texts: Is it really necessary to ground the metal can on crystal oscillators?

texts:
I am modifying a KOSS portable dvd player into a portable raspberry pi computer and have noticed that they grounded the can of the crystal that feeds their microcontroller. I am curious if there is an electrical benefit to this? Maybe this bodge was purely for mechanical adhesion?

I have designed quite a few embedded systems which have crystal oscillators in noisy applications but have never (to my knowledge) experienced an issue with an un-grounded crystal can. This is the first I am seeing this.

I'm just genuinely curious as to why this was done.

Side note: I love finding bodges in the real-world (0ohm shunt to fix the floating ground in the copper pour on the upper left of the crystal).


texts: I am looking for a resource that includes analysis of feedback circuits. I have found something on sedra smith microelectronic circuits but not enough for me. Could you suggest me some resource ? It may be article, book, internet resource or anything else.


texts:
I'm looking to setup my e-bike touring bicycle with a solar outfit so that it can charge on the road, but am unsure of the electronics. I appreciate the size of the panel will be huge, but this can either go over the bike or on a trailer being towed.

The battery is a 36v, 17.5Ah lithium ion, with the following spec -

Maximum Charge Voltage: 42V
Discharge Cut-off Voltage: 28V
Standard Charge Current: 2A (3A maximum)
Charge Method: CC/CV

Bike motor is 450 watts.

What would be a recommended setup to provide an almost constant power (about average 2/3rds of maximum motor pull) stream in say perfect sunlight? What management electronics would I need?

Thanks.


texts: Help understanding circuit in Forrest Mims' Getting Started in Electronics

texts:
I've worked through Forrest Mims' Getting Started in Electronics, but cannot figure out why the below circuit (on page 92 in the fourth edition) claims that LED1 and LED2 alternate in being lit depending on the state of input IN1. From everything I know, the path via LED2 will always be at least equally attractive (i.e. of a lower or equal impedance) to the 9V current in the circuit compared with the path via Q1, so the circuit will alternate between only LED2 lit and both LED1 & LED2 lit, IMHO. I built the circuit (slightly varying the values of the resistors and using a 6V power source) which indeed had LED1 & LED2 lit at the same time when IN1 is high. Am I wrong in my understanding, or is Forrest's diagram incorrect, and if so, how to correct the circuit so it works correctly (apart from inserting a separate PNP transistor). Note that I simulated the IN1 input using a push button and a constant 5V power source.

simulate this circuit – Schematic created using CircuitLab

[UPDATE] Just for the fun of it - here is Forrest Mims' response to my notification on this issue in his book:

  Dear Philip,

  Thanks very much for reporting the omission you described. You are
  correct. All of the 100 circuits in this book were built and tested 4
  times each--but not this one.

  I intended to print “RED” over LEDs 1 and 3 and “GREEN” over LEDs 2
  and 4 and neglected to do so.

  This is copied to the publisher. For the next printing I will add the
  missing colors over the 4 LEDs.

  Thanks again for your kind note. I believe yours is only the second
  omission/error found so far in this book.

  Best regards,

  Forrest

  Forrest M. Mims III


texts: Which stepper motor should be enough to move a water valve and for the TMC2130 driver?

texts:
I need a stepper motor and a driver to control it. But I don't know which would meet my needs. I have an Arduino MEGA 2560 if that's relevant.

Aim

I need to close and open a Nupro valve with precision. I will use some kind of gear to join the motor to the key. The most important is to detect when the stress of the motor changes and stop it when the valve is completely closed, to prevent any damage.

Driver

I have been taking a look and I think the driver TMC2130 could suit my needs. It has the stallGuard2 technology that detects the motor stress and reduces the consumption when the motor is idle. It is common in 3D printers, but it has many other applications.

Is there any better driver? If there is a shield for my Arduino would be more convenient.

Stepper Motor

I would like to know which should be the minimum features of the stepper motor that I need:

Torque. I don't know how much is 1Nm or 1mNm. I mean, I don't know how much I need and how to calculate it
Voltage. 0..46V DC
Current. The driver can work with stepper motors up to 2.0A coil current (2.5A peak)
Wires. I didn't find how many wires are supported by the driver I suggested
Step angle. I think 1.8º would be enough, but I am not so sure

I think one equivalent to this continous servo would be enough. That motor has the maximum of 6V and 190mA.

Would this NEMA 17 stepper motor work?

Update (15 March 2020)

Torque:

I have realised that in the datasheet of the servo is written 38 oz in of maximum torque, 0.27 Nm aproximately. So that should be enough for the Stepper Motor I hope, I will also add some gear and the torque will be a little bit higher and precise
Valve. The documentation of the Swagelok Valve (S Series) is here. The working pressure is 2000 psig = 137 bar.

However, I am going to work just with gas, so I think that 0.27 Nm would be enough so far.

Wires. I will work with bipolar mode. So I just need to pay attention to the cables that go in each coil
Step angle. I will improve the precision adding a gear to the stepper motor. And I will use "Full Step" to keep the motor in the right position as Tony suggests


texts:
I'm looking for a 1kWh battery at 36V, something around 30Ah should be fine.

Browsing popular sites I see that the lower end starts at about $400 which is a bit over what I'd like to pay.

I stumbled into an assembled, BMS included, 36V 14Ah battery pack with unknown cells used and, of course, Chinese origin which only costs $100. I'm well aware it is likely crap, but hey I can always get my money back if it doesn't deliver what they claim.

Anyway what I was wondering is, if I order 2 of those, would it be possible to wire them up in parallel to get something close to 30Ah, given that both of them will have their own BMS?


texts: Tantalum capacitors vs. ceramic capacitors

texts:
I have a negative LDO (-5V from -5.5V to -10V) which requires a tantalum or aluminum capacitor. I'm wondering why it can't use a ceramic capacitor? Is there any specific reason for this?

Regulator is a TC59 (datasheet).

(Correction: the regulator I originally gave was stable with ceramics, this one is not.)


texts: Which one is the real single phase two wire circuit?

texts:
Which one is the real single phase two wire \$(1\phi2w)\$ circuit? i have seem these two type,and both of them were be written in some books

Type A:

https://slideplayer.com/slide/5867350/  0:35 in video

As we can see,this type of \$1\phi2w\$ has just one loading \$Z_L\$,if we assume the voltage of \$V_L\$
,and the impedance of wire is \$R+Xj\$,we can easily know the voltage drop,\$\Delta V\$,of this type of \$1\phi2w\$ and the power which the voltage source transmit ,\$P_t\$,are as below

\$\Delta V=V_p-V_L=I(Rcos\theta+Xsin\theta)\$,\$I \$ is the current flows from the voltage source to the loading
\$P_t=P_L+P_w=P_L+[I^2(Rcos\theta+Xsin \theta)\times 2]\$, \$P_w\$: the power which wire consume;\$P_L=\$loading power

Type B:

https://e.as76.net/asn/tan3.php

As we can see,this type of \$1\phi2w\$ has "two" loading \$Z_L\$,if we assume the voltage of \$V_L\$
,and the impedance of wire ,\$R_1\$ and \$R_2 \$,are both \$R+Xj\$,we can easily know the voltage drop,\$\Delta V\$,of this type of \$1\phi2w\$ and the power which the voltage source transmit ,\$P_t\$,are as below

\$\Delta V=V_p-V_L=2I(Rcos\theta+Xsin\theta)\$,\$I \$ is the current flows from the voltage source to the both loading
\$P_t=P_L+P_w=P_L+[(2I)^2(Rcos\theta+Xsin \theta)\times 2]\$, \$P_w\$: the power which wire consume;\$P_L=\$loading power

So now i want to ask both of them are said \$1\phi2w\$,however,their voltage drop and the transmitted power are both not the same.So,which one is the real \$1\phi2w\$ circuit?you may say depend on which circuit you choose or the question provide,but the big problem is that the question will ask me about \$1\phi2w\$ without providing a \$1\phi2w\$ circuit


texts: Any importance to TVS 'parallel' vs 'series' Topology?

texts:
I am working with an existing schematic which has bidirectional TVS surge protection, laid out like this:

simulate this circuit – Schematic created using CircuitLab

The TVS diodes are discrete and have different breakdown voltages. To me, the above configuration makes less sense than:

simulate this circuit

These connections make more sense since there is no 'extra' 0.7V (or whatever the forward drop is for the diode) added to the breakdown voltage of the reverse-biased diode, which someone may forget.

Is there any particular reason for putting two discrete TVS diodes in 'series', like the above schematic rather than 'parallel'?


texts: Problem with reading values from an analog accelorometer

texts:
I have a Teensy 3.2 MCU (datasheet) hooked up to an ADXL326 analog accelorometer breakout board (datasheet). Visual examination of the board reveals a few SMD capacitors, which are 0.1uF.

I have successfully used a scale value to convert a value to a G value using advice from the manufacturer's forum. For example, when the accelorometer has no force on an axis, it will read 0G. When I apply gravity force, it will change to a ridiculous value like 7G. When the force is removed, it will not go back to 0G -- it will go to a random value from -4G to 4G.

Research has revealed that the accelorometer has an impedence of 32kOhms. See the below image for details on the MCU impedence:

Is there anyway to reliably go from a analog input to a G value using this setup? This is going to be used in a vehicle for data recording during impacts. I have spent $18 on this analog accelorometer, and would not like to purchase a digital accelorometer unless absolutely necessary.

Disclaimer: The truth is, I have no clue what any of this impedance stuff means. I just determined this was the most likely issue from here. They stated that the likely cause is difference in impedance combined with interference from the MCU clock(s). I am not an electronics engineer, I am a software engineer with some basic electronics experience.


texts: Gain and output impedance in a differential amplifier

texts:
When looking at a differential amplifier:

Why does gain increase when the output impedance is increased?

For example, replacing a differential amplifier biased with resistors for an active load (higher output impedance).


texts: What is "voltage output swing from rail" in a TI op. amp. datasheet?

texts:
I'm reading this datasheet about the LM358P op. amp. I'm trying to understand what is the output foltage swing from rail. I suspect it is the amount of volts that the op. amp.'s will deviate from rails if it tries to reach the max. output voltage. That is, if the output should be 4V according to the opamp ideal equations, but \$V_S\$ is 5V, the actual output will be \$5V - OVSFR \approx3.5V\$ (having that OVSFR is the output voltage swing from rail, which in the above datasheet is 1.5V). Is this correct?
According to the above datasheet, the output voltage swing from the negative rail would be of the order of millivolts instead. This means that this op. amp. would work better (from this point of view) in inverting configuration. Am I right?
Note: As you probably have noticed, I'm reading the table corresponding to the LM358, not the LM358P which is the one I have. I do this because there is no data for the LM358P specifically, so my guess is that LM358 will be similar.
What I have tried
According to the above datasheet, part 7.7, the LM358 has a voltage swing from possitive rail of 1.5V @ \$V_{S}=5V\$ \$R_L\geq2kOhm\$.
I have replicated those conditions in my workbench with a non-inverting op. amp. configured for a gain of 2 with an input of 2V. That would be 4V, however it stays at ~3V. That is approx. the 5 - 1.5 = 3.5V I was expecting. I'm assuming that error is caused by not-very-good-quality equipment. In addition, I have slowly increased \$V_S\$ to 9V and have seen the output voltage going up as expected, so I guess that matches my initial guess.


texts:
i'm building a robot (a sort of rover) which includes a 12V/7Ah SLA battery. The robot circuit needs a regulated 12V supply to work correctly.

