texts: Why does this first-order RC filter with an op-amp display resonance?

texts:
I built this circuit and simulated it in CircuitLab and was trying to make an active low pass filter. However, it shows a frequency response like a resonant low pass filter and I can't figure out why.

Here's the schematic:

And the frequency response:

The gain of the frequencies below the resonant frequency is set by the ratio of R2/R1 (x10 with these values), as expected for an inverting op-amp circuit. But I can't figure out why there is the resonant peak at 800 Hz for this first-order circuit, or how to calculate the resonant frequency.

And the response of a few different cap values:

And the response of different values of R1:

Changing the value of R1 has no effect on the resonant frequency, only on the gain of the circuit. I don't understand why this circuit behaves this way. Can anyone explain it to me?

I came up with this equation for the value of \$V_{out}\$:

$$V_{out} = -( \frac{A \times R2}{R1 + R2 + R1R2Cs - A \times R1} ) V_{in} $$

Does this equation look right? It makes sense to me that when \$(R1 + R2 + R1R2Cs) << A \times R1 ,\$ the result is approximately equal to R2 / R1. But I have no idea where the peak at 800 Hz comes from.


texts:
I am using micro USB socket to charge the battery in one of the device and now we are planning to go for CE certification for which we are doing EMI/EMC test. For the ESD IEC 61000-4-2 (+/- 6 kV contact +/- 8 kV air) test standard. The outer shied of micro USB should be connected to ground. But in one of the reference diagram it is connected to ground via some resistor and TVS diode. (Schematic attached below).

Should I connect micro USB outer casing to ground or connect it via some resistor to ground and then employing TVS diode as shown in the schematic?

I think using the second technique the ESD pulse would not affect the common ground and will not affect the sensitive IC connected to the common ground.


texts:
I'm designing a 8-layer PCB. Two layers have been reserved for GND and 2 for various digital supply voltages. Remaining 4 are meant for various signals( mostly serial data, video and USB).

How should the layers be arranged to make most sense considering noise immunity?

FYI: I decided on 8 layers because in 6 layers I couldn't imagine fitting all my signal traces.


texts: How to convert low voltage (< 0.4V) AC to DC

texts:
I've made a mini generator for a mini wind turbine. An oscilloscope voltage measurement shows a +0.4/-0.4 V sinusoidal AC current. I'd like to convert it into DC, in order to put a charge and detect amperes.

I have tried to convert it with a classical "4 diodes bridge", with the smallest diodes I found (1N4148), albeit unsuccessfully: the diodes seem to reduce the voltage too much, and at the end, no current at all is delivered (the oscilloscope does not detect any voltage).

How can I accomplish the AC->DC conversion then?


texts: Arduino will not power on with external power supply

texts:
I have a 5V and 12V Super rechargeable Li-ion Battery, and I'm trying to power my Arduino with it. It's an emergency because tomorrow I have to present a robot and it doesn't work.

My Arduino is an Arduino UNO R3, I try connecting the 12V power to the barrel plug in the Arduino. It doesn't work.

I try connecting the 5V power from the battery to the USB port in the Arduino. It doesn't work.

However when I connect the Arduino by the USB to the computer, it works!

Could someone please provide some insight to this problem?

My code is this:

int led[5] = { 3, 4, 5, 6, 7}; // Assign the pins for the leds

int leftChannel = 0;
int left, i;
int Valor1;
int Valor2;
int Valor3;
int Valor4;

void setup()
{
for (i = 0; i < 5; i++)
  pinMode(led[i], OUTPUT);
}

void loop()
{

left = analogRead(leftChannel);
Valor4 = Valor3;
Valor3 = Valor2;
Valor2 = Valor1;
Valor1 = left;

left = left/5;

if (Valor1+Valor2+Valor3+Valor4==0){
   for(i = 0; i < 5; i++)
     {
     digitalWrite(led[i], LOW);

     }
  }

  else
  {
   for (i = 0; i < left; i++)
    {
     digitalWrite(led[i], HIGH);

    }

    for(i = i; i < 5; i++)
     {
      digitalWrite(led[i], LOW);
     }
  }
}

I believe it is the serial communication, I have tried connecting a 10k resistor from RX/TX to GND but it doesn't work.


texts: How to use a 24v 3A drill motor from a PSU 12V 20A?

texts:
How to use a 24V 3A drill motor from a PSU 12V 20A?
I'm using a motor that at 24V has 28000rpm, and at 12V only 10000rpm. Is there any step-up that I can use or make to use the PSU as input?


texts: Why is gold preferred over silver for bond wire?

texts: Silver is a better conductor than gold and in Integrated Circuit package where exposure to air should not be a concern Gold is used. Any particular advantage of using Gold over Silver?


texts: Reference voltage changes when connected to inverting input of op amp comparator

texts:
The capacitor C2 keeps the value of a slow varying signal for some time. The capacitor discharges through the two resistors R3 and R4 with a time constant of \$\tau = RC = 10\mu F \times 1M\Omega = 10s\$. The voltage across resistor R4 should be half of the voltage across the capacitor. This works as expected when the op amp (NE5534N) isn't connected to the circuit.

When V_R4 is used as reference to the inverting input of the op amp the voltage changes to about 80% of the voltage across the capacitor C2. I have not been able to find a solution to this. Am I missing something here?


texts:
I'm using STM32F407VG. I created a 28 khz square wave by using Timer PWM Generation. When i look at the oscilloscope, i can see it clearly. I'm having a trouble to change frequency of PWM without stopping it.
I found two functions which are __HAL_TIM_SET_PRESCALER() and __HAL_TIM_SET_AUTORELOAD().
HAL_TIM_PWM_Start(&htim2, TIM_CHANNEL_1);
__HAL_TIM_SET_AUTORELOAD(&htim2,99);
__HAL_TIM_SET_PRESCALER(&htim2,29);

I set prescaler and autoreload in cubemx. Prescaler is 2 and ARR is 999 but i want change prescaler to 29 and arr to 99. I can see square wave with HAL_TIM_PWM_Start() but when i added other 2 functions.It goes away. I commented those prescaler and arr functions and i saw that PWM was working.
I dont not know how to change prescaler and arr values without stopping the PWM.


texts: What does high input resistance in fet mean? I always see this term when dealing with fet transistors like jfet and mosfets.


texts:
I need to digitize a weak (-10 dBm) 1-20 MHz signal with a comparator. The output of the preceding stage is 50 ohm.

The comparator I'm using is the LT1715. It's input trip point is ± 5 mV and the bias current is -2.5 µA (-6µA max). Is it correct that the bias current is the current the source needs to provide in order to reliably toggle the comparator?

In a 50 ohm system, I understand, the RMS voltage of a -10 dBm signal is 70 mV. That would be enough for toggling the comparator.

If I now simply connected the signal trace to the comparator input, I assume it would be reflected and the voltage would double. The reflection however would end up in the preceding amplifier and increase the noise.
For an ideal comparator with infinite input impedance, I'd simply terminate the signal with a 50 ohm resistor right at the comparator input.
But that would kill the signal for the real comparator.
How should I go about minimizing reflection (and ideally improving efficiency)?


texts:
https://www.faulhaber.com/fileadmin/Import/Media/EN_AM1524_FPS.pdf
I am using this motor with a 250:1 planetary gear drive, I am moving a mechanism that requires .3 inch pounds of force.  The company says it will produce the required torque at 3.3vdc and only use .26amps, I am having problems with this giving me enough breakaway force to move the mechanism at temperatures of -40*.  Right now the motor is set to 1/4 steps because I was under the assumption that it would produce more torque but, I had another individual that said a 256 step it would give me a more significant breakaway torque but at speed it would be less likely to produce the same torque.
I am not all that smart when it comes to this but, I am asking for your advice.  The motor will only run 12 seconds from hard stop to hard stop and the accuracy isn't all that important due to the gearbox but I do need a good amount of torque when cold.  Would 256 steps work better at cold vs 1/4 steps?


texts: state-space model for bidirectional buck-boost with input capacitors

texts:
I'm having some trouble simulating the behaviour of a bidirectional buck-boost converter for battery charging purposes. The circuit looks as follows:

I would like to create an averaged state-space presentation for the converter using the following state vector: x = [iL,vC1,vC2]T, the input being u = [io,vi]T (so inputting the battery current and bus voltage), and output y = [ii, vo]T. Here lies the problem, however, as the bus voltage is equal to one of my states, vC1. I want to use the bus voltage as an input when I am charging the battery, but I would like to model the converter as a standalone state-space equation so I can use it later in a bigger project.

In general I am familiar with averaged state-space presentations but the fact that I need to have an input that's equal to one of my states is confusing me... I could take ii (bus current) as the input instead, but doing so I wouldn't be able to make sure that the bus voltage stays at my predefined level. Also, I think it might be problematic to have both ii and io as inputs, would it not? because in the steady-state, you'd end up with an overdetermined system (knowing io, ii and Duty).

Any thoughts on this or a good book recommendation would be highly appreciated!


texts: Using Fourier transform to solve current in a circuit with initial condition

texts:
I am trying to solve the inductor current for the circuit below by using Fourier transform instead of Laplace.
The purpose is to see if Fourier transform also works for problems with initial conditions like this.
The voltage source is a DC voltage source.

By KVL:
\$\ -1  + L\frac{\mathrm{di} }{\mathrm{d} x} + R i = 0\$
Fourier transform the equation above:
\$\ -2\pi \delta (\omega ) + j\omega L *I(\omega ) + R*I(\omega ) = 0\$

However, I don't see anywhere that the condition i(0)  is used here.
How can I include the initial condition and solve for the current?

PS. The circuit is taken from this site.


texts: How are programs written into a microcontroller? What role does JTAG play?

texts:
I can write programs for an Arduino, and all I do is plug it in and click "upload". My compiled code gets into the ATMega's program memory. Easy right?

Well, I would like to know what exactly is happening in general. The microcontroller has some memory on it, so there exists some method of taking raw data from a USB cable and writing into the microcontorller as though it were a flash drive or something. However, I happen to know that this isn't possible unless a special bootloader program is already present on the microcontroller.

So now I'm confused. How could I upload programs to an Arduino if it didn't have the bootloader? How do I program other microcontrollers (such as an ARM) without the Arduino's user-friendly interface?

Bonus related question: from reading (and not understanding) a few web pages, I have found out that ARM is programmed through JTAG. What is this doing, exactly? The JTAG module sends data into the ARM, but exactly what data does it send? How can the ARM accept new code without some program already running on the ARM that interprets the JTAG data and writes it into the correct memory?


texts: Under what circumstances can impedances be simplified to simple resistances?

texts:
Consider the following circuit:

This is a simple first-order low-pass RC filter. The cutoff frequency is:

\$ f_c = \dfrac{1}{2 \pi (1k\Omega) (1\mu F)} \approx 159 Hz \$

The reactance of C1 at \$f_c\$ is:

\$ X_{C1} = \dfrac{1}{2 \pi (159 Hz) (1uF)} = 1k\Omega \$

So what if we pretend that C1 was just a resistor, with a resistance that's a function of frequency? If you are a 159 Hz sinusoid, then the circuit might as well be this (I think...):

At least, if we only care about the frequency response, and not the phase response, of the circuit. The voltage between T1 and T2 is half of V1, and this is consistent with the calculation of the cutoff frequency above.

