texts: How does circuit completes when physical ground(earth) is used as neutral?

texts:
In my locality there is no neutral wire. Our transmission company runs only 3 wires(all line/phase) and no neutral(4th wire) at all. Out of three, one runs to our houses. I know it sounds incorrect, but this is the case, they are saving the expense on neutral wire.

Here we use earth wire(physicaly connected to earth) in place of neutral . Each house has its own earthing/grounding. So our earth is our neutral. No difference at all. Everything works just fine, no problem at all.

I know that two wires with different potential are required to create a potential difference. I also understand that we can run loads between two phases. But in this case there is only one. Here we are running loads between a phase and a wire physicaly connected to earth.

I know that current flows in closed loop(it goes back to the source). But in this case, there is only one wire coming from sub-station and another is just physicaly grounded, how the circuit even completes?  Where is the closed loop?


texts: PCB Mounting solutions in outdoor enclosure?

texts:
I've completed the design for my pool timer and now I'm down to designing how this board will actually hold itself inside an enclosure.  I already have a box that I'd like to re-use.  It looks like the t30004r.
I plan to take out the 2 mechanical timers and insert my 3"x3" PCB in there, but I need to mount it inside the box in a safe way.  The PCB itself has external connections coming out on all sides and I'm using many hole-through components.  In addition, I also plan to use the 2 switches that are a part of the panel to still allow the control of the light & pump.  The board takes in 120VAC so I want it to be secure.
The main option here seems to be adhesive standoffs.  Are there better solutions?  Any concerns that I should have with adhesive standoffs?  I do still want it to be removable.

Thanks


texts: I need help with Eagle CAD how do you edit silk screen how to add copper to the empty spaces

texts:
Like the title describes, these are two things I need to know how to do in eagle.
Any pointers?

Thank you.

P.S. if anyone knows a tricky way to get an image into the silk screen it would be amazing.


texts: How to explicitly connect hidden pins in eagle?

texts: I am working on a project where I used a shift register 74HC595N which has hidden GND and VCC pins in Eagle. So I used the invoke property as shown in the pics, and connected the VCC and GND to the +5V and GND of the Arduino board. This connects the two hidden pins of the shift register directly to the Arduino. but in the PCB design phase, both pins are connected to random pins. Is there a way I can connect them explicitly from the schematic?


texts: How to debug error of "unknown type name __progmem__"?

texts:
I'm using atmel studio 6.1 with a code containing
but on compilation conpiler gives error as mentioned above and after googling error,I found that this variable progmem has been depriciated,but no solution for fixing it.
so anyone can plz help me?
I'm writing this code for ATmega32 to control GLCD JHD12864E.
excerpt of code

#ifndef _FONT_H_
#define _FONT_H_
#define __PROG_TYPES_COMPAT__
#include "avr/pgmspace.h"
#include "types.h"

//Constants
#define FONT_OFFSET_WIDTH 2
#define FONT_OFFSET_HEIGHT 3
#define FONT_OFFSET_FIRSTCHAR 4
#define FONT_OFFSET_CHARCOUNT 5
#define FONT_OFFSET_WTABLE 6

//Main Selected Font
const __progmem__ *font;

//Functions
void __GFXInitFont();

UINT8 GFXGetFontHeight();

UINT8 __GFXReadFontData(UINT16 add);

UINT8 __GFXReadPGM(const __progmem__ *ptr);

void GFXSetFont(const __progmem__ *new_font);

#endif


texts: continuous battery monitoring during charging as well as discharging

texts:
My application is basically a power monitoring system in which inverter voltage(RMS),current(RMS) and battery voltage,current are measured. 24V battery is being used in the application. I am using PIC16F877A microcontroller for measuring and do the rest of the functions based on the readings. ADC code is working fine. It is measuring the battery voltage correctly if it is  isolated from charging or discharging. But whenever I connect the battery to charging and inverter circuit the ADC is measuring only a constant value, in my case 25.7V even if the battery is charging. but multimeter is reading incremental voltage as battery charges.
I am using a simple voltage divider to step down the voltage to a microcontroller level voltage.I have added a 100nF cap to ADC input but didn't help. Is there anything I need to consider in circuit side or firmware side to do accurate measurement.

Thanks


texts: Strange behaviour of ne555 + pmosfet circuit

texts:
I was a silent reader for a long time and could solve all the problems on my own, but this problem is really freaking me out.
I was messing around until 3 AM today with this "feature" and still don't know what is going on...

Initial Situation

There is a LED strip, that is blinking with 1.5 Hz (50% on time) and +12 V.
I have to create a circuit, that can be placed between voltage source and the LED strip that delays the blinking by a few hundred milliseconds. It does not have to stop blinking these hundred milliseconds later, delaying the on time is enough. Interrupting the ground connection is no option, because there are a few more more LED stripts that share the same ground potential.

My current circuit

Due to the fact that my LED strip is connected to ground and I have to delay the incoming +VCC signal, I think (am I right!?) the easiest way is to use a P channel MOSFET as high side switch. I know that I could use a N channel MOSFET with a bootstrap driver, but i read a lot of articles that say using a P channel MOSFET is just fine, if you don't care about the higher Rdson (I am switching ~200 mA, so i don't really care about Rdson). In addition my PCB space is limited and a DIP8 driver would not fit well (Whole pcb should be designed as through hole).

The gate signal for the MOSFET is coming from the output pin of a NE555, which threshold and trigger pin is connected between a resistor and a capacitor.

Problem

I have really strange things going on with my circuit. For test purposes, I connect a single LED with a resistor to VCC, to test the functionality, but I just cant get the expected result. First, my circuit was working a little bit, the led blinking was delayed for the expected time, but went on for a few milliseconds when +VCC was applied to the circuit. I think the reason for this is, that the MOSFET is conductive by default, and my NE555 needs a little time to turning the mosfet off.

The other, much stranger problem is that after a few blinking cycles the LED is on the whole time!? First, it is glowing just a bit but then starts flickering/changing its brightness...

I have attached my current circuit.
I would be so happy if somone could tell me what I messed up with this circuit design.

Or if there are much better solutions (maybe attiny13 as gate control!?) I would appreciate every recomendation.

Thank you in advance!!
And sorry for my bad english :X


texts: How to get the PWM frequency and duration of each pulse?

texts: I have an ATmega8 and I started working on servo motor HS-645MG. What frequency works with the HS-645MG? How do I get the frequency of PWM and the duration/length of each pulse? Is there a calculation?


texts: Two different outputs from same type of IC's

texts:
Hello Electrical engineering community.

I am using motor drivers to get 5v to 12v and I am controlling each motor with each IC L293D.

Each motor driver is controlling each motor and the outputs is taken from only one side of the IC.

12v battery -> 7805 voltage regulators -> two L293D IC's with 12v given and the output is taken via diodes to resist back emf-> 100 rpm 12v DC motors.(the other two output pins of the IC are left floating).

Everything is working fine but from 1st pin I am getting an output of 10.23 and 0.72..  and from the second IC I am getting an output of 9.1 and 0.61.

I don't understand why is there a difference of 1v.

Sorry I can't upload a picture of the ckt or make the question in more detailed manner as I am using my phone.

Any help would be appreciated.

I don't understand what tags to be given


texts:
If I was to build a 12->65V boost converter using Texas's LM5002 regulator IC, would it be possible to tie an Arduino I/O pin directly to the EN pin to enable/disable the output, while keeping the 12V at Vin? I would only need a small output current (around 0.1 mA)

simulate this circuit – Schematic created using CircuitLab


texts: What does this sign/element from a circuit diagram mean?

texts:
Can someone help me understand what the V/2 element/sign means and how I should connect it?
I have highlighted them in red.


texts:
As far as I am aware,

HDMI 2.1 does support 12-bit 4K 60fps, Also it doesn't use TMDS, rather FRL. Sends upto 48Gbps

GPUs can do calculation in fp32 and from some reference, I think that it can send 16bpc (48-bit per pixel deep color) (Assuming that it is a high end Quadro GPU) (fp16 had the capability to send 12bpc 36-bit deep color, right?)

But there are monitors that don't support more than 10bpc 30-bit depth deep color
Why is that? Why do displays have limited bit-depth?
Can you give me some idea about the science behind this? Why does it cost more to produce higher bit-depth monitors?
Isn't it like, RGB pixels on the displays are emitting photons? Then how do different displays differ in terms of emitting photons?


texts: Consider a power source supplying 240 v 50/60hz 6amp I know that there is nothing like it but I chose that for my comfort of understanding now if I connect 15 loads drawing 240 v 0.35 amps in parallel to the source which all combined draws 5.2 amps will this circuit work correctly.as I heard that voltage doesn't change in parallel circuit regardless of loads.so just say will the above circuit work wothout any voltage drops.sorry for the silly question as i am new to this.


texts: Simulating circuits online, oscilloscope?

texts:
I'm playing around with some op-amp tutorials, trying to get a grip on how they work. I'd like to build some of them to get a better grip on how they work. I'm on CircuitLab right now since I've got a student license, but I can't seem to find anything resembling an oscilloscope.

For example, I wanted to build a op-amp square wave converter circuit and play around with the resistances and other components right now and watch the response in a scope. What's the best way?


texts:
I'm kinda new to electronics and programming, but I managed to make a DS1307 RTC functional when it is used by only one program (I'm using C code). Buf if I try to use it in multiple programs at the same time, it occasionally gives me some strange dates and times.

For example, I'm using these two programs:

test.c

 #include <stdio.h>
 #include <stdlib.h>
 #include <time.h>
 #include "ABE_ExpanderPi.h"
 void main() {
    int i = 0;
    while( i < 100 ) {
            struct tm datetime;
            char buffer[80];
            datetime = rtc_read_date();
            if (strftime(buffer, sizeof buffer, "%Y/%m/%d;%H:%M:%S", &datetime)) {
            }
            else {
                    puts("strftime failed");
                    exit(1);
            }
            printf("%s\n", buffer);
            i++;
            usleep(10000);
    }
 }

test2.c

 #include <stdio.h>
 #include <stdlib.h>
 #include <time.h>
 #include "ABE_ExpanderPi.h"
 void main() {
    int i = 0;
    while( i < 100 ) {
            struct tm datetime;
            char buffer[80];
            datetime = rtc_read_date();
            if (strftime(buffer, sizeof buffer, "%Y/%m/%d;%H:%M:%S", &datetime)) {
            }
            else {
                    puts("strftime failed");
                    exit(1);
            }
            printf("%s\n", buffer);
            i++;
            usleep(10000);
    }
 }

The DS1307 functions can be found in ABElectronics_C_Libraries.

