texts: Prevent click/pop from transient when bluetooth receiver disconnects?

texts:
I have a Logitech bluetooth receiver connected to my hifi to allow kids etc to play  music from iPhones/ipads.

However, it seems that the receiver itself has a sleep mode when no signal is being sent, and this sends a pop/click which sounds a bit like plugging a jack while still connected (but nowhere near as bad).

Is there any cheap/simple way of filtering this to prevent the noise and/or damage to the speakers?


texts: Confusion in understanding control system?

texts:
I am learning basics of control systems from following link

http://instrumentationandcontrollers.blogspot.com/2010/11/types-of-control-systems.html

It says that automatic washing machine & traffic signal system are example of open loop system. It does not gives detail why??

Despite the fact that "automatic" appears before washing machine

Also please kindly find attached photo of a common door closer.  What type of control system is being used by it?open loop or close loop?


texts: Is there a cost savings associated with 3 phase power at the same device power requirement (kW)?

texts:
I am a Mechanical Engineer looking into purchasing an annealing furnace and have seen that some operate on single phase power while some operate on 3 phase power. I've done some research and have seen that with 3 phase power, you maintain a more continuous flow of power and there is more power transmitted compared to the amount of conductor material used.

However if there are two separate furnaces that each require 15 kW of power to operate, and one runs on 1 phase power while the other runs on 3 phase power, is there any cost savings associated with selecting the 3 phase power furnace? Are there any other benefits to the 3 phase furnace that I am not seeing?


texts: If the part in this question is indeed a dual capacitor, what's it good for? The only thing I can think of is that it would be smaller than two separate capacitors, so space-saving, but then it supposes that you need the two (identical?) values at the same place on the PCB, and a common pin.


texts: I am working on a zero crossing detector circuit. Can anyone please explain the function of highlighted circuit?


texts:
In transformer, the open circuit test is performed at rated voltage and frequency. why so?
How both of these factors i.e voltage and frequency affects the transformer working?


texts:
I have got a PWM board from china that outputs at 5V but at 100 kHz, the voltage drops to about 2.82V. Hence I have implemented a mosfet driver to pull the amplitude ideally to be 10V to drive a mosfet that is part of a SMPS.

The mosfet driver that I was using was Microchip TC427CPA. I used a PSU of 12V while experimenting and the result was only about 5.5V output DC.

I tried adjusting the PSU to 17.5V and I've got an output of 8.28V DC.
Based on the data sheet, it mentioned that output voltage should be Vdd - 0.025.
I've grounded the other input interface and I've connected decoupling capacitance between Vdd and ground as per the datasheet.

Any advice to achieve the desired output?

I tried using Microchip TC4432EPA and while the PSU was set at 12V, I was able pull the output to 10.93V measured at pin 7 (Source Output).
However I'm a bit confused with Pin 6 (Sink Output) and Pin 7 (Source Output) for which pin will be suitable to drive the N Channel Mosfet of my SMPS.

I am also unsure if the Microchip TC4432EPA is suited for SMPS applications as well.
I hope someone can guide me along. Thanks in advance!


texts: Should I expect my power line to be this noisy?

texts:
I'm building a circuit that contains a 555 timer wired to operate in monostable mode.

In the final project, the trigger to the monostable will be driven at around 60Hz, with the output driving some strobing LEDs; the 555 is used to ensure that the pulse width is wide enough.

I don't have my input signal yet, but I wanted to try and tune my output to around 8ms, so I pulled the TRIG pin low with the expectation that I'd be able to fiddle with the potentiometer  on THRESH.

After much frustration, I finally discovered that the voltage on VCC is all over the place (I have a scope). The circuit is powered by 2A power supply (MW122A); the LEDs each draw 20mA and I have 6 in 3 parallel pairs (so around 60mA of draw).

My question: should I expect to see a huge amount of noise on my VCC pin if I hold TRIG low for a 555 in a monostable configuration? Or should I be looking elsewhere? The chip is specced to source or sink up to 250mA, so I don't see how I can be pulling it out of spec.

I've added a schematic on CircuitLab

Below are some scope shots.
The probe is set to 10x.
The Vertical scale is set to 2V with 5x magnification.
Horizontal is 0.2us.

Normal Power line

Problematic power line

Any suggestions?


texts: PCBA Upgrade help - best route for processor upgrade

texts:
I have a PCBA currently which:

Runs a Linux Kernel
Communicates through 4 RS232 serial poets
Communicates through Ethernet port

It currently uses an AM335x processor, which I am finding is not quite powerful enough to process the serial comms.

So what would be the easiest upgrade path, the best processor I can use? Preferably with on chip memory?


texts: In the logarithmic compressor in PCM, which law is used in countries other than the US, Canada and European countries?

texts: US and Canada use A-law and Europe use µ-law. I can't seem to find what India and other countries use?


texts: Push pull CMOS output stage overcoming the distortion problem

texts:
I implemented the simple push pull source follower and I understand that it has this distortion problem. That is between -|VTP| ≤ Vin ≤ VTN there is no output because the output terminal floats since both the transistor are not conducting. I hope my understanding is correct.

In order to avoid this distortion problem there is this push pull with quiescent current output stage shown below.

These are my following questions,

1) How does this new model correct the distortion problem?

2) Should all M3,M4,M5 and M6 be in saturation?

3) Is there any hint on how I could dimension these transisitors?

Also Vss in my case is 0. Any feedback would be much appreciated :)


texts: Another way to represent the voltage of a PV array in change of irradiance and temperature?

texts:
I am working on a PV array on simulink and I need help on a math question.

On the article I'm basing the model on, the model voltage equation is
Vm = VmT - (5- G/0.2) for the voltage to vary in irradiance and not just temperature Vmt = Voc*Cv*(Tm-Tr);

Voc= module open circuit voltage at STC (44.9V);
Cv = temp coefficient(-0.0031);
Tm = module operating temp;
Tr = module reference (STC) temp(25 degrees  Celsius).
Tm varies in time, starts at 27 degrees to 36 back down to 27.
G (irradiance) is suppose to vary in time as well starting at 1 to 1000 then back to 1.

When I represent that equation in simulink, I get a very high voltage which is not correct. I even search everywhere on google to help me find answers but had no luck. I will have the paragraph stated below what the article says about that equation.

Does anyone know another way I represent the voltage in change of irradiance and temperature?

Article paragraph
In a similar way, the PV module voltage as a function of temperature is given by Vm = Voc + V mT (12)

where VmT = VocCv(Tm - Tr) is module voltage at temperature T.

Voc = module open circuit voltage at STC.
Cv = module voltage temperature coefficient given by datasheet.

Changes in V due to variations in G are ignored in (12), as pointed out earlier change in irradiance does not change voltage significantly. Beside a correction term that can modify and correct VmI, as a function of irradiance, can be included by careful inspection of the VI curves. VI curves show that change in V due to variations of G in the operational range is less than 5V and thus a correction term that can modify and correct VmT by o to 5V as a function of irradiance can be included as Vm= VmT - (5 - G/O.2) (13)

http://www.canadiansolar.com/fileadmin/user_upload/downloads/datasheets/v5.4/Canadian_Solar-Datasheet-CS6XP_Maxpower-v5.4C1en.pdf For VI curves


texts: Reconciling power dissipation and output characteristic of BJT

texts:
From the datasheet of 2SC1384 I got the following characteristics. I plan to use this transistor in an RF amplifier.

The power dissipation characteristic sets a limit on the dissipated power of the device of 1 W at 25 degrees ambient temperature for the TO92 package. The other characteristic shows the collector emitter voltage and collector current for different values of base current. For example, the curve for Ib=10mA shows Ic=800mA for Vce=5V. For this condition the power dissipated by the device is 4W, which is obviously in excess of the 1W limit.

I planned to draw a load line on the characteric and noticed the power dissipated in the device is very high according to these curves. I draw the maximum power dissipation hyperbola in the characteristic (not shown on screen), which makes the better part of the characteristic look unusable.

My question is how these two seemingly contradicting characteristics can be reconciled. How can the manufacturer even measure the properties of this transistor well above it's maximum ratings?


texts: What are the main parameters to check display with display controller

texts:
I have MAX9278 deserializer IC which is connected to a 3.1inch TFT display 800 (W) * 480 (H).
Deserializer provides 4 LVDS lanes and 1 clock to the display.
What are the major parameters that I need to check so that I can confirm that the Display will work fine with my deserializer?


texts: RaspberryPi I2C sensor - capacitor's role

texts:
I'm new here and the same goes to my electronics "history". I like to understand things I'm dealing with even if I wasn't provided with a sufficient knowledge background at schools.

What I'd like to ask is: is the capacitor a proper element on SDA line between the external sensor and the Raspberry Pi's SDA line?

I want to use a sensor interfacing it with I2C. I supply the voltage from 3V3 Pi's GPIO pin, the sensor works with both 3V3 and 5V levels. So far so good then. But I was told that due to the lack of more than one fuse/protection on Raspberry Pi, it's recommended to put the capacitor on SDA line, as close to the sensor's output pin as possible and of the biggest Voltage I'll find around. An I'd like to understand why, because what I know about the capacitors doesn't make it clear for me.
I know that the intention was to prevent unexpected peek (please correct me if I'm wrong) from damaging Pi's SDA pin. But isn't it true that the capacitor will stop as many Volts it has written on it and then it'll let the current go through, to the Pi's SDA input?

I'll be very grateful for some clarification or pointing me to the right directions, maybe topics I should understand on the way to find the answer.


texts:
This is my first look into FPGA, but heavy background in software development.  Would like to purchase a board to learn with, but would eventually like to be able to run an early 80's style Z80 based computer (think TRS80 model I say).

I've been looking at Spartan 3E and Spartan 6 boards, but not really sure on the performance/capacity differences.

What I'm thinking is something like this:

Enough room for:

simulated Z80 using the opencores T80 softcore.
simulated onboard peripherals such as video controller, sound controller (simple 1 bit), floppy controller
perhaps a couple of picoblaze controllers to use onboard buttons for selection of floppy images etc...

VGA connector (16 color would suffice, 256 bonus)
PS2 Keyboard connector
Enough onboard flash to hold a number of virtual floppy disk images and system ROM (16Mb should be plenty)
On board display, LCD would be nice, 4x7 segment LED would probably suffice.
some sort of flash card socket would be nice, but not required.
Power connect to run off mains, probably through a power pack.

These are the boards I'm currently considering:

Nexys™3 Spartan-6 FPGA Board
Spartan 3E Starter Board
Spartan 3E-1600 Development Board
Basys™2 Spartan-3E FPGA Board (500K) + 16M Flash pMod
Basys™2 Spartan-3E FPGA Board (1200K) + 16M Flash pMod

EDIT: Just noticed the Basys doesn't have onboard RAM so I'd be limited to the FPGA RAM - not ideal.

