texts:
I have a subwoofer that my friend and I found so I do not know too much about it. When I was transporting it, it fell and one of the knobs on the front was broken. I took it apart to see if I could fix it but I also found the PCB was cracked so I was wondering based on the photos I attached if anyone could help me find replacements for the part? If you need more images to figure it out I can take more.
Also, I did not know where to get help and found this website by accident so if you know of a place that would be better suited for my question that would also be helpful. Any response would be helpful and I just want to say thank you in advance.
Image Links:
Front: https://drive.google.com/file/d/1T9I_n-4sjTiFXymQBnEnkVgmnY3sH_1N/view?usp=sharing
Back: https://drive.google.com/file/d/1giOTlkqJHowH1bMDENl7vEU6BqpArBqp/view?usp=sharing


texts:
Below is the beginning schematic for a circuit I'm working on. We have a previous revision of that product (Rev A), and two sets of recent product (Rev B1 and B2). Rev B1 was made 2 weeks prior to Rev B2. All three products are tested on the same calibration system with the same settings.

When I measure pin 1 from the OpAmp, I get three different values for each product. I've unsoldered the 5.1Mohm resistor and measured it and it is correct.

According to the manufacturer, the components on Rev B1 and B2 are of the same batch but made a different times. Technically, all three revisions should have the same components.

Rev A (Older)                    - 1.21V/1.20V/1.21V

Rev B1 (Manufactured 2 weeks ago)- 1.15V/1.15V/1.1V

Rev B2 (Manufactured last week)  - 1.05V/1.05V/1.05V

My question is: do photodiodes have tolerances? I am inputting the same amount of light into each product, but I get a different output from each version.

Technically, all revisions should be the same. At the very least I would expect B1 and B2 to have the same readings. It just seems very odd to me that every group of product has the same components, but they're all different readings. This is the very first measurement that takes place, and only gets amplified down the circuit.

Any reasons for why this is happening?

Photodiode Datasheet

Ignore R13.


texts: PIC18F26K20 cannot set internal oscillator to high speed

texts:
I have a project using a PIC18F26K20, and I am trying to use the internal Oscillator at 16 MHz. But no matter what I do it always runs at 32 kHz. My configuration is:

#pragma config FOSC = INTIO67               // Internal Oscilaor RA6 RA7 ports
#pragma config WDTEN = OFF                  // Watchdog Timeer disabled
#pragma config HFOFST = ON                  // HFINTOSC Fast Start-up:
#pragma config PWRT = OFF                   // Power-up Timer Enable bit: OFF
#pragma config FCMEN = OFF                  // Fail-Safe Clock Monitor Enable bit:
#pragma config IESO = ON                    // Internal/External Oscillator Switchover bit ON

in code:

OSCCON=0xf7;                    // Internal Oscillator Hi
OSCTUNE=0x00;

Can anyone tell me what I am missing to set internal oscillator to 16 MHz?


texts:
I am using a PIC18F26K80 and an XC8 compiler. I am trying to initialise an SD card and create a file. I have simply formatted the SD card on Windows to have a "FAT32" file system and an "Allocation unit size" of 512 bytes. The capacity of the SD card is 2GB. I am using the MDD library from the MLA Legacy version. My main is the following:

FSFILE * file;
char sendBuffer[22] = "This is test string 1";

//**************************************************
// main function
//**************************************************

int main()
{
    initIO();
    LATBbits.LATB0 = 0;

    // Initialise SPI and SD-card
    while ( !MDD_MediaDetect() );

    // Initialize the device
    while ( !FSInit() );

    // Initialize
#ifdef ALLOW_WRITES

    // Create a new file
    file = FSfopenpgm ( "FILE.TXT", "w" );
    if ( file == NULL )
        while(1);

    // Write 21 1-byte objects from sendBuffer into the file
    if ( FSfwrite ( (void *) sendBuffer, 1, 21, file ) != 21 )
        while(1);

    // Close the file
    if ( FSfclose ( file ) )
        while(1);

#endif

    LATBbits.LATB0 = 1;         //LED

    while(1) {}

    return (0);
}

The program gets stuck inside the function "FSInit()" and the error I get from the function is "CE_BAD_PARTITION", which means "The boot record is bad".

The "initIO()" function is the following:

//==============================================================================
// void initIO( void );
//==============================================================================
// Sets the pins on the PIC to input or output and determines the speed of the
// internal oscilaltor
// input: none
// return: none
//==============================================================================
void initIO()
{
    OSCCON = 0x75;                  // Clock speed = 32MHz (4x8Mhz)

    TRISA = 0;
    TRISB = 0;
    TRISC = 0;

    TRISBbits.TRISB0 = 0;           //LED

    TRISCbits.TRISC3 = 0;           // set SCL pin as output
    TRISCbits.TRISC4 = 1;           // set RC4 pin as input
    TRISCbits.TRISC5 = 0;
    TRISAbits.TRISA5 = 0;
}

The last two bytes of sector 0 are the boot signature and they are meant to be 0x55 and 0xAA and the picture I included confirms that. However, inside the function "LoadMBR" the following check is made:

if((Partition->Signature0 != FAT_GOOD_SIGN_0) || (Partition->Signature1 != FAT_GOOD_SIGN_1))
{
    FSerrno = CE_BAD_PARTITION;
    error = CE_BAD_PARTITION;
}
else
{
    ...
}

and although the bytes are the same the first condition is met and it returns with the "CE_BAD_PARTITION" error.


texts: Is 'R' in impedance equation an AC or DC resistance?

texts: I am using an impedance meter to measure impedance in complex form (R-jX) and an RLC meter to measure R & C values in an RC circuit. The value of DC resistance is equal to the R value in impedance equation. My question is whether the R in impedance an ac or dc resistance?


texts: Identifying a SOIC-8 IC with “302F” marking

texts:
I have a board with an unidentified SOIC-8 IC marked "302F".

I am looking for the part number of this component that is mounted in a 2 cell battery pack PCB designed for AIBO robots by SONY in 1999-2000.
This battery PCB also includes a TI bq2040 fuel gauge and a Seiko Instruments S-8232AAFT battery protection IC.
I would first like to know who you think would be the manufacturer of this component.

Thanks for all the replies.
Edit: I add a part of the retro engineering schematic I did. The naming and type of the pins is a guess for now.

What I'm sure is the connection between the IC and power resources (BAT+ for 2 cell voltage, BATM for 1 cell voltage and BAT-) and the passive components.


texts: Finding Vds in a CMOS without info. on channel modulation?

texts:
"What would (ideally) be the DC voltage at the output in the following circuit?" That's how the question was formulated. Can it be found without having any information on \$V_A\$ or on \$\lambda\$? The only way \$v_o\$ could be evaluated would be by equating the currents through Q6 and Q7, but that would only yield \$v_o\$ provided that I have some information on either \$V_A\$ or on \$\lambda\$.
Could anyone help me settle it?


texts: correct way to represent the inductive reactance ? XL = ωL or XL = jωL

texts: In some cases the inductive reactance is mentioned with j and in some case it mentioned without j. so which is the correct way to mention the inductive reactance.


texts: Help me about system switch control ladder light?

texts: We all know about the system of two switches controlling one lamp(at the ladder) like the picture. Could you help me design a system of four switch to control one lamp ? thanks


texts: Doubts on Implementing a Simple Protocol for XBee Comms

texts:
A system that I'm developing will use XBee modules for a point to point connection between a micro-controller and a PC. Data will only be sent only in one direction -Micro to PC and  at 10-20fps. The data portion of each frame will be 4 Bytes. XBee modules will be run in transparent mode(to begin with at least). On the PC side I'm using python to grab the data from the serial port.

Initially I wrote a very simple python program to grab data 4 Bytes at a time from the serial Port, which worked fine when tested with a virtual com connection (I haven't run any real world tests yet though), but I decided to experiment and ended up implementing a simple frame structure like this.

sync_flag | Payload_length | frame_number | payload

After some research I discovered HDLC and now I'm considering implementing something similar albeit simpler. Before I endeavor to do so Id like to hear what others have to say.

When is such a protocol merited?

What have you done when you implemented your XBee networks?

Being somewhat new to this area I'm sure there's some relevant specifics Iv left out, but at the same time I didn't want to make the question too narrow / system specific, but if necessary Ill update the question.


texts: MOSFET common source amplifier output impedance calculation

texts:
What I've read in microelectronic texts like Prof's Razavi's Fundamentals of Microelectronics is that for calculating output impedance, one has to make all independent sources 0, i.e., short all independent voltage sources and open all independent current sources.

Sighting a simple example of output impedance calculation in common source amplifier given in the picture, if we go by the rules, we'd short Vin and Vdd as shown in the picture.
Now, from the small signal model, the output impedance is said to be Rd||ro.
But my question is that if gate and source both are shorted making Vgs = 0, i.e., lesser than Vth, this implies there is no channel at all for current to flow from drain to source. So, why do we take into account ro in output impedance calculations when no current can even flow through the MOSFET due to Vgs = 0?

P.S.:You may either refer to Fundamentals of Microelectronics by Dr.Behzad Razavi or even his lectures on youtube for the prescribed method my question is based on, the links given below.

The book Fundamentals of Microelectronics :

Razavi electronics lecture 37 - at 45:54

https://www.youtube.com/watch?v=UeXtyA42ElU&index=37&list=PL7qUW0KPfsIIOPOKL84wK_Qj9N7gvJX6v


texts:
I have 3-phase utility mains power supply whose phase voltage is 220 V, 50 Hz.

I keep getting confused about various calculations of the 3-phase mains as follows:

Formula for the line voltage.
Formula for the Average and RMS outputs of 3-phase full bridge rectifier.
If I use this output of the bridge rectifier as my DC Link voltage to feed a 3-phase full H-bridge and drive it with 3-phase sinusoidal PWM then what will be Average and RMS voltages of the resulting 3-phase sinusoids?


texts:
Is there a sensor for the speed of the car that can be programmed to turn on something when a car reaches to a specified speed?

If yes, what is it’s name, and whare to find it online?


texts: Can a MOV properly discharge a X-Capacitor?

texts:
I created an AC-DC SMPS with a EMI filter that consists of a X-Capacitor and Common-Mode Choke. IEC 62368-1 requires that capacitors be discharged below ES1 (60V) within 2s of being disconnected. As can be seen in the picture below, I placed 2x 1.5MΩ across the line to ensure that the X2 Capacitor will discharge if the power is disconnected when the full peak voltage is present on the capacitor (424V in this case).
As you may notice, a MOV is also across the line. Since these always leak some current, how can I ensure it will discharge CX1 in the time required? Are the resistors still required to ensure proper discharge when the MOV fails or ages?


texts: Avoiding ground noise in analog circuit pcb design

texts:
Below single layer PCB is a constant current sink circuit (electronic load), it's pure analog supplied with ±12 V and consumes very low current (~50 mA) except the transistor control part (which indicated with red lines) that's going to carry 10A max.
There's two op amps in the circuit, one configured as differential (measuring the current) and other as integrator (driving the darlington pair), both are dual supply with decoupling capacitors close to the IC.

