texts: Why don't they make germanium power diodes for their lower voltage drop? I have used a diode connected junk-box germanium power transistor for a oneoff   low voltage in house  current  measuring job because it out performed a Phillips   BYV1040 1Amp 40V     silicon schottky. Could they make a germanium schottky diode? Would its voltage drop be about half of a Si schottky?                         Could     such a proposed device  be useful in energy harvesting despite probably having a low PIV and high reverse     leakage current ?


texts: Head to tail transistor pair, not a Darlington pair, not a Szlikai Darlington

texts:
I recently reversed engineered a discrete voltage regulator from a board that was performing quite well, and I stumbled upon a weird transistor pair circuit.

simulate this circuit – Schematic created using CircuitLab
The zener D1 is a TL431 shunt regulator in the real circuit. I put a 5.8V zener just to make the simulation works.
I looked for some time in the literature and dug into some schematics and cannot find any references to that kind of transistor pair. Does they have a name ? What would be the advantage of such an arrangement versus a simple BJT or even a Darlington?


texts: What are the different ways to switch power using a microcontroller (Arduino, Raspberry Pi, BeagleBone, etc.) and what are the pros/cons for each?

texts:
I'm using an Arduino to control a 12v water pump for a self-watering plant wall. I'd also like to use the same power supply for both, and probably need surge protection of some kind to avoid spikes. I would like to understand the pros and cons in general of various methods of switching power.

I've come across various methods of switch power on and off, but have little idea of the pros/cons for each. Here's the ones I know about:

Use a transistor (usually a MOSFET) to switch power.
Use an opticoupler to toggle power.
Use a relay to control power output. The microcontroller usually doesn't have sufficient power to switch the relay. So you end up having to have an additional circuit which controls power to trigger the relay. This seems silly.

To me, it looks like an opticoupler would be the best option. There's no heat buildup from a transistor (I think), and there's no need to use power to trigger switching the power as in a relay. However, it's not the most common way of switching, and I don't understand why.

If this question is too vague, please do flag it, but also help me make it more concise. I might not know the terminology to ask a good question.


texts: Is it possible a microphone sounds different when user hold it(or not)?

texts:
I am a computer-science student working on a signal processing project on smartphones based on recorded microphone signals. For my project, I need a really "reliable" recorded signal. The system works perfectly when I put phones on a table and don't touch it. However, when I touch the phone by my hands (e.g., press a button when phone is static in the table), the recorded data in microphone seems changed dynamically for unknown reason. For example, at certain time period, the received audio (sent from my laptop) is louder.

Since I am not an expert of electrical theory, I would like to know if there is any theory about this phenomenon (such as touching make the diaphragm hard to vibrate) I know the microphone is a MEMS microphone which operates as a condenser type microphone but not sure if there is any reason that the recorded signal changes depends on how user touch the microphone (or smartphone body).


texts: Dac over raspberry pi spi troubleshooting

texts:
I am trying to output a signal with dac124s085 from python code on a raspberry pi 3b, running Raspbian Stretch (kernel 4.14.30-v7+ #1102).

I am sure the spi master driver is enabled - dtparam=spi=on isn't commented out in /boot/config.txt

I am using 20 cm dupont cables between rpi and dac. The pinout is as follows (dac124s085 pinout on page 3 | raspberry pi 3 pinout)

MOSI pin 19 on rpi connected to pin 8 DIN on dac
MISO pin 21 on rpi not used by dac
SCLK pin 23 on rpi connected to pin 10 SCLK on dac
CE0  pin 24 on rpi not used by dac
GND  pin 25 on rpi connected to pin 6 GND on dac
CE1  pin 26 on rpi connected to pin 9 SYNC on dac

pin 7 VREFIN on dac is connected to 5V pin 2 on rpi (decoupled to ground)
pin 1 VA on dac is also connected to 5V decoupled to ground
pin 2-5 VOUTA-D on dac is connected to two stereojacks via adc on each line

whole schematic on github

I am using the py-spidev library (https://pypi.org/project/spidev/). Loopback test on spidev0.0 and spidev0.1:

./spidev_test -D /dev/spidev0.0
spi mode: 0
bits per word: 8
max speed: 500000 Hz (500 KHz)

FF FF FF FF FF FF
40 00 00 00 00 95
FF FF FF FF FF FF
FF FF FF FF FF FF
FF FF FF FF FF FF
DE AD BE EF BA AD
F0 0D

The code I am using:

import spidev
import math

class Dac:

    def __init__(self, device):
        self.spi = spidev.SpiDev()
        self.spi.open(0, device)
        self.spi.max_speed_hz = 1000000

    def write(self, ch, data):
        wdata = []
        wdata.append((ch << 6) | ((int(data) & 0xF00) >> 8))
        wdata.append(int(data) & 0xFF)
        self.spi.xfer(wdata)

    def writeAll(self, ch0, ch1, ch2, ch3):
        self.write(0, ch0)
        self.write(1, ch1)
        self.write(2, ch2)
        self.write(3, ch3)

if __name__ == '__main__':

    dac = Dac(1)

    nsamples = 32
    a = [0] * nsamples
    for n in range(nsamples):
        a[n] = int(2048 + 512*math.sin(2*math.pi*n/256))

    while (True):
        for sample in a:
            dac.write(0, sample)

(dac124s085.py script at github)

How can I troubleshoot this problem? The script should output a sine wave but does not. It actually works if I grab the cables between the circuit and the rpi. Maybe the conductivity of my body does something with the clock speed or pulls any pin high/low?

Is the script correct? I must confess I do not really understand it.

Logic analyzer is showing this when I run sudo python3 dac124s085.py on rpi:

Is this right with reference to timing diagram?

Edit: When I try loop.py the dac actually output a constant signal (without me holding the cables or anything)

from adc124s021 import Adc
from dac124s085 import Dac

adc = Adc(0)
dac = Dac(1)

while True:
    ch0, ch1, ch2, ch3 = adc.readAll()
    print(ch0, ch1, ch2, ch3)
    dac.writeAll(ch0, ch1, ch2, ch3)

But dac out hooked to a speaker I mostly get a noise sound - except from when I am nearby the circuit with dac, rpi and wires (not touching) I will upload a csv file with the datapoints.

Edit 2:

The problem is fixed by adding self.spi.mode = 3 under def __init__ in dac124s085.py

I guess I should have a serious read over www.allaboutcircuits.com/technical-articles/spi-serial-peripheral-interface/


texts:
I have read that electrostatic charges produced by human body can be as high as up to a several thousand volts.

How exactly damage of transistors happens

MOSFET NPN
Electrostatic voltage applied to the drain or source thus causing a reverse biasing of either PN junction with a voltage > breakdown voltage

BJT NPN
Electrostatic voltage applied to emitter or collector thus causing collector-base or emitter-base be in a reverse bias with a voltage > breakdown voltage

Am I correct?

Then, why FETs are subjects to be damaged in particular. I often hear about protection against electrostatics for FETs, but for BJT not so often, and not in mention for diodes, also very rare, although they are also PN junction devices.


texts:
I am doing my first Eagle PCB design. It's been going smoothly so far, however, I just hit a road bump. I am using a TC1269 Regulator, but cannot find the CAD library for it. I have looked into tutorials to creating custom parts, but I was hoping that instead I would be able to find a premade one since the TC1269 employs a 8 pin MSOP package, which is common enough that there should be some CAD equivalents already out there.

Does anyone know perhaps another equivalent part that employs the same package that I can use in place of the TC1269 or perhaps a library with the 8 pin MSOP package?


texts: Working with RF Amplifiers for the first time

texts: I'm designing a circuit to use an IF amplifier, specifically the ADL5536, to amplify the signal of an SiPM array consisting of the MicroFJ-60035 TSV SiPM by SensL. My goal is to use this amplifier to boost the output of a multiplexed array of SiPMs. However, this is my first time using an IF amplifier like this, so I was wondering why is the recommended layout different than a standard op-amp? Usually, with op-amps, you have a positive and negative voltage. However, according to the datasheet of the ADL5536, you only have a +5V power source that goes through a bias inductor, and there is no negative power source. Why is this layout necessary, and how is working with an IF amplifier different than a regular op-amp?


texts: how could a 3 amps transformer deliver 3 amps after filtering?

texts:
I saw this project of a linear power supply, and I couldn't understand how the output can deliver 4 amps assuming maximum current of the transformer of 4 amps before the voltage starts to drop.

I understand that 4 amps(RMS) can deliver 5.5 amps peak, but still,
from my experience when the filtered output is close to the AC peak voltage (which is here), we assume that the transformer's current is twice the load current or more, because of the short duration in which the transformer's voltage is larger, right?


texts:
I am trying to create a 100ms period pwm signal (10Hz) with a PIC18F4520, I followed the PR2 equation to help me create this signal

I have a 20MHz clock frequency with a prescaler of 16 and a PWM period of (100 x 10-3 s) and when I use these values in this equation:

\$ \Large PR2 = ( \frac{PWM Period}{( TOsc \times 4 \times TMR2 Prescaler )} ) - 1 \$

I get 0x31249

I am also trying to run this PWM signal at 50% duty cycle [so 50ms off and 50ms on] by using the duty cycle equation:

Duty Cycle = ((CCPR1L << 7 ) | (CCP1CON bits <5:4>) ) \$ \times \$ TOSC in MHz \$ \times \$ Prescale

Which gives 62500 as a value for the duty cycle.

This whole exercise is for me to learn better about using PWM signals. I am programming the PIC in C18 and simulating it on PROTEUS VSM.

that is a picture of what the oscilloscope is picking up off the PWM signal which DOES NOT LOOK LIKE 50% duty cycle or 10 Hz frequency.

This is the code that I am using on PROTEUS VSM:

include p18cxxx.h
include pwm.h
include timers.h
pragma config OSC = HS
pragma config MCLRE = ON
pragma config WDT = OFF
pragma config LVP = OFF
pragma config DEBUG = OFF
pragma config PBADEN = OFF
unsigned char period = 0x31249;         // assign PR2 to 31249 used to get 100ms period

unsigned int duty_cycle = 62500;  // used to get 50ms on/off

void main(void)
{

    OpenTimer2(TIMER_INT_OFF & T2_PS_1_16 & T2_POST_1_1);

    OpenPWM1 (period);

    SetDCPWM1 (duty_cycle);

    while (1);

}

As it can be seen I am using the PWM library as I heard it was easier to work with.

I am sorry if I appear too unacquainted with how questions are made on this forum or as to how I presented my problem.


texts:
As I understand it, photo beam sensors (and perhaps other emission types) work like this...

it occurred to me, it would be great if there was a "scanning" such sensor...

