texts: How to find the compensating gain required for the 2nd order control system to have 5% overshoot

texts: I have a unity feedback control system with $$G(s) = \frac{1.247}{s^2+9.76s+23.8}$$ in the forward path. Now Imagine, I added a static gain K in the forwards path to make the %overshoot 5%. How can I find the value of K? What if I added G'(s) instead of adding K where is $$G'(s) = \frac{K(s+0.1)}{s}$$What is the procedure to find it? Is there any way to do it using root locus plot?


texts:
I have a STM8S003F3 and a Arduino Micro SD Card Module. I want to create a file inside the Micro SD card. How can I do it? Can you help me?
Thank you in advance.


texts: Why are there two different output voltage ratings on some power supplies? and How it works?

texts:
some power supplies (ex. chargers) have two different output voltage ratings like:

5V 2A  OR  9V 2A

-why is that?

-How the charger knows that my load needs 5V or 9V? and not damaging the load

-How the switching work?

thanks,


texts: Rotate multiple PCB designators in Altium?

texts:
I am copying rooms in a PCB from the right side of a board to the left. Rotating everything in the room is easy - select the objects, Edit > Move > Rotate Selection.

But now all of my designators are upside down:

I don't like this. I figured out how to use the Find Similar Objects function to select all the designators in the room, but Rotate Selection does nothing to them.

Any ideas, besides individually rotating 14 designators? I'll have to reposition them anyway, but at least if I could rotate them in one shot, that would be something.


texts: Chaining pull-up vs push-pull configuration

texts:
The first image is the push-pull configuration.
Current is drained to GND through the PMOS and NMOS

The second image is the pull-up configuration
Current is drained to GND through the large resistor

The only real differences i see are that for the first configuration, higher current will be drawn and for the second configuration less current will be drawn from the power supply to ground. And this is given that there is a HIGH and a LOW signal to the gates.

Does this smaller current affect the transition time from a HIGH to a LOW or LOW to a HIGH registered at the output?


texts: Recognizing the COM port used with STLINK

texts:
I'm using a STM Nucleo as a bridge to flash a BLE EM9304 module and another ST-LINK from another STM Nucleo to flash a STM32. Both MCU are in a third board. So, I'm integrating the sequence of programming in one "software". The question is: When I read the active COM ports, both ST-LINK ports appear with the same title. Is there any way to know which COM port is being used in the process by Python?
OBS.: The nucleo boards are differents (One is with STM32L037Z and the other is STM32F411).


texts: Can I use 15V 2A transformer with this circuit?

texts:
I m trying to build a charger circuit for a 12V 7Ah Sealed Lead Acid Battery. I found this circuit online and it uses 15V-0-15V 1A Transformer as AC input.

Circuit Source

I have a 15V-0-15V 2A Transformer and can I use it with this circuit without any modification?


texts: Why does this adder need two clock cycles (two pushes of the button) to display a result?

texts:
I'm implementing a simple adder with carry out in VHDL on a BASYS2 board.

This is the code below:

entity adder is
    port (
        a, b        : in std_logic_vector(3 downto 0);
        sum     : out std_logic_vector(3 downto 0);
        cout        : out std_logic;
        kopce       : in std_logic;
        ledica  : buffer std_logic
    );
end adder;

architecture sobirac of adder is

signal tmp : signed(4 downto 0);

begin
    process(kopce)
    begin
        if(rising_edge(kopce)) then

            ledica <= (not ledica);

            tmp <= signed(("0" & a)) + signed(("0" & b));
            --sum <= std_logic_vector(tmp(3 downto 0));

            sum(3) <= std_logic(tmp(3));
            sum(2) <= std_logic(tmp(2));
            sum(1) <= std_logic(tmp(1));
            sum(0) <= std_logic(tmp(0));

            cout <= tmp(4);
        end if;
    end process;

end sobirac;

The "problem" is that I need to push the button two times in order for it to generate an output which I'm displaying on the onboard LEDs, why does it behave like this ? If I remove the process statement, and make it concurrent, it works in the instant I give it an input (2x4 switches).

Regards,
Aleks


texts: How to deal with the high current flowing into your wires?

texts:
So i've got this 1000 watt 36V with a full-load current of 35,6 amps. In the circuit I want to wire a switch that can handle this high current. Unfortunately it seems that I cant find a switch (specific reason?). What can I do to deal with the high current. I am making an electric gokart btw.

Ps: In a circuit, does the motor pulls 35,6 amps into my wires or is it the battery?


texts: What is significance of Q factor in series rlc circuit? , and why rlc series  circuits with larger Q factor values are considered better? What is idea behind introducing this term?


texts:
I'm working on a project that requires at least 40 dB gain at 40kHz. I originally used one non-inverting amp using 10k and 1k resistors for a gain of 11. Using cascading rules for linear systems, I cascaded another non-inverting amp of the same gain.
Below is the simulation and circuit that I am trying to implement.

I implement this system using the LMC662 Dual Op-Amp
Datasheet:
https://www.ti.com/lit/ds/symlink/lmc662.pdf?ts=1602456193412&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLMC662
When I run each amplifier separately using Analog Discovery 2 and waveforms, I get the expected frequency responses as shown below.

But when I cascade it, I get a funky response like this:

Why does this not work as expected?
Note: The High Pass Filter is only being used to simulated a receiver system whos frequency response mimics and band pass


texts: how to increase the voltage of a digital signal?

texts:
I'd like my Raspberry Pi GPIO port to communicate with a digital circuit that works at 2x the GPIO voltage. The communication will be at a relatively high frequency (up to 500kHz).

The main question is how do I amplify the voltage on a GPIO output pin. Will a simple 2n2222 transistor suffice? My main worry is the frequency. (Also getting the right circuit diagram and capacitor/resistor values.)

(Bonus question is for the other direction: how to reduce the input voltage. My first thought is a two-resistor voltage divider, but then again, will it work well at 500kHz?)

edit:

Obviously, I haven't heard of level-shifting and level translators. :)

However, the translators that I can see are all 3V3 <-> 5V. I'd like something bidirectional, that could operate around 7V and comfortably withstand 9V. What is the standard next step (if there is one) above 3.3/5?
(I assume there are no 3V3 <-> 7V translators ;), but maybe there's a 9V or 12V standard that has 5V on the lower end and I could serialize 3V3 <-> 5V <-> 9V ?)

Or maybe there's a simple way to roll my own translator for my unusual voltage needs? (with 500kHz in mind, of course)

edit:

Thanks everyone for suggesting a voltage translator.

Indeed, there seems to exist a higher standard - for 15V CMOS.

If I understand correctly, the signal input and output voltages can be controlled by the "power supply" voltages provided for a chip. So I can use whatever weird voltages I want, as long as I can find an appropriate power supply.

Some candidates include TI CD40109B, CD4504 and Pololu 2595.


texts: Connecting an auxiliary cable into three out of 9 serial pins

texts:
Please bear with me as I have no electrical engineering knowledge at all.

I have a device with the following connection (and connecting cable):

which as far as I understand is called an SRT connector.

In every-day use it is connected with a 9-pin serial to another device, which then uses the same connection to transmit data (The small cable is the aux going into the serial, and then another cable leaves the serial, presumably using the other pins):

I would like to bypass the second device and connect the first device directly to my computer, through a 9-pin serial, and get the info it is transmitting. that is I would like to connect it to something like this:

which I'll then be able to connect to my computer.

Is such a thing possible? Suppose I somehow manage to find which of the Ring-Sleeve-Tip is for TX/RX/Ground, and I just build a cable that connects them accordingly, leaving the other 6 pins empty, will it work?


texts: I am building an embedded device (like a phone) that will run FreeRTOS. I am using an ARM Processor. How can I make my homebrew device boot FreeRTOS? Is there a special type of storage drive that I can use to start freeRTOS?


texts: Output of non-inverting op-amp amplifier less than expected

texts:
Why does this result in a 15 V output voltage?
I played a little with different values such as 0.2 V for input, 10k ground resistor and feedback resistor of 80k and the formulas for voltage gain:
$$ V_{gain} = \frac {R_f}{R_{ground} +1 } $$
and
$$ V_o = gain \times V_{in} $$
and it worked but not with image settings.


texts: How do laptops seamlessly switch from AC wall power to battery

texts:
So this is probably a rather simple question but electrical circuits are not my forte. I have been curious about how devices, specifically a laptop, can seamlessly switch between AC wall power (plugged in) and battery power?

This has been on my mind after doing some research on Lithium ion batteries and their lifespan in laptops. Some folks say that when plugged in, the laptop is using power through the battery and simply constantly charging it between that 90% and 100% range as it goes. Now this seems rather detrimental for the lifespan of the battery, so I can't imagine that most laptops are actually doing this. In my mind the simplest solution is just running completely on the AC wall power and leaving the battery alone when it is fully charged. So the question lies in how does the laptop switch from using AC wall power to using the battery, without shutting down for that split second when you unplug the machine from the wall power adapter?

My expertise is in the software realm, so I am rather ignorant on how the actual electrical engineering works in these cases. My simple guess was that a capacitor(s) supplies the power during that short time when switching between power sources. So, could anyone please explain how this actually works? Feel free to be as technical as you'd like. I have an engineering mindset, so I find the low level details interesting.

Thanks! Also, if this is a duplicate question, feel free to close or remove it and link the answered thread. I did some searching and didn't come across a similar enough thread.


texts: Why does my crystal resonate at 4 times the specified frequency?

texts:
I have been experimenting with oscillators this week. And building a computer clock. I got two crystals, one at 2 MHz another at 4 MHz.

simulate this circuit – Schematic created using CircuitLab
everything is super simple. As soon as I stick that crystal in, it starts oscillating.
But, when I measure the frequency with my oscilloscope, I get 8 MHz instead of that specified 2 MHz. And I don't understand why?
Here is the proof. My test circuit:

Here is the scope at 0.1 μs per division. Upper wave is the output of inverter 2, the lower wave is from the additional inverter after that.

Clearly it's 4 periods in 5 divisions and 8 in 10 divisions, so 8 in 1 μs, obviously f = 8 MHz, or T = 125 ns.
How come? When I stick in the "4.000 MHz" crystal, I get double the frequency, so 16 MHz.
I thought that perhaps there is something wrong about this inverter circuit, but I tried 74LS326 and 74LS629 integrated oscillators with those same crystals and I'm getting the same 8 MHz for the "2.000 MHz" crystal.
How can that be?
Finally proof of my oscilloscope setting, and it's not off. When I measure 1 kHz audio waves they sound like 1 kHz and not 250 Hz, so my scope is not off by a factor of 4. [EDIT: this might have not have been true after all.]


texts: How to find current of different parallel components in SR Latch

texts:
I am trying to create an SR Latch with two NOR logic gates that lights an LED.  I am implementing the gates using 2 transistors and 2 resistors each.