I would like to charge my rover using a generic 14-19V DC power supply.

Now the question is, what device should I use to charge the battery when this is connected to the robot circuit and at the same time regulate the output to 12V?

I found the following device, but apparently this will work only if connected to solar panel. Other than this limitation it does exactly what I want to accomplish.

Could you suggest a on-the-shelf product for what i need, or otherwise if simple to create the circuit that I should build?

Thanks for your time :)


texts: Is there a way to reduce inputs or tables

texts:
well I'm working on 4 way traffic light project with pedestrian signals which professor give to me. First I started with defining the problem and figuring out how many states I need. So I came to conclusion that I need 8 states but there are 20 input output variables(or whatever they are called). And I get stucked, I don't know what to do next ? In school we learned that when working with flip-flop counter if we have 3 input variables then we will have 8 different states, but now I have 20 input variables which means I would have just over one milion states.
And also we learned about decoder, in that case table will be more or less the same but I will have 20 K-maps (since there are 20 input variables, right ?).

So my questions is: Is there any way where I can reduce numbers of states when assigning to flip-flop or should I use decoder for that ?


texts: Node method to resolve a simple circuit, I’m stuck here

texts:
So keep in mind that I’m a beginner, this is a secondary exam in my university and i just started with exercises so be kind with me :)

I can’t figure out what happened in that step.
It seems like they used some parallel resistor transformation but really don’t know how.


texts: Is it possible to cut flexible solar PV panels down to size to suit small IoT type devices?

texts:
I've been looking for a supplier for tiny (approx 10mm x 30mm x 1mm) PV cells that you find on solar powered calculators without any success.  Is it possible to cut a larger flex amorphous Si panel down to size without specialized tools? Or does anyone have suggestions on how I might get small quantities of a PV cell(s) of the approx dimensions mentioned above.

[Edit: the keyword I should have been using in my searches is 'thin film'. I'm now finding products of suitable dimensions, including cuttable foil from a company called Infinity PV].


texts: Is there a relay package which can be triggered by a numeric coded pulse?

texts:
I would like to design a simple relay which is triggered by a series of pulses rather than just a high signal.

e.g. the relay would have a serial data input. The relay would need to be "preset" with the code which will trigger it - e.g. 119. Then if you send it 01110111, the relay latches. Then sending a reset code (or the same code) could unlatch it.

I know this would be a fairly simple logic circuit to make, to drive a standard relay, but I'm wondering if such a product already exists, what it would be called so I can find it in component catalogues.

Update: the signal would be sent from an existing system which can be programmed to send pretty much any digital signal sequence (e.g. faking RS232 or other encodings) but only has one output line, and I can add line level conversion if needed.

Update 2: as I only have one driving line, I cannot provide a clock signal, so it must be asynchronous serial.


texts: Advice needed for replacing a microwave fuse

texts:
The fuse from my microwave blew out last week. I removed the fuse and measured it with a multimeter to confirm the problem (It was measuring as infinite resistance)

The fuse cap reads the following: 15A/250VP. At the beginning of this string there is an F symbol encased in an L with a full stop at the end:

From what I understand the F is to show that its a fast acting fuse but I have no idea what the L under it means. I am also unsure what the P at the end of the string (250 VP) means.

The fuse seems to be ceramic and measures 31mm x 6mm. Searching for a replacement online I found this:

https://www.amazon.co.uk/gp/product/B085LGXZRZ/ref=ppx_yo_dt_b_asin_image_o01_s00?ie=UTF8&th=1

Would somebody be able to confirm if this is a suitable replacement? I'm mostly concerned about safety as i'm assuming that a wrong fuse can cause a serious problem down the line.

Any help is much appreciated.


texts: Multiple DC power source to the board protected by schottky diodes

texts:
Provided is the DC power supply block to the micro-controller development board from one of the leading MCU manufacturers.

I need help to understand this arrangement. I will use two sources V5-9V_VIN and V5V_SDA (USB). The document says that multiple DC power sources can be provided simultaneously because protection is provided ( schottky diodes). BTW notice that the same diodes are used, hence the Vforward is the same for all diodes and the voltage supplied could be the same too (threshold turning on/off is the same).

But what happens when I feed, say, USB 5V and VIN=5v simultaneously? One diode turns on allowing +5V to the regulator input and not allowing the other diode to turn on because there is not enough forward potential difference? Can they turn on at the same time?
If only one diode can turn on at a time, then which one? I need to make sure that VIN will be the source whenever/if I connect VIN to the board, otherwise USB supplies the power.

Please clarify.


texts: Settling time of sixth order denominator transfer function

texts:
I have a system whose transfer function is as follows
$$
\frac{V_o(s)}{V_i(s)}=\frac {\text{numerator}(s)}{a_1 s^6 + a_2 s^5 + a_3 s^4 + a_4 s^3 + a_5 s^2 +a_6 s + a_7}.
$$
I am interested in the settling time exhibited by the system, hence the numerator is not in focus (hope I am correct there). I do know that the sixth order polynomial has no analytical solution. Hence I used Matlab to find the numerical solution and settling time. I would like to know which coefficients of the denominator has the most influence on settling time. Any ideas on how to analyze that?
On the other hand, for a given set of values for coefficients, if I am able to figure it out the dependence of settling time on coefficients, for example \$ \text{Settling time} = f(\frac{a_1}{a_2})\$ and then if I change the values of \$a_1\$ and/or \$a_2\$, to lower the settling time then will that work? I reckon that the moment I change the coefficents then the settling time will now be dependent on other coefficients, such as, for instance  \$\text{Settling time} = f(\frac{a_3}{a_4})\$, am I correct?
The aim is to reduce settling time by choosing right values of two variables which appear only in the denominator of the transfer function


texts: Sin cos encoders are used in motors to determine position and direction of motor.      However I am unable to understand its exact working.


texts: Op-amp problem, two inverting amplifiers?

texts:
So I stumbled across a rather strange ideal op-amp circuit that I've never encountered before. I've done enough problems regarding inverting amplifiers, non-inverting, summing, difference, and such, but I haven't done one that involves two amplifiers together. The problem asked to find both Vo and V4, so I figured that perhaps doing one amplifier at a time would help.

Assuming that the voltage difference between the inputs for both inverting and non-inverting terminals was negligible, I framed the left inverting amplifier to include V1, R1, R2, and R3. I attempted at finding the output voltage v_o1, at the end of the left amplifier, through the formula *v_o1 = -(R2/R1)V1, which ended up as -15 V.

However, when attempting to find Vo, I encountered the first roadblock: I know that since the current going into the inverting terminal is zero, i1 = i2 + i3. By using the node-voltage method with this, I identified i2 = (0 - v_o1)/R2 and i3 = (0 -Vo)/R3. This is where I'm unsure if this is all correct. I presumed that the i2 and i3 branches that stemmed off from the node is equal to i1, but could I be wrong about this? I ended up with Vo = 50 V, but I don't fully know whether this is right, or if I'm missing some passive sign somewhere.

As for (b) on finding V4 across the resistor, I think I may had solved this incorrectly. Switching to the second amplifier at the right I assumed that, because we're dealing with ideal amplifiers, the currents from the inverting/non-inverting terminals are zero, such that i4 + i5 = 0. However, considering that Vo might not be correct, I went with my result and ended up with V4 = 90 V. I'm also worried about this because instead of including the whole two amplifiers together, I'm only focusing on one at a time for each part, and that I might very well be missing key variables to include, such as v_o1. Am I wrong in saying this? It would be much appreciated if anyone can provide some insight or advice on this tricky two-stage amplifier circuit. King Regards


texts: Questions on Inductor Selection guide from TI

texts:
I have been researching on Selecting inductors for Buck Application and came across an Application report from TI.

I have few questions which are listed below:

On Page 1, report says

  This application report provides design information to help select an off-the-shelf inductor for any continuous-mode buck converter application.

Does it mean that this report applies to buck converter which always work in Continuous Conduction Mode? What will happen when converter switch to discontinous conduction mode on small load?

On Page 4 (Example 1), the input voltage is considered to a single voltage. However, in reality, the input voltage will be a range. I am assuming we have to consider maximum input voltage to calculate a minimum Inductor. We can increase the inductor value but it will increase with size and cost.
This report has selected P0150 inductor. The vendor has mentioned Et (Volts.usec), Irated and 100 Gauss Et100. The report has considered these values as Inductor's Design Conditions (Et = 59.4 Vusecs, Freq = 250kHz, Idc = 0.99A). It then calculates the temperature rise, Peak Current, Copper Loss, Core Loss and Peak B Value from Inductor's Design Conditions. The report then extrapolate these values to Application Conditions (Et, Idc, dI) (see Page 9 Evaluating the Inductor for the Actual Application) to check if the selected inductor will work at Application Conditions (Et = 38 Vusecs, Freq = 150kHz, Idc = 1A). However, going through datasheets of various Inductors on digikey, I found that most of the vendors mention Saturation Current, Current Rating (considering DCR of the inductor and power handling capability of the inductor). Why do we need to consider the parameters like Et, Irated, Et100? Can I select the inductor with right value and DCR which has Saturation and Current Rating more than Peak Current in my application (with some margin)?

I am assuming it's one of the way (using Et, Irated) to mention Inductors characteristics. The saturation current can be calculated from Et and Irated as well (Saturation Current = Irated + (dI/2) | dI = (Et / L)) and there is no need to calculate B as Saturation current should be sufficient (B scales linearly with Current).

On Page 4, the reports says:

  Since, for loop stability reasons, we should not use any output capacitor of less than 100 mΩ

However, I have gone through datasheets of various buck converters (AP6503, MCP1612, MP8007 etc) and I have never seen any minimum ESR limit on output capacitors. They always recommends to use as low ESR Capacitor as possible.

This report requires an inductor to operate at 150kHz but selects an inductor which is tested at 250kHz. I haven't seen any calculation using the Design and Application frequency conditions to validate Inductor's suitability at Application Frequency. Does it mean I can use any inductor at any frequency as long as the frequency is at-least decade less than Self resonate frequency of the inductance?


texts:
I need to design something like this:

I can do it with polygon pours but modification of a polygone sometimes involves the need to modify other polygon.

