texts:
I have assembled 1000 pcs of PCB. 6/1000pcs have track broken (bottom layer) as pointed in the attached picture. The pad with track connected to an electrolytic capacitor. There are two other capacitors have the same footprints with not track break.
The assembly using wave soldering machine. Temperature 260 C.
The board is FR4 1.6mm thickness 1/2 Oz. ENIG surface finish.
What could be the cause to avoid track break when go to 300,000 pcs??


texts: Is it good practice to use a flood fill ground plane as a pad for a component?

texts:
We have recently had an issue with one of our products and I came across the following while reviewing the PCB. It's worth noting I don't think this is in any way related to the issue I was troubleshooting.
The three components shown in silkscreen clockwise from the top are capacitors that connect between a pin on the chip and the ground plane.
Is it standard practice to layout like this? It may be perfectly normal, it just looked a little odd to me... I would have expected 2 clear pads with a track to the ground plane or another trace. My understanding was that having separate pads would help the components centre themselves during reflow if they were placed slightly out of alignment?


texts: Using B0505 for connecting phone chargers in parallel

texts:
I am planning to charge four 18650 Li ion batteries that are connected to four TP4056 in parallel making 4 amps in total to charge them in their usual rate. I was thinking of connecting two 2 amp phone chargers in parallel to charge the circuit but found this article that it won't work.

Can  I use a B0505 to isolate the connection in between these two chargers?
I only managed to find 1-3 watts of B0505, I calculated a 10 watt B0505 to allow 2 amps to flow through, Can I also connect B0505's in parallel?


texts:
I'm confused with voltage divider..For the voltage going into Base, do I use the formula A or B to calculate? After searching some infos on google, I assume A is the right formula?

What's confusing me is that in my book, it says Voltage XY = 40/50, and Voltage YZ = 10/50.


texts:
I am getting full scale ADC value from 0 to 16348. I am trying to convert it to 4-20mA and then to 0-25 bar pressure, as I am ultimately measuring pressure.

I am using the y = mx+c equation but failing miserably. Can any one please guide so that I can learn something.

I am trying something like

4 = m*0 +c
c = 4.

20 = m*16348 +4.

m = 0.0009789.

My controller is not supporting floating points...hence it's creating trouble for me. Can anyone help me out>?


texts:
I currently need to work with the iM880A-L. As it is annoying and shaky to solder that thing on perfboard and attach cables, I want to create a breakout board with JTAG and SWD plug and pins for all the other pads.

How do you actually connect the pads with your board? I never soldered such a big SMD board, so I wonder. Just bigger pads on the board, as in normal SMD like resistors? Is there another standard and stable way to get pins on the iM880A-L without creating a custom board?

Does anyone know some similar board that I can copy from in Eagle/KiCad (did not decide yet)? How do you call these pads/connections on the iM880A-L? I really did not know what to Google, I tried post stamp, as it looks like one, but that just led me to tiny post stamp sized bords. I am a newbie to custom board design, so please bear with me.

Kind regards


texts: Electrically Controlling A motor direction

texts: I want to control a motor's direction electrically. When the input is a zero, I want it to go one way, and a 1, the other way. The only way I can think of this is a solenoid with a spring attached to a DPDT reverse switch wired to the motor, so when theres current, the switch moves one way, and none it goes to it's original position. This is very inefficient and bulky, so is there a way to control the direction electrically? I prefer transistors and common electronic parts, but if I have to get a chip or something, it'l do.


texts: Does building an inexpensive bridge rectifier cheap flickering LED Christmas lights create safety concerns?

texts:
OK, I bit on Home Depot's door buster LED christmas lights... 150 LED lights for under $5 each. How could I resist? (Answer: By remembering that cheap LEDs flicker, AND that I'm sensitive to it. )

https://www.instyleled.co.uk/what-causes-led-flicker-and-how-can-i-stop-it-happening/

Seeing as how they were door-busters, they are also non-returnable. I'd like to figure out how to make them work. I've done some research, which has shown that it's possible to create a dc rectifier/transformer/ that will make the flickering stop.

https://www.youtube.com/watch?v=mqRd3q7k9OU

Now, I think I can do all of that (I love soldering that gives you that much room to screw up. BUT, I'd rather just pay $5 for a professional version that absolutely positively won't overheat and burn down my house. I can NOT find anything that's not built for uses like under-cabinet lighting or dimmers, and which have specific connectors for specific manufacturers. Does anyone know if anyone sells something like this, or if there are kits that are a little LESS DIY in nature? Thanks!

Only answer at DIY was the suggestion to go with a frequency doubler, rather than a rectifier... but trying to search for those seems to only dig up voltage doublers, rather than frequency. I assume I'm asking the wrong questions, so any guidance would be greatly appreciated.

  EDIT: OK, so this appears to be THE question: IF I insert a bridge rectifier into the string of lights, per the youtube video, and
  keeping the original fuses in the original plug intact BEFORE the
  rectifier, is there an increased chance of fire from the DC current in
  the strand, or will the fuses protect the line?

  (Just re-edited to update the title, too.)


texts: Common collector H-bridge driver - is there a way to do this with MOSFETs? Gate voltage seems too high

texts:
Background

I made 4 of the following push pull circuits like the one below, to use as two H-bridge drivers for motors (stall current about 5A.) Sorry for not drawing the darlingtons in full, I did this in Microsoft Paint. The darlingtons have an integral reverse diode.

My criteria were:

-Forward, reverse and stop available (no particular interest in using the motor as a brake)

-Buildable on stripboard

-No possibility of both power transistors being switched on together due to incorrect input signals

-Component count as low as possible.

I solved this by using back-to-back emitter followers in a push-pull arrangement. I was able to bolt the collectors of Q3a-d to the chassis, and Q2a-d to a bracket/heatsink connected to the positive supply, in order to keep the supply current off the stripboard. The connections to the motor were made with wire all along the stripboard trace to avoid excessive current on the track, See below. +12V Supply wire is black because it is from an inline fuse which has black wire.

See below (Please ignore the way the components have been crushed and the way I made the connection to the positive terminal.)

Question

The base - emitter voltage for a Darlington is about 1.2V, so everything works well. The only thing is, the current gain of the Darlingtons is about 750, which means the value of R2 is quite low in order for Q2 to switch on properly. This in turm means that R2 draws quite a lot of current when Q1 is switched on.

It seems MOSFETS are the way to do things like this these days, but there is a problem. For example in the datasheets http://www.irf.com/product-info/datasheets/data/irf3205.pdf and http://www.irf.com/product-info/datasheets/data/irf5305pbf.pdf it seems in page 3, first image, a 4.5V gate-source voltage will give about the right current. But there is no data for lower gate-source voltages.

Is there a way to replicate / improve on this circuit with push-pull MOSFETs in common drain / source follower mode? All the  MOSFETs I have seen require too much gate-source voltage to switch on to be able to be used in push-pull mode with the drains connected to the supply rails.


texts: When do we actually need bank interleaving?

texts:
Since common DRAM chips support burst transfer and hardware page size (row size) in a bank is quite large, we can amortize the charging & activating time over bytes in a long burst transfer.

I think it has the same effect of bank interleaving, which distributes successive addresses over different banks. And the performance is the same.

So why we need bank interleaving indeed?


texts: Why doesn't this Elektor ramp circuit work?

texts:
I built the following circuit on my breadboard, it is from an old Elektor article:

It is a ramp generator that repeatedly

charges C3 through the dual-PNP current mirror to build a ramp, and
briefly shorts C3 across T1 to reset the ramp & the cycle (triggered by the rising front of the square wave input, differentiated through C2/R2).

The fundamental frequency of the output signal matches that of the control signal.  It is an evolution on a simpler circuit presented in the same article that generates log-shapped ramps as opposed to linear ones.  I have successfully built the simpler version on my breadboard. Differences compared to the schematic above are

the current mirror is just a plain 10k resistor,
it does not have the FET output stage,
there is a 10k resistor between the input signal and its connection to C1/C2, and
C4 is 1μF and C3 is 180nF.

The rest of the topology is identical (see page 113 here, i.e. pdf page 21). I generate the input square wave with an MCU so the it's about 3.3V peak-to -peak (TTL) instead of 4V.
C4' and D1 are optional and not needed in my use-case so I breadboarded the circuit with wires instead of those.  I laid it out on the breadboard twice from scratch using brand new components each time, but no luck. It does not produce the specified output waveform. I am using all the same parts as specified on the schematic except

I use non-graded BC5x7s instead of the two hfe-graded BC5x7Bs, and
the E300 is obsolete so I replaced it with a BF256B.

I have tried powering it with a regulated 5V supply available on the development board, as well as a 9V battery. Both Vcc & common ground hookup wires heat up significantly when the power is on (the more power, the mores so). I have checked and re-checked my layout for shorts but all seems fine.
Per comments below, I measured the current draw on the VCC rail: 900mA @ 5V, 1.3A @ 9V. (By contrast, the simpler topology draws about 320nA, if my multimeter is to be trsted for such low values -- I'm not sure, but not much anyway.)  So it does look like a short, I guess the path VCC > T4 > T1 > GND has a fairly low resistance?
Also per comments, I put in a 3.3uF cap at C4' instead of wire. (The article recommends "no more than 4.7", no unit stated but it's electrolytic so I thought that should be right.) Current draw reduced to 500mA @ 5V, 900mA @ 9V.  Again, I don't need capacitance for my use case so then I also tried a 10kΩ in that position. Current draw measurements were in the same regions as with a 3.3uF cap.
In every case though, the output is a fixed voltage (no signal) between 1.5V and 2V depending on the arrangements. Any idea what's wrong with the topology, or what I am doing wrong with it?


texts: How can I determine what kind of power supply or battery I need for my four NEMA 23 stepper motors?

texts: I am trying to determine what current my power supply needs to have for my mini rover project. The NEMA 23 motor specs are as follows: Bipolar amp/phase is 2.8A and the bipolar resistance/phase is 1.13ohms. If I have 4 NEMA stepper motors, does this mean I need a power supply that can supply 2.8*4 = 11.2A of current drawn continuously? I heard on youtube that the 2.8A/phase is the max current, so would I simply round down to 10A of current drawn (or is this untrue)? Would I just purchase two 5Ah batteries and wire them in parallel to achieve 1 hour of operating time?


texts: Measuring the current of a Wheatstone Bridge, given four known resistances and supply voltage

texts:
Say I had a Wheatstone Bridge with four known resistances and a supply voltage.

How would I go about getting the current across Vg?

I understand how to get the voltage Vg using Ohm's Law and Kirchoff's first rule, but am confused as to how I'd go about getting Ig.

Thanks!


texts:
I've made some tests with my Arduino UNO, all worked great: analog i/o, digital i/o, serial i/o. Then I've noticed that built-in LED on pin 13 is always on.

I've uploaded an empty program like void setup(){} void loop(){} and it still was on. When I manually turned it off by digitalWrite command it switched off. So it works well.

