texts: Why are two capacitors used in capacitive wireless power transfer instead of one?

texts:
I am an engineering student.  I am studying wireless power transfer (WPT) theory.
I understand that from a theoretical point of view it is possible to do capacitive wireless power transfer using a single capacitor, so one plate is used as a transmitter and the other one as a receiver.
In some scientific papers I've seen circuits having two capacitors placed in parallel, so we have two transmitting plates and two receiving plates.
Why this choice? In order to support a larger amount of power?
I've attached an image as example, where P1 and P3 are the transmit side and P2 and P4 are the receive side.
The human skin tissue is the dielectric of these capacitors.


texts: How many amps does a 18v cordless drill draw?

texts: I have bought an old 18v black and decker cordless drill but with broken batteries, for that, I want to buy a boost converter to convert 12v (max 20A ) from a computer power supply to 18v and use this drill as corded drill, but I need to know, how many amps does an 18v cordless drill draw to choose which boost converter to buy 200w 300w 400w ?


texts: Opto-isolation amplifier giving no output

texts:
First of all, thanks to the community for having such helpful answers here - don't post very often but here's one I could really do some help with.
I want to measure a voltage range of 0-100V DC in an isolated manner and using an Arduino Uno. I've got a HCPL 7520 (datasheet) and created an initial test circuit with just 5V input but I'm getting no output. I've got a voltage divider to bring the 5V down to the +/- 200mV range and chosen resistors to bring the current to ~10mA (which is less than the 20mA max).
But whenever I measure voltage between VOut and Vdd2_Gnd, I get 0V. I'm no expert so any advice would be much, much appreciated !


texts: Using BLE, how fast can I get ~50 bytes of data from the master to a slave? How does that change when increasing the number of slaves present?

texts: In personal project of mine I'm looking to have a system where a number peripherals need to have provided to them, in as real-time as possible, small (~50 bytes max) amounts of information from a central controller. I was considering using low power Bluetooth for this and I'm wondering what kind of performance I could expect. How many times per second could I send this 'packet' of data if there was only one peripheral? What about if the number increases to, say, ten?


texts:
I designed an H-bridge that must operate off of 12 volt supply, I have a 2 volt motor I need to power, I was wondering with the TIP120 and TIP125 VBe drops of 5 volts each that it would operate the motor safely? Or would I have to redesign or how would I guarantee 2V output without sacrificing current capacity?

sorry I cant post a schematic not enough rep... but I used two TIP120's and two TIP125's with a 3904 driving the TIP125's from microcontroller output

err I guess I should be looking at VBe(on) which is 2.5 volts not 5V each so the output should be around 7V...? not sure how I can run the motor I plan on using PWM also


texts: VHDL assignment and condition at the same clock edge on parallel processes

texts:
Suppose that I have two processes in VHDL: One process is triggered on the rising clock edge and it is a state machine that sets a flag in one of its states. The second process is also triggered on the rising clock edge and it has a condition statement that reads this flag to see if it is '1'. When will the condition in the second process become 'true'? On the same clock that the flag is set, or at the next clock?

Here is an example:

-- state machine
process (clk)
begin
    if rising_edge (clk) then
        case StateMachine is
            when '0' =>
                flagA <= '0';
                StateMachine <= '1';
            when '1' =>
                flagA <= '1';
                StateMachine <= '1'; -- loop forever
        end case;
    end if;
end process;

-- condition
process (clk)
begin
    if rising_edge (clk) then
        if (flagA = '1') then
            flagB <= '1';
        else
            flagB <= '0';
        end if;
    end if;
end process;

In this example, will flagB become '1' at the same clock that flagA became '1'? Or will flagB become '1' at the next clock?


texts: Why are the inputs of an ideal op-amp "inverting input" and "non-inverting input"?

texts:
Here is the first ideal op-amp circuit, called an "Inverting Amplifier", that many students will encounter:

The gain here is \$G=-\frac{R_F}{R_{IN} }\$. Thus, with a negative gain, \$V_{OUT}\$ is inverted with respect to \$V_{IN}\$. Also, since \$V_{IN}\$  goes into the inverting input, this all makes sense.

Now, if we flip this all around like this:

For this circuit, \$V_{IN}\$  goes into the non-inverting input. However, the gain still has a negative sign: \$G=-\frac{R_F}{R_{IN} }\$, and \$V_{OUT}\$ is still inverted.

So why is this called the inverting input?

Solving the lower circuit, incorrectly:

$$ I_{IN} = I_F$$
$$ \frac{V_{IN}-V_+}{R_{IN}} = \frac{V_{+}-V_{OUT}}{R_{F}}$$

$$ \textrm{If } V_{+} = V_{-} \textrm{ , as is true by definition for an ideal op-amp, and } V_{-} = 0, \textrm{ then } V_{+} = 0 \textrm{ thus } $$

$$ \frac{V_{IN}}{R_{IN}} = \frac{-V_{OUT}}{R_{F}}$$

$$ \frac{V_{OUT}}{V_{IN}} = -\frac{R_{F}}{R_{IN}}$$

What's wrong with this circuit analysis?


texts: Why USB 2.0, USB 3.0, PCI signals must be routed in 85E differential ohm impedance and not 100E impedance?

texts:
USB 3.0 and USB 2.0, pci signals, Why its always recommended to route at 85E impedance and not 100E impedance?
Below are the signals to be routed at 85E
D− (USB 2.0 differential pair)
D+ (USB 2.0 differential pair)
StdA_SSRX− (SuperSpeed receiver differential pair)
StdA_SSRX+ (SuperSpeed receiver differential pair)
StdA_SSTX− (SuperSpeed transmitter differential pair)
StdA_SSTX+ (SuperSpeed transmitter differential pair)


texts:
I learned that the transition faults model checks whether data transition meets the clock or not

  Transition Faults : Assumes large delay defect concentrated at one
  logical node, such that any signal transition passing through this
  node will be delayed past the clock period.

Question is "This was already taken care of in timing convergence during the design cycle, is this same as post-silicon timing check? And can we reduce the frequency and make chip work in case of delay fault"


texts: Both transmission gates and triacs can be used as an analogue switch, but I am a bit confused about what the difference would be in using them for a design. Is one better at higher current situations or if one is better for using in low voltage conditions, or am I completely missed the point of the two devices.


texts: I was thinking about buying a thermistor and a RGB LED and thereby be able to change the light of the LED, but I'm confused by the resistances I see on eBay. I see some of 100 ohm, 10k ohm and 100k ohm. What do these resistances mean, and what should I use for my circuit?


texts: Do kinetic energy and inductor energy violate conservation of energy?

texts:
I posted this question on the physics page. I feel like it might be better suited to this site, though.
Suppose we have an ideal LC circuit (no resistance) and an open switch where the capacitor has an initial voltage \$V_o\$.
Initially, the energy stored in the capacitor at \$t=0\$ is \$\frac{1}{2}CV_o^2\$ and the energy in the magnetic field of the inductor is zero because no current is flowing.
Now at time \$t=0+dt\$ we close the switch and current slowly begins to build up. When the current is a maximum, the energy stored in the magnetic field of the inductor is \$\frac{1}{2}LI^2\$ but now the energy stored in the capacitor is zero.
Thus we must have that \$\frac{1}{2}LI^2=\frac{1}{2}CV_o^2\$ because no energy is dissipated since there is no resistance.
There seems to be something very wrong here at a fundamental level. The charge (the electrons) traveling through the inductor at the instant that the current is a maximum have a non-zero kinetic energy (denote this kinetic energy \$K_{charge}\$.) They have to have non-zero kinetic energy since they constitute a current. But if they do  posses this energy in addition to the magnetic field energy \$\frac{1}{2}LI^2\$, then the total energy at the moment the current is a maximum will equal \$E_{tot}=\frac{1}{2}LI^2+K_{charge} >E_{initial}=1/2CV_o^2\$. So it seems we have created energy in this process.
The only way I can work around this issue is to assume that the kinetic energy is already somehow factored into the magnetic field energy but I am not sure.


texts: Should I buffer my sensor before feeding it into an op amp or does the op amp buffer it for me

texts:
I have a sensor which outputs 10mV pk-pk.. I want to amplify this with some non-inverting amplifiers but my question is:

Do I need to buffer the signal before I feed it into an op amp with gain, or does the gain op amp do the buffering as well?


texts: Why MOSFET switching load effect gate voltage?

texts:
I use this Chinese MOSFET module to drive mini DC pump using control signal from Arduino (simply on off with blibk sketch)

I know that we need to add flywheel diode but it this case unfortunately, it's not.
The problem is when the pump switch on and off there are something happen seem like voltage-spike with Arduino digital output and also effect 5V pin via internal- input eds diode of the Arduino.
My question is what actually happen and how? I think gate is isolated from other pin so I'm confusing right now. Small capacitance between those pin shouldn't be the problem.


texts: tlc5947 LED driver without constantly occupying uC pins

texts:
I am working on TLC5947 chip to control 24 RGB Leds to create different patterns with them.
My concern is, I have to keep giving command to SIN, SCLK, XLAT pin of microcontroller every loop to keep my pattern repeating again and again.

My microcontroller is also doing other stuff, like talking with sensors, controlling external peripherals etc.

Wanted to know if there is any way/hack in hardware/ software by which I can repeat the sequence using LED driver IC while keeping my micro-controller unoccupied?


texts:
B taper pots are linear, A taper pots are "log", and used for volume controls and such.  But the actual specified taper, and what I've measured, is piece-wise linear, not a smooth curve.

Any idea why this would be?  I can't imagine it being any more difficult to make pots with a completely smooth curve.


texts: Magnetometer readings in metal heavy environment

texts:
We have designed a sensor board that consist a magnetometer, an accelerometer and a barometer which we are planning to use this on a forklift to get heading information of the vehicle. I have used Madgwick's sensor fusion algorithm to combine magnetometer and accelerometer values in order to get heading of the vehicle in degrees. This system works almost perfectly when not placed on top of the vehicle. When it is placed on the vehicle, magnetometer readings become unstable and this leads algorithm to fail as expected.
If I use a shield to prevent magnetic field of the metal parts, this will also prevent natural magnetic field, so the algorithm once again will fail.
Is placing the device far away from the metal parts the only way to get stable readings from magnetometer?


texts:
I am trying to implement a parallel CRC in Verilog but having trouble getting it to work. This is a snippet of the code that I'm having trouble with.

  reg val;
  reg [15:0] hashValue;
  reg [3:0] data_in;
  always @(*) begin
    if(reset) begin
        hashValue=16'h58a9; //initial hashvalue
        poly=16'h1021; //the polynomial
    end
    for(i=0; i < 4; i=i+1) begin
        val=hashValue[15];
        hashValue={hashValue[14:0],data_in[0]};
        if(val) hashValue=hashValue ^ poly;
        data_in=data_in >> 1;
     end
   end

The crc block will take in a 4 bit input. The code is inside a combinational always @(*) block. The problem is when the two consecutive nibbles of same type come in through data_in there is no change in the hashValue. What am I doing wrong?


texts:
I give the same voltage to opamp inputs (AD 744) but the output depends on the Vcc value.