So, it would rotate or swing, at many Hz, over perhaps 90 degrees.  (It could rotate mechanically just like an airport radar or I guess a bar-code scanner, or perhaps "rotate" in some solid state manner.)

When an object cuts the beam, in fact it could tell you the angular bearing.

(Of course, if you put two or three of them over an opening, you could calculate a position in 2D nicely.)

In fact, does this technology exist .. is there such a photoelectric beam sensor -like device, which indeed will give you an "angular bearing"?

I've spent considerable time searching but not been able to discombobulate.

(I was astounded to learn there is a lidar-like thing that actually measures distance via time of flight, but that's sort of a further (amazing) complication, not really what I'm wondering about.)  Thx, experts

PS I have no interest at all in model or manufacturer recommendations. I just want to know if such a thing exists. (For all I know, it's completely commonplace .. or it may be obviously "ridiculously impossible" to experts.  Cheers)


texts:
below I have this schematic to find the open circuit voltage gain. This circuit basically utilizes three resistors from which R_f is supposed to be the internal feedback resistor. It also utilizes the voltage controlled current source. My job is to find A_vo = v_o/v_i. My work is illustrated below
\begin{equation}
A_{vo}\:=\:\frac{v_o}{v_i};\:v_o\:=\:-g_mv_iR_2\: therefore \:A_{vo}=-g_mR_2
\end{equation}
but the exact answer looks like this:
\begin{equation}
\:A_{vo}=-g_mR_2\:\frac{1-\frac{1}{g_mR_f}}{1+\frac{R_2}{R_f}}
\end{equation}
somehow am having trouble incorporating R_f into the equation. Any help please?

* My apologies, in the schematic, the dependant source is a voltage controlled current source*


texts: Relation between Resonant frequency and Resistance in series RLC circuit

texts:
simulate this circuit – Schematic created using CircuitLab

I have a series RLC circuit and I calculated the resonance frequency. Say its w (omega).

Now in second experiment, i use the resistor of half the value used in above ciruit. What effect will it have on my resonant frequency now?

Example:

Experiment 1: C = 100nF, L = 100mH, R = 100ohms

Experiment 2: C = 100nF, L = 100mH, R = 50ohms

Only resistor is changed. Nothing else.


texts: VHDL update different parts of large vector (MIG data) from serial data

texts:
I'm trying to write data into an instance of the Xilinx Memory Interface Generator that I receive from a UART. I'm using VHDL in Vivado.

The UART presents data 8 bits at a time, with quite a few clock cycles between each fresh data. The MIG data input is a 512-bit vector.

signal s_app_wdf_data : STD_LOGIC_VECTOR(511 downto 0); -- Output to MIG
signal s_uart_data    : STD_LOGIC_VECTOR(7 downto 0); -- input from UART

I wish to populate the vector with data received from the UART. I will update each part of the vector and then when I get the last byte from the UART I will enable the write signals to the MIG.

I created a counter to keep track of what position in the vector was the relevant position for UART data to be written to, so every time there is fresh data on the UART do something like this:

s_app_wdf_data(v_position downto v_position - 7) <= s_uart_data;
v_position := v_position - 8;

However, this took about an hour to do route_design, and gave timing errors (negative slack).

I was thinking that in order for that to work then the tools would have to synthesise something that essentially allows random access to any part of the vector, so maybe I could help clarify to the tools that only certain parts of the vector would ever be accessed since the position only ever changes in decrements of 8. I wrote out

if (v_position = 511) then
    s_app_wdf_data(511 downto 504) <= s_uart_data;
elsif (v_position = 503) then
    s_app_wdf_data(503 downto 496) <= s_uart_data;
elsif (v_position = 495) then
    s_app_wdf_data(495 downto 488) <= s_uart_data;
etc, etc

It was laborious to type out (a clear sign something is wrong), and in the end had even worse timing errors.

Next I tried to avoid code that would access arbitrary places in the vector, I tried using shifting and updating just the lowest byte.

s_app_wdf_data(511 downto 8) <= s_app_wdf_data(503 downto 0);
s_app_wdf_data(7 downto 0) <= s_uart_data;

This one had the worst Total Negative Slack of the lot.

What is the correct approach here? Or what techniques should I be researching?


texts: Building a stepper in Logisim - Cannot find the error

texts:
I try to build a stepper based on a book. I have been looking for the error for hours now, but still could not find it. Maybe you can help me with this issue?
This is my stepper:

This is a working example:

The squares are 1 bit memories. Somehow when I connect the last output with the left input, the wire gets red, which indicates an error somewhere. If those are not connected, the stepper works just fine:

Many thanks in advance :)
Edit: I copy the internal structure of those squares:
Mine looks like the following:

In the working example it is like that:


texts: Is a 4p4c rj22 plug physically compatable with a 6p6c jack?

texts: cant seem to find any decent panel mount rj22 jacks but rj12 looks pretty close, and I cant help but wonder if it will fit.


texts: V/f ratio for 3 phase induction motor greater than rated speed

texts:
I am a bit confused with V/f ratio. I know it is used to control the speed, as the output is constant. However, for an induction motor I was doing an experiment on, the rated V/f ratio was 230V/50Hz with a rated speed of 1375rpm, whilst experimentally I got 254V/49.26Hz at a speed of 1480rpm. I have read it is possible to get a motor speed greater than a rated speed by increasing the frequency. Surely though, if you increase the frequency, the V/f ratio will be smaller, hence it is no longer constant as it should be?

Hope that makes sense! Thank you.


texts: Large full planes, or moated sections, which is more quiet?

texts:
Take a six layer PCB with lots of circuitry, smaller than you'd like, parts on both sides, with very sensitive amplifiers looking for RF signals in the 100nV range, and digital circuitry.

Top layer, parts and short tracks.
L2 Ground
L3 long tracks
L4 long tracks
L5 Ground
Bottom Parts and short tracks.

The digital section is running, and there are plenty of bypass caps etc, but in the end there will always be currents running around. The low noise sections are laid out very tightly, and as far away from the digital as possible.  For mechanical reasons, I don't have the option of just placing circuitry where I'd like to, many part locations are dictated.

If L2 and L5 are solid ground, then current between any two points will take all possible paths, the majority will take the most direct paths and a small part of the digital noise currents will end up running through the analog sections.

If I carefully "moat" the analog sections, I think that I would get lower noise because that current would be prevented from running through my analog.

Obviously I still need to make a connection, but power in and ground can then be restricted to a single point.

Am I thinking about this correctly?
Experience in support or against?
Authoritative documentation in support or against?

Thanks


texts: I have been struggling with making an Arduino for a while (was successful in making a breadboard version using an ISP programmer cable). They say that the Arduino bootloader is made so that no external circuitry is required to program the ATmega8. But when I looked into the schematics there is the normal circuit required for the serial connection. Then what does the bootloader actually do?


texts: How do I reinforce a cardboard antenna for outside use?

texts:
I bought Mohu Releaf cardboard antenna. It works much better outside than inside. Mohu explicitly advises against outdoor use of its indoor models, yet I wrapped it in a plastic bag and hung it out of window.  It looks a bit shabby so I am looking for ways to improve both the look and protection against elements.
I tried placing antenna between window glasses yet it gets less channels than outside. I have a big outside antenna, again it gets less channels.

Dimensions: 9″ x 11.5″
Effect of elements on Leaf antennas
http://mohu.freshdesk.com/support/solutions/articles/4000026474-can-i-use-my-leaf-curve-antenna-outside-or-in-an-attic-
Releaf model
https://releaf.gomohu.com/#specs
I am considering to check the car paint I have for conductivity in microwave and paint the antenna.
Other ideas are self-adhesive laminate poach, epoxy resin or a plastic container


texts: Why should I specify a 'pulse width' when firing a thyristor rectifier/inverter?

texts:
If I'm correct, the controller will send a gate signal to this bridge (6-pulse or 12-pulse) and even if it sends them with 1 degree of width, the thyristors must close until the current through it crosses zero right?
As reference I was reviewing power_hvdc and power_hvdc12pulse examples included in Matlab / Simulink.


texts: How to route a trace on PCB with 50 Ohm impedance?

texts:
I used some online calculator to calculate parameters of trace so it has 50 Ohm impedance.

I use FR-4, so H=1.5mm, T=0.035mm and Er = 4.5. 2-side PCB, one side with signals, the other with GND. I set the calculator to "microstrip" and for this data it told me to make trace width = 2.73 mm...

That's more than 100mils for width, most of my traces have 8-10 mils. I'm connecting DRAM to uC, there's no possibility I can me those traces so wide.

So how people achieve 50 Ohm impedance with reasonable traces width?


texts: Why are piezoelectric sensors called high impedance?

texts:
Piezoelectric mics and accelerometers are called high impedance aka high Z sensors. And I know that the high impedance sensor output needs to be converted into a low impedance signal first. I think this impedance transformation is needed for carrying the signal with minimum power loss.

But my question is more fundamental here. Let’s take a piezoelectric accelerometer/mic/sensor and model it. As far as I know it is modeled as a voltage source with a series capacitor. Something like:

Now if my model is correct for a piezoelectric sensor, why are these called high impedance sensors? Obviously Xc is frequency dependent which means it is hard to say whether the impedance is high or low here. Where am I wrong?


texts:
I'm trying to calculate the stall current for a 12 V DC gear motor (919D1481):

No load speed = 15800 RPM

No load current = 0.52 A

Nominal speed = 13360 RPM

Nominal current = 2.85 A

Nominal torque = 154.4 g·cm

Stall torque = 1000 g·cm $$$$

\begin{align}
\Delta I &= 2.85\mathrm{A}-0.52\mathrm{A}\\
&=2.33\mathrm{A}
\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad
\end{align}

\begin{align}
\Delta\mathcal{T} &= 1000\mathrm{g·cm}-154.4\mathrm{g·cm}\\
&=845.6\mathrm{g·cm}
\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad
\end{align}

\begin{align}
I_{stall} &= \left(\frac{845.6\mathrm{g·cm}}{154.4\mathrm{g·cm}}\right)*2.33\mathrm{A}\\
&=12.76\mathrm{A}
\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad
\end{align}

Can you tell me if this is correct?Thanks.


texts: Need help to calculate a proper fuse for a 19v transformer

texts:
I've successfully installed my Ring Door Bell Pro yesterday.

Ring Door Bell Pro integrates with an existing door chime. I used a voltmeter and confirmed the transformer's output voltage is 19 V AC.

Due to the Ring Door Bell Pro size, my installation at the entrance door exposes two wires going to the unit. The wires are safe; however, someone can pull them hard and they can short. I tested and when I short the wires, they spark.

