texts: Open circuit fault detection using an Arduino

texts:
I was able to implement short circuit fault detection of under ground cables and I was also able to add a GSM module(SIM900D) with it.
I'm trying to further enhance my project by detecting open circuit fault detection.
It seems a bit difficult as I can't extract any useful information from and open terminal (V=0 and I=0 because of the open terminal.)
I tried searching online and found 2 relevant papers that use an RC meter to count the time constant to find the open circuit location.
The circuit diagram and code are given in the link of pdf. The links are given below:
OPENCIRCUIT & SHORT CIRCUIT CABLE FAULT DETECTION USING ARDUINO
OPEN CIRCUITED UNDERGROUND CABLE DISTANCE LOCATOR
Here is the link to the RC meter.
The problem is that when I generate an open circuit across the charging resistor and change its resistance both the time constant and capacitance change while keeping the resistor constant so it's not really useful for open circuit fault detection.
Can anyone tell me if I'm doing something wrong or how I can implement this differently to get an accurate result?
Here is the pic of my simulation:


texts:
I want to know if the following is possible. I need to log the interval between drips at a fieldwork site in a cave without physically interacting with the drip (ie the drip can't strike any surface). I need to do this with the minimum possible current draw since I need to power this rig with a battery/batteries for 6 months between battery changes.

I see that there are IR beam drip sensors out there, but these typically drain 30-50 mA which would drain my battery (6V lantern batteries) within weeks at best. I was wondering if there might be a lower-power way of doing this. One thought that sprung to mind was to try to use the transient change in capacitance as a drip fell through capacitor plates, but I'm not sure how to start, or how to data-log this.

Has anyone heard of something like this?


texts: Power supply switching - Ground connection

texts:
I am designing a system that has 2 power inputs and has to be working as long as these power supplies are fine. I mean, the system starts working with power supply #1 but if it fails, switches to power supply #2.

I've read some threads and noticed of LTC4417 CI, that does exactly what I want.

The circuits I've found in many threads (as done too in eval board DC1717A) suggests to connect all grounds lines together (http://cds.linear.com/docs/en/demo-board-manual/dc1717af.pdf page 6).

Knowing that every power supply has a ground reference (in essence, a ground line has an electric potential lower to positive terminal), is there any risk connecting all ground terminals together?

Do I have to put any kind of filter between this physical lines?

Thanks in advance.

PD: as an example of a circuit that does this function: Switching between power supplies - USB dominant.


texts: Common-Source Stage with Diode-Connected Load

texts:
I have a question about the small-signal gain in a common-source stage with diode connected load.

I understand there are multiple equations for gm and the one you use depends on what relationship you are looking to investigate
I’m finding it hard to figure out which one to use.
As you can see from above, I get a different small-signal gain depending on what equation I use. Why?
Are they the same equation since the overdrive of M2 is completely self generated depending on how much current and overdrive M1 has?
Derivation of small-signal gain:


texts: How to distinguish PNP and NPN transistors?

texts: I need to know how to distinguish between an NPN transistor and a PNP transistor. If I pluck any transistor from a radio, how can I know its nature using a digital multimeter?


texts:
I've been programming microcontrollers for about 5 years now.  In my current MCU development workflow, I use emacs to edit my firmware, I compile with arm-none-eabi-gcc, and I flash code with a segger j-link tool, all on Linux.

I love this arrangement because I can do hours of work without touching my mouse, and I don't need to go through a verbose and sloppy GUI interface just to add compiler flags (I'm looking at you, Microchip).  Instead, I can just edit the makefile right there in my emacs window.

However, there is a very large FPGA project in my near future, and while I love designing hardware in verilog, I'm absolutely not looking forward with mucking with utter rubbish like Microsemi's Libero or Altera's Quartus (both of which I had the misfortune of using for very small projects).

Does anyone know which manufacturer's chip I will have to spring for if I want to compile my verilog, configure chip options, and generate the programming files ALL at the command line?  Has anyone even had success with doing something like this?


texts: How Close do Batteries Need to Be in Voltage for a Parallel Connection?

texts:
Ok, so wiring batteries in parallel of different voltage is bad because the batteries try to equalize voltage with high currents essentially by discharging. The thing is, even among batteries of the same type, the voltage is slightly different. How far apart do the voltages have to be that I should consider not paralleling them?

So, an example:
I have 3 lead acid batteries (fully charged) that are from the same place, same make, model, and voltage (kind of, they're supposed to be 12V each). They have: 12.75V, 12.78V, and 12.85V. This is clearly a range of voltages, but does the .03 drop from one or the .1 drop in the most extreme case matter much?


texts: Why is Vt usually 26 mV in the diode formula?

texts:
For the diode formula:
$$I_D = I_S(e^{V_D/V_T} - 1)$$
(Where \$I_D\$ is the current of the diode)

Why is \$V_T\$ approximately always 26 mV in a lot of problems?

I can't find the part of the book that says this. It says \$V_T = {kT \over q}\$ but how is that always 26 mV?


texts:
I am working on how to get a strip of 60 leds to generate a pattern or how to get at least a running light with 8 on leds. So I have two questions
a) Can they it be done without the help of Arduino or a Microprocessor, if so how?
b) If it cannot be done, can some one help me with the microprocessors.

Thank you


texts: I have found the Rth=10 ohms, However i can't find the thevenin's voltage(between a &b)

texts:
*I converted the wye network into a delta and found the equivalent resistances in parallel and series and got it to be 10 ohms. However i am stuck at trying to find Vth. I tried applying mesh analysis and found the two mesh currents(source conversion to the center branch was done to obtain a single branch of 50V in series with 10 ohms)
Please do guide me on how to solve this problem.*
[]


texts:
Noob question inbound:

I'm getting into PIC programming, and I'm using a kit to build a microcontroller setup on a breadboard.  Following the instructions here:

http://www.bypic.co.uk/index.php/Part_2_Serial_connection_and_construction

The images below are of the schematic for the circuit, and a photo of an actual wired breadboard.  I want to understand how the schematic relates to the breadboard photo before I start wiring my own.  I think it's making sense to me with one exception:

How is the 3v3 current being applied to pin 28?

I can see how power is being routed to the right rail, and the bridge to pin 13.  The ground connections make sense.  However, I cannot for the life of me see how power is being applied to pin 28.  Am I missing something, or is there a missing wire in the breadboard photo?


texts: How to predict the magnitude of output voltage in a practical differentiator?

texts:
I designed the following differentiator circuit in LT Spice

and the output waveform was as following:

Now my question is how do I predict the magnitude of output theoretically?
The best I have been able to do so far is look at Wikipedia's page on Differentiator and see the frequency response to figure out gain.
However, the calculations do not seem to match.
The first pole \$f_1=\dfrac 1{2\pi R_1C}\$ comes out to be \$\approx 16kHz\$, so some crude calculations suggest that at \$f=1kHz(\approx 1.6kHz)\$, \$ V_{out} \approx \dfrac{V_{in}}{10}\$.
but this is not the case.
So what am I doing wrong? and is there a better way to solve this?


texts: Converting 12-14 car battery voltage to 9v

texts:
I am trying to install a small dehumidifier in the back of my car to help with defogging the back half of my vehicle.

The dehumidifier operates off of 9V at roughly 3 Amps.

I tried using a LM2596 but the IC ended up overheating. I have not tried and put a heatsink on it yet since I don't have one at the moment.

It seems that the dehumidifier operates ok at nearly 12 Volts but since a car battery can get up to 14 Volts, I'm scared to push the limit anymore.

Is there an easier and/or possibly more power efficient way of doing this?


texts:
I will start out by saying that I'm an electronics hobbyist and I'm currently in the process of laying out my first 4 layer board in eagle. Now all of the PCB manufacturers I've looked at either don't support or charge a lot for blind vias.

In eagle I get several options for vias as show in this image.

Now do I just want to select 1-16 and rout on the required layers keeping other traces away, or do I select 1-2 for routing from layer 1-2, keeping in mind that I can't have blind vias.


texts: Can leakage current to ground generate static electricity?

texts:
I'm having a weird issue at my workplace where some industrial equipment is present.

Almost every time I leave my laptop (with grounded aluminum body) for a while and come back I will get a quite nasty static discharge from it.

Even if have touched metallic door handle seconds before, which I think would eliminate charge on my body.

So the question is: Can a ground leakage in other areas of the building generate a static charge on grounded metallic surfaces like my laptop?

Provided of course that they are powered by the same line.


texts: FPGA/VHDL Design guidance: intermittent inputs

texts:
I have an algorithm:

y[n] = x[n] * sum(x[0:31])

x is in the input stream, y is the output stream, both one sample per clock cycle. One condition is that the input is not contiguous, there is a valid flag that indicates that when the input is valid. The entire packet is contained in x[0:255], and generally we only get a single, infrequent packet. I'm trying to figure out what the correct logic structures are for implementing this seamlessly.

First, I thought I would just use a shift register on the input, shifting on input valid. That way I can "stall" the input flow until I have 32 sample summation. The problem I found with this was that after I received the 256 input valid flags, I still had 32 samples stuck in my shift register and no extra valid flags coming in to shift them out.

The next idea I had was to use a FIFO. The FIFO read enable line would be controlled by a flag that indicates that the summation answer is "ready", and that the input FIFO is not empty.

Am I overthinking this? Is there a simple solution for this?


texts: Is this the correct way to AND two signals?

texts:
ARCHITECTURE
    SIGNAL in_adc_1 : unsigned(0 DOWNTO 0)  := (OTHERS => '0');
    SIGNAL in_adc_2 : unsigned(0 DOWNTO 0)  := (OTHERS => '0');

    BEGIN PROCESS -- counter_4_bit
        var count : in std_logic_vector(3 downto 0);
        IF (in_adc_1 = '1' and in_adc_2 ='1') THEN
            var_AddVoltage_ch16 <=  count + 1;
        END IF;
    END PROCESS;
END ARCHITECTURE rtl;


texts:
How is it a 12 volt 40 amp wire in a car has to be approximately 16mm thick but a drone can use 3.5mm thick cable for 12 volt 120 amps.

What is the difference? They both have the same amount of power? How can a esc pull 120 amps from a battery but use ridiculously thin wire?


texts: Can anyone please tell me that how does a 4T SRAM works (4 MOS transistors+ 2 poly resistor)? How does the internal node pulls to a high value? Is it still static or dynamic?


texts:
I'm new to Bluetooth technology and I'm trying to find something capable of sniffing Bluetooth 2.1 + EDR data. I see a lot of BLE/4.0 related devices.