Vcc voltage is 8.00V, the output voltage is going to 7.36.
Vcc voltage is 6.00V, the output voltage is going to 5.78.

Please explain to me what happens.


texts: Fuses, circuit breakers, transistors, ect... are all rated in amps. Why are resistors rated in watts instead of amps? Does their breakdown/failure include more than just heat?


texts: Name of Fibre optic motherboard connector, like ethernet socket?

texts:
I am trying to find the name of fibre optics cable connector, so a fibre optic cable can be used on my design, does it have a official name? for about the past half hour - an hour I have been googling to find it, but so far have come up with nothing.

Like the connectors used on this internet switch:


texts:
Can I use a 14v 2A dc adapter on 12v 1A  dc rated device?
Now what i did is by a buck controller i set the voltage to 12v but there is no variables to control the current in that buck control module. So i don't know how to control 2A current to 1A,because the device that i want to connect is rated as 12V 1A (As it's input).I'm afraid about that the current cause any damage to the device


texts: Why wrap wires around a magnetic donut on a wiring loom?

texts:
Can anyone tell me why you would wrap wires around a magnetic donut on a wiring loom?

There are 3 wires running on the loom, they run from a power source to the stator of a direct drive washing machine motor. They are wrapped 10 times around the donut.

I'm re-using the motor for a different project and am wondering what the effect of  coiling the power cables around a magnetic donut is for.

It is possible that the donut wasn't originally magnetic and may have become magnetised after a few years of being in this configuration, testing it, it is very weakly magnetic.


texts: How to calculate motor parts and energy requirements?

texts:
I’ve been wanting to ask this question for a very long time.

My main thing is knowing if a low power, low current motor is possible using a BPW34 photodiode. I hope you guys can help. Thank you!

I purchased a 3 in 1 soil tester meter https://www.ebay.com/p/3-in-1-Soil-Tester-Meter-for-Garden-Lawn-Plant-Pot-Moisture-Light-Ph-Sensor-Tool/1712433238?iid=311911276636

that comes with a analog panel meter

https://www.jameco.com/z/AVM7030-Velleman-Analog-Voltage-Panel-Meter-30-Volt-DC2-8-X-2-4_316654.html

In the center it has a photodiode BPW34

https://www.digikey.com/catalog/en/partgroup/bpw34/12351

The needle of this meter turns at very low voltages and current.
I measured everything and will post the exact info below.

My question is

How do engineers calculate how much voltage, current, coil resistance, and magnet strength a motor will need to be able to make a full turn?

Let’s suppose the engineer had a smaller magnet, and he wanted to make a smaller meter. How would he know how many coils turns (resistance), voltage, and current he would need to make this thing turn?

For example, in this science project

https://www.education.com/science-fair/article/no-frills-motor/

How did this person know how many turns (resistance) he needed, voltage, current, and magnet strength to make that motor turn?

In my meter, when you apply .5 mV and .5uA it will turn until stopped by a piece of metal at the bottom that holds the magnet.

The coil measures 794 ohms. The armature (coil) and needle weighs .415 grams.
The photodiode causes the coil to turn to full 180 degrees when it reaches .5 volts and 500uA (micro amps).
The bipolar circular magnet weighs 1.81 grams and has about 12 grams of lift force.

Images of my parts

https://www.flickr.com/photos/153503439@N02/39315572332/in/dateposted-public/
https://www.flickr.com/photos/153503439@N02/39315594942/in/dateposted-public/
https://www.flickr.com/photos/153503439@N02/39315601022/in/dateposted-public/
https://www.flickr.com/photos/153503439@N02/38637464474/in/dateposted-public/

Another question that I have is

Since the magnet will stop at 180 degrees when the poles of the coil attract the opposite poles of the magnet, is there a small ic I could use to invert the current so that it would continue to spin? Don’t worry about the stopper. Thank you!


texts: Is it possible to convert the battery power supply in old devices?

texts:
I have an old Yamaha keyboard/synthesizer lying around that I'd like to start using with battery power. However, it takes 6xC (1.5v) batteries to power the thing up. My question is, is it possible to do some tinkering around and get this keyboard to support a more modern power supply?

My ideal (probably naive) solution would be a laptop-style battery pack that I can charge via mains without needing to remove the battery and put it in a wall charger. But mainly, I don't want to have to keep buying 6 C batteries (old, expensive, inefficient) to power the keyboard.

If this is possible, how is it done? If it's not, are there any other solutions that are similar?


texts:
I have recently bought some 74HC595N (datasheet) shift registers to play with using my Raspberry Pi. The Raspberry Pi has a general purpose clock that I think I should be able to make use of, however I am unsure how this would work.

Should I have to programaticaly tell the data pin to go high, then tell the clock pin to go high, then pull the clock pin low again just to shift a 1 into the register?

I have written some code that uses the standard GPIO pins to send the data pin either high or low and then pulse the clock to shift the bit into the shift register, which seems to be working (although it is acting a little strange sometimes which is why I'm asking if I have the right idea about using the clock?)

I feel that I've worded the question rather poorly, but I cant think how else to explain my issue. If you have any questions I'll do my best to answer them.

EDIT: I'm wondering now if it could be acting up because of my voltage levels. The data sheet says that if you are powering the chip using 4.5v the minimum HIGH voltage is 3.15v. I'm using 5v to power it (not listed on the datasheet). It also says that if you're powering it with 6v the minimum HIGH voltave is 4.2v, so maybe I'm just not hitting the voltage threshold occasionally? I'm still interested in how to use the clock correctly though.


texts: Atmega328p ADC - value keeps returning zero when connected

texts:
I'm currently try to connect a DS18S20 temperature sensor to the atmega328p. I have wired AVCC and AGRD to the same power rail on my breadboard as normal VCC/GRD and AREF is not connected.

When I try to connect the data pin of the temperature sensor to the first channel of port A, the value changes to zero and stays zero. Before connecting the data pin, the value jumps around randomly. I have the following code:

volatile uint16_t vOutADCReading = 0U;

void setupAnalogDigitalConversion(){
  ADMUX |= 1<<REFS0;
  ADCSRA |= 1<<ADEN;
  ADCSRA |= 1<<ADPS0 | 1<<ADPS1 | 1<<ADPS2;
  ADCSRA |= ( 1 << ADSC );
}

void adc_read(uint8_t channel){
  ADMUX &= 0xf0;
  ADMUX |= channel;
  ADCSRA |=  (1<<ADSC);

  while(ADCSRA & (1<<ADIF));
  // Set voltage output
  vOutADCReading = ADC;
  // Clear ADIF flag
  ADCSRA |= ( 1 << ADIF );
  _delay_ms(1000);
}

void main(){
  while(1){
    adc_read(0);
    displayOnSegmentDisplay(vOutADCReading);
    _delay_ms(1000);
  }

}

Are there any errors in this code?


texts: Do I have to use a Max485 chip in front of an ATXMega microcontroller

texts:
I'm doing a project which involves receiving DMX 512 information on an ATXmegaA3u microcontroller. I've successfully implemented the protocol using the onboard USART of the microcontroller. Basically, 2 frame errors, then 512 valid bytes.

Regarding the hardware side, DMX is a differential signal protocol, so I have a DMX+ and DMX- which is the other signal inverted. I currently use only the DMX+ line of the 3 pin dmx connector and the ground connected directly to my USART pin on my microcontroller. It all works fine.

Regarding the question now: do I have to use a MAX485 type chip in front of my microcontroller? Or is the USART of the microcontroller doing exactly the same thing but onboard? If optionnal, what would the MAX485 chip provide that the microcontroller cannot do?


texts: I'm needing to measure the coil resistance in several potential relays used in HVAC/R applications, and my current HVAC Fluke meter #902 is only able to read the resistance values in a few of them, I suspect because the resistance is too high for the meter to measure. Presently, I have readings that range from 2245 through 9945, but need to read quite a bit much higher, likely up to around 15K ohms. My question is, are that any other quality multi-meters available that will measure this level of resistance? Thank you, Gary


texts: Changing ltspice export from cortesian to voltage values when using AC anlysis

texts: I'm trying to export a waveform from ltspice into an excel document to be later graphed using Matlab. I am simulating a simple series bandpass filter and when I export the voltage across a capacitor. It is not simply putting the voltage values into the second column. I am only given the option to use polar or Cartesian coordinates. Then when I am parsing the data in Matlab, it is not populating the variables because the second column is being occupies by coordinates. Can I change this export format somehow??


texts:
I want to control AC power switch 230vAC, I used this relay type Relay OJE series SPST. According to the datasheet, it can drive V=5v and the resistance through the coil is 125 ohm
I calculated to get the current through the coil by applying ohm's law and I have I= 0.04A. However, I have this diagram below: so from MCU the voltage is 3.3V and in series with 1k2
to get an Ib= 3.3-0.7/1k2 = 0.00216A.

My question is how do I know this current can switch the relay? does that mean Ib is flowing to the relay current coil?
or in other words, Is this relay type suitable?


texts: Altium Designer - Database library - Parameter: Component Type

texts:
I use altium designer v14 and v15 with external component database (*.DbLib).
The external database is realized in SQL. Everything works fine except the manipulation of the component type. This parameter should also be set from database. As conjunction / relationship from database to altium, I take the name "Component Type". I think it's the wrong name / designation. Does anyone have a solution for this problem?


texts: Simple function generator: is current-limiting/short circuit protection/impedance matching necessary?

texts:
I have designed a function generator with the intent to provide test signals to a microcontroller or ADC of some other device.  However, I may forget that a year down the line and plug it into some circuit on my breadboard.  What I'm worried about is damage from short circuits and high current draw.  At the moment, there's a buffer OpAmp as the last output stage and the output is bipolar.

First of all, do I need to add an Rs or Zs (impedance match), for example of 50 Ohm? The output can go up to MHz.  Does the buffer OpAmp suffice for that?

I have seen the following examples of short-circuit protection/current limiting.  I'm not sure which apply to bipolar wave forms; it seems that some were for DC power supplies.

Two NPNs together, but this is for single rail.

Which I first saw here.  There were a couple variations given, one with a more complicated current mirror-type addition.

