texts: How to calculate the resistance measured between probes in water

texts:
I have read already quiet a lot about the conductivity of water/ fluids but i can not find a formula to calculate the resistance between probes in a fluid.
For example:

use-water-as-a-conductor-for-a-circuit-powered-by-1-5v-battery

In the answer Peter Bennett measured about 50.000kOhms.

I would like to know how I can calculate it and what the parameters are.
Parameters I guess so far:
- average distance of the probes
- copper surface exposed to the water
- conductivity of the water (amount of salt for example)
- volume of the water ??
- critical voltage or linear??

I will be doing some home experiments with copper/metal in water and measure the resistance with a small AC/DC current through the water. But I want to calculate it first and then see if I can reproduce the result.

Edit:

I did some small test with the answers below in mind. Especially the EDLC component was clearly measurable. I did a small test in about 100ml /3.5g salt solution. My findings:

AC: with 5cm /0.2mm probes i got at 5cm about 70Ohm. The amount of probe in the liquid did alter the value. The distance was a key factor, my measurement was not accurate enough to give me a function. Overal very consistent results.

DC: same probes i first tried with around 1.5v and did notice electrolysis at that point the resistance was low but increased rapidly because of the corroded probes. if I lowered the voltage over the probes to 0.5v the resistance was about 1kOhm what was higher than i expected and no visible electrolysis did occur. Please be careful, DC in a salt solution will generate chlorine gas do it in a well ventilated place.

I did the measurements over a voltage divider circuit, will do these again later with a more scientific method and logging. But i did them now to get an overview of what to expect.
I'm still interested in formulas to calculate before I do more tests.


texts: Why is the blower fan not rotating in reverse upon reversing voltage?

texts:
I was try to hack a small blower to suck air instead of blowing air
From what I recall, reversing the supply is the way to go. But it seems that the blowers simply does not move.

Here is a link to the product page: https://robu.in/product/7530-12v-dc-blower-cooling-fan/
Is there some internal aspect of the mechanism that is preventing it from rotating in the other direction
Thanks in advance!


texts: How can I measure differential voltage with ArduinoUNO or UNO32?

texts: First of all, thank you for your time. I need to measure the differential voltage from the temperature sensor Fluke 80T-IR (infrared temperature probe), I need to do this with an UNO32 or Arduino UNO.


texts: Why do we use pull up resistor with PIC?

texts:
I tried to find an appropriate answer for the question but couldn't find what I needed exactly. I found out that "Initially the output from the PIC is floating and we use the pull up resistor R7 to turn OFF the transistor". My specific questions are:

How will the floating output from the PIC affect the base of the transistor? Will it make it fluctuate between ON/OFF state?
What would happen if we don't have the pull up resistor?
Is there any risk of the transistor being destroyed because of the floating output form the PIC?
How will the pull up resistor put the transistor in OFF state when there is floating output from the PIC?


texts: Suggestion in interfacing CT to microcontroller

texts:
I am working on interfacing CT to PIC 18f4550 controller. Please find below my rough circuit diagram. my questions are

i)the Recommended Secondary Burden is 47 ohm. i have used in my circuit as 200 ohm is it advisable?

ii) is the below circuit is reliable and better way for  interface with micro controller

iii)is there any modifications can be done to make it better?

I am using electrohms CT-1169 max i/p 60A rms,turns 1:7000,suggested burden resistor 47 ohm
for datasheet [1] http://www.electrohms.com/data_pdf/CT1169_01.PDF

simulate this circuit – Schematic created using CircuitLab


texts: Historical electronic components used in computers

texts:
Early computers used vacuum tubes and relays as active components to process information. Later on, transistors replaced those as the main components used in computers development (transistorized gates, memmory etc).

But, on a certain period, before the use of semiconductor transistors, IBM was researching a parallel line of development that used a certain component X to achieve the same results as early transistors. Or so was the story that I heard a long time ago...

What I want to know/remember is the name of this component "X" ? I searched the whole net but could not find any reference for it.


texts: Fix gold plating on pins has been to repair charging

texts:
To begin, apologies in advance if this is the wrong place for this kind of question.
I have a Fitbit where the gold plating on the charging pins are fading causing inconsistent charging. Is there a way/has anyone had success repairing charging pins that have this kind of damage? Would I need to replace the gold, or could i just add normal solder?
Thanks


texts: İ am working on a project that needs to charge itself through solar power, but İ need to charge it while using it. I am using a 3.7 v 600 mAH battery:  (http://s.aliexpress.com/NJ3aMBVb). Can ı do that. If possible, are there any risks.


texts: I'm curious why T2 is needed. Couldn't T1 be wired to direct 12v to the relay alone just like the role of T2? They're both the same part numbers


texts: problem with differential amplifier output ..not getting expected voltage at output i.e( V2-V1)..what is wrong here?

texts: i have made the following differential amplifier but facing  problem with this differential amplifier here i am expecting 7v i.e.(V2-V1) at output but only getting 4.999V .what is wrong here ?


texts: Generating -10V or -12V @ 500 mA from +12 / +24V

texts:
I am designing a scaling op-amp circuit that requires approximately 500 mA of -10V power (-12V would be better so I don't have to rely exactly on a rail-to-rail op-amp). The circuit is scaling multiple -10V to 10V inputs by 0.10 (output = -1V to 1V).

However, the only power inputs I have available are +12V and +24V (5A and 10A, respectively). Is there a straightforward way to generate the required negative voltage rail? This is not as obvious as I had hoped, especially at the required power (I need to do this across 5 inputs, so all told worst-case is 500 mA).


texts: Workflow to test the quality of XLR microphone cables, and have a quantitative measure of this quality

texts:
I have more than 10 XLR microphone cables from different manufacturers (some of them quite cheap, some of them more expensive), and as I often do recordings (with condenser microphones) of music / audio samples that have a low SNR (signal to noise ratio), I'd like to do my best to pick the right audio microphone cables.
How to measure the quality of such cables, and have a non-subjective quantitative measure of its quality?
Here is the workflow I'm using for now:

Generate a 10-second long 20 Hz - 20kHz frequency sweep (something like this)
Play it with Soundcard 1 (that is reliable)
Plug the XLR audio output of Soundcard 1 to XLR audio input of Soundcard 2
Record the sound with Soundcard 2
Analyse the spectrogram of the recorded signal

I get such results:

It looks good, but:

Can I be sure that an XLR that is ok to transmit audio signal from Soundcard 1 to Soundcard 2 at "line level" will also be good for microphone signals?

I don't want to involve the microphone in my workflow because everything would be dependent of the ambient noise in the room where I do the tests, and then it won't be very reliable (I tried, and even quiet footsteps from the guy on the floor above changed the low frequency charts!)

Any recommendation?
Note: I sent the audio swipe at various levels to Soundcard 1: -12 dBfs, -24 dBfs, ..., -80 dBfs, but what would be an audio level/voltage that mimics "microphone signals"?


texts: How to create an electronically controllable resistance to a physical movement?

texts:
What is the best way to create an electronically controllable resistance to a physical movement?

For example, at the gym you control the resistance to movement by putting more load, more weight. Is there a way to control that resistance electronically?

I was thinking of a motor, it's possible to use it?
Or through electromagnetism?


texts:
when I am reading the IC datasheet ,operating voltage is they were mentioned 5v,300mA.its means 300mA per sec/min/hour.

Because I have to calculate battery power for a circuit.

1 coulomb= 1 ampere.

so please any one you conform the basic thing it will consume the 300mA per second/minutes/hours.


texts: Best way to connect 5V to GND from ESP (3.3V) - transistor or optocoupler?

texts:
First of all: I read through some of the suggested topics (i.e. connecting a 5V relay to an ESP), but to my (limited) understanding, this seems not to be the problem I'm trying to solve. If it is, please accept my apologies.

What I'm trying to do: I want to emulate an Atari-style joystick (which runs on 5V) with an ESP32 (3.3V). To do that, the direction pins of the joystick port need to be connected to the GND pin.

First I was thinking of using optocouplers because they provide galvanic isolation. However, since the ESP will be powered by the joystick port's 5V pin eventually, this might not be really necessary. So I thought about using transistors and supply the base of the transistor with the current from one of the ESP's GPIO. Collector and emitter would then be connected to GND and the respective direction pin of the joystick port.

Would that work as well and as reliable/fast as an optocoupler? I read about leakage current that can occur on transistors even if the GPIO connected to the transistor's base is off?
And could I use BC547 (NPN) transistors for that purpose, as I have lots of them laying around here? Or would a different type be better? And last question: In some of the examples using a transistor as a switch, I saw that GND would be connected to the collector and the load to the emitter. I thought that current flows from the collector to the emitter via the base, so I would have expected GND to be connected to the collector?

Thanks in advance for any suggestions/explanations!


texts:
Friends,

My robot is actuated by a stepper motor, so I can keep track of positions changes while the power is on. But how can I initialize the robot at power on ? Do I need a sensor ?
This is in case the position has been moved while the power was off.

Here is a Video showing my robot.


texts:
I am new to FPGAs and I'm trying to make a UART receiver in a Spartan 6 xc6slx9 FPGA. I searched online about UART receivers but almost all of them use FSMs. I don't yet know about FSMs. I have written a verilog code for the receiver but it doesn't work as intended. Please tell me where I have gone wrong and how to rectify it. Thanks in advance.

