texts: POE Extraction and port reuse for POE Device

texts:
i need to get out from PoE cable 1A of power in order to drive some LCD Displays and leds, i've digged around and i've found some interesting POE extractor that can fit my requirements (like the RT9400), basically, what i need is:

Extract power from POE Lan cable in order to use and drive my LCD Displays and led devices
At the same moment, reuse (with another female RJ45 female port - J2-OUT) the same POE and data to power up and use a olimex ESP32-POE-ISO device (Schematics Here)

Basically, J1-IN has a branch that will go to RT9400 PoE Extraction module, and J2-OUT will go to the ESP32-POE/ISO.

As you can see, i've only wired a part of the total H2019 transformers.

I'm not sure if it will work for two main causes:

Because the TD and RD transformers of the H2019 will not used
I don't know what can happen when the two devices will negotiate the POE power supply, the RT9400 is a class 0 signature device

This is the main block logical idea:

It can work? do you have some advices?


texts: Equivalent part for this MOSFET application

texts:
I'm designing a circuit based on the LTC4091 typical application:

They use two Vishay SiS447DN P-Channel 20V MOSFETs. Unfortunately those parts are not in stock neither at Mouser nor DigiKey, so I'm looking into replacement parts. I'm not sure what to look for in a compatible MOSFET, besides the Vds = 20V.

I found this dual MOSFET chip : NVMD6P02 which shares some characteristics but Rds(ON), Id and Qd are off by at least an order of 10, so I'm not really sure it could be a good replacement.

If not, what would be a good replacement part, or more generally, what parameter to look for in an equivalent MOSFET ?

Edit : I'm currently designing the PCB so the package is not important as I can change it as long as I find a readily available equivalent part.


texts: Wave Solder an Alkaline Battery on a PCB (any concerns)?

texts:
I have a specific application that requires a board to be powered by Alkaline batteries and would like to solder direct to the PCB using wave solder vs. hand solder (need to consider a high volume manufacturing method).

The battery will NOT be an SMT to the PCB, but thru-hole leads.

The battery will be be on the top of the PCB with other components, but not resting on any of the electronics.

Please send any issues, problems, or suggestions to push this forward and minimize rework, scrap, or wounded materials. Any consideration to damaging the Alkaline battery?

Example of leads, not the actual Alkaline battery to be used.


texts:
I understand that low resistance through a circuit will create a short circuit but what combination of voltage and amps which causes this?

For example, if I had a circuit with just a wire and a battery and it had a high voltage and low amperage, would this cause a short circuit in comparison to a circuit with low voltage and high amperage?


texts: UL Listed Item - fused, but plug rated higher than wiring

texts:
We are installing an item and have some concerns.  The supplier is claiming we will void the UL listing and warranty but the current configuration seems unsafe.

I am curious if the following would be adherent to UL standards?

The input is 28.3 amps into the item. The cord going into the back of the item is 10AWG wiring with a 50-amp plug. 10awg wiring is not rated for 50 amps therefore installing this on a 50-amp breaker will not protect this wiring.

The item is internally fused.

Two exemplary questions:

If instead we had 14 AWG wiring up the 50A plug but the load was fused at 10A would this be cause for concern?  There is a large amperage gap between rated load of the wiring and the point at which a short would trip the breaker.
Is there any UL enforced relationship between plug rating and wiring rating.

Thanks


texts:
This is a part from a (severely amateurish) Piezoelectric transducer amplifier circuit. I
am looking to identify this diode so that I can find a datasheet for it as well as possibly purchase more.

The original circuit PCB is shown below. I have drawn a schematic of the board (also below). Note that the marking in this circuit is of a zener diode; this is an error.


texts:
I made a boost converter with 1 1mH inductor, a mosfet, a 100uF capacitor rated for 400v, a 20 ohm 1/2 watt resistor, and an ICM7555 cmos timer.

Using previous knowledge and wikipedia pages on the subject, I assumed that my volt6age should be brought from a 5v input to 10 volts. I assumed that the inductor effectively became a battery in series with the source. After seeing a ridiculous (and continuously rising) voltage, I became suspicious.

What is going on? I not getting 10 volts, but I am rather getting a continuously rising voltage. My mosfet is rated for 55 volts so I haven't been testing above that, but it rises steadily until I disconnect it at 50 volts. If anyone could take the time to explain what is going on, that would be great.

*NOTE : My 555 timer is connected with unknown capacitors (small) as C and a 1k as Rb and a 10k as Ra.

Circuit diagram:

EDIT : For clarification, I changed "but it rises steadily until it reaches 50 volts" to "it rises steadily until I disconnect it at 50 volts"


texts:
I have a 3.3v line, which I will need to pull low intermittently with a microcontroller to send data.

I have tried using a BC547B NPN transistor (also tried BC337, BC517 and BD139) with the Collector connected to ground, the Base connected to a digital pin of the MCU (an arduino) and the emitter connected to the 3.3v line.

When the MCU needs the 3.3v line to be pulled low, it sends +5v to the Base of the BC547 so the emitter should be pulled low. When the 3.3v line can return to normal, the MCU sends LOW (0v) to the BC547. I have also tried adding a 1k resistor between the Base and the MCU.

What am I doing wrong?   (I know I can use an Arduino to pull the bus low, but I don't want to run the bus directly to the Arduino because it might get damaged)


texts:
I am trying to power an atmega328p, and the esp8266 for one of my projects.
I am trying to drive a relay to switch lights on and off. The problem is that the relay runs on 12v, the atmega runs on 5v and the esp8266 runs on 3.3. I was thinking of using a board mount power supply to use 120v ac, to get 12v for the relay, then use a 7805 regulator to get 5v for the atmega, and finally use a LM3940IT to get 3.3v for the esp8266. I do know that the esp8266 can not be run off of the atmega's 3.3v pin :(

What I am wondering is am I totally off on what I am hoping to do. Is there a better way? I have found a couple articles about switch power but, not as much as I would like.
I am also concerned about the amount of amperage needed for everything. I will use a Darlington transistor to drive the relay from the atmega, I am not sure how much power that will consume.

Here is the board PSU
http://www.mouser.com/ProductDetail/RECOM/RAC04-12DC-230/?qs=F5OEftmZcCAbIVZkvUf1yw%3d%3d
I would really appreciate any help.
Thank you very much.


texts: I am going through a datasheet of AT89C51. The very first feature in the datasheet mentions it be --> Compatible with MCS-51™ Products. what does this mean exactly?


texts: Rectifier circuit with unexpected output

texts:
I am developing a circuit using Proteus 8.
My aim is to get a full wave (discrete) sine output to the load. I use an IGBT to switch the full wave rectified signal and get output in pulse form (purple output in oscilloscope.)
My issue is I do not get the expected output to the lamp.
This is the expected output:

Schematic:

I have connected 2 probes to oscilloscope and measured the signal before the lamp and after the lamp (yellow signal and blue signal outputs.)

Why are these two outputs different?
Why I don't get a full wave signal as output?

(Original Google Drive link to the images is here.)


texts: Better to convert voltage at each individual component or convert once for the entire system?

texts:
My power source is 24v, and each component of the setup wants 5v and a decent number of amps. I know not to convert the same output more times than necessary, and I know not to chain step down converters.

Is there any guideline as to whether it's better to have one large buck converter that can handle the entire current draw of the setup, or keep the voltage at 24v and have small buck converters at each individual component that's needing power?

Say I have 5 long led strips and a controller, if I keep it 24v 5A and just have a small 3-5A converter at each individual strip/the controller, I'm assuming I wouldn't lose as much power as I would with a single 5v 24A power source. The strips would be connected only via data connections and power for each strip would be independent to avoid mixing the slightly different voltage outputs.


texts: Current limiter its not working as it should?

texts:
I have created a voltage regulation circuit using op amp and feedback resistors, now I am trying to add a current limiter to the circuit. have read how to create this using two transistors and a resistor.
So far I know that if the current is to be limited at 10mA, and the transistor base emitter saturation voltage is 0.65V, then I choose a value for resistance using 0.65/0.01 = 65Ω.

At first this seems to work, however when I lower the load resistance, allowing more current to flow, the current is not limiting. I have read into it and followed the steps to create this circuit so I am now confused as to why this will not work the way it should.

If anybody can supply me with a reason as to why this is not doing its job that would be great!

EDIT:-

In regards to the base being connected I have reset the circuit and produced the following results.

Base current 4.34mA
Load current 10.8mA

I am starting to understand that it is a rule of thumb that the output voltage of the op amp must be a volt higher than the output of the load, is this correct? and why ?

Also have been having issues in lowering the gain, allthough the feedback resistors are set to give the op amp a gain of 1.5 I am still getting an output voltage of 11V at the op amp, is there something I am missing ?

To clarify I have added a graph of the current flow constantly rising regardless of the current limiting circuit, I am hoping that if I can allow the gain to give an output of 7.6 using ((1/2)+1), then this will allow more voltage to the transistors allowing them to pass current steadily.

When I discover why the gain seems to be fixed I can go on to lower it and hopefully the circuit will work as it should, if anybody knows how to resolve this please let me know


texts: how many 74LS low-power Schottky inputs can an output of MC9S12DG128 drive?

texts: I need to figure this out for a project and can't seem to find the answer. Does anyone know how I can figure this out? I think there is an equation to find this and can't seem to find the specification sheet for MC9S12DG128. What do I need to figure out about the MC9S12 to find the answer?


texts: Logic NOT gate only works with Oscilloscope probe connected

texts:
I have a very simple circuit that is misbehaving in a way that I cannot explain with my very limited experience.

The circuit that consists of a motion detector:

(http://www.digikey.ca/product-search/en?x=0&y=0&lang=en&site=ca&KeyWords=255-1809-ND)

hooked up to an inverter:

(http://www.digikey.ca/scripts/DkSearch/dksus.dll?WT.z_header=search_go&lang=en&keywords=TC74HC04APF-ND&x=0&y=0&cur=USD).

I have the output of the sensor hooked up to pin 9 (4A) on the inverter, and I am reading the output on pin 8 (4Y) with a 10X oscilloscope probe.

What I am observing is that the output of the inverter just stays LOW at all times. So, even when there is no motion and the sensor is outputting LOW, the output of the inverter is LOW. Upon closer examination there are 5ms spikes in the inverter output, but that's all. However, if I attempt to read the state of the input with another oscilloscope channel, the circuit immediately starts working as it should. I can see the output of the sensor going HIGH/LOW when expected and I see the inverter properly mirroring that.

I looked up the capacitance of my probe, which states 22pF, so I tried to put a 27pF capacitor between inverter input (i.e. sensor output) and ground, which simply caused those 5ms spikes to go away. Now the inverter is really stuck on LOW.

Next I tried to put a 400K pull-down resistor between inverter input and ground. This indeed makes everything work again, except that I am wasting current by sinking the output of the sensor into the ground. I'd say about 40uA, which is really serious, considering that my whole circuit is supposed to run on 50uA. I suppose I could increase the pull-down resistor to 2000K to match the probe, but I'd like to understand why this is necessary before I go out buying such strangely high valued resistors...

