texts:
In my DIY project I need to decide do I want to use piezo buzzer (for sonar-like device) or not. To decide this I need to calculate current consumption of this device. Parameters I was able to find in datasheets for many different piezo buzzer discs include resonant resistance, resonant frequency and static capacitance, max voltage and SPL for some sample volt/freq (e.g. R=150 ohm, f=3.6 kHz, C=90 nF, SPL at 3.6 kHz = 91 dB). If I understand it right piezo buzzer should consume current same as resistor with resonant resistance if run at resonant frequency. I want to estimate what current it will consume on different frequencies and what SPL it will produce. Is there a way to estimate it theoretically using above information from datasheet? Will it be easier to just buy few discs and estimate it experimentally?

Update: I found that some piezo modules have SPL/freq diagram included in it's datasheet, so it is possible to estimate SPL in dB using this diagram.


texts:
I'm doing a home automation system which uses a RF transceiver(nRF24L01+) paired with an arduino to control the relays. Since these require low power DC to run I was researching on ac to dc when I came across capacitative power supplies. This type of supply is needed as there isn't enough of space to throw in a transformer in a back box.

My only concern here is if such a power supply is safe, cause I don't want my house burning down.

This is the circuit I've found so far : http://www.circuitsgallery.com/2012/07/transformer-less-ac-to-dc-capacitor-power-supply-circuit2.html


texts: Is there a simple way to diffuse the light of a "super bright" 5mm LED?

texts:
I want to put yellow leds inside the turning-signal cases used in motorcycles.

The problem is: since the case is not deep enough, when I look from far I can only see the focused, pin shaped LED sources (two, in my case).

The leds I am using are like these:

As I see it, the case from the motorcycle turning light is supposed to receive the an incandescent lamp, so the internal diffusions gives its whole area the same brightness as seen from far away.

So my question is: how should I "unfocus" these leds (which I already bought, by the way)?

Possible options would be:

Cover the led "lens" with some "cap" made of a diffusing material (semi-transparent glue?). Possible problem would be loss of effective luminous power?
Paint the led lens with some suitable diffusing paint or material?
Sand the led lens surface, so as to scatter the light?
Reshape the so that it distributes the light in more directions?

I know I could try every option myself, but I imagine this is not a rare situation, so perhaps someone has already done something about it.


texts: Simple square-wave power inverter circuit question

texts:
This is a very beginner's question - I apologize if this is something completely trivial but I am stuck trying to understand the exact functioning of the circuit below.

The circuit below is supposed to be a simple square-wave power inverter circuit and I am puzzled by: (1) the purpose of several elements, (2) the absence of some (what I think are) important elements.

More specifically:

What is the purpose of D1 and D2 diodes? This looks like some kind of a flyback diode application but I don't see how it helps with flyback for the coil: what would happen when Q6 is suddenly shutdown? Wouldn't the induced EMF from T1 just fry transistor Q6?
What is the purpose of Q2 and Q5 transistors? Couldn't I just connect the multivibrator outputs directly to Q1 and Q6? Is it done to increase the base-emitter currents in Q1 and Q6 respectively because of some kind of output power requirements? If it is only about power, why not just use MOSFETs for Q1 and Q6 instead of BJT?
It seems that there is no resistors in the path from +12V to coil to ground. Wouldn't this path become a short-circuit if there is no load connected to the 220V side of the transformer (and thus, no back EMF)?

The circuit is taken from here: https://archive.is/0yRJc


texts: Will a MMBT5087 saturate with a 1K resistor in the base?

texts:
I am using the configuration in picture and the MMBT5087 PNP transistor. I am not using the top base resistor, just the lower one, so there will be 5V on the base.

My question is: Using a 1K resistor will it saturate? And is it ok to apply 5V directly on the base or it might damage the device?

I want to use 1K to keep the base current as low as possible.

Datasheet


texts: What is the importance of memory depth when selecting a digital storage oscilloscope?

texts:
I'm preparing to purchase a digital storage oscilloscope, to complement my 100 MHz analog oscilloscope. I've been demoing units and narrowing down the choices.

The EEVBlog tutorial on DSOs advises that the three most important properties of DSOs are:

Analog bandwidth
Sample rate
Memory depth

I am looking at a couple of two-channel 100 MHz DSOs, the Tektronix TDS2012C and the Rigol DS2102. Some other features aside, these two appear to have identical performance in terms of analog bandwidth and real time sample rate.

However, the Tektronix oscilloscope's memory depth is a paltry 2,500 points compared to the Rigol's generous 14 million points (expandable to 56 million). This seems like a major reason to opt for the Rigol. (Not to mention it is ~$200 less.)

Is there a reason not to weigh memory depth heavily? Perhaps some reason that the Tektronix doesn't need as much?

I know I want to be able to capture multiple digital events/waveforms from microcontrollers and look for things that change over time, etc. Ample memory depth is needed for this. The fact that the Rigol and Tektronix differ by orders of magnitude concerns me. Tektronix has a superb reputation, whereas Rigol is new to me. The vast difference in memory depth seems to be the final word. Should it be?


texts: Embedded PC with Gigabit Ethernet and SD card interface?

texts:
Where do I find such a module? All of the embedded PC modules I've seen so far have only a slow 10/100 Mbit/s Ethernet interface.

This is for a scanner application. I get incoming data at a rate of 2 MByte/s, which I need to store locally e.g. on an SD card. The whole image is over 10 GByte, which is why I need a fast interface to transfer it to a PC.

Here's one I just found: Technologic Systems TS-7800; it even features an user-programmable FPGA. There are other models available.


texts: How to calculate time constant of this circuit. .. and how the time constant of C1 and C2 are related


texts: Help with PCB design with current sense resistor

texts:
I have to perfomr battery characterization(power and current consumption measurement) of an embedded system module. I have embedded PCD  and an Battery pack PCB.Therefore I am planning to include the following PCB in the attached figure for current measurment. The battery pack PCB has 12 batteries divided into 3 sections. If you see the molex connector,it has the following in configurations.
Pin a - 3 V
Pin b -7.5V
pin c - 7.5V
pin d - ground

I am planning to perform current measurement by getting the embedded PCB to work in different modes according to functionalites.When the embedded PCB is in sleep mode, the current consumption is supposed to be as low as 150Ua and when not in sleep mode, it consumes upto 30mA.

My questions are.
1. Does the following circuit diagram help me in finding and performing current measurement?
2. Do I require any additional components in the circuit.
3.For measurement, I have a Tek MS0 3014 oscilloscope and a Keithley DMM(6 1/2). How can I design a PCB to easily probe in and find adjacent current and voltages.


texts: How can I connect ESP-WROOM-32 to CM3 without the need for a UART-USB Convertor?

texts:
Trying to add the use of the ESP-WROOM-32 and its Wi-fi / bluetooth to my project using eagle however alot of components out there require the use of USB and UART to USB Converters like the CP2102.

What I'm trying to achieve is to be able to connect up the ESP-WROOM-32 directly into the CM3 without the need for adding additional USB connectors / converters.

I spoke to buddy of mine and he suggested this page could be of some use: https://oshlab.com/esp8266-raspberry-pi-gpio-wifi/

Would this work the same for my project? or would I have to adapt the design to work differently.

I'm a newbie to electronics so what may come easy to you may require a bit of in-depth explaining so I can get my head around it. Cheers.


texts: Need a technique to rectify high voltage high frequency

texts:
I recently made a high frequency transformer which I will be using to drive a large spark gap tesla coil. I machined the bobbin at work from nylon and bought the 60x55x15 cores on Mouser to form a 120x55x15 core which I will expect to handle at least 1kw input and has already been tested to over 4kw input and is holding up very well with no signs of failing. I have also made taps on the primary coil (5,10,15turns) to vary output voltage and power respectively. Now I need an efficient technique to rectify this transformer.

I understand I need avalanche rated diodes. My question is, are ultra fast diodes such as a recovery time of <75ns for example automatically rated as avalanche. I do not fully understand what makes a diode avalanche so I'm struggling to find some from RS Components although I do know they are designed to break down to handle reverse voltages in a controlled fashion.

Switching frequency is 45khz on a full bridge, output voltage on the primary tap of 15turns is roughly 20kv on the secondary

Thanks


texts:
I want to measure weight, so I use load cells,

As far I know, commonly 4 load cells are used for this purpose, but I can not understand it's real purpose, maybe 2 will be more accurate than 4? Is it wrong?

Or, what is the optimum condition for it?


texts: How Armature reaction is different from Self inductance?

texts: It was given in "Electric machinery Fundamentals" by Stephen J. Chapman book that Armature reaction and self inductance is different. Contribution from armature reaction is considered as voltage drop \$jXI_{A}\$, with reasoning that \$B_{stator}\$ produced by current through stator coils would induce voltage \$E_{stator}\$. Later as shown in the image attached, net reactance is taken as \$ X + X_{A}\$, \$X_{A}\$ being self inductance. What I don't undertsand is, how armature reactaion is different from self inductance ?


texts: Using digital pins for reading analog value

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When I connect the pressure sensor to an analog pin of WEMOS D1 MINI board I'm getting values between 300 when the sensor is not pressed, and 700 when it is pressed. But I wanted to connect 10 pressure sensors so I connected it to digital pins because I need only 2 states 0 and 1.
I thought that, if the value is less than 512 digitalRead method returns 0, and 1 if the value is more than 512. But now I getting spam on serial port because values are changing all the time. When pressure sensor is not active I'm getting only 000000000 and that's ok, but when I press the sensor I'm getting 01011101.

Am I right that when I connect the sensor to digital I can get values 0 and 1, or should I use an analog multiplexer to connect everything through analog pins?


texts: I'm a beginner in electronics and am working on a Baby10 step sequencer for a project. It consists of a 555 timer for a clock signal, a CD4017 decade counter and 2 more 555s for an Atari Punk Console for the audio part. I constructed both parts separately and they seem to be working fine(The 4017 output was sent to LEDs to visualize the selection output and the Atari Punk console too) but when I send the CV signal from the 4017 to the APC input I don't get any sound but that of a faint metrome. Should I add something like an amplifier between the CV output from the counter and the APC? Is there anything I've missed? This is the schematic I used:


texts: Analyzing the crystal frequency (Bus Clock Frequency) of a HCS12 Microcontroller using an Oscilloscope

texts:
I have an HCS12 Mircocontroller and I would like to capture the crystal frequency from the bus clock on a oscilloscope.

How do I find out where I should connect my probes on the board to analyze this signal on the oscilloscope? I would like to measure the actual crystal frequency before it is divided by 2 or hits any pre-scaled division.

I realize this is a broad question but does anyone have any general guidance to what I should look for to figuring this out.

