texts: Approximate Capacitance of a Multilayer Solenoid Coil

texts:
I'm interested in an expression for the capacitance or resonant frequency of a Helmholtz like coil (the windings are parallel to the plane of the coil) of circular or square cross section and of the order 1 meter in diameter with between around 10 to 100 turns.

I can find numerous approximations for the inductance of such coils, but I can't seem to find any approximations of capacitance.

I suppose this will vary wildly based on the winding technique and frequency, but I'd be interested in any expressions for this.

This answer contains an expression for the capacitance of a single layer solenoid which is almost what I need.


texts: How safe is a Y USB cable where none of the two types of wires intersect?

texts:
I've read that one of the dangers of Y USB cords (if the two Y ends are attached to different devices) is that electricity could go the wrong way, frying a device.

So, in my case, I have the following issue. My Raspberry Pi doesn't have enough power to run itself and power an external hard drive, so what I was thinking of doing, is connect the Red and Black wires exclusively to the charger end, and the white and green wires exclusively to the Raspberry end.

Would this be safe? Do the Data wires and Power wires cross anywhere?


texts: Earthing when two objects need to be earthed

texts:
I recently bought a ‘Push To WAIT’ unit from the Highways Agency. It has a transformer that converts 240V to 48V which goes to the unit.
The trouble is, the transformer and the Push to wait Unit both have earth wires on them, but I can't figure out how to earth these properly (without harming myself.)
I understand that the transformer earth Wire has to go into the plug socket but where do I earth the actual unit to?


texts: Car interior light with multiple "triggers" - 12V DC power

texts:
trying to add some lighting in the foot wells and under the seats in my car so that when someone drops something down there in the dark, it's not something that (at least not every time) requires pulling over and grabbing a flashlight to see. LED strips are cheap as chips, so my thought is I would just tap a 12V power supply, but then thought about it more, and technically I would want these on in 2 cases:

1) If the headlights are on (would only have power while the car was running; essentially: if the dashboard is backlit, the foot wells should be lit as well)

2) If a the dome lighting that corresponds to whatever area is on (in my car, there's a light in front, and another in the back, so if you open the front door, I'd want the front foot wells lit; open a back door, light the under-seat lights)

I am able to put stuff together once provided with an example, and assume I need some type of switching device to make it so I'm not turning on dashboard lights when I open the door / blowing anything up, but, as of yet, haven't figured out what to do there. Any input would be helpful.


texts: Shouldn't the small AC input current in a common emitter amplifier be amplified to DC?

texts:
The following image is the circuit of a common emitter amplifier.

The input AC circuit we supply is between the base and emitter. The supplied input is amplified as it can be seen in the image (though the amplified image should be out of phase with respect to input signal).

My question is that as we have supplied the input between base and emitter (which makes a diode actually) then why doesn't the rectification of input current takes place? Shouldn't the output current be direct current (DC)?


texts: Any Home Made Alternatives to using X-rays to identify ICs?

texts:
I am on the hunt for several ICs by searching for the markings on them. But sometimes the markings are just too vague and I cannot really guarantee that the IC I found is the IC I am looking for. I know that some manufacturers place a logo or something equivalent on the die itself, and that it is possible to x-ray the package in order to see the bare die.

My question is, is there any home-made (preferably cheap) alternative to the x-ray method?


texts: To control motor : 1phase, 230 V brushless, via RaspberryPi

texts:
Is there any preferable or possible way (i am still recognizing the borders),

To have set of equipment, where we would have 1phase, 230 V brushless electrical motor, (with the ventilator on the shaft), which speed would be controlled through RaspberryPi, (not through VFD?)

A design based on SSR (with zeroTime OptoCoupler + Triac) + additional OptoCoupler for security of 5 V pins.

It seems that:

Universal Motor may work (but here we have loud brushes)
Split-phase capacitor motor
This one can work with relays + properly counted capacitor
Split-phase motor
Shaded-Pole motor
Those are probably not controllable without Autotransformator

What kind of engine would be my dreamed (Induction?) sollution, what are limitations of such solutions?

maybe a

A brushless motor is constructed to be a synchronous machine, but the rotating field is timed to match the position of the rotor to generate torque.?

from What does "Brushless DC is an AC induction motor with built-in speed feedback" mean?

is that possible?


texts:
I have M inputs. I want to connect m of them to Vdd and leave other nodes floating. I know that in real experiments the floating nodes can get any value between 0 and Vdd.
I was wondering how HSPICE will consider those nodes. Will HSPICE automatically connects these nodes to 0/Vdd/...?


texts: Altium mechanical layers not showing up in layer selection

texts:
edit: I'm dumb I realized I could just press "l" and manually add in the mechanical layers I need
I have a few .PcbLib documents, and all but one of them I am able to select lines, polygons, extrusions, etc and set them to any layer I want with no problem. In this last document, when I select the "layer" menu under properties it only allows me to select mechanical1. The other options are not there.
Here is a picture of one of the files that works:

And here is a picture of the issue in question:

Is this a setting that I changed on accident? All of my other .PcbLib files do not have this issue.
(I am using a 3D model as an example because it only shows mechanical layers but other things like lines and pads also only show mechanical 1)
Thanks!


texts: TE Shrack miniature relay datasheet confusion

texts:
This relay (TE part number 1393219-3) datasheet has the following drawings in it (below). I am trying to make PCB footprint for it, and having issues with dimensioning.

Length = 20 mm max

Footprint length = 7*2.5 mm + 2*1.4mm = 20.3 mm

It appears that minimal length using footprint drawing is bigger than maximal length on the overall dimensioning drawing.

Second, relay's pins are rigid, and at the distance of 7*(2.54-2.5)=0.28 mm, and, per my experience, it may simply not insert properly. So where's the dimensioning slack here? No pin thickness in the datasheet.

Or maybe this document is NOT a datasheet, but marketing booklet?

Update: I put garbage information into registration window, and downloaded the .scr (script) file for EAGLE 6 (thanks @jsotola). First, why script as it (potentially) can be harmful? Next, created device is a sh*t.

Is it a modern trend not to make proper datasheet but forcing users downloading questionable files not being formal document, and rely on tools to properly executing the script?

And now I have to redraw this sh*t instead of creating thought device at once.


texts: Using WiFi Antenna for 5G Mobile Network?

texts:
I moved to an apartment located in a basement of a complex. I had to build a setup with a set of 2 external LTE (4G) antennas

Wilson Electronics Wideband Directional Antenna 700-2700 MHz
Wilson Electronics 4G Omni Residential Antenna 700-2700 MHz

And 2 Industrial Pepwave LTE routers from Peplink.
I would like to upgrade at least one of them to 5G. I borrowed a "Huawei 5G CPE Pro H112-372" from a friend to test the Internet speed at my place, from outside, speeds are decent.
After connecting the router to my external antenna through a SMA-to-TS9 convertor and testing, results were horrible.
After more research, the datasheet for the H112-372 specifies the used 5G bands "5G: n41/ n77/ n78/ n79"
Where the corresponding frequencies in MHz are as follows:

n41: 2496 – 2690
n77: 3300 – 4200
n78: 3300 – 3800
n79: 4400 – 5000

This is obviously outside the range of my current antennas.
Currently there doesn't seem to be a lot of 5G antennas on the market, some are marketed as 5G ready like the Peplink "IP68 Omnidirectional LTE/GPS Antenna" with "Super Wideband 690-3800 MHz LTE" a very promising solution to my case, minus the "n79" band. Of course we are talking about sub 6 GHz bands here only.
As for the use of a WiFi antenna, there are some posts asking a similar question but for 3G/LTE (4G).
I know that the used frequencies can range from 700MHz up to 2700 MHz depending on country and licensing of bands for both 3G and LTE (4G). So working with WiFi antennas depends on used frequencies.
I had a friend who used to work for a telecom company and he said they used to reallocate their licensed spectrum between different technologies.
If a WiFi antenna is designed to cater for a specific narrow band at 2.4 Ghz and 5 GHz, then this is not a good option.
But as per "IEEE 802.11y-2008" WiFi can be available as a licensed band at 3.65 GHz. Are there special antennas for these frequencies or they use the same WiFi antennas as everyone else?
If WiFi antennas are wide band antennas covering the range between 2.4 GHz up to 5 GHz, then can they be used for 5G mobile networks or not?
Notes:
5G features phased array antennas as a part of the technology to increase speed and efficiency. Obviously using an omnidirectional antenna wouldn't be as good as the complex internal router antenna at this stage.


texts: Cortex M0 - Defining an interrupt routine in assembly

texts:
For a project I have some code that needs to be written in assembly due to precise timing requirements. I'd ideally like to implement my code in a timer interrupt routine. Right now, in C++ I can define an ISR as such:
extern "C" void TIM3_IRQHandler(void)
{
//code here
}

I'm using an STM32F030 chip, which from the datasheet shows that the Timer3 IRQ address is 0x00000080. My understanding is that there is an address stored at this location that marks the start of the interrupt handler.
How do I change the address at the above entry to point to the start address of my assembly code so that I can handle the interrupt in assembly? I know I can technically put inline assembly within the C function above, but there must be a way to handle the interrupt entirely in assembly.
I should note that I'm using the GNU ARM toolchain


texts: Are LCD/Plasma/Smartphone monitors susceptible to EMR eavesdropping?

texts:
Having just read about EMRTempest eavesdropping; I find myself wondering whether

EMR eavesdropping is defeated by FCC regulations on interference
With the advance of technology from CRT to the newer LCD/Plasma monitors, hand-held devices/tablets equipped with a touch-screen and such are as susceptible to EMR eavesdropping as the old CRT monitors.

Thoughts, please?


texts: SiC inverter design w/ STM32 - high switching frequency

texts:
I am designing a SiC inverter using a 72MHz STM32F302CC with the STM32 motor control library. The desired switching frequency is 50-100kHz, depending on the device we select.

Reading the motor control manual, I discovered that "the FOC loop is... executed at the PWM frequency rate (That is: once every PWM Period)." Will I encounter any issues with the complex FOC loop executing so quickly on a 72MHz processor? The only extra processing I plan on doing is some simple state machine logic, receiving torque command CAN messages and sending status CAN messages.

I'm looking into using the STGAP1AS gate driver. Is 100kHz PWM output feasible considering reasonable parasitics? I understand that the typical MCU I/O pin capacitance is 5pF, the gate driver's input should be high impedance (but I can't confirm this in the datasheet), and the MCU and gate driver will reside relatively close on the same PCB.

