texts:
So basically Im working on a counter from  0-9 and I have made a simulation and it works completely fine but when I implement it on the breadboard it does not count. I have implemented it more than 4 times and Im sure that there is no error in placing wires. Im using a 555 timer to make a delay of 1 second.

Am I Using The Correct IC , 74LS90N?
Should I Use 7490N Only?
I heard about adding a 0.01uF capacitor somewhere in the circuit, not sure where.

Here is the schematic:

UPDATE: I grounded the un-used pins. Still not counting.


texts: Purpose of this oscillator (74HCT14-based) on RS-232 to RS-485 converter?

texts:
I am reverse engineering an RS-232 to RS-485 converter to understand how it works. I have attached the schematic that I reverse-engineered from the PCB (apologies for the hand-drawn schematic). I've checked it several times and quite certain that it is correct. The part that confuses me is the oscillator circled in red.

I recognize it as an oscillator based based around C2 & R8, and on my scope I can see it running at about 10kHz. I also see that the five parallel inverters on it's output are acting as some sort of buffer. However, what the heck is it there for?

This converter will work completely powered by RS-232 port, even if just the RX, TX, and ground lines (pins 2, 3, & 5 of the DE9) are connected. It does NOT require the +5~12V line to be connected to an external power supply.

The only theory that I have is that the oscillator is acting as some sort of charge pump to reduce the source impedances of Vcc & -Vcc (which otherwise would be limited by the source impedances of the DE9 pins, plus 4.7k for -Vcc via RN1d), but that's just a guess and I don't really see how/why that would work in practice.

So, any pointers on why that oscillator is there and how it achieves whatever it does would be appreciated!

Edit: thanks for the replies. I've done a bit more digging into RS-232. The idle state of the lines is negative, so connecting the converter will provide the negative rail, and as pointed out, the inverter circuit generates the positive rail from it. What through me off was the +5~12V supply pin on the board; It got me thinking that the positive rail was the one that was initially supplied, which of course is not correct.

[


texts: Relaxation oscillator, how to change the duty cycle

texts:
I have a Relaxation Oscillator here. What I'm trying to do is to change the duty cycle of ca 50% to 10%.

What I thought of and tried to change R1 and C1 values so the time the capacitor loads and unloads changes. But it stays at ca 50%.

What I am trying to find is a way to change the duty cycle to 10%.


texts: Sanity check on an open drain buffer (pull-up to 3.3V but 14V on gate?)

texts: I want to make a simple open-drain buffer using the 2N7000 MOSFET. The input signal on the gate (Vgs) will be 14V and the voltage it is switching is 3.3V (Vds). Usually MOSFETs are used to switch higher voltages not lower ones so I just need a sanity check on whether this is possible. The max Vgs on the 2N7000 is 20V-40V so I'm not too worried about that and if it breaks I'm just working on a proof of concept anyway. Update: switching frequency is 2 times a second so no worries there.


texts:
1st case
I have a R-L series circuit and i connect a DC current source in series with it connected by a switch  and then  close the switch
2nd case
I have a R-C series circuit and i connect a DC source in series with it connected by a switch and close the switch.
Assuming initial conditions to be zero in both cases, I wanted to understand  intuitively how will these two circuits behave just after closing the switch and which case is dangerous practically for a finite value of source.


texts:
I'm repairing a Breville Smart Grinder circuit board and found that the issue is due to a bad capacitor.
I have removed the said capacitor (C15 in the schematic below) and I am now wondering how to find its capacitance value in order to replace it.
The schematic:

I can remove C14 and measure its value but do you have any idea if I can retrieve the value by calculation (I know the values of the resistors) or by the role of the capacitors in the circuit?
Thank you


texts: Understanding IC max current in Datasheets

texts:
I'm hoping someone can help a noob out here. I've been reading a lot of data sheets of late looking for chips that will work for a small project. In short I need to drive a number of outputs (mainly LED) at 5 V 20 mA.  The load is between  the IC and ground (source current?) and it can't be changed. There is a ready made solution and the supplier insists it will be OK but having read the data sheet I don't think it will.

My understanding is that is has a max of 35 mA per pin, but a total of 70 mA for the IC. Am I wrong? Would really appreciate some input.

Data sheet is here:https://datasheet.octopart.com/74HCT573N,652-NXP-Semiconductors-datasheet-9888300.pdf

simulate this circuit – Schematic created using CircuitLab


texts:
I just put my Ipad Air 3 in my bag, it was raining and forgot to close it such that  when I got home, my Ipad and the inside of my bag was extremely wet. I know a bit of physics but not figure whether or not something could happen to the inner workings of my Ipad (so I am reaching out to the wizards):

Does water affect electricity in any way (e.g. slower flow of electrons, less stable) if the water has not destroyed the whole circuit? More specifically for my case, in case some water slipped inside towards the inner workings, and the Ipad seems to be workings just as great as before, could any of the electronic circuits have been affected?


texts: Adding Line Out / Sub Out to LG soundbar

texts:
I have LG Soundbar with wireless sub. I am trying to add Line output, so i could connect a wired sub.
I took some pictures of the boards and chips. If someone could point me in right direction on where to connect to get low level output. My second option is to add High to low converter but that doesn't always provide clean signal.
ps9860 is Multi-channel Digital Audio Processor Eight-channels i think that should be where i could get a connection. If someone could confirm I'd appreciate it.
StackExchange only allowed me to upload one photo, so I'm attaching link to folder with more photos.
https://fil.email/BeJMkJMl


texts:
Here in an interesting discussion about MOV specifications

If I want to protect a 3.3V circuit tolerant to 5V voltage against ESD, I can select a little fuse MOV
for example V3.5MLA0603.

I want to protect some SMBUS lines (connected to a battery bms) against ESD and to SMBUS MCU pins (5V tolerant).

Here are characteristics :

Here are its I/V curve :

We can see nominal voltage (Breakdown voltage ? ) is in range [3.7; 7]V

From datasheet characteristics is V3.5MLA0603 a safe choice for my application?

I would say no, but I'm sure at 100%. With 7V applied to my circuit (@1mA), I think it will be seriously damaged. But, may be my understanding of max clamp voltage must be pratically interpreted in a different way.


texts: Register map using C for a MAX30001 analog front end

texts:
I am trying to follow the best practices in register mapping. I have a MAX30001 analog front end for ECG applications (Datasheet) and in page 38, there is a table that contains user command and register map: 32 words, each with 24 bits of information. Should I use structures or macros ?

Using structures with bit fields:

typedef struct {

    volatile uint8_t Bit0 : 1;
    volatile uint8_t Bit1 : 1;
    volatile uint8_t Bit2 : 1;
    volatile uint8_t Bit3 : 1;
    // ...
    // and so on
    // ...
    volatile uint8_t Bit23 : 1;
} foo;

Using macros:

#define STATUS (*(volatile uint32_t*)0x01))


texts: Soldering a VGA cable - number of wires doesn't match

texts:
I decided to open up a VGA cable which started to produce only red / blue / green colored image. I thought that inside I will find something like shown on  this scheme:

Instead I found that my VGA cable is a more complex one. Allso the wire colors do not mach with the ones in the scheme above:

It has 11 wires instead of just 6. My cable has yellow and cyan cables for V-sync and H-sync but then there are these colours (white, gray, brown, black, dark red and bright red) which I don't know where to solder. I need an advice.


texts:
I am struggling to drive an LCD with a PIC18LF27K42.

The functions are all OK. They are working fine with a PIC18F14K50 with the same clock of 4MHz.

I suspect the error is in my configuration bits. I did review it without success.

Thanks for your help

I am using the following pin definitions:

define ENL      LATCbits.LATC7 (OUT)

define RW       LATCbits.LATC6 (OUT)

define RS       LATCbits.LATC5 (OUT)

define DB7      LATAbits.LATA3 (OUT)

define DB6      LATAbits.LATA2 (OUT)

define DB5      LATAbits.LATA1 (out)

define DB4      LATAbits.LATA0 (out)

Before running the main() I am doing the following initialization:

PORTA   = 0x00;
LATA    = 0x00;
ANSELA  = 0x00;
TRISA   = 0xF0;
PORTB   = 0x00;
LATB    = 0x00;
ANSELB  = 0x00;
TRISB   = 0x1F;
PORTC   = 0x00;
LATC    = 0x00;
ANSELC  = 0x00;
TRISC   = 0x1F;

CONFIGURATION BITS

// CONFIG 1L

 #pragma  config  FEXTOSC = HS

 #pragma  config  RSTOSC  = EXTOSC

 // CONFIG 1H

 #pragma  config  CLKOUTEN= OFF

 #pragma  config  PR1WAY  = ON

 #pragma  config  CSWEN   = OFF

 #pragma  config  FCMEN   = ON

// CONFIG 2L

 #pragma  config  MCLRE   = EXTMCLR

 #pragma  config  PWRTS   = PWRT_OFF

 #pragma  config  MVECEN  = OFF

 #pragma  config  IVT1WAY = OFF

 #pragma  config  LPBOREN = OFF

 #pragma  config  BOREN   = OFF

 // CONFIG 2H

 #pragma  config  BORV    = VBOR_2P45

 #pragma  config  ZCD     = OFF

 #pragma  config  PPS1WAY = OFF

 #pragma  config  STVREN  = ON

 #pragma  config  DEBUG   = OFF

 #pragma  config  XINST   = OFF

 // CONFIG 3L

 #pragma  config  WDTCPS  = WDTCPS_31

 #pragma  config  WDTE    = OFF

 // CONFIG 3H

 #pragma  config  WDTCWS  = WDTCWS_0

 #pragma  config  WDTCCS  = LFINTOSC

 // CONFIG 4L

 #pragma  config  BBSIZE  = BBSIZE_512

 #pragma  config  BBEN    = OFF

 #pragma  config  SAFEN   = OFF

 #pragma  config  WRTAPP  = OFF

 // CONFIG 4H

 #pragma  config  WRTB    = OFF

 #pragma  config  WRTC    = OFF

 #pragma  config  WRTD    = OFF

 #pragma  config  WRTSAF  = OFF

 #pragma  config  LVP     = ON

 // CONFIG 5L

 #pragma  config    CP      = OFF


texts:
I am using a magnetometer to detect metal objects. I typically take a reading when the software starts (zero offset calibration) and assuming that there are no metal objects in the vicinity and then periodically start take a reading from the sensor. If a metal object is placed in the vicinity of the sensor, the readings usually exceed a certain threshold and the presence of an object can be detected this way. So far so good.

However, due to other nearby objects (metal objects not directly in the vicinity etc) and thermal drift the magnetometer base reading will drift from the originally taken one. Are there any algorithms/methods suggested in order to try to maintain a good zero offset?