I think with this circuit, we can pick any frequency, calculate the reactance, replace C1 with a resistor of that value, and get an equivalent circuit for the purposes of calculating the frequency response.

But what about this circuit?

Maybe not so much. Under what circumstances can we simplify impedances this way?


texts: Understanding the working of a NAND GATE using NMOS Transistors

texts:
I'm having incredible difficulties understanding how the "Switching Behaviour" (not sure if that's the correct English translation- in German it is "Schaltverhalten") for NMOS and PMOS transistors actually work. I understand the theoretical part of both of them but now how to take boolean expressions and turning them into transistor logic circuits. Here is the NMOS for a NAND GATE, where Z indicates that it's in a floating state, the bold blue line indicates that the source-drain is set to High, the bold black line indicates that the source-drain is set to Low:

I'll explain my understanding using the first image, with both gates set to Low. The current for NMOS flows from the source to the drain. You have two "inputs" i.e. two NMOS transistors that are connected to each other with the original drain gate of the bottom transistor connected to the source of the upper transistor. When both the inputs are set to Low, the NMOS is turned off which means that there is no current flowing through the circuit. Since there is no current flowing through the circuit, the "connection line" between the two transistors is in a floating state . However, what I don't understand is why there is a resistor at the top (and why its input is set to High) and how this results in a High output for the entire circuit.


texts: How to calculate the Ra and Rb values for the desired frequency and duty cycle?

texts:
I am designing a DC-DC boost converter for Vin = 5V to Vout = 15V. To generate gate pulses, I will be using a NE555P Timer by TI - http://pdf1.alldatasheet.com/datasheet-pdf/view/161277/TI/NE555P.html. For astable operation, from the data sheet I realised the following data [Pg-7]:

Frequency (f) = 10 KHz,
Capacitance (C) = 0.1uF,
Ra + 2Rb = 1K,
Duty Cycle (D) = 1 - (Vin/Vout)
               = 0.66 or 66.6%,

Priod = th + tl = 0.1ms,

Now, how do I calculate the resistance values of Ra and Rb for the desired duty cycle?. And what is the difference between Output driver duty cycle and Output waveform duty cycle?. Which one of these formulae can I use to find Ra and Rb satisfying Ra + 2Rb = 1K?

              //Some Calculations I did until now to find Ra and Rb//

D = Rb/(Ra+2Rb)),
0.66 = Rb/1K,
Rb = 660 ohms,

Ra + 2Rb = 1K,
Ra + 2(660) = 1K,
Ra = 1000 - 1320,
Ra = -0.32K????-----------> Getting a Wrong value since it should not come negative!!,

                     //My next try to calculate Ra and Rb//

D = 1-(Rb/(Ra+2Rb)),
0.66 = 1-(Rb/1K),
Rb = 340 ohms,

Ra+2Rb = 1k,
Ra+2(340) = 1K,
Ra = 320 ohms,

So, 320 +2(340) = 1000, satisfies Ra + 2Rb = 1K( But not getting 66% duty cycle).

So which one is correct? or my approach and understanding itself to finding the values of Ra and Rb is wrong?. Please help.


texts:
So I was looking at an Actel A3P250 FPGA for a future project. It has a core voltage of 1.5V and can use 3.3V for the IOs.

So I'm thinking, how do I provide the 1.5V core voltage. My board has 3.3V, 5V and 8-12V variable input as well as an a bulk battery input of 6V - 30V. National Semiconductor has a neat Webench tool. I use the FPGA option, select the exact FPGA and press "Go". It tells me for a core voltage my FPGA needs 1.5V @ 2A. That's much higher than I expected (having no prior experience with FPGAs), but then it also says I need TWO separate 1.5V @ 150mA power supplies (buck converters) for the 1.5V IO and 1.5V PLL each about $3...! This bumps the cost up to a not insignificant $12 for just the supply - the FPGA only costs about $20!

I want to run the FPGA at 250 MHz, to match my SRAM clock. But the IO will be at 3.3V which is already available on my board. So all I need to sort out is the PLL supply. What's stopping me using a 1.5V LDO here? Is there some need for a buck converter?

Does anyone have any idea on how I should architect this power design?


texts:
I am  trying to make a night lamp.  I especially like the quality and temperature of the light from a Nexus 5x flash switched on and aimed at the ceiling.  It gives out a uniform and cool light through out the room.

The flash on the phone is described as Broad-spectrum CRI-90 dual flash.

How do I build a light like that?


texts:
I'm planning a custom power-distribution / fuse-board for in-car application, but that requires carrying high currents (50A+ @12v*) on a PCB trace. Since I'd like to keep the board cost, and physical size down, can anyone suggest efficient (as in easy & inexpensive) methods for creating a power bus on a PCB?

Feed in would be from a chunky copper cable, most likely with a screw-terminal tag on the end.

My thoughts so far:

Thick trace with thick coat of solder
Same but with some thick copper wire soldered to it
Same, but use a single strip of stripboard
A length of copper or aluminium, either attached with screws through holes in the trace, or soldered down (obviously not soldering aluminium down!)

These are all OK but require special effort to populate the board, whereas something available off-the-shelf would make life easier.

Edit to add more info: The basic layout will be a bus up the board, with feeds off for each item, each of which may draw <30A (but most of them are <10A), so per-connection there can be a little thermal relief to make life easier.

* = Average of maybe 30-40A if the cooling fan's running and all the lights are on, ~10A if not, potentially 100A max although more headroom is better.


texts: How to remove deposit from leaky alkaline cell

texts: I have an LED torch that must have been left turned on when put aside for some time, so one of the AAA alkaline cells in it has leaked and left a white deposit. It is worthwhile trying to recover the torch, that is I might as well try rather than just throw it away, so I have dismantled it as far as I can and immersed the parts in tap water, in a hard water area, for a couple of days. The deposit on the plastic cell holder has gone, but there is still a hard white deposit inside the metal case. How, please, could I dissolve that away, or soften it so that it will rub away? For instance I might need a mild alkaline or acidic solution, but, if so, which? Or, possibly an organic solvent such as alcohol or acetone?


texts: How to calculate inductance (ferrite core) in a induction heater

texts:
this is my third tag and I´m going to accurate my question, I have builded four induction heater and only one works, I´m sure that´s because of the inductor L1, I do not know how to obtain te correct value (I blew up four mosfets). Please help Me

simulate this circuit – Schematic created using CircuitLab


texts: PNP switching circuit - How it will be correct?

texts:
Following circuit is used as a switch in one my circuits. The collector is connected to the Vcc and emitter is supplying current. Theoretically it is wrong, right? The supply should be connected in emitter for PNP for driving. Do you think it is OK?

PS: It is worked for driving a seven segment!!??


texts: Why do parasitic elements (e.g capacitance) appear on only high frequencies?

texts: We know that the impedance of a capacitor is inversely proportional to the frequency then why is it not negligible when at higher frequencies ?


texts: I have an FT232R chip hooked up to my oscilloscope with the TX and RX pins joined. I'm sending characters directly to it via Putty. The logic levels I am seeing are 5V low and 0V high. I thought the output of this chip was TTL (i.e. 0V low and 5V high)? Am I missing something?


texts: Switch poles from inverted power to make negative positive?

texts:
My understanding is that voltage is relative (where you measure affects voltage) and that current flows with voltage difference.

Why can't you just switch the poles/wires of an inverted signal/power supply to get a non-inverted output?

This is mostly in reference to power supplies (switching/voltage regulators) and op-amps, but sort of curious as to theory as well.


texts: Solder doesn't stick wires to connectors

texts:
I'm always having problems soldering wires to connectors. I've read through the Solder won't stick question, but nothing there seems to have helped.

Here's my procedure:

If the connector is being difficult, I rub the surface of the connector with fine-grain sandpaper to clear any oxidisation.
Get my iron up to about 175 deg C (it's a temp-controlled iron)
Brush the tip across a damp sponge.
Add a small spot of solder to the tip.
Line up the wire to the connector, usually with a clamp.
Hold the tip of the iron on the connector for a short time.
Push some solder onto the wire at the edge of the tip, so the solder melts onto the wire.
Remove the iron.
Brush the tip across the sponge again to clean off the excess solder.

The problem I'm having is that the solder just doesn't stick the wire to the connector. It usually holds for a second, then unsticks from the connector as soon as the wire moves. I've tried more solder, less solder, different solder - same issue.

I've started to notice the same issue when soldering onto stripboard, too. The flow seems to be poor, the solder doesn't look shiny, and it's all rather viscous.

Am I doing something wrong? Is my iron / tip bad?


texts: Stepper Motor acceleration profiles for short runs

texts:
I've done a fair bit of reading on stepper motors and acceleration.
I had to wade through a lot of different strategies with a lot of calculations, including one which called for several candles, and "A maiden of virtue pure" Which while interesting, seemed impractical (Not enough space on the Arduino)
Basically they all boil down to this:
"Accelerate using some type of ramp, run at speed, then decelerate to stop"

All good. Accelerating will get the load moving, and smooth deceleration will get the load to stop at the (hopefully) correct position.

My issue is this. All of the reading I've done so far seem to have the assumption that the distance to travel will be enough to accommodate all three phases of travel. ie Accel, Coast at speed , Decel.
I've not found much discussion on how to handle very short distance situations.

For example, moving only two steps will not, can not possibly have enough distance to go through all three phases. step - step - done.
While that particular example seems to be simple enough to solve, what are the best ways of determining if deceleration is required, and if so, when?

At what point do I determine that some sort of deceleration profile will be needed to get the stepper to stop at the required position without overshooting.

So after a whole bunch more looking, and reading and getting confused I decided on the simplest solution.

I stayed with a trapezoidal/triangle profile.
Essentially I determined the distance a constant acceleration ramp would use to get to speed. If the acceleration distance was greater than half of the total distance to travel, I accelerate for only half the total travel distance and not worry about getting to max speed. Because I decided to use a symmetrical approach, the decel part took care of itself.

The equations I utilised are essentially the ones posted by Chuck, although the addition of different acceleration and deceleration rates he uses gives me food for thought.

Many, many thanks to all who contributed.


texts: Switching voltages with demux and switches

texts:
I am trying to design a circuit that, depending on a value that a microcontroller recieves (between 1 and 10), a fixed voltage of 20 V, 40 V, 60 V,... or 200 V (depending on the value recieved by the microcontroller) appears at the output. So, for example, if the value 2 is read, then 40 V should appear at the output; if the value is 6, then 120 V; and so on. In other words, I have to control digitally a switch that short-circuits the output of the circuit with one of the ten voltage sources available.