I would like to know if it is possible in altium to design a part of the component side layer like a split plane (ie drawing the "no copper" lines).

Thanks
Julien


texts:
According to Comsol, a multiphisics simulation software company, a mach zehnder modulator "modulates" the input signal by splitting it into two parallel branches, affecting the relative phase on one or both of the parallel branches, and recombining each branch at the output. The relative phase change is imposed by an electrically controlled index of refraction.

My question:

Is the "phase" mentioned here only applicable to a single sinusoid? If two superimposed sinusoids were input into this system, would they each experience an equal phase shift  or an equal time shift?


texts: Why to use opto-transistors when controlling a DC motor from a microcontroller?

texts:
In the figure(V2 is a DC motor by the way) an isolated way of switching recommended. But what if we use a transistor such as in the figure. Why many say that the motor current would harm the micro controller and we need an opto transistor. I don't get it. Doesn't the current flow in a loop? Motor current according to theory should start from positive end and  return to ground not inside the micro-controller pin?

edit: Ok my schematics is wrong I guess it is because the leg with arrow is base right?? base(arrow) should have been in the middle which is switching via Arduino pin. But I asked this question because I'm mostly concerned with the danger of DC motor current. How can DC motor current flow inside the Arduino pin ebenthough there is a 0 resistance conductor instead of a transistor. Theory says current always flow in a loop from positive to its negative. Is there a path for DC motor current to flow inside the microcontroller?


texts: How to find which landline wires are mine using sensors on my cell phone?

texts:
How do I figure out which one is my line? I know there's a special tool for it, some sort of beeping proximity sensor. I don't want to buy any tools.
My cell phone, like many, has a Magnetometer. Should it get a louder reading if I dial out on the landline at the same time for example?


texts: Energy efficient inrush current limiting

texts:
Short version: looking for simple and energy efficient way to limit capacitive inrush current. Primary design goals are to minimize radiated heat and current draw during normal operation. The schematics must allow intermittent operational current up to 80A going both ways but should limit the rate of change of the startup current to about 25A/s.
Long version: We have several motor drivers and several control modules powered from 24V battery rated up to 80A continuous. All of these have rather large capacitors on the power inputs, resulting in a spike when master power switch is engaged. Recently we changed the battery supplier and new batteries have "smart BMS" which turned out to be too smart. It has short-circuit protection that is triggered by inrush current and the battery disconnects itself. Note that the master switch has built in 80A circuit breaker which does not trip. So, either inrush current never gets that high or (most likely) the spike is too short. Also note, that after the battery BMS is reset it allows up to the maximum rated current with no problems, which leads us to believe that its short-circuit protection reacts not on the momentarily current but rather on its rate of change.
Here are some of the options we considered:

Adding pre-charge resistor as suggested by motor drivers manufacturer prevents BMS from tripping but creates another problem of master control module powering up when voltage on a bus reaches certain point, then browning-out when it drains capacitors and so on;
Adding P-FET based time-delayed limiter is not suitable due to bi-directional requirement (to support braking recuperation current);
Adding NTC ICL alone is not acceptable due to radiated heat;
Adding NTC ICL or simple current-limiting resistor with time-delayed relay is currently most plausible option. Unfortunately the relays capable of switching 80A DC have relatively high coil current. Since the device is supposed to be ON for days at a time it quickly adds up;
Using resistor plus latching relay looks like really good solution, but wile engaging the relay is not a problem we have to come up with a way to reset it after the power disconnected. While not optimal, we can theoretically allow this circuit to draw directly from battery for reset pulse, as long as it does not consume more than couple mA afterwards;
Finally, replacing the BMS with something less skittish is probably the right way to go, but we still want to be able to use already assembled devices for testing purposes.

So, at the moment we are planning on adding a resistor and ~100mA time-delayed non-latching relay. However I hope there is more efficient solution to this problem.
Question: Can you suggest something better than the options listed above? If not, any ideas on a simple relay control circuit that produces one pulse when power applied and another when it is disconnected?
And another rather silly question: how to rate the current-limiting resistor? Using "inrush-current^2 * R" is definitely an overkill, as it is only powered a fraction of a second. But the datasheets do not specify maximum current, unfortunately.
UPDATE
After reading all the comments we did some experiments. Any resistor 2.2R and up stops triggering of short-circuit protection. We also found some 75mA relays rated for 80A DC. While not ideal, still less dissipated heat than NTC. Below is the circuit I've come up with to delay relay activation for about 0.1s. Please, critique.

UPDATE 2
Assembled and tested the above schematics. Works as expected with R1, R2 increased to 47k and 22k respectively.


texts:
Sequential Circuit Diagram: D Flip-Flop

Answer Key

    0   1   2   3   4   5   6
A   1   1   1   0   0   0   1

Q2  0   1   1   1   0   0   0

Q1  0   0   1   1   1   0   0

Q0  0   0   0   1   1   1   0

Above is the sequential circuit diagram and the corresponding answer key from our class review session.

From what I understand:

if D=1, then Q=1
if D=0, then Q=0

I get that column 0 holds the initial values of A, Q2, Q1, Q0.

Questions:

1) How did the rest of the columns (1-6) arrive to the values they have?

2) How was it realized that there will be 7 columns (0-6)?


texts: Is the voltage supplied by an LCD backlight inverter in a laptop dangerous in any way?

texts:
It is my understanding that in a laptop, voltage from a low voltage (say 10V) battery can be converted into higher much higher voltages by way of inverter for an LCD display module. Is this voltage dangerous in any way if I were to put a load on the output, such as my wet finger?

I believe these inverters have a high source of impedance and don't supply much current? Yet I was wondering if there would be a circumstance in which one could possibly feel a shock.

Earlier today, as I was typing on my LED backlit Macbook Pro keyboard, I spilled water all over it while simultaneously having accidentally dug a portion of my finger under a key. Although not part of the display, I thought I would have felt something. Why didn't I?

Apologies for the scattered array of questions.

Thanks


texts: I'm using a variac to control voltage on a heating element and we're having issues with the fuse blowing. The variac is rated for a 10 amp fuse and we're using a 8 amp one. The 8 was suggested to avoid damaging our heating element. The max voltage we've used it at is 7.5 V, and with the element's resistance at 6.4 ohms, we calculate that it should be using less than 1 amp. Is the reason it's blowing because of an issue with our element or the setup, or is it because we're using a lower rated fuse?


texts: Unknown 5-pin opamp / comparator IC with ">10" marking

texts:
I'm trying to figure out what this 5-pin IC from the below image could be:

The SMD Package looks to be TSSOP5.

The component is used in the Kemet SS-430 sensor module. I think, is part of the output amplification circuit for the Kemet PL-N823-01 sensor. My guess is that the IC is some kind of opamp or comparator.

(rectangles = unmarked SMD parts. They are mostly resistors and capacitors, I think.)

Could you help me identify this component with the ">10" marking?

Thanks!

PS:
I would like to use the PL-N823-01 in a project, but unfortunately I did not found a reference design for it yet. So, I'm trying to figure the things out from the SS-430 module.


texts:
I have an optimus STAV 3200 (radioshack parts link) and this component labeled A958 960L blew itself in two taking a resistor with it. The parts list does not specify what the component is or what I would need to replace it with. Any help would be very much appreciated.
On the board it is labeled as Q519R. The resistor (R549R) is 180ohm 5% 1/5w I believe based on the parts list, would you agree?
If I replace the resistor and what ever part this is, do you believe that will be it or is this likely caused by the failure of a different component? Thanks


texts: Why is the LM741 operational amplifier so prolific?

texts:
Possible Duplicate:
  What's the uA741's appeal?

The LM741 seems to be the "prototypical" OP-AMP used in teaching basic analog electronics. Why is this chosen when better designs are available?


texts: How to operate transformers at lower voltage than nominal

texts:
What do I need to watch out for when I operate a power transformer at a significantly lower primary voltage than it is rated for?

How do I derate the power handling capability? Is efficiency degraded significantly?

I would expect that, for the same power, core losses are decreased (magnetic field scales with the voltage). Resistive losses on the other hand scale with the current, so will increase. I am wondering if these are the only effects.


texts: How can I reduce B+ from 460VDC to 420VDC in the power supply of a tube guitar amplifier?

texts:
1977 Deluxe Reverb. Schematic calls for a power transformer input of 120VAC, and a secondary HT winding producing 330VAC (x2, center-tapped). This gets rectified by a 5U4GB (which consumes 50VDC in the process), and is filtered to produce approximately 420VDC B+, and 415V on the power tube plates.

My original power transformer appears to have been wound 'hot'. At approximately 120VAC wall voltage, my HT winding is at 377VAC, not 330. The downstream effect is that my B+ is closer to 465VDC. At the same time, the heater winding is right where it should be, 6.3-6.4vac, at 120-121vac input. So it seems isolated to the HT winding.

The amp works fine, and has for years, but in the interest of learning and experimentation, I'd like to bring the B+ down to spec levels. I'd like to drop 35-40VDC from the B+.

I've googled and come up with shunt regulator, bucking transformer, etc. I don't know what these mean in practical terms, in the context of a vintage tube amp. I'm hoping there's some component, or small analog circuit, I can place after the rectifier and filtering, and before the standby, to reduce the voltage.

I'm aware there are other ways to reduce the B+. I don't want to apply a variac to reduce the input voltage, because it affects the heaters, too. And for this discussion, I don't want to swap the 5U4GB rectifier for a 5R4GB. While feasible, it would only drop a further 10-15V. Also, it's my understanding that this solution would introduce more 'sag' in the power supply. Finally, the capacitor input voltage of the 5R4 is only 20uf, and my (spec) primary filter caps are (total) 32uf. Probably not an issue, but still. In short, I'm trying to get the amp closer to spec, not farther.


texts:
I have a system that consumes 0.497 Ah,
with a voltage of 5V.
I did the calculations to feed the system with solar enegeria:

Watt = 5 * 0.497 = 2.485W
Hours = 48 hours of system use
Total = 149.1W consumption

By calculations I would say I need a solar panel that generates 2.07 ah and a battery 12.42 Ah.
Calculate solar panel:
149.1 / 6 (sun hours) / 12 (system voltage) = 2.07 Ah
Calculate battery:
2.07 * 6 (sun hours) = 12.42
That's right ?


texts: Transient of a circuit when a generic audio signal is applied

texts:
I know the importance of the behaviour of a circuit when a sinusoidal signal is applied: by using Fourier Transform, I can see a generic signal as a (continuous) sum of sinusoidal signals with different frequencies.
The question is: By applying Laplace Transform to a circuit, I can find the transient (if circuit is stable) response to this sum of sinusoidal signals. If the generic signal is an audio signal, does the transient influence what I hear? I mean, when I listen to a song, I should also hear a "transient" audio (which should be annoying), but I don't listen to this transient. Then: How is transient response dealt in audio circuits?