The main thing I'm not sure on is how much room will be left after loading up the T80 softcore.  Any advice greatly appreciated.


texts: Standalone ATmega168, powered by 4xAA batteries

texts:
I'm making a small animating diorama as a present.  There is a switch, two servos, and an LED; all being powered by four AA batteries and all controlled by an ATmega168 chip.  I've prototyped the simple stuff on my arduino uno, but now I want to move the ATmega chip and hook up the battery pack, both of which are new to me.

I'm too new to the site to post any inline images, or for some of the links to be completely valid.  I apologize in advance.

This is the design I put together in Frizting:

http://dl.dropbox.com/u/3144073/diorama/breadboard.pdf
http://dl.dropbox.com/u/3144073/diorama/schema.pdf

I've used these two articles as reference (remove the spaces):

http://www.tkk.fi/Misc/Electronics/circuits/psu_5v.html
http://www.instructables.com/id/Standalone-Arduino-ATMega-chip-on-breadboard

I would be very surprised if I had it all wired up correctly. I'd be very grateful if anyone could comment on what I've done wrong.

PS.  The software polls the state of the toggle switch.  If the switch is on, it sets the two servos to specific values, and turns on the LED.  If the switch is off, it sets the servos to difference values, and turns off the LED.


texts: If RS-232 defines electrical characteristics, what is the transfer protocol?

texts:
From this answer, it says RS-232 defines the voltage levels and what not of a signal.

I want to be able to read barcodes on my microcontroller with something like this.

The closest datasheet I could find to a similar product was this:

Specsheet
Manual

The specsheet states that the scanner runs at 5V. However, from wikipedia:

  For data transmission lines (TxD, RxD and their secondary channel equivalents) logic one is defined as a negative voltage, the signal condition is called "mark". Logic zero is positive and the signal condition is termed "space".

If the scanner works at 5V, how is this RS-232?

And regarding my question, from the datasheets I can't find any information regarding the actual transfer protocol, and how to interface to the scanner at a software level.

Is it assumed that the transfer protocol is UART?


texts: Do all switching converter ICs support multiple topologies?

texts:
I'm trying to design a low-noise power supply for small-signal audio (+/-12-15V, ~1A). As part of this, I'm investigating advanced SMPS topologies like the SEPIC and Ćuk converters. Few controller/converter ICs mention support for these topologies in their datasheets, and the ones that do (such as the LM5001) seem to support a more common topology as well, usually boost. I also found an EE Times article on how to design a negative buck converter using a boost converter IC, and an app note that implements a buck-boost converter using a buck converter IC. What I have not found is a general list of which topologies are supported by each type of controller/converter. Thus, I have two questions:

Can all converter ICs be used to implement multiple topologies?
If so, which topologies are supported by each type of basic converter IC (buck, boost, etc.)?


texts: I need to know how LED status lights like these on my Bose Q35 headphones, are made? Is it a light guide? some kind of foil or what?


texts: High-side gate driver not working under load high current

texts:
I have been trying to implement a current limiting circuit using a high power NMOS and high side gate driver.

My idea is to adjust the PWM duty-cycle of the gate driver to give an limited (average) current to the load. So far, I had good luck with a small load (8 Ohm at 24V). However, when I try a bigger load (2 Ohm at 24V), the gate driver stops working.

My original guess is that the NMOS gate is taking too much current form the gate driver output pin, but the simulations tell me that the TG pin is only outputting 2.4A max (LTC4440 can do 4A max for 1us). Another guess is that the inductance in the wire make the peak current higher than what the simulations show. Does anyone have a recommendation ?

The schematic below shows my setup. The plot shows the output voltage in green, and the current at at the gate of the NMOS in blue.

Here is more information about the experiment I conducted:
The circuit (shown in the schematic) seemed to work great when using a 8 Ohm resistor as a load (at 24V). I was controlling the PWM duty-cycle with a potentiometer, and I was able to vary the (average) load current from 0 to 4A. Then, I changed the load for a 2 Ohm resistor (2000W), which should theoretically draw 12A everytime the FET is on.   JHowever, as soon as I started adjusting the duty-cycle of the PWM, the gate driver stopped driving the gate. I went back to the smaller load (8 Ohm), but the gate driver does not drive the gate anymore. The chip seems to have an issue. I had this issue happened to me three times (gate driver fails at higher load, but works well at small loads).


texts:
I am having trouble understanding this winding schematic from the book "Induction Machines Handbook" by Boldea, Nasar. This is a winding schematic of a capacitor run single phase induction motor.

How exactly is the coil wound, and what orientations do the currents take?


texts: LTSPICE MOSFET based Voltage Divider SImulation and Real Circuit Results Do Not Match

texts:
I am trying to build a very low current voltage divider. I picked high load design using NMOS and PMOS in LTSPICE. In LTSPICE current in R4 is almost zero (nA) when Vin is zero, but in a real circuit i still measure 6.4uA. Can anyone, please, see an issue with this circuit?
Thanks


texts: Linear image sensor output signal processing

texts:
I am working on a circuit reading the TCD1103 image sensor. In the datasheet,
the shown 2 peripheral components are advised.

I wonder if the BJT connected to the OS signal would be neccessary, if an operational amplifier in voltage following mode was connected instead.

Since the output is an analogue voltage signal, I got the impression, that the BJT might have a role in linearizing the signal.

My (simplified) circuit would connect the TCD to an ADC as in 3. In the real circuit there would be additional analogue amplifier stages as per the ADC datasheet, but notably it is lacking the BJT.

Update 1

As suggested in the comments, I will keep the BJT. Since the datasheet does not specifiy any particular model, I'd like to extend the question to which BJT model should be used. My choice wold be 2N3906.


texts: I am trying to simulate variable capacitor in LTSpice. I have gone trough solution for variable capacitor with respect to voltage. But I want to change it with respect to relative permittivity. Any answers would be appreciated?


texts: Why is the peak efficiency of most charge pump less than boost converter,but still can be published in IEEE

texts:
I read some paper about boost converter recently ,and find some author will compare the peak efficiency of their boost converter with charge pump,and the  highest peak efficiency i saw is 33%,the other are 1% or even less 1%,on the other hand ,the peak efficiency for boost converter is 70%,or even higher than 70%,and as i know the peak efficiency is \$ \frac{real}{Theoretical}\$.

So i want to ask :

Why is the peak efficiency of  most charge pump low and  much less than the boost converter?
No offence,but if the most output voltage of charge pump is less than boost converter,and peak efficiency is very small,then what is its,charge pump, advantage?why can the charge pump ,which is small peak efficiency, be  published in IEEE?


texts:
I'm an absolute beginner with LTSpice;  my first test circuit uses a few D flip-flops:  four of them as clock dividers (to divide the clock frequency by 16), and then 3 as delay blocks (to delay the f/16 signal by three clock periods).

Below is the saved .asc file.

The thing is, when I run the simulation the "delayed" signal is not really delayed --- it is an exact copy of the signal at the input of the first delay flip-flop.  Specifically, the Q output of A3 (which is connected to the D input of A4) and the Q output of A7 are identical and perfectly aligned (i.e., without any delay between one and the other).

Am I doing something wrong, or is LTSpice doing something wrong?

Thanks!

Contents of D-flipflops.asc file:

Version 4
SHEET 1 1448 680
WIRE -144 -64 -368 -64
WIRE 80 -64 -128 -64
WIRE 304 -64 96 -64
WIRE 528 -64 320 -64
WIRE -368 48 -368 -64
WIRE -336 48 -368 48
WIRE -160 48 -176 48
WIRE -128 48 -128 -64
WIRE -112 48 -128 48
WIRE 64 48 48 48
WIRE 96 48 96 -64
WIRE 112 48 96 48
WIRE 288 48 272 48
WIRE 320 48 320 -64
WIRE 336 48 320 48
WIRE 752 48 496 48
WIRE 1008 48 912 48
WIRE 1264 48 1168 48
WIRE -160 64 -160 48
WIRE -128 64 -160 64
WIRE 64 64 64 48
WIRE 96 64 64 64
WIRE 288 64 288 48
WIRE 320 64 288 64
WIRE -336 96 -368 96
WIRE -144 96 -144 -64
WIRE -144 96 -160 96
WIRE -128 96 -128 64
WIRE -112 96 -128 96
WIRE 80 96 80 -64
WIRE 80 96 64 96
WIRE 96 96 96 64
WIRE 112 96 96 96
WIRE 304 96 304 -64
WIRE 304 96 288 96
WIRE 320 96 320 64
WIRE 336 96 320 96
WIRE 528 96 528 -64
WIRE 528 96 512 96
WIRE 752 96 720 96
WIRE 1008 96 976 96
WIRE 1264 96 1232 96
WIRE -368 208 -368 96
WIRE 720 208 720 96
WIRE 720 208 -368 208
WIRE 832 208 720 208
WIRE 976 208 976 96
WIRE 976 208 832 208
WIRE 1232 208 1232 96
WIRE 1232 208 976 208
WIRE 832 400 832 208
FLAG 832 480 0
SYMBOL Digital\\dflop 192 0 R0
SYMATTR InstName A2
SYMBOL Digital\\dflop 832 0 R0
SYMATTR InstName A4
SYMBOL Digital\\dflop 1088 0 R0
SYMATTR InstName A5
SYMBOL Digital\\dflop 1344 0 R0
SYMATTR InstName A7
SYMBOL voltage 832 384 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value PULSE(0 5 0 5n 5n 0.5u 1u 20)
SYMBOL Digital\\dflop -32 0 R0
SYMATTR InstName A1
SYMBOL Digital\\dflop 416 0 R0
SYMATTR InstName A3
SYMBOL Digital\\dflop -256 0 R0
SYMATTR InstName A6
TEXT -370 500 Left 2 !.tran 0 30us 0


texts: What is the need for the extra resistors in this equalizer circuit?

texts:
I am working on a final project for my circuits class to design an audio amplifier. We are creating an equalizer circuit that has passive high pass, low pass, and band pass filters. Every where I search I find a design similar to this:

What is the purpose of the resisters outside of the filters? For example, the two 10k resisters on top, or 3.3k resisters in the middle. They aren't part of the filters, are they?


texts:
I have a project to design a new board to be used in specific application. The boards would control and take image from CMOS camera under ground. Because of limitation in power consumption and cost (more than 1,000 boards would be produced), it is fascinating to use the cpu and RAM in the intel's edison board. It has incredibly low power consumption and large storage, but I can't just use it because it's too expensive for my project.

Is it possible to buy just the cpu, RAM and build similar board?


texts: I found a component in a circuit called DNP0603, I have searched in the net and I did not find an explanation to that, does any one knows what it stands for ??


texts: Determining the current from an infrared LED used as photodiode

texts:
Let me talk in general first: I have two LEDs of the same wavelength (940 nm) placed opposite to each other. Between them is a 140 mg/dL glucose solution (only glucose + water). One LED is used as emitter, the other as detector. Of course, the signal generated from detector will be amplified later. But the problem is:

Choosing an opamp depends on how low the current from detector is. Is it in nanoampere, picoampere, or even lower?

How can I know the range of the current generated by the detector? Since every opamp has an input bias current that influences the result.


texts: Help connecting custom ATMega328PB using serial FTDI

texts:
I built this ATMega328PB circuit.