From the same post above in Olin Lathrop's answer, he mentions another config I've seen, which is an OpAmp feeding a MOSFET, which feeds back to its neg. terminal using a sensing resistor. I used something similar in a regulated power supply, but, again, that was DC and I'm not sure it applies here.
foldback supply (Overvoltage protection?)

I would like to avoid a fuse, since I read it's reaction is very slow, plus I don't want to replace it. :)

There's a lot of info on this topic and I feel underqualified to decide which is best for me.  "Best" in this case is a simple design (like the transistor current regulator) that is robust enough to stop me from frying anything if some knucklehead (me) connects the two leads together.  I'm OK with a little attenuation on my signal and a temporarily higher current as long as nothing's damaged.  This is just a workbench tool, so the constraints are somewhat liberal.  Maybe the buffer OpAmp's output stage can handle this, but I'm not sure.

One last thing: should I add diodes to the rails to protect against voltage spikes?  Or would the current limiter also protect against that?

EDIT: The supply I'm using has a voltage regulator with current limiting, which can handle +/- 30mA.  I don't know if that changes anything.  It's a Mitsubishi M5290P and shown below:

Here's my output stage.  OpAmps are STLM358N.

With just the 50Ohm Rs I get no distortion and a current draw of around 1mA.

UPDATE: I simulated the transistor current regulator with multiple values for the elements and it either had sharp edges in pole transitions or completely killed the signal.


texts: Maximum symmetrical swing requires Q point to be at the midpoint of AC load line

texts:
In Schaum series, it is written that:
For maximum symmetrical swing,the Q point must be set at the midpoint of the ac load line.
And we set the Q point at the middle of the DC load line to avoid the excursion into the cutoff and the saturation region. Are these two concepts not the same?

From the above problem, I got the idea of Q point being at the midpoint of the AC load line. Then the following problem created a doubt as I failed to recognize that in the next problem AC load line is the same as DC load line. And so I thought that if maximum symmetrical asks for Q point being at the mid of the AC load line then why in this problem, it has gone for the Q point being at the mid of the DC load line.


texts: How do I wire up this item (BM70 - Microchip BTLE) for prototyping

texts:
I've just received my BM70 (Microchip BLUETOOTH 5.0 BLE MODULE) via DigiKey and I'm wondering how I can wire it up.

According the BM70 Datasheet the pad holes are (are .7mm (outer) and .5mm (inner)).

Those are smaller than items I've worked with on common breadboards so I am just wondering best ways to deal with them.

Is there a common socket for chips of this (rectangular) dimension, which would allow me to pop the entire BM70 into it and then use with a breadboard?

Is it just a matter of soldering (very precisely) to each small pad?

Is this item generally only used by soldering on a PCB?


texts: Access Register/signal from Multiple Modules (Shared Memory)

texts:
I want to implement a data register to store up to 256 8 bit chunks (VHDL). I also need to to be able to access and modify these values from multiple vhdl modules. One module will access the register to modify the values from the spi port. Then another module that implements the EPP protocol to communicate to the PC will shove out the data.

Right now I just have the signal that implements the register in one of my modules:

type type_dataRegisterWithAddress is array (0 to generic_numRegisters-1) of std_logic_vector(7 downto 0);
signal dataRegister: type_dataRegisterWithAddress;

I am not sure of the technical details of a register but I am just storing logic vectors and accessing with a to_integer(address).

I do not know how I would share this to another module as I can't just put in the port map since it is an array. Even if it was in the top level module I still do not know how I would share it.

What is the best method to create some registers that can be accessed from many modules?

EDIT:
To answer some of Dave's questions...

I kinda wanted to implement it in code like I am doing since this is a small storage and I am not actually going to use 256, it is just that the EPP interface can have 256 addresses. But you do bring up a good point.

I am using the Basys2 250k board which has 72Kbits of dual-port block ram. I have only ever used it using the IP Core function in this tutorial/module. I think this may be the best thing to use.

Now that I have the correct term. What is the your personal approach to shared memory?


texts: How to prevent data throttling with audio codec streaming

texts:
I am sampling a incoming audio stream at 8Ksps. I have a codec that takes ~1.6ms to encode a packet of data (80 samples) into an encoded packet (5 samples). At this rate I get 8000*1.662e-3 ~= 13 samples every encoding cycle. But I need 80 samples every cycle. How do I keep the stream continuous? My only guess is slow down the bitrate of the outgoing encode stream but I'm not sure how to calculate this in general such that buffers on the incoming side don't fill up and the receiving side's buffers don't get starved. And besides that doesn't slowing the bitrate take away the point of encoding in the first place?

This seems like a basic tenet of streaming but I can't find any info on methods. Thanks for any help!


texts: Use water as a conductor for a circuit powered by 1.5v battery

texts:
I've tried to create this quite simple circuit.

V1: 1.5 v (AA battery)
LAMP1: 1.5 v, 0.2 a (E10 incandescent light bulb)
"Salt water": 10 ml regular water + 1 g salt

When I connect the wires together, the lamp lights up. When I connect the wires to various conductive materials (a spoon, tin foil, a penny,...), it works as well. But if I put the wires into a tiny bucket containing (salt) water, it does not.

Could you please explain why? (I guess that it is related to the water resistance/conductance but how exactly and how do I calculate it?)

Thank you.


texts:
I would like to cool a laser diode, which has maximum thermal power of 1 W (actually according to datasheet should not be higher than 830 mW).
The operating temperature range is (25-30) Celsius.

I think that the small 15x15 Peltier 2 V should be sufficient.

I have good contact of the laser diode with an aluminum heatsink. I will also use a heatsink with the warm side of the Peltier.

I have a feeling that the power consumption of the Peltier wont be high. So my question is what could be the estimated power consumption of the 15x15 2V Peltier.

Thanks in advance.


texts: Output Impedance of Instrumentation Amplifier

texts:
Just from a theoretical perspective I would like to know what is the source impedance seen by an ADC peripheral.  The analog signal (1kHz) is produced by an Instrumentation Amplifier, goes through a low pass and then reaches the ADC.

I think that this impedance would be the output impedance of the InAmp plus the resistor of the LP filter.
The problem is that i can't find the output impedance of the InAmp (AD8226) in the datasheet, i tried others InAmps from analog devices but none had this information.

edit1: Just to make it clear, i know that the ADC has it own impedance, but the source impedance also affects the minimum acquisition time, that's why i'm trying to figure out this source impedance.
Does anyone has any tip ?


texts: Parallel conversion of signal through a low res & fast ADC and high res & slow ADC

texts:
Would there be any benefit to splitting analogue sensor signals and sending them in parallel through a low res & high throughput rate ADC and high res & low throughput rate ADC, and analysing/comparing the separate data/sticking it together? Any systems this is used in? Maybe the signal would be somewhere imbetween the ADC specs (ie. bandwidth is double/equal the throughput rate and SQNR is high/low)

(

Previously I have used very standard sensor set ups with Arduino Mega etc. This week I have been venturing into EE territory to improve the bit between 'resistance information' and network training. WOW, analog electronics is complicated, hats off to you guys in the know! I mostly work in physics/mathematical modeling of complex systems, so some basic theory is there, however really I have only been doing any EE for 5 days now.

@Wesley Lee The application is using neural networks to predict the various strains from sets of resistance measurements of a stretchy sensor array to predict its position/state.
If it is then I might set something up and see if any significant increase in information (obviously there will be more data points) arises from it. If nobody does this anywhere, that would suggest it isn't worth it.


texts: Laplace transforms for transient analysis

texts:
simulate this circuit – Schematic created using CircuitLab

For t<0 the switch is opened.

Att=0 the switch is closed. The problem asks for the behaviour
 of i(t) after closing the switch. I tried to solve it with KVL but result is different from the book. The current i(t) for t<0 is 1.73A. So I converted the above circuit to the Laplace domain.

simulate this circuit

Then I applied KVL and I found a current and

Using the inverse Laplace the result is different from the one in the book wich is found using differential equations in the time domain.
Can someone try to solve the circuit? Thanks


texts:
I'm a quadcopter FPV addict, and I'm building a new one.

As pointed out i will first explain some acronyms of the rc world

PDB (Power distribution board)
CCD (Type of camera sensor, cmos
ccd... not really relevant to the question)
BEC (A filtered voltage
regulator)
PDB (Power distribution board)
VTX (The video transmitter)

Usually, the video transmitters receives power from regulated 12 V or directly battery voltage (usually 7 V to 24 V)

Most of them also have a 5 V output that is really useful to power the camera.

In this case I'm using one really similar to this one:

As you can see it does not have 5 V output so I'm using a good CCD camera that needs 12 V that will be provided by a separate BEC on the PDB.

My question is, the VTX (The video transmitter) has two different grounds, i suppose one is the 7-24 V power ground, and the other is the ground of the 12 V camera power.

As the VTX does not provide power to the camera, does it really need to have the camera ground? The camera will have the ground from the 12 V BEC and the VTX has the ground from its VCC power.

I could test this when some final parts arrive but if it does not work i will need to resolder a lot of things and i would like to avoid that.

Also the 12 V BEC already has a lot of things on its small pads so i would like to avoid soldering another ground to it.

EDIT

My PDB is something like this:

My camera is already on the 5V BEC and the VTX on the VCC pad so its not filtered and that will induce noise in my VTX right?

Can i say that i can solve it by using the other 12V BEC to power the VTX
OR
Conecting the second VTX ground to the same 5V BEC the camera is grounded to?


texts:
simulate this circuit – Schematic created using CircuitLab

I drew a simplified schematic of the circuit I was analyzing. I was writing the node equation for node B and came up with this:

\$\frac{V_a-V_b}{2}+2=0\$

I put zero because there is no resistance between \$V_b\$ and the ref. Then \$I_{R1}=-4\$, is that correct? Doesn't seem to make sense that the current will be that no matter what is to the rest of the circuit...


texts: Firmware update and data exchange using ethernet

texts: I use PIC18F97J60 because its built in ethernet controller to exchange data via lan cable. I want to update the firmware of the mcu using the same controller which means using bootloader for the controller. Is making a bootloader for ethernet controller means that the port is dedicated for only updating firmare no more no less ? Or it can be used for both transfering data between the MCU and the server and updating firmware at the same time ? Thanks in advance


texts:
How I imagine synchronous digital networks work: data lines are sampled at rising clock edge, a set of transients occur, system settles, and data lines are sampled again on next rising edge. I would place transients at falling clock edges, that way both Tsu and Th time for sampling are clear. (Somewhat similar to SPI bus behavior.)

