texts: Control electrical switch through external mechanism

texts:
I am planning to control a water tank motor switch through some mechanical means( Since I am in a rented house, I am not allowed to change the electrical wiring for this. And the switch is in the ground floor, while I stay in the second floor. I am planning to control the switch from my house).

The switch is similar to this

I am looking for a mechanism in which there will be an external mechanical structure which will hit the switch to turn it on and off. It should retract after hitting the switch to allow manual control as well.

I know the solution has to be something similar to relays but I am not sure on the details.

Please help.

I would be thankful for any suggestions and ideas.

Regards,
Naveen


texts: HDMI 5 port switch detecting LED with Arduino

texts:
Hey all I am wanting to make a project for this HDMI 5 port switch I have. I want to be able, with an Arduino, to detect which of the 5 ports are being used (only 1 can be used at any given time).

Without buying 5 of something like this to detect current (which would be ~$30):

Would it be possible for me to just purchase one of these and hook up different resistors values to each of the 5 LEDs and use the Arduino's Analog input to detect the voltage to determine which port LED was on?

I'm thinking that the standard red led voltage is around 2.0v? And the Android analog input is 5v. If this is possible then what type of values for the resisters for each of the 5 LEDs would be best to use in order to read the difference enough for each with the Arduino's analog input?

Example:

(com Gnd)-------------|
(led1)---/\/\/----\   |   |----------------|
(led2)---/\/\/-----\  |---|[-]         [vcc]-->to Arduino 5v Pin
(led3)---/\/\/------|-----|[+]         [out]-->to Arduino Analog Pin
(led4)---/\/\/-----/      |            [gnd]-->to Arduino Gnd Pin
(led5)---/\/\/----/       |----------------|

Or would this be possible without even using the current sensing module?

UPDATE

Ok how about if I used a 4N25 chip?

One of the LEDs would hook to Pin 1(+) and Pin 2(-). Pin 5 would house a voltage of ~3vdc from a power supply. Pin 4 would be hooked up to the arduino's Analog Pin 0.

So when the LED on the 5 port switch is powered on, it causes the ~3vdc power from the power supply to flow to the arduino where it's read as a voltage value.

Does this seem correct?


texts: SIM to RJ: emulating SIM card as a RJ connector

texts: i recently got in a Goodwill store one of the 2500 model phones https://en.wikipedia.org/wiki/Model_500_telephone#Model_2500 and i want to use it. the problem is that i don't have a phone line in my house, just a cell phone's SIM card. is that possible to build something (like a box) that in one side of the box you put SIM card, other side a power source and in other side a RJ connector https://en.wikipedia.org/wiki/Registered_jack? i need this box to emulate the SIM card as a RJ connector and use the phone.


texts: In microwave frequencies, do you use a circulator when you need a (near) perfect diode?

texts:
I am confused with the "diode concept" in microwave frequencies. As far as I could read, I found that even small signal Schottky diodes have a non negligible capacitance, that may perturb the signal from 1GHz and more (well I've seen a few that work up to 20GHz but they require special mounting etc.).
On the other hand, there are circulators with operating frequencies from 1GHz to 40GHz, and I think they can be used as a diode since a signal entering at port 1 output at port 2 but the inverse path is blocked. Hence my question: is it what microwave engineers use?


texts: Understanding Audio Amplification with OpAmp

texts:
I have what I believe to be a fairly simple schematic, as shown below, to take either a PWM signal from an AVR board to play a song/alarm, or  radio signal.

I'm connecting both of these with a summing circuit OpAmp. Only one of these signals will be on at a time. The rails on the OpAmp are +5V and ground, so a voltage divider was used to feed in a 2.5 volt signal to the non-inverting output. The output I want to get from the OpAmp to the Audio Amplifier is about 0.15 volts, so I selected the appropriate resistors to achieve that voltage level. Rf= 10kOhm, R1 = 330kOhm.

It was recommended to put a 0.1 uF in series with R_2 to block any DC signal on the AVR line. When I start probing the signal after the capacitor the signal appears to just disappear. I've tried AC and DC coupling with 50 Ohm termination and haven't been able to see any noticeable signal. I have tried the set-up without the CAP and it will play the song as expected.

Am I using the incorrect voltage gain equation? Are my resistor values way off? Is the capacitor recommendation incorrect?

Any suggesetions are greatly appreciated and let me know if I need to provide any additional information.

simulate this circuit – Schematic created using CircuitLab


texts: When is it appropriate to use ferrite beads?

texts: In a lot of circuits, I've seen ferrite beads on the Vdd lines to microcontrollers. For my high speed dsPIC33F (80 MHz, 40 MIPS) microcontroller, should I have ferrite beads on the Vdd lines or should I not bother? The datasheet doesn't suggest using them. I'd like to limit EMI/RF interference, as the module will be used on a model plane and this type of interference could cause problems for the onboard radios.


texts: 2's complement subtraction with overflow

texts:
I studied binary subtraction using 2's complement method and understood the rules, which say that after the subtraction process (actually addition) discard any carry in case it occurs and take the answer as it is (with positive sign). In case there's no carry take the 2's complement of the answer and represent it in decimal form with a negative sign.

Now I came across the concept of overflow. It says, in case there's no carry in to the sign bit but there's carry out from it then it indicates an overflow. The correct solution of the subtraction is this number with overflow (or carry) bit included (but it is in complemented form).

In this second case of overflow we are not discarding the carry bit but considering the complete solution. But earlier we were discarding the carry. So how do I deduce new rules to be considered for subtraction using 2's complement in case overflow occurs?

EDIT:

In this example the correct answer was obtained by discarding the end carry

But here, where there is an overflow, the end carry is not discarded for getting the actual result (1 0110 1010 = -150 in binary 2's compliment form). Had we removed the end carry as in earlier example, the result would have been 0110 1010 = +106.

Both examples are employing different treatment on the occurrence of a Carry. Are my observations faulty?


texts: Help Identifying a Voltage Regulator 0 - 5 Volt?

texts:
So this voltage regulator came from a variable resistor for my 06 Infinity QX56 AC blower motor. I have already replaced the unit with a new one but figured I would try to fix this and have a spare. Well the voltage regulater cracked in half and is somewhat unidentifiable to me.

The only info I can provide about its output is that it should be able to provide a 0 - 5 volt.

Any help in figuring this out is most appreciated.


texts: What keeps a delay-off timer energized when you cut off the power?

texts:
I've come to understand the function of the delay off timer as follows:
When it is energized, it instantly changes its contacts. And when you "de-energize" it, it delays for a preset time and only changes its contacts back to their original state after counting down.
So, my question here is how does it stay energized even when the power is cut off, and what devices are used to achieve this?


texts: How to use square pic controllers with breadboard

texts: I've just started learning pic controllers and I'm collecting all the information. I've seen a lot of examples where people used breadboard with pic18. But I want to buy pic32 as the price is just a little higher. All pic32 are square. However, for my university project I want to use breadboard. And I can't understand how I can use this breadboard with square controller. Is it possible? If yes, then how?


texts: If MOSFET is a voltage-controlled device, then why do we need to supply it with high current when using in an H-bridge?

texts:
I might be confusing myself, but from what I am reading so far, a BJT is a current-controlled device and a MOSFET is a voltage-controlled device, which to me implies that a MOSFET requires very low input current.

If that is correct, than why, in say an H-bridge, do we need to use a high side driver to supply 2A? Is it because of the Miller capacitance that we need to charge the gate capacitance for a split second? Please explain.


texts: How do you calculate phase shift induced by a shunt capacitor?

texts:
Given a simple loaded-line shunt-capacitor phase shifter, how can I calculate the phase shift and insertion loss at S21 caused by the shunt capacitor (varicap in my case, but for any cap) assuming I know the capacitance value C1?  I can model this in Sonnet (or perhaps some circuit theory program) but I want to put the calculations in a spreadsheet and see if my simulated model (nearly) matches the mathematical model.

According to Rick Sturdivant the "normalized shunt susceptence" of the capacitor (\$B\$) must be known---but I can't find such a value on varicap/varactor datasheets.  If I can get \$B\$ then Rick says insertion loss is \$ 10\log_{10}({1+{B^2 \over 4}}) \$ and phase shift is \$-\tan^{-1}({B \over 2})\$.

Can \$B\$ be calculated from the value of C(v)? I tried \$B = {1 \over X_c} = 2\pi f C\$ but my values don't line up to his unless his \$f\$ is about 100GHz, which seems unlikely.  (I'm shooting for a center frequency of 146MHz.)

At microwaves101.com they hint that "the reflection coefficient from a shunt capacitor" might be used to calculate phase shift, in which case I don't need susceptence: \$ {\displaystyle \Gamma ={1-j2\pi fCZ_0 \over 1+j2\pi fCZ_0} } \$ .  But once I have \$\Gamma\$, how do I calculate shift?

and Wikipedia:Reflection Coefficient says that "if that load, \$Z_L\$ were measured not directly but through a transmission line, then [...] its phase will have shifted according to
\$ {\displaystyle \Gamma '=\Gamma e^{-i\,2\phi }}\$ where ϕ [is phase]"---but I think thats the S11 reflection phase not the S21 phase.  Even if it is the S21 phase, how do I calculate \$\phi\$?

If you can help me understand what is right, what is irrelevant, and what other information I need to answer the question and how to calculate phase shift and insertion loss then I would greatly appreciate it!


texts: I have an old piece of analog gear from the 70s and I want to motorize the variable resistors on its panel. I don't want to replace the existing pots with motorized ones but rather to add a motor  to the existing pots. Does anyone have any ideas about where to start with this?


texts:
I need to design high-density board with MCU, external RAM, GPS, GSM, Bluetooth, CAN, RGB interface on small size(5x10cm) and got into thinking which stackup should I use.

Currently I have almost half bigger PCB(8x15cm) on 4 layer board(SIG/GND/PWR/SIG) and everything is running well. However I am not happy about how I route PWR plane. Next HW version should meet CE/FCC requirements.

I was thinking about using this stackup(6 layers):

Sig./Loc. ground/Pwr
GND
Sig
Sig
GND
Sig./Loc. ground/Pwr

or this one(4 layers)

Sig./Pwr
Local ground/Sig.
Full ground plane
Sig./Local ground/Pwr

I have only 2 voltage levels(5V/4V/3V3) but I don't think I need power plane.

The problem with 6 layer stackup I think I would have is that my traces would be mainly horizontal so I cannot use vertical/horizontal routing technique while having GND layer in the middle.

Since I don't have experience with custom stackups, how much spacing between layers is required for solution 2 or solution 1? Do you suggest using this stackups? Would it be better to  have full power plane for 3V3 and use 5V/4V as local PWR nets since there is only one IC per voltage?


texts: Detect multiple reed switches in series individually

texts:
I have a device, which has a safety relay, where the relay coil is connected to +12V over 2 reed switches.
Now I want to detect, which of the reed switches is not closed, with a microcontroller, but I struggle a bit with that.

