texts: Current direction in a circuit with 2 transistors

texts:
I'm a beginner trying to learn electronics reading a book with this circuit diagram:

The text accompanying the diagram states:

  C1 charges through R1 and R2 until the charge on C1 is high enough to turn on Q1, which in turn causes Q2 is then switched on.

What I am having difficulty with is the current path when current is flowing through the speaker.  As I understand the most basic definition for a transistor, a small current at the base allows a much larger current to flow between emitter and collector, like a switch or gate. In the previous example in the same book it appears much clearer that current flows from the 6V source to the collector and then emitter and then to buzzer:

So how, in the first circuit, is current flowing into Q1's collector if it's source is the base of Q2?  I know that Q1 is a NPN and Q2 is a PNP but does that mean current is flowing out of the base of Q2?

At a more general level I am having trouble with picturing current flow for all circuits and want to think of like a linear flow like on a flowchart, but that must not be correct.


texts: External Clock Input to Microchip Microcontroller NOT Gate?

texts:
I'm using a PIC24FJ256GB110 connected via SPI to a CAN Bus Controller chip MCP2515. The MCP2515 requires a crystal connected to it but has a Clock Output pin for driving a connected MCU. So I was going to connect the Clkout from the MCP2515 to the MCU.

My question is that in the osillator data sheet for the PIC24F family of processors it shows this external clock connection with a NOT Logic gate in the circuit. I usually get parts from farnell but struggling with what it is I need for this NOT gate. Can it be any general NOT Gate or is it something more specific then that, like a buffer or some sort of impedance magic? Or is it as simple as a single NOT gate used to "clean" up the clock signal?


texts: Safe I/O voltage levels for Xilinx SP605

texts:
Context

I recently got an SP605 Evaluation board from Xilinx, that sports a Spartan-6 FPGA. (check out this link).

This board has a bunch of User I/O and the two I'm most interested right are the two generic I/O SMA connectors on the top right of the board. As a first test, I tried to use them as output, setting them HIGH when a button was pressed on the board. On a scope, this gives out 2.5V.

The highlighted block (red) contains the SMA I am talking about. It is connected to the Bank 0 @ 2.5V, which matches what I see on the scope.

Question(s)

I cannot find a reference for the SP605's ratings, just for the Spartan-6 and even though the latter can accept / drive 3.3V I/O, I don't think this can be extended to the SP605.

Is it safe to assume that a 2.5V INPUT won't fry anything? (assume of course no voltage spikes/overshooting)
Is there a way to change these I/O levels or are they locked in some way on the board?

Cheers!


texts: Calculating Resistor Value in Voltage Divider

texts:
I am trying to reverse an equation to find the optimal resistor value in a voltage divider. But, when I try to reverse it, it never comes out right and I mess it up.

This is the equation:
$$V_{out}^{DC}= \frac{R_{2}}{R_{1} +R_{2}}*V_{in}^{DC}$$

How do I get the value of R2 if:

$$R_{1}=330\Omega$$
$$V_{out}^{DC}=4.5V$$
$$V_{in}^{DC}=9V$$


texts:
This question leads on from a question I asked last night, so some people will know it.
I am using an FPGA with a 1000 ppr rotary quadrature encoder counting 4x (counting all edges is 4000ppr) and had planned on counting the number of pulses every 1ms. The motor rpm range is from around 1000 or 2000 up to 4000 rpm with no gearbox. The encoder is coupled straight to the motor.
I had planned to use this equation:
(Hopefully someone can edit this :)   RPM = ((Pulses per ms) * 60,000) / Pulses per revolution
However when I run this calculation on a calculator I see a change of 1 pulse per millisecond equates to 15 rpm of the motor.
Does this encoder not have enough ppr for this application, or am I doing something incorrect in my maths?


texts: Ft232rl interface and avr - avr damaged when connecting the ft232rl

texts:
I'm trying develop my own Arduino. I'm  using the ft232rl chip so I can program it over USB. Am pretty sure the chip was working before I connected the ft232rl chip.

My AVR seems to have blown because there's on oscillation on the Xtal pins. Just a straight line. I noticed there's a 1k resistor on the txd and rxd pins. Is that because the chip operates at a different logic level or what?

It's not a cable it's an actually self soldered rt232rl on a breakout board. It's 5V for the system voltage. Am using ATmega328P


texts: Arduino receiving correct audio data from analog input?

texts:
I've connected my arduino's analog input to my phone's headphone jack and am trying to visualize the audio data in the serial monitor. I have read on Arduino's site that the Arduino UNO is able to yield a resolution between readings of: 5 volts / 1024 units or, 0.0049 volts (4.9 mV) per unit so I thought it would be able to pick up audio data from the jack. However, after looking at the data which appears totally random, I am not so sure. Do you think at these low level voltages it is possible to get an accurate reading of audio data? For the project I am working on it's important to collect accurate audio data so I can use it to find a repeated segment of the audio clip. Here is my simple code for printing voltages in Arduino ide.

int analogPin = A0;
int val = 0;

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

void loop() {
  val = analogRead(analogPin);
  Serial.println(val);
}


texts: Parallel Resistor Calculation -- Higher Equivalent Resistance

texts: \$R_1\$ and \$R_2\$ are in parallel. What should be the value of \$R_2\$ if \$R_1 = 100\Omega\$ and their equivalent resistance is \$1\text{k}\Omega\$?


texts: Does the solenoid force formula apply to electromagnets?

texts:
Related questions:

How to calculate the repulsion force between two electromagnets

With what force can a solenoid pull?
What assumptions does the solenoid force equation make?

I am trying to design a simple electromagnet, and I'd like a formula to let me calculate the holding force I can expect from a particular design.
I have seen the usual formula:
\$\LARGE F=(N\cdot I)^2 \cdot \frac{u_0 \cdot A}{2g^2}\$
Where 'g' is reportedly "Length of the gap between the solenoid and a piece of metal". What exactly this means, I don't know. Does this assume we're dealing with an air cored solenoid, or an electromagnet with a mild steel bar inside? From which bit of the solenoid are we measuring the distance? From the end of the metal bar, or from the centre of the coil?

Problem: If we're assuming 'g' is measured from the end of the bar, and the electromagnet is actually holding the object, I.E. touching it, then 'g' is zero, and the resulting force is undefined.
What is going on here? Is it just that this formula doesn't work for electromagnets that are actually holding something?  Does a formula exist for the situation where the object is touching the rod?
(My suspicion is that the formula is for a solenoid with a moving plunger, and 'g' is not the distance marked in that diagram, but something else.)


texts:
I'm working with a transmitting radio connected to two antennas. I understand that the power split between the two should result in a loss of 3dB, but a VNA shows a loss of 5.6dB. Does this mean an additional 2.6dB is lost to heat within the power splitter?

What kinds of modifications can I make on an off-the-shelf power splitter to solve this issue?


texts: Altium Designer "NotFited" in BOM with DNP

texts: I heve problem with Altium BOM document generation. I want have multi variants of one project with some DNP elements. It's no problem if I want remove elements from BOM, for this I can add variants with some elements selected as "Not Fitted" and they aren't added to output BOM. But i want have elements with DNP in BOM for protect myself against mistake when I forgot add element (or elements) which should be mounted. Additionaly when i send PCB to factory with assembly options it's naturally that they ask me whats with missed elements in BOM? When I will add (to BOM) elements with DNP descriptions i resolve this two problems. Do you have any ideas for resolve this problem?


texts: Why common-mode voltage is avarage of two input voltages in a differential amplifier?

texts:
I'm having hard time to understand the motivation behind the common mode voltage in differential amplifiers. I came to learn that common-mode voltage is chosen (v1+v2)/2 where v1 and v2 are input voltages of the differential amplifier with respect to ground.

My question is why engineers developed theoretically something called common-mode voltage And why they chose it particularly as (v1+v2)/2. What is the benefit of all these?


texts: How to develop (and print) a PCB starting from a logic scheme

texts:
I am currently working on a rather simple project: basically I have designed a circuit (only for the logic part, I have used logic.ly) that checks if 4 bits (that in my case are switches) represent a prime number, only using NAND gates.
Now I would really like to turn this into a custom PCB, but I don't know where to start.
I tried looking up on the internet (and I am sure that probably I have missed something,) but the only thing that I seem to be able to find are services to print fully developed circuits, so that means I have to figure out where, how and what electronic components I have to put in the circuit.
The problem is that I don't know anything about why and what resistances (for example) I should use in my circuit. Where do I start? Do you have any guide that I can refer to while designing the circuit?
Sorry if I've gone on too long, but I really don't know where to start.
Here is the logic.ly circuit for reference, if you want to take a look at it (sorry if the circuit looks disorganized, but it is one of the first that I designed.)


texts: How do I decide on a proper PCB ground layout?

texts:
I'm trying to figure out best practices regarding ground layout, but it seems the more I read the less I understand about the subject as many recommendations seem to contradict themselves.
So far I am under the impression that when using a ground plane one should route the specific node through a single via / contact directly to the ground plane. Others seem to recommend that stitching multiple vias to the plane works better since that decreases resistance. From what I've read the latter technique could be prone to introducing ground loops though, which I want to avoid. Right now I'm  lost as to how I should layout the following PCB:

The first picture shows the top layer ground filled and both caps and casings directly connected to that fill.

The second picture shows the same layout as the first, but with an additional ground fill on the bottom and stitching vias connecting both ground layers.
The return is for the 3.3V supply only, the two unmarked connectors in the middle transmit the balanced signal to a differential amplifier down the line.
I am under the impression that the second way would be overkill for this example, but I'm trying to learn what would be the best practice here.
Many thanks in advance!


texts:
I just receive 4 A4988 drivers, I plugger one like this and it totally ignore the step signal, the motor just turn according to the dir pin.

except I put the MS1, MS2 and MS3 to GND, I left /enable floating.
So if I connect step to GND, VCC, or send it a square signal it just keep the motor spinning according to the DIR pin level.
I tried 3 of them they all produce the same result.
Did I do something wrong?
Thanks.
PS : link to the A4988 manual : https://www.pololu.com/product/1182 and datasheet https://www.pololu.com/file/download/a4988_DMOS_microstepping_driver_with_translator.pdf?file_id=0J450
EDIT
Turn while ignoring step :
DIR to GND:

Step grounded: turn clockwise
Step to VCC: turn clockwise

DIR to Vcc

Step to grounded: turn anti-clockwise
Step to VCC: turn anticlockwise

Adding a square signal to STEP do not change anything to the rotation speed
The motor and controller came from that kit : https://www.amazon.fr/Quimat-Arduino-Moteur-Imprimante-Compatible/dp/B06XRBSBMV/ref=sr_1_2?ie=UTF8&qid=1509373607&sr=8-2&keywords=quimat+motor
I'm just using a controller on a breadboard with an arduino MEGA


texts: Guided wavelength for a transmission line using MWO TXLINE

texts:
Is it possible to find the guided wavelength for a transmission line using Microwave Office's TXLINE?

I am trying to find the guided wavelength \$λ_g\$ for a transmission line with a characteristic impedance \$Z_0\$.

