texts: Load Sharing/Isolation Circuit with ADP5063

texts:
I'm designing the battery power/charging circuit for the Reform DIY laptop which uses a (big) LiFePo4 cell. For the charger IC I've now settled on ADP5063 as it seems simple and can charge with 1.5A current (more would be even better, but hey...).

The charger's datasheet says it can route 2.1A of current through it's integrated battery isolation circuit. This is not enough to power the system, so I don't want to use the internal isolation and instead implement the load sharing circuit featured in Microchip Application Note AN1149 and some other StackExchange questions. For Mosfet Q2 (in the circuit below), which switches between wall and battery power I chose NDP6020P as recommended in Bil Herd's video on high side power switching using a p-channel Mosfet.

My questions are:
1. Is it OK to basically leave the ISO_Sx of ADP5063 pins unconnected or should I wire them to the load as well?
2. Is this way of load switching "around" this charger sane or can there be adverse effects?


texts: How to implement selective automatic repeat request (ARQ) frame retransmission concept in simulink after detecting frame errors using CRC-4?

texts: I have modelled an acoustic modem in simulink, i have used the CRC-4 (STD-ITU) scheme to protect the data for transmission, On the receiver end, the CRC decoder detects the errors in the received frames. I would like to send a request to the transmitter to retransmit this error frame, I am stuck at this part, Any help regarding this would be greatly appreciated.


texts: Do caps with a higher max voltage have lower ESR?

texts: Does a capacitor of a higher max voltage, all other factors the same, have a lower ESR? If so, is the any relationship between the voltage and ESR differences?


texts: Can I increase the maximum effective range of an accelerometer by rotating it?

texts:
I've been looking for an absolute orientation IMU (usually 9 axis, with accelerometer, gyroscope, and magnetometer) that can measure high g-loads in one direction (max ~20 g). However, the highest rating I can find is around 16g. I am aware that there are accelerometers with higher capabilities, but not of one within a single-chip IMU.

However - since the accelerations only appear significantly in one direction, I was thinking it I could rotate the chip by 45 degrees, so that the acceleration is "partially taken on" by two axes, giving me 16 * sqrt(2) ~= 22.5g (sufficient for my application).

Would this work in practice?


texts:
The reflection coefficient (in circuits, for example) is generally given the symbol Gamma (\$\Gamma\$). What is the symbol given for the pass or transmission coefficient \$1-\Gamma\$?
I've usually just seen it written out in terms of \$\Gamma\$ but I'm trying to be more concise in my notation.


texts:
I am working through a circuit book on my own.  This is not for any school homework.  I have the following problem which I can't seem to wrap my head around.

Two d'Arsonval ammeters are connected in parallel.  Ammeter 1 uses a 2
mA, 100 mV movement and has a full-scale reading of 25 mA.  Ammeter 2
uses a 1 mA, 25 mV movement and has a full-scale reading of 10 mA.
What is the largest current these parallel-connected ammeters can
read?

Taking each ammeter alone I can calculate the shunt resistor.  But when you put them in parallel I am not sure what to do.  They have two different voltage ratings and putting those in parallel is confusing.  Can someone help?


texts:
The question asks to find the equivalent resistance of such a network of resistors.

simulate this circuit – Schematic created using CircuitLab

I have managed to simplify it down to the following:

simulate this circuit

Is there a way to find the equivalent resistance without the use of a delta-transform (as I do not believe those are allowed on this assignment). From a logical point of view since the left and right nodes of the 0.5 ohm resistor are at the same voltage, no current would flow through it and hence it would offer no resistance. Would the equivalent resistance then be the parallel connection of the 1 and 1.5 ohm resistor? or am I completely wrong.

Thank you in advance for your responses!


texts: Inverted switch does not work consistently

texts:
I made an inverted switch circuit that turns off the LED when the switch SW1 is closed and turns on the LED when the switch SW1 is open.
I made several circuits and some of them do not work as they should. Each circuit is definitely the same as the other and uses the same components.

I can assure that the switch SW1 is fully closed but the led is still on. Testing the continuity of the switch SW1 confirms that it is closed.

Is there something that i missed ? how can i solve this issue?

if you are interested in the components:

N-MOSFET - BSS138

LED - QTLP650D4TR

Here is my schematics:

simulate this circuit – Schematic created using CircuitLab


texts: How to build a cheap device to determine where Wi-Fi interference is coming from?

texts:
In this post, the ServerFault guys use a fancy tool to map out the WiFi spectrum under normal conditions, with a microwave running, and with a baby monitor on.  The baby monitor and microwave cause a surprising amount of interference.

Having had to deal with Wifi interference in the past, a tool like that could be very useful.  However, its price - $200 to $1000+ - is way outside my price-range.

I'd like to build something to serve a similar purpose, but my experience with building analog devices is, shall we say, non-existent.

What's the cheapest way to determine where Wi-Fi interference is coming from?  My idea was rig up an old radio to somehow receive around the 2.4Ghz frequency, but I have no idea how to do that.
How can I tell which channel has the least interference?

Please let me know if this is off-topic.  Thanks!


texts:
I would like to create navigation light sequences on old admiralty map of my local area. There are lighthouses and channel markers in area with mix of flashing and times. The single flashes I can use a bought LED flashing kit but its the pulse flashes every x seconds that I'm stuck on e.g. LED flashing twice every 10 seconds. Not every 5 s but at 1 Hz and every 10 seconds so LED flash first sec, flash second sec then off for 8 seconds before repeating.
From what I've seen on the map there 2 flashes or 5 flashes in times given. So that looks like Fl(2) R 6s,  "Flash twice Red every 6 seconds".

I've looked through forums and can't find a direct answer to above, if you've come across anything like this could you help. I'm ok on hardware side of things but programming wouldn't be my strongest suit. Thinking about it I could only come up with two options:

A mircocontroller able to pulse the LED's at 1hzish and able to control power on/off for the associated times.
A asymmetrical timer that would control power to a LED Flashing kit so the power on would be shorter then power off and this would repeat periodically.

Any help would be appreciated.


texts:
as the question stated, this bjt is now under saturation mode. and we have to find v1.
thus, the answer will be somewhat like this
IC=4.8V/2kΩ=2.4mA
IB=2.4mA/50=48uA
Then, by KVL:

V1=VEB+48uA⋅50kΩ=VEB+2.4V
So, assuming VEB=0.7V(a reasonable assumption)

V1=3.1V
but as i know ic is not equal to beta times ib in saturation mode. then how can we assume ic equal to beta times ic to solve the answer in this question?
also if in saturation mode ic remains unchanged even if you increase ib further, then is it possible that after some time ib becomes greater than ic {ib>ic(in sat. mode)}?


texts: What happens when input current in common base amplifier circuit is increased?

texts:
Looking at the equations of the common base amplifier circuit shown below:

The input current  should be given by the equation: $$I_e = (V_{in} - 0.7)/R_e$$
Then, the output current  should be: $$I_c = \frac{\beta}{\beta + 1} I_e$$
Taking KVL on the loop at the right would give: $$V_{cc} - V_{cb} - I_cR_{load}= 0$$
So, this gives us that  is directly propotional to (−0.7), but it is also limited by
 such that it can't increase more than it to keep the third equation valid without getting a negative . Now, my question is, I'm wondering what will happen if a big (or a small ) were present such that  is high and in turn it wants to make a voltage drop across  which is bigger than (considering  to be approximately 0), what will happen after that if  was further increased?


texts: Simple circuit with an inductor in transient state

texts:
I have a problem with this circuit. I am supposed to calculate i(t) at the moment t=(0+).
The parameters are:R=300Ωe(t)=12VL=0.1H Switch is closed at t=0
I know that current can't jump in the branch with the inductor, so
iL(0+)=iL(0)=20mA
but I'm not sure what will happen with the rest of the circuit.
Is there a simple way to get i(t)?
Sorry about quality of the picture.


texts: When bode plot have multi phase margin how to decide the stability the transient would effected by which phase margin


texts: Why are the load resistance and reactance in parallel?

texts:
As highlighted below why are RL and XL in parallel?

SOURCE:
Electrical Machines, Drives, and Power Systems by Theodore Wildi. Sixth edition, 2014.

ISBN 10: 1-292-02458-5
ISBN 13: 978-1-292-02458-5

Pearson Education Limited


texts: Turning an NMOS with substrate terminal into a PMOS

texts:
Some NMOS's come with a substrate/bulk/body terminal so the "Source Voltage" referred to in literature then Substrate Voltage. Say then we  short the gate to the drain and have the substrate take the input. We would then use this in the same NMOS V_DS bias. The higher voltage will go with drain and lower voltage to source.

Well, what's the difference now? Since N-channel MOSFETs need a gate-to-substrate positive differential relative to voltage threshold to go active, then in this configuration, when we pull the substrate terminal, relative to the threshold, the NMOS activates. Leave it within threshold or negative (above the gate), it doesn't go active. Effectively PMOS, though, in terms of Physics, the charge carriers moves from the side with lower voltage (source), instead of the higher one (drain).

Is there a big hole in my logic here? Are there any practical considerations that was not mentioned?

I ask the latter as I'm not even sure if driving from the substrate side will give decent and similar Transconductance. It's usually manufactured just as a wide plane at the back.

On that topic, wouldn't it have been better if we optimized the substrate also so that we can attach a terminal there and expect symmetrical result as with driving from gate? Then we'd have a 2 port monolithic/discrete semiconductor.


texts: Is this a correct way to have a 1 second delay?

texts:
If I have a PIC24 with a 4 MHz frequency. Is it accurate to have a 1 second delay by having 4 million clock cycles?

I made a 1 second delay like this on my PIC24FJ128GA010:

    MOV     #244, W3
DL: REPEAT  #16383
    NOP
    DEC     W3, W3
    BRA     NZ, DL
    REPEAT  #1566
    NOP
    RETURN

Clearly if you calculated the cycles right you will get 3999995 cycles plus 3 for RETURN and 2 for CALL = 4000000 cycles. Can this be exact ? On a LED blink example with a comparison with a real clock, I can see (almost) a very very minor difference between them.

What factors can affect this accuracy ?

P.S: I used many delay techniques, the __delay_ms function in the XC16 C compiler, the timer interrupt in both assembly and C, and the RTCC module for accurate timing. I'm asking this just for practice and learning.


texts:
I build a standalone board for my ATMEGA328P-U chip according to this tutorial (which should be the same as this).

My schematic should look like this

On my real perfboard I have 2 GND lines and 2 5V lines (one pair on each side). I verified that these are 5.02 V.

  Pin - Voltage

  7 - 5.02V

  20 - 5.02V

  21 - 5.02V

  19 - 0.558V

  3 - 1.15V

  4 - 1.15V

  5 - LOW

All Pins that should connect to GND read a voltage near 0V.