TWRS12G128


texts: Electromagnetic compatibility problem with an hairdryer

texts:
I wanted to ask you if you could give me an explanation of this electromagnetic compatibility problem.

I connected my (fully working) TV to a certain electrical socket in my house. I have also a very low cost hairdryer, and I have noticed that each time I connect it to the same socket of my TV (precisely: a socket which comes from the same wires behind the wall), and switch the hairdryer on the antenna signal on my TV disappears. The problem is solved as soon as I remove the hairdryer from the supply socket.

So, I was looking for a possible explanation of this phenomenon, and a possible circuital model. I think it means that, since it is a low cost device, it does not fill the EMC requirements correctly. But what does it happen from a circuital/electromagnetic point of view?

I wanted to analyze this phenomenon with more detail, but I do not know if it is an inductive coupling, a capacitive coupling, a radiation problem etc


texts: Potentiometer bypassing for guitar pedal UI

texts:
Firstly, I'm an electronics/hardware noob.
I'm working on a project using a Raspberry PI pico to collect UI inputs for a digital guitar pedal. I'd like to use the 3 ADC pins to measure 3 potentiometers (to control software-related parameters, signal in/out is handled somewhere else). I had the idea of alternatively allowing the user to plug in an expression pedal for each potentiometer that could allow the user to tweak parameters via their foot.
I'm having a hard time wrapping my head around a circuit that could allow the 3.3 V from the PI to:
A: Go through the onboard potentiometer if no expression pedal is connected
B: Completely bypass the onboard potentiometer when the expression pedal is plugged in and use IT for adjusting the voltage through.
I'm thinking a PNP transistor is going to be the key, but I just can't seem to connect the dots. Any help/suggestions/references would be appreciated.


texts: What's the best procedure to model a real world transformer which is not so simple

texts:
I have a transformer with a 110-1 turns ratio.

The output winding (1100 turns) is typically open circuit, with only its parasitic capacitances as a load.

The output winding has adjacent turn capacitance, layer to layer capacitance as well as capacitance of the output wires.

The input winding is 10 turns.

If I know the inductance and the ringing frequency on the output when pulsed, can I then determine the proper capacitance to put on an ideal transformer in modeling (LTSpice or similar)?

Assume air core so saturation isn't a problem.


texts: Maximum cable length between Raspberry and a 5V WS2812 led strip

texts:
I have a 2 meters WS2812 ledstrip connected to my raspberry and it works fine. Does anyone knows what the maximum length can be between the raspberry and the start of the led strip? I tried a 5 meters long old CAT5 cable I had laying around but this caused already the leds to be less bright and had problems with the refreshrate.
Anyone has any experience with this?


texts: What does this plot represent for 3 phase induction motor?

texts:
I got a 3 phase induction motor with the following plot (please see below).

On Y axis: Pm + Pfe represent the mechanical and iron losses, Pm being the mechanical losses, and PFe the iron losses.
On X axis: That's the electrical nominal tension U. In this case U10n = U1n.
The 3 phase induction motor is being charged at tensions between 80% U1n and U1n where U10 is the charging tension.
Can someone please explain why the plot behaves like that? Like what would be the mechanism behind that behaviour?
Many thanks!


texts: Arduino Due PWM Burst Signal with Phase shift

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Perhaps someone can advise how to properly handle the case on Arduino Due when I need to generate Burst PWM signal relative to the master signal. For example there is a master channel with a frequency of 100 KHz and I need to generate 5 impulses of 1MHz in a certain phase of the master signal. Burst itself can be done easily through the PWM_Handler by counting the number of interrupts but the issue is that it is not possible to do a phase shift of this signal. Another way I thought to use Timers and run the timer with the certain period that will correspond to the phase shift time. But looks like it is not a reliable way since Burst signal starts floating in the time.
I would appreciate any clarification or feedback if it is even possible to do on Due.


texts:
I purchased an amp for photodiodes from Amazon. It came with a 5v power supply. I am powering it with a 9v battery

Everything seems to be working okay, but when I measure the voltage leaving the power supply it reads -14 and +7 so I am wonder if the 9v battery is the correct way to power the unit.

Also there is a 5v terminal next to the diode and I’m not sure what it’s for. So is the 9v battery the correct way to power this and why is there a 5v terminal next to the diode. Your help experience and know how is sincerely appreciated. I tried to contact the seller but received no response.


texts: sim5360 diversity antenna, is it necessary?

texts:
I'm planning to design a board with both GSM and GPS/Glonass functionality so I picked Simcom's SIM5360 module which seems right for me. It has three antennas, one for GSM, one for GPS/Glonass and the other is marked as diversity antenna. Now I looked inside its documents but they never explained what is a diversity antenna and is it necessary to use it.
Can I just leave it unconnected?

Because having 3 antennas would make my design very complicated to use in a special environment I'm planning to use and it would make a lot of extra connections and it's just not practical. Why would there be a need for diversity antenna when there are already two other antennas?


texts: Flipflop value a long time after startup

texts:
After power up in an ASIC, is it save to assume that all flipflops are in a stable state ('0' or '1')? I do not care in which stable state they are, but it is crucial that all metastability has resolved. Adding resets would come at a high cost as these flipflops are part of a clock divider, where all the resets would need to be synchronised to intermediate clocks I do not use. Furthermore, all flipflops are T-flipflops. The time scale in which the flipflops have to resolve their state is in the order of milliseconds as all the power up circuitry like crystal has to start before.

I did read Output of a D flipflop upon power up?, but for me it is more the question about the timescale after which I can assume the flipflops to have resolved or how I could calculate it.


texts: What's the most effective way to prevent EM noise from coupling onto a cable and radiating out?

texts:
I've a PCB radiating noise inside a metal enclosure (this is Product 1 from this question here). Unfortunately, I can't change the PCB itself, so I'm having to tackle the problem by other means.  I can shield the metal enclosure to contain the noise, but I also need to deal with the cables exiting the enclosure. I've got a few questions regarding the best way to prevent the noise from coupling to the cables:

Regarding the cable shields, is it best to connect the shield to ground at the point at which they connect to the PCB, or at the point at which they exit the enclosure?
I'm guessing ferrites are best placed right at the point at which the cable exits the enclosure. Is this correct?
Does it make much difference placing the ferrite on a shielded cable compared to an unshielded one?

a. Is it best to place the ferrite before the cable shield starts, or after?


texts: Step up voltage converter / transformer sizing for electric oven

texts:
I am considering using a step-up voltage converter/transformer to increase the voltage of an outlet (in Los Angeles) from 110 VAC to 220 VAC for use with a 220 VAC electric oven/range (Samsung Model#NE59J3420SS). I'm trying to size/choose the appropriate converter but I'm a little confused on what size I should choose after looking through the oven's specifications and doing some calculations.

The specs say the two front ranges are 3 kW each, the two rear ranges are 1.2 kW each, and the oven heating element is 800 W. I am thinking that to size the converter, I would need to add these wattages up, giving a total of 2*3+2*1.2+0.8=9.2 kW. But if I calculate the amperage of 9.2 kW with 220 VAC, then I get a current of 9200/220=42 Amps.

Considering that these things would usually be used in a house with a 15-20 Amp circuit breaker, I am left wondering if I'm sizing this incorrectly. It seems to me that no one would be able to operate this thing in a house if they operate at such high amperage, so am I not supposed to add all of the power ratings or am I doing this right but people would just need to have a dedicated high-amperage circuit to operate this in their house?

Lastly, I have read that these converters should be sized two to three times the wattage of the equipment that will be used on the converter. So if I calculate 9.2 kW, then should the converter really be sized for 27.6 kW (if I can even find one that big)? Is the large safety factor of 3 here really necessary, or is it more for applications involving compressors or motors? Are there any special considerations that should be taken into account with these types of converters when sizing them for an application?


texts: Bypass capacitor before or after circuit, does it matter?

texts:
My colleague claims it is best practice to put a bypass capacitor "before the circuit" on the PCB, and even complicates the PCB design in order to ensure this rule is followed. I claim it doesn't matter, and as such it it silly to complicate the PCB design when a simpler design with the capacitor "after" would be available, but I however cannot bring any evidence to back up my claim.

(In the sketches, the integrated circuit is replaced by a current source for simplicity. The imperfection of write from power supply is modelled with a small resistor Rwire and a small inductor Lwire).

simulate this circuit – Schematic created using CircuitLab

But I do not see how it would make any difference if the bypass capacitor was "after" the circuit such as this :

simulate this circuit

Does it "before" vs "after" really makes any difference?


texts: Logic family for 3.3 V microcontroller interface

texts:
I need to generate a bunch of chip selects for a SPI bus that I want to use on a project. I will use a 36 position (similar to PCIExpress = cheap) card edge connector and etc.

The bus is simple :

Pin 01 -> Clock
Pin 02 -> MOSI
Pin 03 -> MISO
Pin 04 -> CS#1
Pin 05 -> CS#2
Pin 06 -> CS#3
Pin 07 -> CS#4
Pin 08 -> CS#5
Pin 09 -> CS#6
Pin 10 -> CS#7
Pin 11 -> CS#8
Pin 12 -> CS#9
Pin 13 -> CS#10
Pin 14 -> CS#11
Pin 15 -> CS#12
Pin 16 -> CS#13
Pin 17 -> CS#14
Pin 18 -> CS#15

Other pins on the card edge connector are assorted GND and VCC pins.

I need to generate a chip select from 4 GPIO pins on the microcontroller, in order to select a SPI slave from various devices etc.

A long time ago this would be made using a simple 74LS154 device (1-of-16 decoder). The chosen microcontroller is the only 3.3 V device (EZ80), and I find it hard to find a 3.3 V equivalent to 74LS154.

Please tell me where can I find a 3.3 V 74LS154 device.

Edit:

looking the datasheet from the ez80, its SPI can only do systemclock/2 speed. Its reasonable to think that the max speed at which the chip select pins change is equal to the character rate, that means (50 MHz / 2) / 8 or 3.125MHz. So there is no need for all that speed (50 MHz).


texts: What electric setup do I need to get electricity from a BLDC motor?

texts: I'm trying to create a small  scale wind turbine for a project. I plan on using a BLDC motor with some blades on it to capture artificially created wind. I'm new to electronics, but I was thinking of buying a 3 phase rectifier and connecting that to the BLDC motor to get a DC output. Do I just simply connect the three wires of my motor to the rectifier? I also don't know what to buy to "capture" that DC output so that I can accurately measure how much electricity it has produced. I was thinking some type of power bank but I don't know one that has two input for my DC current.


texts: How to fix servo motor broken by wrong polarity

texts:
I accidentally plugged in my servo with the wrong polarity (with the order of wires being signal, ground and power). It immediately started releasing the 'magic smoke', but I managed to unplug it before 4-5 seconds had elapsed.

