texts: Is the process of adding new parallel (matching) cells into an already built battery pack safe?

texts:
I just built a 5p13s 18650 li-on battery pack with a bms. I realized after the build I add more of the same cells (all new), so I could have built a 7p13s instead.

Is it possible, after setting the new cells to the same voltage as the ones in the pack to add 1 or 2 (or more) cells in parallel without cutting the series connections first?

There won't be external load connected to it, but is the internal resistance an issue while welding them together, as there will be an unbalanced pack during the process... (Part of the pack will be 6p or 7p until all have been welded together)


texts: What does a 'logical AND' in an analog signalflow mean?

texts:
The link aboves shows the functionality of an AD-Converter based on a sawtooth signal.

https://de.wikipedia.org/wiki/Analog-Digital-Umsetzer#/media/File:Single_slope_dac.png

As it is asked in the topic, what is the function of the &-Box (e.g. behind the both operational amplifiers)? I thought it is a mixer, but I'm not sure and it would be nice to know.


texts: RGB LED audio spectrum analyzer - Bandpass or FFT?

texts:
I'm about to build a coffee table which has a RGB LED matrix build in it just like in this video.
https://www.youtube.com/watch?v=4NJDgvV8RZw

I want the matrix to display an audio spectrum that should be calculated in real time from a variable audio source over a 3,5mm audio plug. ( e.g. smartphone, PC, mp3 player )

It sould also just display random and/or programmed visuals patterns. ( not related to the audio input )

So i thought using an AVR microcontroller as the main unit of this project.

The mcu will be programmed once, and does not have to communicate with other devices.

Buttens will be used to switch between modes and/or annimations.

So the basic idea is there, but there are a few things that I'm not shure about:

Should I build a bandpass filter board to get the spectrum data and process it from there on with the mcu or go for the FFT- ( complete-software- ) solution ? Which one is faster / more effective ? Does the speed difference matter in this kind of project ?
( Yes I know there are a couple of questions with the same topic, and I've read a few of theml, but I think the answers wheren't specific enougth for me )
How do I choose the amount of bands for my spectrum analyzer ( collumns of the matrix ) ? Does it matters how many bands I choose ( since I want to design the RGB LED matrix driver board and the table with its dimensions based on my selection ) ?

Thanks for your help and please exscuse my bad english.


texts:
I need a circuit to indicate if the DC voltage across two points is exceeded a certain High value (350 V) by using LED as an indicator. For example if the voltage is 355 V then the LED will light,but if the voltage is 345 the LED won't light. thank you for helping me.
your sincerely Moad Nassar


texts: Controlling two things with a tri-state output using discrete logic

texts: I'm trying to control a bunch of MOSFETs with an Arduino microcontroller, and was wondering if it would be possible to control two FETs with one tri-state Arduino output. There are three states that these two FETs can be in, either one on, or both off, so I don't need to ever have both on. Is there some discrete logic way to do this?  And then I'm trying to control 8 pairs of FETs.


texts: Why is the circuit board abreviation for transistor "Q"?

texts: On circuit boards, I see that transistors are "Q", but why Q? Shouldn't "TR" be transformer, so transistor can be "T" because transistors seem to be more common then transformers.


texts:
I have one of these motors that i want to use as a wind turbine generator.
http://www.ebay.com/itm/181392138415?_trksid=p2057872.m2749.l2648&ssPageName=STRK%3AMEBIDX%3AIT

I want my setup to be fairly inexpensive so ive searched for ages without any result for a charge controller that accepts high enough DC voltage for my 120v DC motor, and doesnt cost a fortune....

All cheaper wind charge controllers seem to run directly of AC and the once that do run of DC cost waaay too much.

Is there any chargers that fit my needs?
If not, how high voltage should i expect from the motor? Could a simple 60V buck converter be enough?
http://www.ebay.com/itm/200W-15A-DC-DC-8-60V-TO-1-36V-5V-12V-24V-Buck-Converter-Step-down-power-module-/181849944290?hash=item2a5719f0e2:g:COAAAOSw3ydV4L2I

I hope you can help me


texts:
I know that the following circuit gives a pwm signal at the output, how can I determine the on-time, off-time and the frequency:

simulate this circuit – Schematic created using CircuitLab

I know that the mathematical relationship between the reference voltage and the duty cycle is nonlinear because the sine wave at the output of the capacitor-input-filter network is not a linear function, but how can find it?


texts: Why recommend tantalum over ceramic capacitor for voltage regulator?

texts:
The LM1117 voltage regulator datasheet recommends using tantalum capacitors on the input and output.  What is the reason for this?  What advantage does tantalum have over a ceramic capacitor?
A 10μF tantalum capacitor costs about 21 cents, while a 10μF ceramic capacitor costs about 3 cents.  The ceramic capacitor is also a bit smaller physically.  Plus, you don't have to worry about getting the polarity wrong on a ceramic capacitor.  I believe there is also less concern about conflict minerals with ceramic capacitors.
What advantage does the tantalum capacitor offer, and why does the datasheet recommend tantalum for the input and output capacitors of the voltage regulator?  What exactly would happen if a ceramic capacitor was used instead?
Note: To everyone who's claiming this is a duplicate of Why does the LM1117 data sheet specifically specify tantalum capacitors?, that question is about tantalum versus electrolytic capacitors, while my question is about tantalum versus ceramic capacitors.  Related, but not the same.


texts: Pulse width discrimination and measurement

texts:
I need to measure the time period between points A and B of this signal.

The trace is 5 volts/div and 1 sec/div.  There are 20 to 50 seconds of
"noise" from point B ta A.  The time between A and B varies from 3 seconds to 15 seconds.

I could use the circuit shown in EEstackexchange/ignore-pulses-less-than-a-given-width-in-a-pulse-train to eliminate the very short pulses from B to A, invert that signal and use another discriminator to eliminate the 1 second pulses from A to B, but that's a lot of circuitry.

Is there a simpler way to process this signal?


texts:
The MSP-EXP430G2 LaunchPad Experimenter Board User's Guide (Rev. C) in chapter 3.2 states:

  The LaunchPad includes a pre-programmed MSP430G2553 device [...]

  Press button P1.3 to switch the application to a temperature
  measurement mode. [...]

  The collected temperature data is
  also communicated via back-channel UART through the USB emulation
  circuitry back to the PC. The transmitted values [...] can be displayed with any terminal application or
  the Temperature Sensor GUI available on the MSP430 LaunchPad wiki page
  http://processors.wiki.ti.com/index.php/MSP430_LaunchPad_(MSP-EXP430G2).
  The serial communication port on the PC must be configured with 2400
  bps, one stop bit, and no flow control to display the values
  correctly.

I've been trying to connect to the serial communication channel from linux using PuTTY (/dev/ttyACM0, 2400Bd, 8N1), but nothing happens.

Similar results with:

stty /dev/ttyACM0 2400
screen /dev/ttyACM0

I haven't seen the LaunchPad USB serial working yet, so I'm trying to figure out whether the problem is with my Linux install or with the LaunchPad.

How can I read the data from the LaunchPad demo in Linux?

EDIT1

I am on Ubuntu 12.10 64-bit

Linux 3.5.0-21-generic #32-Ubuntu SMP Tue Dec 11 18:51:59 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

PACKAGE NAME      INSTALLED VERSION
binutils-msp430   2.22~msp20120406-2
gcc-msp430        4.6.3~mspgcc-20120406-3
gdb-msp430        7.2a~mspgcc-20111205-1ubuntu1
msp430-libc       20120224-1
msp430mcu         20120406-2
mspdebug          0.19-1
srecord
libsrecord-dev
libgmp-dev


texts: What is the purpose of this FPGA + microcontroller based motor driver design?

texts:
I have used microcontrollers (Arduino, PIC, Atmel etc) so I am familiar with what they are and what they do (e.g I know about polling, interrupts and communication protocols like I2C, SPI, UART) but I have never used FPGAs before. So I don't understand why the following motor driver uses a FPGA (Altera Cyclone 2) together with a microchip (Atmel). Can someone explain the design logic? Why can't I just use a microcontroller directly with the two encoders? (Note that this item only has Japanese language info available)
http://t-frog.com/products/motor_driver/


texts: Is it ever useful to add a capacitor between op amp inputs?

texts:
Is it ever a good idea to add a capacitor between the inputs of an op amp?

I'm building an electronic load roughly inspired by some of the Dave Jones derivative circuits out there. I've adopted the standard of being able to fully explain the role of each component in the circuit so I can learn the most from the exercise, and so it's almost as if I've designed the circuit from scratch when I'm done.

One of the popular builds is depicted here:

(from http://mjlorton.com/forum/index.php?topic=29.msg92#msg92)

Notice that C5 (10nF) is attached across the inputs of IC2B. The poster mentioned that he was only able to achieve stability by adding that capacitor.

Something about seeing a capacitor there just seems wrong to me, but being something of a beginner with op amps, I thought maybe I was missing something and just haven't come across that before. The reading I've done on op amp stability seemed to indicate that capacitance on the inputs was a negative factor and something to be compensated for, not added.

I don't actually have a stability problem in my circuit, not yet at least, although I do have bypass capacitors (0.1uF) in there from Vcc to ground and from the non-inverting input to ground (to filter out EMI from the reference voltage pot.

Is adding a capacitor across the inputs ever a good idea or did the designer just get lucky in this case?


texts: Is analog output more accurate than RS232 output?

texts:
Where I'm working they use an electronic device to calculate the exact wind speed. One of the parameters besides humidity and temperature they use is the pressure. And they measure it by using the following device. They both acquire/use RS232 and analogue outputs. But they use analogue output for calculations. Is that because RS232 output will have some quantization error?

Here is the device specs:
http://www.furness-controls.com/assets/library/documents/PPC500_English.pdf

You might wonder why I don't ask them. It is because some other engineers set it up for them before they also don't know.


texts: Is it possible to make a high-impedance voltage follower using a fully-differential op amp?

texts:
With a single-ended op amp, I can create a unity-gain voltage buffer like this:

simulate this circuit – Schematic created using CircuitLab
The input impedance of this circuit is equal to the input impedance of the op amp, which is normally very large.
I'm trying to reuse an existing analog front-end circuit that has a differential input connected to a fully-differential op amp. The op amp is wired to provide gain, similar to this:

I know I can set \$R_f = R_g\$ to get unity gain, but if I understand right, the input impedance of the circuit is \$R_g\$. If I want a differential input impedance on the order of megaohms, is my only choice to put megaohm resistors in this circuit? Or is there some other way to wire it that can take advantage of the naturally high input impedance of the op amp itself?


texts:
I have designed a pcb board (2 layer) that deals with high voltage 220VAC and it also converts it to 5VDC and 3.3VDC.
So, because it is my first design and I deal with high voltage I want to be sure that the design its safe and I havent overlook something important.
The board is meant to use the esp module to turn on and off two relays.
Also, the board shape needs to be circular 50mm radius in order to fit where I want.