Here is the schematic:

simulate this circuit – Schematic created using CircuitLab

The goal is for Switch 1 to be the Reset button and for Switch 2 to be the Set button.
My concern is if there will be enough current to light up the LED (I am hoping to get 5mA-20mA flowing through it).

I am confused on how to find the resistance and current because different paths split into multiple other parallel paths. (i. e. the path that \$R_2\$ is on splits into two, and one of those paths splits into two more)

I know that \$\frac{1}{R} = \frac{1}{R_1} + \frac{1}{R_2} + ...\$ and that \$I = V(\frac{1}{R_1} + \frac{1}{R_2} + ...)\$
But how do I apply this to the different paths of the circuit?

I would like to know how to find how much current is flowing through a component and how much resistance is on a path in schematics similar to this one (meaning they use logic gates implemented similarly).


texts: time domain reflectometer determining impedance

texts:
Lets say I have a 1km long transmission line with a characteristic impedance of 50ohm. With a pulse generator I inject a really long pulse (30µs) the pulse generators termination is also 50 ohm. The response will look like the image below
T
So the amplitude U/2 of the reflections is because of the voltage divider formed by the two 50 ohm impedances. When using a signal generator with a known resistance (impedance) we should be able to calculate the impedance of any cable by the amplitudes of the reflections. Is my assumption correct?


texts: Two-port circuit with input/output duality

texts:
Suppose I have a circuit with two ports. One port is considered the input, and the second port is considered the output.

Assume it's described via

$$V_{out} = \frac{V_{in}}{2}$$

Now assume there's no voltage applied to the input terminals.

Supply the output port with  5 V. If I measure the terminals of the input port, will I see 10 V?

In general, the answer is no, of course, as a voltage divider will show.

What do you call circuits that do satisfy the behavior where you measure 10 V at the input port given a supplied 5 V source at the output port? I'm asking for a general term, but using an example to illustrate what I mean.


texts: How to fix and avoid micro USB connection issues?

texts:
Some of my smartphones / tablets developed after some years problems with their micro USB connectivity.
E. g.:

Motorola Moto E 2nd Generation
Nexus 7 2013
Samsung S3

A connection could only be achieved when bending the cable / connector in a certain angle.
For the Motorola, in the beginning only file transfer problems occurred, later on also for charging. For the Samsung S3 and Nexus both charging and file transfer got difficult / impossible.
This happens for all sort of cables. These cables also work well with my other equipment.
Corrosion does not seem to be the issue: careful scratching away any rust of the socket pins did not help.
I wonder whether the circuit board developed some kind of micro fractions near the USB socket, but I am not sure.
My questions are:
1. How can I fix this problem? (perhaps by creating a 'soldering bypass' on the circuit board?)
2. When I buy new smartphones / tables: how can I avoid this kind of deterioration from the beginning? Are there any models / manufacturers that e. g. don't have the micro USB connectivity directly on the circuit board but designed it somehow replaceable? Or do some of the manufacturers use a different / thicker material for their circuit boards?
3. Is USB-C here any better than micro-USB?
My idea of using a permanent pass-through dongle is probably counter productive, as this would lead to a more frequent strain on the circuit board / socket (when having it in the pocket etc.).


texts:
I have several separate identical PCBs with identical ICs on them. It's fairly critical for this application that all the IC's are synchronized in regards to temperature. E.g. if one increases by 1 deg, they should all increase by 1 deg.

There's two solutions i'm thinking of. One is to simply enclose everything in an enclosure, and create an oven like effect, but this may also create cooling issues.

The other is to use a heat pipe that is snaked across the PCBs and thermal pasted to each of the IC's. I assume that this will help synchronize the temperatures as the heat pipe should stabilize to the mean temperature?

Is there anything else I should be looking at doing?


texts: Compute electric field in complex 3D geometry

texts:
I have a CAD file with a pretty complex geometry. I would like to compute the electric field generated by this geometry when a specific charge density is defined.

I guess I will have to go through some finite elements algorithms (which I have no experience at all, so any suggestions for tutorials and literature is more than welcome)

Could you suggest some toolboxes to simulate the electric field, or more in general to solve partial differential equations, in a complex geometry.

It is not a requirement, but I prefer to use Python or MATLAB as programming languages.


texts: Arduino and motor driver l298n separate power supply circuit

texts:
I have an inquiry regarding the l298n motor driver.

I encountered a problem while using it. It's like this: every time i attach the wires of my dc motors into the board's "motor A" and "motor B" connectors, my dc motors wont move. I re-checked my code to see if there were errors, but there were no errors both in syntax and in logic.

I also noticed, that when i test the voltages at the connectors, there is no voltage output. But every time i remove my dc motors from the connectors and test the voltages at the connectors, there is voltage output. I am confused and i dont really know how to solve this problem. I've searched as much as possibly could in the net, but to no avail.

I am hoping you guys could help me. i would really appreciate it.

Below is a diagram of my circuit. As you can see i plan to power the arduino and motor driver separately, since i am using bigger motors.


texts: Failure Rate calculation based on manufacturing defects (capacitor)

texts:
Electronics failure rates typically follow the exponential distribution and models like Prism, Mil-Hdbk-217 or 217Plus (newer) are used to predict failure rates.

We are currently in the production phase and fielding our electro-mechanical systems but there seems to be a manufacturing defect within the capacitors by the vendor where much higher failures are being experienced attributed to knit-line defects or delamination at the electrode-dielectric junction, and the failures are occurring during final testing just prior fielding or even after they have been fielded.

My question is, if the capacitor have been modeled using our assumptions (exponential dist, power, vibe and thermal stresses), and manufacturing defects or screening escapes have occurred, then doesn't this mean that our modeled failure rate is NOT relevant anymore? Even calculating a point estimated failure rate (number of failures/accrued number of hours) is pointless (pun, ha) since this particular failure trend is un-modeled and a point estimate only represents a failure rate up until that point in time, and tomorrow we could realize we have many more failures in the field and that failure rate isn't a rate as expected.

How can this new failure rate be calculated/modeled given this manufacturing defect/screening escape? I realize the best thing to do is to chase the root cause and have corrective actions in place but at this point that is difficult as there are many fielded systems already in place.


texts: Arduino resetting or malfunctioning when controlling 48V DC motors with relay module

texts:
I'm building an Arduino controlled crane machine out of old crane machine parts.
The motors in a crane machine are 48V DC and I am controlling them with an H-bridge configuration using an 8 channel relay module I got off eBay which is controlled by an Arduino Nano. I'm using an ATX power supply to power the system but I'm using a high power boost converter to get up to 48V for the motors.
The issue I'm having is when the motors are moving, 50% of the time the Arduino will either reset, or will skip a few lines of code, or sometimes the Arduino freezes and will keep going in one direction indefinitely.
It's only programmed to move to the centre of the cabinet, drop the claw until the down switch activates then raise the claw until it hits the top after that, it goes back to the corner, but it only rarely finishes it, usually it resets or keeps going in 1 direction.
I've tried 2 different power supplies, I tried powering the Arduino and relay module over USB, I tried 2 different Arduino Megas. When I try lowering the voltage on the boost converter, it doesn't stuff up as often and when I power it to 12V it hardly does it at all but 12V is way too slow for the motors.  When there is no power at all for the motors, it doesn't reset at all, but obviously that isn't useful when you're trying to make a crane machine.


texts: Servo does not stop in a stable position

texts:
I am currently playing with the HS-485HB servo, and I noticed that very frequently the servo will not stop in a "rest" position after it stops moving, even when external forces applied to it are tiny. Instead it stops in a roughly correct position and continues to "buzz", while drawing more current than it should (~30mA). If I gently tap the servo horn with my finger, it settles into the rest position, the noise stops and the current goes down to about 7mA, which is what I am looking for.

Here's a video that demonstrates the problem:
https://www.youtube.com/watch?v=GSLFnIpSqXw

What are the possible reasons for this behaviour?

EDIT: I acted on a hunch and added a 570uF capacitor in parallel with GND and +5V of the servo. This appears to have solved the problem! And it had to be that large too. For example, using just a 470uF helped the servo park properly only half the time.

I still don't know why that worked, so an explanation would be appreciated.


texts: Can a thyristor regain its forward/reverse blocking capability if the current through it is "instantly" brought to zero?

texts:
I am imagining a situation where we have several series-connected thyristors, say 10, each that can block a voltage of 100V.  So, the ten series-connected thyristors together can block a total voltage of 1kV. I am imagining, now, that in series with these series-connected thyristors is a pair of (low-voltage) anti-series IGBTs.
The rest of the circuit ensures that at t = x seconds, the voltage across the thyristors/anti-series IGBTs is zero; however, the current may not be zero.  My question is: Can I use the anti-series IGBTs to instantaneously decay the thyristor current to zero, so that they can nearly instantaneously regain their ability to block bidirectional voltages? Typically, thyristors require a turn-off time, but this is assuming natural decay of the currents through them.  I am wondering if the turn-off time can be significantly reduced if the current through the thyristors can be forced to zero.


texts:
I have a project in mind. I want to buy an LPC2294 microcontroller, SDRAM IC, and flash IC (those IC's haven't yet been defined). What I want to do is connect those ICs to the microcontroller in order to expand its Program memory and data memory automatically (which means that I don't want to have to create a method to write on the flash or SDRAM, I want the microcontroller to be able to tell that it has those resources, and use them as if they were the microcontroller's on chip memories).

I know how to connect those components physically (since NXP's site has an example of this which was really easy to understand).

My main question: Is it only necessary to connect it via hardware and put LOW or HIGH on some pins on boot for the microcontroller to recognize those external resources as its own, or will I also have to do something else? For example: will I have to alter the memory registers that point to the internal flash and RAM and make those registers point to the external components? How would I be able to put the program on the external flash?

Would I have to write a bootloader and record it manually on theexternal flash or can I just use the internal bootloader, and somehow map it to the external devices?

If someone could explain this to me I would be really grateful. And if there's some code involved, or changes to the configuration files, could you please give me an example of how it works?


texts: Can the idle state of MOSI cause issues?

texts:
I have an issue when communicating with an ADC over SPI. If I imitate the SPI protocol via bitbanging then I have no issues with communication; however, if I use the SPI hardware (I've tried Arduino and mbedOS) then communication fails and no data is received.