So far the closest things I've found were:

PAN1315
FTS4BT

Has anyone tried sniffing BT 2.1+EDR packets before? If so, what solutions were used? Has anyone tried the above modules and can provide some feedback?


texts: Streaming camera solutions for RaspberryPi MCU

texts:
I'm trying to get a Raspberry Pi MCU to stream an A/V feed over the internet to a web server where I'll have some homegrown software capturing each frame and doing analysis with it.

My general strategy here is:

Get a camera and microphone sending audio and video signal to one of the Pi's onboard USB ports
If my choice of technology is correct, the Pi (which would be running GNU/Debian linux) will have the right drivers to ingest the streaming frames and send them off to a tool that would then be able to forward them on to a WiFi or Ethernet adapter
The adapter sends the frames on their way over TCP/IP and then I have to figure out how to handle them server-side

So as far as getting the frames to the MCU, there's two main issues here: (a) the choice of camera and microphone, and (b) the drivers for connecting the cam/mic to the Pi's USB port. There's also the issue of A/V encoding as well as synchronizing the video and the audio feeds together.

I'm beginning to think that a "web cam" might be my best bet, because most web cams have built in microphones, automatically synchronize the audio and video feeds together, encode the A/V frames, and come with drivers - so on the outset they appear to be perfect solutions. But I'm open to anything that gets the job done efficiently and in keeping with best practices.

Here's the kicker - I might (doubtful) want to try and sell this device, so I can't simply take some Logitech web cam and use it due to obvious licensing issues. So that's a huge constraint.

I should also mention that price is sort of a factor as well - I'm comfortable in the $20 - $40 USD range, but over $50 and I'll start to cringe.

The best web cam I've been able to find is from Jameco.

But I am wondering how hardcore, real electronic wizards would attack this problem given the constraints I've mentioned. I'm a software developer so I'm out of my element here in the electronics arena.

Unless I'm missing something, then unless I find a camera that has integrated/synchronized audio, performs A/V encoding for me, and has device drivers all ready to go, then I'll have to do all this myself. If that's the case, I'd be interested in hearing what some solutions could be. I've looked into MPEG encoder chips, so I know it's possible to do this, I just don't want to work any harder then I have to here.

Thanks in advance from a newbie who's fumbling around in the dark here.


texts:
I recently got a big box of Hantronix 20x2 LCD from a friend. They appear to be the negative type, where the 'on' pixels appear as clear and the off are opaque. When he gave them to me he told me that there was no backlight, however it appears that there is something connected to the backlight terminals, and I'd like some help identifying it.

My best guess is some manner of EL panel? If it is a backlight, can someone tell me how to go about enabling it?

I've tried 3v3 across the terminals, to no effect. In case the pictures didn't turn out, the alleged backlight is two flat leads leading into a laminated plastic device sandwiched between the LCD body and the circuit board backing. I've also included a picture of the back connections, in case someone can spot a missing resistor, perhaps?


texts:
Adding input and output capacitors either side of my 5V DC-DC converter doesn't seem to help much, and I'm wondering if some kind of signal interference might be my problem.

I'm running signal from a Teensy 3.1, through 74HCT245 level shifters, then from there through about 4m of 1.5mm^2 3-core stranded domestic power cabling (alongside ground and +12V from a Meanwell power supply—yes, the grounds of the Teensy, level shifters and power supply are tied together) via a combination of Neutrik PowerCON connectors to strips of WS2812B (aka Neopixel) LEDs.

The LEDs don't seem to be getting a clean signal. Every output pin works perfectly individually, but when I get up to about 6-8 of the strings connected, some pins glitch really badly, some glitch a little bit and some are perfectly fine. When I reduce the speed of the signal (using FastLED's sequential output, rather than parallel output) everything is much more solid.

I'm wondering if there's some kind of signal interference, which somehow gets worse as the power supplies get loaded? (Note: there are four power supplies, feeding four strings each—their grounds, but not the +12V rails, are tied together.)

For clarity this diagram only shows one of the signal paths—there are another seven off the pictured 74HCT245, plus another eight off another 74HCT245 not pictured

Without having a oscilloscope (I'm trying to get hold of one), what diagnostic steps could I take to try and rule this out?

SUPPLEMENTAL: We've now tried plugging the strip directly into the control box (omitting the 4m cable in between) and are still getting glitching. So it doesn't seem to be the distance per se.


texts: Is it possible to generate a functional EEPROM (with persistence) inside an FPGA/CPLD

texts:
I'm looking to implement a small persistent 'configuration space' parallel EEPROM within a design.  However, given the volatile nature of FPGAs, this doesn't seem possible without some very clever manipulation of its attendant flash.  I am perhaps mistaken in this assumption (and I would be very grateful for details if that is the case).

That said, the less volatile nature of CPLD configuration intrigues me for this application.  I'm looking to implement the top-level design (and subsequent parallel EEPROM) on an XC9500XL variant, and I'm hoping to do this as a single-chip solution (rather than just add an admittedly cheap external parallel EEPROM).

Thoughts?  Advice?  "JFGI"-death-threats?  Any help is appreciated!


texts: AD620 - pot assembly alternative - filter

texts:
I have been posting questions regarding the AD620, reference voltge and output.
I followed all the instructions from Stack Exchange and voila! The circuit works like charm, thank you! It gives the perfect instrumentation amplifier output.

Now coming to questions I have two questions:

The sensor I am using is a load cell and an extensometer. Now the sensor outputs at zero load or displacement are not exactly ZERO i.e. the difference between them is not zero and we get some error voltage. So to measure this voltage and get output w.r.t. zero (GND) I've added a pot assembly, so I just adjust the pot to zero and I get perfect output.

QUESTION: Can I replace the pot assembly with anything else? Is there an alternative ?

Now I am using AD620 to get output from the load cell and I am going to use an inverting amplifier to adjust the gain of the output.

QUESTION: Do I need to design a filter for better output stability? How do I do that? I don't have a DSO or a CRO?


texts: Is it necessary to connect all power pins to power pic16f877a

texts: I am using a pic16f877a for a project and I noticed that there are two VDD and VSS pins.  I wanted to know weather all 4 pins had to be connected to power or just one VDD and one VSS pin.  A circuit I was working on seemed to work fine with just one connected but I wasn't sure if it was a good idea.


texts: Why real part of load change as we look through transmission line?

texts:
As we move from an imaginary load towards generator through a transmission line, we can see that real and imaginary part of that impedance changes. In fact, an ideal transmission line is comprised of inductors and capacitors. It can alter only the imaginary part of a load; how does the real part of the load change?

Once the transmission line becomes lossy, the constant gamma circle on Smith-chart gradually shrinks down to the center and meets the characteristic impedance. Can anyone explain how this happens?

Thanks in Advance!


texts: Is it the current you have to drive in the input to get a specific, defined voltage at the output? And don't the currents cancel each other when applied to both inputs?


texts:
I have bought the stuff in the image below from eBay in order to generate an electrostatic field.

But the spec of the item is, well ..., written in chineese with some english flavor.
I have tried to obtain informations from the seller and sellers of similar item, but they know nothing.
My question is addressed to persons that have bought the same item, know it, or are able to understand the spec.

Is the device suitable to be connected a long time without being discharged, or will it burn in this case ?

I've tried the device and it chirps as soon as it is connected, is it normal ?

thx.


texts: Will this circuit work? Using USB extension on a potentiometer

texts:
I have the following circuit. It is a simple Arduino project to read analog data from a potentiometer 10K. Click here for video link if you're curious.

The circuit shown above is tested and working as of now.

Now the thing is, I want to extend the wires between the 10K potentiometer and the Arduino and I am planning to use a USB extension cord to achieve it.

USB extension cords have 4 (four) wires in it as seen below.

I am planning to do it like this.

I will have a male and female USB connected one to the potentiometer and one to the Arduino. The length of the USB extension will be about 2 meters.

I will use 3 wires of the USB extension to connect the 10K potentiometer and the Arduino.

Now the question is, will the circuit work as expected when I plugged in the female and male USB? Will it work or not?

I am asking this before I cut my USB extension into two.


texts: Why do LED headlamp bulbs need active cooling?

texts:
I decided to install LED headlamp bulbs in my car in the hope that I can avoid replacing bulbs every year. I was quite surprised to find that I can't fit replacement bulbs in my car due to the bulbs having a huge heatsink and, indeed, a fan to keep them cool. I don't have sufficient space in my lamp housing to incorporate the extra hardware.

Looking on Wikipedia at the relative efficiencies of halogen and LED I see that they are both hugely less efficient than I anticipated:

Halogen 3.5% (typical)

LED 14.9% (worst case)

My usual halogen bulbs use 55 watts, and higher-output LEDs use 20 watts. Therefore, the halogen bulbs are creating:

96.5% * 55 watts = 53 watts of heat

The LEDs:

85.1% * 20 watts = 17 watts of heat.

Why do the LEDs need active cooling when the halogen bulbs don't - yet they create over 3 times the waste heat?


texts:
I'm trying to do high value asset monitoring within a panel van/truck with RFID tags. So this would be a case of a 3m+ range with metal everywhere - mowers, digging equipment, jackhammers etc. A local antenna would interrogate all the tags within range and then relay the information via 3G or WiFi.

Olin Lathrop answered another thread saying passive RFID is impractical for purposes like this.

Active RFID requires batteries however. I feel a practical battery replacement schedule would be over 2 years. For a requirement like this - relatively low range, low scan speed (ie the equipment in the van is there for several hours at a stretch, it's not just passing by), and maximum battery life:

Is there a preferred frequency (VHF vs UHF etc). Does higher frequency mean lower battery life?
Is there good transmit interval time or is it the case that the longer you leave it between transmits, the longer the battery life? Is this a problem with many tags in the one location? ie: something has to sort between all the RF collisions.
Would receiving as well as transmitting (so, waiting for a valid RF signature) badly affect the battery life? Wouldn't this be more secure?

