texts: How to match this given circuit to a model for a simulation?

texts:
I have to simulate the electric field within a gas filled discharge gap generated by a radio frequency voltage generatio. The circuit, provided to me by the experimentators somewhat far away, is given in the second picture below. Numerical values: C1 = 22 nF,
R1 = 2 Ω, L1+L2 = 8 µH, C2 = 3.4 nF [transformer parasitic capacitance], R2 = 100 MΩ, R3 = 1 Ω, L3 = 100 nH. Moreover, it's  running at 1MHz, sinusoidal, about 10kV.

Now the program I use expects me to feed it the time dependend voltage curve and three values do describe the circuit: R, L, C.

  How to match the more complicated real circuit to the model? In any case, I'll have to plug in some values for the three parameters R, L, C eventually.

Lastly, I have no idea if it's of relevance, but I can post the text of the manual of the generator, which I also have, but which isn't really written in my language. I have no idea how the picture even corresponds to the question above. The letter symbols seem a little off. So if the following doesn't make any sense, then ignore it and just take the question above this at face value.

*"This generator simplified block diagram is presented on Fig. 5**' (the third picture). Clock signal generator, protect and control circuits are realized by using programmable logic device(PLD) Xilinx XCR32256XL. This chip configuration(and generation parameters) could be changed in-system by special JTAG (Joint Test Action Group)-programmer. Control signal are boosted by gate drivers and gone to the power switch gates. The converter is designed as half-bridge circuit using MOSFET(Metal-Oxide-Semiconductor Field Effect Transistor) switches and fed by voltage up to 400 VDC. Power oscillatory circuit, included elements C1 and high voltage step-up transformer having loss inductance L and parasitic capacitance C2, forms output voltage. In fire mode this circuit part can be simulated as two coupled oscillators; one of them consists of L and C2 and has resonance frequency about 1 MHz. As a result, output voltage will increase fast, have sinusoidal-like shape and reach breakdown level of load. After discharge gap breakdown, in limit mode, capacitance C2 is shunted by small plasma impedance and we can ignore its influence on power oscillation. Resonance of power oscillatory circuit in this mode will be defined by elements L and C1 and resonance frequency value will be less significantly than clock signal frequency(~1MHz). Output voltage will decrease a lot, its shape is changed to near triangle and power supply passes to limit mode.
Powerful 1.3 kW capacitor charging module is used to feed RF converter circuit. It has galvanic isolation from mains and adjustable output voltage. Control circuits and gate drivers are fed by auxiliary AC/DC and DC/DC supplies.
External synch signal is transferred by digital isolator, it has standard 50 Ω impedance, active level is “HIGH”(+5 Vampl). Control signal is inactive if input connector is not jointed."

I also don't actually know where the voltage they measure (which is supposed to be 10kV) is taken from in the circuit. Maybe the pictures plainly say it, but I can't read it.

Lastly, I want to post this, because I find it pretty amusing:

"High output voltage (up to 25 kV) and high level of electromagnetic interferences require highly experienced personnel to operate with generator. Careless use may be cause of electrical shock, health hazard, malfunction or even damage of nearby equipment."


texts: Need a minimal circuit to obtain 5V from discrete 5V to 20V (5V, 9V 12V, 15V or 20V) input

texts:
I have a Vin that can cycle between a set of discrete levels: 5V, 9V, 12V, 15V or 20V (a USB-C PD source.)
The Vin will be changed depending on the valves' voltage requirements. But, I also need a stable 5V Vout for a MCU.
If I simply feed the Vin into a 7805 or AMS1117-5V, then the Vout might be too low when the Vin is at 5V.
Inspired by Swagatam's "Zero Drop LDO Solar Charger" article, I came up with the following (see screenshot).
My goal is to have a stable 5V for different voltage levels of Vin. Vin should be at 5V most of the time. Vin can be a battery, so I would like to avoid buck-boost just to get the 5V for efficiency and heat considerations.
My attempt uses M1 to pass Vin as-is, when it is at 5v (G of M1 is controlled by D2, a Zener Diode with Vpeak of 5v). When Vin is higher than 5V, M1 will not pass, and M2 pass Vin to a regulator and output 5V.
Would the circuit work in practice? Why or why not?


texts:
Being a total newbie, I have been reading about logic gates. I got some doubts
about flip flops RS(with NOR gates or NAND gates). The flip flops are said to keep a previous state so:

Why an AND gate for example does not mantain its output through time? I mean, if the two inputs are for example 1, the output will be 1 and if I dont change the two inputs, when I read the ouput I will always have 1. So, this is not a way to memorize a value? I am missing something but I dont know what
How electronically speaking, I can read from an output of a gate to know If I have 1 or 0 in its output? I mean, with a multimeter I can read manually the output of a gate but how is done electronically, for example, for reading from an output of a flip flop?
Why is always needed the complemented Q? Its because for reading the Q value and know if I have 1 or 0 I have to read the complemented Q?

Thanks


texts:
I'm looking for a way to solve the following circuit

Without the voltage sources on the circuit, I would be using a simple Y-Δ transform. But I'm not sure how I should proceed with them on.

Which methods should I use ?


texts: Is there a practical way to create/inject some visible interference into a nearby AC mains?

texts:
I have this 230 to 6V rms step-down transformer. I use it to observe the mains voltage.

But recently I needed to create some interference or spike in the mains. So I first tried the following:

I used a filterless power strip. I coupled the transformer's primary side to one of the sockets of the power strip. And at the adjacent socket I plugged a heat gun. I sometimes very randomly saw some tiny fluctuation and that disappeared.

My approach was to see the interference from the nearby AC socket. What type of load would create a visible interference or spike? Or is there any other practical way to achieve this. I want to create a spike or interference by a load and observe that from a nearby AC socket via a scope and a transformer.

More over is there a safe way to observe the Line to earth or neutral to earth voltage on scope? I mean if I use the transformer secondary for the line can I connect the scope ground to the mains earth safely?


texts: Using a Raspberry Pi Zero W GPIO to unlock an electronic lock

texts:
I want to build a safe that can only be opened via an HTTP POST request. In order to do this the safe will contain a Raspberry Pi Zero W hosting a simple ExpressJS server that listens to these requests and uses rpi-gpio.js[1] to unlock an electronic lock[2].
This lock uses a 12V DC @ 2A power supply as the standby power, but it also needs a 12V signal to unlock electronically. I initially wanted to unlock it directly using one of the 3.3V GPIOs on the Raspi, but the lock would not unlock when setting the pin to 1. I tried several GPIOs, checked that they are functioning correctly, and they are indeed outputting the documented signal. I also tried using the 5V pin on the GPIO (that cannot be controlled) to see if 5V would be enough, but no luck on that as well.
The lock does unlock correctly if I feed the 12V @ 2A signal from the power supply (the same power supply I'm using to power the lock on standby) into the positive unlock input on the lock's logic board.
Since I can unlock it using the 12V @ 2A signal from the power supply, I want to use one of the GPIOs on the Raspi as a switch to open/close the circuit. Here's an idea of what I want to accomplish: https://i.imgur.com/AFq2Q6s.png (mirror: https://i.postimg.cc/MH2wLh8m/untitled.png)
I was thinking about using a ready made IRF520 MOSFET board with a reverse emf protection diode across the output to protect it from the voltage generated by the lock coil on power off.
My questions are:

Is an IRF520 suited for this job?
Which diode should I get?

Any insights are appreciated. Thanks for reading.
[1] https://www.npmjs.com/package/rpi-gpio
[2] https://www.amazon.com/Electric-Electronic-TPEKKA-Fireproof-Doorbell/dp/B074Z55WWG/ref=sr_1_110?dchild=1


texts: Error: L6218E: Undefined symbol LCD_X_Config in Keil

texts:
I encountered a problem working with the EMWIN package in keil, this error message:

. \ Objects \ test.axf: Error: L6218E: Undefined symbol LCD_X_Config (referenced from C: \ Keil_v5 \ ARM \ PACK \ Keil \ MDK-Middleware \ 6.2.0 \ emWin \ Lib \ ARM \ GUI_CM3_L.lib (gui_core.o ))

Application code is available at the following link:

https://www.4shared.com/s/f4miYaVFigm

you can see the error here:

Please give guidance if possible.
Thanks


texts: adding two 64-bits number with m-bit carry ripple adder and multiplexer, a questions?

texts:
I ran into a question from computer architecture class. The professor says that for adding two 64-bit numbers A and B we use m-bit carry ripple adders and multiplexers such as following:

and that for a given m, say 8, we get the minimum amount of delay. Why is such a design faster?


texts: This is a long shot, and may come under fire as not being EE-enough of a question for this site, but what conditions will result in a PowerPC processor  (e.g. Freescale 7448) taking a jump to address 0xfff00800? My reading of the family reference manual suggests this is a Floating-Point Unavailable Exception, but in talking to people it's been suggested this is a common place where programs go to die on a bad instruction decode. Assuming that's accurate is there any way to recover what the errant instruction was via poking and prodding with a JTAG debugger?


texts: In heterodyn receiver circuits, why is the LO not chosen to match the target frequency?

texts:
I'm trying to design a device that detects motion using sonar. I'm basing it on a common superheterodyne receiver like this:

Now from what I've read, in radio audio receivers the local oscillator is chosen to be a specific offset from the target frequency, such that the difference is equal to a known value, such as 452kHz.

Why don't they just match the target frequency instead?

I'm planning on simply feeding my output signal into the Mixer as the LO in my sonar. Is there any reason for me not to do that?

This is the article about superheterodyning that my question is based on:
https://fas.org/man/dod-101/navy/docs/es310/superhet.htm


texts:
I am coming from Autodesk Eagle and I am new to Altium Designer. I just have a quick question. In Eagle I was able to have a lot of different libraries available in my library manager and whenever I entered something in the search bar, it searched for the component in all the available libraries. In Altium I added a couple of file base libraries to my component panel (.intlib and .dblib), some from the internet and one from me. When I use the search bar on top now, it seems to me that the search only happens in the library that I have currently selected. I tried it out with a couple of components.
I am aware that there is the manufacturer parts search that goes through Altiums cloud database and the file based search where I exactly have to define of the fields, but that is not what I mean.
Just wondering if there is a search that goes through all my file based libraries and that tries to match whatever I type.


texts: How can i reduce the offset error of the error amplifier of my PWM generator?

texts:
Ls,

My PWM generator has an offset error which gives my whole circuit an error above the allowed 0,1% of full scale which is 5V. The allowed error is 5 mV.

This error is noticed when i graph my input and output and use the least method sqaure on it.

here is the graph where excel did the calculation itself.

I need a full PWM from 0% -100%, 0-5V.