The biggest discernible differences are:

The idle state of the MOSI line. When bitbanging, this line is held low when idle as opposed to high when idle using SPI.
When bitbanging, the MISO line goes high as soon as CS does. When using SPI however, there is a noticeable slew.
Lastly, CS takes a relatively long time to go high after the final clock pulse when using SPI as opposed to nearly immediately when bitbanging.
The time taken to send the messages (visible in the images below). Though I can't imagine that this is an issue.

I am running in SPI mode 0, as according to the ADC datasheet. I've tried an Arduino Uno and a RedBearLabs Blend V2 (running mbedOS).

Below are two scope grabs of the signals.

Trace 1 is SCLK.
Trace 2 is CS.
Trace 3 is MOSI.
Trace 4 is MISO.

I am sending 10000000 on MOSI. The response received is not included in the scope grabs as I believe the issue is with the command sent in the grabs.

BITBANGING

SPI

Thanks.


texts: Is a switches voltage and current rating a hard limit?

texts:
I have a need for a switch that can handle 28Vdc at about ~1A.

The switches I would like to use have a rating of 24Vdc at 5A.

I would think that the limit of switch is the power, so if we take a switch at 24V and 5A, then it can handle 120W. My reasoning is that a switch can run at higher or lower voltage currents, so long as its less than the 120W (in this case). A 24V 5A switch can be used for a 28V 1A application.

Is the reasoning behind that correct ? Am I absolutely limited to 24V 5A spec'd by the datasheet ?

Example switch


texts: Calculating current required for powering multiple robots in parallel

texts:
I'm looking to power multiple robots off a single 230V mains supply in parallel.
I'm using the Micro Magician V2. I can't find out how many amps it draws anywhere but I know the motors I'm using have a stall current of 760mA so I'd guess around 1A per robot?
I will be using 4 robots with this setup
The Micro Magician states it has a:

Built in LDO +5V, 1A regulator (input voltage must be at least 5.5V) to power external 5V devices
Built in LDO +3.3V, 500mA regulator

Does this mean I can have a power supply grid with any amount of amps and the micro controller will protect the board by limiting the amps? The voltage will be around 6V in this grid once I choose an appropriate transformer.
Once I know what amps the power supply grid will need to produce to handle powering the 4 robots I can then choose a transformer?
Let me know if any of the above statements are wrong, I'm quite new to this.
Thank you!
Edit: if anyone is confused about the "power grid" part, I have prototyped this circuit and it works well: Help with a full bridge three phase rectifier powered floor


texts: Is this a good design for a 0...7 counter?

texts:
My daughter's electronics teacher recommends to realize a counter from 0...7 as follows:

It shall give an output pulse (for a subsequent circuit) when the button is hit the 8-th time.
For me this doesn't give sense: when the Outputs are 1-1 and I hit the button a fourth time, there is a race condition within the and-gates and the output of the flip flops. In my simulation it resets (see the async reset inputs) when I press button the 4th time.

Of course, it depends whether which change of the yellow marked nodes is faster...

Maybe it works by accident - but isn't this extremely bad design?

I would solve it like:


texts:
I want to plot the forward diode I vs the V
But i'm getting the wrong result probably because the x axis is not the diode voltage.
How do I change this?
I put the clamp at point A


texts:
I was able to generate I2C transmission through micro controller but still i have a doubt on certain things.

First being, if we send a data like 0x0a, then we can monitor the data as it is a single byte data.
But when the data becomes multiple bytes  like a float/integer (4 Byte/2 Byte), how can we debug whether correct data is coming or not, if we are watching through a scope?
I am sure we have to look up through the scope, but i heard compiler transmits data type in to binary for both integer and float.  I have looked up at single point precision for float and got some idea.

What is the method to check the integer/float data coming is correct through scope?


texts: Can we harvest energy from a Rogowski coil?

texts:
Can we harvest enough energy (4-5 watts of power) from a custom made Rogowski coil?
The primary conductor is 33kV and has an average current of 10A.  I'm aware of the induced voltage and the mutual coupling is weak because of the air core. There should be no other power source except a rechargeable battery or a supercapacitor for initial state of harvesting, if required. This question might be not crystal clear, so I will go thoroughly through all your answers and clarify.


texts: Difference between embedded systems and System-on-a-Chip (SoC)?

texts:
SoC, embedded systems, microcontrollers, microprocessors... I'm always really confused.

So my current understanding is:

Microprocessors/CPUs, generally speaking, are the computing core and are the base for everything else
Microcontrollers = microprocessors + memory + other peripherals like UART, USB, CAN; can be a standalone device
Embedded systems is microcontrollers programmed to do specific tasks, so normally not general-purpose
SoC is microcontrollers + advanced components like GPU, more general-purpose compared to embedded systems; has all the ability of a computer (can run OS like Linux), just inferior in performance

Please point out if my ideas are right and add anything you want!


texts: How to connect the counter below to the counter above

texts:
I am designing a synchronous DOWN counter that is supposed to count down from 20 to 00. I tried many different ways but the logic combinations I tried are obviously wrong as I am getting very weird sequences.
How am I supposed to connect the top counter to the bottom counter? Thanks.


texts: Not Able to Simulate STM32 Program In Keil

texts:
I just start Working on Stm32F070RBT6.I am using CubeMx to Configure Keil and And Keil uVision5 to simulate.I tried Blinky Example and run it in simulator mode.But The Example Is not working perfectly.I tried all the procedure available on internet but Still It is not working.After That I used Breakpoints and Step Debugging and I found That the problem is in Clock Configuration and my Program Stop At some kind of Error Handler.I can't find any solution for that.Pleas Help.
Below I am posting the Point where my Program enter into Error Handler.

  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = 16;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL12;
  RCC_OscInitStruct.PLL.PREDIV = RCC_PREDIV_DIV1;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }


texts: How to measure the negative voltage on the ADC with only positive voltage reference available?

texts:
I have a Phocos CA-08 controller where I wanted to measure a solar cell and a battery voltage with the MCU. The first thing I made was to connect grounds of CA-08 (solar and batt sockets) to MCU ground and positives to ADC inputs. It quickly came out the battery gives the power supply to the solar cell so I read the manual :)
It says (pg. 19) that all positive terminals of the CA-08 are connected (and the grounds are disconnected).
Now, I could reverse the polarity of the signals supplied to the MCU's ADCs but then I needed a reverse voltage reference - I don't have one on my PCB, I just have the Vcc and Vss as the voltage reference available.

What are the options for me now? Can I simply put the diode on the positive line of the solar cell so that the voltage doesn't go from the battery to the solar cell? Or is there other option as well?

What bothers me is what stands behind such design (positive terminals connected, negative disconnected), where is such attitude better than connected grounds?


texts: Amplifying and Reading a 0-1 V signal into Arduino

texts:
I'm trying to read the (0~1V) output of a current transformer (CT) into the 10-bit ADC input of an Arduino Nano. The CT is sensing the L wire carrying 120V at 60Hz.

Current Transformer Specs:

Input Current: 0~30A AC
Output Mode: 0~1V
Non-linearity: ±1%
Build-in sampling resistance（RL): 62Ω
Turn Ratio: 1800:1

Since the Arduno accepts analog input of 0-5V, the CT's output have to be scaled to make full use of the 10 bits.

Additionally, I think the CT's output is a AC waveform, so it would vary between -1V and +1V. If this is correct, I would need to bias the output by AREF/2 (5V/2 = 2.5V) by diving the 5V and GND rails equally using a potential divider made out of 2 resistors.

How should I scale the 0-1V to 2.5V, assuming the output vary between -1V and 1V? Is there a solution that will both amplify the CT's output signal and bias it as well?

The circuit I'm using currently looks like

and a plot of the analogRead() values is shown below, where the x-axis represents the index number of the ADC sample, while the y-axis represent the ADC value (0-1024). Sampling rate is about 9 kHz (110us per sample). Peak-to-peak difference is about 55 samples, giving us a frequency of 165 Hz.


texts: i want to know if the potentiometer is broken or just dirty and if it's broken can i find the same in the market?

texts:
Hi i have speakers labtec arena 530 . i opened the main speaker and the problem is from the potentiometer
I can make a brigde and connect 2 pot of the potentiometer  sound become clean but i loose the volume control
how to know if it's dead or just dirty and can be cleaned  ?
and can i find the same potentiometer if it's dead (there is no réference . i found the same look potentiometer in the internet but it seems not having the same size ( pot found : circular 16*2 mm | pot i have 20 *  3 mm )
Thank you for help !!


texts: Convert logic signals to be able to supply/sink higher currents

texts:
I am making a LED matrix and have the required logic in place to drive the unit. My problem lies in the fact that my matrix is 80x56 diodes large and requires a fair amount of current. Each diode is rated at 20mA with a voltage drop of 2V across.

The screen is scrolling across the 56 columns, meaning that there are maximum 80 diodes lit at once. This translates to a potentioal power draw of 1.6 A. I have 10 8-bit latches representing the logical values of each lead across the displaying column. Is there a way i can draw current from an alternate source with the voltage values coming from the latches?

I have a possible solution consisting of connecting 80 voltage followers to each line but this approach seem very tedious.

This problem translates to the opposing axis where i have an array of demux chips outputting one logical low and 55 logical high at a time. Any way to sink 1.6 amps into the pin that is low?

Any input is appreciated :)


texts:
I have some LED fair lights that run on 30V @ 0.4A supplied from an AC mains supply.  They have been wired to flash using some form of notification to the AC (I'm not interested in them flashing).

I want to wire them from a battery I have at 30 V (off a balance board) but a direct wiring only lights half of the lights.  If I switch the polarity the other half (only) light.

It's going outside so I don't want the original adaptor which needs a minimum of 110 V. Is there a simple fix to make this work?  It's only a simple project - so cheap and simple.


texts: SIM900 SMS timestamps are not accurate enough

texts:
I'm experimenting a bit with a SIM900 module and a Raspberry Pi. I can communicate with it and receive/send SMS messages. However, there's a problem when a message that exceeds the 160 character limit is sent.

When a message, longer than 160 characters, is sent it's actually sent as separate messages under the hood. And then the receiving device needs to glue them together again. I've got that part working, but I can't always glue them together in the correct order.

And that's because each message has a timestamp that's only accurate up to seconds.

Is there a way to get more accurate timestamps with milliseconds? I've been looking at the datasheet but haven't really found a way.


texts: Confused with the formula for Power Factor Correction

texts:
The formula provided in my lecture notes:
$$C=\frac{Q_c}{\omega \:V_{RMS}^{\:2}}$$
Where $$Q_c=Q_{old}-Q_{new}=P\left(tan\left(\theta _{old}\right)-tan\left(\theta _{new}\:\right)\right)$$
Such that \$\theta\$ is the power factor angle, \$P\$ is the real power and \$Q\$ is the reactive power.
I've tried starting with $$Q_c=I^{\:2}_{\:RMS}\left(X_L-\left(\frac{X_LX_C}{X_L+X_C}\right)\right)$$ and then solving for \$C\$ but that didn't help.