When I run both at the same time, it shows me something like this:

...
 2018/07/11;19:07:53
 2018/80/40;05:06:92
 2018/80/40;05:06:92
 2018/07/11;19:07:53
 2018/80/40;05:06:92
 2018/07/11;19:07:53
 2018/80/40;05:06:92
 2018/07/11;19:07:53
 2018/80/40;05:06:92
 2018/07/11;19:07:53
 2018/07/11;19:07:53
 2018/07/11;19:07:53
 2018/07/11;19:07:53
 2018/07/11;19:07:53
 2018/07/11;19:07:53
 2018/80/40;05:06:92
 2041/53/02;90:12:90
 2018/07/11;19:07:53
 2018/80/40;05:06:92
 2018/07/11;19:07:53
 2018/80/40;05:06:92
 2018/07/11;19:07:53
 2018/07/11;19:07:53
 ...

In my project I will be using the RTC more than twice at the same time. Can you help me, please?


texts:
Hi just a dumb question that I have to be sure.
I will be using LM2596

It is stated in its description: IC REG BUCK 5V 3A TO263-5
That its package is TO-263-5.
But on its package is TO-263-6, D²Pak (5 Leads + Tab), TO-263BA.

On the image, there are 5 leads and 1 tab.
Is this the correct footprint for this?

Is Pin 3 also the TAB? which is a ground on typical applications.


texts:
I was studying this discrete voltage regulator used in a guitar amp power supply.

The filtered +-36V supply voltages go straight to the power amp, and if I got it right Q212-Q213 act as variable resistors in order to keep the voltage set by the two zeners. But I don't really get what the rightmost part of the circuit does (the connection from Q214 collector resistor goes to a JFET gate used as a switch, I think, at the power amp input).

How does it determine the reference ground for the circuit?


texts: Measure both sides of an AC and DC circuit

texts:
So I have recently begun messing with diodes and there use in converting AC to DC. What I am curious in trying to do is to hook up my dual channel oscilloscope on bother DC and AC side to view the save form both sides generate. My question is this, is this safe to do, could I damage my oscilloscope by having separate channels measure the voltage on either side of the bridge.

Below is an example of what I would like to try.

simulate this circuit – Schematic created using CircuitLab


texts: What kind of structure is this small GSM antenna?

texts:
Two of these types of antennas comes with the ADALM-PLUTO SDR evaluation kit.

According to this page, they should be JCG401 antennas for the 900 and 1800 GSM bands, but the datasheet does not tell anything about what kind of antenna structure this is.
It looks like a monopole connected to the center conductor, but with some kind of helical structure around it. The helical is connected to the shield(ground?). Wouldn't it interfere with the radiation from the center conductor?
Or is this some kind of dipole structure?


texts: Why are most parallel interfaces half-duplex and serial full-duplex?

texts:
I know what is difference between parallel and serial interface. I know also what does it mean half/full duplex.  However, I don't know why most parallel interfaces are half-duplex, and most of serial interfaces are full-duplex.

Can anyone explain?


texts: Digital temperature meter probe wire length

texts:
I bought a cheap Chinese digital thermometer like this one

with this description Link to product

  Item specifics

Power Type: Button Battery
Model Number: Thermometer
Max Measuring Temperature: 50°C - 69°C
Style: Handheld
Theory: Temperature Controller
Display Size: 2.0 - 3.9 Inches
Display Type: Digital
Usage: Indoor

  Product Description

  Feature:

100% brand new and high quality.
Quantity: 1
Measuring temperature range: -50Celsius~110Celsius
Temperature accuracy: ±1 Celsius
Temperature display resolution: 0.1 Celsius
Operating voltage: 2 x 1.5V button LR44 batteries
Dimension: 48×28.6×15.6mm(approx.)
LCD dimension: 36×16mm(approx.)
Operating Voltage: 1.5v, LR44/AG13(Include
Cable length: 1m
Color: Black

  Package Content:

1X Mini Thermometer Hygrometer Temperature Meter Digital LCD Display

It does not have a Hygrometer as far as I know.

I opened it up and found this

It has a probe wire length of about 1 meter. I wish to use it to find the temperature in the storage tank of a solar water heater about 20 meters away. My question is - can I just extend the wire (2-core wire) without affecting the temperature measurement? I looked up Amazon product reviews for similar products (not sure they are the same on the inside), but I didn't see any reviewers having extended the wire more than a few feet.

Also, what power supply can I use instead of LR44 cells. I cannot make out the chip inside, though some reviewers on Amazon have stated that anything upto 30 Volts would work.


texts: Phase margin is 90 degrees but transient step response shows overshoot

texts:
The bode plot of the loop is as shown here

The transient step response looks like this

The block diagram looks something like this -
Basically a single stage opamp(OPAMP in fig) with high gain(cascode structure) biasing a fet(M1) such that its drain is equal to Vbias. Small signal step is applied at I1 Ibias and transient current through the fet M1 drain is observed.

Am I missing something here?


texts: What would the firmware to control Shift1 system (for 1-pin shift register operation) look like?

texts:
This is a follow on question from this answer by Spehro Pefhany, in which he explains to us how to use 74HC595 serial shift registers with only one digital output pin. Below's the picture he posted.

Out of curiosity, and also to evaluate whether I would be able to control a shift register myself, my questions are:

1. How complicated is it to control shift registers in this way with a MCU, in C, for example?

2. How would the firmware that controls this shift register look like?

3. Are there Arduino libraries to help us handle that (or for other platforms as well)?

I have no idea on how to start.


texts: High energy efficiency through transformers

texts:
We are about to build a large facility, using lots of electricity. The facility is being built in module form, which are copies of one another.

We are unsure of whether the energy efficiency will be better if we use several transformers (5, 12 and 24VDC) to each module or if we should go with a large transformer of each and drag cables to each modules. Is there a way to calculate the energy efficiency? Does it help if the cables/transformers are cooled using fans, thus, lowering the resistance?

Thanks


texts:
I followed this instruction, but I found that it doesnot work (the RGB LED is off).
So, instead of connecting the long leg of RGB LED to ground (-), I connect it to the 5V source (+). And, it works.
But, it does not work as expected. Then, I figure out that the Logic (HIGH/LOW) is somehow inverted, so I invert the logic in my program and it works as expected.
My question is why does that happen?


texts: Choosing transistor for a raspberry pi switch

texts:
I'm trying to design a circuit that will control the power to a raspberry pi with a button. The basic usage is:

first button press-> rasp powers up.
second button press-> rasp continues with power but detects that should shutdown.
(After the shutdown sequence is done, raspberry shuts off).

The design envisioned is a circuit with a normally off button that is connected to a binary counter (74LS161AN).
The idea is to count the button presses and use the XOR of the counter's 2 least significant bits as a control for the power to the rasp. The XOR I intend to use is 74LS86.
The msb of the counter's 2 bits is how the rasp detects it should shutdown.
The rasp cuts its power by ouputing a High to a gpio that is connected to the counter reset.
This button/counter contraption is sort of working on a breadboard but now needs a transistor that actually takes the output of the XOR and controls the voltage in the rasp. power.
Do you think that BD135 is a good choice for this? (datasheet) I chose it because
Raspberry is powered by a 1.2A power supply, therefore the transistor needs to handle more current (bd135 has max collector current of 1.5A). It also needs to be NPN.
I have a few doubts if this is going to work, for example, how do I know if the XOR can supply enough current for the transistor base? Actually what does it mean when the high level output current of the XOR is -0.4mA ?
If this transistor would not work, could you point one that does and explain the reasoning to select it? I am a bit lost..
Thank you very much.
PS: between the button and the counter there is a 555timer in monostable to clear the bounces.


texts: Controlling forward/reverse current using arduino & shift registers

texts:
I'm trying to control multiple solenoids (home made) using a shift register controlled by an Arduino.
Ideally I want to be able to direct them all together either inwards or outward using the current direction.

I had originally looked at using an H-Bridge, but I have about 200 solenoids to control so it was going to become too expensive. I figured I might be able to switch the direction of the current and send 2 sets of values to the shift register, using the first bit to specify the direction.
By daisy-chaining 25 shift registers I can control all 200 (well 199 - but that would be enough).

Something like this:

Bit 0 - connected to mosfet that controls relay that sets the current direction
Bit 1 - connected to mosfet that switches solenoid 1 either on or off
Bit 2 - connected to mosfet that switches solenoid 2 either on or off
etc etc

Datasheets are as follows:

2N7000 Mosfet
74HC595 Shift Register

I've attached a diagram, I've omitted the connections to the arduino for simplicity but I do have a few questions.

Does this look like it will work? Am I totally off the mark?
Do 2n7000 mosfets allow current in reverse?
Would it be better to have 2 mosfets for each solenoid and keep everything separate?
If yes to 3 - do I need diodes in front of them or how do I go about protecting them from backflow?
What would be the best way to arrange the snubber diodes? (assuming that they are needed)

Thanks in advance for any help!

simulate this circuit – Schematic created using CircuitLab


texts: Extending Aerial Range of 360 USB receiver

texts:
I have modded an Xbox 360 usb wireless receiver so that it sits inside my PC, but the problem I have appears to be range as it regularly drops the connection to controlers. The connection from the motherboard to the device is solid so it could be the computer case blocking the signal or would the RFI from the computer and its power supply be corrupting the data?

For reference, here is what the wireless receiver board looks like:

It seems like the gold band around the edge is the aerial. I have tried soldering a cable to this and running it into the front fascia of my PC case (which is plastic), but that seemed to make little difference. I have read that it is possible to extend such an aerial, but I know very little about electronics so I am   not sure what's involved. Am I  using the wrong type of cable ? Is there anything else I am doing wrong?

Any insight onto how to improve the signal by effectively moving the aerial would be great!


texts:
I built up a circuit which did not work as expected.
I reduced the problem to this circuit:

I expect to have a current of ~2.4 A at gate voltages below 10 V, but actually the transistor does not fully switch at 100 V.
What is the Vgs threshold voltage I should assume for the standard nmos? I expected it to work at any value as it is an idealized model, isn't it?
What I'm I doing wrong?!
I tried adding a pulldown at the gat, even though I didn't expect this to enhance the situation...

