texts:
I apologize if this is a repeated question, but I couldn't find one that had the answers I need.

For the circuit in the diagram, the switch has been closed for a long time and at \$t=0\$, the switch is opened. In solving the circuit, the textbook first considers \$t<0\$, during which the switch is closed, the inductor acts as a short circuit, and \$16 \Omega\$ resistor is also short-circuited.

My questions are: Why is the inductor shorted? Why is the resistor also shorted?


texts: Powering board and charging coin cell at the same time

texts:
Here is what I have:

2035 coin cell battery
ATmega328

I want to have an ability to plug micro/mini usb cord and power circuit from usb and charge battery. Circuit has extremely low power consumption (almost a month on 110mAh). Right now I'm swapping batteries. Is there a way to add charging ability?

I know I need to connect them in parallel, but I have hard time comprehending how it looks on schematics.


texts: Range of Electromagnetic Waves/Radio waves?

texts: What basically determines that how far the electromagnetic waves will travel away from the source ? In our world where there is air and other materials how electromagnetic waves would generally response to them ? What will determine their range in our world. Especially radio waves are used all around us now a days. What determines their range ?


texts: Powering microcontroller by bypassing ldo regulator

texts:
I'm working on a circuit design with a microcontroller that runs on 3.3V. I'd like to be able to power it either through a 3.3v supply or a USB port. I'm using an spx3819 regulator.

What would be the best way to achieve this? What I have in mind so far is something like this:

Basically, the 3.3V signal is fed into an inverter, which disables the regulator. This 3.3v signal is also directly fed into the microcontroller (not shown in the schematic).

Is there any better way?

EDIT: The Vout is directly fed into the microcontroller. Vout is 3.3v.
When high, the 3.3v source will disable the chip, regardless of the voltage at Vin (the enable pin disables the chip at < 0.4v).


texts: Finding current through a capacitor in a series AC circuit

texts:
We are tasked to find the current through a capacitor and the voltage of the capacitor in this circuit without using any complex impedances.

simulate this circuit – Schematic created using CircuitLab
the current equation of the capacitor is Ic(t)=C1d/dt(V(t)) so in this circuit we get the following equation of Ic(t) = 0.5d/dt(2sin(50πt)-Ic(t)*100) but i get an exponential solution which shouldnt be the case.Where am I wrong?


texts:
Currently working on my Honours project, we're designing a wide area sun sensor for an attitude control system of a picosatellite platform. We've elected to implement a COtS quad-photodiode package, specifically the Marktech Optoelectronics MT03-004 (http://www.marktechopto.com/pdf/products/datasheet/MT03-004.pdf), for the optical sensor component of our first prototype and in order to do some early system testing and verification we'd like to be able to fabricate a rig with the photodiode and amplifier on a PCB connected with stripwire to our microcontroller, so we can rotate the PCB in space while keeping our light source fixed. Sorry it's taken me a little long to introduce the context, but here's the question: has anyone fabricated a PCB with this component before? If so, could you please point me in the direction of EDA libraries/files for this device, to be able to lay it out preferrably in Altium, but alternatively in KiCAD? A brief Google search turned up files for other devices from the same manufacturer, but not this one, so if anyone either has any on hand or knows where to find them that would be highly appreciated.

EDIT
We've had some comments with regards to the suitability of this particular component for operating in space, we are aware that it's suboptimal for this context, however to clarify: our prototype will not be going into space. At this stage we are simply producing a proof-of-concept, "rough and ready" design. Our scope is restricted as we are undergrads with limited time and budget for the project.


texts:
How is the laser able to move around corners, or able to draw a vertical line?

Is there one laser diode for each red line, and is the diode then being made to sweep the beam along the wall? Are all the diodes then coordinated thus producing those lines and points? Is the sweep at a particular frequency? How is the diode moved? Mechanical or electronic sweep?

Kind of like what a CRT horizontal/vertical deflection ckt does to the electron gun?


texts: Is it possible to make a short-circuit detector for a battery power supply?

texts:
I have a basic understanding of electrical things myself, but semiconductors are not part of it. While pondering about some unrelated things, I came up with this question:

Suppose I want to make an electrical constructor toy for kids. There would be some lamps, switches, relays, magnets, wires, etc. And then there would also be a battery that powers it all (something like 9V or 3V, so no electrical danger exists).

Kids being kids, they will make lots of mistakes when building their circuits, and that's good - they learn. But short circuits can destroy the batteries pretty quickly, and possibly even heat something up enough to cause actual damage. It would be nice if that could be avoided, while still giving feedback that there is a short circuit.

So, is it possible to make such a "battery adapter", which would:

Light a green LED when a circuit is connected and functioning properly (there is some significant resistance in the circuit). Note that this should affect the current/voltage of the circuit as little as possible.
Light a red LED when there is a short circuit (very low resistance of the circuit), while also severely limiting the current flowing through the circuit (so nothing gets destroyed). When the short circuit is resolved, the LED should go off and the current limit be removed.

For bonus points, a yellow LED could light up when two power supplies are chained together, doubling the voltage of the circuit. This is can be used in some educational experiments (like seeing that a lamp suddenly lights up twice as bright), however it also shortens the lifespan of some circuit elements, so there should be a warning. However I do not know if this can be reliably detected from within the adapter itself (without some extremely fancy communications between adapters).

Is this plausible? Can anyone show me a schematic of such a device?


texts: What exactly is reactive power, in concrete terms?

texts:
I've been googling it for hours and frustratingly all I could find are vague hand-waving explanations. I get that \$\textbf{S}=\textbf{VI}^\textbf{*}\$ is useful because \$Re(\textbf{S})= P_{avg}\$, which is the average power used by the load. But how exactly does \$Im(\textbf{S})\$ relate to the power that goes back and forth?

Mathematically, how does \$Im(\textbf{S})\$ relate to \$P=V_{rms}  I_{rms}  cos(2\omega t +\theta_V +\theta_I)\$?


texts: Is it possible to add something, such as a microcontroller, to act as a new node that will integrate into the CAN bus system and be dominant over other nodes or at least speak on the bus to work what you're trying to work other than reverse engineer the whole CAN bus?


texts: Why frequency of a DC signal is chosen as zero? If the period can be anything, isn't it same for frequency?

texts:
This is a page from Oppenheim.

We can assume a DC signal as a repetition of 10 strips per 10 seconds/10 strips per 5 seconds. Like that, if we choose different periods, we get different frequencies also. Then why is frequency chosen particularly to be zero?


texts: Basic circuit diagram question when current isn't given

texts:
How do you calculate the voltage in a diagram when only resistances are given? The question I'm looking at is:

How is V2 6? I used KCL and KVL and couldn't solve the system of equations because there was not enough info


texts: (External Battery) If i have Portable Charger that has a capacity of 50,000 mAh and

texts:
4 ports with 2 amps, 2 amps, 1 amp, and 1 amp that can charge 4 phones respectively. How long will the battery continue to charge these phones, assuming they are pulling the largest load possible?

Based on my calculations

the battery will last for as long as: 5.619 hours. However, this number feels funny to me. I've simply added all the loads together and then divided it from 33,716 mAh (this number was gained by accounting for inefficiency in the output).


texts: What are the ways to make a dual power supply from a single voltage source?

texts: I have a function generator IC XR2206 from EXAR. It's application circuits uses dual power supply +/-9 volts. How can I make such a 9-0-9 dual supply from a single voltage source like a battery or an adapter?


texts: Water pump with opto-isolator MOC3063M and triac BT137

texts:
I have designed a circuit for water pump. Please correct me if I am wrong with schematics. The idea is to to switch on/off AC motor pump with 230V and 7.5A, when water is detected.

I have used opto-isolator MOC3063M and triac BT137.

I have four questions:

 Can be used 1.5V to signal water detection or should be at least 6V? The current should be not more than 25mA.
 Is it RC snubber set up correctly including resistors R2, R3?
 Is it FUSE in right place? Should it places before RC snubber or after that
 Can be used additional measure for heating? For example heatsink or another alternative.

Thanks.

P.S. Water detector is nothing but plate with two conductors to detect water presence.

Additional: Yes you are right 1.5V is too small, because of voltage drops of led D1 and the led in MOC3063. I consider to use 6V DC power source.


texts: Protecting voltage sources against pushing or shorting into each other

texts:
I am designing a PCB where there is a load with peak power of 15 Watts to be powered from a user selectable voltage source.

There are a 35V and a 24V sources and it should be only one of the voltage sources to be active.

The user should be able to chose this, so I decided to go with some jumpers (2 in parallel to increase current capability). Now the problem is, if user leaves all jumpers in, the voltage sources will push against each other and for sure something will go KA-BOOM!

I can only think of adding two diodes per each source, in case user puts the wrong jumpers in.

The problem is, I do not know what rating these diodes should have. Should the diode have power dissipation rating same as the load? what characteristics the diodes should have for this scenario? e.g. should it be fast like schotkey or just a rectifier diode or zener will do?

I think 1N4007 is not the correct choice as datasheet says 1A load is the max. My load can draw up to 5A but usually sits around 2A.

Here is my draft schematic:


texts: How can I evaluate or speculate on a part's production lifetime for long term part sourcing?

texts:
Suppose I have an idea for a product, where if it were successful, would be in production for 5-10 years.  How can I make decisions on what parts to use now such that they will still be available to order in the future?

I'm not old enough to know, but I have heard from those that have been around long enough that some parts, such as some based on the Motorola 68HC11, have been able to stand the test of time and are still available today in pin-compatible and (roughly) code compatible packages and variations.

ARM has looked extremely attractive to me lately, a lot of Cortex-M's seem to fit perfectly for an idea that I have but what guarantees do I have that a pin-compatible variation of a particular micro-controller will still be around in 5 years?  Or 10 years?  How do I even begin to evaluate this?  What are the key factors and does anyone keep data on a chip's production lifetime?


texts:
I am total noob in electronics field. I had some broken electonics appliances lying around house so now I am trying to build something out of it. Can you guys please help me with identifying the motor  shown in the picture and what kind of fuse board should i order so i can run it safely at home. It says its a 110v on the motor itself but i am not sure if it takes dc current or ac. I live in canada so can i directly plug it in the socket ?. And can i use arduino with it ?.  Can i use arduino to run the motor as i want program when the motor should run and for how long ?
Thanks in advance


texts: Is it safe to use my phone while charging it? Does a charger leak electricity?

texts:
My cousins always tell me that it is not safe to use or call someone on a mobile phone while charging it.
Is this just a myth or is this true?
I read somewhere that most phone chargers are isolated(what does isolation mean?)
Please explain in simple terms. I would like to know more.


texts: Why use UART to communicate between Arduino and ESP Wi-Fi module?

texts:
I have been learning about the different communication protocols used between Arduino and other components/sensors, namely, SPI, UART and I2C. I want to add Wi-Fi to my Arduino UNO project using ESP8266 (for now, and maybe later upgrade to an ESP32 as it's more powerful).