I have seen something like this before, but I cannot remember how it can be done with resistors and transistors only. I tried the following, which does not work for SW2 closed. Anyone an idea, how this can be done?


texts: Aircom air connectors, what are they called?

texts: Does anyone know what type of connector this is?


texts: Offline switcher SMPS design with two phase inputs

texts:
I am trying to build a power supply circuit which accepts two phases (220 VAC 50 Hz) and outputs 5V 1A. It must keep working if there is at least one phase present. Both phases can be coming from separate sources so I have taken a worse case phase difference of 180 degrees. Essentially the phase difference can be 0-180 degrees.

The two phases can be any two out of the following:

Phase-1,2,3 are three phases of a 3 phase 4 wire system. Inverter is common household inverter. The household appliances are usually wired like as shown above - Common neutral for all loads. Inverter is usually powered using one of the phases (phase-1,2,3). When that phase goes off, the inverter kicks in. When that phase is present, the power to all loads connected on inverter phase essentially is provided by that phase.

I could think of two ways to tackle this:

1) Use a separate bridge rectifier for both phases as shown below:

However the output voltage on bulk cap varies a lot depending upon whether both phases are present or just a single one is present. Please check the waveforms below:

Fig (above) : Both phases present (180 degrees phase difference, 350 V amplitude)

Fig (above) : Single phase present (180 degrees phase difference, 350 V amplitude)

I see two problems with this solution:

(a) 700 V bulk capacitor voltage will be difficult to handle with regular offline switching ICs.

(b) A voltage difference of 350 V whether both phases are present or not will add further difficulty. Since I'd also want it to work in universal voltage range 90-270 VAC, I guess it will add further complexity to the circuit and part selection. Cost is another concern.

2) Use a half wave rectifier for both phases.

Fig (above) : Half wave rectifier for both phases

(Resistor represents the complete SMPS circuit)

Waveforms are as shown below:

Fig (above) : Both phases present (180 degrees phase difference, 350 V amplitude)

Fig (above) : Single phase present (180 degrees phase difference, 350 V amplitude)

This looks like an easier thing to handle. Voltage levels are same in both cases. The only difference is - one has higher ripple than the other.

As such I am leaning towards going the half wave rectifier way. Am I doing this right? Am I missing something here?


texts:
At t0<0 the current through the inductor was 0.

simulate this circuit – Schematic created using CircuitLab
At time t0 we introduce a current source and a resistor to the solenoid
The current through the inductor will begin rising exponentially.If we change the value of I1 some time before L1 becomes a short circuit:(at t1)

simulate this circuit
How will the current behave then?


texts: Need help identifying SMD DFN-6 component. Top marking 26T6 TIW 957M

texts:
I've been trying to reverse-engineer this circuit but I'm an ME, so my knowledge of electronics is limited to pretty much Arduinos.
I have a simple circuit and I'm trying to identify one of the components.
The component is a small IC, DFN-6 (3x3) package size, and is wired as shown in the drawn schematic. The part number that I can make out I think is 26T6 TIW 957M.
The circuit is on a lithium BMS board and is used for the initial handshake when connecting a tool to the battery.
The circuit is separate from the rest of the BMS as I've isolated the components.
With the circuit isolated, applying a 1 kHz positive square wave produces the signal shown in the below oscilloscope screen capture.
What I've concluded is that it's some sort of fixed/pre-programmed oscillator, but the input is the same as the output...?
(Click on an image for a larger version)

Figure 1: Traced schematic

Figure 2: Oscilloscope capture

Figure 3: Top marking on unknown device

Figure 4: PCB showing unknown device


texts: Help SIM5320 Breakout Board construction for Raspberry Pi model B

texts:
I need a breakout board based on SIM5320 for experimenting web server http requests. I've found the board shown above in adafruit library and thought of using it as reference and slim it down to the requirements by removing unwanted circuitry.As marked in the pic, all the circuits marked with cross are not needed. And the component to which the arrow mark is pointing is the one I need to know how to create one similar to it in Altium or Eagle cad. I see it says GPS BIAS with 33nH inductor and not sure what those half rounded pads with pin nos connected to or the component type used.

Also for this board I'll be using 9V external voltage source along with LDO circuit as mentioned in the SIM5320 Datasheet.I've calculated the required resistances to be used to get the desired LDO output voltage. Also I will be be using all 3 protocols (UART, SPI, I2C) and for these I will be putting separated headers so that I can use the desired ones when needed.I hope that should be enough to RPi to take care of SIM5320 . Need some one to check my approach and let me know If there are any other changes to be done in the circuitry.


texts: Determining values to convert square wave to sine wave at low frequency

texts:
For a project I am working on, I have a 1Hz square wave coming from a real time clock, and need to convert it into a sinusoidal wave to pulse LEDs. After some googling and playing around with simulations I came up with the circuit below. The 1Hz square wave is connected at the net labelled SQUARE and then filtered:

My question now is how do I determine values for the passives to effectively filter out the higher frequencies and get the single sine wave I want? I got the values you see here from messing with a simulator, but I don't understand how to derive them analytically.

Thank you for your help.


texts: Is there a simple way of determining which module causes an interrupt on an ATmega169PA? I have 3,000 units executing the same code and there were 10 units that executed my ISR(BADISR_vect) handler causing these units to stop and display a bad interrupt error code. I'm trying to figure out which interrupt vector is being used or which module is generating the bad interrupt. I disabled the modules by writing a "1" in it's corresponding bit in the PRR except for the LCD, UART and Timer2. Both UART and Timer 2 have their own interrupt handlers and the LCD's interrupt enable bit is "0". The other module's interrupt enable bit is "0" by default. Is it possible that a disabled module can generate an interrupt?


texts:
Just got a (220<-->12-0-12) transformer hooked up with a bridge rectifier and it measured 13 volts DC output from rectifier, but when I added a 1uF capacitor it just jumped up to 20 volts, and same reading(20 volts) from a 0.1uF capacitor, how is that even possible!?

Note: Nothing is connected in the circuit more than a transformer and a bridge rectifier in the first case, and only a capacitor added in the second case along with the voltmeter.


texts: What's the best/easiest way to measure an unkown inductance without an RLC meter?

texts:
Is there a decent way to measure inductance accurately using an oscope and a function generator? The best method I can find is to build a tank circuit and sweep the frequency until the highest voltage appears. Then use the formula below to solve:

$$f = \dfrac{1}{2\pi\sqrt{LC}}$$

It seems like there must be an easier way!


texts: Difference between current sense amplifier filter configuration

texts:
I am trying to figure out what is the effect of the different connections of the C3 capacitor in this circuit. It is the classical difference amplifier configuration used in current sense with some filtering.
C3 is placed there to match C2 which is used for bandwidth limiting.
Does it change something by connecting C3 to GND of 1.65V ?
Is it correct to say that in AC 1.65 and GND are connected together so C3 connection doesn't care?
Thanks


texts: Radiofrequency exposure from portable (vehicle-mounted) satellite uplink antennas

texts:
I came across these broadcasting vans recently in London.

The antenna that's deployed I think is a Vislink Advent uplink antenna, similar to this model, designed to transmit to satellites for television broadcasting.

The antenna wasn't pointing directly at the building on the right, but close enough (the cylindrical beam from the antenna would have passed approximately 2-3 meters from the front edge of the building) to make me wonder about radiofrequency exposure to the building.

My questions are:

How much peripheral scatter occurs with these antennas?
Would transmitting in this configuration raise any RF exposure concerns (a) to the building, (b) to the pavement to the right?
Hypothetically, what would the RF exposure be from direct exposure to the beam?


texts: High Side and Low Side MOSFET Driver... with low supply voltage

texts:
I need to drive a pair of N channel MOSFETs, one on the high side of the load and one on the low side of a load. Most ICs I can find for this application require 10V+ supply voltage to get the the chip to fit in recommended operating conditions.

The VCC at the top side of the N channel is a LiPo, single cell battery (~3.2 to 4.2 V).

The inputs into the driver needs to operating around 3.3V (from outputs of a micro controller), to complicate the requirements even further.

Does anyone know where I can find such an IC? The high side/low side does not necessarily need to be in a single package. The current draw from the MOSFEts are about 3A at VCC.

Any suggestions?


texts: Maximizing force of magnetic mass accelerator

texts: I am planning to build a coil gun to fire small neodymium magnets out of a pipe.  For this I am planning to use a large 400 Farad  2.7 Volt capacitor.  I am wondering how many coils of wire I should make to launch the projectile.  I know that the more coils the stronger the magnetic field, however I am unsure at what point the resistance will lower the current enough to limit the strength of the magnet. The capacitor has an internal resistance of  3.2 mOhms.  In addition, I was wondering whether the electromagnet should have a ferrite core.  While I know that this will increase the strength of the electromagnet I was not sure if it would slow the projectile down as it passed the ferrite because of its attraction to it.  Finally, I was wondering what diode I should use to protect the capacitor from voltage generated be the magnetic field.  Please tell me if this will not be strong enough to accomplish my needs. I do not need the projectile to travel very fast however I would like the projectile to be able to travel through the a little bit for proof of concept.


texts: Distance between 2 arduino's using rf links

texts:
I currently have a setup where I send a char using a Tx of 434MHz and an Uno to a Mega with a Rx. The Mega counts how many times it receives the char and then if it falls below a certain number it triggers an alarm. Is this a viable way to measure the distance between two microcontrollers while indoors or is there a better way.