This is what I've done so far:

The microcontroller recieves a value between 1 and 10 (via USB, but that doesn't matter). The thing is that I put that number in an output port using 4 bits. Those pins enter a demux that is connected to 10 different outputs. So the thing is that I want these pins to control a set of interruptors that make a short-circuit between the output and the voltage sources. I have available ten voltage sources of the ten different values (20 to 200 V). I don't know how to implement this part of the circuit.

I've thought of each output pin of the demux being connected to a MOSFET that would act as switches, but I don't know how to connect them in order to get what I'm looking for. I believe some drivers would be needed here, but again, I can't think of a way to connect them to get the desired result.

Do you have any ideas? If the question is not clear please let me know, and I'll try to clarify it.

EDIT:

The resistance load for the circuit will be 50 \$\Omega\$. The output has to be a rectangular wave (its duty cycle can be varied with a variable resistor). The maximum amplitude of the wave can be 200 V, and the minimum 20 V.

The maximum average output power reaches 1.92 W (there are peaks of instantaneous power of 800 W), and the mean value of the output current is 9.6 mA.


texts: Is it possible to reverse engineer an analogue IC from a physical example?

texts:
Lately I've been investigating custom ICs developed by Roland in the late 70s/Early 80s for their analogue synthesizers.

They stopped manufacturing these components around 1989, there are no datasheets available and they will not release, or do not have information on them.

The IR3109 is a DIP16 filter chip made from four cascaded OTAs and buffers controlled by one exponential converter. A rough internal diagram is provided in some synth service manuals, and people have made clones that sound pretty close.

The one I'm interested in is the IR3R01, a DIP16 'envelope generator' chip. Used to create a DC voltage out in response to keys being pressed on a keyboard and applied to the filter or amplifier.

I was wondering if it is possible to examine these ICs somehow and work out what components and values are inside. Maybe exposing the die and evaluating it under an electron microscope? I'm sure if it is possible it would be very expensive.


texts: How to design a SPICE model from data sheet?

texts:
I am new to SPICE simulation and I am looking for spice model file of LTC 1065 data sheet can be found here here.

I searched a lot on Google but I could not find much help about how one can design a SPICE model from data sheet.

I really don't know whether I can design or a SPICE model or not from the data sheet.


texts: Using negative clock edge in phsical design

texts: In Verilog, is it ok to use negedge of clock. Can a memory element be triggered at the negedge of clock? How robust will be the design practically in the chip?


texts:
I want some of the ESP32's GPIOs to be accessible via 3.5mm headphone jacks or RJ11 jacks and therefore need suitable ESD protection. I wonder how much is needed for optimal protection.
Conditions/constaints:

The board is powered by a 12 V wall plug
The voltage is brought to 3.3 V via a step down converter based on the LM2575
2 Layer PCB. The bottom layer is GND
I want to protect against ESD strikes described in IEC 61000-4-2 (8kV contact, 16kV air-gapped)
IOs should

be working as inputs and outputs
be working with a max. frequency of around 250 Hz
have an output voltage/current enough to drive a bipolar transistor or MOSFET.

My initial idea
Roughly based on this digikey article and other resources found on the Internet I came up with these circuits.

However, I'm still confused by all the info floating around. Let me try to explain my thinking:
Assuming that I have a TVS diode with a clamp voltage between 8 and 16 V. E.g. the T3V3S5

In the event of an ESD strike, I therefore have to assume that the ESP32 is exposed to a voltage between around 8 and 16 V. Through the 1k resistor I want to limit the current so that the pulse for the internal diode remains manageable. Worst-case the internal circuit would have something around 16V-3.3V = 12.7V and (16V-3.3V)/1000Ohm = 12.7mA to cope with, correct? Is that something the ESP32 would survive?
Can I assume that the circuit on the left is already sufficient to protect the ESP? In this case of course the ESP32's internal protection circuit is used. Or should I rather throw external diodes to it like in the example on the right?
Unfortunately I cannot find any documentation on the internal protective measures of the ESP32
GPIOs. If you have some info please let me know.
Questions

Do the circuits make sense? Is one of them suitable to protect the ESP32?
Will the step-down regulator be able to cope with the heightened power rail or do I need some more circuitry there?
Should I rather use something like this to avoid latching up the PSU rail?
What if the board is not powered?


texts:
I have built a simple bus backplane from stripboard and 40-pin female headers for a computer project I am working on. When I tested the backplane to make sure that it functioned, I found that it's soldered properly but that inside one or two of the female headers I used as connectors, there is a short that connects three lines on the backplane.

Visual inspection is of little help, the flaw isn't visible; it is inside the connector shroud somewhere.

So my question is: Is it possible to measure with a multimeter somehow, which of the seven paralleled connectors is the culprit? I would like to salvage the backplane and just replace the offending connector if possible.


texts:
Is there any type of proximity system that detects a microchip or similar?  I am looking at an "mobile" proximity detection system that I could specifically detect an implanted or imbedded microchip or something that it would be designed to only detect that object.  It would also be very beneficial to be microchip size.  This would be for an industrial application.  Thank you in advance.
           JL


texts:
I was looking in the internet and stackexchange for the solution but still I don't know why it is not working. Solutions which I found here shall work but probably I am still doing something wrong.

I am writing VHDL 'code'. I have in my design INOUT ports. In libero soc synthesis and compilation works fine. Now I would like to simulate my design and here is the problem. I am using Mentor Graphics ModelSim. During compilation testbench I have an error

  Nonresolved signal 'data' has multiple sources.

architecture architecture_max11046_interface_tb of max11046_interface_tb is

component max11046_interface is
    port (
        -- Clock and resets
        i_clk           : in std_ulogic;
        i_rst_asyn      : in std_ulogic;
        i_rst_syn       : in std_ulogic;

        -- Max11046 interface
        o_cs        : out std_ulogic;
        o_wr        : out std_ulogic;
        o_rd        : out std_ulogic;
        o_convst    : out std_ulogic;
        o_shdn      : out std_ulogic;
        i_eoc       : in  std_ulogic;
        io_data      : inout  std_ulogic_vector(15 downto 0)
    );
end component;

-- input signals
signal eoc:    std_ulogic := '1';
signal data:   std_ulogic_vector(15 downto 0) := x"ABAB";

-- signals
signal rst: std_ulogic := '0';
signal clk: std_ulogic := '0';

signal ADC_Data: std_ulogic_vector(15 downto 0);
begin
    Conversion_end: process
    begin
        wait until convst = '1';
        wait for 500 NS;
        eoc <= '0';
    ADC_Data <= x"ABCD";
        wait for 50 NS;
        eoc <= '1';
    end process;

    data <= ADC_Data when eoc = '0' else (others => 'Z');

    max11046: max11046_interface
        port map (
            i_clk       => clk,
            i_rst_asyn  => '1',
            i_rst_syn   => rst,
            o_cs        => cs,
            o_wr        => wr,
            o_rd        => rd,
            o_convst    => convst,
            o_shdn      => shdn,
            i_eoc       => eoc,
            io_data      => data
        );

 end architecture_max11046_interface_tb;

I've deleted some part of code to make it easier to read. My question is what can be wrong. Can not I drive internal signal from multiple sources ? In the design I am doing it like this with ports and it is working:

data <= ADC_Data when eoc = '0' else (others => 'Z');

when i am not writing to the port it is in high impedance and i can read data.

P.S. I don't want to use std_logic_vector instead of std_ulogic_vector.


texts:
Is it OK to connect the minus from a DC Power supply, 15v 4A (switched) to a metal chassi as ground?
No electronics will be connected to the chassi.

The jacks that I have found seems to be made of metal, which in my eyes looks like the ”minus” will end up in the chassis.

Is that ok?
Does the minus act as ground through the power supply?


texts: Role of voltage source in relaxation oscillator

texts:
I have found this relaxation oscillator

Where you can put a ground in the anode of the battery.
The role of the battery is to start the oscillation only or what?


texts:
I got some very small coil (OD<1cm). They are made of copper wires at 46AWG. By applying a changing voltage(sine wave), I can get a very small magnetic field (such I could attract some small magnets).

The matter is the coil fail very easily. I have checked that there is no mechanical damage (they are wrapped and protected from any mechanical damage). Also the heat dissipated is very small (at least not noticeable from touch).

It is found that the resistance of damage coil is much larger than than those good coils (Mohm vs ohm). I suppose it would be some wire damage inside...So, what would cause the breakage? Thermal? the frequency of sine wave (stressing on the thin wire)?


texts:
I am trying to amplify a CT sensor.
The sensor is giving 5mV amplitude for low current, 100mV amplitude for higher current.

I built a voltage divider with 220 ohm resistors, and connect to a noninverting opamp with gain that should be 120k/10k+1 or about 13.

I am using 6V battery packs for positive and negative power for the LM358.  The waveform going into the op amp shows on the oscilloscope as 5mV amplitude @60Hz.

The waveform coming out is only positive, and there is no gain.  Since I'm fairly sure I built the circuit correctly, I'm first showing the schematic, assuming that the concept is wrong.  If you experts tell me the schematic is right, then I will have to take a picture of the circuit and attach it to determine how it is built wrong.

Ok, in light of the answer I am posting a revised corrected schematic


texts:
I am looking to build a DC voltage amplifier. In this picture, I am using a 2N3904 NPN transistors. Does this work as a DC voltage amplifier? Does it make sense?

If this doesn't work, how do I make a DC voltage amplifier?? Thank you!


texts: Lowest denominator components to drive salvaged DC motor with 9v battery and Arduino?

texts:
I have the following:

Arduino Uno and/or Duemilanove;
DC motor salvaged from pound shop toy; and
a 9v battery.

What are the missing components to drive the motor, in a single direction, with a ON/OFF only functionality?  I should probably account for PWM in the future, but always one direction only.

From my very quick investigation probably just a MOSFET and a Zener Diode will be required, but I'm not sure. Oh, and a capacitor to isolate the circuitry wouldn't harm, right?


texts:
Can ANY DC motor become a generator if torque is applied to the shaft?
example:
Produce-Electricity-from-a-DC-Motor

And by any, I mean the really cheap ones too.
Or is there a specific type of motor (of which I do not know the name) that can work in both directions (battery to power the shaft OR torque-on-shaft to create a voltage difference between the terminals).


texts: Time shifted unit impulse function in frequency domain

texts: How can we represent a time shifted unit impulse function in frequency domain ? Fourier transform of unit impulse function is 1. So I think it will be an infinite parallel line in frequency domain. What about for the time shifted version ?


texts:
I've just calculated trace parameters so that it would have 50 Ohm impedance on PCB.
Then I've noticed, that its impedance does not change when I make line longer or shorter as long as I leave trace width & distance to ground plane intact.