I don't think the smoke was due to the gears grinding together (that wouldn't match intuition anyway), but actually because of the electronics screwing up (too much current through a component?). So my (edited) question is: can the servo 'motor' be salvaged and converted into a DC one (the various methods for doing so described on Google)?

Googling didn't lead me to any answers, and I'm too much of a n00b to figure this out on my own. I apologize if the question is based on wrong assumptions of mine or or doesn't really ask anything objective.


texts: Is this regulator a suitable replacement for original one?

texts:
I am fairly new to electronics and have done my first project successfully (where it works as assembled PCB). And I am looking for the next step there. In my original project I've used SPX3819M5-L-3-3 to regulate incoming 5V (from micro-USB) into 3.3V.

I am now looking to switch from micro USB to UCB-C connector, which can go up to 20V (the circuit is not the main sink, so another connected device can request up to full 20V). Given that original regulator maximum rating is 16V, I need to change it to something suitable. I've looked at TL760M33 for this purpose as it can go up to 26V and output fixed 3.3V at 500 mA max, which seems perfect for my case.

Being very new to electronics I have my doubts over every single detail.

So in this case my question is -- is this replacement valid and would my circuit function as I expect it to? Additionally I wonder is there any pitfalls or details I missed in choosing a replacement regulator?

Original schematic:

Replacement schematic:


texts: Guitar Pre-Amp stage/filtering and STM32F4

texts:
I am currently involved in an academic project which the topic is to design a Digital Tuner for Electric Guitars.
My knowledge of electronic is very basic, so here I am.

I need to pre-process the signal that goes out from the pickups of a common electric guitar, let's consider passive pickups so....we have an output voltage from 200mV up to 1V of peak, with also negative peaks (of the same magnitude).

I have to use the STM32F4 (Discovery Board), so I need a very simple circuit that drives the On-Board 12-bit ADC, that takes, as inputs, signals with voltage between 0 and 3.3V. So I have to design a pre-amp circuit that amplifies and clamps the guitar's output.

I want to underline that I have never realized an electronic circuit (a real one, not in the simulator) before. I am wondering about:

STM32F4 provides some voltage sources (5v or 3v). Shall I use these sources or is it preferable to go with an external voltage source (e.g., batteries)?
I have chosen an opamp that is not, let's say, "handy" because it needs 2 voltage sources: the TL082. What op-amp do you suggest me to use? (maybe with only 1 voltage source)
I have tried to design a circuit by using LTSpice, but I don't know if it is correct at all. You can also notice that I have inserted a filtering stage (LP w/ cutoff freq. 2,2 KHz)  and a "protection" Schottky diode before entering in the pin of the board.


texts:
For a system I am designing I need go over 500mA limit for a very short time (30mSec). I have designed my system such that during the over 500mA period I am able to sustain my circuits using internal caps. (Internal caps can maintain voltage for my operation). However on the bench using a bench supply I see that I drag the voltage down (500mA constant current mode) to 4.5 during this 30mSec.

Is this allowed? What can go wrong ? (Would USB disconnect ?)


texts:
I want to use a well known AGC circuit (see below) with 3.3V instead of 5V. The description of the circuit can be found here, and state the following about the JFET:

  Other JFETs with VGS(OFF) of 5V or under, such as the 2N5019 or 2N5116, should work equally well in this circuit, although they haven’t been tried. To use JFETs with higher VGS(OFF), such as the 2N3993 (it was tried and worked equally well), increase the supply voltage to 12 V.

Can I still use the J176 when the supply voltage is 3.3V, or do I need to select a different JFET?


texts: Hi I'm using a BLE module connected to a chip antenna, the antenna manufacture establishes the path width is .4mm, if I need to match the network to 50ohm how can I do it? the system has a pi-match C1=0.8pF L=3.9nH and C2 is 0.8pF how can I make sure it matches 50 ohms?


texts: What is the minimum number of NOR gates needed to implement a 2-input multiplexer?

texts:
In the first chapter of The Elements of Computing Systems, the reader is asked to implement basic logic gates like Not, And, Or, Xor, as well as a 2-input multiplexer and de-multiplexer. The authors instruct the reader to build their gates using the universal NAND gate as a basis.

I am able to build all of the requested gates using NAND gates without issue. Using truth tables and DeMorgan's law, I have minimized the gates as much as possible (e.g. Xor can be minimally represented using only 4 NAND gates, as can a 2-input Mux chip).

For the sake of rigor, I decided to build the gates using the other universal gate: NOR. In doing so, I noticed that NAND and NOR representations are pretty much tied in terms of complexity. For example, And gates require 2 NAND gates or 3 NOR gates, but this is countered by Or gates needing 2 NOR gates or 3 NAND gates.

For the 16 boolean functions that exist for 2 inputs, NAND and NOR end up tied. Neither gate is superior in terms of minimizing complexity. However, this doesn't seem to hold when building the Mux chip.

I can build the Mux chip in 4 NAND gates. The de-multiplexer (DMux) chip can be built in either 5 NAND gates or 4 NOR gates. My brain's pattern-recognition wants so very badly to think that the Mux chip must have a NOR representation in only 5 gates, thus making Mux and DMux another set of tied pairs leaving NAND and NOR gates tied once again.

But try as I may, I cannot find a way to implement a Mux chip in any fewer than 7 NOR gates.

Am I missing some minimization trick (as with masks in NAND-Xor or NOR-Xnor)?


texts: Put firewall hardware with ethernet ports between serial ports

texts:
I want to put a firewall hardware product between a RTU and PLC to block some Modbus function codes (e.g. write coil, read coil). (This firewall product is able to do deep packet inspection on Modbus protocol.)

This firewall hardware has two ethernet (RJ45) ports, IN and OUT. But the Modbus uses serial buses (should be RS485) between RTU and PLC. Hence, to solve this issue, can I use two ethernet - RS485 converters to connect firewall hardware between RTU and PLC? Is there any possible issue?


texts: Op amp advertised as BW = 105MHz, but GBP is actually 70MHz, what's being spec'd differently?

texts:
I just came about an op-amp spec where they say, "the Op-amp X is unity-gain stable with a small-signal unity gain bandwidth of 105MHz.." As you continue to read, it then says, "with a gain-bandwidth product of 70MHz, ...."
What is the difference between these specs?  How can its unity gain be specified for two different bandwidths (I understand it says small signal, but I still don't know how I'd use the information).  It seems to me the meaningful spec is the 70MHz GBP and the 105MHz is just "specmanship".  But, if anyone can explain what they mean by that small signal BW, and how that info is useful, I'd appreciate it.  Thank you.
Edit:  I didn’t want to malign it, but at your requests, here’s a link to the OPA2810 data sheet.
https://www.ti.com/lit/ds/sbos789c/sbos789c.pdf?ts=1605745386167&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FOPA2810


texts: ATMega32, Using PORTA as digital io has digital "crosstalk"

texts:
I have multiple switches connected to portA on an atmega32. They are set as an input with internal pullups. There are no external pullups. The switches ground out the pins. I'm not debouncing the switches because their state is latched in software.

My problem is that when button 0, connected to pin0 on porta, is pressed for ~30ms, a 0.4ms pulse appears on the adjacent pins. Like a type of 'digital crosstalk'.

So now I'm forced to debounce to prevent registering and latching false button presses. I attached a logic analyzer to the pins. Here is the screenshot.
http://i.imgur.com/RveN2if.png Channel 5 is connected to the button that I pressed multiple times. You can see the spikes on the adjacent channel.

Any idea what might be happening. Could this have something to do with the port also being part of the ADC module, or possibly the fact that I'm using an older chip?

I have AVcc connected to vcc with 10uF to ground. Aref is internally set to vcc and has an external 3.3uF capacitor.


texts:
I have a Li-Po battery which has a discharge voltage range of (2.5-4.2)V and I want a regulator which is able to convert this voltage to 3.3V. I was told to use a buck boost converter. I have found one which is a buck boost converter and the other a buck converter. Reading the descriptions of both, I think both will work but I would like to ask for your opinions or if you have any other recommendations of components that'll work. Here below are the datasheets of each component:

Buck
Buckboost


texts: Is this current measurement solution okay?

texts:
One wishes to measure the RMS current (12A max.) drawn by an AC motor using a PIC16F887 at intervals of 1 second. One cost effective solution I am considering is using a current transformer, a bridge rectifier and then a large-ish capacitor to filter the signal to be fed into the ADC pin. Like this perhaps:

Are these calculations correct?

For max. primary current: 12A RMS
Turns ratio for this CT: (1/70)
Secondary current = Primary Current * Turns Ratio = 12*(1/70) = 0.186A RMS
Burden Resistor: 33 ohms
Secondary Voltage = Secondary Current X Burden = 0.186 X 33 = 6.14 V RMS
Therefore Secondary peak-to-peak voltage = 6.14 X 1.414 = 8.68V

The DC voltage after the capacitor should then be close to 8.68V? Why does the above Proteus simulation show otherwise?
The diode D1 is supposed to avoid over voltage on the ADC pin due to inrush currents of about 40A that happen about every half an hour. Would that be adequate?
Is there any reason this method should not be used at all/won't work?

Edit:
Simulation with the burden before the bridge:


texts:
I need to solder a WLCSP chip (FAN3852) to a DIP breakout board.
Since the WLCSP chip already has tiny solder balls, would it be possible to hold the chip in place on the breakout board with tape and then heat it with a heat gun? I'd have to monitor the surface temperature to ensure it doesn't exceed the max reflow tolerance (~260C).
https://www.youtube.com/watch?v=T75VzHjnExc


texts: CCD sensor: Digital Counts vs Exposure plot vs Dark Digital Counts

texts:
First, my question concerns an individual pixel/sensor from a CCD array of a digital camera.

From my understanding, the Digital Counts is linear with Exposure time.  However, this line will be different for different light sources.  My intuition led me to believe the Digital Counts of the different lines for exposure = 0 seconds would be the same.

Now, I could also take dark frames by covering the camera lens.  I could take dark frames at different exposure times and estimate the Digital Counts for exposure = 0 seconds.

I also thought the value estimated for the Digital Counts at exposure = 0 seconds would be the same for both the light and dark data collections.  This doesn't seem to be the case.

Can someone explain the Digital Counts at exposure = 0 seconds for the light frames vs the Digital Counts at exposure = 0 seconds for the dark frames?


texts:
In my research for this question, I found this by a new user that hasn't been seen before or since.  His low investment here and the "say goodbye to traditional bad stuff" language makes his answer a bit dubious, but just in case he's onto something, I thought I'd fish for some clarification.

