texts: How to use the BeagleBone's PRU with a modern kernel?

texts:
I am trying to implement a basic LED blinking program on the PRU. Up till now what I found are guidelines for old kernel versions (old in the sense 3.8 to 4.4 kernel version).

Details of my BeagleBone Green:

cat /etc/dogtag
BeagleBoard.org Debian Image 2018-10-07
cat /etc/debian_version
9.7
uname -a
Linux beaglebone 4.14.71-ti-r80 #1 SMP PREEMPT Fri Oct 5 23:50:11 UTC 2018 armv7l GNU/Linux

I have enabled remoteproc by editing the uEnv.txt.
I was following PRU hands-on labs by TI.
In one of the Reference by TI they have mentioned
"PRU firmware binaries exist in the filesystem in the /lib/firmware/ directory."
In /lib/firmware I am expected to see am335x-pru0-fw but it is not there.
Does it have any other method to enable or what I am missing here?


texts: Potential pitfalls/caveats for developing a stencil for solder reflow

texts:
I'm developing a project that requires ICs that are in a QFN package, some have a slug on the bottom of the IC. Since these are QFNs, I'm not interested in hand soldering these; so I'm leaning toward using the toaster oven method to solder the components in place.

However this is my first time doing this and I want to make sure that I'm aware of any caveats or pitfalls one may face when developing the stencil.

Just to clarify, I'm not confused on how to reflow once the components are placed; it's just I can't find any guides online of how to develop a proper stencil. Although comments to the entire process are also welcome.

Currently I'm developing the layout in EAGLE, and I'm looking to order the PCBs from PCB Pool, a company that will provide free stencils with an order.

In EAGLE, the layer that dictates the stencil pattern is the "cream" layers (as far as I understand).

One of the cream layers for my QFN looks like this:

The IC is 7mm x 7mm for perspective.

But I'm told that for the slug in the middle. It shouldn't be a giant square for the stencil, because it will be too much solder paste and when you reflow, it will short all the pins. Therefore, one must alternatively use smaller "holes" (example in blue) on the slug to limit the amount of solder paste is placed on the pad.

I personally never would've predicted this caveat so I'm glad I was notified of this potential issue.

Should I also restrict the solder on the pins as well? I don't want to risk shorting those.

Question

Is this right to place the holes? What other potential caveats or pitfalls one might face when attempting to develop a proper stencil?

Edit

Aha, according to answers so far, the cream should not be the size of the pads. By going to

Design Rules => default.dru => Masks

You can adjust the size relative to the pad. I was just messing around but here's an example:

Obviously the slug is wrong, but I can manually layout the cream boundaries for that particular "pad".


texts: Why does Vbe decreases with the increase in temperature for an n-p-n transistor?

texts:
Microelectronics Circuits by Sedra/Smith says,

  As in silicon diodes, the voltage across the emitter–base junction
  decreases by about 2 mV for each rise of 1°C in temperature, provided
  the junction is operating at a constant current.

$$i_c = I_s e^{\frac{V_{BE}}{V_T}}$$

$$\implies V_{BE} = V_T \ln\left( \dfrac{i_c}{I_s}\right)$$

$$\implies V_{BE} = \frac{kT}{q} \ln\left( \frac{i_c}{I_s}\right)$$

It can be clearly seen that when \$i_c\$ is constant, \$V_{BE}\$ is directly proportional to temperature.

Then why does the voltage decreases instead of increasing?


texts:
1.I need a sensor for measuring the electrical power without cutting the isolation of a wire. Is there a such sensor?

2.Is it possible to use the magnetic field of a wire(220v) to power a very small circuit? Where I can find such a device?

Thank you!


texts: Circuit with one voltage source, calculating voltages at nodes

texts:
So here's the problem, I made the assumption that D1 and D2 are short, whereas D3 is an open, and combined the 500 ohm resistors in series:

But my question is, why is there no Voltage across the 500 ohm resistor that is on the rightmost side? And also no Voltage across the highlighted resistor, isn't it parallel with 1K, and should therefore have the same 20V of voltage?

When I do calculations, there should be voltage there.

So first, you combine the 1k and 500 ohm resistors, which are in parallel.
$$\frac{1000 \cdot 500}{1000 + 500} = 333.3 Ω$$

Voltage across parallel resistors is the same, voltage across combined 333.3 Ω is 20V, therefore 20V is also across the 500Ω resistors into which current "I" flows in in the first picture.

"I" current = $$ \frac{20V}{500Ω}  = 40 mA $$

40 mA verifies that D1 is indeed a short. Diode conducts, and current is more or equal to 0 across a diode.

Voltage across D3 is (0 - 20V) = -20V

Now to find "V", at the positive side of the 500Ω resistor, it's -20V, at the negative side, it's - 20V because +20V is the voltage across the 500Ω resistors that's kinda between D2 and D3 in first picture.

So when calculating "V" it's (-20V - -20V) = 0V

Correct? But there is in fact voltage across an open, right? Just not across the resistor on the rightmost side.


texts:
In l293d datasheet i found that term "High-Noise-Immunity" in the features. so what does it mean?
i didn't find anything explain what it means in the internet


texts:
I'm trying to refurb a old pcb taken from a 30 year old cars indicator unit, it's a pretty simple pcb besides one component I'm unable to identify:

You can see it attached to the back here before I took it out and cleaned it up

Anyone know what this is and where I could source a replacement?
Thanks.
EDIT:
Pictures of the back:
Before I started to clean it up:

After:


texts: How to ensure my device never powers down when using two batteries (Hot swapping batteries)?

texts:
I have a device I am powering using two batteries. My constraint is that I can never let the device power down. For instance, I have multiple cameras that needs to stay on 24/7 but their isn't a battery that can last that long, therefore my goal is cascade multiple batteries and be able to swap them out without powering down the device.

My current solution is to use two batteries in parallel, one with a higher voltage (Power source 2, 14V) than the other one (Power source 1, 12V). When I need to swap my main power source (Power source 2), would the second battery keep the device running?

In other words, Power source 1 should power the device during the swap. Then, when power source 2 is reconnected, it should power the device, and at the same time recharge power source 1.

Batteries I am thinking of:

Power source 1: https://www.amazon.co.uk/gp/product/B00BWW9WRM/ref=ox_sc_sfl_title_1?ie=UTF8&psc=1&smid=A17M1OH9UAKGE7

Power source 2:
https://hobbyking.com/en_us/multistar-high-capacity-4s-20000mah-multi-rotor-lipo-pack.html?___store=en_us


texts: KiCAD: Ideal directory to store custom footprint

texts:
I downloaded a footprint for one IC from the internet.
It contained a .kicad_mod and a STEP file.
I have a directory where my project lives, so inside there are .pcb, .pro, .sch file and so on....
When i imported the library for my new foorprint, the new footprint's location is in a different directory of where my project lives..
Considering i will send my files to a board house for pcb fabrication, should i place my custom footprint inside the folder where my project lives? Or it doesn't matter where my footprint is located, and i can send them my files normally?


texts: Displaying Characters In Verilog With VGA

texts:
I'm taking a intro to ECE course as a CS student and for a final project we are to design a game coded in Verilog using the VGA display on a DE1-SoC board.

I decided to create a hangman game but I am stuck on how to display characters on the VGA screen. I've come up with three options: make the alphabet and underscores as images and upload them to the VGA display, use some sort of character buffer built in (I found info about that part online but I can't find any examples of using it) or just draw each character pixel by pixel.

The pixel by pixel way seems extremely complicated but at the same time, there are almost no resources that I could find about the other two methods. Can someone tell me which way would be the most efficient and easiest to work with for my game? We only really learned about displaying shapes in class but I'm not sure drawing each letter is the most efficient method.


texts: AVR: Using ATmega328 Timer1 to create a delay

texts:
I am having some trouble wrapping my head around this, and it might just be some small error somewhere, that I keep missing .. but as it stands, I am trying to create a hardware "delay" that can run at the same time some code executes.

For practise purposes, I am simply trying to blink an LED at PD4 at an interval of 1 second.

I have used the following formula to determine the prescaler, and the value of the Output Compare Register A (OCR1A):

Using a prescaler of 256, I get a value for OCR1A of 62499:

Looking at the registers TCCR1A and TCCR1B in the datasheet, I set the Waveform Generation Mode bits (WGM) to use CTC and the Clock Select bits to use the 256 prescaler.

Now, in my main function, I am starting of by turning on the LED, then calling my function that should start the timer. I am then checking to see if the overflow flag has been set in TIFR1, and if it has, I am turning of the LED and writing a logic 1 to TOV1 to reset the overflow flag.

int main(void) {
   DDRD = 0xFF;
   PORTD = 0x00;

   while (1) {

      // Turn on LED at PD4
      PORTD |= (1 << PD4);

      oneSecondDelay();

      // Checking to see if the overflow flag has been set
      if (TOV1 == 1) {

         // Turn off LED at PD4
         PORTD &= ~(1 << PD4);

         // Set 1 in the Output Compare A Flag to reset the overflow flag
         TIFR1 = (1 << TOV1);
      }
   }

   return 0;
}

In my function I start off by setting OCR1A to the value that I calculated earlier.
I then set the bits in the TCCR1B register that needs to be set for using the specific prescaler and CTC mode, and I then create a loop while waiting for the overflow event to happen; which I envision should take one second.

void oneSecondDelay() {
   // Set the target value to 62499
   OCR1A = 0xF423;

   // Set prescaler to 256 and start the timer
   TCCR1B |= (1 << WGM12) | (1 << CS12);

   // Waiting for the overflow event
   while ((TIFR1 & (1 <<  OCF1A))) {

   }
}

TLDR: Now the problem is that no matter what I can dream up, the LED is just constantly turned on, and I am not sure if I am setting the the wrong values in the registers, or if I am just having some brain farts?


texts: drilling pin header holes when exact drill size not locally available

texts:
I checked all of the hardware stores in my area and I can buy 1/32 (~ 0.79mm) and 3/64 inch (~ 1.2mm) drill bits. No source in my area carries bits which are between those two sizes which would then be the perfect hole size for various pin headers (like the IDC plugs).

Rather than me wait 4+ weeks in hopes that I can get sufficient perfect drill bits online at the right price (from china?), I'm looking for another feasible (if possible) way to make my own sufficient size hole for the IDC plugs to fit in. I tried fitting them in a 1/32 inch hole and that doesn't work. If I use 3/64 inch, the plug fits loosely and part of the supporting track is gone due to the hole size. That's why I'm interested in a hole size that's in-between, something like 1mm in size.

The only thing I could think of which can rather be dangerous is to use a mini motorized drill and move the motor so the drill (while it's spinning) is at a 20 degree angle relative to the board itself and then keep adjusting the motor so that the drill points at every direction at some point. Another drawback to this method is that the drill bits can easily break.

I also looked into sawing the PCB with the drill bit. I managed to do this before with bigger drill bits when I didn't have the tools in order to create the support holes for the serial port. But I'm afraid if I do this with small bits, I'll break them.

