texts: Change in current while using AMS1117 (3.3)

texts:
I am using a voltage regulator (AMS1117 3.3V) for my microcontroller with an input voltage of 5V and input max current of 600mA. Can I expect to have more current capability from the output? If yes, what could be the approximate output current in this scenario ? If no, is there a simple solution which would increase the output current ?

Note: I am using 10uF and 22uF capacitors at input and output respectively.


texts: Gradient based optimization for microwave filter design

texts:
In S. Amari's paper - Synthesis of cross-coupled resonator filters using an analytical gradient-based optimization technique(2000), for reducing a filter's unnecessary cross-couplings,
the matrix \$[A]\$ given by

\$[A] = [M]-j[R]+ \omega[U]\$ , where all matrices are of order \$N\$. Whereas, in Richard J. Cameron's paper - General coupling matrix synthesis methods for Chebyshev filtering functions(1999), all matrices are defined as (\$N+2\$)th order, which raises my primary concern.

The major issue is this - I defined the cost function from S.Amari's paper as given, but the optimized matrix \$M\$ created both as \$N\$th and (\$N+2\$)th order matrices show wrong results.

e.g., initial \$M\$ = \$ \left[\begin{array}{cc} -0.1332&0.5551&0.7227&0.3135
    \\0.5551&0.8960&-0.2958&-0.0021
    \\0.7227&-0.2958&0.1296&-0.9113
    \\0.3135&-0.0021&-0.9113&-0.1332 \end{array} \right]\$

optimized \$M\$ = \$ \left[\begin{array}{cc} 0.4510&0.5047&0.0050&0.6747
    \\0.5047&0.5501&0.5500&0.5499
    \\0.0050&0.5500&0.5499&0.5499
    \\0.6747&0.5499&0.5499&0.5047 \end{array} \right]\$ , in \$Nth\$ order.

To make it \$(N+2)\$th order, a source-coupling is introduced with one resonator and load-coupling with another resonator as

\$M_{N+2}\$ = \$ \left[\begin{array}{cc} 0&1&0&0&0&0
    \\1&0.4510&0.5047&0.0050&0.6747&0
    \\0&0.5047&0.5501&0.5500&0.5499&0
    \\0&0.0050&0.5500&0.5499&0.5499&0
    \\0&0.6747&0.5499&0.5499&0.5047&1
\\0&0&0&0&1&0 \end{array} \right]\$ , with source and load terminations on \$1 \Omega\$.

However, in both cases, the S21 and S11 plots are undesirable. I am using the MATLAB fmincon() solver with interior-point algorithm using bound constraints. Usage of global optimizers such as GlobalSearch leads to even worse unrealizable couplings. Reducing the matrix with Similarity Transformations(as in Cameron's paper) gives a practical solution. Is there anything wrong with the solver or the cost function definition(code) ?


texts: Source of electromagnetic signal in kHz regime

texts: I was wondering what emits electromagnetic signals in the kHz regime? When I touch the inner pin of an BNC cable connected to an oscilloscope, I see a large sinusoidal signal with ca 40 kHz.


texts: Using an eye diagram for dynamic equalization?

texts:
I was just watching this video Tutorial on Passive Filters, Data Transmission and Equalization. In the video he shows how one can use the size of the opening in the eye pattern as a way to measure the effectiveness of per-emphasis for overcoming bandwidth limitations of a bus or transmission line.

I assume it is a standard practice to optimize pre-emphasis for known transmission lines once and then just leave the values alone.

What I would like to know is do communications circuits exist where the pre-emphasis is adjusted dynamically as the characteristics of the channel change? I am thinking here of circuits like HF radio links over hundreds or thousands of miles where things like phase distortion vary over time. I assume this would also apply to circuits between satellites and earth stations where the satellites are not in geosynchronous orbit.


texts: Butterworth Filter Example Different in LTspice

texts:
I am trying to recreate the example third-order low-pass Butterworth filter from the Wikipedia page. It has the following diagram and frequency response plot. On the wikipedia page it gives the values as C2 = 4/3 F, R4 = 1 Ω, L1 = 3/2 H, and L3 = 1/2 H. Link to the article: https://en.wikipedia.org/wiki/Butterworth_filter.

I have recreated this in LTspice with unfortunately very different results. I tried this both with and without a voltage supply at Vin with the same results. I also tried using both linear and decade sweeps which also had the same output. I've changed the dotted line from phase to the delay to match the Wikipedia plot, but they clearly are not the same.

Any thoughts or advice would be much appreciated!


texts:
I have a desk lamp, that uses 11W/827 CFLs (current one is an Osram Dulux S)

The lamp uses a power supply ("Type BL1"), but it seems the transformer acts more like an AC/AC power converter, as it outputs ~230V AC (I live in Germany, we have 240V AC here.) I opened up the power supply, and the cables going off to the CFL tube, go directly from the secondary, there is no rectifier, etc. I measured the voltage that goes into the CFL at the terminals, it's the  ~230V AC.

The ignition circuit must be therefore inside the (sealed) CFL casing.

I was wondering, if I could make or re-purpose a dimmer switch for this lamp. The idea is to put the dimmer after the power supply. The only dimmer switches I found, were rated for 60W-500W, which is way overkill for the 11W CFL.

What's the best approach? Could anyone suggest me a circuit for such a dimmer?


texts:
I am adding two hex numbers and determining what bits in the condition code register.
The numbers I am adding are 4D (base 16) and 66 (base 16). I converted both to their binary equivalents.

4D (base 16) = 0 1 0 0 1 1 0 1

66 (base 16) = 0 1 1 0 0 1 1 0

Once I added these I got 1 0 1 1 0 0 1 1. By looking at the MSB (bit 7), it is 1 which makes the number negative and the N bit is set to one. I was looking at my notes, when a number is negative, it is represented by its 2s complement.

so:

1 0 1 1 0 0 1 1 = -(0 1 0 0 1 1 0 0 + 1) = - 0 1 0 0 1 1 0 1 = -4D (base 16) = -77 (base 10).

My professor said the V bit is set to 1 because of 2s complement overflow. For the 8 bit processor, the maximum value is +127 (base 10) and the minimum value is -128 (base 10). I thought 2s complement overflow occurred when the answer is outside these bounds. My answer is within these bounds so 2s complement overflow does not occur so I was wondering why the V bit is set to 1.

I put this into a hexadecimal calculator and it says the answer is B3 (base 16) which is what I got by just adding the numbers. This converts to 179 (base 10) which does go outside the bounds and the V bit would be set to 1.

So my professor did an extra step after I added the two numbers to display the negative equivalent. When should I determine if the V bit should be set, and what should the actual answer be, B3 or -4D?


texts: How does positive and negative clock skew affect setup and hold time?

texts:
Does positive clock skew only tightens the hold time and there is no change on setup time, similarly does negative skew only tightens setup time and there is no change in hold time.

Is this right?


texts: Can connecting high demanding current devices to usb port damage it?

texts:
Lets say i powered a led strip rated at 5V and 3.6A by my laptop usb port via usb cable, what will happen?

-will it just be limited to 900mA since thats max current for usb 3.0

-or will it try draw out 3.6A from the usb port and break it

extra: what if i wired the led strip to an arduino that has a max current of 1A  and powered it with usb port, what will happen then?


texts: an arc at what amperage/AC voltage would be at a sufficient temperature to melt most common metals?

texts:
I have come across a video recently (link below) that uses two microwave transformers to step down voltage from a wall outlet to be used to melt metal as an electric arc furnace. However, he neglected to mention the voltage and amperage of the arc. Since I have interest in recreating this device and do this safely, I am interested to know two things: 1. At what amperage/AC voltage will an arc melt most common metals? And 2. Will a live wire with said amperage/voltage be lethal? I looked through the comments section, and some said it was not dangerous because the voltage was too low to penetrate his skin, however i am not one to put my life in the hands of youtube comments, so I thought asking a more professional crowd might be better.
https://m.youtube.com/watch?v=VTzKIs19eZE#

Edit: just to be more specific, to melt 1 kg of steel. Steel has a specific heat capacity of 500 J/kg-k and a melting point of 1643.15 degrees kelvin or 1370 degrees celsius


texts:
I trying to design RF IoT device. In case of power failure, the device must send power-off notification before shutdown. So the MCU and RF transceiver must to stay powered at least 1 minute.

In schematic below are two VDD. First is for powering all components(display, etc.) and second (VDD_BACKUP) is only for MCU and RF transceiver.
MCU and RF transceiver current together will be ~60mA during transmitt.

In case of short period 12V outage, occurs switch to VDD_BACKUP and after 12V ON again, occurs switch back to VDD.
But thanks to softstart, occurs a unwanted MCU restart.

It is there a better solution?
Thank you.


texts:
I am working with a SmartFusion2 FPGA, and I am trying to implement a fine delay line. For that, I would like to control exactly the content of some LUTs, to get cells with no logic properties but interesting timing variations. So, my goal is to describe few individual cells in VHDL and link them to more abstracted VHDL code. I am using Libero SoC v11.5.

My problem is that I cannot find a way to do that with Microsemi's tools.
There is a macro library for the SmartFusion2, with a promising element: "ARI1", but there is two issues:

I don't know how to explore or link that library to my VHDL code.
The "ARI1" macro is the only one that is not listed in the IDE catalog under macro.

Any tips for gate-level design with the SmartFusion2 is welcome.


texts: Is it possible to measure pwm load current using opamp based high side current sensing?

texts:
I am referring this app note, hope to use as unidirectional current sensing for a PWM load
PWM load - load is a resistor,
PWM signal - 100Hz, 150V.
Load current 18mA
Duty 5% (PWM resolution 8 bit)
Duty cycle on time 0.58ms
Duty cycle off time 9.41ms
OPA333 has gain bandwidth 350kHz which is more than enough to capture 100Hz
I have following doubts,
Is the reference design will work for my application spec? (I will use R sense = 5.55Ohm)
Is ADC sampling rate 250Hz enough to capture current from PWM pulses? (250Hz > 2x PWM signal frequency)

I need to capture all PWM pulses when ADC is being read,i can use higher ADC sampling rates eg- 800 samples per second or 800Hz

I need to measure current for short periods- means PWM load is only on for 0.25 sec or 0.75 sec, within those periods I need to measure current to the load.


texts: Underground bundle of wires has a/c interference, slight noises on pairs of wires

texts: Is there a way to mask a/c interference on a pair of underground wires. They are 14 guage wires. I have slight power from a 110 circuit that is bleeding over to several other wires in this bundle. This is causing the circuit low voltage or noise which is effecting the operation of a remote circuit pack. I need to isolate the influence with a device, but I don't know what to use.


texts:
I will start by explaining the problem to make my question clear.