I am thinking to add a fuse right after the transformer. this way, if I am not at home, and any short circuit happens by an intruder, there is no risk of fire in my basement where the transformer is.

What is the proper fuse model, type, number ar amp for such application? It would be nice if I can buy it from HomeDepot


texts:
I am currently working on a prototype that is going to generate a burst of pulse of high voltages (e.g. 1KV).
To do this, I first made a voltage multiplier and feed the mains voltage (230Vrms) directly into it after isolation was done with a transformer (1:1).
I then need to feed this voltage into another cct (discharg the voltage multiplier) in a timely manner. to be exact, a burst of pulses (5ns ON / 10us PERIOD) needs to be generated at the end.It also needs to generate signle pulses at instances as well so PWM is not the only functionality. the following circuit does this:

As you can see, the switch I used was just a spice model. I am planning to design this switch with mosfets as their recovery time is suitable for this application (being on only for 5ns). I have made the circuit below:

simulate this circuit – Schematic created using CircuitLab
I am having some issues as:

A p channel is preferable (M1) how ever the max Vds they can sustain is way lower than what I want (1000 V). can a N-channel MOSFET be used? would the voltage drop across just be too much to bare?
would it better to replace Q1 (NPN BJT) with a N channel mosfet? I don't know if a BJT can coupe with high frequency switching (turning on and going off in 5ns) with an inrush current but I know N channel mosfet does, however the addition of the resistors are going to slow it down so I don't know what to do here!

any help would be greatly appreciated.


texts: Trouble understanding charging capacitor on bridge rectifier

texts:
simulate this circuit – Schematic created using CircuitLab

Boylestad's book says that with the diodes conducting the effect of the resistor is "removed" so the \$RC\$ constant is so small that the capacitor charges with the value of of \$V_1\$ extremely fast. Is it a good approximation to say that it charges instantaneously regardless of the value of \$R\$ and \$C\$? Assuming ideal diodes, voltage sources, etc. This is mentioned in the section of clamper circuits with alternating constant voltage sources, would this be different with a sin wave?

If possible I would like to ask something else. Supposing a forward voltage drop of 0.6 in each diode, the peak voltage on Vo would be V1 - 0.6 - 0.6 = V1 - 1.2. If diodes are considered as ideal with 0V drop in forward bias, then Vo = V1 in this case. There is one exercise here made in my classroom where the peak voltage in Vo is different V1, assuming all diodes ideal with 0V drop, ideal sources, etc. Does it make sense? Could the capacitor not be fully charged by the end of a half-cycle? Thanks again.


texts:
I have  the EL Sequencer from  Sparkfun which  uses JST PH connectors on the DC and the AC side, but my EL panels all  have JST SM connectors. There seems  to be enough  space to solder more connectors on the  underside of the sequencer (although barely) or  I could  even  desolder the PH ones (which are somewhat out-of-spec anyway, as they are rated only up to 50V and EL works with  3x to 6x the voltage).
The question  only remains, which  connectors  to use instead?
My initial idea was to use JST XH  on the board to plug an "extension cable" (maybe sub 1 meter) and use an 8-10 pin connector  on the  other end.
Or should  I  forego the board-to-wire connectors and solder short wires to the board and equip them with wire-to-wire, like  JST SM? (The more I think about it the  more it seems like  the better idea)
I say 8 or 10 pin connector because all the panels end up close to each other (in a pattern) and I want them to be disconnectable in a single action.
My question: Are  there other recommendable connectors that can be used as  wire-to-wire AND  as wire-to-board? I find JST's self-incompatibility on this front annoying.
Are there any faults in my thinking?


texts: Why is there a " - 1" in the pn-junction current equation

texts:
I was studying the Ideal Current–Voltage Relationship and was wondering why there is a "-1" in the pn-junction current equation for a pn junction diode.

Thanks in advance!


texts:
What I've learned so far from Navy school is that operational amplifiers are used as a substitute for transistor amplifiers and they contain three main circuits: the differential amplifier, common collector amplifier and the push-pull amplifier. They are represented by a triangle pointing to the right. My question is, why is the voltage gain \$-\frac{R_f}{R_i}\$

As far as I know, \$R_f\$ provides negative feedback to \$v_{in}\$, but why are we not treating \$R_{in}\$ and \$R_f\$ as part of a voltage divider like a non-inverting amplifier? I can see how they would reason that the incoming current is \$-\frac{v_{in}}{R_{in}}\$ without the voltage divider


texts: What makes a display visible in daylight (such as the Pixel Qi)?

texts:
What characteristics of the Pixel Qi display make it visible under daylight conditions?

It seems to have something to do with "daylight grayscale".  But what exactly does "daylight grayscale" mean?  Is it something that can be accomplished/reproduced in software on any grayscale displays?  Can it be reproduced on a color display?


texts: Adafruit GPS breakout commit setting to ROM

texts:
I have got the following GPS
Adafruit Ultimate GPS Breakout

I want the GPS to only output the GPS information in $GPRMC. I am able to do that with this command: $PMTK314,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*29\r\n. The problem is I can't get the GPS to commit the changes to it's ROM so I don't have to change its settings every time it restarts. Is there any command to do that?

Another related question, why does the GPS send multiple sentences seems a bit redundant.

Following are the datasheets & command set:

1.PMTK command packet

2.GPS Standalone Module Data Sheet


texts: Decoupling caps not near IC pins - global decoupling

texts:
It is common wisdom that decoupling caps should be near the IC drawing power, minimizing loop inductance.
For some time, I have seen that Todd Hubing advocates what he calls global decoupling in some of the youtube examples they have for LearnEMC, if the board has a tightly spaced power and ground plane pair.
The rationale is, that - with tightly spaced power and ground planes - the inductance of the plane pair is anyway smaller then interconnect traces. So if the decoupling caps lowest impedance path is through the plane pair anyway, then it doesn't matter that much where on the plane the decoupling cap is placed. Here is one example screenshot from that video which illustrates the placement of the global decoupling caps.

As a result they advocate, just sprinkling the board with a sufficient number of decoupling caps.
Yesterday, Altium posted a new youtube video with Todd Hubing where he also explains this approach. It sounds quite plausible.
However, I do not recall seeing this school of thought anywhere else and most designs do have the decoupling caps very close to ICs, although I suppose most designs on 4+ layer board do have tightly spaced power and ground areas. As Todd Hubing mentions, caps near the ICs can actually make the situation worse because routing can be more congested when caps are very close to ICs.
So I was interested if there are problems with global decoupling unmentioned by Todd Hunting, that explain why it is not used more often.


texts: Fooling RCA cable into thinking it's connected

texts:
I bought an automotive camera (can post a link to the specific model if this is relevant but it shouldn't be), which is supposed to act as either a rear-view camera or a dash cam. It writes to a memory card, but also has an RCA output cable.

My car does not have a screen of any kind that I could hook the RCA cable up to. This doesn't matter because I only want to use the camera as a dash cam. However, if the camera detects that the RCA cable is not hooked up, it automatically shuts off after about 5 seconds.

So my question: is there a simple (and preferably reversible) way to fool the camera into thinking the cable is hooked up? I'm considering simply using a bit of aluminum foil to short out the RCA cable. Would that do the trick? Might it damage the camera? Unfortunately, I just don't know enough about RCA.


texts: Can I drive MOSFET gate with an isolated voltage source?

texts:
I have two N-channel MOSFETs. I want to make a simple bidirectional solid state relay by using them. I want to place them back to back as seen in the schematic below, and drive them with a controlled gate signal. I will have two isolated voltage sources: \$V_g\$ and \$V_s\$.

simulate this circuit – Schematic created using CircuitLab

I have no doubt that the simpler circuit in the below would work. But, in my circuit, the supply grounds are not shorted, and it is making me unsure. Consider swapping places of \$V_s\$ and the load in this second circuit, then a similar question arises.

simulate this circuit


texts: What is the physical representation of the heap and the stack?

texts: I can easily understand how .bss and the code have physical representations in the processor which has a memory bank for the instructions that a program counter can count up and the bss (block starting symbol) is just global data. But then there is the stack for local variables and the heap for dynamic memory. How are these things put on the circuit physically?


texts:
I am trying to generate some waveforms which are phase shifted from an input signal.

The input signal is around 4.4 MHz and is a square wave at 50% duty. I need a 0 degree and 90 degree phase shift of this waveform, and each wave must be 50% duty cycle. I may also need to shift both waves by 180 degrees i.e. 180 and 270 degrees. (This is for PAL video.)

My idea was to use a PLL to up the frequency to 17.6 MHz. Then, a decade counter and two OR gates would generate the 0 and 90 degree waves. An inverter resets the counter so it overflows at 4. An XOR chip would be needed for the 180 degree shift. The PLL would be a 4046-type device and would also need a divide by 4 counter.

I tested this in a circuit simulator:

Great... the concept works. However, I'm quite limited by board space, and cost. I would need five chips plus the PLL chip to do this. I have never programmed a CPLD before, but it sounds like the perfect application for one. Would I be able to do a basic task like this using a low end CPLD like this one? Or would 32 macrocells be insufficient? Is there a rough estimate for how many macrocells would be required per basic gate, and how many would be required for a complex device, such as a counter?


texts:
General Circuit information :

Function/Purpose: After the user press a tactile and hold for 6 seconds the circuit latches and turns on the mosfet to in turn turn on the power for a system
Power source : 4 X AA batteries 6.8V - 5V

I've tested this circuit first in a simulation application which verified that the Circuit will turn on after 6 seconds, then after building the exact circuit it worked as expected with no problem.

Now after replacing some components to a smaller alternative, the circuit now latches after 3 seconds and the output from the CD4013 which goes into the gate of the N-channel Mosfet which drives the power of circuit immediately shuts down , by playing around with the resistor 10R-470R (gate resistor) and pull-down and the pull-down resistors I am able to prevent the shutdown and get a good 4.5V-5V at the gate of N-channel, but the P-channel at best at its gate would get a 1.8V-3V at gate which seems to be not enough to close the P-channel. So now it's like a pendulum if I try to ease out the pull up at the P-channel gate the CD4013 shuts down and otherwise the p-channel fails to close.

Any help would be greatly appreciated


texts: Series-Shunt Feedback Amplifier Analysis - Finding Loop Gain

texts:
So I'm trying to solve a problem I found in a textbook (won't say which one so people can't use it to cheat on their hw) and I haven't been able to arrive at the answer found in the appendix. Please note this is not a homework problem, I graduated from college last year and just reviewing for my own benefit and so I can finish an analog MPPT controller I'm designing.