(Edited to ask more specific questions)


texts: How to capture, save, and rebroadcast an infrared signal?

texts: I need to capture a signal that is being sent from an emitter (similar to a TV remote). I understand from this question that I can use an infrared receiver to do this.Once this is done, however, I need to be able to continually rebroadcast this signal even when its original source is not broadcasting. Is there a way to save this signal, or does in need to be decoded in some form to be rebroadcasted without the original? How might I go about doing this?


texts: Thermocouple simulator circuit : isolation & voltage reference

texts:
I'm designing a multi-channel (6-10) thermocouple simulator.
For different reasons, all the outputs must be isolated to simulate completely the behaviour of the real-life thermocouple.
To do the task without breaking completely the bank (and also to avoid adressing 10 similar DACs that only have 4 I2C adresses available), I was thinking of using an opto-coupler and a PWM signal that I would then smooth out with a simple RC filter. Bandwidth is not the key here and a 100Hz "refresh" rate is more than enough.
Since the voltage range of a type-K thermocouple is roughly between -10 and 50mv, I tried to go with the lowest voltage source (a voltage reference in this case) to chop. In this case, a 500mV voltage reference (LT6650). Given the PWM resolution is high enough (16bit for general purpose timer on the STM32), that should give me enough resolution.
Then comes an op-amp in unity-gain/follower configuration for impedance matching purposes
The first questions that I have :

Can I use the voltage reference (chopped by a NPN transistor) ? Do I need a follower between its output and the opto-coupler drain ?
Same question with the opto-coupler, do I need another NPN transistor in-between ?

Thanks for your feedback!


texts: Two lights, two switches... one problem!

texts:
I'm looking to set up an AC 240-volt lighting circuit consisting of two lights (let's call them L1 and L2), a standard switch (SW1) and a PIR.

The goal is to have SW1 turn on only L1, but if the PIR activates, to have it turn on both L1 + L2.

In my attempt so far, I've effectively created a standard 2-way circuit, but that has the unintended behavior that either the PIR or SW1 turn on both L1 and L2.

Is this possible using only these components, or is there some other component required to make this work?

Thanks!

Context:
SW1 is an internal switch, and the PIR is outside. L1 are lights in the soffit of a building, and L2 is a security floodlight.

Table 1. (For OP to edit.)

SW1   PIR  |  Lamp1   Lamp2
-----------+----------------
Off   Off  |
On    Off  |
Off   On   |
On    On   |


texts: Regarding the forces created in magnetic field

texts:
This is a homework question of type multiple choices , question and 5 choices  are given below.

And a screenshot of the set up is given below.

These are the things I know

Forces are acting all the four sides of the frame due to the magnetic field and the current
I could take the value of current by using Ohms law, and the value of it is  4A.
Therefore I can calculate  the force acting on side AB.

I found the direction of force acting on AB as the perpendicular direction to which the magnetic field is directed, and I calculate the magnitude of it which is shown below

So these are the things that I  found in this question.  The correct answer fot this question is 2. But how it can be? Initially I choose the answer 5 which is incorrect.

why I am wrong here? what's going on this set-up to decrease it's weight?I can't figure out why my answer is wrong , so that's why I ask this question here in this great website.


texts: Correct way to compute the power of a pulsed signal

texts:
I'm developing an application with my SDR Board and I've managed to produce a calibration table to verify the output power of the transmitter for every TX configuration of antenna gain and IQ digital word, for a given center frequency.

I.e., by setting the transmitter to that fixed center frequency, I've changed the TX gain and then transmitted a sinusoidal signal at different IQ amplitudes, using a spectrum analyzer to obtain the power of the transmitted signal.

So far so good, but I've now reached some problems and I can't seem to find a clear a solution for them online. I'm just an hobbyist, I have no previously experience with RF whatsoever.

The first problem is how should I properly use the RBW (resolution bandwidth) of the spectrum analyzer within my measurements.

For instance, if I measured an output power of 10dbm with a RBW of 100Hz, does that mean that within those 100Hz, there is a total of 10dbm power? Because if that is correct, then how can I correctly measured the power at the frequency of interest (which is inside that bin)? Surely those 10dbm will also account with the power from the frequencies close to the frequency of interest and inside my bin. What is the formula that I can use to correctly measure the output power at the given frequency with some error associated?

The second problem is related to what happens to the power when I change the window applied to the signal. In particular, I have my measurements performed for a CW setup, but I intend to transmit pulses and, at every time, I must know an estimative of the power at the carrier frequency, as well as some estimative of the total power of the signal.

These pulses are just simple amplitude modulation pulses, e.g: gaussian pulses, sinc pulses, hermite pulses, hard pulses, etc...

The way I thought about this problem is that it is just the application of another window to the already rectangular window that I use when I'm obtaining the initial power results. So, my idea was that since I know the shape of the pulses that I'm transmitting, i.e., I know the windowing functions, I should somehow be able to convert the measured power into the new power that is actually sent with the pulse transmitted.

However I can't find any formulas or any theory that would enlight me and I've been stuck in this problem for a few days now. I could just perform the power calibration for different pulse shapes but that would take me ages.

Can someone enlight me with some papers/theory? Is my approach incorrect? What should be my approach then?

Thanks in advance.


texts: Is it possible to connect more than one device on the same SPI?

texts:
Is it possible for someone to connect multiple sensors to the same microcontroller's SPI or I2C port?
If it's possible, how would someone alternate between devices?


texts: Does my open source project need be Arduino based to be successful?

texts:
I am debating which micro-controller to use for a new open source hardware project.  Spec wise, I would rather use an ARM Cortex M3, which is at a similar price-point to an Arduino(avr) based solution but with more processing power/peripherals.  The only concern I have going with ARM based hardware is I don't want to lose potential contributors/developers who might be put off by working with ARM.  Or competition wise--someone reproducing the project but with an arduino instead(e.g. Ardupilot overtaking Paparazzi)

I realize there is no straightforward answer to this question but I would like to hear your thoughts on the topic, and what other factors you think might weigh more on the success of the project.


texts: Do AC coupled inputs suppress voltage offsets in an op amp?

texts:
Background: I'm trying to build an AC coupled pre-amplifier that doesn't succumb to voltage offsets and input bias currents. The input signal has noise ~10 nV level, and I want a factor of a million in gain.

After studying the art of electronics, I'm trying to wrap my head around what are the problems input offset voltage can do, and how it can be circumvented.

Question: Will the following circuit need not worry about the V+ voltage offsets since it's AC coupled anyways?

My reasoning is that the 500k resistor lets the signal float on whatever voltage offset is there, i.e., there is no need to worry about error at 0V input.

The Circuit:


texts:
I am a beginner at verilog and encountered this problem:

  Assume that you have two 8-bit 2's complement numbers, a[7:0] and b[7:0]. These numbers are added to produce s[7:0]. Compute whether a (signed) overflow has occurred.

Now my answer to the asked value of overflow was

assign overflow = ~(s[7]&a[7]&b[7]);

While the correct answer shown was

assign overflow= (~s[7]&a[7]&b[7])|(s[7]&(~a[7])&(~b[7]));

I want to know where I went wrong.


texts:
I have a pcb with a SPI bus with several sensors that have to be connected to this bus. Since 90 degree traces are not recommended in a proper PCB design I ask myself how to connect so many sensors without using sharp turns and perpendicular traces?

I am thinking about making triangles to smooth the connections, but I wanted to ask it here before if there is a recommended way for doing  it.

PS: Maybe someone will say that SPI speeds shouldn't have trouble with this, but still it's a valid question for learning purposes.

EDIT:

Since an image speaks more than 1000 words...

That's the problem I am presenting: "how to eliminate 90 degrees traces in a bus connection?" (even if in this particular SPI case I won't have a problem, it still triggers my curiosity)


texts: When powering a Nrf24L01 hooked up to an arduino by external battery does ground still go to the Arduino ground?

texts:
So as mentioned in this article, the radio chip might have power problems and an external power source is recommended:

http://arduino-info.wikispaces.com/Nrf24L01-2.4GHz-HowTo

My question is for the ground connection, Should I connect this to the ground pin of the Arduino board?  Or, since the power is seperate from the Arduino, does the GND and VCC go to the black and red external leads of the battery directly ?


texts: Up to ~1000 A constant current supply 10-40 VDC

texts:
So a little background to explain the need. Occasionally we need to test starter motors (for engines) and provide enough power when the load (engine) causes the starter to pull in excess of sometimes 1000 A. Granted, this is for quite large starters. The test would need to last a minute or so, but foregoing the need to alter designs, we'd like to just go ahead with a continuous demand rating.

So I've got a fair understanding of linear power supplies and some common designs of higher currents, such as multiple transformers/taps, bridges, parallel transistors (2N3055, etc.), but in my own experience I have only "engineered", mathematically, relatively simple sub-circuits, RLC, and other simple circuits (555 timers, opamp 747, etc.) using Kirchoff voltage/current, Thevenin, systems of ODE/PDEs, phasors, etc. But really I rely on the community for a suggestion on what to look for. (And ideally a schematic!)

Some of the design requirements are

10-40 VDC (some are 24 VDC starters and a few are 36 VDC)
Maximum of about 1000 A at 24 VDC ~ 25000 watts/VAC
Be a current supply more than a voltage supply, similar to the idea of having the load in series with a much larger resistor.
Lastly (I think), is to be able to use single-phase, two-phase, or 3-phase input.

For larger loads, 110 VAC at the main is not going to work. For some idea of portability (we are a start-up business and have plans to grow and move) it would be nice to be able to run off "single" phase or three phase. This way each leg could supply a good amount of the load. (Can these be joined after the rectifier bridge or smoothing cap?)

By the way, companies such as DynaPower, though awesome, are just way too far out of our budget for right now. Besides, it's much more fun to build it yourself!

For what it's worth, we had thought of purchasing a used portable welder but were worried about the voltage adjusting itself to give the required current, and therefore power, to the load. I wouldn't know how to limit voltages at these currents...


texts: Can I ground a digital pin on an Arduino to provide input?

texts:
I want to monitor whether a fan is turned on or off.  No RPM, no voltage levels... simply just is it on or off.  The fan is 12V and is controlled by a relay.  The relay is closed when a thermocoupler reaches a certain temperature and grounds the internal coil, closing the contacts and providing power to the fan.

I was going to go through the hassle (actually I already did, just haven't installed it yet) of building a small circuit to convert the 12V down to 5V.  Then I had a thought... what if I use the internal pull-up pin on the Arduino to set it "HIGH", and when the thermocoupler grounds, let that ground pull the Arduino pin "LOW," signaling that the fan is on?

I expect I will need to put some sort of safety measure inbetween the Arduino and the thermocoupler to guard against over-drawing the Arduino... but that should work right?

EDIT:  A "proper" schematic

simulate this circuit – Schematic created using CircuitLab


texts: Finding the gain difference for a ultrasonic assembly

texts:
I am tuning an ultrasonic assembly for a welding application and tuned the system to operate at 41kHz according to the oscilloscope. The transducer operates at 40kHz, when calculating the gain with the peak to peak voltages from the oscilloscope for the tuned case, it resulted as  -35.7dB. When manually changing the frequency to observe the difference for the ideal 40kHz frequency the waveform resulted having -35.6dB.

