texts: RETLW 0 and RETURN command on PIC10F222 microcontroller

texts:
When I am building a code in MPLAB X IDE v5.15 I get an Warning "Substituting RETLW 0 for RETURN pseudo-op". As I have researched the PIC10 series don't have return command so it changes to RETLW 0. But my question is how the code will change with the RETLW 0 command or it is the same as RETURN command?

Code:

    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              ;Warning:"Substituting RETLW 0 for RETURN pseudo-op"

    END


texts: Differences between controlled rectifier circuits

texts:
I'm trying to determine the pros/cons/applications of a few similar rectifier circuits.

In particular, these two:

My questions are these:

I understand that the second one eliminates the reverse bias voltage across the thyristors with the free-wheeling diode. What is the purpose of doing this? Is it just to make sure that the thyristors don't burn out? Does it increase the average voltage?
Ignoring the freewheeling diode, what is the advantage of having four thyristors rather than two (i.e. replacing T4 and T2 with diodes in the first circuit)? If they accomplish the same thing, wouldn't it always be cheaper to have two? Or is the application of two thyristors specific to the freewheeling diode circuit?


texts: Measuring switching time of 5LN01SP (NMOS)

texts:
I am working on switching time test circuit for 5LN01SP specification.

This is my circuit:

Input test signal is (as per specification) a pulse of 1kHz frequency:
PW = 10us
D.C. == 1%

We can see the t_ON time of the input signal pulse is about 60ns.
Specification says t_ON of the transistor would be about 60ns (18 + 42).
To measure this (by measurement of time vs drain current) I take measure of voltage across one of two 47 Ohm resistors (see scope probe with yellow and red wires) and I get:

We can see that t_ON measured is more than 3 us (~3.5 us).
I would appreciate any help understanding reasons for such huge difference (3.5 us vs 60 ns).
Also not sure about that long observed t_OFF time (~200 us). It's surely because of capacitance, but again huge difference from spec's 295 ns.
[EDIT 1]
I tried shorten gnd and tip connection of the probe with following setup, though inductance and capacitance loaded into testing circuit by scope did not change.

[EDIT 2]
I changed where the gnd tip of the probe is connecting to by connecting it to GND of the circuit, like this:

thus now I am sensing the voltage across same 47 Ohm resistor in series with V_GS. This is OK, since I only need signal's timing and I am not interested in amplitude's absolute value of the signal. The measurements I take now make more sense (I added second probe to plot the input signal):

I get a measurement of t_ON time (voltage drop on resistor + V_GS) around 60 ns, as expected:

I get a measurement of t_OFF time (voltage rise on resistor + V_GS) around 295ns, as expected:

The only question is... why it doesn't work when I perform floating measurement across resistor only, and it's fine if gnd tip of the probe connects to circuit's GND?


texts: What does "Maximum Input Current" in a data sheet mean?

texts:
For example, in the datasheet of ATS030A0X3-SRPHZ, what does the maximum input current mean? Does it mean...

1) This is how much you are allowed to feed into the voltage translator (presumably using a current source) without breaking it?

OR

2) This is how much current the voltage translator will ever draw, so go ahead and design your circuit allocating this much current to this component?

Thanks


texts: Converting S parameters to Z parameters - divergence

texts:
I have cause to convert some Z parameters to S parameters and vice versa. Here is the conversion for \$Z_{11}\$;

$$Z_{11} = {((1 + S_{11}) (1 - S_{22}) + S_{12} S_{21}) \over \Delta_S} Z_0$$

where

$$\Delta_S = (1 - S_{11}) (1 - S_{22}) - S_{12} S_{21}.$$

I thought I'd start nice and simple with an ideal short transmission line of impedance \$Z_0\$. Now \$S_{11}=0\$, \$S_{21}=1\$, \$S_{12}=1\$ and \$S_{22}=0\$. Therefore \$\Delta_S=0\$, so \$Z_{11}\$ diverges (as do the other Z parameters) and something has gone wrong somewhere.

Where have I messed up?


texts: Is there a minimum for charging current for lead acid battery?

texts:
I've recently bought a 9 V, 3 W solar panel that I wanted to use to make a small project in my balcony, then I bought a 6 V, 4000 mAh  sealed lead acid battery, I want the solar panel to always charge the battery through a PWM solar charger whenever possible.

I am a beginner in electronics, because I am just still young, in highschool, but electronics is my no 1 hobby and I need someone to answer my question.

My question is very simple, after dividing watt by voltage, I will get a maximum current of the solar panel which is around 300 mA, ironically I think in my area I would get just 100 mAh, but anyway I've recently read about how to charge a lead acid battery and there is a statement I read before, that a lead acid battery is charged at current of  30% of it's capacity if I applied this rule to my 4000 mAh battery I would need a 1.2 amp to charge it in (2.4 volts per cell), is this a must or any current less than 1.2 amp can charge a lead acid battery?


texts: Radar Receiver How to detect 1 nsec pulse

texts:
I need to design a very short range pulsed radar for classroom/lab use.
For this purpose the pulse width needs to be very short 1-5 ns to avoid the radar blind range. My preference is to digitize the received pulse and do all the processing inside a general purpose processor. But for such a short pulse width radar, I need a very high sampling rate i.e., at least 2 G samples/sec. Digitizers of this rate are very expensive and cannot be afforded in the budget. Can you guys suggest any tips/tricks to detect such a short pulse width at low cost?


texts:
I'm trying to measure current with acs712 30A current sensor connecting to NodeMCU-32S but I'm getting wrong and unstable values. For zero current the ADC pin should read value of 2048 (esp has 12 bit sensitivity) but instead I'm getting values about 2740-2760. So first I have problem with incorrect value and second is unstable reading.
Basically the whole thing look like:

simulate this circuit – Schematic created using CircuitLab

My test code is:

enter dcode here

#include <stdint.h>
#include "esp_err.h"
#include "driver/adc.h"
const int analogIn = 34;
int mVperAmp = 66; // 66 mV/A output sensitivity
int RawValue= 0;
int ACSoffset = 5500/2;
double Voltage = 0;
double Amps = 0;

void setup(){
  Serial.begin(115200);
  pinMode(analogIn, INPUT);
}

void loop(){
  RawValue = analogRead(analogIn);
  Voltage = (RawValue / 4096.0) * 5000; // Gets you mV
  Amps = ((Voltage - ACSoffset) / mVperAmp);
  Serial.print("Raw Value = " ); // shows pre-scaled value
  Serial.print(RawValue);
  Serial.print("\t mV = "); // shows the voltage measured
  Serial.print(Voltage,3);
  Serial.print("\t Amps = ");
  Serial.println(Amps,3);
  delay(250);
}

Thanks.


texts: Is this an encoder? Correct naming of circuitry

texts:
Newby to the digital circuitry world please be nice.

For a rock paper scissors game, I've created the following to determine a winner, however I don't know what this circuit would be called in the realm of correct terminology.

I'm tempted to simply call it an encoder but am both unsure on how loosely that term can be used and also as to how the 2n IN = n OUT could be interpreted to validate this.

Thanks for all help and suggestions]1


texts: How to test desert (Dubai-like) conditions when you are in a temperate climate

texts:
I would like to stress test an electronics device in desert (think it like Dubai) conditions, such as 40-45 degrees Celsius = 100+ degrees Fahrenheit with direct sunlight and zero humidity. I live in a temperate climate with temperature around 25-30 degrees Celsius = 80 degrees Fahrenheit.

My question could be divided in three sub-questions:

how to increase the environment temperature
how to lower the environment humidity
how to increase the sun exposition

The constraint of the question is the budget. Is there any good experience, good tips, low-cost practices how to simulate a "hotter" climate?


texts: Deliver high voltage/high frequency sine wave

texts: I need to deliver a 40 V (minimum), 4.25 MHz, sine wave to a PZT transducer (medical ultrasound application). I have explored trying to use a dc/dc step-up with a switch, but this will only give me a square wave as I understand it. Furthermore, I have tried to search oscillators but most give within the range of 1-3V outputs and as we all know, op-amps can't output more than their supply voltage an I'm trying to stay away from directly supplying 40V to a single element of my circuit. Any suggestions would be greatly appreciated as I feel I have hit a dead end.


texts: Sensor/transducer for low pressure gas measurement?

texts:
First time poster here so let me know if I'm missing key info.

I'm helping a friend create an Arduino-powered data collection system for his coffee roaster, and we'd like to track the natural gas pressure (in W.C.) being sent to the burners.

Can anyone recommend a low-cost solution for this?  I think we'd have to have a plumber install it, because it should be inserted into the pipe leading to the already-installed analog readout and allow us to push data to a microcontroller.  I don't know the exact diameter of the copper pipe but I think it's a standard size.  Even if someone could point me in the direction of the right class of device and/or a manufacturer, that would be great.

Thanks.

EDIT: The range we need is 0-16" W.C.  or 0-40 mbar


texts:
I was looking for an Op Amp input protection circuit and the most common I found looks like this.

When the voltage at Input Signal goes above/below Op-Amp's supply rails schottkey diodes start to conduct.

Let's assume a +100V is applied at Vin.
A current equal to I = (100V - (+15V) - 0.7V) / 5kΩ = 16.86mA will flow from the upper diode to positive supply rail.

The question is, how dangerous is that current flowing to supply rails therefore to the circuit power supply? Would it cause damage to power supply if that amount of voltage is permanent and not transient?


texts:
IEEE 802.3's clause 40.8.3.1 specifies a certain a MDI return loss. The specification states that this return loss shall be maintained at all times when the PHY is transmitting data or control symbols. How does one measure the return loss, when the PHY is transmitting data or control symbols?

The Gigabit Ethernet Consortium (of the IOL from the University of New Hampshire) has published a reference PMA test suite, which lists MDI Return Loss as a test (found in page 11 of the document here). The test procedure there states to put the PHY in Test Mode 4 while performing the Return Loss measurement to satisfy the "when the PHY is transmitting data or control symbols" requirement. But wouldn't this mess up the VNA S11 measurement? If the PHY is already transmitting symbols, how would the VNA differentiate between what the PHY is transmitting versus a reflection of what the VNA is sending into the channel?


texts: Switch Power Supply at 24V using MOSFETs

texts:
As title, here's a schematics:

simulate this circuit – Schematic created using CircuitLab

Is this a correct way to create a power switch or can this schematic be improved?

Board will sink at max. 1A , P-MOS and N-MOS will me chosen to be rated +/-20Vgs.