Here is the design:

Top side:

Bottom side:


texts:
I have a series of questions in regards to grounding and ESD, posting those in one topic as they're all related. This is located in Poland. I'm not too concerned about legality of grounding to neutral, as this definitely shouldn't be done in my opinion and it will be removed asap. I'm concerned about electronic principles as a whole.

We converted the basement in our building to a server room, the
initial power supply to the basement was from the shared basement
light power supply. There was no ground connection, I only realized
that when I felt a tingling feeling when I touched the Earth bolt in
the mains socket. Luckily, I installed an RCD there. During these few
days, an ethernet cable was connected from the basement up to the
apartment. The apartment doesn't have ground either, turns out the
ground is shorted to the neutral wire.
Could that have caused issues, damage the switch for example? Does grounding have anything to do with devices that are powered by 12 volts? I'm aware that there exist isolated power supplies, but then some are grounded to neutral/ground? One of them has no ground bolt at the mains plug even, the rack switch does.
I have since then grounded the basement to a water pipe, there is no
more tingling feeling. However, the apartment upstairs is still on
the neutral ground. I fear this difference can potentially cause
issues with the switches since the ethernet cable doesn't have a
common ground. Am I right?
Yesterday we ran a direct wire from the apartment to the basement so that the basement is under the home electricity meter. Basement is still earthed to the pipe, apartment still on neutral, no common ground between those. This will be fixed as I am pushing to remove the neutral-ground wire connection and to connect the ground wire coming from the basement (which is currently disconnected) so that there is only one grounding point for the apartment and the basement. Is this a good idea? I feel the current setup is dangerous not only due to the possibility of neutral becoming live, but also from the fact my equipment might be damaged.
During this semi-live connection, my dad seem to have touched
something and it shut off the fuse in the apartment which had to be
reset. Since then, my phone charger stopped working. I am really
confused as to why this would happen. Even if he did short something
for a moment, why would the charger die. I kept thinking about it and it made me realize that here in the apartment, I keep getting electrostatically charged by the couch, I used to touch the ground in the mains socket to discharge (since I had sparked my laptop many times by accident). Since ground is connected to neutral, could that spike of voltage damage the charger or pretty much anything connected in the house? This makes no sense to me, since we're talking about AC power and ESD, but I'm trying to understand if my repetitive ESD discharges to the neutral wire could have caused damage to connected equipment or weaken it and it just was a coincidence that the charger failed at the time we disconnected the power during the wire installation.
I keep regularly (yet accidentally) discharging ESD into my laptop
chassis, phone and other things. Sometimes when connected to their
chargers and sometimes when not. What would be the most likely
affected device? I'm believing that when the charger is connected, the charger would take it all since it's 'grounded' in a way?

Thanks, hopefully I explained it right and the answers will help with my understanding of those concepts


texts: Where is the positive on this trimmer capacitor?

texts:
Hello, I'm trying to make project 11 in Dick Smith's book "Funway into Electronics 2." I'm making it on a breadboard because I don't have a kit.

I am struggling to find out where the positive is on the trimmer capacitor.


texts:
Here is what I'm trying to accomplish,  let me know if it's possible and if so where I might find the parts. Thanks in advance for any help and advice you can give me.

I'd like to wire up a LED light bar on my Subaru for traveling during the evening hours in the mountains of MT. I would like to be able to turn it on by flashing my high beam headlights, and turn them off by again flashing my high beam headlights. Where could I find a relay that would function like that. The advantage to wiring it up like that is so I can quickly turn the light bar off as oncoming traffic comes over the the top of a hill or around a corner.  Thanks again for any help you can give me.


texts: Is there a common wire color for PGD and PGC?

texts: Is there a common color for micro controller programming data and clock wires?


texts: How to determine transform angle in field oriented control of three phase induction motor

texts:
I have been developing a control software for the field oriented control of the three phase induction motor. I have studied a lot of application notes and literature about this topic. Based on that I have decided to use the field oriented control which is oriented to the rotor flux.
The main task of the control software is to determine current position of the space vector of the rotor magnetic flux in stacionary reference frame (usually known as \$\alpha\$, \$\beta\$ reference frame) based on the mathematical model of the three phase induction motor. As far as I calculate \$\psi_{2\alpha}\$ and \$\psi_{2\beta}\$ I can calculate the \$\sin\$ and \$cos\$ of the transformation angle between the space vector of the rotor magnetic flux and the stacionary reference frame according to the following equations:
\$\sin(\theta) = \frac{\psi_{2\beta}}{\sqrt{\psi_{2\alpha}^2 + \psi_{2\beta}^2}},
   \cos(\theta) = \frac{\psi_{2\alpha}}{\sqrt{\psi_{2\alpha}^2 + \psi_{2\beta}^2}} \$
Based on that I can determine the torque and flux component of the space vector of the stator current for decoupled control of torque and flux. The problem which I now have is how to determine the transformation angle \$\theta\$ in case the induction motor is deexcited (no magnetic flux is present in the machine yet). In that case the mathematical model will give zero space vector of the rotor magnetic flux.
I have found in literature that there is a method for determining the transform angle in deexcited conditions. The method is described in following manner. At the beginning only the reference value of the flux component of the space vector of the stator current is produced (the reference value of the torque component of the space vector of the stator current is set to zero simultaneously).
This means that the slip has to be zero during excitation (because torque which is proportional to the torque component of the space vector of the stator current is also proportional to the slip). The zero slip means that mechanical speed equals to the synchronous speed according to the equation
\$s = \frac{\omega_s - \omega_m}{\omega_s}\$
My question is whether this method can work in case the three phase induction motor is a traction drive of an electrical vehicle. Because in case I have zero slip the mechanical speed has to be equal to the synchronous speed but how can be the non-zero mechanical speed achieved in case that the reference value of the torque component of the space vector of the stator current i.e. torque reference value is zero and the flux in the machine has not been built yet. Has anybody already met this method and is able to explain how does it work? Thanks for any ideas.


texts: Arc welding near LEDs. is this a terrible idea?

texts:
I have a 16m x 0.8m grid of neopixel-based leds, ziptied to a metal grid of the same size (matrix of 8x120 LEDs).

The LEDs have been waterproofed by inserting them into clear heatshrink, and a glue gun used to seal ends. This means that the LEDs are completely insulated from the metal grid.

Unfortunately a metal connection on the grid has snapped during transport, and we have not yet inspected the rest of the grid, but more may have snapped. To fix the metal grid we will be using an arc welder.

Further misfortune is that the process of attaching the LEDs to the grid is very long, so removing the LEDs from the grid is not feasible.

Question finally is, would it be safe to weld the grid back together with the LEDs still attached? We can of course clear about a half meter radius around the welding spot, to ensure heat isn't an issue. The bigger concern is whether the high voltage of the welding will cause havoc with the LEDs?


texts:
I salvaged both of these parts and the one in the left has a schematic symbol that I've never seen before. I have spent hours trying to look up, but don't know what it is. The markings on it look like a date code for the first day of December 2009.

At first I thought it was a voltage regulator due to the three legs and TO-220 packaging. The markings say SE - B3 and the date code looks like 1D 09.

I put the lower right-hand voltage regulator in there, because I saw that black thing on the input voltage pin and thought it was to prevent arcing or maybe preventing a short circuit. But that is actually a ferrite bead on the leg of a voltage regulator if you can believe it. It's held on with heatsink goo and therefore likely dissipate some amount of heat. The voltage input must be coming from AC mains and the designer of the circuit was either low on space or cash, so that they didn't want to put any sort of other inductor to block the inrush current on the input voltage pin. So they use the tiniest ferrite bead ever made in the most ridiculous use I've seen a magnetic component used.

I cannot tell you what circuit I pulled it from. It could have been a closed circuit television so maybe a CRT. I took one of those apart not long ago but I've also taken apart hundreds of things that I find on the street, so who knows. I have thousands of three terminal TO-220 components that I can either read or identify the part number, so they are more like items for a museum than practical components.


texts: Does an antenna still receive signals without a resonator?

texts: I want to amplify the signal before separating the frequencies out but I don’t know if the antenna even receives signals without being connected to a resonator. I want to connect the antenna directly to an analog to digital converter to analyze all frequencies mixed together. Is that possible?


texts: Which input of NAND is preferred and why?

texts:
Let A and B be two inputs of the NAND gate. Say input A arrives at the NAND gate later than input B. To optimize delay of the two series NMOS inputs A and B which one would you place near to the output?

Edit: Input A arrives Later than Input B. To optimize delay in the NMOS section. how do you place inputs A and B.


texts: How can we actually control the 120 LEDs?

texts:
As shown in the website, 120 LEDs may be controlled with just 17 wires, connected to pins set to OUTPUT.

I get how we can control at least one diode of the pairs below, but what happens when we want to turn on the full board? Is that possible? More specifically, how could we turn on adjacent LEDs in order to form a square, for example?

I hope that the question is not too dumb.


texts: How to test PLL for step input change in phase

texts:
I wrote a simulation for second-order PLL and I would like to test it with an input to see whether my PLL can track the phase.  I would like to change the phase of my sinusoidal signal with step with magnitude 10 rad. Therefore that's what I did:

  F=60;
    t=0:Ts:2-Ts;
    idx=find(t>=0);
    theta(idx)=pi/180*10*ones(1,length(idx));
    in=sin(2*pi*F*t+theta);
    out=pll(in);
    plot(t,out,t,theta)

However, these two phases differ a lot. I am wondering can anyone tell me if there is any problem with the above script.

Here are the commands inside the for loop:

Error(ii)=Kd*in_norm(ii)*VCO_out(ii-1);     % Calculate the Error

prop_out(ii)=Kp*Error(ii);

integ_out(ii)=KI*Error(ii)*Ts+integ_out(ii-1);

lf_out(ii)=integ_out(ii)+prop_out(ii);

phi_out(ii)=lf_out(ii)*Ts*K0*2*pi+phi_out(ii-1);

VCO_out(ii)=sin(2*pi*Fout*(ii-2)*Ts+phi_out(ii));


texts: Stopping a servo before it reaches final position?

texts:
I'm having trouble coming up with a solution for a project. Currently, there is a servo-motor actuating a robotic finger. The position of the servo determines the curl in the finger (straight finger -> servo 0 degrees, curved inwards -> servo 100 degrees). On the finger-tip there is a pressure sensor.

Let's say I tell the servo to move to 100 degrees. The finger will curl until the finger-tips comes into contact with an object. When the pressure sensor senses the finger is squeezing above X amount of pressure on the object, the servo will stop at its current position, say 50 degrees.