What see in a datasheet of a real world device (74595): D flipflops connected in series having a common clock. At the output of the first flipflop, transient on the data line follows rising clock edge with Tpd. The next flipflop needs Th time stable data line after rising edge to operate correctly. Of course it works because Tpd>Th, but it's only a matter of nanoseconds.

My problem with all this is that it's not robust (maybe not the best word). Visualizing stuff on a logic analyzer will be less useful because data lines practically change in sync with clock rising edge. Random errors caused by Th>Tpd are not really visible and go undetected. If I connect another shift register in series from a different technology, which requires longer hold times, the circuit won't work, no matter how slow clock I chose.

Is this the way most commonly synchronous digital circuits are constructed? Only the propagation delay of components make it work? Am I being to idealistic? :)


texts:
What I want is a chip that can be connected to an MCU over an UART which outputs textit receives over VGA or composite in text mode to a display in monochrome or color and optionally accepts VT100 escape-sequences (or something similar) to format text. Optional graphic mode would be nice.

I already asked this question on reddit but I did not get many answers.

Personally I found the TVT-KVGA20, but its resolution (50×18 characters) is a bit too low. Someone on reddit suggested the µVGA, which looks really sweet but is not quite a single-chip solution.

Are there other options?


texts:
How do I create an oscillating output (around 50 to 80 MHz) with both negative and positive voltage (parallel)?

I have got already a 48 MHz oscillator, but I don't mind about replacing it if it's required.


texts: If we want to filter a digital signal let's say through an RC circuit, can we treat it as a sine wave? For example, if there is a 100 kHz clock, my guess is that we can't treat it as a 100 kHz sine wave but we need to perform Fourier analysis and find the frequency spectrum and then work with the dominant frequencies. Furthermore, what role do rise/fall times play in this analysis?


texts: Are there other ways in which 60Hz noise can get into your system?

texts: Are there are other ways in which 60hz can get into a system other than ground loop ?


texts: How do I determine how long I can keep my solenoid powered, for safety sake and before ordering it?

texts:
I got a solenoid recently, a DSOS-0416-24D from DigiKey, but it gets pretty hot after only 2 seconds of engaging it.  How can I know ahead of time what kind of heat a solenoid can withstand, and how long it can stay engaged safely at it's specified voltage?

For a run-of-the-mill "24V solenoid" like this, I can't assume to be able to plug it in and leave it on all the time, right?  Is it limited only to 50% duty cycle and 1.5sec (assumedly through PWM) like it says in the document above?

In reality am I expected to do my own safety tests to find out what is safe for my application and how many seconds it can be on for without catching fire?


texts: How do USB charging and "smart" charging ports (e.g. Anker's PowerIQ) work?

texts:
Software engineer with a hobbyist understanding of EE here.

I've noticed lately lots of claims from producers of USB battery packs that their ports are "smart" and "identify the device" to "deliver the maximum current for the device." A cursory look into the matter seems to imply that this isn't completely marketing language, and there is actually something more complicated going on.

Not understanding the subtle chemistry of lithium-ion batteries or the nature of charge controllers, I would guess that to charge a battery as quickly as possible, you would draw as much current as possible, limiting it only to the battery specs. This must not be the case, since it is documented that devices limit their charging to 1A in some cases, when surely they could draw more. Why is this?

If the current draw is so controlled, what's going on with these smart ports to enable the device to draw more current? From a product page for an Anker battery, they claim their ports identify the device and "speak its unique charging language" (that phrasing makes me nauseous). Maybe I shouldn't react so harshly to that phrasing though - are the USB data lines actually used to negotiate some charging pattern?

Thanks!


texts:
i read some notes that wrote:

for following Function F, has static Hazard, if B=C=D=1, and for each change in value of A, the Static Hazard 1 can be.

Why this statement is True?


texts:
I have an ASM chart design problem that I've been stuck on for ages:

A lift in a building only has a maximum capacity of 2 people. Two sensors detect people entering (input ENTER) and exiting (input EXIT) the lift. A system is required to implement the following conditions:

a)If more than 2 people enter the lift, an alarm should sound. Otherwise, alarm should not sound.

b)If there are no people in the lift, the lights should be turned off. Otherwise, the lights should be switched on.

Assume a maximum of 1 person can enter or exit the lift during any 1 clock cycle. Assume that nobody will try to enter the lift when the alarm is sounding.

How would i go about producing an ASM chart to describe the conditions above?

I know this is quite a trivial problem but any help would be much appreciated.


texts: Spikes in raw acceleration data from AC motor

texts:
I have an MCU with an accelerometer, tightly mounted onto an AC motor inside a production hall.

Once an hour, it collects 1 sec. (Sample rate is 5000) of acceleration data for the motor and saves it.

When I try to display this data, I get these weird spikes:

Can somebody tell me, what these spikes/artifacts could be?

I'm sure my import/chart setup is correct, so I'm pretty sure it's an issue with my components.

Extra info:
The components are located inside a plastic box that's mounted with a metal backplate. Everything should be electrically isolated from the AC motor.
When testing in office environment (On a test motor), these spikes did not occur.

Accelerometer: ADXL357
MCU: FRDM-K64F

EDIT:
I come from software - I'm pretty new to hardware and electronics, so bear with me, thanks! :-)


texts: How do you solve for current through a zener diode once it has reached its zener voltage?

texts:
I am doing test prep for an exam tomorrow and ran into this problem.

The question asks you to plot Vo in terms of Vs. It also provides information that the zener diode is ideal and that its zener voltage is -5V.

The problem before this is identical with the exception of there being no 5k Ohm resistor in series with the zener diode. To me that problem is a bit easier to solve, as when you have reached the case where the voltage across the zener diode is -5V then Vo just becomes and maintains 5V.

However there is something about this added resistor that I cannot wrap my head around.

I know that the current going through the source branch (to the left of the virtual ground) is Is = -Vs/1k and also that Is = I(5k) + I(diode branch)

Anyone have any hints?

Thanks!


texts: logic gates combined with R-C network often violates absolute max ratings, does that hurt?

texts:
I know the theory but don't have much practice with this, so while I am experimenting with little success I ran into this question: what are the bad effects by violating the Absolute Maximum Ratings for a multivibrator build out of logic gates? Here is the relevant part of the schematics, an RC network combined with some logic gates, e.g. as in CD4011:

This is the basic schematic that you will see for a-stable and bi-stable multivibrators. Often you will see a big resistor between C and the input of G2, but because CMOS gates have virtually zero input current, that resistor does nothing and has zero volt.

Online example: https://www.electronics-tutorials.ws/sequential/seq_3.html
schematic: https://www.electronics-tutorials.ws/wp-content/uploads/2018/05/sequential-seq10.gif

When the outputs of G1 and G3 are different, C will be charged and a voltage will be build over C. The voltage over C cannot exceed 5 V, assuming that the gates are powered with 5 V. According to the specs, e.g. https://www.ti.com/lit/ds/symlink/cd4011b.pdf , the output of the gates can be within 50 mV of the supply voltage, if "1", or ground, if "0". But let's be realistic, the idea is that G2 will switch at some point. The transition range is about 1.5 - 3.5 V, so C will be charged at least to 1.5 V when G2 switches over.

When G1 switches, its output changes with about 4.9 V. With 1.5 V on C, the input of G2 will then get a voltage of either 6.4 V or minus 1.4 V. With 3.5 V on C, those voltages are 8.4 or minus 3.4 V.

My point is that such input voltages are way out of spec. The Absolute Maximum Rating for inputs is 0.5 V above the power supply (Vdd), and 0.5 V below zero:

When designing something, you always try to stay within the manufacturer specs of the components. Specs often state that operating a component outside the absolute maximum ratings may affect reliability, which in clear text means that the component may become permanently defective, or "broken". There is no guarantee that it gets damaged after some seconds or days when the input is beyond abs max rating.

Because I see so many applications of RC networks with logic gates, I am really wondering if we should take those Abs Max Ratings serious.

Update:

Two commenters provided answers that made me understand how this issue works, thanks! I also drew a schematic, but don't want to present as an answer, hence this update. In real R-C applications there is an extra R2, and the logic gate has protection diodes that play an active role:

The idea is to make the timing depending on C1 and R1, so R2 should be significantly larger than R1. R1 should be at least 5 kOhm because the 4011 has a maximum of 1 mA output current. The input of the logic gate is high-ohmic because of the FET, if the input voltage is within 0 to 5 V.
When the input voltage raises above power supply or lowers below zero because of G1 switching, one of the input protection diodes will be conducting. R2 must be large enough to limit the input current to 10 mA, just barely visible on my screenshot of the absolute maximum ratings, but this will always be the case because R2 >> R1 and R1 > 5 kOhm.

The answer is that the Absolute Maximum Ratings are NOT exceeded because of the R-C network. Even with R2 of zero ohm, because G1 cannot deliver an output greater than 10 mA, but then the time constant is not just R1 times C1.


texts:
I'm attempting to connect to Loconet(spec) to a PIC32, and I've found a circuit to connect to an Arduino, but I'm not sure what exactly it does:

(source page)

Specifically, I don't know what the LM393N voltage comparator at the top middle of the schematic does.  I think that what is going on is that the LM393N is clamping the voltage to a certain level, between 0 and 5V or so in order for a microcontroller to read it as either a 0 or 1.  I'm assuming that because of the following statements in the spec, as well as the given that VCC=5v:

Page 3:
a) High = 1 = "MARK" : LOCONET+/- voltage above +4.0 Volts with respect to ground conductors.
b) Low =0 = "SPACE" : LOCONET+/- voltage below +4.0 Volts with respect to grounds.
c) The data should be received with 1.0 volt of HYSTERESIS centered on +4.0 volts.
d) Maximum LOCONET+/- high voltage is +24V and nominal is +12V

I've seen another circuit that is similar, but uses an opto-isolator after the voltage comparator to actually interface with the microcontroller, which I'm assuming will then drop the voltage down to CMOS levels if it isn't already.

BONUS QUESTION: The LM393N in the center doesn't appear to be connected to anything, what's up with that?


texts: Arduino's analogWrite() - does it work the same way for NPN and PNP transistors?

texts:
If I'd like to control the NPN transistor with PWM, I'd just have connected the transistor to the output of the Arduino (or actually, ESP8266) and set analogWrite().