During the production of diapers , the machine need continuous supplying material. So Butt Splicer is used to attached the end of expended roller with the start of the next roller using double sided tape. So in the production their will be a defected diaper  ( a diaper  which have a material with double sided tape on it. There is some methods to reject the defected diaper  during the process . But to ensure that this diaper  is rejected , a Metal Foil Tape is used with the double side tap, and a metal detector used after the packaging to reject the bag with the defected metal.

And here is the question,The client want to find these diaper s with metal while they are in the diaper  bag without opening the bags and checking every diaper  with the metal detector. A normal metal detector  which will generate a magnetic field will detect if the metal is on the bag because of the shape of the magnetic field. So I need a sensing method with linear detection ( to scan diaper by diaper , So the scanning depth most by more that 20cm and the thickness at least 3mm.

The project summery:

A device to identify the position of a defected diaper in the bag.

A motor which is controlled by a microprocessor will  hold the sensor (which I am asking about) to scan the diapers bag from the top side

(This picture is only for showing how the plastic poly-bag will be align from the top side)
and once a metal is founded, a marker will mark the position of the diaper in the bag , so the operator could find the defected diaper and identify to the technician which material is not rejected in the process.


texts: If a controller has MPU, will it run Linux efficiently?

texts: I have an EFM32 board having Cortex M3. This board is having an Memory Protection Unit. Will it be a good idea to port Linux on it? I am discouraged because of this answer:  Linux on ARM Cortex-M3 series, especially since I need a fast boot-up and efficiently running OS.


texts:
I'd like to check if a lamp shines and if it's dead, a relay is supposed to switch.
I thought about using an attiny with a hall sensor.
There are some sites that complain about the inconcurrency about the results of it.
I've got three lamps and I need to check each. They're UVC, so I can't use a photodiode tho check for emitted light.

My idea was to use a hall sensor for each supply cable and check the analog output with an attiny.
It would make use of 3 analog inputs and 4 digital outputs. Therefore the attiny84 would work.

If anyone has a better and cheaper idea, I'd be really grateful.

Edit: Thanks for your answers so far.

It looks like the project is going in another direction after all...

I will use UV-C LED strips for the whole project, because they are much better suited for my purpose. However, I do not have the same current flow there as in an amalgam lamp. Is there possibly a possibility to switch my relay in case of x failed LED?

Let's assume that the running meter of LED produces about 9.6W at 24Vdc. I will use about two meters of LED strip. The 24V comes from a transformer. The LEDs will be switched off when not in use. So I have to do the test during the active time. In itself no problem, because I can simply use one of the digital inputs on the attiny. Now the question for me would be if the test with the Hall sensor is possible with the LEDs. The error relay should trip after about ten failed LEDs (I can measure the value for this by simply "leaving out" ten LEDs).

But the whole thing should look relatively professional if possible, because I don't want to have a mess ...


texts: I am currently working on a class A audio amplifier designed to work with line in voltage (about -400mv to +400mv). I plan on using an IRFP240 for the mosfet but am undecided on the transistor stage. resistor values will need changing of course, but I would like to think I have the arrangement of this circuit correct? I would love to know any improvements, as I am a beginner at audio amplifier design and the design goals are to be a simple, but high quality audio amplifier.


texts: Using a PNP to enable a NPN current source not yielding expected current

texts:
Hi I am trying to switch on a brake light with a reed switch. The load is a 12v (0.1A) LED bike light. The following circuit works in the sense that the light comes on when the magnet moves away from the reed switch but the total amount of current i measure is only around 40mA (quite dim) but i am expecting around double this with the resistors i have used.

I have tested the LED just with the PNP and it pulls around 134ma.


texts: Design a 4-bit synchronous counter using D filp-flops and 16 x 4 ROM that can generated any arbitrary counting sequence

texts:
What are the restrictions on the counting sequence? Give the ROM contents for the following sequences: a) 12, 13, 14, 15, 5, 6, 7, 0, 1, 2, 3, 4, 11, 10, 9, 8, 12, 13, etc...
b)8, 9, 0, 1, 8, 9, etc...

This is the question of a sample exam, I have no problem designing a n-bit synchronous counter using any type of flip-flop. My doubts are about the ROM part, on the book I have no example of how to implement a ROM to a counter, can you tell me the step to do it?
and I don't get the question of the restrictions of the sequences, do they refer to the pattern (i don't see it) or what do they mean?
My last question would be, do I need to design two 4-bit counters?, one for each sequence?

Thanks a lot


texts: Why do I have to put my transistor after of my component, instead of before?

texts:
I'm working on a very simple project, where I want to control a 24V LED with my arduino. Since the arduino can't output that voltage, I have a separate power source, and use a transistor. This allows me to use the 5V signal from the arduino to toggle the 24V.

However, after wiring this all up, nothing worked, and after trying a few too many permutations, I also must've burnt my poor arduino. I later found an online circuit simulator, and eventually figured out how to get it working. But I have no clue why one of these ways works, and one doesn't. Here's the one that doesn't work.

I placed the transistor before the the component (replaced here with a multimeter) and it only gets 5V. But this seems to be logical to me - 25V goes into the collector - 5V goes into the base. Base toggles emitter - and should be emitting 25V into the multimeter.

Here's one that does work:

Now, the transistor is placed after our component. We feed 25V directly into our multimeter, and it reads it as such. Then we use the 5V from our arduino to determine whether the circuits get completed or not. This works - and it makes sense that it does. But I can't understand why this works, and the last one doesn't. All it should be doing is opening or closing the circuit - yet that one gets 5V, this gets 25V.

Can anyone explain what I'm missing?


texts: Why are resistors used in a Zener clamp circuit?

texts:
A data acquisition channel is fed by a signal which first passes through a clamping circuit as I draw below. Here in the figure Output goes into the data acquisition board after a 8V clamp circuit:

When I opened the clamp box I saw 2 resistors in series both with input and output of the clamp. Why would those 2 resistors needed along with the Zener diode?

What might be problematic if do not have R1?
What might be problematic if do not have R2?
What might be problematic if do not have both R1 and R2?/Why not only use Zener for clamp?

I could't figure out scenarios when those resistors needed and how to choose in case.


texts: Can USB host controllers be used for device identification?

texts:
Does any USB host device provides any unique IDs which are available from USB controller to device? At software side, I can get the vendor ID (along with other hardware identification data such as BIOS and hard drive IDs), but looking for the way to implement a basic USB key-based protection by looking onto USB host data which is available from both software and hardware side.

In my particular case, I am interested in any fingerprint data that is leaked from standard USB host controllers found in nowadays PCs: BIOS-extended data, PnP/non-PnP requests (for example, will a BIOS trying to negotiate with USB flash key send any host IDs?), a presence signs of other presumably internal USB devices like laptop cardreaders which sit on the same bus, etc.


texts: Applying DC bias on a high voltage rectified ripple 570VAC Peak down near to zero

texts:
I am working on a linear power supply with a 3phase input. I wondering if there was a possibility to shift the  rectified(ripple) power signal shown below which spans between 560VAC to 505VAC ( 55VAC difference @130 ohm load) down near to the zero so imainge it could span between 0 to 55VAC .

If the voltage above is adjusted, then i imagine the voltage supply will need to go into a power transformer with a ratio of 3:1 then a go through a diode in series(half-wave rectification) then if needed go through a linear regulator for ripple reductiona and voltage regulation within reasonable expectations.

My target is to setup a 12V ~100mA linear power supply from 3 phase(4-wire) 330V(max)/phase 50Hz.
I've tried to use this high pass filter to adjust the bias but

it shifts mostly under zero, several iterations got me no-where.
under very small loads @100K ohm load, i'm getting results above zero  around 20VAC, can't get it near that when load increases.

Note: I am bound to have galvanic isolation ( Transformer ) in my application.

I would really appreciate if someone would kindly share their thoughts.


texts: unity gain buffer large input offset voltage

texts:
I'm using a unity gain buffer to drive a power amplifier voltage reference. Here's a schematic for the buffer configuration.

The op-amp in question is a LMV321.

I've set the voltage divider at the amplifier's non-inverting input to output 2.85V. Unexpectedly, I'm measuring the voltage at the inverting input and output as between 2.70V and 2.75V (it changes somewhat which I'm also surprised by). The measured non-inverting input voltage is stable at 2.854V. As you can see from the schematic, the supply voltage is 3.3V (3.28V measured). When the device is off, I measure the DC resistance between the output and ground as \$2.328k\Omega\$.

The max input offset voltage specified in the datasheet is 9mV, not the more than 100mV I'm getting. I've kept the output voltage well below the 3.3V supply (especially considering this is a rail-to-rail op-amp).

The load is the a reference input voltage of a SE5004L power amplifier, which is supposed to be supplied with a voltage between 2.8 and 2.9V. I'm having a little trouble determining what the input impedance of that pin should be although I guess it has to be about 2.328k (op-amp output impedance in parallel with it, which is so high that my multimeter reads OL when attempting to measure the resistance). I unfortunately don't have an extra power amp to measure the impedance, and I'd rather not have to take it off and resolder it. Please let me know if I've omitted relevant information.

Any thoughts on what might be going wrong here?


texts: How to choose a inductor for a buck regulator circuit?

texts:
I am designing a buck-regulator circuit, with possibly the MAX16974 as the regulator. I have never done such a thing before, and actually not too much analog electronics at all. I got stuck at the part where I should select a inductor.
Part of the problem is that there is much to choose from (13000 total from Farnell). I got them filtered down to about a 100. But I am still not completely sure if the values are right, and the how to choose from the rest that are left.
As there will not be made that many copies made, the price is not that big of a concern.
After a bit of googling I found a app note form Texas Instruments concerning the selection of inductors for use with switching regulator, but I have not been able to work out some of the constants used in the equations in it.
UPDATE:
The regulator is going to be used on a 10-20 volt input (mostly around 15 volts). The output is going to be 5 volts with the current around 1A.
I don't really now where the other specs should be. I'd like to be able to power different kinds of devices requiring 5VDC, for example a raspberry pi or charge a phone through usb.


texts: Does using an antenna extension cable violate FCC cert?

texts:
I have a question about FCC part 15 certs. Using the Particle Cellular B series SoM, they have a "Grant of equipment authorization" to use the module as an end device. Link to the module docs below.

Within the terms, it says you must use the same type of antenna and less than or equal to the gain that it was certified with.

My question is, if I use an extension cable, say to get it outside a machine for better signal, does this violate the FCC cert? I do not want to pay for re-certification. The docs don't really say anything about this.

Adding cable does become part of the antenna and could affect things. So I'm not sure if this is valid or not. I'm using the same type of antenna, in fact it's the exact antenna it was certified with, but with a longer cable.

