texts:
I'm trying to design an accelerated CPU (65816) for the Apple IIGS by using a high speed ARM processor combined with a software emulator + software emulated cache. The CPU I'm using is the LPC4300 series, which runs at a high speed (200+ MHz) and also has large amounts of internal SRAM which can be used as the emulated cache.

The problem is that the LPC4300 is based on 3.3V logic, while the IIGS motherboard expects 5V. For most of the pins, I can use a standard bus-transceiver to perform the 3.3-5V conversion. Even most bi-directional pins (for example, the data pins on the CPU) can be handled in this fashion, so long as the bus transceiver has 3-state outputs and enable and direction pins. The problem is with the 'RDY' pin on the 65816, which is both bi-directional but does not have any other pin indicating the direction. The function of the 'RDY' pin (as quoted from the datasheet) is as follows:

  2.24 Ready (RDY)

  The Ready is a bi-directional signal. When it is an output it indicates that a Wait for Interrupt instruction has been
  executed halting operation of the microprocessor. A low input logic
  level will halt the microprocessor in its current state. Returning RDY
  to the active high state releases the microprocessor to continue
  processing following the next PHI2 negative transition. The RDY signal
  is internally pulled low following the execution of a Wait for
  Interrupt instruction, and then returned to the high state when a
  RESB, ABORTB, NMIB, or IRQB external interrupt is active. This feature
  may be used to reduce interrupt latency by executing the WAI
  instruction and waiting for an interrupt to begin processing. If the
  IRQB Disable flag has been set, the next instruction will be executed
  when the IRQB occurs. The processor will not stop after a WAI
  instruction if RDY has been forced to a high state. The STP
  instruction has no effect on RDY. The RDY pin has an active pull-up
  and when outputting a low level, the pull-up is turned off to reduce
  power. The RDY pin can be wired ORed

I do not see a way to use a standard logic level converter here, since it seems that the direction of RDY is not reflected anywhere else. Any suggestions or ideas?


texts: How can I optimise and improve this circuit for audio applications?

texts: I am designing a basic preamp using the LM741 opamp to amplifier frequencies from 20 to 20KHZ to a 10Kohm load, input voltage is 0.5V and I get an output voltage of around 2V, what else can I do to reduce noise and distortion?


texts:
I was looking at the footprints in Altium's Atmel library, and I noticed that many (most?) of the pads had rounded rectangles. However, if you use Altium's own "IPC compliant footprint generator", by default the footprints are rectangular (not rounded).

Is there a specific reason to use one of these over the other? It would seem that rounded pads would be easier to manufacture, and would make a more natural shape during reflow, but that's just complete speculation on my part.

(On a related note, would rounded pads have to be made slightly larger than strictly rectangular pads?)


texts: Asynchronous motor with motor capacitor sometimes won't run backwards when it should

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The long story short:

Is there any chance that an asynchronous motor with a run (or start?) capacitor fails to run backwards when the capacitor ages and loses a significant portion of its rated capacitance?

The somewhat longer story:

An asynchronous motor using a motor capacitor within a single-phase device is controlled by two triacs. The motor itself has three wires, let's call them L1, L2 and N. There's a capacitor between L1 and L2. The two triacs power either L1 or L2 and thereby allow forward or backward rotation of the motor - at least that's what I'm assuming.

Simplified schematic (switch symbols are really triacs):

C is labeled with 4 µF, but it tests out around 2.2 µF (checked by using a RC network with a 100 Ω resistor and finding the corner frequency with a scope and a function generator - in lack of a DMM with a C range...). So yes, C is indeed bad and it's a good idea to replace it... As long as that's in accordance with what I assume concerning the direction of the motor...

Sometimes, it seems that the motor runs forward when it should be running backward, and my guess is that this may be caused by a low capacitance in the motor's run capacitor.

The even longer story, with some background info:

I'm in the process of troubleshooting my dishwasher. My particular model has one pump motor with two wheels. When it runs forward, it pumps water into the interior, happily splish-splashing and rinsing the dishes. When it runs backwards, it pumps the water out of the dishwasher and into the sewer. After having watched it work and fail for a while now, I get the feeling that sometimes, the motor fails to run in the "dump" direction and keeps moving in the "clean" direction, often in a step of the program when it switches quite fast from "clean" (forward) to "dump" (backward). Then, some blinking LEDs on the panel say that something has failed and it stops working. The blink pattern is not in the user's manual, and it's different from other service error messages (like "water in the bottom, micro-switch above floating styrofoam 'brick' has detected leakage", and I made sure there's no leak). I can rule out pretty much everything else, and the only remaining explanation for the problem is the motor's failure to run in reverse direction (dump) every once in a while. It seems like the level switch still tells the controller that water is present (and there is), when the controller assumes that the pump should have dumped the water and, as a consequence, runs into a time-out. Is there any chance that replacing the motor's run capacitor will fix the problem?

Yes, the motivation of this question is that I'm trying to fix a household appliance. But... Asynchronous motors on single-phase systems with motor capacitors are a very common occurrence, and the question is really with a quite general focus... Once the elliptical field created by the capacitor becomes too narrow, couldn't it be that the motor starts off in the wrong direction? Even more so when it's maybe not a run capacitor but a start capacitor? I might still edit info about my particular make and model of dishwasher into the question at a later point, but as it stands, the question is relevant for any equipment with a motor capacitor and a motor that should be able to run forward and backward.

Once, I had to replace a capacitor next to the motor in a washing machine, but there, the problem was not the direction. It just didn't have enough torque once the laundry got wet and heavy in the drum. Here, the pump's torque still seems to be OK, but it appears it sometimes fails to start in the right direction...


texts: Can power factor be calculated based on nominal power and rated input power?

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I have a 3 phase AC induction motor for which I want to calculate the power factor. I have the following nameplate information.

Nominal Power (P2): 2,7 KW
Rated input power (P1): 3,3 KW
Voltage: 400 V
Frequency: 50 Hz
Rated current: 5,4 A

I need the power factor, can I compute this?


texts: Grinder hums but won't run. Capacitor seems good, and so do windings

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My Grandpa gave me a bench grinder recently to fix. He said he was using it a lot, grinding and grinding, then he heard a pop, and it stopped working. Now it just hums, and starting it by hand doesn't work.
I think it's a capacitor run motor, but not 100% sure.
There are 2 windings, and a capacitor in series with one of them, I belive it is 6uF. I charged that capacitor up with 32 volts and it seemed ok.
It did discharge kind of quickly, but that's most likely just because it's so small, and the multimeter I was using is discharging it a little. I also put a digital ohm meter across it, and at first, it  started at low resistance, and slowly went up, and then it jumped to open circuit and stayed there. I'm guessing that was just because it was a tiny bit charged yet.
I saw somewhere it was supposed to start at 0 and go up and then drop off and go back to 0 and repeat if it's good, and it's not doing that.
But how is that supposed to work? If the ohm meter is applying DC voltage on one side and measuring on the other, shouldn't a good capacitor get open circuit like I did?
There shouldn't be any capacitive coupling across it with a DC voltage.
I also measured the resistance of the windings, and the one with the capacitor measures 38 ohms, while the one without it measures 27 ohms.
Is one of the windings shorted or burned out or will a new capacitor fix it? Thanks!
Edit: I found a cap with the same value in an old fan my dad had lying around, and it didn't work. One of the windings must be shorted. It's probably not worth rewinding, I can buy a new one for $35.
Edit: just took it apart to get to the motor.

Yeah. I don't think that's gonna run again without rewinding.


texts:
I'm implementing a 300V MOSFET H Bridge with IR2110 driver.
I decided to first try it in low (and safe) voltages, thus replacing the 300V with 12V as shown in the diagram. The MOSFETs I'm using are P20NM60FP, with a VGS of 5V.
Ideally, I should have this waveform at output load

I've checked every connection and the control signal from my microcontroller is correct (5V high, 1 Hz frequency). However, when I tried it, I get this spiky waveform as a result. Any ideas as to why is this happening?


texts:
simulate this circuit – Schematic created using CircuitLab

Above is a very basic schematic of a project I am working on. It basically detects a copper wire above the sensor and then passes this on output to a timing relay. I did have two questions though. Would a setup like this work with a two wire DC proximity sensor? From what I understand 2 wire prox. sensors can be wired like mechanical switches. My second question would be about the output of the sensor. I'm looking at this sensor and looking at the datasheet it doesn't provide clear instructions on its' output. I've never made a circuit with these sensors, is the output a digital On-Off signal say 5V on 0V off or does act like a mechanical switch and pass the 24V to the relay when it is on?

Thanks


texts: What does this sentence mean in this question (simulator can handle X inputs)?

texts:
In my book, one question requires me to find the verification sequence for a circuit. From what I understand, verification sequence must be such that every path is traversed.
Then the book specifically mentions that to reduce the size of the simulation sequence, I have to assume that the simulator can handle X inputs and use X's whenever possible. Any explanation regarding this is highly appreciated.


texts:
I was reading up about a processor spec and I came across the acronym TBD.

On googling, i could only find only colloqual explanations, but nothing solid. Here is one research paper link (http://www.researchgate.net/publication/3065006_Experimental_evidence_of_TBD_power-law_for_voltage_dependence_of_oxide_breakdown_in_ultrathin_gate_oxides)

I am sorry for pasting link but i dont know how else to explain better.

Any help is appreciated.


texts: Clearing 4-bit asynchronus counter using T flip-flops doesn't work

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I am trying to make a BCD ripple counter that count from 0 to 9 , and I have watched a tutorial on YouTube , I implemented BCD counter as the instructor explained and after the counter reaches the value of 9 it should be cleared in order to begin to count from 0 again.

But my problem is that after the counter reaches 1001 , it clears all flip-flops then make the value of the third flip-flop to one (after 1001 (9) the value will be 0100 (4) not 0000 (0) as I expected).

