a heatsink/enclosure?

Edit: Forgot to say that I need the mounting to have at least basic isolation between all the TO-262 terminals and the enclosure/heat sink.


texts: How do you measure an output designed for a moving coil meter, using an Arduino?

texts:
I have a Yaesu FT-857 Amateur Radio transceiver which has an output for an Analogue Moving Coil meter.

The radio will output a current varying between zero and 1 milliamp (0–1mA), depending on the signal strength received by the set. This is intended to drive the coil of an analogue meter. 1mA indicates a very strong incoming signal, values below are weaker stations.

The spec doesn't give a voltage, but I've measured that this varies between zero and five volts (0–5V). While it does appear that the voltage also varies with signal strength, it's not mentioned at all by the spec, and I'd like to stick to measuring the current, for the definitive value.

What's the best way to measure/sample this signal, so that I can use the Current value in an Arduino, to create a digital coil meter with a 7-segment display?

Note: This transceiver does provide the value digitally using CAT, a serial data link. For reasons I won't go into, I only have the analogue meter line available.


texts: How to solve speed issues in a double buffered + video overlay system

texts:
I've decided to start a small project over this break for creating a very simple GPU. As far as the GPU will go for now is simply receiving pixels and outputting pixels to SDRAM. In addition, there is another part of the circuit that will get pixel data from the SDRAM and output it to an LCD (I've already made the timing controller for the LCD, just need an interface to the SDRAM which makes sense). The last part somehow does a video overlay with a stream from some sort of CCD/CMOS sensor. As for the SDRAM, I've made controllers before and have enough of an understanding of VHDL to do this, so that's a non-issue. My main problem comes in with the timing.

First off, the LCD runs at 9MHz so that's fine so it takes ~111ns per pixel with a 25ns setup time before the falling edge. Suppose I'm running the SDRAM at 100MHz. After a burst setup, I can get 10ns per pixel, so as long as we're in a burst, there's more than enough time to get the data. But this speed is only in a burst. If I were to load the row every single time, I would be cutting it close. This means that during the time where I actively need to read data for the LCD, I am completely held by it. No writes.

The only time I can do the writes are during the columns (~480 col) ~4100ns of Hsync in each line (~280 lines) and the ~525000ns during Vsync. Suppose that worst case, my GPU needs to write to every pixel of the screen. This means that I can do ~410 pixels per Hsync, which leaves maybe a hundred or so pixels left that I need to write during the Vsync. This write data will be writing to a 2nd frame area in the memory (hence, double buffering).

That timing works out, ... assuming my GPU has its own (large) pixel cache during it's waiting times and so on so forth. That's an issue I'm going to deal with later. My main issue right now is the video overlay. In addition to what's currently happening, I have my pixel data from the CCD/CMOS. After my worst case GPU usage, I have less than ~525000ns to write 480x280 (~1344400ns) which is definitely impossible by an order of a bit less than 3.

Am I doing something terribly wrong? How does the computer I have in front of me right now do this? The display is SO much larger and I doubt that SDRAMS with a MUCH shorter latency exist (maybe DDR). :(


texts: Instrumentation amplifier: resistor to ground for input bias current?

texts:
I've inherited an RF amplifier design (50MHz-1GHz) that uses an instrumentation amplifier to accept a DC voltage control signal. Neither myself nor my PI can explain why R8 and R18 are present. My guesses follow.

R8: Reading the spec sheet of related amplifiers, they say that the input bias current must have a DC path to ground for the amplifier to not float / saturate. This doesn't seem to be the case here: the input is just a coax cable with a DC control voltage on it. I think I'd need the 10k if I had a thermocouple, or transformer. But here it seems unnecessary, and makes the input impedance much lower.

R18: Why would you want your opamp to be referenced slightly above ground? Is this to compensate somehow for the offset voltage  (which is 500uV max)?

I'm tempted to remove both to save PCB space, but this is a working design so I'm hesitant to make a change based on ignorance.

Thanks!


texts: Why are there two diodes in series in this test circuit?

texts:
Look at Figure 2 in the following datasheet:
http://www.onsemi.com/pub/Collateral/MMBT3904LT1-D.PDF

Why are there two diodes and not just one?

Thanks.


texts: Understanding the role of 2 capacitors in a pi filter

texts:
I'm trying to understand a pi filter, which typically looks like this:-

I've seen lots of these especially with the valve guys, and C1 = C2 always.  So I made this in LTSpice which is for a 100mA load:-

Notice the parameterised value of C1.  The AC analysis produces this however:-

There is only one curve!  If C1 = C2 and C1 = {X}, you'd expect four curves.  To check my model, I interchanged the parameterised capacitor so that C2 = {X} and got four widely spaced curves as expected.  The analysis is suggesting that C1 has no effect, and I'm confused (again).  Have I misunderstood the nature of a pi filter, or is my LTSpice model incorrect?


texts: KVL equations for this small signal model

texts:
I could figure out how the small signal pi model is obtained from the large signal model and below shows an example circuit where I also draw the pi model:

But from this point does KVL hold? How can we write the KVL equations? The change in small signal vin is not the same thing with the change in vpi. What kind of KVL would be meaningful to form in this case? Or we should use KCL?


texts: Circuit for Neutral point of 3-Phase mains

texts:
I wonder if the 'Neutral Point' as mentioned in the attached image is correctly labeled or not? Is there any mistake in this 3-phase circuit design?

Edit 1:

Also it looks like the 'Neutral point' is electrically at the same potential as DC Bus (+) point. So can we connect the 'Neutral point' with either DC Bus (+) or (-) point? Please correct me if I am wrong.

Edit 2:

What condition will turn-off the opto-coupler 'U6'? It looks like it will always be in ON state.

Edit 3:

Do we really need diodes D1, D2, D3? If the three resistors R5, R7, R8 are used will they also not give the same result?


texts:
I'm trying to design a custom board with Marvell 88E1111 PHY and I want to connect this board to another board with KS8999 PHY on it. I want to connect two phy sides with capacitive coupling.

The distance between two boards is less than 5 inches and I have no option for using another PHY chip or using a transformer. I have searched through web and found these links:

Transformerless design

Design without magnetics

So I think that capacitive coupling is an option.

Micrel KS8999 supports capacitive coupling [here], but there is no specific data in 88e1111 datasheet about capacitive coupling.

Now my question is:

Is it possible to connect two phy sides?
If yes, how to connect lanes in terms of using series capacitors, pull-up voltage at 88E1111 side and pull-up resistor values?

Thanks in advance

KS8999 Datasheet


texts: I have bought a Li-po charger the other day and I looked up the IC and it stated Li-ion. Can you charge a Li-po with a Li-ion IC? And the other way around? The IC I am talking about is the TP4056.  I thought Li-po is quite difficult to charge because if your voltage is to low it does not charge anymore and if it is to high you can blow it up.


texts: Help explain how this ac switch circuit works

texts: Below is an ac switch circuit. COIL1_EN is used to enable or disable the switch. Does any one know how this ac switch work? I think it may be a standard design, can anyone give the related documents?


texts:
I have re-annotated PCBs and back-annotated the schematics countless times before and never saw this problem.

I first make sure that my PCB and my schematic are synchronized and up-to-date. In the PCB I go to Tools -> Re-Annotate. I select my direction, set my comparison threshold, etc and click "OK". The board re-annotates as expected. I save the board and the project. However, once I go back into my schematic and click Tools -> Annotation -> Back Annotate Schematics and select the .WAS file that was just generated, I get the following error:

There are only 294 components in the design. I cannot seem to track down the cause or solution to this problem. What might the issue be?

Once again, I am using the same process I always use and it has always worked in the past. I have even tried resetting all component designators in the schematic, annotating the PCB, and back-annotating to the schematic but that does not work either.