On the left is a fan drive circuit that is being fed from the same transformer but with another bridge rectifier (24 V), there's an small RC filter on the output of both bridge rectifiers to avoid the fan noise coming to the right circuit.
Each bridge have their own linear voltage regulator, the space between two grounds is 1.5mm.

Do I have any ground loops on the right circuit and how do I avoid/eliminate them?

Is the separate bridge rectifier + RC filters + linear regulator ripple rejection enough to eliminate the fan ~70 Hz noise showing up in the right circuit?


texts: Which way does electricity power a circuit?

texts:
Working with some circuits this summer, I ran into what everyone eventually does: Current flows from + to - despite the electrons flowing (well, bumping into eachother) from - to +. I understand the historical background for this, but for me that raises this question:

If I strung an arbitrarily large number of bidirectional incandescent light bulbs on a wire of a length of say 10 light seconds, and hooked it up to a sufficiently powerful battery, what would happen? Would the light bulbs all light up at once? Would they light up from + to -, from - to +? Thank you in advance. This has been really bugging me.


texts: Can simple microcontrollers read signals from a USB to RS232 converter connected to a USB mouse?

texts:
Trying to connect as many usb mice to my arduino and just got informed of usb to rs232 converters.

Can anyone tell me if it is possible to simply connect a usb mouse to a usb to rs232 converter, connect some wires from the rs232 output plug to the microcontroller and then read the data for all mouse events?


texts: What happen when you store something greater than 32 bits on STM32?

texts:
A couple of questions regarding the word size:
STM32 series have 32-bit wide words.

Considering that, what happens when we try to store something more than 32 bits or even uint64_t for instance? I gave it a try and defined uint64_t a = 4294967299; and what I see in the memory is  00000003. What does that mean? Is it truncating?
an address stores 32 bits, isn't it? then why do I see in the resultant bytes (0x00000003) stored at &a different addresses every byte? so from MSB, 0x00 is at 0x20017FE8, the second byte 0x00 is at 0x20017FE9, ... and the last 0x3 is at 0x20017FEA.
Shouldn't each set of 32 bits have a distinct address?

Edit:

a side question: SRAM is a part of the MCU (which contains the cortex Mx processor). Is little/big endian related to the processor or the memory? The value that I see in memory seems to be big endian but according to the RM, it's little endian

Tried this code out to test the endianness:

uint64_t a = 0x00008a5d78456301;
uint32_t b = (uint32_t) a;    // 0x78456301

shouldn't b store the first 32 bits (from smallest address) instead of the latter 32?

Any visuals would help a lot.


texts:
Is there a standard connector used to connect the ground/supply pins on an RF amplifier to a power supply? For example, many RF amplifiers (also attenuators) I've seen use two pins like this:

But I have no idea if there's a standard name/mating connector for them. The reason I ask if that I've accidentally shorted an amplifier using alligator clips, and am wondering if there's an alternative option to limit the amount of exposed metal.


texts:
I need to create a counter that counts down from 59 to zero. For that, i created a simulation in Proteus software where i used 4510 IC as a down counter and created the following circuit.

Now, i thought that, since this 4510 IC, when working in down counting mode, has output Co at logic zero whenever it reaches zero value, that means that when both of these two ICs have Co=0 then, i need to reset them to required value, which is in my case 59, otherwise it would start from 99 downwards.

It works fine when the circuit starts, because it actually starts at 59 and goes down all the way down to 10 and then, instead of going down to 9 it resets to 59, which is not what should've happened, since both Co's should be low when i have 00 combination at the output.

Does anyone have an idea what could be the problem here? Any help appreciated!


texts: Tracing out where pins go on a TQFP-100 package possible?

texts:
I want to trace out some pins on my Atmega2560 based 3D printer controller board.

The problem is the particular one I have is believed to be a clone of a clone hence I don't have a schematic of the board. I can't get off the manufacturer as well. Come on it's bloody based on an open source design anyway.

Are there probes you can attach to a standard multimeter ?
how much am I looking at?


texts: Why does this half-bridge mosfet not short to ground?

texts:
Please take a look at this circuit, which I am using purely as an example:

Please can someone explain why, if a battery was attached, does the circuit not short to ground as I drew in the red arrow?

Surely, if and when the "low" side is on, and the "high" side (HIDRV) mosfet off, then there is a short to ground?


texts: Chokes vs. small capacitors on signal cables

texts:
I know that many signal cables (usb camera to computer cables, etc.) have bulky ferrite chokes  on them to prevent noise.

Why do they all have ferrites instead of ceramic capacitors? Small ceramics also get rid of noise effectively, and would be much smaller (probably cheaper too?) than the ferrites.


texts: I want to make a electronic circuit more hidden. So, I want to make it all black. The easy way is get a spray ink and use it. But will it work? Which ink or paint I can use?


texts: When a charge \$Q\$ is considered and in order to apply Gauss's law, we take a spherical Gaussian surface, obviously we get, \$D\ = Q/(4 \pi r^2)\$ My question is, as we go extremely close to the center, the expression would give extremely large value of D - what does this mean physically?


texts: Having trouble making transfer function from this Bode plot from op Amp datasheet in Mathematica

texts:
I am fairly green to control theory.
I am trying to reproduce the Open loop transfer function of the LT1X28 op amp in mathematica.
I want to get the poles and zeros from the following plots and produce a very similar response with a bode plot. This way I can compensate for the pole-zero doublet that causes ringy-dingy-ness at higher frequencies. Below is the code for how I setup the transfer-function. The parameters are in Hz.

Can someone point me in the correct direction or help out? I believe I am doing something incorrect whether it be mixing up angular frequency and Hz or something.I am getting similar plots but not correct results. The Gain plot looks good but the Phase plot is very inconsistent with the x-axis on the datasheet. Any help is appreciated

Code for copy/paste:
params1028 = {Avol1028 = 146.0, GBW1028 = 75.0 10^6,
   DominantPole1028 = 4.5, SecondPole1028 = 500 10^3,
   ThirdPole1028 = 26.25 10^6, FirstZero1028 = 2.5 10^6};
GofS[Avol_, p1_, p2_, p3_, z1_] :=
 TransferFunctionModel[
  10^(Avol/20) (
   1 + s/(2 \[Pi] z1))/((1 + s/(2 \[Pi] p1)) (1 + s/(2 \[Pi] p2)) (1 +
       s/(2 \[Pi] p3))), s]
Trans1028 =
  GofS[Avol1028, DominantPole1028, SecondPole1028, ThirdPole1028,
   FirstZero1028];
BodePlot[Trans1028[2 \[Pi] s], {2 \[Pi] 1 10^-1, 2 \[Pi] 1 10^8},
 GridLines -> Automatic, ImageSize -> Large]
BodePlot[Trans1028[2 \[Pi] s], { 2 \[Pi] 1 10^4,  2 \[Pi] 1 10^7},
 GridLines -> Automatic, ImageSize -> Large]


texts:
I know that when people say that a gain of amplifier is X dB, they mean that  10*log(Pout/Pin).

However, How can I interpret it when they say that "noise floor is -120dB"? How can I derive voltage level?


texts:
I purchased a Gigapan Epic Pro a while back (www.gigapan.com).

I love this device but I would like to be able to access the buttons on it, from a distance. (I want to mount the unit on top of a camera crane unit - about 10ft off the ground).

I would still need to be able to push the 7 buttons from the ground.

Here is a high res photo of the unit in question

(Original)

(Added image of 7-button control panel)

Preferably I would like to use some kind of remote control unit with a joystick for the movements but this is a preferance not a necessity.

I have no experienc ein robots or engineering at all, so if someone would care to explain the process to get this done I would greatly appreciatte it.


texts: How to make a button activate its corresponding binary address

texts:
I have 15 output buttons and 4 digital inputs. As in the picture:

How do I make each button activate its corresponding address. For example, when I press s3, I want GND to be sent to inputs 0 and 1. When I press s7, I want GND to be sent to inputs 0,1 and 2.I have to do this without one button influencing the other


texts: Why voltage lags by 90° from magnetic flux?

texts:
I was not sure if I should write it here or on Physics board, but I will give a try.

As I understood current (generally emf) can be generated in a system by varying magnetic flux.
For example, let's take AC generator. A loop of wire rotates between N and S magnets.

\$ \Phi = B \times A \times cos(\Omega)\$, where \$ cos(\Omega)\$ is the angle between the magnetic field B and normal of the loop A.

So the maximum flux can be achieved when the normal of the loop is parallel with magnetic field.
But why emf at that moment is 0? And why emf is max when flux is 0?


texts:
Looking at a datasheet picture, I assume this is an SI system value Pcv core loss kW/m³.
I haven't found this mentioned in my studying material.
What does it mean?

Also, related question, how come in the graph in the picture it's possible for me to choose a flux density of 200mT while going up in frequency @25 kHz, 50 kHz, 100 kHz, 200 kHz, 300 kHz, 500 kHz, while in practice the Bs is decreased by core loss as frequency goes up?
Can you still get 200 mT B satauration while increasing core loss immensely at 500 kHz pushing the power output to its limit?


texts: 5 band resistor. Red, orange, black, gold and black. It doesn't fit in to normal rules

texts:
I have a difficulty in identifying a five band resistor. Color sequence is red, orange, black, gold, and black. It doesn't fit in to normal rules.

Depending on the location of its use I expect that to be around 20 ohms. But I want to know if it is any how special as in low tolerance, or temperature etc.


texts: Reason for x86 reset vector being at 0xFFFFFFF0 instead of 0xFFFFFFFF

texts: The top answer to this question on Super User gave an explanation that was satisfactory to me at first as to why the reset vector is not at address 0 (afterwards , I realized that it doesn't why the end of RAM couldn't be put at 0xFFFFFFFF and then grow downwards). But, 0xFFFFFFF0 is such a strange address. Why does x86 begin executing at 16 bytes before the top of the 32-bit address space? Are those 16 bytes used for something special?


texts: Vishay TCST2300 Testing (Transmissive Optical Sensor with Phototransistor Outpu)

texts:
New here and relatively simple question for those experienced with electronics.  Unfortunately, my experience is limited and I'm confused by the TCST2300 datasheet information.

Specifically, I'm trying to debug an optical encoder on an industrial pyramid roller (an "Ercolina CE50 H3") and I first want to confirm that the encoder board has power to the emitter and a signal voltage to the phototransistor.

Question #1:
From the data sheet (page 3) it looks like I should be looking for 1.25 - 1.60 VDC to the "+" side of the emitter [INPUT (EMITTER) section of the data sheet], and either a minimum of 7 VDC or 70 VDC of signal voltage into the phototransistor.  Therein lies my confusion - am I looking for "Collector emitter voltage" - i.e. minimum 70 VDC, or "Emitter collector voltage" - i.e. minimum 7 VDC (again on page 3 under "OUTPUT (DETECTOR)"?

Question #2:
Once I identify the voltages I'm looking to verify, is it safe to simply take either of these pins to any ground on the machine to check the voltage?  I'm assuming that grounding a pin shouldn't hurt anything.

I know that this is a very basic question and it illustrates my lack of understanding, but any help would be greatly appreciated!


texts:
I am designing a power supply circuit. Does anyone have any calculation formulas for resistor which we connect across inductor or capacitor?