I've added two voltage dividers due +24V power source to keep Vgs at 16V. There should be a very low dissipation through resistors.


texts: Do diamagnetic material exhibit induction?

texts: Silly question perhaps, but do metals with the property of diamagnetism also exhibit  inductance? Would a fluctuating magnetic field induce a current in a diamagnetic metal?


texts: Will other devices interfere with programming a ATmega32U4 if attached to SPI bus?

texts: I’m designing a custom PCB around an ATMega32U4. The 32u4 will talk to another onboard component via the SPI bus. Since the SPI pins (MISO, MOSI, SCK) are also used for ISP programming could other onboard component attached to the SPI bus interfere with programming the 32u4? If so, what is are typical ways to deal with other onboard devices on the SPI bus during programming?


texts: Measuring transistor beta (hFE) - Ib anomalies explanation needed

texts:
I've been struggling with details of building accurate (\$\pm1\%\$ tolerance maximum) beta meter. The simplest idea I came with went to a diagram as shown below, with R set to a value providing a \$0.01\ \mathrm{mA}\$ current and a digital ICL7107 meter put to measure \$I_C\$. Obviously, with \$I_B\$ set to a constant value, \$I_C\$ could be easily transposed as a beta meter...

BUT

After building this simple circuit in a simulator, I've noticed that the actual \$I_B\$ shifts a little bit as a function of given beta, with about \$10\%\$ difference between \$\beta \rightarrow 0\$ and \$\beta \rightarrow \infty\$; I provided actual test case betas below (\$\beta=10\$ for a low-current transistor and \$\beta=1\mathrm{M}\$ for a high-current Darlington pair, the difference below goes to approximately \${}8\%\$). Of course, I could say this shift is small enough to be ignored - sadly, it's not (at least not in my case).

What is the source of this difference?
Do actual transistors behave similarly (possibly with recalling actual test results)?

And yes, I'm coming to a conclusion that in this case \$V_{CC}+R\$ can't be treated as a stable base current source. And I'm aware that \$V_{drop}\$ on \$R\$ changes with \$\beta\$, and that \$V_{BE} \mathbin{/} V_{BC}\$ distribution changes as well... but I don't understand how this affects \$I_B\$.

The circuit simulator I used.


texts: My RC Time Constant calculations are wrong, circuit changes my input signal

texts:
I have a simple RC circuit of 22 ohms and 3.3uF
My measured values put the resistor at 22.10 ohms and the cap at 3.15
which gives me a time constant of 68.5 us.
The signal applied is a 100Hz Square wave.
Now as you can see from the oscilloscope image
where the dotted cursor lines cross is about 63.2% which is 1 time constant
however the difference between the solid vertical line and the dotted vertical line is not equal to 1 time constant is is off by A LOT! According to the oscilloscope the 63.2% mark is equal to 540us as opposed to my calculated 68.5us.
Another thing to note is that if I connect another oscilloscope probe to measure the input signal, instead of getting the signal the new channel will just match the RC output. In other words I do not get a square wave. If I measure the square wave alone without RC it measures it just fine. That is why I didn't include the input signal overlayed in the image because it wont be visible -- it will just show the same as the output.
So what is going on here? Funny thing is I have done this before and it works out fine but certain cap/resistor values I cannot get the readings I am expecting.
Note schematic says 3.3F but its uF

simulate this circuit – Schematic created using CircuitLab
So I added a picture of the input versus output wave forms, when I complete the RC circuit my input waveform changes and matches the output? Why? I am sure this is why my measurements are wrong. If I break the circuit the waveform becomes a square wave like it should be.

Okay, given input impedance, then my new schematic resembles this.
And my probe measuring my input signal is essentially in between my circuit and the input impedance.

simulate this circuit


texts:
Here is the circuit we used (BT169 thyristor):

And this is the output:

In theory it should be a straight line when AC source goes negative.

The question is "Why does it go into the negative area? Why is it not a straight line?"


texts:
I have attached my attempt and the solution provided by my instructor. I am confused on 2 things

what it means by "the circuit is in quiescent state" ?
why is he getting sqrt(8) in the current equation ?

Edit1: I have also attempted the same problem using Laplace


texts: What's the difference between the maximum and cut-off frequencies of a single transistor compared to those of a circuit?

texts:
Many publications, when they speak about a single transistor, the maximum and cut-off frequencies are way higher than of the final circuit.
Example: A modern FinFET, some report a maximum oscillation frequency of 150GHz or higher. On the other hand, a CPU runs at only at a base clock of 3GHz.
What is the difference?
If you have any bibliographic references that answer this in detail, could you please share them?


texts:
I want to model SN74LVC1G06 (it's an Open drain Inverter) in MultiSim, specifically the rise and fall time specification. The existing inverter model in the Multisim just have rising and falling propagation delay, which doesn't help my case.
Could anyone suggest how I can model this part in MultiSim.?


texts: Series diode voltage clipper, on Multisim clipping and shifting on positive and negative voltage

texts:
This is my circuit:

I’m testing a Series diode clipper circuit, and the end result should be this:
(I've used 5V in my circuit, not 10V like in this plot, but this is not the issue)

Instead what I get in Multisim 11 is not what I was expecting.

These are the results on Multisim scope:
(the green trace has been shifted 0.2V for visibility)

Please explain :

Why the first three positive periods/peaks are shifted up and not
down by 0.7V (forward voltage drop)?
Why the cycles after the first three have a negative clipper in the
negative phase and the positive peaks are shifted down?

These are the scope results, with dc reading:
(all the periods have now the same amplitude but still the positive peaks are above the 5V division, why?)


texts: Calculating Op Amp gain with voltage divider

texts:
Is there a gain differences between schematic 1 and 2? For schematic 1, the gain would be $$-\frac{R2}{R1} = -\frac{100k}{1m} = -0.1$$ But what about the schematic 2?

Schematic 1:

simulate this circuit – Schematic created using CircuitLab

Schematic 2:

simulate this circuit

Any help would be appreciated. Thanks in advance


texts: How to wire multiple ir photodiodes on one arduino pin?

texts:
I'd like to use 50  ir photodiodes.
But, I'm not sure about it because I want it to be read only on one analog pin of an arduino.

My idea is to wire parallel like in this picture.

But, I'm just not sure if all photodiodes will work if I wire like this...

So, is my schematic right or wrong?
If it is OK, what value should I use for the resistors?

Or do I need another component to connect all the photodiodes to one pin on an arduino?

Thanks


texts: Pearmability Tuning Vs Cap tuning for MW AM

texts:
I constructed a  wide band Hi Fi TRF tuner for MW AM  that sounds great. It used an old 365 pF air spaced  3 gang variable capacitor that had equal sections. Selectivity was marginal at the top of the band despite using cascode JFET amplifier circuits that preserve existing tuned circuit Q.

Almost all vintage MW AM car radios use pearmability tuning for reasons of size and resistance to vibration.

How would a TRF radio go with slug tuning?
Would you need more slugs to get the same performance?
How would tracking go if one attempted to use the existing osc coil in a common 3 slug setup?
Would the gain be higher at the bottom end of the band?
How do the tolerances of inductive slugs compare to 3 gang variable caps?


texts: If the capacitor works by induction of charges, then does it invert an AC signal? (i.e phase shifting the input signal by 180 degrees). In my observation I dont see a phase shift between an input signal (source) and output signal (through a capacitor) in an oscilloscope. The input and output voltages are exactly in phase. Can someone explain this concept or if an keeping wrong settings in oscilloscope.


texts: How to work with eMMC from software developer point of view

texts:
I am facing a problem how to implement parameters management in an embedded
software. Parameters management means that I have some subset of variables
which values should be persistent but they will be changed time to time by user. These variables are for example compare levels for some protections, time
constants of some digital filters or PI controller gains. My control board
contains besides MCU also external eMMC memory. The problem is that I have
no experiences how to work with the eMMC memory from software point of view.
I have spent several hours with looking for some application notes but it wasn't successful. Please can anybody recommend me any resource where I can obtain some basic information how to work with eMMC in software. Thank you for any suggestions.


texts: Any good resources to practice efficiency of code modulation?

texts:
I want some resources to practice code efficiency problems like this:

I looked around online and could not find anything. I also looked in two books and only found a section concerning code efficiency. I am not an engineering student but I have a module called communications engineering. I need the resource to prepare for a test. thank you.


texts: Drive 433Mhz emitter and Attiny with two coin cells

texts:
I would like to detect when the postman put mail in my box, so I was thinking about a simple attiny with tilt sensor (which would wake up the attiny) and a 433 MHz emitter:

The problem is that one cell coin (3V) is really low for this kind of emitter, it is good with at least 5V.
So if I use two cell coins I have 6V and above max attiny voltage.
If I plug it with one cell and emitter with two cells, the data pin will be only of 3V which is not good.

If I plug all on 6v, I have to use a zener diode or a classic diode to get below 5.5v but this diode will drain my battery even when the attiny is sleeping.
How could I get a good voltage for the emitter without draining my battery?


texts: Switch that turns one lamp on while keeping the other one off - Mystery

texts:
We tried to connect outside light bulp (AC) to a switch where an another light bulb is already connected. We did a parallel connection. Roughly like in the schematic. (I'm not an engineer so the schematic can be wrong).

simulate this circuit – Schematic created using CircuitLab

If I understand it right it should work like this: When the inside light is ON the outside light should be also ON. Because both lights are connected to the same switch. Or If I understand it right the outside light should light all the time.

But the lights work like so: When outside light is ON the inside light is OFF and vice versa.


texts: How much will the overall CMRR degrade due to impedance imbalance?

texts:
If the CMMR of a differential amplifier is given as 100dB at 50Hz in its datasheet, this CMRR value assumes the applied voltages wrt to common ground are equal. However in practice, if the line and source coupled to the amplifier are not perfectly balanced this CMRR will degrade.

For instance, Figure 1 below depicts a perfectly balanced case; and Figure 2 is an example of an unbalanced case due to R2 being different than R1.

In Figure 1 above since there is a perfect balance, I can use the datasheet's CMRR value. But how can we quantify the new degraded overall CMRR(CMRR') due to line imbalance in Figure 2?


texts: How do I properly level convert between microcontroller and 3.3V SPI pins

texts:
I am trying to create a PCB that interfaces a type K thermocouple with a microcontroller (STM32F303K8) using kicad 5.0.0

I previously sent the PCB to JLCPCB for fabrication, but now i'm noticing problems with my design, which I overlooked, because I guess I misinterpreted what logic level conversion was (being the first time I came across it)

I wrongly assumed that If I supplied to MAX31856 3V3 to the digital and analogue inputs of the chip then why would I need to level convert? Now I see that I need that for SPI lines.