Transmitter (Mega)

#include <SoftwareSerial.h>

int rxPin=2; //Goes to the Receiver Pin
int txPin=5; //Make sure it is set to pin 5 going to input of receiver

SoftwareSerial txSerial = SoftwareSerial(rxPin, txPin);
SoftwareSerial rxSerial = SoftwareSerial(txPin, rxPin);
char sendChar ='H';

void setup() {
  pinMode(rxPin, INPUT);
  pinMode(txPin,OUTPUT);
  txSerial.begin(2400);
  rxSerial.begin(2400);
}

void loop() {
  txSerial.println(sendChar);
  Serial.print(sendChar);
}

Receiver

#include <SoftwareSerial.h>

//Make sure it is set to pin 5 going to the data input of the transmitter
int rxPin=5;
int txPin=3; //Don't need to make connections
int LED=13;
int BUZZ=9;
int t=0;

char incomingChar = 0;
int counter = 0;

SoftwareSerial rxSerial = SoftwareSerial(rxPin, txPin);

void setup() {
  pinMode(rxPin, INPUT); //initilize rxpin as input
  pinMode(BUZZ, OUTPUT); //initilize buzz for output
  pinMode(LED, OUTPUT); //initilize led for output
  rxSerial.begin(2400); //set baud rate for transmission
  Serial.begin(2400); //see above
}

void loop() {
  for(int i=0; i<200; i++) {
    incomingChar = rxSerial.read(); //read incoming msg from tx

    if (incomingChar =='H') {
      counter++; //if we get bit "h" count it
    }
    delay(5); //delay of 10 secs
  }
  Serial.println(incomingChar);
  Serial.println(counter); //prints the the bits we recieved

  if(counter<55) {
    //if we receive less than 100 bits than print out of range triggers alarm
    Serial.println("out of range");
    tone(BUZZ,5000,500);digitalWrite(LED,HIGH);
  }
  else {
    noTone(BUZZ);digitalWrite(LED, LOW);
    //if we get more than 100 bits than we are within range turn off alarm
    Serial.println("in range");
  }

  counter = 0;
  incomingChar=0;
}


texts: Designing a lock failsafe with arduino. Questions about reliability and design

texts:
I'm making a lock with arduino. I plan on using a servo motor. I need the motor to not consume power when the pins that lock the door and the body together are held in place until it opens. This is because it will be a mechanical failsafe in the case that the electronics fail. I've read that a solenoid can do this, but I didn't find any explanations. Some of the suggestions had ways that didn't consume power to hold it in place but still needed it to unlock it. If this is not specific enough an electronics question, than please move it to the appropriate section

I did a quick mockup, I don't have a mouse so cut me some slack. And this is my first design of a motor system ever. I know I can handle the mechanical aspect well enough. I tried to make it pretty straightforward. The failsafe I mention is a function specific failsafe in which if the electronics fail a mechanism slowly pulls the barrier out of the way over a period of time and lets the spring #1 push the bolt back through to the unlocked position. I know I could probably use 2 solenoids, but I would rather use a servo and a solenoid as I can actually lock the bolt in place after so it can't be tampered with. I see now spring #1 in its current position would definitely be in the way of the second hold, I would move the spring to be pulling it from the other side instead

I suspect I will be laughed at for overcomplicated design with no advantages.


texts: Cable-to-cable crosstalk (Capacitative Coupling)

texts:
I'm having some difficulty understanding the solution to this question.

  Compute the cable-to-cable crosstalk due to capacitive coupling in a
  harness between two cable pairs having an average separation distance
  of 3 mm and a 10 m in a cable tray. The cable diameters are 1 mm and
  both cables are operating at a 100 ohm impedance level. Assume h = 5
  mm, source logic = 3.5 V with rise/fall times of 500 ns.

The lecturer showed the following diagram when he was talking about the capacitative coupling, and the equivalent (part of) circuit representation.

The Capacitive Cross-talk Coupling (CCC) is defined as

CCC(dB) = 20 log (\$V_V/V_C\$)

where \$V_C\$ is the culprit source line voltage and \$V_V\$ is the victim load line voltage.

The solution given is as follows.

  The second corner frequency, \$f_c\$, in the spectrum of a pulse (or
  pulses) corresponding to rise/fall time of 500 ns is:  \$f_c = 1/πτ\$
  = 637 kHz

  \$C_{CV}\$ = 12 pF/m (read from a graph), and \$[ωC_{CV}l]^{-1} =
> \text{2 k}Ω\$, thus CCC dB = -26.4 dB

  Source logic = 3.5 V = 11 dBV, then

  Noise = 11 dB – 26.4 dB = -15.4 dBV = 0.17 V < 0.4 V

  Thus, switching OK.

I have several questions.

1) I don't know how to get CCC dB = -26.4 dB. I know I can use the voltage divider on the circuit representation to find \$V_v/V_c\$, which means I need to find \$Z_v\$. But to do that, I need to find \$C_v\$, which is the capacitance per unit length of the victim wire, and I don't know how to get this value.

2) What is "source logic"?

3) Why does noise < 0.4V imply "switching OK", and why "0.4V"?


texts: Trace width for breaking out 100Ω differential microstrip from 0.5mm pitch BGA

texts:
See bottom of post for the actual questions

First, some context:

I'm making a DisplayPort switch as a hobby project
DisplayPort's high speed lines require 100Ω ± 10% differential impedance, which I'll be requesting impedance control from the fab
Off-the-shelf DisplayPort switch ICs are only available in 0.5mm pitch BGA (e.g., TI HD3SS214)
Ideally I want to support HBR3, which runs at 8.1Gbit/s (8b/10b encoded), or a fundamental frequency of 4.05GHz, so transmission line impedance matters
I can use FR-4 (εr = 4.2~4.4 @ 5GHz) or RO4350B (εr = 3.66) dielectrics
This is my first time working on a high speed design

So due to the 0.5mm pitch BGA limitation, the widest trace I can fit between the balls is 76.6µm (3.02mil). Fortunately, this just fits within the minimum trace width of 3mil on 1oz copper for the fab I've tentatively chosen (WellPCB).

But such thin traces present a problem in achieving 100Ω differential impedance (on a differential microstrip). My fab's standard 1st-to-2nd layer dielectric thickness on FR-4 is 213µm (7628H). Using the minimum trace spacing of 76.2µm (3mil) with the 76.6µm width, this results in Zdiff = 110~115Ω (according to MMTL), which is out of spec! Using the thinnest available RO4350B (168µm) is even worse with Zdiff = 117Ω due to the much lower εr.

While I can increase the trace width if I get around the balls with vias instead of routing between them (the bottom layer already contains other high speed traces), this would mean I would have to add an extra two layers to the PCB ($$$), and would be extra impedance mismatch.
Alternatively I can taper the traces to a larger width immediately after escaping the BGA, but this is annoying to do on my EDA software (KiCAD).

I could also try to ask the fab to use a custom FR-4 stackup, with a thinner upper layer, but I'm not sure how thin they can go.
I simulated the Zdiff on thinner FR-4 (see below image), and it seems 100µm would be ideal.

I also worry that being right on the minimum 3mil trace width and spacing would mean the fab wouldn't be able to perform their own impedance control, since I heard it's primarily done by adjusting the trace width (can't go wider or won't fit between BGA balls; can't go narrower or it goes below the minimum 3mil).

Questions:

Should I be worried in using the minimum trace width and spacing of 3mil, when simulations show this results in a too high impedance? Will the fab be able to properly lower it?
If not, how would you recommend I break out the differential pairs?
Are my Zdiff simulations with MMTL accurate at all? I haven't been able to cross-check with other EM simulators, while simple online calculators have been giving me even higher values.
Have I made any stupid mistakes or incorrect assumptions? First time on a high speed design after all...


texts: How can I make a 'PD' battery port pass 9v instead of standard 5v?

texts:
I wanted to get a standard lightweight phone charger to power my DIY portable device. I have tested it with 9v which works but I'm realizing that for those 'PD' chargers I'll need something on my device to signal to the battery the request for the 9 volts.
How can I make the charger pass me 9v from its 'PD' port?
Cheers!


texts:
Am I right about this Transfer Function:

  My work:

  $$\text{I}_{\text{in}}(t)+\text{I}_{\text{p}}(t)=0\Longleftrightarrow$$
  $$\text{I}_{\text{p}}(t)=-\text{I}_{\text{in}}(t)\Longleftrightarrow$$
  $$\text{I}_{\text{p}}(t)=-\frac{\text{V}_{\text{in}}(t)}{\text{R}_1}$$

  $$\text{I}_{\text{p}}(t)=\text{I}_{\text{C}}(t)+\text{I}_{\text{R}_2}(t)\Longleftrightarrow$$
  $$\text{I}_{\text{p}}(t)=\text{C}\text{V}'_{\text{out}}(t)+\frac{\text{V}_{\text{out}}(t)}{\text{R}_2}$$

  $$-\frac{\text{V}_{\text{in}}(t)}{\text{R}_1}=\text{C}\text{V}'_{\text{out}}(t)+\frac{\text{V}_{\text{out}}(t)}{\text{R}_2}\Longleftrightarrow$$
  $$\mathcal{L}_t\left[-\frac{\text{V}_{\text{in}}(t)}{\text{R}_1}\right]_{(s)}=\mathcal{L}_t\left[\text{C}\text{V}'_{\text{out}}(t)+\frac{\text{V}_{\text{out}}(t)}{\text{R}_2}\right]_{(s)}\Longleftrightarrow$$
  $$-\frac{\text{V}_{\text{in}}(s)}{\text{R}_1}=\text{C}s\text{V}_{\text{out}}(s)+\frac{\text{V}_{\text{out}}(s)}{\text{R}_2}\Longleftrightarrow$$
  $$\color{red}{\frac{\text{V}_{\text{out}}(s)}{\text{V}_{\text{in}}(s)}=-\frac{\text{R}_2}{\text{R}_1\left(1+\text{C}\text{R}_2s\right)}}$$


texts: Why sinusoidally varying torque in induction machine not visible

texts: We know that torque in an induction machine varies as \$k\times[\cos(2wt)+\cos(\beta)]\$ but we don't feel it. Why it's so?


texts:
This is an 11-way connector pair from inside a standalone induction hob. It comprises a cable-mounted female part and a PCB mounted male part.

(Corrected due to sloppy original measuring - thanks @Passerby) Pitch is 2.5mm  and pin length appears to be around 3.3mm. The female part is about 4mm wide and 8mm tall. Does anyone recognise this system?


texts:
This module that I got from ebay

has a cut-off voltage of 2.5V which is way too low. At that point your Lipo is probably dead. Anyone succeeded in increasing this to higher voltage? I would like to have it at 3.3V .


texts: How does a wind turbine protect the bank from a reversal in polarity when spin direction is reversed?

texts:
This is a follow-up question to an answer to How does a wind farm prevent the fastest spinning turbine from driving the slowest one?

Spinning a DC motor will generate electricity on it's terminals. When the direction of the spin is reversed, I expect the polarity at the terminals will reverse too.

So when a wind turbine is run, how is it the battery/bank it is connected to is not damaged when the direction of spin is reversed?

a. Does the charge controller OC when the polarity is reversed?

b. Is the wind turbine geared so it will only spin in one direction?


texts:
The circuit I am designing includes a PWM signal that goes through a voltage divider, and that signal then gets buffered to be read by an AtoD as part of a measurement circuit. It looks like this:

simulate this circuit – Schematic created using CircuitLab
The R_Probe is a varying resistance, depending on what it is measuring at the time. The PWM is driven direct from a port pin of an MSP430FR6927 microcontroller running at 3.3V. My tests have shown driving directly from the port pin will be no problem as the load isn't large. The PWM runs at approx 2kHz. The op-amp is powered directly from the 3x AAA batteries, so is around 4.3V at the time of writing this.
The resistor and capacitor on the AtoD input I have not determined the values that work best yet, but I have done it with multiple values, including just a 0ohm resistor and no capacitor.
When I put an oscilloscope probe on the non inverting input of the Op-Amp, I get a nice, clean square wave, which changes its peak voltage depending on the resistance of R_Probe.
When a measurement is taken, the output of the buffer (measured at the AtoD point) follows the input (measured at the non-inverting input) as expected. However, when NOT taking a measurement (R_Probe is open circuit), the output of the buffer has an overshoot which looks like this:

Where the red is the input signal and blue is the AtoD signal. This only happens when R_Probe is open circuit, which doesn't make sense to me, as the output should always follow the input. Does anyone know what could be causing this? I have disconnected the probe completely to ensure it is actually open circuit, and still get the exact same waveform. I have tried changing the RC values on the output, which just changes the shape of the peak, and have even removed the capacitor and replaced R3 with a 0Ohm link resistor. I have disconnected the AtoD input also, yet the issue remains.
Is there something I am missing here, or do I perhaps have a strangely behaving op-amp?


texts: minimum detectable signal of an IMU (MPU 6050)

texts:
I want to work with the MPU 6050 IMU, but before I have to check, which minimum detectable signal the IMU can measure or rather what is the lowest change of angle the IMU can measures.
I have the specification of the MPU 6050 and I know that the sensitivity is responsible for the measurement limit, but I do not know how the sensitivity influence or determine the measurement limit.

