texts: What is the most sane way to switch between 5v and 3.3v on a PCB on the same lines?

texts:
I apologize for the blasphemy I may spit during this question, I am a newbie in electronics.

That said, I want to design a PCB that will house an ESP8266, the chip I selected provides both 5v and 3.3v . On the PCB I want some pin headers for various electronic devices (mostly sensor) that run either on 3.3v or 5v and (some exotic ones) on 12V.

I don't want to bind the PCB on a set configuration and would like each series of pin headers to be switchable (from the ESP8266) between 5v and 3.3v on. So if I have 4 series of pin headers composed by VCC-SIG-GND I would like to be able to switch EACH ONE of them SINGULARLY between 3.3v and 5v. I was thinking of relays but then I thought, is there a better way? Is a transistor-based circuit a viable solution? I don't want to use step-ups/down. I also would like to avoid to run more lines in the PCB.

Staying on topic, I also wanted to reduce the number of pins (from the ESP8266) needed to switch these voltages so I had thought of a shift register like the 74hc595, that would give me \$ log_{2}n \$ pins needed, but is there a better way (less pins) to do this?


texts: How is "plug-in auto detection" realized with this circuit?

texts:
This question is specific for ACT2802X series 5V/2.5A Backup Battery Pack Manager IC.

On page 15, there is a schematic that provides a solution for auto plug-in detection. However, I cannot understand how this is achieved? What is the thing that comes out from the USB connector's shield in the schematic? I cannot also find a USB connector with "plugged" output.

PB pin is described as:

  Push button input, connect a push button from this pin to AGND,
  internally pulled up  by a 3MΩresistor to battery. PB starts up boost
  converter if HZ pin is grounded and  VIN is not present. For
  ACT2802B/ACT2802C, if this pin is pushed for 3s, flashlight is
  enabled.

...

  For ACT2802QL-T/ ACT2802-T1026, When HZ=0, if PB is pulled low  more
  than 100ms, boost converter is enabled; For  ACT2802B/ACT2802C, when
  HZ=0, if PB is pulled  low more than 30ms, boost converter is enabled.

PB High Input Voltage = 0.9V (typical)

PB Low Input Voltage = 0.75V (typical)


texts:
I am trying to design a microstrip bandpass filter in ADS with a center frequency of 2.4GHz and a fractional BW of 10%. My results from the schematic look great:

When I move to the layout and EM simulation, my results look nothing close to a bandpass filter. I am not sure if it is something with my setup or the physical layout. The schematic and layout is shown below:

The results from the EM simulation are here:

I was thinking it could be with how close the spacing is between the coupled lines, but if anyone can point me in the right direction it would be greatly appreciated


texts:
# Paraphrased Question

When testing for continuity on an old circuit board from a usb powered desktop speaker, i find that the ground is connected to almost all other points including to each feet (anode & cathode) of the indicator LED and to each red & black speaker wires, just to name a few. With a probe on the ground terminal, the multimeter also beep when poking the other probe on every individual feet of all capacitors, resistors, the volume potentiometer, all 3 terminal from the input jack (tip + ring + sleeve) and almost every feet of the the TEA2025B chip - no beep on pin 7 & 10. Is this an indicator of a ground loop or shorted solder trace somewhere on the circuit? What other test can i do to investigate or troubleshoot this board? If this is a faulty circuit board, how do i fix it?

# Original Entry

The following is a situation that i find myself in while using a digital multimeter to learn and practice on the subject matter. Recently someone had given me a circuit board from an old computer speaker to play around and the result from a continuity test seems suspicious thus tickled some concern and curiosity over the potential, quality or possible fault of the board. With a probe on a trace labeled G (ground) the multimeter buzzed on many places poked with the other probe including both feet of the LED indicator in the circuit. Results described here are when the switch is turned on and a probe connected to ground. My confusion started when the multimeter beeped at all 3 terminals (tip + ring + sleeve) of the female audio jack as well as both red and black wires from the left speaker connection. Maybe black wires are usually all connected to the ground but when sticking my probes to the red and black wires there was no beep indicating that the ciruit is not shorted - at least not between the speaker output wires. Is this normal for desktop speaker circuit where many components are grounded or is this an indicator of a ground loop? If this is a potential problem, what other test can i perform to further ivestigate this or possibly mitigate and fix this board without using AC source or isolation transformer? This is just an exercise to help me in learning electronics and any respond, answer or suggestions (other then asking me to get a new board) towards the cause is greatly appreciated. Thank you~


texts: Can an inductive load mess up an ohmmeter's reading

texts:
I've found a something quite odd with measuring the resistance of a 36uH inductive load (see this earlier question). I can measure the resistance, which is quite low, but then disconnect the probe and for some reason the subsequent resistance measurement of other loads become a bit messed up. I would have to wait a bit for it to settle down. Only then can I measure the other loads and it'll be accurate.

At first I thought it was just me (like usual, when doing experiments), but now I'm more sure.


texts: Wanting to know if these formulas are correct for this very basic circuit analysis

texts: Hello for the following diagram below, i was just wondering if these formulas are correct to finding what they state (i.e. Vout and V2). For V2 is R3 and C2 in parallel with C2?


texts: I just moved from Eagle to Altium. I cannot find SMD resistors in Altium libraries. In Eagle, there are almost all general components. In Altium there are only few resistors. Where can I download the libraries? Or, do I need to make my own for every component I use?


texts: ethernet socket interface throught nail bed

texts:
I need to make a test nail bed for a board that has an Ethernet interface:

in the bottom of the board there is access to the socket ethernet pins
i could place test nails under the ethernet socket to access these pins
i would like to connect this pins to another board , ex raspberry & test conectivity.

The problem:
there seems to be a transformer  embedded in  the socket , so if i connect my testpoints BEFORE the socket , i would be missing the transformator and impedance adaptation.

Are there similar transformer like this but Without socket  that i can add to my nailbed board???

any ideas on how doing this in a clean way ???


texts:
I am looking to attach a cable to board in the most compact (yet manufacturable) way possible.  This does not need to be disassembled ever, it can be a permanent connection.

Is there a standard way of attaching cable-to-board without a connector?  Can it be done in a way that can be mass-produced, and does not occupy much room?  Something like a reflow-solderable ribbon cable :)

I need 48-50 wires (possibly 3x 16 or 3x 18).  These are low-frequency analog signals (<1kHz), they can be shielded similar to audio cable, or just rely on the enclosure shield; no special high-speed stuff is needed.  In this case each signal pair goes to a different location 5-10 inches away, so they would split once away from the board (FFC cable or ribbon won't work, split-ribbon may be ok).  Space is at a premium: a standard 0.1 inch header is much too bulky.  Ideally I'd like an assembled height of <2mm and board area <30x10mm. I've looked at Hirose DF-9 or DF-19 and JAE FI-X or FI-R connectors and cables as used for LCD displays - while fairly compact even these are bulkier than I'd like (and the typical cables made for these don't even use all pins, and add significant cost).  Surely there must be a better way?


texts: UV solder mask sticking to cover instead of PCB

texts:
I'm doing the usual DIY PCB process. Lately I got some of the chinese UV solder mask (similar to the one used in this video). I can work with it just fine - it sets under my UV lamp perfectly, within 5-10 minutes.

Unfortunately, it sticks to the wrong part, i.e. the plastic sheet instead of the PCB.  When I peel it the plastic off after the initial curing of the mask, the mask is perfect, but comes off with the plastic and the PCB is completely clean.

I scrub the PCB both mechanically as well as with alcohol before, so I guess it's more the fault of the transparent film I use to cover it. I tried several durations for the curing process, no matter.

Did someone of you have this problem, and did you solve it somehow?

EDIT: Some pictures...

First, you see an attempt with 5 minutes of curing with a junk PCB. The stuff is set quite solidly (see the film to the right), but on the film instead of the board. The board here has not been cleared afterwards, it came off pristine like this. Before, the PCB had been scrubbed vigorously to expose uncorroded copper, and cleaned with alcohol. Note that the bits on the plastic seem cured through, i.e., it is not like the "PCB side" of the green layer is still wet or something like that. Film on the left is another try with 50% success...

Another attempt with 60 minutes of curing. Sticks to the PCB better, but not perfect. Interestingly, when I applied the large blobs of solder (way more + way longer heat input than you'd usually use) the mask also came off at the right upper hand part, but that's nothing to worry about - for normal soldering time it should be fine, that was excessive.


texts: How can I make a PoE circuit that is compatible with 24V passive PoE and 802.3at active PoE?

texts:
I'm designing a PoE circuit that should be compatible with both active (802.3af/at) PoE and also 24V passive PoE. How can I do this?

Can I just use a PD chip that doesn't include a DC-DC converter? It looks like most of them are low-side MOSFET switches that only switch on when the PoE negotiation has successfully happened. But these PD chips support external adapters:

TI TPS2379
AD LTC4265
ONsemi NCP1094

So maybe I could wire up the external input in some way to support passive PoE?

There are also plenty of integrated PD and DC-DC converter controller chips that are compatible with both active / standards-based PoE and external adapters. Maybe it would be possible that they can they be wired to work with non-standards based (passive) PoE?

TI TPS23754 / TPS23756
AD LTC4269 / LTC4278
Microsemi PD70201 (has an 'external enable' pin)
ONsemi NCP1083
Akros AS1135

Alternatively, maybe I can wire my own circuit that performs the PD classification, inrush current limiting, etc. Is that difficult?


texts: What is meant by Voltage current dynamics & current position dynamics?

texts:
What is meant here by voltage current dynamics & current position dynamics ?
Does"voltage current dynamics "means the effect of changing voltage on current??
and "current position" means effect of changing current on position?
Here in this article VTOL means vertical take off and Landing


texts: switch on a long wire end causing microcontroller to shutdown

texts:
i've a push button connected to micro-controller using a 100m 18ga wire that cause the micro-controller to shutdown after few times of working properly

the circuit is fully functional with a short wire, i use 5v, both CN2/3 has lamp/bell load and sw1 wire is the 100m wire


texts: Do I need different isolations among long-wire switches?

texts:
I'm playing with an MCU board (like Arudino) to read the state of several switches in my home (i.e. magnetic switches). The wires between the sensor and the board are quite long: 15+ meters in a star topology.

I would isolate the inputs from the MCU, using opto-couplers.
To provide the voltage needed to turn on the diode I'm going to use an isolated DCDC converter.

Question: do I need to use a different DCDC for each input? Or may I live with only one? In this case I will end up with all sensors that share the same power supply rail.

I.e.: one side of the switch goes to +12V (shared across ALL switches) while the other sides go to the anodes of the opto-couplers.