The problem is I don't know how to make the servo stop at its current position. The servo always goes to the final position I initially set it at. How can this be implemented?

I have thought of 2 solutions, none of which are ideal:

When the pressure sensor reaches a threshold, turn off PWM to the servo completely. This should stop the servo from moving further but I don't think it'll hold the position. Also this creates challenges for the next movement command.
Have another sensor that measures the current position (degrees) of the servo. When the pressure sensor crosses threshold, take down the current position and update the duty cycle to the current position. Problem with this is that I need to find a way to measure current position.

Can anyone advise on a better way of implementing this?


texts: SHT21P temperature and humidity measurements

texts:
I'm looking at Sensirion SHT21P humidity and temperature sensor and I noticed that humidty has 12bit resolution while temperature has 14bit resolution (the datasheet in PDF is here: Sensirion SHT21P datasheet

So does this mean that sensor has 2 ADC's? Or it's one ADC that measures both of those parameters?


texts:
I need an actuator to press a button in a production tester for a device I designed. The seemingly most straightforward way to do this is to use a solenoid. Those should be good for pressing small buttons, yes? It would be nifty to power everything from USB but not essential. I need a push type to actually press a button.

The switch is Würth WS-Tasu side button with 160 gram nominal force. That switch exists from different manufacturers as well with almost identical spec.

https://katalog.we-online.com/en/em/TASU_3_5X4_7_SMD_SIDE_PUSH

After digging into this, it appears you need surprising amounts of juice to make this happen with a solenoid. Initially I looked at miniature solenoids, which would need 25-30W to make that amount of force (+/- 50g spec) happen. 6A at 5V? That's a fairly chunky SMPS circuit to build right there, not to mention nowhere near what USB could supply.

After more research it turns out larger solenoids are more efficient. The bigger the better but obviously there's only so much room available plus having a water bottle sized solenoid pressing a tiny switch is not ideal.

For example C&S Controls SM0 solenoid (38.1mm x 15.9mm x 18.3mm) seems fit for the purpose.

https://candscontrolsltd.com/products/solenoids/

This thing would manage around 2.25 Newtons of force at 2mm stroke and 6W, which you could theoretically power from an USB dedicated charging port. Also 0.5A @ 12V is heck of a lot easier to manage.

The thing I'm having trouble with is that I don't understand the stroke vs force graph.

What I'm not sure about is how to interpret that graph exactly. Where is the maximum force generated? When the rod is fully extended i.e. where it goes when you switch on the power without anything to stop it?

If I arrange a magnet (or a spring) to pull it 2mm away from the end position and switch on the power, about 1N of force is generated at that point, which rapidly increases to ~ 7 Newtons near the stopper? Let's ignore the counterforce for the sake of simplicity. Or presume I'm going to use an electromagnet which only activates when the solenoid is idle.

Here's what CS Controls Ltd's SM0 solenoid force vs stroke graph looks like:

The plunger is a loose metal rod going inside the solenoid, requiring some kind of magnet of spring to pull it back to start position. Like this guy here:


texts: Surface mount soldering - pins won't attach to pads

texts:
I've been doing thru-hole soldering for very many years and also over the past few years some occassional surface mount soldering (both removing and attaching assorted components). I only have basic equipment (temperature controlled soldering iron and rework/hot air station) but I manage just fine without any problems.

However, I've now met my match with a surface mounted connector, a connector type which I successfully removed (a faulty one) and attached (a new one) to a different PCB a few weeks ago. Therefore I've done this procedure before.

The board in question is a motherboard from a Nintendo Switch console, the connector is the USB C connector which acts as a charging port and video/audio output to the Switch's docking station.

Here are some examples of the USB C connector:

https://nl.aliexpress.com/store/product/Replacement-Charging-Port-Type-C-Charger-Socket-for-Nintendo-Switch-NS-Console-10PCS-LOT/1222106_32825690094.html

https://nl.aliexpress.com/item/Original-Charging-Port-Socket-Replacement-for-Nintendo-Switch-NS-Game-Console-Repair/32828938043.html

As you can see, it has two rows of pins which means that, once placed, the reflow of the already tinned solder pads must go smoothly as there's no way to directly access the inner row once the connector is in place.

In this case, for some unknown reason, I can't get the solder on the pins and pads to reflow AND attach. The heat that I'm applying IS sufficient.

I cleaned up the pads on the PCB, re-tinned them and also tinned the pins on the connector. I then attached the connector, applied hot air, let the solder flow, applied gentle pressure to make good contact between the connector pins and the PCB ..... but for some reason the pins aren't attaching to the pads on the PCB. They ARE making good contact, there IS solder on the pads and the pins as well as flux. So why won't they attach?

I have tried both liquid and gel flux.

I CAN get the external row of pads to attach if I manually heat them with my soldering iron and apply more solder, but of course I can't use an iron on the inner row of pads.

I will say that the old connector was particularly difficult to remove and I had to use a lot of heat to get the metal mounting lugs to free themselves, but the pads looks fine and, I'll re-state this, they DO tin okay.

Any ideas please as to what I'm doing wrong or how I can get this connector to attach?

Thank you


texts:
I am trying to design an RFID system. The transmit antennas will be placed along the length of a 12 by 3m rectangular truck container and be placed at the midpoint of the height of the container. The transmit antennas will operate at the same frequency of 928MHz.

What will the minimum separation distance be for the transmit antennas along the length of the container?

N.B.
The container is metal, RFID antennas placed inside the container.


texts:
So, this has been bothering me for a couple semesters, and I guess I'm just too embarrassed to ask the professor for clarification, but I always feel a little in the dark about "choosing appropriate bit length" for output of binary arithmetic.

Say, for instance I am using verilog to code an adder that adds 3 10-bit 2's complement numbers, and will need to output a one-bit overflow detector.  Should I choose the output to be 10-bit?  Or should I increase it to 11 bit to avoid overflow for convenience?

I have no specific code as it's just a conceptual question.

Thanks!


texts: How do i increase the input impedance of an inverting amplifier constructed using an op-amp?

texts: I learnt about bootstrapping a non-inverting amplifier to increase its input impedance. Is there any similar way to increase the input impedance of the inverting amplifier?


texts: Is it possible to measure TDR without a specialized device?

texts:
I've seen dedicated devices for measuring TDR and even layer 2&3 network switches with the TDR capability.
My question is what would prevent a standard home router from being programmed to measure the same metrics? -Being on the 3rd OSI layer instead of layers 2&3 like the advanced switches?
Or do the switches and other devices have a special piece of hardware installed that allows them to detect something that other devices can't?
I've been searching all over Google and even pulled the IEEE ethernet standards to see if that would help me understand better (much of the 802.3 material went over my head).


texts:
I am using an Arduino Uno as a watch dog for a project I a doing; its job is to monitor what is happening in the system and shut down the system if it is not operating within spec.

One of the parameters I need the Uno to watch for is voltage and amps. The system has a combination of 24V, 12V, and 5V components so it is essential that the voltage is monitored.  I was planning on using this DC Current Sensor for reading the voltage.  But I am at a loss on what to use for measuring the current.

I need the max I need to measure is 130 amps at 24V.  Do I need a clamp for this?  Sears makes this AC Clamp-on Adaptor; could this be repurposed for my project? It says AC amps, what is the difference between AC amp clamps and DC amp clamps? I have a clamp-on multimeter that does both AC and DC amps could I modify it to work? If so how? Could I create a circuit that allows the Arduino to measure the amps?


texts: Arduino best way to control external potentiometer of device

texts:
I have a consumer equipment which has a knob and turning potentiometer to control the heating element.
I have not taken apart the device yet to see the exact value of the pot but looking for some advices what is the best way to go with making this both arduino controlled and keeping the manual functionality intacted.

I come up with 2 ideas:

Stepper motor control (this would obviously work but there is not much space inside the case and mechanical elements can break over time)
Using some sort of FETs to emulate the potentiometer's resistance

If I want the arduino set values and the external pot values to be in synchron then the only way I see to do this is to completely take out the original pot from the circuit, hook up the arduino control there and then use (preferably the same) pot to do the same through the arduino so I can override the values from software when I like.

Also I would add an additional on/off switch to decide which value should be the relevant, the arduino's or the external pots. Obviously at reboots it would be always overwritten by what's the external pot giving to the Ardu at the beginning.


texts: Why do we like LFSR and PN-sequence in FPGA?

texts:
Everybody has learnt that we like LFSR in FPGAs because of its simplicity, FPGA like structure. PN-sequence generator is build up from LFSRs. (So we would think that this is FPGA-like generator...)

BUT

PN-seqence generator generates a new bit in each clock cycle, therefore we have to wait n clock-cycle to get an n-bit long word.

So to get a new PN-Sequence word in each clock-cycle we need to implement a much more complicated structure. This repo contains such an "lfsr", however the implemented design wont look alike an LFSR.

My questions:

Am I right? (Is this statement correct?) It isn't a trivial task to generate PN-Sequence word in each clock-cycle.
Why does the industry prefer the PN-sequence than other random generators?


texts: Does self heating matter in a PT100 calibrated in a constant environment?

texts: Higher current through a PT100 results in a bigger signal and better S/N ratio. OTOH, it also creates self heating which results in lack of accuracy. However, if the PT100 is in a fixed environment, for example is fixed to a metal heat sink, and is calibrated in place is that sufficient to remove the inaccuracy due to the self heating?


texts: Energy Consumption of AC Motors with same capacity and same hp

texts:
I have 2 3-phase motors with same capacity of 45kW, hp 60,rated Voltage is 415V, VFD 55kW connected separately to a Vessel Line that is used to  mixing of few components.i.e, it looks like this. (I can say that these two motors are identical)

Vessel 1 --> motor1
vessel 2 --> motor2

When loaded with same size (Load size), Motor 1 consumes high unit 10kWh for a shift (runs for 35 mins) and motor 2 consumes low energy 6kWh (runs for 35 mins). In some cases, for same load size it is vice-versa, motor 2 consumes 7kWh and motor 1 consumes 4kWh.

Any explanation why this happens or any other factor affecting the Energy Consumption of these Motors?


texts:
Currently, IEC 60445 international standard is used for conductor terminal color identifications. I've obtained different versions of the standard (2017 being the latest) and also IEC 60446, which was replaced. In the recent versions of all of these standards line conductor coloring is given by BLACK, BROWN and GREY with clarification given as

  NOTE The sequence of colour codes in 6.2.3 is alphabetical, and does not indicate any preferred phasing or direction of rotation.

However, when I was researching the topic earlier - before I had obtained the standards - the ordering of phases came up as BROWN - BLACK - GREY respectively for 3 phases, in multiple sites such as:

https://en.wikipedia.org/wiki/IEC_60446

https://wiki.openelectrical.org/index.php?title=Cable_Colour_Code

Which refers to the above standards. What is going on here? Is it common practice or is there some other standard for Europe only for example?