His original answer is the classic unformatted block of text with no diagrams, but I think he's describing this:

simulate this circuit – Schematic created using CircuitLab

I'm pretty sure that won't work as described.  Or did I read the description wrong?


texts:
I recently made a slayer exciter by using the circuit diagram attached. But my exciter is not working and I have a question.

Is primary coil supposed to be wound the opposite direction as second coil?

The LED in the circuit is just blinking.

I used 12v instead of 9, 450 turns instead of 275 and 6 turns instead of 3.


texts: How to specify what is printed to silkscreen layer in Eagle?

texts: I am finishing up a PCB design for the first time in Eagle, and I need to know how to print the component names onto the silkscreen layer, how to I set the layers up so the right things are printed?


texts: Transmission of different messages with the SAME ID on a CAN bus

texts:
CAN arbitration is done with IDs, and any node on the bus can transmit with any ID (ideally it should not, but a nasty node can).

What if two different nodes connected on the same CAN bus transmit messages with the same IDs but different data bytes?

My thinking: It will generate garbage on the bus. Whoever has the dominant bits those only will get transmitted.


texts: Information regarding old AB (Allen bradley) potentiometer JAIN056S102MA

texts:
i was looking for information (datasheet) regarding this old potentiometer from 1962 on the internet, JAIN056S102MA type J, 1k-ohm from Allen Bradley and i was not able to find any information about it, i want to replace it because it is not working anymore and it is in a working machine, according from a user of this forum this potentiometer is Type J, 1k-ohm pot that is rated at 2 watts end-to-end and has an an audio taper, what does it mean audio taper?, anyone can help me where to get the datasheet of this pot?, anyhelp is really aprecciated, thank you very much

Omar Torres


texts:
I am trying to do the following small project:

Master MCU have 2 buttons - PINC0 and PINC1

PINC0 will count the clicks

PINC1 will blink the LED n times (n=counter) and send n to the SLAVE MCU

The slave MCU will get the n and blink the LED on his side.

I am using ATmega8

See MASTER code:

#ifndef F_CPU
#define F_CPU 1000000UL
#endif

#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>

#define ACK 0x7E

void spi_init_master (void)
{
   DDRB = (1<<5)|(1<<3);
   SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0);
}

unsigned char spi_tranceiver (unsigned char data)
{
   SPDR = data;
   while(!((SPSR)&(1<<SPIF)));
   return SPDR;
}

void led_blink(int x)
{
   for (int i=0; i<x ; i++)
   {
      PORTD|=(1<<7);
      _delay_ms(150);
      PORTD^=(1<<7);
      _delay_ms(70);
   }
}

int main(void)
{
   spi_init_master();
   DDRD=0xff;
   DDRC=0;
   PORTC|=(1<<0)|(1<<1);
   int counter = 0;
   int flag = 0;
   unsigned char data;

   while(1)
   {
      unsigned char pressed = ~PINC;
      if (PINC & 0x01) {
         flag=1;
      }

      if ((pressed & 0x01) && (flag == 1)) {
         flag=0;
         counter++;
         PORTD|=(1<<PD7);
         _delay_ms(20);
      }
      PORTD=0;

      if (pressed & 0x02) {
         led_blink(counter);
         data = spi_tranceiver(counter);
         counter=0;
      }
   }
}

What I am trying to do here is count PINC0 clicks (counter increase each click), and flashing LED "counter" times on PINC1 button click.

Also - on PINC1 button click I want to communicate with SLAVE SPI MCU, which also blink his LED "counter" times.

The hardware connections is:

Vcc, GND to external source
LED positive led to PD7, negative to resistor connected to GND
Buttons, PC0, PC1 connected to one leg of each button, and the other leg connected to GND.

The issues are:

The button is pull up active low. the button connected by 1 leg to IO pin and other leg to GND. It works, but half of the time the LED blinks on the release as well.
The SPI does not work - did I miss something?

Why are those 2 issues occuring?


texts: Basic ESD common sense for breadboarding and 300+ component storage?

texts:
I've purchased a large batch of items, varying from capacitors to potentiometers to ICs and would not like to ruin the investment in a careless mistake.

I have a metal filing cabinet from IKEA that sits between the carpet and my wooden desk, would there be any harm from to the components just being in there?

I have many Styrofoam blocks to place components (that can be) placed shoved in them, as well as a lot of baggies. Would dryer sheets laced under/between these packages keep them safe - at least from common worries?

I could buy some sort of wrist strap, however am not sure if just touching the metal cabinet or something like a metal window frame would discharge static (even if not "grounded" directly to earth through socket or something), if that works, and the dryer sheets could prevent discharge within the filing cabinet that would put my mind at ease.


texts: What is the voltage between each turn in a transformer winding

texts:
From a perspective of insulation, how much voltage between each individual turn in a transformer?

Example from picture above, the primary winding have 16 turns. Let`s say 800VDC is applied between + and -. The core is made of a magical material that never saturates, and the voltage source is capable of infinite current  (just to focus on the voltage insulation part).

Assuming the core itself is perfectly insulated, is the voltage between each turn simply Vp/turns? Or is this more complicated. In this case 50V between 1st to 2nd turn, 50V between turn 7 and 8...etc?

That would model the turns something like this:

simulate this circuit – Schematic created using CircuitLab

But I assume this is not the case since doubling the turns effectively quadruples inductance, instead of doubling it like the above model implicates.


texts: Producing a boost converter, difference with theoretical analysis

texts:
I'm trying to reproduce a boost converter with these specifications:

Po=200W
Vin=40V
Vout=120V
L=100uH
switching frequency 100kHz

I tried it but the load power does not reach 200W and Iout isn't 1.66A, either. I set the load to be 72 so that 1.66*72=200.
What can I do to get this done correctly?


texts:
My goal is understanding voltage and input impedance difference between calculation and spice simulation in circuit like below:

Predicted: k=U_Rc/25mV=6V/25mV=240 V/V, R_input=(25mV/Ib || 1k)*B || 82k=109k || 82k=47k, hfe=B=420 A/A

Simulated: k=113 V/V, R_input=13k

Whats more, deleting R7 resistor and editing R5/R6 divider for same current (Ic_Q1=30mA) results in dropping (to circa 70%) voltage gain and increasing (two times) input resistance.


texts: How to build distance measuring device that can only detect red light from a common red laser

texts:
I want to make a distance measuring device. Using common red laser. what receiver  should I use to detect the red laser light only? a more sensitive to red light.

Do an Arduino UNO capable of this?


texts: This is on a control board from a crane...not sure of crane mfg or country of origin. Anyway, owner lost 12Vdc to the board and tried to jumper it in...ooops.  This is where the smoke came out...can't seem to find anything on this part.  Another part next door is also designated V but unfortunately it's not the same and I can't find that either. Letters appear to read GP447.  Thanks all!


texts: How can the reverse voltage of an LED decrease?

texts:
I recently build an LED matrix (for LED cube) and when testing I discovered that multiple other LEDs turned on when I triggered a specific one. Upon measuring I found out that several LEDs were "damaged": The lit up when forward biased, but conducted backwards at around 1.7V. This bridged rows of the matrix and allowed other LEDs to get power.

Is this something that can happen by ESD? Or are my LEDs just very strange?


texts: I have a picture of a schematic that has these legends on the resistors. What does N/F stand for? And is it also applicable on other electronic components?


texts: What is the difference between voltage UNBALANCE and voltage IMBALANCE?

texts:
I'm a Brazilian (so not a native English speaker) who just came across the user guide of a power quality analyser which has, among its features, measurement of both "voltage unbalance" as well as "voltage imbalance". The problem is that I'm not sure what is being talked about here... For instance, Google Translator sometimes gives me the same meaning for both words - in Portuguese, "desequilíbrio" - but sometimes I got "desequilíbrio" for Unbalance and "desbalanço" for Imbalance, so this could actually mean two different things. Unfortunately I went to Google and found some resources saying that Unbalance and Imbalance are synonyms in the context of Electrical Engineering, so I got no help from there.

Ultimately, I'm kinda lost: I know there are two different things being talked about by the Power Quality Analyser and that there is a significant difference between Unbalance and Imbalance so they would use those words to mean two different things even though translating them to Portuguese would give the same meaning most of the times and even though some references take them to be synonym (which also means both words are quite close sometimes).

So, my question is: in the context of Electrical Engineering what is (Voltage and Current) Unbalance and (Voltage and Current) Imbalance? Are they actually different or are they actually synonyms (and what happened was that the power quality analyser manufacturer created a private, different value and called it by another but related name?) If they are different, what is the formula for calculating each of them? And even more importantly (although maybe this is not the right place) what is the correct equivalent names of them in Portuguese?

P.s.: a note in the user guide says:

  Imbalance is the rms deviation calculation per channel if the instrument is in Standard PQ Mode. It will display the ANSI definition of unbalance for channels A, B and C if the selected monitoring mode is other than EN50160. When monitoring under EN50160 mode, Imbalance will be a simple value as per IEC definition, defined as the sum of negative sequencing components divided by the sum of positive sequencing components (similar to meter readings under Meter Mode).

and

  Supply Voltage Unbalance: The unbalance of a three phase supply voltage onsists of a loss of symmetry of the phase voltage vectors (magnitude and/or angle), created mainly by unbalanced load.

Unfortunately I'm new enough in the field to not know how to deal with this information!


texts: Unusual behavior when controlling a Button Matrix

texts:
I have a 4x4 matrix for 16 buttons. Each row/column is directly connected to the pins of an unknown microcontroller. When I connect the pins directly to each other, the microcontroller behaves correctly, as if the respective button was pressed.

I want to control the pins directly with an Arduino or connect them directly to GND/VCC. However, when I turn them on this way, the microcontroller either:

does nothing
behaves as if several buttons are pressed at once.

Why is that? Am I missing something, like pullup-resistors?

The microcontroller supports certain button presses at the same time. I think it has to do with the row scanning. <- This turned out to be true, the microcontroller checked one row at the time. So it was necessary to activate the column pin only when the right row was selected.


texts: Harvesting Energy from an Electromagnetic Generator

texts:
I have designed a simple circuit that harvests energy that is generated from an electromagnetic generator.

I would like to know tips  I could use to improve efficiency and minimize the losses I may have by using this design. I have drawn h the circuit for more clarity.

Please note the MOSFETs act like a diode bridge. This circuit has been tested and it works. I am interested in improving the efficiency including any other options that may even be costly.

P.S.

The following are requested information as per comments.

The voltages peaks generated from the harvester has about 7v Pk-Pk. This depends on speed. I have mentioned the average.

The purpose of the zener is only to protect the BQ25505 from receiving beyond 5.5V. That is the maximum input voltage of the BQ IC.