Using the following code

int relayp1 = 1;  // LED on Pin 13 of Arduino
int relayp2 = 2;  // LED on Pin 13 of Arduino
int pirPin = 3; // Input for HC-S501
int LED = 19; // Input for HC-S501

int pirValue; // Place to store read PIR Value

void setup() {

  pinMode(relayp1, OUTPUT);
  pinMode(relayp2, OUTPUT);
  pinMode(LED, OUTPUT);
  pinMode(pirPin, INPUT);

  digitalWrite(LED, HIGH);
  digitalWrite(relayp1, HIGH);
  digitalWrite(relayp2, HIGH);

}

void loop() {
  pirValue = digitalRead(pirPin);

  if (pirValue == HIGH)
{
  digitalWrite(relayp1, LOW);
  digitalWrite(relayp2, LOW);

  delay(120000);

  digitalWrite(relayp1, HIGH);
  digitalWrite(relayp2, HIGH);
}
else
{
  //Safe! Continue usual tasks...
}

}

Not shown in the schematic, I use a HC-SR501 PIR motion detector which is connected to Pin 5 (D3). Pin 3 and 4 are connected to a relay.

The setup does work on the breadboard, using power directly from my arduino uno clone.

The standalone board is powered by a 12V, 1.5A power supply.

As you can see, the output voltages are too low. Besides that, the LED is not powered. I uploaded another sketch, that should switch Pin 3 and 4 HIGH for 5s and LOW for 5s.

int relayp1 = 1;  // LED on Pin 13 of Arduino
int relayp2 = 2;  // LED on Pin 13 of Arduino
int pirPin = 3; // Input for HC-S501
int LED = 19; // Input for HC-S501

int pirValue; // Place to store read PIR Value

void setup() {

  pinMode(relayp1, OUTPUT);
  pinMode(relayp2, OUTPUT);

}

void loop() {

  digitalWrite(relayp1, LOW);
  digitalWrite(relayp2, LOW);

  delay(5000);

  digitalWrite(relayp1, HIGH);
  digitalWrite(relayp2, HIGH);
  delay(5000);
}

Ignore the female PIN headers.

I measure 1.15V still. So I assume the chip is not properly working on the breadboard. Any ideas what to check next?


texts: How does this soil moisture sensor work?

texts: I found information on how a capacitance moisture sensor works, but I couldn't find any information on how the following sensor works. What is the theory behind this sensor?


texts: Op-amp non-inverting amplifier with clamping?

texts:
I am designing a simple electret microphone amplifier for use with Arduino. My current design is shown below:

I was wondering if there was a way to combine the diode clamp (D1 in  the schematic) with the non-inverting amplifier to make the clamping voltage 0V instead of around -.6V. If possible I would like to just use the op-amp in the design and not add in the second half of the MCP602.

Thanks!


texts:
I recently received a Nokia 5110 LCD screen and have hooked it up to my Uno and got it displaying stuff.

I'd like to try using it in a project with an ATtiny85 and found some resources to that effect, however, I'd like to be able to run it from fewer pins than the 5 I've started off with.

I found a few things online which suggested I can tie the RST to VCC and the CE pin to ground.

I connected RST to VCC and that seems to work ok.

Connecting CE to ground doesn't work properly - it either displays half inverted with a bit of garbage or more usually just displays nothing at all. From looking at the datasheet, CE needs to see a falling edge in order to enable.

I reconnected it to a pin and modified my code so that it simply writes it HIGH and then LOW in the setup() function and leaves it alone after that and the screen seems to work happily after that.

Feels like a waste of a pin though! Is there any way I can simulate the falling edge without it needing to be connected to a pin?


texts: Is it possible to build a CPU from content-addressable memory?

texts:
Every modern programming language use objects and not C/C++ style struct/class.
In C/C++ every data member has a size, so addressing a struct member is basically a memory address + offset. But script languages just like JavaScript and many others use an object ID that contains key/value pairs. These key/value pairs can be also an object ID.

So nowadays hardware memory is addressed with memory address + offset or memory address to a lookup table where key/value are stored.

A memory address can contains data or ASM code that is executable by a CPU.

So is it possible to build a hardware that only contains content-addressable memory (CAM)?

I can imagine the following:

Data:

id: 23
  -key: 123, value: 7
  -key: 456, value: 8
  -key: 789, value: 0

This is a scheme of a content addressable memory block. This block can be write with a SetValue(id, key, value) opcode and can read with a GetValue(id, key)

My idea is that if I specify a key/value pair for executable memory block I got a CPU.

If a memory block contains special key value pairs it will act like an opcode. For example if contains a key that is < 100 than it is an opcode

id: 45
  -key: 12, value: 7  // key 12 opcode for add two data
  -key: 10, value: 8  // key 10 is arg1, value is a data
  -key: 11, value: 9  // key 11 is arg2, value is a data

In this architecture every memory block an object and every memory block a minimal CPU at the same time. Do you think is it possible to build such a hardware?


texts: Would increasing regulator rating allow connected components to a system to not cause brownout?

texts:
Currently, I have several ICs connected in a circuit to a 6 VDC wall supply through a 7805T voltage regulator. The outputs of the circuit are LEDs and I also have a test point in my circuit in which I can attach a speaker to hear radio signals.

I have a sub-circuit that contains ICs, an LED and an LCD. This connects to the main circuit via the serial port (not to/from computer) through a 3 feet serial cable.

It seems that the LEDs dim slightly on the main circuit when I connect the sub-circuit but the LCD backlight turns on somewhat dim.

If I have the speaker connected as well as the LCD, the LCD back light dims even more to the point where I can't see it and the LEDs dim slightly.

all LEDs are the ultra-bright RGB type.

I rely on the internal resistor of the LCD when I connect the back light. Maybe that's my mistake. For the rest of the LCD, I have a 2.2K resistor connected between pin 3 (reference) and ground. For LED's I use a 2.2K resistor for red and 10K resistor for the remaining colours. I would expect the LEDs to be dimmer than the LCD back light but the opposite is true.

As my circuitry is extremely large, I want to try to solve this with simple methods. I'm just curious. Would replacing the 7805T voltage regulator with one that has a higher current rating all I need to increase the odds of this problem being fixed?

UPDATE

I then proceeded to add measurements. My circuit comes with a battery charger which is just another voltage regulator.

I tried an adapter that indicates it produces a 12VDC output with 800mA. The RGB LED's continue to have no problem lighting up. The regular LED's as well as the seven segment display also have no problems lighting up (including the larger display with forward voltage of 3.7 to 4.4 at 20mA). However, the LCD back light does not want to light up. I begin to think maybe those LCD modules I purchased for $2 from china didn't come with built-in resistors. I'm not 100% sure.

After the first regulator, the voltage output at the battery connector (which is the output of the LM317 from the charger) is 5.11 VDC. I'm not sure why its so low when the resistor ratio I used is 330 ohm and 1.8K. I was hoping for 7 or 8 VDC so I can charge the batteries as well when needed.

I then measured VCC and GND at an IC socket. VCC is connected to +ve output of the 7805T through a 0 ohm resistor. The result is 1.42 VDC with a battery symbol on the voltmeter. I wonder if my voltmeter is joking.

Next, I tried a 6 VDC 900ma adapter. The LEDs lit more dimly but the larger seven-segment display units did not light at all. And as usual, nothing on the LCD appeared, not even the back light. In both tests, I have A and K pins on the LCD connected to +ve and gnd respectively. I measured the battery terminal and it reports 3.81 VDC. I measured an IC socket and it reports 0.91 VDC.

I'm going to add my charger circuit to see if that's the culprit.

THE CHARGER CIRCUIT

This is the circuit I use as my charger.

The leads on the far right are connected to digital circuitry and that output on the far right I was expecting to be 5 VDC since I'm using 7805T.

For capacitors, P2, P8, CHVREGIN, and CHVREGOUT are 22uF, and C7 is 2.2nF. Both op-amps are from a single LM358 IC.

CHGLIMIT is 100 ohms 1 watt.
CBUFOUT is 10 ohms
VDR1 is 3.3K and VDR2 is 4.7K as I'm trying to make a max charge reference point for the batteries.
RHVD is 330 ohms 1 watt and RHVDG is 1.8K 1 watt.
HVREG is the LM317 voltage regulator.
Transistor is 2N2222A
Diode is 1N4007
The solar jumper is used for an option to use the solar panel to charge batteries only if the plug-in charger isn't used.

chgen was shorted in all tests to make the charging action work and to offer a secondary source of power to the remainder of the circuit should batteries fail.


texts:
I am brand new to PLC's (don't even have a single device in use yet), but I have been programming for more than 20 years and haven taken classes in electrical controls, so I understand machine logic very well.

I am planning an application where a machine will make a simple movement with a preset delay after being triggered.  Specifically, there are many items on a conveyor belt and some of them will be diverted off the belt.  The sensor that triggers this is near the beginning of the belt, and the device to remove them is at the other end.  There will likely be multiple triggers/inputs occurring prior to the end of the previous delayed output.

Is this something most PLC's will readily handle and is there anything special I would need to do to accomplish this?


texts:
I'm a curious person that knows only basic physics, and I want to craft a homemade power generator (eolic, magnetic or hydroelectric, the origin of the energy doesn't matter yet).

I would like to find formulas to determine the possible output in volts and watts. I think these will tell me all the variables like the wire gauge, the number of turns + diameter of the coil, the size/shape/strength of the magnet, etc. Where can I find formulas like these?


texts: How to create constant 5V 300mA from 0...6V variable voltage source (voltage generator)?

texts:
I'd like to solve the above-mentioned problem by using a buck-boost or SEPIC DCDC converter. I haven't successfully found any suitable ICs though. SEPIC converter with input voltages from 4.5V to twenty-some volts doesn't seem the best choice as it would be necessary to have the aimed 5V 300mA output as soon as possible. (Minimum input of 2...3V would be better.) I was thinking on designing a voltage doubler / multiplier between the generator and the converter so that the input voltage is more convenient (4.5V input is reached faster). Unfortunately I don't have any previous experience on voltage multipliers, so I'm not quite sure it would solve my problem.

Efficiency is vital, so I'd prefer keeping it as high as possible. The voltage source will gain the power from the rotating shaft of a small car, thus the voltage will increase monotonously in time until reaching the maximum value of approx. 6V.

Thanks in advance for your help!


texts:
I've got this problem:

So I'm thinking about the discharged section, t<0 s. Mainly my thoughts are how there could be a voltage across the capacitor when it is discharged.
Basically I want to understand what happens when the capacitor gets discharged and charged. My own thoughts are that between -2 ms to 0 ms there is no current flowing because of the switch being open. Then there should be no charge "applied" on the capacitor. Therefore I'm thinking that the volatge over the capacitor should be 0 V between -2 ms and 0 ms.

Am I thinking right?


texts: designing an amplifier with specific characteristics

texts:
I want to design a common emitter amplifier with these specifications:

Av (gain) = 50
VCC = 5 V
Rload = 0.25 kΩ

Maximum symmetrical swing is considered
but I can not get the collector and emitter resistance values correctly.


texts: Proteus failing to load .elf file for arduino simulation?

texts:
I've been writing code for an alarm clock based on the Arduino Uno, and then uploading it to a simulation in Proteus to test it out. Everything was working perfectly until I decided to try changing the Uno for a Mega2560.