I think there must be a way to do this using TXLINE but I can't see anywhere to calculate this.


texts: Porting SPI code from (Intel) Galileo to Edison - Arduino

texts:
I'm currently working to port some Arduino sketches from Intel Galileo that use SPI (using a prototype Arduino Breakout board).

I haven't been able to get it to work so far - but I have used an oscilloscope to have a look at what the SPI is actually doing.

I have observed that the SPI clock signals from the Galileo and Edison are a different shape and are also a different voltage (note the scales on the top of the display). I have also noticed that the Galileo's clock is on the whole time whereas the Edison's switches off and on every few seconds.

The top one is the Edison, and the bottom one is the Galileo.

As a software guy I don't really know what's going on here - does anyone know what could be causing this? Is this something I can change in software or is it definitely a hardware thing? And would this be caused by the Edison itself or the breakout board?

Thanks - any help or guidance is appreciated!

Edit - More information

Below are some more images of the clocks running at different frequencies - NOTE: The Galileo (desired behaviour) is now at the top, and the Edison is at the bottom. The scales have been adjusted to be the same.

125khz

1Mhz

4Mhz

It looks like the clock is becoming more and more distorted on the Edison as we increase the frequency - could this be what is causing our problems? Now the overshoot is so dominant that it appears to be at a higher logic level.


texts:
I was tasked to work on an 'RF Detector Circuit' for work. The circuit has an input RF power of 72 Watts at a 7.5GHz frequency through an 8mm wire. It's supposes to reduce that power and voltage, and be able to illuminate an LED. For the LED I was told to use a Lumex SML LX3939WWC-TR, Schottky power diodes, BZX55C9V5 for the zeners and 10W caps. The circuit I was instructed to use is attached below.

It's been years since I've played with circuits and I can't remember how to be able to pick appropriate values for the resistors and caps to be able to couple to the input specs. This is not my primary job either, just something I was tasked with on the side. Any resources pointing me to the right direction would be greatly appreciated.


texts:
I want to compare signals from my fancy subcircuit (very complex) and multiple subcircuits level1 (should be almost equivalent, but simpler) with different parameters; these parameters should be passed to level2 subcircuits.

Below is a (simplified) nonworking sample code:

Xfncy 2 0 fancy
Xlvl10 2 0 level1 PARAMS: Y1=1 Y2=1
Xlvl11 2 0 level1 PARAMS: Y1=1 Y2=10
Xlvl12 2 0 level1 PARAMS: Y1=10 Y2=1
Xlvl13 2 0 level1 PARAMS: Y1=10 Y2=10

.SUBCKT fancy 1 2
* STUFF
.ENDS fancy

.SUBCKT level1 1 2 PARAMS: Y1=1 Y2=2

.param Z10=1 Z20=1 Z11=1 Z21=1 Z12=1 Z22=1

Xlvl20 1 2 level2 PARAMS: Y3=Z10*Y1 Y3=Z20*Y2
Xlvl21 1 2 level2 PARAMS: Y3=Z11*Y1 Y4=Z21*Y2
...
...
Xlvl28 1 2 level2 PARAMS: Y3=Z18*Y1 Y4=Z28*Y2

.SUBCKT level2 1 2 PARAMS: Y3=1 Y4=1
* STUFF
.ENDS level2
.ENDS level1

Running like this, I get the following error:

  WARNING: Can't resolve .param Y3=Z10*Y1

  Select OK to continue the simulation with the default model or Cancel to quit now

My first version of the  instance Xlvl20 line:

Xlvl20 1 2 level2 PARAMS: Y3={Z10*Y1} Y3={Z20*Y2}

yields the same error. If I change the line to:

Xlvl20 1 2 level2 PARAMS: {Y3=Z10*Y1 Y3=Z20*Y2}

I get:

  Missing expression in

  "{Y3=Z10*Y1 Y3=Z20*Y2}"

Is passing parameters like this even possible in LTSpice and if so, how? Alternative approaches are also welcome.

PS: Yes, I've tried .step param to avoid packing level1 stuff into a subcircuit, but then I can't compare it to fancy, because fancy takes about 30 times more time to simulate.


texts: Charging a car battery with two chargers simultaneously

texts:
My car, which has a 12 V silver calcium battery, is flat and I would like to get on the road as soon as possible. I got two car battery chargers that are not identical, but both can operate at 6 and 12 volts.

Is it possible (and safe) to charge the car battery using the two chargers at the same time?


texts:
I recently ordered a 128x128 graphic black/white display with a ST7541 chip-on-glass. It took me 2,5 days debugging and frustration to discover that they didn't wire SPI through the flatcable.

A big trap for beginners, when you use the datasheet of the ST7541 chip as a reference while coding.

So I rewrote my driver to parallel driving mode and everything is up and running now.

This got me thinking what would be the best option performance wise to continue my product development. SPI or 8080 interfacing?

I drive the display with an Atmega329 and we have enough pins to do 8080.
First I thought 8080 would be the fastest, but I'm not sure if PORTD = displaybyte is a very fast and optimized way of putting so much data through.

I guess the SPI architecture and MOSI pin is designed for higher data throughput? Or are they basically behave exact the same way?


texts: Differentiate between mains and a generator

texts:
This question is related to:

Can I differentiate between a UPS, Generator and Main sine wave using a micro-controller?

I'm only interested in the difference between mains and the generator. Essentially for my PoC I'd like to plug a device into the wall and have a green light if it detects mains, and red if it detects it's on the local generator.

If there's no obvious difference I guess we'd have to train each device at each location - present it mains vs generator and it will have to notice some discerning factor. Possibly a difference in voltage, fluctuation, or frequency?

Any thoughts would be greatly appreciated.


texts: LTSpice Simulations require netlist flattening on higher simulation counts?

texts:
As in my previous question mentioned, i am doing bulk simulation with predefined component parameters for a given amount of runs. These are calculated and written to the file via python scripts i made myself.

When i am simulating a high number of runs, the simulation is slowed down by a process of "Expanding subcircuit ...". This only accurs over about 1000 runs and takes longer the more runs i try to simulate.
After a bit of research i found that this is to flatten the netlist of the circuit and since i am using quite a lot of opamps in the simulation this operation makes sense.

But i do not understand why this only appears on high run counts. I could imagine it being required for every simulation and just "showing up" since it got so slow because of a high run count. But then, why does it slow down at high run counts?

Thanks in advance


texts: ADT7410 I2C temp sensor works only after a power cycle (ESP8266)

texts:
I have an ADT7410 temperature sensor connected to an ESP8266 running nodemcu.

The issue I am having is that I can only get good changing data after power cycling the ADT7410. Until that I get either an reasonable fixed temp reading which doesn't change even if I heat/cool down the sensor or 0x0000 (a disconnected sensor results in 0xFFFF). I tried resetting the IC over I2C but it doesn't change anything.

The system consists of a mainboard/daughterboard. This schematic shows the connections between the boards. Unrelated things on the mainboard have been removed.

How could I solve this so that the device starts working after I plug in power without adding a fet to power cycle the daughter board?

NodeMCU lua code:

---------------------
-- Wifi connection --
---------------------

function is_connected()
    print(wifi.sta.status())
    return wifi.sta.status() == 5
end

function block_connected()
    while not is_connected() do
        print("Waiting for connection")
        tmr.delay(1000000)
    end
    print("WIFI connected!")
end

------------------
-- I2C & Sensor --
------------------

I2C_ID = 0
I2C_PIN_SDA = 2
I2C_PIN_SCL = 1

I2C_ADDRESS = 0x48
I2C_TEMP_REG_MSB = 0x00
I2C_TEMP_REG_LSB = 0x01
I2C_STATUS_REG = 0x02
I2C_CONF_REG = 0x03

function adt_reset()
    i2c.start(I2C_ID)
    i2c.address(I2C_ID, 0x00, i2c.TRANSMITTER)
    i2c.write(I2C_ID, 0x06)
    i2c.stop(I2C_ID)
end

function adt_setup()
    i2c.start(I2C_ID)
    i2c.address(I2C_ID, I2C_ADDRESS, i2c.TRANSMITTER)
    i2c.write(I2C_ID, I2C_CONF_REG)
    i2c.write(I2C_ID, 127)
    i2c.stop(I2C_ID)
end

function read_reg(id, dev_addr, reg_addr)
  i2c.start(id)
  i2c.address(id, dev_addr ,i2c.TRANSMITTER)
  i2c.write(id,reg_addr)
  i2c.start(id)
  i2c.address(id, dev_addr,i2c.RECEIVER)
  c=i2c.read(id,1)
  i2c.stop(id)
  return string.byte(c)
end

function get_temp()
    msb = read_reg(I2C_ID, I2C_ADDRESS, I2C_TEMP_REG_MSB)
    print(msb)
    lsb = read_reg(I2C_ID, I2C_ADDRESS, I2C_TEMP_REG_LSB)
    print(lsb)

    val = bit.lshift(msb, 8) + lsb
    if bit.isset(msb, 7) then
        return (val - 65536)/128
    else
        return val/128
    end
end

---------------------
-- MQTT Connection --
---------------------

MQTT_HOST = "rabbitmq-sysd.containers.ikioma"
MQTT_PORT = 1883

MQTT_CLIENTID = "temp-" .. node.chipid()
MQTT_KEEPALIVE = 120
MQTT_USER = "guest"
MQTT_PASS = "guest"

MQTT_QOS = 1
MQTT_RETAIN = 0

mqtt_connected = false

m = mqtt.Client(MQTT_CLIENTID, MQTT_KEEPALIVE, MQTT_USER, MQTT_PASS)

function mqtt_connected()
    print("MQTT connected")
    mqtt_connected = true
    m:publish("/connections", MQTT_CLIENTID, MQTT_QOS, MQTT_RETAIN)
end

function mqtt_disconnected()
    print("MQTT disconnected")
    mqtt_connected = false
end

function mqtt_get_connected()
    return mqtt_connected
end

m:lwt("/lwt", MQTT_CLIENTID, MQTT_QOS, MQTT_RETAIN)
m:on("connect", function(con) print ("connected?") end)
m:on("offline", mqtt_disconnected)

mqtt_ip = ""

function mqtt_connect()
    m:connect(mqtt_ip, MQTT_PORT, 0, 0, mqtt_connected)
end

function mqtt_connect_with_ip(ip)
    mqtt_ip = ip
    mqtt_connect()
end

function main_loop()
    if mqtt_get_connected() then
        m:publish("/" .. MQTT_CLIENTID, get_temp(), MQTT_QOS, MQTT_RETAIN, function(conn) print("sent") end)
        if to_advertisement == 0 then
            m:publish("/devices", MQTT_CLIENTID, MQTT_QOS, MQTT_RETAIN)
            to_advertisement = ADVERTISE_INTERVAL
        else
            to_advertisement = to_advertisement - 1
        end
    else
        mqtt_connect()
    end
end

----------
-- MAIN --
----------

block_connected()
print(wifi.sta.getmac())
print(wifi.sta.getip())

i2c.setup(I2C_ID, I2C_PIN_SDA, I2C_PIN_SCL, i2c.SLOW)
adt_reset()
adt_setup()

sk = net.createConnection(net.TCP, 0)
sk:dns(MQTT_HOST, function(conn, ip) mqtt_connect_with_ip(ip) end)
sk = nil

ADVERTISE_INTERVAL = 10
to_advertisement = 0

-- run "loop" every 10s
tmr.alarm(0, 5000, 1, main_loop)


texts: In a differential pair BJT amplifier, the individual gain of the transistors should be equal. Why am I getting different gain for each transistor?

texts:
Here I have taken a differential BJT pair.  Both the individual gains are different and the output differential gain is also different.