High Spikes of 6V are reduced because of the capacitors charging effect. We have tested this and its true.

Currently i want to more efficiently harvest the energy bursts coming off the harvester. With lowest dropout voltage.


texts: How not to waste power with digital inputs?

texts:
I am trying to make simple gates with n-MOSFETS, yet I'm not sure how to actually do physical gate inputs correctly.

At first, I tried this (a single-pole, single-throw switch from +5V to gate). However, as I learned recently, this is bad because when the switch is open the gate has a floating voltage.

So then, I thought that I should use a pull-down resistor from gate to ground, and then have a switch from +5V to gate, like this. However, this is undesirable because the pull-down resistor always draws 25mW and has a constant current of 5mA, which seems to me like a huge waste of power and current (especially as I am using USB power, and thus have a max current of 500mA for the entire circuit, which will consist of many more transistors and inputs). Note that I cannot have a very large pull-down resistor, or the transistor stops working correctly, which means that I need to have a small resistor, and thus a large current and power draw.

My next thought was to not use a pull-down resistor, and instead use a single-pole, double-throw switch between power, ground, and gate, like this. This seems to me like the best way to have digital inputs, because there is no constant power drain. However, I would need to buy some of these switches since I don't have any right now.

My question is the following: how do existing circuits (such as those found in my computer) do physical digital inputs? Do they have pull-down or pull-up resistors and waste power and current, or do they even follow any of the methods that I thought of? Is there a better way of doing this that I haven't thought of?


texts: How do I determine what kind of proximity sensor / RFID hardware is in a device?

texts:
I have several objects in my pockets that do stuff when I put them near things:

A token to disable a house alarm
A Transport for London Oyster Card
A security pass

And in the not-too-distant-future, I wouldn't be surprised if my phone used NFC to, for example, pay for stuff.

What kind of hardware do I need to figure out what "protocol" these objects use to communicate? Is there any (affordable) hardware to read from a wide variety of RFID/NFC? The Oyster Card uses Mifare, I think, but I only know that because of a little reading around the web.

I know nearly nothing about wireless communications, so apologies if I'm using the wrong terminology.


texts:
how to calculate doping concentration in the base, and emitter, collector of SiC ?
In the neamen book dont teach that. just propose the constant number. so can you help me?
I hope to calculate NB, NC, NE. i know mobility and Nv, NC
cuz I am calculating about SiC parameters. not Si.


texts: LTSPICE: Unrecognized parameter when defining custom NMOS

texts:
I am trying to edit the existing MOSFET model with the new parameters.
1st image is the MOSFET circuit and spice operative command:

2nd image is the error that I am getting.


texts: Effect of output inductor DCR on switching power supply

texts:
I'm not an EE but I'm attempting to gain hobby levels of the skill.  So I'm building a DC/DC power supply as an exercise.  I built a PCB design for a TI chip (TPS560200) with associated passives based on the information in the datasheet.  After sending the PCB off to fab I decided to throw the chip into WEBENCH and most parameters are on target except for the tool specifies an output inductor with 33mOhm DCR as if that's important.

My question is, is it?  I believe I understand the place of the inductor in the circuit but I can't reason about the effect of DCR.  Maybe a different DCR might effect the balance of the voltage divider but only for the portions of the signal which appear as DC to the inductor?  Is it something else?  Or is WEBENCH just specifying DCR blindly here?


texts: Connecting 50 Arduino slave devices to a single master Raspberry PI

texts:
I am designing a automation system and need to have multiple slave devices(probabaly arduino UNO or NANO) communicating both ways with master device (Raspberry PI).
There is a server and database running on a raspbery PI and I need be constatly sending/reading data from individual arduinos that have sensors connected to it. Based on certain actions from the sensors on arduino boards, raspberry PI will be sending sql querys to the database.
My main concern is how do I talk to individual slave boards with a single master device. I only see 3 options here:

Use RS485 modbus to connect all slaves in a daisy-chain

Since I have 4 USB ports on my raspberry PI 3b+ and use only 1 for keyboard and mouse, i could use USB-HUB to expand the available USB ports and then connect to individual arduinos as such:

Maybe use ETHERNET to connect all devices together? Not sure how would that work and look just an idea..

Any advice is appreciated! Thanks


texts: Using two mosfet in diode connected structure

texts: I read that the structure in green are diode connected. I am only familiar with the single device version of diode connected MOSFET. Can you tell me what's the advantage doing it using two devices as shown? Thank you. I'm self learning please bear with me.


texts:
I'm building a helical antenna at 1.7 GHz from scratch. Theory says that its characteristic impedance is 140 Ohm. The RF transmission line is 50 Ohm so there has to be an impedance transformer in between. What is the proposed  custom implementation of such a transformer? I have come across the LC circuit as a possible transformer, but is it enough for 5 MHz of bandwidth that i require from the antenna? What's the simplest transformer that will do the job for me?

Thank you for your time


texts: What is an electrical relay on a bus (vehicle) made of?

texts: I was driving a bus and had the heaters and defroster on high.  But this turned out to be too much amperage for this old bus -- an electrical relay caught fire and smoke was billowing into the bus.  Does anyone know what the relay is made of? Because I'm still recovering from the effects of this smoke inhalation.


texts:
How is the signal strength calculated in case of cell phones ?

How will the signal strength be calculated in case of WiFi networks ?

I am not certain if the question I am asking is the same as QoS calculation.

I wanted to calculate signal strength for proprietary RF radio couple. Is it advisable to calculate this based on application layer, by calculating ratio of good / bad packet count based on packet checksum ?


texts: circuit design options between switching Servo GND vs switching vcc

texts:
I have couple of design choices wondering which one is more appropriate, I am controlling a SG90 hobby servo with an Atmega328p using a NMOS. I could either switch the servo GND or servo VCC just wondering which is better, your suggestions will be welcome.
Switching servo diode

Secondly is it advisable to use  a flyback diode  ?


texts:
Consider a SIMO (1 transmitter - several receivers) system in which The receiver antennas are used to obtain space diversity and we have a multipath fading channel between transmitter and each receiver.

Obviously, the SNR for different antennas are different (even if the AWN power for all antennas be the same) as the channel for different antennas are different.

The output of the antennas are combined in a method to obtain an estimation of transmitted signal, however I wonder how do you formulate the SNR in this system? Indeed if I want to draw the figure of merit for my system, then I must say ... FER is obtained at ? SNR.


texts: Is there diode with both low forward voltage(<0.2V) and low reverse current(<0.2uA)?

texts:
I want to use MS621FE rechargeable lithium battery as RTC battery.

The working voltage of my circuit is 3.3V.

MS621FE allows a charge voltage from 3.1V to 3.3V.

To prevent the battery try to supply the system I need a diode series with the battery to the VDD.

The problem is,I want to charge the battery the most possibly full, and the lowest reverse current when system is powered-down, which means I need a diode with both low forward voltage(<0.2V) and low reverse current(<0.2uA), is it possible?

I found IN4148, but the forward voltage is too high, and some Schottky diode has the low enough forward voltage, but the reverse current is too high (10uA+).

Current consumption of my RTC module is only 1.4uA, I think I should find a diode whose reverse current is lower than 0.2uA to reach the minimum cost.

Thanks.


texts: SCR which can conduct 230V AC at Zero gate voltage

texts:
As per the image, an operation for manual & Auto logic where manual can overwritten auto command and vice versa. The red circled area is an SCR(Silicon Controlled Rectifier). I'm looking for a SCR which can conduct at ZERO Gate Voltage(Vgt=0) i.e when the Mechanical switch is turned 'ON' the SCR turns 'ON' and it starts conducting 230V AC and when Gate Voltage is provided to the SCR,it turn 'OFF' the SCR and hence turns 'OFF' the load lamp.

I can't use a 'RELAY' or a 'TRANSISTOR' as the current flow in the circuit should be unidirectional.Also in case of 'RELAY' space constraint is an issue.

But either way if I can't find any SCR which conducts at 'Zero' Gate Voltage(Vgt) won't mind using transistor.

Any suggestion for an SCR which can conduct at 'ZERO' Gate voltage as mentioned in above explanation shown in below circuit.

EDIT

As soon as the mechanical switch is closed micro controller gets the signal through the opto-coupler that the 'Load Lamp' is operated from then mechanical switch also the SCR above the 'Load Lamp' starts conducting for 'Zero' Gate Voltage now if one wants to switch off 'Load Lamp' from remote location it can be done through micro controller which triggers Gate Voltage to SCR. Similarly if one wants to turn 'ON or OFF' the 'Load Lamp' from the remote Location it can be done by triggering SCR located on left.
 Opto-coupler connected after the 'Load Lamp' is for feedback from the 'Load Lamp' to the micro controller.

Hence for the logic mentioned above one need an SCR connected between the mechanical switch and 'Load lamp' which can be operated at 'Zero' gate voltage

An Opto Coupler which can operate for 230V AC directly.

Part No of both Opto Coupler which can operate at 230V AC and SCR which can conduct at 'Zero' Gate Voltage?


texts: Buck regulator load regulation voltage drop

texts:
I've built a switched buck regulator using a TPS40057, schematic below, I followed the instructions in the datasheet and used the TI provided spreadsheet to calculate the loop compensation network (which I have no understanding of, but the values for the components look sane).

The ripple is OK under load, about 50mVPP although there is quite a bit of switching noise at the output, about 150mVPP. I need it to handle 3A without getting too hot (about 30C above ambient would be ok). At 3A the inductor gets warm (maybe 45C) but not hot.

The mosfets don't really get hot either, they are Infineon BSC093N04LS which can apparently handle the current I need. Under load, the voltage drops from roughly where it's supposed to be (about 5.95V at 0.1A) to about 5.45V at 3A.

I initially suspected the feedback trace from VOUT to VFB but ruled that out by jumping a 0.5mm copper wire to it, which changed nothing.

I wondered if the inductor was too small (6A rated) so tried a larger one (7.1A rated) which changed the output a bit but didn't solve the problem.

I measured the voltage at the feedback and sure enough it is 0.7V at very light load and drops to about 0.62V under load. But as I mentioned, even with a thick wire connection it still behaves the same. There is very little noise on it, <5mV.

The frequency is set at 325KHz.

I'm really stumped, can anyone see anything obvious? Are the graphs characteristic of a common error?

This is the schematic

The top side of the PCB looks like this, the darker green section in the lower left is SGND, the other green areas are PGND. Purple is VIN and light blue is VOUT, the feedback trace runs along the bottom to the resistor divider, 6mil wide. T1 at the left is where PGND is tied to SGND. It's a 4 layer board with layer 2 mostly ground, layer 3 is VIN pass through to the other side of the board and layer 4 is mostly ground and VOUT passed back to the left side.

