texts: Circumvent 433MHz antenna printed on PCB

texts:
I'm tinkering on a cheap chinaware alarm center which receives signals from its detectors on 433MHz. It is located inside a metal box which forms a faraday cage and apparently reduces the range too much. Moving the alarm center out of the box is not an option because the surroundings are very dusty, I'd like to just extend an antenna out of the box.
I found the receiver on one corner of the PCB, it's a SYN531R.
A conducting path forks off L1, passes a first solder point, goes some 4cm straight up, then 90° right and ends after another some 14cm straight on a second solder point. Apparently, the path between the two points acts as antenna.
My plan is to solder a cheap antenna directly to the PCB, however, I'm no pro, so here are some questions:

Is this antenna a valid choice?
Intuitively, I'd solder the external antenna onto the first solder point, then interrupt the rest of the printed antenna with a cutter. Once done, there's no way back anymore, so maybe there's a less intrusive solution: Could I solder the external antenna onto the first solder point and leave the printed antenna intact? Or maybe solder the eternal antenna onto the second solder point (at the end of the printed antenna)?
As for GND of the external antenna: Can it be soldered onto any solder point carrying GND on the PCB or does it have to be the GND pin of the SYN531R?

Here's a photo of the PCB:

This is the schema taken from the SYN531R datasheet:

Thanks a lot for your hints!


texts: soldering 5x5x1 high power SMD LED: anode, heatsink, cathode

texts:
I've got myself a high power SMD 850 nm LED, 650 mW radiant power. I need to use this non-stop for hours at a time. So I need to solder this to a heatsink to manage the heat. I've got 4 them, actually -- to account for the vast potential for me destroying one or two of these before I get it right. It looks like this (screen shot from its spec sheet, the link is below).

Are there any standard adapters that I could use to make the soldering easier? My previous version (3x less heat dissipation) was on a star adapter which, in turn, was mounted to a finned sink with thermal paste, so I was planning to recycle the heat sink.  That sink is also threaded, to which a glass lens is neatly attached. However, this time I am worried if that thermal paste+star won't be dissipate the heat. If it helps, I have an endmill, and I can modify standard Al or Cu pieces (Al is easier) to make this work. I've got eye protection for the IR as well.

http://www.roithner-laser.com/datasheets/led_highsingle/smb1n-850d.pdf

Thank you in advance!


texts: What exactly do D+ and D- on a USB connection do?

texts:
Of the four pins on the usb I know the power and the ground pins are used to supply power to a USB device. But the other two pins D+ and D- what exactly do they do? whats their function? I think these pins transfer signals to and from the usb device to the computer and vice-versa.

An Electronics StackExchange answer says the two pins refer to differentially encoded transmission scheme that USB uses. What is differentially encoded transmission scheme?

And how does a computer software use these pins to communicate with with the usb device?


texts: What is optimum maximum frequency of DDS?

texts:
According to most DDS datasheets, they can produce up to half the maximum frequency. for example for AD9850, max clock is 125 MHz and it can produce up to 62.5 MHz. But in higher frequencies, the number of DAC steps is reduced and the wave form will start having steps until it is not really a clean sine wave.
Is there any equation ( for example fclock/4 or something ) that shows the maximum frequency in which DDS produces most reliable sine wave?


texts: Millis() Function with Relay Connected to Motor

texts:
I connected my motor to a relay module and everything is working fine, but the timer that I created is what is causing trouble. What I wish to achieve is for my motor to activate after 5 seconds of the light being on and stay on until the photoresistor no longer detects light. It is able to achieve that, but after a few trials, the relay activates as soon as the photoresistor detects light. I can temporarily fix this by pressing the reset button, but again after a few trials, it is the same again.
I have provided a video:
https://youtu.be/XmRjOIuPIRc
int analogValue;
int voltage;
int timer = millis();
void setup()
{
  pinMode(A0, INPUT);
  pinMode(7, OUTPUT);
  Serial.begin(9600);
  digitalWrite(7, LOW);
}

void loop()
{
  analogValue = analogRead(A0);
  analogWrite(7, voltage);
  if(analogValue > 200){
    if((millis() - timer) >10000){
    digitalWrite(7, HIGH);
    }
  }
      else{
        timer = millis();
       digitalWrite(7, LOW);
      }
}


texts:
I am hoping to use a MIL-DTL-38999 circular connector for 10/100 Mb ethernet in acc. to IEEE802.3.
So the insulation voltage should be at least 1500VAC for 1 min.
Most connectors I have seen during my search on Mouser and Digikey are service rating M and hence only 1300VAC.
I have searched the exchange and found a similar question (Link), where the answers state that for IEEE802.3 compliance the insulation rating of the connector must be higher than 1500VAC for compliance.
However, searching “RJ45 dielectric withstanding voltage” on Google yields a plethora of RJ45 connectors with a 1000VAC rating. As RJ45 is THE Ethernet connector how can this be? I am not aware of RJ45 being used for anything other than Ethernet these days. Am I missing something here?


texts:
I'm anxiously awaiting the delivery of my second set of custom designed PCBs from BatchPCB.

The first board I designed was pretty darn simple and didn't have any problems.

This second set includes a full on arduino compatible board plus two shields for it.  Somehow I suspect I made a mistake somewhere.

My question is:  what sorts of things have other folks gotten wrong?  When I start debugging why that board doesn't work, what kind of things should I be looking for?  What are the first things that you check?

As it turns out, my boards have two problems.  The first is that there's a cap too close to the ISP header.  I just didn't allow enough space.  The second is that the holes I specified, while large enough for all my normal through-hole components, are too small for breakaway headers to fit into without manually reaming them out a little bit (almost like it's just the thickness of the plating layer that covers the copper).  Other than that, everything is good.  I very carefully checked all the power connections before doing anything to make sure I wasn't about to short something badly, and held the various boards up to the light and verified alignment of stacking headers.


texts:
I'm fairly new to electronics. I'm designing a simple board with a left and right channel audio input, and two sets of left and right channel outputs. A 16Mhz AVR microcontroller controls two relays (one for each output), which allow each output to be toggled independently. The signals will be line level audio feeding into audio amps, so very little current should be flowing through the signal lines.

In order to minimize noise on the audio signal, what is the best way to handle grounding? Should I have two isolated ground planes, one for signal and one for digital circuitry, or is having one ground plane with the components laid out so that the microcontroller switching current doesn't flow near signal lines sufficient?

Secondly, should I include a relay to switch the signal grounds, or leave them connected? Are there any potential issues with leaving the two output grounds connected, even if only one output is on?


texts: Safely burning resistors - carbon film vs. metal film

texts:
Short:

Are carbon film resistors and metal film resistors equally safe to burn?

Long:

I want to explain to children that they need to carefully calculate and check resistor values. I don't only want to explain it, but also let them feel and see it.

In one step, I use three resistors in parallel, operating at their defined 0.25 W. They will get hot and the children can feel it. However, this may not show the danger enough, so I also want to let one of them catch fire.

A lot of things are obvious when performing this experiment

keep the children in a safe distance
use a fire-proof surface
do the experiment outside, so there's good ventilation
have a fire extinguisher near, just in case
in any of our experiments, we use low voltage DC power source, < 24 V

I was also looking up online sources like Blowing up a resistor and I'm glad that resistors burn but don't explode.

However, there's one open question to me: we have 0.25 W carbon film resistors and 0.25 W and 0.6 W metal film resistors available. Are they equally safe to use?

My assumption would be that the carbon film resistors just burns to ash, but the metal film resistors might melt into liquid metal. Is it maybe even educational to do both experiments, because the result is so different?


texts: LED lighting up dimly when uC is in reset

texts:
I designed a PCB which has an STM32G431CBT6 on it. There are also two LEDs, a red and a green one, connected as shown:

When I powered it on the first time (so no program on the uC yet), the red LED was lighting dimly. After loading a LED blinker program on the uC, it works fine (with full brigthness), however if I press the reset button, the red LED is lighting dimly again and the voltage across R1 is 120mV. So 120uA is flowing for some reason. The other LED doesn't do this, and the voltage across R2 is 0.
Looking at the datasheet I only found this note about PB4 (page 60):

"After reset, these pins are configured as JTAG/SW debug alternate functions, and the internal pull-up on PA15, PA13, PB4
pins and the internal pull-down on PA14 pin are activated."

But even if there is a pull-up on PB4, the LED shouldn't be on, so what causes this behaviour?

Edit:
After setting the project aside for a while, it doesn't do that now, but I don't know what has changed. I was only tinkering with the boot settings in the option bytes (with the ST-Link Utility), although I don't think that has anything to do with the UCPD pull-down.
By the way, I found the default setting for disabling the pull-down:
(and yes, it is called "pull-up" in the settings, but it seems to be a mistake)

When checked (default), it puts the
HAL_PWREx_DisableUCPDDeadBattery();

function call into the HAL_MspInit function.
When unchecked, the LED was lighting dimly even after reset, so it verified the accepted answer to the original question. Until it started to never do the dim lighting again.
Summary:

Originally the LED was dimly lighting up only in reset.
This was because of the UCPD pull-down, which was disabled by the "save power of non-active UCPD - deactive Dead Battery pull-up" checkbox being checked by default. I could verify this by unchecking it and not configuring the GPIO pin for the LED, which resulted in dim lighting even after reset.
Something happened and now it never does that, regardless of the checkbox or being in reset. Maybe the pull-down has broken for some reason? I only know that the GPIO pin itself is functional, it can drive the LED properly when programmed.


texts: Dicharge a Photoflash Capacitor in a coil

texts:
I am trying to do the coin tosser according to this pdf (result here)

So the circuit is supposed to be this one:

simulate this circuit – Schematic created using CircuitLab

However when I did it and tried to charge the 330V Capacitor, it wasn't charging it anymore.
But when I removed the Diode D, it did charge it, but then the discharge in the coil wasn't working great.... and when I put the diode back in position there was a spark. (I took a 400V regular diode with the white band attach to the + circuit part)

Thank you for your help!

NB: Be advised that this circuit is dangerous, and you can get shocked if you don't be careful.


texts: What happens if there is a fault in the neutral wire between the grounding pole and the centre tap of the transformer?

texts:
I was reading through some SE questions/answers on residential power transmission and came up with two scenarios I'm unsure about:

Assume that your house is wired properly (with no degradation), but there is a fault on the neutral wire between the grounding post and the transformer on the corner of your street. Will your outlets work properly?
Similarly, I'm familiar with the case where a fault in the neutral wire between the grounding post and a circuit in your house can pull it up to line voltage. I guess this means that the two 180° out of phase live circuits in your house NEVER share the same physical neutral wire? What would happen if they did and a fault occurred?


texts: How to calculate susceptance of an inductor in series with a resistor

texts:
Given the following part of a circuit, I have to find the susceptance.