I am using Altium 17.1.5.


texts: In wireless communication, what is "channel length"?

texts: In wireless communication, I am confused about what people are referring to when they use the term 'channel length.' Can someone explain the term or provide me a definition?


texts: How to Reduce Serial Noise from a Refrigerator

texts:
I am controlling the compressor of a compact refrigerator using an Arduino Mega and an opto-isolated relay block. The Arduino is connected to the PC using a serial over USB (Atmel version). Since the beginning it has been a struggle to reduce the serial line errors. Here is what I have done and it helped but I still have problems:

Replaced the stock USB cable with higher quality - helped the USB not reconnecting;
Powered the Arduino board with an external switch supply - helped the USB not reconnecting, no more reconnections;

I still have problems with data incoming to the Arduino and it happens only when the Arduino switches the compressor on/off. I have a number of questions:

Do you think this is an EMF problem or power supply problem or ground problem or some interface (for example Arduino to relay board)? Notice that the relay board is powered separately from a lab power-supply.
What do you think is the best possible step to improve the situation. I have been thinking of the following:

Replacing the mechanical opto-isolated relay board with solid-state relays;
Adding ferrites to the power lines? The USB cable already has ferrites on both sides;
Enclosing the relay board in a metal casing;
Enclosing the Arduino board in a metal casing;
Adding a low-pass filter to the compressor?


texts:
Consider below JK flip flop circuit and truth table:

I was guessing how Qn+1 column in truth table is calculated.

Interpretation 1

One text book says:

Consider the case J=1, K=0, Qn=0, Qn'=1, line 5 in truth table.

K=0 forces output of G4=1.
All inputs (J, CLK, Qn') of G3 are 1 which makes output of G3 to 0.
G3 output is fed to G1 input. This forces output of G1, Q(n+1) to 1.
This (output of G1) is fed to input of G2 along with output of G4, both of which are 1 (from point 1 and 3). Hence output of G2, Q'(n+1) will be 0.

So in this case output is correctly Q(n+1)=1, Q'(n+1)=0, which is correctly a Set behavior.

Interpretation 2

I was guessing why it doesnt behave like this:

K=0 forces output of G4=1.
Qn=0 which is fed to G2. This forces output of G2, Q'(n+1) to 1.
Q'(n+1)=1 which is fed to G3.
All inputs (J, CLK, Qn') of G3 are 1 which makes output of G3 to 0.
This output of G3 is fed to G1, which forces output of G1, Q(n+1) to 1.

So in this case both Q(n+1) and Q'(n+1) becomes 1, which is invalid.

Why it doesnt behave like interpretation 2 and give invalid state?


texts:
I’m designing my first PCB and got weird SPI issues after my second revision of the PCB layout. I did a few small changes for the SPI routing in the second revision but nothing that I thought would affect the SPI bus.
The only components I have mounted on my PCB when testing the SPI bus and the display is the Teensy 4 micro controller, 20 pin display connector and the cable to the display.
On my first version of the PCB, the display works flawless and are stable, I've been running it for days. On my second revision I needed to change the SPI routing to make space for new components and after this modification the SPI bus and display are very unstable and the display fades out to black or some other weird color pattern, sometimes after a few seconds and sometimes after some minutes.
I'm pretty sure the problem has to do with the SCK signal, because I soldered a cable from the SCK pin on the Teensy to the display connector and it works much better, far from perfect but better, I get some flickering on the display.
I’m running the SPI bus on 30MHz but have tried to go down to 24MHz but get the same behavior.
Anyone have any tips on how best to do SPI routing?
Display pin layout:

1 VDD +3.2V
2 GND
3 SCK
4 MISO
5 MOSI
6 CS
8 PD

First version where the SPI bus and display works great

Second version where the display is unstable

Soldering SCK

SPI schematics for the display


texts: Troubles on understanding datasheet of a 24V DC permanent magnet motor

texts:
Can you help me on understanding this datasheet of a DC Permanent Magnets motor?

Note that the deleted parts do not add information, they are those not translated into English or referring to other models.

PAGE 1

PAGE 2

Precisely, my doubt is about current, voltage and rpm of this motor.

Consider the first table with these specifications. You may see that this motor can work at S1 (continuous service) at 100 W and at S2 for 25 minutes at 140W. The supply dc voltage is the same (24V), while current is 8.4A in S2 and 6A in S1.

First question: How can I change the current from 6A to 8.4A or viceversa, to set the power? I have physically this motor, it does not have any switch, potentiometer or other tuning mechanism. The only way I think to reduce power (whose nominal value is 140W) is to lower supply voltage, which is not the method shown in this datasheet.

Second question: I do not understand these numbers. Power computation seems not to be correct.

24 V × 8.4 A = 201.6W (and not 140W)

24 V × 6A = 144W (and not 100W)

Now, let's go to the last graph.

Third question: from this table it seems that I can supply the motor also at 50V, and that it is good to do this since efficiency becomes 1. It seems in contrast with the fact that the nominal voltage has been declared to be 24V in the previous page.

Fourth question: Consider for instance 25V of power supply, which from the table near the graph corresponds to 100W, 2500 RPM and 0.5 efficiency. It seems totally in contrast with the initial table of the previous page, since:

power was declared to be 140W (S2) or 100W (S1)
RPM was declared to be 3000


texts: Protecting servo drive outputs from inductive loads.

texts:
Can anyone please help with the following. I am in the process of connecting a Schneider Electric Servo Drive for a Cnc project.

I want to wire a fault output from one of the 5 drive outputs. (Do1-Do5).

The manual says" Use an appropriate external protective circuit or device to reduce the risk of inductive direct current load damage. "

The output will simply be disconnecting the enable to the drive if a fault is detected within the drive. I am not switching any other load.

The question is do I need to protect this circuit as described in the manual or can I wire directly?

I have attached a screenshot of the circuit from the manual.

Thanks


texts: Algorithmic State Machine using D flip Flops - how to deal with don't care conditions

texts:
I have the following state transition table:

where,
A, B - current states of two D flip flops

A+, B+ - next states of the two D flip flops

X1, X2, X3 - inputs to the current states

There are don't care conditions in inputs X1, X2 and X3.

I am trying to make a K-map for A+ using four variables A, X1, X2 and X3. I have dealt with don't cares in the output. But, I don't know how to deal with don't cares when they are on the input side.

How to deal with input don't care conditions ?

(I somehow tried to solve and got the answer: A+ = A'*X2'. Answer key has something else the answer. My state transition table is same as the one given in the answer key. So, I am sure that my state transition table is correct. I am sure that I am making mistakes in building K-maps from table as I don't know to incorporate input don't cares.)


texts: How do I convert a 4-20mA 24V signal to a 0-5V signal, suitable for A-D conversion with a 5V microprocessor?  Can this be done while isolating the 24V from the 5V output?


texts: Create a circuit that can flash IR LEDs at 38.5kHz and be turned on or off by microprocessor

texts:
Several other questions are posted about methods for flashing an LED, but one additional requirement I have is the ability to turn the circuit on or off with a micro controller (Netduino, 3.3v).  This schematic is very close.

What changes would be necessary to achieve 38.5kHz?  Also, how could I make an additional adjustment to start or stop the circuit via a pin on the Netduino?


texts:
I am not an expert in electronics, just the very basics so please bear with me.

I am trying to create beeper alarm for my FPV drone that will activate when it crashes or no movement for certain period.

There are some important requirements.

The device should turn on when external power source (Quad LiPo) is connected.
Alarm will go off, if the power source is removed (separate switch to turn it off) or if no movement is detected for 30 sec.

i don't know how to put this together, like do i have to program a micro controller or is there any other way?

I live in India, where drone parts so hard to find. Therefore i need this DIY.

Any help is appreciated.


texts:
I want to begin with FPGA, but I've never worked with once before.

I want a cheap kit, but I don't know where to start. I can find cheap boards, but then I can't get no information about the programmer or compiler, so I hope that you can help.

I want something real cheap ($30-$40 max), preferentially with some non-proprietary way of programming and debug (perhaps JTAG?) that would be able to program using some languages like WinCUPL or VHDL.

I've found the Diligent Cmod board featureing a Xilinx CPLD on another thread, but I can't find how do I program/debug (software and extra hardware involved).


texts:
i have some doubts about with this thermal design?

first, the calculations and infos:
My load (a motor) uses an average current of 7A, I could not measure the current peak at the beginning of the rotation (we shoot 20A peak).