I was thinking of starting with the initial zeroing perhaps and then upon sensing that the object was removed, a new reading for the zero calibration could be taken. This way it always updates whenever there isn't an object.


texts: Is it true that an 110v electrical device consumes 110v or 220v when it is connected to the 220v power grid?If not,tell me how to make it draw only 110v from 220v without wasting current.


texts: how to lower a power bank USB 5.1v /2.1amps output to 4.5v to power a 150 lumens LED flashlight

texts:
I would like to use a power bank to power a 150 lumens flashlight 3 AAA batteries operated ( https://www.harborfreight.com/ultra-bright-led-portable-worklightflashlight-64005.html ).

I already connected a USB cable to the + and - terminals in the batteries' compartment.  The probkem is that the power bank is too much for the flashlight and it got burned when I power it with the 2.1amps output of the powerbank.

My power bank has two different outputs: a 5.0V/1A and a 5V/2.1A.  The 1amp output is not able to light the flashlight completely; it runs well for about 2 seconds and then it starts to flash intermittently.   The second 2.1amps output is able to supply the current to keep the light on, however, after maybe 20 seconds it burns partially the LED and 4 of the 10 LEDs in the strips do not light up and the rest light emission is very low.  So, I think the voltage supplied by the power bank is too strong for the electronic board/LED strip!?

The real reading in output of the USB port is 5.12v.

What I need/wanted, is to be able to reduce the voltage by adding a resistor to the battery terminal (usb cable connection) to 4.5V which is the right voltage required by the flashlight.

I have another two flashlights (same model) and I will try to replace the little board inside that send the power to the LED strip to see exactly if the board was damaged or if the strips was the burned one.

I would really appreciate your help with this.

added: I forgot to mention that the flashlight has a 10 Ohms 5% resistor at the + terminal where the USB cable is soldered (to connect to the power bank).


texts: what is the wattage rating of a 2 watt resistor in oil?

texts: I have a termination resistor for a antenna and while it is rated at 300 watts, I opened it up and it is not capable of dissipating 300 watts as constructed.  It is in a PVC tube and has sufficient volume to allow filling with mineral oil.  But would like to know the increase in dissipation the termination will have.  It is made up of 22 each 5 watt resistors.  So has an initial power rating of 110 watts.


texts: Wireless RGB led controller circuit with motion sensing - design feedback

texts:
Beginner hobbyist here. I would appreciate some design feedback.

Purpose of this circuit:
It controls an RGB LED strip (5 Meters, SMD 5050) via an IR remote and also automatically powers on/off the LED using an ultrasonic sensor (HC-SR 04). The brain here is the Arduino Nano. The Nano takes input from the IR sensor (TSOP 1738) to determine which color and brightness needs to be output. It uses its PWM pins to control the LED strip via the 3 MOSFETs (IRF3205) which go to each of the 3 color wires of the LED strip. Both the circuit and LED strip are powered by the same power supply ( I confirmed via data sheets that the Nano can be powered by a 12v power supply).

The radio (NRF24L01) module is for this circuit to sync and coordinate with other peers in the room. I plan to have multiple circuits like this powering a stairway. So when someone enters the upstairs/downstairs door, the ultrasound sensor would detect it and let the Nano know to turn on the LEDs, which would in turn pass this on to other Nanos that are further into the stairs but don't have the motion sensor.

Questions:

I've put in 220 ohm resistors between the MOSFET and Nano because I found that on several circuits and tutorials online. Would help an explanation of what exactly its purpose is and how to calculate the value.
The power supply is from a local bazaar that doesn't seem to have any data sheet or guarantee. I'm almost sure the quality of the DC signal is not great and maybe its not even the 5A it claims. Is there any capacitor filter based circuit I can put in to ensure the circuit receives  a) Smooth, clean DC signal and b) protects against unexpected current or voltage spikes?
This may be too broad a question but asking since this will be the first time I'll be trying to print and etch the PCB. Does this layout look fine? Is it even possible to provide feedback on the PCB layout design? I have done my calculations to ensure the track widths are able to handle the current.


texts: Could a time-domain reflectometer, with no access to earth-ground, indicate if a long-wire is attached to the end of a long steel beam?

texts:
Without using any other wiring, optics, RF, sound, or vibration, I need to know if a 100 meter length of electrical wire is attached to the end of a 50 meter long steel beam.
I only have physical access to one end of the beam (not the end attached/unattached to the 100m wire.)

Both the wire and the steel beam are mounted on rubber wheels and have no access to earth ground.
Could a time-domain reflectometer (TDR) somehow be used to detect if this long length of wire were attached, or not, to the remote end of this steel beam?


texts:
Attached you find a photo of an MCU. It is used in an remote controller of an home automation application. It is a low-power an low-cost product. I think the package is TSSOP30.

500T
1531XX00
  JAPAN

ist printed on the package.
Which MCU could it be?


texts: How does this regulator/rectifier circuit work?

texts:
I am working with the following circuit from a motorcycle. It provides 13.8V DC out from a 15V-100V AC generator input.
I understand how the bridge rectifier (BR1) and smoothing capacitors (C1, C2) work, but I am not clear how the SCRs are being used for regulation in this situation.
It seems that they would turn on almost immediately.


texts: Design up counter in VHDL using generate statement

texts:
I need to design an 8 bit up counter in VHDL using T flip flop and generate statement. I know how the counter works, but I am not able to design it in VHDL.

The main problem is "using generate statement" . As I can see, in an up counter (ripple or synchronous ; either is OK ; I decided to use ripple ) , the previous output is fed as a clock. So I can map Q(i -1) for clock in the i'th generated flip flop. But what about the first flip flop ? It has a clock explicitly applied.

So if I use generate statement, I cannot simply map the clock to previous output ; the first flip flop will always create problem. Another thought which came was to initialise first counter explicitly and then use generate statement for remaining 7 flip flops. But here as well, I think, the first (or rather, second) flip flop using generate statement will pose a similar problem ( ie mapping clock).

Am I incorrect or missing something important here ?

Here is the code ( planned code, not actual code) :

component tff is
Port ( t   : IN BIT ;
       clk : IN BIT ;
       q   : OUT BIT );
end component

--Other irrelevant stuff

For i IN 0 TO 7 GENERATE
tffx : tff PORT MAP ( tIn , q(i-1) , q(i) ) ;
end GENERATE ;

--More irrelevant stuff

Thank you.


texts: Where to put a buzzer so that it goes off when there is light (and should stop when there is dark)

texts:
I've successfully created (and breadboarded) this circuit:

simulate this circuit – Schematic created using CircuitLab
I cannot figure out where to put a buzzer so that it goes off when the LED shuts down, and the buzzer to stop when the LED lights up.
I tried to put a buzzer between the transistor collector and ground (with a resistor), but it never stopped regardless of light or dark.
The buzzer is the Ariose Electronics LF-MB12A05, details below:


texts:
I was asked to draw the implementation of three op-amps circuits and I am still learning op-amps from the beginning they have the following outputs \$ v_o(t) \$.

\$ 1 - v_o(t) = 3v_i(t) - 2 \$

However I don't know where to input the potentiometer to gain the -2

\$2 - v_o(t) = 5 v_i(t) +3 \int_0^t v_i(t) dt \$

Also i wonder if this circuit is correct

3- A conditional circuit where we input a voltage varies from 2 to 7 volts gives out an output from 0 to 10 volts

I know that t needs potentiometer but  i still don't understand how to use it


texts:
I need help explaining why I am getting such a large DC offset across the output for my op amp.

I am using an OPA548 to amplify an AC signal and then drive a solenoid shaker. I have the circuit designed to have a gain of 10 and I am not current limiting the op amp (the OPA548 has that capability). Before I input any signal into the op amp, I connected the output, with respect to ground on the circuit, to an oscilloscope and I saw that there was a DC offset around 13.3V.

To clarify more, I am powering the op amp with +-15V and amplifying a 1V pk-pk input to 10V pk-pk. I then adjusted the voltage that I am powering the op amp with (+-15V) and I saw that the offset is completely dependent upon the +15V. Why is that?

I understand that op amps can have DC offset because of the internal circuitry but I never have had it where the DC offset was dependent upon the input voltage to the op amp. Then, when I applied an input signal and then looked at the output voltage signal on an oscilloscope, the DC offset seemed to "go away" because the output signal was oscillating around 0V. I don't understand why that is. The signal still looked clean at that point.

Lastly, I connected the output across the load (solenoid shaker). The picture below is what I saw on the oscilloscope. My guess as to why that is is as follows: The DC offset noticed before still must be having an affect. When I connected the shaker across the output before applying a signal (the time when I noticed the DC offset) I could feel that the shaker was energized. It felt like the weight inside of it was off to one side and operating at a high frequency. My reasoning as to why the oscilloscope graph looked the way it does is because the DC offset must be holding the weight off to one side before enough negative voltage can override and then it goes back to where it was before.

I would like your thoughts on this and potentially how I could fix this issue. I hope I was detailed enough. Please ask for more details if you think that would help. I attached pictures of both the solenoid shaker and the oscilloscope graph that I am trying to interpret. Thanks in advance for your help


texts: How to go about making a keyboard with arduino as the controller

texts:
These are questions I have found that are similar to mine:

Arduino as full fledged keyboard controller? This is somewhat similar but it sounds like op is trying to connect an existing keyboard
How to build a custom laptop computer with original chassis, keyboard, etc? OP here is wanting to make an entire laptop. I just want a small keyboard.
usb keyboard with many simultaneous key presses This one seems most similar but I will probably need more simultaneous presses and they seems further along.

I don't have much info on this so their are lots of different things that need to be solved in order to make this (if keyboard will be ps2,usb,blutooth or all, firmware, case, inner electronics) Right now I'm basically interested in the inner electronics/wiring though any advice is helpful.

Info I do have on my proj

I will use mx brown switches
http://ergodox.org/Default.aspx I'm kind of using this as a guide. I tried to open their pcb files, but couldn't. They use a teeensy usb which would be much smaller than my arduino uno. To save space I was thinking of putting the arduino under the pcb and separating them with strong metal would this work.

Basically, I need advice on how to open others and design my own pcb and if my setup is possible.

Update

So my kb uses layer design press one key for access to a function on another.
M = modifier shift alt etc
L = layer key These determine what functions are available
R= regular key

M
M L   L R R R R
M L   L R R R R
M   L   R R R R


texts:
I have been writing software for the MCU STM32F417. I have been using the STM Studio for debugging purposes. Unfortunately I have found that I am not able to observe content of an byte array. I am able to import only the first element of the array in the Import variables dialog. I can do a workaround based on definition of separate variable for each array element. This method is not suitable for my case because my array consists of 512 bytes.

Does anybody know whether some way exists how to import whole array into the STM Studio? Thanks for any ideas.


texts: Atmega32u4 Pin F0 output is only 3.64V, not 5.00V

texts:
Unlike F4 which outputs 5.0V, my F0 pin only outputs 3.64V.
Is this normal?