I know that the susceptance is \$B=-\frac{1}{reactance}\$.

I know that the resistor does not have a reactance, however, my textbook's solution is \$ B=-\frac{wL}{R^2+(wL)^2} \$. Why does \$R\$ come up in the solution?


texts: Anyone remember a rotary dial adder project from the early 1980s?

texts:
When I was a kid in the early 80s in the US, I remember coming across a published electronics project that involved a rotary dial from a telephone and small lamps, which I think was a simple adder. I have this picture in my mind of a photo in the magazine or book where it was actually constructed out of wood. I also recall that all the parts were specified with Radio Shack part numbers. I also remember that upon going to the local Radio Shack, they had virtually none of the parts (remember, this was the beginning of the long fall for RS).

I'm looking for that specific project or that specific book/magazine. Not just any project involving a rotary dial or an adder. I've tried all combinations of terms on Google and haven't come up with anything that matches my memory.

Here are my speculations.

It may have been a project from the 70s, since the 80s saw rotary dials go into the trash.
I'm also almost positive it used transistors, not tubes.
And, it used lamps and not LEDs.
I haven't exhaustively searched Popular Electronics or Radio Electronics, but I can tell you it is not among the first few years of 80s projects in Radio Electronics.
I am also nearly positive it wasn't a Forrest Mims book.

Any pointers?


texts: How to generate positive and negative power supplies from a single supply with high current driving capability?

texts:
I am trying to build a 1553 military standard bus transceiver (analog front end) and I am required to use a single power supply of 3.3 V. To be able to receive, my comparators need supplies of +/- 3.3-10 V to generate the right CMOS logic levels. To transmit, I need even higher voltage supplies for current feedback drivers to amplify 3.3 V logic levels to as high as 20 V peak to peak. I first thought of using a boost converter to first boost 3.3 V to 20 V, then use a rail splitter to get +/- 10 V. But the possible problem with that would be lower current drawn from 3.3 V supply which could be problem for current mode transmission.

What is the best way to distribute such supply levels from a single low supply voltage?

Plus any advise regarding 1553 analog front end bus transceiver implementation would be highly appreciable.


texts: Drawing circuits with IC pinout diagrams

texts:
I am not sure whether this community or the tex.sx is the most appropriate for my question.
I have an assignement where I am given a boolean expression and I have to implement these expressions using a predifined list of Integrated circuits.
For example: \$ f= xy + z\$ and I have a 4071 OR IC as well as a 4081 AND IC at my disposal.
When drawing \$f\$ as a circuit diagram, I want to use the IC pinout configuration diagrams (like the ones on the image below) and show all the external connections from each pin. That way, I am confident that my approach is clear.

The problem is that I don't know which software allows to draw circuits along with IC pinout configuration diagrams. Or, is there a latex package somewhere that can deal with this? I will mostly use the 4000 CMOS series so I only need that range of diagrams.


texts: Constant Current Source circuit improvisation

texts:
simulate this circuit – Schematic created using CircuitLab

I was wondering whether I could use this circuit as a constant current source provided my load circuit impedance was less than Rb/hfe? All points of view are welcome....:)


texts: 3.2 Gb/s high speed interface over 50m: copper, fiber, other ideas?

texts:
I need to run a 3.2 Gb/s interface over 50m. My client is keen on Cat6e. The lower the price, the better. These are my findings so far:

I'm looking at using a Spartan 6 GTP Tranceiver with copper (Cat6/6a). I've spent most of the past few days digging through Xilinx's documentation on high speed tranceivers (mostly http://www.xilinx.com/publications/archives/books/serialio.pdf), however I'm still a bit unsure about this. The following is what I've found:

The above document mentions that copper is OK for less than 6 Gb/s (GTP max is 3.2 Gb/s, so cool) and for distances less than 20m (I'm looking at 50m or so).
The cat6a specifications are for 100m and 10Gb ethernet (so that's fine?)

So what I'd like to do is maybe use Xilinx 10Gb Ethernet core in the FPGA with the GTP transceiver. (This core: http://www.xilinx.com/support/documentation/ip_documentation/ten_gig_eth_mac_ds201.pdf)

That document mentions that Spartan LXT is compatible with the 10Gb ethernet MAC, however, it doesn't say anything about copper, all the examples are fiber, and I'm assuming that the 10 Gb Ethernet core has a maximum speed of 10 Gb/s, but will work with lower speeds?

ALSO:

Is is possible to use other interfaces (AURORA, XAUI) over Cat6e as long as the specs meet the Cat6e requirements, (and considering that I'm looking at a 3.2 Gb/s interface)? Or do I need to use specific connectors/cables for Aurora/XAUI? (1 channel).

ALSO #2:

How "easy" is a board design/layout for a 3.2 Gb/s tranciever? The xilinx high-speed documentation mentions that special equipment (scopes, etc) is necessary for debugging high-speed interfaces. Since the clock period is 3x bigger than 10 Gb/s, i assume that the tight timing requirements are not as stringent?

I've used Aurora and XAUI before, but always the FPGA HDL design side, never the board design, and we always used high-speed connectors. This is my first high-speed serial board design. A second opinion would be hugely appreciated!


texts: Reuse I2C SCL or SDA Pins to signal interrupt

texts:
In an I2C network, I am using an AVR microcontroller (AtMega328p) as a Master and I hooked it up to multiple sensors as Slaves, such as the TMP102, SI1145, MPU9250, among others.
All of these sensors have pins to signal interrupts to the microcontroller.

Assuming these interrupts never come at once, would the following HW configuration make any sense? :

(assuming all the sensors produced on the falling edge of the signals)
tie the interrupt pins directly to the SCL line
set up an Interrupt Serice Routine reacting to the falling edge of the SCL, enable it
wait for a negative edge on the SCL. At this point, a sensor has tripped a treshold
disable the ISR, normal I2C polling of the sensor ensues

The goal would be to save up space on the PCB design and use existing tracks.

Granted, one would need to poll all the sensors to know who interrupted by pulling SCL low.

My example used SCL, but is the difference between SCL and SDA important in this case? The I2C communication could be reset / timeout when the uC restarts communication with the sensors.


texts: Cascades instrumentation amplifiers with a buffer in between stages: What should I use for buffer?

texts: I have to cascade two instrumentation amplifiers, INA126, and in between the stages I want to use a buffer.  How should I make the buffer? The output from the first INA126 is of few volts.


texts:
How much current can this 74HC245 handle on each output pin? Is it 20mA, 35mA, or 70mA?

I don't understand what the difference between output current, output clamping current, and supply current is.

http://www.nxp.com/documents/data_sheet/74HC_HCT244.pdf


texts: Computers support hotswapping so that a user can replace a harddrive while the system is running. Is that mostly software just powering off the harddrive or is it some special hardware involved? If there were not special hardware then I suppose that you could hotswap any drive but it seems that the drive must support it in hardware.


texts:
Possible Duplicate:
  Any reliable site where hardware engineers can be hired for small (work-from-home/telecommute) projects?

I want to outsource couple of industrial electronics circuit design and development, what are the resource (website) to do so.

my requirement is mostly circuit design / pcb design and two or three development/optimization cycle.


texts: I'm working on creating a wireless interval timer with an Arduino, is there a specific Arduino board required that can work with multiple LEDs and give me the programming capability for providing time, and having multiple timers?


texts: Getting LEDs brighter without drawing much more current

texts:
I am developing a bike light that runs off of a 3.7V Li-Ion battery. I am currently running 3*10mm Ultra Bright White LEDs (~25,000mcd each). They each draw 20mA.

I am relatively happy with the ratio between their brightness and their current draw...but I would like to get the lights a little brighter, without chewing up my 1200mAh battery to quickly. And these LEDs are not very expensive, either.

I am currently using through hole LEDs, but am open to SMDs or any other solution you may have.


texts: What is this style of button / pad called? How can I us them in my own projects?

texts:
I really want to make some custom MIDI controllers. I've gone through the exercise of making a microcontroller talk USB to my PC and breadboarded some button circuits on perfboard. I'd like to step it up to the next level though and use "real" buttons and pads. Problem is, I don't know how to learn what to do next.

I've attached a picture below of the style of pad I'd like to use. I thought this would be a "membrane button" but that isn't really what I want. Can you provide some guidance on what that style of button is and how I can use them in my own project?


texts:
I need to create two isolated power supplies (so that one's electrical noise doesn't affect the other) out of my 12V battery. One has to be at 5V for some logic circuitry, and the other at battery level (12V nominal) for some motors.

For the 5V one, I used a classic linear regulator (L7805), but I don't know how to create one that outputs the same as its input and is isolated from it.

I'm asking this question because at first, I connected the motors directly to the battery. That resulted in my 5V dropping briefly every time the motors went from stopped to running (probably generating a current spike and consequently a voltage drop on the battery), resetting my microcontroller.

My first thought was to use some buck-boost regulator and adjust the output to be the same as the input. There would be some issues though, regarding size, price and the fact that it'd impose a current limit.

Edit:
I'm asking for a way to achieve this isolation. For answers about my project specifically (capacitance and other ways to solve my problem), which I consider off-topic in this question, go to this chat linked in the comments below DKNguyen's answer.


texts:
I bought a 20W soldering iron a while ago and I found the experience very frustrating as the tip does not get hot enough quickly and when it does melt the solder it gets cold so quick I can't get the solder to flow long enough i.e. I end up with blobs all over the place.
A friend of mine heard all my cussing and praying for a more powerful iron when I was putting a circuit together and out of the goodness of her heart she bought me 100W soldering iron from Hong Kong. I was praying for a 60W model. This new soldering iron gets hot, about 420 C and I  an easily get the solder to flow but I am worried about this high temperature killing my PCB or components.

Is a 100W iron safe to use on Arduino type projects?
What are the risks I run with using this type of iron?