Qgc = 100nC
MOSFET Rds: 850 microOhm (VGS = ~7V) (I over estimated
Rds from datasheet)
Power dissipated by the mosfet: P = I² * R
P = 400 * 0.000850 = 0.19125 W

Given this power for dissipation, I have a pad (this right over Q1) in the upper layer of approximately 10mmx20mm = 200mm². and in the lower layer of 20mmx20mm = 400mm². Which are connected though vias

I have two doubts:

Is it possible to use only the upper layer for this thermal dissipation? I would like to manufacture the pcb here in my homemade CNC, and I would not be able to do the "thermal vias" in a homemade way.
Is it possible to decrease the peak current (in-rush current) that the motor consumes while starting? I imagined that placing a capacitor parallel to Gate / Source would increase the time to charge the gate; this kind of worked, but if the turn-on time increased by 5%, it tripled the turn-off time.


texts: Resonance at frequencies different from natural frequency

texts: I am trying to understand the resonance mathematically, by taking sine wave as example. If I add addittional sine wave with the same frequency to mine sine wave, the amplitude increases. If I do this regularly with time, the amplitude continues to increase and I can see the resonance. But the increase in amplitude will happen also if I add sine wave of different frequency than the frequency of my sine wave. Is something wrong in my reasoning?


texts:
I am creating a LED lighting unit for an Aquarium and I have a 240vAC to 24v DC power supply.

I want to output 12V and 5V also in addition to the 24v DC.

I have 2 buck modules - like these http://www.ebay.com/itm/1Pcs-Lm2596-Power-Supply-Output-1-23V-30V-Dc-Dc-Buck-Converter-Step-Down-Modul-A-/301988858332?hash=item464ff049dc:g:5MgAAOSwYmZXEehH off ebay set to 5v and 12v from the 24v input.

Measuring the DC on the output side I get the correct voltage from the output + and - connections.

My question is in my project I have a need for a lot of 5v and GND connections.

Can I just join all the GNDs together?

Will this work or is this a stupid thing to do? What would happen?

The 12v device is an Arduino and the 5v device will be connected to the arduino pins.


texts: What does RA1 stands for in PIC microcontroller?

texts:
TI and Freescale designate PA1 as Port A bit 1.
But Microchip uses RA1 to refer to the same meaning. So what exactly does R stand for ?


texts: What are the "No Connect" terminals on this multiplexer and what purpose do they serve?

texts: I was looking through the datasheet for the ADG506A/ADG507A and on the chip there are these terminal marked as NC and underneath the image it says "NC = NO CONNECT". They are also not explained in the terminology section of the datasheet and I am not sure whether I should have them connected to ground when I am using the chip or just leave them alone. What purpose do the serve anyways?


texts: What is the major difference between a WiFi and RF Module?

texts:
In an interview recently, someone asked me what is the major hardware level difference between a WiFi module (ESP8266) and RF module (nRF24L01+) that I had used in my projects.

I mentioned that both use the 2.4GHz spectrum but the actual frequencies within that spectrum are different in both and also that the WiFi is a more optimized version of RF due to techniques such as beam-forming. The interviewer rejected my answer and said that the major difference is in the range of both, with RF having the greater range.

I believe that range is not the difference and RF’s range is only greater with an external RF amplifier which can also be used for WiFi to increase its range.


texts:
I am making and robotic arm by using arduino and hc - 05 module and controlling that arm using mobile application now problem what i am facing is the mobile app dose not connect to bluetooth device whenever i run the following code
http://pastie.org/p/79sDLtqMdIE9xpS3RN1S3N
but when i run different code the bluetooth get connects with the app and runs withoutany error can anyone help me to figure it out
Thanks


texts: How will a TTL input behave very close to its high/low bounday?

texts: I have an analog control signal and an H-bridge IC. Since I can configure my signal to vary over the TTL voltage range, it seems temping to send it straight to the driver and hope that it will threshold it for me. What will this chip, and in general TTL components, do when they are hooked up to analog signals that sometimes wander close to the high/low boundary?


texts: Backdriven stepper motor "powering" rest of the board

texts:
I have a stepper motor powered by a breakout board that uses the A4983 stepper motor driver (http://www.sparkfun.com/products/10735).

Sometimes when the power is disconnected and the drive wheels are back driven, all the LEDs on the the boards light up and it seems like the system is being powered by the stepper motors.

I have the board set up this way: Stepper motors connected to the stepper motor driver. Power coming from battery is directly hooked up to the driver's motor power supply. A 5v regulator comes off the same battery line and powers the micro controller and other 5v electronics.

Three questions:

1) what exactly is happening? I know when back driving the motor it will create a current, but this is a bipolar stepper, wouldn't the current be AC and thus destroy the circuit? (up until this point, everything still works just fine). How is the current flowing into my other electronics?

2) How harmful is this back driving? Are there serious voltage spikes that I should be worried about or is the stepper motor driver chip dealing with it?

3) how do i prevent or protect the circuits against harmful effects? I'd put a diodes between the motor driver and the motor but bipolar steppers are basically AC motors and that wouldn't work.


texts: Can I change rectangular pads on every pin to rounded rectangular?

texts:
I am currently routing my board with FreeRouting and I noticed that rectangular and oval pads (on KiCad) make FreeRouting do 90° cuts which I simply don't like so I thought I could simply change rectangular and oval to rounded or circle.
Is that OK for things like MOSFETs which have defined rectangular shapes?
Extra question : Why does KiCad have the default footprint for THT resistors with one round and the other oval?


texts: What kind of capacitor blew up in my old IBM monitor?

texts:
I pulled this out of an old IBM 5154 EGA monitor from the 80's. Clearly both are bad (though the monitor itself works anyway...). I know they're capacitors, but what kind? What would a replacement for these be?

I'm also curious about why the monitor would work despite two out of two of these things being in such terrible shape.

Edit: here is a picture of the top


texts: Effect of non-inverting op amp on the AC and DC components of the input

texts: I was wondering what the effect of an op amp like the one in the image below is for an input signal such as \$0.5\sin(2000\pi t) + 0.5\$ V? Are the DC and AC components amplified with the same gain? And also, what would be the phase relationship between the input and the output?


texts:
How do I determine how powerful an H-Bridge I need to control a DC-motor?

In particular, does an H-Bridge need to be able to supply the full amount of current a motor will use when stalled, or would it be okay to use an H-Bridge that supplies enough power for a motor under standard load (and then some, but not stall conditions), and if so, what happens if the motor wants to draw more power than is available?  (Does the H-Bridge fry, or does the motor just stop?)


texts:
Please ignore the graphed lines, those are irrelevant to the question, it's the graph itself that's relevant.

I see this type of graph used all the time, between multiple manufacturers and device types. It's a plotted graph, x * y, where x could be time, and y some value, or vis-versa or a mix of different variables. While I can extrapolate the approximate value of a point between two marked values (ex: The 1 hour and the 10 hour), I still don't know what the in between values should be.

Is each line half between the next highest up? For example. Half way between 100 to 1000 is 500. So that next line up from 100 is 500. Then half way between 500 and 1000 is 750. Then 875, etc? x = y + ((y - z) / 2), where Y is the next marked up, and Z is the last value to the left?

Or is it a simple next value up. 100, 200, 300, etc? If so, why the scaling to the distance instead of linear graph?

And most importantly, do these type of scaled graphs have a specific name or standard attached to them?


texts: Will my HEX file fit in my microcontroller?

texts: I have a hex file with a size of 42 kB.  Does the size matter while loading it in a microcontroller?  Can I load 42 kB hex file in a ATMEGA32 chip which has a memory of 32 kB?


texts: Hooking up a device which is powered externally, to the OBD port of a car

texts:
I have a device called AutoPi (https://www.autopi.io) which is simply a Raspberry Pi Zero aggregated with a couple of more components.

The device takes it's power from the OBD port.

I want to make a simple intermediate circuit between the OBD port and the device to power the device from an external battery (possibly a power bank) instead of the OBD port.

Here is a brief diagram of what I plan to do :

Questions about this is :

Would this circuit possibly cause damage to the device or the car computers ?

I guess that it is unlikely but is there any possibility to introduce noise or cross talk to the data lines, how would one prevent it?

I would also like improve it by adding a switch to disconnect the data lines from the device on demand.

In this case should I leave the data lines floating or should I connect them to ground ?

About the grounds, should I connect my device to the signal or chasis ground or both ?