I didn't even finish connecting the Mega before deciding against it, and used Ctrl+Z to return to the working state with the Uno, but it just stopped working completely.

At first it was giving me an invalid opcode error 0x9419. This error has now stopped showing but now a different error comes up. It says can't load the .elf file into the arduino. I've tried several times, and tried using a hex file too, but nothing works.

I can still write my code but now I can't test as I'm going along, so anybody with any experience in Proteus I would be very appreciative if you could help.

Edit: the opcode error has now come back and the .elf error has disappeared, even though I've not changed anything. The full error is "Invalid opcode 0x9419 at PC=0x16A0"


texts:
I just owned a desktop PC and as display I connected my TV through HDMI cable.
Today I changed the HDMI cable to one that can handle 4K resolutions. So I disconnected the old HDMI cable and then with the new cable I connected first the PC side and the the TV side and I got a spark in the metal part of the HDMI plug when I was trying to connect it. Also if I touch the TV HDMI port a get a little shock in my finger.
The TV only has a 2 prong power cord, so it doesn't have the earth pin.
Does this is potentially dangerous to my PC?
I've read this in different forums but there are very spreaded ideas:

It is very risky and that could fry the GPU.
The earth pin is not necessary because the TV has plastic case (I know that ground is needed to avoid electric shocks to users when live wire touches the chasis but this is not the case)
Coax cable can be the best way to ground a TV (if it has 2 prong plug cable)
Some manuals (of TV with 2 prong plug cable) says that to connect an HDMI device everything needs to be powered off and unplugged from any source to make the connection (this makes sense so the TV will be grounded with the HDMI cable so no shocks and fried GPUs)
Nothing will happen those sparks will be uncharged by the grounded device.

Any of these Ideas are true? (Especially #4)
I really don't know if is safe or not to connect  all again.
Thanks in advance.
Edit:
Just to give more information...
The TV and PC are connected to AVR outlets of a voltage regulator. Also a modem and a Nintendo switch dock are connected there.
The modem has a phone line that is plugged into the voltage regulator phone line protection.
The Voltage regulator has 1000W capacity. And the outlet where is connected is grounded properly.
The TV and modem are connected through Ethernet cable. Also the Nintendo Switch dock is connected through HDMI cable. Nintendo switch dock does not have earth pin.


texts:
I don't under this layout figure (5.c) in pic attached.
This is a screenshot from research paper in this link:-

https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7573442

Alternate link for the paper in case if you are not a member of IEEE
https://1drv.ms/b/s!AuHq5DWFZ2WugWlDfRyx1OofH1-N

My basic Curiosity is that layout are generally in shape of squares and rectangles, but in this layout what is that blot (ink drop) like thing in fig 5.c


texts: What does the wifi amplifier exactly amplify?

texts:
The question is not exactly about the wifi, but on how does this operate in full duplex, in principle?

As an practical example, lets take some commercial amplifier. As we can see from the picture, it has one antenna and one I/O port:

On one hand:

It have to amplify recieved signal, because low power transmitters wouldnt reach it otherwise.
And it have to amplify transmited signal, because low power recievers wouldnt hear it otherwise.

On other hand, its inputs and outputs are shorted in infinite loop. It definetely recieves that it transmits, and amplifies it, then it amplifies what it recieves and transmits, and so on, so on, so on.. In short words, It should hear itelf, self-excitate and burn!!!

How can this radio amplifier have single input, single output and amplify both recieved and transitted signals!?


texts:
I'm looking to make a timer for Rubik's Cube solving, which looks like this:

My design just has some added features and a different output type.

However, I'm not sure how best to replicate the hand sensors. They're just binary, "hand on"/"hand off". The pressure required to trigger the sensor should not be very high.

I have a couple of ideas, but I can't imagine that the actual product does any of these. Which one of these is the best, or is there a better way?

Each hand sensor is just a physical array of, say, 10 small pushbuttons laid out in a horizontal line. Each one is wired in parallel between VCC and signal so that if any are pushed, the signal is pulled high. I would have a plastic sheet over the top of the pushbuttons so that pressing anywhere (or everywhere) on the sheet will trigger multiple pushbuttons.
Have a strip of conductive metal along the bottom of the hand sensor area, and then another strip on top. Separate the two by some sort of spring, and then when pressed the two will contact. There would also be some sort of plastic sheet over the top just to make it look better.
Use capacitive touch sensing. (I'm not sure how cheap this is though, or if it works through a thin plastic sheet.)

The signals (one for each hand) just need to be read by some microprocessor -- I haven't decided on one yet, but probably some simple ATMega.


texts: Big capacitors measurement(LCR meter related)

texts:
I digged up some capacitors from amplifier and decided to test them, one of them is said to be 8200 uF, the other 4700 uF.
I measured them with LCR meter and it gives very strange numbers.
If LCR meter tests on frequencies 1-100 kHz the LCR meter reads 0L, if LCR tests on 100-120 Hz then it reads around 3 mF for 8200 uF cap(yes, milliFarad, so more than two times less said capacitance).  For 4700uF it reads pretty close on lower frequencies, but on higher it is still OL(starting from 1 kHz).
I tested the capactiros for short-circuit - no problem.
LCR meter reads small capacitors without a problem.
What is going on? I've seen this before, but I thought maybe the capacitor is dead, but now it comes again. And again with quite big capacitors. The don't have buldges and have no damage.
I usually don't use such big capacitors, so maybe I measure them in wrong way, but I don't have any kind of special mode on LCR meter for big capacitors.
Caps are electrolytes of course.

UPD:
So the main questions:
Why LCR can't read anything on frequencies higher than 1 kHz for big caps(more LCR meter related quesiton).

*SOLVED - Is it possible for cap to drop it's capacitance to more than two times less? I usually seen capacitance drops for 20-30% for very old caps.
---I found out it is most probably broken capacitor, because other caps I have seem to be within reasonable decrease range.

(source: aliimg.com)


texts:
I am confused about a couple of points:

When the electrons diffuse from N side to P side, and holes diffuse from P side to N side, negative charged region is formed at the junction in P type and positive charged region is formed near the junction in the N type.

The question is:

Why is the positive charge not distributed in the entire N type region (as there are free electrons for conduction in the N type region)?
Why are the charges fixed  at junction despite the presence of holes and free electrons?


texts: Feeding grid transformers via secondary, primary disconnected

texts:
I am interested in how transformers are used in the electrical grid, with a view of one day building an isolated "microgrid" for educational purposes.  I am however having some difficulty getting some concrete answers for how transformers - as used in the electrical grid - work.

There are a number of questions here about running a transformer "backwards" (using the secondary winding as the input) with two common answers.  One is that transformers can be run either way with no special consideration, and the other is that the winding impedance is often much lower on the secondary side, so running a transformer backwards may overload the source AC supply.

Is this true?  If I took say a 50 kVA transformer, 11 kV primary 415 V secondary, and fed 415 VAC into the secondary side, would it try to draw some large current well beyond what you would expect as inrush current?  Or would it simply start at the high inrush current level and quickly drop back to a current draw similar to that model's "no load" rating?  How is this different to connecting the transformer normally on the primary/HV side?  Wouldn't that also have a similar inrush current (though obviously smaller due to the higher voltage)?

My reason for asking is that I can't get a definite answer as to whether you can use a large step down transformer in reverse, and if you can, whether an initial surge is all you have to deal with or whether there's more to it than that.  I suppose what I am getting at, is whether there is actually a design and performance difference between two transformers that are otherwise equal, except one has an 11 kV primary, 415 V secondary and the other has a 415 V primary, 11 kV secondary?

Taking this a step further, if I want to buy a small transformer for my isolated microgrid, is it a problem buying one that is too large for what I need?  For instance it looks like I can source 10 kVA 11 kV transformers from China relatively cheaply, but if I only have say 1 kVA of power available, will it draw too much current even after the inrush current has settled down?

My limited understanding is that there will be an initial spike in current until a magnetic field has been generated inside the transformer, and after this the current draw will drop back to the transformer's "no load" rated current, only increasing again if power is used on the other side of the transformer.  So I could "run" a 10 kVA transformer on only 1 kVA, as long as the power source can handle the transformer's inrush current.  I thought this would apply whether you feed the transformer's primary or secondary, but after reading some other answers here, I am now not so sure!


texts: Need help finding the datasheet of this IC

texts:
I'm trying to find out what this IC is and appreciate any help! It is located inside an EV charging cable and its main task from plugs datasheet is:

"STATIC RESISTANCE
 (FROM PROX. DETECTION TO GROUND) 150ohm
 RESISTANCE WILL INCREASE TO 480ohm WHEN
 LATCH IS DEPRESSED" (No more info on datasheet about this mini circuit)

Here is the reverse-engineered schematics of the small pcb in the charging plug:

Scope picture of unknown IC

I guessed it might have been ADM803/ADM809/ADM810 which is same package but unfortunately pinouts doesnt match.


texts: Calculate absolute values for resistor bridge to use with op amp lm358

texts:
I'm trying to make a simple thermostat using a thermistor and an Op Amp. The relevant part of my circuit diagram is shown below.

simulate this circuit – Schematic created using CircuitLab

R4 is the thermister and R1 is a variable resistor. I'm able to calculate the relative values of the four resistors to each other, but I don't know how to choose the absolute values. How do I decide what power of ten in ohms I should be working in? Ie should the resistors be around 10Ω, 1kΩ, 100kΩ etc.

I assume this decision relates to my power supply and the choice of Op amp, but I've no idea how to make a sensible choice.

Thanks,


texts: Is it possible to use Microcontroller I/O ports as UART ports

texts:
I am using NXP P89LPC954 Microcontroller in my design.It has two UART ports. As it is known that UART are point to point connections between two devices. Hence i can only use two devices to connect to the two UART.

Now if i want to connect third device to the microcontroller is it possible to use normal I/O pins as UART pin through a MAX232 driver. If so what should the microcontroller code contain to make the pin act as UART TXD or RXD.


texts: C64 composite video out of spec? Upscaler rejects it, but accepts TC-2048

texts:
Trying to wrap my head around why a particular CVBS/SVideo to VGA converter I have accepts every composite signal I feed into it, but refuses a C64C CVBS signal (which my 55" Samsung TV doesn't seem to have a problem with). Here's a capture that works (from a Timex Computer):

And here's the one from the C64:

One thing that seems evident is that the voltage amplitude of the Spectrum clone is about half of that of the C64. I've tried a series resistor to no avail. Any ideas?

Some more info here, as I have the C64C, it outputs Luma and Chroma in separate channels. I tried to make an adapter for SVideo, but I'm still out of luck. Here's a sample of the chroma channel:

And the Luma channel:

Could it be that the upscaler doesn't receive enough current from these? I'm thinking in trying to boost the signal with something like this:

Meanwhile, I ordered a different upscaler; though I still wished I could somehow solve this problem, as an academic exercise :)

Here are a couple more of waveforms, with the CVBS of the TC2048 (blue) and the C64C (yellow) side-by-side. First, the Horizontal Blank:

And the Vertical Blank:

A couple more detailed waveform on each Vertical Blank:


texts:
I want to stream video from a camera 640x480 frame of 8-bit approximately.