Just a safety check before I destroy something valuable.
Update:
Been soldering for a while now with both the 20W and 100W and they both have very different uses. The 100W is NOT recommended for smaller jobs and finer components - it is way too powerful. I replaced the tip of the 20W iron and tinned it properly and been keeping it tinned. It is actually not that bad so I suspect my blues started with the tip not being maintained properly. Lesson learned experienced gained.
Update 2:
Finally invested in a proper soldering station (Hakko-FX888) and I am in soldering heaven. I felt like I have been trying to paint the Mona Lisa with rock with my other irons. Life is beautiful again.


texts: Current rating of center-tapped full wave rectifier vs full wave bridge rectifier

texts:
I was going through the Art of Electronics (Horowitz & Hill) and in the section on center-tapped full wave rectifiers (pg.47) it says:

  "The output voltage is half what you get if you use a bridge
  rectifier. It is not the most efficient circuit in terms of
  transformer design, because each half of the secondary is used only
  half the time. Thus the current through the winding during that time
  is twice what it would be for a true full-wave circuit. Heating in the
  windings, calculated from Ohm's law, is I^2R, so you have four times
  the heating half the time, or twice the average heating of an
  equivalent full-wave bridge circuit. You would have to choose a transformer with a current rating 1.4 (square root of 2) times as
  large, as compared with the (better) bridge circuit; besides costing
  more, the resulting supply would be bulkier and heavier. "

Why would the current rating be ~1.4 times more than the bridge circuit?
Also, 'Equivalent full-wave bridge circuit' refers to one with the same output characteristics as the center-tapped circuit right?


texts: 3ph diode-rectifier with RL load : non - active power

texts:
I am studying this circuit. In my book there is an open question about reactive power Q in input in cases 1) L=0 and 2) L=oo

Well I do  know that Q(Var) occurs when there is phase difference between input voltage and current. I proved by some other facts that in the second case there is a really small phase difference and Q=200Var <<<S.( which I guess could be considered not - important) . But in case where L=0 , is there a intuitive way to explain what happen with Q in input ( i guess is 0 but i can't find a way o put into words)?
Maybe you could also provide me with some facts about active power p in input , distortion power (input - output both cases)


texts: Is it safe to clean contacts with an eraser?

texts:
Today, while I was cleaning a RAM module, I was thinking about this.

An eraser is really a easy way to clean gold/copper contacts in such modules.
And it is really tempting to do so.

I did it a few times with RAMs, network cards, graphic cards and other components.

But, my question is: is it safe at all to clean contacts with an eraser?
It at least works, since the module was perfectly working fine this time.


texts: Do surface mount components tend to use less power than through hole components?


texts:
In a simple electronic circuit with a momentary switched LED (or bulb, tube etc.); what can be done to trigger the LED for several seconds before proceeding to break the circuit?

In other words; I want one quick press of the button to activate the LED, and also deactivate it automaticslly after x amount of seconds; just as if I'd been holding my finger on the button the whole time.

I probably didn't explain it very well, but I'm sure it should be easy to infer my meaning. FYI; I'm just trying to teach myself how to build basic, practical electronic circuits by tinkering with a breadboard.

I know it's pretty simple stuff; but at the moment, the configuration basically looks like this:


texts:
I'm (again) placing bypass capacitors around an FPGA, and can't seem to get to a sane solution, given that I have all the pins assigned, and the supply pins are right in the middle of the I/O pins.

As an example, placement around pin 1:

The next pin is another supply again (I can manage that, but I get further and further away), then a few I/Os, then another supply of the high ripple kind right in the middle of the package side.

So far, an avenue I haven't yet explored is shrinking the footprint (I use the standard 0402 from Eagle, which are humongous), and I'm wondering whether I can sensibly do so, and how big I need to leave the SMD pads in order to keep a strong connection.


texts:
let's consider a basic scheme of a receiver.

Now I have two questions:

I was told that the presence of the mixer is important since it is useful to delete the carrier frequency of the received signal. In fact, it is very difficult to work (i.e. amplify, filter etc) with high frequencies and so deleting it will be very useful. But now I have a previous question: why should we impress our signal to a high - frequency carrier, during transmission (and cannot use directly the frequency of our signal)?
In this picture I see an analog voltage entering the antenna, and a digital voltage exiting the envelope detector. My question is: when we speak of digital transmission, is the voltage entering the antenna digital or analog?


texts: Clearance between hole and power plane after removing unused via pads

texts:
After removing unconnected via pads and repuring copper fill, the clearance between the via hole and the fill will be defined by the rules, but the pours will be closer to the hole. Does this bring risk when manufacturing vias, especially when drilling?

Clarification:
Yes, the only guide in this case (as well as many other when making PCB) is to follow PCB manufacturer's guidelines. What made confusion in my case is that the rule which defines clearance between any hole and copper was wrong, so when I remove via unused via pads, the copper comes to close to the hole (DRC was not complaining due to the bad rule).


texts:
I'm working on a two channel DDS function generator for a project. I have done some research and I want to use the AD9833 IC controlled with a Microcontroller, an Atmel chip if possible since I have work with the Atmega328 before.

My question is, since I want two independent channels, how can I control two AD9833 chips with one Microcontroller?


texts:
For the circuit shown below, diodes have these parameters : RD=infinit, Vy=0.6 V.
In forward bias diodes , V=0.7 V .
V1=10 V , V2=-5 V
Vo =?

I don't know if my solution is correct. Please provide any suggestion. Thanks!


texts: What could be causing my APCs to buzz from time to time, and for my Tesla to stop charging?

texts:
I have two issues happening at the same time (very much related).

The APC brand UPS backups in my office all start buzzing at the same time, then click once every 5-10 minutes.  This happens at all times of the day.
If my car is plugged in (Tesla wall charger), the Tesla app starts over when I hear the noise the APCs make.  It does this 3 or 4 times, then the car turns the charging off and I get an alert that the charging is interrupted.

Note, I have tried two different chargers and both do the same thing.  (One charger is the wall charger, and the other is the charger that is never used that came with the car.)
I have called the electrician and the power company and both parties say that everything is normal.  I am having the breaker boxes exchanged out ($5000 later.)  This is scheduled, but doubt this is the cause also.
I don't think this was a surge as the second car charger that I use still does the same thing, and it was not plugged in when this problem first started.
What could the issue here be?


texts: What is the efficiency of a stepper motor driver?

texts: We are using this stepper motor driver (https://www.sparkfun.com/products/12779). In its datasheet, there is no mention of efficiency? How much is the efficiency in motor drivers like these?


texts: What does the USB non-removable strap option actually change?

texts:
I am designing a device that uses a Microchip USB2412 2-port USB hub. The downstream ports of the hub are internally directly connected to other devices. Upstream is a removable USB B for power & data.

The USB2412 has the option to specify that the downstream ports are non-removable.

Should I set those bits to true? I think the answer is yes but maybe those are intended for use when the upstream is non-removable. I've seen references to this being useful when the hub is permanently connected to upstream but none when the hub itself is removable.

But more importantly, will setting the non-removable flags actually change anything for my use case? Does this affect other use cases differently?


texts:
I'm curious if there is a way to reverse the way an SCR works(Current flow to load UNTIL a gate signal arrives). I think this would come in handy for a bunch of hobby circuits I may want to design/build. I tried the following to test out the only way I could think to do it, but it did not work...

Anyways, is it possible to do this and if so, can someone post a schematic of how this is accomplished?

[Edit by OP]

I just tried this, but still no luck...


texts: Is there a way to overdrive a single phase, capacitor start, AC motor?

texts:
I have an AC system that runs on single phase 120v AC. The "motor" is a hermetically sealed compressor, fractional horsepower. It has a single capacitor about the size of pill bottle. Based on that, I think the motor is a capacitor start type single phase motor.

What I want to do is use a VFD, or something similar to run the motor up to perhaps 120% of it's rated speed. This is for an experiment, so I only need the motor to work for a few hours, and if I accidentally destroy it that's an acceptable risk.

I've done a bit of research and it appears that this is not a trivial task. However, it seems like if I were able to create a voltage of 120V+, up to around 72 hz, then that should work. Would it not?

If so what's the simplest way to go about this? I'm considering buying a single phase 240v output vfd, and stepping the output down using a 2:1 transformer. Is there a better way?


texts: Latitude and Longitude DMS conversion in MPLAB XC8

texts:
I am using two function for lat and long DMS conversion.
when I am using those two function ,either lat or lon is display correctly in my UART.when If i will print latitude first in UART,displaying correct DMS value.then when I will print longitude second its dosnt show the right value(0000000).

void lat_DMS(char *lat_data, char *lat_return)
{
                char temp[3],temp1[3];
                float res1=atof(lat_data);
                float flo=res1/100;
                int ilong=flo;
                latdeg[0]=ilong;
                sprintf(temp,"%03d",ilong);
                strncat(lat_return,temp,strlen(temp));
                float lati=flo-ilong;//subtract the values
                float res12=lati*60;//multiply the value differ value with 60
                int minutes=res12;
                latdeg[1]=minutes;
                sprintf(temp,"%02d",minutes);
                strncat(lat_return,temp,strlen(temp));
                float isec=res12-minutes;
                int lasec=isec*60;
                latdeg[2]=lasec;
                sprintf(temp,"%02d",lasec);
                strncat(lat_return,temp,strlen(temp));

}

void lon_DMS(char *lon_data, char *lon_return)
{
                char temp1[3];
                float res2=atof(lon_data);
                float lonflo=res2/100;
                int inlong=lonflo;
                londeg[0]=inlong;
                sprintf(temp1,"%03d",inlong);
                strncat(lon_return,temp1,strlen(temp1));
                float longi=lonflo-inlong;//subtract the values
                float lonres=longi*60;//multiply the value differe value with 60
                int lonminutes=lonres;
                londeg[1]=lonminutes;
                sprintf(temp1,"%02d",lonminutes);
                strncat(lon_return,temp1,strlen(temp1));
                float lonsec=lonres-lonminutes;
                int longisec=lonsec*60;
                londeg[2]=longisec;
                sprintf(temp1,"%02d",longisec);
                strncat(lon_return,temp1,strlen(temp1));

}

I am storing value in arrays for transmitting 4 bytes+4bytes of lat and long(Deg,Min,sec,dire each 1 byte)

in main function

     uartwrite("LAT:");
    lat_DMS(latPtr,&Dlat);
    uartwrite(&Dlat);
    uartwrite("\r\n");
    memset(Dlat,'\0',strlen(Dlat));

 uartwrite("LON:");
    lon_DMS(lonPtr,&Dlon);
    uartwrite(&Dlon);
    uartwrite("\r\n");
    memset(Dlon,'\0',strlen(Dlon));

whether stack is full?
I am confused.i am loading my program on my controller ,its not loading correctly and when loading on second time on micro cont,the previously loaded program is running.I have written uartwrite on while loop more than 2 time its not showing the lat and lon value


texts: Why do rechargeable batteries deplete so quickly compared to non-rechargeable?

texts:
I'm trying to use rechargeable batteries wherever I can, but I have to say that it is quite annoying having to change batteries so often compared to non-rechargeable.