It's not an industrial design: I'm fine if it works without false detections due to the environmental noises.

EDIT

To be more clear.
Two ways:

A

simulate this circuit – Schematic created using CircuitLab

or B

simulate this circuit


texts: How to Bais a tuned rf amplifier and compute I/O Impedances

texts:
Can anyone point me in the right direction on how to implemented the depicted tuned r.f amplifier? Since the load resistance at the collector is replaced by the LC tank how does one go about in calculating the values to bias the circuit? Would the biasing be affected if the LC tank is tunable to adjust the desired frequency of resonant? {ganged with the first LC tank}
Also how does one go about in designing/finding the input/output impedance. I know that at resonant frequency the LC tank has a high impedance and elsewhere low, is this information useful in finding the impedance?


texts: STM32F4 Discovery Board Control Register Value Problem

texts:
In Atollic TrueSTUDIO I open an empty project without any settings.

#include "stm32f4xx.h"
#include "stm32f4_discovery.h"

int main(void)
{
  while (1)
  {

  }
}

void EVAL_AUDIO_TransferComplete_CallBack(uint32_t pBuffer, uint32_t Size){
  /* TODO, implement your code here */
  return;
}

uint16_t EVAL_AUDIO_GetSampleCallBack(void){
  /* TODO, implement your code here */
  return -1;
}

and I observe the values in the CR register.

As seen in the photo it comes full of many bits. Even both HSE and HSI are active. Why? How?

I was just expecting HSI to be active because the reset value of this register is 0x83.

I also cannot reset the values of the bits when I add the RCC->CR=0x83; code to the program. Where am I making a mistake? (I adding the RCC->CR=0x83; code to the top of the while.)

Why are these settings pre-defined? Why doesn't the register change when I assign a value?

STM32F407xx RCC Register from Reference Manual:


texts:
I have a quantity of LCD panels (from a wide range of dead laptop) and I would like to use only the CCFL + diffusors as a "creative" light source for a room in my house.

Is there some sort of "universal" CCFL supply that I can use to replace the panels inverter (that needs various undocumented control signals to works)?

Would those inverters for single CCFL tubes like this works with the panels (that have more than one lamp but just a single connection)?

http://www.lamptron.com/products/view/4_Port_CCFL_Inverter_with_Alum_housing


texts:
I'm a student and am almost ready to have a PCB I designed fabricated, but I'm confused about how the board outline should be defined.

Here's what I currently have:

I also have a 20mil keepout line centered on the board edge, but hid the layer to make the board outline visible.

I'm planning on ordering the board from a company called Gold Phoenix PCB. I've emailed them several times about this, but haven't been able to get a clear answer. They said:

  You only need to design the board in the way you want, size tolerance +/-10mil

Not helpful!

Then after sending the above image:

  Make things simple, you need keep everything 10mil from the edge of the board.

Ok, 10mil from the edge of the board, but what do they consider to be the edge? Is it the center of the 10mil track I placed on mechanical 1, or is it the edge of the track?

The example I gave them when asking how the outline should be defined is:

  Let's say your router bit diameter is 90mils and it follows the center of the line defining the board outline -- that means it would be cutting 40mils too deep into the board, which would not only mess up the connector alignment but also create a risk of shorts since I only have a copper pullback of 20mils.

I've already emailed them four times about this and don't want to get on their bad side, so can anyone explain the correct way to define the board outline to meet my requirements?


texts:
Why is a parallel LC circuit used to filter out the right frequency from the antenna? Shouldn't it be in series?
We have a maximum impedance at resonant frequency if we connect in parallel, so why isn't the signal being blocked?


texts: Circuit element: Rectangle with diagonal

texts:
I am a newbie in electronics, so please bear with me.
I have a Induction proximity sensor which I have to integrate with a data logger. But, I have run into an issue with a circuit element. I am unable to understand the circuit element which is represented as a rectangle with a diagonal. Also, what is the quantification parameter of the same? Please help me out with the same.

Thank you


texts:
I understand that RS232 Communication voltage levels should be between 3 and 25 Volts for positive voltages and the equal negative for negative voltages, but is there a source that can explain the real-life wave forms?
It is pretty obvious seeing a 'perfect' signal, but in real life, I deal with signals that have oscillating and varying voltage levels.
and I do not know what would count as a noisy refutable signal and what doesn't.


texts: Internal reference voltage of Voltage Regulator - what does it depend on?

texts:
I know this might be somehow specific and narrow question but that issue bothers me.

I've implemented the BQ24450 charger controller circuit presented in figure 10 of http://www.ti.com/lit/ds/symlink/bq24450.pdf on the PCB. The circuit is supplied with a 5W 12V solar cell, the charged battery is a 4Ah 6V SLA. The max current that this solar cell can produce is 0.36A. It basically is the same to Fig 10 of this document.

The float charge voltage at +BATT as I measured when it's charged is 6.72V (even though by Ra-Rd resistors values shall be of 6.86V)

My schematics is just a redraw and looks like this:

R19 (Replacement) is not populated.

I measured the VFB voltage, it never reaches 2.30V (internal reference Vref=2.30V) and it settles on 2.27V which for my implementation results in Vfloat voltage of 6.72V instead of 6.86V.

The datasheet says Vref can be in range of 2.275V - 2.325V with the nominal value of 2.30V.
What does this depend on exactly? Why in my implementation it never reaches 2.30V and settles on 2.27V instead, why isn't it 2.325V, how can I influence it?

In my implementation I used MJD32CG instead of BD242 for Qext and S1A instead of 1N4001 for Dext, I really doubt it could make that difference.

I now wonder if I should recalculate Ra-Rb for Vref=2.27V or is that value going to decrease (or increase) afterwards anyway.


texts: What does measuring voltage do to the current or signal of a pin?

texts:
I have a problematic digital signal which starts working when I measure the voltage between the pin and ground. What's the effect of a voltmeter on a pin (or to rest of the circuit) when you measure voltage?

Does it mimic:
- a small or large resistor in series or parallel?
- a pull-down resistor?
- a capacitor?
- a better ground connection for the pin?
- more wires between the pin and target?
- a ferrite bead?
- other suggestion?

I'm looking for a way to implement the obvious effect the voltmeter has on the signal functionality but on the circuit proper.

Can one even state what effect measuring voltage has on that which is measured, or can it behave like any/all of the above suggestions?

EDIT - SOLVED, see answer below


texts:
I am trying to check for the data integrity in fat32 filesystem.Currently I have implemented fat on lpc2478. For the checking of data integrity, I come to know that each sector of a disk has checksum or CRC.But I wanted to find the location of the CRC in the sector.Can you please advice  me on how to find the location of the CRC in a sector of usb pendrive? and will this CRC change with manufacturer of the pendrive.?

EDIT

Oh! thanks for your reply! Is there a way to find out the CRC zone alone. using some editors like winhex?I tried using winhex to find out the zone, but in vain. If this is such a complicated case and prone to hazards,Is there any other way of checking the data integrity?


texts: What book or website should i refer for stm32f0 development from scratch (Ihave worked on AVR microcontrollers )

texts: What book or website should I refer to for STM32F0 development from scratch (I have worked on AVR microcontrollers)? I am searching on net for good resources but unable to do either they are very complex or the model doesn't match with my board ..please suggest some references


texts: Analytically obtaining the hysteresis of an opamp Schmitt trigger with RC network in its inverting input

texts:
This is a follow-up from here. I have got the following Schmitt trigger circuit implemented already on a breadboard. As seen, the input signal at the non-inverting and inverting terminals of the op amp is the same, but with the addition of a RC circuit in the inverting terminal. In this way, I am comparing the input signal with a delayed version of the same signal such that I can identify peaks.

simulate this circuit – Schematic created using CircuitLab

What I am trying to do now is to analytically obtain the hysteresis of the circuit. I have done so using the superposition theorem, but I am not sure of whether the result is right, and if so, how I can apply it.

I followed a similar procedure as in here:

The output voltage of the circuit, \$V_o\$, is given by:
\begin{equation}
V_{o} = A_{v}(V^{+} + V^{-})
\end{equation}
where \$V^+\$ and \$V^-\$ are the voltages at the non-inverting and inverting terminals, and \$A_v\$ is the circuit's gain. This gain is:
\begin{equation}
V_{+} = \dfrac{V_{OH} - V_{OL}}{V_{IH} - V_{IL}}
\end{equation}
where \$V_{IH}\$ is the smallest voltage at which the output voltage is \$V_{OL}\$, while \$V_{IL}\$ is the largest input voltage at which the output voltage is \$V_{OH}\$.

The voltage \$V^{+}\$ is:
\begin{equation}
V_{+} = V_{in}\dfrac{R_{f}}{R_{1} + R_{f}} + V_{o}\dfrac{R_{1}}{R_{1} + R_{f}}
\end{equation}

The voltage \$V^{-}\$ (it is from here where I start doubting) is actually the voltage accross the capacitor \$C^{1}\$:
\begin{equation}
V^{-} = V_{in}(1-e^{-t/R_{2}C_{1}})
\end{equation}

If we assume the initial state of \$V_{o}\$ is \$V_{OH}\$ then:
\begin{equation}
V_{+} = V_{in}\dfrac{R_{f}}{R_{1} + R_{f}} + V_{OH}\dfrac{R_{1}}{R_{1} + R_{f}}
\end{equation}

and the output is:

\begin{equation}
V_{o} = A_{v}\bigg[V_{OH}\dfrac{R_{1}}{R_{1} + R_{f}} - V_{in}\bigg(1 - \dfrac{R_{f}}{R_{1} + R_{f}} - e^{-t/R_{2}C_{1}}\bigg)\bigg]
\end{equation}

So from the previous equation one can see that the output will remain at \$V_{OH}\$ as long as:
\begin{equation}
V_{OH}\dfrac{R_{1}}{R_{1} + R_{f}} > V_{in}\bigg(1 - \dfrac{R_{f}}{R_{1} + R_{f}} - e^{-t/R_{2}C_{1}}\bigg)
\end{equation}

or

\begin{equation}
V_{OH}\dfrac{R_{1}}{R_{1} - (R_{1} + R_{f})e^{-t/R_{2}C_{1}} } > V_{in}
\end{equation}

and the transition from \$V_{OH}\$ to \$V_{OL}\$ will happen when
\$V_{OH}\$ as long as:
\begin{equation}
V_{in} > V_{IL} \equiv V_{OH}\dfrac{R_{1}}{R_{1} - (R_{1} + R_{f})e^{-t/R_{2}C_{1}} }
\end{equation}

If we follow a similar procedure, we find that
\begin{equation}
V_{IH} \equiv V_{OL}\dfrac{R_{1}}{R_{1} - (R_{1} + R_{f})e^{-t/R_{2}C_{1}} }
\end{equation}

And that the hysteresis is:

\begin{equation}
V_{Hysteresis}=V_{IL} - V_{IH}=(V_{OH} - V_{OL})\dfrac{R_{1}}{R_{1} - (R_{1} + R_{f})e^{-t/R_{2}C_{1}} }
\end{equation}

Does all of this make a degree of sense? If so, because of the exponential term, I cannot see how to proceed from here to obtain a measurable value of the hysteresis (e.g., everything beyond some voltage threshold value triggers a transition. What is this voltage threshold value?) I have seen that modifying the resistors \$R_{1}\$ and \$R_{f}\$ allows me to pass higher or lower input voltages, but then at some point I need to change the values of \$R_{2}\$ and \$C_{1}\$ as otherwise I see nothing in the output. How can I relate all of this to the math (or even simulation)?