So my question is, other than waiting 4+ weeks online for a chance to receive drill bits in the mail after ordering them, is there a good way that I can use to create a 1mm hole given that the closest bit sizes available to me are 1/32 inch and 3/64 inch?


texts: "Leeching" clock information from cell towers

texts: I understand that cell base stations transmit very accurate time signals among other things. Do you need a SIM card and an account to receive this information, or is it something you can "leech" with a GSM/CDMA module without establishing a connection?


texts: Finding the correct crimping tool for your contacts

texts:
After choosing a Molex connector (C-Grid III 90142 series housing) for my PCB

I ordered the corresponding crimp contacts.

I assumed I would be able to crimp them using my Knippex crimping pliers.

(source: knipex.com)
I've used the knippex plier a lot for standard crimp pins in Dupont housing.

But I'm having some trouble with these C-Grid III series contacts. It seems that Molex has a (very expensive) tool specifically for the C-Grid III Series.

Am I to assume that some contacts can only be crimped by the manufacturers tools ?
I assumed that a universal crimper would be able to crimp anything you throw at it.
Are there standards when it comes to these crimp contacts (so that universal tools can make use of it) ?


texts: What kind of solar panel is required to keep a mobile alive forever?

texts:
I want to build a webcam from an old mobile and I want it to be solar powered.
The phone use a 3.7V lithium-ion battery of 1500mAh capacity. The phone last 24h hours on one charge.
So if I'm right, it is 3.7V * 1.5Ah = 5.55Wh
I found some solar panels that claim to give at 5V a maximum of 260mA.
5.55Wh / (5V * 0.26A) = 4.26 hours needed to charge the battery at full capacity.
In a sunny day, this will be done quite easily. But on a rainy day or cloudy day, how much mA should I expect from the solar panel? Do I need to have a battery that will sustain many cloudy days in a row? What can I do to be sure I will never run out of battery?
[Update]
Here is the number of hours of sun of the actual location:

And the cloud cover information:


texts: MPLAB Program won`t recognize xc.h header

texts:
I am trying to learn how to program my PIC microcontoller (specifically a PIC24FJ128gc010 MCU), but having some trouble with what should be a very simple program.
I can't declare any pins as outputs or inputs, or do anything really because the
#include <xc.h>
has a yellow underline. I control clicked it to investigate more and MPLAB says that the header file for my specific microcontorller cannot be found, but I was able to find it in my xc16 installation directory (C:\Program Files (x86)\Microchip\xc16\v1.50\support\PIC24F).


texts:
I want to make software that would be capable of solving electrical circuits.

Something like CircuitLab or LtSpice.

I have a good background in electrical circuit solving methods and programing as well. But I struggle on combining the two of these.

To be specific my question consists of two parts:

Are there any topics that direct to this thematic i.e. programming algorithms for solving electrical circuits?
Are there any open source software already written that I could use as reference?

I did do research before posting this question here, but didn't find any satisfying results, so I am asking this question in hope that I can benefit from experienced users in this topic from this community.


texts:
So I am designing my first pcb and using an AT32ucb µc. It says in the data sheet it supports usb interface but on the pin-out listings and functions I can only find usb-id and usb-VBOF. So what am meant to use for the data in and out? I'm thinking like the tx and rx of the usart perhaps but would like clarification on the issue and to know if I am totally off.datasheet below pinout starts around page 7.

http://ww1.microchip.com/downloads/en/devicedoc/doc32059.pdf


texts:
I am designing an RS-485 interface with STM32F0xx series MCU.

The scheme uses USART RX interrupt.

I am wondering, if I set up the baud rate as certain value(for example, 9600), is there possibility that the interrupt fire more often than every  one character time due to noise or some other disturbance in the RS-485 interface?

I am worried that if above happen, it might lock up the MCU and prevent it from doing other tasks.


texts: Using FFT to calculate derivatives of polynomial

texts:
I know that there are several posts about FFT and derivatives, but I don't get it. I also tried in mathematics but no answer.
The formula is:
$$
f(t)→\hat{f}(ξ),f′(t)→2πiξ\hat{f}(ξ)
$$
First, I don't understand what ξ is. When I learned FFT as much as I poorly understand it, we compute it at different complex roots.
Let's take an example, I want to calculate the derivative of the polynomial:
$$
P(x)=−1+2x+5x2−4x3
$$
The analytic solution will be:
$$
P′(x)=0+2+10x−12x^2
$$
Now, I take the FFT of P(x) and get:

What should I multiply this by in order to get the values that by using FFT−1 will get me to P′(x)?


texts:
I want to have a region in my PCB without solder mask while the other regions should have solder mask. I am not sure how do I do it in Altium? To be precise I want say a custom shape solder mask free region in my PCB.
This i can use for tinning as I want more current conductivity.
For such areas is it good to have many vias as I am drawing current from middle layers. Imagine I tinn it and air is trapped in vias. Will this have an adverse effect on my PCB ?

Also, should I first assemble all components and stuff and finally tinn the regions mentioned above or is it otherwise ?


texts: In an ideal transformer circuit, how is power transferred?

texts:
If I have a system of circuits like this:

where Circuit 2 is providing power the Circuit 1, where does the energy come from? Do the inductors store energy? If not, how is power transferred from the Circuit 2 to Circuit 1?

I initially thought that inductors won't store any power and the power must come from the mutual inductance. Am I correct in thinking that?


texts: Altium: Place a component "inside" some other component

texts:
I have a problem with Altium, and unfortunately, I don't even know how to google this one.

I have a board (Switch board) that is connected to another board (User interface board) via a board-to-board connector. These two boards are additionally fixed using PCB spacers. Footprint of the Switch board looks like this:

This footprint is used (placed) on the User interface board, and the problem is that Altium sees this component (Switch board) as a rectangle, and it doesn't allow me to place anything below it (on User interface board). To be more specific, I can't place anything on the User interface board that is within the red rectangle:

However, the only place that is occupied by this component (Switch board) is the connector and the two holes for PCB spacers. How can I fix this?

Thank you in advance!


texts: Import alternative stepper motor in my fritzing sketch

texts:
I have a question, which is on the usage of Fritzing. I'm trying to sketch up a robot I have made. I want make a proper sketch, which I can send to a manufacture.

I found a stepper motor used in this sketch. I cannot find the same stepper motor in the core package of components, that is default with the Fritzing download.

Could someone tell my were to find these extra components and how to import them into Fritzing?

I know the question is not directly about electrical engineering, but I consider it to be an important part, so I still ask the question here!


texts:
I am using Altium designer 15.

How can you rotate a component by 45 degree in PCB mode?

Regards,
MathieuL


texts: Using a GE 65W Boost Converter adequate to charge a 13s6p Lion BMS

texts:
I have a 13s6p Lion array with BMS I want to charge from a 12v source.

This is the Arduino Lion charger project I am attempting

After letting the smoke out of an undocumented Chinese boost converter, I was wisely directed to Mouser where I bought a GE 65W Boost Converter (8Vdc –16Vdc input; 32Vdc to 54Vdc output; 65W Output power (max.)) for the same purpose. Very compact.

Boost converter datasheet

I attached a variable pot to program it's output voltage and managed to tune it to a desirable output of 54v.

My QUESTION regards how to deal with a dramatic voltage drop to 34v when connected to the BMS. I am hesitant to adjust the voltage programming. The resistance adjustment can actually program to module to produce voltage much higher than 54v when there is no load.

Q: Is it safe to adjust it's output (that drops to 34v) back to the desired 54v output when applied to the load of my un-documented BMS?

I know the batteries can be charged at much higher current than I am using (12v at 3 amps input). For 54v, at 65w, the booster is rated for just over an amp which is within the individual battery's tolerance. It seems like it would not be enough however since I have 6 18650's in each cell.

I have ordered an inexpensive 54v charger which is yet to arrive but I would prefer to use this GE module in conjunction with an Arduino and INA219 GY-219 Bi-direction DC Current Power Supply Breakout Sensor Module.

If my boost converter can't keep up a trickle charge I don't want to waste my time.

I am unfamiliar with some of the features for which I would appreciate some clarification (indicated with (?))

Features:
▪ 8Vdc –16Vdc input
▪ 32Vdc to 54Vdc output
▪ 65W Output power (max.)
▪ Output voltage programmable from 32 to 54Vdc via external resistor
▪ Tunable LoopTM to optimize dynamic output voltage response (?)
▪ Power Good signal
▪ Output over current protection (non-latching (?))
▪ Over temperature protection
▪ RemoteOn/Off
▪ Ability to sink and source current
▪ Support Pre-biased Output (?)
▪ Optimized for conduction-cooled applications
▪ Small size: 27.9mm x 11.4mm x 8.5mm (0.8% the size of Chinese model)

As I interpret the datasheet, the "Tunable Loop" feature is intended to handle fluctuations in current draw. I don't know if this is required to fix my problem.


texts: Need Help In Creating and Debugging a 8Mhz CLK Circuit

texts:
I want to create a CLK generator circuit that will work at 8Mhz.
I'm following this design (from http://www.electronics-tutorials.ws/oscillator/crystal.html):

My crystal is 8Mhz HC49/US, with 20pF capacitance as described in the website I bought it from.

I'm using R1 = 10Mohm , R2=1Kohm , and as for C the smallest I had was 150pF so I used 6 of them in series which should give 150/6 = 30pF .
My inverter is a 6 input buffer NOT gate from TI (cd40106b) , I'm using two of its gates for the circuit (AMP + buffer).

After connecting it all, and hooking up my (PC based) oscilloscope, I saw I'm only getting a 1.5Mhz signal , which was very far from a square wave I was expecting - more of a triangle kind of waveform.
Then I removed the crystal from the circuit, and the waveform stayed the same, so I'm obviously doing something wrong here as I'm just seeing the RC circuit oscillating.
I've replace the crystal with two others and got the same results.
The NOT gate should just fast enough for this circuit ,working at VDD=5V , transition time is typically 100nS and up to 200nS and I'm no way near this with my results.

I think I'm using the correct values for R2 and C but I'm not sure.
How do I calculate the correct R and C values to use for my circuit? Could it be the reason for this behavior?
I've also tried to assemble a circuit using CD4060 (counter) like the one from the comment.

to see if the problem is coming from the inverter but I still can't get the input frequency to be 8Mhz.
What can I do to further debug this?


texts: How could I go about determining the component values of the described filter? I know what they are, but not how to get them using proper formulas

texts:
The filter in question takes a mono signal of amplitude between 5 mVp and 200 mVp, and filters the signal based on the frequency.  The potentiometer that leads into the inverting input of the op amp determines how this signal is ultimately affected.  Depending on which extreme the potentiometer is dialed to, the circuit should amplify either low or high input frequencies, while attenuating the other end of the frequency extrema.  When the potentiometer is dialed to the opposite extreme however, its behavior inverts; that is to say that if it amplified high frequencies by a voltage gain of A1 and attenuated low frequencies by A2, it should now amplify the low frequencies by A1 and attenuate the high frequencies by A2.  When the potentiometer is set to exactly 50%, the gain should be -1, as no filtering is actually being done.

