texts: Combining ECG and EDA (skin conductance) in the same chest electrodes. Possible and how could it be done?

texts:
Currently I'm designing a wearable, battery powered module that combines several sensors into a single device. In this device are modules for both ECG measurement (heart beat) and EDA (skin conductance, also known as Galvanic Skin Response, or GSR). Both use electrodes and the ECG electrodes have to be attached to the chest. The main question is, is it possible to use the same electrodes for ECG and EDA measurements simultaniously?

Some background information:

ECG is measured using the AD8232 chip. The design is based roughly on the Sparkfun board. For this measurement two electrodes are used. These electrodes are used to pick up a signal of max 1 mV, generated by the heart. The AD8232 has a gain of 100 to amplify and measure this.
EDA is measured using a Seeed design. With the EDA circuit roughly 0,5V to 1,0V is passed between two electrodes, through the skin, in a voltage divider setup. Because skin resistance changes, so does the amount of voltage that passes through the skin, compared to the set resistor of the voltage divider. The output of the circuit measures the voltage over the skin and using the known resistor, calculates the skin resistance.

Since both modules use electrodes in contact with a stretch of skin, the idea was to combine the two modules over the same electrodes. However, since the AD8232 has such a large gain, I'm worried that the 0,5V to 1,0V of the EDA will destroy the AD8232 if it passes through the same electrodes. The AD8232 has a max voltage on every pin of 3,9V with a 3,6V power supply. Sub-question 1: Will this happen and if so, is it something that can be prevented? I've been told to look at galvanic isolation of the EDA and ECG modules (different ground planes?), but I'm very unsure how to go about this.

I'm also worried that the EDA voltage will contaminate the ECG measurement. Sub-question 2: Can the galvanic isolation separate the two voltages? Can this even be done at all?

Any advice on any of these points is very welcome.


texts: Need help in understanding MUX-NOT flip-flop

texts:
I need help in doing practice problem:

A MUX-NOT flip-flop (MN flip-flop) behaves as follows. If M=1 the flip-flop complements the current state. If M=0, the next state of the flip-flop is equal to N. Derive the truth table and excitation table for an M-N flip-flop.

My book does not give any data about MN flip-flop and I did not find any adequate materials on that online. Can anyone help me to understand the question and the idea behind MN flip-flop?


texts: detecting laser using solar cell and band pass filter

texts:
I need to detect a laser signal using a solar cell.

My first problem is that all I get is a current generated from the solar cell that will vary (as I understand and correct me if I'm wrong) in it's frequency depending on what illuminates it.

So to make this easier I would be using a band pass filter to only detect the laser (which I dunno how yet, just got the idea from here) but the they mentioned it's a 1khz band pass filter which I dunno how that would only detect the 600(ish)nm laser frequency.

I was also thinking about splitting down the units to cells so I would get better accuracy, but I'm still worried about the false positives.

Also, trial and error won't work for me as I don't have any equipment on hand.

Finally, I'm working in direct sun light, but need pin point accuracy and no false positives. I do NOT, however, care about detecting time or intensity


texts: How to increase the distance of effective reach of a magnetic field from an electromagnet

texts:
How can I effectively increase the distance in which some electromagnet can attract a coin (for the sake of simplicity - coin).

Now to show that I've done my homework:
According to Ampere's Law, the strength of the magnetic field is directly proportional to the number of coils. Therefore, more coils (of some sort) right?
How about pressing the coils by virtue of hydraulic press? Wouldn't that allow me to coil more wire at less space? The denser the coil is the better eh?

Also the law tells us that more current will also increase the power of the electromagnet. Well I have 4 3000 mAh 20A/3.6V li-ion LG batteries, are they sufficient? How about using OP-amps? I am not afraid of draining the batteries down quickly.

Best answer will explain why electromagnets loose strength over distance  by the cube of the radius distance from the magnet (as corrected by @Trevor), ways to increase the distance, possibly up to the length of a half hand and explain how to measure what can one achieve, given number of coils, current, coil density etc...


texts: what does built-in LiPo discharge protection look like?

texts:
I bought a 100 mAh LiPo from the b&H website because it specifically said that it had overdischarge protection. I really need a reasonable lifetime for this battery so I hooked up the battery to a 15 kOhm resistor overnight to see what voltage it would be in the morning.

to my surprise, the voltage read 0.17V! Is that correct?

but when I Plug in the charger it rises to 3.0 V super fast almost as if t were there the whole time.

Does this make sense for a circuit with discharge protection? How can I be certain that this is true discharge protection?


texts: Hardware block to determine if a number is a multiple of 8

texts:
Can anyone suggest me an hardware block (I mean its structure/functional units) that is able to detect if a given number is a multiple of 8?

It seems easy but I haven't been unable to find a way to accomplish this.

Thanks


texts: What happens to step down converter effiency when current consumption is very low

texts:
I'm planning to use a MAX640 (Maxim 9 V -> 3.3 V Step-Down DC-DC Converter) to supply a couple of ICs with 3.3 V.

In active mode the current consumption of the ICs are around 20 mA and according to the datasheet the efficiency of MAX640 is around 90 %. Hence the total current consumption will be around (20 mA/ 90 %) = 22-23 mA, right?

But most of the time I want to shutdown ICs (and MCU) to get a consumption of maybe 10 uA.. looking at the datasheet (EFFICIENCY vs OUTPUT CURRENT) it is not even plotted... what will happen? Can I not use the MAX640 if I drop the current consumption that low?

A final question, anyone have a tip of a Step-Down DC-DC converter (or with equal functionality) that also can measure current consumption (analog, spi, i2c)


texts:
I want to build voltage multiplier using Cockcroft–Walton scheme.

I've got bunch of 3kV capacitors (2200pF though), and even bigger bunch of 1N5399 1kV diodes.

So, obviously I want 3 diodes in series to match capacitors rating.

I know that one cannot simply do that, and one need balancing resistors to match reverse current, but I see that for reverse current in datasheet (5uA) I need 200MOhm resistors, which seems to be something I can ommit. I know that at elevated temperatures diode reverse current would increase, but I won't work above 30 C.

Getting Higher-voltage diodes is probably not an option - they are ether too expensive or have too high forward drop voltage (like 20V for TV 14kV generators), and tiny current.

Suggestions, can I go without resistors?

PS. I know that I might want bigger caps, but they are not really common stuff. In this case I will have DC stage providing 3000V single polarity pulses @~30kHz or a bit more, so output current should be sufficient even with 2200pF. Target voltage is 15-20kV, so I will have ~ 7 stages.


texts:
I am solving this circuit and according to the dot convension,the j6 ohm and j8 ohm have opposite polarities. Applying kvl to both loops,
I got, 10 = j5I1 - j3I2 + j3I2
Or, I1 = -j2 A
But I am stuck in the second loop.
It seems like, I2=0 because the mutual impedance of both the opposite polarity inductors with the j5 ohm inductor is same, j3 ohm. Also no active source is present in second loop. Am I right here with dot convention? Please ensure me.


texts: Electrical charger design with power factor correcttion

texts:
Design an Isolated battery charger with PFC( power factor correction), which will take input from 230V 3-phase supply. Calculate the value of inductor, transformer and capacitors used. Also, select appropriate switching devices and mention the components used.Required output :117 volt and 40 Amp.

What i have done is i have used the 3 phase rectifier and the caluculation of output rms is V=304.062v and supply current is =69.28A.

Now i am stuck here what should be my net step for smoothening and for PFC.


texts: Reducing volume for a split-phase 230VAC@60Hz sealed power supply providing 5VDC@50mA

texts:
I'm a hobbyist interested in re-designing and implementing a DC power supply providing a \$+5V_{DC}\pm 200mV\$ output with a current compliance of \$50mA\$ (I could live with \$30mA\$ successfully) from a \$230V_{AC}\$ @ 60Hz split-phase US mains supply. This supply will be completely sealed and there will be no access at all to any conductors outside the sealed package, except for the AC input wires. The DC is used with a microcontroller, which itself will also be inside this sealed package. So there is no way anyone can make any contact with either the DC ground or the \$+5V_{DC}\$ lines. Think of it as a brick with only the two hot AC power input wires, plus ground, leaving the brick. (It is actually a micro that accepts fiber optic signals and controls four SCRs as part of a hybrid relay system gating the \$230V_{AC}\$ for an H1/H2 output. But that's a longer story.)

My goal is to come up with an approach that uses the least volume while using reasonably available parts and/or ones I can reasonably fabricate. (Reasonable is something I can't define well, but it tends to mean that I don't want to use parts that are very expensive or very difficult to come by in hobby quantities.)

This opens up a few questions:

Just use a transformer to get the voltage down close, followed with a bridge, etc. I'm open to the idea of a custom wired transformer, but I suspect I'm going to run into difficulties because of the volt-seconds (Webers) that the core will have to sustain when operating with 60Hz. I think the volume is going to be huge. I need to delve into the specifics and I haven't done that, yet. The question here is: Is my intuition correct that the transformer volume will be large (compared to answers for the following questions), despite my modest current requirements?
Use a capacitive driven power supply. You can see an example of what I'm thinking about, given an existing design I posted here about two years ago: Split-phase \$230V_{AC}\$ transformerless capacitive power supply for \$5V@30mA\$ regulated output — series cap?. No answers developed from that one, but a similar design does work satisfactorily. A problem here is that the capacitor should be non-polar and rated for such use. These are large. This is the reference design I'd like to shrink. The question here, other than providing a reference for the other questions, is: I'm using a \$450V_{AC}\$ rated non-polar X2 capacitor now. Are there reasonable alternative capacitor choices I might consider that are smaller and yet rated for this exact kind of use?
Use some specialized IC designed specifically for this purpose. Those I've examined are complex to design and not so well tailored to my modest ~\$30mA\$ (to \$50mA\$) requirements, enough so that I'm once again not sure about the resulting volume. It would take quite some time to gather these up and test specific designs and given that none I've found are specifically designed for very low currents and voltages a question arises here. Are there any ICs that an experienced designer might suggest I look at, which has a promise of showing a total volume less than what is typical for designs as in (2) above and doesn't use overly exotic parts different to obtain or too expensive? (I'm looking here to narrow the work I have ahead. Not a perfect answer here. I can explore what is offered. So I'm just looking for reasonably educated IC suggestions, and not whole circuits using them.)

(In answering the above, I'm able to wind and test transformers and coils and I do have access to oscilloscopes, lab supplies, and the usual tools that a modest hobbyist might accumulate. And feel free to criticize the earlier design approach, too. I'm just a hobbyist and will take my lumps, with pleasure.)