What I need help on specifically, is the circuitry used to level convert. I have seen in my book that you can just use a voltage divider, but the diagram I am using uses switching diodes and pullup resistors (pulled to 3.3V from the onboard MIC5225-3.3 regulator) on CS, MOSI, and SCK. But not on the SDO.

Ref: https://cdn-learn.adafruit.com/downloads/pdf/adafruit-max31856-thermocouple-amplifier.pdf?timestamp=1583020909

I'm assuming the diodes are acting as some sort of level shifter however I'm not entirely sure. Can someone explain the purpose of the diodes. Also due to blurriness I cannot tell the value of the 3 pullup resistors. They look like 1k, but I have been reading around and have seen "10K" suggested. (edit: I looked at the physical board and saw 1002, meaning 10K), please ignore that the pullup resistors are 1k in my diagram, I have changed them to 10k now

This is my version 2 circuit at the moment:

Here is my original circuit, which I believe is not correct anymore:

Here is the corrected circuit diagram thanks to each of the comments:

Simulation result confirming the shifting circuitry performs as expected:

(5V to 3v3)

(3v3 to 5V)
(Not enough rep to post 8 or more links, so can't show schematic modification)
The pulse was put onto the 3v3 line, and Von was reduced to 3V3 giving 5V on the 5v line.


texts: measure with scope 2 signals from independent systems

texts:
I have 2 independent boards which output a signal ('signal A') to a main computer . Each board has its own oscillator. Each board does not 'know' of the other board existence. Both boards receive as input some data signal, from which they produce 'signal A'. Signal A should be sync to each other (in some kind of error I want to check).

I want to compare this signal A in both boards and verify its sync. While measuring using the scope, both signals has jitters and are very 'jumpy'. I'm using each board gnd for the probe gnd so the measurement should be ok. I'm using one of the signals as trigger.

I was thinking maybe the problem is with the measuring itself, as I do not have a common reference signal (trigger signal) to measure both signals in reference to it and both boards are actually dependent sub-systems in my whole system.

Am I right?

Any ideas?


texts:
Possible Duplicate:
  Why are the pinouts of lpc21xx all over the place?

I have often noticed, and found it quite annoying from a PCB layout point of view, just how illogical many IC's pinouts are.

Let me give you an example:

They've done a good job with port B.  Port A is almost there - A6 and A7 seem to have wandered off a little...  But what is with ports C and D?

Another example - the Z80's data bus:

I mean, that one just makes no sense to me whatsoever.  Not only are then in some seemingly random order, but you suddenly get +5V in the middle.

So what is the reason for this?  Are they doing it just to be annoying, or is there some sound technical reason why the pins have to be in these strange orders?


texts: Finding the equivalent Resistance of acircuit

texts:
simulate this circuit – Schematic created using CircuitLab

I am a little confused on how to find R equivalent of this circuit because of the wire.

Right now I have the following expression:Req=  (R1//R2) +(R3//R4)
Is this correct?


texts: 50 Ohm Single Ended Signal Impedances on PCBs

texts: I have a basic understanding of transmission line theory and how 50ohm traces are designed on a PCB. I was wondering what the origin of this 50ohm impedance is. Are single ended digital signals on ICs designed per this spec? It wouldn't make much sense to create 50ohm traces on a PCB if the driver and receiver ICs were not designed with these characteristic impedances so as to impedance match. Or is this a non-issue for low frequencies?


texts:
I want to buy a laptop powerbank which output AC current, in which I then plug the stock charger of my laptop.

It it a good idea, or I should rather buy a powerbank that directly output 12v so I can directly plug it in the laptop? Is there a big efficiency difference, or a preferred option?


texts: LTC3106 solar harvester example allows current flow into the solar cells

texts:
I'm trying to build a schematic that uses the LTC3106 which is a IC that can have both solar cells and batteries as inputs and gives a regulated voltage on the output.

The datasheet suggests a design for this purpose:

I've highlighted the part I found problematic. There are 4 reservoir capacitors connected in parallel to the solar cell. Given that the solar cells voltage levels depend on the light, under low light conditions the voltage could fall lower that what is on the capacitors. Couldn't that result in a scenario in which the current is flowing into the solar cells?

Note: I'm guessing a diode would fix the problem but would introduce at least a few hundred mV of voltage drop. Am thinking that perhaps I'm missing a pattern that could be related to the differences between the impedances of the cell and the IC input.


texts: Backward measurement of AVcc against reference voltage connected to ADC input

texts:
what you think about ADC backward measuring supply voltage in microcontroller?
It looks interesting for battery-powered devices.

The idea is:

Connect constant voltage (some voltage reference IC) to ADC input (not to Vref!)
Set AVcc as reference for microcontroller ADC
Get ADC value
Calculate ADC reference (our AVcc) from ADC result

My questions:

- is this commonly used method?

- can that method be better than measuring Vcc using voltage divider with ADC reference connected "conventionally"?

My question is inspired by this.


texts:
How do you decide the minimum annular ring size of a buried via?

I remember to have seen one manufacture list this, but generally I can't find the size on manufacture websites.


texts: How do you supply a PMIC beyond its voltage limit?

texts: I'm using a power management IC (PMIC) with a lower max Vin than I want to supply. Is the solution to this as simple as adding a separate, greater voltage regulator in front of it?


texts: Identify this open collector serial protcol

texts:
I'm trying to analyze the serial link between two devices, respectively a  motor controller board and a Li-Po battery manager, which battery powers both devices. The application is a battery-powered gardening tool.

The two devices use the same microcontroller, a Holtek HT66F018, and use what seem to be GPIO pins for the serial link, as the microcontroller doesn't seem to provide any I2C or UART or any other dedicated serial interface. The link uses an open-collector (or open-drain) connection, with external pull-up resistors and separate Tx and Rx lines, on the same wire. Q1 and Q4 are 2N5551, not 2N3055, but I didn't have the part ready and put a similar NPN. Q2 and Q3 wew unmarked in the schematic.

In the schematic uC_2 is the motor control microcontroller, and uC_1 is mounted on the battery management board.

I've tried to read the signal with a scope, but I currently struggle to identify the protocol. uC_1 seems to act as a master, as it always transmits first, and then uC_2 (not always) replies. You can tell one from the other because they pull the line low to different levels: most likely because uC_2 has a 200 Ohm series resistor on the emitter of Q3.

The figure shows an example of an exchange between the two devices: the bus is normally high, the sequence is initiated by uC_1 with a long low pulse and follows with a sequence of pulses with the reply of uC_2.

Things I've noticed:

the baud rate seems to be about 3.2 kbaud, though there is a decent amount of jitter;
the protocol doesn't have a separate clock, but looks a lot like the one in this question, where it was suggested that the series of pulses may be used to synchronize the devices, or that the clock may be embedded in the transmission sequence.
So far, excluding the stop bits, there seem to be no high pulses of more than one bit-length (could also be interpreted as half-bit if this was Manchester coded); there are longer low pulses though, never longer than two bits in a row, except for the start sequence.
The battery manager (uC_1) is expected to monitor battery voltage and temperature, though experiments we made of simulating varying battery voltage and temperature are different to interpret: the message seems to be varying in length, and seem to only change significantly when the battery voltage is critically low.

There are some more considerations, but it's already getting quite long, I'd like to see if anyone has some pointers about what the coding may be.


texts: What is the maximum voltage that the circuit can withstand

texts:
Below is my circuit,

ESD Capacitors Specifications :

C0001, C0002, C0003, C0004 = 47nF, 100V, 10%, 0805
I have 2 basic questions :

When a +4kV pulse & 330pF is applied, Does the 12.77V (Q=CV ; Q =4kV * 150pF = 600nC. Voltage at the top node = 600nC / 47nF = 12.77V) is shared by each capacitor separately (C0001 to C0004)?
So each capacitor will hold 3.1925V?
And what is the maximum voltage can this circuit section withstand in the case of positive pulse? Is it 4 x 100V = 400V ? Or only 2 x 100V = 200V (since the 2 sets of series capacitors are in parallel). 100V is the voltage rating of the capacitor.


texts: Designing flyback converter - Switch voltage drop

texts:
Switch voltage drop is often used in turn ratio calculations, however it is rarely specified in datasheets for converter ICs with built-in FETs. The closest I found is "Rds at Isw". Should I multiply these and use everywhere? Or should I multiply Rds by estimated Iavg or Ipeak? When Vin is low this produces rather huge difference, like 1:5 vs 1:10.

UPDATE:

I think I found an answer on powerelectronics site:
MOSFET conduction loss PCONDmosfet = Imosfeton(avg)^2 x RDSon x D

if PCONDmosfet = Vsw * Imosfeton then Vsw = Iavg x Rds x D
Looks pretty much as I expected, except for that D multiplier.


texts: Drive 4wire stepper motor with PWM type CNC controler

texts:
How can I drive a stepper motor using PWM technique controller, since the stepper motor has 4 wires at 24v?
I want a confirmation.


texts: Tapping into unused Arduino pins with a shield in place

texts:
I am just getting started with Arduino...I figure this is kind of a newbie question but here goes.

I have a Duemilanove and the Sparkfun Speakjet shield.  I've got some breakaway headers (not the stackable headers) for connecting the Duemilanove with the Speakjet shield.  But then I want to interface a bunch of other stuff like switches and LEDs to the Arduino pins that are not used by the Speakjet shield.

Is it required to get the stackable headers to wire up my switches and LEDs to the Arduino pins?  Or is it advisable to just solder wires for my switches and LEDs onto the tiny nubs of the breakaway headers where they poke through the top of the Speakjet shield?


texts: Routing 2 layer PCB: is it ok "solve" isolated GND island with a VIA?

texts:
Every time that I design a PCB I connect the TOP layer and BOTTOM layer to GND (GND pour).
With this PCB I finally ended with an "isolated island", without possibility to use the TOP or BOTTOM layer as GND. I did added a VIA near the cap, but is it a good choice? And if yes, what's the raccomended dimension for the hole for the via?

This is the picture:

Update: PCB without the VIA and Eagle complaining:


texts: Implement send-only (one-way) Ethernet cable

texts:
I want to build a unidirectional comminucation. In transportation layer of this device, it needs a one-way media to send data from side A to side B.