Info: I'm using LTspice XVII from Nov 26 2018 under linux with wine.


texts: Is it acceptable to use decoupling capacitor ground pad as ground for oscilloscope probe?

texts: If one were to probe with an oscilloscope using the short ground spring clip attachment, and use the ground pad of a decoupling capacitor as the ground, would the measurement be thrown off at all by currents moving to ground through the capacitor? Or is something like a test point pad on the top layer ground pour required for peak accuracy? Say I'm probing a pin on an IC and using a local decoupling cap ground pad as the ground as shown in the pic, would this measurement be free of any noise from the cap? If not then what would be the best practice method to do this? Thanks.


texts: I want to create electrostatic force between two isolated objects which are 3 meters apart from each other. The electrostatic force should be very noticeable, so I want to get the objects charged other than using friction. I also now about electrostatic generators like Van de Graaff generator, but I want to get a particular object charged without any large machinery involved. Therefore Van de Graaff generator is not useful for me. I don't want to use battery because as far as I know I have to bind the battery to the object permanently. I just want to get an individual object charged without any connections to other generators or batteries. Thus, is there a way to get an object charged without using battery, Van de Graaff generator, parallel plates and friction? Basically how can I get an object charged and stay charged without any connections to machines?


texts: How to decide bypass emitter resistance value?

texts: This is an amplifier which has voltage gain of 50, quiescent current 1 mA and the input is signals from 20 Hz to 20 kHz. I calculated the collector current which is 1 mA, using that I calculated emitter resistor value which is 1 kohms. Now how did he decide the resistor values of emmiter as 180 ohm and 820 ohm when emitter resistance is 1 kohm?


texts: Simultaneous power supply from battery and USB

texts:
I have such power supply circuit:

It can be powered from battery/wall adapter or from USB.

1) When I connect USB, then the 5V from the USB goes to SMPS output. Is that ok? It has EN pin, but I don't know.

2) What happens if a user connects both USB and battery at the same time?
Especially what happens If there's computer plugged to the USB and I connect battery?

3) Do you know any ICs that could multiplex power supply? Something like: I connect USB PS and battery PS to the chip, it detects which one is present (or has control inputs) and send one of them to the output.

I know about LTC4412 but it's too expensive. I would like to avoid using diodes because of voltage drop (first power loss, second 5V won't be 5V any more).


texts:
Are there any Analog/Maxim (I couldn't find a switching regulator with these characteristics on their websites) ICs that can step-down a voltage between 12 and 220 V (coming from a generator) to a stable 12V?

Thank you!


texts: I have a 12v dc motor and when I run it with load it is drawing 10amp and now I want know what is my power consumption. Theorically equation is Watt = V·I but I know current but I'm not sure voltage. Because when I charged battery average value is 13.5 Volt and while I driving dc motor I check voltage of battery and ıt's write 12.5 volts. So while driving my dc motor what is my real power consumption 13,5 V · 10 A = 135 W or 12,5 · 10 A = 125 W?


texts: Please, define symbols which are pointed

texts:
What do these symbols mean? Please, describe

It is a part of high voltage power supply


texts: What kind of project could help a software engineer become more of an electronic engineer?

texts:
I'm a software developer with practically no electronics background, but I want to get into this since it's relevant to the work I'm doing (infotainment system development). I'm a software engineer, not an electronic engineer, so my background/experience has more to do with application level programming, and maybe a little of system/network programming.

I've heard about Arduino as a flexible project platform and I was wondering what kinds of projects could help someone with my background dig their way to electronic engineering... starting with microcontroller programming and maybe messing with other kinds of peripherals, such as bluetooth, zigbee, wifi, audio, video, I don't know... maybe a kind of project that is typical for electronic engineers during their courses.

In sum, what I'm looking is for a typical/popular kind of project (academic or otherwise) that could help a software engineer develop an electronic engineering skill set at the software level.


texts: Solar requirements for 5000W equivalent system

texts:
I currently run a fridge-freezer and larger freezer, some lights and computers off of a 5000W, 220V to 110V (50 Hz) transformer. I am trying to run that on off-grid solar instead of using the transformer.

Would a 5000W (pure sine wave) inverter be able to run the same loads as the 5000W transformer?

What size battery bank (i.e. how many Ah) on a 24V setup would be needed? (Assuming constant charge from solar & wind sources.)


texts: If amps and volts can vary independently, how does Ohm's law actually work?

texts:
This is a very basic question as I'm just starting to get into things, but I've hit a roadblock with comprehending the definition of voltage as it relates to the relationship defined in Ohm's law.

It might be that I'm misunderstanding the definition of voltage. As it says "voltage is the work needed per unit of charge to move a test charge between two points." My confusion centers around the idea of 'per unit of charge', which suggests to me that amps and volts can vary independently (that is one 'unit' of charge may require different quantities of work to move between two points not related to resistance).

If that's the case, how can I = V/R be a thing? That suggests that current is precisely and deterministically derivable from voltage and does not vary independently. I guess I'm just not really understanding how current actually varies - whether or not it's a property, say, of the conductive medium (copper has 'more available charge' to move, or some such) vs. current actually being directly related to voltage and does not vary independently and I've totally misunderstood the definition of voltage.

I'm hoping I can understand this and move on to more interesting things, but I'm just kept awake at night not really understanding this. My tl;dr question is really summarized in the title.


texts: Should there be a ground clearance from 11 kV line to earth?

texts:
Should there be a minimum ground clearance line to earth at the voltage level 11 kV? I am living in India and I see the trains whose voltage level is 25 kV which is large compared to 11 kV.

Strangely I observed that 25 kV is used in trains whose height is much less compared to 11 kV height (I don't know the exact height?). According to my professor's logic, the height of 25 kV line must be greater than 11 kV? Correct me if I'm wrong.


texts: Can a credit card be demagnetized with a nearby cellphone?

texts:
Suppose I have a standard credit card with a magnetic stripe, lying

right on top of a cellphone, or
in a regular leather wallet that's lying right on top of a cellphone.

The cellphone is on (but not in a call), uses a 3G network, and is in a good reception area.

Will the credit card be demagnetized (to the point where it can't be read) in the above 2 scenarios? If so, how long will it typically take? An answer that shows all assumptions and calculations used would be especially useful!


texts:
This is the datasheet for 6379A:

datasheet

I looked at the timing charts, but I’m still having trouble figuring out how the IC treats the serial input.

Apparently, SI is sampled at positive clock edge, but what indicates the start of the input? I mean where are MSB and LSB? Also, I don’t get what LRCK does either.

Can someone please explain to me, in simple words, how this IC is used?


texts:
TL;DR: Does burying a cable provide shielding? I.e., is a shielded cable in air equivalent to an unshielded cable buried ~ 6 inches in soil?

Long:
I'm a technician at a university. I don't have formal training in electrical engineering, but one of my tasks is designing an environmental monitoring system for the field. Analog voltage sensors (thermocouples) will be read by a device in the field, and the signal will be passed ~100 m to a datalogger via shallow buried cables. In selecting these cables, I was concerned about voltage drop (since thermocouple signal is a very low voltage to begin with) and cable shielding (since there are power transmission lines in the area, and AC power supply for the datalogger in the same enclosure box). I asked a more experienced technician for advice, and he advised that in this application he would be concerned about both things.

However, when I approached the project manager about this, I was told not to worry about voltage drop (no reason given), and that burying an unshielded cable was "the same as shielding it". I can order unshielded cable and spend no further time on the issue... but I'm concerned that the manager is just trying to save a buck, and that this could come back to bite us (i.e., I'll be creating more work for myself) in the future.

I'm also generally curious. Is he correct in saying that a shielded cable and an unshielded cable buried less than 6 inches in soil are equivalent?

*Edit to add detail: the site is a pine forest with well-drained (dry), predominantly sandy soil. I don't have much experience to go on, but I would say it's fairly quiet for EM. There's one high-power line ~200 m from the thermocouples, and 120V AC running through outdoor extension cords - the 120V lines are co-located, and will run alongside the TC's in some cases.

**Edit to clarify: I'm not concerned about voltage drop on the thermocouple itself. I'm concerned about drop on the 100 m cable that will carry the signal from the thermocouple voltage-reader (a Campbell Scientific AM16/32B multiplexer) back to the datalogger (a Campbell CR1000).


texts: How does glass create an electric field?

texts:
I'm reading from Microchip's data sheet regarding their MAXTouch microchip, which details on how to create a touchscreen compatible with their chip, and in discussing the "mechanical stackup" of a touchscreen it is noted that

  Front panel dielectric material has a direct bearing on sensitivity. Plastic front panels are usually suitable up to about 3 mm, and glass up to about 4 mm (dependent upon the screen size and layout). The thicker the front panel, the lower the signal-to-noise ratio of the measured capacitive changes and hence the lower the resolution of the touchscreen. In general, glass front panels are near optimal because they conduct electric fields almost twice as easily as plastic panels.

I'm unsure what this means that glass or plastic conducts electric fields. A typical mutual capacitive touchscreen consists of a set of x transmission lines underneath a set of y transmission lines (with space between them).

I thought that that space and the transmission lines is what causes the electric fields, not the glass which is on top of it all.

There's also a note which says

  Care should be taken using ultra-thin glass panels as retransmission effects can occur, which can significantly degrade performance

So I guess this means that you wouldn't want to try and use a touch screen with no glass/plastic overlay at all?


texts: Vibration frequency measurement with a piezo sensor

texts:
I have a linear resonant actuator like this one:
https://www.gearbest.com/other-accessories/pp_670798.html
I need to control its frequency of vibration and for that I intend to use a potentiometer and an arduino to control de supply voltage and hence vary the frequency of vibration. But first of all I need to know how to measure the frequency so that I can adapt it to my purpose.

I am thinking of attaching a piezo sensor to the motor and with the arduino determine the period and hence the frequency of the signal produced when the piezo vibrates alongside with the LRA. Therefore I have some questions:

Is my idea possible or is it nonsense?
Can you please tell me if the tension produced when the piezo vibrates is sinusoidal and if so is the frequency proportional to the frequency of vibration of the motor?
I need to reduce the tension produced to the levels of the arduino functioning tension but if I use a resistor of 1M Ohm will not that function as a filter and affect the signal?


texts:
When it comes to simple circuit analysis, there is millions of tutorials on how to analyze a resistor circuit, a RC circuit, or those involving LED the non-ohmic devices. However, I did not find a simple and clear tutorial on how DC motors behave within a circuit. I did some experiment, and only got more confused over the result. A brushless motor rated for 0.4A 5V when connected to a 9V it runs full speed without a problem, but then I add a little resistor to limit some current suddenly the motor hardly turns at all.