////////////////////////////////////////////////////////////////////////////////////////////////////////////
module UART_RX(clk,d_in,D_Out);
input clk,d_in;//clock & Data input
output [9:0] D_Out;//Data output

reg [9:0] Clock_Divider;
always @(posedge clk)
begin
Clock_Divider <= Clock_Divider+1;
if (Clock_Divider == 54) //for 115200 baud
Clock_Divider <= 0;
end

reg Clk;
always @(Clock_Divider)
begin
if(Clock_Divider == 54)
Clk <= 1'b1;
else
Clk <= 1'b0;
end

reg latch;
always @(d_in or Rst)
begin
if(d_in == 0)
latch <= 1'b1;
if(Rst == 1)
latch <= 1'b0;
end

reg [6:0] Counter;
always @(posedge Clk)
begin
if (latch == 1)
Counter <= Counter+1;
if (Counter == 76)
Counter <= 7'b0000000;
end

reg Rst;
always @(Counter)
begin
if(Counter == 76)
Rst <= 1;
else
Rst <= 0;
end
///////////////////////////////////////////////////
reg SIPO_0;
always @(Counter)
begin
if(Counter==4)
SIPO_0 <= d_in;
end
assign D_Out[0] = SIPO_0;

reg SIPO_1;
always @(Counter)
begin
if(Counter==12)
SIPO_1 <= d_in;
end
assign D_Out[1] = SIPO_1;

reg SIPO_2;
always @(Counter)
begin
if(Counter==20)
SIPO_2 <= d_in;
end
assign D_Out[2] = SIPO_2;

reg SIPO_3;
always @(Counter)
begin
if(Counter==28)
SIPO_3 <= d_in;
end
assign D_Out[3] = SIPO_3;

reg SIPO_4;
always @(Counter)
begin
if(Counter==36)
SIPO_4 <= d_in;
end
assign D_Out[4] = SIPO_4;

reg SIPO_5;
always @(Counter)
begin
if(Counter==44)
SIPO_5 <= d_in;
end
assign D_Out[5] = SIPO_5;

reg SIPO_6;
always @(Counter)
begin
if(Counter==52)
SIPO_6 <= d_in;
end
assign D_Out[6] = SIPO_6;

reg SIPO_7;
always @(Counter)
begin
if(Counter==60)
SIPO_7 <= d_in;
end
assign D_Out[7] = SIPO_7;

reg SIPO_8;
always @(Counter)
begin
if(Counter==68)
SIPO_8 <= d_in;
end
assign D_Out[8] = SIPO_8;

reg SIPO_9;
always @(Counter)
begin
if(Counter==76)
SIPO_9 <= d_in;
end
assign D_Out[9] = SIPO_9;
endmodule
////////////////////////////////////////////////////////////////////////////////////////////////////////```


texts: Two 200V outputs on 1 DC electronic Load

texts:
I have a product with two 230V outputs. I want to test if the product is also working correctly under high load(2kW on each output) I have an electronic load with 1 output. Can I just connect both outputs to the electronic load and set the load at 2kW? Or do I need to set the load to 4kW? I am a software engineer so I am not totally into this kind of stuff.

edit:
the outputs are 230V DC instead of 200V. The input is 1 phase 230V rms. it is connected to fuse and after that a triac is placed . again another fuse and then the output.

The same holds for the other connector but then with a different phase.

I got a DIB with bridge rectifiers on it. this converts the outputs to 230VDC and after that the load is connected.

I can change this DIB. So maybe an idea is to use a 2 phase bridge rectifier to make from the two phases DC voltage and then put a load on the outputs?


texts: Raspberry 3.3 V to 5 V level conversion at 5MHz

texts:
I have a Raspberry Pi 2 to handle my cards.

I need to convert 3.3 V GPIO of Raspberry to 5 V for my cards.
Actually I use CD4050 (Non-Inverting Buffer) to convert 3.3 V to 5 V.

I have mesaured output GPIO 3.3 V of Raspberry at 5MHz, the signals is correct.

I have mesured output of CD4050 with 5MHz, the signals is very bad.

I use WiringPi with Qt for control GPIO

I think the CD4050 is not able to work at 5MHz (Work in Detect logic level)

I'm new in electronic systems, i would like your idea.


texts:
I'm having trouble finding information related to a "DG" flip-flop as shown in Figure 2-9 of SLAU320AI:

I'm just interested in the truth table for this. I'd guess this is a gated D flip-flop with G being the "enable" (maybe "G" for "gate"?). However, I usually see gated D flip-flops with "EN" as the enable, and ironically a different flip-flop in the same diagram uses "EN". Any hints?


texts: How can I prove there exits a Hamilton path from a vertaix to the other

texts: I know a Hamilton path on the 4 × 4 (n * n)grid that can starts at the top-left corner and ends at the top-right corner, but how can i prove it in word or math ?not program


texts: Amplifying a PWM signal with an op amp. Is the slew rate a problem?

texts:
I need to amplify a PWM signal from 5V to 24V in order to drive a mosfet that in turn drives a small DC motor.
The input signal has a frequency of 500Hz and comes from Arduino uno (pin 9).

For amplifying the signal I thought of using a typical non inverting amplifier configuration

simulate this circuit – Schematic created using CircuitLab

If I use an op amp such as the TL071, the typical slew rate is 16 Volts/microsecond. This means that the op amp will take 24/16 =1.5 micro seconds to reach the high output of the PWM. This seems acceptable to me since with a 500 Hz PWM frequency, the PWM period should be 2000 micro seconds, therefore 1.5 over 2000 is negligible.

Is there any other consideration I should do? For instance, should I consider the time the mosfet needs to charge up the gate?
Is there a better way to amplify a PWM signal?

Furthermore, suppose that I would like to increase the PWM frequency. For instance up to 2.5kHz. in this case the PWM period should be 380 micro seconds. considering 1.5 over 380 the the slew rate still seems acceptable to me.


texts: I have a 2N2222 transistor that I plan to use with an Arduino Uno. My question is how much current can this transistor handle at it's base?


texts: How to make this circuit pass all conditions

texts:
I have this circuit (as part of a larger design):

simulate this circuit – Schematic created using CircuitLab

The resistors are with a tolerance of 1%.

On the input, V1, the circuit gets a pulse whose initial voltage is 28V to a certain voltage (shown later), with the Ton of the pulse being at a certain length (shown later).

The reference voltages are created using a micropower voltage reference IC and op-amps.

I need to make sure that when inputting these pulses, some will assert out2 to '0' and some will make it remain at '1'. (Please note that out1 is not really important here, I just included it in the schematic so you will know it is there).

Here are the voltages and pulse lengths that I am inputting to V1:

Out2 Should Remain at '1'      Out2 Should Assert to '0'
30V/80mSec                     30V/100mSec
40V/10mSec                     40V/20mSec
50V/5mSec                      50V/10mSec

The capacitor C1 is what concerns me. I don't know how to determine it's value. It is a SMT ceramic capacitor.

From what I understand, the capacitor has two jobs:

Filter spikes from the power supply (the P.S is a generator).
Provide timing (together with the resistors), so that certain pulses with certain lengths will assert Out2 to '0'.

The thing is, I have tried so many options for the capacitor and none seem to work for all conditions. I have tried both in simulation and in real life, and of course it doesn't always seem to match...

If I use too small capacitor (for example 1uF), then Vc will reach 3.62V too quickly, and Out2 will be '0' when it's supposed to be at '1'. If I use too big capacitor (for example 4.7uF), then Vc won't reach 3.62V, even at 30V/100mSec, meaning Out2 will not be '0' as intended, and so will remain at '1'. (I am 99% sure that I used LTSpice to simulate this circuit with a 4.7uF capacitor and it actually asserted Out2 to '0', but it did not happen with the actual device when I soldered a 4.7uF capacitor)

So here are my questions:

Lets assume I can use a capacitor and be done with it. How can I determine it's value? I have tried calculations and simulations and experimented with lots of capacitor values and none seem to work for all conditions.
Is there a solution that is smarter than just using a capacitor? Do note that the PCB already exists so I can't change my design too much, so using ICs is somewhat of a problem. I would however love to hear about these solutions, if they exist, both because I would see if it can somehow be implemented and because I would like to learn.

Thank you very much!

Edit:

\$V(t) = V(inf) - (V(inf)-V(0))e^(-t/Tau)\$

\$V(t) = 3.62V\$

\$V(inf) = 3.68V\$ (Because of voltage divider when input is at 30V)

\$V(0) = 3.43V\$ (Because of voltage divider when input is at 28V)

\$t = 92mSec\$ (fall time is 5mSec so I took a margin)

At the end of my calculations I got:

\$Tau = 64.46mSec\$

\$Tau = R1||R2*C = 11.14k*C = 64.46m\$

\$C = 5.786uF\$

But this result does not help me, as like I said, for 4.7uF, Everything passed except 30V/100mSec.


texts: What does exactly mean the power specified in a speaker datasheet?

texts:
I'm making my own guitar tube amp, based on a Fender 5e3 project. The nominal power of the amp is around 15W. Next step would be to choose a speaker, that I already did, the speaker is a 12 inches (8 Ohms) Eminence Legend.

The issue is: On the speaker datasheet says nominal power of 75W, what is exactly that power? Is how much power can be dissipated by the speaker, or is the some kind of equivalent sound power emited by the speaker?


texts: Voltage level when connectiong two power sources

texts:
I've experienced the following situation the other day.
When connected to this smart powers charger (never seen one of those), the battery voltage dropped.

Made me wonder about two questions.

1.

What kind of voltage should the Battery Charger had to have to lower the voltage? -0.6?

2.

When connecting two different power supplies with different voltage levels in parallel to one another is it predictable what the voltage levels will be? Where would I have to measure to get the exact values of voltages U1 or U2 in this scenario? The connection wire should not be considered ideal.


texts:
What is/are the thumb rules for determining an appropriate shape of an electromagnet? By appropriate I mean having a reasonable amount of attraction/repel strength towards metal pieces.

If I were to bend an existing electromagnet (made out of an iron core wound with appropriate wire) into, say, a heart shape, would it still function? Would different sections of it behave differently (distribution of poles across the heart shaped structure)?


texts: How do I build a cheap/efficient mains adapter for some LED lighting?

texts:
I've been considering building some LED lights to replace the mains-supplied lights in my house (as a more efficient alternative). For it to be worthwhile though I'd need to build an efficient UK mains converter to supply each cluster of lights.

What's the most efficient way to turn AC into ~5v to power ~10 luxeon lights?


texts: How can I reverse engineer a simple through-hole board? Trying to do it by eye gets confusing because it's easy to lose track of component orientation and location while flipping the board over. Maybe there's a computer assisted technique that would make things easier?


texts:
I'm just a hobbyist and actually from software side. Trying to build a simple water level indicator and found the following circuit using the IC ULN2003.

But due to my very less knowledge I'm not able to figure out the requirement of that since its straight forward without that IC

Here is the schematic I have got from a search

But its the same if we wire the following way, isnt it?

I'm not able to understand the purpose of that ULN2003 in this case, since in my schematic as well it does almost the same I though..

So what that IC really does in that circuit rather than just closing a circuit


texts: Cannot get a digital square wave on oscilloscope from the GPIO of the Raspberry Pi?

texts:
ENVIRONMENT:

Running "Raspbian" on Model_B Raspberry Pi (Revision 2) w/ ribbon expanding the GPIO out onto a Breadboard as shown in the following image.

SETUP

Here is a close up of the GPIO setup on the breadboard and the connection of my probe. My probe is connected to the Green wire which is connected to pin 7 (CE1). My ground is obviously connected to ground which is the yellow wire.

I'm using GPIO pin 7 (CE1) as an output which I have my probe connected to and my ground is connected to the ground pin. I've set probe on 10:1 setting.

My program reflects the example for the "C" "wiringPi library" program located here . You will need to scroll down as the example is located towards the end. I'm also attaching a image below of my program.

I'm unsure what the (if) statement is doing but as you can see i'm setting the pinMode to (7,OUTPUT) and using a (while) loop to toggle pin on and off as fast as possible. I'm hoping to achieve a digital square wave from this program to view on my oscilloscope. However, i'm getting a bad signal on the screen as you can see below.

THE PROBLEM I'M HAVING:

Can someone help me troubleshoot my setup so I can get a digital square wave to display. The link I attached above gives an article on how they set their test bench up. The even show the signal that was displayed on the oscilloscope. However, for some reason I cannot replicate their results. Below is an article for the spec sheet of the GPIO. Again my board is revision 2.