But i am wondering why in all the schematics that i have seen in my online research, the Arduino is always connected to the ESP8266 module via UART? Why not use SPI or I2C? Why is UART (apparently) considered superior for ESP communication with the Arduino over the two other communication protocols?

Thanks in advance for the help.


texts:
I want to create a mounting hole for my project according to any standard.

I've just found such table here:

The biggest size of the screw is 3.5 mm. Is there any table for more sizes?


texts: why does RC time constant happen to equal 1/e?

texts:
I understand that the time constant in  AC RC circuits is defined the value of resistance (in ohms) x  the value of capacitance (in farads).  Indeed, ohms(R) x farads(C) yields time (seconds).

$$\tau = RC $$

I also understand that when discussing continuous change (growth/decay) it is no surpise that e figures in. What I do not understand is why \$C * R\$ just happens to equal the time constant, \$tau\$,  the point at which the voltage in a capacitor  \$\approx63\%\$ of its final charged state C. In other words, why it it true that after one time constant, \$\tau\$, voltage in the capacitor (in an RC circuit) equals 63.2% of its starting voltage.  Or, why does this hold:

$$0.63 \approx  (1 - \frac{1}{e^1})$$
and
$$V_\tau  = V_0(1 - \frac{1}{e^1})$$

This is related to another question that asks why the RC time constant = 63.2% and not some other value:
Why is the time constant 63.2% and not 50% or 70%?

This post included insightful answers describing that 63.2 is related to e (specifically \$\frac{1}{e}\$),and how e relates to continuous change,  but not why capacitance x resistance yield this value.

It is not as if Georg Ohm or Michael Farady had e, or the time constant, in mind when developing these ideas (or units), correct? Am I missing something obvious?


texts:
I am reading about feedforward in control system. And in this lecture, slide 49, the author says that feedforward is common in human systems. Example, walking, playing basketball, driving a car.
Could you explain how feedforward is used in walking?


texts: What's the need for higher frequency in inductive charging systems?

texts:
Consider an inductive charging system like Magne Charge - it has a rather huge "coupler" coil off the vehicle and a corresponding slot on the vehicle and the coils in the "coupler" and in the slot are aligned perfectly parallel and brought close to each other. So it looks like a good old transformer.

Yet there's a huge box in each Magne Charge system (a wall-mounted unit) that most likely generates higher frequency current. Btw this box seems to be accountable for huge energy losses.

What's the need for that frequency increase? A good old transformer will run at the same frequency as mains - 50 or 60 Hz depending on the region - and have pretty good efficiency. Why would this slightly altered transformer setup need higher frequency?


texts: Ground loops on single trace in the middle of a ground plane

texts: I'm trying to optimize the layout of a MAX1979 TEC driver on a double sided PCB. Is the placement of single, small traces in the middle of a ground place, as seen below on the bottom side of the susceptible to suffer from ground loops around it? It should also be noted that the IC is placed on a bridge between power and  analog grounds, and I have doubts if the small traces will induce noise in the analog part.


texts:
In a nutshell: The below circuit is not working. The signal is distorted and is not amplified. I expect it to be amplified by R_1/R_2.

The op-amp is a TL071.

So my question is, how do I get this thing to work and how do I debug it?

Thing's I've tried:

A resistor approximately (R_1 R_2)/(R_1+R_2) between the third leg and the ground (to cancel out bias current, but it didn't change anything.)
Grounding one of the power supplies (this did things, but not useful things and I couldn't explain why it should be that way to myself so I changed it back.)
Changing components and circuit boards.
Varying sizes of resistors.


texts: What happens when you set a pin in the wrong direction?

texts:
All MCU's have digital pins, which you can configure to function as input or output.

When you set something to 'output' which is wired as an 'input', will there be any possibilities of short-circuits damaging the MCU?


texts:
fixing up a kids toy today that used a USB Micro-B cable/port. The female port was smashed up.
I have started to remove the old female socket and noticed it did not use a standard pin out. Rather than have the 5 pins in one horizontal line they have them on two rows.
Because the old port was severely damaged I am having difficultly identifying the pins and I can't really find anything online.
Could somebody help me identify which pins are +5v and ground?


texts: How to configure PWM on STM32F429I-Discovery Board

texts:
Currently I have some difficulties on the Discovery Board STM32F429I to control the on-board LEDs via PWM. According to the data sheet of the Discovery Board the LEDs are located on pin 13 and pin 14 (PG13 & PG14).

According to my research, it is possible to solve the PWM control with the on-board Timer to dim the LEDs. In the data sheet of the MCU, I don't see any timer assignments as an alternative function to generate the PWM signal at the LED. Enclosed is the mapping table from the data sheet of the MCU:

Is there no "elegant" possibility to control the on-board LED via PWM?

Which alternative ways exist to control the brightness via PWM of the on-board LED?

Thank you very much.

Link to the STM32F429I-Discovery Board user manual:
Link to STM32F429 MCU data sheet:


texts:
Can anyone help me with the speed of rotation in rads/sec.

I am trying to find the equation for it.

I have 730 rpm as my motor speed. It is a DC motor.

So far the equation i have is:  2pi x 730/60

And the answer is 76.445.

Is this the correct equation to use tho find speed of rotation in rads/sec?

Thanks.


texts: Amplification without transistors or tubes?

texts:
Are there any means or technologies that can be used to linearly (or close to linear) amplify an audio or LF RF electrical signal that do not require transistors or vacuum tube technologies?  (Or equivalent tech such as ICs, photo-transistors, klystrons, etc.)

Specifically linear (or "close enough" as are the usual slightly non-linear simple tube or transistor amp circuits), so disqualifying a two state relay as a possible solution.

Were any electromechanical gadgets tried before Fleming and De Forest?


texts:
This may be a stupid question but it seems that I don't have a clear image about how this works exactly.

So my question is:

In the attached schematic, why will there always be a higher current in the A loop than in the B loop. What I mean is: why the current from the 10V source won't take the path marked with yellow in the image?

I understand that a higher voltage (and the same resistance) will give a higher current but I am confused about the path.


texts: Can a Li-Ion cell failing in a battery pack damage the other cells?

texts:
If you have a Lithium Ion battery, made from multiple 18650 cells in parallel, can any failure of one cell damage the other cells when only in electrical contact with the other cells?

More specifically, if each cell in the pack is physically isolated in all ways except for electrical contact, and in the event that a cell vents it's electrolyte, assume it's impossible for the venting gasses and liquids to contact the other cells.

Can any failure of a single cell induce electrical conditions in the other cells that will damage them?

If I didn't explain well enough, please allow me to rephrase things.


texts:
For a hobby project, I want to connect my own circuitry to a PCB which I have not developed. On the PCB is a linear hall sensor which outputs a voltage at about VDD/2 when a magnetic field is not detected and about 0 when a certain pole of the magnetic field is detected. I have posted below a very simplified version of the circuit in order to provide a reference for my questions.

The goal of this part of the project is to occasionally drive the linear output line from "My UC" regardless of the output of the linear hall sensor. By occasionally, I mean that most of the time P1 will be floating.

If the linear hall sensor is driving the line to VDD/2 or 0 what will happen if "My UC" drives the line to 0 or VDD/2?
What sort of issues will this cause with the sensor? (Potentially kill it?)
Is there a way to drive the line from "My UC" without destroying the sensor or without cutting the PCB traces?

EDIT:

Extra information:

What is the actual voltage range of the sensor linear output?
Is your MyUC able to output the same type of signal range as that from the hall sensor device?
How does the voltage range from the MyUC compare with that of the sensor output?
Are you intending to also interconnect the GNDs?
The "My UC" microcontroller will be operating on the same voltage source as all the other components. It will share the same 3.3V VDD and the same ground connection as all other components.

Does the sensor truly output a linear level that changes with magnet position?
The sensor does truly output an analog signal and not a digital value as might be assumed from the limited information in the OP.

If the magnet poles are interchanged does the sensor output start to swing from VDD/2 up to VDD?
If the magnet poles are interchanged the output will range from ~1.5 to ~3.3.

Is the override control you intend to inject going to be digital in nature?
The signal I am planning on using to drive the line is also analog in nature. It will be the output of a DAC in the same range (~1.5V to ~0V).


texts: Thévenin with dependent source and unknowns?

texts:
I have this problem where I need to find the Thévenin resistance. However I have a bit of a trouble of thinking how I should do it with a dependent source and that everything is unknown. How should I go about this problem?

Thanks in advance!

Edit:

I'm trying to figure out the third equation that involves V1. Could some try to give a hint on how to manage that?


texts:
I have a strange  behavior on a custom powerstep01 board I designed.
This is the Schematic of the CP / BOOT section:

simulate this circuit – Schematic created using CircuitLab
The values for the capacitors are chosen from the "typical application" section.

So here is my problem.
I have 2 boards. 1 is 100% working. Another one shows the following behavior of the charge pump.
the device is supposed to be running at 20V to 24V.
When I set STBY to HIGH (get the device out of standby), the charge pump starts running, but at an out of spec. frequency of about 2.6Mhz - 2.7Mhz.
According to the datasheet it should be between 660kHz and 800kHz.

The voltage swing is from 0.3V to 7.3V - so it's about 7V_PkPK \$7V_{PkPk}\$
This results in about \$6.7V_{PkPk}\$ on the diodes and then finally only about 6.3V added voltage to the power rail on the BOOT pin.
This in turn is sometimes not enough to reach the "Turn On Threshold" and the device remains in ULVO (Flag in the register set).

During trouble shouting I figured, when I increase the supply voltage to about 28V, suddenly the charge pump stabilizes to 750kHz with \$7.8V_{PkPk}\$. Which results in about 7V added to the power rail on the boot pin. The ULVO is then not triggered and the whole circuit is working perfectly fine.
After it stabilized I can turn it back to 20V-24V and it remains working.
What I have tried (and failed):
reduce and increase the value of C1.
reduce and increase the value of C2.
Change the diodes (same type).
Tripple checked all solder joints / pins.
I'm running out of ideas
What else could be wrong with my charge pump setup?


texts:
I am looking to create a custom & precise static optical distribution along the length of a fiber optic cable. The idea involves manipulating an optical fiber during manufacturing to produce the distribution along it's length. I want to simulate this concept to see if the optical properties of the modified fiber optic cable are what I expect them to be prior to manufacturing the fiber.

The end goal is to create a tool that utilizes this technology, but at this stage I am looking into testing a minimal proof-of-concept.

Would you know which software tools are typically used to accomplish a feasibility analysis of optical characteristics on a fiber-optic scale?


texts: How to calculate roots using root locus method?

texts:
Find the roots of the following polynomial by use of the root locus method.

  3s⁴ + 10s³ + 21s² + 24s + 30 = 0
  (The root locus plot has not been given.)

Can you please help me with this?