Here is the circuit, \$C\$ is the capacitance of the parallel capacitor that should be added in order to get the desired power factor correction.


texts: Why is 10W resistor getting hot with only 6.5W running through it?

texts:
I am running about 6.5W though a 10W resistor. The ohm rating is 220 ohms, which is correct for the circuit ohms which is calculated to about 225 ohms.

Here is what is running through my 220 ohm 10 watt resistor:

38.4 volts
0.17 amps
225.88 ohms
38.4V * 0.17A = 6.528W

Within a couple minutes it got so hot that it burned me. I'm ok though because I only touched it for a second.

But I was expecting it to stay cool since the resistor is rated at almost double the power that is going through it. The electronics people told me that it shouldn't get hot with double wattage.

Is this normal? Why would the resistor be getting hot? Also, is there a fire risk? p.s. The resistor is resting on brick.


texts:
I designed a new electronic card which has a STM32F4 microcontroller on it. Each peripheral except the Wifi module works. Wifi module is supposed to communicate with the controller via USART channel but I failed to connect RX/TX pins to a USARTx module of the controller. So in brief, the RX/TX pins are connected to simple GPIO pins by mistake. I don't want to modify the electronic card and make it reproduced, it will cost me a lot.

The question is can I write a homemade USART driver for a STM32F4 microcontroller in order to communicate with the Wifi module with using 2 GPIOs (1 for RX and 1 for TX)? I did it many years ago for I2C but I'm not sure if it can be possible for USART.


texts: Is RL-AC circuit's current higher at the first time?

texts:
I've solved the differential equation of the current function of RL-AC circuit.

And then I've checked the plot(graph) and found that the first period of the current is higher.

Why is this happen? Am I missing something?


texts: Can a low current (low power) solar panel charge a battery?

texts: I have a solar panel that provides max 7V and average 5.5V under the sun. But it cannot produce enough current even for a little 3V DC motor. Can this solar panel charge a 3V battery? Or maybe two 3V batteries?


texts:
here below is a TIA stage intended to do I-V conversion, as the maximum supply voltage being 5V for a given feedback resistance of 1K the opamp would saturate for a input current from photo diode of 5mA

lets assume the current be pulsating , what happens if more than 5mA current is given to opamp, obviously it would saturate and after a override recovery it would retain its state again

lets say if my input now is 100mA from the photo diode(which i consider the saturation/close to saturation of the photo diode), as saturation occurs the feedback path would only have 5mA of current flowing in its loop

where exactly has remaining 95mA of current has gone ??? the opamp input doesn’t allow it to pass any way due to very high impedance,

or as it crosses the input current limit, it would burn/enter in to high impedance input even ?

i am beginner to opamp, i have read it and understood it as black box only,
please give me some reference on how an opamp in saturation should be understood, what is the limit of current here even,


texts: How to make 4-20mA Sink Generator to Simulate with PLC or other 4-20mA Instruments?

texts:
I want to test Pressure Transmitters without actually pressure available in LAB. So I want to make 4-20ma Simulator.
I changed my Title to 4-20mA Sink Generator. As I am referring to 2 Wire Transmitter System.
I want to design Sink generator like this with Digital Display.
So switching the Transistor on/off with some fixed PWM Frequency and measuring current accurately using the INA219 module will do?


texts: Shift registers - inductive load vs resistive load

texts:
CONTEXT
I've been working on a project consisting of a matrix of relays switching on and of various capacitors. No need to delve into details here. Classic relay operation - optocoupler, bootstrap diode and so on. I'm using shift registers operated by a uC to drive a relay's coil low to activate the contact. The shift registers I'm using are TLC6C5816-Q1. Relays' coils are on 24V rail, steady state current flowing through one coil is approx. 0.017A. I haven't noticed any reasonable peaks. This is also the current flowing through a shift register pin. According to datasheet the maximum should not exceed 0.050A
After a few hours of testing I noticed that one out of 10 registers broke down and is constantly driving one out of 16 outputs low (default is high). It's still switching the other pins the way it should (according to configurations sent by a uC). The fault disappears after the register's reset (all outputs are switched off by default) and comes back after the first configuration by a uC. It looks as if one bit of the configuration register was no longer writable and was permanently set to 1 disregarding the configuration that is loaded by a uC.
QUESTION:
The shift registers TLC6C5816-Q1 are intended for use in automotive LED application (i.e. resistive loads). Yet I'm using them for relays (i.e. inductive load). Is this a poor engineering concept? In other words, should I aim for shift registers intended for use with inductive load? Would you recommend any?


texts: Determining memory address width from memory size

texts:
Given a computer A with 1024 x 16 memory and a computer B with 16K x 32 memory, how big are the registers of an Accumulator, program counter, instruction, temporary register, address register, data register?

Computer A we have 1K of words that are 16 bits each.
Computer B is 16K of words with 32 bits each.

My understanding is that DR, AC, IR, TR are simply the size of a word. So they are 16 bits for computer A and 32 bits each in Computer B
But AR and PC depend on the width of a memory address. How do you determine a memory address from the 16K x 32 memory information?


texts: BJT NPN Switch not fully turning off under certain conditions

texts:
My first post here, I'm relatively new to electronics and this is my first project that I'm trying to accomplish myself.
First off, some background of what I'm trying to accomplish. I am trying to build a CD Emulator for VW Golf MK5 and have it use a bluetooth module. I have got the emulator and bluetooth part sorted out, my only problem right now is the transistor switch.
I have got this circuit:

Please note that U4 (JST-XH-04) connects to a 12V to 5V DC-DC Voltage regulator, I haven't marked the regulator in the schematic. VCC is 12V.
Both VCC and signal come from the radio, VCC is always on, even with car locked and key out, the signal however is at around 11V when the radio is on (it switches between 12 and 11 depending if engine is running or not) and is off when the radio is off.
Now if I plug in U4 GND and 5V to a USB (off a power supply or computer usb port) and plug in J1 Signal to another usb port (5V) everything works exactly as expected (note: the bluetooth module doesn't have enough power to play songs in this state, as the base resistor was chosen for 12-11V, however it still turns on and connects to the phone, as does arduino). So, using 2x usb cables and connecting them to the 5V, GND and Signal lines, this circuit works exactly as I would expect - when signal is low, circuit is off, when signal is at 5V, the circuit turns on.
However, when I connect it in the car, about 70% of the time the circuit does not fully turn off. At first I thought it could be a floating base, so I connected it to ground through a resistor (should have done from the beginning, but better late than never..).
Then I thought it could be a bad transistor, but I have tried 4 different ones now. I have also tried swapping collector-emitter, just in case I got it wrong, but the resistor went up in smoke fairly quickly when i tried that, so the polarity is also correct.
I have only 1 idea left - somehow the arduino grounds itself through CLK/MOSI/DATAIN, and the circuit completes that way. What should I check to confirm/dismiss this possibility?
Am I missing something? Does anyone have any better ideas?
Again, this is my first project where I'm trying to figure things out on my own, so my terminology or approach will be far from perfect, but I thank you for any and all help.
The circuit is available at https://easyeda.com/binginsin/rcd300-cdc . Anyone is welcome to add to it.
UPDATE:
I have done some testing and found interesting results - on my 2x USB setup, I connected CLK / MOSI / DATAIN to ground without connecting the Signal. This ended up turning on the circuit, so the Arduino just grounds through it's digital pins...
I will do some measuring in the car as soon as I have a chance - I will check if any of the CLK/MOSI/DATAIN lines have a connection to ground (car chassis) when the radio is off. I expect it will have a connection to ground with quite a high resistance. If that is the case, how would I go about ensuring that the arduino does not ground itself through the digital pins? Is that even possible? Is my arduino a dud?


texts: Increasing Potentiometer Sensitivity with Passives:

texts: Imagine a linear potentiometer with a 180 degree rotation range connected between +5 V and 0 V.  Turning the potentiometer from 0 to 180 degrees will sweep through the entire voltage range.  I would like to sweep through the entire (or almost the entire) range of voltages while only turning the potentiometer through part (say 45 degrees) of its total rotational range.  Obviously this can be accomplished with an op-amp, but is there a way to do this with only passive components?


texts: How does a rectifier demodulate radio information and why does its capacitance matter?

texts:
I read in a forum “A point contact diode like OA79 should be used for the demodulation of AM. This diode is a signal diode and is having a low junction capacitance because of its special construction. If a rectifier diode is used for this purpose, the junction capacitance may form an undesirable leakage path ( a bypass) across the diode because the carrier is a RF ( IF in the detector).”

I don’t quite understand what is meant.

How does a diode demodulate the radio signals and why its capacitance matters? Can this be answered with a simple circuit model?


texts: I Want to know how to design good class A amplifier of 10W for 8ohm load. with common emitter stage for input and emitter follower for output.with minimum component quantity.first stage is below Vc is about 12.34V and Ic is 6mA maximum 10 mA. I have 25 v 4A supply please help with detail.


texts: How to dimension a power supply transformer?

texts:
I always hesitate when dimensioning a transformer for a DC power supply, and I guess I sometimes overdimension them. My confusion stems from the difference in transformer and DC voltage.
If I need 10V DC @ 1A, will a 10VA transformer do? My gut feeling says I need more, so I use a bigger transformer, but how much bigger does it have to be?


texts: Audio from Arduino Due's analog outputs to line-in

texts:
Line inputs are high-impedance, Wikipedia says around 10kΩ. Due's DACs provide 0-3.3v (actually less) and are rated at 3mA max. \$\frac{3.3\rm{v}}{10\rm{k\Omega}}=0.33\rm{mA}\$.  According to Wikipedia line levels are 0.316 VRMS for consumer-grade and 1.228 for professional equipment. 3.3v = 1.18 VRMS.

Then, can I assume driving a line-in won't break my DAC or line-in?

I found Groovuino which uses just a 500Ω resistor between the DAC and line-in, but it seems odd he got it working without any DC blocking. Perhaps the device he's plugging to is doing it for him?

Should I put a capacitor around 10μF between the DAC and the line-in just in case I plug somewhere without DC blocking? Is there any reason not to?