I am using an STM32F302 because all my other sub-systems use it, but am not opposed to upgrading if necessary to meet the 50-100kHz switching frequency requirement.


texts: What would a voltmeter measure if you had an electromotive force generated by a changing magnetic field?

texts:
Suppose I had a circuit of this sort, and there was a changing magnetic field through the central triangle:

Faraday's law suggests there will be a voltage through the loop.
The voltmeter is supposed to measure the voltage but there is no notion of voltage potential in the case of the induced field because the field is no longer conservative, so really what is it that the voltmeter measures?
Addendum: Thanks to the answer of Math Keeps me Busy, I learned of the youtube 'war' (it is called drama, but seeing how people behaved it was more like war for me) between MIT professor Walter Lewin and electroboom. I've read through both sides but I still can not come to a definite conclusion on what the voltmeter would measure.


texts: Is the following 8085-based design I/O mapped or memory mapped?

texts:
The above picture is an 8085-based system schematic used for undergrad courses at the laboratory. Now at first sight it seems that the 8085 in the circuit is isolated mapped IO since it uses the IO/M' signal, but when we are enabling IO/M' to write/read, the lines determining I/O ports are A11 and A12 (Where based on 8085 configurations we should only use AD0 to AD7 for determining I/O port). It is also not memory mapped because we are actively using the IO/M' signal.
My question is that is there something wrong with this circuit or if not how exactly is it operating and how can we write in the output ports?
Please consider that the synthesized circuit based on this schematic has been used in the laboratory. I am not completely sure if this exact design was used but it shouldn't differ that much.


texts: Driving power LED modules in microsecond regime

texts:
I am looking for the best solution to switch LED modules on and off at high speed.

There will be 22-24 LED modules of different wavelenghts (UV, white, r, g, b, [...]) with 350 mA forward current (or maybe less, haven't decided yet - the goal is to assure the luminous flux of 1000 lm or more).
They should be switched in a specific sequence, making sure that when one is on, the rest is dimmed.
The on time (actual light emitting) should be in order of microseconds (10-50 ms) but faster will also be OK.

Microcontroller (ARM in this case) will put LED modules in on or off state according to the sequence that can be altered in every moment.
LED module should act as a various color flashes - this is actually the purpose of the project - high speed camera will be triggered each time the color changes, so it will capture the same scene illuminated in all of 22-24 light wavelenghts.

Entire system will be placed on the autonomously operated robotic platform going at the speed of around 1 m/s.
I should also add that size is also a concern, as it will be limited space to fit everything inside.

Do you have any idea how to solve this?

PS It's from my school project that I have not only do in theory, but also practically.

PPS I went through thousands datasheets and couldn't find anything - the closest being drivers for optical communication that are really fast, but they switch only about 100 mA and output 5 V that is not enough in my case.

PPPS I also read two similar topics on stackexchenge, but they didn't help.

EDIT:
(Jack Creasey) What I meant by "LED modules" was not a single component - I just need to somehow achieve 1000 lm (I'll explain why late) - I do not mind using array of multiple LEDs, this was actually my initial idea.

(jonk) The subject is "light source triggering system" - this is for real life application that is currently under development.
The robotic platform will be used to autonomously explore caves that have no daylight access, and are also not accessible for humans.
One of the objectives is to collect geological data (mineral composition of the caves) - this will be done by taking multiple photos of cave walls while platform is in a constant movement. Each frame will be captured while being lit by various wavelength light sources (let's say we fire the white light and take a photo, then the red one and a photo again, yellow - photo, blue - photo, etc.). In total - around 22-24 photos of the same (not counting the slight movement of the platform in between captures). Later analysis will result in a absorbance-transmittance values for wavelenghts used - this will allow to tell if there is any valuable mineral in a cave.


texts: I am using a hair dryer to increase oxygen/air levels in a torch assembly for a forge for metal work. I need to be able to increase/decrease the fan motor speed smoothly and more precisely than the low/high setting. I have a fundamental understanding of electronics and some background in the basics of different electronic components such as resistors, capacitors, diodes etc. It would appear high/low setting simply bypasses or does not bypass a diode limiting negative energy cycles thus roughly halving the speed of the fan motor when the diode is in the circuit blocking negative AC pulses. Is there a way to insert a component into the circuit which would limit the power going to the fan motor and thus reduce the motor speed?


texts: Why this simple DC Motor + PWM circuit is not working?

texts:
I have the following circuit to adjust the speed of a DC motor based on PWM signal (Arduino, 5V) applied to the base of a BJT transistor, but it's not working. The motor doesn't move but I do hear a faint of buzzing sound from the inside.

The PWM is working just fine, I tested it out with an LED + current limiting resistor. The motor works OK when I make a short between transistor's collector and emitter.

Anybody knows what's the problem with the circuit? How can I fix this?

EDIT:

Q1 is an NPN BC547 transistor.
PWM signal comes from a 5V pin of an Arduino board.
Please check the 9V motor's spec here.


texts:
I have a quick question.

I was wondering about the order of cross correlation of two signals.
Suppose there are two correlated signals. \$y(t)\$ and \$e(t)\$.

Does the following expression hold?

\$R_{ye}(-1) = R_{ey}(1)\$

Which is equivalent to:

\$\bar{E}(y(t)e(t+1))=\bar{E}(e(t)y(t-1))\$

Thanks very much in advance,

Mike


texts: What causes 100Hz spuriour emissions on AD9850 WSPR transmitter?

texts:
I've built WSPR transmitter based on AD9850.
AD9850 is driven by 125 MHz crystal. TX frequency is 14 Mhz.
On the receive side there is upconverter (+125 MHZ crystal) and SDR (both RTL-SDR and AirSpy). Both SDRs show the same 100Hz spurious emissions.

What is the source of these emissions? Is it coming from upconverter or from AD9850?


texts: Does NOR flash have better life span than NAND?

texts:
I wanted to know which one has better life span, NAND or NOR flash and what is the reason? By life span I mean the number of erase cycles allowed per block.

I read in the link https://en.wikipedia.org/wiki/Flash_memory that the endurance of NOR for SLC is much greater than NAND SLC, more than 10x. Endurance is the meausure of the number of P/E cycles allowed. Now if NOR has higher endurance, then does that mean NOR has better life span than NAND?


texts:
I am using MAX485 chip for serial communication. But a weird behavior I found which I can not explain.
Can any one help me in understanding why LED is ON in Receiver pin (RO) when I have not given any serial data from pin A and B? As per my understating LED should be always OFF as there is no data connection.

simulate this circuit – Schematic created using CircuitLab
In above circuit, I have just switched on my MAX485 board by connecting source on Vcc and GND
no data pins A and B are connected. And RE is connected with GND to turn board in receiver mode.
So ideally RO should always be off due to no data.
Thanks


texts: Methods/sensors for making a "smart floor" to detect human presence via floor?

texts:
I am looking into making a "smart floor" that can detect when someone steps down onto it. I have done some research and found that the most commonly used sensors are 1) Pressure sensitive floor tiles 2) Electric Field sensors and 3) Vibration sensors.

The pressure sensitive tiles are pretty obvious but i'm not sure what sensors they are using. do they mean piezoelectric floor tiles? I haven't really been able to find help on how i would build one or if there are any commercially available to purchase where i can go to buy them

The Electric field sensors work by measuring changes in electric field when someone is present in the room. I am not sure exactly how but from what i read it seems like you are just stepping on a parallel plate capacitor and measuring the change in the capacitance to determine the amount of pressure.

Vibration sensors came up in my research and i assume they used microphones to detect the peoples steps.

The application:
It will need to detect the presence of a person (and preferably location in the room, but not strictly necessary). It can (hopefully) detect more than one person and estimate how many people are in the room. It's main purpose will be at night where there will be less people walking through the room and people walking less frequently. The room is not huge but not tiny either, probably the size of a typical bedroom. The floor is hard, like marble.

I don't have a set budget but i do want to keep it somewhat reasonable, obviously.


texts: Connect inputs of SN74LS08N to output of other TTL chips

texts: I have a project in which I am making an 8-bit computer from TTL chips, I am using some SN74LS08N AND gates in the ALU. I know to set an input to HIGH, you must leave it unconnected, but for LOW, it must be connected to ground. How can I control the input of an AND gate with the output of an SN74LS32N OR gate? I don't think I can use an inverter for this, because the inputs of that would require the same problem, I think.


texts: How can capacitance values be determined from a cyclic voltammogram?

texts:
I am reading an article (Khomenko, Electrochimica Acta 2005, 50, 2499-2506) that investigates the capacitance of carbon-based electrodes for use in supercapacitors.  In particular, they use cyclic voltammetry (CV) to determine two types of electrodes (a PPy/MWNTs electrode, Figure 3, and a PANI/MWNTs electrode, Figure 4):

From these CV plots, the authors determine the capacitance values of each electrode:

The capacitance value was obtained from the CV curves according to the equation \$C = \frac{i}{s}\$ where \$i\$ is the average current and \$s\$ is the potential sweep rate. According to this formula, the cathodic charge determined by integration of the negative sweep of the CV curves is very high for such electrodes. The capacitance is \$670 \text{ F/g}\$ and \$506 \text{ F/g}\$ of electrode for the PANI and PPy composite electrodes, respectively.

I have a few questions about this method:

Why do the authors say that "the cathodic charge determined by integration of the negative sweep of the CV curves is very high"?  Why do they refer to the cathodic charge, rather than the anodic charge?
What is meant by the average current \$i\$?  What sort of average is meant?  Do they mean consider a single sweep (either the part of the CV curve in which \$E\$ goes from negative to positive, or the part of the CV curve in which \$E\$ goes from positive to negative), and then integrate this sweep to find the average \$I\$?  Recall from calculus that the average value of a function \$f(x)\$ in the interval \$a \leq x \leq b\$ is given by \$\bar{f} = \frac{1}{b-a} \int_a^b f(x) \; dx\$.  Then does this mean that $$i = \frac{1}{\text{0.4 V } - \text{ -0.8 V}} \int_{\text{-0.8 V}}^{\text{0.4 V}} I(E) \; dE \;\;\;\;\text{ for the (-) to (+) voltage direction}$$ or $$i = \frac{1}{\text{ -0.8 V } - \text{ 0.4 V}} \int_{\text{0.4 V}}^{\text{-0.8 V}} I(E) \; dE \;\;\;\;\text{ for the (+) to (-) voltage direction}$$?


texts: Besides address is there other limit on max nodes via RS485 Modbus-RTU

texts:
Since there is 1byte for nodes' address in Modbus frame, the limit should be around 256.But some say there is some limit on this scenario (RS485, Modbus-RTU) base on chips and wire.

Chips support 32 nodes:SN75176,SN75276,SN75179,SN75180,MAX485,MAX488,MAX490
Chips support 64 nodes: SN75LBC184
Chips support 128 nodes:MAX487,MAX1487
Chips support 256 nodes:MAX1482,MAX1483,MAX3080～MAX3089

Are there other limits on this?Like reserved addresses as routine?


texts:
I'm looking at prototyping a design I plan to build using logisim.  The design will make use of a FIFO IC (74HC40105) as a buffer between a data producer process and a data consumer process.  I can't seem to see a reasonable way of building the behaviour of the FIFO out of the basic components that logisim provides, however.

A shift register isn't quite right, because that requires the data to be fed in in advance to fill the buffer, whereas with the FIFO the data is available at the output after the first item is added; I don't need to wait for it to propagate through all the stages.