These are my values of my error amp:
R1 = 30K
R2 = 30K

R3 = 33k
R4 = 30K

Before i used the above value for R3, it was also 30K and used the
underneath formula to calculate my offset with Vref 2,5V i get:

Vo= (1+ (R4/R3)) (R2/(R1+R2))Vref = 2.5V

When i calculate it witg R3 33K i get :

Vo= (1+ (R4/R3)) (R2/(R1+R2))Vref = 2.2V

My problem now is that when i use R3 = 33K for more "current or voltage sensing"
my circuit is able to PWM from 0-100%, but with an error above 0.1% of full scale.

When i use R3 = 30K my circuit is not able to PWM from 0-100% in the range from 0V-5V. It than only needs around 0,5V to go from 0% dutycycle to 50% en 0,5V to 100%.
in total it only needs 1V to go from 0% to 100%.

i tried to research the error amp, read numerous pdf's but i didn't get any wiser on how to solve this.

I will reiterate my question.

What do i need to change in order to have a full PWM from 0-100%, 0-5V, with an error thats is below 0,1% of fullscale (5mV)?

My professor gave me a hint that i needed to something special with Vref.

Do i need to change something about Vref or something else ?
I hope i am clear in my explanation and question.
I've been at it for a while, i hope someone can give me the solution!!!

Thanks in advance.

additional info.
i cant have two or more links
I removed the orginal schematic for my own so you can see what i have done.
if you want to see the original, you can find it as an pdf called slau508.
My use of PWM generator is slighly different than the slau508.

My schematic and its values, hope you can see it.
I forgot to give additional information because i was focusing on the error amplifier

But my PWM is 1KHz, and the values on the sheet is what i had calculated for 1KHZ.
I use a Buffer to connect my agilent Multimeter on to measure my average output (Y)


texts: A problem with designing a time register

texts:
I'm on a project where I need to design a time difference register. In a time register the time information is first converted to voltage, which is stored in a capacitor. Later, when we want the register to output, we use this voltage to generate two signals whose timing information is the same as the input signals'.
The circuit below is part of the TR circuit,  where the bottom inverter is supposed to produce a low-to-high signal as soon as the voltage across the capacitor discharges to exactly 0V (a full discharge of Vc), and the top inverter is supposed to produce another low-to-high signal right at the time the capacitor starts to discharge (or when a RegOUT signal arrives).

The circuitry that charges C is not shown in the image. At the falling edge of the controlling signal RegOUT the capacitor starts to discharge through the resistor R. In order for the time register to give a correct output the capacitor must discharge fully before M1 turns on. I cannot directly connect the analog RC circuit to the inverter, since when Vc=0V M1 has already turned on, which produces an earlier signal at the output. This causes some of the information stored as voltage to be lost. Therefore we need to keep M1 off for as long as it takes for the capacitor voltage to drop to 0V. But how?
Note that I do not want to use a comparator to switch M1. I want to use as fewer transistors as possible to implement the function. Any idea is very welcoming!


texts: Difference between TGC (Time Gain Compensation) and AGC (Automatic Gain Control)

texts:
I'm a french student who work on a portable echograph for the "echopen" association : http://echopen.org/index.php?title=Main_Page
I'm working on the analog part which is composed of theses parts:
* Generate a high pulse voltage
* Integrate a T/R Switch in order to protect the signal process circuit
* Use an amplifier
* Use a filter
* Integrate an envelope detector
* transmit the signal to a redpitaya

I would like to use an amplifier with a control on the gain (the third part). I searched the circuit about the AGC (Automatic Gain Control) but on internet and from some people I heard about a TGC that is used in the medical domain but I can't found any circuit and I don't find the difference. Could you help me please?

Thank you,

Farad


texts:
I came across a rather simple looking circuit of a voltage divider circuit. It has 5V at one terminal and 0V at the other terminal. Let's start by connecting two 1K resistors in series between these two terminals. The voltage at the center is found to be 2.5V(using, say, a Multimeter). Increasing the resistor values to 1M gave the same result. I keep on increasing the resistance values till I get the series resistance equivalent to air and then I remove the physical resistances, leaving the air itself as a resistance. If I now measure the voltage midway between the two terminals I should be getting 2.5V but I do get nothing(0V) instead! Why? What other factors are in play here?

EDIT: Thanks for pointing out the incapability of meter to measure this voltage. My meter might be incapable of measuring this voltage, but is it really 2.5V in the mid over there?


texts: Problems with a RFID reader from SparkFun

texts:
I am hoping someone here can help me.

I am having trouble with a RFID kit I bought from SparkFun. I purchased the USB RFID (SEN-08852) with the RFID Reader ID-12 (SEN-08419) and some RFID cards.

When I hook up the reader or try to use it, it goes into a constant "read" mode. The green "Read" LED flashes constantly and the buzzer clicks with each flash. This will not stop until I unhook the USB cable.

I have found that if I connect the USB part without the reader and then connect the reader to the board, the device works properly for the very first RFID card (and I can read the serial output using PuTTY). As soon as the first card is read, it starts the read loop again.

Any ideas as to why this is happening? Is my device broken, or am I just doing something wrong?

I have Windows 7 x64, and I did not install any drivers when I hooked up the reader - Windows downloaded them for me.

Edit: Apparently the port I was using wasn't providing enough power for the reader - once I tried a powered hub (and eventually another port on my laptop), it was working flawlessly! I now have no problems swiping a card more than once.


texts: Fixed voltage regulator for simple circuit

texts:
I want to use TPS799 for an LED driver circuit.
Here is the datasheet: http://www.ti.com/lit/ds/sbvs056k/sbvs056k.pdf

I am assuming that input will be 5V through power jack on the board, and I will be driving an LED , after regulating the voltage to 3 V.

By what I understand, I don't need a capacitor at either, EN or NR terminals.

I am I understanding its usage correctly? And I am not sure how to have the output to 3 V. I am very new to idea of using a regulator so any help is appreciated.


texts:
My understanding is that if source resistance is low, a bipolar op amp has 10dB less noise than a JFET. I prefer the JFET op amps because the input offset is so low that you can eliminate coupling capacitors and associated componentry.

So is there a bipolar op amp that has a low enough offset that stages can be DC coupled? Even when using a large pull down resistor on the + input a for high impedance input stage?

This would be for audio BTW.

UPDATE: The following circuit is identical to Figure 14.1 of Small Signal Audio Design by Douglas Self minus the output cap and missing output load resistor which are 47uF and 22K in the book.

The next circuit is the circuit that I'm planning to actually use and is largely a combination of 2-3 circuits from the aforementioned book. I believe this circuit shows the impedance environment surrounding the 200uF cap that might be eliminated if a suitable op amp were to be identified. Vertical lines that run off the bottom are to ground.


texts: V CE in the emitter follower configuration

texts: Is it true that voltage between collector and emitter is 0 in the emitter follower configuration? (We intentionally use the saturation region of the transistor)?


texts: Need help designing LiFePO4 BMS disconnect alarm

texts:
I need help designing an alarm for a 12v LiFePO4 + BMS system. I am using an off the shelf BMS. The BMS has internal FET switching which may disconnect the battery for a variety of reasons to protect the battery from damage (e.g. over/under volt, low/high temperature, over current). I would like to build a simple buzzer/beeper circuit to provide an audible alarm when the BMS fires its protections. I would like this alarm to be very reliable and have very low power consumption.

Conceptually, I think this can be done using a normally closed (NC) relay driven from B+ and P-. When the BMS fires and goes open-circuit, the relay would close and the beeper would sound. I might power the beeper from the unprotected battery (B+/B-) or a secondary battery.

In order to keep power consumption extremely low, I think I need to use a solid state relay. I gather that's a "form-B" SSR. The beeper will have very low draw - perhaps less than 25mA.

I need help selecting a reliable SSR for this application. And a realiaty check on this design. Is this the way to go, or is there a simpler way to do this.

Thanks!

5-Apr-2020: Expanding the scope a bit... this is for installation on a boat, where there are many "loads". One of those is a large inverter whose DC current is too large to put through the BMS - and will be bypassing the BMS. But the inverter has remote on/off switch terminals. So the BMS can simply command the inverter off when the BMS trips. This would be a NC circuit that needs to go open circuit on a BMS trip. This circuit as well has a very low amperage requirement. So considering these together, when the BMS trips and goes open circuit, I want to close a circuit on a beeper to raise an alarm, and i want to open a circuit on the inverter remote control terminals to shut the inverter down.

10-Apr-2020: I've explored @Russel McMahon's solution in Circuit Simulator. I've used 1M resistors for R1 and R2. I added R3 to provide some voltage to drive the MOSFET when the load is disconnected. And moved the opto to reverse it's logic (load off when the BMS trips). This seems to work nicely!

Circuit Simulator


texts: Transistor which opens circuit, reverse transistor

texts:
I'm wondering if there is a transistor which, when a voltage is applied to the base / gate, opens the circuit instead of closing it. If there is not, how would such a configuration be created?

EDIT:
Okay, here's some clarification. I have a circuit set up like  this:

Motor-------------Nmos-------------Gnd
                   |
                   |
            voltage from IC

Currently, I am supplying a voltage to the gate of the nmos from my arduino and controlling the motor that way. I want to replace the nmos with something which will perform oppositely. As the voltage increases on it, the current between motor and gnd should decrease.

I hope that helps clarify.


texts:
I've read this article about driving gimbal motors.
I have some questions about these equations:

I don't understand what "ψ" and "Lω" means and generally i don't understand how to calculate the equation. Can someone explain this to me?

In this equation i don't understand what how to calculate d/dt, and i don't understand what "ψ" and "Rω" is.


texts:
I'm interested in trying to estimate the worst-case error when using a particular DFT implementation (CMSIS) and an ADC and voltage reference with known error bounds.

I think that I can work out the math itself without much issue, but I'm not clear what "worst-case" looks like.

I have a vibrating string with constant fundamental harmonic frequency (like a guitar string) per "pluck" - the frequency can change from pluck to pluck though.  The fundamental frequency should have the highest magnitude by a good margin, so higher-order harmonics and outside noise should not present too much problem.

So if I assume that my ADC is, say, +-2 LSB at 2kSamples/s (using a sample size of 1024 points with a perfect voltage reference), and I look at a simple sine wave of representative frequency, what would the worst case look like?

Would it be if the ADC alternated between +2 and -2 LSB on each measurement?
Or maybe it would "throw off" FFT more to have every measurement be +2 LSB for a certain time then all of a sudden be -2 LSB?

Clearly (?) there is some point where you want to ADC measurements to be off by its extremes, otherwise its just a translation of the wave.

Has anyone seen a resource for figuring out this kind of thing before? Or is it better just to run a few thousand examples and do a statistical analysis to determine likely bounds?