This is a question from Control Systems engineering by M Gopal and I J Nagrath 5th edition.

And this is not a homework question or anything related to assignment.
It's a sheer attempt to increase my knowledge on root locus method


texts: Calculating for current in a single transistor amplifier(almost common collector?)

texts:
I was given this circuit for a practice test during one of my classes, but we were never shown how to actually solve it. It's just been bugging me so I wanted to know how others solved for all the different currents and voltages given only the values of the resistors, power supply and the beta dc value(175).(solving for Ie, Vb, Ve, and Vc):

I sort of came up with a formula to solve for it by simulating it and then calling R2 a variable along with collector current. From there I just made this up and it works, but I'm not sure how a pro would solve it. I also don't know the name of this configuration as I couldn't find it in my textbook either.

Here is what I figured out I bet someone has already derived this but I couldn't find it, so I thought it was sort of cool. Comes out to R2 = (Vcc-Vbe-Ic*(R3-R1))/(Ic/Hfe) This picture might help with how I got that, although my math could be derp.

My calculation came out off by 1k for the base resistor but I assume that's fine because the phone simulator only gave me two significant digits.


texts: Minority Carrier Diffusions Equations in the derivation of Shockley equation

texts:
I am trying to get an intuitive grasp of the derivation of the ideal diode equation and I am struggling with a couple assumptions although the math itself looks pretty straightfoward. I am self-stuyding this from Pierret's book.  My major problem is with the boundary conditions at the contacts. It says that
$$
\Delta n_p (x \rightarrow -\infty) =0
$$

When one can assume the diode in question is a wide-base one, meaning whose contacts are several diffusion lengths or more from the edges of the depletion region. This means we can consider them to be infintely far from the depletion region (p beeing on the left side). Yet current in the quasi-neutral p region is diffusion current which is determined by

$$
J_N =qD_N \frac{d \Delta n_p }{dx}
$$

Since the electrical field is nul by assumption.
 Now doesn't the first equation imply the diffusion current to be 0 in the diode. The way I understand it under forward bias the electrons from the n region should cross the now lower potential barrier through diffusion and become minority carriers in the p region where they end up reaching the ohmic contact and eventually the cathode of the battery. Am i missing something here?


texts: Can you explain this solution to find Isource (Thevenin Norton)

texts: I know it is current division method but how is it applied ?


texts: Mathematical Logic behind generating T0 codes

texts:
I'm doing a small project in college where I'm required to convert(encoding) between gray and binary codes and also for bus invert coding in verilog. Its a simple task really as I'm done with code for the above said encoding methods.

Now to the point, I'm required to generate T0 codes from either binary or gray format. I've hit a stumbling roadblock trying to understand what is  this T0 code all about. Rummaging through the internet, I could only find journals that offer only a vague outline about this kind of code.

I'm really good at coding and all I need to know is if it is possible to encode a binary input code to a T0 code or vice versa. If so, I would like to know the mathematical logic or steps performed for generating them. Note that this is just a mini project done just to get the hang of digital logic as part of my university's curriculum.

If the above is not feasible, care to suggest an alternate encoding technique


texts:
Here are some images of a little LED "backlight" board. It just lights two (red) high-intensity LEDs.  There are two ICs on it which could use some identification help please.

2.00mm square package, marked "SB", three pads.  Assume MOSFET. Can see a diode in it towards the left LED below.
3.00 x 1.50mm package, perhaps a Micro6, marked "A40".  Assume CC LED driver.  Most likely this failed.

Any chance someone has an idea what these are?

Orange = 220µF caps (parallel.)

Apologies for the awful 'scope bloom.

Note on measuring this A40 (in-circuit):

Pins 2-1, 2-3, 2-5, and 2-6 all show slightly different ~0.6V diode-drops.
Ditto for pins 4-1, 4-3, 4-5, and 4-6.
Pins 2,4 must be power. They go across the top-right three caps in parallel (including the two orange caps on back.) Guess they were serious about bypass!

EDIT - I found another, slightly different board. This one still has the same "SB" 3-terminal device (all three pins are used), but the "A40" is replaced with an "AAUW":

Thank you!


texts:
I want to measure weight of some  objects which range from 50 grams to 20 Kg. So what kind of sensor should I use to get values with a precision of 1 gram. I tried a strain-gauge load cell of 20Kg, connected it to hx711, and this to arduino. But I get values which are not much accurate.(I may have not done it properly maybe). They show me different values every time I put the same weight.
I wanted to know if there is any good sensor for weight measuring sensor with a good precision of 1 gram.


texts:
Using superposition i first killed V2 and then calculated the parallel of R1 and R2 resulting in the following circuit:

Next using Ohm Law i found the current going through Ir3 = (4/2) = 2 and then the voltage of R3 V=2k(Ohm) * 2mA= 4V

Concluding, the voltage applied by V3 on R3 is 4V.
And i remembered Vo = Vab2 + 4 <=> -2 = Vab2 <=> Vab2 = -2 .
Im stuck on this step because im getting a negative voltage and i dont know where it went wrong and i can't find the voltage of V2.
I can't post the  image but next i killed V3.


texts: Runtime reconfigurable FPGA clock routing

texts:
I have a design with multiple inputs and outputs that should have different bit rates, configurable at runtime. Since there are more I/Os than PLLs, I need to share some PLLs, e.g.:

port 1: 1 Mbps
port 2: 1 Mbps
port 3: 15 Mbps

Ideally, I'd like to route an 1 MHz clock to the output stage of ports 1 and 2, and a 15 MHz clock to the output stage of port 3. If port 2 gets reconfigured to use 15 MHz as well, the clock routing should be changed so port 2 switches to the other clock network. If instead port 3 is reconfigured to 20 MHz, the PLL driving that clock network should be reconfigured at runtime.
Is that possible with normal FPGA architectures to make clock routing elements visible to VHDL, or should I just go with generating a clock that has a high chance of being a multiple of any baud rates I want to support, and dividing it locally on each port with enables?


texts: Inductors voltage substitution from 2 independent equations

texts:
We have this circuit:

simulate this circuit – Schematic created using CircuitLab
The current through the inductor IL = Io(1-e^(-R*t/L)(1):
Now there is an equation VL = -L*dI/dt(2) my question is if we take the derivative of IL with respect time from (1) and plug it in the (2) is that correct?


texts: Does an increase in load current change field winding current?

texts: I would like to know if the current in the field winding of a DC generator using a field winding in its stator increase as the load across the output of the generator itself increases.


texts: Doubts about IIP3 (Third Order Intercept Point)

texts:
I was reading the chapter of the book "The Design of CMOS Radio-frequency Integrated Circuits " (Thomas H. Lee) about linearity of power amplifiers. It introduces the definition of IIP3 by saying that in general the output current of a transistor amplifier is a non-linear function of the input signal, which may be approximated as a 3rd degree polynomial (if the input signal is quite small):

Now it analyzes the situation in which the input signal \$v\$ is the sum of two sine with frequencies \$\omega1\$ and \$\omega2\$.

If we put this expression inside that of the current we get the complete formula. But the most important terms are the first order term (which is the linear term) and the intermodulation products, which are respectively:

DC term and Linear term (note that also the \$v^3\$ term generates a linear component):

Intermodulation products:

Then, it introduces IIP3:

Now, I have the following questions:

1) The book finds IIP3 by putting the amplitude coefficient of the intermodulation product equal to c1A. But it is not the complete amplitude of the linear term: there is also a linear term which comes from \$v^3\$, as we have already said. Why is the last term ignored? I think that a correct definition of IIP3 should compare the total amplitude of the linear signal (so not only c1A) with the total amplitude of the intermodulation product.

2) After having found the expression of A, it finds IIP3 by evaluating the input power corresponding to A. My question is about how to evaluate it: the input signal is the sum of two sine waves, and so, when we use the formula

IIP3 = \$A^2 /(2Rs)\$

what does the factor 2 represent? Is it due to the fact that we should use rms values of amplitude, or to the fact that the the input resistance of the amplifier is supposed to be equal to Rs (source resistance)?


texts: Will the PIC18F14K50 perform well as a CNC machine micro-processor?

texts:
The data sheet can be found here.

I'm trying to select a micro-controller which will eventually run a Wireless 2D Laser Engraver/3D Printer/CNC Machine.

I have very little experience in selecting micro-controllers, and only a rudimentary understanding of the terminology. The micro-controller would need to fit the following requirements:

Run on 5V
Have at Least One Digital Input (I understand that this is called a
UART port.)which will be used to interpret the output signal from a
FM wireless receiver outputting digital data.
Have at Least 13 I/O pins. 1 to run the object on/off (I.E. CNC bit,
Plastic Extruder, Laser.) And 4 pins for each h-bridge which will
run stepper motors running the x-y-z axis.
Be able to house an approx. 16KB C++ program for interpreting the
digital data sent by the radio receiver, and the ability to edit the
on-board program.
Occupy the smallest amount of board-space by having only the
required pins.

I believe that the PIC18F14K50 meets these requirements because the datasheet shows (in the order above):

Runs on 1.8V to 5.5V.
Has an Enhanced Universal Synchronous Asynchronous Receiver
Transmitter pin.  Has 14 I/O Pins.
Can house a 16KB program which is flash memory, I.E. I can rewrite
code at will. (I'm not worried about RAM, as I don't store many variables. The           program is almost real-time.)
Has the minimum amount of pins/board-space to fulfill my needs. (20
Pins.)

I believe I have all the terminology correctly assessed, but I'm not sure enough to order the part without some more experienced input.

A few things I noted were included on the data-sheet and I'm unclear on how to assess my needs for:

CPU Speed
EEPROM (I believe this is the precurssor to flash memory...why would
I need both?) Comperators
8-Bit Architecture

EDIT

It's also worth mentioning that I will need to be sending output to all 13 of those parallel ports every 500ms or so, if that effects the specs I would need I would love an explanation as to how it does.


texts:
I'm in the process of assembling a microcontroller PCB design.  It's essentially just a breakout board.  I'm trying to think of the best way to test the board after assembly.  My first thought is to try to program the board with a test program.

Am I on the right track?  It seems so obvious, but board programming is still non-trivial.  I'm used to moving in more predictable, piecemeal type steps whenever possible.  Are there any less complicated tests I should be performing that could give me more insight?

One of the issues I'm facing is that the micrcontroller has an LGA style package.  With the pins hidden + hand assembly, it's difficult to trust that all the connections are made properly.


texts: Generating square wave to be inputted into a MCU

texts:
There are signals like below picture inputted to MCU STM32f103:
(Offset DC about 800mV, Vmax = 2.4V, f = 66 Hz)

I want to change it to a squar wave from 0V to 3.3V being accepted voltage range for my MCU.
How I can implement it? Using a schmitt trigger implemented by an op amp?
Can you please provide me a schematic?