I considered simulating it using a RAM and read and write pointers to a circular buffer, but the downside with that is that (as noted in the description of this project which used the approach) you can't both shift in and out on the same cycle, which is because logisim's RAM only has a single address port, so can't handle true dual port simultaneous read and write (you could implement one this way in an FPGA, for example, because they usually support dual port RAMs).

Is there another way I haven't considered that would make it possible to implement a FIFO that lets both the data producer and consumer operate entirely independently in logisim?


texts: How to set priority in priority encoder?

texts: If I have four inputs D0, D1, D2 and D3 and I want to give priority to D2, then how would I design with my priority encoder? Similarly if my priority is D1 then what should I do?


texts: Strange behavior of a Colpitts Oscillator

texts:
simulate this circuit – Schematic created using CircuitLab

I've built this schematic from this link (parallel tuned colpitts VCO), and changed it up a bit for my frequencies/components at hand. I temporarily replaced the varactor with a trimmer cap for tuning purposes and to check if the schematic actually works. I had to increase C3 value dramatically, since otherwise the oscillations wouldn't start at all.

The tank circuit values right now are such that it should produce frequencies somewhere around 30 MHz. (If a trimmer is at 20pF than the combined capacitance is 22 pf, and the frequency is 33.9 MHz, according to this calculator). However when probed with the oscilloscope the output frequency is always close to 12 MHz (from 11.5 to 13 MHz). I say always because the frequency doesn't change much neither when I change the capacitance of the trimmer, nor when I solder in different value capacitors entirely, which I did several times.

I am not very familiar with high frequency circuits and it seems to me that something in the circuit acts like a capacitance in a tank circuit which I can not change. Changing C3 value doesn't change the frequency. Changing C1,C2 does neither however at some point the oscillations just stop. Could the internal capacitance of the transistor cause this behavior?

By the way the sine wave itself is not very clean either it is a bit slanted to the right and looks like the bottom part is cut off at the very end.

Can someone explain to me what might cause this strange behavior, and what can I do to solve the problem?


texts:
I have to calculate \$|I_L|\$ in this circuit (which is in the phasor domain and at sinusoidal regime).

simulate this circuit – Schematic created using CircuitLab

The given data is: \$I_g=2 mA\$,\$X_L=10\Omega\$ (in rms).

I did it this way: \$|I_L|=|I_g| |\frac{R}{R+X_L}|=1 mA\$, but the result gives \$\sqrt 2 mA\$. Why is that?

EDIT:

Actually I wasn't doing it with phasor method.

Here is the phasor diagram:

simulate this circuit

So \$|I_L|=\sqrt{I_g^2-I_R^2}\$, but what's \$I_R\$?


texts: Improve signal integrity of Ethernet signals (if indeed is needed)

texts:
Actually it is nothing to do with Ethernet specific, but just to be accurate, I have several SS-SMII Interface signals between an FPGA and a Switch. The interface has 8 data signals, one synchronization signal and a 125MHz clock for each direction. Due to EMC reasons I have inserted 22 Ohm series resistors on the transmitter side of each of the signals.

Unfortunately the board is still not compliant with the required CE Standards for radiated emissions and I am right now trying to improve it further. I have the feeling (after excluding other potential sources of radiation) that the problem lies with these signals.

One possibility I would like to explore is that of the signal integrity of the signals. For this reason I took some measurements with an active probe, making sure the ground loop is minimized.

Now for some wavforms. First a TXCLK signal from the Switch to the FPGA.

Right at the ball of the Switch (transmitter):

and then at the ball of the FPGA (receiver):

Then an RXCLK signal from the FPGA to the Switch.

At the ball of the FPGA (transmitter):

and at the ball of the switch (receiver):

The problem is I don't have the experience to evaluate the measurements myself...!

Some of my thoughts:

Is it normal that all the signals (or at least the mesurements show so) go down until around -400mV? I suppose not, right? What can I do to improve that?
The same as point 1. but for the upper part of the signals. They go up until around 4V (it clearly is a 3.3V Interface).
Is it normal that at the transmitter side of the TXCLK (see the first image above) the Signal looks so bad? What could be the reason for that?
Do I need a termination on the receiver side? Is it acceptable to put both a series resistor and a receiver side termination? I have only seen one of them but not both at the same time.


texts:
i have made simple inverter circuit with z44 MOSFET but circuit work for minutes and the primary coil start heating then shorting finally damage the MOSFETF, it is my 6th time facing this issue. i have no idea how to protect the MOSFET. Why this is happening and is there anything i have to improve ?
any idea would helpful
thanks!!

simulate this circuit – Schematic created using CircuitLab


texts: Mechanically damaged aluminium electrolyte capacitor - is it very toxic?

texts:
I mechanically opened a aluminium electrolyte capacitor and I am afraid now if anything could happen to me.

Can somebody help me please?


texts: stm32f103 - 16 bit mode SPI reading returns 0xFFFF

texts:
I am working with a sensor which communicates through SPI. I am

trying to read MISO line, but it returns 0xFFFF. first I send 0xC000 on

MOSI and the sensor places 0x0032 on MISO. I read MISO using oscilloscope,

but in code, this value is 0xFFFF. I tried to send dummy data but nothing

changed. here is my code:

#include "stm32f10x_spi.h"
#include "delay.h"

#define SPIx_RCC      RCC_APB2Periph_SPI1
#define SPIx          SPI1
#define SPI_GPIO_RCC  RCC_APB2Periph_GPIOA
#define SPI_GPIO      GPIOA
#define SPI_PIN_MOSI  GPIO_Pin_7
#define SPI_PIN_MISO  GPIO_Pin_6
#define SPI_PIN_SCK   GPIO_Pin_5
#define SPI_PIN_SS    GPIO_Pin_4

uint16_t data;

SPI_InitTypeDef SPI_InitStructure;
GPIO_InitTypeDef GPIO_InitStruct;
int main(void)
{
RCC_APB2PeriphClockCmd(SPIx_RCC, ENABLE);
SPI_InitStructure.SPI_Mode=SPI_Mode_Master;
SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge;
SPI_InitStructure.SPI_CPOL = SPI_CPOL_High;
SPI_InitStructure.SPI_DataSize = SPI_DataSize_16b;
SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
SPI_InitStructure.SPI_BaudRatePrescaler=SPI_BaudRatePrescaler_256;
SPI_InitStructure.SPI_NSS=SPI_NSS_Soft | SPI_NSSInternalSoft_Set;
SPI_Init(SPI1, &SPI_InitStructure);
SPI_Cmd(SPIx, ENABLE);

  RCC_APB2PeriphClockCmd(SPI_GPIO_RCC, ENABLE);
// GPIO pins for MOSI, MISO, and SCK
GPIO_InitStruct.GPIO_Pin = SPI_PIN_MOSI | SPI_PIN_MISO | SPI_PIN_SCK;
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(SPI_GPIO, &GPIO_InitStruct);

  GPIO_InitStruct.GPIO_Pin = SPI_PIN_SS;
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_Out_PP;
GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(SPI_GPIO, &GPIO_InitStruct);

RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOB, ENABLE );
GPIO_InitStruct.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_2 | GPIO_Pin_3 | GPIO_Pin_4 | GPIO_Pin_5 | GPIO_Pin_6 | GPIO_Pin_7 | GPIO_Pin_8 | GPIO_Pin_9 | GPIO_Pin_10 | GPIO_Pin_11 | GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_Out_PP;
GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOB, &GPIO_InitStruct);

while(1){
    SPI_GPIO->BRR = SPI_PIN_SS;
    SPI_I2S_SendData(SPIx, 0x4B01);
    while (!(SPIx->SR & (SPI_I2S_FLAG_TXE)));
    SPI_GPIO->BSRR = SPI_PIN_SS;
    // delay for applying setting stably
    delay_ms(2);
    SPI_GPIO->BRR = SPI_PIN_SS;
    SPI_I2S_SendData(SPIx, 0x4C00);
    while (!(SPIx->SR & (SPI_I2S_FLAG_TXE)));
    //while (SPIx->SR & (SPI_I2S_FLAG_BSY));
    SPI_GPIO->BSRR = SPI_PIN_SS;
    delay_ms(2);

    SPI_GPIO->BRR = SPI_PIN_SS;
    SPI_I2S_SendData(SPIx, 0xC000);
    //SPI_I2S_SendData(SPIx, 0x8000);
    while (!(SPIx->SR & (SPI_I2S_FLAG_TXE)));
    while (!(SPIx->SR & (SPI_I2S_FLAG_RXNE)));
    data=SPI_I2S_ReceiveData(SPIx);
    // data is always 0xffff which should be 0x0032
    SPI_GPIO->BSRR = SPI_PIN_SS;
    delay_ms(1);
    }}

Thanks.


texts:
By using PWM I have converted some signal to pulses and inserted it into transfer function of 2/(0.01*s+1)

I then compared between the result of the original output and the output after using PWM (blue line is the original output and the yellow is due to PWM):

It can be seen that the output from the PWM is chattering.

The Simulink model looks as following:

The triangle is made by using the following points:
(0,0.5) , (0.0025,0) , (0.0075,1) , (0.01,0.5)

Also, by increasing the frequency of the sine wave the result seems to be better:

Is there some way to make it with smaller standard deviation for the results?

Thank you.


texts: What's a better way to integrate an ODE for one time-step than the Euler method?

texts:
I'm simulating a simple cart-pendulum system for purposes of testing different control strategies and data-driven approaches.  I need to simulate the dynamical system one time-step at a time.

I'm trying to make the simulation as realistic as possible (non-linear, with disturbances and noise etc.)

At the moment I'm just using the Euler method:

y_dot = cartpend_dydt(t, y)

# Simple state update (Euler method)
y += tau*y_dot

where y_dot is the time-derivative of y, the state-vector (length 4) and tau is the time-step.

Since it's a very fast calculation I can run at 50 steps/second and so I'm sure Euler method is accurate enough.

But what if I want to reduce the sample efficiency to say 10 steps/second (more typical real-world scenario)?

Then I assume I should do something more accurate (and a bit more computationally expensive) each time step.  But what's 'the next step up' from Euler?

I tried using a numerical integrator (in Python):

from scipy.integrate import solve_ivp

sol = solve_ivp(cartpend_dydt, [t, t + tau], y)
y = sol.y[:, 1]

where cartpend_dydt(t, y) is a function that returns the time derivative of y.

I think scipy.integrate.solve_ivp is an "explicit Runge-Kutta method of order 5(4)" by default.

But is this over-kill for a relatively short time-step?  Is there a simpler method that would be better than Euler but not too computationally intensive?


texts:
I have a Carson Reflex Wheel remote control for my RC car.
It has two potentiometers, one for accelerating and one for steering.

My goal is to control the RC Car from my PC by sending commands via the serial connection to the arduino.

