texts: Questions about Li-ion battery charger and battery monitor chips

texts:
I want to build a system powered by 14.8v Li-po battery pack or mains power (selectable power path). When the mains adapter is connected, the battery will be charged and the system will be powered from the adapter.

I've found a family of standalone charger chips by Texas Instruments doing exactly that. It's the bq246xx. This family has some features like over/under-voltage/current protection.

Since the battery I'm using is a 14.8v 4s Li-po battery I must use a cell balance chip. I found this one bq76920 by Texas In. Balancer chips also contain similar features to the charger chips (o/u-v/c protection).

So my  question is: Do I have to use both a battery charger and balance/monitor chips to charge and balance the battery and power the rest of the system at the same time, or can I use only the balancer chip to do these things.

My battery pack is quite expensive ($120) and other people will be using it, so I need a solution that offers maximum safety for the batteries & users.

Thank you for your time


texts:
I need to feed 4 DC motors of 5V on my Raspberry Pi 3 Model B using PWM (Pulse Width Modulation).

Currently, I have the next components: 2 NPM transistors, 1 L293D integrated circuit, diodes, resistors (220 Ohms), wires, etc.

My question is, what is the correct way to feed the 4 motors with 4 GPIO pins?

I will appreciate any kind of help.


texts: Is it possible to test a lithium ion battery for safety? How?

texts:
There have been stories in the news recently about fires that are believed to be caused by the lithium-ion batteries inside hoverboards.

If you had one of these devices and didn't mind taking the hoverboard apart to get at the battery, could you actually test to see if its battery is safe/up to spec/liable to cause a fire? If so, how?


texts: Using capacitor as a rechargeable battery

texts:
As part of my learning of electronics, I'm currently trying to develop my own network of sensors.

So far, I've managed to make myself a satisfying small setup :
A few nodes, built with an atmega328p, a set of sensors and a RF emitter, capture data and send it through RF to a central server, which takes care of that data.

This works well, and I'm now trying to get rid of the battery part.
My current solution works fine with either a 9v battery or a 5V USB charger, and I'd like to try to get other kind of energy inputs (like solar panels, windmills, etc...).

My circuit requirements are simple : 5v / 65mA.
However, these requirements are only necessary for 1 sec every once in a while, since i don't need the circuit to run constantly. a few times a day is largely enough, and it can sleep / power-off the rest of the time.

I got myself what should have been a 0.5W solar panel (5v/100mA). However, when I try to measure the current I get from it, fully facing sunlight, I only get 5v/5mA.
This is not enough for my circuit, so I figured I would go and try to store that energy.

So I was thinking that maybe I could use capacitors :
After reading a bit on it, I've learned how to charge and discharge it.
However, to my knowledge, this always requires some changes on the circuit in order to switch from charging to discharging : Either removing the input battery like Capacitors as a Storage for Electricity, or doing something like this https://www.arduino.cc/en/Tutorial/CapacitanceMeter . I'm not sure if the link could be suitable in my case, because this requires the Microcontroller to be powered, and at this point, it is not.

The other option was to use rechargeable batteries, but I couldn't find really small ones and I would have the same issue as above. I don't want to buy LR44/CR2032 stuff because I would have to change them quite often.

My questions are :

Should I simply replace the solar panel ? Is it normal that the current I read is so low even though the voltage I get is correct ?
Is there a way to make a circuit that charges a capacitor, and when it's reached a sufficient charge, automatically use the energy stored in it in order to power some other part of the circuit until it's emptied, and all over again ?
Same question with a rechargeable battery.
In the case where this would not be possible, which I'm starting to believe, what is the common approach for this ? If possible, I'd like to avoid using classical "AA" or "AAA" batteries, but rather use "in-circuit" batteries (I don't know their name though)

Note : Sorry if anything is unclear or seems stupid. I'm still begining in electronics. Feel free to make any suggestion relative to this project.

Thanks in advance


texts:
I am ordering some parts for the first PCB projects I've designed in EasyEDA.

One of the PMICs I am utilizing is the TP4056 which is listed as being in a "SOP-8_EP_150mil" package.
Doing a broader search on LCSC I came across this IC which listed its package as being "ESOP-8" and is slightly cheaper.

I read through the Wikipedia listing for SOIC and their list of packages but I did not find any references to "ESOP".

So my main question is, what are the differences in ESOP (if any), and can I use this as a direct replacement for a standard SOP-8 chip?

Much appreciated, Thanks.


texts: Typical flyback conductive noise emission simulaton

texts:
I'm trying to understand what is a typical conductive noise emission of a flyback converter.

I made a simplified model (I skip the transformer replaced with a single coil - I think that this simplification does nothing to noise emission, 300 pF capacitors and 70 mH coils (having 700 mOhms serial resistance) represents normal 100 m (or something) long power line.

After I run the simulation I was surprised to see such HUGE ringing on the power line:

The amplitude is start with 170 Volts and frequency about 500 kHz:

I've never see anything like this in real world circumstances.

I suspect that my simulation model is wrong in some way. But my colleague I was able to consult with told me that it looks OK.

Any thoughts?


texts: How to safely replace NiCD/NiMH with Li-ion in a small electric screwdriver?

texts:
I'd like to repair and re-use a small Bosch electric screwdriver. It currently has a battery of 3 small AA-type rechargables (unmarked cardboard wrapping) that has almost the same occupancy volume of a single 18650 Li-ion cell. The existing battery pack has an inline diode between the charging contacts and the battery pack.

I know about the risks as shown in Replacing NiMH with Li ion.

My key question: I want to re-use the two contacts on the base of the scredriver that connect to the battery for recharging. I have an existing external Li-ion charger (so not use the dumb AC brick that came with the drill). Should I (a) use or (b) explicitly not use a diode between the contacts and the cell for short-circuit protection?

Without a diode, I have a small risk of short circuit if something touches both contacts (small, because the contacts are recessed). With a diode I have a voltage drop that can interfere with the voltage sense of my charger.

I'd prefer not to throw away this otherwise perfectly functional screwdriver, and I'm not sure where to buy the same kind of NiMH battery pack.


texts: solar panel model as constant current source + initial values

texts:
I have created a simple solar panel model in Matlab, using the diode equivalent model. The basic equation is as follows:
I = Iph - I0*(exp((V+Rs*I)/(Vtherm*a))-1) - (V+Rs*I)/Rsh

where Iph is the photocurrent, I0 the saturation current, V the voltage over the panel, Rs the total series resistance, Vtherm the thermal voltage and Rsh the total shunt resistance.
I've plotted the IV and PV curves and they look right. I'd like to use the model as an embedded matlab function in a Simulink model, but have troubling getting it to work.
As mentioned above I solve for I within my model. But I'm having trouble getting my head around how to then solve for V because both terms depend on each other, and the external resistance as well. I could now use Newton-Raphson or other numerical method to get V from the above equation, but how can I take into account the presence of an external load?

In the model above I haven't explicitly solved for V and I've just added the current I get from the above equation as a constant source. I'm not sure whether this is the right way to go, however... If I now want to add more panels in series, how can I do so without adding ideal current sources in series as well, which is clearly unphysical?
I don't know how to choose the initial values for V and I, because I need bot to solve for I in the next time step. If I choose I=0 and V=0, the I value is clearly Iph as other terms cancel out. But that, surely, cannot be right as it's the photocurrent of the panel..!
Any help clearing this up would be greatly appreciated.
Thanks in advance.


texts: Multimeter Measurement Problem About Capacitor

texts:
When i am trying to measure a 100 nF capacitor using multimeter, the value which device shows continuously increasing. Do you have an idea about the reason of this situation? Thank you. I have uploaded a video what i mentioned;

https://youtu.be/Cjw1FREHEqw


texts:
I am using a module to convert CAN to UART. This module has 2 programmable masks and 6 programmable filters.
There are 13 message IDs that come in over the CAN bus and I only want 9 of them. The IDs are as follows.
The messages I dont want :
 - 0x404
 - 0x6f1
 - 0x114
 - 0x11c

The ones I do want :
 - 0x36C
 - 0x33C
 - 0x34C
 - 0x35C
 - 0x314
 - 0x31C
 - 0x324
 - 0x32C
 - 0x37C

I have found masking quite confusing and I would love if someone could help me better my understanding of it. Would I set my mask to 0x3ff or 0x300? Then the 0x11c messages will come in?


texts: PWM-modules operating simultaneously on different frequencies

texts:
I am using a PIC16F15345 which has 4 10-bit PWM modules.
In order to minimize electromagnetic interference I tried to use the PWM-modules on different frequencies working simultaneously, but it did not work.
According to the data sheet (page 328) "each module has an independent selection of clock source."
However, the Timer2 is shared by all 4 modules and the PWM period value is stored in the T2PR (PR2) register. As the Timer2 require FOSC/4 as the clock source for PWM I don't see how I can vary the PWM period, via T2PR register, individually per PWM module.
In my trials, the PWM period changes for all 4 modules each time T2PR changes.
Any ideas how to do it or is it not possible?


texts: find the amplitude and phase of the signal

texts: How to write a code to compare the amplitude and phase of these three signal through Arduino?


texts: Rewiring USB LED lights to directly use a 5V DC-DC Converter

texts:
I'm currently helping a friend who is renovating a VW camper to fit some LED lighting as she has no electrical experience. She has a 10 metre set of LED fairy lights that are powered via USB (bigclive reviewed something similar, or indeed the same here). She has until now been powering them by plugging them into one of these mounted in the van but would like a more permanent solution. As a result I bought a 12V to 5V DC-DC Converter and a small switch which I wired up to draw power from the vans leisure battery.

I cut off the USB plug a few inches down the cable and connected the two wires directly to the output side of the converter. As soon as they were turned on though only about the first quarter of the LEDs lit up and they trailed off in brightness which would suggest an obvious drop in voltage. The DC-DC converter was also getting warm so I turned the whole lot off before any of the LEDs burnt out.

Assuming that the LEDs were drawing far too much current I dissected the USB plug looking for a resistor but couldn't find one. I'm hoping I haven't done permanent damage as they would be a pain to replace! These lights do have a bundle of 3 twisted wires so going from what bigclive says it would appear they do not require a resistor.


texts: Identify unknown component on AC LED bulb PCB

texts:
I'm trying to put this back together. The part that's broken off is a mystery, saying only '952' and cutting it open, I'm not sure.

What is the 952 part, please? And is it still usable? Thank you.


texts: What is the benefit of a male output connector on a powersupply?

texts:
I saw several power supplies which use a male output connector. For example the Meanwell OWA 90E series uses a XLR 4P or NEUTRIK NC4MX with 2 pins for + and 2 pins for -.