Summary of question: what is the behaviour of DC motors in a circuit? What does the rating 5V 0.4A mean? (the voltage drop? the forward voltage? etc.)


texts: How do I prevent bridges while soldering SMD Components?

texts: I have noticed that whenever I try to solder a component with many pins close together (like an IC), I get tiny bridges of solder, which shorts the pins. Is there any easy way to solder SMDs without solder bridges?


texts: How does multi-core CPU implement asynchronous coordination?

texts:
I am coming from computer science background and wanting to study process calculus for use in asynchronous circuit design.

So, I am looking around the current practice on asynchronous circuits.
There are many articles that say inability to increase clock speed leads to multi-core CPU architecture. However, none really say how the asynchronous coordination between cores is achieved.

I want you to confirm/correct my following assumptions about how current multi-core CPU handles asynchronous coordination:

Each core has separate clock signals, which does not need to be in phase with each other. Otherwise, clock signal distribution problem would not really be solved, would it?
The cores coordinate only on programming level. That is, doing test-and-set on some memory (RAM or register). And not something low-level like hand-shaking protocol using rendezvous circuit.


texts:
I'm looking for a low-power microSD card for a datalogger, when I came across SanDisk's iNAND technology. What are some real-world advantages of those vs. microSD cards, except for their smaller physical dimensions?

Because many of the features they list seem like marketing-tricks, because normal SD cards have wear-leveling and error-correction too.


texts: Why is this derivation of the unit step function in the Z-domain valid?

texts:
This source states that the unit step function in the Z-domain is \$\frac{z}{z-1}\$. However, in its derivation it states \$\sum_{k=0}^{\infty} z^{-k} = \frac{z}{z-1}\$.

But doesn't that last relation only hold true for \$z>1\$? I don't see how that condition is met. I know that the poles have to be in the unit circle for the system to be stable, but I don't see if and how that connects to the condition above.

What am I missing?


texts: What's the purpose of this ground connection circuit?

texts:
I inherited a power supply circuit design from another engineer, and he used a ground connection method I am not familiar with:

The input comes from an external isolated 48 V AC/DC power brick. The outputs supply several boards within a single enclosure.

My question is about the diode connection between the negative input terminal and the load-side ground.

The effects I see from this are

Isolation provided by the DC/DC converters is negated.
Negative input terminal will be held within about +/- 0.5 V of the load-side ground.
Current might or might not be able to pass freely between the negative supply terminal and load-side ground, depending how the input common mode drifts relative to the circuit ground.

Some other notes about this system:

The load-side ground is connected to chassis.
Reverse-connection protection on the input is provided by other components not shown here.
Several of these systems might be connected in parallel to the same 48 V source.

The question is, what was the design intent of adding the diode connection?.


texts:
I have wondered myself why is that value fixed to around 0.7 V (0.3 Ge). I have researched about this topic over and over again, but I always find the same answer. They say "Because the voltage for Silicon Diodes is 0.7". That is just like saying that the sky is blue because blue is the color of the sky.

I am familiar with the Shockley diode equation, but I don't see the connection with the threshold voltage (I'm saying this because people have given me a link to its Wikipedia page).

I have also read something about the concentration of impurities near the junction being related to the voltage barrier (I am hoping to get an answer related to that, and the manufacture process).

Another answer I have been given is that that is silicons nature (I kind of hate this answer, because what I get from it is that the voltage is an intensive property, instead of extensive - which would make materials more "workable").

So the question per se is: Why 0.7 and not 0.4, 0.11, 1.2 (for Silicon)?


texts: I am trying to simulate the equivalent circuit of an inductor using pspice 9.1. I need to plot its impedance vs frequency to observe the parasitic behavior. I am new to pspice and I don't know how to simulate the Impedance vs Frequency. The circuit is shown below :


texts: Which resistors control the gain of this filter?

texts:
Update2: Nevermind the update1, question went far beyond its scope. Accepted answer was my expectation.

Update1: I have the filter(bandpass) design below, created using texas instruments filter design tool. I am also adding my specs to the question, in case it helps.

Gain at center freq = 1 V/V
Center freq = 1160
Passband width = 80 Hz( I figured lowering this made filter design more easy, more possible, though I would expect the other way around)
Stopband width = 400 Hz ( because of to be able to attenuate -/+ 300 Hz by 20dB, I chose 400 instead of 600 just in case, thinking about the non-ideal problems may occur)
Stopband attenuation = -40dB ( I have chosen 40dB just for in case, 20 or so is enough)
Allowable passband ripple = 1dB (not sure what this affecta, this was standard on filter designer software)
I can reach E12 resistors(%10) and E12 capacitors(%10)

These are the specs I have also used in the design tool.

The filtering action of the circuit below is close to desired. I have examined freq response with an oscilloscope + signal generator combination. I was expecting a gain close to 1 V/V , but it is actualy 0.15 V/V or so. Therefore, I want to increase the gain without affecting the center frequency. Is this possible? I have thought that gain can be arranged by the ratio of R5_S3 and R4_S3, and changed R5_S3 to 10k, but it did not affect gain, actually it did no difference, I can say.

So, I wonder which resistors can control the gain of this filter, if it can be controlled of course.


texts: How to measure the inverse saturation current of a diode?

texts:
I'm trying to measure the inverse saturation current of a diode, for using it in the Schockley equation. I would like to know what is the best circuit for doing this. I already tried the following circuit, but I can't detect anything.

simulate this circuit – Schematic created using CircuitLab
I'm using a 0-30V direct current power supply, a resistance of 230 ohms and a IN4001 diode. Do you have any suggestions?


texts: How to perform System Identification on DC motor?

texts:
I'm taking a class on control theory, and for our final project we've been assigned to choose whichever system we want and develop a controller for it. I've choosen to perform RPM control on a simple brushed DC motor. I have a pair of those motors and I want to set them running at the same speed using an Arduino and PID control.

The problem is: everything I've worked on this class has been very theoretical, and I'm stuck with the System Identification. I know the basics of it: if we don't have a mathematical model for the system (which is my case) we can see how the system responds to different inputs and deduce it's parameters from it.

How do generate a 'plant' model for a DC motor?


texts:
i am trying to send(i2c mode) slave address to IN1307 it is sending 0XD0(add+write mode) after i am getting small spike at ack bit.

How to solve this spike at ACK bit?

Here pull up resisters i am using are 10Kohm.


texts: How many watts does an electrical appliance consume?

texts:
This question is based on the following image:

https://superuser.com/questions/587869/how-can-i-determine-how-many-amps-i-need-to-power-my-laptop

Electrical power equation: Power P = I × V

where power P is in watts,
current I is in amperes (DC) and
voltage V is in volts.

However, there are 2 different currents (A) and voltages given for this laptop.
Q1. Which one should be used to calculate power?

INPUT number

Information given: 100-240V ~ 1.5A(1,5A)    50-60Hz
Pmin = 1.5A x 100V
= 150.0 Watt
Pmax = 1.5A x 240V
= 360.0 Watt
or

OUTPUT number

Information given: 19V : 3.42A(3,42A)
P = 3.42A x 19V = 64.98 Watt
Q2. Why are there 2 different voltages 100-240V in the INPUT section?
Q3. What are the difference between INPUT and OUTPUT in this image?


texts: Will a switch that says 250VAC 3A work directly connected to the wall?

texts:
I'm making a lamp, this lamp has two bulbs in it. Presumably I'm gonna connect this directly with a plug to the wall. To switch the thing on and off I've acquired two on-off switches from and electronic I don't use anymore. On the side they say 3A 250VAC and under that 6A 125VAC, with a simply google search it says houses deliver 20A through outlets. I was told by someone it doesn't matter the amperage of the house because my lamp will only draw as much as it needs, but in the event this is not the case.

How would I go about lowering the amperage of the lamp?

Switch: https://images-na.ssl-images-amazon.com/images/I/71kV5rxckGL.SL1500.jpg

I've been only using DC stuff up till now, new to AC


texts:
I want to detect if main switch of room (placed outside room) is closed and send logic level signals to controller (Arduino?)  according to that.  I need suggestions for way best of doing that. I know I can do it by converting 230V AC to DC but I want to avoid transformers as they'll be little bulky. I have thought about following possible solutions :

The main switch has little red light (not sure if it is LED though, because I don't see anyway for LED to get DC supply) built in which glows when switch is closed (I can upload pic if needed).  There are connections for that light too but I am not sure if I can use them to get DC,  help?
Are there any 'Relays'  which can do this work?  Although I've always seen relay sensing low voltage signals and closing high voltage circuits (using CBs,  if needed).  Can I do it using "No Voltage Relay"?  Like if there are volts,  there will be normally closed contacts which can be used along with small battery and high value resistance.. (But that would need replacement of batteries ).

Any other suggestions are welcome.  Thanks in advance.


texts: RS485 Pull-up, Pull-down and single termination resistor

texts:
Currently I use for Modbus RTU via RS485 with a shielded cable length of about 5 meters and a bitrate of 19.200 bit/s. Wired are 680 Ohm pull-up (A->+5V) and pull-down (B->GND) resistors near to the master. The Pull-Up and Pull-Down resistors came into the installation, because we face frequent transmission problems (BIAS) only with termination resistors. I had not installed any termination resistors, because the transmission worked. Currently I am troubleshooting and rethink about the missing termination resistors.

In existing installations I can easily install one termination resistor (e.g. 120 Ohm). And only one near to the master (where pull resistors located) and not at both ends of the bus due to mechanical accessibility.

My questions: Is the introduction of just one termination resistor at least better than zero termination resistors? Or does it make the bus situation even worse than without any? What are the correct values for one termination resistor (and for the sake of completeness two)?


texts: Are there optoisolators available that output a photovoltage of at least 2-3 V?

texts:
For another circuit idea, I need several cheap simple isolated voltage sources to generate at least 2..3 VDC and a couple of µA.
I was thinking of a blue LED in photovoltaic mode. Are such pieces available in a single optocoupler-like package ?
I want to avoid putting 3-4 regular optoisolators in series, as that seems a bit awkward, expensive and large.


texts: Replace 24VAC 20VA transformer with standard power supply

texts:
I have the following transformer (source):

Sticker reads:

Pri: 120VAC 60Hz 30W
Sec:  24VAC 20VA

I want to replace it with a standard, power supply without screw terminals. Preferably, I want one that will plug into the female end of this cable (source):

How do I translate these numbers to make sure I buy a compatible power supply that doesn't require screwing the wires into the plug?


texts:
I'm a beginner at electronics. I'm trying to use this Infrared phototransistor and my Arduino together: http://www.maplin.co.uk/infrared-transmitter-and-receiver-10379

I'm using the popular library here: https://github.com/shirriff/Arduino-IRremote

I've wired up the phototransistor best I could with my limited knowledge and by searching Google.

