texts: Why the Base of T2 gets no more voltage if S1 is opened?

texts:
When S1 is closed, T2 no longer gets enough voltage to switch. Obviously it is because the capacitor is being discharged when S1 is opened, but what actually happens at the base of T2 when S1 is opened?

And when will T2 switch back again?


texts: FT2232HL - using FIFO to send continous data to processing + signaling information

texts:
I'm designing a Software Defined Radio project.
I want to use an FPGA, DAC, ADC and FT2232HL bridge to handle communication with PC.
Can I stream continously data from PC to FIFO?
If I will use a FIFO mode of FT2232HL, and transmit RF samples continously(for DAC) through it, how can I handle transfer of "signaling data", something like turn ON Transmitter, turn on receiver, turn on standby? Can i use for this also same FIFO channel?
Thank You


texts:
I need to control a remote relay over a 1km (max) distance. Here is a simple block diagram that represents what I'm trying to achieve:

simulate this circuit – Schematic created using CircuitLab

The control signals will generated with a microcontroller. The relay modules needs to be electrically isolated from the controller, and each of them have their, independent 12V supplies. Standard CAT5 cabling will used for connecting modules to controller.

The control signal frequency needs to transmitted is less than 1 Hz (mostly on or off).

What is the best way to reliably transmit the control signal to the relay modules?

Clarification / additional info:

Relay current is 40mA @ 12V

Some thoughts:

Using an optocoupler in relay module, I can buffer my TTL signal with a darlington array and drive that opto then relay.
I can use some kind of current loop?

I also assume that EMI will be a problem with long cabling, it can create false triggers or damage control/receiver sides. Is there anything other than using TVS / clamping diodes on each end of wiring?


texts: Substitute for the PNP D45H11 transistor?

texts: I'm starting the course on edX: "Introduction to Control System Design-Computational State Space Approaches" Link: (https://www.edx.org/course/introduction-state-space-control-mitx-6-302-1x). The course outline involves the construction and control of a propeller levitated arm using state space methods, but the problem is that I just can't find all the components they require, so I'm looking for good substitutes. Especially for one of the transistors, the D45H11. Any tips?


texts: Studying the PCB of a 70s calculator. What were they thinking?

texts:
I've been studying the PCB from an ELSI 8002 calculator from 1974. I'm thinking of repurposing the case for a project, though now that I've fixed it (by re soldering the battery connectors) I don't know if I can bear to pull it apart. (sniff) Maybe, I'll buy a more deeply broken one for my project...

Sentimentality aside, I'm rather confused by the layout of the keypad. The keypad initially looked like a typical matrix keypad, but after carefully studying the traces I've found that it isn't using rows or columns.

At first I thought this might be because they were trying to save pins on the micro controller. A matrix layout with n row and m columns requires n+m pins. But, really, we only need a unique pair of pins for each button. So, really we only need x pins where n*m <= x Choose 2.

A 4x5 matrix has 20 buttons and 20 <= 7 Choose 2 = 21.
(really only 18 buttons are needed since the reset button "C" is mapped in a special way and shares no pins with the other buttons, and there is an unused pad, though maybe it's used in other models?)

I thought this was what was going on since rows and columns don't have a common pin... but the layout uses 9 pins... ? With 9 pins why not just make it a matrix?


texts: find cache hit rate for direct mapped cache memory

texts:
I have this practice exam problem which I am having trouble with. I have gone over many slides but haven't been able to really get it. The question is

I currently have an 8 block main memory with 2 words in each block, as well as a 4 line cache which also has 2 words in each line. Im guessing this is wrong since the 4 bit addresses cant be split to get the block offset, line number and tag. Also I am not sure what I am meant to do past this step.

any help would be appreciated.


texts: Is there any difference between transferring DC over one 36 mm² wire or six 6 mm² wires?

texts:
I am designing an off-grid DIY solar power site where the distance between the solar panels and inverter is going to be several dozen meters, so I would prefer to put a thicker wire to minimize losses.

Though it seems pretty obvious that, in terms of losses, six isolated 6 mm²
copper cables should perform identically to one 36 mm² cable (to be precise, the closest size existing on the market is 35 mm² but let's assume 36 mm² for the purpose of this question), I am willing to double-check this with experts. Will DC flow evenly across all the six cables, or are there nuances/pitfalls I am not taking into account?

The reason why I would use 6 x 6 mm² instead of one 35 mm² is simply that the former is 1.5 times cheaper.

Update:

Just giving a bit more details as there are suggestions that the design might be flawed and I should put the inverter closer to the panels and run a few dozen meters of AC instead.

The set of panels will produce 92–112V. It is capable of generating up to 2900W (full sun at the right angle) so the current will be up to 32A. This calculator shows that for a 40m-long wire I would need 35mm² to keep losses within 2% (and I would actually hate them to be more than 1%). Yes I could possibly erect the power shed within 5m of the panels but that would not look very nice in terms of landscaping. Also, I would prefer to keep the battery closer to the house so that I could feed some DC appliances without double conversion.


texts:
I am referring to IDT7203 datasheet. (  MEMORY FIFO 2048X9 25NS )

Link here: http://www.digikey.com/product-detail/en/idt-integrated-device-technology-inc/7203L25J/800-2478-5-ND/2014356

My question is this FIFO memory is Volatile or Non Volatile type?

Thanks in advance.


texts: How to calculate wire guage when connecting battery cells in series?

texts:
How does one determine what wire gauge to use when building a battery by connecting lower voltage cells in series?
e.g. Let's say one is building a couple of 12V batteries that are expected to supply 100 amps continuously. The first battery is composed of eight 1.5V cells. The second is composed of two 6V cells.
Using a wire gauge table I've determined that one will need a 4 AWG cable  6' or less in length to handle 100 amps with <3% voltage drop.
What guage wire should be used to connect the cells from the examples above in series? Should the internal cables also be 4 AWG? Do the number of cells and their respective voltage matter?


texts: Implement a function 3x8 Decoder with 4 variables

texts:
I'm required to implement a function

  F = ~ABC~D + ~A~B~C~D +  ~ABC + B~CD

using a 3x8 Decoder and any other additional combinational logic.

How can I implement this function if there are 4 variables (ABCD) in the expression but only 3 inputs in my 3x8 Decoder?

If I take only ABC as my 3 inputs on my decoder how can I include D to complete my function.


texts: Can a RF 433.92 Mhz transceiver communicate to a RF 433.42 Mhz Receiver?

texts:
I am working on automating my Somfy Blinds. The idea is to avoid using the remote control which works on 433.42 Mhz and use a simple RF transmitter and an Arduino.
The thing is that I can not find any transceiver at such frequency. I only can get RF 433.92 Mhz transceiver like RFM69 @ 433 MHz among others that only mention 433 Mhz without precision.
I read from other projects that this will work just fine for short distances, let's say 5-10m.
So before buying a module that won't work I just wanted to drop the question here for the expert


texts: Is Rja in parallel with an external heatsink?

texts:
I have done heat sinking before, but now I'm trying to do it on SMT chips which is a bit more difficult. Anyway, I'm wondering whether the resistance between junction and ambient, Rja, is in parallel with the heatsink resistance. So that the actual resistance would be Rja||(Rjc+Rca)?

Also, I'm considering putting the chip on the bottom due to space constraints. However, I'm worried that the SMT heatsink, which seems to only be connected with solder will simply fall off or stress the board too much if it's connected on the bottom. Would that be a problem with such a heatsink.


texts: Oscilloscope measuring of PMT in photon counting mode

texts:
I have a setup as drawn below: DC source of 15V connected to high voltage (HV) source of 1500V connected to photomultiplier tube Hamamatsu, R1-R3 are resistors builtin the socket of PMT (there are actualy 10 of them and some capacitors...). R4 is load resistance to convert PMT current to voltage. I am measuring voltage with oscilloscope. Oscilloscope is powered from isolation transformer. Input DC voltage is also powered from power supply with transformer, so the grounds should be isolated.

My problem is shown below on images: if I connect oscilloscope probes in one polarity I get expected result (photon excited pulses), image 1. But if I change polarity I get weird ripples on 13kHz, image 2. I believe it is the ripple from HV power supply. But I don't understand why am I measuring it. If I change probe polarity I would expect just the change of polarity of measured signal (peaks up, not down).

This makes me puzzled most: it is the same when I use batteries as 15V DC instead of regulated power supply.

Why do I get these results? I want to count pulses but it seems that when I try to do so with ADC and Arduino powered from USB I am counting just the ripples or some similar noice, not the peaks. Is it problem with some ground loops? How can I avoid this? Using instrumental amplifier with R4 in negative feedback loop but with similar result.

simulate this circuit – Schematic created using CircuitLab


texts: Can't Find Further Documentation on Spartan3E IO

texts:
I am trying to find some further detail on the IO resources for a Spartan 3E.

Using ISE, when I open PlanAhead to look at the floor plan I see a lot of names, organization and acronyms that I do not understand. I have read the IOB sections in both the spartan 3 family-manual and the spartan 3E family guide. Neither provided these answers.

Apologies for asking multiple questions in a single post but specifically I would like to know:

Why are there blank pads? I can't move my primitives to any pads that do not have a number (P2, P3). What are they used for and can I use them for anything?
The Pads that do have numbers have a large marking (ex. P98) then in small letters (ex. Pad107). What is the difference? What do each actually mean and why does the order seem to not follow a simple cumulative pattern around the device?
What is a tile?
What does DIFFS and DIFFM mean and what is the difference?
The site properties mentions RPM grid. What is that? The manual talks about Relationally Places Macros but that's for programming the device.

Are there any good resources for learning this more, hands on knowledge, aside from the manuals?


texts: Why must the p type be connected to the power source, and the n type be connected to ground?

texts: When we have mosfet transistors, why must the p-type be connected to the power source, and the n -type be connected to ground? I don't see what will go wrong if we do it the other way. But a book I am reading says that if we do this we will get transmission voltage over the transistor(it doesn't say which?).


texts: Know Network Reciprocity From Scatting Matrix

texts:
Given the scattering matrix,  \begin{array}{l}0.25&0.80-0.80j\\0.80+0.80j&0.30\end{array}

Is this a reciprocal network?

I know that for a two port matrix, it is reciprocal when S21=S12.

In this case they are complex conjugates so they aren't really equal. Therefore, it seems like the network wouldn't be reciprocal. However, should the imaginary part of the complex number be compared anyway? The network doesn't seem to be generating any extra output so, in that definition of a reciprocal network, the current network described by this scattering matrix DOES seem to be reciprocal.


texts: Buck convertor calculation on Vout close to Vin

texts:
I'm currently stuck in calculating the right inductor for driving very bright LED's with The TPS92518 led driver. (http://www.ti.com/product/TPS92518-Q1)

This is a 2 channel LED driver and on every channel I want to drive two of the following LEDs in series. http://www.farnell.com/datasheets/573490.pdf

One LED has 10.2V voltage drop and are rated 640mA max.
So two LEDs in series need at least 20.4V

Since my supply voltage is 24V my Vin en Vout of the bucket convertor are very close to each other.