Quick Answer: The ordering of the phases is defined in the standard CENELEC HD 308 S2: 2001 as BROWN - BLACK - GREY for the CENELEC countries.


texts: What are limitations of Kirchhoff laws in presence of A..C current.what are the bounds on its application in such case?

texts:
I'm not able to understand while Kirchhoff's laws seem to be based on very fundamental logic they are still not applicable in some cases.
I tried to look for answer in text book but got no clear view. On internet too I heaven't got very clear presentation but only lines such as
"They are accurate for DC circuits, and for AC circuits at frequencies where the wavelengths of electromagnetic radiation are very large compared to the circuits."
Please clarify my doubt.


texts: Can I use a resistor for overcurrent protection?

texts:
I have a circuit that draws ~350 mA and uses 6v. Can I put a 5watt 15 ohm resistor in series to prevent overcurrent, (I don’t want the current to go over 400 mA in case of a short circuit). Here’s my math:
I = 6v / 15
I = 0.4 A


texts:
I am going to buy a nickel-chromium wire for my heating element.
I want to power it with one li-ion battery (20A 3000mAh)

Intuition tells me that 84W (Draining the battery to its limit) might be sufficient to heat up 5x3x5 (xyz in cm) volume of space to 200°C, but will drain the battery in less than 10 minutes.

I don't know where I can find formulas for precise calculation (regarding heat transfer in accordance to space). But I will deal with this later.

Now my question is, are my calculations correct that I will need a 3.6cm of 0.21Ω wire in order to use the minimum amount of wire needed to carry out 84W (MPT)?

Addendum: The LG HG2 is rated to have Internal Resistance: of <20 milliohms.
I doubt that such a low resistance is a big factor.


texts: Participation of DC component in total average power of signal

texts:
My task is to calculate participation (in percent) of DC component in total average power of signal from photo:

I represented this signal as complex Fourier series: $$u(t)=\frac{1}{2}+\sum_{n=-\infty,n\neq 0}^{n=\infty}\frac{1}{2n\pi}e^{j\frac{\pi}{2}}e^{jn*500t}.$$

Average power of signal is calculated using formula $$P=\lim_{T->\infty}\frac{1}{T}\int_{\tau}^{\tau+T}(f(t))^{2}dt$$ but how should I use it here? And how to calculate participation of DC component?
Thanks in advance.


texts: Can I hook 5v lipo batteries together to run an electric scooter?

texts:
I have this scooter:

http://www.monstermotorscooter.com/e-500.html

It takes those big batteries all the scooters take. I was looking at these charger packs that have a 5v lipo battery in them:

http://www.ebay.com/itm/Ultrathin-50000MAH-2-USB-External-Power-Bank-Battery-Charger-Pack-for-Cell-Phone-/401033102413?hash=item5d5f6f844d:g:WpEAAOSwzLlXgRji

I was wondering if I could take a few of those and wire them together to be like 15 or 20 volts and hook that too the scooter?  I could make it go 30+ miles I think with that much power.  Would the batteries get hot or something?  Would it be safe to wire them together for increased voltage?  I think if I just hooked 1 to it it would go too slow, because only 5 volts.

Okay I reworded this for a more detailed example which will give me the same solution that I'm looking for.


texts: Charging time of recharge-able battery (TR 18650 8000mAh 3.7V)

texts:
How many hours should I charge this recharge-able battery (TR 18650 8000mAh 3.7V) ?

Too long: battery might overload.

Too short: battery not fully charged

Let's say the charger converts 5V input source to 3.7V internally.

Anyone have any idea how to calculate the charging time based on this specific battery below ?


texts:
Can anyone suggest me a good (possibly open-source) tool able to take a finite state automaton (either deterministic or nondeterministic) and to calculate the corresponding optimal automaton?

It would be great if the tool was able to convert a nondeterministic automaton to a deterministic one.


texts:
I do not understand use of C1, C4 and C5 in this circuit. I have an idea of purpose of other capacitors but I have no idea about these. Can you explain their purpose and effect on the circuit.
https://www.circuitstoday.com/wp-content/uploads/2009/04/fm-transmitter-circuit.jpg


texts: Use a single-output floating supply as a dual relative to ground

texts:
I have a single output 15V supply that is isolated with respect to any ground. I'd like to use it to produce something like +12V and -2V with respect to the ground of my circuit. The current required is less than 500 mA.

Is this possible, and if so, what's the best way to tie it to my circuit ground?


texts: How can I interface bare glass LCD to an arduino?

texts:
I am looking to interface a Casio 991es calculator's LCD to arduino. The LCD is just two bare glass plates glued together with lot of pins. I dont find any driver chip with it. How can I interface this LCD to arduino?

Edit: I think it is a dynamic LCD. This site has some info: http://dataweek.co.za/article.aspx?pklArticleId=2382&pklCategoryId=31
I dont understand the waveforms they provided.


texts: Will an SSR work with mains voltage less than 240V? Which datasheet parameter mentions this?

texts:
I am planning to use an SSR in the secondary of a step down transformer to control a heater. My question is what parameter should I check out in the datasheet of the SSR to ensure that the SSR will operate at input voltages less than 240V?

For reference I linking the datasheet from Schneider. It does not talk about any "input voltage". Any ideas?
Thanks!


texts: How to control a capacitive load using an Arduino Uno

texts:
I'm trying to control a liquid lens using an Arduino Uno, however, the lens driver I've been attempting to get hold of is no longer an option.

The lens needs up to 60Vrms in order to function, and will likely be overdriven in order to minimise the response time. I'm looking into using a DC/DC boost converter feeding into an H-bridge but am unsure whether it would work and seeking advice.

Is there a solution whereby I can control the lens by outputting a PWM signal?


texts: What does it mean by "storage clock" of a shift register?

texts:
I read the data sheet of a shift register and I saw some tutorials on the internet. I can use all pins of my new shift register except pin 12. because I still don't understand what is the meaning of storage clock and how can I use it ? I use the clock of Pin 11 and I understand How a shift register works, only pin 12 is missing.

Datasheet :

http://elinux.org/images/2/2d/74hc595.pdf
https://www.sparkfun.com/datasheets/IC/SN74HC595.pdf

Thanks in advance,


texts: SystemVerilog module instantiation with non-existent parameter

texts:
I am instantiating a module in SystemVerilog that has a lot of parameters.  One of them (this is actually someone else's code) does not exist in the module definition.  What will the compiler do in this case?  Does it just ignore the non-existent parameter?

Here's what I mean:

Module definition:

module DummySystemVerilogModule
# (
parameter parameter0 = 64'd0,
...
parameter parameter999 = 64'd999
) (
input wire port0,
output wire port1 )
[Body of module]
endmodule

Instantiation:

DummySystemVerilogModule # (
.parameter0 (parameter0value),
...
.parameter999 (parameter999value),
.nonexistentparameter (.nonexistentparametervalue)
) (
.port0 (wire0),
.port1 (wire1)
);

Will the compiler simply ignore the nonexistent parameter I accidentally added in the instantiation of the module?


texts: Thinkpad 420 battery not charging despite of Cells inside are good

texts:
My thinkpad 420 battery is not charging. So far I have done following.

Put another battery in my thinkpad and it is charging perfectly.
Opened the defective battery and checked all three sets of 2 cells each (it is a 6 cell battery) and I got reading on voltmeter between 3.95 - 4.05 on those sets and all 6 cells together read 11.8.

I don't know if I can suspect the board inside the battery. Please guide me. Although I have bought another battery but I want to learn something by repairing this battery. Please guide me.


texts: Using 15 V laptop charger to power 14.4 V speakers

texts:
I recently moved from the U.S. to the U.K., to find that the mains voltage is different. Sadly, my speakers do not have a regulated power supply, as they were only designed for U.S. mains. (http://www.tomshardware.co.uk/2,review-1083-7.html)

On the speaker box, where the power cable enters, it says:

  110-120 V, ~60 Hz, 266 mA

So I pulled the speakers apart, and the power cable leads to a transformer/rectifier unit that has written on it the following:

  I/P: 120 Vac 60 HZ

  O/P: 14.4 Vdc 1A

The DC output is then routed to the circuit board inside the speaker.

I have the following questions:

1) Is 266 mA the current the entire unit draws? If so, why is there a transformer/rectifier that can provide 1A?

2) Can I use a 15V 2A laptop charger (possibly with a 0.6V diode on it to drop the voltage) to power the circuit board? Or would the charging circuit be a problem?

Thanks in advance!


texts: How much current can this MC34072 op-amp deliver on the output? Not 100% sure on where to find it in the datasheet.. But is it on page 11 in the pdf document, where the graph shows supply current vs supply voltage?


texts:
I need to protect the 12.8v regulator from the 14.5v battery.

Do I try to just reduce the battery voltage below 21.8V with a bunch of diodes?
Do I just put one diode protecting against current flow into the regulator output?
Do I do both?
The load operates on 6-36V, and 30w.

The reason I put several diodes in the last option is this. If both the sources are connected I would like the load to take power from the regulator instead of the battery. I thought with multiple diodes in there it would take from the regulator instead of the battery. Am I right?

simulate this circuit – Schematic created using CircuitLab

Need to protect the regulator from burning. Which option is correct?


texts:
I am learning, so go easy on me, if you can.

In a video with BigClive, he takes apart a camping light and says it's deadly when you have mains plugged in and usb plugged in at the same time. In that situation the USB can be live.

Here's a picture of the circuit he draws in the video.

I am assuming it is deadly because it uses a capacitive dropper and if the plug is inserted backwards it doesn't drop the voltage and the USB is sitting at 240v?

Or is there another reason?


texts:
Is using a relay and some switches a standard way to reverse a motor or is the preferred method to use a H-Bridge? The circuit for reversing a motor with a relay looks like this:

Note that this circuit is just to show the relay and motor connections. The main control would be the coming from a PIC not an op-amp.

Me and my teacher are having disagreements about the best way/standard/preferred way to reverse motors, so what would engineers do?


texts: How to use off board components in Altium and have them show up in net list & BOM?

texts:
For example, let's say I have a power jack which is mounted on a panel and connected to the PCB using wires. I might also have a few 1/4" audio jacks also mounted on the panel and connected to the PCB using wires.