Taking low-drain things like a TV remote control or temperature sensor as an example - I get maybe half a year from regular batteries or maybe a year before having to change them. I don't even know because you pretty much forget about these things. With rechargeable batteries I have to recharge them every 1-2 month or so.

Besides all the marketing fluff - are there "better" rechargeable batteries for these low-drain scenarios, e.g. Eneloop? Better: keeping their charge longer.
I like using cheap 800mAh AAA for e.g. temperature sensors. I also have 1100mAh AAA or even 2700mAh AA rechargeable batteries lying around. For high-drain things (e.g. camera flash light) I like using the batteries with higher capacity - but is there a benefit in using these for the TV remote? Do they last longer?
If there are differences between all these rechargeable battery types, is there a golden rule? E.g. use Eneloop for TV remotes, use high-mAh for flashlights?


texts:
I'm learning about op amps, and I have the following circuit where the amplifier is used as differential amp

Since both inputs are the same, I was expecting the output to be zero. But instead, I got this (around 9 mV peak)

I don't understand where this output comes from. I simulated the circuit using livewire


texts: N-channel mosfet with negative drain current

texts:
I am trying to simulate the DC characteristic of N-channel mosfet in ADS using a tsmc018nm model.
This is the imported tsmc180nm model.

I have setup the circuit's vdd and vgs as sweep variables to plot IDS vs VDS for different gate voltages.

The drain current is negative, what am i doing wrong?


texts: Non-glass heating element for an etching tank

texts:
I have been using below glass heating element (the part name is ET20) on my etching tank.

The problem is that the glass is too gentle that breaks very easy for many reasons, I already needed to replace a few of them.

I wonder if you could suggest me any non-glass heating element for an etching tank that is not fragile and durable to use?


texts: How many LiFePO4 cells can be in parallel?

texts:
How many lithium iron phosphate (LiFePO4) can safely be connected in parallel, in order to achieve higher power output (and capacity)?  Wired directly together, without components such as resistors or power transistors limiting current flowing between parallel cells.

Precautions taken would include ensuring they're brand new cells from the same manufacturer lot, at about the same state of charge, and letting them rest for a day to equalize before charging or discharging the pack.

This chemistry is supposed to be much safer than other lithium chemistries, as it doesn't catch fire even when punctured.  Is it also safe to add more cells in parallel?  The most I've seen discussed for other chemistries is around 3 cells in parallel.  Would it be possible to get to 10, 20, 30 cells in parallel with this chemistry?  The completed pack would drive a DC motor.

If it's not safe to wire that many directly together, would it be safe if current limiting components or fuse/polyswitch were added between parallel cells?  Or is it better to architect a large pack in strings of at most 3P x (however many) in series?

Note: NOT asking about other lithium chemistries such as lithium polymer.  Specifically LiFePO4 in form factor of cylindrical 18650 or 26650.  Advice about tradeoffs in using much larger cell sizes rather than parallel small cells welcome.

EDIT:

When cells in parallel are new and well-matched, they balance well.  As the cells age, their internal resistances get progressively less matched.  Somewhat self-correcting as a cell with lower internal resistance will charge & discharge at higher current than others - thus getting aged faster and catching up to its peers.

However if one cell fails to open circuit or very low internal resistance, current will now be flowing mostly through that one cell.  Say the pack normally gets charged at 1C rate, now that cell is getting 3C rate.  If there are 20 cells in parallel, now it's 20C rate.  The more cells in parallel, the more current can flow to the most unbalanced cell.  It seems dangerous not to limit this current.

@SpehroPefhany recommends self-protected cells.  Are there methods which add protection circuitry around unprotected cells?  Are lithium iron phosphate cells considered safe enough (no fire/explosion) not to require it, with cell failure simply leading to low pack performance or requiring pack replacement?  How are dead/shorted cells normally handled in these large pack designs?


texts:
I am a newbie when it comes to embedded systems and I am an even bigger newbie when it comes to working with the BeagleBone Black (Rev C in my case). I want to play and discover the PRU on the BBB, but it proves to be a more confusing task than I imagined because a lot of things on the net seem outdated.

What are the steps to take to get the PRU working (a blinky to begin with, even though my interest lies in figuring out how to communicate with the PRU using the shared memory) considering I have a fresh and clean BBB Rev C in hand (new Debian).

Thank you for your help.


texts: Can someone explain how this transistor comparator works?

texts:
I am looking to make a comparator using transistors and I stumble across this circuit claiming to be one:

Unfortunately, the description that came along with it leaves a lot to be desired, referencing components and points that aren't actually here - I assume due to typos but I can't actually work out how it is meant to work.

The purpose for this is I want to have a voltage reference of 1.8 - 2V, and then a supply rail connected to the other side. So long as the supply rail is higher than my reference voltage, it will allow power to be supplied to a component, but if not, it should remove power from it.

Any thoughts as to how this works and whether it is suitable for my application? Diagrams would help me to understand it more but any help would be appreciated.

Extra Information:

I want to use this 'comparator' in a circuit where I have a \$\mu\$C being powered by a current limited ~2V regulator. Currently, if the voltage output of this regulator drops below 2V the \$\mu\$C causes the rail to latch at 1.7V - 1.8V and won't allow it to  rise to 2V again which is a bit of an inconvenience if anything. (How can I get this PMOS to turn off? is another question of mine which contains more information on the issue I am currently having)

I currently have a delay switch that will allow my reservoir capacitor to fill enough to be able to handle the initial start-up current of the \$\mu\$C. There are some problems with this and I just thought I might be able to replace it with a simple comparator, have a ~2V reference on one pin and the rail to the \$\mu\$C on the other and if this falls below my reference, it will simply cut off the power completely - this will prevent it from latching at ~1.7V and will allow the reservoir capacitor to fill up again in order to provide the needed start-up current again.

It isn't something that would happen a lot, and realistically, once fully designed and programmed, the circuit would never cause this rail to drop below 2V - however, there are some circumstances that might cause it to happen so it is a 'just-in-case' type thing.


texts: USB micro B receptacle has 6 mounting tabs. How many do I actually need to ground?

texts:
This USB  micro B has 6 mounting tabs. If I ground none or only 1 of them, will it ruin the signal? There is a pad for the signal ground that is separate from the mounting tabs.

Fyi USB 2.0 has a max signal rate of 400 Mbps, and an effective payload throughput of up to 35 Mbps, according to Wikipedia.

Is there a general best practice for lazy / layout-confined people to decide how many mounting tabs have to be grounded for a tens-of-megabits connector?

If I only ground one of the tabs, should it be the one closest to the board edge (i.e. to the cable)?

Thanks!


texts: Is there an inductor type that has the best inductance per unit volume?

texts:
Inductors come in many types e.g. cylindrical (single and multi layer), spiral (single layer and stacked), toroidal (single and multi layer), and probably others.

For an air core inductor, assuming the same wire pitch and including the volume enclosed by the coils, is there a particular shape/layering method that gives the best inductance per unit volume?

Assume a that the current is low enough that thermal issues are not a concern, i.e. it is a tuning inductor and not a power inductor.


texts:
I currently use the circuit below to power the OUT output when the signal is high (5V). I have a problem related to the size of the circuit, using a relay takes up a huge space. With this I would like to know if anyone has any idea of circuit with the same logic however using MOSFET or BJT. The current OUT consumes is 3A. Signal when it is high has 5V and when it is low it has 0V.

simulate this circuit – Schematic created using CircuitLab


texts: Protecting capacitor from high voltage impulse spikes

texts: The purpose of the circuit below is to produce an extremely high voltage impulse over the inductor so that I can place a spark gap in parallel to it and create a very large spark. According to simulation this should work as designed, but I am concerned about protecting the capacitor. The highest voltage rated cap I could find was 30k, but the simulation predicts spikes of -220 kV. I tried placing a diode in parallel to the inductor, but that drastically reduces the voltage spikes. The source controlling the switch is just a simple pulse function switching every 1.2 seconds.


texts:
I need some ideas for a pushbutton ground selection circuit.

I want to be able to switch grounds using momentary pushbuttons. I could do this simply with a rotary switch, but due to design I'm trying to avoid this. The pushbuttons should deselect the previously selected ground. I have a simplified drawing using LEDs to illustrate the idea.

This is to show the circuit with a rotary switch (trying to avoid this setup).


texts: Two solenoids lower spindle, but it won't raise again... suggestions?

texts:
I purchased an old over-head pin router for my woodshop. It uses two solenoid valves.  They are apart of the assembly that lowers and raises the rotating spindle.  When the electric foot pedal is pushed, I would have assumed that the first solenoid would be activated, (allowing the air to lower the  spindle), while at the same time the second solenoid would be turned off.  (Right?  Wrong?)  Then when the foot pedal is pushed again the 2nd solenoid would be activated and the first turned off, allowing the air to raise the spindle.

But what actually happens when the pedal is pushed, is that both solenoids are turned on at the same time (securely lowering the spindle), and when the pedal is clicked again, both solenoids are turned off and the spindle remains where it is (although it can be raised by hand).  Are my assumptions wrong?  There are no return springs.  Is it possible both solenoids are used to force the spindle down (holding it securely during the routing), and then when the solenoids are turned off the air pressure alone is supposed to return the spindle to its up position? (Implying there is a non-electrical impediment?)  Thanks ahead of time for brainstorming with me.


texts:
Firstly please forgive my electrical ignorance (I'm a competent software developer but that's all).

I am hoping to power a micropump (model M100S standard) for a terrarium, my (possibly naïve) idea is to power it from USB, with a variable resistor to allow me to control the flow.

Ideally I'd like to be able to control the entire system from a PC:  on, off and variable flow.

However I'm aware that this may be massively complicated (an actual USB device as opposed to simply drawing power), so as a first pass I would like to get it safely drawing power over USB.

Any clues as to how to do this?


texts:
I have a 10w solar panel which outputs about 17V 0.5A at full sunlight. I use a small buck converter to charge my SLA 7.2Ah battery. I have currently set the buck converter output voltage to 14v and in the day time it charges the battery and at night I use the battery to power a 10w led (which uses about 9.5W with the fan on). Battery charges at about 0.5A when there is full sun light.