So I end up with a duty cycle of: D = 22 / (24*0.9) = 1.02 (0.9 for efficiency factor)

Basically 102% duty cycle.

I want to be able to analog dim the LEDs and since the LEDs are used in an image recognition setup the switching frequency needs to be >300kHz

How does this work?
Am I working with the wrong chip here?
Because Vin and Vout are almost equal this is not really a buck convertor right?
Or is this called a constant voltage buck convertor?

Does it control the current by changing the switching frequency?


texts: Detecting sparks at the output of a high voltage flyback transformer

texts:
I was trying to generate plasma inside a cylinder for a hobby project, so I decided to use a flyback transformer from an old TV and drive it with a 555 timer as shown in the schematics.

It solves my problem and the plasma looks something like this. Almost evenly distributed across the cylinder.

But, sometimes due to foreign objects like metal pieces or mosquitoes inside the cylinder the entire discharge happens through a single spark (which is obvious). But that's not what I want; I want an even distribution of the plasma. I want to detect these sparks and shutdown the flyback for say 1 sec and then start it again(like in a hiccup mode) or report a fault with an LED.

I tried measuring the current via the R10 shunt resistor to find a change in current waveform during normal operation and during a spark, but I couldn't see much difference between the both. Is there a way to find the high voltage sparks and shutdown the circuit?

PS: I have limited knowledge of electrical engineering.


texts: Altium Designer - How to Remove Green X's (Error Markers)

texts:
I often find myself clicking on a PCB component in Altium and accidentally dragging it ever so slightly. Altium then draws a bunch of green circles with X's in them, which I believe means there is an overlap problem (not enough room for the move). See image below:

My issue is that even after I press CTRL+Z (undo), the moved item is returned, but the green X's are not removed. This is a problem for reading text on nets and pins, and making screenshots.

The only solution I have found is to close the PcbDoc and re-open it, which is in no way convenient.

How can the error markers be removed without reopening the file?
Bonus question: Is there a way to disable the ability to move the component in the first place?


texts: How do I measure time delay from power ON to console messages

texts:
I am working on Microzed board (schematic is here). User guide is here

I want to measure time elapsed right from  Power ON to first message that comes on the console.

The message on cosole comes after around 1 second of power ON, and I would like to accuratly measure this time.

I can use a CRO to capture waveforms, but I am not able to figure out what all pins on the board should I probe.

Can someone help me in this regard?


texts: AREF above operating voltage of the microcontroller

texts:
I’m operating an ATMega32 at 3v3 through USB and a LDO.

Is it possible to connect the AREF pin directly to the USB voltage of 5V so that I can read voltages between 0 and 5V when reading from the analog pins?


texts: Problem configuring RTC of STM32F4 using LSE

texts:
I want to use RTC of STM32F4. When I configure this with LSI, I have no problem. But when I use LSE, I have a timeout error in SystemClock_Config function when it wants to configure RCC Source with HAL_RCC_OscConfig(&RCC_OscInitStruct).

Another question is which type of oscillator should be used for LSE?


texts: Is a loose psu plugged into a three prong outlet but off a good thing to clip to an esd mat aligator clip?

texts:
I bought an anti static mat, ifixit portable, so I wear the wrist strap, clip it to the mat, the ground wire that came with the mat clips the the mat the other aligator clip clips to the grill of a plugged in but off loose psu from an old rig on the floor (carpet).
Is this a decent setup?
I keep seeing people in videos with no nothing on their hands doing all kinds of mods but I already bought the stuff, I'm cautious I guess, but don't want to plug into the ac direct or anywhere near the plate because I think my house might be wired in a weird way because it was wired by the owner 60 years ago.
I was going to sell the psu for a few bucks but it has better purpose if this will work.


texts:
I've recently gotten the itch to build a POV Display. I'm wanting to build the sort that rotates "vertically" (like a fan or bicycle rim) and I'm finding very little information on how to actually do it. Can anyone find any resources for actually building it and what math is involved?

Also, is it possible to have the POV control circuitry located in an area that is not spinning and just have LEDs (and maybe LED drivers) actually spinning?


texts:
Background

This is a follow up to an earlier question I asked - I have an ATmega2560 running a number of sensors and servos. There are two separate SMPSs running off a single 12V battery, one generating 3.3V for the ATmega and the digital stuff, one generating 5V for the servos. When measuring current consumption at the battery (only place I can easily splice in), I see a baseline of about 3mA @ 12V until the servo kicks in, then consumption varies from about 50mA to as much as 200 (@ 12V). When the servo kicks in, I see something like this:

And then when it's shutting down, I see something like this before it stops:

Accompanied by a low rumbling noise coming from the servo, with it vibrating, but not moving.

The SMPS is a TI TPS562200, rated for 2A, with an inductor rated for 3.1A. I recorded the scope reading above running this from 8xAAA batteries in series. The servo has a 470uF electrolytic cap next to it.

Regulator circuit + layout:

Servo driver (I've played with different cap values from what's there)

Question

Is the voltage drop at startup a concern, or normal servo behavior? Is the second waveform the servo trying to reach a position it can't get to? I'm starting to think that because the waveform seems to be fairly well-formed, which makes me think it's some sort of sampling/adjustment/seeking action going on.


texts:
I am currently designing with the PIC32 Micros and the 2 embedded CAN bus Controllers

As the CAN bus architecture from node to node can be very complex with CAN messages, nodes filters, masks, CAN channels RTR, etc. I was wondering if there is any software out there that can simplify the layout design.

At the moment I am using a drawing package to display the message layout for each node and drawing filters, masks, CAN message addresses etc.

This is very time consuming, and easy to add incorrect information

Just wondered if anyone knows of a custom designed program to aid me in this process

Thank you in advance for any help and info


texts: Altium error: Un-connected Pin Constraint

texts:
I have a pad in a IC left unconnected. I have set No ERC on that pin in the schematics to suppress of all violations.

But I still get "Un-connected Pin Constraint" error in PCB.

How can I suppress this error in PCB editor?


texts: Parallel plate capacitance to co-pplanar capacitance

texts:
So in my previous experiment, I made a parallel plate capacitor by putting 2 copper plates parallel to each other (the third figure in the image). I then hooked up the AD5933 evaluation board (which is an impedance analyzer) and then I put in things in between and observed the dispersion in biological materials (fruits and veggies).

My task now is to "open" up the plates to they're co-planar. I have done that and placed an active shield at the back of the plates to direct my electric fields. However, now I see no observable change on the impedance analyzer when I bring myself or fruits/veggies close to the fields. I do "feel" the field since I sense a bit of warmth closer to the plates. I observed the oscilloscope which is hooked up to the end of the receive plate and I don't see much of an observable difference, rather I see a very small change. I must include the fact that I've tried with the active shield, passive shield and even without the shield. And they all have the same effect ie: no change of impedance.

PS...even in my parallel plate configuration, the change in the oscilloscope observed is very minimal.

My question is NOT about why I am NOT getting any change. I know the reason, I would just like to validate it before I take it up with my superiors.

I think the reason that I am NOT observing an change of impedance is because a) the impedance analyzer requires a calibration for the open-plate setup ie: the capacitance across the open plates is obviously NOT the same as the capacitance across the parallel plates. And change of capacitance = change of impedance = new calibration range needed. And b) also, co-planar capacitance is complex and has to be simulated and only then will I arrive at a value.

So would it be right to think that I first need to analytically look at the open-plates and then based on some simulations, apply the formula/value to calibration for the impedance analyzer.

Another fact is that the impedance analyzer cannot measure below 1kOhm. This value can actually be lesser; but in my case I'm using the evaluation board so its limited to 1kOhm - 1MOhm. But this of course comes in WHEN I know the capacitance of these co-planar plates.


texts: What determines current through a VS in parallel with a resistor?

texts:
This is more of a conceptual question with ideal voltage sources, I am fully aware of its impracticality, but bear with me for the sake of a theoretical discussion. Consider a simple circuit shown below.

simulate this circuit – Schematic created using CircuitLab

now I know that if V1=4V there is 2A of current going through voltage source V1 because of KCL.
But in terms of an intuition, is it more correct to say that V1(VS) gets the leftover current from KCL in the node on top of it or should I say that to maintain 4V at the node, it has to consume power and hence the current through it? or are they equivalent statements?


texts: Higher resistance resistor in place of higher wattage?

texts:
Engineering newbie here. I'm fairly sure I already know the answer to the question, but I figure I'll ask anyway.

I've got an LED lying around, that according to an LED calculator requires a 80R 1/2w resistor. However, I don't have any 1/2w resistors laying around. I do have like a hundred different 1/4w resistors laying around of varying resistance.

Using a higher resistance would not make up for the lower wattage, correct? The amperage would still likely overheat and blow up the resistor?

I'm fairly sure this is true, just wanting to be sure.


texts:
I am working to develop an Android accessory hardware. Currently, I am trying to generate an random number (C language) on a embedded system, but the value doesn't change. I am wondering if there is any entropy source that I can use to generator random number.

If there is another way of generating random number other than using an entropy way, I would greatly want to hear it from you!

The software I am using:

MPLAB IDE Version 8.73 MPLAB C Compiler for PIC24 and dsPIC v3.30

The device/tools I am using:

DM240415 - PIC24F Accessory Development Starter Kit for Android


texts: Equivalent "capacitative reactance" for calculating rms current under mixed-frequency AC voltage waveform

texts:
I want to analyze a very simple circuit subject to a not-so-simple driving AC voltage waveform. In particular, my circuit consists simply of a single capacitor with capacitance \$C\$ and an AC voltage source \$V\$. Now, if \$V\$ were operating at a fixed angular frequency \$\omega\$, then I could calculate the the capacitative reactance \$X_c\$ very simply as:
$$X_c(\omega) = \frac{1}{\omega C}$$
However, what if my voltage source waveform is composed of a mixture of frequencies given by a spectral density function i.e., Fourier transform):
$$f(\omega):\int_{0}^{\infty} f(\omega)d\omega = 1$$
Question:I was wondering if there exists a way to get an "equivalent capacitative reactance" \$X_{c,eqiv}\$ such that:
$$I_{rms} = \frac{V_{rms}}{X_{c,eqiv}} $$
??
My initial reaction is that \$X_c(\omega)\$ is additive across the frequencies, and so we get the functional :
$$X_{c,equiv}= \int_{0}^{\infty} \frac{f(\omega)}{\omega C}d\omega$$
With the requirement that
$$\lim_{t\to 0}\frac{f(t)}{t} < \infty$$
to ensure that the improper integral converges.
If \$f(0)=0\$ then we can use L'Hospital Rule to strengthen this to:
$$f'(0)<\infty$$
Question: Is this the correct approach to getting \$X_c\$ for mixed-frequency circuits?