I don't want to use wi-fi. I capture the data, encode it, transmit the signal over RF and receive it. Decode the signal.

My goal is to make a quadcopter streaming live video over radio frequencies. How is this achievable?

I am in my final year of electrical engineering in telecommunication.


texts: Which parts of an AC relay does the electrical current flow on?

texts: Below is a common relay that is used in Arduino projects. When the AC lines are connected, if I touch the screws that holds the AC lines (marked as "1" in the image) do I get an electric shock? Of course, I am not going to intentionally do that, but just want to know. What if I touch the soldered pins at the bottom of the relay (marked as "2" in the image)? Do I get an electric shock?


texts: Double tap push button which resets if not pressed twice in quick succession?

texts:
I'm new to electronics, so don't know where to begin -

I'm trying to create a push button which needs to be pressed twice in quick succession, to actually power on a device. Pressing it just once, or having a long gap between presses should be equivalent to not pressing the button at all.

Is there a way to do this ? How would I get started ?


texts:
I need to implement the following circuit in LTSpice but I don't know if my schematic is ok and what values \$C{inf}\$ and \$R_2\$ should be.

The following constraints are imposed:

\$V_{CC}=10V\$
\$V_{CM} = 1.5V\$
\$R_1= 15k\Omega\$
\$Vg\$ is  a  sine  wave  with  a  frequency  of  1  kHz, whose amplitude  will  be  chosen  so  as  to ensure minimal distortion of the output signal (i.e. \$v_0\$ should also be a sine wave);

I need to choose a value for \$R_2\$ and \$C_{inf}\$ in order to have a (theoretical)gain value \$A_v=1500\$. Also, how can I compute the theoretical   expressions of the DC collector currents of bipolar transistors  \$Q_1–Q_8\$, considering \$V_{BE}\approx 0.6V\$ and the theoretical expression of the small-signal voltage gain \$A_v= \dfrac{v_o}{v_g}\$?

The first picture is the schematic and the second one the LTSpice implementation.


texts:
Need of SSC:

Spread spectrum clocking (SSC) is a special way to reduce the radiated emissions of digital clock signals. These levels or energy is radiated and therefore this is where a potential EMI issue arises.

Doubt:

Assume that SSC clock has range from -5300 to 300 ppm, assuming down-spreaded SSC. SSC clock is only driven to output lines (USB Tx D+/D- lines) or given to whole system blocks?

If it is only at the PHY-Layer, then how does it compensate for the clock difference for data exchange between PHY to/from Upper Layers? (Need buffer at SerDes?)
If core clock (with generated SSC) is given to whole system blocks then does it affect Fmax of designed system? (Frequency of operation may vary!!), every thing including SerDes have same source of frequency.

Any idea which is preferable or best way other than these two that I have outlined?


texts: Bluetooth module (BLE112) USART: do I need to use its own microcontroller?

texts:
I am looking into the this module.

All I need it for in my design is USART connection to my MCU (TX/RX connections). I don't care for the internal microcontroller (yet).

My question: if I connect, with my host MCU, TX <---> RX and vise versa, do I need to use the BLE112 internal microcontroller at all to initialize functionality, or can I just be up and running with my host MCU over USART?

Thanks.


texts: Use ACS712 current sensor in two-phase electrical system

texts:
I'm thinking about using the Allegro ACS712 current sensor for measuring house equipment current consumption (for example TV). The issue I'm facing is that my house energy supply is built around two 110VAC phases. My equipment works with 220VAC but not in Live-Neutral configuration, but in Main1-Main2 configuration.

Having the two connections "active" confuse me a bit... I don't know how to proceed. Should I use two sensors, one for each main? Should I measure only one cable? Will the equipment current flow from only one main or from both of them?

Any guide will be appreciated.

Thanks a lot!

EDIT:

This image represents what I want to do:

Also, the values you see stated were measured by my multimeter. Maybe this helps to sum up what I was trying to say and reduce confusion.


texts:
My code on ATtiny13A:

#include <avr/io.h>
#include <stdint.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <stdlib.h>

#include "dbg_putchar.h"

void ADC_init()
{
    // Set the ADC input to PB4/ADC2
    ADMUX |= (1 << MUX1);
    //ADMUX |= (1 << ADLAR);
    ADMUX |= (1 << REFS0);

    // Set the prescaler to clock/128 & enable ADC
    // At 9.6 MHz this is 75 kHz.
    // See ATtiny13 datasheet, Table 14.4.
    ADCSRA |= (1 << ADPS1) | (1 << ADPS0) | (1 << ADEN);
}

int adc_read (void)
{
    // Start the conversion
    ADCSRA |= (1 << ADSC);

    // Wait for it to finish
    while (ADCSRA & (1 << ADSC));

    uint8_t low  = ADCL; // must read ADCL first - it then locks ADCH
    uint8_t high = ADCH; // unlocks both

    int ADC_val = (high<<8) | low;

    return ADC_val;
}

void wyslij_wynik_pomiaru(int wynik)
{
    char str[4];
    itoa(wynik, str, 10);
    dbg_putchar(str[0]);
    if (wynik > 9) dbg_putchar(str[1]);
    if (wynik > 99) dbg_putchar(str[2]);
    if (wynik > 999) dbg_putchar(str[3]);
    dbg_putchar('a');
}

int main(void)
{
    DDRB = _BV(1);
    dbg_tx_init();
    ADC_init();
    int wynik_poczatkowy = adc_read();
    int wynik_nowy;
    while(1)
    {
        wynik_nowy = adc_read();
        if (abs(wynik_poczatkowy-wynik_nowy) > 150) {
            wynik_poczatkowy = wynik_nowy;
            PORTB |= _BV(1); //turn on ESP8266
            _delay_ms(5000);
            wyslij_wynik_pomiaru(wynik_nowy); //send data
            _delay_ms(5000);
            PORTB  &= ~_BV(1); //turn off ESP8266
            _delay_ms(14900);
        }
        _delay_ms(100);
    }
}

When you read the voltage level of the ADC and it is less than 1023, but steady, then everything works correctly: IF loop executes only once, however when the voltage level read on the ADC is equal to 1023, then the IF is executed continuously (condition is still met, but it should not).

Why is this happening and how to fix it?


texts:
I found this chip in the FCC filings for a pair of headphones that I have. I'm not planning any serious reverse engineering project here, but I am curious what brand this chip is (I assume getting anything more than a brand from this image is going to be pretty hopeless). As far as I can tell, it either reads "am" or "om", or potentially "WD" in the other orientation. It is very likely a DSP (used to implement noise cancelling), although I guess it could be a general purpose microcontroller.

Original picture:

Scaled up a little:


texts:
The EAGLE docs says the Reference layer (#49) is for "reference marks".

Is this referring to mechanical data for automated assembly such as fiducials and component outlines?  Or is it something else entirely?


texts: How to deal with a DC adapter with irregular voltage output?

texts:
Background information:
I tried hard to get a Schmitt-trigger working, but it kept failing. By accident I figured out, that my AC-to-DC adapter produces a very irregular voltage output (I could hear the 50Hz very clearly). After putting a strong electrolyte capacitor (over 4000 microF) on the DC output, it started working.

However, I'm asking myself, if the DC output it stable enough that way, or if I could experience difficulties in the future when building (let's say) a radio.

What are common ways of stabilizing the DC output of such an adapter?


texts: What Voltage rating for DC-blocking capacitor between circuit stages in microphone preamp

texts:
What DC rating should I pick for DC-blocking caps between 2 stages of an audio circuit using opamps (5532) operated on +16/-16v rails.

Is it about the AC voltage that will pass through it that can go as high as 26 Vpp or about the DC voltage that I read can leak out of an opamp but I was barely able to measure (+- 10mV).

Here is the circuit:

I've seen, 10v cap rating, even 6.3v. I guess it's about what is called DC bias or something? Also, I'v always seen the + side of caps looking at the output of the preceding opamp stage, is it always how it should be?

Thanks


texts: Connection problem with RS485 system on PC with RS232 port

texts:
I am developing a system in which I have to integrate hardware. I am from computer background, so I don't have much knowledge about hardware systems.

The issue is I have to integrate with London based taximeter with MR400S model. This taximeter gives output according to RS485 system. My application is on PC and I want to receive signal from this taximeter. My PC can read data from RS232 cable. I have RS232 cable so I have connected the RX and TX of taximeter to TX and Rx of cable. But my PC is not detecting this hardware, so can anyone help me solve this issue?


texts:
I wonder what's wrong with my circuit. Voltage between VIN and GND is 0.5V instead supposed 3.3V.
Is there design issue? Assembly was maded by JLCPCB
VIN voltage: stable 3.3V from PSU (VIN - B_GND) (testing purposes)
VIN: Battery plus pin
B_GND: Battery ground pin
GND: Circuit ground
Schema:

PCB:


texts:
I am wondering if anyone can recommend a logic analyser for a Apple Mac environment with similar features as the SCANALOGIC 2 PRO around the same price would be great as well.

or some thing that is similar, what type of features am I after for working with SPI and I2C. Fairly new to the Digital electronics

Beginner's logic analyzer? is all PC based.

Was just wondering if anyone knows of any that work with Mac at all. that aren't $199+ dollars


texts:
It's time for another rousing round of "Name That Component"!

Today's participant hails from a Bluetooth combo keyboard/mouse, where it detects finger motion across it which the Bluetooth chip translates into relative motion HID messages. It (supposedly) uses an imager of some sort to detect motion of an object that contacts the surface. Does this little beast have a proper name?

(The other side only has a metal key dome under a white sticker which when depressed the Bluetooth chip converts to a middle-click HID message.)


texts:
After putting battery in freezer overnight (in ziplock bag to avoid moisture (according to sites battery loses >20% Capacity in >3 months to a year) Does the rapid heating up cause by turning phone on and games harm battery after storing it in a cold place like a freezer?

Exactly how much is it safe to discharge? (I've found to avoid full discharge on several sites but no site says exactly how much of a discharge isn't harmful except about 20% but with no sources to back it up and I don't know how accurate is that "about".)

please see at least this comment on bottom of this page


texts: Which schematic is better for keypad connection to an MCU?

texts:
I have this three keypad connection sketches, all of which i've seen in various application, and some i've also used, but i want to know if there is any advantage of one over the other.

The keypad will be connected directly to DIO pins of a PIC microcontroller, PIN 1,2,3 as OUTPUTS, and PIN A,B,C,D as inputs.

The keypad will not be on board, but will be connected via cables to the PCB board, i don't know if this makes any difference.


texts:
I was wondering why would anyone use a MOSFET amplifier?
Since a MOSFET amplifier is nonlinear, it produces significant amount of distortion.
To minimize distortion, textbooks suggest using small voltage variation around the Q-point, which makes amplifier very inefficient.
Why not then use a standard BJT amplifier instead?


texts: Combining two PWM outputs for finer granularity

texts:
Follow-up to: Is it okay to use a MOSFET in its resistive region with a heat sink?