Source: Jmb at English Wikipedia (CC-by)
I do not understand why anyone wants to use a plug where pins could be touched and short circuit accidentally. The device itself would not take any damage (short protection: hiccup mode.)
I would expect female contacts which can not be touched or shorted easily.
What feature is worth the risk of accidental contacts on the output?


texts: Good tools or methods for understanding structure of bootloader?

texts:
I recently figured out the cause of a nasty bug I've been working on with an Atmel AT91SAM9G20 SBC running U-boot, an open source bootloader. The core of the problem was that U-boot expected the hardware to be configured differently than I had built it, so some of the device registers were misconfigured.

Now that I've figured out the problem, I need to tweak U-boot to configure the registers correctly. I can do this blindly by adding a few lines of code at the end of the program, but that's messy.

This brings me to my question: how can I figure out how U-boot works more efficiently than starting at main() and reading all possible code paths across all files? I've tried grepping around in the files and looking at the code near relevant identifiers. This has proved ineffective; it seems that most of the code is drivers for subsystems I don't care about. I actually understand how the bootloader works pretty well by now, but I'm hoping there exists a better method than my naive approach.


texts: If I use a CAT 2 10x probe does my DSO need to be CAT 2?

texts:
I need to measure the harmonic distortion on a solar inverter (power output). I need to buy all the equipment from scratch and was wondering if my DSO needs to be CAT 2 rated if I use a CAT2 10x probe.

The mains output will be Grid tied and be at 230V 50Hz.

The DSO should only see 35V.

Alternatively, could I "just" use a AC transformer to reduce the voltage down to a lower more manageable level? As I understand, the harmonics should be higher frequency, so should have better flux linkage in a transformer, so should be measurable on the transformer secondary (given a ohmic load eg 10MOhm DSO)?


texts: I am trying to create a cheap and small heating element capable of reaching temperatures of at least 260 degrees C. I am considering using a resistor. Is there such thing as a cheap resistor capable of reaching these temperatures for extremely long periods of time without degrading. If so, how many volts/amps would I need to supply it.


texts: Weather Balloon Wireless Mesh Networking

texts:
I am trying to get real-time data feed from a homemade weather balloon radiosonde with the objective of sending HD video during the flight; this could be relevant for GoPro-ers who want to send their images during their adventures rather than storing them on onboard memory or to have data sent to multiple places to decrease the chances of data loss due to destruction of the onboard memory during the adventure. It could also be used for disaster communication, remote location communication, or rescue operations.

I plan to use a 2.4GHz 6dBi antenna in the payload (http://www.l-com.com/wireless-antenna-24-ghz-6-dbi-omnidirectional-antenna-n-female-connector ) and two 18dBi ground stations of the same frequency (http://www.titanwirelessonline.com/Ubiquiti-NanoBridgeM-2GHz-18dBi-p/cp-nb2m-18.htm). I want to have the two ground stations and space them out to allow for better reception and a better chance of getting data as the payload rotates and increases in altitude.The network is also not part of ISM spectrum, employing IEEE802.15.4A, allowing me to take advantage of higher operating Tx power while remaining in the unlicensed range.

Now I have read about aiming and reflecting and the like for buildings and/or radio towers which don’t move. Does anyone have any good experience, knowledge or resources where I can find how to calculate the best gain level vs vertical beam width for ranges 0-80,000 ft, the placement of the ground stations such that they lie in the beam width following the GPS data received via full duplex, and the hardware used for a moving transmitter and receiver?


texts: I am using ads8320 ADC IC which have IN+ and IN- analig inputs. I need to operate this IC with 3.3V VCC and 3.3V Vref. My analog sensor gives 0V-12V range signal which is required to set 0V-3.3V  by using an Inverting amplifier. As far now I found the load of the inverting amplifier can be Resistive load or Current output. I don't know what to use in my application.The circuit i have added was generated using Texas Instruments Web-bench. And I have used resistive load.Can I directly connect upper end of the load resistor to my IN+ of the ADC IC (ads8320)


texts: Is there another method than the Area product method to size the core of a transformer

texts:
I m reading some documentations and it is not the first time that I read that the area product method for sizing the core of a transformer is not accurate. Do you know another method for sizing a core ?

Thank you very much,


texts: 89 Hz Wien bridge oscillator output signal does not appear

texts: The circuit is designed to generate 89 Hz, but in this case, the sine wave does not appear.


texts:
in "Lessons in Electric Circuits", VOL III, ChPT 14, there is a SPICE simulation of this transmission line:

The author writes:

Running this simulation and plotting the source impedance drop (as an indication of current), the source voltage, the line’s source-end voltage, and the load voltage, we see that the source voltage—shown as vm(1)(voltage magnitude between node 1 and the implied ground point of node 0) on the graphic plot—registers a steady 1 volt, while every other voltage registers a steady 0.5 volts: (Figure below)

and inserts this graph with all voltages referred to the node 0:

You may see that the point 0 is chosen as a reference node. How can this choice be correct? The points indicated with 0 in the first figure are not a single circuital node, since they don't have the same electric potential.


texts: Evaluating Hall Effect Sensor - Practical Explanation of Bops / Brps?

texts:
I am trying to choose between two types of hall effect diodes with internal pull-up resistors.

What is the practical explanation when comparing the Bop and Brp of the types (red square):
 - AH3781 and AH3782?

Do the Bop and Brp of the hall effect sensor determine the sensitivity of the sensor?


texts: Does this circuit need any additional protection? Arduino to Pressure Transducer

texts: So I'm powering and reading a Honeywell Pressure Transducer from my Arduino Mega board. I've got the circuit wired up as shown in the schematic below with the Excitation line from the Transducer going to the 5V on the Arduino, the Common to the Gnd, and the Output to one of my Arduino analog input pins. Currently when I read the transducer over the analog pin it is giving me mostly reasonable values but I wanted to see if I need any resistors in line or anything else to protect both the Arduino and the transducer. What should I check in the future to determine this on my own?


texts:
I am designing a schematic with TI ADC12DJ3200.

This ADC is differential 100 Ohm input impedance ADC.

In Eval Board of this ADC a Balun is used to convert single ended input from SMA to differential to ADC as shown below:

Signal from SMA is directly connected to input of Balun.

But sometimes I see that a 50 Ohm pull down is placed at SMA and then a capacitor and then signal is connected to Balun as shown below as example although pull down resistor in this example is DNP:

Which configuration should I use in my schematic?

Does this 50 Ohm pull down at SMA helps to see the balun a 50 Ohm impedance at input so that 100 Ohm impedance can be maintained at Output of balun?

I have seen that in some schematics a 50 Ohm pull down is used at SMA and in some schematics no pull down is used at SMA.

I am confused how to know when to use a 50 Ohm pull down at SMA and when to not?


texts: Will this High Frequency AC Signal Generator Circuit work?

texts:
I am going to make a variable DC to AC (10-100kHz). The circuit controlled by 2 PWM Signal from microcontroller to drive NMosfet connected to pull signal from two  Ferrite core Transformer primary coil end which the CT connected to 3.3V. Here is the circuit

I simulated the circuit in Eagle, CircuitLab, and MultiSim. The circuit works great on MultiSim, sometimes work on CircuitLab, but it wont work on Eagle. Which makes me a bit hesitant.

What do you think about the circuit? will it work?
I am using [78253/35JC]2 for the transformer.

Thank you


texts: reversing direction of single phase motor

texts:
I would like to change the direction of rotation of a single phase 240v motor.

I understand to do this I need to reverse the polarity of the start coil - but I'm not sure what wires are the start coil.

Unfortunately there are no markings or instructions with the motor.

Inside the cover, there is a terminal block with U1, U2, V1, V2, W1, W2 connections and the start and run capacitors.
From a search on the web, this block configuration seems fairly standard, and I'd hoped changing the direction would be as simple as moving the jumpers from horizontal to vertical - but this makes no difference.

Also there are five wires running to the motor, i thought there would be four for the two coils, but perhaps the fifth has some other purpose?

I stuck a meter over the coils and gave the rotor a spin by hand, thinking I'd see the centrifugal switch cut in on the start side.

On the black pair, the was no change to the conductivity of the wire pair when spinning the rotor.

But on the other side, the three way group, there was a definite break in conductivity when I gave the rotor a spin. The break was three way though, the conductivity was broken between all three wires. I'm more confused than ever now.

Should I have seen the centrifugal switch cut in with a hand spin, or was I seeing something else?

Thanks
Dave


texts: Why are rare earth metals important for electronics?

texts:
I've been hearing a lot in the media about how important rare earth metals are (from the economic standpoint of China limiting their export), but what do some of them actually do that makes them so essential that can't be done with more common elements like silicon, gold, copper, aluminum, germanium, etc?  It seems all the building blocks of a digital computer such as transistors can be made without them, so why all the fuss?

I've dug around a little for articles, but all of those are written for the general public and only name what devices require rare earths rather than actual components.


texts: Can 2 circuits exist and work independantly in an electric guitar

texts:
An electric guitar typically has 1 circuit for the pick ups, and mixing active (powered by a battery) pick ups with passive pick ups (no battery) appears to be not possible on 1 circuit.

I am trying to do understand if it is possible if you have 2 circuits though.

I'm not an electrical engineer, but I am hoping the diagram above gives an indiciation on what I'm trying to achieve. The 2 circuits are split by colour (light blue and light green).

The light green are active and require a battery, each pick up has a tone pot and both active pick ups share the same volume. The active pick ups also have a 3 way switch to blend the sound from 1 or both pick ups.

The light blue is my passive pick up. It has it's own dedicated volume control.

The 2 circuits share nothing in common, other than the switch.

Does the 'circuit' I've drawn make sense? Or is there a reason why this would not be possible


texts: SIM900 email send recive Firmware > 1137B11SIM900M64 ST?

texts:
I just received what I believe is the latest version of firmware SIM900, 1137B11SIM900M64 ST. I did the upgrade and
I try to implement without any results, commands reported in SIM900_Email_AT_Command_Manual_V1.02

One thing I find curious is that these new commands are not reported in the manual very last 1.05 of AT commands

Already beyond anyone had any experience with this version/, can tell where the problem is, or is it that there is a newer version of firmaware have to implement?

for each command to implement the response is ERROR. this is what tells me that probably this is not implemented

for example: cmmd resp

AT+EMAILCID? > ERROR

AT+EMAILCID=? > ERROR

AT+EMAILCID=1 > ERROR

and thus to each and every one of the commands reported in the manual.


texts:
With inductors quality is increasing with L and frequency and decreasing with R.

Quality is supposed to also tell us how much energy is stored in each cycle compared to how much is dissipated by resistance.

But when it comes to capacitors the quality decreases if we increase C. Is the energy stored higher if we have a smaller capacitor? This sounds very counter intuitive.


texts:
I'm having trouble with a flyback converter I got. My output voltages are not what they are supposed to be. Flyback schematics is below:

If you cannot see very clearly, primary number of turns is 200 and 15 and 5 on 15V and 5V secondaries respectively. Problem with my output voltages is that they are not what they're supposed to be. 15V is too hight and 5V is too low.