I have done the following although some of the terminology I'm using may be wrong:

Anode of the phototransistor to +5v through a 56K resistor
Anode also to Arduino pin 11
Cathode of the phototransistor to ground

I've used one of the example sketches from the Arduino library to print to the serial monitor whatever is received from my Logik TV remote.

This only receives information when I'm really up close and the bytes it receives are different every time with the same remote control button. However if I get super up close the bytes start to look more similar. When I'm within a few mm, the library actually recognises the protocol as NEC.

What is wrong with my circuit that I need to be up so close? Am I not putting enough volts through the IR PT? Or is it something else? My TV works fine so I know it's not the remote. I've tried following this schematic as closely as I could:

And this is how I have physically connected the breadboard:


texts: Can a dental X-Ray machine be used to look at PCB

texts: I have an old castaway PCB board that was being thrown out, but I am having a hard time figuring out where all the traces go. Could a dental x-ray device be used to scan it (thus making it easier to follow the traces). I am not worried about getting permission (I have not advanced to that stage yet), I just want to know the possibility of doing so (and what risks I am taking towards the x-ray device).


texts: Can I use a serial module with a barebones Arduino?

texts:
I have recently bought a couple Bluetooth modules that connect to the Arduino via TTL/USB/UART (you use Serial(); to communicate with it).

I don't know if the UART chips are in the chip or if it is in another part.

Since I only connect it to pins 0 and 1, do I need a TTL to USB converter for a setup like this?

I am following this guide: http://arduino.cc/blog/2010/06/08/minimalist-arduino/


texts:
I have some basic question about current. I have this picture here.

Why does the ground have more voltage drop across than the cabels connecting the metal poles together?
I could not wrap my head around this. All I could assume is that current stays constant, therefore, the voltage drop must increase when there is higher resistance to maintain the same current throughout the circuit. Is this right? If so, I still don't get why. Why does it have to maintain the same current? I thought current was the dependent variable in simple circuit.


texts:
what type of switch will normally be off/ open but when activated and held in the on/ closed position will then go back to the off/ open and rest when the switch is released?
I am wanting a to make a light flash once with each press of the switch and not stay on and then i want it to reset when released so that when switched the process will start all over again. so picture a gun you pull the trigger and a bullet comes out and when you release the trigger it resets and is ready to fire with the next pull or trigger in fact this is exactly what i want to do but instead of bullets I want a laser to flash.
there is a video of the part I would like to make at Min 4:00 & 7:45
 youtube.com/watch?v=B0Yax6VeOF4
and this page you can see how small the switch is, how ever there is a bit more room if I had to make it a bit bigger.
 http://www.glockstore.com/training-resources/training-devices/laser-module-only-for-ar-15


texts: Details on current ingress-protection implementations

texts:
This paper  systematically describes several ingress-protection (IP) implementations in smartphones at the time of its publication.
Is there a website or other resource that systematically catalogs IP implementations for various mobile device handsets?


texts:
I bought a IC (AD5933), its mounting Style is SMD/SMT.
I would like to do a test with it in the protoboard, however I am confused about the type of adapter.
I want to use an adapter that does not need soldering, like this.

But, I'm not sure exactly the right size for my case (150mil, 300mil, ...).
I do not understand if those values (150mil, 300mil) are for height or width.
Can someone help me?

Here are the specifications according to website Mouser:

Product Category:           Data Acquisition ADCs/DACs - Specialized

Manufacturer:               Analog Devices Inc. RoHS: RoHS Compliant Details

Product:                    DDS Direct Digital Synthesis ICs

Type:                       DDS Impedance Converter Resolution: 12 bit

Number of Channels:         1 Channel

Operating Supply Voltage:   2.7 V to 5.5 V

Mounting Style:             SMD/SMT Package / Case: SSOP-16 Packaging: Tube

Brand:                      Analog Devices

Development Kit:            EVAL-AD5933EBZ

Height:                     1.75 mm Length: 6.2 mm

Number of Converters:       1 Converter Sampling Rate: 1 MS/s

Series:                     AD5933

Factory Pack Quantity:      77

Supply Voltage - Max:       5.5 V

Supply Voltage - Min:       2.7 V

Width:                      5.3 mm

Unit Weight:                130 mg


texts: Is it must to have freewheeling diodes for ULN200x when used with dc motor?

texts:
I need to eliminate the MOSFET drive circuit from my PCB by replacing uln2004 or uln2803, should I still keep the back EMF diode across the dc motor?
motor supply 5V
current 70mA


texts: Should I use a separate power supply or separate grounds in this scenario?

texts:
Regarding one of my previous question I decided to implement the follwing wiring scheme for a scenario.

simulate this circuit – Schematic created using CircuitLab

The scenario is to trigger remote devices(module shown in blue box above) through their hardware trigger inputs simultaneously from a single trigger source which has a timer output. So basically the 0/5V pulse-train at around 40Hz will trigger many devices simultaneously. The maximum distance between the trigger source and the device is 60 meters. Total number of devices is three. In this case the Circuit above is just a buffer.

For the sake of simplicity I only made a diagram above for one device/module. The device is this module. As you see above an STP cable will both provide power and trigger to the module. A photodarlington optocoupler such as 4N32 will be placed right before the trigger input of the module to isolate from the input signal ground. P is the power and G is the power ground terminal of the module. A and B are trigger terminals.

Vs1 is 5V and powering the analog circuit on the left so that Vs1, Vin and Circuit shares the same ground call it GND(triangle symbol). On the very left however a separate power supply Vs2 is used to power both the output of the optocoupler and the module. So I called the ground of Vs2 as GND2 in the schematics to indicate that GND and GND2 are not connected/isolated.

The part I'm stuck at is on the right side the module and the optocoupler share the same ground because they are powered by the same power supply Vs2.

I cannot make a further judgement at this point. Should I use a separate power supply to power the module? Or should I use two separate return ground wires for the module and the optocoupler?

edit:

Is this scheme better(one ground for each)?:


texts: unexplained short circuit with PWM signal?

texts:
Something happened that i haven’t been able to explain , I wrote a program to output a PWM signal, this to activate a transistors base using a PWM which I could change the frequency using a potentiometer, the program worked fine, and the circuit too, however something was happening,

1)  When I lowered the frequency of my PWM the motor stopped spinning however a “buzz” could be heard from inside the motor

2)  When I tried to verify my PWM signal using an oscilloscope, like in the picture, , a spark came out at the tip of the probe and the circuit stopped working, the microcontroller on my board died, (it just gets way to hot in seconds) however I still have no idea why this happened,

Hopefully someone here can explain to me what happened, I did plug my PWM signal directly to the oscilloscope before  with no problems however when tried to debug in the working circuit this happened, as i recall the probe was gorunded with the circuit , but you might also want to consider the case of it not being grounded


texts:
I'm using three geophones to triangulate impact events inside the triangle, e.g. a mallet hitting the floor. Since the magnitude of the event is unknown, the position is calculated only by the timing differences of the peak hitting each of the geophones. I know how to do this theoretically, though this also requires knowing the exact location of the geophones relative to each other, and the sound qualities of the floor.

The geophones I'm using are here. The geophones provide a voltage proportional to vertical velocity, and behave as high pass filters with a corner at around 5 Hz.

Just using an oscilloscope to look at the voltages across the terminals gives me data that looks like this:

Here, the impact is mostly centered, but closest to the Channel 1 geophone.

And here's one where it's ~10 inches from #3.

I know I need amplifiers for each of the geophones so that they don't have to drive the relatively long wires to a central DAq circuit. I also know what to do once I have 3 time values relative to an arbitrary start.

I'd like to do as much of this middle piece in analog as possible, since I already know how to get the whole waveform and process in MATLAB. I was thinking of using a Schmitt trigger to ignore the later peaks, since these may or may not have the same time delays. Can I use 1 line being high to start two ramps, and then sample and hold one ramp when 2 lines are high, and then sample and hold the other when all three are high? How can I tell which was which?

I'd like to be able to resolve down to a few centimeters, which given the speed of sound in concrete means around 320 kHz at least.


texts:
I want to obtain the signal power in dBm (RMS) as it would be displayed by a power meter using a spectrum analyzer (in my case EXA N9010A).

But one thing makes me confused: The spectrum is a plot with frequency on x-axis and y-axis is in dBm. In my case, signal bandwidth is 20 MHz. Depending where I put my the marker, I get different answers. Inband, for example -12 dBm. Out-of-band (noise floor) -80 dBm. This would suggest to me that the actual unit is dBm/Hz, not dBm. However, this makes no sense either: I would need to integrate the power across the spectrum to obtain the total RMS power. In my example, to first order: -12 dBm + 10*log10(20e6) = 61 dBm. Clearly wrong!

So which kind of power does the spectrum analyzer actually show and why is it frequency dependent?


texts:
Does anyone know of a code template to properly configure clocks, PLL, latency, etc. for the STM32L4x parts?  I'm using a NUCLEO board with this part (L476RG) and have struggled for days with the datasheet in vain to learn how to set up the clocks before even beginning to write a "blinky" program to toggle a port pin.

I know of ST's CubeMX program but I'm using the MikroElectronika mikroC compiler (for which CubeMX doesn't produce native output).  Tried that and failed too.  Anyone have a clue how I might get traction here?


texts: How do I protect against voltage surges from sensors?

texts:
I'm attempting to use a CT to measure AC current.  I got a lot of information in this answer to another question which led me to huge amount investigation.

I want to measure the current in use by an AC appliance from a 5V ADC chip (e.g. an arduino, but I've got a couple different things, so it might be an arduino itself).

My first attempt involved taking the output of a CT, hooking it up to a bridge rectifier, grabbing a 10k resister and measuring the value relative to 5V off the ADC.  My test appliance is a lamp with a 75W bulb.  It basically worked, but was giving me "off the chart" numbers when I turned on the lamp.  This made me think something bad was happening.

The other poster suggested I put a 3300 Ohm resistor across the voltage of the output.  The expectation was that I'd get 680mV.  Doing this with my old DMM wasn't giving me much information, so I ordered an oscilloscope and decided to see what was really going on.

This is basically my story of attempting that.

While the voltage seems to go slightly negative, the difference between my minimum and maximum seems to be the predicted 680mV.  However, you can see a giant spike of 7.12V when the device is actually turned on.

I'd like to not plug 7.12V into the 5V ADC, so how might I go about suppressing that?