I have attached a circuit with  highlighting a connections of resistors.

simulate this circuit – Schematic created using CircuitLab


texts: How does a bidirectional level shifter work?

texts:
I have the following circuit with an NPN HEXFET Q1 (BS170)

Correct me if I'm wrong:

When the TX-3V3 microcontroller is 3.3V i.e. logical 1, the TX-5V is a logical 1. This is because the gate of Q1 is CLOSED when \$V_{GS}\$ is greater than 0, and OPEN when it's not. So right now it is OPEN since \$V_{GS} = 0\$.

Question:

I get confused when the TX-3V3 microcontroller is 0V i.e. logical 0. I know from my measurements that the result is that the TX-5V is 0 in this instance. I don't understand why.

I would say the gate of Q1 is closed, since \$V_{GS} \approx 3.3V \$. Possible scenario's I can think of, please correct me where my thought process is wrong, I want to know my mistakes:

The TX-5V has impedance, and since current takes the path of least resistance my guess is that the current coming from the 5V supply will flow towards the TX-3V3. However, then what happens? I always think of current as marbles moving through a tube. Since the TX-3V3 is a 0, then where will the marbles flow to? There's no ground connected...
Another one of my guesses is that the voltage across the R2 resistor will be 5V, so the potential left over at the TX-5V is 0V. In this scenario there's still no ground though. So where can the current go? Please answer this question: Since the current has nowhere to go, does this mean theres no voltage across R2?

According to the assignment, the TX-5V can also control the logical '1' or '0' for the TX-3V3. Can one of you explain the scenario where the TX-3V3 is 0V and the TX-5V is 5V? How will the TX-5 be able to control the TX-3V3, like the TX-3V3 controls the TX-5?


texts: Regulator solution for 5 volts at +2ish amps

texts: I  have been looking at a lot of different regulators. Generally speaking switching regulators will give me a wide range of input voltages at the out put amps I am looking for with added efficiency. However, the simplicity of a linear regulator is really appealing for the project that I'm looking at. The problem that leaves me with is that most linear regulators will do between 0.5 and 1.5 amps. Is there a way to hook up two regulators so that they provide my 5 volts with their combined amp output like with batteries?


texts: Solar Cell - Preventing overcharge of an NiMH battery

texts:
I am trying to design a circuit and was wondering how to design it that the 12V 800mAH NimH battery I am using will not overcharge. I have researched trickle charging and as far as I understand, a zener diode that regulates the voltage down to about 13.3-13.7V should do. I chose a 14V Zener, taking into account the .6-.7V drop.

I have heard that trickle charging is not the best for the battery, but am not sure how much more work designing a smart charger would take.

I was also thinking of using another diode to prevent flow back to the panels from the battery.

simulate this circuit – Schematic created using CircuitLab
The three voltage sources on the left represent the solar cells, with the NiMH battery on the right.

I was wondering if I needed any additional components if I were to use three 5.5V solar cells in parallel outputting 40mA (16.5V total at 40mA, regulated to 13.3V by the zener) in order to prevent overcharging.

A similar question to mine was asked at How do I avoid overcharging a battery? However, this dealt more with a larger lead-acid battery and used a voltage regulator with a schottky diode.

Smart charging circuit for NiMH battery pack This link discusses almost my exact same question, but I was confused to the answer given which said that up to 1.45V per cell could be charged, taking my max charge voltage up to 14.5V.

Considering I am only outputting 40mA to an  800mAH battery, it seems that I may not need any more battery protection, but would love any input.


texts:
After watching some tear-down videos on YouTube with various lithium battery products (portable chargers, laptop battery, power tools) they all (apart from mobile phones / tablet battery) seem to feature cylindrical battery cells.

Is there a technical reason for this, other than it's a uniform size that tiles relatively well to give manufacturers flexibility in incorporating the cells?


texts: Two way wiring with relay during power failure

texts:
I have below circuit employed at my home.
Since I used 2 way wiring between relay and manual switch, during power failure, I face problem of Lamp turning On or Off depending on switch position.
Out of 4 positions of two way switches 2 are working fine and other 2 are working opposite.
Please help me with some circuits preferably using relays or switches to overcome this problem during power failure. Other design are also welcome.
UPS takes over without any issues but SPDT relay 2 used for home automation system loses power from mains, changing contacts thereby toggling the lamp.
Since the space is limited, kindly give me some idea, where after power failure SPDT Relay 1 switches to UPS mode but due to power loss SPDT Relay 2 changes contact there by Lamp is toggled.
Suggest me to keep the state of Lamp, when taken over by UPS (SPDT Relay 1 works fine and Phase from UPS) after mains power failure (SPDT Relay 2 changed state).


texts: Wireless internet signal bi-directional amplification?

texts:
So I have little to nothing experience with anything wireless related. the WiFi modem I have in my house is far from my room and the signal is weak, so it reduces the communication rate. my first question is this:
A) Isn't the information transmitted encoded in ASK or FSK, if this is, then why would the reduction in the amplitude of the signal reduce the speed of communication? I can see how the reduction would introduce errors into the system, but not how the system can still maintain functionality but at a lower rate and the only thing I can think of is frequency attenuation, but it does not make sense to me. I remember reading somewhere that the telephone lines are analog coded signals (However, my common sense tells me fiber optics are digital because of the way they work!), as in FM or something similar, and the WiFi modem basically changes that to a digital signal (ASK, FSK or PSK)
As a solution, I was thinking i could make a PCB to:

receive the signal from the modem
amplify it and transmit it again
my PC receives the signal
my PC transmits it's signal
PCB recievs PC's signal and amplifies it, and transmits it

B) Would this system work? is this something that can be implemented? I think I have sufficient knowledge in designing suitable amplifiers for this purpose. one other thing that comes to mind, is that would this receiving/amplifying/transmitting procedure introduce any interference? Say my PC receives both the original signal and the amplified one at the same time, can it differentiate between the 2? is this going to cause problems?
PS: I know EMI could cause me legal problems (EMI/EMC standards in the UK), but I have dealt with it before (in terms of standards they have to pass) so I think I am fine at that front :)


texts: Why are replacement plugs in the US only rated at 125V even though many of our devices can also be run on 220V?

texts:
When I search for replacement plugs at Home Depot or Amazon (US), all I see are plugs rated at 125V. Even plugs marketed as "heavy duty" are still only 125V. Here is one such example. The only ones I've found rated for higher voltages are the big 20-amp plugs with non-vertical prongs. Yet all kinds of devices around the house are rated for 110-220V, even ones with small, flimsy plugs.

Why are the bigger and seemingly more sturdy replacement plugs only rated at 125V? Is it just a conservative rating? I had been under the impression it was more the wire and power transformer you have to watch out for, not so much the plug.

The reason I ask is because I would like to replace a plug on a device with a 110-220V power supply, that I would conceivably take abroad some time. Of course I would use the appropriate plug adapter.


texts: Capacitor measurement in existing circuit

texts:
I am searching for the cap load formula of C2 of the following circuit:

In the end I want to be able to determine the capacitance of C2 through the ADC-IN voltage.

The unknown part is a driver which sits besides the C2. The C5 is measured with and RLC meter after substracting the 4.7nF of C1. I applied 20VDC (30V/µs supply) and saw a voltage drop of 7V accross C2 - R5 is a pure assumption but seems to be accurate even with different FP voltages.

When i split the sections of the circuit, can I assume the following?:

I added R1 so the tau is in a measureable region.

C1 and R2 are a highpass filter which should send noise in the upper 100MHz against ground. - Can I ignore this part for the calculation?

R3 and R4 is a voltage divider for the ADC, this parallel to R5 is 53,85k Ohms.

I made the following assumpter:

At time = 0s and FP= 20V:
Voltage is divided between R1 and (R3+R4)//R5 and the C1 and C5 start to load against 7V (resulting from the voltage divider).

I assume that R1 is my load resistor and I can ignore the R2-R5 for loading.
So I have a capacitance of 10,085nF and after 1 tau (R1*(C2+C5)) I should be at 4,41V (63%)?

When I look at the graph measured parallel C2 i get 4nF:

Calculated with:
Load time divided by R1
I tried with the load formula solved to get C. I get a slightly different result but still nearly 4nF.
When I measure without C2 and then with and substract the result, I get the CAP (Result varies a bit, but I guess thats a user error)

What am I missing here?

Edit

I can remove C2 freely, so even if the CAPs have toleranz I have the possibility to remove C2 - make a measurement - and then add C2 and compare the two measurements.


texts:
I'm currently using this circuit to control my load from MCU logic HIGH

 why just not do like this ?

 circuit ? It's safe for my MCU ?
I use NDP6020P is a Vgs(th) max -1V my VCC is 3.7V.

I know in the last circuit when MCU is LOW my load is "ON" instead the first circuit "LOW" = "OFF"

Regards


texts: how is it possible that an inverter absorb reactive power

texts: It's always said that reactive power is interpreted as magnetic field in motors (or transformers) it can also be the electric field in capacitor, but where does an inverter "store" that reactive energy?


texts: AVR: Serial communication gives strange characters

texts:
I am having some serious problems trying to get the serial monitor to output the correct characters. I have looked over a lot of the posts with similar problems, but nothing seems to solve it.

I am an absolute rookie when it comes to this stuff, and we are working with embedded systems for a university course and the teacher isn't at much help.

I am simply trying to print the character "a" to the serial monitor, but all I get is these wonky characters that can be seen in the picture.

I attached the code and the picture, in hopes that someone more knowledgable in the area can pinpoint me in the right direction!

Basic Info:

Programming through a Arduino nano

programmer: arduino

baud rate: 56700

chip: atmega328p

#define  F_CPU 1000000UL

#include <stdio.h>
#include <avr/io.h>
#include <util/delay.h>
#include "usart.h"

int main(void) {

    uart_init(); // open the communication to the microcontroller
    io_redirect(); // redirect input and output to the communication

    while(1) {

        _delay_ms(1000);

        printf("a");

    }
    return 0;
}

The usart.c and usart.h files are provided by the university. I can compile and flash to the chip no problems, just getting strange characters as output.

Every value of the baud rate under 57600 gives me this this response from avrdude.

There is one exception when I try to use 9600, I get the response:

avrdude: stk500_getsync() attempts 1 of 10: not in sync: resp=0xff
avrdude: stk500_getsync() attempts 2 of 10: not in sync: resp=0xff
avrdude: stk500_getsync() attempts 3 of 10: not in sync: resp=0xff
...

As I am totally new to this, I have no idea what it means, and google didn't help a lot. The only baud rate I can even flash to the chip, is at 57600.