Any advice would be appreciated.


texts:
Q) Suppose each bridge resistor is capable of dissipating 250mW. Can the bridge be left in the balanced state without exceeding the power-dissipating capacity of the resistors, thereby damaging the bridge?

A) yes

simulate this circuit – Schematic created using CircuitLab

I can't extremely understand why the answer is 'yes'.


texts: Whats a N (+,N,-) terminal on battery connection to UPS?

texts: We have a 3 phase ABB powerline series in our site, and we are installing it. In connecting external batteries to the UPS, 4 terminals are given +,N,- and PE. I understand +,- and PE, but for what  "N" stands for? is it neutral? how can we have a neutral in DC battery connection? Please clarify, thanks.


texts: In power electronics, when we build the important circuits like Totem pole PFC circuit or Quadrant VII  converters etc, how do we start looking into parasitic elements (inductance and capacitances ) and do the calculations  or simulations at  specified frequencies.


texts: Small-signal analysis of transformer BJT oscillator

texts:
In an attempt to improve my circuit analysis skills, I've been trying to understand how this photo flash charger circuit works.

I am mainly focusing on the oscillator part on the left, which I've redrawn as follows

simulate this circuit – Schematic created using CircuitLab
To analyze the circuit's stability, I "broke the loop" at the base of the BJT to derive an expression for the loop gain. Unfortunately, my expression for the loop gain does not at all mirror the simulated loop gain obtained by simulating the circuit in LTSpice. From what I can tell, there are three possible sources of error:

My small signal equivalent circuit is wrong
Due to the oscillator's large signal swing, the linearized small signal model is not representative of the actual circuit behavior
I did the algebra wrong.

This is the small signal equivalent circuit I used for the analysis. Does anyone see anything wrong with the way I drew it?

simulate this circuit


texts: 24V battery to drive a 5V arduino speed controller and a motor

texts: I would like to use a 24V power supply to power (1) an arduino that will act as a speed controller and (2) a DC motor by using an NPN transistor. I am wondering how I can use the same battery to split the power between the collector of the transistor and the arduino. I first thought of using a voltage divider for the arduino, but then the excess voltage gets grounded. How can I accomplish this?


texts: How to detect AC signal and use as logic-level input to microcontroller

texts:
Hi community, what I'm trying to do with this circuit is to get a 5V signal on the output whenever an input AC signal is present. That simple. It works perfectly with 9VAC on the input but when it goes down to around 5VAC, the transistor starts supplying the regulator less (around 4-5Volts) and output voltage goes down to 3Volts.

I am still learning electronics and just found out that I have to limit the current going into the base of the transistor with a resistor. What else am I missing here? Any comment would help. Seemed like an easy application.


texts: Maximum Voltage That Can be Applied to a Motor

texts: I was reading about 87Hz technique. I saw we can configure the drive for a motor 400Y/230D as 400V /87hz. I know v/hz ratio should be kept constant and when we configure drive as 400V and 87 Hz and wire it delta this ratio is still constant. But there will be 1.7 times more voltage applied to motor windings. Is it ok for winding. Is there no risk of damaging insulation ? For example Can we apply 800V and 174 Hz to a motor without damaging assuming that we can source it?


texts: Anything obviously suboptimal about this design?

texts:
RF novice here, this is the first PCB I've designed and I'm just wondering if anyone more experienced than I (which is most people) sees anything glaringly wrong/bad/in need of improvement with this before I send off the Gerber files.
I'm working on a compact 1x4 distribution amplifier schematic here for wireless microphone use; frequency range of interest is 470-613 MHz. BNC input for antenna on left side, goes to high and low pass filters, then LNA, then an attenuator so that the device operates at unity gain input-to-output (factoring in the power divider and insertion loss of all the other components), then the power divider, to SMA outputs.
LNA receives power through a DC input jack (roughly outlined on right side of unit, with wires soldered to through holes in bottom right corner), diode for reverse polarity protection, and LDO regulator flanked by decoupling capacitors.
This is a 4 layer 63mil board. Top layer in red is RF signal (plus a couple traces for DC input); I did the math to ensure 50 ohm Zo throughout (14.6mil wide traces, 1.4mil thick copper, 6.7mil thick FR408 prepreg with Dk 3.69 @1GHz). 2nd layer in yellow is continuous ground plane. 3rd layer in pink is moving some DC supply voltage around, and bottom layer just has additional pads mirroring pads 1 and 3 of the SMA connectors to tie both sides of them to ground vias.
Would love to hear any feedback that folks have if there are any obvious issues with this layout; I'm an audio engineer not an RF engineer so this is all new for me! Assume I've done my homework and all the components have sufficient power handling for this application and I've followed the recommended application circuits where provided.
One specific question I have is that some of these components have recommended PCB layouts on their datasheets that presume the use of coplanar waveguide transmission lines. This design implements microstrip transmission lines throughout; what might some consequences be of failing to surround these components with a copper pour tied to the ground plane by vias?
Grateful to hear any thoughts you may have! Thanks in advance!


texts: Hard reset for SD Card interfaced with FPGA?

texts: So I have been successfully able to interface a Sandisk SD Card with Spartan 3 FPGA (using verilog). The card after power up initializes correctly and is able to read and write data sector wise correctly. The only problem that remains is that after power up if I press the reset button the card hangs and stops working. I have also not been able to find out what a hard reset means for the SD card. Should it get reinitialized somehow? What command should I send to the card for that? Any help is appreciated.


texts:
What are some of reasons that PC terminal receives garbage characters from one microcontroller?

I am using BeagleBone and UART works okay, but after few transmitted command characters from PC terminal  to microcontroller, PC terminal starts to receive weird characters while I am trying to send those char commands? What can be the problem?

UART won't work properly for some time, but after few minutes it starts again to work and respond to char commands.

Bauds are same on both sides.

UART acts the same on every PC terminal software.


texts: Handling large number of inputs in PIC microcontroller

texts:
I am interfacing PIC32 MCU with 24 inputs and UART. When any inputs comes, this data is transferred to PC via uart. I am using multiple if condition like

if(input1==high)
{
  putsUART("input 1 ON\n");
}
if(input2==high)
{
  putsUART("input 2 ON\n");
}

What this if condition is doing is whenever an input comes, it keep on printing the data like

input 1 ON
input 1 ON
input 1 ON

and it goes on. I want it to be displayed once only. For example, if I applied input1, input 1 ON should be printed once and if remove the input input 1 OFF should be displayed once.
I don't know how can I run this if condition only once. Please help. Thanks.!

CODE(just for 3 inputs):

 int main()
 {
  TRISAbits.TRISA6 = 1;
  TRISAbits.TRISA7 = 1;
  TRISGbits.TRISG13 = 1;
  while(1)
  {
   if(PORTAbits.RA6 == 0)         //INPUT 1
  {
   putsUART2("Input: 1 ON\n");
   Delayms(1000);
  }
  if(PORTAbits.RA7 == 0)          //INPUT 2
   {
   putsUART2("Input: 2 ON\n");
   Delayms(1000);
  }
  if(PORTAbits.RG13 == 0)          //INPUT 3
  {
   putsUART2("Input: 3 ON\n");
   Delayms(1000);
  }
 }
}


texts: I have an old Westinghouse motor with a missing wiring diagram.  It runs but is slow to start and sometime needs help.  The terminal block has four connections, two labeled as line.  I've measured resistance across all terminals and it is nearly the same.  The data tag call out a capacitor size but I'm not sure were to connect it.


texts: DRAM timing with row and column decoders

texts:
Consider a 64Kx1 DRAM memory which means the number of rows is 256 and the number of columns is 256. In other words, two 8x256 decoders are needed for selecting the right row and column.

Since, each memory location is 1-bit wide and we usually read 8 bits. Does that mean with a single row number, the column number must changed 8 times in order to read 8 bits?

I have seen timing diagrams for row and column strobes. Are these valid for one bit? That has a high timing overhead for multiple bits then. Isn't that?


texts: Heat dissipation by convection for ICs placed upside down

texts:
I'm currently designing a PCB with a couple of fast electronic elements (600MHz ARM, DDR3 ram etc.) and I'm quite puzzled which layer should those elements be placed upon.

The product will be closed in not-so-airtight plastic enclosure, but airflow will probably be rather constrained.

One might imagine that air coming in contact with warm IC package should be directed upwards, which would help the heat to be dissipated by convection. If such IC would be placed upside down, on the bottom layer, the heated air would have "nowhere to go", and the element would become considerably hotter.

The question is, does this effect really exist? Even so, is it noticeable enough to considerably affect working temperature of such IC packages?


texts: why in-wheel BLDC motor have more pole than normal BLDC motor?

texts: I am using a In-wheel BLDC Motor having poles 46 but another normal BLDC motor have less pole as 8 pole. I have searched about other In-wheel BLDC motor and it also have 42 poles.


texts: How to design a safe RF switch using latching relays?

texts:
I'm working on a design for an RF switch using latching relays to switch two transceivers between four antennas.  Each transceiver will be connected to at most one antenna at a time.  But suppose one of the relays fails, and both transceivers are connected to the same antenna.  This could result in damage to one of the transceivers.

What is the simplest way to prevent against this condition?  Can I use one set of contacts on each relay to verify the state of each relay? I was thinking of doing something like this and applying AND or NAND to the control circuit based on the state of the relay's contacts.

I imagine there is a best practice for doing this but I haven't been able to find any write-ups about it.


texts: Measure AC Voltage using this circuit & Microcontroller ADC

texts:
High guys,

i have got this circuit where R2 is 1M, R1 and R3 are 1K each.

What is the way to measure the value of AC voltage using ADC of the Microcontroller.

Frequency of voltage is 50Hz and Max value is 500V


texts: Enc28j60 - no communication over ethernet

texts:
the problem is: no communication over the ethernet - no packet is received or send from my board. Both diodes indicate that theres should be connection (one constantly lit other blinks on packet) and wireshark sees only packets sent bt PC. Tried both crossed and non-crossed ethernet cable. Tried swapping ENC - same result, revision is read properly - so there shouldn't be any problems with communications with uP.
The story behind: couple weeks ago, while working with previous version of this board everything was OK (packet reception and sending) suddenly coil next to RJ burnt. Do not know why. Resoldered it, swapped RJ socket and ENC - nothing helped. Now i'm working with new version of it and the problem still occurs.
Anyone could tell me whats the problem?


texts: Noise from switch mode power supply and ground loops

texts:
I've got a piece of equipment that has pretty severe noise on it that I'm trying to improve.  It's an older system (built in '96 but a lot of the design is probably late 80's) and is mostly bundles of hook up wire run through it instead of shielded cables with twisted pair wires.  It's also largely an analog system, lots of sensors and boards with op amps.  Depending on what/where I measure on the system I can get anywhere from ~300mV to ~1.8V of high frequency noise, which seems excessive.
It has a stainless steel enclosure that has DC power supplies, breakers, terminal blocks, some AC distribution.  Connected to this is another stainless enclosure that houses a VMEBus computer with various cards that have all the digital/analog inputs/outputs.  These enclosures are earth grounded (a 2" copper strap tied to building steel).
It has 2 modular DC power supplies (MeanWell MP650's), one large 24V and one that has 7 outputs (+5, +5, +12, -12, +15, -15, +24).  All of the DC- terminals on the power supplies get tied to the enclosure, then most of the DC+ terminals go to breakers then terminal blocks.  There's also DC- terminal blocks that are also tied to the enclosure.
The +5V supply that's used to power the VME has pretty severe high frequency noise on it, ~1V pk-pk at ~10MHz. I've got a scope pic attached.  From testing that I've done turning various breakers and parts of the system off I think this line is the largest source of noise on the system.