But what if I want to control the PNP and NPN transistor? Can I control PNP transistor using the same function? Will connected LEDs by these transistors be illuminating in the same way with the same configuration of analogWrite()?


texts:
I’ve been building an off grid home for a few years - recently moved in full time.  Living in VT, with limited solar, we depend on a Honda EM6500SX 240v generator to occasionally recharge 20 batteries via an XW4024 Inverter/charger.  I’m thinking ahead to options available for future generator failure and would appreciate help.
We also have a nice little EU2000 generator for camping, but it only supplies 110 v.  I assume that’s no help recharging batteries since system designed for 240.  BUT, I’m wondering if, just to “get by,” could I bypass my inverter - and supply one half of my house panel at a time, with the small generator?
My hope is that I could “unplug” from my failed 240 volt 6500w generator and, alternatively, plug into my own special female connector - which I would equip with two male “pigtails(?),” making a sort of “splitter.”  Each of the male connectors would use ground and white - with one using red and one using black.  In my naive theory, I could use existing house switching to bypass my 240v inverter - and deliver 110v EU2000 power to one side of the house panel at a time.  Which circuits get power would be determined by which plug I activated by generator.  [Not perfect - but helpful.]
Abandoning battery system for a while, this might allow me to “get by” since we would temporarily have no 240v need.  Am I missing some problem, please?


texts:
I'm fairly new to all of this as well. So I'm working on this project and I have to connect an external ADC, the TLV571 (datasheet), to an Arduino Mega 2560. I know it's complicated and it isn't the easiest solution but that's what I have to work with.

Unfortunately, I don't even know where to begin. I have been looking at the data sheet for the TLV571 all day and am just clueless.

Can anyone help me or give me advice? Even the smallest piece of advice would be helpful!


texts:
Is there anything below 32-bits for an ARM processor? I was wondering if there is or ever was an 8-bit ARM processor. I've searched but not seen any and so it seems that ARM processors are either 32 or 64 bits. Why is that?

I also noticed while writing this question, that the tag for ARM even says 32-bit microcontroller IP.


texts: How to split custom device symbol into separate parts in Eagle (within a single footprint)

texts:
So I am working on a complex design that includes a BGA device with rather large number of pads that are grouped by functions (an ARM MCU and groups are MDIO, MMC, SERDES etc). This is my first project of doing such complex one, so forgive the lame question.

I've created a custom library device for this (since I could not find a ready device for this chip). And for this device I've created 1 symbol and 1 footprint.

I, of course, can work on schematics with this single symbol, but that is going to be a huge mess (~400 pins on this symbol).

I can see plenty of schematics (exported into PDF) show these are split into independent groups. Such as one schematics sheet would show everything power related and another for example everything MMC related (and symbols on each sheet would be that of only relevant pins of the chip). See attached pic below.

How do I achieve that in Eagle?

Additional question: I see in those schematics also that the whole design is split into blocks (i.e. as on attached picture with B2B_xxx connections) and the wire would resume on another sheet. How would I go about doing that?


texts: Increasing current draw of generator receptacles within total generator head rating

texts:
I am looking at a generator that is rated for 2600 watts, total current draw 25 amps. It is currently set up with two hot lines separately connecting to a duplex receptacle rated for 15 amps and together connected to a receptacle rated for 15 amps at 240 volts. The supply paths include an 11 amp thermal breaker before the receptacle.

May I connect both hot lines together and instead replace the receptacle and breakers with one rated for the total current rating of the generator head without damaging the generator head windings?

I will also link to a similar question asking if multiple paths from supply to ground increases the allowable current draw but I don't think this is a duplicate as the focus is whether or not it exceeds the rating of those windings in the generator head. I will link to an answer to another question that discusses this.

Am I drawing more current if I'm giving multiple paths from supply to ground?
https://electronics.stackexchange.com/a/7776/131959
http://www.northerntool.com/shop/tools/product_21008_21008


texts: Does lacquer coat protect a PCB from ESD damage?

texts:
Does lacquer coat protect PCB from ESD?

It seems that it actually does, because lacquer is isolation and it's a barrier from my body to the circuit. But I'm not sure.


texts: Could an external circuit with 74HC series IC reliably test a 24 MHz crystal?

texts:
I made a circuit where the microcontroller works. I made a duplicate of the same circuit with a working micro, but that circuit does not start and there is no smoke and the PCB is clean (no loose wires touching in bad places) So I suspect my problem is the crystal circuitry.

In my micro setup (as with any other 8051 micro), I have an external crystal connected close to the micro's XTAL1 and XTAL 2 pins and each of those pins are grounded through the ceramic capacitors.

Since I use a socket for my micro IC to insert into, I want to make an in-circuit crystal "tester" circuit so that I can touch probes to the correct metal pins of my micro IC (representing XTAL1 and XTAL2 and GND). I want this tester circuit to distinguish between a working and a non-oscillating crystal arrangement.

I looked up pierce oscillators online and based on schematics, the only way I could see me possibly pull this off is to use some sort of inverter from a logic IC like this:

and hooking up its output to something (555 timer?) to lower the frequency and output that to a speaker so I hear a screech if the crystal works.

Could I use a 74HC04 inverter here to complete the tester without any issues in the inverter not handling the 24 MHz crystal frequency?

Also, what should the maximum length be for the test wires if the wires were at 24AWG thickness before the crystal circuit doesn't function correctly?

For clarification, in my test, C1, C2, and X1 are already soldered on to the target board.


texts: To what are transistor's "E, B, C" voltages relative to?

texts:
I've seen \$V_{CE}\$ and \$V_{BE}\$ in context of transistors, where they clearly denote a voltage between two points. But then I also see things such as:

From a table in Wikipedia:

Applied voltages | B-E junction bias (NPN) | B-C junction bias (NPN) | Mode (NPN)
E < B > C        | Forward                 | Forward                 | Saturation

Where do those voltages comes from in a circuit? "\$V_{E-to-what}\$ < \$V_{B-to-what}\$ > \$V_{C-to-what}\$". To my understanding a voltage has to be relative to another point in a circuit, so what are these E, B and C relative to?

I've been told I'm missing something. Any ideas?


texts:
I am working on a simple solar system for heating water. The idea is to use sun power and if not enough, use the power grid at night. I have a solar panel and a MPTT boost converter which collects the power from the panel and sends it to the boiler. I am using a timer controlled mechanical SPDT relay to switch between the solar and the power grid - grid at night, solar at day. My problem is that my controller sometimes burns out during the switching of the SPDT relay. What I suspect is that there is a shoot through during the switching time, which places 220V AC from the grid on the MPTT controller output. The MPTT controller is designed for 100V DC max. I noticed also that this does not happen always. It probably depends on the point at which the relay cuts the 220V sine wave, because the relay sometimes sparks, sometimes not. The shoot through is always accompanied with a spark.
Is it possible, that the spark (when it happens) crosses the air gap of the relay contact? Is there a simple way to solve the issue? (The overkill for me would be to build my own time delayed spdt relay)


texts: Is it safe to plug a transformer into a surge protector?

texts:
All my searches have come up with "DO NOT PLUG A SURGE PROTECTOR INTO A TRANSFORMER," but what I need to know is the opposite (if I can plug a transformer into a surge protector without issue).

What I want to do is plug a transformer into a surge protector and then take an output of 110V converted to 220V to power a 1.5kW spindle motor's VFD. Are there any issues doing this?


texts: what is the value of Rin? (different problem)

texts: I calculated voltage at Vx. How to know the input impedance? V- is at virtual gnd. Will it be Ra+(Rb||R1).  My question of input impedance seeing from node Vs is right or should we consider only from node Vx. I’m trying to intuitively understand opamps.


texts: Why do large PCB traces have solder points/islands/stripes on them?

texts: This is from a power supply for an old PC monitor. I opened it up to see if I could fix it (likely bad caps) and saw this rectangle matrix. What's the purpose?


texts: In D flip flop, D means DATA. In SR flip flop, S means SET and R means RESET. What is the meaning of JK flip flop's J and K?


texts:
In a general purpose computer(like normal pc), how does the CPU read the RAM, assuming that it first reads from the Cache.

Assuming the cache is an n-way set associative cache. Again, we would have L1 Cache and L2 Cache.

Usually, CPU reads a block of data from the RAM. So these blocks can be several words. Doesn't this cost a lot of time/clock cycles? How is/can this be made more efficient? (Not talking about using cache here, but about the data transfer)
RAM is quite slower than the CPU, how does the CPU still manage to be efficient?


texts:
Whenever I start a new project, one of the first things I must do is search for suitable components to see if the project is feasible. Most of my projects are desperately space constrained, so I don't always have the luxury of just using parts I'm familiar with. Often I have to start from scratch, visiting each manufacturer's web site, and trawling through dozens of parts, using their part filters (which often don't filter by the attributes I'm interested in, like part size). I'll also go to the suppliers (Farnell, Mouser, etc.) to find parts. I often need to read each datasheet to discover the missing details. Finally I record them in a huge spreadsheet, so that I can select the 'optimal' part.

Even when I've done this, I can't help feeling that I must have missed some manufacturers. Maybe I should have checked Allegro, or Melexis...

This must be a common problem for electronic engineers trying to select the optimum components. It certainly is for me.  How do other EEs approach this task? Is there some global electronic component search engine I haven't heard of?


texts: How to determine FET switch specifications

texts:
I am working on a DIY drone, and I (preferably) need to be able to disconnect my ESCs from the battery via the transmitter (a Raspberry Pi). After looking for solutions for a while, I concluded FET switches are my best bet to automate this. However, I am not certain how to determine the requirements for the switches (I have no engineering knowledge, I am learning on the fly).
Considering that the maximum current draw for the motors is 12A, the battery is 11.5V, and the RPI's pins for control are 3.3V and can take a maximum draw of 16mA, are my assumptions correct:

Switches need to have Vds>11.5V, and Vgs<2.5V
The draw on the gate can be neglected because it is ~0

Also, what considerations should be made about the S->D current draw? And am I missing other factors?


texts:
I faced with problem in my project. I have to build circuit in OrCAD that should to generate triangle signal. I tried to use IC 555, but get sawtooth signal. After that i used hours and tens of circuits to figure out triangle signal in OrCAD, but it didn't help.
I found a lot of circuits and it works in LTSpice or in real circuits, but not in OrCAD.
I have 5V supply and 10-15 kHz frequency.
If somebody has this circuit, i will be very gratefull

this circuit that i found in internet

this is mine, how i see it( i'm newbee in OrCAD)
[enter image description here][2]

[![enter image description here][2]][2]


texts: How to build synchronous boost converter with IR2104 mosfet driver?

texts: Does anyone know how to build a synchronous boost converter with IR2104 mosfet driver? I am a beginner and I have noooo ideaaa how to connect the circuit. The placement of inductor and capacitor especially. The boost converter is meant to step up 12V to 24V. Any help would be much appreciated.


texts: H-Bridge Adjustable Slew Rate: Why is a decoupling capacitor needed?

texts:
I am designing a simple 3-phase inverter for BLDC Motor control. For that purpose, i plan to use a IFX007T from Infineon. The slew rate is controlled via a resistance connected in series to SR pin.