For this specific purpose, I need A1 to be 3 and A2 to be 1/3, i.e. A2 = 1/A1.  I have values that I obtained somewhat coincidentally that achieve this behavior, which are shown in the circuit below.  My question, finally arises from my lack of understanding of how to actually approach this circuit.  It's almost like a band-pass filter, but not quite as one of the ends will amplify the voltage by the same amount it would have been attenuated.  That's pretty much where my confusion lies.  In this schematic, the circuit is designed to work towards the gains previously described, and is built to handle frequencies ranging from 20 Hz to 20 kHz.

simulate this circuit – Schematic created using CircuitLab

I know that:
C1 = C2
R1 = R7
R2 = R6
Due to the gain of the circuit being the impedance of the right hand divided by the impedance of the left, and at 50% of the potentiometer, this must equal 1.  If the potentiometer is split 10k and 10k for both impedances, then in order for it to equal -1 the above relationships must hold true.

R3 is always a 20k potentiometer.  However, as far as the other components go, they can vary so long as they fall in accordance with those relationships.  My issue lies in that I'm not quite sure what to do next to get the answers I came up with.  I think I maybe have to compare how the expression for gain changes at each extreme with the expression for a gain of -1, but I'm not sure.  If anyone can walk me through this, as well as correct any incorrect assumptions I've made, it would be a great help.


texts: What is the difference of cutoff frequency to -3dB frequency in an active filter?

texts:
This table shows the K values of a particular Q value on a Sallen-Key active filter:

Why is the \$K_c\$ value (cutoff value) different from \$K_3\$ value (-3dB value) on all Q's (except 0.707 which is a butterworth approx) ?
I mean, isn't the cutoff frequency pertains to the -3dB frequency? What is the difference of a cutoff frequency to -3dB frequency?


texts: What is the typical pin designator convention for footprints?

texts:
Altium (and I'm sure other PCB Design software) supports both numeric and alpha for pin designator. This is not the pin display name, like you would see on a schematic. This is how the footprint will align with the schematic symbol.

I've used pin numbers to align symbols to footprints in the past, but I'm curious what the general practice is - pin numbers vs pin names ?

Are there any benefits (short term or long term) to choose one or the other ?


texts: What does it mean when we say signal is 20% modulated or 40% modulated? Need detailed explanation. Also i want to know what happens when signal is overmodulated?


texts: Is there any dynamic antenna for varying frequencies in 1 GHz to 10 GHz?

texts:
I want to use an antenna for my project and want to use it in the frequency domain: 1GHz to 10 GHz. Is it possible to use a single antenna with dynamic input range?
I read about reconfigurable antenna's but couldn't find anything concrete on it.


texts:
I am looking for Transformerless power supply design. I have MCU 5V. and would like to drive 12V/24V relay with single LED.
i have 4 pots 10K/200k for timing
So i prefer 230VAC to 12V/24Vdc output with min 0.5A current.5v 500mA

Power supply


texts: How to connect an industrial 24V sensor to a 3.3V input Raspberry Pi pin?

texts:
Background

I want to read how efficient an industrial manufacturing line is without tampering with the PLC code. The simplest solution I can think of is using a Raspberry Pi, thus creating an isolated OEE information gatherer. I know this is not meant for industrial environments, but it is only for proof of concept.

Question

I have a 24V SICK WTE11-2P2432 industrial sensor with the following connection diagram. Datasheet here.

I need to connect the output from pin 4 to a Raspberry Pi 3 Model B. Given that I am using the standard I/O pins for the Raspberry Pi, what is the best way to do so? Maximum voltage on an input GPIO pin is 3.3V.

I am trying to detect 1 part per second.

I am trying to avoid voltage dividers and building PCB's.


texts:
I have almost no electrical experience, so I apologize about the simplicity of the question in advance.
I have 4 resistors a diode and a transistor in a 22mm x 14mm x 8mm enclosure.
My concern is that the resistors will get too hot considering the tight space.

Red/Blk wire is 12volts and Brown wire is Ground.

Schematic:


texts: Where can I find good tutorials on sensor circuit design?

texts: I'm looking for tutorials/explained examples on circuit design in general, but specifically on using various sensors.


texts: My serial receiver verilog implementation does not act as expected

texts:
I have coded my own implementation of a serial receiver. It will work for incoming data at a baud rate of 115200.

Here's my code:

module my_serial_receiver(
    input clk,
    input reset_n,
    input Rx,
    output reg [7:0] received_byte,
    output reg byte_ready
);

parameter IDLE = 4'd0, BIT_0 = 4'd1, BIT_1 = 4'd2,
                BIT_2 = 4'd3, BIT_3 = 4'd4, BIT_4 = 4'd5, BIT_5 = 4'd6,
                BIT_6 = 4'd7, BIT_7 = 4'd8, BYTE_READY = 4'd9;

reg [3:0] state = 0;
reg [7:0] baud_rate_clock = 0;

always @(posedge clk) begin
  if (baud_rate_clock == 8'd216) begin
    baud_rate_clock <= 0;
  end
  else begin
    baud_rate_clock <= baud_rate_clock + 8'd1;
  end
end

assign baud_tick = ~|baud_rate_clock;

always @(posedge baud_tick or negedge reset_n) begin
    if (~reset_n) begin
        state <= 0;
        byte_ready <= 0;
    end
    case(state)
        IDLE: begin
             byte_ready <= 0;
             if (Rx == 0) state <= BIT_0;
        end
        BIT_0: begin
           received_byte[0] <= Rx;
           state <= BIT_1;
        end
        BIT_1: begin
             received_byte[1] <= Rx;
             state <= BIT_2;
        end
        BIT_2: begin
             received_byte[2] <= Rx;
             state <= BIT_3;
        end
        BIT_3: begin
             received_byte[3] <= Rx;
             state <= BIT_4;
        end
        BIT_4: begin
             received_byte[4] <= Rx;
             state <= BIT_5;
        end
        BIT_5: begin
             received_byte[5] <= Rx;
             state <= BIT_6;
        end
        BIT_6: begin
             received_byte[6] <= Rx;
             state <= BIT_7;
        end
        BIT_7: begin
             received_byte[7] <= Rx;
             state <= BYTE_READY;
        end
        BYTE_READY: begin
             byte_ready <= 1;
             state <= IDLE;
        end
        default: state <= IDLE;
    endcase
end

endmodule

Here are my simulation results:

So basically, the simulation is reacting exactly how I want it to.

I sent 0x55, 0x74, and 0x40, and that is when byte_ready is asserted, so I know that's correct.

Furthermore, my baud_tick signal is properly asserted 115200 times a second.

Over all, my simulation appears to be perfect.

When I actually program the FPGA and connect the Rx line, nothing happens (as in, no LEDs are flashing). I have coded it such that the 8 LEDs take on the values of the 8 bits of the byte. I have tested this method before with someone else's implementation and it worked perfectly for testing the module.

I have even used the SignalTap logic analyzer and confirmed the incoming Rx data is correct, and the baud rate is correct with + or - 0.5% error.

I have no idea what to do from here. Any suggestions?


texts: What is the schematic symbol for resettable fuses?

texts: I have seen symbols for one shot fuses and circuit breakers, but not for resettable fuses which reset themselves when the fault goes away. What is the recommended schematic symbol to use?


texts: How to create hamming distance using xor and adders?

texts:
My goal is to create n bit hamming distance circuit but using only xors and adders. I do understand that xor is required to compare two bits, but once I have all comparison results, how I can add them using adders to get the total count.

If the result of XOR is ABCD (four bits) then one approach can be:

A ADD B = S_0,C_0
C_0(S_0 ADD C)= S_1,C_1
C_1(S_1 ADD D)= S_2,C_2

However, if we set all A,B,C,D to 1 then this gives 1000 which is not equal to 4. Can you please let me know which part I am missing in the solution? Thanks


texts: Replacing 1.2v Ni-Cd battery with supercapacitor

texts:
I have a trimmer which uses 1.2V 600 mah AA battery. Is it possible to replace it with a super capacitor ? Reason to replace is that the trimmer takes about 5-6 hrs to fully charge itself but the super capacitor (SC) can be charged in few seconds.

I googled a lot ( and still trying to find ) if this was feasible and what specification SC I would need. From what I found I google I would need a SC with a voltage higher than charging voltage of trimmer so I guess 2.7v SC will be enough but how do I find how much Farad capacity  capacitor I would need ? Can I connect the SC directly to the positive and negative terminals where I insert the Ni-Cd battery ? Will I need any stabilizer or anything of such short to stabilise the output of capacitor. How long will the charge last ? Can it last enough so that the trimmer can do its job i.e. trim the beard ?


texts:
Hi,

I've a question, what is the role of the capacitor C in this circuit? What should be capacity of this element, and how can i find/calculate the voltage gain of this circuit ? Thanks for reply :)


texts: Using a microcontroller to produce a shock

texts: I am currently working on a project for school and we are creating a mock pavlock although much simpler. We basically want a microcontroller to be able to keep time and shock at specific times. We currently have the RTC and microcontroller working together, but we are a little stumped as to how to use the controller to produce the shock. I've been reading other posts about how to produce a shock, but how would we be able to adapt that circuit for a microcontroller? We are also using a lipo battery so it can only produce a max voltage of 3.7


texts: What is the difference between Eplan/Elcad/Autodesk Electrical vs Altium/Eagle/KiCAD?

texts:
Recently I came across the programs Eplan, Elcad and Autodesk Electrical. As far as I can tell, they are used to draw schematics. Is it possible to do the same thing with a PCB design software like Altium, Eagle or KiCAD? With the latter three it's also possible to draw schematics and do an ERC check. Am I missing an important feature of the former three programs?
Many thanks in advance!


texts: Confirming validity of schematic for dual stepper motor PCB

texts:
I'm trying to make my first schematic for a PCB that would sit atop an RPI and allow for control of two stepper motors. I have an LM2576 to take 12v from the motor supply and step it down to 5v for the RPI, and I took the schematic from Pololu's DRV8225 as the driver for the motors.
I did however modify a couple of things, such as add a single capacitor to act as voltage spike protection for both the LM2576 and the two DRV8225 ics. I also tethered reset and sleep to 5v on the board, and enable as I would want to keep the driver running so long as the board is on.
I am just very worried that if I order the PCB there's no turning back, so I want to make sure I have everything right before I start. My biggest ask is that on Pololu's schematic for the DRV8225, they have this circuit separate from the ic off to the side, I assumed that if it changed the power supply, I would only need one per board despite having two of the driver ics.
Here is my schematic so far, which I have designed in easy eda

And here is a link to a pdf if this is too blurry
I just really want to know if this would work with the way I have it set up, I'm sorry if some of my design (or all of it) is unorthodox in methods, this is my first time so go easy on me aha.


texts: Assigning a 16 bit number to two bytes of a buffer

texts:
Currently I have this out buffer that I am assigning values to like this:

char out_buffer[OUT_DATA_SIZE];
…
out_buffer[7] = 0xD0;
out_buffer[6] = imu_union_ACC_Y.byte_data[1]
out_buffer[5] = imu_union_ACC_Y.byte_data[0];
out_buffer[4] = imu_union_ACC_X.byte_data[1];
out_buffer[3] = imu_union_ACC_X.byte_data[0];
out_buffer[2] = imu_union_ACC_Z.byte_data[1];
out_buffer[1] = imu_union_ACC_Z.byte_data[0];
out_buffer[0] = 0xC0;

I would like to assign a int16_t value to two of the bytes. The variable name is a_y_filtered. So essentially instead of sending out x,y  and z. I'd like to send x, y, and y filtered.


texts: Signals and Systems - Taking Integral of Unit Step Function

texts:
I am a taking signals and systems course and my professor posted the solutions to our latest homework and I am trying to understand one of the steps. Below is the solution. Bracketed in red is what I am trying to understand.