All commercial products use SFP. I tested some SFP devices but they have negotiation between the two sides and cutting RX fiber is not possible.
Is it possible to implement One-way connection with CAT5 cable?

SideA { tx --> rx } SideB


texts: Standard nomenclature for component types

texts:
What prefixes should be used on reference designators for components of various types?  I think we can all agree that "R##" refers to a resistor, "C##" refers to a capacitor, and "L##" refers to an inductor.  Beyond that, it appears to be a mishmash of conventions.

I've seen both "IC" and "U" used for chips.   "Q", "T", and "M" have been used for transistors and MOSFETs.  Ordinarily, "D##" is used for diodes, but LEDs and Zeners get special treatment on some boards.

What standards are available for reference, and who endorses them?  JEDEC, ISO, IEEE, and other standardization bodies are welcome references (though I'd prefer an inexpensive standard), but I'm also curious to see what's used at various companies other than my own.

Edit:  What I'd really like to see is a list in an answer here which complies with the standard (even if it's just a quote).


texts: LTspice parametric sweep: how to force the simulator to continue with the next step?

texts:
I'm running transient simulations as I am sweeping a couple of parameter values (resistances, capacitances) to give a first hint about what range of values make a certain circuit stable. In addition, I want to extract certain measurements from the wave form, in order to basically give me a figure of merit for the given parameter combination. These measurements limit how short time period I can use for the simulation (as in, it turns out I can't go below about 200µs if I want the measurements from that run).

Each run takes a fairly long time, so I would like to avoid, if possible, running the whole transient simulation if I can already see that these particular values causes oscillations.

Is there any way to tell LTSpice that "no, this parameter combination is dead in the water, skip this and continue with the next"?


texts: seeking help identifying small buzzing transformer from my UPS, or advice on how to silence it

texts:
i have an APC brand UPS installed inside another project, and have just recently powered it up for long durations for the first time. and i've picked up an annoying buzz in a small transformer on the main circuit board :<

i'm certain this little jerk is the only thing buzzing, but i've failed to find it online for R&R.

the text reads :
430-0271-Z.
VIKING F-1.
LEI-4 BJ08.

the buzzing is present intermittantly when the mains power is connected, and transitions to a steady sound when battery is unplugged. it goes away completely when battery is plugged in and mains is disconnected, so i conclude it's part of the charging circuit.

could a faulty battery cause this problem?

if it's a custom part for APC, and i can't source a replacement, is it safe to muffle the buzzing with some self-adhesive duct foam? i mean the black mat material used to insulate commercial air conditioning ductwork. it's a dense heat-resistant rubber foam.


texts:
I am learning to use an FPGA (Papilio development board,which has a xilinx spartan3e, using vhdl).

I need to divide an incoming pulse by a (hard coded) number.

I can see 3 options - roughly, as pseudocode (using 10 counts as an example):

Initialize to 0, on input rising edge increase by 1, compare to 10; if they are equal, reset to 0 and trigger output pulse
Initialize to 10, on input rising edge decrease by 1, compare to 0; if they are equal, reset to 10 and trigger output pulse
Initialize to 9, but make sure there is at least 1 leading "0" bit, which is my output bit. On input rising edge decrease by 1. On rising edge of the output bit, reset.

The duty cycle is unimportant.

Is one of these better than the others? Is there an even better method that I haven't thought of?

Is there a "standard" way that will give the compiler the best chance of optimizing?


texts: How to check what is the percentage of charge in my lead acid battery?

texts:
http://www.allbatteries.co.uk/media/pdf/AMP92108_FR.pdf

I want to know how much percentage of the battery charge is left without buying any fancy equipment to measure it.


texts: Proper or instinctive design choices for trimpot direction

texts:
We all know its customary for a VOLUME control on any audio product should require turning CW to make it louder. In fact for user accessible rotary adjustments, clockwise almost universally means "more". This despite the fact that all plumbing faucets do the opposite. But it seems whenever I design a circuit where a trimpot makes the most sense, I'm always self debating this, and even when I reach what I think is a sensible decision I often find I'm later second guessing myself.

Consider, for example a trim pot that limits the maximum GAIN in an amplifier. On the one hand, it would seem to follow the "volume control" logic that CW should be more gain. But then again when you make adjustments looking at a schematic, sometimes it seems like the opposite might make more sense. Especially when only 2 legs of the trimmer is used, maybe CW should always mean more resistance.

I doubt there is a right or wrong to this, so I always try to notate my schematics with an arrow near the trim pot wiper with either "CW" or "CCW". Right or wrong, that way at least I know what to expect. But for as many times as the final adjustment direction didn't seem to make as much sense as I thought it would on paper, I thought it might be interesting to see if there is some consensus or set of conventions, as there already is for user level adjustments.


texts: Half wave rectifier connected to a npn transistor - how to compute its output

texts:
Above is the circuit i need to analyse. I already have the gain and Q-point of the first transistor, now i will have a half wave rectifier consisting of elements D1, C3 and R5.

Here's the gig, i done some simulations on LTspice and some of the results can be seen below:

Above this is the gain which i think it's pretty self explanatory.

Now the image below is the transient + stationary response when the input is 50sin(1000t), i can tell D2 glows (On) and the npn transistor is in the active region.

The Image above shows the part where i dont understand. The capacitor first charges then discharges, i can see the ripple (almost non existent), but then it just goes up and up. Why does that happen? How can i explain that on a general input? Of course if i increase the time to get rid of the transient part all i see is a DC signal which is what i want as my input voltage for Q2.

On a normal half wave rectifier with a capacitor this is what i was expecting:

Vout always stays below Vp-VDon


texts:
I need to power up an IC, but there is no description of reference design. Just an image.

This is the image:

This is a circuit to add to IC. But i can't understand it's use. Do it provide me a short of voltage stabilization? Do it provide me a power up sequence?

I have no more information that i can provide. Can someone help me to understand electronic function that this circuit provide me?

Thank you.


texts: Why are chokes nonlinear around 0A ? What inductors do not exhibit this behaviour?

texts:
I want to demonstrate that I can control the current in the winding of my single phase motor (a limited angle torquer) with a bandwidth greater than 3kHz. The phase resistance of the motor is 20Ohm, and its inductance 100mH, for a supply voltage of 100V.
To this effect, I have wired in series a power resistor of 20OHm with one winding of a 190mH common mode choke (Wurth Elektronik 7448050219).

Then I have configured a Copley Controls ACCELNET (motor driver) in Brushed motor mode current control (small signals, 0.1-0.5A) and no feedback, internal frequency generator as control input, and tried out a couple of loop tunings (P only, PI autotune etc.). The bandwidth cannot go any higher than 300Hz, which is quite surprising, but above all the signal gets distorted very rapidly. When inputting a low frequency square wave (10Hz), the following behavior can be observed: there is a dead-time during which the current setpoint increases but the output current stays at zero, until it brutally catches up resulting in some ringing.

Apologies for the crude drawings, my cameraphone battery was dead when I was at the lab.

I am convinced this phenomena is what causes the controller to lose control without saturating, and I have tried with linear amplifiers such as a Kepco BOP 50M-2 with similar results so this has to come from the inductor.

It almost seems as if the inductor had the equivalent of "dry friction" - which opposes some resistance to a certain point, then brutally changes the speed with some overshoot. I'm thinking it could come from the non-laminated core, which exhibits some hysteresis? What do you think? And finally, how can I build an inductor which IS linear?


texts: What type of transformer is used in LLC converters? Is resonant or pulse the same thing?

texts:
Often in the description of LLC converters, I hear the mention of a resonant transformer.
On Wiki, I found both resonant and pulse transformers.
In the photos of the LLC converters - the transformer is very similar to the pulse one. Only there, next to it, there is also a magnetizing inductor (Lm).
Questions:

What kind of transformer is used in LLC converters?
Are resonant transformer and pulse transformer the same?

If not, what are their main differences? (constructive / theoretical).
Thank you!


texts: Why do electronics systems stop working? What kind of parts are almost certain to fail after a certain amount of use? Can some keep going for centuries? In data sheets I don't think I've ever seen an estimated lifespan with the exception of LEDs, rechargeable batteries and mechanical switches. I presume the common reasons for failure are mechanical damage, overheating, oxidation/other chemical deteriorations, and damaging surges from static, EMI and other external factors such as power supplies. Is it more often the quality of the manufacturing of the system (e.g. PCB quality, mounting and enclosures) rather than of the individual parts that results in the significant failure rates? I appreciate this is a lengthy topic, but any general principles, pertinent statistics or resources for further reading would be appreciated.


texts: Power supply voltage climbs after disconnection

texts:
I've got a motor controller for a Bldc and I'm in the process of tuning the controller with both PWM frequency, duty cycle and commutation frequency.

Anyway, this power supply is a 30v 10A supply and when I drive the motor, the voltage and current limits kick in.  I start at 12V and allow 10A, but the supply sags to 9.5V @ 3.5A.  Then, when I shut the motor inverter off, and disconnect the supply, the power supply voltage indicator climbs up to 50V!  I have to short out the terminals to get it back under control.

So, two questions :

Why doesn't my supply current limit at 10A like its supposed to? If I short the terminals, I can get 10A, but the motor won't pull 10A.

And, why does the voltage climb after being disconnected?

Edit:
Well, it seems like it's something more serious that this... The power supply is very laggy when changing voltages, the voltage is unable to go below 2.5V, and it ramps up and down when it is initially turned on.... This was after leaving it sit for over an hour and then turning it on, open circuit.

I think she's spent.


texts: Opening MOSFET's gate with low voltage PWM

texts:
I have PWM of very low frequency and very low duty cycle. And max voltage comes out are 3.3. But thats not enough to open the MOSFET's gate(IRFP250N). Now I want to amplify the voltage. I do not have op-amp right now. But I tried to use LM393P comparator but its seems too slow. So if I put LED direct to PWM output I can see it blinking but if I put it on output from comparator it stays on. So I assume comparator is not switching fast enough to make it blink.

Now, I'm thinking of using PNP transistor to switch on the MOSFET gate, but I'm not sure which one to buy ? or should I need to try something else ?

PS: I'm learning through internet and still very beginner. So I might have missed something.

Edit :

PWM Frequency : 4Hz
PWM DutyCycle : 2ms
PWM Max Voltage : 3.3V

Edit 2 : For testing I used 12V instead of 200V.