SPEC SHEET FOR THE GPIO:

http://elinux.org/RPi_Low-level_peripherals

PROBLEM HAS BEEN RESOLVED:

Thanks to K-Sid's comment below and the wonderful link I have fixed the issue. I'm posting the new image of the signal being analyzed. It's showing a frequency of 4.3MHz which is around what it should be.


texts: Selection of DC-DC converter for boosting 4.2V to 5.0V

texts:
I need to boost 4.2V (out of MPPT/ 18650 battery charge) to 5V (input for ESP8266.) To accomplish that I've bought this item, a 2.0 - 24V boost converter, which supports 2A.
But when trying to do so - though voltage is converted as needed and does not drop during boot - the MCU does not power up.
I tried to add 100 microfarad capacitor at input and output of the converter. No luck.

Is there a way to "fix" this converter to power an MCU?

If not, what type of converter would be suited for the job?


texts: Transformer with Single Turn Secondary in an Induction heater

texts:
I was thinking of a circuit which essentially has a series LC circuit connected in between an H bridge. There were certain things, I wasn't sure if I understand correctly, and would appreciate any input about it.

Neglecting the details of the L & C values. Now if I was to turn on M1 and M4 at the same time, while turning off M2 and M3 and the other way around in the other cycle.

I would expect an AC square wave, which when passes through the LC low pass filter, I would expect a Sine wave in the middle of L and C.

Here is the part I want to confirm I understand correctly:
Now if I was to run this at resonance, then the voltage in the middle will have the highest peak at that frequency.

If my Inductance was actually a work coil(that is used in an induction heater) and I was to play a steel rod in between or across it, then am I correct in assuming that this will behave like a step down transformer ?

So my work coil will be the primary with the high voltage, and the steel rod would be the single turn secondary, thus voltage steps down and CUrrent multiplies and causes eddy currents in the rod to heat it up.

Thanks for looking.


texts:
I'm using Arduino UNO for a pid line follower robot. The robot works great, but when it detects a T line, it deviates from the line. So I try to set the condition if all the sensors see black and then see white, deviate to left, that's what my intention. But the problem is with the if condition is never executed, it nevers see that all sensors are all black and then white. here is my code

void loop()
{
// convert analog signals into digital ones

    for (int i = 0 ; i < 5; i++)
      {

        if (sensors[i] > 900)
        {
          sensor[i] = 1;

        }
        else
        {
          sensor[i] = 0;
        }
      }

      for (int i = 0 ; i < 5; i++)
      {
        Serial.print(sensor[i]);
        Serial.print("\t");
      }
      Serial.println();

      if ((sensor[0] == 0) && (sensor[2] == 0) && (sensor[3] == 0) && (sensor[4] == 0))
      {
         if ((sensor[0] == 1)  && (sensor[2] == 1) && (sensor[3] == 1) && (sensor[4] == 1))
        {
          set_motors(0, 255);
          bLine = true;
          Serial.print("black");
        }
   }


texts:
In this circuit and explanation, it all makes sense except I'm having a hard time picturing Q2 not turning on until C1 has discharged first.

When C1 is discharging through Q1 why doesn't Q2 turn on as it's discharging since it's base is higher than 0.6v through R2?

Also is C1 discharging only by the + plate having a path to ground rather than both + and - plates of C1 being connected together?


texts: PSoC: Question on Productizing using a PSoC

texts:
BAM! Just like that I came across Cypress PSoCs. I'm from software background so started trying to understand more about them and the more I learn about PSoCs the more I'm getting attracted to it.

What I've understand so far is that - there is a lot of flexibility and designing a product using PSoCs, their IDE and so on is both very easy and effective.

But one thing I would like to understand is, let's say:

I've bought CY8CKIT-030 PSoC® 3 Development Kit and CY8CKIT-025: PSoC Precision Analog Temperature Sensor Expansion Board.
I interface the two, I write an application which will run on the PSoC 3 8051 micro controller, read the temperature from the sensor using a PSoC ADC and finally display it on the LCD.
I'm satisfied and I've proved that my concept works. I'm done with the eval kits. I've successfully designed a micro-controller, on the basis of my needs.
I would like to now build a product out of it, say I wish to make 100000 temperature measurement/display devices.

What should I do? What are the next steps? Do I need to place an order to Cypress: I need 100000 processors with the following requirements and here are the design files for my micro-controller? What's the price for 100000 such processors?

From their website/videos all I see is them talking about kits, capsense and the ease of designing. I would like to know more on what's after the kits and the end of design phase.

Kindly explain.


texts:
I'm trying to identify these tiny ICs. They're in a 0.8mm square 4 lead package. The pins seem to be something like:

GND
VBAT
CE
VOUT

VBAT comes from the battery and VOUT is a stable 3.0 volts. When CE is driven high, the output is enabled. I've tried searching for the designations but no luck. Some sort of LDO with an enable pin?


texts: Should I put a windup guard on each term of the PID, or just the I, or maybe the whole output?


texts: A combination of 1N4007 diodes in place of M7

texts: Can I use a combination of 1N4007 diodes in place of M7? If yes, what's the arrangement? M7 is a surface mount general rectifier with a reverse voltage of 50  to 1000 and a forward current of 1 amp.


texts: Obtaining 12 V from a 20-250 V DC source

texts:
I need to get 12 V DC from a high voltage source. The high voltage comes from a wind turbine. The voltage level changes randomly according to the wind speed. Its voltage can go up to 250 V DC. This 12 V DC will be used to run the control circuits at the start-up only; the main power will be supplied from an integrated SMPS unit as soon as the overall system starts working.

I designed the following circuit for this purpose:

I thought that directly dropping 250 V to 12 V would be risky and make the system unstable, so I decided to drop it down to an intermediate voltage level (i.e.; 60 V) first.

Is there a better (and as simple as this) way of doing this?


texts:
Wikipedia says that power supply rejection ratio (PSRR) is the ratio of output noise referred to the input vs noise at the power supply:

  The PSRR is defined as the ratio of the change in supply voltage to the equivalent (differential) input voltage it produces in the op-amp

Good Quality Design of Analog Cmos Integrated Circuits by Razavi seems to say the same thing:

  The power supply rejection ratio (PSRR) is defined as the gain from the input to the output divided by the gain from the supply to the output.

So the overall rejection from power supply to output vary with the closed-loop gain of the op-amp?

So an op-amp with +40 dB gain and 100 dB PSRR, with 0 dBV noise at the power supply would have -60 dBV noise at the output?  The Wikipedia example seems to say that it would be -120 dBV instead, which I don't understand.

Is there also an output component of PSRR?  Like if you lower the gain of the amp, the input referred noise would decrease, right?  But is there then a constant component coupled from the power supply through the output stages that starts to dominate?

Analog Devices MT-043, on the other hand, says:

  PSRR or PSR can be referred either to the output (RTO) or the input (RTI). The RTI value can be obtained by dividing the RTO value by the amplifier gain. In the case of the traditional op amp, this would be the noise gain. The data sheet should be read carefully, because PSR can be expressed either as an RTO or RTI value.

Is this true?  How do you find out from the datasheet which method is used?


texts: How do the three wires for each HDMI Channel relate to a single signal?

texts: I'm working on an HDMI ASIC and the HDMI spec is very clear on everything except for the way that the +, -, and shield wires are used to transmit a given signal.  The TDMS channels and the clock are all split into +, -, and shield.  What do I need to do to get a correct single digital signal from those bundles of wires?


texts:
I have seen CPUs conforming to Harvard architecture with dedicated ports for program memory and data memory. I have also seen that instruction and data caches (read-through caches) are connected to these ports.

Is it possible for a CPU to have only one port [like a Von-Neumann machine] and two dedicated caches [Instr-L1 and Data-L1] connected to the single port? If the caches were of look-aside type, I am thinking this could be possible. If there was a LLC, how would this then be connected to the Instr-L1 and Data-L1?


texts: A few questions about High Current on PCB

texts:
Original schematic:

My attempt at drawing the PCB:

The routes are drawn on both layers and the thickness of the power route is 600 mil(300 on top and 300 on bottom). It is necessary to support ~15A. The question is, how do I make the current pass from the top to the bottom if the component pads are small or very small? Can I put vias near the pad, and how? Is it necessary to add vias next to each component? :)
Is parasitic capacity formed between the same routes if they are on the top and bottom, or is ok? Is the voltage the same on the Top and Bottom on the same route? What rules should I take into account in this case?


texts: How would I solve this Block Model diagram of a DC motor?

texts:
Sorry if this website isn't the place for this question but I am really lost on how to solve this and I'm being tested over it tomorrow.

I somehow keep on getting the answer 475 instead of the correct one, 425. How would I go about solving this? I think the main place I'm getting lost is dealing with the 1/s block. What do I do with that? One of my friends said that I should just consider s as converging to 0 and treat it as if it was indeed zero.


texts: Kicad Eeschema window does not respond when opened in windows 10 (Not working)

texts: I have just started with Kicad. Never used it before. I downloaded and installed kicad, opened it, created a new project. Everything is fine until that point. But when I open Eeschema window for schematic, the mouse cursor keeps on loading and the eeschema window never opens (not responding). I have tried the 32-bit stable version of the software as well but it did not solve my problem. I posted this problem on kicad forum as well but no one responded. I would really appreciate it if someone points me in the right direction. Thanks.


texts:
I've designed an H-bridge for a 15A DC motor. Power is applied by plugging in a very high-capacity Lithium battery. Unfortunately, when I plug in the battery, one of the transistors goes pop instantly and shorts across itself. This ultimately shorts the battery to itself which makes me unhappy. V_BATT is a 14.8V Lithium battery. The transistors are N-channel MOSFETS. U1 is an H-bridge driver IC.

I've come up with two possible root causes. I'd like some help figuring out which one is more likely.

1) A nasty inductive spike is being generated during the initial current surge due to the natural inductance of the battery cables and copper traces. The spike exceeds the Vds of the FETs, causing them to fail. The Vds of the FETs I'm using is 40V, so I find it likely the inductive spike is exceeding that. I plan to use a snubber and voltage clamp circuit to reduce the spike.

Or,

2) The sudden rise of voltage on the drain of the FETs causes the gate voltage to also rise due to the intrinsic capacitance between the drain and the gate. This effectively turns on all of the FETs and causes shoot-through and burns them out.

I'm leaning towards #1 being the main culprit, but I can't justify why #2 isn't also causing a problem. Especially since I have 50\$\Omega\$ resistors on each gate pin. Even if the gate drive pins of U1 are trying to hold the pins low, the resistors would isolate the gate pins for a short time.

Is it likely the problem is a combination of both items? Or is #2 not really an issue? If #2 is actually happening, what can be done to suppress it?


texts: attiny85 drops voltage level on an output pin... why?

texts:
I am in the process of building a wireless transmitter that is driven by an attiny85. I have programmed the MCU to encode the data using Manchester encoding and I have used an oscilloscope to show me the wave form that results on the output pin of the MCU when I send 2 bytes of data.