It runs at 3.3v from 1.5v battery using booster and 8MHz from external resonator (CSTCE8M00G52A-R0).

Using USBTinyISP I set fuses: Low-FF (for 8MHz), High-D8 (Boot Reset Vector Enabled), Ext-FD.

Using VisualStudio and vMicro plug-in I compiled a program for UNO. vMicro created a HEX file of my program WITH a bootloader which I uploaded over ISP and it runs well (blink the LED).

My final goal is to make a customized 8MHz bootloader but as intermediate steps
I am trying to get a sign of life over serial using FT231X FTDI, and than upload a sketch over it.

I cut the 5v jumper on FT231X and connected 3.3v jumper instead.
Then connected (without a battery):

ATmega328   FT321X
---------   ------
Vcc         Vcc
GND         GND
GND         CTS
RST         DTR (over 0.1uF)
RxD         TX
TxD         RX

Since the default UNO bootloader UBRR register is set for 16MHz, I initialize it manually and try to push data over serial.

#define myubbr (8000000/16/9600-1)
void setup()
{
    pinMode(6, OUTPUT);
    // Init serial
    UBRR0H = (unsigned char)(myubbr >> 8);
    UBRR0L = (unsigned char)myubbr;
    UCSR0A = 0;//Disable U2X mode
    UCSR0B = (1 << TXEN0);//Enable transmitter
    UCSR0C = (3 << UCSZ00);//N81
}

void loop()
{
    digitalWrite(6, HIGH);
    delay(100);
    digitalWrite(6, LOW);
    delay(100);

    char * str = "Hello World";
    while (*str) {
        while (!(UCSR0A & (1 << UDRE0)));
        UDR0 = *str++; //send the data
    }
}

On the PC I run: avrdude -v -p m328p -c arduino -PCOM8 -b 9600

Avrdude recognizes the correct com port but gives:

avrdude: stk500_getsync(): not in sync: resp=0x00

The RX and TX LEDs on the FT231X never blink.

I don't even know if the problem is HW or SW. What am I doing wrong. What else can I try?


texts: Is this resistor leaking? If so, is it a concern?

texts:
I found this resistor on the control board of an old Whirpool washing machine:

Is that fluid leaking from the resistor? (Why would that happen?) Could it be something like stray epoxy or a chemical reaction with the substances in the machine like water vapor/soap instead?
If it is fluid or a chemical reaction, what implication does that have for the longevity/safety of the resistor?


texts: Deliberately Blowing Up an LM386N-4 Power Amp

texts:
This is a somewhat unusual, although hopefully not too irresponsible, question (I also hope it falls within the remit of this site, I can't think of anywhere else online where I'd get a trustworthy answer). I'm making a short film in which a simple LM386N-4 power amp chip explodes and catches fire. It will appear to be in the audio amp circuit like the one shown here, but need not in reality be connected to anything (the magic of film...)

(source: hobby-hour.com)
By accident, I've found that when the chip is in the circuit above and is supplied with 13.2v, and 13.2v is then applied to pin 5 (output) it dies immediately and a small plume of smoke appears.
My question is this: taking the obvious safety considerations as a given (I'll be wearing safety goggles, will be standing a good distance from the chip, next to the mains switch, and I have a CO2 fire extinguisher for if things get serious), what voltage should I apply, and to which pins, to get some smoke, a few flames and maybe an initial flash?
I'm guessing that putting a full 240v between pin 5 and ground (switched using a relay for safety) might be overdoing it. The datasheet for the LM386N is here and I'm using the -4 type, which takes a maximum voltage of 18v.


texts: Is there a meaning of stripes on RS485, Phone and Ethernet cable?

texts:
I recently bought some RS485 cable, it had two pairs, both had stripes. One was mostly blue with a white stripe and the other was white with a blue stripe.

I'm mostly used to ethernet with a pair consisting of completely solid and white with a stripe.

Large phone cables have solid with white stripes, and solid.

So is there a meaning to any of these? Is the striping set by manufacturers or have any meaning beyond indicating a pair?


texts: Schematic layout for inline and pull-up/down resistors

texts:
I find it often difficult to make a readable schematic for simple boards that have a microcontroller or FPGA that has lots of connections to some other components, where each connection goes through a small resistor (to avoid smoke in case of programming errors) and also needs a pull-up or pull-down.

Obviously, this is the worst possible way to do it:

An approach I've seen often is to draw the inline resistor near the "central" microcontroller, then place the label behind it, and somewhere else define the pull-up attached to the label, but this leads to a forest of label/pull-up/power rail symbols on some page, which isn't entirely obvious either.

How would you draw a schematic like this, making it clear that the non-inverted signals have pull-down resistors, the inverted signals have pull-up resistors, and all of them have in-line resistors to protect the controller?


texts: Wiring CanaKit Relay and Southco EM-05 Electronic Lock

texts:
I am attempting to wire this relay http://www.canakit.com/4-port-usb-relay-controller.html to this lock http://www.southco.com/en-us/em-05. I have done some work with Arduinos before, but I am not an electrical engineer, therefore I am having trouble figuring out how to wire these 2 together in order to get the relay to power (and open) the lock. Any help would be appreciated!

The relay channels each have NC, COM, and NO.
The lock has GRD, POW, SIG, COM, and NO.


texts: Finding the (Q) point for V(Collector-Emitter) and Collector Current?

texts:
The question gives the following schematic and says to find the Q point for the Voltage(Collector to Emitter) and the Q point for the Collector Current. It gives beta as 50.

I'm using two standard equations from my book to find the (Q) point for the Voltage(Collector to Emitter) and the Collector Current. I followed step by step instructions from the book and I'm being told I'm wrong. Could someone calculate these two values and maybe tell me where I went wrong.

I'm told that when finding the (Q) point I can't use these two equations because (B) beta is completely independent. But when I look in my book all the equations are identical to the ones finding a value related to a (Q) point. I've listed the equations below with my answers.


texts: Do I need anything between a microcontroller and a basic FM transmitter to cut out EMI?

texts:
Below is my circuit of a basic FM transmitter attached to an output pin of the AT89C2051 micro controller. I haven't tested it and I might decide to connect R1 to the NPN collector instead of to VCC. VCC here is also 5 volts. TP1 is the antenna.

The frequency I will be working with is between 200 and 500Mhz but I might have decided on 350Mhz.

The crystal for the micro-controller will be a low-profile crystal running at about 20Mhz.

What I want to do is limit the EMI produced by the circuit and only have it transmit the data fed from micro controller port P1.7.

Should I adjust the values of C1, C2, or C4? Should I include an LC filter between P1.7 pin and C4? Should I add an additional resistor from VCC to one part of the circuit?

I want the transmitter to be long-range but not to produce EMI.

Any suggestions welcome.


texts: Need a switch/circuit breaker that stops power supply to equipment when power comes back after outage

texts:
I need a switch that stops power supply(220VAC) to led tv when power comes back after outage. So i need a circuit breaker that breaks the circuit when power supply is off and needs manual switch on from this circuit breaker device when power supply is on. I have two ideas:

I feel its possible using microcontroller and relay but i think it would be costly and time consuming to make such device.
I am also having idea about using magnetic coil as in magnetic circuit breakers but not confident about its effectiveness.
As i am unable to find such device on commercial websites, so i need help in finding such device if commercially available and/or making such switch/circuit breaker in a simplest and cheapest possible way.


texts: Advantages of depletion mode FET devices over enhancement MOSFETs

texts:
I've grown the impression that JFETs and depletion mode MOSFETs are not used very much nowadays, especially in new designs.

I know that they need different bias networks, especially as discrete components, so I guess there might be some advantages in using them, but the current trend doesn't seem to corroborate that guess.

Are depletion mode devices being made obsolete by the development of the technology of enhancement MOSFETs? Are there still applications where the use of a depletion device gives distinct advantages, especially as discrete components (I know that depletion mode MOSFETs can be used as active loads in IC MOS technology, so they may still be needed there)?

On a related note, I'd like also to know whether JFETs are still actively used in new designs, since it seems that they could be replaced by depletion MOSFETs (assuming one really needed a depletion mode device for some reason).


texts: Turn a transistor on when any one of nine LEDs is on using an LM3914

texts:
I'm wanting to turn a transistor on when any LED from LED2 through LED10 are on with an LM3914 in dot mode.

Basically, I want the transistor to be normally off until at least LED2 begins to light (using dot mode). Edit: there is some confusion with the diodes D1,D2,D3, and the capacitor C1. This causes LEDs 2,3,and 4 to blink when their on state is triggered based on this answer here: Make three respective LEDs blink with an LM3914 in dot mode

The answer to my new question needs to let the transistor be a solid on and not turn on and off with these blinking LEDs 2-4 in the schematic below:

Here is a picture of the circuit I'll be using for the LM3914.


texts:
In this circuit from (Grey,Meyer Analysis and Design of Analog Integrated circuits fifth edition) It is stated that : "In the quiescent
condition,\$ V_o = 0\$ and \$V_1 = 0\$ ."
What forces V1 and Vo to be equal 0 when \$V_i =0\$ ?Aren't there other sources (\$V_{cc}, -V_{cc}\$) which may cause \$V1\$ to be >0 ?

edit :It is actually mentioned that this is a simplified schematic of the output stage of the 709 op amp


texts: Unifilar (non-stranded) copper wires flexibilty

texts: we all know the 26 AWG wires that come inside UTP cables. Those surely are flexible. But what a bout an AWG 15-16 such copper wire, is it flexible enough to use as feeding cable for the 12 V car lighter socket ?


texts: Maximum power available of a generator derivation

texts:
I'm having a hard time with the maximum power disposable from a generator derivation, it's something that I should know but I'm confused about it.

simulate this circuit – Schematic created using CircuitLab
My Professor started with this circuit and the complex power
$$W_g= \frac{V_g I_g^*}{2}$$
Where \$V_g\$ and \$I_g\$ are phasors, he then said \$I_g=\frac{V_g}{Z_g+Z_a}\$, then we hypotize the MPT condition (Maximum Power Transfer) so \$Z_g=Z_a^*\$.
Now we have $$I_g=\frac{V_g}{2R_g}=\frac{V_g}{2R_a}$$
At this point we can substitute the Ig in the formula of power obtaining:
$$W_g= \frac{V_g I_g^*}{2}= \frac{|V_g|^2}{8R_g}$$
Ok so the result is correct but the mathematical passage is not clear to me, because if you substitute the current there is a 2 factor that doesn't show in the math.
Edit with solution
The problem was stupid because i named Vg over the resistor and the Vg of the  voltage generator the same, I had to use the voltage partition formula over \$ R_g\$ to get the \$V_{g_{resistor}}\$ and then multiply it by the current.
in formulas:
we have (MPT) $$I_g=\frac{V_g}{2R_g}=\frac{V_g}{2R_a} $$
$$V_{g_{resistor}} =\frac{R_g}{R_g+R_a}V_g = \frac{V_g}{2}$$
$$W_g= \frac{V_{g_{resistor}} I_g^*}{2}=\frac{V_{g} I_g^*}{4}=\frac{|V_g|^2}{8R_g}$$


texts:
How to with a few volts [5v] give an alternated current safe shock?