My questions are,

14V is the best voltage to charge the battery on CV or I should change the voltage of buck converter ?
Is it okay to charge a SLA battery using this method even if I used a power supply to charge it?  (power supply ------buck converter------battery)
Is it okay to leave the battery charging at 14v for longer periods of time in case if I dont use the battery at night to power the light ?


texts: Does placing additional capacitors in parallel with CJ7805 affect its performance?

texts: I'm not sure if this is a stupid question, but I'd still prefer to ask than regret it later. I'm designing a PCB with the CJ7805 which, like the LM7805, can supply a steady 5 volts. In this case, it's to power a Teensy 3.6. There's a recommendation to place a 100nF capacitor between the Vin pin of the Teensy and ground. I already have capacitors (100nF and 330nF) situated around the CJ7805 as specified by the datasheet. I was thinking of placing a capacitor for the Teensy, but I was wondering if that would affect the overall performance of the CJ7805 since it would change the net capacitance? Or maybe capacitors work differently when placed far apart on a PCB? Would I even need to place additional capacitors on the PCB when it's already being monitored by one capacitor? I've seen boards use soo many capacitors before, and I'm getting a little confused. I'm new to PCB design so I'm still trying to find and understand the proper ways of keeping noise to a minimum. Any help would be appreciated. Thank you!


texts: Finding distance travelled by differential drive robot

texts:
In a two wheeled differential drive robot, with wheel radius 7cm. bot starts from rest and the two motors are randomly actuated. Left wheel has rotated by 270 degrees, and the right wheel rotates by 320 degrees both in the clockwise direction. Find the distance travelled by the centre of the bot?
I am new to robotics, please help me the way such questions are tackled. Thanks


texts: If a circuit is connected to a separate power supply from an Arduino that communicates with it, should I connect the grounds together?

texts:
I am using an Arduino (actually an onboard co-processor AVR on an x86-based SBC) to control 120 Neopixel LEDs. Obviously, the power requirements of this many LEDs requires a separate supply.
I can't just use a single large power supply for both, because the SBC requires 11-15V if using the DC input connectors. The Neopixel strings require 5V.
I believe that I should connect one of the ground pins of the SBC to the ground terminal of the large power supply that the Neopixel is using so that communications works properly and won't damage the Neopixels somehow.
However, is it possible that doing this could somehow hurt the SBC? That would be bad, because it was about $350. I suspect there will be no issue, but I wanted to ask engineers, because again, $350.
The way I understand it is that if there's no path to the positive terminal on the PSU, that there's no potential between the SBC and the PSU's ground, but it does provide a common "floor" so that the two devices can safely interact. But can the connection to the data input on the Neopixels from the SBC potentially be dangerous in this scenario?
If there's a risk of damage, I suppose I can get a voltage regulator to bring the 5V PSU up to 12V and then power the SBC from it.


texts: Can I use an inductive load in an ATX-to-bench supply project?

texts:
I'm doing my second ATX-to-bench supply conversion, and this time, I've decided to follow the "book" and place the correct minimum loads on all the rails instead of merely the 5V rail. This involves fairly small loads on the 3.3V rail and 5V rail (under 2W each), but a fairly sizable load on the 12V rail (12W). I've sourced very cheap cement resistors to provide the loads, but I understand that they are inductive loads, and I would like to know, will that cause a problem?

I assume it will not, because many of the loads in a normal computer are already inductive (HDD motors etc), but I would like confirmation from someone who knows a lot more about switching power supply design than I do.


texts: How to Convert between dB Voltage and Power

texts:
We read that the formula for expressing microvolts in decibels is different from that for milliwatts by a factor of 2:

\$U = 20\log_{10}{\frac{u}{u_0}}\$

\$P = 10\log_{10}{\frac{p}{p_0}}\$

(Note the leading factor of 20 versus 10.)

Why is this the case? Why do we not use the factor 10 everywhere?


texts:
I see on the internet showing CPW( coplanar waveguide) always placed on TOP layer with ground underneath. This is what I usually do.
Is it possible to place a CPW in an internal layer? if so what should I take in consideration?
On top layer I have components and various signals.
Unfortunately I can't place the GPS chip on the edge of my board and I have to route it all the way to the edge. The CPW would be 30mm long.

Thank you in advance


texts: Is this power switching circuit ok? Switching between VIN and USB

texts:
I am using a STM32F105FBT6 to create a CANbus analyser.

I plan to have a simple PC application that displays the CAN messages and lets the user put messages onto the Bus.

I also what to be able to program the device to continue sending a particular message on the bus when the device is disconnected from the PC and powered by VIN.

The device can be powered by VIN (8-30v) or the USB port, both can be powered at the same time.

I don't need really need 5v as all my components are 3v3.

I have come up with a pre regulator circuit using a MIC4680BM which brings VIN down to 5v. I then have another regulator which brings 5v down to 3.3v.

I have used part of the circuit that switches from VIN to USB from the Arduino Uno because this is the simplest application which is most similar to mine.

Their mosfet switch takes VIN though a voltage divider, I need a way to apply VIN to the mosfet which is always above 3.3v and not greater than 5.5v.

My questions would be:

Is this circuit going to work? (Providing I sort the voltage divider problem).

Could I just replace the voltage divider with a separate LDO circuit to take VIN to 5v solely for use as the input for the LMV358 (IC7)?


texts:
As long as I know the accepted methods for measuring the resistivity of electric grounding grids, once they are built, for any kind of building (in cities, at industrial level, transmission towers, etc) are:

Fall of potential using 3 stakes (I have seen this method the most)
Using a clamp-on tester and rods.
All sort of, in my opinion, unreliable 'things' using normal testers and cooper bars.

Does anybody know about other methods which are accepted according to norms or at least reliable enough?


texts: What is this IC Chip on this circuit board?

texts:
Very new to electronics outside base knowledge.
This board is from a small smartphone toy, where pressing and holding the button displays 1 color on an attached RGB LED and quickly double tapping the same button changes it to another fixed color. There's no way (on board) to cycle through the various color values, it's just a hard change between different values.
I'm trying to build my own circuit that does the same thing, but I'm not sure what that IC is below the push button. There's no text on it or even an image, so I can't look up the data sheet. Searching the silkscreened "TLBZ-039-V2.0" also yielded no results. My first thought was that it was a generic 555 chip because all it has to do is change the voltage going to the different pads, but all the datasheets I've found for a 555 chip show pin 1 is GND and on this board, it has pin 1 being VCC.
Without taking the IC off the board it also looks like pins 2 and 3 just aren't used, or they disappear somewhere beneath the chip. I can post more pictures of the bare board with the traces once I get the button/IC off.


texts: How to determine which camera batteries will take the most photographs?

texts:
I recently bought a used digital camera, complete with 6 lithium-ion batteries.

The batteries all have different date codes on them, but some of the older batteries seem to last longer than the newer batteries.

I want to determine the relative power capacity of each battery, to learn which ones will take the most photographs.

The simplest, but most time-consuming, way to accomplish this is to:

Charge a battery
Take pictures until the battery depletes
Count the number of pictures
Repeat for the next battery

This likely will take many hours to complete.

Is there a faster, reasonably accurate way to determine the relative power capacity of each battery (I hope I'm using the correct term)?

I do have a simple digital multimeter at my disposal.

UPDATE

Per request, here is what the batteries look like:

And for reference, here is an image of a compatible battery showing the electrical contacts:


texts: How can I use this HP power supply as hobby power supplly

texts:
I have an HP notebook that is dead. So I thought abount using its power supply to play around with my arduino and my DC projects. So I removed the jack of the power supply

This is my power supply (18v 4A)

The problem is that when I removed the jack came out 3 wires: black, white and blue. I already tried making BLACK and WHITE as + and - and leaving blue disconnected, but my circuit turns on for 3 seconds, after that it turns off for 1 second, and start again and again.

What is going on? Cant I use a notebook power supply as my hobby power supply for arduino, LEDs...?


texts: Common cathode LED resistor with 4017 decade counter

texts:
Is it possible to use a common cathode resistor for all 10 LEDs with 4017 decade counter? I try it but only the first LED (output 0) lights up.

EDIT: I got it working. My wiring was wrong. I use a 9V battery power supply. I plan to cascade multiple 4017s (up to 10 of them) to a single LED sequence - so I may get 100 LEDs hooked to a single common resistor.


texts: Location determination in electromagnetic digital pen

texts:
I was reading an article that explains how SPen from Samsung works. There is one coil in pen. I think there should be one or multiple coils on the sides of the tablet. I guess other graphic tablets may also use the same mechanism.

My question is, how can S pen find the location? Are there multiple coils in the tablet, or is there just one? As in these cases the tablet can detect the pen from about 10mm distance, the capacitive or resistive touch is not responsible for this and there might be another mechanism.

I've also read this article that shows that it is possible to measure the distance with the aid of two coils. Does this pen use the same mechanism?


texts: Battery choice: Effect of "pulse current" and "continuous current (maximum)" rating differences

texts:
I am trying to understand the consequences (if any) of  substituting a CR2450 battery for the specified CR2340 lithium battery in a small device.  The device is constantly "on" and transmitting a signal, which is intended to be picked up by receiver based on proximity of the small device to the receiver.  (When the small device is close enough to the receiver, a solenoid engages and stays on until the small device is again out of range.)

My hope is that -- because they have the same voltage and current rating -- the CR2450 will work and provide much longer battery life in the small device than the CR2430, but I just don't know enough to understand the impact of the specs that are different for these two batteries.

As mentioned, the CR2450 and the CR2430 have the same "nominal voltage" (3.0V) and the same "standard current" (0.2mA) ratings.

Physically, they are the same diameter (24.5mm), but different heights (CR2450 = 5mm; CR2430 = 3mm).  [However, height won't be an issue here].

The difference in these two batteries' "nominal capacity" ratings (CR2450=600MAh; CR2430=270mAh) are the reason I hoped the CR2450 would last about twice as long as the CR2430.

BUT, they have different ratings for "continuous current (maximum)" (CR2450=1.0mA; CR2430=3.0mA) and "pulse current (maximum)" (CR2450=15mAh; CR2430=20mAh), and I just don't know whether or how either or both of those spec differences relates to this proposed battery substitution.

So can someone help me understand "continuous current (maximum)" and "pulse current (maximum)" with respect to batteries, and particularly how those spec differences might produce any practical differences if I substitute a CR2450 battery for the CR2430 battery that this small device was designed to use?

Thanks


texts: Diode meter of my DMM does work for red LEDs but not for white LEDs

texts:
I have a diode meter on my DMM Powerfix Profi and I want to measure the forward voltage. (actually it is not so profi at all).

So I tried the steps needed, and found the Vforward of a red led to be 1.7 V which is as expected.