Is there a problem with my circuit? Why is it happening?


texts:
Problem:
 An impedance 1000(1 + i)  Ohms  (and note it contains an imaginary
part) is connected across an AC voltage source of amplitude 10 V
and frequency 60 Hz. What's the power dissipated during one cycle
within the impedance?

Relevant equations:

P = Re(V*I), where V* is complex conjugate of voltage
I=V/Z

Solution Attempt:

So it's alternating current, so I first take the RMS V: 10/\sqrt{2}. Then I = V/Z, so I get

V*I = V*V/Z = 100/2 1/(1000(1+i)) = (1-i)/(20*2). Then I take the real part of this, which is 1/40. Am I doing this right?

Thanks!


texts:
The specifiation of my solar panel are:
Power = 80W
Voltage = 5V
Current = 16A

How can I reduce the current to 8A by using resistor, what must be the value of my resistor?


texts: Someone know if there is a way to program uC via bluetooth? I'm referring to a device that receives an hex/elf file from another BT device (smartphone or PC) and sends it to a uC (xmega in this case) via PDI port.


texts:
I can't figure out how to do a differential amplifier with AC sources. I've built the generic DC one that I was taught in school (see attached image) but it's giving me weird values. For example, it's producing a positive voltage even when the negative terminal has a greater voltage.

My signals are primarily 10 to 22kHz. I would really like to do this with one op amp. Transistors are okay, but I'm trying to minimize the amount of connections that I would need to solder to a PCB.

The op amp is powered by a DC source (single supply, 5V).

Technically, these AC sources are oscillating DC voltages with a voltage offset originating from a headphone jack. What I mean is, the voltage oscillates from 0 to 1 volt. The changing frequency drives a coil next to a magnet inside a headphone. I would like to amplify the difference in sound coming out of the headphones (left minus right) and feed it into a circuit. It's on the order of 100 mW total power. I don't know whether this makes them technically AC or DC, but I'm assuming that this is what's causing the issues with the op-amp.


texts: USB - C connector purely for charging a battery

texts:
I'm looking for an ultra slim charging connector to attach to a li-ion battery pack. All I need are positive and negative pins. I have read that USB C supports up to 5A current. If I get a product like this:

https://www.globalsources.com/gsol/I/USB-C-connector/p/sm/1164613438.htm#1164613438

And something similar for the socket end and if I solder positive and negative of the battery to VBUS and GND of the socket and positive and negative of the charger to same pins of the plug... will I be able to charge my battery at about 2A?

I know it seems stupid to try use a data/power connector purely for charging but I can't find a 2 way power connector close to its compactness.

Thanks in advance!


texts:
I designed a board with a stm32F303K8T uC, but I have some strange behaviours. This is not the first board I designed with this uC and I had never any trouble with this design before. The first uC I soldered on this board I could read out with the STUtility tool, but I could not program it. Then I exchanged the uC, but the same thing happened to the second one. What especially seems very strange is, that the PA15 and PB4 on both uC had a constant voltage of around 1.2V applied, which comes somehow from the uC itself and was measured with an oscilloscope. The voltage regulators seem to work fine, and I don't have much ripple on the 3.3V output. When the uC is desoldered, there is no voltage applied at the PA15 and PB4 pins.

Has anyone an Idea what goes wrong here?

Edit: I tried to put the capacitor C4 after the inductor, but also this seems not to do any change. The Voltage seems anyway very stable and there was never any voltage drop that could cause a shutdown. I soldered a completely new board, where I only added the STM32, the necessary capacitors and resistors and the voltage regulators, but this leads to the exactly same problem. I don't get also why PA15 and PB4 are high when the STM32 is not programmed, this isn't normal, right?

Further here is my layout:


texts: How to prove identities of a boolean equation?

texts:
I have a equation which I'm trying to solve but stuck at a point.

$$(a + b).(\bar{a}.\bar{c} + c).(\overline{\bar{b} + ac}) = \bar{a}.b$$

This is what I've tried so far,

$$(a + b).((\bar{a} + c).(c + \bar{c})).(\overline{(\bar{b} + a). (\bar{b} + c)})$$ $$-->c + \bar{c} = 1$$
$$(a + b).(\bar{a} + c).(\overline{(\bar{b}.\bar{b})+(\bar{b}+c)+(a.\bar{b})+a.c})$$

I feel like there's a mistake here. Any help is appreciated.


texts:
First, a video:

longer, higher quality

This is a closeup of my TV, of a still picture (the Xbox One menu)

There is no motion, the TV has all filtering, sharpening, etc disabled.

Could it be that the TV can't make the color range needed so it toggles pixels to approximate it? I remember software on the Atari ST and Amiga toggling between to images to approximate extra colors.

The TV is a LCD TV and the connection is through HDMI.


texts:
I'm trying to dig up the "rule of thumb" value for what a telephone company would consider acceptable path loss when they run a new line out to a customer. I spent a lot of time in digital telephony but the number for a regular voice line is eluding me.

I'd always considered 3-4dB to be the number, but some of the articles I'm pulling up are saying 5.5dB to even 8.5dB as within spec.  This seems to be an awful lot of loss which would translate to quiet audio. I know the actual path loss varies with the length of the loop, but there are typical and maximum values that I'm trying to find.

Does anyone have any rules of thumb or experience in this area? What is the typical path loss of a telephone line and at what level of attenuation will a telco actually do something to remedy the situation?


texts:
I am working on a university project at the moment.
Creating a pulse oximeter by using a red and an infrared led to shine on a phototransistor coupled common emitter.
The result is that when no finger is present = ~ 0V on the output
When finger is present =~ 4.9V oscillating with +/-200mV.

This signal (the pulse) I need to amplify and offset as input to my ADC/Microcontroller. I have limited space to the circuitboard (40x40x30mm). Looking a calculations for RL or RC circuits result in physically large components which is not an option.

Question: How can I design a Highpass or Bandpass filter with common uni components in this reduced space? My primary goal is to remove the DC component for easier offset and amplification.

Question: Can I use electrolyte or tantal capacitors for this?

Edit: Signal is heartrate in the range of 2/3Hz to 5Hz.
Edit: Since the microcontroller only accepts analog input in the range 0-5V I want to cut away the dc components before the op amp so I can use the 10 bit ADC fully

Best regards.

Edit:

Description: LED1 is the phototransistor, C1 and R6 form the highpass filter, R2 is voltage offset. Non-inverting Op amp with gain of (1+((R4+R5)/R7) = 150. C2 and R7 form a similar highpass filter.

What I was hoping for:
Output of Phototransistor when fully illuminated ~ 2.5V due to the voltage divider of R2+R6.
Output of phototransistor when finger is detected => 2.5 +/- AC signal of heartrate/pulse between 0.67 and 5Hz roughly.

Op amp's job = amplify the AC (~200mV peak to peak) to 2V peak to peak.
Since the Op amp serves as input for the ADC/Atmega microcontroller, is impedance still an issue?
And why is this not working as intended? Output has massive noise from 10Hz to 3kHz.
and voltage when "no signal" is not sitting at 2.5V as hoped

Edit:I was able to find the components needed to create a highpass filter, even a ceramic capacitor since the electrolyte ones as I read had other issues.

Testing the parts separately (Sensor I/O), Highpass filter and amplification circuit worked, although together did not show the desired results.

Going to rework a simple solution which will result in less bandwidth of the ADC input.


texts: How Does an Unearthed Socket Close its Circuit?

texts:
From what I'm to understand, earthed sockets send their electrons (through the neutral wire (assuming no fault)) to the circuit breaker which is then wired to earth ground. How does this work in unearthed sockets/breakers if there is no earth ground? Where is the rest of the circuit going, back to the power station?

Update 0:
I was talking about wiring in the U.S.; my bad.


texts:
I have an application to sense magnetic north and position. GPS works well for position but cannot determine orientation without spinning the object 3 times.
My application is stationary and I cannot spin anything.
Is there a magnetic sensor that can detect the earth's magnetic north pole?
Thanks,
Stu


texts: Help with designing a circuit with TEC3-2419 DC-DC Converter

texts:
I'm designing my first circuit and I have to use the TEC3-2419 DC-DC converter (datasheet) to convert 28V to 9V.

Until not long ago I used to work as a hardware tester where I tested and troubleshooted circuits that use completely different buck converters, such as this one.

When I looked at the datasheet for these buck converters, I saw there are one-by-one steps on how to properly design the part of the circuit with the buck. For example, how to choose the right inductor value, choose input/output capacitor, etc...

The datasheet of the TEC3-2419 does not provide those kind of instructions and this leads me to confusion about how to properly design this, which is why I have these questions:

Why do I have Vout(+) and Vout(-)? From what I know about buck converters there are multiple switching pins, okay, but why both positive and negative Vout pins?
Do I need an inductor at the output? If so, how do I calculate the value?
I suppose it would be a good idea to connect bypass capacitors at the input and at the output. How many do I need and what should be their values?
Pin #3 is On/off. Does that mean EN pin? If so, should I put a resistor between this pin and the VCC pin (again, something I saw in previous buck converters). What value should the resistor be?
What is the difference between single and dual as noted on page 4 of the datasheet? Or, is there a website you can direct me to? I have Googled it but couldn't find any information about this.

Thank you!


texts: Why are these instrumentation amplifier circuits equivalent?

texts:
I am confused about the circuit of an instrumentation amplifier. In class we solved the following example:

simulate this circuit – Schematic created using CircuitLab

No big deal; with negative feedback we say that V+ = V- on the op-amps and find the voltage using KCL. However, the professor waved his hands and said due to symmetry, it is equivalent to the following circuit:

simulate this circuit

The difference is that that ground is removed and the two resistors are connected. I don't understand how this would be equivalent. Current would flow from node A to node B or vice versa. It would completely change the calculations. I've been working through the equations and I get an ugly mess of equations, not the elegant solution: $$\frac{R_4}{R_3}\left(1+\frac{R_2}{R_1/2}\right)(V_2-V_1)$$

My question is, why does this work? Why doesn't connecting the two resistors change everything like I think it should?


texts: Can't write to GSM module through Serial connection from ARM board

texts:
In our Graduation project, we're supposed to connect a GSM module (ADH8066) to our ARM board (OK-6410) which is running Embedded Linux (Qtopia) and communicate with it.

When we first operate on the module, it sends a "Ready" message, then we can communicate with it through AT commands. We've communicated with it successfully using Hyper-Terminal and managed to send a simple SMS.