Why does u(t) disappear when you move the bounds of the integral to infinity to zero? I am just trying conceptually understand why instead of just accepting it as fact.


texts: Boosting output current of mosfet Driver IC

texts:
Continuing my work on a half bridge driver . I faced problem of slow Turn on/off of the mosfet due to the "relatively" low output current of the IR21844 mosfet driver (1.4A source and 1.8A sink).

Using the equation I=Q/ton . I found that for the total gate charge of 2500nC (5 mosfets in parallel) switched at 20khz , with the desired Ton 0.5us . I would need 5A.

Searching for a solution lead me to IR application note 978 containing this circuit

I was thinking if it can be simplified ( 4 transistors per output is too much space for me ) maybe something like 1  STS01DTP06 Or TC4420 on each output (HO and LO) although this is not the purpose of this IC. I am also open for other methods or suggestions that doesnot involve changing the main gate driver.

thanks in advance !


texts: Why does a faster clock require more power?

texts:
If you overclock a microcontroller, it gets hot.

If you overclock a microcontroller, it needs more voltage.

In some abstract way it makes sense: it is doing more computation, so it needs more energy (and being less than perfect, some of that energy dissipates as heat).

However, from a just plain old Ohm's law level electricity and magnetism, what is going on?

  Why does the clock frequency have anything to do with power dissipation or voltage?

As far as I know, the frequency of AC has nothing to do with its voltage or power, and a clock is just a super-position of a DC and a (square) AC.  Frequency doesn't affect the DC.

  Is there some equation relating clock frequency and voltage or clock frequency and power?

I mean does a high speed oscillator need more voltage or power than a low speed one?


texts: Can a high current switching load damage a bench power supply?

texts:
I am powering an electronic speed controller (ESC) driving a BLDC from a bench supply capable of supplying 40V at 128A.  The maximum load the ESC presents is 42A.
The wires from the supply to my setup are about 3 feet long (long!), and thus I added a capacitor bank at the ESC end to protect the electronics on the ESC, since the inductance of the wires will create large voltage spike at the ESC. I use the supply's sense lines to ensure I regulate the voltage at the ESC end.
The supply started to misbehave recently, after months of use testing my ESC design.  Initially, the ammeter on the supply stopped working. Now, I believe the supply is having difficulty regulating when the switching current load is high.
Is it possible that voltage spikes (maybe capacitor bank is undersized - need to confirm this) at the ESC supply input damaged the sense lines and control circuitry in the bench supply over time? Is there typically protection circuity to limit voltage excursions on these lines?
I found the the manual for this old Agilent 6684A supply, but at first glance, I didn't find these types of specs --I'll look more carefully.  Are there typically specs provided on what sense lines can take, or how fast the supply responds to step changes to the sense line voltages, etc?
I have another supply to use, but I don't want to kill it as well overtime if I could be potentially damaging it testing the ESCs.


texts: Differential Amplifier's Unusual Behavior

texts:
This circuit is made of one differential BJT transistor pair and voltage-amplification stage with negative feedback.

simulate this circuit – Schematic created using CircuitLab

About this circuit for DC conditions. Current through current source equals 2 mA and collector current through each differential transistor pair equals 1 mA. Current into base of VAS (Voltage Amplification Stage) is 20 uA and therefore collector current through it is 10 mA. For loop-gain ratio I firstly decided to be 11 (therefore PF1 was 2,2 kΩ) but then added 100 kΩ potentiometer to it to vary its gain in wide range.

As we speak about small signal analysis or AC conditions if this circuit, things here get a bit more stranger:

1.) Referring to this Bode plot here . The low frequency gain roll-off starts at already 2 kHz! Since I am interested mostly in designing audio amplifier this LF gain roll-off began here to quickly - I was aiming for at least 100 Hz or at 10 Hz of LF gain roll-off if possible. What should I do about it? I did put 100 pF compensation capacitor for improving amplifiers gain bandwidth. (I sampled some values here: (at 100 mVpp input sine) 2 kHz -> Vout = 1 Vpp, 1 kHz -> Vout = 0,88 Vpp, 100 Hz -> Vout = 0,18 Vpp)

2.) Many of you know that, if the closed-loop gain of amplifier is high, that means we have smaller phase margin and greater influence of overshoot/undershoot and ringing at the output (we can see that from square input signal applied to it). And also, if the closed-loop gain of amplifier is low, that means we have larger phase margin (improved stability) and smaller influence of overshoot/undershoot and ringing, but the output signal has longer rise time.

Well, I did some measurements with my scope and function generator. And yes, I did see overshoot/undershoot, ringing, settling time and rise time within output (square) signal, when I was varying the closed-loop gain of amplifier in wide range of values. But there was something strange about it. When the closed-loop gain was high (around 500), I could saw slower rise time of output signal and when closed-loop gain was low (approx. 11), I clearly saw the presence of overshoot/undershoot and ringing within output signal - did I messed up things when I was learning about step response of amplifier or are things that concern overshoot, etc. showing up in reversed order?

3.) I was also trying to find high frequency gain roll-off of amplifier. At high closed-loop gain (around 500), the HF gain roll-off started at around 15 kHz to 20 kHz. But at low closed-loop gain (approx. 11), the HF gain roll-off didn't start at all - in fact the gain was slightly increasing with increasing the input frequency of signal (at 1 MHz it was still increasing!). So the first case seems pretty normal to me, but the second one seems rather extremely unusual than normal. Any ideas what is happening to this circuit at lower closed-loop gains? I thought that amplifier is very stable at low closed-loop gains but obviously not?


texts: Maintaining fixed shaft position of BLDC/PMSM

texts:
I intend to control the position and speed of a BLDC motor (still to be selected) using field oriented control (FOC) and an Encoder to determine shaft position and speed.

From what I understand from FOC, the Id reference should be set to 0 as the and with Iq the torque is controlled. Iq can be set from a PI controller which works with the error signal between the reference shaft speed and the actual shaft speed.

What is still not clear to me is how could I control the position of the shaft? for example, moving from speed control (speed= 10sec/rev, position: don't care) to position control (speed= 0 rev/unittime, position 36°). Could this be done setting the reference speed to zero and adding a PI control (similar as with the speed) to control Id (instead of setting Id) to zero?

Thank you very much for your help. It is much appreciated

Edit:
Something like this @user28910 @Gregory Kornblum?

i.e. setting n_ref to zero and using pos_ref? and when speed control is desired, use n_ref but not adding the output of the PI controller what works with pos_ref and pos_real?


texts: Common-mode filtering long LED driver cable

texts:
I am designing a board to power a WS2815 style LED strip. This strip has three inputs: 12V, GND, Di. This wire -> LED strip will be up to 60ft away from the control board. As such, I want to filter it to prevent common-mode noise on that wire. I will be using 20AWG twisted pair for the 12V/GND pair. I also plan on using a common mode choke. The Di wire will be smaller, say 26AWG.
Due to size constraints, it is not possible to have the Di line in the twisted pair bundle with the 12V/GND, and they will be run next to each other.
My question is, since I am filtering CM on the 12V/GND, do I also need to do anything with the single Di line? My thought is yes, since CM noise could propagate off of my control board, travel on the Di line, and radiate (or noise couples to the Di, and travels back to my control board.)
If I do need to filter it, what options do I have? Other than having a isolated termination on one side of the data line, I can't just have a single CM filtered line of course. I suppose a ferrite or a PI filter with a cutoff above the data transmission speed could also be an option?


texts: Controlling the speed of a single speed AC exhaust fan motor

texts:
I have this single speed exhaust fan: 30" Exhaust Fan with Shutter - Direct Drive - 1/4 HP - Single Speed.
When it's running it's way faster and louder than I'd like it to be. So I'm trying figure out if I can slow it down somehow.
Obviously some sort of AC dimmer was my first thought but looking online seems like that might not work with this motor.
My second idea is to setup a micro-controller to just turn it off an on. For example, turn it on for 1 second, turn it off for 2 seconds, turn it on for 1 second etc... This would prevent it from reaching full speed. This way I'm not messing with the frequency or voltage, and I assume turning the motor off would help prevent overheating.
I'm just not sure if switching it off and on like that could damage the motor. Is there any risk of that?
UPDATE: Even though you are NOT supposed to do this, I was able to successfully use a basic fan speed controller like this: https://www.amazon.com/gp/product/B07T9BLJ7L/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1
It has been working great for about a year now. As expected, the slower the fan is going, the hotter it will get. But I was able to find a happy medium where it's still moving enough air to keep itself cool.


texts: Understanding ADC/Sensor Voltage Conversion to Integer Output

texts:
I'm having a hard time understand my observations. Summary: ADC reports 2660 when I expect 2570.

Main question: This discrepancy seem large enough to have a justification.  I'd like to understand what the source could be.  Additionally is the difference in ADC excitation voltage and reference voltage the source?

I built a simple ADC/Sensor circuit. The ADC reading appear higher than I expect, though. Voltages:

Reference voltage supplied by MCP1541.  Measured at 4.095V
Excitation voltage supplied by PSU. Measured at 5.139V
Analog voltage supplied by sensor with no stimulus. Measured at 2.580. Implied by excitation voltage to be 5.139/2 = 2.57V

It is a 12 bit ADC. so I expect 4096/4.096 units/V.  This implies my 2.57V resting voltage should give be a value around 2570.  The confusing aspect is my baseline reading of 2660.