Response to Andy aka comment
Andy requested a specific scenario. Below is a example of a setup that I am analyzing:

simulate this circuit – Schematic created using CircuitLab
The voltage source waveform \$V(t)\$ has the following Fourier transform in the frequency domain (\$f\$ in kHz):
$$S(f) = \frac{e^{-\frac{1}{2} \log^2(f)}}{\sqrt{2 \pi} f} $$
I will be monitoring the current at the point indicated and calculating the rms value of the resulting current waveform.
That's a pretty typical setup, although the specific values will change, or I may use a different distribution over frequencies.


texts: Hot-plugging power kills switch-mode converter

texts:
We have a small IoT device, that runs of an external 24v DC power supply brick (https://www.rapidonline.com/tt-electronics-t6367st-24vdc-60w-installation-smpsu-85-3795)
This 24v supply connects to the input side of a switch-mode converter (TPS56637) through a power barrel (L722RAS), that converts it to 3.4v used internally in the device. The switch-mode supply is designed by TI's Webench Power Designer (https://webench.ti.com/power-designer/switching-regulator?powerSupply=0). The specific design report is available here: https://www.dropbox.com/s/2uqugyhv0k8v8zb/Power%20supply%20report%20-%203v5.pdf?dl=0
The problem is, that we sometimes experience that plugging in the power connector kills the switch-mode controller. We cannot seem to figure out why this happens, though we suspect high in-rush currents from the output capacitors in the AC-DC brick? What is the appropriate way of solving an issue like this? We can replicate the problem by inserting and removing the power connecter a few times within a short timeframe.
Relevant parts of the schematic:


texts:
I'm wondering a bit about implementing critical code sections on a Cortex-M3 where exceptions are not allowed due to timing constraints or concurrency issues.

In my case, I'm running an LPC1758 and I have a TI CC2500 transceiver on board. The CC2500 has pins which can be used as interrupt lines for data in the RX buffer and free space in the TX buffer.

As an example, I want to have a TX buffer in SRAM of my MCU and when there is free space in the TX buffer of the transceiver, I want to write this data in there. But the routine which puts data in SRAM buffer obviously cannot be interrupted by the free-space-in-TX interrupt. So what I want to do is to temporarily disable interrupts while doing this procedure of filling this buffer but have any interrupts occurring during this procedure execute after it finishes.

How is this done best on Cortex-M3?


texts:
"The art of Electronics" is often adviced as a basic, non-academic textbook for beginners and for all the enthusiasts. It is referenced also in several questions like this one. But in the Table of contents it does not have a chapter dedicated to vacuum tubes.

Is there some other book, with a similar approach, which specifically deals with vacuum tubes and shows some amplifier example?


texts:
Can I use an SCR such as BT151 or BT136 (or even a triac such as TYN616), to pass a high voltage(400V) high frequency signal (pulsed DC at 50KHz) for a fixed period?
such as 1 second on, then off for another second, then on again?


texts:
Help me identify this component: test results identify it as a diode. I believe the manufacturer is Vishay, but I can't find anything when I search for it. There is a label placed on the component: ".1 J 50-".

Any ideas?

Thanks in advance.


texts:
Please help me with calculation

I read in the link
https://www.thorlaser.com/LLLT/calculating-LLLT-dosage.htm

A 500mW laser with a beam area of 0.25Cm2 used for 20 seconds
delivers 40 J/cm²
A 200mW laser with a beam area of 0.1Cm2 used for 20 seconds
delivers 40 J/cm²
A 30mW laser with a beam area of 0.015Cm2 used for 20 seconds
also delivers 40 J/cm²
Each of these probes apparently apply the same "dosage". However, the total energy delivered is clearly different [10 Joules, 4 Joules and 0.6 Joules respectively].

--------So what it is the formula for energy delivered by laser or LEd ??
many thanks


texts: Calculating required thermal resistance (rsa)

texts:
If I have a TO-220, with max power dissipation of 10w and the worst case ambient temp is 50°c, with a \$R_{jc}\$ of 4°c/w and a max allowed junction temp of 150°c (ignore any thermal resistance between case and heatsink).

Would the heatsink's required thermal resistance \$R_{sa}\$ be 6°c/w?


texts:
I just wanted to ask if this power switching circuit is well done.
I used an opamp and a MOSFET to select between two different power supplies connected at once. This circuit would select the highest input voltage, in this case, 12V
Here's a pic:

Following Tony and Jack's steps, I tried to make some changes and improve the circuit, but I'm not sure it's 100% functional,
 well, I'm a noob at electronics :)


texts: Why does LTspice have a hard time to simulate this?

texts:
update : when the two-transistor structure is replaced by a darlington model provided as spice model by the manufacturer, the gain dependence of stable waveforms disappeared. Now, without those gain setting resistors, everything is fine.

If the circuit is like that, when the opAmp is connected to out node with R13 and R14 gain mechanism, everything is fine. It simulates easily and plots nice waveforms.

However when I decrease the gain, by deleting all gain mechanism(making direct connection to out node from inverting input) or by just setting R13 to 1k(to lower gain again); it really stucks while simulating(transient). The simulation speed is comperably slower than the first case and also the drawings of waveforms related are like these:

or a close lookup

So, it is not about the values of resistors because I have tried with 82 and 10 and it was nice. It is about the ratio of R13 to R14, which is the gain simply if I am not wrong.

Vcc is 7 volts and the signal at the non-inverting input is a sinusoidal wave 1Vpp at 1kHz.


texts:
I wonder which of commonly used crystals in PC have higher short- and long-term stability, in stable temperature & voltage environment?

Crystals I commonly see there are:

32kHz watch crystals used in RTC clocks on motherboards (are these still optimized for human wrist temperature? Hehe)
~20Mhz crystals used for generating all system clocks
50-100Mhz crystals in square metal case on videocards


texts: What is the purpose of a schottky/zener couple on an isolated flyback topology?

texts:
This isolated flyback topology has been generated by TI's webench. It's a classic schematics with a feedback going through an optoisolator.

There are, however, two diodes connecting the switching side of the primary coil with Vin which are puzzling me.

The input is 5-15V but the Zener chosen is 22V. The schottky is rated 60V. I really don't understand their purpose. It seems like they are just going to introduce noise in Vin with voltage spikes generated at the end of the primary coil.

Could someone more enlightened than me take the time to have a look at it?


texts: AMOLED display vs. LCD display: Power consumption when displaying white only?

texts:
LCD's power consumption only depends on the screen brightness setting, not on the displayed content, unlike AMOLED, where brighter colours (towards white) cause more power consumption, while black means that the pixel is completely turned off (=no power consumption).

Now, what consumes more power at the same brightness?

LCD?
AMOLED displaying white?


texts: Differential amplifier circuit - output voltage

texts:
I have a homework problem.

  We have a differential amplifier circuit with two supply sources: \$V_{CC}=-V_{EE}=5V\$, that has two identical NPN transistors and three identical resistors. T2's base is connected to ground.

  Draw the transfer characteristics of both outputs, if \$V_{IN1}\in<-1V;1V>\$
  Draw \$V_{OUT1}(t), \ V_{OUT2}(t)\$ if \$V_{IN1}(t)=1\cdot\sin(2\pi\cdot100t)[V]\$

  \$V_{BE}=0.7V, \ V_{CE(sat)}=0.2V, \ \varphi_T=25mV\$

The circuit looks like this:

And \$R_{C1}=R_{C2}=R_E\$

Firstly: \$V_{OUT1(max)}=V_{OUT2(max)}=V_{CC}=5V\$

Now we need to calculate \$I_{EE}R_C\$: \$V_{IN2}-V_{BE}-I_{EE}R_E=V_{EE}\rightarrow I_{EE}R_E=I_{EE}R_C=0-0.7-(-5)=4.3V\$

Hence, \$V_{OUT2(min)}=V_{CC}-I_{EE}R_C=0.7V\$

And \$\overline{V_{OUT1}}=\overline{V_{OUT2}}=\frac{5+0.7V}{2}=2.85V\$

Now we need to calculate, when T1 becomes saturated:

\$V_{CC}-I_{EE}R_c-V_{CE(sat)}=V_{IN1(sat)}-V_{BE} \\ \\
V_{IN1(sat)}=5-4.3-0.2+0.7V=1.2V > 1V\$

so we do not have to care about saturation

The transfer characteristics look like this:

sorry for the lack of English here, but it is self-explanatory

Now, the outputs.

\$V_{OUT1}=\overline{V_{OUT1}}+V_{IN}\cdot G_{DM1}+V_{IN}\cdot G_{CM} \\ \\
V_{OUT2}=\overline{V_{OUT2}}+V_{IN}\cdot G_{DM2}+V_{IN}\cdot G_{CM} \\ \\
G_{DM1}=-\frac{g_mR_C}{2}=-\frac{I_{EE}R_C}{4\varphi_T}=-47V/V \\ \\
G_{DM2}=-G_{DM1} \\ \\
G_{CM}=-\frac{R_C}{2R_E}=-\frac{1}{2}V/V \$

So far so good (I hope)

The second output, \$V_{OUT2}(t)\$ is simple - it will be an amplified sinus oscillating around \$2.85V\$ and everything above \$5V\$ and below \$0.7V\$ will be limited by the power supply (i.e. will be cut off).

And now what I am struggling with: what will \$V_{OUT1}(t)\$ look like? I am not really sure how to interpret this "slope" for \$V_{IN}>2\varphi_T\$.

Edit
Here is the proper transfer characteristic, the previous one is incorrect


texts: voltage and current after closing the switch

texts:
In this circuit, the switch has been open for a long time that is the 2F capacitance is full. Now we close the switch. what is the equation of the current and voltage of the 2F capacitance after closing the switch?

Here is my solution which I think is wrong:

$$
3\frac{dv}{dt} + v = 2
$$

$$
3\frac{dv}{dt} + v = 0
\\
v = ae^{bt}
\\
3b + 1 = 0
\\
b = \frac{-1}{3}
\\
v = ae^{\frac{-1}{3}t} + 2
$$

in t = 0 V should be 2 :
$$
a + 2 = 2
\\
a = 0
$$

which means that V will be constant after closing the switch and no current will pass through the 1F or 2F capacitance which is wrong.


texts: Transformer and MOSFET combination not working

texts:
I am working to understand the circuit of a vibrating needle used in factories to scratch a mark on a soft surface. Essentially, this circuit drives a MOSFET bridge which then drives a Transformer. Output of the transformer goes to the needle. The needle vibrates, and hence any surface can be cleaned using this needle.

The input comes from TP7: 4.8V when OFF and 0.5V when ON.
TP7 results in voltage at TP8: 0V when OFF and 22V when ON.
TP8 goes to transformer, probably its main primary voltage.
The two ICs U30 (programmable oscillator) and U41 (MOSFET driver) go to TP10 and TP11 and drive Q43 and Q44 - whose purpose I do not know.

I am facing trouble understanding this circuit.

The doubts I have are -
What is the transformer doing?
What kind of transformer is this one? (here is how the board looks like)

What is the purpose of Q41 and Q42?
What is the purpose of Q53?

This is how the hand-piece/needle looks like. There is a needle connected to its leftmost end. This probe connects to the output port of PCB by means of a connector.


texts:
I am currently working on a project for PV tracking systems. I have two stepper motors, one for each axis to track the position of the sun and the power generated would need to primarily recharge the batteries that are used for the whole circuit, the excess would be used to power an application that would be decided at a later date.