My voltage waveforms are:

CH1: Command signal

CH2: VDD (supply to chip)

CH3: 15V output

CH4: Primary voltage

And also with 5V output on CH4:

Anyone has any idea what is happening and what might be the problem?


texts: LED blinking while loop not working AVR timer 0

texts:
It is strange and rare. I am trying to blink a LED at PD0 at 2hz, but it doesn't work. Seems to me that while loop doesn't work at all. I have triple checked the code. what is the problem here?

uint8_t c=0;

int main(void){

DDRD= 1<<0 ;
TCCR0 = (1 << CS02) |  (1 << CS00); // (clk_i/o )/1024 ( Prescaler)

TIMSK |= 1<< TOIE0;
sei();

  while (1){
  if ( c >=30 ) { PORTD ^= 1<<0; c=0; }                //61.035/30= 2.034 hz
  }

  }

ISR (TIMER0_OVF_vect){
  c++;   //16000000/1024/256=61.035 hz
  }

Of course, I know the solution. It's by adding a random line of code to the while loop, and it works again. Strange!! What would be the problem? compiler bug??

uint8_t c=0;

int main(void){

DDRD= 1<<0 ;
TCCR0 = (1 << CS02) |  (1 << CS00); // (clk_i/o )/1024 ( Prescaler)

TIMSK |= 1<< TOIE0;
sei();

  while (1){
  if ( c >=30 ) { PORTD ^= 1<<0; c=0; }                //61.035/30= 2.034 hz
  _NOP();
  }

  }

ISR (TIMER0_OVF_vect){
  c++;   //16000000/1024/256=61.035 hz
  }


texts: Old capacitor markings (M) letter - actual capacitance

texts:
I am repairing an old tube audio gear from Japan. There are several old oil capacitors, some of them are labelled .01 (M) or .033 (M). Is it 0.01 and 0.033 μF?

There are other capacitors from the same manufacturer and they are clearly labelled with either pF or μF. I do not have a possibility to measure the capacitance. Also, I do not have the schematic.

It looks like this:


texts:
I hope this is the right forum, I've only ever used StackOverflow and am new to Electricals.

I have written an Access Control program in Delphi which sends an 8bit value to one of the three parallel ports (278, 378 or 3BC) for a certain length of time. This is in order to bypass expensive PCI cards & control boxes, and a client has specifically requested Parallel.

As Parallel/Serial ports are not always available it would be useful to be able to write to usb-parallel convertors too. With serial-USB the PC simply lists the attached serial device as a COM port and the software writes to it as usual.

However when I plug the USB-parallel convertor in to my XP machine (with no parallel ports) it shows up as an HID rather than LPT, which would require me to write a separate procedure.
When I plug it in to my Windows2000 PC (which has parallel) it displays as an Unknown Device - IEEE-1284 Controller and requires drivers.

My question - is there a way I can make the PC recognise the USB device as an LPT port?

But going forward, which method should I look in to which is the standard way of relaying a 1bit message to Access Control hardware? Should I be trying to write to HID port so that a PIC controller can pick up the message?

Thanks


texts:
I'm doing some analysis of op-amp circuitry including the high-pass filter shown below.

I was given three questions to try further my understanding on the analysis of such system.

However, I am not quite sure where to start on this one. I have listed the three questions below, the derivation of the transfer function is where I'm currently stuck.

Derive a general expression for the transfer function of the filter
shown.
Let R1 = 3.9 kΩ, R2 = 1.8 kΩ, and C = 0.33 μF. What is the filter frequency magnitude response at very low frequencies?
Calculate the frequency at which the magnitude response will be 3 dB lower than it is at high frequencies.

Any help would be greatly appreciated.


texts: Combining a 9v Battery and Bench Power Supply to power Opamp and circuit

texts:
G'day
I want to provide a few op-amps with +-9V. However I only have a single 9v battery. Is there any problem with dialling up 9v on my lab psu and combining them to get the +-9V?

I would use a voltage divider  but I think I might have trouble with the current load.


texts:
Here i am trying to light a single LED using a 1.5V battery. Forget About LED voltage rating.

What i need here is , where will my ground connection go? what is the significance of that ground and how does that ground works?

I am really newbie to electricals stuff and i find this place to learn.

Kindly help me!


texts:
I'm currently learning about the transportation of electrical energy through power lines. I now know that transporting current at a very high voltage cause minimal power loss compared to transporting it at a very high amperage.

However, one of the formulas I've been given to calculate power loss is P=V^2/R, which in this context produces ridiculously high numbers. For example,

P=40,000^2/1 (assuming the cable has a resistance of 1 ohm) = 1,600MW. This obviously isn't what happens in reality. So, is the formula only applicable in certain circumstances? Should I only use it when working with closed circuits?


texts:
Context:

I got this fancy freezer from Liebherr a while ago and it stopped working. The compressor would fail to run continuosly. I have narrowed down the issue to the control board (behind the front panel). The micro-controller would constantly attempt to turn the triac ON, but fail to maintain the ON state. The triac is responsible for switching on the compressor.

Suspect:

The following power supply circuit (might be wrong though... multilayer PCB):

simulate this circuit – Schematic created using CircuitLab

The C1 is X2 MPF capacitor. R1 is a 0.5W resistor. C2 is an electrolytic (already replaced). The two diodes next to the ceramic capacitor are two schottky diodes.

If I attach a regulated 3V power supply across the capacitor (the polarized one), the micro controller is happily chooching. The current draw from the external power supply does not seem to be high. but as soon as I switch off the external feed, the leds on the display dim and the micro-controller fails to keep the triac in the on state.

So the question is: how do I troubleshoot this further?

Picture:

Another Detail:

The X2 Metalised polyester foil capacitor is rated 680nF but my multimeter reads 104nF. Could that be the issue?

Update

Failed Component: C1. Thanks to Simon B


texts: Nonzero current at voltage zero-crossing when consuming reactive power

texts:
In a circuit that consumes some reactive power, the current waveform indicates current flow even when the supply voltage is at the zero crossing. This seems paradoxical since there cannot be current flow at zero volts, barring some kind of superconductivity effect.

What is the best way to understand this aspect of reactive power?


texts: Finding the output voltage for op amp circuit

texts:
I've got this circuit
and I want to find the output voltage \$U_A\$. We are given the values of the resistances, the input \$U_E\$ and the "supplying" Voltage \$U_V\$ (which isn't drawn here):
\$U_E = 10V\$; \$U_V = \pm 15V\$;
\$R_1 = R_2 = 3,9 k\Omega \$; \$R_3 = 8,2 k\Omega \$ ; \$R_4 = 2,2 k\Omega \$
We were supposed to assume that \$U_{E-} = 0\$ and \$ I_{E-} = I_{E+} = 0\$
Attempt at solution:
By KCL I know that: \$ I_1 = I_2 + I_3 \$ and also that \$ I_2 = I_4 \$
By KVL I know that: \$U_E - U_{R1} - U_{R2} = 0\$
and: \$U_E - U_{R_1} - U_{R3} - U_{R4} = 0\$
However, I don't know what happens to \$I_3\$. Is \$I_3\$ just \$I_4\$ or \$I_3 = ?? + I_4\$ and how all of this relates to \$U_A\$ (unless \$U_A = U_{R4}\$ but I am not sure).


texts: How to do Norton equivalent circuit? Why part of the circuit can be ignored?

texts:
I read the solution. It said that the 10mA and 10Kohm is not going to affect the circuit, so that it can be ignored. However, I don't understand why. Please help.

If I really want to include those 10mA and 10Kohm, how I can approach this question?


texts:
This is my theoretical (haven't tested yet) circuit I have designed for a project of mine.
Electrics is a new field for me so please raise flags if my circuit has flaws.

Assuming the circuit is fine, the question I now have relates to component protection and noise.
What is the best way to protect the MC and the motor Driver from potential back-EMF?

What size capacitor should be used over each DC?

Will the noise from the DC motors effect the circuit? if so, what can be done?

Anything else that should be done, please let me know. thanks


texts: How dangerous is to have the USB (2.0) D+/D- lines are exposed in the open (ESD et al)?

texts:
Sometime ago I designed an bespoke enclosure for an el' cheapo action camera (GoPro clone), which pinned out the USB's power lines outside the waterproof enclosure - something like this, with the diodes on a tiny PCB inside the enclosure:

simulate this circuit – Schematic created using CircuitLab
The camera, with its enclosure, would be placed in a bespoke cradle to be charged (outside voltage of course slightly more than 5V to compensate for D1's Vf). The idea is that the enclosure will stay shut all the time, as this is important to the application (there also other specifics, which is why we haven't employed standard waterproof USB connectors in the first place).
I have a request to expose the data pins as well in a similar fashion, because they want to download movies from the camera quickly (the existing WiFi-based transfer is slow). I'm not well-versed with why the USB standard is designed the way it is, but I do remember that all USB connectors make sure that

the power rails mate first, then D+/D-
the D+/D- contacts are recessed, so it would be hard to accidentally apply ESD to them.

If I redesign the whole thing to pin out D+/D- outside the waterproof shell, I would likely violate the first point, and certainly will violate the second.
Question
How dangerous is this? Can't I just make the small PCB inside the enclosure a bit more complex and add e.g. ESD protection diodes from each data line to the power rails? Would the USB communication be affected by such protection measures?


texts: Solar Inverter makes 15kHz noise at ~70dB when running

texts:
I have a solar power setup with an array of panels running to an inverter, which is connected to a set of batteries and to two other devices for monitoring the net metering, power output, and so on.
When the inverter is receiving power from the panels and is inverting it, there is a 15kHz whine/scream from the inverter. It's unbearably loud to me and my wife, but 15kHz is high pitched enough many people can't hear it.
Further - I have 2 appliances from LG that are "smart inverters": a microwave and a washing machine. When the inverter runs, these appliances also emit the exact same 15kHz screech and it's unbearably loud inside. Other appliances like my computer monitors, cable modem, hue lightbulbs, audio receiver ALSO make the 15kHz noise, but not to the degree of the LG microwave.
We have tried:

Disconnecting the batteries such that it's a simple solar setup
Changing settings on the inverter to various power settings per the manufacturer's advice
Adding toroids to the battery cables - this caused a spreading of the 15kHz spike into a more spread out curve from 14kHz to 16kHz, but didn't really change the ear splitting effect. When we did this, the devices inside also spread out their screech.