The problem happens when we try to communicate with it from the ARM board.

We manage to receive the "Ready" message, but then we don't have any response.

Here is the code we've developed till now:

int main(void){

    int fd;
    char *dev ="/dev/ttySAC3";
    struct termios options;

    char buffer[20];
    char buffer2[20];
    char *bufptr;
    char *bufptr2;
    bufptr = buffer;
    bufptr2 = buffer2;
    int nbytes,nbytes2=0;

    fd = open (dev, O_RDWR | O_NOCTTY);

    tcflush(fd, TCIOFLUSH);

    tcgetattr(fd, &options);

    cfsetispeed(&options, B115200); //Set Baud-rate to 115200
    cfsetospeed(&options, B115200);

    options.c_cflag |= CLOCAL | CREAD; //Enable the receiver and set local mode
    options.c_cflag &= ~PARENB; //No parity (8N1)
    options.c_cflag &= ~CSTOPB;
    options.c_cflag &= ~CSIZE;
    options.c_cflag |= CS8;
    options.c_cflag &= ~CRTSCTS; //Disable hardware flow control

    options.c_lflag |= (ICANON | ECHO | ECHOE); //enable input-canonical mode

    options.c_iflag = IGNPAR; //Ignore parity errors
    options.c_iflag &= ~(IXON | IXOFF | IXANY); //Disable software flow control

    options.c_oflag &= ~OPOST; //disable output-processing mode

    tcsetattr(fd, TCSANOW, &options);

    printf("Hello GSM\n");

    tcflush(fd, TCIOFLUSH);

    //capture the "Ready" message
    while(1){
        nbytes = read(fd, bufptr, 1);
        if (0!=strstr(buffer,"Ready")){
            printf("\nReady Found!\n");
            break;
        }
        bufptr += nbytes;
    }

    tcflush(fd, TCIOFLUSH);

    // send simple "AT" AT command
    int y = write(fd,"AT\r\n",4);
    if (y==4)
        printf("Written\n");

    //trying to capture the "OK" response for the above AT command
    while(1){
        nbytes2 = read(fd, bufptr2, 1);
        printf("%c\n",*bufptr2);
    }

    return 1;
}

we got this response:

Hello GSM

--- Ready Found! ---
Written: 3

and then it blocks and stays idle.

If we manage to capture the "Ready" message, doesn't that mean that "read" is working fine?
and If "written" is printed above, doesn't that mean that "write" is working fine?

So, why can't we communicate with the module?

Thanks.


texts: PCB HDMI high speed routing suggestions on my layout

texts:
I would like to get suggestions from all the high speed PCB layout experts on my PCB design.

I have a board with HDMI transmitter IC whose output is going to HDMI switch IC. The switch IC also has an HDMI input coming from a HDMI connector.
The output from switch IC also goes to HDMI connector as well. So its a 2:1 switch.

The switch IC seems to works fine and it switches when enabled. On the HDMI transmitter IC side, my HDMI output only works on TV or displays which are <=32 inches. Any bigger display like 50" or 55" inch TV of any brand would not work with when it switches to HDMI transmitter side, but it works fine when its switched to other input coming from the HDMI connector.

In my Rev A layout, I had my differential pairs going through 4 layers, and they were longer than 2 inches. I believe its a signal integrity issue on PCB layout, where on higher resolutions it didn't work on the HDMI tx side of output.

So I made some changes in my PCB layout in Rev B and made differential pairs shorter and only kept them in top and bottom layer.

"Side Note: HDMI tx works fine with bigger displays on evaluation board."

Below is the picture of my Rev B PCB layout. In the picture, yellow arrow shows the HDMI tx IC, and white arrow is pointed to HDMI switch IC.

Now is the second picture, white arrow again shows HDMI switch IC, but with both HDMI connectors on the other side. HDMI connector on top left is input and HDMI connector on the top right is output. This side of the layout is also new and needs verification as well.

On my PCB layout I also made sure to match impedance, differential pair lengths, and followed all the high speed rules.

I would really appreciate your suggestions on the layout so I can make sure it would work in Rev B.

Thank you


texts: How to view the internal signals of module in ModelSim using the testbench?

texts:
I have looked over this tutorial (Tutorial - Using Modelsim for Simulation, for Beginners.
) how to add waves and write test benches for VHDL module
I looked over some answers as well like this one to find out but I could not use it.
Quartus, Modelsim, VHDL - Viewing Internal Signals
Now, if I want to add some internal signals and view them, how can I do since I am using the vhdl code as components in the testbench?
and to clarify it well, here is the code of the module:
 library ieee;
 use ieee.std_logic_1164.all;

 entity and_gate is
 port (
 input_1    : in  std_logic;
  input_2    : in  std_logic;
 and_result : out std_logic
 );
 end and_gate;

 architecture rtl of and_gate is
 signal and_gate : std_logic;
 signal not_and  : std_logic;
 begin
 and_gate   <= input_1 or input_2;
 and_result <= and_gate;
 not_and    <= not and_gate;
 end rtl;

and here is the code of testbench
library ieee;
use ieee.std_logic_1164.all;
 entity and_gate_tb is
 end and_gate_tb;

 architecture behave of and_gate_tb is
 signal r_SIG1   : std_logic := '0';
 signal r_SIG2   : std_logic := '0';
 signal w_RESULT : std_logic;

 component and_gate is
 port (
  input_1    : in  std_logic;
  input_2    : in  std_logic;
  and_result : out std_logic);
 end component and_gate;

 begin

 and_gate_INST : and_gate
 port map (
  input_1    => r_SIG1,
  input_2    => r_SIG2,
  and_result => w_RESULT
  );

process is
begin
r_SIG1 <= '0';
r_SIG2 <= '0';
wait for 10 ns;
r_SIG1 <= '0';
r_SIG2 <= '1';
wait for 10 ns;
r_SIG1 <= '1';
r_SIG2 <= '0';
wait for 10 ns;
r_SIG1 <= '1';
r_SIG2 <= '1';
wait for 10 ns;
end process;

end behave;

and here are my signals are all went to red eventhou I added their waves:


texts: Is there any reason why Q11 is left out on 4060 IC? I've read it was done to extend the max pulse time (highest clock divider) but why was it done on Q11? Why not Q12 and therefore have a full 8-bit counter (Q4-Q11)?


texts:
I feel a bit silly asking this..

I have a relay, which has a switch that turns it on/off.
Next to the switch I have an indicator light which needs to turn on when the switch is turned on.

I tried putting the LED in parallel (seen below) and in line, but no luck.

What am I missing here?

(by the way, the 22k resistor is a good value for this LED at this voltage)


texts: Switching two optocouplers based on different voltages

texts: I want to build a (I think) simple circuit where I want to transmit the state of two switches across two wires (ground and live). Let's say I have a circuit with which I can set three output voltages between these two wires from the two switches (switch A pressed, switch B pressed, both pressed): 1V, 2V and 3V. How would I go about driving two optocouplers so that when the 'input' voltage is 1V, optocoupler 1 is 'closed' (if that's the right word); when the input is 2V, optocoupler 2 is closed; and when the voltage is 3V, both are closed? Thanks.


texts:
in the process of building a class D amplifier I am now stuck at the point in which I have a lot of audible noise and I don't know where this is coming from.

I know there could be a lot of causes but I want to be sure about the pcb design. I read something about ground current loops but I don't understand how to design the pcb in order to minimize this issue.

My pcb is basically divided in 4 areas:

Power supply regulators and caps
Input signal conditioning (jfets, opamps, ...)
The digital part (ADC, PWM) at low power
The power stage (mosfet drivers, inductances, ...)

My specific questions are:

1) In order to minimize noise in the Vsupply and Gnd pins, should each of these areas have their own ground plane? Connecting the 4 gnd planes at the supply gnd.

2) If the gnd current loops are caused by gnd plane points at different voltage, would be better to increase the number of gnd connections from the power supply to the pcb (in order to make the gnd voltage more stable)?

Thank you


texts: Determine best op-amp order for PCB design

texts:
In my current design, I use 3 op-amps from a quad package (DIL 14). One is not used. For the design, it doesn't matter which op-amp is used when, since they should be identical.

For example, I'm currently using the amp 1 first, amp 3 second and amp 2 third because this was easier on breadboard. However, it may well be possible that on PCB it's more convenient to use amp 3 first, amp 4 second and amp 1 last.

Now I want to make a PCB out of it. How can I see or calculate which op-amp can be used in which stage for the best (when in doubt, shortest total wire length) PCB lay-out? Drawing all of them would take 4! = 24 drawings. I'm looking for a more efficient method.


texts: Review of PCB Design Requested: AC/DC Converter to ESP32 Module to Control a Relay

texts:
I am designing a circuit board that will sit in an enclosure that will eventually sit in a garage to control a dust collector via an external relay. I have designed the PCB and I just wanted to make sure I have considered all the safety concerns when it comes to AC to PCB board that humans interact with using push buttons.
PLEASE PLEASE BE AS CRITICAL AS YOU COULD!!
Some info:

AC input will only need to handle a max of 3 Amps (Trace Width is currently 60 mils external)
The MCU is an ESP32 DevKitC module
The 433MHz Receiver is a basic breakout board (433Mhz Rf Transmitter and Receiver Module Board Link Kit)
AC line inputs are coming in with a wire-screw to board connector.
The AC/DC converter is a RAC03-05SK which converts from AC (85VAC-265VAC)

Concerns:

How do I protect our kind human when they are interacting with the module (say pressing a button) and to ensure no AC wondering current just flow through them. I have access to the Earth but I am unsure what I should do with it or where to connect it.
Is my DC ground bottom pour good enough?
Since this device is going to be in a garage I am sure dust will be involved. Is there anything that I need to be worried about when designing for a place that has pollution and if so what kind of worry should I have?
Do I need any fuses?

I know this might be a very simple design but I just become concerned when it involves AC. DC I am not too worried. Any suggestions, recommendations and any critiques are much much MUCH appreciated!
Thank you so much in advance.
Here is a picture of the PCB design with the ground pours shown:

Here is a picture of the PCB design without the ground pours shown:

The overall schematic:

EDITs for anyone that might find this helpful! Please review the answers for details:

Removed the AC part of the circuit and just moved it to a wallwart which is much safer and less liability! Thanks @Kyle B for your help!


texts:
What is the difference between embedded systems and control systems?
I have to choose my future career and I don't now the difference.


texts: USB PD Power Delivery Skip 9V Requirement

texts:
Is there any way possible to implement a USB C PD port that only sources 5V and 15V? As I read the spec (USB Power Delivery Specification Rev. 3.0, Version 1.2, June 21, 2018) it seems that I cannot avoid the 9V requirement. Section 10 page 556.

https://www.usb.org/document-library/usb-power-delivery


texts: How to put several nRF24L01 adapters (+module) on a breadboard?

texts:
I want to use several nRF radios together with an adapter like this:

Also, for the device I'm using these for (two nRF's) also I have other components which I put on a breadboard.