I just want to know if I've broken the board somehow or it's just some feature, which I do not get?

NOTE: a mate of mine has the same board with the same problem. Any ideas?
Thanks much!


texts: How to import PCB 3D model (step file) designed in MCAD software in Altium and place PCB footprints, and route it?

texts: I have my PCB board from Mechanical Design software as a Step file. Now, I want to import it into Altium Designer and place PCB footprints, and do the routing etc. I am looking for some guidelines or Tutorials. Any and all help is appreciated.


texts: Optical isolator (VO0600T) circuit not working

texts:
I have a circuit where a 3.3 V DATA signal is optically isolated using the VO0600T IC. The circuit is as follows:

In the schematic, VEE = 5 V (pin 8). Note that there are 2 separate grounds on either side of the optical isolator IC. The datasheet recommends a 0.1 uF capacitor between pins 5 and 8 - it is not indicated in the above circuit diagram, but it is present on the actual circuit that I am testing.

From the VO0600T's datasheet, it is indicated that pin 7 can be used for strobing. In my application the output state of the isolator circuit is constantly monitored, therefore pin 7 is connected to VEE so that the output of the isolator IC is always active. The truth table on page 2 of the VO0600T's datasheet confirms that if pin 7 is HIGH, the output (on pin 6) will be the inverse of the DATA signal. Thus, when DATA is LOW, DATA_OUT should be HIGH, and vice versa.

When I measure the output at pin 6 with a multimeter (when DATA is LOW), it reads a fluctuating value between 0.01 V and 0.04 V. When DATA is HIGH, the multimeter reads 0.00 V (which would be expected due to the inverting output of the IC). Thus, my issue is that DATA_OUT does not go HIGH when DATA is LOW.

I have had brief access to an oscilloscope when this was tested. The following image illustrates what is happening with DATA_OUT when DATA is LOW:

It is clear from the above image that DATA_OUT is oscillating, which explains the fluctuating reading on the multimeter. Unfortunately I did not take a measurement with the oscilloscope when DATA is HIGH (I also do not have direct access to an oscilloscope to make that measurement now).

Can anybody explain why I am experiencing this issue? Am I missing something obvious in my circuit layout? Any assistance will be greatly appreciated.


texts:
Does anyone know how to use the 555 timer control voltage? My thoughts are if -input in the upper ("Threshold") comparator is at 2/3Vcc, then any voltage should act against the 2/3Vcc into the -input. But would it increase the voltage at 1/3Vcc into the +input of the lower ("Trigger") comparator?
Essentially how does the control voltage affect the voltage divider and current through the voltage divider line?
Thanks


texts: System Generator: Does an fft block need a buffer?

texts:
I wonder if is necessary  to put a buffer before a FFT block. I want to do a fft, with N = 16 (samples).
Is necessary to design a temporal memory system to save 16 samples before loading into FFT or the FFT block has it´s own internal buffer to save these values?
Thank you so much for your help.


texts: How much information would a network protector need to determine if a backfeed is due to feeder failure or power export?

texts:
Many downtown or otherwise densely built-up areas, as well as some major metropoles (much of NYC, most notably), use secondary network electrical service to maximize service reliability and keep utility equipment costs reasonable.  This works well, until you start adding a high degree of distributed generation capacity (whether renewable or not) to the network.  Then, under low loads, the network protectors start tripping out, as they're designed to identify any power export from the secondary network as a sign of a faulted or shut-off primary cable and trip.  The resulting "pumping" (short cycling) of the network protectors can damage them beyond repair, meaning that DG additions on secondary network services are often prohibited or severely restricted.
However, the downstream/upstream logic in network protectors only looks at local power flow at that network protector, with no awareness of what other protectors in the network are seeing.  In theory, though, assuming the network transformers all share the load/generation equally, a faulted or shut-off primary cable can easily be distinguished from a true power export situation by looking at the direction of power flow on a network-wide basis.  Specifically, under that equal-sharing assumption, an export situation would be identified by all the network protectors registering an export of power, while a faulted or shut-off primary cable would stand out like a sore thumb as the only cable trying to export power, while the remaining network protectors still register power imports.
That raises two questions, though.  First, how far from the equal-sharing ideal do actual secondary distribution networks operate at?  And second, in a network running at practical levels of transformer-to-transformer imbalance, how much knowledge of the rest of the network's power flows is needed for a network protector to distinguish between bona fide power export and backfeed due to a failed primary line?  I ask this because I wonder if some means of inter-network-protector communications/restraint could be used to allow network services to support deep DG penetration without the need for a costly DG "overlay" service system.


texts:
I am trying to initialize a 4x20 LCD using a PIC18 in 8bit serial interface. This is an LCD I found lying around in the lab and I cant find a datasheet for this exact one.

I am struggling to get it to work as all I ever achieve are blocks on the LCD.
I have spent countless hours with no sign of success. Is there something in the code that I am missing?

All help is appreciated.

LCD.c

#define DataBus PORTA      //Data is set to 8 pins on port A
#define RS PORTCbits.RC0
#define RW PORTCbits.RC1
#define Enable PORTCbits.RC2

void LCD_CmdWrite(int Cmd){
DataBus = Cmd;   //Sets command on Port A pins
Enable = 0;
RS = 0;
RW = 0;
Enable = 1;
__delay_ms(20);  //Delay for LCD
Enable = 0;

__delay_ms(10);

}

void LCD_intialize(){
RW = 0;
__delay_ms(20);

LCD_CmdWrite(0x38);  //LCD 8 bit mode
LCD_CmdWrite(0x01);  //Clears LCD
LCD_CmdWrite(0x06);
LCD_CmdWrite(0x0F);  //Display on, cursor on, blink on
LCD_CmdWrite(0x80);

__delay_ms(2);
}

main.c

#include <xc.h>  //Allows access to device specific features like TRIS etc.
#include <stdio.h>  //Allows access to input/output pins
#include <stdlib.h>  //Memory management and text conversion

#include "LCD.h" //Includes LCD Display functions

void main(void) {
OSCEN = 0b01000000;
OSCCON1 = 0b01100000;
OSCCON2 = 0b01100000;
OSCFRQ = 0b000101;   //Sets clock at 16MHZ

TRISC = 0x00; //Sets PORT C as Output
TRISA = 0x00;//Sets PORT A as Output
PORTC = 0;
PORTA = 0;

__delay_us(200);
LCD_intialize();  //Initializes LCD

__delay_us(200);
LCD_clear();  //Clears LCD again

while(1);

}


texts: Use the metal in a metal core PCB as the GND layer

texts: As I understand in a metal core PCB there's a copper layer, thermally conductive dielectric layer and then the metal layer for the heat dissipation. Can vias come to this metal layer so that it can act as the GND layer in a PCB design?


texts: voltage drop across collector and emitter when using transistor as a switch

texts:
I am trying to send TTL pulse from Arduino to 8 raspberry pi simultaneously. For this, I am using npn transistor as a switch. Below is the circuit for same:

Note: MB102 is a power supply that takes in 5v or more and regulates it to 3v3 http://www.petervis.com/Raspberry_PI/Breadboard_Power_Supply/YwRobot_Breadboard_Power_Supply.html.
I am using q1 2n3904 transistor. Also, Arduino is connected to a recording system which takes 5v pulse rather 3.3v.

Issue
the voltage drop across collector-emitter is 2.51v whereas it should be 0 when the TTL pulse is HIGH. The voltage drop across Pi is 0.67v whereas it should be ~3.3v. What is wrong with the circuit? What can be changed?


texts: What is the breakdown voltage of the following?

texts:
I actually have multiple questions and I decided it would be more efficient if I were to ask a question with multiple questions attached.
Background
I’m an experimenter that now has a new project in mind. I call it the 10,000 project when really it should be called the 25,000 project. I’m using 4 microwave oven transformers (MOTs) with a voltage doubler circuit using high voltage capacitors.
I am attempting to make a high voltage supply that has an input of almost 100 amps.
So besides my point let’s get right to my questions.
Questions:

What is the breakdown voltage of the typical magnet wire insulation in a microwave oven transformer?

What is the breakdown voltage of vegetable oil?

What is the breakdown voltage of PVC tubing with a thickness and air gap of 1 cm?

Please, if you or someone else has any knowledge you or they would like to share given experience or knowledge I would greatly appreciate it.
Note: the frequency is 60-50 Hz
Further Notes: Yes I know the size of capacitor I need.
No it won't output 100 amps, sorry for the typo. It should be fixed. it uses 100 amps. My shop has a 200 amp breaker switch. With 48,000 watts and 240 volts 3 phase access.
Thanks


texts:
I want to build a simple as possible ethernet HUB.
I'm new to electronics (just made few arduino robots/projects but no big stuff).

I don't know where to start, can someone please explain me how it "electronically" works and what whould the best way to build one ? Also, I'd like it to be as small as possible (but that doesn't really matter for the first experiment)

I really want a Hub, not a switch or a router : i wanna capture all the data going through it


texts: The classic Envelope Detector is very old and very cheap and very simple .Sure there are now better schemes like synchronous detection ,PLL etc.The circuit is responding to the peak of the Amplitude modulated carrier .The decay time constant is arranged to ensure that the highest audio frequency can be reproduced and there is reasonable carrier ripple attenuation .For Medium wave Broadcast AM the carrier frequency to be demodulated would most likely be 455KHz and the highest Audio frequency would be 9KHz .These frequencies are geometricly far enough apart for the simple circuit to work well enough for most receivers.My Question is would an averaging type of detector with an averaging time constant large enough to attenuate the 455KHz ripple and small enough to pass 9 KHz give a signal to noise advantage over the peak scheme that could hang up on impulse noise ?


texts: Using a li-ion battery instead of an AC adapter

texts: I have a board that uses a 19v 3.42A AC adapter as a power supply and I want to replace that with a Li-ion battery. What should the voltage of the battery be? I ask this because my laptop for example uses a 14.4v battery while having a 19v 6.32A AC adapter.


texts: Photodiode - Turn Digital Input pin into 1 with little light Input

texts:
Currently I am trying to work with a photodiode(SFH 203) that is supposed to detect very small amount of light.
Using the digital of an arduino  the photodiode cannot turn the pin to 1 due to the low level of light.
If I measure light with an anlaog pin I receive a value arnd 25-30.

Is there any way to bring the digital value to turn 1 using a small amount of light?


texts: Is it possible to attach leads to surface mount component?

texts:
I ordered an op amp to experiment with. I knew this was a surface mount component when I ordered it. I assumed that I would be able to somehow attach leads to it, so I could use it on my breadboard. Using a simple soldering iron - is there a way I can attach leads to this component to use on my breadboard?

I know when these components are surface mounted they are only rated to come in contact with high temperatures for a second or two. I was thinking of getting a small bead of solder on the end of a wire - getting the bead to melt using the iron - then touching the wire and bead to the one of the pins on the component (so the soldering iron doesn't touch the component directly).


texts: Hardware requirements for 10Gbps line rate packet processing

texts:
How do I calculate the horse power required for worst case packet processing scenarios?

