texts: Proper way to solve first order circuit with voltage dependent voltage source


texts:
I am looking for some help with wiring for a large battery array using 18650 lithium ion batteries.

Ok so I am looking at going solar and lead-acid batteries are too low overall capacity and their life span is too short.

I would like to make a number of batteries using 18650 wired in parallel to give me overall a 12v or 24v (depending on charge controller) 2500Ah or 1250Ah depending.

I am thinking I can in a 12v system wire 4 18650 batteries in series, that will be my cell and then say 100 cells in parallel and call that a block. I can take 4 of these blocks to give me a large battery with enough capacity for running my house and using a solar array to charge them via the charge controller. I want to know if this is practical and what are the balancing issues?
Each 18650 battery is 3.7v 4900mAh.
By my calculations and please explain where I am going wrong
Cell: 12v * 4.9 = 58.8Wh
Block: 12v * 490a = 5880Wh
4 Blocks: 5880Wh*4 = 23520Wh

The Batteries I can get at around $1.3 USD a piece.
I am aware of the need for balancing and am concerned about safety issues.


texts: Weird voltage measurements on transistor

texts:
Just as an experiment, I decided to put together the following "circuit":

I then went ahead and measured Vbe, Vbc and Vec and this yielded the following results:

Vbe = 0.602 V
Vbc = 0.589 V
Vec = 0.013 V

Here is the question: As you can see from the circuit above, the Collector is not connected to anything so shouldn't Vbc be an absolute zero? Why am I measuring 0.589 V?

Thanks.

EDIT: I wanted to be more specific regarding what is really confusing me, I am not sure if this will make a difference or not but here it goes:

First let’s take the circuit mentioned above and replace the transistor with the diode equivalent analogy. I realize that replacing a transistor with two diodes is not truly equivalent but I just want to make a point.

Looking at the circuit above, it is clear that the diode representing the collector pin is doing absolutely nothing. As a matter of fact, it should be perfectly fine to just remove that diode and the circuit should behave exactly the same right?

What this reveals is that the collector plays no part whatsoever in this circuit (it should be like it is not there at all) and yet, somehow, I am getting a Vbc voltage. Is that crazy or what?

Of course, the fact is that the collector IS playing a role here, this is the only logical explanation for the reason there is a voltage across Vbc. But why is this happening? Is the diode analogy of a transistor not accurate?


texts: Is the PWM rail of a 4pin pwm Computer fan Positive or negative

texts: I am wiring a 4 pin computer fan to a 12v dc power source and I am wondering the pin for the PWM is positive or negative.


texts: Circuit that switches one led or all three

texts:
For an analog photo enlarger (yep, that vintage stuff) I own, I would like to build my own lightsource.  For the prototype I found 3 colored super bright led panels they use 12V

The problem is that I need to turn on the lights in a specific setting:

The Green Led source OR
The Blue Led source OR
The Red led source OR
All three at the same time (Green Red Blue, thus delivering white light).

I know how to put the lights on power, how to solder them on a board, but I have no idea what a smart solution should be for such a circuit, what kind of switches I need. The solution must provide ONLY the settings as described. So e.g. a Blue and Green at the same time is not allowed.

some background information: The black and white photo paper is sensitive to blue and green light, but in a different manner. By mixing both color's exposure times I can influence the contrast and the tone of the result. The paper is insensitive to red light, that enables me to project the image on the paper without starting the exposure process. The white light (RGB) is used for focussing purposes.


texts: How to design compensator for control system

texts:
I wanted to make this system so that there is zero steady-state error when there is a ramp input.

As far as I know there is no steady-state error in a type 2 system so to turn G(s), a type 1 system to type 2 system I add an integrator (1/s) so that there will be 2 poles at the origin thus making the system type 2 but by doing this the system become unstable and no matter how I adjust the gain it is still unstable because there will always be a positive pole.

And as far as i know to fix this, i have to add a lead or lag compensator but the problem is i dont know how to design one. I watch a lot of videos in youtube regarding designing a lead/lag compensator but i still dont understand. Hopefully someone can help me with the design of this compensator.

I think that is how and what i am suppose to do to ^


texts: High power factor but maximum current at resonance in series RLC circuit

texts: In a series RLC circuit, at resonance, the power factor is unity but the current is high. But since in high power factor the current drawn is low, then isn't this a paradox? High current is undesirable, so we have high power factor, but the current is maximum at resonance frequency in a series RLC circuit. Can any one explain?


texts: What is the meaning / significance of this Capacitor Symbol?

texts:
In the SanKen data sheet for an Off-Line PWM Controller (found here) they use, in several places, a schematic symbol for an electrolytic capacitor that I haven't seen before (see C6 in the image below).

The image was taken from Chapter 12. Reference Design of Power Supply. And from the Bill of Materials they list "C6 Electrolytic 22 μF, 50V".

What is the meaning / significance of the the three slanted lines on the capacitor symbol?


texts: how could i decrease residual voltage of 11KV bus that Is created by direct online 9MVA induction Emotor?

texts:
We have power grid 11KV (bus A & bus B) with 2 incoming and one coupling breaker between them;bus A have a outgoing that feed 9MVA induction Emotor;
incoming A and B and coupling Equipped with ATS system;
after cut off incoming A voltage ATS system opens up incoming A and close coupling and bus A now fed by incoming B;
after close coupling breaker because of existence residual voltage in the bus A that comes from 9MVA induction Emotor ; 9MVA induction Emotor trip by i differential that Arises of coupling voltage of bus B and residual voltage of bus A
question is:
1.how could i decrease mentioned residual voltage?
2.Is there protection relay that in the proper time provide permit to close the coupling breaker to prevent of create i differential in the mentioned Emotor? (except of 27R because we have it and it is not proper function for this reason)


texts: What is the purpose of the NLSF457 from On-Semi?

texts:
I was browsing On-Semi just looking around when I ran across the NLS457.
I hit Google and Bing and after trying multiple search terms have came up with 0 hits would answer my question.

The weird part is that I can not find anything even mentioning it, wither at On-Semi or via search engines.  I can't believe that they would go through efforts to design, make and sell a chip that has no purpose.  It's a new chip(2018) in a small package and so might be useful in a modern device of some kind, I just don't have a clue what it could be.

It takes the output of two AND gates, each of which has an inverted input and feeds it to an OR gate.  It looks like something that might clock related, but in that case I would have thought Schmidt trigger inputs would have helped it's usefulness.

It's most likely something real obvious, but all of my schooling was over 25 years ago, most of which was not working in electronics.  I'm getting the feeling that I'm going to be feeling rather stupid after it is pointed out to me.


texts: ATMega328P control servo motor speed with potentiometer

texts:
I'm trying to develop an application in atmel studio 7.0 which will allow me to control the speed of my servo motor with my potentiometer. Now, the problem is that I don't really know how to do that? Also my servo motor spins around and around instead of going 0 -> 45 -> 90 degrees and then back the same way again. I've managed to do a successfull convertion of analog signals to use, and I've set my admux input channel to 2; also, my pwm channel is 10 for the servo motor. I use an Arduino Uno with Atmega328P processor with 16 000 000 Hz.

Might also say I'm pretty new to the use of PWM, which is why this would be an exciting thing to do.

Heres the code this far:

void initPWM();
void initADC();
uint16_t doConversion(void);

int main(void)
{
    DDRD = 0b11111111;
    DDRB = 0xFF;
    initADC();
    initPWM();

    while (1)
    {
      PORTB = 0b00000100;
      OCR1A=250;   //0 degree
      _delay_ms(2000);

      OCR1A=375;  //45 degree
      _delay_ms(2000);

      OCR1A=500;  //90 degree

      _delay_ms(2000);

      OCR1A = 0;

      _delay_ms(5000);
    }
}

void initPWM(){
   TCCR1A|=(1<<COM1A1)|(1<<COM1B1)|(1<<WGM11);        //NON Inverted PWM
   TCCR1B|=(1<<WGM13)|(1<<WGM12)|(1<<CS11)|(1<<CS10); //PRESCALER=64 MODE 14(FAST PWM)
    ICR1 = 4999 ; // 50 Hz
}

void initADC(void) {
    // Configure the ADC module
    ADMUX = 0b11000010; //Set channel 2
    // REFS1:0 = 01 -> AVCC as reference,
    // ADLAR = 1 -> Leftadjust
    // MUX4:0 = 00000 -> ADC0 as input
    ADCSRA = 0b10000111;
    //ADEN = 1: enableADC,
    // ADSC = 0: don't start conversion yet
    // ASPS2:0 = 001: pre-scaler= 2
    // ADATE = 0: disable auto trigger,
    // ADIE = 0: disableADC interrupt
}

uint16_t doConversion(void){
    uint16_t result;
    // Start conversion by setting flag ADSC
    ADCSRA |= (1 << ADSC);
    // Wait until conversion is  completed
    while(ADCSRA & (1 << ADSC));
    // Read the all bits, output to PORTB
    result= ADC;
    return result;
}

I used 4999 as the value for ICR1 since I have a 16000000 Hz CPU and use a prescaler of 64.

My servo motors degrees are based on the following:
0 degrees = 1000 microseconds
45 degrees = 1500 microseconds
90 degrees = 2000 microseconds

PORTB is for using the pwm, and the potentiometer is connected to channel 2.

Does anyone know what I did wrong? Or can help me solve/accomplish what I'm trying to do?


texts: Confusion about relationship between energy per coulomb, and the amount of coulombs in current

texts:
I am trying to understand how a power supply works and working from the ground up I am learning about electricity, voltage, current, amps, and wattage. I am new to this stuff so I apologize if this is an easy or already answered question.
From what I have read so far, here is my understanding:

electricity in a current is the movement of free electrons through a conductive material. The free
electrons "hop" from one atom to the next.

a coulomb is a unit of charge.

Charge by itself is just a property of an object, number of electrons or lack thereof. When charges are separated, they create an electric field, which then allows you to define potential energy that an object in the field would have, depending on its location in that field, regardless of its charge. The potential energy is the Joules/Coloumb at that specific point in the e-field, which is volts. If you take volts * charge of object in the field at that point, you get the electric potential energy that the charge would carry.

That electric potential energy is converted to some other energy for useful work as the charge moves through the current - light, heat, or power for a component. This is analogous to how potential energy of a falling object in a gravitational field is converted to kinetic energy.

The AMOUNT of charge, moving past a specific point, is the Amperes. This is a rate measurement in coulomb's per second.

Voltage and Amps are directly proportional. If you take voltage, which is joules per coulomb, and you take amps, which is coloumbs / s, and you multiply them, you get joules / s. This intuitively to me, means the amount of energy that can be provided to some component in a circuit, per second. This is Watts.