To this Halloween i want to make and door that give a shock, but have to be safe and very lite. Like that pens that when you press, it gives you a shock.

ps.: will be one shock in 3 seconds, durning 015 ms
ps2.: i dont want to kill somebody =]


texts: PIC:How to interface MPL115A1 pressure sensor to PIC24FJ16GA?

texts:
I have one pressure sensor which I want to interface to microcontroller PIC24FJ16GA to measure pressure.

I don't know which pin of controller to interface a sensor.

I am already using SPI1 in my project in that configuration controller is worked as a slave.

How to interface using SPI2?

I am little bit confusing when read a datasheet of controller.

If some demo code is available then is better understanding for me.


texts:
I have just started studying about IoT a few days ago, and now I'm trying to work with the wifi module ESP8266.
I want to do something like this: I send a cmd from Android device to a server, which have some php code to handle my GET or POST data. Then, it will send some data, like json or something, to the ESP8266, and to a micro controller like AVR via UART to handle the changes. And sometime the MCU can send some data to server, and server will noti the android (a reverse process).
I have understood how to send data from wifi module to an URL with Get and Post method (not fully, but maybe enough). I just dont understand how to send message from server to the module! Does the module need to send request to server and get the respone again and again in a loop?!
I am a newbie so please give me a clear and answer! Thanks and sorry for bad English =)


texts: Does the increment of a timer on pic is equal for a pic16 and pic32?

texts:
The question is because in porting code from a PIC16F15324T using MCC to a project using a PIC 32MX470F512L.

There are portions of code where i have code like this:

    TMR1 = 0; // Starts counting
    while (TMR1 < TIME_BIG_PULSE_CONFIRM) // Minimum time to be considered big pulse
    {

        if (!data_in_get_value()) {
            if (!data_in_get_value()) { // Simple debounce - confirm twice
                break; // Get out of the while
            }
        }
    }

This may seem like a noob question, but are do the increments of TMR happen what same time if i configure both timers for 8us? Of course i know that the pic with the higher frequency is supposed to execute instrutions a lot faster (that would be true if MCC was optimized for the pic32)

PIC16 MCC:

PIC32 MCC:


texts:
I'm trying to figure out how to choose a power supply for a 5-meter strip of SMD 5630 LEDs, and I can't wrap my head around which current values I should use.

The Samsung spec sheet for their 5630 rates their device (forward current) at 150 mA, but throughout the majority of the document, they use a forward current of 50mA.  The "50 mA" number is also referred to as "sorting current," which is a term I'm not familiar with.

So, the question: when specing a power supply for a SMD 5630, which number do I use (or perhaps better asked: under which conditions would I use one number over the other)?

Here's the link to the spec sheet I'm referencing.


texts: Selection criteria for microcontroller to read data from a car's CAN bus (from OBD2 to microcontroller)

texts:
I want to read data from a car's CAN bus using a micro-controller. The micro-controller is used outside the car (via OBD to micro-controller).
A few micro-controllers i found with CAN interfaces are Teensy 4.0, ArduinoDue with dual CAN interface shield,LPC1768 etc.

Im not sure as to:

On basis of what parameters to choose a microcontroller?
What are the components need to make a connection from the OBD port to microcontroller, do we need a CAN transciever and a controller with a microcontroller? which i found being used in
threadInterpreting CAN bus data from OBD port

Im new to embedded systems.Any suggestion would be really helpful.

Thanks :)


texts: Isolating or suppressing possible servo noise from signal lines

texts:
I will be building a circuit to control a robot arm which is not a small toy kit. There will be motion sensors, feedback systems, robot arm controlling modules. So digital signals will be flying all around. The data communication will be over I2C.

The robot arm has 6 servo motors, 2 x Servo 5521MG (Running Current 750 mA - 1.2 A @ 6V), 4 x Servo MG996R (Running Current 500 mA - 900mA @ 6V) and their potential noise concerns me.

I am planning to use separate power sources but ground has to be common to pass the servo control signal.

I found some ideas such as using ferrite on servo cables, opto isolator, which one would be best option?

Which pcb design practices I should follow to prevent noise influence over signal lines?


texts: Wanting to build an automotive grade solid state relay center

texts: I am wanting to build a solid state relay and fuse center for motorcycle applications.  It will be used to drive the positive side of all components, such as fuel pump, lights, solenoids, exc.  I would like to use fets to do this.  The imputs to turn them on are negative or ground.


texts:
When I was calculating the following netwerk:

Where given was: R=5,L=1,C=4,V_C(t)=10,I_T(0)=-2,V_in(t)=20.

So the ODE that we get was:

$$
\begin{cases}
20\text{V}'_{C}(t)+\text{V}_{C}(t)+4\text{V}''_{C}(t)=20\\
\text{V}_{C}(0)=10\\
4\text{V}'_{C}(0)=-2
\end{cases}
$$

Solving this ODE, gives me:

$$\text{V}_{C}(t)=20-\frac{40\cosh\left[t\sqrt{6}\right]+17\sqrt{6}\sinh\left[t\sqrt{6}\right]}{4e^{\frac{5t}{2}}}\space\space\space\text{V}$$

QUESTION:

If I plot my found solution, than on the t-axis we get a line, but in which scale? Is it seconds, minutes? or what


texts: How latches are used to implement High-speed VLSI Designs?

texts:
I read a article saying "Latch-based designs, however, have smaller dice and are more successful in high-speed designs in which the clock frequency is in the gigahertz" but I am unable to understand how latch based design can help in lower clock time period.

While latches allowed time-borrowing but it seems that total path delay should always be less than clock time period (Considering case where Negative level latch placed in between two posedge triggered flops)?


texts: What effect does having 'measured' as a parameter in additive white gaussian noise?

texts:
I'm comparing the bit error rate of various modulation schemes with additive white gaussian noise in MATLAB.

There's the option to have this noise using 'measured' which measures the power of a signal before adding noise to it. When using this, the signal ossicilates a lot more, but I don't understand why/how this is.

If it's just measuring the power, why would this affect the BER performance?

Link to the MATLAB documentation.


texts: Consumer Batteries Needed to Ignite a 10ohm Resistor

texts: What is the best battery(ies) to ignite a 10ohm 1/4w carbon resistor? Something that I can buy at my local supermarket. I hear the main problem is internal resistance in the batteries. Ideally, I would like to make a package the size of a zippo lighter to ignite them.


texts: Which capacitors can deliver the highest amount of current in short bursts

texts:
Ultra capacitors can store a huge amount of charge but can it discharge the fastest? In other words I am looking for a capacitor with the lowest internal resistance,also it should be at least in the microfarad range.
Now the internal resistance varies with time for some caps, but in my case I would discharge it in a fraction of a second so it wouldn't probably matter if the internal resistance goes high after half a second or so.

I am also willing to build my own if such capacitors are not easily available commercially.


texts: How can I set a wire to one of 3 voltages from a simple digital controller (e.g. Raspberry Pi)?

texts:
Here's my problem. I have a device to control that needs to always have one of three voltages applied to it: 5V, or 6V, or 7V. And I need to be able to programmatically switch between them.

What I have available is a general mirocontroller with GPIO pins that I can set at some different voltage (e.g. 3.3V). I have a feeling relay circuits could do this but I can't figure out how to switch between my 3 different voltages.

Question summary:

What circuit would implement this with simple components? How should I create the 3 voltages I need? Assume I can buy whatever simple parts from Amazon etc.


texts: What 'rated voltage' means in VDE certificates?

texts:
In a VDE certificate for a component (plugin green terminal blocks), a column gives the "Rated voltage(s) / V" with a value of "400" without specification wether it's VAC or VDC.

Does this mean that the component is safe to use for both DC and AC at this voltage ?

A 400VAC voltage will be applied on the component (three phases, one neutral, one earth wire / Europe). As the voltage on the  electrical network can fluctuate, is this "rated voltage" given with these variations taken in consideration ?


texts: How to store all those spare cables and connector cords?

texts:
One thing that it seems I have many of are cords and connector/patch cables.

I don't want to throw out all of them, but am looking for useful storage tips?

Most are under 6 foot / 2 metres long, they are the usual assortment of TV cable, stereo-cable, serial cable, ethernet, 12-volt power, etc.

Looking for some way to store them efficiently, while I can still see both ends.  Coiling is a possibility, but then there's just a stack of circles that I have to dig through.

Ideally, some sort of hanging method, that has them semi-secur, but still accessable/visible.

How do you store all those cables? (and hope this is Electronics-enough!)


texts: Phase Velocity in case of Electromagnetic Transmission

texts:
I'm presently going through the theory of electromagnetic propagation. While studying the case of propagation of EM wave in arbitrary direction, I came across a derivation which proves:

$$c \le \text{phase velocity} < \infty$$

Further it says that the product of group and phase velocity of an EM wave is constant and equal to the square of speed of light. How it is possible that phase velocity is greater than the speed of light? Plus, what does it signify physically — I mean what does the meaning of infinite phase velocity imply physically?


texts: mechanical excitation of tuning fork and electrical readout

texts:
For my experiment, I am trying to mechanically excite a quartz crystal tuning fork and measure the voltage across the tuning fork. When the TF is driven at its resonance frequency, there should be more charge accumulation and hence greater voltage.

I have just encountered a mystery though.  A quartz crystal tuning fork has a dip and a peak: series and parallel resonances.  When I was electrically driving the tuning fork, I was able to perfectly understand them and depending on the measuring scheme I was employing, either the series or parallel resonance peaked and the other one dipped.

Yet, for the mechanical excitation scheme, when measuring the voltage across the tuning fork, I wasn't sure which of the series and parallel resonances would peak.  When I started measuring the voltage value, I ended up seeing the series resonance peaking (left plot of 2nd image).

Strangely, when I just swapped TF lead 1 and TF lead 2, the amplitude profile was basically turned upside down: the series resonance dipped and the parallel resonance peaked (right plot of 2nd image).

Also, when I swapped shear piezo lead 1 and shear piezo lead 2, I saw that the amplitude plot's peaks reversed.

I wasn't able to find anything related to my observations in the existing literature.

simulate this circuit – Schematic created using CircuitLab


texts:
I was looking at getting an induction furnace for home/experimental use, and I just don't understand how these devices can operate within FCC limits. Dumping several kilowatts into an unshielded coil at frequencies in the hundreds of kilohertz seems like it would interfere with primary services in the area using those frequencies. Am I misunderstanding the operation of induction furnaces here or the FCC guidelines or both?