The target volume is something smaller than \$1 \, in^3\$. The existing design uses commonly available parts.


texts: How to connect a CD40109BE Voltage Level Shifter

texts:
I have a circuit requirement using a Texas Instrument CD40109BE Voltage Level Shifter.  This chip incorporates 4 low to high level shifting circuits.  I plan to use two of these circuits, A and B with C and D disabled.

The input voltage for both channels is 5 V TTL level and the output is 12 VDC, from two independent power supplies.  In addition, I will be switching the input level at a frequency between 500 Hz to 2 kHz with a square wave from a Pulse Width Modulation source of variable duty cycle.  The 12 VDC output to follow the 5 V TTL input waveform.

I'm not an expert in electronic component design and was wondering if someone can provide a detailed circuit connection diagram for such a circuit.


texts: Understanding why use Laplace transforms for circuits

texts: I am an Electrical Engineering student and in my Circuits class, I learned that using Laplace transforms is helpful while analyzing circuits. I see how it makes our calculations easier but I still don't get the intuition behind it. If someone can explain me that/point me to some links that explain the big idea behind using Laplace transforms. Also I don't get why we change s to jw when looking at impedances.


texts: What is the bottleneck of a SD Card to USB transfer via microcontroller?

texts:
I am using a microcontroller (PIC32MZ) to transfer the data from an SD Card to USB, with this configuration:

simulate this circuit – Schematic created using CircuitLab

I managed to have everything working using Harmony v1.09 framework, and I could get a transfer rate of about 1.5MBytes/s, which is pretty good, but...when using SD Cards with large memory, this rate still looks to slow. For example, it requires 6h to transfer 32GB!!!!

Looking at the components one by one, I can't see why the transfer rate is not higher:

The actual card I am using for my test reached the speed of 20MBytes/s when plugged into my computer. It probably used 4 wires, but then it would be around 5MBytes/s on each wire
The PIC can support High Speed USB, which has a transfer rate of 60MBytes/s (480Mbits/s)
The SPI bus between the card and the micro is running at 50MHz, which corresponds to a maximum rate of 6.25MBytes/s

Why can't I get at least something closer to 5MBytes/s, which seems to be the lowest rate of the system? What is the bottleneck here? Is it possible to improve it?

Datasheets:

Microcontroller
SD Card
Board1 (PIC32 starter kit)
Board2 (MEBII)
Firmware: msd_sdcard demo of Harmony v1.09 (SPI and USB drivers set to 50MHz)


texts:
I'm using a hardware-based debouncing circuit to trigger an interrupt on a Particle Photon development board.

I use a similar circuit with two buttons:

Sometimes when a button is pressed, the interrupt linked to the other button is also triggered.
What is the reason for this behaviour? How to solve this issue?


texts:
I have a current source connected to the inverting terminal of the op-amp, with the non-inverting terminal grounded. There is a feedback resistor connecting the inverting terminal to the output of the op-amp. If I connect a ground connection to both the supply voltage points of the op-amp, what would my output be?
I do not know the specifics of some components. I am using a CD pickup unit (KSS-213C) which houses a photodiode IC (CXA2586M), of which, all photodiodes have this circuit.

simulate this circuit – Schematic created using CircuitLab


texts:
why do you need the or gates at the end of this circuit? cant you just tie all the would-be-inputs of the or gates together instead? also, what would be an example when you need to use or gates instead of tieing the outputs together?

thank you and sorry for my bad english


texts: Access device commands on Lenze 9400 Highline driver via Twincat3

texts: I want to access the device commands on a Lenze 9400 Highline driver via CANoverEthercat(Twincat3). Is that possible and how can I do it? Specifically, I want to access the Device command 51: Identify pole position (360) via twincat using CoE.


texts: Why do standard cells typically have slower timing with high temperature, and faster timing with low temperature?

texts: Threshhold voltage typically falls with increasing temperature, which would seem to indicate that high temperature operating conditions should result in faster gates than low temperature OCs. However, standard cells typically have slower timing with high temperature, and faster timing with low temperature. What is the physical explanation as to why this is the case? I would guess that it has to do with the carrier mobility.


texts: I tried to come up with a design where if the input voltage is bigger than -8 volts the output will be input, if smaller than -8 volts it will be grounded. I ran the simulation on LTSpice and it works as i intended but would it work in real life properly? I'm asking this because i searched for a desing for this purpose on the internet and couldn't find anything and we have never done something like this in classes.


texts:
Good morning everybody, I'm trying to build a 5v solar panel charger for a smartphone like the one in the picture.
I would like to add also a 3.7v 3A Lipo battery with protection circuit to store energy when phone is not plugged.

Do you know an easy why to make the circuit only charge usb output when phone is plugged and battery when is not? (Possibly without using a manual switch).
I understood adding a resistor to the battery will make charge mainly the phone but will keep charging only partially the battery when phone is not plugged.

Basically I'm interested in knowing if there is a way to address circuit energy to a different output depending if a device is plugged to the usb.
Maybe a mosfet but not sure how.

Thanks in advance for your help and let me know if you need additional information and please forgive me also in advance for any mistake you can find.
Andrea


texts: How does the input voltage affect the current consumption of a microcontroller?

texts:
Is there a relationship between the current used by a microcontroller unit (MCU) and its input voltage?

In other words, given a MCU with a wide-input range (e.g. 2.7 to 5.5V for the ATmega328P), will it use the same amount of current for a given operation undepending on the input voltage?

I'm not sure if there is a generic answer to the question as it might depend on the particular MCU. I'm asking this question because low-power figures (e.g. in datasheets) seem to always be expressed as current (e.g. 1 μA for deep sleep mode) and never in Watt or similar.


texts: Serial Over USB Reading With GNU Octave Problems

texts:
I am having difficulty reading a USB virtual comm port into GNU Octave, and there are some bizarre goings-on that I would like some input on.

Currently I have a USB CDC virtual comm port device that I programmed to respond to commands over serial with the computer. The device is a microcontroller board (STM32F401C Discovery board) with a gryoscope. The gryoscope is read over SPI onto the microcontroller and then the micro relays the data to the computer. It waits until it receives the "x", "y", or "z" commands to send data and then it continues to send data for that coordinate until a stop bit (anything other than "x", "y", or "z", I usually use "s") is sent.

Using CuteCom I am able to interact well with the device e.g. sending the command "xs" will return a single 6-byte packet of the x-axis angular rate data (maybe something like "+00021"). Using GNU Octave and its instrument-control package I can read in all coordinates, but sending the string "xs" will cause the device to only receive the "x" byte and it will relay x-axis data continuously.

This can be worked around by adding a 1ms character delay. The STM device reading the serial commands waits 1ms between bytes it reads in as well, because previously it was able to send many strings for the x-axis before it received the "s" command.

So it works then, right? Apparently not. The strange behavior starts here, as when I run the command-then-read sequence in Octave by one time everything works, but in a loop the data read in is only the x-axis. I thought this was a timing problem, and I was curious to see what was being read from the port directly using CuteCom.

When CuteCom is monitoring the serial port for data, Octave reads data properly for the duration of the loop. But when it is not monitoring the serial port, it will only read the x-axis.

I do not understand why having CuteCom running in parallel with the Octave script would cause the process to perform as expected, but without CuteCom running the data comes in corrupted. Here is the GNU Octave script:

pkg load instrument-control;
pkg load signal;

s1 = serial("/dev/ttyACM0");
set(s1,'baudrate',115200);
set(s1, 'bytesize',8);
set(s1,'parity','n');
set(s1,'stopbits',1);
set(s1,'timeout',100); %10.0 seconds

sleep(0.5);
srl_flush(s1);

datax = [];
datay = [];
dataz = [];
negativex = false;
negativey = false;
negativez = false;
xd = 0;
yd = 0;
zd = 0;
delaytime = 1000; %delay time in microseconds (us)

hold on;
for i = 1:500
  srl_write(s1,"x");
  usleep(delaytime);
  xd = str2num(char(srl_read(s1,6)));
  srl_write(s1,"s");
  usleep(delaytime);

  srl_write(s1,"y");
  usleep(delaytime);
  yd = str2num(char(srl_read(s1,6)));
  srl_write(s1,"s");
  usleep(delaytime);

  srl_write(s1,"z");
  usleep(delaytime);
  zd = str2num(char(srl_read(s1,6)));
  srl_write(s1,"s");
  usleep(delaytime);

  datax = [datax xd];
  datay = [datay yd];
  dataz = [dataz zd];

  if mod(i, 10) == 0
    hold off;
    plot(datax,'r');
    hold on;
    plot(datay,'b');
    plot(dataz,'g');
    drawnow;
  endif
endfor
%

The result for the three axes when CuteCom is not running (note how the data is copied for all three lines, with the small delay between them):

The result for the good data output, when CuteCom is running (note the data for each axis is consistent and clear):

Has anyone come across something like this before? What mistakes were made to cause this to happen?

Thanks in advance.

Sam


texts: PCB design issues for handling 50A current

texts: I am working on a combiner circuit that will monitor the current and voltage rating of my device. The device and the combiner must handle 50A Current. Im using a shunt on my combiner PCB to measure the voltage/current. Now while testing as I increased the current supplied above 20 25 A, the PCB track started to melt and smoke up. Im using a 2oz thickness and a pretty wide track. Are there any ways to manage heat dissipation or even generation(Im measuring Current, so the only parameter that I can control at source is resistance. While beyond a limit isnt the best solution)


texts: What is the difference between a USB port and a USB receptacle?

texts:
The Wikipedia article USB hardware states:

Standard connectors

The type-A plug. This plug has an elongated rectangular cross-section, inserts into a type-A receptacle on a downstream port
on a USB host or hub, and carries both power and data. Captive cables
on USB devices, such as keyboards or mice, terminate with a type-A
plug.
The type-B plug: This plug has a near square cross-section with the top exterior corners beveled and inserts into a type-B receptacle on
an upstream port on a USB device, such as a printer. On some devices,
the type-B receptacle has no data connections, being used solely for
accepting power from the upstream device. This two-connector-type
scheme (A/B) prevents a user from accidentally creating a loop.


texts: Medium Voltage Synchronous Motor Protection

texts:
How is the wound field of a medium voltage synchronous motor protected from voltage surges? We do know that the stator is protected from surges by either one of the following:
1. RC Snubber Circuit
2. Surge Capacitor
3. A surge arrester in combition with point 1 or 2 above.


texts: Exploiting stack buffer overflows on an Arduino

texts: Is it possible exploit stack buffer overflows on an Arduino board?


texts: Please see attached slide for a Routh-Array. I'm struggling to see why the encircled element is 4. Rather, according to my calculations it is 0 as the determinant will give zero. Unless I'm doing something fundamentally wrong...


texts: Protecting Test Equipment During an ESD Test

texts: I am planning to run an ESD test on a product running traffic to some test equipment over gigabit ethernet and some other signaling interfaces (RS-232, USB, etc.) How do I decouple the ESD spikes from my test equipment so that I don't accidentally induce a failure in the test equipment instead of the device under test?


texts: Differential pair length matching considering phase

texts:
According to Microchip's document Implementation Guidelines for Microchip’s USB 2.0 and USB 3.1 Gen 1 and Gen 2 Hub and Hub-Combo Devices, the Superspeed differential pairs should be length matched while considering phase. I.E. the length-matching squiggles are inserted as close as possible to the location of the phase error:

The squiggles are inserted directly into the corners.
Questions:

Does this type of length matching have a name?
Does Altium have a way to generate this geometry? If so, how?
If not, how can one create this geometry correctly?


texts: Can a digital multimeter damage a powered circuit when measuring resistance?

texts:
I wanted to make sure my ESD wrist-strap is in working order. So I tested like this:

Connected the wrist-strap to household ground (via wall socket).
Measured the resistance between the wrist-strap and the exposed ground of my PC's front USB port (using a non-name brand digital multimeter).