Thank you for your support.


texts: Selecting a logic level MOSFET compatible with 3.7V power source

texts:
Continuation of prior question:  Logic level mosfet to switch on 3.7v battery

I am a 'mature' entrepeneur Arduino level electronics noob, apologies.  Want to build a flashing alert using 3W LEDs in parallel powered from a 3P 18650 (3.7V) battery pack.  I think I have crude solutions using LEDs in series and a 3S battery pack, but not appealing due to uneven LED performance in series configuration, and problems with charging a 3S (balancing, access to 5V/USB charging solutions).

The last answers/comments recommended then un-recommended a P-channel MOSFET, specifically the FQP27P06, because the max Vgs(th) was too high at 4V.  In 'fun with sparks' websites I found the Fairchild NDP6020P as an alternative.  Finally my question.  The Vgs(th) for this MOSFET is -0.4 min to -1 max.  Seems like this would be exceeded when I'm using 3.7V source.  Consequence, could be MOSFET destruction up to small burst of shrapnel, counterproductive for a safety invention.  I read about protecting with a Zener diode and series resistor, but that seems complicated and also primarily designed for surges and polarity reverses.

Kinda yes or no, am I going down the right road with the Fairchild NDP6020P?  Bonus points for continuing my education, and much appreciated.


texts: Serial Servo Controller using Basic Stamp

texts: How can you control a Servo using a Basic Stamp?


texts: Using Breadboard Power Rails for i2c Bus

texts: I'm working on a raspberry pi project that will use about a dozen i2c devices (mostly mcp23017s) and the wiring is getting a little crazy. Are there any downsides to routing SDA and SDL to one of the power rails and using them as a sort of bus?


texts: Is a device with high voltage and low current safer than a device with low voltage but high current should you accidently bump into the +/- pins?

texts:
For example, my lead acid car battery is rated at 12 V/700 A, whereas my switch mode power supply has 250 V/6.3 A.

If I were to accidentally bump into the +/- pins of either battery (forming a full circuit), which one would be "safer" i.e. cause the least amount of bodily harm?


texts: What is an appropiate way to isolate a DC signal?

texts:
The question might sound kind of funny, but I'm unsure how else to word it. So...

Pictures!!

Currently, I have a setup like this:

simulate this circuit – Schematic created using CircuitLab

What I would like to have is something like this:

simulate this circuit

For the digital stuff, an optoisolator does the trick, and for AC signals an isolation transformer does the the trick and in each one of these devices, the input and output grounds are separated.

What method, or what should I be looking into in order to isolate two DC system grounds
from each other? (The DC signal can vary from mV to 10's of volts.)


texts: I have a big LED screen covered by plastic surface (removable). I want to change image on that screen when someone touches it. Could you give me advise how to do it or some sensor names for further research?


texts: Reverse engineer a custom (failed) transformer

texts:
I am attempting to repair an aged air conditioner I have tracked the issue to a failed secondary on a current transformer.

Very helpfully schematics are available for the circuit board and inform me that the part is a ETQ19Z59BZ this appears to have no information available so I suspect it is custom.

I have closely inspected around the terminals of the transformer with a loupe and cannot see any broken wires.

With a open circuit secondary is there any easy way to identify the properties of the transformer to allow me to select an appropriate replacement.


texts: Adequate Power Supply for 300 Daisy-Chained LEDs

texts:
I have 300 LEDs (ws2812b) wired in a series. They were sold as 150 LED/5 meters and rated to power at 9W/m, so 45W/5m strip. I would need 90 Watts to power my entire 300 LED strip. I have a 3-rail power supply that has an output of 5v 40A (200W), would this be adequate to power the LEDs?

Naively, I thought I could power them straight from the PS but got major color change around the halfway mark (expectedly where the second strip is connected). I soldered +V and -V of the second rail to the halfway point and it helped my situation but not entirely and I am worried I am going about it wrong. If anyone could shed some light (haha) on my situation I would greatly appreciate it !!!


texts: JFET Audio switch, does not work in simulation?

texts: This is a circuit I've found online and apparently it is taken from the very rare audio book by National semi. The circuit is used to switch a signal on and off at a transition time that the user sets using the RC input. The problem is that I can't seem to get this to work in simulation. Any ideas what I might be missing out of?


texts: I'm using four batteries with a total of 6 volts, but the lightstrip only needs five. How would resistance work?

texts:
The strip uses .5-2A and 5 volts. I'm using four AA batteries, so the voltage becomes 6. What do I do to reduce the voltage, and get the right current? Will the strip itself just draw the current in it's own way since it's remote controlled? I read online something that said something like the equation for the extra volts is you take the original volts, and subtract it by the end voltage you want. Then you take the difference and put it in a ratio to the end voltage. Like 6-5=1. 1:5, meaning you use two resistors, the second of which being 5 times the first resistor. Is that correct? And if so, what about the current?

Edit: What if I used 4 rechargeable AA batteries. Each is like 1.2 volts, 4 of them would make 4.8 volts. Online it says that the internal resistance is about 30mΩ-100mΩ. That means .03Ω-.1Ω right? Using ohms law to find the current, V/R=I, and the max resistance, that should be 1.2/.1=12. So a single rechargeable AA battery can pump out 12 amps? Correct me if I'm wrong


texts: Efficiently sensing the voltage of a battery pack

texts:
I'm looking to sense the voltage of a battery pack that is powering a device by the device. Depending the the level of the pack (2 cell LiPo 1200mAh) the device will change it's behavior. As the pack voltage decreases the device will shut down peripherals until it safes completely. Also when the device is being charged that it will only partially function.

The sense circuit will be attached all the time and i'm trying to minimize the drain on the battery from it. My though is to use a voltage divider with very high value resistors then buffer the signal with a low quiescent current OpAmp. I'm looking at the TI LPV511 OpAmp and a 1M and 3M ohm resistors. The OpAmp is rated at 1.5uA max and the voltage divider should be 2.5uA worst case. The uC is a 3.3v device.

Is this circuit sufficient or are there alternatives I haven't thought of?

simulate this circuit – Schematic created using CircuitLab


texts: How can I compare a TVS diode with a varistor?

texts:
For a 120Vac line protection element, comparing this TVS diode:

With this varistor:

The immediate differences I see are:

The varistor is marginally cheaper
The varistor specifies a maximum working voltage much, much smaller than its clamp voltage. There seems to be no maximum working voltage on the diode, only the breakdown voltage.
The diode is well-specified, and includes many graphs of its I/V characteristics. The varistor only has one graph, of clamp voltage against surge current.

In a simple application of a parallel AC line protection element, why would I choose a varistor over a bidirectional TVS diode?


texts: Is Kalman filter suitable for smoothing sound spectrum?

texts:
I'm implementing a software similar to a real-time spectrograph with a modified FFT. The output vector summarizes the intensities of various musical tones present in the input signal. Its size is a small constant (compared to the FFT window size) and the values can be continuous. The problem is there is a lot of noise both from the signal itself and from the transformation process. I think that some kind of smoothing could help since the tones that should be emphasized are typically of longer duration and the noisy values vary much from one frame to another.

I've came across the Kalman filter which is used mainly in real-time control systems. It seems to be very powerful. As I've dug into the literature I've gotten unsure if this kind of filter is really suitable for my problem. It seems that the Kalman filter requires modelling the underlying linear process. On the other hand I don't assume any particular process behind the signal. Should I just model a trivial steady-state process or this kind of filter is not suitable?


texts:
The answer to another question identified two PCB-mounted scope probe "holders":

I can't find these at any distributor's web site because I don't what they are called. Can someone, please, give me the nomenclature I need to purchase these items?


texts: What are the different possibilities for delay distortion in fibre optic cabling?

texts: Fibre optic cabling is often known for its extremely high speeds but is there anything that may develop delay issues in transmission via fibre optic cabling?


texts: Logism: Add/Subtract 4-bit Oscillation Apparent Problem

texts:
I currently have a problem within my circuit design of 4-bit adder that has a function of subtraction in Logisim. My 4-bit adder has an output of 5-bit with maximum of decimal 30 (Because 1111 (15) + 1111(15) = (11110). In my addition process, all went well without any problems.

Below is the image of the adder. 0 means addition in the left-side input.