Groovuino's 500Ω resistor is very small compared to line-in. Why is it there? To plug headphones? Perhaps also to protect the DAC from an eventual short to ground?


texts:
I charge my iPhone 4 right next to where I build my circuits, so I'm always simultaneously looking up datasheets, texting and so on. What's interesting is whenever I touch the rail/antenna of the iPhone, and any grounded part of the circuit, I feel a searing heat and surge of current focussed on the spot where contact with the circuit's ground is made.

Why is this? I measured for current and voltage just with a multimeter and found nothing. Is it the positive signal of the antenna being shorted to ground?

Thanks.


texts: This model of a D-Flip flop with Enable not working as expected

texts:
This is a Verilog model of an array of D flip-flops with enable line along with a test bench used in ModelSim Altera:

module Register_Design #(parameter Width = 4)
(
    input Clock, Reset, Load,
    input  [Width - 1:0] In,
    output reg [Width - 1:0] D
);
    always @(posedge Clock or negedge Reset) begin
        if(~Reset)
            D <= 0;
        else if(Load)
            D <= In;
    end
endmodule

module Register_Design_Test;
    reg Clock, Reset, Load;
    reg [3:0] In;
    wire [3:0] D;

    Register_Design #(4) REG0 (Clock, Reset, Load, In, D);

    initial fork
        Clock = 1'b0;
        Reset = 1'b1;
        Load  = 1'b1;
        In    = 4'h0;
        #2 Reset = 1'b0;
        #10 In = 4'b0010;
        #20 In = 4'b0100;
        #30 In = 4'b1000;
        #40 In = 4'b1100;
        #40 Load = 1'b1;
        #50 In = 4'b1111;
        #70 In = 4'b1110;
        #80 In = 4'b1100;
        #90 In = 4'b1000;
        #100 In = 4'b0000;
    join

    always @(Clock) #10 Clock <= ~Clock;

    initial #500 $stop;
endmodule

Here is a picture of the simulation output:

As you can see despite the Load input is being 1 which should load a new value into the D flip-flops, the output is always 0000 which is the default state at reset. What am I missing here?

Instead of using a behavioral dataflow model, I used this one and it worked just fine:

D_FF D0 (Clock, Reset, M[0], D[0]);
D_FF D1 (Clock, Reset, M[1], D[1]);
D_FF D2 (Clock, Reset, M[2], D[2]);
D_FF D3 (Clock, Reset, M[3], D[3]);

MUX_2x1 MUX0 ({In[0], D[0]}, Load, M[0]);
MUX_2x1 MUX1 ({In[1], D[1]}, Load, M[1]);
MUX_2x1 MUX2 ({In[2], D[2]}, Load, M[2]);
MUX_2x1 MUX3 ({In[3], D[3]}, Load, M[3]);

module MUX_2x1 (In, S, Out);
    input  S;
    input  [1:0] In;
    output reg Out;

    always @(*) begin
        case (S)
            1'b0:    Out = In[0];
            1'b1:    Out = In[1];
            default: Out = 1'bx;
        endcase
    end
endmodule

module D_FF (clk, reset, d, q);
    input d, clk, reset;
    output reg q;

    always @(posedge clk or posedge reset) begin
        if(reset)
            q <= 0;
        else
            q <= d;
    end
endmodule


texts:
I am using 75leds  having forward voltage 3.3-3.4V and 60mA forward current. I connected 3 in series with a 39ohm 1/4watt resistor. My power source is a 12-0-12v_3A transformer with a rectifier circuit.
The problem is when i connect the leds the resistor begins to smoke. Is it because of my power source?


texts:
Using thevenins or norton theorem, we can easily find current through the resistor as 1 amps.
But if we convert the current source to voltage source , current turns out to be zero amps . Why?


texts: I have a (unregulated) wall wart that feeds into a regulator circuit. The wall wart is rated 24V nominal, and measures 23V when open with a multimeter set to DC. When connected to the regulator it measures 35.5V, but the input capacitor on the regulator is only rated 35V. I don't/haven't seen any damage yet, but should I be worried over the long-term effects of this?


texts:
Can somebody briefly explain the different types of grounding with examples?

Chassis ground
Earth ground
Signal ground


texts: Controlling high voltage devices with Arduino Relay module

texts:
Goal: I want to build a circuit that converts 700V DC supply to 700V pulses of 15ms duration.

From what I have learnt from online, is that Arduino controller can be used with Relay module to control such high voltage. But the voltage is limited to 250V AC or 20-30V DC.

Question: Is there any specific relay module that can control such high voltage (700) that can be controlled with Arduino. If not any other ideas are appreciated.

(Update on the question, adding details)

I am trying to do electroporation for zebra fish embryos. The details can be found here. For that i need two pulses of 0-700V of 15ms duration
which will create 3500V/cm electric field. My lab has already bought Trek Model 2210 as DC source which will vary from 0-1000V. I have to design a pulse
generator which will generate only two pulses of 15ms duration and 700V. More than two pulses will destroy the cells. My plan is to

Arduino----Buffer circuit---relay/power MOSFET (will be connected with 1000V source)---cell

When the Arduino will provide voltage to relay it will switch on and supply the voltage 0-1000V. How long it will stay on will be controlled by ARDUINO.

However, i am not getting any relay which can handle such high voltage. I am open to suggestions how i can solve the problem.


texts:
I am working on a project which requires low power persistent storage. It needs to store 1 kB of data at most. The data is organized in blocks logically. So, a update of one block requires 100 B to be written to storage.

The project will be powered from a coin cell so it needs to be power efficient.

Low endurance of flash is not a problem. The deciding factor for my project is power, cost and write speed.

25LC640 EEPROM datasheet at http://ww1.microchip.com/downloads/en/DeviceDoc/21223H.pdf states that it needs up to 5 ms to write a single byte. So, to update my logical block, it would require 500 ms. This is the problem for my project.

I need to decide whether to use flash or EEPROM and deciding factors are cost, power and write speed.

Please help by telling me typical write speed, cost and power of flash and EEPROM of approx. size 1 kilo bytes.

Edit-1 :

I understand that they will be trade-offs.
All I want from this community is to share their design experience with me. I am not asking for a particular product. I am looking for typical figures for cost, power and write speed.

Edit 2:

My project is a BLE device. It needs to store bonding information, service context, application context and other information persistently. I am implementing a very simple filesystem and each information can be stored in a file. The problem with larger write cycle is that i can't write data instantaneously and i have to queue the request to store the data persistently. It may lead to inconsistent state in my device. Again, i can solve it by making my firmware smart enough but i want to look for other alternatives from the community.


texts: Is there any XML schema to describe electric/electronic circuits? I am thinking of something like a netlist, but using XML markup.


texts: Please review my schematic for vision processing kit - Raspberry Pi Compute Module 3+ and camera

texts:
I'm very new to board design and i want to get a review for my schematic.

I'm making a vision processing kit using a Raspberry Pi Compute Module 3+ and the Raspberry Pi camera that can be powered using passive PoE or a 12 V input.

There's also an extra USB port to connect external devices and a USB Micro-B so I could flash the Pi. Please tell me if I did everything correctly and if I can improve my design.
Thanks.

schematic as pdf


texts:
If I want to calculate the resistance between \$a\$ and \$b\$, that is,  \$R_{ab}\$. How do I calculate the equivalent resistance of this kind of circuit? All resistors are \$22Ω\$

I know we we ignore the resistors between two point, take a and b for example, if we want to calculate the equivalent resistance between \$a\$ point and \$b\$ point, but in here, I am not sure about which resistors should I ignore first, R1~R5 resistor?

The answer is \$R_{ab}=10Ω\$, but I don't know how to calculate it! Can anyone teach me how to calculate the resistor between \$a\$ and \$b\$, that is, \$R_{ab}\$?


texts: Does an oscilloscope subtract voltages as phasors?

texts: I want to measure two voltages on an oscilloscope. They are not in phase. I want to know the magnitude of the voltage difference. The oscilloscope has an in-build math function to subtract the voltages from each other. But does it do that phasor wise ? Let us say V1=10V and V2= 15V and the phase angle is 20 degrees. We want the magnitude of V1 - V2. Does the oscilloscope give 5V, or does it take the phase into considerations when subtracting ? I am using the tektronix TDS 2024C.


texts: Is it possible to power down all the PLLs and VCO of a MAX 10 Device?

texts:
We are developing a board in which we would like not to use the analog features, like PLL, VCO and ADCs of a MAX10. UG-M10CLKPLL par. 2.3.6 states : "The only time that the VCO is completely disabled is when you do not have a PLL instantiated in your design". Does it mean that without instantiations of a PLL in the design we can assume that all the VCO are powered down or do we also need to connect to GND the VCCA pins? Unfortunately this last action does not accomplish what suggested in PCG-01018, which states "Connect these pins to a 3.0- or 3.3-V power supplies even if the PLL and ADC are not used" on Table 7.

Thank you


texts: How to solve this exercise to find maximum average power

texts:
How can I proceed to solve this exercise? I know that pMAX= |VTh|^2 / 8 * RTh
I tried to calculate the Thevenin Resistance, but I didn't manage to do it, because I can't put together anything in parallel or in series so I really don't know how to find it here.
For the Thevenin Voltage I have the same problem, I don't know which "tactics" I could use here to find the voltage.


texts:
Working with circuits to get high input impedance. This is to capture signals while introducing as little interference as possible to the preexisting circuit, to load the source as little as possible. One circuit I asked about here before used an instrumentation amplifier design. But there was a problem with input bias and the recommendation I got here would lower the input impedance a lot:

By adding the two Rbias resistors the input impedance would be lowered. This is a partial circuit showing the recommended addition of two 100K resistors. The op amp has a 200 picoamp input bias, so perhaps a larger value could be used?

In another circuit I am working with there is a higher input impedance.

Has anyone had any experience with this circuit configuration? I think it is called a Bastode circuit. It is for a very different application than the in-amp one, but there is the same requirement: the source of the signal must not be affected in any significant way by connection of the circuit. It is really more of a level shifter as well as to isolate the source from interference.


texts: Is it possible to accurately calculate how long a Li-Ion cell takes to charge?

texts:
Since Li-Ion cells are charged using both Constant Current and Constant Voltage modes during their charging cycle, and the transition between these points depends on the cell voltage. Is there an accurate way to work out how long charging for a specific cell would take?

The naive approach of just dividing the capacity by the charging current won't work by my estimation as the CV mode is by far the longest segment of the charging cycle.

Assuming I'm using a single cell (for example LG HG2), how would I calculate the ideal charging time, taking into account CC/CV modes?