Example: if vin is a generic audio signal and by using Fourier I get vin= Asin(wt) + A'sin(w't) + A''sin(w''t) + ... and if the circuit is a simple amplifier with a gain equal to k, then vout = kvin
In this case I have the same original audio signal, just amplified by a factor k. But we know that every input sinusoidal signal gives raise to transient (that will extinguish if the circuit is stable), then the output is vout = kvin + transient and thus the output audio signal is no more equal to the input audio signal (and i should hear some "modification" to the song I'm listening to...)


texts: How to scan and differentiate multiple switches through a single input/output pin?

texts:
I was reading through the document tips and tricks using 8 bit controllers by microchip and found this diagram.I have seen this in application in some electronic circuits over internet but never found a satisfactory explanation on how the four switches were differentiated from one another.

The three switches were connected to a single I/O pin of micro controller.

The document says:

  A timer is used with a comparator or changing digital input to measure
  the capacitor charge time. The charge time is used to determine which
  button is pressed.

Software sequence:
1. Configure GP2 to output a low voltage to
discharge capacitor through I/O resistor.
2. Configure GP2 as one comparator input and
CVref as the other.
3. Use a timer to measure when the comparator
trips. If the time measured is greater than the
maximum allowed time, then repeat;
otherwise determine which button is pressed.
When a key is pressed, the voltage divider
network changes the RC ramp rate.

can anybody help me to understand this method in a lucid manner.I'm not sure about  how to do away with this and differentiate the switches.I'm sure this will be of help to some one working to limit the use of GPIO pins.

If any other alternative ways are available all options and suggestions are whole heatedly welcomed.

Thank you
With Regards,

Rookie


texts: How do you set an STM32F4 IRQ handler without using the HAL?

texts:
I'm using the STM32F405xx/407xx architectures, which is a Cortex-M4.
The online documentation and tutorials on this subject are overwhelmingly HAL-based. I am converting a project over from another uC architecture and would like to know how to set my function as interrupt service routine, assign the IRQ a priority, and clear its associated interrupt mask bit so that it is ready to handle timer update interrupt events.
Do I just write an address into the vector table itself? Would I follow that with a NVIC_SetPriority() and NVIC_EnableIRQ() call?


texts: Does using "16's complement" for hex always yield the same result as two's comp for binary?

texts:
I'm sure it's obvious as day, but i'm having a hard time convincing myself with all these carries and conversions...

Given that i'm operating on the same number (say, 0xA451) in different representations(0x and 0b), is it always safe to use "16's complement" (not an actual term) to represent the opposite number instead of "going down" to binary and using two's complement?

I.e. I want to know what minus 0xA451 is so i do (0xFFFF - 0xA451) + 0x0001 = 0x5baf.
Else, i could have done 0xA451 = 1010 0100 0101 0001, flip them bits and add one:

0101 1011 1010 1110 +
 0000 0000 0000 0001 =
0101 1011 1011 0000, which is indeed 0x5baf.
I would appreciate somebody confirming that this is always true.


texts: how to lower reactance of an electromagnet?

texts:
I have an electromagnet that I want to switch on or off quickly. After making the prototype I found that the magnetic force remains for about 1 sec after I turn the current off . This is a problem as I want the magnetic force as quickly on or off as possible.
Right now the electromagnet is made of a 2000 turn solenoid, and current in the solenoid stabilizes at 0.6 amps (after the annoying slow ramp up).

If I were to bundle 4 strands of magnet wire and coil the bundle 500 turns (500 x4 =2000 turns) and then connect each wire in parallel, then adjust the voltage so that the current in each wire is still 0.6, would that improve the response time of the magnet (by lowering the impedance and therefore reactance of each individual coil) ??

simulate this circuit – Schematic created using CircuitLab


texts:
I'm trying to solve the following question:

Determine the output-tuned circuit voltage in Fig. 4.P-7. The tuned circuit is resonant at \$\omega_0\$ and has \$Q_T = 20\$.

My try: I don't know how to apply KVL and KCL correctly. Solving for DC: $$I_E = \frac{12 - V_{EB}}{12} = \frac{12 - 0.7}{12} \approx 0.941 \ \text{mA}$$Is the following equation true for AC analysis?
$$\frac{v_1 - v_{eb}}{50} = i_e + \frac{v_{eb}}{12\times10^3} \\ v_1 = 0.3\cos(\omega_0 t)$$ Also we have $$i_E = I_{ES}e^{\frac{v_{EB}}{x}} = I_{ES}e^{\frac{v_{eb} + V_{EB}}{x}}= I_{ES}e^{\frac{V_{EB}}{{x}}}e^{\frac{v_{eb}}{{x}}} = I_Ee^{\frac{v_{eb}}{{x}}} \\ x = \frac{kT}{q} \approx 26 \ \text{mV}$$I don't know how to proceed further. Obviously these equations hold: $$v_1 - 50i_1 - v_C - v_{EB} = 0 \\ 12 - 12\times10^3i_2 - v_{EB} = 0 \\ i_1 + i_2 = i_E \\ i_E = I_{ES}e^{\frac{v_{EB}}{x}} \\ i_1 = C\frac{dv_C}{dt} \\ v_1 = 0.3\cos(\omega_0 t) \\ x = \frac{kT}{q}$$
but it's really difficult to solve them directly and some simplifying assumptions should be made.


texts: How to set up goal value, low and upper value in bisection in Hspice?

texts:
I'm working on the project that request to use bisection in Hspice ( example, I want to use bisection to measure setup time). I have read the documents related to Hspice, but they only showed syntax and examples with goal value and upper&lower limits already. I'm confused that what kind of factor or element that we need to focus to find/measure/calculate goal value, upper and lower limit. Here is one of example I took from document:

DFF_top Bisection Search for Setup Time
PWL Stimulus
v28 data gnd PWL

0s 5v
1n 5v
2n 0v
Td = "DelayTime" $ Offsets Data from time by DelayTime
v27 clock gnd PWL
0s 0v
3n 0v
4n 5v

Specify DelayTime as the search parameter and provide
the lower and upper limits.
.PARAM DelayTime= Opt1 ( 0.0n, 0.0n, 5.0n )
Transient simulation with Bisection Optimization
.TRAN 0.1n 8n Sweep Optimize = Opt1

Result = MaxVout$ Look at measure
Model = OptMod

This measure finds the transition if it exists
.MEASURE Tran MaxVout Max v(D_Output) Goal = ‘v(Vdd)’
This measure calculates the setup time value
.MEASURE Tran SetupTimeTrig v(Data)Val = ‘v(Vdd)/2’

Fall = 1
Targ v(Clock)Val = ‘v(Vdd)/2’
Rise = 1

Optimization Model
.MODEL OptMod Opt

Method = Bisection
.OPTION Post NoMod

In this example, I saw that they wrote Goal = v(vdd/2), but what is the value of v? what does it mean?
Thank for your help.


texts: Why peak output current is greater than short circuit output current in 7805 voltage regulator?

texts:
This is the datasheet of 7805 voltage regulator produced by "Continental Device India Limited".

Question:

Why is the peak output current greater than short circuit output current?
Shouldn't the short circuit output current be greater than the peak output current since at short circuit resistance is zero and maximum current will flow?


texts:
background: My goal is to use an Arduino with two proximity probe (sensors) to achieve some output.

It is worth mentioning that the output of the proximity probe has two components:

DC output that determines the position or the GAP
AC component on the top of that DC voltage to determine the vibration

The proximity probe sensor has a negative voltage output from -5 to -12 volt DC and then the AC is on the top of the DC,

I have two parts in my circuit to achieve two outputs suitable for arduino as they should be from 0-5 volt

the first one is to get the AC of the signal ,  as appears on the upper part of the whole circuit, the filter is a second order high pass filter to separate the AC from the DC, which will give an AC output oscillating around zero volt.. This output needs to be shifted up by 2.5 volt so that my signal will be centered around 2.5 volt not zero.
the two resistors a will take care of that
it works fine separately !
the second part is to get the raw signal , what I am doing basically is that, I have a 15 volt adapter to shift the negative sensor signal and then two resistors as a voltage divider, so that will make the signal suitable for arduino
example: if my signal is -7 volt DC and 1 volt AC , the shifting circuit will shift the signal by 15 to be + 8 volt and then this 8 volt will go through a voltage divider as appears on the lower part of the signal

the two circuits work separately !but when I implemented them together they didn't work, the conflict is obvious from the picture, there is one node connected to different voltage values( 15 volt and 2.5 volt) which will cause the circuit not to work ( I discovered that after I implemented the circuit on a strip board for 10  channels !)

my question is how to solve this voltage conflict ? is there any other way of doing this using these components ?

when I built the circuit in the real life, my 2.5 volt output for the AC shifting was connected to an opamp voltage follower that produces constant 2.5 volt, it was working separately ( just the AC coupling part ) but it seems like it damaged after connecting the the whole thing ( it doesn't) produce 2.5 v any more, it gives zero volt,

will the conflict cause such thing ?

sorry I couldn't think of better topic name !


texts:
How does the red (rot) LED at the input to the base provide a constant current to the other two LED's after the collector, via the transistor?
(I have been told that the NPN transistor here has a default voltage of 0.6v, and the red LED at the base is providing an additional 1.2v, for a total of 1.8v)

If I short-circuit one of the LED's, the brightness of the green (grun) and the yellow (gelb) LED does not fluctuate. What is happening when I do this?


texts: Single transistor Amplifier analysis (Q point values)

texts:
Could somebody please check to see if what I have done is right? I posted a similar question a few days ago and someone said V(CE) is equal to V(CC)/2. Is it ok to do this?

So I got V(CEQ) = 6V and then I(C)=1mA

I tried to solve I(B) on the left side first but got a negative value for it? So that can't be right.

I don't need any help with part b)

Thanks


texts: N-Channel MOSFET Selection - SOA & determination of VDS - LED Application

texts:
To  begin, I've thoroughly searched for answers to my question/s and have yet to find any clear & concise data.

I'm in the progress of determining an appropriate N-Channel MOSFET to be used as a switch for an array of LED's. I need to remain in the SOA (safe operating area) of the MOSFET which is generally determined by a chart in the datasheet based on current and drain source voltage (\$V_{DS}\$).

The LED array will be composed of 2 strings of 10 LEDs (20 total) and use 1 A of current at 36 V.

The anode of the first LED in the strings will be connected to the 36 V power rail and the cathode of the last will be connected to the drain on the MOSFET. The source will be connected to ground.

The question I pose is this... How do I determine the \$V_{DS}\$ to be used in the SOA chart in my application?