The scale range I want to use is +-250°/s

The scale factor/sensitivity for this scale range is 131 LBS/°/s

I hope you can help me.


texts:
I'm designing an I/O module by using optocouplers for the inputs and outputs which I want to control by a microcontroller.

Here are my questions:

In the datasheet of optocoupler's output current (per channel) is 50mA, and for the output port(figure 1) Relay nominal operating current is 16.7 mA. By knowing these can I calculate how much current will I need for the system. Which parameters do I know?

There are 12 relays, 20 optocouplers (5 module) in total. 3 Opto module for output, 2 for input ports

By directly connecting the GPIO pin and output of the optocoupler to the switches (as input), Can I control the inputs shown in the figures. For the input ports, I don't know how to make the connections. What should I connect to the collector pin?


texts: What is the maximum height of a wifi signal in atmosphere? I am not mentioning range and also I dont want answers in milliWatt. I want to know answer in kilometers or meters.


texts:
I'm trying to write a SPICE Directive that I can use to measure the consecutive peaks of an exponentially-decaying transient response but can't find any way to do so. I've tried adding RISE and TRIG/TARG commands to the measure directive but they do not function properly. Any help?

Edit: Command used was .meas TRAN max V(n002), but appending RISE=n to that did not change the output. I’m trying to measure consecutive peaks on an exponentially decaying sine wave.

Circuit (kind of, just a bandpass filter), Command I tried (Original Command is still preferred), and Waveform ^


texts: Averaged Non-Linear Buck PWM Switch Model

texts:
I'm trying to fully understand this application report from TI on chapter 3: Buck Power Stage Small Signal Modeling. The idea is to linearize the switching components so the voltage and currents are averaged over a switching cicle Ts resulting in this equations on page 14:

You can see the meaning of each variable in this image:

Now, with this two equations the circuit between points a, c and p is replaced by this equivalent one:

Quoting them about this image:

  The above model is one form of the PWM switch model. However, in this
  form it is a large signal NONLINEAR model. We now need to perform
  perturbation and linearization and then the PWM switch model will be
  in the desired form, i.e., linearized about a given operating point.

Why is this model non-linear? It must be something trivial because they don't explain it in detail but I'm struggling to understand why.


texts: LED radiation angle appears to be changing with distance

texts:
I am trying to measure the radiation angle of an LED.

Below are my measurements which I've gone over many times:

d is the distance between the tip of the LED and a sheet of paper.

r is the radius of the spot reflected from the paper.

a is the angle calculated from r and d (arctan(r/d).

d = 200 mm, r = 45 mm, so a = 12.6
d = 150 mm, r = 35 mm, so a = 13.1
d = 100 mm, r = 25 mm, so a = 14.0
d = 50 mm, r = 8.5 mm, so a = 9.6
d = 25 mm, r = 7.5 mm, so a = 16.6

So the angle appears to be changing with distance. I've tried several LEDs and the same happens (different measurements, but the angles still appears to change with distance).

The measurements above (d & r) are certainly correct. I've gone over them many times. Am I calculating the angle incorrectly (arctan(r/d))? The LEDs should radiate a cone of light, and this appears to be the case when I observe the light beam with a sheet of paper positioned in parallel to the LED (I see the light take the form of a triangle on the paper), so I should be able to calculate the angle with arctan(). Also, when measuring the radius of the spot on the paper, the spot takes the form of a circle, which would suggest it is a cone of light.

The measurements above were taken from this LED: C503B-RAN-CA0B0AA1 (datasheet)

Where am I going wrong please?


texts: Having noise problem designing a stereo amplifier with TDA2030

texts:
So, I have successfully made a mono TDA2030 amplifier using a single-power-supply which worked flawlessly without any noise. But when I tried to design a stereo circuit with 2 TDA 2030 ICs, both of the speakers are having very high noise . Here is the circuit I have tried.

simulate this circuit – Schematic created using CircuitLab
Please note that the both TDA 2030 circuits given above, are connected to a 12-0 volt DC (Non center tapped Transformer with full bridge rectifier)  not 12-0-12.
So, where did I make a mistake? Please point me the mistake with proper schematic and markings also please describe the issue.
Thanks for your precious time...


texts: The effect of input current from a voltage regulator

texts:
I have an input voltage of 24VAC and I'm converting that to 5VDC by using a simple diode and an LM2596S-5.0 (A switching regulator powered by a simple half-wave rectifier).  I expect to draw roughly 1.5A@5VDC.  How many amps can I expect to draw from the source's perspective?  is my calculation correct to simply do:

P = VI.  P = 5*1.5, therefore I can expect a draw of around 0.3125A?


texts:
I wish to operate a LVMAX Sonar EZ1 sonar rangefinder.

They say

  With 2.5V - 5.5V power the LV-MaxSonar EZ1 provides very short to long-range detection and ranging, in an incredibly small package. The LV-MaxSonar-EZ1 detects objects from 0-inches to 254-inches (6.45-meters) and provides sonar range information from 6-inches out to 254-inches  with 1-inch resolution. Objects from 0-inches to 6-inches range as 6-inches. The interface output formats included are pulse width output, analog voltage output, and serial digital output.

I wish to control this using an Altera DE2 Education and development board,
User manual, Getting started guide

They say:

  The Altera® DE2 Development and Education board is an ideal vehicle for learning about digital logic, computer organization, and FPGAs. Featuring an Altera Cyclone® II 2C35 FPGA, the DE2 board is suitable for a wide range of exercises in courses on digital logic and computer organization, from simple tasks that illustrate fundamental concepts to advanced designs.

I am not sure how I can do this. The two possibilities I see are the expansion headers and the rs232. But i have never used them and am not able to find any links on how to do analog read using the expansion headers. The rs232 serial interface just looks a lot more challenging.


texts:
I'm sending some serial data (UART) from PC to an FPGA. I have implemented a serial protocol on an FPGA according to the usual description of the uart: low bit for start bit, high for stop bit and data bits in between. I am using Realterm software to send the data, a hex value of 0x50 in this case. This is what the output looks like on the oscilloscope:

From what I expect the output of 0x50 sent via UART should be:

0(start bit)0101 0000 1(stop bit).

The actual output is completely inverted though including the start and stop bits. Is this how UART transmit usually works? If not can it be somehow inverted?


texts:
I have this doubt which is freaking me out. First of all I am all confused between open and closed and ideal characteristics of the OPAMP. My main doubt is this: Considering the OPAMP as Inverting Amplifier.

Which mode are we using the OPAMP in? Single mode or differential mode?
What is getting amplified? The input source or the difference between the two voltages at the the two terminals ?


texts: Why don't volts and amps necessarily increase together in Watts = Volts*Amps? Don't more volts = more amps and vice versa?

texts:
I'm trying to understand modern American housing circuitry, which have 15 and 20 amp breakers and work on 120v circuits. They're described using the simple formula Watts = Volts*Amps.
I'm using physics logic I've read online to understand this.
I understand volts as electrons in a high state of energy ready to move to a lower state of energy (because they constantly repel each other) and the higher the voltage the faster they travel through a circuit once released (120v vs 240v for example).
I understand amperes as the amount of a fixed quantity of electricity (electrons), called a coulomb, that can travel through a circuit in a second, so
1 amp = 1 coulomb/sec
Just from these definitions, I don't understand how more amps don't automatically increase voltage given that voltage is the actual force that is pushing the coulombs through the circuit? What allows more coulombs to travel through a circuit per second is literally the voltage isn't it? Therefore, as one increases, the other should also increase. However, this is not the case, and it makes housing circuits confusing for me.
For example, with 15 and 20 amp American housing circuits:
120v15amps = 1800 watts and 120v20amps = 2400 watts
How exactly can amps increase (amount of coloumbs traveling through circuit per second) without increasing the voltage and how can voltage increase without inadvertently increasing the amps?
Btw, I'm assuming higher voltage with even lower amps than 120v*15amps is also possible. I'm also assuming that somehow resistance and AC vs DC is related to this somehow.
I apologize if this is a dumb question, but I'm genuinely confused.
Edit:
I'm not confusing the total amount of energy from a housing circuit with energy required for a specific load. I was using the differences in the max loads of 15 and 20 amp circuits to describe how amps can be different with a fixed voltage. I shouldn't have said "breaker," and I should have used a more specific example.
The meat of my question is really how amps can be different for a load with a fixed voltage, i.e an iPhone vs a toaster connected to 120v circuit have different amps. How can amps increase or decrease without also increasing or decreasing the voltage? Voltage dictate the speed the coulombs are moving aka amps. They seem to literally mean the same thing or are directly proportional somehow. How can more or less energy (different amps) be traveling through a 120v circuit if the 120v's traveling is intrinsically that energy?
Another way to say this, what does it mean in a physical sense for 15amps to travel through a circuit vs 20 amps to travel through a circuit?


texts: Getting -12v from motorcycle Indicator connection

texts:
Problem Solved, it was a silly mistake, I confused the battery positive with negative.

I am making a circuit where I need input from Indicator signals . But the connection plugs for both the Indicators are giving -12V reading with respect to the negative probe of bikes battery. Any idea why???
Help me out guys.


texts: Is it possible to have any CAN baudrate?

texts:
Is it possible to have any CAN baud values? e.g. 507 baud

If not, on what basis is the standard values are derived?


texts: Reading to PIC32MX's memory in C and XORing big sets of data

texts:
I have a project in which I have 102 8-bit PISO shift-registers in daisy chain configuration and they are outputting to a common SDI line connected to a PIC32MX controller.

There is a total of 816 bits I need to read and store in the memory so I can manipulate the data being read. Also, I'll have to read them 34 times because the application requires that I XOR those 816 bits for each of these read operations.

I have two questions:

How would you store the data? I'm worried because I'll have quite a bit of data to handle and I'm trying to optimize processing to the very minimum. Note that I need to be able to extract the (row, col) indexes so I can compute other values accordingly.
After XORing the data, I'll need to traverse the structure and find occurrences of '0's. What do you suggest in terms of search algorithm?