I would like to unplug the potentiometers and put the pins (in the white box -> see image) on two Arduino pins so the Arduino can control the remote control. This would exclude the potentiometers from the circuit and make the arduino kind of replace them.

The remote control operates at 12V.

The two potentiometers are connected with the black red yellow wires.

What circuit do I have to use between the pins (in the white box -> see picture) of the remote control and the Arduino?

UPDATE: I recently got a multimeter.
The voltage between the yellow and black pins is 5V (constant).
Between the other pins there is no voltage unless the potmeter is connected.
In this case the voltage between black and red varies from -4.9 (left), -2.9 (center) to -0.4 (right).
Between red and yellow it's 0 (left), -2 (center) and -4.4 (right).
(depending on the position of the steering wheel)


texts: Snap-lock connector part identification?

texts:
I'm currently working on a design that requires connection to a peripheral with a snap-lock interface. The part I need on the design is the male 'button' style contact found on electrodes such as those shown below. Ideally I'm looking for a surface mount part equivalent to that connection, however a name of the technology or anything that can point me in the right direction would be greatly appreciated.

The other half of the connector (the 'socket' that mates with the 'button') can be found on cables like the ones below typically.

The only reference to the connectors themselves I can find is that they are "sewing snap buttons size 3", but I am looking for a professional solderable electrical equivalent (although I'm sure the sewing versions would probably work fine, I think the BOM may look a little strange to my colleagues...).

Any information that can be found would be greatly appreciated!


texts: How to measure the torque (of a stepper motor) with a (belt) drive accurately?

texts:
I have a project that requires really accurate torque measurement of a motor or a motor + a belt drive. How do I do that?

I am guessing that measuring current through a stepper motor is is proportional to the torque? How about when there is a belt drive attached? There is some resistance in the belt and the output torque drops.

I accurate I can go? Is it possible to get into micro Newton meter (uNm) region. Assuming that I have a quality stepper motor, quality parts and I know what I am doing (well, I know a guy...).

An example of parts would be nice or commercial products or something to kickstart the project. This is related to this question:

How to achieve very accurate/fine rotation with motor

but with accurate torque measurement.

P.S. other drives than belt drives could work also. I have no experience on harmonic drives so I don't know if they are good or bad for this project.


texts: Make a double-tapping button (ideally without ICs or keeping ICs to a minimum) for a small "tiny cell" powered device

texts:
Conditions:
small device, extremely space constrained (large caps are a no-go)

Powered by a small battery (something like under 120 mah)

Thus, adding a few more ICs like the 555 or "TimeBlox LTC6992" is not desirable

Currently have:

A normal mechanical button that completes a circuit when pressed, and disconnects on release.

+2v, currents  below 5 mA

Needed:

to execute a second short (200ms +/- 50ms) "pulse" when the button is released , but not instantly (after a delay of 150 +/- ~50 milliseconds, effectively producing a fast double-tap on every press-release cycle)

I realize it could be done using a latch IC like MAX16054 and a XOR and several delays... but, once again, space and power constraints make that suboptimal.

Question: is there a way to achieve the double-tap effect keeping additional ICs to a minimum?

P.S.:
While I do realize that a dedicated double-tapper microcontroller may be a good idea (and am interested to hear which microcontroller would be best to use here), I am curious to learn whether there are other, non-microcontroller clever solutions to this


texts:
It seems easy to add teardrops for connections in Altium. But in my design, after adding teardrops, it throwing errors which indicating the 'teardrops' violate my clearance constraint such as:

  Clearance Constraint: (0.144mm < 0.2mm) Between Pad
  U16-A13(65mm,52.6mm) on L1 And Region (0 hole(s)) L1

Won't Altium resize the teardrop size according to the clearance rules? How to solve this problem?


texts: Modelling current to remain in particular range for fixed simulation time

texts:
I am a novice in SystemVerilog. I wish to know how to model a 8-bit signal X to attain four levels for certain ranges of time. For example,let the legal values of X be from 40 to 80(40 < X < 80)

40 - X - 50  for 70% of simulation time   : State 1
50 - X - 60  for 10% of simulation time   : State 2
60 - X - 70  for 10% of simulation time   : State 3
70 - X - 80  for 10% of simulation time   : State 4


texts:
EE.SE

I'm working on a amature high power rocketry project, in which a 4 inch rocket with multiple tracking systems and igniters are used to deploy chutes and ignite a  second stage. Traditionally, we run wires from screw terminals down to igniters. This works, but is difficult to integrate, and wires can break under the shock and vibe. (This Japanese rocket project broke last year likely due to a wire failure)

We are currently using ESP8266 modules connected to temperature and strain gauge sensors to collect structural data about the rocket. This works, but these sensors are not mission critical.

We would like to move to a wireless system linking the several avionics bays, altimeters, sensors, charges, etc. However, this thing is a safety hazard if it fails, and so we need to evaluate the reliability of this.

Does anything have experience with high reliability short range RF systems? Is the ESP8266 a valid choice, or should we be using something like 433Mhz? (our current air<->ground RF link).

Thanks for the feedback. Also feel free to brainstorm, as anything we decide on will go through lots of review before it ever sees the light of day.

Thanks

Tim

Edit: Clarification
This is not a question of long range communication between the rocket and the ground, that is already handled. This is a matter of communication between the altimeter electronics and various other components in the same airframe. I dont think bit error rate is really the  issue in this case (correct me if I'm wrong). The proposed ESP8266 system has a strong link and has never failed for the sensors. the issues is how to qualify a system to not fail for a more important role.


texts: Do BAD capacitors work less in the cold?

texts:
This might seem a very strange question and I'll try and not make this about fixing my damn faulty TV but I will give you the history in why I'm asking.

I have a faulty TV and it repeatedly turns on and off, but after clicking for about 20-30mins, it turns on and continues to work until turned off for at least 1hour, of which it'll do the clicking again.

DON'T LAUGH! ~ but this morning was very cold and I had to turn the heating RIGHT up for the damn thing to turn on! it was awful listening to my partner whine for 90mins

I have done lots of online research and found this to be a common problem with the brand and model that I have, all fingers seem to point to bad capacitors, looking at the capacitors they don't look bulged but it is my understanding they don't need to be after reading this question and answer already on the Electronics Stack.

Anyway... strangely the TV turns on within 5-10mins if the room is warm and even faster if the room is hot. I consulted with a repair guy and I never brought up the room temperature and he said if its clicking, then he uses a hair dryer on the main board and see if it turns on, if not he then repeats the process on the PSU...

I've never heard of this before but then again I don't know much, which brings me to the point!

Question(s):

Do BAD capacitors work better in warm climate?
If true... why?


texts:
I have a ~12 V battery (automotive, so VERY noisy) that I would like to measure the voltage of on an Atmega.  I'm wondering what would the most effective method to do that be?  An ADC that is ~12 V tolerant but communicates on 5 V logic power? Some sort of optocoupler to isolate the 12 V signal, then resistors to drop down to 5 V?

tl;dr: Have 5 V microcontroller, how to sense 12 V voltage from vehicle without frying the microcontroller if overvoltages occur.


texts:
I also posted this at All About Circuits but I thought I would get some more opinions as I'm quite worried.

I was using my power supply to power an electronics project (Super OSD.) The power supply is a TM035-3/GM035-3 0-3A 0-35V CC/CV power supply. When I turned the supply off, then on again, it made a little pop sound from inside and the RCD for the sockets tripped. (Lights remained.) It also blew the 5A mains input fuse. Obviously both safety features helped protect against a bad failure. After untripping the RCD and replacing the fuse, all is well - it still works perfectly fine. I am now a little concerned about how the power supply blew both the fuse and tripped the RCD! I have turned the supply on and off many times before. I am thinking inrush current but why only this time?


texts: How are these layers like LCD added in Altium Designer?

texts:
How are these layers like "LCD" added in Altium Designer?
My Altium version is 21.


texts: Are inductors usually hand-wound or bought pre-wound? For the former, how is the inductance measured? Is there some test instrument that can be used or is it done by measuring the length and radius (What about non-solenoid shapes?)? If it's the latter, where are they normally purchased? I've only ever seen choke coils being sold, in stores. I don't know if those are the same.


texts: I have encountered the word "interoperability" in many papers with regards to "microgrids". However, there are no clear explanation for it. What does it exactly mean?


texts: Trigger analysis for a Half Bridge Self oscillator

texts:
First of all, I'm sorry for bad English because I am not native. I am very interested to electronics self-oscillation.

I watched a video in youtube about a self-oscillator Half-Bridge Converter and I captured its schematic blow. 2 questions:

1- If the DC-voltage current (created by 4 diodes and 22micro capacitor) passes T2 transformer, how does it can produce a AC-voltage current in T2 secondary?

2- How does the trigger section work?


texts: Switched Mode Power Supply : Voltage Mode Control and Error Amplifier Output

texts:
I am trying to understand how regulation happens on Cycle-Cycle basis in the case of Voltage Mode Control (VMC) and Current Mode Control (CMC).

I understand that in the case of VMC, an error amplifier compares Vout of the power supply with a fixed reference (Vref) and generates an error output Vc. It is this Vc which then compared with a sawtooth waveform of fixed frequency resulting in PWM of varying duty cycle. To cut a long story short, Vc influences the duty cycle.

What exactly is the nature of Vc and how does it change?

Lets imagine that a power supply has Vin = 12V and Vout = 3V. Designer has wished that Vc = 1V when Vout = 3V. Yes, we are discussing a text-book buck.

Imagine the case when the load increases resulting in Vout falling to 2.1V. Vc must therefore rise. When Vc rises to e.g 1.5V, the duty cycle increases and consequently Vout rises again to 3V.

With Vout rising again to 3V, what will be the value of Vc now? Will it stay at 1.5V or will it fall back to 1V?

If Vc fell back to 1V, then Vout will always be hovering between 2.1V and 3V? Is this correct understanding? Is this the reason why VMC is deemed unsuitable for large load changes?

There is a compensation network on the output of op-amp error amplifier. What does it do?

I apologize but Kindly strive not to explain in terms of poles/zeroes, bode-plots, control theory, transfer functions etc. I have not reached a stage where I would be able to appreciate them.

My next question on CMC will follow once I have a better understanding of VMC.


texts: How to power a 6-12v Piezo siren from an Arduino?

texts:
We are trying to power a Piezo siren, which requires 6-12v, from an Arduino, which only outputs up to 5v. We are planning on using an external 9v battery to power the Piezo siren, although we do not know how to set this up.

How to power a 6-14v piezo from an Arduino?

We have a MOSFET IRF510 transistor instead of the 2n7000. Any help would be appreciated.


texts: Parameters of transformer: open-circuit test and short-circuit test

texts:
Ok I have the following circuit and data (when the subscript is "ef" it means "rms" values):

I am asked to determine the paramenters of the transformer r1 L11, L22 and LM with the given experimental data.