I plan to use two PWMs to very slowly (exponentially) turn on an LED strip, from 0.002% to 0.004%... to 100% power over twenty minutes. 0.002% seems to be a safe brightness that doesn't seem jarring when suddenly turned on, but I can't push much higher than that. The formula I chose (for its very slow start) is: power=(2^(t*15)-1) / 2^15 where t is the normalized time, from 0 to 1. I don't care about the number of steps, so long as none is perceptually large. (So 97%→100% is fine because it's unnoticeable, but 0.002%→0.5% would be quite jarring.) 255 steps would be a great plenty if I could take a step every few seconds, but if the steps represent linear brightness increments, I need more like 51000 steps.

Both PWMs are 8-bits. The high power part PWM1 will take over when the low power part PWM2 reaches a certain level. In fact, the "low power" part of the circuit could drive the light from 0 to 100%, but that half of the circuit (left) is analog, and I can't easily model the brightness. Hence, at the level where I no longer need extremely small gradations, I'll switch over to driving the light with PWM1, which is mathematically nice but incapable of the extremely low power needed for the early steps.

Is this a reasonable circuit to drive a transistor Q2 with both a PWM signal (PWM1) and an analog voltage (after a low-pass filter from PWM2), but not at the same time?

Note: I will probably not be combining PWM1 and PWM2 dynamically in a "most significant digit / least significant digit" configuration, because the voltage->brightness response from PWM2 is way too nonlinear.

Potential problem:

The low-pass filter may not respond fast enough, so when PWM1 starts sending its signal and PWM2 turns off, the low pass filter may not step down fast enough to avoid a flash. (The flash would occur if the low-pass filter remains on during the early OFF portions of PWM1's signal.) This would manifest in a brief doubling in brightness.

Potential solution: maybe with a diode, capacitor, and a couple resistors, I can hold the base voltage of Q1 high when PWM1 becomes active, even during the off-portion the signal.


texts: Simulation of sensor in proteus using Atmega16

texts:
I have trouble reading data from sensors using ATmega16 in Proteus. We use either light sensors for which I use LDR in proteus, or LM35 temperature sensor for temperature reading. The problem is, doesn't matter which sensor I use, I get an "[AVR AD CONVERTER] Reference value = 0 " error when I run the Proteus simulation and a big reading on the display, I think it's the max value.

The problem is somewhere in reading the value from the ADC channel, namely CH0 or PA0 in my case. At least I think it is.

Here is the code for the temperature sensor:

#define F_CPU 7372800UL
#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include <stdlib.h>
#include "lcd.h"

void writeLCD(uint16_t adc) {
    lcd_clrscr();

    char adcStr[16];
    itoa(adc, adcStr, 10);
    lcd_puts(adcStr);
}

ISR(ADC_vect) {
    uint16_t temp = ((ADC * 5.0/1024) - 0.5) * 1000/10;

    writeLCD(temp);
}

int main(void) {
    DDRD = 0xff;

    TCCR1A = _BV(COM1B1) | _BV(WGM10);
    TCCR1B = _BV(WGM12) | _BV(CS11);
    OCR1B = 64;

    lcd_init(LCD_DISP_ON);

    ADMUX = _BV(REFS0);
    ADCSRA = _BV(ADEN) | _BV(ADIE) | _BV(ADPS2) | _BV(ADPS1);

    sei();

    while (1) {
        ADCSRA |= _BV(ADSC);

        _delay_ms(1000);
    }
}

... and the proteus scheme:

Light sensor code:

#define F_CPU 7372800UL
#include <avr/io.h>
#include <util/delay.h>
#include <stdlib.h>
#include "lcd.h"

void writeLCD(uint16_t adc) {
    lcd_clrscr();

    char adcStr[16];
    itoa(adc, adcStr, 10);
    lcd_puts(adcStr);
}

int main(void)
{
    DDRD = 0xff;

    TCCR1A = _BV(COM1B1) | _BV(WGM10);
    TCCR1B = _BV(WGM12) | _BV(CS11);
    OCR1B = 64;

    lcd_init(LCD_DISP_ON);

    ADMUX = _BV(REFS0);
    ADCSRA = _BV(ADEN) | _BV(ADPS2) | _BV(ADPS1);

    while (1) {
        ADCSRA |= _BV(ADSC);

        while (!(ADCSRA & _BV(ADIF)));

        writeLCD(ADC);

        _delay_ms(100);
    }
}

Scheme:

Am not sure if I should change the ADMUX register or maybe add an external capacitor ? Because when we use the sensor irl we add a capacitor between the AREF and ground pins. Any suggestions are appreciated, thank you in advance.

P.S. The codes are a bit different cause we used different triggering mechanisms for data conversion but that is irrelevant here. Same error for both codes.


texts: Multiple Parallel LED Drivers with Single Thermal Derating NTC Thermistor

texts:
I am looking at powering Some multi color High power LEDs e.g LED engin LZ4 or LZ7 (probably a string of five) using
a tps92691 based Circuit

these being high power leds it seems wise to include thermal derating circuitry

the tps92691 suggests using a voltage divider with a NTC thermistor from its on voltage regulator
e.g

simulate this circuit – Schematic created using CircuitLab

The LEDs however are either 4 or 7 LEDs in one die so using multiple PTC seems redundant and complicates track layout near the LEDs . I am therefore looking for the best way to connect multiple drivers to a single NTC thermistor.

The simplest circuit would be

simulate this circuit

but that makes assumptions about the TPS92691's 7.5V LDO Regulator and that they wont "fight" with each other.

and external regulator is possible but is that really necessary?

is this a sensible way of doing this or is there a better way?


texts:
I am having difficulty calculating the gain and input resistance of the circuit below.
Neglecting ro, capacitance, and considering Ibias as ideal (infinite resistance), would this mean that the current from M1 is 0 (gm1Vgs)?
And further, indicating that the output voltage is 0?
Regarding the input resistance, I am not sure how to treat small-signal vo. I found a similar case regarding a common source with source degeneration, where the author (Razavi) was calculating the output impedance, and he shorted the small-signal input. I am not sure if this applies to the circuit below. Also, similar to the case above, since gm1Vx = 0, would this mean the input resistance in 0?
M1 is causing me lots of problems. If the input resistance is 0 this would imply that the noise figure would be 0. If you consider a source with resistance Rs, the alpha value (Rin/(Rin+Rs)) is 0, thus the noise from Rs is zero. Meaning the total noise figure would be each noise contribution divided by 0.


texts:
According to the ITU-T G.709 (OTN) specification, a single frame has 4 'rows' and 4080 'columns' of octets, arranged like this:

    1  2  3  4  5  6  7  8  9  10 11 12 13 14 15 16 17 ... 3824 3825 ... 4080
   +-----------------------------------------+-----+-----------+-------------+
 1 |  frame alignment   |        OTU header  |     |           |             |
   +-----------------------------------------+ OPU |           |             |
 2 |                                         | he- |           |             |
   |                                         | ad- |  payload  |   error     |
 3 |                 ODU header              | er  |           | correction  |
   |                                         |     |           |             |
 4 |                                         |     |           |             |
   +-----------------------------------------+-----+-----------+-------------+

The OTU header contains stuff related to transport, and the ODU and OPU headers contain information related to the payload (I don't know the details here).

When the frame is sent, this 2 dimensional representation has to be translated into a (1 dimensional) sequence of octets. Section 11.1 of the specification says that this is done by transmitting all the octets in row 1, then all the octets in row 2, and so on up to row 4.

Why is the frame transmitted in this order? To me, it seems easier to transmit the whole header (columns 1-16) all at once, then transmit the entire payload (columns 17-3824), then transmit the error correction (columns 3825-4080). Is there some advantage to interleaving the header, payload, and error correction?


texts: Special requirements 100Mbps (Ethernet) connection to PCB

texts:
Is there any special requirements/limitations to how 100Mbps Ethernet conductors can be connected to the PCB?

For instance in the design prompting the question I have a Ethernet connection entering the enclosure via a M12 panel mount (4-pin, D-coded), on the other side of the M12 are 4 conductors - these conductors need to be connected to the PCB holding the Ethernet PHY.

Can I put them into the board via a screw/spring loaded terminal? should I solder directly? Are there special connectors for this purpose that I have not yet stumbled across?


texts:
I am currently attempting to design an inverter in Microwind layout software that has equal rise and fall times. Rise time is defined as the time for the circuit's output to go from 10 percent to 90 percent of its full value, and fall time as 90 percent to 10 percent of its full value.

My understanding is that, since hole mobility is not as fast as electron mobility, the PMOS needs to be sized such that its width is anywhere from two to three times as great as that of the NMOS. However, it seems that I cannot get a complete match on rise and fall times.

My workflow is such that I design the inverter in Microwind, and export it as a PSPICE netlist format --using Level 3 models for the NMOS and PMOS-- that I then simulate with LTspice to investigate the rise and fall times. I have done so with three cases: P-width is equal to N-width, P-width is 2.5 times N-width, and P-width is 3.0 times N-width.

I can observe the difference between rise and fall times drop from 2.277ps to 1.177ps to 1.073ps as the ratio increases from 1 to 2.5 to 3.0, respectively. However, I don't know if this is "good enough" or not. For lab purposes, my professor has indicated that it is sufficient to simply show the improvement, but I'm bothered by the difference.

Is this simply an artifact of my simulation caused by some aspect of the MOSFET models? Is this indicative of a problem with my design in layout? I've attached a netlist for the 3.0 simulation. The only parameters that seem to change from ratio to ratio are the widths of the PMOS (the "W=" parameter on the "MP1" element) and the capacitors that Microwind is adding to the netlist. I suspect this might be where I'm going wrong. If these capacitances are crunched from the physical lengths of, say, the Vdd and Gnd lines, then perhaps the additional capacitance from those lengths is sufficient to sway my rise and fall times a little bit (My Vdd and Gnd lines are not perfectly identical across layouts).

My apologies if this question has been answered, but numerous different queries to the search engine for the site didn't seem to bring up any entries that address the rise and fall time issue as investigated in simulation (Equal rise time and fall time in CMOS circuits ; this entry only seems to address the "whys" of equal rise and fall times being desirable).