Edit: I am specifically asking about how to calculate how long a Li-Ion cell would take to charge given its datasheet parameters. I do not want to apply hardware to this problem yet as I know Gas Gauges can be used to measure SoC


texts:
Very newbie in the field of electronics and starting to learning about it and playing with EasyEDA.
I'm copying a schematic and can't find the component I show in the  named NM. What is it?


texts: Charge board timer conditions/disabling - mcp73213

texts:
Datasheet for MCP

The MCP73213 has a built in timer.  In the datasheet it states the typical timer elapsed values are 0(disabled) 4, 6, and 8 hours.  The conditions column is empty.

I need to disable this timer, or at least set it to 8 hours (or max allowed time).  Is there any way to?  I have contacted Microchip support with no response.  Has anyone had success with their support?


texts: Is this phenomenon capacitive coupling or human antenna effect?

texts:
I injected a 90 MHz signal into an electrical cable via a signal generator. And I used a spectrum analyzer to measure the signal strength of 90 MHz at the other end of the cable. Then I found the measurement changed when I was walking around in the room. The changes were not so large, but detectable.

I have been told that the human body can pick up the radio frequency signal as it is a conductor. But I am not sure why the signal along the cable also changes


texts:
What is difference between single and common cathode configuration? If I want to use 2804 for rectifying, will it act as 2800?

HSMS2800 https://datasheet.octopart.com/HSMS-2800-BLKG-Avago-datasheet-7087620.pdf


texts: Contactor vs. Breaker-type Automatic Transfer Switches

texts:
What is the difference between a contactor-type and a circuit breaker-type automatic transfer switch?

See example products at Eaton.com.


texts:
I want to generate a precise frequency in the 500MHz range, and have therefore purchased a VCO (200MHz to 400MHz).

To measure the VCO output frequency, I'm trying to build a high frequency counter up to 500MHz.

The way I have been trying to do it, is using the MC100E016 (ECL Synchronous Binary Up Counter). Take the Q6 (/64) output and feed this into my oscilloscope (and later MCU). But this seems hard to get to work, because the PECL logic sets high demands on the input.

Do you have any good and easy way to build a frequency counter, or even just a divider would be fine (my 100MHz oscilloscope can measure the output from the divider).

Or even better, generate a 200MHz to 400MHz range frequency, who's frequency can be set (digital or what ever).


texts: Another opamp question. Most opamps seem to be voltage feedback amplifiers (VFA), but there also seem to be current feedback amplifiers (CFA). When would you use a CFA, and what are their (dis/)advantages?


texts: How to implement "burst" functionality for bare-bones function generator

texts:
Some fancy function generators have a burst feature which gives precise control over on-time and periodicity of the desired waveform.
Ex: For my application, I have a 25 MHz sin wave (2.5 Vpp) and, in the burst settings, I could set the following:

Number of cycles = 10 cyc

This would mean that my on-time would be only 5*(1/25e6) = 400 ns

Burst period = 50 us

For my application, the period must be greater than or equal to 50 us.

However my function generator, which is actually just an oscilloscope (Rigol DS1104Z+) with 2 programmable sources, does not have this burst feature. I tried to find some workaround by looking through the source related commands in the programming guide (pages 125–136) to no avail. The closest I got was using the built in amplitude modulator with a square wave envelope but there is no way to control the duty cycle.

If there is no programmatic way to obtain this functionality, is there an easy (and cheap) way to do this with simple external hardware?


texts:
I'm trying to determine the common mode gain and differential mode gain of the follow amplifier.

Now I understand what the common mode voltage and differential mode voltages are, but I'm unclear as to what the common mode gain is. My best guess is the output voltage / common mode voltage.

Also how would I go about determining these given the current mirror connected to the emitter of the amplifier?

Appreciate any help.


texts: I have two PCB which has PIC32 as a Controller and two serial port. I tested the 1st PCB and serial port was working fine. I was able to send and receive data. But when I started testing the 2nd PCB, it was only sending the data but was not able to receive any data. I am testing it by using a simple UART code. Both the designs are same. The Tx Rx pins of the controller are connected to a MAX232 IC and from MAX232 IC, a serial connector is connected. I tested for any break in the track but everything seems to be alright. What can be the issue.?


texts: Process corner variation in analog circuit design

texts:
I have designed an LPF demodulator. In a normal situation it's working fine, however when i carried out the Process corner simulation, the threshold voltage of MOSFET changes which is obvious, due to which MOSFET's operation region changes, ultimately change the output.
My question is :
1-How to deal with the process corner variation?
Note: I have attached the simulation circuit along with the table which illustrates variations in : Threshold voltage, Id, and region during different process corners.
Region: 0 "cutoff"; 1 "linear"; 2 "saturation"; 3 "subth"
Process Corners:
tm = Normal situation
wp = worst-case power
ws = worst-case speed
wo = worst case one
wz = worst-case zero
Thanks.


texts:
I would like to know if there are any applicable standards when coding microcontroller firmware (ARM) in order to achieve a specific quality level.

In my case, I would like to code firmware for a consumer IoT BLE device.

Something similar to IPC standard when routing a PCB.


texts: please tell me in the following link (https://www.onsemi.com/pub/Collateral/ESD9101-D.PDF),  the ESD diode with zener configuration is equivalent to a circuit containing diode,  transistor and zener diode,  so how this could be equivalent and how this equivalent circuit works


texts: i want to know the cut off frequency on the 2 OPAMPS ... Do I take 6K resistor and 5K resistor for OPAMP#2

texts:
I hope some one can check, I have a signal coming from a source and it goes in to 2 OPAMPS, and both has to be checked for cutoff frequencies...
I know 1/2*pi*RC is the formula but my question is how to calculate in case of resistor R1 and R3 and R2

How do I know what is Cutoff in this case? the knee is too broad to know...


texts:
Hi, I received an electronic card to repair. The user says that it doesn't work and didn't say anything more, such as why it was broken or which part is not working.
So I want to plug in an energy source to the board to check capacitor's voltages, or if is there too much warming parts on board. But I dont have any experience on this kind of board, this is the first time that I get a sewing machine's electronic board.

this question is for general situations.
If I want to give energy to an electronic board, how should I do successfully? There is a 250V 6.3A fuse, and there are fuse varistors which are 220V rated. Also there is a GND point on board (first image) left up, at the side of varistor and a +33V point just below the fuse. There are lots of clues. How can I give energy to this board, reading correctly thoses clues?


texts: can someone help me or point me to a site or supplier. I would like three or four lights (each say 60W 120V) to fade in and out. The fade time should be about 15 seconds. The lights should be bright for say 90 seconds. The application is: I perform live music and would like a minimal lighting setup but NOT flashing lights. The music is Portuguese in a small restaurant so the lighting needs to be subtle. Many thanks, Alan


texts:
This is my first DIY wiring project, I'm taking an RGB LED and using four potentiometers to control (1) overall brightness, and (3) each color level.  Wanted to make it simple.

For my purposes, all it seems I just need to use them all as variable resistors. But there are a couple thing's I don't get which I'm sure are obvious to most, but so incredibly basic it's basically assumed I know.  Like it would be insulting for an article on resistors to say what I'm looking for.  So these questions may seem dumb and I apologize for that.

If I have a 10K resistor and a hot wire (construction lingo) with less than some amount called f(10K) (that can be found using a function I don't know yet), nothing will pass through right?  Or does a relatively small amount pass through, but never zero?
I can't figure out what the difference between a voltage divider and variable resistor is.. kind of.  Mostly what I don't get is whether or not the resistance between far left and right is ever less than full (in this case 10K).  And if the resistance is always the full 10K, then it seems like the outer one would never change (with knob turn), while the center one would.  Which is just the exact same thing as a variable resistor, but with a wire coming out the other side that has 10K resistance on it.  Or maybe the divider configuration changes both, but then it would be like two Variable Resistors that just share one knob.  Or maybe they could be used like an amplifier, but no.. the knob does the variable resistance.  Point being, I don't get what a divider does, or how, or what for.


texts: Is it OK to have a connection between 0 and PE on a DC device?

texts:
I have a device meant to be used inside electrical cabinets. It has a metal casing and is powered by 24V DC. It has three power connectors: 24V, 0V and PE.

I was surprised to find out that 0V and PE are shorted, as well as the metal casing. I was under the impression that this was not OK. Is this an actual issue or are they allowed to make such a device?

As a side question: is there anything to be gained by shorting earth and zero inside a device like this?

Edit: The actual device that got me to ask the question is a strobe controller IPSC2, currently owned by Mavis/Framos.

It's basically a programmable pulse current source for powering LEDs in machine vision. It doesn't really have a datasheet, but there is a manual on the original manufacturer's website:

https://www.smartek.vision/media/downloads/SMARTEKvision_StrobeController_User_Manual_v2_2_1.pdf


texts:
I have bought a webcam from which I would like to remove an LED (burning it is also fine for me).

By doing so, I could obviously change the way the circuit works, so my questions are:

Should I remove the LED (or its resistor) or burn it?
Is a burnt LED short circuit or open?
How can you be sure of what to do? Is there a convention for connecting LEDs?

By the way, the guy here just snapped the LED right off, but I couldn't understand how did he figure out that that won't damage the camera.

Also, there's this project, which shows the insides of another camera (which looks very much the same as mine)


texts:
I bought the LDR NORPS-12.

I tested it in a completely dark room and the resistance keeps increasing after 1 mega ohm. Right now it has reached 5 megaohm. Why is that so?


texts: Why does the Oscilloscope show a longer period of time than my code sets?

texts:
So I'm programming a TSL1401R-LF line scan camera module that reads in a a 1 X 128 array of pixels. I've run into a problem with the accuracy of the output. Basically the camera becomes less accurate as the delay times decrease. For debugging I hooked it up to an oscilloscope and monitored the SI and CLK pulses sent to the clock as well as the analog signals coming from it.

That's why I noticed the the duration of the CLK signal appeared to be over 300 microseconds long. This is strange because my code sets the duration to 170 microseconds. Since this is my first electrical project I'm not sure what to make of this so I'm hoping someone can take a look at my code and a screenshot of the oscilloscope and let me know if what I'm seeing is natural or not.