My confusion is that I don't understand the relationship between "amount of charge" and "energy of charge". A common analogy used here is water and water pressure. If I have a tank filled with water, and I attach a hose at the bottom, and I apply X amount of pressure, a certain amount of water (measured volume of water) will move past a certain point in the hose at a rate of Y. If I increase X, then the water molecules move more quickly through the hose, meaning numerically more water molecules move past the certain point, so Y (flow rate volume / second) increases. So, more pressure causes water molecules to move faster, meaning more water gets through the hose - i.e more volume of water per second.
With voltage and charges, voltage is supposed to represent pressure. If I increase the voltage, the numerically more electrons - more units of charge - flow through the circuit. But due to what? In other words, my question is:
Which of the following is correct?

More couloumbs AND more energy per coulomb: When voltage increases, amount of energy per unit of charge increases. This means each unit of charge is more "energized", and BECAUSE of that, moves faster through the circuit. Faster charges means MORE charges move through the circuit per second, and because each charge is MORE energized, there is more joules per second at any given point in the circuit (more work).

More coulombs BUT same energy per coulomb: When voltage increases, more units of charge flow through the circuit. But each unit of charge still has the same amount of energy as before the voltage increase. The increase in potential energy is spread across more coulombs of charge.

Same number of coulombs BUT more energy per coulomb: When voltage increases, the number of coulombs flowing through the circuit remains the same, but the energy per coulomb increases.

I know 3 will not be true because of V = IR, but I want to understand this on an intuitive level. Does the increase in voltage equate to increase in energy per unit of charge, or does an increase in voltage keep energy per charge equal but forces more charges to flow through the circuit?


texts: Where might the fault be in this battery checker circuit from an old camera?

texts:
I'm repairing an old rangefinder camera, a Canonet QL17 GIII.

I have had to do a lot of internal rewiring. All is now working, except for the battery checker functionality. I've included that part of the circuit diagram below.

When the switch closes, the bulb X61-7132 should light up (if the battery is still in good shape), but doesn't.

The battery is a 1.4V SR44 battery, instead of the mercury cell that the camera was originally designed for. I am pretty sure this shouldn't affect the operation of the checker circuit.

If I connect the lamp directly across the 1.4V circuit, it lights up, so I know that works.

When the switch is open, everything in the circuit floats up to 1.4V (actually, 1.53V according to the meter).

I have numbered some junctions in red in the diagram. When the switch is closed, I read (relative to ground):

1.53V at junction 1
1.15V at junction 2
0.40V at junction 3

I am not sure if this seems correct, or what else to check.

However, it seems odd to me to read 1.53V at 1. I would expect at least a small voltage drop there, but it seems to be floating up. What should that transistor (2SC 182R, according to the parts list) be doing?

What should (and how) should I check next?


texts:
I am trying to create a capacitor bank and don't know what voltage to put through. Do i add the voltage of all the capacitors up and apply that or just provide the voltage for one.

e.g. If I have 10 16v capacitors can i apply 160v?


texts:
Just wanted to clarify my understanding before I design my circuit.

This is based on my previous question

I have an 3.3V LDO Regulator.

Vin = Regulated 5V

Vout = 3.3V

Load Current = 100mA.

At the output of the LDO, I have a PI Filter Capacitor.

I am having a reverse current of 16uA flowing into the LDO.

Can someone help me to understand how does a reverse current builds up my output voltage from 3.3V to 4.2V.

I am planning to add a Zener rated 3.6V after my Pi filter. I just want to understand how does a small reverse current of 16uA builds up my output voltage from 3.3V to 4.2V?

Does this reverse current hit the inductor of the pi filter and get accumulated near the output side of the inductor to finally bring the output voltage from 3.3V to 4.2V?
Or what's happening?

Thanks


texts: Derivation of output voltage of a Colpitts Oscillator

texts:
I have been researching how the oscillations across the Drain and Source terminals of a FET occur when it is switched off. I have come across this explanation that it is due to feedback from parasitic capacitance across the Drain to Source terminals of the FET.

This PDF document I found online (Toshiba - Parasitic Oscillation and Ringing of Power MOSFETs) explains it in more detail stating that the reactances across the terminals of the device act as a Colpitts oscillator.

With all that I have read on the subject of Colpitts oscillator I cannot see how the expression for V2 is derived below:

I watched a video online about how a Colpitt's oscillator can be constructed using an Op amp where a gain applied to the input will permit a continuous (non decaying) sinusoidal output provided that it has the resonant frequency.

Here an expression can be determined simply using the voltage divider rule at the output of the Op-Amp with respect to the Impedance network shown on the left.

I then thought to apply the same logic to the circuit shown in the PDF as follows:

My guess was that I could calculate the Impedance due to the parallel RC combination as follows:

(Please excuse my use of photos to explain my logic. I at present only have my phone to work from and entering formulas etc. is difficult.)

Only it doesn't matter how hard I try to resolve this network to find how this expression is calculated, or repackage my own derivation, I can't make sense of this.

Does anybody see something I'm not seeing?


texts: I need to open a .brd or. sch file in proteus professional. What should I do?

texts:
I want to simulate a project which is in .sch and .brd files.
So I've installed Proteus pro 8.10. Now I can't open the project in it. What should I do now?


texts: Motors on autonomous driven vehicle free spin in opposite direction they are turning while powered

texts:
I work as a project manager for an Automated Guided Vehicle manufacturer located in Germany. I have a small team of technicians that assist me in installations and maintenance support in the US.

Currently we have a vehicle that is causing an issue with the motors. We can give this vehicle a drive command, which it follows. When we apply force in the opposite direction, the unit will roll in that direction. As soon as we let go of the AGV it continues to drive forward again. We have ruled out any input failures from the controls, since it releases the brake and actually drives forward or reverse when told to.

Does anyone know if this sounds like a mechanical failure inside both motors? What could cause a DC motor to exhibit these conditions?


texts:
I have just started learning the basics of electronics. I found a circuit which uses NPN as signal Amplifier and powered by 12V source. The signal source is a audio from Mobile headphone jack.

I tested the circuit, it works as expected. Now I need this circuit powered by a 3V Button cell. So I can pack the whole circuit in tiny enclosure and I guess it's completely okay to power a IR LED by 3v battery. I know I need to replace the resistor by lower value resistors and I don't know what resistors to use.

As I'm reducing power source to 1/4th of 12v. Do I need to use 1/4th of resistor used?
Also explain how to find out and Math behind it.


texts: I've created a temperature monitoring system using multiple DS18B20 temperature sensors and now I want to add some humidity sensors to it. The problem is that I cant find any 1-wire humidity or temperature/humidity sensors that use ID logic similar to DS18B20 (when you can get all IDs in the beginning and after that ask each by it's own ID). Is there really no such humidity sensors or I'm just missing something?


texts:
I am trying to find out why this system:

should have an Open Circuit Voltage of:

\$U = U0 + I0*R2 + 0*R3\$

\$  = U0 + I0R2\$

I understand why the R3 component doesn't change anything but I fail to understand why R1 isn't contributing anything.

To be clear with all of you. This is an old exam question that I'm using to study for the test but can't find the answer in either the textbook or in the lecture material.

Thanks in advance


texts: How do I redirect/regenerate an input clock to an output pin in my FPGA design (Verilog)

texts:
I've got an ADC that requires me to send it 20 clock pulses when requesting to read data out of its internal register (after I've triggered it to read data from my sensor).

I was able to simulate this just fine in ModelSim but I'm new to Verilog and didn't realize that I would run into problems during synthesis when creating the pulse train like this:

reg [4:0] counter = 5'b10100;
parameter counter = 0;

always (posedge clk and negedge clk)
  begin
   if (counter > 0)
     begin
       counter <= counter - 1;
       serial_out <= ~serial_out;
     end
  end

I tried splitting this into 2 always blocks: one which sets serial_out to 1 on a posedge clk and another which sets serial_out to 0 during negedge clk, both checking if the counter is greater than 0. This is problematic because I'm attempting to drive counter in two places and get errors stating "can't resolve multiple constant driver for net counter .."

Perhaps there is a better way to do this?

I've seen some posts suggesting to double the clk frequency to read the data off of the posedge of the clock. This would work but I need to keep the clock at 30 MHz (can't go to 60 MHz for other reasons).

How would you suggest that I conditionally route/replicate 20 pulses of my always-on periodic 30 MHz input clock to an output pin?

Any help will be greatly appreciated.


texts: MOSFET Over Heating. So hot it's melting the solder

texts:
Alright, continuing with the debugging of my new board tonight I found another issue worse than the one before: My switching MOSFET is getting so hot that I'm getting molten solder.

I replaced the MOSFET with a short circuit just to see if the components sorounding the MOS were the cause of the problem (mostly a big Inductor I have right next to it) but the copper reaches a temperature of 110°F, not enough to melt solder.

This is my schematic:

As you can see, my VGS is around -11V and I'm running 3A through it using an Electronic Load. Based on the datasheet of my NTD20P06L-D this thing can do up to 15.5A.

Any ideas of what might be going on?

The only thing I could think of was that the heat on the copper could be increasing RDS(on) but at that particular low current it shouldn't be so serious.

I am using the TO-252-3, DPak (2 Leads + Tab) package.


texts: Increasing ESD protection on Isolator part of the board

texts: How it is possible to increase ESD protection of isolator ISOW7842DWER to tolerate 8KV ESD spike?


texts: How do you plan and check if a device will be compatible with every other device it will encounter in the field?

texts:
Hello I have a question that hopefully I can clearly state my question well enough.

I work in television broadcasting and simply take off the shelf converters that take various signals and convert them to fiber. The issue I found was with taking a analog genlock signal such as blackburst or trilevel converting it to fiber and patching it back to coax for the camera (so a transmitter and receiver configuration).

The Sony HDC-P1 camera has no issue with the signal. However, the Sony HDC-P1 "R" series will not accept the genlock from the receiver. The converter is a VOS-1000FT/R, and I found it simply takes the analog video signal converts it to digital via a ADC, goes into a FPGA, gets serialized and passed to a SFP where the receiver de serializes and goes to a DAC, and finally through a filter and to the camera genlock input.

Now the signal looks darn fantastic on the output, no noise in the output and looks to be coupled via a capacitor, BUT has a horrible DC offset of 1.7VDC. Only if I take the signal out of the DAC before the filter (Voltage at .5VDC) and pass it though a RC circuit of 100 Ohm and 100 pF and plug it into the camera genlock port does the voltage drop to .1VDC and it's happy all day.

I am familiar with using opamps and other feedback methods to clamp the signal and the more expensive yellobrik converters and bluebell do a better job, by generating their own analog video signal on the output and clamping all in a isolated fashion. Voltage measurements on both devices and found to be close to zero.

Finally, my question is about designing a product that needs to meet a standard for all devices that it will interface with. How do you determine this and build it in to the product?

The composite signal coming out of the cheap converter looked fantastic and very clean but had the DC issue that the other camera had no issue with. And all the chips are commonly used and look the be implemented using best practice.

How does a large company such as AJA with certainty know there products will interface appropriately with every other device produced is it in the test equipment used?