Initially I assumed that I should be looking for a MOSFET that has a \$V_{DS}\$ of 36 V and current of 1 A that falls within the Safe Operating Area. But as I thought about it further, the MOSFET will never be exposed to 36 V because each LED diode has a forward voltage drop and the MOSFET itself will be at the end of the chain. Am I being led astray with this assumption?


texts:
What does the slope in this graph present

I know this might be a silly question, but my answer was:

  slope = VI = Pw (Pw is power)

And the answer in my text book was differet from mine, it was:

  slope = -r (r is the internal resistance of the battery)

And I think the book answer was related with the equation:

  Vb = V -Ir (where Vb is the emf of the battery, V is the voltage across the battery, (I) is the intensity of current and r is the internal resistnce.

So, are the two answers correct? Or it is only one?


texts:
I have designed an voltage divider bias with thermistor and the output voltage is given to adc pin of my nRF. But the internal reference voltage of my nRF is 3.6V so I did not get any accurate values and also , i cannot supply 5V as reference as it may damage the board.
Is it possible to convert 5V to 3.6V and give it as supply to voltage divider of thermistor.
Any other suggestions please tell me !!!
Thanks


texts: What physical properties differentiates the classes of PT100?

texts: I know how the accuracies are defined by the various classifications of PT100, eg Class A, Class B etc. What is it that is physically different between them?


texts:
I'm working on building a soft-latch power switch. Before I build the entire thing, I'd like to ensure that I can simply latch power on, without adding off functionality. I am wondering why the following circuit won't latch. If I press the switch, the LED lights up. But upon releasing the switch, the LED switches off.

I don't understand why the base of the bottom transistor doesn't 'see' the voltage at the emitter of the top transistor.

I am using ZTX457 NPN transistors. http://www.diodes.com/datasheets/ZTX457.pdf

Any thoughts?


texts: Why are the contacts for the Data lines in USB A and B plugs shorter than the contacts for Ground and Power?

texts:
I was reading up on USB connectors on Wikipedia and I've noticed that the contacts for the data lines (D+ and D-) are shorter in both the Type A and Type B plug.

What could be the reasoning behind this design?


texts: Is this part (given picture) an EM relay, relay-controller, snubber?

texts:
Here is a rather bad (low resolution, grainy) picture of a circuit board that claims to be a 2-channel 315MHz ASK/OOK type remote controlled relay set. I can identify the relays, but not the big blue boxy thing behind them (see picture, with red-arrow).

Can someone help identify what it is ?

Also, is that white thingy labelled "Carli" part of this blue part, or separate ?


texts: Does a coiled wire have a higher resistance than straight wire?

texts: If you take a straight piece of wire that is insulated and coil it around a non ferrous object like piece of wood would the resistance change?


texts: PIC16F15345 Microcontroller, RA5 Digital Input Pin Issues

texts:
I've been having a very strange problem with my PIC16F15345 microcontrollers. I'm trying to read a digital input state from a specific pin on the microcontroller (Pin2, or RA5). My setup code is below:

#include <xc.h>
#include <pic.h>
#include <pic16F15345.h>

#define _XTAL_FREQ 32000000

#pragma config WDTE = OFF

void main(void){
    OSCFRQbits.HFFRQ = 0b110; //set HFINTOSC to 32MHz
    OSCCON1bits.NOSC = 0b110; //set clock to HFINTOSC
    TRISA = 0b11111111; //set all portA bits to input
    ANSELA = 0b00000000; //set all portA bits to digital input
    while(1)
    {
        //loop forever;
    }
    return;
}

I'm using the latest XC8 compiler, MPLABx IDE, and a PICKIT3 programmer. I'm using an arduino's output pins to toggle the state of the input pin on the PIC, so I don't have to worry about debouncing and can trigger state changes via software.

If I want to measure RA4, or pin3, I can use the debugger to check the value of the PORTA register, and it shows a change of state corresponding to what I'd expect. PORTB and PORTC are also working normally.

However, for some reason, RA5 will always read 0, no matter what the input voltage at the pin is (I've verified 4.8V at the pin with a multimeter).
At first I thought maybe I damaged my input via ESD, so I changed to another IC of the same model (I ordered 3 from Digikey), and the problem persisted. I changed to the 3rd and final chip, but the problem was still there.

I've been trawling the microchip forums for answers, but no avail so far. Any advice is appreciated!


texts: Different behavior of FTDI USB RS485 on different computers

texts:
I use a FTDI USB-RS485 adapter cable to connect a RS-485 device to a computer.

The communication is fairly simple, the computer sends periodic requests, the device answers them.

On one computer (Dell laptop, Win XP) this works as expected, but with another (Fujitsu laptop, Win XP) I have some problems.

Every couple of request, the device does not answer them and claims a parity error. From what we see with PortMon and an oscilliscope the requests are always the same, so should be answered.

The application on the laptops is exactly the same and all drivers (CDM 2.08.24) are the same. One difference is that the problematic laptop had a previous version of the driver installed.

Any hints what I should check?

Edit:

So wie investigated the issue a little more:
2 laptops are working fine (HP, Dell, both WinXP and Intel Centrino), three others don't work (2 Fujitsu, Sony, WinXP, Win7, all Intel i5 or i7).

We measured the signals with an oscilloscope, which are sent to the device. The not working laptops send signals, which jitters around between 3-6 microsec. So we assume, the device is not able to recognize the correct bits due to that jitter.
We used different FTDI USB-RS485 cables, but always same symptoms.
The working laptops have a jitter of max. 1 microsec.

So my question: why jitters the signal transmitted by the cable on some computers, on others not?

We also contacted FTDI support, but no sufficient answer yet.

Edit2:

So far we have 2 working laptops and several not working. It seems older laptops with Centrino stuff work, so far no newer laptop with Intel i5/i7 CPU worked.

We suspected that there's no internal clock on the adapter and the adapter uses a clock from the laptop, but FTDI support confirmed that the adapter has its own internal clock.
FTDI support hasn't heard of this problem in the past and has no solution so far.


texts: QI Charging - Differential Manchester encoding

texts:
The WPC-Design document reports that:
"Transmitter use a differential bi-phase encoding scheme to modulate data bits in the Power Signal."

which encoding method do they mean?
 - Differential Manchester encoding?

Thanks


texts:
I'm building a quadcopter using Cortex A8 and I would like to use this USB WIFI dongle.

According to the description this is 3000 mW. What does this mean? 3000 mW consumption? In the USB 2.0 the maximum power can is the following 500 mA x 5V = 2500 mW. What is the 3000mW in this case? I also saw other WiFi dongle with 6000 mW powered from USB 2.0.


texts: Can I use the internal Atmega32u4 clock for USB applications?

texts:
I believe I can set a fuse in the atmega32u4 to tell it to use its internal clock rather than an external crystal.

Would the internal clock be acceptable for using the microcontroller as a USB HID device?


texts: Why does an LHCP (or RHCP) antenna reject RHCP (or LHCP) signal?

texts:
I have no background knowledge about antennas. I am trying to intuitively understand how an antenna transmits and receives a circularly polarized (CP) Electro-Magnetic (EM) wave.

From the knowledge, I could gain after searching a lot about this on the internet is we can assume a transmitting antenna to have a "wave transmitter", that rotates continuously and keeps transmitting signals as it rotates. Based on the direction of rotation we can either an LHCP EM wave or RHCP EM wave gets transmitted. Is this intuitive understanding correct?
Please see this animation to get what I am trying to say:

(Image source as used on the Wikipedia page: Circular polarization)

If I assume the above understanding is right. I can think of a receiver antenna to be something similar - in this case, instead of a rotating wave transmitter I would have a "rotating wave receiver".

If we assume 2 is correct (at least intuitively), then the wave receiver could be rotating in one direction (i.e. it can have one particular CP) and the incoming EM wave might have the same or the opposite CP. Now, how can we prove that for a wave receiver with given CP - only the incoming EM waves having one particular polarization (LHCP or RHCP) get received, but the other one doesn't?

Please correct me if my understanding is wrong. I would be happy if you can also share some links where I can get to understand the above material better.
Thank you!


texts: What are these things called in a bode plot

texts:
Here is a low pass filter bode plot:

In the bode plot theory, what is K called? What is ω0 called? What do these two represent for a low pass filter? Does K not represent an amplification or attenuation of the main signal regardless of the low pass filter?

A peculiar thing is that the gain which is a magnitude is being divided by K and the frequency axis is being divided by ω0. Why is?

Why does it specifically start from 0.1 on the frequency axis?


texts: How to make a current source that supply constant current independent of a voltage power supply?

texts: I want to design the simplest possible circuit that drives an LED. The LED must load the same amount of current whatever the voltage is at the input, between 5 and 9 V. The current could be 10 mA. I assume that must be a certain constant current source? Or maybe a window comparator?


texts: Driving a MOSFET with fastest rise time possible

texts:
I'm working a circuit to send very short pulses to a load, with the requirement that the pulses have the fastest rise time possible (~10ns or less).

I've picked out a driver that has a fast rise time, the UCC27524P (http://www.ti.com/lit/ds/symlink/ucc27525.pdf).

I have a question about choosing a MOSFET, is it the driver that determines the rise time or the MOSFET's rise time in it's datasheet?

I couple of MOSFETs I'm looking at has rise times of around 20ns, are they simply unable to switch any faster?

I've attached a simple circuit to illustrate.


texts:
I am adding a bluetooth receiver to an old suitcase style record player / am radio.

I have a bluetooth receiver which runs of 5v (usb normally). I have connected this to the volume pot, through the radio/gram switch, so that the bluetooth is only connected in gram mode (when it's silent with no record playing).

This works fine. The only issue is that the volume is quite loud, even when the volume knob on the stereo is at it's lowest setting. I tried to fix this, by putting in a 500ohm-10k resistor on the common connection of the audio cable, however as soon as I did this, I can hear radio interference on the stereo in gram mode and some ticking (a bit faster than 1 per second).

I hear the same interference when the common connection is disconnected!

Any ideas how I can get the volume down without introducing this interference sound?


texts: What is the most available high-temp superconductor for samples and study?

texts: I could only find one named Amperium on the web, but not on the eBay or any little shops. It is very interesting material with conductivity 40 times better than copper. Is it possible to buy anywhere a little sample of material like this?


texts:
I am attempting a project with USB OTG functionality. I've read quite a number of documents already but there is some contradicting information out there, so I want to find out if anyone can shed some light on a couple of things.

First some background on what I aim to achieve. I want to design a low cost device that needs some form of diagnostics interface. At the moment the idea is to have a microAB USB port which can be used to either connect to a PC, or to a custom bluetooth module(powered by the device) to connect to a smartphone for instance, the device acting as the OTG host in the latter case.

My questions are:

Is this the right type of application for USB OTG?

What is the maximum amount of current a OTG host may supply, and/or a OTG peripheral may consume? I've read a couple of places that this is only 8mA, but the USB OTG supplement to the USB2.0 spec states 8mA to 5000mA. I am more inclined to believe this spec, but I just want to make sure I am not misunderstanding something.