Am I right in saying there is a 14% difference in the intensity of power produced with the ultrasonic assembly being out of phase by 3.9dB, I understand decibel is a logarithmic scale however, cannot put into perspective the exact difference in intensity.


texts: 18m diffuse PNP photoelectric sensor and arduino

texts:
I need some confirmation on how to connect an 18m PNP diffuse photoelectric sensor to an Arduino.

I am power the unit via an external 12 volt  power supply.  The ground  between the power supply and the Arduino is shared.
The black wire is connected to pin 8 of the Arduino.

When I read the value of pin 8 and output it to the serial monitor, the values are jumping between high and low (0 and 1) when the sensor is triggered.

Essentially I am looking for a stable high or low reading when the sensor in triggered.


texts: How does a moving magnetic field cause motion in the Al strip rotor?

texts:
Consider the following information:
https://www.youtube.com/watch?v=7snjbmdYlDI

How would you explain how the moving magnetic field causes motion in AL labeled rotor?


texts: Is there a socket for SOP8 packaging with SOP8 pins?

texts:
25Q128 is a flash memory for an IP camera. I want to dump its firmware but also try to write my own firmware. I have all the soldering equipment to remove it safely. I also bought the breakout board for SOP8 package so I can solder the flash memory in to dump it. However, if I want to test lots of firmwares, then I can't keep soldering it back and forth on every new firmware.
Is there such thing as a socket that I can solder in the place of this flash memory so I can insert it there?
Another option would be to solder wires into it but I have the feeling that powering the flash memory might power adjacent things that might try to read/write into it, makign impossible for me to do a clean write/read, so I guess my only option is to desolder and put it into a socket.


texts: Decaying envelope when audio passes through diode

texts:
This is a basic question about passing AC (audio) signals through a diode. I'm trying to use an audio signal to power an LED (which in turn heat-shrinked to an LDR) in order to control the behaviour of a simple audio oscillator. At the moment I'm simply passing the audio input signal through a 1k resistor that's in series with the LED - this is working, but it has the annoying feature that the amplitude of the audio signal (and hence the brightness of the LED) decreases over time, over a period of several seconds.

The same thing happens when the signal passes through an ordinary diode, such as a 1N4002 - the signal starts loud, then decreases over several seconds. Here's a screenshot of the output seen when a sine wave (around 70 Hz) is passed through a 1N4002 - as expected, the output is rectified, but has a decaying envelope.

Why's this happening, and is there a way to power an LED (such that its brightness follows the amplitude of an audio signal) where this effect won't happen?

EDIT: here's an incredibly crude diagram of what I'm up to - I'm sending a sine wave from an output of my computer's soundcard to a breadboard, putting a diode in series with the signal, and recording the output from the diode back into the computer.

EDIT: Here's an image of the output waveform when a 100 ohm resistor is put between the output of the diode and ground, as per Kaz's answer below. When the output is goes directly into a pair of headphones instead of the computer, the effect is much less pronounced but still audible, suggesting that the problem lies partly with the computer's audio interface.

EDIT: There's no obvious frequency dependence - here are the recorded waveforms of:

A 1k sine wave without the diode in place (i.e. just recording the output back into the computer)

A 1k sine wave with the diode, as in the diagram above. The signal is attenuated and has the same decay envelope. The same general shape is seen for frequencies going from 50 Hz up to 8k.


texts: DC Motor Power Supply Connection (Arduino)

texts: I am currently working on a project using Arduino UNO and two 3 volts DC motors. I chose a 9 V Goldtop battery to power my Arduino. The two motors draw voltage through the 3.3 V pin in the Arduino. The problem is, they seemed to work fine until after some time, a very short time, the two motors do not work well anymore. I have read somewhere that the DC motors should not draw their voltage from the Arduino directly and they should have their own power supply. How can I connect this separate power supply?


texts: Battery powered sensor node power down circuit

texts:
I am using the BQ24079T to control power for a wireless, battery powered sensor node. The MCU will operate in one of two modes: periodic sample mode where it takes sensor readings and then sleeps, or idle mode where it does nothing but sleep and wait for the next command. If it is in idle mode for too long, it should shut down completely to save battery power. To turn it on again, it would have to be attached to the charger.

I figured that an easy way to do this would be to use the SYSOFF pin on the charger to disconnect the battery from the system when commanded by the MCU. Here is my current circuit for this .

The SYSOFF pin goes to an I/O expander (PCA9557)) chip which is held low as long as the device wants to stay powered. When it wants to turn off, the pin is released and pulled to VPP, turning VCO off.

Maximum possible battery life is very important for this project, so I am trying to eliminate as much load during sleep mode.  All peripherals on the board are on switchable power and are turned off while the MCU is asleep.  The only thing it cannot control power for is the charger chip itself and related circuitry.

The 200k pull-up on SYSOFF will constantly draw between 15 and 20 uA, depending on battery voltage, while the MCU is powered on, and the charger itself will draw around 6.5 uA. This is not a huge amount of current, but as a constant load, it amounts to several months from the 300 mAh Li-ion battery that I am using.

I was thinking that I could use a flip-flop or latch controlled by the MCU in place of the pull-up to reduce static load, but I am not sure how that would work.

How would you handle this?


texts: Thick spiral, faint orange glow - what type of old bulb is this?

texts:
In a museum in Germany, I saw this lightbulb-shaped device mounted in a E27 mount, seemingly on 230V AC. It contained a thick black spiral, with a visible gap at the top, emitting a soft deep orange glow when switched on. It was definitely not bright enough to have been used for general lighting (or perhaps degraded over the years so that it is no longer bright?), as seen when compared to a normal 40W bulb in the second picture. The glass seemed darkened, perhaps by something ablating from the spiral.
Any ideas what this is?


texts: Extract firmware of an old electronic toy

texts:
I'd like to extract the firmware of an old electronic toy.
Is has two electronic components, made by Texas Instruments:

a PC35303NL - QB 8649, which is the main controller I guess
TMP50C40AN2L - CM54157, which is the ROM I guess

A picture of the mother board can be found: .

I've searched the web for information about these parts but could only find a reseller who has some in stock. I could not find any datasheet.

Any idea on how can I make progress ?


texts: Why is the common base current gain giving me 0.01?

texts:
To calculate the current gain I did:

\$Gain\, of\, current=\frac{I_{out}}{I_{in}}=\frac{3,96\times 10^{-5}}{3,548\times 10^{-3}}=0,01\$

Is it normal to give a current gain, so low? What did I do wrong?


texts: What is the power consumption of Fimer PowerGain?

texts:
Fimer/Power One (former ABB) solar inverters contain a feature called PowerGain. Power Gain periodically scans the full MPPT range to find the absolute optimum power point.
According to the manufacturer, the optimum point is found within milliseconds.
What amount power is lost due to the scan when there is no shading?


texts: Transistor switching noise problem (Guitar pedal idea troubleshooting)

texts:
Have a simple circuit :

i want to create a gated effect that cuts signal in and out .. it works but i can hear the switching sound of square  wave generated by arduino through my amp speaker .. (click ,click, click..)

Does anyone have a solution to get rid of this sound and maybe someone could inform me how this happens in 1st place .. im guessing its noise caused by the magnetic field created by the on/off cycle? or maybe not lol?


texts: Can I put a low current relay between line (or neutral) and the ground wires to detect polarity?

texts:
Can I put a low current (<5 mA) 230V coil,  NC (normal close contact) relay between one wire of mains and the ground (earth) wire in order to check mains polarity?

In theory if the wire is line (hot) the relay will switch and prevent the equipment to power on.

On the other hand, if the wire is neutral (correctly) the relay will not switch, as supposed to be at same potential of the ground and the equipment can be turned on.

Is this insane?

Of course there  be a LED circuit to show if ground connection is good.


texts: Array of leds without limiting resistor?

texts:
I need to run 9 leds (7 white and 2 red). I found this circuit

but there is no limiting resistor in the upper line of leds. Is it ok? If no, how I can modify this circuit?


texts: I'm trying to measure the power consumption of my device using a shunt resistor. I'm measuring both the voltage over my shunt resistor and the source voltage. With a math function i'm trying to calculate the average power consumption. What is the best way to do this? I've tried by using the Mean function and RMS function. Since the results are so different i'm a bit confused. I think the Mean function is the way to go, but i can't figure our why the RMS value is so much higher? Attached you can find the measurements.


texts: AC switch & power supply reverse engineering

texts:
Below is schematic of self-powered(by passing little current not enough to operate) switch reverse-engineered from PCB.

simulate this circuit – Schematic created using CircuitLab

Zener diode(D7) seems like 1N47 but not sure.

This is connected in serial with load. (one to mains live and one to load)

I omitted fuse and inrush current limiting varistor

How does this exactly work and is there a name for this circuit?

As far as I understand:

R3 and C2 is for smoothing
D1, D2, D5, D6 is diode bridge
C3 is for smoothing
D7 is for limiting voltage
When S1 is closed, current flows into R1

I can't figure out the purpose of D3 and D4/C1, R4, D8, D9 and S2/L1 and how it limits current(resistor value seems too small).

Also how can I calculate current?


texts: Need help understanding Ultra Low Power Wakeup on PIC16F887

texts:
I am trying to implement the "Ultra Low Power Wake Up" feature on a small PIC project. The idea is the chip will go to sleep, and then be woken up in the future by the ULPWU interrupt.

The idea behind the ULPWU is that you connect a capacitor to this pin, charge it and put the chip to sleep. When configured, the ULPWU pin will slowly discharge the capacitor. Once the voltage on the cap falls to some value, the chip wakes up and possibly generates an interrupt.

This application note (PDF) from Microchip explains how the ULPWU is programmed and implemented. See Example 2 and Figure 2 (below).

Example 2:

BANKSEL PORTA           ;
BSF PORTA, 0            ;Set RA0 data latch
BANKSEL ANSEL           ;
BCF ANSEL, 0            ;RA0 to digital I/O
BANKSEL TRISA           ;
BCF TRISA, 0            ;Output high to
CALL CapDelay           ;charge capacitor
BANKSEL PIR2            ;
BCF PIR2, ULPWUIF       ;Clear flag
BANKSEL PCON            ;
BSF PCON, ULPWUE        ;Enable ULP Wake-up
BSF TRISA,  0           ;RAO to input
BSF PIE2, ULPWUIE       ;Enable interrupt
MOVLW B’11000000’       ;Enable peripheral
                        ;interrupt
MOVWF   INTCON          ;
SLEEP                   ;Wait for interrupt
NOP                     ;

I have carried this out but am stuck with a strange problem.