And the test with LM393, the LED stays on, it doesn't blink. But if I turn off PWM, LED gets off too.


texts: Controlling a single phase AC fan with a 0-10V DC input

texts:
I have a fan motor which is a permanent split phase single phase capacitor motor:
http://uk.rs-online.com/web/p/axial-fans/2781543/

I currently control this fan's  speed with the following controller: http://uk.rs-online.com/web/p/fan-speed-controllers/6685345/?origin=PSF_438361|acc

As you can see the speed-controller is manually controlled by a knob(by hand).

I need to control this fan's speed by a computer software which uses a DAQ board. The DAQ board outputs voltage in 0-10V DC range. So I need to vary the fan speed by a DC input.

Here is the full photo of the controller circuit(They don't share schematics):

As you can see this small controller uses W06 silicon bridge rectifier. The rest of the circuit consists of a diac, resistors, capacitors, a 220K poti, a toroid inductor, a fuse and an adjustable component(next to +MIN SPEED and I couldn't figure out what it is). UZ and U goes to the fan. N, L and PE are for the AC mains input.

There is a triac-like component in the copper side.
Here is the other side of the circuit:

First thing confused me was that there is only bridge rectifier without a triac and I'm wondering how this works without any PWM signal? And what happens when the potentiometer is turned? Here is a short video when I turn the poti(I can only show the upper part of the voltage since the scope cannot plot all): https://sendvid.com/5xr3yn4l The scope shows the voltage between motor's terminals(UZ and U). As you can see the  freq. remains constant but the waveform changes and  the RMS value of the voltages also changes(I checked with a voltmeter).

I was planning to interact with this circuit for my aim(to control it with a DC voltage input), but it seems not an easy task.

Either I need to build a new circuit or buy another controller. I couldn't find any speed-controller in the market for my case where one can control this AC fan with a DC input in 0-10V range. I think I need something like a dimmer which is controlled by a DC input and can supply this fan motor.

I would be glad to hear some circuit suggestions or any such controller in the market. If I need to build one, do I really need a uC for this purpose?


texts: What is the miminum voltage for series NiMH pack?

texts:
Suppose a pack of 8 AA NiMH cells are serially attached and its known NiMH cells should not go below 900mV per cell.

Does this really mean the pack should not be discharged past 7.2v?


texts: Measuring frequency of a signal above 5V with a microcontroller

texts:
I want to measure the frequency (up to 300 Hz) of a rectangle signal, that varies between 0V and Vtop, where Vtop is anything between 5V and 15V. Because I cannot apply more than 5V to the microcontroller (PIC16F1827), I need to limit the voltage somehow.

My first idea was to use a voltage divider. But then the 5V input signal would be to low.

The second approach is using an opamp (TS914). When I am powering it at 5V, the output would not exceed 5V. I already have this opamp in my design, to filter another voltage measurement. But when I look in the datasheet it says (In section "Absolute Maximum Ratings"):

  The magnitude of input and output voltages must never exceed VCC+ +0.3V.

Should I add another opamp, e.g. LM324? The datasheet says (Input Common-Mode Voltage Range (Note 10)):

  The input common-mode voltage of either input signal voltage should not be allowed to go negative by more than 0.3V (at 25˚C). The upper end of the
  common-mode voltage range is V
  +
  − 1.5V (at 25˚C), but either or both inputs can go to +32V without damage (+26V for LM2902), independent of the magnitude
  of V
  +
  .

So the LM324 would not be damaged, but would it work in my design (outputing a 5V rectangle signal)?

The last idea I had, are using zener diodes. Would this work?

What would you do to solve this problem? Is there another possability I didnt think about?


texts:
I have a water cooler that is using a B3950 10K sensor.
For energy saving reasons, the microcontroller is limited to 6 degrees celsius (R=24k for the 10k ohm)
I can't modify the microcontroller or how it works however I want to manipulate the reading sent to the micro controller to achieve lower temperatures.
Typically I want the real R=28k (3 degree celsius) to be read by the micro controller as 24k (6 degree celsius)
Is this possible and how can it be achieved?
Another thing I thought of is using additional resistors to make the 10K ohm act as a 5K ohm and map the temperatures as per the B3950 data sheets?
Please share your thoughts
Thanks in advance


texts: How to calculate initial voltage in a simple Electrical Circuit?

texts:
I can't find the rules about how to calculate the initial voltage across the capacitor \$C_1\$.
A my friend told me that I can calculate \$C_1\$ following the meshes lines: if I do this, I will come across \$R_3\$ and \$R_1\$ or \$R_2\$ and \$L_1\$. So I am tempted to say \$V_c(0^-) = |V_{R_1}|+|V_{R_3}|=|Ia*R_1|+|Ib*R_3|\$, is this correct? If yes, what are the signs (+ or -) of \$|V_{R_1}|\$ and \$|V_{R_2}|\$?

simulate this circuit – Schematic created using CircuitLab


texts:
I am using LTSpice for simulation, but I am finding that I have to look through many different online sources to find what I am looking for e.g. the section on analog behavioral modeling here http://www.ecircuitcenter.com/SPICEsummary.htm

Is there a free comprehensive guide that includes all of SPICE's features or do I need to get one of the SPICE books? I am reluctant because they all seem too old.

Something specific to LTSpice would be even better.

Thanks


texts:
I'm looking to make a circuit that takes a 20-30VDC input and, when that goes high, generates a signal that also goes high, but to a different voltage (2-10VDC). Then after some time of being high (on the order of hundreds of milliseconds to seconds), I want it to transition to a ~600Hz, ~50% duty cycle PWM.
I'm thinking of a monostable 555 and an astable 555 with the outputs into an or gate. Powered off a linear regulator to drop down the input voltage. This seems a bit inelegant. Any other concepts of how this might get accomplished?


texts:
I'm interested into know what semiconductor manufacturing process use the most common PIC and AVR microcontrollers, in particular 8 bit microcontrollers.

Obviously they are not at the same level of modern CPUs and GPUs (~20 nm), what is the gap between these two "categories"? Are microcontrollers still in the order of micron?

Is the microcontrollers frequency limit (tens of MHz) only due to the worst manufacturing process or are they other factors that affect their maximum operating frequency?

Is just the extremely high cost of better manufacturing process that prevents its use in cheap microcontrollers? Or are there other reasons?


texts: How to insert copper coil to output terminal?

texts: I recently purchased a cheap induction heater circuit from ebay. Upon receiving I tried inserting the copper coil to the output terminals but it’s too small. I tried unscrewing the screws on the top but nothing happened. I have no idea if I’m doing something wrong and would like a second opinion.


texts: I'm new to microcontroller programming. How can i configure one pin for input and another for output. If I am not wrong this could be done with GPIO registers that control device pins that are not connected to peripheral functions.


texts: Arduino Detect something is connected to relay

texts:
I have a diesel generator controlled using arduino, 8-ch relay board and it works great but sometimes during monthly maintenance workers unplug start/stop contactor coil wires from the arduino relay board causing the generator not be operated automatically, so i'm thinking of a way to monitor if start and stop contactor coils are connected to arduino relay board or not.
I came up with the following circuit, to use a voltage divider using the contactor coil with known value resistor and the resulting voltage will indicate a connected contactor coil or not:

This is the High power relay used to start and stop the generator, and i'm using arduino relay board to control this relay

My question is aside from the coding part as I will be monitoring analog reading on A0 pin if value less than 2.5v then coil is connected else not connected.
will this circuit works or it could affect my arduino?


texts:
I've got a battery powered synth that uses two 9v batteries to make a split rail power supply (±9 and ground). I'm trying to use a regular AC-DC power adaptor to replace the batteries. The adaptor outputs 12v and I'm regulating it down to 9v with the LM317 voltage regulator. To get the required -9v I'm using the ICL7660 CMOS voltage converter. The problem I have is with the noise created by the power supply, when i hook up the synth it works, but there's some oscillations and artifacts on the audio output. Does anyone know if there's a way I can filter out this noise?

here's the circuit so far -


texts: SMPS Layout, capacitors in parallel placement

texts:
I'm laying out a buck converter based on the TPS54308, and the datasheet recommends the following, which I'm trying to replicate:

Webench (the interactive design tool by TI), however, recommends 2 large MLCC (2*10uF) on the input instead of only 1 large cap.

So I have two options, leave 10uF + 100nF close to the TPS54308 and another 10uF further away, which keeps the loop quite compact:

Or I place all the input caps together (2*10uF + 100nF), which tends to make the loop apparently much larger:

Is this likely to have any real-world impact at all? Is any of the options better than the other? I mean, both will work, but if there is one that is better I would prefer to know.


texts:
I would like to make a USB flash drive easy to disconnect (rather than plug it in, unplug it).

To do this, in lieu of breaking the connection on all four pins, could I simply remove the +5vDC pin (SPST on this pin itself)?

The thought here is that I could have several of these behind a hub, and use buttons to (from an EE perspective) mount and unmount the device.


texts: How does an SD card communicate with a computer?

texts: Could someone please give me a concise explanation to how an SD card sends and receives data from a computer. Does it do this one bit at a time? How does the computer/SD card combine these individual bits into useful bytes? I can see all the pins and what they do but could someone explain how it all comes together to create the read-write functions were all use to?


texts: isolate ADC & transformer in terms of supply?

texts: I'm working on a circuit where I'm connecting transformer parameters like voltage, current to ADC.how do I isolate transformer & ADC in terms of supply?


texts: Minimum Requirements of a microcontroller to run embedded Linux?

texts: I am looking for the cheapest microcontroller to run embedded Linux. what should I be looking at, which class of microcontrollers or microprocessors is compatible? is there a minimum system requirements (RAM, Flash, clock, etc)?


texts:
I am designing a system to measure voltages from bio-potential sources and feed them into an ADC after filtering and amplification. The source has the following charactristics:

amplitudes are in 10's of uV
frequency band of interest is 3Hz to 50Hz.
3.The 2 differential inputs from the bio source would have a DC offset (sometimes as high as 900mV)

As it happens, the vast majority of other designs filter, amplify and then feed the signal into a MUX, which in turn connects different signals to the ADC to be read, something like this if we had 2 sources:

simulate this circuit – Schematic created using CircuitLab
The first thing that went through my mind, was that depending on the application, the op amps used in filtering stages will be expensive.
Is there something fundamentally wrong connecting the sources to the MUX and then feed them into the filtering circuitry? like this:

simulate this circuit
Highest frerquency of interest is 50Hz, am i wrong in assumming that the response time (transient response) of even an oridnary filter would be more than sufficient for such a low frequency?


texts: How to split audio signal into 3 separate channels?

texts:
I have been working with the following circuit:

to build a audio mixer where you can take multiple line inputs, cd players, computer, phone, synthesizers, etc... and mix them together to a single stereo "master" out.