Thank you very much for taking the time to read this and answer. I'm only 27 years old and can only lean on the backs of a few of my elder friends who worked for Motorola in the 70s and 80s, and these technologies are too far outside of their experience.


texts: Help understanding/selecting SMPS to drive capacitive load

texts:
I recently bought several SMPS buck converter supplies for a project. They all had about the same specs, typically 90-270VAC input, 12VDC output. Having an expected worst case continuous load of about 200mA, I selected devices with output ratings of between 300mA and 500mA. Also, since my circuit employs a fairly large capacitor (2700uF), I was careful to select units claiming to be short-circuit tolerant, specifically stating "output returns to normal when short condition stops".

Well the results were a really dismal eye-opener except for one company! Surprisingly, the best device I tested was made by a China based company (SANMIC) and was only rated 300mA. Yet it took on the load, capacitor and all, like a champ. Unfortunately that was NOT the case for at least 4 other boards made by other companies with similar specs. These would basically oscillate slowly (maybe 5hZ) attempting to drive the load, but would never actually start. The diagram and graph I'm posting is admittedly a crappy image made with a paint program, but it fairly accurately depicts what I'm seeing in all but one of these supplies.

So other than the obvious answer of "buy better supplies", I'm hopping to understand (1) Why its so hard for these supplies to "bring up" a capacitive load to rated voltage, and (2) what key features should I look for to get a better (and RELIABLY better!) result. Obviously "short circuit tolerant" has proven to often be false. I can't simply choose an arbitrary higher current rating, since a capacitor at time=0 will always seem to demand infinite current. Obviously some companies know how to do it, but I'd never be able to tell them apart by the specs!

By the way, its irrelevant to the question, but the reason for the capacitor is because an MCU, upon detecting the power "going away", needs to do several things including opening relays in an specific sequence and saving all its program states to NV ram. The 2700 uF gives me about a second to do that.


texts:
I am designing a buck converter. I have found an inductor to use for it but it consists of 4 pins. Will I not need only 2 pins? The inductor is: WURTH ELEKTRONIK  7446622002  CHOKE, COMMON MODE, 2.2MH, 2A.

Heres the link to datasheet:http://www.farnell.com/datasheets/1735935.pdf

Can you please tell me how can i use (which pins to connect) this inductor for my application?


texts: Will a PWM-Enabled MCU Work With Any Motor?

texts:
Why do so many MCUs specify what kind of motors they work with?
For example: http://www.microchip.com/pagehandler/en-us/technology/motorcontrol/

Surely, the MCU has no concept of a motor and it simple outputs a PWM signal which can then be interpreted by anything (e.g a VFD).


texts: hall effect sensor as a toggle swich for a 12v strip of LEDs

texts:
I'm trying to use a unipolar hall effect sensor as a power switch to turn off and on a 12V strip of LEDs, powered by a 12V 6.6Ah battery. I just tested the current draw of the LED strip with a multimeter and got a value of 442mA (much less than the 5A the seller on ebay claimed... maybe they weren't taking into account the resistors that were already integrated in the strip?).

I've seen some Hall effect sensors that can handle up to 500mA, but some of them are a bit expensive and I already purchased some of these. They're rated for 4.5-24V, with a continuous Output current of 25mA. It's supply current is 9mA (not sure if that's important).

If I use a resistor to limit the current that the Hall effect sensor gets, that would also make the LEDs appear less bright too, right... or am I wrong? Using ohm's law, it looks like a 480 ohm resistor is what the hall effect sensor needs (12V/0.025A = 480 ohm resistor).

Would it be possible to use an N-Channel MOSFET between the 12V 6.6Ah battery, hall effect sensor and LED strip, or would I need a microcontroller (arduino/attiny) and a 5V regulator to do that?

I'd rather avoid using a microcontroller, and keep this as cheap as possible unless there's no other way to avoid majorly affecting the brightness of the LEDs.

Any advice would be appreciated, Thanks!


texts:
I have a nitro engine that’s idling at 1600 RPM. As the title says , I also have a BLDC coupled directly to the nitro engine working as a generator. That generator is capable of producing 3.5kW of power. Here’s the diagram:

So , generator is capable of producing 3.5kW of power at around 2000RPM. Let’s say engine is revving up and we have 3.5kW out of the generator. Up until this point , let’s assume an ideal condition and we have a constant power supply of the said 3.5kW .

My plan is to supply this power directly to my quadcopter. Is it possible to work it this way without looking at the current or voltage draw by the motors as long as all four of my motor’s Current times Voltage is less than 3.5kW ?


texts: less-than-unity inverting op amp oscillating. Why?

texts:
I've got a GPS disciplined oscillator design I'm working on. Suddenly, the prototype I'm working on at the moment seems to be suffering from what is being caused by oscillation in control voltage.

Here's the portion of the circuit of interest:

simulate this circuit – Schematic created using CircuitLab

Not included in the schematic is a 0.1 µF bypass cap across the power supply pins of the amp. The actual amplifier is an AD8538, but CircuitLab doesn't have one of those.

The input to this portion of the circuit is the output of an AD5061 DAC. The output of this circuit goes to the control voltage pin of the oscillator. The input includes a low-pass filter (the 22 ohm resistor and 10 µF cap), as the actual voltage is only expected to change every 100 seconds or so. The purpose of this amp is to reduce the swing range of the DAC and to act as an impedance buffer between the DAC and the oscillator. The 10k resistor on the output is additional loading, as the oscillator actually has a 100k input impedance.

What I'm seeing is around 6 mV P-P of an approximately 22 MHz sine wave being imposed on the output.

No me gusta.

The power supply has around 2 mV P-P of ripple, but it's not anywhere near the 22 MHz of the oscillation I'm seeing. The oscillator's output frequency is 10 MHz, so it doesn't seem like it's coupling that to me.

What's going on?


texts: Motor Voltage and Current Limit of Brushed DC Motor

texts:
What fundamentally limits the applicable voltage in a motor? From what I understand, the input to the motor is a relatively constant impedance (since speed is on the order of 100 Hz) and it is primarily just the winding resistance.

Then, if I increase the voltage, the current increases, and so does the magnetic force that moves the actual windings. If I put in more and more current through the motor, the drivable mechanical load theoretically can go higher unbounded, but in reality, the temperature will get too high. Does the temperature getting too high increase the winding resistance and limit current? If I could theoretically remove all generated heat, could even the smallest motor drive huge loads because I wouldn't really have any current limit (assuming mechanical components don't break)?


texts: Delay-off circuit for h-bridge motor control

texts:
I'm looking for the easiest way to generate a variable PWM signal (set by hardware) without a microcontroller for a set amount of time when a microcontroller is turned off.

The H-bridge (image below) is driving a 12VDC fan that is sitting directly underneath about ~1,200W of heating coils in a coffee roaster, heating the air up to ~500C. If the power is cut to the arduino, I would like the fan to be driven with a PWM signal (~50% - 70% duty cycle) for ~3 to ~10 seconds, so that it isn't heat soaking into the plastic fan blade below it.

I'm not sure what 'CT' and 'VT' are, I'm assuming this dual motor driver is controlled by the 'LPWM' and 'RPWM' and I'd just use a single input / single output for the fan.

Can I use something like a 555 timer to generate the PWM signal, and then use a resistor between that and the Arduino pin tied directly to the H-Bridge input, so that when the arduino is powered off and enters high-impedence mode, the ~50%-70% duty cycle signal takes over, but when it is powered on and driving the pin, it is irrelevant?

How can I also time this out after a set period after the arduino has lost power? I'm looking to do this safety feature without adding a second microcontroller, if possible.


texts:
The input of the band pass filter is 30Khz triangular wave of 1Vpp. I want the band pass filter to allow 27k-33k Hz . I have used these values based on the formulas I found online for this band pass filter.

Unfortunately the problem seems to be , that at high frequencies eg. 60kHz it does not cut them off and the second problem that it reduces the 1Vpp to 500mV Vpp which I don't want either.

This is with input of 30khz(in green ) and band pass output (in blue)

And this is with 60kHz input (same colours)

To me it seems they are the same, which is bad. What I am doing wrong , which values should I use

ps. the formulas for the values I used are on this site http://www.electronics-tutorials.ws/filter/filter_7.html


texts:
I am trying to determine the mesh currents in the following circuit. I consider the mesh currents (from left mesh to right mesh) to be called I1 and I2.

simulate this circuit – Schematic created using CircuitLab

Considering the two meshes present in the circuit, I obtain the following system of equations:

Mesh 1

(400k)I1 - (180k)I2 = -24

Mesh 2

(-180k)I1 + (457k)I2 = 27.3

Solving the above system of equations on my own yields the results:

I1 = 40.25uA and I2 = -43.88uA

I've double checked and everything seems okay in terms of mesh equation setup. Then I've verified my results with a simultaneous equation solver. However, I've simulated this circuit and the results of my simulation do not agree with the system of equations... Here are the results of my simulation, what is going on?

In case you cannot see the image, the results of the simulation are...

I1 = 57.82uA and I2 = 36.96uA


texts: Playback volume from old Sony voice micro cassette recorder is very low

texts:
I have an old Sony V.O.R M-529V microcassette recorder. It was found in a box packed away years ago.
I put in some fresh batteries and tried to play some old micro cassettes I had, but the play back volume from the recorder even at full volume from the speaker was almost inaudible. I tried plugging in an earphone and the audio was a bit more audible but still quite low for full volume.
I tried a few different tapes but that did not make any difference. I tried changing the recording speed modes, but no change. I tried different batteries, again the same thing.
As a last resort I cleaned with some q-tip and head cleaning solution. Again, no change.
I opened up the recorder and see that the belt of the pulley is fine, the board also looks perfectly fine. No corrosion or damage of any kind inside.
Do you guys think the magnetic head is damaged or maybe the audio IC on the board is dead? Any suggestions on what I should look into?
Update: First of all thank you so much for the replies and suggestions. After looking at the feedback from you guys I decided to open up the recorder and inspect the head connections, the belt and the board components thoroughly. Head and belt seems to be fine.  But I did notice that after recording if I try to plug in a headphone or computer speaker via the 3.5mm jack the audio does play but had a lot of noise and distortion. But pressing down the JRC 2128 IC made the sound louder and distortion sometimes reduced but was still present. I took a closer look and found the soldering connections had a slightly white crusty coating all over the connections on most components and some residual brown stuff mostly flux I guess. Which can be a a bit corrosive at time. Any way I put flux all over the board and reheated all the connections & reapplied solder and then cleaned it with ethyl alcohol. Then sprayed the volume pot and jacks with CRC co-cleaner contact.
Now I tried playing back and the volume from the main speaker was a lot louder but there was lot of distortion. I'm confused if this is a blown speaker or some issue with a component like a short SMD capacitor or something. But playback through the 3.5mm audio jack is perfectly fine now! :) The cassette on the right is okay but audio recorded on the left one seems to be the better. I tried recording a song and then playing back via the 3.5mm jack and its fine.
Also as KristoferA mentioned I need to change the electrolytics as they may have dried up. But the issue is some of the newer replacements of those values are much taller and will not allow the board to be seated.