Here you can see the uart_init function:

void uart_init(void) {

    UBRR0H = UBRRH_VALUE;
    UBRR0L = UBRRL_VALUE;

    #if USE_2X
    UCSR0A |= _BV(U2X0);
    #else
    UCSR0A &= ~(_BV(U2X0));
    #endif

    UCSR0C = _BV(UCSZ01) | _BV(UCSZ00); /* 8-bit data */
    UCSR0B = _BV(RXEN0) | _BV(TXEN0);   /* Enable RX and TX */

}


texts: Why does this schematic have 4 diodes plus a quadruple one?

texts:
The schematic can be found here.
On the sim card section it has 4 diodes (ULC0511C) plus a quadruple (SMF05C).
Shouldn't it be either the 4 of them or the quadruple one?
Why use the 4 ones plus the quadruple?


texts: The battery voltage and current relation

texts: While a battery is discharging ,its voltage is decreasing , what happens to the the current? Does it decrease ,increase ,or stay constant?


texts:
I'm working a project which is almost same method with hedge trimmers. But my project is going to be use harvesting, anyway. I design and mounted machine everything but now I have no motor driver to use machine safety. Problem is while machine is working when blades hit big plant branch the motor could can stop and until I takeoff the button the motor will draw high current.
My question is without motor driver can I use my motor and if I force motor or take off late my hand to button the motor would burn ?
Or in other words while motor in stall how much time I have to take my hand of and how many times o could do this ?
Motor is Mabuchi Rs775 12dv dc motor. 13000rpm.( this all is test, after a time I will make ture motor driver for this situation)
An ideal motor driver in bosch hedgetimmer: https://www.youtube.com/watch?v=YCRji7BMwwc


texts: Does the TL431 have a "dropout voltage" per se?

texts:
I want to get a stable 3V reference from a +3.3V ±5% supply (so it can go as low as 3.135V and as high as 3.465V.)

I know the TL431 is a shunt/zener regulator, so doesn't really have a dropout voltage, but there probably is some point above 3V at which it cannot maintain the 3V output. What I want to know is will a typical TL431 be able to handle this?

My circuit configuration is below:

         115R
+3.3V-+-/\/\/\---+----------+-------+-- 3V out
      |          |          |       |
     --- 100n    /          |      --- 4.7u
     --- 16V     \ 634R     |      --- 10V
      |          /       ___|__|    |
     ---         |       | / \     ---
      -          +--------/___\     -
                 |          |
                 /          |
                 \ 3.16k    |
                 /          |
                 |          |
                ---        ---
                 -          -


texts:
Commonly there are basic motor generator sets (with or without automatic throttle to compensate for load variations) and then there are those with an inverter to produce a cleaner sine wave using switching technology. The inverters are more costly and produce less power for the size and weight of the equipment. Conventional advice is that electronic equipment like PCs might be harmed by the basic sets and therefore one must use inverter sets to power them (in a mains backup situation). I wonder if this is any longer good advice.

My thinking is that all modern PCs use switching power supplies anyway.They are capable of working off a wide range of voltages and frequencies, and have plenty of filtering to remove the spikes that they themselves cause. So it seems to me PCs are ideally suited to running off a dodgy basic motor generator.

What's wrong with my reasoning?


texts: I have 2 identical overhead projectors with bad diodes, but the diodes have different numbers. How do I find the right one that works?

texts: I have 1 overhead projector that blows a new lamp right away. The correct lamp is rated 82Vac and 360W. I have 120Vac to the lamp, which makes sense why the lamp is blowing immediately. The only items in front of the lamp in the circuit are a fuse and a diode. Similar problem with my second projector except my voltage to the lamp is 24vac. I believe I have 2 bad diodes, but each diode has a different number even though they look very similar. I don't know which one could be the right one. The manufacturer can't tell me because they don't sell parts for these, they just warranty them out with full replacement. I don't qualify for direct replacement unfortunately. Does anyone know how to figure the right diode for what I need in this circuit? I'm an electrician but I don't work with electronic components. All I know is diodes allow current flow in one direction.....


texts: Maximising power received using two sets of data

texts:
I have done simulations where by I am varying two variables i.e. powerTransmit and frequency within an equation, for example:

powerReceived = powerTransmit - 20*log(frequency) - 20*log(distance)

The distance is kept constant.

I am runing a permutation menthod. So I first loop through all the frequencies first, then I increment the powerTransmit and then loop it.

I then get two sets of data. The first set is percentage of power received against the frequencies. The second set is percentage of power received againt powerTransmit. Now clearly the units do not match up. But how do I plot these two sets of data on the same axes. So I can find the point of intersection that maximizes the percentage of power received against the frequency and powerTransmit?

power received =

120 (%)       -> freq = 862(MHz), power = 30(dBm),

120       -> freq = 866, power = 30

180       -> freq = 862, power = 33,

180       -> freq = 866, power = 33

213       -> freq = 862, power = 34

213       -> freq = 866, power = 34

246       -> freq = 862, power = 36

246       -> freq = 866, power = 36

N.B the percentage going beyond 100% is expected in my simulations


texts:
Lets say I have 2 capacitors, one rated 100 µF, 10 V and the other 100 µF, 300 V.

Now I charge them both with 5 V for 1 min (or until they reach 5 V, fully charged) and connect them to a same load, for example an LED one at a time.

Will they both light that led up for same amount of time?

Please, no tank examples...


texts: How to Transition from "Basic" Microcontrollers to ARM Cortex?

texts:
I have many years of experience with 8-bit cores from various manufacturers - namely 8051, PIC, and AVR - and I now have a Cortex M0 to figure out.  Specifically this one, but I hope we can be more general than that.

It's turning out to be a bit more than I bargained for, with multiple documents that describe different parts of the system in varying levels of detail and none really that I've seen to connect it all together.  This compared to having one datasheet that explains everything.  I understand having much more stuff to document in the first place, but the change in format is throwing me for a loop.

The website above has one document that's a good overview of each subsystem and peripheral in isolation, and another one that describes each register in detail, and I have all the source code for their SDK including header files and some complex examples, but I still see nothing that describes how it all connects together.

Is there a concise walkthrough of the Cortex architecture that explains the function of things that smaller controllers just don't have - like multiple layers of busses from CPU to peripherals, each with its own watchdog timer - and how they all connect together?


texts:
A single phase supply requires 2 wire one for forward and next for returning path. However a 3 phase supply only requires 3 wire why?
How does the circuit complete with 3 phase supply?


texts: transfer function and error gain function

texts:
simulate this circuit – Schematic created using CircuitLab

I know the difference between those two functions , but i want to see the relation between them , i think that the error gain function , is given by the transfer function , and the best transfer function which is

stable.
has an error gain function equal to 1.

if this is true , how can i derive the error gain function , from transfer function ?


texts: Open-loop gain of Op Amp at low supply voltage

texts:
I'm new in electrical engineering (since I'm  a chemical engineer) but I've been working on system dynamics through simulation of a DC circuit that involves Op Amps. One of my main variables to watch is supply voltage. Now, I'm struggling with relating the open-loop gain to supply voltage, especially at low values of the latter. Data handling from simulations of a class of Op Amp (LMC6482) in NI Multisim showed that open-loop gain drops drastically when a certain supply voltage is reached (from high to low voltages) as is expected, but it continues decreasing, reaching almost zero when supply voltage is not zero yet. Is it physically possible to get open-loop gain values that low? Can saturation voltage levels play a part in this situation by decreasing too much while open-loop gain remains at low but not-less-than-unity value? Is there a way of relating other Op Amp parameters to obtain the open loop gain as a function of supply voltage?

I attached a plot showing the numerical data obtained in NI Multisim.

If simulation data is not trustworthy at supply voltage lower than recommended operation conditions, what could be the best way to approach to transition between the Op Amp operating from active to passive?


texts: Operator synthesis VHDL, numeric_std.vhd

texts:
if i include the library numeric_std.vhd
(the implementation is here https://standards.ieee.org/downloads/1076/1076.2-1996/numeric_std-body.vhdl) you can see that the operator *,+ (as instance are implemented in the following way)

Unsigned sum

function ADD_UNSIGNED (L, R: UNSIGNED; C: STD_LOGIC) return UNSIGNED is
    constant L_LEFT: INTEGER := L'LENGTH-1;
    alias XL: UNSIGNED(L_LEFT downto 0) is L;
    alias XR: UNSIGNED(L_LEFT downto 0) is R;
    variable RESULT: UNSIGNED(L_LEFT downto 0);
    variable CBIT: STD_LOGIC := C;
  begin
    for I in 0 to L_LEFT loop
      RESULT(I) := CBIT xor XL(I) xor XR(I);
      CBIT := (CBIT and XL(I)) or (CBIT and XR(I)) or (XL(I) and XR(I));
    end loop;
    return RESULT;
end ADD_UNSIGNED;

Multiplication

function "*" (L, R: UNSIGNED) return UNSIGNED is
    constant L_LEFT: INTEGER := L'LENGTH-1;
    constant R_LEFT: INTEGER := R'LENGTH-1;
    alias XXL: UNSIGNED(L_LEFT downto 0) is L;
    alias XXR: UNSIGNED(R_LEFT downto 0) is R;
    variable XL: UNSIGNED(L_LEFT downto 0);
    variable XR: UNSIGNED(R_LEFT downto 0);
    variable RESULT: UNSIGNED((L'LENGTH+R'LENGTH-1) downto 0) := (others => '0');
    variable ADVAL: UNSIGNED((L'LENGTH+R'LENGTH-1) downto 0);
  begin
    if ((L'LENGTH < 1) or (R'LENGTH < 1)) then return NAU;
    end if;
    XL := TO_01(XXL, 'X');
    XR := TO_01(XXR, 'X');
    if ((XL(XL'LEFT)='X') or (XR(XR'LEFT)='X')) then
      RESULT := (others => 'X');
      return RESULT;
    end if;
    ADVAL := RESIZE(XR, RESULT'LENGTH);
    for I in 0 to L_LEFT loop
      if XL(I)='1' then RESULT := RESULT + ADVAL;
      end if;
      ADVAL := SHIFT_LEFT(ADVAL, 1);
    end loop;
    return RESULT;
end "*";

Now i'm not sure of how it would work a VHDL compiler, but my question is...
Since basically the algorithms i shown are "ripple carry adder" and "sum and shift" respectively apart logic optimization that the compiler usually could do wherever you use the operator "*,+" the compiler will always synthesizes a "ripple carry adder" and a "sum and shift" isn't? i mean usually the compiler don't try to draw a carry look ahead adder or a better multiplier by their own, so apart from options related to optimized delay or optimized area (which are performed at logic level not at architectural level) the programmer has to perform architectural optimization by his own isn't?