I don't know what is the cause of the problem, is it due to the clear input ?
I simulated the circuit using logisim.


texts:
I working on a project and witnessed that there are different stepper motors with same NEMA DD but different weight and different amp rating.
what does these different notations with same NEMA signifiy and how does these affect torque?


texts: How do you calculate Input output voltages of a trans-resistance op amp?

texts:
simulate this circuit – Schematic created using CircuitLab

(a)Find Vn, Vp, and Vo
Ideal op amp
Vn = Vp
I think this is a transresistance (or transimpendance op amp) op amp
So Vo= -R1 x I1= 10k x 0.3mA = -3V,
Vp = [R2/(R2 +R3)]Vo= 20k/(20k+30k)=-1.2V
→ Vn = -1.2V

(b) Putting a resistance in parallel with the 0.3mA source, find Vn, Vp, and Vo.
My answer to this is that we will get the same results as in a because the new resistance is connected between Vn and ground and since there’s no current flowing into Vn that infers that there is no current flowing into the new resistance and consequently there is no voltage across it. What do you think about these answers in a and b?


texts:
I am playing with an atmega328p microcontroller to try and build a simple circuit which open/close a relay to control a garden light, my problem is that while the circuit works fine on my breadboard for some reasons the mcu does not seems to boot when in the prototype board.

the circuit is fairly basic, I can post the full diagram but the relevant part is a standard application circuit with a 16MHz crystal and two 22pf capacitors:

And here is the beautiful result on the prototype board:

(you can see the two capacitors at the bottom, the crystal is on the other side, sorry for the crappy quality I have nothing better currently than my iPhone 3GS :/)

And another version with an ugly overlay to show better what is connected where:

the blue line at the bottom is the ground "rail", the big rectangle is the atmega socket on the other side of the board (the top of the chip is on the right) and the other green thing is the crystal on the other side too

That's my second attempt at building a prototype board circuit with an atmega328P, the first one went flawlessly and is powered and has been working fine for months now but with this one the chip won't boot.

I have the working prototype on my breadboard so what I did to try isolate the problem:

upload a blink program turning the realy on and off with the 1s delay to the chip, checked that it worked on the breadboard and then put this atmega on the prototype board: the relay stays off.
I checked the power rail of the prototype board and that the atmega chip was receiving proper volatage (5V), everything was fine (I power the circuit from an arduino like the breadboard).
If I try to upload a sketch via the arduino IDE to the prototype board it fails because the programmer is not responding.
I tested each connection with a multimeter and there is no bridge or faultly connection, I am fairly confident that everything is connected where it should be (first thing I checked).

I have really run out of ideas, my guess is the clock does not "start" but I am not familiar with clock circuit and I admit I am not clear how a crystal works, is it possible that the way I soldered the capacitors and the crystal on the board prevent the normal behavior of the clock circuit ?

Can I test that the crystal is working fine with basic tools (I only have a multimeter) ?

Thanks for any help, failing is not a problem as long as you manage to learn something from it when you have no idea what has gone wrong this is really frustrating :(


texts: Transfer function and frequency of Common-drain Colpitts with ballast coil

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Whilst looking for a circuit to test some unidentified RF filters and coils I have lying about, I came across a FET based Common-drain Colpitts used in this youtube channel hosted by RF enthusiast radiofun232 (https://www.youtube.com/watch?v=Ng49kGF3n8o).

A screenshot of the ltspice simulation is shown below.  Notice the frequency.  By my calculation, this oscillator should be oscillating at a frequency of about 77kHz.  Instead it oscillates at 300kHz. If I substitute a resistor in place of L2, it oscillates at the frequency predicted by the standard formula (1/2*pi*SQRT(LCt)) ~ 77kHz.

EDIT: for those interested, I calculated the 250uH L2 value using an online calculator and feeding in the specification given by Ko: 330 turns of "ape hair" and 6mm diameter air core.

Clearly, L2 is affecting the frequency.  I tried a number of "obvious" alterations to the standard formula, such as paralleling L1 and L2 - but I still didn't get 300kHz (or near it).  So, it was time to develop the transfer function including L2.

This document (Pota) provides a good analysis of the standard CC Colpitts and I used the same methodology.

The AC model I used is given above and is an alteration of the Pota model to include L2.  The KCL equation thus includes L2 and the resulting transfer function is as follows:

and here's the full working using Maxima (the last step combines Vo with Vx/Vi to give Vo/Vi):

When I substituted jw for s and took the imaginary part to zero, I got 1/2*pi*SQRT(L1*C1), which is clearly bullshit.  One thing I noticed was that the new transfer function includes an imaginary term in the numerator, that wasn't present in the original TF.  I'm a little out of my depth with all this stuff and while the insights are plenty, I'm still not at a level to grasp all of this.

So, my simple questions are, where did I go wrong and how do I get the frequency I'm after?

UPDATE: Anyone got any suggestions?  It's not often you guys don't leave any comments!:-)  I'm hoping it's because the question is difficult and not because of my utter stupidity.


texts:
Just a forewarning I am a complete rookie when it comes to capacitors

I am looking to supply a 0.5mV charge into a capacitor, then have the capacitor discharge to a battery once the accumulated charge reaches 4V. Once the stored charge on the capacitor is below 4V, the capacitor should store the energy again until the accumulated charge reaches 4V to repeat the cycle listed above.

So basically I am looking to have a low voltage input into a capacitor, and have the capacitor discharge to a battery only when the stored charge is above 4V. What type of circuit is capable of this task? Will just a super capacitor work?


texts: Is it true that the higher the resistance the higher voltage would drop?


texts: Are there BJTs based on metal-semiconductor junctions?

texts:
So, I know that the fundamental part of a BJT is having a very thin base region that allows minority carriers to diffuse through it before they recombine. It seems to me, then, that it should be possible to use two back-to-back Schottky junctions just as effectively as back-to-back pn junctions--but "Schottky transistor" means something entirely different.

Are there any transistors, or is one even possible, comprising a thin layer of semiconductor sandwiched between two metals? I can see some obvious manufacturing difficulties, so I can certainly understand if none actually exist, but I am curious whether it would be possible.


texts: Why electret microphone with Op Amp circuit cause signal negative half wave to distort

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This circuit works quite well with low signal levels, but when the RMS ac signal is appr. 0.8 to 1.0 V (measured on pin #1 of the opamp), the negative half wave of sinusoidal signal is distorted so much that you can see it clearly on the oscilloscope. I am not asking, how to correct this circuit, but like to know the reason for this behavior. This is an existing circuit, and I know how it must be changed.

Added: Image from oscilloscope shows that the "negative" part of the signal is like wider quite much and has clearly different form. So it is not cutting, and if I add voice level to the microphone, cutting starts at the positive half wave first.


texts:
So here's my idea:

Two rings of 36 LEDs (so 72 total).  Starting at the bottom of the first ring, I want to have the first LED illuminate and stay lit, and so on, until the entire ring is lit.  Then, the second ring should do the same while the first ring stays lit.  Once the second ring is completely lit, they should both turn off and start the illuminating process all over.  One complete illumination cycle should take about 5 seconds.

Also, I want the same LEDs to be able come on all at once and blink at a rate of about 2/sec. triggered by a separate input. All 72 LEDs to be all-on, all-off, all-on at a rate of 2 per second.

This is for a 12v DC application.

I hope I was specific enough.  I'm good at the idea and building parts of these kinds of things, but not so good at the designing aspect.  Any help is greatly appreciated.


texts:
I came across a question about assembly that I was confused on.
We are given the following table for addresses and instructions:

The question says: replace the labels of PC-relative targets with their immediate values. What is the
offset value of bnez at address 0x20? Write your answer in decimal.
I put -6, since if bnez, it goes to loop, which is at 0x14. However, the answer given is -12.
How did they get that?


texts: Noise when using SPI LED driver on 2m cable?

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I've made a 2 letter 7 segment display using this LED driver

https://www.st.com/en/power-management/stp16cp05.html

when I connect it with a 10-20 cm cable to my MCU board it all works OK, but fails when on about 2 m.
also I have 3 other mosfet outputs going through the same cable, the cable is YSLCY 10 x 0.5
so there's 10 wires:

MOS1 GND
MOS2 GND
MOS3 GND
MOS and 7SEG shared +12V
GND
+3V3
LA
OE
SCK
MOSI

the cable is shielded, so it should be good from outside EMI, but fails miserably as I recently found out, especially when I also switch ON any of the PWM MOSFET outputs.

Later on I tried to separate the mosfet outputs from the signal part, and it was a bit better, but still not acceptable. I've read about using twisted pair cables, termination resistors, ribbon cables, not exactly sure if that would work.

Also application note here https://www.st.com/resource/en/application_note/dm00038253-led-array-drivers--stmicroelectronics.pdf on page 52, mentions filtering, also not sure what to do.

So looking for help or a guideline on what to do??

If I cannot fix the SPI noise, I was thinking of putting LED driver to my MCU board and connect the 16 LED outputs with cable to my LED series (hoping that would not have interference as well), or just use something else other then SPI


texts:
I am a EE and would like to get my 10 y.o. nephew familiar with the fun side of electrical projects.  I'd like to start with basic principles and projects to re-enforce the basics.   The  goal is to build a repertoire of small projects (fundamentals) that will enable and position the child to perform more advanced projects (simple robot level of complexity).  The end goal is to build confidence in the child.
I am trying to introduce binary addition and translation to and from binary, with limited success.
If you have experience with STEM (particularly as a volunteer or teacher) please state this in your reply.  I am interested in links to curriculum that list these fundamentals.  Any projects that re-enforce a particular skill is also appreciated.
Is there a a generally accepted project equivalent to "hello world"?


texts: The clocks of CPU's have gotten faster than RAM. So computers have to wait a particular number of clock cycles between sending an address and receiving data. But how does a computer know how many clock cycles to wait? What does the computer do during the in between clock cycles? As well, how does your computer manage the timing if you change the clock speed (overclocking) wouldn't changing the clock speed completely mess up your computer since the RAM only works at a particular speed?


texts: Light intensity is dropping on large LED bulb display when it sequences

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I have assembled an LED display controller using an Arduino Mega 2560. The controller runs a display sequence on an array of (25) large LED bulbs that draw about 125 mA each. It also has a smaller indicator display of simple yellow LEDs to show the operator what is flashing. The 100K pot is connected to A0 of the Arduino and outputs to PWM on pin 9. Pin 9 then drives and npn transistor that is tied to (2) PNP transistors to regulate the positive 12V and provide dimming.

The trouble I am having is that on some of the flash patterns the bulbs are sequentially turned on together and as they do so they drop in brightness with each step. This happens each time the number of lights is increased. I tried to use capacitors (C3-C5) to smooth out the voltage but it didn't have much effect. There is plenty of power to run all the lights full blast.

I am not sure, but is it possible that driving the base of all of the (16) 2N2222 transistors is too much for the Arduino to handle and causing it to send a decreasing amount of voltage to the bases? I tested the voltage to the base and it does seem to decrease as the number of lights increase by between .01V and .03V. Is that enough to cause a drastic shift in the display? Would a darlington array of transistors to drive the base of the 2N2222 transistors be needed to allow the Arduino to handle them all? I have also seen several LED circuits using inductors that seem to be smoothing out the voltage. Would that be better and how might I implement that on my circuit?