Additional possibly useful details:

Sensor: http://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Data+Sheet%7F834M1_Accelerometer%7FA%7Fpdf%7FEnglish%7FENG_DS_834M1_Accelerometer_A.pdf%7FCAT-EAC0018
ADC: http://ww1.microchip.com/downloads/en/DeviceDoc/21298e.pdf
Reference voltage: http://ww1.microchip.com/downloads/en/DeviceDoc/21653C.pdf
Standard deviation of the baseline measurement: 5.3 units

Measurement: (trying to calibrate my y-axis to 0)


texts: I am trying to find a replacement connector for this board which came out of a clarion factory car stereo (Subaru).  I've tried searching various types of connectors but haven't been able to identify it.  There appears to be some very tiny markings on the top: "IRS" and "C2", has anyone seen this before or have an idea of what to search?


texts: Exciting an RC Circuit at its TRUE Pole on the Sigma (Real) Axis in the Left-Half Plane

texts:
Yeah, you probably are reading this question and thinking I'm one of those engineers who hasn't learned about the s-plane. I can assure you I'm not! I know that the transfer function of an RC circuit (Vout/Vin) has a REAL pole, with no imaginary component at s= -1/RC + j0. I am curious what happens when we excite an RC circuit at its TRUE pole, which is a decaying exponential with the expression e^(-t/RC).
Of course, the output of an RC Low-pass filter will never blow up to infinity. But what about the ratio of the output to the input, which after all, is the transfer function I originally defined?
Well, let's take this to LTSpice. Below is what I've simulated:

I would expect Vout/Vin to be infinity everywhere, however what I see is a ramp. I suspect I'm missing something about how to properly interpret the magnitude response of my transfer function with its true pole as an input. A time-domain view such as what I have should explain something, but I can't understand why it's a ramp.
If anyone has any intuition behind this question, please let me know.


texts: Verilog code to drive a signal high always

texts:
I am learning Verilog fundamentals recently. I want to drive a signal always high using reg. I wrote this and it didn't work.

    reg b;
    always@*
    begin
       b <= 1'b1;
    end

b is always 'X' in simulation.

In VHDL, I was able to do similar thing:

signal b: std_logic;
process(all)
begin
b <= '1';
end process;

b is always high in simulation.

I know we can do this using assign statement with wire. But, is it not possible with reg ?


texts: Stepper motor causes massive spikes in power supply when decelerating

texts:
I am running a bipolar stepper driver from one of Pololu's DRV8825 stepper driver boards. I have followed the recommended minimum wiring diagram, with a 220uF capacitor right across the input and another 470uF cap a few centimeters away.

I set my power supply to 20V. Stays right at 20V while the motor accelerates. However, when the motor is cruising at about 6000 steps/sec (30 rps), the voltage shows spikes to about 25V long enough to register on the power supply voltage display, not just my scope. Estimate about 0.1s (dubious number).

The real problems come when my motor begins to decelerate. The current draw drops a ton, often down to 0.00A. Also, the voltage shoots up too: I have seen spikes to about 40V, and the voltage is over 35V for at least 1/4 second.

Has anybody else noted this? Does anyone know why this is happening? What should I do to stop it?


texts:
I'm using an LTC1983ES6-5 to provide a negative rail for both a MAX4311 and a MAX4395. LTC1983 provides up to 100 mA, but I cannot find in the other datasheets how much current is required for the negative supply rail of the components.

What parameter(s) I should look to?


texts: How to make battery controller with arduino?

texts: I want to make simple UPS with means of arduino, to learn the processes from it, and be able to record and monitor at PC. For the start i want to implement buffered usage charge mode. Logic is simple - when voltage is less than defined(say it battery voltage is less than 13.6V) - then gate should open and connect battery to charger. If voltage is greater then gate should close, disconnecting charger and preventing battery and load from excessive voltages. So, it would do kind of clever PWM. I am asking for a help, i dont know how to connect gate to arduino. If i explained bad please look at illustration:


texts: Why isn't my 555 cascading timer working?

texts:
I've made a 555 cascading timer. First stage is approx 90 seconds, second is 30 seconds.

The first two led's light up in sequence as expected, but the 3rd doesn't light. I've checked all connections. I can't figure out why the 3rd light won't trigger.

Is there anything in the schematic that gives a clue?

Circuit is running on a 9V battery. The push button connecting to pin 4 of each 555 is just to reset the circuit


texts: Noticed something weird in derivation of relationship between ICBO and ICEO in BJTs

texts:
So I'm currently studying Electronic Devices and Circuit Theory by Boylestad and Nashelsky (11th ed.) and I'm confused as to how the relation between \$I_{CEO}\$ and \$I_{CBO}\$ is derived.
So the derivation in the book starts with the equation
$$I_C = \alpha I_E + I_{CBO}\ \tag1$$
But since \$I_E = I_C + I_B\$ ,
$$I_C = \alpha (I_C + I_B) + I_{CBO}\ \tag2$$
Rearranging yields
$$I_C = \frac{\alpha I_B}{1-\alpha} + \frac{I_{CBO}}{1-\alpha}\ \tag3$$
Then it goes on to say that \$I_C\$ when \$I_B = 0\$ is assigned the notation \$I_{CEO} = \frac{I_{CBO}}{1-\alpha} \approx \beta I_{CBO}\$ which is consistent with other sources.

The weird thing I noticed is that letting \$\alpha I_E = I_C\$ in eq. 1 produces
$$I_C = I_C + I_{CBO}\ \tag4$$
and letting \$ \frac{\alpha I_B}{1-\alpha}=\beta I_B = I_C\$ in eq. 3 produces
$$I_C = I_C + \frac{I_{CBO}}{1-\alpha}\ \tag5$$
which are surprisingly not the same in addition to being paradoxy/fallacious... So my question is what went wrong?


texts:
How strong is the field of a magnetic strip on a credit card? In other words, at the typical distance of a read head, say 0.001" how strong is the magnetic field from the stripe?

(Note this is NOT a question about how strong a field is needed to erase the stripe. I already know that. It is how strong the field is that is created by the stripe.)


texts:
I want to power some accessories in my car using illuminated switches on the dashboard.  These switches will be wired to the dash illumination circuit, which is normally 12V but can drop as low as 6V when fully dimmed.  Can I use a 6V relay here to give 12V power to the accessories?  According to this data sheet, it's max switching voltage is 16V so I think this should be safe.

https://www.mouser.com/datasheet/2/164/fbr51-52-472017.pdf


texts:
I'm just starting with digital-logic but I now face a little problem: I learned that AND, OR, NOT were basic gates and that one basic gate could not be made from a combination of two others. How comes that this combination:

produces an OR truth table from only AND and NOT gates?


texts: Doubt about potential difference through a resistor?

texts:
First of all let me give you the schematic diagram of the circuit,

Here, how to find the current passing through 150 ohm resistor?
These are the things I have tried,
Since I want to find the current  through 150 ohm resistor I need the potential drop across that resistor , therefore in order to do find the potential drop across 150 ohm resistor what I did was I marked the nodes as shown below

After that I took the voltage through-out  (green)node  as 10V(10V battery is on green node) , likewise I took the voltage throughout red colour node as 5V.
Then I could find the voltage drop through 150 ohms, so let's assume it as K
Therefore 10V - k = 5V
So K=5V
Then the current through that resistor is ,
V=IR
5V/150
I = 0.03A
But the answer is wrong, The correct answer given is 0.1A.
What is the mistake I have done? Please help me


texts: Came across these small Zwave controllers here .These are small enough to fit inside the electrical switch housing in the wall. Just wondering how is this device so small as the AC->DC transformer is usually pretty big. Are they using some special kind of smaller transformers that are there?


texts:
I am trying to design an amplifier with a transistor model. I followed some basic tutorials online (http://microwave.eecs.utk.edu/ECE545_files/02_Lab_2.pdf) and designed a transistor model for BJT/MOSFET. I am stuck in making the amplifier work in RF frequencies. I guess either I am using a low-frequency model or improper circuitry and not sure which one of

Now, for MOSFET/BJT I fixed a bias point (for maximum transconductance in MOSFET/ fix Beta,VBE,IC,IB in BJT) and then designed the biasing circuitry and simulated the S-Parameter/AC simulation. I am getting the S21/Gain dropping to 0dB near 150 MHz. I guess this has to do with transit frequency.

I guess two mistakes - either I am using a low-frequency model or improper circuitry and not sure which.

My circuit looks like the one below for BJT:


texts: Why is the Anode positive if Anions are negative...?

texts:
When I was younger I learned in Chemistry class that Anions were negatively charged and Cations were positively charged (Fun fact: I memorized this because anion sounds like onion which makes you cry and is therefore negative; while cation has cat in it and cats are cute, so it's positive :P).

Now that I've started getting into electronics, I've learned that the Anode is the positive lead while the Cathode is the negative one. It seems odd to me that they're reversed; can someone explain why this is?


texts: Arduino stop RGB fading (3rd party library) at interrupt

texts:
Using the following code, the fading process only stops after a full cycle has been run (as predicted). What would be the optimal way to stop the color cycling when the interrupt is called (so I can switch to another cycling mode)

/**
 * RGBController
 * author: peterrus
 * License: Attribution-ShareAlike 3.0 Unported (http://creativecommons.org/licenses/by-sa/3.0/)
 * rgbled library: https://github.com/msparks/arduino-rgbled
 */

#include <rgbled.h>

static const int kRedPin = 10;    // red channel pin
static const int kGreenPin = 9;  // green channel pin
static const int kBluePin = 11;    // blue channel pin

// Brightest value (intensity) to use for any channel.
static const uint8_t kMaxBrightness = 255;

// Delay between color changes.
static const int kDelay = 3;  // milliseconds

// Create the RGBLED object to control our 3-channel LED.
RGBLED led(kRedPin, kGreenPin, kBluePin);

boolean cycle = false;

void setup()
{
  //modeswitch button
  pinMode(2, INPUT);
  digitalWrite(2, HIGH);
  attachInterrupt(0, doCycleToggle, LOW);

  // set fading delay.
  led.defaultDelayIs(kDelay);
}

void loop()
{
  if(cycle)
  {
    // Fade through the color spectrum.
    //   red -> violet -> blue -> cyan -> green -> yellow -> white -> red -> ...

    // Red -> red + blue (violet).
    led.fadeChannel(RGBLED::kBlue, 0, kMaxBrightness);

    // Red + blue -> blue.
    led.fadeChannel(RGBLED::kRed, kMaxBrightness, 0);

    // Blue -> blue + green (cyan).
    led.fadeChannel(RGBLED::kGreen, 0, kMaxBrightness);

    // Blue + green -> green.
    led.fadeChannel(RGBLED::kBlue, kMaxBrightness, 0);

    // Green -> green + red (yellow).
    led.fadeChannel(RGBLED::kRed, 0, kMaxBrightness);

    // Green + red -> green + red + blue (white).
    led.fadeChannel(RGBLED::kBlue, 0, kMaxBrightness);

    // White -> red.
    uint8_t mask = RGBLED::kBlue | RGBLED::kGreen;
    led.fadeChannels(mask, kMaxBrightness, 0);
  }
}

void doCycleToggle()
{
  if(cycle) { cycle = false; } else { cycle = true; }
}


texts: What is "VDCI" in terms of output voltage?

texts:
I am trying to bring back an old monochrome plasma screen from the dead.  I have little information on the device, its from a Compaq Portable (Luggable) III PC.  The manual for the unit lists power supply output specs as follows:
+5.0 VDC
+12.0 VDC
-12.0VDC
+200VDCI
5.0VDCI

That is exactly whats printed in the manual (minus a few columns about min. current, avg. current, and tolerance), not sure why the one "5VDCI" line doesn't have a "+" in front of it.

But more importantly, I have no idea what "VDCI" means.  Is this some old notation (the manual has 1987 as a first print date)? Is this just a typo? Is it some term I have never heard of before? Or is it absolutely nothing at all and simply means volts DC?