And here's two graphs, the blue is using the smaller 6A inductor and 120K / 16K resistors in the feedback divider (VREF 0.7 so 5.95V), and the orange is the larger inductor and resistors 82K / 11K (= ~5.92V) - I tried lower values in case 120K was too high, the datasheet example used 100K for the top resistor.

OK, I measured it wrong (at the wrong end of the cable, so there was a voltage drop due to the losses in the cable), this new graph has an added trace in green which is correctly measured. The actual drop starts between 0.6A and 1.1A, then tails off. I think the gradual linear drop after 1.1A is also measurement error but I can't get round it and it's not a concern. The big drop from 0.6 to 1.1A is the problem.


texts:
Eagle 9.2.2.standard software
Windows 10 64 bit

Somehow I broke the link between the .sch and .brd files. Now I get the error "Board and schematic are not consistent!...."

I spent a lot of time with the physical location of the components on the board and would like to be able to recover some of the board layers (e.g. layer 21).

I have created a new .brd file and removed all the wires, etc and saved. I created a new project, imported my schematic and imported the new .brd file but cant get the wiring information from the schematic to the new .brd file.

Any suggestions? (I have the standard paid version 9.2.2)


texts:
Super simple question here. Is it possible to use an if statement in a .param LTSpice directive? If so, what is the syntax? Shown below does not function.

Note that the .step function can not be used for my purposes, to the best of my knowledge, because I want to simulate a step response over time.


texts: How to a build a payphone controlled iPhone?

texts:
I'm trying to create a project for my kitchen that involves using the shell of an old payphone and a modern cell phone ( perhaps iPhone ) to actually make calls. Basically, I would like the user to be able to pick up the receiver, press one of the number buttons, and have the unit auto-dail one of nine pre-defined numbers. With the microphone and speaker in the payphone being functional.

As I try to conceptualize a way to build this, here is what I came up with. Use an external iPhone microphone and speaker and place them in the handset. Use an actual iPhone as the unit that makes the call since I don't have anologue service at my house.

The part I'm a little unclear on is, how do I use the payphone button pad to somehow trigger the iPhone to make a call to 1 of 9 numbers in memory, and how do I terminate the call once the user hangs the phone up.


texts: Norton Equivalent and current convention

texts: Consider that we are trying to find the Norton equivalent of a certain circuit . According to my understanding , while finding the short circuit current or the Norton current , we should point it downward across the Short circuit terminal. But if we find that the actual direction of the Norton current is upward , should we in this case also reverse the current source direction of the Norton equivalent circuit to point upward ?  If yes , then why ?


texts: Static sound when running amplifier and usb charger off same battery

texts:
I am running a 12VDC 2A Lepai amplifier off an 18V Li Ion power tool battery using a 1.5 maxA step down voltage regulator. All was working fine until attempting to add in a 12V to 5V 1000mA USB charger (the idea being the power tool battery could duelly power amplifier and charger for Ipod). Individually both the amplifier and USB function as intended, however when the Ipod is simultaneously charging and playing through the amplifier there is a strong static coming through the speakers.

I then switched to a 3A step down voltage regulator but the static remained the same.
How can this static noise be eliminated?


texts: Share circuits between different simulators

texts:
How do we share circuits between different simulators ?

Say, we have 3 simulation tools ; Proteus, multisim, and LTSpice ( or anything else). How do we share the circuits made in one of the simulation tools ?

Say I have a circuit in Proteus. Now I want to work with the same circuit in Multisim without having to build it again. Is it possible ? If so how ?

Thank you


texts: AGM Batteries: Comparison of Auto to Marine

texts:
Research (links go through to the actual product descriptions, for those who read specs):

Diehard AGM Auto Group 34 775 CCA: $153
Diehard AGM "Marine" Group 34 880 CCA: $250
West Marine house brand "Dual Purpose" Group 31 $310
Mastervolt (via West Marine) Group 31: $320

Assume (I know hazards therein) a generic recreational boat setup of starter bank and house bank. I'm thinking the "auto" AGM battery is fine for both banks. Agree?

Marinizing: It's a sealed system afterall. I don't see what marinizing would bring to a AGM battery, except a higher price. Or am I offbase, and there is a significant (commensurate with the price jump) difference between an auto AGM and a marine AGM?

Deep Cycle: What is this Dual Purpose label on the West Marine house brand? Wouldn't any AGM battery be good for both starting and house bank? I thought the deep cycle battery distinction was for lead-acid batteries and was irrelevant with AGM. True?

UPDATE I asked this Q in another forum, and got this very helpful reply:

  The only real difference between marine & auto is primarily the terminal. Threaded studs with lock nuts are routinely used in group 24-group 31 batteries. 4D, 8D & other commercial batteries tend to have posts and other custom terminals specific to the application. Autos tend to use the posts. The "Dual Purpose" label would be used to identify a battery that is not a true deep cycle, nor is it a high calcium content cranking battery. An AGM lends itself very well to being a true dual purpose as it has significantly higher cranking amps then a gel cell (in the same size or class). In addition you will get reserve capacity that is closer to a traditional wet cell deep cycle of the same size.


texts: Analog Switch cannot provide 0V output when OFF

texts:
I'm trying to simulate in LTSPICE the following simple circuit, and I cannot get 0V output when the analog switch is open.

Can anyone please explain why?


texts: Is power the rate of energy flowing in and out a capacitor?

texts: I was wondering if power is the rate which energy is stored in and released by a capacitor with a sinusoidal voltage source applied? I thought this was true, but my friend said false. ):


texts: How can I regulate brightness of a LED strip with a potentiometer

texts:
I have  a 12V, 5m long LED strip and an adapter (12V 1A). I want to control the brightness of the LED strip with a potentiometer, I found a simple circuit that involves only a pot and IRFZ44N transistor.( datasheet here ) It was working great, but it wasn't very bright.
When i connected the LED strip only to the adapter it was very bright but as I soldered the circuit it wasn't very bright. Also I measured that the output voltage dropped from 12V to about 9.6V.


texts: Can I make my cellphone a 3.5mm jack bluetooth transceiver?

texts:
I want to hear sound from my TV using my Beats Solo3 wireless headphones the problem is that the TV doesn't have a bluetooth transmitter (or any wireless connectivity) it has USB and 3.5mm headphone jack exits (among others).
I've tried to connect my cellphone and my TV using  3.5mm Male2Male jacks cable and BT connect my cellphone to the headphones, but I didn't hear no sound.
Can a cellphone receive audio signals with it's 3.5mm jack (essentially becoming headphones) using a 3rd party software or electronically that's impossible ?
Thank you


texts: Why are bulky SCR power controllers used when the same can be achieved with a relay?

texts:
This is kinda noob question. I recently got an SCR Power controller (WATLOW DIN-a-mite DB20-24CO-0000 Style B). This is the first time I actually got to test an SCR controller for myself. The input trigger is 4VDC to 32VDC, which I powered with a fully charged Li-ion at 4.1V . AC input:115VAC from 12V inverter and out is a 115V digital panel meter (I wanted to try first with a low powered device) though its meant for a heater.

As per the specs the SCR is rated for 25Amps. Similar or even higher rated current relays are available and much smaller in size.

So,is there any specific reason for using an SCR power controller over a higher current relay/contactor? Also, is an SCF power controller same as an Solid State Relay?


texts: How does this strobe light circuit work?

texts:
I took apart the top of my strobe light and couldn’t exactly understand parts of the circuit. Could someone explain how it works?

When the strobe is plugged in, it immediately starts flashing and doesn’t stop until unplugged. The three wires are attached to a knob on the outside, that increases the flash speed as it’s turned clockwise.


texts: using solenoid magnetic field to press a button

texts:
I'm looking for a simple way to make Arduino press a spray button. I don't care which button to use, it can be either this type:

or the following:

I know there are ways to solve this problem using a servo, but I'm trying to think about a simpler way that won't demand an engine (or will demand one but will be simple to implement).
I thought of the following - Perhaps I could place a weight on the cap of the spray, inside a solenoid and connect the solenoid with electric wires to the Arduino. I could pass current in the solenoid and create a magnetic field which will press the weight which in return will press the spray cap. The Arduino will control when to pass the current and when to halt. A sketch of the system is shown in the drawing below:

I'm not sure if it's possible (If I can get enough force to press the cap without a huge solenoid or extremely high currents which I can't produce at home) so I'd like to hear your opinion.
I thought it will resemble the principles of operation of a magnetic train such as this one.
The math:
I can use the following formula to calculate the magnetic field within the solenoid: $$ B = \mu nl $$
where $$ n = N/L $$ It probably won't be the exact magnitude of the magnetic field since the formula is ideal, but I guess that if I take a solenoid which produces bigger magnetic field (in magnitude) it will compensate for the inaccuracy of my ideal state calculations.
now I can use this formula to calculate the force which is applied on the weight when it is pressed and reaches a steady state: $$ F_{gravity} + F_{solenoid} $$ when $$ F_{gravity} = mg $$ and $$ F_{solenoid} = IBl $$ where I is the current which flows through the solenoid and I determine it, B is the mangnetic field inside the solenoid which I already clculated (depends on the type of solenoid I will choose to work with) and l is the solenoids length. The forces are shown in the force diagram below:

I can calculate the desired force for the button pressing using something like this solution.
From the former I can calculate choose the solenoid type and the weight which is needed.
My questions are:

What do you think about the solution? Will it be easy to execute? Is it an overkill? what other idea do you have?

I'm not sure which solenoid to choose - when I looked at some solenoids for sale, they never mention the n factor (how many turns per unit length) or the permeability factor mu.

I'm not sure how to calculate the drag of the air which occurs at the beginning of the movement and may diminish the net force I get which the weight "feels". Perhaps it can be neglected since it'll operate for very short period of time (when the button will be pressed it'll stay like this in the exact location without any velocity, so the drag will be 0 by this equation)?

Thank you.


texts:
I'm building a eurorack synth module, and I'm about to do the final tests on the design to make sure that the module cannot be destroyed (electronically, using what's available in the rack, so protection against sledgehammers etc is not relevant here) by the user.

Since the system power rails are \$\pm12\mathrm{V}\$, I've taken as my guideline that all front panel inputs and outputs should be able to withstand an indefinite short to either power rail, or anything in between. I believe, but have not yet tested, that my current design should withstand any of the signal voltages shorting to the power rails. All connections are on TS or TRS minijacks.

To test this, I've built a "module" which has outputs with power rails connected directly to the signal pin, i.e. I can get either the \$12\mathrm{V}\$ or \$-12\mathrm{V}\$ rail connected to a miniplug lead, which I'd then stick in to the various inputs to make sure nothing gets destroyed.