The wiring for this supply is a little weird and I'm not sure what the best course of action would be.  On the power supply DC- terminal there's one wire that connects to the enclosure and one that goes to the VME.  The power supplies DC+ terminal has one wire that goes to the VME and one that goes to a breaker then a terminal block to go to a couple other devices.  Now the VME also has two ground straps between the DC- and the enclosure.  With this I've got unequal currents running through the two main lines that power the VME because half of it is returning via the stainless enclosure.  These two lines are also bundled with ~20 other wires that go to various places.
I've got a diagram attached showing these connections and roughly how it's laid out in the enclosures.  I'm thinking that I should remove the two ground straps on the VME use a twisted cable between it and the power supply.  I would like to also add some sort of filter onto it, but I'm not sure what would make sense.

Edit: How can I reduce the high frequency noise on this system?


texts: AC Adapter gives much more voltage than it's supposed to

texts:
Hello!
I have this one older AC-DC adapter from Korg (wallwart?)...

...that I have been using for my (guitar) effect pedals for a few years, and I recently found out (when I was doing some electronics doodling) that the adapter gives much more voltage than it's supposed to.
 I should give out +9V (as it is clearly seen from the picture), but when I measured the voltage by my multimeter, it is showing...

...more than 14V! It freaked me out a little bit, since I may have been using it like this as a +9V adapted for my (expensive) delay, and that certainly could have been good for the pedal.

Does anyone have an idea of what's wrong with the adapter, since I have never opened it up or messed with it? Or am I measuring it wrong? And possibly, is there an easy fix?

Thank you!

EDIT: How can I find out that the adapter is "unregulated" (is it the same as unstabilized?) and it's not broken?


texts: Bypassing single supply op amps biased at mid-supply

texts:
When working with single-supply op amps biased to mid-supply ( virtual ground rail ) how does one achieve proper bypassing at the IC given that the virtual ground should be as noise-free and stable as possible?

In the schematic below, lets refer to the amp labeled "IC5B":

Power rail is 5V, labeled as +5V/1, and comes from an LDO.  The GND of the LD0 is labeled as ISO_GND.   VGND is supplied by a 2.5V, +/-10mA reference IC, powered from the same VDD.   The ADA4528 is a chopper amp with a chopping frequency of ~200kHz.   The amp's VDD pin is connected to +5V/1 and the amp's VSS pin connected to ISO_GND.

If this were an op amp with dual supplies and didn't care about ground noise, I would bypass each power pin from its respective rail to VGND, like this:

Since the system's entire reference is the VGND plane, and chopper amps draw current in pulses at the chopping frequency, and the op amp's noninverting input pin is connected to VGND and supposed to be noise-free,  I am worried about injected noise voltage because of shunted high frequency current into VGND.  In that case, would I use only a single bypass cap between the amp's VDD/VSS pins ... like this?

Are there any other considerations from a noise perspective that I should follow in this system?


texts: RSSI to identify zones indoor specifcally bluetooth hc05

texts:
i was making an indoor positioning system using bluetooth HC-05 and i was wondering if i can use the rssi reading from 3 static beacons will remain inside a certain zone inside a certain range of readings ? for example if i have 4 rooms and i will take the reading of rssi from 3 bluetooth beacons hc-05 modules and check the minimum and maximum for each room while a person moves with an hc-05 module inside a room when done moving i will record the max and min reading of RSSI for each room then when trying to identify a new location i will compare the current reading of RSSI with the previously recorded data to see to which range the new reading belongs to . meaning for the current reading of 3 beacons compare the value to check in which range it falls among the 3 beacons they will fall in a certain range for a certain room then this is my zone .
is that correct and how can i enhance ?


texts:
I'm trying to create my first PCB after having too many problems wire-soldering every single wire.

I learnt KiCAD yesterday and so far it seems like a very good application.

For creating the scheme, it was relatively easy, and I think it looks quite neat (but if you have improvements, let me know). Note: I haven't checked all resistor values yet, for me most important was to learn how to make a PCB.

It is a MIDI In/Thru/Out PCB.

However, when I route it (manually), it's getting quite messy.

I want to use two layers to reduce cost (it's a hobby project).

Some questions:

There are quite some complicated routings, however, when I rotate or move symbols (components), I have to restart routing those again, which is quite time consuming. So the best is probably to place/rotate the symbols as good as possible before starting to route the wires, however, it's hard to see beforehand what wires will cause problems (especially when using references in the circuit above). Is there some guideline how to tackle this problem?
Should I start wiring the short/simple wires first, or should I start with the difficult ones (one hoping the difficult ones will not make even the simple routings to be harder)?
According to the KiCAD manual it is a good practice to use one layer for GND, however, I use some vias. What I now did is to use the via and continue via the GND plane. Or is it best to make the via's via the GND plane as short as possible and use another via to return to the main layer as soon as possible (thus using two via's, one to go to the GND plane and one to return from it) ?
Or should I - since I only have two layers - forget about a GND plane, and try to find a better way to divide the routings over the layers? (e.g. GND + VCC via one lane, signals via the other, or signals + GND via one layer and VCC via the other?

(note: I also see now there is some unfinished line, but I will ask how to find those in the KiCAD forum). The above questions seem very generic.

Sorry for these - for you - probably basic questions, for me it's my first 'real' PCB.


texts: Troubleshooting adding a bluetooth receiver to my intercom system

texts:
I have a Nutone IMA 4406 intercom system with several intercoms throughout the house.

I am interested in wiring a Bluetooth receiver to its Auxillary line in connection so that I can stream music from my phone to the speakers throughout the house.

The Nutone is powered by 2 801t transformers (18VAC, 72VA) hooked to the intercom in parallel. I also hooked up a Ring doorbell to one of the transformers in parallel without a problem.

Nutone installer manual:
http://www.nutone.ca/PDF/InstallGuides/62377.pdf

My project included using an AC/DC converter to convert 18V AC to 12V DC using this:
https://www.amazon.com/gp/product/B00R5GO4YU/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

I then connected the 12V DC to the Bluetooth receiver (that can accept up to 24V DC as an input) https://www.amazon.com/gp/product/B07VPG2ZZY/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

This circuit was attached to one of the 801t transformers and run in parallel to the intercom wiring.

With this setup, the Bluetooth receiver worked fine, connected to my phone and output music to headphones connected to the 3.5mm output jack.

However, when I connected the 3.5mm out from the receiver to the auxiliary input jack on the intercom, the transformer fuse blew.

Both the AC/DC converter, and the bluetooth receiver are still functioning without issue.

I am trying to figure out why this happened and how I could prevent it. Would a 1:1 audio transformer help prevent this? What else should I be evaluating to troubleshoot this? I suspect if I use a separate power supply, I would not have this problem, however, that would defeat the ability to have a packaged solution sitting behind my intercom station.

Thanks

UPDATE:

I tried a "ground loop isolator" and put that in the circuit. Based on the description it looks like a 1:1 isolation transformer:

https://www.amazon.com/gp/product/B019393MV2/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

This allowed the circuit to work and for the bluetooth receiver to send audio to the intercom, but then it did short out after a few minutes so not sure if it is the component quality or something more.


texts: Date of introduction of TO-92 transistors

texts:
I'm trying to date a circuit from an organ. It contains transistors in a TO-92 (plastic) package.

Approximately when did these transistors first appear?


texts: Stepper motor phases and torque output from shaft

texts:
I have a 5 terminal 12 v unipolar stepper motor. Can I consider it as a 2 phase motor?

Secondly I am driving the motor with a uln driver from a micro controller. I know the input voltage and input current. With this how can I calculate the motor output power from the shaft? I know the speed in rpm too. With the following data , i should be able too calculate torque output from shaft inturn. Please help me


texts: Why did my Gameboy shut off during takeoff?

texts:
When I was young I remember playing my Game Boy Advanced SP in the airport terminal. When we boarded we were asked to shut off all electronics. I was setting a high score in Pokémon Pinball: Ruby & Sapphire, so of course I left it on. During takeoff, it shut off. I checked the power switch, it was definitely still up. Later I switched it off and back on, and it worked just fine.

Why did my Gameboy shut off?

I was guessing it's an electrical reason, but if this isn't the correct StackExchange site to ask this question please let me know.


texts: Are high power ceramic resistors waterproof?

texts:
I need to put some resistors on my jeep.  I picked up 2x 22ohm, 10watt resistors at a local electronic store.  They do the job well, but are they waterproof?  Can they hold up to the elements?

I put the resistors under the hood, so they should not get wet under normal usage - and I covered them in heat shrink. On the off chance that they get wet, will it chance their resistance?

I'm not talking about the striped cylindrical resistors, but the white rectangular ones.


texts: How can I have two analogue inputs, control two PWM outputs on PIC16f?

texts:
I'm looking to have dual PWM out from a PIC16f1619. This is part of a power supply project that has pots for limiting voltage and current. I'm simulating control of the regulator with just two LEDs at the moment.

In debug mode (on Microchip Curiosity board) the Analog_AN0 never seems to run, yet both RC6 and RC7 output dependent on PORTA0 only (not seperately controlled).

I can't have set the PWM and ADC correctly but I am unsure why.

Any help would be appreciated as I am pulling my hair out over what I am sure is a simple problem.