When the chip goes to sleep, there is 5V being supplied by the ULWU pin (RA0). If I connect this pin to ground, the chip wakes up and does what it is supposed to do.

My question is, why is there 5V on this pin when it is supposed to be an input? If I have this pin connected to a charged capacitor, the capacitor never discharges (the 5V on the pin is keeping it charged).

EDIT
Here is my test code. I am not using a capacitor in this case. I am simply switching the RA0 pin from high to low. The question remains, why is RA0 High when it is supposed to be discharging a capacitor in order to trigger the wake up feature?

INCLUDE registers.asm
__CONFIG 0x2EFF20E5
     ORG    0x00
    GOTO    MAIN
;***********************************************
;Interrupt Service Routine
;turn on an led and return
;*********************************************
    ORG 0X04
ISR
    BANKSEL PORTD
    BSF PORTD,7
RETFIE

MAIN
    CALL    SETUP
    CALL    SETUP_WU
    SLEEP
TRAP
    GOTO    TRAP

SETUP
    BANKSEL ANSELH
    CLRF    ANSELH      ;CONFIGURE ALL PINS FOR DIGITAL IO
    CLRF    ANSEL
    BANKSEL TRISD   ;PORTD IS OUTPUT
    CLRF    TRISD
    BANKSEL PORTD
    CLRF    PORTD
    RETURN

SETUP_WU
    BANKSEL PORTA
    BSF PORTA,0
    BANKSEL ANSEL
    CLRF    ANSEL
    BANKSEL TRISA
    BCF TRISA,0
    BANKSEL PIR2
    BCF PIR2,2
    BANKSEL PCON
    BSF PCON,5
    BSF TRISA,0
    BSF PIE2,2
    MOVLW   B'11000000'
    MOVWF   INTCON
    RETURN

END


texts: Xilinx bit file different between builds

texts:
I'm trying to understand what happens to binary results after building same VHDL sources using Xilinx latest ISE. I have heard conflicting information about the resulting bit/bin files.

Is the expectation that in two builds bit and bin files result in the exact same binaries reasonable?

Does host OS (Windows vs. Linux) influence the resulting binaries?

Can I do MD5 on two files from different builds and expect them to match?


texts: Can I generate random numbers on PIC from INTOSC vs crystal?

texts:
Generating truly random numbers on a microcontroller is a known difficult task.

One way is to run two different clocks, and measure the clock drift between them.

The PIC16F1783 which I'm using does have two clocks. One using an external crystal and the LFINTOSC which powers the watchdog.

Is there any way to get at the LFINTOSC, while running from the external crystal clock?

One idea I had was to let the watchdog expire, and check the value of TMR2, but it doesn't work because TMR2 is reset by watchdog resets.

One could write a counter to EEPROM in a tight loop and let the watchdog expire, and then inspect the contents of EEPROM, but this seems very inelegant. Edit: It's much better to write to RAM, as suggested in one of the comments.

Is there a better way? Without using external circuitry, and without relying on ADC-noise (which might not always be present)?

Datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/40001579E.pdf

Edit: I want the random number to generate a GUID to be able to tell apart multiple devices sharing the same RS485 bus. My idea is to use something similar to 1-wire device discovery. But to do this I need to have different GUID on different devices, and I'd like to avoid the hassle of having to program them with unique ID:s.


texts: How do I convert a +10v to -10v single input to dual 0-5v outputs?

texts:
I am currently trying to interface a input voltage with an Arduino that reads between +10v and -10v after it has been brought down to appropriate levels. The original use of this voltage drives a motor forward or backward based on the bias of the voltage.

My current idea to interface with the Arduino is to use a voltage divider to lower the voltage to the 5v range, and then to split the positive and negative voltages to separate analog input pins.

I have successfully pulled down the voltage to +5v to -5v, but I am struggling to convert the -0.01v to -5 to its own 0-5v analog input for the Arduino.

Does anyone have an idea on where to go with this? Or a better idea on where to start?


texts:
I want to use a servo taken by a radio-controlled car. However, I found out that wheels' rotation (front wheels) is not performed by a servo, but from a motor to move the wheels and a mechanism for control, into a steering box.

Specifically, there are 2 wires (red/black) that connect controller board with a motor. Motor communicates with a set of gears.

Control (this is the part I can't figure out) is performed by 4 wires, that end up to a simple circuit. Depending on which wire transfers electrical current, it's conductive area has current too. Set of gears that motor communicates with, connects to this circuit with 4 metallic cyclic endpoints.

Does anyone know how exactly control is performed? Is important to decode the operating mode, as I intend to use mechanism for another implementation.


texts:
Background: I'm working on a CANBUS and sensor project for an offroad racing truck. Heat, reliability, and RF interference are all big concerns. I'm designing the PCB's and enclosure, so can be very flexible. The project will be powered off of the truck's battery which typically runs at about 14v. The PCB for the power regulation will be separate from the PCB with all of the logic, primarily for heat isolation. We need about 1A a 5V, and about 600mA at 3.3V.

Question: would a voltage regulator like a LM7805A or a 5v buck converter like a MP2307 be more effective for this particular use?


texts: Increase emf received from a coil without changing flux source

texts:
I have a situation where I'm trying to increase the amount of power received by a coil. To my understanding, I can increase the emf (voltage) by doing one of 4 things:

Increase the number of coils (\$ N \$)
Increase the field from the source by increase the current (\$B\$)
Increase the area of the coil (\$A\$)
Decrease the time it takes to change field (\$t\$)

Which is coming from the following equations below:

emf Equation:
$$\epsilon = -N\frac{\Delta \Phi}{\Delta t}$$
where
$$\Phi=BAcos(\theta)$$

\$A\$ is the area of the coil, and \$B\$ is the flux given by $$ B=\frac{\mu_0 I}{2\pi r} $$

so without chaning anything about the source of the field, the only way i can increase the emf of the coil is to change the number of coils, or change the area, right?

let's say my coil is a wrapping around the source of the field, with the source of the field running through the middle as shown below, and the coil is a square coil with equal height and width.

I'm wanting to know if I can do one of the following to increase the emf.

1) can I simply increase the area of the coil by increasing the height as shown below (note, i might do this if my width is limited but my height isn't)? I'm not sure if this will have any negative effects since it's not as uniform in all directions, and if there are negative effects, how big of a deal they are.

2) can i keep my square coil roughly the same shape width and height wise, but then wrap the that around my source in a helix form. if i wrapped my wire around a long thin rod, and then wrapped that rod around my source, I'd get something like below. My thought is that i would increase my area, and the number of turns, and that it might easier to make then simply increasing the height as seen in the previous diagram.

I feel like this helix method will have some downsides. I'm thinking that the field created by the coil with be fighting itself, thus reducing the over all emf... maybe this can be reduced by stretching the helix out... but by doing that i'll be increasing my \$\theta \$, which will reduce my \$ \Phi = BA cos(\theta) \$... maybe the increase in coils or area will overcome this decrease from the angle... I'm not sure. Is a helix coil even done?

I feel like could acheive the same thing with multiple coils in series like the diagram below. I think I would run into the the same issue of my fields fighting against each other, but my \$theta \$ would still be zero, so i wouldn't be losing any energy from my angle.

Do any of these methods sound like a valid way of increasing my emf? are they're better/easier ways of doing this apart from just increasing the number of turns in my coil, or increasing my coil in both width and height? Thanks for any feedback!


texts: How does the bootstrapping capacitor in this diagram operate

texts:
I am curious to know how the bootstrap capacitor Cbst in the following example charges up to Vcc + Vin?

https://www.homemade-circuits.com/wp-content/uploads/2019/04/bootstrapping.jpg

According to my understanding, during the clock input which turns the low side mosfet ON, the Cbst is charged at Vcc via Dbst, during the next clock the low side mosfet turns off and the high side mosfet begins turning ON through Vcc via the emitter of the NPN buffer. This allows the drain voltage to reach the source of the mosfet which simultaneously passes through Cbst via the NPN buffer to the mosfet gate. When this happens the stored Vcc inside Cbst comes in series with the instantaneous mosfet source voltage, and together they execute the Vcc + Vin for turning ON the high side mosfet.

A brief clarification on this will be greatly appreciated!


texts: What is the general rule of thumb regarding UL's creepage clearance regulation?

texts:
I've read a whole bunch of material but I'm still quite confused regarding creepage clearance, specifically:

How to calculate the minimal clearance on a PCB board?
How to calculate the width of the air gap (pcb cutout, hollowed slot of pcb) to enhance clearance should you really, really not be able to meet the minimum clearance in question #1 and decide to use air gap instead?

Elaboration:

Based on what I've read, for 300Volts WORKING circuit, the minimum clearance is expected to be 3.2mm, so I assumed, since my working voltage is 220v and maximum input voltage is 305v, a 3.3mm clearance will suffice. But according to this online calculator (http://www.creepage.com/) the minimum clearance is only 2.1mm (I could have remembered it wrong in which case I apologize) so how should I actually crunch the numbers?

I also heard that UL test labs will tune the input all the way to 2kv, sometimes higher (though I don't know for how long), and apply it to your board and your board have to survive without giving out sparks or outright be reduced to nothing but a charred wreck. This further perplexed my understanding of the minimal clearance: there is no way I can cater 2kv???

My board is tightly packed and some places really can't enable me to afford the 3.3mm luxury, which bring us to question #2, how wide should I make the air gap to offset the negative effect of the small distance? Is there a way to calculate that too?

This is really all too overwhelming as there are just too much information to process. So what would be the general rule of thumb, speaking particularly from experience?

BTW my pollution level is 2.


texts:
I did this circuit in my protoboard, and it worked for a while, but the quality sound was terrible, and suddenly it stoped working. Can anyone explain me in which part of the circuit i did something wrong? any sugestions to improve the sound quality and make it work?

the transistors used are both BC546, and the microphone was acctually an input for an mp3 player, but i didn't found in the programam that i did the schematics, so i put i microphone.


texts: ARM8/ARMv4 properties for qualitative comparison between RISC, CISC, and MISC processor designs

texts:
Question:

I'm wondering if anyone knows roughly what kind of power consumption one can expect from an ARM processor having the ARM8 architecture (ARMv4 instruction set)?  (Edited)

Note: I'm not looking for technical specs, but rather a ballpark power consumption in 'typical' circumstances (typical is left open.)