EDIT:
Based on ChrisStratton`s comment:     Cost and power do not matter. I am going to obtain frequency of signal by MCU Timer/Counter. In fact my ultimate goal is to have the frequency to calculate speed. One hertz could be an accepted precision and the frequency is less than 1 KHz. Actually the first thing I tried was AC coupling being able to remove DC offset. However, the amplitude was not what I want. To sum up, I need to have a square wave with the same frequency and 0 V to 3.3 V amplitude.


texts: Best replacement for this faulty inductor from a computer power supply?

texts:
Edit: Looks like replacing the inductor resulted in the same problem, and my newly wound inductor started causing some smoke. :(
I recently acquired a faulty Corsair CX750M Power Supply that makes a burning smell when turned on. I think that this inductor was the culprit and reached temperatures of >120 degrees Celsius, even with no load on the PSU. I measured the resistance of the two coils, both read exactly 0.0 Ohms. I am guessing that the inductor was heating up because it was internally shorted as the ohm reading should have been above 0.
I have read this forum post: https://linustechtips.com/main/topic/890851-corsair-grey-label-cx750m-burning-smell-fault-finding-and-repair/
Which is by another person with the EXACT same problem. He said he replaced it; (I think he manually wound the coil with new wires?), but that also burnt up instantly.
Here is what the inductor looks like. As you can see, the blackened insulation is rubbing off very easily.

I tried searched Digi-Key for a potential replacement according to the dimensions and type of inductor. However, I could not find the exact inductor and I am unsure of what similar inductor I can use as a suitable replacement. I am also unsure what inductance in henries I should get.
I am hoping someone can help me in finding a similar inductor I can get, or maybe replacing the inductor would not fix it because of some underlying PSU circuity flaw?
Any advice is greatly appreciated!
Thanks.


texts: Why does RC circuit create 180 degree phase shift in current?

texts:
I was playing around with capacitors in LTspice today to grasp a better understand of how they shift the phase of voltage and current. I created what would be considered a 1st order filter. See image below
I then plotted the current through the resistor and the current through the capacitor. To my surprise, they are 180 degrees out of phase. How is this possible? Shouldn't the current be exactly the same through any element in the circuit?


texts: What does "Default Output State" mean for a digital isolator?

texts:
I do not understand the term "Default Output State" of the SI8422AB-D-IS
digital isolator. I saw it on this datasheet at page 3:

Does it mean "the default output voltage if the input pin is floating"? (so this means that the input pin is pulled up internally?)
Just for the record, I want to use a digital isolator for a USB communication protocol between a computer and a MCU, at around 9600 Baud, if that matters.


texts:
I have been working on a circuit go make a solenoid switch polarity with arduino. I originally used transistors (NPN) rated for 1A and 625mW in between the ends of the solenoid and ground. These all burned out when the polarity of the solenoid was switched (using a relay and switching which transistor was open and closed). I did the math and with a 60 ohm solenoid the voltage drop should be almost fully across the solenoid so the 10 V should be dropped across the solenoid, and the current should be (and was limited to using my DC power supply) .5A. I think this has something to do with inductance but I cannot figure out exactly what? I have solved this by using MOSFETs that can deal with higher power but I still need an explanation for why the transistors burned out.
Thanks
-Noam

Thank you so much for the explanation. My problem now is when I reverse the direction of the current that diode will simply short out the circuit. I could put a transistor after each diode but is there a better way of doing this?

The issue is if In order to switch the polarity of the solenoid I reverse the ground and power so if I put diodes there most of the current would simply flow through one of the diodes (I would need 1 in each direction the circuit always including when the ground and power are flipped from their original position using a relay and transistors)  to ground shorting out my circuit


texts: Correct Notation of Radiation Pattern of an Antenna

texts: I have a confusion regarding the notation of radiation pattern of an antenna array. Some literatures use, say, $$F(r,\theta,\phi)$$ to denote the same while others use $$F(\theta,\phi)$$I would appreciate if anyone tells me the proper notation for the same. I am writing a report and I am not sure which notation to follow to represent the radiation pattern(field/power).


texts:
I found a scruffy old generator on an auction site.
As it's 'we're all home' I bought it for a very good price, stripped it and cleaned everything, then mounted it on a board with screw terminals for ease of use. (See picture below.)
It's had very little use - the brushes are very long, not worn down.
That's the background of this little monster and now the 'can I do that' bit.
It has two outlets, (calling left and right) the motor draws 3amperes at 12V according to my clamp meter, the left output is showing 1888 volts on my multimeter set at 600V DC and is stable.
The righthand outlet is showing 1475V (can't see a decimal point on either display) and that is a rough average because it's flicking up and down by twenty or so.
Now, this is the question:
Can I have it self powering and charging a 24V battery bank?
I'd love a list of bits and a diagram.


texts: Adding DC offset to PWM through a unity gain buffer

texts:
I have a PWM signal with a period of 200uS and a duty cycle of 20%. For prototyping reasons (this is simulating a pulse that I'll be receiving from circuitry later on in the project), I want to read the PWM signal via an ADC on an STM32F7. The ADC has a Vref of 2.5V from a TI 5025. The real world pulse will have a signal that drops below 0V before it recovers, so I want to add a DC offset that is half of the Vref (1.25V).

The voltage reference is working fine and I have added a voltage divider on the output to give me half the 1.25V offset that I want. As the pulse will interfere with the Vref signal I've opted to add a unity gain buffer (MAX4167) to the output to isolate the 2.5V reference and the 1.25V offset to add to the signal. The buffer outputs the expected DC voltage.

All of this circuitry works as expected.

What doesn't work is when I add the PWM signal to the output of the buffer. I expect to get my 1V PWM signal output with an offset of 1.25V but what happens is the DC offset remains but the signal gets completely lost. I want my PWM signal to be identical but with an offset. I've attached a picture of what I've done and what I want. It's much easier to digest visually

PWM signal that I'm generating via signal generator:

Output that I'm getting from the buffer when I add the PWM signal to the output:

Any suggestions as to how I can solve this problem would be great. I've not done a lot of work with Op Amps before so I'm sure it's something simple. Thanks


texts: Is there a minimum amount of electricity that can be fed back into the grid?

texts:
This is not fully related to electrical engineering, but I have been reading lately about Feed-in-Tariffs and solar energy production and I cannot find any information on the amount of energy that can be fed back into the grid.

My question is, can every amount of energy be fed into the grid for a remuneration according to the Feed-in-Tariff or should the electricity be first accumulated (using an energy storage system) to, lets say a kWh, or is any quantity possible to be fed back?

I have looked at the Feed-in-Tariff method and normally the payment is for a kWh, if the price per kWh is 8 cents, would I be paid 0.8 cents for 100 Wh or would I first have to produce a minimum of 1 kWh?


texts:
I need to make an dc accurate low pass filter. Actually, I need to measure the dc/average value of a waveform. Suggest me some good and practical 0hz low pass filters. That is, the filter that can block other frequency waveforms but pass only dc component of a wave.
The waveform can be as:


texts:
In the formula I = V / R it makes sense that in a circuit such as the one found in homes the amount of current as proportional to number of electrons passing through a slice of wire per unit time is proportional to the push of the voltage and inversely proportional to the resistance due to how much electricity the martial of the wire allows to pass and its length.

But then what is the point of multiplying I and V in P = IV. How do I interpret this equation taking it further than seeing it as the product of two quantities related by Ohm's law?

Thanks.


texts: How can I program Mega2560 with Atmel Studio 6.2

texts:
I have got the SainSmart Mega2560.

The problem is now: how can I program it with Atmel Studio 6.2?

I can find no way to upload code, because the controller is not in listed and with ISP I can not do it, because STK600 is needed which I don't have!

Is there another way to program the Mega2560 with Atmel Studio 6.2?


texts:
I have the function: \$f(x,y,z,w) = wx + yz\$

I found its complement function to be: \$f '(x,y,z,w) = w'y' + w'z' + x'y' + x'z'\$

I have to show that: \$f + f '=1\$  but I can't see how to do it.

It seems as if there just isn't anything that cancels each other out.

Edit

As suggested, I have now used DeMorgan's theorem and found this:

\$f + f' = wx+yz+(w+y)'+(w+z)'+(x+y)'+(y+z)'\$

But it still seems to me that there is nothing that brings me closer to the realization of \$f+f' = 1\$


texts: Dark current of photodiode gets higher after heating, why?

texts:
I'm doing some experiments using photodiodes. I raised the temperature to about 1000 degree Celsius for 1 second with melting AuSn near the PIN junction. Then the dark current of photodiode is higher than before. What are the causes? Is the photodiode broken?

PS:
more info.

I'm using Si photodiode.
It's the heating plate that reaches 1000 C, temperature around PIN junction is about 500 C. my mistake.


texts: How can I simulate microwave radio link transmission?

texts:
My task is to simulate a two-way data transmission microwave link. The fixed parameters are distance, transmitter power, carrier frequencies, bandwidth, receiver noise figure, intermediate frequency, adjacent channel crosstalk. The variable parameters are data rates, and modulation formats. The task doesn't say anything more, but just to "examine the transmission", but in my opinion, I should check the bit error rate of the links.
I've already tried to simulate this in AWR Design environment (Microwave Office), with the system diagram option, but the problem was that I couldn't adjust the antenna distance. If you know how to add this parameter, or you've already done some simulation in System diagram, please help me.
So, U don't really know which program should I use for this task. Maybe Matlab Simulink would be appropriate, but I think it's too general, and it would be circumstantial.
I would be thankful if you could help me with this problem, even if you just tell me which program should I use.
PS: sorry for bad English.
Thanks everyone.


texts: SPI communication between FPGA(ZC-706) and Amega128

texts:
I'm trying to write a communication protocol between an FPGA and a Microcontroller through an SPI, the µC being the Master here.
FPGA: ZC-706 (Zynq-7000)
µC: ATmega128
Here is the code which i used for the FPGA part. https://github.com/souktha/zybo_spi_slave/blob/master/spi_slave.v
Here's how the code is supposed to look like (as explained in the link above):
. Four wires: MOSI (input from master), MISO (output to master), _CS (chip select from master), CLK (clock from master).
. Phase and Polarity fixed to mode 0.
. Support back-to-back transfer.
. Use MIO/EMIO routing interface of the zynq7000.
. 8-bits command/data.
. Basic command support: Read ID (0x1d), Read(0xea), Write(0xad). Limited to three commands for simplicity. Any other commands is rejected.
I have to write data from the microcontroller(data on ADC pin) and read to fpga. Please find the below mentioned microcontroller code.
// SPI interface pins
#define   MISO       PB3
#define   MOSI       PB2
#define   SCK        PB1
#define   CS         PB6
#define   DDR_SPI    DDRB
#define   CS_low        PORTB&= ~(1<<(PB6))
#define   CS_high       PORTB|= (1<<(PB6))

#define spi_read_addr  0x00000020      // recieve register address from FPGA
#define spi_write_addr 0x0000001c      // Transmit register address from FPGA