The inverter is a Sol-Ark 12kW. I don't know much about electronics, but here's a spec sheet: https://www.sol-ark.com/wp-content/uploads/2021/02/12K-Spec-Sheet-2-4-2021.pdf
I've read that more economic manufacturing processes will reduce cost in ways that increase noise production. This came up as I read about FCC 15 class B for unintentional radiators. But in reading the specs for the upper sonic range (10kHz-20kHz), I don't know how to approach measuring to see if my inverter meets the spec. The product itself has been confirmed as compliant with that regulation, so my question is more... Is it something in my house causing this?
Another thing to note: WHILE the washing machine runs, when the motor turns the basin, the noise spikes at 15kHz regardless of the inverter running or not. If I then muffle the sound and put my spectral analysis app on my microwave, I can see the 15kHz pulsing when the motor from the washing machine pulses.
These noises are essentially inaudible if the inverter is not running, but at this point I'm 6+ months into a worthless solar installation that I'm paying for because when it runs I have ringing in my ears 24/7 and nonstop headaches.
From an electronics standpoint - does anything stand out? Am I overlooking something? Is there a standard way to get electricians/installers to take this seriously if they themselves can't hear the noise?


texts: Current and Voltage Ratings for Multi-Conductor Connectors

texts:
I am currently looking at some multi-conductor connectors that will handle reasonably high currents (approximately 30 A at 24 v). When reading datasheets, I see that the connectors have both a maximum current and a maximum voltage. For example,

  Voltage Rating: 600 VAC / Current Rating: 9 Amps Max. in 2-position applications.

I am having a hard time interpreting this. My understanding is that the maximum current is dictated by the resistance of the pins. My intuition is that this means that it would be safe to use the conector for any application that draws less than (9 A)(600 V) = 5.4 kW of power as long as the voltage does not exceed 600 VAC.

Is this true? If so, why isn't there a single "maximum power" rating? If not, can you explain how to interpet the rating at different voltages?


texts: Certain property of a bus admittance matrix

texts:
I have got a simple network for my assignment:

I know bus admittance matrix have certain properties that let us form the matrix without writing so many lines of KCL. But is there any property such that one could, without matrix formation, say sum of values in row 2 of the matrix is zero, whereas the sum of values in row 4 is –j1?

I have formed the admittance matrix and I can confirm that above statement is true but I was wondering what is the rationale behind that statement?


texts: Why do 0v have to be connected when using two power supplies and ULN2803A?

texts:
The other day I was playing with a ULN2803a and a stepper motor. I spent ages trying to work out why it wasn't working and why i was reading ~14V as an output on the PIC I was using. So why did I have to connect the 0V of both supplies together?
Thanks in Advance,
Dean


texts: At a Power-Factor-Correction (PFC) circuit, Why mostly using Continues Conduction Mode (CCM) for high power applications, ex. above 300 kW, and using Boundary Conduction Mode (BCM) or Discontinuous Conduction Mode (DCM) for low power applications?


texts:
I am just not sure that why in development labs, current sources are not as popular as voltage sources.

I have worked in different places, and they all have been using voltage sources.

I just want to find out why, in practice, voltage sources are much more popular than current sources. And, if there are applications that current sources are actually being used instead.
And what are the main advantages/disadvantages of using one vs. the other.


texts: What is the pinout on my K F455P 7An filter?

texts:
I have a ceramic filter that I'm using for an AM receiver, but I don't know the pins for it. The lettering on it says K F455P 7An. I know that it's a 455 kHz signal filter and I think that it has a bandwidth of 7 kHz. I haven't been able to test it, though, because I don't know the pinout. Looking for datasheets returns nothing helpful. I think that it is made by Murata. Has anyone used this filter before?

In the image shown you can see the front of the filter. There are three pins on the opposite side of this filter.


texts: What is an ABT scan test? What does the acronym stand for?

texts:
I am translating an electronics parts catalogue from English into Hungarian and have come across the phrase ‘ABT scan test’. I am a physicist with a limited background in electronics so I have tried to look it up but have only found datasheets (like this) which do not explain or even resolve the acronym.
Your help is greatly appreciated.


texts: Can a Z80 be powered at 3.3v and still run reliably at 3-4MHz?

texts:
I have various Z80 CPU's in my parts bin.  Some are from Zilog and some are from other companies (IIRC).  Some of them are hard to see the part numbers so I can't tell who made them but I'm sure they are Z80's.

Anyway, I need to build a circuit that uses the Z80 as the primary CPU (mini-computer) but I want to connect it to 3.3v devices like the propeller or other microcontrollers.

I've looked in various datasheets that I can find but none of them mention if the CPU can be powered from 3.3v.  I read they can "tolerate" -0.3v to 7v on all input pins but nothing (that I can find) says they can be driven by a 3.3v power supply.

The frequency I would like to run the CPU would be the NTSC colorbust frequency of 3.57954 MHz but it could go as high as 4 MHz.

Thanks for any information.


texts:
What type of headers are used by digi-international in the Development Kit of modules xbee 868lp. Are they commercial or are they developed by Digi?

Digi XBee® SX 868

Thanks and best regards,
Fran Martin.


texts: Saving microcontroller pins to drive seven segment display

texts:
I am working on a project where I have to display different letters (r, g, b, u and n) on a seven segment display using a PIC18F45K20 microcontroller and assembly language. This is as simple as connecting each of the segments to 8 pins of the PIC and then outputting the right logic values on these pins to get the character I want however that is rather costly on the pin count and I'd like to use as little of these pins as possible to drive the common anode seven segment. Any suggestions on how I could reduce the pin count? I'm thinking I should maybe use a bcd to seven segment display driver such as a 74LS47 to do this, that way I could get it down to 4 pins. I'm not quite sure how I would do characters with the driver though?

Are there any other better ways to do this?


texts: Hello and I apologise if my first question is rather basic as I am new to electronics. I have started to repair vintage amplifiers and have found transistors that I need to replace are no longer available. I suspect in most cases modern equivalent transistors may have a better specification but what I need to find out please is the critical characteristics I must match or exceed in equivalent trs? I assume values for Pc, Vcb, Vce and Veb are critical but what about Ic, Tj, Ft, Cc and Hfe? Thank you for your help. Tim


texts: Maximum power transfer problem. Find the resistance

texts:
I'm new here and I would like to know if anyone here can help with this question below.
Which resistor must be connected to the circuit of the following image to transfer to it the maximum power?

My attempt:


texts: How can i generate a negative potential/current and alternate the pin-input between positive and negative potential/current using an arduino uno?

texts:
My goal is to make the barmagnet rotate by activating two coils and use both forces at the same time with an Arduino Uno. One coil should have a positive potential or current to attract the negative side of the magnet, the other coil should have a negative potential or current to attract the other side. I was able to make it rotate by activating only one coil at the time, but i want to make the movement a bit smoother by using the forces of two coils instead of one. Now my questions are:

How can i generate a negative potential/current?

and then

How can i alternate the input on the same pin between positive and negative? I am thinking about something like this:

    int delayBetweenCoilActivations = 50;

    void setup() {
      pinMode(2, OUTPUT); //a pin for each coil
      pinMode(3, OUTPUT);
      pinMode(4, OUTPUT);
      pinMode(6, OUTPUT);

    }

    void loop() {
    digitalWrite(Pin1, LOW);
    digitalWrite(Pin2, (negative)HIGH);
    digitalWrite(Pin3, LOW);
    digitalWrite(Pin4, (positive)HIGH);

    delay(delayBetweenCoilActivations);

    digitalWrite(Pin1, (positive)HIGH);
    digitalWrite(Pin2, LOW);
    digitalWrite(Pin3, (negative)HIGH);
    digitalWrite(Pin4, LOW);

    delay(delayBetweenCoilActivations);

    digitalWrite(Pin1, LOW);
    digitalWrite(Pin2, (positive)HIGH);
    digitalWrite(Pin3, LOW);
    digitalWrite(Pin4, (negative)HIGH);

    delay(delayBetweenCoilActivations);

    digitalWrite(Pin1, (negative)HIGH);
    digitalWrite(Pin2, LOW);
    digitalWrite(Pin3, (positive)HIGH);
    digitalWrite(Pin4, LOW);

    delay(delayBetweenCoilActivations);
    }


texts: Atmospheric attenuation calculation for a 1550nm link budget

texts:
My apologies in advance if this is the wrong place to ask this question. I was told that there were some RF communications experts here, so i figured there might be some FSO experience here as well.

Anyway, I am trying to put together a link budget for a 1550nm laser communication system in low earth orbit (~600km), and I have been seeing some contradictory information regarding the contribution of atmospheric attenuation (absorption, scattering, scintillation). I am not looking for an exact figure at this point, but I do need to have some idea in order to spec out the rest of the system. I have read from multiple sources that the minimum (clear air) attenuation for light in this region is about 0.2 dB/km.

In "Free-Space Laser Communications: Principles and Advances", the following example link budget is proposed:

Unfortunately, no justification is provided for the "Clear air transmission loss" term, which is about 11km at 0.2dB/km, rather than 483km.

In another system, a comparable attenuation term is used

Is the atmospheric attenuation this low because it decreases with altitude (and 0.2 dB/km is the attenuation coefficient near sea level)? How do you go about making that computation. If the altitude dependence is significant, it is not discussed in the book. If the effect of atmospheric attenuation becomes negligible beyond a certain altitude, where would that be?


texts: Do I have to worry about the depletion of IPv4 addresses in embedded applications?

texts:
We're nearing the exhaustion of IPv4. What should be my concern about it for embedded devices?

I don't know about others manufacturers but until today, Microchip TCP stack doesn't implement the IPV6.


texts: I made a mistake and find my schematic will not fit on a single sheet. Can I change to a hierarchical model without redrawing the whole thing?


texts: Need a review on my first schematic. A 3-speed mode blowers schematics

texts:
I am currently on my own project building a blower that can be controlled using a switch with 2-3 speed mode powered by 12V Li-Ion Battery with hope this can support local health workers. However, I kind of hitting a wall since I less familiar with electricals, and currently did not have anyone close to consulting these particular matters in college due to the pandemic.
The question that I would ask is whether this is a proper schematic or not?

I also add some feature like a low-bat indicator alarm, battery indicator module, and make sure the battery disconnects while charging. However after I run several tests to this schematic, I find that 1) the blower sometimes stutters, 2) Whenever I change one of the trimpot value it affects the other speed mode (Like I want this "Fast" mode a Lil bit faster, but when switched to "slow" mode the speed changes despite the "slow" trimpot value left untouched). 3) Run test on the alarm, it was supposed to go off on low voltage. But what I got is it go off at high-volt, not when low-volt. 4) I happen to add some filters and found the pressure drop was too great and I was intended to add more speed to the blower. But I cannot figure it out which to alter. Changing the trimpot only adds more power a bit or should I change the regulator to higher output?
The blower I used is WM7040. However, it has its own speed controller using a potentiometer. After looking at its datasheet (Here's the datasheet), I did some redesign substitutes the rotary pot to 102/103 trimpot or you might see in schematic listed under R5, R6, and R7. X2-x; and X4-x connects to the blower controller. X1-x connects to the battery, and X3-x connects to the bat-indicator module.

The following question appears after the last test:

Did I need to add a higher voltage to the controller? I did use a 9V regulator on the blower.
Why problem number 2 happens? Thought it was Kirchoff laws apply here, or it just comes from the controller schematic? if it did comes from the controller, did the blower powered not directly powered from the 5v pin to the potentiometer I presume?