However, the nRF adapter does not have pins so I cannot stick it in a breadboard, but I want to keep it together. I don't like two nRF's dangling when I move the breadboard for example. Also, there does not need to be a connection from the nRFs to the breadboard.

Is there some smart idea how to connect such adapter to a breadboard? Glueing to the breadboard is not an option, since I want to reuse the breadboard.
I was thinking about glueing it to IC sockets and stick them in unused holes in the breadboard but those sockets are not meant for breadboard... I can use tape maybe, but probably I'm not the first one having this 'problem' and there are better ideas.


texts:
I have a question about the secondary protection schemes for ESD for the I/O inside integrated circuits.

I understand the purpose of the two clamping diodes closest to the I/O pad.
Q1: Why is there a resistor R_ESD and then another two clamping diodes closer to the inverter? I understand that the two additional diodes are for secondary clamping closer to the inverter but what is the purpose of R_ESD?
Q2: About ESD strikes in general - I see in several places, they talk about a strike being 1000 V and also a certain amperage. Why do they sometimes specify a certain current, won't that be dictated by the resistance that the strike voltage sees?


texts: What is the specification need to be followed for SPI

texts:
I dont think we have a standard specification for for SPI unlike CAN and LIN.
After Googling it found that motorola SPI and TI SPI are more commonly used but not able to find the referance documents
How do I get the motorola or TI SPI documentation so as to know the differences and their implementation ?


texts: LiPo charging circuit to supply 1mA peak current, to charge a custom 1mAh LiPo cell

texts:
I am searching for a schematic or design that would help me charge a very small 1mAh 3.7V LiPo battery. I've done a pretty thorough search and the closest off-the-shelf IC I can find provides 10mA minimum current. My LiPo is only rated for 0.5C-1C charging, so ideally I'd like to charge it with 0.5mA max current to be safe. I've already tried using a really large resistor attached to the standard PROG pins of various LiPO charging ICs, but it doesn't work because 1mA is so much lower than the minimum 100mA. I have not tried with the 10mA charging IC, but I imagine similar behavior could be expected.
One thought I have, is potentially using the 10mA minimum current LiPo charging IC I found here and connecting a constant current sink to the output, set to sink 9mA or so. I believe this may interfere with the chip's auto shut-off feature though and cause risk of overcharging. There may be a way to add some shut-off logic based off of the CHARGE output of the IC, where I could shut off the current sink thus shutting off the entire circuit.
I really hope that creating a LiPo charger from scratch is not necessary. However, I have minimal experience with electronic design (primarily software engineer) so I am not sure how difficult or not this would actually be. I am able to create and route PCBs, but to do so I need help with a schematic to accomplish this 1mA peak LiPo charging current and this is what I am struggling with. Any help here would be greatly appreciated!


texts: Linear aproximation of an inductor in a switch circuit

texts:
Most of DC-DC switching circuit analysis uses linear approximation of an inductor voltage and current according to graphs below.
If we use basic formula for the inductor,
v = L di/dt
It is clear that linear changes in current produces constant voltage so from mathematical point of view it is clear.
However, I have trouble to fit this concept into the physical picture of the inductor, knowing that the transient changes on a inductor are described with an i(t) = I(1-e(-t/Tau)) and i(t) = Ie(-t/Tau).
What troubles me is the constant voltage of the inductor given in a approximation.
When the inductor is connected on DC power supply it will build magnetic field, which induces voltage that opposes to the source voltage, which than produces current that opposes the original current.
So the original current through the inductor cannot raise nor decline instantly.
Induced voltage will be "temporary" present and will tend to reach almost 0 after magnetic field is completely formed and reaches saturation.
So approximation of the constant voltage is not quite clear to me from a physical point of view.
How can this approximation be physically interpreted?


texts:
I am interested in finding Vgs for E-MOSFET for desired Id or/and Vds. Referring to those equations of drain current in saturation region, value of conduction parameter "K" would be nice to have but it isn't given by any data sheet. For me it seems, that calculating Vgs through Id is impossible, if this mentioned parameter is not given.

I have been trying to find any other useful formula, but without success.

So I am wondering, if anyone else maybe knows formula for determining Vgs for given Id or/and Vds?

The formula I was referring to:


texts: Connecting 220V mains switches (with on-indicator lights) to 12V COB LED lights in series

texts:
I wil be switching COB Led lights (each one rated at 12V, 200mA) individually with these switches.

One end of each of the  60 COB LED lights is connected to 12V, the other end to 60 of these 220V mains switches with lights in series. So all 60 leds are connected in parallel, and all 60 switches are connected in series. The LED adapter will be a 12V 4Ah constant voltage adapter.

Q1. Will these switches turn on the led lights at full power? Or will the light diode act like a resistors and makes the LEDs go dimmer?

Q2. Will the on-indicator lights of the switches light ip or not, in this 12V system?


texts: How to change the width of a given square wave with duty cycle 50% without using microcontroller or ramp solutions?

texts:
Is there a simple way to change the width of a given square wave with duty cycle 50% without using microcontroller or ramp solutions?
Actually, this square wave is switching frequency for my boost converter and I'd like to do PWM.


texts: What does the diode do in this switch and lamp?

texts:
The following illustrations are from a pinball machine repair manual.

What purpose does the diode perform on the lamp and switch?


texts:
I got a problem with how to calculate the current going through R and L in this circuit.

I have calculated the following.

Xc= 79.6Ω at -90°

Xl = 251.3Ω at 90°

ZRL = 128.8Ω at 30.8° (R||L)

ZT = 111.48Ω at -7.03°

Vc = 10.8V at - 83°

Vr = 17.33V at 37.83°

Total current(IT): 0.135 A at 7.03°

everything above this point ive checked in my answer key and they seem to be correct. Now to where im not correct, the current IR and IL.

I use IR = ((XL/(R+XL) * IT) = 0.084A at 97.03°
IL = ((R/(XL+R) * IT) = 0.05A at 7.03°

Where am i going wrong? IL and IR are supposed to be IR = 0.115A and IL = 0.069A


texts: Any more subtle alternatives for LED's to indicate status?

texts: Is there a low-cost, less annoying alternative to a buzzer or LED for displaying the status of an operation? I want my clock radio on at night, but it has this really annoying power indicator LED. I'd like to keep some form of power indicator, so replacing the LED with an equivalent diode or just removing it isn't an option, but I also need to have it on. I have the LED removed, I just need some non-irritating indicator that I can still check if I want to, but without emitting any light.


texts: What really is voltage, what effect does a higher voltage have on an unit of charge and what makes electrons flow?

texts:
I have been reading a lot about the subject, I've seen lots of videos (youtube, udemy) and even read some scholar papers about it and everyone explains the above in so many different ways. We all know what the scientific definition of what voltage is but I still don't know what effect it has on the electrons.

The water analogy which is used so much, seems to fail when we compare higher voltage vs lower voltage, because the higher the pressure of water in a tank is, the faster the water current will be once the tap is open, but the same does not apply to electrons. In fact, from what I've read, the velocity at which electrons move (drift velocity) is quite slow - small drift changes which propagate across the wire is what allow the fast delivery of electricity.

The other thing I have a problem is is how the voltage is represented in a circuit. I keep reading over and over again and seeing in the water analogy too, that voltage is what pushes the electrons, but if that's the case why is voltage lower at the negative terminal?

If I put a few springs in a box and apply pressure to close the box, some springs will contract and will probably fly away once I open the box, so using this analogy, is voltage the force necessary to keep the springs tight in the box?

The electrons don't really need a push to move across the hire, they have that desire, they are attracted to the positive side, how what is really the voltage role here?

Using another analogy, it seems that voltage is to electrons what fuel is to my car. At the end of a working day all I want to do is to drive home. I will always have the desire to reach home, but if I don't have enough fuel in the tank, I will never be able to, in the same manner, if there's no enough voltage the electrons will never reach the other end of the hire, even if that's all they want.

To me, it seems that voltage is simply the force that pushes electrons apart from each other. I also see in so many videos, electrons flowing from the beginning of the circuit to the end, when in fact the electrons barely more.

The more I read the more confused I become.

UPDATE 1

This is the best explanation I have read so far:

"A voltage appears whenever there is an imbalance of electrical charge (i.e. electrons). Since like charges repel and opposite charges attract, any collection of electrically charged particles creates some kind of force on each other. If there is an imbalance of negative to positive, a kind of "pressure" or "push" is formed. In conducting materials, electrons are free to flow through the material, as opposed to being fixed in atoms, and will therefore flow to the point of least "pressure"."

What exactly is voltage?


texts: What are the most common compounds used today in CMOS IC pn junctions?

texts:
Many many moons ago I was using germanium-based transistors but I know we have been able to exponentially speed up switching response times with newer doping compounds.

I believe newer IC’s also incorporate MOSFETs, those compounds are also requested.

In modern CMOS integrated circuits, what are the most common base and doping compounds or elements used to achieve the best performance?


texts:
I'm attempting to use an oscilloscope to measure the power draw of a Raspberry Pi 2. I've got a circuit set up that looks something like this:

simulate this circuit – Schematic created using CircuitLab

I'm measuring on either side of R (I know that to determine the actual power consumption of the RP2, I'll need to measure either side of it as well. Then I can determine the current I through R, multiply that by the RP2 voltage, and voila!).

I'm getting some very noisy readings off on my o-scope however and after zooming in on the signal I'm seeing this (apologies for the faint coloring):

There's a pretty obvious dampened oscillation going on here, and as I've always been a far better coder than a circuit build, I have absolutely no clue what this is. Especially since I'm seeing this after unplugging the USB power supply from the wall.

Could someone help me identify what this noise is from, and what I can do to minimize it (and try and get a cleaner reading)?


texts: Possible to make Touch Tone Phone Ring with no phone line?

texts: I am making an "Activity Board" for my toddler. I'm wanting to make an old touch tone phone ring when he pushes a button or picks up the phone. I am hoping someone can help me or point me in the right direction of making the phone ring. To clarify, it is NOT hooked up to a phone line.


texts: How long to charge a super-capacitor with LM317

texts:
I am trying to charge a super-capacitor to 2.5V with LM317. According to datasheet the maximum output current of LM317 is 1.5A and there is internal current regulator in side it. So what is the charging time now if there is no resister in series between LM317 output and a 600F super-capacitor?
I don't think using t=RC and see R=2.5V/1.5A is still useful here.
Can anyone tell me what to do in this condition?


texts: I need to create a system which will make vibrate horizontally a plastic tube of diameter 4cm, of height 3cm, which axis is vertical, and whose weight is 11g. The frequency should be modifiable between 1Hz and 1kHz, and the amplitude should be roughly between 0.5mm and 3mm. The amplitude don't need to be precise. Does someone knows a way to produce such a mechanical vibration source ? What would be the orders of magnitude of the intensity/voltage of the generator ? Thanks !


texts: do you multiply the 120 V ac with same DC 2500 mAh ?

texts: I have 2500 mAh on the battery and 3.7 V normal voltage and I get 55 watts for the pack in DC, then after changing my voltage to 120 AC, how can I calculate the wattage? I mean multiply the 120 V ac with same DC 2500 mAh on the battery? point is does it change? the mAh on the battery ?


texts:
I am using Logisim and I can not work out how to make sine wave.
I have searched on google and can't find out how I can do this.


texts:
Is it possible to write a module with 3 wires a,b,c that would output either :

z (disconnected) if a=b=c=z
a if a=(0 or 1) and b=c=z
b if b=(0 or 1) and a=c=z
c if c=(0 or 1) and a=b=z
x (dont care) otherwise

In verilog?


texts: Does anyone use Statistical Element Selection for matching integrated circuit components or is this a university exercise?

texts:
I have to fix the transistor mismatch on a finfet amplifier design.  I've seen lots of papers on Statistical Element Matching, all from universities, but haven't seen anything reported by companies actually selling products.
https://users.ece.cmu.edu/~xinli/papers/2008_CICC_mismatch.pdf
Does anyone know if this method is real or just theoretical?  Are there circuit designs in production?


texts: Non-regenerative braking on a PMSM/BLDC motor

texts:
Problem

I have been working on drives for a while, but one problem that I never seem to be able to really get around is the regeneration that occurs when our PID loop commands a lower speed/torque value while the motor is spinning and I am looking for the 'Aha!' that will guide us.