Is that correct and why is that?


texts: RN4020 BLE module authentication without I/O Capabilities and mysterious datasheet

texts:
I'm trying to activate authentication for my RN4020 Bluetooth module in a way I dont have to enter PIN or Passcode during this process because my RN4020 wont have any displays or keyboards where to display or enter PIN.

This is what datasheet(table 2-7, page 29) says about it

  SR,<hex32>

  This command sets the supported features of current RN4020
  module. The input  parameter is a 32-bit bitmap that indicates
  features to be supported.

Auto Advertise 0x20000000

Enable Authentication 0x00400000

I/O Capabilities 0x000E0000. I/O capability of the module. Only useful if the Enable Authentication bit is set.

‘b000 = Display Only
‘b001 = Display Yes/No
‘b010 = Keyboard Only
‘b011 = No Input, no output
‘b100 = Keyboard Display

This is already where the mystery starts because its not said in the datasheet where the (I suppose) binary values for these I/O capabilities are supposed to be in this hex32 number.

I read here about disabling pin when making authentication(pairing) process

  First, disable authentication, so that RN4020 won't ask for a Pin
  code. For the parameter of command "SR", bit 0x00400000 should be
  cleared.

which is already weird because why would I disable authentication if I'm trying to do it and I/O capabilities are working only if the Enable Authentication bit is set. And next...

  On the other hand, declare that RN4020 has no I/O capability, so the
  peer device won't ask Keyboard I/O authentication. For the parameter
  of command "SR", the 3 bits 0x000E0000 should be set to 0x00060000 to
  indicate RN4020 has no I/O capability.

What the number 6 is standing for? And again if authentication is disabled by disabling bits 0x00400000 then these 0x000E0000 I/O capabilities are not supposed to work at all. But mystery is that when I use SR,20060000 it actually works and I can bond devices without using PIN. Can anyone explain this?


texts:
My doubt is regarding the dynamic phase control while routing differential pairs in allegro. If anyone knows kindly clear my doubts on these questions. For your reference, I have attached a snapshot here.
            1. Why dynamic phase is important in differential pairs?
            2. Kindly give clear content on How the dynamic phase works on
              differential pairs?
            3. How to understand the DRC? And how to clear those DRC.
Thanks for your good answers

![snapshot of dynamic phase routing(mismatches with constraints)
 ]1


texts: I'm using BJT (NPN) that is supplied with 7V DC signal at the collecter, 5V DC signal at the base and need a 12V output at emitter. Right now i'm getting 4.35V at emitter. How can i implement it?


texts: What is the purpose of holes on edge of the PCB?

texts:
Here is a photo of one of Texas Instrument's RF EVMs.

Please pay attention to edge of the PCB that has multiple tiny holes. I marked 3 of them with a red circle on the photo.

What is the purpose/benefit of them? The edges are V cut, is it something to do with it? Or if it is kind of performance improvement, then how do you determine what size of the hole to use and the distance between the holes?

EDIT:

Here is the gerber view of the board (not the same edge), as I can see, they are just holes (not vias)


texts: How to detect the rising edge of a pulse that is not in sync with the clock

texts:
This may be a trivial question.

I have a microcontroller that will attempt to recognize the rising and falling edges of a pulse.  This pulse is not in sync with the microcontroller's clock or any clock.  For my intents and purposes, the voltages are adjusted to the voltages that the microcontroller requires.  How should I expect the microcontroller to behave if it tries to detect the rising edge when...

...the pulse begins near the beginning of the clock cycle?
...the pulse begins in the middle of the clock cycle?
...near the end of the clock cycle?

As well, what should I expect if I try to detect the falling edge with the same timings? (1. near the beginning, 2. in the middle, 3. near the end)

I don't know if this question depends on the specifics of the MCU or the pulse.  If so, I can provide specs.  Thanks!

EDIT: I think I worded my question poorly.  I understand that the MCU will only sample each clock cycle.  I was mostly asking what would happen if the pulse were to change polarity in the 1. beginning, 2. middle, 3. end of a clock cycle.  Will this affect what the MCU samples?

Specs: ARM9 MCU http://www.nxp.com/documents/data_sheet/LPC3141_43.pdf

Pulse: Pulses are generated by an avalanche photodiode.  Each pulse represents the arrival of one photon.  Pulse high lasts 30 ns, pulse dead time is minimum 50 ns.  The current goal of my project is to use the internal timer to time these pulse arrivals.


texts:
I want to run a 130V dc motor 2hp. I have 6 solar panel 120V dc out.

I connected them in series to the motor directly and it runs, but when I check the voltage at the terminal when it is running it read 60V. Where is the rest of the voltage and why not all the volt is use it up?

What can I do to make it run full power?

Second question: Can I attach a dc-dc boot converter at the end terminal of the solar panel and increase the voltage directly without using anything else? What is wrong with that idea?

thank you for your responses.
I am trying to run a water pump. I have purchase a mppt unit that has 80v input max, and two lead batteries deep cycle, but I notice that I have to convert the voltage to ac then back to dc and make it 130v. how can I make this work, do I connect the panels in parallel and then charge batteries, have ac inverter and ac-dc inverter, I am not sure if this Is practical at all and how many batteries do I need, can I


texts:
I am using the LT3845 to obtain 1.3V of output. From the formula given for calculating the resistors to obtain 1.3V, I conclude that R5(the one tapping into the Vout) should be approx5.69Ohms and the other resistor be 100KOhms. The test schematic simulation in LTSPICE is as shown below -

.

But, the Vout is almost 0V. The waveform is as shown below -

Why so?


texts: Do commercial AM radio stations broadcast a carrier?

texts: A possibly dumb question: I'd like to know if commercial AM radio stations broadcast a carrier tone along with signal sidebands. To ask my question is a different way; if I could measure (view) the spectrum of a transmitted commercial AM broadcast signal presumably I'd see the two symmetrical sidebands' spectral energy. But would I also see a single narrowband spectral component, a carrier tone, in the center of the two sidebands? (I've searched and searched the Internet trying to find out if commercial AM broadcast signals are suppressed-carrier AM signals. But I've found no clear answer.)


texts: Biasing an AC signal for sampling - detect minor changes via Arduino

texts:
I am trying to bias an AC signal and to the best of my knowledge I've come up with this circuit. please be easy on me am just getting used to the concept/terms of sampling and biasing.

I am trying to get the slightest variation on of the AC signal and when simulating on LTSpice i can see a difference of .1 to .7v. Wish to know if this design would be enough for MUC such as the arduino sample. Should i smooth the signal ?

What am i trying to achieve ?
A way to read the current from the secondary winding of a MOT (Microwave Oven Transformer for spot welding 18650 cells) by reading the voltage and a known resistance and by using Ohms Law I=V/R calculate the current putout during weld.

So i could use a current transducer but for the thickness of the cable of 25mm2 a CT would be very expensive. hence thought of going this way, I have two variables already which is voltage and Resistance hence within the code i could get the current. To get the voltage i have tapped on 2 points on the secondary cable at 40cm apart and i get a sinewave of 1 to 3 Vpp. So just need to scale the ac voltage safe enough to be fed into an arduino ADC and the easiest way would be to add a dc biase (i hope i've used the terms correctly) or some say it as level shifting with an opamp and some resistors and caps.

simulate this circuit – Schematic created using CircuitLab


texts: Why are multimeter batteries awkward to replace?

texts:
I teach introductory physics labs, and inevitably when we do our labs on introductory circuits or mapping electrostatic potentials, there are one or more multimeters whose batteries die or fuses blow.  This is always something of a hassle, since you have to find a screwdriver, undo the screws, open the case, swap out what actually needs to be swapped out, and refasten the screws.  It would be simpler if the batteries and fuses were in a separate compartment that could be opened easily, the kind that slides open/closed and latches shut when in place.
Why are multimeters designed this way?  I can think of a few possibilities:

There is some reason, related to how a multimeter works, that means that the batteries/fuses need to be very securely inside the case, and which a separate compartment with an access door would not satisfy.  But I have no idea what this reason would be.

It would cost more to design & manufacture multimeters with this extra compartment.  Perhaps, but multimeters are already pricey enough that I have a hard time believing that it would make a significant difference in the purchase price.

It's always been done this way.  What's more, people who use multimeters are already the types of folks who are used to opening up the case of a malfunctioning device with a screwdriver, and in fact find some pride & enjoyment in doing so.  So there is an active incentive for manufacturers to design multimeters this way.  This requires a bit more armchair psychoanalysis of multimeter users than I'm comfortable with, though.

Does one of the above reasons explain it sufficiently?  Or are there other factors that I'm not thinking of?


texts: I recently had my ICD3 programmer stop working. I received a replacement today and before returning the old ICD3 wanted to test the new ICD3 out. I connected the new ICD3 to my PC and Windows XP Professional SP3 32-bit prompted me to install the drivers for the device. I selected the drivers located in the MPLAB IDE (v8.63) directory. When the installer reached the NcGen.sys file the computer hung up and I had to force the system to power down using the power button. Has anyone else had and resolved this issue with the Microchip ICD3?


texts:
hello i dont sure what is the difference between voltage ampere and watts.
voltage is only the potential difference between points high voltage will not cause to the electrons to move faster
so why volt is needed?
and if i have led that need 5 volt and 20ma why its neede to write 5 volt if the ampere is the result of the volt?


texts:
This is my first post and I am happy I stumbled across this forum. I am preparing for a job interview and have been given a Delta-wye transformer schematic and have been asked to discuss the phase shift between the primary and secondary windings. I know that there is a phase shift of 30 degrees, but in this particular drawing there is a neutral line on the delta side with no clear connection point marked. I haven't dealt with transformers in a while and am wondering specifically where the neutral is connected to in this schematic? I am assuming I will be asked more about this transformer configuration and would like to completely understand what is going on here with that neutral. Any help is greatly appreciated!

simulate this circuit – Schematic created using CircuitLab


texts:
The problem I'm trying to solve: I have a vehicle that has 3 wires for the tail/brake light.  When the vehicle is on there is 12v+ between the red and black wires and there is 7v+ between the red and Orange wires.  When you hit the brakes the 7v+ between the red and orange wires steps up to 10v+.

So I need to create a circuit that will turn on a set of LED lights when the voltage goes above 9 volts.  Currently, my circuit consists of a voltage divider (changing 12v down to 9v), an LM324N OPAMP and an FQI50N06 MOSFET (Schematic shows IRF540).  For some reason, on the OPAMP, when there is no input, the output is on, when the non-inverting input is higher than the inverting input the output is on and when the inverting input is higher than the non inverting input the output is off.  So in my mind, this circuit is working, except when there is no input, the the output should be off.

EDIT:
Something that just popped into my head as soon as I posted this, I wonder if putting a diode on the output would prevent the output from being on when there is no input.

Please see the attached schematic:]1

EDIT2:

EDIT3:


texts: How does the power supply noise generated by digital ICs affect the output of regulator?

texts:
I have learned that the digital ICs would generate the power noise in the power supply line,however, I am not so clear about how.