I'm asking this because i don't know if specific toolchain (except external package or library, which are used by the programmer anyway) could perform such kind of optimization by itself.


texts:
I am trying to build a night clock projector, inspired by this project: https://microengineer.eu/2018/05/01/diy-night-clock-projector/
As I am more a computer scientist than an electrical engineer, I prefer ready-to-use/plug-and-play solutions (I am not very good at soldering, and not at all at SMD soldering...).
The linked project recommend to use a small LCD screen with a power LED. But I had a hard time finding such LCD screen, compared to the cheap OLED alternative: https://www.buydisplay.com/serial-spi-i2c-white-0-42-inch-arduino-raspberry-pi-oled-display-72x40
However, this screen is advertised as 120 cd/m^2, and it doesn't seem enough to be projected to a ceiling 2 meters away (I did not manage to get anything projected, other than the activity LEDs of my RPi ^^')
In comparison, the LCD alternative (with pre-mounted backlight) is bigger and is advertised as 200 cd/m^2 (which is a rough average value for LCD). Finally I am not even sure that it is bright enough for clear projection.
Finally, I found this LCD screen (with no backlight) which is FAR more expensive, require a backlight (like this LED) and some soldering to connect all these things together.
Here, it is hard to get some brightness comparison with other solutions.
What I come to is:

120 cd/m^2 times the size of the screen gives 0.008 cd for the pre-mounted OLED screen
200 cd/m^2 times the size of the screen gives 0.136 cd for the pre-mounted LCD screen
87 lm over 85 deg gives 30 cd for the LCD + LED

Is this comparison correct?
Is there a way to compute the required brightess/luminance/luminous flux/luminous intensity/illuminance for this kind of application?
Is there some "in-between" solution, with more than 0.136 cd but less than 30?


texts:
Initially I trawled posts and forums (initially to debug some noise, squeals, and oscillations on some LM386 circuits I built). I've synthesised all of that knowledge and re-approached this IC, calculating a load of component values.
I get that there are lots of posts/questions about LM386. I'm asking if I've stitched all of the answers together properly and therefore wanted to run this past some people more knowledgable than myself. I've not breadboarded this yet as I don't have all the components and was looking for some feedback before I order.
Also, please note that I am a complete amateur here. I’m more than capable of plugging numbers into calculations but I don’t fully understand all of the concepts behind these. I’d never heard of Xc for example.
Here's the datasheet for anyone who needs it - https://www.ti.com/lit/ds/symlink/lm386.pdf
Here's a schematic:

So, first of all, C1, the input DC blocking capacitor. The 10K volume pot in parallel with the IC's 50K input impedance results in 8.3K input resistance.
I'm aiming for Xc lower than 8.3K/10 at 100hz (this is low enough for my application, 20hz seems excessive for me). A 2.2µF cap gives Xc of 0.72KΩ at 100Hz so this seems good to me. This is higher than any other LM386 amplifier design I’ve seen online though (ranging from 47nF to 1µF)?
Next, C2. I went by the datasheet which shows 50µF as the best frequency response (Fig 2. Power Supply Rejection vs Frequency). The graph is for 6V supply though and I’m using 9V so I’m unsure what impact that might have. Again, 50µF is higher than the e.g. 0.1µF I’ve seen elsewhere.
For C3, I’m connecting to a miniature 8Ω speaker (well actually vibration speaker element so a speaker coil driver without the cone). The chip’s output resistance is 0.1Ω so I have a total output resistance of 8.1Ω. To work out the capacitor I’m aiming for Xc less than 8.1Ω/10 at 100Hz. A 2,200µF cap gives me 0.72Ω at 100Hz. This is much higher than used in many other circuit. Size and cost seems a more likely factor behind this and I have seen 2,200µF recommended elsewhere.
C4 and R1 form part of the Zobel network. Rather than take the standard values seen in many circuits (generally 10R and 47nF) I calculated these. My speaker has a voce coil/DC resistance of 7.4Ω. recommended resistor value is this times 1.25 and so 9.25Ω. 10Ω resistor is fine. For the cap the calculation is Le (voice coil inductance) / R (9.25Ω above) * R (well R squared but I can’t do superscript 2). Le for my speaker driver is 0.06mH. I dived this by 1000 to get Henries (and multiplied the result of the calculation by 1000000 to get µF) resulting in 0.61µF. I understand that going higher should be fine so a 1µF cap is an easy value.
C5 and C6 are power supply filtering/decoupling. I couldn’t find a source to calculate this so went with a range of advice and settled on 100µF and 0.1µF.
I’m leaving pins 1 and 8 open as 20 gain should be enough for me.
I’m using the inverting input (pin 2) as it’s suggested that it sounds better.
As my calculations result in some higher value capacitors than I’ve generally seen I’ve plumped for some polarised elctrolytics where I don’t usually see them (C1 and C2) so I’m unsure about polarity here.
Phew, so that’s the schematic. I’ve also laid out a board design based upon all of this and taking into account best practice I’ve seen. There’s especially an issue with keeping in, out, and power grounding separated and so I’ve done my best here at star grounding on pin 4 (any good?). I’m using non-standard symbols (heavily drawn from Peter Blasser’s paper circuits) but the one’s which should be hardest to figure out are the circles with black triangles next to them. These are for the input and output jack grounds. Oh, and the weird 'power obelisk' to the right is where the 9V battery supply will connect.

I appreciate that there’ll be a range of factors such as space and cost and so I’m just aiming for something more ‘ideal’ than practical at this stage.
So, anyone who actually understands all of this properly able to comment?
Thanks for your time.(


texts:
How can I use 15 servos with arduino mega2560 without stepping down voltage?

because I want to control 15 servos by one board (arduino mega 2560).


texts:
In Altium I don’t have any connections (ratnest) showing.  They were showing previously, and in the viewer they are ok.  They should be visible after going to view->connections->show all but are not.
This happens on all the boards and workspaces I open.

There are plenty of unconnected SMD that highlight when I mouse over.  The DRC report gives lots of unconnected pins.  The net color doesn't match the background, and a few nets have special color assigned.  All of this seems like the connections should show, but no luck.


texts:
I am currently looking for a high side current sense IC. I have noticed that most of them that are without galvanic separation, are using an op amp with bjt transistor like in bellow schematics:

The datasheet of TSC101 describes more or less how to calculate the output current, but I would like to understand what exacly is happening in here and why is it this exact circuit always used for high side current sensing. I just mean the 1st opamp with bjt transistor config. I get the voltage follower part. If I were to build this from semidiscrete elements, can the op amp be powered from voltage ie. 5V and sense current on a lot higher potential with this circuitry?
I would apreciate all help and explanation.


texts: 1A Voltage Regulator - Maximum or output?

texts:
I want to design a circuit that has 12V1A output from a battery. I am using a 12V voltage regulator

Do I want a 12V 3A Regulator or 12V 1A regulator?

If a 12V 1A voltage regulator gives me a better dropout voltage, should I use that?

The current is dependent on what the load will draw, right?

Sorry if its a bit of a simple question, but even searching I can't find the answer, it just gives me different questions.

Thanks


texts:
I am having trouble using my BiBox developing platform after its battery charging module got damaged due to lightning.

The platform has got a USB microB charging port.
I am wondering if there's a way to use it by directly plugging it to the mains with my phone's charger.

NOTE: I an OK with the platform being wired in during usage.


texts:
In which case shall I consider output resistance(ro)?

I found that in case of re model for common emitter configuration we are considering output resistance(ro) but there is no (ro) in emitter follower configuration which is confusing me.If the output characteristics of both CE and CC configurations are similar then why different re models?

Shall I consider (ro) while solving numericals or can I neglect it as it's value is very high?


texts: Zener Diode + fuse overvoltage protection for LEDs with constant current driver- fast or slow blow fuse?

texts:
I am working with a 6-axis robot (UR5) with a smart camera mounted on the end of arm, and I want to add a ring light to the camera lens which I will power using tool outputs from the robot interface.  The tool outputs can supply either 12V or 24V, and the voltage is chosen programmatically using a touch screen or script.

The LED light rings have a constant current driver requiring 12-18V, so there is a potential for a programming mistake sending 24V which would damage them.  I want to prevent that by adding a voltage protection mechanism in front of the ring light, so that if I or anyone else mistakenly sets the outputs at 24V instead of 12V the ringlight is protected.

As an aside, I also want my circuit to be very small, with the fuse fitting in a 150 series inline fuse holder from Littelfuse, catalog # 150274,
And the zener diode fitting on this tiny PCB, which I can fit inside the case with existing electronics: 5050 LED breakout PCB, product ID 1762 from ADAFruit.
I have located components already that fit these, so I don't need help with that part; I just wanted to point out my design requirement.

I'm a mechanical engineer, and not well-versed in electronics, so I want to make sure I am doing this overvoltage protection correctly before I implement it.  Below is a diagram of what I've come up with after extensive internet research.  My question is specifically about the fuse, but if anything else stands out that I am doing wrong, please feel free to comment and correct me.

I based my circuit off of this: (http://www.learningaboutelectronics.com/Articles/Overvoltage-protection-circuit.php)
and I did a lot of reading on zener diodes, fuses, thermal runaway in LEDs, constant current vs. constant voltage drivers, etc.  Here it is:

Here is how I understand this: the Zener diode will prevent more than 12V from reaching the circuit.  So if 12V is applied the Zener acts like an open circuit.
 If 24V is applied, the Zener dissipates 12V of that and the LEDs still get 12V...is that right?  And am I correct in assuming that the Zener will draw the maximum current it can from the output, causing the fuse to blow?  That is what I am hoping. I want the fuse to blow and alert the user to the programming error so the Zener doesn't just sit there and get hot.

I've chosen a zener diode that is 12Vz with a 5W power rating.

I couldn’t find a fast fuse in the size I want (more than 300mA, less than 600mA), but the slow blow fuse I spec’d out will take 3-20s to pop at 200% current rating.  Is that good enough, or do I need a fast fuse?  I've calculated 0.330Ax12V=3.96W across the Zener if the circuit has 24V applied to it, which is within its rating...Have I done this correctly?

If someone can clear this up for me, that would be great, and as mentioned above, if I have made other mistakes or taken the wrong approach let me know.  Thanks a bunch!


texts:
If I connect 2 FTDI cables together reversing tx and rx would I end up with a usb to usb cable ?

If so, I could connect a wireless FTDI adapter to a FTDI cable and get wireless usb.

Would I also need to alternat the CTS DTR lines ?


texts: Why does AVR-GCC apparently waste 6 cycles here?

texts:
This line...

            if (thisWindowsSinceLastFlash <=1 ) {

...complies to this code...

11e8:   81 e0           ldi r24, 0x01   ; 1
11ea:   8d 15           cp  r24, r13
11ec:   38 f4           brcc    .+14        ; 0x11fc

Why didn't the compiler use the cpi like this...

1204:   01 30           cpi r16, 0x01   ; 1
1206:   39 f4           brcc    .+14

and save the cycles and space and register used by the cp?

Both cp and cpi seam to update the same flags and leave everything in the same state...

What am I missing?

Note that the cp ended up being much more expensive that just the extra cycle because it forced a push/pop sequence on r24, which costs an additional 4 cycles (6 cycles in total).

I am using the AVR8/GNU C Compiler : 5.4.0 that is included with Atmel Studio 7.0


texts: fixing the amplifier in an old arcade machine

texts: I just joined and need help.  I'm trying to fix the amplifier in my Chicago coin speedway arcade machine.  It basically works but it has a bad hum in it.  I did replace a couple capacitors that were in bad shape but the hum is still there.  I finally checked the two germanium transistors in the preamp stage and they both seem to be shorted or out all together.  I did order a couple new ones but my problem is I think the schematic is not correct.  I'm going to replace the 2N2429 transistor and the A104 transistor.  What's bothering me is the schematic calls for an A104 transistor which is a PNP transistor.  The symbol shows a NPN transistor.  Can someone tell me what is really suppose go in that spot?


texts: Saturation of Constant Temperature Anemometer

texts:
Continuation of this question, apologies for the schematic. Rwire and Roh are depicted in balanced state.