I am mulling over whether to regulate the PWM on the negative side and drive the bases with PWM. Would that require less power? It seems like it would use the same amount to drive the bases. I really appreciate the input.


texts: Minor electric shocks from touching appliances, loose ground?

texts:
I get minor electric shocks when handling everyday home appliances barefoot. These appliances include laptop when the charger is connected and fridge etc. Can the reason for this be loose ground connection?

Additional Information: All appliances have two wires, live and neutral, there is no earth.
We have an inverter for backup power.

Edit: In the country I live in, there are no earth wiring in residential houses.

The shock is not due to static charge, it's continuous steady bearable shock as long as you are in contact.


texts:
I'd like to build an Intel 8085 trainer for a final year project. The trainer will be used by students and will basically accept machine code entered by students, load these into RAM and run the code. Students will also be able to single-step through the code, examine memory and registers, all basic functions of a trainer. There will also be GPIO (for LEDs and such) on-board as well as some other components (LCDs, seven-segs) you might find on a dev board. A touchscreen would be a nice touch, for input and display. There should also be the option of power using cheap batteries, since electricity isnt at all reliable here. All on a PCB with packaging etc.

I've done a bit of research and thinking and concluded that there are 3 main ways I could do this:

Get a PIC18 (or some other MCU) and program it to understand and execute all machine code input. Basically the PIC18 will emulate an 8085.
Get a PIC18 and an 8085. Let the PIC18 serve as a monitor and control everything except running the user code.
Get an 8085 and let it do everything from running user code to blinking LEDs on-board. Use EPROM to store the monitor code.

I have other school work that will occupy a lot of my time and it takes a month at least for ordered components to get to me (when they do), so I wont have as much time as I'd like. So I'm inclined to go with the 2nd option since it saves me the work of having to delve too deeply into the 8085 instruction set and all the associated assembly programming, which is something I barely know. Plus I think its also efficient, since it lets the 8085 do what it does best and lets the PIC handle the rest. My main aim is straight-forward (i.e. least effort :)) and effective.
I'll be using 6116 for RAM and the usual 74373 for address latching. Not sure what chip to use for I/O yet (I/O-mapped I/O).

What I'd like to know is:

Is this option really as straight-forward as it seems? Any pitfalls I should be aware of?
Is there a better way? Maybe one not among my listed options?
How feasible is battery power with 9 V batteries? Any better cheap alternative?
Any advice on input? I'd like to use a resistive touchscreen and not buttons to give a modern feel (like this 7-inch TFT) but i'm worried about all the extra pin usage and if it will even be big enough? Maybe just use pushbuttons for input and use a far smaller screen for display alone?
Any general advice on the whole thing?

Thanks in advance.


texts:
I've designed (and mostly implemented, now) a system for turning on and off 24VAC solenoids. In order to achieve this, I used optocouplers with TRIAC output (Sharp PR26MF1xNSZ series). The datasheet for this device describes it as a "Solid State Relay", "an integration of an infrared emitting diode (IRED), a Phototriac Detector and a main output Triac."

My interest in such things has lead me to look around for other options for this part. I happened upon Vishay Semiconductor's offerings for similar parts, and Vishay divides this type of component into two distinct categories: solid state relays and optocouplers with TRIAC output.

I looked at Vishay's datasheets for two representative devices, and I discovered that while the optocoupler seems to be quite similar to the Sharp part, the solid state relay part doesn't use a TRIAC for output. Instead, it seems to use a pair of MOSFETs as the output stage.

What are the advantages and disadvantages of these two different types of parts? What would be the benefit of using MOSFETs as the output stage instead of a TRIAC? Is there a real distinction between "solid state relay" and "optocoupler with TRIAC output", or is "solid state relay" a term used for any device that can be used to switch AC or DC?


texts: designing LC filter for linearizing PWM output

texts:
I have designed an h-bridge to run a TEC element. The circuit outputs

output current is 4A
output voltage is 4V
Runs on PWM with frequency 5kHz
Load resistance is 75Ω

I wanted to linearize the output from the h-bridge before feeding it to the load, so I am trying to design a LC filter.

I am confused on two points:

What values to select for L & C?
Where to connect the negative leg of capacitor? (Should i ground it or connect it to the lower pin on h-bridge circuit?)

I had selected inductor of 560uH and 4.7uF capacitor after alot of reading on the internet, but it didnt help at all. Also the inductor had a resistance of .65Ω, wouldn't that effect my output as well?


texts:
I am hoping to get some more opinions to supplement my own.

I am hoping to optimize my system to use I2C to handle all of my error reporting.

My system may be understood by the following photo.

My system is made up of only Arduino UNO's and each of them has their own internal processes, however I want warnings and errors to be reported to the a central error handling UNO as the attached diagram shows.
The "Worker" UNO's have their own processes and will continue about their individual business as long as the "All Good Flag" is High(A HIGH GPIO read on the "Workers" side) .

If the Central UNO detectes a catastrophic error it would shut the entire system down by pulling the "All Good Flag" Low.

I am anticipating the I2C lines to remain decently quiet. I am looking to make use of the I2C on the "Workers" side so that whenever there is an error on one of the "Worker" Processes the "Worker" will send the error to the "Central" Board where it catalogs which board sent the error and decides what to do with the said error.

I believe that to best achieve this I would make the "Central Error Handler" as the Master(Listener) and the "Workers" as the Slave(senders), however I am a bit unsure as to how to implement a this sort of system.

Note: All Uno's are within 2 feet of each other.

Any Guidance is extremely appreciated.

Thank you all in advance,
Carlo


texts:
I'm designing a circuit for driving multiple loads (min. 16, up to 64) like the one shown below

simulate this circuit – Schematic created using CircuitLab
The input source is from a multi-channel DAC driven by an ATMega-like uC that can range from 0 to 5 V, and it should be able to generate a sawtooth with a minimum frequency of 1 kHz. As for the maximum frequency, this will be a trade-off between the resolution and speed of the scan.
With this design, the circuit should be able to provide up to 50 mA to the load. The load resistance can vary from 100 to 3000 Ohm.
The problem is, I need to know accurately how much power is delivered to the load and I have a tight requirement of max 100 mW for each.
For this reason, I'd like to introduce a monitor on the voltage using a multi-channel ADC and send it back to the uC. In this way, besides having a power monitor, I'd have a closed-loop feedback for better control.
However, I'm afraid that placing the monitor in this way would cause a number of issues:

(minor) Output resistance of the current source would be affected by the monitor (e.g. using a voltage divider before the ADC)
(major) Need to share the SPI bus between the DAC and the ADC, lowering the maximum frequency I can obtain.

Before considering another uC, do you have any suggestion on how you would implement such functionality?
Would you also consider the possibility to disable the monitoring for open-loop control?


texts: is it possible to get 20 volt 2a from 2 powerbank which have 5v ,2a 4x output?

texts:
is it possible to get 20 volt , 2 a from 2 power bank by connecting 4 usb port (each 5 v ,2.0a) .

if can what  should i use to prevent damage , short circuit , and catastrophic .

i making a device whare you can use 2 power bank to get 20 volt to charge your laptop .
i have 2 powerbank which have 40 watt(combine 80 watt) , so i can charge my laptop up to 2 times.
 is it possible to connect 4 usb 5v , 2  to get 20 , 2a volt or 4 x usb 5v 2a to get 1a current (parallel circuit and buck)


texts: Switch to battery when voltage supply drops certain threshold

texts:
I have made this circuit but can't quit make it work.

Vext is my main supply from a car (9 - 14V)
Vbat is 8 AA batteries (10 - 13V)
Vout supplies power to a SMPS

As it is now, supply "fades" between Vext and Vbat when Vext is around the zener-voltage.

How can I make a clean cut between Vext and Vbat and a certain voltage, ie. 10V ?


texts: Understanding a Momentary Switch Circuit to Power Up Mains

texts:
Source: http://www.amb.org/audio/epsilon24/

I have been trying to understand the operation of the above circuit. To simplify, I am ignoring K1, Q1, R4 and D2. I also assume there is a jumper across T1 and T2. Since I assume there is no K1, I assume that R3 is connected to 12V rail and the LEDB junction is connected to the drain of Q3.

As I understand, this is a circuit which is used to power up a device from mains (through a 12V relay) using a momentary switch. When the circuit powers up C3 will charge up to 12V. Q3's drain is also at 12V. Q3's gate, because the capacitor charges up to 12V, should be at almost 0V and therefore it should be off.

What I don't understand is what happens when the switch is pressed: I assumed that Q3's drain is at 12V and the cap is also at 12V. But if that is the case, nothing should happen when the switch is pressed because both points are at 12V.

So I must be wrong with some of my assumptions.


texts: Analog linear interpolation of AC signals

texts:
I have two AC signals in audio range \$V_1\$ and \$V_2\$, both around \$2\,\mathrm{V}\$ p.p.. I need to interpolate between the two linearly through some external control voltage \$V_c\$ (ideally also in audio range, but can be slower if it's not feasible) that varies between \$0\,\mathrm{V}-3\,\mathrm{V}\$, something like
$$V_{out}=\left(1-\frac{V_c}{3\,\mathrm{V}}\right)V_1+\frac{V_c}{3\,\mathrm{V}}V_2.$$
I, however, have no idea how to approach this. I'd bodge a solution by figuring out some sort of voltage controlled potentiometer, but I don't really know of anything of the sort either.


texts:
Could someone suggest a place where I could request people to look over my schematic/board design?

If this is the place, here it is: https://easyeda.com/be.mihai22/project-hawk

EDIT:

As I see people started looking at this, here's what my thing looks like:

The three diagrams will form a circuit that will fly a quadcopter. It contains 3 ICs (accelerometer/barometer/magnetometer/gyro) for drone stability, one IC for detecting current/voltage.

What is more, it has an interface for raspberry pi zero which will generate +  communicate a PPM signal (like a receiver) from 4G/Wifi.

I will also keep a list of things that you have suggested for change in this header:

Problems:
 1. Sourcing 12V directly into ATMEGA328P Many thanks to Ron Beyer


texts: Reducing effect of MOSFET parasitic capacitance with resistor in series with gate

texts:
I have a MOSFET in series with the output of my amplifier to switch the amplifier output to the downstream circuitry. The MOSFET parasitic capacitance is seen as a load capacitance by my amplifier, and hurts its stability. The gate is driven by a DC signal that switches the MOSFET on/off. The body is biased at a negative DC voltage. I am thinking to use a resistor in series with the gate and a resistor in series with the body to reduce the effect of the gate-drain, gate-source, body-drain, and body-source capacitance.

Question

Are there any trade-offs to placing a resistor in series with the gate and the body?

I am aware that the switching speed of the MOSFET is dependent on the time constant of the series resistor and the gate capacitance.