My motivation is to discover if I can know a priori if I should go with an ADC of less precision and accuracy, i.e. if a certain ADC is overkill.


texts:
Does anyone have any experience using zero-ohm resistors in an RF signal path to select antennas? I've typically used RF switches for this purpose, but that's also when it was necessary to allow the antenna selection to be changed "in the field". But for cases where the antenna selection is a manufacture-time option, I'm considering simple zero-ohm resistors (i.e. populating one or the other to complete the particular signal path to the antenna).

Of course using zero-ohm resistors for this sort of thing in a digital circuit path is a no-brainer, but I'm specifically interested if there is anything I should watch out for since this is an RF path (two separate paths: 868-915MHz and 2.4GHz). Can I treat the zero-ohm resistor as essentially being part of the PCB trace, or will this cause problems?

PS - The two antenna path options are an on-board ceramic antenna and an off-board connector. The zero-ohm resistor would be a surface-mount component.


texts: Will it hurt a non-powered power supply to see 12/24V on the output?

texts:
For an RC (mostly LiPo) battery charging setup I've got a 48V Meanwell AC->DC PSU supplying power to the charger. I'm considering simple ways to power the charger either by this PSU or directly by a 24VDC deep cycle battery bank. The charger is smart enough to have profiles that have limits so I can be sure I won't draw too much from my chosen power source.

Off the top of my head, one simple way would be to just tap into the lines that run between the PSU and the charger, and connect the 24V battery there. This is obviously a really bad idea if the PSU was on, but given my use case the whole setup will either be in a location where AC is available or it'll be in a location where only the deep-cycle batteries are available.

My question is: Will it harm the PSU or be dangerous if 24VDC is seen on the PSU's output terminals when the PSU has no AC on the input side?


texts:
I'm designing a drone to use a relatively new form of propulsion, electrostatic fluid propulsion, which requires extremely large voltages (in the order of 10-100kV) running through a wire to ionize the surrounding air which is attracted to a positively charged collector below.

The issue, however, comes from the power source. I've never worked with voltages of such a high magnitude before, and even though I'm going to limit the current to infinitesimal ranges, I want to be absolutely certain that there is no chance of injury or death if someone were to come into contact with a HV wire. As far as the power source goes, I'm running current from a standard house outlet (120V) through a rectifier, and then a 4-stage transformer, wherein the voltage is stepped up by a factor of six in each stage. To martial the current levels, I'm using 15 1MΩ resistors in series, for a estimated current of 1mA (and a total power draw of 150W).

Is that combination of amperage and voltage is particularly lethal? Is there a better way to step up the voltage or martial the current?


texts: Is there a standard definition of LPF stop band starting point in terms of dB attenuation

texts:
Below illustrates a LP filter bands:

I can say that the transition band starts at -3dB.
But the transition band ends at some point and there the stop band starts.
In this example it is -70dB they call this Stop Frequency above.

It seems that the transition band always starts at -3dB, but is there a consensus about the location of the beginning of the stop band(end of the transition band)? How is that quantified?(In the above case -70dB. Is that always -70dB? Who decides that? Or is this something about mathematical reasoning?)


texts: Implementing a simple two door security system

texts:
This is a very simple task and I understand most of it (already has a solution), but there are some things which I need clarification for.
The problem is: There are two doors (one behind the other), and a card reader next to them. The corresponding door will open if the card is inserted into the reader and if the correct password is typed on the reader's keyboard. The truth table for the card reader looks like this:

To unlock the DOOR1 you have to type one of the correct passwords, which are: 101 and 110. To unlock the DOOR2 you have to type one of these passwords: 101 or 011. If the wrong card is inserted or the wrong password is typed, the alarm will turn on.
I have to implement this using only standard logic gates.
The problem lies in this truth table below (which is a solution). I don't understand what X, Y and Z are.


texts: How should I wire this sensor and board for rugged experimentation?

texts:
I want to use this Hall sensor on my bike for some experiments. At my desk, I've simply been using the quick connector and loosely connecting the wires to an Arduino featherboard to write the software and test.
I'm planning on improvising a solution to mount the featherboard and sensor on the bike. My question is, how should I wire it? I'm a total beginner at electronics engineering, so looking for tips and tricks on good ways to do it. e.g. Barring any better ideas, I'm planning on continuing to use the quick connector on the sensor side, then cutting the excess wire and soldering the wires to the appropriate connection on the board.
I'm ok with permanently connecting it, although a reusable solution would be even better.


texts:
I'm currently designing a PCB with inter-board interconnects - I figure that right-angle 0.1" headers will be sufficient. I'll be "mass producing" the boards (only a couple of dozen...) so I need them all to be the same.

But it turns out that some of the pins will be optional; that is, configurable at construction time. So I want to design in some PCB pads that can be quickly soldered across to implement - or not - the required functionality. I've seen pads that look like -CD- or -Pd- (imagine the 'holes' in those letters filled with copper, just waiting for a solder bridge...)

I'm using Eagle (7.6.0) and thought there'd be a "component" that could be added to the schematic, and therefore the PCB, but I can't find anything. Am I not looking correctly? (I don't know the search term.) Or do I have to learn the whole "solder pad" system of Eagle too?


texts:
Being a newbie hobbyist, I have a hard time finding a certain part or how to find a replacement.

I plan to control a few electroluminescence wires via a microcontroller. The tricky part about these is that they need to be driven by "higher" voltage (about 60V to 120V AC) and frequency (somewhere between 400Hz and 2kHz, it seems). There are several possibilities here but to me the most appealing one is a nice IC with an I²C interface that can drive up to four wires/panels: Maxim MAX14521E. Getting that isn't the problem…

But it requires a tapped inductor for operation. The datasheet mentions the following values: 2.3μH/115μH, 1:7 ratio (ISAT = 0.7A, RS = 1Ω). I wasn't able to find such a component (or any "tapped inductor" for that matter) on the typical electronic component shops, which undoubtedly is due to me not knowing what kind of "aliases" such a component may be known as or how to search for it. As far as I've understood, it's a single coil inductor with an additional contact "in between" both ends but I'm not even sure about that.

There's a part specifically made for the MAX14521E which is often used (it's used in Maxim's development kit and also on other boards that I've seen using this chip): the Coilcraft GA3250. It's characteristics are 1.9μH/112μH, 1:8 ratio (ISAT = 0.7A, RS = ?). Unfortunately, it's only available via the manufacturer's homepage with ridiculous shipping fees and takes a whopping 9 weeks delivery.

So I need to find a different part that does the job but I have no idea how to actually search for one. What are the common names for these parts and how do I find them in the large electronic component online shops? I lack the vocabulary and knowledge to actually do a search for similar component and would like to know which terms and parameters (for the parameterised searches) are going to help me find a replacement.


texts:
i'm designing an Effects pedal, (for guitar, mic, bass, etc.) to be used on stage.

The effect has several stages, which none of them really matter to this question except for a high gain stage.

I'm deciding the kind of supply i'll use for this pedal. My idea is to keep it simple and small so i want to do it with an external DC supply, but here comes the trap.

There's a tube involved in the circuit, typical 12AX7 double triode, so the heater already needs 12V - 150mA.

Ok, so i think of a typical 12V - 500mA supply to be sure BUT! i want to use 20 to 30Vdc for the rest of the circuitry. I wanted to avoid using a transformer with several windings, so i came up with this:

I though of a simple solution with a step-up built with a 555 timer to double those 12Vdc, o even go an get a simple switcher IC. Found this:

I chose the 555 circuit because of its simplicity, its cheap dont need to supply a lot of current (<20mA), and because i don't have a switcher IC at hand at the moment.

The circuit worked like a charm (changed C2 and C3 to 470uF, and changed R1,R2 and C1 to 4k7, 22k and 390pF to work at around 70kHZ, way above audible frequency and low enough to use simple components like 4148 diodes. (besides, if R1 was 100ohms like circuit says it will probably be set on fire).
I went ahead and built the pedal on a breadboard.

It worked pretty good overall except for (what every one here already guessed) ... NOISE. Half way Gain stage pot, amazing amplified supply noise.

Measures i took to solve the problem:

Right next to the output of the supply, a Fe Bead and then a passive double stage low-pass filter (with a cutoff freq. of 0.3Hz).
On every IC Vcc pin, a small 100pF cap to ground.

I still get noise with the gain set to 1/2 and above (a lot less than before, you could actually use the pedal now, but i HATE noise).

After all this explanation i want to ask two questions:

First: Can i possibly eliminate this kind of noise when it comes to a switching supply for audio, maybe with a better filter or something with simple components, or do i have to go running back to the old transformer+linear regulator for this kind of application? (which i really don't want to do)

Second: When it comes to a using this kind of devices on stage, usually there are a lot of sources from noise (electromagnetic, ground loops, etc..).
Is a Transformer+Regulator more or less immune to this kind of noise than a switching supply? Please explain

Thank you, regards.

EDIT:
I lowered the switching frequency as adviced by @Jhon D. Its working at 30kHz. The noise came down just a little bit, bit still it appears.
To clearify some comments, the diodes are 1N4148, and transistors are BC337 and its complement. So they couldn't be the ones causing the noise, at least not in regards to the working frequency.

I give you two pictures, first the 24Vdc rail. Hellish

Now the Output of the pedal, with NO input (input is grounded), Volume = Max, and Gain = max.


texts: Will a CAN bus also work for on-board communication, without twisted pair cabling, between 2 or more microcontrollers on the same PCB board?


texts: I want to implement an Z transform Equation in C (with saturation limits)

texts:
I will start from the beginning . I had a PI controller with saturation limits (+4 and -2) whose Laplace equation is as follows (0.05s + 0.5)/s. Sampling time of 40 micro seconds
Using Tustins method I have converted this equation in the Z domain , which is
F(z)=(0.05001 - 0.04999z^-1)/(1-z^-1)
If I am not wrong the output equation after taking inverse z transform is =
Y(i) = 0.05001U(i) - 0.04999U(i-1)  + Y(i-1)
Saturation limits : if output is greater than 4 the output is 4 and if output is less than -2 then output should give -2
here Y(i) is output ,U(i) is input and U(i-1) is previous input and Y(i-1) is previous output
I am assuming the previous input and output value should be set to zero initially
I need to implement this equation in C and don't know how and confused


texts: How can I electrically switch between taps on a transformer?

texts:
If I have a transformer with X number of taps on the primary side, and I have a fixed input voltage that I'd like to change the output from.

In its lowest state the two outer taps are active and the coil is whole, this is a lowest voltage output in secondary. By switching to the next tap from one end the coil is effectively shortened and the output voltage is higher. This goes on for however many taps there are.

Obviously this can be done with an array of relays, or alternatively a different set of drive transistors on each tap.

What is the best (cheapest/simplest) way I can achieve this? All ideas welcome.

Specs:
~100-200V
~20A


texts: Improving RTD Sensor filtering and readout

texts:
For an application a temperature sensor is required. an accuracy of around +-3 degrees is acceptable.