The problem:

simulate this circuit – Schematic created using CircuitLab

Assume each mosfet in the above figure is biased so gm = 4mA/V and that the ro of each mosfet can be ignored. Find the loop gain AB assuming the value for RF is 900 Ohms (the value I calculated for making the closed-loop gain ideally (1/B) 10V/V in the first part of the problem, which is correct)

My attempt at an answer
I used the test-voltage method, where a break is made in the feedback loop and a test voltage is applied and then measured at the other end with t-model for Mosfets:
$$I_{o} = g_{m}V_{T}$$ $$I_{D1} = I_{F}\frac{R_{S1}}{R_{S1} + 1/g_{m}}$$
$$I_{F} = I_{o}\frac{R_{S2}}{R_{S2} + R_{F} + R_{S1} || 1/g_{m}}$$
$$I_{D1} = \frac{g_{m}V_{T}R_{S2}}{R_{S2} + R_{F} + R_{S1} || 1/g_{m}} \cdot \frac{R_{S1}}{R_{S1} + 1/g_{m}} $$

Output voltage of M1: $$V_{o1} = I_{D1}R_{D1}$$
Voltage at opposite end where feedback loop broken:
$$V_{r} = -g_{m}V_{o1}R_{D2} = -g_{m}I_{D1}R_{D1}R_{D2}$$

Loop Gain (Where Vt is test voltage):
$$A\beta = -\frac{V_{r}}{V_{T}}$$
$$A\beta = \frac{g_{m}^{2}R_{D1}R_{D2}R_{S1}R_{S2}}{R_{S2} + R_{F} + R_{S1} || 1/g_{m} \cdot (R_{S1} + 1/g_{m})} $$

However, this gives me the wrong answer, the value for loop gain should be 31.33 according to the appendix.

I must be doing something wrong in calculating the voltage gain of each stage but I haven't been able to wrap my head around it. Any insight in how to approach the problem and some background I might be lacking would be highly appreciated. Guess I'm a little rusty on my circuit theory...


texts: is this 12V power supply functioning properly and will it power my device?

texts:
I have purchased a Rhino 12V DC CCTV Camera Power Adapter. The specs are Input 100-240 VAC, Output 12V DC. I cut off the 2.1mm plug and currently have the Red (Power?) and Black (Negative?) wires stripped ready to solder. My first concern is that when using a continuity tester, I put the alligator clip of the tester on the black wire and the needle on the red wire and I have continuity. When I flip flop the two there is no continuity. Also I have not found any continuity when I test the prongs to the wires in any arrangement. I am not familiar with this hardware so if anyone can shed light on this I would appreciate it.

Also I have a device that can be powered through a DB9 serial port. When looking at the Pinout however I would like some confirmation on which wires to solder to. The pins that are relevant are labeled as (5) Ground,  (6) 120VAC Charger Input, and (9) Voltage Input External voltage input 6VDC-16 VDC.  My thought is to solder the Red wire from the 12VDC adapter to pin 9 on the serial cable and the Black wire to the 5 Ground wire. Then I could simply plug my power adapter (now with the DB9  end) into an outlet and into my device. This is assuming that my power adapter is functioning properly.

Opinions and ideas appreciated. Thank you.


texts: Why is the voltage divider formula used in this circuit to find the terminal voltage?

texts:
I'm going through the book Practical Electronics for Inventors and there is a chapter about voltage sources that talks about practical voltage sources.

It calculates the terminal voltage of the circuit below using the voltage divider formula.

Why is the voltage divider formula used since the resistors are in series and why can't we calculate it using ohm's law, i.e find the current across the first resistor and multiply it with the second resistor?

simulate this circuit – Schematic created using CircuitLab


texts:
I'm aware that there have been many questions about this series of relays, but I've read them and still can't get this working.

I have this version, with 4 relays.

I'm currently wiring:

5v Arduino -> VCC
GND Arduino -> GND
I/O 13 Arduino -> IN1

I have bridged VCC and JD-VCC.

I'm running the Arduino blink example sketch, but nothing happens. I've checked it's using the right pin, I've checked that the code is running correctly, but I still can't get it working.

No noise is heard when the IN1 switches from high to low or visa versa, and the status LED doesn't come on either.

I've also tried switching out Arduinos, in case it was an issue there, but no luck.

Can anyone help?


texts:
So i am completely new on this topic. i have a problem which looks something like this.

i have a  light which is designed with a 7 segment display which gives the reading of various parameters . the light's orientation by default is vertical with display on bottom. Problem is if we rotate the light by 180 degrees , the result would be display on the top and light on the bottom in an inverted vertical orientation. the light and display would function properly but the digits will also be flipped vertically. I am looking for solution to this, i want that the 7 segment display should be displaying figures properly according to the orientation . eg:- if its in default orientation then 7 segment display must also be in default, but when light is vertically rotated by 180 degree , the display must change in such a way to display result properly. I would really appreciate if somebody could come up with an idea to overcome this problem.

and the last one is really easy , what would be the best way to break the circuit if the input exceed 225 volts ?.

thank you so much.


texts:
It's been a while and in need of some guidance please:

I have 3 inverters controlling motors via remote potentiometers. Each of the inverters uses it's own galvanically isolated internal switch mode DC supplies to give 0-10vdc which is sent to the pots for reference.

I want to be able to monitor and control the pots using MCU either by PWM or more probably an SPI Digital Pot for each.

Will a dual rail SPI Digital Pot allow me to power the MCU from a separate local DC supply without having the grounds tied together, do I need to tie the grounds together of all the supplies or...

I have read (the rather large) manual for the inverters and can't find a parameter to set an external voltage supply for the analogue inputs and am a bit stumped on how to control the external pots due to the non-common grounds.

Hope this is clear and if I have the wrong end of the stick please bash me with the right end :)

Thanks for any help.

EDIT: HERE IS THE MANUAL IF ANYONE CAN SPOT WHAT I SHOULD DO TO USE EXTERNAL VDC


texts: Circuit to select 12v or 5v power source

texts:
My design involves 2 micros that operate at 3.3v.  I have output line drivers that operate at 5v.  One of the micros is a wifi device so I want to stay away of switching power supplies.

5v or 12v can be applied to the POWER IN to the board (Vin).  I have a P-Fet providing reverse battery protection (90 milliohms ).

I need to get to 5.0v ... from there I have a 3.3v LDO reg supplying the micros.

My question is the best way to implement the circuit between the Rev-Bat P-Fet (either 5v or 12) ... and get to 5v.

I would normally use a boost-buck regulator but not with the radio being so near.

I need about 400 milliamps ... so I'm designing for 1A.

I can get several 1 or 2 amp 5v linear reg (under $3) that have an enable control.  The main micro can come up and keep current low until it decides how to configure the vreg control.

So - I can have the 5v linear on by default (assuming 12v is applied) and measure the input voltage.  If I determine Vin is actually 5v -- I can turn off the 5V vreg and enable a bypass switch to route the Vin of 5v to the input of the 3.3 LDO.

So ... after all of that --- what is the best circuit design for the bypass that can be controlled by the micro?  More than likely another P-Fet -- I'm just not sure of the actual circuit design.

Another question ... I've been out of hardware design for 45 years -- now software.  At 400ma and 7v being dropped across the 5v Vreg when Vin is 12v -- that almost 3W the regulator has to dissipate.  How hot is that?  How hot with a finned heat sink?


texts:
I am thinking about ordering this:

http://www.ebay.com/itm/x100-Fairchild-PN2222A-2N2222A-NPN-Small-Signal-TO-92-Transistors-US-Seller-/171520659038?pt=LH_DefaultDomain_0&hash=item27ef6d8e5e

and I have no idea (Google has not proven helpful) what is the big difference between a 2n2222 and 2n2222a Transistor. I am using these for logic gates (for now just basic AND, NOT, and am working on my own full adder). I wish to buy the 100 pack on EBay, as it is cheap compared to buying a 15-pack at RadioShack (which only contains 5 of the kind I use) for a couple of bucks. What should I know, though, about 2n2222a and its use in logic gates (like different collector, emitter, base, etc.)?


texts:
So I am trying to model a thyristor switching circuit but the results I get are as if the SCR that is used as a switch lets the current go through even though the gate current hasn't been applied yet.

I've also observed that the switch for the gate current doesn't really work. Is that the reason of the problem? How can I fix this?

This is the circuit design on ORCAD Capture and simulation settings:

This is the current/time graph of R5 and R6:

This is the current/time graph of R6 (zoomed in) which shows me that the switch doesn't work:


texts:
As a scientist, I have a good theoretical grasp on the quantum mechanics behind a diode/pn-junction, capacitors, inductors etc.. however, I have practically no hands-on experience with designing an analog circuit.

As a consequence, I would like to read a book on basic analog circuit design which emphasizes practice, not theory. Roughly speaking, I am looking for a book aimed at engineers, not physicists. Any good recommendations?


texts: Controlling Buck converter (XL4016) with microcontroller

texts:
Briefly the project I'm working on is made up of a blue pill, rotary encoder, acs712 30 amp current sensor and an OLED display. Everything is in functional state. The aim is to provide a stable controllable voltage starting from a 4s (16.8v max) lithium, BMSed, battery. At start I tought I could just use a good MOSFET and smooth that out with a filter on the output. Later on I discovered these xl4016 modules around the web Xl4016 module(xl4016 datasheet) that give 8 amps (which is a good start, there's also a 12 amp model) and these seems to give a stable output without much hassle. So the plan now is to control the vari-volt which on the board is made by a potentiometer.
Looking around for a solution I found some possibilities:

generate a pwm signal, smooth it out trought a low pass filter, and feed it to feedback pin trough an opamp in voltage follower mode.
use a digital potentiometer (don't know if there's one up to spec)
use a DAC such as mcp4275

So the question is which one is the right way?

Additionally, tapping in the feedback pin could interfere with the xl4016 feedback mechanism. So the aim would be also keep that voltage stable (between 0-12v) even though battery is discharging, so I somehow should sense the battery voltage and the output voltage? In the project every cell voltage is monitored trough voltage dividers. Can I just use an external ADC?
Thanks for the attention, and just ask for whatever is needed to provide an answer.

Update:

here in the datasheet I can see : Vout = 1,25 (FBK) * (1+R2/R1) ----> if we put a fixed 10k resistor instead of the pot, can I inject voltage somehow on the feedback pin, maybe with a DAC? To get let's say a 12 V out following the formula it should be 2.97 V.


texts:
I am using ATtiny2313 microcontroller along with a RS232 to establish communication between my microcontroller and the laptop.
Here's my question :
What is the predefined system for the laptop to make sense of the data that i send using the microcontroller ? (i.e. what is the number of parity bits, start bits... that the laptop expects to make sense of the data ?)