#define _XTAL_FREQ 16000000 //16mhz
#include <xc.h>

#define RS RC0
#define EN RC1
#define D4 RC2
#define D5 RC3
#define D6 RC4
#define D7 RC5

void Analog_AN0(void)
{
    PWM3CON = 0b10000000;//Enable the PWM3 H/W
    RC6PPS = 0b00001110; //Sets RC6 to output PWM3
    ADCON0 = 0b00000001; //pin RAO is connected to AN0. ADC ON
    ADCON1bits.ADCS = 0; //Conversion clk of fosc/2 (time required to convert each bit)
    ADCON1bits.ADPREF = 1; //Vref is VDD 3.3V
    ADCON1bits.ADFM = 0; // will right-justify the result and store the 10bit value  in the16bit register ADRES
    ADCON2 = 0;
    PWM3DCL = ADRESL;
    PWM3DCH = ADRESH;
}
void Analog_AN1(void)
{
    PWM4CON = 0b10000000; //Enable PWM4 H/W
    RC7PPS = 0b00001111; //Sets RC7 to output PWM4
    ADCON0 = 0b00000011; //pin RA1 is connected to AN1. ADC ON
    ADCON1bits.ADCS = 0; //Conversion clk of fosc/2 (time required to convert each bit)
    ADCON1bits.ADPREF = 1; //Vref is VDD 3.3V
    ADCON1bits.ADFM = 0; // will right-justify the result and store the 10bit value  in the16bit register ADRES
    ADCON2 = 0;
    PWM4DCL = ADRESL;
    PWM4DCH = ADRESH;
}
void main (void)
{
    OSCCON = 0b01011000;//sets clck to 1mhz
    ANSELC = 0x00; //Sets PortC as digital
    TRISC = 0x00;
    ANSELA = 0b11111100; //all pins on A are digital except 0 and1
    TRISA = 0b00000011; //all pins on A are output except 0 and 1
    INTCONbits.GIE = 0; //No interrupts
    CCPTMRSbits.P3TSEL0 = 0; //Associates TMR2 with PWM3
    CCPTMRSbits.P4TSEL0 = 0; //Associates TMR4 with PWM4
    //Set up Timer 2
    T2CON = 0b01110000; //TMR2 OFF, prescaler 128, postscaler 1;
    T2CLKCON = 0x00; //fosc/4
    PR2 = 19; //10ms NEED TO RECALCULATE
    TMR2 = 0x00; //Starting condition
    PIR1bits.TMR2IF = 0; //Empties the flag to begin
    T2CONbits.T2ON = 1; //init. timer
    //Set up Timer 4
    T4CON = 0b01110000;//TMR2 off, pre 128, post 16
    T4CLKCON = 0x00; //fosc/4
    PR4 = 19; //10ms NEED TO RECALCULATE
    TMR4 = 0x00; //Starting condition
    PIR2bits.TMR4IF = 0; //Empties the flag to begin
    T4CONbits.T4ON = 1; //init. timer

    while (1)
    {
        PIR1bits.ADIF=0;//makes sure that the flag is clear
        Analog_AN0();
        __delay_ms(10);
        Analog_AN1();
        // ADCON0bits.GO=1; //Conversion now starts

    }
}


texts: Does a name patch on a dissipative ESD smock also have to be ESD compliant?

texts: Does a name patch on a ESD smock also have to be ESD compliant?


texts: Why is it that in every triac analog dimming circuit I find that the triac triggering circuit is fed through the load and not straight from the mains??


texts: Thinking of using a Murata 78602/3C, which is a 1:1:1 pulse transformer. Described as two primaries and a secondary. My question is whether these terms for primary and secondary are arbitrary given it's 1:1:1. Can any winding be used like any other?


texts: Protecting circuit from piezoelectric disc voltage spike

texts:
I have a piezoelectric disc, and I'm trying to use to build a primitive sonar. I connected the disc to an oscilloscope and if I press very hard on the disc, I see that the voltage can spike pretty high. I'm not sure how much current there is.
In an application with a piezoelectric device, should I use a voltage regulator on the output of the piezo, and would that protect my circuit on the other side? I want to connect it to an ATTiny85 without frying the chip.


texts:
Note: I'm asking this question for a friend. I'm not into Electricity, but I will show him the answers.

What is the relation between the frequency and the phase shift in a common emitter amplifier. Is it always a 180 degrees shift whatever the frequency is?


texts: I use a PCB mill to make my boards, and it doesn't etch off excess copper.  I'm designing a breakout board for an RF tuner (400MHz), and I planned to have the ground plane on the top and the traces on the bottom.  The traces will be surrounded by copper that isn't part of the circuit, just left over from the milling process.  Is it ok to connect this top ground plane (left over copper) to the bottom ground plane, to help noise reduction?  Or is there a problem with having ground planes on the top and bottom?


texts: Fitting a USB C plug onto an laptop power adapter

texts:
First post, be kind !
Bought a DELL laptop power adapter DL65195334 but want to put a USB C on the end of it.

Snipped off the connector , expecting to see 2 wires but saw 3 (BLack, Brown and white)
the Black and Brown make 19.5V which is what I need.

Bought a USB to USBC cable and snipped off the usb end and connected the Red and Black (to Brown and Black)

This should have given me 19.5 volts to the USB-C but when I connect it to my laptop, it does not charge.

Questions
A. What is the 3rd white wire for in a Dell Power Supply
B> Why didn't it not work when I joined the black/brown & black/red to my USB cable - the usb cable had 4 wires (Red and BLack for Power) and then (green and white for data)
C. Anyone know how to get a USB C on the end of the power supply so I can power my Lenovo laptop ?, from a Dell power supply which has the correct outputs ?
Many thanks
TK


texts:
In general (and maybe this is impossible to answer "generally"), is it possible to supply an external clock source to a microprocessor that supports a directly-connected crystal (and a pair of small caps)?

Specifically, I'm looking at an ESP32, which supports a 32.768KHz crystal as a source for its internal RTC. Everything I've found references an actual crystal, but what I'm trying to do is use a temperature-compensated clock source instead, so I'm essentially not using the ESP32's internal oscillator circuit, but instead feeding it a square wave from the TCXO.

I've used other microprocessors in the past that specifically (i.e. according to their datasheets) can support either a crystal or an external clock source, so I'm inclined to try it with the ESP32 (connecting the TCXO to the pin labeled "crystal input"), but I thought I'd ask before I potentially smoke my ESP32.


texts:
In the datasheet of the ADC of a microcontroller it was mentioned that: "The maximum recommended impedance for analog sources is 10k."
In a high voltage divider circuit such as this, how does one calculate the input impedance to the ADC?
Is it 990k || 2k2 , or 2k2 or 990k?
The circuit node Vdiv is connected to the ADC.


texts:
I always try to tune my pcb antennas in length, so they operate in resonance, by cutting the antenna with a scalpel and then matching the tuned antenna to the transmitter.

But recently an RF engineer told me, that you could sometimes get the same radiated power, by matching the impedance without trimming the antenna to resonance.

I have measured an untuned IFA to have impedance of Zin = 7.7+j90 @ 865MHz.

Should I try to tune this antenna to resonance, or will it (in practice) work just fine to match the untuned antenna to my transmitter ?


texts: Connect two lab bench power supplies in series safely

texts:
Lets assume in European Union, that I have two power supplies, that each have 3 terminals. One marked +, second - and third GND.
I assume that GND is connected to the protective earth of AC power cord and that PE can be disconnected from - on one of the power supplies.
Is it possible to connect them both with safety against electric shock maintained?

I imagine that I leave GND and - connected on the first supply,
and I'll disconnect GND from - on the second supply, then connect GND of both of them to prevent shock from touching the chasis of the second supply. Next I connect + of the first supply to - of the second supply and take output voltage from + of the second supply. Lastly I plug them to the AC outlet and power them on.

EDIT: Could someone please elaborate on how does connecting GND of my circuit on bare PCB to protective earth protect me from electric shock?


texts: Reason for 1/2 watt resistors marked as 2 watt resistors

texts:
I recently took apart a combination VCR/DVD player. Along with other questionable quality inside including a green LED display viewed through a red acrylic front panel and a DVD player assembly using only 3 brushed DC motors, I found that there were 3 mystery components marked as 27KΩ 2W resistors in a form factor that I have never seen resistors in.

As you can see in the picture, I decided to cut one open and found that it was a 1/2 watt carbon composition resistor potted in a plaster-like material. It had also failed short for an unknown reason.

What is the reason for potting the resistor in a larger package like this?

Update: I cut up another one of these resistors in the name of science and it appears to have a metal film or wire wound resistor inside. The core is too hard to cut with diagonal cutters.


texts: Impedance seen by the inverting terminal

texts:
Actually it is given in Sedra smith that  to reduce input offset current effect is to use a resistance at non-inverting terminal of the opamp whose value is same as the DC resistance seen  by  the  inverting  terminal.

I am actually confused that what is meant by "resistance seen by the inverting terminal"?   Is he referring to calculate Thevenin resistance from inverting terminal?


texts:
I've found a lot of schematic diagrams that use this style of symbols, specially in the Wikipedia. I think these symbols are pretty clear and stylish. I would love to use them for the schematics I make but I've found just a few in the format I want (SVG). They are auploaded by diferent users so I think they are getting those from different sources.

I make schematics containing mostly MOSFET and BJT transistors and there are not much of those symbols in this style.
Does this kind of symbols (blue/grayish shading, solid component lines, thin wire lines, etc) have a name? and where to find more?


texts:
I am looking into a reference design which was probably done using Orcad. I am using KiCAD for my design.

In the reference design, there are schematic symbols like >> and <<. According to this guide, they seem to be 'off-page connector'. The guide says

"Off-page connectors are used to connect signals to
like-named off-page connectors and hierarchical ports on
other schematic pages within the same schematic folder. "

So, what is the off-page connector (>> or <<) equivalent at KiCAD? Global label or hierarchical connector?


texts: how do I output through GPIO pins instead of RS232 from a Z8 Encore MCU?

texts:
I'm currently learning about MCUs in school (read: n00b) and I'm trying to fool around with the equipment at home. Problem is that I only have a netbook and don't have any serial IOs on it, so I have to make due with a USB connection. The MCU is a Z8 Encore! 64K Series Z8F6423. But to hook up a output i have to hook it up to a filter board that my school built (i think), which I have photographed and uploaded to the album below. To power the filter board, it's hooked up to a Spartan-3 FPGA board which also is in the picture.

I'm trying to program the MCU to output a simple "Hello World!", but instead of sending it through UART0, I'm trying to send it through the GPIOs, into another board my school made, which then should output it through a USB cable. The USB should be visible in the pictures here: album

My question is simply, how do I send the output through the GPIO to the USB, which then should show up in PuTTY on my laptop? Is this possible for you to answer, or do you have to know the exact schematics of the filter board? Based on the code below, it is sending the signal through the UART0, but where should I send it if I want it to go through the GPIO?

The program is as simple as this:

#include <eZ8.h>
#include <sio.h>

void main() {
    init_uart(_UART0_DEFFREQ,_DEFBAUD); // set-up UART0 to 57600, 8n1
    printf("hello world\n");
    do {} while (1 != 2); // stay here forever
}


texts: How to prevent the fluctuation of LEDs due to motor and music with loud bass?

texts:
I have a 12V DC power supply/battery supplying a class D audio amplifier, 12V DC linear actuator (controlled by Raspberry Pi through an H-bridge,) LCD screen and LED light strip (lighting intensity controlled by Raspberry Pi through an L293D.)
My problem is that when music is played through the amplifier, the LED light flickers with the bass of the music and I can see the voltage and current fluctuating on the multimeter. Also, when I start to raise the linear actuator the same thing happens with the lights and the screen glitches.
How can I solve this problem such that everything is still connected to the same power source?


texts:
I have made a voltage divider with two trim pots set at 900k and 14k with a source voltage of 300V DC. I am supposed to get 4.5V at the center, which I do get and checked by a standard multimeter. Now when I feed this point to any of the analog input A0/1/2/3/4/5 of the UNO and try to read the analog value, I get somewhere around 560 for a couple of seconds and then around 650 for a couple of seconds and it keeps repeating. After a reboot the values change but they always seem to jump between two levels. I know these values are from 0-1023 range but 4.5V should have given anaolog value of somewhere in the region of 900. There is a delay of 1 second in the loop. The arduino is powered by a 12V adapter through the barrel jack.
I checked whether the analog inputs are good by using a acs712 ampere sensor at the analog input, and it works fine and gives proper analog values with respect to the load.


texts: I have this PCB where 13 cable pins used to be soldered to. I'd like to replace that with a standard FFC connector socket. Is this possible given the pattern shown in the image?


texts:
I have a question about finding the voltage across a circuit element when the circuit contains a energy storage element.