This is literally my first measurement I ever took with an oscilloscope, so I could really use some help interpreting the results. The encoding looks correct, except that the whole wave form is linearly dropping down on the screen! The amplitude of the pulses stays the same, but the ground level drops almost a volt over the ~70ms.

The MCU is powered by AA batteries and there is nothing hooked up to it except the 10X oscilloscope probe on the output pin.

What does this mean? How can the ground level drop? Is this really happening, or is something going on with the way I am taking the measurement?


texts: My own millis() function not accurate in the arduino

texts:
I wrote a program myself to implement the millis() and delay() function without the arduino library. I included a counting variable which counts every second and send its value every second via serial port. What I found is its value runs away from the true value by almost 2 seconds every 3 minutes. Is there anything wrong with my code? Or is that Serial.print() the culprit which may lag that routine? How much time does that Serial.print() takes to execute?

Here is the code:

Edit: I edited the code like this, but the count on the arduino still lag around 4seconds after 4 minutes. It lags 13 seconds after 10 minutes ie, it counts only 587 seconds after actual 600 seconds.

Edit 2: Here is my updated code. Still there is lag in the timing. I get a lag of around 6 seconds in 5 minutes.

#include "Arduino.h"
#include <avr/io.h>
#include <avr/interrupt.h>

void toggle_led(void);

unsigned long volatile millis_count = 0;
volatile char state = 1;
unsigned long volatile current_count = 0;
unsigned int volatile count = 0;

ISR(TIMER0_COMPA_vect) {        //Timer interrupt ISR

    millis_count++;
    if (millis_count - current_count == 1000) {
        current_count = millis_count;
        toggle_led();
        Serial.println(count++);
    }

}

int main(void) {

    init();

    TCCR0B = 0b11;  //Timer settings for interrupt at every millisecond
    OCR0A = 249;
    TIMSK0 |= 0b10;

    sei();
    Serial.begin(9600);
    DDRB |= 1<<5;

    for (;;) {

    }
}

void toggle_led(void) {

    PORTB ^= (1<<5);
}


texts: ATMega/Tiny barely working on breadboard without ISP

texts:
currently I want to get an ATMega328P and an ATTiny85 to work on a breadboard, which should talk to each other and an LCD via TWI.

Anyway, I came across some issues I don't seem to be able to fix at all.
Without an ISP attached the ATTiny doesn't do a thing(programmed it to flash a light for now), connecting the ISP makes it work just fine. Similiar thing with the ATMega, when the ISP is disconnected I can't get correct data over USART. Either it stops transmitting entirely or some garbage is transmitted.

When I started I had a really barebones breadboard wired up, but as suggested in other forums and on here, I added a couple components in the hope to fix it finally.

Here's what it looks like right now:

Inititally I had a 4.7k as a pull-up on the reset pins, but it was suggested that 10k was better(with AVR circuit design considerations as source). Als the caps for the VCC/GND were added later on to reduce the affects of noise in the power delivery. The caps on the crystal were calculated with the spec sheet of it and a formula found in the ATMega spec sheet.

But nothing really helped. Even when I remove the ATTiny and have the ATMega on it's own, it won't really work.

Also it seems that the voltage on the reset pin is just 20mV. What could be the reason for that?

As a power supply I'm using a board called "ywRobot Power Board" plugged to a adjustable power plug which outputs 12V and can deliver 300mA max.
The crystal is a 20MHz HC-49.

Fuse Bits on the ATMega328P: 0xFF/0xD9/0xEF(Ext/High/Low)(factory default, except clock-source and CKDIV8)

Fuse Bits on the ATTiny85P: 0xFF/0xDF/0x62(Ext/High/Low)(factory default)


texts: How do you know which way round a 6-pin SOT23 goes?

texts: Well, I have a 6-pin SOT23 and it is absolutely tiny. When I say tiny I mean it. Anyway, it is unclear which way it goes around as it has no indicator, so I don't know how I can install them on my boards. It has some writing on it but that is the only clue on how they are aligned. For those who need to know it is an LT1933 or LM2734Y (depending on the version.) I'm actually starting to wonder how feasible it will be to assemble these boards of mine with such tiny components, even using a reflow method.


texts:
I was trying to do a project on LT spice for the frequency response for Sallen-Key low Pass filter.
But when I tried the Following circuit, I am getting a roll off 20db / decade instead of 40db/decade. Even I am getting a lower cut off frequency than expected. I had done this with 1 nF capacitor and circuit was behaving as expected.
Please help, I want an explanation for this deviation.


texts: ETSI[Europe] Regulations for 2.4Ghz ISM Bandwidth Limit and RF Power

texts:
I am trying to interface my STM32 with NRF24[2.4 Ghz ] or TI
CC2500[2.4 Ghz] models. I am finding issue regarding maximum
allowable Bandwidth and RF power set by ETSI[Europe] EN 300 328 and EN 300 440(Short Range Devices[SRD])
regularity body. Kindly if someone have knowledge regarding this
please share it. I am unable to find relevant info I have even
consulted ETSI Official Documents but of no avail.
Can I even use 12Mbps speed if I use cc2538 SOC.
What is better to use a RF Transceiver (TI CC2500) or SOC RF Module
(TI CC2545 or TI CC2538).


texts: How to transfer data between arduino and mysql data base?

texts:
I am trying to create a database that communicates with the arduino to execute functions (such as activating leds) and read sensors to store the values in the database.
I am confused on how to make this communication between mysql and arduino.
some help?


texts: Is there a circuit that outputs high indefinitely once one high is received by the circuit?

texts:
Apologies if the question is worded oddly/weirdly, but specifically I have a comparator with an unstable output which I know could be fixed with hysteresis, but I would rather just have some circuit output high indefinitely once the correct conditions are met and the comparator outputs high once. I know I could use a microcontroller and program it to keep track using memory, but I was just wondering if there was something simpler I could use. I'm still an electonics newbie, so any help/pointers/or even just the name of such a circuit would be much appreciated!

If it helps, I could go more in depth on what my circuit is/draw up a schematic, but I didn't want to drag this on for too long. Much thanks for reading this!


texts:
If I had a 12V battery and wanted to use an LED that used 2V and 20mA, then I need a resistor that will drop 10V and provide enough resistance to produce a current of 20mA.
Therefore I would use R=V/I = R = 10/0.020 = 500 Ohms.

Therefore I would need a 500 Ohm resistor. I believe this is correct so far?

My confusion comes from when we then look at the circuit as a whole. The circuit has a current of 0.020A and a resistance of 500 Ohms, which when looking at V=IR equals 10V (the resistor), not the 12V that it should be there for the whole circuit?

Where am I going wrong? How do I make V = IR work regarding the whole circuit so that V = 12?

I'm pretty new to this sort of thing and no doubt I've probably made a daft mistake but if someone could just help clear up my confusion it would be appreciated.

Thanks.


texts: Scattering matrix of matched a device with matched ports

texts:
The scattering matrix of a device with matched ports has zeros at the position of the corresponding diagonal element(I am referring to equation 7.2 or 7.4 in Microwave Engineering by David M Pozar, 2nd Edition). I've read and understood this from various sources on and off the internet.

However, what eludes me is the following: The S-matrix is meant to relate the reflected voltage at a port to the voltage incident at every port for a given microwave network. The S-matrix is itself independent of the voltage that appears across its ports or the kind of load that is attached to a port and that's why it's helpful. Hence, if we say that the port which is terminated by a matched load has a corresponding zero entry in the matrix, doesn't it violate the fact that the S-matrix is a characterization of the system's reflected-incident voltages independent of the conditions a network is made to operate at?


texts: Need to find out one "a-Si TFTLCD" driver

texts:
I need to work with one 5" TFT LCD working with STM32 MCU, So I find out one 5 inch TFT LCD wich in seller website don't have written anything about isn't the driver.

The LCD specification in web site shown below:

TFT LCD 5.0 INCH 480x272 RGB with touch

Panel Type: a-Si TFT-LCD, LCD screen
Panel Size: 5.0 inches
Resolution: 480 (RGB) x272
Display Mode: TN, often white display, transmissive
Finish: matte
Brightness: 300cd/m2 (Typ.)
Contrast Ratio: 500:1 (transmission)
Display Color: 16.7M (8-bit)
Response time: 10/15 (Typ.) (Tr / Td) (ms)
Viewing Angle: 70/70/50/70 (Typ.) (CR ≥ 10) (left / right / up / down)
Scanning frequency: 60Hz
Lamp Type: 6S2PWLED
Signal Interface: Parallel RGB (1 ch, 8-bit)
Panel voltage: 3.3V (Typ.) (VCC)
Operating Temperature: -10 ℃ ~ 60 ℃
Storage Temperature: -20 ℃ ~ 70 ℃
Aspect Ratio: 16:9 (width: height)
Pixel pitch: 0.231x0.231mm
Weight: 83g (Typ.)
Display area: 110.88x62.832mm (horizontal and vertical)
Viewable area: 113.90x65.85mm (horizontal and vertical)
Dimensions: 120.775.8mm (horizontal and vertical

So I Need to know does this TFT LCD need an external IC Driver and have not any Driver IC? and based on which IC I must write my code via KEIL For STM32 MCU.

Finally, I would be so happy, if you know any TFT LCD 5.0 INCH proper for working with ARM's MCU And SHare your information with me.

Thanks a lot.


texts: How small can a low-power Qi inductive receiver be?

texts: I'm looking to do a quick turn-key solution utilizing a Qi inductive power receiver to charge a few supercaps to power a tiny microprocessor (8pin msp430 or similar) for a few minutes; however, I cannot seem to find any "small" pre-made Qi inductive power receivers.  My target coil size is on the order of the dimensions of a nickel.   Is there such a thing?  Will such a small coil work with a Qi charger?


texts: Apple devices - "Vibrating feel" when charging

texts:
I am absolutely not experienced when it comes to electrical stuff at all which is why I hope you can help me out on this one because I am a bit worried right now.

I own a bunch of Apple devices and after making the switch to a new 2017 MacBook Pro I noticed a weird, vibrating feel when striking over the aluminum. I instantly thought that it has to be related to the device being charged right now and indeed: Depending on whether it's charging or not and depending on the shoes I am wearing I can feel this weird, vibrating, tingly feeling.