PWM Method

We generally use a standard 3-phase Space Vector Modulation (SVM) technique, which means that - aside from dead time - there is always a MOSFET that is 'on' in a particular phase.  We like it that way as our switches operate most efficiently using this method.

Braking Methods we have Known

I know that this isn't a comprehensive list, but we have considered a few things and I feel that it might be informative to include them.

Brake Resistor

We integrate drives into small motors (P < 200W), so we simply don't have the space for a braking resistor that is large enough to handle the peak powers involved.  We have a motor with ~41J when it is rotating at 50krpm that we need to decelerate in ~300ms, which means that the expected peak power is ~136.7W for a short time.  Anything on the size order of a TO-220 would be out of the question.

Large Energy-Storage Capacitor

For many of the same reasons that we wouldn't be able to use the resistor, a large capacitor would not work as well.  In order to get a 10V rise, we would have to be able to store the 41J directly on the capacitor, requiring ~1F.

Coasting the Motor

"Releasing" the PWM and allowing the motor to coast is OK in some of our applications, but not most.

Shorting the Low Sides of the Motor (Dynamic)

For very fast deceleration from high speed without regeneration, we have resorted to shorting the low-side MOSFETs for a period.  This has the unfortunate side-effect of being an uncontrolled deceleration.

Plugging

Effectively, reversing the voltage across the motor.  This generates some pretty high currents, but does brake the motor.  The problem with this one is deciding under what conditions to plug.  We have never deployed this one to production because of the high currents involved and the uncertainty of when the software should begin plugging.  Small braking events shouldn't plug, but large braking events should... this is a viable option if we could get the software right.

What do I Want from You Guys?

Ideally, I would like to find some PWM technique or timing/conditions that would allow me to effectively plug (see above) in a controlled and predictable manner.  I'm under no illusions that I don't have to shove the stored energy somewhere, but I would prefer that the somewhere be across the motor winding since we aggressively cool the winding.


texts:
I am interfacing an MCU (CC1110) with Vdd of 3.3 V to a battery gauge IC (BQ27510-G2) with Vdd of 2.5 V.  Currently, I am pulling the bus up to 3.3 V with a circuit that I blindly copied from a datasheet:

I am a software-focused CompE, struggling to remember my EE courses, so I have a few dumb questions about this circuit:

As I understand it, the Zener diodes are meant to clamp the lines to a maximum voltage (5.6 V in this case) to protect the devices on the bus, and is especially useful for long I2C transmission lines.  Is my understanding correct?
My MCU has an absolute max I/O pin voltage of 3.9 V, so I would want a Zener rated somewhere below that, right?
Do I need clamping diodes if all of my I2C slave devices are on the same board, relatively close together?
What do the series resistors do, and do I need them?
The battery gauge IC allows up to 6 V on its SDA/SCL pins, so is it ok to pull the bus up to 3.3 V, even though the gauge is running at 2.5 V?
Would it be better to level shift them to 2.5 V?

If possible, I would like to simplify this circuit to just the two pull-ups, but I just want to make sure that there will not be any ill effects due to the varying voltage levels.


texts:
I'm trying to figure out if I can send and receive serial data on ports 23 and 25 of the Arduino Mega 2560, and I'm very confused by seemingly contradictory information on the Arduino website.
From the SoftwareSerial page:

  Not all pins on the Mega and Mega 2560 support change interrupts, so only the following can be used for RX: 10, 11, 12, 13, 50, 51, 52, 53, 62, 63, 64, 65, 66, 67, 68, 69

On the Arduino Mega page:

  A SoftwareSerial library allows for serial communication on any of the Mega2560's digital pins.

The pins it specifies as compatible with interrupts are:

  2 (interrupt 0), 3 (interrupt 1), 18 (interrupt 5), 19 (interrupt 4), 20 (interrupt 3), and 21 (interrupt 2).

and have no overlap with the pins that the first quote. These seem completely contradictory. Am I missing something? Can I use serial on ports 23 and 25?


texts: Analyzing Accelerometer / Gyroscopic Data

texts: I have created a data logger that logs acceleration and Gyroscopic data on to an SD card. The logged data is about 1.5GB in the form of txt files.  I wish to perform thorough analysis on this data via graphs but I do not know what tools can be used to achieve this. I am interested in proprietary or open source tools to get my work done. I would appreciate any help on this matter.


texts: Can I use a higher ohm resistance relay?

texts:
I'd like to build the circuit detailed here, which calls for a 12V DC 260Ω resistance relay:

Looking at some relays, what consequence would using a 400Ω relay have? Would I be able to use one without a problem?

Unrelated: I believe it's a non-latching SPST NO relay that I need here, right? From what I understand, a SPDT can function as a SPST by ignoring one of the pins; is this correct?


texts: I have a wire dipole antenna that I am connecting to a PCB.  I know that ground should be cleared under most antennas.  However, in my case the wire will be mounted away from the PCB.  Do I need to clear the ground away from and underneath the pads that the two wires of the dipole will solder to?


texts: Analysing AC-Coupling differential opamp configuration

texts:
I built an audio DSP board based on CS4272 and used its reference design for the output section. The signal is getting extremely distorted when summed signal exceeds ~0.7Vpp. (Rail voltages 0V-5V and OPAMP is OPA1642 rail-to-rail type, so nearly 5Vpp should be possible.)

Now I want to modify the output circuitry but I don't really understand how to analyse and dimension this. As far as I understand it's a differential opamp configuration but extended with some filters.

Can someone help me analyzing this circuitry and how to modify it to reduce the gain? How to calculate high pass characteristics?
Question: Why is it necessary to have additional frequency filters when we already have a 22uF AC-Coupling capacitor in the end?


texts: One MOSFET slowly activates itself, the other won't fully activate

texts:
I built the following circuit. +3.3V GPIOs and +5V driven by an RPi Zero. Common-anode RGB LED wired to three IRLB3034 MOSFETs. These have Vgs(th)-min/max of 1V/2.5V.
The GPIOs are supposed to switch the MOSFETs to drive the LEDs on the 5V rail. Each LED is supposed to pull about 700 mA.
Symptoms

The red LED works perfectly.
The green LED was turning on as soon as the RPi was connected to power. I could stop this by shorting the gate to ground, but it would slowly build up again. Once the GPIO pin was explicitly set to 0 it would also stop. I "solved" this with a 100 Ω resistor from its gate to ground. Not really sure why this works.
The blue LED doesn't fully turn on. If I apply 5V to the gate it does, but 3.3V just doesn't cut it (maybe 10% brightness).

Possibilities

I've misunderstood something about the MOSFETs?
The blue MOSFET is broken?
Poor construction. I made this using an AdaFruit protoboard, big wires for the high-current and lots of solder. Have checked again and again for shorts.
Something else??

Updates

The 100 Ω resistor I added only for the green LED, and have now added to the diagram.
This is the LED: link and datasheet
The LED voltages are R: 2.5V, G: 3.6V, B: 3.6V.


texts:
I want to take part in a direction finding exercise on 145.300 MHz FM.
I have a 25-25 centre zero micro amp meter, which I intend to use to detect the direction of the FM carrier via an antenna.
I am reasonably familiar with electronics but not clever enough to design a circuit, please can any one help with a circuit for the above?


texts: Why does the resistance of this JFET VCR change?

texts:
I'm trying to build an automatic gain control (compressor) for my audio amplifier. For this I'm using a 2N5458 JFET as a voltage controlled resistor. The circuit looks like this in LTSpice:

The drain-source resistance should be constant at a constant Vgs, if Vds is kept sufficiently small. However, when the Vgs is kept somewhat constant (about -358 mV to -363 mV), the resistance in the JFET still changes. This can be seen here:

Because of this change in resistance, the compression changes as the signal oscillates, generating an asymmetrical compression of the output. The input (blue) and the output over R14 (green) can be seen underneath. The output has peaks at 2.77 V and -3.12 V which is not symmetrical:

I also considered whether or not the Vds was to big, which would result in a non-linear output response from the JFET. However, checking the datasheet for 2N5458, it can be seen that the Vds of about 700 mV combined with a Vgs of about -360 mV does not exit the ohmic region. The graph from the datasheet can be seen here:

So my question is: Why is the compression asymmetrical even at a constant Vgs, when we are still in the ohmic region?
PS.
I tried lowering the input voltage and thus the Vgs. This did make the output a bit more symmetrical, but not entirely. It peaks still varied with about 200 mV.
I read somewhere that the Vds should be kept positive, which it is not here. I tried adding a DC offset, but the asymmetricality was still there.


texts:
i program my atmega with USBasp ,and i set the fuse bits hfuse:0xC9 and lfuse :0xff.
when i upload my simple code

int main(void)
   {
       DDRB |= 1<< PINB1 ;

       PORTB|= 1<<PINB1;
       while (1)
            {

            }
  }

the MCU keeps resetting(led keeps blinking), i tried using usbasp as power supply and also i tried using 9v volt battery with regulator but still the same problem ( and i have 0.1uf capacitor between vcc and ground and pullup resistor in the reset pin).
i also bought a new atemga328p ( i thaught the other is dead) but always the same problem.


texts:
I have a 4 KHz piezo buzzer and a microcontroller (arduino) that outputs that 4 KHz from one of it's pins. All is fine if I connect the buzzer to the output with one pin and to the ground with another. Also all works as expected if I try to control it with MOSFET: +5V to the drain, buzzer between source and ground, and the output pin to the gate.

However if I replace MOSFET with BJT, something goes wrong and the buzzer emits just a very-very-very quiet sound. Here's what I have:

Buzzer between +5 V and the collector
Output pin connected to the base through 2K2 resistor
Emitter connected to the ground

I have tried few other configurations with BJT, but result is the same. I use BC337 as a transistor (AFAIK it is analogue of 2N2222).