I do not understand how this resistance is used to adjust the slew rate but i suppose the analog magic behind it far too complex and beyond the scope of this question. What i would like to know is: What is the purpose of the capacitor connected parallel to this resistance in the reference design? As far as I know, its a decoupling capacitor that basically sends any high frequency components to GND.

The reason I am asking is; in older versions of this H-Bridge such as BTN7930 there is only the resistance connected to the SR pin and no caps what so ever. Since I am a little tight on space, I wonder if it would be alright to omit it with IFX007T.


texts: Concerns with running a transformer at frequencies greater than what is specified?

texts:
My office has a few of these (http://www.hammondmfg.com/182.htm)

and I came across a circuit which are driving these up to 5KHz. To my knowledge, the circuit worked and has been used in the past for a few years. I can't speak with the original designer because they aren't with the company anymore. I'm curious of the possible implications (if any) of running a transformer at frequencies much higher than what was specified.

Now the data sheet says that the it's intended for 50/60Hz. I understand the problems that can arise when you run a transformer below its rated frequency but I've not come across anything that really talks about what happens if you run it faster.


texts: Magnetic rotary position sensor on a BLDC/PMSM : Mechanical vs Electrical Degrees

texts:
I am controlling a 3-phase motor with  3 120° phase-shifted currents, which is done blindly, i.e without any sensor feedback, at the moment.

I have a Magnetic rotary position sensor which i communicate via SPI and want to integrate it to my control scheme. I already checked the related decomposition techniques, namely Clarke transformation, to find the corresponding values for the optimal driving (rotor angle + 90 °).

My question is: The sensor has 14 bit resolution and i tried and validated that it works properly. The confusing part is, 14 bit resolution apparently stands for 1 mechanical revolution (360° mechanical degrees) and since i have a 7 pole-pair motor, the resolution for 1 electrical cycle drops to (2^14 / 7) and as far as i have understood it is the electrical degrees that i should apply the inverse-clark transform on.

This resolution is still pretty acceptable but i am not really sure if my way of thinking is correct. It didnt make sense to me that the sensor resolution depends on the number of poles. Any clarification is much appreciated.

Link to the mentioned sensor: http://ams.com/eng/Products/Magnetic-Position-Sensors/Angle-Position-On-Axis/AS5147


texts: Arduino + ESP8266 electromagnetic interference

texts:
I made a board for a weather station that has an Arduino chip on it with an ESP8266 WiFi module mounted right next to it.
When I power the board, the ESP8266 seems to be unable to connect to my WiFi network.
It took me a while to figure out why as the module worked perfectly fine when connected directly to a USB-to-serial converter and writing AT commands directly to it.

So I tried to connect the ESP8266 module to my board using a ~15cm ribbon cable and suddenly it all works.
Seems like there is some electromagnetic interference when the Arduino (board) and ESP8266 are placed close to each other.

Has anyone encountered this before and is there another solution than placing the 2 parts away from each other?

EDIT: Added pictures to clarify

This doesn't work:

This works:


texts: Do different address spaces exist for RAM and ROM in a typical microcontroller?

texts:
If a microcontroller has 16 bit address space from 0000H to FFFFH, will the RAM, I/O registers, memory mapped I/O and ROM(Flash/EEPROM) share the same address space linearly, or will there be a separate address space for ROM alone(like another 0000H to 1FFFH), or is it manufacturer dependent?

I guess I read lot of documents and confused myself into this. Please help.


texts: Convert millivolts from shunt on DMM on a 50A, 75 mV Shunt

texts:
Please excuse my awful math/s. Can anyone please help me calculate/convert the mV reading from a 50A shunt? For example if i was reading 1.5mv how do i convert please. Please keep it simple as math is (obviously) not my strong point!
Thank you

Slightly embarrassed at the state of my maths but thank you all for comments. However going with (50/75) x the Amp reading isnt agreeing with my two ammeters!

The ammeters are reading 2.06 and 2.12, and the DMM is reading 12.0mV - so - (50/75)x12 =8 oops. Any ideas folks?

It is a series circuit 12v battery, fuse holder with cheap ammeter plugged here, switch, bulb, earthed through chinese shunt with second ammeter reading here along with DMM. Appreciate shunt and cheap ammeters may not be 100% but im not getting close even. How might ammeters not be reading total circuit current pls?.

Schematic (description below)

The two ovals at (a) represent a fuse holder (fuse removed). into this is inserted an ammeter (c) which accepts the removed fuse (b).
(d)represents the shunt with the other ammeter attached and this is where the voltmeter reading are taken off either side of shunt.
Excuse poor schematic drawing/symbols etc.

simulate this circuit – Schematic created using CircuitLab

Schematic added by Transistor. OP to edit / correct.

Update - PROBLEM SOLVED Brilliant - I was taking the mV reading from the wrong place, on the large, outer terminals when I should have been reading from the the smaller terminals. Here I get 3.5mv which then gives me a close amperage figure (50/75*3.5=2.4).

Lesson learnt - thanks to all - admin please feel free to edit this to make it more useful to others.


texts: Altium : how to delete vias and path that are outside of board

texts:
This might be a stupid question but I moved a room, resulting in some vias and path in negative coordinates. You can see below a 3D view. I would like to delete
them but in 2D mode, I can't zoom out to see the elements that are in negative coordinates. So I can't select them...

I tried to flip the view but it's not better.

Thanks for your help.


texts:
I have been trying to figure out how to properly measure battery voltage for a few days. The more I read, the less I understand. I know there are many questions like this out in the internet and I have read most of them, but I haven't properly understood many of them. Also, many of them have no examples. Perhaps you can help me to understand some of the aspects.

What I'm trying to do:

I want to measure battery voltage which is 4.5V (3 x AA batteries) when full. I'm using an ATmega328P ADC to do that. My system runs on 3.3V. I have low power step down regulator to convert 4.5V to 3.3V.

My system takes max 50mA. I'm definitely concerned about battery life and accuracy. I would like to see about 50mV accuracy.

What I have read / what are my options (ideas):

Obviously the simplest solution is to use just voltage divider to feed the ATmega ADC. As I understand the ATmega, AREF is around 1.1V so I need to calibrate it 1/4 down. I was thinking about using 1 Mohm and 330 kohm resistors.
Then I read using P-MOSFET to switch it on and off when measuring, would be way to save power. Definitely it is. Problem is that I need additional N-channel to control P-MOSFET, and additional resistor/resistors. Not sure how good it is in terms of battery saving. Also many additional components.
I read about using an additional buffer between the ADC and divider. Now I started reading about impedances. In my case it probably won't matter, but just out of curiosity can anyone explain me simply enough when and how impedances matter when using ADC and how op-amps help?

I know a bit of theory behind them and understand that an op-amp input has high impedance and an op-amp output has low impedance. It would be really nice if I would get some examples. All links are welcome as well. I already tried to understand it, but I'm still confused. Examples would be great.

Also how accuracy/resolution depends on resistor values? Higher resistors seem to have the worst accuracy.
I ended up reading about differential amplifiers. Obviously it is overkill in my case.
I thought to use a specific μC for that.


texts: How does battery "passthru" charge power affect lifetime capacity?

texts:
Let's suppose we have a new very healthy fully charged AGM battery that is ready to put into service and it is rated at 12V 100Ah (at a 12 hour drain rate, therefore it has 600 Wh of usable energy per charge).  Also suppose during its lifetime, it can be charged and discharged 500 times each, down to 50% SoC, therefore having a lifetime capacity of 500 * 0.6 KWh = 300 KWh.

Case 1: we put a 50 watt load on it for 12 hours a day, which is 600 Wh of drain, then charge it back to 100% SoC in the next 12 hours and repeat that cycle 500 times.

Case 2: we leave the 50 watt load on 24/7, however, during the daytime, it can be assumed that the battery will be charged full within 12 hours of daylight using a solar panel (assume 150 watts average over the 12 hour daylight period, enough to compensate for inefficiencies of AGM batteries and  solar charge controller inefficiencies).  So the battery will drain down to about 50% SoC overnight and then slowly go back to 100% SoC during the 12 daylight hours.

So how will case 2 affect the total usable lifetime capacity?  Is having 100 watts of charge power and a 50 watt load simultaneously similar to no load and a 50 watt charger?  Will the battery have the same # of charge discharge cycles in these 2 cases?  Does a battery behave differently having a 50W load and 100W of charge power vs no load and only 50W of charge power, or can those 2 cases be considered pretty much identical?


texts: Question on battery basics (I'm confused and not sure how to state my question)

texts:
I'm new to the mathematics behind the electrical engineering and quite confused. I have done some searching around and haven't found anything, probably because I'm asking the wrong question.

On a 9V battery, it says '9V'. What does that mean? Does it mean it always has a voltage of 9V (Around that since the battery drains), or that up to 9V can be pulled?

I guess this also hooks into another question: If you have an LED in a circuit, What decides how much voltage it gets? Does the LED limits the amount of power going through it, or does the battery force a particular voltage and current through it, which can be modified by resistors to lower the amp and up the volt?

Sorry if I am completely asking wrong.


texts: How do I connect multiple shields to my arduino and have them all function?

texts:
I'm sorry if these are stupid questions but with my little knowledge about this stuff I don't really know any better.

My project is basically just a data logger storing the output from 3 accelerometers.

I picked up a Arduino Mega, 3 ADXL-335 accelerometers, and a Ethernet shield.

I also had some fun playing with a SainSmart LCD keypad
http://www.sainsmart.com/module/lcd-module/sainsmart-1602-lcd-keypad-shield-for-arduino-duemilanove-uno-mega2560-mega1280.html

I had all of them working individually.  My question is how to making them all work together.  With the shields I am not sure what pins they are using and what are available.  Can I stack the LCD on top of the Ethernet shield?  Kind of afraid just to wire it all up before knowing if I'd hurt anything.

So in short can I connect 3 Accels, SD card, and a LCD screen to 1 Mega and make them all coexist nicely?

If there is a better hardware combination then what I have please let me know.


texts: Connecting Headphone Jack to Amplifier Help

texts:
I have this image that is for the amp I am using which allows you to add a headphone jack to it:

I have already hooked up the regular speakers and power to the amp, now I just want to add a headphone jack. It says to wire the grounds from both speakers together, then to the jack, and to wire the left and right audio points to it directly. Can someone explain what the "wire to internal speaker" points mean? I know it sounds simple, but for instance what are the arrows for? They look like diode symbols to me (I thought this because they could have easily done without the arrows).


texts: CP2108 with level converter txb0108 - UART communication TTL and LVTTL

texts:
My project uses four different modems (one 3v3 LVTTL(?) and three 5v TTL) for AT communication.