texts: Why does setting up some GPIOs cost so much memory?

texts:
I'm trying to write a library for my hobbyish purpose and it's almost ready for a smoke test. The only thing that annoys me is a called-once fuction :

(Note: all uppercase phrases are macro constants)

{
/////////// Interface clock enable
LCD_CTRL_PORT_CLK_EN;
LCD_DATA_PORT_CLK_EN;

//////////// Config control pins
//// pull up
LCD_CTRL_PORT->PUPDR &= ~LCD_CTRL_PORT_32BIT_MASK;
LCD_CTRL_PORT->PUPDR |= ( (0b01 << (LCD_CS_POS*2U))
                        | (0b01 << (LCD_RS_POS*2U))
                        | (0b01 << (LCD_WR_POS*2U))
                        | (0b01 << (LCD_RD_POS*2U))
                        | (0b01 << (LCD_RST_POS*2U)) );
//// set output direction
LCD_CTRL_PORT->MODER &= ~LCD_CTRL_PORT_32BIT_MASK;
LCD_CTRL_PORT->MODER |= ( (0b01 << (LCD_CS_POS*2U))
                        | (0b01 << (LCD_RS_POS*2U))
                        | (0b01 << (LCD_WR_POS*2U))
                        | (0b01 << (LCD_RD_POS*2U))
                        | (0b01 << (LCD_RST_POS*2U)) );
//// Max output speed
LCD_CTRL_PORT->OSPEEDR &= ~LCD_CTRL_PORT_32BIT_MASK;
LCD_CTRL_PORT->OSPEEDR |= ( (0b11 << (LCD_CS_POS*2U))
                            | (0b11 << (LCD_RS_POS*2U))
                            | (0b11 << (LCD_WR_POS*2U))
                            | (0b11 << (LCD_RD_POS*2U))
                            | (0b11 << (LCD_RST_POS*2U)) );
//// all control pin set HIGH (idle)
LCD_CTRL_PORT->BSRR |= (LCD_CS | LCD_RS | LCD_WR | LCD_RD | LCD_RST);
////////

//////////// Config data pins
LCD_DATA_PORT->PUPDR &= ~LCD_CTRL_PORT_32BIT_MASK;
LCD_DATA_PORT->OSPEEDR &= ~LCD_DATA_PORT_32BIT_MASK;
LCD_DATA_PORT->MODER &= ~LCD_CTRL_PORT_32BIT_MASK;

#if LCD_USE8BIT_MODE == 1
LCD_DATA_PORT->PUPDR |= ( 0x5555 << (LCD_DATAPORT_OUTPUT_OFFSET*2U) );
LCD_DATA_PORT->OSPEEDR |= ( 0xFFFF << (LCD_DATAPORT_OUTPUT_OFFSET*2U) );
LCD_DATA_PORT->MODER |= ( 0x5555 << (LCD_DATAPORT_OUTPUT_OFFSET*2U) );
LCD_DATA_PORT->BSRR = ( 0xFF << (LCD_DATAPORT_OUTPUT_OFFSET*2U) );
#else
LCD_DATA_PORT->PUPDR |= 0x55555555;
LCD_DATA_PORT->OSPEEDR |= 0xFFFFFFFF;
LCD_DATA_PORT->MODER |= 0x55555555;
LCD_DATA_PORT->BSRR = 0xFFFF;
#endif

I'm using True Studio and the platform is STM32F3. The function just plainly modifies some registers with constants derived from some macro constants.

But why it does cost almost 1 kB of flash (in .text section, I'm using Truestudio's build analyzer) although it isn't quite long ? Even HAL-GPIO function is 3x smaller.

Example macro:

#define LCD_XXXX_PORT  GPIOX
#define LCD_XXX        GPIO_PIN_X
#define LCD_XXX_POS    POSITION_VAL(LCD_XXX)


texts: How to turn on/off a sub circuit with a transistor

texts:
I bought a dtc144 transistor because it was written in its datasheet that it could do a "Switching circuit" ( as it is written in the Applications section in the datasheet). I though it meant that I could turn on/off a sub-circuit in my PCB design, but when I tested, it didn't worked as I imagined.

Did I misunderstand what switching circuit means? How can I use this transistor to turn on/off a sub circuit?

The datasheet (first page) has the following image:

(if you can not see the image, check the datasheet. I am having problems to upload the image)

I thought that as a transistor, if I put a GND in the "in" pin, the transistor would behave as high impedance between the "out" and the "gnd" pins, and low inpedance if I put VCC instead of GND in the "in" pin. But it seems that I am wrong.

I'd appreciate if you could help me understand. Thanks.


texts: RAM device that plugs into microSD slot?

texts:
I have a pair of small battery-operated self-logging 3-axis accelerometer devices that each use a microSD flash device for storage (the GCDC X250-2). Unfortunately, the devices do not buffer microSD writes, so the recorded data has frequent gaps.

I would like to find/create a portable device that has a cable that plugs into a microSD slot, and connects to a large ram cache, so writes can proceed without delay. Ideally, this device would spool to an SD card or other permanent storage.

There are many microcontrollers available that can talk to the SPI bus, simulate an SD card, and write data to RAM. It should also be possible to program a small Linux PC to do this, effectively emulating an SD card. The problem is finding a cable or something that can plug into a microSD slot!

Any ideas for a complete system, or the components needed to build one?


texts: Can I use one 12v 2A power adapter to power two LED light strips, or do I need to get a 12v,4A adapter to power both?

texts:
I'd like to link two 20' LED light strips together. Each strip comes with a 12v, 2A Power adapter. The adapters that came with these sets make a humming noise, so I want to replace them. Rather than have to buy two new power adapters, I'm wondering if I can just buy one same (but quieter) adapter for both sets. If that would not be powerful enough, could I buy one 12v, 4A adapter or maybe even a 5A for more power?

I have 8 LED sets in total for my project and I want to link 2 together for 4 different places so that would be a total of 8 new power adapters or just 4 if what I'm asking above will work. Please let me know.  Thanks!

J


texts: Large excursions in thermocouple readings with MAX6675

texts:
I have a 3d printer that has the ability to read the gcode from the sd card so it knows what to print.

I have added to this a MAX6675 thermocouple driver. I believe the sd card shares the same spi bus. I am getting major problems with temperature readings shouting up and down when I'm printing.

since they both have to in real-time i.e. ideally no delay  could my woes be because the arduino (mega 2560) is simply struggling to do both at the same time hence the temperature goes down then shoots up when the SPI is available again?

The max6675 is meant to be support by the marlin firmware. Am guessing they didn't mean it to be used in conjunction with the sd card reader.

[moderator note
The original title of this question was: "Two slave devices on the same SPI bus.  What are the limitations?"
On closer examination, however, this turned out to be an analog thermocouple problem, rather than a digital SPI problem.]


texts: What is the maximum power that I can get from a flyback controller?

texts:
I'm trying to design my own power supply and I decided to use flyback topology.
But before chosing a controller for the circuit this question came up: how far can i get with the output power? since I will design the feedback winding for the current measurement why can't I just "fool" the controller by changing this parameter(feedback turns)?


texts: Identifying an SMD diode and an SMD Zener diode

texts:
I'm trying to repair an DG96-00216C inverter board from a Samsung appliance. My knowledge in electrical engineering is pretty limited.
The board is plugged in to 240VAC with a 25A slow fuse. This board sends power for the right back and right front induction coils.
There's a simmer & boost mode option for each. It's the boost mode that has ended the life of the two IGBTs of the bigger cooking zone.
Here is the list of bad components I've found so far:

2 IGBT (IXGR40N60C2D1 600V 56A 170W)
Rectifier bridge (D25XB60 600V 25A)
6 10Ω SMD resistor
some SMD diode (marking W1)
some SMD zener diode (marking ZB)

Here is my list of replacement parts:

2 IGBT (IXGR72N60C3D1 600V 75A 200W)
Rectifier bridge (GBJ2510-BP 1kV 25A)
6 10Ω (1206 casing) 1W SMD resistor

As for my diodes, I have no clue. I have a DMM but I don't know any way to measure them.
I can't really measure the voltage on the board since it is not working.

I've checked all capacitors and they all seem to be good. I've checked the regulator transistors and they are good, too. Continuity test was performed on all transformers.
Sorry for the poor diagram. I just learned what an IBGT and a bridge rectifier was this week. All symbols might be wrong (capacitor types & diode types.)

What might the diodes marked W1 and ZB be?

Update - 9th November
I bought a 0-30V variable power supply and I did some test. With two DMM (one setted for amp measurement and the other for voltage measurement) and my PSU I found the zener voltage of my zener. \$V_z = 19 \text{v}\$. \$V_f = 0.7 \text{v}\$.
I bought somes Rohm KDZTR18B (Rohm KDZ18B is 18V).
As for my diode, \$V_f = 0.6 \text{v}\$, but the reverse voltage is still unknow. By connecting my 32V PSU and two other 12V PSU I was able to reach a 56V without even reaching his breakdown voltage (protected with a big resistor, my diode had only 50µA through it). So I'm roughly guessing \$V_r ≥ 75  \text{v}\$.
I decided to buy somes 100V 2A schottky RB068MM100 and some 100V 300mA 1N4148WQ-7-F. I don't which one I will use yet. They are both fast recovery diode. I've selected higher voltage and amp just to be sure they do not blew up.


texts:
I would like in a class project to couple a PowerBank and a mouse.

Imagine a powerbank in a parallel circuit with a mouse in such a way that one can charge his phone with it and recharge the powerbank while using it as a mouse.

That's my idea.

My question is how do I go about it ? Any suggestion guys ?

Thanks for sharing.


texts:
I made a custom circuit with bno055 it shows i2c address 0x70 is it possible?
I used the Arduino i2c scanner. I am not getting any data aswell

nothing else is connected to Arduino nano board as well,

I am using 5v to 3v3 TTL logic level converter board as well

vdd 3v3

11 and 14 not connected to Arduino

I tested with 3v3 esp32 using Arduino i2c scanner,
Still, I am getting the same address 0x70, without the converter, above PCB directly connected to esp32


texts: Programming and controlling microcontrollers and FPGA using Laptop (USB port)

texts:
Formerly laptops had serial and parallel port and it was really easy to connect laptop to micro-controllers and FPGAs. But USB has its own protocol and its not as easy as parallel port to implement different connections.

There are some ways to convert USB to other protocols using micro-controller.

Is there any good way to go to have protocols easy using USB? Do Programmers make specific cable and USB converter to every single protocol?


texts: Amplifier Settling Time and ADC Resolution

texts:
Like the circuit in the figure below, i have an Amplifier that is driving an ADC with 10 bits (3.3v Ref). Its sampling frequency is 10kHz and the signal is a sine wave with a frequency 1kHz and 1Vp. Does in this situation, where amplifier is just tracking a sinusoidal signal and not a pulse, the settling time  of the amplifier affects the signal accuracy ?