Any help is much appreciated. Thanks.


texts: Add isolation to a switching power supply

texts:
Actually I'm using a simply switching buck regulator that perform a 24v to 12v convention. I'd like to add isolation between power source and regulator. I've checked already all-in-one isolating DC-DC converters, but they are expensive and have low current supply (about 200mA , actually I've 800mA-1.0A peaks) with low input range, where at about 26V they fries.

Another application that I've found are DCM Fly Back ICs coupled with common inductors. Like LT8301/2, but they are also very expensive ICs with also 400mA limitation at 12V.

Are there inexpensive solutions to add an isolation between DC power supply source and my DC regulator?

Is it possible, something simple, like to put a 1:1 DC:DC coupled inductor between 24V and DC buck regulator?


texts: What is the correct way to handle inrush currents from a DC/DC converter with short-circuit protection?

texts:
I have been using CUI VESD2-S24-D12 to generate 24V to run a circuit board. That regulator has been EOL'd with the recommended replacement being PEM2-S24-D12. The two are effectively identical except that the PEM2 has continuous short-circuit protection, which I would typically consider an advantage.

However, this poses a problem. My circuit board has an LCD module that draws a brief (~5mS) inrush current of several hundred milliamps. My previous regulator would handle that just fine. The new one, however, current limits itself, so the output voltage crashes and it won't bring the display board up.

I see two obvious fixes. One, find a new regulator that's not current limited. Two, add some active circuitry so that my regulator first charges a cap before the actual load gets connected to the output of the regulator. The cap should handle the startup current, keeping the voltage from collapsing.

My question is, is that the most reasonable approach to solving my problem? Is there a standard, canonical, or otherwise "correct" way of handling this situation?


texts:
I have a small snow machine that I purchased.  It comes in a wooden box with metal, I assume aluminum or maybe stainless steel, trim  around it.  It connects directly to a standard 110vac power.  Obviously there is liquid involved as well.

The strangest thing is happening.  I have one worker who, whenever he touches the metal trim, gets shocked.  It is continuous and happens regardless of how many times he touches it, so it isn't static.  Everyone else can touch it without getting shocked.  But if he touches someone while they are touching it, they both get shocked.  He has tried different clothing, shoes, etc to figure out why he is the only one, but no matter what, he is the only one who gets shocked.

It makes no difference if the machine is turned off or on.

Anyone have any ideas?  It's got me stumped.


texts: How to properly connect ESD mat and sockets

texts:
I'm covering my workbench with a ESD mat (3100x900mm.)
I will also install 4 x ESD Sockets under the workbench (see below.)

I will connect everything to an ESD EU plug:

In the end the mat and sockets will both connect to EU ESD plug.
My real question is if there's a problem with that connection. The ESD sockets already have 1Mohm and the EU plug have another 1Mohm, that connection will make a 2Mohm resistance. Plus if I use a wrist band with another 1Mohm resistor that result in a final 3Mohm to earth.
Will that decrease the effectiveness, or will be just fine?
Result:


texts:
I need to join 4 wires together: a 6 gauge wire, two 10 gauge wires and a 22 gauge wire. The 6 gauge wire is the current source, the two 10 gauge wires will draw a continuous current of up to 30A and the 22 gauge wire about 20 mA. I need to do that twice - one for each leg of a 208/240v circuit. This is for an electric vehicle charging application.

I have been using a large size wire nut for this, but twice now it has failed due to overheating.

Left to my own devices, my next attempt would be with a split bolt, but then I'm going to need to wrap it all in a mile of electrical tape.

This is all going to be inside of a sealed chassis. The chassis will be portable, but all of the wires will have strain relief at the chassis entrance.


texts: Why is a railway's third line or overhead line DC and not AC?

texts:
As the title states, in the rail industry, why are the majority of railway's third line or overhead line in DC volts and not AC volts?  My initial guess would be that it is in AC since it is easier to distribute AC over long distances.  I do know there are a few overhead lines that are 25KV AC, but the majority are 600-750 V DC.

EDIT: I found this article which explains the difference a little bit, but it still doesn't explain why the majority are DC.


texts: Is there such a thing as a switch that can be actuated automatically?

texts:
I'm interested in a toggle switch that can be toggled without user input. That is, the physical state can be toggled electrically. It would need to incorporate some sort of motor or magnetic actuator. My google-fu is weak in this area, and I haven't been able to come up with the correct combination of search terms.

Note that I'm not talking about a relay; I'm talking about a normal toggle switch:

Except that it can be toggled without user input. As in, the lever physically moves. Like a "useless machine" except that the mechanism is internal to the switch.


texts: Taking output from FIFO implemented in verilog

texts:
I have a big design implemented in Verilog. The design has FIFO as shown in the image below. Due to some reason I have to add a new "Consumer" block shown.

The issue is, this block needs all the rows from the source block (FIFO in this case, which I cannot modify) simultaneously in single clock.  What should I do? what intermediate block I can implement that will satisfy the requirement of the Consumer block.    Right now the read pointer is reading data sequentially.


texts: What places, or where Can i get a AC transformer that will Increase voltage too 150KV + from household power

texts:
I am currently in need of locating a Transformer that will step up my household wall power to output in the ballpark between 150kv - 500kv.

Having a bit of a hard time

My project is a table top particle accelerator and the primary need for the device is Ultra High AC voltage

Current Amperes are very low and are not to important so eddy currents and heating hopefully will be manageable.


texts: Ideal Voltage/Current Sources in the Theoretical Total Resistance of a Circuit

texts:
If someone wants to find the total resistance of a circuit he has to deactivate the independent current sources.

As an ideal independent voltage source has zero resistance and the ideal independent current source has infinite resistance, either working or not, why do we need to deactivate them? Can't we just leave them be and just consider their resistances as zero and infinite respectively?

Simply put do we need to disable them so no current can flow in the circuit (for some reason) or we just do it as a visual aid in order to point out that those element has those resistance "values" in an attempt to simplify the circuit?

My question is purely theoretical and it doesn't have to do with real circuits and resistance measurements with a multimeter.


texts:
the converter in question

Hello for the converter in the link above when converting AC to DC should I have both inputs to the same AC source or do I just need one output connected? I have used the above with DC to DC successfully but I don't want to damage the component with an AC source. The two input wires are not shorted together. And I appologize but I was not able to find the datasheet for this converter.


texts: How to read a PWM with a separate ground using PIC?

texts:
I have a PWM signal that looks like the attached image. It's 12V with pulses of 0V at a 5% duty cycle. The frequency ranges from about 5Hz to about 50Hz. I'm reducing the signal voltage with a simple divider to keep it about 5V or so.

I want to drive an interrupt on each pulse using a PIC uC but I'm not sure how best to go about it. I don't mind using ECCP (the chip I'm using has it) but it's simpler for my code to just drive a simple interrupt. I can't use the signal's ground for my PIC as there is no usable corresponding live. My original plan was just to use an IOC on that pin...but I figure that won't work with a separate ground? Any ideas?
Second image is to check my understanding of first answer...


texts: Subthreshold Analog Accelerator - How is current derived through two sub-threshold transistors in series?

texts:
Was browsing the following paper:

Fick, Laura, et al. "Analog in-memory subthreshold deep neural network accelerator." 2017 IEEE Custom Integrated Circuits Conference (CICC). IEEE, 2017.

When I ran into the following:

Both transistors are kept in subthreshold region by opamps which set precise values across the two transistors. I understand how the threshold voltage of the SONOS (right) transistor is logarithmically programmed to represent a weigth (of a neural network):

$$ \omega_{i}=e^{-V_{th_{i}}} $$
And I'm assuming it's possible to specify the input as :
$$ V_{gs_{i}} = \ln(\alpha_{i})$$
(actually confused about this too, but that's a different question) which allows:
$$ I \propto e^{V_{gs_{i}}}e^{-V_{th_{i}}} \propto \alpha_{i}\omega_{i}  $$
But how is \$\alpha_{i}\$ multiplied by \$\omega_{i}\$ when \$\alpha_{i}\$ is applied to the gate of the NMOS and \$\omega_{i}\$ is represented/applied to the "gate" of the SONOS transistor? It seems that Vin(N) should be applied to the SONOS transistor gate instead of the NMOS. How is the current through both transistors derived?

The author of this paper wrote a thesis describing it in more detail.


texts:
Circuit Link

I am very confused about negative voltage in capacitor, it can even light a led as you can see in the circuit.

My questions are;

1-Why capacitor gives ~-2 V in its negative terminal when we tie its positive terminal to ground?

2-How can that LED work by connecting its positive to battery's negative pole and its negative to our negative voltage?

I have been searching this for long time, what i found about first question is this site's "Some Capacitor Theory", why capacitor acts like this?

May you please explain it as simple as you can, because i am interested with electronics as hobby, i really don't understand clearly when it is explained in formulas,mathematics etc

Circuit Image:

Thank you very much.


texts:
I am trying to design a CAN bus expander. In this case I could implement star topology  of multiple buses in parallel. It would avoid having problems with reflections and delay.
For this purpose I prepared a simple schematics, that basically reflects RX signal from the CAN transceiver to the open-drain bus and then connects it to other RX and TX pins of other transceivers. My understanding is that this should work with CAN bus, keeping in mind dominant bits have priority.
The only question remains: Is it OK to connect RX via open-drain circuit to TX of the same bus? I would say it is, but this is the part I am asking actually.
My circuit (drawn on tablet)

Image shows 3 different CAN transceivers connected in parallel. No matter on which bus signal is received, other 2 should see the same on their output.
This is schematics that works (verified), which I try to optimize. You can connect as many blocks as you want.


texts:
I am working on a project using multiple MEMs sensors that communicate to a microcontroller where the data is processed before sending it serially via RF.