However, when measuring a 3mm and 5mm white LED it did not show anything. Probably because the LED has a higher forward voltage and the batteries inside the DMM (I think 2x1.5V) are too less to power the LED.

Is there a way to measure a white LED anyway with the diode function of a DMM?


texts: Steady Voltage Supply for extended runtime: Batteries in Parallel?

texts:
I have a device to measure tilt which is powered by 2 batteries (9 Alkaline Battery, Industrial by Duracell). So essentially, the voltage supply is 18V. I am using it for a project that came with a "black box". This black box has essential has a switch that changes the supply from battery to a supply from mains and a converter to step it down to 18V.

I need to log the tilt measurements for large amounts of time (a few weeks or months even). The mains supply can run forever but it is just too noisy and distorts the data. Digital filtering and smoothing doesn't help as the recovered value is wrong and accuracy is very important. The battery supply is fas less noisy and I am able to get accurate readings, however, the batteries only last about 3 days.

My question is, to provide a stable supply for a long time; would connecting multiple batteries in parallel solve the issue a will there be some shorting if there is a mismatch in voltages.

Is there any other solution (to make it work with batteries)? Smoothing the mains even further?


texts: I was wondering if there was any protective systems in place for if a power line falls like one that would stop the electricity going to it but I can't find any. Does anyone know if there is and what its called?


texts: What is a good methodology to identify small SMD components?

texts:
Having been in the position of trying to identify a strip of mystery 0603 components I found on my floor, I thought a good general question to pose to this community might be what a recommended set of steps could be to identify similar unknown components.

I identified these by using package (0603) and color (black) and then thinking about where they might have come from, and how they might have ended up being on the floor. Luckily I didn't need to use any test equipment to work out they are a 4.7 \$\mu\$H inductor because I'm not sure how I would have proceeded to get to this end result without my extra clues; hence this question.

I'm looking for a reasonable set of steps and methodology to follow that would allow me to identify most small components (new or recovered) with no (or simple) markings. Presumably identifying package is the first step and the last steps would be using test equipment.

I searched and did find resources like this that mainly deal with through hole and traditional components but very little on these surface mount items many of which share similar packaging.


texts: Is it possible to connect eight digital inputs to a digital output?

texts: Can eight digital inputs (at 20-Mhz) output to 160-Mhz? Does a multiplexer work for this? Thanks for your answers.


texts:
As stated in this question: Antiresonance of multiple parallel decoupling capacitors: use same value or multiple values? I have been curious to the real-world effects of different capacitors and their frequency responses. Using Spice with a small signal analysis is easy to do, but it really can't be replicated on a real board to my knowledge.
If I wanted to take a board, put a high speed IC on it with it clocked at a high frequency to test various decoupling capacitor schemes, what would be the best way to quantitatively see results? I see a few options:

Check the ripple voltage on the input supply to the IC. This would show how well the decoupling caps are able to supply the IC with high F voltage spikes. The issue is measuring the AC on top of the DC is not easy to do with a normal scope setup. See here: https://www.tek.com/blog/a-better-method-for-analyzing-ripple-on-power-rails It would require a high bandwidth scope and high cost probes.
Use a spectrum analyzer to see the frequency content on the power rail. Similar to how conducted emissions would be checked. I really don't know much about this method, so I'm not sure it it would work.
Use a spectrum analyzer to check the radiated emissions from the PCB. This would work, but requires a very noise free environment which I don't know if I can do.

Ultimately, I don't need to achieve a real-world comparison with any standard. I just need a quantitative value to compare one board to another, with the only difference being the decoupling scheme.


texts:
According to this link, the equivelent circuit diagram of a transformer (seen from the secondary side) looks like:

Now, I want to find the values of the following constants:

$$R_p,X_p,R_c,X_m,R_s,X_s\tag1$$

So, my idea was to set \$V_p=10\sin(2\pi ft)\$ and \$n=N_p/N_s=1\$. Now I vary the input frequency and I measure a RMS current trough the load resistor that I put in series with \$X_s\$ (at the output). If I do that for six different input frequencies I can solve for the six constants in \$(1)\$.

  Can I use that method of finding all the constants that I described in \$(1)\$?


texts:
Error:

../Src/main.c(107): error:  #253: expected a ","

code part:
uint8_t maskPWR_MGMT_2[2] = {0x6c, 0b00000111};//6c


texts: Allowable reverse current into Alkaline battery

texts:
Anyone know what happens to alkaline battery if a small current pumped in?  For example 0.5uA into a 9V battery alkaline?

I want to add a simple 9V battery + rectifier as backup voltage to a 12v circuit.  Voltage regulation isn't important, and 9V would be acceptable.  To minimize voltage drop, I need to use a Schottky but in reverse bias, they aren't exactly open circuits.  So, the question is, is 0.1uA unintentional "charging" current a problem for shelf-life of standard 9V alkaline?

I have thoughts on a safer battery backup solution (i.e. with relays or rechargeble batt), but its important for me to keep the solution as simple as possible and with maximum battery self-life, and I just want to know the risks of pumping in a small leakage current into the alkaline.


texts:
I'm trying to select a solder flux and so many references (and one or two SE questions) discuss the types and differences.  They mention "activity", such as "Rosin Activated (RA) flux has a higher activity than Rosin Mildly Activated (RMA) flux."
What is "activity"?
What is it that RA flux does a lot of, that RMA flux does a little of and R flux does barely at all?


texts: Is there any way to use Half Duplex RS485 without using a dedicated controller pin for RE - DE?

texts:
I have attached the reference circuit I am using for a simple MODBUS (Read Coil) communication application. I am short of Pins on my controller and I do not want to use a dedicated controller pin for RE and DE.

In the above circuit,
is there any way MAX-485-CTRL always remains LOW and is pulled HIGH automatically when there is a signal on DI by using some capacitor combination?


texts: LTE, downlink multiple antenna channel estimation with and without Channel State Information (CSI)

texts:
In an LTE downlink with CSI at the transmitter, is the radio Tx in the base station and Rx at the user end hardware part of the channel estimation?
example: Tx to Tx and Rx to Rx isolation between different transmit and receive paths in a multiple antenna system
How about  TDD without CSI: is Tx to Tx and Rx to Rx isolation included in calibration?


texts: Non-inverting op-amp saturating incorrectly

texts:
Background

Hello, I'm trying to amplify an audio signal using an LM324N in a non-inverting configuration. I'm not trying to build an audio amplifier to drive speakers, I just need to amplify it a bit for another project.

The problem is when the opamp is on a signal supply (12V to GND) and the input signal goes below 0V the opamp saturates positively (Figure 1) when I expect it to saturate negatively. However when I use a bipolar supply (12V to -12V) it works as anticipated. In my application I would only be able to use the signal supply. I checked the datasheet and the minimum input CMRR is 0V so isn't that an indication that it should be able to swing all the way to the negative rail? I'm not sure what's the issue with the single supply vs the bipolar supply and saturation.

Question

How can I fix this circuit to work on a single supply (Figure 1) and saturate negatively when the input signal goes negative?

Figure 1

Figure 2

EDIT 1:
Added biasing and AC coupling on input and output(figure 3)

Figure 3

EDIT 2:
Connected R4 to Vcc/2 (Figure 4)

Figure 4

EDIT 3:
Changed AC coupling caps to 100uF

Figure 5


texts: Please Help with Syncing 2 Linear Actuators

texts:
I am a complete noob in regards to electrical wiring and scoured countless hours on the internet for help. I bought 2 DC12V 16inch Stroke Linear Actuators and connected it with a 20 AMP 12V - DC Motor Rocker Switch (dpdt?) and a 12V 6A AC DC power supply. The purpose was for a standing desk. It works really well but i noticed that it’s not synced (i am aware that it’s not possible to get it perfectly synced).

I read online that i am able to buy a DC speed controller to control the speed so I bought a 12V-40V 10A PWM DC Motor Speed Controller but it did not fix the issue. I wired the power supply directly into the speed controller P+/- and connected a wire from the dpdt that previously used to connect the power supply to the M+/- slot in the speed controller. Is it possible if I just buy an additional speed controller and connect a linear actuator to each controller in the M+/- slot and then plug the power supply where the linear actuators were previously plugged in the dpdt? For P +/-, i would introduce new wires for each controller and then crimp the wires together (- to -, + to +) and plug it to the dpdt to try and control each actuator separately. Do I need to use a relay? I'm confused as how to wire that together if necessary.
Sorry if this is very confusing as I don’t know the correct way to explain it.
Thanks in advance!


texts: What exactly is the purpose of a Hall sensor in a BLDC?

texts: I was reading an articles about brushless DC motor, used in CPU fans, from this link. First I thought that the Hall sensors are used only for measuring the speed, but that is not correct, it has something to do with the current flow in the coils. Because, even a two wire CPU fan has a hall sensor inside. Can anybody explain the exact use/uses of this sensor in a BLDC?


texts: Question about FM and PM and Angle Modulation

texts:
I am having a bit of trouble understanding how FM works mathematically. I fully understand the conceptual basics regarding how information is transfered by modulating the frequency, but what I don't get (from the equation below), is how this expression inside the cosine term actually changes the frequency. When I think of trying to change the frequency, it makes more sense to me to 2π(fc)(t) a function of Xm [ex. 2π(fc)(1 + Xm)(t) which comes out to be 2π(fc)(t) + 2π(Xm)(t)]. Why do they have the integral in there? And why is the amplitude of the carrier (Ac) specified, when it shouldn't make a difference to the output signal?

Also, would you be able to clarify the difference between FM and PM and angle modulation (a combination of both), and how/when each should be used. Thanks for the help


texts: how can i make compile stage shorter in VCS (synopsys) after logic changed?

texts:
if I changed few lines from a specific Verilog of design and now I want to recompile, can I compile just the related files or I need to compile the whole design again?
i'm using VCS tool by Synopsys.


texts: Why the rotor core losses are very tiny compared to the stator core losses in an induction motor?

texts: Book says rotor mostly runs at speed near to synchronous due to which the relative velocity between rotor and stator magnetic field is very less. Correspondingly making rotor core losses tiny and stator big. I also know that voltage induced in rotor depends on the relative velocity. I dont get it what does relative velocity have to do with core losses and how does it make stator core loss big and rotor tiny?


texts:
I busted my STFjoy boombox by dropping the box with the charger port plugged in. I opened the box and found the USB charger port needed to be resoldered. I bought the soldering equipment and found I had to ply out the entire usb female port. During soldering I left the soldering tip on the circuit too long and I'm wondering if I should buy a new charger port off amazon or throw the entire fix away. My concern lies with the way I burned the PCB.