I know that if i'm measuring a pulse or a switching between signals, i need to wait the settling time of 0.1% to match the adc resolution(10bits), but when we are talking about sine waves and the transition is not a step 0-1V, how does it work ?


texts: How fast do power plants need to respond to demand?

texts:
I've heard the layman's description of electrical grid response time before - it usually contains the word "instant" or "real-time".  But I'm interested in the actual response times of the various types of power generation.

My limited ability to research has led me to articles on the three major "layers" of power generation: base load generation, load following generation, and peaking generation.  I understand the high level difference between the three generation types, and roughly the kinds of plants that fulfill them.  It seems that fuels like nuclear or coal serve the base load because they have slow response times.  And on the other end of the spectrum, fuels like natural gas serve the peak load because the generation systems can be set up for fast response times.

That high level information has been easy to find, but I'm having trouble finding actual numbers.  These are the only numbers I have so far:

Base load coal plants coal can take many hours to start up.
Peaking plants like hydro batteries can start up in tens of seconds, and simple cycle gas turbines can start up in tens of minutes.

But I feel like "start up time" is very different from response time, and I can't find any data on that.  But maybe I'm working with bad assumptions - do these plants actually need to respond to instantaneous changes in load after they've started up?

If yes, which plants handle that kind of response, and how fast do they react?

Electrical engineering and power systems are quite far from my day job, so I'm not very good at constructing queries to answer my questions.  Apologies if this has a trivial answer sitting somewhere else.


texts: What limits the current in a Darlington pair?

texts:
I am unsure how the TIP120 doesn't blow up in the given equivalent circuit from the datasheet:

I understand that the user will probably use some sort of current limiting resistor before the left transistor, but when the left transistor turns on wouldn't it feed a lot of current through to the base of the right transistor? There is no current limit from the left transistor to the right. Also, what are the purposes of R1 and R2?

Thanks!


texts: Don't understand this zero pole plot example

texts:
I'm reading a book (see figure 5-12) about (among other things) pole zero plots and there is an example I don't understand. For the schematics and formula below:

it adds the following zero pole plots:

and says:

The individual pole zero plots show the dc gain of 1/2 plotting as a straight line from the
–6 dB intercept. The two zeros occur at the same break frequency, thus they add to a
40-dB/decade slope. The two poles are plotted at their breakpoints of ω = 0.44/τ and
ω = 4.56/τ. The combined amplitude plot intercepts the amplitude axis at –6 dB because
of the dc gain, and then breaks down at the first pole.

I understand why the breakpoints are located at the mentioned points and why the slopes go up/down where they do. However, I don't understand why the individual plot starts at 0 dB while the combined one starts at -6 dB.
I have noticed this:

[...] The combined amplitude plot intercepts the amplitude axis at –6 dB because of the dc gain, and then breaks down at the first pole.

First, I don't see why the dc gain is -6 dB for all \$\omega < \frac{0.44}\tau \$. Second, I don't see why this dc gain is applied only to the combined plot and not to the individual one.


texts: purpose of feedback capacitor in operational amplifier

texts: Can someone explain what is the reason of using feedback capacitor in an amplifier? does it even matter if we don't use it?


texts: Why does my LM7805CV output voltage drop at loads <= 150 mA?

texts:
According to this answer the LM7805 has no minimum load. The data sheet also indicates that the output voltage should remain between 4.8 and 5.2 V for output currents of between 5 mA and 1 A.

I have a LM7805CA from an unknown manufacturer (I don't recognize the logo, which is an upward-pointing triangle to the left of a downward facing triangle enclosed by lines on all but the bottom side), but the additional markings appear to be "GOOKJ V6" and "MAR 918." (Unfortunately the printing on it is such that it's difficult to read and near-impossible to photograph.)

I've got the output hooked up to a constant-current variable load and the input is around 9 V (I see similar behaviour throughout a 7 V to 12 V input range) from a bench power supply, like so:

The LM7805 is underneath the red alligator clip (you can just see the edge peeking out the top) and test clips you see there lead to my multimeter; I'm taking all voltage readings from that since it's more accurate than the load's display. (The actual output voltage in the piacture is 4.96 V.)

As you can see in the image, with about 170 mA of load the output voltage is within spec. As I increase the load to 200 mA the output voltage increases to around 5.02 V and stays there even up past 500 mA.

However, when I reduce the load to around 120 mA the voltage drops to 4.84 V (still within spec, but barely) and at 80 mA the output voltage drops to 4.72 V. The load won't reliably sink much less than this (I have seen 4.66 V at around 60 mA), but earlier, playing with just an LED and 330 Ω resistor in series between the output and ground (on a breadboard), I saw the output voltage drop even further, to around 4 V.

So what's going on here? Is this device really going out of spec, or is it something to do with the way I'm measuring things?


texts: Detecting two arduinos coming in proximity of each other

texts:
I want to hook up LEDs to two arduinos and then have them turn their LEDs on if they are within about 3 feet of each other, what module would I use to detect this? I was thinking NFC like a RFID but those usually need to be as close as 10cm.

Bonus if I could also access the received signal strength.

Could I do this with two esp8266 using one as an ad hoc Network and attempting to connect with the other one? Would I like that give me received signal strength?

I want one to be worn by me and one by another person and when we get in some proximity have the Arduinos know and do stuff


texts: How do I split a mains power source between two devices

texts:
This is my first attempt at working with electronics so sorry for the potentially stupid question!

For my A-Level Product Design project I am making a digital photo frame with built in bluetooth speakers. I am using a Raspberry Pi as the controller for the photo frame and plan to use a bluetooth amp for the speakers.

I need my product to use a mains power supply, however I don't know how to split a single mains cable to 2 separate devices on the inside of my product.

From research I have found that the Raspberry Pi needs 2.5A "Recommended PSU current capacity" and 5.1V Power supply (I wish I knew what this meant). Since I have no idea what i'm doing, I am yet to order the bluetooth amp until I know for sure which will work.

My question is; How do I split a mains power between two devices, and do I need to order a bluetooth amp with the same statistics as the Raspberry Pi?

Any help is much appreciated,
Ollie


texts: Trying to identify this potentiometer marked "B5K"

texts:
I'm trying to identify this potentiometer as accurately as possible:

On the rear it says: B5K.

It has two rows of 3 pins each:

(1,2,3)
(1,2,3)

Below are some measurements taken with my multimeter between pins 2 and 3, and the unit is: kΩ.

When taking the measurements, I was making small increments. I tried to make the same increment amount each time. But you know, I'm human and the increments were not totally perfect. I did this 4 times, see the following graphs:

Can you identify this potentiometer?

What's the nature of this potentiometer? linear, logarithmic, etc?

Where I could buy it?

Is there any other data I would need to provide, in order to properly identify it?

Thanks!


texts:
I have used Altera FPGAs from last year and I would like to know how the PLLs inside works.
Mainly, really have any kind of analog circuitry inside in order to measure phase-offset between VCO and external signal?
This pretty pieces are so reliable along wide freq range (currently 100MHz and beyond even on cheapest models) that I am impressed.


texts:
I'm in the process of designing a very simple binary weighted resistor DAC for an output stage of a RGB VGA driver. There will be 3 bits for R and G components and 2 for B. The output signal is analog voltage, from 0 (black) to 0.7 V (full brightness). The input bits (D0-2) will be driven by an ARM Cortex-M microcontroller, now tied to Vcc for simulation purposes.

VGA output was chosen for overall cost, so a cheap analog output buffer is desirable. I was thinking about three op-amps in non-inverted follower configuration and this is refected in the schematic, but I have NO practical knowledge whatsoever on implementing op amps in real life.

So I'd need any advice on:

1) The application itself. Am I choosing the right resistor values (current and voltage divider to 0.7p) having in mind that they will be handled by a MCU?

2) Op-Amp connection and IC part (single supply I think, three/four op-amps in a single IC desirable): Should I need a resistor in the feedback loop? What IC part would your recommend for this application?

3) A VGA cable 75 ohm impedance match on the analog output is desirable. is the schematic ok in this respect?


texts: Why would smaller LSB reduce SNR performance in an ADC?

texts:
As a follow up to my previous question there is another argument I have difficulty to understand. First here the related information from the text:

Above what I understand is there are two ways to reduce LSB hence to obtain better resolution. One is to reduce the reference voltage. The second way is to use a higher resolution ADC.

But the text says for both ways when the LSB is reduced SNR performance degrades. As far as I know the quantization noise decreases with better resolution as the formula is  (6.02n + 1.76) dB where n is the the number of bits available for discretization.

But the text is talking about loss in SNR performance due to lowering the LSB value. Loss in SNR performance I guess means SNR gets worse.

How does making the resolution better degrade the SNR performance? I dont get why would SNR of the input signal decrease/degrade by doing that. Can this be explained in a clear fashion?


texts: How do I choose a fuse? Fusible Links vs Polyfuse?

texts:
I realise this is an extremely broad subject area but I need to know how to choose a fuse to protect a circuit.

Recently, a cheap PSU of a friend's blew up quite spectacularly (the two primary MOSFETs blew up - dead shorts.) It claimed 400W but on the PCB said 235W (more lying power supplies.) Despite 235W being approximately 1A at 230Vac, it used a 5A glass fuse. Why so over-rated? The fuse, however, was blown during this, so the fuse did do its job. The plug fuse did NOT blow up.

On my Super OSD project I am trying to protect a circuit which uses 455mA max. I am using a 500mA polyfuse. Does similar advice apply to polyfuses? Would I need a bigger polyfuse?


texts: What are the compulsory tasks of a charge controller for a lead acid battery?

texts:
Solar charge voltage regulators should coordinate the charging process of a battery. Suppose that I would like to design a very basic charging regulator controller with the following specs:

The battery charged is a 12V 12Ah lead acid battery.
The power supply is a 12V 10W solar panel.
During the day the battery is not used.

What are the minimum requirements and specs that are required? At the top of my mind I thought of the following:

Over voltage protection (the charging should stop when Vbattery > Vmax)
Over current protection (the current should be less than the maximum allowable by the battery) but this seems not to be an issue since the PV module is just 10W 12V.

If you need a battery for reference, then just take this one.


texts:
I was trying to solve this circuit(find the Q Point, voltage gain, input and output resistances in midband region, the lower cutoff frequency using SCTC method), but I was confused by the absence of RD.

What does it change instead of the classic CS degenerated amplifier?

Drawing the small-signal circuit, in the second case I find that RL is in parallel with RD; so, when RD is zero, RL is short_circuited? But it doesn't make sense because VO would also be zero.

Thanks everybody for your answers

P.S. This is the common-drain circuit shown in my textbook. It looks quite different to me.


texts: Regarding PMDC motor attached to gear box

texts:
I am using PMDC motor to rotate the actuator through gear box.We are using this actuator to rotate the solar tracking system.
Motor specifications:
No load current:0.6Amps
No load speed:3400 rpm
After gear box attachment:
No load current:0.9Amps
No load speed:58 rpm.
Load current:7A(after connecting actuator to solar tracker load).