The test worked fine but I realised that the PC was powered on. I've always been told not to measure resistance on a powered circuit because the multimeter applies a voltage to do its measurement.

So, doing what I just did, any chance of damage to the USB port/controller/PC? I don't know enough about electronics to figure this out, though my gut instinct is that tickling ground in the way I did shouldn't matter at all. Still, a definitive answer would be nice!


texts:
I would like to program a microcontroller board directly in Assembly (any instruction set) in the most direct way. I don't want to use any IDE or bootloader code to handle the flashing. My aim is to flash a binary file containing the instructions, directly to memory and have the microcontroller boot from it.
I have noticed that many or the more popular microcontrollers have their own flash tools or very high level IDE interfaces to communicate to the microcontroller.
Can anyone suggest me a specific microcontroller and a method for transferring assembly code to microcontroller?


texts:
I've got a cheap chinese lightsaber and want to make some adjustments to it. The item looks great but its volume is too loud and my neighbours get mad when I switch it on. It doesn't have any way to control it. I contacted the seller and confirmed that there was no internal control.

I'm not an expert in electronics, I only know basic teoric concepts and how to use a soldering gun.  My first idea was to install a potentiometer between the control board and the speaker, because there is some space behind the speaker, but after I searched this site I discovered it was a bad idea, that the sound will be distorted, the amplifier could break and there would be unnecessary power consumption in the resistance. At least that is what I understood.

I've tried to locate the amplifier, but it doesn't seem easy to make mods to the PCB, as it is really small and it fits in the hilt without much free space.

So the question is, considering that controlling the volume at the amplifier input is not an easy option, and that the system itselt is not a Hi-Fi and small distortions could be accepted, will installing a potentiomenter be dangerous and break the amplifier? What about a voltage divider?

If the risk is too high, could I simply take the speaker off? Altghough I think it can sound silly asking this, I read in another question that it could break the amplifier too, due to infinite resistance. I really don't know if that responses only related to guitar amplifiers or if it applies to small ones.

The speaker specs are 8 Ohm 2 W, 20 mm in diameter, while the battery is 3.7 V 2000 mAh.

The cables on the left down corner of the PCB go to the speaker; the right side ones go to the leds. I cannot extract the PCB more than that without cutting any cable, I hope this helps.

Thank you in advance.


texts: How is the asymmetry of a Schottky diode obtained?

texts:
A Schottky diode is constructed with two metal conductors bonded to a doped semiconductor. One of the metal-semiconductor junctions is a Schottky contact, and the other metal-semiconductor junction is an Ohmic contact. If the doping in the semiconductor is uniform, and the two metalic contacts are made of the same metal, I would presume the device would be symmetric, and would not be useful as a diode. If it had two Schottky contacts, they would be in opposing orientations. If it had two Ohmic contacts, it would just be a resistor composed of doped semiconductor.
My question is, how it the asymmetry between the two contacts achieved? Is there a doping gradient in the semiconductor? Are the two metal conductors composed of different metals? Is there some third alternative that I am missing?
(The common internet literature on Schottky diodes explains why the Schottky metal-semiconductor junction acts as a diode, but I have not seen an explanation of how the Ohmic contact in the same device is made to be different).


texts: Should I count transistor power while transistor is switching?

texts:
When transistor (bipolar transistor in common emitter amplifier) is closed (not conducting) or opened saturated (enough base current, collector current is limited by the resistance of the load), it dissipates the power well within its limits. However switching from opened to closed obviously goes over all intermediate values (it is probably not possible even theoretically to be otherwise, the question is just how fast).

Should I normally care that transistor would stay within its power limit at the intermediate values, if I truly believe that thermal issues are highly unlikely (controlled by digital input that has only two values and changes fast)?

There are no time based limits on the specification sheet. Are there any generic rules about this maybe?


texts: Why do we use this particular approximation for the bilinear transform?

texts:
As I understand it, for a signal \$f(t)\$ in time, its Laplace transform \$\mathfrak{L}\left\{f(t)\right\}=F_1(s)\$ and Z transform \$\mathfrak{Z}\left\{f(t)\right\}=F_2(z)\$ are related by a transformation \$z=e^{sT}\leftrightarrow s=1/T\,\log(z)\$ where \$T\$ is the sampling period (since the Z transform is discrete in time).

In practice, this is approximated to the first degree as follows $$\begin{align*}z&=e^{sT}\\&=\frac{e^{sT/2}}{e^{-sT/2}}\\&\approx\frac{1+sT/2}{1-sT/2}\end{align*}$$and thus \$(1-sT/2)z\approx1+sT/2\$ so \$sT/2\approx(z-1)/(z+1)\$ and ultimately \$s\approx\frac2T\frac{z-1}{z+1}=\frac2T\frac{1-z^{-1}}{1+z^{-1}}\$.

Now, I understand up to here, but I fail to understand why we use this particular first-order approximation over, say, \$z=e^{sT}\approx1+sT\leftrightarrow s\approx(z-1)/T=\frac{1-z^{-1}}{Tz^{-1}}\$.

Does this approximation 'behave' in some significantly poorer way for most purposes?

Sorry about the tags -- I tried various things like 'bilinear-transform' but they did not exist and I lack the points to create them.


texts: Zero Cross Detection Circuit for line voltage

texts:
Possible Duplicate:
  How can I detect a power outage with a microcontroller?

I'm doing some research with the goal of eventually creating a light dimmer controllable from a micro controller.  I've figured out how to do the dimming of the light and now I need a zero cross detection circuit that I can use to determine when to phase shift the AC power.

I have a few opto-couplers which should do the trick.  However (and this is my question), it appears that the AC side of the circuit takes around 1.7V (assuming I'm reading the datasheet correctly).  How do I get the line voltage down from 120V to 1.7V.  I assume that I could use a high value resistor, but wouldn't this generate too much heat?  Seems to me like it would just fry the resistor.  I'm pretty hesitant to just try this as I enjoy having all of my fingers attached.

I've seen people discuss connecting the line voltage directly to the micro controller through high value resistors here, which seems like a pretty bad idea.

To summarize my question:  How can I connect AC line voltage to my opto-coupler?  And if that's done with a resistor, how do I determine the correct ohms/watt rating to use?

Thanks!


texts:
So I was trying to write a code to connect an SD card to my atxmega128 . Code is nearly ready but when I want to compile it in Atmel Studio, I get errors about not declaring some codes. Some of the undeclared codes are "PORTD , PORTD_DIR, ... " .
Question : Aren't these port codes part of the atmel studio software? Do I need to define some source codes for them ? What should I do to make it work ?


texts: Could interference on a stripboard be affecting my input from a shift register?

texts:
I've built an interface board to connect an LED matrix and a home made games controller to an Arduino Due board.  The interface and code for both the matrix and the controller were tested independently before combining them into a single circuit on a Stripboard.

I am bad data from the controller switches sometimes when the display is running which is making me wonder if some sort of interference/induced signals could be affecting the data I'm getting back from the controller.  I'm thinking interference as the problem only happens when certain images are displayed on the matrix.  I've checked twice for any short circuits and I'm pretty sure the code itself is not the cause of the problem.

The controller is reading 8 switches (which are pulled low when open with resistors) in parallel via a shift register and sending its data back to the Arduino serially via 3 wires.  I read the new value of the switches every 8 seconds.  I have set up test code which displays the current state of all switches in real time on the LED matrix and, depending on what is displayed on the screen, it either displays as expected or will show errors in the form of the wrong switches showing as being pressed including times when multiple switches show as pressed even though I'm only pressing one.

The LED matrix is driven by 13 lines, some of which can be pulsing at up to approximately 40MHz.  The lines are only active in very short bursts.  At the start of a display frame the clock pulses 32 times with 6 data lines possibly switching in parallel with each pulse.  This repeats 7 times with a delay (that doubles each time) in between.  The above process is then repeated 15 times for other lines on the screen (with 4 row select lines being set between each line) and the whole process repeats 60 times per second.

I have managed to "fix" the problem by optimising the code that reads from the shift register.  Tweaking the delays between latch and clock pulses on the shift register also helped but can also make the problem re-appear depending on what is displayed on the screen.  I don't consider this a fix.  I suspect that at some point the problem will show up again when I implement new games that display different images on the matrix.

Here's a photo of my circuit:

The red circles show the pins to/from the Arduino for the controller interface, the green ones show the pins for the LED matrix interface.  I've drawn in cyan to give an idea of what connects to what.  The four green pins nearest the controller pins are the row select lines which 'only' change ~1000 times per second.

Is it likely that some flaw in my design/circuit is causing false highs on the controller's shift register's clock or latch lines that are spoiling the output?  I've not broken the tracks on the stripboard that are used and are longer than they need to be, is that a bad idea - could it also be contributing to the problem?