This is my code:

DDRF  |= (1 << 0);  // Set F0 to output
PORTF |= (1 << 0);  // Set F0's internal pull-up

I have 2 identical boards and only 1 exhibits this behavior.


texts: What is the role of the capacitor within the assembly

texts:
I have some questions regarding my assembly and especially on the role of the capacitor within the circuit.

Before I added the capacitor I encountered 2 issues:

when the piezo was squeezed (a pulse is generated) then the pressure was maintained for some time and then released, the piezo generated a positive pulse that I wished to get rid of.
when the pressure was maintained on the piezo film, I had such a sensitivity that the LED was still flashing. The brightness was weak though.

Adding the capacitor fixed these issues but I can’t explain why for the 1st one or rather I don’t know why. Of course, why I added the capacitor was for the 2nd point, I wanted to discharge this phenomenon through a capacitor. And it's working well.

And also I don’t get why since I’ve added the capacitor, the voltage seen on the oscillator is different. It’s pretty low now around 20mV while without the capacitor I have an input voltage of 20 mV to 800 mV depending on the pressure applied on the piezo film and an output voltage (right after the op amp) around 2.5V-2.8V.

Thanks in advance ;)


texts:
I have implemented a constant current source for an high power LED. I am using the following topology.

I have the following problems:

Even a small noise on IN+ causes some current to pass through Rsense and make the LED turn on, although it is very weak, it consumes power and not ideal. How can I make this work only above certain voltage on IN+, for example 1V.
I couldn't push the current through LED to very high numbers. I use a 5A capable BJT and MCP6021 as opamp. I can see up to 1.5A but cannot get pass that. (1.5A measured on Rsense's voltage drop). The capacitors are 4x 420uF Electrolytic. (I didn't have a 1mF handy so I put in 4 parallel caps) Do I need a special cap?


texts: How do I select the correct inductor value for the following buck regulator?

texts:
First of all, I suck a bit at math, and I'm no electronics genius, so the stuff I do is for fun and for learning purposes...

I'm working on a buck converter circuit to convert my USB Vbus 5V to 3.3V. I've selected the AP5100 and finding it quite challenging to figure out the correct values on some of the components.

The datasheet neatly specifies the values for R1(49.9kΩ) and R2(16.2kΩ) in Table 1 on page 6, to establish an output voltage of 3.3V, but I'm finding it a bit of a train smash understanding how to calculate the inductance value for the L1 inductor. The datasheet indicates 3.3µH on page 2, Figure 3:

I'm wanting to understand better how the 3.3µH was calculated, and if this is in fact the correct value for my application.

Now back to the datasheet, the formula for calculating L is stated as:

$$
L = \frac{Vout \times (Vin - Vout)}{Vin \times \Delta IL \times fSW}
$$

Where ΔIL is the inductor ripple current, and fSW is the buck converter switching frequency.

The datasheet states:

  Choose the inductor ripple current to be 30% of the maximum load current. The maximum inductor peak current is calculated from:

  $$
IL(MAX) = ILOAD + \frac{\Delta IL}{2}
$$

Alright, this is where I'm horribly lost, and trying my best to wrap my tiny brain around the value.

I know the following:

Vin = 5V (USB Vbus)
Vout = 3.3V
fSW = 1.4MHz
I = 2.4A (I think)

How does one determine the ΔIL (ripple current) in order to get to the inductor value?

My formula should look something like this in the end, right?

$$
L = \frac{3.3V \times (5V - 3.3V)}{5V \times \Delta IL \times 1.4MHz}
$$

But what is ΔIL?

Also I thought the buck converter was supposed to allow a range of inputs for Vin, in the case of this one, 4.75V to 24V?

Here's my schematic I'm drawing in Eagle CAD:


texts: A confusion about radial schemes in power distribution

texts:
My lecture notes about distribution systems/radial schemes say the following:

•In this scheme, feeders radiate from a substation in all
directions and feed distributors at one end only.

• SA is the feeder which feeds the distributor BC at its end B.

The lecture includes the following picture of a radial scheme:

Question: How does this form a complete circuit ? Put differently, the service lines are not part of a circuit as far as I can see.


texts:
I have 4 switching sensors for all around detection, they output either 24V or 0V.
I want a counter that will add 1 everytime one of the sensors detects something (sometimes 3 of them will detect together), that means add 1 everytime states go from 0 to 24V. Then, I'll need 3 displays to display the result (but I guess 2 would be fine).
Is it possible without micro controllers? Too much hasle? Easy peasy?
Better off with 8051? Consider on the cheap.

Thank you!


texts:
How do you find the gate delay for a basic multiplier circuit that ANDs each bit of the multiplicand with the multiplier then shifts the multiplicand left and the multiplier right until the multiplier is empty, then adds the columns?

I'm trying to figure out the general timing equation for this type of multiplication as well as for the faster carry-save multiplication. If anyone knows of a link that has this information that would be really helpful also.


texts:
Scenarios

So, I set up an induction loop, just a simple single wire loop around a house with a little pickup coil for picking up the loop audio.

Lets say I want to run this in REVERSE

I have heard "If an antenna can transmit, it can usually receive as just as well".

I hook up the amplifier to the loop around the house, and all I hear is 60hz HUM, and when I play audio up to the little pickup coil, i don't hear anything through the amplifier, just 60 hertz.

Can I indeed run an induction loop in Reverse, or not?

Second Scenario

When hitting an Amateur Radio repeater, I sometimes can hear it full quieting, but when I transmit, they can't hear me.

So is "If an antenna can transmit, it can usually receive as just as well" True?


texts:
I think sharing the video will be the easiest way of describing the situation.

The transistors are electrically isolated from the heatsinks, I have checked with multimeter.

Few days ago, I have asked this question, it was related to the same circuit. There were answers and comments helped me, however, I think there might be a more descriptive answer, and wanted to focus this question on the reason for this behaviour.

I observed that, if I touch the heatsinks, as long as I keep contact, the noise disappears, also grounding the heatsink solves the problem. But, why an already electrically isolated metal piece creates noise? Some kind of radiation?

For my previous question, there were answers which states after isolating the heatsink, it is not a must to ground it. Which, comes not totally true, as I understand from my experiments.

Thanks in advance.


texts: Altium: error since net connects only to Output Port objects

texts:
I am tasked with creating a schematic (in Altium) which will be instantiated in somebody else's design later. Altium is giving me errors:

The chip is a microcontroller, and its output goes directly to an output port (so that my colleague can simply make "black-box" connections to my circuit).

However, Altium complains:

[Error] Net ADF5355_CLK has only one pin (Pin U1-16)

(and similar errors for the other pins as well).

I don't understand this error. Why is this a problem?


texts: Calculate the upper cutoff frequency of a common gate

texts:
JFET:

I am trying to calculate the upper cut-off frequency of this circuit. Gain gave me 5, as it did in the teacher's solutions. But I'm applying the expression to the condensers and it's giving me negative values!
The initial circuit is as follows (the generator is ideal):

\$c_{gs}=8\,pF;\,c_{gd}=4\,pF;\,I_{DSS}=7\,mA;\,V_P=-4\,V;\,r_0\rightarrow \infty\$

The small signal model I did with the calculation that is giving me a negative value is as follows:

The teacher's solutions are as follows (I did not understand where the final solution expressions come from):

New model:

First try:


texts:
I made a silly beginner's mistake: I purchased some surplus rotary solenoids from electronic goldmine without paying close attention to their power requirements ("Oh, they are so cheap!"), so I assumed they were 12v and reasonably powerful. There are no specs - just the catalog blurb (below).

Neither assumption is true, as it turns out. My benchtop power supply only goes to 30 volts and at that power, the solenoids have almost no force.

Before I try to find a 40 volt power supply, I'd like to know: will force increase by any significant amount with the increased voltage?

Of course a 40 volt power supply will probably cost more than just sourcing 12 volt solenoids but I thought I would ask.


texts:
Note: Can skip all images except last, which is a schematic created using the editor.

I am at a point in the design process where I have created a schematic of the circuit that I want to create. I am using a buck converter to step down a 24V DC battery to 5V and using that battery to power an arduino. This arduino is acting as a speed controller, using PWM and getting input from external switch to set the speed. The input from this switch will be programatically read to set the speed output. The 5V output signal from the arduino then gets run through an op-amp configured as a non-inverting amplifier and drives a motor. The schematic follows: []1

This is the first real circuit I have created, and I don't know where to go from here. It is more than likely that I have made a mistake somewhere or forgotten a part or some heat/power consideration, but I don't have the slightest idea (1) how I could check my circuit for those things or (2) how I would remedy them.

I was wondering how I could go about doing these things and improving my knowledge of electronics in this way. I apologize if this question is somewhat vague; however, I really respect this community and the years of experience you have in the field, and I was hoping that your insights would be valuable in this question, as I don't really know how I could make it more specific. Thanks.

EDIT 1: Ok, after suggestion I am replacing the op-amp with an n-channel MOSFET as follows (Edit 2: added a 10K pull-down resistor on the gate of the MOSFET):

EDIT 3: Added pull down resistor to schematic and flipped MOSFET:

EDIT 4: Adding a full schematic (Edit 5: switched NMOS and Motor position):

simulate this circuit – Schematic created using CircuitLab


texts: Are date code 2010 micrcontrollers OK in 2014?

texts:
The microcontroller we use on our boards have been out of stock for an extended period of time with all the major players, we had enough stock to cover us for 4 months but it's running dry. After pushing digikey a bit they used the 'expediter' to ask Atmel ( i assume ) for some stock.

They found some with date code 2010.

I'm a bit hesitant, what should I keep in mind here, what are the pitfalls?


texts: LTSpice simulation stalls after 100ms transient with 'Heightened Def Con'

texts:
I simulate a system of two mutually delay-coupled electronic clocks (DPLLs - digital phase-locked loops). This worked well and also in reasonable time so far. However, moving into a particular regime of the parameter space of the individual DPLLs, i.e., very low cut-off frequencies of the loop filters (fc=14Hz) compared to the free-running frequency of about 1kHz for the LTC6900 VCOs at a high coupling strengths causes problems. The transient simulation runs fast for about 100ms and then suddenly stalls with convergence problems of the solver (excerpt, full log-file below):

Heightened Def Con from 2.31358e-012 ++++++++++++to 2.3174e-012
Heightened Def Con from 0.0100466 to 0.0100466

I tried different solvers and limits, however I could not solve the problem.
This is the state at which the simulation stalls:

This is the schematic I am simulating

This is a link to the netlist:
link to netlist (dropbox)
This is a link to the spice-log file:
link to spice-log (dropbox)
Specifically my questions are:
What besides changing the solver parameters can I do to solve the problem?
How can I find out more easily on which calculation the solver gets stuck?
Did I miss something in the schematic that could cause the stalling?


texts: What's the difference between a microprocessor and a CPU?

texts:
Possible Duplicate:
  What’s the difference between a microcontroller and a microprocessor?