This is a common Constant Temperature Anemometer circuit, however the diff amp output (Vbridge) keeps on saturating. I think the problem is on the INA118 output (Vina). A voltage divider analysis at the bridge would show that if Rwire < Roh / 10 then Vwire < Voh and hence Vina = G(Vwire - Voh) would have different polarity with Vbridge. Similarly, when Vwire > Voh then Vina would have the same polarity with Vbridge.

The table above shows a couple of measurement I did and it can be seen Vwire > Voh for all cases, but Vina have different polarity with Vbridge everytime. This differs with the analysis, I thought the diff amp may be messing with the inamp output but not sure why. Assuming that the components are not broken (I checked but maybe I'm wrong) what else could cause this?


texts: What is the scope of Electronics Engineering in Robotics/Automation?

texts:
I am beginner in Robotics .I have taken admission for Electronics engineering one year back as we hardly have specifically Robotics Engineering Branch in my Country.Now,I am suffering from questions like what is the scope of Electronics( not Electrical) Engineering in Robotics/ Automation?
Also,if I don't like to do programming ,are there other options to stick to Robotics / Automation field as per my branch(Electronics Engineering ) is concerned (i.e.. Where should I give focus?).


texts: I'm currently designing an e-ink panel driver. My choice is MC34063 for generating required voltages and I want to use two of these for step-up and inverting converters. However I'm somewhat confused with the saturation voltage needed for calculations. In datasheet there are two values provided (for Darlington and non-Darlington connection), in AN920 application note few other values are used. I would appreciate a clear explanation where to find or how to choose proper Vsat value for specific configuration. Thanks!


texts: BJT Amplifier has different gain for negative and positive inputs

texts:
There were some errors in my old question so I decided to close it and redo it here.

I am working on a 3 stage npn bjt amplifier for my circuits class. The first two stages are common emitter stages. These are responsible for achieving the required voltage gain of at least 1800. The last stage is an emitter follower which provides for low output impedance. My group is having a strange issue when we run the circuit through cadence (a circuit simulator). Everything looks fine, we have a good transfer function the expected cut-off frequencies. However when we ran the transient analysis we noticed that the bottom peak of the sin wave at the output is larger than the top peak. We are unsure why. We checked the voltages across all of the bjt and they are all in the FAR region. Has anyone seen this before or have any advice.

Here is the diagram of the circuit we are working on.  Sorry if it is a little messy since it has undergone a lot of revision.

Here is the transfer function of this circuit plotted from 1 Hz to 1 MHz.  This transfer function seems to fulfil the requirements.  Also if you are wondering the capacitor which goes to ground at the end of the circuit acts as a lowpass filter since out 3DB cutoff was too high.  We ran the analysis without it an it did not change the problem.  We also tested the stages individually and they only seem to distort the output when combined.  The distortion is visible after the second stage when combined with the first.

Finally here is a picture of the distortion.  This is from a transient (minus DC) analysis with a 20 uV input running at 1 kHz.  See how the top peak goes up to about 69 mV where the bottom goes to -76 mV.  Also note that I have tried running it with smaller and larger input voltages. We get the same issue.

Note that I also just tried to run the transient analysis at different frequencies.  This does not change anything and the problem is still there.


texts:
I am using the FQP30N06L MOSFET: http://www.fairchildsemi.com/ds/FQ/FQP30N06L.pdf.

As far as I understand the data sheet, if I connect 5V to the gate and run 2A through drain to source then with a \$R_{ds}\$ of \$0.035\$ I should get \$0.14 W\$.

\$I * I * R = P\$

\$2 * 2 * 0.035 = 0.14\$

So, with a R-theta junction-ambient of \$62.5 °C/W\$ that gives me \$8.75°C\$, or \$47.75 F\$.

So, if the ambient temperature is \$70 F\$ then that would make the junction \$117.75 F\$.

The data sheet says the max junction temperature is \$175 °C\$, so that should be fine, right? It will be hot, but should work OK.

Am I doing this right?


texts: How to burn hex code program file into AT89S52?

texts:
I am a beginner in Embedded. I have 8051 microcontroller development board with AT89S52 microcontroller. The board has max232 for serial communication.  I have connected this development board with my laptop using USB to SERIAL Converter written C program in Keil uvision 4 and created a hex file. I want to dump this hex file into AT89S52. For that  I am using FLASH MAGIC tool.

But the problem is that  AT89S52 micro controller  is not in FLASH Magic's device database. So what should I do now? Can anybody please tell me is there any other software which supports the at89s52 and windows 7 with usb to rs232 cable?


texts: What type of connector is this? (bridges two boards by means of a row of rigid, uninsulated wires)

texts: Trying to repair a friend's older Panasonic LCD TV I came upon this weird type of connector shown in the pic. How is it called and how should I go about disconnecting it without breaking anything?


texts: How does connecting a capacitor across a DC power supply with varying voltage produce a constant voltage?

texts:
I'm a British high school student (doing a certificate called A levels) and question 16 in this past paper (1st Link ) is baffling me. The answers to the questions are on the mark scheme (2nd Link). I want someone to please explain the scenario for me. Part (b)i) is the hard part. The circuit is shown in part (c) of the question. I've done 10 hours of solid work on this question, and I have an idea of what the answer may be, but I'm finding it hard to articulate my thoughts because I keep running into too many inconsistencies.

Here is what I would like to kindly ask an answer for:

May someone please explain the graph describing the variation in the voltage of the D.C power supply?
May someone please answer part (b)i) in a more coherent form than the mark scheme? (This is the most important question of all.) Qualitative analyses are preferable, but mathematical ones are welcome if that is how you think.
May someone please explain how the graph in part (c) of the question arises?


texts: What's the standard way to detect a digital signal transition?

texts:
The 2-phase dual-rail protocol in the concept of asynchronous handshaking relies on detecting signal transitions.

How do we detect a signal transition from LOW to High or HIGH to LOW? What is the output of this detection? A permanent High? or LOW? or another transition?

I need the transistor level schematic or at least a few words on the design concept to help me come up with the design by myself.

My initial thought is to put a memory element on the signal and then after the transition happens we can compare the signal with previous value and detect a change, but then how do we detect the transition itself?


texts: Low pass filter in the input of ADC supply

texts:
Attached figure shows a LPF connected to the input of an ADC preset in the microcontroller. Can anyone please explain why an inductor is connected in parallel with the resistor.

Regards
Hari


texts: Pin confirmation on pic for sd card connector?

texts:
I've had a first version of a connection to a sd card connector (DM3CS-SF) for my PIC32MX470F512L that did the following connections:

After trying to run an harmony example, using this config, the sd card didn't work.

I did then, some digging on the datasheet, i found that the SDI and SDO couldnt be used with that pins.

Input pin selection:

Output pin selection

With this i wired this way:

SDO -> RPD3

SDI -> RPF5

Am i right? I want to check before making a new PCB.


texts:
So I'm building what you might call an intentionally janky electric vehicle, and need some advice.
In case anyone is wondering, the vehicle in question is a Ripstik -  I currently have four of these brushed DC motors driving two 6in pneumatic tires under the back platform, while the front remains un-changed. For all intesive purposes it's an electric skateboard.
My biggest problem is coming switching the motors. You see the aforementioned intentional junkiness is due to the fact that the device is either in full forward, full brake, or coasting - One button for each. Put simply, I'm looking to use some sort of switch to turn the motors on or off - I have no need for an in-between ie some sort of ESC.
The motors I am using are supposedly rated for 130 amp stall current at 12v, but I plan to run them at ~16v for a higher top speed. The batteries that I'm using can supply 400amps in bursts of several seconds.
By my logic, this means that I need a switching device that can switch ~400amps at ~16v, and sustain lesser currents for longer periods of time.
I was initially looking into relays, because they are simple, but the only adequate ones I could find online would have run me 150 USD each, so I was hoping there is some other alternative.
I was looking into N-Channel mosfets, but I have no earthly idea how I would go about using one in this application.
Any and all help is appreciated!!


texts:
How do I access the subsecond counter (1/256 second) on the MAX32660 rev A2?
I tried reading MXC_RTC->ssec, when busy=0 and ready=1, as suggested in Chapter 9 of the user guide, but this register has a mostly useless value (lower 8 bits of a 4096Hz counter, apparently). For example, reading it at 32Hz, the subseconds change by 128 units at each measurement, instead of the expected 8 units:
02183058us seconds=75564, subseconds=095, busy=0, ready=1
02214244us seconds=75564, subseconds=223, busy=0, ready=1
02245431us seconds=75564, subseconds=095, busy=0, ready=1
02276617us seconds=75564, subseconds=223, busy=0, ready=1
02307804us seconds=75564, subseconds=095, busy=0, ready=1
02338989us seconds=75564, subseconds=223, busy=0, ready=1
02370176us seconds=75564, subseconds=095, busy=0, ready=1
02401362us seconds=75564, subseconds=223, busy=0, ready=1

I am using the following struct definition from Maxim's SDK:
/**
 * @ingroup rtc_registers
 * Structure type to access the RTC Registers.
 */
typedef struct {
    __IO uint32_t sec;                  /**< <tt>\b 0x00:</tt> RTC SEC Register */
    __IO uint32_t ssec;                 /**< <tt>\b 0x04:</tt> RTC SSEC Register */
    __IO uint32_t ras;                  /**< <tt>\b 0x08:</tt> RTC RAS Register */
    __IO uint32_t rssa;                 /**< <tt>\b 0x0C:</tt> RTC RSSA Register */
    __IO uint32_t ctrl;                 /**< <tt>\b 0x10:</tt> RTC CTRL Register */
    __IO uint32_t trim;                 /**< <tt>\b 0x14:</tt> RTC TRIM Register */
    __IO uint32_t oscctrl;              /**< <tt>\b 0x18:</tt> RTC OSCCTRL Register */
} mxc_rtc_regs_t;

The errata sheet says zilch about RTC, so there cannot be hardware bugs.
Is there some switch to select the proper clock source for the subsecond counter, or am I reading the wrong register?
Update 1 I took the exact same code, but used it on the EVkit board with the system initialization code that came with the EVkit, and it is working properly: subseconds is 256Hz as expected. I still do not understand how the system init code can affect subseconds frequency.
Update 2 Same image as Update 1, but running on my custom board. subseconds is 4096Hz. I'm starting to like @Justme's theory about a hardware issue. The thing is though, if this is a problem with the crystal circuit, how come seconds is still 1Hz? This makes no sense.
Here are the possible relevant hardware differences:

EVkit: MXC_GCR->revision == 0xa1. Using this crystal (6pF version) on the board. seconds=1Hz, subseconds=256Hz (as expected).
My board: MXC_GCR->revision == 0xa2. Using this crystal (6pF version) on the board. seconds=1Hz, subseconds=4KHz (unexpected).