However, I realized there's a snag: since the TS (and TRS) -jacks momentarily short the signal pin to ground when inserting, this means that when sticking my test lead in the the jack, I will be shorting the system power rail to ground. I'd imagine this can't be good for my module, which has sensitive parts such as a microcontroller. Also, I'm not sure if the other modules or the PSU can withstand the short.

Question:
I see a few ways forward:

I simply plug the test lead to each jack when powered off, and then see that the system survives powering on.
This of course includes the implicit assumption that the user also does not have actual access to the power rails (which no sane module should provide, but people do DIY etc etc).
I conclude that (unless I make all inputs differential) I cannot protect against the power rails themselves, since the jacks always provide direct connection to the system ground. Therefore I relax my requirements and decide on some finite minimum impedance which I'll use to test the input protection. If so, how do I choose a reasonable impedance?
I stick to my guns, and connect also the ground pins of the jacks via some finite size resistors that will survive the full \$\pm12\mathrm{V}\$. However, this will degrade my signal quality and/or require full differential input stages. I haven't seen any other eurorack module go this far.

Which of these approaches, if any, sound reasonable? Maybe both 1. and 2.?


texts: Calculating the time for current reducing to zero from a charged inductor in a series LC circuit

texts:
I'm wondering how you calculate the time taken for the current in a charged inductor to reduce to zero with the only current path being through a capacitor. I'm looking at this from the perspective of an unloaded boost converter where at the end of the switching phase, the inductor is charged up to a certain current with the only current path being through a diode (neglected in my question) and into a capacitor (without an extra load).

Obviously the capacitor voltage will increase as the current through it is positive (the integral of the current will be non zero and positive) but how do I calculate the time for current to hit zero given a peak current in an inductor and the value of both inductance and capacitance, ignoring circuit losses?


texts: Voltage Drop on I/O Pin of AVR Tiny Micro-controller

texts:
I am working on a project based on AVR Tiny85 Microcontroller interfacing with an RGB LED. In order to test the Tiny Board I/O pins I have written a sample test code to toggle I/O.

Test Code

#include <avr/io.h>
#include <util/delay.h>

// This program will turn the LEDs on for 100ms,
// then off for 200ms, endlessly.

int main(void)
{
  // Set Port B pins for 3 and 4 as outputs
  // PORTB bit 3 = physical pin #2 on the ATTINY85
  // PORTB bit 4 = physical pin #3 on the ATTINY85

  DDRB = 0x18;  // In binary this is 0001 1000 (note that is bit 3 and 4)
  // AVR-GCC also would accept 0b00011000, by the way.

 // Set up a forever loop
 for ( ; 1==1 ; )  // loop while 1 equals 1
  {
    // Set Port B pins for 3 and 4 as HIGH (i.e. turn the LEDs on)
    PORTB = 0x18;   // If we wanted only PB4 on, it'd be PORTB=0x10

    // Use a function (defined in delay.h) to pause 500 milliseconds
    _delay_ms(500);

    // Set PORTB to be all LOWs (i.e. turn the LEDs off)
    PORTB = 0x00;

    // Delay for a 500ms
    _delay_ms(500);
  }

return 1;
}

Issues:

When I am driving the I/O pin as 1 or 0 the output should reach the Vcc or GND respectively. But when I connect the LED to GND and one of these I/Os (Pin 3 and 4), the pin drives the LED up to VCC, but for the off condition, the I/O still has some voltage relative to GND. In this case, LED is not completely turned off.

What could be the possible reason for this issue?
Please advice

Thank you

Scope Output:

I have changed the delay time to 500 msec to get a visual indication of ON and OFF state

Schamatic:


texts: I have four AC electromagnets that I want to drive 90 degrees out of phase with each other. I want this device to work on regular wall-socket power. I could drive two electromagnets 180 degrees out of phase by swapping the leads on one of them - but how can I get the other two to be 90 degrees out of phase from them? I have thought about using a capacitor to tune them, but I am not sure if that is practical.


texts:
Above is a mic jack going into a pre-amp. As you see the tip of the jack and the ring of the jack are both connected to the plus side of the electret microphone.

And when plugged in, it seems like the tip of the jack is coupled to the blocking cap of the pre-amp. And the ring of the jack establishes the connection for supplying biasing voltage for the mic through 2k resistor.

So as we can see the electret microphone's positive terminal needs two junctions to be coupled to two different points at the preamp side. There is two segments here: the tip and the ring.

But how about the connections in the case for a TRRS jack and a preamplifier? There is only one segment spared for the mic in a TRRS jack. How does biasing and AC coupling works in that case? I couldn't find any illustration or circuitry similar to the one I provided above.


texts: Using a mobile phone power bank in place of AA batteries

texts: I was looking for rechargeable batteries to power a device I was making, however the high costs of chargers and even the batteries themselves made me want to consider other alternatives. I came across a few mobile phone portable chargers which provide enormous amounts of energy (15000+ mAh) and charge very fast despite costing less than £15. I was wondering whether these power banks would be of any use for powering an arduino and a few motors instead of rechargeable batteries. Are there any (operational) differences (apart from the cell chemistry and voltage) in the two?


texts: Looking for a 24vac switch from 3v inputs

texts:
I'm really new to building electronics, so please forgive my ignorance.

I'm looking to be able to supply 24vac (~.5A) to one of 16 outputs using 4 3.3v, 50mA inputs.
(Edited)  The 4 3.3v inputs are from a microcontroller, that I want to use to select one of the 16 outputs (traditional multiplexer problem).  I was hoping that there is some sort of multiplexer that I could hook up down stream from a relay in order to supply the power with few components.  So I'm looking to find/build a multiplexer circuit that takes 4 on/off low power inputs and the "data" line is 24vac.  My alternative is using a multiplexer and relays/TRIACs.

I've seen posts where people use TRIACs/relays directly for this, or use a multiplexer to run a number of TRIACs and relays.  I also saw someone talking about using MOSFETs...  I'd rather use less components if possible.

EDIT:

After doing some more research, I think I need a 1:16 analog switch.  I think I need something with an optocoupler or something that will protect my circuit board from the 24vac that will be switched.  I looked at the DG406DJZ and
NTE4051B... but I really can't tell if they meet my needs.

EDIT:

Well, I ended up buying this: DG406DJ-E3 : http://html.alldatasheet.com/html-pdf/249648/VISHAY/DG406DJ-E3/219/1/DG406DJ-E3.html.  The 5 data lines will be 3.3V, 50mA.  The analog connect will be 24vac at .5A or so, to be switched to one of 16 outputs.  I think this is an isolated circuit so I shouldn't have to worry about ruining my board in cases of failure.  Is this really going to work like I think it will?  Will my microcontroller be protected with this setup?  Is there something else I should be considering?  This seems like a simple design based on some of the others I have seen.


texts:
I have a 12 pin PMOD interface on my Nandland Goboard FPGA and I would like to turn on an external LED with it.

I can do it on my using pins 5 and 6 which are GND and VCC but I can't figure out how to turn it on using one of the pins controlled by the FPGA. Do I hook the LED to ground and one of the output pins set to logic 1?

Or is it supposed to be output pin logic 1 and VCC? Or some combination?


texts: Transmission of information in terms of information theory and protocol

texts:
I am a student studying wireless communications.

First of all, I learned that

  In AWGN channel, i.e., y=x+n with n~N(0,sigma^2), the amount of information that can be transferred (i.e., capacity) is maximized when x follows Gaussian distribution.

Actually, from a point of view of Mathematics and definitions of Shannon capacity (and etc.), the above statement can be proved. However, I do not understand what "\$x\$ follows Gaussian distribution" means.

For example, we can say 1) if \$A\cos(2\pi f_c t + \phi)\$ is transmitted, the receiver can make a decision that information (corresponding to \$A\$) is  transferred, on the other hand 2) if \$x=0.5A\cos(2\pi f_c t + \phi)\$ is transmitted, the receiver can make a decision that information (corresponding to \$0.5A\$) is transferred.

That is, I mean that the information (symbol) to be transmitted is deterministic at the transmitter, which is not a random variable (RV).

To sum up, the information to be transmitted is deterministic, which means that the waveform (transmit signal) is also determined according to which information (symbol) will be transferred. Although \$x\$ is deterministic depending on the transmit information, why do people consider \$x\$ as a random variable when analyzing the capacity?


texts: Can I add flyback diodes to my car window motors?

texts:
I have an older car with a known issue with the window switches: they carry all the motor current, and after a while the contacts suffer carbon buildup presumably from flyback arcing. Commonly, owners will add relays (one for each direction of each window) to spare the switches, but wouldn't it be simpler to add flyback diodes?

If so – since the motors can be driven in either direction, so a regular diode can't be added at the motor – is it better to use two regular diodes at the switch (addressing the flyback arcing where it's occurring), or two Zener diodes (or similar?) at the motor? And in each case, what would be an appropriate diode choice? (The circuit is ~13V, protected by a 30A fuse, and the resistance measured at the switch connector is 1.8Ω for driver side and 2.4Ω for passenger side, for a calculated 7.2A and 5.4A respectively.)

simulate this circuit – Schematic created using CircuitLab

I have found references to adding flyback diodes in this application, but only to the switching coil of the added relays (which I know some relays even have built in), not the actual window motors.

Thanks in advance for any and all answers!


texts: Shorting a remote control push button with GPIO and a transistor potential conflict?

texts:
I'm trying to control my garage door remote with a GPIO pin from my Raspberry Pi. The following is my schematic diagram of what I am thinking of using:

Would there be a potential problem if I were to hold down the push button and activate the transistor and allow current to flow through at the same time?

*If there is no conflict could you explain why that would be the case?


texts: Get temperature via ADC of microcontroller

texts:
I want to manipulate the physical value of temperature. Here is the characteristic of this µC:

Resolution: 12 bits
Supply: 5 V
Min Mesure: -45
Max Mesure: 75
Min ADC IN: 0.4
Max ADC IN: 4.8

Here is the formula which i used:

 Value = (Digital value * Max ADC IN) / 4095.0;

I used the rule of three.

Max ADC IN (4.8) ===> 4095 (depends on the resolution (12 bits))
Value            ===> Digital value from ADC

If I use this formula, it is sufficient to read the physical value?