Could anybody clarify why this happens?

UPD:

I've measured voltage levels. I have 2.51 V between the microcontroller output and the ground. I get 5 V / 2 because it generates square waves, isn't it? Then I have 2.1 V around the base resistor. And, surprisingly I've got 5 V around the buzzer! Shouldn't I get 2.5 V?

Also I noticed that once I measure voltage across the buzzer the sound become a bit louder. So I've tried to add a resistor in parallel to it. Aaaand… now it works!

The question left open: why it doesn't work as expected if I remove R2?


texts: Protecting a low voltage (RS485) bidirectional bus from direct mains connection

texts:
I have a bunch of devices that will sit on a two-wire bidirectional RS485 bus (DMX-like, but not quite DMX).

I'm trying to protect against an edge case, where a user mis-wires a ballast, and inadvertently connects mains voltage to the bus, causing the it to become live and potentially injuring anyone else working on it.

I will be installing an 'isolating box' between the bus and the user, essentially behind a wallplate, such that the bus itself can never be directly accessed. The connection to the bus itself would be through opto-isolators and associated circuitry (with a separate isolated supply), however I'd like to 'protect the protection circuitry' if possible, such that it won't catch fire and can gracefully recover.

Would a couple of PTCs, and a couple of TVSs (for redundancy) as below, be enough to reliably save any low voltage circuitry to the left of the circuit, when IO1 and IO2 are connected directly to 240V mains?

Normally, IO1 and IO2 would see ~22v at roughly 2mA.

Thank you kindly


texts: Need some help identifying these circuit components

texts:
Hi everyone,

I'm trying to decipher a circuit that was potted in epoxy and am doing pretty well, but could use some help identifying a few things. The basic circuit appears to be a monostable 555, with some other stuff tacked on.

I know that two are diodes, and one a resistor, but what's the brown axial device? Also what is the tan dome shaped device at the bottom of the pic?

Thanks!

Ok, I've printed the schematic as far as I've deciphered it:

The circuit is used to adapt a 1960's vintage tachometer to a present day electronic ignition system's tach signal. The tach signal is a 0-12V square wave at 20% duty cycle, and the tach is expecting an inductive kickback pulse from the original style Kettering points ignition system. I'm thinking that the 555 is configured as monostable in order to shorten the pulse length from the 20% duty cycle, and it triggers the IGBT just as if it were the points and L1 was the coil.

Positive power comes in via the RED connection, and the pulse is measured by the tach on the same connection (seems weird to me but that's how it works). The 0-12V square wave is applied to the WHITE connection, and for this style of tach the PURPLE connection isn't used.


texts: Are all packages referenced in JEDEC JEP95?

texts: Or in essence, does JEP95 represent all packages available on the market today?


texts: Transceiver and RF Emissions (Unintentional)

texts:
My question is simply what is RF emissions (unintentional) and how does it relate to a device (such as a smart phone) which contains a transceiver or transmitter (baseband IC) ? Which part of a RF embedded device is emitting the emissions (unintentional) the transmitter or transceiver ? Is the RF emissions related (in any way) to the transmit frequencies of the RF embedded device ? Can the RF emissions be measured in order to discover the transmit frequencies of the RF embedded device (such as a smart phone) ?

Thanks


texts: PIC MCU PIC16F887 not working with external power

texts:
I am a newbie with PIC doing my first project to understand how PICs work. I have some experience with Arduino and trying to learn PIC now.

I have chosen PIC16F887 (40 pin DIP package) as my first PIC chip. I am using MPLAB v5.30. I am only trying to blink an LED attached to pin 20 (RD1) in my first project. But what I am experiencing is that the PIC BOTH Runs and Debugs well when its connected to PICKIT3, but when I am supplying the power through an external source, nothing happens at all.

While connected to PICKIT3, in order to run the project in "release mode", I am using the option "Program device for Production Main Project" from MPLAB. To debug, I am only running - "Debug Main Project" from the debug menu. Both these options end up with PIC running on the breadboard. I understand that with the external power source, the MCU is not supposed to work with a debug build. Hence before powering from external source, I am using the "Program device for Production Main Project" MPLAB option to program the chip. I also tried option - "Run Main Project", but this option does not work, neither with PICKIT3 connected nor with the external power. That seems strange.

For external supply I am using the L7805CV 5v voltage regulator. I am also pulling up the pin1-MCLR using the resistor "R1" when using external source. Have tried various values of R1 from 4800 ohms to 68000 ohms with no luck. I am attaching the hand drawn circuits here which I am using both with PICKIT3 and external power. My code which I am trying to run is also mentioned below. I have tried setting MCLRE as OFF, ON and default (not mentioning in code at all) with no luck. The crystal frequencies tried as 8, 20 and 32 mhz.

Can someone please see whats missing in the circuit or the code? Also notice that, this MCU has two VDD and VSS pins. Seems unlikely to me, but do I need to supply voltage to both of them in order for the chip to work? I have only one chip currently, do not want to fry it, hence have not tried this option.

// PIC16F887 Configuration Bit Settings

// 'C' source line config statements

// CONFIG1
#pragma config FOSC = INTRC_NOCLKOUT// Oscillator Selection bits (INTOSCIO oscillator: I/O function on RA6/OSC2/CLKOUT pin, I/O function on RA7/OSC1/CLKIN)
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled and can be enabled by SWDTEN bit of the WDTCON register)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config MCLRE = ON      // RE3/MCLR pin function select bit (RE3/MCLR pin function is digital input, MCLR internally tied to VDD)
#pragma config CP = OFF         // Code Protection bit (Program memory code protection is disabled)
#pragma config CPD = OFF        // Data Code Protection bit (Data memory code protection is disabled)
#pragma config BOREN = OFF      // Brown Out Reset Selection bits (BOR disabled)
#pragma config IESO = OFF       // Internal External Switchover bit (Internal/External Switchover mode is disabled)
#pragma config FCMEN = ON       // Fail-Safe Clock Monitor Enabled bit (Fail-Safe Clock Monitor is enabled)
#pragma config LVP = ON         // Low Voltage Programming Enable bit (RB3/PGM pin has PGM function, low voltage programming enabled)

// CONFIG2
#pragma config BOR4V = BOR40V   // Brown-out Reset Selection bit (Brown-out Reset set to 4.0V)
#pragma config WRT = OFF        // Flash Program Memory Self Write Enable bits (Write protection off)

// #pragma config statements should precede project file includes.
// Use project enums instead of #define for ON and OFF.

#include <xc.h>
#include <stdio.h>
#include <stdlib.h>

# define _XTAL_FREQ 20000000

void main()
{
    TRISD1=0;

    while(1)
    {
        RD1 = 1;
       __delay_ms(1000);
       RD1 = 0;
        __delay_ms(1000);
    }
}


texts:
I am currently programming / configuring an Atmel AT86RF233 radio and trying to get it to communicate with an digi xbee.  So far I have set the following fields on the Atmel radio:

extended address
pan ID
operating channel
not coordinator (i.e. the radio's role is a "router").

The digi xbee is still not able to discover the Atmel radio (using the ATND) command.
At a conceptual level, how can I debug something like this? Is it possible I can use a spectrum analyzer to see the RF emitted from the Atmel radio?

Would it be a better idea to get two Atmel radios to talk to each other first, and then try Atmel radio <---> digi xbee communication?

Basically my question is what is the best methodology to attack / debug a problem like this?


texts: Can I connect a CAN node with 250 kbit/s to a CAN bus running at 500 kbit/s?

texts:
I'm trying to connect an automatic car gearbox which is using the CAN bus at 250 kbit/s to car with bus speed 500 kbit/s.

Is it possible to have nodes with different speeds on the CAN bus?
If it is not possible to have different speeds, is there a way to accomplish what I want to do? Anyway, a starting point would be great.


texts: How Prepreg types and number of plies affect mechanical and thermal properties of the PCB

texts:
What are advantages and disadvantages when using a single ply of 7628 type prepreg as compared to say 2 plies of 1080 or a similar prepreg. I'm primarily concerned about any mechanical and/or thermal differences (advantages/disadvantages) that might arise. Most most of the resources i found on the internet focus on the electrical performance which is fairly well understood.
I've read somewhere (cannot find now where) that higher fiber-glass content may affect the feature size (higher surface roughness) and the min hole size (higher fiberglass density tends to dull drill bits more often).
If I want to maintain a certain voltage isolation between two copper layers, is it better to go with 7628 (high glass content) or 2 x 1080 (higher resin content).
Some usefull resources I used
Whitepapers at Isola group website (link to website)
Shengyi materials (link to website)
Disclamer
I'm not extensively familiar with this matter. The two links I posted above were two primary resources I used to inform myself about the matter. What I did see that few times my PCB manufacturer would use say 6 x 106 prepreg between the cores. This left me wondering why is that, and why not simply use thicker prepreg like 7628. Is this purely a convenience where the manufacturer used the prepreg material type that was available to him or there are some other reasons?


texts: ATMega328P Programs at 2V but not at 1.8V

texts:
I'm perplexed by this one:

I'm trying to run my ATMega328P at 1.8V.  The voltage at the chip (pin 4 and 21) sits at 1.82V (BK Precision Multimeter).  When using the AVRISP mkII, the programmer LED lights up green (recognizing a powered chip) but fails to program.

Using an bench power supply, I discovered that at exactly 2V, the ability to program the chip returns.  This is true regardless of the BOD/Extended Fuse setting (which I have set off with 0xFF).

I did notice the 1.8V BOD setting (0xFE for the extended fuse) keeps the MCU from powering on even after flashing.  With it off, the chip will run using the 1.8V rail.  I thought this might be useful debugging information, but Ignacio in the comments pointed out that this is expected behavior given the specced range of BOD threshold.

Did I miss something obvious?
Is 1.8V programming not actually supported at 1MHz on the ATMega328P?
Do I need to design a 2V power supply instead if I want to be able to flash?
Does the BOD circuit has some protective effect during programming, even when disabled?  Could it be the programmer?

Thanks for any suggestions/debugging ideas!

Edited: Ignacio pointed out that the BOD cutoff for the 1.8V setting could vary up to 2V, so the BOD is behaving as expected.  I thought perhaps the 'misfiring' of the BOD was a useful clue for why it mightn't be programming, but that no longer seems to be the case.  The above was edited for clarity.


texts: Generating sine wave from noisy pulsed signal

texts:
I have a pulsed signal approximately 80MHz, 40mV amplitude. I need to create a clock signal for an ADC which requires a phase locked sine wave of about 0.5Vpp.

Is there a simple COTS solution for this? Or something that can be easily built?
Can I just filter with an 80MHz bandpass + opamp amplifier? Do I need a PLL?

Example of input signal:


texts: Need to make a 4 position switch using one button input and SMD IC's

texts:
I have a system that can only have one push button input and I positions      . I'm limited on space and power, however I will gladly yield some power to save space.

I'm trying to find integrated circuit packages that can take a single input and drive one of four outputs. I'm new to the electrical field and after a few days of searching through digikey and reading datasheets, I'm not finding what I need.