When is it appropriate to use \$V_0e^{t/RC}\$ and when is it appropriate to use KCL, KVL and plug them in to each other?  Or are they interchangeable? Using the circuit below as an example.

\$KVL: 5 = V(t) + C*10000 \frac{dV(t)}{dt}\$ Around the right loop gives.

Re-writing to make the derivatives coefficient 1 gives:

\$ \frac{dV}{dt} + \frac{V}{C*10000} = \frac{5}{C*10000}\$

This makes  \$Tau = 10000 * (1*10^{-6})\$. For \$V_0(t->\infty)=5\$

Then I get \$V(t) = 5e^{-100t}\$

I just want some clarification on the process because I never feel like I do these correctly.


texts: What is this PCB spark-gap on common-mode-choke for?

texts:
I came across this PCB spark-gap on the coil legs of a common-mode-choke.

As far as I know, there needs to be some high voltage between two points for a spark to occur. Assuming there is a 1mm gap, there needs to be 1 kV of voltage difference.

Now, since a coil is almost short-circuit (0.8 ohms in this case), what is the purpose of the spark-gap in this case? Is it there in case of there is some kind of failure on the coil?

The circuit and the layout are taken from this application note from ROHM, for a flyback circuit.


texts: How to pick a step down transformer for powering MCU?

texts:
I need to select a transformer to power my microcontroller, relay, 7 seg display and few LEDs. The maximum current draw will be 300mA. I doubled that to improve reliability. So the AC current works out to be around 860mA(0.7 x DC current).
My questions are:

Do I need a 100% safety margin for the current?

There are lot of options for transformers. As low as $1 from eBay to $10 from mouser. What makes them different if they are rated for same voltage and current?

What are the safety components I should look for in a transformer to ensure that it does not injure some one, cause fire or some catastrophe when it fails? I have included a fuse as the first thing when mains enter the product.

Thank you!


texts: Health index / performance curve of a motor

texts:
I am collecting daily data of motors that consists of vibration in  three direction x,y,z , RPM, Temperature, kVAh, kWh, kVArh, average voltage (LL), average voltage (LN), average PF,  average current and frequency.

I am supposed to plot a health curve/Performance curve of this motor using the given parameters like this.(an example how the health curve should be.

May I know what parameters are important to plot performance curve of motor? I know speed, temperature, vibration, kWh are to be considered. But i have no idea how to use these parameters to state a performance of motor.

Here are some calculations to find out torque and plotting speed-torque curve, temperature- current, temperature- voltage.

How do i use all these plots, curves to depict a health index of motor?

Thank you.


texts: If Pointer Extension = 1, what should Pointer become then in J1939 standard - CAN bus

texts:
Assume that we have the EEPROM address 647 and we want to read to it. That can be done in J1939-21 CAN bus standard. But the problem I faceing is that if I'm using Pointer Extension = 1, then I can't use the address 647, as 647.

So to send a DM14 memory request on address 647, which has only 1 byte element memory size
byte1 = 0b00000001 // Memory size LSB
byte2 = 0b00000011 // Memory size MSB, Pointer Type = 0, Command = 1 = Read, 1
byte3 = 0b10000111 // Address LSB
byte4 = 0b00000010 // Address
byte5 = 0b00000000 // Address MSB
byte6 = 0b00000001 // Pointer Extension = 1 = Read EEPROM
byte7 = 0b11111111 // No Key LSB used = 0xFF
byte8 = 0b11111111 // No Key MSB used = 0xFF

But when read it, I read at WRONG address.
I found some information at page 56-57 here http://www.unece.org/fileadmin/DAM/trans/doc/2006/wp29/WP29-140-06e.pdf
Question:
How should I interprent this text below? If I have the address 647 and pointer extension = 1. The pointer address will then become....?


texts: How to measure currents between 0.1mA and 100mA?

texts:
Summary of question:

I need to measure (using a microcontroller, not via a meter) currents between 0.1mA and 100mA, with a reasonable level of accuracy - say, to within 0.2 of a mA. My power supply is single-rail 5V.

I have tried the ADC of such chips as the ATtiny85 and the PIC16F1503. I have tried the INA219 and the LMP8640. I have tried homebrew op-amp solutions.

How can I measure such currents accurately and reliably using a microcontroller?

More detail:

The INA219 and LMP8640 gave wildly fluctuating readings. One minute they would be fairly accurate; next minute they'd be wildly erroneous. I don't understand why this should be.

The same happened when I tried to use the ADC of a microcontroller. These things just don't seem to cope well with really small currents (or voltages).

I tried this board:

But having adjusted it to produce sensible results for 2.2mA, I found that it was a whole mA out by the time I got to 10mA.

Then I tried this op-amp circuit:

I didn't get any useful results from it; probably due to the fact that it's not a rail-to-rail op-amp. Even if it were, I doubt it'd be sufficiently close to the rails to give me a useful output across the entire range.


texts: I have a hard time with determining the input impedance of the problem shown as well as the equivalent lumped circuit model with this Zin

texts: This is the work I have done so far. I am not confident in my work and was having a hard time with determining the input impedance. If you have a correction or opinion on this work please comment.


texts: Ferrite Bead: How much impedance do I need?

texts:
I understand that ferrite beads can be used to reduce noise from a power supply input to an IC.

I understand that one selects ferrite beads based on its resistance at the noise frequency one wishes to reduce and I need to select the ferrite based on what frequencies I expect digital switching noise.

My question is: how do I know how large the impedance of the ferrite bead needs to be in the resistive region @ my target freq? This is the part it seems that every guide I can find on the subject excludes.

Does it not really matter precisely as long as the bead has a maximum current rating 50% higher than the expect operating current?


texts: Which one is better to say? Volt or Volts?

texts:
This question might be quite premitive, But I really want to know what is the standard way of saying for example:

2 Volts or 2 Volt
1 Volts or 1 Volt (the Volt seems to be a better choice!)
0.5 Volts or 0.5 Volt?


texts: Driving 3V chips from 3V3 chips and vice versa

texts: Are there going to be any problems mixing logic levels derived from chips driven by those different voltages? My initial view is "no" because of the 300mV clamping diode drops, but just checking other opinions...


texts: Will a live wire tester screwdriver work if I am hanging in air?

texts:
I have a very basic electric live wire tester. A simple device that otherwise looks like a screwdriver with resistor and a neon inside it. Image source WiKi

I connect one end to the live wire and when I touch the other end the neon glows if the tester in fact was connected to the live wire.

I have gone thru this post and it’s very informative. Still it’s hard for me to understand its working! Just a question comes to my mind, what if while I touch the other end of the tester, I am completely floating in air, even my shoes not touching any ground? Will the neon glow in that case? Can circuit complete thru ground then air then human body and the tester?


texts: Why doesn't the output of the opamp change with the source impedance?

texts:
The datasheet of this opamp says the input impedance is typically 100Meg. So I expect the voltage gain to be halved with a source resistance of 100Meg. But the following simulation doesn't reveal that and gain almost doesn't change:

Above the voltage gain is two. Applied input is 1V. So with a 100Meg source resistance I was expecting 1V output(half of the gain). But the plots show the gain is not affected from the source impedance and is still two.

Why 100Meg source impedance is not halving the output gain if the opamp input impedance is 100Meg?


texts: Determine input frequency of square wave w/ ICR in Atmega328p

texts:
I'm trying to obtain the input frequency of a square wave using the input capture register of an Atmega328p. So far, it works sporadically -- which is to say, when I input a 75 kHz square wave, the output looks like this:

244
244
75117
74766
75117
75117
79207
80402
82051
82901
84656
85561
87431
244
244
244
88888
90395
244
244
244
-941176
-271186
244
-246153
244
244
244

Does anyone know why this might be the case? I've tried messing with the data types, but otherwise I'm not really sure what the problem could be. The code I've written is below.

// # of overflows
volatile long T1Ovs;

// timestamp variables (store TCNT at time of input capture interrupt)
volatile long Capt1, Capt2;

// capture flag
volatile uint8_t Flag;

volatile long ticks;
volatile double period;
volatile long frequency;

void initTimer1(void)
{
  TCNT1 = 0;
  // initialize timer to 0

  //timer/counter1 control register b
  TCCR1B |= (1<<ICES1);
  // input capture edge select; rising edge triggers capture

  //timer/counter1 interrupt mask register
  TIMSK1 |= (1<<ICIE1);
  // ICIE1: input capture interrupt enable

  TIMSK1 |= (1<<TOIE1);
  // timer/counter1 overflow interrupt enable
}

void startTimer1(void)
{
  TCCR1B = (1<<CS10);
  //start timer with pre-scaler = 1

  sei();
  //enable global interrupts

}

ISR(TIMER1_CAPT_vect) // interrupt handler on input capture match (rising edge in this case)
{
  if (Flag == 0)
  {
    Capt1 = ICR1;
    // save timestamp at interrupt (input capture is updated with the counter (TCNT1)
    // value each time an event occurs on the ICP1 pin (digital pin 8, PINB0)

    T1Ovs = 0;
    // reset overflows
  }

  if (Flag ==1)
  {
    Capt2 = ICR1;
  }

  Flag ++;
}

ISR(TIMER1_OVF_vect) // interrupt handled on timer1 overflow
{
  T1Ovs++; // increment number of overflows
}

void setup()
{
  Serial.begin(9600);

  initTimer1();
  startTimer1();
}

void loop()
{
  if (Flag == 2)
  {
    ticks = Capt2 - Capt1 + T1Ovs * 0x10000L;
    // (second timestamp) - (first stamp) + (# of overflows) * (ticks/overflow = 65535)

    frequency = 16000000/ticks;
    // ticks * seconds/ticks = seconds
    // 1/seconds = Hz

    Flag = 0;
    // reset flags

    T1Ovs = 0;
    // reset overflow count

    TIFR1 = 0b00000000; // clear interrupt registers

    Serial.println(frequency);

    TIMSK1 |= (1 << ICIE1); // enable capture interrupt
    TIMSK1 |= (1 << TOIE1); // enable overflow interrupt

  }
}

Thanks in advance!