But after changing the input to 1 so that I can have a subtraction function, an error occurred and it still display 16 in my screen as shown below.

Any help is very much appreciated. Thank you.


texts:
I'm having a simple problem with IAR Embedded Workbench, programming an STM32 using an ST-LINK/V2 programmer. I'm trying to run a program that temporarily switches off the JTAG pins, so I can't run it all the way through in debug mode. What I would like to do is load and run the program (without debugging), then connect the debugger to the running program to check a few values and make sure it actually ran.

I can't figure out how to do either of these steps with IAR. I've tried doing a "Download active application" followed by a "Debug without Downloading," but either the program didn't start running or when the debugger connected it reset the program. When I try to use the "Attach to Running Target" option, I get an error message saying "The debugging session could not be started."

Any ideas on how to do this?


texts: Does it help to replace the battery if phone is slow?

texts:
Some people I know say that replacing the battery helped their smart phone improve its decreased speed resulting of two years of use.

My initial guess is that this would not have any influence because the speed is mostly about the phone's processor and built-in memory.

But then I got to wonder if I'm mistaken. Maybe if the battery is old, it does not deliver sufficient power and forces the processor, and thus the whole system, to work slower. Or maybe even, that the smart phones switch to "economy mode" (does that even exist in a smart phone?) when it detects that the power delivery is not sufficient.

Any thoughts?
Thanks


texts:
I'm trying to figure out if my power distribution setup is hurting my circuitry.

Below is a picture of the setup for one device:

The power supply is a wall adapter rated for 6VDC/900mA output.

The middle item is a special power hub I created from two pins of each USB plug and it is powered from the wall adapter through an LM2940 regulator with the 10uF cap on the input and the 22uF cap on the output.

I then connect various USB to C+ plugs to power other circuits off the same hub (hence the right-most box in the diagram). Power to those circuits is passed through its own LM2940 regulator as well.

Some circuits contain a max232 chip for interfacing the circuit with a PC but when I test the circuits in my setup, my baud rate must be very limited, and I'm thinking with two LM2940 regulators in series, I'm not getting enough voltage or current to the max232 and I feel my only way(s) out could be to ditch the hub and power each circuit from its own wall wart or use a wall wart that can deliver higher current.

any ideas?


texts: STM32WB - sensor data sent via BLE and saved on SD card (SPI)

texts:
I have an STM32WB and I am trying to get the data from some pressure, temperature and humidity sensors through DMA and send them to my Android via BT, while at the same time saving it as well on a SD card with SPI.

Both programs work quite well separately, both for SD and for BT (I used the Hands On from STM where you send random temperature data to the app), however when I put them together neither of them works. Here I think I lack the knowledge of setting the Clock Source.

For my SD card and receiving of sensor data, I normally use the PLLCLK with 32 MHz on CPU1 and 16 MHz on CPU2. However for the BT app, I used the HSE_SYS clock source with both CPUs on 32 MHz.

I can't seem the wrap my head around how to set the clock in order for both these functions to be able to work together.

Also as a second question would be: How do you suggest to implement the two functions in a same program? I want the data to be transmitted simultaneously via BT, while also storing the same sensor data on the SD card.

I notice that after I get to the UTIL_SEQ_Run function that starts my BT, everything else from main is ignored, so I cannot go for my SD card functions. How could I combine this? Does it have anything to do with the scheduler? I am not so sure how to have these two tasks run in parallel.


texts: Hello I need a TCXO with tunable frequency 10 to 12MHz. I find the part here A18ST but this company is not responding and I don't find their distributors. Please help me if anyone knows a company that provides such TCXOs. I will be grateful. Thankyou.


texts:
Im learning about electrical measuring instruments(PMMC).In this textbook it is said that a rectangular coil is wound on a aluminium former.Inside which there is an iron core.

My question is what exactly is a core?Isn't it the thing on which the coil is wound on?
How can the coil be rectangular(isn't it wire's).Question might sound stupid,but please give some explanation.


texts: Can I have 2 different voltage regulators output 3 different voltages?

texts:
I'm wondering if it is possible to get three voltages out of two voltage regulators. Let's say I have a 9V and a 12V regulator in a circuit. Would I be able to get the 4 voltages below out of this setup (if I include the input)?

24V input
9V out
12V out; and
3V (difference between the 9V and 12V)

I can not see why this won't work.


texts: Problem with interrupt-based timer on STM32F411

texts:
I was following this online tutorial and cannot get the interrupt-based timer to work.  I know the timer is running because if I uncomment the five lines in the main loop, I get a nice square wave output.  But with those lines commented out, the timer interrupt is not firing and I cannot figure out why.  Can someone suggest what I'm doing wrong?

#include "stm32f4xx_hal.h"

void SysTick_Handler(void)
{
    HAL_IncTick();
    HAL_SYSTICK_IRQHandler();
}

static TIM_HandleTypeDef s_TimerInstance = { .Instance = TIM2 };

void InitializeTimer()
{
    __TIM2_CLK_ENABLE();
    s_TimerInstance.Init.Prescaler = 160;
    s_TimerInstance.Init.CounterMode = TIM_COUNTERMODE_UP;
    s_TimerInstance.Init.Period = 100;
    s_TimerInstance.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
    s_TimerInstance.Init.RepetitionCounter = 0;
    HAL_TIM_Base_Init(&s_TimerInstance);
    HAL_TIM_Base_Start(&s_TimerInstance);
}

void InitializeLED()
{
    __GPIOA_CLK_ENABLE();
    GPIO_InitTypeDef GPIO_InitStructure;
    GPIO_InitStructure.Pin = LD2_Pin;
    GPIO_InitStructure.Mode = GPIO_MODE_OUTPUT_PP;
    GPIO_InitStructure.Speed = GPIO_SPEED_HIGH;
    GPIO_InitStructure.Pull = GPIO_NOPULL;
    HAL_GPIO_Init(LD2_GPIO_Port, &GPIO_InitStructure);
}

void TIM2_IRQHandler()
{
    HAL_TIM_IRQHandler(&s_TimerInstance);
}

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
    HAL_GPIO_TogglePin(LD2_GPIO_Port, LD2_Pin);
}

int main(void)
{
    HAL_Init();
    InitializeLED();
    InitializeTimer();

    HAL_NVIC_SetPriority(TIM2_IRQn, 0, 0);
    HAL_NVIC_EnableIRQ(TIM2_IRQn);

    for (;;)
    {
//        int timerValue = __HAL_TIM_GET_COUNTER(&s_TimerInstance);
//        if (timerValue == 50)
//            HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin, GPIO_PIN_SET);
//        if (timerValue == 100)
//            HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin, GPIO_PIN_RESET);
    }
}


texts: What happens when MLCC breaks due to over voltage?

texts:
I am curious about what will happen to the characteristics of the capacitor when 220VAC is applied to 50V rated capacitor?

Will it short or open?


texts:
I'm trying to obtain an op-amp's open loop DC transfer characteristic curve on an oscilloscope, and from the curve, the open loop gain.

Here is an image (from some random website) showing the curve I wish to obtain:

My attempt at attaining the curve was:  tie one of the inputs to ground and the other to the function generator, then get the function generator to put out a ramp function (representing my DC sweep).  I then looked at the output of the op-amp with the scope and zoomed in and was able to see an image similar to the image I in the above link.  I then tried putting the scope into x-y mode (and though that worked, the result was pretty low quality), so I gave up on the x-y idea.  I then tried to calculate the open loop gain (would should be around 100dB = 100kV/V) by shifting the two curves on the scope so they both equaled 0V at the same time, I then got a point from the output of the op-amp and the corresponding point from the ramp function and found the gain to be way out...  It was around 800...  So my two issues are, the open loop gain is way off and the whole approach seems so inaccurate.  I can even zoom in much on the curve  because I don't really have anything to trigger off.

Does anyone have any suggestions as to perhaps what I've done wrong, or a better way to the transfer characteristic of the op-amp on the scope?