Lastly, can any USB pheripheral only device be connected to a OTG host provided that the driver is available, or do I need a OTG specific device.


texts: Define LTI system from a single input output pair

texts:
I am currently studying signals and systems, and am learning about LTI systems right now. I know any LTI system whose impulse response is known can be completely defined through the use of the convolution sum.

I am trying to find out if given an arbitrary input signal, I can obtain the impulse signal by adding shifted and scaled versions of the original input signal( just as we can obtain any signal by adding shifted scaled versions of the impulse). That would allow me to find the impulse response of the system in question, because the system is given to be LTI. Then I could define the system completely based on a single input output pair.
Viewing a signal as a function, this would also mean I could represent any function in terms of sums of shifted scaled versions of any other function, because I can represent any function in terms of the delta function via convolution, and I could represent the delta function in terms of any function(given what I am asking about was true)

Please tell me if this is possible. Is there a way to mathematically prove that this can (or cannot be done)? If there exists such a proof, does it extend to all functions, discrete, as well as continuous?

I apologize for any lack of rigor, if I violated the etiquette of this forum somehow, please let me know(I am a new user, sorry).


texts: Op Amp - Specifications are given for unity gain, how to choose another gain?

texts:
TL081 datasheet gives the following specifications:

How can I find the open loop amplification?
I know that the relationship between the differential voltage amplification and the (closed or opened?) amplification is A=Avd vid+Avc vic where Avc is much lower than Avd, but how can I find A?
The bandwidth for unity gain is 3MHz. Assuming that I have a single pole, I will cross 20 kHz (I want to have an open loop gain of, minimum, 20kHz for audio applications) at an open loop amplification of approximately 40 dB. That's very bad. Does that mean that TL081 is not a good op amp for audio?

I need to design a preamplifier using that op amp, and the only information I have is the image I posted. This is an exam exercise, I don't have more information.
Thanks!


texts:
Is it possible to make a D type flip flop without a clock input? How would one set the logic to 0 or 1 without using a clock input?
Thank you.


texts: How to change the clock frequency of a STM32H753ZI

texts:
just got a new MCU for testing and having a hard time changing its clock speed to the maximum (480MHz)
Using bare metals or directly manipulating the registers as I never liked the HAL interface.
What is throwing me off is usually STM32 in the Flash section will tell you which Wait State you need to configure the MCU for a Clock speed that you desire, however when it comes to this MCU it doesnt tell which Wait State for a the clock speed you want at all, instead it tells you the AXI peripherals.
Reference Datasheet: STM32H753ZI Table 17 Page 159


texts:
I am trying to evaluate a circuit with a lot of parts given their associated tolerances and I'm really struggling.

For the electronic parts with 2% tolerance I am guessing the values are to specification by about 5 \$\sigma\$ spread, for 1% perhaps 4 \$\sigma\$ and 0.05% parts perhaps 3 \$\sigma\$.

What can I do to to arrive at a unified value representing 3 \$\sigma\$ spread overall?  Would I adjust the tolerance value according to some function and re-run the max-min calculation or do I need to evaluate each item separately with the other parts set to nominal values (0% tolerance)?

Thanks in advance.


texts: Is it possible to control the color of 50-100 RGB LEDs using an ESP32?

texts:
I'm wondering if it's possible to control the color / brightness of 50 - 100 RGB LEDs using an ESP32
If so what is the wiring?
These would be 4-pin RGB LEDs  that are common anode where the voltages differ by color:
Red = 1.8 - 2.0V
Green = 3.2 - 3.4V
Blue = 3.2 - 3.4V
My initial thought was to set the whole thing up in parallel, which is apparently a beginner error.
So as 4-Pin RGBs can they be wired up in series in such a way that the ESP32 can control the color/brightness of all?  If so, how does the wiring work, what are the limitations, potential problems?
(The goal would be to control the color of all LEDs in unison, as opposed to each LED independently).


texts: Plotting the instantaneous power of an RLC circuit

texts:
So I've been solving some basic instantaneous power/ average power problems and I've been asked to "draw" $$p(t)$$ which is the instantaneous power function of the circuit, I guess there are two ways to accomplish this task:

First, you basically sketch the voltage waveform and the current wave form and keep picking points on both traces and multiplying them (I don't think I'm going to do this)

second, and this is what I actually did, found $$p(t) = \frac{V_mI_m}{2}cos(2\omega t+ϴ_v+ϴ_i) + \text{avgpower}$$

and sketched the graph manually.

OK my question is if it's possible to check my answer using any simulation program -multisim maybe- by constructing the circuit and plotting the power waveform just like the oscilloscope plots voltage waveform?


texts: Improving a permanent magnet alternator. Replacing magnets / reducing air gap

texts:
In the case of a 3 phase PMA radial flux type, used as a wind turbine, with magnets on the surface of the rotor, is it safe or even doable to stack another magnet with the same geometry on top of the existing ones, to reduce the air gap ? (supposing that the air gap is poorly designed in the first place by being way too large).

I suppose that the current magnets are glued to the rotor frame by epoxy. It would be cumbersome to knock them off easily.

The new magnets would be glued with epoxy too on top of the first layer.

The main problem I would see in this case is that a reduced air gap may cause
the rotor to seize by striking the stator poles due to axial tilt in case of high vibrations / high RPM.
or, the added magnets becoming loose at high RPM.

Any other mechanical issues to consider besides higher torque ?

In case of performance, I would expect higher starting speed and overall lower RPM at a given wind speed, lower destructive RPM tolerance, but higher power output and overall higher efficiency.

Anything I should take into account besides higher EMF at a given RPM for my rectifier circuit ?


texts: Device to detect current (for cable including hot, neutral, ground)

texts:
I am trying to determine if an electrical device is on in a non-invasive way using an arduino. My understanding is that devices like current transformers and Hall sensors must enclose only the hot or only the neutral wire.
Am wondering how products like the iVac work as it is clamped around both hot and neutral wires. What components could I get to achieve this?


texts: Optical Smoke Detector design with Arduino: buzzer problem

texts:
I'm working on an Optical Smoke Detector using Arduino UNO board. Here is the circuit diagram:

Whenever smoke is detected by the smoke sensor, the buzzer and LED should work. From the Arduino board, I'm only controlling the smoke sensor. When I run simulation of the circuit, the buzzer and the LED is not working. Though, the smoke sensor works fine. Here is an screenshot of the serial monitor:

The higher values means that IR are being passed without any deflection inside the smoke sensor. As the value decreases, it means some object (or smoke) has been detected.

How should I make LED and buzzer respond as well ? It would be great if someone can point out my mistake and help me to improve it. :)

Note: Resistors value can be seen in the screenshot of circuit diagram. Rest are as follows:

Capacitor 100uF, 25V.
Potentiometer of 10 kilo-ohms.
Transistors of BC547A

EDIT: I have taken these two actual schematics into consideration in designing this circuit:

Connecting Optocoupler 4N35 (smoke sensor) with Arduino. Since the TinkerCad was not having MOC-7811, I have used IC 4N35.

The rest of circuit is same after MOC7811. I have removed 4.7K potentiometer and 100 ohms resistor.

Arduino Code:

int inputPin = 1; // select the input pin for the interrupter
int val = 0; // variable to store the value coming from the sensor

void setup()
{
    Serial.begin(9600);
}

void loop()
{
    val = analogRead(inputPin); // read the value from the sensor
    Serial.println(val); // print the sensor value to the serial monitor
    delay(50);
}


texts:
As a complete beginner in the field of electrical engineering, I am trying to build an alarm system on an Arduino board. I want to power my board using an external 10V power supply. In case of power shortage (probably in form of an intruder that is smart enough to pull the plug below my alarm system) I want the board to seamlessly switch to a built-in 9V backup battery.

According to the Arduino documentation, the board will automatically use the higher voltage power supply, so my external should be used whenever available.

Now I am struggling to get the circuit working. So far I came up with this:

But this does not look right to me (connecting V_IN to the kathode came pretty natural to me, but I haven't quite figured out how to close the circuit). Could someone please explain how to properly design the circuit?

My circuit has one more issue I want to address: as you can see, there is a voltage divider parallel to my pseudo power supply. This is to allow me keeping track of the battery voltage and warning early when to exchange batteries. Using these resistor values the voltage of a fresh battery on AD0 comes across as about 0.85V. Will this drain a lot of my battery capacity while the battery is not even used?

Thanks in advance.


texts: Can multiple LC circuits be connected to the same antenna to listen to different frequencies all at once?

texts: I am very new to this. I am trying to make a radio that listens to multiple stations at once and signal processing circuit that separates frequencies from a microphone signal.


texts: Can an unpowered 2.4 GHz transceiver exist?

texts:
I just read an internal presentation from the company I work for announcing the release of a small consumer device with an embedded RFID tag and 2.4 GHz transceiver. The presentation made note of the fact that the device does not need to be turned on or off. I am assuming that means the device is unpowered, but I'm wondering about the feasibility of an unpowered transceiver.

Does such a transceiver exist (I could be wrong about it not needing a battery)? How much data could such a low-powered/unpowered transceiver transmit? Could it be used to fix a location within a wifi network?


texts: Using Matlab poctave function under 3 Hz

texts:
I would like to get the Fourier transform of my data from 0,5 to 80 Hz at every 1/3 octave.

I tried using Matlab poctave function but that one is only working over 3 Hz.

My question is there a way to make the poctave function work under 3 Hz or there is another way for me to get the Fourier transform of my data.

Thank you for your help in advance and sorry if I was not clear enough!


texts: How to design a heat bed / radiator using resistors?

texts:
I have to add some resistors to an aluminium plate on a 3D printer, because it only goes to 67'C without foam insulation. The heated bed currently reads 1.6 ohms (90W at 12V)

I wish to add about 96W of resistors to the aluminium plate, to run on 12V, to reach 110 degrees in 10 minutes. There is a 3cm margin of free aluminium at both ends for attaching resistors.

Are $4 Chinese power resistors like this reliable at 110 degrees? I can't find their temp rating and mean time before failure.

If use 2s2p of 1.5 ohm 50W resistor, same as 2x 100W 3 ohm resistors, it'll draw 96W, with 104W of safety in case i insulate the resistors?

I am going to:

buff the aluminium contact surfaces
glue them with arctic silver adhesive/bolt them
insulate the underside so that the heat goes into the aluminium
put them on a different power supply with an on/off switch

Am i missing some pitfalls?


texts: 4-20mA PLC analog output ground referencing for other devices

texts:
I'm currently using a PLC to control an induction heating coil.

I'm using a chinese induction driver that allows 4-20mA PID input. This device runs off standard australian 230v AC 50hz.

I've successfully operated the device using a standalone PID controller that also runs off mains power.

My PLC runs of 24v DC and has it's own din rail mounted power supply.