(I'd also like to level out the results so I can get a solid read, but that's a different problem I'll try to solve after preventing chip explosions when switches flip)


texts: Help with powering LEDs in parallel with maximum brightness

texts:
I'm pretty new to engineering stuff and I'm scared that I may burn out my LEDs if left to my own devices (literally.) I'm trying to power 16-18 LEDs in parallel at maximum brightness. I have a surplus of 470 ohm resistors that I'd like to use if possible.

Here is the data sheet

Bonus question: What would it take to make them fade at adjustable levels via Arduino? I'm trying to make a red heart beating effect and blinking is kinda boring.


texts:
I am new to Simulink software and want to design a battery with 8 cells whoose voltages are 12 Volts. Their capacity is 12Ah. Both have internal resistance of 0.1 Ohms. The aim is to obtain a 24 Volts battery pack by arranging these 8 cells. The load will be 10 Ohms. In the simulink i design the following model. However, i cannot see any result on the current measurement part while i can see the 24V in the voltage measurement part. I have some several questions?
1) Even though there is no load connected to the circuitry there is this internal resistance which cause current in the branches.Why there is no indication of  current in the scope?
2) I know that there should be a ground and a resistance in the circuit. However, since they are from different librarires they are not connected. I try interfaces but nothing changes.
Anyone who have any idea about these issue please answer this question. If you want to propose another model it is also okey. Thank you for your answers in advance.


texts:
I'm working on a project to control single phase ac induction motor in which I planned to use two IGBTs, one for switching the PWM to the motor (for AC chopping, PWM frequency is fixed @16khz) and one for freewheeling the motor. A symbolic circuit is included here:

I know the dead time of IGBTs is going to have some effect on the system. I want to know how worst the system is going to be effected because of this dead time and what are the remedies with respect to hardware and software.

What will happen if i completely ignore the dead time?


texts: waveforms showing effect of trace-length matching for SHORT ddr/ddr2/ddr3 traces?

texts:
I've seen lots of waveform plots that illustrate the beneficial effect of things like on-die termination, and the effect is unmistakable.  For example, see page 6 of this Micron technical note.  I'm also easily convinced that trace length-matching matters when you're talking about 8cm traces or passing through a DIMM connector.

However I'm not convinced that trace-length matching is terribly important in a highly-optimized layout where you've got a memory chip butted directly up against the ASIC/FPGA that controls it, and the traces are all less than 1.5cm long.  In a situation like that the "wiggles" required to match trace length will significantly increase the floor on the equalized trace length, probably doubling it.

Does anybody have actual scope plots showing the improvement, if any, gained by trace length matching when all traces are less than ~1.8cm long?

Of particular note the highest-speed memory standard (GDDR5) explicitly abandoned trace-length matching since it requires the component be on the same board as the controller (no DIMMs) and located very nearby.  The JEDEC spec explicitly instructs board designers not to match trace lengths, but rather to minimize them independently instead.


texts:
This is my first question so please let me know what improvements can be made, if I need to edit things, etc.

I've recently salvaged a heating element from an old single cup coffee machine that I want to use for an automated brewing machine. I want to include a holding tank, much like commercial units, that would hold about a litre or two of water and be mounted above the heating element. The water is going to be gravity fed into the heating element and I'm considering using a solenoid valve below the tank to shut off the flow of water so that I can control the amount of water boiled at one time. I'm not terribly mechanically inclined, so my question is how do I determine the "size" of solenoid valve needed?

I checked around for similar questions on this site, but most I found were about how to drive the solenoids or "can I use X to power solenoid Y" type questions. If there is an already answered question, if someone could point me to it, then I will gladly close this one.

Thank you for your time.

Edit: Link to solenoid valve removed, as it was determined that the valve will not work in this given situation (as mentioned by DrFriedParts).


texts: SSR controllable by independent touch button (TTP223) and I/O for Micro-controller

texts:
I am looking to solve the following problem.
I want to drive an optocoupler, which will drive a triac, and I want the following to hold.

I can toggle the state of the optocoupler input via a momentary output of a TTP223 capacitative module.
I can also set/reset or read the state of the optocoupler input via a microcontroller gpio pin.

Further information:
Following the approach provided by Swagatam (https://www.homemade-circuits.com/build-these-simple-flip-flop-circuits/?unapproved=88094&moderation-hash=b2e33d4d54dc810e6d71964c0ac3e91e - Schematic 4)
Here is my modified schematic
The I/O pin from Microcontroller is set with PULL_UP mode. Can you please be so kind to advice me on whether the schematic is correctly made. I replaced the Switch with 2 NPN transistors to mimic the switch action from controlling signal (TTP223 and GPIO from Microcontroller).
With this setting, the optocoupler will still be controllable when Microcontroller is not operational.
Please help to guide me through with thanks


texts:
On MOSFETs with multiple source pins, is the so-called "Kelvin-connected source pin" connected any different internally? Or is it just like every other source pin?

EDIT: Just to be clear, I am not asking what the Kelvin connection is for. I'm asking whether it is physically implemented any differently than the other source pins or whether it is just an extra regular, old source pin.


texts: MOSFET High Side Switch of high DC voltage (60V), improvement and advice

texts:
This is my first post in this stack group, so please forgive me for any shortcomings of my question.
I'm designing a circuit for a high side switch of around 60V DC (battery). Attached is a sketch of the circuit I have so far. VBat is around 60V, the switch here is a voltage controlled switch, switching for 2 seconds - in real life it will be a simple "hand controlled" momentary switch. R7 represents the load (which will be a voltage regulator in the end).
When simulated the circuit seems to work, but I don't know if this approach is reasonable.
My three main questions are:

The voltage divider R1 / R2 brings the 60V down to 10V, because most momentary switches seem to be built for 12V. That's why i choose R1 / R2 to be so high, to get the constant leakage current down as much as possible. Do I have to fear any antenna, or other undesired effects with such high resistances?
Is there a better approach, without leakage current, to use 12V switches?
Is there maybe a better approach in general?

Just to be on the same page, here is a short description of what the circuit should do:
As long as somebody presses (and holds) the momentary switch (voltage regulated in the schematic just for simulation) the load, represented by R7, should be switched to 60V on the high side. Later the load will be a voltage regulator that ouputs 5V to power a micro controller and some leds. That's why I was thinking about a high side switch, to have the same ground for all components.

simulate this circuit – Schematic created using CircuitLab


texts: Investigate methods for analog Input Overvoltage fault protection

texts:
I have 8 analog input coming from various 5v and 3.3v sensors that have to be interfaced to a 3.3v micro-controller. The main system voltage is 24v-48v , i need to protect the ADC inputs against over-voltage from misuse , not ESD events. So if by mistake the 48v is connected instead of the sensor.
after looking into the following threads :
How would I design a protection clipper circuit for ADC input?
ADC over-voltage input protection while keeping accuracy
i tried the following :

Approach 1: Resistor and Zener

This approach is fine on digital pins but confirmed what people said in the posts about voltage drop and ADC error. I heard that using a shunt regulator like the TL431 instead could help but haven't tried it!?

Approach 2: Series Resistor and External clipping diodes

The approach works fine it have tries BAS70,BAT54 and similar , in order to get lower drop i have found that using power (1A) schottky is better because they have much lower voltage drop at 1-25mA .

Approach 3: OPAMP, Resistor and diode

this approach i have found is not very common , and work fairly well , similar to approach 2 but more complicated.

Approach 4: Unity Gain opamp with internal Clamp

Texas instruments have a product for this role exclusively.
OP698
BUT: this lowest single supply is 5v not 3.3v , and the maximum clamping voltage is lower than the rail . and it does not tell how much is the maximum input voltage. and it takes PCB space , 4 resistors and 1 SO-08 IC per input.
Question :
At this point of search i got a bit frustrated and i think now that Approach 2 is the best in terms of robustness and space, please help and state any other approach i am missing ??
I am also interested in exotic solutions similar to automotive Input/ Output ICs that have multiple inputs and protection built in to interface the processors to harsh environment. similar to this MAX6816 used for digital signals.


texts: How do IR rangefinders accomplish centimeter precision without high speed / high cost parts?

texts:
I'm currently working on a system that requires an RF rangefinder with ~15 cm precision, over a range of about 50 meters. My research into the field has shown that I'll need complex and expensive electronics, clocked at nearly 2GHz, to get anywhere near my desired accuracy. 1 / (time for light to travel 15 CM). My question, then, is what method do IR rangefinders (the simple little ones for hobby robotics use) use to accomplish the centimeter precision that they display in such a small, inexpensive package? Is the method that they use something that could translate to RF to power my project?

Background info:
I'm trying to localize an aircraft within a defined box for autolanding purposes (think home-grown ILS localizer). So, I'm currently thinking about the system described here, where the aircraft has a small repeater to throw back any received signals, for a time-of-flight range calculation. 3 ground beacons arranged in a triangle, and you have X,Y,Z coordinates. Obviously IR as a medium is out, because the systems needs to operate in broad daylight, over 50 to 100 meters. I considered using an RF signal strength based rangefinder (beacon on the aircraft with a tightly controlled transmitting power), however between the RF noise from the motors and control systems and the trees and buildings surrounding my testing area, I don't think that is going to work within my required accuracy.


texts: Connecting a supply voltage from linear encoder to camera IO board with a current limiter

texts:
I have a TTL output from an incremental linear encoder which also supplies a 5V output at 140 mA. I would like to use this 5V output voltage to power a camera IO board with RS422 Interface which has a specification of 5V/50mA.

How do I reduce the current from 140mA to 50mA. Can I just use a 150 Ohm resistor or have you got any suggestions ?

simulate this circuit – Schematic created using CircuitLab

Please find the camera IO board specifications below :
Pin......Level.............Description..........Default
1........RS422.............GPIO_P0(input).......Incremental encoder(high)
2........RS422.............GPIO_P1(input).......Lightbarrier(high)
3........LVCMOS............GPIO_P4..............Can be used for lightbarriers
4........LVCMOS............GPIO_P2..............Reserved
5........3.3Vover100Ohm....Power................Output
6........LVCMOS............GPIO_P3..............Master/Slave-interface
7........0V................Ground...............-
8........LVCMOS............GPIO_N4..............Master/Slave-interface
9........RS422.............GPIO_N0(input).......Incremental encoder(low)
10.......RS422.............GPIO_N1(input).......Lightbarrier(low)
11.......0V................Ground...............-
12.......LVCMOS............GPIO_N2..............Reserved
13.......0V................Ground...............-
14.......LVCMOS............GPIO_N3..............Reserved
15.......5Vover100Ohm......Powersupply..........Output


texts:
How can I interface Audio IC PT2314 with 8051 series micrcontroller (AT89C2051). The audio IC requires SCL SDA (I2C Interface) to control. But in datasheet of AT89C2051, there is no hardware I2C pins.