On the PCB they have place for the wires and not a footprint. How can I have these parts in the schematic and show up in the BOM and if possible the net list as well?


texts: What the difference between pin and pn diodes i-v curve?

texts:
For my understanding there should be no big difference in i-v curve between regular p-n junction and p-i-n junction, the only difference i can think about is do to the bigger resistance of the intrinsic layer. The curve should look the same only the current will rise little bit slower, because of the resistance.
Am i right?


texts: By simple inspection calculating the gain of a circuit

texts:
I'm studying the following filter:

So this is a RC second order high pass filter. I am trying to answer the following question:
Only by inspection and simple analysis of the circuit calculate the filter gain at low frequency (f -> 0)
and at high frequency (f -> infinity). Write out the value in dB and write the symbolic equations you use.
So for infinite frequency it is pretty easy. The capacitors is so low they behave as short-circuit, therefore we can simplify the parallels C1//R1 and C3//R3 as short-circuits. Therefore, the output resistance R4 is now in parallel with the input source voltage therefore Vo=Vi and the filter gain is 1 (0 dB). I'm not sure what the question means with symbolic equation but I assume it's all this in math format
$$Vi=ZRC1*I1+ZRC3*I3+Vo$$
$$ZRC1=\frac{1}{j 2 \pi f C1 }//R1=0 // R1 = 0$$
$$ZRC3=\frac{1}{j 2 \pi f C3 }//R3=0 // R3 = 0$$
$$Vi=Vo$$
Simple. Now my question is when we go through zero frequencies. So now the impedance of the capacitors is infinitely large and they can be seen as open-circuits. We can simply remove them from the circuit.
So now we have all the resistances.
My question is if now there is an easy way to calculate the low-frequency gain. I know it should be very small (close to zero). But I wonder what approximations I can make and what is a simple way to calculate it.
I thought about calculating the input and output resistance but I'm not sure how that would help me, as it doesn't make it simple to relate output and input voltage.
I just need some guidance on what path I should follow, I can then analyse the circuit by myself.
Any help is much appreciated.


texts: Flash and debug of multiple STM32 in JTAG with J-LINK

texts:
I have a board where 3 STM32 are connected to a JTAG port. The 3 STM32 are daisy chained. I am using a JLINK EDU Mini with Atollic TrueStudio IDE.

One STM32F746 is a master for the two slaves STM32L451. The NRST pin of each slave is connected to a different GPIO of the master as well as a different push button. The NRST pin of the master is connected to the NRST pin the JLINK EDU Mini as well as a push button.

The GPIOs of the master (NRST of the two slaves) are configured as open drain output with a pull-up resistor and they are set as HIGH by default.

First, I tried to flash only the initialization code for each STM32, with only the GPIOs of the master initialized. It went well and I can connect, flash and debug each of the three MCU without any problem.

Then, the main program has been flashed to the master STM32 without any problem. The main program of the first slave has been flashed to the first slave without problem but then, it became impossible to connect to any of the STM32 (master or slave).

When trying to connect, I either have "unable to connect under reset" error which I can solve by keeping the slave under reset. I also have "Unable to read XXXXXXX register which I can't solve.

To sum up, I can flash and debug any of the MCU with basic code but as soon as the code is "complex", I can't connect to any of the MCU anymore. I have to erase the MCU with JLINK Commander in order to come back to the first configuration (only GPIO initialization code).

Does anybody have any idea of what can be the issue here ? To me, it seems like some of the peripherals (SPI, I2C, UART, etc) of the slave STM32 is entering in conflict with the JTAG.


texts: Where does the power supply current return?

texts:
I am a bit confused about return currents on a ground plane. I try explain it based on drawing. Let be a PCB with ground plane that is powered by external power supply through a connector.  An LDO regulates appropriate voltage for component on board.

Does the current of this component return to the LDO ground or to the main ground connection? (Which of 2 arrows does the return current follow?)

simulate this circuit – Schematic created using CircuitLab

This confusion stems from uncertainty in my head, how to treat the power connection. If it should be treated like a signal, the the current returns to the LDO. On the other hand an LDO doesn't "produce" current, but simply dissipates excessive external power. It itself returns current to the ground connecter. Thus, it ground pin serves double purpose: return current to the ground connector and receive return currents from the component(s), which seem odd to me. Rather it seems to me that the true surce of current is the main power connector and that's where the current return.

Understanding this problem is important for how I place LDO and components, that it powers, relative to each other.


texts: Connecting an environmental sensor to multiple smart phones

texts:
Newbie heading for the deep end here, I am working on a project where a number of students will use smart phones to connect via bluetooth to sensors placed around a woodland.  It has occurred to me that with 20 or so phones looking for the correct bluetooth to connect too could be a bit confusing. I am hoping to enable the correct connection using QR smart tags.

My other problem is a bit more difficult....for me anyway....
Most blue tooth devices can handle 8 connections at once it seems, unfortunately the sensor device I am using can only connect with one mobile device at a time.
A suggestion has been made that it could be possible to use one android phone to blue tooth connect to the sensor then relay the information to other blue tooth connected phones...

....I believe I am talking about making the first phone a bluetooth hot spot???? This will run the APP for the sensor. Add in a smart tag to connect student phones to the first mobile.

This is just one option I am looking at and I could do with some help please.

Is it possible to re-transmit what is on the screen of the first mobile to up to seven student smart phones at a time? Or maybe re-transmit the incoming signal to the first phone and run the same app on all the others?

If this turns out to be a total non starter I do have a plan "B" but I would like to stick with this at the moment...... unless an expert out there has a plan"X" that does what I want without any major design work!


texts: How can I protect the through holes copper which is electroplated from being etched away by the ferric chloride?  Is there a resistive solution or it`s just the conductive ink.


texts: Does anyone know what means when AC servo motor driver displays error code for "regenerative discharge", and stops working. What this mean in practical situation. This happens from 1 to 10 minuts after turning on. If it helps, servo motor is for one axis of cnc cutting machine. AC servo motor driver is "panasonic msda023a1a", and error code is "Err_18". Thanks.


texts: Changing delay duration in _delay_us() changes code size

texts:
I was programming an ATtiny13A when I accidentally noticed that when I change the delay time in _delay_us() my code size changes. Here's the sample code:
#include <util/delay.h>

int main(void)
{
    while (1)
    {
        _delay_us(500);
    }
}

And here are the different code sizes I get when changing the delay value:
_delay_us(500):    52 bytes
_delay_us(499):    50 bytes
_delay_us(498):    48 bytes
_delay_us(497):    52 bytes
_delay_us(496):    50 bytes
_delay_us(495):    52 bytes
_delay_us(494):    50 bytes
_delay_us(493):    48 bytes
_delay_us(492):    52 bytes
_delay_us(491):    50 bytes
_delay_us(490):    52 bytes

I have a lot of _delay_us() in my code with different delay times. Now it doesn't matter at all if they are a few micro seconds longer or shorter, but it does matter if I can get each one 2-4 bytes smaller.
So I was wondering if someone can tell me what exactly is going on here, so that I can change all delay values across my code to yield the smallest code size. Like say I have a delay that needs to be around 1000us, how do I come up with the number that has the smallest size? Because trial and error is not an option due to the number of these delays in my code.
This has been tested in Arduino IDE with MicroCore and Atmel Studio.
F_CPU is 9.6MHz


texts:
I have a NAIM amp (some audio amp) working very well. Recently, added a ARCAM phono preamp (some pre-amp for turntable) to it. Once the phono preamp is connected to NAIM amp, there will be clear buzz noise, even not turning on the phono preamp.
It looks to be a ground loop issue. Bought two ground loop isolators, both just work little bit, still clear buzz noise. The NAIM amp is the only one with 3 pins plug power cable. The same phono preamp put on other amp with 2 pins plug power cable, there is no noise.
Two signal grounds on each device is connected, but still strong noise.
Some friend suggest this may not be a ground loop issue, instead missing signal ground to earth ground.
Get more confused. Will connecting signal ground to earth ground introduce a new ground loop? Also, is there any safety concern? (In the NAIM manual, it clearly state, the ground is not supposed to connect earth ground.)
Thank you very much.


texts: How to get the square wave output at Photodiode

texts:
LED flashing light captured by camera

Displayed image detected by Photodiode

I have a 2V p-p square wave signal of 500µs. This signal drives a LED and when I measure the waveform across the resistor connected in series with the LED I get a square waveform. I have a camera which is takes this flashing light as an input and this camera signal I am displaying on the display. I have designed a Photodiode circuit ( photodiode and 100K resistor in series ) having a supply of 5V and placed this circuit next to display in dark room. When the flashing light of LED taken by camera is displayed the Photodiode is activated. But the problem is I am not able to see the variation in waveform as when it is activating, output is directly 5V DC. I need to see the variation in square waveform. I Want to calculate delay between camera input and output at Display. Please help me out for getting square wave across photodiode so that I can see the difference in waveform from LED and Photodiode. Let me know where I am going wrong and what are the steps I should follow.

Photodiode info:

http://www.produktinfo.conrad.com/datenblaetter/150000-174999/153005-da-01-ml-PIN_PHOTODIODE_BPW34_OSR_de_en.pdf


texts: Insufficient Power when using one power source vs two

texts:
So I've been working on a wireless remote relay switch using several components and have struck a break wall. The issue I'm having is that the D0 siginal output triggers the relay but only at short range. When using 2 different power sources the relay behaves as it should with pretty good distance.

Basically the issue I think I'm having is related to a power one which is beyond me and hopefully someone can guide me in the right direction.

Below is the some details of each main component:

315mhz SC2272-M4 Receiver (5v)
315mhz 4-CH SC2262 Transmitter (12v)
High & Low Level SRD-05VDC-SL-C Relay circuit for Uno 3 (5v)

Here's what I've tried.

simulate this circuit – Schematic created using CircuitLab

Basically what I'm finding is that D0 is dropping mA and not driving the high level trigger, but it works fine with its own power source, something I hoped to correct by using a 1AMP+ Mains USB supply. Is there a better way to resolve this issue. Oh, I've also messaged the seller of the high low level trigger relays to find out the exact mA at which the low and high triggers trigger on.

Updated:

As recommended I have tested the circuit with a multimeter and here's what I've discovered.

When activating relay:

Data 0 (DCA - 20m) drops from 8.70 to 7.75 (very unstable sometimes can drop as low as 1.0)
Data 0 (DCV 5v) drops from 5v to 4.3v (very unstable when range is increased, as low as 0.33v)


texts: What's wrong with this circuit to convert 0-5V to +10/-10V

texts:
I'm trying to come up with a solution to use the analog output of a DAC to drive the X-Y axis control of a commercially available laser 'closed-loop moving magnet' driver.

I found an explanation on how to use an op-amp to create a differential amplifier here and a calculator here, but I can't get that to work without a 2.5V reference voltage.

I also found a simpler design for such a circuit here, but when I try that in a simulator (I use iCircuit on my iPad) it doesn't swing from -10V to 10V but from -8V to 12V (approximately). This is the circuit:

This is my testing in iCircuit:

Tried it with the included circuit simulator, don't know how it works exactly:

simulate this circuit – Schematic created using CircuitLab

My question is, is this simpler design the way to go, but are my resistor values wrong? Or do I need to go with the first circuit design but need to add something to get a 2.5V reference?