If I want to reduce the load current from 7Amps to 3 Amps,
What are the changes need to do in my gear box??


texts: Auto shutdown and start of Raspberry Pi (remote application) using powerboot 1000c - need help debugging the circuit

texts:
In my application, the raspberry pi (A+) is remotely located and is powered using Powerboost 1000c. The powerboost is connected to a battery (lipo) and a solar panel. The battery is rechargeable and is charged via solar power. In the ideal case, I would love my Rpi to run 24/7, but since I have limited battery and solar power only works in the daytime, I need to shutdown Pi whenever it is not feasible to run it anymore.

In my understanding, the powerboost chip works as follows:
If V_usb==ON (i.e. solar power is ON), then it powers the pi and charges the battery (if required).
If V_bat > 3.2v (critical voltage), LBO is shown as HIGH. But if V_bat drops below 3.2v, it is pulled down to LOW

We can classify the operation into the following cases:
Case 1: V_usb (solar power) == ON and LBO == HIGH -- Trivial
Rpi is powered by solar power
Case 2: V_usb == ON and LBO == LOW -- Trivial
Rpi is powered by solar power and the battery is also charged simultaneously.
Case 3: V_usb == OFF and LBO == HIGH
Rpi is powered by the battery.
Case 4: V_usb == OFF and LBO == LOW
Shutdown the Rpi and wait for the solar panel to re-charge the battery.

So far with the help of community, I came up with the following circuit:

The idea behind the circuit is as follows:
The diodes (A, B) are used in parallel to create a logic OR gate, the purpose is to keep the power ON if either V_usb==ON or LBO==High. The output of the logical OR gate is fed to the capacitor+resistor discharging circuit, which takes around 10secs to discharge after the power is switched OFF (i.e. V_usb==OFF and LBO==Low) which is enough time to execute a shutdown script on the PI.
So far the circuit works as expected i.e. Keep the Pi ON if either V_usb==ON or LBO==High, otherwise execute complete shutdown.
But, since the powerboost chip is not disabled after the complete shutdown, it continues drawing the power which can damage the battery. To handle this issue, what I did was fed the capacitor voltage to the base of a PNP transistor, where the collector is grounded and the emitter is connected to the Enable pin on Powerboost. The idea is to ground the En pin as soon as the capacitor is completely discharged (to disable the powerboost chip).

Now what happens is after the capacitor is completely discharged (10 secs after LBO==LOW and V_usb==OFF is detected), the chip is disabled with the help of the above logic. But right after that, the LBO pin is detected as High (I am not sure why this is happening, but I think it is because there is no load on the powerboost chip and that's why LBO goes to high again). This causes pi to boot up again because the voltage at the base of PNP transistor > 0 which in turn enables the En pin, but since the battery is already at the critical voltage and there is no solar power, the pi goes back to halt. In summary, the above logic is causing the pi to boot in a loop (boot --> shutdown --> boot ...). Is there way I can avoid this undesired bootup+shutdown behavior?

Any help is appreciated!


texts: Merge Altium Schematic Libraries (and PCB libraries)

texts:
I want to combine two Altium schematic libraries into one, eliminating any duplicates as defined by the symbol reference.

There is a command to remove duplicates in a library as so:

Unfortunately, if I copy/paste the contents of one library into another in the SCH Library dialog, duplicates are re-named with a trailing '_1' etc. so they are no longer duplicates.

There is a library splitter command, and a remove duplicates command so I assume there's some way to put back what can be split asunder but I have not been able to find it so far. Any suggestions would be appreciated.


texts:
Recently I have been quite interested in OpenCL of the Khronos Group, and already gained some experiences with the language. I'm excited to know that OpenCL now works with Altera FPGA.
http://www.altera.com/products/software/opencl/opencl-index.html

For beginners to explore the idea of OpenCL running on Altera, can you please suggest some suitable Altera toolkit? Also, the tutorial given by Altera is not so clear. If you have tried this out, can you give me a brief tutorial?

Thank you for the help!


texts:
When I compile my project in Altium, I got some warning telling me I have Label of the grid.

Does anybody know how can I correct this warning error in once without replacing all the net one by one?

Which grid size do you usually use when you draw a schematic ?


texts: Problems getting correct readings from ACS71020

texts:
Me and my team are developing an LED light controller for street lighting applications.
We are trying to measure current draw, voltage and power consumption using Allegro's ACS71020 but the readings don't seem to make any sense. We have achieved a successful communication using I2C, since we can write and read multiples registers. For example, we changed the default slave address to 0x45, and to do that we had to write the customer code to a specific register, and then set 0x45 address (which involves another write operation). After that, we read the register that holds the I2C slave address and it appears changed. So we take from that that we're reading and writing successfully.
We're testing this IC using the evaluation board ASEK71020KMAB-090B3-I2C. We're using two different step-down circuits (recommended by the chip documentation), which are shown in the schematics attached (let's call circuit 1 to the purely resistive one, and circuit 2 to the one with capacitors).

Here's another schematic showing the hardware setup, where the step-down circuit can be circuit 1 or circuit 2 (the image shows circuit 1).

We're working with a 220V/50Hz power source. For the circuit 1 we're using an Rsense of 2.2k and for the circuit 2 a 1.8k resistance. From these values we have calculated a Full Scale Voltage of 500V for the first circuit and 610V for the latter, using the formulae on the documentation. We used 90A as the Full Scale Current.
After reading the corresponding register (0x20) for the Vrms and Irms readings we use the following code to decode the reading.
v=(RXData[1]*256+RXData[0])/0x8000 ;
i=(RXData[3]*256+RXData[2])/0x4000 ;

Where RXData is an array that stores the received bytes from the I2C reading operation in the order specified by the acs71020 user guide.
To test the ACS71020, we're using an incandescent lightbulb as the target load. Measuring its current draw, we see that it consumes 360mA @220V. The results using either the capacitive circuit or the resistive circuit are pretty similar. When the bulb is off we get Vrms = 224V, and i = 3.1A ; and when it's on Vrms = 224 and i = 2.8A.
The next two tables contain the data obtained from the chip:
Table 1: The lightbulb is off

Table 2: The lightbulb is on

Here's the C code we're currently using to get the readings:
float acs71020_get_voltage(){
    float aux_v=0;

    acs71020_read(REG_IRMS_VRMS);
    aux_v=((float)(RXData[1]*256+RXData[0]))/0x8000;
    aux_v=aux_v*(FULL_SCALE_V);

    return aux_v;
}

float acs71020_get_current(){
    float aux_i=0;
    float aux_2=0;

    acs71020_read(REG_IRMS_VRMS);
    aux_2=(RXData[3]&0x7f)*256;
    aux_i=(aux_2+RXData[2])/0x4000;
    aux_i=aux_i*(FULL_SCALE_I);

    return aux_i;
}

Those are for current and voltage, the procedures for power and power factor are similar.
We believe something is wrong with the setup in the chip. We couldn't find any examples of the chip configuration settings.
Current state of the configuration registers:
0B:
raw values: 00 20 00 00
by fields:
qvo_fine = 0
sns_fine = 0
crs_fine = 0
iavgselen = 1

0C:
raw values: 00 00 00 3C
by fields:
rms_avg_1 = 60 (decimal)
rms_avg_1 = 0

0D:
raw values: 00 1F E0 00
by fields:
pacc_trim = 0
ichan_del_en = 0
chan_del_sel = 0
fault = 255 (decimal)
fitdly = 0
halfcycle_en = 0
squarewave_en = 0

0E:
raw values: 00 08 20 00
by fields:
vevent_cycs = 0
vadc_rate_set = 0
overvreg = 32 (decimal)
undervreg = 32 (decimal)
delaycnt_sel = 0

0F:
raw values: 00 00 03 14
by fields:
i2c_slv_addr = 69 (decimal, or 0x45)
i2c_slv_addr = 1
dio_0_sel = 0
dio_1_sel = 0

What are we doing wrong?
I hope to get some help!
Thanks in advance


texts: Lumped-element delay lines using LC circuit

texts:
I was told that the above circuit is used to delay signal. The time constant per element is t = sqrt(LC). The expression was provided by the book I'm reading, but it did not include how the time constant was derived. Can someone please provide an explanation of how the circuit work and how to derive said expression?

Note: I took a course in electronics 3 years ago, so the more details you can provide, the better.


texts:
consider this file : tb_sr_latch.v

`include "sr_latch.v"

module tb_sr_latch;
    reg [4:0] t_in;
    wire out;

    sr_latch M1(t_in[4], t_in[3], t_in[2], t_in[1], t_in[0], out);

    initial begin
        $dumpfile("tb_sr_latch.vcd");
        $dumpvars(0);
        t_in = 5'b00000;
        repeat(32) begin
            #1 t_in = t_in + 5'b00001;
        end
    end
endmodule

and this file : sr_latch.v

module sr_latch(input set, reset, enable, preset, clear, output out);
    assign out = ((!clear && (preset || !(reset && enable))) &&
            (!clear && (preset || (out || (enable && set)))));
endmodule

I compiled tb_sr_latch.v with the following command:

iverilog tb_sr_latch.v -o a.out

and when I tried to run a.out with the following command:

./a.out

it stuck [maybe] in a loop with this message:

VCD info: dumpfile tb_sr_latch.vcd opened for output.

Can anyone help me to solve my problem ? please tell me where Im wrong and why it happends, because I know it is possible to implement it with always block instead of using gates.


texts: Programming many Atmega328p at once for mass production

texts:
How can I program multiple ATmega328p at once?
Like, for example, the Arduino Uno. How do they program it for mass manufacturing production?


texts:
The datasheet for the AD625 instrumentation amplifier shows an example circuit with 'Auto Zero' (Figure 36), below. In this circuit an op-amp AD711 is being used to give an offset voltage to zero the instrumentation amplifier.

But surely the op-amp is configured as an integrator not as a sample and hold? or am I missing something. Is the data sheet just plain wrong?

Thanks


texts: I was given an ATmega8U2 chip by my friend and I have been doing a bit of research about  it. It says it does not come with a pre-programmed with a boot loader, so I was just interested about how to go about getting a c program on there? Do I have to download a boot loader to the chip or something?


texts: Inductor Saturation Current and Temperature Rise Current

texts:
I have an inductor at the output of my boost converter. My output RMS inductor current is 271mA and the peak switch current is 1.3A. I have selected a 22uH / 2A Inductor as we select the inductor keeping the peak switch current in mind.

I dont understand what the below three points in the image are trying to say. Can someone explain me with my case and how to interpret that graph. My Ambient temp of the board is 80degC. So, how should I understand those three points? Please help.