Here is an example of the type of furnace I am looking at.


texts: Communication within 5-10 meters: RS-485 or Wireless?

texts:
As a follow-up for my previous question, can anyone please recommend for my application (communication between two floors of a building) as whether to use RS-485 or any wireless technique (I am thinking of using cheap 433 MHz based ASK transmitter or please suggest if there is any other low-cost wireless solution for my need).
The typical datarate for communication will be around 115200 bps. I have also heard of ZigBee OR XBee but I want to go for a cheaper option (but reliable too in terms of data integrity, as the application involves sending 2-3 types of sensor data which play an important role in my feedback system).
Any suggestion is appreciated.


texts:
I have some RGB LEDs (common anode) and I'd like to control them via sound from my stereo (line level). I'd like to be able to switch the two behaviors of the LEDs from flickering off when the input is high (LEDs always on), to flickering on when the input is high (LEDs always off). I've come up with the circuit below:

I'm wondering if I leave the emitter from the NPN and the collector from the PNP connected if I will see any adverse behavior? If so how could I fix this?


texts: How can I turn on and off a switch every 20 minutes?

texts:
I want to make the above switch which will stay on for 20 minutes and then off for 20 minutes. This should be continuous. Actually, I want to place this switch for my air conditioner which I do not want to run the whole night but off itself every 20 minute interval and restart after 20 minutes. This will save my electricity by half.. since the thermostat function of the air conditioner is not of much use and also I do not want my appliance to run for the whole night.

The device I'm going to switch takes between 5 and 15 Amps circa.


texts: MPU6050 accel/gyro noise that behaves strangely - what might be doing this?

texts:
I'm experimenting with an MPU6050 six-axis accelerometer/gyro reading data with a Raspberry Pi via I2C. The six-axis response makes sense in general as I rotate it by hand, rotating moves the gravity vector correctly per the accelerometer channels, and short rotations around each axis generate reasonable-looking gyroscope values.

But when I set it down on something that should isolate it from vibrations and just take data for a long time, I see strange non-statistical noise in some channels.

I wrote a short script (shown below) that samples all six channels for 400 iterations, then increments the low pass filter (seven levels from 0x00 to 0x06) and then increments the gain for both accel and gyro (four levels; 0x00, 0x08, 0x10, 0x18). So that's 28 tests with 400 samples each. The data rate is about 55 to 60 measurements of all six axes per second. The characteristic frequency for each setting of the digital low-pass filter from the register map pdf is:

and the data sheet pdf.

Below I show the data which ranges from -/+ 32,767. The only thing I've changed is to subtract the mean of the 400 measurements at each setting so just the noise is displayed.

As the seven low-pass filter settings increase, the frequency decreases and the noise decreases as expected. However, there are these sudden spikes of +/- 200 to 300 ADC counts. They are not exactly 256, but in that ballpark with seems slightly suspicious.

I also show the raw data and standard deviations per test in the second plot.

Question: Does this kind of behavior - this non-statistical, spiky noise - look familliar to anyone? I'm waiting on a second gyro to compare, but that will take many days, and I'd like to see if there is anything I can do in the mean time. Each of the six channels has a very different behavior wrt noise. Inside the IC there are six separate MEMs devices each connected to its own dedicated ADC.

Script for the Raspberry Pi to read the module via I2C:

#!/usr/bin/python

import web
import smbus
import math
import time

urls = ('/', 'index')

pwrmgmt_1 = 0x6b
pwrmgmt_2 = 0x6c

dlpf_set_addr    = 0x1a
gyro_scale_addr  = 0x1b
accel_scale_addr = 0x1c

scales = 0x00, 0x08, 0x10, 0x18
dlpfs  = 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06

pairs = ((0x3b, 0x3c), (0x3d, 0x3e), (0x3f, 0x40),
         (0x43, 0x44), (0x45, 0x46), (0x47, 0x48))

setups = []
for scale in scales:
    for dlpf in dlpfs:
        setups.append((scale, dlpf))
nsetups = len(setups)

bus = smbus.SMBus(1)

address = 0x68

ic       = 0
isetup   = 0
nsamples = 400

def read_six():
    vals = []
    for ahi, alo in pairs:
        high = bus.read_byte_data(address, ahi)
        low  = bus.read_byte_data(address, alo)
        val  = (high << 8) + low
        if val >= 0x8000:
            val = -((65535 - val) + 1)
        vals.append(val)
    return vals

class index:
    def GET(self):

        global ic, nsamples
        global isetup, nsetups, setups
        global accel_scale_addr, gyro_scale_addr, dlpf_set_addr

        six = read_six()
        six_str = str(six)[1:-1]

        ic += 1

        if not ic % nsamples:
            isetup += 1
            scale, dlpf = setups[isetup % nsetups]
            bus.write_byte_data(address, accel_scale_addr, scale)
            bus.write_byte_data(address, gyro_scale_addr,  scale)
            bus.write_byte_data(address, dlpf_set_addr,    dlpf)

        return six_str + ", " + str(isetup)

if __name__ == "__main__":

    # wake the 6050 up since it starts in sleep mode
    bus.write_byte_dta(address, pwrmgmt_1, 0)

    time.sleep(0.5)

    scale, dlpf = setups[isetup]

    bus.write_byte_data(address, accel_scale_addr, scale)
    bus.write_byte_data(address, gyro_scale_addr,  scale)
    bus.write_byte_data(address, dlpf_set_addr,    dlpf)

    print "setup scale: ", scale
    print "setup dlpf:  ", dlpf

    time.sleep(0.1)

    ic  = 0

    app = web.application(urls, globals())
    app.run()


texts: Why doesn't an open-secondary transformer violate Ampere's law?

texts:
If we open-circuit the secondary winding of a transformer and put a constant current through the primary, flux $$B=\mu H$$ will be generated by the coil in accordance with Ampere's law. The flux should travel around the core even though the secondary is open, as shown below:

However, given that the secondary current is zero (open-circuit), the ∮H⋅dℓ=Is equation cannot be valid. This seems to be a paradox - what am I missing here?

Edit: An alternative, perhaps clearer formulation of the question:
Under DC at steady-state, a real transformer with an open secondary acts as an inductor - so obviously flux is generated in the primart winding; I presume this flux flows around the core, therefore there is flux through the secondary winding - so why is there no current?


texts: Sinusoids represented using Euler's formula notation, confusion

texts:
EM plane waves are represented using the equation (ignoring amplitude) $$E(x,t) = e^{j (wt - kx)}$$

They are also represented in this form: $$E(x,t) = \cos(wt - kx)$$

I want to get the electric field squared. In the first form, I set $$E^2(x,t) = e^{2j(wt - kx)} = \cos(2(wt-kx)) + j\sin(2(wt-kx))$$

Taking the real part, I get \$\cos(2(wt-kx))\$. For the latter form, I instead get \$\cos^2(wt-kx)\$, which these two do not equal.

Since, the above is false, why is it valid to represent plane waves with $$e^{j (wt - kx)}\:?$$ Performing a simple operation on this yields a false answer. It's been a while since I've worked with waves, so I've forgotten a lot.


texts:
I have a really bizarre issue here...
I'm using this 6-24v DC motor which I connect to a 18v power source. When I connect it as it is, it runs smooth and strong, high rpm. All good here! BUT once I attach a small fan to it, it suddenly runs very slowly, weak, and in pulses (not in constant rate).
This video demonstrates the problem (turn sound on to hear how weak and irregular the motor runs with the fan on it).
Can anyone explain me why this happens? How to try and solve it?
I have no idea what is happening here.
(The fan is made of 3d printed parts (PLA) and a metal sheet, and it is lightweight)


texts: Clock Configuration of Zynq Processing System

texts:
In the configuration of Zynq clock there are different types of clocks:
input clock 33.3333 MHz
Processor clock 666.6666 MHz
DDR Clock 533.3333 MHz
PL clock 250 MHz.
What is the difference between them?


texts: LTSpice Simulation - How to design pulldown with voltage supply

texts:
I am trying to simulate a circuit which should pull the supply down.

Problem here is, that the supply is a not current limited and the whole voltage is dropping accross the 0.1Ohm RC of Q4 and the voltage doesn't go down.

Is there a voltage component which behaves like the way I want to? Or what is the right way to simulate a pull down behaviour?

What I want to do, is shorten the supply with the GND when the transistor is in saturation.

Edit 1:
For the comments and Arisers answer:
After your input I saw that it would be better to name the question: How to design a non ideal voltage source and limit its current.


texts: Phone charging problem with vehicle power adapter

texts:
Let's compare 2 situations:

My smartphone is totally discharged. I plug a standard phone charger (standard 5V adapter, with micro-USB, wall adapter), then the battery increases of, say, 1% percent every 10 minutes. You can use the phone at the same time in normal conditions (messaging, but no video), it's still charging. Normal behaviour.
The same smartphone is totally discharged. I plug it on my car's "lighter adapter" with the following devices:

CAR 12V LIGHTER PLUG --> LIGHTER ADAPTER TO USB --> USB-TO-MICRO-USB CABLE --> SMARTPHONE

Then I notice, that even if I use the phone in same conditions as before (i.e. no GPS or other high-current-consumption tasks), while someone is driving (i.e. motor of the car on!), the battery doesn't charge. At best it keeps the same percentage: if battery was 5%, it will stay around 5% for hours, but no increasing charge.

Why?

Is the problem:

the car lighter power 12V adapter that has a current-limitation system (how does this work?)
the lighter-plug-to-USB car adapter (see picture before)? Do such devices include a current-limitation system?
something else?

Is there a solution: how to get a properly charging phone in car?


texts: Impedance matching for broad bandwidth voltage amplifier

texts:
I need some basic advice for impedance matching: I have a photodetector (Det01CFC from Thorlabs) that generates a current. For my experiment, I would like to amplify this signal with an amplifier. The amplifier that I can use is the LNA-1440 with an input impedance of 50 Ohm.
What kind of circuit would you use to get the best performance in terms of bandwidth and gain? For example, would it work to connect the photodetector directly to the amplifier since they seem to have a matching impedance, or do I need something in between?
Thank you very much for your help :)


texts: Can I include component supplier url in Altium Designer BOM file?

texts:
I'm new to Altium Designer and experimenting with a small pcb. Now that I've finished it I was considering ordering it at Seeed Studio and was curious about the posibilities to have it assemblied. I noticed they wanted links to the supplier pages of each component.
I suspect there must be a way to automatically include these links in the generated BOM file, since I've added all components through the Manufacturer Part Search. Yet I can't find a way how to do that.


texts: Charging two 12V lead-acid series batteries separately with one 12V solar panel

texts: I am working on a senior design project and just wanted to ensure the following charge configuration would work. I have a 12V solar panel that I plan to run its' output to TWO separate PWM solar charge controllers. Despite the vehicle running off a a 24V system, I would like to charge the batteries separately. I think that I need some sort of changeover relay to alternately charge the two 12V batteries .I think I need some control for the relay . Could I use just one PWM charge controller if I employ the relay ? Do you think that my concept will be cheaper than 2 solar arrays and 2 PWM controllers?     Just wanted some input from those who have more experience than me with solar energy. Thanks for the help and sorry for the rotated picture!


texts: How to determine potential difference of a point on a circuit relative to another point?

texts:
I know this is a simple question for many of you. But still I am a beginner in this field.So I hope it is vital to know about this.