I had no problem extracting data from the open circuit experiment.
Using the fact that the active power is given by
$$P=r_1 I_{rms}^2$$

I found $$r_1=10 \Omega$$

Then applying induction law  in both primary and secondary leaves us with:

$$u_1(t)=r_1i_1(t)+L_{11}\frac{di_1(t)}{dt}$$
$$u_2(t)=-L_{M}\frac{di_1(t)}{dt}$$

Applying phasor notation and taking the rms values will lead us to obtain

$$L_M=\frac{U_{2_{rms}}}{\omega I_{1_{rms}} }=31.83 mH$$
$$L_{11}=\sqrt{(\frac{U_{1_{rms}}^2}{I_{1_{rms}}^2} - r_1^2) \frac{1}{\omega^2}}=55.13 mH$$

Ok and there is no more data we can extract form the open-circuit experiment.

Passing to the short-circuit experiment I will obtain from induction law again:

$$0=-L_{M}\frac{di_1(t)}{dt}-L_{22}\frac{di_2(t)}{dt}$$

Which leads to

$$L_{22}=\frac{L_M I_{1_{rms}}}{I_{2_{rms}} }$$

Problem now is I don't know the value of the root-mean square of current 2 and have no idea how to find it out.
My guess is that I need to use the reactive power. But how?
I know from Poynting complex theorem:

$$P_Q= 2\omega ((W_e)_{av} - (W_m)_{av})$$

But, and that is another question I have and would like to get ans answer on?
How should I apply this formula.
For the electrical energy, should I take the capacitor? But what's the voltage value? The same as the open-circuit experiment?
And for the magnetic energy? What inductances  should I consider? Do I need to calculate an equivalent circuit?

I'm really confused and would appreciate some help. Thanks!


texts: Identifiying and Cleaning leaked capacitor (which it was not)

texts:
I'm trying to fix a device that has a huge cap that leaked badly.

The leak is like molasses. Maybe thicker. And there is around 2 puddles of 2-3 teaspoons each.

I cannot clean the thing very well. So I can't read the specs on the cap so far. I am not sure if black was the original electrolytic (if it even is that) color or not. I also do not have the blueprints and the service manual i have is garbage.

So, the question is, if I do not find a way to read the marks on the cap, or if the marks are not useful for id, what is a good way to identify which fluid I am dealing with?

And what are common solvents for the most common fluids in a cap?

edit:

OK, this is a bust. I finally managed to pry trhu the black glue, and indeed, it is glue. as @DaveTweed mentioned.

When i removed the top cover, i was surprised to not find the explosion of goo inside. Instead, after removing the whole assembly, the back of the board, which is covered in glue for waterproofing (and unserviceability), had a crack and the black thing clearly oozed from that crack.

It was already solid. and the black part was mixed with the clear part, all around a burned out transformer.


texts:
The Li-Ion battery has 4 stages of charging :the initial trickle-charging to bring battery to Pre-charge stage, then constant current charging, then constant voltage charging(its like floating....right?) & final stage Top-up charge" .
Can anyone reply with the stages of charging for Li-Polymer ( iPhone use Li-Polymer), or suggest some link which explains about Li-polymer charging details.


texts: How does increasing the duration of the transient response become a problem?

texts:
I'm looking at the TI TPS727 LDO regulator datasheet and it says this:

  8.2.1.2 Transient Response

  As with any regulator, increasing the size of the output capacitor reduces over- and undershoot magnitude but increases duration of the transient response.

So the datasheet is saying it's detrimental to widen a transient spike or pulse, why is this?


texts: Lowering the voltage range of a variable DC bench power supply

texts: I've been shopping for components to build a bench-top DC power supply, much like the one built in Great Scott's video. I'm planning on using a LTC3780, which has an output voltage range around 0.8-30V and a current range around 0.8-6A. I would like this unit to be able to go to smaller current and voltage values in order to test small circuits (ie. 0-28V;0-5A), but I'm not sure what the right approach is. I thought about just using a resistor in series with the output lead, but from what I've read that that's not the way to go. Any help would be appreciated!


texts:
If i have a 4 input mux with the output being in the form of

S1 AND NOT(s0)

MY truth table therefore looks like the following (remember NOT(S0)).

S1   S0   X
0    0    0A
0    1    0B
1    0    1C
1    1    0D

Does that mean that the inputs have to be A=0 B =0 C=1 and D=0 in order for the output to be the above boolean equation?


texts: Deciding between USB and UART for interfacing with a Qt application

texts:
I'm planning on writing GUI application using Qt in C++ that would interface with the microcontroller. In other words, it would be taking user input and displaying something received from the MCU.
Questions:

does using UART over USB make sense? I have never used USB in this context but have used UART for a terminal-based embedded application before. I guess it's the speed that distinguishes them?

does cubemx generate the driver code for USB (I doubt it but still curious) or I'd have to write the driver myself?


texts:
I have developed a 48v -> 6v DCDC switching regulator using the LTC3810. It works well, except that there is some ringing on the output at each switch. You can see the 'scope trace on the picture. This measurement was taken across the input cap of the 3.3v regulator, approximately 30cm of wire away. I get one of these every 4us (250kHz). The amplitude looks to be about 200mv p-p. The ringing is bad enough to go right through the next regulator (another DCDC 6v -> 3.3v) and is causing problems with my EtherCAT transmission.

What is the best thing to do about this?  Should I try adding a little inductor or a resistor somewhere at the output? I already have a pretty massive output cap (5600uF).

Added:

I have tried adding ferrite beads, inductors and caps as suggested, but they did not help. I'm now trying a larger main inductor.


texts:
From what I understand a saturation for an BJT is when the B-E voltage doesnt change the collector current anymore. In other words, Saturation simply means that an increase in base current results in no (or very little) increase in collector current. However, the section for Saturation in the graph is when the current and voltage rise almost linearly together for a fixed base current. Isnt this contradicting? Shouldn't the slope be somewhat similar to the 'active region' and be flat?

I meant if we change B-E voltage, the collector still should be the same. Am I missing something here? Thanks


texts: What's your approach when making footprints from a drawing with relative dimensions?

texts:
I want to make a footprint for a mini USB connector. Here's the recommended layout from the datasheet:

I'm not very experienced with making footprints and find the dimensions inconvenient since they are all relative and not with respect to an origin.

My current plan is to choose the center of pin 1 as the origin and then work out the coordinates of the center of every pad using a pen and paper. This isn't going to be very efficient, though, and I'm wondering if there's a better way.

What would you use as your origin? What would your approach or process be when tackling a footprint like this?


texts: RFID Transponder transmission and reception working

texts:
I am reading about RFID systems and designs, and I stumbled upon this Digikey article.

I am really confused with Figure 5 in that article.

In the above IC diagram, I am really confused with pin 2, pin 4, pin 14. How do these three pins work?

How is the transmission TX from pin 2 and pin 4 happening? And how is the information at pin 14 received?

Doesn't pin 14 receive whatever pin 2 sends? - I agree when some passive RF Antenna is bought nearby, RX plays a role. But I am not clear on how this IC functions in proper operating conditions.

Request you to explain how the pins 2, 4 and 14 work during RF transmission and reception and how the values are selected.


texts:
I'm getting confused here about the sign of the V on the capacitor.

Why is it \$-I_0 \times R\$ and nor \$I_0 \times R\$?

note that the second circuit is at t=0+.


texts: Is a bad practice make variations on power's tracks width in pcb?

texts:
Its is about a circuit to source power and communicate with a car's key. I don't know exactly the current necessary, but I know that it is low, a few mA. The voltages are 5.5V and 3.3V.
The frequency of the signals are not high , a few units of KHz, something near 10kHz.

I would like to know if variation on tracks's width like the signalized in red on the figure below are very problematic. The signalized on the figure are GND, and VCC.


texts:
I am struggling with reading the datasheet for the STLED316S 7-segment/Discrete LED driver IC.
I'm writing code for an STM32 chip, but also using Arduinos as well.  I'm having no problems writing the code, but really struggling with interpreting the datasheet (apparently so are a number of other people according to a google search) to send the correct bits across the SPI interface.
Basically all I want to do is set the display to on, and then write in the value to the segments but I just don't really know where to start - is the data meant to be sent over one byte at a time, or strings of bytes? I'm not using the key interrupt at the moment, so fortunately that doesn't complicate too much.
The datasheet can be found here.
Any insight into this would be much appreciated.

Edit:
I think I may have made a little headway, but still don't think its correct.
Right, I think, although I could be horribly wrong, that I have it. No thanks to the datasheet, but fortunately another similar chip from ST (here) had a slightly better one with an example!
Okay, so:

STB LOW
Turn on display 00001101
STB HIGH
STB LOW
Configure 7-segment display 00100000
Set configuration 011111101 (Brightness 14/16, constant brightness, 6 digits in display)
STB HIGH
STB LOW
Define address 00100000 (LED 2/7)
Write bytes to turn on segments 11111110 (writes 8, no DP)
Write byte to turn on segments of LED 3/7 11111110
STB HIGH

I think it's what the datasheet is trying to say? The last 2 bytes go against what the datasheet says, but I don't really see any other way to write it... I think the rest is correct though.


texts:
We have two types of procedural blocks in verilog: initial and always block.
The statements inside these blocks are executed sequentially. Does that affect the timing of these signals? For example, in the code below:

initial begin
  a = 1'b0;
  b = 1'b1;
end

Will the assignment of b will take place a small time after the assignment of a?
If not what will be the difference between this and the concurrent blocks in verilog, i.e.,assign statements?

assign a = 1'b0;
assign b = 1'b1;


texts:
This my 12V boost converter shematic and Vin voltage 6.6V to 8.4V. I use Texas Instruments LM3478 boost converter.

I calculated my capacitor value, resistor value, inductor value, switching frequency etc. with formulas in the datasheet. This shematic works fine when the 12 V current is bigger than 10 mA, but when current lower than 10 mA I hear a voice in inductance. I analyzed it with osciloscope and there is no gate drive.

i can add a resistor to 12V like 2k2 ohm, but my V in batary, i dont want power loss.
i think maybe, its capacitor esr problem.
i can add a mosfet Vin and i can switch it when current bigger than 10mA. But i must change my firmware, shematic and pcb.

Also I have search this problem and i found discontinues mode. But i dont know how can i change my shematic.