Sorry if I explain it too vague. You did not have to answer directly right away. I just kind of bamboozled or lost in thought, a review on my first schematics, and a few hints of improvements are welcomed.
Thank you in Advance


texts: EM MWD Gap Sub Telemetry Theory Explanation in Drilling Applications

texts:
I have been doing an extensive amount of reading on EM (Electromagnetic) Telemetry in MWD (Measurement While Drilling) applications.  From my reading, there are a few considerable gaps in my understanding which I am trying to fill.

Now this is how I understand the theory works.  Just behind a drill bit, a gap sub is placed which provides an electrical isolation from the two ends of the drill pipe.  This isolation creates an altered voltage between the two sides of the gap sub.  An electric field is emitted (and orthogonally a magnetic field) from the gap sub.  On the surface, an antenna is created using a ground rod and the top of the drill string.  This antenna is used to retrieve the signal created by the EM field.  That signal is then decoded to retrieve the data.

First, many of the sources stated that the signal generated is on the order of 5-10 Hz.  If this is the case, would not the antenna have to be several hundred kilometers wide (since wavelength = speed of light / frequency) in order to retrieve the signal?  This leads to my second question.  All of sources stated that an EM FIELD is generated.  An EM field is not the same as an EM wave.  How does a field have a frequency?  I feel like I am overlooking something fundamental here in regards to EM theory.

Lastly, a co-worker and I had a very long discussion about how this works.  He stated that an EM wave actually isn't emitted at all, but a voltage gradient is created across the gap sub.  He also stated that the drill string is essentially used as one leg of a transmission wire and the earth is used as the other.  In other words, the drill string is used to transmit data up to the surface and the earth is used to receive data from the surface, or vice versa.  To me, this is just seems plain wrong, but perhaps I am the one mistaken.  If this was the case, would not the two sides of the transmission wires (the earth and drill string) essentially short themselves out since they are in constant contact with each other?   His reasoning was that current follows the path of least resistance and thus will not dissipate to the earth but travel up the drill string to the surface.

Any help, insight, or other reference is greatly appreciated.  Here is about the best image I could find to help describe the general theory http://www.netl.doe.gov/Image%20Library/technologies/oil-gas/natural-gas/projects-n/ep/DCS_31103.jpg


texts: Why do MCUs typically have so little buffering on the USARTSs?

texts: I am currently working with Atmel AT91SAM7X256. It has a CAN i/f with multiple multibyte message boxes. However, the USARTs only have a single byte of buffering, which is a bit of a pain when I'm trying to do RS485 packet based stuff.


texts:
I have a part of Apple's product information sheet and I was wondering if I can make an assumption :

I am wondering if I can say : "hmm, if the Wh rating of AirPods Charging Case is 1.52Wh, then a 5V adaptor would supply 1.52 / 5 ~= 300mAh and make it full in a little over an hour since the charging case has the capacity of 398mAh."

I am just wondering if this is an educated approach.


texts: Playing WAV audio files from an SD card on Wiring board?

texts:
I'm using the Wiring framework for building a custom alarm clock. So far, I've been able to work with several Arduino libraries on Wiring, just by including  Wiring.h instead of Arduino.h, as suggested by Wiring's creator.

Regarding audio, I've used the TMRpcm library on Arduino Uno with success. One needs to have an SD or a micro SD configured, convert the audio files to a specific format (WAV, 8-bits, 16kHz), optionally make an amplifier circuit, and the like. I already have that done. All works on the aforementioned Arduino.

However, since Wiring S gives me twice the memory than Arduino Uno (my script already exceeds Arduino UNO's memory), I'd like to implement my project on Wiring. I'm working with a Wiring S, Wiring v.1.0.1-dev as IDE, and already changed all include <Arduino.h> by include <Wiring.h> on all files in the TMRpcm library.

When I run the basic example (adjusting the audio file name and setting the SD_ChipSelectPin to 20, and the speaker pin to 16) I get the following error message:

core.a(WHardwareTimer.cpp.o): In function `__vector_15':
C:\Users\toshiba\Downloads\wiring-v1.0.1-dev\cores\AVR8Bit/WHardwareTimer.cpp:140: multiple definition of `__vector_15'
TMRpcm\TMRpcm.cpp.o:C:\Users\toshiba\Downloads\wiring-v1.0.1-dev\libraries\TMRpcm/TMRpcm.cpp:650: first defined here
core.a(WHardwareTimer.cpp.o): In function `__vector_12':
C:\Users\toshiba\Downloads\wiring-v1.0.1-dev\cores\AVR8Bit/WHardwareTimer.cpp:145: multiple definition of `__vector_12'
TMRpcm\TMRpcm.cpp.o:C:\Users\toshiba\Downloads\wiring-v1.0.1-dev\libraries\TMRpcm/TMRpcm.cpp:569: first defined here
collect2.exe: error: ld returned 1 exit status

If I comment these definitions in the library (TMRpcm.cpp file) or in the WHardwareTimer.cpp file included in Wiring, the code does compile and I can upload it to my Wiring S, but the audio file is not reproduced or it cannot be heard.

Here you can get a 31KB sample audio file (already converted to the required format).

Could you please help me solve this problem? What am I missing? I can provide you with more details if needed.


texts:
I accidentally short-circuited LiPo battery 7.4 V 2200 mAh 35 C. I measured the pack's overall voltage, but multimeter showed nothing. I also measured the individual cell voltages (via the balance tap plug) and only one cell showed 3.85 V.

Is this a mark that the other cell is totally dead or is there a chance of cables got unsoldered inside the battery, during the short-circuit? What should be my next steps?


texts:
I'm currently working my way through electronics for dummies, where I am shown a simple voltage divider circuit comprising of a 6V battery and 2 resistors, R1 (220 ohm) and R2 (1000 ohm) in series.

To calculate the current, I will be using I = V (battery) / (R1 + R2)

As V1 can be calculated by the equation V1 = I x R1, by subbing this into the equation above, we get:

Equation 1

V1 = [ V(battery) / (R1 + R2) ] x R1

This is where I begin having problems, as the book then rearranges the equation by saying that I can rearrange the terms, without changing the equation to get:

Equation 2

V1 = [R1 / (R1 + R2)] x V(battery)

The problem I have is that I have no idea how the conversion from Equation 1 to Equation 2 takes place.

I have a poor background in mathematics so that accounts for my inability to decipher this seemingly simple conversion.

Could anyone help me out by listing the steps in order, for the conversion?

P.S I'm not sure if this should be under mathematics, but I placed it here since it concerns Ohm's law.


texts: Should the unused areas on the top layer of my RF PCB have ground pours?

texts:
I realize there are some questions that are related to this topic but I didn't see any that are really RF specific.

I am working on a 2-layer Bluetooth module and I have some unused spaces on the top layer that I can't decide if they should be ground pours with stitching vias to the bottom layer (which is primarily a solid ground plane) or not. I've been doing a lot of reading/research and there seems to be conflicting ideas about top layer ground pours. So, I'm reaching out to you folks and hoping that someone with experience in this (RF board design is a plus) can shed some light on this topic for me.

Thanks!

For anyone else looking into this or are just interested here are some good resources that I've found helpful:

http://www.maximintegrated.com/en/app-notes/index.mvp/id/5100#10
http://www.eeweb.com/blog/circuit_projects/basic-concepts-of-designing-an-rf-pcb-board
http://www.eetimes.com/document.asp?doc_id=1279446
http://www.atmel.com/images/atmel-42131-rf-layout-with-microstrip_application-note_at02865.pdf
http://www.icd.com.au/articles/Copper_Ground_Pours_AN2010_4.pdf
http://www.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=swra367a&fileType=pdf

Most of the sources above mention ground pours, and overall RF design.


texts: Inconsistency/Differenct Voltage Each Output Op Amp LM324

texts:
I use Arduino Pin to make PWM and give input to Op Amp LM324.

I would like to know, why my op amp has difference output. I have gain 2x. I multiply input from 0-5 Volt to 0-10 Volt because the gain is 2x. Output Pin 1,7, 14 is okay (has similar voltage).

But in output pin 8. It has different voltage almost 1 Volt. Let say Max Output for Pin 1,7,14 is 10.00. Then, pin 8 has around 9.1 Voltage.

How could be like that? I try to change my IC with new one. And has some problem. Why does it go?

My circuit is okay also. I double check my circuit.

Edit (Attach circuit)

RG = RF = 100 kOhm

Vin = 0-5 Volt

Vout = 0-10 Volt

I ground all of in one point. Also with Ground of Arduino. All of other 3 op-am is typically same circuit as above.


texts:
I have several questions about the current sensing through a resistance.
The resistances are 2-SMD package and I will use the 4-wire kelvin method for the layout.(see image) Specifically, there are three resistors, one of 1 mOhm and another two of 10 mOhm.the layout would be approximately like this:

The PCB is two layers with components only in the top layer and the ground plane in the bottom layer.
Due to restrictions in the layout, I can not find a way to route the sense tracks through the upper layer since they cut different power planes, so I will have to use vias and to route the sense tracks in the bottom layer.
Due to my limited knowledge of electronics, I am presented with the following questions:

Each sense track will route using two vias (top to bottom layer and then bottom to top layer). As long as the resistance of each sense tracks are the same, should the use of vias not affect the accuracy of the measurement, right?
Route the sense tracks in the bottom layer (where is located the ground plane), would it affect the accuracy of the measurement?
Should I increase the trace width to minimize the effects of the EMI?

Thanks!


texts:
I'm trying to build an IR proximity sensor using a simple tutorial found online. Here is the schematic

and here is the link of the tutorial : https://www.instructables.com/id/IR-Proximity-Sensor-1/

I wired it using solder lines and checking it with a multi-meter doesn't show any short.

there is a video which demonstrates how it works and it works for them (They used 2 IR LEDs). Here is the video link :
https://www.youtube.com/watch?v=y83o_gfQRN8&feature=emb_title

But when activating it, the LED only turns on, the IR sensor and Photodiode doesn't give any impact from the output whatsoever. Giving it an opaque barrier doesn't help and turning the potentiometer slightly down only turns it on and off.

Reading the output signal with a serial plotter in arduino gave me these results :

As you can see, there is a point where the output rose up dramatically. That's the point where the potentiometer turns on the LED, while the point where it is at zero is the near exact point the LED turned off while turning the potentiometer. It only has like less than a degree difference. Putting my hand near and far the IR receiver-transmitter doesn't change the output even the slightest. Any suggestions? Is it possible that the potentiometer i am using is the wrong kind or is it possible the photodiode does not give a strong enough signal?


texts: Switch that turns on both arduino and motor shield that use different power supplies

texts:
I have the Arduino Uno and the Adafruit Motor Shield, and they are powered by separate power supplies.

I want my toggle switch to turn on and off those two, I would
appreciate if someone post a picture with the hardware connection
and whatsoever, followed by a brief explanation.
What kind of batteries should I use to power the Arduino and to
power the motor Shield?
When I was powering both with the same battery, my ultrasonic
distance sensor wasn't getting correct results when the motor
was enabled, why is that?