Thanks for any help/advice.


texts: How do I get the name or number of device?

texts: In many cases when I am designing a circuit, I use transistors, ICs, etc, by using calculations. But when I go to the market I have to ask the product by its name which I don't know. How do I get the name of device,I am looking for? Is there any simple way? Or I have to memorize hundreds of datasheets?


texts: What is the impedance of a multi-tap impedance matching transformer when all taps are used at the same time?

texts: So if I have an impedance matching transformer with two taps, one 8ohm and the other 4ohm, and both taps have a winding relationship so that the other side "sees" a 4kohm load, what is the impedance if I use both taps at the same time assuming both loads are correct to their respective taps? what about the power if a signal is applied on the 4kohm side? will it split through each one of the other two loads? with what proportion?


texts: Why is it possible to have undistorted power amplifiers?

texts:
In Albert Malvino's book "Electronic Principles," he says there is a 10 percent rule for small signal amplifiers wherein the AC signal current must be less than 10 percent of the emitter current so that the resulting amplified signal is not distorted.

But in power amplifiers we can use very high AC signal as input (i.e. class B amplifiers.) Won't this surely produce highly distorted amplified signal in output?

The curve below clearly state that if we ever input high AC signal to VBE, the resulting emitter current will be distorted:


texts: johnson counter sine wave resistor network

texts:
I saw one schematic which uses an 8-bit shift reg to produce a sine wave with a resistor network.

I am guessing the resistors will be voltage dividers, but how are the values calculated? I tried to setup equations for different states but it looks like a mess with all the variables for resistor values.


texts: Should I avoid a switching frequency close to my target SPI or CAN frequency?

texts:
I have a kind of an open-ended question.
If I'm designing a board with a buck converter and have picked out my peripherals, and say for example I want to run my CAN FD interface at 1MHz baud and maybe a SPI signal at 1MHz, and I am now looking at power supply design.
I am looking at a buck switching regulator which has a switching frequency at 1.4MHz.  Is there any big EMI issues with having the switching frequency so close to the frequency of my other signals running through the board?  Should I aim at either a higher or lower frequency?
Pretty open-ended question, but I never really thought of it until I ran into it.


texts: How can you get the analogue sensor data into Max MSP?

texts: How can you get the analogue sensor data into Max MSP with an Arduino?


texts: Help needed on op amp chip and identifiers

texts:
Hi all.

I am starting my own company designing selling studio/guitar based gear.  My first item is a distortion pedal.  I spent years testing pedals etc, and came down to two op amp chips I liked.  The NOS JRC and a burr brown.  I leaned towards the burr brown and that is what I'm going with when it comes to designing my own pedal.

So in the development stage I ordered 10 BB chips among others to do my tests/prototypes and they worked out great.   After a few revisions designing with an overseas manufacturer the prototypes sounded great.

So I've purchased hundreds of my pedals, I've had the boxes silkscreened and all of the electric aspects/components are being soldered.  I've shipped them my own stash of NOS pure copper solid core internal wire, quality solder and 100's of these NOS burr brown chips from the same manufacturer I got the initial 10 from (only a year later).

I've just been told production has ground to a halt because the first 3 production pedals sound different/off compared to my prototype. They narrowed the audio issue down to the chips and asked did I get the wrong chips as they suspect they are fake/copies, and I explained I got them from the same people I got the initial 10 from.

I never saw the large chip order because I shipped that straight to the manufacturer.  So I asked were there any visual differences and they noticed that the codes are different and an r is missing.

Please check out the images.  Should I be having this issue?  What do the lower codes signify on the chips?  They are different to the initial 10 prototype chips that look like the top image.

Below are the bulk order/faulty ones.   A year has passed.  Are these fakes or just a new batch of production with different codes?  Do the codes mean different voltages or something?  I'm not experienced with op amp chips etc.

I'm worried because nobody else produces the original specific lower code on this Opa2143pa chip.  So I'm worried that all my boards will only work with the obsolete chips and not sound as good?


texts: Suggestions for solar / LiPo powered 3.3v supply for Arduino

texts:
I am building several slightly-differently-purposed Arduino + Xbee systems to monitor various things around my home and property.  Some of these are line powered, while others must use solar.

Many LiPo solar + DC chargers exist, but most output 5 VDC.  I'm hoping to find one that puts out 3.3 VDC, directly rather than having to then use an on-board linear regulator, and waste that power.  Of course, with the addition of a large enough cell, a drop from (say) 4v to 3.3v is unlikely to waste much heat.

I believe I need about 250 mA to be safe, but for very short bursts.  When the Arduino is sleeping along with the Xbee, I cannot even measure its current draw with the three meters I have on hand.  The majority of the current draw comes from the Xbee's transmit power requirements of up to 205 mA.  The Arduino itself should be fairly constant, so with the 8 MHz clock running and a nominal 3.3 V supply, it looks like the Arduino will draw under 10 mA.

My ideal system would have connections for a solar source input, a DC input (or USB) and have indicators I can read the status of, to have the Arduino report on its own power supply state.

I am assuming a single cell LiPo here, or a package with internal cell balancing.  Also assume I am doing all the smart stuff (powering down the unused components on the Arduino, setting the clock speed to its lowest setting, sleeping and waking only when there is something interesting to do, and sleeping the Xbee unless there is something to transmit.)  I can calculate the power requirements and size the solar / LiPo properly.


texts: What is the advantage of having multiple remote terminal (RTs) in 1553B terminal?

texts:
I have been trying to understand the difference between 1553B terminals with single and dual Remote Terminals (RTs). I have given 2 links below for the references:

link 1: Single RT

link 2: Dual RT

How this extra independent remote terminal will help to connect an extra sub-system.

In the following figure, when the Bus Controller BC (Mission Computer) switch to the Remote Terminal, how it will be helpful if there are two independent Remote Terminals available? Is if for connecting multiple sub-systems through SPI interface?


texts: Help wiring a Raspberry Pi and odd DB9 connection

texts:
I need to send a signal from a Raspberry Pi 4 to a PC running software that listens on a COM port and I'm having some trouble understanding the necessary wiring.

Here is the documentation I have for how to communicate to the software through a DE-9 port:

I have a DB9 breakout board:
https://www.amazon.com/gp/product/B00WPBXDJC?pf_rd_p=ab873d20-a0ca-439b-ac45-cd78f07a84d8&pf_rd_r=Y5WXCRKKDNTY4GC84C4R

Am I able to use the built-in pull-up resistors on the Raspberry Pi 4? What wiring do I need to send the correct signal?

It sounds like I can keep the DB9 #6 pin high (3.3V) by connecting it directly to a Raspberry Pi GPIO port that has a pullup resistor (making sure to enable it in software). When I want to trigger the device, it sounds like I can set that pin LOW for a few milliseconds. Is that correct? Or, do I need additional setup?

If necessary, I also have a relay on-hand I can use: https://www.amazon.com/gp/product/B01M0E6SQM/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

Thank you for any help you can provide - I'm a software guy and this electrical setup is pretty foreign to me!


texts:
I have recently purchased several Atmel's touch sensor IC's AT42QT1010 which are extremely tiny (1.6mm x 2.9mm) and I would like to be able to mount them on a breadboard. I have tried soldering them to a PCB but I just can't solder that precisely so I always end up soldering the pins to each other.

Is there any IC socket (or anything else) that would increase its size or at least the space between the pins?


texts:
I have read that in RFID systems, the range is almost always dependent on the tags sensitivity to pick up the signal, not the readers. But this information is related to UHF RFID systems, and I would like to ask if it's the same in low frequency systems?

I'm asking this, because I'm doing a COMSOL Multiphysics simulation on determening the read range of a tag in a certain environment, and I would like to know, that can I make the evaluation of the range based only on how far the tag still can receive a strong enough signal to activate itself and send the signal back?


texts: Sending an impulse to oscilloscope from software?

texts:
I am currently trying to measure the time it takes from [the moment a flag is set programmatically in software before rendering some graphics] to [[the moment the graphic is actually displayed on the screen]].
Though I have some programming experience, my experience in electrical engineering and its surrounding knowledge is close to nil so please bear with me. I've been told oscilloscopes are often used to measure latencies, and I've seen some examples in which the latency from user input to screen displays were measured. From my limited research, these were usually done by attaching pressure sensors on the user input devices and photodiodes on the screens, and then measuring each with oscilloscope probes. In my case however my starting point of measure is from within software, and even with my limited knowledge I don't think sticking a probe in the computer is the right move. With that in mind, I'm wondering if something like, a USB-based Oscilloscope that comes with its own SDK could help me send something like an impulse from my program, so that I could compare the timing with probe-measured signals (i.e. photodiode)? Is this possible? Or are there better ways to achieve what I want?
I'm aware that general computer operating systems introduce various lags from system scheduling and background tasks etc., because general purpose systems are not built with precision in mind, and because of that my hypothetical software trigger will not be precise. But for my needs a reasonable millisecond-level measurement will suffice, and I believe I can tolerate several milliseconds of error. I'm also willing to take steps to minimize background service/tasks etc. to lower jitters caused by the OS doing what it does.
If you have better setups or ideas that you'd like to point me to, I'd be most grateful. Thanks in advance!


texts: Voltage drop assumption on diodes (LEDs, etc.)

texts:
I've always wondered why is it valid to assume some voltage drop (different from the junction voltage drop) on diodes or LEDs from the power up of a circuit. It simplifies the analysis, but it's unclear to me why it is a valid approach.

For example, in the question Capacitors charging in a DC circuit, the assumption is a drop of \$2V\$ across the LED.

What is the explanation?


texts: How to solve excessive CPU load Proteus error?

texts:
I'm simulating a virtual Arduino on Proteus. When I test my code, This error appear:

  Simulation is not running in real time due to excessive CPU load

For me, It does not matter to watch the real time output wave form. Can I record it and see it later or something like that to solve this issue? I just need to see the first 5 seconds of the output wave form?


texts: Electrical Circuitry Programs aimed at Children / Beginners

texts:
I'm sorry of this is off topic, but I figured I have a better shot asking the question here then anywhere else.

What I'm looking for is an Electrical Circuity program that was released around 2000 that makes it easy to make circuits on the computer. The program that I am talking about came with a computer mag that I had in England, this was around 2000 or 2001. It allowed you to make a circuit on the computer and test it. It gave you items like light bulbs, switches, batteries and much, much more. I remember being able to over volt light bulbs (with to many batteries) and having them break, so you would have to replace them with a working one. It was very simple and child friendly, I used it for one of my school projects.

Does anyone know of this application, and where I could get it? Or do you have a list of applications like this that you could post here. I will accept applications that are in the same vein, that are better then what I'm asking for. But I would like to emphasize that it should be able to be used by children relativity easily.


texts:
Everybody is probably going the other direction, moving their systems etc. to linux. I have the following problem. I like to use a WiFi chipset along with its Linux driver on my RTOS (FreeRtos). If I do this the conventional way, it will take me 3 months to port it. (Now I work for a small company, therefore I don't expect any support from the chipset vendor with my volumes. However I have a very strict cost target so I cannot use this really expensive but easy to use modules. I am targeting sub 5$ wifi module here)

Is there a simple way or do I have to really go in deeply understand the driver and port it slowly. I don't know Linux but I know RTOS concepts relatively well. I am looking for a wrapper some sort that translates Linux system calls to more conventional RTOs stuff.