!

Edit: I might have tried resoldering the usb port too many times. The connectors dont look the same anymore and the PCB looks damaged. Thoughts? Repairable?


texts: How to generate a controlled frequency sine wave using a microcontroller like PIC18F4550?

texts:
I'm designing a phonic wheel emulator. I have a PIC18F4550 and the following power supplies: +5V, -5V, 12V. I need to geneate a sine waves from frequencies near 500Hz up to approximately 8kHz. The shape does not need to be a perfect sine, but the amplitude needs to be at least 10V or higher for all frequencies.

The controlling of the frequencies can be made manually or digittaly (it means the person can vary the frequency using a potentiometer or typing the frequency on the device)

I thought to generate a square wave by the microcontroller and use a active filter to filter the high order harmonics, but I think this is not a good approach because the frequency band is relativelly wide.
I heard about sine lookup table and DAC, but PIC18F does not have DAC module.

I read about LTC1066-1 at the best answer chosen to this question. But I didn't understand very well, it seems to use a PLL and  a LTC1066, it seemed a bit expensive and complex to me.

Another approach is one that I found here. But it sems to be even worse because it does not have a explanation of the signals required only a electrical scheme with some signal inputs that I don't know from where it come from.

Is there a simpler and non expensive way of reach this purpose ? Does someone have any suggestion ?


texts: Impedance Matching: Distance H is to prepreg or to core ?

texts:
I have a doubt about something:

Considering a 4 layers PCB where the configuration is as follow:
Toplayer / Prepreg / Ground Layer / Core / Power Layer / Prepreg/ Bottom Layer

Do I understand well that when performing impedance matching and width strip calculation on a micro strip on top layer (for an antenna strip for example), the calculation of W should be done using the dielectric constant of prepreg and H of prepreg being just below the top layer ?

When I ask our supplier what is the material used for prepreg and its related dielectric constant, they seems to be confused: one time they say FR4 and send the datasheet, another time they say 2116 but seems uncapable to give datasheet (hence I have no dielectric constan available and prepreg thickness calculation).


texts:
I am aiming for a breakaway PCB design for a small series where an unneeded compartment can be broken off. (See Image below)

I saw this for example on the STM32 Nucleo boards, where it is used to take off the flash interface once you're done with it. So I guess it shouldn't be a problem concerning the dangling PCB traces on top and bottom layer.

But what about internal layers?
- Is it problematic to have a supply and ground layer going across the predetermined breaking point?
- Would it be ok to do this when I make sure to have no traces intesecting throughout all layers?
- Is it concidered bad practice to do something like this?


texts: Driving a 5v logic input from a 3.3v output

texts:
I have a device which requires a 5v logic input. That input ordinarily needs to be high and the device is activated when the input goes low. I need to drive this from a 3.3v output (RasPi GPIO) which is low when the RasPi is booting. In summary: when the RasPi 3.3v pin is low, the 5v input needs to be high and vice versa.
What is the best way to achieve this? I'm thinking of using a PNP transistor but I'm struggling to understand how to drive this as the 3.3v input isn't enough to stop the transistor passing current. I've seen a few example circuits that pair the PNP with an NPN but these all require the input to the NPN to be high before the PNP passes current.
Is a Logic Level Converter a more sensible way to achieve this?


texts: How do I calculate deformant and real power of this circuit?

texts:
I have this circuit, the load is RL:

I need to calculate the apparent, real, reactive and deformant power assuming L is very large. Since L is very large that means Q= 0 var and Pload=~Uav*Iav and S=3*Urms*Irms. My problem is how to calculate real power and deformant power.


texts:
I need one camera IN & TWO outputs to feed into 2 DVRs.Just a resistor divider ok ?
Like this? Camera Types are AHD & Analog.

simulate this circuit – Schematic created using CircuitLab


texts: Interfacing AVR microcontroller to ADC, waveform generator and other peripherals

texts:
I am doing first project with AVR microcontroller ATmega32-A.

In this project I am interfacing with ADC (AD7798), waveform Generator (AD9833), Multiplexer, Capacitive sensor, Demodulator. I have attached simple block diagram for understanding purpose.

I have to generate sine wave and give it to sensor and in return I will get sensor output with some phase shift. I have to select the sensor output and input signal using Multiplexer. The selected signal will pass through demodulator and to the ADC. Finally ADC to Micro controller.

The concept is I want calculate phase difference between two signals such as Input(Vg) and output(Vr). To calculate the phase value I have implemented algorithm as like below.

  Phase of Vg (and so Vr in return) is what I can change, phase of
  demodulator switch (square signal from frequency divider) is constant
  and it is my background. I can put both Vg and Vr signal through
  demodulator.

  The algorithm must look like this: put Vg through demodulator, sweep
  WGP(waveform generator signal phase) until you get highest DC value
  (now you store how many degrees it takes to get this highest DC, and
  you calculate Vg amplitude from that).  Then put Vr signal through
  demodulator and also sweep WGP until highest DC value. This phase
  shift WGP value will be different for Vg and Vr.  In result you have
  the amplitude of both signals and phase difference between them.

I have wrote all functions like To read ADC value, Generate signal with specified frequency,Changing phase of the signal, Phase sweep from 0 to 360 degrees etc.

I have written the fallowing code to select signal using Multiplexer and change the phase of the signal from 0 to 360 degree by one degree at each time and getting the max value of D.C voltage.

From the above code I am able to select signal using "MUXSEL" Command and I am able to sweep phase from 0 to 360 degree, I am able to get max D.C voltage and corresponding Phase value. I am able get above value whenever I add delay.

  delay_ms(100);

If I delete this delay from "Phaseshift" function, it is giving nothing even if I reduce also.

If I place that delay then I am getting Max D.C voltage and corresponding Phase after 45 secs. This is too large time in my application. Then I have change channel then it also take 45sec and i have to use this values in other calculation so it takes large time.

I want get Max D.C voltage and corresponding Phase value with in 2 to 3 sec.

Any one help me how to do this.
![enter image description here][3]

[AD7798][4]
AD9833

added spi() function.

unsigned char spi(unsigned char data)
  {
  //Start transmision
  SPDR = data;
  //Wait for transmision complete
  while (!(SPSR & (1<<SPIF)));
 return SPDR;
   }

[4]: http://www.analog.com/static/imported-files/data_sheets/AD7798_7799.pdf


texts: What is the Thévenin equivalent of the mains power supply?

texts: Thévenin's theorem says that any voltage source can be modeled as an ideal source in series with some complex impedance. How does one quantify this model for AC mains supplies? What parameters are relevant? And are there any broad assumptions that can be made about these parameters on AC mains supplies worldwide?


texts: Microcontroller with rotary encoder and bluetooth capabilities

texts:
I am looking for advice on (what to use/how to make) a rotary encoder that I can connect to through bluetooth. I am writing an app that needs to display on screen in real time to the user the number of rotations as they are turning it. Also, I need to have the micro-controller record the revolutions per day so I can keep track of revolutions if their computer is asleep.

Criteria:

Must be stand alone
Has to be bluetooth compatible with a pc, mac, android and iphone.
Has to be able to store up to 7 days of data (this would be a very small amount of data, just the number of rotations per day and the timestamp).
Has to be small and cheep.

I was thinking a microcontroller with just a rotary encoder and bluetooth capabilities.

I have seen microcontroller like the Arduino and think they would be good to start with but I was looking for something that could actually be used in a final product.


texts:
I am making a remote monitoring system using STM32F1 MCU in which there are few digital and analog sensors attached and I would send their readings to a remote server periodically. Can I use JSON string to send over GSM to the remote server?

I am using M95 GSM Module for TCP Socket connections. The data is over 3G connection.


texts:
I am developing a voltmeter using FRDM-KL25Z and I needed a voltage divider with a 1.65V offset, and here is the circuit I am using:

Does the offset work well? Is there any other (easy) way to do it?
Thanks


texts:
While searching for something totally unrelated to this, I came a cross a website that derived it in this fashion:
the instanteous power in a capacitor is given by $$p_c= v_c(t)\cdot i_c$$
since $$i_c(t) = C\frac{dv_c}{dt}$$, this becomes $$p_c = v_c(t)\cdot C\frac{dv_c}{dt}$$
No issues so far....but, he then proceeds to write:
$$\frac{dw_c(t)}{dt}=\frac{d}{dt}[\frac{1}{2}Cv_c^2(t)]$$.
power is the derivative of energy, so I get the left hand side of the equation.  However, how does $$C\frac{dv_c}{dt}\cdot v_c(t)=\frac{d}{dt}[\frac{1}{2}Cv_c^2(t)]$$ on the right hand side of the equation?


texts: So this might be a hilarious question for some, but I think this is where my gap in understanding of digital logic design lies. I know the parts before simplification of minterms and so on. And now I am studying decoders, multiplexers and so on. In the middle I feel I have missed something. Decoders, for example, output the possible minterms. K maps use minterms. Why?


texts: What's the proper way of mounting surge arresters on TN-S system?

texts: I'm attaching a diagram with surge arresters put on each line. Most of the experts in the field say a proper defense against lightnings and switching events has three surge arresters - one between phase and ground, one between neutral and ground, and one between phase and neutral. So what is the proper way of connecting the surge arrester between phase and neutral?


texts:
I have been developing a C language software for software oscilloscope
which is part of a control software. From timing point of view the
software consists of two execution loops.
The first execution loop (let´s say "fast loop"- FL) is interrupt service
routine (ISR) for the "end of A/D conversion" interrupt. This ISR is
invoked with \$100 \mu\mathrm{s}\$ period and is responsible for recording samples of
given physical quantities into associated circular buffers which creat
core of the oscilloscope. It is also responsible for pushing samples
into another circular buffers for FIR filter calculations.
The second execution loop (let´s say "slow loop" - SL) is a FreeRTOS task
which is executed after 8 executions of FL. This loop is responsible for
dividing the oscilloscope circular buffers into the "pre-trigger"
and "post-trigger" parts based on commands comming from software running on the
PC, storing the osciloscope records into the external flash memory and FIR filters
calculations based on values in the associated circular buffers.