For cost reasons I have chosen for this RTD. The sensor is sampled by a 12 bit ADC of an Microcontroller. The RTD is placed in an wheatstone bridge with a regulated 3.3v supply (looking at the supply with an scope I did not find much noise/ ripple). The Wheatstone Bridge is connected to an MCP6N11 Instrument amplifier.

simulate this circuit – Schematic created using CircuitLab

The RTD is mounted on a separate board with about 50cm of wire, which runs through a noisy environment. Therefore the filter stage is placed between the bridge and amplifier.

The desired temperature range is between 50 and 200 Celsius. The gain of the amplifier is set to 15, and is supplied by a single 3.3v supply.

Unfortunately, the measurements are constantly off by 30 to 50 percent. As well as there is still some noise sneaking through the filter. The amplifier is connected directly to the 12 bit ADC.

What can i do to improve this circuit?


texts: Whats the usage of logic buffer( NC7SP126) in this design, how to troubleshooting it?

texts:
I am troubleshooting my devices which are subjected to battery drain issue. I  have never worked with this buffer chip before. Can Anyone can tell me what is the purpose of adding this chip to the Microprocessor? Will malfunction of this buffer chip affect battery life of the design?

The design used 3.6V lithium battery. MCU is MSP430F155, operate under 2.8V.

Any input will be appreciated, Thanks!


texts: Testing an automotive relay with a diode

texts: How is it possible to test an automotive relay to determine that the flyback diode is not shorted or open?


texts: I know that IZT is the test current at which the zener's reverse voltage is established. But what is IZ? (So I can enter the characteristics of one in CircuitLab.


texts: EEPROM Reading/Writing without Use of Programmer

texts:
I am designing a small password based door lock project which is fully made from logic gates and ICs without the use of any sort of programmable devices(it is a simple university project for the Logic Design Course).

And as assigned to me, I need a non volatile memory for this lock in order to store the password, return its value and rewrite it whenever I want. I first thought of EEPROMs but many told me that an EEPROM should be removed from the circuit in order to be reprogrammed which is not acceptable_the memory of the circuit should stay inside the circuit with respect to my project. In addition I was told that the EEPROM is only reprogrammed through a PROGRAMMER.

Here is my problem:
How I could implement the EEPROM so that I can read/write to it data without removing it? that's to say my own circuit should be able to read and write to the EEPROM without using a PROGRAMMER .
So is this possible? Is there a way for such implementation? Or should I think of another non volatile memory other than the EEPROM to store, read and rewrite the password? If there is another way, please let me now.

Any help is appreciated. I am really a beginner.


texts: Is the FET gate resistance counted on the RC time constant?

texts:
As I understand, a logic "1" output to an input of another IC can be modeled like this :

simulate this circuit – Schematic created using CircuitLab

with C1 representing output capacitance, R1 the Rds(on) of the internal FETs of the "emitter" IC, C2 representing the input capacitance, and R2 representing the resistance at the gate of the "receiving" chip.
(all values are sample values from a few datasheets; R2 is extrapolated conservatively.)

But, when trying to calculate the time for the gate to receive the "1" (which I supposed to be the instant at which the voltage across C2 is equal to the threshold voltage, as, if it were based on the voltage across R2, it would be immediate, and I know that the RC time constant does cause problems at high speeds, so it can't be that.) (R1 is not taken into account to facilitate calculations)

$$ ESC = (\frac 2 5 * 10^{12} + \frac 2 7 * 10^{12})^{-1} = 1.25*10^{-12} F$$
$$\tau = 1.0*10^7 * 1.25*10^{-12} = 1.25*10^{-5} s$$
$$Q(t) = 1.25*10^{-12} * 5(1 - e^{{-t} / \tau})$$
or : \$ V = \frac Q C\$
so, solving this equation for t should do :
$$ 3.5 = \frac {Q(t)} {2.5 * 10^{-12}}$$
$$ \Rightarrow 3.5 = \frac {1.25*10^{-12} * 5(1 - e^{{-t} / ({1.25*10^{-5}})})} {2.5 * 10^{-12}}$$
$$ \Rightarrow 3.5 = \frac {1.25 * 5(1 - e^{{-t} / ({1.25*10^{-5}})})} {2.5}$$

$$ \Rightarrow 3.5 = \frac {5(1 - e^{{-t} / ({1.25*10^{-5}})})} {2}$$

$$ \Rightarrow 7 = 5(1 - e^{{-t} / ({1.25*10^{-5}})})$$

$$ \Rightarrow 2 = -5 * e^{-t / ({1.25*10^{-5}})}$$
$$ \Rightarrow \frac 2 5 = -e^{-t / ({1.25*10^{-5}})}$$
$$ \Rightarrow \ln (\frac 2 5) = -\frac {-t} {1.25*10^{-5}}$$
$$ \Rightarrow -1 * \ln(\frac 2 5) * 1.25*10^{-5} = -t$$
$$ \Rightarrow t \approx -0.00001145363 s$$

But that is obviously wrong. If the "typical" propagation of the signal between ICs, why make ICs who have propagations times in the nanoseconds, as the carrying of the signal is far more restraining than the actual "compute" time ?

I'm sure I've made a mistake somewhere, maybe in my assumptions, certainly in my equations, the result being negative. What is it ? And what is the correct way to think about input/output capacitance ? I think it has to do with the FET's gate resistance, but I'm not sure...


texts: Does ISA bus (or PC/XT bus) have some means of arbitration to resolve bus contention?

texts:
My understanding of ISA bus is that the CPU places an address on the bus and any expansion card is free to respond to that address by taking control of the data bus. I presume that tri-state buffers are used. So my question is, are there any arbitration mechanisms in ISA and/or PC/XT-bus to prevent two cards from responding to the same address? My understanding of tri-state logic is that if this were to occur the tri-state buffers would likely get fried. Perhaps there was some sort of lesser mitigation to prevent such damage in the case of contention?

Looking online I see no mentioning of arbitration or damage mitigation, and yet I also know no stories of people with fried ISA expansion cards due to address overlaps.


texts: How to delay a "not gate oscillator" to make it run at a desired frequency?

texts:
I want to blink an led(0.75 seconds on and 0.75 seconds off) repeatedly. I was thinking of using an idea from a book called "But How Do It Know" by J. Clark Scott. A part of the book tries to explain how to make an oscillator to use in a computer(The book tries to teach the reader how to make a functioning computer)but doesn't really go into the details about how to change the frequency etc. A schematic to show a square wave generator is provided in the book. Here it is(Diagram 1):

simulate this circuit – Schematic created using CircuitLab

The author says that the output will be too "fast" to be used for anything. He then says that to slow it down you have to lengthen the wire like so(Diagram 2):

simulate this circuit

This is obviously over simplified and impractical because you can't extend the wire for a long length without running out of space. How can you "slow down" the output of the circuit in Diagram 1 to produce a desired frequency(0.75 seconds HIGH and 0.75 seconds LOW). Here is a clock digram of what output I want(in hertz I think this would be 0.75 Hz, Correct me if I am wrong):

simulate this circuit

My question is: How do I slow down the output of the "not gate oscillator"
(Diagram 1), to the desired output of(0.75 seconds "on" and 0.75 seconds "off") and is this frequency 0.75 Hz?


texts:
I found this(link below) video on Youtube, it's a RGB stereo Vu meter based around (obsolete) LM3915 dot/bar display driver. Since author didn't provide schematics and I want to build something similar, I'm curious how to do it. But, I'm curious more about what dot/bar display driver does in whole story?
My idea is to use Y 3.5mm adapter from PC, then somehow split signal into low, mid and high tones, amplified them and what now? Can someone explain what dot/bar display driver does?
Video:
https://www.youtube.com/watch?v=dIYQ0l-WAZI
Thanks!


texts: Is difference amplifier a differential amplifier with a voltage gain of one?

texts:
I see these two terms are used in same context.
But what is the difference in meaning?
Is difference amplifier a subset of differential ampfier with unity gain? I couldnt find a duplicate question.


texts: How do I reduce the DC output voltage of a power supply?

texts:
I have a DC power supply which takes 240V AC as an input, and steps down to 30V AC with a 200VA step down transformer c/w rectifiers, but the output voltage which I get is about 43-44V DC. The voltage which I need to get in the output is in a range of 32V DC to 33V DC.

How can I reduce the output voltage down from 44V DC to 33V DC without changing my transformer, considering that my current requirement is about 5-6A?


texts: Why the television manufacturers (Samsung, Sony, LG, so on) exceed the voltage capacity on led strips (backlight) on TV's?

texts:
I dont understand why manufacturers always exceed voltage to backlight tv (led strips). For example i'm fixing a TV with some led burn out.

This is the backlight :

There are two LED's strips. Each strips have 9 leds. And each LED consumes 3 volts. ALL LEDS AND STRIPS ARE IN SERIE.

So it would be : 3 volts * 9LEDs * 2 strips = 3 volts * 18 LEDs (2 strips are in serie ) = 54 volts.

Just with 54 volts is enough to "on" the backlights.

So why in SMPS of the tv , when I test the voltaje to backlight,  this one ( the SMPS )  delivers 133 volts DC.

It's 80 volts above capacity of all LEDs together. Why LEDs doesn't burn out instantanisly ?

Thanks in advance.


texts: Tips for fine pitch and rugged connector

texts:
I'm looking for a connector with following qualities:

fine pitched (max 1.0 mm, preferably 0.8mm or less)
double row
pin count of 20 or more
rugged design, resistant to vibrations
relatively affordable - but quality is most important

After a long search, I found the Hirose DF50 series. DigiKey describes the following:

  " Its latch prevents uneven locking that is commonly attributed to side locks and incomplete mating. This provides security that is invaluable when dealing with high vibration and other critical applications. (https://www.digikey.com/en/product-highlight/h/hirose/df50-board-wire-rugged-small-form-fact-conne-system)"

The DF50 series is not expensive, so it seems perfect for the job. But the crimp handtool is almost $2000 (part no. HT305/DF50-2830HC). So I end up with two questions:

If you've ever used the DF50 series from Hirose, did you use the handtool? Perhaps one doesn't really need it..
Do you have another favourite connector type that meets the requirements above?


texts: SD card responds with illegal command (0x04) when I send Write_Block (or Read_Block)

texts:
I'm trying to roll my own SPI SD card management. So far, I can get the card initialised (details of that further down). Once initialised, when I send the Write_Block (CMD24) or Read_Single_Block (CMD17) commands, the SD card always returns 0x04 (illegal command) as an R1 response. Has anyone seen this before?

Some more detailed information about how I setup the card etc:

I send 74 empty bits to the card with CS high,
Send CMD0 with CRC 0x95 until I get 0x01 as a response,
Send CMD8, argument 0x1AA, with CRC 0x87, and get an R1 response of 0x01, R7 response of 0x1AA,
Send CMD55/ACMD41 until I get an R1 response of 0x00

(I've stepped through all these steps with a debugger to check that I'm getting the responses that I expect)

At this point I send CMD17 or CMD24 and get a response of 0x04. I've tried a few different arguments as addresses, 0x00, 0x01, 0x200, but all with the same result. Anyone got any ideas here?