How can I interface this? I am coding in C.
Any example code and circuit would be of great help.


texts: Can a ground plane be used as a current return path? (DC only, no signals, no AC)

texts:
I'm creating an adapter which hosts two connector types and simply routes two connections from one connector into the other.

Only two traces/connections are used; Vcc (about 6v) and GND
Operating current is up to 1A max
Power is DC only, no signals

So my design uses only one "trace", which is for Vcc, while the ground simply uses the entire ground plane, which fills everything on the PCB other than the Vcc trace, as the return path. Both connectors have pins mounted to the ground plane, so it seems to me like it'll be fine (if not best) to just use the ground plane as the return path instead of creating a trace for it which connects to the ground plane at some point anyway. I've never seen a board use a ground plane as the "primary" return path (with no dedicated trace), though, and I'd like to confirm that this isn't some soft of bad design practice.


texts: Can a GPS receive its signal from within the engine compartment of a vehicle

texts: I want to place the GPS and GPS antenna inside the engine compartment of a vehicle. Will the device acquire an accurate fix?


texts:
I've been reading a bit on negative voltage, but I have a question that will probably reveal some ignorance, so I apologize ahead of time.  If someone tells me that they want a (2) 5A breakers, (1) for a +24 circuit and (1) for a -48 circuit, would the same 5A, 80V breaker work for each?  As I understand negative voltage, it's just relative to an arbitrary ground point, so if a piece of dual voltage telecom equipment is pushing out +24V and -48V, wouldn't that breaker be good for each?  Or am I missing something basic?

Thanks.


texts: How to replace a potentiometer with a digital solution in a buck feedback loop?

texts:
I have a simple pre-made buck converter that looks something like this:

The output voltage can be easily adjusted, by turning the R2 trimpot, which adjusts the voltage the feedback pin is getting.

What I would like to do, is to take this mechanical way of setting the output voltage and change it to a digital one, where I can set the output voltage I want with something like an Arduino.

My first idea was to simply rip out the R2 trimpot and replace it with a digital potentiometer, but this turned out to be a no-go, since the digital pots I have (and most cheap digi pots I have seen) have voltage limits of around 0 - 5V, and I will be outputting voltages between 1.2 - 23V (The power source feeding the buck is 24V)

My second idea would be to somehow use an op amp to replace the R2 trimpot, but I have not been able to figure out how to go about this.

What would be some simple way to achieve my goal?


texts:
Background
I'm looking at the RF (LNA_IN) pin of ESP32 as described in esp32_hardware_design_guidelines.
According to this document, the output impedance of the RF pins of ESP32 are (30+j10) or (35+j10) Ω (depends on package), while the antenna impedance is expected to be 50Ω.
It suggests the following π-type matching network:

Now I would like to model (simulate) this circuit to test the impedance matching.
Question 1
To simulate the source output impedance I've added a 30Ω resistor in series to the source. But what would be the best way to model the imaginary part j10?
Question 2
To simulate the antenna impedance I've added a 50Ω resistor. Let's say this is a 50Ω MIFA pcb trace antenna like this one. Does such antenna have an imaginary impedance part and how do I model it?
So I tried this:

simulate this circuit – Schematic created using CircuitLab
Simulating DB(MAG( (V(Out) * I(R1.nA)) / (I(I1.nA) * V(In)) )) on frequency domain:

Question 3
At first glance it more-or-less makes sense (-0.3dB on 2.4Ghz).
What puzzles me is that the result of the simulation is independent of the source impedance value. For example, here I tried to sweep R2 from 0Ω to 100Ω. The graph below looks the same for every value of R2. What am I missing here?

Here is another implementation for the impedance matching circuit I found in another design, probably a "tapped capacitor" matching:

simulate this circuit
Here, a nice 0dB peak on 2.4Ghz, but when sweeping the value of R2 the result remains the same, independent from R2 resistance. So Question 3 applies here too:

Question 4
In general, what would be the considerations for selecting either the π-type or the "tapped capacitor" matching network? The simulation graphs look quite different, I wonder what works best from practical aspects.


texts:
Is there any rule or limitation for the capacitance in the output of a switching dc to dc step down regulator or PMICs?

I mean, could I put the double capacitance in the output to make sure the heavy load responses?


texts: Transformers connected series at secondary side

texts:
For some reasons, I want to connect secondary sides of two transformers in series as you see in the schematics.

Computer simulation is as you see in the graph. (Notice that the corresponding signal values \$V_{out1}\$ and \$V_{out2}\$ are printed at the right side for the graph.)

The two transformers are identical. Their electrical parameters are shown in the image above. Their dot-conventions are shown in the schematics.

The load will not always be resistive; it can be a more complex circuit with an arbitrary impedance value, or it can be a diode rectifier. And, of course, it is assumed that all of the circuit elements will stay in their rated working range.

My question is, would this circuit work in practice? Could there be any instability or any other unpredictable problem? Is there any reason that you wouldn't advice me to use this configuration?


texts: Generating Channel Select for Multichannel ADC

texts:
I am using a FPGA to control a 4-channel ADC (ADC084S101) to sample four different analog voltages. In order to tell the ADC which channel to sample next, there is a control register that can be written with 00, 01, 10, or 11 to sample channels 0, 1, 2, or 3, respectively (See the table below).

I'm not sure if the approach that I'm taking with this module is correct. What my intention is that the module will take the same CS and SCLK signals that are going to the ADC and also a 2-bit number that corresponds to the next channel that is to be sampled. Then, upon each falling edge of CS, reset a counter to 0. On each rising edge of SCLK, clock out the appropriate bit of the stream using the incremented count as an index, either 0 if it's don't care or the 2 bits that correspond to the next channel if at the appropriate index.

module GenerateNextAddr(
input cs,
input sclk,
input [1:0] addr,
output reg dout
);

 reg [4:0] count;
 reg [1:0] currentAddr;

 always @(posedge sclk or negedge cs) begin
    if (cs) begin
        count <= 0;
        currentAddr <= addr;
    end else    begin
        count <= count + 1;
        if ((count != 4'b0011) && (count != 4'b0100)) begin //If we're clocking out any of the 'dont care' bits of the ADC
            dout <= 0;
        end else if (count == 4'b0011) begin
            dout <= currentAddr[1];
        end else if (count == 4'b0100) begin
            dout <= currentAddr[0];
        end
    end
 end
endmodule

I am struggling to get the Verilog implemented for outputting this bitstream (I am a software developer that has only been working with Verilog for  a few months). The Verilog module that I have written above is not synthesizable and I'm not sure why (my development board is a Nexys 3 from Digilent). The error message is, "Assignment under multiple single edges is not supported for synthesis."


texts: Can I use individual strands in cat5 or cat6 solid core wire for pcb mods / jumper / repairs?

texts: I have a small PCB repair I need to make. I am reading that wire-warp is a suitable option. I don't have any wire wrap, but I do have tons of cat5 and cat6 solid core wire. I was thinking about gutting one of those and using an individual strand from  as a jumper. Is this a bad idea? Or is this a case of if it works then it is a good idea?


texts: Half-wave rectifier with resistor and inductor load

texts:
I am studying a half-wave rectifier with a resistor and inductor load.
It is commonly taught that the diode conducts when it is forward biased-  that is, the anode voltage is greater than the cathode voltage. The half-wave rectifier with a resistor and inductor seems to violate this.
Why does the diode continue to conduct even when the source is in the negative half cycle?


texts: Pulling power off a battery stack at different voltages

texts:
If I'm powering a device with a series-connected stack of rechargeable batteries, can I pull different voltages at different points and route them to different components?  I need to run a 12V solenoid, an Arduino (6V-12V recommended), some stepper motors (around 5 or 6V), and possibly a servo (though that can probably come straight off the Arduino).

If I have, for example, four 3V cells, can I grab 6V from two of them and 12V from all four at the same time, or will that do bad things to the cells' relative charge?  Space and complexity are constraints here, so adding a regulator might be possible but would make things more complicated.

Alternatively, would using higher-capacity cells adding up to 6V and a boost converter to get the 12V work?  I'd be concerned about current, but my fears might be baseless.


texts: What are the functional differences between monolithic and disc ceramic capacitors?

texts:
I've inherited an older part numbering scheme, in which ceramic capacitors are divided into disc and monolithic types. Is this actually a firm division in their characteristics? If so, what are the differences? Is that nomenclature common, or are other names used more often? Are there other classifications of ceramic capacitors in addition to those two?

Edit: If I have two capacitors, a monolithic and a disc, of equal voltage and capacitance, why would I use one over the other?


texts: Strange behavior of the DALI controlled luminaires

texts:
I faced a strange behavior of a DALI controlled LED luminaires circuit. I have 48 LED luimianires with a MeanWell ELG150-C700-DA drivers connaected according to the scheme below:
I commissioned the system and it works OK but sometimes I can't switch some luminaires OFF via the DALI commands. When I send DAPC 0 or OFF command this luminaire go OFF, but in a second the go back to 100% of their output. Besides that this problem is floating, because in a different days different luminaires start to work in a such way. Moreover sometimes ALL luminaires go ON spontaneously.

I doubt that the problem is in LED drivers because when I tested some other drivers from the same bunch, everything was OK. I think that something is wrong with the DALI bus installation quality, but I don't know from where to start the thoubleshooting.

I am a novice in a DALI theme, could you advice me what parameters I should check to find the root of the problem?

Here is a DALI signal at the beginning of the DALI bus near the 905 router

By the way why the signal amplitude for 2 DALI packets is different?


texts: How to discover reliable speed to use a logic gate?

texts:
It seems to be very hard to get consistent numbers for the performance of logic chips. I am interested in using the SN74F574 component (8 bit register).

Looking at DigiKey, when I search for the component it shows a results grid with a clock frequency of 100Mhz and max propagation delay of 8.5ns. This is inconsistent as 8.5ns is equal to 117Mhz, a not insignificant difference in my opinion. Should I take the lower of these two numbers?

So I open up the datasheet of the component and inside it has a grid showing the propagation delays. The maximum value in the grid is 35ns and so surely the only safe way to use the part is to ensure you can handle the maximum. So that would give an actual speed of 28Mhz.