For size of the ARM8/ARMv4 instruction set, I haven't found a source that simply lists them all for the ARM8 (apart from the datasheet -- which would require counting manually!).  Surprisingly, I wasn't able to find any marketing material or technical summary that listed the size of the instruction, unlike for Intel, where it was easy to find that 80486 has about 190 instructions.

Edit: Loosely counting the ARMv4 instruction set, I get roughly between 75-100 instructions, depending on whether one includes minor variations or not.

Context: (Edited)

I'm hoping to use the information to make a rough but qualitatively correct comparison between similar chips of similar capability but having different designs, i.e. RISC, CISC, or MISC (minimal instruction set).

For CISC, I have the Intel 80486 at about 50 MIPS, 190 instructions, but using a whopping 1.2 million transistors, and consuming ~3W power.

For RISC, I have the ARM8 at 84 MIPS, 75-100 instructions, using fewer than 50k transistors, and consuming ??W power.

But most interesting in my opinion is MISC, specifically Chuck Moore's MuP21 Forth-in-hardware chip which is listed at about 80 MIPS performance, has only 25 instructions, only 7k transistors, and 50 mW power consumption.

Filling in the ARM chip information will hopefully support factor / order of magnitude comparisons between the three designs.


texts: Two different ultrasonic range finders to minimize interference

texts: Basically, I am building a robot that needs to be able to detect the distance from multiple sides. My plan is to use multiple ultrasonic range finders on each side, but I'm worried about interference between the sensors. Do there exist sensors that output and receive different frequencies to ensure that they don't interfere with each other?


texts:
I am currently working on project that uses the spectrum created by the diffraction grating. I am using a stepper motor to rotate my grating.  I want the stepper motor to move exactly 0.01 degrees and wait for detector to take the reading.  After the detector is done taking the readings, again rotate for 0.01 degrees and repeat the above procedure.

I have been searching through the internet to find a stepper motor that rotates only 0.01 degrees but so far i have no success. After searching for a while, i found that microstepping will help me achieving the required angle but i am not sure about it.


texts:
I want to power a Raspberry Pi and a set of speakers from one power supply. I thought about uncasing the existing power supplies and connecting them to a power connector but that seemed a bit dangerous? I then found a HDD power supply that already provides 5 and 12v.

(http://www.ebay.co.uk/itm/HDD-POWER-SUPPLY-AC-12V-5V-2A-FOR-HARD-DRIVE-MOLEX-EU-/320705061192?pt=UK_Computing_Drive_Cables_Adapters&hash=item4aab82e148)

I guess this is a normal female molex connector that I could then plug to a male connector and then connect to the cable with the connectors for the devices on? A bit like the (rough) diagram below?

Also the power supply puts out the voltage at 2A but I need it to be at 1500mA and 500mA for each device. Any suggestions how to do that here? Its been a long time since my high school science so please forgive the "basicness" of my question.

Thank You!


texts:
I am trying to learn filters.
In the following circuit, the author says that negative and positive feedback are used. I couldn't understand what the circuit parts do.
Actually I got the negative feedback highpass parts but the low pass part is a little different from normal filters because C2 doesn't bind with ground.


texts: Elegant non-mechanical way to switch on battery-powered device the first time

texts:
For a primary-battery powered device, that will be stored for a period of time before first use, what is the most elegant non-mechanical* way to switch it on for the first time, after which it will operate for the life-time of the battery?

The device operates in low-power mode most of the time, with bursts of activity. The only thing powered during low-power mode is a real-time clock, drawing something like 20 nA.

I have considered NFC and maybe even capacitive touch, and it seems to me that those could work to signal and power a switch to turn on, but in that case something else would have to keep the switch on afterwards. Maybe the switch could be to the RTC's VCC pin, and afterwards it could hold its own power switch in the on state, but that seems a bit dodgy.

I can't think of a really elegant way to do this.

*
Meaning that the device is hermetically sealed, and it is not desirable to have a switch, button, pull-string or similar sticking out.


texts: Designing two stage CE amplifier with negative feedback

texts:
I'm trying to design two stage ce amplifier with negative feedback using 2n2222 transistors. The circuit must have certain voltage gain, Rin, Rout, Vcc, low and high frequency filter. This is the circuit:

I am a noobie with electronics and I've no idea where to even start designing such amplifier. I find it especially hard to design this circuit with certain voltage gain, Rin and Rout. I can't really wrap my head around it.

Any help would be greatly appreciated.


texts:
I'm preparing to cut apart a non-trivial $ device and try to extend a 4-conductor cable, so I have been practicing my splicing skills. I figured a USB cable would be a good test.
I spliced, heat-shrink-insulated each solder splice and also soldered the ground wire. I wanted to see if the thing would actually transmit data once I was done, so I tried to get the original foil shield re-wrapped around the splices, but of course they wouldn't quite go.
I figured I could get a connected layer of aluminum around that spot fairly easily if I wrapped the works with some aluminum foil from the kitchen. I had foil on foil on ground wire, squeezed it tight, then heat-shrink wrapped the whole thing. It seems to charge fine right around 5 volts, and plugging my Anrdoid phone into my PC, the data flow seems good too. I ran some file operations on the phone from the PC and copied a few folders of music for a minor test.
I'm curious if that aluminum foil is working as a shield or if  shielding not that big a deal in such conditions.
Is an aluminum foil wrap working as a shield in my spliced USB cable?


texts: Purpose of PNP transistor in ultrasonic driver circuit

texts:
This question is related to my other question

What is the purpose of Q2, R2, C1 and C6 in the circuit in the original question?

When I remove these components from the simulation nothing appears to change, it still oscillates.

In my understanding L1 is blocking the oscillations from getting to the input (Q1), but it appears to work fine without the other 4 components (in the simulation).


texts:
I am working on a small project and this is my requirement:
I already have a headphone which I can plug into an audio jack. I need to make this headphone wireless. Right now all I can think of is attach an audio sender dongle to the two line audio jack and a receiver at the other end.Is this the right way to go? Or are there some other alternatives?
The key area that I would like to focus on is building the radio transmission along with its reciever. Needless to say the bluetooth protocol is something i would definitely have to focus on.


texts: Can someone help to find / create / add a device in Eagle Library?

texts:
I want to use FSL176MRT a  integrated Pulse Width Modulation (PWM) controller and SenseFET IC in my SMPS's PCB design in EAGLE.

It is not available in any library.
Its a 6 lead TO-220 package device

I've tried but it has different pin structure than normal IC's

Any help is very much appreciated..thanks :)


texts: How does a voltage controller specifically L7805CV work ( detailed )?

texts:
I have used this vc in a project but for the file I'm not able to find any info on how this thing works like how and which transistors are in it. Anyone knowing anything about it please share.
Thank you.


texts: Can I convert a mini guitar-amp into a portable auxiliary speaker?

texts:
Being a guitar player, my brother got me one of those guitar shirts for Christmas that has a board with pressure sensors attached to it and an actual miniature amplifier. When the sensors on the board are being pressed, a signal is sent to the circuit within the little amp and a guitar sound is played through the speaker. It also has a three-pin volume pot and apparently some kind of digital tone control. I've attached photos of the amp and the circuit down below.

Of course, the sensors don't really work perfectly and while it was a nice gift and we had some fun with it, I don't see an actual use for it. However, I do see a use for the little amp, since my laptop's speakers don't work anymore and I've considered buying a portable speaker of that size to play sound when I need to (which rarely happens, but it would be helpful for school presentations and such).

Would it be possible to either unsolder the front output jack and solder it back somewhere into the circuit as an auxiliary input to connect a laptop's headphone out to the amp (or connect an additional mini audio jack in that way)?

I would like to "tap" into the existing circuit to use it this way:

Audio Out - Audio Cable - Amp Input - Amplifier/Volume Control - Speaker

Unfortunately, I don't know where the amplifier circuit begins and where I would have to connect the tip and sleeve of an audio input jack.

Can someone here see if and how this could be possible?

Photos:

Front side: Power switch, power LED, output jack, tone pot (6-pin), volume pot (3-pin).

Circuit: Orange, green and blue cables connect to power switch, white to the speaker, red and black to the battery (4x AAA 1,5V in series), the 8 pins on the bottom left connect to the board with the sensors and would not be needed anymore.

Circuit, other side: Self-explanatory, front pots and output jack visible, the second pair of center red and black wires go to the LED.

UPDATE:

With Jasen's help, I attached a 3.5mm audio cable to the amp for testing. Unfortunately, I wasn't able to get any sound out of it, so far.

I've connected both signal wires with 10k Ohm resistors in between to the first pin of the volume pot and a ground wire to the output jack's sleeve connection on the amp. All connections make contact (I tested them with a multimeter). At first, I didn't want to cut the original trace on the PCB to the pot, so I just cut the corresponding pin on the pot itself and bent it forward, so that it didn't have a connection to the PCB anymore.

When I turned the amp on afterwards, I just heard a silent hissing sound and no input from my phone which I used for testing. I thought that I had to cut the old trace anyway and cut a small nick into the side of the PCB so that just the outer trace was damaged. Then, I got no sound from the speaker at all anymore. As far as I can tell by measuring the other connections, no other traces on the PCB were damaged.

I also tried to shorten the wires from the audio cable to the pot directly without the resistors, because I thought they may have been rated too high, but that resulted in no change.

Did I do something wrong or is there another way to get sound into the amp?

I've attached another photo of how the circuit looks now down below:


texts: Can an ADS1231 be used in place of an ADS1115?

texts: I have a working millivolt recording device which uses the ADS1115 16-bit adc. I would like to move up in resolution to the ADS1231 which is 24-bit. The Ads1115 is described as an i2c-compatible serial interface device using SDA and SCL lines to the microcomputer. I've never used the ADS1231. It is described as a "two-wire serial digital interface" using SCLK, DRDY/DOUT, CLKIN lines. Does this mean its easy to exchange chips or next to impossible?


texts: Determining the coil inductance of a relay when the relay is on

texts: I'm trying to measure the coil inductance of a relay when the relay is on and the  normally open pairs of contacts are closed. The relay has a rated AC voltage of 110V and a rated current of 21mA. I know that \$V = L\dfrac{di}{dt}\$, but I'm not sure how to use the formula to find the inductance for a relay running on sinusoidal voltages and currents. Can somebody shed some light on this please?


texts: RS232 which pin i can connect together to receive a input signal in my Java application listening on ttyUSB0 or ttyS0?

texts:
I am trying to make a very simple BUTTON (simple wire RED/YELLOW only). Now if the Button is pressed (RED touch YELLOW) i want to receive input signal in my Java application (that button was pressed).