I was thinking of creating a matrix with [34,816] dimension and sequentially XOR the rows to a single, 816 column array and then search for '0's in the array, but I'm not sure how to do it, any thoughts?


texts: Measuring Current by rectifying or voltage-doubling a Current Transformer

texts:
Originally, my plan was to just get the voltage output of a current transformer (obviously with the burden resistor circuit stuff and DC biasing circuit stuff) before ADC'ing it, averaging it’s output per second to get the average current per second. However, I will be using all 6 analog pins in the uC to get 6 outputs from a 60hz current transformer, and the uC only has one ADC, which will make my readings kind of inaccurate. Or is it really inaccurate? Please enlighten me.

https://openenergymonitor.org/forum-archive/node/156.html

I was thinking of rectifying the output of the transformer first and using a capacitor to smooth out the output to get a more stable reading, but since I will be dealing with small voltages, I don’t think that's a viable option. Is there some kind of trick in rectifying small signals with as little drop out as possible?

Source: https://www.electronics-notes.com/articles/analogue_circuits/diode-rectifiers/full-wave-bridge-rectifier.php

Also, I was wondering if it is possible to use a voltage doubler circuit to boost the voltage output of this transformer, since the highest voltage that can be attained by this circuit is 2Vp, but is this really 2Vp? Or is there also a voltage drop from the diodes that needs to be taken into consideration?

https://www.electronics-tutorials.ws/blog/voltage-multiplier-circuit.html


texts: How to calculate the angle for the phasor form?

texts:
I have the following problem:

A one-phase voltage of v(t) = 150⋅sin(wt)is connected to a load with impedance Z=2+4j Ohm.
What is the current through the load, on phasor form? (use the supply voltage as reference)

My problem:
I think the magnitude is 23.7  (taking 150/sqrt(2) and dividing by 4.47 since r=sqrt(2^2 + 4^2).  But how do i calculate the angle for the phasor form?


texts:
I found a circuit to protect DC motors from stalling:

this is the schematic:

and this is the board I made based on that schematic:

When the power is connected to the circuit makes all LEDs on but no power in LOAD, when i press the SW1 push button motor connected to the LOAD is working only one LED is on but as soon as i release the SW1 motor stop working. stalling the motor cause short circuit. VR1 have no effect.

Why isn't the circuit working? In the video it is working...

https://www.youtube.com/watch?v=zsJ7oE0ykVA

edit: the IC number in schematic is LM358 but mine is LM358N, not sure if there's a difference...


texts:
I want to ask why battery open circuit voltage drops when battery is discharged.

For alkaline battery - chemical reactions theoretically give 1.43V voltage.

(source: wikipedia)

  The half-reactions are:

  $$Zn(s) + 2OH^−(aq) \rightarrow  ZnO(s) + H_2O(l) + 2e^−\ [e° = 1.28\,\mathrm{V}] $$
  $$2MnO_2(s) + H_2O(l) + 2e^− \rightarrow Mn_2O_3(s) + 2OH^−(aq)\ [e° = +0.15 \,\mathrm{V}] $$

  Overall reaction:

  $$Zn(s) + 2MnO_2(s) \Leftrightarrow ZnO(s) + Mn_2O_3(s)\ [e° = 1.43\,\mathrm{V}]$$

So - why new alkaline battery have voltage above 1.6V and it drops to 0.85-1V when battery is empty?

Voltage from chemical reaction (theoretical 1.43V in alkaline) is not constant?


texts: The goal of the circuit below is to use a PMOS to turn an NMOS on and off which will blink the LED. A microcontroller is providing the square signal. Both MOSFETs are logic level and when I use them individually with the LED the behavior is what I expect. However in the circuit below when I send 5V to the gate of the PMOS the LED will just remain ON, but I expect it to turn off. Is it incorrect to wire the drain of a PMOS to the gate of an NMOS?


texts:
I've been reading a lot about USB communication for a while. I've already made two projects with PIC18F4550 using USB and it all works perfectly. But I still have one unanswered question in my mind. How does the USB stack know if there is new data or not?

I mean, I'm using Microchip's USB HID examples to guide me. So my chip is working in polling mode. My device will receive data constantly and transmit it to the computer through USB. But the computer will also send back some data. The thing is that the computer output data will only happens sometimes. Here's part of the code:

void QueryPCData(void)
{
if (!HIDRxHandleBusy(lastReceived))
{
    lastReceived = HIDRxPacket(HID_EP,(BYTE*)&hid_out, HID_OUT_LEN);
    if ((hid_out[0]==0xEF)&&(hid_out[1]==0xEF)&&(hid_out[2]==0xEF))
        LED_ON;
    else
        LED_OFF;
}

//If the last transmision is complete
if(!HIDTxHandleBusy(lastTransmission))
{
    lastTransmission = HIDTxPacket(HID_EP, (BYTE*)&hid_in, HID_IN_LEN);
}

return;
}

Looking at the code it seems that every loop it tries to update all data (TX and RX). But what if I did not send any data from the computer? My hid_out array will keep last value until it actually receives new data?

If I want to send  a single command through USB then I should send it one time and then send blank spaces or something to prevent repeating the last command (sending it twice)?


texts: Will this transistor setup work for powering a LED?

texts:
I think this should work but I would love for someone to confirm it to me. Transistors aren't really something I'm very familiar with.

Goal:
Power on D1750 (Orange LED) when VCC42 is low - Power off when VCC42 is high
Power on D1760 (Green LED) when VCC33 is high - Power off when VCC33 is low.

Basically an orange standby light and a green power on light.

Supplies:
VCC33_HOT: Always on supply, running when the power is plugged in - Created from a TPS62177 IC
VCC33: 3.3V Supply only running when the device is in an "ON" state - Created from a TPS62135 IC
VCC42: 4.2V Supply only running when the device is in an "ON" state - Created from a TPS62140 IC

Schematic:
BC857 (The transistor, T1)

My 'design':

Thanks in advance, much appreciated!


texts: Battery Considerations For RP2040 and NEO-M9N GPS Logger

texts:
I am a software engineer, but new to hardware hacking, so I apologize if this is missing any detail, I will try to be thorough and update with any requested information. I also tried to keep this as specific to the topic as I could.
I am working on a small tracking system as a personal project. I am using a SparkFun Pro Micro board based on the RP2040 that I had laying around as a microcontroller, and I want to use the SparkFun Ublox NEO-M9N as the GPS unit. I had a spare ceramic antenna that I attached to the GPS unit's antenna socket. For the software side I installed MicroPython on the MC board.
I have the system working, but now I have to think about how to get as much battery life out of this as I can. My requirement is to get 7 days of life out of the device between charges. It looks like at full throttle the system needs ~180mA. I am also somewhat constrained in that this tracker must be 0.25" thick or less.
The thickness requirement ruled out a lot of connectors and cable based solutions like a LiPo. I can build outward using up to a standard letter sized envelope in surface area, but the depth is a hard requirement. My plan is to solder power or a female port to the board/use, or a small USB-C cable to use the Pro Micro USB-C port.
As for getting the most out of whatever power solution works best:
My natural inclination is to introduce waits and deep sleeps through MicroPython, configure the GPS board to poll less frequently, and other software based efficiencies. I don't want to spend a lot of time optimizing something with little effect on the power issue, however, and worry I overestimate the role of software in getting power supply right. (If all the software optimization is equal to cutting off the LEDs I should skip the code at first)
I have come across some people talking about voltage converters and such to decrease the power waste, but I am struggling to find a good primer on how to think about power consumption and supply.
I know very skilled electrical engineers can make hearing aids that last weeks on coin-cell batteries, but I have a hunch I can get done what I want without such sophistication.
Finally:
I have a 2500 mAh battery that supplies 3.3V, if I connected that to the board it should last (in theory - disregarding wear on the battery) 2500/180 ~ 14 hours, correct?
Is the best way to do this to just use a multimeter and go from that benchmark?


texts:
I am using this IC in boost converter configuration : boost converter

It steps up the voltage from 16.5V to 23V.

It drives a load current of 270mA.

I need to calculate the input current of the converter.

I understand that output power/input power is efficiency.

Since I know the output power, can I take the efficiency value from the graph 21 of the attached datasheet (86.8% approx - obtained from fig 21 graph) and find the input power?

With the input power, and since I know the input voltage, I can calculate the input current.

Is this the right way?

And I want to check if all the components at the output of the IC are properly rated.

Which parameters and components should I check and how to check?

Sorry for the poor image quality. The two transistors are taken from the SWE pin.


texts: Maxterm: misinformation or different approach to understanding

texts:
I have found myself in a crossway of two different explanations regarding Boolean algebra, Maxterm. However, I cannot grasp, whether there is a trick to it or whether one of explanations is an actual misinformation.
Here is a truth table for Minterms and Maxterms (table was found by searching it though the web):

This is another truth table for Maxterms only, however the order of indexes (\$M_0,..., M_7 \$) is exactly opposite from the table above (this table was provided by my university professor):

As I asked him for explanation, he answered that in the end, order of indexes doesn't matter, as long as it is true, that DeMorgan theorem applies to Minterms and Maxterms.
However I don't understand the relation between Minterms and Maxterms regarding DeMorgan's theorem.
The problem occurs when one asks for sum-of-products regarding a logic function given in a Maxterm form. For example, a function $$ f(x_1,x_2,x_3)=\prod M(1, 3, 6) $$ could be written as (regarding upper truth table)
$$ f(x_1,x_2,x_3) = (x_1+x_2+\bar x_3)\cdot(x_1+\bar x_2+\bar x_3)\cdot(\bar x_1+\bar x_2+x_3) $$
but could also be written as (regarding lower truth table)
$$ f(x_1,x_2,x_3) = (\bar x_1+\bar x_2+ x_3)\cdot(\bar x_1+x_2+x_3)\cdot(x_1+x_2+\bar x_3) $$
If I am not mistaken, only one of logic functions given in sum-of-product form, is correct. Here lies the confusion I cannot explain myself and would like to hear, what others think about this matter. If possible, one could explain it though Boolean algebraic expression.


texts: How to power 24 7-segment displays with Arduino?

texts:
I'm working on an Arduino project where I need to power 24 7-segment displays (model Kingbright SC56-11YWA).

I decided to control them using 8 bit shift registers (model 74LS164N). This is working fine for one prototype. But already I notice that the segments are brighter when there are only two lit up as opposed to all 7.

Will an Arduino (Mega) be able to handle this when I connect all 24? Or is it OK if I use an external 5 V power source (converted from AC) for all the shift registers?

There's a 220 ohm (around that number) resistor connected at the 7 segment GND. I suppose decreasing that number or eventually omitting the resistor, would also do something, but maybe not enough for 24 of them.

I hope my question is clear.


texts: How can I find the DC gain or the constant of a given Bode diagram with no y-axis given (H(s)=K(s(s+1))/((10s+1)(s+10)(s+100)))?

texts: The answer is K= 1000 but i dont get why. Calculating gives me G(0)=0.001


texts: How to debug a circuit that uses Charlieplexing and PWM with LEDs under ISIS?

texts:
Using mikroC and Proteus ISIS, I have built a circuit that uses a PIC12F629 (link to datasheet PDF). It controls several LEDs using Charlieplexing technique (and additionally PWM them to change their brightness over the time).