My question is, if I have 2x NEMA 23 (2.5V, 2.8A) Stepper Motors, and 1x LiPo Battery Pack (3.7V, 6Ah)

how much power are the stepper motors going to draw, is it calculated by the movement or per hour?
what are the calculations for these ratings in order to determine how long my batteries will last taking into consideration I have a 9W solar panel where it will recharge them?
is this battery pack enough to power the stepper motors or will I need a higher battery pack, or possibly lower rated stepper motors?
does the L293D driver IC work with these two stepper motors or is there another driver IC I would need to use?


texts: Lt-Spice doesn't give me all the information

texts:
Here is my LT-spice simulation of a simple circuit.

I need to find the voltage across R6, but Lt-Spice doesn't give me that information.

Does anybody know why this is or if there is something wrong?


texts:
I have a PWM signal at 100Hz ("Vg" label at circuit) with variable duty cycle (10%-90%). Because I had voltage spikes I managed to eliminate them by placed three capacitors which types and values are below. My query is if the ESR of these capacitors is right for this frequency (100Hz) that I am using and if no which value of ESR is the right?

P.S. I don't want to place ceramic capacitors because they produces an acoustic noise/buzz.

Tantalum Capacitors - Solid SMD 35volt 0.1uF 10%
T494A104K035AT
Tantalum Capacitors - Solid SMD 35V 1.0uF 10% "A"
T491A105K035AT
Tantalum Capacitors - Solid SMD 10V 10uF 10% "A"
T491A106K010AT


texts: In the solution to this problem, why is the electron charge omitted?

texts:
The problem reads as follows:

A silicon pn junction with a cross-sectional area of 10-4
cm2 has the following properties at T = 300K:
n region:
\$N_d = 10^{-17} cm^3\$
\$\tau_{p0} = 10^{-7} s\$
\$\mu_n = 850cm^2/V \cdot s\$
\$\mu_p = 320cm^2/V \cdot s\$
p region:
\$N_a = 5×10^{15} cm^3\$
\$\tau_{n0} = 10^{-6} s\$
\$\mu_n = 1250 cm^2/V \cdot s\$
\$\mu_p = 420 cm^2/V \cdot s\$
(a) Sketch the thermal equilibrium energy-band diagram of the pn
junction, including the values of the Fermi level with respect to the
intrinsic level on each side of the junction. (b) Calculate the
reverse-saturation current I at a forward-bias voltage of 0.5 V. (c)
Determine the ratio of the hole current to total current at the space
charge edge \$x_n\$.

The saturation current (asked for in part (b)) is correctly calculated as 4.48 × 10-15 A. The reverse saturation current due to the bias is however calculated this way:
$$I = I_s \cdot \exp\left(\frac{V_bias}{kT}\right)$$
$$I = 4.48 × 10^{-15} × \exp\left(\frac{0.5}{0.0259}\right)$$
$$I = 1.08 \mu A$$
...which is wrong AFAIK. Shouldn't it be done this way:
$$I = I_s \cdot \exp\left(\frac{qV_{bias}}{kT} - 1\right)$$
$$I = 4.48 × 10^{-15} × \exp\left(\frac{1.6 × 10^{-19} × 0.5}{0.0259} - 1\right)$$
$$I = 1.65 × 10^{-9} \mu A$$


texts:
USB3 offer a much faster bandwidth than USB2 but, technically, at the price of more wires that results in a thicker cable.
USB3 is build with 9 wires, 4 are standard USB2 and 5 are the USB3 serial (2 differential transmit, 2 differential receive and one GND).

In an effort to make a thin & flexible cable, would it be possible to make a 5 wire cable, just with the USB3 wires? Assuming that both sides of the cable are USB3?


texts: Can LTSpice used in command line on MacOS?

texts:
Can LTSpice used in the terminal by a command line?
Is there any example there ? I only saw examples in Windows OS

How would simulating a circuit file using LTSpice using terminal in MacOS? (like using NGSpice in command line)


texts:
if i changed a 63v 1000uf electrolytic capacitor for a 35v 1000uf  what would happen

its a main smoothing cap on a power regulator board thats running @ 67v dc 8amp and i want to reduce the voltage

it all starts with the toroidal transformer  witch is 220 v ac 6.25 amp that connects to the board
i just wondered if i changed a 63v 1000uf electrolytic capacitor for a 35v 1000uf  what would happen

say i change the toroidal transformer to a ac 220volt in and 2x 25v out and change the smoothing cap to a 35v 1000uf  that should work on the above board
to get near enough to 28volts dc


texts:
I'm attempting to switch a resistive DC load (50VDC @ 10 amps) using an N-channel MOSFET.
This is the particular MOSFET I'm considering.
https://www.ti.com/lit/ds/symlink/csd18536kcs.pdf
On page 1 there is a plot for Vgs vs Rds(on). I will be powering the gate using a microcontroller GPIO pin at 3.3VDC.
Rds(on) appears to be very large at 3.3V, meaning a lot of heat will need to be dissipated, correct?
In my circuit, I have 7VDC available (regulated down to 3.3VDC for the microcontroller). I was thinking of driving the power MOSFET gate with another MOSFET at 7VDC.
Is this commonplace? Is this there a name for this pairing? Using this pairing, under a watt of power will need to be dissipated as heat, correct?


texts:
We are working with an Raspberry Pi project where the time precision is very important.

Money could be potentially lost if the clock is compromised.

How would you build a tamper-safe clock module?


texts: Control inverter using Arduino PWM output

texts:
I'd like to control a frequency inverter using an Arduino Uno board and inverter analog input, in order to control AC motor speed. To do this I need to vary inverter analog input voltage. Inverter analog input is 0-40mA and 0-10V. Is it possible to build a circuit to accomplish this function using Arduino PWM output? Is there any other way to accomplish this?

update:

I've created a simple Sketch below and a prototype to test the circuit you've showed.

int potPin = A0;    // select the input pin for the potentiometer
int potValue = 0;  // variable to store the value coming from the sensor
int outPin = 3;      // select the pin for the LED

void setup() {
  // declare the outPin as an OUTPUT:
  pinMode(outPin, OUTPUT);
}// setup

void loop() {
  potValue = analogRead(potPin);
  analogWrite(outPin, map(potValue, 0, 1023, 0, 255));
  delay(300);
}// loop

The potentiometer is responsible to generate a PWM 0-10V output by pin 3.
I've plugged 12V source to Arduino and tested each part using a multimeter.
First I've measured red arrow and GND and checked 0-5V was ok.
But when I measured amplifier LM324N output pin 14 (blue arrow) and GND, it's always 0 Volts even moving potenciometer to each way.
Could you help me solving this problem?
Do you need any other information?


texts:
I wanted to do a project where I used an LED to indicate the strength of 2.4GHz RF noise around the device (presumably mostly wifi signals). I wanted it to be super cheap and hopefully without a microcontroller, because I was hoping to make quite a few of these devices. That said, I was hoping I would be able to simply make a copper wire antenna and hook it up to an led, obviously with some components in between the two.

I've been doing some research, but I've had some trouble - I haven't been able to find the procedure for making a 2.4 GHz antenna. I saw some articles online (like https://www.techwalla.com/articles/how-to-build-a-copper-wire-antenna) that mentioned how to, but it seemed strange to me that I could just cut a length of wire and it would work perfectly well as an antenna in a circuit. Is there something I'm missing?

Also, I know that I will need some sort of amplification circuit between the antenna and the led (https://electronics.stackexchange.com/a/260600/144475 says the led's glow would be far too faint to see), but for now I'm just focusing on the antenna.

Thank you so much for your help.


texts:
I want to know that if I want to enable the MAM Function in lpc 2468 should i specify both the MAMTIM AND MAMCR registers or only MAMCR.

  Is it necessary to specify MAMTIM along with MAMCR for enabling the
  working of MAM

MAM means MEMORY ACCELERATOR MODULE which is used to enhance the performance of ARM processor.

MAMTIM means MAM TIMING REGISTER which determines how many CCLK's are used to access Flash memeory.

MAMCR means MAM CONTROL REGISTER which determines the operating mode of MAM.

MAM has three operating modes:

MAM disabled

2.MAM partially Enabled.

MAM fully Enabled.

LPC2468 datasheet here - 85 pages.

User manual here - 792 pages !!! :-)


texts:
I know how normal PCBs are etched, but every time I grab a magnifying glass and examine the edge of a multi-layer board I'm astounded by the precision that must be required during production. On top of that, some of them have buried vias and other such trickery, which must further complicate the process.

How are these boards made?


texts: I have connected 14V supply terminal from alternator to 12V battery terminal and has taken the load across these terminals . But the load is operating still in 12V, and when measured across the battery terminal it show 12V only. What is happening , why not 14V across the battery terminal.


texts: What's the right replacement for vintage "glass cloth insulation" that transfers heat in Variac?

texts:
I ripped apart a broken 1950s-era Variac autotransformer to diagnose an internal short in the core, and found a layer of gooey insulating fabric mat between the coil/taps and the mounting plate:

The short seems to have been caused by some sort of deterioration over time/hole in the fabric at the site of one of the taps. I'd like to replace the insulating mat, and I'd like to know what a suitable current material/product would be for this. The 1955 document describing the cross section of the Variac says:

The coil and base are in contact over a large annular surface, with a glass-cloth insulator between them so good thermal conductivity is maintained.

As seen in the photo above this fabric material is drenched in a dark goo that looks and feels like molasses but I'm sure is not molasses (I did not attempt to taste it). The goal seems to be electrical insulation AND thermal conductivity for heat sinking. There is plenty of "fiberglass cloth" stuff around but most of it is described as being heat resistant. I assume the gooey stuff was intended to help with this but I don't know what this is even called?
What can I use to replace this arrangement?


texts: How to burn Arduino Uno bootloader to ATMega328P via CP2102 USB-2-UART?

texts:
Following the The Shrimp I've acquired CP2102 USB to UART converter. I already have ATMega328P but without burned bootloader. I want to burn Arduino UNO bootloader to it using the CP2102 converter under Windows.

Any ideas?

Thanks in advance

PS I have no any Arduino boards neither want to buy any, so please skip the advices pointing to how to use Arduino for this job :)


texts: I designed a constant speed PWM motor driver using an op-amp and mosfet. Will it work? Can you point out some problems?

texts:
I'm currently working driving two motors using some sort of PWM or switching such that they run at constant speed, regardless of load. I want to control this entire circuit using one Arduino PWM output pin.I believe that the mosfet I'm using is a logic-level one intended to be driven at 4.5V. The two motors combined shouldn't draw more than 30A stall.

Here's what I have so far:

simulate this circuit – Schematic created using CircuitLab

The two diodes are for protection. The resistor divider is simply to account for the fact that the Arduino can only output 5V. My logic is as follows: If the voltage drop across the motor is too low, then the op-amp turns the mosfet on, allowing current to flow. If the voltage across the motors is too high, then the mosfet turns off.

My concern is that, rather than oscillating, the mosfet will just end up in a stable state, thus dispersing a lot of heat. Will this happen? If so, how can I make the circuit oscillate to avoid this problem?

Thanks!


texts: Beep using buzzer just when battery died or 5V connection died using capacitor

texts:
I have a small circuit where i am using Arduino PRO MINI to make a beep using buzzer at regular interval.