Alternatively, if someone manages to hunt down operating specs of the LCD in there, that would be just as awesome.  I've put many hours in to figuring out what I have thus far.


texts:
I tried the following circuit but the LEDs for me are always on and don't blink, i checked connectivity, changed capacitors and tested transistors but same problem. what could be the issue?

edit:
left transistor is 13001 s8d, right on is 13002 HJ B1


texts: Is qNaN easier than trapping on overflow?

texts:
According to James Demmel's article, "Faster Numerical Algorithms via Exception Handling", IEEE Trans. on Computers 43 (1994), 983-992, the way a floating-point processor handles overflow can be important to the speed of operations that are not typically expected to overflow, because it is often the case that we have a choice between a fast algorithm that can overflow for rare inputs, or a slow algorithm that guards against overflow in all cases, so it is useful to be able to use this strategy:

Try the fast algorithm
In the rare case where overflow occurred, go back and redo the calculation with the slow algorithm

There are basically two ways to detect overflow:

Trap. To be usable for this strategy, it must be possible to trap to user code. To trap at the precise operation would incur an unreasonably large performance penalty for pipelined implementations, so it has to be accepted that it will be imprecise.
Infinity/quiet NaN/sticky status bit. Keep going, but remember that an overflow occurred, so that an explicit check can be carried out occasionally. To be usable for this strategy, the presence of NaN operands must not cause too dramatic a slowdown. (There have been a number of processors on which NaNs slowed arithmetic operations by a couple of orders of magnitude.)

Modern processors like x64 typically default to the second strategy.

My question here is about the hardware implementation of floating-point traps versus NaN. Is it actually less costly to implement quiet NaN without slowdown, than to provide even imprecise trap on overflow? Or is quiet NaN widely used today for a different reason?


texts: Why choose delta over star connection for a 3 phase motor with a VFD?

texts: With respect to a particular application, why is it better to use a delta connection over a star? I have a motor/pump hooked up to a vfd in delta. For my application, Im required to adjust the flow rate of the water in the pipeline. The motor was in delta initially when the project was given. I assume they use the delta connection because, when using a vfd, there is no need for a high current to get the motor running because there's no direct online start. The motor will speed up according to the vfd ramp up time and setpoint frequency. Delta can also provide higher torque as opposed to star. Is my assumption correct? Also, why wouldn't I connect it in star?


texts: Copper Coil and Electromagnetic Induction

texts:
Waiting for answer

Does mixing thickness of wires affect the Induction?
What I mean is that I've like some 2mm and 1mm copper wires joined together.
Basically I remove insulation on copper wire ends and then I just tie those wires. After that I just tied those 2 wire ends.
When making a coil out of copper wire, what could increase efficiency of electromagnetic induction, the thickness of coil  (Gaps between windings)  or surface area.

Answered

Why copper is most common in electronics? Is it because of it's valence electrons that makes him more conductive?

I will be waiting for your answers :)


texts: Effects of a voltage divider on an audio DAC

texts:
Background:

I'm planning on using a TI TS5A22364 SPDT Switch with Negative Signaling to connect AGND to the Left and Right Channels of the TI PCM5102A Audio DAC when the DAC is powered down as an analog mute solution, since the XSMT functionality of the DAC does not meet my needs.

The TS5A22364 supports a maximum voltage swing of 5.5v. The PCM5102A outputs 2.1v RMS which is (2.1 * sqrt(2)) * 2 = 5.93Vpp + 7% FSR = 6.355Vpp / 2 = -3.1775v - 3.1775v which puts it above the 5.5v maximum of the TS5A22364 (even though the L/R channels won't be routed through the switch, the outputs share this maximum and voltage above it could trigger the ESD diodes).

Proposed Solution:

Using a voltage divider (R1=2710Ω, R2=10kΩ) on the L/R channels of the PCM5102A to drop the voltage to 5v.

Questions:

Are there any issues with this solution or better methods than the voltage divider?

My limited understanding of analog audio leads me to believe that the voltage divider should not impact quality, but only inhibit volume. Is this correct?


texts:
I am refering to the document SLMA002G PowerPAD™ Thermally Enhanced Package from TI. Kindly refer to page 9(screen shot attached).
this is related to thermal vias present on the ther or open pad which solders to the open pad of an IC.

The statement in question is state below -
The experiments conducted jointly with Solectron Texas indicate that a via drill diameter of
0.33 mm (13 mils) or smaller works well when 1 ounce copper is plated at the surface of the board and simultaneously plating the barrel of the via.

This means that if the layer is of 1 Oz then a drill dia of 13mils for via is enough for decent thermal dissipation,right ?
What if the Cu is 0.5Oz how much would the drill dia need be changed ?


texts: How to get a 1.6 times higher supply voltage

texts:
I trying to build a UV exposure box so I can do my own PCB at home. The problem is I don't have a power brick that can output 32V @ 1A. the matrix consists of 10 columns \$\times\$ 10 rows.

The power brick am using is 20V @ 4A.
Be much easier to buy one but I thought this might be good exercise to do.


texts:
"For each of the values calculate P and Q" (average)

V = 250 \$\cos (\omega t +45)\$
I = 4 \$\cos (\omega t -30)\$

The way I would try solving this would be by converting to phasors, taking the product and multiplying by a half. I will then be left with a phasor with phase shift of \$15\$ deg. But turns out the final phase shift is \$75\$ deg. I assumed this may be as a result of taking the current max at \$t = 0\$. So that way we just shift both the current and voltage by \$30\$ deg. But then the next question...

V = 18 \$\cos (\omega t -30)\$
I = 5 \$\cos (\omega t - 75)\$

If I now shift by \$75\$ deg, then \$-30 + 75 = 45\$ deg and not \$105\$ deg as stated in the memo. What is happening?


texts: Is this a safe way to measure mains power on an oscilloscope?

texts:
I wanted to use my cheap battery powered single-channel oscilloscope or my Rigol 1054Z to see the 120V AC mains signal in my house. No particular reason, just curious.
I at least knew enough to not just blindly stick the probe in the wall socket so I got on YouTube and found a lot of information, some of it contradictory. So taking what seemed like a reasonable approach, I built an "isolation transformer" from an old wall wart I had laying around. (Yes, this was an actual transformer and not just a switching power supply.) Now I'm wondering if this is actually a safe approach.
Upon opening the case, I saw the transformer and a small circuit board with a full bridge rectifier. So I removed the circuit board, which left me with just an AC - AC transformer. Using my DMM, I measured 115 VAC in and 9.9 VAC out. I then soldered the two leads from the transformer to two banana jack ports. There was plenty of room in the case to drill holes and mount these so they can be accessed externally. See the attached picture.
I tried this out with my battery powered oscilloscope and got the expected results. The 9.9V signal was a clean sine wave at 60Hz and I didn't fry anything or die, so I figured that was a success. My questions for you - Is this safe? Can I hook it up to my mains-powered Rigol? Or is there an important point I've missed? Thank you for your help.


texts:
I'm trying to simulate an AC to DC voltage regulator. I'm trying to go from 115 Vrms to 5 V DC at 1 amp max, though 0.5 amps nominally. I initially thought of using the LM317 at first, but after discussion, it seems that it would give off too much heat. Thus, I decided to go with a different IC, the TI LM2596 as shown in my circuit below. From what I've researched, it should use up less current than the LM317, so I thought it would be a good replacement without fear of overheating.

simulate this circuit – Schematic created using CircuitLab

The transformer rectifies the voltage to a DC voltage of 13.63 volts held by C1, and that input goes into the IC which outputs 5 volts at the output. I never worked with buck converters before so I followed the recommended circuit layout, but is this the correct configuration when working with unfiltered DC voltage from a rectifier? Should there be some circuit protection at VIN to protect the IC, or is it fine as it is? I'm trying to get this working in simulation, but compared with working with the linear LM317, the SPICE model is really slow and sluggish, so it's hard to get accurate results about the circuit.

EDIT: After some thoughtful discussion, I had to change my design to fit some new requirements. See the new schematic. I used one single transformer to rectify the secondary to two 13 V, and I use two IC configurations to output a positive and negative voltage with a start-up delay. Regarding the new edition, does it still hold true, or should some parameters change?


texts: Current measuring in a simple resistor and voltage circuit

texts:
I have a problem with this simple circuit.

For LKC we know that the current on the node is

i1 = i2

since i3 (the current going down is zero ).

In my ignorance I would measure i1 like i1 = V1/R1 and not like

i1 = (V1 - V2 - V3)/(R1 + R2)

It is clear that I cannot understand how this works.


texts: Manufacturing Microcontrollers for portable vaporizer by first prototyping with Arduino

texts:
This question I have mainly has to deal with approaching an electronics company with just a working Arduino Nano prototype.

Say I want an electronics component manufactured which consists of an Arduino Nano microcontroller, some RGB LEDs, and a thermocouple.

The device works as follows:

The thermocouple will detect the temperature of an applied heat source, and will change the color of the RGB LEDs accordingly. Basically for below 200 degrees Celsius, the leds will turn blue, at 200 they turn green and above 200 they turn red. I have a working prototype built with an Arduino Nano, but I want it massed produced for a vaporizer that I am developing.

Is there a way for me to take just this prototype to an electronics company and get a product that can be mass produced? Also what will be the cost of doing this sort of thing?
Will I have to use a program like eagle, or can I just show them the prototype that I created and give them the dimensions of the device?

The best case scenario for me is if I can approach a company, tell them what I want and how small I want it to be made, so I can fit it into the vaporizer. How much money would it cost to specifically do this?


texts: instrumentation amplifier with [2 opamp + ADC] vs [3 opamp + ADC]

texts:
I have an 16bit ADC able to do differential measurement with range -5V to +5V (ADS1115), do you think both circuits would work?

It's required that the adc input is within -5V and +5V range, else it would fry.

I think the 3-OPAMP circuit has the advantage that output would be always -5..+5, so no risk for the ADC. I would use a basic OP-07C opamp for this.

Note: I didn't draw the RC circuits.

Similar thread but the circuitry is complicated


texts: How to properly bend leads of box-type film capacitor?

texts: How to properly bend leads of film capacitor (radial type), mounted horizontally? (PCB height limitation) I need to bend leads safely, with normal bend radius, to avoid cracks in the resin or disconnection of the lead wires from the internal element.


texts: I have been trying to simulate this but it won't and it gives me those 2 errors

texts:
I have been trying to simulate this citcuit

but it won't and it gives me those 2 errors


texts: Is it safe to replace a ceramic fuse with a radial one?

texts:
I have to repair a led tv with a blown fuse. On the power board the fuse required is a T4.0AH/250V fuse, but I couldn't find it at the shop. They gave me instead a radial fuse, claiming that it's the same.
Is it possible to replace a ceramic fuse with a radial one or could blown other parts of the board?


texts: How to realize a zero at infinity ? RC synthesis

texts:
I'm just trying to synthesize this bellow pole-zero map.