Example:

LED1 100%
LED2 75%
LED3 0%

A few ms after :

LED1 75%
LED2 100%
LED3 25%

If I run the simulation step by step, everything works fine (LEDs turn on and off at each step when they are supposed to).

However if I run the simulation at full speed, the only result I get are the LEDs blinking like crazy (they turn on/off randomly). Anyway, I know that if I run circuit using real components, result should be totally different (like in my first example, with percentages).

Here is what I think happen: LEDs turn on/off very fast under ISIS, but not fast enough to recreate the persistence of vision effect as in real life.

Is it possible, using ISIS, to simulate what i would get in real life?

It would be nice, for example, to have a special type of LED component in ISIS (to place on the circuit) that would render every 50ms (not only when the status has changed). It would render LEDs brighter or darker depending the signal since last check (e.g., signal was "high" 90% of the time since last 50ms, render as bright red, signal was "high" 10% of the time, render dark red, and so on).


texts: Why was restoring a dead lipo battery possible?

texts:
Have been charging completely dead and inflated Lipo batteries (no longer fit for use)individually outside the balancer. Charged with CC/CV following the limits set in the datasheet. This ofcourse with all the preventive measures in case something went wrong. The temperature remained at room temperature.
After completing the charging cycle the inflation was gone and after connecting the batteries back to the balancer everything seems to work correctly. The standard charger works again and the batteries show a normal behavior under load.
I wonder why this was possible?


texts: Need to make this circuit with a different transistor

texts:
I need to make this circuit with a BC337 transistor, but I'm not sure if I need to change the resistor or capacitor values. If I do, could you tell me how you came to that conclusion.

The circuit is meant to invert a signal from the state pin of a HC-05 Bluetooth chip for the Arduino Uno reset pin.


texts: Combining interrupts and debouncing on a keypad

texts:
I would like to interrupt a program when a key is pressed on a keypad, and figure out which key has been pressed. I do not care much for ghosting effects, this is supposed to be operated with one finger.
I came up with the following schematic, and I would like to know if this is going to work.

Normally, this circuit protects against shorts from wrong output configurations.
It provides 15Hz debouncing, and a common interrupt pin.
Note the KEYPAD_INT net is connected to D13 on an Arduino Mega, which is connected to a LED. I assumed this is not an issue since the ~100k input pullup is not enough to light it, and pushing a key will always force ~0.3V on this pin.
The columns are all inputs, built-in pull-up removed.

In sleep mode: all rows are driven LOW. When a key is pressed, KEYPAD_INT is driven low and a pin change interrupt is generated.
In ISR: all rows are high-Z, and for each row, drive it low and loop on each column until a low is detected. If none detected, it's a key release.


texts: Power management switch for Low-Power Application

texts:
In my low-power application I have a MCU waiting for an interrupt to wake up. (see picture) There are two sensor ICs (IC1, IC2) which consume very little and wake up the MCU via the interrupts. After waking up, power-heavy ICs (two transmitters IC3, IC4 and one ADC IC5) should be switched on. I consider to use three NPN transistors for this.

The system runs autonomously and is supplied most of the time by lithium primary cells. Very rarely the application is connected to the mains. However, the duration is sufficient to charge some Li-Ion batteries. Therefore I consider to use additional Li-Ion batteries (e.g. 18650) in order to use them for a time after disconnecting the application from the power supply and to spare primary cells. As soon as these are drained, the primary cells should continue to supply the application with power. But for this I need a possibility to switch automatically between the energy sources (a kind of Power-MUX).

Is the transistor variant the most optimal (in terms of energy-saving) variant for switching power-greedy ICs?

Is there a kind of "Power-MUX" or comparable ICs to manage different DC input sources?

Thank you


texts: How can I find and remove servo/motor noise from this audio amplifier?

texts:
I am troubleshooting an audio noise problem in project which has several components wired together as follows:

Overview:

The overall project does some motion control with a servo and has an audio notification that is triggered by one of the servo channels.

For the audio pathway, it uses an Arduino Uno with Wave Shield as the source of audio, a Kemo M034N amplifier of unknown class, and a single 4Ω speaker. On the servo side of things, there is a buck converter to drop the voltage from 12V to 6V, a Spektrum RC receiver, and a generic Futaba servo. One of the RC channels connects to the Arduino so that the audio can be remote triggered.

The 6V from the RC receiver to the Arduino is not connected, but the grounds are tied together.

The Problem:

The amplifier is picking up the noise of the servo motor, but I haven't been able to decouple it. The amplifier has unusual connections in that the ground connection is the same as one of the audio lines (indicated in green on the block diagram).

If I simply disconnect the audio out from the Arduino, the problem goes away (but of course no desired audio reaches the amp in this case). I believe this tells me that the problem is not present on the Vcc and ground connection to the amplifier.

Connecting an oscilloscope to the audio output of the Arduino shows a clean signal, even when the servo is being driven. However if I reconnect them, then connect the scope to the amplifier end of the wires, about 12 cm (~5 in), the waveform is much noisier and has the servo noise present.

What I've Tried:

I tried running a shielded wire from the Arduino to the amplifier, connecting the shield to ground. I've tried adding three capacitors of different sizes (1000μF, 100μF, and 0.1μF) in parallel to both the amplifier and Arduino power input to try and decouple them from the rest of the circuit. Neither of these had any improvement.

If I connect headphones to the Arduino and ignore the amplifier and speaker, the sound is clean and no servo noise is present.

Edit: I've also tried using two separate power supplies; one for the audio components and one for the servo components. That also solves the problem, but ultimately I need to have just one power supply. The problem occurs whether I use a 12V 5Ah battery, a regulated bench power supply, or the intended 12V 10A SMPS.

Question:

I'm not sure what else to try. Is there some sort of ground loop? Am I decoupling improperly/insufficiently? What else should I try to eliminate the noise?


texts:
I've seen a few schematics of USB hubs and they all seem to have a small ammount of intricacy.    My question is: Can a USB hub just be a bus with 5v provided?

Example:


texts: Does different bulbs in one circuit lead to shorter lifespan?

texts:
I had a conversation with my family regarding lifespans of bulbs. They claimed that they had observed that when different wattage bulbs are plugged in the same hanging light, the bulbs would die sooner. Specifically, they noticed that in a 3-way arrangement with one bulb of different wattage, that one lamp would be the first to die. That could also be the case in different arrangements.
I didn't believe them and I put it down to the quality of the lamps tested, since none of the physics or maths I know would explain it. However, I cannot test the theory because it would take too much time and (electrical) energy. Am I missing something?
Is it possible that the bulbs would die sooner if connected in the fashion described? Could some malfunction of the hanging light be the cause?
Necessary info: I live in Europe so the mains voltage is 230V/50Hz AC and, given that the rest of the bulbs would stay on, the lamps are wired in parallel. The bulbs were probably incandescent bulbs.
I am asking because I am going to change some dead bulbs so hopefully the answers will help me on whether I have to make sure that the new LED lamps have the same wattage as the old or the other ones. If I don't have to, I might as well use some bulbs I have lying around.
I know those are a lot of questions so
Thanks a lot!
P.S.: I did search the web and only found this but it doesn't cover anything about the lifespan of the bulbs. Also, if this is not the correct site, notify me of the right one.


texts:
I am trying to select common mode chokes for a board that I am designing. The point of doubt is common mode and differential mode noise filtering and the parameters/values of the components selected.

Now, the system consist of the following - battery connected to my PCB via wires(Vcc and GND) of 20V or so, Buck regulator and the rest of the system.
Now, having long wires from the batteries I understand that there can be common mode noise that can creep into my system. So I am having a common mode choke (XFMR1). L1 and C1 will filter out differential noise.

I understand how these 3 work. Now, what purpose does C1 serve ?

Suppose my buck regulator supplies 4Amps,this would mean I will have to select a common mode choke greater than 4Amps rating,right ? Now, the common mode choke has the property of having a high impedance at specific frequencies. What frequency will my choke be of ? As it is coming from the battery and since the battery is connected to many other boards, it is difficult to zero in on a certain frequency,right ? How do I start about it please ?

simulate this circuit – Schematic created using CircuitLab


texts: How to proceed with resistor that is series to the diode in a half wave rectifier circuit?

texts: The formulas I normally use don't have R1 on them and I don't know what to do.


texts: How to replace this NPN transistor with a MOSFET?

texts:
Here is the schematic of the circuit I'm trying to build (source) but I only have an IRF9530N Mosfet; I don't have any  NPN transistors at hand.

What would the schematic look like with a MOSFET instead of the NPN?


texts: Short NMOS differential pair amplifier question?

texts:
In my book it says that in the NMOS differential pair:

$$V_{G1}=V_{G2}=V_{CM}$$

But does not explain why. Can you please explain to me why the voltage in each gate is equal to the common mode voltage?


texts: FT2232H Compatible Oscillator (SiT2024B?)

texts:
I've got a board with an FT2232H and 12 MHz SiT2024B with drive strength 'L' running at 3.3 Volts. It does not appear to be working properly. The FTDI chip does not appear in the FT_PROG scan. Is the SiT2024B capable of driving the FT2232H if the default drive strength were used, or do I need to find a different solution for the oscillator?
FTDI would only say that the oscillator has to be USB High Speed compatible, and run at 12 MHz +/- 30 ppm. The SiT2024B looks like it should be able to handle this task, but I may be mistaken.


texts: Simplifying a logic expression with 3 variables

texts:
Below is a problem that I did. I am hoping that somebody can verify that my work is correct or tell me where I went wrong.
Thanks.

Problem:
Simplify the following expression using Boolean Algebra:
$$ x = (M + \overline N)(\overline M + P)(\overline N + \overline P) $$
Answer:
\begin{align*}
x &= (M \overline M + \overline N \, \overline M  + MP + \overline N P) (\overline N + \overline P) \\
x &= ( \overline N \, \overline M  + MP + \overline N P) (\overline N + \overline P) \\
x &=  \overline N ( \overline N \, \overline M  + MP + \overline N P) +  \overline P ( \overline N \, \overline M  + MP + \overline N P) \\
x &=  \overline N \, \overline M  + \overline N MP + \overline N P +  \overline P ( \overline N \, \overline M  + MP + \overline N P) \\
x &=  \overline N \, \overline M + \overline N P +  \overline P ( \overline N \, \overline M  + MP + \overline N P) \\
x &=  \overline N \, \overline M + \overline N P +  \overline P \, \overline N \, \overline M  +  \overline P MP +  \overline P \, \overline N P \\
x &=  \overline N \, \overline M + \overline N P +  \overline P MP +  \overline P \, \overline N P \\
x &=  \overline N \, \overline M + \overline N P +  \overline P \, \overline N P \\
x &=  \overline N \, \overline M + \overline N P \\
\end{align*}
Let me call the original expression \$e1\$ and the simplified expression \$e2\$. I want to look at both expressions
for the case of \$M = 1\$ and \$N = 1\$.
\begin{align*}
e1 &= (1 + \overline 1)(\overline 1 + P)(\overline 1 + \overline P) \\
e1 &= (0  + P)(0 + \overline P) = P \overline P \\
e1 &= 0 \\
e2 &= \overline 1 \, \overline 1 + \overline 1 P = 0 + 0P = 0 \\
\end{align*}
Therefore, it checks for this special case. Now I will consider the special case of \$M = 0\$ and \$N = 0\$.
\begin{align*}
e1 &= (0 + \overline 0)(\overline 0 + P)(\overline 0 + \overline P)  \\
e1 &= (1)(1 + P)(1 + \overline P)  = 1 \\
e2 &= \overline 0 \, \overline 0 + \overline 0 P = (1)(1) + 1P \\
e2 &= 1 \\
\end{align*}
Therefore, it checks for this special case.


texts:
May anyone of you please point me, how to order this Zener Diode?