Thanks in advance.

EDIT:
I had another kind of timing issue that caused this - my clock was relatively garbled (one very long pulse, and then 7 short ones for each byte), and that seems to have caused the problem (I'm not sure, since I'm still working through other issues). I'm surprised I managed to get the card to initialise at all.


texts:
I found this circuit as a gps module on the internet . i look to datasheets and it looks ok. I want to make it for test. is this correct and will work ?

Credit:
https://www.electroschematics.com/neo-6m-gps-module/


texts:
I see the question has been asked a few times about using rectifiers in parallel to get a higher current rating and this is not advisable however I wanted to ask how this would apply to a active mosfet regulator and rectifier namely the fh020aa commonly found in bikes having a peak current of 50 Amps.

My application will generate 120 amps peak and at 12 volts and a standard 3 phases rectifier would lose a lot of that power so I wish to use two of these in parallel with a brushless motor to gain 100 amps peak.

Can it be done? Or is there a more suited rectifier capable of taking the current?


texts:
I was reading about ARM M series and somewhere it was written that:
 "the flash memory area is aliased from address 0x0000 0000".
what does it mean?


texts:
Some suppliers recommend to use the original micro-usb cables for usage with there device. One example is syncing via Samsung Kies. I also exerienced that some devices seem to be realy sensitive to the cable used.

Where are the diffences comeing from (e.g. shielding, capacity, resistance)?
Are different 'quality classes' for micro-usb cables defined? When I want to by a new cable, how can I be sure that it will work with all devices?

I'm more concerned about the Quality of data transfer, than on the chargeing time.


texts: Simplify the boolean function $$Z=A\bar B \bar{C_i} + \bar A B \bar{C_i} + \bar A\bar B {C_i} + A B {C_i}$$

texts:
I want to simplify the following boolean function:
$$Z=A\bar B \bar{C_i} + \bar A B \bar{C_i} + \bar A\bar B {C_i} + A B {C_i}$$
Here's my attempt:
\begin{align}
Z &= A\bar B \bar{C_i} + \bar A B \bar{C_i} + \bar A\bar B {C_i} + A B {C_i} \\
& = \bar{C_i}(A \bar B + \bar A B) + C_i(\bar A \bar B + AB) \\
& = \bar C_i(A \oplus B) + C_i(A \equiv B)
\end{align}
I thought this was the end of it but in my textbook it continues and has:
\begin{align}
Z &= A\bar B \bar{C_i} + \bar A B \bar{C_i} + \bar A\bar B {C_i} + A B {C_i} \\
& = \bar{C_i}(A \bar B + \bar A B) + C_i(\bar A \bar B + AB) \\
& = \bar C_i(A \oplus B) + C_i(A \equiv B) \\
& = A \oplus B \oplus C_i \\
& = A \equiv B \equiv C_i
\end{align}
I'm confused about what happened between the third and fourth step. What boolean algebra rules are being used here?


texts: I need to lock reading my mega328 flash but be able to write to the eeprom

texts:
I need to be able to prevent other from copying my program placed in the flash, but want to still be able to write to the EEPROM.

I tried the lock bits by setting them to Mode 3 (0x3C). But that will prevent me from writing to the EEPROM.

Is there a way of prevent reading the flash while continue to allow writing to the EEPROM?


texts: Power sequencing with LDO without enable pin

texts:
What is the right way to provide a power sequence using LDO (or any other power source) without the enable pin?

I'm using DAC7718 from Texas Instruments and it require a quit complex power sequencing:

  For proper power-on initialization of the device, IOVDD and the digital pins must be applied before or at the same
  time as DVDD. If possible, it is preferred that IOVDD and DVDD can be connected together in order to simplify the
  supply sequencing requirements. Pull-up resistors should go to either supply. AVDD should be applied after the
  digital supplies (IOVDD and DVDD) and digital initialization pins (LDAC, CLR, RST, CS, and RSTSEL). AVSS can
  be applied at the same time as or after AVDD. The REF-x pins must be applied last.

Hence I need to:

apply IOVDD and DVDD togheter
apply AVDD and AVSS
apply REF-x

In my circuit IOVDD and DVDD are +3.3V and come from a MCP1703; AVDD is +12V and comes from an AC/DC converter (TUHS15F12); AVSS is -12V and come from an ICL7660; REF-x is 2.5V and come from REF3025.

The simplest way I'm thinking at is to use some mosfet controlled by the MCU:

IOVDD and DVDD go straight to the DAC7718
AVDD is fed by a PMOS
AVSS is fed by a NMOS
REX-x is fed by a PMOS

of course I will need some interfacing/level translation to control those mosfet from a 3.3V.

Is this approach correct?


texts: Am I right in analyzing this simple RL circuit?

texts:
I'm given this circuit which is in steady state:

At some point the switch closes. What happens to the voltage across the inductor and the current through it?
Well, the way I see it is that if the circuit reached steady state, the inductor is a short so adding a resistor in parallel with it does nothing as no current will run though the resistor which means no voltage will build up at the junction between the inductor and two resistor. The voltage across the inductor is 0V and the current through it is 20/10k = 2mA no matter when I check after reaching steady state.


texts: SMD LED: How to calculate optical power (in mW) from luminous intensity (in mcd)?

texts:
I chose an LED for my application but I need optical power, in mW.

In the data sheet, luminous intensity is shown in mcd but I did not find formulas for calculation although there are graphs, etc.

Where luminous intensity is 180 mcd and viewing angle 120°, etc.

Please provide any necessary formulae for my case.

I could not find the exact formula on this website.


texts:
The output plot for Vo/(Vg) is not outputting a smooth curve. I chose a decade sweep with starting frequency 1 Hz and end frequency of 10 GHz. Why is the plot not smooth? I am pretty sure I built the circuit correctly.

This is the simulation at 10 points/decade.

Simulation at 1000 points/dec.


texts: Implementing 4-16 decoder using BCD to decimal (4-10) decoder

texts: Is it possible to implement a 4-16 decoder using BCD to decimal decoders without using enables and how can I go on doing this?


texts: What's wrong in my low pass filter design?

texts:
I use the magnitude of the transfer fuction |H(ω)|=1/sqrt(1+(ωRC)^2) to calculate the wanted output/input ratio at 0.1.
I use R=1kohms, C=0.5uF for a 20kHz noise input.
Why do I get nearly nothing for the simulation output?
According to my calculation, it should be 0.1V if my input voltage amplitude is 1V.


texts: Connecting grounds of DC-DC converter at one point

texts:
There have been questions regarding connection of grounds of an isolated DC-DC converter. However I could not find anything that discusses whether the two grounds (when connected) should only be connected at one point.

I have connected the input and output returns of the isolated DC-DC converter using a jumper at a single point, and consequently created two split grounds on the bottom layer (as shown in the image of the layout). Is this advisable? Just to be clear, there are no other analog circuits on this board (ADC, DAC, etc), only the typical components that accompany a DC-DC converter: fuse, TVS diode, filtration caps, and LC filter.

Thank you!


texts:
I have a 1kN force transducer which can output (through an amplifier) +/-10V for +/-1kN nominal force range and I sample it with a DAQ device which is 24-bit and has +/-10V range. The overall noise floor is 20mV rms.

Now my question is, using the same DAQ device settings (+/-10V input range & 24-bit) but now if I halve the amplification and match the 1kN force transducer range to -5/+5V instead and assuming the noise floor is also halved to 10mV rms, how can I quantify and compare SNRs of both cases? Is one case anyhow better than the other one?


texts: I have a circuit taken from an FTDI app note that takes USB +5V VBus and filters it into 5V Vcc. This circuit works well. I now want to modify this circuit to output +3.3V and I am unsure exactly what to do about the filtering. Should the filtering be placed before or after the 3.3V regulator? Is it best to filtering the 3.3V after the regulator (bottom drawing)? Or is it better to filter the 5V and then run that through the 3.3V regulator (top drawing)? Below are circuits for both configurations.


texts: USB & 12V-Power-Supply simultaneously - Diode?

texts:
I'm currently designing a (fairly easy) circuit, which is powered by an ordinary 12V Power Supply. To flash the embedded µC and/or get debugging output, I use an onboard USB-UART-Interface.
To make the circuit programmable even when not connected to 12v, I want to power the circuit via USB.
Therefore my question is whether it's safe to connect USBVCC to the 12v rail over just a single Diode (e.G. 1N4148)? The voltage drop across the diode is not a problem in my case, since they only feed a LDO which requires about 4V:

Most circuits I saw online (e.G. the Arduino UNO Power Supply) use an OpAmp & FETs to switch between the power sources, but from my understanding, the Circuit shown above should do the job, as long as the Voltage Drop across the Diode is no problem.
If the suggested circuit is ok to use, I'd like to get a few advises on how to make the circuit more safe to use. If the diode ever fails, the circuit would kill the USB Controller of the Computer it's connected to (best case) or even kill a whole x-k$ notebook.
I think an 5V-Varistor and an additional fuse should to the 'additional safety' (see second circuit), but would the varistor & fuse would react fast enough to protect the USB-controller from being damaged?

(P.S.: Yep, i have caps for the LDO, just left them out here for simplicity)


texts: when modeling a component, do you use the top or bottom view?

texts:
I'm modeling a component from this datasheet, they provide both a top view and bottom view of the components seen below, does my pcb footprint represent the top view or the bottom view? This has been very confusing to me.

TOP VIEW:

BOTTOM VIEW:


texts:
if i join two battery cells in series then the voltage will be added. what if i replace one of the two battery cells with a DC generator?

My reason is because batteries (excluding Lipo) have modest C ratings, thus the current extracted is modest relative to its size.

In electric cars, batteries are setup in parallel and series (Tesla for example uses 385v) however if I am trying to develop a race electric car, I’ll have to balance between current and voltage, thus if I average out 500–600 volts for a high RPM electric motor then the current extracted from the batteries would be so much that I might kill the battery pack.

Therefore I got this idea of a hybrid system where all the batteries are connected in parallel for current, and then a DC generator is connected in series for voltage.

If I have 2 battery cells connected in series, shouldn’t I be able to substitute one cell with a DC generator is series!!?? I personally think so if we neglect the affect of sinusoidal current which can be solved with a capacitor.