The output 4-20mA signal is referenced to the chassis of the PLC.

When I connect my PLC PID output to the chinese induction driver PID input, the driver short circuits catastrophically.

I believe this is due to the ground reference of the driver unit and my PLC being different. I confirmed this by measuring the potential difference between the two PID signal negatives and found that there was a 109V DC difference, which explains why the driver overloaded.

My question is, how can I reference the ground of my PLC to the induction driver unit?

I've gone through the circuitry of the induction driver and believe it does not have any features for sharing a ground reference. It receives it's power by L and N wires from a mains outlet. The control board of the induction driver has no grounds to it's chassis enclosure as such, I believe connecting the two chassis would provide no solution.

The standalone PID controller that worked perfectly also operates off mains power (L and N wires with no earth) and provides a 4-20mA signal that the induction driver seems to agree with.

Any information would be greatly appreciated, thank you.


texts: Circuit analysis with 2 inductors and a diode

texts:
I've got a circuit for analysis when I am learning half-wave rectifiers. Can anyone show me the method to analyze this circuit?

IC is the initial condition, this means the initial current for L1 is 10 mA and L2 is 30 mA. The initial current direction for L1 is from down to up, the initial current direction for L2 is up to down.

Can you show me how to analyze this circuit?

Note, here the diode is nonlinear element. Thanks!


texts:
Let me start by saying that I am not talking about the free energy or "overunity" idea of back EMF. When searching around for information I can only seem to find information from free energy sites, which isn't too helpful (perpetual motion and all of that).

With that said, I see a lot EMF suppression and flywheel circuits that take back EMF from an inductive load. These seem to be largely designed to protect other circuitry, but one has to wonder, can't you harvest this EMF, store it in a capacitor for the next cycle? Is there a downside I am not seeing, perhaps the gain is not worth the extra circuitry?


texts: regulating voltage through Op Amp Non-Inverting amplifier

texts:
I am building a CDI for my bike. The input voltage from the pulse coil of my bike is 150 mv at low rpm, but increases upto 20 volts at higher rpms. I want to regulate the pulse voltage to 5 volts at all rpms. If I use a different pulse coil the input voltage at low rpms is 3 volts but at higher rpms it reaches upto 30-40 volts. But generally the Pulse generated at low rpms is 100-150 mv. So I though of adding a non-inverting OP-amp circuit in between the pulse coil and the Micro-controller. The rpm range is 0-20000. Also The input is an ac pulse So I thought of adding a diode between the pulse coil and the Pin#3 of the 741 op-amp
I hardly know few things in electronics.
So will plz any one help me with the schematics.


texts: A question about sharing excitation supply for multiple sensors

texts:
Note: this question updated, please see the major edit.

I need to wire four or two of  accelerometer and perform data-acquisition with a single-ended daq device. It seems this is single ended output, and I want to use the DC output with a CAT6 cable for each accelerometer. The model I deal is LNC, so it has both power ground and signal ground. The manual/data-sheet shows the pin numbers of the sensor as: A, B, C, D, E, F as:

Since I don't have split supply, I will make a +/-12V split supply from from two identical 12VDC SMPS power supplies.

Below I draw how I'm planning to wire the setup for two accelerometers:

My question is:

Since I will have one split supply and two or more accelerometers, is it fine to use the same excitation for all of them as shown above in my diagram? Is there anything wrong in this way of wiring?

MAJOR EDIT:

I blew up one of the power supply when playing with "DC OK".

So here is my new setup:

I will use a regulated 24VDC power supply and a rail-splitter circuit with a virtual ground instead.

But I'm still afraid if I might cause damage because of wrong grounding.
I checked B and F are internally connected in the accelerometers. So power ground and signal ground are connected to each other. In the DAQ side VGND might be earthed(single-ended earth grounded config.). But I will not use earth wire for the 24VDC power supply. Am I safe from shorts in this case? Can I trust the isolation resistance even though Im not gonna use the earth wire on the left side(24VDC power supply side).


texts: What bandpass Q factor do I want for 12dB/octave roll off?

texts:
Sorry for what may be a dumb question.
I'm used to thinking about low and high pass filters in terms of db/octave (e.g. 6db for passive RC filter).

Whats the equivalent Q factor for a bandpass filter that would give me 12dB rolloff per octave in either direction from the centre frequency?

e.g. Fc = 150kHz
At f = 75kHz and 300kHz, signal should be 12dB down.

Is there a simple conversion?


texts: TFT LCD panel product no.FH12A-40S-0.5SH(55) (Or Psp 1001 screen) to Xbox VGA

texts: I received a broken PlayStation Portable the other day and decided to try and use the 4.3 LCD screen in a custom Xbox 360 console.  Here is the .PDF for the panel. Page 6 and 7 contain the pin-out for the screen and back-light (40 & 4 wire ribbons). Here is the VGA pinout from the Xbox. As you can see the Xbox VGA requires 1 of each color data signals, while the LCD panel calls for 8 including a LSB and MSB data sig. Can I group the panels colored data sigs. into one so I can attach it to the VGA port?  Any information would be great. Thanks in advance.


texts: Need reference materials for BLE hcitool?

texts: I am preparing commands for FCC certification.  I got some hcitool commands from the BLE chip vendor, but not sure what it means.  What is ocf, ogf?  What is OCF=0x0051 or OGF=0x3F? Looked around the web and found nothing.  Can anyone please provide me some reference materials?


texts: What is the length of one symbol sent through WiFI?

texts:
Having a WiFi emitter sending a frame, how much time does each symbol take? And therefore, what distance do they spread over?

This depends on the Modulation Coding Scheme. I would like to know which of the various 802.11 norms has the shortest symbols.

Here is an example with 802.11b:

at 11Mb/s using DQPSK it encodes one symbol per chip, each symbol carry 2 bits
this means roughly 5.5M symbol/s
1.81818182e-7 s per symbol
54.5 m per symbol

We could note that one symbol spreads over 436 periods, each one spreading over 12.5 cm at the speed of light.

Am I right?
Are there any other 802.11 norms that have shorter symbols?


texts: Building a Sub-nanosecond Monostable with ECL Flip-Flop

texts:
I'm trying to understand whether it's feasible to build a monostable multivibrator from an ECL flip flop w/ reset. The goal is to produce a 300-400ps pulse when the flip-flop is clocked and D is also high.

My understanding is that the output of a flip flop can possibly be fed back to the reset in order to produce a monostable function.

As an example consider the part SY10EP51V and specifications

How can the minimum pulse width (500ps) be longer than the propagation delay from Reset->Q (320ps)? Can the output "un-reset" after the change has already propagated, if the reset isn't held for the full 500ps?

Can the flip flop reliably produce a pulse if the output is simply wired directly to the reset? Otherwise what sort of feedback network is required?


texts: How to distinguish between Thermistor, Varistor and disk capacitor?

texts:
How to distinguish between Thermistor, Varistor and disk capacitor they usually look the same.

Is there any way to distinguish between the three? What are some ways I could do that?


texts: Does an AC lightswitch dimmer/light combination consume the same power no matter its setting?

texts: I'm hoping to resolve an argument here. Someone else said that lightswitch dimmers don't actually cut back on power used, since they're just resistors and just divert the power to additional heat. I agree that dimmers are just resistors, but from my thinking, V=IR and P=IV gives us P=V^2/R. Voltage is constant in this system, so as resistance increases between the dimmer and the lightbulb in series, power will go down. Who is correct?


texts:
I'm creating a simple circuit and I need it to turn on when I press a button and stay on for the time that I choose on the timer (choose the time on a potentiometer, and it needs to go from like a few minutes to 3 hours).
Eg. I choose 1 hour, press 'start', the light stays on for an hour and it turns off.
The problem is that I can't find a timer that would work that way, can anyone help?

Ps: I don't want to use a microcontroller

Thanks


texts: series battery connection with different voltages

texts:
I am trying to make 9.6 V out of 8 AAA rechargeable 1.2 V batteries. My answer is to make a series connection.

I have two 3 battery holders and one 2 battery holder for my 8 batteries. Now can I connect those three battery holders to make 9.6 V. I know that I need batteries of the same type and voltage and capacity, but technically all these batteries are the same. Will it work?


texts: Momentary overloading of a mains transformer at low duty cycle operation - what could go wrong?

texts:
I'm planning on using a 120 VA Hammond 1182P12 toroidal transformer to deliver 24 VAC to a 2.5 Ω resistive load (a JBC C245 soldering iron cartridge), implying 9.6 A RMS, 230 W if continously applied. A microcontroller-driven solid state AC switch in series with the load would open or close at zero crossings, modulating the delivered power. A slow fuse would protect the device at the primary side.

simulate this circuit – Schematic created using CircuitLab

The transformer is rated for 5 A continous (at 24 V), and I suspect this limitation to be determined almost exclusively by the heating of the transformer due to losses. Mains transformer losses can be split into two components - core losses (hysteresis and eddy currents), which are mostly load invariant (determined by primary frequency and voltage) and copper losses, which are only proportional to the square of the load current (neglecting the small primary current present due to core losses).
Assuming a worst case scenario where all transformer losses are due to copper losses, half a cycle (50 ms) of operation at 9.6 A produces the same losses as 50 ms * (9.6 A)2 / (5 A)2 = 184 ms at the rated 5 A.

My control algorithm would make sure that:

DC balance is maintained to prevent core saturation (the number of positive half cycles delivered to the load always matches the number of negative ones, +/- one)
The average power delivered on a timescale of 10 minutes or more is always 85 W or less (with the above assumptions, 85 W average in the form of 9.6 A pulses generates the same copper losses as 5 A continous)
The average power delivered on a timescale of 5 s or more is always 140 W or less

Can I avoid a bulkier, heavier and more expensive transformer and larger case?


texts: Find the output for the series (RC) low pass filter

texts: How can I solve this problem? Sorry if it is too simple but I learn from home due to COVID-19 and can not get in touch with my teachers


texts:
I am planning a Rev2 of a previously successful motor driver PCB and I want to simplify it.
Rev1 was a bit 'belt and braces'. It took 24V from a main board and passed that through an adjustable switching voltage regulator PCB assembly, an Amazon off-the-shelf job which inserted by header pins and was there to support reusability and modularity. That VOut then went to a motor (I use 5, 12 and 24V in my project); down to an IRF540N MOSFET driven by Arduino PWM (0.5 or 1 kHz) and then to Ground.
The schematic is attached. You'll also see bits like a switch to bypass the voltage regulator, fuses, flyback diodes, standard resistors around the MOSFET, and a DPDT latching relay acting as an H-Bridge. They're incidental to the question I think.