I have done reverse engineering to this switching power supply, yes it is a Chinese sound amplifier and there is not official schematic for it.

I found 3 broken components, 2 1N5399 diodes bridge (AC to DC) blown and one SMD Zener diode blown also. I can't figure out the Voltage Zener(Vz) of this last one to order it.

There is another smd zener diode that looks exactly to the blown found, and under test it is a 12V zener voltage. But when you have a Chinese circuit you can't assume are the same voltage rated even if they looks same.

I attach the schematic, it is not rules well designed but I am excited it is my first reverse engineering PCB and I've made sure are corrected connections.

Looks the blown SMD Zenner Anode is going to Emitter of the bipolar NPN C1815 Transistor, and the Cathode is going to the Emitter PNP C1015 Transistor that control pulse of the MOSFET SVF4N65F 650V. Transistor I may understand.

What need to be the tech specs to order it; **what Could be the wattage? Zener Voltage? Tolerance? Power, Impedance, Voltage Forward (Vf) (Max) @ and Current - Reverse Leakage @ Vr(those two most important I may say) or I just order another 12V Zener? **

Thank you in advance.


texts: What should I put on my almost empty PCB layer?

texts:
I have a 3"x3" 4-layer PCB where my stack up is:

Signal 1
Ground
5v Power
Signal 2

My Signal 1 layer has a few traces that carry 500 MHz on them, some high resolution ADCs, and microcontroller/usb circuitry. I have SMA connectors that are carrying the 500 MHz on to the board. Currently this will just be "open air" sitting on a test bench, but long term into will end up in a case in which everything will be contained internally.

My Signal 2 layer has almost nothing on it, specifically it has the following:

MCLR from programmer connector that is 0.1" long
SPI Data and Clock line that are both about 0.1" long
Negative voltage (for powering 2 op-amps) trace that is about 2" long

I feel like it is somewhat of a waste to have so much unused PCB. I am considering the following options:

Fill the layer with my negative voltage rail
Fill the layer with ground
Leave the layer empty

Is there any benefit of one of the options over the other? What is usually done in these situations?

Some Additional Details

The system will be pulling a peak of 300 mA off of the 5v rail. While the -5v rail will only have about 2 mA load.


texts: Has LT Spice recently changed the current load simulation?

texts:
To answer a question here, I started an older simulation an got unexpected results...
So here is a minimal simulation to demonstrate my issue:
It seems a neg. Voltage over a current load source does not result in zero current but neg. current:

Can anybody replicate / verify this issue?

http://ltwiki.org/index.php?title=I_Current_Source
states the behaviour I am used to:

If the source is flagged as a load, the source is forced to be dissipative, that is, the current goes to zero if the voltage between nodes n+ and n- goes to zero or a negative value.

Update: Analog Devices answered my question if this is a bug

...to clarify that, the load current indicating zero while the supply is negative, was considered as an bug in the model previously. As the current will alternates and changes the direction of current flow this is indicated in the flow of current will change the direction as well. If you plot the power you can see that the power supplied is equal to power consumed at the load.


texts: when should high z mode of oscilloscope be used to measure signals?

texts: My textbook says that high z mode allows the Vout to closely match Vin in value.(Is this impedance matching?) If this is the case, in what sort of scenarios should I be using a High Z mode vs. a 50ohm mode on an oscilloscope?


texts:
I came across the following slide on power combiner circuit and I have questions about it.

Why traverse across the upper half circle ?
Why "ZT-line is the geometric mean of Zout and Zin." ?


texts: Why does this laptop adaptor have two metal shields with different thicknesses?

texts:
Yesterday, I opened my laptop adaptor to learn something. First off, faced to this kind of shielding:

There are two shields that cover the circuit. A thick shield which is covered by a thin shield and there is an insulator between them.

A close-up image of the shields:

Why two shields?
Why is one of them thick and the other thin?
Are there two grounds?

Edit: Another image from underneath:

Edit2: The images of the thin shield


texts: Why do simple H-Bridges that use PNPs combined with NPNs not short themselves out immediately (or do they)?

texts:
There is a simple design for an H-bridge that I keep seeing all over the place.

simulate this circuit – Schematic created using CircuitLab

This design is featured on the Sparkfun tutorials website as well as other places (just google image search pnp h bridge). There's a similar design I found that is even more common, and was even discussed on this SE site where it's been referred to as a "textbook example". It's a little different, but still has the same problem, just not as severe.

In the first example per se (leaving the two data inputs out of it), is this not a short circuit? Positive current from VCC would flow right into Q1 and out Q3, partly activating both transistors (to an equilibrium state), and the exact same thing happens on the other side with Q2 and Q4.

I would expect the same to happen in the latter example, however for current coming from VCC to activate both transistors on either the left or right-hand sides, current would need to flow through 2 kOhms. When I ran this exact example in a simulator with a 12 V VCC (without the additional signalling electronics plugged in), I observed a fluctuating ~0.5 A current through each transistor.

Now I understand that the signalling electronics change things a bit. Since the second example here has those resistors, as long as the 4093s are sinking current, the bottom transistor won't activate. However when the 4093s are sending a high voltage signal, it better be at least equal to VCC/2 or there'd be a voltage drop over the top transistor on that side and both would activate. This is going to briefly be the case during switching. Now imagine using this with a PWM signal.

The first example is even worse. In order to prevent the PNPs from activating the signal would need to exert an un-resisted high voltage, basically shorting out your microcontroller or other electronics. And before someone answers that the first example is just "conceptual", take a look at the other circuits exemplified on the same Sparkfun page - lots of resistors and short circuit protection.

I tested these in a simulator which seemed to confirm my intuition. Is there something I'm not seeing? Do these designs somehow function differently in reality than expected for some reason? Why are these designs so popular and why would anyone consider them safe?


texts:
I have a PCB (let's call it PCB #1) that has a Li-ion battery as its power source, sourcing 12V to 17V.
The power from the battery is used to step down to 6V using a buck converter on PCB #1.
A cable connection sends the input power (12V-17V) to the second PCB (let's call it PCB #2). The 12V-17V is regulated to 12V using a non-isolated DC-DC converter.
Both the 6V from PCB #1 and the 12V from PCB #2 are sent (using cables) to the third PCB, PCB#3.

Aside note: PCB #1 and PCB #2 are "set in stone" and cannot be changed.

Update: added the note regarding 5V DAC outputs.

A 5V DAC sends two outputs to the 12V circuitry (used as control signals for two HV DC-DC converter modules).

My question is whether the 5V return and 12V return on PCB #3 should be joined together? If I do join them, would that not create a ground loop?

Currently I have them separated and I have a copper pour for each.
The 12V return is shown in the top image as light green; the 5V return is shown in the bottom image as dark green.

If they should be connected, should I:

(a) simply join them together and instead of having GND-12V and
GND-5V, I'll have GND?
(b) join them at one spot using a low-impedance connection, i.e. using a 0 Ohm resistor or a jumper?
(c) join them at one spot using a resistor? (I have personally never done this but it has been done)
(d) join them together, but keep them separate with a slit in the ground pour/plane?
(e) should I leave them as is, i.e. separate from each other on PCB #3?

Thanks in advance.


texts:
I have laid out this board that includes (among other lower speed connections) a 1 upstream and 2 downstream ports on a 0.5mm FR4. The USB differential traces are 0.6mm wide with 0.15mm spacing between them. Can you give your opinion if this is going to work?

It's an open-source project, here is the link : https://tools.upverter.com/eda/#tool=pcb,designId=6f8c466dba06e940

Thanks for you time.


texts: MAX412 configuration for non inverting input

texts:
I hope someone with experience in maxim operational amplifiers could assist me. I try to use MAX412 operational amplifier to amplify a signal with the following parameters:

Signal Type : AC
Amplitude: (1-4) mV Peak-Peak
Frequency : (0.6-30) Hz
Constraints : Power supply of 3.3v (negative portion is ignored.

Output needed :

Signal Type : AC
Amplitude: (1 up to 2) V (The higher the better)
Frequency : (0.6-30) Hz without additional frequency components.

I checked MAX412 datasheet and upon the design, I made a simulation for gain of 2000.

Although the output was promising, when I implemented it, nothing was shown :) . I was testing using function generator (50 ohm output impedance) and an oscilloscope.

Your help is appreciated. Thanks


texts: How can I tell if my power supply/regulator will accept backfed current?

texts:
Some power supplies and regulators don't like to have current flowing back into the output terminal. It's something I've seen casually mentioned in various answers here and it sounds reasonable enough. This has never been a problem for me until now because my designs have always had a net outflow of current, but now that I'm designing a motor controller, I need to make sure that my power supply will be able to accept potentially large transients flowing back into the supply from the flyback diodes.

Common regulators like the 7805 (not that I would use one anywhere near motor control) do not indicate a reverse current limit on their datasheets, so how do I look for a regulator that will tolerate these transients without self-destructing?

(My motor is a little 24V/35W BLDC to clarify scale.)


texts: Logic gate circuit to close when sensor signal turns ON and then OFF, but must ignore another ON?

texts:
I am trying to put a permanent magnet in a transformer between both coils, so that the transformer can utilize the flux from the permanent magnet by guiding its flux periodically.
We have one primary coil that will change the direction of the flux from permanent magnet towards the other secondary coils one by one.
I want primary coil to change polarity when the first secondary coil rate of change of flux becomes zero.
So I'll put a reed switch to detect the magnetic field that causes inducing of voltage into secondary coil. I want another switch named switch A to turn ON, when reed switch turns OFF after turning ON, but when the same reed switch turns ON (and OFF) again  (on collapsing the magnetic field in secondary coil) the switch A should do nothing. And then how would I reset the reed switch to detect the change in magnetic field again?
Timing diagram (edited on request).
              __    __    __    __    __    __    __    __    __
    Reed  ___|  |__|  |__|  |__|  |__|  |__|  |__|  |__|  |__|  |__

                 __          __          __          __          __
Switch A  ______|  |________|  |________|  |________|  |________|

I couldn't find it on internet, can somebody please draw the circuit to achieve the same?


texts: What happens if you rotate a stepper motor by hand while it is powered?

texts: There is some resistance to it, but it can be rotated without excessive force. When would this cause damage?


texts: Running 5VDC circuits off a rechargable ni-cd batteries that can recharge in-circuit from a DC power supply

texts:
Here's what I'm trying to do.