I am trying to make a beep when my 5V adapter loses power (electricity gone) or even if am attaching it to a battery which died.

I don't have a plan to use extra battery for the same nor i know how to use it as well.

Is it possible i can use capacitor say 1 Farad which when battery died will discharge and made a beep (2 small beep will be good for identification) for a second and then everything is dead.

Some concerns were:

Is these cheap buzzers have any affect if it put them on opposite direction as they will beep on discharge of capacitor
Does they get impacted if the electricity comes back while it is being discharged
The capacitors does not charge linear i.e their voltage drops will that be too bad for my buzzer

I really don't want to try something as it can burn my ICs etc.


texts: Arduino Controlled adjustable current 0-1A,18V

texts:
Hello Masters of Electronics,

I'm civil ingeneer, electronics are big unknown to me, but it wakes up my interest. I would like to control proportional pressure with electronic proportional pressure regulator. If I got right I need to control it with current from 0-1A at constant voltage of 18V. I would like to control it from Arduino.

In last weeks I was looking for helping material on internet... and I found Youtube series from EEVBlog (https://www.youtube.com/watch?v=CIGjActDeoM   ...Circuit is shown at time 20:00) about making own Power Supply Unit. I took out "Costant Current" part, bought 18V, 1A Adapter... Here is Shematic pdf to download LINK

First I would really apreciate if someone can take a look onto Shematic and check if it is fine.

Secund thing...I want to reduce Arduino output 0-5V to 0-1V. I tried to do it with putting resistor in series in ratio 4:1 (look at shematic) but I doesnt work, I get much lower reduction as expected. Whats wrong, how ca I achieve it.

Instead of 1Ohm at the end I put 5Ohm resistor at the end for now...I expected current from 0-1A, but I got just 0 - approx.0,6A. Why is this like that?

Any help, suggestion, comment is highly appreciated.

Regards,
Damir


texts: Will a motor be safe if i over voltage it a little bit?

texts: If i have a 7,4v motor (like this one), can i safely run it at 8v or 9v without shortening the lifespan or destroying the motor.


texts: Calculate resistor for red Led in series

texts:
Hello guys i am really confused about the whole resistor issue. I have visited so many sites that tells you what resistor you need but i don't know the volt drop that asks to complete or the current.

I want to power 3 RED LEDs with a 9 Volt battery


texts: Can a 12V power supply provide more than the rated current at lower voltages?

texts:
This might be a silly question but if I'm using a 12V power supply rated to provide 5A does that mean that if I was to regulate the voltage down to 5V I could theoretically draw 12A at 5V?

If Watt = Amp X Voltage, then the supply should be apply to provide 60W in any configuration of amps and Volts(provided the voltage is under 12V)

Is this correct?


texts:
I have a multiple-winding transformer with the following configuration:

primary: 230V
secondary: 2x 10-12-15V
frequency: 50Hz
power : 66VA
current: 2x 2.2A

As far as I can understand from its specs the connection should be done like this:

the primary coil should be connected to the main's AC by using the pair 4-7
for the secondary coils we can connect the pin as following:

to get a 10VAC we may use the pair 9-12 or pair 2-17
to get a 12VAC we may use the pair 9-13 or pair 2-18
to get a 15VAC we may use the pair 9-14 or pair 2-19

I think it's obvious how to get a 10VAC or 2x10VAC from this transformer, right? The same apply for the 12/15 VAC outputs.

I know that in general we can connect these secondaries either in series or in parallel (thus increasing the secondary voltage or the current rate).

So my questions are:

I'm wondering if it's safe to assume that by connecting the pair 9-13 in series with 2-18 I could expect to get a 24VAC. The same for 9-14 with 2-19 which should give a 30VAC.
It is safe to assume that by connecting the pin 9 to 13 then 13 to pin 2 I would get a 24VAC between pins 9-18 ?

Assuming that the both questions above would get a YES answer, what else should I know before doing that? Any tips?


texts:
Simply my project is to connect a Huawi USB modem to my STM32F407 Discovery board, and start using AT commands to send text SMS.

so here is what I've and what I want :)

I've OTG USB capability on my board.
I've the USB Host Controller Driver and Embedded USB Host Stack.

What I want or to know more about is:

USB CDC-ACM Class Driver

Here is a simple diagram to give more overview:

I found many commercial drivers, whither by Micrium or by Micro Digital, but I'm sure there must be a free something of everything anywhere :)

I appreciate your help in advance :)


texts:
I'm a beginner in electronics, and started the 2nd chapter of AoE, regarding transistors. I've decided to design my own LED driver, as mentioned on page 76 (3rd ed.)

simulate this circuit – Schematic created using CircuitLab

Some specs:

V1 = +3.3 [V], V2_LOW = 0 [V] , and V2_HIGH = +3.3 [V].
The current (I1) through D1 should be 5 [mA].
Using a green LED (for example), the voltage drop V_D1 is 2 [V] at 5 [mA].
BETA of Q1 is at least 25.

Given the above, I need to figure out the values of R1 and R2. Here's my attempt:

To make sure that I1 = 5 [mA] when there is a signal, I'll need to find an appropriate R1:

V_D1 + V_R1 = V1, so the voltage drop across R1 (V_R1) is 3.3 - 2 = 1.3 [V].
V_R1 = I1*R1, so R1 should be 1.3[V]/5[mA] = 2.6 [k].

Now, I need to find R2 such that there is saturation when there is a signal:

I1 < BETA*I2 = BETA*(V2/R2), so R2 should be no more than BETA*V2/I1 = 16.5 [k].

In conclusion, R1 = 2.6 [k] and R2 = 16.5 [k].

Is my solution correct? If not, where and why is it faulty?


texts: OrCad PSpice: Did I design the circuit wrong?

texts:
I keep getting 0 volts when I design this circuit but I was supposed to get a value of 1V at least.

How I would be able to fix this circuit?

The circuit that we were supposed to design was Fig(74).

Every time I do a new simulation and plot the output and input, the voltage output is just a flat line at 0V.

What could I possibly be doing wrong?


texts: Speed of electricity (signal propagation?) through copper for communications delay

texts:
I would like to be be able to calculate the delay for communications
data within TCP/IP networking through cat5e networking cable.

That is a pretty vague request so I will do my best to clarify (it is very likely I am missing a piece of fundamental electrical know-how here so sorry if that question is moot by its very definition!)

Lets imagine a very basic scenario of two computers with 100Mbps Ethernet NICs connected directly together sending data from one to the other, over a 10 meter piece of cat5e cable. Also lets image the same scenario with a 100 meter cable.

Transferring data at a rate of 100Mbps means we are encoding 100,000,000 bits of data on to the wire every second (ignore fancy encoding techniques that reduce this). That is one bit every 10 nanoseconds.

In the first scenario with a 10m cable length, after 10ns of initiating the transfer, one data bit has been encoded onto the wire as an electrical signal. How much more time will pass before it has reached the other end of the cable? How much later would it be if it was a 100m cable?

I assume this is some sort of propagation formulae taking into account the resistance of the material or similar, but I have no idea where to being, and I am a complete novice at electronics so please go easy on me :)


texts: What does the third-order intercept point (IP3) tell me?

texts:
I'm searching for an appropriate RF amplifier and it prompted me to read up on the third-order intercept point IP3. I came across a rhetorical question that pretty much summarizes mine.

  Why should we concern ourselves with some fictitious point that the
  amplifier will never reach? The answer is that there is a mathematical
  relationship between the two. Given the intercept point, we can
  calculate the intermodulation product for any input/output power.

"Calculating noise figure and third-order intercept in ADCs"

But I felt that the pure theoretical explanation was a bit of a let-down. How do I use the IP3 when I'm speccing an amplifier?

Also, is it possible to output the signal at the IP3 beyond the 1-dB compression point?


texts:
I want to make my lab variable power supply from an old laptop power adapter (19V 6A) with an LCD to show Volts and Amps. The LCD needs an independent powersupply. Can I make a circuit to give me the power from the laptop supply in a way that is 'independent' or should I find another solution?

This is what I have in mind. Just a couple of Buck Converters, one of them will have the POT's moved to the front of the case and the other small one to power the LCD, fixed at 5v.

simulate this circuit – Schematic created using CircuitLab


texts: What happens to the torque/speed curve of a brushless motor when I increase the voltage?

texts:
Here is a an image of the torque/speed curve. My guess is that increasing voltage will simply translate the curve up because the slope is the torque constant, which is a physical motor property that will not change with added voltage. I know from this post that increasing voltage will increase stall torque:

Does increasing voltage increase the torque of a brushless motor?

So does the increasing voltage not only increase the stall torque, but also the overall range of torques the motor can achieve? In other words, the same RPM now correlates to a higher torque in the higher voltage curve?

Additionally, if the above is true, here is another question. If the original stall torque in the lower curve is 2.5 N-m, but the stall torque of the higher curve is 3.5 N-m, does this mean that with the added voltage I can now run the motor at 2.5 N-m more safely than I could before since it is no longer the stall torque? Or is the power dissipation the same in both curves so that 2.5 N-m will still be dissipating the same heat? So, if the motor was going to burn up at 2.5 N-m, it will still burn up at 2.5 N-m at the higher voltage input?


texts: max32660 sudden uart slowdown above 3MBaud

texts:
I am trying to set up UART1 for debugging on a MAX32660. At various  baudrates, I print Hello, world!\n 1000 times, and measure the time elapsed for each case.
140 bits/write,   14 characters/write

921600 baud: 149us / write      93Kcps
2MBaud:       69us / write     203Kcps
3.0MBaud:     47us / write     298Kcps
3.1MBaud:    691us / write      20Kcps
4MBaud:      551us / write      25Kcps
6MBaud:      382us / write      37Kcps

Why does the throughput drop as the baudrate increases above 3MHz?
Measurements are made and reported on the Tx side, and there is no flow control (Flow control is disabled via UART_FLOW_DISABLE in sys_uart_cfg). I am using TMR_TO_Elapsed() to make the measurements, and I checked it against my stopwatch in all cases, so it's not like the UART setting is affecting a common prescaler.
What could explain the sudden 16X transmission slowdown when the baudrate exceeds 3.0 MHz?
Update I hooked up a scope; the baudrate actually seems to be dropping about 16X. So maybe uart.c is not working right?
Update I read out MXC_UART1->baud0. The value is 0x00000001 not 0x00040001. So the value of FACTOR is 0 instead of 4 as expected. This would exactly explain a 16X slowdown. But how can this be? Surely the baudrate code in the eval kit is right?
Per the above observation, perhaps hardware only supports FACTOR <= 3 (though I see nothing about this in the errata).
So I tried changing MAX_FACTOR to 3 in uart.c. While this leads to the correct setting of baud0 and baud1, it appears that hardware runs at a very very slow baudrate if baud0.ibaud==0.
requested baudrate 3.0MHz:
baud0 = 00030001
baud1 = 00000003
actual baudrate: 3.0MHz

requested baudrate 3.1MHz:  (MAX_FACTOR = 4   -- uart.c as shipped from Maxim)
baud0 = 00000001
baud1 = 0000006d
actual baudrate: 200KHz

requested baudrate 3.1MHz:  (MAX_FACTOR = 3   -- uart.c modified)
baud0 = 00030000
baud1 = 00000075
actual baudrate: 1500Hz

I agree with the uart.c output in this last case. According to the user manual, it should yield a baudrate of:
DIV  = ibaud + dbaud/128
     = 0 + 0x75 = 0.91
baud = PeriphClk / [DIV * 2^(7-factor)]
     = 48MHz / [0.91 * 16] = 3.3MHz

which is the right speed to use, according to the framing error erratum (which itself gives me a great feeling too but enough on that topic).
Yet the observed baudrate (on the scope) is not 3.3MHz, but 1500Hz. Off by a tad.


texts: Developing an understanding of capacitor

texts:
I want to develop a better understanding of capacitors, thought about several problems and would like to check with more experienced, if my current understanding is correct and enough for solving these problems.