So, to underline the fact that I have absolutely no clue about any of that I hope that anyone in here feels like giving me a hand and explain to me what I am experiencing here. I am indeed worried because apparently that applies to all of my current Apple devices - The same happens when I use my non original charger (with 24W) on my iPad.


texts: Using a Counter to Determine next MSB position in polynomial division

texts:
I am working on implementing a polynomial divider the operation is as follows:
Check MSB of Numerator:
if 1 XOR with Denom then shift Denom right
if 0 Num is the same and Denom also shift right

When doing the following shift for the Denom the new MSB of the numerator to compare with is the old MSB-1
Therefore I have implemented a Down counter that starts with M downto 0
at each step the new MSB is the value read from the counter

on VHDL Implementation I got an error on the following

if(numerator(ctr_reg)='1')

the obtained error is:
type identifier with "ctr_reg" does not agree with its usage as "natural type"

How can I solve this? should be done with a variable inside my process?
And what is the hardware translation of a variable used in such case

Thank you

Included Libraries

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
use ieee.numeric_std.all;
use work.classic_multiplier_parameters.all;

Error From updated statement:

if(numerator(to_integer(unsigned(ctr_reg)))='1') then


texts:
I am using the well-known I²C level shifter from that appnote from Philips.

The 3V side is supplied by an LP2950-3.0 regulator and is loaded only moderate (a few quite lazy 74's).

The problem I'm obserivng is that the 3V side is being pulled to 5V.

I loaded the 3V side with a resistor and calculated that the level shifter presents a resistance of only 2.7 kOhms. I consider this rather low and I wonder:

Is that normal behaviour or did I make some mistake?
Isn't this harmful for the devices on the 3V side? There are several ICs that according to the datasheet are explicitly not 5V tolerant, not to forget the regulator.


texts:
I am trying to build a pH meter using the below circuit.

I am trying to understand the function of Op Amp U1. As I understand it, the LM4140A-1.0 is a voltage reference outputting 1.024V, which is split into 0.512V by the voltage divider. This is fed into the Op Amp and through to the pH electrode where it offsets the voltage it generates (from -400mV to +400mV).

My question is, why do I need that unity-gain (buffer) op amp, why can I not just connect the 0.512V from the voltage divider into the pH electrode.

For completeness, I plan to take the high impedance output from the pH Electrode and pass it into a dedicated ADC, not the Op Amp U2 as described below, if this has any effect on the answer.

http://www.national.com/an/AN/AN-1852.pdf


texts:
When creating electronic devices there are times that we want to make it difficult for an unauthorized person to open the device.

I was wondering where there might be a list of methods or common techniques used to accomplish this.

What comes to mind are the following:

Hiding screws behind stickers
Special screws (non-standard heads)
Cover contains contact that closes circuit so when disconnected/open circuit does not power on

What are some other (or more sophisticated) methods available?


texts: AC-AC Converter 3 phase, Line to line voltage calculation

texts:
I’m working one some assignment like this circuit (AC-AC converter 3 phase, 89 degree firing period). I've done this on PSIM software with 110 Volts 3 phase voltage source.

I've been told to analyze the line to line voltage. The waveform and the value looks like this

My question is, can somebody tell me what is the equation to solve the line to line voltage value?
I've been googling around and found nothing related to this particular circuit.


texts: Is the carbon-zinc battery that I am characterising overloaded? Using HPPC

texts:
I am trying to characterise a 9 V battery using a pulsed load measurement. The battery is a 9 V zinc-carbon eveready super heavy duty. The load is a controllable constant current source. When I discharge it for extended periods I observe curious behaviour.

Equipment

The circuit is as follows:

simulate this circuit – Schematic created using CircuitLab

Omitted for clarity are a 100k resistor pulling down the non-inverting input to the op-amp for when there is no control voltage, and some decoupling.

The MCP6241 is a rail to rail op-amp so when the control voltage is 0 V I get sufficiently low current draw through the load resistance. It is powered by a single 5 V rail. The control voltage defines the current through the load as V=IR. I am pulsing a 100 mA current so the voltage gets to 500 mV. This is tested and functioning pretty well (it's really about 496 mV).

The FET is logic level and seems to work fine being turned on by the op-amp. It does heat up but there is a small heatsink, and by my calculations it shouldn't reach the limit of the operating temperature range.

The battery voltage is measured using a buffered DAC with high input impedance, while the control voltage is generated by a buffered ADC. Both are a part of an NI myDAQ, sampling at 2 kHz then downsampled to 500 Hz.

Results

The test is a high-performance pulse characterisation (HPPC): the battery is pulsed with a load current and then allowed to 'recharge' back up to its open circuit voltage when the load is removed. The measurement was designed for rechargeable batteries (lead-acid, li-ion) and is detailed here. NB it is not designed for the zinc-carbon battery I am using. Here are 6 sequential pulses overlayed to demonstrate the difference in behaviour:

The plot is zoomed to the relevant time window that shows the problem. The lower the curve, the later in the measurement they are, i.e. the top line is the first discharge. I expect the pseudo-linear discharge characteristic from the later curves, but at the start the discharge seems to drop the voltage very low and unstable.

Question

Is this expected behaviour of a battery when it is pushed too hard? Is this a temperature issue or something to do with the battery chemistry?

Or is it more likely to do with the measurement equipment? I don't think it is because the equipment functions fine for the later curves.

Has anyone seen similar behaviour?


texts: how do I supply 3.3V from my 5V arduino pro mini?

texts:
I have a 5V Arduino Pro Mini that I want to connect with this 3.3V nRF24L01+ module. (On the other end I have the same nRF24L01+ module connected to an Arduino Uno which has a 3.3V pin that I know is safe to use.)

The nRF24L01+ modules I have are these.

The Arduino board this question relates to is this one.


texts:
I'm having trouble with TC4421A MOSFET drivers in a new PWM DC Heater design blowing. The 12V power supply used during testing is capable of 25A. While doing my initial testing, I started off with higher value load resistors with a 5 kHz PWM duty cycle of 25%. I successfully tested the design at up to 4A. That's when the TC4421A driver failed and literally caught fire. The MOSFET was not damaged. The PWM is generated by a PIC with a Vdd of 5V. My test setup had approx 2 feet of wire connecting the dc supply. Not the most ideal setup, but I didn't expect the driver to fail. The P-Chan MOSFET is rated at 80A and the driver is rated at 9A peak. Also, the 100 ohm gate resistor was not damaged nor was the PIC. I'm hesitating with any further testing until I at least make some attempt to keep the driver from blowing up. My ultimate goal is to be able to deliver up to 100W into a resistive load by varying the PWM duty cycle.

Thanks in advance for any advice.


texts: When do the positive sequence negative sequence, and zero sequence apprea?

texts:
I have analyzed three phases current in different cases, but I am still confused about some cases.

Positive and Negative sequences are appeared but not the zero.
Zero sequences is appeared, while Positive and Negative sequences not appeared.

I know if the system imbalance, the three sequences will appear, otherwise Positive or Negative sequences will appear (depend on the source sequences)

What does 1 and 2 tell?


texts: Determine the voltage at which the comparator output switches from 0V to 10V

texts:
I have the following problem:

Consider the circuit below

Assume that Vo = 0 V, and that Vin slowly increases. At what value of Vin does Vo switch from 0V to 10V?

I'm not sure how to tackle this. I know that:
\$V_o=10V\$ if \$V_{id}>0\$
\$V_o=0V\$ if \$V_{id}<0\$
But I don't know how you would determine the exact point that this happens? Can node equations help me? Or maybe mesh currents?


texts:
I have a question about reading and writing operations.
Say if i wanted to read or write the column WL0, i would enable the WL0 lines.
For either a read of a write i would drive the bit lines to either Vdd or Vdd/2
What about when i don't want an operation to be performed in any row of WL0?
Consider a 1 stored across the capacitor in WL0 and row 2, if WL0 is enabled the capacitor will discharge through the bit line on row 2. If the bit line is 0 initially it increases in voltage, does the capacitor then decrease in voltage? If so, is it fully discharged?


texts: Why this H-bridge with only N-channel FETs didn't work?

texts:
Based on this answer here in StackExchange and the Motorola article it cites, I've designed a dual h-bridge motor driver with push-pull transistors to switch the FETs faster, layed out a PCB in KiCad and built it.

The restrictions were to use only N-Channel FETs found in an old computer motherboard, and I had no gate drivers (actually I've bought a couple IR2110s, but they will take a long time to arrive).

When I tested this first version with a toy RC helicopter motor, it ran for a couple times, but eventually half of each h-bridge (there were 2 of them) got shorted (lots of smoke and all). Everything ran on 2 li-ion cells (7.4V) for VCC and a third small phone cell (3.7V) in series for a 11.1V total in Vdrive.

I used the multimeter to check and looks like IMZ1A couldn't pull the high side FETs down for some reason. Initially they could, but then they stopped working. The 2N7002s were all fine. Tried replacing both the shorted power FETs and IMZ1As for new ones, but the same problem happened again.

Tired of burning stuff, but still trying to prove the point a simple N-channel only bridge could be designed, I made this new circuit:

This one actually worked and is working till now, despite being very simple. The question is: why the first circuit didn't work? Is there anything wrong with the design?

EDIT: Acquired some waveforms for the last circuit:
This one under no load condition

And this with the motor. Measured armature resistance was about 2.2R and inductance about 240uH.


texts:
Can anyone please explain how to calculate Vout for both cases below?

1 case, simulation shows Vout is -1V
2 case, simulation shows Vout is +2V!

I understand how things work when there is a virtual ground, but when there is a reference voltage applied and resistor on the feedback, I can not get the logic where -1V and +2V came from.


texts: Programming for the Arduino without the Arduino IDE.. but with the provided libraries?

texts:
I recently started a new project using my Arduino that's been collecting dust for a while. Along with the physical board collecting dust, so has my copy of avr-gcc and the Arduino libraries. I can manage updating avr-gcc, but I can't remember how I compiled the Arduino libraries. With the Arduino source, there is listed source files and such, but no makefile (that I can see) for actually building the library. I don't care about building the IDE, I just want the library in binary format and the header files that I'll need. Is there any documentation or such for doing this?

I don't want to use the Arduino IDE, I prefer using my own text editor and a makefile.


texts: Why is frequency of a sine signal is equal to its "rate of change of phase"?

texts:
I want to learn more about PLL but I'm stuck with the concept of "rate of change of phase" which is said that is equal to frequency. At the moment I'm very ignorant at the topic so I need to understand this mathematical foundation before I can proceed.

I couldn't decide whether this is a math question or can also belong here since its about analog signal. Is there an easy way to relate the phase to frequency? How is frequency equal to the rate of change of phase and isn't the phase of a sine fixed always given a sinusoid? So is this about signals where their phases changing by time? I could find any easy derivation on the topic.


texts: Do I have to do anything special if I want to connect to a chip with SWD and SWDIO and nRESET are on the same pin?

texts: I want to wire a MDBT40-256RV3 to a SWD programmer and on the programmer nRESET and SWDIO are on separate pins but on this chip they share the same pin, so how should I wire that?


texts: Communication between PLC and Arduino using IO-Link

texts: I have a small device based on an Arduino and I want to send some data to a PLC that has no RS232 port but can have an optional IO-Link master card. I looked around but found no info about Arduino and IO-Link, are there any projects using Arduino as a IO-Link slave device?


texts: Must the characteristic impedance of a transmission line be non-real for it to be lossy?

texts:
In Does conductance in the transmission line model represent a physical quantity? it came up that a non-real characteristic impedance just means the line has some loss. With real transmission lines having a little (but perhaps negligible) loss, we could expect all real transmission lines to have a characteristic impedance with at least a small imaginary component.