The reason for this system is that if I am trying to develop a high performance electric race car, with this solution I’ll be able to lower the current demand per cell and provide the need for high voltage by connecting the batteries to a DC generator in series.

does this idea work?
does it help prolong battery life by reducing current demand per cell?


texts: Should I consider this 1.57V open pull-up pin on ESP32 faulty?

texts:
I'm working with a ESP32 NodeMCU32 dev board.
When I set INPUT_PULLUP on pin 23, and measure its voltage, I get 1.57V. If I do the same for pin 22, I get 3.23V. Both pins are open (not connected to anything) and I've done these measurements on a "pure" platformio build, code below.
As far as I know, pin 23 used to work as I expected (i.e. like pin 22). Is this board faulty or damaged, or could I be setting something up wrongly?
Could be a red herring, but I'm suspicious that 1.57 * 2 is very close to 3.23.
EDIT: Datasheet (section 5.3) says minimum high DC output is 0.8×VDD, which would be about 2.6V (far higher than the 1.57V I'm getting). I assume this is what the pull up is connected to, so perhaps this indicates the chip is not in spec (faulty).
Here's the code I used for the tests.
#include <Arduino.h>

void setup() {
  Serial.begin(115200);

  pinMode(22, INPUT_PULLUP);
  pinMode(23, INPUT_PULLUP);
}

uint8_t counter;
void loop() {
  Serial.print("Test! ");
  Serial.println(counter++);
  delay(1000);
}


texts: Clock signal on toggle flip-flop - does it have to be a pulse?

texts:
simulate this circuit – Schematic created using CircuitLab

I'd like to actuate a relay using a controller output that is already in use by another part of my system. This output is supposed to stay true during normal operation, but I can flash it to false then back to true without affecting the function of anything else.

So my idea is to use the quick turn-off/turn-on of this output from my controller to actuate a bistable relay for another output, as I am running out of outputs on my controller. I've tried using a flip-flop in toggle configuration but the low-high transition of the clock signal is not affecting the outputs in any way.

Could this be because I am leaving the signal high and not actually giving it a "pulse"? Is there a maximum width associated with clock pulses?

I selected the SN74HC109 from TI and, according to the truth table, if I drive /PRE, /CLR and J high (5 V) and drive K low (0 V) then when CLK goes from 0 V to 5 V, it should swap the states of Q and /Q. But I am not seeing any changes to Q and /Q on the rising edge at all.

The datasheet is listed here: http://www.ti.com/lit/ds/symlink/sn54hc109.pdf


texts:
In many datasheets and application guides there is always an equation for ripple current, because it is fundamental to the operation of a buck or boost converter, but I never see a direct equation for ripple voltage.

I know the ripple comes from the finite capacitance that needs to discharge the load current during the off-part of the duty cycle, so I suspect the equation is a second order (since the derivative of the capacitors voltage depends on the derivative of the inductor current). I also know the capacitor’s ESR plays a role.

I ask out of experience. Once I built a boost converter and the output voltage ripple grew to over 100mV at max load, whereas another time I build a boost converter and the ripple was constant at 4mV across all loads. These were clearly satisfying very different power requirements, but what is the interplay between capacitance ESR and the pure inductive/capacitance relationship in determining output ripple? And when does it start to vary significantly across loads?


texts: How to calculate the voltage across Va and Vb?

texts:
Attached is the circuit I have been analyzing.

Here the intention is to calculate the voltage across V_A and V_B - (See the red colored letters in the circuit diagram.)

I have calculated V_R1 using Kirchhoff's voltage law as follows,

Edit
I have taken voltage across V_A and V_B as follows,

Can anyone verify the calculation.


texts: Replacing a broken 3.5mm audio jack with a different one, why does each cable have different amount of wires?

texts:
I found a nice speaker system that seems to work except the 3.5mm audio jack is damaged (it's missing the tip of the conductor for left channel audio). I gathered some broken audio cables with 3.5mm jacks to fix the speaker system's audio input.

My first step was cutting cables. My next step was reading about the problem. (I realize I have an out of sequence operating procedure.)

Even having read up on this type of fix, I'm still confused by the difference in conductors I see within each cable. Here's what I'm working with:

Note the top jack is missing its tip! My confusion comes from seeing only a red cable (presumable 'hot' or 'audio') and bare copper (presumably ground or, lacking more wires, neutral) on the replacement jack. The replacement jack is a similar size as the original and more importantly it has the same amount of partitions on its prong (see below diagram) so I'm surprised it doesn't have the same amount of wires as the original jack.

Image via this Q&A: Why are there not more incompatibilities in 3.5mm audio jacks?

My question is how I can replace the original jack? I planned to do it via wire splice to a different jack, but I understand I might have to take apart a working jack and solder the original cable to that. In the latter case, any explanation I should have in mind about why the working jack has fewer wires to begin with?


texts: Thevenin equivalent with dependent and independent generators

texts:
Considering the following circuit

When calculating the Thevenin equivalent, I calculate the Thevenin resistance value Rth.

Why do I have to consider the controlled voltage generator?
And furthermore, why can't I eliminate the current source I1 and why does it gets replaced by an 1A current source in this example? Is it in similar cases always true that the controlled generators are not to be eliminated and the other generators (current and voltage) are thus to be replaced by unitary generators?


texts: Is it possible to implement RC-5 not using interrupts?

texts:
The problem with my atmega8 is that I don't have the external interrupts INT0 or INT1 available. There are some nice libraries, e.g. this one, that rely on the interrupts, however, I would like to achieve that by not using them.

Is it a feasible plan?


texts: What the forklift is this gold piece on my push/pull connector?

texts:
I got a pseudo-lemo connector that seems to go together in the order the parts are laid down on the plastic baggy. The solder cup goes into the sliding part, and the rubber goes on the end to give some support to the wire.

Only problem is the gold piece doesn't fit on anything. What is it, where does it go? Also, what is the tiny hole next to V8 used for?


texts: Current flow with a potential difference

texts:
I have a small question, I am trying to wrap my head around the different types of ground connections in electronics.

For earth ground connection

In an earth ground connection electrons can sink to the earth with only a single connection to earth correct? The way I am viewing it is by looking at it in a CMOS perspective. In CMOS circuits there is dynamic current flow and it is from one of the power rails to the parasitic capacitance on the output, there is no "closed path" but the current still flows. So when we have a basic resistor circuit with one resistor we can follow the same convention, in which charge will flow from a point of higher potential to a point of lower potential, there does not need to be multiple connections to ground to create a closed loop, we only need a single connection from a point of higher to lower potential.

Floating ground

There is no actual earth connection, it is just a reference point. There will be EHP recombination at this reference point.

My main concern is about the earth ground, one connection should be enough. If we only have one connection to ground lets say it looked like this:

The positive side is at a higher potential than the ground would current flow until there is no potential differences between the source and ground?


texts: what is the difference between tplace and tdocu layers in eagle pcb?

texts: It seems that they both show graphics on the PCB. However, it is not clear which is used when.


texts:
Well, the title of this question tells it all, but repeat it here:

"Can a low current device be damaged by a high current device when in parallel?"

Came along this article:
http://www.embedded.com/design/prototyping-and-development/4423709/Protecting-your-low-voltage-electronic-devices-from-electrical-overstress

For example, when you have a bluetooth module that consumes only 80mA and an amplifier that can consume a max of 2A, is it possible that the bluetooth module will be damaged by high current peaks on the powerrail (on the long term)?

If so, what is the easiest way to do to avoid this?


texts:
I'm using a dsPIC33 and want to just send basic SPI data out.  No Rx, only Tx for now to control a digipot.  Hardware does include slave at other end, and I'm sniffing the output with a logic analyzer.  I've just seen literally 10different deprecated ways of doing it, but none of them seem to be working.

Problem: Random data coming out.  Every once in a while it makes sense like a 3 or 7, but otherwise garbage.

I'm also not sure if it's OK that the MOSI line does not always return to a default high or low.  It usually starts high, writes data, ends low, then ends high on the next round which seems odd.

Other: Short wires, no (potentially damaged) IC at other end, 10k pull-up resistor on chip-select (CS) line, slowest possible baud rate (default spi prescaler and postscaler are largest), tried 8 and 16-bit modes, tried all settings on logic analyzer (MSb first and LSb first, etc), RPn pins can't also be analog by default, RPn pins are not RPn input,...

Is it not just this simple?  What might I be missing?

uint16_t main(void) {
  UC_ConfigureOscillator();
  TMRS_Init();
  SPI_Init(38, 39);

  // prime any timers that require it
  TMRS_Start(TX_TIMER, TX_PERIOD);
  volatile uint16_t val = 0;

  // watch the data being transmitted with a logic analyzer
  while (1) {
    // periodically transmit a message
    if (TMRS_Expired(TX_TIMER)) {
      TMRS_Start(TX_TIMER, TX_PERIOD);
      SPI_SendWord(val);
      if (++val > 10) val = 0;
      }
   }

   return 0;
}

void SPI_Init(uint8_t sdo_pin, uint8_t sck_pin) {
  // Configure and initialize the chip-select pin
  _TRISB8 = 0;
  _LATB8 = 1;

  // Configure the SPI clock and MOSI pins
  __builtin_write_OSCCONL(OSCCON & 0xBF);
  _RP39R = 0b001001;
  _RP38R = 0b001000;

  // Configure the interrupt
  _SPI2IE = 0;              // Disable the interrupt
  _SPI2IF = 0;              // Clear the interrupt flag

  _SPI2IE = 1;              // Enable interrupts for this spi module
  _SPI2IP = 2;              // Assign the interrupt priority

  SPI2CON1bits.MODE16 = 1;  // Use in 16-bit mode
  SPI2CON1bits.MSTEN = 1;   // Configure this device as master
  SPI2STATbits.SPIROV = 0;  // Ensure the receive overflow flag begins cleared
  SPI2STATbits.SPIEN = 1;   // Enable the SPI module
  SPI2CON1bits.SMP = 1;     // Sample input data at END of data output time
}

void SPI_SendWord(uint16_t word) {
  uint16_t garbage;

  // lower CS
  _LATB8 = 0;

  // write the given word to the Tx/Rx buffer
  SPI2BUF = word;

  // wait for the transmit buffer to clear
  while (SPI2STATbits.SPITBF == 0);
  // wait for the transmit to begin
  while (SPI2STATbits.SPITBF == 1);

  // Dummy-read the SPIxBUF register to clear flag???
  garbage = SPI2BUF;
}

// Called on 16bits finished shifting in OR out of SPI2 buffer
void __attribute__((__interrupt__, auto_psv)) _SPI2Interrupt(void) {
  // Return CS high
  _LATB8 = 1;

  // Clear the source of the interrupt
  _SPI2IF = 0;
}


texts: STM32F4 boot concepts and vector table relocation

texts:
There are some things I don't understand on the boot process of the STM32F4 microcontroller.

My understanding is as follows:

The ARM Cortex-M4 boots expects the stack pointer initialization value and the interrupt vectors on 0x00000000 + SCB->VTOR, whereas SCB->VTOR is cleared at reset.
There is no memory at that location. Flash memory starts at 0x08000000, SRAM at 0x20000000.
In order to make booting possible, the µC can map the flash or SRAM memory range to 0x00000000. The memory range to be mapped is defined by the state of the boot pins.