The "master" out can be a power amplifier or powered speakers. So far tested powered speakers and works good and I expect this to work with "professional" grade amplifier/speakers. I.e: Mackies, Adams, Bryston etc... I will test with as much gear I can get my hands on...

So what I want to do is split the "master" out to 3 outputs: master, room and record and each with their own volumes.

I'm thinking of taking R8A, R8B (the master POT) and replacing with a regular 22K resistor.
Split the stereo signal after R9 and R10 and add 3 22K POTs there
Finally line to 3 separate "stereo" jacks/channels

I'm going to do some testing. But I don't have enough gear to test it all, I'm thinking it will be ok so long the input impedance of the destination devices is bigger enough then the total out?

Does my plan sound sane or do you think I should add buffers to each of the split signal?

Update:

Pots are log.

Sample impedances:

http://www.bryston.com/PDF/Manuals/3B_4BSST_MANUAL.pdf 50 Kohms single ended, 20 Kohms balanced
https://www.adam-audio.com/en/ax-series/a7x/ 30 kOhm
https://www.zoom-na.com/products/field-video-recording/field-recording/zoom-h4n-handy-recorder 480 kΩ unbalanced

Update 2:

Using TL072 as the op-amp.


texts: How to calculate Nichols' chart contours?

texts:
Nichols grids show contours of constant closed-loop G(jw) magnitude for the associated open-loop transfer function L(jw)
G(jw) = L(jw) / (1+L(jw))

For instance, the 6 dB contour shows the collection of phase/magnitudes (of L(jw)) that result in magnitude of G(jw) to be 6 dB. But I can't wrap my head around how these contours are being calculated?


texts:
I want to build a circuit that shows the real-time frequency components of an audio signal on a number of bar graphs of some sort. Currently, my plan is to build 12 band-pass op-amp filters, and then use a rectifier and RC circuit to create a DC envelope for each output, and then use that signal to drive a LED bargraph or something similar.

The circuit will use a single +3.3V supply, and using 12 band-pass filters is not really negotiable. If I want a 12-channel bar graph, am I stuck using 12 bar-graph LEDs and bar-graph LED Driver pairs? That comes out to $45! Is there a better/less expensive/simpler method of getting a similar result? Ideally, I would not need a microcontroller.


texts: Should I get a response when beeping two GND pins on a CPLD?

texts: I have an Altera CPLD, 5M570ZT100I5N (100 pins, Quad-Flat-Package) mounted in a socket adapter to get access to the pins. I try to beep two GND pins on the same edge of the package, but get no response. Is this an indicator that something is wrong with my socket adapter ? BTW, the CPLD is not programmed, nor has any power connected to it. I would still expect any two GND pins on the same IO-bank to be connected. Am I wrong ?


texts: four-order filter bandwidth and the two-order fileter bandwidth is same?

texts: I have a two-order bandpass filter, the fc = 10k, bandwidth = 2k. Is the bandwidth changed, if I use this to make a four-order bandpass filter ? if No, why the image


texts: How to add minimum 3 serial ports to a Raspberry Pi?

texts:
How to add  at minimum 3 serial ports to a Raspberry Pi?

I thought about:

1) On hardware

2) On USB

For the the second one i thought about some circuit that exposes 3 serial ports and has an USB port that connects to the Pi. I.e.

                 |===COM1
USB=======circuit|===COM2
                 |===COM3


texts: Why is the light emitted by the LED not of a single wavelength but consists of a narrow range of wavelength instead? Spectral linewidth change?

texts:
I do understand that the wavelength of the lights depends on the energy gap of the semiconductor, but why does it consist of a narrow range instead of a fixed value? is it because during recombination the photons have random phases?
Also, how does the spectral linewidth change if I increase the temperature? If I increase the temperature, the electron distribution in the conduction band will increase as more electrons jump from VB to CB. How does that exactly change my spectral linewidth?


texts: How can I read the data of all nodes at the simultaneously with LoRa

texts:
assume that we have 4 e32 433T30d nodes we are measuring temp and sending to a center point. as a image atteached. I am using arduino.

I am using this library with arduino https://github.com/xreef/LoRa_E32_Series_Library
and center point is reading incoming mesages with this code (arduino code)
void loop()
    {
    if (e32ttl.available() > 1){

    ResponseStructContainer rsc = e32ttl.receiveMessage(sizeof(Message));
    struct Message message = *(Message*) rsc.data;
    Serial.println(message.type);

    Serial.println(*(float*)(message.temperature));
    Serial.println(message.message);
    // free(rsc.data);
    rsc.close();
    }
    }

How can I read the data of all nodes at the simultaneously without the nodes getting mixed up? it looks like reverse broadcast mode. how can achive that without losing data and constantly reading the same point?


texts: Will EMI strongly affect my sensor reading

texts:
I'm using an Arduino to read analog values from my sensor running at 5V using a voltage divider. The sensor contains a force resistive sheet where the resistance of the sheet decreases as force is applied on it, and the sensor is used to determine whether someone has stepped onto it (it doesn't need to measure the amount of force applied). I'm using a voltage divider to read the voltage change and at the Arduino side I will determine that the sensor is being stepped on when the value exceeds a certain threshold value.

Apart from the sensor, 2 additional parallel wires will be running along the same path as the sensor, and the two wires (12V and GND) are connected to a 12V led strip at 100mA.

The length of the 4 parallel running wires are 10m each, and I've received 2 different sets of advice -

(1)The wires are long so they are acting like antennas and will be affected by EMI, so I should use ADC/comparator placed as close as possible to the sensor to transmit the data digitally.

(2)The wires are running at relatively low voltage and low current, and the application is running at low speed (my Arduino is reading the analog values at 10 times/sec) so it will not be affected by EMI. Hence, reading analog value using the voltage divider will not be a problem.

Can someone advice?


texts: How does a device that is RF enabled power up the main CPU by way of RF?

texts: Suppose you have a device such as a wireless video camera and the only way to power on the device is by way of RF. If the video camera has a CPU how can the baseband IC power up this CPU ? Is it possible to embed the baseband IC's with some ASIC integrated circuits (Boolean logic gates) with the capability of processing the data (command to start up the CPU) which the RF wave is carrying ?


texts: Powering 5V Laser with Raspberry Pi 4 GPIO Pins

texts:
I am powering a 5V, 5mW laser that draws ~30mA (KY-008) with a GPIO on my Raspberry Pi 4. From my research, GPIO pins have a voltage output of 3.3V, so I'm not supposed to be doing this. Unfortunately, I do not have the option of hooking the laser up to the 5V pin on my RPi, and I need to be able to control it, so the GPIO's are my only options.
I have been doing this for weeks now and the only issue I notice is a drop in the power output of the laser. I plan on soldering the wires (S pin of the laser module to GPIO 8 and - pin of laser module to GND) soon. Is there something I can solder in between those connections to improve performance and possible save my RPi from destruction, like resistors or a transistor? I saw something online about how with a small enough current draw requirement, the overstep in voltage might not be an issue, which I'm hoping is the case for this.


texts: How come radio signals don't interfere with each other all the time?

texts:
I'm a newbie on wireless technologies and I'm trying to understand how they work.

One thing I don't understand is this: How come transmissions from different devices don't interfere with each other all the time?

For example, I'm living in a dense metropolitan area. There's a router on my desk, and a laptop connected to it via WiFi. I would bet that in the 100 meter radius surrounding me, there are at least 100 more routers, and at least 200 more devices (laptops or cell phones) that are connected to the aforementioned routers. They are all communicating with each other at the same time. How can my humble laptop and my humble router send messages to each other? When my router send a message, how can my laptop pick it up from all the noise on these frequencies?

This question applies to phone networks as well. How can a phone reliably communicate with its tower when there are 500 phones nearby who are communicating with the same tower? How do they know which data belongs to which phone?

Thanks for satisfying my curiosity!


texts: OLED is garbled when powered by 3.7 battery but not when powered by USB or variable regulated power source?

texts:
I have an esp8266 on a breakout board for programming hooked up to an OLED via GPIO 0 and 2. It works fine if I power it via the FTDI/USB. It also works when I power it at 2.8-3.0V using a desktop variable power supply. But no matter how I connect a battery it won't work. I don't want the breakout board in my final project and I want it to be powered by lipo. I've tried making a voltage divider but the divider did not produce the voltage my calculations indicated.

I have 220 and 550 ohm resistor to bring the 4.04v of the battery down to 2.9v but when connected it takes it down to 1.1v which is not enough to power the esp8266 wifi module. I tried adding a capacitor over the +/- rails to improve the current, but I'm honestly still learning how that works.

The esp8266 works fine at a wider range of currents but the OLED seems to be very sensitive.

How can I get this working with the battery?


texts: Is IRFD 014 an appropriate FET for switching an array of (about 40) UV LEDs?

texts:
We have an array of UV LEDs. The LEDs are rated at 3.2 V – 3.4 V at 20 mA, and we plan to use a 5 V supply for simplicity. We will be using a dedicated 100 Ω resistor for each LED (the power dissipated at each resistor is at max. 40 mW, so no issues here).

The LEDs will be wired in parallel and thus will drain a total current of up to 720 mA (or 900 mA, depending on the actual number of LEDs we’ll use).

simulate this circuit – Schematic created using CircuitLab

To switch the LEDs using a microcontroller (probably ATtiny2313A), we are about to pick IRFD 014. We have no fast switching requirements. Switching time can be well over 10ms, ≤100ms would be desirable.

Now the question: Is the IRFD 014 a suitable part for this purpose? From the datasheet, I think it should be fine to use:

\$I_D\$ max at 100°C is 1.2 A, which is at least 20% more than we need.
\$R_{ΘJA}\$ is 120°C/W. We’re expecting an absolute maximum of 1A Drain-to-Source, so with the \$R_{DS(on)}\$ of 0.2Ω, this gives a temperature rise of 24 K. As the device will be operated at room temperature, for not longer than one minute and there will be lots of free space, we don’t see this even remotely as an issue.
\$V_{GS(th)}\$ is 4.0 V max, which is great for driving it with an ATtiny at 5 V operating voltage, and the diagram suggests that we can expect \$I_{DS}\$ currents above 1 A when driving the gate with 5 V.

Have we overlooked anything? A remaining concern I have is that most of the current and temperature ratings in the datasheet are given at \$V_{GS}\$ of 10 V. Do we have to expect any problems when driving the gate with less than that?