Rev2 I was considering combining the MOSFET and the Voltage Regulator as they're basically the same concept. I know that motors generally are pretty resilient against high-frequency voltage variation but I was wondering if the motor would cope with being PWM'd at a peak voltage of multiple times its rated voltage with a suitably low duty cycle.
If it's better practice to smooth it out, I was thinking about putting capacitors in, one between VCC and MOSFET Drain and another between VCC and MOSFET Source. Back-of-the-envelope suggests that to keep fluctuation around +-10% would take 500uF of capacitance (dV = 2V, dT = 1ms, I ~ 1A with 24V, 50% duty cycle @ 500 Hz). Simplified schematic (less fuse, bypass switch and relay) attached. Inductor/resistor pair represents motor.
I also wonder if I'd cause any weird side effects with the MOSFET by doing that, or any other weird side effects I haven't considered. P.S. any other feedback welcome!


texts: Power line voltage out of phase with ambient 60Hz electrical noise - why?

texts:
I just bought my first oscilloscope and have been tinkering with the measurement of different signals just to learn the ropes and familiarize myself with the scope.

One of the first things I noticed was the ambient 60Hz "noise" that is picked up when a probe is connected to the scope. It is obviously originating from the electrical lines in the building, and I can verify this by holding the probe in my hand and placing my other hand nearer or farther from an electrically powered object or cable - the amplitude of the noise increases or decreases respectively.

Then I probed the mains voltage to see how clean the incoming power is. Next, I viewed the aforementioned 'noise' signal on one channel and the mains power on the other channel.

What I saw was surprising and I don't understand the reason:
The mains voltage shows a clean 60Hz sine wave.  The 'noise' signal is a jagged sine wave, still obviously 60Hz but with a lot of static.  However, the two signals are out of phase, by what appears to be approximately 90 degrees if my measurement is correct.  I would have expected the phase of the mains power to match the phase of the noise.
I was concerned my scope had some sort of delay between sampling the two channels, so I switched the inputs and still saw the exact same phase difference.  Attached is a screen capture showing the two signals (red = mains, yellow = noise).

A little more research shows that transformers can cause phase shift between the input and output sides.  (TI pdf)
Is this what I'm observing? or is something else in play?

If I'm missing a basic point, please help me understand it or at least guide me in the right direction.


texts:
I'm developing a simulation model of a component that I need in my design.
To make it fast and simple I decided to only create it in a behavioral manner (eg not synthesizable).

To do so I'm using a CASE statement (representing an FSM) with WAIT statements inside.

main : PROCESS
BEGIN
    CASE state IS
         WHEN S0 =>
            WAIT UNTIL start = '1';
            state <= S1;

         WHEN S1 =>
            WAIT UNTIL stop = '1';
            state <= S2;

         WHEN S2 =>

            ...

         WHEN OTHERS =>
    END CASE;
END PROCESS;

The problem is that state enters S1 when the startsignal is asserted but doesn't enter S2when stopis asserted.

I always thought that using a WAIT statement in a CASE stucked the process in a given state until the condition is valid but this example shows that I'm wrong. What do you guys think of this?


texts: Toggle transistors with an shiftregister to light up an LED

texts:
First of all I'm quit new to electrical engineering. I had it 3 years in class but I didn't do well.

So here is what I plan. I got some shift-registers (74HC595) Which I'll set with an arduino mega 2560. With this I'd like to light up an LED. First I thought I could do it without any other circuit by just adding the right resistor to the 5V lane of the register.

simulate this circuit – Schematic created using CircuitLab

But I noticed that the register can handle up to 700mW so it wouldn't be possible and I think that the idea overall is bad. So I decided to add transistors to the circuit.(2N3904)

simulate this circuit

So my question is, if I need a resistor in front of the Base of the transistor? If so what value or let me know how to calculate it so I can answer it myself for the secont transistor. (see second question down here)

And I got one more question to it. I'd also like to disable LED's by disabling the mass with an transistor. Can I just do it as shown above?

(To mention this here. I'll use it to light up 75LEDs (25RGB) in 5 Layers. By disabling the mass of a layer I can set one layer of leds at once. This will be mulitplexed to handle each led)

Update: So in total it should be something like this to handle more then one LED:

simulate this circuit

Since i got kathod LEDs it should need to be like this:

Calculation should be simmelar right?


texts: Do tunnel diodes exhibit Zener breakdown? Since tunnel diodes are more doped than Zener diodes they should, but I am unsure.


texts: UART Tx stops working without UART Rx connected

texts:
So my problem is that when I have both Tx and Rx connected to an FTDI cable with ground connected as well. When I have both cables connected I can send message as expected. But as soon as I disconnect the Rx cable the transmissions stop and I have to restart the device in order to get it going again. Just reconnecting the Rx cable doesn't work.

Im using a PIC processor that I transmit from and I use Putty to monitor the data.

Summary

All cables connected
Send data in endless loop ( works fine )
Disconnect the Rx cable -> all transmissions stops

As far as I've understood I should not need the Rx cable to be connected at all since the uart is configured to be asynchronous. But correct me if I'm wrong.


texts: How do Arduino-based 3D-printers control several stepper motors at the same time?

texts:
I have been using an Arduino to control a stepper motor using an A4988 stepper driver.
The driver requires the direction and step signal to move the motor. The most straightforward method is to use a digitalWrite and delay to indicate the stepping. During this delay the Arduino is frozen and is not able to process other commands. I later realized that my 3D-printer also uses an Arduino and analogous stepper drivers to move all the motors at the same time.
How can Arduino-based 3D-printers with a minimum of 4 motors (x, y, z, extruder) control all motors at the same time?
It seems to me the Arduino is just not fast enough to use a delay()-based method to control 3D-printers, and I was under the impression common stepper libraries are based on the delay command.


texts:
I'm working on a low-power application with data storage on a microSD card. In the interest of minimizing power consumption, I'm planning to buffer data to RAM before writing, and I suspect that the optimal buffer size would be an integer multiple of the flash block size in the SD card, as this would minimize/eliminate high-power/slow block erase/rewrites. Unfortunately, I've had little to no success finding any info about flash block sizes in SD cards; the best I've found is that they apparently range from 16Kb to 2Mb. Naturally, being a consumer product, manufacturer tech details are practically nonexistent. Is there some esoteric command in the SD spec or something I can use to determine flash block size? Is this approach unnecessary/overkill/otherwise pointless?

Whoops, found it: SECTOR_SIZE (erase sector size) in the CSD register.

So I guess a followup is whether or not it's useful to sector-align writes for power saving purposes, but at the very least I'll probably be able to measure that.


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I am currently working on an energy meter that requires to know the Power Factor in order to get the Actual Power in the circuit.
The circuit diagram attached shows my circuit diagram and it is working fine (when simulated)
But I now want to build the physical circuit, and I'm confused if all the grounds in the circuit should be connected together or not.
Is it safe to connect all together?
Any insight shall be appreciated


texts: Given a constant R,C, and the input voltage at any time, what is the output of a low pass rc circuit?

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In other words, what is the transient response Vo(t) of any arbitrary input signal for a continuous voltage input Vi(t) for a low pass filter?

We can make some assumptions:

A for any given Vo(t), we only know Vi(n) from n=0 to t.

R and C are constant.

Vo(t) cannot be discretized, that is to say whatever method is used to calculate Vo, must not be iterative, and should not be a running / recursive method.

I've tried so far is the differential equation
Dvo/Dt = (vi(t)-vo(t))(1-e^(-1/RC)), but this doesn't accurately reflect known responses.


texts: ADC Clamping Rrotection Circuit with Dual serial Diodes - Formula proof

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I am trying to undestand and calculate why in the first circuit we measure 5.7Volt (if forward noltage diode is 0.7Volt) and not 12V. I used the Superposition Theorem which first I replaced the Vcc source with ground and calulate the Vr1 and then I replaced the V1 source with ground and I calculate the Vr1 again. Finally I add the two voltages that I found but the result is not match with expect result. Does any know's with which law/rule the circuit can be prooven mathematically? Also something that I noticed one the simulation program (multisim) is when I decrease the R1 the Vr1 increases and when I increase the R1 the Vr1 decreases.
With Vcc replaced with GND the Vr1a is: 0.7V (D1 is biased and parallel with R1)
With V1 replaced with GND the Vr1b is: 0V (D1 is not biased)
Total Vr1 = Vr1a + Vr1b = 0.7V + 0V = 0.7V


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I am using a ZVS driver to test some properties of induction and power transfer. I have never PREVIOUSLY had a problem with MOSFET heating in my designs.

Today I changed one coil for another larger one to test more power.  I modified the capacitance and inductance as necessary to achieve a similar frequency (which I will fine tune later). This is just a copper coil with .33uF on the first and 2uF on the second.

I am getting some strange behavior on the scope and heating of the MOSFETs using the larger coil.

Following are some oscilloscope pictures: 1 & 2 are probing each side of the coil, the math line (purple) is 1-2.  The problem with the second coil is that even though it is producing a nice aggregate sine wave each side of the coil is getting noisier.

What I get normally:

What I get using the larger coil:


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I have a basic circuit using a BJT common emitter which I have constructed to pulse a red LED on to use as a strobe with 1us ON time (@12V) and plenty of time to cool down (<< 1% duty cycle). The pulse is coming from an Arduino MEGA 2560.

Initially I was running it with a series resistor as it that is the way I have been taught is 100% necessary when using LED's, however I have been testing without one, and it is pulsing brighter (measuring using a photodetector) and not burning out.

Just wondering what kind of lifetime I could expect from operating a LED in a manner like this, or any other effects that I should be aware of. And also if I am correct in assuming that the internal resistance of a LED is on the order of 10 ohms?

I am  90% sure this is the datasheet for the LED.
http://www.jaycar.com.au/products_uploaded/ZD1790%20-%20TLCR5800.pdf

Thanks


texts: What is the correct instrumentation to measure a pulse height of 10's of microvolts with a pulse width of 10's of picosenconds?

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I'm working with a sensing material and want to better understand its response. I have the theoritical elements worked out, but now want to begin testing and have no idea what type of tools/instrumentation would be required for the task.

What I'm testing:

Two terminal device
A photon interacting with this device creates a change in current (10-100nA).
The signal generated from this interaction could last between 10-100ps (picoseconds).

My question is what is the instrumentation required to measure at such high speed  (10-100ps) with such a small change in current (10-100nA)?

Thank you for your time.
Cheers


texts: Tweeter speaker enclosure size and material

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I try to make a system that generates high frequency tones ( 12-17kHz ) only.
Use some cheap tweeters like :
https://www.banggood.com/100W-Piezo-Horn-Speaker-Tweeter-30KHZ-Piezoelectric-Head-Driver-Loudspeaker-Treble-p-1418120.html?cur_warehouse=CN
Is the size and material of a speaker enclosure important to get the highest possible sound pressure out of a tweeter?
How far can high frequencies ( > 12 kHz ) reach outdoors?
Why low frequencies travel more far outdoors?
Thx!