I tried reading the data using python but all data reads 0xff
my avr code sends a constant byte 0x01010101 every one seconds and laptop detects every new byte every 1 second. But every byte is sensed as 0xff.
What could be the problem ?
(i am using the screen function in the mac terminal to view the RS232 data).

Please help


texts:
I want to know the input impedance at transistor T1's base.
1/Z=1/R4+1/R+1/Rin and Rin=beta(re+RE)
But how do I calculate RE ?
My guess : R3 is 0 because the wire at T1 collector is removed, thereby RE=Lp ?
Thanks


texts:
I've got a project I'm working on, which is essentially a set of MCU-controlled relays. I'd like to set up a test harness for the system, using something visual on the outputs. I was thinking some small, low-power light bulbs.

I've got 28V AC output, and I need a bulb that would draw ~0.2A. How do I go about locating and choosing a suitable bulb?


texts: Upgrading STM32L1 firmware takes a long time

texts:
I have a STM32L152R8T6-A MCU. A new firmware is downloaded over HTTP (as a .bin file) and is stored in an external flash memory. After that a bootloader copies the new firmware into MCU flash (address 0x8000000) and resets the micro.
Everything is OK except the process of firmware copy. Actually it takes a long time. For an average-sized bin file (10 KB) it may take 2 minutes to copy the firmware.
I have searched about this problem. Moving the copy function to SRAM is proposed as a solution. I performed this but nothing changed.
This function writes an array in MCU Flash:
progStatus Program(uint32_t start,uint32_t* Data, uint32_t size)
        {
        HAL_FLASH_Unlock();
        for (uint32_t i=0;i<(size);i++)
                {
                if (HAL_FLASH_Program(FLASH_TYPEPROGRAM_WORD, start, Data[i]) == HAL_OK)
                    {
                    start +=4;
                    }
                    else
                    {
                        HAL_FLASH_Lock();
                        return PROG_ERROR;
                    }

        }
    HAL_FLASH_Lock();
    return PROG_OK;
    }

The only way to program micro flash is by a single 32-bit aligned word at once. The following function is provided by ST.
HAL_StatusTypeDef HAL_FLASH_Program(uint32_t TypeProgram, uint32_t Address, uint32_t Data)
{
  HAL_StatusTypeDef status = HAL_ERROR;

  /* Process Locked */
  __HAL_LOCK(&pFlash);

  /* Check the parameters */
  assert_param(IS_FLASH_TYPEPROGRAM(TypeProgram));
  assert_param(IS_FLASH_PROGRAM_ADDRESS(Address));

  /* Wait for last operation to be completed */
  status = FLASH_WaitForLastOperation(FLASH_TIMEOUT_VALUE);

  if(status == HAL_OK)
  {
    /* Clean the error context */
    pFlash.ErrorCode = HAL_FLASH_ERROR_NONE;

    /*Program word (32-bit) at a specified address.*/
    *(__IO uint32_t *)Address = Data;

    /* Wait for last operation to be completed */
    status = FLASH_WaitForLastOperation(FLASH_TIMEOUT_VALUE);
  }

  /* Process Unlocked */
  __HAL_UNLOCK(&pFlash);

  return status;
}

Finally we read 256 bytes from external SPI flash, erase a sector and then program the internal flash:
                    read3=mx_read(&addr,data,sizeof(data));
                    for(q=0 ; q<256 ; q++)
                        {
                        crc2=crc32h(data[q],crc2);
                        }

                        status=ReAlign(data,sizeof(data),Data1,sizeof(Data1));
                        erase_status1=ErasePages(start,1);
                        prog_status=Program(start,Data1,sizeof(Data1));
                        start+=0x100;
                        addr.page++;
                        q=0;

We profiled the entire code. Calculating CRC32 and external flash read are performed very fast. The only bottleneck is the internal flash programming functions.
Is there any solution to overcome this problem?


texts: if my microstrip trace width is about 50 mil, how large should my via drill size be? Should it also be around 50 mil? Thanks!


texts: What's the possible risk of using a board with a solder splash on vias? I couldn't clean it and it's passed ICT test. please advise.


texts:
I was about to go and learn common emitter amplifier configuration in details and the problem occurred right at the beginning of it. I have found this equation of calculating the C1 (capacitor that blocks DC component at the input of the junction transistor) for its value (it shouldn't be to high or too low (the capacitance) because it also puts on a high/low-pass filter on the input of the transistor).

So, I almost perfectly understand the whole equation but what I don't understand is how should I get the required capacitance for C1 from this calculation.

- low frequency break point of the filter

 - resistance from R1, R2 resistors (from voltage divider) and the input resistance of transistor - in parallel manner

For C2 equation is the same except there is resistance of load instead of those parallel resistances mentioned before.


texts:
In this circuit, either the battery or the charger will be powering the load depending on the voltage of the battery. The problem is that both battery and charger can potentially be 16.8 V sources and the load can only tolerate 14.5 V max.

In a circuit like this, is it possible to limit the voltage to the load from charger/battery to 14.5 V, while still allowing the battery to charge to its maximum 16.8 V? I'm using a Li-ion battery and cannot change to LiFePO4 because I need high energy density.


texts: Can a capacitor prevent over-amperage of lithium ion batteries?

texts:
I have an electric motorcycle I've built, I have 7 Nissan Leaf battery packs in series to make 48v nominal. Unfortunately, after a month of enjoying the acceleration a bit too much, the batteries no longer hold charge for more than 15 minutes.

Some research shows that the max amperage is around 240 amps, could a capacitor, or several capacitors be used to provide 360-400 amps over a short period of time (a few seconds) and keep the batteries from being damaged, or is my best route (which will be costly and VERY difficult) to figure out where to stuff double the amount of batteries and run a series of paralleled pairs?


texts:
How cooktop buttons works? In this picture can see circles (marks) from control board.

Here are control board with buttons. If i touch that black "buttons", it is like dish wash sponge.

How that buttons works ? Because in glass have no holes or some wires. Those black "buttons" are some special material?


texts:
I do not understand the NE556 circuit depicted in this data sheet:
https://cdn-reichelt.de/documents/datenblatt/A200/NE-SA-SE556-TI.pdf
on page 6 in figure 1.

More specifically I do not understand why they loop 'Out' back to 'Vcc'. I also don't understand how 'RL'´s resistance will influence the circuit.

I am sorry if this question is trivial in any way. I just don't know where to ask apart from here. Thanks


texts:
I purchased a "1200W DC-DC Boost Converter Power Supply 8-60V 12V Step up to 12-83V 20A 24V 48V" off eBay. My applications are for charging a DIY 48v e-bike battery I assembled from 78 individual SAMSUNG 25R 18650 2500mAh HIGH DRAIN 25A Rechargeable batteries in 13 cells of 6 each). My other application is as a 40v bench power supply (from 12v) for a motor.

The following minimal documentation, which I assume was translated from Chinese, was included:

DOCUMENTATION:
Supports a wide input voltage 12-60V, 12- 83V wide adjustable output voltage, low dropout voltage.

SPECIFICATION:
Input voltage: 8-60V
Input current: 20A
Quiescent current: 15mA(12V liter 20V, the output voltage, the higher the current will increase too quiet)
Output voltage: 12-80V continuously adjustable
Output current: 20A MAX over 15A, please enhance heat dissipation(input, output pressure related, the greater the pressure the smaller the output current)
Constant Range: 0.5-20A
Working temperature: -40℃~85℃
Operating frequency: 150KHZ
Conversion efficiency: up to 95%
Overcurrent protection: Yes
Short circuit protection: Yes
Input reverse polarity protection: None
Output Counter filling: Yes

NOTE:
1. The input power supply voltage must be above 8V.
2. Do the input power supply switching power supply, the case load of the first connected input source and regulate voltage. Then pick up the load. (Must ensure that the switching power supply has been working), or regulate the first no-load voltage, then switch the power supply open the case. When the voltage is lower than 8V, the chip has not been working. It is easy to MOS tube breakdown.
3. When a constant voltage to constant-current mode have to ensure a constant voltage must be higher than the input voltage.

(end)

Secondary questions:

Q1: What is "dropout voltage"?

Q2: What is "quiescent current"? Why would it be quiet?

Q3: What is "output counter filling"?

Q4: I don't understand 2nd note. Maybe poor translation maybe me. Someone clarify it for me.

Q5: Can I also use this unit as a buck converter?

Now my primary question is about the pots in the image below and how they are used properly.

I can see that "Pot 3" regulates output voltage.

Q6, Regarding pot 1: Adjacent to input with no label, I assume it regulates the input voltage somehow. Can you tell me how and why I would need to do this in relation to the other adjustments?

Q7, Regarding pot 2: Labeled "CC A-ADJ", I believe it regulated the current and realize this is important. My test meter does not gauge amps. How can I practically adjust this for my applications?

Lastly Q8 regarding the battery I intend to charge:

I was told I can charge the whole mass gently at ~52v. I suspect it would be better to charge the 4.7v cells in blocks of 3, if wired to do so. What would be the best method?


texts: Searching for a cheap low-friction rotary encoder

texts:
I am currently building a weatherstation with an ESP32. For the wind direction measurement I have planned to use a windvane and measure its angle (where 0° = N) with a rotary enconder. A precision of 1 deg would be good. I have some rotary enconders, which would be suitable for that job, but unfortunately they all have a lot of mechanical friction (or lock quite firmly after every step).
I wanted to know if anybody knows a suitable rotary enconder?

Price below 10 dollars, would be great, too.


texts: Verilog works in simulation but not FPGA hardware

texts:
I have created a shift register circuit and corresponding test bench using verilog.  I have run this through ModelSim and get the desired wave outputs so I believe my design is correct.  However when I try to load the design onto an FPGA using QuartusII, the circuit does not behave as expected.

Initially, I connected the FPGA to LEDs and switches on a breadboard to test it but it behaved erratically.  I thought maybe it was a problem with the switches bouncing so I then connected the FPGA inputs to an Arduino and drove the logic through that but I still get incorrect results.