The antenna in question is the Taoglas FXUB63. It is a flat flex PCB (flat patch) antenna with a U.FL connector. So can I use a U.FL to U.FL extension cable and still be within the Grant of equipment authorization? Or maybe even a U.FL to SMA and an long SMA extension and then back to U.FL. You get the idea.

You can find the FCC certification docs here: https://docs.particle.io/datasheets/certifications/certification/

Antenna: https://www.digikey.com/product-detail/en/taoglas-limited/FXUB63.07.0150C/931-1329-ND/4965532


texts: Voltage increases speed/ current increase torque?

texts: I don't understand how current reduces speed in an electric motor,while voltage increases it. Wouldn't a stronger magnetic field mean there is a stronger "force" thus should be a higher acceleration, therefore a higher speed of rotation?


texts: Mechanical to electrical power conversion calculations

texts:
I'm working on an electrical power generation project , where the prime mover's shaft rotation speed is variable (for example a wind turbine). We have an initial guess at the optimal speed and torque available at a nominal operating point.
What computational steps are required to determine:

(a) shaft input power, given an estimate of torque at various speeds
(b) the efficiency and optimal speed/torque for maximum mechanical power extraction to the shaft
(c) the voltage coefficient of the shaft driven  electrical generator given a desired DC or AC bus voltage
(d) an estimate of the electrical power generated and efficiency at the optimal operating point
(e) an estimate of how efficiency and electrical power output would drop either side of optimal.

Originally posed as:
Im doing a certain project of power generation from rotating shaft that is  not uniform (rotations). I just know the shaft rotations  that can be produced. What would be the next calculations to predict the generated power value ?


texts:
I am designing a DC-DC step-down converter (asynchronous) and I would like to achieve a Li-Po charging with it (18 - 22 V input voltage). My goal is the CC/CV charging but to do this, I need constant voltage (4.2 V) on the output. I have simulated the circuit in MATLAB simulink (with battery model) but I can only measure the battery voltage.
I am monitoring the input current/voltage and the output current/voltage too.
I am so confused with this now, I have read many topics, articles.
Can I achieve CC/CV with asynchronous buck converter?

EDIT:

I have found a CC/CV design for buck:
https://e2e.ti.com/blogs_/b/powerhouse/archive/2017/11/24/how-to-design-a-simple-constant-current-constant-voltage-buck-converter

Can I achieve it with asynchronous buck too?

EDIT2:

simulate this circuit – Schematic created using CircuitLab


texts:
I have a question about eval board schematics of STMP1.

I noticed that zero ohm resistors were used in the PMIC reference circuit.

Why these resistors used in series to the power lines? Need I them really?


texts: How can I couple 50Hz/60hz mains interference to a signal cable in practice?

texts:
I want to create a 50Hz noise on signal transmission line options which are a coaxial cable with BNC connectors and the other is an STP cable with BNC connector. Cables are like 10 meters long or more.

As receiver system I have two data-acq. systems, where one is single-ended input and the other is diff-input.

Imagine the output impedance of the source is balanced or neglect it.

So there are four combinations:

Coaxial to single ended daq

Coaxial to diff ended daq

STP to single ended daq

STP to diff ended daq

I want to experiment and demonstrate these in case of 50Hz interference.

But I dont know how can I create 50Hz interference on the lines.

How can I couple a significant 50Hz magnetic inference to a cable in practice? Is there an easy practical way?


texts: What is the typical value for thickness of via plating?

texts: I use PCB tools and sometimes they ask for via plating thickness, what is a value that I can approximate most via plating thickness? What value would you use and why? If I wanted to bound the thickness (min,max) what values could I use?


texts: How can I multiplex fully isolated differential signals?

texts:
The issue quickly explained

I would like to switch between two fully opto-isolated Tx differential signals (RS422). How can I achieve that if the grounds are different for the signals and the analog switch ?

The issue explained

This question comes after another one but a reminder is always good. To be specific : I have 8 opto-isolated RS422 Ports coming out from a PC card. This is a full opto-isolation : every port I have is opto-isolated from each other and opto-isolated from the PC ground. Consequently I have 9 separated ground : 1 for the PC et 8 for every port.

I would like to multiplex the TX (transmit) differential signals from two of those ports, let’s say P1 and P2 but I don’t know what to use since I have to keep the ground isolation intact and separated.

The picture above depicts the basis of what I am trying to achieve. The signals Tx+ and Tx- at the top-left come from the PORT1 of my PC card, this PORT1 is isolated from the PC Ground and from the other PORTx. At the bottom-left are the Tx signals from the PORT2 of the PC Card. It is also isolated from the PC Ground and the other PORTx. Thus, PORT1 and PORT2 are isolated from each other.

I would like to have only one signal at the output of my custom card, signal I could choose between PORT1 and PORT2 via a command signal on a MUX.

The Analog Switch ?

First of all I thought of using a simple analog switch 2 x SPDT (or 2 x (2:1) ) such as the TS3A27518E from Texas Instrument or the ADG5234 from Analog Devices (or equivalent). But the more I thought about those components the more I could feel something went wrong with this solution. After all, both PORT1 and PORT2 have their proper ground (respectively GND B and GND C if we refer to ma drawing above). The analog switch will also have its proper ground and probably it will be PC ground (GND A). How can the switch work properly if its ground is different from the signals I try to switch (signals Tx I connect to its inputs) ? It can’t, am I right ?

The electromechanical relay ?

I thought about a second the solution with an electromechanical relay. But it is too expensive, too heavy, it takes too much space and it is not power I want to multiplex but signals. I don't think it is a good solution but maybe I am wrong.

What else ?

I didn’t manage to find how different isolated signals can be multiplexed. Is it because I am not looking in the right direction when I did my research ? Is it because actually a simple analog switch will do the job (despite the FET tech, BJT or whatever needs a reference) or is it because it can’t be done (but I doubt) ?

Thanks (again) !


texts: Using Linear Voltage Regulators in Series?

texts:
I'm trying to design a power supply circuit that can output four voltages from the same circuit using linear voltage regulators. I'm still learning a lot of this, and trying to stick to the LM7800 series for this application. The circuit currently uses the following regulators with a 15V input supply to produce four output voltages:

    LM7812 straight to output 12V DC
    LM7809 to output 9V DC
    LM7805 input connected to LM7809 output for 5V DC (to try and avoid excessive heat output from the LM7805)
    LM7810 on a 4kΩ+2kΩ voltage divider (if these values are too much, any ratio of R1/R2 = 2/1 will work) to step down to 3.3V DC

To that effect, I have a few questions about the design of the circuit:

    Is it a good idea to use the voltage output of one voltage regulator to power the input of another? I did read that the LM7800 series exhausts excess energy as heat, so I'm trying to avoid driving the LM7805 with the full 15V input.
    If #1 is not a good idea, would it be possible to use a voltage divider before the input of the LM7805 instead?
    Is there a voltage regulator in the LM7800 series that provides 3.3V directly instead of relying on a stepped-down LM7810? I did a quick search on Google for LM78033, but most of the results that I got were for defunct pages or for products that are no longer offered.

My primary circuit design constraint is simplicity. I'd like to make it compact enough, preferably using THT components, to fit on a PC board that can be turned into a DIP package for breadboard use.


texts: Do Linear regulators have a minimum current to maintain their output voltage?

texts: When I was searching Digikey for a ~6V to 3.3V Linear regulators, there was a minimum current column in the listing results. This kind of threw me because I didn't know that there was such a thing, or it was negligible. Since the uC in my design goes to deep sleep, this could be a problem. Do common regulators, like a LM1117-3.3 have this limitation? I didn't see it in the datasheet.


texts:
I have built an instrumentation amplifier out of two op-amps in a quad op amp (MCP6L04T).
The input signal is coming from a low-impedanece source (~17k) and most of the information in that signal is below 10 Hz. Although I can see the outline of the desired signal, it is made of a bunch of peaks - as if the op amp's supply keeps getting cut off every time it reaches its intended output value. Why is it doing this? Both scope caps were taken at the output of the op-amp, before the filter, but they can also be seen after the filter.

The other two amplifiers in the package are being used as follows: one is a non inverting amplifier for the output of this amplifier, and the last is a peak detector for the output of that amplifier.

This is running off a fresh CR2032 battery.
A previous design that used a dedicated instrumentation amplifier IC had the same input and output filters and power supply and worked flawlessly.

The op-amp has a 1 uF bypass cap right next to the pin, and a 10 uF cap further away. Both are ceramic. Looking at the supply pin with a scope revealed a fairly smooth supply - it doesn't jitter with these weird spikes.

FYI the paralleled resistors are there to increase the overall tolerance of each pair of resistors. It's giving me an extra ~3 dB of CMRR without the cost of 0.1% resistors.

The circuit:


texts: How will supply ripple affect OCXO performance?

texts:
To feed 3.3V/1.5A to my IQOV-164, I wonder if I should go for a low noise LDO with 6uV RMS noise or, to the other extreme, if I can simply feed supply voltage from a step-down converter with 20mV ripple.

Design goal is good short-term stability, long-term is not a concern (I am aware that IQOV-164 may not be the best choice for this objective).


texts: Small Battery able to withstand 400°F [204°C]?

texts:
Is there a small (watch or car alarm size) battery on the market that can withstand 400 deg F for 1-3 hours?
If not, what would a higher temp battery specifications be?


texts:
I have been doing some experiments with the STM32F405 and audio and discovered an interesting issue and wonder if anyone else has encountered the following?

I have a stereo codec CS4344 running at 96k using the 12S interface and code similar to audio examples from STM32F4Discovery.

I am also using ADC2 with DMA2 stream2 to sample control voltages from potentiometers etc.
I have a running average on the ADC data inside the IRQ generated by the stream transfer complete IRQ and I started seeing glitches
in my audio (popping sound) when switching from 48k to 96k.

The audio signal generation code is very short (just a sine wave with LUT) so there is no
issue with overhead.

I then experimented by moving the ADC averaging calculations outside the ADC IRQ and just setting a flag and glitches disappeared.

The crux of this is it seems is that just enabling the IRQ for the stream like this:

            NVIC_EnableIRQ(DMA2_Stream2_IRQn);

alone does not set a priority for the interrupt that allows it to be nested. What seems to be happening is when ADC IRQ is being serviced the audio I2S HT and TC IRQs are not able to interrupt the ADC IRQ. Setting the ADC interrupt with priority in the more conventional way seems to fix it.

    NVIC_InitStructure.NVIC_IRQChannel = DMA2_Stream2_IRQn;
        NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority= 2;
        NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
        NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
        NVIC_Init(&NVIC_InitStructure);

The DMA priority of High,Medium, Low that is set as part of the DMA config alone does not seem to be enough to permit nested interrupts if using the stream interrupt alone.