Thanks for your help


texts:
Sorry if this is a really basic question - software engineer here, so I'm a little out of my element.

I'm working on an IoT project, and I'm planning on using this button with a red LED inside of it.

For most of their products, this manufacturer lists how much current their stuff draws. However, in this case, they don't. The information they give is:

The forward voltage of the LED is about 2.2V so connect a 220 to 1000 ohm
resistor in series just as you would with any other LED to your 3V or higher
power supply.

I'm planning on powering it using a 2N2222 transistor connected to the 5V rail on a Raspberry Pi.

I would have naively tried simple Ohm's law, but I know that can't be correct here.

EDIT: I did a little digging through some old textbooks.

Since I'm powering it from the 5V rail, $$V = 5V = 2.2V_{LED} + V_{RESISTOR}$$

So,

$$V_{Resistor} = 2.8 V$$

Which, from Ohm's law, then gives:

$$ I_{Resistor}=I_{LED}={2.8V\over1000\Omega}=2.8mA$$

Are my calculations/reasoning correct?


texts: cirrus/wolfson wm8731 - Connecting Analog Input to Codec

texts:
I am currently working on an embedded audio processor project based on the stm32f4discovery board and the wm8731 codec from cirrus/wolfson.

I was wondering if anyone here is familiar with the codec in question. Through my own research, I've come to find the codec is renowned for having documentation that is difficult to understand.

My issue is specifically with the VMID pin. The recommended external connections on the datasheet found here http://www.cirrus.com/en/pubs/proDatasheet/WM8731_v4.9.pdf (pg 60) show two parallel capacitors to ground. However, the datasheet (pg 22) mentions that VMID is responsible for internally biasing incoming signals.

When searching online I came across a similar project by Eric Brombaugh at http://ebrombaugh.studionebula.com/synth/stm32f4_codec_v2/stm32f4_codec_v2_schematic.pdf where VMID was wired as in the datasheet. I don't understand why this is because there is no added DC offset on the two LINEIN inputs.

Am I missing something here?
Do I need to supply a voltage to VMID to bias my inputs? Or is it done regardless?
Also, is it possible to just add the offset to the inputs myself prior to the codec ADC's?

Edit/update From the replies below it is now clear that a DC offset on analog inputs is not necessary, but this gave rise to another query. Initially, because of previous experience with other ADC's, I approached the input design under the notion that it was.

The inputs were to take a signal from an electric guitar, amplify it and then add an offset (redundant now). This is shown in the schematic below.

The preamp is of the common source self biased topology based on the j201 JFET. The potentiometer P2's purpose is to attenuate some of the gain so that the AC swing could be limited between -1.65v and +1.65v. The next stage is a voltage divider that adds dc offset to bring AC swing to 0 - 3.3v This was one of the methods mentioned in another question shown on the page DC biasing audio signal

Before this revision, R4, R5 and R6 were all 100k values, which in theory is perfectly fine. What I found was that when I connected R6 to just after C2, to add the bias, most of the gain from the preamp stage was attenuated. This was because adding the DC offset stage loaded down the lower half of the voltage divider created by P2. The solution was to change the values of the resistors so that they would be much larger than the potentiometer. This fixed the gain issue, but I then found the dc offset was slightly off. I then had to decrease R4 to get the clean 1.65v I needed.

The reason I explain all of this is because I now wonder if removing my dc offset stage and connecting it to the codec LINEIN will have a similar effect. If so, I wouldn't be able to adjust the internal resistor values of the codec to compensate.

Please let me know of any misconceptions you think I may have.


texts: How to control a seven-segment display with 4 digits?

texts: I've taken this seven-segment display with 4 digits from a broken micro wave. Any ideas how to find out how it works? Finding an appropriate data sheet would be great.


texts:
I have found a problem with the PIC18f46K40 datasheet or a problem in MCC - I am using the 44-pin TQFP package.

In the datasheet, the pin layout for the PIC18f46K40 is given below:

The MCC (MPLABX IDE v4.15) pin layout is given below:

The NC pins are not consistent. Which layout do I use in my design?

I have a strong feeling the MCC pin layout is right and the datasheet is incorrect for some reason.


texts: MOC3010 & BT136 with Arduino as trigger to power AC light

texts:
I've spend days debugging this circuit and have exhausted all possible solutions.  I'm trying to use an Arduino PWM pin to light a 120V AC lightbulb.  In order to do this I'm using a MOC3010 opto-isolator and a BT136 Triac.  The goal is to be able to fade up and down a 120v light.

Below is my circuit (Vcc is 5v arduino pin):

I'm certain I soldered everything correctly.  I'm  certain the components are working (tested with multimeter).  The issue is getting the photocell within the opto-isolator to trigger the gate of the Triac.  Currently when I plug this circuit in - the light doesn't turn on.

One weird thing is that when I touch the line between pin 4 and the gate with a multimeter- sometimes the light flickers.  I'm thinking that the voltage difference isn't correct and that my probe is inducing a difference that allows the gate to be triggered for a very very brief moment.

Has anyone been able to make this circuit work before?  Is the 180 ohm resistor too small/big for my appllication?

This simple circuit has now become the hardest circuit I've ever worked on... Please help!


texts: Interesting observation on strange behaviour using motors and IR transceiver

texts:
I am working on a robot with with the following specs:

Two coin type vibration motors rated at 3V for locomotion
Motors triggered using two darlington transistors (sample schematic shown below)
Transistors triggered using PWM pins on the microcontroller ATMEGA164PA
An IR transceiver module for communication
Using two coin cell batteries in parallel each rated at 3V, 300mAh

I am only receiving IR signals at the moment for which I am polling the RxD pin to check when it is slow and increment a counter each time the pin goes low (RxD is active low)

I am facing a strange problem. I am using PWM on Timer 0 to drive the motors and when I set the PWM on the OCR0x registers to 0 (or any other value), I noticed that the RxD pin starts to receive signals (getting low) even though I am not sending any signal to the transceiver module. When I disable Timer 0 though, everything is fine and the transceiver only receives when I send something to it.

I am not able to figure out why that is. Is there something wrong that I could be doing? I have a noise suppression capacitor close to the motors as well as the flywheel diode.

EDIT

Another interesting observation. When I drive the motors directly by switching on the GPIO pin (same pin as PWM_1) instead of using the PWM, I noticed that there is no interference with the IR transceiver which shows that the Timer is a problem.

Note: more observations to come as I make progress


texts: Thevenin Termination Current Calculation and Iol/Ioh

texts:
I am calculating the current draw for a thevenin termination and am having issues with the Iol and Ioh from the datasheet.

From my understanding, when the source goes high (Voh), then Vtt (dest input node) will go to Voh (ideally, Vdd). The current is then Vdd / R2 and current flows through the source and into ground. There is no contribution from R1 branch since Vtt and Vdd are equal and there is not voltage drop.

If Vdd = 1.8, then the current I calculate is 18 mA (1.8V/100ohm), but the datasheet below for HSTL I 1.8V has -8 mA for Ioh. Aside from the wrong direction, it seems as though it would not be able to push out 18 mA in any case.

Vcco = 1.8V and Vref = 0.9V. 50 ohm represents a 50 ohm impedance transmission line.

Source page 7

Can someone help explain what I am missing here? Thank you.


texts: 1000V MELF Diode Intermittent Failure. Diode shows degrading reverse voltage characteristics

texts:
Hello to the electronics community in this forum. I am currently facing a MELF diode intermittent failures. These diodes failed when the final assembly (potted) is tested in a functional test after just 2 minutes of running. The diodes were then removed from the assembly and tested using an oscilloscope, where it showed a spike.

The diode was then tested using a curve tracer, where it shows degrading reverse voltage characteristic. Few diodes were used for an experiment where it included milling off 0.2mm of the surface of the diode to remove "contaminent", washing in DI water, washing in isopropanol, baking for 8hours at 200C and baking for 12hours at 100C.

The milling of the surface of the diode, washing with DI water and Isopropanol failed to revert the diode back to the original reverse voltage characteristic. However both baking the diodes makes the diode revert back to its good reverse voltage characteristic.

This clearly indicates that the diode has moisture trapped during the manufacturing process. My question here is how do I prove this is caused by moisture? Which types of experiments are suited to proof the moisture?

Need professional advise on how to move forward.


texts: How do I find resistor values for an LSTTL to ECL interface?

texts:
LSTTL is a 74LS10 three input NAND gate
ECL levels are -0.75 volts and -1.55 volts
Supply voltages are +5 volts and -5.2 volts

I am really not sure how to proceed with this. I've tried setting the output of the LSTTL to the V[OH] and V[OL] given in the data sheet but got nowhere useful.


texts:
So I have a piece of circuitry that contains the schematic below. Q10 on this schematic keeps blowing and I'm looking for help to figure out why. +VBATA can be anywhere from 7V to 18V, the output going off the right side of the screen just goes through a resistor into a micro controller to be read and the A2D_READ_BAT input shown goes to the same controller to turn on Q10.

Q10 (BSS138W) Characteristics:

Vdds: 50V
Vdgr: 50V
Vgs: +-20V
Id: 200mA
Pd: 200mW
Vgs: 1.2V
Rds: 1.4Ohm

A2D_READ_BAT: 3.3V

Is there simply something I'm just not seeing?


texts:
I have a project to build heating element using silver ink.
My specification is the heating element must be in range 2 to 2.6ohm
I will design the circuit for the heating element, but have a problem
how to theoretically measure the resistance of the circuit(before send to print house).

Based on reference on this website

http://circuitcalculator.com/wordpress/2006/06/14/conductive-ink-traces/

the resistance can be measure as below
Resistance = Sheet_Resistivity*(Length/Width)*(Ref_Thickness/Thickness)
In my case,
Sheet Resistivity = 10miliohms/square,
Ref_Thickness = 1mil(0.025mm)
Thickness = 1mil(0.025mm)

1) Based on the quotation, if I have 50mm x 50mm & another one is 10mm x 10mm
silver ink with same thickness, the ohm will be the same which is 10miliohms.
Is it logic?

2) Another question is, how to measure the resistance if I design a complicated
circuit as per attached image? In the image, 1box considered as 1mm x 1mm
Point "A" and point "B" will be connected to battery(+ve & -ve).
Blue color indicate the silver ink

Your advice and explanation will be very helpfull. Thank you.


texts: Where do the mux select lines come from in a CLB?

texts:
I am trying to understand the inner workings of a CLB in an FPGA but I can't seem to find out exactly how the routing multiplexers WITHIN the CLB work. Well, I understand how they work and what they do but I can't seem to find out where the information to configure the multiplexers is stored.