Let's be given a very simple circuit with a voltage source, a capacitor and an opened switch.
Closing the switch makes the capacitor become charged at one plate with electrons, building up an electric field between the plates and making the electrons of the other plate be repelled and thus creating another flow of electrons in the circuit.
First problem: What happens, if the switch is opened abruptly.
I guess, the electric field between the plates immediately collapses and the electrons of the first plate, try "to escape" (the capacitor can no longer store the energy), creating a voltage spike and the electrons look for a voltage sink. (Maybe they will try to move back to the voltage source or to the 2th plate)

Second problem: Now there is also a resistance bypass over the capacitor. I consider the capacitor to be of "infinite" resistance thus not storing any energy at all.
Switching off or on doesn't do much and nothing fancy can happen.

Third problem: The bypass is only activated, if the switch to the capacitor is opened. If the switch is opened, the electrons would create a very strong electrical current through the capacitor. (If the capacitor only has a considerable low resistance, it should become extremely hot. Not what, what happens, if the resistor has resistance 0.

Fourth problem instead of an resistance a coil is used. I would expect the coil to produce a very strong magnetic field, however for just a short time. Is there actually formula for computing how long the magnetic field can be kept alive, if the switch is abruptly opened? I could even imagine that field instantly comes into existence and collapses.

At the moment these are all questions I have. I would be very happy, if someone has the time to reply and can offer some constructive critique. As always thanks in advance.


texts: Why did the resistance go up on my inductor?

texts:
I was testing an inductive load on a frequency analyzer, and apparently the resistive component went up from 2 to 25 ohms from 0 to 20kHz. Is there any reason for this or am I taking my measurements wrong?
Thanks.


texts: Runs with debugger but not standalone, using ATSAMD10D13 and Atmel ICE

texts: I made a custom board with 2 ATSAMD10D13AM parts. The are 8k flash/4k sram Cortex-M0 24QFN parts.  When I power the board the IC's start but then freeze (I have LED's blinking that go solid). When I attach the debugger and start debugging, it runs fine. The debugger senses power and does not supply it. The code is modified reference design code for the Xplained Mini, it uses the same part except 16k flash. I am pretty sure I changed the part everywhere. I think maybe the ramp isn't perfect. It is supposed to be 25us or greater from 0 to 2.5V. I will measure it with a scope. Otherwise what could it be?


texts: Is it ok to feed the output of one LDO regulator to the input of another?

texts:
Sorry if this is a stupid question, but I am mainly working with 5V PIC circuits and now want to integrate a component (nRF24l01+) that needs a 3.3V supply.

As I have a box full of ~7V wall-warts, I normally use a 7805 or similar LDO regulator to power the circuit. Now I want to also get 3.3V without using a separate external supply.

I'm looking for guidance on the "right" way to do this. I think the options are:

Use a voltage divider on the output of my 5V regulator to get 3.3V
Use a 3.3V LDO regulator fed directly from the 7V wall-wart
Use the output of the 5V regulator as input to a 3.3V regulator

I can see that all of these would work (would they?) and that option 3 seems to waste least power, but I don't know what gotchas might arise by chaining two regulators like this.

What things do I need to consider when making this choice?


texts: How to detect when the lid of a box is loosened (as soon as the screws are unscrewed)?

texts:
I have an aluminium box (dimension about 10 × 10 × 10 cm) with a lid closed with 4 screws (such as this: https://www.hammfg.com/electronics/small-case/diecast/1590).
I would like to put a simple electronic circuit inside the box with a small battery such that the circuit is activated as soon as the screws are opened and the circuit is deactivated when the lid is pushed tightly in place on the box.
One possibility could be to use some kind of switch installed between the box and the lid such that the switch is activated when the pressure is released when removing the screws.
Is there such a simple switch or any alternative that achieve the same goal?
It is not sufficient to activate the circuit when the lid is (fully) removed.


texts: Photomultiplier BNC cable impedance matching

texts: I'm not sure how to connect the 50 ohm resistors to match the BNC cable's 50 ohm impedance. I draw something but it could be different.


texts: Strange result when simulating RF low pass filter with Pspice

texts:
I'm trying to simulate a RF low pass filter in Pspice.  The result don't match with my calculations and a filter simulator I found online.

Does anyone know what I'm doing wrong in Pspice?

My source has a 50 ohm resistance. It seems strange that I already have so much attenuation at the input.

The filter is a 5th order Chebyshev filter with maximum 3dB in the passband at 500MHz and 30dB attenuation at 750MHz.

How can I solve my Pspice settings to get a correct result?

EDIT:
I tried some different things from the feedback I got here. It's still not showing the right result( see last image.)

Why is there a 6-12dB attenuation in the passband?


texts: Estimating response of a filter given its order and roll off frequency

texts:
As far as I know, for any filter we if we know that filter has 1kHz bandwidth we can infer that the 3dB point is at 1kHz. In some cases I only have the limited data for the filter. For example this module's filter is given as 1kHz. In an other document the filter is specified as 6-pole filter. But I cannot figure out whether the filter is Bessel or Butterworth or ect. I also noticed another manufacturer produces the same modules with same naming here. They look exactly the same but they both do not mention each other and different brand labeling on them.

So I have the knowledge of the filter that it is 6-pole and 120dB per Decade above 1kHz:

But I dont have the transfer function or the name of the name filter. In that case, how can I estimate the dB at lower frequencies? Can you give an example how can we estimate the dB at 100Hz and 500Hz for instance?


texts: How to relate the counter torque of a generator with its speed?

texts: Is there a way or formula which can let us to calculate the counter torque at a generator? If the generator rotor is rotating at a constant speed, does that mean the counter torque is equal to the applied torque?


texts:
I have connected 7segment display to PORTB (RB1-RB7), RB0 is external interrupt pin which is turned on

to display number 8, I wrote 0b11111110, so what will happen to external interrupt when I write 0 on 0th bit

 // IM TRYING THIS
 unit8_t sevenSegDigit[10]={
 0b11111110,  // 0
 0b10010000,  // 1
 0b11010100,  // 2
};

this will create any problem ?

any solution to create a lookup table like above code without writing the interrupt bit/pin ?  PIC16F876A


texts: How does a microprocessor control its transistors?

texts: Or in other words, what is the more fundamental building block of an IC below transistors? When I load a code onto my microprocessor, how (fundamentally, sure some people here could write books about this!) does it translate these virtual instructions into a set of real world actions? I assume transistors are pretty fundamental to the process, but what then controls those transistors? Many thanks!


texts: Bessel function if frequency modulation and modulating index

texts:
If amplitude of a message signal is kept fixed and frequency is increased then modulating index will decrease?
According to bessel function side tones will be more spaced if frequency increases but if modulating index decreases then amplitude of central tone frequency should increase (if modulating index goes below 2) then how bessel 0 point is achieved?


texts: What happens to the initial voltage of resistor as soon switch changes?

texts: For when the switch is at x for a long time , i've calculated that the 30 nF capacitor reaches a steady state OCing around 120V. So when it switches instantaneosly, how does it affect the resistor voltage? How to calculatee voltage of resistor (60kOhm)


texts: Integrated circuit which acts as a switch

texts:
I have the following problem.

I have an electronic door lock with opens the door whenever it is feeded with 12v (tested and it works perfectly).

My main issue is that the signal for opening the door won't be a physical switch, but a raspberry pi which can send up to 3.3V and no more than 51mA.

My first idea was using a relay, but as the raspberry doesn't have much current, it wasn't able to give enough power to the coil.

My second option was using an LM393 I had by connecting the raspberry to the input supply, but it seems that whenever there is no input the voltage just passes through.

My last attempt was was trying to use a 2N2222 and it did not work.

Consider that all these attempts probably were failed due to my deplorable knowledge, they might be right but they were used on the wrong way.

What should I use for acting just like a switch?


texts: Not understanding SSD1306 Oled display datasheet

texts:
Just out of curiosity I would like to write my own oled display SSD1306 I2C driver using arduino nano board and atmel studio 7.

I analyzed the Adafruit I2C initialization which sends byte 0x00 after sending slave address 0x78.

I read the SSD1306 datasheet but something still is not clear to me. It's about bit7 and bit6 of each received byte.

The datasheet states:

If the Co bit (bit7) is set as logic “0”, the transmission of the following information will contain data bytes only.
The D/C# bit (bit6) determines the next data byte is acted as a command or a data. If the D/C# bit is set to logic “0”, it defines the following data byte as a command. If the D/C# bit is set to logic “1”, it defines the following data byte as a data which will be stored at the GDDRAM. The GDDRAM column address pointer will be increased by one automatically after each data write."

My question is: what happens if both bits are set to zero? It seems like a contradiction.

bit7 is zero : so next databytes should be non display memory related databytes
bit6 is zero : so next databyte will be a command

It seems from the Adafruit initialization that the next byte will be a command...

I Hope someone can help me out.


texts: Damped AC oscillations are produced in LC circuit by charging and discharging of capacitor and inductor but how it is achieved through an RC circuit as RC circuit is used in Colpitts Oscillator?


texts: Implications of dynamic frequency scaling in an embedded system

texts:
Dynamic frequency scaling is used to increase or decrease the speed of a processor to conserve power, heat, etc. I've seen my own processor fluctuate between 3GHz and 3.5GHz.

What are the implications of the clock frequency changing? There's a 500MHz difference going on in my example above. Are there any design considerations in an embedded device that must be observed when designing for a variable clock? Is there dangers in a device controlling its own clock rate?

Assume in the design scenario we have no power, heat, or any other physical limitations. The device's clock can be set to any frequency.


texts:
Transmitting and receiving antenna should have same polarization(vertical or horizontal). Why?

I know that this is needed for maximum signal reception. But how? If electric field is in same plane of receiving antenna then magnetic field is perpendicular to antenna plane. So, we are not able to receive magnetic field to maximum. Am I wrong?


texts: How can the FFT analyze a wave in which the components are changing?

texts:
Based on what I've read about Fourier Transforms, it seems that they are designed to work on waves whose components are constant.  For example, a simple square wave is

\$\sin(\theta) + 1/3sin(3\theta) + 1/5sin(5\theta)+ 1/7sin(7\theta)\$

However, there are times when a Fourier Transform is used to compute a spectrogram for a file such as a song in which the frequencies that the instruments are playing often change or disappear completely.  How does a Fourier Transform know that a given frequency does not exist for a certain period of time?  Does it have to break the file down into components and analyze each of those?  The presence of time, frequency, and amplitude on a spectrogram suggests that it works, but I don't fully understand how.  Thanks in advance for your help.


texts:
I'm new to embedded systems and C programming. I am Currently trying to program a PCB using an STM32 microcontroller to control an array of 8 fans upon receipt of a single command. i.e 00001011 will switch on fans 5, 7 and 8. There are a total of 256 possible combinations and it wouldn't be very efficient to program each individual one.