(Probably it's obvious that I'm not an expert on the subject, I'm actually just starting to learn this kind of stuff, so I would appreciate if you guys could keep it simple).

This is a picture of what I'm trying to do:


texts: Is this ESP8266 voltage regulator *really* 12v compatible?

texts:
I recently acquired some 'ESP8266 SMD Adapter Boards' from Electrodragon. Up till now, they've been working fine. Except... I think I just broke one by attaching it to a 12v power supply. The power supply says it's a 12v 2A DC supply, which would seem to play nice with this (from that linked product page):

  On board LDO for 3V3 power, 0.5-1A output (NOT for serial port and other IO pins), input voltage range 5-12V

I have a water sensor and a buzzer soldered to the ESP board, and the requisite GPIO16-RST connection so that sleeping the chip works. I also got some simple DC connectors to take a standard 5.1mm plug and use it as a power supply. Here's a picture of the overall setup.

This has been working perfectly when powered through my FTDI cable, but it's tedious holding the power/ground pins manually (this build doesn't have headers on it, the plan was for this to be a stepping stone to 'mass production' (which is seven units, but still).

I tested the 12v power supply, my multimeter said it was outputting 12.18v. I plugged it into the system, and... poof, magic smoke and a red-hot pin. It came from the little black chip at the bottom of the board:

The middle pin on the near side of the chip is where the smoke was apparently coming from. I unplugged the connection, but the board wouldn't power on again.

The chip that was smoking is imprinted, in barely legible type, "352". It might be "L352". Assuming this is a voltage regulator, is it rated for 12v? Was I sold a falsely-marketed product? I can't find a spec sheet for it, and before I ruin another one I'd like to know if these are 12v tolerant.

Or, is there something wrong with my circuit/soldering? I'm brand new at this, so it's messy, but here are some additional pictures: bottom of the ESP, side view showing some connections better, water sensor module. Don't hesitate to ask if there's any additional information I can provide!

Edit: I've just hooked a fresh board up to 12v power, and watched it a little closer. I seemed to confirm that the voltage regulator couldn't dissipate heat:

It desoldered itself. Impressive.

I'm going to get some 5v power supplies.


texts: Stepper Motor current rating and microstepping

texts: I am working with stepper for first time and want some suggestions. Motor runs smooth but the problem is it gets hot after a few seconds. reason may be that i am giving it a bit higher than the rated current. I am planning to limit current to 0.31 Amp as rated. Please help me understand would it be possible to go for microstepping with this limited current? or motor requires more current in microstepping modes?


texts: Puzzled by voltage readings of a simple resistor network

texts:
I have tried in vain to understand why the voltage readings across the resistors in the simple resistor network below are what they are, but I can't work it out. I know that when you place resistors in parallel the resistance is halved because the electrons have two paths to follow. In the circuit below, why aren't the voltages across R2 and R3 equal?

The actual voltage according to the multimeter is 5.14 volts, not 5 volts as in the diagram.
I'd appreciate an answer (if you have time), or a link to some further reading. Apologies for the newbie question.


texts: Small DFN chips come out twisted from the oven

texts:
This is a 2 x 2 mm chip with 12 no lead contact points. Half of the time I get it out of the reflow oven, it's twisted like in the image below.

I am using a stencil in order to lay the paste down and then tweezers for placing the little chips. There is no fan in the oven and I let the boards drop to < 170 C (leaded solder paste) before pulling them out. There are also some even smaller 0603 parts which never twist / tombstone.

How do they become crooked, and what can I do in order to avoid it ?


texts: How would I find the gain equation for this circuit?

texts:
I can neglect the Early Effect for the BJT, and assume the capacitance is infinite.
Using the small-signal AC model, I calculated $$r_e = 25 \Omega$$.
My question is, how do I set up my equations/circuit model to find Vo/Vsig?


texts: Why do 0.02A fuses not protect a person? Why no protection from shocks?

texts:
I understand the user here so that fuses do not protect people from shocks. I am planning to put put fuses such as fast-blown fuses and PPTC fuses around all kind of positions such as computerUSB-microprocessor-link and wet-electrode-circuit link. I feel it is far better to blow up fuses than to blow up computer or get shocks. Now the user does not recommend any substitute to protect from shocks so how to protect from shocks? Not with fuses? What then? I operate with EM the level of coming from MBA.

Further reading

EOS versus ESD -thread by TI


texts: I acquired an old telegraph sounder, marked Western Electric 140 Ohms, and have a Morse code key.  What voltage should I drive the sounder with to hear the proper Morse code click sounds when keyed?  Is any additional series resistance and/or a flyback diode required in the circuit, since the sounder contains an electromagnetic coil?


texts: How do you set the time resolution in Synplify?

texts:
I am generating a 1khz pulse from a 32MHz clock, naturally via a counter. Not a difficult task, so you can imagine my surprise when the result runs at 992Hz...

Simulating the behavioural model of this counter, I can see either correct or incorrect behaviour with no source code changes whatsoever.

The crux of the code is this:

constant Clock_Frequency : natural := 32_000_000;
constant Clock_Period : time := 1 sec / Clock_Frequency;
subtype DelayType is natural range 0 to Clock_Frequency;

constant Period : DelayType := 1 ms / Clock_Period;
report "Delay " & DelayType'image(Period) severity NOTE;

which reports (in simulation) as follows:

(Xilinx ISIM : as expected)

  at 125 ns: Note: Delay 32000 (/testbench/UUT/UUT/).

(Modelsim : surprise!)

  ** Note: Delay 32258
      Time: 128 ns  Iteration: 0  Instance: /testbench/uut/uut

And 32MHz divided by 32258 does indeed give the 992Hz signal I was observing.
Changing Modelsim's time resolution from its default (presumably 1ns) to 1ps, gives the expected result. So the correct period (31.25 ns) is being rounded down to 31 ns, resulting in incorrect calculation of the delay counter load value.

But the implication is that Synplify (specifically, Actel Edition from MicroSemi Libero 9.1) uses 1ns resolution as its default for time unit resolution.

So, how do I change this to 1ps or 1 fs for more accurate calculations involving time? I can't find any such information in the obvious sources.


texts: What do we use to convert AC to DC current in houses

texts: Do we use an active or passive rectifier to convert AC current to DC current, and why?


texts: How to solve Bus Contention problem in my case?

texts:
The following image describes the problem:

Processor 1 has no RS232 channel, but has an SPI one, so we used a UART driver and a level translator ICs.

The two processors are on separate boards, and the RS232 receiver will be connected to them by one cable that will be split into two to be connected to each board.

How can we solve this bus contention problem?

Edit #1

Unfortunately, I can't modify hardware. Is there any software solution?

Edit #2

I thought of a solution but don't know if it's applicable or not. I read through the MAX3223 level translator chip datasheet, and found that if the input level to the IC is undefined "Irrelevant", the output is high impedance. I found the following function table in its datasheet:

In my circuit, FORCEON and EN~ signals are tied low and FORCEOFF~ is tied high.

How can I send an unidentified level to it?


texts:
I'd like to test the non-repetitive avalanche energy (EAS) of a particular Schottky diode (VS-12CWQ10FN-M3), but I've never done this test before and can't find a typical test circuit. This comes from the absolute maximum ratings in the datasheet:

Here's something that I cooked up. Will this do the trick or should I be looking for a different method?

simulate this circuit – Schematic created using CircuitLab

The other question I have pertains to the nature of the damage caused by EAS. A 12 mJ transient doesn't seem like it should have nearly enough heat energy to damage the hefty diode by thermal means. How does going above the EAS value actually cause degradation or damage to the diode? Is it something similar to secondary breakdown in BJTs where heat gets concentrated in a very small area?


texts:
I'm considering putting a small lithium battery on my Super OSD Pro boards. The battery would provide power to the RTC. I am wondering how small can you get a battery? I don't really care about capacity, I expect current draw to be less than 1µA, so it's really only size I'm looking for.

Best solution would be one that is removable, because I'd like people to be able to replace the battery when it does go flat.

And I'm open to suggestions on how to control the power to the main bus which has some heavier current draw devices which would overwhelm the 1µA for the RTC (the RTC is provided by a PIC24F in deep sleep mode.) I'm thinking of a power monitor, but it needs to be able to switch at least 100mA for the MCU when it's running full speed.


texts:
Turn ratio is defined as high voltage to low voltage ratio as per IEEE standards.
Now my doubt is:
In 3 phase transformer,
Is it phase voltage ratio/or line voltage ratio?


texts:
I have an older FRANCE PG-1 Series neon sign transformer. It is a type that contains a SCGFP potted module in top compartment of transformer. There are a number of leads originating from the potted transformer, which I am trying to identify.
3 of the leads, black, white and green,  ring out as extensions from the input power posts. This is the 120 VAC supply to the unit.
There are 4 remaining leads:

(1) blue
(1) blue with white stripe
(1) orange
(1) orange with black stripe

Can anyone tell me what these 4 leads do and how to reconnect them, once the SCGFP potted module is removed?


texts:
In an article on Wiki, there is a plot that shows a positive reflection coefficient. How is this possible? I can't seem to see how you can get a positive one from this equation alone:

$$
\Gamma_= \frac{sin(\theta)-X}{sin(\theta) + X}
$$
$$
X_{horiz}= \sqrt{\epsilon_c - cos(\theta)^2}
$$
$$
X_{vert}= \frac{\sqrt{\epsilon_c - cos(\theta)^2}}{\epsilon_c}
$$

Image in question:

http://en.wikipedia.org/wiki/File:Reflection_co-efficient_ground_reflection_of_radio_waves.jpg

Article with the image: http://en.wikipedia.org/wiki/2-Ray_Ground_Reflection_Model

I tried plotting it in MATLAB w.r.t theta, and I don't see the plateau, nor do I see the positive reflection coefficients. I'd appreciate some clarification.


texts: Can I use a ferrite bead instead of a resistor on the data wire of my LED strip?

texts:
I have a WS2812B[PDF] LED strip which I want to control with the PWM0 pin (GPIO18) of my Raspberry Pi.
Multiple sources highly recommend to insert a 330-470 resistor in between the data pin of the controller and the DIN of the first LED.
It looks something like this:

simulate this circuit – Schematic created using CircuitLab
Apparently the resistor is there “for impedance matching between the [Raspberry Pi's] low-impedance output and the WS2812B's high-impedance input. When using long wires, they act like transmission lines, causing reflections, resulting in unwanted oscillations, ringing and noise.” quote This could damage the IC, cause flickering in the LED or something like that.
image source
But I'm currently missing such a resistor, so my first thought was that maybe a ferrite bead could as well do the job. (Therefore the question.)
The LED strip without any resistor or ferrite bead looks fine to me and I also don't own an oscilloscope, so I cannot verify if a ferrite bead would work equally well.
I also lack the skills in electronics and electrical engineering to be confident enough that I'm not talking complete nonsense here. If somebody could help me out with that, I would appreciate it. Thank you very much in advance!


texts: Why does my AVRISP MKII Programmer not work?

texts:
I am using Ubuntu and I am trying to upload a hex file (called src.hex) to my ATtiny85 with my AVRISP MKII programmer with avrdude. But I get a strange error. I run this command:

sudo avrdude -p t85 -c avrispmkII -P usb_device -U flash:w:src.hex

I get this error:

avrdude: stk500v2_command(): command failed
avrdude: stk500v2_program_enable(): bad AVRISPmkII connection status: Target not detected
avrdude: initialization failed, rc=-1
         Double check connections and try again, or use -F to override
         this check.