This picture is from a Xilinx spartan-3 manual. I understand that the configuation data loads values into the LUT and sets the mux to choose routing but if I'm not mistaken the chosen signal to the mux needs to be consistently on or off, i.e. the mux has no memory. This selection information must be stored somewhere, but where?


texts: Is FM index affected by frequency multiplication?

texts:
I came across this question which goes

An FM signal with modulation index mf is passed through a frequency tripler. What will be the modulation index at the output of the tripler?

and according to the reference book the answer is 3mf.

Modulation index as we know is the ratio between the frequency deviation and the maximum modulating frequency, both of which are multiplied by the same factor when the signal is fed to say a class C amplifier. So I suppose the modulation index will not be affected by any frequency multiplication since the factors would just cancel each other out. Am I correct or is there something I'm missing out on?


texts: Effects of current/voltage limiting of LEDs

texts:
First of all, I have read many articles about the non-linear effects of voltage vs current of LEDs. I also know that current will rise as temperature rises, batteries have resistance, LEDs brightness is not linear. All in all, LEDs are finicky devices.

But lets say we have a 100% perfect scenario:

The LED is rated for 9v at 700mA. The temperature somehow stays a constant 25C
The power source, never mind what, is DC 1000000 volts and can output 1000000 amperes. The voltage remains constant no matter what the load is, i.e. 0 resistance.
We have a switching voltage regulator that somehow handles all the power and is 100% efficient with 0 ripple, etc.

If I have a CC/CV setup with the output at 9v and current limited to 700mAh. The LED should now be at full brightness.

Let's say that I want to dim the LED by keeping the voltage output at 9v and reducing the current to 350mA.

This would dim the LED right? Theoretically, 1/2x the CURRENT = 1/2x the brightness (Ignoring the fact that our eyes are non-linear and that the voltage stays at 9v)
Is there anything wrong with doing this? Will I damage the LED by forcing 9v through it and allowing it only 350mAh?
Is it really better to do keep current limiting at 700mA but reduce the voltage? This would result in the current used by the LED plummeting if I reduce the voltage a teensy bit

Now let's say I want to put the brightness back up to 100%. Assuming I reduced the current limiting to 350mA before and kept the voltage at 9v, I would now have to increase the current limit back up to 700mA

Alas! I accidentally increased the current limit to 200 Amperes! (but kept the voltage at 9v)
This shouldn't do anything, should it? The perfect LED simply draws 700mA at 9v (because current is simply drawn, it generally cannot be forced?)

If I reduced voltage before, yet kept the current limiter at 700mA, I would then have to increase the voltage. (keeping the current limiter at 700mA)
 - Oopsie! I accidentally increased the voltage to 15V. Now this is far beyond the overvolt acceptance for LEDs, The current would try to skyrocket, but it is being limited to 700mA.
 - Is there any detrimental impact on having the LED run at 15v 700mA? Any normal unregulated LED would have surely burnt itself up by now.

So here are the scenarios for the LEDs in a nutshell:

350mA @ 9v

500mA @ 7v

700mA @ 9V

700mA @ 15V

Would doing any of the above destroy the LED necessarily? Except for that 4th one.

It is not possible for me to use PWM to control the brightness of the LEDs

Sorry for exaggerating everything, I just wanted to make things crystal clear. Is anybody able to brighten me up on this topic? Thank you


texts:
I was wondering what effects do rough solder joints have on electrical components.
Specifically, I have a hard time soldering wires to a male-male connector, as can be seen in the added photo.

Assuming little physical stress will be applied to the joints, do jagged soldering have any effects on say the electrical functionality of the components? Or are there any other implications? Thanks


texts: Which motor would work best as a generator?

texts:
i've been doing a lot of research into motors to use as a generator in a medium sized wind turbine project.

I am lost as to what to do, will a large AC motor with a bridge rectifier be a good approach? They seem relatively inexpensive compared to DC motors. I want the set up to charge a 12V battery. Will this require some sort of controller? Which motors will work best? Will a single phase AC motor with a bridge rectifier be able to charge a battery if used as a generator?


texts: Classic transistor differential ampliﬁer - problem with a single-ended output

texts:
I have a differential amplifier like at the pic below:

And I am not sure if I am doing everything right.

We know that the input signal is a triangle wave with \$ V_{pp}>100\text{mV}\$, no offset and \$f=1\text{kHz}\$ and our output signal is a square wave that changes from \$0\$ to \$5\text{V}\$. And my task is to calculate:

-\$ V_{CC} \$

-\$ R_C \$

-\$ G_{diff} \$

The first thing is to calculate \$I_0\$ - on both \$10k\Omega\$ resistors there is  \$7.5V\$ voltage, thus \$7.5V-0.7V-I_0\cdot 3.4k\Omega = 0\rightarrow \ I_0=2\text{mA}\$

Next step: we know that the maximum output voltage is equal to 5V, so \$ V_{CC}=5\text{V}\$

Now let's say, that we have such input voltage, that T1 is in cutoff mode, then
\$I_{C}=I_0=2\text{mA}\$

This means, that \$V_{CC}-I_CR_C\$ is equal to the minimum output voltage, i.e. 0V. Thus: \$R_C=\frac{V_{CC}}{I_0}=2.5k\Omega\$

As for the gain: I think it is \$ G_{diff}=\frac{R_C\cdot I_0}{2\varphi_T}\$

Is my solution correct? Thank you in advance.


texts: RGBW 4 channel LED strips: Do I need externalpower supply or is the LED controller enough?

texts:
Not a beginner but still a novice :)

Main goal is to find out if the LED controllers I have chosen can drive my LED strips or if I need external power supply. And to understand ofcourse :)

Equipment first:
Controller Milight LS2 USD 10 each, buying 8 of them
Voltage: DC12V/24V, Output: Max. 6A/Channel, Total output Max.15A

LED strips
USD 10 each. Aliexpres so no data sheets... 5 pin RGBW 60 chips per m. RGB+W integrated in each chip, analogue I suppose. Miss Ali says about 0.2W per chip = 60 W per 5 meters but I thought most strips were 72 W???

Q: I thought that RGBW would use more power since it has white too?? No?

Q: I thought that amps were constant so is RGBW less bright than RGB per colour? What about total lumens?

Now, can one LS2 controller drive one 5 meter strip?
Strip lengths: Mostly 4-5 meters, some up to 10 meters.
Please correct me:

1) I understand that channel is red, green, blue and white. Is that correct?

2) Plain green and I get 60W green, mix 2 colurs and I get 30 each? Is this correct?

3) I understand it as one LS2 controller can drive one LED strip up to 5 meter long and I would only need an external power supply if I make a longer than that, say a 10 meter strip => connect up in serial (same zone). Is this correct?

How long can I pull a 1 mm? 22 AGW extension wire before it affects performance, just approximate.

Thanks
Michael


texts: Perf board parasitic capacitance fries microcontroller?

texts:
Recently one of my mirocontrollers fried in a project on a perf board. Eight of the outputs are PWM, and aside from the power lines, there are no other outputs from the MCU. The PWM frequency is 40 kHz. All these output lines are routed to a connector with long, beefy solder tracks under the board. After going through the connector, each line meets a 2.2k resistor (series) and drives some transistor circuitry.

Two of the PWM channels worked on their own for quite a while before connecting the other six, so I first thought my troubles could be the result of continuous overcurrent. The MCU is rated for 200 mA max, but 5 V/2.2 kohms * eight channels only comes out to 18 mA.

I am inclined to say that the fast switching frequency combined with the beefy solder tracks pushed too much current in and out of the parasitic capacitance before the series resistors.

How much parasitic capacitance can lead solder introduce? I realize I could put the resistors closer to the MCU BEFORE the long tracks, but there is always a degree of parasitic capacitance in everything.

I would like to know if the following reasoning is correct:

If I solder a wire to a large copper ball (say apple-sized) and then plug the end of the wire onto my MCU PWM output pin, I will fry the unit as high current quickly rushes in and out of the ball's parasitic capacitance. If I did the same thing with just a bare wire, the capacitance would not be great enough to fry the controller. I have done several times in projects with no issues.

If the reasoning is correct (I would not like to test it :)) and all capacitors can draw huge momentary current, why does the ball fry the MCU and the wire doesn't?
Is there a calculation to help me understand this better?


texts: PSC motor behavior when changing run capacitor value

texts:
I was browsing and read alot of articles and forums around the web
and i didn't find a full explanation about the behavior of the current
and the voltage in the PSC motor.
Here are two situations that i would like to understand(and please,
correct me if i wrong about something).

if i will connect an higher value capacitor than the original rated,
the impedance in the series capacitor-start winding branch will be lower,so
i assume that the current and the torque,when the motor will be turn-on,will be higher
by using this higher value cap and the current will be also higher(of course,
compare to the original cap value)during the normal operation of the motor.
In that case,what will happen in the main winding?
Does the current will be the same/higher/lower,when we start the motor?
Does the current will be the same/higher/lower,during the normal operation of the motor?
In the other hand,if i will connect a lower value capacitor than the original rated,the impedance
in the series capacitor-start winding branch will be higher,so i assume,that the
current and the torque,when the motor will be turn-on,will be lower and
the current will be lower,also,during the normal operation of the motor.(along the start winding).
As in the first question:what will happen in the main winding?
Does the current will be the same/higher/lower,when we start the motor?
Does the current will be the same/higher/lower,during the normal operation of the motor?

Thanks in advance.


texts:
Can you name this schematic symbol?
What does this schematic symbol mean?


texts: Reducing a state space equation to a controllable and observable equation

texts:
I need to check that I'm solving this question correctly and where to go afterwards. I'm reducing the given equation to a controllable and observable equation.

From the picture, it is clear the A matrix is in Jordan form where λ1 is in a 3x3 Jordan block and λ2 is in a 2x2 Jordan block. The B matrix that corresponds to λ1 is the top 3 elements. Since the third element is 0, λ1 is not controllable.
The B matrix that corresponds to λ2 is the bottom 2 elements. Since the 5th element is 1, it is controllable.

For Observability, I need to check the C matrix. Since the first element is 0, λ1 is not observable, and since the fourth element is 0, λ2 is not observable.

So I know λ1 is not controllable or observable and λ2 is controllable but not observable. How do I write the corresponding state equation?


texts: Timing delay is random for SPI write - read command

texts:
I am using ioctl() half duplex SPI command (Linux base) to send command and read the ADC result from ADC chip(slave) to a MCU (master). However, the reading of ADC sometime will show me wrong value, out of 1000 data and I get 5 invalid data("255"), roughly 0.5% error.  Is the ADC and SPI should be 100% working all the time? I am not sure what causing the problem.