I know it is a long shot but I had to try.

And, do not suggest uCLinux as the OS, I have been down that road, it seems to be the best way however the code size is prohibitive to run with the on chip resources of my CPU.

Bonus question: Any WiFi experts out there who could recommend a b/g chipset with RTOS drivers that are readily available. I have looked at CSR,Realtek and Nanoradio, they all provide Linux drivers but no RTOS support. Atheros didn't even entertain to talk to me, I guess the effect of Qualcomm.


texts:
I'm looking at making a very basic, automatic cat feeder for the odd occasion I'm not around at 2pm when she gets fed. I figured I'd keep things simple by having a door that is spring loaded, but held closed by some kind of mechanism.

I'm so blissfully ignorant with regards to electronics, but figured that perhaps a solenoid valve (valve, switch?) would work well, keeping the door shut so the cat cannot open the door itself.

When 2pm comes around, a timer (not figured that bit out yet) would hit the solenoid thus releasing the door to open under spring tension.

Is there an easier approach than this, any other suggestions as to how to keep the door closed?

Many thanks,
Ben


texts: What limits system clock in MCU? How high can I go?

texts:
I'd like to produce PWM outputs at f_PWM ~= 100kHz and I'd like to connect the ADC to sample
at least once during each high-time interval of the PWM output.

Everything in my configuration of these peripherals seems to tie back to the system clock (F_CY) which I get from an external resonator (and then goes through a PLL and then I get my clock).  So, without having to move to specialized IC's, I'm trying to understand how fast I can go?

Is it just the limit of how nice of a resonator I can buy?  I've never used a resonator beyond 20MHz.

I know things eventually are limited by parasitic capacitances etc, but how do I find my limit practically?


texts: charging a li po battery while using it through piezoelectric crytals

texts:
My friends and I are working on a project that requires a pretty long battery life. Since we can't fit any battery powerful enough in the project, we had to use a smaller one, but now, we have to charge it through piezoelectric crystals. Is this possible? If yes can anyone send a circuit diagram showing me how?

                                                              Regards,
                                                              Yigido


texts: I will like to understand the term efficiency in a SMPS design. Is there a way to determine the best efficiency for a particular design?


texts: Does Differential Amplifier Emitter behave as ground in AC-analysis?

texts:
I am trying to solve various differential-amplifier homework problems for which I have the solution to study.

For the simplicity of most problems we are able to neglect base-currents. Moreover, it is to be assumed that the transistors are perfectly matched with a Beta = 100 for both Q1 and Q2.

However, for the example shown below, if we neglect any additional base current, by deduction, are we also able to remove (short out) the emitter-resistance as well? It appears that is what the solution manual did, though, there is no explanation.

Given Schematic:

simulate this circuit – Schematic created using CircuitLab

Where the derived AC-equivalent is:

simulate this circuit

And where I derived the expression for the differential gain Ad as:

But the solution somehow derived the following equation:
For which I could only surmise that in the AC-analysis, considering one-half of the amplifier, since they are identical mirrors, the common-emitter node gets grounded?


texts:
I'm analyzing a power supply design. A Current mode PWM controller is used to step down the i/p 45-57 V/350 mA to 5 V/3 A. The design uses this part, http://datasheets.maximintegrated.com/en/ds/MAX5974E-MAX5974F.pdf

I read the datasheet but I couldn't understand, how exactly the stepping down is taking place? and how the o/p current is determined?


texts: Anything Wrong with my Light box Design?

texts:
I am creating a custom box that will contain 3 * 400 watt metal halide bulbs (1200 watt total). The box will remain closed for 60 minutes, open for the next 60 minutes, then closed, then open and so on.. for a period of 10 hours. The box will open/close from the the front panel (the "door") using Arduino and Servo motors.

Since the bulbs will be generating a lot of heat I will attach a Duct Fan at 240 CFM on top of the box (is the top the best place to put it?). Something like this: http://www.amazon.com/dp/B005KMTYFK/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=V2E1GXE4DR4J&coliid=I3B1JSME5M15UN

The box itself will be made out of wood so I will coat it with a heat resistant spray from the inside so it doesn't catch on fire. Something like this: http://www.amazon.com/dp/B000CPJLV2/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=V2E1GXE4DR4J&coliid=I122VPINWI1GBY&psc=1

When the box is open I will need the box to emit as much light as possible. Therefore, I will coat the inside with a reflective substance (something like this: http://www.amazon.com/Rust-Oleum-1915830-Metallic-Silver-11-Ounce/dp/B000PQGE2M/ref=pd_sim_hi_3?ie=UTF8&refRID=0DKBGQGVVCT0YSWCW1WB) so all light rays are dispersed from the box..

What do you think?

Thanks


texts: Crystal in temperature controlled environment vs OCXO

texts: Are there any studies on the performance of crystal oscillators in temperature controlled environments vs an OCXO? I mean do you control just the temperature in OCXO, or do you need to account for other factors e.g. Pressure, humidity etc.


texts: What are these uniform traces that extend to the board edge?

texts:
These Super Famicom cartridge PCBs have what appear to be uniformly-spaced traces extending all the way to the extreme left and top of the board.  They don't look castellated (and there are easier ways to make test points besides).  The ICs are traditionally mask ROMs, so there shouldn't be any additional interface required for programming.

I would guess they were going for some sort of isolation between the various fills, but that wouldn't explain why they needed to be uniformly spaced at the edges.  The source of the edge traces seem to be "non-essential" in that they don't run to any of the "important" chips.
To my eye, they're just antennas without a purpose.  A friend suggested the boards might have been machined on the left side (removing the mouse bites) after-the-fact, making this even more mysterious.
Can anyone shed some light on what purpose these might serve?  Thanks!


texts: Is torque constant times the motor current the only way to estimate torque feedback in a servo motor?

texts:
Consider a torque and position tracking servo motor. Once the motor reaches the target position (assume no external torque applied), the end effector should apply a torque which tracks the torque reference signal by comparing the torque feedback with the current torque.

Is the product of the torque constant (\$K_t\$) with the sensed (possibly filtered to denoise) motor current the only way to estimate torque feedback in DC or AC servo motors? Although it well understood that the back EMF is related by direct proportion through the EMF constant (\$K_e\$) to the angular speed of the motor, is it possible to relate it to the applied time-varying torque in order to measure it?


texts: Interfacing AD7321 ADC with Arduino using SPI

texts:
I'm trying to interface an AD7321 ADC with the Arduino Uno/Mega or Raspberry Pi for data acquisition of signals from my breadboard to computer.
I am able to communicate with the ADC through SPI with an Arduino Uno by sending the required 16 initialization bits, however the output of the ADC does not correctly represent the analog value when observed with an oscilloscope.

The image below is a snippet from the datasheet of the expected I/O for the SPI pins.

Since this is a 13bit (12+sign) ADC, I would expect a digital range from 0-4096 excluding the sign, however the images attached show otherwise.

This is a graph showing the ADC output at 5V DC.

This is a graph showing the ADC output at 0V DC.

The 2 return bytes given by the ADC in 0V DC graph

00001100 00010100  (Flat line)
Which is when converted into decimal is 3092.

From the first image of the datasheet, the first 3 bits can be ignored when finding the absolute value of the desired signal.

I am trying to use this ADC to sample my signal (+-10V) at 100ksps which this ADC is capable of, however I cannot get an accurate reading from it.

Could someone who is more familiar with the AD732x chip shed some light on the behaviour of this chip?

Any help is appreciated
Thank you!

EDIT: Thanks for the comments, I have amended the post to ensure the information is available.

This is the schematic, there are a few decoupling capacitors from Vdrive/Vcc to ground and both analog and digital grounds are connected at a star junction to reduce wire inductance noise.

The graphs above have Vdd = 5V and Vss = 0V, however I have also tried Vdd = 10V, 7V and Vss = -10V, -7V and -5V, but encounter the same issues.

In terms of code I have attached them below. The initial bits sent to the ADC are currently configured to read at +-5V single ended mode, no sequencing, binary code from channel 0.

#include <SPI.h>
#define CS_PIN 10 //Pin 10 defined as the CS Pin.
void setup()
{
  Serial.begin(115200); //Initalise port to print in serial terminal
  pinMode(CS_PIN,OUTPUT); //Pin 10 as CS
  digitalWrite(CS_PIN,HIGH);
  SPI.begin();  //Intialise SPI PORT
  SPI.setBitOrder(MSBFIRST);
  SPI.setClockDivider(SPI_CLOCK_DIV4);
  initialise();
}

void loop()
{
  uint16_t adcOut;
  float value;
  initialise();
  adcOut = readADC(0);

  adcOut = (adcOut<<3); // Bitshift to take last 13bits
  value = (adcOut>>3);
  Serial.println(value);
  delayMicroseconds(1); //Delay
}

uint16_t readADC(int channel)
{
  uint16_t output;
  digitalWrite(CS_PIN,LOW);
  byte msb = SPI.transfer(0x00);
  byte lsb = SPI.transfer(0x00);
  digitalWrite(CS_PIN,HIGH); // Deselect slave by pulling CS_PIN HIGH.
  output = (msb << 8 | lsb); //Combine MSB with LSB to form the 16 Bit Analog read  Value.
  return output; //Output Value
}

void initialise()
{
  digitalWrite(CS_PIN, LOW); //Select the connected chip by pulling CS_PIN LOW.
  SPI.transfer(0b10111001);  //Defines range register -> | Write (1) | 0 | Register Select (1) | Vin0A | Vin0B | 0 | 0 | Vin1A |
  SPI.transfer(0b10000000);  // | Vin1B | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
  digitalWrite(CS_PIN, HIGH);
  delayMicroseconds(1);
  digitalWrite(CS_PIN, LOW);
  SPI.transfer(0b10000000);  //Defines control register -> | Write (1) | 0 | Register Select (0) | 0 | 0 | ADD0 | Mode1 | Mode0 |
  SPI.transfer(0b00110000);  // | PM1 | PM0 | Coding | Ref | Seq1 | Seq2 | 0 | 0 |
  digitalWrite(CS_PIN, HIGH);
  delayMicroseconds(1);
}


texts: The voltage between two identical PMOS in series are not evenly distributed (in practical and simluation)

texts:
When I connect two PMOS in series and let both of them working in cut-off region, it seems the voltage drops of those MOS are not evenly distributed: for example, when I apply 24V (higher than the breakdown voltage of a single MOS), one of them has a voltage of almost 20V, and the other takes 4V; and when I apply 22V, one of them has 20V and the other takes 2V....  this also applys for the simluation (LTspice,not here strangely lol). P.S. the breakdown voltage of a single MOS is 20V, I have a application which requires 27V, so I want to 'increase' it a bit, I only need them to work in cut-off.
the circuit can be seen below:

simulate this circuit – Schematic created using CircuitLab

simulate this circuit

VDD/V V1/V V2/V

15    15    0

20    19    1

21    19.1  1.9

23    19.3  3.7

25    19.5  5.5

my current soultion is to connect a 1M resistor to each of those MOSs parallelly, but I wonder why this happens: why are the voltage not evenly distributed? or is there any better ways to even the voltage (I tried using Cap instead of resistors but not working)?