I have been thinking about robust solution for exchanging data between
the FL and SL and vice versa. I need to ensure:
a) as soon as the SL starts calculation of the FIR filters these calculations
has to be done with 8 values gathered in the last 8 executions of the FL i.e.
it has to be ensured that despite the FL is still running and periodically
interrupting execution of the SL and has new samples the SL still uses the
same "snapshot" of the 8 samples (which was valid at the beginnig of SL
execution) for whole SL execution time.
b) as soon as the SL decides to change the division between "pre-trigger" and
"post-trigger" (based on command comming from the PC) by changing position
of a dividing point the dividing point position is allowed to change at the
beginning of next FL execution despite the fact that the request could come
during FL execution.
Can anybody give me an advice how to solve that? Thanks in advance for any
suggestions.


texts: So why do SSD disks have a reputation for power efficiency?

texts: Why do SSD disks have a reputation for power efficiency? I've just looked at some the spec sheets for SSD and mechanical hard disks. In a lot of cases, the even during idle state, SSDs use slightly more watts than their mechanical counterparts? Can anyone explain this one?


texts: Measuring pulsating current using current sensor

texts:
I am measuring the current of the ignition coil using the hall effect sensor(ACS712)Datasheet. But the output of the hall effect sensor is pulsed analog signal. At zero current the output voltage is 2.5 volt. During operation the output is from 2.5 to 4.5 based on the current reading.
Now i need to measure the peak of the pulsed analog signal using Ni DAQ. Now what should i do.

Smoothing the signal using RC filter is good way or using software filter is good way

Igniter coil is operated at 192 Hz at 25% duty cycle. Frequency is generated using 555 IC


texts: How do I measure the output voltage of an RGB LED controller?

texts:
I want to replace an RGB LED controller (much like this one) with my own MCU.

Therefore, I think I need to know what voltage(s) the RGB LED controller outputs so I can make my MCU/component have the same output voltage(s). Then I can control the colours with the MCU.

The RGB LED controller has a 12V input, and a 12V + R + G + B output that connects to an LED driver unit.

Unfortunately, I currently only have a basic knowledge of circuits. I have a DC power supply and a multimeter, how would I go about finding out what voltage(s) the RGB LED controller outputs?

Thanks.

Edit
Here's the lighting circuit I have


texts:
I did some calculations for hybrid renewable energy system and I calculated the energy from PV and Wind. Then I modeled a battery for both the PV and the Wind energy systems.
I found that energy production is 720 kWh less than the electrical load, so battery discharges and 855 kWh of battery capacity is reduced in providing that 726 kWh.
I need to find the discharging rate of the battery.
Can you please help me in that?
How can I find the discharging rate with the data given above?


texts: What's the difference between measurement resolution and digits per second in time measuring devices

texts: In time/frequency counters/analyzers in technical specifications you can almost always find resolution and digits per second values next to each other. What is the difference?


texts: How does heater's air-flow sensors work?

texts:
I'm trying to deeply understand how the air-flow sensors mounted inside heaters works.
They are composed of a U-shaped PCB with an NTC on each end. For example:

This PCB is inserted into a tube where the air must flow.
If one of the NTC was shielded from the air-flow I can guess you can detect the movement due to the lowering of the temperature measured from the other sensor.
But because both will be affected by the air-flow it's not clear to how to measure such a movement.
Is this solution effective also in open air? I mean, placing this kind of sensor at the center of a room, could it detect any movement in any direction?


texts:
I'm trying to read a temperature sensor (Lm35) from my pic16f887 ADC. The thing is I'm getting a difference of about +/- 15 ticks in the results. Is this expected? Should I be doing the mean of several acquisitions?

The Lm35 gives temperature in mv, where 10mv = 1 celsius degree. The range goes from (20mv to 1.5v), roughly 2º to 150º. Because this in theory the ADC has an accuracy of 0.5º. (1024 ticks = 5v from which we get 307 ticks = 1.5v and since this is 150 degrees 150/307 = 0.5º).

To improve on this half a degree accuracy I've added a 2.5v zener diode to vref+ with a 10uc capacitor. Thus the final circuit I have is this.

simulate this circuit – Schematic created using CircuitLab

But I'm still getting variatons of +-15 ticks variatons, which is a lot in degrees!

And the code I'm using is this.

#include <xc.h>
#include <pic16f887.h>

#define _XTAL_FREQ 8000000

#pragma config FOSC = INTRC_CLKOUT, WDTE = OFF, PWRTE = OFF
#pragma config MCLRE = ON, CP = OFF, CPD = OFF, BOREN = OFF
#pragma config IESO = ON, FCMEN = ON, LVP = OFF

typedef unsigned int uint;
typedef unsigned char uchar;
typedef unsigned short ushort;

void uart_init(const long int baudrate) {
    SPBRG = 12;
    TXEN = 1;
    SPEN = 1;
    SYNC = 0;
    TRISC6 = 0;
    TRISC7 = 1;
}

void uart_write(char data) {
    while (!TRMT) {}
    TXREG = data;
}

uchar uart_tx_empty() {
    return (uchar)TRMT;
}

void uart_write_l(char *text, uint size) {
    for (int i = 0; i < size; i++) {
        uart_write(text[i]);
    }
}

ushort read_adc() {
    ADON = 1;
    __delay_ms(100);
    GO_DONE = 1;
    while (GO_DONE) {}
    ADON = 0;
    ushort res = 0;
    res = ADRESH << 8;
    res |= ADRESL;
    return res;
}

void main(void) {
    uart_init(9600);
    ANS0 = 1;
    TRISA0 = 1;
    PORTD = 0; // Set led port
    TRISD = 0; // LED Output
    OSCCON = 0x70; // 8mhz internal clock
    ADFM = 1;  // right justified
    VCFG0 = 1; // Vref+
    ADCON0 = 0b11000000;
    while (1) {
        ushort result = read_adc();
        char *arr = (char *)&result;
        uart_write_l(arr, 2);

        RD1 = 1;
        __delay_ms(500);
        RD1 = 0;
        __delay_ms(500);

    }
    return;
}


texts: FPGA: efficient way to collect data from many cores within SoC

texts:
I am looking for an efficient (in terms of footprint) way to periodically collect data from a multitude of processing elements (PEs) within an Spartan6-based design.

I currently have 16 PEs, but when the design scales up it may become up to 64. Each PE outputs two 16-bit words of data (A and B) at a frequency of ~100 KHz. The output data from all PEs needs to be collected and added to two sums (A_sum and B_sum). The system clock will be >100 MHz, so I have >1000 clock cycles to collect the data from the PEs.

The easiest way to do it would be two 16-bit wide multiplexers (A_mux and B_mux) with one input per PE each. For 16 PEs, this would cost 128 slices plus 512 interconnect lines within the chip, and it would take 16 clock cycles to collect the data. Since it doesn't need to be that fast, I am wondering if there is a more resource-efficient way to do it.

I was thinking of serializing the data in some way. This would save interconnect lines, but I would use more slices to implement the serializers in every PE. I would also need shift registers with parallel outputs (hence no SRL32) for de-serialization.

UPDATE

Some of you suggested I may have answered my own question. Serialization obviously comes to mind, however I am not sure whether it is really going to be more efficient. My question is not so much whether serialization is feasible, but I am concerned that serializers for every PE will use up more FPGA resources than a 16-bit multiplexer with inputs for every PE. Maybe there is some clever implementation I haven't thought about, but it seems to me that the fat mux is really the most resource-efficient way. Am I wrong?


texts:
I have to measure signals using oscilloscope on all the four lines in following circuit. J1, and j5 are headers given by the manufacturer on the board (MACHX02 1200-ZE). I connected ground lead of the probe to the ground on the board and other lead on of the lines one by one.

My friend says that you should not look at the waveforms this way, instead you must isolate/disconnect two chips, FT2232H and MachX02, and then measure the signals.

Is it really required to do so?


texts: Comparator Inputs Approaching the Same Voltage

texts:
Please excuse any mistakes or blatant errors, I am a beginner.
This circuit is meant to have the op-amp function as a comparator, and produce peaks on the output that I want read by a microcontroller. The issue is after simulating this "Data Slicer" op-amp circuit multiple times, I noticed that eventually, the two inputs are approaching the same voltage. This is causing quite a bit of unwanted chattering on the outputs.
I believe this circuit has an RC network with a time constant of 0.1 s.

How can I fix this, so that the output is consistent with the change provided by the photo-transistor, and get rid of that chattering?
Thanks


texts: Can 5okW be transferred using resonant wireless power transfer?

texts: I don't mind efficiency or loss, but simply can it be transferred? I'm wondering more about the size of the receiver than the transmitter. If the receiver is positioned within the power transfer field just how fast can the power transfer be initiated? I'm assuming the receiver needs to detect and initiate the resonance to initiate the power transfer and it can start very fast in the order of nano seconds.


texts:
Preface: I am designing a UPS such that if the AC main fail the device can continue to run for at least 10 days. My goal here is to make a design that can last years off a non-rechargeable battery. When starting this I originally thought to use a comparator, but after looking/googling I found that the diode approach was superior.

Design:
What: A 3.3 Volt .5 Amp UPS(Uninterrupted Power Supply)//I know you guys like numbers :)

Questions:

1) Use a diode or schottky diode?

schottky diode pros -  I will enjoy the efficiency on the low voltage drop when operating from the battery

schottky diode cons - The higher reverse leakage current will decrease the lifespan of the battery which is my biggest design constraint.

2)Is this sufficient with regard to the battery not supplying current back towards the mains? Should I include a diode from the mains towards the load?

3) Would it make more sense for the back up power to come after a voltage regulator? I know that AC mains can fluctuate quiet a bit so this could remove any instance were the battery may engage when its not needed.

4) Are there cheap/simple alternatives to the diode approach that could provide superior results to my proposed method?

Thanks,
Josh


texts: MLCC vs Tantalum: For Decoupling, input to regulator and ripple reduction

texts:
I require a 3.3uf capacitor in a 30 VDC environment for three different purposes:

decoupling of precision ADC or DAC;
input to a regulator (linear, switching, LDO); and
output of any regulator for the purpose of ripple reduction.

I can either use an MLCC (Multi-Layer Ceramic Capacitors) or Tantalum capacitor. I know the main drawback of MLCCs compared to tantalums is that the effective capacitance is reduced by applying DC voltage to them. So I set off to find suitable capacitors with voltage ratings of 50 VDC (to be on the safe side). I'm looking for 3.3uf Tantalum and MLCC whose effective capacitance is 3.3uf @ 30VDC.

Results:

Tantalum: 3.3uf 50 VDC costs about $2.00
MLCC 10uf 50 VDC X7R dielectric with effective capacitance of 3.3uf @30VDC costs about $0.70

Is there any reason that I might have missed which would warrant using the pricier Tantalum instead of the MLCC for aforementioned three purposes (exclude the case where a MLCC would make a regulator unstable due to the extremely low ESR) ?