I have all pins connected correctly, I have my programmer plugged in my computer, I have the cdc-acm module running, and I have a .rules files places in the director /etc/udev/ (from this question).

How can I resolve this error?


texts: Any reliability concern if I don't add UVLO protection circuit?

texts:
I am designing a lithium-ion battery operated device.  My concern is when the battery voltage drains to near min. operating voltage (3.3V) of the system, the system starts to reboot and struggles to be up.  If I don't add any circuit to cut the voltage off, is there any reliability concern?  My system consists of only digital and analog ICs, like microprocessors, modem, USB, PA, buck, boost.  Thanks.

Edit: The battery has its own protection circuit for over-discharged, overcurrent, etc.


texts:
I have been working on a Schroff/Cherokee Europe PE1947/23B SMPS (circa 2004?) and have had trouble identifying a component within the circuit.

This SMPS features the following outputs:

+12v DC @ 8A
-12v DC @ 4A
+5v DC @ 36A

All of the outputs appear to be generated from a central transformer with a winding for each output. From the way it is structured, it appears that each output is electrically isolated from all other outputs.

Across the output windings of the transformer are a small brown component, shown below, that I cannot identify. The component has six leads (three per side) and a metal cover along the top of the component, under which appears to be ferrite material.

In the circuit, the two larger leads (which pass through to the top of the device) are connected across the transformer winding for the applicable rail to a rather esoteric control circuit. Note that these winding voltages are much higher the final output voltage (around 55v and 120v AC for the 5 and 12v rails, respectively). These then look like they are fed through a rectifier and then a buck circuit.

Within the circuit, the smaller leads are bridged to the adjacent lead (as shown in the image below), and each of these feeds to a rather esoteric control circuit the output transformer secondary winding for the associated output.

I have removed one of these components from the circuit, and found that the two smaller leads on one side are not connected to each other, but they are connected to the corresponding lead on the opposite side of the device. Resistance between the two larger leads is approximately one ohm, and looks like it feeds a coil inside the device.

The resistance seems too low to be a relay. I note that the +12v and -12v rails have this (component), but the +5v rail does not (possibly due to its higher current rating).

This leaves me with the following questions:

Where can I find a datasheet for this device?
What is the likely purpose of this device in the circuit (I'm thinking some kind of current sensing)?

Update 1 (clarification):

In the image below, the black circles are the terminals of the device. The yellow text shows the resistances between various terminals (measured at DC with a digital multimeter). The green areas show how the terminals are connected on the PCB.

Update 2 (more clarification):

Below is the control daughterboard mentioned in the comments. This appears to be shared between a few different Cherokee Europe power supplies. These supplies were also made by or for Phillips, and appear in various telecommunications oriented power supplies, as well as the Phillips Allura nuclear gamma camera.

This is the control PCB in circuit. The ribbon cable at the bottom of the image is connected to each of the three output rails. Under the heatsink near the top left corner is an LM340T15, which is fed from a 20v transformer tap via a half-wave rectifier. The two power transistors near the centre right of the image are both BD132 PNP transistors.


texts: Is it possible to use a YIG tuned filter to make a YIG tuned oscillator?

texts:
My application requires an oscillator continuously tunable between 1GHZ and 10GHZ (or a wider range). The output (somewhere between 1mW-15mW) has to be coupled to an ultrawide band antenna. No PLL allowed. Generous phase noise and frequency stability allowed.
I've read a lot in the web, and it appears that yttrium iron garnet sphere (YIG) tuned oscillators are probably the solution. Unfortunately, unless I throw a fortune (relative to my modest budget), the best range I can obtain is 2-20 GHz (so the upper bound is OK, but not the lower bound).
On the contrary, YIG tuned filters offer wider suitable ranges at affordable prices; I've read somewhere this is because they use several YIG spheres to cover the full range. I know nothing about the construction of YIG tuned filters, but assuming they use one YIG sphere at a time, shouldn't it be possible to build the oscillator by myself, using the filter as the resonant part and microwave transistors?


texts: How can you calculate a railgun's exit velocity?

texts:
Having a cylindrical iron container with wall thickness of 20 cm, and a total weight of 50 tons when filled with its cargo, how would you be able to calculate its required voltage and current input in a vertical railgun system, with a needed exit velocity of 12km/s? For example, the rail diameter would be 80cm. There would be 4 in total, 2 positive terminals and 2 negative terminals, connected to each other independently, through an 'insulated channel', so it doesn't make contact with the container itself.

Also, is there any formula that can be used for calculating current and voltage required for a certain exit velocity, or exit speed having a certain current and voltage input? Would it depend on many other factors, if so, which?

If any more specifications would be required for such a calculation, please make some as an example, it would be very helpful.


texts: 72-pin SIMM RAM: how do ground (Vss) and supply (Vcc) voltage pins work

texts:
I have a P1004B746400 B7464 REV.A board which is a 72-pin SIMM RAM with two TI TMS418169DZ chips on it. According to 72-pin SIMM configuration, the pins #1, #39 and #72 are ground Vss and pin #10 is supply Vcc.

However, those ground and supply pins are connected to no where, I mean, there is no trace on the board connecting to those pins. Now, I wonder what I'm missing and how the ground and supply pins work.

Pins #1 and #72 are shown below which have no trace connecting to them.


texts: PCB design, Ground plane and power plane issues

texts:
This is the first time I am designing a 4 layer PCB. The circuit will work on multiple frequencies: Signal acquisition part works on few Hz to 200 Hz(max), but one portion of the circuit will generate 13.56MHz. Power supply is 3.3V from a Lipo battery. I am planning to stack the layers as follows:

Signal
Ground Plane
Power Plane
Signal

I am using KiCad. I have already created ground plane and power plane. I have connected the negative terminal of battery to the ground plane by via. The schematic has a lot of ICs which require ground. I am just connecting those pads to the ground plane by vias too.

My question is: Do I have to route the connections in ground plane layer(all of them together, I mean do I have to connect them together again in ground plane-2nd layer of my PCB) or will the vias from the IC pads (supposed to be connected to ground as schematics) to ground plane will do? My understanding is, ground plane is full of copper unless I route any signal through them.


texts: Optical coupler and splitter difference and explanation

texts:
Internally, what is the difference between an optical coupler and an optical splitter. If I have an input A on a 3db splitter, creating outputs B and C, can I send signals on B and C and have them combine and come out of A?

-D


texts: Steady error control system sinusoidal disturbance

texts:
Consider the control system closed-loop represented such a block diagram below:

Given that: \$G_C(s) = K\$ and \$G(s) = 1/s\$

a) Determine the values of \$ K\$ which the closed-system loop is stable.

b) Suppose that the disturbance \$ d(s)\$ be sinusoidal with amplitude A and frequency \$ w\$. The exactly value of \$ w\$ is unknown, but know itself \$ 0 \leq w \leq 10 \$ rad/s

Is it possible to choose a value of \$ K\$ such that, in steady state, the amplitude of the output value is less than or equal to 1% of the value A?

If your answer is "YES", so compute the value of \$ K\$ that guarantees this attenuation.

If your answer is "NO", so show that there is no value of \$ K\$ that guarantees this attenuation.

  However my question is very similar, i have some doubts about the letter b)

\$ \dfrac{y(s)}{d(s)}=\dfrac{1}{1+KG(s)}\Rightarrow \bigg|\dfrac{y(s)}{d(s)}\bigg|_{s=j\omega}=0.1\$

\$\frac{1}{|1+K\frac{1}{j10}|} = 0.1\Rightarrow 10 = \sqrt{1+\frac{K^2}{100}}\Rightarrow 100 = 1+\frac{K^2}{100}\implies \,\,\,\,\boxed{K = 10\sqrt{99}}\$

Is this correct?


texts: Unused select line combination in 3x1 MUX?

texts:
While designing a 3:1 mux we require 2 select lines, but one combination is not useful, say 2'b11. If this combination occurs the output becomes 0 irrespective of the value of input lines. Is not the output of 'x' correct in this case ? So, is an extra condition for making the output 'x' required in this code?

module mux(
  input wire a,
  input wire b,
  input wire c,
  input wire[1:0] sel,
  output wire y
);
  assign y = (a&(sel==2'b00))|(b&(sel==2'b01))|(c&(sel==2'b10))|(1'bx&(sel==2'b11));
  endmodule


texts:
I am using a TLG10UA03 WiFi interface together with my Arduino board. The intension is to send sensor data to a web server in order to publish it on a web site.
I managed to run the TLG10UA03 as a server, in auto mode as well as in command mode. Now I am trying to run it as a client. I can open a socket, connecting to my web server. But I am not able to send the GET command to the web server. No matter what I try the command seems not to arrive at the server.
Is there anybody out there having some experience with this module?


texts: How to solder this broken Gameboy Color part back on?

texts:
I'm trying to repair a GameboyColor where a part that held a battery broke off. I tried soldering it back on but it didn't stick. (I'm new to soldering)
I took some pictures, any feedback and advice is welcome.
Gallery:https://imgur.com/a/7IX5ONk


texts: can only proportional controller be used in smps feedback?

texts: in SMPS when there is a difference between actual output signal and desired output an error signal is being generated. this error signal vanishes as soon as actual output reaches to desired output. so have doubt that how only proportional controller works in this scenario.


texts: How many inrush current limiting thermistor do I need and where should I place them?

texts:
In most designs they place a single NTC thermistor in series before the bridge rectifier and in some two or four:

simulate this circuit – Schematic created using CircuitLab

Isn't a single thermistor sufficient for limiting the inrush current? when and why do we need four thermisotrs?


texts: Algebraic way for finding a transfer function of a filter

texts:
I've the following filter and I tried to write the transfer function for it:

simulate this circuit – Schematic created using CircuitLab

And I wrote for the current nodes the following equations:

$$\text{I}_1=\frac{\text{V}_\text{in}-\text{V}_1}{\text{R}_1}+\frac{\text{V}_1}{\frac{1}{\text{s}\text{C}_1}}+\frac{\text{V}_1-\text{V}_2}{\text{R}_2}=0\tag1$$
$$\text{I}_2=\frac{\text{V}_2-\text{V}_1}{\text{R}_2}+\frac{\text{V}_2-\text{V}_\text{out}}{\frac{1}{\text{s}\text{C}_3}}+\frac{\text{V}_2-\text{V}_3}{\text{R}_3}=0\tag2$$
$$\text{I}_3=\frac{\text{V}_3-\text{V}_2}{\text{R}_3}+\frac{\text{V}_3}{\frac{1}{\text{s}\text{C}_2}}=0\tag3$$
$$\text{V}_+=\text{V}_-\space\implies\space\text{V}_3=\text{V}_+=\text{V}_-=\text{V}_\text{out}\tag4$$

  Question: are my equations correct? And how can I find \$\frac{\text{V}_\text{out}}{\text{V}_\text{in}}\$ from this (if they are correct of coruse)?


texts: Is NXP's PCA9548A compatible with TI's TCA9548A?

texts:
I am using TI's TCA9548A in my Projects, but I would like to know if I can substitute it with PCA9548A from NXP.