I am using the Parallax Propeller Chip for it's ability to run multiple processes simultaneously. However, the SPIN language is quite slow and complex floating math algorithms get messy very quickly in SPIN. So I transitioned to the Catalina C compiler made for the Propeller but for the life of me cannot find any function libraries. I managed to toggle a few LEDs in C but am a long ways away from figuring out how to implement I2C, SPI, and serial communications in C. If you are familiar with this compiler, any pointers would be greatly greatly appreciated.

Cheers!
Jason


texts: How reliable or trustworthy are LTSPICE demo circuits?

texts:
I'm looking at a few switching power supplies and one of the demo .asc files for the particular controller I was looking at really seems to fit my requirements.

Can I use their schematics in designs as is or are their some hidden 'gotchas' between what they demo vs real life ?

Edit

The controller I am considering using is the LT3748 and the LTSPICE model I was looking at is LT8309 & LT3748 Demo Circuit - 60W, 12V Output, Isolated Telecom Supply (36-72V to 12V @ 5A

For those that do not have LTSPICE and just want to see the schematic


texts: What type of antenna is this? (glide slope aircraft antenna)

texts:
This is a glide slope antenna from an aircraft. They are installed in or near the nose cone of an aircraft for the reception of the glide slope signal beams.
The antenna is tuned for 329 to 336 MHz and has an impedance of 50Ω.

I have no idea what the center tube is for, the connector on the other side is behind one of the legs with the rubber glands. Sometimes the antenna is missing the center post, perhaps it's only for rigidity.
You can somewhat see the way it mounts to the fuselage in this picture:
You can see the N connector, and it seems the center post is directly screwed into the bottom plate.
I'm wondering what type of antenna this is. To me it looks like a folded monopole antenna or something, but I'm not sure. I'd like to know the beam characteristics of it, how to calculate the dimensions, etc.
I have no idea how the internal structure of the antenna is, since the connector is one of the legs, so I can only assume the rubber glands isolate the element from the bottom plate. Perhaps it's like an end-driven λ/2 dipole that is folded back or something, I'm really confused and I don't know. But I'm very interested.


texts:
I am designing a constant current source(35mA) circuit using transistor.Thought of usingthis below circuit but the problem with that is my resistance R is fixed( 2.3 ohm ) which I could not change due to the requirement.Could you please suggest some design ideas how to meet the requirement.

Provide constant current source of 35mA
Resistance R is fixed with 2.3ohm


texts: How to choose RF choke in the biasing circuit of varactor-tuned resonant circuit

texts:
I am new to circuit and has a very basic question about how to set biasing circuit of varactor.   I need to use varactor to tune the resonance behavior of Split ring resonator (SRR) structure when illuminated by plane wave. (If you are not familiar with SRR, you can think that SRR illuminated by plane wave is just a RLC circuit driven by AC voltage), See Fig.1.

I tried to find some guidance online. Some said that I need to use RF choke (an inductor) to isolate DC voltage from AC circuit, see Ref.1. Somme said either inductor or resistor could be used, see Ref.2. Some uses both inductor and capacitor, see Ref.3. (Fig7, Page12). This make me confused, so, what should I do?

My own understanding is that, RF choke is to make the DC biasing circuit 'unseen' by AC signal, so, at working frequency of the AC circuit (f0), the impedance of inductor should be much larger than that of the varactor, so that the current flowing in the DC branch is negligible comparing to the AC branch,See Fig.2. Am I correct?

If there is anything wrong, please correct me. Besides, external resources could be helpful, too. I looked up several textbooks on circuit, but no detailed information about how to bias varactor was found.

Thank you very much for your kind help! (By Jingwei)

Reference

1.http://www.radartutorial.eu/21.semiconductors/hl13.en.html

2.https://radio-electronics.com/info//data/semicond/varactor-varicap-diodes/circuits.php

3.
RF Diode design guide


texts: Is high impedance important for a differential amp measuring a battery voltage?

texts:
I want to measure voltages of multiple cells which are connected in series. I want to do that using a differential amplifier. I read about low input impedance, and what to do about it in this case. So I found this schematic:

simulate this circuit – Schematic created using CircuitLab

I'm wondering, whether it's really important to have high input impedance here, because the battery has a very low resistance, so the input voltage of the OP AMP should be almost the same as the battery voltage, no? So is it indeed better, to add those two voltage followers, or stick with the simpler differential amplifier variation?


texts: LT4320 Ideal Diode Bridge Controller - supply voltage max ratings reference point

texts:
The LT4320 and MOSFET bridge was suggested as a low dropout bridge rectifier in another post. I hadn't come across it before so I investigated further.

I'm puzzled by the IN1, IN2 maximum ratings.

What point is being used as reference for these input voltages?

Duh!

As the Dave's answer and Brian's comment point out, the answer is in the notes which I missed on the next page. Let this post stand as a reminder to others to read the notes!


texts:
From the datasheet:

  http://robocraft.ru/files/datasheet/28BYJ-48.pdf

and this post:

  Stepper motors - stride angle? angle

I know that we need 4048 pulses to rotate the output shaft for one revolution. But when I use the module ULN 2003, with the sequence of pulses are: 1A-1B-2A-2B-... I only need 2024 pulses to rotate for one revolution.

What is the reason for this?


texts: Something that is confusing me on the Arduino is the Analog Inputs. Can they be used as normal I/O Digital or only I Analog?


texts: What are the types of measures that combine accelerometer data (Ax, Ay, and Az acceleration values) in one value. For example, D = f(Ax + Ay +Az)

texts:
What are the types of measures that combine accelerometer data (Ax, Ay, and Az acceleration values) in one value?
For example, D = f(Ax + Ay +Az)
Can we ask the same question for the gyroscope? such that E = g(Gx + Gy + Gz)
Thanks


texts: I am trying to implement a circuit using mosfets that will detect the state of a pin with 2 outputs. The input (I) to output (O) relationship I want is this:


texts: What's the name of the device I'm looking for

texts:
I'm looking for a device which monitors a 3.3V line. When the line drops below, say, 2.7V, I would like it to switch power over to a battery backup (3V lithium coin cell.) It would also be good if it provided a logic signal to alert of the supply failure so the MCU in my project can switch over to a low power mode. It needs to be able to switch up to 120mA when the supply is high. What is the name of this device? I have a feeling it's quite common in applications like laptop computers.

Ideally it would have 5 pins: Vin main, Vin backup, GND, Vout, Logic out.


texts: Step down transformer for vintage tube amplifier

texts:
Hi so I've just bought a 60's tube guitar amp from the U.S, I live in Australia. Through searches across the internet I've found a few potential issues with the safety of running the amp through a 240-110v step down transformer.

Firstly, the amp has no power transformer, it rectifies the line voltage directly. A common safety modification is to add an isolation transformer, I figured I could avoid doing this by using an isolated step down transformer

Secondly, the amp isn't grounded so if a certain capacitor inside the amp fails, the chassis of the amp becomes live. The standard fix is to add a 3 prong plug and ground the chassis, but I've read that the ground plug in isolation transformers dont actually ground.

Thirdly, would the 50hz of Australian mains damage the output transformer or any other component of the amp, designed for 60hz?

Thanks in advance

Here is the schematic for the amp

http://www.magnatoneamps.com/schematics/magnatone_401_412.pdf


texts: Protect Inverter from Transformer's Inrush Current

texts:
Consider a "small" autonomous grid, which is based mainly on RES and has a few diesel generators, like in the following figure

Everything runs smoothly, feeding the small load. Suddenly, the big angry load tries to connect and its transformer draws a large magnetization current (let's say 3 or 4 times the nominal current).

My question is: Is there a reliable strategy to follow so that the DC/AC converter manage that current without shutting down? Obviously, there will be a current limiting function, but is it fast enough?

Some conditions

Load's transformer in inaccessible
We cannot depend only on the diesel generators to supply that current
We want to avoid a partial shut down of the system
Voltage drop, for 10-15 cycles is allowed

I know the question is broad and the answer depends on various parameters, but is there an "standard" method to deal with this problem?

EDIT

The nominal current is not strictly specified, but if we consider that the big load is ~ 1MW @ 400 phase-phase, the current is \$ I = \frac{1MW/3}{\sqrt3 \cdot 400} = 480 A \$

EDIT #2

The big load is mostly resistive - it heats up water. There may be some motors, but this is not the issue.


texts:
I am using LTspice parametric sweeps to generate a series of different cases and plot waveforms and measured values. I have two sweep variables and 5-6 points for each variable. Now I want to see how my measured quantities (using .meas) vary with respect to the sweep variables.

Currently, when I want to figure out which line corresponds to which sweep variable value, I am looking at the colour preferences order. This becomes a bit troublesome when I have many sweep points.

Is there a way to include a legend in LTSpice graphs for a sweep variable?
Of course, I can export the data and use some other tool to do all the further analysis. But here I am wondering if there is a way to make it easier with LTspice itself. (for waveforms, the solution provided by @aconcernedcitizen is very useful to group the results and display separately. But for measured quantities it does not work.)


texts: Re-broadcasting a wideband satellite television signal over a short distance?

texts:
Normally a coax cable connects a satellite dish to the receiver. I'm in a situation where I can't easily install a coax cable, but a wireless signal ought to be possible because it's only 10 meters through a wooden house (no steel or concrete), but not line-of-sight.

I'm wondering whether a device exists or if it's possible to design a device that can wirelessly send the raw satellite signal to a receiver? Would something like this product work?

Note that I'm interested in "wirelessifying" the connection to the sat receiver. I don't want to distribute the signal coming out of the receiver toward the TV set.

[sat dish] ... [wireless signal??] ... [receiver*)] ... [HDMI] ... [projector]

My receiver is not a separate box, I've got a Windows Media Center PC with two internal tuner cards that can accept DVB-S. A ceiling projector is attached to the PC by HDMI cable, and that's how I watch TV and anything else.


texts: Access Variable that is in code space in Assembler

texts:
Keil's C51 allows the use of sharing global variables between C and Assembler code. However I need to store a variable in the code space of an 8051 microcontroller. Yet when I try to access the variable in assembler I get some errors.

I have the following declaration in my c source file:

unsigned char code STATE = 0xFF;

And in my header file it looks like:

extern unsigned char code STATE;

With the Keils C51 compiler it is possible to access global variables in C using the EXTERN keyword in your assembly code so in my assembly I have:

EXTERN CODE (STATE)

However when I try to access the variable in my assembly I get the error: DATA-ADDRESS EXPECTED:

 MOV     A, STATE ; Move state to A;

Also as it is in the code space it should access using a MOVC instruction so this should work:

 MOVC     A, STATE ; Move state to A;

Yet this yields an EXPRESSION TYPE DOES NOT MATCH INSTRUCTION error(AX51 error A22).