Thx for your time and looking forward to anyone's suggestions!


texts: Buffering AC supply voltage and detect power loss?

texts:
I'm designing a system integrating:

an industrial PC with 230V AC input (~300W)
various peripherals requiring 24V DC (150W max)

In case of external AC power loss, the DC components (2) need to be supplied with backup power for up to five minutes. This is not a problem and suitable PSU are available.

However, for a reason I cannot control, the industrial PC requires an advance signal (about 1 second in advance, possibly less) indicating that its supply power is about to be lost.

So I'm looking for suitable 230V AC buffer with power loss notification. Compliance with IEC 60601-1 (3rd) would be a big plus.

I don't know exactly what I'm looking for. I would like to avoid a full-blown UPS, even though a battery is needed for the 24V PSU. Could anyone direct me to the right kind of component?


texts: How can a transceiver pin be used if its clock is so much faster than the FPGA clock?

texts: I'm trying to understand how a transceiver pin can actually operate at, say, 2.5GHz given that the clock speed of an FPGA is so much slower. In my understanding, to transmit data you need to synchronize pulses so that, given that you have a lot of data to send, you 'pulse' for a certain time, and that time is controlled by the clock. Or am I misunderstanding how transceiver pins work?


texts:
I bought some 7-segment LED displays along with some BCD-7 segment decoders. The clerk said he didn't have the exact part I asked for and instead gave me a Texas Instruments CD4056BP. He said it was compatible but now that I've seen the datasheet, I'm not so sure as it describes the device family as a liquid-crystal display driver.

The datasheet makes no mention of use with LED displays, however the presence of the display frequency input suggests the IC can drive other display types

Quoting the datasheet, emphasis mine

  The 7-segment outputs are controlled by the DISPLAY-FREQUENCY (DF) input which causes the selected segment outputs to be low, high, or a square-wave output (for liquid-crystal displays). When the DF input is low the output segments will be high when selected by the BCD inputs...

With that in mind, is it safe to directly drive the LED display from this device?


texts:
I want to design a BDC driving board with Infineon BTN8962.(Infineon BTN8962 is a half of H-bridge IC)

As we all know,BDC driving circuit is just like this:

In this picture,We set a High side MOS(QA) as Open,and set a High side(QC) and a Low side(QB) MOSes as close.We just have to ouput a PWM signal to control the speed of BDC.

But when I use Infineon BTN8962,I found I cound not do this unless using the INH pin as PWM signal input pin.(But in fact,this pin is sleep mode enable pin.It can close its MOS.)

Which pin should I set as PWM signal output pin?


texts: Confusion with serial controlled mux devices

texts:
I have 8 channels each with 3 possible unique inputs, see diagram below. I would like to be able to select which input each output connects to. The inputs are signals from ranging from a simple step to sine/square/triangle waves up to 4Mhz, 5V peak to peak.
Ideally I would like to send my selection choice via I2C or SPI & this is where my confusion starts. When ever I look for I2C mux or I2C switches I'm just running into devices that fan out the I2C signal eg the PCA9546A or the TCA9548A. This is NOT what I want. I specifically want to be able to choose between 3 analog inputs for a given channel.
What keywords should I be using? That is assuming such devices exist


texts: Potentiometer heats up after changing wiring

texts:
I changed wiring on my LED array. I switched from a 24 AWG to 18 Gauge cable. I used the following potentiometers. However after changing wiring, all potentiometers (tried new ones and unused) started heating up really fast and slowly turning off probably from overheating protection. A significant change was that I increased the length of the wiring by 6 feet.
Any idea on what could cause that? If I plug the LEDs directly into the power supply they work fine for prolonged times.


texts: Is it feasible to use fiber optics to increase the detection area of an infrared photodetector array?

texts:
I'm working with an infrared emitter/detector system based on an Osram SFH 4545 IR LED collimated through a 40mm dia, 120mm fl lens and a sensor array based on three separate sets of three Vishay TSOP 34856's all running a 56kHz signal.  Both emitter and detector are designed to mounted on a wide variety of fully mobile objects and so cannot be physically connected.

The issue is the mobile elements mounting the sensor arrays are typically much larger in terms of surface area then the detectors can cover, especially considering the number of components used.  Also, by design the sensors must be exposed during a highly physical process thus requiring additional protection and maintenance.

Would it be possible to use fiber optic lines as a light pipe to bring the IR signal to the sensor array?  I am imagining arranging multiple lines over a broad area of the target element, thus increasing the area each array can cover and also allowing the delicate sensor components to be moved to a more protected location.  Ideally, I would like to be able to utilize the same detectors or at least one with similar parameters so as to avoid any redesign or reprogramming.

If this is possible, what type of cable would be required?  How would the ir signal be collected at each cable?  I can't imagine that you would have raw cable ends sticking out everywhere, but I can't seem to find any termination components that aren't designed to physically connect to a light source.  I've researched this fairly thoroughly via Google and several other message boards and haven't found the information I need.  My team and I are firmly in the DIY camp and so our knowledge base is deep only in specific areas.  Fiber optics is not one of them.  Any help would be appreciated.


texts: PNP Transistor - Use IC 555's internal resistance as pulldown?

texts:
I have a circuit that uses a PNP transistor to enable or not the current to flow and turn on a LED. The point is, is it a good engineering practice to conect the base of the transistor to the Vcc of my NE555P, so that it will be grounded through the ~15kOhm resistance of the IC and saturated whenever there is no voltage in it, and when there is 12V in Vcc it will open the transistor as I desire?
Another solution would be using 2 NPN transistors in a logic that would do the same job.


texts: What are the advantages to a separate processor when there is an FPGA present?

texts: Consider an embedded application with both a discrete processor(ARM, AVR, PIC, etc) and an FPGA to offload some of the work or interface with specific hardware.  Assuming there are sufficient resources in the FPGA to fit a soft core equivalent of the external processor, what are the advantages of using a hard processor instead of a soft core?


texts: Is Ethernet synchronous or asynchronous serial?

texts:
I already tried googling but I cannot find an exact answer. Some say it is synchronous, some say asynchronous.
For example, see these links:
https://www.quora.com/Is-Ethernet-synchronous-or-asynchronous
https://superuser.com/questions/260965/what-is-ieee-802-3-ethernets-communication-type-synchronous-or-asynchronous#:~:text=Ethernet%20is%20Asynchronous.,no%20clock%20pins%20or%20pairs.
Ethernet has no separate wire for clock signal, so does it make it asynchronous?
But Ethernet also does not use start and stop bits, so does it make it synchronous?
And by the way, can we encapsulate Ethernet into RS-232? That is, can we use RS-232 to carry or transport Ethernet?


texts: Differerent connection for Y-capacitor (EMI filter)

texts:
What is the difference between these two connections Y-capacitor (EMI filter)?
*high-voltage side to isolated 12V DC output *isolated 0V DC output rail and a "GND"
Could you tell me the raison of each connection ?and what the right way to do that ?


texts: High Frequency (16 Mhz-48 MHz) Peak Hold/Envelope Detector Circuit?

texts:
I'm trying to make a peak hold circuit for a very high frequency bandpass filter that needs to be able to operate at 16 Mhz, 40 Mhz, and 48 Mhz.

I've singled out the peak hold part of my overall circuit to try to get it to work. Here's the one I'm currently trying, which isn't working:

Here(below) is the rest of the circuit with one of the other peak hold circuits I tried using (also doesn't work.) The circuit is supposed to take in a frequency and determine whether or not it is within ~500 kHz of 16 Mhz. I'm using a 2nd order Chebshev resonant frequency filter as a bandpass for the incomming signal, then I'd like to use a peak hold circuit to get the amplitude of it before pushing it to a comparator, which will determine if it is within the desired frequency. If there is a easier way to approach this that doesn't involve and FPGA, that will work as well.

I was mainly wondering if there are other peak hold circuits that will work at high frequencies (16, 40 and 48 MHz.) I've tried other circuits with BJTs and they haven't worked either. Do the OP amps I have selected have anything to do with these problems?

Thanks


texts: Battery status monitoring of 1 cell NiMh battery powered embedded device

texts:
I am developing an embedded device (integrated RF controller) using 1 cell NiMh battery of 1.2 volt.
I am figuring out ways to estimate the remaining battery capacity of the system. I have come across various ICs to do the task for multiple cells i.e 3 or 4 cell NimH but did not get any specific IC for 1 cell. Please let me know if there is some IC for estimating the remaining capacity of 1 cell NiMh battery or any other method that can be adopted to complete the task.


texts: 1980s AVTEL 4 colour mechanical display, how is the pixel state reset?

texts:
I stumbled on a retro Dutch video from 1983 where a large four color mechanical display is shown.
Each pixel consists of a cube which can be turned in order to change the pixel color between 4 colors (white, green, red and blue), a carriage moves behind the screen and slowly updates the screen by altering the rotation of the cubes. Ah this retro electro-mechanical stuff, I love it.
My question is: how does the update carriage know the rotational position for each of the pixels?
Or is the rotational state not obtained but reset in some way? The pixels have small cams on their sides, but they seem similar for each color, I can't really see it properly. When the carriage passes it performs only one color-shift per line (90 degrees), and each pixel is always cycled during an update, even for cases where there is no difference between the initial color and target color of the pixel.
Other details:
The displays seems to be branded "AVTEL". And seems to consists of 3 smaller displays next to each other.


texts: A large resistor in series (parallel) with a small resistor has the resistance of the larger (smaller) one, roughly?

texts:
I am currently studying the textbook The Art of Electronics, third edition, by Horowitz and Hill. Chapter 1.2 Voltage, current, and resistance says the following:

A large resistor in series (parallel) with a small resistor has the resistance of the larger (smaller) one, roughly. So you can “trim” the value of a resistor up or down by connecting a second resistor in series or parallel: to trim up, choose an available resistor value below the target value, then add a (much smaller) series resistor to make up the difference; to trim down, choose an available resistor value above the target value, then connect a (much larger) resistor in parallel. For the latter you can approximate with proportions – to lower the  value of a resistor by 1%, say, put a resistor 100 times as large in parallel.