In my opinion, two contributors: the change of the current would lead to output voltage deviation of the regulator due to the load transient response. Also, the load regulation would result in another deviation.

For example, a lm1117 regulator supplies power to a MCU. A 0.5A step current change causes more than 100mV deviation(figure 1). And 15mV max deviation if load current changes from 0 to 800mA(figure 2).

Is my opinion correct? Any other opinion? Thank you very much!

simulate this circuit – Schematic created using CircuitLab

figure 1.

fugure 2.


texts:
I need to regulate and possibly adjust an AC output voltage during operation, owing to certain circumstances. Problem is that the unit is pretty much too remote and inaccessible to replace any relay stuck or otherwise failed and I'm not in full control how many cycles they need to go through but the upside is that price isn't an issue and low volume.

Search terms for transformer tap changers gives plenty of results, but they are almost all for in-tank MVA-sized transformers. I'm in the 100-1000 VA range.

COTS SSRs for 230 Vac are plentiful, but they were all SPST. If I put one of the on each tap (primary or secondary), that would mean that two selected at once would blow a fuse (and possibly the SSR) which is not acceptable. Is there a standard method to use SPST in a SPDT fashion where two inputs (or outputs) cannot be selected at the same time by design? Is there a search term I'm missing here?

My design goals are:

No maintenance required (or possible really).
Impossible to short a winding (and blow a fuse) due to MCU/PLC doing something bad.

There is some hold-up on the secondary side downstream so if a few cycles are missing during switchover, that's acceptable.

Is there a standard solution for this? I don't need you to design it for me, I'm more looking for a search term to move forward.

simulate this circuit – Schematic created using CircuitLab


texts: 3D Rotation Using Fixed Point Arithmetic - Rotating Object is Deforming (and Shrinking)

texts:
I have an FPGA board (Virtex 5) for which I have created a Wireframe GPU with the ability to rotate a sample object using a 3 Axis Trackball.  Additionally, I have connected the board to a PC Monitor.

Initially the object can be seen intact (with no deformations)?  However, when I begin to move the trackball I notice the object begins to deform and shrink.

I have tried various methods to provide immunity to the problem but can not keep the object from deforming.

Primarily, I have tried to to multiply each coordinate by a correction factor on rotation so that as the points shrink I multiply by the correction factor (determined by the original distance to the center for each point divided by the new shrunk distance).

With these methods in place I still am unable to prevent the deformation.

Is there any way in fixed-point to keep the object coordinates intact on rotation?


texts: servo not strong enough to move robotic link fully

texts:
I'm currently working on a robotic arm. The servo I'm using is the MG996R. i'm trying to make the servo lift a link that weights 55 grams and 20 inches long. The servo itself is powered with a 9v to 7v LM2596 voltage regulator(i'm only using one 9v dura cell battery). however, the servo will only go from 270 degrees to 180. if i want to go from 180 degrees to 0 degrees, i will have to manually move the arm in position. The stall torque for the servo is 12kg * cm.

so my question is that do i need more power or the servo is not strong enough and that i need to decrease the weight of the arm?

Links for the servo i bought and a robotic arm calculator that i use to get an idea of the torque that i might need

http://www.ebay.com/itm/4Pcs-MG996R-Digital-Metal-Gear-Servo-High-Torque-Upgraded-MG995-MG945-RC-Model-Y-/281830599332?hash=item419e69aaa4:g:NXcAAOSwI-BWIbDG
http://www.robotshop.com/blog/en/robot-arm-torque-calculator-9712


texts: Simulate RF transmission lines at Low frequencies

texts:
I would like to simulate RF transmission lines in how they propagate, and how impedance mismatches at the end of the transmission line cause reflections and power transfer does not work.

It would be nice if I could send an audio frequency through the "transmission line" and watch the output, hooking up different resistors until it is matched to the characteristic impedance of the line, and max power transfer occurs.

A fun hands-on simulation project built from electronic components would help me grasp a better understanding of radio wave propagation through transmission lines, and would be a fun project for my electronic club in high school, attempting to understand RF a little more.

Any ideas on a circuit? It isn't really practical to make a big line multipule wavelengths of the Audio Frequency and I am thinking maybe using large inductors and capacitor arrays, possibly a circuit similar to the picture below.


texts: Arduino ADK + Android LED blink example compiling errors

texts:
I'm trying to make a project using the Arduino ADK board  and a Sony Ericsson Xperia Play running Android 2.3.4. For starters all I want to do is blink a LED from my Android device, using the nice tutorial found here. I managed to compile the Android app but I'm having big difficulties on the Arduino sketch. I can't resolve the imports and it won't compile. I understant there are some Arduino IDE version issues. I tried compiling on both 0023 and on 1.0. The furthest I could go with the code was getting these compile errors:

D:\arduino-0023\libraries\AndroidAccessory/AndroidAccessory.h:37: error: 'EP_RECORD' does not name a type
D:\arduino-0023\libraries\AndroidAccessory/AndroidAccessory.h:50: error: 'EP_RECORD' has not been declared
D:\arduino-0023\libraries\AndroidAccessory/AndroidAccessory.h:50: error: 'EP_RECORD' has not been declared
D:\arduino-0023\libraries\AndroidAccessory/AndroidAccessory.h:64: error: 'USB_NAK_LIMIT' was not declared in this scope

I think I read the whole documentation and I can't find a solution to my problem. Setting this up is such a pain... I really need to make this work.


texts: Electrical resistance converted to wire temperature

texts:
I'm trying to get a formula that I can reuse to help me determine wire size and properties. The goal is to heat a 430' wire between 40-100F using 12 volts and 10 amps of direct current.
Everyone is talking about ambient temperature but I'm more interested in the actual wire temperature, properties (copper, zinc, aluminium) and resistance. I'm looking to engineer the wire to fit the purpose not make my system fit the wire (too late).


texts: What is the difference between the Bandwidth and the Gain Bandwidth product that we usually find in datasheets of OP AMPS and comparators ? and why have we defined the Gain Bandwidth Product and we did not stick with the The Bandwidth parameter ?


texts: Since SPI contains data and clock, this makes it "source synchronous" doesn't it?

texts:
I read in a Xilinx application note that as data rates became faster became developed source synchronous transfer technique and later came the self-synchronous methods that make use of 8b-10b or some other encoding and the data is extracted from the input data stream.

However, while SPI is very old and not really "high speed" unlike how we communicate with DDR RAMs using source synchronous transfers, it still sends out data with clock. Thus, is it correct to say that SPI is a simple low speed source synchronous data exhange protocol?

Besides this, usually protocol contains data along with information about data like start of packet, end of packet, CRC, source, destination bits e.t.c. However SPI does not contain any of this. Is it still correct to call it protocol?

While serial data transfer being asynchronous, has start bit and end bit thus in my understanding the simple serial transfer e.g used in RS-232 is a protcol but SPI does not posses such information. What am I misunderstanding here?


texts: ESP12e: analog reading not working with voltage divider

texts:
I'm trying to read from an analog sensor (a capacitive soil moisture sensor). I'm using a ESP12E, not a development board, so the ADC pin can only take 1V max. Since my sensor can output up to 3V, I need a voltage divider to not fry my board.

Here is my wiring:

https://imgur.com/4NYRfzt

simulate this circuit – Schematic created using CircuitLab

Could you please confirm the wiring is ok?

I use micropython and the following code to read from the sensor:

from machine import Pin, ADC
from time import sleep

pot = ADC(0)

while True:
    pot_value = pot.read()

    print(pot_value)

    sleep(1)

However, the analog reading is always 0. When I disconnect the ADC pin, I get other, fluctuating values. So I think the problem comes from my voltage divider.

The sensor works with a ESP32 devkit board, so the problem doesn't come fro m the sensor (the devkit board has a voltage divider, so I didn't need to make one myself).


texts: Optimal signed integer flooring divider circuit?

texts: I've never seen a flooring divider circuit; only ever truncating, occasionally with a vague note that flooring is "cleaner". What does that actually mean, though? Can it skip some checks? Can it operate agnostic of sign? I can't find clarity anywhere.


texts: USB Design Standpoint: On-Chip USB vs. Dedicated Chip

texts:
Soon enough, I will be facing a decision on implementing USB into one of our products. At first, I though that programming USB device and host drivers won't be that much of a problem, but it seems I was dead wrong.

A few days ago, I stumbled upon some pretty cool FTDI chips, that provide an interface which I can connect to easily on both ends. And since the additional price ($2) for such little QFN is not an issue, I am seriously considering this option.

They also provide some pretty cool host-side WHQL-signed drivers that we can(?) use. Namely, it is 1. VCP (Virtual Com Port) driver, 2. D2XX driver, providing a DLL based application-USB interface.

My question is, can anybody direct me either way? That is - will I make my life an order of magnitude easier by using an FTDI chip, or will I run into some wall that I'm not seeing right now?

Thanks for sharing any experience.


texts:
I have been studying multivibrators lately, but I have hit a wall right now. I have attached a sketch for an astable multivibrator. I know the basic stuff. When Vout is high then Vin will rise as CT1 is charging. Since the op-amp has negative feedback, then Vref will follow Vin until the upper limit of the Schmitt trigger is hit. Then Vout will turn low.
My problem is that in the split second where Vout changes from Vcc to 0V, then CT1 will discharge through R130. Vref is also higher than 0V, so a current will go through R107 and towards Vout.
So what I see is two positive currents moving towards Vout. But this current has to go somewhere. Vdd of the op-amp is connected to ground, so I can't imagine a current moving into the output of the op-amp, but it is the only solution as I see it.
I hope someone can clarify how the currents are moving when the capacitor is discharging.


texts: USB charger with voltage different than 5 volt

texts: Can somebody explain why and how certain USB charger can supply higher voltage than the standard 5 volt? Apparently certain devices require higher voltage (e.g. ASUS Transformer tablet--requires 15 volts; or Motorola Droid  requires 9 or 9.5 volt. Somehow there is a handshake process when the USB plug is connected to the right device--then the charger knows how to switch to the higher voltage to enable charging. Without this proper handshake, the charger seems to politely issue the standard 5V. What kind of handshake is this, and what's the electronic/logic to determine the demanded voltage?


texts: Wiring power supply, battery and charger for portable speaker

texts:
I'm planning to build myself a small portable speaker. I'd like to include a Li ion battery and a jack for an external 12V-ish power supply. I'd also like to add a jack that will be used to charge the battery from an external Li ion charger.

If the first one turns out well I might make more to give as gifts. As such, I'd like to make the design as dummy proof as I can. I'd like to wire the power supply jack and the charger jack so that:

1) When the power supply is plugged in, the battery is disconnected from the circuit to prevent the power supply from damaging the battery.

2) When the battery is charging, the battery is disconnected from the amp so that I'm not drawing current from the battery at the same time that I'm trying to charge it. (Again to protect the battery)

3) I can run the speaker from the power supply while simultaneously charging the battery with the charger.