*
* IC Technology: CMOS 90nm - 6 Metal
*
VDD 1 0 DC 1.00
VA 6 0 PULSE(0.00 1.00 0.48N 0.03N 0.03N 0.48N 1.00N)
*
* List of nodes
* "Z" corresponds to n°3
* "A" corresponds to n°6
*
* MOS devices
MN1 0 6 3 0 N1  W= 0.80U L= 0.10U
MP1 1 6 3 1 P1  W= 2.40U L= 0.10U
*
C2 1 0  0.975fF
C3 3 0  1.160fF
C4 1 0  1.233fF
C6 6 0  0.033fF
*
* n-MOS Model 3 :
* low leakage
.MODEL N1 NMOS LEVEL=3 VTO=0.35 UO=500.000 TOX= 1.8E-9
+LD =0.008U THETA=0.300 GAMMA=0.400
+PHI=0.150 KAPPA=0.200 VMAX=130.00K
+CGSO=100.0p CGDO=100.0p
+CGBO= 60.0p CJSW=240.0p
*
* p-MOS Model 3:
* low leakage
.MODEL P1 PMOS LEVEL=3 VTO=-0.35 UO=200.000 TOX= 1.8E-9
+LD =0.008U THETA=0.300 GAMMA=0.400
+PHI=0.150 KAPPA=0.150 VMAX=100.00K
+CGSO=100.0p CGDO=100.0p
+CGBO= 60.0p CJSW=240.0p
*
* Transient analysis
*
.TEMP 27.0
.TRAN 0.01N 2.00N
* (Pspice)
.PROBE
.END


texts: What is the mode of a square waveguide \$TE_{11}\$ that is deformed into a circle?

texts:
I am trying to solve the 2013 paper set by ISRO for electrical engineers. I want some help to solve Question no 17 is correct.

So I don't even know how to approach the problem, what will be the new deformed radius? will volume be conserved? Can I say \$r = \frac{a}{\sqrt{\pi}}\$


texts: Powering 3 identical laptops using a solar panel

texts: I have 3 identical laptops rated at 45W and 20V. The combined wattage of all 3 is 135W. I want to charge these laptops via a solar cell. Do I go for a solar cell rated 135W 20V or one rated 45W 20V?


texts:
My LCD screen operational pins are driven by 5V whereas my STM32 MCU outputs 3.3V maximum.

I would like to shift 3.3V to 5V for about 6 pins. I could use opamps to amplify the input, but in my opinion that would energy, space and cost inefficient.

I have came across level shifter ICs and they seem to do exactly what I need.

Specifically, I got hold of MC14504BCP Hex levelshifters which seem to be more advanced than I need.
I don't have much experience with electronics and I have never used them before.  I would really appreciate if anyone could help me to understand how they work.

Datasheet: http://www.onsemi.com/pub_link/Collateral/MC14504B-D.PDF


texts: Where do I place linker sections in my FLASH memory?

texts:
I'm trying to write my own bootloader and an entire program to be flashed to my microcontroller from scratch (STM32F303RE based on the ARM Cortex-m4 architecture)
I've been watching a tutorial series and at this point in a video I am completely lost as to where he found this memory map diagram. My reference manuals, programming manuals, and technical reference manuals have no diagram that looks like this. It's a FLASH memory diagram that explicitly illustrates the sequence of sections as they appear in the FLASH memory. I know that the Vector Table is always at the beginning, but what exactly says that the .text , .rodata, and .data sections are all after in that order?
I'll provide a screenshot right here too:


texts:
I'm creating an embedded application that hosts a USB mouse.  I'm trying to make it generic for any USB HID mouse/trackball/whatever.  I've discovered that mice report differently... while they mostly all report +-127 relative X/Y coordinates the 'feel' of the application changes drastically between different models, in that some move very slowly and others move very quickly.  I'm assuming that this relates to the physical size of the logical space the mouse reports.

While HID descriptors have specific fields for this, mice never use them... at least, for the boot-mode I'm using (no drivers here!) (edit: mice don't start out in boot mode, my mistake).  At this point I'm reduced to creating tables keyed on VID/PID; this means that I'll have to test each mouse and create tunings for it, something I'm already tired of (and the customer's tired too!).

You can take these mice and plug them into Windows and get decently equivalent movement from them.  I'm watching for special drivers and the normal driver I see is the generic 2006 HID from MS.

My main question:  how is this handled in typical OS's?  Am I missing something, like perhaps that mice that move more quickly have a shorter reporting interval (I haven't read the endpoint descriptor)?  Or did someone have to go through and make a table of DPI for all VID/PID combinations?  If they'd just put in physical vs. logical into the report descriptor then this would work like it should!  Please help...


texts:
While looking at how other circuits bring AC mains into their circuits, I came across this design where there are 3 differently shaped vias (from top to bottom):

Figure of 8
Octagonal ring
Ellipse

Why are the vias shaped differently?

At the bottom, why are the vias for the HOT and NEUTRAL vias completely surrounded by the trace (pads?), while the AC-OUT and AC-IN vias do not?


texts:
I am currently developing an apparatus for feeding and monitoring my dog remotely. The basic idea is to make this using 2 main components:

The first component will be composed of a camera pointing to my dog's plate and a microcontroller with a servomotor which will open and close the food door from the food container. In this place there is no WIFI access nor power outlets, so it will run on batteries. I hope the computing in this component to be as low as possible, so if it can be done without it running on linux or other OS it would be great.
The second component will communicate with the first one and with my router so I can access it remotely via Internet. This one can be plugged to a power outlet.

The usage of this would consist on me being able to log on my phone (with an app I create) to the second component for it to show me the live video and send a signal through it to open the food container door for a set amount of time. I have one BeagleBone Black I can use for this project, which I think I will apply on the second component.

My questions:

1) What protocol would be suitable for the communication between both components (bluetooth, zigbee, 6lowpan, etc)? The camera will probably be 640*480 or higher and there is no problem on delays (~ 15s - 20s) as long as I can watch relatively continuous live video to check my dog is eating and well. It should be as low-power consuming as possible for batteries to run a long time.

2) Is there any way to make the first component be able to stream the video without it running an OS?

I know there are some more logical solutions (extend the wifi network, buy an already on market solution, etc) but I am wishing to use this project as a learning instance for IoT as well. I have done research, but have not been able to land on any convincing conclusions. I hope you guys can help me on this or at least point me on the right direction. I (and my dog) will be very grateful.

Thank you very much.


texts: my breadboard simulation doesn't work properly

texts:
I'm trying to simulate the below circuit on a breadboard but it seems I'm missing something because the numbers don't seem to be correct. Here is the circuit I am trying to build:

Here is my breadboard layout:

I'm new to breadboards and don't know what I have done wrong.


texts:
I'm using the USB FTDI dongle to convert USB to RS485, half duplex, 3 wires (A+, B-, GND) with 115200 baud rate.

I'm working with controller of NXP (K64) and I'm experiencing random tx enables on the input signal of the MX3362 (half duplex RS485 to UART). the tx enable is caused due to noise (?) coming from the outside into the inputs of the max3362 (I think).

When I disconnected the GND wire, the problem disappeared. When I'v lowered down the baud rate to 9600, also, the problem disappeared, so I'm guessing it is concerned with noisy ground.

Some board I've tested act the same, but others still have issue, nevertheless, when lowering down the baudrate, it seems those phenomenas has decreased but not vanished (in those boards).
Any ideas how to overcome that issue?

Attached my electrical scheme:


texts:
This is a long post as I want to take you through all the work I've done. The TL;DR version is I've got an unknown controller for a mechanical heat pump and I'm trying to reverse engineer the signal and data....so if you think you can help, then please read on.

First off, I'm not an electrical engineer. I'm a software engineer who is a bit out of his depth.

I have an ITS heatpump and it has a controller I want to reverse engineer in order to read data from the sensors and set some parameters in software. I've looked for technical specifications and asked the manufacturer, but they told me to GTFO. In the end, reverse engineering seemed the only way to get what I wanted.

Between the unit and the control panel is a 3 wire connection. From what I've been able to deduce it is GND, +12V (to power panel) and a signal wire.

I then got myself a Saleae protocol analyser to see what I could see. I've confirmed that the single data wire is used for both RX/TX. I thought the easiest point to tackle is the control panel and disconnected the signal wire so that I could read only what the panel is transmitting. A sample can be found at http://tinyurl.com/ppuemv7 . I am using the 1.1.24 beta version for decoding. It seems to decode nicely using Async Serial 8N1 autobaud. I've tried a bunch of other decoders and parameters but all of them get framing or other errors.

I then started systematically changing the values on the controller to see how the byte stream changes. I changed parameter 1 using values [51-55] and this was the result (spaced intentionally for ease of spotting differences) of the byte streams.

Format <Param>-<value>:<decoded byte string in hex>
01-51:8055DD555555555555555555555555555575577557F58075757757 DD 757577577755DD55555D7777775577755D 55 5D 77 FD
01-52:8055DD555555555555555555555555555575577557F58075757757 D5 DD7577577755DD55555D7777775577755D 55 77 77 F5
01-53:8055DD555555555555555555555555555575577557F58075757757 5D DD7577577755DD55555D7777775577755D 55 75 77 FD
01-54:8055DD555555555555555555555555555575577557F58075757757 75 DD7577577755DD55555D7777775577755D 55 D7 77 F5
01-55:8055DD555555555555555555555555555575577557F58075757757 DD D757DD5D7755D757555D75DD7755DDD575 57 D5 77 57

From that the pattern wasn't obvious so I decided to change another parameter (param:0 changed to 16 from 15) keeping parameter 01 at 52 and this is what I got.

Format <Param>-<value>:<decoded byte string in hex>
00-15:8055DD555555555555555555555555555575577557F5807575 7757 D5 DD7577577755DD55555D7777775577755D 55 77 77 F5
00-16:8055DD555555555555555555555555555575577557F5807575 5555 D7 57DD5D7755D757555D75DD7755DDD57557 55 77 F5

Those of you quick on the draw will notice that the 00-16 capture is 1-byte shorter. My only conclusion is that either I'm using the wrong decoding or the panel is doing some compression.

I need advice on what to attempt next as I feel pretty stuck.


texts:
Does differential impedance between D+ and D- not only depends on separation between and wire gauge of D+ and D-, dielectric constant of the insulation, but also the GND wire and shielding?

I want to connect two EVMs which use PCIe connection by using the impedance controlled USB cable at hand.

However, I don't know if I should also connect the GND and shielding of the USB cable(of course, I will use common ground for two boards). If the differential impedance between D+ and D- does not depend on separation between D+, D- and GND, shielding, I think I can leave these two wires floating.


texts: Flyback protection for a DC latching solenoid?

texts:
I'm looking for a solution for "flyback" protection when driving a 2 wire DC latching solenoid. You cannot use the traditional diode solution as the polarity of the coil is reversed to open or close the solenoid.

My CCT uses two relays to switch the solenoid - the first (SPST) applies power to the second relays contacts (DPDT) which does the polarity reversal for the power to the solenoid coil.

Of course my relay coils already have conventional flyback diodes connected - what I'm looking to protect against is the back EMF from the actual solenoid coil itself.


texts:
I'm installing a cheap IR led board like this.

Do they need any kind of driver? Or just a 12V power supply switched with a relay (to power on/off) If so, is there any kind of consideration I need for the relay?

(I'm controlling the thing from a raspberry pi keeping power source separated)


texts: Handling high voltage input range to comparator

texts:
I'm using 3 comparators for sensorless back EMF commutation of a BLDC motor. This involves comparing the voltage of each motor phase to a neutral point to detect zero crossings. See Microchip AN970 (PDF) for further details on the application.