I have very little information on the exact electrical requirements of the scanner, but I'm assuming it's a product designed to be used in an ILDA laser device and fairly compatible to that standard.

UPDATE In iCircuit, I replaced the lower 10K resistor with 20K and the feedback resistor from 15K to 30K, and it looks like I'm getting the desired output now. Still, I don't know if this is trustworthy or not.

Bonus question: I have an ST LM324N opamp lying around from an old lab kit. Do you consider this device suitable for this task, if I supply +12V/-12V to it?


texts:
I am working with a 60 year old schematic and test procedure. The latter refers to adjusting rheostats to "300 DCMI" or "between 100 and 130 DCMI". There are voltage and ammeters attached to different terminals. Typical usage in the document would be:

  Adjust the rheostat RA for 50 DCMI indication on meter A1.

(Meter A1 in the drawing is in series with the signal, so it is almost certainly a current meter, but this is not explicitly called out.)

The procedure is rather vague, but I'm almost certain that it's referring dc mA. That said, the procedure was probably written by a British firm and I'm wondering if DCMI means something else entirely or if there are subtleties I'm not aware of.


texts:
How do I convert a real power line limit to a current flow magnitude line limit?

Specifically, for a line connecting bus \$i\$ to bus \$k\$ (with \$j\$ denoting the imaginary element), I compute current flow magnitude (denoted \$f_{i,k}\$) as \$ f_{i,k} := |v_i e^{j\, a_i} - v_ke^{k\, a_k}| \times |Y_{i,k}|\$. If the flow limit is \$f_{i,k}^{\max}\$ and the real power limit is denoted \$P_{i,k}^{\max}\$, what is the relationship between \$f_{i,k}^{\max}\$ and \$P_{i,k}^{\max}\$?


texts: How are RS 485 transceivers implemented?

texts:
I would like to know how transceivers (which are used to send and receive  differential signals) are implemented. AFAIK the receiver the transmitter (TX) could be something similar to an H bridge. I already took a look at datasheets of some popular transceivers but I could not find any details about the inner working.

EDIT : the term transceiver might be a little to large, by transceiver I mean the ones used for RS 485 (eg : for USB or DMX-512)


texts: Termination resistors with DDR3, are they needed?

texts:
I'm using a DSP processor with one chip Micron DDR3 MT41J128M16JT in a project.

I read a lot about the termination resistors, but I'm still confused about if I really need those, I didn't start the layout yet, but I can try to match the traces lengths, so the skew will within the accepted range, and also in this chip there is ODT which is implemented in the Data lines, so termination resistors are not needed there.

So, the question is: Do I really need termination resistors when using single chip? or there are some tips I can use so I will be in no need for them?


texts: How to use touch screen shield for GLCD?

texts:
I know this is a very elementary question. I was wondering if it is possible to use a touch screen shield on a normal GLCD to change it into a touch-GLCD.
I have seen a product which is a transparent shield with 4 pins (something like the one covering this module

I searched google for a good tutorial on using this 4-pins device but of no avail. Can anyone give me a manual/tutorial or description?


texts: Non-optimal clock IOB/BUFGMUX placement correctable in software or hardware?

texts:
I am getting this nasty error when synthesizing my design using ISE Studio for Spartan-6:

ERROR:Place:1108 - A clock IOB / BUFGMUX clock component pair have been found
   that are not placed at an optimal clock IOB / BUFGMUX site pair. The clock
   IOB component <PIN_ADC_CLKOUT_P> is placed at site <C17>. The corresponding
   BUFG component <adc_clkout_BUFG> is placed at site <BUFGMUX_X2Y10>. There is
   only a select set of IOBs that can use the fast path to the Clocker buffer,
   and they are not being used. You may want to analyze why this problem exists
   and correct it. If this sub optimal condition is acceptable for this design,
   you may use the CLOCK_DEDICATED_ROUTE constraint in the .ucf file to demote
   this message to a WARNING and allow your design to continue. However, the use
   of this override is highly discouraged as it may lead to very poor timing
   results. It is recommended that this error condition be corrected in the
   design. A list of all the COMP.PINs used in this clock placement rule is
   listed below. These examples can be used directly in the .ucf file to
   override this clock rule.
   < NET "PIN_ADC_CLKOUT_P" CLOCK_DEDICATED_ROUTE = FALSE; >

This particular input is an LVDS input and I have in my code:

wire adc_clkout;
IBUFDS ibuf_adc_clkout(.I(PIN_ADC_CLKOUT_P), .IB(PIN_ADC_CLKOUT_N), .O(adc_clkout));

and the ucf file reads:

NET "PIN_ADC_CLKOUT_P"  LOC="C17" |IOSTANDARD=LVDS_25 |DIFF_TERM=true;
NET "PIN_ADC_CLKOUT_N"  LOC="A17" |IOSTANDARD=LVDS_25 |DIFF_TERM=true;

There are other LVDS signals with identical definitions from whom I do not get this error.

I tried everything I imagine to get rid of this error without success. In the end I just used CLOCK_DEDICATED_ROUTE = FALSE and called it the day.

However, now I am getting timing problems when I change Verilog code that has nothing to do with the place where the error occurs. However, it has to do with this CLKOUT line. So I imagine it could have to do with this error and would like to resolve it.

However, the hardware has already been built, I can not change I/O pins!

Can I somehow get rid of this error in software?

Some remarks:

This is not a clock signal in the sense that it is used in multiple locations, so I would not need a clock tree etc. It is just a skew-matched clock provided by the ADC together with the serial data so I can latch the data at the rising edge of this clock.
The ADC clock is generated by myself within the FPGA. The PIN_ADC_CLKOUT signal is merely a skewed copy of that, skew-matched to the data lines and the skew is given by the processing of the ADC and the PCB trace roundtrip
This ADC clock is "duty cycled". For reference, the ADC is the LTC2323 and the timing looks like this:


texts: What is the difference between excitation table and truth table?

texts: In flip-flops what is truth and excitation table iam getting confused between them ,earlier I learnt a truth table of flip-flops but now its called excitation table so I wanna know whole thing behind this in detail ,what's the difference between truth table and excitation table and how are truth table and excitation table for a flip-flops are constructed.Detailed answer will be appreciated a lot.


texts: How to wire DotStar LED strip with 6 wires at the start of the strip

texts:
I bought some of these LEDs:

They have six wires at the start of the LED strip. I thought that perhaps the separate red and black wires were to power the LEDs, and that, for the 4 wire JST, the black would go to ground, and the other 3 would be red, green, and blue controls.

But Adafruit's DotStar tutorial only shows how to wire a 4 wire led strip.

I don't want to burn these out, so I'm trying to get a better understanding of how to do this properly. I can't seem to find any reference photos online for this 6 wire configuration.


texts: Is there a way to add Bluetooth functionality to an ErgoDox EZ keyboard?

texts:
It would be nice to have some sort of mini-USB accessory that could bluetooth-enable an ErgodoxEZ keyboard.

I found some related discussion here: https://www.reddit.com/r/ergodox/comments/8kugs5/is_it_possible_to_add_bluetooth_functionality_to/, but that thread has been archived, and there's not yet a clear solution yet, so I'm moving the discussion here.  The stackexchange format is better for such discussions anyway.


texts: How to make a battery level indicator for arduino (The battery is powering the arduino also)

texts: Hi I am building a pocket altitude, temperature and humidity meter with 1.8" TFT display. I have a 1000mah 3.3v Li-ion battery to power the whole system. I also need to display the battery level in percentage in the device. I am confused about which way i need to use. The same battery is powering the device so using voltage divider is not useful because of the ADC reference depends on the battery. Can you guys help me to overcome this?


texts: Trying to understand how this op-amp sound module works

texts:
This is a schematic for the ZX sound module:

My understanding is that the first part is a high-pass filter followed by a non-inverting amplifier.

But isn't the second op-amp a comparator? It seems to me that it would output a HIGH if V- < 0.01*Vcc, or LOW otherwise. So, I am just wondering how it outputs a "0-5V varying output" as described in the note above the schematic.


texts: Open multiple files on SD Card using FatFs

texts:
The code is to log data in multiple files on SD card. The problem is that the SD card only opens and saves 1 file. When the if condition occurs in the 2nd time, the old file is deleted and the SD card is empty.

The condition here is that if a is between 110000 && 95000, time should be logged into the SD Card.

code:

char hours[5];
char seconds[2];
char min[2];
char year[4];
char month[2];
char day[2];

sprintf(hours, "%d" , sTime.Hours);
sprintf(day, "%d", sDate.WeekDay);
sprintf(seconds, "%d", sTime.Seconds);
sprintf(min, "%d", sTime.Minutes);
sprintf(year, "%d", sDate.Year);
sprintf(month, "%d", sDate.Month);

   /* Mount SD Card */
   if(f_mount(&fs, "", 0) != FR_OK)
      Error_Handler();

   /* Open file to write */
   if(a <=110000 && a>=95000) {
      if(f_open(&fil,"second.txt", FA_CREATE_NEW | FA_READ | FA_WRITE) != FR_OK)
         Error_Handler();
   }

   /* Check free space */
   if(f_getfree("", &fre_clust, &pfs) != FR_OK)
      Error_Handler();

   total = (uint32_t)((pfs->n_fatent - 2) * pfs->csize * 0.5);
   free1 = (uint32_t)(fre_clust * pfs->csize * 0.5);

   /* Free space is less than 1kb */
   if(free1 < 1)
      Error_Handler();

   /* Writing text */
   f_puts(hours, &fil);
   f_puts(min, &fil);
   f_puts(seconds, &fil);
   f_puts("\n", &fil);
   f_puts(year, &fil);
   f_puts(month, &fil);
   f_puts(day, &fil);

   /* Close file */
   if(f_close(&fil) != FR_OK)
      Error_Handler();

   /* Open file to read */
   if(f_open(&fil, "second.txt", FA_READ) != FR_OK)
      Error_Handler();

   while(f_gets(buffer, sizeof(buffer), &fil))
   {
     //printf("%s", buffer);
   }

  /* Close file */
   if(f_close(&fil) != FR_OK)
      Error_Handler();

   /* Unmount SDCARD */
   if(f_mount(NULL, "", 1) != FR_OK)
      Error_Handler();


texts: Techniques for Attenuating a 5GHz Signal Between?

texts:
I need to set up to radios with high gain directional antennas to talk to each other within a relatively small distance. The radio in questions is a RADWIN 5000 jet. The max distance I can set them up is about 20 feet from each other. Each antenna has a gain of 20dBi and the lowest power the radios will transmit at is -1dBm. So without attenuation each radio will receive a signal about 1/2W and we have a concern this will damage the receiver. Traditionally we could use a wave guide filter to attenuate the signal before the antenna but since this device is an all in 1 package (radio and antenna in one case) we don't have this option.