But is that really true? Let's say \$Z = Y = 1+1j\$. The characteristic impedance of this line is real:

$$ \sqrt{  1+1j \over 1+1j } = 1 $$

And the attenuation constant is 1 [corrected by edit]:

$$ \operatorname{Re}\sqrt{(1+1j)(1+1j)} = 1 $$

Which to my understanding, means this line is lossless. But how can this be when it has both a non-zero conductance and resistance?


texts:
I am building a robot using two 12v windshield wiper motors. I wish to buy a good quality LiPo battery on the following weeks, but until I do, I am thinking of using an old Li-ion 11.1v 4100mAh laptop battery.

I think I can't safely connect the motors straight to the battery, because they can draw up to 30A and that kind of current draw would most likely make that battery burst into flames.

Is there a way I could limit the current draw from the battery? I'd love to be able to feed constant 5A to the motors, for example (I know torque on the motors would be greatly reduced).


texts:
I've been trying to simulate a solar cell with LTSpice to generate an I-V curve. The model I've been using is the simplified equivalent circuit model with a current source in parallel with a diode. See image from NI:

The problem is that I can't find what kind of values the components should have.

I'm using an IKEA PV module from the Sunnan lamp and I want to have a simulation of this to show the curve compared to measured. There is unfortunately no information on the module, but I have measured 1.64V open circuit indoor and about 260µA short circuit. Is there a way to base the simulation on that information?


texts: Why pick 262144 Hz oscillator frequency?

texts:
Some Bulova watches (for example the Precisionist collection) use 262144 Hz crystal oscillators instead of the usual 32768 Hz. What are the true advantages of this higher frequency, if they even exist?

The usual quartz clock frequency is 32768 Hz because that's the lowest power of two above 20 kHz. This means the usual frequency is above human hearing range, but still allows ticking at one second intervals by simply dividing with 2^15.

Bulova claims their ~262 kHz watches are an order of magnitude more precise (~10 seconds per year vs the ~15 seconds per month of standard quartz watches). Do higher frequencies really help with precision or is it just marketing?

Their ~262 kHz watches also tick eight times per second. Many people enjoy this smoother motion, and it feels a bit more like a mechanical watch. But couldn't they achieve exactly the same effect by just dividing the usual ~32 kHz by 2^12? It seems like they chose to maintain the 2^15 divisor, for some reason.


texts:
I am trying to drive the output current Iout but I am not getting what it is shown on the graph.
Can you have a look and let me know what I got wrong please? Thanks

here is my attempt


texts:
I am building a home beer brewing rig that has several electrically actuated components controlled by an Arduino.

The typical scheme is Arduino -> Shift Register -> Relay -> Component.

One of the components is an electrical BBQ igniter. The problem is that when I turn it on, the shift registers go all wonky and randomly turn their outputs on and off with every spark.

I realize that the main problem is that the igniter is being energized by the same power supply as the rest of the system and that it creates a power surge when it generates a spark. But, how do I neutralize that problem?

One idea I had was to put a capacitor across the igniter input. That didn't help. My analog circuit knowledge is not so awesome.

Anybody have any ideas? Much appreciated.

P.S. The shift registers are 74HC595.


texts: Are conventional fridge thermostats active or passive?

texts:
I am talking about specifically this thermostat used in cooling systems

My query to engineers & technicians is that: Can we check the working of above thermostat with only continuity tester and without connecting it to Main Power supply?

In other words, can this thermostat toggle from On to Off state without needing any external power?

When I did experiment on my side, I found that it remains in On state (continuity exists between terminals of internal relay) whether I put it in hot or cold environment. I guess, that without actually installing it in operational-condition we can’t check it with a continuity tester.


texts: Are these 2 equations some of general formulas of infinitesimal length?

texts:
Given below. \$x\$ is a variable.

\$r:=\text{resistance between the nodes A and B}\$
\$l:=\text{length of the resistor }r\$
\$\rho:=\text{resistance per unit length of }r\$
\$\frac{1}{\rho'}:=\text{leakage conductance per unit length of }r\$
\$V:=\text{potential at point }P \$
\$I:=\text{current which flows the point }P \$
\$dV:=\text{change of the voltage in }dx\$
\$dI:=\text{change of the current in }dx\$
$$
I=-\frac{1}{\rho}\frac{dV}{dx}\label{1}
$$
$$
dI=-\frac{V}{\rho'}dx\label{2}
$$
Currently I can't get the above 2 equations. How do I interpret it? Are these some of general formulas? This is the first time for me to handle infinitesimal changes in voltage, current.


texts:
I am a novice in digital design and are learning things using "Advanced Digital Design with the Verilog HDL" along with a Spartan-6 LX9 board by Xilinx. So far I have managed to blink few leds on the board by starting with an example from Xilinx's web site. The code can be found here. I couldn't fully figure out DCM part of the example, though. As I understand, this is some vendor-specific module that is used to shift clock phase etc. Basically, a module that adjusts the raw clock input. I couldn't find a documentation for that module for my LX9 board, and the closest one I found is for Spartan-3A (here). So I have few questions:

Is there any documentation for that is generic or covers Spartan-6 LX9 board?
Is using this module is absolutely necessary in this example? Is that possible to do the same thing easily w/o using that module?
How people usually go about vendor specific things like clock? For example, if one wants to target both Altera FPGAs and Xilinx ones. What is the process to achieve that? Is it similar to ordinary C pre-processor typedefs etc?

Also, why is it now allowed to move assign LED[3:0] = led_count[26:23];
 inside the always @ block? Is it because LED is a not a register variable? And how often that "code line" is getting executed then? In the book I am reading, everything usually goes into the always @ scope (but they don't work with specific output ports though).

Thank you very much for your help.


texts: In the circuit diagram below do I connect to two TUNE1 points together? Or am I misinterpreting what this means?


texts: How to suppress terrible noise from MAX7219?

texts:
On the same power supply I have connected MAX7219, which is producing terrible noise to amplifier so I can hear refreshing frequencies of MAX7219. If I hook up amplifier to battery power supply the noise is gone. I've also tried to connect 220uF electrolytic capacitor to power supply input of this board, which decreased the noise but not removed completely. Shutting down MAX7219 for a moment, eliminates the noise. Still I can hear it even from far distance. Amplifier board is on small PCB. MAX7219 is on breadboard connected to Arduino. All powered from Arduino.

I understand breadboard wiring may produce some noises, but this one is too loud. Unfortunately I don't have the scope to tell the noise spectrum, but MAX7219 update frequency from datasheet is 800Hz.

This video is to show the sadness of situation.
[watch video]

[Enlarge]


texts:
I'm developing a project that has a bluetooth module transmit to an android phone. The project is extremely power limited (it's energy harvesting) and I'm wondering how much power am I looking at to transmit Bluetooth data?

The bluetooth module will be getting sensor data and transmitting that data to a phone about 10 feet away, ideally whenever the user calls for it, but can limit it to maybe every 30 minutes minimum wait.


texts:
I am currently working on a project where I am required to design a Class A Audio Amplifier using BJTs.

The requirement of the amplifier is as follows:
 - Acquire a variable gain of at least 10 (Av >=10)
 - Be powered using a 9V DC Power Supply
 - Amplify a signal of max 0.1Vpk, 20Hz-5kHz without any distortion or clipping.
 - Will work after attaching a low impedance speaker (8 - 180 Ohm)

I designed a primary circuit (attached in the picture) but I am having several problems.

I designed a Common Emitter stage where I was able to get a gain of almost 20 (that's what the oscilloscope showed), but I can't seem to figure out how to connect it with the Common Collector Stage. The output signal seems to not to be equal in the first half cycle and the second half cycle. Moreover, there is phase shift (not equal to 180) in the lower frequencies.

I wonder if anyone can help me with this circuit, and tell me what is the correct procedure for designing such circuits in the future.


texts: Driving Mosfet, why is it burned? How should the circuit be modified?

texts: I using MIC5018 to drive Mosfet (driving 48V，3A DC motor). Each power supply is powered independently. I am using a 48V, 3A DC motor. Before power-on, if it is connected to the computer (5V) and the signal is determined, it works normally. Once it is not connected to the computer before power-on, it may be burn the Mosfet.How should it be modified?


texts: Portable Headphone Amp Power Supply 18V MCP73871 TPS61178 TPS7A470

texts:
Disclaimer: I'm fairly new to diyaudio, amplifiers, power supplies, schematics, PCB design and everything that this forum touches on (read: noob), so I urge you to be patient with me - I am eager to learn though.
Anyway, on to the point: Recently I came across @xrk971 thread Hakuin SE Class A HP Amp which got me interested into building my own amp (PCB design and everything).
But, since X hasn't opened source his power supply schematic I decided to tackle that on my own (without some extras he implemented). Basically what I tried to do is: Battery Charger --> Boost Converter --> LDO.
Spent last few days reading through data sheets and reference designs and this is what I came up with. I would greatly appreciate if you could fact check the schematic and suggest things I should do (things that I probably missed).
I plan to use Samsung's EB-BJ710CBE battery (if possible).
Data Sheets:
MCP73871, TPS61178, TPS7A470


texts:
Im trying to learn more about the depths of computer design, I;m talking about CPU design. Down to the very very low level of Computer Organization.

I took a few EE (I did a CS degree so...) classes in college, but it was mostly Introduction and Logic gates (which I do understand). However it never went much further than that.
Im not looking to build a Computer from scratch or anything, but what would be the most SIMPLE starting point for someone interested in this. I was thinking maybe a 4 bit adder? or something similar? I have done a bit of electronics work, so Soldering and such I know the basics (as well as components).

Ideas/Suggestions for an Intro project? Or some documentation would be super helpful?
a few people recommended this book:
Elements of Computing Systems

but I do not know how much "hands on" it would be. When I talk simple Im talking about a simple adder using LEDS for the output or something similar.

Im super interested in this but don't know where to start. I have the third edition of Computer Organization and Design, but it doesn't have much hands on stuff.

edit: The depths of my knowledge is basically basic logic gates, I'll need to go back and refresh myself but I do understand adders and such (virtually) but I wouldn't know how to implement them on a breadboard (or any of the hardware parts of it).

edit2: Maybe something similar to this:
http://projects.coobird.net/build/building_adder.html


texts:
If you use a buffer gate as separate power source where does that extra current come from??? They are drawn as single input and single output.  Is there always assumed that there is another power supply there? And if that’s the case why not just use a sinking digital output with a single transistor?