Each modem has a UART interface (TTL compatible).

For my application, i chose the CP2108 to communicate with those four modems using one USB connexion.

In the modem's datasheet, the operating voltages of the UART are not indicated. Just "TTL compatible".

I chose to add a level converter to protect the input of the cp2108 which can only accept 3v3.

I took the reference txb0108 to do the convertion. I supplied a voltage of 3V3 for side A and 5v for side B. for the 3V3 modem i change the voltage of side B to 3v3 instead of 5v for the other modem. In the datasheet of the txb0108, it's ok for having the same voltage on both side of the level converter (A and B).

When I look at the oscilloscope, I observe the level conversion correctly and i can communicate with the modems.

but I still having a problems to communicate with one modem (5v).

For side A, the voltage does not drop enough to get a logic '0'.

I've add a pull down resistor of 6k8 on the pin and it's seems working.
but for me it's not a proper solution because in the documentation of the level converter the suggested pull down resistance must be greater than 50k.

I tried with a 100k but without success.

I have read few articles about using the txs0108e instead of the texb0108 level converter and some people get apparently better results.

I do not know if this will solve my problem.

I also read some stuff about push-pull and open drain for the UART.
i don't know wich technology is the best for my application.

Is the TXB0108 finally a good reference for my application ?

What would be the best schematic to handle communication with my CP2108 and 5v uart modem (other solution exist)?

Thank you.

EDIT:

Here is more information about the 5v modems. I will only use the RX / TX pins.

Input TTL compatible:
VI Hi min +2V
VI Lo max +0.8V
VI max +5.5V

output TTL compatible:
VO Hi min +2.4V
VO Lo max +0.4V

I found this reference to do the conversion:

SN74LVC2T45

http://www.ti.com/lit/ds/symlink/sn74lvc2t45.pdf

What do you think about it?


texts: How do you construct a dual-input switch using transistors?

texts:
I have part of a circuit that I wish to disable power to depending on two input signals (digital, active low). How do I realise this, preferably using transistors?
Application
The two signals comes from a LiPo protection circuit representing over-charge and over-discharge. When either is low the rest of the circuit must be disabled to prevent battery damage and potential danger.
Example
This is what I tried, using two N-channel enhancement mode MOSFETs. It works for one of the signals, but when input 2 is low, it does not fully turn of (LED is still lit).
What the schematic software didn't allow me to do is that there is a diode between source and drain of the transistors, as in the second picture. An explanation to that would also be nice, as I have a feeling it affects the setup.
Example circuit (Vdd = 2.7 – 4.3 V)

Actual symbol of MOSFETs used

Source: http://simreal.com/mediawiki/images/2/26/Fig06-02.jpg


texts: CML signal to ground terminated line or peak sensing ADC for short pulse

texts:
I'm currently designing the prototype of a timing instrument. One sensor gives an analog CML (current-mode logic) signal, from an amplifier  (ADN2880). One end of the pair is routed to a comparator (ADCMP572).

Is there a way to use the other end of the pair for 50 ohm ground terminated line?
The solution must not induce distortions in the positive side of the pair.
It must work at 700MHz-1GHz. DC or AC coupled.
What I am really interested in is the amplitude of a short pulse (>=
200ps) from that sensor. I would like to put a peak sensing ADC instead of that 50 ohm line if possible. I don't know where to start to design such circuit, so any insight will be welcome.


texts: Properly charging and discharging Lithium cells during battery testing?

texts:
I'm working on some software that automates charging and discharging battery cells to generate discharge curves. I have a few concerns about properly charging and discharging of lithium-ion / lithium-polymer cells:

Concerns:

I understand when charging, bringing a lithium cell to maximum voltage doesn't necessarily mean it's been charged to full capacity.
I've read that charging only up to 80% capacity is optimal for long storage life.

Questions about Testing:

Should I bring cells to full capacity or just 80%?
After maximum voltage is reached during charging, what percentage should current drop to before I terminate the charge?
Is discharging to cutoff voltage equivalent to a complete discharge?

Note: the cells I'm using don't have protection circuitry, but the load and power supply I'm working with will enforce minimum and maximum Voltage limits.

References: [1], [2], [3], [4]


texts: How do I measure current with a microcontroller

texts:
OK, having given myself a crash course in op amps, I think I've got it figured out.

I am looking to build an in circuit battery monitor, and I wish to measure the current being drawn from each individual cell in a series-parallel battery pack.

I think the circuit below will do all I want it to do, and I now think I've got the resistor values right to give me the correct gain. And I think I've got the right bias voltage to force the output positive over the desired range of -2.5 to +7.5 Amps.

I have been informed that I was nearly correct. 4 diodes in series gives me a handy two point FOUR volt reference, and as much current as I care to waste in the power shunt resistor, to supply the microcontroller, as well as provide an offset bias for the voltage sense module. A hefty cap holds enough charge to drive the microcontroller during its wake time as well as the IR-llLED derived opto-Xceiver, to allow me to maximise the value of the power shunt resistor. Hopefully 1mA continuous should be enough.

What I need is for AN1-7 to read across the range of -2.5 to +7.5 (Amperes through shunts/fuses @ 10 mA/div) and An0 to read actual voltage across the range of 2.8 V to 4.4 V. @ <2 mV/div.

Unless I am completely mistaken this (slightly modified, and broken into its functional blocks) circuit should let me monitor the precise health and charge status of every individual cell in a battery pack, identifying those not delivering their fair share of the load, and/or which self-discharge, dragging down cells connected in parallel.

By keeping a record of each cell's performance over multiple charge and discharge cycles, the right software would be able to maintain a charge map of the battery and recommend cell swaps to keep the battery perfectly in balance, whenever cells drift out of spec, or when a dud cell is replaced.

Big question, do I have it right, or have I made some fundamentally stupid error?

simulate this circuit – Schematic created using CircuitLab


texts:
I know many of the lower-end PICs have fixed hardware stacks that can become an issue during firmware development.  I've recently heard that the PIC24-series (and maybe just anything above PIC18 series) have software-defined stacks?  Does that mean they're dynamically allocated while the code is running or is the size just assigned by MPLAB when you compile?

I know this is more of a nuanced question, but I appreciate any help there might be out there.  It just doesn't seem to be talked about much on the datasheets or product pages.


texts: I am trying to identify this 5 pin connector. Any ideas?


texts: Electret condenser microphone, LM386 amplification... does size matter?

texts:
I've built a motorcycle intercom, of which comprises of two amp units, one for the rider, one for the pillion. Both are powered by a 9v battery each, and the option (using a jumper) to enable boost.

The problem we're having is that they're very quiet... not ideal on a motorcycle. When I enable the boost on the LM386 (0.1µF cap, pin 1-8) the sound quality is distorted beyond an acceptable level.

My question is, does the size of the electret condenser mic make a difference to the input of the amp, and thus the volume (or quality) of the output? If so, any pointers on what I should be looking for?

I don't have any specs on the microphones I'm using, but here's a picture. It's about 5mm wide, as you can see:

If it helps, here is my amp unit schematic:

please excuse my schematic skills... I think it's right


texts: Can you explain this differential amplifier exercise to me?

texts:
So we have the exercise in the figure

The figure is

The solution according to the book is

VE=-0.7 Volt thus I=(-0.7+5)/4.3=1 mA so re= 50 ohm.Why is re=50 Ohm here?

a) Ad=V0/Vd=α*2/2re .Why is Re ommited from this formula? Isnt it supposed to be  Ad=α*2/(2re+2Re)?


texts:
I'm working on a simple circuit where I have to vary the capacitance across two pins of an IC in the run time. Right now, I use 6 capacitors from 0.001uF to 1uF and switches between them manually using sticky push buttons. I could use a gang capacitor and vary the value by turning a knob. But I think using some digital controls will be a bit more smarter, such as I replace presets with digital potentiometers like this one. Is there any off-the-shelf digitally controlled capacitor ICs? Is there any work-around for this by using some other components?

Update: The following is the circuit I'm working with. I need to replace the external timing capacitor C with a digitally controlled variable capacitor.


texts: What does this mosfet switch circuit do?

texts:
I found this piece of circuit in a battery powered sensor. It's a magnetic door sensor.

I am not able to figure out what does this do?


texts: How many clock cycles does a RISC/CISC instruction take to execute?

texts:
According to Digital Design and Computer Architecture by Harris and Harris, there are several ways to implement a MIPS processor, including the following:

The single-cycle microarchitecture executes an entire instruction in one cycle. (...)
The multicycle microarchitecture executes instructions in a series of shorter cycles. (...)
The pipelined microarchitecture applies pipelining to the single-cycle microarchitecture.

Architectures are often classified as either RISC or CISC. From RISC vs. CISC:

RISC processors only use simple instructions that can be executed within one clock cycle.

Since MIPS is RISC architecture, I am a litte confused by the above definitions and wonder if there isn't some sort of contradiction between them. More specifically:

If a RISC instruction can be split into shorter cycles (Fetch, Decode, ...), how can we say that it only takes one clock cycle to execute the whole instruction? Doesn't it take one clock cycle to execute each of the steps?
Does it really take one clock cycle to execute one RISC instruction? What happens, for example, if a cache miss occurs and the processor has to wait for slow DRAM? Shouldn't this prolong the execution of the instruction by quite a bit?
What exactly is one instruction cycle? Is it the time that it takes for one instruction to finish (i.e. one/multiple clock cycles)?
How long does one CISC instruction take in clock/instruction cycles?


texts: Bjt circuits, "Vbe = 0.7 at edge of conduction"

texts:
could you explain what "eoc" and" eos" (edge of conduction and edge of saturation) is?

The problem says "Vbe = 0.7 at edge of conduction" , is that in cutoff mode?


texts:
I have to read the resistence of three different electrochemical gas sensors. The ranges are:

3k - 60k Ohms MiCS 2611 for O3 reading
100k - 1.5M Ohms MiCS 4514 for NO2 reading
0.8k - 20k Ohms MiCS 4514 for CO reading

Some suggestion for an easy to use circuit? I think to interface this sensor board with an atmega8.


texts: electrons of the collector in NPN transistor

texts:
What happens to the electrons in the N region of the collector of npn transistor that operates in active mode ?

I know that electrons coming from emitter split to base current and collector current , i am asking about electrons in the N region of the collector due to doping , do they add to collector current ?


texts:
I am trying to understand the following oscillator from a Cyclone 40 transceiver (http://www.4sqrp.com/cyclone.php).