If there is no accurate way, does anyone have any idea of how I could just obtain the open loop gain of the op-amp?  Since it's open loop gain is roughly 100dB, it means that I need to generate like 1uV on one of its inputs just to get 100mV output...


texts: Does a capacitor discharge and recharge in a loop while power is going through it? or only when power is cut off?

texts:
Beginner Question. I'm trying to understand how a simple LED flashing circuit works, here is a picture of the circuit:

I know that much like a Relay, a Transistor could be used as a switch by using it's base and passing a small amount of power to it.

Now something needs to Connect and Disconnect the power to the transistor to make it work as an automatic switch or the LED will not flash and remain On.

In the picture above, what is taking care of that power oscillation? is it the Capacitor? Does a capacitor discharge and recharge in a loop or only when its cut off power? if not then what does the capacitor do here?


texts: Accessing and storing a bit from a uint8

texts:
I need to access a particular bit from a uint8 variable, and store this bit value to another uint8 variable. Right now I am doing the following to achieve this:

bit_value = (uint8_variable & (1 << BIT_POSITION)) >> BIT_POSITION;

Is this the right method? If it is right, is there a simpler way to achieve this?

Update:
One more question. I need to set a particular bit in a uint8 to a value X(not toggling the bit).
eg: In 1100 0101, I need to set bit 2 to X, without modifying the other bits - to obtain 1100 0X01.
I have been racking my brain, but I can't land on a straight forward solution.


texts: 2's complement of negative fractional number

texts:
I have tried to search it out on google before posting it here but didn't find explained way.My question is as follows:

What is 2's complement representation of -5/8 ?

It would help even if way is provided to get 2's complement of negative fractional no ?

Thanks


texts: JFET stabilised wien bridge component ratios

texts:
I find myself in need of a sine wave oscillator and have decided on the wien bridge. I have followed all the tutorials but have a few questions that do not seem to be answered elsewhere.

Firstly, I understand the ratio between Rf and R3 determines the negative feedback loop gain set to 3, or just above, at a ratio of 2:1. But there are lots of combinations of resistances which would give that ratio, so what effect would say using a 1 OHM : 2 OHM resistance be compared to 10 OHM : 20 OHM? And the same question about the capacitor resistor combinations in the lead lag circuit.

Second, how do the values of Rf and R3 get selected when there is a JFET paired with R2? I figured that to get a gain of 3 after the gate voltage comes up then I would add the Rds(on) of the JFET to R3 and count them as one, so then when the JFET is off, there would be no resistance through it and the gain would be higher than 3, allowing oscillations to start. Is this correct? Any particular ratio between the JFET Rds(on) and R3, does one dominate, equal or does not matter?

Third, the negative peak detector which drives the gate of the JFET charges a capacitor, which has a resistor in parallel. What is that resistor R4 doing and how is its value determined? How is the capacitors value determined?

Lastly, what determines the output voltage? Say, I need a 0.1 v output to feed a BJT amp, what values would I need to change and how would I calculate them? I figured the output would be determined by the maximum peak to peak printed on the datasheet, but how would I bring this down?

Thanks for any replies


texts:
I want to reduce my amplifier output to line-level.

I found this tutorial, Connecting speaker signals to line level inputs, which is compatible with 50 W output power. There is also mentioned what to do if amplifier is more powerful than that.

So if 10 kΩ resistor handles 50 W and 33 kΩ handles ~300 W, what is compatible with my amplifier which output power is 120 W per line? Or can I just use the 33 kΩ resistor?


texts: Printing current when using sinus voltage source?


texts: Photo-voltaic power source connecting to a grid: can I feed the greed?

texts:
Let's say I have a PV power source generating 50/60 Hz 230VAC power. I could connect this power directly to the grid assuming that I will consume all generated power for my own needs or, if the power generation exceeds my needs (and if the battery is fully charged), I can 'sell' the energy to the grid.

However I prospect that I will not be able to sell the power to the grid at least not in any case. For example in my country (Russia) I would need to get very expensive certificate (as I know Alstom got this one for about $50 000 several years ago) to be able to connect to grid as a power source. I don't know what is the situation in other countries (probably with more distributed power generation strategy). Most of my interest is Germany experience.

However I could connect the house to PV power source and use grid only if I don't have enough power from PV elements or from the battery. If I generate MORE power than I (and battery) need - I will through it to the heat.

Moreover: I heard about "Power islanding effect". Let's say part of grid was turned off for maintenance but my PV system will still feed the grid and make it dangerous to maintenance.

Could anyone comment my thoughts on the topic?


texts: What is the lowest voltage a cmos transistor can operate?

texts:
I am trying to do some hspice simulation with some free 45nm CMOS transistor models. I found that an inverter can simulate properly with voltage as low as 0.25V, though it's slower.
My question is, in a controlled environment when speed is not a concern and the device is shielded, can such device run correctly at such low voltage?


texts: Overcharge a sealed 12V lead-silver-calcium battery with a power supply to prevent sulphatation

texts:
I read that lead silver calcium battery need 14.8 V to fully charge. The max with my charger (ctek) is AGM setting which is 14.7 Volt. I fear this lower voltage this will lead to sulphatation of the battery
I have a regulated powersupply which can go up to 30V and 10A and it will deliver amps to the battery when I set it at 14.8V. I can hear the bubbling from the battery
I understand that these sealed batteries undergo a process where the hydrogen gas produced is somehow recombined back to water, but how should I charge this battery to the max without excessive gassing and loss of water. Max voltage, how long time?


texts:
I'm looking for a 2 or 4 bit shift register that I can shift data into, and on the 5th shift into the device it will shift the previous data back out on the Dout.

I am looking for a shift register that acts a lot like the MAX6969 from Maxim, yet is smaller than that.


texts: I have a 240-volt mains supply and I want to run two identical BLDC motors rated at 120 volts each. Without the need for a transformer with just the help of IGBTs and inverter can I run the motors? Connecting in series might work, but what about back emf? Basically is it possible to divide the voltage by a factor of two when using identical BLDC motors? If not, will it work for an ac motor?


texts:
In the prototype I'm working, I'm using my phone to communicate with the Bluetooth module RN4871 (https://www.microchip.com/wwwproducts/en/RN4871). Now I'm planning to buy a chinese Android industrial tablet to control the machine, but according to the seller, it's Bluetooth version is "Single band Bluetooth, 2.4G".
How can I know if it'll be able to communicate with the RN4871 module? Obs: the tablet only send/receive strings and the RN4871 controls a PIC18F through RX/TX.


texts: Why are capacitors use in transistor cicuits? What does it do with biasing operations? I always see capacitors on transistors being used as amplifiers.


texts: How can I store energy from short pulses of current?

texts:
BACKGROUND:
I am an intern with a local company.
We have a powerful 60 KW Engine that runs throughout the day. We have a two Machineries that are powered off the Engine directly (using clutches and gears of cause).

The first Machinery runs a feed continuously, while the second Machinery is periodically engaged to cut strips of sheet metal (Cutter)

MODE OF OPERATION FOR THE SECOND MACHINE:

The cutter is engaged to the engine;
It spins at a very high speed
cuts a strip briefly
and disengaged

--> After it is disengaged, I've noticed the cutter spins for almost 40secs before coming to a halt.

--> I also estimated an initial Idling Torque 20 - 30 Nm ...@3000+ rpm (rough calculations from data I retrieved from as-built documents)

PROBLEM:
We want to install a brake for the cutter; And am working with a staff on the brake design;
** I feel I can propose installation of a little Generator to utilize the free-spin energy. I believe this can act as a Soft brake. (using clutches still)

Obviously, only a small amount of current can be produced for a few seconds...

QUESTIONS:

I want to know if I can store electricity that is generated for a few
seconds repeatedly (non-constant intervals). If so how?

I know quite a bit on Capacitors and Batteries, but is there any battery that can be charged under these conditions? ...I have done lots of fruitless Google searches

Some staff have told me its a fruitle idea with no convincing reasons...(@least to me)
Please give me further directions on what to read

NB: I am an Undergraduate Mechanical Engineering student


texts:
I am designing switch circuit that switches on and off a relay that switches on and off a 115AC light.So the switching speed is not a concern as it is a once in a while on or off.

The relay for the circuit is not accessible to me and therefore I can't add a flyback diode across it.
My question is will the shown snubber circuit be sufficient to protect the Mosfet Drain-source? Do I still need a TVS? Thank you

http://imagizer.imageshack.us/v2/700x500q90/661/HzLU7u.jpg


texts:
All,

I know this isn't likely a pure electrical engineering question, but it is about a tool that may have been found in a lab, or that someone here knows about.