Thank you.


texts: Understanding the inner workings of nRFL2401 module with different PTXes

texts:
So i'm writing drivers for nRFL2401 radio module and need to clarify something before I get down to coding it out:
The following is a high level diagram of the point-to-multi-point kind of setup where you have one central node interfacing with other modules.
Each data pipe seems to have its own configuration i.e payload widths, address field widths, tx/rx buffers, IRQ settings. Am I correct? Is data pipe 1 dependent on data pipe N in any way? from the looks of it, no, and if that's the case, it makes sense to have a generic struct with all these parameters as member struct and then in main, the object is created in main for each data pipe/PTX that's being used.
Is my understanding correct?
Something like on the PRX side:
typedef struct {
    uint8_t *rxBuffer;
    uint8_t payloadLength;
    uint8_t txDevicesUsed;      // upto nRF24_MAX_DATA_PIPES
    uint64_t *txAddressesList;  // pointer to an array containing addresses of all PTXs
    uint8_t *rxPayloadWidths;
    uint8_t *enableRxDataPipes;

    // config register parameters
    uint8_t configReg_maskRxDR;
    uint8_t configReg_maskTxDS;
    uint8_t configReg_maxRT;
    uint8_t configReg_pwrUP;
    uint8_t configReg_primRX;

} radioRX;

Config register:

The common things across all data pipes seem to be (which could be defined in the main and specific things in the struct:


texts:
Old Topic:

Can I make robot only circuit without microcontroller?

What knowledge should I know, where can I get it?

UPDATE:

How to learn BEAM robotics


texts: Control relay using split core current transformer

texts:
I have a YHDC SCT013-03 split core current transform which lists an output range from 0 V to 1 V for an input up to 30 A. My objective is to use this to open an close a contact switch.

The way I was thinking this could be achieved was to attach both the transformer and the contact switch to a relay. The transformer could open/close the relay causing the contact switch to open/close.

If I understand what I read correctly we get AC out of the transformer with a range from -1 V to 1 V. All the relays I have used in the past are controlled by DC.  Should I be looking for an AC relay? It is not know at this time at what voltage we need the relay to open, and ideally we could somehow have an adjustable set point. I was also really hoping the thing could be self powered.

Any suggestions an the simplest way to do this?


texts:
I have a SD card socket in a server that i can't get to work right (it wa damaged when i got it). As far as i read i need to connect CD (Card Detect) to GND if the card is inserted so i did and it seems it's somewhat detected, i say that because it's shown in the server bios as detected but not in the OS and the system behaves a bit weird when the card is inserted. I have a feeling something is not right.
What i did was to hot glue the SD card adapter and then i wanted to be able to exchange the microSD cards when needed but for the most time the SD card will be connected all the time since i boot off it.
Any ideas ? Actually i was reading some where else that CD should be connected to VCC when the card is inserted but before doing that i wanted to investigate more. This might be the problem that the card is inserted but the CD thinks it's not ?
Here is how it looks :

The blue/white wire is my connection of GND and CD.


texts:
Left side of the voltage divider is a bit confusing. How would AC react with DC voltage?
Considering a high frequency ac source, capacitor would act as a wire. So what will be the output voltage?
Logical answer instead of a mathematical one would be more appreciable.


texts: Capacitive Voltage Divider and Discrepency in Output Signal

texts:
Question:

Why is my measurement of the output voltage of my capacitor voltage divider not matching the theory?

Background:

I designed a capacitor voltage divider for the purpose of measuring the voltage step up of a resonator. Before I measure the voltage step up I wanted to measure the voltage divider ratio to ensure it matches the theory.

My Circuit and Theory Result (LTSpice Parameters: Vin = Sinewave,5Vpp,@ 40MHz):

The Theory: Vout = (C1/(C1+C3))*Vin ==> Vin/Vout =~ 76

Physical Measurement:

-Signal generator parameters (Sinewave, 5Vpp, 40MHz)

-Measured output with Oscilloscope (input Impedance = 10MOhms, 13pF)

-Result : Vin = 5V, Vout = 0.2V; Vin/Vout = 25 ??! ~32% off?

Question:

-Is there some parasitic capacitance or some problem with my measurement technique that I am not taking into account? Thanks for the help.

-Also, if anyone can help me with the EE Stackexchange equation writing syntax that would be great.


texts: Boost Converter Output Voltage dependence

texts:
Does the output voltage depend on anything except for the Duty Cycle?
Assuming no losses across switch, inductor and caps.


texts: I want to send data to seven segment display without micro-controller

texts:
I'm new to embedded systems
I want to send data to seven segment display from my pc
could i connect the seven segment display to my pc via serial or usb port or i have to use a micro-controller between them.
the seven segment display i would use like https://www.sparkfun.com/products/11442


texts:
I'm trying to learn about how transistors work. As a simple test I created the following circuit:

My idea is that when the second transistor will keep the first one active after I click the button for the first time, but it isn't. What am I doing wrong?


texts: Help me understand this circuit schematic

texts:
Please keep in mind that I am very new to reading circuit diagrams, and electronics in general. I am interested in using V-USB to connect my AVR microcontroller to my computer via USB. On the V-USB website, the following sample diagram is given, and I have some questions.

USB Pin1 to ATTiny VCC: Why is there a ground connection as well, and what purpose does C4 serve? Traditionally, I am used to connecting a wire running 5V to VCC, but not hooking that up to ground too. I thought the ground connection is made internally, because I am connecting the ground from the power supply (in this case, USB cable) to the GND pin of the microcontroller already.
You see how C2 and C3 are connected via one line to GND? Would this be equivalent to connecting them individually as well? So the negative end of each capacitor would be running on its own to ground instead of meeting up, and then going to ground. Or is it depicted like this to save space in the diagram?
What is the purpose of C1? Isn't it creating a short circuit? I don't understand why it is there if the loop from USB Pin4 to USB Pin1 (which has C1 in it) does not access any of the pins on the microcontroller. Does C1 still impact the overall circuit somehow?
Why does D- have R3 and a voltage connection, whereas D+ does not?
Is R3 meant to pull up D- to a high logic level when PD3 (on the ATTiny) is not providing any input? Why?

I know these are a lot of questions, but I need to overcome my fear of circuit diagrams. I think there is a fundamental flaw in my process of understanding them. I think of the lines as physical wires and think of current as little dots following the paths in diagram - childish, I know.

Thanks for your help, any advice in general about reading circuit diagrams would be awesome too.


texts:
I've recently begun doing a school project. For one of the subsystems , I intend to mount a buzzer and vibration sensor on a walking stick and configure it such that the buzzer sounds when the walking stick falls and hits the ground.

I'm assuming the the impact of the walking stick hitting the ground will cause some deflection on the tip of the vibration sensor which will generate a voltage signal.

The problem is that I cannot seem to get the vibration sensor to work. What I have done was just to connect it to a 5V DC source and a 1K Ohm resistor and measure the voltage drop across it when I push the tip with my finger. However , the voltage drop across this vibration sensor does not change no matter how much I deflect the tip.

I'm using a MEAS MSP-1006 ND vibration sensor.

Thank you.


texts:
I made a circuit in Orcad Capture and I want to co-simulate it in Simulink, for other future operation, and a problem appeared: I can't connect my PSpice Block to a VDC source from Simulink (see picture.), although I made the next settings for PSpice block (see second picture.), where V10 is a VDC source (5V).
I made some research and I saw that a 'Solver configuration' is necessary at a point and all components must be from the same Library (but my block is not in the default library of Simulink).


texts: What is the effect of the reflection coefficient?

texts: I know that the reflection coefficient is the ratio of the backwards wave with the forward wave in terms of the characteristic and load impedances. But what does this mean? Does this represent a loss in energy in the line? Is the backwards wave creating a loss in the forward wave? How does this ratio affect the line?


texts: Clarification of "strobe pin" 4-bit latch/4 to 16 line decoder

texts:
I'm wondering if I can get a specific behavior out of this chip. I have read the data sheet and am having some trouble understanding the usage of the Strobe pin.
CD4515BM96 Datasheet PDF
USE CASE
I'm trying to design a computer from IC chips, using no microprocessors or micro controllers. I would like to use this chip to decode and address upto 16MB of memory split into 512KB SRAM ICs. The data address bus is 24 bits. The highest bit will be used to switch between the high 8MB and low 8MB of memory, the higher 8MB will most likely address removable non-volatile memory. The next highest 4 bits of the data address bus will go to the LY625128SL ic that I would like to ask about. It's outputs will go to the Output Enable/Write Enable pins of the corresponding SRAM. (I might switch them with another IC to get this behavior or i might just have two CD4515BM96)
DESIRED BEHAVIOR
I don't want to worry about pulsing the clock to the strobe pin on this ic, because I belive it may not be necessary. If I simply tie the Strobe pin high will it bypass the latch? I don't need the latch in this chip because I can simply use the output of the data address register storing the four bits it needs.
Is there a better ic for my use case? Is my proposed solution (tying the strobe pin high) correct?
Thank you for your time. I'm but a programmer all this electrical engineering stuff makes my head spin.


texts: Find Information On This Component Of Fire Alarm

texts:
I have been trying to search for information on the component of a fire alarm that sounds the siren. My goal is to remove the siren and use the power and ground to connect to an arduino. I want the arduino to be alerted instead of sounding the alarm. The component has 3 prongs that are soldered into the board and I cannot figure out what each one does. Pictures are below:

Note: No this alarm will not be used as a normal fire alarm in a life or death situation.


texts: Can you damage an LCD screen with a camera flash, high-powered flashgun/speedlight?

texts:
I'm curious as to what the limitations are in regards to uv radiation on LCD screens when subjecting them to high intensity light sources such as camera flashes (such as a nikon or canon speedlight).

What measures can you take in order to protect against this damage? Dichroic filters? Hot mirrors?

Thanks in advance!


texts: How can electronic devices remain waterproof (no short circuits) while they have exposed charging connectors

texts:
I am a happy owner of a Garmin Fenix3 fitness watch and a developer for watch faces as well.
I noticed my watch charges and communicates data through 4 pins (probably for the USB layout 0,VCC, Data+, Data-) on it's back side as shown here (http://i219.photobucket.com/albums/cc18/gaijinnv/fenix-3-back_zpsoxagq2pb.jpg)
I have been using my watch in numerous occasions underwater (swimming etc) and i was always curious on how these pins (and especially the charging ones) are not short circuiting leading to power failure or "crazy" behavior.

This charger layout might be helpful too https://forums.garmin.com/filedata/fetch?id=1176424&d=1454672325


texts: Relation between collector current and IF current in an optocoupler?

texts:
I need to use an optocoupler to drive BJT. BJT will let 10 A current pass. BJT's have commonly 100 - 150 Bf(current gain) so for 10A transmission I need at least 100 mA current draw from the optocoupler.

Current transfer ratio is defined as IC/IF. So I chosed 150% and above CTR in digikey. However, when I examine random datasheets, I see this:

Maximum collector current is seen as 50 mA. I don't understand, in digikey's spec, this component brags about 200% @ 5mA CTR. But if you allow maximum 50 mA collector current, why do you show such a useless data? Or am I reading this wrong?