The shift register code is as follows:

module shift_register(
  input wire clock,
  input wire serial_in,
  input wire latch,
  output wire [7:0]parallel_out,
  output wire carry_out
  );

  reg [8:0]back;
  reg [7:0]front;

  assign parallel_out = front;
  assign carry_out = back[8];

  initial
  begin
    back = 0;
    front = 0;
  end

  always @(posedge clock)
  begin
    back = {back[7:0],serial_in};
  end

  always @(posedge latch)
  begin
    front = back;
  end
endmodule

I am using the following Arduino code to test it:

int DELAY = 100;
int latch = 5;
int clk = 6;
int data = 7;

void writeBit(int bit) {

  digitalWrite(data, bit);
  delay(DELAY);
  digitalWrite(clk, HIGH);
  delay(DELAY);
  digitalWrite(clk, LOW);
  delay(DELAY);
  digitalWrite(data, LOW);
  delay(DELAY);
}

void writeByte(byte data) {
  for(int i = 0; i < 8; i++) {
    writeBit(data & 0x1);
    data = data >> 1;
  }
}

void setup() {
  pinMode(latch, OUTPUT);
  pinMode(clk, OUTPUT);
  pinMode(data, OUTPUT);

  digitalWrite(latch, LOW);
  digitalWrite(clk, LOW);
  digitalWrite(data, LOW);

  delay(1000);

  writeByte(0);

  delay(1000);

  writeByte(0xAA);

  digitalWrite(latch, HIGH);
  delay(DELAY);
  digitalWrite(latch, LOW);
}

My intention is for this code to initially clear all bits in the shift register and then to set every other bit so that my LEDs should alternate between on and off.  The LEDs should not change until the latch is toggled at the end.

However the behaviour I am seeing is that the LEDs are set as follows: 11011011 with a carry of 1.  Also the LEDs show every change made instead of waiting for the latch signal.

I have tried adjusting the DELAY constant anywhere between 1 and 1000 but the result is always the same.

I am very new to FPGAs and Quartus and have probably made some obvious mistake somewhere but I cannot see it.

I have triple checked all my pin assignments without success.

Any ideas?

Edit

The FPGA I am using is a Altera Cyclone IV EP4CE6E22C8N

It is mounted on a development board like this one: ALTERA Cyclone IV

A 9V power supply is connected to the Arduino Uno.  I then take the regulated 5V output and ground from the Arduino Uno board to the breadboard.  I connect the 5V input and ground on the Cyclone board to the same 5V and ground lines on the breadboard - i.e. both chips have a common power supply and ground.

Here is a schematic:

simulate this circuit – Schematic created using CircuitLab

Here is the bdf from Quartus:


texts: Non-round through hole issues for Micro USB

texts:
I'm on a project where a microUSB connector seems to need a bit more mechanical strength than a surface mount, so I'm looking at through hole receptacles.

The pic is of a Hirose part, bottom of page 6 in THIS PDF, and Molex has similar footprints

A few questions -  Do the non-round through holes need to be plated for increased mechanical strength, or is the solder connection to both sides good enough?

If they need to be plated through holes, and I'm using EagleCad, I assume the only way I'm going to get it done right is to communicate with the board house.  Does anyone have any experience with non-round plated through holes and Eagle that they can share?


texts: Exchanging Li-ion batteries: what to take into account?

texts:
I am looking forward to exchange a swollen Chinese Li-ion battery with a 'normal' one.
The device had this one:
https://www.aliexpress.com/i/32908652788.html
and I am considering to exchange it with this one:
https://api-lemona.lt/TI/En/Pdf/accu-18650_spcb.pdf
The voltage is the same, charging voltage as well. Is there anything else, one should pay attention to by using a different model of a battery? Charging happens through the device it self, so let's say that the charging conditions will remain the same and I have no influence on this.
In case it is not ethical or whatever to discuss the particular products, let's answer the question neutral:
What are the main specifications to take into account when exchanging batteries.


texts: Why does my Kill-a-Watt read Power of only half the Voltage times Current?

texts:
My Kill-a-Watt is displaying that its output is 120 V, 0.16 A, and 10 W.

I'm confused... I thought P = V × I from basic EE. Why do I see only half the expected value here?

(This is a USB charger, and I'm trying to calculate the charger output current indirectly.)


texts:
Can I see the editor and the plot in MatLab (docked view) in parallel?
This function doesn't work any longer and it was partially what I needed.
set(h, 'WindowStyle', 'Docked');

I don't want to arrange it manually all the time to get this.


texts: How does an open-collector gate work by using resistors?

texts: I understand that that the purpose is to drive multiple signals to a wire bi-directionally. The two logic states are either 0 or flow (high-impedance). However, how do resistors come into play for the logic states?


texts:
I'm looking to complete one of my first electronics projects so I was looking for inspiration from youtube Great Scott and this project caught my eye.

In short, his project converts the stereo signal to mono, amplifies it then compares it using a voltage divider network to light up rows of LED's based upon the voltage of the audio signal.

My question is looking at the circuit to me it looks like the OP amp can be used as a non-inverting amp for the audio signal. But then should this signal be used with a comparator and the voltage divider network to drive the MOSFET's rather than the OP amp circuit that is shown?

I didn't know much about OP amps before but this doesn't look like how they should properly be used?

and Youtube video.


texts:
I just got my 556 timers and I wired it up just like the 555 but now: it flashes one HighTime and stays off then...

I used this calculator and basic diagram: http://www.ohmslawcalculator.com/555-astable-calculator

And changed it to fit the 556:

You guys have any idea why this is not working?

(P.S.: I used green wires here if lines are overlapping)

Thank you!


texts: what connector/cable for 22pins connection

texts:
In one of my project, I want to connect 2 PCB. I need to be able to have 22 wires minimum between the 2. on those lines, 19 are meant for +3.3V signals, 1 for a +5V power line, 1 for a +3.3V power line and 1 ground

I'm looking for a small connector with easily buyable cable or connector but the big number of pin make it hard to find what I need.

I thought about using multiple micro USB3 or micro USB2 sockets to connect all but it would need at least 3 which meen 3 separate cables.

I also throught about using IDE connector as IDE wire are widly available but they are a bit wide to my taste.

TL;DR :

I'm looking for a connection to connect 2 PCB board
With at least 22 pins
For a small distance (10-20 cm)
Somewhat uplugable (I may plug/unplug those a few times a year)


texts:
I need to buy some IR LED Detectors but I am having a hard time finding anything except for the 940nm.  It seems that there are only three types of IR LED emitters and detectors sold.
850nm, 880nm & 940nm.  Is this correct?  My main question is can I use a 940nm detector with the 850nm and 880nm?  Will it detect those two?  Can anyone recommend a place to get IR LEDs that has all of these?

I use them because I service redemption and other coin-op games.  Many times these things are used in the games but they don't tell you what the part number is. I needed to replace two pairs on a game the other day and they wanted $55.00 for it. That was four LED's mounted on a short wiring harness.  So I want to stock up on all of the likely IR LEDs and then swap them in until I get the game working.

Thanks again
Russ


texts: how interpret polarization from radiation pattern

texts:
There is an official definition for polarization which is amplitude and phase dependant as shown bellow,but the plot is E_theta vs E_phi.
when we look at the radiation pattern,we can look on the endfire and broad side cross-section vs angle
How can we extract the data about the phase and amplitude needed for the polarization?
Thanks.


texts: Thermal grease / adhesive: Higher Conductivity & Lower Impedance or vice-versa?

texts:
I have been reading a fair bit about Thermal grease & adhesive comparisons.
There is a lot of information out there - even including tests made with tooth paste(!), which is mind blowing for me.

I have access to a limited variety of thermal grease & adhesive products, however.
And I would like to understand what to look for when buying these products.

My question:

Given two similarly priced thermal grease, paste, or adhesives:

Do I go for the one with higher conductivity level AND lower impedance, or vice-versa (ie., lower the conductivity & higher the impedance), or other?


texts: Does Bluetooth Mesh violate normal Advertising Rules?

texts:
According to Silicon Labs AN1137, Bluetooth Mesh employs two kinds of retransmissions:

at the network level
at each relay

Furthermore the document states:

  The minimum delay between repetitions, called the retransmission interval = (Relay Retransmit Interval Steps + 1) *
  10ms + 0-10ms random delay, is typically 15 ms per hop.

In other words it seems that the minimum resend interval is 10ms.

Bluetooth Mesh is based on undirected Bluetooth LE advertisements (Mesh Profile specification Section 3.3.1).

Now, according to the Bluetooth Specification 5.2, Section 4.4.2.2.1, the advertising interval (the time between the start of two consecutive advertising events) for undirected advertisements must be at least 20ms:

  T_advEvent = advInterval + advDelay

  The advertising interval (advInterval) shall be an integer multiple of 0.625 ms in the range of 20 ms to 10,485.759375 s.
  The advDelay is a pseudo-random value with a range of 0 ms to 10 ms
  generated by the Link Layer for each advertising event.

Does that mean that Bluetooth Mesh violates the usual rules of Bluetooth?
And regarding the 10ms lower bound (wherever it may be specified), does that apply to network-level retransmissions as well or only to per-relay retransmissions?


texts: Attaching an Amplifier to 555 timer. Collector Voltage is going haywire

texts:
I'm currently trying to power a Piezoelectric Transducer with an oscillating signal. I am doing this because I want to experiment with "acoustic levitation." The piezoelectric transducer is a 50W 40kHz device. From my understanding, my input power does not have to match this wattage because it is just a maximum power spec.

To produce this oscillating signal, I am using a 555 timer with a transistor at its output so the current is high enough to power a transformer to step up the voltage; to provide a power sufficient enough to turn the transducer on.

I am doing everything step by step so I can make sure everything is working properly and right now I am stuck at amplifying the current from the output.

This is my circuit right now.
I planned on having the transformer connected to the collector, which is why I put a 1k resistor there as a 'place-mat'

The problem lies in the voltage and current timing diagrams. The collector voltage and current waveforms are going crazy meanwhile the base and emitter mimic the square wave perfectly and I can't understand why.

Does anybody have any idea why?


texts: Voltage Divider Supply (Unloaded and Loaded)

texts:
The loading down of a system is the process of introducing elements that will draw current from the system. The heavier the current, the greater is the loading effect.

This is the the highlighted definition in my book in describing the term "loaded" in use with a voltage divider supply. Therefore, my question is as follows....

1.)I'm not understanding what a voltage divider supply is and need some clarification on how it's related to the term "current drain"?

Next question is in regards to how it's further used later in the chapter. In my textbook a paragraph containing the following is confusing for me to completely grasp on what is being explained.

66.21V / 20ohms = 3.31A

98.88V / 1kohms = 98.88mA < 0.1A

"If the load resistors are changed to the 1kohms level, the terminal voltages will all be relatively close to the no-load values."

"As demonstrated above, the greater the current drain, the greater is the change in terminal voltage with the application of the load. This is certainly verified by the fact that 3.31A is about 33.5 times larger with the 20ohm loads."

2.)My question is like i just mentioned, I'm having trouble understanding the concept in bold and what exactly this is trying to tell me.