This is a one-off design, and for assembly simplicity we would prefer through-hole (and not SMT) devices.


texts: Current limiting required for float charge?

texts:
I'm trying to make a simple float charge circuit for battery backup of an alarm.
The battery specifications state that a voltage of 13.8 is required for float charging and there is no limit on the current.
My power supply is rated at 13.8v and 2.5a. Presumably I need to regulate the charge current to ensure there is sufficient headroom to run everything else that is connected to the circuit (controllers sensors etc).
I've looked into using an LM317 as a current limiter but from what I've read it will cause a voltage drop and isn't particularly efficient?
Thanks


texts: Gernerate random circuits to measure with multimeter

texts:
I want to create a game, where players have to analyse a circuit in order to solve a puzzle. The players see 6 measuring points A to F and have a multimeter/continuity tester. They also have a few different schematics. They now have to find out which schematic is representing the circuit they have in front of them. The Circuits have random shorts or diodes between the measuring points and can look like this:

The thing now is, that I want to be able to generate random circuits with the help of a microcontroller. I'd like to have something like an Arduino simulating different circuits. They don't actually have to work, they just have to look like one of the circuits to a continuity tester.
If I could bruteforce my way through it, I could use 15 relays (one for each connection AB, AC, AD, AE, AF, BC, BD, ...) to switch on and off a short and 30 more relays for 15 diodes in one direction and 15 diodes in the other direction. But my PCB isn't big enough for that ;-)
Is there any other way to simulate shorts and diodes to a continuity tester using a microcontroller? I'd even be happy with something like "The microcontroller senses which points get measured and outputs something the multimeter/continuity tester can interpret". As I said, the circuits don't actually have to work.
Edit: I don't want to simulate the continuity tester. I want the players to learn how to use the "real thing".


texts: Meaning of "short circuit current" in datasheets

texts:
This a general question regarding what should we understand when we see the term "short circuit current" in a given device datasheet. Does it always exactly mean the output current when we short the output to the ground? Or should we look for further explanation in the datasheet?

Here is an example from the datasheet of "AD56x8" digital to analog converter below. AD5628/AD5648/AD5668

It says, the short-circuit current is 30 mA at Vdd = 5 V. I assume, it means that there is an output current protection on the device since it should be way above 30 mA considering the output impedance is 0.5 ohms. Is that a correct assumption? Does this also mean that the maximum current we can draw from the device is 30 mA (there is additional info about the current behaviour in this datasheet, what if there wasn't any)?


texts: How is H(jw) = jw correspond to a slope on bode plot?

texts: I cant understand how H(jw) = jw always intersects at "1" , also how the slope of the line is 20dB, Kindly explain, im having a hard time understanding because in book such stuff is not discussed,only a straight foward graph is given for individual components such as \$H(jw)=jw\$ and so on.


texts: LCD pixels: how chess-board pixel fill patterns are called?

texts:
I have just recently bought a 4k hdr 55 inch tv (Vizio P55 F1).
Here is photo of brightly lit pixels from https://www.rtings.com/tv/reviews/vizio/p-series-2018

https://i.rtings.com/images/reviews/tv/vizio/p-series-2018/p-series-2018-pixels-large.jpg

Picture shows that pixels are clearly squared and uniform

Often when I look at uniform color on the screen (think Playstation menus, but in the real-life videos as well), I see that on various mid-bright spans of same color pixels lit in a chessboard pattern instead of uniform.

https://i.imgur.com/iUekscp.jpg

https://i.imgur.com/jTGzBjd.jpg

On the last image white letters seem more or less uniform, but grey background is definitely not. I draw 2 green lines - top one is going through green subpixels that are brightly lit, and bottom one is going through green subpixels that are dim. Same goes with blue lines, and same goes with red subpixels.

When I get a 4k screen and output a 4k content to it, I expected it to be displayed pixel by pixel, but that is obviously not the case (or is it PS4 generate this patterns by itself?).

I couldn't find anything about it on the internet because I was not able to find proper name for this effect.

I must add that I just recently saw a tv that doesn't have this effect, but I don't remember the model.

My question is - what is the name of this approach, so I can read about it and understand the reason behind it?

Bonus questions - what is the rationale under it? Is uniformly lit tv is better or worse? Is it generated on the source of signal (ps4) or on the tv?


texts:
I bought this DC-DC Adjustable Power Converter Module, to convert 12V DC to 5V DC.

Initially it was working fine, but I connected IN- and OUT- pins to the each other and used it as a common ground for LED Display driver which takes both 12V and 5V as input but has one ground. After this it doesn't seem to work, the output voltage is stuck at 1.24V, no matter how much I vary the resistor which is there to control the voltage.

Can you help me find out what component I have damaged and how?

Edit 1: This is the schematic of my circuit:

The output of DC-DC converter is 5V, which is fed to the pin 3 of the Display driver,
I have a major question regarding the connection of ground pins.

The Pinout for the LED Driver is here:

Datasheet for the driver can be found here.

I have questions regarding the ground of the display driver. There are two grounds, are both the same grounds? Should they be connected to the DC-DC converter input ground or output ground?


texts: JTAG TAP Design code verilog( Advanced Debug Interface)

texts:
I am designing a JTAG unit for a processor. For that, i have initially designed a TAP controller by looking at the FSM of the TAP. Now, i have being given this snippet of code:

reg [`IR_LENGTH-1:0]  jtag_ir;          // Instruction register
reg [`IR_LENGTH-1:0]  latched_jtag_ir;   // latched_jtag_ir_neg;
wire instruction_tdo;

always @ (posedge tck_pad_i or negedge trstn_pad_i)
begin
if(trstn_pad_i == 0)
   jtag_ir[`IR_LENGTH-1:0] <= `IR_LENGTH'b0;
else if (test_logic_reset == 1)
   jtag_ir[`IR_LENGTH-1:0] <= `IR_LENGTH'b0;
else if(capture_ir)
    jtag_ir <= 4'b0101;          // This value is fixed for easier fault detection
else if(shift_ir)
    jtag_ir[`IR_LENGTH-1:0] <= {tdi_pad_i, jtag_ir[`IR_LENGTH-1:1]};
end

assign instruction_tdo = jtag_ir[0];  // This is latched on a negative TCK edge after the output MUX

// Updating jtag_ir (Instruction Register)
// jtag_ir should be latched on FALLING EDGE of TCK when capture_ir == 1
always @ (posedge s_clk_neg or negedge trstn_pad_i)
begin
  if(trstn_pad_i == 0)
     latched_jtag_ir <= `IDCODE;   // IDCODE selected after reset
  else if (test_logic_reset)
     latched_jtag_ir <= `IDCODE;   // IDCODE selected after reset
  else if(update_ir)
     latched_jtag_ir <= jtag_ir;
  end

s_clk is the inverted clock

I am not able to understand this part of the code.Firstly, the comments at various points read that the data needs to be latched at the negative edge of the cycle. I am not able to understand how is the assign statement doing it ? Also,why has he used 2 ir- 1)JTAG_ir 2)latched_jtag_ir.

I have gone through various modules.All of them say that the IR contains some cells and needs to be designed according to IEEE standard 1159.4. Could some tell me what is the purpose of the two registers?


texts: RF generator TX antenna with low impedance can damage generator?

texts:
I got an RF generator R&S HAMEG HM8135 that I use in a testsystem to generate FM and AM stimuli in order to check if FM antenna and AM antenna is correctly mounted on the testobject in a production line. Therefore I do transmitt with as low RF power as possible. Due to spacing and production considerations, I can only have one common antenna place quite close to the test object.

I do use a Schwartzbeck HFRA 5155 TX Loop antenna covering 100 kHz to 300 MHz, which will work for both FM and AM band range.
HFRA 5155

However, if I look in the datasheet, I can see that the impedance around 100 MHz is about 50 ohm, but for 1MHz, it is only about 3 ohm. My test system works (I need so weak AM signal to detect if antenna is not solded correctly, but needs to run the RF generator at about 0 dBm), but my concern is that since I do have so low impedance at 1 MHz (AM test), there must be a lot of power reflecting back into the RF generator (R&S HAMEG HM8135).

Questions:

What impact does the low impedance at 3 ohms for 1 MHz have on my RF generator? Can it be damaged?
Do I need to add anything in order to protect the generator? I do not want to change the RF setup like using two antennas or switching. Just something simple.


texts: A simple way to detect an AC 3 phase induction motor ON/OFF state

texts:
Background:

There is a 3 phase motor running by an inverter. motor specification is about 1.8KW power and 230/400V and 1.13A. I want to drive another DC motor synchronized with that AC motor so the DC motor goes ON and OFF with AC motor. there is no Neutral connection to motor so I can't use a relay or contactor, also inverter is connected to PLC through Modbus connection and I don't want to modify inverter or PLC.

What I have done and my questions:

I thought about using a current sensor (or hall effect sensor) to monitor AC current going to motor, and I found too many different kinds of it. I also tried 3 phase monitoring relay, when I connect it to main 3 phase supply it works correctly and a relay activated inside of it but when I connect it to motor/inverter it doesn't work in 6 different connection type I tried. why?

Is it right to use current sensor for this
application? for example allegro current sensor IC ACS758 is it
the right choice for this application? as the inverter make different frequencies, doesn't it cause to make buzzing at sensor or op-amp outputs? should I connect 3 different sensor for each phases and SUM their output into an Op-amp?
or is it better to use a non-invasive clamp current sensor (this) around all 3 phases wire? and/or one of the phases?
why the phase control relay not works when I connect it to motor/inverter ?

my problem solved:

I use inverter discrete I/Os terminals to detect motor ON/OFF state.

  *inverter model is: Schneider ATV12H018M2
  *phase control relay is: Schneider RM17TG20


texts: How do pixels in a LCD display are individually controlled by a electrode?

texts: How do tiny subpixels in the Led displays are controlled by those indium tin oxide electrode.How do they provide different voltage for each pixel


texts: SMD precision resistor color code (0805)?

texts:
We have specified some 0805 resistors to be 0.2ppm/C. On some boards/batches these are green. On others more "normal" looking. We specified Vishay. Is there some color code that indicates ultra-precision packages?

We have noticed different temperature sensitivity between the boards


texts: Advantages of carbon wires for igniters?

texts:
I was troubleshooting the spark ignition on a gas oven and was surprised to discover that the ignition wire, which carries the high voltage to create the spark, had a carbon core instead of metal.