Unfortunately, I can't find a comparator that I can run off my wide 6-50V VCC input range. The best I can find in that regard is the LM339 that takes 2-30V, but nothing higher.

That leaves me in a situation where I have to divide the back EMF voltages down to fit whatever supply voltage I run the comparators from. If I run the comparator off a fixed voltage supply (call it VDD) and divide the signals down so that the max signal voltage @ VCC = 50V is within VDD, I'd be worried about attenuating the signal too much when VCC is lower. I guess my first question is, would this signal attenuation actually be a problem? I'd be looking at attenuating it 10:1 to run a comparator off my 5V supply.

Assuming the answer to the above is yes, I've come up with a couple of possible solutions so far (alternatives welcome):

Divide the signals down as described above, keeping the fixed VDD as high as possible to reduce how much I have to divide the voltage signals down. I'd prefer to avoid adding a Boost converter off my 5V rail for cost reasons, but a simple charge pump doubler like an LM2767 would at least get me to VDD = 10V and 5:1 attenuation.
Generate a VDD supply that is proportional to VCC (probably about VCC/2 for the LM339) and scale the voltage signals by the same amount. This would be preferable, but I'm not sure about is how to best generate a VDD = VCC/2 supply that I can use for the comparators. Can I get away with a resistor divider here? I was considering a step-down charge pump but I didn't have any luck finding a charge pump regulator with a high enough input range. Maybe even just switching VCC through a FET at 50% duty cycle?


texts: Sprinkler system - long wires or long pipes?

texts:
I am in the process of installing a sprinkler system using a commercial controller. There is quite an extensive area to be covered, and I am wondering whether, for the further-away sections, it would be preferable to have long pipe runs (with possible loss of water pressure) or long cable runs (with possible loss of voltage).

Plan A

Blue lines are water, red and black lines are the wiring.

In this plan the solenoids to control the water flow are located near each other, with a 4-core wire controlling them (one per solenoid plus a common). Some sprinklers however would require a fairly lengthy pipe run. The plan isn't to scale, but I have indicated distances on it.

Plan B

In this plan the solenoids are located remotely from each other (they would each need their own nearby water supply of course). I would now need to run a pair of wires to each one, with the common wire shared. My concern with this is that with this arrangement the common wire in particular might act as an aerial and possibly pick up static or pulses which could affect the controller's behaviour.

These are all outputs from the controller, but still.

From an electrical point of view, which is preferable? Plan A or Plan B? Or won't it make any real difference?


texts:
We have setup, where 16-24, 2.5" Drives will be arranged in mobile racks of( 8 or 12 each).

We are selecting ATX SMPS to satisfy these needs.

We need to power these drives with a ATX Power Supply.

As these drives only takes current from 5V rail only. 12V and other rails were just not much required (12V required upto 100W).

I have seen specifications suggest maximum current from 5V rail close to 20A for 500W/600W ATX SMPS, and mainly(largely) power is mentioned on 12V rails.

If we are using only 5V on ATX SMPS of 500W, whether complete 500W or maximum portion of power can be taken from 5V?                           if no, How to find what is the peak current (for short duration) can be taken from 5V rail?


texts: How to measure voltage across (pre-charged) capacitor using an MCU?

texts:
I have a pre-charged capacitor of which I want to read the voltage from using an MCU. The ADC pin can read the voltage of a separate supply but it gives very high values when I try to read the voltage across the capacitor using a voltage divider. Using a multi-meter I can for example read out 2V across the capacitor but my MCU gives the wrong value. Is it because I need somehow a ground connection or so?

SUPPOSE THE VOLTAGE ON THE CAPACITOR GETS EMPTY after for example 10 minutes so not that is drained in 1 second...


texts:
I currently have a PCB that I designed using a STM32L031G6 MCU. I have designed many boards with STM32 chips as well as other MCU's. Typically I have a simple cap and pullup resistor on the RST line to help with power on reset and/or brownout. I have never had an issue before this board.

I have two of these made, as they communicate together. One is powered from a 3v3 benchtop supply, the other from 3V from AA batteries. Both of them will only start properly around 10-20% of the time. I have to power cycle many times to get it to finally start correctly. If I reset or program it from my STLink, it starts perfect every time.

I know I can use a POR supervisor and that should fix it, but it is surprising to me that in 10+ designs I have had with STM32 chips, it has never been an issue. It's also tough because this is a low cost design, and we really don't have the BOM cost for a $0.30+ part..

We have changed the Brownout reset threshold level's using option bytes, and it didn't have a large impact. Also changed C9 to a 10uF and nothing changed either.

Any thoughts?


texts:
I have the following tank circuit. Now at resonance of about 50.054 MHz, the output voltage should be same as input, as the tank circuit would have a high resistance.

I have calculated the impedance of the tank circuit at the resonance frequency to be

\$Z_{total} = \dfrac{j\omega L}{1-{\omega}^2 LC}\$ = 4.5M\$\Omega\$

Then why is the output voltage so much attenuated?

Also as a second question, what would be the output impedance of this circuit?

I found it to be

\$\dfrac{1}{Z_{out}} = \dfrac{1}{R1} + \dfrac{1}{Z_{total}}\$

\$\Rightarrow Z_{out} = \dfrac{1}{\sqrt{(\dfrac{1}{R})^2 + (\dfrac{1}{X_{total}}) ^2}}\$ = 1k\$\Omega\$. Is this correct?

Note: The series resistance of the inductor is zero, and not the default of 10m\$\Omega\$


texts: Current mirror design - gate to drain feedback

texts:
In my texbook [Analog VLSI: Circuits and Principles] there are two circuits that function as a current mirror. The first uses two nfets with a shared gate, and the drain of the first nfet (M1) is tied to the common gate. The current through M1 is then mirrored through M2.

The book also shows a Winner Take All circuit that uses a current mirror where the gate of M2 is tied to the drain of M1. And the gate of M1 is tied to the source of M2.

The book states "We should remember that Vg is determined by the gate charge, which cannot be directly influenced by the input current due to the infinite impedance between channel and gate." For the second current mirror design, how is the current getting mirrored to M2 if the gate can not be directly set by the input current in M1?

simulate this circuit – Schematic created using CircuitLab


texts:
simulate this circuit – Schematic created using CircuitLab

Using a rc network to smooth a PWM signal from a microcontroller, to a true analogue voltage.

What will be the effect of having the resistor on the source (microcontroller) side of the capacitor vs the load side?

What would be the effect of having the resistor in series with the capacitor but parallel to the load and source?


texts: LDO or Switching for 24V Input, 5V Output

texts:
I have a 24VDC supply that needs to be regulated down to 5VDC to power an Arduino Mega and a XBee Series 2 module.

How would you choose between a Switching Regulator (LM2576T) and a LDO Regulator (LM3480IM3)? I think 100mA is sufficient to drive the Arduino and XBee.


texts:
Every time I try to program my hex file I get an error:

The following memory area(s) will be programmed:
program memory: start address = 0x0, end address = 0x3b
configuration memory
program memory
Address: 0 Expected Value: 25 Received Value: 0
Failed to program device

Even my asm code BUILD SUCCESSFUL, I still get an error and can't program any code.

Do you know where is the problem?

I am using Pickit3 with ICD2 PIC10F222 microcontroller. MPLAB X IDE/IPE v5.15

Code:

;**********************************************************************
; This file is a basic code template for assembly code generation *
; on the PIC10F222. This file contains the basic code *
; building blocks to build upon. *
; *
; Refer to the MPASM User's Guide for additional information on *
; features of the assembler (Document DS33014). *
; *
; Refer to the respective PIC data sheet for additional *
; information on the instruction set. *
; *
;**********************************************************************
; *
; Filename: xxx.asm *
; Date: *
; File Version: *
; *
; Author: *
; Company: *
; *
; *
;**********************************************************************
; *
; Files Required: P10F222.INC *
; *
;**********************************************************************
; *
; Notes: *
; *
;**********************************************************************

list p=10F222 ; list directive to define processor
#include p10F222.inc ; processor specific variable definitions

__CONFIG _MCLRE_ON&_CP_OFF&_WDT_OFF&_MCPU_OFF&_IOFSCS_4MHZ

;***** VARIABLE DEFINITIONS
TEMP_VAR UDATA
temp1 RES 1 ;DELAY REGISTER1
temp2 RES 1 ;DELAY REGISTER2
temp3 RES 1 ;DELAY REGISTER3
temp4 RES 1 ;DELAY REGISTER4
temp5 RES 1 ;TIMING REGISTER
temp6 RES 1 ;TINING REGISTER

;**********************************************************************
RESET_VECTOR CODE 0xFF ; processor reset vector

; Internal RC calibration value is placed at location 0xFF by Microchip
; as a movlw k, where the k is a literal value.

MAIN CODE 0x000
movwf OSCCAL ; update register with factory cal value

INITIALIZE
MOVLW B'0010'
TRIS GPIO ; INITIALIZE
CLRF ADCON0 ; ADC DISABLE
CLRF GPIO
MOVLW B'00001000'
OPTION ; ENABLE GPIO2 AS A DIGITAL PORT
CLRF GPIO

START:

SCAN1:
BTFSS GPIO,1
GOTO SCAN1
ENSURE:
BTFSC GPIO,1
GOTO ENSURE
CALL LOOP1
COUNTDOWN:
MOVLW 0xFF
MOVWF temp5
MOVLW 0xFF
MOVWF temp6
COUNTDOWN2:
BTFSC GPIO,1
GOTO RELAYACTIVATE
DECFSZ temp5
GOTO COUNTDOWN2
MOVLW 0xFF
MOVWF temp5
DECFSZ temp6
GOTO COUNTDOWN2
GOTO SCAN1

RELAYACTIVATE:
BSF GPIO,0
CALL LOOP1
CALL LOOP1
CALL LOOP1
SCAN2:
BTFSS GPIO,1
GOTO SCAN2
ENSURE2:
BTFSC GPIO,1
GOTO ENSURE2
CALL LOOP1
COUNTDOWN3:
MOVLW 0xFF
MOVWF temp5
MOVLW 0xFF
MOVWF temp6
COUNTDOWN4:
BTFSC GPIO,1
GOTO RELAYDEACTIVATE
DECFSZ temp5
GOTO COUNTDOWN4
MOVLW 0xFF
MOVWF temp5
DECFSZ temp6
GOTO COUNTDOWN4
GOTO SCAN2

RELAYDEACTIVATE:
BCF GPIO,0
RESET

LOOP1:
MOVLW 0x00
MOVWF temp1
MOVLW 0xF0
MOVWF temp2

LOOP2:
DECFSZ temp1
GOTO LOOP2
DECFSZ temp2
GOTO LOOP2
return

END


texts: Algorithm for balancing LI-PO batteries?

texts:
The answers to this question provide a good overview of how a single lipo cell is charged:

  Algorithm for charging LI-PO batteries?

Most chargers that handle lipo packs have a balance mode that ensures each cell is charged to the proper maximum voltage.