I understand basic laws of parallel and series dc circuits. I'm just now getting into the chapter of series-parallel circuits and this certain section above is hard for me to understand. Any explanation or guidance/direction in helpful sources I could use to research this more is greatly appreciated.


texts: How is dynamic resistance of a diode modeled for large voltage variations?

texts:
The resistance of a diode changes with the voltage across it which is called dynamic resistance. If the voltage across the diode is constant we can find the dynamic resistance from the slope of the I-V curve. So for small variations we can use that dynamic resistance value in the diode model.

But if the voltage across the diode varies a lot like in a AC to DC rectifying diode, I guess we cannot just model a diode’s dynamic resistance with a constant series resistance. If we want to formulate the diode current in such case how is the diode dynamic resistance modeled? Here aren’t we facing a non-linear resistor?


texts:
I'm looking to measure distances from a submersed robotics project in the range of 1 to 20 feet (around there at least).  However, the only options I seem to come across are rather heavy sonar modules that cost hundreds of dollars.  Are there lighter, cheaper alternatives?  I don't need great resolution or accuracy, just a decent measurement.  Perhaps it's possible to waterproof a normal distance sensor (IR or ultrasonic)?

I intend to interface the sensor with a microcontroller so it would be nice to have something that outputs 0-5 V, but that's not a requirement.

Thanks.


texts:
I'm assembling a receiver kit from QRP labs. It is an inexpensive kit designed to cover HF. This kit has a BS170 at the input which I assume is intended to disconnect the receiver when the transmitter is active. Here is the relevant part of the schematic:

So I'm guessing the idea is when TX is high, the gate of Q1 is pulled low, thus isolating the RF input from the rest of the receiver (because the transmitter is active). When TX is low the transmitter is inactive, and Q1 is on, connecting the RF input to the band-pass filter and on to the rest of the receiver.

The transmitter normally paired with this has a nominal 200 mW output, and originally I was considering what modifications might be necessary to accommodate a higher power.

But then I got to thinking: even 200 mW corresponds to a peak voltage of 4.4V. That means when the transmitter is active, the drain of Q1 could be 4.4V below the source. This is more than sufficient to forward-bias the body diode.

I suppose this would only be a transient condition, since once the body diode begins to conduct the current will increase the voltage across C7 until the minimum voltage at the drain of Q1 is no longer sufficient to forward-bias the body diode. And at 200 mW, the negative consequences might be negligible.

Is my reasoning correct here? Does this seem like an OK design?


texts: Voltage drop problem using diodes with CNY 70

texts:
I am trying to build a complex sensor to read black and white colors that has many CNY 70 sensors inside. The schematic I am using for each individual CNY is this:

simulate this circuit – Schematic created using CircuitLab

If I read voltage at Vo, I get approximately 4,2 V for black color and 100 mV for white, which is nice, but I would like to get more accurate, so I changed it for this schematic:

simulate this circuit

Since the voltage drop of the 1N4007 diode is 0,6 V, the Vo voltage should turn to 3,5-3,6 V for black and 0 V for white. But if I read the V0 using a 1 kΩ resistor between the diode and ground, I get 80 mV and 0 V. Why is this happening?


texts: EAGLE change name of wire label in all similar label

texts: I've some schematics with, for example, a power wire with name VCC. I need to change this name to USB_VCC on all wires which have by name VCC. Since I've a lot of wires with names to change, there is a function in EAGLE that allow me do somethig like: "Change all wire VCC to USB_VCC"? It'll save me much time and ensure to change all wires and to not do errors in rename.


texts: How to calculate capacity of a battery from the readings of current and time?

texts:
The requirement is to compute the capacity of the battery in order to calculate the capacity degradation.

The input which can be acquired are current, voltage, relative time, battery level (in terms of percentage).

As per as formula

  Capacity = Integral of Current over time. (of discharge cycle)

So the doubt is, does the time here mean from reaching, say, x voltage to y,
or from battery level 100% to 0% on discharging?

Basically, how is the interval to calculate capacity is considered?


texts: Can the bldc motor works without hall sensors?


texts:
I am very new to FPGA programming. Got my Atlas DE0-Nano-SoC 5CSEMA4U23C5N board today and now trying to program the board using Quartus Prime Lite. Have created some VHDL code and run analysis and synthesis successfully, done the pin assignment and compiled and the programmer is picking up my device however when i add my output file and hit 'start' i just get "failed" in the progress bar. I suspect it has something to do with the configuration settings on the board. My university tutorial material mentions putting the switch with RUN and PROG on RUN however i have no idea what these switches are. (consultation of device manual didn't clarify this either.)

I currently have the configuration set to 1 up 2 down 3 up 4 up 5 down 6 down.

Could someone please explain what each switch does on the configuration and what it should be set to in order to put my program on the board. I am using Windows 10. Have put images of current configuration, code and the error below.

    library ieee;
    use ieee.std_logic_1164.all;

    entity FirstProject is
        port (  i1, i2  :   in  std_logic;
                o1      :   out std_logic);
    end FirstProject;

    architecture dataflow of FirstProject is
    begin
        o1 <= i1 and i2;
    end dataflow;


texts:
Preface: I don't have any MAX232 ICs handy, and only need unidirectional communication (from TTL to RS232). It's just a quick test to see if an old GPS OEM board still works. I don't have any MOSFETs on hand either - just some basic BJTs, as shown in the schematic. I'm using a dual supply instead of parasitic voltages from the serial port.

Here's the translation I was after:
TTL_Tx --> RS232_Rx
    0V         ~ +12V
    5V         ~ -12V

simulate this circuit – Schematic created using CircuitLab

I thought this would work (and it does in LTSpice).
Q1 - Turns Q2 on when the TTL input is high, providing a path for current to flow
Q2 - Provides a translation of 5V->12V and 0V->-12V at its collector
Q3 - Inverts Q2's collector signal for the final output

It works perfectly in LTSpice, but on my oscilloscope I see that the output is not being pulled down to the negative rail:

Of course, this actually works fine. The serial port is happy and the values are in spec. But I'm still trying to figure out why the circuit doesn't behave as I expected.


texts:
I'm building a solar project to monitor charge current and discharge current as well as lipo 'State Of Charge'.

The configuration is a 5V solar panel feeding a TP4056 which B+/- connect to a MAX471 bidirectional current monitor which connects to a LiPo in parallel with a MAX17043G lipo fuel gauge.

Unfortunately in this configuration with sensors on the B+/- outputs I cannot associate my TP OUT ground pin to those sensors without creating a ground loop that would prevent TP protection from working properly.  I understand this is a non-typical configuration but this is the only way I could monitor charge & discharge current with one sensor and one analog pin.

Any input would be greatly appreciated.

Datasheets:

CHRG - https://dlnmh9ip6v2uc.cloudfront.net/datasheets/Prototyping/TP4056.pdf
Current Sense - https://pdfserv.maximintegrated.com/en/ds/MAX471-MAX472.pdf
Fuel Gauge - https://datasheets.maximintegrated.com/en/ds/MAX17043-MAX17044.pdf

Module references:

TP4056
MAX471
MAX17044


texts:
I am planning to create a water valve controller using an MCU and a set of solenoid-controlled valves. The solenoids run on 24VAC (40mA inrush, 20mA holding).

The MCU is on a board that draws ~100mA, and it has an on-board regulator, so I can supply it either 5V directly (bypassing the regulator) or 6-12V through the on-board regulator. I also wish to run some other 5V peripherals (i.e. sensors, a display, some LEDs, and whatnot), so let's say I'll need 500mA of regulated 5VDC.

I could theoretically take the rectified/filtered output from the 24VAC transformer and regulate it down to ~12V and use the onboard regulator to further regulate it to 5V, but I'd be dissipating a LOT of power (comparatively) as waste heat. My regulators would need to be heatsinked and possibly actively cooled (this would all go in a box in a garage where it would regularly get to ~110F...). I've also considered using a switching regulator instead of a linear regulator, but I've got ZERO experience with those, and I wouldn't know how to put together a schematic to do what I want, or whether it's even as theoretically realistic as the linear regulator idea.

I've toyed with the idea of using a center-tapped 24VAC transformer and rectifying/regulating the 12V from the center tap down to 5VDC to run the MCU and using the 24VAC across the full output to drive the solenoids.

Is this an appropriate design? Is it OK to use the center tap in this way?


texts: DC motor spun clockwise then counter clockwise creates AC current?

texts: I am making a generator with a DC motor but the style of turning the rotor would be clockwise and then counter-clockwise, and I would want to capture as much current as possible so I hope it could be turned into AC current somehow.  If so how?


texts: Trace Dimensions limitation for JTAG signals

texts:
I have a JTAG bus that I need to go over PCB (or could make cable) for about 12 inches. I am trying to figure out the signal integrity specs for the JTAG bus ... what trace width vs. trace length I can use and how much dB loss per unit length?

Trying to understand how long traces can be.


texts: For BIBO stability, the poles cannot lie on imaginary axis?

texts:
Is this a true statement:

"for BIBO stability, the poles cannot lie on imaginary axis" because in that case we can excite the circuit with a bounded sinusoidal [that could match the resonant frequency of the cicuit]"

This one has me a little bit confused because they just finished explaining that all poles in the left half of s-plane is stable.

Now they throw in a rule that you can't use the imaginary axis if you want stability?  I don't know... it smells wrong to me...


texts:
I have a L78S05V voltage regulator (5V output). The datasheet's maximum ratings suggest the maximum input voltage (35V). I would like to know, is there a minimum input voltage?

I have a circuit that is powered from a 5V power supply. For "forward compatibility" (i.e. if my custom power supply broke) I want to add 5V voltage regulators on the input stage, so I can change the power supply with a 12V one and still have everything powered at 5V.
I can add some jumpers to route the 5V input or 12V input (via voltage regulators), but if the 5V voltage regulator works well with a 5V input I can get rid of the jumpers and work with any input voltage between 5V ad 35V without worrying.

Thanks!


texts: How Do You Decide Between Analog Chip Manufacturers?

texts:
I'm an electronics beginner and I find myself often needing to pick an IC for an analog application with no prior knowledge.

In the domain of microcontrollers, it's very clear that I should use Atmel AVR since many hobbyists use the ATMega8/128/168/32u4 etc. due to Arduino + I've got the toolchain setup for that now. I've familiarized myself with the line at this point and I don't bother looking elsewhere.

But when I'm researching something like signal conditioning, I'm always finding myself asking: so do I get an IC from Analog, Linear, TI or Microchip? Especially these three companies have a lot of overlap in the signal conditioning domain, but I'm sure you can find other groups of companies with similar overlaps in other domains.