Please inform me of the difference, if any.


texts:
I want to buy this power supply Here
It says that it can last from 5-8 years. It can last 5-8 years by using it constantly? Also why do they fail? What component inside them causes them to fail? Sorry for my bad english


texts: Circuit design review - battery powered attiny with Zener voltage regulator

texts:
Would some kind soul review the design of my circuit? I have a couple of design challenges. I'm using a ATtiny85 with a voltage range of 5.5 V to blink a UV LED with a forward voltage of 3.7 V. It will be battery powered, and I cant use a single cell because it wont achieve the needed forward voltage of the LED.

So, D1 is a Schottky diode intended to protect against accidentally installed the battery backwards. D2 is a zener that is intended to serve a voltage regulator similar to this tutorial. It's meant to keep voltage < 5.1 V.

The ATtiny85 will be programmed using a clamp-on ISP programmer, so there's no connector designed into the circuit.

How'd I do? Does everything seem okay?


texts: What is this connector called? TDS Meter connector

texts:
I am trying to extend my sensor's cable as it is only 50cm.
I do not want to cut the cable in case I want to revert back. The sensor has a male 2 pin connector on the end and the board has the female connector
I just want to know what the connector is called please.
P.S should I expect any issues with extending an analog cable by 50cm to 100cm ?


texts: How to encode a large number of digital input signals into a signal result

texts:
I would like to know how I can detect simultaneous pulses on several wires.  Essentially I will have several wires that will serve as connection points when pressed upon.  A simple visualtization of this is if you were to view several wires draped over (but not touching) a metal plate.  The plate would be connected to the negative end of the battery & the wires would be connected to the positive end of the batter.  When touched, the wire will hit the plate & pulse.  Initially I was thinking something like a 64-6 encoder, but I now I feel that there are much better solutions.

So, in short, what is the best way 'hardware' to encode 2^n into n data lines.

Any help is appreciated!


texts: Reading noise from allan variance plot for MEMS sensor per IEEE Std 952-1997

texts:
I am following the Standard Sensor Performance Parameters from the "MemsIndustryGroup" to test some Gyroscopes:

I conducted a test and plotted the square root of AVAR (Allan Deviation) against Time per IEEE Std 952-1997 using MATLAB:

I am confused however, by how I can read the Quantization Noise, Angle Random Walk, Bias Instability, and Rate Random Walk from this plot.  The Standard Sensor Performance Parameters state to read them when T = 3^1/2, T = 1, Slope = 0, T = 3.

When I read these values, my results look like this:

I was wondering if I am doing this correctly.  The example plots from both Standard Sensor Performance Parameters and IEEE involve slope lines that do not have anything to do with reading my plot:

EX1

EX2

What is the proper way to read these noise parameters from my Allan Variance/Allan Deviation plot?

Is my approach of reading the values correct, or should I try to make my graphs use the slopes as seen in the two examples? Etc.


texts: How to troubleshoot non-working RS232 to USB connection

texts:
I have bought a RS232 inclinometer and a FTDI USB to RS232 cable.

The inclinometer spec sheets states:

RS232 full duplex communiction
Supply voltage 4.9 - 15V
Wires:

Red: +ve
Blue: ground
Yellow: RS232 Tx
Green: RS232 Rx

The USB cable specs:

Supply voltage 5V
Wires:

Black: Ground
Brown: CTS#
Red: Power
Orange: TXD
Yellow: RXD
Green: RTS#

I have connected them as follows:

  USB cable        Inclinometer
     Red    < - >    Red
   Black    < - >    Blue
  Orange    < - >    Yellow
  Yellow    < - >    Green

When I plug in the USB cable and try to access the inclinometer, I get only a blank screen. I have tried using the terminal (screen /dev/tty.usbserial 9600), I have tried CoolTerm and I have tried the inclinometer software provided by the manufacturer. All methods just show me a blank screen, without data.

How can I troubleshoot this issue?


texts: Can I extend an AC adapter with 18/2 thermostat wire?

texts:
I have a camera mounted at the top of a wall in my house.  The AC adapter that came with it is not long enough to reach the outlet below.  I'd like to 1) extend the AC adapter to the outlet below and 2) conceal the wire.

My initial preference is to drop the cable behind the wall and have it come out next to the outlet, where it can just plug into the outlet.  My question is do you see anything wrong, dangerous, or non-compliant with the following setup.

The AC adapter is rated at 5 volts and 2 amps.  I am going to splice CL2R 18/2 thermostat wire into the AC adapter to make it longer.  The thermostat wire will be the only portion that runs behind the wall, and the splices will happen outside of the wall.

Here's a link to the thermostat wire specs for reference:
http://www.homedepot.com/catalog/pdfImages/36/36984981-2640-4d88-a1c5-13317341df11.pdf

I like this option because it's easy and I already have everything I need.  If this is a a bad idea, I could add a new outlet near the camera, conceal the power cord on the wall with a raceway, etc.  Thanks!!


texts: DALI Protocol: Is it valid to include this for manchester decoding convenience?

texts:
Understanding: DALI uses Async data decoding using 1 start bit and 2 stop bits. The 1 start bit is logical one (1), also encoded during Manchester encoding and the 2 stop bits(Signal is HIGH for long periods, at least 2*833us) designate the idle_signal.

Now, if I am decoding this data using the measured pulse width method or sampling method, I will not have a closing interrupt for last bit "1"!! I am specifically using pulse-width method decoding for Manchester decoding.

I can solve this problem by checking the LSB bit during Manchester encoding. If LSB is 1, I will include a short reset-set signal at the end. I will make sure that I will ignore the rest of the data after I have received my required frame. Anyway, this short reset-set signal will not fall in my long or short range and I can also stop my timer to respond to any other interrupt after the required frame is received!

Question:

Is it valid according to DALI standard?? What could go wrong with my approach?
In general, which method is used for DALI standard? Sampling-based or pulse-width based??
The lack of preamble, does it cause any problems?

Thanks in advance!

PS:

I am not sure of the terminology "Asynch data decoding", what I meant is that there is no preamble data involved giving the decoder enough time to sync!
Sampling-based [page 7], pulse-width based [page 6] methods are described in this app-note.
Image from this source.

EDIT: My logic of Manchester_Decoding is here.

EDIT2:

Yeah! It is a clear misunderstanding, as soon as I put the logic on Paper, I got it figured! I was thinking how the last pulse will end if the SIGNAL is high for longer times but as we can see from the figure the last 1 will be decoded before itself.

Still, I wish to know about the general implementation standard for DALI and problems caused by lack of preamble data in DALI context.


texts: STM32 USB: detecting connection and disconnection

texts:
Using STM32F4 USB Mass Storage Controller example in Device Mode, how do you detect connections and disconnections with a host controller?

I tried polling the VBUS pin state yet it could be high from a wall adapter or high without any communication with the host.

Is there a register to check? I noticed DSTS (status I guess?) in the USB library structs but couldn't find its documentation nor any useful comments in the code.


texts: Interview Question, what's limiting the output frequency for the FPGA circuit?

texts:
I recently received a question in an interview that partially stumped me.  It went something like this:

You have an FPGA circuit that is supposed to be generating a signal with a frequency of 500MHz, but is only outputting at 300MHz.  How would you go about troubleshooting this and finding out the cause of delay?

My first reaction was to check the impedance and capacitance across the circuit to see if it was somehow acting as a lowpass filter, but aside from that I couldn't think of any ideas.  Can someone help me out, is there an obvious answer that I'm missing?


texts:
Any recommendations for gas discharge tube mathematical modeling references?

Lieberman and Lichtenberg (2005) Principles of Plasma Discharges and Materials Processing (see @AdilMalik 2020-12-21 recommendation)
Lin, Hui, and Chua (2014) Gas Discharge Lamps Are Volatile Memristors (see @jonk 2020-12-21 recommendation)
Raizer (1991) Gas Discharge Physics
Raizer (2017) Spark Discharge
Smirnov (2014) Theory of Gas Discharge Plasma
Howatson (2013) An Introduction to Gas Discharges


texts:
In the following problem, the equation i(t) = i(∞) + [i(0+) − i(∞)]e^(−t/τ) was used to calculate the current at time t given the initial and final currents. Then, vo(t) was found by equating it to L(di/dt), thee negative of the voltage across the inductor. Instead, why is not possible to use the expression v(t) = v(∞) + [v(0+) − v(∞)]e^(−t/τ) to find v(t) given that v(0) = 6 V and v(∞) = 0 V? Then i(t) could be found by integration, but the results are not consistent.
]4


texts:
I have the following circuit and I need to get the mean value of output voltage.

simulate this circuit – Schematic created using CircuitLab

This is a parallel RC circuit, powered by a current source which as you can see has the following waveform.

I was thinking that to get the output voltage first, the input current should be represented by a series of Fourier, since it is a periodic signal.

Once this was done, it could obtain the relation between the output voltage and the input current, by means of a current divider and multiplying by the output resistance.

I'm not very related to the use of Fourier series for circuit analysis and I think that would even imply the use of phasors to get temporary expression of output voltage. So I think in this way it would be very difficult.
Am I wrong or is there any other way to do it?


texts: Why does my bus-power-only USB hub enumerate as self-powered?

texts:
When I plug in a Sweex NPUS0480 4-port USB 2.0 hub, it is enumerated as self powered (according to the windows USBView application).

However, it is in fact bus powered. There is no DC connector on the pcb, nor any provision for one.

I was just wondering if this is normal, or could it be a mistake?
Or is it just something to do with the type of usb-hub controller chip that is used?

I could not find an answer in the USB 2.0 spec, although Table 11-12 does mention the following option:

  This hub is capable of both self- and bus-powered operating modes.  It
  is currently only available as a bus-powered hub.

In addition, the hub is enumerated as a low power device (MaxPower 100mA). If I plug in a high power (500mA) device, the hub still enumerates as 100mA. Is that to be expected?


texts: What makes planar inverted F-antenna omnidirectional but doesn't make the microstrip patch antenna omnidirectional?

texts: I see some designs without antenna substrate for PIFAs. I mean there's a patch over a ground plane meanwhile substrate is almost used in all designs of microstrip patch antennas. What's the exact and fundamental reason for PIFAs to be omnidirectional?


texts: How can I calculate voltage in this circuit?

texts:
I know this circuit is called 'Negative Impedance Converter' and for this case, works as -100 ohm resistance.
What is the voltage of the lowest bifurcation when I apply triangular wave(0 to 0.1 to 0 V, period 0.1 s)?
I thought the current flows from the ground, so the voltage should be negative, but I checked that's not correct with my LTspice simulation.
How can I calculate the voltage properly?
(+) LTspice simulation

I apologize for my haste,(I should've fully checked some errors I've mentioned.)
but I think the question is being developed by your advice.
Here is my second try. The input voltage has uV scale and position of Vcc, Vee were corrected. There are 2 new questions.