First, a little more background, I'm building a device for packet analysis. My test box currently runs on Linux with an Intel chip set and using DPDK for packet capture. I want to support at least 10Gbps links.

Not counting jumbo frames, the line rate for Ethernet packets on a 10Gbps link is between 812,740 and 14,880,960 packets a second. So when I say worst case, that implies having to process the max payload size. In order to sustain line rate processing of 812,740 pp/s what kind of hardware is necessary? I know the actual analytics will play a big role but I haven't yet optimized or profiled the algorithms however, getting at least a minimum hardware baseline will still be helpful.

So, what I'm trying to understand is the hardware piece and I have a lot of questions; x86 vs ARM vs MIPS, CPU speed and cores, memory configuration and bus speed, temporary disk storage settings, etc.

What kind of minimum hardware configurations can support 812,740 pp/s on a 10Gbps link?


texts: Under Voltage Protection for LiPo Battery

texts:
I have a 3Cell LiPo battery which I am going to use with an RC Car, and I want to design a circuit to protect the battery cells from going under ~3.3v each. So what do you think of this design?

As you can see in the schematic, I am using the MCP111-315 which detects voltage drop below 3.08V (active-low, open-drain).

Diodes are used to increase the detected voltage level, so it will detect the power at 3.08 + Vf (3.3 is my preferred value). However, the MCP111 only draws 1.75uA (max) and most datasheets only provides Vf for as low as 1mA. Is there a more reliable way to get this ~0.2 voltage drop at such low current? maybe a voltage divider?
I am using optocouplers since I don't have a common ground between Cell 1 & 2 and the MCU
Any cell that falls below 3.3V should pull the MCU pin down (MCU Internal pull-up resistor is turned on on that pin)
C1, C2 and C3 are bypass capacitors for the MCP111, whereas R1 & R2 are series resistors for the optocouplers LED.

Any suggestions on this design or do you have a simpler idea?


texts: Altium: Grouping "Not Fitted" Components In Excel BOM

texts:
I would like to include "Not Fitted" components on my Excel BOM exported from Altium. This part is easy, all I need to do is check the "Include Not Fitted Components" box in the "Source Options" panel of the BOM configuration window. However, I would like to modify my Excel template to have a section specifically for "Not Fitted" components, with its own header, and have Altium automatically place the "Not Fitted" components in that section. What would I need to do in my Excel template to accomplish this?

In other words, I need to have Altium look at the "Fitted" column in the BOM and if it sees "Not Fitted" it needs to place these components in a separate section of the BOM (designated by the Excel template).


texts: Why do the LEDs flash in the attached circuit diagram when adjust the variable resistor

texts: My son is studying the attached circuit. He found that LEDs will either grow consistently or flash when if adjust the variable resistor. However, we cannot figure out how this happen. How does the current flow? Could anyone explain how does the circuit work? Thank you.


texts:
I have an old P-CAD library file and need to import it to Altium. The library file format is .LIB

I tried to use Import wizard -- P-CAD Libraries and select the file. But I receive a messeage; the file is not recognized. Please select P-CAD PCB or schematic files.

I have also tried to Add Library and open the file, but could not see any component on it.

How to import or open this type of files in Altium ?


texts:
I'm trying to build a two stage opamp inverting amplifier with a gain of ~90 @160kHz. The purpose of doing multi stage amplification is so I can have a high input impedance along with the first stage is used to drive a ADC for digital processing. The inverted signal is then used to drive a high voltage circuit. I've simulated the circuit using LtSpice and get the result I am expecting:

After testing the physical circuit I noticed that a large amount of feedback capacitance is present between the output of the second stage and input of the first stage (~100pF). This greatly reduced the gain that I am able to achieve as increasing the gain just causes the input signal to drop more and more.

Assuming the Opamps have the required gain width product and other parameters is there a possible feedback network that would compensate for the reduced gain due to capacitive feedback? Could this also be an issue with my layout that could cause such insane capacitive feedback? I was considering using coax to improve the isolation between input and output (close proximity on pcb). Is this a good direction to explore?

Layout


texts: How can I load a data file into external SRAM via Quartus

texts:
I am working with a Cyclone V GX starting board. It has 4mb of external SRAM. I have written a very simple memory interface for accessing it. That works.

Now I would like to load a raw (hex?) file into the external SRAM on my board for my FPGA to work with. Is there an easy way to accomplish this via Quartus II?

edit:

I am not looking for a way to program my FPGA (by loading a design), this is clear to me. My FPGA has already has my micro-controller design loaded. Now I want to load a program (in the form of raw data) for it into the external SRAM on my board.


texts:
I'm implementing a very simple LC circuit where the power supply is connected to an inductor (of 4 micro Henry specifically), and the inductor is connected through a diode to a capacitor going to ground (of 1 micro Farad). I was expecting that the capacitor will accumulate twice the input voltage, however I am consistently only reading that it accumulated exactly the input voltage.

I included below a schematic of the situation and the explanation of my thinking. I added a dummy load resistor \$R1\$ but in the derivation I assume to simplify matters that \$R1 = \infty\$.

I would be grateful for any explanation of why this circuit doesn't seem to work "in the real world".

simulate this circuit – Schematic created using CircuitLab

We now have by Kirchoff's current law, and the definition of capacitor and resistance, (note that \$V3 = V2\$ so \$V3 / R1 = V2 / R1\$),
$$
I1 = \frac{d V2}{dt} \cdot C1 + \frac{V2}{R1}
$$
Differentiating this we get,
$$
L1 \frac{d I_1}{dt} = \frac{d^2 V2}{dt} \cdot L1 \cdot C1 + \frac{d V2}{dt} \cdot \frac{L1}{R1}
$$
Now using the definition of inductor the left-hand side is equal to \$V1 = Vin - V2\$. Therefore collecting everything together we get
$$
Vin - V2 = \frac{d^2 V2}{dt} \cdot L1 \cdot C1 + \frac{d V2}{dt} \cdot \frac{L1}{R1}
$$
It's easier to solve it if we assume that \$R1 = \infty\$. In that case we get $$
V2 = Vin + c_0 \sin \Big ( \frac{t}{\sqrt{L1 C1}} \Big ) + c_1 \cos \Big ( \frac{t}{\sqrt{L1 C1}} \Big )
$$
Now specializing we see that \$c_1 = - Vin\$ and differenating we see that \$C1 \cdot d V2 / dt = I2\$ which is also zero at \$t = 0\$ hence \$c_0 = 0\$. We conclude that
$$
V2 = Vin - Vin \cdot \cos \Big ( \frac{t}{\sqrt{L1 C1}} \Big ).
$$
Since we imagine that \$R1 = \infty\$ and there is a diode, we notice that the circuit will stop when the current \$I2\$ turns negative. When this happens \$V2 = 2 Vin\$.


texts: Extra spacing between some traces and the ground plane

texts:
I have seen several designs where there is extra spacing between some traces and the ground plane. For example, see the traces between the points A and B or C and D in the following picture (this is a Raspberry Pi 2, but I have seen it on other boards too):

What is the purpose of this extra spacing?

My guesses:

Reducing ground plane noise.
Controlling trace impedance (for high speed signals).
Perhaps for some EMC reasons.


texts:
You hear in grade school that the input to silicon foundries is sand and ICs come out the other side, but you never much more about the refining process or what is actually involved in extracting silicon from the overall sand composition.

How is silicon for foundries sourced and/or extracted from sand?  Does it come from a special beach in an exotic location?  From the nearest creek to a foundry?


texts: Can someone explain this solution to a basic circuit analysis question?

texts:
Problem:

Solution:

I would have labeled my reference marks for Rx's voltage with the positive to the left of it and the negative to the right of it since the current is flowing from left to right, so applying KVL with this convention would have made Vx positive. However,the solution labeled as Vx negative, why?


texts:
I'm 16 and interested in getting into audio electronics so I can make things like mixers and speakers, etc. I currently only have a rudimentary understanding of electrical circuits which extends only to that contained in the book Make: Electronics.

I'm seeking out advice and recommendations of any books or online courses for either electronics in general or audio electronics specifically.


texts: Can anyone identify this 433Mhz OOK protocol?

texts:
I am working with some wireless devices that use 433MHz OOK transmitters and receivers. They use a simple protocol for the data sent between the nodes. I feel it is reminiscent of common IR remote control protocols - the long high pre-amble, the pulse coded data, the length of pulses.

Examples:

RC-5 has 1778\$\mu\$s long pulses and 14 bits.
NEC has a long start bit as do others

It is different to any of the weather station or remote sockets protocols I have seen.

Some of the devices in the system are large ASIC DIPs, others are much more modern SMT microprocessors. I suspect this protocol has been used for a while and may have a name.

I have tried searching for the pulse lengths as ranges on Google to no avail.

Does anyone recognize this protocol? I would concentrate on the 14 bits of data, the length of pulses rather than the checksum and multiple bytes - this may be a higher level of protocol.

Here is a link to the full size image.

The salient details are:

Pre-amble - 5410\$\mu\$s high
0 and 1s are both 1850\$\mu\$s long
0 is 385\$\mu\$s low, 1465\$\mu\$s high (79% duty cycle)
1 is 980\$\mu\$s low, 870\$\mu\$s high (47% duty cycle)

In case the data content of the packets are important, they follow this general form:

3 bytes of address information
1 byte of status information
Checksum

or

3 bytes of address information
1 byte of status information
2 bytes (4 nibbles) representing data 0-9 x 4
Checksum

As per the image the checksum is the sum of the lowest 10 bits of the sent data segments, take the two's complement, and add one i.e. -SUM(data) + 1


texts:
I'm almost sure this is a ceramic capacitor, but I have trouble finding its characteristics.

The first picture is the top side, the second the bottom side.

The first shows: 120G (or 12OG)  and an F.

On page 4 of datasheet shows how to read the aprt number, but I cannot map it (maybe I have a wrong datasheet).

Can someone identify or give a correct datasheet for this component?


texts: What does n/o and n/c mean on a schematic diagram?

texts: Okay so I have two questions. I am looking at a schematic diagram of a remote control for a toy car and I can't seem to figure out what the "n/o" and "n/c" components stand for that are attached to the motor supply. Also not sure if they are the same component or they just have different looks. My other questions is what is the RL1 component with the swirls and the two lines?


texts: Why does my resistor start smoking when current runs through my circuit?

texts:
This is my circuit:

simulate this circuit – Schematic created using CircuitLab
However, when I wire it up, R2 starts smoking - why does this happen?
[Edited to remove incorrect wire]


texts: Discharging high voltage and capacitance capacitor?

texts:
I need to discharge a 4.4mF (millifarads) capacitor storing 1200V in about 5 seconds. I did the t=R*C' and got a resistance value of approximately 227ohms. I did a calculation for the energy in the capacitor E=1/2*C*V^2 and got out 3168J. I had a look online at resistors and they either have the power or voltage but not both. They are also rather large and I'm hoping to keep it as small as possible so my overall project isn't too big. Is there a way of connecting the resistors in parallel or series that might achieve the power and voltage requirements without damaging the resistors?