ISR (ADC_vect)
{

    vol_buf= read_ADC();
    volt = (vol_buf*2.56)/1024;

    if(volt >= 0.9 && volt <= 0.9075)
    {
        PORTB = 0x01;
        PORTE = 0x30;
    }

    else if(volt >= 0.91 && volt <= 0.9175 )
    {

        PORTB =  0x01;
        PORTE = 0x40;
    }
 }

void init_ADC()
{
    ADMUX = 0x03;
    ADMUX |= ADMUX | 0xc0;                  // Internal 2.56V Voltage Reference & ADC3 is selected
    ADCSRA|=(1<<ADEN)|(1<<ADPS1)|(1<<ADPS0);               // ADEN enable & ADIE=0
}

uint16_t read_ADC()
{
    ADCSRA |= (1 << ADSC);
    while (ADCSRA & (1 << ADSC));
    return ADC;
}

void init_SPImaster(void)
{
    DDR_SPI = (1<<MOSI) | (1<<SCK) | (1<<CS);  // set MOSI, SCK and CS as output and others as input
    SPCR = (1<<SPE) | (1<<MSTR) | (1<<SPR0);  // SPI enable , set as master and clock = fck/16
}

void SPI_masterWrite( unsigned char DataAddr , signed int count )
{
    if(volt>= 0.9 && volt <= 0.95)
    {
        SPDR=DataAddr;
        while(!(SPSR & (1<<SPIF)))
        {
            //
        }
    }

}

void SPI_masterRead( unsigned char Addr , signed int count_ )
{
    if(volt>= 0.9 && volt <= 0.95)
    {
        SPDR=0;
        while(!(SPSR & (1<<SPIF)))
        {
            //
        }
    }

    Addr = SPDR;

}

Is the microcontroller code correct or not? How should I call read write function in main loop?


texts: If you wire together two TTL outputs, which one wins?

texts:
If you connect together two outputs from 7400 NAND gates, which output will dominate - high or low?

Background: I'm reverse-engineering a 1969 circuit board, and in multiple cases they tie together two outputs from 7400 NAND gates, presumably to make a wired-OR. This would be reasonable if they used open-collector chips, but these are SN7400N chips, so it seems a bit sketchy. (In other places, they leave an input floating, presumably to high, which also seems sketchy.)


texts: For Brushless DC Motors would one expect harmonics to be different between Delta and Y stator windings?

texts:
Given two 3-phase brushless DC motors with the only difference being that one is wound delta, the other Y with center grounded, would I expect to see high frequency voltage-current harmonics to be significantly different between the two?

So in each case the measured terminal to terminal phase resistance and inductance would be the same, the number of poles and PM magnet geometry would be the same,the effective torque constants would be the same, the frame size would be the same, and the drive would be the same.

Realizing of course that making all these other factors the 'same' is a hypothetical situation, and may not be physically realizable.


texts:
Rather than using an Ethernet magnetics component, is it possible / reasonable to simply use individual isolating transformers?

Inside the magnetics component, it's clearly made up of individual transformers. Is there some reason that people always seem to get these as a single package, rather than using them discretely?

What I'd like to do is to get rid of the large plastic casing, and try to save a little precious space on my stupidly tight PCB.

Added:

After a lot of searching, I think I have found a suitable transformer: Wideband Transformer with 2 Windings and Tap.

Turns ratio 1:1:1
3dB Band Limits (MHz) : 4.5 - 1000
Loss at 20 MHz (dB) max : 0.7

Added:

Just discovered that you can buy those from Mouser, and they are very expensive!


texts: What is this 8 pin PCB to wire connector

texts:
I have tried searching all over the internet, and haven't managed to get anywhere with this - does anyone know what this 8 pin PCB to wire connector is? It is approximately 18mm wide. It is used for both data and power (5v).

Any help is greatly appreciated!


texts: How does a non contact voltage tester work?

texts:
How does a non contact voltage tester pen detect voltages and/or currents? Are they limited to voltages of a certain range or type (AC or DC)?

Here's some experiments I have conducted that lead to this question: Using a cheap pen I bought for a couple bucks, I can detect the usual 120V AC in an American outlet, but I also have been able to detect voltage in a USB cable connecting a switching power supply to a smartphone (this setup is usually referred to as charging one's phone). Here, of course, the voltage in question is DC with a negligible ripple. I also noticed that while the detector can detect the 5V of a phone charger cable, it cannot detect the voltage in a USB keyboard cable. The only difference between these two scenarios is the current level and perhaps some minor signaling differences.

A final question: In what voltage/current scenario would you have to use a current clamp sensor and not a non contact voltage detector for merely detecting the presence of power non-intrusively?


texts: Simple Two wire SPI communication between two PIC24s

texts:
I am trying to achieve a simple SPI communication of 16-bit data from a PIC24FJ64GA002 to another of the same microcontroller.
By following the data sheet to the word, I wrote the transmitter and receiver code as below,

Transmitter:

unsigned int i = 0;

void main()
{
    RPOR2bits.RP4R = 7;  // Data out through Peripheral Pin 4
    RPOR2bits.RP5R = 8;  // Clock out  through Peripheral Pin 5
    SPI1CON1bits.MODE16 = 1; //16 bit mode
    SPI1CON1bits.MSTEN = 1;  // Master enable
    SPI1CON1bits.SSEN = 0; //No slave selection
    SPI1STATbits.SPIROV = 0; //Receiver Overflow cleared as told in datasheet
    SPI1STATbits.SPIEN = 1; //SPI is enabled
    while (1)
    {
        while (SPI1STATbits.SPITBF); //Waiting for any transmission to complete
        SPI1BUF = i; // Data is written
        i++
    }
}

Receiver:

unsigned int i;

void main()
{
    RPINR20bits.SDI1R = 0; //Data in through Peripheral pin 0
    RPINR20bits.SCK1R = 2; //Clock in through Peripheral pin 2
    AD1PCFG = 0xFFFF;
    TRISA = 0x0000;
    SPI1CON1bits.MODE16 = 1;
    SPI1CON1bits.MSTEN = 0; // Slave mode
    SPI1CON1bits.SSEN = 0;
    SPI1CON1bits.SMP = 0; //Must be cleared in slave mode as told in datasheet
    SPI1CON1bits.DISSDO = 1; //Receiver only receives data
    SPI1STATbits.SPIROV = 0;
    SPI1STATbits.SPIEN = 1;

    while (1)
    {
        while (!SPI1STATbits.SPIRBF); //waiting for receive to complete
        LATA = SPI1BUF; // pushing Received data onto A
    }
}

The transmitter seems to be transmitting the data (clock and data lines show expected cycles), but for some reason the receiver does not receive the data and push it onto A terminals.

The configuration settings for both microcontrollers are:

Primary Oscillator Select: Primary Oscillator Disabled
I2c1 Pin Location Select: Use default SCL 1/SDA 1 pins
IOLOCK Protection: Disabled
OSCO Pin Configuration: OSCO functions as port I/O
Clock Switching and Monitor: Clock switching is enabled, Fail-safe Clock Monitor is enabled
Oscillator Select: Fast RC Oscillator (FRC)
Sec Oscillator Select: Default Secondary Oscillator (SOSC)
Wake-up timer Select: Legacy Wake-up Timer
Internal External Switch Over Mode: Disabled
External Watchdog Timer Postscaler: 1:32,768
WDT Prescalar: Prescaler ratio of 1:128
Watchdog Timer Window: Disabled
Watchdog Timer Enable: Disabled
Comm Channel Select: Emulator EMUC1/EMUD1 pins are shared with PGC1/PGD1
Background Debug: Disabled
General Code Segment Write Protect: Disabled
General Code Segment Code Protect: Disabled
JTAG Port Enable: Disabled

The only two connections are the Clock and data lines from the respective peripheral pins. What is the problem here and how to receive the data?

It seems impossible that this actually works, has anybody ever achieved this?


texts: How to find linear LEDs (light power(mW) vs current)?

texts:
I'm looking to use an LED in a control application.
(feedback via LED to photodiode.)

I found a few questions that didn't fit.

Adjustable linear led driver? Linear, not PWM.
Light intensity and photodiode current.

I'd like to make it all linear, no PWM.
(I worry about the led turn on/off time with PWM, I can average, but that's slower.  Even with pwm having a linear 'current' control knob might help.)

What frequency you ask?; I guess 1-10 MHz, for a start, but faster
is better. :)  I dream of finding an LED whose light output (in mW) is linear
with current, from say 1 uA to 1 mA.  Is there some search phrase I can look for?  Searching for leds on the web is a fire house.
I know this is kinda a shopping question, Is there a meta-shopping type
question?  How to shop?

Let me edit: Yes a linear opto-coupler would be even better. If it was
fast.  > 1MHz.


texts: Is it possibile to use a CAN transceiver to send RS485 data?

texts: Looking at the signal ranges I'm not sure if I can use a CAN transceiver (not controller!) to send data to a single RS485 device.


texts: SSR Switches Off Intermittently By Itself

texts:
I have a 24 ~ 380 V 100 Amp AC relay. It can be driven between 3 ~ 32 V, and I'm using a Raspberry pi to drive it with 5 V.

The relay has a red LED that indicates it is "on". When checking up on the relay, I've noticed its off half of the time while the Pi is still running and supplying 5 V.
I don't know if it goes off and comes on by itself again - but when I pull out the positive and negative wires from the relay and wait a minute before re-attaching them, the relay works for a short while before going off again.