Also, another concern of mine is:

this is a photovoltaic device, meaning when internal diode flashes, darlington base starts to draw current no matter what. So, let say if this coupler gives 5A Collector current for 5mA IF current, and if there was no room for that current to flow, could the optocoupler burn out?

Thanks in advance.


texts: How to project a FET transistor as an amplifier?

texts:
I am trying to solve a problem on using an FET transistor as an amplifier with the common source configuration. The model should be appropriate for high frequencies.

The problem gives the equivalent circuit for the AC analysis like below where gm is 4 mA/V:

To model the circuit I used the DC circuit of the amplifier with common source and ended up with this:

I found that Rg = Ri and Rs is given. But I am having difficulty in finding Rd and proper Vcc and Vss sources to make it work. Any advice on how to approach this problem would be appreciated.


texts: In disassembly, I see instruction LI, but I can't find such instruction in MIPS instruction set

texts:
I have little test project for PIC32MX CPU, here's a part of disassembly:

(I know this code is not atomic, I'm just testing things. Actually, I'm pretty newbie in MIPS)

 72:                        LATEbits.LATE0 ^= 0x1;  //-- toggle LATE0
9D0015BE      B309   LW V1, 36(PC)
9D0015C0      9B80   LW A0, 0(V1)
9D0015C2      6A01   LI V0, 1       <--- what is this?
9D0015C4      6D01   LI A1, 1       <--- and this one
9D0015C6      EC4C   AND A0, V0
9D0015C8      EC11   ZEB A0
9D0015CA      ECAE   XOR A0, A1
9D0015CC      EC4C   AND A0, V0
9D0015CE      9B40   LW V0, 0(V1)
9D0015D0      4DFD   ADDIU A1, -3
9D0015D2      EAAC   AND V0, A1
9D0015D4      EA8D   OR V0, A0
9D0015D6      17EF   B 0x9D0015B6
9D0015D8      6100   BTNEZ 0x9D0015DA
9D0015DC      6120   BTNEZ 0x9D00161E
9D0015E0      6120   BTNEZ 0x9D001622

Is command LI an alias for something? I have checked MIPS Architecture For Programmers Volume I-A and II-A, but don't see any occurence of LI.

More, I have this assembly code (it is from TNKernel RTOS, I'm not author of this code):

tn_enter_critical:

        la      $t0,    tn_sys_context
        lw      $t0,    0($t0)
        bne     $t0,    $zero,      1f          /* return if non-task context */
        nop

 ....................

There is instruction la in this code, and in disasm this instruction is shown as LUI:

                                                  119:   tn_enter_critical:
                                                  120:
9D000020  3C08A000   LUI T0, -24576               121:           la      $t0,    tn_sys_context
9D000028  8D080000   LW T0, 0(T0)                 122:           lw      $t0,    0($t0)
9D00002C  15000006   BNE T0, ZERO, 0x9D000048     123:           bne     $t0,    $zero,      1f          /* return if non-task context */
9D000030  00000000   NOP                          124:           nop
                                                  125:
 ....................

Now, reversed situation: I see instruction LUI in the docs, but can't find LA. It makes me believe that there really should be aliases, but I can't find them too.

Please explain it to me.


texts:
I have a problem with adding harmonics to park-clark transformed 3 phase value. Here is transformations I'm using:

Vsd= 1, Vsq= 1, x=angle;
sinA = sin(x);
cosA = cos(x);
a= Vsd * cosA - Vsq * sinA;
b= Vsd * cosA + Vsq * sinA;
Va= a;
Vb= -1/2*a + sqrt(3)/2*b;
Vb= -1/2*a - sqrt(3)/2*b;

and on the graphs I get following result:

When I'm trying to add harmonics to sine and cosine, for example 3rd harmonic:

sinA = sin(x) + sin(3*x);
cosA = cos(x) + cos(3*x);

I'm getting mess instead of M shaped waves on all 3 phases:

what I'm doing wrong ?


texts: How are DACs integrated in color LCD screens?

texts:
I'm having trouble imagining what actually happens inside an LCD screen.

I picture digital RGB data for each pixel getting sent to the screen through a connector. Lets say we have 24-bit color for each pixel, so 8 bits each for red, green, and blue subpixel. Inside the LCD, for each subpixel a voltage must be applied to control its intensity. This is where a DAC must come in to convert each 8 bit intensity value (digital) to a proportional voltage (analog). But, surely there is no DAC for every subpixel? My laptop screen is 1920x1080 so it has over 6 million subpixels.

So, how are these DACs integrated into the architecture of this LCD? How many DACs are in a single LCD screen?

I read that a transistor is used to select a particular liquid crystal cell and charge it/light it up, and a capacitor holds the charge briefly until the next refresh cycle. So that would eliminate the need for 6 million DACs, although it would mean you need 6 million transistors and capacitors. But I'm still wondering about these DACs - they never seem to get mentioned because people consider LCD screens "digital".


texts: How to use UART port for sending status in verilog

texts:
I am developing various verilog modules with state machine for a fpga board.

When i have done simulation of the modules i have used "$display" to get what is happening in the module or otherwise the status information.
Now i am implementing the same modules on the fpga. As "$display" does not support in hardware i thought of using UART to send the status information to a terminal in PC or Computer.
For that i am using the UART verilog model obtained from opencore.org. But at a time only one byte can be supplied to UART for transmission.
But status information contains various lengths of characters such as "Test passed", "Entered reset state" etc.
Is there any easy method to send variable length strings on UART port much like a $display syntax.


texts:
I'm implementing a voltage regulation circuit for some audio and video equipment. Input voltage can vary between 12V and 18V DC.

Currently using the MC78T12C 3A regulator but it's getting a little warm.

The unit is being powered by a 4C LiPo battery which presents 16.8VDC when fully charged. Seems that the 4.8V voltage drop may be a little bit too much for the regulator to manage.

At present the circuit isn't heatsinked, but this can be easily done.

Is this voltage drop too much for the regulator I am using or will a suitable heatsink solution be enough?


texts: ICSP on an AVR with broken CLKI returns 0x00's

texts:
For fun, I have been working on a development board for the Atmel ATmega128RFA1, similar to the official board and the sparkfun one. Mostly I'm doing it because it's fun – I'm a software guy.

I assembled two boards yesterday, on both I was getting:

avrdude: Device signature = 0x000000
avrdude: Yikes!  Invalid device signature.
         Double check connections and try again, or use -F to override
         this check.

so I went back and re-checked everything I could find, had a few pins pulled the wrong way but still no luck.  I then noticed that I had connected my ICSP header to MISO/MOSI/SCK instead of MISO/MOSI/CLKI, which I guess is the problem, unfortunately one of the things I learnt quickly on soldering a VQFN64 is that I should have exposed pads for everything, but haven't.  I've tried, and can't get a good solder joint on the side of the IC to that pin.

Am I right in thinking this is the cause of my 0x00's, and if so, is there a way I can use ICSP (through an Arduino Uno and avrdude on osx) to program it using the normal 16MHz oscillator?

Thanks in advance,

Matt


texts: Fast knock detector circuit with digital output

texts:
I am trying to design a fast, simple circuit that will send a short (~2ms) logic-level pulse (either high or low, don't care) to a micro controller, every time a Piezo Transducer detects a knock. The circuit needs to have as few components (especially as few ICs) as possible, because I need to build a lot of them. They should all be through-hole components, and all ICs operating off a single positive rail. I don't want to use a micro controller for the knock detection.

The knocks often come in very rapid succession (up to 20 per second), and vary widely in magnitude, giving anywhere from 100mv to 4 volt peaks.

The piezo gives a diminishing AC sine wave, when knocked, which is offset positively, staying above ground 90% of the time, but does stray slightly below zero sometimes. The piezo signal tends to ring, so the decay is sometimes upward of 200ms for the bigger knocks.

After some research, it seems like I need :

piezo -> Op Amp buffer -> envelope detector -> slope detector -> rising edge detector -> output.

Can anyone think of a simpler way to achieve these same results?

If this is indeed the best way to proceed, what is the simplest circuit design (ie. with the lowest parts count) that could achieve these results?

edit: here are some screen caps of typical piezo knocks in an oscilloscope, these examples are piezo -> 10 kΩ load, there would be a shorter or longer decay if the load was higher or lower.


texts: For 3.5" mini stereo (TRS) to RCA stero cable, are any passive/active components used?

texts:
Are any passive (or active - unlikely) components used in the 3.5mm mini stereo headphone (TRS) plug to RCA audio plug converter cables, such as this one ?

Asking because, during a quick search I came accross some DIY cable post, where a poster commented that they find the audio volume to be extremely low when using such a cable, indicating serious attenuation.

For line-in/line-out (on PC), I found the following Wikipedia entry that talk of the electrical characteristics, but nothing (so far) for RCA audio connectors and the 3.5" mini (TRS) headphone plug.

Also found this interesting post, but it is in reference to RCA to SPDIF conversion (chain), but still not much helpful with respect to my question.


texts: How does the dish size increase reception range of radio signals?

texts: For example if you want to transmit a song through FM, does the receiver's dish size actually increase the range in which he can detect these signals? if it does then how?


texts: Quad SPI series resistors on lines for short circuit protection?

texts:
I am designing a circuit where MCU connects to LCD driver IC (FT813) using Quad SPI. Since there is a risk of Both MCU and FT813 pins becoming output at the same time with different values (i.e. one Gnd and the other VCC) and creating a short circuit, I plan on placing 220ohm resistors on the SPI lines for protection.
However, I am worried that these resistors will corrupt the signals. The distance from MCU to Ft813 is about 10cm and I'm aiming for an SPI clock rate of about 3 to 6 Mhz.
Am I taking the right approach? And where is the best position to place the resistors (middle or near closer to one of the ICs)?
thanks


texts: What specification for IR communication to AV equipment?

texts: I'd like to task a micro-controller to use it as a universal remote. What is the specification used for IR communication to AV equipment (TV's, etc.) and where can I find it?


texts: Why is one of the transistors in ROM sense amplifier twice the width of the one opposite of him?

texts:
The picture is of Sense Amp design of ROM component in which a 'dummy' bit line is used to imitate the current so that the proper information can be derived from the memory cell by comparing the currents.

I would like to know why does the right transistor have a width of 2Wx and the one on the left Wx?


texts: How much current can I supply to power PIC12F675?

texts:
I have a power supply that outputs 5.9V at 375mA that I'm running through a 5V regulator.

I'm wondering if 375mA is too much for a PIC12F675? I dont want to fry this little guy.

If it's too much how can I reduce it?

Thanks!


texts:
I am designing an SMPS with flyback topology. The PWM IC is viper.
I have a doubt that should I place the IC at the bottom side of PCB or both the transformer and the IC on the same side(top side) in order to get less EMI. As I know transformer will generate EMI and as the IC is operating at high frequecy it will also produce EMI. Or their placement would not affect the  generation of EMI that much?


texts: SD card as ROM memory in a microcontroller

texts: Can I use an SD card as ROM for my microcontroller? What other options are there if I want a large amount of ROM memory (cheap)?