So how can I access this variable in assembler?


texts:
Anyone have experience adjusting the Voltage reading on these? My less expensive meters have a single pot for calibrating, but this one has three. Labeled on the circuit board as V1, V2, and V3. I'd be interested to find out what each of them does, but mainly, I need to know which adjusts the Voltage reading.

Thanks!


texts: Why output signal is not symmetrical? What to do?

texts:
I am trying to design a 2-stage amplifiers with first stage C.E with PNP transistor and second C.C with NPN transistor.
The amplifier is supposed to have a gain more that 40.

After designing the problem is my output voltage wave form is not symmetrical.

Anyone has an idea?


texts: Help check my pcb layout and routing please

texts:
This is my first time fabricating a simple PCB.
Could you help check for any mistakes in my PCB layout and routing?

The power line is 20-25mil. Does the width of the power line vary with the specific magnitude of current or just make it as wide as possible?
Due to little component, is it necessary to make lines except power wider?
Are there other mistakes in layout and routing?

Update PCB with labels.


texts: Automatic Self-Test Circuit in GFCI outlet

texts:
What kind of self-test circuits or method do they used in the GFCI outlets generally? Is it just firmware or is there a physical addition (and what it is usually?)

This is because after 2015, it is required by UL. But there were many old stocks without it and the physical appearance of the product is the same. So is there any way to recognize or test the function if I buy a product which both has the function and not (depending on whether manufactured after or before 2015 which they don't specify?)

Note: This isn't about the manual test button, but a circuit inside... see

  New Self-Test Requirements:

  n Underwriters Laboratories (UL) made new revisions to the UL 943 (GFCI) standard that will take effect on
  June 29th, 2015.

  n UL REVISION 943 STATES:

  All GFCI receptacles must have an auto-monitoring (self-testing) feature.
  If auto-monitoring determines the GFCI can no longer offer protection, one or more of the following will happen:
  (1) Unit is no longer able to reset and denies power.
  (2) Unit can reset and is subject to the next auto-monitoring test
  cycle within 5 seconds of power to the device.
  (3) All GFCIs must provide audible or visual indication if it does NOT
  go into power denial.
  Provisions to ensure receptacle will not reset if miswired during installation as well as reinstallation.
  "


texts: Several battery connections independant of each other

texts:
I'm trying to create a battery bank for dac's, preamp's etc. I've ordered 3 x 15Ah 3.2V lifepo4 batteries which will run in series through a 3S BMS, providing around 9.6V total.

But, I'd like to make 3 or 4 outputs/connections from the BMS, one for the dac, one for the preamp etc. I guess I can just wire all these connections to the 2 output terminals on the BMS.

But can I in any way make sure, that these connections to the same terminals are completely independant? That is, that a large surge on one connection won't effect the voltage on the others?


texts: Where to start designing a ~1Hz to ~60Hz square wave oscillator as a switch for a Klomp dirty video mixer?

texts: So I built this circuit and in messing around with it I found if I switched quickly between a camera (feedback) source and a video source in quick succession with the switch I obtained an aesthetically pleasing result. So I want to automate that switching behaviour and control the rate of that oscillator with a potentiometer. I got a 555 chip because I thought that might help, but I have no idea how to actually design a circuit, or if the 555 is even capable of doing what I want.


texts: LDO quality with current measurement shunt

texts: I'm designing a power supply block and need to measure the current flowing trough a LDO. It is clear that the current in front of the LDO and after the LDO are the same (apart from some tiny bit used by the LDO). But does it matter if I mount the shunt in front of the LDO or after the LDO? Are there any differences in noise or voltage precision?


texts: N-FETs behaving strangely when connected in parallel

texts:
I've got the resistive network generating 1V from 3V, but when I connect two N-FETs on the output with gates tied to sources tied to ground (that should result in them closing, right?), the voltage drops to near zero. Works as expected with only 1 N-FET connected. I'm using BS170 specifically.

Works fine in simulation:

Why is that?


texts: Why does LTspice resistor noise disappear when setting value with .param?

texts:
When performing a noise analysis in LTspice of a 1kΩ resistor, a noise level of 4nV/rtHz is simulated.

However, if this resistor value is set to 1kΩ using .param, its noise decreases to 129fV/rtHz. Changing this resistor value does change the noise linearly. What causes this noise decrease, and what can I do to prevent it?

The schematic is shown below:


texts: Display Amber/Orange on LED Strip with no control module?

texts:
I have a set of LED strips that have the following four wires:

Positive
Negative

Red Channel
Blue Channel
Green Chanel

Given these wires, I can produce the following colors without additional components:

Red
Blue
Green
Purple (Combine red and blue.)
Cyan (Combine green and blue.)
Yellow (Combine red and green.)
White (Combine red, green, and blue.)

However, the control module (now fried due to a crossed wire) has an option for amber/orange. The question is, how can I produce this color? I believe I may have to combine green and red to produce yellow, and add a resistor or similar to the green channel to reduce the current to that color thus displaying more red and possibly producing the desired color.

Additional Details

The lights are powered by a 12v source (car battery).

How can I use the above to create an amber/orange color from the lights?

If the answer is simply adding a resistor, what is the lowest resistor I should use in the 12v circuit?


texts: What exactly am I messing up in this control loop?

texts:
I am creating a simple control loop for a safety door for a machine. When the door is opened, the machine turns off. When its closed, the machine can operate. The way I have it set up now is that we are looking for the door to be open, and if its open the sensor will tell the controller and the controller will flip a switch and the machine will turn off. I feel like the output just does not make sense. I think I am maybe confusing what the set point should be, but I am not sure. This is just a little project I am doing to better understand safety/security control loops, but I think I may be over thinking this one a bit. Any help appreciated.

Here's a link to my current design.


texts: What's wrong with this schematic? Multisim doesn't generate oscillation. Also I changed R3=1000, R3=500 but all the same.


texts: How to use Control Register inputs of LPT port?

texts:
I would like to use Control Register controlled pins of LPT (1, 14, 16, 17) as inputs. These are said to be normally used as open collector outputs, but have the ability to operate as inputs too. This site describes the use of this pins as inputs, but I'm a bit confused and don't really understand what I'm supposed to do.

Here's what the circuit looks so far. This fails for Control Register pins, but works for Status Register pins (10, 11, 12, 15). How do I need to change my schematic to make it work for with the other ones?


texts: How can I control this latch with Positive Logic?

texts: Here is a simple 2 transistor latch circuit controlled with 2 switches to ground. How can I control this using 3-5 volt sources instead of switches?


texts: How to set polygon clearance around the edge of the board in Eagle?

texts: I created a polygon that I intend to use as a heatsink. The problem is that there is a lot of clearance at the edge of the board, much more than around traces even, why is that? How can I set board clearance independent of isolation setting of the polygon?


texts: Laser diode driver circuit analysis help

texts:
I'm looking up for some circuitry to drive my laser diode and I came across this tutorial.
I understand the basic operation of this schematic; however, there's one thing that confuses me:
I cannot understand the purpose of R6 and the pair C3, R4. (Jt seems like a RC filter, doesn't it?)


texts: Getting the wrong Thevenin equivalent resistor

texts:
Its been a while since last time I worked with circuits.

Im trying to find the Thevenin equivalent resistor to this circuit.

This is how I tried solving it.

The correct answer according to the solutions manual is 3 ohms. What did I do wrong?


texts: It is said that measuring the terminal voltage of DC battery directly with a voltmeter, it can give misleading values and it is always advisable to take such readings while the battery is connected in a circuit with a certain resistance. Can anyone explain the reason behind this? And a simple one why have we never come across an AC Battery?


texts: What would happen if you connect a solar panel to a buck-boost converter?

texts:
What would happen if you connect a solar panel with the following characteristics:

Max Power:3.5W

Voltage:    6V

Open Voltage:  7.2V

To a buck-boost converter that convert an input voltage in the range 1V-6V to a voltage of 5V? Who would "win" the fight to set the voltage? The buck-boost converter can work with any input voltage and the solar panel can work at different output voltage. I can't figure a way to calculate the input impedance of the buck-boost converter.

Bellow is the representative circuit diagram for a solar panel on the left and the buck-boost converter on the right with the converter switch represented with the letter S.


texts: Incremental encoder - polling or interrupts?

texts:
I took over a project including PIC18f25k80 microcontrollers and incremental encoders. Basically I just need to follow the position of the motor using the encoder, and drive a device to specific locations. I know that there are more methods to read an encoder and update the position. The motor does not turn fast at all, no high speeds are involved here.
If I were to develop the whole thing from scratch, I probably would hang one channel of the encoder to an interrupt pin on let's say port B, and in the ISR I would check for the state of the other pin. To me, this seems to be the cleanest solution, this method probably catches all position changes, correct me if I am wrong.
Another method would be to poll the 2 channels in the main loop. There is not much in the main loop, basically just adjusting the motor speed and direction based on the position, so at slow speeds, I guess that I would not miss position changes, but it bothers me, that it is still a possibility to miss changes in the encoder channels.
A third option could be to initialize a timer interrupt, and in that interrupt routine, I could check for the pin states. This interrupt could occure twice as fast as a state change would occur at the highest speed, so I guess I would not miss any changes with this method as well.
Now that being said, my question is as follows: which option should I chose?
As I said, I would go with the first one, the encoder channels are attached to RB4 and RB5, so I could just enable the interrupts on port B. But as far as I know, and this is where I am not sure, I can only enable the interrupt for the whole port B on a PIC18f25k80, and not for single pins. That means that all pins on port B would create an interrupt, not just the one I want. And not just the other channel of the encoder, but all of the pins on port B are attached to something, and I cannot change the layout, only the software. Do I see it right, that in this case this method is out, because all pins would cause an interrupt on port B and that would be too much overhead?
And the end of my question: if I see the above problem correctly, which method would you chose, polling of fixed timer interrupts? We are talking about 5 rotations per second tops.
Thanks for the answers in advance!
This is the encoder in question: https://www.power-tronic.com/wp-content/uploads/2019/11/Type-Magnetic-Incremental-2019-01-08.pdf


texts: Why does the PMOS burn out in a buck boost converter when I increase the power supply voltage?

texts:
My MOSFET warms up and even burns out when I change the power supply
to 8V.  I get an input current of 1A , and the MOSFET burns.
This is the datasheet.
I dont know why.  I have an IRF9540n MOSFET.
This is my schematic:


texts:
I'd like to know, how long/big should be an ACK from a slave to its master? I am communicating with a module using the I2C protocol. But the large blank space in the middle, is this an ACK from the slave to the master (µc) as expected?