Side note: I had a look online at the parallel and series connections but I'm not quite sure if you still need to voltage rating or power rating to be high enough or do they add together?


texts: 555 timer Theremin - capacitor choice, and question about mixing signals

texts:
I'm trying to create 555-timer based Theremin, but I have a few questions that I don't quite understand. For now, I'm building it on a breadboard (yes, I know it's not the best option), but I don't want to commit yet to some schematic that might be wrong. My current idea is to use 555 timer in 150 kHz range.
For this, I have 50 pF C, R1 of 1 kOhm and R2 of 100 kOhm (following this convention).
Checking with an oscilloscope I get around 100 kHz. But when I connect a wire (antenna) to pin6 I don't get any change in frequency. My idea was that connecting an antenna to pin6 would create a capacitor in parallel with 50 pF, and that my hand should then vary that capacitance, thus varying frequency. But the only change in frequency occurs if I touch the bare wire, not by proximity.
Am I doing something conceptually wrong, or is my 50 pF capacitance too large (I'm guessing "antenna" capacitance is probably less than 5 pF?)
Oscillator difference
My other question is concerned with mixing of two signals for Theremin (one from fixed oscillator, one from variable oscillator - the one connected to antenna). I've seen schematics where op-amp is used to subtract signals, but I'm not sure how relative phase of the signals affects the output of the op-amp? Surely this all works only if they are in phase? How is this problem solved in other signal mixers?


texts: How to solve this error for PCB Design in Altium Designer?

texts:
I am new to PCB designing and Started with Altium Designer for PCB Design. I have created the Schematic doc for Arduino Nano with all its components having their schematic and Footprints in the schematic library and PCB library. And I have also Net Labeled all the components in Schematic Doc. Now when I Go to PCB doc for Creating the doc for creating designing and placement of by components,
I go to Design--> Import Changes from "filename "( when My PCB doc is opened)
I get these windows

Now I am not able to understand these errors and how to solve them, why they are coming. So anybody can provide their valuable suggestions?


texts: I'm looking to build a remote firework launcher. I'm using parts from an rc car for the remote, but I need a circuit that can switch a large current (~2-3amps) with 6v. Can I do this with a transistor, or will I need to buy a voltage relay?


texts: Why aren't resistors lowering the current flowing in my circuit?

texts:
I have a simple breadboard setup with my multimeter inserted to measure the current. I'm trying to see current changes from different resistors. No matter what resistor I seem to put, the current doesn't change.

Is this because nothing is drawing charge?
(does this have anything to do with the law conservation of charge?)

I'm trying to get the current right on my circuit before I hook it up to a little motor. I can't hook up my motor until I get the current right so I have nothing to hook up to my circuit to draw current. Is there a way I can cause a circuit to draw current so I can correctly read reduced voltages? Or could something else be wrong?

(I was using a rechargeable lithium ion 9volt and then switched to a regular one to see if that was it. But a lithium ion power source shouldn't effect current right?)


texts: Ways to connect 14 AWG to small PCB solder tabs

texts:
I have 14 AWG wires that need to connect to the + and - of the below PCB board.
What way should I connect it to provide the cleanest look? Is there some sort of connector I can attach the wire to first, then solder to those tabs?


texts: How much power does DDR3 RAM draw when unused?

texts:
I have a RAM-using application that

would occasionally find extra RAM helpful, and
can afford the extra hardware, but
has a tight power budget.

Thus, I would include the extra RAM only if this extra RAM did not draw too much power when unused.

How can I calculate the power the RAM draws when unused?

I am trying to calculate this power as follows.  Please tell me if and where I err.

Here is a sample datasheet for a 4-gigabit DDR3 chip:  Micron's MT41K1GM4 DDR3L-RS-1600.  Relevant specs:

Burst refresh current:  215 mA.
+45-degree-C temperature self refresh:  6.0 mA.
VDD = VDDQ = 1.35 V.

As far as I know (though I could be wrong), the "Burst refresh current" is irrelevant to my question.  If this is right, then I believe that I need a power-overhead budget of (6.0 mA)(1.35 V) = 8.1 mW to carry this chip when my device is not using it, which will be most of the time.  By, unused, as @Rocketmagnet has observed, I mean that no reading or writing is going on; I do not mean that the RAM can forget its data.

If all this is right, I can afford the 8.1 mW.  However, am I overlooking something important, please?  I ask because I cannot afford much more power just to carry hardware that won't much be used.


texts: How to chose the right decoupling/bypass capacitor variant for comparator power rails?

texts:
I would like to rephrase this previous question, but with regard to comparators.  I can't decide if a comparator is a digital or analogue device, but I realise that digital devices might be bypassed differently from analogue ones.  Clearly the slew rate of a comparator output is way faster than an op amp.

For example, I have a LT1011A - Voltage Comparator in my hand.  If I wanted to use it in a comparison circuit at up to say 8 MHz, how would I bypass it's power supply?  The datasheet only gives an example of a hysteresis circuit, and I don't want hysteresis.  Linear Technology suggests 100nF + 2uF Tantalum in that example.


texts: Understanding photodiode modes and practical effect on noise vs response time tradeoffs for audio applications

texts:
I am an experimental musician with admittedly very little electronics experience (but I do have a mathematics degree) trying to find a decent photodiode for a project where I send audio signals via laser, potentially with another medium in between (such as ink or paint in water, or smoke) to color the sound.
My first goal is to simply get a clean signal through air using a laser and a photodiode. My initial prototype using cheap parts had some success, but it also had a lot of noise, even when operated in a completely dark environment.
I have read that many/most photodiodes roughly have two modes - one where some reverse bias is applied and which has faster response times but higher dark current and another where no reverse bias is applied that produces voltage via photoconductivity with lower dark current but also slower response times.
On a practical level, what should I consider when picking my photodiode with regards to this trade off? The datasheets I've read only specify the rise times at a given reverse bias voltage, at nothing when used purely photoconductivity. Should I worry more about dark current impacting noise or slow rise times clipping the detail frequency range of an audio signal? And is there any place one can easily evaluate directly how the continuum of reverse bias voltages effect dark current and rise times for a typical photodiode?


texts:
I am trying to control the speed of a 15W DC-motor with operating voltage of 12V using an IRF640 n-channel MOSFET as shown in the picture below but without the pull-down resistor RMS = 10kOhm. Instead of it, I always set the Arduino PWM digital pin to value 0, thus when the motor should turn off the MOSFET gets 0V at its gate.

:
:

The problem I face is that even with the maximum value of PWM (255) I don't get the motor to rotate as fast as it does when it's plugged directly into 12V. I get that there is a voltage drop in the MOSFET, but the speed should not drop as much as half of its normally is.

Can the absence of the pull-down resistor Rms 10kOhm case this effect?

Do I need to use a MOSFET gate driver in order to achieve better performance of the DC-motor? (The maximum power the motor uses during operation is not higher than 18 W)
If yes, what MOSFET gate driver should I use in this case?

Arduino pins work with voltages 0V - 5V and maximum current that can pass trough them is 20 mA.

EDIT: Arduino Uno's PWM signal frequency is 490 Hz on each pin except for two pins where the frequency of PWM signal is 980 Hz. Source


texts: Ambient operating temperatures for *duino boards

texts:
If this has already been ask I apologize as I cannot find it using the search option, please send link.

For my first project I'm thinking of building a monitor, in stages, for my outdoor pond (about 30 feet from the house) with wireless data transmission for various conditions like water level, waterfall pump failure, icing, and maybe even the occasional Heron that likes to feed on my Koi. I'm also leaning heavily towards the Netduino board as I would like to leverage my C# skills.

Anyhow, when I look at the specification for the Netduino board, it specifies an operating temperature of 0 to 70C. Right now it's -8C outside and will probably go to -13C tonight. The coldest I ever remember it being here (Rochester NY) is maybe about -28C (-18F maybe -20F) but that is very very rare.

The Arduino site lists no specific temperature specification, but links to the Atmel specification.

The Atmel processors (ATmega328 and AT91SAM7X512) for both both boards are rated from -40C to +85C; well withing my requirements.

So the question is, can I also assume the Arduino board is also limited to some range less than the microcontroller? What board factors might limit the temperature range for such a project?

Thanks


texts:
I have a total of 20 IRF3205 mosfets in a H bridge configuration for switching a transfromer to get pure sine wave output. (Five mosfets at each end of thr H bridge).

Datasheet says total gate charge of 150nC max for each mosfet. Switching frequency is 26khz max. Gate voltage is limited to 12V max because regulated 12V supply is fed to driving IC.
Driving IC is HIP4082 with peak current of 1.25A.
Gate resistors for each mosfet is around 110 ohm. Single pulldown resistor for each 5 mosfets(100k). 18V Zener diodes for protection.
Max load current is 200A. They are all mounted on seperate beefy heatsinks and I will be using heatsinks as drain terminals.

Questions

Will I be cooking those fets in transition state or will they just do okay?
Is there a better value of gate resistors and pulldown resistors for each mosfets?

Edit:
Question
*Should I even care about drive problems? Frequency is just 20-30khz.


texts: Why don't relays incorporate flyback diodes?

texts:
Warning: this may be an extremely naive question (if so, please enlighten me).

Many applications of relays require a flyback diode to protect against inductive voltage. I'm unable to find any relay that incorporates a flyback diode.

Since it's such a common need, why don't relays include a flyback diode inside the relay package? Are there just too many factors to consider, making it hard to guess the circuit's need?


texts: 2003 Chevrolet Truck Suburban 2500 4WD 6.0L FI OHV Volt Drop test on fuel pump

texts:
I performed a voltage drop test on my 2003 Suburban fuel pump and the negative side of the fuel pump returned a voltage drop of only .02 Volts using the 20 Volt setting my multimeter. That's only 20 millivolts. Is that even possible to drop so little voltage and for my fuel pump to be that efficient?
I cleaned several ground contacts after I dropped the tank and replaced the fuel pump already and the new fuel pump didn't work. That led me to learning about volt drop testing. At first I rear probed the connector on top of the fuel pump and came back with .06 on the positive side and 0.00 on the ground side. I eventually pulled out my rear probe and put it in again and the ground came back .02 after several tests which is only 20 millivolts...well under the .3 volts max droppage allowed.
I was just glad to get a reading on the negative side greater than 0.00.  I'm hoping that I have now confirmed that either my new pump is bad OR that the ground contacts I cleaned were bad contacts and now are good clean ground contacts.
Looking forward for some feedback. I LOVE This shit for the record fixing my own stuff!!! I'm a 100% Independent Life insurance broker by day and a closet mechanic at night. Thanks in advance for any and all feedback!


texts: Can I remove a GSM module from an old cell phone?

texts: I found this project that uses a GSM module (scroll down to see Picture 5). It seems the module has to be bought separately. I have old GSM cell phones lying around in the house. Shouldn't these phones contain such a chip? Is it possible to remove the chip and use it on a circuit board as shown in some of the pictures in the project?


texts: Source with variable output impedance / Fast large signal voltage variable resistor

texts:
I need a source that has an adjustable output impedance.