I've had the relay for only a few weeks with a max current of 220 V AC. Can anyone tell me what could he wrong with the relay?


texts: I'm trying to communicate through I2C with a temperature sensor (STS21) using interrupts on STM8S003F3 board but i can't manage to make it work

texts:
I've been trying for some days to make this code work but I can't manage to do it. The variable in which I try to store the the temperature (which should be around 20-22 degrees Celsius), contains the value 4.82, which is far from the correct answer. I tried looking at the example code offered by ST Electronics, but still didn't help me. I'll post the main code and the interrupt one here maybe someone can tell me what I'm doing wrong.
main:
#include "stm8s.h"

static void CLK_Config(void);
static void I2C_Config(void);
static void GPIO_Config(void);
static void Delay(__IO uint32_t nCount);

static void CLK_Config(void) {
    CLK_SYSCLKConfig(CLK_PRESCALER_HSIDIV1);
    CLK_PeripheralClockConfig(CLK_PERIPHERAL_I2C, ENABLE);
}

static void I2C_Config(void) {
    I2C_Cmd(ENABLE);
    I2C_Init(10000, 0xA0, I2C_DUTYCYCLE_2, I2C_ACK_CURR, I2C_ADDMODE_7BIT, 16);
    I2C_ITConfig(I2C_IT_EVT, ENABLE);
    I2C_ITConfig(I2C_IT_BUF, ENABLE);

    //B4 - SCL
    //B5 - SDA
}

static void GPIO_Config(void) {
    GPIO_Init(GPIOB, GPIO_PIN_4, GPIO_MODE_IN_FL_NO_IT);
    GPIO_Init(GPIOB, GPIO_PIN_5, GPIO_MODE_IN_FL_NO_IT);
}

static void Delay(__IO uint32_t nCount) {
  for (; nCount != 0; nCount--);
}

int x,i;
void main(void)
{
    CLK_Config();
    GPIO_Config();
    I2C_Config();
    enableInterrupts();

while (1){
    I2C_GenerateSTART(ENABLE);
}

}

#ifdef USE_FULL_ASSERT

/**
  * @brief  Reports the name of the source file and the source line number
  *   where the assert_param error has occurred.
  * @param file: pointer to the source file name
  * @param line: assert_param error line source number
  * @retval : None
  */
void assert_failed(u8* file, u32 line)
{
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */

  /* Infinite loop */
  while (1)
  {
  }
}
#endif

interrupt:
float T;
int y;
uint8_t a, b;
uint16_t v;
INTERRUPT_HANDLER(I2C_IRQHandler, 19)
{
  /* In order to detect unexpected events during development,
     it is recommended to set a breakpoint on the following instruction.
  */
    I2C_Send7bitAddress(0x4A, I2C_DIRECTION_RX);
    y = I2C->SR1;
    y = I2C->SR3;
    a = 0;
    while (I2C_GetFlagStatus(I2C_FLAG_RXNOTEMPTY) == SET);
    I2C_AcknowledgeConfig(I2C_ACK_NONE);
    a = I2C_ReceiveData();
    b = 0;
    while (I2C_GetFlagStatus(I2C_FLAG_RXNOTEMPTY) == SET);
    I2C_AcknowledgeConfig(I2C_ACK_NONE);
    b = I2C_ReceiveData();
    b &= ~(1<<0);
    b &= ~(1<<1);
    I2C_GenerateSTOP(ENABLE);
    v = 0;
    v += a;
    v = v << 8;
    v += b;
    T = 0;
    T = -46.85 + 175.72 * ((float)v / 65536);
}


texts:
I'm reconditioning my hybrid battery. To do so requires multiple complete discharges which I do not have time to be around for. To avoid damaging my battery I've been attampting to design a circuit that would step down load as the voltage of the battery drops and totally secure the voltage once the end point is reached.
Starting voltage ~240 +/- 5 Vdc

I would like ~200-300W draw at 2-4amps till 190V

~100W till 170V

~50W till 168V

~25W till shut off Voltage.

Would it then be possible to have a selector for the shut off voltage of 17V/85V/134V depending so as to successively discharge deeper over multiple runs?

If not I'd like a shut off V of 85V.


texts:
I have a problem with my circuit and I want some help.
I have an input connector connected to a dry sensor. It will send 0 when it's ON. So I made this circuit to protect my CPU.

My problem here is if someone puts 24V in Input connector, that's why I used 24V in pin 1 of the relay. Is it a good solution? What will happen in that case (24V in pin 1 and 2)?
If it's not, is there another solution using relay?


texts: Unknown DC-DC converter topology in ST datasheet

texts:
I have found this weird DC-DC converter topology in datasheet of MC34063 from ST.

The primary charging is single ended, so at first it seems like flyback, but it has four diodes on the output instead of only two. Is this some forward or flyback hybrid? What is it called? Or is there a mistake in the datasheet?


texts: Tippmatic auto shut-off switch - how to use it?

texts:
Some products in my company are now required to use an auto shut-off switch to be compliant with new regulations in European space (European Eco-Design Directive ErP).

I got word that the device being integrated into the current products will be the TIPPMATIC iF by Johnson Motor.

Can anyone please explain how these devices are supposed to operate?

The only datasheet I found for this is more of the mechanical kind, and has no guidelines whatsoever towards its use case.

The datasheet has a graph that displays a \$V_{coil}\$ level during a certain \$T_{(on)}\$ and then displays 0V during a \$T_{(off)}\$. It also provides the following values:

\$I_{coil\,peak}: 1.0 +0.2/-0.3A\$
\$I_{coil\,steady}: 20mA \,DC\$
\$R_{coil}: 20 \pm1.5\Omega\$
\$T_{(on)}: 3 \times 10^{-3}s\$ (coil command pulse length)
\$T_{(off)}: 2s\$ mininum (dead time for next disconnection)
\$V_{coil}: 20VDC\$

This is the representation it provides:

simulate this circuit – Schematic created using CircuitLab

From what I could make of it, I should  connect the mains' line between pins 1/1. and neutral to N. Then, should I pulse 20VDC for at least 3ms, and the switch should be "armed" (enabling operation on the load). Then I can't "arm" it again for at least 2s (even if it triggers meanwhile, disconnecting from the load). Can someone attest if this is correct?

Simply put, it's almost as the switch requires a "keep-alive" signal of sorts, that each 2s, requires a 20VDC for 3ms in order to remain closed, right?

EDIT: Still can't make much sense of what I read here - but I know the problem is me above anything else! :) Anyway, the manufacturer's FAE, told me this:

  you have to connect the switch in this way.

  N: neutral

  main voltage

  1 to the load (heater, etc...)

  On the drawing the switch is shown in OFF position
  the puls 5vdc should be done during 1-2ms
  You have to wait at least 2s to do again the operation otherwise a shorter time will heat >up the coil.

This validates @SpehroPefhany suggestion (+1'd), although, I'm still missing the whole auto shut-off feature they claim. The way I figure it, if we enable (turn on, close) the switch manually, it should operate as if no switch was there. Then, should we want to disable (turn off, open) the switch we have to pulse it at 20V for 3ms, is that it? If so, at what point does it shut-off automatically?


texts: Does it matter if I connect an antenna via SMA or not?

texts: I am using this LoRa Radio shield and want to connect a simple ¼ wave wire antenna to it. There is a hole for soldering an antenna on close to the SMA jack, but then I would be skipping the 50 ohms of resistance the SMA connector provides. Would that be bad? I am very new to radio technology, so I am sorry if its quite a basic question...


texts: Why can't I implement a frequency divider using a mux in this way?

texts:
I found an interesting interview question for FPGA engineer online - Implement a counter with Mux, so I decided to try to do that. I tried to keep it simple and so implement a counter with two bits, so it can count only to 3 and then reset.

I came to a conclusion I need 3 multiplexers, two for each bit, and the other one to serve as a frequency divider for the clock (I'm sure there are other ideas, would love to hear them as well).
Note that I wanted this frequency divider to work at the falling edge of the clock.

Basically this is what I tried to do:

simulate this circuit – Schematic created using CircuitLab

I used a clock of 1Hz just so it won't be too fast (though maybe it doesn't matter?), With mux1 being the frequency divider.

The idea here is that the counter is like this:

Q1 Q0
0  0
0  1
1  0
1  1

So, since Q0 changes with every clock edge, I connected the clock to mux3. Since Q1 toggles every two clocks, I tried to design a frequency divider which will make sure that Q1 will toggle every two clock (clk1) falling edges.

I thought it would work well, but in a simulation (used Multisim for that, because I don't know how to simulate it work circuitlab, would love if you could show me how I can do that), I got a very strange result - the simulation just stopped. Here is how it looked (the output of mux1):

When I zoomed in at the falling edge (at 500ms) it looked like this:

So my questions are:

Why doesn't my frequency divider work?
Is this implementation of a counter even good, if that frequency divider worked? Is this even possible?


texts:
For a project I am working on, I need some kind of way for a micro-controller (preferably Arduino, since I have background knowledge) to identify a certain symbol on a piece of paper (e.g. recognising an ampersand drawing), and then run some code depending on what it sees. The more symbols it could recognise, the better.

I understand that for identifying pictures in almost any program, you need a database to refer to. I assume this wouldn't be too difficult, but some tips on managing a database would be appreciated.

If there aren't any simple Arduino programs that exist, I could work with a pre-existing IC built for this purpose (I don't know if that would make sense, but just throwing ideas around). A link to a datasheet would also be appreciated.


texts: How to place thermistor for reading temperature in NiHM single AA cell charger?

texts:
I'm laying out a PCB for a NiMH single AA cell charger following the AVR450 Application Note - Battery Charger for SLA, NiCd, NiMH and Li-Ion Batteries but I'm not sure where to place the NTC thermistor that will read the cell temperature throughout the charging process.

I plan to lay out the cell holder like in the picture below. The holders are the Keystone model 92. The red arrows represent positions where I think I can place the thermistor.

I wanted to place the thermistor so that it makes best thermal contact with the battery cell, but the AVR450 application note doesn't mention NTC placement at all. Looking at the board shown on the AN, the NTCs are not present either. They are external to the board as the design allows the use of different battery packs and chemistries through the use of external battery holders. I've also searched the Net but couldn't find anything relevant.

My understanding is that these tin coated holders I'm using present high thermal conductivity, and thus, will be at a similar temperature as the cell. But I don't know whether the cell temperature is uniformly distributed throughout the cell when it's charging.

So, my questions are:

Where should I place the thermistor? Should I place it in contact with the negative (position A) or positive (position B) battery holder terminals? Which one? Or should I try to locate the thermistor near the middle of the cell (position C)?
What should I do to ensure good thermal contact between the battery and the thermistor? Should I apply thermal paste or something like that?
Is it ok to use the thermistor like the one in the picture below? Or is there a more appropriate thermistor package for my application?


texts:
I'm trying to have 3 touch sensitive buttons on an ATtiny48 device using Qtouch library.

The code was generated using the library wizard inside Atmel studio. I've only added a single condition to act when touch is sensed (only a single button is checked in this code).

int main( void )
{
    init_system();
    init_timer_isr();
    touch_init();
    __enable_interrupt();

    DDRD |= (1<<PD0);

    while(1)
    {
        touch_measure();

        if (GET_SENSOR_STATE(0))
            PORTD |= (1<<PD0);
        else
            PORTD &= ~(1<<PD0);
    }
}

As for the hardware, I've used 10nF film cap. across the button outputs and the sense pad is connected using a 12k resistor. Please see below:

I can see pulses on the sensing pins but nothing else. I'm not even sure how the generated code knows the system clock freq. for correct timer operation.


texts: Is there a practical way to increase the input impedance of an instrument?

texts:
I have a Lock-In amplifier with an input impedance of 10 MOhm. I am planning on measuring a resistance of many time higher than that.

Is there any practical solution that I can do to increase the input impedance?


texts: Measure the current draw of a motor with a slow multimeter?

texts: I have a motor that is in a printer housing (inkjet - the one that moves the head back and forth). The motor is attached to the printer head assembly. I want to measure the current draw of the motor, but I cannot take it out of the printer assembly without breaking it. I know how to do this with a multimeter, but by the time my multimeter is able to get a reading on the current, the printer head would be at the other end (causing more stress on the motor) and would draw more current than it normally should. Is there any way for me to measure the reading of it while it is moving the printer head?


texts: What is this amber like substance on capacitor and inductor?

texts:
What is the mysterious substance on the inductor and (failed) capacitor?
What is its purpose, and how do I replace the failed capacitor with it there?
The substance is hard and translucent, but I can make a very small impression with my finger nail.
This comes from a Belkin n-wireless router I am trying to fix, if that helps.