Since now I have come up with the following equation.

$$Z(s) = \frac{(s+1)(s+3)}{(s+2)(s)}  $$

But I have no idea about how could I fabricate a zero at infinity there?
 $$ \lim_{s \to \infty} {Z(s)} =1 $$ does not equal to zero there. So any idea how could I made it possible to make it go to zero when it goes 's' to infinity ?
How could I change my impedance function? Could you suggest a change?


texts: Which is this component, using in remote car key PCB?

texts:
A friend's car key was not working properly, and an electronics repair shop took it to that key. they offered a very high price for the repair and my friend refused and got his key back. Now he brought me the key and asks me to fix it. but before me the crafty person removed some of the components of the switch from the PCB. This is the switch board. Well, you can still see some components being soldered there but no clue.

If I type PCB number in Google, the same boards appear there. however, I don't have enough experience to determine what these components are and what their value is. Can you help me find these 3 components?

there are some links for other images
Full resulation
24 pins component datasheet
Another full resulation image


texts: Is there a relatively easy way to convert a 14VAC wall wart to power a 9VAC guitar pedal?

texts: I bought a used guitar pedal that didn't come with the 9VAC adapter but I have a 14VAC adapter that works. I did power up my unit with it and it does work but I'm afraid the higher voltage might damage the unit so I would like to drop the voltage down. I'm not using my pedal at the present time because of this. I'm familiar with voltage dividers for DC. Is there a similar circuit for AC? Thanks


texts: How to correctly test a 4-channel Logic Level Converter?

texts:
I have a 4-channel logic level converter (it says Level Converter MH on its back and seems to be a very common one for Raspberry Pi and Arduino usage) and wanted to test it's functionality. I don't have a data sheet for it, but its this thing: Link to the product at mepits.com.
Here are images of my board:

I use a 545043 YwRobot breadboard power supply, which provides 5v on one side and 3.3v on the other of my breadboard.

On the low-voltage side of my converter I connected LV to + of the 3.3v side of the power supply and GND to -.
On the high-voltage side I did the same but to the 5v +/- on the power supply.

I then connected LV1 to +3.3v (directly from the power supply), to simulate HIGH, and expected to measure +5V on HV1 against the GND on the high-voltage side, but my multimeter only showed 2.9v.

This is my wiring:

The negatives are already connected together on the power supply on the left side, but I added a direct connection to double-check anyways.
The upper side is the 5V side, the lower the 3.3V side.

So my question is, did I understand something wrong and wired it up wrongly?


texts: What operations on flash(NOR/NAND) effect Flash Program/Erase(P/E) cycles

texts:
I want to implement a counter which can save values through power cycles, so I should use flash memory(I have option to choose NOR or NAND) but as my counter values will be increased frequently. I want to optimize number of erases(considering only erases i.e making bits 0 to 1 will effect the flash life span).

For that I want to implement tick counter In which sequence of bytes(around KBytes, depends on my counter maximum value, usually equal to block size) allocated to counter for each increment successive bits will be set to 1 to 0 starting from MSB. I will write custom flash driver to take care of counter operations.

Ex:

Val0: 1111 1111 1111 1111 ....
Val1: 0111 1111 1111 1111 ....
Val2: 0011 1111 1111 1111 ....

Advantages tick counter:

Erase required only when we want to make counter to zero.

But is it possible to program a bit from 1 to 0 without erasing(NAND/NOR), if yes will that effect P/E cycles count?


texts: Is electrical energy wasted when a device is fully charged?

texts: Many a times I leave the laptop connected to the charger with the switch on for the entire day. When it becomes fully charged does it still consume electrical energy?


texts: Identification of connector used in a plastic card printer

texts:
2 position power connector (24 V) needs to be identified.
Outside dimmentions: 7,7 x 7,2 mm.
Pin pitch: 4,0 mm


texts:
I have recently discovered that my AVR Dragon has a busted voltage regulator (see this). I am trying to remove the voltage regulator IC so I can perform the mod specified on that page, however it is a SON package with what looks like all of the pins under the chip.

Is there any way I can desolder this with a (very good) temp controlled iron? I have given it a whirl with some extra solder + braid with no luck.


texts:
Please take a look at a PCB like this one (STM32 Nucleo64 board):

They utilized so called "double deck" or "stacked" headers, meaning they can be used from both sized (top and bottom).

My question is- how does one solder them, since they come in such package:

Source: https://www.tme.eu/gb/details/zl2019-2x20/pin-headers/ninigi/zl2019-40/

I mean, you want the PCB to be in between the pin holding materials. It seems to me that one of them should be taken off after the initial soldering. The problem is that there is no good position for soldering without touching the holding bars:

Should the bards be altered by hand? That makes it easy for the pins to be soldered uneven... I just don't see it. I would appreciate all help regarding this topic.


texts: Alternatives to RC circuit for simple variable delay up to 2 minutes

texts:
I'm looking for a simple and cheap way of creating a variable delay of up to about 2 minutes.

simulate this circuit – Schematic created using CircuitLab

I want to know if there's an alternative to using an RC circuit that is simple and cheap. Other concerns are secondary, within reason.

The problem with this circuit is it just seems a bit 20th century.

Firstly, the capacitor needs to be large physically because of leakage current and the small current required to turn Q3 on. This means the cost possibly leaves room for improvement. The size, weight and lifespan can probably be improved. The delay consistency can certainly be improved.  (Since the capacitor's internal leakage and other leaks will vary significantly with temperature, humidity etc). Plus there's the surge when the cap gets charged.

Are there any tricks I could use? I'm wondering if there are any off-the-shelf ICs which are dirt cheap that perhaps combine a small RC circuit and some way of configuring the delay that is perhaps implemented by a binary counter.

I'm still playing around with ideas so I'm not sure what there will be in the way of power rails; if necessary I could make a 5v rail available, but it would be useful to know if there's a solution that could work on as little as 1 volt. So this question is less about solving my specific problem, but checking that I'm not oblivious to some general purpose alternatives.

[Re: duplicate: This is not a duplicate question. The answers given for the question identified as a possible duplicate offer no improvement as requested by my question. A 555 timer still uses an RC circuit without a solution for a large capacitor!]


texts:
I'm building a full adder circuit using transistors. I am only doing it for fun, that's why I'm not using IC gates.
I am feeding it 5V and I'm getting really strange outputs. And it isn't even consistent, sometimes it does one thing and other times, other things. The outputs are around 3-4V, the LEDs sometimes shine normally, sometimes very faintly, sometimes not at all. And I just can't get it working. Can you see something off in my schematic?
And yes, I checked my PCB, I soldered everything good, there are no bridges.
I tried removing the resistors before the grounds, (R1, R6, R9, R18, R21, R26, R29, R32, R33) but it still doesn't work.
Here is the schematic:


texts: Electrolytic caps exposed to reverse voltage... permanently damaged?

texts:
Accidentally a bridge rectifier was installed backwards and the capacitor bank was exposed to reverse voltage, not for too long, maybe 20-40 seconds.
There were a few different brands and values of electrolytic caps being used, 1 or 2 types became very warm to the touch after the exposure and I removed these. The rest were still cold, surprisingly the ones to get warm were cheap caps, and the ones that seemed unaffected were all better quality ones, the warming didn't seem to be related to the values and ratings.
I have powered up the circuit with the remaining caps after correcting the reversed bridge rectifier, after running into a load for a while they have not shown any physical signs of failure/damage (heating, bulging, leaking etc.)
Do you think these caps are still to use i.e the performance has not have been considerably degraded  in some way(increased leakage, decreased capacitance, decreased life span)?


texts: How do I calculate the MOSFET losses from reading the datasheet?

texts:
I'm trying to figure out how to calculate my MOSFET (DATASHEET CLICK HERE) losses while following the guide below.  However, I'm not really sure what values to use whilst calculating the Conduction and switching loss as the graphs in the guide are different to the ones in my datasheet. There's quite a few equations in the guide but not sure which one would be applicable relating to my datasheet. Any guidance would be helpful!

Thank You!!


texts: 74HC595 +TLC5940 multiplexing 128 leds -> not enough power

texts:
Apologies in advance for probably missing a lot of things. I'm pretty new to electronics.

I'm building a 128 led (monochrome) multiplexed array, driven by an Arduino. I'm using a 74HC595 as the current source and a TLC5940 for sinking and PWM. The output consists of an 8 (74HC595) x 16 (TLC5940) array of leds. Any number of the leds can be on at a given time.

I'm doing the multiplexing by turning on a column with the 595, one at a time, and then setting the appropriate values for PWM for the TLC, lighting the rows in a columns at desired value.

Multiplexing works fine already but scale becomes a problem with the current 8x6 array i have built (6 out of 16 so far connected to the TLC). I'm pretty sure my problem is that turning on a column with the 595 can not supply enough juice for the 16 leds in it. The leds have a forward voltage of 3.3V with 20mA current. This would mean the 16 leds in series would eat up ~53V @ 320mA, which is far above what the 595 can provide and the TLC can sink. How would i go with making this work? Is there some magic i can do in software to help with this (my guess is not)?

I've been looking at adding a darlington array (something like ULN2803) to pump up the voltage to 50V per channel. This i guess would be fine if all 16 leds would be on at the same time but if only 1 is on the led will most certainly fry. Because of this i guess i need to be able to add a resistor that changes value depending on how many leds are on at a given time. I was thinking of putting in a digital potentiometer to do this but it feels a bit overkill + i haven't come up with a good solution for hooking this up (without putting a single one on each 2803 output)?

Ideally i'd keep the circuit quite simple but i'm open for ideas so any suggestions are more than welcome! Also I wouldn't be surprised if i'm totally missing the point on the problem..

If what i'm trying to do is not clear enough i can create a schematic for it

thanks


texts: How to avoid voltage drop on undervoltage protection circuit?

texts:
I'm having trouble with a circuit I designed and I'm hoping someone here may help me fix it.

I've successfully used the circuit below a few times. It was proposed by Russel McMahon in this answer. It let's the user power up a circuit by closing SW1 (Go!) long enough so that the MCU then can keep the circuit powered by keeping the signal HIGH_TO_RUN high. To turn it off, the MCU just have to bring the same signal low.

simulate this circuit – Schematic created using CircuitLab

This time I'm using two NiMH AA cells (~2.5V) to power a boost DC/DC converter based on the MC33063 IC which in turn brings the voltage up to ~5V and deliver about 125mA to an ATmega328P circuit. The circuit is the following.

The problem is that the minimum input voltage on my MC33063 is about 2.5V and Q1 is dropping it below that, to about 2.0V.

So, my questions are:

How can I modify the circuit so that I can deliver ~200mA@5V to my load from the same two NiMH AA cells?
Can I replace Q1 with an P-Channel MOSFET (such as the IRF9530) to decrease the voltage drop on the transistor? What changes to the circuit should be made then?

Note: The linked datasheet says that the minimum input voltage for the MC33063 is 3.0V, but I'm pretty sure there are variants out there that take less voltage (1.8, 2.0 and 2.5V if I'm not mistaken). I'm pretty sure mine is the 2.5V variant (at least I've tested it).


texts: Can I use a laminated silicon steel transformer core as a low frequency boost converter core?

texts: Since laminated silicon steel is used in low frequency transformers, can't I also use it as an inductor in a low frequency boost converter, at maybe 100Hz, theoretically shouldn't this work as well as high frequency ferrite core boost converters?


texts: Converting universal AC to 3.3v DC @ 0.1A

texts:
There's a bunch of topics around this but i haven't found something that fits my requirements. I'd imagine this is a fairly common thing though so any pointers would be appreciated

Basically i want to design a circuit that can use mains power anywhere (85-265v AC) and power a simple system with max power consumption of around 100mA.