So my questions is this: does anyone have any suggestions on type of materials or sets ups I can put between the 2 devices  to attenuate a 5GHz signal by say 30dBm?


texts:
Can these chip read audio files from an SD card/USB flash drive and generate an SPDIF digital stereo audio output?

VS1053 or VS1063a  or PCM2906

EDIT: I think this is the DEVICE I need. SD card / USB host / Bluetooth SPDIF output


texts: How can I make a current source that can supply 1uA?

texts:
Is there anyway I can make a constant current source which has an output of 1uA or can I get it from the market?
The load is around 200kOhms, and I need accuracy to 1%.


texts: How can I turn off a 3.3V circuit with a 3.3V microcontroller

texts:
I'm working with ATTiny85 that has low current (40 mA) GPIO. In the other side I have a power supply (battery with ~5V) connected to a LM317 and an ESP8266 that demands high current (more than the ATTiny85 can give, around 170 mA) and uses 3.3V.

I need to switch the ESP8266 (on/off). I tried some Darlington transistors, MOSFET and optocoupler but nothing works. All the examples that I see in the web is to switch from a 3.3V signal to a 5V (or more) circuit. In my case I want to switch from a 3.3V signal (ATTiny85 low current) to a 3.3V circuit (ESP8266 high current). Is this possible? And is so, how can I do this?

(I have a little background in electronic but I'm from computer science, so please try to be soft with your answers, thank you)


texts:
I'm in the need to create a "drivetrain" for a smooth and slow rotation and need only very low torque (for a Christmas pyramid). Such a Christmas pyramid usually is driven by candles and turns very slow (magnitude of ~10min-1), has very low friction (a metal tip rotates inside a tiny, concave glass plate similar to a contact lense) and continues to rotate a couple of times for itself. Using a gearbox is no option for me.

Using a stepper motor would allow the slow rotation, but I think it will not be smooth enough for the required low speeds. Would it be possible to use an old BLDC (hard disk) motor to run at so low speeds smoothly? Are there other options of low-torque slow motors?


texts: Can I use a power amplifier for power stage of a pure sine wave inverter?

texts:
As the title reads, I wish to use a power amplifier (say OPA541) in the power stage of a 50W pure sine wave inverter? How to find the efficiency of this approach? Since the amplifier itself will be sourcing all the current...efficiency may be low? is that true? how low will it be?

I need a variable frequency variable voltage AC source where I can move the frequency from 40Hz to 80Hz. It should be easy to create a variable frequency sinewave, either analog or mcu based. This can be sent to the input of a power amplifier to get the required signal which can then be stepped-up using a suitable transformer. The amplitude can be changed by changing the feedback resistance on the amplifier.
My power requirements are 120VAC, 3A for the output. So I was thinking OPA541 (80VDC, 10A) should be a good option.

Is this a good design for a lab source?

what I really need is a 3 phase inverter !!. Once single phase is done, I was planning to use a cd4027 to get 120degrees phase shifted signals and send them to independent power stages.

Your insights shall be very helpful.

Thanks and best regards,
Vishal


texts: Can the SMPS IC works only with power from startup resistors without using Aux winding power?

texts: my turbo charger burned out.in the circuit, the smps ic's VCC connected to 230VAC using start up series resistor and also to aux winding power. My question is, will the smps ic work if it is powered only from startup resistor(general case)?.. Here the startup series resistor is followed by a capacitor(ie. RC circuit is used for Start up).


texts:
I am having trouble turning ON a relay from the ESP8266 output pin.
I have wired the relay as shown in the picture below. The only change is that the transistor is BC556. Other specs of components are:
Relay 5V , running this on 5V power supply. Here are some more facts:
- I have wired the exact same circuit on the bread board and it works perfect.
- I am using GPIO2 as the output PIN and apart from driving this relay , it also has a pull up resistor of 10K connected to GPIO2.
- The relay works fine sometimes but many times it either does not work or is very slow in reacting. For eg. when my output tuns LOW, it soemtimes takes several seconds to turn ON the relay.
- I measured the voltage across the transistor Vce = 1.1 V which means the voltage across the relay pins is 3.9V. I thought this is the reason why the relay is not able to trigger but then I have exact measurements on my breadboard circuit and it works fine. I even tried switching the relays but I get the same result.
- From BC556 datasheets it says saturation Vce is .09 - .25V but I get 1.1 voltage drop Is this normal? I tried BC 557 with the same result. I even varied the base resistor to decrease it till 100 ohms but the Vce improve by 0.1 V only.
Any suggestion on what should I do to troubleshoot this further would be helpful. Thanks


texts: How come nRF51822 evaluation kit isn't recommended?

texts:
Looking at the nRF51822 Evaluation Kit's page, it explicitly states that it's not recommended and is replaced by nRF51 DK. Does anyone know in what ways the nRF51 DK is an improvement over the nRF51822 Evaluation Kit? It seems that the nRF51 DK was launched in 2014, so it's not exactly new (either).

Any thought appreciated.


texts: How to make proper copper trace transmission line calculations using wCalc?

texts:
Oli Glaser gave a fantastic answer to a question regarding termination resistors: Termination resistors: are they needed?

I am trying to replicate his wCalc and SPICE simulation calculations for learning purposes.

I've got about everything figured out except how exactly he came to his wCalc results.

Here is a screenshot at my failed attempt of coming to the same result as Oli did using wCalc.

Oli gets:

Zo = 177.6Ω
L = 642.9 pH/mm
C = 0.0465 pF/mm
R = 34.46 mΩ/mm
Delay = 530.4 ps

I get:

Zo = 117.6Ω (considerably off)
L = 642.8 pH/mm (only 0.1 ph/mm off)
C = 0.0465 pF/mm (same)
R = 9.072 mΩ/mm (considerably off)
Delay = 530.3 ps (only 0.1 ps off)

Since some numbers, L, C, and Delay are equivalent or off by just a fraction, but Zo and R are considerably off, I'm a bit perplexed.


texts: Measuring the capacity of a 40v lithium ion, lawnmower battery

texts:
I purchased a 40v Greenworks lawnmower battery, and it's listed capacity (6,000 mah) doesn't seem to be accurate based on what I'd expect to get out of it when mowing a lawn.
How would you go about measuring the capacity of this battery as easily/cheaply as possible (e.g., with components [resistors, step-downs, load testers] I can purchase from Amazon, Lowes, HD, Ebay, or the like)? I'm having trouble following more generalized examples, don't want to start a fire, but also want to understand how to do it.
Thanks!


texts: How to find voltage across the resistor?

texts:
How to calculate the voltage V0 across the 8ohm resistor?
Using mesh analysis I get an answer(120V) which is different from the correct answer.
Left loop,
$$4I_1+V_1=120$$
Right loop,
$$10I_2+2I_3+V_2=0$$
Outer loop,
$$-120+4I_1+8I_3-8I_2=0$$
Solving I get,
$$I_3=15A \text{ and }V_0=120V$$


texts:
Are there any conventions regarding which side of board should be top and which should be bottom? The only convention I can think of is placing the user-facing side on top if the bare board is going to be visible (say, in a shield/hat).

To be clear, I am not asking what to put on top or bottom layer. My question is more akin to, "given a complete board, which side would you call top and which bottom, and why?".


texts: Why is there a diode on the RX pin of the Adafruit Ultimate GPS board?

texts: I can't seem to understand why there is a diode at the Rx pin on this Adafruit Ultimate GPS board. If we are sending data to the GPS, why put a diode that prevents current flow into this pin?


texts: Boost converter to high voltages (20 kV+)

texts:
I am interested in making a mini, potentially portable ion thruster.
The Question: Is it possible to create a boost converter that takes low voltage batteries ranging from 3.7 V to 24 V and boost that to 20 kV or higher which is continuous voltage (not pulsed)?
The Reason: So far I have used an old 20 kV AC DC power supply to make a ion thruster, but now I would like one that doesn't necessarily have to be plugged into the wall.
I have looked online and have seen high voltage inverters, the problem is that they are too low in voltage output to be effective (and AC), or they have high voltage output but its pulsed - and I would like a continuous flow.
Thanks and I look forward to hearing your comments!


texts: Determining the angular displacement of a steering wheel

texts:
I am working on a project in which I am designing a vehicle driving simulator.

In this project I need to measure the angular displacement of the steering wheel. The car in software simulator environment will change its direction based on the degree with which the steering wheel will be rotated.

Can someone please guide me how can I measure the angular displacement of the steering wheel?


texts: Correct model for interference from an unterminated transmission line branch

texts:
Question about the correct mathematical model for a branched transmission line
Baseline Setup

Waveform generator: Output 10-60MHz sine wave, 8Vp-p, Output impedance 50Ohms
RG58 50Ohm coax: propagation speed 0.659c  (length ~0.5m, but that should not be relevant)
50Ohm "feed through" terminator connected to
200Mhz digital oscilloscope

Result: 4Vp-p sine wave. Amplitude flat across frequency range. 50% attenuation, as expected, due to "voltage divider" of the 50Ohm source with 50Ohm terminator
Interference Setup

Add a coax-T before 50Ohm feed through terminator
Connect additional ~1.6m piece of RG58 coax to the 3rd leg of the T.
Leave the end of the ~1.6m piece unterminated.