Why is the voltage of right next point to the input(plotted over the circuit) not identical with the given input??
And why can't I acquire the voltage of the blue-squared point over R3(by clicking there)?
(+)(might be last edit...)
I found the position of resistances in the figure above is wrong, so I've corrected them.
I found that the supply voltage of op amp affects the result(voltage of blue-squared point over R3). I know that 'voltages of +- input voltage be identical when there is feedback resistance' and 'output voltage of op-amp is A(V+-V-)'.
How I understand the output voltage can be nonzero is 'V+ and V- is actually have very small difference and A is sufficiently large'. Is it correct?


texts:
Above is a screen-shot from an LTSpice simulation. It is a freq. response of an LC tank circuit with a 5V sinusoidal AC source.

When I plot it, the y-axis is in dB.

When I look at the voltage it is 13.979dB which corresponds to 5V from the formula 20*log(V1/1).(1 is the reference voltage?)

But the current is plotted in negative dB. Why is that so? What does -dB mean here for the current? is that something to do with reference current in 20*log(I1/Iref)?


texts: What is a ferrite bead? How is it different from an inductor? How is it rated? What are its important parameters? What allows me to chose between an inductor or ferrite bead to filter out frequencies that are greater than 8kHz in a signal with a current in milli amps?(The signals here i'm referring are input and output signals of a DC/DC Converter)


texts: How to draw output resistance vs frequency in simulation?

texts:
I have a task to simulate this circuit and draw Rout vs frequency in the simulator. any idea how can I do this.
I am using OrCad


texts:
Okey, let's try this again. The board I am working with is the Smartfusion2 (M2S010-FG484 package) Starter Kit. Link-> here. My main question is If I can interface an analog signal to a pin of the breadboard the BSB provides without having to use an external ADC. I want my FPGA to work with a binary digital signal translated from a analog one.
In one of the documentation files, it is stated the signal name assigned to a pin of the breadboard area, and its name is ADC. As I have pointed out before there are several signal with this name. File can be found here.(page 8). This leads me to think that maybe it is possible to do what I want to do. However, after noting that the web page of the SF2 dev kit specifies it has an ADC whereas in the case of my board, there is no mention, I dont know what to think.

I am a newby in this and I do not know a lot about I/O standards and interfacing signals. Let me know if you need more info about my question.

thank you in advance.


texts:
What is the difference between these features on STM32G0 "Scan Conversion mode" and "Continuous conversion mode" and "DMA continuous request" features?
When you go on CubeIDE you will see these features on ADC configuration.


texts: What does an angle bracket pair () do in VHDL?

texts:
I am looking at some VHDL code and the following lines are present:

type obj_code_t is array(integer range <>) of std_logic_vector(7 downto 0);

and

OBJ_CODE : obj_code_t;

What does the <> signify?


texts: How to remove flickering on car-powered LEDs?

texts: I am powering an array of LED lights via the car alternator (the LEDs are connected to the car battery leads, but only run when the engine is on). The problem with this setup is that the natural alternator/battery voltage spikes cause the LEDs to flicker slightly. I would like to remove this flickering, however I am unsure how. The setup is an array of 12v LED strip lights. Should I use capacitors or some other method? Note that there is a large number of individual LED strips, totaling about 30 amps of current draw.


texts:
UCC2863x, High-Power Flyback Controller
with Primary-Side Regulation and Peak-Power Mode

In a design of a fly back converter the transformer used has 3 windings i.e. primary 328 μH and secondary and auxiliary windings and the primary winding has 54 turns but in the construction details the primary was split in two i.e. 27 windings each.

My doubt is should the primary windings have 4 pins on bobbin or just 2? The transformer guy used 3 pins for the primary. I have limited knowledge of transformers so if someone could help it would be great.


texts: Which SMD footprints can be hand soldered and which can't?

texts:
This was the first question I had once I was given a project that didn't restrict the use of SMD components.

I feel like there are a lot of different SMD footprints out there, and surely it's been established which are the ones that can be hand soldered and which are the ones that require ovens or other technology.

Please help me collect this information here?


texts: Implementing Communication Protocols on CC2420 motes powered by TinyOS

texts: I would like to load TinyOS on CC2420 radio motes to operate on certain communication protocols (e.g. epidemic routing, probabilistic routing, etc.). However, I have no prior experience in programming motes to perform the protocols I want. I'm just wondering about the most applicable resources for reference and how difficult (if not impossible) was implementing such mentioned protocols. It would be great to hear from you. Thanks in advance!


texts: what is simultaneous switching output noise?

texts:
Can someone explain to me what simultaneous switching output noise is (SSO) is it the same thing as simultaneous switching noise (SSN)? from what I understand when lots of pins are switching together it affects current draw from the source and this is a problem for parallel loads. this also may be crude way of putting it, but are these the Vcc version of ground bounce?

Thanks.


texts: RFID module always finds the same non-existent tag when seeking

texts:
I'm wondering whether anyone has any experience with the SM130 Mifare module. I've managed to get my hands on one, sans antenna of course, and seem to be having a few issues with it.

I've got the module connected to an FTDI 5V USB to TTL converter via the UART lines. I've added capacitors over the power rails for good measure. I've got the SM130 module connected to a single wire, a home-brew PCB antenna and a whole 50m roll of thin hookup wire as an antenna. In all cases, I've used the SMRFID software from SonMicro directly, which identifies the device correctly and can enable the RF field and disable it just fine. I took out my SSB shortwave receiver and I can hear the field being energized and de-energized.

Here comes the problem:I've ordered a fair amount of the Mifare transparent and ABS tags, however, when I select seek for tag, SMRFID always reports finding TAG TYPE: 55 SERIAL: 2E31204D, despite there being no tag in the field. Even with a tag in the field, it refuses to find it and reports the same details. I've tried relocating the device and antenna somewhere else, thinking it's interference, but still it didn't help. I also tried toggling the reset pin a few times; still no change.

The datasheet says that it should return an L representing "Seeking for tag" right after a seek command and sit there until a tag enters the field. Instead, my module seems to be reporting an L, then barely 10 seconds later, will report the same data.

At this point a short list of possibilities would be helpful; a total solution is not expected.


texts: For Intrinsic cap calculation what should be time interval for integration of current?

texts:
I am trying to get VDD cap of SRAM memory macro. I am ramping VDD by 50mv in a specific time interval and then integrating the I(VDD) for the same time interval.

For different time intervals like 50n, 2n, 2p 0.002p I am getting different values of cap.

So the question is How should I decide the time interval ??

Thanks


texts:
I'm solving some problems on three-phase systems. I'm doing pretty OK, but there is one problem that I'm not sure about the answer so I have some questions.

We have a three-phase circuit connected in a star connection, which is balanced (since the three impedances have the same value). The neutral wire has an impedance too, that has a value of 5 Ω and 30º. (This value it's different to the other impedances).

They're asking me the value of electric current on the neutral wire. I know it's zero when the system is balanced. However, I'm not sure if the fact of having an impedance on the neutral wire can affect on this.

I know it's a very basic question, but I'm a bit messed and I couldn't find this anywhere, thanks so much for the answers on beforehand!


texts: Trouble replacing a reed switch with a wired sensor along long stretches of wire

texts:
I have a wireless security door sensor, which has a reed switch, and I'm trying to replace the reed switch with my existing wired security door sensors (thus not having to mount the wireless door sensor on my door when I already have one there).

I soldered two short wires to where the reed switch connects to the circuit board, and when I touch the two wires, it completes the circuit as expected. However, if I connect these wires to my wired sensor via 30' wire, then when I first close the circuit, the wireless sensor registers it as closed, but when I break the circuit, it continues to register the sensor as closed.

I confirmed with a multimeter that the circuit opens/closes when I trigger the door sensor.  I also just used a 20' wire without a wired sensor on the end, confirming it fails in that case.  When I use an 8' wire, everything works as it should.

I'm using 22/2 unshielded wire, so I'm wondering if this, combined with the distance is my issue.

Can anyone with more electronics experience explain why this would be failing? And, are there any solutions with my existing wiring?


texts: I tried to make a mux for implementing a carry  bypass adder(carry skip adder ).The image attached is the mux I tried in ltspice. But it is giving me from x no matter what S is(btw -S and -S are compliments ). Can you tell me where the error is ?


texts:
I've designed the following IR remote control circuit. I need to put 2 LEDs on it so I can physically, simultaneously point the remote at my wall mounted TV and my VCR, etc which is all situated much lower down.

I am planning to put these LEDs in series with no current limiting resistors given the voltage drop of 1.5V across each. I think this is more efficient than having them in parallel as each will then need a resistor.

I'm not regulating any voltage from the cells as the diagram shows.
I've set the fuses on the MCU accordingly and the crystal running it is at 8MHz (not shown). I will probably turn off the brown-out detection fuse so that this can run ok as the voltage from the cell slowly depletes.

My question is, is there anything problematic with this design?
Will there be any frequency related problems with running an IR remote protocol at 38kHz?
Is setting up the LEDs in parallel going to give any advantage that more than offsets the power loss that would result by then having to include current limiting resistors?

simulate this circuit – Schematic created using CircuitLab


texts: Are there any single supply OP amps with negative supply voltage?

texts:
I learned that basically the only difference between a "single supply" OP amp and a dual supply one is that the former can drive much closer to the negative supply rail.

Furthermore if I understand correctly, if you enable a "single supply" OP amp to drive closer to the positive supply rail too, then it becomes a rail-to-rail OP amp.

Then my question, which I believe is something not unnatural to come up with at this point, is that there can be "negative single supply" OP amps which drives close to the positive supply rail but not negative.

Has there been any such product, at present or in the past?
Or is it meaningless to develop such a product (e.g. it costs more than an rail-to-rail device so it makes no sense.)?

It may be a stupid question but I will be glad if you could share me your knowledge.

Thank you in advance.

EDIT: I am sorry that I must have clarified that I am not asking about how to handle negative input with generic OP amps but about some existence (or possible application) of a weird device easily imagined to be validly designed.

I wanted to know whether there is (or has been) an "inverted" version of the so-called single-supply OP amps which has the capability to operate around the positive supply rail but not around negative in terms of the output voltage, so that it can be typically used with negative supply (thus I called them "negative single-supply OP amps").

Such device would be advantageous over rail-to-rail OP amps if it could be sold cheaper and the users are sure that they are never operating near the negative supply.

This is analogous to "positive single-supply OP amps" which are preferred because of lower cost when the users are sure they are never operating near the positive supply rail.

I understand there is very little demand for such a product because the range of application is limited, but I kept wondering because I have seen far weirder devices.

I apologize for the lack of explanation in the original post.


texts: What is the gas valve section of this dryer schematic doing?

texts: This Whirlpool gas dryer has an interesting collection of inductors (electromagnets operating valves) and a flame sensor that opens as soon as the ignitor gets hot enough to light a flame. What's happening here when the switch opens?


texts: Avoiding ground loops with multiple coax cables

texts: I have to connect two devices with multiple coax cables each carring a signal that has frequency components ranging from DC to a few GHz. I don't know how to avoid ground loops with this type of connection, this answer(https://electronics.stackexchange.com/a/192554/205214) says to break a ground connection on all but one ground paths but it is impossible in this situation because that would interfere with a return path of a high frequency components of those signals. Is there a solution to this problem?


texts: Calculating voltage drop (and power requirements) for multiple devices

texts:
I am trying to calculate the power supply required for 3 cameras (1A each), each with 150 metres of cable (0.75mm2), connected to a common power source (AC-DC PSU).