Thanks in advance!


texts:
I have design a switching mode power supply which converts the 5V to 3.3V for microcontroller and some other peripherals ICs supply.
The chips is TI's LMR10520Y, a low input range step-down switching regulator.
The total cost is very low and is the reason that choosing this IC.
The other reason is the efficiency, instead of a Dropout of a LDO.

The question is: What if, suddenly, voltage in the output (due to hardware problem) exceeds at too high magnitude and over the absolute maximum voltage of my ICs? (e.g. Vout > 3.6 Volts).
What is the most easy and cheaper way to protect my sensitive ICs from those undesirable overvoltages?

A LDO protect us from this fact but with "cost" in efficiency (max dropout voltage for the corresponding price product).


texts: My question is whether is it possible to declare string parameters in LTSpice? My specific problem is that I would like to use PWL files for the simulation, and it would be very useful if I could give the file name as a parameter. (reason: there are several other parameters belonging to a PWL file, and these parameters could be handled together).


texts: fastest gate setup to add 7 integer of 32bits

texts:
I would like to add 7 integer of 32 bit each together, using gates. The naive solution is to add two together, than the sum of these two with the third integer. The the sum of the first three added to the fourth integer... etc. However this is probably the slowest solution. I am looking for a fast way to do it. This is for sha256 algorithm. The main speed bottleneck is caused by a 7 input 32 bit adder.

Consider the 32 bit labelled: a, b, c, d, e, f, g. I would like to output a+b+c+d+e+f+g using gates asap.

A faster way would be

(((a + b) + (c + d)) + ((e + f) + (g)))   //This is performed in 3 steps.

(((((((a + b) + c) + d) + e) + f) + g)    //This is performed in 6 steps.

I would like to know if it can be done faster than the 3 steps process, by using special adders that can take multiple inputs.


texts: Finding the value of a specific resistor

texts:
Let say you have a network of resistors. All resistors have values but one of them is labeled "R"

Given the value of a total voltage and a total current, find the value of R.

My head start would be using Ohm's Law to compute for total resistance. But after that, I don't know what to do. I did tried doing the usual method of solving resistors in series and parallel. But I ended up having a negative answer.

How can I get the value of R?


texts: Audio Demos on DE10 Standard not Working

texts:
I bought the Terasic DE10 Standard and am having issues trying to run the demos related to audio.
I am trying to run the two demos, DE10_Standard_Audio, and DE10_Standard_i2sound, while connecting apple headphones to line out, and 3.5 lavalier microphone to mic in, but I am not able to record anything and play it back for the 1st demo, and I don't hear anything when I speak into the microphone for the second demo either. The microphone and headphones work fine on my laptop.
DE10 Standard user manual: https://www.intel.com/content/dam/altera-www/global/en_US/portal/dsn/42/doc-us-dsnbk-42-5505271707235-de10-standard-user-manual-sm.pdf
I am using a lavalier mic (https://www.amazon.com/Professional-Microphone-Omnidirectional-Recording-Conference/dp/B01AG56HYQ) and connecting it to the mic-in, and then using apple earphones to line-out.
The 2 demos are Audio Recording and Playing, and Karaoke Machine as listed in the manual. I did check that some of the other demos indeed do work.
Can anyone offer any advice at all? It really seems like the demos should work? I don't know what I'm doing wrong :(
I know this may be too general of a question, but I can provide any other information needed.
Thanks!!
EDIT:
I have tried a TS, TRS, and a TRRS type jack for the microphone input, and neither of these work unfortunately
EDIT:
I forgot to mention that I can hear when I directly breathe into the microphone, but nothing else. Unsure if this is relevant or not though.


texts: Closed loop bandwidth vs open loop bandwidth

texts:
Is closed loop bandwidth always greater than open loop bandwidth ?
If not on what factors does it depend ?
When can it be greater?


texts: Which is the best material to create a magnetic field?

texts: I'm trying to create a magnetic field and I'm also trying to induct electricity wirelessly to a light bulb. What I have to do is create a round coil but I'm not sure what is the most conductive material, is copper the best material for these kind of things?


texts:
I have an LM75 temperature sensor connected to a STM8, 80KHz I2C peripheral. the devices on the bus consist of this sensor and an I2C character LCD (PCF8574T). the LCD works perfectly fine but the temperature sensor, returns a temperature much under the actual value, but if I disconnect it (all pins) and reconnect it, it becomes normal. because all libraries are written by myself, I don't consider them fault proof so I included the logic analyzer outputs. the first write command to chip, is for setting internal register pointer, which is temperature. temperature register is 16 bits, which the MSB is the real part and the LSB is don't care (except the MSbit of LSB). the BAD one which reads 6 degrees which is wrong (I FEEL it!):

and the GOOD one, same sensor after disconnecting and connecting it again. (the data temperature reads are in HEX, so it's 21 degrees)

what I've done so far ? (without any luck abviously)

the logic level and supply voltages, are 5 volts
I've tried 2 sensors, same sensor PCB shape, various connection cables. they have on board bypass caps.
the wrong temperature goes up when I touch the chip and with the same rate as the working case.
I've tried various I2C speed. from 50 to 100 and 200KHz. the clock speed is checked on Logic analyzer.
the cable length is under 30cm
there are two sda/scl pull-up pairs. one pair on the main PCB (where the MCU is located) and another one on the LCD board. I've tried sensors with and without pullups on board. no luck. the pull-ups are 10K, and are pulled up to 5 volts.

what would be the problem ?


texts: DC motor speed and torque circuit equation, why is the current changed while voltage constant?

texts:
so i have a power window motor with spec the voltage 12V, continues torque 3 N.m, max load current 12A, and 90 RPM. the resistance is 2.5 ohm
i understand that torque is correlated with current and the speed with voltage. since the ideal equation for motor is

I=(Vs-Vemf)/R

and if have load so the torque is 1 N.m and i apply 12V, the motor will run with constant 90 RPM. from the equation(suppose Vemf is 2) i get the current

(12-2)/2.5=4A

but if i add the load so the torque is 3 N.m and my voltage still 12V, my motor still rotate at 90 RPM but with higher current. i'm lost in this point, i assume my current will be 9A according to the spec, but from the equation it doen't make sense

9 x 2.5+2=24.5V ??

the voltage is changed to 24.5V, but my voltage supply still 12 V

how does this happen?

thank you


texts: Two's complement overflow at a 4-bit adder circuit

texts:
I made this 4-bit binary adder, with the great help from this great person here,

and it works like a true charm. I thought that this adder, however, is only for "simple" adding, so I tried to find a way to make it work for numbers in the two's complement system.

So the circuit should (?) have a probe that shows when there's overflow.

I thought that might a AND-3 gate with the first two switches (S1, S5) and the final carry probe as inputs, but that's not quite of a solution.

Do you guys have any idea?


texts: Custom >NAME group for components in EAGLE

texts:
I'm designing custom component library for my project and I'd like to create custom naming subset for my custom parts.

When ever I create custom part the default naming order is U$1, U$2 etc., when I add them to my projects later on. I'd like some custom part types to be listed as E1, E2, ... or some along with other resistors like R1, R2, etc. How to configurate parts in my custom library to belong to some specific letter group?


texts: How to choose a MOSFET with as low Vgs as possible?

texts:
I'd like to build a schematic which would work in a wide span of output voltages. The low boundary of this span will be defined by the Vgs voltage of chosen FET. The test schematic is the following:

The current is pretty low (up to 500 uAmps) so this mode usually don't described in devices datasheets. If I'd use any of part searcher like digikey - all the things I can filter of is Vgsth at some given current and drain-source voltage. Usually they are pretty high for me, moreover many of devices with Vgsth specified digikey as 400mV @ 100uA by digikey have no confirmation:

But NO confirmation in the datasheet, all graphs start with much higher Vgs:

Earlier I tested a MOSFET and I find out that in practice Vgs can be much lower at small currents (I've got the schematic worked at 0.6 V when anything predicted 1,67 V). I found an article "The MOS Transistor in Weak Inversion" which was pretty helpful for understanding of what happens inside the FET below specified "ON" state.

However, I can not be satisfied by only knowing the theory - I need the MOSFET able to work with as low voltage as possible. But: how I can pick one?

I tried to pick the devices by opting Vgsth with as low Vgsth as possible (digikey for instance starting with 400mV) but I need to read out all datasheets and compare devices in the region which is usually not specified. I tried to pick the devices with Rds specified at 2.5...2.7 Volts (assuming that those FETs can probably work at low Vgs)...

Now I stuck with BSS138 and IRMLM6244 which are chip and available at local dealer. So I can put them to the test to compare datasheets with my measurements and test in the low current region. But I'd like to have more devices to choose from.

The main question: is there any parameters of MOSFET which directly or indirectly can affect on a possibility to work under Vgsth and I can use to filter devices out? For instance: gate capacitance? Maximum Vds voltage?..


texts: When/why would you use a Zener diode as a flywheel diode (on the coil of a relay)?

texts:
I have just been cogitating on the tutorial at http://www.electronics-tutorials.ws/io/io_5.html, and in the discussion of flywheel diodes it includes this sentence without further elaboration:

  As well as using flywheel Diodes for protection of semiconductor components, other devices used for protection include RC Snubber Networks, Metal Oxide Varistors or MOV and Zener Diodes.

I can kind of see how an RC network might be needed if it is a large device and therefore the coil could be kicking back more current than you want to dissipate through a single diode. (Please correct me if that's not the reason.)

I don't have a clue what an MOV is so for the moment I'll ignore that one. :-)

I have read a bit about Zener diodes, but I don't understand why their lower reverse breakdown voltage might be desirable here?

Edit: I'm also puzzled by the following diagram from the tutorial above:

Wouldn't this take any flyback voltage and dump it into the Vcc net? Would it not be a better idea to have the relay coil be between TR1 and ground, and the diode dissipating the flyback voltage to ground?


texts: How do network devices detect whether an ethernet cable is connected?

texts:
I have a bit of kit with an FPGA on it which includes an ethernet adapter. I'm trying to diagnose why it's not working and while I do that I've noticed that with an ethernet cable connected to my laptop, I see the network coming up and then dropping out again.