Result: As expected, we get reflection at unterminated end. This results in interference being seen by oscilloscope. Amplitude measured by oscilloscope collapses to near zero (about 200mVp-p in reality) at about 31Mhz. Given prop-speed of \$1.98e8m/s\$ this is at \$\lambda = 6.38m\$, which is a good match for \$\lambda / 4 = 1.63m\$.
At 10Mhz \$\lambda \approx 20m\$ and interference almost perfectly "constructive" resulting in an observed amplitude of ~4Vp-p, very similar to the baseline. (note there is no "doubling" due to constructive interference, see below)
Question
What is the correct relationship for observed amplitude in the interference setup as a function of frequency?
My attempt was to just model sinusoidal addition from here:
https://dspguru.com/files/Sum_of_Two_Sinusoids.pdf
gives us:
$$
A \cos(\omega t + \alpha) + B \cos(ωt) = \sqrt{A^2 + B^2 + 2AB \cos(\alpha)}
                                  \cos(\omega t + \arctan(\frac{A \sin(\alpha)}{A cos(\alpha) + B}))
$$
And if we assume near perfect reflection (we nearly have that), then A and B are equal. Just focusing on the amplitude of resultant we have:
$$
Resultant Amplitude = \sqrt{2  A^2 + 2 A^2 \cos(\alpha)}
$$
This does indeed give the rough shape of the frequency response however the scale is wrong. Expression above gives 2A at \$\alpha = 0\$ which is clearly wrong by factor of 2 (no doubling). It correctly shrinks to zero at \$\alpha = \pi\$. The amplitudes at the intermediate frequencies are also too high.
A simple linear scale factor to push the low frequency amplitudes down to the correct, observed value, fails to align the frequencies around 20Mhz.
I suspect this is because we are not modelling the actual network of impedances here, and the reflected wave is not a "second source" (hence no doubling).
There is also the potential issue that the reflected wave may(!) see two 50Ohm loads in parallel, ie 25Ohms and that there will therefore be a secondary reflection back to the open ended stub?
I am ideally looking for a simple electrical equivalent circuit, for example:

Z will be changing from an "open circuit" at low frequencies to a "short circuit" ~ 31Mhz.
So, in summary, what I am looking for is an expression for the signal seen by the oscilloscope across the 50Ohm feed through terminator which incorporates a good model for the changing Z.


texts:
Had a waveguide system set up similar to picture, to compare measured to calculated power ratio or path loss (differences between positions). With an SWR meter the following was recorded at various distances between horn-antennas:

0.0dB @86cm, -1.1dB @136cm, -1.3dB @186cm, -1.5dB @236cm.

Question is how to calculate expected path loss power ratio based on distances only, to check if these measurements agree with theory?

I thought one could say P = k/d^2 , such that P2/P1 = d1^2/d2^2
But I don't really see how to apply it to fit the results?

EDIT:
I expected the data to simply being able to illustrate the inverse square law, but unsure if that should apply to the distance between antennas, or if the waveguide signal path must be included(?)

(We used a straight wave guide, not bent like in image)


texts:
I'm troubleshooting issue of a motor from a washing machine I bought from a garage sales.  Based on the service manual, I'm suppose to replace the motor assembly. So I decided to take a closer look at the motor assembly. I notice that the 2 carbon brushes are no equal in length. One is significantly shorter and only 3mm of extension left when secured.

After about a week, one night it tripped the RCD. I didn't plug in to confirm the source of the trip, but measuring Live vs Earth give me 4MOhm of resistance, which I think might not be the cause. So next day I open the motor again and clean it with WD40. After drying and putting it back, the motor jerks and turn slowly when I tested it. I'm not sure if this is caused by the cleaning, shorten carbon brush, burn coil (physically I don't see any color change on the coil) or control board (The driving source rectified 220VAC going through 3 relay controlling the rotor and stator for speed and direction). I'll try replace the carbon brush later evening.

At the mean time any input on this? It's not easy to get a motor assembly in my country, so I would like to save the washing machine as much as possible.

EDIT: Since this motor uses brush, so no issue with capacitor or such. The bridge rectifier and relay is the only component that drive the motor from direct AC. This motor is commonly used in Whirlpool and Samsung as well.

EDIT: The exact model of the motor is here and a similar one as shown at the video here. The schematic for a similar model which uses a similar motor is here at page 14.

The jerk happens at a constant frequency, which caused me to worried that it's a burn amateur, probably only 1 winding. But I can't see any obvious color change on the winding.

This is how the carbon brush looks like. I've only manage to get a bigger sized on, so I'll shape it and try it out in a few days time.

EDIT: I've replaced the carbon brush. Still the same. This is the video of how it looks like.

EDIT: madrivereric was right. The 5 winding on the armature is shorted. After running the motor using 12VDC, I found 5 continuous section on the commutator that doesn't produce torque, but has current. So I isolate the 5 section, and now the motor runs smoothly. But there's arc when the brush enters and exit the 5 section. Can I short the 5 section +1 before and after so the current can connect continuously? I know I'll loose some torque, at least I can try it out while waiting for the motor to arrive, which might take months. Btw, I think the armature is wave wounded.


texts: Editing/Creating a Triangular Solder Bridge Footprint

texts:
I wish to use a triangular solder jumper (solder-jumper) in my PCB and I am using KiCAD. The only available solder jumper - the one pointing in one direction (as in the attached image), is 2.45 x 1.50 mm. I wish to edit this and make it 1.25 x 1.25 mm.
Issue is I am unable to change the dimensions of the footprint in the footprint editor ( I have a copy which I am editing not the main one ) nor am I able to create an entirely new one as whenever you change the dimensions in the edit dialog box, the size remains the same. The Triangular Cu area seems specifically edited in some way.
Is it possible to make a custom F.Cu shape like the one used for the Solder Jumper Triangular in KiCAD ? If yes, how to do it ?
Thank you.


texts:
I have an LM34 sensor that I've used in the past for "hello world" projects, so I know at least it used to work. A while ago though.

I just recovered it from the bottom of a pile of components to do something with it, but I'm getting very strange behaviours:

when I touch it or apply a heat source to it, the output voltage goes down, not up.
when I use a 3V button battery or a stack of two (6V), I can touch it, but...
when I use a 9V battery it gets really hot (untouchable)
assuming the 9V battery issue is because it's drawing too much current, I use resistors, but I still get the output going down issue.
Knowing that this worked in the past with a microcontroller, and googling a bit, I found a really simple arduino project that requires no other components, and connects the pins to the 5V and ground. As soon as I do this, it again goes really hot (untouchable).

The issue of it getting really hot somehow makes sense to me, but I'm sure I've used it in this configuration before and I'm seeing articles about it too. Add to it the reversed output voltage, and I'm left completely confused, and just assuming, is it just broken? And did I broke it by connecting it straight into a 9V battery on the first place?


texts:
following is a pulse which i obtained from a circuit and i want to get a count when the pulse is initiated. My circuit is to detect a lightning and i obtain this pulse in our high voltage laboratory using impulse generator. Is there any way to get a input signal to arduino uno when this pulse happening?
or is there any better way to get the count when this is happening?
Thank you


texts: No matter what I do, I still have these errors. I don't know what to do to fix this. Please help!!


texts:
I am trying to draw the logic diagram of this Verilog Code of a counter using mux, d flip flop, nand, and.

module CNT1 (Q, QN, To, CLK, D, L, RB, Ti);
output Q, QN, To;
input CLK, D, L, RB, Ti;
reg q, tout;
function mux;
input [3:0] in;
input [1:0] s;
case(s)
2'b00: mux=in[0];
2'b01: mux=in[1];
2'b10: mux=in[2];
2'b11: mux=in[3];
endcase
endfunction
always @(RB) begin
if (!RB)
assign q=1'b0;
else
deassign q;
end
always @(posedge CLK) q=mux({D,D,~q,q},{L,Ti});
always @(Ti or q) tout=Ti&q;
assign To=tout;
assign Q=q;
assign QN=~q;
endmodule

I have drawn this but I am not sure. Do you have a suggestion related to logic diagram of this code?


texts: How to run 25 RGB LEDs by an arduino Duemilanove

texts:
I am constructing a 5x5 LED grid that has an RGB LED under a plastic cover, and a piezo sensor that changes the RGB LED to one of 8 colors when pressed.

So as far as I can tell I need 75 outputs for the RGB LEDs, plus 1 more to power everything that can be daisy chained between the 25 RGB LEDs. I will also need another 25 inputs for the piezo sensors and 1 ground that can be daisy chained together.
The Arduino has nowhere near enough I/O pins on it but I have heard of a thing called multiplexing. However, I am not sure if you can run RGB leds with multiplexing.

If this helps at all I am using a led strip that I can cut into 3 LED sections to put under each square.

I hope I was not to vague with my question, thanks for your help.


texts: Multicolor LED based on different input voltages

texts:
Is it possible to have one LED produce different colors of light at different voltages.
Ex.
2v - Red
3v - Green
4v - Blue

I have looked at some other answers and searched on Google but it seems there might be a need to have comparator circuit. This is not the solution I am looking for.

So, if i buy a multi-color LED and hook it to a variable voltage adapter, can I get 3 different colors at 3 different voltages?


texts: Risk in limiting current with light bulbs in parallel

texts:
I'd like to make a current limiting device on the cheap using some light bulbs. I've seen somewhere the idea of connecting light bulbs in series to limit the current.

For example, I'd wire a 250w light bulb in series to limit the current used by the circuit to 250w. Which has a resistance of 193.6 Ohms according to this formula:

P = VI
V = IR

250 = 220 * I
250 / 220 = I
1.136 = I

V = IR
220 = 1.136 * R
220 / 1.136 = R
193.6 = R

simulate this circuit – Schematic created using CircuitLab

Here, the lamp is limiting the current going into the main winding of the transformer to 250w.

In theory, if I wanted to increase the maximum current going into the transformer, I'd have to modify the circuit to have more light bulbs in parallel like this.

simulate this circuit

Since the resistance in parallel can be calculated this way:

1 / Rtotal = 1 / R1 + 1 / R2 + ... + 1 / Rn
1 / Rtotal = 1 / 193.6 + 1 / 193.6
1 / Rtotal = 2 / 193.6
1 / Rtotal = 1 / 96.8

Which reduce the resistance to 96.8 ohms and then the maximum current flowing in the transformer should be:

V = IR
220 = I * 96.8
220 / 96.8 = I
2.272727273 = I
I*220 = 500

In theory adding any light bulb with a certain wattage rating in parallel to other light bulbs but in series with the transformer should increase the maximum current flowing to the transformer.

That said, I was wondering what happens to the sine wave coming out of the light bulbs? Is it possible that the sine waves goes out of sync even though all light bulbs are rated for 50hz or something else that I'm not aware of?


texts: Shift register clocking and latching delay from microcontroller

texts: When latching or clocking a shift register from a microcontroller, should there be a delay in between setting the clock or latch pin to high and then resetting it to low? How long is this delay typically? For example if I set the data pin, and then set the clock to high and then immediately back to low in the next line of code, would that be sufficient to clock in the data?


texts: Using XR2206 function generator with split supply

texts:
I have an Exar XR2206 to generate triangle wave with single supply Vcc. This wave has peak value 12 volt and 0 volt.

How to make this IC operate in split-supply?

Hence I got triangle wave with peak value +6 Volt and -6 Volt.


texts: How long can I leave components in a breadboard?

texts:
In school, I was told not to leave components in a breadboard for extended periods of time.  However, this length of time was never quantified.  The reasoning was that the contacts would eventually lose their "springiness"; at some point later in time, you'd be debugging issues with a circuit, only to find out that the contacts were bad.

I have no idea if this is really true, or if breadboards are now made so well that it's not an issue.  I have some nice ones, but in the end they seem to use the same narrow white piece that everyone else uses.

I've got some prototypes put together that I don't want to take apart yet, and I also don't know when I'll get back to it.  My mbed board has now taken a back seat to the Netduino that I just received.  :)