LM3478 Datasheet


texts: How to prove \$ A_d / A_{cm} = V_{cm} / \Delta V \$ in the CMRR equation

texts:
CMRR is defined by the ratio of differential gain to common-mode gain:
$$ CMRR = {A_d \over A_{cm}} $$
And CMRR is measured by the change in output voltage (\$ \Delta V \$) when a common-mode input voltage is applied:
$$ CMRR = {V_{cm} \over \Delta V} $$
That implies the following relation, of which I cannot prove mathematically:
$$  {A_d \over A_{cm}} = {V_{cm} \over \Delta V} $$
I tried various algebraic combination and the only way I could reach the above relation is this:
$$ \begin{align} V_{out} = A_d(V_2-V_1) + A_{cm}V_{cm} &= A_d(V_2-V_1±\Delta V) \\ \\
A_{cm}V_{cm} &= ±A_d\Delta V \\\\ {V_{cm} \over {\Delta V}} &= ±{A_d \over A_{cm}} \end{align} $$
But this derivation would imply \$ \Delta V \$ is measured at the input instead of a value measured at the output. \$ \Delta V \$ in the equation is also amplified by the differential gain - so it's not a voltage that you can measure at the output either.  I researched online but they just laid out these two equations side by side without mathematical proof of their relation.
[Edit]
How to go from \$ A_d \over A_{cm} \$ to \$ V_{cm} \over {\Delta V} \$?
$$ CMRR \equiv {A_d \over A_{cm}} = {\text{my question here for the missing steps}} = {V_{cm} \over {\Delta V}} $$


texts:
I have a latching switch and I want to know if there is anyway I can change the switch, so that when it is pressed the circuit is open, but when it is released the circuit is closed.

The situation is I have a PTT button which shorts out the mic+ and the GND which mutes the mic, but for this to work I have to have the button pressed in.

Can I make it so it is muted without the button pressed, without using a normally closed momentary switch?


texts: Is there such a thing as a multimeter with needle prongs as small as an exacto knife tip?

texts: im working with repairing cell phones and I need to test connectivity, but the multi-meters that i have too big of a tip. are there micro tip multi-meters for precision use on tiny chips as small as 1mm-3mm?


texts: What is the meaning of Bootstrapping Phenomenon in MOSFET,What are its Consequences & How to avoid it?

texts:
According to what i have read from book Bootstrapping occurs because of capacitance b/w Gate & drain of mosfet,Bootstrapping Phenomenon results into Glitches at the output.I have read from somewhere that Bootstrapping Phenomenon occurs due to high frequency of input voltage.

Here is the image of extract on Bootstrapping from book CMOS VLSI Design by weste and harris.


texts: C struct v union in embedded programming - why?

texts:
Is there anything that a union can do that a struct cannot?

I know that one might use a union to save memory space, but these days it hardly matters.


texts:
I just designed a simple class D amp pcb in which the ground plane is in a star configuration with the IC as center as suggested by the datasheet (cuts in signal areas vs big cap areas, etc..). VCC plane is on the other side. It is as "clean" as I can do it. On the remainder of the board (borders mostly) I have blank pcb space (the pcb has to be this size). I was not sure if it would be a good idea to put a ground plane around all that as I think it would disrupt the star scheme, so I left a floating plane on both sides of the PCB. Would this be detrimental in any way? Is there a better option?

Floating plane is highlighted.


texts:
It's been a while since I've looked at the recent Microchip processors & I've been trying to learn a little bit about the PIC32 MIPS instruction set. I noticed there are two sets of branch instructions; the programming guide says this:

  4.1.3.2 Branch Delays and the Branch Delay Slot

  All branches have an architectural delay of one instruction. The instruction immediately following a branch is said to be
  in the branch delay slot. If a branch or jump instruction is placed in the branch delay slot, the operation of both
  instructions is undefined.

  By convention, if an exception or interrupt prevents the completion of an instruction in the branch delay slot, the
  instruction stream is continued by re-executing the branch instruction. To permit this, branches must be restartable;
  procedure calls may not use the register in which the return link is stored (usually GPR 31) to determine the branch target
  address.

  4.1.3.3 Branch and Branch Likely

  Branch instructions execute the instruction in the delay slot.
  Branch likely instructions do not execute the instruction in the delay slot if the branch is not taken (they are said to
  nullify the instruction in the delay slot).

  Although the Branch Likely instructions are included in this specification, software is strongly encouraged to
  avoid the use of the Branch Likely instructions, as they will be removed from a future revision of the MIPS
  Architecture.

Could someone clarify what they're saying here? Do they differ in the # of CPU cycles taken in each case?

I'm used to the branching architectures of the 8- and 16-bit PICs ("branch skip") where you either execute or jump over an instruction (this sounds like Branch Likely), and I'm used to the branching architecture of the TI C2000 DSPs (where all you get is a branch or branch conditional to an address). But I don't quite understand how to map the MIPS branch instructions onto my existing knowledge.


texts:
I am working on an LED panel video wall project made up of 3x8 squares of 128x128 pixel panels.  Each panel has a worst case power draw of 65W and typical of 35W.  I can get the panels as either 24V or 48V supply voltage (an embedded DC to DC switcher will make 5V for the LEDs).  I plan to put the 24V or 48V power supplies in a NEMA box at floor level and run power cables 10ft up the wall (either inside the wall or in a raceway enclosure).  Space constraints won't allow me to put the power supplies in or near the video wall.

I am leaning toward choosing the 48V supply to reduce the current through the power cables.  But I am confused by the NEC specifications for low-voltage systems in this case.  Some sections refer to less than 50V, Article 411 Low-voltage lighting uses less than 30V,  Table 11 says Class 2 power supplies between 20 and 60V.  Does the low-voltage lighting section apply to this case?  Would the 24V panels be a safer route to meet NEC requirements?  Am I missing an obvious section in the NEC that would apply to powering a video wall with 24VDC or 48VDC?

Also, in Table 11a on Class 2 power supplies, they set the maximum VA to 100 for 20-60V supplies.  Does that mean that I need to use 16 100W power supplies?  But then to have less than 100W per power cable, I would need to run 24 separate cables to each panel since 2 panels combined could add up to over 100W.  Then I would need 24 100W power supplies.  This seems absurd to me, I must be misunderstanding the NEC.  I would prefer to use 6 300W or 4 500W supplies, then run 6 or 4 separate power cables up to the video wall and distribute the power to each panel.  Is there something in the NEC that would allow this?

I appreciate any feedback on this.


texts:
So I'm having trouble understanding critical paths.

I have the following example question:

Draw the critical path that shows how fast the counter can count:

Delays are specified as follows: Delay for OR gate is 4ns, Delay for AND gate is 5ns, Setup time for latch is 3 ns, hold time is 1 ns, propagation delay 2 ns.

The solution manual marks the following critical path(the image is the full design with added red lines for critical path):

But I don't understand this answer, isn't the critical path supposed to be the slowest path for the input to affect output?

Wouldn't it be a lot slower to then go through the latches like this:

So why isn't image 2 the critical path?

Path in image 1 has 19 ns delay. To my calculations path in image 2 has 29 ns delay.


texts: What is the minimum safe voltage for NiMH batteries, if at all?

texts:
Is there a minimum voltage below which a NiMH battery shouldn't be discharged to?
One of the contributors on this website writes

800 mV is where you definitely want to stop to avoid damage. There is so little energy left at that point that there is no benefit in draining the cell further anyway.

Nevertheless, the website www.batteryuniversity.com claims that to "restore" a Nickel-based battery it should be discharged slowly to "about 0.4V/cell and lower".


texts: How do I give several classes access to the single RTC on my MCU

texts:
I'm writing my first large-ish C++ embedded program on a STM32F413.  I've become a reasonably firm believer in object oriented coding but am not particularly knowledgeable.  The STM32F413 has one RTC but almost all my classes need to time stamp events. I have a class for each of my sensors like GPS, pressure, pH, humidity and so on.  Every time a new piece of data comes in from any sensor, it needs to get time stamped. I'd like to write a RTC class and give many other classes access to the RTC date and time through a single public "getDateTime" method.  The only way I know how to do this is with a singleton.  Is there a better way?
Thanks in advance


texts: Amplified microphone signal output to ADC input. How can I eliminate DC offset?

texts:
I'm making simple sound level meter. I try to make it precise. I'm using ADC ref voltage (2,048) so rms calculation can be simpler.

Can I use this ref voltage to set offset voltage to (Vref/2) and measure this signal by diffrential measurement so it eliminate DC offset form readings?

I must use battery supply and 3V3 is from voltage regulator. Entire module is supply by 3,3 volts including ATxmega microcontroller. I'm using electret condenser microphone. I'dont want to use dual polarity supply if this is not necessary.


texts: GPS Accuracy - is it relative or absolute?

texts:
If a GPS unit reports accuracy to 1 meter, does that mean that the receiver's absolute location at any time could be up to 1 meter incorrect in any direction, -or- does it mean that the initial location of the GPS is inaccurate to 1m but every relative movement of the GPS receiver is accurate to sub-millimeter level, relative to the initial position?

In other words, in scenario 1 above, your GPS could show your initial coordinates, and any movement of up to 1 meter in any direction may NOT be reflected as a change in coordinates.  In scenario 2, every movement (down to the millimeter) would be reflected, but would all be offset by the initial error value.


texts: Converting a Lithium Ion Model from a Foster Network to a Cauer Network

texts:
It is possible to convert common thermal RC-models between the Foster form and the Cauer form, as seen here:

I was wondering if and how this is possible with lithium-ion cell models, which commonly use a voltage source and not a current source, for example:


texts: How can I find the RMS value of a wave in irregular form?

texts:
As a sine wave passes through a circuit, it clips and the waveform in the figure is formed.
How can I find the RMS value of a full wave?


texts: Project Considerations: From POC to Consumer product

texts:
I come to you for advice. I am a software engineer with some background in electronics, since I studied mechatronics engineering. However I would say that my experience with electronic projects has been more on university stuff, using protoboards and proof-of concept circuits.
Now, I have in mind to combine these two areas in order to develop an IoT solution by creating a project that can perform some simple measurements on office spaces (humidity, temperature), offer dashboards, alerts, and so on.
Now, since most of my experience comes from software development I think of this project to use some principles of Scrum methodology, i.e. to deliver value to the clients as fast as possible. The roadmap that I envision is as follows:

Start as a simple project that uses some hobbyists components such as ESP32, MQ135 sensors for CO2, BME280 for temperature, etc. These will be mounted on protoboards, and will serve to validate communication to our IoT Hub, dashboards, reporting, communication and so on

Once this proof of concept has been validated, I will try to move these components to a more permanent setup, i.e. design casing for individual sensors, mount them into a proper soldered board, install them on my office and run them for a couple of months. Fix issues and identify possible extra functionality

Now until this point I feel pretty confident, since even though the project would still be in somewhat a proof of concept phase, it would be running in-house so any issues can be identified and solved efficiently.
Moving forward is what makes me nervous since I identify the following issues

Replicating this project into other offices that would be our customers would require for our electronic systems to be robust enough to withstand any tampering, overcurrents, etc.

Also, the form factor and pricing could be important, im guessing that we might want to move from hobbyists dev boards to a more granular solution (im thinking specific PCB's?)