Whole view

Close-up left

Close-up middle

Close-up right

What I am doing in software as pseudo-code is:

setSlaveAddress(0x48)
sendData(0x55);


texts: Can humans feel electricity without muscle's reacting to electricity?

texts:
I've talked to people and seen stories that believe electricity can be felt as a vibration or some other way by touching something that is electrified. I don't have any questions about electromagnetic hypersensitivity aka better call Saul , or any questions about feeling the muscle spasms from electric or static shocks.

A specific example I can think of is someone touching the steel support beam of an industrial machine and saying they can feel the leakage current, can people feel electricity without feeling the muscle spasms associated with the shock?

For example if you applied an electric signal to your hand that was large enough for you to feel, then you took a drug that prevented your muscles from contracting and then applied the same signal, would you still feel it?

I asked this at skeptics.se before but it's on hold for being unclear.


texts: Trying to create a 555 timer but nothing shows up in my transient analysis

texts: I'm trying to learn more about 555 timers but my transient analysis renders me this empty graph. Is there something wrong with the way I am setting up my MultiSim Circuit?


texts: Experiment to identify of all the poles from the input output data irrespective of pole zero cancellation?

texts: The pole zero cancellation reduces the order of the system. As a result we can't identify all the poles from the input output data. Given, input output data, can I devise an experiment such that I can identify all the poles?


texts: Finite State Machine to find Greatest Common Divisor

texts:
Ok so here is the problem we are given:
Consider the following datapath. Assume the width of the datapath n is 4.

The ALU has a 1-bit operation code OP. If OP=0, the ALU performs A-B. If OP=1, the ALU performs B-A.
The Compare circuit generates a 2-bit comparison code CC. CC=00 if A=B. CC=01 if A>B. CC=10
if A <  B.
The  Greatest Common Divisor (GCD) of two positive integers can be found by the Euclid’s Algorithm,
which is given below:
LOAD A
LOAD B
WHILE (A != B) DO
IF (A > B) THEN
A = A – B
ELSE
B = B – A

// GCD(A, B) is stored in both registers A and B
Design a Mealy-type FSM to control the datapath to find the GCD of 14 and 4. The FSM should set an
output FOUND to 1 when the GCD is found.
I just don't get how to start making this GCD finder... Would love some help on this!


texts: I hate to add to the list of equivalent resistance problems, but having browsed through the existing questions here and elsewhere online I am still unable to redraw the following circuit to find the equivalent resistance between points C and D. All the resistors have equal resistance R. Can this be solved by redrawing and applying Kirchoff's laws? Or must other techniques be used?


texts:
I am designing a PCB which has +5V input from a USB jack and I want this power trace to be as large as possible to reduce input resistance. While doing my large traces on my PCB tool, one of the stock design rules is giving me an error that my neck down is too large.

I don't see how this can cause a problem. Is there a reason why this type of design rule exists?


texts: Is it possible to write/read text files on a USB Mass Storage Device using one of the USB ports on the Tiva Launchpad?


texts: Should power supply be fused on input and outputs?

texts:
I'm building an automation control panel.  It uses a 120VAC to 24VDC power supply to power several IO cards and signal lines.  The entire system will draw less than 500mA when in operation.

This PSU is rated to output 24VDC at up to 5A.  The sticker also states that it draws up to 2.6A on the input side.

I have already installed a fuse on the input side, rated for 2A.

Should it also have a 5A fuse on the output?  or will the 2A input fuse open if the output is overloaded/shorted?

What is the best practice in this situation?

Thanks!


texts: Oscilloscope triggers unexpectedly when horizontal scale is large

texts:
When I set the horizontal axis to something large (40ms/div or greater) and hit the Single button, the scope triggers immediately, although no trigger event has occurred. I tried the following:

Setting the trigger to something ridiculously high and grounding the channel that it triggers on, to make sure that noise was not triggering it. It still triggered immediately.
Setting the horizontal scale to 20ms/div, hitting the Single button, and then increasing to 40ms/div. This worked; i.e. did not trigger until the trigger event actually occurred.

I am using a Tektronix MSO54, but I also recall observing this phenomenon on another scope in the past.  This has got to be something obvious, but for the life of me I can't figure out what.


texts:
I'm trying to do double buffering using the hardware, STMF32492I.. so
first I'm initalizing two layers in two different addresses.

Then I write to the back buffer, switch the back buffer..

But The problem I get multiple copies of the sprite that is animated, so its either I'm drawing to the front buffer multiple times, or the back buffer needs to be cleared.

Here is how I'm doing it

void main
{
 while (1)
    {

        LTDC_switch_framebuffer();
        // draw spries
    }
}

void LTDC_switch_framebuffer(void)
{

    LTDC->SRCR = LTDC_SRCR_VBR;                     // reload shadow registers on vertical blank
  while ((LTDC->CDSR & LTDC_CDSR_VSYNCS) == 0);    // wait for reload
    ;
    flip ^= 1;
    BSP_LCD_SetLayerVisible(flip, ENABLE);
    BSP_LCD_SelectLayer(1-flip);

}


texts: Why is the internal resistance of BJTs considered in small signal AC analysis but not in DC analysis of BJT amplifiers?

texts:
Specifically, I want to know why "r" parameters are considered in AC analysis but not in DC. I am reading from Electronic Devices by Floyd.
For example, in the picture below, VB is calculated by multiplying IE with r'e, but if it were DC analysis, we would consider VBE approximately 0.6-0.7 Volts.

I am a newbie in electronics, so probably there is something I missed about the analysis of BJT amplifiers.


texts: Sampling 133MHz bus with OWLS Logic Analyser

texts:
The OWLS specs state that it can operate in two sampling modes:

200Msps captures up to 100MHz waveforms on 16 channels
100Msps captures up to 50MHz waveforms on 32 channels

Does this mean that 100MHz is the maximum signal frequency I'd be able to sample at? I'd like to sample the data lines on a 16-bit SDRAM IC, which runs at 133MHz. Am I likely to get useful results?


texts: Control the RGB tape with only one output of the microcontroller

texts:
I need to control the colors of an RGB ribbon. This requires 3 PWMs. But I have only one output of my microcontroller available. So for this I need to find a circuit that stays between the microcontroller and the RGB tape that allows me to change the colors receiving only a signal from the microcontroller (as in the image) I thought of an analog converter for PWM but I do not know how to do it or if it is possible.

simulate this circuit – Schematic created using CircuitLab


texts:
Assume we have a simple Verilog module with 1 input (in1) and one output (out). Please look at the truth table at the end of this question.

I want to send a signal with the voltage between 0-VCC0=3.3v to input in1=PIN3 of a FPGA ( this case XC3S400). All Vref pins of the relative  bank are connected to 1.8V. Now I want to see a logic 1 on out=PIN4 when the voltage of in1 is higher than verf and a logic 0 when it is less.

I know it is a feature of single ended I/O standards that is supported in FPGAs but I don't know how to assign this vref comparison in ISE. I just can guess to write some attributes in the verilog or assigning vref in ISE (PlanAhead).

In ISE Plan Ahead , one can assign fixed vref standards ( GTL, GTLP,...). but these are fixed Vref standards. I am looking for a way to set vref to any voltage which is desired. For example can I set vref to GTL=0.8v but connect 1.8v to vref pins of the bank?


texts:
This is the circuit of a PWM temperature sensor, I will give you some details about the circuit:

The Electronic control Module which supply power (+8V) at terminal (A)
The Electronic control Module provide ground circuit at terminal (B)
The output signal from the sensor at terminal (C)
The oscillator, which provides the carrier frequency signal, depending on the application, the internal oscillator will provide a carrier frequency that can have the following approximate values 5kHz for temperature sensor
A "Thermistor" element which varies its resistance with the changes of temperature, this variation is received by the amplifier and converted to a digital signal PWM.
An output of the amplifier, which controls the base of a transistor and generates an output of "the duty cycle", measured in percentage of time that the transistor (this also provides protection against preserve circuits between C and B, and C and A terminals) "on" against time that it has been off.

Well I don't have enough experience in electronics so I want to know the sequence of how this circuit works:

For example, with the oscillator, what does it mean to provide carrier frequency and what's the function of it in the circuit?
How does the operational amplifier work in this circuit?
How is the signal converted to PWM?
How about the transistor; how does it work as a switch or what is the output signal at terminal (C)?


texts:
I'm working on a VHS adapter that uses a VHS Cassette casing with some electronics in it. The hardware contains a battery and some sort of IC which I can Not program, it's not a micro controller, it's a fixed piece of hardware that does a specific task.

I do not want to use a microcontroller, the hardware that I use is the only hardware that I am allowed to use because of energy efficiency reasons.

To run the hardware I use a 3.7 V LiPo battery and the only thing I need now is an analog/mechanical momentary switch which is linked mechanically/magnetically (preferred) to one of the wheels of the VHS Cassette.

This momentary switch makes sure that the hardware is powered ONLY when the VHS Cassette wheel is spinning.

How do I create such a momentary switch?

I have one solutions to this but then again I'm not sure how to accomplish it.

Solution: Putting a magnet on one of the wheels, and use a reed switch to charge a capacitor that in turn powers the rest of the hardware.

Pros: should be really cheap, is more or less solid state. Awesome!

Remember the following things:

I only allowed to use the hardware mentioned: The IC, the battery and a momentary switch.
-There should be as little moving parts as possible, it's preferred to be completely solid state.
-No digital sensors allowed.
-No microcontroller allowed.

Illustration:


texts: How come esp8266 is able to generate 2.4 GHz wifi signals

texts: I am wondering how it is possible to generate 2.4 GHz, if its core clock frequency is much lower than GHz scale.


texts: Measure 230V mains with 300V CAT II probe?

texts: I need to measure harmonic distortions on a 230V 50Hz AC mains circuit. The Tektronix P2220 probes I have for my scope are rated for 300V CAT II when set to 10X impedance. Are these probes safe to use with 230V mains, or should I look into a 100X probe?


texts:
I had a either a surge or a part failure cook a few components on board. The board is rather old from a discontinued product. On the board the only components I've not been able to identify that need to be replace are, from what I can tell, are 2 identical varistor's.

This is the component:

This is schematic from what i've been able to tell.

If anyone is able to help I would greatly appreciate it.


texts: Can a MOSFET generated high voltage (315v) pulse train be measured using a DMM in AC mode?

texts:
I am using a 5V pulse train generated from a UC3845 PWM controller to trigger a MOSFET (K2645) which is biased with 317VDC in series with Rd= 120ohms, Rs=20ohms and primary of the PWM transformer. I am able to see the pulse train of UC3845 but since I don't have an isolation transformer, I can't use it to see the PWMT waveform, which is also not detected on a DMM(AC mode). I have varied the pulse width to see the effect on the output. My DMM is only measuring in millivolt AC (both primary & secondary.