With logic analyzer, I notice that the delay time between sending and reading ADC result is always not consistent. I am not sure is it a common symptom for SPI communication or what and I suspect this is the root cause for the error reading.

programming step:

start ADC
delay for ADC completion
send read command
// Inconsistent delay happening between step 3 and 4, even though my coding has not set any delay in between.
receive ADC result
loop back to step 3 and continue next reading.
// Inconsistent delay also happening in between step 5 and 3.

The error reading appear every time when the unknown delay time(approx. 1-12ms) is longer than normal. (Normal delay time should be in the range of 40us according to other successful reading)

From website or reading material about SPI, most of them showing the perfect/ideal condition, timing is as accurate as we think it should, but I believe the real application wouldn't be the case. Or I am wrong about it, I am not sure, this is the first time I am trying to implement SPI for data communication in my small project.

Please share your experience if you have encountered the same problem that I am facing now.


texts: Which implementation of a safety stop is more accurate?

texts:
I recently got into an argument with a friend over what the correct implementation of a safety switch for a motor with a spark gap is.

So for intents and purposes, here is the simplified schematic with the engine generator, the fly-back transformer and the spark plug.

Here is what I think the wiring should be for a safety switch

I think it should be this way because any modification would cause the engine to not start, which I think is essential.

My friend thinks that an E-stop should be wired like so:

with the rationale that a faulty switch wouldn't cause an engine out.

In this case, what is more correct, and why?


texts: What's the purpose of the capacitor in this circuit?

texts: If this trigger pulse is starting the process of sweep generation, seems to me like it would be going directly to the base of the transistor (Q701) to switch it on and off, so the series of multiple transistors downstream can do their thing to generate a nice big sawtooth wave. However, with a capacitor being placed in-between the input signal and the transistor, it seems to me like it's killing the signal. The signal isn't actually doing anything now. The signal is dying post-capacitor. How is that productive?


texts: Heating Element for Small Solar Power Supply

texts:
I'm working on a solar-power, portable desalinator for my undergrad senior project. I'm hitting a major wall when it comes to a heating element for this project. In order to have a solar panel that's a) portable and b) not extremely expensive, I can only get in the range of 12 volts and 10 watts. I was planning to directly hook the solar panel to some type of heating element to bring the water to boiling. It doesn't have to be super fast, but I was hoping to evaporate 2 liters over the course of a day.

Does anyone have a suggestion that doesn't involve ordering something custom from OEM or the like?

Or should I just try to venture on making my own element. All I know about that is that I need resistance wire. I'm not sure what I would want to insulate it with or how to hook it up to the panel.

Thank you so much for your time and input.


texts: How does this board achieve snapability (ESP8266 programmer) for a SMD IC?

texts:
There is a programmer for the ESP8266 that allows you to snap the ESP module in and out of the board to program without soldering? I never seen this type of connector before, does anyone have a part name for it?

Here's a YouTube video demonstration of it: https://www.youtube.com/watch?v=pHxV9xdCF5M

I figure if I can find a part name that would be all I need to incorporate this into my own boards.


texts: Why does the common collector specifically have a high input impedance?

texts:
When looking at a chart comparing different BJT amplifiers, the common collector/emitter/base, it is usually said that the common collector has a high input impedance, therefore it is suitable for use as a buffering circuit. The
Wikipedia page on common collector lists the input impedance of the circuit as $$r_{\pi }+(\beta _{0}+1)R_{\mathrm {E} }\ $$

But according to the page on common emitter, the input impedance of that circuit is also calculated using the same expression (assuming an emitter resistor is in place).

If the input impedance of both amplifiers are calculated using the same formula, why is it said the common collector configuration has an especially high input impedance?


texts: Charge on plates of two capacitors in series are not equal

texts:
I have a simple circuit below with two capacitors are initially charged to Vo1 and Vo2 respectively. The two capacitors are in series however the charge on plates are not equal.

Could anyone tell me what is wrong here?

PS:

It seems that no one understands my confusion. Lets me express it again. What I want to check is the charge on plates of two capacitors (with initial charged voltages not zero) are the same. However from the calculation, you can see the expression for Q1 and Q2 are different. So in general, they are not the same. I would like to know why they are not same even the two capacitors are in series.


texts: Static shielding bags for PCB protection

texts:
As I understand it, metallic static shielding bags act as a Faraday Cage once sealed which protects the contents against external electrostatic discharges. They also prevent triboelectric charge buildup, protecting the contents inside the bag.
However, does this stay true if for example a PCB is wrapped in plastic or paper before being inserted into a metallic static shielding bag which is then sealed? Would this material be able to damage the PCB even though it is contained inside the faraday cage?


texts: Voltages not what I expect when charging a capacitor with another

texts:
I experimented with charging a capacitor (in my case, 100 microfarad) from by power supply (to 10V) and connecting it parallel to another cap of the same capacitance, with the matching polarities together.

I read this derivation on what should happen:

https://www.edn.com/electronics-blogs/living-analog/4394290/Capacitor-charge-transfer-

I understand that half of the energy in the first, charged capacitor is lost. The voltage across both capacitors should now be half of the original voltage applied across the charged capacitor.

However, this is not what my oscilloscope shows! If I charge the first capacitor to 10V, and connect them, I see around 2 volts across. If I charge the first cap to 8V, I see around 1 volt across the two capacitors! Below is a picture of my setup, can anybody tell what is it that I'm doing wrong or what is happening here? Why am I not seeing half of the original applied voltage across the parallel capacitors?

To clarify, I first took the left capacitor to the left of the breadboard, connected the voltage from my supply across it, and then moved it parallel to the right capacitor. I've checked everything I can think of, all the connections are correct.. And I was careful moving the capacitors, I did not short the leads with my fingers or anything similar.


texts: Why are these resistors considered in parallel in the DC equivalent (Com Emitter Amp)

texts: So here is a page from my text book, the Common Emitter Circuit is on the top and on the bottom right you can see the DC equivalent circuit , my question is that by looking at that dc circuit i do not understand why when finding the R-thevenin R1 and R2 are said to be in parallel if , from my perspective, they seem to be in series... and then funny enough when finding the voltage equivalent it does treat them as a series voltage divider....


texts: In a 4-layer PCB, operating at a 8-16 MHz clock speed, should there be any copper pour on the top and bottom signal layers?

texts:
Currently I am designing a 4-layer PCB, with the layers as follows:

(1st layer, top) signal
(2nd layer) ground
(3rd layer) power
(4th    layer, bottom) signal

The clock frequency is either 8 MHz (running at 3.3V) or 16 MHz (running at 5V).
There are no active RF components on the board, just surface-mounted SPI-based devices.
The total board dimensions are ~4cm x ~3cm.

My current design has no copper pour on the signal layers, but have copper pour on the ground and power layers.

So under these circumstances, would it make any difference whether or not I have a copper pour on the top and bottom signal layers?


texts:
Note: (W/L)ratio of M5 = 3 * (W/L)ratio of M7

I would like to ask if there is a preferable method for accurate current mirroring between the two schematics below. To make it clear what I would like to say, in the left schematic we have a simple current mirror and we want to provide in the load three times the current of M7 (so the purpose is the Iload = 3mA).To achieve this I will choose the W/L ratio of M5 to be three times greater than the W/L ratio of M7.

On the other hand to achieve the same purpose in the right schematic we place four identical transistors (M1,M2,M3,M4) with the same W/L ratio. So I know that the load will have again three times bigger current (3mA).Which schematic provide better accurate current mirroring?

Advantages, Disadvantages for these typologies?

I have read that the right schematic gives us better accuracy. Is it true?


texts:
I am currently trying to build an audio amplifier circuit with the TDA8571J that should run with 6V supply voltage.
This is my circuit:

The part in the middle on the left is a 5V regulatorwhich has nothing to do with this.
However when I power this up and add some signal from my mobile to the inputs 1 and 2, I don't get any output signal.
I double checked all connections and everything and have no idea what could have gone wrong.
All outputs deliver constant 3V but the audio signal is not on it.
Any help or ideas are greatly appreciated.
The datasheet for the TDA8571J can be found here


texts: Right motor for a camera gimbal and what kind of a gimbal motor is this?

texts:
From information on the Internet I understood several things:

Low KV motors are better for gimbals. For lower KV thinner wire is used with more turns.
Outrunner motors have more torque than inrunners.
More poles give smooter rotation and finer resolution.
PMSM motors are driven by sinusoidal signal and therefore are rotating smoother than BLDC.

Please correct me if I am wrong.

So, now, this is a medium sized (60mm OD) motor from a gimbal which has very high torque. The wire is thick, its inrunner, has low pole count. All these things oppose the information above. What is going on here?


texts: double power supply for optocoupler (is it necessary?)

texts:
I have optocouplers in my AVR Controlling PCB so The question is:

In order for secure protection, is it recommended to use two separate power supplies: one for the Micro-controller side and other for the optocoupler power supply?
I use opto for triggering one IGBT which have its own power supply (one bridge rectifier and one capacitance without transformer), which could not be used as power supply for microcontroler or opto.
Clearly i have two option:
using 2 power supply, 1th as micro and optocopler power supplier and the other as IGBT power supplier line.

using 3 power supply, 1th for micro, 2th as optocopler power supplier and 3th as IGBT power supplier line.

So as you can see in this schematic, we have two power supply:
1 +5D
2 +5A

The output of Opto's going to one Buffer (74LS240) and then going to IR2130.

So Could i have use one power supply instead of two power supply.

The output side is here:


texts:
I'm in need of a diplexer that'll separate RF signals from a single feedline to two antennas. What I designed and built was a diplexer that would allow ~38 Mhz and below out port 1, with ~38 MHz and above out port 2. This is primarily to use a separate antenna on the 6M ham band and a separate antenna for the remaining HF frequencies with an output power of 100 watts.

I followed these directions: http://vk3atl.org/technical/Diplexer_1cc.pdf (PDF) using the student version of Elsie. Layed out a PCB, etched it, populated with the parts calculated by Elsie. Here's the design:

As built:

I soldered a 51 ohm resistor across each output port, then fed the input with an MFJ analyser. Below the crossover, SWR is ~1.7:1. Above the crossover, the SWR ~2.1:1. I was thinking the SWR should have been lower on both ports - around 1.5:1 or better. 1.7:1 isn't all that bad for the HF port but >2.0:1 on the VHF port isn't. My initial thoughts are the coils are too close together and need to be spread out. That's all I can think of at this point. I would redesign the PCB to have more distance between coils and make them orthogonal. What other modifications to this design should I do?