I think I can solve the first issue using the switched power jack as in the following (poorly drawn) diagram.

I'm not sure how to do #2, but I imagine I would have to include a switched jack for the charger as well. Just not sure how to hook it all up. Anyone have any ideas? Thanks!


texts: What components draw the most power in a wireless receiver?

texts: Let's assume I'm talking about a typical single-antenna 5 GHz center-frequency 40 MHz bandwidth 802.11 receiver, but I'm interested more generally. What components in a wireless receiver draw the most power? And how do the power consumption of these components change as a function of bandwidth?


texts:
I just started working on a computer science project that requires me to do some hardware stuff, but I am a complete noob most of it. For a part of the project I need to be able to forward a current stream depending on its voltage. Something like in the picture.

I was wondering if there is an electrical component that can do it.
Thanks in advance and sorry if the question violates any of the stackexchange's rules!


texts: is connecting high end high power leds in series feasible and are there light quality or other issues

texts:
i'm building high power high CRI cine lighting mostly to illuminate softboxes and have chosen Cree XLamp CMT2850 LED 1400mA 36V (Fidelity 95plus CRI).
I plan to build about 12 units for the studio.
I will be using 4 LEDs per unit with total wattage when fully powered 50.4W x4 = 201.6W which will be fitted onto 15cm X 20cm X 1cm copper bar with extra heat sinks connected to the rear of this to keep operation temp below 85C. The drivers will have a 1-10V dimming included to get the right strength of light.
I have a choice of using 4 drivers 1400mA 36V (1 per LED)
or 2 drivers @1400ma 72V with 2 LEDs connected in series.
i don't want to go up to 144V with 4 LEDs in series due to the units being touched and don't want that kind of potential voltage coming into human contact.
my question is will running two high end LEDs connected in series affect in any way their performance , the colour temp (K) or the CRI performance , or affect the life of the LEDS ?


texts: ESD protection for battery powered device

texts:
I have module that will be plugged into another device. The unit itself has no power and receives all power, and signaling from the mating devices. It has a 10 pos exposed connector (male pins) to the outside world.

I have a few questions with regards to ESD protection for these types of devices. (I have looked over the other Q/A but have not found something that gives me a complete picture).

To clarify what "these types of devices" - this includes the inputs of the class D audio amp PAM8302, a WP59SURKSGW bicolor led, and the outputs of a MCP6547 comparator

Will clamping diodes be effective ?
I have thought about placing clamping diodes across the sensitive pins. After some thought, I think that they would not be effective, whereas a colleague of mine thinks that it would. My reasoning is that there is no "voltage" to clamp too and that the diodes simply won't turn on. My colleague argues that, the diodes will turn on, because the VCC and GND would be effectively the same due to the various capacitors on the board.
Does every pin require protection or simply signal paths that have sensitivity to ESD  (for example, a VCC pin, or GND pin) ?
What are clamping diodes effective for  (in terms of ESD) ?
What are TVS diodes effective for ( in terms of ESD) ?
What are MOVs effective for (in terms of ESD) ?
What is a good reference to learn more and become more familiar with ESD protection mechanisms/designs for battery/isolated systems ?


texts: Need help with my initial attempt at a headphone jack switcher

texts:
I'm attempting a little project where I can have three 3.5mm jack inputs, then a switch to direct to a single 3.5mm headphone output.
Based on a simmilar Instructables page but attempting to adapt it for three inputs rather than two.
Here's the highly detailed diagram from that page:

Coming across this diagram for a three position switch, I thought I had a plan:

So I've attached all the components and given it a test

But it has become apparent that it works a little more like this:

I'm now coming across diagrams like this one in the bottom right, talking about external jumpers between the pins?

Am I just using the wrong kind of switch, or do I need to re-jig my wiring and add some jumpers in?
Any guidance would be most appreciated.
Thanks.


texts: Supercapacitor and an applied exterior magnetic field?

texts:
I'm curious of the effects of an exterior magnetic field to a Supercapacitor, in both states of charging & discharging.

If the Supercap. is placed inside an area where an exterior magnetic field \$B_{ext}\$ is applied, while the capacitor is charged, and connected to a load, would the +/- ions move quicker(since the electrostatic force would push like charges away + the Lorentz force) from the double layer towards the electrolyte?

Likewise, for the case of charging, would the ions feel a force(Lorentz) while moving towards the electrode to form the double layer from their initial positions from the electrolyte?

Finally, if I moved the Supercap. in any state(charged/discharged) would the ions feel a Lorentz force(depending on \$v_{SC}\$)?

The exterior magnetic field can be in any direction \$B_{ext}\$ = \$B\hat{i}\$ , \$B\hat{j}\$ , \$B\hat{z}\$


texts: how to calculate Ic as the current through the collector and function of the transistor

texts:
I am going through this tutorial, they state that "Ic is the current through the collector and function of the transistor" however I haven't really been able to look at the data sheet and figure out where that information is. I am guessing you need to calculate it somehow but I am not sure what information to use.

I see the section where they give some typical values of beta with different ranges of current but I don't get how that is a function of the transistor.

Thanks


texts:
Although I have average programming skills, I'm not far from being an noob concerning electronics!

I therefore want to kindly ask you to help me connect my (already programmed) Arduino Uno to the gadget where it should fulfill it's duties.

As you can see I want the mc to "know" every time the circuit at the bottom closes.

I also want the mc to be able to bypass the switch on the top.

I wanted to use opto-isolators for this purpose, as an opto-isolator would guarantee that my project never could damage the original gadget.

As you can see the main problem is the different voltages.

Thank you in advance for your help!


texts:
I am looking for a machine for PCB fabrication.

Can you help me understanding the type of machines available on the market for a hobbyst use?


texts: What sort of a ferrite core will I need to make core memory?

texts: I am building a homebrew computer using core memory. What sort of a ferrite core will I need?


texts: Ok, so I am new to electronics and unclear about something. Let's say I have a closed loop inverting op-amp. So there's 2 resistors, 1 feedback resistor, and the resistor at Vin. So I want a gain of perhaps 10 and I know voltage gain is the feedback resistor divided by the resistor at Vin. What should my resistor values be? Whats the difference between 1ohm & 10ohm resistors or 1kohm and 10kohm resistors? Appreciated if anyone can help


texts: How to integrate NEMA x-15-P into mechanical/electrical design

texts:
What are some ways (or what is the typical way) that a wall mount device mechanically and electrically attaches the AC blades/plug into a design?  I've worked with panel mount IEC320 and cabled power entry in the past, but I'm curious what the common means of using NEMA plugs is.  I'm thinking of something like the ubiquitous AC-to-USB power converters that are everywhere.  Are the prongs molded into the plastic and then wire attached to PCB holes/pads?  Do they direct solder the prongs to the PCB?  What about in the case of foldable plugs?

Fixed prongs example

Foldable prongs example


texts:
I was wondering what is the power consumption of opening and closing a switch.
I mean when you put two conductives plates together for closing a circuit and then you take away the two plates for removing the contact, what is the power consumption ? mechanical cost ? thanks


texts:
This term is mentioned in the Micron Application Note: Hardware Tips for Point-to-Point System Design on page 10 (...For signals with lead-in termination...), however I've been struggling to find out exactly what lead-in termination means.

It's quite a difficult google search term: I finally found a reference to "Lead-in vs loaded routing" in this, one of the last pages.

Searching for "Lead in vs loaded routing" gives 3 results, one of which is the above, the other two are not particularly helpful.

Can anyone explain what lead-in termination is, or point to me to a book, or a synonym that's more widely used?


texts: Best way to go about biasing a Class B audio amplifier?

texts:
I am trying to bias the class be audio amplifier in the provided pdf. None of the resistor values are correct so the bjts are unbiased. What is the best way to go about starting to bias this?

Circuit:

simulate this circuit – Schematic created using CircuitLab


texts: Schmitt Trigger Functionality Not Working, Questions

texts:
I'm trying to build a Schmitt trigger like the one described here: http://pcbheaven.com/drcalculus/index.php?calc=st_nonsym_sp

However, it isn't working as expected, and I'm thinking it may be due to a number of reasons, only a few of which I have a suspicion of. It would be a great help if someone could advise me on how to properly build a Schmitt Trigger because I'm quite new to this and don't have much experience.

I used a LM358 op-amp from TI, which I'm thinking might not work because I'm not sure if it's a two-rail op-amp. I don't know exactly why a two-rail op-amp is necessary, but a couple of videos I have watched mentioned that it was necessary.
The resistors I used have relatively small values. In the PCBHeaven link I posted above, R1 = 1kOhm, R2=10kOhms, and the feedback resistor was 10kOhms as well. I don't know why this matters, but might it have something to do with saturation of the op-amp? I really don't know.

I'm more frustrated because I see certain videos floating around online such as this one: https://www.youtube.com/watch?v=-JW1fv2O73A and the circuit set up seems pretty much exactly the same as mine, save for the larger resistor values and the different op-amp.

I know that the Schmitt Trigger is supposed to output either a high or low logic level when the thresholds are passed, however I'm not observing this. For example, if I supply the op-amp with 5V and also make V+ 5 volts, I observe the following results:

When input voltage = 5V, output voltage = 2.85V
When input voltage = 0V, output voltage = 3.91V
When input voltage = 3.3V, output voltage = 3.91V

Which are extremely confusing results, especially since none of those values are near 0V as I would expect to represent a logic low. I become more confused when I directly test the functionality of the op-amp by comparing the negative and positive terminals, and the op-amp correctly produces a logic high when the positive terminal > negative terminal, and produces a logic low when negative terminal > positive terminal.

If anyone has any idea or suggestions for where I went wrong, or have general advice for building a Schmitt Trigger, please let me know!


texts:
I'm thinking about building a simple electronic watch in my spare time.

Not a lot of functions, no LCD, just keeping time and displaying the time using LEDs.

However, I have never created a time-keeping circuit so I'm wondering if using a µC's internal clock is enough to keep track of time or do I need something else?

I have seen some people using 32.xxkHz for time-keeping. Why do people choose this particular value (maybe it's just coincidence I came across a few projects using that value).

Links to projects are always welcome.


texts: Is a buffer required for this gas flow sensor to ADC connection?

texts:
I'm designing part of an application that will consist of an Omron D6F-P0010A1 MEMS flow sensor. The analog output of the sensor will be connected to a TI ADS1114 ADC.

I'm trying to figure out from the respective datasheets whether I'm going to need a buffer in front of the ADC or not.

The datasheet for the Omron sensor doesn't mention source impedance anywhere, only that its charts were measured at a load resistance of 10k. The datasheet for the ADC specifies common-mode/differential input impedances of 3M and 2.4M at the scale I am likely to use.

I'd like to get accurate readings from the sensor, so do you think that a buffer will be necessary?


texts: What happens to the extra electricity (amps) created by an off-grid solar (PV) array?

texts:
On a grid-tie solar panel array all the electricity created which is not used by the home is feed back into the electrical grid.