Okay let's assume  we have a circuit like below.

In this circuit how to find the potential drop of A and B. What I know is the potential difference in resistors which are in parallel is same. Therefore I assume potential difference on the wires which the 1000  ohm and 1200 ohm resistors are placed  should be 6V, but I'm not sure whether I am correct or wrong .

I have done questions when a one point of a circuit is grounded. On such types of questions I know  the potential difference of the grounded pointn is zero, i.e I could find potential drop at any point.

But I am confused  here . Because there is no such a point. The only stuff I know is there is battery with voltage 6V. So how can I come out of this ?


texts:
Above is a connection of half-wave dipole antenna. The book states that the current profile is same at any given time instant on both the radiators, each of quarter wavelength length.

Now my confusion is clearly the coaxial cable is connected to both radiators. Say I am sending the signal through centre wire and the braid of the coaxial cable is always at ground. Now at any given time instant, only left end of the cable is going to have non zero potential, while the right end is always at 0V. Then how come both radiators would have same current profile at any given time when the excitation is different for left and right radiators!

To be very specific, say at any given time instant the voltage at the left end is 2.3V, so standing wave is generated in the left radiator, but on the right radiator the voltage is zero (braid is at ground), so how any excitation would happen don the right radiator.

Support will be greatly appreciated. I am a total newbie in antenna systems.


texts:
We are trying to control a bunch of 3 phase contactors using an HMI. The contactors' coils are activated by two lines of the 240V 3 phase source (L1 and L2).

We are trying to figure out if the relays needed for activating the coils should be rated at 120V or 240V, or if we need another type of relay.

We did a test with 120V relays(SSR) but one of the contactors' coil burned out after leaving it connected(OFF State) for about 3 days, we measured for current leakage on the relays but we didn't get any measure. We did another test measuring the current with a manual activation using a button an we get a reading of 70mA when contactor is ON.


texts: What is the meaning of "ground" and "-V" in a simple push-pull circuit?

texts:
In this simple "push-pull" circuit, there are +V, -V and ground connections.
up until now, i always considered ground to be the minus side of the battery.
but that is also the way i understand -V, so i don't see how current would flow through the PNP transistor from ground to the -V

If i am using this circuit to drive a simple DC motor forwards(push) and backwards(pull) with a battery
what would the -V and ground connections mean ?


texts: Unexpected Resonance in LTSpice Op Amp Circuit

texts:
I was simulating a circuit similar to the one shown in the schematic below (educational, but not for school), and noticed the peak in the Bode plot at around 100 kHz. The circuit shown has been slightly reduced from the original, which is why it seems somewhat pointless, but still displays the same unexpected behaviour (details of original don't seem relevant, but are available upon request).

At low frequencies, I expected the capacitors to act as opens, so the circuit would reduce to a unity gain non-inverting amplifier. At high frequencies, I expected the capacitors to act as shorts, reducing the circuit to a voltage follower. Both of these extremes match the simulation, but I'm failing to come up with an explanation for what appears to be resonance at 100 kHz.

Switching to an ideal single-pole op amp eliminates this artifact, but it is present other op amp models, so it is not unique to the LT1001. Other models yield different frequencies and magnitudes, but the spike is still present. For reference, the most realistic model I have prior exposure to is a finite-gain single-pole op amp.

Can anyone shed some light on this simulation result? What nonideality is responsible?


texts:
I'm trying to build a generic IR remote controlling device using an arduino.

I've done some investigation to discover the IR protocol used by my NAD SR8 remote controller.

I've connected a simple IR photodiode to an oscilloscope in order to dump the signal coming from the remote (VOL UP key).

I got the following:

This signal looks like a NEC IR protocol regarding the documentation. I've decoded the signal:

1110 0001 0011 1110 0001 0001 1110 1110

I don't know why but this signal does not fully comply with the protocol specification:

[1110] 0001 [0011] 1110 0001 0001 1110 1110

Am I wrong somewhere (wrong protocol) ? Is the remote controller broken ?


texts:
I am designing a counter circuit that will perform the following function:

A sequential circuit with three flip-flips A, B and C and two inputs X and Y.
If X=0 and Y=0, the counter remains in the same sate.
If X=0 and Y=1, the circuit goes through the state transition from 000, 001, 010, 011,100,101, 110, 111, back to 000, and repeats.
If X=1 and Y=0, the circuit goes through the state transition from 111, 110, 101, 100, 011, 010, 001, 000, back to 111, and repeats.
If X=1 and Y=1, the counter reset to 000.

I'm a little confused about the two inputs 01 and 10, and how to account for the inputs to JK.


texts:
As someone with no background in electronics whatsoever, I wonder:
why are ICs packed inside ceramic or plastic?  I thought we wanted the heat to go out as fast as possible, and ceramic is a good thermal insulator.


texts: Missing steps to simplify this complex impedance

texts:
The problem is:
complex imped http://imagizer.imageshack.us/v2/640x480q90/673/tgoToD.png

How would you you simplify the equation to get down to \$716.97 - j450.47\Omega\$? I tried  multiplying by the conjugate but that doesn't work.


texts: Time taken by power supply to reach output voltage

texts:
My question is regarding programmable power supplies. If I send a SCPI command to the power supply using USB/RS-232 or some other serial communication, how do i know the time taken by the power supply to reach the programmed voltage or time taken by the power supply to interpret the command.

Is this parameter usually mentioned in the data-sheet of the power supply?
I am planning on renting a power supply which can turn off and turn on remotely within 4 msec, so i want to be sure that the power supply which i rent has that feature before i put my money down on it.

The power supplies I'm looking at are:

Sorensen XG60-28 DC Power Supply, 0-60V, 0-28A,1700W
Keithley Series 2260B 360W
Tektronix PWS4305

Update: Found an example of what I'm looking for:
RIGOL DP800A Series Programmable Linear
DC Power Supply1

I need some similar timing parameter which can process the command in less than 1 mSec


texts: battery enclosures - i am not geting the hang of it

texts:
I find it so hard to search for some casings for my board...

Why are the battery casings so rare ? I must be missing something.

Other questions

Will this case fit 2 AAA batteries ? how do I generally find out ?
http://www.tme.eu/en/details/g500b-bc/multipurpose-enclosures/gainta/g500bbc/

This one seems to be missing the battery compartment altogether. It only has a small cap for quick access to some batteries but nothing else. What would I need to buy together with this casing ? (looking to fit 2 AAA into it)
http://www.tme.eu/en/details/z-55/multipurpose-enclosures/kradex/z55/


texts: What is this wire out of an smps transformer?

texts:
I have a PSU that has the same transformer. so what is that wire for?

edit: looking at PCB traces it seems to be connected to the pin of the heat sink
could it be for thermal purposes?


texts: ADC wire is picking up noise from cellular antenna [EMC]

texts:
I have a 5 wire micro jst cable with a line for ADC readings from an IR sensor that is picking up interference from the cellular antenna of the microcontroller. Will I be able to reduce this noise if I use a USB cable with grounded shielding? What is the best way I can reduce this interference noise?

Thank you!


texts: How to solder qlpf48 (or how to fix it)?

texts:
I think I'm really not so good at soldering.

All places say it's it's fairly easy to hand solder LQFP ICs, but for me it isn't... On videos the tin nicely melts between the pins, and do not create solder bridges.

I tried today a board with 0802, 0603, 0402, SOT23 and SOIC16 and at least under a microscope (cheap one) it looked not great, but good enough. I couldn't measure everything but all 0802, 0603 and 0402's were soldered ok.

Than I tried my (sub) goal: to solder a LQFP48 (STM32F103) on an adapter board and this went horribly wrong.

I used my rework station to have it removed, which worked, but I doubt I can use both the IC and adapter board again. Also, I couldn't make any useful picture.

However, I maybe you can give some advice what to do better next time, and maybe how to fix it. I have a clue: I think I use too much solder, but it's so hard to know how much to use (or when there is accidentally a bit too much on the soldering tip).

What I do is:

I use 0.5 mm solder iron (with lead)
I use a fairly small wedge type tip
I used quite some flux (flux pen)
350 degrees Celcius (650 degrees fahrenheit)
Put a bit of solder on the tip
Put it on the adapter board
Tack the first pin
Slide as carefully as I can from the yellow spots in the picture below, outwards. However, this results sometimes in a soldering bridge between two (or more) pins, i.e. the yellow spots (which extend over the pins itself which is ok, but not between the pins).
Sometimes I create accidentally solder bridges at the red spots. This is even worse, as they are 'higher' above the adapter board.
In all cases, I cannot use my soldering iron to remove it; the solder just will not find its way to one of the pins (especially near the red bridges)

I tried solder wick, but as the yellow spots are lower than the pins, it doesn't work. For the red solder bridges it's even worse as they are higher.

Another problem might be that the tip 'wiggles' a little bit, however the solder fairly easy melts (and I could do the practice board without any problems).

I don't mind if I ruin 1 or 2 ICs now, however I want later to order PCB's where I want to solder STM32's onto (or at least one on a board), so at that time I hope I be able to.

Below are (as requested) pictures of the solder tin I use and flux pen (both chinese).

The solder tin has the following description: 0.5 mm, 63/37 solder flux 2% Rosin core.


texts:
I am very new to wireless communication protocols so please excuse me if this is a silly question.
I am using a PIC to communicate between two Zigbee modules. However I also own a 2.4GHz RF transceiver module. Would it be possible to use the RF transceiver module to read the data coming from the Zigbee module?

The Zigbee module is the MRF24J40MA
The RF transceiver is the nRF24L01P RF transceiver chip with 2.4 GHz chip antenna.


texts:
In Melbourne, Australia I see a lot of utility poles like the one in the picture below. There are power lines on two levels. Three lines on the top level and four lines in the lower level.

I assume, that the lower level carries the three phases of AC plus the neutral line. From the lines on the lower level, all the lines to individual premises branch off, so I assume that these lines carry 230/400 V.

As there are only three lines on the top level, I assume, that these are the three phases of AC at a higher voltage. Is this the case?

Bonus question: Is the box at the top level a switch to disconnect the top-level power line?

After my question has already been answered, I will nevertheless answer my own question. A couple of streets from where I took the initial picture, there is a utility pole, which would have answered my question all by its own.
It even features the fuse holders mentioned in the accepted answer to my question.


texts: Simultaneous sampling with ADC - Portenta H7

texts:
I am a beginner in Arduino programming.
I want to acquire two analog signals using an Arduino Portenta.
In the technical specification of the Portenta H7, it mentions that it has 3 ADCs. Since 1st analog read command consumes some time before reading the 2nd analog read, how do I get away with the time-gap between the reading of these two analog signals? What should I incorporate through code that it will dedicate 1st ADC for 1st analog signal acquisition and 2nd for the 2nd sensor so that both of them are processed at once?


texts: My application requires a energy meter so i interface a ATM90E32AS energy meter IC with dsPIC microcontroller. when i gone through the data sheet it was really confusing about power calculation. As per the data sheet power registers are 32 bits wide. There is MSB register and LSB register for active/reactive/apparent power. My confusion is whether MSB and LSB of power registers are 32 bits wide each or both MSB and LSB of power registers combinedly 32 bits wide? And what is complement means which is shown in the comment section? The power register values are attached as image.


texts: Voltage protection with 555 timer not working

texts:
Briefing

I am using Multisim to simulate a circuit before building it.