My question is how do the priorities of the DMA as set in the DMA_InitStructure interact with the IRQ channel Preemption Priority?
What is the significance of the DMA priority of High,Medium, Low ?


texts:
Where does the additional energy for flyback with multiple outputs come from?
It appears that I can add as many secondary outputs as I want, but the primary voltage is Vin, and the primary current can be deduced from V=Ldi/dt => i(t) = Vin*t/L (when switch is on), therefore power in primary is constant (V*I), therefore I am not sure where the power for the additional secondary windings come from if the power in the primary stays the same. Thought that maybe it has to do something with voltage\current mirroring to the primary.


texts: Can i put lighting current arrestor before F1 in main distribution board?


texts: high voltage coil protection with epoxy resin

texts: I have a high voltage cylinder coil with iron core. I want to protect it with epoxy resin. What is a good and easy way to do it for single use in a lab environment? What are the pitfalls?


texts:
I was reviewing a design earlier, and I noticed something interesting. The designer had removed unused pads on the chip. I have never seen this done before.

Is this something that is good practice? Is it even okay?


texts: I'm having issues setting up the LM13700 as a floating resistor and measuring the correct resistance values

texts:
So I'm still learning how OTA's work, and have an application using the LM13700 as a floating voltage controlled resistor as seen below:

I'm using +/-12V rails for this circuit. I have it set up so that I am injecting a 1mA bias current into the Vc/Iabc pin. With the Ra & R values I'm using, I'm expecting to get an Rx of around 500 ohms. But when I build this thing out and measure the resistance between pins 12 and 5 (the outputs), I'm reading on the order of megaohms(2.5 to 3 megaohms to be specific).
Is measuring the resistance of this floating resistor as simple as putting a voltmeter across pins 12 and 5 after you've implemented the circuit as shown above, or am I missing something?


texts: First things first,I am a total newbie to the 8051 MCU. I want to get started with 8051 MCU (At89s52). I've got the compiler and all (sdcc),now all I need is a bootloader.However I can't find one,Do I need to create my own or is there any pre existing bootloaders


texts: How to reliably secure stranded wire in terminal block?

texts:
My 18AWG stranded wire continues to come out of the terminal block it's screwed into.  What are some ways that I can more reliably secure this in an industrial environment?

Strip extra wire and loop/fill more of the chamber before fastening down?
Twist strays and then tin the ends of each wire tip before fastening down?  How much of a solder blob are we talking about?
Twist down harder? (I'm worried about cracking the solder and/or ripping off the terminal block)


texts:
I am trying to connect together

PID Controller (ALTEC PC410, Output Relay (NO, max. 250VAC, 3A))
K-type thermocouple
SSR (uxcell SSR-25 DA 25A 3-32V DC / 24-380V AC Solid State Relay + Heat Sink)

Question Do I connect

SSR Input Pins 3 and 4 to the PC410 OUT1 pins 4 and 5?
110VAC L to PC410 pin 1 and SSR Output pin 1
110VAC 'N' to PC410 pin 2 and one end of Load
SSR Output pin 2 to the other end of Load

Proposed Wiring Diagram

On the SSR, top 2 pins are labelled LOAD, bottom 2 pins INPUT


texts: How to interpret diode-mode readings from a multimeter

texts:
I'm using this multimeter to examine a heat gun fan.  The fan has four contacts placed in a circle (well in a square inside a circle).  Two opposite each other are labeled + and -; the other two are unlabeled.  When I extracted the fan from the heat gun, the AC inputs were connected to the unlabeled contacts.

Visible on the other side of this circular piece of PCB are four black cylinders with silver stripes at one end.  Each end of a cylinder connects to a contact from a different pair (i.e. they go around the circumference of the squared circle, forming the "edges" of the square).

My primitive understanding of electronics leads me to conclude that these cylinders are diodes arranged so as to create a full-wave rectifier, which I suppose makes sense since they are regulating the powering of a fan motor.

When I measure across these contact points using the multimeter in diode mode, I get values of 500-700 for adjacent (non-paired) contacts and 1200-1400 for the AC contacts (consistently varying by about 100 depending on polarity).  Conversely, measuring the resistance across the DC contacts gives about 6 ohms.

Are these diode-mode readings normal?  What conclusions can be drawn from them?  Is it possible to determine from them whether or not there is a continuity problem in the circuitry that would prevent the fan from running on AC power?  I have tested it with success by hooking a 9V battery up to both pairs of contacts.


texts: Building a midi project with Arduino + scrap components (optocoupler and diode)

texts:
Original title: 300V output Optocoupler in a 5V circuit

I'm (new to this) trying to build a midi controller (in and out) with arduino and scrap. I guess I had several questions in one so I changed the title.

Schematic of the first tutorial I found

The few tutorials I found use the 6N138, I don't have it but found a PC725V. It didn't work but I realize I didn't wire it correctly. I found here that it was too slow anyway (and even the 6N138 should be replaced with the H11L1). So I have a PC705V also which seems faster (not under the 2µs range but 3-4 is close enough for testing I guess) so I'm going to try it.

Also I didn't have the 1N4148 diode so I use a V1040.

Arduino and midi are 5V and these opto are respectively made to handle 300V and 70V Collector-emitter and Collector-base output...

My initial question was: Is it just overkill (so ok for scrap) or can it be an issue? And if there is, is it manageable?

Now it is: What specs should I look in components for midi usage and what is critical/manageable for components with different characteristics?

edits: (1) added schematics, (2) new title and informations.


texts:
I want my AVR microcontroller based device to communicate via SDLC (Synchronous Data Link Control) physical interface with another device, SDLC is RS-485 based.

The SDLC interface must have the following connections:
1) Tx data+,
2)Tx data-,
3)Rx data+,
4)Rx data-,
5)Tx clock+,
6)Tx clock-,
7)Rx clock+,
8)Rx clock-

I thought I could use RS-485 chip to provide those 8 connections, but the problem is RS-485 chips have connections 1 to 4 (Tx data+, Tx data-, Rx data+, Rx data-), so no clocks (Tx clock+, Tx clock-, etc).

Anybody know of any chip or circuit that I can use so at the end my microcontroller can communicate via SDLC on eight interface pins?

Thanks.


texts: How to obtain POS from the Karnaugh map?

texts:
I know there is a way of getting both without having to draw two maps, which is to draw the minterms on the map and then the Maxterms and organize them in groups just like the minterms.

My question is, what to do next? I've read in a book that the way to do it is to write the maxterms as minterms, like you would for a SOP, and then take the complement. In my professor's solutions there's an exercise he solved by writing the minterms direct as maxterms (ie: cd' = (c+d')). I'm confused. Here's his solution:

I could just ask him but I don't want to be that person and I've already pointed out a mistake in another solution, so...
He also wrote "POS" above the one for the SOP and SOP above this one so I am a bit confused.


texts: Amplifier impedance matching with constant voltage speaker systems

texts:
I understand that in order not to potentially overload an amplifier one should connect a speaker with an impedance no less than that specified, and I have just recently come to understand that for maximum power transfer the amplifier and speaker impedances should match.

So here, I know the AMP and speaker impedance should match for the best possible power transfer, and that a speaker impedance should not exceed the amplifiers specification:

However, I don't fully understand the implications for a constant voltage speaker system, like this:

The constant voltage speaker system makes perfect sense to me, I understand that like national power transmission, the high voltage low current means less loss... but... my question is...

Does the transformer coil impedance now have to match the amplifiers impedance/specification, OR, because of the dark magic of reactance, or other forces beyond my comprehension, does the presence of the two transformers become irrelevant so that one must still match the amplifier and speaker impedances?

I'm afraid that despite reading numerous articles I must admit I have yet to fully grasp impedance, reactance, inductance, capacitance, admittance, conductance, susceptance. I obviously now have SOME understanding, but really it's mostly far to shaky for much practical use yet.


texts: Capacitor rise/fall time varying with supply voltage

texts:
While testing the capacitor voltage fall times for my board at 3 different voltage levels I see that for 6V the fall time is higher than for 18V.
I checked the same on a breadboard with a capacitor in parallel with a resistor and DC voltage supply across it.
If time constant is only dependent on R and C then why is it that the fall time is varying?
Or is it because the internal resistance of the voltage source varies with voltage and this value has to be considered with the R in my as well?

Thanks,

Edit 1 - Added the schematic


texts: Development Kit doesn't provide Real-Time Access to Data

texts:
I have a development kit and an accelerometer from Bosch, and I am using their Bosch Development Desktop 2.0.

Their development desktop allows me to save the data into a .txt or a .csv once the testing has been completed.  However, I am trying to pull the data in real-time, but their development desktop doesn't allow me to access the data during the course of my test.  Only after I stop the data collection do I have access to the file.

Aside from trying to find a different development kit and sensor from a different supplier - does anyone have any ideas about how to transmit the data in real-time (like, into Python or Matlab) so that I can run some algorithmic analysis on the data in real-time?


texts: Why edge triggering is preferred over level triggering?

texts:
I am trying to understand why edge triggering is preferred over level triggering. In my book it is not explained clearly. After searching online I came to know that edge triggering is insensitive to glitches whereas level triggering is sensitive. What does it mean?

Also I am not able to understand the following:
"If the clock is level sensitive, the new \$Q_n\$ can rush through the logic network and change the output. To avoid this we need an short pulse to capture the output and hold it constant. But such short pulse is not easy to create, hence we go for edge triggering. The feedback problem is solved because there's insufficient time for the new output to race back to the input within duration of a single rising edge"

I did not understand why the output would not rush in level triggering and why we need a short pulse to hold the output.

Secondly, the feedback problem, since the level triggering duration is long as compared to the edge triggering, in the case of the former, the output would be fed back again to the input and it will keep doing this as long as the clock is active. What is the feedback problem?

But how will it be solved in edge triggering? If the time for falling or rising is very short, how will the output be able to propagate through all gates? Is it like, once edge triggering is applied the output will be propagate through all gates and next inputs will be considered only at the next clock edge ?


texts:
I'm writing a PLC program (Q Series Mitsubishi PLC, GXWORKS 2 Software) for a package sorting machine.
The logic of the machine is the following:

Packages are induced in the conveyor. A barcode reader scanner gets the package barcode.
Barcode is send to our SMS (sorting management system), it calcules the exit and send it back to the PLC.
Package travels to the calculed exit, then is derived into the chute.