How does the hardware detect that the cable is plugged in? Is it watching for a clock sig


texts: I connected the V- pin to ground and the V+ pin to +5V. I then connected in+ to ground and in- to +5V. I expected Vout to be a low value near ground (0V) but I'm getting about +1.7V. Is this normal?


texts: what were the ENIAC's equivalent to the modern CPU's elements?

texts:
If a  modern CPU contains these elements:
- 3 or more register units
- ALU
- control unit

and the CPU is connected to a RAM composed of several addresses, what were the equivalents of these components in ENIAC?
ENIAC used:
- 20 accumulators formed by decades
- delay lines
- electromechanical switches as a buffer between the electronic components and the input punched cards
- a control of the process

How was ENIAC carrying out the fetch-decode-execute cycle? Were the accumulators acting as both CPU's registers and RAM? What was the role of the delay lines?


texts: How do we define resonant frequency for a circuit, that has arbitrary combination of resistors,capacitors and inductors?

texts:
How do we define resonant frequency that has arbitrary combination of resistors,capacitors and inductors?

For instance inductors and capacitors may neither be in series or parallel, but may arbitrarily be connected with resistor.

For the given figure, how do we define resonant frequency?


texts:
I am using L6235 to drive a BLDC motor with hall sensors, but I am not sure about the motor's wire connection. Can you tell which connection is correct by looking at the waveforms?
datasheet of L6235: https://www.st.com/resource/en/datasheet/l6235.pdf
Below are the waveforms captured at the output pin, are the waveforms correct?

(channel 1: voltage, channel 2: current)
However, if I swap 2 of the phase, the motor is still rotating and the IC gets really hot. Why is it like that? And I got some waveforms:

(channel 1: pin OUT1, channel 2: pin OUT2)

(channel 1: pin H1, channel 2: pin OUT1)


texts: What is the difference between a buzzer and a speaker and are there any other basic electric/electronic things that output sound?

texts:
I am playing with a speaker and a microcontroller and in some documentation the speaker is called buzzer. The assistant told us that is a mistake and we are dealing with a speaker.

I am wondering what exactly is the difference between the two, where can I learn more about these kind of devices and if there are any other similar or not so similar devices that are able to output sound.

EDIT:
What is the difference between a piezo buzzer and why isn't buzzer a tag but piezo-buzzer is a tag ?


texts: Need some help in bit error rate calculation for QPSK when using Gray coding

texts: Why is Probability of Bit Error = 2 times the Probability of Symbol Error in QPSK with Gray Coding. Is it because one bit error has the potential to cause two symbol errors (2 symbols where they differ by 1 bit from the original symbol being sent) ? Or there is a more rigorous mathematical proof ?


texts: Why are polarity assigned to resistors in the circuit in questions?

texts:
I have confusion on questions that assign polarity to the resistors. Are these polarities arbitrary or are these polarities actually true? Do I have to consider these polarities while doing the circuit analysis?

For example; if I consider drop of the potential as negative, I get this equation according to assigned polarity in the question.

$$ 35-V_x-2V_x+V_0=0 $$

Also, by ohm's law,
$$ V_x = 10*i $$
$$ V_0 = 5*i $$

This is my solution, but I don't know if it's correct or not.
Basically, I have confusion on as to whether consider polarity as given by the question or not.

Also, this one. Are these polarities provide only to confuse students?


texts: Is UL approval only required for the power supply?

texts:
Suppose a mains powered device has a PSU in the assembly that has a detachable cable to the mains. Is it just the PSU that needs to be UL approved/compliant? Is the whole device therefore UL-compliant as long as the PSU is?

Let's say an electric golf cart that takes 48VDC for charging the SLA batteries. Does the cart itself need to be approved or does only the charger need to be approved?


texts: Can you run low voltage current through galvanized steel suspension cable?

texts:
The fact that I can find hardly anything about running current through galvanized steel suspension cables on Google should probably tell me I shouldn’t do it, but I thought I’d ask here anyway.

I’m messing around with some DIY hanging lamp ideas with 12 V LED strips. I’d like to suspend it from the ceiling, and I like the simple look of the steel cable you can buy from Lowe’s by the foot (1/16 or 1/8 inch). Anyway I have seen many hanging lamp designs suspended in such a way, with an additional, traditional lamp cord powering it.

I know steel is a poor conductor, but I’m wondering if using a <4ft. run I could get away with both suspending and powering the LED strip through a steel cable? It’s 12 V, and probably around 12 watts for the length of LED strip I plan to use in the lamp.

Edit: To clarify what I have in mind. I'm imagining two steel cables coming out of the ceiling ~3 feet apart, running straight down and suspending a 4 ft. horizontal dowel which houses the LED strip. One serving as the positive and the other as the negative lead to the LED strip. All powered from a 12V 40ish Watt transformer.


texts: how to represent a bridge in eagle pcb schematics?

texts:
i'm trying to show that points 7,8,10,11 are connected to ground and point 9 is connected to R18 resistor. but the visuals is misleading. how to create that "jump"

(sorry i don't know the correct lingo for that operation, please edit if you know, thankyou)


texts: Why does an oscillator want a capacitor between Output and Tri-State?

texts:
I'm looking at the datasheet for an oscillator: ECS-3225MVQ-500-CN-TR
https://www.mouser.se/datasheet/2/122/ECS_3225MVQ-1825332.pdf

As you can see, if Tri-State is not connected(NC) or pulled high (70% of Vdd voltage), then the Output is active. If Tri-State is pulled low to the ground or 30% of Vdd voltage, then the Output is not active.
But then the datasheet recommends a capacitor between Tri-state and Output. Why?


texts:
Recently I ordered a Peltier unit online and received it yesterday. Naturally, I was very excited to play with it. When I first turned it on, One side got hot, an another very cold. I had read that I should attach a heat sink to the hot side of the unit. So straight away, I attached a heat sink and a fan to the hot side (The fan is pulling air out).

I also added a heat sink to the cool side. However, both sides started getting very hot. I have tried reversing the polarity, changing the fan to push, and used voltages from 4 to 12. After nothing worked, I removed the heat sink on the cold side, But still, both side remain stubborn  and insist on getting painstakingly hot.

Anyone got Any Ideas as to what's wrong?

Also, If it helps, at 12v the unit is using roughly 2A...


texts: How to turn a coffee machine on/off with a microcontroller?

texts:
So the thing is, I'm a computer science major and working on an IoT project which is a coffee machine powered by a Particle Photon and controlled with an Amazon Alexa skill. The problem is I have absolutely no experience with electrical engineering and am terrified I'm going to hurt myself with this. I have a bread board, jumper wires, and relays and have done a fair amount of tutorials with the photon and arduino so I know the basics of how they work.

But today, I tore into the coffee machine to see the wire configuration and am at a complete lost. I've never done anything like this.

The coffee machine is operated by a simple ON/OFF switch. You flick the switch ON- it brews coffee. I just don't know how to achieve that through a micro controller.

I've included some photos of what the inside of the coffee machine looks like. Any help in pointing me towards the right direction would be great. I truly have very little idea where to start with this.

Thanks so much! Like I said, a total newbie at this so sorry if I sound super naive and out of place.


texts:
I've been working on a project where an OMAP Linux SPI master interacts with 6 SPI slaves peripherals (5x A/D converters and single magnetometer).

I can set the SPI clock frequency and have experimented with 50 kHz, 100 kHz, and 1MHz.

I attached a wiring/board diagram showing length from SPI master and all peripherals.  The SPI bus length (all wire lengths) away from master is roughly 970mm for my experiment case.

The problem I've found is that communication with 1 peripheral fails as I add more of the other peripherals on the bus.  Even if communication gets through to the magnetometer on the far side of the bus, communication with the A/D converters on the other side fails until the magnetometer harness stub is removed and then the A/D section returns.

I've done some reading here:
SPI Bus Termination Considerations
and here:
Short Distance Board to Board Communication

where it's recommended to put a RC LPF as close to any driving node, so SCLK and MOSI on master side and each of my 6x MISO/SOMI signals.  I've seen similiar approach done for USB with  47pF/27R RC network.  My intention is to try this on my circuit in an effort to reduce the sharp edge fast ~100nsec edge transition.

Is this the right procedure I'm following here with adding a RC LPF?  This seems really shakey, is there better practice?  I saw an app note from TI where they talk about extending SPI for longer bus distances, is this an appropriate solution here or my problem simply one of high frequency harmonics from the high speed edge transition?
http://www.ti.com/lit/an/slyt441/slyt441.pdf

Thanks,
Nick


texts: Actuator can use either 24V DC or 24V AC. Which should I choose?

texts:
I will be using a damper actuator which can have either an AC or DC power supply. I do not have any strong preference for either, so what would you recommend? I assume that transforming 230V AC to 24V AC will be more efficient than converting 230V AC to 24V DC and thus will waste less heat, right? Are there any reliability differences?

Details about the actuator in case it matters: Belimo model LM24-SR-F (in case the old model's document should stop being available, it is replaced by newer model LM24A-SR-F, alternative link).


texts: I have designed the PCB on Eagle. Most of the components are SMD pakages. This is for the first time i have designed the PCB. I want to print this PCB in the industry (Chinese industry) but i have no idea how this works. What else do i have to mention except schematics and PCB layout. I have designed my own libraries so i am bit confused. I am sending design file with my friend and there is no way to contact any of the officials from the industry. Any suggestion would be appreciated. Thanks in advance.


texts: How can I have a pulse of 30V at .7A for 30ms then a holding current of 3V at 50mA for as long as I want?

texts: How is this possible with either controller, microcontroller or a circuit?


texts: Possible to use a voltage level shift IC for Arduino and external IC?

texts:
One of my projects require a 3.3V supply.
Its an audio codec, TIs AIC3254, to be interfaced with Arduino Uno.

The codec requires almost 300mA of current, so was thinking of using a level shifter connected to the 5V output of the Arduino board, which can supply 400mA, instead of using an external supply with LDO.

Can the Arduino 5V output be used efficiently with level shifter? Or external supply is the best option?

Thanks.
PS - Codec schem

Ignore the USB part


texts: Single IC for LiPo 18650 cell charger and boost?

texts:
I discovered USB power banks for a mere $1 (excluding battery) that seem to have an IC that handles everything from charging the battery to boosting output to 5v. It is apparently rated at being able to supply 500mA. The PCB and IC can be seen here:

What's most curious is it has so few components: three capacitors, an inductor and the IC; And two LEDs which indicate power and charging status.

I have a couple of questions:

I have not been able to find any information on the IC. Are there ICs that perform both charging and boosting, from/to 5v? I have not been able to find any - so is this power bank is potentially dangerous? Or perhaps the IC is an ASIC developed by / for the manufacturer of the actual power banks? What are the chances that I could develop such a power bank circuit by using some widely available IC?

The simplest circuit I can conceive of would have a minimum of 2 ICs, probably 3 or 4, plus quite a few more components, and that's ignoring USB specs that require that current draw greater than 100mA shoukd be negotiated (Which is known to be commonly ignored). I get the sense I'm missing something.

I know that many of these 18650 batteries incorporate charging and discharging protection circuits, so perhaps this powerbank relies on that, meaning it just needs to worry about boosting the output?