Requirements:

85-265v AC input
3.3v +-5% DC output
10-100mA current
Size as small as possible
~10mV ripple
Cheap (less than ~$10)

This is for a networked device and will be totally enclosed (no buttons etc) so i don't think it has to be isolated although it of course wouldn't hurt.

I've looked at existing PCB mount PSUs but the price is a bit too high. Also they can be fairly big (mostly tall) and provide much more current than i really need.
A simple solution with AC -> Transformer -> Diode bridge -> Voltage regulator would probably work but the transformer size becomes very big. Also i'm unclear how this will work with the universal voltage range.
Basically i probably want something similar to the 3rd solution here: https://electronics.stackexchange.com/a/41944/6809

The components from Power Integrations seem to be what i should be looking at but i'm slightly unsure where to start. Also very few of the examples give 3.3v out and usually at a much higher wattage than i need (= i'm thinking i can make something smaller/cheaper as i only need .1 Amp)


texts: No Feasible Entries for Subprogram "rising_edge"

texts:
It's my first time coding in VHDL and I ran to some problem I have absolutely no idea how to solve. When I try to compile my code in modelsim it gives me "No Feasible Entries for Subprogram rising_edge". Here's my code.

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.MATH_REAL.ALL;
use IEEE.std_logic_unsigned.all;
use IEEE.std_logic_arith.all;

ENTITY cnt IS
    PORT(
        clk, res_cnt, cnt_en : IN BIT;
        dataOut: OUT INTEGER
    );
END cnt;

ARCHITECTURE base OF cnt IS
    SIGNAL data: INTEGER;
BEGIN
    PROCESS (clk)
    BEGIN
        IF rising_edge(clk) THEN
            data <= 1 WHEN res_cnt = '1' ELSE (data + 1);
        END IF;
    END PROCESS;

    dataOut <= data;
END base;


texts:
Here's a picture of two chips next to each other:
The ATTiny85 and the nRF24l01+.
The ATTiny85 will fit in a standard 8Pin DIL, but the nRF chip won't because the connectors are more tightly spaced together. Does anyone know if there is any "standard" the connections on the nRF24l01+ chip are following? 2x4 pin single in line?


texts:
I have an ADH8066 GSM module that I'm trying to get up and running. I'm powering it with 4V (via a 2A adjustable regulator), and I'm using a Bus Pirate connected to its RX0 and TX0 lines. I'm not using RTS/DSR/CTS, because the datasheet says it doesn't do flow control by default. I do have a SIM card installed, but it's a non-activated one. I don't expect that to make a difference to whether or not the UART interface is available.

I'm pulling ONKEY low for about 2 seconds to turn it on. It's powering up, and I get the following output:

IIII
SystemInit
+ADSYS: BK=0x1,0x11, RV=0x1, Fail=0x0
+ADSYS: FLASH VERIFY OK

Ready

However, it doesn't seem to accept any input. I believe that remote echo is turned on by default, but I get nothing echoed back to me. AT does not result in OK, and no other informational command gives me any output. I've sent commands with explicit "AT+CGMM" 13 10 to ensure the line ending is correct.

During all this, GPIO10 (ready for AT command) remains low. The datasheet doesn't say which state is active, but I'm assuming active high based on some people's LED wiring.

Is there something else I'm not doing?


texts:
I have a SIMCom SIM808 2G GSM module on a custom PCB based upon the Adafruit FONA. I got a bunch of 2G SIM cards from Aeris.net. The problem is when I first put the SIM cards in my device, I get "Registration Denied" (+CREG: 3) and the device will never register with the network. My AT commands and responses look like this;

AT

OK

SMS Ready
AT+CREG=1

OK

+CREG: 3

+CREG: 2

+CREG: 0

+CREG: 2

+CREG: 0

+CREG: 2

+CREG: 0
[and on and on for hours...]

Now if I take that same SIM and insert it in an old Samsung Galaxy S5, turn it on and wait a few minutes for the cellular bars to appear, then take the SIM out and put it back in my device, it registers with the network immediately and forever after. It looks like this:

AT

OK

SMS Ready
AT+CREG=1

OK

+CREG: 5

It appears that the Android phone is doing some magic to the SIM card or my account that makes the SIM card work in my SIM808. Aeris support can't see the device attempting to register.

What's going on here? What does it take to first register this SIM card from my SIM808? It not going to be possible to first put each card in an Android phone before using with the SIM808.


texts: Opamp + FET oscillate in voltage regulator for inductive load

texts:
I'm currently trying to regulate the voltage on an inductive load. The idea is to use an opamp to divide the actual voltage across the coil down, compare it to a set voltage and drive a FET so that the desired voltage is reached.

This is my current design. The first try was without the push-pull buffer but adding it (because the OP can't deliver much current) didn't really improve things. I know that I'm actually measuring the voltage across the transistor, not the coil, but since they're in series, it should have the same effect.

Current through the coil will be between 1 and 1.5A, the coils DC Resistance is 10.5 Ohms.

simulate this circuit – Schematic created using CircuitLab

The circuit works in simulation but is heavily oscillating in reality. When I turn the potentiometer, the "duty cycle" of the oscillation changes, but it only ever stops oscillating if the control voltage is either 0 or 5V.

It looks like this on the scope, where the pink trace is the control voltage on the - input of the OP, yellow is the divided down voltage across the FET on the + input of the OP and blue is the output of the OP:

I would be very greatful if someone could point me in the right direction. I don't know, what else I could try.

Thanks in advance

Edit: I kind of improved the situation by leaving out the push-pull stage and conencting the opamp output via a ~200kOhm series resistor to the FET gate. The circuit looks like this now:
The first stage calculated the differential voltage across the coil and divides it by approximately 7 so it can fit in the 5V rails of the opamps.

simulate this circuit

It does what it's supposed to, now, at least somewhat reasonably. Any hints on how to reduce the ringing on the step response would be much appreciated though.
(Blue trace is a step on the control voltage, yellow is the response)


texts: How to determine u(t+1) - u(t-1) as even, odd or neither?

texts:
x(t) = u(t+1) - u(t-1) is given.

How do we determine if it is an even or odd signal or neither? Do we plot it out or do we use the condition and convert it.

and also, is it even or odd?


texts: Why shouldn't I use a Zobel network to improve the power factor of an electric motor?

texts:
This is a homework question, so I would prefer something that would make me think and maybe promote discussion.
I understand the use cases for a Zobel network in an audio setup, but I struggle to see the connection to electric motors.
My guess is that we use Zobel networks to improve our power factor, but sometimes we wouldn't want to do that for an electric motor on purpose. If improving the power factor for a motor means improving its horsepower, I can understand how we would want to have some control over the horsepower of a motor in some applications.
If my household is set to 110V 60Hz, I am limited to how I want to control the horsepower of my ceiling fans, furnace fan, bathroom fans, etc.
But, maybe I am getting this all wrong.  Why would I not want to use a Zobel network to improve the power factor of an electric motor?


texts: What does "configuration" refer to in PCI and PCIe? How is this different from "Enumeration"

texts:
I am not being able to find a clear description of what configuration means in PCI and PCIe. I have found something called as configuration space, but without knowing what configuration means, it is not possible to really understand what configuration space is.

So what does configuration and a configuration space in PCI and PCIe mean? And how is this different from "Enumeration"?


texts: Why are laptop power supplies marked "IT equipment only"?

texts:
Laptops are often shipped with switching power supplies that among other have a phrase for use with information equipment only on their body.

Why can't I use the same power supply to power a motor or a set of LEDs or a lamp given it's output voltage and its wattage are suitable? I mean it outputs say 36 volts of direct current and can supply say 50 watts - okay, that would do for my motor/LEDs/lamp, why can't I use that supply?

What's so special in those power supplies that they bear the "IT equipment only" mark?


texts:
Is there a way to identify a blue LED? I only know it's bright (like a high intensity white LED), needs a higher voltage than the equivalent red bright LED, and has T1 (3mm) form factor.

Note By "identify" I mean find out what the part number is, so that I can google the datasheet. In particular to make it run as bright as possible without burning it in the long run.


texts: Is there any truth to the fact that an op-amp will behave ideally in closed-loop configuration only when it's closed-loop gain << open-loop gain?


texts:
I'm probing an RF (~75 MHz) oscillator.  I'm trying to measure the voltage drop across a capacitor.  (I'm afraid I may be pushing it's limits.)  When I attach my x10 'scope probes it loads down the circuit some.  (C probe = 16pF)  Can I add a series capacitor (1-2 pF) to make another voltage divider and turn my probe into ~ x 100 (I'll have to calibrate it from another stiff source.)

Edit:  So I tried it.  Massive fail on the first attempt because of the inductance in the long ground lead of the probe... (long is ~10cm).  I made a little ground clip.  And soldered it on.

And that worked better.
Here's the 'scope shot with x10 probes top and bottom of the 2.2 pF cap that I have in series.

Channel 2 (in blue) is the "x100" side.  I'm getting what looks like more bandwidth with the x100.  This is not too surprising the x10 probe is an HP10071A Bandwidth = 150 MHz. But also the calibration factor is only about x30.  20 Vp-p vs. 7 Vp-p... Is that to be expected?


texts: Programming a PIC16F84A Microcontoller in assembly with MPLAB increment problem

texts:
I'm programming a PIC16F84A microcontroller to automatically increment a number with a 1 second delay, and get it displayed on a 7 Segment Display. The 7 segment display is already set so there's no need to worry about it.

The following is the code I wrote:

COUNTERA EQU d'12'         ; delay counter1 points to register file 12
COUNTERB EQU d'13'         ; delay counter2 points to register file 13
COUNTERC EQU d'14'         ; delay counter2 points to register file 13

            ORG 0x00        ; program starts here
            BSF  STATUS, RP0; switching to Bank1
            CLRF TRISA      ; PORTA is output
            BCF  STATUS, RP0; switching to Bank0
            CLRF PORTA      ; clearing PORTA

TASK1       MOVLW D'6'
            MOVWF COUNTERC
            MOVLW D'24'
            MOVWF COUNTERB
            MOVLW D'167'
            MOVWF COUNTERA

COME_AGAIN  INCF  PORTA
            GOTO  LOOP
            GOTO  FINISH

LOOP        decfsz COUNTERA,1 ;the 1 second delay loop
            goto LOOP
            decfsz COUNTERB,1
            goto LOOP
            decfsz COUNTERC,1
            goto LOOP
            GOTO COME_AGAIN
FINISH
            END            ; program ends here

When I run a simulation on Proteus Demo, it only increments once (goes from 1 to 2) and then it stays at 2. However, my goal is to keep it incrementing from 1 -> F, then restart it from zero.

I suspect that the code is off on the INCF PORTA line, but I don't know how to fix it.