The tracking of the products is done by an encoder and a shift register. This means that every memory address represents a physical position in the conveyor. Then, the shift register move the bits representing the packages along the memory buffer, till the bit arrives to an address that represents an exit, so the package can be derived.
My problem is not the tracking of the product, but the product ID tracking:
When a package enters in the conveyor, an ID is set for that product (1,2,...,n). The idea is that this ID is used to track the state of that package, for example if the package was derived in the correct exit, if it has a damaged barcode, etc.
My question is, how can I track this ID along in an efficient way. I was thinking in use the same shift register not moving a sole bit, but moving a larger number for example |1|0000011|, where the first bit acts like a flag that represents the existence of a product and the rest of the numbers is the product ID. When the flag gets to the exit address I can substract 10000011 - 10000000 = 00000011, to get the product ID.
Is any more efficient way to do this ?


texts: Check for if I've picked the correct flyback and zener diodes for a solenoid valve driver

texts:
I want to use an arduino power driver shield which contains the RFP30N06LE MOSFET to drive the 12V version of a solenoid valve which has a power consumption of 2.0 Watts (so 167 mA current draw I think?).

The power driver circuit does not appear to have any components to eliminate back EMF which I didn't even realize was an issue until I read some other attempts at driving solenoids with similar circuits (see: How to control a 12V solenoid valve with a mosfet?).

I'm planning to wire a flyback diode and zener diode as shown in the third circuit from the left in the first opening figure of: Can a Zener diode that protects a switch against inductance when the switch opens, affect turn on speed of the valve when you close it again?

So, my question is:
Will the following flyback diode and zener diode that I've chosen work? Are there better options?

Flyback Diode (?): 1N4007 (probably overkill? But they're cheap)

Zener Diode (?): BZX85C36 (I'm a lot less sure about this one, but I think I need to choose a Zener Voltage that is high so that the solenoid discharges quickly but not over the MAX that the RFP30N06LE can handle?)

I'm quite inexperienced with electronics so any other tips would be greatly appreciated!


texts:
I reflowed an SMT board using a hot plate. Afterwards, I noticed that two small pitch QFN components are shifted by about 1mm, and I'm worried that the contacts aren't right. I haven't added any through-hole components yet, so my two options right now are:

put it back on the hotplate, basically reflowing it again, and adjust then
use my hot air rework station to reflow the two chips separately

I'm fairly confident in my ability to do either of those to the same level. The question is, what's better for the health of the rest of the components? I'm assuming it's the spot rework, but want to confirm.


texts: Discrete Logic with Seven Segment Displays Problem

texts:
As a small project, I decided to make this circuit from Gadgetronix. However after wiring it, the display is stuck on 20 and when I activate the pushbutton, the 0 (display of IC2) just dims, and when I let go it goes back to normal. Now, I know just showing the circuit and telling you this is far from being sufficient to solve my problem, but I didn't think posting a picture of a rat's nest of wires was going to be helpful...

Is there any place in the circuit that has the possibility of causing this problem? A probable place where I could have shorted out a couple of pins?

Thanks!


texts: Fritzing doesn't treat breadboard power rails as conductors

texts:
I'm starting with Fritzing and created a simple schematic. All good. Now I want to turn in into a breadboard layout for my son to follow.

All the components are there and connected with dotted lines. Now I can't figure out how to make Fritzing understand that all the power rails and the vertical 5-holes are like wires? It insist on connecting all the components and power supply with explicit wires instead of letting me run the power supply to the top and bottom power rails and feed the circuit from there. Same with connecting resistors, capacitors, etc. Fritzing seems to disregard the breadbord internal connectors and insists on running wires everywhere.

Must be a some simple trick somewhere but I can't figure out what it is. What am I doing wrong?

Thanks!


texts: 4 layer PCB- fill free space on Top and Bottom

texts:
I design 4 layer PCB

Top - Signal layer
Layer2 all voltage (2V8, 1V1...),
Layer3 GND,
Bottom - Signal Layer

I'm considering what should i do with free space on Top and Bottom. I always filled them with GND (It can remove crosstalk) but recently I heard that i should use gnd planes only in those places where i need to provide return path. So if i have gnd plane on layer 3 which covers whole circuit area there i should fill free spaces on top and bottom via gnd plane? I also know that the manufacturers recommended to ensure provide an equal field of copper on every layer to prevent from bending during soldering. What do you think?

My pcb:


texts:
I have some trouble figuring out a power supply. I understand most parts of it, but have some doubts. Is D2 and D4 both zenerdiodes to get the wanted voltage
 at the output? And how does the switching of the transistors for the relay function?

Thanks in advance!


texts: Arduino driver for lots of high power LEDs

texts:
This is my first Arduino/electronics project and I am a little bit confused about the components I need to handle huge amount of currents and the circuit.

I want to have full control of 32 (maybe 40) 6-pin 3W RGB LEDs from an Arduino Uno. By saying full control I mean to be able to adjust the brightness of each led independently.

LED specs:
DC Forward Voltage (VF) : RED:2.3-2.6V,GREEN:3.4-3.8V,BLUE:3.4-3.8V
DC Forward Currect (IF) : 350mA per channel, ~1050mA total

If all LEDs are on we need 32 amps at least. Of course I'll need an external power supply. I was thinking of a common computer PSU but I'm not sure if that's enough. Any other suggestions?

Other power issues that I have to solve:

How can I provide the appropriate voltage to each LED color from a PSU? Is there any better way instead of buying a DC to DC converter for each LED x3 channels?
I'll use shift registers to control all led channels. How should I connect them and with what type of transistors and be sure that I won't burn anything?

I've searched around the internet about similar stuff but I got confused since there lots of electronic components around the circuit and so many ways to connect them.

Any schematic and details about the components I'll need will be appreciated.


texts:
I have used a single rectifying diode to lower power of 60W Chinese soldering iron due to overheating.
Though I am pleased with the result, I still plan to have variable power output for heavy soldering.
This is where I got the idea of PWM.
I am thinking of rectifying the mains with a full wave rectifier as I have found that these soldering irons work with DC as well. Then stepping th mains to 9V for the 555 timer in PWM configuration (the circuit I used is the electronoob's one) feed it to an NPN BJT and use the soldering iron in series with the collector. Additionally I plan to use the 13003/5/7 as the BJT (I also plan to use it in a Darlington pair for higher gain.)
Shall I go for it? Is there any problem with this method?
Also I am compelled to use only 555 as the PWM source.


texts: Capacitors on a voltage regulator? Or just in general

texts:
In a very concise description, what does a capacitor do for a voltage regulator (for example a 3.3v).  I have used the regulator with and with out the capacitors and no difference (that I can tell).

Also what does a Capacitor do in general?  I understand why most electronics work, but I don't really understand the uses that I have seen for the Capacitors for.

I am hoping others can also use this to understand it a bit more.


texts: As far as I understand in delta connection 3 lines and earth is connected to the ac motor. But if wye connection should one use the neutral or earth to the motor?


texts: PID controller - How is plant equation derived?

texts: During our control systems course we often work on control techniques where the plant equation/state space model is given .However , how are these derived? For example, if I wanted to build a soldering iron or just an ordinary iron . How should I go about modelling it as a plant and applying what I learnt in theory?


texts:
I have a question about a resistor divider circuit. PLease see my circuit below. I have to design 2 seperate circuits for the following 2 cases each with their specific requirements as shown. I am flexible on the resistor values R1, R2 & R3 and the Rail Voltage "V". I don't know if this is possible does anyone have any suggestions ?

simulate this circuit – Schematic created using CircuitLab

Case 1:
\$ \text{    } V_{in} = 0.2 V  \Rightarrow V_{out} \ge 2.0 V \$
\$ \text{    } V_{in} = 0 V  \Rightarrow V_{out} \le 0.8V V \$

Case 1:
\$ \text{    } V_{in} = 0.05 V  \Rightarrow V_{out} \ge 2.0 V \$
\$ \text{    } V_{in} = 0 V  \Rightarrow V_{out} \le 0.8V V \$


texts:
I have found the following expression:
c = (a'.b)

what does it mean?
I know a.b is a and b (Boolean Algebra), but what does a'.b  mean?


texts: What are the considerations for choosing Bluetooth baudrate?

texts:
I have an Arduino UNO which will be using an HC-05 bluetooth module to connect to a program running on PC.
Its baud rate can be configured from as low as 4800 to as high as 1382400.

I know that there are the following considerations concerning choosing a proper baud rate:

Data speed (Higher baud rate = faster transmission)
Connection range (long distance ==> more distortion / loss ==> can only support lower baud rate)
Power (Higher baud rate = more power hungry)
Max / Min baud rate of PC & Arduino

My question is:

Did I get anything wrong?
Are there any other considerations for choosing the proper baud rate?
Suppose I disregard power and connection range will be at most 1 meter, what baud rate should I choose for fastest data transfer?


texts: How does this circuit work to fade an LED in and out?

texts:
I'm new to electronics. I'm trying to figure out how this circuit works to fade the LED light in and out:

This is how I think it works (of course, I'm wrong):

When you initially connect the circuit, power flows from the 9V power source (I know electrons actually flow in the opposite direction, but I'm sticking with convention) to pin 8 and 4 on the 555 timer. Both the "set" and "reset" comparators inside the 555 timer output 0, causing the flip-flop inside the 555 timer to keep its initial state (i.e. 0) and output 0, which gets passed to the output stage inside the 555 timer, causing the output stage of the 555 timer to allow pin 3 of the 555 timer to act as a source of power. The 33K resistor (i.e. R1) dramatically reduces the voltage across pins 6 and 2 to some value less than 3V, such that both the "set" and "reset" comparators within the 555 timer continue to output 0. However, the current flowing through pin 3 begins to charge the 100uF capacitor (C1), as well as flow through the base of the NPN transistor (Q1), which also allows the much greater current from the 9V power source to flow through the LED, illuminating the LED (although maybe not very brightly, as the current flowing through the base of the transistor is very low and the amount of current that gets through the transistor from the battery is in proportion to that current).
As C1 becomes more charged, less current flows into C1 and more current flows through the base of the transistor, making the LED light shine brighter. Eventually, the charge across C1 results in a voltage across pin 6 and pin 2 greater than 6V, causing the "set" comparator to output 1, which sets the state of the flip-flop to 1, which causes the output stage to change pin 3 from a power source to a power sink. C1 starts to discharge across R1, as well as through the base of the NPN transistor (Q1) - first quickly, causing the LED to continue to shine brightly at first and gradually become less bright as the charge across C1 diminishes.
Eventually, the charge across C1 results in a voltage across pin 6 and pin 2 that is less than 3V, causing the "reset" comparator to output 1 (the "set" comparator already started output-ing 0 when the voltage dropped below 6V), causing the flip-flop's state to change to 0, causing the output stage to allow pin 3 to act as a power source again.
The process repeats.

Is my thought process correct? Did I miss anything?


texts:
I'm using an onboard parallel port on an otherwise disused laptop to try and sample the MIDI output of a very old keyboard. MIDI is a serial link at fixed 32 kbit/s, and so far i've managed to connect the output of the keyboard to the SELECT pin of the parallel port; however, i can't make sense of the data i get (it doesn't appear to conform to the MIDI spec), and i suspect that's because the signal is getting distorted somewhere along the way, or perhaps the parallel port isn't fast enough and is therefore missing some bits...