My questions:

Why is the STM32F4 reference manual saying on page 69 that

  When the device boots from SRAM, in the application initialization code, you have to
  relocate the vector table in SRAM using the NVIC exception table and the offset register.

? In my point of view this is not necessary, as the whole memory region is aliased anyway. Interestingly this doesn't seem to be required when the flash region is remapped to 0x0 space.
The only use for booting from SRAM I can think if is to reduce write cycles on the flash during development. Before you release the µC from reset, you write the program to SRAM using the debugger and then boot from there. However, as you have debugger access, there wouldn't be any restrains on where to boot from anyway. So why having this feature?

That the boot position is derived from pins indicates (at least in my oppinion) that this feature is to be used not during development but in final operation. And in final operation, SRAM is clear at boot time. Hence it doesn't make sense to boot from SRAM.


texts:
I am working on a cooler controller board. I am using 4 wire fans (12V, GND, HALL, CONTROL), I am using a simple 555 timer circuit to control the speed of the fans. However it would be nice to display on the control board if a fan is spinning lower then it should.
I am looking for a discrete way to add or subtract the two signals and use the result as PWM signal for an LED. (I am aware that it's not going to be exactly 0, but I can live with that.)
What am I after? I was trying to find a solution but had no success. I am would like to keep it simple, so no fancy MCUs can come into play here.


texts:
I am having trouble resizing the PCB after components have been placed. I know this is not the usual method, but I have been given a .brd file and .sch and the board dimensions were decided already. Now I would like to move a few things about and create space to shuffle things about and add to the schematic, but could someone please help me increase the PCB size please?
I wondered if I did resize it relative to the origin, would the components not be centred any more and how would I get them back in line too?
I would be very grateful for any help from here please!


texts: Why does this 6V solenoid activate on 4 AA batteries but not on a MT3608 step up booster?

texts:
I have a JF-0530B 6V solenoid that is rated at 300mA, and if I hook it up to 4 AA batteries it indeed activates on the roughly 6V the batteries supply. However, I also have an MT3608 step up converter hooked up to a 5V line on an ATX power supply. I have set the potentiometer on the converter so that it outputs 6V - I measured this using a multimeter just to make sure.
If I hook the solenoid up to the power converter, nothing happens, despite it outputting 6V, like the batteries. The power converter is rated to put out 2A max, with a recommended 1A output, which is more than enough for the 300mA solenoid. Yet, nothing happens.
Why can the solenoid activate on the 6V supplied by 4 AA batteries, yet not on the 6V supplied by the power converter?
Edit: if I measure the solenoid's resistance, I measure about 3.8 ohms, which is surprising because at 6V that would mean about 1.5A, not the 300mA it is rated at. If I measure the current of the circuit when hooked up to the batteries, I measure 1.1A, which is lower than calculated but still a lot. When hooked up to the converter, the current is 0.95A. I measured the converter's output under load, and it's 3.35V. So that would at least explain why the solenoid isn't activating. However, those currents all seem to be within range of the converter's output..
This is the converter in question, basically it's one of those ubiquitous cheap MT3608-based step up converter circuits out there.


texts: I'm using this break beam https://www.adafruit.com/product/2168 with an arduino. Currently both sides are are powered by the 5V from the arduino. I want to move the led half of the break beam to the far side of a doorway so it can be used to count foot traffic. Is there a way to hook up the ir led to a 9V battery without using a breadboard? Can I use electrical tape to affix a resistor between the battery and the led? Here is my project page https://devpost.com/software/door-counter thank you in advance for any advice on how to power the led separately from the the receiver.


texts:
I have done the nodal analysis for the following question, and everything appears to have been done correctly as far as I can see. However, when I simulate the results I get values for the circuit which are wildly different.
Where would the error have been introduced? All sign conventions are followed and I've doubled checked the working out.
Edit :  Ix = (v1-v2)/2  | This was not included in the diagram


texts: Is "True RMS" applicable only to measuring AC voltage?

texts: Higher end multimeters feature "True RMS" rather than "averaging" voltage measurement.  Is this applicable only for AC voltage measurement?


texts: Will 802.3af device work on 24v passive poe?

texts:
I have seen a lot of questions and answers all over SE about using a passive POE device on an 802.3af network. But can you use an 802.3af device on a passive POE network?

In particular, I have this POE injector that outputs 24V @ 0.5A (12 W?), and a Mitel 5320e IP phone that uses 4.3 W. The phone is 802.3af-compliant, which means it is expecting 48V, but is it reasonable to assume that it would still work on 24V? Or could I expect do damage the device by undervolting it?

It sounds like some people have tried this and it worked OK, but were they just lucky?

What about for the general case: if you have a passive POE injector that outputs 48V, would most 802.3af devices still work on it?

From what I understand, the handshake between the 802.3af POE injector and the device only determines if power will be sent; the device has to adjust the voltage to its needs. Once a 802.3af injector determines the device wants POE, it sends 48V, no matter what. This makes it sounds like 802.3af is just to protect non-POE devices. If that is correct, than a passive injector is only dangerous to non-POE devices; it shouldn't be dangerous to POE devices, even if they use a different standard. Is that correct?

More details on what I'm trying to do here


texts:
I am working on interfacing a JTAG interface to a MSP430BT5190. Below is a showing of how it should be connected.

Looking at the pin out of the JTAG, I see there is a TDO and TDI. When connecting this to the MSP, is it inverted such that TDO Prog -> TDI MSP and TDI Prog -> TDO MSP, as it is with a UART interface (TX->RX and RX->TX)?

MSP430BT5190 Datasheet: Click to View

(source: wiki.ti.com)


texts:
I was looking at this site http://www.electronics-tutorials.ws/power/insulated-gate-bipolar-transistor.html

Here an IGBT is an NMOS with a BJT> But the BJT looks to be a pnp device. When the NMOS turns on, Vbe =0 , how will the pnp conduct? Making the gate negative, mean no channel exists in the NMOS, and the NMOS is off. The 2 ends could actually be at any potential. How does this circuit actually work?


texts: Differential Amplifier with Global Negative Feedback

texts:
This question refers to audio amplifier design, using BJTs only.

I am wondering how differential stage amplifier plays an important role in hi-fi audio amplifiers.
According to this book (where picture was copied from) I have, a part of output signal is feeding the base of Q2. Q1 and Q2 somehow amplify input signal and at the same time cancel out some of distortion that is being brought back from the output to the differential input stage of amplifier.

I want to understand the process of this differential stage and how it manages to cancel out some of the output distortion.

I almost completely understand functions of other transistor stages so there is no need for explaining how the whole circuit works.

*Source: G. Randy Slone : High Power Audio Amplifier Construction Manual


texts:
I am attempting to build my very own 8086 computer. (I know, awesome right?) But not to confuse you, this post focuses only on the 8284A. We have started to cover the Intel 8086 chip in my microprocessor class but unfortunately the class only covers textbook and Assembly stuff, not the actual hands on hardware.

I thought the systems clock would be a good place to start. After all without a good clock the processor is wasted. I purchased a handful of 8284As and a 15MHz crystal to use with the x1 and x2 outputs. I have put together my test circuit and it is shown below.

The wave output from the CLK pin looks like this:

Based on the datasheet for this chip the clk output is suppose to be 5Mhz with a 33% duty cycle. The output is extremely close to 5Mhz. The time division knob is set to .1us. The voltage is also consistent. However, it looks like the capacitors are discharging too soon. It's no where close to a square wave! My guess is bigger capacitors on the x1 pin. Any suggestions?

As always, thanks for your help.


texts: Prevent a floating output to PWM input on MCU reset

texts:
I wired a DC motor driver with a MCU, just like the following simplified figure. Simple.

The PWM output frequency is 2kHz and it has 3.3V logic. It works very well as I expected. However, I have one minor problem with this: the MCU has a floating output on reset so the DC motor spins so fast until the MCU initialize the PWM out pin. I have a couple of questions about this problem.

A solution I can come up with is to add a pull-down resistor between the PWM line and GND. Is that a right solution, or are there other ways to prevent the floating output on reset?
If yes, what's the preferable resistance for the pull-down resistor??

Thank you in advance.

EDIT: The host MCU is STM32F446RET and the motor driver IC is MAX14871. The PWM output in in question is PA8.


texts: Resetting a counter when it reaches 6, without logic gates

texts:
I have a 3 bit ripple counter (using t flip flops) and I want the counter to reset to one when it reaches 7 i.e. the counter counts from 1 to 6. My idea was that I could hook the three outputs from the counter together and place a resistor and led in series such that when the counter reaches 111 (6 in binary) that it will be able to overcome the resistor and light up the led (the led is just to test if it works, then I can hook the led up to the necessary reset and set pins of the counter). When the number is 001 or 011 for example, there will not be enough power from the outputs to over come the resistor.

I was just wondering if this theory is possible, or if there is another way to do this without using logic gates. I'm currently using a 9v battery and the  cmos dual d-type flip flops are 4013be components.

Also i'm pretty new to electronics so sorry if I'm missing anything obvious!

Regards,
David


texts: What is the commonality between a radio, a welding power source and an induction heater?

texts:
I was reading into the basics of welding power supply (because I have taken up TIG welding) and inductive heating (because it is part of a number of applications in metal fabrication), and I noticed that the two seem to share basic concepts also found in radio circuitry, namely the idea that you adjust the frequency of an AC signal.

To my newbie eye, it seems like an inductive heater is a high power radio sans the information encoding and with a coil where the antenna was, and the welding machine seems to replace the coil with an arc, but I might well be off track there.

Now, I only have a very rudimentary understanding of electronics, yet. I have worked with sensors that measured electricity for a couple of years, so I have a basic understanding of AC power, and I have heard of inductive and capacitive loads.

If I were to draw a block diagram (with functional groups instead of the actual circuitry), what would be common elements in the three types of devices? It seems I usually have a rectifier followed by an inverter, to change grid AC to "my-frequency" AC. Then there seems to be something called a "resonant tank circuit", and I have read the Wikipedia page, but I am not exactly sure if I have really understood it already.

My immediate goal here is to have a map for learning more about these topics, i. e. I would like to understand the larger building blocks of those devices first, gain some vocabulary that I can use for further study, and then work my way down to how the details work. Pointers to learning resources are appreciated.


texts: Can I connect many SX1272 (LoRa) based devices to a gateway?

texts:
Simple question: Is SX1272 chip by Semtech capable of sending data to LoRa gateways?
I'm a little bit confused about LoRa and LoRaWAN. What is the difference?


texts:
I have circuit demanding a 2.4Ghz antenna inside a metal enclosure.
I cannot place it on the external casing since the case it's movable and will also be exposed to other issues.