I am thinking of using an array to achieve this using something like;

fan_array[8] = {fan1, fan2, fan3, fan4, fan5, fan6, fan7, fan8};
printf ("Input fan state"); // user would input binary number as shown above
scanf (%d, fan_array);

Would this set the GPIO pins controlling each fan high or low according to the binary values input into the array?


texts: How close can I place two 0603 resistors on a PCB?


texts: Can a bulged capacitor prevent a CPU from booting?

texts:
I am trying to revive my old CPU. But it won't turn on. The fans don't turn ON, but they are working. PSU is also working. I have changed my CMOS battery.

I found that one of the capacitors has bulged slightly. I want to know if this bulged capacitor is causing my CPU to not boot?

The capacitor between DIMM2 and IDE2 has bulged.


texts:
Modelling a capacitor whose dielectric has resistance as a circuit element @ Physics Stackexchange

The issue of 'how to model the capacitor' arises if the dielectric of a parallel plate capacitor has a finite resistance.

As the diagram indicates, current can flow through the capacitor. However, this does not mean that the capacitor acts as a closed circuit. The $r$ is quite large and allows very little current through the dielectric. The current through the dielectric won't enough to prevent a charge build up on the plates. Therefore, the capacitor does not lose its capacitor related properties.

Idea #1 (capacitor with resistance = ideal capacitor and ideal resistor in series):

It might seem intuitive to pull the resistor out of the capacitor and assume that they function as an ideal capacitor and an ideal resistor separately.

This model will immediately run into problems because:

If you use a DC source, after very long time, the potential drop across the capacitor will be equal to the E.M.F of the source. This would prevent any current from flowing. The potential difference across the capacitor is caused by the charge separation. However, as the dielectric can conduct electricity, the charge on the plates could move. This would never allow the potential difference across the capacitor to be equal to the E.M.F of the source.

Therefore, this model will fail.

Idea #2 (capacitor with resistance = ideal capacitor and ideal resistor in parallel):

After trying Idea #1, the next attempt would be to analyze if considering the dielectric resistance to function as a resistor in parallel.

This idea has the following problems:

After a sufficiently long time, there would be a constant current in the circuit as the capacitor behaves like an open circuit. There won't be any current passing through the capacitor branch. But with the original capacitor, the charges on the plates of the capacitor can flow through the capacitor. So you cannot have a constant potential difference across the capacitor.

How do you model a capacitor which has a finite resistance?

Would I need to go scrap all the capacitance and resistance concepts and start from the fundamentals?


texts:
I have an open collector output interfaced board using that how should I control an input of another equipment with below characteristics:

0 Ground
1 Open

Thanks.


texts:
For an electric car charger I need to design a square wave of ±12V at 1kHz [SAE J1772]. I would like to make this one with a adjustable duty cycle so that the charging current can be adjusted. I designed the following schematic:

simulate this circuit – Schematic created using CircuitLab

This design lets me adjust the on time vs the off time but not the duty cycle. Is there a way to realize this? maybe with a programmable IC because the 0-5V square wave will be generated by a micro controller.


texts: How to output an amplitude of 10 volts PWM signal?

texts:
I have constructed a Pulse width modulating circuit that should output an amplitude of 10 Volts PWM signal. The control input signal is a 5Vpp, 10KHz sine wave and a pulse input of 10Vpp, 100Hz square wave. I know that the VCC value controls the amplitude of the PWM output signal. However, I tried setting it to 10 volts and the oscilloscope did not display any signal. The only time the oscilloscope displays an output is when the VCC is set to 6.5 volts and below.
 The red signal is the PWM signal, the blue square wave is the pulse input and the green signal is the control signal.
Any thoughts as to why my circuit does not output an amplitude of 10V PWM signal? Please help me solve this problem.


texts:
simulate this circuit – Schematic created using CircuitLab

A) Derive the expression for \$ \mathcal{H}(s)\$ where \$\mathcal{H}(s) = \frac{V_o}{V_i}\$

I started by using the voltage divider at the \$V_{out}\$ node.

\$V_o = \frac{R}{R_c+\frac{1}{sc}+R}\ \cdot V_i\tag1\$

B) At what frequency will the magnitude of \$H(j\omega)\$ be maximum?

The frequency response of the system is as follows

\$ \mathcal{H}(s) = \frac{CRS}{CRS+CR_CS+1} = \frac{RCS}{(R+R_C)CS+1} = \frac{\frac{R}{R+R_C}S}{S+\frac{1}{(R+R_C)C}} \tag2\$

\$ \mathcal{H}(j\omega) = \frac{\frac{R}{R+R_C} j\omega}{j\omega+\frac{1}{(R+R_C)C}}\tag3\$

The magnitude will be maximum when the frequency is infinity. This is because when the frequency of the voltage source is infinite (\$\omega = \infty \$), the capacitor behaves as a short circuit, and thus there is no voltage across the capacitor.

\$ \mathcal{H}(j\omega) = \frac{\frac{R}{R+R_C} \infty}{\infty+\frac{1}{(R+R_C)C}} \tag3\$

However, why wouldn't \$ \omega = 0\$ work? Because the capacitor will act as an open circuit when the frequency is zero thus \$V_{out}\$ will receive no voltage. Therefore, \$ \omega = 0\$ is minimum.

C) What is the maximum value of the magnitude of \$ \mathcal{H}(j \omega)\$?

\$ |\mathcal{H}(j\omega)|_{max}=\frac{R}{R+R_C}\tag4\$

D) At what frequency will the magnitude of \$\mathcal{H}(j\omega) \$ equal its maximum value divided by \$ \sqrt{2}\$

We start off finding the magnitude of the transfer function

\$ | \mathcal{H}(j \omega)| = \frac{\frac{R\omega}{R+R_C}}{\sqrt{\omega^2+(\frac{1}{(R+R_C) \cdot C}})^2} \tag5\$

Now we can use the equation \$ | \mathcal{H}(j \omega_c)| = \frac{ | \mathcal{H}(\omega)|_{max}}{\sqrt{2}} \$ to solve for the cutoff frequencies

\$ \frac{\frac{R\omega}{R+R_C}}{\sqrt{\omega^2+(\frac{1}{(R+R_C) \cdot C}})^2} = \frac{\frac{R}{R+R_C}}{\sqrt{2}} \tag6\$

Solving for \$ \omega \$ in this equation I get

\$ \omega^2 = \frac{1}{C^2(R+R_C)^2} \rightarrow \omega = \frac{1}{C(R+R_C)} \tag7\$

E) Assume a resistance of 5 ohms is connected in series with the 80 \$\mu F\$ capacitor in the circuit. \$R_C\$ is 20 ohms. Calculate \$\omega_c\$

\$ \omega_C = \frac{1}{C(R_C+R)} = \frac{1}{(80 \times 10^{-6})(5+20)} = 500
 rad/sec\$

Plugging this back into the transfer function:

\$\frac{\frac{20}{20+5}j\times 500}{j \times 500+\frac{1}{(20+5)\cdot (80 \times 10^{-6})}} = 0.5656 \angle 45\tag8\$


texts: Why is the sum of resistances different?

texts:
For the following circuit,

I found the total resistance with the following equation:

However, the solution calculated the resistances in the left and right portion of the circuit in summation with the middle resistance:

Why is the resistance added this way, rather than my version?


texts:
I am using the LIS331HH and the FRDM-K22F board.

I can write to the power register and turn on the LIS331HH, I can also write to the interrupt control register (23h) and read out the value I've written.

For some reason though I cannot read from the INT1_CFG (30) register, INT1_SOURCE(31) register or any of the other interrupt related registers.

It seems though that I can write a value to them.

The STATUS_REG (0x27) also always returns 0.

I wondered if anyone has come accross this issue with this device? How would I go about verifiying the device isn't broken at a hardware level?

I'm not sure if I should post code here, but I need to, please let me know.


texts: Is the Roll-Off of Butterworth Filter of degree N always N*20db/dec?

texts:
I am trying to implement a fourth order Butterworth high pass filter under a Sallen-Key topology. Two frequencies, one at the passband and another for the stopband, are set to be at some specific gain/attenuation.

Consulting the Butterworth tables, I was able to design a functioning circuit with two cascaded Sallen-Key networks. The higher frequency (passband side) has no problems and is within my expectation. The problem is with the lower frequency. The filter fails to assign the lower frequency to the set attenuation level.

This is because the Butterworth filter has a linear 80 db/dec since it is a fourth order filter. I am under the impression that the slope cannot be changed. With that, I am confused as to what possible steps I should take to solve the problem.


texts:
I'm attempting to adapt a project with the wiring diagram shown here:
http://www.glacialwanderer.com/hobbyrobotics/?p=9

But instead of the electromechanical relay used in the above link, I'm using an SSR with a 25-amp load current capacity
(this one: http://www.fotek.com.hk/solid/SSR-1.htm)

My question is, should I still include the diode and transistor as shown in the first link's wiring diagram? Would that be redundant/unnecessary when using an SSR as compared to an EMR? Just wiring up the Arduino pin to the SSR seemed to successfully be able to toggle the SSR's load circuit (with the AC disconnected of course) but I think I should be concerned about adequate safety, reliability etc...


texts: Is 0603 vs 0402 assembly mass production cost optimization still relevant?

texts:
Historically, choosing a design avoiding 0402 and finer pitch components was advantageous for mass production cost savings. The yields were improved and accuracy requirements for pick and place machines were reduced. This allowed vendors to choose from a larger number of manufacturing facilities and identify cost saving opportunities.

Does that kind of thinking still hold any water given that 0402s and BGAs have been popular for a long time? Are there still factories that specialize in low cost larger pitch manufacturing?

Just to be clear, I'm only talking about production volumes in the millions.


texts:
Firstly apologies for any stupidity here.

I am needing to purchase two 9dbi antennas for use with a router. I found someone online, bought them, then started noticing SMA and RP-SMA. Unbelievably I simply paid no attention before and long story short I bought the wrong thing.

In my brief reading I can see the differences between the connections, which is confusing to say the least and I see that RP means reverse polarity. I have also come across some converters for RP-SMA female to SMA male coax.