Given that both boards count seconds at 1Hz, I doubt that the crystal is at fault. The crystals are electrically very similar, and obviously both boards are getting accurate 32768Hz, even if in one case the subseconds register doesn't want to admit it.
Maybe I can order an a1 or desolder from the EVkit to try it on the other board...


texts: What to be concerned about with NFC using external antenna located off board?

texts:
Working on an NFC application (NFC tag) and it looks like the NFC antenna will be located off-board. This is a sticker type of antenna.
The concern that I am possibly having is that I need to run some wires from the NFC IC to the antenna, and I fear this may be a problem for FCC / CE testing as the 13.5MHz gets radiated along the wires. The length of the wires/cables is currently not known.
To have a high chance of success in passing, what can I do (cost-effectively) to increase my chances of success?


texts: RS485 unmatched line - what will be the impact?

texts:
I am doing an experiment where I have a computer with an rs485 transceiver on it and data rate of 1Mbs.
an rs485 30m long with Z0 of 120ohm (also have one with Z0 100ohm).
at the end of the cable I have another rs485 transceiver .
In the experiment I had to cut the cable to two half's of 15m each, and added a board circuit in the middle.
In the circuit I am passing the data on copper wires without anything in the middle (not even repeaters).
The circuit itself would try to 'snub' the data without interfering but my question is about the data channel I just described.

when connected to the Board is there a difference if I connect through a connector or just solder them to the board?

assuming my copper wires on the board will have a max of 5~10Ω each will it make the line unbalanced/unmatched? if I understand correctly the Z0 impedance of a line is formed mainly by the L/C ratio and I guess my board won't change it much (hopefully).

if it does make the line unbalanced - what to expect?


texts: How can I measure my smartphone transmitted power?

texts:
I was wondering if I can measure my phone's transmitted power with an SDR by tunning in the transmission bandwidth but then, I'm not sure how to know whether this power is coming out of my phone or it's the base station received power at my phone?

Also, I tried using this app but again, I'm not sure if the dBm correspond with the Rx or Tx power. I contacted the developpers but they didn't answer. Maybe anyone knows another app or a way to do this?


texts: Why is waveform of the voltage across the DC-link capacitor alternating?

texts:
So I am connecting a full-wave rectifier to a half-bridge inverter as shown in the circuit below. I added a smoothing capacitor of 0.47 Farad to get a smooth DC output voltage (see the first graph), so why is the output voltage across the DC-link capacitors (C1 and C2) alternating (see the second and third graph)? As you can see in the fourth graph this also affects the waveform of the output voltage of the inverter.

Edit 1: Changing the capacitance of the DC-link capacitors C1 and C2 to 40,000 micro-farad fixed the issue (See waveform below). Isn't there a formula I can use to determine this capacitance?


texts: How to make a voltage controlled adjustable resistor?

texts:
I need it for simulating PT100, PT500, PT1000 RTDs, and thermistors in a temperature range of 0-200 °C.
What I want to do is for example: enter 50 °C using a microcontroller, and through the DAC output, it generates me a specific voltage, which I can use to adjust a resistor.
I have to connect it as a two-terminal to devices, and it has to behave like the temperature is 50 °C.


texts: Supposed to be a trapezoidal BLDC Back-EMF waveform?

texts:
INTRO: The project bellow was designed in simulink to drive a BLDC motor. It has a matlab function that basically receives the rotor's angular speed (w) and using N = 6 (N is the number of pole pairs) outputs a vector with the 6 gate signals in respect to the 6 step -commutation method for BLDC to the inverter subsystem called "Three-phase inverter".

SYSTEM: See what's inside the blocks:

OUTPUT: The output is as shown bellow:

MY QUESTIONS ARE..:
1.Is the first graph supposed to be more "symmetric"?
2.Why the right and left slopes start and end in different heights?
3.Why the total amplitude (100V) is double the power supply applied to the H bridges (50V)?
4.Why the slops are not continuous and presents a voltage pull up/down in the middle of the slop?
Thanks everyone for sharing the magic.


texts: Math behind Zener resistor for MOSFET Vgs

texts:
The following circuit is from Texas Instruments: http://www.ti.com/lit/df/tidrb35a/tidrb35a.pdf

What is the math behind the string of six 470k resistors at the MOSFET gate? I know that they are for the 12V zener. If I say that the DC bus voltage is 1200VDC, then I would have (1200-12)/(470k*6) = 421.28 uA. This seems too low for a zener, but as the load for the zener is the FET gate, then no matter how low the current is, right?

Diagram with crucial balance of circuit shown and that you can actually read when clicked for full size version:


texts: Why would an AC motor heavily shake when driven with certain frequencies?

texts:
I have an AC motor from an old TCL 160 Boxford NC Lathe, it has three wires named U V and W.

I thought that incorparating the original driver to a modern control interface card would be difficult or unreliable, so I got the motor out and wired it to a Lovato VE1 04 A240 3-phase AC motor driver for tests.

Motor is free on a table and shaft is not connected to anything. When I run the motor using that driver, between the frequencies 20 and 40 Hz, motor starts to shake heavily as if there is an eccentric disk on the motor shaft. But on the other frequencies, 0-20 Hz and 40-100 Hz, there isn't any shake it runs considerably smoothly so I think it's not related to a mechanical problem like a bearing failure.

The original driver was a 0.43 kW one and the one I'm testing is 0.4 kW, and I set the maximum current to 1.5 A just to be safe.

I don't know if the motor is an AC synchronous or AC asynchronous, the only guess I can make is that the motor is AC synchronous because it feels like if the rotor wasn't able to catch up with the frequency fed into it and is shaking like a stepper motor. Also it runs at 1500 RPM with 50 Hz input, and 3000 RPM with 100 Hz input, as far as I can measure with my smartphone stroboscope.

What do you think the reason would be? What would I do to make it run correctly?


texts: Why might an N MOSFET switch output flip with no change in gate voltage (and then stick)?

texts:
In lots of places, we use a simple N-FET switch to turn on/off 24V outputs. We use a 30V rated part and stay well under the power/current limits.
We've started to see recently however a couple of instances of LEDs turning on of their own accord when wired as below:

simulate this circuit – Schematic created using CircuitLab
In a non-failed state, if the MCU pin goes high, the FET is turned on, the voltage at the Drain (LED's cathode) goes to 0V and the LED lights.
In the failed state, even when the MCU output is 0V, the LED lights and the Drain voltage is ~0.15V. A high output still pulls the Drain to 0V, but it returns to 0.15V when the FET is switched back off.
I realise that when the switch is open the drain of the FET is floating rather than in a defined state, but how is the LED turning on when there is nowhere for current to flow to?
The datasheet for the part we are using does stipulate a "Zero Gate Voltage Drain Current" (no FET is an ideal switch) but it's measured in micro-amps which is orders of magnitude too small to light the LED.
Using the datasheet we can also see that the part is being used within spec as we don't come close to the maximum voltages/currents.
Can anyone suggest what might be going on?


texts: What characteristics of magentic coil is the most important for VLF sensitivity

texts: I try to sense a VLF magnetic field (1-100Hz) by using a coil. The field is very weak and in most of reading there is too much noise. Is there the most important characteristic of the coil, should I look at first if I want to improve my readings?


texts: Are aluminum electrolytic capacitors suitable for encapsulation/potting?

texts:
Because aluminum electrolytic capacitors generally incorporate a venting mechanism for over-temperature/over-pressure events, are they suitable for complete encapsulation in potting compound?
Specifically, I am evaluating the compatibility between a surface mount 10V Nichicon UWT-series cap and a polyurethane-based potting compound used in automotive applications.
Is it OK to pot this type of capacitor? If encapsulation is not recommended, what alternate types should I consider for 100µF bulk capacitor purposes?


texts:
I have a custom data logger attached to a sensor being powered by a solar panel(charge controller and battery). I have a problem where I'm getting 10 milliVolt one sided spikes in my ADC readings as seen in the picture below.

I only encounter this problem when my logger is powered by the charge controller and only when the solar panel is plugged into the charge controller at the same time. (When it is only a battery and the charge controller, or when I'm running my system off of wall power and an adapter this problem doesn't occur.)

I have tried adding an off the shelf input filter as well as a low pass with big capacitors on the power input of the data logger to try and solve this since it seems to be an input power issue but it seems to have no effect whatsoever. These spikes are prevalent on all my ADC channels as well, so its not just the sensor.

Does anyone have any idea as to how I might go about reducing these spikes?


texts:
I found the DS1077, a "dual-output, programmable, fixed-frequency oscillator". I was wondering if it would be possible to let this chip provide the clock signal for the PIC(18F46K22) that operates the chip over I2C. So, what I'd like to do is this:

simulate this circuit – Schematic created using CircuitLab

The advantage of this would be that I would be able to change the frequency (i.e. the MIPS) on the fly. What I'm going to do with that, I don't know yet.

The thing is, I'm not sure if the output signal of the DS1077 will be compatible with the PIC and what kind of circuit I'd need for this. Until now, I only used crystals and the internal oscillator.

Also, I don't know if there will be a problem with the I2C communication when I change the frequency of the PIC on the fly?


texts: How do I calculate the frequency of an FM transmitter circuit?

texts:
Below is an FM transmitter circuit I found on the web that I would like to build from scratch:

How I would calculate the carrier signal frequency so that I know where to tune my FM radio?

If I want this to transmit my own signal, instead of the microphone signal, could I just replace the microphone with the output of a TRS connector?


texts: (Arduino Uno) Wrong Input on Pin 2 even though it's not really connected

texts:
I'm new to Arduino and I have following problem:

I tried to control a servo with two buttons (left, right) and it worked perfectly. But today I tried to do the same but with some additional LED feedback. (if going left, left LED. If right, right LED)

I connected everything how it should be, but now every time I power the board the left LED is going on and off very quickly and the servo is going to the left. (I'm not pressing anything)

I disconnected the wire, going from the pin(Arduino) to the pinboard. But it's still the same thing happening. (a simple wire without anything on it connected to the Arduino and its telling me that I push the button ?)

I disconnected the LEDs, the servo and the right button and wrote an program to tell me if the button is pushed(1) or not(0). So I can see whats going on.

int pushButton = 2;

void setup() {
  Serial.begin(9600);
  pinMode(pushButton, INPUT);
}
void loop() {
  int buttonState = digitalRead(pushButton);
  Serial.println(buttonState);
  delay(5);
}

It's showing me exactly the same that the LED showed me. Like i would press the Button very quickly a several times per second.

Left Button = Pin2, Right Button = Pin3, Left LED = Pin4, Right LED = Pin5, Servo = Pin13. (all digital of course)

I used 330 Ohms for the LED and 10K Ohm for the Buttons. Everything is connected to the 5V.

The Arduino UNO is connected via USB to my laptop and to an Additional 9V for the Servo.

simulate this circuit – Schematic created using CircuitLab


texts: Initial pluse from schmitt trigger switch debouncer

texts:
I want to use a momentary, normally open, SPST switch to act as a clock pulse on 16x2 character display.  Of course, my switch has some bounce so I was looking at debouncing circuits and I always see the same one that uses an RC circuit in conjunction with a schmitt trigger inverter.  For example, this one (which includes an extra diode that some folks use and some don't):

The problem I see with this circuit (if I understand it correctly) is that the capacitor starts out at 0v, then charges up, which should result in the circuit putting out a high-to-low transition when it powers on the initially.

Am I misunderstanding this, or do most folks not care about that initial transition?


texts:
Some power boards are failing a high current (lightning) test where an MOV lead is used to transfer the current to the bottom of the board - see MOV lead and pad attached.

The issue seems to be that the manufacturer can only guarantee 70% wicking over the solder wave and the small section of PTH that is solder free is not able to carry sufficient current (even a filled barrel with a concave joint as shown is not sufficient).