NOTE: NO MICROCONTROLLERS please. Seriously, let's not be lazy.

I can typically find this on my own, but this time I can't seem to find the right IC.


texts: LCD usb controller design - is my pot suitable

texts:
Hi
I've been asked to construct an lcd usb controller for an art project.  The lcd am using is ST7066. It's spec sheet has told me that the LED. I'm using a 10K pot to adjust the contrast. The 10K pot I have can handle 0.5W power.

  [power supply (logic)] vdd  0.3(min)
  7.0(max)

  [power supply (LCD)]   V0   Vdd - 13.5
  Vdd + 0.3

In my case VDD = 5V

The led forward current is 240ma. At 5V 240ma equals to 1.2W of power so does that mean my pot needs to be able to withstand 1.2W?

The reason I ask is the last time I used a pot, it set on fire as soon as I turned on the circuit. There was no bridges in my soldering so I can only assume I overloaded it.

  Correspond to high speed MPU bus
  interface
  -- 2 MHz (when VCC = 5V)

Also it's going to be connected to an ATMEGA16-16PU. The spec for the lcd says the logic runs at 2MHZ. So does that mean my avr must also run 2MHZ?

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=720-0235


texts: How to drive a battery-powered heating element with temperature feedback control

texts:
Preface (not necessary to answer question)
I am not an electrical engineering student, so I am very far out of my element. However, I do have to complete this part of the project and am having a lot of difficulty doing so on my own. So, please feel free to educate me like I'm 5. I have some rudimentary knowledge of electronics but the depth isn't there for me. Please also link me to additional resources you think may be helpful for me to continue pursuing this problem on my own.
Problem Statement
Using a microcontroller (Arduino/ATTiny), drive power to a heating element based on the element's current temperature, with a target temperature of 40 C.
Relevant Info and Constraints

The heating element is a small coil of nichrome wire.
The production-level PCB must fit within a circle of a diameter of < 30 mm.
The height of the production-level PCB must be thin to fit within the form factor of the device it will be placed into.
The heating element must not exceed 40 C, and should have power cut off when it reaches the setpoint.
The production-level PCB will be coated in an epoxy such that the circuit is safe from extremely humid environments as well as storage temperatures up to 125 C (not operating temperatures), however the heating element will be connected outside of the epoxy puck.

I have below a (very) rough schematic. For now, I am not too concerned about values of components, but more concerned about what components I need to make this work. I am reasonably confident I can work out the math once I know what I should be working with.

Description of what I intended for the above circuit to accomplish:

Current flows to the MCU powered by the Vin pin and grounded to the negative terminal of the battery. The MCU is in parallel with the heating element, and transmits a PWM signal to an optocoupler acting as the gatekeeper for power to the heating element. The temperature of the heating element is read into the input of the MCU by a currently unknown method for measuring its temperature, and this temperature is used to influence the duty cycle of the PWM signal. As the temperature nears the setpoint, the duty cycle decreases, and is at 0% upon reaching the setpoint temperature.

Questions

Green Question Mark Do I need to galvanically isolate the MCU from the heating element, or is the current connection setup okay? If it needs to be isolated, how would I accomplish this since the battery is the sole power source of the device?
Pink Question Mark Should I include an additional resistor here? What about a voltage amplifier and/or regulator?
Red Question Mark Should I use an NTC/PTC thermistor to measure the temperature of the element? A thermocouple? Or something else? How would I wire it the above schematic?
Would a MOSFET be better than an optocoupler here? Or a BJT? Or is an optocoupler a suitable switching method?
I want there to be some sort of thermal failsafe, similar to a circuit breaker, that will cutoff the circuit entirely in the potential event that the heating element gets too hot and isn't being controlled by the MCU. I looked into fuses, but the issue is that the device will be subject to temperatures of 115 C plus in some situations, and think the fuse would melt and break the circuit after simply being in the environment despite not overheating. What are other solutions that might accomplish this?
Are there ICs that do what I am trying to do here that can simplify my design? Are there better solutions I should pursue that fit within my constraints?


texts:
I would like to use two (or more) 1838 IR sensors, to be able to read a (TV?) remote control for controlling my project.

The reason I want two or more is that I want to be able to point at the device from multiple directions.

I checked on some websites and it seems it is quite hard (on an Arduino) to use more than one of them. I'm not sure if I will make it on an Arduino or STM32 yet. But I wonder if there is some circuit to 'combine' them together, so I can use only one pin (not for saving a pin, but not having to check multiple sensors)... is there such a circuit and how would it look like?


texts:
For my power electronics course, I need to design a basic boost converter that is converting 5 V to 12 V with 0.5 A output current. Below you can see the simulation results. MOSFET is driven by 20 kHz 0.58 duty 5 V square waves. And rest is as it is seen.

I use IRF510 as switch, 1 mH inductor, 220 uF 25V cap. and 25 Ohm load. However when I attempt to the experiment I stuck around 3-4 V output voltage with IL of 200 mA. When I change the load to 1 kOhm I get the output voltage as I desire, yet the current drawn drops to around ~10-15 milliamp as you might guess.

At the bottom you can also see the driving pwm output that is generated by NE555.

Solution: Problem was using a resistor-like inductor, I tried using a coil inductance  (1mH) and got the desired result. Resistor-like inductors get saturated after few 100 milliamps, so be careful checking that.


texts:
I'm working on a project where I'm controlling a Yamaha YM2612 with an Arduino MEGA.  I can communicate with the chip just fine, but I'm having problems with the audio signal the chip is outputting. I'm running the signal to an audio op amp module to boost the signal the chip outputs, but there's a lot of noise in the signal.  I've listened to the output of the module without the chip on and it's very very clean, so I'm sure there's something I'm not doing right in my circuit. I've tried other 2612 chips I have but the noise seems to be the same.

Details:
Circuit is on a breadboard

Arduino MEGA is using USB power

YM2612 clock signal generated from Arduino MEGA

YM2612 "datasheet" https://datasheetspdf.com/pdf-file/865751/Yamaha/YM2612/1

breadboard circuit schematic https://gyazo.com/f2d06e9e316e6bbcc85c20f805142bb4


texts: Combining outputs of dual channel equalizer

texts:
I'm building a two channel equalizer, essentially a bandpass filter and I've run into a small problem. I've successfully gotten my low and high pass filters to work but I can't get them to "add up" properly. At first, I was having issues with the outputs being 180 out of phase so I added an inverting amp to correct that but now I'm unsure of how to combine the two outputs.

The green line is how I want the end result to output(ish)

My code: https://pastebin.com/55hEQRxc


texts:
I researched but I could not find anything like this, should I be worried about what is this symbol?

This schematic is a part of a board I'm working on, the part that regulates voltage from 2.6 - 4.2 Vin to 3.3 Vout.
I got it from WEBENCH, and as stated there:

The TPS61022 Device will operate in Pass-Through mode when Vin is greater than Vout. In Pass-Through mode, Vout is not regulated to
the set Vout, instead Vout is Vin with the drop across the FET?s on-resistance and the DCR of the inductor. 2. This is a Boost Converter with
0.5V ultra-low input voltage. 3. The efficiency validation is done only for FPWM mode. Charts may be inaccurate for AutoMode at light loads and
hence they are disabled for light loads.

Also on the page, Iout is described simply as Iout operating point.

I don't know which of those infos are relevant here really, but I hope some of it will be, since I have no idea what that symbol means it also does not help me on how to explain my situation much.

If there is more info I could add, I'll be glad to.

I thought it was some kind of Ampmeter? Is it just to symbolize output? I don't know.

Thanks!


texts: Understanding a CMOS logic gate with strange details

texts:
I'm trying to understand which logic is implemented by the following CMOS gate.

Comparing with the following CMOS NAND gate, I feel like the above logic gate could be a NOR gate, I'm not sure. My problem is that there are some extra details on the above CMOS gate which I'm not familiar with, like Via or Poly contact. Also I assume Metal 2 is the output, but I don't understand why Metal 2 (output) is directly connected to Metal 1 (drain/source) with Poly contact. I wonder if anybody can explain why.


texts: What is the best radio protocol for long range serial communication?

texts:
I'm working on a project that would require up to near time (<=5mins) of packet base communication over Long Distances of upwards to 80 Gm. Obviously the base station would have to be scaled for this but what would be the best protocol in this use case?

UPDATE

Thanks to everyone whom commented. We are initial looking to use a point-to-point communications medium over an unlicensed band however do realize the limitations of 2.4-5Ghz bands can cause for long distance communications. Hence why we're reaching out.


texts: Is there a reason for the anvil and post in a LED having the shape they do - other than making it easier to distinguish between the anode and cathode?


texts:
I would like to make usb-charging sockets from two sides of the bed, and I don't like the idea of power supply working 24/7 so I decided the following scheme to have power ON while me or my wife are charging:

simulate this circuit – Schematic created using CircuitLab

But the power on my side socket will be ON, when my switch is OFF, if my wife's switch is ON (being continuously charged is not good for battery). So I have the idea to use DPST switch to also switch usb socket off:

simulate this circuit

Is it OK to use DPST switch between 220vAC and 5vDC circuits?
Does it depends on it's characteristics, how to select right on?
Would be there some kind of cross talk between circuits?


texts:
I am trying to learn more about the performance of different routings in my design using Xilinx ISE. I've figured out how to move logic around by changing which CLB/Slice holds which piece of using the User Constraint file. Is there a way to manipulate the routing? Or, at the very least somewhere I can get it to give me a text description of the routing paths?

Further details:
I have implemented a simple AND gate in a spartan3E_100 and moved around the IOBs and the LUT which holds the logic. Every time I do so I look in the FPGA editor and the chosen routing is completely different. I'm sure it figures out the optimal but what I would like to do is modify the routing then look at how the performance changes. Is that possible? Second, is there any way to get a text description of the routing similar to the the info given in the UCF/PCF file?


texts: Output impedance of a differential line receiver

texts:
Let's say I have an INA134 (http://www.ti.com/product/ina134) from Texas Instruments in my design. I want to take the output of that IC and feed it into a resistor network which can have a flexible input resistance (from 100 ohm to 100k ohm).

What is the reason that the output impedance of the IC is not specified in the datasheet? It's based on a simple opamp circuit after all.

Does it make sense to follow the INA134 by a OPA134 to allow for more drive capability?


texts: Is it possible to combine two fuses together (with different current rating) to make a bigger fuse?

texts:
Let's say I need a 45A fuse.
However, I have only a 40A and a 5A fuse in my pocket.
If I put them together in parallel, will it act as single 45A fuse ? (so it will  blow up if current is superior to 45A).

My guess is the 5A fuse might blow up before reaching 45A, because the resistance ratio of each fuse might not be the same as the ratio of their current rating (5/40). Because of that, there might be more than 5A going trought the 5A fuse before reaching 45A.


texts:
If i have a current source and a resistor in parallel, i will have two nodes,if i ground the the node which faces in the direction of current of the current source will all the current flow to the ground? or will any current flow into the resistor?

simulate this circuit – Schematic created using CircuitLab