This explanation seems contradictory to me:

to trim up, choose an available resistor value below the target value, then add a (much smaller) series resistor to make up the difference

The author said that a large resistor in series with a small resistor has the resistance of the larger one, roughly. So why would using a resistor below the target value, and then placing it in series with an even smaller resistor, be equivalent to a large resistor that satisfies our target value?

to trim down, choose an available resistor value above the target value, then connect a (much larger) resistor in parallel

The author said that a large resistor in parallel with a small resistor has the resistance of the smaller one, roughly. So why would using a resistor of value above the target value, and then placing it in parallel with an even larger resistor, be equivalent to a small resistor that satisfies out target value?

to lower the  value of a resistor by 1%, say, put a resistor 100 times as large in parallel.

And how does the reasoning then lead to this?
Perhaps I am misinterpreting what the authors are saying here. I would greatly appreciate it if people would please take the time to clarify this.


texts: Create specific resistances across a constant current source

texts:
I'd like to emulate the controls on a garage door circuit programmatically. As far as I can tell the circuit acts like a constant current source and sends out 10mA to the wall console. I'd like the wall console to stay in place and be usable at the same time. Here's a simulation of it:

(On falstad)
I know I could do it by just replacing the switches with 3 relays, but I'm looking for something smaller/simpler. I'd rather use just one relay to my 'override circuit', but I can't figure out how to create the apparently load on the circuit. It seems anything I put in there results in too much of a voltage change on the original circuit (considered analogue switches, mosfet, bjt, digital pot).
Here's a version of the circuit with relays.

Would anyone be able to provide a suggestion on another way this could be done?
Edit: Switch to 3 relays.


texts: Why does a DC motor doesn´t move with low OCR values

texts:
I'm using a 6V DC motor for the first time and I've set up a timer on an atmega328p to create the PWM signal that then goes to the H-bridge (L293D).
My question is why, for example, using a 8 bit timer with a prescaler of 256, if I set the OCR below 80 the motor can't start moving but if I use a power supply, directly connected to the motor, it works perfectly to any voltage?

In other words: (80/256)*100% = 31% duty cicle ---> 6V *31% = 1.86V

When I use the power supply with 1.86V all the way down to 0V the motor moves.

What's the reason for this to happen and how can I make the motor to move at slower speeds if I can't use low values? I'm trying to make PID control to control the motor position, I haven't started programming the PID but I am sure that it will need small PWM signal.

The motor has a gearbox with a ratio of 10:1

Motor Datasheet: Micro DC-Motor Modellspezifikationen


texts: What is the "DC OK" relay used for on a power supply?

texts:
I am using a Meanwell SDR-120-12 power supply for a project. I noticed it has terminals for "DC OK" which the datasheet refers to as a relay contact rated for

60Vdc/0.3A, 30Vdc/1A, 30Vac/0.5A resistive load

It also says:

Contact Close = PSU turns on / DC OK.
Contact Open = PSU turns off / DC Fail.
Contact Ratings (max.) = 30V / 1A resistive load

The block diagram seems to show that this is a relay that's operated by the power supply being energized. I assume this contact might stay open if the power supply did not pass some sort of self test at power-up? If that's true, then is the "DC OK" terminal meant as a means for equipment to detect if power is fully available (sort of like how a computer PSU communicates to a motherboard)?
How is this different from simply using output power from the supply to operate a device and not utilizing the relay at all?


texts: Equation for a capacitor charged by a decaying current source (solar cell)?

texts:
I have a solar cell charging a capacitor. I want to find the amount of time it'd take for the capacitor to be charged to, say, within 0.01% of the final value (the open circuit voltage). I'm trying to derive an equation or relation that lets me calculate the required time. Normal capacitor charging equation obviously won't apply as this isn't an ideal constant voltage source. It can only source a current limited by short circuit current. The best description I have for the solar cell's behaviour here is that it is a decaying current source. The open circuit voltage remains constant and the current decays from a fixed short circuit current value to zero.

I did some digging in the internet and found the linear approximation to be true in the behaviour of charging upto 60 or 70% of open circuit voltage. i.e,

$$I = C\frac{dV}{dt}$$

$$dt = \frac{C\,d\,V}{I}$$

However this relation fails when the voltage across capacitor comes closer to the open circuit voltage of the solar cell.

If I had an equation on the nature of current decay, I could've just used the

$$V = \frac{1}{C}\int{i\,\,dt}$$

Is there any specific relation here? Can one be derived? My actual interest is to design a value of capacitor given the charge time required.


texts:
I've removed a voltage regulator from my circuit and replaced it with a series of BJTs. The regulator was just switching voltage. But I need the circuit (which happens to power/wake the micro) to be on by default. So I've come up with this scheme. I've modeled it and it seems to work well for both turning on and turning off. The load will be limited to 100mA which is also the limit of the BJTs I believe. In truth it will be around 10mA at most.
PWRIn will be from 4.5V to 21V. PWR1_Dis will be most likely 3.3V GPIO.

Have I violated any rules with my design? Should I have any protections that I have over looked? Do I have any extra components? Any general advice for this?

Thanks!


texts:
I want to build an embedded system that reads external data and logs it to a file saved in an SD card. However this system is accessed through a password and I want either the SD card or the file in it to use this password as well. How can I do it?
About the file, I thought of saving it with a .CSV extension because it uses rows and columns. Can this type of files have password? Any suggestions?

To be more specific with the question:
I will use a microcontroller, programmed with C language. What commands should I send to the SD card in order to be password-protected? Or, what is the format of a file in order to have an access password?

EDIT:
I want to add a password so that only the user is able to open the file and read it using his/her PC.


texts: Does anybody know or can please verify if my solutions and answers are correct?

texts:
Solve for Vout

If R3 is a potentiometer, what must be its value if desired VOUT=24V.

What must be the range vaue of R2 if the desired Vout is 10 - 25V?
R1=125 OHMS, VREF=1.25 V


texts: Why are different names given to the same bit in MPLAB XC8?

texts:
I am using PIC18F45K22 and MPLAB XC8. Recently I stumbled upon something while reading ADCON0 register. A particular bit in the register, GO/DONE has many representations while I try bit addressing it in xc8 (something like ADCON0bits.GO_NotDone). These are Go, Done, Go/Done, Go_notDone, Go_nDone.

My question is why are so many representations required for the same bit? It could have simply been something like GO_NotDone. Am I missing something in my understanding? Any insights are welcome, thanks.


texts: Need assistance in choosing diode for seat heater circuit

texts:
Background:
I have been working on car seat heater circuit. I purchased the universal seat heater with manual 2 level (high and low) switch. Instead of manual switch, I re-wired the seat heater circuit to electronic control relay with trigger latch to set either high and low setting using car oem button and mechanical relay(that fits in dash).
My current question is relating to diode use on high output terminal from electronic relay.
The high output terminal has ~14V when ON and is connected directly in parallel to seat heater pads (2; for seat cushion and back). The low output when ON is connected as series to the same pads and it uses the high output connection to establish a series between pads. In Low level state, i get ~7v of backfeeded electricity in high terminal which i want to block using diode.
What type/size diode is needed to do this job? The high level wire is 16g stranded and forward electricity is 14v (amps at max ~15A---but a mechanical relay in circuit has rating of 40A) the back current which i want to block is ~7v (amps i am unsure). And I want it to be blocked to correctly set high and low level LEDs.
edit:
This is the general diagram. My diode point is yellow wire at the switch to block reverse current when the circuit is in low level (i.e white wire is +12v)

A. 1 press of switch will trigger T1 ON/T2 OFF via flip flop latch (interlocking). T1 = HIGH setting, will output 12V via YELLOW wire to both heater pads and the black from upper heater wire is earth and red wire from lower heater pad is connected to earth via relay pin 30-->87a connection. One LED light in the switch will turn ON.
B. 2 press of switch will trigger T2 ON/T1 OFF via flip flop latch (interlocking). T2 = LOW setting, will output 12V via PINK wire complete relay circuit by charging 12V to pin 86 (pin 85 connected to earth). Pin 87(12V) will connect to pin 30 sending 12v down the lower heater pad and the circuit is then completed by yellow wire connecting both heater pads in series. Both LED lights in the switch will turn ON (This is what i do not want). Both LED turns on because red wire of relay 2(low) is 12v and yellow wire of relay 1 (high) has 7v (because of series connection). The switch LED has input voltage range of 5v-12v (ideally 5v)and is connected via resistor which drops voltage around LED to ~2v.
What i want is:
a. 1 press>high setting activated> 2 LED on (not one)
b. 2 press> low setting activated> 1 LED on (not two)
HOW? I need help!
I was thinking of adding diode at yellow wire at relay 1 insertion with banded side away from relay so current can move forward but blocked reverse. Then i will take 2 output wires from both ends of diode to my switch. What it will do is
a. 1 press> high setting> both LEDs glow ( as both are connected to yellow wire and current is flowing in that direction across diode
b. 2 press> low setting> one LED will glow ( the 7v at the banded side of diode on yellow wire will glow the LED but the LED on the blocked side will not.
Any thoughts??


texts: Why does a soldered IPEX MHF4 (WIFI card) connection result in signal attenuation?

texts:
In my laptop, the WIFI card was connected to the 2 antennas by IPEX MHF4 connections, which look like tiny coax connectors. Unfortunately the antenna connectors got broken, so I have removed them and soldered the antenna wires directly onto the WIFI card connectors (1/2 in the picture.)
It worked, but the WIFI signal strength now is much worse. I can rule out that the wires got mixed or cold solder joints.
Why that loss of signal strength? Is that because the impedance no longer matches (guess it is 50 Ohms?)?
If it is a problem with the impedance, could I buy a preconfigured cable with IPEX 4 connectors, cut the cable off after a few centimeters and solder it to the antenna cable? I would not like to replace the whole antenna because it requires me to disassemble sensitive parts of my laptop.
Is the length of the antenna cable relevant (must it have an exact length?)?
By the way, do the inner and outer pin of that connector carry the same signal, or is that shielded? The antenna cable is just 1 wire, so not shielded, but just to make sure - or is the outer ring connected to ground?


texts: What do I need to close an electrical circuit for a certain amount of time

texts:
I need something that closes an electrical circuit for a certain amount of time when it receives an electrical pulse.
In my case, two wires touch, even for a second, the device I need will supply power for 30 seconds to another device.


texts:
This is regarding an automotive transmission control module(TCM) solenoid driver. The schematic diagram of the driver is very similar to the below image. Only difference is the TCM has the low side switching whereas this schematic has high side switching.