I'm trying to make it where I can run any circuit requiring 5 volts off of 7.2 volts. I get 7.2 volts from combining two 3.6v ni-cd phone batteries but for simplicity I show it as one center battery in my circuit.

The source power shows as a battery but I plan to use a wall adapter that outputs either 9VDC or 12VDC, but I figure 9VDC is more efficient.

The battery shown on the right is the output (5V). I could replace it with an LED and resistor in series but I used a battery symbol for simplicity.

Here are my questions:

If I used such a circuit, would I be able to successfully charge a ni-cd battery to max charge without blowing up the battery or is my circuit flawed?
If my circuit can be successful, is there a way to modify my circuit so that I can connect a wire to a GPIO pin of an AT89C2051 so that it can detect when a battery is charged/still charging without negatively affecting the charging process.

and

Could I change the variable voltage regulator (LM317) to an 8V fixed voltage regulator to charge the 7.2V battery with a resistor in series? If so, what resistor value?

I'm asking all this because I want to make a low-priced in-circuit battery charger for my microcontroller projects and I don't want to have to remove the battery in order to charge it.

Why this question isn't duplicate

I want to build the charger circuit using discrete components that are commonly available in anyone's junk box. I don't want to have to purchase a special IC and wait weeks for it just in order to charge batteries. Additionally, I'm looking for a modification to this circuit to make my charger more efficient. I adapted parts of it from talkingelectronics.com.


texts: help understanding this reverse polarity protection circuit

texts:
Going through LT4363 evaluation kit DC2062A-B (schematic here), I came across a reverse protection circuitry that protects downstream components from reverse transients and reverse DC voltage:

In short, this circuit protects the downstream components by shorting the negative voltage when present at INPUt to DGATE and thus turning off Q2. when the voltage at INPUT is positive, Dgate gets biased via D2.

from DC2062A demo manual:

  The DC2062A features reverse protection circuitry that protects
  downstream components from reverse transients of up to –150V. This
  number is limited by the BVDSS of Q2. The reverse protection circuitry
  also protects against reverse DC voltage of up to –30V.

My questions are:

Why is the reverse DC voltage protection limited to only -30V? I simulated the circuit at input -100V and couldn't find what components are stressed or damaged at this voltage. So where did the number (-30V) come from? Am I missing something here? I want to know this as I would like to make the circuit block negative voltages upto -100V.
A similar circuit is implemented in LTC4366 DEMO circuit DC1850A-A but with a -100V reverse DC voltage protection:

What are the pros/cons of using zener diode and capacitor in the first circuit over using the simpler solution of the second circuit? I'm guessing that the capacitor is used as a tank help turn off the mosfet Q2 quicker when the input voltage is suddenly switched from a posotive voltage to a negative one. I'm not sure.


texts: Drift auto-corrector for any microcontroller

texts:
I've made multiple microcontroller circuits in the past, but now when I look at everything, drift has become a problem. I know this when I try to connect two micros together serially via wireless modules. I also know drift is an issue because communication is only perfect when the programs in both microcontrollers run at the correct time.

So now what I am trying to come up with is a way to adjust time on one board so that it can synchronize with any board of my choice.

Based on this circuit, what I'd like to happen is for the 8051 microcontroller to load a value into P1 to define the drift offset, then set that value by bringing P3.5 low. This will then give a resistance value which is fed into the 555 timer to alter its timing (hopefully) which in turn alters the timing of the microcontroller itself.

The problem with this setup is that when I use the serial port, I need to run at a rate in which standard baud rates above 19K can be used. In my previous designs, I used a 22.1184Mhz crystal with 33pF 5% NPO capacitors but that didn't help with timing for syncing multiple boards. I don't think the 555 has the ability to be stable at a frequency higher than about 2Mhz.

Is there an alternate circuit I can use besides this that achieves the functionality I'm looking for but also allows the microcontroller to be driven at 22.1184Mhz speed?


texts:
Hint: in my calculations below, to make math easier, i assume that the
      diode = ideal(there is no 0.7 voltage drop across the diode)

Vrms = 0.707Vp => Vp = 14.1v, therefore Vp(load) = 14.1v assuming diode = ideal and Vdc = Vp/π = 14.1/π = 4.49v, which is pretty close to my screenshot(it says Vdc = 4.22 V ).

I want to compute Vdc. There is a formula for half wave sine: form factor = Vrms/Vdc = 1.57 . My naive mind says:
Vdc = Vrms/1.57 = 10/1.57 = 6.369 . The simulator says Vdc = 4.22. :-(

I would like to use the form factor formula and get a correct result. What is my mistake?


texts: Do I really need motor drivers for a quadcopter?

texts: I am planning to build a quadcopter, so I searched about motor drivers, then I thought "Do I really need a motor driver?", I mean the only thing I want to control is the motors' speeds, so won't MOSFET be enough for that?


texts: Control system basic feedback loop, what's happening at the initial state?

texts: How can the system output be dependent on itself, when at the initial state there is no system output? I don't understand how it can work physically.


texts: SPICE modelling output/input coupling in ultrasonic transducer driver

texts:
The real device is this.
The LT SPICE model is here.

The schematic of the driver part of the circuitry (omitting power supply circuitry and relay circuitry that basically switches the driver between the 2 outputs):

Trying to understand particulars of this circuit besides that it has positive feedback and resonance producing oscillations.

One question that I have is how to model the effect of the oscillations at the transducer somehow coupling into the input (base of Q1) (I think modelling this and then playing with the simulation may help to understand other parts of the circuit better).

The measured oscillations at the transducer (unloaded) and at the input look like this (CH1 - input, base of Q1; CH2 - output to the transducer, collector of Q3):

When the transducer is loaded (palm pressed firmly against it) the coupling to the input almost disappears:

The simulation with the linked SPICE model doesn't show this kind of output/input coupling, the input is just a clean 5V step.

What do I need to add to the SPICE model to get the kind of output/input coupling observed on the real device?

I tried:

Giving the voltage sources series resistances
Connecting all ground points to the common ground through
resistances

Note: the transistors in the simulation don't match the real transistors, LTSPICE doesn't have the transistors the real device has. The real transistors are Q1 - KTC9014, Q2 - KTC9012, Q3 - KSC2073TU.


texts: Choosing a suitable Opamp to output a voltage reference

texts:
Part 1: the circuit and how it's connected

I'm trying to take from the 2.5V coming from a voltage reference IC AD780 to go through a unity gain buffer then go through a 2x Gain opamp stage to finally output 5V with a worst case scenario of current sinking 25 mA . Bear in mind that this application is part of a system that will be placed behind the back seat in a car so i believe ambient temperature may be around ( 40 - 50 °C ) .

Part 2: my conclusions so far

Here's what i finally came up with after searching and filtering through a lot of rail to rail o/p op amps :

MCP6H02
LMC6482

Part 3: my questions

Which one is most suitable for the application. If none please suggest and state why (so others may benefit).
I figured I'm just using a DC signal (I believe) and not AC one so I'm a bit confused to which parameters do I need to worry about in the datasheet.

Part 4: schematic ( Simulation using Proteus Isis )

I did a simulation for the LMC6482 and it worked fine with 25 mA load but after all this is a simulation and other real factors (temperature, other parameters that I am unaware of ... ) .


texts: Can I buy a motor that vibrates or pulses very precisely?

texts:
I'm trying to make an item with a number of pads that will pulse individually or in sequence with a given signal. I have looked at vibration motors but these are like the ones in video game controllers - they vibrate but the duration is too long. I want to put the motor in a pad that could be worn and give a much more precise 'pulse' or 'beat', potentially at a rate of up to three times per second.

Any ideas where I can find such a motor or other feedback component?

Many thanks.


texts: Creating a 5 volt (ish) power pack from 18650 batteries

texts:
I want to create 5V power supply for a portable lighting project, using 18650 batteries.

The power supply needs to provide power to an arduino (which can take 3.3V to 13V input) and some addressable LED strips, which would take 5 volts input ideally, but a somewhat lower voltage is acceptable.

The project would draw a maximum of 2 Amps (10 watts) with all LEDs on.

I’d like to use 18650 batteries as the power source, which are nominally 3.7V but which I believe would provide an actual voltage rannging between around 4.1V (when fully charged) down to maybe 2.5V (at which point they would be considered discharged).

The options I’m considering are:

2 18650s in series, with a buck converter to step the voltage down to 5v.
a single 18650, with a buck booster to bring the voltage up to 5v.

EDIT

I’m aiming for around 3 hours of battery life. I think the average draw of the project would be maybe 5 watts, so I need ~15Wh of capacity. A good quality panasonic 18650 provides around 12Wh, so if I went with the boost option I’d consider adding a second 18650 in parallel. Perhaps this means I’d also need a BMS?

END EDIT

I don’t believe that an LDO voltage regulator is a good approach - it would be pretty inefficient and would need a lot of heat dissapation support, given the wattage of the LEDs.

Are there any majors pros or cons between these options? Are there other options I haven’t considered?

My main decision factors are efficiency (for longer battery life) and cost.


texts: Can I connect TTL gates directly to the address bus of a Z80 CPU?

texts:
I need to know when the 14 MSB bits from the address bus of a z80 CPU are high. To do so my first idea is to use 4 74LS08 ICs (TTL AND gates) reading those lines but I don't know the maximum amount of current that can be drained from the CPU.

The 74LS08 has a maximum input current is of 0.1mA hence 1.4mA from the z80 but I cannot find the maximum z80 ratings on the zilog datasheet. The z80 datasheet mentions a TTL chip select decoder connected to the address bus but no mention of the IC ratings are given.

so, can I connect 14 TTL inputs to the z80 address bus without overloading the z80 outputs?

z80 datasheet
74LS08 datasheet

Clarification
One TTL input per address line, not 14 TTL inputs per address line.


texts: High Side Driver IC - Application Information

texts:
I have a question regarding VN5025AJ-E: High side driver IC.
Datasheet link - https://www.st.com/resource/en/datasheet/vn5025aj-e.pdf

In the figure you can see the application schematic. In the datasheet they have suggested to use a resistor at the ground pin for reverse battery protection (automotive circuits). I was just trying to analyze the path the current flows during normal operation and also during reverse battery condition.

Why are there two Zeners in parallel and also a resistor between the anodes of the Zener diodes? What will the output be under reverse battery?


texts: Will a short circuit in analog A/V cables cause electrical damage to connected equipment?

texts:
Most people don't take especially good care of analog A/V cables, and they are often subjected to getting stepped on repeatedly, chewed by pets, etc.

If an analog A/V cable (component, composite, etc.) is damaged and the center conductor shorts with the outer shield, would this result in any electrical damage to the connected devices?