However, on a off-grid system with batteries - where does the extra amperage created by the solar panels go if the batteries are full?


texts:
I'm having some problem with my code and I can't get my two loops working properly. I'm new to C programming so I might have got the basic loop concepts wrong. I've got 10 LED lights connected to my different ports on my microchip which are rotating in order from the first to last, and then back to the first again. The issue I'm facing is that I'm trying to get one of the buttons on the microchip to work as a start for the loop, but my code won't work.

void delay(int d);

int main(void)
{
    TRISCbits.TRISC3 = 0;
    TRISCbits.TRISC4 = 0;
    TRISCbits.TRISC5 = 0;
    TRISBbits.TRISB4 = 0;
    TRISAbits.TRISA9 = 0;
    TRISBbits.TRISB2 = 0;
    TRISBbits.TRISB0 = 0;
    TRISAbits.TRISA1 = 0;
    TRISAbits.TRISA11 = 0;

    while (1)
    {
        if (PORTAbits.RA11 == 1) {
            PORTCbits.RC3 = 1;
            delay(500);
            PORTCbits.RC3 = 0;
            delay(500);
            PORTCbits.RC4 = 1;
            delay(500);
            PORTCbits.RC4 = 0;
            delay(500);
            PORTCbits.RC5 = 1;
            delay(500);
            PORTCbits.RC5 = 0;
            delay(500);
            PORTBbits.RB4 = 1;
            delay(500);
            PORTBbits.RB4 = 0;
            delay(500);
            PORTAbits.RA9 = 1;
            delay(500);
            PORTAbits.RA9 = 0;
            delay(500);
            PORTBbits.RB2 = 1;
            delay(500);
            PORTBbits.RB2 = 0;
            delay(500);
            PORTBbits.RB0 = 1;
            delay(500);
            PORTBbits.RB0 = 0;
            delay(500);
            PORTAbits.RA1 = 1;
            delay(500);
            PORTAbits.RA1 = 0;
            delay(500);
            PORTBbits.RB0 = 1;
            delay(500);
            PORTBbits.RB0 = 0;
            delay(500);
            PORTBbits.RB2 = 1;
            delay(500);
            PORTBbits.RB2 = 0;
            delay(500);
            PORTAbits.RA9 = 1;
            delay(500);
            PORTAbits.RA9 = 0;
            delay(500);
            PORTBbits.RB4 = 1;
            delay(500);
            PORTBbits.RB4 = 0;
            delay(500);
            PORTCbits.RC5 = 1;
            delay(500);
            PORTCbits.RC5 = 0;
            delay(500);

            PORTCbits.RC4 = 1;
            delay(500);
            PORTCbits.RC4 = 0;
            delay(500);
        }
        else {
            TRISCbits.TRISC3 = 0;
            TRISCbits.TRISC4 = 0;
            TRISCbits.TRISC5 = 0;
            TRISBbits.TRISB4 = 0;
            TRISAbits.TRISA9 = 0;
            TRISBbits.TRISB2 = 0;
            TRISBbits.TRISB0 = 0;
            TRISAbits.TRISA1 = 0;
            TRISAbits.TRISA11 = 0;
        }
    }
    return 1;
}

void delay(int d)
{
    int i;

    while(d)
    {
        i = 100;
        while (i)
        {
            i--;
        }
        d--;
    }
}


texts: How to implement a discrete transfer function into an arduino?

texts:
I am here asking how does one transfer a difference equation into a MCU? I have never done it personally and looking into this topic I was never able to find a good answer. Its usually used with Matlab but never a MCU.

I have a continuous transfer function:

$$LPF_A = \frac{1}{6.416\cdot 10^{-11}s^2+1.133\cdot 10^{-5}s+1}$$

Its a 2nd Order Butterworth filter with a \$F_c = 20\text{kHz}\$.

Using the Tustin method I have the discrete equation:

$$LPF_D=\frac{0.1441z^2+0.2881z+0.1441}{z^2-0.6777z+0.254}$$
With a sample of \$T_s = \$ 8e-6 seconds, in scientific E notation.

The difference equation:

\$Y\$ = Output

\$U\$ = Input

$$Y_i =0.1441U_{i}+0.2281U_{i-1}+0.1441U_{i-2}+0.6777Y_{i-1}-0.254Y_{i-2}$$

I know I have to make my ADC output = \$U_i\$ and initialize \$U_{i-1}\$, \$U_{i-2}\$, \$Y_{i-1}\$, \$Y_{i-2} = 0\$, But after that no idea.

I have no idea what to do with this after. I have always used Matlab's embedded ways of doing it but never have transferred a difference equation into a MCU before. Any help would be appreciated.

Edit: Here's the code based on what I think

  unsigned short x;
double Y_i[10] = {0,0,0,0,0,0,0,0,0,0};
double U_i[10] = {0,0,0,0,0,0,0,0,0,0};
double Y_i_1 = 0;
double Y_i_2 = 0;
double U_i_1 = 0;
double U_i_2 = 0;

void setup() {

  ADMUX |= 0xC0;
  ADCSRA |= 0x8F;
  ADCSRA |= 0x40;
  Serial.begin(9600);
}

ISR(ADC_vect) {
 x = ADCL << 2;
 x |= ADCH;
 ADCSRA |= 0x40;
}

void loop() {
  //Yi = 0.1441Ui + 0.2281Ui-1 + 0.1441Ui-2 + 0.6777Yi-1 - 0.254Yi-2
  for (int i = 1; i < 4; i++){

    if (i == 1) {
       Y_i[i] = 0.144*x + 0.2281*U_i_1 + 0.1441*U_i_2 + 0.6777*Y_i_1 - 0.254*Y_i_2;
       U_i[i] = x;
    } else if (i == 2) {
      Y_i[i] = 0.144*x + 0.2281*U_i[i-1] + 0.1441*U_i[i-2] + 0.6777*Y_i[i-1] - 0.254*Y_i[i-2];
      U_i[i] = x;
    } else {
      Y_i[i] = 0.144*x + 0.2281*U_i[i-1] + 0.1441*U_i[i-2] + 0.6777*Y_i[i-1] - 0.254*Y_i[i-2];
      U_i[i] = x;
    }

  }

}

What happens after the iteration is done? It resets? thats it?


texts: HLG-40H-20B class 2 power supply to a 24 LED 's (stage) light and regular power extension

texts: I would like to know which wires in a HLG-40H-20B class 2 power supply (output +20V ... 2.0A     i am supposed to connect to a 24 LED 's (stage) light and the regular power (extension)


texts:
I have been testing the GPS / GPRS development module A9G, Aithinker which uses an active GPS antenna, according to the schematic reference diagram, the value of the inductance is 82nH:

The question is how did they reach the value of 82nH? and how the other parameters of the inductor are chosen, taking into account that the data of the antenna are:

High performance Beidou + GPS Antenna

Frequency range 1561MHZ 1575.42MHZ

Gain    28dBi

SWR ≤2.0

Beam width  right-handed circular polarization(RHCP)

Input impedance 50Ω

Voltage 3-5v

Thank you


texts: I understand that the output of a flip flop is also called as the state and the output of the flip flop before the clock pulse is applied is called as present state and after the application of clock pulse is called  as next state. But what is state in a general sequential circuit, is it the output of the logic gate from which the output is taken as feedback?


texts: Why INL DNL analysis of ADC gets wrong with 00 logic value

texts:
bellow we have two cases of DNL INL analisys .
the first one without 00 logic acts great the INL is the the sum of the previos DNL.
In the second case when i include 00 logic and we have 4 members.
Its just get wrong?
Why its ruining the DNL INL behavior?
Thanks.


texts:
All of the ADCs I found online have an input range on the order of few volts, e.g. 0 to 5 or -4 to +4. But my signal is in the mV range. Are there any ADCs with such a small input range? I know I can add an op amp but if I can avoid that it will be better.

Edit: required resolution is 16 bits, sampling rate is 300 ksps.


texts: Current flowing through neutral to ground

texts:
The neutral wire of the 3 phase 4 wire system is 0volts compared to the ground.
We also know that it provides the return path for phase currents.
Under unbalanced loading, current does flow in the neutral wire as  Ineutral =-( Ia + Ib + Ic)

So how does the current flow from neutral to ground through human body sometimes  when both of them are at same potential ?


texts: 12V Signal -> Relay -> Voltage Regulator -> Arduino mega analogue input. Will this work?

texts:
I have a system that sometimes generates a 12V signal to a DPDT relay coil, which switches on a 12V connection through the relay pins that can be used as a boolean signal to the arduino. I plan to do this by connecting a 5V L7805 regulator, followed by a 1n4007 diode to drop the voltage to approx 4.3V +-10% which should be safe.

My question is, should I be concerned about inductance from the relay coil? I know arduinos don't like inductive loads. Also, are any additional resistors necessary in this configuration, i.e. with the arduino i/o pins configured as inputs with pullup resistors?

If you can foresee any problems with this setup, please let me know.


texts:
I'm in need of electronic component that is able to be tapping, giving a type of massage on the skin. I did some search and can't find anything that is as big as the tip of the finger with the nail.
Do you know about something? I'm thinking of using some type of ATTiny controller to control the rhythm and the sequences. I was thinking of some electromagnetic type of a pump or servo that could be used but didn't find anything.
Thanks a lot.


texts: DisplayPort, high speed data transfer & breadboards

texts:
I want to experiment with hooking up a laptop display to a desktop computer. From what I've read, in terms of connectivity this should not be too hard - modern laptop displays use eDP (embedded DisplayPort) which is to a large extent compatible with regular DisplayPort. However, the connectivity is a bit different (the panel I'm looking at uses a 40 pin, 0.5 mm pitch connector).
I am very new to electronics and PCBs (I've experimented a little bit with an Arduino and LEDs but that's about it) and am trying to figure out the right approach here. I've found that I can buy breakout boards for both DisplayPort connectors and the 40 pin connector, which makes me think that I might be able to connect those to my breadboard, add some other circuit elements (mainly the backlight power supply) and get going.
Is this feasible or am I being very naive? I've also read that with high-speed components (which I imagine a DP connection might be) breadboards can result in all sorts of electromagnetic interference.
Of course I can just try and see, but any input on whether I'm thinking in the right direction or if other approaches (e.g. a soldered prototyping board?) would be more hopeful would be very helpful. Thanks!


texts: Routing decoupling capacitors to a micro-controller

texts:
I'm attempting to design and make a Keyboard PCB and have stumbled onto a question I can't seem to find online (probably because I'm not searching for the right thing/lack of info)
When routing decoupling capacitors in parallel you do not place them next to one another, correct?
There should be one right next to every VCC pin?
ie. Not like this:

But like this:

Per @Sparky256's suggestion here is the ground plane:


texts:
Is it possible to increase the amount of current available to a stepper motor using 2 or more of the same drivers in parallel?