So what i'd like to ask is: Have i made a bad choice of input pin? Should i use some status line other than SELECT, or is it indifferent?

I've written a custom program in assembly which runs standalone, so there is no other task or OS to muck up the timings... The port itself is one of the later ones, supporting EPP/ECP, though i'm not sure whether i'm making use of those advanced modes... I'm simply sampling the status byte of the port in a tight loop.

Any advice?

P.S.: As per the comments below, i'll try to refine and clarify my query. I realise that connecting a MIDI Out port to a parallel port involves the use of an optocoupler; i'm using one of those cables that connect MIDI to a soundcard's gameport, and i believe it contains an optocoupler built-in already (since multimeter readings don't show direct connections between any of the pins on both ends). I know the cable works because i used it back in the era of soundcards (so, a long while ago).

So what i'd like to know, specifically, is whether a parallel port is fast enough to accurately read a 32 kbps bitstream on one of its status pins. I chose the SELECT pin, only because i assumed any input pin would do equally well. Should i have used another?

The parallel port in question is one of the later ones, right before laptops stopped coming with them altogether, and i can devote the full resources of the PC to the task (no other programs, not even an OS).


texts: Bluetooth low energy Power Consumption in Sleep state

texts:
I constantly read about the low power consumption of BLE and websites stating

Power consumption:
Since a Bluetooth low energy device is in sleep mode most of the time - the maximum/peak current draw is only 15 mA and the average current draw is of only about 1 uA.

However whats confusing me is, when they mention sleep mode, does this mean the BLE module is not adverstising itself to the world and is undiscoverable?

I am trying to find out what actually occurs in sleep mode.

I am working on a small home project, and trying to find the least power hungry BLE, currently i have a standard BT module and when is discoverable mode it uses anywhere between 4mAH -30Mah and this is way to much.

Is it possible to get the 0.1mAH and still have the module advertising and then connect once a iPhone becomes in pairing range>?

Thanks


texts: Pin mount of horizontal pins without bending

texts: Related to my question from last time (Pin mounts horizontal pin rows): I have the same device, but now I don't want to bend the legs, rendering SIP/DIP sockets useless. But I do not care anymore about the removability. What are then good ways to fixate the device on a pcb? One idea I had was to use overdimensioned smd pads, and solder it on them. Is that useful, or are there better ways?


texts: How change circuit to get 15VDC@1A rather than 15VDC@.6A?

texts:
I have designed a power supply circuit which gives output as 15VDC@0.6A... but I am in need of output as 15VDC@1A...

How to increase the current value alone?
I have gone through many search in internet but it gives me the answer as "current increases as voltage decreases"... I need 15V@1A as constant output....
what is the way to achieve?!

In the image, instead of LM7812, I used LM7815 to get 15VDC...


texts: using a vibration / noise sensor as edge finder in a CNC machine

texts:
I have a desktop CNC machine which has just the basic functionalities like controlling the speeds and position with a somewhat reasonable accuracy / precision. I also have an edge finder which I can use to measure things and theoretically set the origin of the coordinate systems. However when I switch tools and replace the edge finder with the spindle I have something like a 0.3mm error. It means the milling tool either cuts more or less than what was intended.

So I'm thinking of measuring acoustic noise or mechanical vibrations on the vase to detect when the milling tool actually touches the part and compensate for those errors. For example consider the set up below:

I want to have a acoustic sensor (e.g. microphone) or a vibration sensor (e.g. accelerometer?) on the vise and then see the noise on a computer. I know Arduino and serial communication reasonably well, but I don't know what sort of sensors I can use for this purpose and how they should be wired. Thanks for your support in advance.

P.S.1. I have also posted this question here and here on Reddit.

P.S.2. I am gonna check if I can do it myself. So here I asked a more specific question about vibration monitoring.

P.S.3. So for those who end up here, I'm still pursuing this idea as it seems the most viable option for me. Here I have asked for good microphones to record the acoustic noise. And here I managed to plot an spectrogram of an audio file recorded with my cellphone. And eventually found  Friture Free, Open Source Software to get spectrorogram and FFT of auditory inputs in real time.


texts: Operational Junction Temperature with LM7800 series regulators

texts:
I am building a DSLR cooler (something I actually started last year, and ended up shelving when winter hit, and which I've picked up again for this coming summer), and I'm trying to regulate the power to one or two TECs via PWM outputs on an Arduino. I'll be using a few sensor inputs to the arduino as well as a pot to control the PWM level to the TEC(s).

The TECs require 12V power, however depending on the exact Arduino unit I end up using, I may be limited to 5V for the Arduino (i.e. Arduino Mini). So I've put together a circuit diagram that uses an LM7805 to regulate the voltage down. I am trying to build a pretty compact cooler, and while I am not going to be drawing a lot of amperage (130mA tops I think, given the various sensors and LEDs I'm going to be using, and accounting for the 12-15mA the Arduino itself will draw) , I am worried that a 7V voltage drop in the regulator will produce a lot of heat. It's just shy of 1W energy dissipated in the regulator itself.

The datasheet for the LM7800 series regulators states that the maximum thermal resistance junction-ambient for a TO-220 package is 50°C/W (interestingly, a TO-3, which seems a good deal larger in terms of footprint, is only 35°C/W). Assuming I experience the maximum, that would mean a 1W dissipation would increase the temperature of the unit by 50°C? If I'm running at 25°C, then I'd have a 75°C regulator temperature?

Or is there a lower actual operational temperature, below 50°C, that I should take into account? I've scoured various forums, mostly audio forums, and I've seen members throw out junction-ambient temps of 10°C or 25°C for TO-220 packages before, and I'm curious why. It seems like a 50°C increase for just 1W thermal dissipation is a lot, but maybe that's just the reality of things.

Thanks!


texts:
I am a newbie to electronics and hope someone can help.  I am looking to test a SSR for my own experimentation to see if I understand this correctly.

I have a SSR for 120 AC. (I am not plugging in for fear of not understanding yet) When I apply the small DC (say 3-9 V) the connects for 120 should become closed if I understand right and should have continuity.  So basically I am trying to test this SSR by applying a small DC voltage across the DC pins and then testing the continuity across the AC pins.

I am not getting continuity across the AC pins when applying DC voltage across the DC pins.

Am I not getting a closed circuit because there is not enough load across the AC pins?

Thanks for any help.


texts: Impedance of waveguides shorter than 1/10 of wavelength

texts:
I read already several times that it is a common rule of thumb, that matching the impedance of a waveguide to the external network impedance is only necessary for waveguides longer than 1/10 of the wavelength of the incident signal. Is that true? And why is that so? Can someone give me a physical science basis for why that rule of thumb is true? Maybe someone knows literature where this rule is confirmed?

Thanks a lot in advance!


texts:
I've connected an op-amp (TL071) as buffer, with Vcc+ = 5V and Vcc- = 0V (ground).

When the input voltage (v+) is greater than 1.44V I get the expected result (the output is the same as the input).

However, if the input is below 1.44V, the output saturates.

Anyone knows why this might be and how can I get around it? My goal was to amplify the signal of a LM35 (a temperature measurement).

Thanks.

simulate this circuit – Schematic created using CircuitLab


texts:
I am trying to understand ground current in a power distribution system.

The basics, of course, are simple: in the power grid, the "hot" wires carry high voltage, while the return path (the neutral wire) is connected to ground, so ground forms part of the circuit.

Some people seem to claim that this ground current is harmful. Be that as it may - I am not trying to argue about that question, but rather want to understand how ground current really flows.

The only source I could find was by Duane A.Dahlberg, and to be frank, I could not make heads or tails of it. Other than that, I have not been able to find any reputable source of information.

One of the claims I read was that somebody standing on the ground could experience a potential difference of 0.5 V between his right foot and his left foot. That seems very hard to believe.

I am most interested in how ground current would flow related to a 500kV overhead line, about 100 miles long.

Specifically, what I would like to know.

What voltage and amperage (order of magnitude) is the actual ground current? Obviously, in a 220kV line, most of the 220kV should go into the load. How much is lost on the actual wire, and, what is the voltage between ground on one end of such a transmission line to ground on the other end?
Does the ground current travel along the surface, or does it penetrate into the ground?
How does the type of material affect ground current (e.g., dry soil, rock, ground water, etc.)
Are there differences between AC and DC power lines with respect to ground currents?


texts: How to build fast visible light detector

texts:
I need a circuit which can detect flickering of light too fast. I have Digital LDR Module which is too slow can I replace LDR with L14G2.

Digital LDR Module -

Digital LDR Circuit -

Can we replace LDR with L14G2 or PT334-6C in above circuit.


texts:
So lets say that we are looking at NPN transistor:

simulate this circuit – Schematic created using CircuitLab

I know the practical and theoretical basics of transistor but what I don't understand is next:

1.) Collector current flows in and out of transistor if we have load on the collector. How is that possible - in and out at the same time?

2.) Ic=β*Ib, right? So when we are using this equation, which Ic do we use - Ic in or Ic out?


texts: why use OFDM, not PSK/QAM for high speed data transfer

texts: Why is it harder to modulate/demodulate the PSK signals on high baseband frequencies(1 Ghz for instance) with high sample rates than modulate a multicarrier OFDM signal - do IFFT, FFT to receive/transmit.


texts: On/off switching of current from USB Tx line

texts:
I'm making a device that will have contact with water, so the electronics are encapsulated in epoxy. I want to have the option to reprogram the microcontoller, so I want to add contact points that I can connect USB micro lines to. Problem is I obviously can't have current leaking out of those points when not connected to USB and it's in the water. I can stop the vin from reverse flow using a diode, but I can't figure out how to stop current from the tx line of the micro.

I tried a diode there too, but when connecting the tx line to the USB, I need current to flow from the micro. I tried an n channel mosfet using an I/o pin to control the gate and had the tx line divided between drain and source, but it didn't seem to work quite right.

Ideally I'd like the gate to be automatic, where it opens when the USB is connected/detected, but I could use an I/o pin to control a gate too because the micro has Bluetooth. The voltages are low--5v from USB, micro is 3.3v.

How do I stop the USB from leaking current when its not in use?


texts:
I'm looking to do some measurements with a
Sharp GP2Y0A21YK0F IR Analog Distance Sensor.

Vcc 4.5-5.5 V

The Analog Output is: max Vcc+0.3V

Unfortunately, my DAQ can only handle 0-3V analog-in.

So my idea is to just scale the voltage down from the sensor by using resistors in a voltage divider.