In which ports of RS233(DB9) i should patch the RED/YELLOW wire? So that any button pressed i get in my application input signals?

Thanks


texts: RTD readout using wheatstone bridge and MCP6N11

texts:
For a project I require simple temperature sensing. The specifications are as follows:

temperature range: 50-250 Celsius
costs resonably low (< 10 US)
accuracy +/- 2 degrees

for cost and availability reasons I selected the following RTD: (farnell)

The trick now is to get the temperature information into a micro controller. This will be accomplished using an Wheatstone bridge and an MCP6N11 (farnell). The gain of the amplifier has to be around 6. A proposed schematic can be found below (note that the RTD is placed between "R_uit" and "R_in").

There rests only one question. How do I properly set Vref? Considering that the micro controller can measure between 0 and 5V, which I prefer to utilize fully. In the datasheet is stated that Vref "lifts" the output voltage. With that in mind, isn't it best to just ground Vref? It is provided that the MCP6N11 is a rail-to-rail device.

In the User guide of the demonstration board they talk about setting Vref around 1.8V when Vdd is 5V.


texts: Dead time in Half bridge gives weird output

texts:
I was working on the half Bridge and I introduces a dead time between two complementary signals to avoid shoot through.

I get a very strange output when both of the switches are off (in the death zone).

Since both the switches are off so the oscilloscope probe is connected to nothing and it's in floating state. So I should ideally get a zero output in this time(dead). But I get overshoots or ripples in the output waves (red).
 Why is this happening?
I think its something to do with the parasitic capacitance of MOSFETs.

Blue: Gate Control Signal to upper side optocoupler.
RED: Bridge output with respect to ground.

Circut Diagram  Mosfets supply is 4.5V instead of 12. And lower Mosfet source is connected to ground. And Load is not connected.


texts:
I need to shift the phase of a signal in the 2 GHz range. However, the problem is that this phase shift needs to be trimmable. It must be adjusted only once. Unfortunately it is very difficult to properly simulate the necessary phase shift in advance, and there may also be some manufacturing tolerances.

I wonder whether there is a way of making an adjustable phase shifter, for instance with a trimmer cap? The phase shift should be adjustable in a range of, say, 90°. Further, of course the phase shifter must be matched to 50 ohms.

I thought a RC network may do the job, but unfortunately it is not matched at its ports and further has a lowpass or highpass characteristic, which I would like to avoid.


texts: What bias voltage is applied to a PIN photodiode when connected only to multimeter

texts: If I take just a PIN photodiode (e.g.  BPW34 FAS ) and connect a multimeter to its terminals to measure current, for example: expose the photodiode to the sunlight and read current of  ~1 mA on the multimeter. In what region do I operate the photodiode with respect to bias voltage, that is do I have zero, forward or reverse bias voltage ? What is the bias voltage  (or how it can be found) if not zero ?


texts:
In my code, I have two interruptions, one is coming from the overflow of the TMR0, and the other one is when a button is pressed.

this is the code in MikroC :

int compt = 0;
int seconds = 10 ;
int enable = 0;

void interrupt(){

     if (INTCON.INTF) {
        PORTD = 9;
        enable = 1;
        seconds = 10;
        INTCON.INTF = 0;
     }

     if (INTCON.TMR0IF) {
        compt++;
        INTCON.TMR0IF  = 0;
        TMR0 = 0x06;
     }
}

void main() {

     TRISB = 0x01;
     PORTB = 0;

     PORTD = 0;
     TRISD = 0x00;

     INTCON = 0xB0;
     OPTION_REG = 0x44;
     TMR0 = 0x06;

     while(1){

        if (compt == 625){
           if (enable) seconds--;
           compt = 0;
        }

        if (seconds > 0 && enable == 1) {
           PORTD = seconds;
           PORTB.RB1 = 1;
        }  else {
            enable = 0;
            PORTB.RB1 = 0;
            PORTD = 0;
        }

     }

}

what I am trying to achieve with my code is as the following :

When I press one of the push buttons, the countdown starts and the LED illuminates until the countdown ends, and if the user pressed the button while the countdown still didn't hit 0, it starts over, until the countdown hits 0 again, then the LED should turn off.

What I'm facing here, is that the interruption from IRB0 works only once, the second time I press the button, nothing happens.

I am not sure if the TMR0F has something to do with that or not, tried many things, but couldn't make it to work.

I Hope that you could see something i didn't notice, and help me.


texts: Does this solar panel setup with batteries meet my power needs?

texts:
I'm working on a network setup for the middle of no where. I want to try and use solar to run the network hop completely. I have never built anything like this before so I wanted to run it by some people who will know more than me. Please let me know where I'm wrong here and help me understand if I'm making a mistake with the calcs. Thanks.

So the setup has 3 network devices.

I'm using an UBNT Rocket AC PTP radio on the backhaul.
24V, 0.5A Gigabit PoE Adapter
Max. Power Consumption 8.5W

and a Rocket AC PTMP Radio on the AP
Also
24V, 0.5A Gigabit PoE Adapter
Max. Power Consumption 8.5W

To power both the units and provide some basic routing and monitoring I'm using an UBNT Tough Switch 5 POE
24VDC, 2.5A Power Adapter
Max. Power Consumption 60 W
PoE Out Voltage Range 22-24VDC

At most the switch will draw 60W.
Each POE can do up to 8.5W max so 5x8.5 = 42.5W. The switch probably draws 17.5W (Probably less but I'd rather overestimate.)

So at most I should be drawing 8.5W + 8.5W + 17.5W = 34.5W.

34.5W / 24V = 1.4375amps. I want this to run 24 hours a day so that's 34.5ah.
Because I don't want my batteries to drain more than half and because we will have cloudy days I will use 50ah batteries (2 of them for 24 v). That will give me 50ah at peak usage.

I will mount the switch and the batteries and charging unit in a vented box at the bottom of the pole. The pole will be 40ft high and have both the radios at the top with cable ran down to the box. On the pole I'm mounting 2 50w 12v Solar Panels.

50w at 12v = 4.16amps of output. 4.16 x 2 panels = 8.32 amps per hour. It won't be 100% efficient so let's say 70% so figure 5.824amps per hour.

I'll only get that, at best 7 hours a day at the lowest point so that generates 40.768amps. Which is more than my useage for the entire day of 34.5ah.

Even at 6 hours of sunlight I'm at 34.9ah so I should still be ok?

This should work shouldn't it?

Thanks for your time and thoughts.


texts:
I currently have a system consisting of two PCB connected via a 5 cm cable.

Each PCB has a microcontroller, the two microcontrollers are communicating via SPI at 1Mbps Data rate.

Now the system will go into EMC and EMI testing, and i never dealt with a system were i should consider both the sourcing and receiving end, usually i only design the receiving end of the signal.

I considered adding an RC filter in the received signal and a series resistor to the sourced signal but i dont know if this would distort signal, can anyone suggest the best solution to pass the tests?


texts: Digital pot leaking and vcc/2 impedance doubt

texts:
I have been trying to use a digital pot to control the volume of an audio signal. I am aware that most digital pots don't take negative voltages and also that digital pots have a high wiper resistance in comparison to analogue pots, so some leaking will probably always occur. Still, I want to make it work as best as possible with my setup, even if not perfect.

I have a mega2560 controlling a digital pot (MCP4241 502) and the audio player (DF Player, a cheap mp3 module). There is a circuit for shifting the DC voltage up (VCC/2) so the digital pot will respond properly. Yet, I'm getting a lot of leakage when the volume is set to 0.

I kind of understand the voltage divider to shift the voltages up (R2 / R1 + R2 x Vin so 100K / 200K * 5v = 2.5), but I don't understand what values to choose for the 2 identical resistors. According to an article by Maxim:

"The input impedance of the input resistor network must be large enough so that an external source can drive the signal into the preamplifier. Also, the input capacitor must be large enough that it does not attenuate the low-end frequency response, and the resistance of the R2 resistors must be small enough that it does not attenuate the signal across the digital potentiometer." (https://www.maximintegrated.com/en/app-notes/index.mvp/id/161)

So it seems that the resistance values are determined by impedance, still, I'm not sure how to find out which values to use in my setup. So:

1st: How can I choose the identical resistor values properly for shifting the voltage? What would these values be in my setup?

2nd: Is there anything I can do to attenuate the sound leaking (when volume is set to 0) in my circuit?


texts: outdoor ultra sound positioning system robotic lawn mower

texts:
I have a dream to build robotic lawn mower that uses a positioning system, so that can cut grass once and effective. Building the robotic lawn mower is not a problem, but the navigation system is, so I came up with an ultrasound idea to locate the lawn mower on a field.

.

Basically the lawn mower will have mic mounted on it and will be listening for a signal from the speakers. There will be four ultrasound speakers in each corner emitting sound. At a start lawn mower will send by RF signal to first speaker to send sound and then will measure time and calculate distance. Then will do this process with second speaker and so on. When it will come to the end it will take all distance and calculate where exactly is it on field.

Now I have some questions will this system work outside and in greater distances like 100 meters X 100 meters? Which ultrasound speaker/mic is best for this job? Is there a better way to control position of lawn mower? Will this system ever work?


texts:
What is the time needed for discharging, when a charged capacitor is connected to an uncharged one in a circuit along with an AC voltage source?
Since a lot of people asked to give more information about my doubt, I was watching professor Behzad Razavis video on voltage doublers whose link is https://www.youtube.com/watch?v=uni-behIRN4 at the 54th min in this video the circuit is simplified into the circuit I have drawn, so in this even though one capacitor already has a charge over it, he said that the whole capacitive circuit works as a voltage divider for only the input voltage  and I think he ignored the voltage already present on the capacitor. Can any one look into this please?

simulate this circuit – Schematic created using CircuitLab


texts: How to fix an N-channel MOSFET that's always on, without using resistors

texts:
First things first: I'm very new to electronics
Getting right into it: I am trying to use an N-channel MOSFET as a LED strip light switch, with 12V at 1.5A supplied to the source and 4.5V from a battery supplied to the gate:

simulate this circuit – Schematic created using CircuitLab
However, I find that even without connecting the wires to my battery, my mosfet seems to allow flow from source to drain.
I'm hoping that someone may be able to tell me what is wrong and how I can fix it. The MOSFET I have is an FQU13N10L.
In addition I also have some particulars about the answers:

This circuit is just a test for a larger project which involves about 60 MOSFETs on a breadboard, which cramps my breadboard. I need a solution that does not involve resistors or capacitors that will cramp up a lot of space on my bread board;
Second, if needed I can change the 4.5V to be 3V or 3.3V by using different batteries;
Third, it may be important to note that the gate voltage of 4.5V is controlled by a GPIO pin on a PIC microcontroller. I do not know if that matters but I need nothing to go through the 4.5 lines that may hurt the microcontroller, which can not handle 12V.