UPDATED

Pulled one of the 51 ohm resistors off the board and tested it with my LC meter. Sure enough, it looks like these resistors are wirewound.

EDITED to reduce image sizes


texts: Can anybody help me understand, what exactly a high side and low side driver is? In which scenario would either of them be used?


texts: Unstable DC voltage ~ 300v to regulated 120V conversion

texts:
I need your advice for transforming DC voltage which is coming directly from many bridge rectifiers connected the pluses and minuses (from custom made multi phase wind alternator).

At the bridges output, I get from 150 to 350 volts (depends from the speed of the wind).

Because I got many phases I decide to bridge them all and then to use some kind of shunt limiter or buck converter or some circuit that may be do the job, to drop the DC voltage anywhere from 12 to 120 volts but with as much current possible.

Edit: Or if there is a efficient way to drop the AC voltage before the transformation to DC somehow.

Can you help? thanks alot guys!


texts: axcache, axprot and axqos values for dma data transfer

texts: I am working to understand the DMA which has an APB4 slave interface for configuration and a AXI4 master interface for DMA transfer. As AXI4 has axcache, axprot and axqos signals, I want to know that for a valid DMA transfer what will be the appropriate values for these signals considering memory-to-memory, memory-to-peripheral, peripheral-to-memory and peripheral-to-peripheral data transfers?


texts:
I have a servo controller that outputs a +-10 V velocity command for a motor. How can I take this signal and turn it into a pair of PWM outputs to drive an H-bridge?

A value of 0 to 10 V will control duty cycle on the forward output, and a value 0 to -10 V will control the duty cycle on the reverse output.


texts: Linear regulated supply from noisy input voltage

texts:
I have been working to redesign a faulty circuit board.

One of the problems I have identified is the power supply on the board.

The input voltage is nominally 13.8V DC from an AC switchmode powersupply but can drop sharply by about 1.5V when a number of solenoids that are connected to the same voltage activate and draw a large current. When the device is operating off the backup lead acid battery the input voltage becomes 12V.

Currently they are using a small SMD 7805 LVR to produce the 5V supply for a microprocessor and RFID chip. The LVR chip is overheating and heating up the whole circuit board (some parts are too hot to touch) which I am going to fix by using a TO-220 and proper heatsink.

However the change in the supply voltage causes a 100mV change in the 5V output before the LVR recovers. I think this may be causing the RFID's output frequency to fluctuate temporarily causing it to lose track of tags.

What is the best way to fix this? Would it be better to switch to one of those miniature DC-DC switchmode supply daughter boards combined with a LDO?

EDIT:

Current figures:
Worst case current through LVR is ~400mA, have measures up to ~300mA.
From memory each solenoid draws ~200-300mA when on, but they are latching solenoids so they are only momentarily on.
Each circuit board operates one solenoid, and depending on the product there can be up to 50 circuit boards and solenoids driven from the same 13.8V power supply.

They were having worse problems voltage drop due to running the circuit boards off a shared 5V line run over several metres of ribbon cable (with two conductors), but they then put the LVR to run off the 13.8 to get around that. They then had problems with the 13.8V line also run over the ribbon cable (five conductors) so they started running 16AWG lines to junction boards along the ribbon cable. They also chucked some big electrolytic capacitors on the ribbon cable but I don't think it made much difference from my testing.

The relays are near the board due to the physical layout of the product so not much can be done with that except to carefully design the board to prevent noise getting into it. It may be possible for the RFID antennas to pick up a bit of noise as they are on a long lead up to 0.5m, but only some of the lead is on the circuit board side of a steel plate, the wires then pass through a small hole so I don't think they pick up noise after that.

EDIT 2:

Should also mention all 50 relays sometimes get activated at once (can't change that unfortunately). However I have seen the voltage drop with just one relay activating which is puzzling, and it seems to be mainly when the relay is pushing out (instead of when it pulls) unless I am imagining things.


texts:
I am trying to repair/refurbish an old Farnell L30d power supply, 0 - 30v and current limiting to 2 amps.
There are two caps inside, one of which has blown. The caps are Hunts 3132A. Hunts no longer exist.
I have a circuit diagram for the ps and it shows these caps are 2200nf 63v high ripple.

Can I just replace the caps, with any old modern 2200nf 63v electrolytic caps? The ones I have found on eBay are considerably small tha  the ones fitted, so is it just a case of securely mounting the new ones? They are connected in parallel.


texts:
I'm trying to control a LCD screen from my PC. I have a W78E52B MCU with a sample code written in a .c file which I want to compile and upload to the device, preferably from a Linux environment for automation purposes.

The code looks like this:

#include<reg51.h>
#include<intrins.h>
//========================================================
sbit RES=P3^5;
sbit CS1=P3^3;
sbit A0=P3^0;
sbit E=P3^2;
sbit RW=P3^1;
sbit DB0=P1^0;
sbit DB1=P1^1;
sbit DB2=P1^2;
sbit DB3=P1^3;
sbit DB4=P1^4;
sbit DB5=P1^5;
sbit DB6=P1^6;
sbit DB7=P1^7;
sbit key1=P3^4;
sbit key2=P3^6;
sbit key3=P3^7;
...

What tool do I use to build this program into a hex/binary which can be transferred to the MCU? What is the relation between "8051" that I see here and there, and the MCU that I have?


texts: Safely wiring two strands of halloween LED string lights in series?

texts:
I have ~20 ft of perimeter to cover and it seems everything sold online is sold by ~10 ft lengths.
I've decided I want to buy two strands of these lights and connect them start to end.
What considerations do I need to take in to account here? I plan on powering both from mains using something to convert the power from mains down to the ~5V (actually 4.5) we could expect from three AA batteries in series, this is what I've chosen for now.
Now because these are all in series, I'll require a higher voltage right? Double the length so double the voltage, (4.5 * 2 = 9) right? Anyone ever done something like this that can provide some help, thanks!


texts:
Total novice to electrical engineering.
Is it possible to light a led bulb with AA battery?
What are the factors to consider here. For example resistance, consistent power supply, etc.
Why does a short circuit happen if a single led is plugged directly to wall socket?


texts: Adding SMA conectors to a device whose metal casing is connected to earth ground through at a single point

texts:
We are iterating a device whose metal chassis is internally connected to an ESD guard ring that is connected to the PCB signal ground through a 0Ohm resistor in a single point close to the power connector (image A). It also has two USB connectors and one RJ45 connector with their chassis connected to this guard ring. Everything has worked very well with this device.

Now we have added five SMA connectors to this device and we are not sure how to connect the ground pins of these SMA connectors with the signal ground of the PCB.

Since the SMA connectors have a metal body, if we connect them directly to signal ground they will be grounding the metal chassis of the device.

Do we have to connect the body of the SMA connectors directly to signal ground, connect the chassis of the device directly to signal ground and not have the ESD guard ring? (image B).


texts: Why Increasing Collector Voltage Reduces Collector-base Capacitance

texts:
I'm looking at some transistor radio circuits and the book I'm following makes the following statement with regard to AC gain: "By raising the DC voltage at the collector, the internal collector-base capacitances of the transistor are reduced".

Here's a circuit to help understand what's going on:

Here the author has killed the DC gain by placing an inductor in parallel with R2 whilst leaving the AC gain intact: collector reactance (L1||R2) / emitter reactance (C3||R3).

I have a reasonable grasp of the effect of Miller Capacitance on an inverting amplifier, where the inverted output acts negatively on the input.  What I don't understand is why increasing the collector voltage acts to reduce collector-base capacitance.

Does the increase in current flowing through the collector-emitter junction have anything to do with it?


texts: How to check the sampling rate of a Data Acquisition device?

texts:
I got a USB sampling DAQ device, which says it is capable of e.g. 100kS/s per channel.

How would I test if it is indeed capable of doing so? I don't seem to find any hints of where I'd start with that...


texts:
Got a great deal (1.75 EUR) on 10 used 18650 Li-ion accumulators salvaged from old laptop batteries which should have around 9000 mAh together. I measured them with a voltmeter and some have 3.7V, some have 3.8V and some have 4V. If my understanding is correct, when I wire them in parallel they will all reach the same voltage in a short time, which will cause them to heat up. My question might sound stupid, but is 0.3 V dangerous or negligible when wiring them in parallel?

TLDR: Will 3.7V and 4V accumulators wired in parallel reach dangerous temperatures?

Bonus question: How can I check how many mAh they actually have after I wire them in parallel?


texts: Identify 4 pin DC power supply connector

texts: Can you please identify this 4 pin DC power supply connector:


texts: Distinguishing simple FSK and Manchester coding?

texts:
I'm examining the signal sent by my car's fob. Using an RTL-STR and GNU Radio Companion, I've been able to capture and demodulate the signal.

Now I'm working on decoding the signal. What I'm not sure about is whether the signal is just FSK (frequency shift keying) or if it is FSK with Manchester coding.

Is there a way to tell if a signal is Manchester coded?

Image of the waveform captured after demodulation:


texts:
I wanted to know if there is a way to protect the circuit from a relay.

Usually you add a backwards diode for protection, because when you turn off the relay, the magnetic field in the coil collapses and tries to keep the current flowing, if there is no escape path, it turns into a high-voltage pulse that can destroy anything connected to the coil, adding the diode bleeds the pulse off to the positive rail before it can do any damage.

So now my problem is I have is that I can't access the relay to put a diode protecting the transistor.

The relay I have is VF4-11F13-C01, it's 12V rated at 40A.

So how can I create a circut that will be able to protect itself from this, the relay is connected to a 12V 40A battery.

Can I use a mosfet, or hexfet, or some other combination that can be used to protect the circuit.

EDIT: This is what I was thinking but some people said that it can't be done, so I asked on the forum.

Relay, I removed the case, but it's still encased in something black, the wires go under and come out of a terminal so I have no idea what's inside.


texts: open wire detection of open drain output

texts: I am working with a commercial dc  motor speed controller it has a open drain output which can be used for generating fault signals , i am taking that output to a pcb through wire , i am giving it a pullup to use the open drain output as logic level output .whenever there is fault the mosfet is on and the output is low ,when there is no fault the mosfet is off and output is pulled high. i want to make circuit to detect if there is disconnection between open drain output and the pcb_wire_connector and also give logic level fault signals


texts: Can I use a series crystal in an parallel crystal optimized oscillator?

texts:
Based on this application note from Maxim Integrated in section "Resonance Mode":

"Crystals have two modes of resonance, parallel and series, and all crystals exhibit both   resonance modes. The oscillator circuit is calibrated for one mode or the other, but not both."

I've been using this series crystal in PIC16F and NXP Cortex-M LPC1114 MCUs and since this is a series crystal I do not use small capacitors parallel to the crystal as usual seen in schematics.