Here is the code:

int delayTime = 170;

void timming()
{

  //The timing for the impluses was found through direct experimentation.
  //(Meaing that I played around with different delayTimes until the code worked)

  digitalWriteFast(SI, HIGH);
  delayMicroseconds(delayTime/2);
  digitalWriteFast(CLK, HIGH);
  delayMicroseconds(delayTime/2);
  digitalWriteFast(SI, LOW);
  delayMicroseconds(delayTime/2);
  digitalWriteFast(CLK, LOW);
  delayMicroseconds(delayTime);

  for(int i = 0; i < 129; i++)
  {
    digitalWriteFast(CLK, HIGH);
    delayMicroseconds(delayTime);
    digitalWriteFast(CLK, LOW);
    delayMicroseconds(delayTime);
  }

}

Here is the screenshot

The yellow Line is the SI pulse, the light blue is the CLK pulse and the purple is the analog output.


texts: Building a series RLC circuit using a given resonant frequency and bandwidth value

texts:
Assuming that we have to build a simple series RLC circuit in such a way that the its resonant frequency must be 200 krad/s and its bandwidth as 20 krad/s, we have these components:

Resistor: 1000 Ohms
Inductor: 2.5 mH
Capacitor: 2.5 nF

We can add or remove any components as we wish. Now, I have done the calculations using the resonant frequency formula (1/sqrt(L*C)) and the resonant frequency is twice the original value (400 krad/s). Is it possible to add more inductor/capacitor or other components to modify (decrease) the resonant frequency of the circuit? Or is it impossible? Any clarification is helpful.


texts: Input circuit - Current and Voltage calculation

texts:
I have

Input voltage : 6.5V
Zener breakdown is 3.6V.

Does the 3.9K and 4.7k ohm resistor acts as a voltage divider? or what purpose does the 4.7k ohm serve?

And can someone help me how to calculate the current through 68k ohm resistor?


texts: Method for Measuring Power Flow in a Distribution Network?

texts:
Considering a mostly meshed distribution network (with some radial spurs) connecting zone substations (loads) to grid exit points (GXPs or sources). I am attempting to find the proportion of the network each loads utilises i.e. what proportion of the total power flow in a particular constituent part of the network does each load contribute? I would also like to then do a similar analysis on embedded generation, for example, a small hydro or wind plant connected to one of the zone substations, how much of the total capacity in the constituent parts of the network would this generator utilise?

There are three main constituent parts that make up a network, these are sources (both embedded generation and GXP), zone substations (and their loads), and lines. There are also shared assets, for instance, ripple injection plants, backup lines (lines normally out of service), but these can be ignored.

Before embedded generation needed to be considered this problem was normally solved by a "superposition", where all but one substation/load was turned off and the power flow in each branch/part of the network was measured using a load flow program. This was repeated for every substation on the network (sharing the same GXP) and the load flow results for every branch were then aggregated together to give a total. The proportion asset utilisation was worked out by then dividing the load flow results for a particular zone substation (load) by the aggregated total for that particular constituent part of the network. This method does however have a problem in that there is squared relationship between current and power losses, so for large loads the aggregated sum is less than the results recorded in the loadflow under normal operating conditions (it seems to work okay for the smaller loads). One of the problems with extending this "superposition" concept to multiple sources is that depending on the load which is turned on a small embedded source may or may not have enough capacity to fully supply the zone substation (load) in question.


texts: What currents are entering/exiting this end of the supernode?

texts:
I assigned the following currents. For one end of the 14V supernode, I have i1.
I'm not sure where the other end of the 14V supernode actually ends, so do I include only i3 in the KCL equation for it, or do I include i3 and i, or i3, i, and i2 (the rightmost current)?


texts: Optimally convert (small) boolean expressions into NOR form by hand

texts:
Is there a way to easily convert a boolean expression with only few variables into a NOR form?

Let's take the half-adder as an example:

a b | sum
---------
0 0 | 0
0 1 | 1
1 0 | 1
1 1 | 0

The sum of products is:
$$sum = \overline{a} b + a \overline{b}$$

If I convert that to a form which only involves NAND gates with 2 inputs, I get:

$$sum = \overline{a}b + a\overline{b} = \overline{\overline{\overline{a}b + a\overline{b}}} = \overline{\overline{\overline{a}b + a\overline{b}} + 0} = \overline{\overline{\overline{a + \overline{b + 0}} + \overline{\overline{a+0} + b}} + 0}$$

I count 6 NOR gates.

However, if I first write the boolean expression as a product of sums:
$$sum = (a + b) \cdot (\overline{a} + \overline{b}) = \overline{\overline{a+b} + \overline{\overline{a} + \overline{b}}} = \overline{\overline{a+b} + \overline{\overline{a + 0} + \overline{b + 0}}}$$

Now, there are only 5 NOR gates.

As I guess this is a heavy optimization problem (as suggested by this paper, I'd like to ask whether there is a way to 'optimize' it in small boolean expressions (e.g. < 3 variables).

Furthermore, I'd be interested in an answer regarding the same question with NANDs as well as the same problem appears there, too.


texts: i need a circuit to kiss NO contacts no matter how long you hold the button

texts: I am working on a license camera at a gated community and the nvr is holding the gate up to long. the lowest setting is 5s but I need it to be 1 sec. I looking for a made relay or a circuit to build that will just kiss the contact even if the momentary is held for 5 seconds but then reset and trigger again when pressed again.


texts: I draw like the first figure in the program, but when I save the program it automatically becomes the second shape. Do the two mean the same thing?


texts:
Okay, so I have what could be considered a silly question I should've probably learned when I started working electronics way back when, but I just now thought of it and haven't really needed to ask it until now.

I noticed on a AC-DC adapter yesterday that the ratings going in were 1.5A @ 120V, and the ratings coming out were 6A @ 12V.

So if I was to convert down to 5V, would I be able to squeeze out even more amperage still? Is there a mathematical formula?

I've just never pondered this before or had it explained


texts: Solution for accepting 3-24v as digital high for microcontroller

texts:
I'm after any suggestions for converting a digital input in the range of 3-24vdc to a 3.3v signal for a microcontroller.

I need to handle a total of 32 inputs (each of which could vary anywhere between those voltages), so density is more important than cost.

Someone suggested a non-inverting hex buffer like TI's CD4050 (http://www.ti.com/lit/ds/symlink/cd4050b.pdf) might be the solution, but I'm not entirely sure if it will handle multiple different input voltages.

Thanks in advance for your suggestions.

EDIT: The inputs will be connected to either:

Various mechanical switches which may pull the line to GND or to a voltage anywhere in the given range of 3-24v

or

Sensors of various types with digital outputs. Those outputs could be low (gnd) or high with voltages that could be anywhere in the given 3-24v range, depending on the type, make and model of the sensor.

Any of the inputs could be connected to any type of switch or sensor within the limits specified above.

EDIT 2: Multiplexers and the like are unfortunately not possible as timings are VERY tight and interrupts of varying priority are to be used extensively which requires direct connections to the microcontroller pins.


texts: How to turn on a 12V Buzzer when transistor is OFF in the given circuit using minimal components?

texts:
In the given circuit i need to add an alarm circuitry where the 12V buzzer is ON when relay/transistor is OFF.

Please guide me how to connect the 12V buzzer with minimal additional components


texts:
I m trying to trigger an Arduino Mega interrupt pin from a 3.3V sensor.

This voltage doesn't seem to be enough, since Arduino recognizes the interrupt only when I move the wire (probably since it causes the voltage to spike).

Can I use a transistor or any other solution to send 5V to the interrupt from a 3.3V source?


texts: How to generate Assembly drawing in eagle

texts: Hi all for the production purpose the ems partner asked me assembly drawing of my pcb  is there any easy way to create an assembly drawing with part name inside the boxes as in the picture  in eagle?


texts:
I am wanting to use the AD9850 for a particular application to generate sine wave signals in the 100Hz to 5kHz range. I've purchased a AD9850 module from ebay which just looks like the standard ones that are floating around at the moment. I noticed that I get quite significant harmonics even at these low frequencies. I'm not sure how to design a filter for this because ideally I would just filter off everything above 5kHz but I've seen that when I set the AD9850 to 1KHz I get harmonics at 2 and 3KHz which are noticeable. So it seems like I would need to have a variable filter that gets rid of harmonics above whatever frequency the AD9850 is set at. From what I've read about this particular DDS chip I would not have expected harmonics at these frequencies but probably would expect it as the frequency gets into the MHz range.

Can any one offer any advice on this problem or suggest any simple modifications that could be made to the AD9850 module board to reduce, or ideally, get rid of these harmonics?

Thanks!


texts: How to determine what voltage and current I should use for a Kanthal heating element?

texts:
I'm in the process of making a plastic forming "tool".
It has a hot wire inlaid into the top.
I have not come up with the power supply yet but have a few iron core transformers laying around.
The hot wire is 24ga Kanthal A1 wire.
I don't remember the exact length off hand but the resistance is 3.01 ohms at room temperature.
I would like the temperature to be around 250 degrees F but anywhere between 230 and 300 will work. My largest transformer has a secondary voltage of 24V @ 60Va, not sure if that would be "overkill" or not.


texts: How to tell if a buzzer is passive or active?

texts:
I see a lot of buzzers (like this one) that are sold online and don't advertise whether they are active (a DC power signal produces noise) or passive (to make noise they require both the DC power signal and an additional signal).

How can I tell if a buzzer is passive or active if its not immediately advertised by the distributor/website?


texts: Using an opto-isolator in a car's circuit. How to ground?

texts:
So I have a microcontroller that will read some of the car's sensor output (0-5v) and i plan to send the signals through an opto-isolator. The problem is that when i simulate this, it seems i cannot connect the car's ground with the MCU's ground. I later learn that this should not be done in an opto-isolated circuit. My question now is, how is this going to work if my MCU is powered off the car's power source?

car's 12-14v & GND  -> switching regulator-> 5v -> powers MCU
car's sensor -> opto-isolator-> GND

How can I get it to work without the two GND's coming into contact with each other? Would the 5V regulator isolate the two GNDs'?


texts: Reference designators and bill of materials?

texts:
If my schematic has 31 OR gates and 99 AND gates while using
CD74HCT32 - High Speed CMOS Logic Quad Two-Input OR Gates

CD74HCT08 - High Speed CMOS Logic Quad 2-Input AND Gates
what would my reference designators and bill of materials look like? Below is the schematic:


texts: Why would you use a shared-gate multi-channel MOSFET device?

texts:
This device has 8 drain channels, shared source, and a single shared gate:

DMN1250UFEL

How is this different from tying all the drains together and using a single FET?
I suppose you could have different drain voltages, but what might be a real-world application?


texts: Is it possible to provide power using (effectively) a single wire?

texts:
I come to this question after a few thoughts on capacitors.

A capacitor essentially transfers (and stores) energy using an electric field through an insulator. The plates of a capacitor are not connected, in the sense that the electricity is not passed through using a true conductive path.

Consider a simple, two-plate capacitor. This capacitor has a charge, a capacitance, and a distance separating the plates. If we increase the charge, the capacitance increases. If we decrease the distance, capacitance increases. Therefor, if we increase the distance, we will lower the capacitance, but if we comparatively increase the charge, the capacitance will remain the same. The insulator would simply be the air.