Corner parameters are: Voltage range: +-5V, large signal BW > 10 MHz, output impedance range at least 1k to 500M. Larger would be better.

A big plus would be if the output impedance adjustment could to be fast, in the 10ns range.

I thought about a FET as a voltage variable resistor, but a) the signal amplitude is too large and b) the larger resistances are difficult to achieve.
Programmable resistors have values not large enough and don't have enough BW. The fastest ones I've found only go up to 5 MHz.

The best I've come up with so far is to use a series of switched resistors. The downside is the large stray capacitance, which severely limits the BW in the high resistance mode.
I would prefer a source with two analog inputs, one for the amplitude and one for the impedance. The smallest possible stray capacitance at the output is important to get a large BW.

Any ideas?


texts: Metal detecting using a small inductance

texts:
I have a coil with approximate indutance of 15uH used to detect metal through changes in inductance. I want to use an op amp or 555 to oscillate with frequency based on the inductance. However this frequency needs to be ~< 10kHz to be read by a sound card.

Are there any circuits that can oscillate at these low frequencies with small inductances or is there a limitation?


texts: Designing circuit with Arduino and optocoupler: beginners problem

texts:
Firstly, I am a beginning hobbyist starting doing some electronics and this is my absolutely first attempt in trying to automate something. Here is my circuit (or what I intend):

I don't know if my circuit-design is correct or not. If not, feel free to comment on it with suggestion to make it better next time.

What I intend to do:

Let me explain my intention in my circuit. As soon as the power is switched on (the power to DC motor is already on but needs to be activated with the optocoupler-U1 in the figure), the led L2, L3, L4 in the figure (actually lasers, but should mean the same thing in this case) comes on and strikes the photo-resistors R7, R8 and R9 in the figure. Thus their resistance becomes low and the voltage across R1, R2 and R3 which goes to their respective input pins to Arduino become high. Also the motor and L1-inductor (actually solenoid valve) gets their power from 12 V supply. I have isolated two circuits because motor draws 1A current and I think this might be the best way to separate two circuits.

The motor is actually the pump which draws liquid from the tube. As soon as liquid reaches certain level, L2 light emission is blocked by liquid and R1 goes low. When that happens, the output from Arduino (denoted by line crossed with slanting orange line) is set high which equalizes the voltage across R4 to be zero and the motor is then stopped for remainder of time. Now the liquid starts moving downwards again since the pump is off. As soon as it gets below L3, timer kicks in Arduino and starts recording time which eventually stops when the liquid level gets below L4.

The pump firstly draws the liquid up crossing all L2, L3 and L4.

My problem:

Actually, nothing serious. However since I am just starting doing stuff like this, I would like to be sure before attaching the circuit and make sure that my Arduino does not get fried. I am thinking about common ground between Arduino, the LED and photo-resistor circuit plus the circuit of motor with 1A current. Does common ground pose some problem in my case? Is something wrong in my circuit that needs to be rectified.

I have not given the values for the resistance because I can do the math but I want to check the accuracy of my circuit.


texts:
I have built very basic non-inverting op amp circuit and for some reason it outputs just 4V DC line instead of amplified sine wave. It happens only on breadboard, simulation works ok. I'm pretty sure everything is connected in a right way.
I tried to replace the chip, but its the same for every chip. What's wrong?


texts:
Does anyone know if its possible to wire up a MOSFET transistor as a zener diode? I have been happily making normal diodes from my MOSFETs by shorting the gate and the source

simulate this circuit – Schematic created using CircuitLab

But now I need a zener diode for a voltage regulator an am struggling to come up with anything! Any ideas would be great...


texts:
On freshly installed LTspice on MacOS I have no libraries. In "Top directory is only /, but there is no way to edit this path, also in settings there is no tab described here:

How to change the top directory in LTspice?

Updated settings screens:

maybe, there will be a way to edit configuration file manually, bu I don't know the key:

$ plutil -p Library/Preferences/LTC.LTspice.plist
{
  "AllowShortedCompPins" => 0
  "AutoDotRawDeletion" => 1
  "DampInductors" => 1
  "GridColor" => 9868950
  "InActiveAxisColor" => 9868950
  "NetlistEditorColor0" => 0
  "NetlistEditorColor1" => 32512
  "NetlistEditorColor2" => 16711680
  "NetlistEditorColor3" => 155
  "NetlistEditorColor4" => 16777215
  "NoJFETtempAdjIsr" => 0
  "NSNavLastRootDirectory" => "~/Documents"
  "NSNavPanelExpandedSizeForOpenMode" => "{712, 448}"
  "PlotLineThickness" => 1
  "PrintListing" => 0
  "RadianMeasure" => 0
  "RandomizeSeed" => 0
  "ReverseMouseWheelScroll" => 0
  "RoboMouse" => 1
  "SaveDeviceCurrents" => 1
  "SaveOneCurrentPerDevice" => 0
  "SaveSubcircuitDeviceCurrents" => 0
  "SaveSubcircuitNodeVoltages" => 0
  "SchematicColor0" => 16711680
  "SchematicColor1" => 16711680
  "SchematicColor2" => 16711680
  "SchematicColor3" => 16711680
  "SchematicColor4" => 12648447
  "SchematicColor5" => 0
  "SchematicColor6" => 0
  "SchematicColor7" => 0
  "SchematicColor8" => 13107200
  "SchematicColor9" => 16711680
  "SchematicColor10" => 65535
  "SchematicColor11" => 0
  "SchematicColor12" => 12632256
  "SchPenWidth" => 1
  "Solver" => 0
  "TSKtrtol" => 2
  "WaveColor0" => 0
  "WaveColor1" => 11513775
  "WaveColor2" => 65280
  "WaveColor3" => 16711680
  "WaveColor4" => 255
  "WaveColor5" => 11513600
  "WaveColor6" => 16711935
  "WaveColor7" => 8421504
  "WaveColor8" => 32768
  "WaveColor9" => 11468800
  "WaveColor10" => 32943
  "WaveColor11" => 8388736
  "WaveColor12" => 128
  "WaveColor13" => 44975
}


texts:
As a follow-up to my previous question, where I seek to determine the amplitude of a 2 MHz sine wave, I've settled for an op amp based solution. To recall, my input has a maximum 240 mV amplitude -- in fact I'd like to go lower than this, so long as output accuracy is not significantly affected. Having relaxed my accuracy requirements for the circuit (I'm willing to accept 5% error on the amplitude/RMS value of the sine wave), I've found a cheaper op amp, namely the MAX4453. The main specs of interest are: 200 MHz bandwidth, 95 V/µs slew rate, 400 µV typical input offset and 800 nA typical input bias current. Maxim provides a SPICE model for this op amp.

In principle, after rectifying the wave, I could low-pass filter the output and read the DC value \$V_{DC}\$, which would be related to the peak value \$V_{pk}\$ by \$V_{DC} = V_{pk}/\pi\$ for a half-wave rectifier, and \$V_{DC} = 2 V_{pk}/\pi\$ for a full-wave rectifier. Hence I simulated the following circuit (the same mentioned in my previous question):

I determined that there is some distortion in the output wave, especially near the zero-crossings, where \$A_1\$ switches between open and closed loop, as shown in the following simulation:

Obviously, such distortion would introduce uncertainty in the value of \$V_{DC}\$ and hence reduce the accuracy to which \$V_{pk}\$ can be determined.

Hence I decided a peak detector might be a more appropriate solution. Adding a 1 µF capacitor to the output of the rectifier above, I get the following simulation result:

Zooming in after the capacitor has settled:

The average value of the output is ~215 mV vs. a 240 mV input, so around 10% error and hence outside my specs. Apparently the op amp output current limit prevents the 1 µF capacitor from charging quickly enough. The obvious solution would be to reduce the capacitance; unfortunately, the high output impedance of \$A_2\$ (due to \$R_2\$) translates into excessive droop in the capacitor.

I've tried a few alternative circuits, with similar results. In particular, the following very simple half-wave rectifier circuit appears to work just as well as the circuit above:

simulate this circuit – Schematic created using CircuitLab

The lower output impedance of the op amp in this circuit means that droop is acceptable with a 1 nF capacitor. Here is the simulation result:

Zooming in after the capacitor has settled:

It is clear there is no improvement (although of course the circuit is simpler and cheaper).

My questions: are there alternative circuit topologies I should try, which would get the output closer to the peak value of the input? Should I look for another op amp? Which specific characteristics of the op amp should I seek to improve?


texts: Can I determine the original resistance of a burnt/failed resistor?

texts: How to find the (original) value of a burnt resistor? Let's suppose a condition in which initially I don't know the value of its resistance. Now because of its low watt, it burnt. So is there any method to find out the resistance?


texts: Is it wise to use an Arduino to power a crystal oscillator?

texts:
I'm building a small VGM audio player.

I currently have a SN76489 (here) that is clocked from a 3.579 crystal oscillator.

When I first power on the circuit, the SN76489 can have any random value which causes a really annoying tone/buzz until the Arduino Micro (here) powers up and starts running my code.

I know some of that is the bootloader in the Micro and when I put a permanent microcontroller in some of that may go away.  But I still want the SN76489 to be immediately silent at power-on.

So I thought I would connect an output pin on the Arduino as the VCC for the crystal.

Works great.

BTW, even tying the SN76489 CE to HIGH at startup and switching it to GND doesn't work.  Whatever was left on the chip is what plays.

Anyway, before I did that I measured the current for both the oscillator and the SN76489 to see which draws the lesser amount.  The Arduino says it can provide 40mA per output pin.  For the SN76489 my multimeter said 1.2mA and the oscillator said 0.72mA.

Now even though the Arduino is providing VCC to the oscillator, the multimeter is now displaying 1.87mA.

Why would it now draw more current when connected to the 5v OUT of the Arduino?

And, does this seem like a smart way to do this or is it not wise to power small devices like this?

Thanks!


texts: Why do some DC-powered LED circuits flicker?

texts:
Flickering LEDs are everywhere. I can think of a number of reasons why an LED might flicker:

Supplied from an AC outlet (traffic lights in ex-USSR)
Addressed one chunk at a time (most multi-position 7-segment displays, for example)
Fading (dimming)

But some occurrences have me stumped. In particular, the LED-based stop lights on some cars. I can see no reason for these to flicker: they are supplied with DC, and they are either entirely ON or entirely OFF, so no addressing issues and no dimming. And yet they flicker.