UPDATE***********************************

The second iteration of code, using enumerated types to make a state machine:

  typedef enum {
      CAPTURE_1,
      CAPTURE_2,
      WAIT
  } timer_state_t;

  timer_state_t flag = WAIT;
   volatile long Capt1, Capt2;

  volatile long T1Ovs;

  void InitTimer1(void)
  {
     //Set Initial Timer value
     TCNT1=0;
     //First capture on rising edge
     TCCR1B|=(1<<ICES1);
     //Enable input capture and overflow interrupts
     TIMSK1|=(1<<ICIE1)|(1<<TOIE1);
  }
  void StartTimer1(void)
  {
  //Start timer without prescaler
  TCCR1B|=(1<<CS10);
  //Enable global interrutps
     sei();
  }

  ISR(TIMER1_CAPT_vect) {
   switch(flag) {
   case CAPTURE_1:
       Capt1 = ICR1;

       flag = CAPTURE_2;
       break;
   case CAPTURE_2:
       Capt2 = ICR1;

       flag = WAIT;
                    Serial.println(flag);

       break;
      }

  }

  ISR(TIMER1_OVF_vect)
  {
    T1Ovs++;
  }

  void setup()
  {
    Serial.begin(9600);

    InitTimer1();
    StartTimer1();
  }

  void loop() {
    flag = CAPTURE_1;

    while (flag != WAIT);
     Serial.println("loop");

    Serial.println(Capt2 - Capt1 + T1Ovs * 0x10000);
  }


texts:
I built a simple project using an arduino to control a I2C digital potentiometer being controlled by a remote control via a IR Detector. The purpose is to be able to control the input signal of a audio amp using a remote control. It works just fine, but at the point I set the power up volume to default at -49dB.

But I thought in using the internal EEPROM to hold the volume between power cycles. But my question is when should I write to the EEPROM? Because I don't have a power down signal, and I don't want to write on every key press, because someone can change the volume a lot in a day.

Should I set a counter variable and watch for changes like every 30 seconds or so, and write to the EEPROM?

The value I want to store is a uint8_t.

I'm very new to the field, so I'm looking for any clever tricks.


texts:
I have been trying to simulate a counter ram, successive-approximate type voltmeter in Proteus. Below I have tried the simulation of it in Proteus. Everything seems right but I don't get the reading output in the display properly.

Please let me know what the possible mistake could be. I have give 5V as the DC values to all DC generators. The possible mistakes I could think of was:

The battery is not a sutable input.
I tried using a DC generator but that also didn't work.
Maybe the input states 1 and 0 were not appropriate or there was some mistake in the clock.

This was the circuit diagram from a textbook on the counter ramp circuit.
Please let me know what could the possible errors be and how to correct it.
edit:
I made the following changes after following your suggestions

I have used the voltage of 5V to the anode as suggested. The order of LEDs is also reversed. I believe the mistake could be because of the logic states at RO1 and RO2. Could you suggest what changes could be tried there. Also should I use something else for the battery as the input. I flipped the second opamp vertically with - on top. Could that be a possible mistake. let me know how I can improve the project to make it work.


texts: Connecting more than one input of IC together

texts:
I'm interested in using SLG7NT402V Load Switch and I was wondering if it's okay to connect pins 3,4 together and 6,5 together.
what is the difference between this and using only one pin?
does this allow me to consume more current through pins?
here is the design that I'm intending to make using SLG7NT402V:


texts:
What does XMC module stand for in hardware engineering?

I have seen industry mention this but does it have a fullform?


texts:
I am working on a control system project which involves making a transfer function using op amps. The circuit I need to make is the following  . My question is if I can substitute the 4 LM741 op amps with 1 LM324N so that there wont be a need for a negative voltage,right? I am a bit confused since the professor told us to use the LM741 explicitly but after q quick search the LM324N seemed liked a better choice.

Also could anyone tell me whats the difference between op amps that need negative voltage and those that don't? like the LM324N.


texts: KiCAD: Footprint selection for common through hole parts (resistors and capacitors)

texts:
I am in the stage that I have finished my schematic and I have to select footprints for my components before heading over to PCBnew.
However, I could not find a guide on how to select footprints for my few through hole resistors and capacitors.
I am very scared of this part, because this is the most important part, if your components will match the footprints.
I looked up the order I did from the website consisting of my components.
The resistors I bought fall under two categories (regarding their size.)
These two categories are:

Body dimensions = 2.5 x 6.8mm AND Leads dimensions = 0.6 x 28mm (like this one: https://www.acdcshop.gr/resistormetalfilmtht2k06w121625x68mm50ppmc-p-28928.html 1)

Body dimensions = 1.9 x 3.7mm AND Leads dimensions = 0.45 x 28mm (like this one: https://www.acdcshop.gr/resistormetalfilmtht100komega04wplusmn1oslash19x37mm50ppmdeg-p-15162.html)

As far as the capacitors go, there is only one type I  think

Terminal pitch = 5mm (this one: https://www.acdcshop.gr/capacitorceramic100pf100vp350n10005tht5mm5524785c-p-21315.html 1)

NOTE: Another set of capacitors I have is this one (https://www.acdcshop.gr/capacitorceramic100nf100vy5v2024780tht5mm5524785c-p-21321.html 1). As you can see, the terminal pitch is the same. I am just adding this, because I do not know if terminal pitch is the only factor I should care about, but it is the only info provided by the page. There are no datasheets for the capacitors as you can see, unfortunately.


texts: I am using an inverting DC/DC converter from TI (TPS6735)(5V,200ma). When connecting a load of 100ohms it's output dramatically drops to -1V.May I know why it happening like that.Sending my schematic along with this mail.output is taken across C22.


texts: Calculating attenuation of coax cable run

texts:
This question is related to my question about long-distance Ethernet.

I discovered the Netsys NH-310C, a reasonably-priced device for converting Ethernet to coax for long-distance runs.  The manufacturer provided an attenuation/bandwidth chart to determine the maximum expected bandwidth at various distances, as well as the user manual, which indicates the frequencies utilized by the device are in the 12 MHz to 44 MHz range (on page 5).

I am looking to use this cable.  Attenuation per 100 feet is specified as: 1.60 dB for 55 MHz signals and 0.58 dB for 5 MHz signals.  So I assume the attenuation for 44 MHz signals is somewhere between these values, probably around 1.4 to 1.5 dB per 100 feet.

Here is the diagram showing approximately how the cable will be run, underground in 1/2" PVC conduit, with pull points along the run, requiring couplers.

I'm trying to determine if I am calculating the attenuation value correctly for the cable, and also how to calculate the value for couplers/splitters.  Here is what I have so far:

Total cable length: ~2200 feet
Splitter (tee) needed: 1
Couplers needed: 2
Cable attenuation (max @ 44 MHz): 22 x 1.5 = 33 dB
Splitter attenuation: ???? ________
Coupler attenuation: ???? _______

How to determine the splitter and coupler attenuation values?  The specs I am finding are related to cable TV channels (in the 200-300 MHz range) so they list much larger attenuation than would be encountered at 44 MHz.

From the specs I have given, does this setup look reasonable?  Do you think the signal levels are suitable to provide approximately 100 Mbit operation (i.e. in the Green link quality section) per the manufacturer's spec?

It was suggested by the Netsys engineer that I could add active amplifiers if needed.  However, I only have power available at each building.  No power available at the connection points between.

Any suggestions or advice appreciated!


texts: 5x7 LED Matrix on a µC without additional parts

texts:
I want to use a small 5x7 LED Matrix on a ATmega.

I havn't that much space, so I don't want to use a dedicated driver chip.

My thought would be to switch the columns via a transistor and use a resistor on the rows to limit the current.

After a little bit research I found some products wchich use the a LED Matrix without a current limiting resistor and even transistors:

https://wiki.raumzeitlabor.de/wiki/Hacklace/en
http://www.adafruit.com/products/950

How does this work?
In my understanding, the current of all colums (or rows, depending on the multiplexing) adds up on the row (column) pin and exceeds the current limit of the µC pin.
And also the lack of current limiting resistors seems a little bit strange.

The only way I could think of this would reliably work is that the current is limited via the multiplexing timings. Is this the case? And is there a way to calculate such things?


texts: When should one switch from ASCII to advanced serial protocols?

texts:
All my microcontroller devices that communicate with the PC via UART use ASCII strings for sending commands and receiving data (as implemented in Arduino). That's what I learned when I began digging into electronics and I always found sending bare strings to be enough. However I noticed that most devices I came across use sophisticated binary protocols that include function codes, addresses and CRC error checking.

When is basic ASCII communication acceptable and when should I consider something more advanced, like Modbus? Do commercial devices use such ASCII? Industrial?


texts: What kind of microscope is used to see the electronic flow on a microchip?

texts: I've found an image, where anybody can see the electron flux on an active microchip (especially the conducting-path's). It's pretty amazing to see such electric flow and so I would like to know what kind of microscope is used for that? Can somebody help me please.


texts: Above is a push pull Amplifier. As we all know the 8 ohm speaker is not receiving enough juice from the supply rails, in fact its only getting around 16 watts of power, how can we double that amount to make it like 40 watts. It appears that varying the resistors value has no effect. How can we make the speaker receive more current (we can make it absorb more current by lowering the speaker's impedance but let's say the impedance is fixed at 8 ohms).


texts:
My MCU cannot wake up from UART data, so I wanted it to wake up from the RTS line, but Im having problems understanding the concept.

When Im sending data from my MCU to the peripheral, I see the peripheral set its line to HIGH when its buffer is full. And as soon as I set my line to HIGH, the peripheral stops sending me any data.

This allows for full-duplex communication, but I expected the peripheral to notify me before sending any data, by setting its own line to HIGH. This doesnt allow for full-duplex communication, but this peripheral doesnt support simultanous TX/RX anyway, so that would be no problem.

So are there two modes of CTS/RTS flow-control? And do I just have bad luck that the peripheral supports the wrong mode? Does anyone have any other suggestions how I can wake my MCU before the UART data is coming in?


texts: About current distributions and skin effect

texts:
I'm reading a book about signal integrity.
And I have a question.

Within each conductor, the current wants to spread apart to decrease its partial self-inductance.
-> I don't understand the reason why for the current to spread apart will decrease it's self-inductance.

Could anybody explain me the reason?

Thank you.


texts:
I designed this charger circuit and I really appreciate any hints or advices so I can modify it and choose right components values.

I'm charging a 6V 4Ah Lead-Acid battery.


texts:
I am trying to control a RS-485 RTU device (Love 16C-3) using a Python script (pymodbus library) that runs on a Windows 10 PC. The hardware is connected to the computer using a USB-RS232 cable.

In my initial test, the Python script is not able to read anything off the RS-485 device.

What is the RS-485 pin out for the DB9 connector?
Should a USB-RS485 cable be used instead?


texts: Sigfox RF module TD1208R: design a 50 ohm microstrip line on a PCB (Proteus ARES)

texts:
I'm designing a PCB (I have very little previous experience). Among other components, I am using the microcontroller MSP430G2553 and the RF module Sigfox TD1208R (868 MHz). I have doubts to design the trace from the RF pin of the TD1208 to an U.FL connector. As I understand it, this trace has to be a 50 ohm microstrip-line (same impedance as the RF pin of the TD1208) but, how do I do it with Proteus ARES?