The voltage protection circuit with a regulator works fine and the timer circuit works fine as well separately. When I try using the output of the protection circuit as input for the timer Multisim gives me an error.

Circuit Functionality

When an input is supplied to the voltage protection circuit only if the input is equal or greater than 47V should it activate and supply the regulated 14.5V coming from U4, next this input is used as a trigger for the timer as long as this voltage protection output is high the timers LED is active, should the voltage protection circuit go low the timer waits a few seconds and then the output goes low.

Please note, everything as I said works, the voltage protection alone and the timer works as intended but when I try to combine the two circuits is where it fails.

This is the voltage protection circuit:

This is the timer circuit:

This is the full circuit when I try to combine

This is Multisim error


texts: On the wikipedia page Board support package it mentions the term "boot line". What is the meaning of "boot line"?


texts:
I need some explanation about Shaded-Pole Motor.

In the book: "Electric Motors and Control Systems" by Frank D. Petruzella (published by McGraw-Hill), in Chapter 5, Part 4, on page 113 under "Shaded-Pole Motor" it is written that:

  Unlike other types of single-phase motors, shaded-pole
  motors have only one main winding and no start winding or switch. As in other induction motors, the rotating part is a squirrel-cage rotor. Starting is by means of
  a design that uses a continuous copper loop around a
  small portion of each motor pole, as illustrated in Figure 5-51. Currents in this copper loop delay the phase
  of magnetic flux in that part of the pole enough to provide a rotating field. This rotating field effect produces
  a very low starting torque compared to other classes of
  single-phase motors. Although direction of rotation is
  not normally reversible, some shaded-pole motors are
  wound with two main windings that reverse the direction of the field. Slip in the shaded-pole motor is not a
  problem, as the current in the stator is not controlled
  by a countervoltage determined by rotor speed, as in
  other types of single-phase motors. Speed can therefore
  be controlled merely by varying voltage, or through a
  multitap winding.

But when looking on the motor I have, it seems that copper wire is circulating through whole main winding, instead of only part of it. So how is it that additional magnetic field can be generated, to turn the rotor into motion?


texts: Total inductance of two parallel aiding inductors

texts:
The voltage across the two parallel aiding inductors above must be equal since they are in parallel so the two currents, i1 and i2 must vary so that the voltage across them stays the same. Then the total inductance, \$L_T\$ for two parallel aiding inductors is given as:
$$L_T=\frac{L_1 L_2-M^2}{L_1+L_2-2M}$$

But, if the two inductances are equal and the magnetic coupling is perfect (\$M=k\sqrt{L_1 L_2}\$, where \$k=1\$ and \$L_1=L_2=L\$), using the formula above we get:

$$L_T=\frac{L^2-L^2}{2L-2L}$$

and my workbook says we should get \$L_T=L\$.
What am I missing?


texts: Measure picofarad capacitances accurately

texts:
I need to measure or sense capacitance from 0 pF to 5pF, with an accuracy of 0.1pF or better. I know capacitance to digital convert chips claim to do that, but is there a simpler/easier way to breadboard a circuit to measure these ultra-low capacitances?

I have a small concentric cylinder where the outer cylinder is physically fixed (and tied to some potential) but the inner one is moving in and out. It's this movement I need to track. The change in overlapping area between the two cylinders produces a change in capacitance. In that way, I keep track of its position at all times by monitoring the change in capacitance.


texts: How do solar panels affect the short circuit fault currents of a network?

texts:
As title suggests, I'm trying to find out how adding PV, both residential and solar farms, have an effect on the short circuit fault current of a network.

I wasn't given much info to go off, so I am going to say that it would be an inverter fault. This is for more of a general case, so if there is a rule of thumb for the fault levels that would be great.

If not, looking mainly at fault levels that might be seen at a residential setting, as well as at 150MW plant.

If the inverter fault is smaller than some other fault associated with a solar pannel, please let me know.


texts: What's wrong with my amplified ear circuit?

texts:
Good day! I just want to ask what's wrong with this circuit?
Since the livewire doesn't have a microphone component, i replaced it with an AC source since our goal is to amplify the signal.
It's odd because when I simulate the circuit the output is distorted.

Hope you can help me.

Edit:

This is the circuit I used:

www.talkingelectronics.com/projects/HearingAid-2/HearingAid-2.html

UPDATE:
I tried to fix the circuit based on the comments. It seems that the input and the output is not pulsating. From what I know, this is supposed to amplify and not distort the output waveform.

//---------------------------------------------\

UPDATE:
I've added a link for the project file.ProjectFile


texts: What amount of current should I use to charge a 12V car battery?

texts:
I'm planning to use two 12V car batteries in series for running 24V motors. Presently, I'm planning to charge them individually or parallel with a 12V DC adapter. I was going to buy the one with the highest power rating (400W) to charge quickly, but I heard it hurts battery life to run that much current (33A) at a time.

Doesn't an alternator push even more current (~50A at idle engine revs) when it charges the battery?
Either way, if 33A is too high, how much current should I be aiming for? My battery capacity will be about 80-90 Ah and I plan to use discharge 20-30 Ah per cycle. I'd ideally like 1 battery recharged (30 Ah) in 2 hours max.

Any help would be appreciated. Thank you.


texts:
Last night I pulled the battery holder out of a toy RC car to test the voltage with my meter.  The pack has 4 AA batteries.  The combined voltage at the terminals of the pack was well under 1 volt, and then I tested each battery individually.  These are ordinary AA alkalines (not rechargables).  They were in good condition, with no leakage.

The first two batteries showed about 1.2V; the third had a small negative voltage, about -0.2, which I thought was pretty interesting, and the last showed about -1.2v.  I have never come across a negative voltage on a battery.

Now before you ask, yes, I double-checked, and then triple-checked, that my leads were plugged in correctly.  And I was not holding the batteries upside down.  I had all four right in front of me, all pointing the same way.  Two showed a positive voltage, one slightly negative, and one -1.2v.  I did this repeatedly,

So my question is, what the heck?  How does a battery get a negative voltage on it?  The pack had been in the RC car for a couple of weeks, with the car switched on.  I think, but cannot prove now, that they were all inserted the right way in the holder.  But even if one or two were in backward, how could this happen?

Now the batteries are Canadian, and my meter was made in the USA, but I don't think that explains it.  [That's just a joke.]


texts: VHDL configuration: Selecting architecture

texts:
I'm learning the use of configuration statement. For this I've created a top level entity not_gate and an architecture structural. I've also added another vhd file to this program, and that vhd file (notgate) has a single entity and two architectures. I want to choose a specific architecture from the pair. To distinguish between the two, I've decided that the behavioural model of notgate will perform just like a buffer.

not_gate.vhd:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity not_gate is
    Port ( NI : in  STD_LOGIC;
           NO : out  STD_LOGIC);
end not_gate;

architecture structural of not_gate is
COMPONENT notgate IS
Port (  invin : in  STD_LOGIC;
        invout : out  STD_LOGIC);
end COMPONENT;
begin
INV: notgate PORT MAP (NI,NO);
end structural;

CONFIGURATION config1 OF not_gate IS
FOR structural
FOR INV: notgate USE ENTITY WORK.notgate(notarch);
END FOR;
END FOR;
END config1;

The vhd file notgate was added to this.

notgate.vhd:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

ENTITY notgate IS
PORT (invin : IN STD_LOGIC;
        invout: OUT STD_LOGIC);
END ENTITY notgate;

architecture notarch OF notgate IS
BEGIN
invout <= NOT invin;
END ARCHITECTURE notarch;

architecture notbeh OF notgate IS
BEGIN
PROCESS(invin)
BEGIN
IF invin = '0' THEN invout <= '0';
ELSIF invin = '1' THEN invout <= '1';
ELSE invout <= 'U';
END IF;
END PROCESS;
END ARCHITECTURE notbeh;

When I run not_gate.vhd, according to the configuration statement I wrote, the architecture notarch must be selected from notgate.vhd and the NOT operation should occur. However, it seems that vhdl is still selecting the last compiled architecture, that is, notbeh. Thus, the NOT operation doesn't occur. The configuration statement doesn't seem to be working. Could someone tell me where  went wrong?


texts: How to surpress coupling between two circuits

texts:
I have the following setup:
2 piezo transducers are placed 0.7 meter apart from eachother in water facing eachother. 1 piezo (PA) acts as the sender, the other piezo (PB) acts as the receiver.
PA sends periodically a pulse that the receiver picks up. The pulse gets generated by a microcontroller switching a MOSFET according to the following circuit.

With the send pulse:

PB receives the pulse and is connected to the following amplifier circuit.

With the amplified receiving trace:

The two circuits are only connected to eachother through earth (microcontroller + send-circuit are supplied by a 230V AC to 5V DC converter, the receive-circuit is supplied by 2 benchsupplies).
Extra logic is added so I can detect if the pulse arrives or not. This works, however I seem to get coupling on my scope image from PA onto PB. For now I filter this away in my code but I rather fight the cause instead of the symptoms.
As you can see, the send pulse also is visible on the receive trace (the left most pulse). Both traces are captured with the same scope, though at different times and with only 1 probe connected.
Is there a way to surpress this signal? Later on, the setup will consists of more piezo's as well as both sending/receiving capabilities and I rather keep crosstalk (?) to a minimum.
EDIT:
Following the questions in the comments:
1) Are you sure that the coupling is electrical and not, say acoustic ?
=> Yeah I'm pretty sure that it's electrical. If I connect both probes the left most receiving pulse is at the same time as the send pulse. If you take the time difference between both pulses (around 476us) and the speed of sound in water (1480 m/s), you can calculate the distance between the 2 piezos x = 1480 * 476e-6 = 70cm

(upper is receiving, lower is sending)
2) Why is the send a pulse and not a sinusoid ?
=> I'm still tweaking the send pulse circuit. I send a single pulse as the setup is to detect if something (fish) goes through the circle (only 2 piezos at the moment at the diameter). Hence receiving a pulse is nothing in between, not receiving a pulse is something in between. The setup is NOT for transmitting data.
3) Is the output of the micro controller on the send side a single pulse or a a sequence of pulses tuned to the resonant frequency of the piezo transducer ?
=> It's a pulse of 40us at the moment.The pulse gets created on the down slope.

4) Are they immersed in water ?
=> Yeah they are immersed in water. Not deep at the moment but later on this will be in the meters.