Is there some reason why someone would intentionally make LEDs flicker in such circumstances? Perhaps one can get more light per watt out of them this way or something like that?


texts: Why does this DC connector have holes at the ends of the  pins?


texts: VNA reflection and transmission of stripline stub

texts:
Testing this stub board.
I understand S12 is attenuated at 1.79GHz due L=λ/4.
So I calculate relative permitivity:

εr = (c / 4Lf)2 = 3.3

But what does (εr) represent in a physics perspective? Is it permitivity of the board dielectric? If so how does the signal interact with the ground plane in this stub?

Second: What is the cause of the reduced S11 reflection at 3.09GHz?


texts:
I'm using a 555 to create a throbbing effect on a LED, like in this project.

Is there a simple way to delay the signal for a second (then third, then forth...) LED to have them fade in and out at different times?

EDIT: I appreciate the workaround suggestions, but I'm really interested in the original question:

Is there a simple way to delay or phase shift the signal?

Even "it's not possible" or "it's very complicated" are good answers.


texts: How to use two timers for one interrupt vector on avr?

texts:
I want to use timer1 and timer2 for same vector TIMER#_COMPA_vect isr on atmega328p.
Idea is to start and stop one when requested, for time sensitive functions. And to keep another running always for clock time keeping.

When initializing both timers, they don't work. Whereas they do when initializing separately.

Timer2

void timer2CtcInit(void){

  //Timer 2 interrupt service routine CTC settings, 1 uS:
  TCCR2A = 0;
  TCCR2B = 0;
  //set CTC mode
  TCCR2A |= (1 << WGM21);
  //prescaler 1 for timer2
  TCCR2B |= (1 << CS20);

  // value for 1 usec
  OCR2A = 15;

  //set compare match for register OCRA
  TIMSK2 |= ( 1 << OCIE2A);
}

Timer1

void timer1CtcInit(void){
//timer1 for 100 ms
  cli();
  TCCR1B = 0;
  TCCR1A = 0;

  //set CTC mode
  TCCR1B |= (1 << WGM12);
  // enable compare match interrupt
  TIMSK1 |= (1 << OCIE1A);

  sei();

  // set OCR0A value for 100 msec
  OCR1A = 0x0619;
  //set 1024 prescaler
  TCCR1B |= (( 1 << CS10) | (1 << CS12));
}

Followed by two ISRs

ISR (TIMER1_COMPA_vect){
tmr1Count++;
}

and

ISR (TIMER2_COMPA_vect){
    if(timerFlag)
      tmr2Count++;
}

All this does not work together.

Edit

I guess OP is somewhat misleading of my aim.
I want to use two timers for different time interrupts. One for keeping clock time on LCD and other for giving pulses at certain times. For some reason Timers don't work as expected when initializing both - Timer2 gets higher priority and Timer1 is not working.
Timers are tested on LCD display, Timer2 for seconds and Timer1 minutes.

How to set two timers running simultaneously ?


texts: What register or setting can control the brightness of an ST7735 based 1.8" TFT Display?

texts:
I'm using a KMR-1.8" display which uses a ST7735  driver and it is working ok with the Adafruit_ST7735 library.  The problem is the display is very dim once the library has initialized.

If I reset the board, the last display buffer is still visible and gets about 3 times brighter until the driver initializes the ST7735 again.  If I hold the reset down, the last display in the buffer remains on the screen 3 times brighter for as long as I hold down the button.

The LED brightness pin is tied directly to the 3.3v output of a voltage regulator.

My conclusion is that there must be something the driver sets that effects the brightness.  I don't see anything that looks like a brightness setting in the spec. sheet or in the driver source code.

Update:  I've systematically disabled all of the driver settings except the
bare minimum and haven't been able to get the display to brighten up.  I've even added commands to adjust the Gamma curve and it had minimal affect.

I've also breadboarded the display using a test rig and the display actually
worked without issue on the breadboard, maintaining it brightness.  This used
the exact same register settings as the PCB version which dims.


texts: Is it wrong to assume the op-amp has the same voltage at its both terminals when deriving its non-inverting closed-loop gain?

texts: I am referring to the approach taken in this video, at about 00:43. I know that the op-amp "tries" to balance the voltages at its both terminals but is it a completely correct approach to take V+ = V- when deriving the op-amp's closed-loop gain? As far as I know, in practice, V+ is never equal to V-. But from a theoretical point of view, would it always be correct to assume V+ = V- when calculating the op-amp's closed-loop gain?


texts:
In norton equivalent theorem I don't get how I = in (I can be equivalent to in)
Also I don't get how iN can be 2A
How can I get iN?

""edit:**
Then how come this In is 1A? What is the difference between question 2?


texts:
I'm designing simple ALU for my own that use 2 bits for select operations. Suppose that, my operations is as follows:

00 C <= A & B
01 C <= A + B
10 C <= NOT (A)
11 C <= '0' & A (7 DOWNTO 1)

And my ALU contains two register for input with load enable LE and one output register with load enable LE and output control OC. Firstly, I design a input register using VHDL Module as below:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity RegIn is
    PORT (
        LE: IN STD_LOGIC;
        INPUT: IN STD_LOGIC_VECTOR (7 DOWNTO 0);
        OUTPUT: OUT STD_LOGIC_VECTOR (7 DOWNTO 0)
    );
end RegIn;

architecture Behavioral of RegIn is
begin
    PROCESS (LE)
    BEGIN
        IF (LE = '1') THEN
            OUTPUT <= INPUT;
        END IF;
    END PROCESS;
end Behavioral;

When, LE is high, INPUT will be place instead of OUTPUT value. I have two input register name TEMP1 and TEMP2. I design output register using input register except it contains OC signal as buffer control. It shows in continue:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity RegOut is
    PORT (
        LE, OC: IN STD_LOGIC;
        INPUT: IN STD_LOGIC_VECTOR (7 DOWNTO 0);
        OUTPUT: OUT STD_LOGIC_VECTOR (7 DOWNTO 0)
    );
end RegOut;

architecture Behavioral of RegOut is
    SIGNAL INPUT_OUTPUT: STD_LOGIC_VECTOR (7 DOWNTO 0);

    COMPONENT RegIn
        PORT (
            INPUT: IN STD_LOGIC_VECTOR (7 DOWNTO 0);
            OUTPUT: OUT STD_LOGIC_VECTOR (7 DOWNTO 0);
            LE: IN STD_LOGIC
        );
    END COMPONENT;
begin
    RPM:
        RegIn PORT MAP (
            INPUT => INPUT,
            OUTPUT => INPUT_OUTPUT,
            LE => LE
        );

    PROCESS (OC)
    BEGIN
        IF (OC = '1') THEN
            OUTPUT <= INPUT_OUTPUT;
        ELSE
            OUTPUT <= "ZZZZZZZZ";
        END IF;
    END PROCESS;

end Behavioral;

Now, I want to implement my ALU using code such below:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity ALU is
    Port (
        TEMP_1_LE: IN STD_LOGIC;
        TEMP_2_LE: IN STD_LOGIC;
        TEMP_3_LE: IN STD_LOGIC;
        TEMP_3_OC: IN STD_LOGIC;

        TEMP_1_IN: IN STD_LOGIC_VECTOR (7 DOWNTO 0);
        TEMP_2_IN: IN STD_LOGIC_VECTOR (7 DOWNTO 0);

        C: IN STD_LOGIC_VECTOR (1 DOWNTO 0);

        CF: OUT STD_LOGIC;
        ZF: OUT STD_LOGIC;
        SF: OUT STD_LOGIC;

        TEMP_3_OUT: OUT STD_LOGIC_VECTOR (7 DOWNTO 0)
    );
end ALU;

architecture Behavioral of ALU is
    COMPONENT RegIn IS
        PORT (
            LE: IN STD_LOGIC;
            INPUT: IN STD_LOGIC_VECTOR (7 DOWNTO 0);
            OUTPUT: OUT STD_LOGIC_VECTOR (7 DOWNTO 0)
        );
    END COMPONENT;

    COMPONENT RegOut IS
        PORT (
            LE, OC: IN STD_LOGIC;
            INPUT: IN STD_LOGIC_VECTOR (7 DOWNTO 0);
            OUTPUT: OUT STD_LOGIC_VECTOR (7 DOWNTO 0)
        );
    END COMPONENT;

    SIGNAL TEMP_1_OUT, TEMP_2_OUT, TEMP_3_IN: STD_LOGIC_VECTOR (7 DOWNTO 0);
    SIGNAL TEMP: STD_LOGIC_VECTOR (8 DOWNTO 0);
begin
    RTEMP1:
        RegIn PORT MAP (
            LE => TEMP_1_LE,
            INPUT => TEMP_1_IN,
            OUTPUT => TEMP_1_OUT
        );

    RTEMP2:
        RegIn PORT MAP (
            LE => TEMP_2_LE,
            INPUT => TEMP_2_IN,
            OUTPUT => TEMP_2_OUT
        );

    RTEMP3:
        RegOut PORT MAP (
            LE => TEMP_3_LE,
            OC => TEMP_3_OC,
            INPUT => TEMP_3_IN,
            OUTPUT => TEMP_3_OUT
        );

        PROCESS(TEMP_3_OC)
        BEGIN
                IF (TEMP_3_OC = '1') THEN
                    TEMP_3_IN <= TEMP_1_OUT + TEMP_2_OUT;
                ...
                END IF;
        END PROCESS;

end Behavioral;

In my test bench, I force TEMP_3_OC to '1' but it does not change to '1' and still is '0'.

What was wrong? How can I correct it ?

Thanks in advance :)


texts: Current through a diode paralleled with a resistor

texts:
I'm confused on a homework question in my intro to electrical systems class. I have a simple dc circuit with a voltage source of 4.7 volts in series with a 40 ohm resistor, that then connects to a 50 ohm resistor paralleled with a diode in series with a 20 ohm resistor that then connects back to the negative terminal of the voltage source. The problem is that I've calculated the current through the first resistor as 117.5 mA, and I'm trying to find the current through the diode, which after getting the question wrong the homework program tells me the answer is 45.3 mA. Yet that would mean the 50 ohm resistor has 72.2 mA flowing across, which is greater than the current flowing across the 20 ohm resistor.

Why is it that a paralleled resistor does not have more current flowing across the path with less resistance?

what affect does the diode have on current?

assuming the diode is ideal and has voltage drop of .6 V


texts: How to Use a 2.4GHz Chip Antenna for ESP32 Design

texts:
I am designing a circuit board that will use a 2.4GHz SMD chip antenna from Molex. I am a n00b/amateur at PCB design so forgive my ignorance - does it work nearly the same as how a PCB antenna works?
I have spent quite a while trying to dig through the datasheet for the Molex SMD 47948 chip antenna (details here) but I cannot make much sense of how to use it.
Is this the correct way to use it? I've used PCB trace antennas in the past and they work perfectly. However, with PCB antennas, usually they have two connections, signal and GND as two inputs going into the antenna trace. But with this chip antenna it only seems to have a single input? Do I also need to connect the trace going into the antenna to ground as well?


texts: LED's for a project won't work in parallel

texts:
I am currently working on a model kit and am wiring up all the LED lighting in parallel and have run into a problem. When using blue or white LED's they work fine in parallel and then when I add a red,green, or yellow LED only the red,yellow, or green will light up even though they appear to be the correct polarity.