I have done these before with single cameras, however I'm unsure how multiple devices affect voltage drop. Is voltage drop calculated using the entire length of the run (ie 450 metres-note the cameras are not daisy-chained, each 150m length of cable goes directly between camera and PSU) and the combined current draw (3A)? Or do you calculate each run separately (150m and 1A) and then add them together? Or, most likely, something different? Image added below

At each camera there will be a 12v regulator, but I'm unsure on what voltage I should start with.

Any help on how to proceed much appreciated. TIA]1


texts: What's the difference between a decade counter and a "Divide by 10 counter"(MOD 10 Counter)?

texts:
I have a project of creating a digital clock out of multiple 7-segments. In order to display digits 0 to 59 in 2 7-segments which is better and easier to use: cascaded decade counters or a "divide by 10 counter" and a "divide by 6 counter"?

Here is the project I'm creating http://electronics-course.com/digital-clock


texts: Estimating the capacity of unknown LiPo cell

texts:
I recently salvaged this small (30 x 9.5 x 3.5 mm) LiPo single cell battery from an old device that lied broken for at least 3 years.

Therefore I expected it to be garbage ready for recycling, but when I measured its voltage it read 2.8V, so it seems to be in good shape. Hence I decided to keep it in my junk bin for experimentation purposes.

The problem is that I couldn't find any datasheet or info on the Internet, so estimating its capacity is a problem. In particular, I'm well aware of the LiPo charging technique that requires a constant-current phase followed by a constant-voltage phase, as this TI application notes explains. Excerpts:

  At present, the major Li-Ion cell manufacturer recommends 4.200 +/- 50 mV as the ideal set point voltage, and 1c (a charging current rate equal to the A-hr rating of the cell) as the maximum charging current that can be used.

  [...]

Since I never played a lot with LiPo batteries, I'm clueless at guessing its capacity (for what I know it could be anything between 100mAh and a couple of Ah).

Can anyone suggest me, if possible, a reasonable and safe estimate for its capacity or C rating, so that I won't be risking to overcharge it in the CC phase?

EDIT (to incorporate some more info, as prompted by comments)

the cell weighs approximately 1g (something between 1g and 2g)
it was embedded in an old (6-7 years) Bluetooth receiver for indoor usage (one of those small boxes that can be connected to the headphone jack of an amplifier to send the PC audio to your Hi-Fi system or whatever)
as far as can be seen by close visual examination, it doesn't embed any protection circuitry


texts:
I am using a P-channel MOSFET as a switch in my design & I have connected the drain to the load. The load needs 0.8mA of current. How can I decide whether the MOSFET is conducting that much current if I connect the source of the MOSFET to 3V ? The MOSFET used is BSS84 from Fairchild & the link for BSS84 datasheet is given below.

BSS84 P-channel MOSFET


texts: I've been looking for some straightforward method or trick to obtain the transfer functions of active filters (like the Sallen-Key filter , the butterworth or Cauer topology etc...) since KCL or KVL requires a lot of algebraic manipulations . I've heard that SFG (signal flow graphs) could be very helpful , but with my minimum of experience i can not found any worth reference that treat the subject , so what i am looking for is some brief explanation of SFG with introductory applications to the basic models and topologies of active filters and thanks.


texts:
I'm trying to configure the MSSP module of a PIC18F25K22 into SPI master mode.  I'm looking at the timing and the clock doesn't remain steady through the whole transmission.  A picture shows it better than words.

After a bit is sent, the clock shortens, and not by the same amount each time.  I've not worked with SPI before, but the diagrams I've found on Wikipedia and other resources don't ever show this.  I also hooked up an Arduino and did not see this behavior.  My code is:

    #pragma config FOSC = INTIO67   // Oscillator Selection bits (Internal oscillator block)
#pragma config PLLCFG = OFF     // 4X PLL Enable (Oscillator used directly)
#pragma config BOREN = OFF      // Brown-out Reset Enable bits (Brown-out Reset disabled in hardware and software)
#pragma config WDTEN = OFF      // Watchdog Timer Enable bits (Watch dog timer is always disabled. SWDTEN has no effect.)
#pragma config MCLRE = EXTMCLR  // MCLR Pin Enable bit (MCLR pin enabled, RE3 input pin disabled)
#pragma config LVP = OFF        // Single-Supply ICSP Enable bit (Single-Supply ICSP disabled)
#pragma config XINST = OFF      // Extended Instruction Set Enable bit (Instruction set extension and Indexed Addressing mode disabled (Legacy mode))

void main(void)
{
    OSCCON = 0b11100110;
    spi_setup();
    __delay_ms(10);
    byte temp;
    while (TRUE)
    {
        temp = spi_transfer(0x00);
        temp = spi_transfer(0x01);
        temp = spi_transfer(0x02);
        temp = spi_transfer(0x03);
        temp = spi_transfer(0x04);
        temp = spi_transfer(0x05);
        __delay_us(1);
    }
}

void spi_setup(void)
{
    SSP1STAT = 0b00000000;
    SSP1STATbits.CKE = HIGH; // data transmitted on rising edge
    SSP1CON1 = 0b00000000; // enable Master SPI mode
    SSP1CON1bits.CKP1 = LOW; //clock idle state is low
    //i2c bits, all don't matters for SPI, cleared just in case
    SSP1CON3 = 0;
    // baud rate generation
    SSP1ADD = 0; //FCLOCK = 8Mhz /2 = 2Mhz
    // configure pins for output/input as needed
    SDI1 = INPUT;
    SDO1 = OUTPUT;
    SCK1 = OUTPUT;
    SS1 = OUTPUT;
    SSP1CON1bits.SSPEN1 = HIGH; // enable pins for serial mode
}

unsigned char spi_transfer(unsigned char data)
{
    SS1_LAT = LOW; // select slave
    PIR1bits.SSPIF = LOW;
    SSP1BUF = data;
    //while (!SSP1STATbits.BF); //wait for receive to complete
    while( !PIR1bits.SSPIF );
    SS1_LAT = HIGH; // deselect slave
    PIR1bits.SSPIF = LOW;   // clear interrupt
    return SSP1BUF; //return data from the slave
}

(also https://gist.github.com/stumpylog/5095250  )

Has anyone encountered this or have suggestions as to the cause?

What I Did

In the end, I was unable to get the MSSP1 module working.  However, changing it to the MSSP2 module, exact same code, did not exhibit this behavior.  I can't explain it, but this solved the problem.


texts: Does voltage rating increase on ceramic capacitors have any effect on the performance of the capacitor?

texts:
If I have a circuit that is designed for a ceramic, SMD, 0402, 1uF, 10%, 10V rated capacitor, and I swap in a ceramic, SMD, 0402, 1uF, 10%, 25V capacitor would anything change in the circuit?

Would the performance of the capacitor change in any significant or measurable way?


texts: Electronic switch with negative and positive voltage

texts:
I want to use a micro-controller to send data through a max232 that will convert the 0v/5v signals into -12/+12v signals. The problem with this IC is that when there's no signal, it sends a +12v signal which I don't want. I want to be able to control exactly when to send a signal. So I would like to use a transistor  (or something else) to make an electronic switch and connect an additional pin of my micro-controller to open and close the switch when I need to.
I've made a diagram so it makes more sense. This diagram is an idea I've had, but I don't know how to make it work, I read the data-sheet of the 2n2222 transistor and seems like negative current won't go through.

Here's the Schema simplified :
Basically, it sends the data to the receiver when and only when the Switch is turned on, the rest of the time, the switch is off and no data transit. I'm just looking for an electronic equivalent of that switch that I could control with a microcontroller.


texts:
Here is the circuit, A and B are connected to the 2 plates.

Here is how it is supposed to work.

Q1, how safe is this trap to a human?

Q2, Basically how does it work?

Q3, Is there a current limiting circuit or is this a dead trap for human too?


texts: Using an Arduino Mega GPIO pin to enable MAX1771 DC/DC converter

texts:
TL;DR: DC/DC booster does not work, and MOSFET seems stuck.

I have a 12V fan that I wish to power with a 7.4V battery via a MAX1771 DC/DC converter chip (datasheet in hyperlink). The fan is rated at 0.06A.

I am utilising the 12v preset output, bootstrapped circuit to power my fan. My SHDN pin is connected to a GPIO pin on the Arduino Mega such that when I write digital HIGH, it is 'off', and when I write digital LOW, it is 'on'. The Arduino is also powered by the 7.4 V battery and shares common ground with the MAX1771.

The issues I am facing are these:

I implemented the example circuit in the datasheet (Fig 2a). I followed the datasheet as closely as I could, with the exception of Rsense (I soldered 30 1.2 ohm resistors in parallel to give 0.04 ohms), and using 3 100uF aluminium electrolyte capacitors in parallel to give 300uF for C4, and the substituting the MOSFET for a BUK9575. Im afraid I cannot remember the names of the other types of capacitors/inductors, but their values are the same, and are polarised as per the datasheet specifications.

The first time I put everything together, it seemed to work fine, perhaps a little loss (output was approx 11.68V). But once I shifted all the components over to a new breadboard (yeah it was breadboarded for display purposes) and trimmed the components so they fit snugly in the breadboard (trying to be neat and tidy here) without any extra long leads, the converter suddenly loses its functionality, so the output is now at 6.8 volts instead of the previous 11.68 volts.
Failing that, I decided to see if regardless if the converter was not able to step up my voltage, I figured if I could at least enable/disable the converter all wouldn't be lost. So I created a code in Arduino 1.6.9 IDE that tells my GPIO pin thats connected to the SHDN pin on the MAX1771 to go LOW for one second, and HIGH for another second continously. Tested the code out on an LED and it blinks fine. However, doing this for the MAX1771 causes it to stay permanently on.
 The MTD was a MOSFET recommended by datasheet. I substituted it with one I had on hand for testing

So these are my 2 issues. I would like to ask what could be the cause of what made my converter unable to boost, and why my arduino is unable to disable the max1771.

Research: Ceramic and tantalum capacitors were recommended by the datasheet, but since the circuit worked with regular ceramic and aluminium electrolyte capacitors, I figured its not such a big deal.

Also, I figure maybe its because my arduino's HIGH and LOW signals aren't clean enough. Should I add additional caps to filter the Arduino's GPIO?

Is my MOSFET sensitive enough to changes in gate voltage? I hope I did not blow it by accident.


texts: PID Control implementation for charging battery really necessary?

texts:
If one is to make a battery charger, lets say a Li-Ion battery charger (using a micro-controller with buck converter), is it necessary to do some kind of control implementation inside the micro-controller for e.g P , PI , PID ?