Now, to be honest I don't want to have a full fledged 100% fail safe electronic's board before launching this as a product, since first we would like to test this with local markets, neighbouring offices or small buildings to which we can easily give support or replace parts in case something goes wrong. I would be comfortable to have a solution that moderately addresses these issues but that can be scalable.
Maybe then, if the project has success then we will be looking into creating this a mass production model but this is far away in my roadmap (~4 to 5 years in case its succesfull)
Now, back to the point, my question to you is, do you recommend any literature, have any advice as into how could we get this project working from a POC phase to a consumer product? Most of the resources I find on the net are either very "hobby" like (bare protoboards lying around the house) or really obscure. I just want to know what your suggestions are as far to a roadmap that I could follow so that I dont hit a wall moving from a phase to the next.
Thanks!


texts: understanding current shunt monitor reference voltage

texts:
I would like to monitor the current and voltage being harvested by a solar panel (models varying from 6V to 18v and current from 340mA to 1A) that is being used to power a mcu (3.3V). The solar panel will be wired to a MPPT buck converter.

I did some research and seems that high-side current shunt monitors ICs would be the best approach. Am I right?

The doubt.. almost all shunt monitor ICs that I've found so far are used to monitor a large Bus voltage and needs a small Reference voltage (those names differs between vendors).

For example, this one from Maxim. It needs a Vcc from 2.5V to 5.5V and monitors a Vin from -0.1V to 28V:

Or this one from TI, that monitors a V+ from 2.7V to 26V and requires a Reference Voltage:

I'm not understanding, since the voltage from a solar panel can change how would I provide those two different required input voltages to the shunt monitor?  would be necessary to have a small battery just to do this measurement or both can be derived from same source (the solar panel) ?

thanks


texts:
I have stm32vldiscovery project. I want to use external interrupt by PA0 (user button).
When I press the button (PA0), then function EXTI0_IRQHandler must set ldOn equal 0. But ldOn always is 1. Debuger shows what function EXTI0_IRQHandler runned on. ldOn change value to 0, and again stay equal 1. Why?
Have this code:
main.c

#include "main.h"
...
uint8_t ldOn = 1;

int main(void)
{

  HAL_Init();

  SystemClock_Config();

  MX_GPIO_Init();
  HAL_GPIO_WritePin(LD4_GPIO_Port, LD4_Pin, GPIO_PIN_SET);

  while (1)
  {
        if(ldOn == 0)
            HAL_GPIO_WritePin(LD4_GPIO_Port, LD4_Pin, GPIO_PIN_RESET);
  }
}

it.c

#include "main.h"
...
extern uint8_t ldOn;
void EXTI0_IRQHandler(void)
{
  ldOn = 0;
  HAL_GPIO_EXTI_IRQHandler(GPIO_PIN_0);
}

When I used stm32f4-disc1 board, this construction works perfectly...


texts: Why can't I get transformer output as written on the label?

texts:
TLDR: I've made a short video about this, if you like looking at a video more than reading this. It's  here: https://youtu.be/51235iFywI4

The problem is pretty straighforward.

I have a (toroidal) transformer that has two secondaries (completely independent), each giving 12V 10A as written on the label of the transformer. In reality, I can't even get close enough to this.

To test it, I've assembled the simplest circuit possible. One output of this transformer goes into a full bridge rectifier (rated 15A), then an ammeter, then a 2 mF capacitor for filtering (that's a 2 millifarad, as in 2000 uF) and then it's connected to a variable load device I've made earlier (inside this device there are only power resistors and a single power transistor, so the device itself is purely resistive load; no capacitors, no coils; although in DC I'm thinking it shouldn't matter.)

Initially, with no load, I have around 15V (which is normal). The more current I draw, the more the voltage drops and it goes below the level that I would expect. If I draw only 4A of current, the voltage is already around 9.5V. If I remember correctly, it goes down to 8V at 5A and so on.

The transformer is new, in perfect condition, almost never used. I've used this one only because it's got a clear label on it, but the exact same problem occurs on other transformers as well.  I also have 2x classic transformers (meaning not toroidal) of 2x12V 3A and I can't even get 1A from them @ 12V.

So, basically, I have 2 questions:

Why does this happen? If it's rated 12V 10A, why can't I even get half the current while still keeping the voltage?
What kind of transformer should I buy in order to actually have 10A @ 12V (or higher?) Should i get a 30A, 40A?

To further test my setup a little bit, I've taken a switching power supply and put it to the test. Yes, I know, these are completely different things. Switching power supplies are complex electronic devices, transformers are passive components, they cannot be compared. I know and I'm not even making a comparison. I just wanted to test this experiment and have a different perspective. And the test was successful.  I was able to draw 1.8A and the voltage dropped only to 11.7V (it's a 12V 2.1A supply). I didn't wanted to push it to the limits, the test was good enough for me.

P.S.: Please don't tell me to ditch the transformer and use a switching power supply. For what I want it's not an option for multiple reasons.


texts: Does current still flow through ballast with fluorescent bulbs removed?

texts: I have a 3 fixtures each with 4 fluorescent tubes with ballast replaced about 8 years ago and these fixtures are connected to the same switch in the kitchen. This am there was an smokey smell and the fire department believes it originated from a bad ballast. I removed all tubes from the offending fixture of 4 and I am wondering if current will still flow through the 'bad' ballast if I turn on the lights to the other 2 banks (again on same switch).


texts:
I want to de-amplify the sound volume of my television.
My native language is not english, and I do not know the correct word, if any, for the opposite of amplify.
When my TV is turned from volume zero to volume one, the heard sound jumps to something that is too loud.

TV volumen scale              :  0, 1, 2, 3, 4, 5,...,49,50,51,52,...100
Corresponding subjective scale:  0,11,12,13,14,15,...,59,60,60,60,...60

What I would really like is a sound volume on this subjective scale from e.g. 3 to 20. So I would like to decrease the volume by a factor of app. three. Can it be done by connecting a suitable resistor in series or in parallel with the internal speakers?


texts: dc motors to control unmanned ground vehicle

texts:
This is my first large project as an electrical engineering student and I'm working with DC motors for the very first time.

I'm working on designing an unmanned ground vehicle that will weigh approximately 1200 pounds maximum.

I'm having trouble determining the power rating and type of DC motor and electric drive-train to use. Each wheel must have independent motor.

I Cannot use Lithium Ion type batteries.

It must also be durable and rugged.

I've looked at the in-hub type DC motors but I am having trouble determine what size each motor must be, and how to control the speed of each of the in-hub motors.

Any suggestions on how to calculate motor size and ratings, control mechanisms.


texts: Hooking up multiple RGB LEDs while using a minimal number of PWM pins on an Arduino?

texts:
I currently have an anode RGB connected to the 11, 10, & 9 PWM pins on my arduino. However I would like to add 3 more LED's to my project, but I don't want to necessarily take up every single PWM pin (I still want to attach a shield). Is there a way for me to hook up all 4 LED's & still be able to only use a minimum number of pins? Keep in mind that I do want to use all 12 resistors for the 4 LEDS. Oh and all the LEDs will do the exact same thing (They all will be red, and all turn blue, etc) if that helps.

Here's how my board looks right now:

I have three NTE123AP transistors I can use for this project.

P.S. I attached the .fzz file so that if any of you would like to edit the schematic image, it would be super easy. In fact that would be better since I'm new at this, and it would be easier to follow! : )


texts:
What is the difference between an FPGA Intellectual Property core and an Accelerator Function Unit?

As far as I understand, an AFU is an IP core developed by the end-user (as opposed to IP cores delivered in the hardware by the vendor). Is it correct?


texts:
I am attempting to build a really cool thing (at least I think).

The goal is to build an arc lighter that I can shake to charge (kinetic power).

It's a circuit that combines an arc lighter circuit with a 3.7V input, a supercapacitor to power it instead of a lipo battery, and the power system of one of those "shake-to-charge" flashlights from the '90s. Here's what those flashlights looked like:

I'm really only an electronics hobbyist and have never really designed a circuit board before, but I've been learning EasyEDA and have gotten decently proficient.

As far as I know, I need to combine the arc lighter circuit like this one:
Increase Arc Lighter Spark Gap

with this power circuit:

and also make sure I choose a super-cap with enough storage to fire the spark for at least a few seconds if not longer.

My question to you guys, among others, is: Is this feasible, and if so, where do you suggest I start?

Any and all advice is valued and I am so grateful to have found a community where electronics wisdom exists and I can ask questions. Thanks!

edit:
I did some power requirement math and put it down below. So far you guys have been so helpful. Thanks for everyone who’s helping in any way!

I found a brand of arc lighter that put their tech specs in the FAQ on their site and figured I'd start with that: https://www.arclighter.com/arclighter-faq

“[the lighter] …can light 90 times on a single charge based on 8 seconds per light.”

8 seconds per light x 90 lights = 720 seconds of arc firing per charge

“What are some of the charging characteristics of the [product name]?
Nominal Capacity: 450mAh
Input: 3.7V
Output: 6A“

450mAh@3.7V / 720 seconds

0.625 mAh per second @ 3.7V

Converted 3.7V 450mAh to Joules: with  (mAh x voltage x 3.6 = Joules of energy)

~6000 J of energy per battery

6000 J / 720 seconds

= 8.3J/second while firing the arc (for this brand of lighter)

I have to keep in mind I will not be using lithium batteries and instead using supercaps. I have no idea if there are any negative ramifications other than not needing lipo charging circuitry, and I can instead use a Zener Diode to prevent capacitor overcharging.


texts: How to calculate rotor flux of the three phase squirrel cage induction motor?

texts:
I have a three phase squirrel cage induction motor with given parameters (stator winding connected in delta)

nominal power: \$P_n = 22.4\,\mathrm{kW}\$
nominal stator voltage: \$V_{sn} = 230\,\mathrm{V}\$
nominal stator current: \$I_{sn} = 39.5\,\mathrm{A}\$
nominal stator frequency: \$f_{sn} = 60\,\mathrm{Hz}\$
nominal speed: \$n_n = 1168\,\mathrm{min}^{-1}\$
number of pole pairs: 3
stator resistance per phase (T equivalent circuit): \$R_s = 0.294\,\Omega\$
stator leakage inductance per phase (T equivalent circuit): \$L_{sl} = 0.00139\,\mathrm{H}\$
rotor resistance per phase (T equivalent circuit): \$R_r = 0.156\,\Omega\$
rotor leakage inductance per phase (T equivalent circuit): \$L_{rl} = 0.0007401\,\mathrm{H}\$
magnetizing inductance per phase (T equivalent circuit): \$L_{m} = 0.041\,\mathrm{H}\$

I have been struggling with calculation of the nominal value of the rotor flux.
My idea was that I will use the T equivalent circuit for that purpose

and I will use nominal values of the motor quantities i.e. I set the motor
operating point into the nominal operation point (nominal slip, nominal stator voltage etc.). Then I calculate phasor of the stator current (\$\hat{I}_s\$) and phasor of the rotor current (\$\hat{I}_r\$) according to the below given set of equations
$$
\begin{bmatrix}
\hat{V}_s \\
0
\end{bmatrix}
=
\begin{bmatrix}
R_s + j\cdot(X_{sl} + X_m) & j\cdot X_m \\
j\cdot X_m & \frac{R_r}{s} + j\cdot(X_{rl} + X_m)
\end{bmatrix}
\cdot
\begin{bmatrix}
\hat{I}_s \\
\hat{I}_r
\end{bmatrix}
$$
For the motor parameters mentioned above the Scilab command linsolve gave me
$$
\hat{I}_s = - 34.946619 + 17.574273j
$$
$$
\hat{I}_r =   35.797115 - 3.954462j
$$
Based on the known phasors of the stator and rotor current I used the below given equation for calculation of the phasor of the rotor flux
$$
\hat{\lambda}_r = (L_{rl} + L_m)\cdot\hat{I}_r + L_m\cdot\hat{I}_s
$$
which gives \$\lambda_r = 0.5554856 - 0.0613638j\$ i.e. \$|\lambda_r|=0.5588647\,\mathrm{V}\cdot\mathrm{s}\$.
This value seems to me to be too low. So I have doubts regarding the way I have used for its calculation. Unfortunatelly I don't know any other way for its calculation which I can use for verification. Can anybody tell me whether the applied procedure is correct or not? I would also appreciate any idea how to verify my results. Thanks in advance.


texts: Identify TI motor driver IC (from old HP printer) or its control protocol

texts:
For fun, and as an exercise in reverse engineering junk hardware, I am trying to understand the internals of an HP DeskJet 840c printer from 2001.