The PCB properties can be seen in this image:

Using this data, I have calculated the trace width in this Microstrip Impedance Online Calculator and the trace width should be 100 mils:

These are the doubts I have:

1. Have I made any mistakes in the previous steps?

2. Both the PAD of the RF pin of the TD1208 and the PAD of the U.FL connector are have a width much less than 100 mils. How should I decrease the width of the track to connect it to the PADs? Should I reduce the track width slowly or quickly?

3. What length should the microstrip line have? How much shorter is better?

4. If the U.FL connector is placed as close as possible to the RF PAD, is the trace width less important?

Finally, searching in google, I found in this blog (ioter.io) the files in EAGLE of a TD1208 development board  for the RF module TD1208 but the width of the RF track (70 mils) is lower than it should be according to the online calculators of microstrip-line and the properties of the PCB. For this reason I have decided to ask, because I do not know if that design is correct because it does not agree with the theory (or so I think).

Best regards,

Fran Martin


texts:
I was looking through to buy a few relays and found the nominal DC contact voltages (~30v) are much smaller than the nominal AC contact voltages (250v). What is the reason for such a large difference?

Relays from newark.


texts: Impedance mismatch vs Signal attenuation

texts:
I'm currently designing a 50Ω grounded coplanar waveguide (GCPW) which connects an antenna to an LTE modem. My question is: does there exist a standard graph/chart that attempts to generalise impedance mismatch against signal attenuation? Essentially, I'd like to be able to predict the impact of small impedance mismatches on signal strength.

Thanks


texts:
It's been a while since I had to deal with physics, in general, and I try to wrap my head around this and it's confusing.

So as I know, if you wire n batteries in series, Ah remains the same while voltage increases. While wiring them in parallel makes the Ah increase.

So in abstract, a battery can hold infinite Ah as long as the voltage is low enough since, in theory, you could split the battery into virtual ones that have lower voltage and are connected in series, and then you connect them in parallel. Also, this means, in theory, you can create a battery with huge Ah and low voltage. But this sounds to me somewhat infeasible (and limited by atom size).

But can I can't explain to myself why. Can you?

And I think it all starts because I can't completely understand why series batteries combine their Ah, even though is intuitive.


texts: 3-Phase Inverter Control with SPWM(Sinusoidal PWM) for 3-phase sinusoidal output

texts:
I intend to control a motor with 3 120° phase shifted sinusoidal signals. I already implemented the SPWM to output a sinus shaped voltage, but i am a little bit confused at how should i implement it with my custom design inverter. The inverter has 3 legs/6 Mosfets which can be controlled indivudally.

I will quickly describe what i have in mind and would appriciate any comment/clarification on if it is a good idea or not.

With a 3 phase sinusoidal signal, the outputs are always a permutation of + + - or - - + (momentary sinus values). If you add them up you should get 0. And the inverter legs are HHL or LLH accordingly(Of course LLH or LHL. etc is possible). Lets take the HIGH-HIGH-LOW case :

Here i thought i can identify the different phase (LOW in this case) and control the other 2 with PWM (according to a look up table). What i am confused at is, is it really necessary to seperately control the 3. leg(which should be low ) ? Cant i just turn on the low side switch fully on, while the other 2 are positive and being controlled by a varying PWM duty cycle. This will function as a current return path and since the sum has to be 0, it will automatically take the value it is supposed to take. And in the LLH case, H-leg will be on as long as the other 2 are L and controlled by PWM. This will be alternated with a state machine.

Please let me know if the way i am thinking is correct. I am aware of more advanced methods like SVPWM (Space vector) but would like to stick to SPWM.


texts:
In AD19 as far as I remember the pad preview in the footprint editor would show a nice 2D model where we could see the X and Y dimensions (of a rectangle for example) clearly.

With the new AD20 I see this fancy useless 3D preview:

Does anybody know how to revert back to the 2D view?

Thanks


texts: altium : can I customize a comporent reference depending on the sub-sheet?

texts:
In my project, I have a sheet that is re-used several times. Imagine, it's a motor driver. The sheet includes the driver and the connector to the motor.
This sheet is used several times as a "sub-sheet" because I'm running serveral motors.
Now, I want the connector to be a different color for each motor. It's same packaging, only color is different, so I need to set a custom component reference for the connector in each sub-sheet.
Can I do that? how?
I choose not to "externalize" the connector from the sheet to keep it while using the "copy room format" function.


texts: Simple, compact 9V DC to 400V DC step up

texts:
I'm attempting to create my own Geiger-Muller counter based on an old, soviet STS-5 tube.

I want it to be as compact as possible. I don't want to use ready-made modules, like this one, instead I want to put everything on one PCB. My only struggle concerns the high voltage part. I want the circuit to be as compact as possible, hence I wonder if there's a simpler, more compact option to bring, let's say 9V to the required 400+ V DC. Using a simple transformer and a MOSFET to switch the 9V on primary would be the easiest method, but maybe there is something better, more compact, that I have no knowledge about yet?


texts:
I have a transformer (12 0 12 5 amps) and I am using it for a variable bench power supply. Currently I am using it in full wave rectifier configuration and I'm getting around 40volt at no load after filter capacitors (2*25 volt series) so I was planning to use a Xl4015 based voltage buck converter but its max input is 36 volt only.
Then I thought of using the center tap in half wave configuration and getting around 20 volt at no load. In this case I was planning to use a boost converter but as we know when voltage increases current decreases. That means i will be getting 24 volt at around 2.5 amps.
So now my question is is there any way I can modify my transformer to output 12 volts at 10 amp. I have read a couple of articles that mentioned connecting the secondary coils in parallel, something like this https://www.electronics-tutorials.ws/transformer/multiple-winding-transformers.html
Any views on this is appreciated


texts:
I'm working on a project where I should send an overload signal if the strain is bigger than 40 ppm.

So far I found this answer:

Strategy to balance a Wheatstone bridge for strain measurement

The wheatstone bridge consists 2x 120 ohm, GF 2 strain gauge and two 120 ohm 0.1% resistor.

Using the answer above I'd make it so that at 40 ppm the in-amp's output would drive a JFET.

I think that a ina-128 would be a good choice, but the power source is x piece 1,5 V battery so I'd need 4.

Is it a good choice, can you recommend a better for this application?


texts: How can I change the reference voltage and resolution of SAMPLE and HOLD block in LTSpice?

texts:
I have a question about LTSpice.
I put a Sample & Hold block in a sheet to quantize a continuous sine signal like below:

But the resolution is not desired. I have a 16-Bit ADC with a 1v reference voltage.
even I changed the spice lines and opened the SAMPLE.asy symbol but I really couldn't find any solutions.

Thanks

@andy-aka
I really appreciate you for your reply. (due to my low reputation I couldn't upvote for you)
Yes. I had forggoton the principle :) actually N=Fs/F. so we have N=10Meg/1Meg=10 points per each cycle.

if it's possible I have an another question :)
when the ADC resolution is Vref/(2^16), can I implement it in LTspice like below:

Vres=Vref/(2^16)
out=int(Vin/Vres)
if abs(Vin)>=Vref
Vin=1
end


texts: Creating a constant current source using an Arduino, BC548 transistor and LM317LZ Voltage Regulator

texts:
I'm trying to create a constant current source that can be turned on/off using Arduino's digital output.

I'm supplying the BC548 with a 5V vcc supply from the Arduino. The base is supplied with 5V using arduino's digital output. The output of the BC548 is sent to the input of the LM317LZ to produce a constant current source based on the design on http://www.bristolwatch.com/ccs/LM317.htm

The issue is that the voltage at the Adj pin of the LM317LZ changes with R1. With R1 set to 100 Ohms, the voltage at the Adj pin is 1.25 V as expected, but when R1 is set to 50 Ohms, by adding another 100 Ohms in parallel, the voltage changes to 1.73 V.

Here's the circuit diagram:


texts: Best way to isolate a white noise source from the rest of my circuit?

texts:
I have an acoustic project that self-calibrates every so often by playing white noise and doing some processing on it. My white noise source circuit is below. My plan is to direct the white noise through an analog switch (TS5A3359 or similar) along with either a pure tone output or grounding, so I can kill speaker output when it's not needed. However, I'm concerned that when I'm not using it, the noise is still being generated, but the output is basically floating.

My questions are:

Is this even a concern when the WhiteNoise connection is floating? and,
If so, how to best isolate/shield/protect/whatever this section of the circuit from the rest of the PCB?


texts: Are Buck converters conceptually same in low/high power applications?

texts:
I am new to power supply circuits. I am studying datasheet of  buck regulator LM22676 which generate 5V/3.3V dc for micro-controller supply in one of my system.The datasheet says it has a N-channel mosfet capable of driving upto 3A.

The place i first read about buck-boost converter is in Power electronics class in EE which uses a thyrsitor as switch with additional L,C filters.In power electronics the focus of study was  driving high power dc loads  like dc motors with dc-dc converters circuits with thyristor and gating circuit.

Is the buck converter principle used in LM22676 same compared to power electronic theory?
Do integrated power converters exist in power electronics as well instead using thyristor based circuits?


texts: Second Order Circuit, Sadiku's Fundamentals of Electric Circuits

texts:
I would like some help with Sadiku's exercise about second order circuits.

I did'nt understand why the solution says that V (0) = -30 V.

Also, I did not understand why the capacitor's voltage (Vc) is -30 V.

Isn't the voltage for t <0  (when the capacitor is loaded) the same as the voltage source?

The exercise asked i(t) for t>0 . The switch opens at t=0 after a long time closed.

If I change to + - in the capacitor as suggested.

For t<0: V(0)= 30 V and i(0)= 15 A

For t>0:

α= R/(2L)= 2/(2*0,5)= 2

omega = 1/sqrt (LC) = 1/sqrt(0.5*0.25) = 2.82942712475

Under-damped:

di/dt= -2(15 cos(2t)+ B sin(2t))e^-2t + (-2*15 sin (2t) + 2 Bcos(2t))e^2t

di(0)/dt = -30+ 2B = -(1/L) [R*i(o)+ Vc(0)] = -2 [30+30] = -120

-30+2B=-120

B= -45

i(t)= 15 cos (2t) + (-45 sin (2t))e^-2t A

So, the answer isn't the same as the book's solution.


texts: I have a dc voltage regulator 12 volts in 9 volts out. it is drawing 8 milliamps. the battery is 12 volt dc 7 amp hour. how long will this battery last at this load?


texts:
I want to add two voltages.

I have tried using the Op-Amp adder here. The resistor schematic before the summing amplifier contains resistors in parallel which would average the voltage.

My problem is that I would have one steady voltage and another variable voltage coming from a pressure sensor. It would vary.