Presumably these will be sufficient for my purpose? Will there be any issues, loss. Am I better off purchasing another set of antennas with the correct connectors.


texts: How can I safely tie the output of a sensor high or low?

texts:
I would like to ask a general question and get a discursive answer, but I know that's discouraged here so I'll ask the general question, then pose a more specific one.
In general: What happens if I tie the output of a binary, logic level sensor high or low, will it damage the output of the sensor? I am guessing the answer depends on what the sensor is, in which case are there common features to look for when trying to understand how that sensor works, such as a resistor on the output stage? The binary logic-level sensors I'm talking about would be breakout boards like small PIRs such as the AM312 or microwave sensor breakout boards.
Specifically: Assuming you have no idea what I mean by the above, let me pose this question more specifically. I have a 5V microwave sensor breakout board, an RCWL-0516. I have a microcontroller (ESP8265) with only one digital input, but I wish to connect this microwave sensor AND a physical retractive switch to this input pin, i.e. in parallel. This is so that either the retractive switch OR the sensor could cause a trigger. Should I simply place a resistor inline between the sensor output and the microcontroller input?


texts: i2c : When writing to Slave Read 255 seen on bus

texts:
I am using Renesas RH850 controller in which I am writing 48 byte of data to slave device (Ublox IC) over i2c every 100ms and sometimes I can see 255 in between my data transfer which results in failure of transmission.
What is the reason in which I am seeing this issue. Am I missing something in i2c protocol ?
Thanks in Advance.


texts: Is it possible to determine capacity and voltage rating of an unknown electrolytic capacitor?

texts: Today I found a big electrolytic capacitor in a scrap yard. It is about 9 cm in diameter and 16 cm high. The only thing that is marked on it is polarity but nothing else. How can I measure its capacitance when I even don't know its maximum voltage rating?


texts: Can you charge a NIMH battery with a trickle charge NiCad battery charger

texts: Purchased older RC airplane complete kit Air Tronics transmitter in kit not made anymore old NiCad battery (10 plus yes) was replaced with new 9.6v NIMH battery can the old NiCad trickle charger that plugs into the transmitter be used to charge the new NiMh battery that is now in the transmitter ? Thanks Vern


texts:
I'm having a little trouble understanding this circuit and could use some help.

So far I understand that this is an AC coupled circuit, and the capacitor is a blocking capacitor. I also know that this is a high pass filter, but if I was to find the cutoff frequency, what resistance would I use? Would I simply use the 2k lower resistor or combine both resistors for a 4k resistor here?

Also what does this circuit do to an input signal? Is everything offset by +10V here,  or does the capacitor block this so any signal from V(t) have an average voltage centered around 0?


texts:
I've designed a few PCB's now, but never put much thought into good practices. They were small boards and most of the emphasis was put into just making sure everything that needed to be connected was connected.

Now I want to get more serious into making well designed boards. I've designed and redesigned my current project multiple times trying to come up with a good looking layout.

This project is based around the ATXMega256 mCU running on a 16Mhz crystal, around 60 total components and 7 or 8 of them being IC's.

For my next redesign, I plan on giving "Manhattan Routing" a go to at least try and help with crazy traces going every which way - but that's a little bit off topic.

The problem I seem to run into the most is understanding an appropriate method of running power to each IC. Normally, I would just daisy chain them but that is said to be a bad practice.

Here are my questions relating to feeding power

I've heard of the "Star Configuration" where all the IC's tie directly into the regulator but haven't seen a real life example of that so I'm not sure how to design that into my projects. It sounds like a mess of traces coming off of one pad in my mind. Can you post an example of a well designed Star Configuration?
What would be some advantages and disadvantages of using the star configuration as opposed to a power plane, other than the obvious of power being everywhere with a plane.
When is it ok or not ok to use a plane for VCC, specifically for a 2 layer board as I've heard that it's not as common on a 2 layer board?
If I shouldn't use a power plane, which is better in the case of traces needing to cross each other: using via's for GPIO or via's for power?
If it is ok to use a power plane on a 2 layer board, should VCC be on the top layer or bottom, obviously I would have a Ground plane as well.

I know there isn't a win/win answer to these questions because every project is going to be different and require different planning, but I think the basic concept behind it should be somewhat universal that people follow. You have to know the rules before you can break them.

I also realize that these questions may be beyond the scope of online discussion, but I'm looking for more general answers that can help push me in the right direction.


texts: Ways to Protect Mosfet from Burning on PWM for running universal dc motor?

texts:
I want to control one universal dc motor (vacuum cleaner Motor 220V,8A) with AVR micro and one high power mosfet. So the power part schematic is here:

But the problem is here when input voltage going to near 220V the mosfet is breaking down. So as you can see (top of the photo) I have made one ac to dc converter without a transformer  and only with one bridge rectifier and two cap (1th 660 uF2th 330 nF ), could be the problem form miss converting and harmonics in dc voltage which going to MOSFET (not complete DC which have some harmonics)?

I guess some part of this problem came from here!!!

My Mosfet is here:

So what could I do for it's protecting from inrush current which came back form motor solenoids, could I use zener diode in this high power (8A,220V) or there are better way?

Edited:
According to its datasheet, does it have not any anti parallel fast diode, and how much protection it would have with this kind diodes?

I changed MOSFET to IRFP460 (20A  500V, 80A pulse drain current) So it's working in voltage below 180V AC (Auto-transformer) but in 220V AC It's Mosfet broken down, SO i guess there is some problem in the source power for drain of Mosfet, i Guess there is no enough DC Voltage, So the cap i used there are 1300 uF, Dose i need to increase it's amount for reaching Better DC voltage for power supply of Mosfet (drain-source)?

Another Que:

Somebody did say, you must use 7 X multiplier of your motor  normally current Mosfet , which means i must use 8x7=56 A Mosfet for driving this kind DC motors, So dose it correct, any kind of this rules ?!!!

Thanks a lot.


texts: What kind of diode is this? Marked "1934 MZ"

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My drone's power distribution board heated up.
There is a diode in the picture - I could not identify it.
Can anyone help?


texts: Odd step in derivation of phasor Telegrapher's equations

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In the derivation of the phasor form of the Telegrapher's equations (in "Fundamentals of Applied Electromagentics" by Ulaby), there is a step I'm not following:

When going between eq. 2.16 and eq. 2.18a, why does the complex exponential disappear when taking the derivative of the V and I phasors? Since the derivative is being performed with respect to z and the complex exponential being defined in terms of t, shouldn't it remain after that derivative as a constant (and only the exponential would remain)? If being used as a function, wouldn't the product rule would leave a cosine and its derivative?


texts: What is the easiest way to connect a breadboard to a multimeter?

texts: The test leads on my multimeter are too large to fit in the holes in my breadboard. How can I easily connect my multimeter to test voltage on my breadboard?


texts: How to stop ESP32 resetting when motor starts?

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This is my first post here and I'm new to electronics. I am trying to control a motor using an ESP32 Cam. See attached image for a rather crude schematic. The power supply is rated for 2.4A. I am using a 12v DC 5rpm worm gear motor like this DC 12V Worm Gear Motor .
When the motor starts, the ESP32 resets (I figured this out by making the ESP blink on startup). Meanwhile the motor continues spinning without interrupt (I have ESPHome on the ESP32 and treat 2 GPIO pins as interlocking switches [only one can be on at a time]).
From reading online, it seems like the surge on motor startup may be causing a voltage drop on the ESP32 (potentially called "brownout") causing a reset. How can I prevent this in a simple way?
I found that if I put the motor on a different power supply, the issue is fixed, but I'd rather not use two power supplies.
References of similar issues:

How to prevent a battery powered microcontroller(ESP32) from reseting when motors start running?
Arduino restarts when DC motors are turned on
Fast DC motor resets Arduino?!

Possible solutions

Different PSU for motor. I've tried this and it works, but I'd rather not have to use a second PSU. I think the ESP32 draws ~250mA and the motor ~100mA, so I think I'm well within spec of the 2.4A PSU.
Schottky diode - I don't have one of these and don't want to wait for an order
"Decoupling capacitors". I have a bag of assorted electrolytic capacitors. Which should I use and where do I put them?
PWM - gradually apply pwm to bring motor up to speed. Would this work with my circuit, with pwm before the boost converter? Will the boost converter just boost it to 12v anyways, either just using capacitors or using PWM?

Note

The DRV8833 is rated to 10v, which is why I set boost converter to 10v and not 12v. The motor still seems to run fine on 10v.

Edit
Many thanks to the people who have posted here, @winny, @vir, @bobflux, and @thebusybee. I've implemented the PWM acceleration method, which works. There's a loud high pitched whining sound, at the mid-range PWM values that goes away once the motor comes up to speed. Audio available here:
https://streamable.com/3xgxy0


texts: Should I define default register values in start up code?

texts:
It has come to my attention that some ARM programmers set some CPU registers with values that are the same default values of the register on microcontroller reset.

For example: the default value of IOCON_PIO2_9, parameter MODE on LCP1114 is 0x02 (pull-up resistor enabled). In Olimex's example code this value is set to 0x02 in software initialization but this is already the default value.

This behavior occurs with many other registers.

Why would someone do that? In my opinion, this extra code just pollutes everything and make code readability worse. Is this a good programming practice?


texts: Can I use a regular 2512 SMD Resistor (0.001 ohm) for HLW8012 IC shunt Resistor

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Can I use a regular 2512 SMD Resistor for the shunt resistor as current sensing resistor for the HLW8012 power meter IC.
As per the data schematic, the manufacturer recommend to use a shunt resistor of 0.001 ohms.


texts:
I am here to clarify my doubt on what is antipad? in padstack creation,and why it is used ?
If we create non plated pad  then there is  necessity of anti pad?  Thanks for your good answer .


texts: How to get up to 24 I/O pins from the PIC4550

texts:
Im trying to implement  and understand the CRC by making a circuit, by using 1 byte (8 bits), and a highest power of the polynomial of four, these 2 values should be XORed until i get a final output, that should be 12 leds confirming the proper data was recieved

I was wiring my leds, in order to use the PIC4550 however Im not sure I have enough digital ports to do this, all the inputs and outputs should be shown in ledbars, thats 8 ports for the input, 4 ports for the polynomial, 12 for the output thats a total of 24 ports

Im already checking the datasheet, trying to find out mos of these questions, however i wanted to throw the question to confirm

1) If i cant do it with a 40pin DIP then what else can i use to make it work?

2) Is it posible to override the analog inputs and use them for this porpuse?


texts: Is this way of plotting AC current gain in LTspice correct?

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I want to plot the AC current gain versus the collector current in common base configuration. Ac current gain "alpha ac" for CB configuration is defined as the change occurring in collector current IC for a given change in emitter current IE when Vcb is held constant.

But if I apply AC signal to the input the current will change, and so will the collector-base voltage Vcb will change.

So the only way to hold Vcb constant I shorted the load as shown below and increased IE from 1mA to 100mA in transient analysis in one second, and plotted the expression:

AC current gain D(-Ic(Q1))/D(Ie(Q1)) versus collector current.

Is this way of doing it in transient analysis correct?


texts:
I have succeeded in displaying an image on a VGA monitor using FPGA, by generating a ROM loaded with a coe file. But knowing that a video is a succession of images, how can I do that? Any ideas please?
Note that the video that I want to display is not retrieved from camera or real-time, it's just a short mp4 video file.
I have FYI looked in multiple books like that of Volnei A.Pedroni, Cem Unsalan and Bora Tar, and Pong P. Chu about displaying a video but all they talk about is the generation of a single image, which is what I have done.