I could use a second opinion on this

Thanks!


texts:
I have this spool (image) and did some testing with a multimeter before I disassembled it. It's working range was [-3.3v,0v,3.3v].  When I tested it by just applying the battery after disassembly nothing happens.

Does this work in other ways then just applying the correct voltage?


texts: Why do we need to keep the terminal here negative when connected to an oscilloscope?

texts:
As you can see, both the right terminal of diode and top terminal of the resistor is negative.

This has something to do with shorting the negative terminal of an oscilloscope, but I don't under stand why. Why do these terminals both need to be negative?

From what I remember, the negative terminal of an oscilloscope is ground, so if the top resistance is positive, there will be a short circuit. I don't have any idea what that is or if that really was what I heard.

The experiment was to find the I-V characteristics of a diode.


texts: Is it intuitively correct to think of voltage as a “propellant” force?

texts:
From my understanding

voltage is an electromagnetic force that creates current by exerting a force on an atom that causes that atom to transfer one of its valence electrons to the neighboring atom. The atom that lost a valence electron becomes a positively charged ion and then “steals” a valence electron from the succeeding atom to restore charge balance. This effect propagates throughout the circuit.
Voltage and current are directly related. the larger the voltage/emf, the faster one atom’s valence electron  jumps to the next = larger current/electron propagation

Assuming this is in essence all accurate: say we have a simple series circuit with a 5V supply and 2 equal resistors.

The voltage drops throughout the circuit from 5 -> 0, but as we know current is the same across a series circuit

So intuitively, Speaking about series circuits only, is it valid to think of voltage as a “propellant” force or only as a force that “gets the electrons moving” initially and depending on the amount of force, sets the speed at which they “move.”

As an example of this, if we have a person who slingshots a rock in space (space so that the velocity of the rock is constant), voltage would be the force exerted on the rock initially that determines how fast the rock moves through space but after the rock left the slingshots pouch, that force would have no effect on the rock after that point.

Or is voltage more of a “driving force”?

An example of what I mean, if we have a person who’s pushing a boulder on a flat plane, voltage would be the force that’s exerted on the boulder. If the person stopped pushing, the boulder/electrons would stop moving/propagating.

I ask this because voltage drops across the circuit From 5v to 0v but current remains the same, so it seems as if voltage’s only responsibility is to start and set the speed of the current in the beginning of the circuit, but after that current acts independently of that voltage.


texts: SPI bus – how to route two Slave Select lines to the same slave

texts:
We have legacy system of four boards: one containing chip acting as SPI master, three others containing chips acting as SPI slaves.

My goal is to eliminate two of the slave boards; however, the master board won’t work unless all three slave boards reply to its ping.

Therefore my intent is to put a small board together with SPI slave chip that will fake replies to master pinging. Typically I’d have used two chips, each receiving one slave select line meant for each of the legacy slave boards being eliminated. Is there any way I could combine these two slave lines together and only use one chip acting as SPI slave?

Thank you.


texts:
I got my firmware running on a MSP430FR596 and I want to add a condition on the FW (how long the FW has been running, or how many certain interrupts it has received) that if satisfied, the whole system should shut down without erasing the main memory.

The MCU is directly connected to the battery and disconneting it is not an option.

What is best to do here? Should I disable interrupt? Or there are better ways?


texts: How to get input voltage of 5 and 6 volts

texts: I have an interesting problem in building something with robotics.  I am using a PIC16F877A micro-controller to control the robot.  The motors of the robot require 6 volts and the PIC requires 5 volts.  I was wondering if there was an easy way to get both of these required voltages from a common voltage source.  The motors suggest running on 4 AA batteries, and I was going to just use a 7805 voltage regulator to than reduce the voltage to 5 volts, but the regulator requires at least 7 volts to function correctly.  I also thought that I could use a voltage divider network, but none seemed to be convenient.


texts:
I'm currently reading the art of electronics 3rd edition and have stumbled upon this transistor power amplifier towards the end of chapter 2 (see picture below).

The open loop (cutting point X from its connection to the output and grounding it) output impedance is about 20 ohms assuming beta of about 100 for Q4\Q5 since the 1.5k resistor looks like a 15 ohms resistor when looking through the push-pull output stage.

The closed loop (with the output connected to the input) the output impedance is reduced by the desensitivity which is just (1+loop-gain).In this case the loop gain is about 70 since the total amplification at the quiescent point is about 2100 and we feedback about 1/30 of the output back to the input. Thus the closed loop output impedance is 20/71=0.3 ohms.

Side note: I understand that the gain will vary as the input swings because the differential amplifier gain is dependent on the base emitter resistance which changes with collector current, although I'm not sure how will this affect the circuit's output impedance.

In the book they state that the closed loop output impedance we calculated i.e. 0.3 ohms is only true for small signal calculations and does not mean that the the amplifier can drive a 3 ohm load  to full swing.

My question is -why? what in our analysis have we neglected that limits our results to small signal only?

If it may help the book states that the 5 ohms resistors in the output stage limit the the large signal swing and for example a 4 ohms load can  only swing 10Vpp.

Edit: I see the 1 ohm load caused some confusion, indeed 1 ohm is too close to the output impedance so please ignore that when answering my question ( I deleted it from the example and changed it to 3 ohms instead so it will not load the 0.3 output impedance considerably). my question still remains though.


texts: Why do we need a pull-up resistor if we can just make a short to the power source?

texts:
I saw the term pull-up resistor being mentioned everywhere, but I haven't grasp the reasoning behind its use.

For example, I saw one in the book Practical Electronics for Inventors, in this schematic for 555 timer arranged for monostable operation. .

It is explained that

  ... pin 2 is normally held high by the 10-k pull up resistors.

But why use a resistor? If we want to keep pin 2 high, can we just make a short from this pin to Vcc? If we just want to limit the current, I thought we can do it somewhere else, for example by adding a resistor between the output pin 3 and the ground?


texts: Linear actuator. Monitor end switch with arduino

texts:
For a hobby project I am developing a solar tracker. For this I obtained a linear actuator. It contains a DC motor, 2 Hall sensors and an end switch. I am using an Arduino Uno and a Polulu motor driver for control. Below is a link to a simple electrical schematic of the actuator

http://www.solar-motors.com/inc/getfile.php?id=783163FD-16DB-4AE0-9A48-C1CD71093105

I have managed to run the motor and read out the hall sensors. My problem is with the end switch. I am not sure how to wire this and read this signal.

I am powering the Hall Vcc with 5V form the arduino, which works well with the hall sensors, but when I connect the end switch to a digital input pin I get no signal when the actuator is at its end.

Does somebody have an idea on how to set this up. Thanks


texts: What are the consequences of not having a magnetic field in the atmosphere on electronics?

texts:
Electronics super-noob here! (I did EE in school but have managed to forget practically everything since, to an alarming degree!).
I'm wondering how the field of electrical engineering and electronics would be affected if humans, say, colonized any of the planets that have no magnetic fields?
I understand that without a magnetic field in the atmosphere, humans would be more easily exposed to harmful radiation. As far as technology goes, how would things be affected?
You can still created magnetic fields in space by creating moving electric fields, right?
Would normal electro-mechanic forces works the same way? Is there any consequence for radio technology or satellites? Obviously, humans have sent probes into the vacuum of space that send data back, so I understand that it works, but I'm curious if there's any different considerations.
What technology would stop working on a planet with no magnetic field (besides compasses)?


texts: Limiting battery input current to avoid voltage drop when activating LoRa radio

texts:
I have a battery-powered wireless sensor system that sends sensor information periodically. One requirement is that it has to be functional at very low temperatures. Powering this system is a Tadiran TL-5903 lithium battery, which are batteries made to power systems at very low temperatures and supplies 3.6V.
When the sensor sends out a transmission by LoRa radio, it can consume a peak current of around 100mA+. At low temperatures, the battery cannot provide enough current to supply the load during transmissions and the battery voltage drops from normal operation of 3V to below the minimum operational voltage of the microcontroller (2.2V).
The current power supply IC is a buck-boost chip TPS63802. It takes in the battery's voltage range (2.0V to 3.6V) to an operating voltage of 3.0V. However, the IC doesn't have an input current limiter that can limit the current so that it doesn't take too much peak current from the battery. At low temperatures, we can't take in too much current from the battery or else the voltage drops substantially.

simulate this circuit – Schematic created using CircuitLab
We tried putting a super cap at the output of the switching regulator but it doesn't seem to make much difference in the voltage drop when doing radio transmissions.
Is there an IC or a simple circuit that can limit the current coming into the regulator without dropping the voltage at the input of of the switching regulator?


texts: Low power sleep with WDT wakeup on PIC32MM

texts:
I'm trying to put a PIC32MM0256GPM028 into sleep mode and have it woken up by the Sleep Mode Watchdog Timer (say 1/4 second later- adjustable by SWDTPS anyway). Once it goes to sleep (current drops), it just stays there.

This post seems the closest PIC32 sleep mode with watchdog wakeup failing, but that seems to deal with a reset occurring instead of a wakeup.

I've got this as a standalone function:

void sleep(uint32_t t){                     //sleep for t WDT periods
    static uint32_t oldRCON=0;
    SYSKEY = 0x0;
    SYSKEY = 0xAA996655;                    //unlock
    SYSKEY = 0x556699AA;
    //OSCCONbits.SLPEN=0;                     //enable idle
    OSCCONbits.SLPEN=1;                     //enable sleep
    SYSKEY = 0x0;                           //lock
    while(t){
        WDTCONbits.ON=1;                    //enable
        WDTCONbits.WDTCLRKEY=0x5743;        //magic sequence to reset WDT
        oldRCON=RCON;                       //dummy read
        RCONCLR=0xDF;                       //clear all reset reason flags
        __builtin_disable_interrupts();      //disable interrupts

        asm volatile( "wait" );             //sleep/idle as per SLPEN

        Nop();
        WDTCONbits.ON=0;                    //disable
        t--;
    }
}

WDT Fuses (PS4096 is 4096ms etc, slowed down so I can watch what it does):

// FWDT
//#pragma config SWDTPS = PS1024       // Sleep Mode Watchdog Timer Postscale Selection bits ~in milliseconds
#pragma config SWDTPS = PS4096       // Sleep Mode Watchdog Timer Postscale Selection bits ~in milliseconds
#pragma config FWDTWINSZ = PS25_0       // Watchdog Timer Window Size bits (Watchdog timer window size is 25%)
#pragma config WINDIS = OFF             // Windowed Watchdog Timer Disable bit (Watchdog timer is in non-window mode)
#pragma config RWDTPS = PS1048576       // Run Mode Watchdog Timer Postscale Selection bits (1:1048576)
#pragma config RCLKSEL = LPRC           // Run Mode Watchdog Timer Clock Source Selection bits (Clock source is LPRC (same as for sleep mode))
#pragma config FWDTEN = OFF             // Watchdog Timer Enable bit
//#pragma config FWDTEN = ON             // Watchdog Timer Enable bit

The Power Saving Modes section (61130) of the PIC32 manual gives a code snippet (example 10-1) which is even less than what I've got (eg this code deosn't do the syskey unlock):

// Code example to put the Device in sleep and then wake the device using
// the WDT
OSCCONSET = 0x10; // set Power-Saving mode to Sleep
WDTCONCLR = 0x0002; // Disable WDT window mode
WDTCONSET = 0x8000; // Enable WDT
// WDT time-out period is set in the device
// configuration
... user code ...
WDTCONSET = 0x01; // service the WDT
asm volatile( “wait” ); // put device in selected power-saving mode
// code execution will resume here after wake
... user code ...
// The following code fragment is at the beginning of the ‘C’ start-up code
// to find whether the wake from Sleep is due to the WDT
if ( RCON & 0x18 ) // The WDT caused a wake from Sleep
{
asm volatile( “eret” ); // return from interrupt
}

I've got the eret code in my reset and nmi handler and at the start of main, but it's not even getting to reset. I'm not setting window mode off  as its disabled in the fuses, and it shouldn't stop the WDT from triggering anyway.