When you're picking an IC, do you have a favorite or "go to" company that you'll start with? Or do you compare the specs from all the main companies and go with the "best" one? Do you leave it up to chance and go with the first thing you find that satisfies the requirements?

Do things like the general quality of datasheets, customer service, website UX and marketing influence your decisions?


texts: Upload XBee firmware without a PC and XCTU

texts:
So, as the title suggests, I would like to know if there is a way of uploading a firmware to a XBee module, throug the serial without a PC. What I mean is, I have a microcontroller, I would have the firmware file(s) stored in some kind of memory (like an SD card, flash...) and directly upload this firmware through serial without the need to get assistence from a computer.

I don't really know if this is possible, I don't hink it is, but it would be great for my project if it was! :) So, since I didn't find anything relevant on this matter, maybe one of us had experienced this and/or tell me with certainty that it is or is not possible!

Thanks!


texts: EEPROM is a "Read Only Memory," so why can I write to it?

texts:
Electrically Erasable Programmable Read-Only Memory (EEPROM):

If it's using Read-Only Memory (ROM) then how am I able to write to it?


texts: I'm looking for help to find a specific connector to complement a PCI Express/PCI Connector. I show it in the red circle mark. The photos are from this HAT for a RaspPi. What is the name of this type of connector?


texts: Control USB powered light with PWM, would it work?

texts:
A few weeks ago, I asked about controlling a DC powered LED lamp using PWM here, I was told that if I can get a LED lamp that uses an external DC adapter to power up, I can use a MOSFET and control it using PWM.

So I have found a LED lamp from Ikea, it's the HARTE LED Lamp, it is powered off a USB cable. As far as my understanding go, USB provides a DC power, so I am understanding that I should be able to control it, dim it by modifying the USB cable, attach a MOSFET to it, is that right?


texts: What is the purpose of perpendicular "smaller" magnets in between the main magnets in a rotor of a motor? had never seen this before. Do they help?

texts: I am trying to build my own generator at home for fun, I saw on a video in youtube https://www.youtube.com/watch?v=YsSm65DAcCg where the guy placed smaller magnets in between the main magnets of the rotor (at around the 10 minute mark). I was wondering if whomever has seen this done before, if it is actually helpful, especially since I am looking to use this as a generator and not as a motor. I would imagine it skews the magnetic lines to one side, but I am not sure. Any help would be appreciated before I buy magnets. Thanks.


texts: Logic level converter for NodeMCU (ESP8266): Input 24V/16V (Hi/Lo), 500 Baud

texts:
I want to use a digital input pin of a NodeMCU board (ESP8266) to read a digital signal. The signal line idles at 24V DC. The logic levels are 24V and 16V. The signal speed is 500 Baud (each signal sample is approx. 2 ms long). How do I convert the signal for the NodeMCU board?

EDIT:

Unfortunately I do not have an oscilloscope. What I already did is: I connected the bus lines to the microphone port of an USB sound card using a voltage divider with 1MOhm and 1kOhm and used the software Soundcard Scope. Does this tell you something about how the bus works?

24V high, 16V low. No 24V supply available near the NodeMCU board. Not sure about the maximum transmitter load. It is the 2-wire communication bus of a door intercom system (TCS, https://www.tcsag.de/).

BTW, in TCS:BUS documentation I found the hint that bus messages are either 16 or 32 bit long.

EDIT:

Soundcard Scope screenshot with Windows Automatic Gain Control (AGC) turned off for the microphone input:

EDIT:

This diagram is the result of capturing bus voltages with analogRead():

Any idea how this protocol could be working?


texts: What does "Driven low/high" mean in terms of electronics?

texts:
I keep seeing in specs/manuals to drive a pin high or low, what does that really mean?
For example I'm working with a voltage regulator that has an ENABLE pin that says will switch the board to a low power state when "Driven Low".


texts: Differential amplifier with common voltage far above the rail?

texts:
I have a thermocouple with one end connected to +24V. I want to be able to read the voltage (-5mV - +20mV) on it using a 3.3V ADC. The most reasonable solution I see is lowering the voltages using resistor dividers, than two voltage followers and a differential amplifier (like here: https://electronics.stackexchange.com/a/93467/61946).
I could also power the op-amp from a higher voltage rail, though that would mean constraining the output voltage in some other way.
Is there a simpler solution I am missing?


texts:
I have made a dc motor with two coils and 4 commutators with 2 brushes.
It has been powered by a 12v 1.5amp adapter and the coils have been wrapped 40 times on each end.
However when I turn the power on it does not spin and goes back and forth or just vibrates. Can anyone help/tell me what I have done wrong?


texts:
I just would like to ask about the small-ripple approximation and output ripple of buck/boost converters:
I understand that in a buck converter, there is an LC filter at the output. If correctly designed, the cutoff frequency of the LC filter will be much less than the switching frequency, hence the output voltage should have minimal ripple and we can approximate this to zero ripple at the output. This approximation is valid as long as the switching period is much smaller than the natural time constants of the circuit - hence we only see the linear portion of the inductor current and capacitor voltage response and not a full second-order sinusodial solution.

This all makes sense. However, the notes further go on to say that:

Now, here is my confusion. There is still a current ripple! I assume this current ripple will go to the capacitor and cause a voltage ripple at the output. This ripple is at the switching frequency! This is against our small-ripple approximation made above
Does this mean that our LC filter hasn't worked? I'm having a hard time distinguishing the sources of ripples


texts: Why is this angle incorrect for AC current I_norton?

texts:
I cannot seem to get the correct angle. I've done this problem multiple times and still get -75 degrees.

All I do is 162cos(200t - 30) ->

convert to phasor domain (162cos(-30) + 162i*sin(-30)) = Vs

To get I_norton, I divide this result by the impedance of the resistor and inductor (10 + 50 * 10^(-3) * j * 200). Right? Why is this not yielding the correct answer?


texts: Solve using both approaches first using small signal analysis and then using feedback analysis.


texts: Long Range (100m) USB(PC) to USB (microController USB module) Communication

texts: I have a system that communicates between PIC32MX250F256D (USB module) and PC via USB (2 meters apart). And I need to increase the range of this communication to 100 meters. Due to typical 5m limit of USB, I am thinking of using 2 USB to RS485 PCBA from FTDI and connect their RS485 sides together to increase the cable length to 100 meters. In this way, one USB side will go to PIC32MX250F256D and the other to PC. The PIC circuit or code cannot be altered. Whatever I do can only be done after PIC.  The communication is 2-way. Baudrate is 115200. The reason for not using USB hubs is to keep the cable system clean as this solution will be mass produced if it works. My question is to know if this would work and what problems do you guys see in this? Any recommendations are more than welcome.


texts: I have this type of battery. When it was fully charged I read with the multimeter aroud 38-39 volts. Now I read 21 volts. The question is: When I connect the battery (discharged - 21,22 v) to a bldc motor load, the voltage drops to 0, the motor only spins for 2 seconds every time o plug the battery. Do you have any ideea why the voltage drops to 0 ?


texts:
For a DIY project BGA reflow soldering is really expensive to get it done by commercial means. I approached a university which allowed me to avail the help of their staff but they said they would only do the BGA part.

I thought of getting the other parts done through commercial means since they don't cost much and then get the BGA done. Would this work?

I checked the datasheets and some components have second reflow capabilities whereas its not specified for others. Can I use something like epoxy glue to hold the others in place while the BGA is being reflowed?

Its a pretty tight knit board with about 300 components packed into a 7cmx4cm board, so I'm pretty concerned about them shifting during the second reflow.


texts: Forward biasing a diode past built-in voltage

texts: Why can't we forward biase a diode past its built-in voltage/potential? What's the problem in doing so?


texts: DC Output Voltage of BJT Differential Amplifier with Active Load

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I want to compute the value of VO.

simulate this circuit – Schematic created using CircuitLab

I would have guessed that VO = VCC - VEB. Asuming VCC = 5V and VEB = 0.6 V, that would render VO = 4.4 V, as in the left branch of the circuit.

But doing the simulation I found that VO is actually much lower: VO = -459.9 mV

So, how should I do to compute VO properly?


texts:
simulate this circuit – Schematic created using CircuitLab

assuming this circuit is run for 5 seconds period, the switch is closed for 1 second starting at t=3s

we can calculate average power as average  = 1.8 W
but apparent power S = Vrms * Irms = 4.023 VA
and the difference will be the reactive power which is >0, right?
what does this reactive power mean? in rl or rc circuit it's the powered stored in inductor or capacitor but switch cannot store power.


texts: Can I, Bi-Directional Level Shifter as Motor(3V) controller with Arduino Lilypad (3.3V)?

texts: Basically this could be easily done by using a BJT NPN, but since I want to control two motors(3 V, 45-60mA) and 5 LEDs was thinking of using a Bi directional level shifter instead of using transistors for each application. Could this be possible ?


texts: resistor doesn't make a difference connected across a supernode, why?

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I'm using KCL to analyse the circuit that has a voltage source between two non-reference nodes connected in parallel with resistor R3.

I'm regarding the voltage source and the resistor as a supernode. To solve the circuit I need the constraint equation that can be obtained by applying KVL to the supernode.

Why isn't the resistor R3 important in this case, when connected across a supernode?

simulate this circuit – Schematic created using CircuitLab


texts: PWM with op-amp, but can't figure out formulas/how it works

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I want to make a way to control the high time with a control voltage, instead of using a variable resistor.
For this I have found this diagram with an op-amp, and I have tested it in Multisim (a simulation tool for electronics.) It seems to do some kind of PWM.
I can't figure out how it works and the formulas that I have found to calculate the high and the low time (from this website) don't seem to match the simulation.
Can somebody help understand the circuit and help me with calculating the high and the low time?
MAX998 datasheet


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Background

I've arrived to a dilemma in my personal project where I'll need to design a circuit like the following:

The logic makes sense to me, but I found that I am unsure in what nature would it be best for me to implement a gate in my circuits.

Let's take the NOT gates for instance; I thought making a NOT gate would involve one single transistor:

However I read an article that criticizes this approach, saying it is crude. Instead it offers this insane thing:

The article states that it "maximizes voltage gain", but doesn't explain how very well. The article also goes on to explain how the circuit works, which I admit is clever, but  I don't see the advantage of this over the single transistor method. The above circuit also seems like overkill. Is the single transistor method no more than an academic exercise?

The Actual Question

What's a real, practical way to implement small logic in circuitry? In the case of the NOT gate, I have the single transistor, multi transistor and IC approach. Integrated circuit inverters however sell only in arrays (that I can find), so this also seems like overkill to me.

To me, the most pragmatic approach is the single transistor, but I'm unsure if this is a correct assumption.