I need some advice regarding antenna placement.

I thought about making a horn antenna to drive waves outside through the hole.

But then is the antenna current position right or should be vertical inside the horn (its axis to be perpendicular to horn axis)?

A profile-view drawing below:


texts: Does phone battery last longer if I charge often or less frequently?

texts:
Which practice will help my Android phone lithium battery last longer?

Charge often. Whenever phone battery drops to, say, 70%, charge it back to full 100%.
Charge less frequently. Charge phone to full 100% after it has dropped to between 0% to 20%.

An explanation for the choice would be helpful.


texts:
I've tried to turn on my old PC with my old LCD monitor, which is powered by a kettle cable directly from mains, no power supply brick).
When trying to get it to work, I have noticed the following phenomena:

1) The VGA connector from the monitor produces electrical sparks against the PC case, even when the PC PSU is switched off (but both are connected to the same extender cord) - See video: https://youtu.be/6Jxlndc2ZUA

2) While bending down to look at the connector (with the VGA cable connected), and touching the PC case with my hand, my head accidentally touched one of the strings on my electric guitar and I felt an electric spark on my head (not very strong but noticeable). The guitar is connected to an external sound card, which in turn is connected via USB to my main PC, which is connected to a different power outlet.

At first I assumed it's some kind of grounding problem on my monitor. So I hooked up some random grounded electrical device I found in the house (the base of an electric kettle) to the same extension cord, and tried to brush the VGA cable against its metal casing while the other end is connected to the monitor. I couldn't see any sparks this time.

I have also tested this the other way - I have connected the VGA cable to my PC, and tried to see if it produced sparks when rubbing the other end against the electric kettle base casing, and nothing happened.

Since I am alive and the sparks don't look too big, I assume the VGA cable isn't really live with 220V but instead something else is going on.

Can anyone suggest an explanation to the above situation?

Update:

I have repeated the experiment using a different wall plug and extension cord, one that I have personally tested with a multi-meter and made sure that is wired correctly regarding live/neutral/gnd.

Turns out that one of the kettle cables I have been using is indeed missing a ground prong, and has a hole instead:

This is meant for sockets that have a ground prong (mine doesn't), so effectively, it wasn't grounded.

I have tested the following combinations:

1) ungrounded monitor, grounded pc (psu off) - VGA cable is arcing against PC casing
2) grounded monitor, ungrounded pc (psu off) - VGA cable is NOT arcing against PC casing.

In this case, I assume there is some kind of issue with the computer monitor. Getting a grounded power cable for it would merely hide the problem, and I should probably replace it.

Is there anything else I should look at before dismissing the issue, just to be safe?


texts: Altium Designer space bar doesn't rotate components

texts:
I am having a strange behaviour in Altium 14. When I place a component on the PCB in PCB Editor, if I press space bar, instead of rotating the component by 90°, it only opens a dialog where I have to enter the number of degrees by which I want to turn the component -- this is very annoying.

I have already checked the PCB Editor Preferences in DXP Preferences and the rotation step is already set to 90°, but still it asks me how much I want to rotate every single time I press space bar...

I also found that pressing L opens the View configurations instead of flipping components.

Any idea how to change this?

PS: I have already tried to reset the default settings from the Preferences, still without success.


texts: Transition time (rise time) and propagation delay

texts:
Recently in class I have encountered the following calculation of the propagation delay of the following digital circuit:

Could anyone please explain to me the addition of the rising time of X2 and C? I fail to understand why this addition is regarded as the "real" propagation delay.


texts:
I have some home automation, and want to put a rain sensor far away (about 30') from my computer.

(EDIT: Rainfall meter or rain gauge, not a sensor. as per Transistor)

The sensor uses a mechanical teeter-totter with a magnet that momentarily triggers a reed switch as it tips.

I want to use the reed switch to set a flip-flop (74?109) that the computer can read at its leisure, then I want the computer to clear the flip-flop.

Do I put the flip-flop far from the computer and near the sensor running Vcc, Gnd, Clr, & Sens, or put the flip-flop near the computer only running the reed closure through the wire?

Reliability, of course, is paramount. I am thinking noise issues, and impedance.

Reasoning?

My arguments for each case...

If I put the flip-flop near the reed switch, the reed switch will reliably trigger the flip-flop, but there may be a lot of noise on the clear line triggering false clears.

On the other hand, putting the flip-flop close to the computer will make that reliable, but the 60' of wire may not trip the flip-flop as the magnet goes by. Also, there may be noise on that line and may trigger false sets.

In either case, I have lots of old 4-conductor telephone (CAT3?) cord.

Thanks.


texts: Calculation of switching transformer at 100kHz

texts:
I am not able to desgin transformer for switching frequency 100kHz. It´s easy to desgin usual transformer for 50 Hz. But I´m totaly out when comes to switching transformers. What material should I use? Im not sure if Ferrite core E55 is enough.

My desired parameters is: approx. 315 V primary (after 230V rectifying), 12V secondary and 1000 VA of power.
and full-bridge switching mode.


texts: High temperature+humidty and electronics

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I am using a temperature sensor and accompanying devices to prototype a circuit which will be placed in high temperature and humidity conditions. Temperatures up to 40°C and humidity up to 75%. Do I need to make considerations here regarding safety and efficiency or are these conditions not significant enough? I am most worried about humidity as I have found that the temperature I will expose these things to are well within limits of most electronics.

In particular I am wondering, does all wiring need to be insulated and do integrated circuits (such as an Arduino) need to be covered in some way?

As an example, I am using the following temperature sensor which needs to be wired to an Arduino. Does the temperature sensor itself have to be insulated as well ??


texts: Uninterruptible Power Supply - Reset the load when power is restored

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My system is powered by a redundant supply (UPS).
When the input power supply is removed, the system detects this event and it performs a safe shutdown (actually it is a microcontroller that enters a power-down mode after performing few operations).

I would like a recommendation for an IC that resets the MCU when the input power is restored to restart the system.

I found some MCU supervisor circuits (like CAT825, TLV803) that reset the MCU at power-on, but they also keep the MCU under reset when the input voltage falls below a threshold, which is not desirable on my situation.

I know it can be done with a "one-shot" circuit built with a 555 IC, but I am looking for a small dedicated IC.

Thank you.


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I am currently trying to control at least 16 RFID readers (RC522) over SPI communication. The setup is like this:

1 mainboard PCB with 16 sockets for ribbon cable connectors
16 satellite board PCBs, each with ribbon cable connector and a header for the RFID reader

On the mainboard, a Particle Electron drives the circuit and addresses each RFID reader individually using a shift register for the slave select pins.

Everything works fine until I connect the 7th satellite board + reader. I'm assuming that it has something to do with load capacitance and that it hits some kind of limit there.

Right now I can go two ways: Either try to enhance the SPI signal with the current setup somehow (which I do not know how to do), or do a bigger redesign.

In terms of redesigning, my idea was to put an ATmega168 or 328 on each satellite board and have that control the individual RFID readers. The mainboard could then communicate with the satellite boards over I2C, making each satellite board an I2C slave. In order to avoid the same capacitance issue as before (just on the I2C lines), I considered using a bus extender such as the P82B715. This solution would also require far less wiring, as each satellite board could be daisy-chained since I2C doesn't use a slave select line.

However, my hope is that there is a better / easier solution than doing a redesign. Adding ATmegas increases the cost of the system (which becomes important long-term), and it adds more steps in terms of flashing the MCU on each satellite board.

Basically, I would like some comments or suggestions in terms of which approach would be most suitable, moving forwards. I am open to everything, I just need to pick a direction which will result in a more robust system, even if it requires redesigning.

Any suggestions? :-)

Thank you!


texts: Crystal Oscillator Design and "Crystal Drive Level"

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I followed the video at the link http://www.analogzoo.com/2015/07/ .  The video directs watchers to a tool at http://www.analogzoo.com/lab/pierce_bjt.html to help determine parameters to cause resonation/clock generation.

I watched the video a few times and added appropriate parameters in the tool to get a Crystal Load Capacitance, Crystal Loaded Q, and Gain Margin in spec with what the video describes.

I match my Crystal Load Capacitance to my crystal of 12pf.  I have a Q of about 87 and a Gain of about 5.  If I built the circuit, I would think it would resonate.

Everything looks good, yet, my Crystal Drive Level is at 0uw.

Does this matter?  I understand this to be the power consumed by the crystal and that too much can damage the crystal.  Having 0 is probably a good thing.  I am wondering about that.  I have 5 Volts supplied. 2.5 peak to peak, c1 and c2 = 182pf, etc,

If I built this circuit, what lines show resonation?  I am expecting to put my oscilloscope to ground and the line (on the right side) between the amplifier and the crystal.  I would expect it to oscillate about 6.4 Mhz.

If I do this, I then would wish to put some counters to divide the clock a few times and see the division on my scope.  Should adding additional ICs to divide the clock couse the clock to change much?

Thanks,
Jeff


texts: Resources for IBM PC compatible motherboard / Intel 80486 development

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I'm trying to find some resources on designing motherboards, but there doesn't seem to be much out there. I'm also looking for information about interfacing with an Intel 80486. I mostly understand the datasheet of the Intel 80486, and I'm already familiar with x86 asm and the x86 architecture, but there isn't much out there (that I could find) in terms of a high level initialisation / execution overview. I'm also not sure whether a full-blown BIOS is a requirement, or whether I could cheat my way out of using one (i.e. replace it with an AVR microcontroller or similar).

My end goal is to build something that runs DSL. What I'm aiming for isn't a full extensible board with PCI/ISA slots and USB support, but rather a complete bare-bones board that will run the OS. I'd be going for the absolute minimum requirements - CPU, RAM, basic GPU, IDE controller, PS/2 interface.

I'm aware that this is a hugely ambitious project, and will probably end up taking me several years, but it's something I've got a lot of interest in.

Any good resources for this level of stuff? Surely the guys who design modern motherboards must learn it from somewhere!

Update:
I'm not trying to come across as conflictory here, but I just want to take a second to pre-empt the nay-sayers. I fully understand how complex and insane this project is. I get that I can't just breadboard this stuff up - it takes a lot of time and money to do it at all, let alone do it right. I know there are a multitude of issues that make this kind of circuitry difficult to deal with - high frequency, high current, low noise requirements, tight tollerance requirements, high pin/trace density, lack of datasheets, proprietary requirements, etc. I'm still dedicated/insane enough to give it a go. I'm not asking you to explain how to do it, I'm just asking for some links to websites or books that deal with this kind of thing. I'd be extremely grateful for any useful information I can get.


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Problem description:

The following is what I've worked out:

Now, to find the steady state response vo(t), which I assume is just vout(t), I would just have to multiply the transfer function by the input. My question is how exactly do I express the input in Fig. 3 as an equation ?