By comparing the datasheets this seems to be indeed the case, but I am wondering why they have different names.

By the way, is it really like this regarding these logic chips, that same numbers under different manufacturers mean same functionality? Like the in the case of 74HC595 for example?


texts: What are Y5V or Z5U capacitors good for?

texts:
I was thinking decoupling, but you would have to overdimension them because of the high tolerance and temperature stability. And doesn't a 1uF capacitor (instead of 100nF) have the same inductance problems as a 1uF X7R for decoupling?
Are there other applications where the tolerances and variations are so little important that a Y5V or Z5U could be preferred over X5R or X7R? I realize they're somewhat cheaper but that doesn't count if the quality is too bad to be useful, IMO.


texts: I was able to figure how to make a NOT gate easily enough, but I'm stumped trying to figure out how to make an AND gate. Is it even possible?


texts:
This is probably a question that only I can answer, but I fear I lack the experience. It is relatively harder to source Atmel parts where I live. For instance, I recently had to order the AT Mega 128L from the USA because it was not available in my country (the 5V version Mega 128 was there, though). The PICs are more widely available. They also seem to be cheaper here.

Up until now, I've only had experience with just AVRs. Not because I prefer them or anything but I was/am a beginner and all the research I did led me to think that it doesn't really matter when you're starting out. So I bought a AVR ISP MKII and Mega 168 and learned to program on it.

The other thing that really attracts me towards the PICs is a massively cheaper debugger. The PICKit 3, it seems, has in-circuit-debugging and the AVR ISP MKII that I own does not. I suppose I could purchase the AVR Dragon, but I have heard it has its own problems. And the AVR JTAG ICE MKII is $300. I was considering this, but then I started thinking about purchasing a PICKit 3.

Finally, I feel that I should know how to program on both platforms. I think this would be quite beneficial because I would be able to choose a controller best suited for the job.

My main requirements, at the moment, are really only that it should have

SPI
3.3V input voltage
In-Circuit-Debugging
50 or so I/O pins (I think 64-pin TQFP would be great)

Would you folks tend to agree that a PIC would be better option because of the availability, price and the cheaper debugger?


texts: What's the difference between coax cable and regular electric wire?

texts:
Electric Wire
vs Coax Cable

The only difference are the few other insulator of Coax... but they are both copper wire. What makes Coax good use for Audio/Video and not the regular electric wire?


texts: Can I use a TVS diode as an EMI suppressor in long cables?

texts:
I'm using a microcontroller to do some things when I press pushbuttons, which are located 20 to 30 meters apart from the MCU.
Should I use TVS diodes as EMI suppressors?
edit - The EMI  I'm mentioning is the usual long distant cable problems, such as induced electricity due to switching events. the sense wire is running closer to the normal main wire network, when I switch on a fan in other room, my MCU seems to trigger the event without actually pushing the button
TVS diode datasheet


texts:
I am looking for a cheap single wired solution to transfer data of some sensors connected to a uC over a distance of 1 KM from a control room on UART. The data is of 16 bytes, no high speed communication is required and also the data would flow only in one direction ie from sensor to control room.

What solution would you recommend and which kind of wire should I use?


texts:
I'm using LTspice on Mac, and trying to only use netlists, no GUI. I'm trying to follow berkeley ee240. They use a model that I don't think is available online so I'm just using default mosfet models.

So I need to sweep length, and plot the resulting Vth parameter. I cannot plot V(vout) without manually selecting the trace, it will not show up using the '.plot DC V(vout)' command.

I cannot access the Vth parameter. I have tried various combinations of lv9 and vth but can't get anything to appear on the plot. V(Vout) only appears on the plot if it is selected from the GUI. Vth is not an option in the GUI. Netlist:

.model nm1 nmos(level=14)
.param length=1u

* netlist

Vgs vgs 0 1.2
Vds vds 0 1.2

M1 vout vgs gnd gnd nm1 L={length} W=1e-6
R1 vds vout 1k

* analysis
.op
.DC lin param length 90nm 500nm 50nm
.plot DC V(vout)

.end


texts:
When the base side of the transistor giving a voltage 0 V, across the collector side getting 2.3 V and if give to the base side only voltage 3.0 V, the collector giving voltage 2.9 V. It is not decreasing why?

transistor NPN MMBT3904.
Resistor 2.2 k.
collector voltege 5 V.
base Refernce voltege is 3 V

I want to get if 0 V collector side get voltage is 0.2 or 0 V.
If 3 V, I want to get 3.02 or 2.90 V.


texts: Drawbacks of changing a standard voltage-current converter to amplify the signal?

texts:
I was wondering if there is any practical consequences on changing the standard Voltage to current converter configuration by adding a gain to it.

On picture I've uploaded, both circuits (standard on the left + an OPAMP with the same gain) has the same objectives and seem to work quite fine. I am just worried about implementing the second configuration and later finding a problem with the voltage-current circuit.


texts: How does the Arduino Deumilanove Auto-Reset Function work?

texts:
I'd like to hear some explanations as to how the Arduino Duemilanove resets the ATMega328P over USB through the FTDI FT232R transceiver.

I know it involves the IDE playing some games with the DTR serial handshaking signal. After looking at the schematics, what I'm really interested in getting a better handle on is how the circuit works:

        100nF           10kOhm
DTR -----||------+------^v^v^----- VCC
                 |
                 +--/RESET

The 10k resistor is the usual pull-up on the reset line. So what does the capacitor accomplish in this circuit?

As a sidenote, I used this as an excuse to try and learn/use LTSPICE, so I'm no pro at this tool. I modeled it in LTSPICE as follows, but it looks to me like the /RESET signal just matches the DTR signal exactly, which doesn't really make sense to me. I modeled the DTR signal as a Pulse Voltage source, maybe that's the wrong model. Is it the nature of the FTDI's DTR driver (e.g. perhaps it's open collector) or the internals of the /RESET pin on the MCU that are not present in the circuit I've drawn that make this all hang together electrically?

Also, here are some of the relevant links to datasheets and schematics for reference.

FTDI FT232RL datasheet
ATMega328P datasheet [Arduino
Duemilanove schematics


texts: Tuning PID coefficients for stationary stability of brushless DC motors

texts:
I'm using a commercial off-the-shelf brushless DC motor controller. It combines a PID controller and an absolute encoder to regulate position. When my motor reaches its target state, it generates a lot of audible noise (sounds like a buzz) as it jitters back and forth. Monitoring the measured encoder position, I can see the reading oscillating back and forth between the target and (target+1), or (target-1).

Is there a general principle to apply to the PID coefficients to reduce or eliminate the buzzing sound? Asked another way, is there an intuitive first thing to try in this circumstance?


texts:
if drain terminal of an nmos is open and source terminal is connected to 1v+ and the gate  is also biased to a positive voltage, the Id=0 and Vds=0. can anyone explain? especially "Vds=0"
I thought when a terminal is open it means we don't know its voltage, how does it say: Vds=0??


texts: How to transfer data via an Apple Lightning port

texts:
I have a board on which a microcontroller reads the output from a sensor. I am thinking of connecting it to an iPhone so that the iPhone can read data from it. The board should also be powered by iPhone/iPad. If it were in Android, I would look for the docs related to USB On-The-Go. But I am not sure what I should do with iOS devices. Can anyone give some hints? Thanks!

Update: I just find one needs to participate Apple's MFi program to develop accessories for Apple devices. So it may or may not be something for hobbyists. But apart from that, I am still eager to know the technical solution to my question.


texts: Is there a free hosting site for electrical engineering projects?

texts: I've recently completed a functional CPU and instruction set simulated in Logisim and an example program for it. I'm now just wrapping up all the documentation for the whole design and would like to post it up so people can get to it as an educational resource. However, I'm not interested in paying to host it since I just spent a few months designing it. Is there some place that hosts projects like this in the way that Sourceforge hosts software projects and Opencores hosts soft processors? Thanks in advance for any direction you can give me.


texts:
Anyone know how, or if it is even possible to create an array of parts/instances in gschem and netlist it with gnetlist. I'm trying refdes=name<0:n> and refdes=name[0:n] but gnetlist compains with:

Found unknown component.  Refdes = x<0:62>
Invalid refdes ('x<0:62>')

I would also like to do the same with nets. In addition, how would you concatenate arrays of nets/buses? For example netname=a<5>,a<0:4>.


texts: Why do some tactile switches have 4 terminals?

texts:
I am wondering why some tactile switches have 4 terminals instead of two? For example, take a look at these switches, like the image below:

(source: pranelectronics.com)

What is the use of the two remaining pins? If the pins of the exact opposite side are always shorted then why don't they have just 2 pins?


texts: What is the right clock chip for making a speedometer with an AVR

texts:
I am building a hot rod and I decided to make a speedometer myself with a 3 digit nixietube display. I am planning on using an Atmel AVR microtroller (ATmega32 I beleive). I would like a CMOS clock that I can use to compare time for to keep the speedo as accurate as possibile.

What is a good clock chip to use?
How to I wire interface it to the AVR?
How do I properly use it in software?

Here is what I have so far:

Pulse generator for transmission (sign wave, will use the self
powered 4069 square wave converter circuit but power it off the ps
not the wave)
Nixie tubes and sockets
Atmel microntroller and socket
Nixie tube driver chips
Programming socket for AVR

I would like to make one order to Mouser and get the hardware breadborded ASAP so any help is appreaciated.


texts: Is my solution to this power factor question correct?

texts: I'd be very thankful if it would be possible for someone to check my solution to this question and highlight any mistakes which I may have made in the working. I have checked through it myself several times and am pretty confident that it is correct - I would just appreciate a second opinion.


texts: 7400 chip register with common in/out pins

texts:
First of all, I don't know if this kind of question is allowed here, so sorry if it isn't.

I am looking for a 7400 series register which has common in and out pins (like for the RAM ou EEPROM: ) with a load signal and a store signal. I searched on Google but I didn't found anything (maybe my searches are wrong).

Does it exist and if yes, what is its name/reference?