I don't believe this to be an issue with current as multiple white and blue can be in parallel while it only takes one red to turn the others off.

Power source is a 3V battery cell.


texts: What sort of oscillator topology is used in WiFi/BT transmitters?

texts:
Thinking of cheap(er) consumer wireless products. Modulator aside, how is the RF carrier signal generated?
Do they use really small capacitances/inductances on a chip die to make an RLC (say, Colpitts-like) oscillator? Phase shift? Do they use a DAC/R-network to synthetize the signal (with potentially added harmonics)? Or do they do it some other way?
Thanks!


texts: Turning led strip on with car battery power

texts:
I'm trying to find a good and cheap way to turn on some led strips with car battery without burning or stressing the leds. I've found out it can be done with a resistor but it's not the best way to do it, since it will get dimmer/brighter depending on the voltage of battery at the time. Also found out it can be done with constant-current led drivers (made with lm317), but the problem is that these regulators have a voltage drop (3v for lm317 I think). So the output voltage will be less than 12v. Will the leds turn on with less than 12v? (It will be around 9v if i'm not wrong.) If not what should I do?
Also this is the driver i'm talking about:

I think I'm getting lost  ._.


texts: analog shut down whilst turning on an LED

texts:
I am a EE student from Denmark, in the middle of making a class D audio amplifier.
In this matter, I have stumpled across a needed circuitry. I need a way to shut off my gate driver (essentially the output stage). The gate drivers I use have an active high disable pin. I will be running the logic on 5V.

In this sense, I for startes need to be able to use a switch turning off the gate-driver using the disable pin, whilst it turns on an LED.

The picture above shows my temporary try. I use an opamp, because I will eventually implement OT protection etc. Thus starting out with an op-amp, makes that addition easy.

Here I thought I would be able to feed the disable labelled wire to the disable pin, whilst it turns on the LED.
However whilst simulating, I cannot get it to work properly. I cannot draw more than approximately 2 mA in the LED.

Do you guys have any suggestions, if so I am welcoming them gratefully.

It should be noted, that the opamp is a rail-to-rail output THS4222, and it is supplied with 5V.

Thanks in advance.

Jacob


texts:
I'm using TI DRV595 power driver in an application requiring several amperes of current. My observation using thermal camera has been that at 3.5 A the driver IC core reaches temperatures around 90 degC. The circuit is rated +/- 4A and has an over-temperature trip point around 150 degC.
In my application the PCB is at around 40 degC of ambient temperature and is ventilated by a fan.

My questions are:

Ballpark, How hot can driver ICs get without severely reducing their working life?
Assuming no physical contact against other surfaces - are there any safety issues in regard to end user with having circuits running at around 100degC in non-sealed devices?

Assumption: The temperature of the driver does not affect any surrounding components or function of the device.


texts: Control magnet through stainless steel wall

texts:
I'm a mechanical engineer enthusiastic about learning electrical engineering and I speak french so I thank you in advance for your comprehension and your help.

I would like to be able to activate an electromagnet to pull a pop-up switch throught a thin stainless steel wall (1 mm or 1/32 inch). I'm using an arduino but I guess an external power source will be necessary.

The magnet need to pull a spring to drain a liquid from a tank.

I know thant it would be easier to use a solenoid valve but I can't change the piping.

I was thinking of a u-shaped metal rod wire copper wiring and a relay but I guess that would need a lot of power. Which way would you recommend to achieve this goal?

Once again thank you for helping a mechanical engineer to convert to the electric engineering!

EDIT:

First of all, wow thank you for all theses excellents answers!

Is there any way for me to give you a positive feedback?

Secondly, the tank is non-magnetic but that is an excellent comment and I will need to be careful.

I think a lot of small magnets would do a pretty good job. This is so simple that I did not think about it.

I will try that and will update my post once I succeed!


texts: Does anyone know the names of these two components labeled 50 Hz and 60 Hz, so I can find them in proteus program?


texts: I'm buying my first PIC, what kit do I need?

texts:
So I'm probably going to buy a dsPIC33F to build a synth with.

I've used Atmel micros in the past, but this will be my first PIC chip, I wanted to know if there's anything in particular I need or will have to look out for?

I'll need to be able to program the chip using my laptop which has USB and is running a Linux based operating system (Ubuntu).

Thanks.

Edit: (To clarify my question)-

I will be using the dsPIC33F from Microchip Technology Inc
I want to use it for real time audio synthesis, probably additive synthesis using wave table generated sine waves, much like the application discussed in this question on the electronics.stckexchange. I have a crummy old Dell laptop with which to program the dsPIC33F chip with, it has USB 2.0 ports on it, and that's about it. I run a Linux system (Ubuntu 10.10 Maverick Meerkat to be specific), what software / hardware will I require to program the dsPIC33F chip using the afore mentioned computer system??


texts: Developing hardware in FPGA with LED Driver Chip

texts:
I asked related TI TLC5944 LED Driver questions here, here and here

Actually initially I was supposed to simulate the following design. I had to simulate the driver functionality also (as the driver chip was not available to us).

But now my mentor is asking me  not to bother about the simulation of the driver, as he will be getting the driver very soon.  So now my task is to write Verilog code (for lighting a row of a LED matrix) which will run on a lattice board. I can not test my code  as I do not have the real chip with me as of now. But I have to write the code assuming I have the driver chip.

I have already read the specification of this driver and have understood it. I have understood how the signals are coming , and what signals are required to lit a particular LED row. The problem is I have never used any external chip along with an FPGA. And so I am not feeling comfortable with this project.  In past I have done some small projects such as converting a 24 bit BMP image to 1 bit image, designing counters, arbiter, image compression etc. In none of these I had to communicate with any external chip.

How do I start working for my current design which is having external chip i.e driver?
What is the basic idea involved?

Update

Just to clarify more: My problem is NOT that I have to write the code without actually having the driver chip, rather it is that how do I write code when the FPGA will be communicating with the external driver. I have never written code in FPGA that interacts with an external chip.


texts: Simple counter circuit resets at the wrong value

texts:
I wanted to create a circuit that would count from 2 to 12.

In order to do so, I created a simple synchronous counter that resets itself when I have logic Highs at the third, second, and zero flip-flops. So that means that it will reset when I try to reach number thirteen. However, it resets when I try to go from seven to eight.

I suspect it has to do with the delay time of elements. I doubt that it's due to the flip-flops, because it's a synchronous counter so the delay due to the flip-flops is the same for every step. So it has to be due to the logic AND gates, but I can't figure it out. This is the schematic:

Any help appreciated!


texts: How to determine the right spec of a servo motor given an inertia moment?

texts:
I'm working on a trash bin which lid is controlled (opened/closed) by a microcontroller and thus i decided to use a servo motor.

The lid is 47 x 47 x 0.1 cm and because its made from steel has a density of 7.874 g/cm^3. Assuming uniformity, this means that this lid has an inertia moment of 0.096057 kg.m^2 with the axis being on the bottom-middle of the lid. I want the servo to be able to open the lid 60 degree in 2 seconds for convenience reasons.

When choosing from a variety of servo motors, i noticed that they write torque not in Nm but in Kg/cm which makes no sense to me.  I just gave it a shot and use a 17 kg/cm servo and placed it in the middle of the lid but apparently its not strong enough. So how to properly calculate the right spec of a servo motor given this application ? Thank you so much beforehand i'm still new to this


texts: Power recirculation rig using rectifiers and BLDC motors

texts:
I am currently trying to set up a rig to test my 3d printed gears under different torques and motor speeds. The power input side is going to be the BLDC motor, driven by a hobby ESC (BLHeli_32), powered by a generic AC to 12V PSU. On the braking side of the gears I am reluctant to wiring up a 3 PWM-controlled resistors across the "braking motor" as it would be very wasteful of energy and produce heat, as I intended to run the motor at around 100W for many hours or days.

I am instead considering using a full wave three-phase bridge rectifier and connect the DC outputs back into the DC-in circuit (still with PWM MOSFETs to control torque). What starts confusing me is that, under the assumption of ideal, identical, lossless motors, the output voltage would be sqrt(3)*V_in (minus diode losses). Something feels confusing about it as the voltage would exceed supply voltage, and I can't figure how the system would reach equilibrium. Is this system possible? Would I need to use significantly lower kV motor on the output side? Would I need to put a diode or flyback diode to protect the PSU against backflow of electricity when the input motor throttles down?

I've schemed loosely what I think purely-electrically this circuit should look (bar the PWM on output), but may have made mistakes as I have very little electronics knowledge (aerospace engineer).

simulate this circuit – Schematic created using CircuitLab


texts:
I'm looking for a way to control a VGA screen with a PIC. External components are OK, so a VGA chip with I2C or SPI or something is okay too.

Requirements:

Resolution: max 1024x768, no minimum
Language: C (C18 compiler) or Jalv2
Only text, no graphics necessary (but it would be okay if it had that too)
One colour is enough, so DA converting is out of the scope of this question

In my project I have a text buffer which I want to have on a screen. You can compare it to using an LCD display for text displaying, but now with VGA.


texts: Designing a board for NXT/EV3 with MANY ports

texts:
I'd like to design a board for Lego Mindstorms NXT/EV3 that has many I/O ports.

The board, like the original "smart" bricks, would have 2 kind of ports:

sensor ports (two modes: analog, and I2C)
motor ports

However, unlike the original "smart" bricks, which are quite limited, it would have at least 8 motor ports and 8 sensor ports.

I'm asking help to find a suitable board, or a suitable design for this large number of sensors/motors.

Each sensor port requires an ADC (for sensors operating in analog mode, like temperature and touch sensors), and requires two digital I/O ports for the I2C protocol (SCL, SDA).

So, the sensor ports put a requirement of at least 16 I/O ports, and 8 ADCs.

Each motor port requires two PWM lines thru a motor driver like L293D, and two digital inputs for reading the quadrature encoder output, with programmable interrupts.

So, for at least 8 motors, there is a need for another 16 PWM ports, and 16 I/O ports with programmable interrupts.

In total: 48 I/O ports (16 output ports with PWM, 32 input/output ports with programmable interrupts), 8 ADCs.

Now this requirement is a bit beyond the specs of popular amateur boards like Arduino, Galileo, etc...

How would you recommend to design this solution?
Are there boards with this number of ports at a reasonable cost?

Would be more cost effective to attach further ICs to one of such boards? In detail:

a PWM driver like the TLC5940 would satisfy the PWM requirements (and it is daisy-chainable, in case one would like to double the number of motors)
external ADC, or perhaps simple analog multiplexer ICs can satisfy the requirement of ADC ports

However, the number of IO ports with interrupts is quite high... I'm not sure if each port needs dedicated ports with programmable interrupts. Maybe there exist a solution to shrink this number of ports to a minimum, by using some kind of multiplexer or other trick..?