I apologize if I sound demanding in this, I am just trying to be as clear in my purpose as possible, thank you for all your answers


texts: Is a Van de Graaff generator a voltage or current source?

texts: I'm currently studying basics of electrostatics and this question comes to me as any generator must be from either of the two types but which is the fact I'm not able to justify which. From its internal construction it does not simply fit in either of the two.


texts:
Trying to set up the initialization of the HD44780. Is this bad practice to have done it like this? Or is it going to try and send all those lines to LCD_DATA at once?

enter code here
always LCD_RW = 1'b0;

initial begin

LCD_RS <= 1'b0;

#15; //delay 15ms until set function

        LCD_DATA <= 8'b001101xx; //set 8 bit function
#4.2;
        LCD_DATA <= 8'b00001100; //turn lcd on, with cursor off and not blinking
#0.04;
        LCD_DATA <= 8'b00000001; //clear display
#1.53;
        LCD_DATA <= 8'b00000010; //Entry Mode Set, Cursor moves right and output does not shift
#0.04;
 end


texts: when and how is the machine language (binary stream) mapped to an existing instruction?

texts:
I'm trying to better understand the entire process of coding, which involves translating the higher level languages (c++/java/python and so on) into binary data that tells the CPU to execute operations based upon its native instruction set.

My question would be how, exactly, do the assembler instructions get translated into a sequence of 1s and 0s . Where does the mapping of a line of code like, say

addi $s0, $s0, 1

becomes a binary sequence based upon the opcode (addi) and so on. Where is the related mapping table (for assembler language to specific instructions) stored and how is it used to instruct the ALU part of the processor to, well, perform tasks?

I'm sorry for posing a great deal of questions, but I hope I'm making myself clear by expanding the issue.

Thank you!

Edit: I was mainly not aware of the loader's role (mainly the OS, in most of the nowadays programs) in the entire "compile-assemble-link-LOAD (and I have to emphasize on the next part: IN MEMORY)" process; that's what I found hard to understand - the whole memory storing process. Now it makes a lot more sense that, after the program is stored in memory, the required operations are performed by the CPU following the instruction set layout and the program executes it's intended task(s).


texts: How much does the gate charge of a MOSFET change over lifetime?

texts:
Is the total gate charge of a silicon power MOSFET changing over lifetime, as long as it is used inside its rated operation conditions?

I am using a SIHB6N65E (650 V, 600 mOhm) were the datasheet gives me a Qg of 24 nC typical, the max value is 48 nC. I am wondering, if I need to consider even higher charges than 48nC over a couple of years.


texts:
https://wiki.analog.com/university/courses/electronics/electronics-lab-19

Hi, I have some confusion about this (It's a stupid question).

Initially, the capacitor has no charge stored with S1 and S2 open.
S1 is closed and it now has charge C1Vin (after a while).
S1 is opened and S2 is closed. Now, shouldn't the C1Vin charge already on the capacitor get discharged to Vout? Why would the capacitor change it's charge stored to C1Vout? Or should I think of it as the charge passed to the output will depend on the Vout level? So it's possible that the capacitor isn't fully discharged and only C1Vout get's pushed out.


texts:
I'm quite often taking things apart to salvage the parts and use them in my projects. Right now I'm taking apart an old PC-power supply for a switch-mode lab-supply project.

The power-supply in question is Delta Electronics DPS-460DB A. Below is a picture of the transformer that I've tried to find info about. Essentially what I'm asking is how in the world does one find basic information on transformers, just like other components? This is not the first time I've pulled my hair out after surfing the "deep-web"(not THE deep-web of course) for info about a transformer and scored absolutely zero. Are almost all transformers custom parts and therefore lack a basic, public, datasheet? What's going on here?


texts: DIY Computer UPS - Smoothing DPDT Relay 80ms Cutover

texts:
I was shopping for a small UPS for my home networking lab closet; total load under 300w at 120v. But then realized I have a spare AGM car battery, 12v solar panel maintainer and 12-120v sine wave inverter. So I'm DIY home brewing up a project.

I sourced a 15A automatic transfer switch designed for this application - essentially a DPDT relay from what I can tell online. This is for line voltage loads and utility to backup inverter seamless switching. And I'll mount and integrate it to home electrical standards in metal boxes and EMT conduit on its own circuit. The 5v and 12v modem and wifi loads are getting 7812 and 7805 voltage regulators to keep them pure DC off the battery.

While I'm comfortable with the plug and play aspect of this design I am a bit concerned with the reported 80ms cutover time of the relay and power transfer. Goal being to keep a small server and network gear with internal AC/DC supplies from rebooting or struggling during any power flickers and utility to inverter switching.

Is there a capacitor or induction coil design you can help spec that I can place on the load side of this to help smooth this out? A big motor start capacitor or something would be my uninformed thought but don't have the EE skills to know what to do with it. I realize the computer power supplies likely have similar in their circuits but would like to help if I can. I will have TrippLite ISOBARs in line which I believe have induction coils in them.

Am I over thinking this at 80ms delay? Or is there a drop in big coil or cap I should integrate? I realize that commercial UPS designs probably have the inverter in use at all times with a trickle charger, so it's a constant AC > DC > AC flow but I'd like this transfer design to save wear on my basic inverter. Power outages are rare enough here I'm not battling ongoing outages or anything; maybe a few times per year. Any other holistic design aspects I'm missing? TIA!

tldr: Is 80ms too long of a cutover to keep a server and big network switch from rebooting?

Details on

Server PSU
Network Switch
Transfer Switch
Lead Acid AGM Battery


texts:
I'm moving into my car and I may need to wire up ventilation that doesn't depend on the engine running. So I found these case fans. However, because I'm not going to be using the car battery, I need a power source. I've been looking at a few power stations such as this one, but nowadays I tend not to trust obscure sellers on Amazon; regardless of the review rating, and even though the price is more than I want to spend it's far less than the going rate for the same specs, which screams to me "to good to be true".

Alternatively, I thought about just using rechargeable D cell batteries. The fan's max draw is 12V at 0.16A. Which is 1.92W each, assuming max load which I am. If I have 4 fans running while I'm sleeping, and let's assume a 10hr sleep, that is 76.8Wh or 6.4Ah at 12V.

I found these rechargeable D cells on Amazon. They're 10Ah each. If I wire up seven of them in parallel that should give me 70Ah at 1.2V or 84Wh; for anyone that knows what the usable percentage of that will be, that would be helpful. So it would appear that with six of these batteries fully charged, I'll have the energy to fully power the fans at full blast all night long. Is this correct? -- assuming they could run at 1.2V, which they can't.

Now, I'm going to have to step them up. And since we're assuming max load, that puts me at 7Ah at 12V. Will stepping it up reduce the energy enough such that I need to add more cells?

And finally, I'd like to be able to charge them while the car is running, transparently, i.e. without having to remove them from the circuit. Can they be both attached to the fan circuit and wired up to be charged simultaneously? Is running the fans off them and charging them at the same time possible?

So to summarize the important questions:

1) Are 7 of these cells enough assuming connecting them in parallel and stepping up the voltage to 12V?

2) Can they be both attached to the fan circuit and a charger at the same time?

That's all I got I think. Any help would be greatly appreciated!


texts: What are the low level programming waveforms for the Atmel ATF16V8B?

texts:
I want to program some ATF16V8B chips for a project. Naturally I don't have a programmer. No problem, I'll homebrew it with a Raspberry Pi.  It will be fun.

I only need one thing - I need the programming waveforms. Specific sequence enter programming mode, what voltage to apply and for what duration for each byte to be programmed, etc. All the stuff that they used to put in the datasheets before they replaced that whole section with "Program PLDs using a programmer".

Can anyone provide?


texts: PIC12F508 saving last count of compressor

texts:
I have this project which is aircon controller and I used PIC12F508 as microcontroller, the operation of this project is that the compressor will turn on for 1hr and after it will stop for 5 minutes and the problem is the pic will reset and it will count again for 1hr.

My goal in this project is that when the time the pic will reset I want to save the last time or count and when it turns on again it will count the remaining time within that 1 hr . I have researched the possible solution and EEPROM can help but I used PIC12F508 which does not have EEPROM, is there any other way aside from EEPROM but still I'll used PIC12F508? thanks

This the code I used MPLAB X and XC8 compiler:

/* * File: controller.c * Author: Jeaneth * * Created on July 30, 2016, 10:44 AM */
include
include

// PIC12F508 Configuration Bit Settings
include

// CONFIG
pragma config OSC = IntRC // Oscillator Selection bits (internal RC oscillator)
pragma config WDT = OFF // Watchdog Timer Enable bit (WDT disabled)
pragma config CP = OFF // Code Protection bit (Code protection off)
pragma config MCLRE = ON // GP3/MCLR Pin Function Select bit (GP3/MCLR pin function is MCLR)

void main()

{ for(;;)

{

    TRIS = 0b000000;
    GP0 = 0; //LED OFF
    GP1 = 0; //COMPRESSOR OFF
    GP0 = 1; // LED ON
    GP1 = 1; // COMPRESSOR ON
    runcomp();
    GP1 = 0; //COMPRESSOR OFF
    stop();

}

}

int minute()

{

for(int i =1; i>0; i--)
_delay(1000000);
return 0;

}

int runcomp()

{

for(int x =1; x>0; x--)
    minute();
return 0;

} int stop()

{ for(int y =1 ; y>0; y--) minute(); return 0;

}


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I have a  ESP32-WROOM-32D , it support I2c protocol but when i refer the i2c

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datasheet is given below.

which pins that support i2c protocols?

datasheet

thanks


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texts: Passive riser creating PCI-E lanes seemingly out of nowhere?

texts:
I'm trying to understand how it's possible that a passive riser has the following specs:

  Output: (3) PCI-E x16

  Signal: (1) PCI-E x16 (2) PCI-E x8

This would seemingly be creating 48 PCI lanes out of 32! And yes the vendor is insistent that it's a passive riser.

The riser in question is Supermicro p/n RSC-R2UW-2E8E16. Their riser matrix is here: https://www.supermicro.com/en/support/resources/riser

Thanks!


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