Specifically I am trying to understand how the motor controller works, with the goal of being able to send my own signals to its input pins and drive the 2 brushed DC motors and the stepper inside the printer.

The motor controller is made by TI, but googling the identification codes yields nothing useful, so I suspect this chip was made specifically for HP. I also tried to find similar parts on the TI site, but nothing came up.

By following the traces on the main PCB I identified the output pins by working backwards from the motors, then I identified the input pins by working backwards from the CPU.

MC1 to MC9 connect to CPU pins.
X1 to X4 connect to a stepper motor.
M1A and M2A connect to different DC motors.
All the pins near any corner connect to GND.

Using a logic analyzer I capture the signals exchanged between the drivers and the CPU when one of the DC motors is running.
The CPU seems to send a constant stream of "packets" with 1000ns period (even when the motor is not running).
Each packet is divided in 8 intervals of 125ns each, which I tried to attempt to interpret as byte values.
There are patterns, for example most packets start with 11 and end with 01 but apart of that I could not make any more sense of the protocol, other than identifying which sequences seems to tell the motor to move left or right, or stay still.

My next step would be to inject my own copy of the input from a separate microcontroller, to see if the driver accepts it.

But before going ahead with that I would prefer to understand the protocol, so I know for sure what I'm asking the driver to do, instead of just having to copy what I get from the analyzer.

Can anyone help identify the motor driver and find a datasheet for it, or at least understand if the control protocol is something standard that I can learn ?


texts:
I am working on a GPRS communication design. What I want to do to connects two modems together via GPRS. But I found that i could not connect.

I was able to connect both modems to the internet using TCP connection AT Commands, and able to establish a connection to a server with a known/fixed IP address( e.g google ), but i could not connect both modem's together, knowing each IP addresses.

I know the IP for the modems are dynamic, which shows to be the reason why i cant connect them, but i want to know if there is another way to go about this.

My design intention is to use a smart Mobile Device (e.g my phone), which connect to a Modem (say at Home), enabling me communicate with certain appliances at the house remotely.

Are there any way around this?


texts: Problems in design of a BLDC motor driver

texts:
I have been building a driver circuit for a RS2205 BLDC motor and have gotten decent results so far using back EMF feedback for commutation control.

The motor is driven by a PWM wave from a Arduino Uno MCU with a frequency of 4kHz and 60% duty cycle.

The successful tests have been made using a 5 volt power supply in order to protect the components as much as possible since the process pretty much has been a trial and error approach and I have pretty limited experience in electronics design. During these tests, the "high-side" MOSFETs have reached a pretty high temperature (too hot to touch) but other then that it seemed to be working fine.

The real problems appeared when I tried using a 12 volt power supply (the motor is rated for 3-4s LiPo batteries) where the motor started to emit white smoke after a few seconds on low velocities even when no feedback control was enabled. Any ideas of why this might happen and is it normal for the MOSFET transistors to get such a high temperature during operation with only a 5 volt power supply?

Driver schematic:


texts: Earth leakage from isolated power supply

texts:
I have recently put together a DIY bench power supply using a DPS5015 from Rui Deng and an old laptop power supply. Everything seems to be working fine except for a small amount of current leaking to earth even when the output is turned off.

I noticed this when I was testing after assembly. I was connecting an LED to the binding posts and noticed that if I was holding one leg of the LED it would light up when the other leg touched the binding post.

Now where I start to get confused is that the laptop power supply that I’ve repurposed has no earth connection and should therefore be floating. I believed this would mean leakage to earth was not possible as there was no return path for the current. I’ve confirmed the current is AC 50 Hz(I live in Australia with 50 Hz mains). Measuring the current straight to earth I get 148 uA. Current through my body is 133 uA. Current through my body with my feet insulated is 34 uA.

So my main questions are how can current leak to earth from a power supply that is not earth referenced and why does current still flow when not even connected to earth.

Am only a hobbyist just learning and would really love to understand what’s going on. Does this represent a safety risk? Are there any changes that can be made to reduce this effect/improve any safety factors?

Thanks in advance.


texts:
I am about to attempt make my first audio amplifier (beyond an LM386 amp). I chose the TDA2030A (dataheet http://www.st.com/web/en/resource/technical/document/datasheet/CD00000128.pdf). Since its a dangerous thing to do I chose an smps power supply, which is 24V and 2A. I have been training for this task for the last month and a half, learning to make PCBs etc. Yet realizing the nature of electronics, where there is always some piece of knowledge that is hiding in the bushes and that I wasn't aware of, I decided to ask the community some questions that will help me make this amplifier without killing myself in the process. Just for background, Electronics has been a hobby for the last 3 months and I am an Industrial Engineer myself.

If you look at the circuit diagram, the amps use pin 1 as their non inverting input. In this diagram taken from the datasheet, the amp on the right has its non inverting connected to a resistor that is connected to ground. Both amps drive a single speaker. My question is that if I connect the right amp to the right audio channel and the left of the left audio channel, unlike shown in the diagram, can I drive two speaker? I don't see why it cant be done.
For proper grounding, I create ground planes on my pcb. Then I need to make a hole in my PCB on the ground plane and connect it via wire to the Ground on the smps. Right? (am asking stupidly obvious questions just to know if I am right). Proper grounding seems the key to any proper functioning electronic circuit.
Do I need to have a complex filtering system like capacitor for ripple etc? I ask this because this is smps purchased from the market, it would already have the required components.
What is the V ADJ pin on my SMPS? How do I use it?

Thank you. Any help will go a long way in insuring a long life for me.


texts: AMS vs LD vs ZLDO vs NCP in 1117 Linear Regulators

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I was in the process of choosing a 3.3V Linear Regulator for my ESP based Project when I stumbled upon the different types of these voltage regulators.

The 1117 regulator had different prefixes, AMS, LD, ZLDO, NCP. What do these mean and how do I choose the right regulator with the right components to go with it..?

To my knowledge, most of these prefixes are abbreviations of the manufacturer name (AMS - Advanced Monolithic Systems) and some of them describe their feature (LD - Low Dropout).

But, a few sources online said that the AMS1117 needs a different type of capacitor than the NCP1117 which raised the question that if the functionality varies with the manufacturer.

How do I decide which of them is the best for my project..?


texts: transferring raw schematic to breadboard and PCB

texts: i have some schematic from TINA pro, pspice, orcad and the lite. Is there a way to automatically convert it into a both breadboard and PCB layout. This is a bright idea since it will save time. What are your suggestions?


texts: If the depletion layer of a transistor collector/base junction is thick, why are majority carriers still collected?

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In "Principles of transistor circuits, 8th edition" (top of p26) it is said that once holes have been injected in the base region by a forward biased base-emitter junction (which I understand) of a PNP transistor, they diffuse towards the collector and are then swept across.

However, I thought the collector-base junction was reverse biased which means that the electric field created by the external bias adds to the potential barrier? How is it that holes spontaneously cross this huge potential barrier?

Edit after the answers: After drawing a diagram it is much clearer. The potential barrier creates a field reinforced by the reverse bias, but that field goes against holes going towards the base - it's actually accelerating holes from the base to the collector.


texts: How do you use an LED's log V/I curve to force an exponential current change in the LED for a linear voltage change?

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The info needed to make log and exponential converters with silicon is widely available. The saturation current, intrinsic resistances, and the Ebers-Moll equation are sufficient. A few other numbers help extend the functional range.
Does similar information exist for LEDs? If so, can someone point me to it?
How much voltage increase does it take to double LED current? Is it the same for different LED colors and semiconductor formulations? How much does it vary with temperature? How much current can you push through one before the internal resistance contributes too much error? How little current can you push through one before nonlinearities and errors overwhelm the signal? Do they need to be blacked out so that ambient light can't affect them?


texts: Some more info about voltage/current electricity safety

texts: I'm using a 400W PC power supply that is able to deliver at 12V 12 Amperes and 15 Amperes (i' m not sure why there are 2 values). I have connected 3 simple (disk drive) DC motors in parallel and when all of the three run, I get 0.12 Amp on the multimeter. I calculate the watts are 1.44 Watts. When i forcibly stop these with my finger the current jumps to 0.7 Amps (8.4 Watts and more) and growing (the potentiometer i use to control current starts smoking). Now i read that 90mA are able to produce pain, and at 500mA it could be lethal. Can someone advice me by providing some example how i can electrocute myself with such a circuit.


texts: Broken potentiometer on old computer speakers

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I have an old set of computer speakers. The 10k potentiometer broke off, and now I'm trying to figure out how to rig it to 100% volume without the POT.

The POT appears to be dual channel, and has a total of 6 terminals on it, all of which are in use on the PCB.

I cannot make any rhyme or reason out of this, when it comes to understanding how this is implemented. I'm looking for a way to not replace the POT, but instead install jumpers or resistors to complete the circuit at 100% volume. I just can't figure out what to connect to what, as it's not clearly labeled what's what.

How should I rig this up to work?


texts: I need to do a tehnology mapping (group gates and flip flops) given a D ff and a MUX. Now I know what FPGAs mean and I understand I need to group them so that they "fit" in the given cell. But if I have only a D ff in my cell doesn't that mean I can group only the gates that are connected to the ff? A little help would be great cause I tried looking over some tutorials but didn't understand much.


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I have a thyristor with the connection as in this thyristor (fig 1) and i am trying to use it as a traic.

Edit: I am using 3020 optoisolator and resistor value as shown in fig.2 Supply is 220V. Can I try this?


texts: Can I use the main power battery as a RTC battery as well?

texts: Im currently thinking of a Nixie-Watch. Because I have almost no space on my PCB, I would like to use the 3.3v battery which powers the whole system also as the RTC Battery. I could connect a 3.3v voltage regulator if needed. What do you think about it? Could it work?