(Left is receiving, right is sending)
5) Are the leads to the transducers well insulated from the water ?
=> No! The leads are not shielded. So maybe some electromagnetical interference? I also think they are not twisted, it has a housing around it. I will pry one open to see further.
Also the water is rainy water, with apparently some algaea too.


texts: On this problem, why are they disregarding the collector for the KVL?

texts: I've tried this problem 3 times before looking at how the professor solved part (a), and every time I keep coming up with the same KVL equation. Why is my KVL wrong?


texts:
I need your help

Given:

AC beta (Bac) = 160
Ie = 3.8 mA

Find :

a) Rin (TOTAL)

b) Rin (BASE)

c) Av (voltage gain)

I am uncertain of the process.

I have Rin (Base) = Rs + R1||R2 or is it the Rin (total)? If not, where is Rin (total)?

Then I compute for Ib = Vs/Rin(Base)

Substitute Bac = Ic/Ib values to compute for Ic

Then formula for re'=25mV/Ie

Then c) Av = Rc/re'


texts: Frequent supply switching for a microcontroller

texts:
I want to create a LED chaser using pic12f683. The operation will be using a push button to turn on the uC.

Once the uC gets power it first of all incremennts a variable and writes it to the EEPROM. This variable defines from which point to start the sequence of the LED flashing program so that every power up it starts from a different point. I got 13 flashing modes in the program.

The uC will be on and keep flashing LEDs as long as the button is held.

I'm wrorried that the frequent and maybe very short pushes on the push button might damage the uC. Especially since the first thing it does is reading and writing to the EEPROM.

Ive implemented a 30ms delay before the read/write operation at start up as recommended. This is with the power up timer disabled.

Also I thought about putting a large capacitor in parallel to the battery supply so that VDD will fall a bit slowly.

How bad this design is to the uC?

Is it still really bad with my solutions?

What else should I do about it?

How to figure out a good value for the large capacitor if it is a decent solution?


texts: PWM 12V DC motor using lower supply voltage for lower speed operation?

texts: I am using a 12vdc PWM to control the speed of a 12vdc motor that can draw up to 25 amps of current. The speed I usually run the motor is at the very low end of the PWM which makes it very sensitive when controlling the speed. Can I reduce the voltage going into the PWM so the output range is between maybe 0 and 7 or 8 volts instead of 0 to 12 volts? Will this damage the PWM or the motor?


texts:
I have two 12v DC motors sharing the same input power supply connected in parallel sharing and spinning the same load thus splitting the work.
How can I attach an LED to each motor to inform me that each motor is indeed powered up and is running, but more importantly allow me to see if a particular motor is not active and needs service?
Each motor when powered up reaches a max current draw of about 2.5 amps.
I thought about running an led in series with a input connector on each motor thus giving me the status information I'm looking for but as we all know a led cannot handle a 2.5 amp current following through it. So I quickly steered away from that idea.
As you can see I'm a little stuck. Thus any help would be greatly appreciated and thanks in advance.


texts: How do I use the printf function on STM32?

texts:
I am trying to figure out how to use the printf function to print to the serial port.

My current setup is STM32CubeMX generated code and SystemWorkbench32 with the STM32F407 discovery board.

I see in stdio.h that the printf prototype is defined as:

int _EXFUN(printf, (const char *__restrict, ...)
               _ATTRIBUTE ((__format__ (__printf__, 1, 2))));

What does it mean? Where is the exact location of this function definition? What would be general point of finding out how to use this kind of function to output?


texts: Continuous Reset generated by LDO to Microcontroller

texts:
I have the below schematic

Datasheet of the LDO - L4995 -SSO24 package

LDO Specification :

Input Voltage : 12-16V
Output Voltage : 5V

Load Current : 100mA

Issue :

My LDO is generating RESET pulses continuously.

Objective:

I am trying to program my microcontroller initially. But since, the RESET is continuously generated by this LDO, my debugger is not able to program the microcontroller.

Steps taken :

I removed the R2705 resistor. My microcontroller cannot provide the watchdog pulse since it has not been program yet.

I tried removing the C2704 capacitor, C2703 capacitor each one at a time and tested. But still RESET is generated.

Below is the waveform obtained after removing R2704 and C2704.

Measured at pin 19, 20 and 21.

Questions:

What is the reason? Like the time period and the delay are set by the capacitors C2704 and C2703. Without that also, how is the LDO generating a RESET? Can someone please explain.
And, what should I do to make the RESET line high so that I can program my microcontroller through the debugger?


texts:
I'm trying to control five * 5v relays from a micro-controller. However I'm having issues powering more than two at a time

Some notes

The power source is a 800ma 10V ac adapter.
7805cv voltage regulator
The relays are 5v relays. (Data sheet here - http://www.mantech.co.za/datasheets/products/NT73-NFWD.pdf)

Here is the circuit

I can power two relays but any more and they wont switch. I get the same result without the PIC, i.e. if I just provide 5v to the transistor or even the relays directly.

I have three concerns

Should I be using a resistor in series with the relay?
Why can I not power more than two at a time?
I suspect my diodes are in the wrong place to protect the pic?

Thanks


texts: Multiple power supplies of different current ratings for efficiency

texts:
I've got a 30V 2A isolated DC/DC supply. I need to be capable of outputting 1A for short periods of time (3 sec, exception condition only), so with temperature derating that's what I picked.

However, in normal operation the current draw is only 20-60mA.  The poor efficiency of this is really bothering me.  (It's like 10%)

How much trouble would it be to use two 30V supples, one for say 150-300mA and the other this 2A supply, and switch between them as the current needs change?  How to best handle the transition?  If using FETs, should I swap the FETs at the same time and depend on caps to carry the current during the transition?

I can handle maybe 500mV droop as it swaps. Limiting at 150mA for a few hundred milliseconds while the 2A supply comes up is also okay.

EDIT

Okay, so here's a bit more detail. I'm controlling a network of devices. Depending on the number of devices, this can draw anywhere from 20-300mA. Most configurations would probably be around 60mA.

If there's a short somewhere on this network, the devices can disable sections of the network to work around the short... but they require about 1A for 3 seconds to detect this condition. This test would reoccur periodically to detect when the network is restored. The devices are someone else's product and so the behavior can't be changed.

EDIT 2

Sorry, input voltage range 9-36V nominally 24V.


texts: Trouble applying water pressure analogy to electrical circuits

texts:
I am preparing a lesson plan on voltage for a class and it's been a while since I've studied electronics. I like to use analogies to help students understand concepts that are often hard to grasp.

Currently (npi), I am trying to describe how voltage is analogous to water pressure and how resistance is the obstruction of water flow. By partially covering a water hose's opening thereby creating resistance, the output water pressure increases, but the amount of water flowing is the same. The analogy, however, seems to fall apart when you consider that adding a resistor in series decreases the voltage, but the current increases. Moreover, if I connect a Y hose fitting to the water hose, creating a parallel connection, the output water pressure decreases, but in a electrical circuit the voltage is the same.

Is my understanding correct? If so, how can I explain voltage in terms of the analogy?


texts: Reduce overshoot and undershoot of square wave (trigger signal)

texts:
I am testing my FPGA board (spartan 6) by taking external trigger signal (square wave 5V 50%.)

The rising edge of the signal is shown below with overshoot and undershoot, so my FPGA can not detect the trigger.

Any advice about method or technique to reduce theis overshoot and undershoot? I would like to do it in hardware by adding some IC or filter.


texts: VHDL: Convert std_logic to std_logic_vector

texts:
I'm trying to make a 4 bit adder with carry in & out, but I am having trouble converting Cin (Carry-in) to the type std_logic_vector when summing Sum and Cin together below in the architecture.
Do you have any idea how i can make these types fit so that I can perform arithmetic on them together?

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity four_bit_adder_simple is
        port(
                A, B : in std_logic_vector(3 downto 0);
                Cin : in std_logic;
                Sum : out std_logic_vector(3 downto 0);
                Cout : out std_logic);
end four_bit_adder_simple;

architecture unsigned_impl of four_bit_adder_simple is
    signal total : std_logic_vector(4 downto 0);
begin
        Sum <= std_logic_vector(resize(unsigned(A),5) + resize(unsigned(B),5));
        total <= Sum + Cin;
        Cout <= total(4);
end unsigned_impl;

EDIT: It was an error that I made Cout a 2 bit std_logic_vector. It should just have been a simple std_logic.


texts: maximum distance between IC power pins and decoupling capacitor

texts:
Since I introduced decoupling caps to my design, my auto-routing progress has dropped.

Currently my PCB track width is set between 0.24mm and 0.26mm (I'm trying to aim for 0.26mm depending on how routing goes).

What I want to know is what is the maximum distance allowed between an IC VCC/GND pins and the decoupling cap before performance of the IC degrades? I'm told to keep the capacitor as close to the IC as possible but when doing a single-sided board with the fewest jumper wires possible, keeping it ridiculously close is impossible.


texts: How to replace a monitor proprietary DC connector?

texts:
My Samsung S23700D (120Hz / 3D PC Monitor; 14V / 4A) has a loose DC connector, which caused the monitor to randomly turn off. After a lot of tinkering, the middle part of it broke : in short, I have to replace the DC connector. The problem is that I can't find a replacement online nor desolder the connector.

My idea is to directly solder on the board one end of a DC (2.5mmx5.5mm) cable, as well as replace the original male DC plug of the power source.
My soldering iron (48W), even at max power, damages the plastic but doesn't remove the solder on the board. I don't have much practice with soldering, but the solder I usually use (tin-based) easily melts. I also thought about breaking the connector, as a last resort.

How should I proceed? All suggestions are welcome.

Note that the DC connector has a 6.1mm OD with pin center, based on the male plug. It seems to be a proprietary format.

The original DC plug and the parts I intend to use:


texts: What do i need to look out for when selecting components?

texts:
I'm pretty new to electronics as a hobby - been picking it up on and off for the past 2 years or so - and there's always one thing i always stumble and doubt myself on, how do i select components?

For example, I am currently looking for triacs to switch mains AC voltages, I originally ordered some T3035H-6T's but cancelled the order after seeing This question where the asker (seemingly trying to accomplish the same goal) has decided to use BT136's, which made me doubt my decision.

I have done the same before when buying Mosfets, and basically any transistor i have ever gone to use, is there are real, tangible difference when selecting components like this? when i look at the datasheets for the respective components i am seeing little difference between the two (obviously this wont apply across the board, but for the pair i have given as examples), does this mean they are basically a pair of components that are freely interchangeable between?

Am i being stupid and reading the datasheets wrong, or are my assumptions correct?


texts: When is it theoretically possible to fit PCB circuit on x Layers (emphasis: x =1)

texts:
When is it theoretically possible to fit a given circuit on a certain number of layers?  (Presumably PCB layers.)

What is/are the name of the mathematics/algorithms that might determine this, or what are some implementations that will determine this for you?

I know this may not be the most immediately practical question, but this pertains to when it can be done.


texts: Spark when connecting battery module to DC power supply

texts: I am using a 60v DC power supply to charge a 48v battery module. I set current and voltage limits first, turn off the DC power supply, connect positive to battery's positive side. When I try to connect the negative side there was a spark, I wonder why it happened and how do I get rid of it.