So if we have two highly-charged plates, separated by a distance, shouldn't it be possible, in theory, to have a single-wire connection rather than a whole circuit?


texts: Looking for op amps alternatives for Pico-Amps pA4-00125-76

texts:
I am trying to read photodiode for a certain purpose.

As I am unfamiliar with electronics, I have read some papers. And one of papers said Pico-Amps pA4-00125-76. But I couldn't find information about that amplifier.

Currently I am thinking about using SSC P4 as light source and Hamamatsu S6036 PIN diode as sensor. And as an amplifier, I will use NE5532P from TI.

Since there is no information about pA4,
I cannot figure out how pA4 and NE5532P are different or similar.
(Actually, I saw a picture of pAx series. and it seems totally different with NE5532P.
Thus, I am worried that I've picked a wrong amplifier)

Could you give me an information about pA4?
Or, will NE5532P operate well with my circuit?
In my circuit, ADC after amplifier can accept +/- 3V.
Current is unknown (I will check for it.) And amplifier can process signal with bandwidth from 100 kHz up to 8 MHz.
Alternatively, could you suggest another amplifier that fits for my case?

If there isn't enought information given, please let me know it.


texts:
I was reading the chapter of The Art of Electronics about bipolar transistors (chapter 2), and I came across this paragraph:

But why should I use transistors, specifically, for interfacing? Why not op-amps? Are FET transistors also good for interfacing?

Could you give concrete examples (circuits) using transistors for interfacing?


texts: What is the beginning state for Q in a SR latch?

texts:
In this diagram

what would be the beginning state for Q?  Since the first NOR for S and R rely on previous results, there must be something for the first iteration?

NOTE:
I'm in a first year digital logic class, so the question is for theoretical use (table making, various homework problems it applies to, etc.), not actual implementation.  Just for things like "if R is __ and S is __ what is Q?"  Simple things like that.


texts: How to compute active power with current

texts:
I'm working with an electric resistor (oven resistor) and I want to compute the active power with an embedded system.

My idea is to use a current probe around the phase wire to acquire the current values. I would avoid to acquire the voltage values because this implies the addition of a circuit to sample the voltage.

With the oscilloscope I can compute the active power: V(t) * I(t).

Is it possible to compute the active power only sampling the current?
Is it possible to use a sampled voltage period to perform the computation?

Thanks for the help!


texts: Need help identifying what kind of Li-ion battery I have and what to do when they're below 2,5V.

texts:
Hi I've have a couple of batteries of these two types, some of them are below 2,5V making me unable to make a CAP test on them, whenever I try my Foxnovo 4-Slots Intelligent Battery Charger beeps four times and "seems, not sure" to remove some voltage from the battery?

The one with the purple top has "A NJGA59 034688" written on it.
The one with the orange top has "C IEOFJT4 077773" written on it.

They come from a semi-old dell laptop battery, from Toshiba and Sanyo I believe.


texts: What is the operating voltage of Media access controllers?

texts: Do MAC and PHY operate on same voltage levels?


texts: BlueSmirf and Adruino - TX seems not to be working

texts:
I'm testing transmission of data via bluetooth. The data are recognized by my Arduino module. But I don't get any signal come out from my bluetooth module. I have no idea how to test that. (The TX and RX LED from my Arduino are not blinking too when I connect the blueTooth module. I don't know if it is normal. They are blinking normally when I don't connect anything into the UART).

I'm working in the Monsky Wifi project if that can help you. (from Make things talk book).

What is strange is that when I'm testing my Ardiuno from USB, the dialogue is working great between my processing program and my Arduino. My processing program send a signal, my Arduino module respond to it. And when my processing program has all the data it needs, it asks for more to the Arduino and the cycle continue.

Now, when I do the same with the bluetooth serial connection, the connection is well done (my blueSmirf green LED is up), data are sent (when my Arduino receive a signal, a LED blinks for this purpose). But my processing program doesn't receive any data signal.
I have already checked the baud rate (9600 for the bluetooth). And I'm connecting to the /dev/tty.myBluetooth. So I don't know what is wrong.

Do you have an idea of what could make this happen?

* Edit *

Ok I figured out. To those who will get into this kind of trouble, it was really the baudRate who was misconfigured into my bluetooth module. That explain why the transmission of data worked, not the reception.

The fact is I was changing the bluetooth Bps rate but not permanently, so when I was reading the bluetooth configuration it was actually diplaying the not permanently BaudRate. So typping the

  SU, 96

in my bluetooth command mode resolved my issued. (My arduino was configured to send at 9600 too, of course).


texts: Will the antenna be detuned by the presence of the MHF3 plug in parallel?

texts:
This is a design question. Below is the layout of a project that involves some features, including an ESP32 circuit and its antenna:

The part of the schematic related to both images is:

THE PROBLEM: The connection between the MHF3 plug and the jumper J4 is around 10mm, and it stays just below the actual 2.4GHz antenna (Pro-ob 440).
Will the presence of this "long" track and the MHF3 plug detune the antenna or cause any serious problem related to this parallel configuration?
EDIT: The following picture was upgraded to contain the RF signal as much as possible aside the upper border:


texts:
currently I have a problem with an USB Charging Plug (from china).

There are some designs, where the D+ and D- line is shorted together, in other there are held to 2.7V.

On my plug on the table, there are blank pads and no resistors at all, so the D+ and D+ are floating (to GND).

In my opinion, the charged device has to presume, that it's a normal USB port on the other side and just take up to 500mA.

On the other hand I have an iPhone 7, that is not charging with this plug at all. Is it possible, that the iPhone refuses to charge, if the D+ and D- are floating? Or it's trying to get more than 1A out of the plug?


texts: Arduino still on after ground disconnected

texts:
I am using an Arduino to communicate with an OBD car scanner. It uses 2 digital pins for communication (7 and 11 SoftwareSerial.) I connected 12V power to VIN and GND. I also added ON/OFF switch in the middle of the GND wire.
When the switch is off, the Arduino diodes and the 2x16 LCD connected to 5V remain on (but dimmer.)
I expected it to completely turn off
The OBD scanner is always ON.
Pins 7 and 11 are connected to the OBD scanner which has 3.3V and 5V on those pins. Is it possible that the 1.7V difference between those pins is somehow powering the Arduino? If so, why? Any other reasons?


texts: Semiconductor diffusion current over time

texts:
Suppose you have an injection of holes into a semiconductor such that at some time you have this linear hole profile:

Because the diffusion current at any point is proportional to the slope of P at that point, the diffusion current is equal everywhere from 0 to L. I think this suggests that P(x) should not change over time, as long as this linear profile remains. But it seems to me that this completely linear profile can only exist for an instant since at x=L the charges need to end up somewhere, and if this is some block of P-type silicon of length L then the charges will start to stack up so that P(x) will increase from x=L back toward X=0. So then P(x) will gradually become flat, at which point there will be no more diffusion current. Is this correct?
I'm also wondering about the typical exponential carrier profile, as seen here for example:

Here since the slope of P(x) decreases as x increases, the current (pointing towards the right) decreases as x increases. So for some point x, \$ P(x) > P(x+ \Delta) \$, so at some instant in time more charge is entering some point from the left than is leaving it towards the right. This is generally explained by saying that the diffusing carriers are recombining as they go toward the right. However, like in the linear case, this particular form of P(x) is only valid at some instant, and as time goes on (toward the steady state), P(x) is becoming more flat, i.e. the holes are becoming evenly distributed and so will stop diffusing due to lack of gradient. Doesn't this mean that an alternative explanation of the decrease in current as you go to the right is that some holes are simply starting to build up in certain spots and so stop diffusing, thus leading to less current towards the right?


texts: Need help for using N-Mosfets to switch on either one battery or the other

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I'd like to add a second battery (36V Li-ion) to an ebike to increase its range. My goal is to use one battery at a time, not using both in parallel with e.g. ideal diodes or something. I'd like to keep it as simple and as safe as possible and just use a 2 way switch to choose which battery the motor will pull current from. The 36V ebike motor draws about 20-25 A max so I figured out it would be best to use 2 N-channel mosfets to control which battery is being used. The N channel mosfets I plan to use are rated for 80V, 150 A and have a resistance from drain to source (RDS) of only about 3 milliohms (see https://www.mouser.ch/datasheet/2/427/sup60020e-1595623.pdf). This means at 25A the mosfet will dissipate 1.875 W. This should be okay without heat sink because the mosfet can be used without heatsink up to 3.5 W at an ambient temperature of 35°C.

I'm a noob in electricity/electronics so I tried to educate myself about mosfets and came up with the following circuit:

The idea is that when the switch in the center of the diagram is in the I position, battery 1 will power the motor. on the other hand, when the switch is in the II position, battery 2 will power the motor. However battery 1 will always be on the bike so it would be used to control the gate on the mosfets. The two resistors R1 and R2 are used as a voltage divider in order to drop the input voltage of battery 1 from 36V down to about 10 V in order to power the gate of the 2 mosfets since these mosfets have a max voltage from gate to source (VGS) of 20 V.

Now I have a few questions about this circuit:

1) when the switch is e.g. in position I, the mosfet on the left will allow the motor to run from battery 1. However, this also closes the path from the positive terminal of battery 2 to the negative terminal of battery 1...meaning that the motor would also be running from battery 2 as well. Is that correct?? The same occurs when the switch is in position II. This allows battery 2 to run the motor but the positive terminal of battery 1 becomes connected to the negative terminal of battery 2 so that the motor would also be running from battery 1 at the same time. Does this mean there is a huge issue with my circuit?

2) What happens if the two batteries don't hold the same charge e.g. battery 1 is at 30 V and battery 2 is fully charged at 42 V? I want to use a switch to properly isolate each battery from the other (I don't want to run the 2 batteries in parallel with e.g. ideal diodes). Would this circuit allow any cross-current to flow from the battery with the highest charge to the battery with the lowest charge? In other words, is it safe?

3) Should I be concerned with voltage spikes and inrush current when switching either battery on? What should I do to prevent such inrush currents from damaging parts in the circuit (above all, I want to avoid any damage to occur on the Motor controller and battery BMS)

4) Any change recommended on that circuit?

Thanks a lot for your help!


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why do we need pre-post amble for READ or WRITE DQS ?

1 ) one reason could be -->
Because transitions of voltages from logic level 0 to 1 or 1 to 0 take time to complete: so the strobe is asserted a suitable time after the start of data lines transitions to tell the reader that the data is valid in the sense that the transitions between logic levels on the lines have been completed.

---------- but there is DQS to do this job....then why extra pre and post amble ?