Could you comment on this project? Which board would you choose? How would you design it? Which ICs would you add?

I said 8 motor ports and 8 sensor ports, but the more the merrier :)


texts:
I'm reading Advanced FPGA Design and the first example, one of simply raising a number to the 3rd power, quickly diverges into various quite clever optimizations to make the valuation faster.

Now, personally, I'd argue that such minutae is best left to the computer, so my question is this: is supercompilation (synthetically combining program elements until an optimal algorithm is found) used when appled to HDL?

TBH, I always assumed that that's exactly what synthesis is: taking HDL code and making sure it runs in optimal time. But the book hints at that not being the case, and altering code to shorten the evaluation path actually makes a difference.


texts: Capacitor not reaching supply voltage with LED in series

texts:
Totally new to electronics here.

Without the red LED "charging indicator", the capacitor charges fully to 10V, but with the diode the capacitor maxes out at about 8.42V.

I don't understand why the LED causes the capacitor to not fully charge.

Running two LEDs in series drops the voltage across the capacitor down to 6.7V or so.

simulate this circuit – Schematic created using CircuitLab

Thanks


texts:
I have substantial experience programming computers, but never programmed micro controllers or built digital equipment. The closest I ever came was controlling modems by reading & writing "registers" from interrupt handlers.

And now I'd like to build and program something physical, just as a hobby. I didn't decide on the scope of the project yet, but I'd like to be able to do more than LED flickering, maybe a toy car that would sense an object and change a direction, something like that, with both handling physical inputs and making mechanical motions.

So I'm looking for a starter kit that would be easy enough for a novice to begin and extendable enough to do more advanced things later. Googling things and asking around yielded Arduino, Raspberry Pi, Parallax, and Lego robotics kits. I'd like to get an advice which kits would be preferable for an experienced computer programmer but a complete novice in electronics to start with.

Also, I presume for most projects one would need a wide variety of electronic components beyond the micro controller and the board. I'd like a suggestions which kits would be best to start with.

One more thing: I'd prefer to connect components by plugging them into something like a breadboard rather than soldering, even for the completed project.

Thanks for the advice.


texts: Powered riser safety for dual PSU, GPU system

texts:
I am very much a novice w/ electronics. I'm trying to evaluate these risers for use in a system where I need to add additional GPUs and a 2nd PSU (the first PSU is 1600W and maxed out w/ 4 GPUs, the CPU, etc.). I'm not using the system for mining and need as much PCIe bandwidth as I can get, which rules out the low cost, x16 to x1 risers which allow for power isolation. There are eGPU risers which go from x16 to x4 which I suppose I could settle for if this riser is risky.

Is it correct to say this riser would feed 12V from the new PSU over the molex/peripheral connector, cutting off the 12V which would have come from the original PSU over the PCIe slot? Or is it just meant for additional power?

Is the capacitor meant to filter the 12V coming from the 2nd PSU? Or is it meant to bridge some presence detect pins?

Is this a reasonably safe way to do this, assuming a good job was done fabricating/soldering everything together?

The PCIe slot still provides 3.3V at up to 3A, which is passed through by this riser. Why is this not an issue in terms of the 2 PSUs? Is it because there is typically some kind of isolation on a graphics card between the 12V and 3.3V lines/circuits? If so, how can one know in advance whether a particular card does this without having to physically try it?

There is also these powered risers, which mention they 'add additional power' but seem to have additional circuitry beyond the ones I linked above. Are these a better alternative for power isolation between the 2 PSUs?

EDIT:

The question I asked is a bit too specific to these non-standard products so let me clarify (w/ another non-standard product ;)).

Let's say I have a PCB w/ a PCIe x16 slot and a circuit as shown below. I found the schematic here. It looks like it's taking in 12V from an 8-pin PCIe connector (JP1), feeding it through a power MOSFET (Q1) and then feeding it to the card (+12vPCIE). It also uses a DC-DC converter (U1; part # TPS564201DDCT) to generate 3.3V for the card as well.

There are 4 individual connectors, each of which would connect to an LVDS cable providing 4 PCIe lanes. These cables would connect to some separate PCB which would plug into a PCIe slot on the system. One of the cables seems to provide 3.3V from the motherboard (+3.3v_Host).

My question is does this circuit seem sound? Is there anything glaring/obvious to change? From my perspective:

There's a fuse
The power MOSFETs (datasheet) continuous drain current @ 70C is shown as -16A. Is this the right field to look at for knowing how much current this MOSFET can handle?
The 8-pin PCIe connector is rated up to 150W (3 12V lines each capable of ~4A) which should be enough since the 12V rail on PCIe slots only draws up to ~5.5A/66W (+ 3A @ 3.3V) or a total of ~75W
The 3.3V from the host doesn't seem to really provide any real current and as I understand it just turns on/off BJTs? (does this mean its 'power isolated'?)

If it's sound and I can find the corresponding cables and associated adapter I'm wondering if it would be a good idea to have this fabricated.

Thanks for any help/suggestions


texts: I'm working with Proteus and I'll be needing an IC which has packaging TO-99. This package is not available in ARES. I don't quite understand the data sheet of this package to make it, though I saw a few tutorials on Youtube. How to make out which type of hole is there and all. i.e, which one needs a pad and which doesn't. I'm not able to visualize it and that is what is creating the problem. Can someone throw some Light on this?


texts: PC ATX12VO (12V only) standard - Why does everybody say it has higher efficiency?

texts:
To my understandings, the new 12-volt only standard moves the 5V and 3.3V supplies off from the ATX power supply "box" to the motherboard.
According to PC World (which is cited by Wikipedia), Gamers Nexus, and Linus Tech Tips, the new standard "improves efficiency" by not generating the 5V and 3.3V rails.
Why?

Modern PC parts still need those rails, for example, SSDs usually use 1.5V 3.3V for main operation.
We use 5V in USB devices to charge up cellphones and power personal beverage coolers.
So the need is not going away (any time soon) just because Intel has published a new standard.
Buck converters are cheap. Buck converter controller chips are tiny.
Why not throwing a few more components into the ATX power supply "box" and down-convert from the high-demand 12V rails?
The new standard calls for the conversion to happen on the motherboard. Isn't it just the same?
Linear regulators commonly found on cheap adapters like M.2 to SATA generates 3.3V rails by consuming all the power from the rest of 8.7V as a space heater.
Aren't these more problematic and should be eliminated first?
I understand a part of their claims is that traditionally all rails are directly converted from the main line (110V or 220V).
But you can easily design a multi-stage converter using the main just once.

To summarize: We still need the 5V and 3.3V rails. We do it either in the power supply "box" or on the motherboard. We can use buck converters instead of linear regulators anywhere anytime. Why does moving the 5V and 3.3V rails to a different place -- still doing the same thing -- improve efficiency?


texts: Active power output calculation of hf generator unit based on measured volt acorss a load

texts:
I have an electrosurgical hf generator unit that produces a modulated signal with duty cycle in blend mode. I have the output of this unit connected across a load. With scope connected across the load, I measure peak-peak volt of a signal with a duty cycle in a pulse.  The waveform looks like as shown. It has hf sinusoidal oscillation in active part.

I want to calculate active power delivered by the unit. What would be the correct way of calculating the active power output? How to calculate RMS volt from Vp-p?


texts: How to increase the gain of Operational transconductance amplifier by changing the sizes of transistors.

texts:
Here is the schematics of the OTA.

By changing the length of the transistors I am having more gain but I cannot reach the gain of 200. The maximum gain I reach is 110.35. I want to reach the gain of 200 only by changing the sizes of the transistors.


texts:
I'm building a power converter that will take 20 VDC input. I have a cable with a 1.7 x 4.0 mm plug, so I'm trying to find a suitable panel mount jack.

Online, I've found this model.
On the Philmore Web site, the specs say this jack is rated at 6.3 VDC.

How much of a chance would I be taking by using this underspec'ed jack? I haven't found another suitable model.


texts: How to prototype current sense circuit on bread board?

texts: Connectors on a breadboard have some resistance, when prototyping a current sense circuit with a 0.01 ohm resistor can the connectors resistance affect the circuit? and if yes how can we prototype sensitive circuit like this?


texts: What do I need to do to use a R3 Ethernet shield with a R3 Arduino Mega 2560?

texts:
I want to use my newly bought Ethernet shield without making any hardware changes, buying anything, and (preferably) add no extra jumper wires. However, it doesn't connect to pins 50, 51, and 52 on the Mega like it says it uses here. Pin 53 has to be kept a output.

I have already looked at this page from this question, but Arduino claims Rev 3 is Mega Compatible. I doubt I would have to modify the board to get this to work. However, the new board has a header to connect to the ICSP that the old one doesn't. Does the ICSP header connect to those pins?

So what I'm assuming:

I don't have to modify any hardware
I can use all the pins except:

a.) The enable/disable pins (4 and 10 which I write one HIGH when I want to use it and make sure the other one is LOW).

b.) 51, 52, and 53

c.) 53 I can only use as an output, but I can still use it for anything that needs a output.


texts:
I have a question regarding DC motor.
I was just curious to read on what factors does the motor RPM depend upon. I read that the rated voltage is the parameter that defines the speed of the motor.
But isn't current a defining factor?
I have 2 related questions:

I understand that since motor is just a bunch of coils (low resistance), the current through it would be more as the coils are low resistance. Am I correct? Is there any way to calculate the current through the motor coils?

Can someone explain with a little more intuition on how applied voltage determines the motor speed rather than the current through the motor coils?

Is the above answer same for DC motor and stepper motor as well?


texts: My books states that when a TTL input is high, the emitter diode cuts off and the emitter current is approximately zero. This animation shows that when a transistor input is high, the emitter diode isn't cut off. https://youtu.be/7ukDKVHnac4?t=327


texts:
I am trying to find a datasheet for one of the following cores: BCM11311 or bcm21654.
Which have an ARMv7-A architecture and ARM cortex 9 processor.
However I am completely unable to find any usefull datasheet of the BCM11311 or bcm21654 on the internet. I have seen there is code available to port freertos to a cortex A9 processor, so I am looking for any chip which has this architecture. So I can lookup all the register addresses and analyze all the code.

Why can't I find a datasheet of any of these?


texts:
I'm new here so please bear with me.

I'm planning to replace my old central alarm system with a new raspberry pi, which takes 5 VDC input.

My old central uses a separate 230 VAC to 16/18 VAC transformer and 12 Volts lead-acid battery as backup.

I'd like to leverage, if possible, the transformer and the battery in order to build a UPS which would feed 5 VDC into the raspberry pi.

Does it make sense to re-use these components? I'd like it to be energy efficient since it would run 24/7. If so, I'd appreciate any help on how to get started.

Thanks,
Juan