How do chargers typically handle this?  Do they apply different voltages to each cell, or do they discharge cells with higher voltages until they match the voltages of the less charged cells?  What kind of circuit would be used for the discharge phase (if any)?


texts: IC voltages and low power design, What todo?

texts:
I’m working on a low energy device consisting of a couple of IC’s.
What is confusing to me is the following, All ICs has a vcc supply range of 1.7 to 3.6V and most of the time the current reading is given @3.3v supply. Chasing the most efficient design what is actually better running at the bare minimum supply ( assuming the internal LDOs has less power to dissipate ) or run at 3.3v?

I have tried to read if there is reduced performance at lower voltage but it is not apparent. The other question that then comes of the back of the previous question, if all ICs has a supply range 1.7 to 3.6 and all IO pins is rated to 3.3v can I run some ICs at 1.8v and other at 3.3v without effecting let’s say SPI or I2C communication ?

These are the ICs MCU infocenter.nordicsemi.com/pdf/nRF52832_PS_v1.4.pdf Radio semtech.com/uploads/documents/sx1272.pdf GPS u-blox.com/en/product/sam-m8q-module. I found a new MPPT DC reg from ST this one. st.com/content/st_com/en/products/power-management/… The idea is to run the MCU from the 1.7v LDO and only when Battery charge is sufficient enable the 3.3 VDO that feeds the rest of the system. My concern would be the UART and SPI coms between GPS and Radio IC... and MCU

Any advice is appreciated


texts: Help identifying compact, flat connector found on brushless DC motor

texts: Do you know the manufacturer or model number of the connector shown in this picture?  It came on an unidentified brushless DC motor.  Contacts shown are receptacles, not pins.  The contact pitch is 0.050 inch / 1.27 mm.


texts: Implementation of multiplier system of processor using sequence system - is it possible?

texts:
I am in the course of learning about the processor, sequential systems, etc. I came across this question:

Is multiplier processor may be implemented as a sequence system?

I can not answer that. Can someone explain this?


texts: Does this circuit detect frequency or magnetic field?

texts:
I have built this circuit but the LED lights even when I move it near DC not only AC.
Does it detect the frequency or the magnetic field?


texts: how can i calculate decoupling capacitor value?

texts: How can i calculate decoupling capacitor value? Which amount of noise we can filter use it.why use here 10uf , 0.1uf capacitor?


texts:
I need to design a controller that can switch On and Off a line conducting high currents.
the power line: it is supplied by a banks of capacitors
the switch: it must close the circuit when a signal is given and stop it when another one comes.

the circuit will give a burst of current that may be a lot under the 1second of time, the timescale is in deciseconds or centiseconds

I was thinking to use a button for engage it and a beam-interruction sensor for disengage it.
Pushing the button will engage the capacitor banks that will magnetize a coil producing a high magnetic force over a piece of metal, when that piece moves in the tube an ir receiver will see that the ir led is covered by the metal and he will switch off the capacitors.
The control of the logic isn't a big problem, I can just use 1-2 little relays for control the switch.

I thought at a GTO thyristors but creating a negative current will be a handicap.
There are relays that can keep high currents?
the cheapest way? (I don't trust a lot transistors, they may suffer from magnetic field...etcc)
the capacitors will be 2-3 at 300-350 working volts at around 200-500 uF at the start, but they might be 3800uf at 68 V or lower.

I can use without any problems the GTO if the signals can come from a different power sources

what is the best way for solve that?
tank you
Giulio


texts:
I am attempting to make a board for the tlc5951 24-channel led driver to drive an 8x8 rgb led array. I have made what I think is a good eagle library for the sop-38 package, but I am not sure what to do about the pad on the underside of the ic. The datasheet has thermal characteristics with and without the pad soldered, but I suspect I will want the heat dissipation provided by the pad. This is my most ambitious soldering project yet, and I have a few questions I would like to straighten out before I have the first round of boards made.

Should I hook the heatsink to my ground polygon on the bottom side, or leave it disconnected? I'm not sure if it will cause problems with grounding if it heats up too much.

Is my only option to reflow this, or is there a way to do it by hand? I have never done any reflow soldering, and I am much more comfortable hand soldering. I am definitely not comfortable having a stencil made to do this kind of thing. Is there any kind of thermal compound or something that can make a thermal connection comparable to a solder joint, or is solder best?

The datasheet has very specific dimensions for pad size, via patterns, and stencil opening. Should my solder mask pretty much follow the stencil opening outline on the datasheet?


texts: Connecting phototriac substrate to adjacent pins

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For a regulatory exercise I am analyzing the result of a short fault between a phototriac's substrate (MOC3023) and its anodes (one at a time).  The datasheet warns DO NOT CONNECT but what is the result of this fault?  Where is this pin connected on the TRIAC structure?

I am using this device to trigger a discrete TRIAC much like Figure 12 in the datasheet:

EDIT: Here is ON Semiconductor's response to my question regarding this pin:

  In response to your question the Pin 5 must be left unconnected in application. It is connected to detector die`s substrate. This is mentioned in data figure 1 (see the attached picture). It does not affect the insulation property between input side (LED) and output side (triac driver) of the optocoupler. However, connecting pin 5 to either pin 4 or pin 6 may cause the detector side to behave differently such as being falsely triggered on. Therefore, pin 5 must be left unconnected.

The attached picture was simply Figure 1 of the datasheet with a green box around the DO NOT CONNECT note.


texts:
This post is regarding exersise 4-8 from the following book:
Hughes Electrical And Electronics Technology 10th Ed.
Here it is:

Let's focus on what I tried for solving part (b) :
Since this is an exercise under the chapter for delta-star transformations my first thought was to try and perform some such transformation. However this was a combination of both star and delta connections so I didnt really know whether the resulting resistances would be in series / parallel or neither, with the already existing ones, so I tried both series and parallel:

However neither worked.
My next thought was that maybe I have understood something very badly about the resulting resistance of two points in a circuit. So after a little bit of digging I tried the following:

However I again got a wrong result in regards to the given answers at the end of the book.
Conclusion:

Which approach (if any) was correct?
If no approach was correct, which concept do I need to understand better?

Any help/hint is very much appreciated


texts:
I have been studying some electronics schematics to get background information on a power generator we use in my work. In one of these schematics I ran into the schematic I drew below. As seen here the Zener diodes are in opposite direction of each other.

simulate this circuit – Schematic created using CircuitLab

My first impression was that I was looking at a (1)Transient-voltage-suppression diode that would catch voltage spikes.
(1) https://en.wikipedia.org/wiki/Transient-voltage-suppression_diode

But in electronics this is indicated with the below symbol:

simulate this circuit

As far as my knowledge goes on electronics (I am not an experienced electrician) zener diodes (or diodes in general) only conducts current in one direction. So I am curious to know what the function is of the diodes in the schematic from my work. Cause in my opinion they could be removed since they do not add any value to the circuit. Since if there is a current spike, it wont be caught.

None of my college knew the function of these and I haven’t been able to find any information or example on google or this site. I am hoping someone can explain it to me.

So my question is: What is the function of the zener diodes used in this setup?


texts:
Want to get binary Pin 7 output (0V or 3.3V), dependent on light intensity on the photoresistor. But the output is not as expected.

I have built the circuit below with the help of LF33ABV 3.3V voltage regulator. Using 9V battery as the main power source (those elements not shown). Have added the pin connection numbers of TL084CN in the figure.

Here are the outputs, when I play with the light intensity. (Made the measurements with a multimeter)

Pin 5: 1.64V, Pin 6: 1.23V, Pin 7: 2.58V; (was expecting Pin 7 railed to 3.3V)
Pin 5: 1.64V, Pin 6: 2.20V, Pin 7: 1.33V; (was expecting Pin 7 railed to 0V)

Is there a mistake that attract your attention? Thanks

TL084CN data sheet


texts: Zedboard 512x512 matrices, % utilization problem

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My objective is to read seven 512X512 float matrices from the SD card to the DDR memory (step accomplished already with each matrix occupying around 1Mb), then pass them from DDR to my custom IP block (I'm doing this transition with AXI DMA block), normalize them innside the custom IP block and then output them to DDR memory (also with the AXI DMA block).

Well, I'm doing my custom IP block in Vivado HLS and following the steps that I saw in this Xilinx manual (which shall be the ideal way to do this since its from Xilinx). It works for a 32x32 matrix.

But unfortunately, when increasing the matrix dimensions to 512x512, even doing only a multiplication by 2.0 of each matrix' parameter, the BRAM_18K utilization is 365%!!

What can I do do brutaly decrease the % of resources used? I'll need to do lots of operations to the matrices inside the custom IP block and if a simple multiplication by 2.0 uses 365% of BRAMs a solution that decreases the amount of this example to 80/90% is not good enough. What I'm looking for is a solution that sets the BRAM utilization to around 5% in this example.


texts: Join the microphone and audio lines from a headset for recording

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Question

What are the steps required to join the microphone and audio lines from a typical cell phone headset into one line so that the audio can be recorded by a standard voice recorder using the microphone and/or line-in input?

Practical use

The practical use for this is for the purpose of recording cell phone conversations with the use of a headset.

In Depth

Intuitively, I would just splice all the lines together. However, this approach seems to have the problem of creating an echo from the mic line to the audio line. I've also heard that it could blow some circuits in the phone, audio recorder or both.

It seems that the job of "splicing: these lines together without interfering with the call is more complex, requiring the use of some components to make it work correctly.

Here is a device that I found on Ebay that does exactly this:

I purchased a similar device off Ebay that has its own headset attached and cracked it open:

Here is a close up of the cracked open part. It does not look very complex, but I'm not sure exactly what it is doing:

(Other side:)


texts: avr signature doesn't match, flash address 0x0000 wrong

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I'm new to electronics.

I've bought an ATmega32 (a link to docs) and I'm trying to light up a single LED. I have managed to do it a few times, but then I tried to change the hookup wires to a single 10 pin wire and after a few failures, I went back to wires.

The problem is, when I try to program the device, it gives me a warning:

WARNING: FLASH byte address 0x0000 is 0x00 (should be 0x0C).. FAILED!

When I read the signature of the device straight after plugging it in, it says it's

0x1E 0x95 0x02

and it says it matches the device. Then when I try to erase it (or program it), I got the mentioned warning. Also, after doing this, when I read the signature of the device, it reads it from the device as

0x00 0x01 0x02

There's also a warning that 'signature does not match selected device'.
I can erase the device and it says that erasing device was OK.

I'm not sure if that's relevant or not, but I've also realised that fuse bits (low to high) are at the beginning 0xE1 0x99 and later 0x04 0x04 and after erasing it changes the

SUT_CKSEL Int. RC Osc. 1 MHz; Start-up time: 6 CK + 64 ms; default value

to

SUT_CKSEL Int. RC Osc. 8 MHz; Start-up time: 6 CK + 0 ms

(it also changes some other fields there as well, e.g. brown-out detection from VCC=2.7V to 4.0V)

I'm using AVR Studio 4.18.716, and a JTAG ICE programmer.

Is there anyway I could fix this or have I killed it?