Hand soldering the top of the lead passes the test.

While I will be working with the manufacturer to try and improve wicking I was hoping that some on this list might have ideas for a solution that did not require manual soldering.

Thanks in advance.

Edit: added layout for clarity

Edit: Has anyone used a rivet type solution for transferring high current?


texts: Is there support XC5VLX110 list in ISE Project setting?

texts:
I'm just trying to setup ISE envirmonent.
But There's not XC5VLX110 in Device list at the Project Settings in ISE as below picture.

What should I do for solving in this situation?


texts: At which point can a power supply can rate itself at a certain current

texts:
Say if you have a power supply rated "9V @ 5A". Typically the open circuit voltage is slightly greater than the voltage rated, possibly 9.7V or something and levels off when drawing current (EDIT: levels off to nearly exactly 9V).

At the 5A at which it was rated, how much can the voltage output drop below 9V to be able to rate itself at "9V @ 5A".


texts: How to calculate the time of turning on/off LEDs in four 8-bit shift registers with ATtiny2313-20U

texts:
I am planing to build a project with 4 8-bit shift registers (74HC595) connected in series (daisy chain) and the MCU is ATtiny2313-20U.

I know the max frequency for the MCU is 20MHz. Based on that, how do I figure out how fast I can blink the LEDs, given that I have to input 32 (4x8) bits of data to the shift registers.


texts: Are wireless links symmetrical in practice?

texts:
From the top of my knowledge in the theory of EM propagation, two antennas show the same gain if used to transmit from A to B or viceversa, provided that they use the same transmission gain (reciprocity principle). And this holds regardless of reflections, directionality of the antenna and obstacles.

But is it true in practice, at least from an engineering point of view?


texts: PIC24FJ128GA202 UART2 and UART3 not working?

texts:
I am working in pic24fj128ga202 microcontroller with L80 and M95 module. here L80 module connected with uart2 and M95 module connected with uart3. now uart1 working normally but uart2 and uart3 not working (i.e) I didn't get gps and gprs data .below I have attached both uart.h and ioconfig.h files
main.c

#include "p24FJ128GA202.h"
#include <stdio.h>
#define led PORTAbits.RA2
#include "UART.h"
#include "IOCONFIG.h"
int main()
{
    GSMPwrkey=1;
    init_processor();
    uartx1( uart2rx());
   return 0;
}

UART.h
#include<stdio.h>
/* transmit a character in uart1 */
void uartx1(char in_c)
{
    while(U1STAbits.UTXBF == 1);
    U1TXREG = in_c;
}
/* transmit a character in uart1 */
void uartx2(char in_c)
{
    while(U2STAbits.UTXBF == 1);
    U2TXREG = in_c;
}
/* transmit a character in uart3 */
void uartx3( char in_c)
{
    while(U3STAbits.UTXBF == 1);
    U3TXREG = in_c;
}
/* Receive a character in uart1 */
char uart1rx()
{
    char c;
    while(U1STAbits.URXDA == 0);
    c = U1RXREG;
    return c;
}
/* Receive a character in uart2 */
char uart2rx()
{
    char c;
    while(U2STAbits.URXDA == 0);
    c =U2RXREG;
    return c;
}
/* Receive a character in uart3 */
char uart3rx()
{
    char c;
    while(U3STAbits.URXDA == 0);
    return U3RXREG;
    return c;
}
/* transmit a string in uart1 */
void uartstr1( char *s)
{
    while(*s!='\0')
    {
        uartx1(*s);
        s++;
    }
}
/* transmit a string in uart3 */
void uartstr3( char *s)
{
    while(*s!='\0')
    {
        uartx3(*s);
        s++;
    }
}

IOCONFIG.h

#include<stdio.h>
#include<stdint.h>
#define GSMPwrkey PORTBbits.RB12
#define GPSreset PORTBbits.RB15
void Timer1DelaymsInit(void);
void Delayms(uint16_t delay);
void init_Processor(void);
void Timer1DelaymsInit(void)
{
    T1CONbits.TCKPS = 0; //Timer1 Prescale Select bit
    T1CONbits.TCS = 0;   //Timer1 Clock source(FOSC/2)
    PR1 = 3760;
    TMR1 = 0;
    IEC0bits.T1IE = 0;
    T1CONbits.TON = 1;

}
void Delayms(uint16_t delay)
{

    while(delay>0)
    {
        TMR1 = 0;
        IEC0bits.T1IE = 0;  //Reset interrupt flag
        while(!IEC0bits.T1IE);// Wait here for timeout
        delay--;
    }

}
void init_Processor(void)
{

  /* uart1 Tx and Rx pin setup */
    RPINR18bits.U1RXR = 7;      //portB RB7 RX pin
    RPOR4bits.RP8R   = 3;       //portB RB8 TX  pin
 /* uart2 tx and rx pin setup */
    RPINR19bits.U2RXR = 14;     //portB RB14 RX pin
    RPOR6bits.RP13R   = 5;      //portB RB13 TX pin
 /* uart3 tx and rx pin setup */
    RPINR17bits.U3RXR = 10;     //portB RB10 RX pin
    RPOR5bits.RP11R   = 19;     //portB RB11 TX pin
    //Congifure analog and digital
    ANSA = 0x0003;
    ANSB = 0x0000;
    PORTA = 0x0000;
    TRISA = 0X001B;
    PORTB = 0x0000;
    TRISB = 0x4680;
    // Init UART1
    U1MODE = 0x8000;
    U1STA = 0x3400;
    U1BRG = 25;
    // Init UART2
    U2MODE = 0x8000;
    U2STA = 0x3400;
    U2BRG = 25;
    // Init UART3
    U3MODE = 0x8000;
    U3STA = 0x3400;
    U3BRG = 25;
    IFS5bits.U3RXIF   = 0;
    IEC5bits.U3RXIE   = 1;
    U3MODEbits.UARTEN = 1;
    U3STAbits.UTXEN   = 1;
    // Init ADC
    Timer1DelaymsInit();
    GSMPwrkey=1;
}


texts: "Coupling" gain-setting resistors in a single-ended source, differential amplifier?

texts:
I am working on a fully differential amplifier design that receives a single-ended differential voltage from a piezo sensor.
I computed a theoretical gain and selected appropriate resistors and it works. However, I want to be able to fine-adjust the gain. Obviously this is difficult when the resistor values must exactly match.
Is there a way I can couple the two feedback resistors (if selected to be matching) in a differential setup to both be "divided" by a common value set via trim pot?


texts: Implementing CAN bus software termination

texts: I noticed that a lot of CAN new test equipment allow you to enable/disable the termination via software.  Is there an new transceiver in the market or an accepted way to implement this??


texts: HF transformer fed fed diode rectifier not working

texts:
As part of my pure sine wave inverter, I have a DC - DC subsystem in which a
signal stepped up through a HF transformer is put through an uncontrolled diode
rectifier to get a DC output which I am o feed into my PWM inverter (not shown
in circuit).

I am using a 12V to -12V square wave as input to the transformer
and getting the required 475 to -475 V wave output, but the moment I connect a
diode rectifier to it, the output of my transformer sinks to a range of 4 to -4
V on the secondary.

I am using a threshold voltage of 1.7 V and a diode
resistance of 0.57 ohms.

Rpri = 2.48 mOhms
Rsec = 0.411 Ohms
Lpri = 1.909 uH
Lsec = 2.98 mH
Lm = 27.51 uH
Npri = 2
Nsec = 79
SWG 19 wire (1mm diameter) used on primary coils
SWG 24 (0.5 mm diameter) for secondary

MOSFET ON STATE resistance = 0.015 Ohms


texts: How to work out how much pulling power an electric motor has in kg?

texts:
Say I have 5 kg mass on a spindle that has a diameter 5 cm and I want to move it up at 6 cm/s (just example numbers). How would I find out the specs needed for what electric motor I would need?

I have found a lot of info online but most things need info the motors stat sheet has not got and trying to get that info is just confusing me
here is an example motor... also why has it got some things 2 times? like "Current" and "Speed" Standard (High Power) D.C. Motors 20000 RPM


texts: What is the problem with the GSM 590e module?

texts:
I have a M590e GSM module (assembled from a kit)

it is this kit in this link

http://www.laser-shop.eu/arduino-platform/1277-arduino-gsm-gprs-module-m590e-900m-1800m-kit-1460408201.html

I have sucessfully interfaced he module a PC and it does recognise AT commands sent through the serial port.
When the module starts up (with sim inserted) it does NOT say PBREADY. After waiting a few minutes after startup.

I type in the command (with the sim inserted of course)

AT+CREG

I get the response

0,2

which I think means it is searching for a network.
When I take the sim card out of its holder and measure the voltage pins that supply power to the sim card (the VCC,GND pins in the sim card holder) I get a reading of 0.01v with a multimeter-is this normal?-should it be at least 1.8v here?-does the voltage increase in specific circumstances when the sim is inserted?
Im not sure, but is my module faulty?
I cant figure out what the fault is. I have been unable to connect any sim to a UK network so far-and I have tried three different sim card (all known to be working from testing in a phone).


texts: Re-soldering SMD with SMD rework station

texts:
I recently purchased a clone 858D SMD rework station and would like to get familiar with de-soldering and re-soldering SMD chips.

I was able to de-solder fine, but when trying to re-solder I can't seem to get all the legs to solder onto the PCB. My question is, what could be the cause of this?

Here's the steps I took before re-soldering:

Added flux to the pads on the PCB
Cleaned up/added solder to the pads
Add a bit of solder to the legs of the SMD chip

One big thing I noticed is that before re-soldering, the chip didn't sit flat at all on the pads.

This was the PCB before soldering:

The outcome after soldering:


texts:
Are test pins on sensitive signal lines likely to cause problems? For example, if there is a test pin sticking up from the board on a line going to a 20 bit ADC is there a danger of increasing the noise?

Has anyone experienced such problems?


texts:
I am trying to drop the voltage coming from a USB power line to 3.3V. I actually plan on using resistors to create a voltage divider (which I may have questions about later), but for now I was trying to experiment with the 1N4148. As I understand from the data sheet, it has a forward voltage of about 0.70V. Well, what I did was connect one to VCC, and checked what the voltage was. Prior to attaching the diode, I was getting about 5.42V, and after connecting, I was getting about 5.0V. Why is the drop not close to the forward voltage?

Thanks. If a diagram is needed, please let me know (although this is quite a simple circuit).

EDIT: Please find a diagram below


texts: Simulating an Electric Car Battery in LTSpice

texts:
I am sorry if this is a general question:
Does anyone know who to simulate an Electric Vehicle Battery (EVB) in LTSpice (or other free downloadable software)? Are there models I can download online? Where can I find them?
Here is why I "need" such EVB models. My original goal is to recreate/redesign an electric scooter battery for a senior project, but due to COVID-19 I might not get Lab access and so I have to prepare to do things online. A brief description is as follows: solar panels convert solar energy into DC electric current, which passes through a DC to AC converter to make a AC current. This AC current flows through an iron rod transformer and delivers charge onto the electric battery
Also any ideas/suggestions on how to get started on implementation?