As far as I can tell, these two images are the exact same thing.


texts: How to test the input impedance of a Microphone Preamp?

texts: How would someone test the input impedance of a microphone preamp? I have all the necessary equipment i.e. oscilloscope and multi-meters but I'm struggling to find information on the topic.


texts: How to latch on very short digital pulses?

texts:
How to latch on 2ns square pulse, if the propagation delay of our fastest gate is greater (let's say 10ns) ?

In other words how to detect pulses shorter that the inertia delay of our fastest gate?


texts:
The red framed element is on a PCB of a 1973 Hewlett Packard 5300A Measuring System, Digital Multimeter Board.
The double wire seems to have normal resistance.
What is the screw for?


texts: i have a Artix7 board with 4 SATA connector on it, i want to use these connectors for GTP transceiver, just connectors and i don't want to use SATA protocol, actually i do not know how to write XDC file for my SATA connectors, should i change the default xdc file? or the default xdc connects one tx to rx of other port? do i have to connect tx and rx myself?


texts: How do some microcontrollers implement baud rates even though it uses crystal frequency not scalable to standard baud rates?

texts: I just realized that the 8051 family uses 11.0592 MHz and its multiples so as to generate standard baud rates. But there are SoCs which use 15 MHz. How do they do this then?


texts: Can an SPI slave start a transmission in full-duplex mode?

texts:
As far as I know, SPI transmission for an SPI slave works like below:

Master selects a slave using SS pin
Master and slave send data to each other simultaneously
Master starts clock and data transmission at the same time (there is no clock before write operation)
Master stops transmission any time it wants (by stopping write operation and clock generation), even if slave has more data to send.

Is there any SPI slave configuration which allows slave to transmit data without permission of master?

I'm just thinking out loud. Assume that there is only one slave and a continuous clock is provided by master etc.

Even if assumed statement is true, don't master and slave lose byte synchronization (i.e. receives bit stream) since there is no start-stop bits for SPI?

I'm asking such a question because I've read the following section from this document.

  2.2 SPI Example

  The attached SPI example illustrates the use of the USART in
  synchronous mode. USART1 is configured as slave, whereas USART2 is
  master. The following transactions take place:

  Data transmission from master to slave.
  Data transmission from slave    to master.
  Data transmission from master to slave and from slave to    master simultaneously.

The document gives SPI example but realizes the example using USART devices. And I get that a USART slave can start a transmission without permission of master.

I couldn't find the source code that is referenced by the document.


texts:
I am a beginner at electronics and I want to build a simple logic probe for TTL circuits. I found this diagram online:

Which does exactly what I want. However, I would like to make it play a high pitched sound when it is in high state and a low pitched sound when it detects a low state.
I guess I would need some kind of speaker, but I don't know much about them, so basically I don't know where to begin or how to accomplish this, so any help will be appreciated.


texts: 8085 Memory address decoding with a NAND Gate

texts:
I have a problem for homework that has me stumped. Basically, what I'm given is 2 R/WMs, each 2048 bytes * 4. Connected to each of their CS pin is a NAND gate with pins A12-A15 connected from the 8085 microprocessor. The CS pins of both modules are in parallel with the gate. The RD and WR pins of each are connected top MEMR and MEMW. The pins of the modules are connected to A0-A10 of 8085 microprocessor. A11 is a don't care at logic 0 (I have no idea what this means).

The problem asks to identify the memory addresses. I've determined based on the NAND gate that the range would be from F000 to F7FF. This is where I'm stumped. First of all, that's a range of 800. Since that's in hex, I would think that gives only a range of 2048 bytes, which doesn't seem right.  There's a total of 16k between the two modules, so something seems to be wrong.

I would think my problem is with the high order bits, 12-15 which go through the NAND.  Could someone point me in the right direction?  I've included a diagram of the problem below.


texts: Unable to read Gantner RFID wristband from my gym

texts:
I have an RFID wristband from my gym, of which I know they use the Gantner systems, so I assume it must be this (however I can't be sure, but it looks exactly like the black one on that website):

https://www.gantner.com/product/electronic-wristband-with-rfid-gat-chipband-20/
https://www.gantner.com/download/585/?v=586

The second link (pdf) states the following specs:

Frequency: 13.56 MHz (MIFARE®)
Unique number: 7 byte
RFID chip: “F7“ = MIFARE® 7byte

I am unable to read the tag via my Android phone using the "NFC tools" app as well as with my Arduino + RFID-RC522 reader.

The reader used at the gym is one built into either one of of those:

https://www.gantner.com/product/ticketing-terminal-gat-access-6600/
https://www.gantner.com/product/access-control-terminal-for-turnstiles-gat-access-6350/

However: I ordered an RFID wristband (SILA09 MIFARE® Classic 1K; ISO Standard: 14443A) from Amazon that looks the same like the Gantner:

https://www.amazon.de/gp/product/B07SMBGY6J/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

and I can read this just fine with both my Android as well as RFID-RC522 reader.

So, I'm really wondering what the difference between the two might be?

(I'm fairly new to RFID.)

Additional note: I also have a 125 khz reader and I can confirm it doesn't read the Gantner wristband either, just to make sure it's not a 125 khz tag.


texts: Using an Ethernet Phy and XFMR instead of RS422

texts:
We've been using a quad RS485 setup for some time. No problems.
Now we'd like to increase the speed over what we can get away with on RS485 with the micro we're using. Essentially, we've been implementing an SPI port using four RS485 parts.
I've started wondering about using an Ethernet PHY and transformer as a physical layer and sort of "bit-banging" the MII interface to it. Is this a common technique, or am I missing something critical?
Goals: keep the differential benefits, better isolation, increase speed considerably.
Distance would never be greater than 10 meters.
Thanks in advance!


texts: Is it better to have a poor top layer copper pour or no copper at all?

texts:
For a few small 2 layers boards I'm doing, I'm using the top layer for parts and signals and a ground pour on the bottom layer with no or very short traces, based on comments and answers to my previous question

Since the top layer becomes too chopped-up with a lot of islands, which makes it practically useless and I'm also trying to minimize the current loop between the ICs and decoupling caps (if I leave the top layer it will connect to the caps and the ground pins separately and not in a single point), so I decided not to use a copper pour on the top layer at all for the mentioned reasons.

The problem with this approach is the manufacturing side of things, if I understand correctly FR4 material could wrap if the copper on both sides of the PCB is unequal (although I don't understand why that doesn't happen with a 4 layer board typical stack-up sig-gnd-vcc-sig), so I'm back where I started

I've been going back to this a lot doing a lot of research but still can't find a conclusive answer and I can't decide what to do.

This is an example board, the one on the right without top copper pour.

Update: based on your comments, I revised the board to avoid breaking the ground as much as possible, but still can't decide on the top layer though.


texts: Sprinkler Control Power supply requirements questions

texts:
Not sure if this is the right forum or not...

I am looking to build a custom sprinkler controller using a Raspberry Pi and a relay board. The question is around the power supply. The valve (http://www.sprinklerwarehouse.com/Hunter-Sprinkler-Irrigation-Valve-p/pgv-075-asv-s.htm) is listed as having these specs: 24VAC, 370mA inrush current, 190mA holding current, 60 cycles; 475mA inrush current, 230mA holding current, 50 cycles

I have a power supply that is 1000mA (http://www.sprinklerwarehouse.com/Hunter-Controller-Transformer-p/52-6500.htm).

First question is I am confused why the two different specs on the valve, 50 vs 60 cycles?

Second question is if the power supply is 1000mA and I connect through a relay that means if I turn the relay on the valve will be getting close to 1000mA. Will this cause problems in the short or long term for the valve?

Let me know if there is any questions.

Thanks in advance for the help!


texts: How to detect source presence using LTC4412?

texts: I'm using 2 power sources as shown in below picture. The status pin is suggested to pull HIGH to VCC(which can be the adapter input). As mentioned that Status pin OUTPUT is LOW when Wall adapter present, but the actual voltage I'm getting is 6.8V and when only battery(7.4v) is present the voltage is 7.2V. So how can I detect source presence using LTC4412. Kindly help regarding this issue.


texts: Is it possible for a DC LDO to be able to take in AC and DC

texts:
I have an LDO TPS7B69 which takes in up to 40V DC and regulates it to 5V. This LDO typically takes in DC, but I would also like it to be powered by AC 40 volts peak max at 50Hz or greater.
Rectification would first come to mind, and I would prefer using a full bridge rectifier since it will utilize both positive and negative cycle thus not needing huge caps values, which also help against Reverse Input protection (?) when using DC. But I do not know if a DC input on the FBR would also yield a DC output. I personally think it would work since it would just be like a peak voltage on an AC.
Is my approach acceptable? Are there any better ways to do this?


texts:
I need to build 0.1V@100-500A power supply - and I wonder what's the best way to approach this task? I guess here are not much specific IC's suitable for such DCDC... Should be current-stabilized, 10% ripple is ok, no requirements on switching frequency...

What's the rough estimation for the size/quantity of components we always need in DCDC (inductors/caps/number of channels) for such PSU?

This is for heating metal stripes, which have very low resistance. 20mm^2 copper connections is not a problem.

Some thoughts:

Even my AWG4 wire would give me 0.8mOhm per meter... If I place DCDC right next to consumer, I can have like 0.2m connections and 0.16mOhm resistance... But If I want to have switching regulator, I'll need lots of FETs & inductors... Fortunately, I already have bunch of 5mOhm N-FETs, so I can run 20-30 of them in parallel, and bunch of 1uH inductors out of some 1.5mm^2 wire which I also can run in parallel (all this from a batch of damaged PC motherboards)... The question is what's the most realistic way of driving all these things - I am thinking about having microcontroller driving all these FETs (using simple discrete driving circuits) and feedback through onboard 1msps ADC.. I wonder what should be switching frequency given that inductors are only 1uH?

Bounty comments: Still want to hear thoughts on DCDC way, without transformers. Compact DCDC might fit right inside vacuum chamber, which is impossible for transformer. And yes, the task is to heat tungsten foil of different geometry in vacuum (up to some 1000C).


texts:
I'm working on a test program on an ATmega164A that toggles a 12V relay on and off (with no load) through a ULN2003A. For my test program, I'm toggling the relay at 100ms. I've got an IN4001 diode across the coil. Additionally, I've got an LCD that displays a milliseconds counter, which increments in an interrupt. In normal operation, it goes on forever without any issues. I noticed that one of my relay sockets was wonky, so sometimes I need to fiddle with the relay in the socket to get it working again. When I did this, I noticed that sometimes the main loop would hang and I'd get some garbage on the LCD. If I fiddled with the relay some more (and specifically the coil contacts in the socket), the main loop would resume, but the counter value would be correct, indicating that the main loop would be paused but the interrupts would continue.

I mostly fixed the garbage on the LCD by putting a 0.1uF cap right at the power pins, but the main loop will still hang if I do what I mentioned above. I know this is kind of a weird situation and it should never really happen, but I'm just trying to understand it. I just figure that if the main loop gets interrupted somehow, then surely the interrupts wouldn't still be working correctly.


texts: Directly controlling an AC load with a power phototriac

texts:
Searching for a phototriac to use in an AC dimmer circuit, I've come around this power phototriac -- VO2223A.