What I want is to add 0.5 volts to the voltage from a sensor (say 1.5) so that resultant voltage is 2.0.


texts: Is there any symbol for Alternate action switch?

texts:
There are some switches, that looks like push-button switches, but acts like On-Off switches (i.e. can maintain contact). In one-press they turns-on (and looks slightly deeper), and in next-press, they turns off (and looks slightly higher),
like this one:

I saw them frequently  ( in TV-sets, Water purifiers, old radios, etc. )

Now, is there any any circuit- symbol for them?


texts: Charged Capacitor in serial RLC-Oscillator

texts:
So one of my Professors has given out a practice example I'm unable to finish. Given is the following circuit:

Determine the time function \$u_C(t)\$ by solving the differential equation:
$$u_C''+\delta u_C'+\omega_0^2u_C=0
$$
So I get the (presumably) correct solution, for the following values: $$
C=5.6\mu\mathrm{F}\text{ with: }U_{C,0}=u_C(0)=48\mathrm{V}\\
L=43.3664\mathrm{mH}\\
R=176\Omega
$$
My solution is:
$$
u_C(t)=\mathrm{e}^{-\delta t}(K_1t+K_2)+U_0
$$
With a DC-Source voltage \$U_0=19.5\mathrm{V}\$ I can determine \$K_2\$ to be the following:
$$
u_C(0)=1(K_1*0+K_2)+19.5\overset{!}{=}48\Leftrightarrow K_2=48-19.5=28.5\mathrm{V}
$$
So my Prof lists in his possible solution for \$K_1\$ to be non-zero, which to me makes no real sense, since the circuit is open for \$t<0\$ and the inductor cannot have a jumping current, meaning the current at \$t=0\$ is \$0\mathrm{A}\$. Or am I completely missing something?
Edit: apperently I don't know how to write inline Latex in MathJax
Edit 2: fixed inline-latex


texts:
I am a software engineer ,Recently I have completed an industrial project using raspberry pi and some other components .
The project essentially is to measure pressure(pressure sensor)and displacement(rotary encoder) and plot a Realtime Graph using the sensor outputs which are placed on a machine.
Now one of the customers (B2B model) suggested that this project can be done using a PLC and could be done in low cost .

Questions :

1)Is it posiible and viable to use PLC for a standalone machine just for two sensors?

2)I had to write a total software for this project which would take data, plot output graph and perform various calculations using the graph ,is it replacable by PLC software ?


texts: Which is the right voltage divider formula?

texts:
I've come across two variations on the voltage divider formula, when solved for \$x_2\$:
$$R_2={R_1V_{out}\over V_{in}-V_{out}}$$
$$R_2={R_1\over {V_{in} \over V_{out}} - 1}$$

I solved the one equation I can find that most sources agree on for \$R_2\$
$$V_{out}={V_{in}R_2 \over R_1+R_2}$$
and got the first equation. This question seems to agree with that result. However, Wikipedia and this calculator have another version (use a test set of values to check the calculator).

I graphed both, to the best of my ability assigning constants to the voltages, and they are not equal. Which equation is right, and if it's the second how, how do you get there from the base equation?


texts: Best way to use sets of 4 rechargable batteries with appliances that need only 2 or three?

texts:
I have various sets of 4 rechargable AA or AAA batteries and a number of appliances (camera flash, bike flashlight, hand flashlight, portable phone handset, wireless keyboard/mouse, etc.) which require 2, 3 or 4 batteries. All of them are Ni-MH, some ordinary, some of the eneloop brand (Sanyo first generation or Panasonic make). Altogether I have 20 batteries in sets of four.

For charging I use a charger with separate circuitry for each battery, four loading status displays and a discharge function (the charger can either charge or discharge, cannot charge one battery and discharge another at the same time).

I've been told some time ago to follow these rules:

Full charge, full discharge whenever possible,
one to three 'refresh cycles' from time to time, less so with the
eneloops,
don't combine different capacities or brands or newer batteries with older ones.

My question is what should I do to make best use of the batteries while being able to grab some and use them for whatever I need at the time (not having a set designated to a particular single use).

I ask this because the way I use the batteries contradicts some or all of the three rules above - namely I can't always get the same level of wear or I'd like to use batteries from different sets which sometimes lay idly when the rest is used somewhere else etc.


texts: Capacitor for current transformer measurement circuit

texts:
I want to measure an AC current with a current transformer and an arduino device. I found on a website (http://www.homautomation.org/2013/09/17/current-monitoring-with-non-invasive-sensor-and-arduino/) that measurement circuit:

My question is, why do I need a capacitor here? The explanation from the website is:

  The capacitor C1 (10uF) has a low reactance – a few hundred ohms – and
  provides an alternative path for the alternating current to bypass the
  resistor.

But why do I need an alternative path for the alternating current?


texts: How is vertical sync done in YPbPr component video

texts: All the literature I have read about YPbPr component discusses only the horizontal sync, but I have not found anything about vertical sync.


texts: What's the difference between filters with the same cutoff frequency, but different component values?

texts:
I've heard mention of this topic, and it seems pretty useful, as I'd like to design high-quality audio equipment & synthesizers. But I've never heard it explained, only mentioning that it "changes the sound".

Say I want a low pass filter with a cutoff of 1 kHz. There's a (theoretically infinite) number of component values I can choose. Two examples:

15 Ω resistor, 10.61 µF capacitor.
47 kΩ, 3.39 nF cap.

I heard it mentioned from an EE guru that this changes the sound of the filter. I even found the paper he mentioned of how it changes, but I couldn't make head or tails of it as it was heavily centered around math instead of sound. I'll try to find it again so ya'll can take a look at it.

If anyone can explain it — especially in terms of what value it would have for the sound of something — it would be fantastic.


texts:
I've run into an issue where, it appears, my interrupt only fires once, then simply refuses to fire again on my ATMega32U2. I have the following (stripped down) code:

void init(void) {
    DDRB = 0xff;
    PORTB = 0x00;

    TCCR0A = (1 << WGM01);
    // 1024 prescaler
    TCCR0B = ((1 << CS02) | (1 << CS00));
    // Interrupt every 4096 clocks
    OCR0A = 3;
    // Enable timer compare match interrupt
    TIMSK0 != (1 << OCIE0A);
}

ISR(TIMER0_COMPA_vect) {
    PORTB++;
}

int main(void) {
    init();

    sei();

    while(1);

    return 0;
}

When I plug an LED into each pin of PORTB, the first pin is high, while the rest are low. The most I can deduce from this is PORTB is incremented to 0x01 by the interrupt firing once, then left alone as the interrupt never fires again using the TIMER0_COMPA_vect vector.

However, if I replace the compare interrupt with an overflow interrupt (TIMER0_OVF_vect) and configure the registers differently, it works fine; PORTB cycles through 0 - 255 very quickly as I'd expect. This is my working code with the type of interrupt I don't want:

// Different timer config
void init(void) {
    DDRB = 0xff;
    PORTB = 0x00;

    TCCR0B |= (1 << CS01);

    // Enable timer 0 interrupt
    TIMSK0 |= (1 << TOIE0);
}

// This time, it's an OVERFLOW vector, not a compare vector
ISR(TIMER0_OVF_vect) {
    PORTB++;
}

int main(void) {
    init();

    sei();

    while(1);

    return 0;
}

I've read what there is to read on Google, however the only fixes posted are logical errors that I don't think I have. I've read this forum post and had a look at the timer configuration registers, and they're exactly the same as my first example. I've also read this question, but that didn't help.

I've been following the tutorial on this page (PDF) for the TLC5940 LED driver chip and am on Chapter 4 (refactoring code to use interrupts). Please note that I don't want to use the ready built library; I'm using this as a learning experience.


texts: Audio Signal Noise: Understanding & Troubleshooting

texts:
Today, I'm wearing a pair of active headphones for a change.. ( Running on 2x AAA batteries ).
I've hooked them up to a synth and noticed this really annoying monotone  buzz / hum in the background.

I spent some minutes trying to troubleshoot it, and noticed that; if I stick my finger into the empty USB port on the back; the audio signal clears up, instantly.

What's going on? Why does that happen?


texts: What kind of inductor for DC-DC converter module's EMC filter?

texts:
I'm looking at the datasheets for a number of switching DC-DC converters.  They suggest for EMC filtering to add an inductor and a capacitor or two on the input side of the converter.

The question: what kind of inductors are required?  How critical are the values?

I'm not after product recommendation, I'm after clarification of the type of component.

Are they "axial-leaded high-frequency inductors", in a resistor-like package?  Open coils?  I've been looking at Epcos BC+ (datasheet), Bourns 78F (datasheet), Wurth WE-TI (datasheet).

The converter datasheets show a filter circuit as follows:

simulate this circuit – Schematic created using CircuitLab

I'm really just trying to lay out my PCB at the moment (grid is 0.127 mm, Vin is top left.)

For reference, these are the values from the DC-DC converter datasheets:

Recom R78E-0.5 series (datasheet) suggests EN 55032 EMC filtering: Class A filter L1 3.9μH, C1 4.7μF/50V, no C2; Class B filter L1 12μH, C1 10μF/100V, C2 4.7μF/50V.
Traco power TSR-1 series (datasheet) suggests Class A filter L1 5.6μH/3.5A, C1 10μF/50V, C2 10μF/50V.


texts: New type of TVS diode - where do I find one, if it even exists?

texts:
I've been looking at various TVS's and recently came across one I'd never seen before:

This particular part is used by Citel for a transient suppression, and concluded that this part had been released out in the world recently.  It seems to be the equivalent solid-state version of a three-pole gas discharge tube.
Wishing to find a datasheet for said "DBC", I performed a Google search for some manufacturer, but ended up turning up nothing. I couldn't even find a theoretical reference.
So my question: is  this a proprietary part by made by Citel, or is it a generic part that I did not recognize that is in common use, but failed to enter the correct search terms for?


texts:
I am self-taught in electronics, and I am learning using several different sources, both online and off.  This URL shows a circuit (and I've seen similar before) of a low-power voltage divider using an emitter follower.

https://learn.sparkfun.com/tutorials/transistors/applications-ii-amplifiers

However, on the output, there is both a load and a 1k resistor in parallel.  What is the 1k resistor for?  It seems to me to be a waste of electricity.  Won't the voltage after the emitter always be 1V with or without the load resistor?  It also doesn't seem to be a current limiter since it is in parallel.  I can't think of what its function would be.

Any ideas?


texts: What is the purpose of wiring pins 2 and 3 of a potentiometer together?

texts:
I build a lot of audio devices - amplifiers, effects processors etc. I've been doing it for about a year and learned a lot of principles. However one thing I still don't understand is wiring pots 1 and or 2 and 3 of a potentiometer together. How is it different from using only pins 1 and or 2 and 3?
I'm talking about this sort of thing (from here):

simulate this circuit – Schematic created using CircuitLab
Rather than this (from here):

simulate this circuit
Please ignore resistance values, just examples.


texts:
What are my options when it comes to reprogramming an AVR in-circuit? The new program will be received via a wireless connection, so it will need to be stored in some temporary memory container.

I know the AVR can be programmed in this manner via a wired connection using SPI. Would it be necessary to implement a dedicated programmer slave controller that would receive the new program and have hard-wired connections and re-flash via SPI?

Any suggestions?


texts: Is this cheap extension cord safely rated for 1625W?

texts:
Comparing two cables that I have, a cheap extension cord and an expensive "heavy duty" extension cord, both are rated for the same load.

Is this an inflated rating or is it accurate for the white extension cable?