I recently ordered a used HP/Agilent (actually, just HP) 6200B DC power supply off of eBay, and it arrived today. All of the knobs, switches, and lights work. I need to make sure everything's still on the money with a nice multimeter, but other than that, everything seems in good order.

Now, I just want to know approximately how old it is. Agilent's website has a .pdf of the user's manual with a revision date of 1966. HP spun off Agilent in the late 90s. It was definitely built between those two dates, but that's quite a bit of room.

Below are pictures of the unit itself. I've included the serial number in case anyone knows how the production run dates correspond to it. I've also looked at the circuit board... the traces are really "loose" instead of the tight, precisely-packed circuits you see today. Anyone have an idea of a range of when this unit was made?


texts: What do the letters W, Z and G stand for on an extension cord (USA)?

texts: G seems to be obviously (G)round, but I have no idea which of the others is Neutral and which is Hot.


texts: Where to source crimp dies for small uninsulated wire terminals

texts:
I have a Durite 0-703-51 crimp tool handle with replaceable dies, and have been searching everywhere for dies that go both smaller and larger. The die presently has 0.5-1.0 Econo/Superseal and 1.0-2.0 Super 2.8 compatibility. I have some small JST terminals for some 22 and 26 gauge wire. They are tiny and these crimp die jaws barely make contact.
I am looking for something that goes down to 0.1 or maybe 0.25, bu they don't seem to exist? What tools are being used to crimp these tiny terminals?


texts: Is EMI/EMC still a big concern for a PC case?

texts:
I've recently started looking into researching potential concerns when it comes to using a non-metal material for a custom PC case, specifically wood. I've seen people talk about heat, electrical grounding, and EMI.
I've found that the first two are not that big of a deal to worry too much about, but what I'm unsure of is the last one; EMI.
Some people have reported no detectable interference from their devices, while others have reported the opposite (one even said their power supply alone was at fault).
My knowledge on the topic is only second-hand from such reports (of which I'm not sure how much can still be applied to today, as technology improves over time), and it seems to me that some of the concern comes from the individual parts that a case with a full metal enclosure can simplify the solution for, though my question is:
Should there still be concern for proper EMC shielding in a PC case, especially when one is using parts from well-known reputable brands for their computer?


texts:
I'm getting back into basic electronics with an Arduino after many years away from the hobby, and I've forgotten a lot of my knowledge.

One thing I'm finding is that I really need to get an oscilloscope to assist in designing filtering circuits to give me smooth output from PWM.

I'm not after anything fancy and my budget it small, so what sort of things are on a an oscilloscope must have list?


texts: I came across this SMPS topology that I don't recognize.  It looks sort of like a combination of a buck converter and a boost converter, but I can't quite figure it out.  I haven't been able to find any topologies that match this anywhere.  Does anyone know?


texts:
I need to identify this pin so I can order more.

RESEARCH: I've pored over Molex.com, Allied Electronics, and here with no success. I also reached out to JST and Allied directly but they were unable to identify it.

SOURCE: These are found inside an aftermarket automotive headlight produced in 2000 by an obscure company that stopped making them years ago. I tried contacting the OEM and various parts stores to no avail. Other components in the vicinity of these pins/terminals were made by JST, hence why I contacted JST directly.

ITEM IN QUESTION: It really looks like two pins mated together, but it's one piece. It's secured by opposing winglets which are depressed by the removal tool.

Additional photos include the pin and measurements plus some online sources I've found selling the plug + pins. Shipping on these would take far longer than I am able to wait, plus these aftermarket headlights are wired differently than stock, so those pre-wired ones are definitely out.

Additional photos here: https://imgur.com/a/uOGwJjy

Last time you all were able to do the impossible. Thank you in advance for your help this time around.


texts: Unable to Power Arduino and DC Motors via 2 AAA Batteries

texts:
I am using 3.7 V 2000mah battery.
I am stepping it up to power an arduino board via an NCP1402. It has a continuous output current of 200mA.
I am trying to run two Micro Metal Gear motors with stall current 700mA. This setup works fine.

However when I try to use 2 AAA batteries and power it up, it does not seem to run the motors.
Any idea why? Any ideas as to how to overcome this issue?
Thanks!


texts:
I'm struggling with the design of a MOSFET based switch for high input voltages.
See schematic of the basic circuit that I've come up with:

simulate this circuit – Schematic created using CircuitLab

When M3 would be ON, the voltage on it's drain would be approximately 0.
This also means that M2 Vgs ~= (-50)V, exceeding the AMR for this MOSFET.

MOSFETs can't sustain this kind of high voltage on Vgs... What could be an appropriate solution for this?


texts: Are there CPLD / FPGA toolchains and workflows that bypass vendor IDEs?

texts:
Custom programming for FPGA boards is a similar and helpful question for any with the same as this, but they are different. In that thread they discuss custom options and building their own. This question is about what exists already (i.e. nothing need be custom.)

Another newbie here. Very limited EE education but experienced in software development trying to get started with CPLDs and FPGAs.

Any help with my terminology would also be appreciated.

From what I can tell there are two major manufacturers, Altera(Intel) and Xilinx. They both provide full IDEs for working with their chips. From drivers to design to testing and deployment (Is this Synthesis or is that another thing entirely?)

I've also noticed there are open source simulators around such as GHDL and Icarus Verilog. However, to get the designs you simulate with these onto the chip, it seems you still need the Altera/Xilinx solutions above. Is this correct?

Ultimately it would be nice to be able to develop the Verilog / VHDL in a text editor. Launch it in a simulator. Then if it seems good, deploy it to the chip via terminal (i.e. using a usb blaster.) Even better using all open source and free tools. Is this possible?

I do realize the IDEs provide a lot of good things and pro projects and the like will need all that, but for someone coming from a software background wanting to play around as a hobby, a short simple workflow would be very nice.

All pointers appreciated. Thanks for reading.


texts: Why are monochrome red OLED display hard to come by

texts:
It looks like the majority of monochrome OLED display modules available on the market are white, orange/yellow, green or blue. There seems to be only a very limited amount of red displays available.
Are there any technical limitations preventing or making the production of red OLED displays more difficult?


texts: Most small / cost effective way to detect changes in altitude?

texts:
I want to make a device, which when placed on someone skiing or snowboarding, will be able to tell whether that person is sliding down the slope. The problem is two-fold. I must first detect whether the device is moving. Then, I must know whether the device is gaining or losing altitude, because I want to do something different depending on if someone is sliding down the slopes or going up the chairlift. As such, there would be 3 total states:

Not moving (the skier is stopped anywhere)
Skiing (the skier is moving towards the center of the earth)
In a chairlift (the skier is moving away from the center of the earth)

It's not required accuracy about the altitude but just understand the variations.

A few options have been mentioned:

A GPS, which is expensive and unrelaible for the altitude metrics
An accelerometer
A barometer

Ideally, the materials required for this detection would cost under 20$. I would also ideally need to arrange them in something smaller than a car remote like this one.


texts:
We have an opto-isolator diode connected to a contact closure to ground. When the contact is closed, the cathode reads 0V when measured to ground. When the contact is opened, will I measure a voltage that is close to 28V? I can't remember if that node is treated as a "floating" node or not.

simulate this circuit – Schematic created using CircuitLab


texts: PIC18 how to explain : you write bit 1 by making TRIS input

texts:
I'm reading 1_wire header file for PIC18 with C18 compiler.
in the write_byte function, they specified that in order to write bit1; we make line input and that will take it high.
can we specify high or low output value in the TRIS port which specify i/o direction?