Q1. Can these high voltage pulse train be measured using a DMM in AC mode? Why not?


texts: sallen key butterworth interfacing with arduino Due

texts:
I am using this stethoscope circuit
I want to give TL072 butterworth filter output to Arduino Due ADC which input is max 3.3 but the supply of the mentioned circuit is split +9-0-(-9) volts. How can I interface this?

I tried to shift reference voltages with two back to back diodes but it did not give output

My question is what is the best way to interface this circuit to arduino due ADC so that we can sample data there
Thanks


texts: Calculating Yaw Pitch and Roll from Quaternions in MPU6050 without Gimback lock but giving problems

texts:
I am trying to convert quaternions provided by a MPU6050 to heading attitude and bank values but at least one of the three calculations is broken, for example in the third calculation (the uncommented one) the yaw and pitch are in the same axis and the other two almost do not change, do you know which specific formula should apply here, or at least some theory on different ways of quaternions representation that helps me figure out the maths behind this?
float heading;
float attitude;
float bank;
double test = q.x * q.y + q.z * q.w;
if (test > 0.499) { // singularity at north pole
  heading = 2 * atan2(q.x, q.w);
  attitude = M_PI / 2;
  bank = 0;
  return;
}
if (test < -0.499) { // singularity at south pole
  heading = -2 * atan2(q.x, q.w);
  attitude = - M_PI / 2;
  bank = 0;
  return;
}
double sqw = q.w * q.w;
double sqx = q.x * q.x;
double sqy = q.y * q.y;
double sqz = q.z * q.z;
/*
 //http://www.euclideanspace.com/maths/geometry/rotations/conversions/quaternionToEuler/
heading = atan2(2 * q.y * q.w - 2 * q.x * q.z , 1 - 2 * sqy - 2 * sqz);
attitude = asin(2 * test);
bank = atan2(2 * q.x * q.w - 2 * q.y * q.z , 1 - 2 * sqx - 2 * sqz);
*/
/*
 // https://www.i2cdevlib.com/forums/topic/24-roll-and-pitch-angles-ranges/
heading = atan2(2 * q.x * q.y - 2 * q.w * q.z , 2* sqw + 2 * sqx - 1);
attitude = asin(2 * test);
bank = atan2(2 * q.x * q.w - 2 * q.y * q.z , 1 - 2 * sqx - 2 * sqz);
*/
//https://www.euclideanspace.com/maths/geometry/rotations/conversions/quaternionToEuler/indexLocal.htm
heading = atan2(2.0 * (q.x*q.y + q.z*q.w),(sqx - sqy - sqz + sqw));
bank = atan2(2.0 * (q.y*q.z + q.x*q.w),(-sqx - sqy + sqz + sqw));
attitude = asin(-2.0 * (q.x*q.z - q.y*q.w));
Serial.print("conversion\t");
Serial.print(heading * 180 / M_PI);
Serial.print("\t");
Serial.print(attitude * 180 / M_PI);
Serial.print("\t");
Serial.println(bank);


texts: Which Ampere range and precision does my amperometer need to monitor a current of 220V between 50W and 300W

texts:
I need to measure the evolution of the electric power at the level of the electric plug of a computer in function of its CPU usage percentage.

The voltage is 220V and the wattage between 50W and 300W.

For this, I plan to plug a amperometer in series and take at least 20 measures as the CPU consumption curve increases.

I don't have access to expensive material such as oscilloscopes. I need to purchase a amperometer but cannot figure it out which model would fit, in particular

What precision should my amperometer have
What range should my amperometer have


texts: Help identifying two lead component with glass cover and serpentine trace under it

texts: I ordered an IR pair of components from Amazon and received this which I do not think is an IR emitter or receiver. Does anyone have any ideas to what this component is? I could not find anything by searching.


texts:
I'm working on a rocket project; we need to open a door to deploy the parachute. This door will be subject to great forces and must stay closed, until it gets the right signal.
I have a few questions:

Which of the solenoid or the electric strike can endure more strength?
What is the electrical circuit for a 12V solenoid or strike?
What can I do for the solenoid to go back to its initial position, when it doesn't have an integrated spring?

We need the door latch to return to the initial position to avoid having to dismantle the rocket to close the door during the controls.
Thanks.
PS: English is not my mother tongue, sorry for the mistakes.


texts: Is it possible to change the side of component and existing track and via in altium

texts:
almost everything is in title.
I have a existing routing track and via. I would like to change side of all component.
It's a 4 layer, so, in a perfect world :
top component goes to bottom layer

top track to bottom layer
bottom track to top layer
ground layer does nothing
and mid layer with routing is flipped.

for the the last 2 options, I'll understand if this is not automated.

Does an automatic option exist for this kind of needs ?

Thanks a lot !


texts: oscilloscope performance at slow <1 Hz signals

texts:
My question needs a little background, I apologize for this in advance.

I have slowly changing signals typically in the 0.1 - 1 Hz which I want to observe on a scope. I'm measuring things like slowly-changing temperatures.

When making any change on the scope front panel while observing slow signals here are the 3 types of scope responses I've observed:

The scope screen freezes for 6-12 seconds before it "comes alive" again and shows the moving trace. I have observed this behavior in a Rigol 1054Z and Keysight DSO-1002A.
Scope clears the screen and immediately starts a new trace from the edge of the screen. But no 6-12 second dead time. I see this behavior in an Instek GDS-2104E and an Instek GDS-1054B.
Scope immediately performs the front panel setting you made and simply carries on with the display at the new setting: No 6-12 second dead time, no blanking and restart of the trace. Just keeps going. This is the best behavior of course, and I see this on a Tek DPO-3034 and Tek TDS-2012.

My Question is: How do I refer to this behavior, that is, what do I call it? If I'm talking with an apps engineer at an instrument company and I want to know if their scope handles this scenario (slow signal display) according to options 1, 2, or 3 above, what do I ask??

I've searched here and on oscilloscope forums and I don't see this feature of scope operation addressed. Is this addressed in the spec sheet for a scope? What do I look for? I know most folks don't care much about how well a scope goes slow; we want them to go fast, right? ;-) But I would appreciate if anyone could point me to where I can find some answers...

Thanks all, and again sorry for the long-windedness.


texts: Overclocking an AVR microcontroller by using an external oscillator with higher frequency than uC supports

texts: What would happen if I would connect an external oscillator that has a higher frequency than the microcontroller (AVR) supports? Will it blow up, constantly reset, or what?


texts: Are film capacitors affected by DC bias?

texts:
After looking around, I have found quite a few things about how DC bias reduces effective capacitance for a ceramic, or electrolytic capacitor, however nothing seems to talk about the effect on film capacitors. I've found a couple of papers about film caps (such as: TDK Film capacitors - General technical information), and they mention frequency and temperature, but I can't find anything about DC bias reducing capacitance.

I have obviously checked the data sheet of the component I plan on using (TDK - MKT Film capacitors), but there isn't anything about DC bias in that (unless I've just failed at spotting it).

This suggests to me that they aren't affected by DC bias, but that seems a bit of a bold claim, and I can't see that stated anywhere.

Are film capacitor values affected by DC bias? If so, can anyone point me to some data about what the roll off is?

I am planning to use some film capacitors in an application with 48-60V DC across the capacitors and a ripple current around 30 amps.


texts:
I have a magnetically permeable element (98% pure iron) vibrating at 3-5Hz between two electromagnets (with iron cores) which is experiencing too much damping, presumably due to eddy current losses.

I know I can reduce this damping by constructing my vibrating element from thin laminated layers, or by using an electrically non-conductive material (ferrite?).

Is it possible to produce a damping reduction via control system? I'm imagining sensing the displacement/velocity of the core versus time and using this to somehow vary the power output to the solenoid coils.

If it's possible, I'd be grateful for details on how it would work.

The vibrating element is cylindrical with approx 35mm diameter. My end goal is to electromagnetically control the (negative) stiffness of a system without adding much damping.


texts: I'd like to run a 5v fan on 2 3.7v batteries

texts: I have zero experience so if this is a stupid question please at least be kind. It seems obvious that I couldn't run the fan on one 3.7v battery but then I'm not an electronics guy. So I was thinking I'd need to step down the voltage from 2 batteries? Would the fan run in 6v without burning it up? Is there such a thing as a 5v battery? Is need as long a run time as possible. I'd also need a switch for it but I think I can figure that out.


texts: Device with independent voltage and current

texts:
I have had some philosophical reflections about the voltage/current relationship.
Assume we are somehow able to have a determined fixed current AND voltage on a device.
This device could theoretically exist by having a Resistance and thereby a power dissipation that simply adjusts on the current and voltage.
Ie P(U,I) where U and I are independent variables, so basically a device whose U-I relationship can not be described by a function but covers the whole UxI space.
Now to my question:
Does such a device exist? Or is there something approaching this concept of independent U and I.

Sorry for bothering you with a problem that probably is contradictory by itself.


texts:
I am trying to figure out a simple, DC based way of approximating the internal resistance of the battery. I am familiar with the concept of instantaneous measurement, like here:
https://retrotechlab.com/how-to-measure-the-internal-resistance-of-a-battery/
But the problem with that is that this method does not specify the time after which the measurement has be taken after applying load. This makes me believe there should be a continuous method, in which we sample the voltage with load with time and draw a curve that would somehow help to estimate the resistance.
How can this be achieved?


texts: Can I Relocate Code on ARM Microcontroller?

texts: I am working on a project which includes an ARM microcontroller. At runtime, I want to load code from an SD card into program flash and then execute that code. My question is, since ARM code seems to work with relative jumps, whether it matters where in memory I am putting the code. If I can just compile my code and relocate it anywhere in the address space, this greatly simplifies the task. I am using TI Code Composer Studio with a GCC compiler toolchain.


texts:
I'm trying to integrate a video splitter for CVBS signal into my circuit. The Video amplifier I'm using is ADA4853 from Analog Device.