I want to drive a 3A stepper but I can't seem to find any reasonable 3A+ drivers out there. Could I use two of the drivers, in parallel, on this board to somehow get 3A of current to my motors (provided proper heat sinking)?


texts: How to send a digital signal when analog sensor (QRE1113) reaches a threshold value without resorting to wasting analog input pin?

texts:
I'm building a miniature pinball machine and I am attempting to use an infrared reflector sensor (QRE1113) to detect when the ball rolls over it (I got the original idea from Ben Heck's videos).

In my testing the sensor does respond adequately to a ball rolling over it, and it's easy to make this determination through the Arduino analog input.

However a pinball machine has way more rollover sensors than the Arduino has analog inputs (final playfield will have ~10-20 rollovers).

My Arduino code doesn't need to know the analog value of the sensor, all it needs to know is whether the value has dropped below a certain threshold meaning a ball is on top of the sensor.

So ideally I would like to convert this analog value to a low or high depending on whether that threshold has been reached, and to then send that result to a digital pin instead of an analog one.

I sort of solved this problem by hooking the sensor up to a digital pin, but using a potentiometer to adjust the sensitivity so that the threshold voltage I want to detect happens to line up with the threshold of what Arduino considers to be high or low.

This is essentially identical to this schematic (but I'm NOT using the sparkfun breakout board, I'm using the bare sensor):
http://cdn.sparkfun.com/datasheets/Sensors/Infrared/QRE1113%20Line%20Sensor%20Breakout%20-%20Analog.pdf

The only difference from that schematic is that instead of the 10K resistor I have a 1M resistor and a 500K potentiometer in series in place of where the 10K resistor would be (I think their schematic has a mistake, a 10K resistor gave me terrible results and through trial and error I found 1M works best).

This solution works but it feels cludgy because I'm not actually generating a proper 3.3V HIGH or 0V LOW signal and instead sending an analog signal that just so happens to match up with what Arduino considers the fringes of a high or a low.

Is there a better more "official" way to do this instead of my hack that would allow me to send 0V or 3.3V to the Arduino digital pin based on the analog sensor reaching a certain threshold (ideally adjustable since it takes some trial and error to get the right sensitivity).

I'm building this machine mostly to learn electronics so the "lower level" the solution the better. I know there are ADC boards will expand how many analog inputs I have via "magic", but it would be way more satisfying to build something out of basic components that I can understand.

PS: I'm mostly a software guy. Building electronics circuits is new to me so if I'm thinking about the problem all wrong let me know as well.


texts: Finding the impedance of a transmission line

texts:
I would like to find the impedance of a transmission line, which in my case happens to be conductive spray paint on paper.

However, I want to do this simply with a single DAC (TX) and ADC (RX) pair that can send arbitrary pulses/CW waves etc. (no VNA or multimeter involved here)

My idea is to place the TX and RX close to each other. Send a pulse, measure the reflection, determine the reflection coefficient, then calculate the impedance of the transmission line.

Does this method make sense? If not what are possible problems I might face? I'm wondering if I would even be able to see the reflection, or if it might be too small.


texts:
I am trying to design a minimalistic current source to drive an LED from a lithium polymer battery and with a small number of components to minimize board space usage.
First I wanted to use the same type of current source shown in the datasheet of the LT3080 :

then I noticed the LT3080-1 is the same but with a 25 mOhms resistor in the output of the functionnal diagram. So my question is :
Can I use LT3080-1 as current source with only the integrated 25 mOhms as output resistor?

It seems to work in LTSPICE with the following schematic with a 3.2 voltage source (not with 3 as on the picture) for a 65 mA current source (although there is a slight offset, which is okay for my application and can be accounted for anyway) :

But I am wondering if maybe there are imprecisions which will prevent repeatability of current accuracy in production? The current reference inside the component seems precise enough but I don't know the accuracy of the 25 mOhms resistor.

I want to use this component because of the low voltage drop (~0.3V) and the fact that I am driving an LED from a LIPO battery (4.2V max, 3.2V min) with a Vf= 2.9V. The 25 mOhm resistor also minimizes the voltage drop around the output resistor.

I don't want to use buck boost LED drivers because they are even more expensive and require more components.


texts: How is the difference between sdf back annotation and spf back annotation?

texts:
I'm  a rtl engineer.
I'm confused between the difference of sdf and spf back annotation.
As I know sdf came from STA( PT)  and SPF came from STAR-RC.
So  In my experiance, the sdf used to timing close the netlist without RC elements.
then this netlist to send a PNR team. After extraction RC elements in layout team by starRC. Then finally we once again do post sim with spf(a.k.a back annotation) .

Is this rtl synthesis flow right ? Then where is to do CTS flow?


texts:
I have seen many different ways of driving TRIACs, and would like to understand what should I consider when choosing between them.

One option is turning the TRIAC by connecting the gate to the load:

Another option is connecting it to the voltage source:

And at last, there's the option of driving the gate independently from the load (in the example, a microcontroller is used, but I guess one could do the same with a triac driver and a resistor):

So, what are the advantages/disadvantages of these configurations?


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I am building an amp for 6th order subs which is based on two transformers which have around 25 VAC, and I am trying to rectify them for 2 subwoofer module filter boards (12-32vdc) and for two TDA7498. Each pair has its own transformer.
I tried my luck first with one eBay board based on some LM voltage regulator but the TO220 literally exploded despite the fact that it was rated to 25 VAC. I figured it could be the current was too large. So I brought bigger rectifier boards based on xl4016 which should accommodate  up to 25 VAC @ 6 amps. I have used these with 2.1 tpa3116 and various Transformers around 25v and they have been working flawlessly.
I still have one module which works in my system well. I ordered 3 new . I used first one set that on open voltage of the transformer to 24 vdc so I don't fry my amp and module and then I connected it (actually turned off connected and turned on). What follows was basically very wild release of fumes from one cap on the board. I was prepared for such situation so I didn't inhale anything(after my unlucky experience with cadmium oxide in thermorelay from eBay).
I measured before failure 34 VDC output as if output pot failed and send through only rectified voltage from bridge. Why did capacitor exploded on this module and  not on the other module? I put textile tape to prevent short-circuit because boards are attached to metal. Could over-voltage of AC (extra 1.5-2Volts)caused the faiure? is that a significant problem tuning the pot to lower voltage then input ac voltage?
If input is AC25v and I set it on the pot to 24vdc do I cause somewhere excessive heat?
Thank you


texts:
I was looking for answer to following question: what for are driver transistors used? Can someon explain to me why circuit (simple class A amp) under this link does not work correctly:

While this circuit works fine:

Original conversation is here: https://www.electro-tech-online.com/threads/how-to-connect-common-emitter-with-emitter-follower-to-speaker.90240/

Regarding the working circuit:
Why is the Q1 needed to drive Q2? Wouldnt it be enough to drive Q2 straight away from R1 R2 divider? If not, why? Thanks for help:)


texts: How to calculate the maximum current a AA battery can deliver for a short period of time?

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I want to measure the maximum current a AA battery (full charged) can deliver for a short period of time (let's say one second)

I have in mind to do this with a multimeter :

setup multimeter to measure amps, on the highest value. My current multimeter has an input rated 10A (for max 30 seconds)
plug negative probe to negative side of battery
plug positive probe to positive side of battery (for one or two seconds)
read value on device

Usually when you need to measure current for given load, the multimeter is wired in series in the circuit. Since here, there is practically (almost) not load at all I have decided (to best of my knowledge) to connect the multimeter directly to the battery.

This will create a short circuit. In theory, current should be incredibly high (because resistance is almost zero), but since AA battery has internal resistance (IR), it will be limited (fortunately).

Is this a good idea? Or will it kill the device or give not the desired effect for measurement ?

Note : I have in mind doing this using AA battery only, doing this on mains AC current for example would (I guess) be very dangerous (220V AC short circuit) and destroy device immediately.

by current the battery can deliver I mean ampere not ampere-hour (Ah) which is a different unit.


texts: Smartphone Fast Charger with Lipo and UBEC

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I have a 3 cell, 11.1V Lipo and a 5V@3A UBEC that I am using to charge my Samsung S8+ with USB type C cable.

This works fine, but my phone reports "slow charging" and takes about an hour to charge 10%. If I use the phone while its charging this way, I will still slowly lose power.

When I plug the cable into the "fast charger" provided by Samsung, the phone will charge from 0% to 100% in about 40 minutes.

The adapter for the fast charger reports 9.0V@1.67A OR 5.0V@2.0A

Shouldn't a 5v@3A UBEC be able to match or beat this speed? How does my phone know that one is the fast charger and the other isn't?


texts:
I'm pretty new to solar panels and basically, I'm trying to charge a 40V 4Ahr lithium ion lawn mower battery using solar panels. 40V solar panels aren't nearly as common of a size as 12V so I'm thinking maybe I could just wire up a few solar panels in series to stack up the voltage but I'm now unsure of how I should go about that.
Say I did four 12V solar panels in series to get 48V, could I safely charge the 40V battery with that? Is it dangerous to supply more voltage than a battery is rated for? I would have a solar charge controller of course but I'm not sure if that would help with supplying too high of a voltage.
Or maybe I should just do three 12V solar panels to get 36V? Would that harm the battery at all supplying too little voltage?


texts: Electromagnetic coupling structure of a generator?

texts:
I was referring to this paper (pg. 7) for designing my own small-scale permanent magnet generator. I came across this electromagnetic coupling structure of the proposed APMM:

I am not able to understand the winding diagram. What do 'a,b, c and d' represent in this diagram? How many terminals are present and would it be possible to get a better illustration of this arrangement to illicit better understanding?

Also is it possible to get better power output from a better magnet and coil arrangement with the same size/spacing constraints? Here, they are getting power output averaging 1 W.


texts: How do I prove that the Pi and T models of a BJT are equivalent?

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I want to prove the equivalence of the Pi and T-models of an npn BJT.
The only way I can think of doing this is by showing that both circuits have the same Z parameters. To do so, you would need to use the images bellow.

I have no idea how to extract the Z parameters from the circuits above. Here's my best attempt for the circuits in figure 2:
$$V_{1}=r_{\pi}I_{1}\Rightarrow Z_{11}=r_{\pi} $$
$${Z_{21}=?}$$
$$I_{2}=g_{m}V_{1}\Rightarrow{Z_{12}=\dfrac{1}{g_{m}}}$$
$${Z_{22}=?}$$
Here's my best attempt for the circuits in figure 3:
$${I_{1}+g_{m}V_{1}-\dfrac{V_{1}}{r_{e}}=0}$$
$${\Rightarrow Z_{11}=\dfrac{V_{1}}{I_{1}}=\left(\dfrac{1}{r_{e}}-g_{m}\right)^{-1}}$$
$$Z_{21}=?$$
$${I_{2}=g_{m}V_{1}\Rightarrow\dfrac{V_{1}}{I_{2}}=\dfrac{1}{g_{m}}}$$
$${Z_{22}=?}$$