Here the the VFO (in the actual device, the inductor has a bolt through it to tune the oscillator):

In my simulation, the voltage at the gate rises until around 1.6V, which I assume is the threshold voltage of the device.  At that point, a small amount of current starts going into the drain.

Can someone help me understand how this oscillator works?

Also, is the transistor in its triode region the entire time (in steady state)?  I think it is, as Vgs < Vds - Vth.  If I zoom in at the bottom of the Id current curve, it does a funny upwards hop before going down again - what is that?


texts: Power supply in parallel connection test

texts:
I have 2 power supplies in parallel. Can I detect if they both are connected by only using the outputs and a multimeter. The power supplies have 24V 10A each.

This is what I figured:

Connect an electrical load that demands more than 10A of current. If the voltage drops of cuts off only one power supply is connected. Can this work and would it harm any device? This test will be executed 2 maybe 3 times. Thanks.


texts:
I'm designing a musical instrument in which two oscillators (one based on a Quad NAND gate, the other on a 555) are controlled by a signal from a condenser microphone. At the moment the mic is being phantom powered via my computer audio interface, then coming from an output of the interface and entering the circuit at line level.

I now need to add a 48v phantom power circuit so that the mic can be powered directly from the instrument. I've purchased a 12v-48v DC-DC converter (this one) which seems to work fine. My question is about how to incorporate this without damaging the subsequent circuitry.

This is essentially my proposed circuit. Phantom power works by putting both signal pins of the XLR at 48v with respect to ground; the mic signal is amplified by a LM386N-4 power amp and this signal controls the oscillators via an LED-LDR arrangement. I haven't included the rest of the circuit, since I'm mainly worried about whether the phantom power will damage the LM386N-4.  (I'm also not too bothered about audio fidelity, as the mic signal is only used to control the oscillators, and won't be directly audible - it just needs to be high enough going into the rest of the circuit):

What I'm particularly worried about is blowing up the LM386N, perhaps by it internally referencing either of its inputs to ground (and hence seeing 48v across some of its internal structure). Will this circuit work, in the sense that it will amplify the mic signal without damaging anything?

Incidentally, the phantom power circuit proposed here suggests putting a pair of zener diodes between each signal line and ground, as shown below - would using these in my proposed circuit prevent damage to the LM386N-4, or any subsequent circuitry?


texts:
How do I transmit 16 bits of data with UART to a 16 bit array?  I've got two elements in my array, my UART is set up as 8N1 and my DMA is set to circular.

I'm using some HAL stuff, and here's my setup:

extern uint16_t tx_buffer[2];
extern uint16_t rx_buffer[2];

  MX_DMA_Init();
  MX_USART1_UART_Init();
  HAL_UART_Receive_DMA(&huart1, (uint8_t *) rx_buffer, 4);

However, when I send a string  of 4 8N1 bytes, my array looks like this:

p/z rx_buffer
{0x88, 0x00}

I've tried a few different permutation of changing the type for the pointer in the HAL_UART_Receive_DMA function as well as the type for the arrays...I've also tried 2 & 4 for the DMA length, but still nothing works.

Any idea why this is happening?

Thanks


texts:
I have two 24v LED warning lights for a driveway gate, red and green. The gate opener unit has a circuit so that when the gate is open, it lights up the green LED and when it’s closed the light goes off. I need to be able to do the inverse of that, ie when then gate is closed, the red LED illuminates. I can provide constant 24v from the gate opener for the circuit as well as the switched 24v. I don’t know how to switch on the red light when the gate is shut, any help would be greatly welcomed!

Table 1. '?'s to be fixed by OP. [Transistor]

Gate        Contact   Existing   Desired
========    =======   ========   =======
Closed      ?         off        red
Opening     ?         ?          ?
Open        ?         green      off
Closing     ?         ?          ?


texts:
I needed a circuit to take a short pulse in, and then hold a pin high for longer than the input pulse. I came up with this solution:

Note that the output went to the base of an BC548 NPN transistor, via a 1k resistor. The circuit runs on 3V3.

I've probed the circuit and drawn in the scope traces at various probe points.

The circuit works, but is it a good solution? Could I have done anything better?

Thanks.


texts:
In this electronics problem, I want to determine the expression of the capacitor voltage.

The switch closes at t=0. The initial capactior voltage is 10V.

I tried to do a Thevénin equivalent circuit, and for that I assumed that the switch was on. I had no problem finding the R equivalent. But when I tried to determine the Thévenin voltage due to the current source, I wasn't able to obtain it.

What I did:
\$\ 7I=I_1+I_2\$ (1) and\$\ R_1I_1=R_2I_2\$ (2)

But because \$\ I=I_2 \$, the equation yields\$\ I_1 =6I_2\$ and i get nothing when I substitute this result into the (2) equation.

If I could have the value of the V thévenin, I think I could solve this easily.

But if this problem isn't meant to be solved by the equivalent circuit, should I I consider the closed switch and the current \$\ 7I \$ to flow through the capacitor?Am i missing something?

Thanks in advance.


texts: how to trip a MCB without short circuit or over load?

texts:
I want trip a MCB whenever I want to trip using some ckt.I have found that there is two mechanism by which mcb trip:
1)Bi Metallica expansion
2)Solenoid effect.
So i think of controlling the solenoid by some external connection.But till now nothing works.
Plz give a way so that i can do it.


texts: What are holes? How they exist in pn junction

texts:
I always wonder that what are holes
I know electron and I can imagine it
But how holes exist...


texts:
Get ready for a question about an absurd idea I'm trying to determine the feasibility of. I want to both heat and cool a flat 3mm aluminum sheet of dimensions 50x50cm (half meter squared). If cost isn't an issue, and power considerations aren't either, is there a way to wire 100 Peltier plates (with dimensions 50x50mm each) together in a grid to provide temperature control over the aluminum sheet? I was thinking of using 12V, 30W ones.

The aluminum sheet would have to be cooled to 10 degrees C and also have the capability to heat the aluminum sheet to 80 degrees C. There needs to be uniform temperature on the entire surface of the plate within plus or minus 0.2 degrees C. Ideally it should reach the temperature set by the control system in approximately 15 minutes (no longer than an hour)

What kind of heat sink system would I need to have both cooling and heating capability (possible to swap hot and cold sides with reversing current direction)? Could I make a system that has the aluminum sheet as the top layer, then one side of the Peltier connected to the sheet by thermal paste, then on the other side a heat sink system with fans that pull air away from the Peltier?


texts: Connecting Solid State Relays To AC Heating Elements - Is this circuit correct?

texts:
I'm converting a 1500W toaster to a reflow oven with PID control, but I'd like to focus on the hardware aspect.

I've pulled the switches and controls out of the oven and I'm left with something like this as if the oven is in bake mode which is all heaters and the convection fan:

simulate this circuit – Schematic created using CircuitLab

At the bottom is the "new circuit". Is this a "good circuit" for the controlling the top and bottom heating elements? Anything to look out for? I'm open to suggestions for improvement of the design as well.

I'd like to keep the convection fan intact as to keep the top and bottom more evenly heated.(It's a shaded pole motor like this)

I'll be using all of the correctly rated hardware electrically and thermally speaking. Heatsinks and cooling fan will be used on the SSRs.

Update:
The second, modified, circuit with the SSRs works.


texts:
(Originally asked on engineering StackExchange, I was directed to ask it here)
For a project, I need to create a spark gap that only triggers when there is a conducting material between the 2 contacts. That wouldn't be a problem, normally, but in this specific case, the arc would have to close a distance that is larger than the distance between the poles. I provided an image for explaination.

I need a way to sort of direct the electric field in such a way that it basically follows that path and, when the conducting material is placed there, it would simply arc down to the next connector. Think of it as a wire leading to the material. But I have no idea how to create such an "air wire", or if it even is possible. I considered something akin to a cathode tube, the electrons here move in the form of a beam and don't "search" for their own path. However, this wouldn't work, as then we'd already have an electron flow, instead of it beginning to arc when the conducting material closes the spark gap. Does anyone know how to solve this? Thanks.


texts: Idea for a modern LightGun, would it be possible?

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Old lightguns used CRT monitors to work, and are not compatible with modern systems anymore.

I've com up with an idea and would like to know if it's doable and what problems there could be.

The idea is to stick a Infrared Laser inside the gun, and fit a webcam right underneath the laser.

When you shoot the webcam sees the monitor (brighter than the surrounding) and sees a bright spot from the laser where you shot. With some graphic modules it could straighten the image and calculate where you have shot. With the modern quad-core raspberries it might be powerfull enough to calculate this fast enough and send the coordinates to the console/pc.

Would it be possible?

Thanks


texts: Why did my meter read 6 volts dc in the speaker output of a car radio?

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While probing a "live" car stereo pins, I also probed the speaker output pins but left the meter in dc volts mode and got a reading of 6v, wich I think is odd, as I asume the output should be considered AC.

I want to know why would the meter show that reading? Is it the meter or could be the radio?

I had the black probe connected to vehicle ground and was probing all the unused pins with the red one (trying to find is the radio had a 12v pin that where "hot" when the radio was ON, like the connection used to turn on external amps...) The back of the radio has three connectors but only one is used in my car (I know one is for external CD changer and the other for rear speakers) however, I could not find the exact information for my unit but for a similar one, that's why I probed all the pins, in case some of them didn't match the description I had.

It was the same reading regardless of how much I Increase the volume, but if I turned the radio off, the voltage reading would slowly drop to zero (taking somewhere beetween 30 seconds to a minute to get to zero). Any of the speaker pins would give out that reading, the marked as negatives included.

I do not think the radio puts a DC voltage through it output as it would make the speaker cones go up (or down) and "stay there" or oscilate around that offset position, wich it doesn't. It also does not pop or click the speakers when powering on or off.

The radio is a factory unit made by Panasonic Automotive Systems (Thailand), (Model no UN36 66 9CO, CQ-LM8282TA) and is labeled to use 4Ohm speakers.


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What does P indicate in this expression?
F(A,B,C,D) = P(4,5,6,7,8,12,13)+d(1,15)
And does d(1,15) represent don't care condition?


texts: I have completed a lab studying using an AC step down transformer. However, I am wondering under normal operating condition, when would a transformer be operating at full power? It seems that during the lab all power ratings were very low, which makes sense to me. However, is there a case in which full power would be reached? perhaps testing?


texts: How to find the operating current consumption of the op-amp?

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I am trying understand the worst power consumption of an op-amp. Lets take this part: LM833. Supply voltage +/- 5 V and the supply current is 8 mA. I am considering that the total operating power as 5*8 + -5*-8 = 80 mW.

How this can be wrong?

LM833 Datsheet