In the datasheet, there's a sample circuit for video splitter and I'm following that strictly.
At the output, the signal going through a TBU (R is around 7.5Ohm) and an analog mux (DG409LEDY-GE3) (Ron is about 17Ohm). Hence I'm matching the output impedance at R3 and R5 with the resistor of 50.5 Ohm. And because I don't have that value in house, I'm using  63.4 Ohm instead.
When I connect the output of the splitter to a TV, the video signal only shows up for a split second, then disappears, then shows up again. I tried to probe it with a scope and this is what's shown for the output signal

Here's what I have tried and failed to resolve the issue

Changed from x2 gain to unity again (remove R1 and R8 and short R2 and R6).
Changed various R3 and R5 to see if the impedance matching was the issue
Checked my control signal Amp1_EN and Amp2_EN from the microcontroller to see if they had any issue or not. And they were constantly on during the process

What I haven't tried is to put a 75Ohm at the positive terminal of the OpAmp. Other than that, I don't know what else I need to do. Is the issue I'm having related to impedance mismatch or it's something completely different? Any advice would be great.
Thank you


texts: Gate Voltage dropping under load condition

texts:
We have designed a custom board using the MABC_001_DP000L. We are Using this custom board to provide Biasing voltages to the QPA1022 Amplifier.
We tested the custom board with the following set-ups:-
SETUP-1:- WITH NO LOAD(Power amplifier)
Under this setup Gate voltage is being generated and can be varied by varying VR1(10K pot).
VDS is being generated and controlled by TTL input.
SETUP-2:- WITH LOAD(Power amplifier)
Under this setup, the Gate voltage is being dropped to -1.5V, because of this we are unable to set the Drain current but the Drain voltage is being generated.
For the reference find the SETUP-1, SETUP-2 and schematic snapshots..
SETUP-1

SETUP-2

SCHEMATIC- PAGE1

SCHEMATIC- PAGE2

I am unable to debug the issue. Can somebody help me in this?


texts: Op-Amp based schmitt trigger working in simulation but not in reality

texts:
I'm trying to build a simple schmitt-trigger to convert an audio input signal to an approximate square wave of the same frequency. The output of that will then be fed to a microcontroller to detect the pitch of the input signal.

The schematic of the schmitt-trigger part can be seen here.

It works nicely in a SPICE simulation.

However, when built on a breadboard, the circuit doesn't work as expected. The scope shows the input signal in green, op-amp output in red.

I built it with the resistor and capacitor values as shown, around a MC1458P Op-Amp. Supply voltage is 5V (power supply is a wall-wart, not a lab supply; however a PIC18F452 and LCD character display run without glitches on it). Actual input is from a rather hot guitar pick-up, so actual AC voltage on input should be similar to the simulation.

I'm a bit stumped, as I don't quite see what could be the problem. I've tried both amps of the same IC, no difference. What would be the best way to tackle this problem?


texts: Darlington pair base resistor value calculating

texts:
Let me know how to calculate the TR1 base resistor value in the following darlington pair
and also explain the role of pull up and pull down resistor in a circuit                 thank you.


texts:
I need to design a circuit to delay an input signal by a given amount of time (around a second, trimmable). The delay should be set through the use of passive components (resistors or capacitors). The input signal is basically a TTL level that goes high at a certain time, stays high for some time (100ms should be nice value), then goes back low.

I cannot use a micro or other programmable device because the firmware certification process is too expensive.

I realized a working solution that uses an RC network feed into a Schmidt triggered comparator (with a fixed voltage reference placed in input against RC voltage level). I'm not very satisfied with this solution for two main reasons:

the needed delay implies large caps that are pretty inaccurate;
the input signal high level need to last at least as much as
'delay';

Overall requirements:

delay duration 1 sec +/- 500 ms accuray +/- 10%
The delayed event should last for a reasonable time lets's say at least 100ms (and less than 200ms).


texts: I have a 240v/30a table saw and want to automatically start my dust collector, 240v/20a by means of a current sensing switch and relay. I have a 30a double pole relay w/ 24v coil. A 24v transformer 40va,  and a Dwyer series ccs current switch,  amprage sensing range 0 -200a  ac,  switch rating 1a @ 240 vac. My problem, in my very limited understanding, is the switch voltage in the sensing unit. Can i use these items. If not what do i need?


texts: Differences between oscilloscope, multimeter, and power supply voltage readings

texts:
So I recently got myself an oscilloscope and am trying to learn how to use it by starting with the basics, a circuit with a voltage source, and a resistor. When I set my power supply to 5V, the multimeter reads 4.995V and the oscilloscope reads 5.02V rms. I have found a thread already explaining how to tell which one is more accurate, but I am looking for more of an explanation of the other things at play here causing these to be different.
I figure the power supply is just giving an estimated reading, it was a fairly cheap one so I understand if it dent exactly output the voltage it reads.
After this picture I realized the different locations of where I am measuring might be a factor as breadboards tend to have undesirable effects to circuits. It didn't change anything.
What are some other possible sources to the discrepancy and what can I do to try and remediate it (already calibrated the oscilloscope), if anything?


texts: Is aluminium foil a good substitute for kapton tape when soldering?

texts:
Can I substitute kapton with aluminium foil when de/soldering a component onto a PCB?

I want to desolder a tiny surface mount button from the motherboard of a phone... There are a lot of similarly tiny components surrounding it that I do not want to damage with heat from the soldering iron. Can I use aluminium foil in lieu of kapton tape to protect these components?


texts: Arduino not outputting square wave with 50% duty cycle

texts:
I’m currently using an Arduino and my main goal is to output 2 signals from 2 digital pins. Pin 1 (D7) would output a 1 kHz signal with a 50% duty cycle and pin 2 (D8) would output half of pin 1's frequency.

I wrote some a simple code in Arduino that turns the output pins on and off but when I connect the outputs to the scope, they have a lower than expected frequency and a duty cycle of 66%.

I’m not sure about if it's a hardware or software issue. I think it might be software as when I was using a single pin, there was no issue.

Here's the code:

int channel_1 = 7;
int channel_2 = 8;
int time1 =492;
int time2 = time1/2;

void setup()
{

  pinMode(channel_1, OUTPUT);
  pinMode(channel_2, OUTPUT);

}

void loop()
{
  int state = 0;
  while(1)
  {
    digitalWrite(7, LOW);
    delayMicroseconds(time1);
    digitalWrite(7, HIGH);
    delayMicroseconds(time1);

digitalWrite(8, LOW);
delayMicroseconds(time2);
digitalWrite(8, HIGH);
delayMicroseconds(time2);
/*
//492 = 1Khz
//992 = 500Hz
delayMicroseconds(0.01);
*/
  }
}


texts:
I can't find out how this transistor fuse works. I know that the R1 is there because of voltage drop 0,7 V when the voltage on output is at its highest possible value. But I don't understand why there is the diode and  reverse biased. And my next question is how the transistors operate. How is it possible that there is output immediately after it is turned on, shouldn't there be an small current to open the T2? But the base of T2 is grounded.

Thank you

simulate this circuit – Schematic created using CircuitLab


texts: Which wires goes to appliance's ground and on/off switch?

texts: I have an electric hair trimmer whose power kept getting interrupted.  I knew the problem was in a particular spot in the cord because when it would bend there, the trimmer would lose power.  I cut the cord at that spot and discovered one of the wires inside the outer black insulating rubber was broken.  My plan was just to strip the outer black insulating rubber and re-splice the two wires together and then cover the area back up with a few layers of electrical tape.  Problem is I forgot to label the wires before I cut them and now I'm not sure which wires coming from the plug go to which wires that are attached to the cutter.  Is it that the wire belonging to the wider prong on the plug goes to the trimmer's ground and the wire belonging to the narrower prong goes to the trimmer's on/off switch?  What happens if it's wired backwards - does it just not work or is it dangerous?  Would I get electrocuted?


texts:
Is it more energy efficient to have active high or active low pins (I'm thinking shutdown, reset, active type of pins)? Pins that one would not expect to change very often so they will be in one state for a while before transition.

I'm looking at this from a hardware perspective, does a 1 or a 0 cause a greater voltage drop (ie less efficient). I would think this depends on if the underlaying hardware was implemented as a P (PNP, PMOS) or N (NPN, NMOS) based device.  After reading this post, it seems that if the hardware is PMOS it is better to have it be active low because when it is in a low voltage state the current flows therefore creating a voltage drop. And for NMOS circuits it would be better for it is be active high because that is when current would flow.

Is this a correct analysis?


texts:
I am trying to build a current limiting circuit using LM317.
The goal is to limit output current to ~150mA with 25V input and output at >20V.

I built the circuit according to ST datasheet, using the circuit diagram in Figure 13, page 12 as a base model, changed R1 to 120ohm, R2: 2200ohm, R3: 4.7ohm, in LTspice, I successfully simulated the current cut off at around 150mA with a maximum DC output at ~23VDC.

But the actual circuit is limited at a maximum DC output of ~10V.
What is going on?

EDIT: Turns out the Q1 diode I used was inverted. See comments from @BruceAbbott

Reference: ST LM317 datasheet, figure 13 on page 12


texts: Ways to communicate GPS coordinates to a central server wirelessly from a wearable device

texts:
I am currently looking at designing a wearable device for a client, which can communicate GPS coordinates back to some sort of central server (to then be sent out to other communicating devices such as mobile phones). The area of the tracking system would be known, and would be a confined space (let's say within a 3 mile radius).

I have no experience in this field and want to know the different options available for sending the GPS coordinates out from the device. The way I see it there are 2 options (that I know about):

Use mobile networks and some sort of SIM card to communicate the coordinates back
Use a local WIFI network and some sort of wireless communicator in the device

There may be other types of hardware that I know nothing about, hence why I have asked this question on here to get a bit of advice.


texts:
I have a device that I'm trying to send a trigger too, it has a 50\$\Omega\$ termination and suggests a pulse between 2-5 volts, ~1\$\mu\$s width. The way things are set up, the trigger needs to come from an AND gate (part # MC74F08N); however, the IC is expecting to drive a high-Z load. My thoughts to accomplish this would be to set up a circuit like this:

simulate this circuit – Schematic created using CircuitLab

I was wondering if this is the right approach, or if there is a better way to go about it?

If it is, would this inverter be suitable?

Edit 1

Reflections aside, my understanding of impedance matching with a detector is based on a simple voltage divider.

simulate this circuit

If the source is expecting to drive a high-z load (\$R_{\rm load} >> R_{\rm src}\$) then it would need to generate a 5V signal. However, if (\$R_{\rm load} \approx R_{\rm src}\$), then the source would need to generate something closer to 10V. My understanding is that a typical logic gate can't sync the necessary current to do this, and is, therefore, not suitable for driving a \$50\Omega\$ load. Would a MOSFET be a reasonable solution to this? To mitigate reflections, do I need to match the resistor values of the receiver and the load on the FET (i.e. does the 1k\$\Omega\$ resistor need to be a \$50\Omega\$ resistor in the first figure?)

Edit 2

Initially, I incorrectly stated that my receiver was expecting a TTL pulse. The device suggests approximately a +5V pulse, triggering threshold is ~1V.