With the load current of 1A, it looks like it could replace the traditional optocoupler-triac combo (IC1, T1):

Would that work?


texts: 125kHz RFID System Design/Troubleshooting

texts:
I am trying to build an RFID system to track animals. I am using 125 Khz glass capsule tags by Sparkfun implanted under their skin. I initially used an ID-12LA reader, but I am not getting reads most of the time, possibly due to tag angle, tag orientation, read range...etc.

I am moving on to an ID-3LA in order to utilize its external antenna capabilities. This reader requires an antenna producing 1.337 mH. So, I bought a 46 mm antenna capable of producing 2.8 mH. I connected the system as follows:

but unfortunately, I am unable to get reads at all.

Here are my design/troubleshooting questions:

1) In general, if I have an antenna capable of producing inductance higher than that required by the reader, will this compromise the system? If so, what are ways to reduce inductance (without having to remove turns)? According to my research from previously asked questions on this website: people spoke of adding a capacitor to increase inductance but I haven't seen anyone speak of decreasing inductance. Are there any tricks using resistors...etc.?

2) Is there a physical limitation in my system: small tag, antenna with small diameter, read range of 46 mm (or in other words read range inside the circular antenna)? Am I possibly activating the tag, but unable to read it back because of the magnitude of its "identity signal"?

Thanks


texts:
I am working on a project where I have used MC-34063 boost supply on 3 pcb's and all the 3 places I have the same issue ie

output voltage is steady on open circuit, but soon as ANY load is connected, MC starts drawing massive amount of current, and puts the Bench Supply from CV to CC mode. (it goes upto 1.5amp)

I am not sure what is the issue here as I have taken care of these precautions

4 layer board
consistent ground plane
very small ground loop for any return paths
100-150 mohm ESR caps and inductors

I am really clueless as to why the voltage is sagging, in all cases when I boost voltage from either 3.3v to 12 or 5v to 12v.
Current requirements in either case is less than 100mA and inductor is rated for 1.8amp.
if it helps, what I have noticed is disconnecting the 180ohm/drive resistor even though there is no boost, but there is no huge current consumption either!
Additionally, I tried

changing drive resistor to lower values of 10ohm and higher values of 1kohms
adding more capacitors at output
added additional LC filter at output

Please see below for circuit daigram,  layout and pcb pictures.
lastly please note, all the schematics, layouts and PCB's are pretty similar for both 5V and 12v, except for

feedback resistors (1k, 9K) for 12V, and (1k, 3K) for 5v and
output capacitors ratings of 10V for 5v boost, and 16V for 12v Boost


texts: Calculate rated power(P) of transformer?

texts:
I have a transformer-type PT 13/2/6 as the following page (Versions 34 to 37 from 68). Image like this:

  The voltage between points A and B is V AB (primary)= 230 vac

  The voltage between points C and D are V CD (secondary 2) = 6 Vac

  The voltage between points E and F are V EF (secondary 1)= 6 Vac

I have 2 loads, first load 5VDC/2.5A put on EF and second load 12VDC/1A put on CF(DE shorted).

My question: How much total power do I need? Is power rate 13VA enough?


texts:
I have been trying to troubleshoot a problem with my Protek 506 DMM, and I think that the problem may lie within its MAX134CMH+D A/D Converter chip, named U2 on the attached schematic diagram. The DMM has an issue with its diode test function and its 4VDC measuring range. These functions I believe are associated with pins 24-28 on the MAX134.  Pins 25-28 are connected to a resistor-divider network component,RN1,  which is connected to the rotary switch CN15 at "ATT-B", then finally to the positive test lead at "V" CN6. Pin 24 seems to connect directly to "V" CN6 via R1 and VR5.
Unfortunately, the datasheet available for the MAX134 does not include a pinout for the MQFP44 case version which this DMM has, but I found a hand-drawn image on a Russian forum.
Here is a screenshot of the Protek 506 schematic diagram:
Here is another pinout from the web:

I am not fully understanding how the relevant part of the MAX134 works, or how it is associated with the resistor divider network RN1 connected to pins 25-28, and the 10 Ohm input at pin 24.
Using another DMM, with its negative test lead attached to the "COM" CN5 socket of the subject meter, I detect the following voltages when the subject meter is on the 4VDC range:
Pin 24:  alternating between 1.84V and 0V
Pin 25:  2.987V
Pin 26:  0V
Pin 27:  0V
Pin 28:  0V
Further, the common leg of RN1 shows a continuity with GND, at 0.2 Ohms.
On the display of the subject meter, when it is on the 4VDC range, it shows two continually alternating values: 3.999V and 00.00V. If there is a voltage applied to the test leads, it will display two continually alternating values of 3.999V and whatever the voltage being measured is.
When the meter is on the Diode Test mode, it will only display the word "OPEn" and the voltage of 3.999V, even when it has a diode between the test lead probes.
I've checked the componentry and rotary switch connections between the "V" CN6 socket and Pins 24-28, and everything seems within specs. MAX134's voltage reference Pin 34 measures 0.542V
Below is a photo of the display on my Oscilloscope, when connected to Pin 20 integrator Output, compared with figures 6 and 8 on the datasheet. The same results on meter's DCV or ACV inputs, and if there is no voltage being measured, or a 9V battery being measured.

Any thoughts, ideas?


texts: What is the best practices of placing of termination resistor

texts:
Usually I placed the 120 Ohm termination resistor pads in the PCB. So I could place the resistor or not during the PCB assembly for different applications.

However I suppose that the termination resistors should be a part of the transmission line - not the device. Besides, device user could be unaware of the fact that the termination resistor is already on the board and as the result - overload transducers.

On the other hand in case I don't have terminators on the PCB I will need them on the line which equals extra external components (terminal blocks, resistors...).

So the question is: which way will be the most convenient in terms of installation? Probably I could use 3-way RS485 terminal blocks (A, B, terminal resistor connected to the A or B). I could put a jumper accessible from the outside. Or finally I could skip the terminator at all as the speed id only 9600 baud (in my case).

Any thoughts?


texts: Disassembling a camera - dealing with a flash capacitor

texts:
I'm disassembling a broken old camera (an Olympus FE-110) and I've learned that I should be really careful with the capacitor inside. I wanted to follow the guide linked at the bottom of this article, though in this camera make it's not that easy getting access to the circuit board. I opened up the camera as far as this:

There's a bit of wire sticking out from underneath the red and black coating on the capacitor wires. I prodded the two with a voltmeter and got a reading of 0.

The camera very likely hasn't had any batteries inside it for a year. Should I assume the capacitor is empty and be as reckless with it as I want? Or, considering I'm still pretty new at electronics, should I put the casing back on and not mess with high voltages until I know a bit better?

The capacitor is 330V / 160 uF, in case the picture isn't clear enough.


texts: Calculating the time it takes for a battery to fully charge

texts:
I was looking at the following question: How to Calculate the time of Charging and Discharging of battery?
And I was wondering if the voltage takes part in the calculation somehow?
For example, I have the following items:
- 5v 1000mAh battery
- 6v 1000mA charger
- 12v 500mA second charger
both chargers have a power of 6 watts

Which one of these will charge the battery faster and how fast?

On one hand my logic says that because both chargers have the same power, they deliver the same charge to the battery,
but on the other hand it seems that battery charging is calculated according to the current only.


texts: Power 24V external component + blue pill, control external component

texts:
Please take into account I'm a beginner with microelectronics.

I want to build an automated air humidifier.

For this, I'm using a STM32 blue pill and a si7021 I2C sensor. The I2C sensor regularly measures the temperature and humidity in the room. That's the part of my project that properly works at the moment.

Depending on the humidity level in the room, I'd like to trigger an ultrasonic water atomizer. I bought a pack of atomizers here: https://www.amazon.fr/gp/product/B07F3YY6K7

From what I could find, these atomizers should be powered by a DC 24V current, which is obviously way more than what the blue pill can provide on its own.

That's where my knowledge ends. I don't know how to power and control these atomizers. What's coming is no more than an educated guess.

I imagine I need to get a 220V AC mains to 24V DC adapter. This 24V current then needs to be split:

to 5V to power the board, and maybe other components (like a bluetooth chip)
to 24V to directly power the atomizers

But once all the components are powered, the blue pill needs to be able to enable/disable the power to the atomizers.

So what I'm missing is (I guess):

a way to convert 24V to 5V
a way to control the power to the atomizers from the blue pill

Can you point me in the right direction please?


texts: How can I safely use an aluminium enclosure without an earthed socket

texts:
For a mains-supplied circuit I want to use an aluminium case, so the case can act as a heat sink.
However, I want it to be safe, also when there's no earth connection in the socket where the circuit is plugged into (this is still quite common in Europe).

What is the common way to make the circuit safe to use in an aluminium case?

I know that normally you would connect the earth-wire to the case, so in case one of the wires internally touches the case, the circuit breaker will turn off the power, protecting people from touching the enclosure while there is 230V on it (see also this question). But of course this does not work when the socket has no ground connection...


texts: Mosfet part number? How to find a replacement otherwise?

texts:
I did a quick google search based on the numbers on this Mosfet and found nothing. How would you go about finding a datasheet and replacing a part like this?

GP7NabOHDa
CCos1
MRC - 502

This part is located on an Ametek 1000W blower. I believe it is used to control the speed of the motor.


texts: I would like to design an op Amp based 25Mhz Hartley oscillator

texts: Hello i am a beginner at this and i would like your guidance . I would like to design an op Amp based 25Mhz Hartley's oscillator . I did some calculations and came up with the oscillator below , but it doesn't oscillate please help me


texts:
I need to drive n-mosfets to switch on/off resistors in parallel with Lion cells.
Each cell+mosfet is in a series - 50 cells.
It looks much like a BMS except it NOT a BMS, but a cell test system. See the "idea" schematic of each single cell below.
Cells will be charged (M2 off, M1 on) powered from 40A current source. As cells reach nominal voltage, they are "taken out" of circuit by switching M2 on and M1 off.
Then they will be discharged, taken out of circuit when low voltage reached.
Cells will necessarily be (hopefully only slightly) different, so they must be managed individually, although they are in a series.
How to drive the mosfets, if reference for each is not ground (because they are stacked) and not constant (common mode voltage will reach ~150V for cell 1)?
(incidentally, which mosfets to use, Ids=40A, Vds 3.7V, Vgs~3V?)

simulate this circuit – Schematic created using CircuitLab


texts: Connect the oscilloscope to equipment with a common neutral and ground

texts: I watched a video. At 3 minutes, the situation is shown when neutral and ground are joining. Why can this be dangerous? If we are talking about an oscilloscope, the crocodile must already be connected to the earth and nothing threatens me. The way I understand the connection, I showed in the picture. Is it possible to get "tickled" with such a picture?