Like generally we would be measuring the voltage and current being fed to the battery, and try to keep the current constant (by adjusting PWM duty cycle being fed to the buck converter) for the first phase of charging. After that when a certain Voltage is reached, we would try to maintain that voltage by reducing the current, until a current value is reached where charging has to be terminated.

But my MAIN QUESTION is that, is it necessary always to implement some kind of control technique (P,PI or PID) in our micro-controller to adjust this value of voltage and current being fed to the battery (by adjusting the PWM cycle off course) ? If yes why ? and if not then why not ?

P.S i searched online and came to find out mostly people have implemented PID control in micro-controllers for running motors. I couldn't find much regarding this with respect to battery charging. I was thinking that may be its because the response time of the system (time to implement the current/voltage change needed) is very small in case of motors operation as that compared to battery charging. Am i right ?

Thankyou !


texts: Which decoupling capacitor to choose for electro optic circuits?

texts:
Background:

My application is a typical electro optical design where analog electric pulse from a photo diode is digitalised, Pulse Width=10ns, pulse repetetion rate= 20uS

my anlog pulse to digital conversion is like below, with a gain of 1K through TIA and pulse inversion using limiting amplifier and digital conversion through high speed comparator

I-V conversion > limiting amplifier > High speed comparator

as i am working with a pulse of rise time 2ns, my BW of operation would be <200MHz

Problem Statement

when i have read the previous question and answers i have seen people suggested to go for a 0.1uF,0.01uF ceramic capacitor near to the power supply pins

i am clue less which capacitor to choose exactly for high frequency circuits which are working around 200MHz

  to confuse me more i have seen a app note saying this idea of
  choosing 0.1uF is age old for high frequency circuits

when they say high frequencies do they mean really > 1Ghz ?

do i really have to worry ? or for my 200MHz i can choose the 0.1uF and 0.01uF in parallel proceed ?


texts: Biasing circuit with mosfet: am I missing information or misreading it?

texts:
I have the following circuit with MOSFET (cascode amplifier).

Information given:
$$V_t=1V$$
$$I_1=20\mu A$$
$$k=10 \mu AV^{-2}$$

Knowing that \$V_b\$ is 5V determine the minimum value of the output voltage so that both transistors are saturated.

I'm kinda confused on how to proceed on this.
First of all, don't we need VDD? How to relate VB with this?
I started by assuming both transistors had the current I_1 (I assume this is correct).
Then I used the MOSFET equation for saturation $$i_D=k(v_ {GS}-Vt)^2$$ to determine \$v_{GS}\$ in both transistors. obtaining 2.4 V.
Then I applied the boundary condition for saturation $$v_{DS}=v_{GS}-V_t$$ and so obtained for both transistors \$v_{DS}=1.4V\$
So the minimum value of \$v_O\$ is 2.8V.

This is incorrect, the answer should be 4V. I'm really not understanding how to proceed... Can someone give me an hint on how to do this? Thanks!


texts: How to fuse batteries connected in series?

texts:
Is it possible to wire each battery in a series to the next using a fuse wire, so that the individual batterie's max power output is not exceeded?

here is an illustration, suppose each battery had a maximum safe output of 60w, would it be possible to use 60w fuse wire in the place of the blue lines?


texts: How to turn on LED with temperature sensor

texts:
I'm new to electronics and I want to control a device using a temperature as an input.

Right now I saw this video on youtube and want to follow it as well as know what the components are for.

https://www.youtube.com/watch?v=PkRJBQgjLrc

From the video I know that the NTC MF52-103 is the temperature sensor and that its output is a resistance. I just don't know how to set/configure the resistance to the temperature I want to control as well as what are the purpose of the two other transistors.


texts:
Was reading about OP AMP and saw a article on "Active Negative Resistor" on wikipedia @ http://en.wikipedia.org/wiki/Negative_resistance.

Question to the gurus: How practical is this? Can I build a op amp circuit and replace one of the gain resistance with this "active" resistance and control the gain using voltage (like VCA)? The gain steps(between a finite gain) can be infinite in theory, if this works.


texts: Why is my circuit not providing the right voltage to my motor?

texts:
I have a circuit which is supposed to vibrate a vibrating motor. The circuit is fairly simple and uses a BJT to step up the current to the motor. The motor also has a capacitor and diode in parallel to protect from surges.

Here's a picture of the circuit:

When I hook everything up, the motor doesn't turn on. I tested the voltage drop between the leads and it only read 0.2-0.4V. Do the values for the resistors/capacitors make sense? I'm fairly new to circuit design so I may have made a very simple mistake.

EDIT: I forgot to mention the motor needs to run around 3V with 75mA


texts: Is this the proper way to create a high voltage (low current) straight DC signal from a 9V battery?

texts:
My goal is to create a circuit that will take in a 9V DC battery as input and produce a high steady +1500V DC signal. I don't need high current at all. 1 microamp of current will do. The scheme goes like this: I use an astable multivibrator to generate a square wave.

I replace the speaker with a transformer to step up the voltage (and step down the current). I hook up a rectifier to make the now high voltage DC alternating signal to a steady straight +1500V DC signal. Is this the proper way to go about this problem?


texts: How Do I Calculate The Power Of A Rail Gun?

texts: I am thinking of making a rail gun and I have done my research on parts but I would like to know how to calculate how strong the rail gun will be. I am thinking of running 12 400v 2200uf caps in series firing 2 inch long 3/8 inch diameter steel nails through a rail that is 5 feet long. Thanks!


texts: how to make the eclipse IDE to be compatible for PIC devices?

texts: I am looking for a PIC development environment that is better than MPLab.  Is it possible to to install and configure Eclipse to work with PIC microcontrollers?


texts: Why does low frequency audio take up more power

texts:
When I say more power, I know that fundamentally it takes more energy to move the speaker cone to produce lower frequency audio. However, in my experiences, higher frequency content takes up something like x10 less current than its lower frequency counterparts, and this is using similar impedance tweeter and woofers from the same amplifier output.

I know that the impedance value of the woofer doesn’t drop off that rapidly, so what’s with the way higher power consumption?

Does a higher frequency audio signal have a smaller amplitude or something of that nature? I’ve been trying to figure it out for some time but can’t seem to wrap my head around it.

Edit 1: To clarify this, impedance of subwoofers or woofers don’t change dramatically for frequencies before or after the resonant spike. So if you’re driving let’s say, a 10W speaker and 2W tweeter with the same amp ie the same voltage, how does the tweeter not get burnt out? Is there just more spectral content below a certain frequency in the overwhelming majority of songs?


texts: Whats does "hr" mean among "V" and "Ah" in batteries?

texts:
I have a battery which indicates 12V25Ah/10hr.
What does 10hr mean here? I guess "hr" stands for "hour".
But 25Ah already means if battery is fully charged and if I load 12V 25A (=300W) to it, it should last for an hour (correct me if I am wrong).

What does "/10hr" mean here?
How many watts I can load to use the battery for an hour?


texts:
I'm designing a VGA controller in VHDL and for video memory I decided to use SRAM memory. In order to manage the RAM I created a controller that must be interfaced with the VGA Controller. So far I have always programmed with sequential languages and so I have some problem in interfacing the two controllers.
For example: write a data in the SRAM takes a T time and when the controller has finished the operation it will trigger a READY signal. How do I make sure that the VGA controller wait for this signal? From what I have seen the VHDL WAIT statement can't be synthesized.


texts: Purpose of capacitor and resistors on the output of three-state buffer

texts:
I intend to use a buffer with three-state output in one of my designs. The datasheet of the buffer IC shows the following circuit:

What's the purpose of CL, RD and RU on the output of the buffer. As I understand the values of RU and RD are equal - leaving the output floating between VI and GND maybe? But why?
Link to the datasheet: NC7SZ125


texts: What's the difference between logic/if system and drive system of a display?

texts:
I've been looking at the current consumption of a display and the datasheet says the following:

Can anyone tell me the difference between "drive system" and "logic/if system"?


texts: What wavelength will achieve higher speed in optical fiber?

texts:
I've got quite easy question (and my attempt to solve it). So there is an optical fiber with Dispersion index: D = -100ps/nm•km, length: L = 10km. The question is: which wavelength will achieve faster speed and the end of the optical fibre: λ_1 = 1000nm or λ_2 = 1001nm?
In my opinion if the speed of the wave is dependent on the refractive index which will be the same in the same fibre then the speed of both wavelengths will have the same speed. Is it true? Does dispersion have any impact here?


texts: WeMos self-turn-off with N-channel MOSFET

texts:
I'm trying to build an internet-connected button. When button is pressed, WeMos D1 turns on, makes a network call and then cuts off the power by pulling the irlb8721 gate to LOW.

Video: https://photos.app.goo.gl/QEpIgPa3gxHatTyG3

Here's the program I currently use for test:

void setup() {
  pinMode(2, OUTPUT);
  digitalWrite(2, LOW); // Turn on built-in LED

  pinMode(5, OUTPUT);
  digitalWrite(5, HIGH); // Keep ourselves powered after button is released
  delay(5000); // Do the work, e.g. make a network call
  digitalWrite(5, LOW); // Cut off the power
}

void loop() {}

The problem is that after the power is turned off, there's still ~20mA current leaking, which is a deal-breaker for a battery-powered button. Disconnecting the pin 5 (D1) gets rid of that for some reason.

Resistor between gate and source is 676kOhm, between D1 and gate - 10kOhm. Thanks for your help!


texts:
I found an oled screen at work, that I want to use, but it doesn't have a datasheet, just has its model number printed on the back, it is P19702. The only thing that I found online was this:http://www.spelistopto.com.tw/index.php/en/application-products/item/22-no19-p19702

I was wondering if someone knew anything about this oled screen, or what the general rule is to find the pinout for an oled screen.


texts:
I'm just getting my head around RLC dynamics.

After some analysis and math i get,

\$\frac{d^{2}v_{\text{c}}}{dt^{\text{2}}} + \frac{R}{L}\frac{dv_{\text{c}}}{dt} + \frac{1}{LC}v_{c} = \frac{1}{LC}v_{\text{S}}\$

and the characteristic equation:

\$s^{2} + 2\alpha s + \omega_{0}^{2}\$

and

\$ v_c = V_S + A_1e^{s_1t} + A_2e^{s_2t}\$

3 cases:

case 1: \$ \alpha = \omega_{0}\$ --- critically damped,
then,

\$v_c = V_S + A_1e^{-\alpha t} + A_2te^{-\alpha t}\$

I understand that no sinusoids here. But I note texts drawing some overshoot before the response continues to the final value, with no clear explanation. I tried to crunch my head with little maths to explain the overshoot, but failed. Any one to explain the overshoot?