So do I clock at 28Mhz, 100Mhz or 117Mhz? Why don't datasheets make your life easy and specify a clock speed (or the matching ns) that it can be clocked at?


texts: Second Order Passive RC Low Pass Filter Doesn't Have -6dB at cutoff Frequency in LTSpice

texts:
For Second-Order RC filter the cutoff frequency is: $$fc = \frac{1}{2\pi \sqrt {R_1C_1R_2C_2}}$$

I have taken R1 = R2 = R = 1K Ohm and C1 = C2 = C= 0.1591 micro Farad. So the cutoff frequency comes out to be 999.717 Hz or approximately 1KHz.

Now according to this article the gain of the n-order filter at its cutoff frequency is given by: $$\left(\frac{1}{\sqrt 2}\right)^n$$

It is a second order filter(n=2) so the gain should be -6dB (and similarly for 3rd order filter it should be -9dB). But when simulating the filter in LTspice it shows differnt result.

Filter Circuit:

LTSpice Bode Plot:

Here in the plot, it can be seen that at the cutoff frequency, at v(p001) the gain is -6dB and at V(p002) the gain is -9dB. But according to the theory, the gain at V(p002) should have been -6dB.

Also, according to its transfer function $$H(s)=\frac{1}{(sRC)^2+s(3RC)+1}$$
the gain at cutoff frequency comes out to be -19.08dB

Three different results

-6dB according to the formula
-9dB in LTspice simulation
-19dB according to the transfer function.

Why is it so? What am I doing wrong?


texts: How to convert a temperature readout to a K-type thermocouple voltage? (reverse thermocouple converter)

texts:
I am working with a commercial heating controller device which takes in a thermocouple input in order to regulate the heating temperature. However, in some cases, the thermocouple junction just isn't suitable to accurately measure the temperature being generated by the heating element -- the only method to reliably measure the temperature in that case is an infrared camera.

Now, the infrared camera gives out readings through serial communication to a computer... and I have no way to give this input to the commercial controller which takes ONLY thermocouple input. Due to this, I am forced to manually read the temperature from the Infrared camera and control the output by hand which wastes a lot of my time and ends up with terrible temperature control.

So, is there an easy way to rig up/buy something which can easily convert a temperature readout to a thermocouple output? This is an exact reverse of the traditional thermocouple readout ICs which are available in plenty in the market.


texts:
I am working on a project which involves using an Arduino Mega, and I am trying to use an NMOSFET (BUZ101S) and an NPN BJT (2N3904) to drive the 5V output from the MCU back and forth between 0V and 12V across "SOL".

At the moment, the problem I have is that Vgs always stays high, thus driving SOL on all the time, and I cant figure out why this occurs.

Here is my circuit diagram:


texts:
The project is design of both LowPass and HighPass sections (2 poles, freq range 10Hz-1.5MHz, Gain=1, moderate Q<1, equiripple filter), variable cutoff freq selected by analog mux (e.g. DG408). Focused on Multiple Feedback and Sallen-Key schemes. Selected first MFB when last cutoff was about 100kHz; now need to push to 1.5 MHz.

Q1:  MFB, using OpAmp as integrator, is more demanding in OpAmp performance than SK, correct?

Thought to move to SK in the attempt to exploit better OpAmp bandwidth, that represents a hard constraint (cannot be stretched). Presently, I have selected AD8065: FET input, 145 MHz BW, stable offset. Hard to find better ones for BW, noise, temp stability.

SK has issues of input->output leakage, reduced attenuation in stopband, and some noise problems (minor) synthesis of Sallen-Key issues.
What is relevant is the "kick" at high frequency beyond cutoff that is caused by combination of i) increase of OpAmp Zout, ii) mentioned leakage, iii) insufficient OpAmp GBW product.
Texas Instrument paper gives some insight in these limitations (see e.g. Figure3) without clarifying and distinguishing.

Zout of AD8065 is 0.01ohm up to 100kHz, then increases 20dB/decade.

Q2: Do you have any ref/info for influence of GBW and Zout on filter response?

Zout to be compared to XC2 and R2 in LP and HP, respectively, correct?
designed filter has G=1; Zout is given by Analog Devices for OpAmp G=1, that's not the same;
found "unofficial" rule for GBW to be > 10 x filter cutoff: too low; imho I would go for a margin of 50-100 times.

Q3: For the said I->O leakage, in EDN article it is suggested to add an input RC stage (going to a 3-pole filter). The added stage is not buffered by additional OpAmp, but seems incorporated in the design of the 2-pole stage. Correct interpretation? Have you ever verified this method?

Thanks!


texts: Am I risking damaging this LED backlight?

texts:
I have a 12 key matrix keypad with an LED backlight that I am wiring up with an Arduino. The datasheet for it is here;

http://www.farnell.com/datasheets/1359150.pdf

It states pretty clearly that the LED has Vmax = 4V and Vnom = 3.5V. I take this to mean that I should power the LED with 3.5V and never more than 4V. Is this correct?

The Arduino puts out 5V and I am able to use a resistor to drop the voltage to about 3.2V (measured with a multimeter). The problem with this is that the backlight seems fairly dim at that voltage. If I power it directly with 5V (for short periods of time) the backlight seems nice and bright and how I would like it to be. If I leave it like this will it eventually damage the LED? I plan to get some more resistors to try to get a voltage closer to 4V but I don't have any to hand just yet.


texts: Bypass capacitor selection for <100MHz PCBs

texts:
For general purpose PCBs that consist of an MCU (simple 8-bit, 20MHz), switching vreg (1.5MHz), and perhaps some SPI and I2C clients (such as sensors, wifi, gps modules, etc), what are recommended and typical baseline capacitors recommended to place near the power supply pins of each component?

I realize some ICs provide some recommendation on their datasheets, but many of them don't.

Assume, that the maximum inter-IC frequency is on the order of MHz (perhaps 1-4MHz at the most).  Although it also matters that the actual transistor switching frequency inside these chips is equally (perhaps more) important.

I've seen references of adding a few capacitors at each IC, differing by "decade capacitance".  In the past, I've typically just used 10uF in parallel with 0.1uF, MLCC capacitors, which seems to have worked.  However, I'd like to know if there are other recommendations.  How about adding a 1uF or a 0.001uF in parallel as well?

I suppose the answer to this question depends on trace length, possible noise sources, IC characeristics, etc...but assume general/typical/average case.


texts:
I have an image below of a leaky bucket image that I am trying to understand for my telecommunications class, and I was hoping for some guidance/verification if my train of thought is on the right track.
I am trying to determine the average and peak data rates, maximum burst length (bytes), and the time taken to transmit this maximum length burst.
Bucket 1:
Is it correct to say that the maximum capacity of this bucket is N1 = 700? I am not sure what the unit of this capacity is, I think it might be tokens - Is this correct? Can I say that in this case, tokens = packets, as the image states '1 token per packet'? Also, a new token will arrive at bucket 1 at a maximum rate of 480 us - Is my understanding correct?
For bucket 2:
The bucket can only hold 1 token, and a new token can arrive at bucket 2 at a maximum rate of 80us.
I was wondering, is there any way I can determine the rate at which tokens are released from each bucket? The rate of arrival for each bucket is given, but I am not sure about the rate of release.
I appreciate any guidance and help. Thank you :)


texts: Identical CP210X USB-Serial converter conflict?

texts:
I am troubleshooting an Ubuntu 14.04 system that has two serial devices connected to it. They both have identically configured Silabs CP2102 USB-Serial converters.

Device #1 reads inputs
Device #2 outputs data

I am seeing errors that are tremendously difficult to troubleshoot in terms of Device #2.

So my question is: Can identically configured USB-Serial chips ever have conflict?

Here is the ouput of usb-devices:
{Identical outputs besides the top line of each}

T:  Bus=01 Lev=02 Prnt=02 Port=01 Cnt=02 Dev#=  7 Spd=12  MxCh= 0
D:  Ver= 1.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=10c4 ProdID=ea60 Rev=01.00
S:  Manufacturer=Silicon Labs
S:  Product=CP2102 USB to UART Bridge Controller
S:  SerialNumber=0001
C:  #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=100mA
I:  If#= 0 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=00 Prot=00 Driver=cp210x

T:  Bus=01 Lev=02 Prnt=02 Port=03 Cnt=03 Dev#=  6 Spd=12  MxCh= 0
D:  Ver= 1.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=10c4 ProdID=ea60 Rev=01.00
S:  Manufacturer=Silicon Labs
S:  Product=CP2102 USB to UART Bridge Controller
S:  SerialNumber=0001
C:  #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=100mA
I:  If#= 0 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=00 Prot=00 Driver=cp210x

Just wondering if this is normal in the peripheral world.

Thanks,
Roger


texts:
I have the following circuit to condition signals reaching my microcontroller's pins.

This circuit reads both digital signals in the range 0 to 30V, and analog signals in the range 0 to 3.3V.

Components Explanation

R2 and R3 are never populated both at the same time. They are pull-up/down resistors for digital signals.
R1 serves dual role. On the one hand it is part of the RC filter along with C1, and on the other hand it is a current limiter for the D1.
D1 just makes sure that voltage (in signals greater than 3.3V) will be clamped, protecting the uC.

However the D1 zener diode creates a problem. If I choose a 3V6 zener, then higher voltage than desired will reach the uC. If I choose a 3V3 zener, then weak analog signals tend to be clipper earlier (i.e. the zener starts conducting a small current earlier than its rated voltage). To make matters worse even if I could somehow ensure that the voltage will be clamped at exactly 3V3, and for any reason Vcc, is even a bit lower than 3V3, then the ADC will report wrong result.

What I need here is a circuit that will clamp voltage exactly at Vcc, with a sharp transition so as it will not affect the ADC range.

Any ideas?


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I was looking at how to get a sign wave from a 555 chip and found this article.

It seems to say it's using an astable 555 circuit outputting to an LC resonant circuit.

However, the circuit diagram does not match up with any astable 555 circuit I can find anywhere else, and although he has some examples of different value components for different outputs, it might be easier to work with a standard astable 555 circuit.

I found this question regarding alternate astable 555 circuit designs, but the design in the linked article is different again, it doesn't use the discharge pin (pin 7). Functional difference between various astable 555 circuits

Are there benefits to this alternate circuit for this use case? Would you be able to describe how this is functionally different, especially how the RC network he refers to comes into it. Would calculations for resistors and capacitors in other circuits work for this one? Finally, would the LC resonant circuit on the output, calculated for the correct frequency, work for any square wave source, including the standard 555 astable circuit?