My problem is the power transistor highlighted in yellow becomes burning hot within one minute of operation. It becomes really hot such that the transistor falls off from the PCB. I don't find any short causing the transistor collector current to exceed its rated value. Is there any other obvious reason why Q3 is getting too hot?

R1 - 3 ohms |
R2,R6 - 47 ohms |
R4 - 18 ohms 10 watt |
Q3 - 2sb1016 |


texts: How do I use pin5 to control duty cycle of a 555 based PWM?

texts: I have built a simple PWM using a 555 IC to drive a motor for an optical chopper and I want to be able to use the output of the chopper signal as a speed correction feedback for the PWM. I think I should be able to do this using pin 5 on the 555 chip but I have no real idea how to do it. The current idea is to take the signal from the chopper through a F/V converter, into some sort of comparator and then use that output to increase/decrease the duty cycle of the PWM to adjust the speed of the motor up or down. I think I'm on the right track, I just have no real idea how to go about doing it because I'm an astronomer who dabbles in electronics but doesn't have any real training in circuit design. Please help if you can.


texts: Zener diode in parallel with both the input terminals and the output terminals

texts:
"There is a zener diode in parallel with both the input terminals and
the output terminals. Combined with the fuse these should help in
reverse polarity situations (it should blow the fuse before damaging
onboard components)."

How would that look in a schematic?

Its from this website: https://quinled.info/2018/10/12/quinled-dig-uno-hardware-guide/ I want to understand it.
That is my try but I´m not sure if it works:
.


texts:
How can we explain the development of electric field in a MOS capacitor(not connected to any circuit)?

To be more precise,I want to know what was the driving force for the accumulation of positive charges at the interface between the metal and insulator and negative charge in the bulk of semiconductor near the interface of semiconductor and insulator.

Is it because of the difference in concentration of electron in metal and semiconductor that electron flow from metal through insulator to semiconductor that the charge is developed?


texts: How come consumer products aren't powered by power banks?

texts: I wonder why no commercial battery-powered consumer product is designed to be powered by power banks. All of the ones I know of have either built-in battery holders or internal LiPos with charger chips. How come they don't just provide a 3V/5V external power connector and supply a separate power bank (or let the user supply their own)? The circuit can become simpler too. Is it a result of some regulatory requirement or mere aesthetic consideration?


texts: Unclear marking on a surface mount resistor

texts:
I have this resistor on a board.
Can someone can help me determine the value from the photo?
I did a ohms reading, and actually just around 22k Ohm. Which cannot be right. I asked about this in a previous post, but guess I needed a separate thread.


texts: Need to run a 75mmx30mm 12v .24a blower for 10 sec

texts: Hey I am very new so I appreciate any help here I am trying to run this small blower off a computer or 3D printer.  it’s a 75mmx30mm 12v .24A  I need to have it turn on and run for anywhere from 6-8 sec by push of a button and then shut off also would prefer it to run off a small battery possibly and 18650 can anyone advise me I am an ac tech and trying to expand my knowledge thanks again


texts: USB HID keyboard: why 4 URBs are generated for a keypress instead of 2?

texts:
This is system log when keyboard is plugged in:

usb 5-1: new low-speed USB device number 7 using uhci_hcd
usb 5-1: New USB device found, idVendor=04f3, idProduct=0103
usb 5-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
input: HID 04f3:0103 as /devices/pci0000:00/0000:00:1d.0/usb5/5-1/5-1:1.0/0003:04F3:0103.000D/input/input23
hid-generic 0003:04F3:0103.000D: input,hidraw0: USB HID v1.10 Keyboard [HID 04f3:0103] on usb-0000:00:1d.0-1/input0
input: HID 04f3:0103 as /devices/pci0000:00/0000:00:1d.0/usb5/5-1/5-1:1.1/0003:04F3:0103.000E/input/input24
hid-generic 0003:04F3:0103.000E: input,hidraw1: USB HID v1.10 Device [HID 04f3:0103] on usb-0000:00:1d.0-1/input1

Then I run wireshark and press a key. But instead of 2 URBs there are 4. What part of the URB contains the pressed key code and what for are two extra URBs? Here is the trace.

These are images, one per packet:


texts:
Lets say I have this program

int main(void)
{
  #define STOP 0
  #define RUN  1
  flag = getEvent();
  while(flag != STOP)
  {
    func1(); // A function that takes 1 seconds to finish it's job
 => func2(); // A function that takes 60 seconds to finish it's job
    func3(); // A function that takes 1 seconds to finish it's job
    func4(); /// A function that takes 1 seconds to finish it's job
  }

func2()

int func2()
{
  int status = BUSY;
  while (status == BUSY)
    status = doSomeJob();
  if (status == SUCCESS)
     return FINISHED_WITH_SUCCESS
   else
     return FINISHED_WITH_FAILURE

getEvent() shall permanently read the state of an input signal: For example if I click on a button, the system shall stop regardless of the running function otherwise the flag is on RUN and the system runs normally.

Is it possible to implement such a system using interruptions and without using an RTOS?

Why RTOS?
for me, the idea is to a add two tasks with different priorities. the first task reads permanently the input and second one executes the system. If an event appears the first task takes the scheduler and block the system.


texts:
The requirements are different from similar questions I've found here.
TXB/TXS are expensive for my needs.
Sparkfun's logic shifter is bi-directional, while I need two uni-directional conversions,  RX<->TX pairs.

As far as I understood from datasheets of both devices, the logic levels
ATMega328P (VCC=5V) page 313

\$V_{l}\$ = 0v - 0.3v
\$V_{h}\$ = 0.6v - 5v

and GPS receiver's page 16

\$V_{l}\$ = 0v - 0.8v
\$V_{h}\$ = 2v - 3.3v

I've tried to do that with voltage divider, but doesn't look like it's possible or maybe I am missing something.


texts:
I am totally new to electronics, so be patient with me please, it is very basic question :)

I have a 6V DC motor which I reused from an old device, that means I don't know its specs. I connected it to a power supply provides 6V DC, 2.3 A max. the motor worked great with a good rotation speed but extremely overheated after 3 minutes. So I connected it to a 5V with 1 A max, it worked fine without overheating but with lower RPM.

My question is: How to increase the rotation speed of the motor with the 5V, 1 A power source or How to prevent the overheating of the motor with the 6V, 2.3 A power source?


texts:
I have the following simple circuit. However, when I put the multimeter on the receiving end I'm always getting a current and I can't shut the gate, can anyone help please?
I'm using the following MOSFET: Infineon AUIRL1404Z N-channel MOSFET Transistor, 180 A, 40 V, 3-Pin TO-220AB
Power source is an 11.1V 5000mAh LiPo battery.

simulate this circuit – Schematic created using CircuitLab


texts: dc-dc step down converter model and the command of a JFET in LTspice

texts:
I am trying to reproduce this command circuit of a JFET semiconductor:
 and there are many components I am struggling to reproduce in LTspice. For instance, for the dc-dc converter, does LTspice provide a simple model or do I have to remake it from scratch?  Also, this figure is a screen shot of the datasheet of the component of interest. Is an IXDD component an "AND component"? and What about the Opto part?  This has been bothering me for quite a while now. I woud be very appreciative for pieces of advice and your help.


texts: Can I connect DC12v on VAC output (2A 100-240V) relay?

texts:
Solid State Relay G3MB

This relay's output says "2 A at 100 to 240 VAC".   If I wanted to connect something like DC12v 2A to this relay output,

It is not going work?
It might work, but it will damage the relay circuit?

I know this is a very stupid question, I googled but couldn't find a page explaining the differences between VAC and VDC output relay.

Hope somebody can clarify the differences.
Thanks in advance.


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In this video the man present this schematic (at 6:20):

And he say that you've to add some capacitors but I don't understand why. I've to model a solar-cell and I have to use the most complete schematic model of a solar-cell, so the question is what is the most complete schematic model of a solar-cell?


texts: What do I need to drive my big LED chip?

texts: I’m buying a 10 or 20W RGB led chip and I plan to power it with a Li-ion 18650 battery. For big led’s like I’m using, they specify voltages from 6-30VDC depending on the individual led and range from 500-1000ma draw per channel. I’m somewhat of a novice in EE so I need help figuring out what to do from here. I know I will need a voltage booster step up module to get up to the higher voltages I need. To maintain constant voltage as the battery drains, do I also need a voltage regulator module? Or is there some alternative piece of hardware that can manage all of this for me? Let me know the best option.


texts: Reactive power overcompensation causing voltage increase at generator buses?

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Consider the following system below, nine buses, 3 loads and 3 generators. From my understanding of reactive power, lagging power factors (per unit voltage less than 1) causes the reactive power to flow from the load to the generator which causes a voltage drop thus less than 1 per unit voltage. Inversely for over compensating for, it over excites the generator causing more voltage to be produced causing a per unit greater than 1.

So to stop reactive power flowing from the generators to the source and vice versa, the reactive power is locally generated on the same bus as the load. In the system above, I have found that if a load draws 85Mvar, and I supply 85Mvar of capacitance on the same bus, it causes a per unit greater than 1 on my generators. In the image above, with that current system, every generator has a per unit voltage greater than 1, why? Im not supplying enough capacitive Mvar for each load so the system per unit should be less than 1. Secondarily, how is the amount of capacitance calculated?


texts:
I am working with PID controlled temperature controller (SELEC TC544) . I have set P = 5 / I = 0 / D = 3.

System get long time to stable at my set point. How to reduce that time?


texts: Consider the NPN BJT. Normally, if you want to use it as a diode, you short base to collector and treat the emitter as the cathode. But in principle, you could also use the base emitter junction by itself (collector floating), or even the base collector junction (emitter floating). I guess you could even tie the emitter and base together and treat the collector as the cathode. What would the properties be of these diodes? Anything that might be useful in special circumstances?


texts: Difference between I2C STM32 HAL functions

texts: I'm using I2C in a project on STM32, and i was wondering what's the difference between HAL_I2C_Master_Transmit and HAL_I2C_mem_write, and the difference between HAL_I2C_Master_Receive and HAL_I2C_mem_read.