EDIT:

i.e. isn't the figure below the case?

or in the case of source-free RLC.


texts: Depending on the orientation of a nulling coil I need an adjustable voltage supply from ~+5V to -5V upto ~200mA. I've tried a few circuits similar to Class AB amplifiers such as the one shown below, but these normally expect an AC coupled input. Has anybody got any other suggestions?


texts: ST32F4 interrupt handler not getting called

texts:
Disassembly shows that MCU gets stuck at NMI_Handler so that means that interrupt is working.
Why isn't the interrupt handler getting called ?
My code-
    #include <intrinsics.h>
#include <stm32f4xx.h>

 void TIM6_DAC_IRQHandler(void)
{
  TIM6->SR = 0;
   GPIOA->ODR &= ~(1<<7);
   GPIOA->ODR |= (1<<7);

}

void TIM6Config (void)
{

    /************** STEPS TO FOLLOW *****************
    1. Enable Timer clock
    2. Set the prescalar and the ARR
    3. Enable the Timer, and wait for the update Flag to set
    ************************************************/

// 1. Enable Timer clock
    RCC->APB1ENR |= (1<<4);  // Enable the timer6 clock

// 2. Set the prescalar and the ARR
    TIM6->PSC = 90;
    TIM6->DIER |= 1;
// 3. Enable the Timer, and wait for the update Flag to set
    TIM6->CR1 |= (1<<0); // Enable the Counter
    while (!(TIM6->SR & (1<<0)));  // UIF: Update interrupt flag..  This bit is set by hardware when the registers are updated
        NVIC_EnableIRQ(TIM6_DAC_IRQn);

}

void GPIOConfig (void)
{

    /************** STEPS TO FOLLOW *****************
    1. Enable GPIOA clock
    2. Set the PIN PA5 as output
    3. Configure the output mode
    ************************************************/

    // 1. Enable GPIOA clock
    RCC->AHB1ENR |= (1<<0);  // Enable the GPIOA clock

    // 2. Set the PIN PA5 as output
    GPIOA->MODER |= (1<<14);  // pin PA5(bits 11:10) as Output (01)

    // 3. Configure the output mode
    GPIOA->OTYPER &= ~(1<<7);  // bit 5=0 --> Output push pull
    GPIOA->OSPEEDR |= (1<<15);  // Pin PA5 (bits 11:10) as Fast Speed (1:0)
    GPIOA->PUPDR &= ~((1<<14) | (1<<15));  // Pin PA5 (bits 11:10) are 0:0 --> no pull up or pulldown
}

int main (void)
{

    TIM6Config ();
    GPIOConfig ();

    while (1)
    {

    }

}

Disassembly of vector table
__vector_table:
    0x8000000: 0x20002000     ANDCS     R2, R0, R0
    0x8000004: 0x08000165     STMDAEQ   R0, {R0, R2, R5, R6, R8}
    0x8000008: 0x0800011b     STMDAEQ   R0, {R0, R1, R3, R4, R8}
    0x800000c: 0x0800011b     STMDAEQ   R0, {R0, R1, R3, R4, R8}
    0x8000010: 0x0800011b     STMDAEQ   R0, {R0, R1, R3, R4, R8}
    0x8000014: 0x0800011b     STMDAEQ   R0, {R0, R1, R3, R4, R8}
    0x8000018: 0x0800011b     STMDAEQ   R0, {R0, R1, R3, R4, R8}
    0x800001c: 0x00000000     ANDEQ     R0, R0, R0
    0x8000020: 0x00000000     ANDEQ     R0, R0, R0
    0x8000024: 0x00000000     ANDEQ     R0, R0, R0
    0x8000028: 0x00000000     ANDEQ     R0, R0, R0
    0x800002c: 0x0800011b     STMDAEQ   R0, {R0, R1, R3, R4, R8}
    0x8000030: 0x0800011b     STMDAEQ   R0, {R0, R1, R3, R4, R8}
    0x8000034: 0x00000000     ANDEQ     R0, R0, R0
    0x8000038: 0x0800011b     STMDAEQ   R0, {R0, R1, R3, R4, R8}
    0x800003c: 0x0800011b     STMDAEQ   R0, {R0, R1, R3, R4, R8}
NVIC_EnableIRQ:
    0x8000040: 0xf0102201     DC32      0xf0102201 (-267378175)
    0x8000044: 0x408a011f     ADDMI     R0, R10, PC, LSL R1
    0x8000048: 0xb240491d     SUBLT     R4, R0, #475136         ; 0x74000
    0x800004c: 0xf8410940     SRSDA     SP, #0
    0x8000050: 0x47702020     LDRBMI    R2, [R0, -R0, LSR #32]!


texts: Controlling LP Gas burner with microcontroller: flame sensor ideas needed

texts:
I'm building a system using a microcontroller (like an Arduino maybe) to automatically control the temperature of a kettle of liquid being heated by an LP gas burner with a PID algorithm to turn the burner on and off.

I'm having difficulty figuring out how to sense presence/absence of the flame so I can deactivate the igniter and then monitor for flame blowout.  I looked at flame sensor rods as used in furnaces (rectifier type), but can't find anything on how to interface one to the microcontroller.

I considered using a thermopile, but they seem to be used mostly for pilot flame, so I'm not sure if would work for the main flame.  I looked at a fire sensor (transistor based) for the Arduino, but it doesn't detect natural gas flame, so I'm not sure if would work for LP.

I need a solution.

Safety is not a big concern since this will never be used indoors, and will always be monitored constantly while in operation.  A common approach for this is to manually ignite the burner and monitor a thermometer in the liquid.  The burners are periodically adjusted using a ball valve.  I'd just like to make the process a little easier, but have no intention of leaving it unattended.  So I guess you could say that adding a

flame detector is just a secondary extra safety measure.

Thanks everyone for your input.  I've began analyzing an electric alternative.  I'll need to go 220V with around 5500W elements in the liquid, but it is definitely doable.  I can use a SSR to feed the power and regulate the temperature.  It's definitely a cleaner and simpler alternative, so I may go that way.  Thanks again for being so responsive.

Now, I need to finalize on the microcontroller selection.  I'm thinking maybe an Atmel.  I see there are some opinions already posted on this.  Anyone have specific suggestions on models, and rational for the proposed selection?


texts: I'm designing a 4 layer board in Altium Designer 20.0.1 with an STM32F103RBT6 and am doing the 8MHz and 32kHz crystal layouts. According to the recommended layout each crystal is supposed to have a ground plane beneath them, a small gap around between the crystal grounds and the ground plane and have a single trace connecting them. The second layer from top is GND and I made a Polygon cutout. I then made the separate ground polys for the crystals but they won't fill. I can see the border of the polygon but they won't fill. I suspect it won't fill because I have a poly cutout and then planes in the cutout but I can't figure how to get i to work.


texts: Interesting driving circuit of a voice coil actuator

texts:
I have an interesting circuit to drive the voice coil stage of an old acoustic microscope. I am struggling to understand what the different functions of the opamps in this circuit are.
The circuit looks like this:

On the top left side, the input signals are connected to the board. At the bottom right side, the output signals are connected to the voice coil. The stage has an optical position sensor which means that the input signals to the board (GGM, ENX) are already the result of a closed loop system.
I know that the current of the coils is produced by the H-bridge at the top right. I am struggeling to understand what the opamps part is necassary for and why there is another feedback system with N1.3.


texts: using a step-up voltage transformer designed for 110V input with a 100V input

texts:
I relocated to Japan (where electricity is served at 100V) recently and I am looking to buy a step up voltage transformer to be able to use my TV which accepts 220-240V.

While I managed to find some options, it seems that majority of the transformers out there are designed for US-Europe conversion, ie accepting input of 110V and not 100V.

Could I use such a transformer instead, assuming it can generate output of 240V? (I'm assuming transformers work in multipliers, so a "max transformation ratio" would be 240/110, and 100*(240/110) would get me very close to 220V). Are there any other considerations why I should not try this besides voltage calculations?


texts: How to know if a multimeter is defective?

texts: One of our service engineers asked me(or tested me) how to know if an analog multimeter is defective without measuring any current, voltage or resistance. Just by looking at the device itself. Do you have any thoughts about this?


texts: 1000Base-LX or SX Output and Input Requirement Standard

texts:
I have a question regarding the 1000Base-LX or SX standard. The question is mainly on the electrical characteristics of the output and input requirements of the 1000Base-X.

The standard is based on the IEEE 802.3z. After trying to read through the standard document, I couldn't figure out what is actually the output and input requirement of the 1000Base-LX/SX interface. In other words, what is the standard output to an optical transmitter and what is the standard input requirement from an optical receiver that conforms to 802.3z.

802.3z documents

I'm fairly new to Ethernet and I have to admit, I dont quite understand all the wordings especially when I'm simply looking for the input/output standards.
Thanks for any help in advance.

UPDATE

The reason I'm asking is because I'm developing a low-power receiver with differential output of VCM=0.2V and Vswing=0.2V (single ended), with SFP interface to interface it to a typical RJ45-SFP media converter (gigabit ethernet).

I need to know if my receiver output is compatible with the typically-used 1000BASE-X-compliant media converters out there. If it is not compatible, maybe I would need to use a limiting amp in my receiver to boost the signal, but I'd prefer to keep the limiting amp out to preserve my low-power spec.


texts:
From my last question Propgation delay

I tried to solve for the time delay that occurs at the last carry

Not sure if I have done it right .. Please correct me if I m wrong


texts: Solving a circuit with a resistor in series with an LC circuit

texts:
I want to analyse a circuit that I've drawn above. It is a series connection of a resistor and an LC circuit (parallel type) driven by a sine wave of variable frequency. No assumptions can be made about the values of the voltage, frequency or the values of the components.

I'm particularly interested in the voltage across the capacitor. I would also like to know how to calculate the resonant frequency of this circuit, as well as its bandwidth and Q factor.

I understand that normally with a simple LC parallel circuit, resonance occurs when the impedances of the capacitor and the inductor are equal, and therefore the impedance of the overall circuit is maximum. But does the resistor change things, and if so, how? Next to the drawing of the circuit is my very primitive attempt at a solution, but I did not get far. The voltage of the source clearly equals the voltage across the resistor and the LC, and the voltage across the cap and the inductor are clearly equal. Also the current the resistor equals the currents on the cap and the inductor. But I really cannot make progress beyond this.

I'm also guessing that by assumption of R being very large, I could say that the voltage source with the resistor approximates a current source, but this is not what I want to do. I would like to analyse a basic LC circuit connected to a signal generator, with the R being the internal resistance of the signal generator. In an earlier question of mine I asked why I'm not getting the resonance at the frequency calculated with the usual formula of resonance of parallel LC circuit, and I understood that the internal resistance of the signal generator affects the circuit.


texts: What is the best way to design an emergency button circuit?

texts:
I am using an Arduino ATMega as a controller and I have a few methods in mind to operate the emergency button (hardware and software.)

utilizing the interrupt button
while loop, with a pull down button as the emergency button

Are there any methods better doing this?