I don't have the datasheet of the sensor, the microcontroller is 68HCs12.


texts: Diode doesn't work in a [attempt of] power supply simulation with QUCS

texts:
As a simulation exercise, I am trying to work out a power supply and actually I am at the point provided in the figure below

There is a message of error which I don't understand, but I realized it happens only with the presence of the diode in the circuit.
In fact, in order to understand this, I did two other attempts: a separate circuit on the right with a diode which works fine and a short circuit around the diode itself which is reported in the next figure

and still it works fine.
So the question is:
which is the problem with adding that diode in the circuit?


texts:
I'm making progress on building a portable light for my kayak.
It will use 3 of following chips: 50W, 12V chips.
The battery will have to be portable so I'm planning to wire them in parallel.  I calculate 11.25 Ah needed so thinking to get the battery between:

12V, 14Ah
12V, 18Ah
12V, 35Ah

It is just going to depend on weight.
Each light will be in an aluminum housing and only turned on under water.
I've read about the troubles with overworking one LED when in parallel.  Can I put a resistor before each of the 3 lights and if so, can someone direct me there?
Also, can I add switches to each light to conserve battery without overworking? That is, only turn on the lights I need?


texts: Find the phase angle of the of the sinusoidal input that will make the natural response zero

texts:
Say we have a simple rl circuit with R = 0.5 ohms, L = 0.1 H and the sinusoidal input of : $$ V_s = 13800√2sin(120πt+β)$$
Then we were tasked to:

I know the form of the solution of i(t) would look something like:
$$ i(t) = natural + forced $$
$$ i(t) = I_ne^{-t/tau} + I_msin(ωt + β) $$
So the natural response would be the decaying exponential right? But i'm not sure how would it become zero. I was thinking of looking for beta such that the whole term inside of sin would go to zero, but then that would also make the forced response zero. What am i missing?


texts:
I'm trying to use a Xilinx xc9536xl to decode a current modulated signal but am having an issue with the pull ups on the pin. From what I've gathered the CPLD has pull-ups on the order of 10s of k ohms and they cannot be turned off which I did not anticipate.

The problem is that my circuit uses 500k resistor to generate the desired voltage level which is no where near strong enough to pull the CPLD input back down.

I have a PMOS currently available on the design that I could use and I've attached a proposed modification (in red) that I tried to implement unsuccessfully. Basically I'm trying to translate the 6V pulses on the output of the opamp into clean, 3V pulses on the input of the CPLD. Does anyone have any other suggestions to solve this issue?

Edit:
In order to solve the problem initially, I fed the output of the opamp directly to the CPLD, however this swings from 0-6V which while tolerable isn't ideal, and it is not a very clean pulse.

After implementing my suggested changes, the output of the opamp only swings goes as high as 2V on most pulses (3V on some) and I'm missing pulses on the CPLD input.

Edit #2: Modified the circuit to remove opamp feedback and now I'm getting nice clean 6V pulses on G1 (0~6V) and the inverse on G2 (0~3V). The issue is that without the feedback loop I'm seeing some weird behaviour at the end of the pulses I wasn't seeing before.

Further, if the feedback loop is not required as I've found, would it make more sense to connect D1 to 3V3, replace the 500k with a strong pull down and drive the CPLD off S1? Should I put a series resistor on G1?

Edit #3: Modified the circuit to use NMOS to drive CPLD directly. Without the feedback circuit I was able to replace the weak pulldown with a strong one and eliminate the need for the PMOS or to invert CPLD input. The stray pulses at the end of the data still exist without the feedback circuit. Any idea what's causing it?

Edit #4: Stray pulses are still there after adding hysteresis, but the pulses are much cleaner. I think the driver is actually generating these pulses unnecessarily.


texts: Formula calculation and printing negative value.

texts:
I am successfully reading external ADC value using ATmega32-A.

 Unsigned int adc;
 adc = AD7798_16(0x58, 0xFFFF);                           // read register
       printf("ADC value is %d\r\n", adc);

I am getting ADC value as decimal number range between "0 to 65535". I want to convert it into analog voltage using the fallowing formula.

  Code = 2N – 1 × [(AIN × GAIN / VREF) + 1]

  where:
  AIN is the analog input voltage.
  N = 16 for the AD7798, and N = 24 for the AD7799.

I have simplified the formula and calculating

// formula to caluculate analog voltage from digital output :Code = 2N – 1× [(AIN × GAIN/VREF) + 1]
// GAIN / VREF = 1 / 2.5 => 0.4
// 0.4 Ain = ((adc / 32768) - 1)

float Ain;

Ain=(((((float) adc) / 32768) - 1) / 0.416);

printf("value:%.2f [v]\r\n", Ain);

The above formula returns always negative value. I want to print that negative value. I have tried as above but its not working. How  to print Ain value? here adc is unsigned value so I am converting into float.

I have tried like this also

Ain = (((adc / 32768.0) - 1) / 0.416);

printf("value:%.2f [v]\r\n", Ain);

but I am not able to print that value.


texts:
I am using this SSR connected to an Arduino.

I am running a very simple code similar to this one: (like the Blink example)

loop(){
   digitalWrite(1, HIGH);
   delay(1000);
   digitalWrite(1, LOW);
   delay(1000);
}

When I start with the Arduino pin LOW the SSR is off.
But after setting the Arduino pin to high my problem is: the SSR stays always on.
Even if I set the Arduino pin to LOW the SSR won't stop letting the current pass through.
What do I have to do set the SSR to off again? (Or do you even think the SSR is broken?)

Schematic http://solutionit.ch/schematic.png


texts: How can I find an AVR chip with built-in RF transceiver?

texts:
I'm going to build a couple of small devices that communicate wirelessly. To simplify construction, I've decided to look for a chip (preferrably on a breakout board) that combines a programmable microcontroller with an RF transceiver module.

I've found the nRF24LU1+, but I'd prefer an AVR microcontroller since I've used those before and know how to program them. How can I search for such chips/board? I've tried search terms such as "avr rf module" and "combined avr rf", but have only managed to find RF modules.


texts:
I have stumbled upon a soft power switch with low part count on EEVBlog, which I found very interesting for my hobbyist projects: https://www.youtube.com/watch?v=Foc9R0dC2iI

Since it uses a PMOS and I only had a NMOS to try the circuit out, I have mirrored the whole circuit:

Initially there was no R5 but I found the circuit to be unstable (it sometimes switched to on without pushing the button), so I added R5.

The circuit works now, but the expected oscillation with continually pressed button is very "short-pulsed", i.e. it stays off pretty long (1 s) which is okay, but there is only a short on-time (0.1 s). Since keeping the button pressed is a possible usage scenario from the POV of the user, I would like to have a longer on-time. But this would require an overly big capacitor or an enormous R4.

Honestly I don't understand why it produces an asymmetrical wave form, because discharge of C1 goes over R4+R3+R5 (and RLOAD in parallel if it is there) which is only marginally larger than R4 for charging.

Is there a way to "symmetrize" this oscillator so that on- and off-time become the same?

PS: in response to your question, Jonk, some more information: ideally I would like to have a toggle-flipflop with as few parts as possible, and with zero power consumption in the off-state (aside from some leakage current of a mosfet). My impression was that the solution from EEVBlog was as close as it could get, but with the drawback of oscillating behavior instead of bistable.

When I tested it, I noticed that the duty cycle of the oscillation feels pretty much like a pathological user experience because it is like 10%. Suppose I miss the first on-period, then it turns off for a longer time and then turns on very briefly, so after I have missed it, it is practically impossible to turn it back on by just keeping the button pressed. Instead I will have to wait a certain period until the the capacitor has discharged again, until I try again to turn the thing on.

This is what I wanted to fix by "symmetrizing" the duty-cycle. If I already have to accept oscillating behavior with a short period, then at least it should allow to turn it on after missing the first period by just keeping the button pressed.


texts: I want to design a circuit to to drive an electromagnet solenoid, over a long piece of cable. The cable could be damaged (short-circuit or open-circuit), so the circuit must detect these conditions. Driving the circuit can be seen later, I just want to know how can we detect these conditions? I would appreciate anyone who could help me with this


texts: Current limitation of a power supply by using transistors

texts:
DALI standard limits the maximum current as 250mA. I have a 12V source that is capable of supplying more current.  I implemented from one of Motorola reference design the below schematics that limits the 12V source to 250mA.

DALI has 2 wires which are short circuited. so TX and RX can be thought as a loop. when 250mA is driven by R13 (2.7), it turns on Q3 which switches off the Q2 transistor, so that the power supply. It usually works fine but I experience that Q3 transistor burns. When Q3 burns it makes the all circuit to be useless. It happens rarely but it is till not a reliable solution. As it happens rarely I don't know how I can debug it. I assume a spike may cause the problem.

How can I improve the circuit so that Q3 would not burn and it would still limits the current supply to 250mA? Or would there be a better solution instead of the below circuit?


texts:
I've been working with PIC16F877. Can someone please explain how to configure its pins to be analog or digital?

I saw somewhere that we need to configure ADCON1, but don't really understand how that works.


texts: Can LM35 temperature sensor be used to measure temperatures in bone in an in vitro setting? are they comparable to K type thermocouples?

texts:
I belong to the medical field. I have zero knowledge about electronics.
For my thesis, where I will be measuring temperature within the bone during drilling, I am required to use a temperature sensor of diameter not more than 0.8-1mm with decent accuracy (0.1°), and low margin of error.
From what I read, a K-type thermocouple seems like the choice of sensor. But I was advised to use a LM35 sensor with Arduino Nano.
Please throw some light on how to select, comparison, and the advantages and disadvantages of each.


texts: What kind of wave should i feed the input of sample and hold,which is in the sar adc

texts:
There is sample and hold in the sar adc,but i am not sure that i should feed a ramp wave or sine wave to the sample and hold?

Are there any relations to sar adc output and sample and hold input wave?


texts:
Why a separate power supply is needed for L293D while interfacing with microcontroller.

I have searched it but didn't got any proper/relevant answer.


texts: How much Amperage can pass through a BMS and DC stepup boost converter?

texts:
In my Mini UPS project for my router, I made a little circuit by using a 18650 li-ion battery charger module, a 3.7v /2800mAH li-ion battery, and the DC step-up boost converter. My router requires 9v/0.6A current. So once I connected this UPS for my router and switch it on and

simulate this circuit – Schematic created using CircuitLab
It seems quickly light up and disappear all lights in the router (Not working)
What i went wrong here? Have BMS or step-up converter a certain output power limit? Are my BMS, step-up converter, and or the battery not enough power to driving my router?


texts: Where to cut my power supply for Arduino?

texts:
I have no vocabulary for this, so forgive my clumsiness in explaining.

I need to hook up a power supply to use with solenoids and an Arduino, but I'm not sure where to cut it. Just before the power plug there is a thing (not sure of the name, bottom right of picture in the link below), do I need to cut before or after it?

Here is a link to the picture, I'm a new user so I can't embed it.

If you know the name of the mystery thing, I'd also love to know.