Most of examples etc seem to be for MX/MZ variants, so I wonder if there is a subtle difference I've missed.

How do I get the PIC32MM to go to sleep and resume on WDT?


texts: What does this bus signal representation mean?

texts:
Often, when looking at digital system signal plots over time there are these graphs with two parallel lines that often "swap" place. I am wondering what precisely they represent? I noticed they usually are used for buses, but for the rest I'm clueless. It's probably quite trivial.

This is an example of the graphs I mean, in this case from a discussion about how CPU's execute instructions:

I've tried googling, but I couldn't find an explanation.


texts: use of toroidal ring in hair dryer safety plug

texts:
I am having trouble understanding the Khan academy video of a hair dryer teardown here: https://www.youtube.com/watch?v=gFFvaLzhYew. In this video, the lecturer explains how the safety plug works (so you don't fry yourself if you drop the hair dryer in the sink). At 3:50, the lecturer says that the copper coil can sense when the neutral and hot wires are charged differently, and it then alerts the control chip to turn off the power. The explanation of the operation of the coil was very vague. The picture below points to the part I'm talking about:

What is the copper coil that he shows in the video? How does it work? Is there a more specialized name for the coil when used like this ("safety coil" or "difference coil", etc.)? I ask for the name because I couldn't find an explanation of this via Google, probably because I didn't know what to search for.


texts: Hierarchichal netlist vs Flatten netlist?

texts:
I'm learning about synthesis of VHDL code and I have the doubt about the advantages and disadvantages of Hierarchichal vs Flatten netlists. The first is like interconnection of blocks and the second one is like all the resources interconected?

Thanks,


texts: Modelling 3-phase induction motor and filter for inverter output in LTspice

texts:
I am designing an inverter in Ltspice and am looking to have a simple circuit to represent the motor load and filter out the PWM harmonics in order to obtain outputs. The motor characteristics are:

Synchronous Inductance: 500 uH

Resistance (line-neutral): 500 mohms

Will a RLC filter circuit similar to the image shown below work? If so what values should I use for the components (the PWM frequency I am trying to remove is 20kHz, will this use f=1/2*pi*RC)

I think I could do it for single phase however I am struggling with a 3 phase motor especially because of both resistor and inductor when calculating the values required for the filter.

Here is the overall circuit


texts:
I have been told that when laying out a PCB to keep all the polygon pours uniform on each layer. So, for example, in a corner of the PCB, you do not want the pour on one layer slightly offset relative to the other, like this:

The red layer is the top layer, brown is the second, blue is the third.

I have been told this is bad, but why? No one can give me a reasonable answer, and I don't want to do something just because someone told me to do it this way, I would like to understand what issues can come up with this sort of design.

Or is it just down to aesthetics?


texts: How to avoid signal interference between 5 volt analog video signal and 415 volt servomotor and drivers, when working nearby

texts:
I am using a 5V borescope analog camera (Sony CCD, PAL/NTSC) for visualization purposes. This camera has a 20 meter 4 core wire, which transmits power and video signal to and from the camera. Along with this, I am using a servo motor (Siemens V90, takes 3 phase 415V AC) which moves pulls and pushes the 20 m wire (in turn moves the camera inside a pipe).

Problem: The image fed by the camera has lot of noise. I could make out that, the noise disappears when the servo motor and driver is switched off. Since the motor takes 415V and the camera is operating at 5 V DC, there is a signal interference.

Can you suggest any possible solutions to avoid the noise in the image?

Note: I have added the wiring drawing of the camera and the TV that displays the live video from the camera. The green circle is the 4 core wire I m using (one unused wire). Please let me know if more information is required about the servo drive/motor and camera.

The below image shows the noise appearing in the screen


texts: P channel FET reverse polarity protection - toggle switch on base

texts:
I am trying to add a reverse polarity protection in my circuit using a P channel FET, but I also want to have a SPST toggle switch in series with the gate for the user to turn the circuit on or off.

I just tried this circuit on a breadboard, but it is staying on regardless if the switch is closed or open, but I am not sure why. I am thinking that when the polarity is backwards, the gate receives EMF and that is what's happening, but I am not sure.

Could anyone explain this to me, and if there is another way to do what I want?

Thank you


texts: Drive voltage vs phase voltage of a BLDC motor

texts:
Background

This video on using an oscilloscope to view the line-to-line phase voltages of BLDC motors demonstrates the "virtual" ground necessary for such measurements. I understand this idea: you need to make a virtual ground for the probes because the oscilloscope's channels are all grounded to the same point (earth).

However, I don't understand the video's results in the context of an electric motor model:
$$v_{applied}(t) = 2i_{phase}(t)R + e_{l-l}(t) = 2i_{phase}(t)R_{phase} + k_{e}\omega$$
Where the units of \$k_e\$ make sense (I think it should to be defined in E-RMS/(rad/s), but I've seen so many different definitions). Sufficed to say, back-EMF = func(speed).

Questions

Are the phase voltages seen in the video (snapshot below) equal to the voltage applied by the ESC (\$v_{ac}(t)\$)? Or are the measured voltages equal to the difference in the applied voltage minus the back-EMF (\$2i_{a}(t)R_{phase}\$)?
Unless the virtual ground somehow negates the back-EMF, I don't see how these voltage measurements don't also include back-EMF.

Heck, I'm even more confused now about the sensorless speed control programs used in hobby ESCs: how do hobby ESCs measure back-EMF? If an ESC only energizes 2 phases at once (say, A is HI, B is LO) and measures EMF on the third phase (C), then why does the back EMF on phase C matter if it doesn't affect Vab?


texts: Complex signals is the same as natural signal

texts:
I am working using a sinuasidal signal along with the complex signal derived form it and when I plot the signals spectrum using FFT I got the same spectrum and it turns out that the signals are the same which I don't get?
import scipy
from scipy import fftpack
from scipy.signal import butter, lfilter,filtfilt
from scipy.signal import freqz
import numpy as np
#from scipy.signal import butter,filtfilt# Filter requirements.
import plotly.graph_objs as go
import matplotlib.pyplot as plt
import pandas as pd

def butter_bandpass(lowcut, highcut, fs, order=5):
    nyq = 0.5 * fs
    low = lowcut / nyq
    high = highcut / nyq
    print()
    print("low is ",low)
    print("high is ",high)
    print()
    b, a = butter(order, [low, high], btype='band')
    return b, a

def butter_bandpass_filter(data, lowcut, highcut, fs, order=5):
    b, a = butter_bandpass(lowcut, highcut, fs, order=order)
    y = filtfilt(b, a, data)
    return y
freqs = [7,20,30]
sins = ['sin', 'cos', 'sin']
amps = [1,0.5,0.2]
phases = [0, np.pi/4, np.pi/3]
def m_signal(t, freqs, sins, amps, phases):
  ops = np.zeros(t.shape)
  for f,s,a,p in zip(freqs, sins, amps, phases):
    if s == 'sin':
      ops += a*np.sin(2*np.pi*f*t + p)
    if s == 'cos':
      ops += a*np.cos(2*np.pi*f*t + p)
  return ops

fs = 240
T = 2
nsamples = fs*T
time = np.linspace(0, T, num=nsamples)
sig0 = m_signal(time, freqs, sins, amps, phases)

def time_signal(n):
  return np.sin(2*np.pi*n*7) + np.cos(2*np.pi*n*30 - np.pi/4)

# Complex Signal
def signal(n):
  s1 = np.exp(1j*2*np.pi*n*7)/(2*1j) - np.exp(-1j*2*np.pi*n*7)/(2*1j)
  s2 = 0.5*np.exp(1j*(2*np.pi*n*30 - np.pi/4)) + 0.5*np.exp(-1j*(2*np.pi*n*30 - np.pi/4))
  comp = s1 + s2
  return comp

# If fs is 240 Hz and T (time) is 2 sec, then the number of samples is fs*T
fs = 240
T = 2
nsamples = fs*T
time = np.linspace(0, T, num=nsamples)

time.shape

def plot_spectrum(nsamples, x, fs):
  Xf = fftpack.fft(x, nsamples)
  ff = np.linspace(0.0, fs/2, int(nsamples/2))
  # print(ff)
  fig, ax = plt.subplots(figsize=(20,3))
  ax.plot(ff, 2.0/nsamples * np.abs(Xf[:nsamples//2]))
  plt.grid(True)
  plt.show()

sig = time_signal(time)
csig = signal(time)

sig.shape

# Signal on time domain
plt.figure(2, figsize=(20,3))
plt.clf()
plt.plot(time, sig, label='Signal')
plt.grid(True)
plt.show()

sig

csig

# Complexified signal (Magnitude)
plt.figure(2, figsize=(20,3))
plt.clf()
plt.plot(time, np.abs(csig), label='Signal')
plt.grid(True)
plt.show()

# Complexified signal (Phase)
plt.figure(2, figsize=(20,3))
plt.clf()
plt.plot(time, np.angle(csig), label='Signal')
plt.grid(True)
plt.show()

# Spectrum of the signal sig
plot_spectrum(nsamples, sig, fs)

# Spectrum of the complexified signal csig
plot_spectrum(nsamples, csig, fs)

print(csig)
```


texts: Where can I purchase this "stuff" called neutral cure silicone rubber?

texts: I read your posting about the "What kind of glue should I use for PCB-mounted components to avoid vibrations?" and you mentioned that the "superb solution" was "neutral cure silicone rubber". Where can this be readily be purchased without having to buy cases of 48 or 144 etc. which was about all I could find "on line"?