#define OW_LAT LATCbits.LATC1
#define OW_PIN PORTCbits.RC1
#define OW_TRIS TRISCbits.TRISC1

void ow_write_byte(unsigned char data)
{
    char i;
    for (i=0;i<8;i++)
    {
        // DQ Low
        OW_LAT=0;
        OW_TRIS=OUTPUT;
        // Keep it low for 10us to start the WRITE
        Delay10TCYx(10);
        // Keep low i.e. keep output mode and low if WRITE0 (bit 0)
        // or release line i.e. make input to take it high if WRITE1 (bit1)
        OW_TRIS = data & 0x01;
        Delay10TCYx(50);
        // Release the line. Total of 60us
        OW_TRIS=INPUT;
        // Some recovery time between the bits 2us
        Delay10TCYx(2);
        data =data >>1;
    }
}


texts: Is there a good and reasonably priced way to make a custom RFID reader and barcode scanner that runs Android?

texts:
I'm building a system for a small manufacturing business that requires a mobile barcode scanner (at minimum) and would be great if it could be an RFID reader too. I would really like this to be a powerful device that runs Android and could have custom applications written in Java on it. However, I'm a software guy and I'm not sure where to start on the hardware side.

Is there a good hardware option for this?


texts: Compatibility & Interchangability of KT88, KT100, KT120 and KT150 Tubes in Tube Amplifiers

texts:
Are (immediately from the start or over time) the tubes that come with a tube amplifier (say the popular KT88 in Single Ended mode or Push Pull mode) replaceable with say the larger KT120 or KT150 any other tube from the "KT" series?

Q1) In other words are the KT88, KT100, KT120 and KT150 Tubes safely interchangable generally speaking in a well built tube amplifier?

Q2) are there any downsides (from a musical quality point of view) why one should NOT want to upgrade to a larger KT tube? In other words is the newly desiged KT150 generally a better (sounding/lifespan) tube than the KT120 tube?


texts: How can i drive a 5v 120VAC 80mA with 15A contacts with a raspberry pi?

texts: I don't have a very good knowledge of electrical engineering yet but I'm working on it. I will like to know as simple as possible, how can i drive a latching relay that needs about 70-90mA if the raspberry pi can only deliver about 40mA. I need to find a relay that can handle home appliances but can be controlled by the raspberry pi.


texts: Which is the cause of "scan losses" in a linear phased antenna array?

texts:
in a linear phased array it is possible to move the peak angle ("beam steering") by applying proper phase shift between the excitation currents:

The second picture represents the array factor for different beams angle. Last picture taken from here.
What I see in the second picture is that beam steering increases all the lobes width but does not change the lobe peak. So, the peak value of the array factor is (or at least seems to be) the same for each scan angle.
Always there it is written that if beam steering is used, there will be some "scan losses":

Another characteristic of all active antennas is the loss of aperture gain as the beam is steered away from the boresight direction — defined as Ɵ=0. This characteristic, called scan loss, follows 10*log(cosN(Ɵ)) power, where Ɵ is the scan angle off boresight and N is a numeric value, typically in the 1.3 range, which accounts for the non-ideal isotropic behavior of the embedded element gain. Fig. 6 plots scan loss in dB vs. scan angle, measured in degrees. Note, at the origin, where the boresight angle is zero, there is no scan loss. As the scan angle is increased to 45 degrees, there is 2 dB scan loss. If you increase scan angle to a practical limit of 60 degrees, there is 4 dB scan loss.

The following picture is then shown:

So, which is the scan loss? From my initial picture it doesn't seem to be caused by the array factor. But, if it were caused by the single element pattern, how could we say that it is linked to the scan angle with a fixed equation not dependent on the single element pattern?


texts: Get LED that is steady to flash when voltage drops below set value using 3V battery

texts:
I am using a 3V battery to light 2 LEDs that have a forward voltage of 2.7 V and a third led with a 2.4V forward voltage that acts as an indicator to tell the user the power is currently on.
All 3 LEDs are in parallel.  The circuit is currently drawing 9ma and is only on for 5 seconds when used, which is maybe 3 times a day.
I am looking for a circuit diagram to make the indicator LED flash when the battery voltage drops below 2.7 volts, otherwise it stays on when the other unit it is turned on, so when a user turns it on and it is flashing the user knows to change the battery.
I understand that these low voltages are a problem to get working.  Any and all ideas would be greatly appreciated.


texts: Is it normal for 24" LED monitor to emit 1000 odd mV/m?

texts:
I have a 24" LED monitor, we have a cell phone tower on a building next to ours, so we bought an EMF meter to see if there was any high radiation from it. Throughout the house, the radiation was above 600 mV/m sometimes it fluctuated to 400 mV/m. Is this safe or normal? As one might expect, there was above 1 V/m near WiFi routers.

But what struck me as odd was monitor, it is 24", LED, and near some spots, it was emitting more than 1000 odd mV/m. Is this normal? There was no known WiFi device near the monitor. It was emitting the same amount, regardless of whether the monitor was on or off.


texts: MOSFET threshold voltage calculation across temperature using normalised values

texts:
I have an application in which the gate voltage is 300mV to turn off the MOSFET which is active when on. The data sheet for the ZVN3310F specifies the threshold at 0.8V-2.4V at room temperature. A normalised threshold graph is also presented. I want to know whether the MOSFET would remain off across temperature so my question is;

1/ Would one use the temperature or the normalised threshold voltages in deriving the percentage difference in the threshold voltage across the temperature of interest?

2/ Once the percentage difference has been derived, for say a temperature of -40 degrees C, would we use the worst-case threshold tolerance of 0.8V, given that the threshold voltage is inversely proportional to temperature and multiply the percentage difference by that value?

3/ Similarly, at 125 degrees C say, would we calculate the threshold using the maximum threshold specified or stick with the minimum value of 0.8V as the worst case minimum?

e.g.

(125 Deg C - 25 Deg C) / 125 Deg C = 0.8 x 0.8V = 0.64V

Is this correct for the expected threshold voltage at 125 deg C?


texts: Quadrature encoder has one synced edge and one phase-shifted edge, is this a special encoding scheme?

texts:
Special encoder output scheme?

I am testing an inexpensive encoder and encountered a strange but consistent output pattern. In other encoders I've used, the A signal consistently has a 90 degree or -90 degree phase shift, depending on the rotation direction. Both rising and falling edges exhibit this phase shift.

The encoder I am testing right now consistently has one edge in sync, and one edge showing a phase shift. For clockwise rotation, for rising edges, signal A consistently leads signal B. For falling edges, signal A and B are in sync. For counterclockwise rotation, for rising edges signal A and B are in sync. For falling edges signal A consistently lags behind signal B.

The following Arduino Serial Monitor plots show the output. Signal A is plotted in blue, signal B is plotted in red.

Clockwise rotation

Counterclockwise rotation

Setup for testing

I used an Arduino Uno to test the encoder. I've hooked up the encoder following the schematic below, as described in an article by Electro Schematics.

The encoder signals are attached to pins 6 and 7 (both non-interrupt pins). I am using the Teensy Encoder library to decode the encoder output. The library is only able to parse the encoder rotating in one direction (counterclockwise). If I substitute the encoder by one that has both signal edges phase-shifted, the output is parsed perfectly.

Question

Now if the output were noisy, or if I only encountered this issue with a single encoder I would assume the encoder to be faulty. The output however is perfectly consistent and shows this pattern every time. Furthermore, I've ordered the encoder as a pack of 5, and all encoders show the exact same output. Even more, a while ago I encountered another encoder that shows the exact same output pattern as these ones. As the output is consistent, it is technically possible to decode the output signals.

Because of this, my question is whether this is intended functionality? Is this perhaps an encoding scheme different from quadrature encoding? Could this be an encoder intended for rotation in one direction only? Or did I receive 6 different encoders with the same manufacturing error where two contacts are not offset?

The images below show the two encoder types with the strange output.

The following image is the encoder with normal quadrature output that I am able to decode.


texts: How to keep the arduino uno up on serial connections?

texts:
Each time I open a Serial connection to my arduino it restarts.
Is there a way to unactivate this ?

Cheers.


texts: Clarification needed regarding average power through a load

texts:
The question for the following circuit was to find the average power through the load \$ Z_{L} \$.

The first and second image shows that \$ I_{2} \$ and \$ V_{2} \$ were found. I assumed that the average power through the load could be then found by the formula:

$$
I_{2(rms)}*V_{2(rms)} * cos(18.43 + 45)
$$

However, this appears to yield a different answer to that obtained in the image, where the average power is found directly via the resistor and \$ P = 62.51W \$ is obtained:

Could someone please explain why this is the case?