Why are carbon wires used for high voltage igniters/spark plugs?  The best explanation I could find is from https://www.magnecor.com/magnecor1/truth.htm and talks about the higher wire resistance reducing EMI.

Is reducing EMI the primary/only purpose of using carbon wires?  If so, why is this approach used instead of the (seemingly more simple) metal wire with a series resistor?  Also, are carbon wires still commonly used in new equipment, or are they a thing of the past?


texts:
I am looking to add a pulse to a sinewawave. The input is high voltage AC so I cant use an op-amp adder. I have also used tried to combine the signals through large resistors but that only averages the signal. It attenuates it by 2. I could amplify the signal by 2 but I would rather not. Is there a straight forward way to impose the pulse on the sinewave, (like in the image below). Its easy to do in LTSpice, not so easy in reality.

Thanks.

Edit 1:

Its part of a 3-phase rectifier which uses IGBT's instead of diodes (added below). I will use a separate circuit to generate the pulses accordingly.

The circuit and timing works fine. The plot below shows the gate-emitter voltage with the 10V pulse imposed on it. (the sine wave is only 20V in this simulation but will be a higher voltage in reality, these components don't work at higher levels).

The problem here is adding the pulses to the real-world circuit.


texts:
I have a switch who have not the power over ethernet capability.

I want to power very small devices with the power available on the utp cable.

Do you know the max value (HP 24 ports switch) ?

Thanks


texts: Mains AC Reverse Polarity - Has this damaged my fridge/freezer PCB?

texts:
In the UK, I had a smart meter installed a few weeks ago. My 4 year old Panasonic fridge/freezer (NR-B53VW2-WB) was working fine before the electric meter switch. After the install, after the engineer had left my home, it became apparent that the appliance was dead.

The meter tails have been labelled L and N, crossed out and then re-labelled correctly N and L. This leads me to believe that during the install the engineer accidentally switched the Live and Neutral wires, energised my circuit, tested a socket, found reversed polarity, fixed the mistake and then re-labelled the meter tails.

Meter tails labelled by engineer:

Panasonic have been very difficult to deal with and their third party support are only dealing with in warranty claims, so I've had a local refrigeration engineer take a look at the appliance. He found the main PCB to be faulty, but can't rule out other damage to other PCB's and the compressor. When supplying power to the unit, he said there appears to be live all over the board, but no neutral.

So I've now removed the main PCB and it appears that the rectifying diode ARS157 at location D202 is burnt out. I don't know much about electronics, but having done some research, it looks like this board uses a full wave centre tapped rectifier. Maybe the diodes at D203 and D204 are part of this, so I'm not sure what the diode at D202 does.

Currently my energy supplier EDF will not accept liability for the damage. Can anybody please help to explain if reversing the polarity of my electrical supply would cause this damage to this particular appliance? It would really help with my claim if I have some more details on what has caused the unit to become damaged.

Thanks.


texts: Source of poles and zeros in a physical system?

texts: From where does the poles and zeros come into the transfer function of any system? And I am not looking for an answer in terms of mathematics but want to know what is there in any physical system that turns out forming poles and zeros when represented in the transfer function form. As in terms of mathematics, we have the dynamics of the physical systems in the form of differential equations which we transform using Laplace transform for the ease of calculation. Then using the poles and zeros, which are the solutions of the denominator and numerator polynomials of the transfer function, we do the stability analysis and rest all mathematical analysis. But this does not give me an intuition of what is there in the physical system that turns out to be a zero/pole in the system transfer function or what physical phenomenon in a system ultimately ends up forming a pole and zero.


texts:
I have a 100 Mhz clock and I need a 0.5 Khz clock. So I wrote this code:
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity clkdiv is
    Port ( clk : in STD_LOGIC;
           reset : in STD_LOGIC;
           clkout : out STD_LOGIC);
end clkdiv;

architecture Behavioral of clkdiv is
signal temporal : std_logic := '0';
signal counter : integer range 0 to 99999 := 0;
begin
process (reset, clk) begin
if (reset = '1') then
       temporal <= '0';
       counter  <= 0;
elsif rising_edge(clk) then
    if (counter = 99999) then
        temporal <= not temporal;
        counter <= 0;
    else
        counter <= counter + 1;
    end if;
end if;
end process;
clkout <= temporal;

end Behavioral;

And testbench for it:
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values
--use IEEE.NUMERIC_STD.ALL;

entity testbench is

end testbench;

architecture Behavioral of testbench is
component clkdiv
Port ( clk : in STD_LOGIC;
           reset : in STD_LOGIC;
           clkout : out STD_LOGIC);
           end component;

signal clk : std_logic := '0';
signal reset : std_logic := '0';
signal clkout : std_logic;
constant clk_in_t : time := 10 ns;

begin
uut : clkdiv port map (
    clk => clk,
    reset => reset,
    clkout => clkout);

    process
    begin
    clk <= '0';
    wait for clk_in_t / 2;
    clk <= '1';
    wait for clk_in_t / 2;
    end process;

process
    begin
    reset <='1';
    wait for 100 ns;
    reset <= '0';
    wait;
    end process;
end;

However, testbench results are like that:

Can anyone tell me what's wrong? Thank you all.


texts: How to read an already existing NgSpice raw file

texts:
This has taken me a couple of days to solve.
I have a set of NgSpice raw files that I would like to exploit so as to visualize the voltage distributions in different circuits. What is the python command to use or python package to import in order for me to achieve this.
Note: I am a bit familiar with the PySpice python package, but from what I have read and understood it works when you use it to create your netlist and run it, by using the already stored variables in its memory. In my case however, raw files are already generated...
Hope I was clear enough.


texts:
It's the one dead center of the circle that exploded. I was thinking it was either a diode or a capacitor of some kind, but I don't know how to tell its value from its markings. This picture is of a motherboard that came out of an Acer netbook (Acer One D255E). I'm assuming that the wrong type of charger was plugged into this netbook to cause the damage. This also seems to be the only noticeable damage. Does anyone have experience with repairing this? Or at least what it is?

If any more info is needed just ask.


texts: Short circuit protection for high current wearable: fuse, polyswitch, TBU, circuit breaker, something else?

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I am thinking about design elements for a rather high current, battery powered, wearable application. Maximum current of 40A at 5V, but typically around a third to a half of that.

Power would come from RC car battery packs through a DC-DC converter. The packs typically do not have built-in over current protection, so I would need to provide my own.

I want the over-current protection for two reasons:

Personal safety. If you try and draw more than the rated current out of a lithium chemistry battery strapped to your back, you're gonna have a bad time.
Circuit protection. It's a wearable application and things move, grind against each other and short out. I don't want to kill the battery itself or the rest of my circuit when that happens.

From my investigations so far, it seems a glass fuse or polyswitch won't trip quickly enough, a TBU tops out at hold currents of under 2A, and most circuit breakers are built for AC house wiring.

What kind of device should I be looking for?


texts: Programming an MCU with an unknown toolstack/SDK

texts: I want to add Wi-Fi functionality to existing circuitry on a PCB by wiring in an ESP8266. However, this requires me to reprogram the existing MCU on the board. I have identified the MCU as an SG8F080P Programmable Touch Sensor Controller manufactured by SigmaChip. However, I am unable to find any reference material for programming or flashing the chip. SigmaChip's website is outdated and does not have a product page for this MCU. Even the products that do have their own page contain no resources for programming. I reached out to the email on their website about a week ago and have yet to hear back from them. I was somehow able to find the datasheet, but I am still at a loss for where to start. Does anyone know anything about programming without a known toolchain or SDK? Or am I better off ditching the chip and rewiring the PCB for a CAP1188?


texts: How are radar returns sorted in range space in Synthetic Aperture Radar?

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I'm trying to understand how a SAR system is able to place returns it receives in range space.
Consider the scenario when an airplane is passing over terrain and is imaging it using SAR, as shown in this image from radartutorial.eu:

If it relies on the timing of the return, it seems that there would be ambiguous cases where a tall object further in the swath could have returns that are received earlier than a short object in the near swath. How would a SAR system ever sort out the elevation of the terrain being scanned in the swath?
From what I've found it doesn't seem like there is any sort of servo tracking the beam along the swath width (and it would have to be moving quite fast for this to work). This leads me to think that there must be some signal processing wizardy used to sort these returns that prevents timing ambiguities. What is going on?


texts: How can I meet these PCB design conductivity/isolation requirements?

texts:
The specifications required are as follows:

The resistance between ground pins on a connector and the case (chassis) ground should be less than 3 Ohms.
The resistance between any other signal on the connector and case ground should be more than 100 Mega Ohms.

How can I guarantee that my PCB design achieve the two mentioned specs? Isn't there any kind of simulation to this?

I use Mentor Graphics Expedition for PCB design and Hyperlynx for signal integrity analysis.


texts: Voltage divider to drop volume of one speaker by 1.5dB

texts:
I have a a balanced stereo audio source, being fed into a headphone amplifier. Both source and amplifier are connected via a pair of 3-pin XLR cables, one for each channel. The amplifier then outputs to some studio monitor headphones.

Due to some hearing loss, my right ear has about a 1.5dB loss over the left. As such, I need to cut the left speaker down by around 1.5dB. Neither the source or amplifier have balance/panning controls.

I want to build a resistor-divider circuit that would sit between the source and amplifier which does the job of attenuating the left channel.

How do I calculate the resistor values needed to reduce the left channel by 1.5db?
Are there any special considerations required given that I'm using a balanced (positive, negative, ground) configuration for each channel?


texts: Regulating high voltage high current ac supply

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I am trying regulate ~250 ac to have regulated 400v 5A dc.
I have a variac and also a step up transformer (1:5). I know for this type of high voltages full bridge SMPS are used. But actually I don't have time to design one.
So is it possible to achieve this with normal rectifier topology with huge capacitors and high voltage-current diodes, maybe with the help of an inductor to help capacitors?
One main purpose to use a variac is that, I only need stay at 400v and 5A for 1 second. (rising 0 to 400v should take 3 seconds)
Load is 80ohm


texts: Reasoning for voltage across the diode in a precision half wave rectifier

texts:
During the positive cycle operation of the circuit, the reasoning goes as this:

Vin is positive, hence voltage to the left of the diode  D2 is positive.
Hence the diode D2 is forward biased.

My problem is with the second sentence in the reasoning:
  How can we assume that D2  is forward biased? We know voltage to the left of D2 is positive, but we do not specifically know the voltage to the right of D2 (there is no ground or anything). So how can we reason out that D2 is forward biased?