My projects have always been working well and I haven't any problems so far. But after reading the aforementioned application note I started to worry about how I designed the oscillator part of the MCUs.

Also, when talking about "the oscillator circuit is callibrated for one mode or the other...", I couldn't find that information on the MCUs manuals or datasheets. The LPC1114 datasheet does not says anything about the resonant mode of its crystal oscillator circuit. However it clearly show in the drawings that a crystal with ceramic capacitors are expected to be connected in a parallel configuration, so I assumed that it's a parallel optimized oscillator circuit. And since I'm using a series crystal in a circuit that expects a parallel crystal I'm worried.

1 - Is it ok to use a series crystal in a parallel optimized oscillator? Can you affect the oscillation performance/accuracy doing that?

2 - How can I find out the type of expected resonant mode of a MCU if the datasheet does not inform that?


texts:
I am trying to verify a block I created using Modelsim but am having a little trouble with the clock generation. I would like the testbench to produce a 5ns (200MHz) clock using the code below...

Period:

CONSTANT period : time := 5000 ps;

Process:

-- system clock signal generation
clock_proc : PROCESS
BEGIN
    WHILE (true) LOOP
        clk_i <= '1'; WAIT FOR period/2;
        clk_i <= '0'; WAIT FOR period/2;
    END LOOP;
    WAIT;
END PROCESS;

However, in Modelsim a 4ns period clock is generated. But as all my asserts are based off wait statements like the following...

    WAIT FOR 1 * period;

these still trigger off of the desired 5ns clock. What am I doing wrong in the clock generation? I have tried using 5000ps in case Modelsim can't handle the floating point number generated from 5ns/2 but this produced no difference.


texts: Constructing Bode plot from experimental data and constructing a transfer function

texts:
I've been trying for a few days to convert an experimentally obtained (frequency against magnitude and frequency against phase) graphs to a Bode plot and then construct a transfer function from  the Bode plot

I constructed a table:

Converted each frequency from Hertz to rad/s by multiplying it by \$2\pi\$
Converted each magnitude to dB by multiplying it by \$20\log(\text{magnitude})\$

Note: As seen in the original graph, all the magnitudes are negative. When converting to dB, you cannot take the log of a negative number so I assumed it to be positive. Am I correct? Will this affect my Bode plot?
The table can be seen below:

Then I plotted the Bode plot below:

I understand that my transfer function will be a first order because the phase shifts 90 degrees meaning the highest power of the denominator will be 1. In other words, there will be 1 pole in the denominator.
In summary, my questions:

Was I correct in converting the negative magnitude to db by ignoring the negative value?

What will be the final transfer function of the constructed Bode plot?


texts: Why can't masters talk to each other in a I2C bus?

texts:
I came across an I2C article which lead me to a question. Specifically this part is creating some confusion:

"Also, unlike SPI, I2C can support a multi-master system, allowing more than one master to communicate with all devices on the bus (although the master devices can’t talk to each other over the bus and must take turns using the bus lines)" Sparkfun

Why can't masters talk to each other in a I2C bus if you supposedly have an unique address bit for each of the devices connected to it?


texts:
The task says:

Determine the value of resistance \$ R\$ so that true power of loads is maximum (biggest possible).

Picture of a circuit that came with task:

I solved it this way:
I know that \$ P = I^2 * R_{real} \$ and as \$ I = \frac{U}{\sqrt{(R + 3)^2 + 4^2}}  \$
so \$ P = \frac{U^2*(R + 3)}{(R + 3)^2 + 4^2}\$, when I derived that, I get \$ (3+R)^2 + 4 - 2(3+R)^2 = 0 => (3 + R)^2 - 4 = 0 => 9 + 6R + R^2 - 4 = 0 \$ which gives me \$ R_1 = -5, R_2 = -1\$. The answer that I should've got is R = 5, I don't know what I've did wrong.


texts: How surface refractivity affect radio propagation?

texts:
This question is related to the following link and Longley-Rice Propagation Model

https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.453-11-201507-S!!PDF-E.pdf

In the Longley-Rice Propagation Model the surface refractive index is taken into account and it also discussed how it is dependence on height. The question is: how does it affect different frequencies? I could not find any literature explaining its characteristic related to frequency? Any suggestion how to understand the effect of earth surface refractive affect RF propagation,?


texts: Unable to program ATmega128 - 16AU using USBasp

texts:
I am trying to program an ATmega128 microcontroller (bought from Robokits). I have connected the 10 pin ISP header from the USBasp programmer to the 6 pins (MOSI, MISO, SCK, RESET, VCC, GROUND) of the MCU.

But whenever I try to program the MCU the result is:

C:\Documents and Settings\intern>avrdude -p m128 -c usbasp
avrdude: warning: cannot set sck period. please check for usbasp firmware update
avrdude: error: programm enable: target doesn't answer. 1
avrdude: initialization failed, rc=-1
     Double check connections and try again, or use -F to override
     this check.
avrdude done.  Thank you.

Also I tried connecting an external 8MHz crystal to the MCU as indicated in this post, but it didn't work.


texts: Mechanism of On Chip Slew-Rate Limiting Mechanism

texts:
In the old designs of data communication there was a capacitor to reduce the
slew rate of a data communication line. But these days there is a some module
called 'on chip slew rate limiter' circuit configuration that does exists
independent from it's cable length or the cable characteristics. How does that
driver work? What's the mechanism behind that?

Is that they use a microprocessor to calculate the dynamic transfer function
of the medium so that they could switch between internal capacitors , is that how
it work?


texts: I know that \$τ = \frac{L}{R}\$, but what is \$R\$ in this formula? It seems to be the total resistance, but how to find it in the schematics?


texts: FOC Induction Motor Control - Rotor Flux Angle

texts:
In Field oriented control of induction motor it's necessary to do:

Clark Transformation
Park Transformation

According to the note (page 3):
http://ww1.microchip.com/downloads/en/AppNotes/ACIM%20Vector%20Control%2000908a.pdf
To calculate Park trans. (flux and torque stator current components /Id, Iq/) rotor flux angle is needed - it's described at page 4 how to calculate it.

My misunderstanding is how to do it if at these equations (EQ 1: Magnetizing current, EQ 2: flux speed) there is a necessity to have Id, Iq current which we haven't (as I mentioned to calculate it rotor flux is needed)?

What are the steps to do it exactly?


texts: Replace SOT-23 (5 pin) package in production with wire

texts:
I have found a hardware bug on a board design after many PCBs have been manufactured but not populated. I can fix the problem by removing a SOT-23 component and putting a wire across two of the pads.

I have too many PCBs manufactured that manually installing a wire across the two pads of the removed component is not economical in time or money.

How can this be fixed using an automated production method? Are there components available to fix this kind of problem, i.e. a package with just a wire between the two pins?

Edit:

The link in question is one of the SOT23-5 diagonals.

One suggestion is to use a zero ohm resistor. These typically come in rectangular packages with rectangular leads.

Would a pick-and-place machine handle resistors placed at 45 degrees to the pads?

What would happen during reflow? Would the surface tension due to the incorrect alignment of the leads to pads cause the resistor to spin and detach from the intended pad?


texts: Plug n' Play protocol for synced devices

texts:
I'm developing a highly customizeable lights system for emergency vehicles that consist on a series of devices, all of them in sync, with the posibility to program diferent sequences (of a moderate complexity) and with some type of plug n' play funcionality. So i need a way for syncing and configuring the individual patterns of the lights.

I was thinking in I2C, but i would have to implement some kind of dynamic adresses assignation. Also, i don't know how to sync a series of slave devices with out a master.

In summary, i need to keep all the devices in sync, but working with their own sequence and with the posibility to reprogram each device's pattern independenly using an external device connected temporaly.

So, any idea?


texts: Counting signal frequency with binary counter

texts: I'm trying to count the frequency of an audio signal using a 393 binary counter which is read by an Arduino without using its ADC. If the reading is done once per second, should the counter be somehow stopped when the counter is READ in order to avoid additional counts before the output pins are read? Perhaps, keep the input signal high with a MOSFET? What is the canonical approach to reading binary counter outputs?


texts: How to allow thread and interrupt safe writing of incoming USART data on FreeRTOS?

texts: I have a [circular] buffer that is written with incoming data from the USART using IRQ.  I also have other tasks reading data from the buffer as well.  What should I do in a scenario where a task has the mutex for the buffer but IRQ executes with incoming data?  Should I create a tmp variable which stores the data and sets a flag in IRQ so that data gets written to the buffer after the mutex is given?


texts: Creating a truth table for two 4 bit numbers A[3:0] and B[3:0] for inputs and an output that is 1 when A and B are equal and 0 when false

texts:
I am having trouble creating this truth table. I know truth tables have every possible outcomes of A and B, such as A[3:0]

0000

0001

0010...

But when I place the inputs along together, A and B are always equal. This doesn't seem logical to me. Could anyone explain?


texts: Why is the length of a cable-type radio-antenna usually determined by c/f regardless of the preceeding pcb trace length?

texts:
especially when dealing with low power IoT-devices or these arduino-style radio-modules that don't come with fixed rod-like antennas but rather those cable-type antenna-tails, the length of the antenna-cable is described as a critical factor for the signal range - and is calculated by dividing the speed of light by the signal frequency.
I wonder though, wouldn't the length of the pcb-trace leading towards the antenna-connector need to be included in the length-calculation as well?
If not, how is it that the receiving part only begins at the antenna-connector?


texts:
i am working with LTSpice simulation. And i am creating a bodeplot of an special circuit with the AC Simulation.
How can i use the meas. command to measure the amplitude by -135° phase?
I already tried using .meas AC bw FIND v(out) AT phase(V(out)=-135° but it failed.
I don't find any answers researching this problem in the internet.
Thank your for your help!


texts: What exactly does a capacitive touch screen need to register input, and how can that signal be produced?

texts:
There are active styli out there, and they take 3A or 4A batteries and don't require any wireless connection. How do those emulate human touch?

EDIT: I am specifically interested in iPad touch screens. After some research, I have realized that there are many types of capacitive sensor tech, but most people seem to be in agreement that Apple uses mutual capacitive projected capacitance sensor arrays.
These are set up with a grid of capacitors. A voltage is applied to one axis, and the other axis reports change in voltage when the local electric field of a finger alters mutual capacitance of the capacitors directly underneath it.

EDIT 2: what I really want is something with a fine tip like a ballpoint pen to project about a 5mm electric field the same way that a human finger does. There are styli on the market that try to work with a fine tip, but they all fail and I do not want one. I want to make my own because DIY projects are way more fun than buying an overpriced failure of a product.